Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

14 files changed, 15856 insertions, 0 deletions

diff --git a/fs/fuse/Kconfig b/fs/fuse/Kconfig
new file mode 100644
index 000000000..40ce9a1c1
--- /dev/null
+++ b/fs/fuse/Kconfig
@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config FUSE_FS
+	tristate "FUSE (Filesystem in Userspace) support"
+	select FS_POSIX_ACL
+	help
+	  With FUSE it is possible to implement a fully functional filesystem
+	  in a userspace program.
+
+	  There's also a companion library: libfuse2.  This library is available
+	  from the FUSE homepage:
+	  <https://github.com/libfuse/>
+	  although chances are your distribution already has that library
+	  installed if you've installed the "fuse" package itself.
+
+	  See <file:Documentation/filesystems/fuse.rst> for more information.
+	  See <file:Documentation/Changes> for needed library/utility version.
+
+	  If you want to develop a userspace FS, or if you want to use
+	  a filesystem based on FUSE, answer Y or M.
+
+config CUSE
+	tristate "Character device in Userspace support"
+	depends on FUSE_FS
+	help
+	  This FUSE extension allows character devices to be
+	  implemented in userspace.
+
+	  If you want to develop or use a userspace character device
+	  based on CUSE, answer Y or M.
+
+config VIRTIO_FS
+	tristate "Virtio Filesystem"
+	depends on FUSE_FS
+	select VIRTIO
+	help
+	  The Virtio Filesystem allows guests to mount file systems from the
+	  host.
+
+	  If you want to share files between guests or with the host, answer Y
+	  or M.
+
+config FUSE_DAX
+	bool "Virtio Filesystem Direct Host Memory Access support"
+	default y
+	select INTERVAL_TREE
+	depends on VIRTIO_FS
+	depends on FS_DAX
+	depends on DAX_DRIVER
+	help
+	  This allows bypassing guest page cache and allows mapping host page
+	  cache directly in guest address space.
+
+	  If you want to allow mounting a Virtio Filesystem with the "dax"
+	  option, answer Y.
diff --git a/fs/fuse/Makefile b/fs/fuse/Makefile
new file mode 100644
index 000000000..8c7021fb2
--- /dev/null
+++ b/fs/fuse/Makefile
@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for the FUSE filesystem.
+#
+
+obj-$(CONFIG_FUSE_FS) += fuse.o
+obj-$(CONFIG_CUSE) += cuse.o
+obj-$(CONFIG_VIRTIO_FS) += virtiofs.o
+
+fuse-y := dev.o dir.o file.o inode.o control.o xattr.o acl.o readdir.o
+fuse-$(CONFIG_FUSE_DAX) += dax.o
+
+virtiofs-y := virtio_fs.o
diff --git a/fs/fuse/acl.c b/fs/fuse/acl.c
new file mode 100644
index 000000000..f529075a2
--- /dev/null
+++ b/fs/fuse/acl.c
@@ -0,0 +1,105 @@
+/*
+ * FUSE: Filesystem in Userspace
+ * Copyright (C) 2016 Canonical Ltd. <seth.forshee@canonical.com>
+ *
+ * This program can be distributed under the terms of the GNU GPL.
+ * See the file COPYING.
+ */
+
+#include "fuse_i.h"
+
+#include <linux/posix_acl.h>
+#include <linux/posix_acl_xattr.h>
+
+struct posix_acl *fuse_get_acl(struct inode *inode, int type)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	int size;
+	const char *name;
+	void *value = NULL;
+	struct posix_acl *acl;
+
+	if (fuse_is_bad(inode))
+		return ERR_PTR(-EIO);
+
+	if (!fc->posix_acl || fc->no_getxattr)
+		return NULL;
+
+	if (type == ACL_TYPE_ACCESS)
+		name = XATTR_NAME_POSIX_ACL_ACCESS;
+	else if (type == ACL_TYPE_DEFAULT)
+		name = XATTR_NAME_POSIX_ACL_DEFAULT;
+	else
+		return ERR_PTR(-EOPNOTSUPP);
+
+	value = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!value)
+		return ERR_PTR(-ENOMEM);
+	size = fuse_getxattr(inode, name, value, PAGE_SIZE);
+	if (size > 0)
+		acl = posix_acl_from_xattr(fc->user_ns, value, size);
+	else if ((size == 0) || (size == -ENODATA) ||
+		 (size == -EOPNOTSUPP && fc->no_getxattr))
+		acl = NULL;
+	else if (size == -ERANGE)
+		acl = ERR_PTR(-E2BIG);
+	else
+		acl = ERR_PTR(size);
+
+	kfree(value);
+	return acl;
+}
+
+int fuse_set_acl(struct inode *inode, struct posix_acl *acl, int type)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	const char *name;
+	int ret;
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	if (!fc->posix_acl || fc->no_setxattr)
+		return -EOPNOTSUPP;
+
+	if (type == ACL_TYPE_ACCESS)
+		name = XATTR_NAME_POSIX_ACL_ACCESS;
+	else if (type == ACL_TYPE_DEFAULT)
+		name = XATTR_NAME_POSIX_ACL_DEFAULT;
+	else
+		return -EINVAL;
+
+	if (acl) {
+		/*
+		 * Fuse userspace is responsible for updating access
+		 * permissions in the inode, if needed. fuse_setxattr
+		 * invalidates the inode attributes, which will force
+		 * them to be refreshed the next time they are used,
+		 * and it also updates i_ctime.
+		 */
+		size_t size = posix_acl_xattr_size(acl->a_count);
+		void *value;
+
+		if (size > PAGE_SIZE)
+			return -E2BIG;
+
+		value = kmalloc(size, GFP_KERNEL);
+		if (!value)
+			return -ENOMEM;
+
+		ret = posix_acl_to_xattr(fc->user_ns, acl, value, size);
+		if (ret < 0) {
+			kfree(value);
+			return ret;
+		}
+
+		ret = fuse_setxattr(inode, name, value, size, 0);
+		kfree(value);
+	} else {
+		ret = fuse_removexattr(inode, name);
+	}
+	forget_all_cached_acls(inode);
+	fuse_invalidate_attr(inode);
+
+	return ret;
+}
diff --git a/fs/fuse/control.c b/fs/fuse/control.c
new file mode 100644
index 000000000..24b4d9db2
--- /dev/null
+++ b/fs/fuse/control.c
@@ -0,0 +1,401 @@
+/*
+  FUSE: Filesystem in Userspace
+  Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>
+
+  This program can be distributed under the terms of the GNU GPL.
+  See the file COPYING.
+*/
+
+#include "fuse_i.h"
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/fs_context.h>
+
+#define FUSE_CTL_SUPER_MAGIC 0x65735543
+
+/*
+ * This is non-NULL when the single instance of the control filesystem
+ * exists.  Protected by fuse_mutex
+ */
+static struct super_block *fuse_control_sb;
+
+static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file)
+{
+	struct fuse_conn *fc;
+	mutex_lock(&fuse_mutex);
+	fc = file_inode(file)->i_private;
+	if (fc)
+		fc = fuse_conn_get(fc);
+	mutex_unlock(&fuse_mutex);
+	return fc;
+}
+
+static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf,
+				     size_t count, loff_t *ppos)
+{
+	struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
+	if (fc) {
+		if (fc->abort_err)
+			fc->aborted = true;
+		fuse_abort_conn(fc);
+		fuse_conn_put(fc);
+	}
+	return count;
+}
+
+static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
+				      size_t len, loff_t *ppos)
+{
+	char tmp[32];
+	size_t size;
+
+	if (!*ppos) {
+		long value;
+		struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
+		if (!fc)
+			return 0;
+
+		value = atomic_read(&fc->num_waiting);
+		file->private_data = (void *)value;
+		fuse_conn_put(fc);
+	}
+	size = sprintf(tmp, "%ld\n", (long)file->private_data);
+	return simple_read_from_buffer(buf, len, ppos, tmp, size);
+}
+
+static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf,
+				    size_t len, loff_t *ppos, unsigned val)
+{
+	char tmp[32];
+	size_t size = sprintf(tmp, "%u\n", val);
+
+	return simple_read_from_buffer(buf, len, ppos, tmp, size);
+}
+
+static ssize_t fuse_conn_limit_write(struct file *file, const char __user *buf,
+				     size_t count, loff_t *ppos, unsigned *val,
+				     unsigned global_limit)
+{
+	unsigned long t;
+	unsigned limit = (1 << 16) - 1;
+	int err;
+
+	if (*ppos)
+		return -EINVAL;
+
+	err = kstrtoul_from_user(buf, count, 0, &t);
+	if (err)
+		return err;
+
+	if (!capable(CAP_SYS_ADMIN))
+		limit = min(limit, global_limit);
+
+	if (t > limit)
+		return -EINVAL;
+
+	*val = t;
+
+	return count;
+}
+
+static ssize_t fuse_conn_max_background_read(struct file *file,
+					     char __user *buf, size_t len,
+					     loff_t *ppos)
+{
+	struct fuse_conn *fc;
+	unsigned val;
+
+	fc = fuse_ctl_file_conn_get(file);
+	if (!fc)
+		return 0;
+
+	val = READ_ONCE(fc->max_background);
+	fuse_conn_put(fc);
+
+	return fuse_conn_limit_read(file, buf, len, ppos, val);
+}
+
+static ssize_t fuse_conn_max_background_write(struct file *file,
+					      const char __user *buf,
+					      size_t count, loff_t *ppos)
+{
+	unsigned val;
+	ssize_t ret;
+
+	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
+				    max_user_bgreq);
+	if (ret > 0) {
+		struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
+		if (fc) {
+			spin_lock(&fc->bg_lock);
+			fc->max_background = val;
+			fc->blocked = fc->num_background >= fc->max_background;
+			if (!fc->blocked)
+				wake_up(&fc->blocked_waitq);
+			spin_unlock(&fc->bg_lock);
+			fuse_conn_put(fc);
+		}
+	}
+
+	return ret;
+}
+
+static ssize_t fuse_conn_congestion_threshold_read(struct file *file,
+						   char __user *buf, size_t len,
+						   loff_t *ppos)
+{
+	struct fuse_conn *fc;
+	unsigned val;
+
+	fc = fuse_ctl_file_conn_get(file);
+	if (!fc)
+		return 0;
+
+	val = READ_ONCE(fc->congestion_threshold);
+	fuse_conn_put(fc);
+
+	return fuse_conn_limit_read(file, buf, len, ppos, val);
+}
+
+static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
+						    const char __user *buf,
+						    size_t count, loff_t *ppos)
+{
+	unsigned val;
+	struct fuse_conn *fc;
+	struct fuse_mount *fm;
+	ssize_t ret;
+
+	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
+				    max_user_congthresh);
+	if (ret <= 0)
+		goto out;
+	fc = fuse_ctl_file_conn_get(file);
+	if (!fc)
+		goto out;
+
+	down_read(&fc->killsb);
+	spin_lock(&fc->bg_lock);
+	fc->congestion_threshold = val;
+
+	/*
+	 * Get any fuse_mount belonging to this fuse_conn; s_bdi is
+	 * shared between all of them
+	 */
+
+	if (!list_empty(&fc->mounts)) {
+		fm = list_first_entry(&fc->mounts, struct fuse_mount, fc_entry);
+		if (fc->num_background < fc->congestion_threshold) {
+			clear_bdi_congested(fm->sb->s_bdi, BLK_RW_SYNC);
+			clear_bdi_congested(fm->sb->s_bdi, BLK_RW_ASYNC);
+		} else {
+			set_bdi_congested(fm->sb->s_bdi, BLK_RW_SYNC);
+			set_bdi_congested(fm->sb->s_bdi, BLK_RW_ASYNC);
+		}
+	}
+	spin_unlock(&fc->bg_lock);
+	up_read(&fc->killsb);
+	fuse_conn_put(fc);
+out:
+	return ret;
+}
+
+static const struct file_operations fuse_ctl_abort_ops = {
+	.open = nonseekable_open,
+	.write = fuse_conn_abort_write,
+	.llseek = no_llseek,
+};
+
+static const struct file_operations fuse_ctl_waiting_ops = {
+	.open = nonseekable_open,
+	.read = fuse_conn_waiting_read,
+	.llseek = no_llseek,
+};
+
+static const struct file_operations fuse_conn_max_background_ops = {
+	.open = nonseekable_open,
+	.read = fuse_conn_max_background_read,
+	.write = fuse_conn_max_background_write,
+	.llseek = no_llseek,
+};
+
+static const struct file_operations fuse_conn_congestion_threshold_ops = {
+	.open = nonseekable_open,
+	.read = fuse_conn_congestion_threshold_read,
+	.write = fuse_conn_congestion_threshold_write,
+	.llseek = no_llseek,
+};
+
+static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
+					  struct fuse_conn *fc,
+					  const char *name,
+					  int mode, int nlink,
+					  const struct inode_operations *iop,
+					  const struct file_operations *fop)
+{
+	struct dentry *dentry;
+	struct inode *inode;
+
+	BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
+	dentry = d_alloc_name(parent, name);
+	if (!dentry)
+		return NULL;
+
+	inode = new_inode(fuse_control_sb);
+	if (!inode) {
+		dput(dentry);
+		return NULL;
+	}
+
+	inode->i_ino = get_next_ino();
+	inode->i_mode = mode;
+	inode->i_uid = fc->user_id;
+	inode->i_gid = fc->group_id;
+	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
+	/* setting ->i_op to NULL is not allowed */
+	if (iop)
+		inode->i_op = iop;
+	inode->i_fop = fop;
+	set_nlink(inode, nlink);
+	inode->i_private = fc;
+	d_add(dentry, inode);
+
+	fc->ctl_dentry[fc->ctl_ndents++] = dentry;
+
+	return dentry;
+}
+
+/*
+ * Add a connection to the control filesystem (if it exists).  Caller
+ * must hold fuse_mutex
+ */
+int fuse_ctl_add_conn(struct fuse_conn *fc)
+{
+	struct dentry *parent;
+	char name[32];
+
+	if (!fuse_control_sb || fc->no_control)
+		return 0;
+
+	parent = fuse_control_sb->s_root;
+	inc_nlink(d_inode(parent));
+	sprintf(name, "%u", fc->dev);
+	parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
+				     &simple_dir_inode_operations,
+				     &simple_dir_operations);
+	if (!parent)
+		goto err;
+
+	if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
+				 NULL, &fuse_ctl_waiting_ops) ||
+	    !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
+				 NULL, &fuse_ctl_abort_ops) ||
+	    !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
+				 1, NULL, &fuse_conn_max_background_ops) ||
+	    !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
+				 S_IFREG | 0600, 1, NULL,
+				 &fuse_conn_congestion_threshold_ops))
+		goto err;
+
+	return 0;
+
+ err:
+	fuse_ctl_remove_conn(fc);
+	return -ENOMEM;
+}
+
+/*
+ * Remove a connection from the control filesystem (if it exists).
+ * Caller must hold fuse_mutex
+ */
+void fuse_ctl_remove_conn(struct fuse_conn *fc)
+{
+	int i;
+
+	if (!fuse_control_sb || fc->no_control)
+		return;
+
+	for (i = fc->ctl_ndents - 1; i >= 0; i--) {
+		struct dentry *dentry = fc->ctl_dentry[i];
+		d_inode(dentry)->i_private = NULL;
+		if (!i) {
+			/* Get rid of submounts: */
+			d_invalidate(dentry);
+		}
+		dput(dentry);
+	}
+	drop_nlink(d_inode(fuse_control_sb->s_root));
+}
+
+static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fctx)
+{
+	static const struct tree_descr empty_descr = {""};
+	struct fuse_conn *fc;
+	int err;
+
+	err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
+	if (err)
+		return err;
+
+	mutex_lock(&fuse_mutex);
+	BUG_ON(fuse_control_sb);
+	fuse_control_sb = sb;
+	list_for_each_entry(fc, &fuse_conn_list, entry) {
+		err = fuse_ctl_add_conn(fc);
+		if (err) {
+			fuse_control_sb = NULL;
+			mutex_unlock(&fuse_mutex);
+			return err;
+		}
+	}
+	mutex_unlock(&fuse_mutex);
+
+	return 0;
+}
+
+static int fuse_ctl_get_tree(struct fs_context *fc)
+{
+	return get_tree_single(fc, fuse_ctl_fill_super);
+}
+
+static const struct fs_context_operations fuse_ctl_context_ops = {
+	.get_tree	= fuse_ctl_get_tree,
+};
+
+static int fuse_ctl_init_fs_context(struct fs_context *fc)
+{
+	fc->ops = &fuse_ctl_context_ops;
+	return 0;
+}
+
+static void fuse_ctl_kill_sb(struct super_block *sb)
+{
+	struct fuse_conn *fc;
+
+	mutex_lock(&fuse_mutex);
+	fuse_control_sb = NULL;
+	list_for_each_entry(fc, &fuse_conn_list, entry)
+		fc->ctl_ndents = 0;
+	mutex_unlock(&fuse_mutex);
+
+	kill_litter_super(sb);
+}
+
+static struct file_system_type fuse_ctl_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "fusectl",
+	.init_fs_context = fuse_ctl_init_fs_context,
+	.kill_sb	= fuse_ctl_kill_sb,
+};
+MODULE_ALIAS_FS("fusectl");
+
+int __init fuse_ctl_init(void)
+{
+	return register_filesystem(&fuse_ctl_fs_type);
+}
+
+void __exit fuse_ctl_cleanup(void)
+{
+	unregister_filesystem(&fuse_ctl_fs_type);
+}
diff --git a/fs/fuse/cuse.c b/fs/fuse/cuse.c
new file mode 100644
index 000000000..a37528b51
--- /dev/null
+++ b/fs/fuse/cuse.c
@@ -0,0 +1,659 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * CUSE: Character device in Userspace
+ *
+ * Copyright (C) 2008-2009  SUSE Linux Products GmbH
+ * Copyright (C) 2008-2009  Tejun Heo <tj@kernel.org>
+ *
+ * CUSE enables character devices to be implemented from userland much
+ * like FUSE allows filesystems.  On initialization /dev/cuse is
+ * created.  By opening the file and replying to the CUSE_INIT request
+ * userland CUSE server can create a character device.  After that the
+ * operation is very similar to FUSE.
+ *
+ * A CUSE instance involves the following objects.
+ *
+ * cuse_conn	: contains fuse_conn and serves as bonding structure
+ * channel	: file handle connected to the userland CUSE server
+ * cdev		: the implemented character device
+ * dev		: generic device for cdev
+ *
+ * Note that 'channel' is what 'dev' is in FUSE.  As CUSE deals with
+ * devices, it's called 'channel' to reduce confusion.
+ *
+ * channel determines when the character device dies.  When channel is
+ * closed, everything begins to destruct.  The cuse_conn is taken off
+ * the lookup table preventing further access from cdev, cdev and
+ * generic device are removed and the base reference of cuse_conn is
+ * put.
+ *
+ * On each open, the matching cuse_conn is looked up and if found an
+ * additional reference is taken which is released when the file is
+ * closed.
+ */
+
+#define pr_fmt(fmt) "CUSE: " fmt
+
+#include <linux/fuse.h>
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/kdev_t.h>
+#include <linux/kthread.h>
+#include <linux/list.h>
+#include <linux/magic.h>
+#include <linux/miscdevice.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/stat.h>
+#include <linux/module.h>
+#include <linux/uio.h>
+#include <linux/user_namespace.h>
+
+#include "fuse_i.h"
+
+#define CUSE_CONNTBL_LEN	64
+
+struct cuse_conn {
+	struct list_head	list;	/* linked on cuse_conntbl */
+	struct fuse_mount	fm;	/* Dummy mount referencing fc */
+	struct fuse_conn	fc;	/* fuse connection */
+	struct cdev		*cdev;	/* associated character device */
+	struct device		*dev;	/* device representing @cdev */
+
+	/* init parameters, set once during initialization */
+	bool			unrestricted_ioctl;
+};
+
+static DEFINE_MUTEX(cuse_lock);		/* protects registration */
+static struct list_head cuse_conntbl[CUSE_CONNTBL_LEN];
+static struct class *cuse_class;
+
+static struct cuse_conn *fc_to_cc(struct fuse_conn *fc)
+{
+	return container_of(fc, struct cuse_conn, fc);
+}
+
+static struct list_head *cuse_conntbl_head(dev_t devt)
+{
+	return &cuse_conntbl[(MAJOR(devt) + MINOR(devt)) % CUSE_CONNTBL_LEN];
+}
+
+
+/**************************************************************************
+ * CUSE frontend operations
+ *
+ * These are file operations for the character device.
+ *
+ * On open, CUSE opens a file from the FUSE mnt and stores it to
+ * private_data of the open file.  All other ops call FUSE ops on the
+ * FUSE file.
+ */
+
+static ssize_t cuse_read_iter(struct kiocb *kiocb, struct iov_iter *to)
+{
+	struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(kiocb);
+	loff_t pos = 0;
+
+	return fuse_direct_io(&io, to, &pos, FUSE_DIO_CUSE);
+}
+
+static ssize_t cuse_write_iter(struct kiocb *kiocb, struct iov_iter *from)
+{
+	struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(kiocb);
+	loff_t pos = 0;
+	/*
+	 * No locking or generic_write_checks(), the server is
+	 * responsible for locking and sanity checks.
+	 */
+	return fuse_direct_io(&io, from, &pos,
+			      FUSE_DIO_WRITE | FUSE_DIO_CUSE);
+}
+
+static int cuse_open(struct inode *inode, struct file *file)
+{
+	dev_t devt = inode->i_cdev->dev;
+	struct cuse_conn *cc = NULL, *pos;
+	int rc;
+
+	/* look up and get the connection */
+	mutex_lock(&cuse_lock);
+	list_for_each_entry(pos, cuse_conntbl_head(devt), list)
+		if (pos->dev->devt == devt) {
+			fuse_conn_get(&pos->fc);
+			cc = pos;
+			break;
+		}
+	mutex_unlock(&cuse_lock);
+
+	/* dead? */
+	if (!cc)
+		return -ENODEV;
+
+	/*
+	 * Generic permission check is already done against the chrdev
+	 * file, proceed to open.
+	 */
+	rc = fuse_do_open(&cc->fm, 0, file, 0);
+	if (rc)
+		fuse_conn_put(&cc->fc);
+	return rc;
+}
+
+static int cuse_release(struct inode *inode, struct file *file)
+{
+	struct fuse_file *ff = file->private_data;
+	struct fuse_mount *fm = ff->fm;
+
+	fuse_sync_release(NULL, ff, file->f_flags);
+	fuse_conn_put(fm->fc);
+
+	return 0;
+}
+
+static long cuse_file_ioctl(struct file *file, unsigned int cmd,
+			    unsigned long arg)
+{
+	struct fuse_file *ff = file->private_data;
+	struct cuse_conn *cc = fc_to_cc(ff->fm->fc);
+	unsigned int flags = 0;
+
+	if (cc->unrestricted_ioctl)
+		flags |= FUSE_IOCTL_UNRESTRICTED;
+
+	return fuse_do_ioctl(file, cmd, arg, flags);
+}
+
+static long cuse_file_compat_ioctl(struct file *file, unsigned int cmd,
+				   unsigned long arg)
+{
+	struct fuse_file *ff = file->private_data;
+	struct cuse_conn *cc = fc_to_cc(ff->fm->fc);
+	unsigned int flags = FUSE_IOCTL_COMPAT;
+
+	if (cc->unrestricted_ioctl)
+		flags |= FUSE_IOCTL_UNRESTRICTED;
+
+	return fuse_do_ioctl(file, cmd, arg, flags);
+}
+
+static const struct file_operations cuse_frontend_fops = {
+	.owner			= THIS_MODULE,
+	.read_iter		= cuse_read_iter,
+	.write_iter		= cuse_write_iter,
+	.open			= cuse_open,
+	.release		= cuse_release,
+	.unlocked_ioctl		= cuse_file_ioctl,
+	.compat_ioctl		= cuse_file_compat_ioctl,
+	.poll			= fuse_file_poll,
+	.llseek		= noop_llseek,
+};
+
+
+/**************************************************************************
+ * CUSE channel initialization and destruction
+ */
+
+struct cuse_devinfo {
+	const char		*name;
+};
+
+/**
+ * cuse_parse_one - parse one key=value pair
+ * @pp: i/o parameter for the current position
+ * @end: points to one past the end of the packed string
+ * @keyp: out parameter for key
+ * @valp: out parameter for value
+ *
+ * *@pp points to packed strings - "key0=val0\0key1=val1\0" which ends
+ * at @end - 1.  This function parses one pair and set *@keyp to the
+ * start of the key and *@valp to the start of the value.  Note that
+ * the original string is modified such that the key string is
+ * terminated with '\0'.  *@pp is updated to point to the next string.
+ *
+ * RETURNS:
+ * 1 on successful parse, 0 on EOF, -errno on failure.
+ */
+static int cuse_parse_one(char **pp, char *end, char **keyp, char **valp)
+{
+	char *p = *pp;
+	char *key, *val;
+
+	while (p < end && *p == '\0')
+		p++;
+	if (p == end)
+		return 0;
+
+	if (end[-1] != '\0') {
+		pr_err("info not properly terminated\n");
+		return -EINVAL;
+	}
+
+	key = val = p;
+	p += strlen(p);
+
+	if (valp) {
+		strsep(&val, "=");
+		if (!val)
+			val = key + strlen(key);
+		key = strstrip(key);
+		val = strstrip(val);
+	} else
+		key = strstrip(key);
+
+	if (!strlen(key)) {
+		pr_err("zero length info key specified\n");
+		return -EINVAL;
+	}
+
+	*pp = p;
+	*keyp = key;
+	if (valp)
+		*valp = val;
+
+	return 1;
+}
+
+/**
+ * cuse_parse_dev_info - parse device info
+ * @p: device info string
+ * @len: length of device info string
+ * @devinfo: out parameter for parsed device info
+ *
+ * Parse @p to extract device info and store it into @devinfo.  String
+ * pointed to by @p is modified by parsing and @devinfo points into
+ * them, so @p shouldn't be freed while @devinfo is in use.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static int cuse_parse_devinfo(char *p, size_t len, struct cuse_devinfo *devinfo)
+{
+	char *end = p + len;
+	char *key, *val;
+	int rc;
+
+	while (true) {
+		rc = cuse_parse_one(&p, end, &key, &val);
+		if (rc < 0)
+			return rc;
+		if (!rc)
+			break;
+		if (strcmp(key, "DEVNAME") == 0)
+			devinfo->name = val;
+		else
+			pr_warn("unknown device info \"%s\"\n", key);
+	}
+
+	if (!devinfo->name || !strlen(devinfo->name)) {
+		pr_err("DEVNAME unspecified\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void cuse_gendev_release(struct device *dev)
+{
+	kfree(dev);
+}
+
+struct cuse_init_args {
+	struct fuse_args_pages ap;
+	struct cuse_init_in in;
+	struct cuse_init_out out;
+	struct page *page;
+	struct fuse_page_desc desc;
+};
+
+/**
+ * cuse_process_init_reply - finish initializing CUSE channel
+ *
+ * This function creates the character device and sets up all the
+ * required data structures for it.  Please read the comment at the
+ * top of this file for high level overview.
+ */
+static void cuse_process_init_reply(struct fuse_mount *fm,
+				    struct fuse_args *args, int error)
+{
+	struct fuse_conn *fc = fm->fc;
+	struct cuse_init_args *ia = container_of(args, typeof(*ia), ap.args);
+	struct fuse_args_pages *ap = &ia->ap;
+	struct cuse_conn *cc = fc_to_cc(fc), *pos;
+	struct cuse_init_out *arg = &ia->out;
+	struct page *page = ap->pages[0];
+	struct cuse_devinfo devinfo = { };
+	struct device *dev;
+	struct cdev *cdev;
+	dev_t devt;
+	int rc, i;
+
+	if (error || arg->major != FUSE_KERNEL_VERSION || arg->minor < 11)
+		goto err;
+
+	fc->minor = arg->minor;
+	fc->max_read = max_t(unsigned, arg->max_read, 4096);
+	fc->max_write = max_t(unsigned, arg->max_write, 4096);
+
+	/* parse init reply */
+	cc->unrestricted_ioctl = arg->flags & CUSE_UNRESTRICTED_IOCTL;
+
+	rc = cuse_parse_devinfo(page_address(page), ap->args.out_args[1].size,
+				&devinfo);
+	if (rc)
+		goto err;
+
+	/* determine and reserve devt */
+	devt = MKDEV(arg->dev_major, arg->dev_minor);
+	if (!MAJOR(devt))
+		rc = alloc_chrdev_region(&devt, MINOR(devt), 1, devinfo.name);
+	else
+		rc = register_chrdev_region(devt, 1, devinfo.name);
+	if (rc) {
+		pr_err("failed to register chrdev region\n");
+		goto err;
+	}
+
+	/* devt determined, create device */
+	rc = -ENOMEM;
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		goto err_region;
+
+	device_initialize(dev);
+	dev_set_uevent_suppress(dev, 1);
+	dev->class = cuse_class;
+	dev->devt = devt;
+	dev->release = cuse_gendev_release;
+	dev_set_drvdata(dev, cc);
+	dev_set_name(dev, "%s", devinfo.name);
+
+	mutex_lock(&cuse_lock);
+
+	/* make sure the device-name is unique */
+	for (i = 0; i < CUSE_CONNTBL_LEN; ++i) {
+		list_for_each_entry(pos, &cuse_conntbl[i], list)
+			if (!strcmp(dev_name(pos->dev), dev_name(dev)))
+				goto err_unlock;
+	}
+
+	rc = device_add(dev);
+	if (rc)
+		goto err_unlock;
+
+	/* register cdev */
+	rc = -ENOMEM;
+	cdev = cdev_alloc();
+	if (!cdev)
+		goto err_unlock;
+
+	cdev->owner = THIS_MODULE;
+	cdev->ops = &cuse_frontend_fops;
+
+	rc = cdev_add(cdev, devt, 1);
+	if (rc)
+		goto err_cdev;
+
+	cc->dev = dev;
+	cc->cdev = cdev;
+
+	/* make the device available */
+	list_add(&cc->list, cuse_conntbl_head(devt));
+	mutex_unlock(&cuse_lock);
+
+	/* announce device availability */
+	dev_set_uevent_suppress(dev, 0);
+	kobject_uevent(&dev->kobj, KOBJ_ADD);
+out:
+	kfree(ia);
+	__free_page(page);
+	return;
+
+err_cdev:
+	cdev_del(cdev);
+err_unlock:
+	mutex_unlock(&cuse_lock);
+	put_device(dev);
+err_region:
+	unregister_chrdev_region(devt, 1);
+err:
+	fuse_abort_conn(fc);
+	goto out;
+}
+
+static int cuse_send_init(struct cuse_conn *cc)
+{
+	int rc;
+	struct page *page;
+	struct fuse_mount *fm = &cc->fm;
+	struct cuse_init_args *ia;
+	struct fuse_args_pages *ap;
+
+	BUILD_BUG_ON(CUSE_INIT_INFO_MAX > PAGE_SIZE);
+
+	rc = -ENOMEM;
+	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+	if (!page)
+		goto err;
+
+	ia = kzalloc(sizeof(*ia), GFP_KERNEL);
+	if (!ia)
+		goto err_free_page;
+
+	ap = &ia->ap;
+	ia->in.major = FUSE_KERNEL_VERSION;
+	ia->in.minor = FUSE_KERNEL_MINOR_VERSION;
+	ia->in.flags |= CUSE_UNRESTRICTED_IOCTL;
+	ap->args.opcode = CUSE_INIT;
+	ap->args.in_numargs = 1;
+	ap->args.in_args[0].size = sizeof(ia->in);
+	ap->args.in_args[0].value = &ia->in;
+	ap->args.out_numargs = 2;
+	ap->args.out_args[0].size = sizeof(ia->out);
+	ap->args.out_args[0].value = &ia->out;
+	ap->args.out_args[1].size = CUSE_INIT_INFO_MAX;
+	ap->args.out_argvar = true;
+	ap->args.out_pages = true;
+	ap->num_pages = 1;
+	ap->pages = &ia->page;
+	ap->descs = &ia->desc;
+	ia->page = page;
+	ia->desc.length = ap->args.out_args[1].size;
+	ap->args.end = cuse_process_init_reply;
+
+	rc = fuse_simple_background(fm, &ap->args, GFP_KERNEL);
+	if (rc) {
+		kfree(ia);
+err_free_page:
+		__free_page(page);
+	}
+err:
+	return rc;
+}
+
+static void cuse_fc_release(struct fuse_conn *fc)
+{
+	struct cuse_conn *cc = fc_to_cc(fc);
+	kfree_rcu(cc, fc.rcu);
+}
+
+/**
+ * cuse_channel_open - open method for /dev/cuse
+ * @inode: inode for /dev/cuse
+ * @file: file struct being opened
+ *
+ * Userland CUSE server can create a CUSE device by opening /dev/cuse
+ * and replying to the initialization request kernel sends.  This
+ * function is responsible for handling CUSE device initialization.
+ * Because the fd opened by this function is used during
+ * initialization, this function only creates cuse_conn and sends
+ * init.  The rest is delegated to a kthread.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static int cuse_channel_open(struct inode *inode, struct file *file)
+{
+	struct fuse_dev *fud;
+	struct cuse_conn *cc;
+	int rc;
+
+	/* set up cuse_conn */
+	cc = kzalloc(sizeof(*cc), GFP_KERNEL);
+	if (!cc)
+		return -ENOMEM;
+
+	/*
+	 * Limit the cuse channel to requests that can
+	 * be represented in file->f_cred->user_ns.
+	 */
+	fuse_conn_init(&cc->fc, &cc->fm, file->f_cred->user_ns,
+		       &fuse_dev_fiq_ops, NULL);
+
+	fud = fuse_dev_alloc_install(&cc->fc);
+	if (!fud) {
+		kfree(cc);
+		return -ENOMEM;
+	}
+
+	INIT_LIST_HEAD(&cc->list);
+	cc->fc.release = cuse_fc_release;
+
+	cc->fc.initialized = 1;
+	rc = cuse_send_init(cc);
+	if (rc) {
+		fuse_dev_free(fud);
+		fuse_conn_put(&cc->fc);
+		return rc;
+	}
+	file->private_data = fud;
+
+	return 0;
+}
+
+/**
+ * cuse_channel_release - release method for /dev/cuse
+ * @inode: inode for /dev/cuse
+ * @file: file struct being closed
+ *
+ * Disconnect the channel, deregister CUSE device and initiate
+ * destruction by putting the default reference.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+static int cuse_channel_release(struct inode *inode, struct file *file)
+{
+	struct fuse_dev *fud = file->private_data;
+	struct cuse_conn *cc = fc_to_cc(fud->fc);
+	int rc;
+
+	/* remove from the conntbl, no more access from this point on */
+	mutex_lock(&cuse_lock);
+	list_del_init(&cc->list);
+	mutex_unlock(&cuse_lock);
+
+	/* remove device */
+	if (cc->dev)
+		device_unregister(cc->dev);
+	if (cc->cdev) {
+		unregister_chrdev_region(cc->cdev->dev, 1);
+		cdev_del(cc->cdev);
+	}
+	/* Base reference is now owned by "fud" */
+	fuse_conn_put(&cc->fc);
+
+	rc = fuse_dev_release(inode, file);	/* puts the base reference */
+
+	return rc;
+}
+
+static struct file_operations cuse_channel_fops; /* initialized during init */
+
+
+/**************************************************************************
+ * Misc stuff and module initializatiion
+ *
+ * CUSE exports the same set of attributes to sysfs as fusectl.
+ */
+
+static ssize_t cuse_class_waiting_show(struct device *dev,
+				       struct device_attribute *attr, char *buf)
+{
+	struct cuse_conn *cc = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", atomic_read(&cc->fc.num_waiting));
+}
+static DEVICE_ATTR(waiting, 0400, cuse_class_waiting_show, NULL);
+
+static ssize_t cuse_class_abort_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t count)
+{
+	struct cuse_conn *cc = dev_get_drvdata(dev);
+
+	fuse_abort_conn(&cc->fc);
+	return count;
+}
+static DEVICE_ATTR(abort, 0200, NULL, cuse_class_abort_store);
+
+static struct attribute *cuse_class_dev_attrs[] = {
+	&dev_attr_waiting.attr,
+	&dev_attr_abort.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(cuse_class_dev);
+
+static struct miscdevice cuse_miscdev = {
+	.minor		= CUSE_MINOR,
+	.name		= "cuse",
+	.fops		= &cuse_channel_fops,
+};
+
+MODULE_ALIAS_MISCDEV(CUSE_MINOR);
+MODULE_ALIAS("devname:cuse");
+
+static int __init cuse_init(void)
+{
+	int i, rc;
+
+	/* init conntbl */
+	for (i = 0; i < CUSE_CONNTBL_LEN; i++)
+		INIT_LIST_HEAD(&cuse_conntbl[i]);
+
+	/* inherit and extend fuse_dev_operations */
+	cuse_channel_fops		= fuse_dev_operations;
+	cuse_channel_fops.owner		= THIS_MODULE;
+	cuse_channel_fops.open		= cuse_channel_open;
+	cuse_channel_fops.release	= cuse_channel_release;
+	/* CUSE is not prepared for FUSE_DEV_IOC_CLONE */
+	cuse_channel_fops.unlocked_ioctl	= NULL;
+
+	cuse_class = class_create(THIS_MODULE, "cuse");
+	if (IS_ERR(cuse_class))
+		return PTR_ERR(cuse_class);
+
+	cuse_class->dev_groups = cuse_class_dev_groups;
+
+	rc = misc_register(&cuse_miscdev);
+	if (rc) {
+		class_destroy(cuse_class);
+		return rc;
+	}
+
+	return 0;
+}
+
+static void __exit cuse_exit(void)
+{
+	misc_deregister(&cuse_miscdev);
+	class_destroy(cuse_class);
+}
+
+module_init(cuse_init);
+module_exit(cuse_exit);
+
+MODULE_AUTHOR("Tejun Heo <tj@kernel.org>");
+MODULE_DESCRIPTION("Character device in Userspace");
+MODULE_LICENSE("GPL");
diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
new file mode 100644
index 000000000..2739e218d
--- /dev/null
+++ b/fs/fuse/dax.c
@@ -0,0 +1,1366 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * dax: direct host memory access
+ * Copyright (C) 2020 Red Hat, Inc.
+ */
+
+#include "fuse_i.h"
+
+#include <linux/delay.h>
+#include <linux/dax.h>
+#include <linux/uio.h>
+#include <linux/pfn_t.h>
+#include <linux/iomap.h>
+#include <linux/interval_tree.h>
+
+/*
+ * Default memory range size.  A power of 2 so it agrees with common FUSE_INIT
+ * map_alignment values 4KB and 64KB.
+ */
+#define FUSE_DAX_SHIFT	21
+#define FUSE_DAX_SZ	(1 << FUSE_DAX_SHIFT)
+#define FUSE_DAX_PAGES	(FUSE_DAX_SZ / PAGE_SIZE)
+
+/* Number of ranges reclaimer will try to free in one invocation */
+#define FUSE_DAX_RECLAIM_CHUNK		(10)
+
+/*
+ * Dax memory reclaim threshold in percetage of total ranges. When free
+ * number of free ranges drops below this threshold, reclaim can trigger
+ * Default is 20%
+ */
+#define FUSE_DAX_RECLAIM_THRESHOLD	(20)
+
+/** Translation information for file offsets to DAX window offsets */
+struct fuse_dax_mapping {
+	/* Pointer to inode where this memory range is mapped */
+	struct inode *inode;
+
+	/* Will connect in fcd->free_ranges to keep track of free memory */
+	struct list_head list;
+
+	/* For interval tree in file/inode */
+	struct interval_tree_node itn;
+
+	/* Will connect in fc->busy_ranges to keep track busy memory */
+	struct list_head busy_list;
+
+	/** Position in DAX window */
+	u64 window_offset;
+
+	/** Length of mapping, in bytes */
+	loff_t length;
+
+	/* Is this mapping read-only or read-write */
+	bool writable;
+
+	/* reference count when the mapping is used by dax iomap. */
+	refcount_t refcnt;
+};
+
+/* Per-inode dax map */
+struct fuse_inode_dax {
+	/* Semaphore to protect modifications to the dmap tree */
+	struct rw_semaphore sem;
+
+	/* Sorted rb tree of struct fuse_dax_mapping elements */
+	struct rb_root_cached tree;
+	unsigned long nr;
+};
+
+struct fuse_conn_dax {
+	/* DAX device */
+	struct dax_device *dev;
+
+	/* Lock protecting accessess to  members of this structure */
+	spinlock_t lock;
+
+	/* List of memory ranges which are busy */
+	unsigned long nr_busy_ranges;
+	struct list_head busy_ranges;
+
+	/* Worker to free up memory ranges */
+	struct delayed_work free_work;
+
+	/* Wait queue for a dax range to become free */
+	wait_queue_head_t range_waitq;
+
+	/* DAX Window Free Ranges */
+	long nr_free_ranges;
+	struct list_head free_ranges;
+
+	unsigned long nr_ranges;
+};
+
+static inline struct fuse_dax_mapping *
+node_to_dmap(struct interval_tree_node *node)
+{
+	if (!node)
+		return NULL;
+
+	return container_of(node, struct fuse_dax_mapping, itn);
+}
+
+static struct fuse_dax_mapping *
+alloc_dax_mapping_reclaim(struct fuse_conn_dax *fcd, struct inode *inode);
+
+static void
+__kick_dmap_free_worker(struct fuse_conn_dax *fcd, unsigned long delay_ms)
+{
+	unsigned long free_threshold;
+
+	/* If number of free ranges are below threshold, start reclaim */
+	free_threshold = max_t(unsigned long, fcd->nr_ranges * FUSE_DAX_RECLAIM_THRESHOLD / 100,
+			     1);
+	if (fcd->nr_free_ranges < free_threshold)
+		queue_delayed_work(system_long_wq, &fcd->free_work,
+				   msecs_to_jiffies(delay_ms));
+}
+
+static void kick_dmap_free_worker(struct fuse_conn_dax *fcd,
+				  unsigned long delay_ms)
+{
+	spin_lock(&fcd->lock);
+	__kick_dmap_free_worker(fcd, delay_ms);
+	spin_unlock(&fcd->lock);
+}
+
+static struct fuse_dax_mapping *alloc_dax_mapping(struct fuse_conn_dax *fcd)
+{
+	struct fuse_dax_mapping *dmap;
+
+	spin_lock(&fcd->lock);
+	dmap = list_first_entry_or_null(&fcd->free_ranges,
+					struct fuse_dax_mapping, list);
+	if (dmap) {
+		list_del_init(&dmap->list);
+		WARN_ON(fcd->nr_free_ranges <= 0);
+		fcd->nr_free_ranges--;
+	}
+	spin_unlock(&fcd->lock);
+
+	kick_dmap_free_worker(fcd, 0);
+	return dmap;
+}
+
+/* This assumes fcd->lock is held */
+static void __dmap_remove_busy_list(struct fuse_conn_dax *fcd,
+				    struct fuse_dax_mapping *dmap)
+{
+	list_del_init(&dmap->busy_list);
+	WARN_ON(fcd->nr_busy_ranges == 0);
+	fcd->nr_busy_ranges--;
+}
+
+static void dmap_remove_busy_list(struct fuse_conn_dax *fcd,
+				  struct fuse_dax_mapping *dmap)
+{
+	spin_lock(&fcd->lock);
+	__dmap_remove_busy_list(fcd, dmap);
+	spin_unlock(&fcd->lock);
+}
+
+/* This assumes fcd->lock is held */
+static void __dmap_add_to_free_pool(struct fuse_conn_dax *fcd,
+				struct fuse_dax_mapping *dmap)
+{
+	list_add_tail(&dmap->list, &fcd->free_ranges);
+	fcd->nr_free_ranges++;
+	wake_up(&fcd->range_waitq);
+}
+
+static void dmap_add_to_free_pool(struct fuse_conn_dax *fcd,
+				struct fuse_dax_mapping *dmap)
+{
+	/* Return fuse_dax_mapping to free list */
+	spin_lock(&fcd->lock);
+	__dmap_add_to_free_pool(fcd, dmap);
+	spin_unlock(&fcd->lock);
+}
+
+static int fuse_setup_one_mapping(struct inode *inode, unsigned long start_idx,
+				  struct fuse_dax_mapping *dmap, bool writable,
+				  bool upgrade)
+{
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	struct fuse_conn_dax *fcd = fm->fc->dax;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_setupmapping_in inarg;
+	loff_t offset = start_idx << FUSE_DAX_SHIFT;
+	FUSE_ARGS(args);
+	ssize_t err;
+
+	WARN_ON(fcd->nr_free_ranges < 0);
+
+	/* Ask fuse daemon to setup mapping */
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.foffset = offset;
+	inarg.fh = -1;
+	inarg.moffset = dmap->window_offset;
+	inarg.len = FUSE_DAX_SZ;
+	inarg.flags |= FUSE_SETUPMAPPING_FLAG_READ;
+	if (writable)
+		inarg.flags |= FUSE_SETUPMAPPING_FLAG_WRITE;
+	args.opcode = FUSE_SETUPMAPPING;
+	args.nodeid = fi->nodeid;
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	err = fuse_simple_request(fm, &args);
+	if (err < 0)
+		return err;
+	dmap->writable = writable;
+	if (!upgrade) {
+		/*
+		 * We don't take a refernce on inode. inode is valid right now
+		 * and when inode is going away, cleanup logic should first
+		 * cleanup dmap entries.
+		 */
+		dmap->inode = inode;
+		dmap->itn.start = dmap->itn.last = start_idx;
+		/* Protected by fi->dax->sem */
+		interval_tree_insert(&dmap->itn, &fi->dax->tree);
+		fi->dax->nr++;
+		spin_lock(&fcd->lock);
+		list_add_tail(&dmap->busy_list, &fcd->busy_ranges);
+		fcd->nr_busy_ranges++;
+		spin_unlock(&fcd->lock);
+	}
+	return 0;
+}
+
+static int fuse_send_removemapping(struct inode *inode,
+				   struct fuse_removemapping_in *inargp,
+				   struct fuse_removemapping_one *remove_one)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+
+	args.opcode = FUSE_REMOVEMAPPING;
+	args.nodeid = fi->nodeid;
+	args.in_numargs = 2;
+	args.in_args[0].size = sizeof(*inargp);
+	args.in_args[0].value = inargp;
+	args.in_args[1].size = inargp->count * sizeof(*remove_one);
+	args.in_args[1].value = remove_one;
+	return fuse_simple_request(fm, &args);
+}
+
+static int dmap_removemapping_list(struct inode *inode, unsigned int num,
+				   struct list_head *to_remove)
+{
+	struct fuse_removemapping_one *remove_one, *ptr;
+	struct fuse_removemapping_in inarg;
+	struct fuse_dax_mapping *dmap;
+	int ret, i = 0, nr_alloc;
+
+	nr_alloc = min_t(unsigned int, num, FUSE_REMOVEMAPPING_MAX_ENTRY);
+	remove_one = kmalloc_array(nr_alloc, sizeof(*remove_one), GFP_NOFS);
+	if (!remove_one)
+		return -ENOMEM;
+
+	ptr = remove_one;
+	list_for_each_entry(dmap, to_remove, list) {
+		ptr->moffset = dmap->window_offset;
+		ptr->len = dmap->length;
+		ptr++;
+		i++;
+		num--;
+		if (i >= nr_alloc || num == 0) {
+			memset(&inarg, 0, sizeof(inarg));
+			inarg.count = i;
+			ret = fuse_send_removemapping(inode, &inarg,
+						      remove_one);
+			if (ret)
+				goto out;
+			ptr = remove_one;
+			i = 0;
+		}
+	}
+out:
+	kfree(remove_one);
+	return ret;
+}
+
+/*
+ * Cleanup dmap entry and add back to free list. This should be called with
+ * fcd->lock held.
+ */
+static void dmap_reinit_add_to_free_pool(struct fuse_conn_dax *fcd,
+					    struct fuse_dax_mapping *dmap)
+{
+	pr_debug("fuse: freeing memory range start_idx=0x%lx end_idx=0x%lx window_offset=0x%llx length=0x%llx\n",
+		 dmap->itn.start, dmap->itn.last, dmap->window_offset,
+		 dmap->length);
+	__dmap_remove_busy_list(fcd, dmap);
+	dmap->inode = NULL;
+	dmap->itn.start = dmap->itn.last = 0;
+	__dmap_add_to_free_pool(fcd, dmap);
+}
+
+/*
+ * Free inode dmap entries whose range falls inside [start, end].
+ * Does not take any locks. At this point of time it should only be
+ * called from evict_inode() path where we know all dmap entries can be
+ * reclaimed.
+ */
+static void inode_reclaim_dmap_range(struct fuse_conn_dax *fcd,
+				     struct inode *inode,
+				     loff_t start, loff_t end)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_dax_mapping *dmap, *n;
+	int err, num = 0;
+	LIST_HEAD(to_remove);
+	unsigned long start_idx = start >> FUSE_DAX_SHIFT;
+	unsigned long end_idx = end >> FUSE_DAX_SHIFT;
+	struct interval_tree_node *node;
+
+	while (1) {
+		node = interval_tree_iter_first(&fi->dax->tree, start_idx,
+						end_idx);
+		if (!node)
+			break;
+		dmap = node_to_dmap(node);
+		/* inode is going away. There should not be any users of dmap */
+		WARN_ON(refcount_read(&dmap->refcnt) > 1);
+		interval_tree_remove(&dmap->itn, &fi->dax->tree);
+		num++;
+		list_add(&dmap->list, &to_remove);
+	}
+
+	/* Nothing to remove */
+	if (list_empty(&to_remove))
+		return;
+
+	WARN_ON(fi->dax->nr < num);
+	fi->dax->nr -= num;
+	err = dmap_removemapping_list(inode, num, &to_remove);
+	if (err && err != -ENOTCONN) {
+		pr_warn("Failed to removemappings. start=0x%llx end=0x%llx\n",
+			start, end);
+	}
+	spin_lock(&fcd->lock);
+	list_for_each_entry_safe(dmap, n, &to_remove, list) {
+		list_del_init(&dmap->list);
+		dmap_reinit_add_to_free_pool(fcd, dmap);
+	}
+	spin_unlock(&fcd->lock);
+}
+
+static int dmap_removemapping_one(struct inode *inode,
+				  struct fuse_dax_mapping *dmap)
+{
+	struct fuse_removemapping_one forget_one;
+	struct fuse_removemapping_in inarg;
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.count = 1;
+	memset(&forget_one, 0, sizeof(forget_one));
+	forget_one.moffset = dmap->window_offset;
+	forget_one.len = dmap->length;
+
+	return fuse_send_removemapping(inode, &inarg, &forget_one);
+}
+
+/*
+ * It is called from evict_inode() and by that time inode is going away. So
+ * this function does not take any locks like fi->dax->sem for traversing
+ * that fuse inode interval tree. If that lock is taken then lock validator
+ * complains of deadlock situation w.r.t fs_reclaim lock.
+ */
+void fuse_dax_inode_cleanup(struct inode *inode)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	/*
+	 * fuse_evict_inode() has already called truncate_inode_pages_final()
+	 * before we arrive here. So we should not have to worry about any
+	 * pages/exception entries still associated with inode.
+	 */
+	inode_reclaim_dmap_range(fc->dax, inode, 0, -1);
+	WARN_ON(fi->dax->nr);
+}
+
+static void fuse_fill_iomap_hole(struct iomap *iomap, loff_t length)
+{
+	iomap->addr = IOMAP_NULL_ADDR;
+	iomap->length = length;
+	iomap->type = IOMAP_HOLE;
+}
+
+static void fuse_fill_iomap(struct inode *inode, loff_t pos, loff_t length,
+			    struct iomap *iomap, struct fuse_dax_mapping *dmap,
+			    unsigned int flags)
+{
+	loff_t offset, len;
+	loff_t i_size = i_size_read(inode);
+
+	offset = pos - (dmap->itn.start << FUSE_DAX_SHIFT);
+	len = min(length, dmap->length - offset);
+
+	/* If length is beyond end of file, truncate further */
+	if (pos + len > i_size)
+		len = i_size - pos;
+
+	if (len > 0) {
+		iomap->addr = dmap->window_offset + offset;
+		iomap->length = len;
+		if (flags & IOMAP_FAULT)
+			iomap->length = ALIGN(len, PAGE_SIZE);
+		iomap->type = IOMAP_MAPPED;
+		/*
+		 * increace refcnt so that reclaim code knows this dmap is in
+		 * use. This assumes fi->dax->sem mutex is held either
+		 * shared/exclusive.
+		 */
+		refcount_inc(&dmap->refcnt);
+
+		/* iomap->private should be NULL */
+		WARN_ON_ONCE(iomap->private);
+		iomap->private = dmap;
+	} else {
+		/* Mapping beyond end of file is hole */
+		fuse_fill_iomap_hole(iomap, length);
+	}
+}
+
+static int fuse_setup_new_dax_mapping(struct inode *inode, loff_t pos,
+				      loff_t length, unsigned int flags,
+				      struct iomap *iomap)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_conn_dax *fcd = fc->dax;
+	struct fuse_dax_mapping *dmap, *alloc_dmap = NULL;
+	int ret;
+	bool writable = flags & IOMAP_WRITE;
+	unsigned long start_idx = pos >> FUSE_DAX_SHIFT;
+	struct interval_tree_node *node;
+
+	/*
+	 * Can't do inline reclaim in fault path. We call
+	 * dax_layout_busy_page() before we free a range. And
+	 * fuse_wait_dax_page() drops fi->i_mmap_sem lock and requires it.
+	 * In fault path we enter with fi->i_mmap_sem held and can't drop
+	 * it. Also in fault path we hold fi->i_mmap_sem shared and not
+	 * exclusive, so that creates further issues with fuse_wait_dax_page().
+	 * Hence return -EAGAIN and fuse_dax_fault() will wait for a memory
+	 * range to become free and retry.
+	 */
+	if (flags & IOMAP_FAULT) {
+		alloc_dmap = alloc_dax_mapping(fcd);
+		if (!alloc_dmap)
+			return -EAGAIN;
+	} else {
+		alloc_dmap = alloc_dax_mapping_reclaim(fcd, inode);
+		if (IS_ERR(alloc_dmap))
+			return PTR_ERR(alloc_dmap);
+	}
+
+	/* If we are here, we should have memory allocated */
+	if (WARN_ON(!alloc_dmap))
+		return -EIO;
+
+	/*
+	 * Take write lock so that only one caller can try to setup mapping
+	 * and other waits.
+	 */
+	down_write(&fi->dax->sem);
+	/*
+	 * We dropped lock. Check again if somebody else setup
+	 * mapping already.
+	 */
+	node = interval_tree_iter_first(&fi->dax->tree, start_idx, start_idx);
+	if (node) {
+		dmap = node_to_dmap(node);
+		fuse_fill_iomap(inode, pos, length, iomap, dmap, flags);
+		dmap_add_to_free_pool(fcd, alloc_dmap);
+		up_write(&fi->dax->sem);
+		return 0;
+	}
+
+	/* Setup one mapping */
+	ret = fuse_setup_one_mapping(inode, pos >> FUSE_DAX_SHIFT, alloc_dmap,
+				     writable, false);
+	if (ret < 0) {
+		dmap_add_to_free_pool(fcd, alloc_dmap);
+		up_write(&fi->dax->sem);
+		return ret;
+	}
+	fuse_fill_iomap(inode, pos, length, iomap, alloc_dmap, flags);
+	up_write(&fi->dax->sem);
+	return 0;
+}
+
+static int fuse_upgrade_dax_mapping(struct inode *inode, loff_t pos,
+				    loff_t length, unsigned int flags,
+				    struct iomap *iomap)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_dax_mapping *dmap;
+	int ret;
+	unsigned long idx = pos >> FUSE_DAX_SHIFT;
+	struct interval_tree_node *node;
+
+	/*
+	 * Take exclusive lock so that only one caller can try to setup
+	 * mapping and others wait.
+	 */
+	down_write(&fi->dax->sem);
+	node = interval_tree_iter_first(&fi->dax->tree, idx, idx);
+
+	/* We are holding either inode lock or i_mmap_sem, and that should
+	 * ensure that dmap can't be truncated. We are holding a reference
+	 * on dmap and that should make sure it can't be reclaimed. So dmap
+	 * should still be there in tree despite the fact we dropped and
+	 * re-acquired the fi->dax->sem lock.
+	 */
+	ret = -EIO;
+	if (WARN_ON(!node))
+		goto out_err;
+
+	dmap = node_to_dmap(node);
+
+	/* We took an extra reference on dmap to make sure its not reclaimd.
+	 * Now we hold fi->dax->sem lock and that reference is not needed
+	 * anymore. Drop it.
+	 */
+	if (refcount_dec_and_test(&dmap->refcnt)) {
+		/* refcount should not hit 0. This object only goes
+		 * away when fuse connection goes away
+		 */
+		WARN_ON_ONCE(1);
+	}
+
+	/* Maybe another thread already upgraded mapping while we were not
+	 * holding lock.
+	 */
+	if (dmap->writable) {
+		ret = 0;
+		goto out_fill_iomap;
+	}
+
+	ret = fuse_setup_one_mapping(inode, pos >> FUSE_DAX_SHIFT, dmap, true,
+				     true);
+	if (ret < 0)
+		goto out_err;
+out_fill_iomap:
+	fuse_fill_iomap(inode, pos, length, iomap, dmap, flags);
+out_err:
+	up_write(&fi->dax->sem);
+	return ret;
+}
+
+/* This is just for DAX and the mapping is ephemeral, do not use it for other
+ * purposes since there is no block device with a permanent mapping.
+ */
+static int fuse_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
+			    unsigned int flags, struct iomap *iomap,
+			    struct iomap *srcmap)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_dax_mapping *dmap;
+	bool writable = flags & IOMAP_WRITE;
+	unsigned long start_idx = pos >> FUSE_DAX_SHIFT;
+	struct interval_tree_node *node;
+
+	/* We don't support FIEMAP */
+	if (WARN_ON(flags & IOMAP_REPORT))
+		return -EIO;
+
+	iomap->offset = pos;
+	iomap->flags = 0;
+	iomap->bdev = NULL;
+	iomap->dax_dev = fc->dax->dev;
+
+	/*
+	 * Both read/write and mmap path can race here. So we need something
+	 * to make sure if we are setting up mapping, then other path waits
+	 *
+	 * For now, use a semaphore for this. It probably needs to be
+	 * optimized later.
+	 */
+	down_read(&fi->dax->sem);
+	node = interval_tree_iter_first(&fi->dax->tree, start_idx, start_idx);
+	if (node) {
+		dmap = node_to_dmap(node);
+		if (writable && !dmap->writable) {
+			/* Upgrade read-only mapping to read-write. This will
+			 * require exclusive fi->dax->sem lock as we don't want
+			 * two threads to be trying to this simultaneously
+			 * for same dmap. So drop shared lock and acquire
+			 * exclusive lock.
+			 *
+			 * Before dropping fi->dax->sem lock, take reference
+			 * on dmap so that its not freed by range reclaim.
+			 */
+			refcount_inc(&dmap->refcnt);
+			up_read(&fi->dax->sem);
+			pr_debug("%s: Upgrading mapping at offset 0x%llx length 0x%llx\n",
+				 __func__, pos, length);
+			return fuse_upgrade_dax_mapping(inode, pos, length,
+							flags, iomap);
+		} else {
+			fuse_fill_iomap(inode, pos, length, iomap, dmap, flags);
+			up_read(&fi->dax->sem);
+			return 0;
+		}
+	} else {
+		up_read(&fi->dax->sem);
+		pr_debug("%s: no mapping at offset 0x%llx length 0x%llx\n",
+				__func__, pos, length);
+		if (pos >= i_size_read(inode))
+			goto iomap_hole;
+
+		return fuse_setup_new_dax_mapping(inode, pos, length, flags,
+						  iomap);
+	}
+
+	/*
+	 * If read beyond end of file happnes, fs code seems to return
+	 * it as hole
+	 */
+iomap_hole:
+	fuse_fill_iomap_hole(iomap, length);
+	pr_debug("%s returning hole mapping. pos=0x%llx length_asked=0x%llx length_returned=0x%llx\n",
+		 __func__, pos, length, iomap->length);
+	return 0;
+}
+
+static int fuse_iomap_end(struct inode *inode, loff_t pos, loff_t length,
+			  ssize_t written, unsigned int flags,
+			  struct iomap *iomap)
+{
+	struct fuse_dax_mapping *dmap = iomap->private;
+
+	if (dmap) {
+		if (refcount_dec_and_test(&dmap->refcnt)) {
+			/* refcount should not hit 0. This object only goes
+			 * away when fuse connection goes away
+			 */
+			WARN_ON_ONCE(1);
+		}
+	}
+
+	/* DAX writes beyond end-of-file aren't handled using iomap, so the
+	 * file size is unchanged and there is nothing to do here.
+	 */
+	return 0;
+}
+
+static const struct iomap_ops fuse_iomap_ops = {
+	.iomap_begin = fuse_iomap_begin,
+	.iomap_end = fuse_iomap_end,
+};
+
+static void fuse_wait_dax_page(struct inode *inode)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	up_write(&fi->i_mmap_sem);
+	schedule();
+	down_write(&fi->i_mmap_sem);
+}
+
+/* Should be called with fi->i_mmap_sem lock held exclusively */
+static int __fuse_dax_break_layouts(struct inode *inode, bool *retry,
+				    loff_t start, loff_t end)
+{
+	struct page *page;
+
+	page = dax_layout_busy_page_range(inode->i_mapping, start, end);
+	if (!page)
+		return 0;
+
+	*retry = true;
+	return ___wait_var_event(&page->_refcount,
+			atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
+			0, 0, fuse_wait_dax_page(inode));
+}
+
+/* dmap_end == 0 leads to unmapping of whole file */
+int fuse_dax_break_layouts(struct inode *inode, u64 dmap_start,
+				  u64 dmap_end)
+{
+	bool	retry;
+	int	ret;
+
+	do {
+		retry = false;
+		ret = __fuse_dax_break_layouts(inode, &retry, dmap_start,
+					       dmap_end);
+	} while (ret == 0 && retry);
+
+	return ret;
+}
+
+ssize_t fuse_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+	ssize_t ret;
+
+	if (iocb->ki_flags & IOCB_NOWAIT) {
+		if (!inode_trylock_shared(inode))
+			return -EAGAIN;
+	} else {
+		inode_lock_shared(inode);
+	}
+
+	ret = dax_iomap_rw(iocb, to, &fuse_iomap_ops);
+	inode_unlock_shared(inode);
+
+	/* TODO file_accessed(iocb->f_filp) */
+	return ret;
+}
+
+static bool file_extending_write(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+
+	return (iov_iter_rw(from) == WRITE &&
+		((iocb->ki_pos) >= i_size_read(inode) ||
+		  (iocb->ki_pos + iov_iter_count(from) > i_size_read(inode))));
+}
+
+static ssize_t fuse_dax_direct_write(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+	struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
+	ssize_t ret;
+
+	ret = fuse_direct_io(&io, from, &iocb->ki_pos, FUSE_DIO_WRITE);
+	if (ret < 0)
+		return ret;
+
+	fuse_invalidate_attr(inode);
+	fuse_write_update_size(inode, iocb->ki_pos);
+	return ret;
+}
+
+ssize_t fuse_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+	ssize_t ret;
+
+	if (iocb->ki_flags & IOCB_NOWAIT) {
+		if (!inode_trylock(inode))
+			return -EAGAIN;
+	} else {
+		inode_lock(inode);
+	}
+
+	ret = generic_write_checks(iocb, from);
+	if (ret <= 0)
+		goto out;
+
+	ret = file_remove_privs(iocb->ki_filp);
+	if (ret)
+		goto out;
+	/* TODO file_update_time() but we don't want metadata I/O */
+
+	/* Do not use dax for file extending writes as write and on
+	 * disk i_size increase are not atomic otherwise.
+	 */
+	if (file_extending_write(iocb, from))
+		ret = fuse_dax_direct_write(iocb, from);
+	else
+		ret = dax_iomap_rw(iocb, from, &fuse_iomap_ops);
+
+out:
+	inode_unlock(inode);
+
+	if (ret > 0)
+		ret = generic_write_sync(iocb, ret);
+	return ret;
+}
+
+static int fuse_dax_writepages(struct address_space *mapping,
+			       struct writeback_control *wbc)
+{
+
+	struct inode *inode = mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	return dax_writeback_mapping_range(mapping, fc->dax->dev, wbc);
+}
+
+static vm_fault_t __fuse_dax_fault(struct vm_fault *vmf,
+				   enum page_entry_size pe_size, bool write)
+{
+	vm_fault_t ret;
+	struct inode *inode = file_inode(vmf->vma->vm_file);
+	struct super_block *sb = inode->i_sb;
+	pfn_t pfn;
+	int error = 0;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_conn_dax *fcd = fc->dax;
+	bool retry = false;
+
+	if (write)
+		sb_start_pagefault(sb);
+retry:
+	if (retry && !(fcd->nr_free_ranges > 0))
+		wait_event(fcd->range_waitq, (fcd->nr_free_ranges > 0));
+
+	/*
+	 * We need to serialize against not only truncate but also against
+	 * fuse dax memory range reclaim. While a range is being reclaimed,
+	 * we do not want any read/write/mmap to make progress and try
+	 * to populate page cache or access memory we are trying to free.
+	 */
+	down_read(&get_fuse_inode(inode)->i_mmap_sem);
+	ret = dax_iomap_fault(vmf, pe_size, &pfn, &error, &fuse_iomap_ops);
+	if ((ret & VM_FAULT_ERROR) && error == -EAGAIN) {
+		error = 0;
+		retry = true;
+		up_read(&get_fuse_inode(inode)->i_mmap_sem);
+		goto retry;
+	}
+
+	if (ret & VM_FAULT_NEEDDSYNC)
+		ret = dax_finish_sync_fault(vmf, pe_size, pfn);
+	up_read(&get_fuse_inode(inode)->i_mmap_sem);
+
+	if (write)
+		sb_end_pagefault(sb);
+
+	return ret;
+}
+
+static vm_fault_t fuse_dax_fault(struct vm_fault *vmf)
+{
+	return __fuse_dax_fault(vmf, PE_SIZE_PTE,
+				vmf->flags & FAULT_FLAG_WRITE);
+}
+
+static vm_fault_t fuse_dax_huge_fault(struct vm_fault *vmf,
+			       enum page_entry_size pe_size)
+{
+	return __fuse_dax_fault(vmf, pe_size, vmf->flags & FAULT_FLAG_WRITE);
+}
+
+static vm_fault_t fuse_dax_page_mkwrite(struct vm_fault *vmf)
+{
+	return __fuse_dax_fault(vmf, PE_SIZE_PTE, true);
+}
+
+static vm_fault_t fuse_dax_pfn_mkwrite(struct vm_fault *vmf)
+{
+	return __fuse_dax_fault(vmf, PE_SIZE_PTE, true);
+}
+
+static const struct vm_operations_struct fuse_dax_vm_ops = {
+	.fault		= fuse_dax_fault,
+	.huge_fault	= fuse_dax_huge_fault,
+	.page_mkwrite	= fuse_dax_page_mkwrite,
+	.pfn_mkwrite	= fuse_dax_pfn_mkwrite,
+};
+
+int fuse_dax_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	file_accessed(file);
+	vma->vm_ops = &fuse_dax_vm_ops;
+	vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
+	return 0;
+}
+
+static int dmap_writeback_invalidate(struct inode *inode,
+				     struct fuse_dax_mapping *dmap)
+{
+	int ret;
+	loff_t start_pos = dmap->itn.start << FUSE_DAX_SHIFT;
+	loff_t end_pos = (start_pos + FUSE_DAX_SZ - 1);
+
+	ret = filemap_fdatawrite_range(inode->i_mapping, start_pos, end_pos);
+	if (ret) {
+		pr_debug("fuse: filemap_fdatawrite_range() failed. err=%d start_pos=0x%llx, end_pos=0x%llx\n",
+			 ret, start_pos, end_pos);
+		return ret;
+	}
+
+	ret = invalidate_inode_pages2_range(inode->i_mapping,
+					    start_pos >> PAGE_SHIFT,
+					    end_pos >> PAGE_SHIFT);
+	if (ret)
+		pr_debug("fuse: invalidate_inode_pages2_range() failed err=%d\n",
+			 ret);
+
+	return ret;
+}
+
+static int reclaim_one_dmap_locked(struct inode *inode,
+				   struct fuse_dax_mapping *dmap)
+{
+	int ret;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	/*
+	 * igrab() was done to make sure inode won't go under us, and this
+	 * further avoids the race with evict().
+	 */
+	ret = dmap_writeback_invalidate(inode, dmap);
+	if (ret)
+		return ret;
+
+	/* Remove dax mapping from inode interval tree now */
+	interval_tree_remove(&dmap->itn, &fi->dax->tree);
+	fi->dax->nr--;
+
+	/* It is possible that umount/shutdown has killed the fuse connection
+	 * and worker thread is trying to reclaim memory in parallel.  Don't
+	 * warn in that case.
+	 */
+	ret = dmap_removemapping_one(inode, dmap);
+	if (ret && ret != -ENOTCONN) {
+		pr_warn("Failed to remove mapping. offset=0x%llx len=0x%llx ret=%d\n",
+			dmap->window_offset, dmap->length, ret);
+	}
+	return 0;
+}
+
+/* Find first mapped dmap for an inode and return file offset. Caller needs
+ * to hold fi->dax->sem lock either shared or exclusive.
+ */
+static struct fuse_dax_mapping *inode_lookup_first_dmap(struct inode *inode)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_dax_mapping *dmap;
+	struct interval_tree_node *node;
+
+	for (node = interval_tree_iter_first(&fi->dax->tree, 0, -1); node;
+	     node = interval_tree_iter_next(node, 0, -1)) {
+		dmap = node_to_dmap(node);
+		/* still in use. */
+		if (refcount_read(&dmap->refcnt) > 1)
+			continue;
+
+		return dmap;
+	}
+
+	return NULL;
+}
+
+/*
+ * Find first mapping in the tree and free it and return it. Do not add
+ * it back to free pool.
+ */
+static struct fuse_dax_mapping *
+inode_inline_reclaim_one_dmap(struct fuse_conn_dax *fcd, struct inode *inode,
+			      bool *retry)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_dax_mapping *dmap;
+	u64 dmap_start, dmap_end;
+	unsigned long start_idx;
+	int ret;
+	struct interval_tree_node *node;
+
+	down_write(&fi->i_mmap_sem);
+
+	/* Lookup a dmap and corresponding file offset to reclaim. */
+	down_read(&fi->dax->sem);
+	dmap = inode_lookup_first_dmap(inode);
+	if (dmap) {
+		start_idx = dmap->itn.start;
+		dmap_start = start_idx << FUSE_DAX_SHIFT;
+		dmap_end = dmap_start + FUSE_DAX_SZ - 1;
+	}
+	up_read(&fi->dax->sem);
+
+	if (!dmap)
+		goto out_mmap_sem;
+	/*
+	 * Make sure there are no references to inode pages using
+	 * get_user_pages()
+	 */
+	ret = fuse_dax_break_layouts(inode, dmap_start, dmap_end);
+	if (ret) {
+		pr_debug("fuse: fuse_dax_break_layouts() failed. err=%d\n",
+			 ret);
+		dmap = ERR_PTR(ret);
+		goto out_mmap_sem;
+	}
+
+	down_write(&fi->dax->sem);
+	node = interval_tree_iter_first(&fi->dax->tree, start_idx, start_idx);
+	/* Range already got reclaimed by somebody else */
+	if (!node) {
+		if (retry)
+			*retry = true;
+		goto out_write_dmap_sem;
+	}
+
+	dmap = node_to_dmap(node);
+	/* still in use. */
+	if (refcount_read(&dmap->refcnt) > 1) {
+		dmap = NULL;
+		if (retry)
+			*retry = true;
+		goto out_write_dmap_sem;
+	}
+
+	ret = reclaim_one_dmap_locked(inode, dmap);
+	if (ret < 0) {
+		dmap = ERR_PTR(ret);
+		goto out_write_dmap_sem;
+	}
+
+	/* Clean up dmap. Do not add back to free list */
+	dmap_remove_busy_list(fcd, dmap);
+	dmap->inode = NULL;
+	dmap->itn.start = dmap->itn.last = 0;
+
+	pr_debug("fuse: %s: inline reclaimed memory range. inode=%p, window_offset=0x%llx, length=0x%llx\n",
+		 __func__, inode, dmap->window_offset, dmap->length);
+
+out_write_dmap_sem:
+	up_write(&fi->dax->sem);
+out_mmap_sem:
+	up_write(&fi->i_mmap_sem);
+	return dmap;
+}
+
+static struct fuse_dax_mapping *
+alloc_dax_mapping_reclaim(struct fuse_conn_dax *fcd, struct inode *inode)
+{
+	struct fuse_dax_mapping *dmap;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	while (1) {
+		bool retry = false;
+
+		dmap = alloc_dax_mapping(fcd);
+		if (dmap)
+			return dmap;
+
+		dmap = inode_inline_reclaim_one_dmap(fcd, inode, &retry);
+		/*
+		 * Either we got a mapping or it is an error, return in both
+		 * the cases.
+		 */
+		if (dmap)
+			return dmap;
+
+		/* If we could not reclaim a mapping because it
+		 * had a reference or some other temporary failure,
+		 * Try again. We want to give up inline reclaim only
+		 * if there is no range assigned to this node. Otherwise
+		 * if a deadlock is possible if we sleep with fi->i_mmap_sem
+		 * held and worker to free memory can't make progress due
+		 * to unavailability of fi->i_mmap_sem lock. So sleep
+		 * only if fi->dax->nr=0
+		 */
+		if (retry)
+			continue;
+		/*
+		 * There are no mappings which can be reclaimed. Wait for one.
+		 * We are not holding fi->dax->sem. So it is possible
+		 * that range gets added now. But as we are not holding
+		 * fi->i_mmap_sem, worker should still be able to free up
+		 * a range and wake us up.
+		 */
+		if (!fi->dax->nr && !(fcd->nr_free_ranges > 0)) {
+			if (wait_event_killable_exclusive(fcd->range_waitq,
+					(fcd->nr_free_ranges > 0))) {
+				return ERR_PTR(-EINTR);
+			}
+		}
+	}
+}
+
+static int lookup_and_reclaim_dmap_locked(struct fuse_conn_dax *fcd,
+					  struct inode *inode,
+					  unsigned long start_idx)
+{
+	int ret;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_dax_mapping *dmap;
+	struct interval_tree_node *node;
+
+	/* Find fuse dax mapping at file offset inode. */
+	node = interval_tree_iter_first(&fi->dax->tree, start_idx, start_idx);
+
+	/* Range already got cleaned up by somebody else */
+	if (!node)
+		return 0;
+	dmap = node_to_dmap(node);
+
+	/* still in use. */
+	if (refcount_read(&dmap->refcnt) > 1)
+		return 0;
+
+	ret = reclaim_one_dmap_locked(inode, dmap);
+	if (ret < 0)
+		return ret;
+
+	/* Cleanup dmap entry and add back to free list */
+	spin_lock(&fcd->lock);
+	dmap_reinit_add_to_free_pool(fcd, dmap);
+	spin_unlock(&fcd->lock);
+	return ret;
+}
+
+/*
+ * Free a range of memory.
+ * Locking:
+ * 1. Take fi->i_mmap_sem to block dax faults.
+ * 2. Take fi->dax->sem to protect interval tree and also to make sure
+ *    read/write can not reuse a dmap which we might be freeing.
+ */
+static int lookup_and_reclaim_dmap(struct fuse_conn_dax *fcd,
+				   struct inode *inode,
+				   unsigned long start_idx,
+				   unsigned long end_idx)
+{
+	int ret;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	loff_t dmap_start = start_idx << FUSE_DAX_SHIFT;
+	loff_t dmap_end = (dmap_start + FUSE_DAX_SZ) - 1;
+
+	down_write(&fi->i_mmap_sem);
+	ret = fuse_dax_break_layouts(inode, dmap_start, dmap_end);
+	if (ret) {
+		pr_debug("virtio_fs: fuse_dax_break_layouts() failed. err=%d\n",
+			 ret);
+		goto out_mmap_sem;
+	}
+
+	down_write(&fi->dax->sem);
+	ret = lookup_and_reclaim_dmap_locked(fcd, inode, start_idx);
+	up_write(&fi->dax->sem);
+out_mmap_sem:
+	up_write(&fi->i_mmap_sem);
+	return ret;
+}
+
+static int try_to_free_dmap_chunks(struct fuse_conn_dax *fcd,
+				   unsigned long nr_to_free)
+{
+	struct fuse_dax_mapping *dmap, *pos, *temp;
+	int ret, nr_freed = 0;
+	unsigned long start_idx = 0, end_idx = 0;
+	struct inode *inode = NULL;
+
+	/* Pick first busy range and free it for now*/
+	while (1) {
+		if (nr_freed >= nr_to_free)
+			break;
+
+		dmap = NULL;
+		spin_lock(&fcd->lock);
+
+		if (!fcd->nr_busy_ranges) {
+			spin_unlock(&fcd->lock);
+			return 0;
+		}
+
+		list_for_each_entry_safe(pos, temp, &fcd->busy_ranges,
+						busy_list) {
+			/* skip this range if it's in use. */
+			if (refcount_read(&pos->refcnt) > 1)
+				continue;
+
+			inode = igrab(pos->inode);
+			/*
+			 * This inode is going away. That will free
+			 * up all the ranges anyway, continue to
+			 * next range.
+			 */
+			if (!inode)
+				continue;
+			/*
+			 * Take this element off list and add it tail. If
+			 * this element can't be freed, it will help with
+			 * selecting new element in next iteration of loop.
+			 */
+			dmap = pos;
+			list_move_tail(&dmap->busy_list, &fcd->busy_ranges);
+			start_idx = end_idx = dmap->itn.start;
+			break;
+		}
+		spin_unlock(&fcd->lock);
+		if (!dmap)
+			return 0;
+
+		ret = lookup_and_reclaim_dmap(fcd, inode, start_idx, end_idx);
+		iput(inode);
+		if (ret)
+			return ret;
+		nr_freed++;
+	}
+	return 0;
+}
+
+static void fuse_dax_free_mem_worker(struct work_struct *work)
+{
+	int ret;
+	struct fuse_conn_dax *fcd = container_of(work, struct fuse_conn_dax,
+						 free_work.work);
+	ret = try_to_free_dmap_chunks(fcd, FUSE_DAX_RECLAIM_CHUNK);
+	if (ret) {
+		pr_debug("fuse: try_to_free_dmap_chunks() failed with err=%d\n",
+			 ret);
+	}
+
+	/* If number of free ranges are still below threhold, requeue */
+	kick_dmap_free_worker(fcd, 1);
+}
+
+static void fuse_free_dax_mem_ranges(struct list_head *mem_list)
+{
+	struct fuse_dax_mapping *range, *temp;
+
+	/* Free All allocated elements */
+	list_for_each_entry_safe(range, temp, mem_list, list) {
+		list_del(&range->list);
+		if (!list_empty(&range->busy_list))
+			list_del(&range->busy_list);
+		kfree(range);
+	}
+}
+
+void fuse_dax_conn_free(struct fuse_conn *fc)
+{
+	if (fc->dax) {
+		fuse_free_dax_mem_ranges(&fc->dax->free_ranges);
+		kfree(fc->dax);
+		fc->dax = NULL;
+	}
+}
+
+static int fuse_dax_mem_range_init(struct fuse_conn_dax *fcd)
+{
+	long nr_pages, nr_ranges;
+	void *kaddr;
+	pfn_t pfn;
+	struct fuse_dax_mapping *range;
+	int ret, id;
+	size_t dax_size = -1;
+	unsigned long i;
+
+	init_waitqueue_head(&fcd->range_waitq);
+	INIT_LIST_HEAD(&fcd->free_ranges);
+	INIT_LIST_HEAD(&fcd->busy_ranges);
+	INIT_DELAYED_WORK(&fcd->free_work, fuse_dax_free_mem_worker);
+
+	id = dax_read_lock();
+	nr_pages = dax_direct_access(fcd->dev, 0, PHYS_PFN(dax_size), &kaddr,
+				     &pfn);
+	dax_read_unlock(id);
+	if (nr_pages < 0) {
+		pr_debug("dax_direct_access() returned %ld\n", nr_pages);
+		return nr_pages;
+	}
+
+	nr_ranges = nr_pages/FUSE_DAX_PAGES;
+	pr_debug("%s: dax mapped %ld pages. nr_ranges=%ld\n",
+		__func__, nr_pages, nr_ranges);
+
+	for (i = 0; i < nr_ranges; i++) {
+		range = kzalloc(sizeof(struct fuse_dax_mapping), GFP_KERNEL);
+		ret = -ENOMEM;
+		if (!range)
+			goto out_err;
+
+		/* TODO: This offset only works if virtio-fs driver is not
+		 * having some memory hidden at the beginning. This needs
+		 * better handling
+		 */
+		range->window_offset = i * FUSE_DAX_SZ;
+		range->length = FUSE_DAX_SZ;
+		INIT_LIST_HEAD(&range->busy_list);
+		refcount_set(&range->refcnt, 1);
+		list_add_tail(&range->list, &fcd->free_ranges);
+	}
+
+	fcd->nr_free_ranges = nr_ranges;
+	fcd->nr_ranges = nr_ranges;
+	return 0;
+out_err:
+	/* Free All allocated elements */
+	fuse_free_dax_mem_ranges(&fcd->free_ranges);
+	return ret;
+}
+
+int fuse_dax_conn_alloc(struct fuse_conn *fc, struct dax_device *dax_dev)
+{
+	struct fuse_conn_dax *fcd;
+	int err;
+
+	if (!dax_dev)
+		return 0;
+
+	fcd = kzalloc(sizeof(*fcd), GFP_KERNEL);
+	if (!fcd)
+		return -ENOMEM;
+
+	spin_lock_init(&fcd->lock);
+	fcd->dev = dax_dev;
+	err = fuse_dax_mem_range_init(fcd);
+	if (err) {
+		kfree(fcd);
+		return err;
+	}
+
+	fc->dax = fcd;
+	return 0;
+}
+
+bool fuse_dax_inode_alloc(struct super_block *sb, struct fuse_inode *fi)
+{
+	struct fuse_conn *fc = get_fuse_conn_super(sb);
+
+	fi->dax = NULL;
+	if (fc->dax) {
+		fi->dax = kzalloc(sizeof(*fi->dax), GFP_KERNEL_ACCOUNT);
+		if (!fi->dax)
+			return false;
+
+		init_rwsem(&fi->dax->sem);
+		fi->dax->tree = RB_ROOT_CACHED;
+	}
+
+	return true;
+}
+
+static const struct address_space_operations fuse_dax_file_aops  = {
+	.writepages	= fuse_dax_writepages,
+	.direct_IO	= noop_direct_IO,
+	.set_page_dirty	= noop_set_page_dirty,
+	.invalidatepage	= noop_invalidatepage,
+};
+
+void fuse_dax_inode_init(struct inode *inode)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	if (!fc->dax)
+		return;
+
+	inode->i_flags |= S_DAX;
+	inode->i_data.a_ops = &fuse_dax_file_aops;
+}
+
+bool fuse_dax_check_alignment(struct fuse_conn *fc, unsigned int map_alignment)
+{
+	if (fc->dax && (map_alignment > FUSE_DAX_SHIFT)) {
+		pr_warn("FUSE: map_alignment %u incompatible with dax mem range size %u\n",
+			map_alignment, FUSE_DAX_SZ);
+		return false;
+	}
+	return true;
+}
+
+void fuse_dax_cancel_work(struct fuse_conn *fc)
+{
+	struct fuse_conn_dax *fcd = fc->dax;
+
+	if (fcd)
+		cancel_delayed_work_sync(&fcd->free_work);
+
+}
+EXPORT_SYMBOL_GPL(fuse_dax_cancel_work);
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
new file mode 100644
index 000000000..8ac91ba05
--- /dev/null
+++ b/fs/fuse/dev.c
@@ -0,0 +1,2346 @@
+/*
+  FUSE: Filesystem in Userspace
+  Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>
+
+  This program can be distributed under the terms of the GNU GPL.
+  See the file COPYING.
+*/
+
+#include "fuse_i.h"
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/poll.h>
+#include <linux/sched/signal.h>
+#include <linux/uio.h>
+#include <linux/miscdevice.h>
+#include <linux/pagemap.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+#include <linux/pipe_fs_i.h>
+#include <linux/swap.h>
+#include <linux/splice.h>
+#include <linux/sched.h>
+
+MODULE_ALIAS_MISCDEV(FUSE_MINOR);
+MODULE_ALIAS("devname:fuse");
+
+/* Ordinary requests have even IDs, while interrupts IDs are odd */
+#define FUSE_INT_REQ_BIT (1ULL << 0)
+#define FUSE_REQ_ID_STEP (1ULL << 1)
+
+static struct kmem_cache *fuse_req_cachep;
+
+static struct fuse_dev *fuse_get_dev(struct file *file)
+{
+	/*
+	 * Lockless access is OK, because file->private data is set
+	 * once during mount and is valid until the file is released.
+	 */
+	return READ_ONCE(file->private_data);
+}
+
+static void fuse_request_init(struct fuse_mount *fm, struct fuse_req *req)
+{
+	INIT_LIST_HEAD(&req->list);
+	INIT_LIST_HEAD(&req->intr_entry);
+	init_waitqueue_head(&req->waitq);
+	refcount_set(&req->count, 1);
+	__set_bit(FR_PENDING, &req->flags);
+	req->fm = fm;
+}
+
+static struct fuse_req *fuse_request_alloc(struct fuse_mount *fm, gfp_t flags)
+{
+	struct fuse_req *req = kmem_cache_zalloc(fuse_req_cachep, flags);
+	if (req)
+		fuse_request_init(fm, req);
+
+	return req;
+}
+
+static void fuse_request_free(struct fuse_req *req)
+{
+	kmem_cache_free(fuse_req_cachep, req);
+}
+
+static void __fuse_get_request(struct fuse_req *req)
+{
+	refcount_inc(&req->count);
+}
+
+/* Must be called with > 1 refcount */
+static void __fuse_put_request(struct fuse_req *req)
+{
+	refcount_dec(&req->count);
+}
+
+void fuse_set_initialized(struct fuse_conn *fc)
+{
+	/* Make sure stores before this are seen on another CPU */
+	smp_wmb();
+	fc->initialized = 1;
+}
+
+static bool fuse_block_alloc(struct fuse_conn *fc, bool for_background)
+{
+	return !fc->initialized || (for_background && fc->blocked);
+}
+
+static void fuse_drop_waiting(struct fuse_conn *fc)
+{
+	/*
+	 * lockess check of fc->connected is okay, because atomic_dec_and_test()
+	 * provides a memory barrier mached with the one in fuse_wait_aborted()
+	 * to ensure no wake-up is missed.
+	 */
+	if (atomic_dec_and_test(&fc->num_waiting) &&
+	    !READ_ONCE(fc->connected)) {
+		/* wake up aborters */
+		wake_up_all(&fc->blocked_waitq);
+	}
+}
+
+static void fuse_put_request(struct fuse_req *req);
+
+static struct fuse_req *fuse_get_req(struct fuse_mount *fm, bool for_background)
+{
+	struct fuse_conn *fc = fm->fc;
+	struct fuse_req *req;
+	int err;
+	atomic_inc(&fc->num_waiting);
+
+	if (fuse_block_alloc(fc, for_background)) {
+		err = -EINTR;
+		if (wait_event_killable_exclusive(fc->blocked_waitq,
+				!fuse_block_alloc(fc, for_background)))
+			goto out;
+	}
+	/* Matches smp_wmb() in fuse_set_initialized() */
+	smp_rmb();
+
+	err = -ENOTCONN;
+	if (!fc->connected)
+		goto out;
+
+	err = -ECONNREFUSED;
+	if (fc->conn_error)
+		goto out;
+
+	req = fuse_request_alloc(fm, GFP_KERNEL);
+	err = -ENOMEM;
+	if (!req) {
+		if (for_background)
+			wake_up(&fc->blocked_waitq);
+		goto out;
+	}
+
+	req->in.h.uid = from_kuid(fc->user_ns, current_fsuid());
+	req->in.h.gid = from_kgid(fc->user_ns, current_fsgid());
+	req->in.h.pid = pid_nr_ns(task_pid(current), fc->pid_ns);
+
+	__set_bit(FR_WAITING, &req->flags);
+	if (for_background)
+		__set_bit(FR_BACKGROUND, &req->flags);
+
+	if (unlikely(req->in.h.uid == ((uid_t)-1) ||
+		     req->in.h.gid == ((gid_t)-1))) {
+		fuse_put_request(req);
+		return ERR_PTR(-EOVERFLOW);
+	}
+	return req;
+
+ out:
+	fuse_drop_waiting(fc);
+	return ERR_PTR(err);
+}
+
+static void fuse_put_request(struct fuse_req *req)
+{
+	struct fuse_conn *fc = req->fm->fc;
+
+	if (refcount_dec_and_test(&req->count)) {
+		if (test_bit(FR_BACKGROUND, &req->flags)) {
+			/*
+			 * We get here in the unlikely case that a background
+			 * request was allocated but not sent
+			 */
+			spin_lock(&fc->bg_lock);
+			if (!fc->blocked)
+				wake_up(&fc->blocked_waitq);
+			spin_unlock(&fc->bg_lock);
+		}
+
+		if (test_bit(FR_WAITING, &req->flags)) {
+			__clear_bit(FR_WAITING, &req->flags);
+			fuse_drop_waiting(fc);
+		}
+
+		fuse_request_free(req);
+	}
+}
+
+unsigned int fuse_len_args(unsigned int numargs, struct fuse_arg *args)
+{
+	unsigned nbytes = 0;
+	unsigned i;
+
+	for (i = 0; i < numargs; i++)
+		nbytes += args[i].size;
+
+	return nbytes;
+}
+EXPORT_SYMBOL_GPL(fuse_len_args);
+
+u64 fuse_get_unique(struct fuse_iqueue *fiq)
+{
+	fiq->reqctr += FUSE_REQ_ID_STEP;
+	return fiq->reqctr;
+}
+EXPORT_SYMBOL_GPL(fuse_get_unique);
+
+static unsigned int fuse_req_hash(u64 unique)
+{
+	return hash_long(unique & ~FUSE_INT_REQ_BIT, FUSE_PQ_HASH_BITS);
+}
+
+/**
+ * A new request is available, wake fiq->waitq
+ */
+static void fuse_dev_wake_and_unlock(struct fuse_iqueue *fiq)
+__releases(fiq->lock)
+{
+	wake_up(&fiq->waitq);
+	kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
+	spin_unlock(&fiq->lock);
+}
+
+const struct fuse_iqueue_ops fuse_dev_fiq_ops = {
+	.wake_forget_and_unlock		= fuse_dev_wake_and_unlock,
+	.wake_interrupt_and_unlock	= fuse_dev_wake_and_unlock,
+	.wake_pending_and_unlock	= fuse_dev_wake_and_unlock,
+};
+EXPORT_SYMBOL_GPL(fuse_dev_fiq_ops);
+
+static void queue_request_and_unlock(struct fuse_iqueue *fiq,
+				     struct fuse_req *req)
+__releases(fiq->lock)
+{
+	req->in.h.len = sizeof(struct fuse_in_header) +
+		fuse_len_args(req->args->in_numargs,
+			      (struct fuse_arg *) req->args->in_args);
+	list_add_tail(&req->list, &fiq->pending);
+	fiq->ops->wake_pending_and_unlock(fiq);
+}
+
+void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget,
+		       u64 nodeid, u64 nlookup)
+{
+	struct fuse_iqueue *fiq = &fc->iq;
+
+	forget->forget_one.nodeid = nodeid;
+	forget->forget_one.nlookup = nlookup;
+
+	spin_lock(&fiq->lock);
+	if (fiq->connected) {
+		fiq->forget_list_tail->next = forget;
+		fiq->forget_list_tail = forget;
+		fiq->ops->wake_forget_and_unlock(fiq);
+	} else {
+		kfree(forget);
+		spin_unlock(&fiq->lock);
+	}
+}
+
+static void flush_bg_queue(struct fuse_conn *fc)
+{
+	struct fuse_iqueue *fiq = &fc->iq;
+
+	while (fc->active_background < fc->max_background &&
+	       !list_empty(&fc->bg_queue)) {
+		struct fuse_req *req;
+
+		req = list_first_entry(&fc->bg_queue, struct fuse_req, list);
+		list_del(&req->list);
+		fc->active_background++;
+		spin_lock(&fiq->lock);
+		req->in.h.unique = fuse_get_unique(fiq);
+		queue_request_and_unlock(fiq, req);
+	}
+}
+
+/*
+ * This function is called when a request is finished.  Either a reply
+ * has arrived or it was aborted (and not yet sent) or some error
+ * occurred during communication with userspace, or the device file
+ * was closed.  The requester thread is woken up (if still waiting),
+ * the 'end' callback is called if given, else the reference to the
+ * request is released
+ */
+void fuse_request_end(struct fuse_req *req)
+{
+	struct fuse_mount *fm = req->fm;
+	struct fuse_conn *fc = fm->fc;
+	struct fuse_iqueue *fiq = &fc->iq;
+
+	if (test_and_set_bit(FR_FINISHED, &req->flags))
+		goto put_request;
+
+	/*
+	 * test_and_set_bit() implies smp_mb() between bit
+	 * changing and below FR_INTERRUPTED check. Pairs with
+	 * smp_mb() from queue_interrupt().
+	 */
+	if (test_bit(FR_INTERRUPTED, &req->flags)) {
+		spin_lock(&fiq->lock);
+		list_del_init(&req->intr_entry);
+		spin_unlock(&fiq->lock);
+	}
+	WARN_ON(test_bit(FR_PENDING, &req->flags));
+	WARN_ON(test_bit(FR_SENT, &req->flags));
+	if (test_bit(FR_BACKGROUND, &req->flags)) {
+		spin_lock(&fc->bg_lock);
+		clear_bit(FR_BACKGROUND, &req->flags);
+		if (fc->num_background == fc->max_background) {
+			fc->blocked = 0;
+			wake_up(&fc->blocked_waitq);
+		} else if (!fc->blocked) {
+			/*
+			 * Wake up next waiter, if any.  It's okay to use
+			 * waitqueue_active(), as we've already synced up
+			 * fc->blocked with waiters with the wake_up() call
+			 * above.
+			 */
+			if (waitqueue_active(&fc->blocked_waitq))
+				wake_up(&fc->blocked_waitq);
+		}
+
+		if (fc->num_background == fc->congestion_threshold && fm->sb) {
+			clear_bdi_congested(fm->sb->s_bdi, BLK_RW_SYNC);
+			clear_bdi_congested(fm->sb->s_bdi, BLK_RW_ASYNC);
+		}
+		fc->num_background--;
+		fc->active_background--;
+		flush_bg_queue(fc);
+		spin_unlock(&fc->bg_lock);
+	} else {
+		/* Wake up waiter sleeping in request_wait_answer() */
+		wake_up(&req->waitq);
+	}
+
+	if (test_bit(FR_ASYNC, &req->flags))
+		req->args->end(fm, req->args, req->out.h.error);
+put_request:
+	fuse_put_request(req);
+}
+EXPORT_SYMBOL_GPL(fuse_request_end);
+
+static int queue_interrupt(struct fuse_req *req)
+{
+	struct fuse_iqueue *fiq = &req->fm->fc->iq;
+
+	spin_lock(&fiq->lock);
+	/* Check for we've sent request to interrupt this req */
+	if (unlikely(!test_bit(FR_INTERRUPTED, &req->flags))) {
+		spin_unlock(&fiq->lock);
+		return -EINVAL;
+	}
+
+	if (list_empty(&req->intr_entry)) {
+		list_add_tail(&req->intr_entry, &fiq->interrupts);
+		/*
+		 * Pairs with smp_mb() implied by test_and_set_bit()
+		 * from fuse_request_end().
+		 */
+		smp_mb();
+		if (test_bit(FR_FINISHED, &req->flags)) {
+			list_del_init(&req->intr_entry);
+			spin_unlock(&fiq->lock);
+			return 0;
+		}
+		fiq->ops->wake_interrupt_and_unlock(fiq);
+	} else {
+		spin_unlock(&fiq->lock);
+	}
+	return 0;
+}
+
+static void request_wait_answer(struct fuse_req *req)
+{
+	struct fuse_conn *fc = req->fm->fc;
+	struct fuse_iqueue *fiq = &fc->iq;
+	int err;
+
+	if (!fc->no_interrupt) {
+		/* Any signal may interrupt this */
+		err = wait_event_interruptible(req->waitq,
+					test_bit(FR_FINISHED, &req->flags));
+		if (!err)
+			return;
+
+		set_bit(FR_INTERRUPTED, &req->flags);
+		/* matches barrier in fuse_dev_do_read() */
+		smp_mb__after_atomic();
+		if (test_bit(FR_SENT, &req->flags))
+			queue_interrupt(req);
+	}
+
+	if (!test_bit(FR_FORCE, &req->flags)) {
+		/* Only fatal signals may interrupt this */
+		err = wait_event_killable(req->waitq,
+					test_bit(FR_FINISHED, &req->flags));
+		if (!err)
+			return;
+
+		spin_lock(&fiq->lock);
+		/* Request is not yet in userspace, bail out */
+		if (test_bit(FR_PENDING, &req->flags)) {
+			list_del(&req->list);
+			spin_unlock(&fiq->lock);
+			__fuse_put_request(req);
+			req->out.h.error = -EINTR;
+			return;
+		}
+		spin_unlock(&fiq->lock);
+	}
+
+	/*
+	 * Either request is already in userspace, or it was forced.
+	 * Wait it out.
+	 */
+	wait_event(req->waitq, test_bit(FR_FINISHED, &req->flags));
+}
+
+static void __fuse_request_send(struct fuse_req *req)
+{
+	struct fuse_iqueue *fiq = &req->fm->fc->iq;
+
+	BUG_ON(test_bit(FR_BACKGROUND, &req->flags));
+	spin_lock(&fiq->lock);
+	if (!fiq->connected) {
+		spin_unlock(&fiq->lock);
+		req->out.h.error = -ENOTCONN;
+	} else {
+		req->in.h.unique = fuse_get_unique(fiq);
+		/* acquire extra reference, since request is still needed
+		   after fuse_request_end() */
+		__fuse_get_request(req);
+		queue_request_and_unlock(fiq, req);
+
+		request_wait_answer(req);
+		/* Pairs with smp_wmb() in fuse_request_end() */
+		smp_rmb();
+	}
+}
+
+static void fuse_adjust_compat(struct fuse_conn *fc, struct fuse_args *args)
+{
+	if (fc->minor < 4 && args->opcode == FUSE_STATFS)
+		args->out_args[0].size = FUSE_COMPAT_STATFS_SIZE;
+
+	if (fc->minor < 9) {
+		switch (args->opcode) {
+		case FUSE_LOOKUP:
+		case FUSE_CREATE:
+		case FUSE_MKNOD:
+		case FUSE_MKDIR:
+		case FUSE_SYMLINK:
+		case FUSE_LINK:
+			args->out_args[0].size = FUSE_COMPAT_ENTRY_OUT_SIZE;
+			break;
+		case FUSE_GETATTR:
+		case FUSE_SETATTR:
+			args->out_args[0].size = FUSE_COMPAT_ATTR_OUT_SIZE;
+			break;
+		}
+	}
+	if (fc->minor < 12) {
+		switch (args->opcode) {
+		case FUSE_CREATE:
+			args->in_args[0].size = sizeof(struct fuse_open_in);
+			break;
+		case FUSE_MKNOD:
+			args->in_args[0].size = FUSE_COMPAT_MKNOD_IN_SIZE;
+			break;
+		}
+	}
+}
+
+static void fuse_force_creds(struct fuse_req *req)
+{
+	struct fuse_conn *fc = req->fm->fc;
+
+	req->in.h.uid = from_kuid_munged(fc->user_ns, current_fsuid());
+	req->in.h.gid = from_kgid_munged(fc->user_ns, current_fsgid());
+	req->in.h.pid = pid_nr_ns(task_pid(current), fc->pid_ns);
+}
+
+static void fuse_args_to_req(struct fuse_req *req, struct fuse_args *args)
+{
+	req->in.h.opcode = args->opcode;
+	req->in.h.nodeid = args->nodeid;
+	req->args = args;
+	if (args->end)
+		__set_bit(FR_ASYNC, &req->flags);
+}
+
+ssize_t fuse_simple_request(struct fuse_mount *fm, struct fuse_args *args)
+{
+	struct fuse_conn *fc = fm->fc;
+	struct fuse_req *req;
+	ssize_t ret;
+
+	if (args->force) {
+		atomic_inc(&fc->num_waiting);
+		req = fuse_request_alloc(fm, GFP_KERNEL | __GFP_NOFAIL);
+
+		if (!args->nocreds)
+			fuse_force_creds(req);
+
+		__set_bit(FR_WAITING, &req->flags);
+		__set_bit(FR_FORCE, &req->flags);
+	} else {
+		WARN_ON(args->nocreds);
+		req = fuse_get_req(fm, false);
+		if (IS_ERR(req))
+			return PTR_ERR(req);
+	}
+
+	/* Needs to be done after fuse_get_req() so that fc->minor is valid */
+	fuse_adjust_compat(fc, args);
+	fuse_args_to_req(req, args);
+
+	if (!args->noreply)
+		__set_bit(FR_ISREPLY, &req->flags);
+	__fuse_request_send(req);
+	ret = req->out.h.error;
+	if (!ret && args->out_argvar) {
+		BUG_ON(args->out_numargs == 0);
+		ret = args->out_args[args->out_numargs - 1].size;
+	}
+	fuse_put_request(req);
+
+	return ret;
+}
+
+static bool fuse_request_queue_background(struct fuse_req *req)
+{
+	struct fuse_mount *fm = req->fm;
+	struct fuse_conn *fc = fm->fc;
+	bool queued = false;
+
+	WARN_ON(!test_bit(FR_BACKGROUND, &req->flags));
+	if (!test_bit(FR_WAITING, &req->flags)) {
+		__set_bit(FR_WAITING, &req->flags);
+		atomic_inc(&fc->num_waiting);
+	}
+	__set_bit(FR_ISREPLY, &req->flags);
+	spin_lock(&fc->bg_lock);
+	if (likely(fc->connected)) {
+		fc->num_background++;
+		if (fc->num_background == fc->max_background)
+			fc->blocked = 1;
+		if (fc->num_background == fc->congestion_threshold && fm->sb) {
+			set_bdi_congested(fm->sb->s_bdi, BLK_RW_SYNC);
+			set_bdi_congested(fm->sb->s_bdi, BLK_RW_ASYNC);
+		}
+		list_add_tail(&req->list, &fc->bg_queue);
+		flush_bg_queue(fc);
+		queued = true;
+	}
+	spin_unlock(&fc->bg_lock);
+
+	return queued;
+}
+
+int fuse_simple_background(struct fuse_mount *fm, struct fuse_args *args,
+			    gfp_t gfp_flags)
+{
+	struct fuse_req *req;
+
+	if (args->force) {
+		WARN_ON(!args->nocreds);
+		req = fuse_request_alloc(fm, gfp_flags);
+		if (!req)
+			return -ENOMEM;
+		__set_bit(FR_BACKGROUND, &req->flags);
+	} else {
+		WARN_ON(args->nocreds);
+		req = fuse_get_req(fm, true);
+		if (IS_ERR(req))
+			return PTR_ERR(req);
+	}
+
+	fuse_args_to_req(req, args);
+
+	if (!fuse_request_queue_background(req)) {
+		fuse_put_request(req);
+		return -ENOTCONN;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fuse_simple_background);
+
+static int fuse_simple_notify_reply(struct fuse_mount *fm,
+				    struct fuse_args *args, u64 unique)
+{
+	struct fuse_req *req;
+	struct fuse_iqueue *fiq = &fm->fc->iq;
+	int err = 0;
+
+	req = fuse_get_req(fm, false);
+	if (IS_ERR(req))
+		return PTR_ERR(req);
+
+	__clear_bit(FR_ISREPLY, &req->flags);
+	req->in.h.unique = unique;
+
+	fuse_args_to_req(req, args);
+
+	spin_lock(&fiq->lock);
+	if (fiq->connected) {
+		queue_request_and_unlock(fiq, req);
+	} else {
+		err = -ENODEV;
+		spin_unlock(&fiq->lock);
+		fuse_put_request(req);
+	}
+
+	return err;
+}
+
+/*
+ * Lock the request.  Up to the next unlock_request() there mustn't be
+ * anything that could cause a page-fault.  If the request was already
+ * aborted bail out.
+ */
+static int lock_request(struct fuse_req *req)
+{
+	int err = 0;
+	if (req) {
+		spin_lock(&req->waitq.lock);
+		if (test_bit(FR_ABORTED, &req->flags))
+			err = -ENOENT;
+		else
+			set_bit(FR_LOCKED, &req->flags);
+		spin_unlock(&req->waitq.lock);
+	}
+	return err;
+}
+
+/*
+ * Unlock request.  If it was aborted while locked, caller is responsible
+ * for unlocking and ending the request.
+ */
+static int unlock_request(struct fuse_req *req)
+{
+	int err = 0;
+	if (req) {
+		spin_lock(&req->waitq.lock);
+		if (test_bit(FR_ABORTED, &req->flags))
+			err = -ENOENT;
+		else
+			clear_bit(FR_LOCKED, &req->flags);
+		spin_unlock(&req->waitq.lock);
+	}
+	return err;
+}
+
+struct fuse_copy_state {
+	int write;
+	struct fuse_req *req;
+	struct iov_iter *iter;
+	struct pipe_buffer *pipebufs;
+	struct pipe_buffer *currbuf;
+	struct pipe_inode_info *pipe;
+	unsigned long nr_segs;
+	struct page *pg;
+	unsigned len;
+	unsigned offset;
+	unsigned move_pages:1;
+};
+
+static void fuse_copy_init(struct fuse_copy_state *cs, int write,
+			   struct iov_iter *iter)
+{
+	memset(cs, 0, sizeof(*cs));
+	cs->write = write;
+	cs->iter = iter;
+}
+
+/* Unmap and put previous page of userspace buffer */
+static void fuse_copy_finish(struct fuse_copy_state *cs)
+{
+	if (cs->currbuf) {
+		struct pipe_buffer *buf = cs->currbuf;
+
+		if (cs->write)
+			buf->len = PAGE_SIZE - cs->len;
+		cs->currbuf = NULL;
+	} else if (cs->pg) {
+		if (cs->write) {
+			flush_dcache_page(cs->pg);
+			set_page_dirty_lock(cs->pg);
+		}
+		put_page(cs->pg);
+	}
+	cs->pg = NULL;
+}
+
+/*
+ * Get another pagefull of userspace buffer, and map it to kernel
+ * address space, and lock request
+ */
+static int fuse_copy_fill(struct fuse_copy_state *cs)
+{
+	struct page *page;
+	int err;
+
+	err = unlock_request(cs->req);
+	if (err)
+		return err;
+
+	fuse_copy_finish(cs);
+	if (cs->pipebufs) {
+		struct pipe_buffer *buf = cs->pipebufs;
+
+		if (!cs->write) {
+			err = pipe_buf_confirm(cs->pipe, buf);
+			if (err)
+				return err;
+
+			BUG_ON(!cs->nr_segs);
+			cs->currbuf = buf;
+			cs->pg = buf->page;
+			cs->offset = buf->offset;
+			cs->len = buf->len;
+			cs->pipebufs++;
+			cs->nr_segs--;
+		} else {
+			if (cs->nr_segs >= cs->pipe->max_usage)
+				return -EIO;
+
+			page = alloc_page(GFP_HIGHUSER);
+			if (!page)
+				return -ENOMEM;
+
+			buf->page = page;
+			buf->offset = 0;
+			buf->len = 0;
+
+			cs->currbuf = buf;
+			cs->pg = page;
+			cs->offset = 0;
+			cs->len = PAGE_SIZE;
+			cs->pipebufs++;
+			cs->nr_segs++;
+		}
+	} else {
+		size_t off;
+		err = iov_iter_get_pages(cs->iter, &page, PAGE_SIZE, 1, &off);
+		if (err < 0)
+			return err;
+		BUG_ON(!err);
+		cs->len = err;
+		cs->offset = off;
+		cs->pg = page;
+		iov_iter_advance(cs->iter, err);
+	}
+
+	return lock_request(cs->req);
+}
+
+/* Do as much copy to/from userspace buffer as we can */
+static int fuse_copy_do(struct fuse_copy_state *cs, void **val, unsigned *size)
+{
+	unsigned ncpy = min(*size, cs->len);
+	if (val) {
+		void *pgaddr = kmap_atomic(cs->pg);
+		void *buf = pgaddr + cs->offset;
+
+		if (cs->write)
+			memcpy(buf, *val, ncpy);
+		else
+			memcpy(*val, buf, ncpy);
+
+		kunmap_atomic(pgaddr);
+		*val += ncpy;
+	}
+	*size -= ncpy;
+	cs->len -= ncpy;
+	cs->offset += ncpy;
+	return ncpy;
+}
+
+static int fuse_check_page(struct page *page)
+{
+	if (page_mapcount(page) ||
+	    page->mapping != NULL ||
+	    (page->flags & PAGE_FLAGS_CHECK_AT_PREP &
+	     ~(1 << PG_locked |
+	       1 << PG_referenced |
+	       1 << PG_uptodate |
+	       1 << PG_lru |
+	       1 << PG_active |
+	       1 << PG_workingset |
+	       1 << PG_reclaim |
+	       1 << PG_waiters))) {
+		dump_page(page, "fuse: trying to steal weird page");
+		return 1;
+	}
+	return 0;
+}
+
+static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
+{
+	int err;
+	struct page *oldpage = *pagep;
+	struct page *newpage;
+	struct pipe_buffer *buf = cs->pipebufs;
+
+	get_page(oldpage);
+	err = unlock_request(cs->req);
+	if (err)
+		goto out_put_old;
+
+	fuse_copy_finish(cs);
+
+	err = pipe_buf_confirm(cs->pipe, buf);
+	if (err)
+		goto out_put_old;
+
+	BUG_ON(!cs->nr_segs);
+	cs->currbuf = buf;
+	cs->len = buf->len;
+	cs->pipebufs++;
+	cs->nr_segs--;
+
+	if (cs->len != PAGE_SIZE)
+		goto out_fallback;
+
+	if (!pipe_buf_try_steal(cs->pipe, buf))
+		goto out_fallback;
+
+	newpage = buf->page;
+
+	if (!PageUptodate(newpage))
+		SetPageUptodate(newpage);
+
+	ClearPageMappedToDisk(newpage);
+
+	if (fuse_check_page(newpage) != 0)
+		goto out_fallback_unlock;
+
+	/*
+	 * This is a new and locked page, it shouldn't be mapped or
+	 * have any special flags on it
+	 */
+	if (WARN_ON(page_mapped(oldpage)))
+		goto out_fallback_unlock;
+	if (WARN_ON(page_has_private(oldpage)))
+		goto out_fallback_unlock;
+	if (WARN_ON(PageDirty(oldpage) || PageWriteback(oldpage)))
+		goto out_fallback_unlock;
+	if (WARN_ON(PageMlocked(oldpage)))
+		goto out_fallback_unlock;
+
+	err = replace_page_cache_page(oldpage, newpage, GFP_KERNEL);
+	if (err) {
+		unlock_page(newpage);
+		goto out_put_old;
+	}
+
+	get_page(newpage);
+
+	if (!(buf->flags & PIPE_BUF_FLAG_LRU))
+		lru_cache_add(newpage);
+
+	/*
+	 * Release while we have extra ref on stolen page.  Otherwise
+	 * anon_pipe_buf_release() might think the page can be reused.
+	 */
+	pipe_buf_release(cs->pipe, buf);
+
+	err = 0;
+	spin_lock(&cs->req->waitq.lock);
+	if (test_bit(FR_ABORTED, &cs->req->flags))
+		err = -ENOENT;
+	else
+		*pagep = newpage;
+	spin_unlock(&cs->req->waitq.lock);
+
+	if (err) {
+		unlock_page(newpage);
+		put_page(newpage);
+		goto out_put_old;
+	}
+
+	unlock_page(oldpage);
+	/* Drop ref for ap->pages[] array */
+	put_page(oldpage);
+	cs->len = 0;
+
+	err = 0;
+out_put_old:
+	/* Drop ref obtained in this function */
+	put_page(oldpage);
+	return err;
+
+out_fallback_unlock:
+	unlock_page(newpage);
+out_fallback:
+	cs->pg = buf->page;
+	cs->offset = buf->offset;
+
+	err = lock_request(cs->req);
+	if (!err)
+		err = 1;
+
+	goto out_put_old;
+}
+
+static int fuse_ref_page(struct fuse_copy_state *cs, struct page *page,
+			 unsigned offset, unsigned count)
+{
+	struct pipe_buffer *buf;
+	int err;
+
+	if (cs->nr_segs >= cs->pipe->max_usage)
+		return -EIO;
+
+	get_page(page);
+	err = unlock_request(cs->req);
+	if (err) {
+		put_page(page);
+		return err;
+	}
+
+	fuse_copy_finish(cs);
+
+	buf = cs->pipebufs;
+	buf->page = page;
+	buf->offset = offset;
+	buf->len = count;
+
+	cs->pipebufs++;
+	cs->nr_segs++;
+	cs->len = 0;
+
+	return 0;
+}
+
+/*
+ * Copy a page in the request to/from the userspace buffer.  Must be
+ * done atomically
+ */
+static int fuse_copy_page(struct fuse_copy_state *cs, struct page **pagep,
+			  unsigned offset, unsigned count, int zeroing)
+{
+	int err;
+	struct page *page = *pagep;
+
+	if (page && zeroing && count < PAGE_SIZE)
+		clear_highpage(page);
+
+	while (count) {
+		if (cs->write && cs->pipebufs && page) {
+			/*
+			 * Can't control lifetime of pipe buffers, so always
+			 * copy user pages.
+			 */
+			if (cs->req->args->user_pages) {
+				err = fuse_copy_fill(cs);
+				if (err)
+					return err;
+			} else {
+				return fuse_ref_page(cs, page, offset, count);
+			}
+		} else if (!cs->len) {
+			if (cs->move_pages && page &&
+			    offset == 0 && count == PAGE_SIZE) {
+				err = fuse_try_move_page(cs, pagep);
+				if (err <= 0)
+					return err;
+			} else {
+				err = fuse_copy_fill(cs);
+				if (err)
+					return err;
+			}
+		}
+		if (page) {
+			void *mapaddr = kmap_atomic(page);
+			void *buf = mapaddr + offset;
+			offset += fuse_copy_do(cs, &buf, &count);
+			kunmap_atomic(mapaddr);
+		} else
+			offset += fuse_copy_do(cs, NULL, &count);
+	}
+	if (page && !cs->write)
+		flush_dcache_page(page);
+	return 0;
+}
+
+/* Copy pages in the request to/from userspace buffer */
+static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes,
+			   int zeroing)
+{
+	unsigned i;
+	struct fuse_req *req = cs->req;
+	struct fuse_args_pages *ap = container_of(req->args, typeof(*ap), args);
+
+
+	for (i = 0; i < ap->num_pages && (nbytes || zeroing); i++) {
+		int err;
+		unsigned int offset = ap->descs[i].offset;
+		unsigned int count = min(nbytes, ap->descs[i].length);
+
+		err = fuse_copy_page(cs, &ap->pages[i], offset, count, zeroing);
+		if (err)
+			return err;
+
+		nbytes -= count;
+	}
+	return 0;
+}
+
+/* Copy a single argument in the request to/from userspace buffer */
+static int fuse_copy_one(struct fuse_copy_state *cs, void *val, unsigned size)
+{
+	while (size) {
+		if (!cs->len) {
+			int err = fuse_copy_fill(cs);
+			if (err)
+				return err;
+		}
+		fuse_copy_do(cs, &val, &size);
+	}
+	return 0;
+}
+
+/* Copy request arguments to/from userspace buffer */
+static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs,
+			  unsigned argpages, struct fuse_arg *args,
+			  int zeroing)
+{
+	int err = 0;
+	unsigned i;
+
+	for (i = 0; !err && i < numargs; i++)  {
+		struct fuse_arg *arg = &args[i];
+		if (i == numargs - 1 && argpages)
+			err = fuse_copy_pages(cs, arg->size, zeroing);
+		else
+			err = fuse_copy_one(cs, arg->value, arg->size);
+	}
+	return err;
+}
+
+static int forget_pending(struct fuse_iqueue *fiq)
+{
+	return fiq->forget_list_head.next != NULL;
+}
+
+static int request_pending(struct fuse_iqueue *fiq)
+{
+	return !list_empty(&fiq->pending) || !list_empty(&fiq->interrupts) ||
+		forget_pending(fiq);
+}
+
+/*
+ * Transfer an interrupt request to userspace
+ *
+ * Unlike other requests this is assembled on demand, without a need
+ * to allocate a separate fuse_req structure.
+ *
+ * Called with fiq->lock held, releases it
+ */
+static int fuse_read_interrupt(struct fuse_iqueue *fiq,
+			       struct fuse_copy_state *cs,
+			       size_t nbytes, struct fuse_req *req)
+__releases(fiq->lock)
+{
+	struct fuse_in_header ih;
+	struct fuse_interrupt_in arg;
+	unsigned reqsize = sizeof(ih) + sizeof(arg);
+	int err;
+
+	list_del_init(&req->intr_entry);
+	memset(&ih, 0, sizeof(ih));
+	memset(&arg, 0, sizeof(arg));
+	ih.len = reqsize;
+	ih.opcode = FUSE_INTERRUPT;
+	ih.unique = (req->in.h.unique | FUSE_INT_REQ_BIT);
+	arg.unique = req->in.h.unique;
+
+	spin_unlock(&fiq->lock);
+	if (nbytes < reqsize)
+		return -EINVAL;
+
+	err = fuse_copy_one(cs, &ih, sizeof(ih));
+	if (!err)
+		err = fuse_copy_one(cs, &arg, sizeof(arg));
+	fuse_copy_finish(cs);
+
+	return err ? err : reqsize;
+}
+
+struct fuse_forget_link *fuse_dequeue_forget(struct fuse_iqueue *fiq,
+					     unsigned int max,
+					     unsigned int *countp)
+{
+	struct fuse_forget_link *head = fiq->forget_list_head.next;
+	struct fuse_forget_link **newhead = &head;
+	unsigned count;
+
+	for (count = 0; *newhead != NULL && count < max; count++)
+		newhead = &(*newhead)->next;
+
+	fiq->forget_list_head.next = *newhead;
+	*newhead = NULL;
+	if (fiq->forget_list_head.next == NULL)
+		fiq->forget_list_tail = &fiq->forget_list_head;
+
+	if (countp != NULL)
+		*countp = count;
+
+	return head;
+}
+EXPORT_SYMBOL(fuse_dequeue_forget);
+
+static int fuse_read_single_forget(struct fuse_iqueue *fiq,
+				   struct fuse_copy_state *cs,
+				   size_t nbytes)
+__releases(fiq->lock)
+{
+	int err;
+	struct fuse_forget_link *forget = fuse_dequeue_forget(fiq, 1, NULL);
+	struct fuse_forget_in arg = {
+		.nlookup = forget->forget_one.nlookup,
+	};
+	struct fuse_in_header ih = {
+		.opcode = FUSE_FORGET,
+		.nodeid = forget->forget_one.nodeid,
+		.unique = fuse_get_unique(fiq),
+		.len = sizeof(ih) + sizeof(arg),
+	};
+
+	spin_unlock(&fiq->lock);
+	kfree(forget);
+	if (nbytes < ih.len)
+		return -EINVAL;
+
+	err = fuse_copy_one(cs, &ih, sizeof(ih));
+	if (!err)
+		err = fuse_copy_one(cs, &arg, sizeof(arg));
+	fuse_copy_finish(cs);
+
+	if (err)
+		return err;
+
+	return ih.len;
+}
+
+static int fuse_read_batch_forget(struct fuse_iqueue *fiq,
+				   struct fuse_copy_state *cs, size_t nbytes)
+__releases(fiq->lock)
+{
+	int err;
+	unsigned max_forgets;
+	unsigned count;
+	struct fuse_forget_link *head;
+	struct fuse_batch_forget_in arg = { .count = 0 };
+	struct fuse_in_header ih = {
+		.opcode = FUSE_BATCH_FORGET,
+		.unique = fuse_get_unique(fiq),
+		.len = sizeof(ih) + sizeof(arg),
+	};
+
+	if (nbytes < ih.len) {
+		spin_unlock(&fiq->lock);
+		return -EINVAL;
+	}
+
+	max_forgets = (nbytes - ih.len) / sizeof(struct fuse_forget_one);
+	head = fuse_dequeue_forget(fiq, max_forgets, &count);
+	spin_unlock(&fiq->lock);
+
+	arg.count = count;
+	ih.len += count * sizeof(struct fuse_forget_one);
+	err = fuse_copy_one(cs, &ih, sizeof(ih));
+	if (!err)
+		err = fuse_copy_one(cs, &arg, sizeof(arg));
+
+	while (head) {
+		struct fuse_forget_link *forget = head;
+
+		if (!err) {
+			err = fuse_copy_one(cs, &forget->forget_one,
+					    sizeof(forget->forget_one));
+		}
+		head = forget->next;
+		kfree(forget);
+	}
+
+	fuse_copy_finish(cs);
+
+	if (err)
+		return err;
+
+	return ih.len;
+}
+
+static int fuse_read_forget(struct fuse_conn *fc, struct fuse_iqueue *fiq,
+			    struct fuse_copy_state *cs,
+			    size_t nbytes)
+__releases(fiq->lock)
+{
+	if (fc->minor < 16 || fiq->forget_list_head.next->next == NULL)
+		return fuse_read_single_forget(fiq, cs, nbytes);
+	else
+		return fuse_read_batch_forget(fiq, cs, nbytes);
+}
+
+/*
+ * Read a single request into the userspace filesystem's buffer.  This
+ * function waits until a request is available, then removes it from
+ * the pending list and copies request data to userspace buffer.  If
+ * no reply is needed (FORGET) or request has been aborted or there
+ * was an error during the copying then it's finished by calling
+ * fuse_request_end().  Otherwise add it to the processing list, and set
+ * the 'sent' flag.
+ */
+static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file,
+				struct fuse_copy_state *cs, size_t nbytes)
+{
+	ssize_t err;
+	struct fuse_conn *fc = fud->fc;
+	struct fuse_iqueue *fiq = &fc->iq;
+	struct fuse_pqueue *fpq = &fud->pq;
+	struct fuse_req *req;
+	struct fuse_args *args;
+	unsigned reqsize;
+	unsigned int hash;
+
+	/*
+	 * Require sane minimum read buffer - that has capacity for fixed part
+	 * of any request header + negotiated max_write room for data.
+	 *
+	 * Historically libfuse reserves 4K for fixed header room, but e.g.
+	 * GlusterFS reserves only 80 bytes
+	 *
+	 *	= `sizeof(fuse_in_header) + sizeof(fuse_write_in)`
+	 *
+	 * which is the absolute minimum any sane filesystem should be using
+	 * for header room.
+	 */
+	if (nbytes < max_t(size_t, FUSE_MIN_READ_BUFFER,
+			   sizeof(struct fuse_in_header) +
+			   sizeof(struct fuse_write_in) +
+			   fc->max_write))
+		return -EINVAL;
+
+ restart:
+	for (;;) {
+		spin_lock(&fiq->lock);
+		if (!fiq->connected || request_pending(fiq))
+			break;
+		spin_unlock(&fiq->lock);
+
+		if (file->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+		err = wait_event_interruptible_exclusive(fiq->waitq,
+				!fiq->connected || request_pending(fiq));
+		if (err)
+			return err;
+	}
+
+	if (!fiq->connected) {
+		err = fc->aborted ? -ECONNABORTED : -ENODEV;
+		goto err_unlock;
+	}
+
+	if (!list_empty(&fiq->interrupts)) {
+		req = list_entry(fiq->interrupts.next, struct fuse_req,
+				 intr_entry);
+		return fuse_read_interrupt(fiq, cs, nbytes, req);
+	}
+
+	if (forget_pending(fiq)) {
+		if (list_empty(&fiq->pending) || fiq->forget_batch-- > 0)
+			return fuse_read_forget(fc, fiq, cs, nbytes);
+
+		if (fiq->forget_batch <= -8)
+			fiq->forget_batch = 16;
+	}
+
+	req = list_entry(fiq->pending.next, struct fuse_req, list);
+	clear_bit(FR_PENDING, &req->flags);
+	list_del_init(&req->list);
+	spin_unlock(&fiq->lock);
+
+	args = req->args;
+	reqsize = req->in.h.len;
+
+	/* If request is too large, reply with an error and restart the read */
+	if (nbytes < reqsize) {
+		req->out.h.error = -EIO;
+		/* SETXATTR is special, since it may contain too large data */
+		if (args->opcode == FUSE_SETXATTR)
+			req->out.h.error = -E2BIG;
+		fuse_request_end(req);
+		goto restart;
+	}
+	spin_lock(&fpq->lock);
+	/*
+	 *  Must not put request on fpq->io queue after having been shut down by
+	 *  fuse_abort_conn()
+	 */
+	if (!fpq->connected) {
+		req->out.h.error = err = -ECONNABORTED;
+		goto out_end;
+
+	}
+	list_add(&req->list, &fpq->io);
+	spin_unlock(&fpq->lock);
+	cs->req = req;
+	err = fuse_copy_one(cs, &req->in.h, sizeof(req->in.h));
+	if (!err)
+		err = fuse_copy_args(cs, args->in_numargs, args->in_pages,
+				     (struct fuse_arg *) args->in_args, 0);
+	fuse_copy_finish(cs);
+	spin_lock(&fpq->lock);
+	clear_bit(FR_LOCKED, &req->flags);
+	if (!fpq->connected) {
+		err = fc->aborted ? -ECONNABORTED : -ENODEV;
+		goto out_end;
+	}
+	if (err) {
+		req->out.h.error = -EIO;
+		goto out_end;
+	}
+	if (!test_bit(FR_ISREPLY, &req->flags)) {
+		err = reqsize;
+		goto out_end;
+	}
+	hash = fuse_req_hash(req->in.h.unique);
+	list_move_tail(&req->list, &fpq->processing[hash]);
+	__fuse_get_request(req);
+	set_bit(FR_SENT, &req->flags);
+	spin_unlock(&fpq->lock);
+	/* matches barrier in request_wait_answer() */
+	smp_mb__after_atomic();
+	if (test_bit(FR_INTERRUPTED, &req->flags))
+		queue_interrupt(req);
+	fuse_put_request(req);
+
+	return reqsize;
+
+out_end:
+	if (!test_bit(FR_PRIVATE, &req->flags))
+		list_del_init(&req->list);
+	spin_unlock(&fpq->lock);
+	fuse_request_end(req);
+	return err;
+
+ err_unlock:
+	spin_unlock(&fiq->lock);
+	return err;
+}
+
+static int fuse_dev_open(struct inode *inode, struct file *file)
+{
+	/*
+	 * The fuse device's file's private_data is used to hold
+	 * the fuse_conn(ection) when it is mounted, and is used to
+	 * keep track of whether the file has been mounted already.
+	 */
+	file->private_data = NULL;
+	return 0;
+}
+
+static ssize_t fuse_dev_read(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct fuse_copy_state cs;
+	struct file *file = iocb->ki_filp;
+	struct fuse_dev *fud = fuse_get_dev(file);
+
+	if (!fud)
+		return -EPERM;
+
+	if (!iter_is_iovec(to))
+		return -EINVAL;
+
+	fuse_copy_init(&cs, 1, to);
+
+	return fuse_dev_do_read(fud, file, &cs, iov_iter_count(to));
+}
+
+static ssize_t fuse_dev_splice_read(struct file *in, loff_t *ppos,
+				    struct pipe_inode_info *pipe,
+				    size_t len, unsigned int flags)
+{
+	int total, ret;
+	int page_nr = 0;
+	struct pipe_buffer *bufs;
+	struct fuse_copy_state cs;
+	struct fuse_dev *fud = fuse_get_dev(in);
+
+	if (!fud)
+		return -EPERM;
+
+	bufs = kvmalloc_array(pipe->max_usage, sizeof(struct pipe_buffer),
+			      GFP_KERNEL);
+	if (!bufs)
+		return -ENOMEM;
+
+	fuse_copy_init(&cs, 1, NULL);
+	cs.pipebufs = bufs;
+	cs.pipe = pipe;
+	ret = fuse_dev_do_read(fud, in, &cs, len);
+	if (ret < 0)
+		goto out;
+
+	if (pipe_occupancy(pipe->head, pipe->tail) + cs.nr_segs > pipe->max_usage) {
+		ret = -EIO;
+		goto out;
+	}
+
+	for (ret = total = 0; page_nr < cs.nr_segs; total += ret) {
+		/*
+		 * Need to be careful about this.  Having buf->ops in module
+		 * code can Oops if the buffer persists after module unload.
+		 */
+		bufs[page_nr].ops = &nosteal_pipe_buf_ops;
+		bufs[page_nr].flags = 0;
+		ret = add_to_pipe(pipe, &bufs[page_nr++]);
+		if (unlikely(ret < 0))
+			break;
+	}
+	if (total)
+		ret = total;
+out:
+	for (; page_nr < cs.nr_segs; page_nr++)
+		put_page(bufs[page_nr].page);
+
+	kvfree(bufs);
+	return ret;
+}
+
+static int fuse_notify_poll(struct fuse_conn *fc, unsigned int size,
+			    struct fuse_copy_state *cs)
+{
+	struct fuse_notify_poll_wakeup_out outarg;
+	int err = -EINVAL;
+
+	if (size != sizeof(outarg))
+		goto err;
+
+	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
+	if (err)
+		goto err;
+
+	fuse_copy_finish(cs);
+	return fuse_notify_poll_wakeup(fc, &outarg);
+
+err:
+	fuse_copy_finish(cs);
+	return err;
+}
+
+static int fuse_notify_inval_inode(struct fuse_conn *fc, unsigned int size,
+				   struct fuse_copy_state *cs)
+{
+	struct fuse_notify_inval_inode_out outarg;
+	int err = -EINVAL;
+
+	if (size != sizeof(outarg))
+		goto err;
+
+	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
+	if (err)
+		goto err;
+	fuse_copy_finish(cs);
+
+	down_read(&fc->killsb);
+	err = fuse_reverse_inval_inode(fc, outarg.ino,
+				       outarg.off, outarg.len);
+	up_read(&fc->killsb);
+	return err;
+
+err:
+	fuse_copy_finish(cs);
+	return err;
+}
+
+static int fuse_notify_inval_entry(struct fuse_conn *fc, unsigned int size,
+				   struct fuse_copy_state *cs)
+{
+	struct fuse_notify_inval_entry_out outarg;
+	int err = -ENOMEM;
+	char *buf;
+	struct qstr name;
+
+	buf = kzalloc(FUSE_NAME_MAX + 1, GFP_KERNEL);
+	if (!buf)
+		goto err;
+
+	err = -EINVAL;
+	if (size < sizeof(outarg))
+		goto err;
+
+	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
+	if (err)
+		goto err;
+
+	err = -ENAMETOOLONG;
+	if (outarg.namelen > FUSE_NAME_MAX)
+		goto err;
+
+	err = -EINVAL;
+	if (size != sizeof(outarg) + outarg.namelen + 1)
+		goto err;
+
+	name.name = buf;
+	name.len = outarg.namelen;
+	err = fuse_copy_one(cs, buf, outarg.namelen + 1);
+	if (err)
+		goto err;
+	fuse_copy_finish(cs);
+	buf[outarg.namelen] = 0;
+
+	down_read(&fc->killsb);
+	err = fuse_reverse_inval_entry(fc, outarg.parent, 0, &name);
+	up_read(&fc->killsb);
+	kfree(buf);
+	return err;
+
+err:
+	kfree(buf);
+	fuse_copy_finish(cs);
+	return err;
+}
+
+static int fuse_notify_delete(struct fuse_conn *fc, unsigned int size,
+			      struct fuse_copy_state *cs)
+{
+	struct fuse_notify_delete_out outarg;
+	int err = -ENOMEM;
+	char *buf;
+	struct qstr name;
+
+	buf = kzalloc(FUSE_NAME_MAX + 1, GFP_KERNEL);
+	if (!buf)
+		goto err;
+
+	err = -EINVAL;
+	if (size < sizeof(outarg))
+		goto err;
+
+	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
+	if (err)
+		goto err;
+
+	err = -ENAMETOOLONG;
+	if (outarg.namelen > FUSE_NAME_MAX)
+		goto err;
+
+	err = -EINVAL;
+	if (size != sizeof(outarg) + outarg.namelen + 1)
+		goto err;
+
+	name.name = buf;
+	name.len = outarg.namelen;
+	err = fuse_copy_one(cs, buf, outarg.namelen + 1);
+	if (err)
+		goto err;
+	fuse_copy_finish(cs);
+	buf[outarg.namelen] = 0;
+
+	down_read(&fc->killsb);
+	err = fuse_reverse_inval_entry(fc, outarg.parent, outarg.child, &name);
+	up_read(&fc->killsb);
+	kfree(buf);
+	return err;
+
+err:
+	kfree(buf);
+	fuse_copy_finish(cs);
+	return err;
+}
+
+static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
+			     struct fuse_copy_state *cs)
+{
+	struct fuse_notify_store_out outarg;
+	struct inode *inode;
+	struct address_space *mapping;
+	u64 nodeid;
+	int err;
+	pgoff_t index;
+	unsigned int offset;
+	unsigned int num;
+	loff_t file_size;
+	loff_t end;
+
+	err = -EINVAL;
+	if (size < sizeof(outarg))
+		goto out_finish;
+
+	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
+	if (err)
+		goto out_finish;
+
+	err = -EINVAL;
+	if (size - sizeof(outarg) != outarg.size)
+		goto out_finish;
+
+	nodeid = outarg.nodeid;
+
+	down_read(&fc->killsb);
+
+	err = -ENOENT;
+	inode = fuse_ilookup(fc, nodeid,  NULL);
+	if (!inode)
+		goto out_up_killsb;
+
+	mapping = inode->i_mapping;
+	index = outarg.offset >> PAGE_SHIFT;
+	offset = outarg.offset & ~PAGE_MASK;
+	file_size = i_size_read(inode);
+	end = outarg.offset + outarg.size;
+	if (end > file_size) {
+		file_size = end;
+		fuse_write_update_size(inode, file_size);
+	}
+
+	num = outarg.size;
+	while (num) {
+		struct page *page;
+		unsigned int this_num;
+
+		err = -ENOMEM;
+		page = find_or_create_page(mapping, index,
+					   mapping_gfp_mask(mapping));
+		if (!page)
+			goto out_iput;
+
+		this_num = min_t(unsigned, num, PAGE_SIZE - offset);
+		err = fuse_copy_page(cs, &page, offset, this_num, 0);
+		if (!err && offset == 0 &&
+		    (this_num == PAGE_SIZE || file_size == end))
+			SetPageUptodate(page);
+		unlock_page(page);
+		put_page(page);
+
+		if (err)
+			goto out_iput;
+
+		num -= this_num;
+		offset = 0;
+		index++;
+	}
+
+	err = 0;
+
+out_iput:
+	iput(inode);
+out_up_killsb:
+	up_read(&fc->killsb);
+out_finish:
+	fuse_copy_finish(cs);
+	return err;
+}
+
+struct fuse_retrieve_args {
+	struct fuse_args_pages ap;
+	struct fuse_notify_retrieve_in inarg;
+};
+
+static void fuse_retrieve_end(struct fuse_mount *fm, struct fuse_args *args,
+			      int error)
+{
+	struct fuse_retrieve_args *ra =
+		container_of(args, typeof(*ra), ap.args);
+
+	release_pages(ra->ap.pages, ra->ap.num_pages);
+	kfree(ra);
+}
+
+static int fuse_retrieve(struct fuse_mount *fm, struct inode *inode,
+			 struct fuse_notify_retrieve_out *outarg)
+{
+	int err;
+	struct address_space *mapping = inode->i_mapping;
+	pgoff_t index;
+	loff_t file_size;
+	unsigned int num;
+	unsigned int offset;
+	size_t total_len = 0;
+	unsigned int num_pages;
+	struct fuse_conn *fc = fm->fc;
+	struct fuse_retrieve_args *ra;
+	size_t args_size = sizeof(*ra);
+	struct fuse_args_pages *ap;
+	struct fuse_args *args;
+
+	offset = outarg->offset & ~PAGE_MASK;
+	file_size = i_size_read(inode);
+
+	num = min(outarg->size, fc->max_write);
+	if (outarg->offset > file_size)
+		num = 0;
+	else if (outarg->offset + num > file_size)
+		num = file_size - outarg->offset;
+
+	num_pages = (num + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	num_pages = min(num_pages, fc->max_pages);
+
+	args_size += num_pages * (sizeof(ap->pages[0]) + sizeof(ap->descs[0]));
+
+	ra = kzalloc(args_size, GFP_KERNEL);
+	if (!ra)
+		return -ENOMEM;
+
+	ap = &ra->ap;
+	ap->pages = (void *) (ra + 1);
+	ap->descs = (void *) (ap->pages + num_pages);
+
+	args = &ap->args;
+	args->nodeid = outarg->nodeid;
+	args->opcode = FUSE_NOTIFY_REPLY;
+	args->in_numargs = 2;
+	args->in_pages = true;
+	args->end = fuse_retrieve_end;
+
+	index = outarg->offset >> PAGE_SHIFT;
+
+	while (num && ap->num_pages < num_pages) {
+		struct page *page;
+		unsigned int this_num;
+
+		page = find_get_page(mapping, index);
+		if (!page)
+			break;
+
+		this_num = min_t(unsigned, num, PAGE_SIZE - offset);
+		ap->pages[ap->num_pages] = page;
+		ap->descs[ap->num_pages].offset = offset;
+		ap->descs[ap->num_pages].length = this_num;
+		ap->num_pages++;
+
+		offset = 0;
+		num -= this_num;
+		total_len += this_num;
+		index++;
+	}
+	ra->inarg.offset = outarg->offset;
+	ra->inarg.size = total_len;
+	args->in_args[0].size = sizeof(ra->inarg);
+	args->in_args[0].value = &ra->inarg;
+	args->in_args[1].size = total_len;
+
+	err = fuse_simple_notify_reply(fm, args, outarg->notify_unique);
+	if (err)
+		fuse_retrieve_end(fm, args, err);
+
+	return err;
+}
+
+static int fuse_notify_retrieve(struct fuse_conn *fc, unsigned int size,
+				struct fuse_copy_state *cs)
+{
+	struct fuse_notify_retrieve_out outarg;
+	struct fuse_mount *fm;
+	struct inode *inode;
+	u64 nodeid;
+	int err;
+
+	err = -EINVAL;
+	if (size != sizeof(outarg))
+		goto copy_finish;
+
+	err = fuse_copy_one(cs, &outarg, sizeof(outarg));
+	if (err)
+		goto copy_finish;
+
+	fuse_copy_finish(cs);
+
+	down_read(&fc->killsb);
+	err = -ENOENT;
+	nodeid = outarg.nodeid;
+
+	inode = fuse_ilookup(fc, nodeid, &fm);
+	if (inode) {
+		err = fuse_retrieve(fm, inode, &outarg);
+		iput(inode);
+	}
+	up_read(&fc->killsb);
+
+	return err;
+
+copy_finish:
+	fuse_copy_finish(cs);
+	return err;
+}
+
+static int fuse_notify(struct fuse_conn *fc, enum fuse_notify_code code,
+		       unsigned int size, struct fuse_copy_state *cs)
+{
+	/* Don't try to move pages (yet) */
+	cs->move_pages = 0;
+
+	switch (code) {
+	case FUSE_NOTIFY_POLL:
+		return fuse_notify_poll(fc, size, cs);
+
+	case FUSE_NOTIFY_INVAL_INODE:
+		return fuse_notify_inval_inode(fc, size, cs);
+
+	case FUSE_NOTIFY_INVAL_ENTRY:
+		return fuse_notify_inval_entry(fc, size, cs);
+
+	case FUSE_NOTIFY_STORE:
+		return fuse_notify_store(fc, size, cs);
+
+	case FUSE_NOTIFY_RETRIEVE:
+		return fuse_notify_retrieve(fc, size, cs);
+
+	case FUSE_NOTIFY_DELETE:
+		return fuse_notify_delete(fc, size, cs);
+
+	default:
+		fuse_copy_finish(cs);
+		return -EINVAL;
+	}
+}
+
+/* Look up request on processing list by unique ID */
+static struct fuse_req *request_find(struct fuse_pqueue *fpq, u64 unique)
+{
+	unsigned int hash = fuse_req_hash(unique);
+	struct fuse_req *req;
+
+	list_for_each_entry(req, &fpq->processing[hash], list) {
+		if (req->in.h.unique == unique)
+			return req;
+	}
+	return NULL;
+}
+
+static int copy_out_args(struct fuse_copy_state *cs, struct fuse_args *args,
+			 unsigned nbytes)
+{
+	unsigned reqsize = sizeof(struct fuse_out_header);
+
+	reqsize += fuse_len_args(args->out_numargs, args->out_args);
+
+	if (reqsize < nbytes || (reqsize > nbytes && !args->out_argvar))
+		return -EINVAL;
+	else if (reqsize > nbytes) {
+		struct fuse_arg *lastarg = &args->out_args[args->out_numargs-1];
+		unsigned diffsize = reqsize - nbytes;
+
+		if (diffsize > lastarg->size)
+			return -EINVAL;
+		lastarg->size -= diffsize;
+	}
+	return fuse_copy_args(cs, args->out_numargs, args->out_pages,
+			      args->out_args, args->page_zeroing);
+}
+
+/*
+ * Write a single reply to a request.  First the header is copied from
+ * the write buffer.  The request is then searched on the processing
+ * list by the unique ID found in the header.  If found, then remove
+ * it from the list and copy the rest of the buffer to the request.
+ * The request is finished by calling fuse_request_end().
+ */
+static ssize_t fuse_dev_do_write(struct fuse_dev *fud,
+				 struct fuse_copy_state *cs, size_t nbytes)
+{
+	int err;
+	struct fuse_conn *fc = fud->fc;
+	struct fuse_pqueue *fpq = &fud->pq;
+	struct fuse_req *req;
+	struct fuse_out_header oh;
+
+	err = -EINVAL;
+	if (nbytes < sizeof(struct fuse_out_header))
+		goto out;
+
+	err = fuse_copy_one(cs, &oh, sizeof(oh));
+	if (err)
+		goto copy_finish;
+
+	err = -EINVAL;
+	if (oh.len != nbytes)
+		goto copy_finish;
+
+	/*
+	 * Zero oh.unique indicates unsolicited notification message
+	 * and error contains notification code.
+	 */
+	if (!oh.unique) {
+		err = fuse_notify(fc, oh.error, nbytes - sizeof(oh), cs);
+		goto out;
+	}
+
+	err = -EINVAL;
+	if (oh.error <= -512 || oh.error > 0)
+		goto copy_finish;
+
+	spin_lock(&fpq->lock);
+	req = NULL;
+	if (fpq->connected)
+		req = request_find(fpq, oh.unique & ~FUSE_INT_REQ_BIT);
+
+	err = -ENOENT;
+	if (!req) {
+		spin_unlock(&fpq->lock);
+		goto copy_finish;
+	}
+
+	/* Is it an interrupt reply ID? */
+	if (oh.unique & FUSE_INT_REQ_BIT) {
+		__fuse_get_request(req);
+		spin_unlock(&fpq->lock);
+
+		err = 0;
+		if (nbytes != sizeof(struct fuse_out_header))
+			err = -EINVAL;
+		else if (oh.error == -ENOSYS)
+			fc->no_interrupt = 1;
+		else if (oh.error == -EAGAIN)
+			err = queue_interrupt(req);
+
+		fuse_put_request(req);
+
+		goto copy_finish;
+	}
+
+	clear_bit(FR_SENT, &req->flags);
+	list_move(&req->list, &fpq->io);
+	req->out.h = oh;
+	set_bit(FR_LOCKED, &req->flags);
+	spin_unlock(&fpq->lock);
+	cs->req = req;
+	if (!req->args->page_replace)
+		cs->move_pages = 0;
+
+	if (oh.error)
+		err = nbytes != sizeof(oh) ? -EINVAL : 0;
+	else
+		err = copy_out_args(cs, req->args, nbytes);
+	fuse_copy_finish(cs);
+
+	spin_lock(&fpq->lock);
+	clear_bit(FR_LOCKED, &req->flags);
+	if (!fpq->connected)
+		err = -ENOENT;
+	else if (err)
+		req->out.h.error = -EIO;
+	if (!test_bit(FR_PRIVATE, &req->flags))
+		list_del_init(&req->list);
+	spin_unlock(&fpq->lock);
+
+	fuse_request_end(req);
+out:
+	return err ? err : nbytes;
+
+copy_finish:
+	fuse_copy_finish(cs);
+	goto out;
+}
+
+static ssize_t fuse_dev_write(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct fuse_copy_state cs;
+	struct fuse_dev *fud = fuse_get_dev(iocb->ki_filp);
+
+	if (!fud)
+		return -EPERM;
+
+	if (!iter_is_iovec(from))
+		return -EINVAL;
+
+	fuse_copy_init(&cs, 0, from);
+
+	return fuse_dev_do_write(fud, &cs, iov_iter_count(from));
+}
+
+static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
+				     struct file *out, loff_t *ppos,
+				     size_t len, unsigned int flags)
+{
+	unsigned int head, tail, mask, count;
+	unsigned nbuf;
+	unsigned idx;
+	struct pipe_buffer *bufs;
+	struct fuse_copy_state cs;
+	struct fuse_dev *fud;
+	size_t rem;
+	ssize_t ret;
+
+	fud = fuse_get_dev(out);
+	if (!fud)
+		return -EPERM;
+
+	pipe_lock(pipe);
+
+	head = pipe->head;
+	tail = pipe->tail;
+	mask = pipe->ring_size - 1;
+	count = head - tail;
+
+	bufs = kvmalloc_array(count, sizeof(struct pipe_buffer), GFP_KERNEL);
+	if (!bufs) {
+		pipe_unlock(pipe);
+		return -ENOMEM;
+	}
+
+	nbuf = 0;
+	rem = 0;
+	for (idx = tail; idx != head && rem < len; idx++)
+		rem += pipe->bufs[idx & mask].len;
+
+	ret = -EINVAL;
+	if (rem < len)
+		goto out_free;
+
+	rem = len;
+	while (rem) {
+		struct pipe_buffer *ibuf;
+		struct pipe_buffer *obuf;
+
+		if (WARN_ON(nbuf >= count || tail == head))
+			goto out_free;
+
+		ibuf = &pipe->bufs[tail & mask];
+		obuf = &bufs[nbuf];
+
+		if (rem >= ibuf->len) {
+			*obuf = *ibuf;
+			ibuf->ops = NULL;
+			tail++;
+			pipe->tail = tail;
+		} else {
+			if (!pipe_buf_get(pipe, ibuf))
+				goto out_free;
+
+			*obuf = *ibuf;
+			obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
+			obuf->len = rem;
+			ibuf->offset += obuf->len;
+			ibuf->len -= obuf->len;
+		}
+		nbuf++;
+		rem -= obuf->len;
+	}
+	pipe_unlock(pipe);
+
+	fuse_copy_init(&cs, 0, NULL);
+	cs.pipebufs = bufs;
+	cs.nr_segs = nbuf;
+	cs.pipe = pipe;
+
+	if (flags & SPLICE_F_MOVE)
+		cs.move_pages = 1;
+
+	ret = fuse_dev_do_write(fud, &cs, len);
+
+	pipe_lock(pipe);
+out_free:
+	for (idx = 0; idx < nbuf; idx++) {
+		struct pipe_buffer *buf = &bufs[idx];
+
+		if (buf->ops)
+			pipe_buf_release(pipe, buf);
+	}
+	pipe_unlock(pipe);
+
+	kvfree(bufs);
+	return ret;
+}
+
+static __poll_t fuse_dev_poll(struct file *file, poll_table *wait)
+{
+	__poll_t mask = EPOLLOUT | EPOLLWRNORM;
+	struct fuse_iqueue *fiq;
+	struct fuse_dev *fud = fuse_get_dev(file);
+
+	if (!fud)
+		return EPOLLERR;
+
+	fiq = &fud->fc->iq;
+	poll_wait(file, &fiq->waitq, wait);
+
+	spin_lock(&fiq->lock);
+	if (!fiq->connected)
+		mask = EPOLLERR;
+	else if (request_pending(fiq))
+		mask |= EPOLLIN | EPOLLRDNORM;
+	spin_unlock(&fiq->lock);
+
+	return mask;
+}
+
+/* Abort all requests on the given list (pending or processing) */
+static void end_requests(struct list_head *head)
+{
+	while (!list_empty(head)) {
+		struct fuse_req *req;
+		req = list_entry(head->next, struct fuse_req, list);
+		req->out.h.error = -ECONNABORTED;
+		clear_bit(FR_SENT, &req->flags);
+		list_del_init(&req->list);
+		fuse_request_end(req);
+	}
+}
+
+static void end_polls(struct fuse_conn *fc)
+{
+	struct rb_node *p;
+
+	p = rb_first(&fc->polled_files);
+
+	while (p) {
+		struct fuse_file *ff;
+		ff = rb_entry(p, struct fuse_file, polled_node);
+		wake_up_interruptible_all(&ff->poll_wait);
+
+		p = rb_next(p);
+	}
+}
+
+/*
+ * Abort all requests.
+ *
+ * Emergency exit in case of a malicious or accidental deadlock, or just a hung
+ * filesystem.
+ *
+ * The same effect is usually achievable through killing the filesystem daemon
+ * and all users of the filesystem.  The exception is the combination of an
+ * asynchronous request and the tricky deadlock (see
+ * Documentation/filesystems/fuse.rst).
+ *
+ * Aborting requests under I/O goes as follows: 1: Separate out unlocked
+ * requests, they should be finished off immediately.  Locked requests will be
+ * finished after unlock; see unlock_request(). 2: Finish off the unlocked
+ * requests.  It is possible that some request will finish before we can.  This
+ * is OK, the request will in that case be removed from the list before we touch
+ * it.
+ */
+void fuse_abort_conn(struct fuse_conn *fc)
+{
+	struct fuse_iqueue *fiq = &fc->iq;
+
+	spin_lock(&fc->lock);
+	if (fc->connected) {
+		struct fuse_dev *fud;
+		struct fuse_req *req, *next;
+		LIST_HEAD(to_end);
+		unsigned int i;
+
+		/* Background queuing checks fc->connected under bg_lock */
+		spin_lock(&fc->bg_lock);
+		fc->connected = 0;
+		spin_unlock(&fc->bg_lock);
+
+		fuse_set_initialized(fc);
+		list_for_each_entry(fud, &fc->devices, entry) {
+			struct fuse_pqueue *fpq = &fud->pq;
+
+			spin_lock(&fpq->lock);
+			fpq->connected = 0;
+			list_for_each_entry_safe(req, next, &fpq->io, list) {
+				req->out.h.error = -ECONNABORTED;
+				spin_lock(&req->waitq.lock);
+				set_bit(FR_ABORTED, &req->flags);
+				if (!test_bit(FR_LOCKED, &req->flags)) {
+					set_bit(FR_PRIVATE, &req->flags);
+					__fuse_get_request(req);
+					list_move(&req->list, &to_end);
+				}
+				spin_unlock(&req->waitq.lock);
+			}
+			for (i = 0; i < FUSE_PQ_HASH_SIZE; i++)
+				list_splice_tail_init(&fpq->processing[i],
+						      &to_end);
+			spin_unlock(&fpq->lock);
+		}
+		spin_lock(&fc->bg_lock);
+		fc->blocked = 0;
+		fc->max_background = UINT_MAX;
+		flush_bg_queue(fc);
+		spin_unlock(&fc->bg_lock);
+
+		spin_lock(&fiq->lock);
+		fiq->connected = 0;
+		list_for_each_entry(req, &fiq->pending, list)
+			clear_bit(FR_PENDING, &req->flags);
+		list_splice_tail_init(&fiq->pending, &to_end);
+		while (forget_pending(fiq))
+			kfree(fuse_dequeue_forget(fiq, 1, NULL));
+		wake_up_all(&fiq->waitq);
+		spin_unlock(&fiq->lock);
+		kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
+		end_polls(fc);
+		wake_up_all(&fc->blocked_waitq);
+		spin_unlock(&fc->lock);
+
+		end_requests(&to_end);
+	} else {
+		spin_unlock(&fc->lock);
+	}
+}
+EXPORT_SYMBOL_GPL(fuse_abort_conn);
+
+void fuse_wait_aborted(struct fuse_conn *fc)
+{
+	/* matches implicit memory barrier in fuse_drop_waiting() */
+	smp_mb();
+	wait_event(fc->blocked_waitq, atomic_read(&fc->num_waiting) == 0);
+}
+
+int fuse_dev_release(struct inode *inode, struct file *file)
+{
+	struct fuse_dev *fud = fuse_get_dev(file);
+
+	if (fud) {
+		struct fuse_conn *fc = fud->fc;
+		struct fuse_pqueue *fpq = &fud->pq;
+		LIST_HEAD(to_end);
+		unsigned int i;
+
+		spin_lock(&fpq->lock);
+		WARN_ON(!list_empty(&fpq->io));
+		for (i = 0; i < FUSE_PQ_HASH_SIZE; i++)
+			list_splice_init(&fpq->processing[i], &to_end);
+		spin_unlock(&fpq->lock);
+
+		end_requests(&to_end);
+
+		/* Are we the last open device? */
+		if (atomic_dec_and_test(&fc->dev_count)) {
+			WARN_ON(fc->iq.fasync != NULL);
+			fuse_abort_conn(fc);
+		}
+		fuse_dev_free(fud);
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fuse_dev_release);
+
+static int fuse_dev_fasync(int fd, struct file *file, int on)
+{
+	struct fuse_dev *fud = fuse_get_dev(file);
+
+	if (!fud)
+		return -EPERM;
+
+	/* No locking - fasync_helper does its own locking */
+	return fasync_helper(fd, file, on, &fud->fc->iq.fasync);
+}
+
+static int fuse_device_clone(struct fuse_conn *fc, struct file *new)
+{
+	struct fuse_dev *fud;
+
+	if (new->private_data)
+		return -EINVAL;
+
+	fud = fuse_dev_alloc_install(fc);
+	if (!fud)
+		return -ENOMEM;
+
+	new->private_data = fud;
+	atomic_inc(&fc->dev_count);
+
+	return 0;
+}
+
+static long fuse_dev_ioctl(struct file *file, unsigned int cmd,
+			   unsigned long arg)
+{
+	int err = -ENOTTY;
+
+	if (cmd == FUSE_DEV_IOC_CLONE) {
+		int oldfd;
+
+		err = -EFAULT;
+		if (!get_user(oldfd, (__u32 __user *) arg)) {
+			struct file *old = fget(oldfd);
+
+			err = -EINVAL;
+			if (old) {
+				struct fuse_dev *fud = NULL;
+
+				/*
+				 * Check against file->f_op because CUSE
+				 * uses the same ioctl handler.
+				 */
+				if (old->f_op == file->f_op &&
+				    old->f_cred->user_ns == file->f_cred->user_ns)
+					fud = fuse_get_dev(old);
+
+				if (fud) {
+					mutex_lock(&fuse_mutex);
+					err = fuse_device_clone(fud->fc, file);
+					mutex_unlock(&fuse_mutex);
+				}
+				fput(old);
+			}
+		}
+	}
+	return err;
+}
+
+const struct file_operations fuse_dev_operations = {
+	.owner		= THIS_MODULE,
+	.open		= fuse_dev_open,
+	.llseek		= no_llseek,
+	.read_iter	= fuse_dev_read,
+	.splice_read	= fuse_dev_splice_read,
+	.write_iter	= fuse_dev_write,
+	.splice_write	= fuse_dev_splice_write,
+	.poll		= fuse_dev_poll,
+	.release	= fuse_dev_release,
+	.fasync		= fuse_dev_fasync,
+	.unlocked_ioctl = fuse_dev_ioctl,
+	.compat_ioctl   = compat_ptr_ioctl,
+};
+EXPORT_SYMBOL_GPL(fuse_dev_operations);
+
+static struct miscdevice fuse_miscdevice = {
+	.minor = FUSE_MINOR,
+	.name  = "fuse",
+	.fops = &fuse_dev_operations,
+};
+
+int __init fuse_dev_init(void)
+{
+	int err = -ENOMEM;
+	fuse_req_cachep = kmem_cache_create("fuse_request",
+					    sizeof(struct fuse_req),
+					    0, 0, NULL);
+	if (!fuse_req_cachep)
+		goto out;
+
+	err = misc_register(&fuse_miscdevice);
+	if (err)
+		goto out_cache_clean;
+
+	return 0;
+
+ out_cache_clean:
+	kmem_cache_destroy(fuse_req_cachep);
+ out:
+	return err;
+}
+
+void fuse_dev_cleanup(void)
+{
+	misc_deregister(&fuse_miscdevice);
+	kmem_cache_destroy(fuse_req_cachep);
+}
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
new file mode 100644
index 000000000..b0c701c00
--- /dev/null
+++ b/fs/fuse/dir.c
@@ -0,0 +1,1945 @@
+/*
+  FUSE: Filesystem in Userspace
+  Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>
+
+  This program can be distributed under the terms of the GNU GPL.
+  See the file COPYING.
+*/
+
+#include "fuse_i.h"
+
+#include <linux/pagemap.h>
+#include <linux/file.h>
+#include <linux/fs_context.h>
+#include <linux/sched.h>
+#include <linux/namei.h>
+#include <linux/slab.h>
+#include <linux/xattr.h>
+#include <linux/iversion.h>
+#include <linux/posix_acl.h>
+
+static void fuse_advise_use_readdirplus(struct inode *dir)
+{
+	struct fuse_inode *fi = get_fuse_inode(dir);
+
+	set_bit(FUSE_I_ADVISE_RDPLUS, &fi->state);
+}
+
+#if BITS_PER_LONG >= 64
+static inline void __fuse_dentry_settime(struct dentry *entry, u64 time)
+{
+	entry->d_fsdata = (void *) time;
+}
+
+static inline u64 fuse_dentry_time(const struct dentry *entry)
+{
+	return (u64)entry->d_fsdata;
+}
+
+#else
+union fuse_dentry {
+	u64 time;
+	struct rcu_head rcu;
+};
+
+static inline void __fuse_dentry_settime(struct dentry *dentry, u64 time)
+{
+	((union fuse_dentry *) dentry->d_fsdata)->time = time;
+}
+
+static inline u64 fuse_dentry_time(const struct dentry *entry)
+{
+	return ((union fuse_dentry *) entry->d_fsdata)->time;
+}
+#endif
+
+static void fuse_dentry_settime(struct dentry *dentry, u64 time)
+{
+	struct fuse_conn *fc = get_fuse_conn_super(dentry->d_sb);
+	bool delete = !time && fc->delete_stale;
+	/*
+	 * Mess with DCACHE_OP_DELETE because dput() will be faster without it.
+	 * Don't care about races, either way it's just an optimization
+	 */
+	if ((!delete && (dentry->d_flags & DCACHE_OP_DELETE)) ||
+	    (delete && !(dentry->d_flags & DCACHE_OP_DELETE))) {
+		spin_lock(&dentry->d_lock);
+		if (!delete)
+			dentry->d_flags &= ~DCACHE_OP_DELETE;
+		else
+			dentry->d_flags |= DCACHE_OP_DELETE;
+		spin_unlock(&dentry->d_lock);
+	}
+
+	__fuse_dentry_settime(dentry, time);
+}
+
+/*
+ * FUSE caches dentries and attributes with separate timeout.  The
+ * time in jiffies until the dentry/attributes are valid is stored in
+ * dentry->d_fsdata and fuse_inode->i_time respectively.
+ */
+
+/*
+ * Calculate the time in jiffies until a dentry/attributes are valid
+ */
+static u64 time_to_jiffies(u64 sec, u32 nsec)
+{
+	if (sec || nsec) {
+		struct timespec64 ts = {
+			sec,
+			min_t(u32, nsec, NSEC_PER_SEC - 1)
+		};
+
+		return get_jiffies_64() + timespec64_to_jiffies(&ts);
+	} else
+		return 0;
+}
+
+/*
+ * Set dentry and possibly attribute timeouts from the lookup/mk*
+ * replies
+ */
+void fuse_change_entry_timeout(struct dentry *entry, struct fuse_entry_out *o)
+{
+	fuse_dentry_settime(entry,
+		time_to_jiffies(o->entry_valid, o->entry_valid_nsec));
+}
+
+static u64 attr_timeout(struct fuse_attr_out *o)
+{
+	return time_to_jiffies(o->attr_valid, o->attr_valid_nsec);
+}
+
+u64 entry_attr_timeout(struct fuse_entry_out *o)
+{
+	return time_to_jiffies(o->attr_valid, o->attr_valid_nsec);
+}
+
+static void fuse_invalidate_attr_mask(struct inode *inode, u32 mask)
+{
+	set_mask_bits(&get_fuse_inode(inode)->inval_mask, 0, mask);
+}
+
+/*
+ * Mark the attributes as stale, so that at the next call to
+ * ->getattr() they will be fetched from userspace
+ */
+void fuse_invalidate_attr(struct inode *inode)
+{
+	fuse_invalidate_attr_mask(inode, STATX_BASIC_STATS);
+}
+
+static void fuse_dir_changed(struct inode *dir)
+{
+	fuse_invalidate_attr(dir);
+	inode_maybe_inc_iversion(dir, false);
+}
+
+/**
+ * Mark the attributes as stale due to an atime change.  Avoid the invalidate if
+ * atime is not used.
+ */
+void fuse_invalidate_atime(struct inode *inode)
+{
+	if (!IS_RDONLY(inode))
+		fuse_invalidate_attr_mask(inode, STATX_ATIME);
+}
+
+/*
+ * Just mark the entry as stale, so that a next attempt to look it up
+ * will result in a new lookup call to userspace
+ *
+ * This is called when a dentry is about to become negative and the
+ * timeout is unknown (unlink, rmdir, rename and in some cases
+ * lookup)
+ */
+void fuse_invalidate_entry_cache(struct dentry *entry)
+{
+	fuse_dentry_settime(entry, 0);
+}
+
+/*
+ * Same as fuse_invalidate_entry_cache(), but also try to remove the
+ * dentry from the hash
+ */
+static void fuse_invalidate_entry(struct dentry *entry)
+{
+	d_invalidate(entry);
+	fuse_invalidate_entry_cache(entry);
+}
+
+static void fuse_lookup_init(struct fuse_conn *fc, struct fuse_args *args,
+			     u64 nodeid, const struct qstr *name,
+			     struct fuse_entry_out *outarg)
+{
+	memset(outarg, 0, sizeof(struct fuse_entry_out));
+	args->opcode = FUSE_LOOKUP;
+	args->nodeid = nodeid;
+	args->in_numargs = 1;
+	args->in_args[0].size = name->len + 1;
+	args->in_args[0].value = name->name;
+	args->out_numargs = 1;
+	args->out_args[0].size = sizeof(struct fuse_entry_out);
+	args->out_args[0].value = outarg;
+}
+
+/*
+ * Check whether the dentry is still valid
+ *
+ * If the entry validity timeout has expired and the dentry is
+ * positive, try to redo the lookup.  If the lookup results in a
+ * different inode, then let the VFS invalidate the dentry and redo
+ * the lookup once more.  If the lookup results in the same inode,
+ * then refresh the attributes, timeouts and mark the dentry valid.
+ */
+static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
+{
+	struct inode *inode;
+	struct dentry *parent;
+	struct fuse_mount *fm;
+	struct fuse_inode *fi;
+	int ret;
+
+	inode = d_inode_rcu(entry);
+	if (inode && fuse_is_bad(inode))
+		goto invalid;
+	else if (time_before64(fuse_dentry_time(entry), get_jiffies_64()) ||
+		 (flags & (LOOKUP_EXCL | LOOKUP_REVAL | LOOKUP_RENAME_TARGET))) {
+		struct fuse_entry_out outarg;
+		FUSE_ARGS(args);
+		struct fuse_forget_link *forget;
+		u64 attr_version;
+
+		/* For negative dentries, always do a fresh lookup */
+		if (!inode)
+			goto invalid;
+
+		ret = -ECHILD;
+		if (flags & LOOKUP_RCU)
+			goto out;
+
+		fm = get_fuse_mount(inode);
+
+		forget = fuse_alloc_forget();
+		ret = -ENOMEM;
+		if (!forget)
+			goto out;
+
+		attr_version = fuse_get_attr_version(fm->fc);
+
+		parent = dget_parent(entry);
+		fuse_lookup_init(fm->fc, &args, get_node_id(d_inode(parent)),
+				 &entry->d_name, &outarg);
+		ret = fuse_simple_request(fm, &args);
+		dput(parent);
+		/* Zero nodeid is same as -ENOENT */
+		if (!ret && !outarg.nodeid)
+			ret = -ENOENT;
+		if (!ret) {
+			fi = get_fuse_inode(inode);
+			if (outarg.nodeid != get_node_id(inode) ||
+			    (bool) IS_AUTOMOUNT(inode) != (bool) (outarg.attr.flags & FUSE_ATTR_SUBMOUNT)) {
+				fuse_queue_forget(fm->fc, forget,
+						  outarg.nodeid, 1);
+				goto invalid;
+			}
+			spin_lock(&fi->lock);
+			fi->nlookup++;
+			spin_unlock(&fi->lock);
+		}
+		kfree(forget);
+		if (ret == -ENOMEM || ret == -EINTR)
+			goto out;
+		if (ret || fuse_invalid_attr(&outarg.attr) ||
+		    fuse_stale_inode(inode, outarg.generation, &outarg.attr))
+			goto invalid;
+
+		forget_all_cached_acls(inode);
+		fuse_change_attributes(inode, &outarg.attr,
+				       entry_attr_timeout(&outarg),
+				       attr_version);
+		fuse_change_entry_timeout(entry, &outarg);
+	} else if (inode) {
+		fi = get_fuse_inode(inode);
+		if (flags & LOOKUP_RCU) {
+			if (test_bit(FUSE_I_INIT_RDPLUS, &fi->state))
+				return -ECHILD;
+		} else if (test_and_clear_bit(FUSE_I_INIT_RDPLUS, &fi->state)) {
+			parent = dget_parent(entry);
+			fuse_advise_use_readdirplus(d_inode(parent));
+			dput(parent);
+		}
+	}
+	ret = 1;
+out:
+	return ret;
+
+invalid:
+	ret = 0;
+	goto out;
+}
+
+#if BITS_PER_LONG < 64
+static int fuse_dentry_init(struct dentry *dentry)
+{
+	dentry->d_fsdata = kzalloc(sizeof(union fuse_dentry),
+				   GFP_KERNEL_ACCOUNT | __GFP_RECLAIMABLE);
+
+	return dentry->d_fsdata ? 0 : -ENOMEM;
+}
+static void fuse_dentry_release(struct dentry *dentry)
+{
+	union fuse_dentry *fd = dentry->d_fsdata;
+
+	kfree_rcu(fd, rcu);
+}
+#endif
+
+static int fuse_dentry_delete(const struct dentry *dentry)
+{
+	return time_before64(fuse_dentry_time(dentry), get_jiffies_64());
+}
+
+/*
+ * Create a fuse_mount object with a new superblock (with path->dentry
+ * as the root), and return that mount so it can be auto-mounted on
+ * @path.
+ */
+static struct vfsmount *fuse_dentry_automount(struct path *path)
+{
+	struct fs_context *fsc;
+	struct fuse_mount *parent_fm = get_fuse_mount_super(path->mnt->mnt_sb);
+	struct fuse_conn *fc = parent_fm->fc;
+	struct fuse_mount *fm;
+	struct vfsmount *mnt;
+	struct fuse_inode *mp_fi = get_fuse_inode(d_inode(path->dentry));
+	struct super_block *sb;
+	int err;
+
+	fsc = fs_context_for_submount(path->mnt->mnt_sb->s_type, path->dentry);
+	if (IS_ERR(fsc)) {
+		err = PTR_ERR(fsc);
+		goto out;
+	}
+
+	err = -ENOMEM;
+	fm = kzalloc(sizeof(struct fuse_mount), GFP_KERNEL);
+	if (!fm)
+		goto out_put_fsc;
+
+	refcount_set(&fm->count, 1);
+	fsc->s_fs_info = fm;
+	sb = sget_fc(fsc, NULL, set_anon_super_fc);
+	if (IS_ERR(sb)) {
+		err = PTR_ERR(sb);
+		fuse_mount_put(fm);
+		goto out_put_fsc;
+	}
+	fm->fc = fuse_conn_get(fc);
+
+	/* Initialize superblock, making @mp_fi its root */
+	err = fuse_fill_super_submount(sb, mp_fi);
+	if (err) {
+		fuse_conn_put(fc);
+		kfree(fm);
+		sb->s_fs_info = NULL;
+		goto out_put_sb;
+	}
+
+	down_write(&fc->killsb);
+	list_add_tail(&fm->fc_entry, &fc->mounts);
+	up_write(&fc->killsb);
+
+	sb->s_flags |= SB_ACTIVE;
+	fsc->root = dget(sb->s_root);
+
+	/*
+	 * FIXME: setting SB_BORN requires a write barrier for
+	 *        super_cache_count(). We should actually come
+	 *        up with a proper ->get_tree() implementation
+	 *        for submounts and call vfs_get_tree() to take
+	 *        care of the write barrier.
+	 */
+	smp_wmb();
+	sb->s_flags |= SB_BORN;
+
+	/* We are done configuring the superblock, so unlock it */
+	up_write(&sb->s_umount);
+
+	/* Create the submount */
+	mnt = vfs_create_mount(fsc);
+	if (IS_ERR(mnt)) {
+		err = PTR_ERR(mnt);
+		goto out_put_fsc;
+	}
+	mntget(mnt);
+	put_fs_context(fsc);
+	return mnt;
+
+out_put_sb:
+	/*
+	 * Only jump here when fsc->root is NULL and sb is still locked
+	 * (otherwise put_fs_context() will put the superblock)
+	 */
+	deactivate_locked_super(sb);
+out_put_fsc:
+	put_fs_context(fsc);
+out:
+	return ERR_PTR(err);
+}
+
+const struct dentry_operations fuse_dentry_operations = {
+	.d_revalidate	= fuse_dentry_revalidate,
+	.d_delete	= fuse_dentry_delete,
+#if BITS_PER_LONG < 64
+	.d_init		= fuse_dentry_init,
+	.d_release	= fuse_dentry_release,
+#endif
+	.d_automount	= fuse_dentry_automount,
+};
+
+const struct dentry_operations fuse_root_dentry_operations = {
+#if BITS_PER_LONG < 64
+	.d_init		= fuse_dentry_init,
+	.d_release	= fuse_dentry_release,
+#endif
+};
+
+int fuse_valid_type(int m)
+{
+	return S_ISREG(m) || S_ISDIR(m) || S_ISLNK(m) || S_ISCHR(m) ||
+		S_ISBLK(m) || S_ISFIFO(m) || S_ISSOCK(m);
+}
+
+bool fuse_invalid_attr(struct fuse_attr *attr)
+{
+	return !fuse_valid_type(attr->mode) ||
+		attr->size > LLONG_MAX;
+}
+
+int fuse_lookup_name(struct super_block *sb, u64 nodeid, const struct qstr *name,
+		     struct fuse_entry_out *outarg, struct inode **inode)
+{
+	struct fuse_mount *fm = get_fuse_mount_super(sb);
+	FUSE_ARGS(args);
+	struct fuse_forget_link *forget;
+	u64 attr_version;
+	int err;
+
+	*inode = NULL;
+	err = -ENAMETOOLONG;
+	if (name->len > FUSE_NAME_MAX)
+		goto out;
+
+
+	forget = fuse_alloc_forget();
+	err = -ENOMEM;
+	if (!forget)
+		goto out;
+
+	attr_version = fuse_get_attr_version(fm->fc);
+
+	fuse_lookup_init(fm->fc, &args, nodeid, name, outarg);
+	err = fuse_simple_request(fm, &args);
+	/* Zero nodeid is same as -ENOENT, but with valid timeout */
+	if (err || !outarg->nodeid)
+		goto out_put_forget;
+
+	err = -EIO;
+	if (!outarg->nodeid)
+		goto out_put_forget;
+	if (fuse_invalid_attr(&outarg->attr))
+		goto out_put_forget;
+
+	*inode = fuse_iget(sb, outarg->nodeid, outarg->generation,
+			   &outarg->attr, entry_attr_timeout(outarg),
+			   attr_version);
+	err = -ENOMEM;
+	if (!*inode) {
+		fuse_queue_forget(fm->fc, forget, outarg->nodeid, 1);
+		goto out;
+	}
+	err = 0;
+
+ out_put_forget:
+	kfree(forget);
+ out:
+	return err;
+}
+
+static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
+				  unsigned int flags)
+{
+	int err;
+	struct fuse_entry_out outarg;
+	struct inode *inode;
+	struct dentry *newent;
+	bool outarg_valid = true;
+	bool locked;
+
+	if (fuse_is_bad(dir))
+		return ERR_PTR(-EIO);
+
+	locked = fuse_lock_inode(dir);
+	err = fuse_lookup_name(dir->i_sb, get_node_id(dir), &entry->d_name,
+			       &outarg, &inode);
+	fuse_unlock_inode(dir, locked);
+	if (err == -ENOENT) {
+		outarg_valid = false;
+		err = 0;
+	}
+	if (err)
+		goto out_err;
+
+	err = -EIO;
+	if (inode && get_node_id(inode) == FUSE_ROOT_ID)
+		goto out_iput;
+
+	newent = d_splice_alias(inode, entry);
+	err = PTR_ERR(newent);
+	if (IS_ERR(newent))
+		goto out_err;
+
+	entry = newent ? newent : entry;
+	if (outarg_valid)
+		fuse_change_entry_timeout(entry, &outarg);
+	else
+		fuse_invalidate_entry_cache(entry);
+
+	if (inode)
+		fuse_advise_use_readdirplus(dir);
+	return newent;
+
+ out_iput:
+	iput(inode);
+ out_err:
+	return ERR_PTR(err);
+}
+
+/*
+ * Atomic create+open operation
+ *
+ * If the filesystem doesn't support this, then fall back to separate
+ * 'mknod' + 'open' requests.
+ */
+static int fuse_create_open(struct inode *dir, struct dentry *entry,
+			    struct file *file, unsigned flags,
+			    umode_t mode)
+{
+	int err;
+	struct inode *inode;
+	struct fuse_mount *fm = get_fuse_mount(dir);
+	FUSE_ARGS(args);
+	struct fuse_forget_link *forget;
+	struct fuse_create_in inarg;
+	struct fuse_open_out outopen;
+	struct fuse_entry_out outentry;
+	struct fuse_inode *fi;
+	struct fuse_file *ff;
+	bool trunc = flags & O_TRUNC;
+
+	/* Userspace expects S_IFREG in create mode */
+	BUG_ON((mode & S_IFMT) != S_IFREG);
+
+	forget = fuse_alloc_forget();
+	err = -ENOMEM;
+	if (!forget)
+		goto out_err;
+
+	err = -ENOMEM;
+	ff = fuse_file_alloc(fm);
+	if (!ff)
+		goto out_put_forget_req;
+
+	if (!fm->fc->dont_mask)
+		mode &= ~current_umask();
+
+	flags &= ~O_NOCTTY;
+	memset(&inarg, 0, sizeof(inarg));
+	memset(&outentry, 0, sizeof(outentry));
+	inarg.flags = flags;
+	inarg.mode = mode;
+	inarg.umask = current_umask();
+	args.opcode = FUSE_CREATE;
+	args.nodeid = get_node_id(dir);
+	args.in_numargs = 2;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.in_args[1].size = entry->d_name.len + 1;
+	args.in_args[1].value = entry->d_name.name;
+	args.out_numargs = 2;
+	args.out_args[0].size = sizeof(outentry);
+	args.out_args[0].value = &outentry;
+	args.out_args[1].size = sizeof(outopen);
+	args.out_args[1].value = &outopen;
+	err = fuse_simple_request(fm, &args);
+	if (err)
+		goto out_free_ff;
+
+	err = -EIO;
+	if (!S_ISREG(outentry.attr.mode) || invalid_nodeid(outentry.nodeid) ||
+	    fuse_invalid_attr(&outentry.attr))
+		goto out_free_ff;
+
+	ff->fh = outopen.fh;
+	ff->nodeid = outentry.nodeid;
+	ff->open_flags = outopen.open_flags;
+	inode = fuse_iget(dir->i_sb, outentry.nodeid, outentry.generation,
+			  &outentry.attr, entry_attr_timeout(&outentry), 0);
+	if (!inode) {
+		flags &= ~(O_CREAT | O_EXCL | O_TRUNC);
+		fuse_sync_release(NULL, ff, flags);
+		fuse_queue_forget(fm->fc, forget, outentry.nodeid, 1);
+		err = -ENOMEM;
+		goto out_err;
+	}
+	kfree(forget);
+	d_instantiate(entry, inode);
+	fuse_change_entry_timeout(entry, &outentry);
+	fuse_dir_changed(dir);
+	err = finish_open(file, entry, generic_file_open);
+	if (err) {
+		fi = get_fuse_inode(inode);
+		fuse_sync_release(fi, ff, flags);
+	} else {
+		file->private_data = ff;
+		fuse_finish_open(inode, file);
+		if (fm->fc->atomic_o_trunc && trunc)
+			truncate_pagecache(inode, 0);
+		else if (!(ff->open_flags & FOPEN_KEEP_CACHE))
+			invalidate_inode_pages2(inode->i_mapping);
+	}
+	return err;
+
+out_free_ff:
+	fuse_file_free(ff);
+out_put_forget_req:
+	kfree(forget);
+out_err:
+	return err;
+}
+
+static int fuse_mknod(struct inode *, struct dentry *, umode_t, dev_t);
+static int fuse_atomic_open(struct inode *dir, struct dentry *entry,
+			    struct file *file, unsigned flags,
+			    umode_t mode)
+{
+	int err;
+	struct fuse_conn *fc = get_fuse_conn(dir);
+	struct dentry *res = NULL;
+
+	if (fuse_is_bad(dir))
+		return -EIO;
+
+	if (d_in_lookup(entry)) {
+		res = fuse_lookup(dir, entry, 0);
+		if (IS_ERR(res))
+			return PTR_ERR(res);
+
+		if (res)
+			entry = res;
+	}
+
+	if (!(flags & O_CREAT) || d_really_is_positive(entry))
+		goto no_open;
+
+	/* Only creates */
+	file->f_mode |= FMODE_CREATED;
+
+	if (fc->no_create)
+		goto mknod;
+
+	err = fuse_create_open(dir, entry, file, flags, mode);
+	if (err == -ENOSYS) {
+		fc->no_create = 1;
+		goto mknod;
+	}
+out_dput:
+	dput(res);
+	return err;
+
+mknod:
+	err = fuse_mknod(dir, entry, mode, 0);
+	if (err)
+		goto out_dput;
+no_open:
+	return finish_no_open(file, res);
+}
+
+/*
+ * Code shared between mknod, mkdir, symlink and link
+ */
+static int create_new_entry(struct fuse_mount *fm, struct fuse_args *args,
+			    struct inode *dir, struct dentry *entry,
+			    umode_t mode)
+{
+	struct fuse_entry_out outarg;
+	struct inode *inode;
+	struct dentry *d;
+	int err;
+	struct fuse_forget_link *forget;
+
+	if (fuse_is_bad(dir))
+		return -EIO;
+
+	forget = fuse_alloc_forget();
+	if (!forget)
+		return -ENOMEM;
+
+	memset(&outarg, 0, sizeof(outarg));
+	args->nodeid = get_node_id(dir);
+	args->out_numargs = 1;
+	args->out_args[0].size = sizeof(outarg);
+	args->out_args[0].value = &outarg;
+	err = fuse_simple_request(fm, args);
+	if (err)
+		goto out_put_forget_req;
+
+	err = -EIO;
+	if (invalid_nodeid(outarg.nodeid) || fuse_invalid_attr(&outarg.attr))
+		goto out_put_forget_req;
+
+	if ((outarg.attr.mode ^ mode) & S_IFMT)
+		goto out_put_forget_req;
+
+	inode = fuse_iget(dir->i_sb, outarg.nodeid, outarg.generation,
+			  &outarg.attr, entry_attr_timeout(&outarg), 0);
+	if (!inode) {
+		fuse_queue_forget(fm->fc, forget, outarg.nodeid, 1);
+		return -ENOMEM;
+	}
+	kfree(forget);
+
+	d_drop(entry);
+	d = d_splice_alias(inode, entry);
+	if (IS_ERR(d))
+		return PTR_ERR(d);
+
+	if (d) {
+		fuse_change_entry_timeout(d, &outarg);
+		dput(d);
+	} else {
+		fuse_change_entry_timeout(entry, &outarg);
+	}
+	fuse_dir_changed(dir);
+	return 0;
+
+ out_put_forget_req:
+	kfree(forget);
+	return err;
+}
+
+static int fuse_mknod(struct inode *dir, struct dentry *entry, umode_t mode,
+		      dev_t rdev)
+{
+	struct fuse_mknod_in inarg;
+	struct fuse_mount *fm = get_fuse_mount(dir);
+	FUSE_ARGS(args);
+
+	if (!fm->fc->dont_mask)
+		mode &= ~current_umask();
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.mode = mode;
+	inarg.rdev = new_encode_dev(rdev);
+	inarg.umask = current_umask();
+	args.opcode = FUSE_MKNOD;
+	args.in_numargs = 2;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.in_args[1].size = entry->d_name.len + 1;
+	args.in_args[1].value = entry->d_name.name;
+	return create_new_entry(fm, &args, dir, entry, mode);
+}
+
+static int fuse_create(struct inode *dir, struct dentry *entry, umode_t mode,
+		       bool excl)
+{
+	return fuse_mknod(dir, entry, mode, 0);
+}
+
+static int fuse_mkdir(struct inode *dir, struct dentry *entry, umode_t mode)
+{
+	struct fuse_mkdir_in inarg;
+	struct fuse_mount *fm = get_fuse_mount(dir);
+	FUSE_ARGS(args);
+
+	if (!fm->fc->dont_mask)
+		mode &= ~current_umask();
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.mode = mode;
+	inarg.umask = current_umask();
+	args.opcode = FUSE_MKDIR;
+	args.in_numargs = 2;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.in_args[1].size = entry->d_name.len + 1;
+	args.in_args[1].value = entry->d_name.name;
+	return create_new_entry(fm, &args, dir, entry, S_IFDIR);
+}
+
+static int fuse_symlink(struct inode *dir, struct dentry *entry,
+			const char *link)
+{
+	struct fuse_mount *fm = get_fuse_mount(dir);
+	unsigned len = strlen(link) + 1;
+	FUSE_ARGS(args);
+
+	args.opcode = FUSE_SYMLINK;
+	args.in_numargs = 2;
+	args.in_args[0].size = entry->d_name.len + 1;
+	args.in_args[0].value = entry->d_name.name;
+	args.in_args[1].size = len;
+	args.in_args[1].value = link;
+	return create_new_entry(fm, &args, dir, entry, S_IFLNK);
+}
+
+void fuse_flush_time_update(struct inode *inode)
+{
+	int err = sync_inode_metadata(inode, 1);
+
+	mapping_set_error(inode->i_mapping, err);
+}
+
+void fuse_update_ctime(struct inode *inode)
+{
+	if (!IS_NOCMTIME(inode)) {
+		inode->i_ctime = current_time(inode);
+		mark_inode_dirty_sync(inode);
+		fuse_flush_time_update(inode);
+	}
+}
+
+static int fuse_unlink(struct inode *dir, struct dentry *entry)
+{
+	int err;
+	struct fuse_mount *fm = get_fuse_mount(dir);
+	FUSE_ARGS(args);
+
+	if (fuse_is_bad(dir))
+		return -EIO;
+
+	args.opcode = FUSE_UNLINK;
+	args.nodeid = get_node_id(dir);
+	args.in_numargs = 1;
+	args.in_args[0].size = entry->d_name.len + 1;
+	args.in_args[0].value = entry->d_name.name;
+	err = fuse_simple_request(fm, &args);
+	if (!err) {
+		struct inode *inode = d_inode(entry);
+		struct fuse_inode *fi = get_fuse_inode(inode);
+
+		spin_lock(&fi->lock);
+		fi->attr_version = atomic64_inc_return(&fm->fc->attr_version);
+		/*
+		 * If i_nlink == 0 then unlink doesn't make sense, yet this can
+		 * happen if userspace filesystem is careless.  It would be
+		 * difficult to enforce correct nlink usage so just ignore this
+		 * condition here
+		 */
+		if (inode->i_nlink > 0)
+			drop_nlink(inode);
+		spin_unlock(&fi->lock);
+		fuse_invalidate_attr(inode);
+		fuse_dir_changed(dir);
+		fuse_invalidate_entry_cache(entry);
+		fuse_update_ctime(inode);
+	} else if (err == -EINTR)
+		fuse_invalidate_entry(entry);
+	return err;
+}
+
+static int fuse_rmdir(struct inode *dir, struct dentry *entry)
+{
+	int err;
+	struct fuse_mount *fm = get_fuse_mount(dir);
+	FUSE_ARGS(args);
+
+	if (fuse_is_bad(dir))
+		return -EIO;
+
+	args.opcode = FUSE_RMDIR;
+	args.nodeid = get_node_id(dir);
+	args.in_numargs = 1;
+	args.in_args[0].size = entry->d_name.len + 1;
+	args.in_args[0].value = entry->d_name.name;
+	err = fuse_simple_request(fm, &args);
+	if (!err) {
+		clear_nlink(d_inode(entry));
+		fuse_dir_changed(dir);
+		fuse_invalidate_entry_cache(entry);
+	} else if (err == -EINTR)
+		fuse_invalidate_entry(entry);
+	return err;
+}
+
+static int fuse_rename_common(struct inode *olddir, struct dentry *oldent,
+			      struct inode *newdir, struct dentry *newent,
+			      unsigned int flags, int opcode, size_t argsize)
+{
+	int err;
+	struct fuse_rename2_in inarg;
+	struct fuse_mount *fm = get_fuse_mount(olddir);
+	FUSE_ARGS(args);
+
+	memset(&inarg, 0, argsize);
+	inarg.newdir = get_node_id(newdir);
+	inarg.flags = flags;
+	args.opcode = opcode;
+	args.nodeid = get_node_id(olddir);
+	args.in_numargs = 3;
+	args.in_args[0].size = argsize;
+	args.in_args[0].value = &inarg;
+	args.in_args[1].size = oldent->d_name.len + 1;
+	args.in_args[1].value = oldent->d_name.name;
+	args.in_args[2].size = newent->d_name.len + 1;
+	args.in_args[2].value = newent->d_name.name;
+	err = fuse_simple_request(fm, &args);
+	if (!err) {
+		/* ctime changes */
+		fuse_invalidate_attr(d_inode(oldent));
+		fuse_update_ctime(d_inode(oldent));
+
+		if (flags & RENAME_EXCHANGE) {
+			fuse_invalidate_attr(d_inode(newent));
+			fuse_update_ctime(d_inode(newent));
+		}
+
+		fuse_dir_changed(olddir);
+		if (olddir != newdir)
+			fuse_dir_changed(newdir);
+
+		/* newent will end up negative */
+		if (!(flags & RENAME_EXCHANGE) && d_really_is_positive(newent)) {
+			fuse_invalidate_attr(d_inode(newent));
+			fuse_invalidate_entry_cache(newent);
+			fuse_update_ctime(d_inode(newent));
+		}
+	} else if (err == -EINTR) {
+		/* If request was interrupted, DEITY only knows if the
+		   rename actually took place.  If the invalidation
+		   fails (e.g. some process has CWD under the renamed
+		   directory), then there can be inconsistency between
+		   the dcache and the real filesystem.  Tough luck. */
+		fuse_invalidate_entry(oldent);
+		if (d_really_is_positive(newent))
+			fuse_invalidate_entry(newent);
+	}
+
+	return err;
+}
+
+static int fuse_rename2(struct inode *olddir, struct dentry *oldent,
+			struct inode *newdir, struct dentry *newent,
+			unsigned int flags)
+{
+	struct fuse_conn *fc = get_fuse_conn(olddir);
+	int err;
+
+	if (fuse_is_bad(olddir))
+		return -EIO;
+
+	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
+		return -EINVAL;
+
+	if (flags) {
+		if (fc->no_rename2 || fc->minor < 23)
+			return -EINVAL;
+
+		err = fuse_rename_common(olddir, oldent, newdir, newent, flags,
+					 FUSE_RENAME2,
+					 sizeof(struct fuse_rename2_in));
+		if (err == -ENOSYS) {
+			fc->no_rename2 = 1;
+			err = -EINVAL;
+		}
+	} else {
+		err = fuse_rename_common(olddir, oldent, newdir, newent, 0,
+					 FUSE_RENAME,
+					 sizeof(struct fuse_rename_in));
+	}
+
+	return err;
+}
+
+static int fuse_link(struct dentry *entry, struct inode *newdir,
+		     struct dentry *newent)
+{
+	int err;
+	struct fuse_link_in inarg;
+	struct inode *inode = d_inode(entry);
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.oldnodeid = get_node_id(inode);
+	args.opcode = FUSE_LINK;
+	args.in_numargs = 2;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.in_args[1].size = newent->d_name.len + 1;
+	args.in_args[1].value = newent->d_name.name;
+	err = create_new_entry(fm, &args, newdir, newent, inode->i_mode);
+	/* Contrary to "normal" filesystems it can happen that link
+	   makes two "logical" inodes point to the same "physical"
+	   inode.  We invalidate the attributes of the old one, so it
+	   will reflect changes in the backing inode (link count,
+	   etc.)
+	*/
+	if (!err) {
+		struct fuse_inode *fi = get_fuse_inode(inode);
+
+		spin_lock(&fi->lock);
+		fi->attr_version = atomic64_inc_return(&fm->fc->attr_version);
+		if (likely(inode->i_nlink < UINT_MAX))
+			inc_nlink(inode);
+		spin_unlock(&fi->lock);
+		fuse_invalidate_attr(inode);
+		fuse_update_ctime(inode);
+	} else if (err == -EINTR) {
+		fuse_invalidate_attr(inode);
+	}
+	return err;
+}
+
+static void fuse_fillattr(struct inode *inode, struct fuse_attr *attr,
+			  struct kstat *stat)
+{
+	unsigned int blkbits;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	/* see the comment in fuse_change_attributes() */
+	if (fc->writeback_cache && S_ISREG(inode->i_mode)) {
+		attr->size = i_size_read(inode);
+		attr->mtime = inode->i_mtime.tv_sec;
+		attr->mtimensec = inode->i_mtime.tv_nsec;
+		attr->ctime = inode->i_ctime.tv_sec;
+		attr->ctimensec = inode->i_ctime.tv_nsec;
+	}
+
+	stat->dev = inode->i_sb->s_dev;
+	stat->ino = attr->ino;
+	stat->mode = (inode->i_mode & S_IFMT) | (attr->mode & 07777);
+	stat->nlink = attr->nlink;
+	stat->uid = make_kuid(fc->user_ns, attr->uid);
+	stat->gid = make_kgid(fc->user_ns, attr->gid);
+	stat->rdev = inode->i_rdev;
+	stat->atime.tv_sec = attr->atime;
+	stat->atime.tv_nsec = attr->atimensec;
+	stat->mtime.tv_sec = attr->mtime;
+	stat->mtime.tv_nsec = attr->mtimensec;
+	stat->ctime.tv_sec = attr->ctime;
+	stat->ctime.tv_nsec = attr->ctimensec;
+	stat->size = attr->size;
+	stat->blocks = attr->blocks;
+
+	if (attr->blksize != 0)
+		blkbits = ilog2(attr->blksize);
+	else
+		blkbits = inode->i_sb->s_blocksize_bits;
+
+	stat->blksize = 1 << blkbits;
+}
+
+static int fuse_do_getattr(struct inode *inode, struct kstat *stat,
+			   struct file *file)
+{
+	int err;
+	struct fuse_getattr_in inarg;
+	struct fuse_attr_out outarg;
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+	u64 attr_version;
+
+	attr_version = fuse_get_attr_version(fm->fc);
+
+	memset(&inarg, 0, sizeof(inarg));
+	memset(&outarg, 0, sizeof(outarg));
+	/* Directories have separate file-handle space */
+	if (file && S_ISREG(inode->i_mode)) {
+		struct fuse_file *ff = file->private_data;
+
+		inarg.getattr_flags |= FUSE_GETATTR_FH;
+		inarg.fh = ff->fh;
+	}
+	args.opcode = FUSE_GETATTR;
+	args.nodeid = get_node_id(inode);
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.out_numargs = 1;
+	args.out_args[0].size = sizeof(outarg);
+	args.out_args[0].value = &outarg;
+	err = fuse_simple_request(fm, &args);
+	if (!err) {
+		if (fuse_invalid_attr(&outarg.attr) ||
+		    inode_wrong_type(inode, outarg.attr.mode)) {
+			fuse_make_bad(inode);
+			err = -EIO;
+		} else {
+			fuse_change_attributes(inode, &outarg.attr,
+					       attr_timeout(&outarg),
+					       attr_version);
+			if (stat)
+				fuse_fillattr(inode, &outarg.attr, stat);
+		}
+	}
+	return err;
+}
+
+static int fuse_update_get_attr(struct inode *inode, struct file *file,
+				struct kstat *stat, u32 request_mask,
+				unsigned int flags)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	int err = 0;
+	bool sync;
+
+	if (flags & AT_STATX_FORCE_SYNC)
+		sync = true;
+	else if (flags & AT_STATX_DONT_SYNC)
+		sync = false;
+	else if (request_mask & READ_ONCE(fi->inval_mask))
+		sync = true;
+	else
+		sync = time_before64(fi->i_time, get_jiffies_64());
+
+	if (sync) {
+		forget_all_cached_acls(inode);
+		err = fuse_do_getattr(inode, stat, file);
+	} else if (stat) {
+		generic_fillattr(inode, stat);
+		stat->mode = fi->orig_i_mode;
+		stat->ino = fi->orig_ino;
+	}
+
+	return err;
+}
+
+int fuse_update_attributes(struct inode *inode, struct file *file)
+{
+	/* Do *not* need to get atime for internal purposes */
+	return fuse_update_get_attr(inode, file, NULL,
+				    STATX_BASIC_STATS & ~STATX_ATIME, 0);
+}
+
+int fuse_reverse_inval_entry(struct fuse_conn *fc, u64 parent_nodeid,
+			     u64 child_nodeid, struct qstr *name)
+{
+	int err = -ENOTDIR;
+	struct inode *parent;
+	struct dentry *dir;
+	struct dentry *entry;
+
+	parent = fuse_ilookup(fc, parent_nodeid, NULL);
+	if (!parent)
+		return -ENOENT;
+
+	inode_lock_nested(parent, I_MUTEX_PARENT);
+	if (!S_ISDIR(parent->i_mode))
+		goto unlock;
+
+	err = -ENOENT;
+	dir = d_find_alias(parent);
+	if (!dir)
+		goto unlock;
+
+	name->hash = full_name_hash(dir, name->name, name->len);
+	entry = d_lookup(dir, name);
+	dput(dir);
+	if (!entry)
+		goto unlock;
+
+	fuse_dir_changed(parent);
+	fuse_invalidate_entry(entry);
+
+	if (child_nodeid != 0 && d_really_is_positive(entry)) {
+		inode_lock(d_inode(entry));
+		if (get_node_id(d_inode(entry)) != child_nodeid) {
+			err = -ENOENT;
+			goto badentry;
+		}
+		if (d_mountpoint(entry)) {
+			err = -EBUSY;
+			goto badentry;
+		}
+		if (d_is_dir(entry)) {
+			shrink_dcache_parent(entry);
+			if (!simple_empty(entry)) {
+				err = -ENOTEMPTY;
+				goto badentry;
+			}
+			d_inode(entry)->i_flags |= S_DEAD;
+		}
+		dont_mount(entry);
+		clear_nlink(d_inode(entry));
+		err = 0;
+ badentry:
+		inode_unlock(d_inode(entry));
+		if (!err)
+			d_delete(entry);
+	} else {
+		err = 0;
+	}
+	dput(entry);
+
+ unlock:
+	inode_unlock(parent);
+	iput(parent);
+	return err;
+}
+
+/*
+ * Calling into a user-controlled filesystem gives the filesystem
+ * daemon ptrace-like capabilities over the current process.  This
+ * means, that the filesystem daemon is able to record the exact
+ * filesystem operations performed, and can also control the behavior
+ * of the requester process in otherwise impossible ways.  For example
+ * it can delay the operation for arbitrary length of time allowing
+ * DoS against the requester.
+ *
+ * For this reason only those processes can call into the filesystem,
+ * for which the owner of the mount has ptrace privilege.  This
+ * excludes processes started by other users, suid or sgid processes.
+ */
+int fuse_allow_current_process(struct fuse_conn *fc)
+{
+	const struct cred *cred;
+
+	if (fc->allow_other)
+		return current_in_userns(fc->user_ns);
+
+	cred = current_cred();
+	if (uid_eq(cred->euid, fc->user_id) &&
+	    uid_eq(cred->suid, fc->user_id) &&
+	    uid_eq(cred->uid,  fc->user_id) &&
+	    gid_eq(cred->egid, fc->group_id) &&
+	    gid_eq(cred->sgid, fc->group_id) &&
+	    gid_eq(cred->gid,  fc->group_id))
+		return 1;
+
+	return 0;
+}
+
+static int fuse_access(struct inode *inode, int mask)
+{
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+	struct fuse_access_in inarg;
+	int err;
+
+	BUG_ON(mask & MAY_NOT_BLOCK);
+
+	if (fm->fc->no_access)
+		return 0;
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.mask = mask & (MAY_READ | MAY_WRITE | MAY_EXEC);
+	args.opcode = FUSE_ACCESS;
+	args.nodeid = get_node_id(inode);
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	err = fuse_simple_request(fm, &args);
+	if (err == -ENOSYS) {
+		fm->fc->no_access = 1;
+		err = 0;
+	}
+	return err;
+}
+
+static int fuse_perm_getattr(struct inode *inode, int mask)
+{
+	if (mask & MAY_NOT_BLOCK)
+		return -ECHILD;
+
+	forget_all_cached_acls(inode);
+	return fuse_do_getattr(inode, NULL, NULL);
+}
+
+/*
+ * Check permission.  The two basic access models of FUSE are:
+ *
+ * 1) Local access checking ('default_permissions' mount option) based
+ * on file mode.  This is the plain old disk filesystem permission
+ * modell.
+ *
+ * 2) "Remote" access checking, where server is responsible for
+ * checking permission in each inode operation.  An exception to this
+ * is if ->permission() was invoked from sys_access() in which case an
+ * access request is sent.  Execute permission is still checked
+ * locally based on file mode.
+ */
+static int fuse_permission(struct inode *inode, int mask)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	bool refreshed = false;
+	int err = 0;
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	if (!fuse_allow_current_process(fc))
+		return -EACCES;
+
+	/*
+	 * If attributes are needed, refresh them before proceeding
+	 */
+	if (fc->default_permissions ||
+	    ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))) {
+		struct fuse_inode *fi = get_fuse_inode(inode);
+		u32 perm_mask = STATX_MODE | STATX_UID | STATX_GID;
+
+		if (perm_mask & READ_ONCE(fi->inval_mask) ||
+		    time_before64(fi->i_time, get_jiffies_64())) {
+			refreshed = true;
+
+			err = fuse_perm_getattr(inode, mask);
+			if (err)
+				return err;
+		}
+	}
+
+	if (fc->default_permissions) {
+		err = generic_permission(inode, mask);
+
+		/* If permission is denied, try to refresh file
+		   attributes.  This is also needed, because the root
+		   node will at first have no permissions */
+		if (err == -EACCES && !refreshed) {
+			err = fuse_perm_getattr(inode, mask);
+			if (!err)
+				err = generic_permission(inode, mask);
+		}
+
+		/* Note: the opposite of the above test does not
+		   exist.  So if permissions are revoked this won't be
+		   noticed immediately, only after the attribute
+		   timeout has expired */
+	} else if (mask & (MAY_ACCESS | MAY_CHDIR)) {
+		err = fuse_access(inode, mask);
+	} else if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode)) {
+		if (!(inode->i_mode & S_IXUGO)) {
+			if (refreshed)
+				return -EACCES;
+
+			err = fuse_perm_getattr(inode, mask);
+			if (!err && !(inode->i_mode & S_IXUGO))
+				return -EACCES;
+		}
+	}
+	return err;
+}
+
+static int fuse_readlink_page(struct inode *inode, struct page *page)
+{
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	struct fuse_page_desc desc = { .length = PAGE_SIZE - 1 };
+	struct fuse_args_pages ap = {
+		.num_pages = 1,
+		.pages = &page,
+		.descs = &desc,
+	};
+	char *link;
+	ssize_t res;
+
+	ap.args.opcode = FUSE_READLINK;
+	ap.args.nodeid = get_node_id(inode);
+	ap.args.out_pages = true;
+	ap.args.out_argvar = true;
+	ap.args.page_zeroing = true;
+	ap.args.out_numargs = 1;
+	ap.args.out_args[0].size = desc.length;
+	res = fuse_simple_request(fm, &ap.args);
+
+	fuse_invalidate_atime(inode);
+
+	if (res < 0)
+		return res;
+
+	if (WARN_ON(res >= PAGE_SIZE))
+		return -EIO;
+
+	link = page_address(page);
+	link[res] = '\0';
+
+	return 0;
+}
+
+static const char *fuse_get_link(struct dentry *dentry, struct inode *inode,
+				 struct delayed_call *callback)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct page *page;
+	int err;
+
+	err = -EIO;
+	if (fuse_is_bad(inode))
+		goto out_err;
+
+	if (fc->cache_symlinks)
+		return page_get_link(dentry, inode, callback);
+
+	err = -ECHILD;
+	if (!dentry)
+		goto out_err;
+
+	page = alloc_page(GFP_KERNEL);
+	err = -ENOMEM;
+	if (!page)
+		goto out_err;
+
+	err = fuse_readlink_page(inode, page);
+	if (err) {
+		__free_page(page);
+		goto out_err;
+	}
+
+	set_delayed_call(callback, page_put_link, page);
+
+	return page_address(page);
+
+out_err:
+	return ERR_PTR(err);
+}
+
+static int fuse_dir_open(struct inode *inode, struct file *file)
+{
+	return fuse_open_common(inode, file, true);
+}
+
+static int fuse_dir_release(struct inode *inode, struct file *file)
+{
+	fuse_release_common(file, true);
+
+	return 0;
+}
+
+static int fuse_dir_fsync(struct file *file, loff_t start, loff_t end,
+			  int datasync)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	int err;
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	if (fc->no_fsyncdir)
+		return 0;
+
+	inode_lock(inode);
+	err = fuse_fsync_common(file, start, end, datasync, FUSE_FSYNCDIR);
+	if (err == -ENOSYS) {
+		fc->no_fsyncdir = 1;
+		err = 0;
+	}
+	inode_unlock(inode);
+
+	return err;
+}
+
+static long fuse_dir_ioctl(struct file *file, unsigned int cmd,
+			    unsigned long arg)
+{
+	struct fuse_conn *fc = get_fuse_conn(file->f_mapping->host);
+
+	/* FUSE_IOCTL_DIR only supported for API version >= 7.18 */
+	if (fc->minor < 18)
+		return -ENOTTY;
+
+	return fuse_ioctl_common(file, cmd, arg, FUSE_IOCTL_DIR);
+}
+
+static long fuse_dir_compat_ioctl(struct file *file, unsigned int cmd,
+				   unsigned long arg)
+{
+	struct fuse_conn *fc = get_fuse_conn(file->f_mapping->host);
+
+	if (fc->minor < 18)
+		return -ENOTTY;
+
+	return fuse_ioctl_common(file, cmd, arg,
+				 FUSE_IOCTL_COMPAT | FUSE_IOCTL_DIR);
+}
+
+static bool update_mtime(unsigned ivalid, bool trust_local_mtime)
+{
+	/* Always update if mtime is explicitly set  */
+	if (ivalid & ATTR_MTIME_SET)
+		return true;
+
+	/* Or if kernel i_mtime is the official one */
+	if (trust_local_mtime)
+		return true;
+
+	/* If it's an open(O_TRUNC) or an ftruncate(), don't update */
+	if ((ivalid & ATTR_SIZE) && (ivalid & (ATTR_OPEN | ATTR_FILE)))
+		return false;
+
+	/* In all other cases update */
+	return true;
+}
+
+static void iattr_to_fattr(struct fuse_conn *fc, struct iattr *iattr,
+			   struct fuse_setattr_in *arg, bool trust_local_cmtime)
+{
+	unsigned ivalid = iattr->ia_valid;
+
+	if (ivalid & ATTR_MODE)
+		arg->valid |= FATTR_MODE,   arg->mode = iattr->ia_mode;
+	if (ivalid & ATTR_UID)
+		arg->valid |= FATTR_UID,    arg->uid = from_kuid(fc->user_ns, iattr->ia_uid);
+	if (ivalid & ATTR_GID)
+		arg->valid |= FATTR_GID,    arg->gid = from_kgid(fc->user_ns, iattr->ia_gid);
+	if (ivalid & ATTR_SIZE)
+		arg->valid |= FATTR_SIZE,   arg->size = iattr->ia_size;
+	if (ivalid & ATTR_ATIME) {
+		arg->valid |= FATTR_ATIME;
+		arg->atime = iattr->ia_atime.tv_sec;
+		arg->atimensec = iattr->ia_atime.tv_nsec;
+		if (!(ivalid & ATTR_ATIME_SET))
+			arg->valid |= FATTR_ATIME_NOW;
+	}
+	if ((ivalid & ATTR_MTIME) && update_mtime(ivalid, trust_local_cmtime)) {
+		arg->valid |= FATTR_MTIME;
+		arg->mtime = iattr->ia_mtime.tv_sec;
+		arg->mtimensec = iattr->ia_mtime.tv_nsec;
+		if (!(ivalid & ATTR_MTIME_SET) && !trust_local_cmtime)
+			arg->valid |= FATTR_MTIME_NOW;
+	}
+	if ((ivalid & ATTR_CTIME) && trust_local_cmtime) {
+		arg->valid |= FATTR_CTIME;
+		arg->ctime = iattr->ia_ctime.tv_sec;
+		arg->ctimensec = iattr->ia_ctime.tv_nsec;
+	}
+}
+
+/*
+ * Prevent concurrent writepages on inode
+ *
+ * This is done by adding a negative bias to the inode write counter
+ * and waiting for all pending writes to finish.
+ */
+void fuse_set_nowrite(struct inode *inode)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	BUG_ON(!inode_is_locked(inode));
+
+	spin_lock(&fi->lock);
+	BUG_ON(fi->writectr < 0);
+	fi->writectr += FUSE_NOWRITE;
+	spin_unlock(&fi->lock);
+	wait_event(fi->page_waitq, fi->writectr == FUSE_NOWRITE);
+}
+
+/*
+ * Allow writepages on inode
+ *
+ * Remove the bias from the writecounter and send any queued
+ * writepages.
+ */
+static void __fuse_release_nowrite(struct inode *inode)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	BUG_ON(fi->writectr != FUSE_NOWRITE);
+	fi->writectr = 0;
+	fuse_flush_writepages(inode);
+}
+
+void fuse_release_nowrite(struct inode *inode)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	spin_lock(&fi->lock);
+	__fuse_release_nowrite(inode);
+	spin_unlock(&fi->lock);
+}
+
+static void fuse_setattr_fill(struct fuse_conn *fc, struct fuse_args *args,
+			      struct inode *inode,
+			      struct fuse_setattr_in *inarg_p,
+			      struct fuse_attr_out *outarg_p)
+{
+	args->opcode = FUSE_SETATTR;
+	args->nodeid = get_node_id(inode);
+	args->in_numargs = 1;
+	args->in_args[0].size = sizeof(*inarg_p);
+	args->in_args[0].value = inarg_p;
+	args->out_numargs = 1;
+	args->out_args[0].size = sizeof(*outarg_p);
+	args->out_args[0].value = outarg_p;
+}
+
+/*
+ * Flush inode->i_mtime to the server
+ */
+int fuse_flush_times(struct inode *inode, struct fuse_file *ff)
+{
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+	struct fuse_setattr_in inarg;
+	struct fuse_attr_out outarg;
+
+	memset(&inarg, 0, sizeof(inarg));
+	memset(&outarg, 0, sizeof(outarg));
+
+	inarg.valid = FATTR_MTIME;
+	inarg.mtime = inode->i_mtime.tv_sec;
+	inarg.mtimensec = inode->i_mtime.tv_nsec;
+	if (fm->fc->minor >= 23) {
+		inarg.valid |= FATTR_CTIME;
+		inarg.ctime = inode->i_ctime.tv_sec;
+		inarg.ctimensec = inode->i_ctime.tv_nsec;
+	}
+	if (ff) {
+		inarg.valid |= FATTR_FH;
+		inarg.fh = ff->fh;
+	}
+	fuse_setattr_fill(fm->fc, &args, inode, &inarg, &outarg);
+
+	return fuse_simple_request(fm, &args);
+}
+
+/*
+ * Set attributes, and at the same time refresh them.
+ *
+ * Truncation is slightly complicated, because the 'truncate' request
+ * may fail, in which case we don't want to touch the mapping.
+ * vmtruncate() doesn't allow for this case, so do the rlimit checking
+ * and the actual truncation by hand.
+ */
+int fuse_do_setattr(struct dentry *dentry, struct iattr *attr,
+		    struct file *file)
+{
+	struct inode *inode = d_inode(dentry);
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	struct fuse_conn *fc = fm->fc;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	FUSE_ARGS(args);
+	struct fuse_setattr_in inarg;
+	struct fuse_attr_out outarg;
+	bool is_truncate = false;
+	bool is_wb = fc->writeback_cache;
+	loff_t oldsize;
+	int err;
+	bool trust_local_cmtime = is_wb && S_ISREG(inode->i_mode);
+	bool fault_blocked = false;
+
+	if (!fc->default_permissions)
+		attr->ia_valid |= ATTR_FORCE;
+
+	err = setattr_prepare(dentry, attr);
+	if (err)
+		return err;
+
+	if (attr->ia_valid & ATTR_SIZE) {
+		if (WARN_ON(!S_ISREG(inode->i_mode)))
+			return -EIO;
+		is_truncate = true;
+	}
+
+	if (FUSE_IS_DAX(inode) && is_truncate) {
+		down_write(&fi->i_mmap_sem);
+		fault_blocked = true;
+		err = fuse_dax_break_layouts(inode, 0, 0);
+		if (err) {
+			up_write(&fi->i_mmap_sem);
+			return err;
+		}
+	}
+
+	if (attr->ia_valid & ATTR_OPEN) {
+		/* This is coming from open(..., ... | O_TRUNC); */
+		WARN_ON(!(attr->ia_valid & ATTR_SIZE));
+		WARN_ON(attr->ia_size != 0);
+		if (fc->atomic_o_trunc) {
+			/*
+			 * No need to send request to userspace, since actual
+			 * truncation has already been done by OPEN.  But still
+			 * need to truncate page cache.
+			 */
+			i_size_write(inode, 0);
+			truncate_pagecache(inode, 0);
+			goto out;
+		}
+		file = NULL;
+	}
+
+	/* Flush dirty data/metadata before non-truncate SETATTR */
+	if (is_wb && S_ISREG(inode->i_mode) &&
+	    attr->ia_valid &
+			(ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_MTIME_SET |
+			 ATTR_TIMES_SET)) {
+		err = write_inode_now(inode, true);
+		if (err)
+			return err;
+
+		fuse_set_nowrite(inode);
+		fuse_release_nowrite(inode);
+	}
+
+	if (is_truncate) {
+		fuse_set_nowrite(inode);
+		set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
+		if (trust_local_cmtime && attr->ia_size != inode->i_size)
+			attr->ia_valid |= ATTR_MTIME | ATTR_CTIME;
+	}
+
+	memset(&inarg, 0, sizeof(inarg));
+	memset(&outarg, 0, sizeof(outarg));
+	iattr_to_fattr(fc, attr, &inarg, trust_local_cmtime);
+	if (file) {
+		struct fuse_file *ff = file->private_data;
+		inarg.valid |= FATTR_FH;
+		inarg.fh = ff->fh;
+	}
+	if (attr->ia_valid & ATTR_SIZE) {
+		/* For mandatory locking in truncate */
+		inarg.valid |= FATTR_LOCKOWNER;
+		inarg.lock_owner = fuse_lock_owner_id(fc, current->files);
+	}
+	fuse_setattr_fill(fc, &args, inode, &inarg, &outarg);
+	err = fuse_simple_request(fm, &args);
+	if (err) {
+		if (err == -EINTR)
+			fuse_invalidate_attr(inode);
+		goto error;
+	}
+
+	if (fuse_invalid_attr(&outarg.attr) ||
+	    inode_wrong_type(inode, outarg.attr.mode)) {
+		fuse_make_bad(inode);
+		err = -EIO;
+		goto error;
+	}
+
+	spin_lock(&fi->lock);
+	/* the kernel maintains i_mtime locally */
+	if (trust_local_cmtime) {
+		if (attr->ia_valid & ATTR_MTIME)
+			inode->i_mtime = attr->ia_mtime;
+		if (attr->ia_valid & ATTR_CTIME)
+			inode->i_ctime = attr->ia_ctime;
+		/* FIXME: clear I_DIRTY_SYNC? */
+	}
+
+	fuse_change_attributes_common(inode, &outarg.attr,
+				      attr_timeout(&outarg));
+	oldsize = inode->i_size;
+	/* see the comment in fuse_change_attributes() */
+	if (!is_wb || is_truncate || !S_ISREG(inode->i_mode))
+		i_size_write(inode, outarg.attr.size);
+
+	if (is_truncate) {
+		/* NOTE: this may release/reacquire fi->lock */
+		__fuse_release_nowrite(inode);
+	}
+	spin_unlock(&fi->lock);
+
+	/*
+	 * Only call invalidate_inode_pages2() after removing
+	 * FUSE_NOWRITE, otherwise fuse_launder_page() would deadlock.
+	 */
+	if ((is_truncate || !is_wb) &&
+	    S_ISREG(inode->i_mode) && oldsize != outarg.attr.size) {
+		truncate_pagecache(inode, outarg.attr.size);
+		invalidate_inode_pages2(inode->i_mapping);
+	}
+
+	clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
+out:
+	if (fault_blocked)
+		up_write(&fi->i_mmap_sem);
+
+	return 0;
+
+error:
+	if (is_truncate)
+		fuse_release_nowrite(inode);
+
+	clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
+
+	if (fault_blocked)
+		up_write(&fi->i_mmap_sem);
+	return err;
+}
+
+static int fuse_setattr(struct dentry *entry, struct iattr *attr)
+{
+	struct inode *inode = d_inode(entry);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct file *file = (attr->ia_valid & ATTR_FILE) ? attr->ia_file : NULL;
+	int ret;
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	if (!fuse_allow_current_process(get_fuse_conn(inode)))
+		return -EACCES;
+
+	if (attr->ia_valid & (ATTR_KILL_SUID | ATTR_KILL_SGID)) {
+		attr->ia_valid &= ~(ATTR_KILL_SUID | ATTR_KILL_SGID |
+				    ATTR_MODE);
+
+		/*
+		 * The only sane way to reliably kill suid/sgid is to do it in
+		 * the userspace filesystem
+		 *
+		 * This should be done on write(), truncate() and chown().
+		 */
+		if (!fc->handle_killpriv) {
+			/*
+			 * ia_mode calculation may have used stale i_mode.
+			 * Refresh and recalculate.
+			 */
+			ret = fuse_do_getattr(inode, NULL, file);
+			if (ret)
+				return ret;
+
+			attr->ia_mode = inode->i_mode;
+			if (inode->i_mode & S_ISUID) {
+				attr->ia_valid |= ATTR_MODE;
+				attr->ia_mode &= ~S_ISUID;
+			}
+			if ((inode->i_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
+				attr->ia_valid |= ATTR_MODE;
+				attr->ia_mode &= ~S_ISGID;
+			}
+		}
+	}
+	if (!attr->ia_valid)
+		return 0;
+
+	ret = fuse_do_setattr(entry, attr, file);
+	if (!ret) {
+		/*
+		 * If filesystem supports acls it may have updated acl xattrs in
+		 * the filesystem, so forget cached acls for the inode.
+		 */
+		if (fc->posix_acl)
+			forget_all_cached_acls(inode);
+
+		/* Directory mode changed, may need to revalidate access */
+		if (d_is_dir(entry) && (attr->ia_valid & ATTR_MODE))
+			fuse_invalidate_entry_cache(entry);
+	}
+	return ret;
+}
+
+static int fuse_getattr(const struct path *path, struct kstat *stat,
+			u32 request_mask, unsigned int flags)
+{
+	struct inode *inode = d_inode(path->dentry);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	if (!fuse_allow_current_process(fc)) {
+		if (!request_mask) {
+			/*
+			 * If user explicitly requested *nothing* then don't
+			 * error out, but return st_dev only.
+			 */
+			stat->result_mask = 0;
+			stat->dev = inode->i_sb->s_dev;
+			return 0;
+		}
+		return -EACCES;
+	}
+
+	return fuse_update_get_attr(inode, NULL, stat, request_mask, flags);
+}
+
+static const struct inode_operations fuse_dir_inode_operations = {
+	.lookup		= fuse_lookup,
+	.mkdir		= fuse_mkdir,
+	.symlink	= fuse_symlink,
+	.unlink		= fuse_unlink,
+	.rmdir		= fuse_rmdir,
+	.rename		= fuse_rename2,
+	.link		= fuse_link,
+	.setattr	= fuse_setattr,
+	.create		= fuse_create,
+	.atomic_open	= fuse_atomic_open,
+	.mknod		= fuse_mknod,
+	.permission	= fuse_permission,
+	.getattr	= fuse_getattr,
+	.listxattr	= fuse_listxattr,
+	.get_acl	= fuse_get_acl,
+	.set_acl	= fuse_set_acl,
+};
+
+static const struct file_operations fuse_dir_operations = {
+	.llseek		= generic_file_llseek,
+	.read		= generic_read_dir,
+	.iterate_shared	= fuse_readdir,
+	.open		= fuse_dir_open,
+	.release	= fuse_dir_release,
+	.fsync		= fuse_dir_fsync,
+	.unlocked_ioctl	= fuse_dir_ioctl,
+	.compat_ioctl	= fuse_dir_compat_ioctl,
+};
+
+static const struct inode_operations fuse_common_inode_operations = {
+	.setattr	= fuse_setattr,
+	.permission	= fuse_permission,
+	.getattr	= fuse_getattr,
+	.listxattr	= fuse_listxattr,
+	.get_acl	= fuse_get_acl,
+	.set_acl	= fuse_set_acl,
+};
+
+static const struct inode_operations fuse_symlink_inode_operations = {
+	.setattr	= fuse_setattr,
+	.get_link	= fuse_get_link,
+	.getattr	= fuse_getattr,
+	.listxattr	= fuse_listxattr,
+};
+
+void fuse_init_common(struct inode *inode)
+{
+	inode->i_op = &fuse_common_inode_operations;
+}
+
+void fuse_init_dir(struct inode *inode)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	inode->i_op = &fuse_dir_inode_operations;
+	inode->i_fop = &fuse_dir_operations;
+
+	spin_lock_init(&fi->rdc.lock);
+	fi->rdc.cached = false;
+	fi->rdc.size = 0;
+	fi->rdc.pos = 0;
+	fi->rdc.version = 0;
+}
+
+static int fuse_symlink_readpage(struct file *null, struct page *page)
+{
+	int err = fuse_readlink_page(page->mapping->host, page);
+
+	if (!err)
+		SetPageUptodate(page);
+
+	unlock_page(page);
+
+	return err;
+}
+
+static const struct address_space_operations fuse_symlink_aops = {
+	.readpage	= fuse_symlink_readpage,
+};
+
+void fuse_init_symlink(struct inode *inode)
+{
+	inode->i_op = &fuse_symlink_inode_operations;
+	inode->i_data.a_ops = &fuse_symlink_aops;
+	inode_nohighmem(inode);
+}
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
new file mode 100644
index 000000000..13d97547e
--- /dev/null
+++ b/fs/fuse/file.c
@@ -0,0 +1,3538 @@
+/*
+  FUSE: Filesystem in Userspace
+  Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>
+
+  This program can be distributed under the terms of the GNU GPL.
+  See the file COPYING.
+*/
+
+#include "fuse_i.h"
+
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/sched/signal.h>
+#include <linux/module.h>
+#include <linux/compat.h>
+#include <linux/swap.h>
+#include <linux/falloc.h>
+#include <linux/uio.h>
+#include <linux/fs.h>
+
+static struct page **fuse_pages_alloc(unsigned int npages, gfp_t flags,
+				      struct fuse_page_desc **desc)
+{
+	struct page **pages;
+
+	pages = kzalloc(npages * (sizeof(struct page *) +
+				  sizeof(struct fuse_page_desc)), flags);
+	*desc = (void *) (pages + npages);
+
+	return pages;
+}
+
+static int fuse_send_open(struct fuse_mount *fm, u64 nodeid, struct file *file,
+			  int opcode, struct fuse_open_out *outargp)
+{
+	struct fuse_open_in inarg;
+	FUSE_ARGS(args);
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.flags = file->f_flags & ~(O_CREAT | O_EXCL | O_NOCTTY);
+	if (!fm->fc->atomic_o_trunc)
+		inarg.flags &= ~O_TRUNC;
+	args.opcode = opcode;
+	args.nodeid = nodeid;
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.out_numargs = 1;
+	args.out_args[0].size = sizeof(*outargp);
+	args.out_args[0].value = outargp;
+
+	return fuse_simple_request(fm, &args);
+}
+
+struct fuse_release_args {
+	struct fuse_args args;
+	struct fuse_release_in inarg;
+	struct inode *inode;
+};
+
+struct fuse_file *fuse_file_alloc(struct fuse_mount *fm)
+{
+	struct fuse_file *ff;
+
+	ff = kzalloc(sizeof(struct fuse_file), GFP_KERNEL_ACCOUNT);
+	if (unlikely(!ff))
+		return NULL;
+
+	ff->fm = fm;
+	ff->release_args = kzalloc(sizeof(*ff->release_args),
+				   GFP_KERNEL_ACCOUNT);
+	if (!ff->release_args) {
+		kfree(ff);
+		return NULL;
+	}
+
+	INIT_LIST_HEAD(&ff->write_entry);
+	mutex_init(&ff->readdir.lock);
+	refcount_set(&ff->count, 1);
+	RB_CLEAR_NODE(&ff->polled_node);
+	init_waitqueue_head(&ff->poll_wait);
+
+	ff->kh = atomic64_inc_return(&fm->fc->khctr);
+
+	return ff;
+}
+
+void fuse_file_free(struct fuse_file *ff)
+{
+	kfree(ff->release_args);
+	mutex_destroy(&ff->readdir.lock);
+	kfree(ff);
+}
+
+static struct fuse_file *fuse_file_get(struct fuse_file *ff)
+{
+	refcount_inc(&ff->count);
+	return ff;
+}
+
+static void fuse_release_end(struct fuse_mount *fm, struct fuse_args *args,
+			     int error)
+{
+	struct fuse_release_args *ra = container_of(args, typeof(*ra), args);
+
+	iput(ra->inode);
+	kfree(ra);
+}
+
+static void fuse_file_put(struct fuse_file *ff, bool sync, bool isdir)
+{
+	if (refcount_dec_and_test(&ff->count)) {
+		struct fuse_args *args = &ff->release_args->args;
+
+		if (isdir ? ff->fm->fc->no_opendir : ff->fm->fc->no_open) {
+			/* Do nothing when client does not implement 'open' */
+			fuse_release_end(ff->fm, args, 0);
+		} else if (sync) {
+			fuse_simple_request(ff->fm, args);
+			fuse_release_end(ff->fm, args, 0);
+		} else {
+			args->end = fuse_release_end;
+			if (fuse_simple_background(ff->fm, args,
+						   GFP_KERNEL | __GFP_NOFAIL))
+				fuse_release_end(ff->fm, args, -ENOTCONN);
+		}
+		kfree(ff);
+	}
+}
+
+int fuse_do_open(struct fuse_mount *fm, u64 nodeid, struct file *file,
+		 bool isdir)
+{
+	struct fuse_conn *fc = fm->fc;
+	struct fuse_file *ff;
+	int opcode = isdir ? FUSE_OPENDIR : FUSE_OPEN;
+
+	ff = fuse_file_alloc(fm);
+	if (!ff)
+		return -ENOMEM;
+
+	ff->fh = 0;
+	/* Default for no-open */
+	ff->open_flags = FOPEN_KEEP_CACHE | (isdir ? FOPEN_CACHE_DIR : 0);
+	if (isdir ? !fc->no_opendir : !fc->no_open) {
+		struct fuse_open_out outarg;
+		int err;
+
+		err = fuse_send_open(fm, nodeid, file, opcode, &outarg);
+		if (!err) {
+			ff->fh = outarg.fh;
+			ff->open_flags = outarg.open_flags;
+
+		} else if (err != -ENOSYS) {
+			fuse_file_free(ff);
+			return err;
+		} else {
+			if (isdir)
+				fc->no_opendir = 1;
+			else
+				fc->no_open = 1;
+		}
+	}
+
+	if (isdir)
+		ff->open_flags &= ~FOPEN_DIRECT_IO;
+
+	ff->nodeid = nodeid;
+	file->private_data = ff;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fuse_do_open);
+
+static void fuse_link_write_file(struct file *file)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_file *ff = file->private_data;
+	/*
+	 * file may be written through mmap, so chain it onto the
+	 * inodes's write_file list
+	 */
+	spin_lock(&fi->lock);
+	if (list_empty(&ff->write_entry))
+		list_add(&ff->write_entry, &fi->write_files);
+	spin_unlock(&fi->lock);
+}
+
+void fuse_finish_open(struct inode *inode, struct file *file)
+{
+	struct fuse_file *ff = file->private_data;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	if (ff->open_flags & FOPEN_STREAM)
+		stream_open(inode, file);
+	else if (ff->open_flags & FOPEN_NONSEEKABLE)
+		nonseekable_open(inode, file);
+
+	if (fc->atomic_o_trunc && (file->f_flags & O_TRUNC)) {
+		struct fuse_inode *fi = get_fuse_inode(inode);
+
+		spin_lock(&fi->lock);
+		fi->attr_version = atomic64_inc_return(&fc->attr_version);
+		i_size_write(inode, 0);
+		spin_unlock(&fi->lock);
+		fuse_invalidate_attr(inode);
+		if (fc->writeback_cache)
+			file_update_time(file);
+	}
+	if ((file->f_mode & FMODE_WRITE) && fc->writeback_cache)
+		fuse_link_write_file(file);
+}
+
+int fuse_open_common(struct inode *inode, struct file *file, bool isdir)
+{
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	struct fuse_conn *fc = fm->fc;
+	int err;
+	bool is_wb_truncate = (file->f_flags & O_TRUNC) &&
+			  fc->atomic_o_trunc &&
+			  fc->writeback_cache;
+	bool dax_truncate = (file->f_flags & O_TRUNC) &&
+			  fc->atomic_o_trunc && FUSE_IS_DAX(inode);
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	err = generic_file_open(inode, file);
+	if (err)
+		return err;
+
+	if (is_wb_truncate || dax_truncate)
+		inode_lock(inode);
+
+	if (dax_truncate) {
+		down_write(&get_fuse_inode(inode)->i_mmap_sem);
+		err = fuse_dax_break_layouts(inode, 0, 0);
+		if (err)
+			goto out_inode_unlock;
+	}
+
+	if (is_wb_truncate || dax_truncate)
+		fuse_set_nowrite(inode);
+
+	err = fuse_do_open(fm, get_node_id(inode), file, isdir);
+	if (!err)
+		fuse_finish_open(inode, file);
+
+	if (is_wb_truncate || dax_truncate)
+		fuse_release_nowrite(inode);
+	if (!err) {
+		struct fuse_file *ff = file->private_data;
+
+		if (fc->atomic_o_trunc && (file->f_flags & O_TRUNC))
+			truncate_pagecache(inode, 0);
+		else if (!(ff->open_flags & FOPEN_KEEP_CACHE))
+			invalidate_inode_pages2(inode->i_mapping);
+	}
+	if (dax_truncate)
+		up_write(&get_fuse_inode(inode)->i_mmap_sem);
+
+out_inode_unlock:
+	if (is_wb_truncate || dax_truncate)
+		inode_unlock(inode);
+
+	return err;
+}
+
+static void fuse_prepare_release(struct fuse_inode *fi, struct fuse_file *ff,
+				 int flags, int opcode)
+{
+	struct fuse_conn *fc = ff->fm->fc;
+	struct fuse_release_args *ra = ff->release_args;
+
+	/* Inode is NULL on error path of fuse_create_open() */
+	if (likely(fi)) {
+		spin_lock(&fi->lock);
+		list_del(&ff->write_entry);
+		spin_unlock(&fi->lock);
+	}
+	spin_lock(&fc->lock);
+	if (!RB_EMPTY_NODE(&ff->polled_node))
+		rb_erase(&ff->polled_node, &fc->polled_files);
+	spin_unlock(&fc->lock);
+
+	wake_up_interruptible_all(&ff->poll_wait);
+
+	ra->inarg.fh = ff->fh;
+	ra->inarg.flags = flags;
+	ra->args.in_numargs = 1;
+	ra->args.in_args[0].size = sizeof(struct fuse_release_in);
+	ra->args.in_args[0].value = &ra->inarg;
+	ra->args.opcode = opcode;
+	ra->args.nodeid = ff->nodeid;
+	ra->args.force = true;
+	ra->args.nocreds = true;
+}
+
+void fuse_release_common(struct file *file, bool isdir)
+{
+	struct fuse_inode *fi = get_fuse_inode(file_inode(file));
+	struct fuse_file *ff = file->private_data;
+	struct fuse_release_args *ra = ff->release_args;
+	int opcode = isdir ? FUSE_RELEASEDIR : FUSE_RELEASE;
+
+	fuse_prepare_release(fi, ff, file->f_flags, opcode);
+
+	if (ff->flock) {
+		ra->inarg.release_flags |= FUSE_RELEASE_FLOCK_UNLOCK;
+		ra->inarg.lock_owner = fuse_lock_owner_id(ff->fm->fc,
+							  (fl_owner_t) file);
+	}
+	/* Hold inode until release is finished */
+	ra->inode = igrab(file_inode(file));
+
+	/*
+	 * Normally this will send the RELEASE request, however if
+	 * some asynchronous READ or WRITE requests are outstanding,
+	 * the sending will be delayed.
+	 *
+	 * Make the release synchronous if this is a fuseblk mount,
+	 * synchronous RELEASE is allowed (and desirable) in this case
+	 * because the server can be trusted not to screw up.
+	 */
+	fuse_file_put(ff, ff->fm->fc->destroy, isdir);
+}
+
+static int fuse_open(struct inode *inode, struct file *file)
+{
+	return fuse_open_common(inode, file, false);
+}
+
+static int fuse_release(struct inode *inode, struct file *file)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	/* see fuse_vma_close() for !writeback_cache case */
+	if (fc->writeback_cache)
+		write_inode_now(inode, 1);
+
+	fuse_release_common(file, false);
+
+	/* return value is ignored by VFS */
+	return 0;
+}
+
+void fuse_sync_release(struct fuse_inode *fi, struct fuse_file *ff, int flags)
+{
+	WARN_ON(refcount_read(&ff->count) > 1);
+	fuse_prepare_release(fi, ff, flags, FUSE_RELEASE);
+	/*
+	 * iput(NULL) is a no-op and since the refcount is 1 and everything's
+	 * synchronous, we are fine with not doing igrab() here"
+	 */
+	fuse_file_put(ff, true, false);
+}
+EXPORT_SYMBOL_GPL(fuse_sync_release);
+
+/*
+ * Scramble the ID space with XTEA, so that the value of the files_struct
+ * pointer is not exposed to userspace.
+ */
+u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id)
+{
+	u32 *k = fc->scramble_key;
+	u64 v = (unsigned long) id;
+	u32 v0 = v;
+	u32 v1 = v >> 32;
+	u32 sum = 0;
+	int i;
+
+	for (i = 0; i < 32; i++) {
+		v0 += ((v1 << 4 ^ v1 >> 5) + v1) ^ (sum + k[sum & 3]);
+		sum += 0x9E3779B9;
+		v1 += ((v0 << 4 ^ v0 >> 5) + v0) ^ (sum + k[sum>>11 & 3]);
+	}
+
+	return (u64) v0 + ((u64) v1 << 32);
+}
+
+struct fuse_writepage_args {
+	struct fuse_io_args ia;
+	struct rb_node writepages_entry;
+	struct list_head queue_entry;
+	struct fuse_writepage_args *next;
+	struct inode *inode;
+};
+
+static struct fuse_writepage_args *fuse_find_writeback(struct fuse_inode *fi,
+					    pgoff_t idx_from, pgoff_t idx_to)
+{
+	struct rb_node *n;
+
+	n = fi->writepages.rb_node;
+
+	while (n) {
+		struct fuse_writepage_args *wpa;
+		pgoff_t curr_index;
+
+		wpa = rb_entry(n, struct fuse_writepage_args, writepages_entry);
+		WARN_ON(get_fuse_inode(wpa->inode) != fi);
+		curr_index = wpa->ia.write.in.offset >> PAGE_SHIFT;
+		if (idx_from >= curr_index + wpa->ia.ap.num_pages)
+			n = n->rb_right;
+		else if (idx_to < curr_index)
+			n = n->rb_left;
+		else
+			return wpa;
+	}
+	return NULL;
+}
+
+/*
+ * Check if any page in a range is under writeback
+ *
+ * This is currently done by walking the list of writepage requests
+ * for the inode, which can be pretty inefficient.
+ */
+static bool fuse_range_is_writeback(struct inode *inode, pgoff_t idx_from,
+				   pgoff_t idx_to)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	bool found;
+
+	spin_lock(&fi->lock);
+	found = fuse_find_writeback(fi, idx_from, idx_to);
+	spin_unlock(&fi->lock);
+
+	return found;
+}
+
+static inline bool fuse_page_is_writeback(struct inode *inode, pgoff_t index)
+{
+	return fuse_range_is_writeback(inode, index, index);
+}
+
+/*
+ * Wait for page writeback to be completed.
+ *
+ * Since fuse doesn't rely on the VM writeback tracking, this has to
+ * use some other means.
+ */
+static void fuse_wait_on_page_writeback(struct inode *inode, pgoff_t index)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	wait_event(fi->page_waitq, !fuse_page_is_writeback(inode, index));
+}
+
+/*
+ * Wait for all pending writepages on the inode to finish.
+ *
+ * This is currently done by blocking further writes with FUSE_NOWRITE
+ * and waiting for all sent writes to complete.
+ *
+ * This must be called under i_mutex, otherwise the FUSE_NOWRITE usage
+ * could conflict with truncation.
+ */
+static void fuse_sync_writes(struct inode *inode)
+{
+	fuse_set_nowrite(inode);
+	fuse_release_nowrite(inode);
+}
+
+static int fuse_flush(struct file *file, fl_owner_t id)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	struct fuse_file *ff = file->private_data;
+	struct fuse_flush_in inarg;
+	FUSE_ARGS(args);
+	int err;
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	err = write_inode_now(inode, 1);
+	if (err)
+		return err;
+
+	inode_lock(inode);
+	fuse_sync_writes(inode);
+	inode_unlock(inode);
+
+	err = filemap_check_errors(file->f_mapping);
+	if (err)
+		return err;
+
+	err = 0;
+	if (fm->fc->no_flush)
+		goto inval_attr_out;
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.fh = ff->fh;
+	inarg.lock_owner = fuse_lock_owner_id(fm->fc, id);
+	args.opcode = FUSE_FLUSH;
+	args.nodeid = get_node_id(inode);
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.force = true;
+
+	err = fuse_simple_request(fm, &args);
+	if (err == -ENOSYS) {
+		fm->fc->no_flush = 1;
+		err = 0;
+	}
+
+inval_attr_out:
+	/*
+	 * In memory i_blocks is not maintained by fuse, if writeback cache is
+	 * enabled, i_blocks from cached attr may not be accurate.
+	 */
+	if (!err && fm->fc->writeback_cache)
+		fuse_invalidate_attr(inode);
+	return err;
+}
+
+int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
+		      int datasync, int opcode)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	struct fuse_file *ff = file->private_data;
+	FUSE_ARGS(args);
+	struct fuse_fsync_in inarg;
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.fh = ff->fh;
+	inarg.fsync_flags = datasync ? FUSE_FSYNC_FDATASYNC : 0;
+	args.opcode = opcode;
+	args.nodeid = get_node_id(inode);
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	return fuse_simple_request(fm, &args);
+}
+
+static int fuse_fsync(struct file *file, loff_t start, loff_t end,
+		      int datasync)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	int err;
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	inode_lock(inode);
+
+	/*
+	 * Start writeback against all dirty pages of the inode, then
+	 * wait for all outstanding writes, before sending the FSYNC
+	 * request.
+	 */
+	err = file_write_and_wait_range(file, start, end);
+	if (err)
+		goto out;
+
+	fuse_sync_writes(inode);
+
+	/*
+	 * Due to implementation of fuse writeback
+	 * file_write_and_wait_range() does not catch errors.
+	 * We have to do this directly after fuse_sync_writes()
+	 */
+	err = file_check_and_advance_wb_err(file);
+	if (err)
+		goto out;
+
+	err = sync_inode_metadata(inode, 1);
+	if (err)
+		goto out;
+
+	if (fc->no_fsync)
+		goto out;
+
+	err = fuse_fsync_common(file, start, end, datasync, FUSE_FSYNC);
+	if (err == -ENOSYS) {
+		fc->no_fsync = 1;
+		err = 0;
+	}
+out:
+	inode_unlock(inode);
+
+	return err;
+}
+
+void fuse_read_args_fill(struct fuse_io_args *ia, struct file *file, loff_t pos,
+			 size_t count, int opcode)
+{
+	struct fuse_file *ff = file->private_data;
+	struct fuse_args *args = &ia->ap.args;
+
+	ia->read.in.fh = ff->fh;
+	ia->read.in.offset = pos;
+	ia->read.in.size = count;
+	ia->read.in.flags = file->f_flags;
+	args->opcode = opcode;
+	args->nodeid = ff->nodeid;
+	args->in_numargs = 1;
+	args->in_args[0].size = sizeof(ia->read.in);
+	args->in_args[0].value = &ia->read.in;
+	args->out_argvar = true;
+	args->out_numargs = 1;
+	args->out_args[0].size = count;
+}
+
+static void fuse_release_user_pages(struct fuse_args_pages *ap,
+				    bool should_dirty)
+{
+	unsigned int i;
+
+	for (i = 0; i < ap->num_pages; i++) {
+		if (should_dirty)
+			set_page_dirty_lock(ap->pages[i]);
+		put_page(ap->pages[i]);
+	}
+}
+
+static void fuse_io_release(struct kref *kref)
+{
+	kfree(container_of(kref, struct fuse_io_priv, refcnt));
+}
+
+static ssize_t fuse_get_res_by_io(struct fuse_io_priv *io)
+{
+	if (io->err)
+		return io->err;
+
+	if (io->bytes >= 0 && io->write)
+		return -EIO;
+
+	return io->bytes < 0 ? io->size : io->bytes;
+}
+
+/**
+ * In case of short read, the caller sets 'pos' to the position of
+ * actual end of fuse request in IO request. Otherwise, if bytes_requested
+ * == bytes_transferred or rw == WRITE, the caller sets 'pos' to -1.
+ *
+ * An example:
+ * User requested DIO read of 64K. It was splitted into two 32K fuse requests,
+ * both submitted asynchronously. The first of them was ACKed by userspace as
+ * fully completed (req->out.args[0].size == 32K) resulting in pos == -1. The
+ * second request was ACKed as short, e.g. only 1K was read, resulting in
+ * pos == 33K.
+ *
+ * Thus, when all fuse requests are completed, the minimal non-negative 'pos'
+ * will be equal to the length of the longest contiguous fragment of
+ * transferred data starting from the beginning of IO request.
+ */
+static void fuse_aio_complete(struct fuse_io_priv *io, int err, ssize_t pos)
+{
+	int left;
+
+	spin_lock(&io->lock);
+	if (err)
+		io->err = io->err ? : err;
+	else if (pos >= 0 && (io->bytes < 0 || pos < io->bytes))
+		io->bytes = pos;
+
+	left = --io->reqs;
+	if (!left && io->blocking)
+		complete(io->done);
+	spin_unlock(&io->lock);
+
+	if (!left && !io->blocking) {
+		ssize_t res = fuse_get_res_by_io(io);
+
+		if (res >= 0) {
+			struct inode *inode = file_inode(io->iocb->ki_filp);
+			struct fuse_conn *fc = get_fuse_conn(inode);
+			struct fuse_inode *fi = get_fuse_inode(inode);
+
+			spin_lock(&fi->lock);
+			fi->attr_version = atomic64_inc_return(&fc->attr_version);
+			spin_unlock(&fi->lock);
+		}
+
+		io->iocb->ki_complete(io->iocb, res, 0);
+	}
+
+	kref_put(&io->refcnt, fuse_io_release);
+}
+
+static struct fuse_io_args *fuse_io_alloc(struct fuse_io_priv *io,
+					  unsigned int npages)
+{
+	struct fuse_io_args *ia;
+
+	ia = kzalloc(sizeof(*ia), GFP_KERNEL);
+	if (ia) {
+		ia->io = io;
+		ia->ap.pages = fuse_pages_alloc(npages, GFP_KERNEL,
+						&ia->ap.descs);
+		if (!ia->ap.pages) {
+			kfree(ia);
+			ia = NULL;
+		}
+	}
+	return ia;
+}
+
+static void fuse_io_free(struct fuse_io_args *ia)
+{
+	kfree(ia->ap.pages);
+	kfree(ia);
+}
+
+static void fuse_aio_complete_req(struct fuse_mount *fm, struct fuse_args *args,
+				  int err)
+{
+	struct fuse_io_args *ia = container_of(args, typeof(*ia), ap.args);
+	struct fuse_io_priv *io = ia->io;
+	ssize_t pos = -1;
+
+	fuse_release_user_pages(&ia->ap, io->should_dirty);
+
+	if (err) {
+		/* Nothing */
+	} else if (io->write) {
+		if (ia->write.out.size > ia->write.in.size) {
+			err = -EIO;
+		} else if (ia->write.in.size != ia->write.out.size) {
+			pos = ia->write.in.offset - io->offset +
+				ia->write.out.size;
+		}
+	} else {
+		u32 outsize = args->out_args[0].size;
+
+		if (ia->read.in.size != outsize)
+			pos = ia->read.in.offset - io->offset + outsize;
+	}
+
+	fuse_aio_complete(io, err, pos);
+	fuse_io_free(ia);
+}
+
+static ssize_t fuse_async_req_send(struct fuse_mount *fm,
+				   struct fuse_io_args *ia, size_t num_bytes)
+{
+	ssize_t err;
+	struct fuse_io_priv *io = ia->io;
+
+	spin_lock(&io->lock);
+	kref_get(&io->refcnt);
+	io->size += num_bytes;
+	io->reqs++;
+	spin_unlock(&io->lock);
+
+	ia->ap.args.end = fuse_aio_complete_req;
+	ia->ap.args.may_block = io->should_dirty;
+	err = fuse_simple_background(fm, &ia->ap.args, GFP_KERNEL);
+	if (err)
+		fuse_aio_complete_req(fm, &ia->ap.args, err);
+
+	return num_bytes;
+}
+
+static ssize_t fuse_send_read(struct fuse_io_args *ia, loff_t pos, size_t count,
+			      fl_owner_t owner)
+{
+	struct file *file = ia->io->iocb->ki_filp;
+	struct fuse_file *ff = file->private_data;
+	struct fuse_mount *fm = ff->fm;
+
+	fuse_read_args_fill(ia, file, pos, count, FUSE_READ);
+	if (owner != NULL) {
+		ia->read.in.read_flags |= FUSE_READ_LOCKOWNER;
+		ia->read.in.lock_owner = fuse_lock_owner_id(fm->fc, owner);
+	}
+
+	if (ia->io->async)
+		return fuse_async_req_send(fm, ia, count);
+
+	return fuse_simple_request(fm, &ia->ap.args);
+}
+
+static void fuse_read_update_size(struct inode *inode, loff_t size,
+				  u64 attr_ver)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	spin_lock(&fi->lock);
+	if (attr_ver >= fi->attr_version && size < inode->i_size &&
+	    !test_bit(FUSE_I_SIZE_UNSTABLE, &fi->state)) {
+		fi->attr_version = atomic64_inc_return(&fc->attr_version);
+		i_size_write(inode, size);
+	}
+	spin_unlock(&fi->lock);
+}
+
+static void fuse_short_read(struct inode *inode, u64 attr_ver, size_t num_read,
+			    struct fuse_args_pages *ap)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	if (fc->writeback_cache) {
+		/*
+		 * A hole in a file. Some data after the hole are in page cache,
+		 * but have not reached the client fs yet. So, the hole is not
+		 * present there.
+		 */
+		int i;
+		int start_idx = num_read >> PAGE_SHIFT;
+		size_t off = num_read & (PAGE_SIZE - 1);
+
+		for (i = start_idx; i < ap->num_pages; i++) {
+			zero_user_segment(ap->pages[i], off, PAGE_SIZE);
+			off = 0;
+		}
+	} else {
+		loff_t pos = page_offset(ap->pages[0]) + num_read;
+		fuse_read_update_size(inode, pos, attr_ver);
+	}
+}
+
+static int fuse_do_readpage(struct file *file, struct page *page)
+{
+	struct inode *inode = page->mapping->host;
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	loff_t pos = page_offset(page);
+	struct fuse_page_desc desc = { .length = PAGE_SIZE };
+	struct fuse_io_args ia = {
+		.ap.args.page_zeroing = true,
+		.ap.args.out_pages = true,
+		.ap.num_pages = 1,
+		.ap.pages = &page,
+		.ap.descs = &desc,
+	};
+	ssize_t res;
+	u64 attr_ver;
+
+	/*
+	 * Page writeback can extend beyond the lifetime of the
+	 * page-cache page, so make sure we read a properly synced
+	 * page.
+	 */
+	fuse_wait_on_page_writeback(inode, page->index);
+
+	attr_ver = fuse_get_attr_version(fm->fc);
+
+	/* Don't overflow end offset */
+	if (pos + (desc.length - 1) == LLONG_MAX)
+		desc.length--;
+
+	fuse_read_args_fill(&ia, file, pos, desc.length, FUSE_READ);
+	res = fuse_simple_request(fm, &ia.ap.args);
+	if (res < 0)
+		return res;
+	/*
+	 * Short read means EOF.  If file size is larger, truncate it
+	 */
+	if (res < desc.length)
+		fuse_short_read(inode, attr_ver, res, &ia.ap);
+
+	SetPageUptodate(page);
+
+	return 0;
+}
+
+static int fuse_readpage(struct file *file, struct page *page)
+{
+	struct inode *inode = page->mapping->host;
+	int err;
+
+	err = -EIO;
+	if (fuse_is_bad(inode))
+		goto out;
+
+	err = fuse_do_readpage(file, page);
+	fuse_invalidate_atime(inode);
+ out:
+	unlock_page(page);
+	return err;
+}
+
+static void fuse_readpages_end(struct fuse_mount *fm, struct fuse_args *args,
+			       int err)
+{
+	int i;
+	struct fuse_io_args *ia = container_of(args, typeof(*ia), ap.args);
+	struct fuse_args_pages *ap = &ia->ap;
+	size_t count = ia->read.in.size;
+	size_t num_read = args->out_args[0].size;
+	struct address_space *mapping = NULL;
+
+	for (i = 0; mapping == NULL && i < ap->num_pages; i++)
+		mapping = ap->pages[i]->mapping;
+
+	if (mapping) {
+		struct inode *inode = mapping->host;
+
+		/*
+		 * Short read means EOF. If file size is larger, truncate it
+		 */
+		if (!err && num_read < count)
+			fuse_short_read(inode, ia->read.attr_ver, num_read, ap);
+
+		fuse_invalidate_atime(inode);
+	}
+
+	for (i = 0; i < ap->num_pages; i++) {
+		struct page *page = ap->pages[i];
+
+		if (!err)
+			SetPageUptodate(page);
+		else
+			SetPageError(page);
+		unlock_page(page);
+		put_page(page);
+	}
+	if (ia->ff)
+		fuse_file_put(ia->ff, false, false);
+
+	fuse_io_free(ia);
+}
+
+static void fuse_send_readpages(struct fuse_io_args *ia, struct file *file)
+{
+	struct fuse_file *ff = file->private_data;
+	struct fuse_mount *fm = ff->fm;
+	struct fuse_args_pages *ap = &ia->ap;
+	loff_t pos = page_offset(ap->pages[0]);
+	size_t count = ap->num_pages << PAGE_SHIFT;
+	ssize_t res;
+	int err;
+
+	ap->args.out_pages = true;
+	ap->args.page_zeroing = true;
+	ap->args.page_replace = true;
+
+	/* Don't overflow end offset */
+	if (pos + (count - 1) == LLONG_MAX) {
+		count--;
+		ap->descs[ap->num_pages - 1].length--;
+	}
+	WARN_ON((loff_t) (pos + count) < 0);
+
+	fuse_read_args_fill(ia, file, pos, count, FUSE_READ);
+	ia->read.attr_ver = fuse_get_attr_version(fm->fc);
+	if (fm->fc->async_read) {
+		ia->ff = fuse_file_get(ff);
+		ap->args.end = fuse_readpages_end;
+		err = fuse_simple_background(fm, &ap->args, GFP_KERNEL);
+		if (!err)
+			return;
+	} else {
+		res = fuse_simple_request(fm, &ap->args);
+		err = res < 0 ? res : 0;
+	}
+	fuse_readpages_end(fm, &ap->args, err);
+}
+
+static void fuse_readahead(struct readahead_control *rac)
+{
+	struct inode *inode = rac->mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	unsigned int i, max_pages, nr_pages = 0;
+
+	if (fuse_is_bad(inode))
+		return;
+
+	max_pages = min_t(unsigned int, fc->max_pages,
+			fc->max_read / PAGE_SIZE);
+
+	for (;;) {
+		struct fuse_io_args *ia;
+		struct fuse_args_pages *ap;
+
+		nr_pages = readahead_count(rac) - nr_pages;
+		if (nr_pages > max_pages)
+			nr_pages = max_pages;
+		if (nr_pages == 0)
+			break;
+		ia = fuse_io_alloc(NULL, nr_pages);
+		if (!ia)
+			return;
+		ap = &ia->ap;
+		nr_pages = __readahead_batch(rac, ap->pages, nr_pages);
+		for (i = 0; i < nr_pages; i++) {
+			fuse_wait_on_page_writeback(inode,
+						    readahead_index(rac) + i);
+			ap->descs[i].length = PAGE_SIZE;
+		}
+		ap->num_pages = nr_pages;
+		fuse_send_readpages(ia, rac->file);
+	}
+}
+
+static ssize_t fuse_cache_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct inode *inode = iocb->ki_filp->f_mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	/*
+	 * In auto invalidate mode, always update attributes on read.
+	 * Otherwise, only update if we attempt to read past EOF (to ensure
+	 * i_size is up to date).
+	 */
+	if (fc->auto_inval_data ||
+	    (iocb->ki_pos + iov_iter_count(to) > i_size_read(inode))) {
+		int err;
+		err = fuse_update_attributes(inode, iocb->ki_filp);
+		if (err)
+			return err;
+	}
+
+	return generic_file_read_iter(iocb, to);
+}
+
+static void fuse_write_args_fill(struct fuse_io_args *ia, struct fuse_file *ff,
+				 loff_t pos, size_t count)
+{
+	struct fuse_args *args = &ia->ap.args;
+
+	ia->write.in.fh = ff->fh;
+	ia->write.in.offset = pos;
+	ia->write.in.size = count;
+	args->opcode = FUSE_WRITE;
+	args->nodeid = ff->nodeid;
+	args->in_numargs = 2;
+	if (ff->fm->fc->minor < 9)
+		args->in_args[0].size = FUSE_COMPAT_WRITE_IN_SIZE;
+	else
+		args->in_args[0].size = sizeof(ia->write.in);
+	args->in_args[0].value = &ia->write.in;
+	args->in_args[1].size = count;
+	args->out_numargs = 1;
+	args->out_args[0].size = sizeof(ia->write.out);
+	args->out_args[0].value = &ia->write.out;
+}
+
+static unsigned int fuse_write_flags(struct kiocb *iocb)
+{
+	unsigned int flags = iocb->ki_filp->f_flags;
+
+	if (iocb->ki_flags & IOCB_DSYNC)
+		flags |= O_DSYNC;
+	if (iocb->ki_flags & IOCB_SYNC)
+		flags |= O_SYNC;
+
+	return flags;
+}
+
+static ssize_t fuse_send_write(struct fuse_io_args *ia, loff_t pos,
+			       size_t count, fl_owner_t owner)
+{
+	struct kiocb *iocb = ia->io->iocb;
+	struct file *file = iocb->ki_filp;
+	struct fuse_file *ff = file->private_data;
+	struct fuse_mount *fm = ff->fm;
+	struct fuse_write_in *inarg = &ia->write.in;
+	ssize_t err;
+
+	fuse_write_args_fill(ia, ff, pos, count);
+	inarg->flags = fuse_write_flags(iocb);
+	if (owner != NULL) {
+		inarg->write_flags |= FUSE_WRITE_LOCKOWNER;
+		inarg->lock_owner = fuse_lock_owner_id(fm->fc, owner);
+	}
+
+	if (ia->io->async)
+		return fuse_async_req_send(fm, ia, count);
+
+	err = fuse_simple_request(fm, &ia->ap.args);
+	if (!err && ia->write.out.size > count)
+		err = -EIO;
+
+	return err ?: ia->write.out.size;
+}
+
+bool fuse_write_update_size(struct inode *inode, loff_t pos)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	bool ret = false;
+
+	spin_lock(&fi->lock);
+	fi->attr_version = atomic64_inc_return(&fc->attr_version);
+	if (pos > inode->i_size) {
+		i_size_write(inode, pos);
+		ret = true;
+	}
+	spin_unlock(&fi->lock);
+
+	return ret;
+}
+
+static ssize_t fuse_send_write_pages(struct fuse_io_args *ia,
+				     struct kiocb *iocb, struct inode *inode,
+				     loff_t pos, size_t count)
+{
+	struct fuse_args_pages *ap = &ia->ap;
+	struct file *file = iocb->ki_filp;
+	struct fuse_file *ff = file->private_data;
+	struct fuse_mount *fm = ff->fm;
+	unsigned int offset, i;
+	bool short_write;
+	int err;
+
+	for (i = 0; i < ap->num_pages; i++)
+		fuse_wait_on_page_writeback(inode, ap->pages[i]->index);
+
+	fuse_write_args_fill(ia, ff, pos, count);
+	ia->write.in.flags = fuse_write_flags(iocb);
+
+	err = fuse_simple_request(fm, &ap->args);
+	if (!err && ia->write.out.size > count)
+		err = -EIO;
+
+	short_write = ia->write.out.size < count;
+	offset = ap->descs[0].offset;
+	count = ia->write.out.size;
+	for (i = 0; i < ap->num_pages; i++) {
+		struct page *page = ap->pages[i];
+
+		if (err) {
+			ClearPageUptodate(page);
+		} else {
+			if (count >= PAGE_SIZE - offset)
+				count -= PAGE_SIZE - offset;
+			else {
+				if (short_write)
+					ClearPageUptodate(page);
+				count = 0;
+			}
+			offset = 0;
+		}
+		if (ia->write.page_locked && (i == ap->num_pages - 1))
+			unlock_page(page);
+		put_page(page);
+	}
+
+	return err;
+}
+
+static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
+				     struct address_space *mapping,
+				     struct iov_iter *ii, loff_t pos,
+				     unsigned int max_pages)
+{
+	struct fuse_args_pages *ap = &ia->ap;
+	struct fuse_conn *fc = get_fuse_conn(mapping->host);
+	unsigned offset = pos & (PAGE_SIZE - 1);
+	size_t count = 0;
+	int err;
+
+	ap->args.in_pages = true;
+	ap->descs[0].offset = offset;
+
+	do {
+		size_t tmp;
+		struct page *page;
+		pgoff_t index = pos >> PAGE_SHIFT;
+		size_t bytes = min_t(size_t, PAGE_SIZE - offset,
+				     iov_iter_count(ii));
+
+		bytes = min_t(size_t, bytes, fc->max_write - count);
+
+ again:
+		err = -EFAULT;
+		if (iov_iter_fault_in_readable(ii, bytes))
+			break;
+
+		err = -ENOMEM;
+		page = grab_cache_page_write_begin(mapping, index, 0);
+		if (!page)
+			break;
+
+		if (mapping_writably_mapped(mapping))
+			flush_dcache_page(page);
+
+		tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes);
+		flush_dcache_page(page);
+
+		iov_iter_advance(ii, tmp);
+		if (!tmp) {
+			unlock_page(page);
+			put_page(page);
+			bytes = min(bytes, iov_iter_single_seg_count(ii));
+			goto again;
+		}
+
+		err = 0;
+		ap->pages[ap->num_pages] = page;
+		ap->descs[ap->num_pages].length = tmp;
+		ap->num_pages++;
+
+		count += tmp;
+		pos += tmp;
+		offset += tmp;
+		if (offset == PAGE_SIZE)
+			offset = 0;
+
+		/* If we copied full page, mark it uptodate */
+		if (tmp == PAGE_SIZE)
+			SetPageUptodate(page);
+
+		if (PageUptodate(page)) {
+			unlock_page(page);
+		} else {
+			ia->write.page_locked = true;
+			break;
+		}
+		if (!fc->big_writes)
+			break;
+	} while (iov_iter_count(ii) && count < fc->max_write &&
+		 ap->num_pages < max_pages && offset == 0);
+
+	return count > 0 ? count : err;
+}
+
+static inline unsigned int fuse_wr_pages(loff_t pos, size_t len,
+				     unsigned int max_pages)
+{
+	return min_t(unsigned int,
+		     ((pos + len - 1) >> PAGE_SHIFT) -
+		     (pos >> PAGE_SHIFT) + 1,
+		     max_pages);
+}
+
+static ssize_t fuse_perform_write(struct kiocb *iocb,
+				  struct address_space *mapping,
+				  struct iov_iter *ii, loff_t pos)
+{
+	struct inode *inode = mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	int err = 0;
+	ssize_t res = 0;
+
+	if (inode->i_size < pos + iov_iter_count(ii))
+		set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
+
+	do {
+		ssize_t count;
+		struct fuse_io_args ia = {};
+		struct fuse_args_pages *ap = &ia.ap;
+		unsigned int nr_pages = fuse_wr_pages(pos, iov_iter_count(ii),
+						      fc->max_pages);
+
+		ap->pages = fuse_pages_alloc(nr_pages, GFP_KERNEL, &ap->descs);
+		if (!ap->pages) {
+			err = -ENOMEM;
+			break;
+		}
+
+		count = fuse_fill_write_pages(&ia, mapping, ii, pos, nr_pages);
+		if (count <= 0) {
+			err = count;
+		} else {
+			err = fuse_send_write_pages(&ia, iocb, inode,
+						    pos, count);
+			if (!err) {
+				size_t num_written = ia.write.out.size;
+
+				res += num_written;
+				pos += num_written;
+
+				/* break out of the loop on short write */
+				if (num_written != count)
+					err = -EIO;
+			}
+		}
+		kfree(ap->pages);
+	} while (!err && iov_iter_count(ii));
+
+	if (res > 0)
+		fuse_write_update_size(inode, pos);
+
+	clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
+	fuse_invalidate_attr(inode);
+
+	return res > 0 ? res : err;
+}
+
+static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct address_space *mapping = file->f_mapping;
+	ssize_t written = 0;
+	ssize_t written_buffered = 0;
+	struct inode *inode = mapping->host;
+	ssize_t err;
+	loff_t endbyte = 0;
+
+	if (get_fuse_conn(inode)->writeback_cache) {
+		/* Update size (EOF optimization) and mode (SUID clearing) */
+		err = fuse_update_attributes(mapping->host, file);
+		if (err)
+			return err;
+
+		return generic_file_write_iter(iocb, from);
+	}
+
+	inode_lock(inode);
+
+	/* We can write back this queue in page reclaim */
+	current->backing_dev_info = inode_to_bdi(inode);
+
+	err = generic_write_checks(iocb, from);
+	if (err <= 0)
+		goto out;
+
+	err = file_remove_privs(file);
+	if (err)
+		goto out;
+
+	err = file_update_time(file);
+	if (err)
+		goto out;
+
+	if (iocb->ki_flags & IOCB_DIRECT) {
+		loff_t pos = iocb->ki_pos;
+		written = generic_file_direct_write(iocb, from);
+		if (written < 0 || !iov_iter_count(from))
+			goto out;
+
+		pos += written;
+
+		written_buffered = fuse_perform_write(iocb, mapping, from, pos);
+		if (written_buffered < 0) {
+			err = written_buffered;
+			goto out;
+		}
+		endbyte = pos + written_buffered - 1;
+
+		err = filemap_write_and_wait_range(file->f_mapping, pos,
+						   endbyte);
+		if (err)
+			goto out;
+
+		invalidate_mapping_pages(file->f_mapping,
+					 pos >> PAGE_SHIFT,
+					 endbyte >> PAGE_SHIFT);
+
+		written += written_buffered;
+		iocb->ki_pos = pos + written_buffered;
+	} else {
+		written = fuse_perform_write(iocb, mapping, from, iocb->ki_pos);
+		if (written >= 0)
+			iocb->ki_pos += written;
+	}
+out:
+	current->backing_dev_info = NULL;
+	inode_unlock(inode);
+	if (written > 0)
+		written = generic_write_sync(iocb, written);
+
+	return written ? written : err;
+}
+
+static inline void fuse_page_descs_length_init(struct fuse_page_desc *descs,
+					       unsigned int index,
+					       unsigned int nr_pages)
+{
+	int i;
+
+	for (i = index; i < index + nr_pages; i++)
+		descs[i].length = PAGE_SIZE - descs[i].offset;
+}
+
+static inline unsigned long fuse_get_user_addr(const struct iov_iter *ii)
+{
+	return (unsigned long)ii->iov->iov_base + ii->iov_offset;
+}
+
+static inline size_t fuse_get_frag_size(const struct iov_iter *ii,
+					size_t max_size)
+{
+	return min(iov_iter_single_seg_count(ii), max_size);
+}
+
+static int fuse_get_user_pages(struct fuse_args_pages *ap, struct iov_iter *ii,
+			       size_t *nbytesp, int write,
+			       unsigned int max_pages)
+{
+	size_t nbytes = 0;  /* # bytes already packed in req */
+	ssize_t ret = 0;
+
+	/* Special case for kernel I/O: can copy directly into the buffer */
+	if (iov_iter_is_kvec(ii)) {
+		unsigned long user_addr = fuse_get_user_addr(ii);
+		size_t frag_size = fuse_get_frag_size(ii, *nbytesp);
+
+		if (write)
+			ap->args.in_args[1].value = (void *) user_addr;
+		else
+			ap->args.out_args[0].value = (void *) user_addr;
+
+		iov_iter_advance(ii, frag_size);
+		*nbytesp = frag_size;
+		return 0;
+	}
+
+	while (nbytes < *nbytesp && ap->num_pages < max_pages) {
+		unsigned npages;
+		size_t start;
+		ret = iov_iter_get_pages(ii, &ap->pages[ap->num_pages],
+					*nbytesp - nbytes,
+					max_pages - ap->num_pages,
+					&start);
+		if (ret < 0)
+			break;
+
+		iov_iter_advance(ii, ret);
+		nbytes += ret;
+
+		ret += start;
+		npages = (ret + PAGE_SIZE - 1) / PAGE_SIZE;
+
+		ap->descs[ap->num_pages].offset = start;
+		fuse_page_descs_length_init(ap->descs, ap->num_pages, npages);
+
+		ap->num_pages += npages;
+		ap->descs[ap->num_pages - 1].length -=
+			(PAGE_SIZE - ret) & (PAGE_SIZE - 1);
+	}
+
+	ap->args.user_pages = true;
+	if (write)
+		ap->args.in_pages = true;
+	else
+		ap->args.out_pages = true;
+
+	*nbytesp = nbytes;
+
+	return ret < 0 ? ret : 0;
+}
+
+ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
+		       loff_t *ppos, int flags)
+{
+	int write = flags & FUSE_DIO_WRITE;
+	int cuse = flags & FUSE_DIO_CUSE;
+	struct file *file = io->iocb->ki_filp;
+	struct inode *inode = file->f_mapping->host;
+	struct fuse_file *ff = file->private_data;
+	struct fuse_conn *fc = ff->fm->fc;
+	size_t nmax = write ? fc->max_write : fc->max_read;
+	loff_t pos = *ppos;
+	size_t count = iov_iter_count(iter);
+	pgoff_t idx_from = pos >> PAGE_SHIFT;
+	pgoff_t idx_to = (pos + count - 1) >> PAGE_SHIFT;
+	ssize_t res = 0;
+	int err = 0;
+	struct fuse_io_args *ia;
+	unsigned int max_pages;
+
+	max_pages = iov_iter_npages(iter, fc->max_pages);
+	ia = fuse_io_alloc(io, max_pages);
+	if (!ia)
+		return -ENOMEM;
+
+	ia->io = io;
+	if (!cuse && fuse_range_is_writeback(inode, idx_from, idx_to)) {
+		if (!write)
+			inode_lock(inode);
+		fuse_sync_writes(inode);
+		if (!write)
+			inode_unlock(inode);
+	}
+
+	io->should_dirty = !write && iter_is_iovec(iter);
+	while (count) {
+		ssize_t nres;
+		fl_owner_t owner = current->files;
+		size_t nbytes = min(count, nmax);
+
+		err = fuse_get_user_pages(&ia->ap, iter, &nbytes, write,
+					  max_pages);
+		if (err && !nbytes)
+			break;
+
+		if (write) {
+			if (!capable(CAP_FSETID))
+				ia->write.in.write_flags |= FUSE_WRITE_KILL_PRIV;
+
+			nres = fuse_send_write(ia, pos, nbytes, owner);
+		} else {
+			nres = fuse_send_read(ia, pos, nbytes, owner);
+		}
+
+		if (!io->async || nres < 0) {
+			fuse_release_user_pages(&ia->ap, io->should_dirty);
+			fuse_io_free(ia);
+		}
+		ia = NULL;
+		if (nres < 0) {
+			iov_iter_revert(iter, nbytes);
+			err = nres;
+			break;
+		}
+		WARN_ON(nres > nbytes);
+
+		count -= nres;
+		res += nres;
+		pos += nres;
+		if (nres != nbytes) {
+			iov_iter_revert(iter, nbytes - nres);
+			break;
+		}
+		if (count) {
+			max_pages = iov_iter_npages(iter, fc->max_pages);
+			ia = fuse_io_alloc(io, max_pages);
+			if (!ia)
+				break;
+		}
+	}
+	if (ia)
+		fuse_io_free(ia);
+	if (res > 0)
+		*ppos = pos;
+
+	return res > 0 ? res : err;
+}
+EXPORT_SYMBOL_GPL(fuse_direct_io);
+
+static ssize_t __fuse_direct_read(struct fuse_io_priv *io,
+				  struct iov_iter *iter,
+				  loff_t *ppos)
+{
+	ssize_t res;
+	struct inode *inode = file_inode(io->iocb->ki_filp);
+
+	res = fuse_direct_io(io, iter, ppos, 0);
+
+	fuse_invalidate_atime(inode);
+
+	return res;
+}
+
+static ssize_t fuse_direct_IO(struct kiocb *iocb, struct iov_iter *iter);
+
+static ssize_t fuse_direct_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	ssize_t res;
+
+	if (!is_sync_kiocb(iocb) && iocb->ki_flags & IOCB_DIRECT) {
+		res = fuse_direct_IO(iocb, to);
+	} else {
+		struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
+
+		res = __fuse_direct_read(&io, to, &iocb->ki_pos);
+	}
+
+	return res;
+}
+
+static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+	struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
+	ssize_t res;
+
+	/* Don't allow parallel writes to the same file */
+	inode_lock(inode);
+	res = generic_write_checks(iocb, from);
+	if (res > 0) {
+		if (!is_sync_kiocb(iocb) && iocb->ki_flags & IOCB_DIRECT) {
+			res = fuse_direct_IO(iocb, from);
+		} else {
+			res = fuse_direct_io(&io, from, &iocb->ki_pos,
+					     FUSE_DIO_WRITE);
+		}
+	}
+	fuse_invalidate_attr(inode);
+	if (res > 0)
+		fuse_write_update_size(inode, iocb->ki_pos);
+	inode_unlock(inode);
+
+	return res;
+}
+
+static ssize_t fuse_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct file *file = iocb->ki_filp;
+	struct fuse_file *ff = file->private_data;
+	struct inode *inode = file_inode(file);
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	if (FUSE_IS_DAX(inode))
+		return fuse_dax_read_iter(iocb, to);
+
+	if (!(ff->open_flags & FOPEN_DIRECT_IO))
+		return fuse_cache_read_iter(iocb, to);
+	else
+		return fuse_direct_read_iter(iocb, to);
+}
+
+static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct fuse_file *ff = file->private_data;
+	struct inode *inode = file_inode(file);
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	if (FUSE_IS_DAX(inode))
+		return fuse_dax_write_iter(iocb, from);
+
+	if (!(ff->open_flags & FOPEN_DIRECT_IO))
+		return fuse_cache_write_iter(iocb, from);
+	else
+		return fuse_direct_write_iter(iocb, from);
+}
+
+static void fuse_writepage_free(struct fuse_writepage_args *wpa)
+{
+	struct fuse_args_pages *ap = &wpa->ia.ap;
+	int i;
+
+	for (i = 0; i < ap->num_pages; i++)
+		__free_page(ap->pages[i]);
+
+	if (wpa->ia.ff)
+		fuse_file_put(wpa->ia.ff, false, false);
+
+	kfree(ap->pages);
+	kfree(wpa);
+}
+
+static void fuse_writepage_finish(struct fuse_mount *fm,
+				  struct fuse_writepage_args *wpa)
+{
+	struct fuse_args_pages *ap = &wpa->ia.ap;
+	struct inode *inode = wpa->inode;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct backing_dev_info *bdi = inode_to_bdi(inode);
+	int i;
+
+	for (i = 0; i < ap->num_pages; i++) {
+		dec_wb_stat(&bdi->wb, WB_WRITEBACK);
+		dec_node_page_state(ap->pages[i], NR_WRITEBACK_TEMP);
+		wb_writeout_inc(&bdi->wb);
+	}
+	wake_up(&fi->page_waitq);
+}
+
+/* Called under fi->lock, may release and reacquire it */
+static void fuse_send_writepage(struct fuse_mount *fm,
+				struct fuse_writepage_args *wpa, loff_t size)
+__releases(fi->lock)
+__acquires(fi->lock)
+{
+	struct fuse_writepage_args *aux, *next;
+	struct fuse_inode *fi = get_fuse_inode(wpa->inode);
+	struct fuse_write_in *inarg = &wpa->ia.write.in;
+	struct fuse_args *args = &wpa->ia.ap.args;
+	__u64 data_size = wpa->ia.ap.num_pages * PAGE_SIZE;
+	int err;
+
+	fi->writectr++;
+	if (inarg->offset + data_size <= size) {
+		inarg->size = data_size;
+	} else if (inarg->offset < size) {
+		inarg->size = size - inarg->offset;
+	} else {
+		/* Got truncated off completely */
+		goto out_free;
+	}
+
+	args->in_args[1].size = inarg->size;
+	args->force = true;
+	args->nocreds = true;
+
+	err = fuse_simple_background(fm, args, GFP_ATOMIC);
+	if (err == -ENOMEM) {
+		spin_unlock(&fi->lock);
+		err = fuse_simple_background(fm, args, GFP_NOFS | __GFP_NOFAIL);
+		spin_lock(&fi->lock);
+	}
+
+	/* Fails on broken connection only */
+	if (unlikely(err))
+		goto out_free;
+
+	return;
+
+ out_free:
+	fi->writectr--;
+	rb_erase(&wpa->writepages_entry, &fi->writepages);
+	fuse_writepage_finish(fm, wpa);
+	spin_unlock(&fi->lock);
+
+	/* After fuse_writepage_finish() aux request list is private */
+	for (aux = wpa->next; aux; aux = next) {
+		next = aux->next;
+		aux->next = NULL;
+		fuse_writepage_free(aux);
+	}
+
+	fuse_writepage_free(wpa);
+	spin_lock(&fi->lock);
+}
+
+/*
+ * If fi->writectr is positive (no truncate or fsync going on) send
+ * all queued writepage requests.
+ *
+ * Called with fi->lock
+ */
+void fuse_flush_writepages(struct inode *inode)
+__releases(fi->lock)
+__acquires(fi->lock)
+{
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	loff_t crop = i_size_read(inode);
+	struct fuse_writepage_args *wpa;
+
+	while (fi->writectr >= 0 && !list_empty(&fi->queued_writes)) {
+		wpa = list_entry(fi->queued_writes.next,
+				 struct fuse_writepage_args, queue_entry);
+		list_del_init(&wpa->queue_entry);
+		fuse_send_writepage(fm, wpa, crop);
+	}
+}
+
+static struct fuse_writepage_args *fuse_insert_writeback(struct rb_root *root,
+						struct fuse_writepage_args *wpa)
+{
+	pgoff_t idx_from = wpa->ia.write.in.offset >> PAGE_SHIFT;
+	pgoff_t idx_to = idx_from + wpa->ia.ap.num_pages - 1;
+	struct rb_node **p = &root->rb_node;
+	struct rb_node  *parent = NULL;
+
+	WARN_ON(!wpa->ia.ap.num_pages);
+	while (*p) {
+		struct fuse_writepage_args *curr;
+		pgoff_t curr_index;
+
+		parent = *p;
+		curr = rb_entry(parent, struct fuse_writepage_args,
+				writepages_entry);
+		WARN_ON(curr->inode != wpa->inode);
+		curr_index = curr->ia.write.in.offset >> PAGE_SHIFT;
+
+		if (idx_from >= curr_index + curr->ia.ap.num_pages)
+			p = &(*p)->rb_right;
+		else if (idx_to < curr_index)
+			p = &(*p)->rb_left;
+		else
+			return curr;
+	}
+
+	rb_link_node(&wpa->writepages_entry, parent, p);
+	rb_insert_color(&wpa->writepages_entry, root);
+	return NULL;
+}
+
+static void tree_insert(struct rb_root *root, struct fuse_writepage_args *wpa)
+{
+	WARN_ON(fuse_insert_writeback(root, wpa));
+}
+
+static void fuse_writepage_end(struct fuse_mount *fm, struct fuse_args *args,
+			       int error)
+{
+	struct fuse_writepage_args *wpa =
+		container_of(args, typeof(*wpa), ia.ap.args);
+	struct inode *inode = wpa->inode;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	mapping_set_error(inode->i_mapping, error);
+	/*
+	 * A writeback finished and this might have updated mtime/ctime on
+	 * server making local mtime/ctime stale.  Hence invalidate attrs.
+	 * Do this only if writeback_cache is not enabled.  If writeback_cache
+	 * is enabled, we trust local ctime/mtime.
+	 */
+	if (!fc->writeback_cache)
+		fuse_invalidate_attr(inode);
+	spin_lock(&fi->lock);
+	rb_erase(&wpa->writepages_entry, &fi->writepages);
+	while (wpa->next) {
+		struct fuse_mount *fm = get_fuse_mount(inode);
+		struct fuse_write_in *inarg = &wpa->ia.write.in;
+		struct fuse_writepage_args *next = wpa->next;
+
+		wpa->next = next->next;
+		next->next = NULL;
+		next->ia.ff = fuse_file_get(wpa->ia.ff);
+		tree_insert(&fi->writepages, next);
+
+		/*
+		 * Skip fuse_flush_writepages() to make it easy to crop requests
+		 * based on primary request size.
+		 *
+		 * 1st case (trivial): there are no concurrent activities using
+		 * fuse_set/release_nowrite.  Then we're on safe side because
+		 * fuse_flush_writepages() would call fuse_send_writepage()
+		 * anyway.
+		 *
+		 * 2nd case: someone called fuse_set_nowrite and it is waiting
+		 * now for completion of all in-flight requests.  This happens
+		 * rarely and no more than once per page, so this should be
+		 * okay.
+		 *
+		 * 3rd case: someone (e.g. fuse_do_setattr()) is in the middle
+		 * of fuse_set_nowrite..fuse_release_nowrite section.  The fact
+		 * that fuse_set_nowrite returned implies that all in-flight
+		 * requests were completed along with all of their secondary
+		 * requests.  Further primary requests are blocked by negative
+		 * writectr.  Hence there cannot be any in-flight requests and
+		 * no invocations of fuse_writepage_end() while we're in
+		 * fuse_set_nowrite..fuse_release_nowrite section.
+		 */
+		fuse_send_writepage(fm, next, inarg->offset + inarg->size);
+	}
+	fi->writectr--;
+	fuse_writepage_finish(fm, wpa);
+	spin_unlock(&fi->lock);
+	fuse_writepage_free(wpa);
+}
+
+static struct fuse_file *__fuse_write_file_get(struct fuse_conn *fc,
+					       struct fuse_inode *fi)
+{
+	struct fuse_file *ff = NULL;
+
+	spin_lock(&fi->lock);
+	if (!list_empty(&fi->write_files)) {
+		ff = list_entry(fi->write_files.next, struct fuse_file,
+				write_entry);
+		fuse_file_get(ff);
+	}
+	spin_unlock(&fi->lock);
+
+	return ff;
+}
+
+static struct fuse_file *fuse_write_file_get(struct fuse_conn *fc,
+					     struct fuse_inode *fi)
+{
+	struct fuse_file *ff = __fuse_write_file_get(fc, fi);
+	WARN_ON(!ff);
+	return ff;
+}
+
+int fuse_write_inode(struct inode *inode, struct writeback_control *wbc)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_file *ff;
+	int err;
+
+	/*
+	 * Inode is always written before the last reference is dropped and
+	 * hence this should not be reached from reclaim.
+	 *
+	 * Writing back the inode from reclaim can deadlock if the request
+	 * processing itself needs an allocation.  Allocations triggering
+	 * reclaim while serving a request can't be prevented, because it can
+	 * involve any number of unrelated userspace processes.
+	 */
+	WARN_ON(wbc->for_reclaim);
+
+	ff = __fuse_write_file_get(fc, fi);
+	err = fuse_flush_times(inode, ff);
+	if (ff)
+		fuse_file_put(ff, false, false);
+
+	return err;
+}
+
+static struct fuse_writepage_args *fuse_writepage_args_alloc(void)
+{
+	struct fuse_writepage_args *wpa;
+	struct fuse_args_pages *ap;
+
+	wpa = kzalloc(sizeof(*wpa), GFP_NOFS);
+	if (wpa) {
+		ap = &wpa->ia.ap;
+		ap->num_pages = 0;
+		ap->pages = fuse_pages_alloc(1, GFP_NOFS, &ap->descs);
+		if (!ap->pages) {
+			kfree(wpa);
+			wpa = NULL;
+		}
+	}
+	return wpa;
+
+}
+
+static int fuse_writepage_locked(struct page *page)
+{
+	struct address_space *mapping = page->mapping;
+	struct inode *inode = mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_writepage_args *wpa;
+	struct fuse_args_pages *ap;
+	struct page *tmp_page;
+	int error = -ENOMEM;
+
+	set_page_writeback(page);
+
+	wpa = fuse_writepage_args_alloc();
+	if (!wpa)
+		goto err;
+	ap = &wpa->ia.ap;
+
+	tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
+	if (!tmp_page)
+		goto err_free;
+
+	error = -EIO;
+	wpa->ia.ff = fuse_write_file_get(fc, fi);
+	if (!wpa->ia.ff)
+		goto err_nofile;
+
+	fuse_write_args_fill(&wpa->ia, wpa->ia.ff, page_offset(page), 0);
+
+	copy_highpage(tmp_page, page);
+	wpa->ia.write.in.write_flags |= FUSE_WRITE_CACHE;
+	wpa->next = NULL;
+	ap->args.in_pages = true;
+	ap->num_pages = 1;
+	ap->pages[0] = tmp_page;
+	ap->descs[0].offset = 0;
+	ap->descs[0].length = PAGE_SIZE;
+	ap->args.end = fuse_writepage_end;
+	wpa->inode = inode;
+
+	inc_wb_stat(&inode_to_bdi(inode)->wb, WB_WRITEBACK);
+	inc_node_page_state(tmp_page, NR_WRITEBACK_TEMP);
+
+	spin_lock(&fi->lock);
+	tree_insert(&fi->writepages, wpa);
+	list_add_tail(&wpa->queue_entry, &fi->queued_writes);
+	fuse_flush_writepages(inode);
+	spin_unlock(&fi->lock);
+
+	end_page_writeback(page);
+
+	return 0;
+
+err_nofile:
+	__free_page(tmp_page);
+err_free:
+	kfree(wpa);
+err:
+	mapping_set_error(page->mapping, error);
+	end_page_writeback(page);
+	return error;
+}
+
+static int fuse_writepage(struct page *page, struct writeback_control *wbc)
+{
+	int err;
+
+	if (fuse_page_is_writeback(page->mapping->host, page->index)) {
+		/*
+		 * ->writepages() should be called for sync() and friends.  We
+		 * should only get here on direct reclaim and then we are
+		 * allowed to skip a page which is already in flight
+		 */
+		WARN_ON(wbc->sync_mode == WB_SYNC_ALL);
+
+		redirty_page_for_writepage(wbc, page);
+		unlock_page(page);
+		return 0;
+	}
+
+	err = fuse_writepage_locked(page);
+	unlock_page(page);
+
+	return err;
+}
+
+struct fuse_fill_wb_data {
+	struct fuse_writepage_args *wpa;
+	struct fuse_file *ff;
+	struct inode *inode;
+	struct page **orig_pages;
+	unsigned int max_pages;
+};
+
+static bool fuse_pages_realloc(struct fuse_fill_wb_data *data)
+{
+	struct fuse_args_pages *ap = &data->wpa->ia.ap;
+	struct fuse_conn *fc = get_fuse_conn(data->inode);
+	struct page **pages;
+	struct fuse_page_desc *descs;
+	unsigned int npages = min_t(unsigned int,
+				    max_t(unsigned int, data->max_pages * 2,
+					  FUSE_DEFAULT_MAX_PAGES_PER_REQ),
+				    fc->max_pages);
+	WARN_ON(npages <= data->max_pages);
+
+	pages = fuse_pages_alloc(npages, GFP_NOFS, &descs);
+	if (!pages)
+		return false;
+
+	memcpy(pages, ap->pages, sizeof(struct page *) * ap->num_pages);
+	memcpy(descs, ap->descs, sizeof(struct fuse_page_desc) * ap->num_pages);
+	kfree(ap->pages);
+	ap->pages = pages;
+	ap->descs = descs;
+	data->max_pages = npages;
+
+	return true;
+}
+
+static void fuse_writepages_send(struct fuse_fill_wb_data *data)
+{
+	struct fuse_writepage_args *wpa = data->wpa;
+	struct inode *inode = data->inode;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	int num_pages = wpa->ia.ap.num_pages;
+	int i;
+
+	wpa->ia.ff = fuse_file_get(data->ff);
+	spin_lock(&fi->lock);
+	list_add_tail(&wpa->queue_entry, &fi->queued_writes);
+	fuse_flush_writepages(inode);
+	spin_unlock(&fi->lock);
+
+	for (i = 0; i < num_pages; i++)
+		end_page_writeback(data->orig_pages[i]);
+}
+
+/*
+ * Check under fi->lock if the page is under writeback, and insert it onto the
+ * rb_tree if not. Otherwise iterate auxiliary write requests, to see if there's
+ * one already added for a page at this offset.  If there's none, then insert
+ * this new request onto the auxiliary list, otherwise reuse the existing one by
+ * swapping the new temp page with the old one.
+ */
+static bool fuse_writepage_add(struct fuse_writepage_args *new_wpa,
+			       struct page *page)
+{
+	struct fuse_inode *fi = get_fuse_inode(new_wpa->inode);
+	struct fuse_writepage_args *tmp;
+	struct fuse_writepage_args *old_wpa;
+	struct fuse_args_pages *new_ap = &new_wpa->ia.ap;
+
+	WARN_ON(new_ap->num_pages != 0);
+	new_ap->num_pages = 1;
+
+	spin_lock(&fi->lock);
+	old_wpa = fuse_insert_writeback(&fi->writepages, new_wpa);
+	if (!old_wpa) {
+		spin_unlock(&fi->lock);
+		return true;
+	}
+
+	for (tmp = old_wpa->next; tmp; tmp = tmp->next) {
+		pgoff_t curr_index;
+
+		WARN_ON(tmp->inode != new_wpa->inode);
+		curr_index = tmp->ia.write.in.offset >> PAGE_SHIFT;
+		if (curr_index == page->index) {
+			WARN_ON(tmp->ia.ap.num_pages != 1);
+			swap(tmp->ia.ap.pages[0], new_ap->pages[0]);
+			break;
+		}
+	}
+
+	if (!tmp) {
+		new_wpa->next = old_wpa->next;
+		old_wpa->next = new_wpa;
+	}
+
+	spin_unlock(&fi->lock);
+
+	if (tmp) {
+		struct backing_dev_info *bdi = inode_to_bdi(new_wpa->inode);
+
+		dec_wb_stat(&bdi->wb, WB_WRITEBACK);
+		dec_node_page_state(new_ap->pages[0], NR_WRITEBACK_TEMP);
+		wb_writeout_inc(&bdi->wb);
+		fuse_writepage_free(new_wpa);
+	}
+
+	return false;
+}
+
+static bool fuse_writepage_need_send(struct fuse_conn *fc, struct page *page,
+				     struct fuse_args_pages *ap,
+				     struct fuse_fill_wb_data *data)
+{
+	WARN_ON(!ap->num_pages);
+
+	/*
+	 * Being under writeback is unlikely but possible.  For example direct
+	 * read to an mmaped fuse file will set the page dirty twice; once when
+	 * the pages are faulted with get_user_pages(), and then after the read
+	 * completed.
+	 */
+	if (fuse_page_is_writeback(data->inode, page->index))
+		return true;
+
+	/* Reached max pages */
+	if (ap->num_pages == fc->max_pages)
+		return true;
+
+	/* Reached max write bytes */
+	if ((ap->num_pages + 1) * PAGE_SIZE > fc->max_write)
+		return true;
+
+	/* Discontinuity */
+	if (data->orig_pages[ap->num_pages - 1]->index + 1 != page->index)
+		return true;
+
+	/* Need to grow the pages array?  If so, did the expansion fail? */
+	if (ap->num_pages == data->max_pages && !fuse_pages_realloc(data))
+		return true;
+
+	return false;
+}
+
+static int fuse_writepages_fill(struct page *page,
+		struct writeback_control *wbc, void *_data)
+{
+	struct fuse_fill_wb_data *data = _data;
+	struct fuse_writepage_args *wpa = data->wpa;
+	struct fuse_args_pages *ap = &wpa->ia.ap;
+	struct inode *inode = data->inode;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct page *tmp_page;
+	int err;
+
+	if (!data->ff) {
+		err = -EIO;
+		data->ff = fuse_write_file_get(fc, fi);
+		if (!data->ff)
+			goto out_unlock;
+	}
+
+	if (wpa && fuse_writepage_need_send(fc, page, ap, data)) {
+		fuse_writepages_send(data);
+		data->wpa = NULL;
+	}
+
+	err = -ENOMEM;
+	tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
+	if (!tmp_page)
+		goto out_unlock;
+
+	/*
+	 * The page must not be redirtied until the writeout is completed
+	 * (i.e. userspace has sent a reply to the write request).  Otherwise
+	 * there could be more than one temporary page instance for each real
+	 * page.
+	 *
+	 * This is ensured by holding the page lock in page_mkwrite() while
+	 * checking fuse_page_is_writeback().  We already hold the page lock
+	 * since clear_page_dirty_for_io() and keep it held until we add the
+	 * request to the fi->writepages list and increment ap->num_pages.
+	 * After this fuse_page_is_writeback() will indicate that the page is
+	 * under writeback, so we can release the page lock.
+	 */
+	if (data->wpa == NULL) {
+		err = -ENOMEM;
+		wpa = fuse_writepage_args_alloc();
+		if (!wpa) {
+			__free_page(tmp_page);
+			goto out_unlock;
+		}
+		data->max_pages = 1;
+
+		ap = &wpa->ia.ap;
+		fuse_write_args_fill(&wpa->ia, data->ff, page_offset(page), 0);
+		wpa->ia.write.in.write_flags |= FUSE_WRITE_CACHE;
+		wpa->next = NULL;
+		ap->args.in_pages = true;
+		ap->args.end = fuse_writepage_end;
+		ap->num_pages = 0;
+		wpa->inode = inode;
+	}
+	set_page_writeback(page);
+
+	copy_highpage(tmp_page, page);
+	ap->pages[ap->num_pages] = tmp_page;
+	ap->descs[ap->num_pages].offset = 0;
+	ap->descs[ap->num_pages].length = PAGE_SIZE;
+	data->orig_pages[ap->num_pages] = page;
+
+	inc_wb_stat(&inode_to_bdi(inode)->wb, WB_WRITEBACK);
+	inc_node_page_state(tmp_page, NR_WRITEBACK_TEMP);
+
+	err = 0;
+	if (data->wpa) {
+		/*
+		 * Protected by fi->lock against concurrent access by
+		 * fuse_page_is_writeback().
+		 */
+		spin_lock(&fi->lock);
+		ap->num_pages++;
+		spin_unlock(&fi->lock);
+	} else if (fuse_writepage_add(wpa, page)) {
+		data->wpa = wpa;
+	} else {
+		end_page_writeback(page);
+	}
+out_unlock:
+	unlock_page(page);
+
+	return err;
+}
+
+static int fuse_writepages(struct address_space *mapping,
+			   struct writeback_control *wbc)
+{
+	struct inode *inode = mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_fill_wb_data data;
+	int err;
+
+	err = -EIO;
+	if (fuse_is_bad(inode))
+		goto out;
+
+	data.inode = inode;
+	data.wpa = NULL;
+	data.ff = NULL;
+
+	err = -ENOMEM;
+	data.orig_pages = kcalloc(fc->max_pages,
+				  sizeof(struct page *),
+				  GFP_NOFS);
+	if (!data.orig_pages)
+		goto out;
+
+	err = write_cache_pages(mapping, wbc, fuse_writepages_fill, &data);
+	if (data.wpa) {
+		WARN_ON(!data.wpa->ia.ap.num_pages);
+		fuse_writepages_send(&data);
+	}
+	if (data.ff)
+		fuse_file_put(data.ff, false, false);
+
+	kfree(data.orig_pages);
+out:
+	return err;
+}
+
+/*
+ * It's worthy to make sure that space is reserved on disk for the write,
+ * but how to implement it without killing performance need more thinking.
+ */
+static int fuse_write_begin(struct file *file, struct address_space *mapping,
+		loff_t pos, unsigned len, unsigned flags,
+		struct page **pagep, void **fsdata)
+{
+	pgoff_t index = pos >> PAGE_SHIFT;
+	struct fuse_conn *fc = get_fuse_conn(file_inode(file));
+	struct page *page;
+	loff_t fsize;
+	int err = -ENOMEM;
+
+	WARN_ON(!fc->writeback_cache);
+
+	page = grab_cache_page_write_begin(mapping, index, flags);
+	if (!page)
+		goto error;
+
+	fuse_wait_on_page_writeback(mapping->host, page->index);
+
+	if (PageUptodate(page) || len == PAGE_SIZE)
+		goto success;
+	/*
+	 * Check if the start this page comes after the end of file, in which
+	 * case the readpage can be optimized away.
+	 */
+	fsize = i_size_read(mapping->host);
+	if (fsize <= (pos & PAGE_MASK)) {
+		size_t off = pos & ~PAGE_MASK;
+		if (off)
+			zero_user_segment(page, 0, off);
+		goto success;
+	}
+	err = fuse_do_readpage(file, page);
+	if (err)
+		goto cleanup;
+success:
+	*pagep = page;
+	return 0;
+
+cleanup:
+	unlock_page(page);
+	put_page(page);
+error:
+	return err;
+}
+
+static int fuse_write_end(struct file *file, struct address_space *mapping,
+		loff_t pos, unsigned len, unsigned copied,
+		struct page *page, void *fsdata)
+{
+	struct inode *inode = page->mapping->host;
+
+	/* Haven't copied anything?  Skip zeroing, size extending, dirtying. */
+	if (!copied)
+		goto unlock;
+
+	if (!PageUptodate(page)) {
+		/* Zero any unwritten bytes at the end of the page */
+		size_t endoff = (pos + copied) & ~PAGE_MASK;
+		if (endoff)
+			zero_user_segment(page, endoff, PAGE_SIZE);
+		SetPageUptodate(page);
+	}
+
+	fuse_write_update_size(inode, pos + copied);
+	set_page_dirty(page);
+
+unlock:
+	unlock_page(page);
+	put_page(page);
+
+	return copied;
+}
+
+static int fuse_launder_page(struct page *page)
+{
+	int err = 0;
+	if (clear_page_dirty_for_io(page)) {
+		struct inode *inode = page->mapping->host;
+		err = fuse_writepage_locked(page);
+		if (!err)
+			fuse_wait_on_page_writeback(inode, page->index);
+	}
+	return err;
+}
+
+/*
+ * Write back dirty pages now, because there may not be any suitable
+ * open files later
+ */
+static void fuse_vma_close(struct vm_area_struct *vma)
+{
+	filemap_write_and_wait(vma->vm_file->f_mapping);
+}
+
+/*
+ * Wait for writeback against this page to complete before allowing it
+ * to be marked dirty again, and hence written back again, possibly
+ * before the previous writepage completed.
+ *
+ * Block here, instead of in ->writepage(), so that the userspace fs
+ * can only block processes actually operating on the filesystem.
+ *
+ * Otherwise unprivileged userspace fs would be able to block
+ * unrelated:
+ *
+ * - page migration
+ * - sync(2)
+ * - try_to_free_pages() with order > PAGE_ALLOC_COSTLY_ORDER
+ */
+static vm_fault_t fuse_page_mkwrite(struct vm_fault *vmf)
+{
+	struct page *page = vmf->page;
+	struct inode *inode = file_inode(vmf->vma->vm_file);
+
+	file_update_time(vmf->vma->vm_file);
+	lock_page(page);
+	if (page->mapping != inode->i_mapping) {
+		unlock_page(page);
+		return VM_FAULT_NOPAGE;
+	}
+
+	fuse_wait_on_page_writeback(inode, page->index);
+	return VM_FAULT_LOCKED;
+}
+
+static const struct vm_operations_struct fuse_file_vm_ops = {
+	.close		= fuse_vma_close,
+	.fault		= filemap_fault,
+	.map_pages	= filemap_map_pages,
+	.page_mkwrite	= fuse_page_mkwrite,
+};
+
+static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct fuse_file *ff = file->private_data;
+
+	/* DAX mmap is superior to direct_io mmap */
+	if (FUSE_IS_DAX(file_inode(file)))
+		return fuse_dax_mmap(file, vma);
+
+	if (ff->open_flags & FOPEN_DIRECT_IO) {
+		/* Can't provide the coherency needed for MAP_SHARED */
+		if (vma->vm_flags & VM_MAYSHARE)
+			return -ENODEV;
+
+		invalidate_inode_pages2(file->f_mapping);
+
+		return generic_file_mmap(file, vma);
+	}
+
+	if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
+		fuse_link_write_file(file);
+
+	file_accessed(file);
+	vma->vm_ops = &fuse_file_vm_ops;
+	return 0;
+}
+
+static int convert_fuse_file_lock(struct fuse_conn *fc,
+				  const struct fuse_file_lock *ffl,
+				  struct file_lock *fl)
+{
+	switch (ffl->type) {
+	case F_UNLCK:
+		break;
+
+	case F_RDLCK:
+	case F_WRLCK:
+		if (ffl->start > OFFSET_MAX || ffl->end > OFFSET_MAX ||
+		    ffl->end < ffl->start)
+			return -EIO;
+
+		fl->fl_start = ffl->start;
+		fl->fl_end = ffl->end;
+
+		/*
+		 * Convert pid into init's pid namespace.  The locks API will
+		 * translate it into the caller's pid namespace.
+		 */
+		rcu_read_lock();
+		fl->fl_pid = pid_nr_ns(find_pid_ns(ffl->pid, fc->pid_ns), &init_pid_ns);
+		rcu_read_unlock();
+		break;
+
+	default:
+		return -EIO;
+	}
+	fl->fl_type = ffl->type;
+	return 0;
+}
+
+static void fuse_lk_fill(struct fuse_args *args, struct file *file,
+			 const struct file_lock *fl, int opcode, pid_t pid,
+			 int flock, struct fuse_lk_in *inarg)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_file *ff = file->private_data;
+
+	memset(inarg, 0, sizeof(*inarg));
+	inarg->fh = ff->fh;
+	inarg->owner = fuse_lock_owner_id(fc, fl->fl_owner);
+	inarg->lk.start = fl->fl_start;
+	inarg->lk.end = fl->fl_end;
+	inarg->lk.type = fl->fl_type;
+	inarg->lk.pid = pid;
+	if (flock)
+		inarg->lk_flags |= FUSE_LK_FLOCK;
+	args->opcode = opcode;
+	args->nodeid = get_node_id(inode);
+	args->in_numargs = 1;
+	args->in_args[0].size = sizeof(*inarg);
+	args->in_args[0].value = inarg;
+}
+
+static int fuse_getlk(struct file *file, struct file_lock *fl)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+	struct fuse_lk_in inarg;
+	struct fuse_lk_out outarg;
+	int err;
+
+	fuse_lk_fill(&args, file, fl, FUSE_GETLK, 0, 0, &inarg);
+	args.out_numargs = 1;
+	args.out_args[0].size = sizeof(outarg);
+	args.out_args[0].value = &outarg;
+	err = fuse_simple_request(fm, &args);
+	if (!err)
+		err = convert_fuse_file_lock(fm->fc, &outarg.lk, fl);
+
+	return err;
+}
+
+static int fuse_setlk(struct file *file, struct file_lock *fl, int flock)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+	struct fuse_lk_in inarg;
+	int opcode = (fl->fl_flags & FL_SLEEP) ? FUSE_SETLKW : FUSE_SETLK;
+	struct pid *pid = fl->fl_type != F_UNLCK ? task_tgid(current) : NULL;
+	pid_t pid_nr = pid_nr_ns(pid, fm->fc->pid_ns);
+	int err;
+
+	if (fl->fl_lmops && fl->fl_lmops->lm_grant) {
+		/* NLM needs asynchronous locks, which we don't support yet */
+		return -ENOLCK;
+	}
+
+	/* Unlock on close is handled by the flush method */
+	if ((fl->fl_flags & FL_CLOSE_POSIX) == FL_CLOSE_POSIX)
+		return 0;
+
+	fuse_lk_fill(&args, file, fl, opcode, pid_nr, flock, &inarg);
+	err = fuse_simple_request(fm, &args);
+
+	/* locking is restartable */
+	if (err == -EINTR)
+		err = -ERESTARTSYS;
+
+	return err;
+}
+
+static int fuse_file_lock(struct file *file, int cmd, struct file_lock *fl)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	int err;
+
+	if (cmd == F_CANCELLK) {
+		err = 0;
+	} else if (cmd == F_GETLK) {
+		if (fc->no_lock) {
+			posix_test_lock(file, fl);
+			err = 0;
+		} else
+			err = fuse_getlk(file, fl);
+	} else {
+		if (fc->no_lock)
+			err = posix_lock_file(file, fl, NULL);
+		else
+			err = fuse_setlk(file, fl, 0);
+	}
+	return err;
+}
+
+static int fuse_file_flock(struct file *file, int cmd, struct file_lock *fl)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	int err;
+
+	if (fc->no_flock) {
+		err = locks_lock_file_wait(file, fl);
+	} else {
+		struct fuse_file *ff = file->private_data;
+
+		/* emulate flock with POSIX locks */
+		ff->flock = true;
+		err = fuse_setlk(file, fl, 1);
+	}
+
+	return err;
+}
+
+static sector_t fuse_bmap(struct address_space *mapping, sector_t block)
+{
+	struct inode *inode = mapping->host;
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+	struct fuse_bmap_in inarg;
+	struct fuse_bmap_out outarg;
+	int err;
+
+	if (!inode->i_sb->s_bdev || fm->fc->no_bmap)
+		return 0;
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.block = block;
+	inarg.blocksize = inode->i_sb->s_blocksize;
+	args.opcode = FUSE_BMAP;
+	args.nodeid = get_node_id(inode);
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.out_numargs = 1;
+	args.out_args[0].size = sizeof(outarg);
+	args.out_args[0].value = &outarg;
+	err = fuse_simple_request(fm, &args);
+	if (err == -ENOSYS)
+		fm->fc->no_bmap = 1;
+
+	return err ? 0 : outarg.block;
+}
+
+static loff_t fuse_lseek(struct file *file, loff_t offset, int whence)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	struct fuse_file *ff = file->private_data;
+	FUSE_ARGS(args);
+	struct fuse_lseek_in inarg = {
+		.fh = ff->fh,
+		.offset = offset,
+		.whence = whence
+	};
+	struct fuse_lseek_out outarg;
+	int err;
+
+	if (fm->fc->no_lseek)
+		goto fallback;
+
+	args.opcode = FUSE_LSEEK;
+	args.nodeid = ff->nodeid;
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.out_numargs = 1;
+	args.out_args[0].size = sizeof(outarg);
+	args.out_args[0].value = &outarg;
+	err = fuse_simple_request(fm, &args);
+	if (err) {
+		if (err == -ENOSYS) {
+			fm->fc->no_lseek = 1;
+			goto fallback;
+		}
+		return err;
+	}
+
+	return vfs_setpos(file, outarg.offset, inode->i_sb->s_maxbytes);
+
+fallback:
+	err = fuse_update_attributes(inode, file);
+	if (!err)
+		return generic_file_llseek(file, offset, whence);
+	else
+		return err;
+}
+
+static loff_t fuse_file_llseek(struct file *file, loff_t offset, int whence)
+{
+	loff_t retval;
+	struct inode *inode = file_inode(file);
+
+	switch (whence) {
+	case SEEK_SET:
+	case SEEK_CUR:
+		 /* No i_mutex protection necessary for SEEK_CUR and SEEK_SET */
+		retval = generic_file_llseek(file, offset, whence);
+		break;
+	case SEEK_END:
+		inode_lock(inode);
+		retval = fuse_update_attributes(inode, file);
+		if (!retval)
+			retval = generic_file_llseek(file, offset, whence);
+		inode_unlock(inode);
+		break;
+	case SEEK_HOLE:
+	case SEEK_DATA:
+		inode_lock(inode);
+		retval = fuse_lseek(file, offset, whence);
+		inode_unlock(inode);
+		break;
+	default:
+		retval = -EINVAL;
+	}
+
+	return retval;
+}
+
+/*
+ * CUSE servers compiled on 32bit broke on 64bit kernels because the
+ * ABI was defined to be 'struct iovec' which is different on 32bit
+ * and 64bit.  Fortunately we can determine which structure the server
+ * used from the size of the reply.
+ */
+static int fuse_copy_ioctl_iovec_old(struct iovec *dst, void *src,
+				     size_t transferred, unsigned count,
+				     bool is_compat)
+{
+#ifdef CONFIG_COMPAT
+	if (count * sizeof(struct compat_iovec) == transferred) {
+		struct compat_iovec *ciov = src;
+		unsigned i;
+
+		/*
+		 * With this interface a 32bit server cannot support
+		 * non-compat (i.e. ones coming from 64bit apps) ioctl
+		 * requests
+		 */
+		if (!is_compat)
+			return -EINVAL;
+
+		for (i = 0; i < count; i++) {
+			dst[i].iov_base = compat_ptr(ciov[i].iov_base);
+			dst[i].iov_len = ciov[i].iov_len;
+		}
+		return 0;
+	}
+#endif
+
+	if (count * sizeof(struct iovec) != transferred)
+		return -EIO;
+
+	memcpy(dst, src, transferred);
+	return 0;
+}
+
+/* Make sure iov_length() won't overflow */
+static int fuse_verify_ioctl_iov(struct fuse_conn *fc, struct iovec *iov,
+				 size_t count)
+{
+	size_t n;
+	u32 max = fc->max_pages << PAGE_SHIFT;
+
+	for (n = 0; n < count; n++, iov++) {
+		if (iov->iov_len > (size_t) max)
+			return -ENOMEM;
+		max -= iov->iov_len;
+	}
+	return 0;
+}
+
+static int fuse_copy_ioctl_iovec(struct fuse_conn *fc, struct iovec *dst,
+				 void *src, size_t transferred, unsigned count,
+				 bool is_compat)
+{
+	unsigned i;
+	struct fuse_ioctl_iovec *fiov = src;
+
+	if (fc->minor < 16) {
+		return fuse_copy_ioctl_iovec_old(dst, src, transferred,
+						 count, is_compat);
+	}
+
+	if (count * sizeof(struct fuse_ioctl_iovec) != transferred)
+		return -EIO;
+
+	for (i = 0; i < count; i++) {
+		/* Did the server supply an inappropriate value? */
+		if (fiov[i].base != (unsigned long) fiov[i].base ||
+		    fiov[i].len != (unsigned long) fiov[i].len)
+			return -EIO;
+
+		dst[i].iov_base = (void __user *) (unsigned long) fiov[i].base;
+		dst[i].iov_len = (size_t) fiov[i].len;
+
+#ifdef CONFIG_COMPAT
+		if (is_compat &&
+		    (ptr_to_compat(dst[i].iov_base) != fiov[i].base ||
+		     (compat_size_t) dst[i].iov_len != fiov[i].len))
+			return -EIO;
+#endif
+	}
+
+	return 0;
+}
+
+
+/*
+ * For ioctls, there is no generic way to determine how much memory
+ * needs to be read and/or written.  Furthermore, ioctls are allowed
+ * to dereference the passed pointer, so the parameter requires deep
+ * copying but FUSE has no idea whatsoever about what to copy in or
+ * out.
+ *
+ * This is solved by allowing FUSE server to retry ioctl with
+ * necessary in/out iovecs.  Let's assume the ioctl implementation
+ * needs to read in the following structure.
+ *
+ * struct a {
+ *	char	*buf;
+ *	size_t	buflen;
+ * }
+ *
+ * On the first callout to FUSE server, inarg->in_size and
+ * inarg->out_size will be NULL; then, the server completes the ioctl
+ * with FUSE_IOCTL_RETRY set in out->flags, out->in_iovs set to 1 and
+ * the actual iov array to
+ *
+ * { { .iov_base = inarg.arg,	.iov_len = sizeof(struct a) } }
+ *
+ * which tells FUSE to copy in the requested area and retry the ioctl.
+ * On the second round, the server has access to the structure and
+ * from that it can tell what to look for next, so on the invocation,
+ * it sets FUSE_IOCTL_RETRY, out->in_iovs to 2 and iov array to
+ *
+ * { { .iov_base = inarg.arg,	.iov_len = sizeof(struct a)	},
+ *   { .iov_base = a.buf,	.iov_len = a.buflen		} }
+ *
+ * FUSE will copy both struct a and the pointed buffer from the
+ * process doing the ioctl and retry ioctl with both struct a and the
+ * buffer.
+ *
+ * This time, FUSE server has everything it needs and completes ioctl
+ * without FUSE_IOCTL_RETRY which finishes the ioctl call.
+ *
+ * Copying data out works the same way.
+ *
+ * Note that if FUSE_IOCTL_UNRESTRICTED is clear, the kernel
+ * automatically initializes in and out iovs by decoding @cmd with
+ * _IOC_* macros and the server is not allowed to request RETRY.  This
+ * limits ioctl data transfers to well-formed ioctls and is the forced
+ * behavior for all FUSE servers.
+ */
+long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
+		   unsigned int flags)
+{
+	struct fuse_file *ff = file->private_data;
+	struct fuse_mount *fm = ff->fm;
+	struct fuse_ioctl_in inarg = {
+		.fh = ff->fh,
+		.cmd = cmd,
+		.arg = arg,
+		.flags = flags
+	};
+	struct fuse_ioctl_out outarg;
+	struct iovec *iov_page = NULL;
+	struct iovec *in_iov = NULL, *out_iov = NULL;
+	unsigned int in_iovs = 0, out_iovs = 0, max_pages;
+	size_t in_size, out_size, c;
+	ssize_t transferred;
+	int err, i;
+	struct iov_iter ii;
+	struct fuse_args_pages ap = {};
+
+#if BITS_PER_LONG == 32
+	inarg.flags |= FUSE_IOCTL_32BIT;
+#else
+	if (flags & FUSE_IOCTL_COMPAT) {
+		inarg.flags |= FUSE_IOCTL_32BIT;
+#ifdef CONFIG_X86_X32
+		if (in_x32_syscall())
+			inarg.flags |= FUSE_IOCTL_COMPAT_X32;
+#endif
+	}
+#endif
+
+	/* assume all the iovs returned by client always fits in a page */
+	BUILD_BUG_ON(sizeof(struct fuse_ioctl_iovec) * FUSE_IOCTL_MAX_IOV > PAGE_SIZE);
+
+	err = -ENOMEM;
+	ap.pages = fuse_pages_alloc(fm->fc->max_pages, GFP_KERNEL, &ap.descs);
+	iov_page = (struct iovec *) __get_free_page(GFP_KERNEL);
+	if (!ap.pages || !iov_page)
+		goto out;
+
+	fuse_page_descs_length_init(ap.descs, 0, fm->fc->max_pages);
+
+	/*
+	 * If restricted, initialize IO parameters as encoded in @cmd.
+	 * RETRY from server is not allowed.
+	 */
+	if (!(flags & FUSE_IOCTL_UNRESTRICTED)) {
+		struct iovec *iov = iov_page;
+
+		iov->iov_base = (void __user *)arg;
+
+		switch (cmd) {
+		case FS_IOC_GETFLAGS:
+		case FS_IOC_SETFLAGS:
+			iov->iov_len = sizeof(int);
+			break;
+		default:
+			iov->iov_len = _IOC_SIZE(cmd);
+			break;
+		}
+
+		if (_IOC_DIR(cmd) & _IOC_WRITE) {
+			in_iov = iov;
+			in_iovs = 1;
+		}
+
+		if (_IOC_DIR(cmd) & _IOC_READ) {
+			out_iov = iov;
+			out_iovs = 1;
+		}
+	}
+
+ retry:
+	inarg.in_size = in_size = iov_length(in_iov, in_iovs);
+	inarg.out_size = out_size = iov_length(out_iov, out_iovs);
+
+	/*
+	 * Out data can be used either for actual out data or iovs,
+	 * make sure there always is at least one page.
+	 */
+	out_size = max_t(size_t, out_size, PAGE_SIZE);
+	max_pages = DIV_ROUND_UP(max(in_size, out_size), PAGE_SIZE);
+
+	/* make sure there are enough buffer pages and init request with them */
+	err = -ENOMEM;
+	if (max_pages > fm->fc->max_pages)
+		goto out;
+	while (ap.num_pages < max_pages) {
+		ap.pages[ap.num_pages] = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
+		if (!ap.pages[ap.num_pages])
+			goto out;
+		ap.num_pages++;
+	}
+
+
+	/* okay, let's send it to the client */
+	ap.args.opcode = FUSE_IOCTL;
+	ap.args.nodeid = ff->nodeid;
+	ap.args.in_numargs = 1;
+	ap.args.in_args[0].size = sizeof(inarg);
+	ap.args.in_args[0].value = &inarg;
+	if (in_size) {
+		ap.args.in_numargs++;
+		ap.args.in_args[1].size = in_size;
+		ap.args.in_pages = true;
+
+		err = -EFAULT;
+		iov_iter_init(&ii, WRITE, in_iov, in_iovs, in_size);
+		for (i = 0; iov_iter_count(&ii) && !WARN_ON(i >= ap.num_pages); i++) {
+			c = copy_page_from_iter(ap.pages[i], 0, PAGE_SIZE, &ii);
+			if (c != PAGE_SIZE && iov_iter_count(&ii))
+				goto out;
+		}
+	}
+
+	ap.args.out_numargs = 2;
+	ap.args.out_args[0].size = sizeof(outarg);
+	ap.args.out_args[0].value = &outarg;
+	ap.args.out_args[1].size = out_size;
+	ap.args.out_pages = true;
+	ap.args.out_argvar = true;
+
+	transferred = fuse_simple_request(fm, &ap.args);
+	err = transferred;
+	if (transferred < 0)
+		goto out;
+
+	/* did it ask for retry? */
+	if (outarg.flags & FUSE_IOCTL_RETRY) {
+		void *vaddr;
+
+		/* no retry if in restricted mode */
+		err = -EIO;
+		if (!(flags & FUSE_IOCTL_UNRESTRICTED))
+			goto out;
+
+		in_iovs = outarg.in_iovs;
+		out_iovs = outarg.out_iovs;
+
+		/*
+		 * Make sure things are in boundary, separate checks
+		 * are to protect against overflow.
+		 */
+		err = -ENOMEM;
+		if (in_iovs > FUSE_IOCTL_MAX_IOV ||
+		    out_iovs > FUSE_IOCTL_MAX_IOV ||
+		    in_iovs + out_iovs > FUSE_IOCTL_MAX_IOV)
+			goto out;
+
+		vaddr = kmap_atomic(ap.pages[0]);
+		err = fuse_copy_ioctl_iovec(fm->fc, iov_page, vaddr,
+					    transferred, in_iovs + out_iovs,
+					    (flags & FUSE_IOCTL_COMPAT) != 0);
+		kunmap_atomic(vaddr);
+		if (err)
+			goto out;
+
+		in_iov = iov_page;
+		out_iov = in_iov + in_iovs;
+
+		err = fuse_verify_ioctl_iov(fm->fc, in_iov, in_iovs);
+		if (err)
+			goto out;
+
+		err = fuse_verify_ioctl_iov(fm->fc, out_iov, out_iovs);
+		if (err)
+			goto out;
+
+		goto retry;
+	}
+
+	err = -EIO;
+	if (transferred > inarg.out_size)
+		goto out;
+
+	err = -EFAULT;
+	iov_iter_init(&ii, READ, out_iov, out_iovs, transferred);
+	for (i = 0; iov_iter_count(&ii) && !WARN_ON(i >= ap.num_pages); i++) {
+		c = copy_page_to_iter(ap.pages[i], 0, PAGE_SIZE, &ii);
+		if (c != PAGE_SIZE && iov_iter_count(&ii))
+			goto out;
+	}
+	err = 0;
+ out:
+	free_page((unsigned long) iov_page);
+	while (ap.num_pages)
+		__free_page(ap.pages[--ap.num_pages]);
+	kfree(ap.pages);
+
+	return err ? err : outarg.result;
+}
+EXPORT_SYMBOL_GPL(fuse_do_ioctl);
+
+long fuse_ioctl_common(struct file *file, unsigned int cmd,
+		       unsigned long arg, unsigned int flags)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	if (!fuse_allow_current_process(fc))
+		return -EACCES;
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	return fuse_do_ioctl(file, cmd, arg, flags);
+}
+
+static long fuse_file_ioctl(struct file *file, unsigned int cmd,
+			    unsigned long arg)
+{
+	return fuse_ioctl_common(file, cmd, arg, 0);
+}
+
+static long fuse_file_compat_ioctl(struct file *file, unsigned int cmd,
+				   unsigned long arg)
+{
+	return fuse_ioctl_common(file, cmd, arg, FUSE_IOCTL_COMPAT);
+}
+
+/*
+ * All files which have been polled are linked to RB tree
+ * fuse_conn->polled_files which is indexed by kh.  Walk the tree and
+ * find the matching one.
+ */
+static struct rb_node **fuse_find_polled_node(struct fuse_conn *fc, u64 kh,
+					      struct rb_node **parent_out)
+{
+	struct rb_node **link = &fc->polled_files.rb_node;
+	struct rb_node *last = NULL;
+
+	while (*link) {
+		struct fuse_file *ff;
+
+		last = *link;
+		ff = rb_entry(last, struct fuse_file, polled_node);
+
+		if (kh < ff->kh)
+			link = &last->rb_left;
+		else if (kh > ff->kh)
+			link = &last->rb_right;
+		else
+			return link;
+	}
+
+	if (parent_out)
+		*parent_out = last;
+	return link;
+}
+
+/*
+ * The file is about to be polled.  Make sure it's on the polled_files
+ * RB tree.  Note that files once added to the polled_files tree are
+ * not removed before the file is released.  This is because a file
+ * polled once is likely to be polled again.
+ */
+static void fuse_register_polled_file(struct fuse_conn *fc,
+				      struct fuse_file *ff)
+{
+	spin_lock(&fc->lock);
+	if (RB_EMPTY_NODE(&ff->polled_node)) {
+		struct rb_node **link, *parent;
+
+		link = fuse_find_polled_node(fc, ff->kh, &parent);
+		BUG_ON(*link);
+		rb_link_node(&ff->polled_node, parent, link);
+		rb_insert_color(&ff->polled_node, &fc->polled_files);
+	}
+	spin_unlock(&fc->lock);
+}
+
+__poll_t fuse_file_poll(struct file *file, poll_table *wait)
+{
+	struct fuse_file *ff = file->private_data;
+	struct fuse_mount *fm = ff->fm;
+	struct fuse_poll_in inarg = { .fh = ff->fh, .kh = ff->kh };
+	struct fuse_poll_out outarg;
+	FUSE_ARGS(args);
+	int err;
+
+	if (fm->fc->no_poll)
+		return DEFAULT_POLLMASK;
+
+	poll_wait(file, &ff->poll_wait, wait);
+	inarg.events = mangle_poll(poll_requested_events(wait));
+
+	/*
+	 * Ask for notification iff there's someone waiting for it.
+	 * The client may ignore the flag and always notify.
+	 */
+	if (waitqueue_active(&ff->poll_wait)) {
+		inarg.flags |= FUSE_POLL_SCHEDULE_NOTIFY;
+		fuse_register_polled_file(fm->fc, ff);
+	}
+
+	args.opcode = FUSE_POLL;
+	args.nodeid = ff->nodeid;
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.out_numargs = 1;
+	args.out_args[0].size = sizeof(outarg);
+	args.out_args[0].value = &outarg;
+	err = fuse_simple_request(fm, &args);
+
+	if (!err)
+		return demangle_poll(outarg.revents);
+	if (err == -ENOSYS) {
+		fm->fc->no_poll = 1;
+		return DEFAULT_POLLMASK;
+	}
+	return EPOLLERR;
+}
+EXPORT_SYMBOL_GPL(fuse_file_poll);
+
+/*
+ * This is called from fuse_handle_notify() on FUSE_NOTIFY_POLL and
+ * wakes up the poll waiters.
+ */
+int fuse_notify_poll_wakeup(struct fuse_conn *fc,
+			    struct fuse_notify_poll_wakeup_out *outarg)
+{
+	u64 kh = outarg->kh;
+	struct rb_node **link;
+
+	spin_lock(&fc->lock);
+
+	link = fuse_find_polled_node(fc, kh, NULL);
+	if (*link) {
+		struct fuse_file *ff;
+
+		ff = rb_entry(*link, struct fuse_file, polled_node);
+		wake_up_interruptible_sync(&ff->poll_wait);
+	}
+
+	spin_unlock(&fc->lock);
+	return 0;
+}
+
+static void fuse_do_truncate(struct file *file)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct iattr attr;
+
+	attr.ia_valid = ATTR_SIZE;
+	attr.ia_size = i_size_read(inode);
+
+	attr.ia_file = file;
+	attr.ia_valid |= ATTR_FILE;
+
+	fuse_do_setattr(file_dentry(file), &attr, file);
+}
+
+static inline loff_t fuse_round_up(struct fuse_conn *fc, loff_t off)
+{
+	return round_up(off, fc->max_pages << PAGE_SHIFT);
+}
+
+static ssize_t
+fuse_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
+{
+	DECLARE_COMPLETION_ONSTACK(wait);
+	ssize_t ret = 0;
+	struct file *file = iocb->ki_filp;
+	struct fuse_file *ff = file->private_data;
+	loff_t pos = 0;
+	struct inode *inode;
+	loff_t i_size;
+	size_t count = iov_iter_count(iter), shortened = 0;
+	loff_t offset = iocb->ki_pos;
+	struct fuse_io_priv *io;
+
+	pos = offset;
+	inode = file->f_mapping->host;
+	i_size = i_size_read(inode);
+
+	if ((iov_iter_rw(iter) == READ) && (offset >= i_size))
+		return 0;
+
+	io = kmalloc(sizeof(struct fuse_io_priv), GFP_KERNEL);
+	if (!io)
+		return -ENOMEM;
+	spin_lock_init(&io->lock);
+	kref_init(&io->refcnt);
+	io->reqs = 1;
+	io->bytes = -1;
+	io->size = 0;
+	io->offset = offset;
+	io->write = (iov_iter_rw(iter) == WRITE);
+	io->err = 0;
+	/*
+	 * By default, we want to optimize all I/Os with async request
+	 * submission to the client filesystem if supported.
+	 */
+	io->async = ff->fm->fc->async_dio;
+	io->iocb = iocb;
+	io->blocking = is_sync_kiocb(iocb);
+
+	/* optimization for short read */
+	if (io->async && !io->write && offset + count > i_size) {
+		iov_iter_truncate(iter, fuse_round_up(ff->fm->fc, i_size - offset));
+		shortened = count - iov_iter_count(iter);
+		count -= shortened;
+	}
+
+	/*
+	 * We cannot asynchronously extend the size of a file.
+	 * In such case the aio will behave exactly like sync io.
+	 */
+	if ((offset + count > i_size) && io->write)
+		io->blocking = true;
+
+	if (io->async && io->blocking) {
+		/*
+		 * Additional reference to keep io around after
+		 * calling fuse_aio_complete()
+		 */
+		kref_get(&io->refcnt);
+		io->done = &wait;
+	}
+
+	if (iov_iter_rw(iter) == WRITE) {
+		ret = fuse_direct_io(io, iter, &pos, FUSE_DIO_WRITE);
+		fuse_invalidate_attr(inode);
+	} else {
+		ret = __fuse_direct_read(io, iter, &pos);
+	}
+	iov_iter_reexpand(iter, iov_iter_count(iter) + shortened);
+
+	if (io->async) {
+		bool blocking = io->blocking;
+
+		fuse_aio_complete(io, ret < 0 ? ret : 0, -1);
+
+		/* we have a non-extending, async request, so return */
+		if (!blocking)
+			return -EIOCBQUEUED;
+
+		wait_for_completion(&wait);
+		ret = fuse_get_res_by_io(io);
+	}
+
+	kref_put(&io->refcnt, fuse_io_release);
+
+	if (iov_iter_rw(iter) == WRITE) {
+		if (ret > 0)
+			fuse_write_update_size(inode, pos);
+		else if (ret < 0 && offset + count > i_size)
+			fuse_do_truncate(file);
+	}
+
+	return ret;
+}
+
+static int fuse_writeback_range(struct inode *inode, loff_t start, loff_t end)
+{
+	int err = filemap_write_and_wait_range(inode->i_mapping, start, LLONG_MAX);
+
+	if (!err)
+		fuse_sync_writes(inode);
+
+	return err;
+}
+
+static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
+				loff_t length)
+{
+	struct fuse_file *ff = file->private_data;
+	struct inode *inode = file_inode(file);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_mount *fm = ff->fm;
+	FUSE_ARGS(args);
+	struct fuse_fallocate_in inarg = {
+		.fh = ff->fh,
+		.offset = offset,
+		.length = length,
+		.mode = mode
+	};
+	int err;
+	bool block_faults = FUSE_IS_DAX(inode) &&
+		(!(mode & FALLOC_FL_KEEP_SIZE) ||
+		 (mode & FALLOC_FL_PUNCH_HOLE));
+
+	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
+		return -EOPNOTSUPP;
+
+	if (fm->fc->no_fallocate)
+		return -EOPNOTSUPP;
+
+	inode_lock(inode);
+	if (block_faults) {
+		down_write(&fi->i_mmap_sem);
+		err = fuse_dax_break_layouts(inode, 0, 0);
+		if (err)
+			goto out;
+	}
+
+	if (mode & FALLOC_FL_PUNCH_HOLE) {
+		loff_t endbyte = offset + length - 1;
+
+		err = fuse_writeback_range(inode, offset, endbyte);
+		if (err)
+			goto out;
+	}
+
+	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
+	    offset + length > i_size_read(inode)) {
+		err = inode_newsize_ok(inode, offset + length);
+		if (err)
+			goto out;
+	}
+
+	err = file_modified(file);
+	if (err)
+		goto out;
+
+	if (!(mode & FALLOC_FL_KEEP_SIZE))
+		set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
+
+	args.opcode = FUSE_FALLOCATE;
+	args.nodeid = ff->nodeid;
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	err = fuse_simple_request(fm, &args);
+	if (err == -ENOSYS) {
+		fm->fc->no_fallocate = 1;
+		err = -EOPNOTSUPP;
+	}
+	if (err)
+		goto out;
+
+	/* we could have extended the file */
+	if (!(mode & FALLOC_FL_KEEP_SIZE)) {
+		bool changed = fuse_write_update_size(inode, offset + length);
+
+		if (changed && fm->fc->writeback_cache)
+			file_update_time(file);
+	}
+
+	if (mode & FALLOC_FL_PUNCH_HOLE)
+		truncate_pagecache_range(inode, offset, offset + length - 1);
+
+	fuse_invalidate_attr(inode);
+
+out:
+	if (!(mode & FALLOC_FL_KEEP_SIZE))
+		clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
+
+	if (block_faults)
+		up_write(&fi->i_mmap_sem);
+
+	inode_unlock(inode);
+
+	fuse_flush_time_update(inode);
+
+	return err;
+}
+
+static ssize_t __fuse_copy_file_range(struct file *file_in, loff_t pos_in,
+				      struct file *file_out, loff_t pos_out,
+				      size_t len, unsigned int flags)
+{
+	struct fuse_file *ff_in = file_in->private_data;
+	struct fuse_file *ff_out = file_out->private_data;
+	struct inode *inode_in = file_inode(file_in);
+	struct inode *inode_out = file_inode(file_out);
+	struct fuse_inode *fi_out = get_fuse_inode(inode_out);
+	struct fuse_mount *fm = ff_in->fm;
+	struct fuse_conn *fc = fm->fc;
+	FUSE_ARGS(args);
+	struct fuse_copy_file_range_in inarg = {
+		.fh_in = ff_in->fh,
+		.off_in = pos_in,
+		.nodeid_out = ff_out->nodeid,
+		.fh_out = ff_out->fh,
+		.off_out = pos_out,
+		.len = len,
+		.flags = flags
+	};
+	struct fuse_write_out outarg;
+	ssize_t err;
+	/* mark unstable when write-back is not used, and file_out gets
+	 * extended */
+	bool is_unstable = (!fc->writeback_cache) &&
+			   ((pos_out + len) > inode_out->i_size);
+
+	if (fc->no_copy_file_range)
+		return -EOPNOTSUPP;
+
+	if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
+		return -EXDEV;
+
+	inode_lock(inode_in);
+	err = fuse_writeback_range(inode_in, pos_in, pos_in + len - 1);
+	inode_unlock(inode_in);
+	if (err)
+		return err;
+
+	inode_lock(inode_out);
+
+	err = file_modified(file_out);
+	if (err)
+		goto out;
+
+	/*
+	 * Write out dirty pages in the destination file before sending the COPY
+	 * request to userspace.  After the request is completed, truncate off
+	 * pages (including partial ones) from the cache that have been copied,
+	 * since these contain stale data at that point.
+	 *
+	 * This should be mostly correct, but if the COPY writes to partial
+	 * pages (at the start or end) and the parts not covered by the COPY are
+	 * written through a memory map after calling fuse_writeback_range(),
+	 * then these partial page modifications will be lost on truncation.
+	 *
+	 * It is unlikely that someone would rely on such mixed style
+	 * modifications.  Yet this does give less guarantees than if the
+	 * copying was performed with write(2).
+	 *
+	 * To fix this a i_mmap_sem style lock could be used to prevent new
+	 * faults while the copy is ongoing.
+	 */
+	err = fuse_writeback_range(inode_out, pos_out, pos_out + len - 1);
+	if (err)
+		goto out;
+
+	if (is_unstable)
+		set_bit(FUSE_I_SIZE_UNSTABLE, &fi_out->state);
+
+	args.opcode = FUSE_COPY_FILE_RANGE;
+	args.nodeid = ff_in->nodeid;
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.out_numargs = 1;
+	args.out_args[0].size = sizeof(outarg);
+	args.out_args[0].value = &outarg;
+	err = fuse_simple_request(fm, &args);
+	if (err == -ENOSYS) {
+		fc->no_copy_file_range = 1;
+		err = -EOPNOTSUPP;
+	}
+	if (err)
+		goto out;
+
+	truncate_inode_pages_range(inode_out->i_mapping,
+				   ALIGN_DOWN(pos_out, PAGE_SIZE),
+				   ALIGN(pos_out + outarg.size, PAGE_SIZE) - 1);
+
+	if (fc->writeback_cache) {
+		fuse_write_update_size(inode_out, pos_out + outarg.size);
+		file_update_time(file_out);
+	}
+
+	fuse_invalidate_attr(inode_out);
+
+	err = outarg.size;
+out:
+	if (is_unstable)
+		clear_bit(FUSE_I_SIZE_UNSTABLE, &fi_out->state);
+
+	inode_unlock(inode_out);
+	file_accessed(file_in);
+
+	fuse_flush_time_update(inode_out);
+
+	return err;
+}
+
+static ssize_t fuse_copy_file_range(struct file *src_file, loff_t src_off,
+				    struct file *dst_file, loff_t dst_off,
+				    size_t len, unsigned int flags)
+{
+	ssize_t ret;
+
+	ret = __fuse_copy_file_range(src_file, src_off, dst_file, dst_off,
+				     len, flags);
+
+	if (ret == -EOPNOTSUPP || ret == -EXDEV)
+		ret = generic_copy_file_range(src_file, src_off, dst_file,
+					      dst_off, len, flags);
+	return ret;
+}
+
+static const struct file_operations fuse_file_operations = {
+	.llseek		= fuse_file_llseek,
+	.read_iter	= fuse_file_read_iter,
+	.write_iter	= fuse_file_write_iter,
+	.mmap		= fuse_file_mmap,
+	.open		= fuse_open,
+	.flush		= fuse_flush,
+	.release	= fuse_release,
+	.fsync		= fuse_fsync,
+	.lock		= fuse_file_lock,
+	.get_unmapped_area = thp_get_unmapped_area,
+	.flock		= fuse_file_flock,
+	.splice_read	= generic_file_splice_read,
+	.splice_write	= iter_file_splice_write,
+	.unlocked_ioctl	= fuse_file_ioctl,
+	.compat_ioctl	= fuse_file_compat_ioctl,
+	.poll		= fuse_file_poll,
+	.fallocate	= fuse_file_fallocate,
+	.copy_file_range = fuse_copy_file_range,
+};
+
+static const struct address_space_operations fuse_file_aops  = {
+	.readpage	= fuse_readpage,
+	.readahead	= fuse_readahead,
+	.writepage	= fuse_writepage,
+	.writepages	= fuse_writepages,
+	.launder_page	= fuse_launder_page,
+	.set_page_dirty	= __set_page_dirty_nobuffers,
+	.bmap		= fuse_bmap,
+	.direct_IO	= fuse_direct_IO,
+	.write_begin	= fuse_write_begin,
+	.write_end	= fuse_write_end,
+};
+
+void fuse_init_file_inode(struct inode *inode)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	inode->i_fop = &fuse_file_operations;
+	inode->i_data.a_ops = &fuse_file_aops;
+
+	INIT_LIST_HEAD(&fi->write_files);
+	INIT_LIST_HEAD(&fi->queued_writes);
+	fi->writectr = 0;
+	init_waitqueue_head(&fi->page_waitq);
+	fi->writepages = RB_ROOT;
+
+	if (IS_ENABLED(CONFIG_FUSE_DAX))
+		fuse_dax_inode_init(inode);
+}
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
new file mode 100644
index 000000000..ceaa68683
--- /dev/null
+++ b/fs/fuse/fuse_i.h
@@ -0,0 +1,1239 @@
+/*
+  FUSE: Filesystem in Userspace
+  Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>
+
+  This program can be distributed under the terms of the GNU GPL.
+  See the file COPYING.
+*/
+
+#ifndef _FS_FUSE_I_H
+#define _FS_FUSE_I_H
+
+#ifndef pr_fmt
+# define pr_fmt(fmt) "fuse: " fmt
+#endif
+
+#include <linux/fuse.h>
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/wait.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/mm.h>
+#include <linux/backing-dev.h>
+#include <linux/mutex.h>
+#include <linux/rwsem.h>
+#include <linux/rbtree.h>
+#include <linux/poll.h>
+#include <linux/workqueue.h>
+#include <linux/kref.h>
+#include <linux/xattr.h>
+#include <linux/pid_namespace.h>
+#include <linux/refcount.h>
+#include <linux/user_namespace.h>
+
+/** Default max number of pages that can be used in a single read request */
+#define FUSE_DEFAULT_MAX_PAGES_PER_REQ 32
+
+/** Maximum of max_pages received in init_out */
+#define FUSE_MAX_MAX_PAGES 256
+
+/** Bias for fi->writectr, meaning new writepages must not be sent */
+#define FUSE_NOWRITE INT_MIN
+
+/** It could be as large as PATH_MAX, but would that have any uses? */
+#define FUSE_NAME_MAX 1024
+
+/** Number of dentries for each connection in the control filesystem */
+#define FUSE_CTL_NUM_DENTRIES 5
+
+/** List of active connections */
+extern struct list_head fuse_conn_list;
+
+/** Global mutex protecting fuse_conn_list and the control filesystem */
+extern struct mutex fuse_mutex;
+
+/** Module parameters */
+extern unsigned max_user_bgreq;
+extern unsigned max_user_congthresh;
+
+/* One forget request */
+struct fuse_forget_link {
+	struct fuse_forget_one forget_one;
+	struct fuse_forget_link *next;
+};
+
+/** FUSE inode */
+struct fuse_inode {
+	/** Inode data */
+	struct inode inode;
+
+	/** Unique ID, which identifies the inode between userspace
+	 * and kernel */
+	u64 nodeid;
+
+	/** Number of lookups on this inode */
+	u64 nlookup;
+
+	/** The request used for sending the FORGET message */
+	struct fuse_forget_link *forget;
+
+	/** Time in jiffies until the file attributes are valid */
+	u64 i_time;
+
+	/* Which attributes are invalid */
+	u32 inval_mask;
+
+	/** The sticky bit in inode->i_mode may have been removed, so
+	    preserve the original mode */
+	umode_t orig_i_mode;
+
+	/** 64 bit inode number */
+	u64 orig_ino;
+
+	/** Version of last attribute change */
+	u64 attr_version;
+
+	union {
+		/* Write related fields (regular file only) */
+		struct {
+			/* Files usable in writepage.  Protected by fi->lock */
+			struct list_head write_files;
+
+			/* Writepages pending on truncate or fsync */
+			struct list_head queued_writes;
+
+			/* Number of sent writes, a negative bias
+			 * (FUSE_NOWRITE) means more writes are blocked */
+			int writectr;
+
+			/* Waitq for writepage completion */
+			wait_queue_head_t page_waitq;
+
+			/* List of writepage requestst (pending or sent) */
+			struct rb_root writepages;
+		};
+
+		/* readdir cache (directory only) */
+		struct {
+			/* true if fully cached */
+			bool cached;
+
+			/* size of cache */
+			loff_t size;
+
+			/* position at end of cache (position of next entry) */
+			loff_t pos;
+
+			/* version of the cache */
+			u64 version;
+
+			/* modification time of directory when cache was
+			 * started */
+			struct timespec64 mtime;
+
+			/* iversion of directory when cache was started */
+			u64 iversion;
+
+			/* protects above fields */
+			spinlock_t lock;
+		} rdc;
+	};
+
+	/** Miscellaneous bits describing inode state */
+	unsigned long state;
+
+	/** Lock for serializing lookup and readdir for back compatibility*/
+	struct mutex mutex;
+
+	/** Lock to protect write related fields */
+	spinlock_t lock;
+
+	/**
+	 * Can't take inode lock in fault path (leads to circular dependency).
+	 * Introduce another semaphore which can be taken in fault path and
+	 * then other filesystem paths can take this to block faults.
+	 */
+	struct rw_semaphore i_mmap_sem;
+
+#ifdef CONFIG_FUSE_DAX
+	/*
+	 * Dax specific inode data
+	 */
+	struct fuse_inode_dax *dax;
+#endif
+};
+
+/** FUSE inode state bits */
+enum {
+	/** Advise readdirplus  */
+	FUSE_I_ADVISE_RDPLUS,
+	/** Initialized with readdirplus */
+	FUSE_I_INIT_RDPLUS,
+	/** An operation changing file size is in progress  */
+	FUSE_I_SIZE_UNSTABLE,
+	/* Bad inode */
+	FUSE_I_BAD,
+};
+
+struct fuse_conn;
+struct fuse_mount;
+struct fuse_release_args;
+
+/** FUSE specific file data */
+struct fuse_file {
+	/** Fuse connection for this file */
+	struct fuse_mount *fm;
+
+	/* Argument space reserved for release */
+	struct fuse_release_args *release_args;
+
+	/** Kernel file handle guaranteed to be unique */
+	u64 kh;
+
+	/** File handle used by userspace */
+	u64 fh;
+
+	/** Node id of this file */
+	u64 nodeid;
+
+	/** Refcount */
+	refcount_t count;
+
+	/** FOPEN_* flags returned by open */
+	u32 open_flags;
+
+	/** Entry on inode's write_files list */
+	struct list_head write_entry;
+
+	/* Readdir related */
+	struct {
+		/*
+		 * Protects below fields against (crazy) parallel readdir on
+		 * same open file.  Uncontended in the normal case.
+		 */
+		struct mutex lock;
+
+		/* Dir stream position */
+		loff_t pos;
+
+		/* Offset in cache */
+		loff_t cache_off;
+
+		/* Version of cache we are reading */
+		u64 version;
+
+	} readdir;
+
+	/** RB node to be linked on fuse_conn->polled_files */
+	struct rb_node polled_node;
+
+	/** Wait queue head for poll */
+	wait_queue_head_t poll_wait;
+
+	/** Has flock been performed on this file? */
+	bool flock:1;
+};
+
+/** One input argument of a request */
+struct fuse_in_arg {
+	unsigned size;
+	const void *value;
+};
+
+/** One output argument of a request */
+struct fuse_arg {
+	unsigned size;
+	void *value;
+};
+
+/** FUSE page descriptor */
+struct fuse_page_desc {
+	unsigned int length;
+	unsigned int offset;
+};
+
+struct fuse_args {
+	uint64_t nodeid;
+	uint32_t opcode;
+	unsigned short in_numargs;
+	unsigned short out_numargs;
+	bool force:1;
+	bool noreply:1;
+	bool nocreds:1;
+	bool in_pages:1;
+	bool out_pages:1;
+	bool user_pages:1;
+	bool out_argvar:1;
+	bool page_zeroing:1;
+	bool page_replace:1;
+	bool may_block:1;
+	struct fuse_in_arg in_args[3];
+	struct fuse_arg out_args[2];
+	void (*end)(struct fuse_mount *fm, struct fuse_args *args, int error);
+};
+
+struct fuse_args_pages {
+	struct fuse_args args;
+	struct page **pages;
+	struct fuse_page_desc *descs;
+	unsigned int num_pages;
+};
+
+#define FUSE_ARGS(args) struct fuse_args args = {}
+
+/** The request IO state (for asynchronous processing) */
+struct fuse_io_priv {
+	struct kref refcnt;
+	int async;
+	spinlock_t lock;
+	unsigned reqs;
+	ssize_t bytes;
+	size_t size;
+	__u64 offset;
+	bool write;
+	bool should_dirty;
+	int err;
+	struct kiocb *iocb;
+	struct completion *done;
+	bool blocking;
+};
+
+#define FUSE_IO_PRIV_SYNC(i) \
+{					\
+	.refcnt = KREF_INIT(1),		\
+	.async = 0,			\
+	.iocb = i,			\
+}
+
+/**
+ * Request flags
+ *
+ * FR_ISREPLY:		set if the request has reply
+ * FR_FORCE:		force sending of the request even if interrupted
+ * FR_BACKGROUND:	request is sent in the background
+ * FR_WAITING:		request is counted as "waiting"
+ * FR_ABORTED:		the request was aborted
+ * FR_INTERRUPTED:	the request has been interrupted
+ * FR_LOCKED:		data is being copied to/from the request
+ * FR_PENDING:		request is not yet in userspace
+ * FR_SENT:		request is in userspace, waiting for an answer
+ * FR_FINISHED:		request is finished
+ * FR_PRIVATE:		request is on private list
+ * FR_ASYNC:		request is asynchronous
+ */
+enum fuse_req_flag {
+	FR_ISREPLY,
+	FR_FORCE,
+	FR_BACKGROUND,
+	FR_WAITING,
+	FR_ABORTED,
+	FR_INTERRUPTED,
+	FR_LOCKED,
+	FR_PENDING,
+	FR_SENT,
+	FR_FINISHED,
+	FR_PRIVATE,
+	FR_ASYNC,
+};
+
+/**
+ * A request to the client
+ *
+ * .waitq.lock protects the following fields:
+ *   - FR_ABORTED
+ *   - FR_LOCKED (may also be modified under fc->lock, tested under both)
+ */
+struct fuse_req {
+	/** This can be on either pending processing or io lists in
+	    fuse_conn */
+	struct list_head list;
+
+	/** Entry on the interrupts list  */
+	struct list_head intr_entry;
+
+	/* Input/output arguments */
+	struct fuse_args *args;
+
+	/** refcount */
+	refcount_t count;
+
+	/* Request flags, updated with test/set/clear_bit() */
+	unsigned long flags;
+
+	/* The request input header */
+	struct {
+		struct fuse_in_header h;
+	} in;
+
+	/* The request output header */
+	struct {
+		struct fuse_out_header h;
+	} out;
+
+	/** Used to wake up the task waiting for completion of request*/
+	wait_queue_head_t waitq;
+
+#if IS_ENABLED(CONFIG_VIRTIO_FS)
+	/** virtio-fs's physically contiguous buffer for in and out args */
+	void *argbuf;
+#endif
+
+	/** fuse_mount this request belongs to */
+	struct fuse_mount *fm;
+};
+
+struct fuse_iqueue;
+
+/**
+ * Input queue callbacks
+ *
+ * Input queue signalling is device-specific.  For example, the /dev/fuse file
+ * uses fiq->waitq and fasync to wake processes that are waiting on queue
+ * readiness.  These callbacks allow other device types to respond to input
+ * queue activity.
+ */
+struct fuse_iqueue_ops {
+	/**
+	 * Signal that a forget has been queued
+	 */
+	void (*wake_forget_and_unlock)(struct fuse_iqueue *fiq)
+		__releases(fiq->lock);
+
+	/**
+	 * Signal that an INTERRUPT request has been queued
+	 */
+	void (*wake_interrupt_and_unlock)(struct fuse_iqueue *fiq)
+		__releases(fiq->lock);
+
+	/**
+	 * Signal that a request has been queued
+	 */
+	void (*wake_pending_and_unlock)(struct fuse_iqueue *fiq)
+		__releases(fiq->lock);
+
+	/**
+	 * Clean up when fuse_iqueue is destroyed
+	 */
+	void (*release)(struct fuse_iqueue *fiq);
+};
+
+/** /dev/fuse input queue operations */
+extern const struct fuse_iqueue_ops fuse_dev_fiq_ops;
+
+struct fuse_iqueue {
+	/** Connection established */
+	unsigned connected;
+
+	/** Lock protecting accesses to members of this structure */
+	spinlock_t lock;
+
+	/** Readers of the connection are waiting on this */
+	wait_queue_head_t waitq;
+
+	/** The next unique request id */
+	u64 reqctr;
+
+	/** The list of pending requests */
+	struct list_head pending;
+
+	/** Pending interrupts */
+	struct list_head interrupts;
+
+	/** Queue of pending forgets */
+	struct fuse_forget_link forget_list_head;
+	struct fuse_forget_link *forget_list_tail;
+
+	/** Batching of FORGET requests (positive indicates FORGET batch) */
+	int forget_batch;
+
+	/** O_ASYNC requests */
+	struct fasync_struct *fasync;
+
+	/** Device-specific callbacks */
+	const struct fuse_iqueue_ops *ops;
+
+	/** Device-specific state */
+	void *priv;
+};
+
+#define FUSE_PQ_HASH_BITS 8
+#define FUSE_PQ_HASH_SIZE (1 << FUSE_PQ_HASH_BITS)
+
+struct fuse_pqueue {
+	/** Connection established */
+	unsigned connected;
+
+	/** Lock protecting accessess to  members of this structure */
+	spinlock_t lock;
+
+	/** Hash table of requests being processed */
+	struct list_head *processing;
+
+	/** The list of requests under I/O */
+	struct list_head io;
+};
+
+/**
+ * Fuse device instance
+ */
+struct fuse_dev {
+	/** Fuse connection for this device */
+	struct fuse_conn *fc;
+
+	/** Processing queue */
+	struct fuse_pqueue pq;
+
+	/** list entry on fc->devices */
+	struct list_head entry;
+};
+
+struct fuse_fs_context {
+	int fd;
+	unsigned int rootmode;
+	kuid_t user_id;
+	kgid_t group_id;
+	bool is_bdev:1;
+	bool fd_present:1;
+	bool rootmode_present:1;
+	bool user_id_present:1;
+	bool group_id_present:1;
+	bool default_permissions:1;
+	bool allow_other:1;
+	bool destroy:1;
+	bool no_control:1;
+	bool no_force_umount:1;
+	bool legacy_opts_show:1;
+	bool dax:1;
+	unsigned int max_read;
+	unsigned int blksize;
+	const char *subtype;
+
+	/* DAX device, may be NULL */
+	struct dax_device *dax_dev;
+
+	/* fuse_dev pointer to fill in, should contain NULL on entry */
+	void **fudptr;
+};
+
+/**
+ * A Fuse connection.
+ *
+ * This structure is created, when the root filesystem is mounted, and
+ * is destroyed, when the client device is closed and the last
+ * fuse_mount is destroyed.
+ */
+struct fuse_conn {
+	/** Lock protecting accessess to  members of this structure */
+	spinlock_t lock;
+
+	/** Refcount */
+	refcount_t count;
+
+	/** Number of fuse_dev's */
+	atomic_t dev_count;
+
+	struct rcu_head rcu;
+
+	/** The user id for this mount */
+	kuid_t user_id;
+
+	/** The group id for this mount */
+	kgid_t group_id;
+
+	/** The pid namespace for this mount */
+	struct pid_namespace *pid_ns;
+
+	/** The user namespace for this mount */
+	struct user_namespace *user_ns;
+
+	/** Maximum read size */
+	unsigned max_read;
+
+	/** Maximum write size */
+	unsigned max_write;
+
+	/** Maxmum number of pages that can be used in a single request */
+	unsigned int max_pages;
+
+	/** Constrain ->max_pages to this value during feature negotiation */
+	unsigned int max_pages_limit;
+
+	/** Input queue */
+	struct fuse_iqueue iq;
+
+	/** The next unique kernel file handle */
+	atomic64_t khctr;
+
+	/** rbtree of fuse_files waiting for poll events indexed by ph */
+	struct rb_root polled_files;
+
+	/** Maximum number of outstanding background requests */
+	unsigned max_background;
+
+	/** Number of background requests at which congestion starts */
+	unsigned congestion_threshold;
+
+	/** Number of requests currently in the background */
+	unsigned num_background;
+
+	/** Number of background requests currently queued for userspace */
+	unsigned active_background;
+
+	/** The list of background requests set aside for later queuing */
+	struct list_head bg_queue;
+
+	/** Protects: max_background, congestion_threshold, num_background,
+	 * active_background, bg_queue, blocked */
+	spinlock_t bg_lock;
+
+	/** Flag indicating that INIT reply has been received. Allocating
+	 * any fuse request will be suspended until the flag is set */
+	int initialized;
+
+	/** Flag indicating if connection is blocked.  This will be
+	    the case before the INIT reply is received, and if there
+	    are too many outstading backgrounds requests */
+	int blocked;
+
+	/** waitq for blocked connection */
+	wait_queue_head_t blocked_waitq;
+
+	/** Connection established, cleared on umount, connection
+	    abort and device release */
+	unsigned connected;
+
+	/** Connection aborted via sysfs */
+	bool aborted;
+
+	/** Connection failed (version mismatch).  Cannot race with
+	    setting other bitfields since it is only set once in INIT
+	    reply, before any other request, and never cleared */
+	unsigned conn_error:1;
+
+	/** Connection successful.  Only set in INIT */
+	unsigned conn_init:1;
+
+	/** Do readpages asynchronously?  Only set in INIT */
+	unsigned async_read:1;
+
+	/** Return an unique read error after abort.  Only set in INIT */
+	unsigned abort_err:1;
+
+	/** Do not send separate SETATTR request before open(O_TRUNC)  */
+	unsigned atomic_o_trunc:1;
+
+	/** Filesystem supports NFS exporting.  Only set in INIT */
+	unsigned export_support:1;
+
+	/** write-back cache policy (default is write-through) */
+	unsigned writeback_cache:1;
+
+	/** allow parallel lookups and readdir (default is serialized) */
+	unsigned parallel_dirops:1;
+
+	/** handle fs handles killing suid/sgid/cap on write/chown/trunc */
+	unsigned handle_killpriv:1;
+
+	/** cache READLINK responses in page cache */
+	unsigned cache_symlinks:1;
+
+	/* show legacy mount options */
+	unsigned int legacy_opts_show:1;
+
+	/*
+	 * The following bitfields are only for optimization purposes
+	 * and hence races in setting them will not cause malfunction
+	 */
+
+	/** Is open/release not implemented by fs? */
+	unsigned no_open:1;
+
+	/** Is opendir/releasedir not implemented by fs? */
+	unsigned no_opendir:1;
+
+	/** Is fsync not implemented by fs? */
+	unsigned no_fsync:1;
+
+	/** Is fsyncdir not implemented by fs? */
+	unsigned no_fsyncdir:1;
+
+	/** Is flush not implemented by fs? */
+	unsigned no_flush:1;
+
+	/** Is setxattr not implemented by fs? */
+	unsigned no_setxattr:1;
+
+	/** Is getxattr not implemented by fs? */
+	unsigned no_getxattr:1;
+
+	/** Is listxattr not implemented by fs? */
+	unsigned no_listxattr:1;
+
+	/** Is removexattr not implemented by fs? */
+	unsigned no_removexattr:1;
+
+	/** Are posix file locking primitives not implemented by fs? */
+	unsigned no_lock:1;
+
+	/** Is access not implemented by fs? */
+	unsigned no_access:1;
+
+	/** Is create not implemented by fs? */
+	unsigned no_create:1;
+
+	/** Is interrupt not implemented by fs? */
+	unsigned no_interrupt:1;
+
+	/** Is bmap not implemented by fs? */
+	unsigned no_bmap:1;
+
+	/** Is poll not implemented by fs? */
+	unsigned no_poll:1;
+
+	/** Do multi-page cached writes */
+	unsigned big_writes:1;
+
+	/** Don't apply umask to creation modes */
+	unsigned dont_mask:1;
+
+	/** Are BSD file locking primitives not implemented by fs? */
+	unsigned no_flock:1;
+
+	/** Is fallocate not implemented by fs? */
+	unsigned no_fallocate:1;
+
+	/** Is rename with flags implemented by fs? */
+	unsigned no_rename2:1;
+
+	/** Use enhanced/automatic page cache invalidation. */
+	unsigned auto_inval_data:1;
+
+	/** Filesystem is fully reponsible for page cache invalidation. */
+	unsigned explicit_inval_data:1;
+
+	/** Does the filesystem support readdirplus? */
+	unsigned do_readdirplus:1;
+
+	/** Does the filesystem want adaptive readdirplus? */
+	unsigned readdirplus_auto:1;
+
+	/** Does the filesystem support asynchronous direct-IO submission? */
+	unsigned async_dio:1;
+
+	/** Is lseek not implemented by fs? */
+	unsigned no_lseek:1;
+
+	/** Does the filesystem support posix acls? */
+	unsigned posix_acl:1;
+
+	/** Check permissions based on the file mode or not? */
+	unsigned default_permissions:1;
+
+	/** Allow other than the mounter user to access the filesystem ? */
+	unsigned allow_other:1;
+
+	/** Does the filesystem support copy_file_range? */
+	unsigned no_copy_file_range:1;
+
+	/* Send DESTROY request */
+	unsigned int destroy:1;
+
+	/* Delete dentries that have gone stale */
+	unsigned int delete_stale:1;
+
+	/** Do not create entry in fusectl fs */
+	unsigned int no_control:1;
+
+	/** Do not allow MNT_FORCE umount */
+	unsigned int no_force_umount:1;
+
+	/* Auto-mount submounts announced by the server */
+	unsigned int auto_submounts:1;
+
+	/** The number of requests waiting for completion */
+	atomic_t num_waiting;
+
+	/** Negotiated minor version */
+	unsigned minor;
+
+	/** Entry on the fuse_mount_list */
+	struct list_head entry;
+
+	/** Device ID from the root super block */
+	dev_t dev;
+
+	/** Dentries in the control filesystem */
+	struct dentry *ctl_dentry[FUSE_CTL_NUM_DENTRIES];
+
+	/** number of dentries used in the above array */
+	int ctl_ndents;
+
+	/** Key for lock owner ID scrambling */
+	u32 scramble_key[4];
+
+	/** Version counter for attribute changes */
+	atomic64_t attr_version;
+
+	/** Called on final put */
+	void (*release)(struct fuse_conn *);
+
+	/**
+	 * Read/write semaphore to hold when accessing the sb of any
+	 * fuse_mount belonging to this connection
+	 */
+	struct rw_semaphore killsb;
+
+	/** List of device instances belonging to this connection */
+	struct list_head devices;
+
+#ifdef CONFIG_FUSE_DAX
+	/* Dax specific conn data, non-NULL if DAX is enabled */
+	struct fuse_conn_dax *dax;
+#endif
+
+	/** List of filesystems using this connection */
+	struct list_head mounts;
+};
+
+/*
+ * Represents a mounted filesystem, potentially a submount.
+ *
+ * This object allows sharing a fuse_conn between separate mounts to
+ * allow submounts with dedicated superblocks and thus separate device
+ * IDs.
+ */
+struct fuse_mount {
+	/* Underlying (potentially shared) connection to the FUSE server */
+	struct fuse_conn *fc;
+
+	/* Refcount */
+	refcount_t count;
+
+	/*
+	 * Super block for this connection (fc->killsb must be held when
+	 * accessing this).
+	 */
+	struct super_block *sb;
+
+	/* Entry on fc->mounts */
+	struct list_head fc_entry;
+};
+
+static inline struct fuse_mount *get_fuse_mount_super(struct super_block *sb)
+{
+	return sb->s_fs_info;
+}
+
+static inline struct fuse_conn *get_fuse_conn_super(struct super_block *sb)
+{
+	struct fuse_mount *fm = get_fuse_mount_super(sb);
+
+	return fm ? fm->fc : NULL;
+}
+
+static inline struct fuse_mount *get_fuse_mount(struct inode *inode)
+{
+	return get_fuse_mount_super(inode->i_sb);
+}
+
+static inline struct fuse_conn *get_fuse_conn(struct inode *inode)
+{
+	struct fuse_mount *fm = get_fuse_mount(inode);
+
+	return fm ? fm->fc : NULL;
+}
+
+static inline struct fuse_inode *get_fuse_inode(struct inode *inode)
+{
+	return container_of(inode, struct fuse_inode, inode);
+}
+
+static inline u64 get_node_id(struct inode *inode)
+{
+	return get_fuse_inode(inode)->nodeid;
+}
+
+static inline int invalid_nodeid(u64 nodeid)
+{
+	return !nodeid || nodeid == FUSE_ROOT_ID;
+}
+
+static inline u64 fuse_get_attr_version(struct fuse_conn *fc)
+{
+	return atomic64_read(&fc->attr_version);
+}
+
+static inline bool fuse_stale_inode(const struct inode *inode, int generation,
+				    struct fuse_attr *attr)
+{
+	return inode->i_generation != generation ||
+		inode_wrong_type(inode, attr->mode);
+}
+
+static inline void fuse_make_bad(struct inode *inode)
+{
+	remove_inode_hash(inode);
+	set_bit(FUSE_I_BAD, &get_fuse_inode(inode)->state);
+}
+
+static inline bool fuse_is_bad(struct inode *inode)
+{
+	return unlikely(test_bit(FUSE_I_BAD, &get_fuse_inode(inode)->state));
+}
+
+/** Device operations */
+extern const struct file_operations fuse_dev_operations;
+
+extern const struct dentry_operations fuse_dentry_operations;
+extern const struct dentry_operations fuse_root_dentry_operations;
+
+/**
+ * Get a filled in inode
+ */
+struct inode *fuse_iget(struct super_block *sb, u64 nodeid,
+			int generation, struct fuse_attr *attr,
+			u64 attr_valid, u64 attr_version);
+
+int fuse_lookup_name(struct super_block *sb, u64 nodeid, const struct qstr *name,
+		     struct fuse_entry_out *outarg, struct inode **inode);
+
+/**
+ * Send FORGET command
+ */
+void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget,
+		       u64 nodeid, u64 nlookup);
+
+struct fuse_forget_link *fuse_alloc_forget(void);
+
+struct fuse_forget_link *fuse_dequeue_forget(struct fuse_iqueue *fiq,
+					     unsigned int max,
+					     unsigned int *countp);
+
+/*
+ * Initialize READ or READDIR request
+ */
+struct fuse_io_args {
+	union {
+		struct {
+			struct fuse_read_in in;
+			u64 attr_ver;
+		} read;
+		struct {
+			struct fuse_write_in in;
+			struct fuse_write_out out;
+			bool page_locked;
+		} write;
+	};
+	struct fuse_args_pages ap;
+	struct fuse_io_priv *io;
+	struct fuse_file *ff;
+};
+
+void fuse_read_args_fill(struct fuse_io_args *ia, struct file *file, loff_t pos,
+			 size_t count, int opcode);
+
+
+/**
+ * Send OPEN or OPENDIR request
+ */
+int fuse_open_common(struct inode *inode, struct file *file, bool isdir);
+
+struct fuse_file *fuse_file_alloc(struct fuse_mount *fm);
+void fuse_file_free(struct fuse_file *ff);
+void fuse_finish_open(struct inode *inode, struct file *file);
+
+void fuse_sync_release(struct fuse_inode *fi, struct fuse_file *ff, int flags);
+
+/**
+ * Send RELEASE or RELEASEDIR request
+ */
+void fuse_release_common(struct file *file, bool isdir);
+
+/**
+ * Send FSYNC or FSYNCDIR request
+ */
+int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
+		      int datasync, int opcode);
+
+/**
+ * Notify poll wakeup
+ */
+int fuse_notify_poll_wakeup(struct fuse_conn *fc,
+			    struct fuse_notify_poll_wakeup_out *outarg);
+
+/**
+ * Initialize file operations on a regular file
+ */
+void fuse_init_file_inode(struct inode *inode);
+
+/**
+ * Initialize inode operations on regular files and special files
+ */
+void fuse_init_common(struct inode *inode);
+
+/**
+ * Initialize inode and file operations on a directory
+ */
+void fuse_init_dir(struct inode *inode);
+
+/**
+ * Initialize inode operations on a symlink
+ */
+void fuse_init_symlink(struct inode *inode);
+
+/**
+ * Change attributes of an inode
+ */
+void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
+			    u64 attr_valid, u64 attr_version);
+
+void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
+				   u64 attr_valid);
+
+/**
+ * Initialize the client device
+ */
+int fuse_dev_init(void);
+
+/**
+ * Cleanup the client device
+ */
+void fuse_dev_cleanup(void);
+
+int fuse_ctl_init(void);
+void __exit fuse_ctl_cleanup(void);
+
+/**
+ * Simple request sending that does request allocation and freeing
+ */
+ssize_t fuse_simple_request(struct fuse_mount *fm, struct fuse_args *args);
+int fuse_simple_background(struct fuse_mount *fm, struct fuse_args *args,
+			   gfp_t gfp_flags);
+
+/**
+ * End a finished request
+ */
+void fuse_request_end(struct fuse_req *req);
+
+/* Abort all requests */
+void fuse_abort_conn(struct fuse_conn *fc);
+void fuse_wait_aborted(struct fuse_conn *fc);
+
+/**
+ * Invalidate inode attributes
+ */
+void fuse_invalidate_attr(struct inode *inode);
+
+void fuse_invalidate_entry_cache(struct dentry *entry);
+
+void fuse_invalidate_atime(struct inode *inode);
+
+u64 entry_attr_timeout(struct fuse_entry_out *o);
+void fuse_change_entry_timeout(struct dentry *entry, struct fuse_entry_out *o);
+
+/**
+ * Acquire reference to fuse_conn
+ */
+struct fuse_conn *fuse_conn_get(struct fuse_conn *fc);
+
+/**
+ * Initialize fuse_conn
+ */
+void fuse_conn_init(struct fuse_conn *fc, struct fuse_mount *fm,
+		    struct user_namespace *user_ns,
+		    const struct fuse_iqueue_ops *fiq_ops, void *fiq_priv);
+
+/**
+ * Release reference to fuse_conn
+ */
+void fuse_conn_put(struct fuse_conn *fc);
+
+/**
+ * Acquire reference to fuse_mount
+ */
+struct fuse_mount *fuse_mount_get(struct fuse_mount *fm);
+
+/**
+ * Release reference to fuse_mount
+ */
+void fuse_mount_put(struct fuse_mount *fm);
+
+struct fuse_dev *fuse_dev_alloc_install(struct fuse_conn *fc);
+struct fuse_dev *fuse_dev_alloc(void);
+void fuse_dev_install(struct fuse_dev *fud, struct fuse_conn *fc);
+void fuse_dev_free(struct fuse_dev *fud);
+void fuse_send_init(struct fuse_mount *fm);
+
+/**
+ * Fill in superblock and initialize fuse connection
+ * @sb: partially-initialized superblock to fill in
+ * @ctx: mount context
+ */
+int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx);
+
+/*
+ * Fill in superblock for submounts
+ * @sb: partially-initialized superblock to fill in
+ * @parent_fi: The fuse_inode of the parent filesystem where this submount is
+ * 	       mounted
+ */
+int fuse_fill_super_submount(struct super_block *sb,
+			     struct fuse_inode *parent_fi);
+
+/*
+ * Remove the mount from the connection
+ *
+ * Returns whether this was the last mount
+ */
+bool fuse_mount_remove(struct fuse_mount *fm);
+
+/*
+ * Shut down the connection (possibly sending DESTROY request).
+ */
+void fuse_conn_destroy(struct fuse_mount *fm);
+
+/**
+ * Add connection to control filesystem
+ */
+int fuse_ctl_add_conn(struct fuse_conn *fc);
+
+/**
+ * Remove connection from control filesystem
+ */
+void fuse_ctl_remove_conn(struct fuse_conn *fc);
+
+/**
+ * Is file type valid?
+ */
+int fuse_valid_type(int m);
+
+bool fuse_invalid_attr(struct fuse_attr *attr);
+
+/**
+ * Is current process allowed to perform filesystem operation?
+ */
+int fuse_allow_current_process(struct fuse_conn *fc);
+
+u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id);
+
+void fuse_flush_time_update(struct inode *inode);
+void fuse_update_ctime(struct inode *inode);
+
+int fuse_update_attributes(struct inode *inode, struct file *file);
+
+void fuse_flush_writepages(struct inode *inode);
+
+void fuse_set_nowrite(struct inode *inode);
+void fuse_release_nowrite(struct inode *inode);
+
+/**
+ * Scan all fuse_mounts belonging to fc to find the first where
+ * ilookup5() returns a result.  Return that result and the
+ * respective fuse_mount in *fm (unless fm is NULL).
+ *
+ * The caller must hold fc->killsb.
+ */
+struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
+			   struct fuse_mount **fm);
+
+/**
+ * File-system tells the kernel to invalidate cache for the given node id.
+ */
+int fuse_reverse_inval_inode(struct fuse_conn *fc, u64 nodeid,
+			     loff_t offset, loff_t len);
+
+/**
+ * File-system tells the kernel to invalidate parent attributes and
+ * the dentry matching parent/name.
+ *
+ * If the child_nodeid is non-zero and:
+ *    - matches the inode number for the dentry matching parent/name,
+ *    - is not a mount point
+ *    - is a file or oan empty directory
+ * then the dentry is unhashed (d_delete()).
+ */
+int fuse_reverse_inval_entry(struct fuse_conn *fc, u64 parent_nodeid,
+			     u64 child_nodeid, struct qstr *name);
+
+int fuse_do_open(struct fuse_mount *fm, u64 nodeid, struct file *file,
+		 bool isdir);
+
+/**
+ * fuse_direct_io() flags
+ */
+
+/** If set, it is WRITE; otherwise - READ */
+#define FUSE_DIO_WRITE (1 << 0)
+
+/** CUSE pass fuse_direct_io() a file which f_mapping->host is not from FUSE */
+#define FUSE_DIO_CUSE  (1 << 1)
+
+ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
+		       loff_t *ppos, int flags);
+long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
+		   unsigned int flags);
+long fuse_ioctl_common(struct file *file, unsigned int cmd,
+		       unsigned long arg, unsigned int flags);
+__poll_t fuse_file_poll(struct file *file, poll_table *wait);
+int fuse_dev_release(struct inode *inode, struct file *file);
+
+bool fuse_write_update_size(struct inode *inode, loff_t pos);
+
+int fuse_flush_times(struct inode *inode, struct fuse_file *ff);
+int fuse_write_inode(struct inode *inode, struct writeback_control *wbc);
+
+int fuse_do_setattr(struct dentry *dentry, struct iattr *attr,
+		    struct file *file);
+
+void fuse_set_initialized(struct fuse_conn *fc);
+
+void fuse_unlock_inode(struct inode *inode, bool locked);
+bool fuse_lock_inode(struct inode *inode);
+
+int fuse_setxattr(struct inode *inode, const char *name, const void *value,
+		  size_t size, int flags);
+ssize_t fuse_getxattr(struct inode *inode, const char *name, void *value,
+		      size_t size);
+ssize_t fuse_listxattr(struct dentry *entry, char *list, size_t size);
+int fuse_removexattr(struct inode *inode, const char *name);
+extern const struct xattr_handler *fuse_xattr_handlers[];
+extern const struct xattr_handler *fuse_acl_xattr_handlers[];
+extern const struct xattr_handler *fuse_no_acl_xattr_handlers[];
+
+struct posix_acl;
+struct posix_acl *fuse_get_acl(struct inode *inode, int type);
+int fuse_set_acl(struct inode *inode, struct posix_acl *acl, int type);
+
+
+/* readdir.c */
+int fuse_readdir(struct file *file, struct dir_context *ctx);
+
+/**
+ * Return the number of bytes in an arguments list
+ */
+unsigned int fuse_len_args(unsigned int numargs, struct fuse_arg *args);
+
+/**
+ * Get the next unique ID for a request
+ */
+u64 fuse_get_unique(struct fuse_iqueue *fiq);
+void fuse_free_conn(struct fuse_conn *fc);
+
+/* dax.c */
+
+#define FUSE_IS_DAX(inode) (IS_ENABLED(CONFIG_FUSE_DAX) && IS_DAX(inode))
+
+ssize_t fuse_dax_read_iter(struct kiocb *iocb, struct iov_iter *to);
+ssize_t fuse_dax_write_iter(struct kiocb *iocb, struct iov_iter *from);
+int fuse_dax_mmap(struct file *file, struct vm_area_struct *vma);
+int fuse_dax_break_layouts(struct inode *inode, u64 dmap_start, u64 dmap_end);
+int fuse_dax_conn_alloc(struct fuse_conn *fc, struct dax_device *dax_dev);
+void fuse_dax_conn_free(struct fuse_conn *fc);
+bool fuse_dax_inode_alloc(struct super_block *sb, struct fuse_inode *fi);
+void fuse_dax_inode_init(struct inode *inode);
+void fuse_dax_inode_cleanup(struct inode *inode);
+bool fuse_dax_check_alignment(struct fuse_conn *fc, unsigned int map_alignment);
+void fuse_dax_cancel_work(struct fuse_conn *fc);
+
+#endif /* _FS_FUSE_I_H */
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
new file mode 100644
index 000000000..9ea175ff9
--- /dev/null
+++ b/fs/fuse/inode.c
@@ -0,0 +1,1767 @@
+/*
+  FUSE: Filesystem in Userspace
+  Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>
+
+  This program can be distributed under the terms of the GNU GPL.
+  See the file COPYING.
+*/
+
+#include "fuse_i.h"
+
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/seq_file.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+#include <linux/statfs.h>
+#include <linux/random.h>
+#include <linux/sched.h>
+#include <linux/exportfs.h>
+#include <linux/posix_acl.h>
+#include <linux/pid_namespace.h>
+
+MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
+MODULE_DESCRIPTION("Filesystem in Userspace");
+MODULE_LICENSE("GPL");
+
+static struct kmem_cache *fuse_inode_cachep;
+struct list_head fuse_conn_list;
+DEFINE_MUTEX(fuse_mutex);
+
+static int set_global_limit(const char *val, const struct kernel_param *kp);
+
+unsigned max_user_bgreq;
+module_param_call(max_user_bgreq, set_global_limit, param_get_uint,
+		  &max_user_bgreq, 0644);
+__MODULE_PARM_TYPE(max_user_bgreq, "uint");
+MODULE_PARM_DESC(max_user_bgreq,
+ "Global limit for the maximum number of backgrounded requests an "
+ "unprivileged user can set");
+
+unsigned max_user_congthresh;
+module_param_call(max_user_congthresh, set_global_limit, param_get_uint,
+		  &max_user_congthresh, 0644);
+__MODULE_PARM_TYPE(max_user_congthresh, "uint");
+MODULE_PARM_DESC(max_user_congthresh,
+ "Global limit for the maximum congestion threshold an "
+ "unprivileged user can set");
+
+#define FUSE_SUPER_MAGIC 0x65735546
+
+#define FUSE_DEFAULT_BLKSIZE 512
+
+/** Maximum number of outstanding background requests */
+#define FUSE_DEFAULT_MAX_BACKGROUND 12
+
+/** Congestion starts at 75% of maximum */
+#define FUSE_DEFAULT_CONGESTION_THRESHOLD (FUSE_DEFAULT_MAX_BACKGROUND * 3 / 4)
+
+#ifdef CONFIG_BLOCK
+static struct file_system_type fuseblk_fs_type;
+#endif
+
+struct fuse_forget_link *fuse_alloc_forget(void)
+{
+	return kzalloc(sizeof(struct fuse_forget_link), GFP_KERNEL_ACCOUNT);
+}
+
+static struct inode *fuse_alloc_inode(struct super_block *sb)
+{
+	struct fuse_inode *fi;
+
+	fi = kmem_cache_alloc(fuse_inode_cachep, GFP_KERNEL);
+	if (!fi)
+		return NULL;
+
+	fi->i_time = 0;
+	fi->inval_mask = 0;
+	fi->nodeid = 0;
+	fi->nlookup = 0;
+	fi->attr_version = 0;
+	fi->orig_ino = 0;
+	fi->state = 0;
+	mutex_init(&fi->mutex);
+	init_rwsem(&fi->i_mmap_sem);
+	spin_lock_init(&fi->lock);
+	fi->forget = fuse_alloc_forget();
+	if (!fi->forget)
+		goto out_free;
+
+	if (IS_ENABLED(CONFIG_FUSE_DAX) && !fuse_dax_inode_alloc(sb, fi))
+		goto out_free_forget;
+
+	return &fi->inode;
+
+out_free_forget:
+	kfree(fi->forget);
+out_free:
+	kmem_cache_free(fuse_inode_cachep, fi);
+	return NULL;
+}
+
+static void fuse_free_inode(struct inode *inode)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	mutex_destroy(&fi->mutex);
+	kfree(fi->forget);
+#ifdef CONFIG_FUSE_DAX
+	kfree(fi->dax);
+#endif
+	kmem_cache_free(fuse_inode_cachep, fi);
+}
+
+static void fuse_evict_inode(struct inode *inode)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	/* Will write inode on close/munmap and in all other dirtiers */
+	WARN_ON(inode->i_state & I_DIRTY_INODE);
+
+	truncate_inode_pages_final(&inode->i_data);
+	clear_inode(inode);
+	if (inode->i_sb->s_flags & SB_ACTIVE) {
+		struct fuse_conn *fc = get_fuse_conn(inode);
+
+		if (FUSE_IS_DAX(inode))
+			fuse_dax_inode_cleanup(inode);
+		if (fi->nlookup) {
+			fuse_queue_forget(fc, fi->forget, fi->nodeid,
+					  fi->nlookup);
+			fi->forget = NULL;
+		}
+	}
+	if (S_ISREG(inode->i_mode) && !fuse_is_bad(inode)) {
+		WARN_ON(!list_empty(&fi->write_files));
+		WARN_ON(!list_empty(&fi->queued_writes));
+	}
+}
+
+static int fuse_reconfigure(struct fs_context *fc)
+{
+	struct super_block *sb = fc->root->d_sb;
+
+	sync_filesystem(sb);
+	if (fc->sb_flags & SB_MANDLOCK)
+		return -EINVAL;
+
+	return 0;
+}
+
+/*
+ * ino_t is 32-bits on 32-bit arch. We have to squash the 64-bit value down
+ * so that it will fit.
+ */
+static ino_t fuse_squash_ino(u64 ino64)
+{
+	ino_t ino = (ino_t) ino64;
+	if (sizeof(ino_t) < sizeof(u64))
+		ino ^= ino64 >> (sizeof(u64) - sizeof(ino_t)) * 8;
+	return ino;
+}
+
+void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
+				   u64 attr_valid)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	lockdep_assert_held(&fi->lock);
+
+	fi->attr_version = atomic64_inc_return(&fc->attr_version);
+	fi->i_time = attr_valid;
+	WRITE_ONCE(fi->inval_mask, 0);
+
+	inode->i_ino     = fuse_squash_ino(attr->ino);
+	inode->i_mode    = (inode->i_mode & S_IFMT) | (attr->mode & 07777);
+	set_nlink(inode, attr->nlink);
+	inode->i_uid     = make_kuid(fc->user_ns, attr->uid);
+	inode->i_gid     = make_kgid(fc->user_ns, attr->gid);
+	inode->i_blocks  = attr->blocks;
+
+	/* Sanitize nsecs */
+	attr->atimensec = min_t(u32, attr->atimensec, NSEC_PER_SEC - 1);
+	attr->mtimensec = min_t(u32, attr->mtimensec, NSEC_PER_SEC - 1);
+	attr->ctimensec = min_t(u32, attr->ctimensec, NSEC_PER_SEC - 1);
+
+	inode->i_atime.tv_sec   = attr->atime;
+	inode->i_atime.tv_nsec  = attr->atimensec;
+	/* mtime from server may be stale due to local buffered write */
+	if (!fc->writeback_cache || !S_ISREG(inode->i_mode)) {
+		inode->i_mtime.tv_sec   = attr->mtime;
+		inode->i_mtime.tv_nsec  = attr->mtimensec;
+		inode->i_ctime.tv_sec   = attr->ctime;
+		inode->i_ctime.tv_nsec  = attr->ctimensec;
+	}
+
+	if (attr->blksize != 0)
+		inode->i_blkbits = ilog2(attr->blksize);
+	else
+		inode->i_blkbits = inode->i_sb->s_blocksize_bits;
+
+	/*
+	 * Don't set the sticky bit in i_mode, unless we want the VFS
+	 * to check permissions.  This prevents failures due to the
+	 * check in may_delete().
+	 */
+	fi->orig_i_mode = inode->i_mode;
+	if (!fc->default_permissions)
+		inode->i_mode &= ~S_ISVTX;
+
+	fi->orig_ino = attr->ino;
+}
+
+void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
+			    u64 attr_valid, u64 attr_version)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	bool is_wb = fc->writeback_cache;
+	loff_t oldsize;
+	struct timespec64 old_mtime;
+
+	spin_lock(&fi->lock);
+	if ((attr_version != 0 && fi->attr_version > attr_version) ||
+	    test_bit(FUSE_I_SIZE_UNSTABLE, &fi->state)) {
+		spin_unlock(&fi->lock);
+		return;
+	}
+
+	old_mtime = inode->i_mtime;
+	fuse_change_attributes_common(inode, attr, attr_valid);
+
+	oldsize = inode->i_size;
+	/*
+	 * In case of writeback_cache enabled, the cached writes beyond EOF
+	 * extend local i_size without keeping userspace server in sync. So,
+	 * attr->size coming from server can be stale. We cannot trust it.
+	 */
+	if (!is_wb || !S_ISREG(inode->i_mode))
+		i_size_write(inode, attr->size);
+	spin_unlock(&fi->lock);
+
+	if (!is_wb && S_ISREG(inode->i_mode)) {
+		bool inval = false;
+
+		if (oldsize != attr->size) {
+			truncate_pagecache(inode, attr->size);
+			if (!fc->explicit_inval_data)
+				inval = true;
+		} else if (fc->auto_inval_data) {
+			struct timespec64 new_mtime = {
+				.tv_sec = attr->mtime,
+				.tv_nsec = attr->mtimensec,
+			};
+
+			/*
+			 * Auto inval mode also checks and invalidates if mtime
+			 * has changed.
+			 */
+			if (!timespec64_equal(&old_mtime, &new_mtime))
+				inval = true;
+		}
+
+		if (inval)
+			invalidate_inode_pages2(inode->i_mapping);
+	}
+}
+
+static void fuse_init_inode(struct inode *inode, struct fuse_attr *attr)
+{
+	inode->i_mode = attr->mode & S_IFMT;
+	inode->i_size = attr->size;
+	inode->i_mtime.tv_sec  = attr->mtime;
+	inode->i_mtime.tv_nsec = attr->mtimensec;
+	inode->i_ctime.tv_sec  = attr->ctime;
+	inode->i_ctime.tv_nsec = attr->ctimensec;
+	if (S_ISREG(inode->i_mode)) {
+		fuse_init_common(inode);
+		fuse_init_file_inode(inode);
+	} else if (S_ISDIR(inode->i_mode))
+		fuse_init_dir(inode);
+	else if (S_ISLNK(inode->i_mode))
+		fuse_init_symlink(inode);
+	else if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode) ||
+		 S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
+		fuse_init_common(inode);
+		init_special_inode(inode, inode->i_mode,
+				   new_decode_dev(attr->rdev));
+	} else
+		BUG();
+}
+
+static int fuse_inode_eq(struct inode *inode, void *_nodeidp)
+{
+	u64 nodeid = *(u64 *) _nodeidp;
+	if (get_node_id(inode) == nodeid)
+		return 1;
+	else
+		return 0;
+}
+
+static int fuse_inode_set(struct inode *inode, void *_nodeidp)
+{
+	u64 nodeid = *(u64 *) _nodeidp;
+	get_fuse_inode(inode)->nodeid = nodeid;
+	return 0;
+}
+
+struct inode *fuse_iget(struct super_block *sb, u64 nodeid,
+			int generation, struct fuse_attr *attr,
+			u64 attr_valid, u64 attr_version)
+{
+	struct inode *inode;
+	struct fuse_inode *fi;
+	struct fuse_conn *fc = get_fuse_conn_super(sb);
+
+	/*
+	 * Auto mount points get their node id from the submount root, which is
+	 * not a unique identifier within this filesystem.
+	 *
+	 * To avoid conflicts, do not place submount points into the inode hash
+	 * table.
+	 */
+	if (fc->auto_submounts && (attr->flags & FUSE_ATTR_SUBMOUNT) &&
+	    S_ISDIR(attr->mode)) {
+		inode = new_inode(sb);
+		if (!inode)
+			return NULL;
+
+		fuse_init_inode(inode, attr);
+		get_fuse_inode(inode)->nodeid = nodeid;
+		inode->i_flags |= S_AUTOMOUNT;
+		goto done;
+	}
+
+retry:
+	inode = iget5_locked(sb, nodeid, fuse_inode_eq, fuse_inode_set, &nodeid);
+	if (!inode)
+		return NULL;
+
+	if ((inode->i_state & I_NEW)) {
+		inode->i_flags |= S_NOATIME;
+		if (!fc->writeback_cache || !S_ISREG(attr->mode))
+			inode->i_flags |= S_NOCMTIME;
+		inode->i_generation = generation;
+		fuse_init_inode(inode, attr);
+		unlock_new_inode(inode);
+	} else if (fuse_stale_inode(inode, generation, attr)) {
+		/* nodeid was reused, any I/O on the old inode should fail */
+		fuse_make_bad(inode);
+		iput(inode);
+		goto retry;
+	}
+done:
+	fi = get_fuse_inode(inode);
+	spin_lock(&fi->lock);
+	fi->nlookup++;
+	spin_unlock(&fi->lock);
+	fuse_change_attributes(inode, attr, attr_valid, attr_version);
+
+	return inode;
+}
+
+struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
+			   struct fuse_mount **fm)
+{
+	struct fuse_mount *fm_iter;
+	struct inode *inode;
+
+	WARN_ON(!rwsem_is_locked(&fc->killsb));
+	list_for_each_entry(fm_iter, &fc->mounts, fc_entry) {
+		if (!fm_iter->sb)
+			continue;
+
+		inode = ilookup5(fm_iter->sb, nodeid, fuse_inode_eq, &nodeid);
+		if (inode) {
+			if (fm)
+				*fm = fm_iter;
+			return inode;
+		}
+	}
+
+	return NULL;
+}
+
+int fuse_reverse_inval_inode(struct fuse_conn *fc, u64 nodeid,
+			     loff_t offset, loff_t len)
+{
+	struct fuse_inode *fi;
+	struct inode *inode;
+	pgoff_t pg_start;
+	pgoff_t pg_end;
+
+	inode = fuse_ilookup(fc, nodeid, NULL);
+	if (!inode)
+		return -ENOENT;
+
+	fi = get_fuse_inode(inode);
+	spin_lock(&fi->lock);
+	fi->attr_version = atomic64_inc_return(&fc->attr_version);
+	spin_unlock(&fi->lock);
+
+	fuse_invalidate_attr(inode);
+	forget_all_cached_acls(inode);
+	if (offset >= 0) {
+		pg_start = offset >> PAGE_SHIFT;
+		if (len <= 0)
+			pg_end = -1;
+		else
+			pg_end = (offset + len - 1) >> PAGE_SHIFT;
+		invalidate_inode_pages2_range(inode->i_mapping,
+					      pg_start, pg_end);
+	}
+	iput(inode);
+	return 0;
+}
+
+bool fuse_lock_inode(struct inode *inode)
+{
+	bool locked = false;
+
+	if (!get_fuse_conn(inode)->parallel_dirops) {
+		mutex_lock(&get_fuse_inode(inode)->mutex);
+		locked = true;
+	}
+
+	return locked;
+}
+
+void fuse_unlock_inode(struct inode *inode, bool locked)
+{
+	if (locked)
+		mutex_unlock(&get_fuse_inode(inode)->mutex);
+}
+
+static void fuse_umount_begin(struct super_block *sb)
+{
+	struct fuse_conn *fc = get_fuse_conn_super(sb);
+
+	if (!fc->no_force_umount)
+		fuse_abort_conn(fc);
+}
+
+static void fuse_send_destroy(struct fuse_mount *fm)
+{
+	if (fm->fc->conn_init) {
+		FUSE_ARGS(args);
+
+		args.opcode = FUSE_DESTROY;
+		args.force = true;
+		args.nocreds = true;
+		fuse_simple_request(fm, &args);
+	}
+}
+
+static void fuse_put_super(struct super_block *sb)
+{
+	struct fuse_mount *fm = get_fuse_mount_super(sb);
+
+	fuse_mount_put(fm);
+}
+
+static void convert_fuse_statfs(struct kstatfs *stbuf, struct fuse_kstatfs *attr)
+{
+	stbuf->f_type    = FUSE_SUPER_MAGIC;
+	stbuf->f_bsize   = attr->bsize;
+	stbuf->f_frsize  = attr->frsize;
+	stbuf->f_blocks  = attr->blocks;
+	stbuf->f_bfree   = attr->bfree;
+	stbuf->f_bavail  = attr->bavail;
+	stbuf->f_files   = attr->files;
+	stbuf->f_ffree   = attr->ffree;
+	stbuf->f_namelen = attr->namelen;
+	/* fsid is left zero */
+}
+
+static int fuse_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	struct super_block *sb = dentry->d_sb;
+	struct fuse_mount *fm = get_fuse_mount_super(sb);
+	FUSE_ARGS(args);
+	struct fuse_statfs_out outarg;
+	int err;
+
+	if (!fuse_allow_current_process(fm->fc)) {
+		buf->f_type = FUSE_SUPER_MAGIC;
+		return 0;
+	}
+
+	memset(&outarg, 0, sizeof(outarg));
+	args.in_numargs = 0;
+	args.opcode = FUSE_STATFS;
+	args.nodeid = get_node_id(d_inode(dentry));
+	args.out_numargs = 1;
+	args.out_args[0].size = sizeof(outarg);
+	args.out_args[0].value = &outarg;
+	err = fuse_simple_request(fm, &args);
+	if (!err)
+		convert_fuse_statfs(buf, &outarg.st);
+	return err;
+}
+
+enum {
+	OPT_SOURCE,
+	OPT_SUBTYPE,
+	OPT_FD,
+	OPT_ROOTMODE,
+	OPT_USER_ID,
+	OPT_GROUP_ID,
+	OPT_DEFAULT_PERMISSIONS,
+	OPT_ALLOW_OTHER,
+	OPT_MAX_READ,
+	OPT_BLKSIZE,
+	OPT_ERR
+};
+
+static const struct fs_parameter_spec fuse_fs_parameters[] = {
+	fsparam_string	("source",		OPT_SOURCE),
+	fsparam_u32	("fd",			OPT_FD),
+	fsparam_u32oct	("rootmode",		OPT_ROOTMODE),
+	fsparam_u32	("user_id",		OPT_USER_ID),
+	fsparam_u32	("group_id",		OPT_GROUP_ID),
+	fsparam_flag	("default_permissions",	OPT_DEFAULT_PERMISSIONS),
+	fsparam_flag	("allow_other",		OPT_ALLOW_OTHER),
+	fsparam_u32	("max_read",		OPT_MAX_READ),
+	fsparam_u32	("blksize",		OPT_BLKSIZE),
+	fsparam_string	("subtype",		OPT_SUBTYPE),
+	{}
+};
+
+static int fuse_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct fs_parse_result result;
+	struct fuse_fs_context *ctx = fc->fs_private;
+	int opt;
+
+	if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
+		/*
+		 * Ignore options coming from mount(MS_REMOUNT) for backward
+		 * compatibility.
+		 */
+		if (fc->oldapi)
+			return 0;
+
+		return invalfc(fc, "No changes allowed in reconfigure");
+	}
+
+	opt = fs_parse(fc, fuse_fs_parameters, param, &result);
+	if (opt < 0)
+		return opt;
+
+	switch (opt) {
+	case OPT_SOURCE:
+		if (fc->source)
+			return invalfc(fc, "Multiple sources specified");
+		fc->source = param->string;
+		param->string = NULL;
+		break;
+
+	case OPT_SUBTYPE:
+		if (ctx->subtype)
+			return invalfc(fc, "Multiple subtypes specified");
+		ctx->subtype = param->string;
+		param->string = NULL;
+		return 0;
+
+	case OPT_FD:
+		ctx->fd = result.uint_32;
+		ctx->fd_present = true;
+		break;
+
+	case OPT_ROOTMODE:
+		if (!fuse_valid_type(result.uint_32))
+			return invalfc(fc, "Invalid rootmode");
+		ctx->rootmode = result.uint_32;
+		ctx->rootmode_present = true;
+		break;
+
+	case OPT_USER_ID:
+		ctx->user_id = make_kuid(fc->user_ns, result.uint_32);
+		if (!uid_valid(ctx->user_id))
+			return invalfc(fc, "Invalid user_id");
+		ctx->user_id_present = true;
+		break;
+
+	case OPT_GROUP_ID:
+		ctx->group_id = make_kgid(fc->user_ns, result.uint_32);
+		if (!gid_valid(ctx->group_id))
+			return invalfc(fc, "Invalid group_id");
+		ctx->group_id_present = true;
+		break;
+
+	case OPT_DEFAULT_PERMISSIONS:
+		ctx->default_permissions = true;
+		break;
+
+	case OPT_ALLOW_OTHER:
+		ctx->allow_other = true;
+		break;
+
+	case OPT_MAX_READ:
+		ctx->max_read = result.uint_32;
+		break;
+
+	case OPT_BLKSIZE:
+		if (!ctx->is_bdev)
+			return invalfc(fc, "blksize only supported for fuseblk");
+		ctx->blksize = result.uint_32;
+		break;
+
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void fuse_free_fc(struct fs_context *fc)
+{
+	struct fuse_fs_context *ctx = fc->fs_private;
+
+	if (ctx) {
+		kfree(ctx->subtype);
+		kfree(ctx);
+	}
+}
+
+static int fuse_show_options(struct seq_file *m, struct dentry *root)
+{
+	struct super_block *sb = root->d_sb;
+	struct fuse_conn *fc = get_fuse_conn_super(sb);
+
+	if (fc->legacy_opts_show) {
+		seq_printf(m, ",user_id=%u",
+			   from_kuid_munged(fc->user_ns, fc->user_id));
+		seq_printf(m, ",group_id=%u",
+			   from_kgid_munged(fc->user_ns, fc->group_id));
+		if (fc->default_permissions)
+			seq_puts(m, ",default_permissions");
+		if (fc->allow_other)
+			seq_puts(m, ",allow_other");
+		if (fc->max_read != ~0)
+			seq_printf(m, ",max_read=%u", fc->max_read);
+		if (sb->s_bdev && sb->s_blocksize != FUSE_DEFAULT_BLKSIZE)
+			seq_printf(m, ",blksize=%lu", sb->s_blocksize);
+	}
+#ifdef CONFIG_FUSE_DAX
+	if (fc->dax)
+		seq_puts(m, ",dax");
+#endif
+
+	return 0;
+}
+
+static void fuse_iqueue_init(struct fuse_iqueue *fiq,
+			     const struct fuse_iqueue_ops *ops,
+			     void *priv)
+{
+	memset(fiq, 0, sizeof(struct fuse_iqueue));
+	spin_lock_init(&fiq->lock);
+	init_waitqueue_head(&fiq->waitq);
+	INIT_LIST_HEAD(&fiq->pending);
+	INIT_LIST_HEAD(&fiq->interrupts);
+	fiq->forget_list_tail = &fiq->forget_list_head;
+	fiq->connected = 1;
+	fiq->ops = ops;
+	fiq->priv = priv;
+}
+
+static void fuse_pqueue_init(struct fuse_pqueue *fpq)
+{
+	unsigned int i;
+
+	spin_lock_init(&fpq->lock);
+	for (i = 0; i < FUSE_PQ_HASH_SIZE; i++)
+		INIT_LIST_HEAD(&fpq->processing[i]);
+	INIT_LIST_HEAD(&fpq->io);
+	fpq->connected = 1;
+}
+
+void fuse_conn_init(struct fuse_conn *fc, struct fuse_mount *fm,
+		    struct user_namespace *user_ns,
+		    const struct fuse_iqueue_ops *fiq_ops, void *fiq_priv)
+{
+	memset(fc, 0, sizeof(*fc));
+	spin_lock_init(&fc->lock);
+	spin_lock_init(&fc->bg_lock);
+	init_rwsem(&fc->killsb);
+	refcount_set(&fc->count, 1);
+	atomic_set(&fc->dev_count, 1);
+	init_waitqueue_head(&fc->blocked_waitq);
+	fuse_iqueue_init(&fc->iq, fiq_ops, fiq_priv);
+	INIT_LIST_HEAD(&fc->bg_queue);
+	INIT_LIST_HEAD(&fc->entry);
+	INIT_LIST_HEAD(&fc->devices);
+	atomic_set(&fc->num_waiting, 0);
+	fc->max_background = FUSE_DEFAULT_MAX_BACKGROUND;
+	fc->congestion_threshold = FUSE_DEFAULT_CONGESTION_THRESHOLD;
+	atomic64_set(&fc->khctr, 0);
+	fc->polled_files = RB_ROOT;
+	fc->blocked = 0;
+	fc->initialized = 0;
+	fc->connected = 1;
+	atomic64_set(&fc->attr_version, 1);
+	get_random_bytes(&fc->scramble_key, sizeof(fc->scramble_key));
+	fc->pid_ns = get_pid_ns(task_active_pid_ns(current));
+	fc->user_ns = get_user_ns(user_ns);
+	fc->max_pages = FUSE_DEFAULT_MAX_PAGES_PER_REQ;
+	fc->max_pages_limit = FUSE_MAX_MAX_PAGES;
+
+	INIT_LIST_HEAD(&fc->mounts);
+	list_add(&fm->fc_entry, &fc->mounts);
+	fm->fc = fc;
+	refcount_set(&fm->count, 1);
+}
+EXPORT_SYMBOL_GPL(fuse_conn_init);
+
+void fuse_conn_put(struct fuse_conn *fc)
+{
+	if (refcount_dec_and_test(&fc->count)) {
+		struct fuse_iqueue *fiq = &fc->iq;
+
+		if (IS_ENABLED(CONFIG_FUSE_DAX))
+			fuse_dax_conn_free(fc);
+		if (fiq->ops->release)
+			fiq->ops->release(fiq);
+		put_pid_ns(fc->pid_ns);
+		put_user_ns(fc->user_ns);
+		fc->release(fc);
+	}
+}
+EXPORT_SYMBOL_GPL(fuse_conn_put);
+
+struct fuse_conn *fuse_conn_get(struct fuse_conn *fc)
+{
+	refcount_inc(&fc->count);
+	return fc;
+}
+EXPORT_SYMBOL_GPL(fuse_conn_get);
+
+void fuse_mount_put(struct fuse_mount *fm)
+{
+	if (refcount_dec_and_test(&fm->count)) {
+		if (fm->fc)
+			fuse_conn_put(fm->fc);
+		kfree(fm);
+	}
+}
+EXPORT_SYMBOL_GPL(fuse_mount_put);
+
+struct fuse_mount *fuse_mount_get(struct fuse_mount *fm)
+{
+	refcount_inc(&fm->count);
+	return fm;
+}
+EXPORT_SYMBOL_GPL(fuse_mount_get);
+
+static struct inode *fuse_get_root_inode(struct super_block *sb, unsigned mode)
+{
+	struct fuse_attr attr;
+	memset(&attr, 0, sizeof(attr));
+
+	attr.mode = mode;
+	attr.ino = FUSE_ROOT_ID;
+	attr.nlink = 1;
+	return fuse_iget(sb, 1, 0, &attr, 0, 0);
+}
+
+struct fuse_inode_handle {
+	u64 nodeid;
+	u32 generation;
+};
+
+static struct dentry *fuse_get_dentry(struct super_block *sb,
+				      struct fuse_inode_handle *handle)
+{
+	struct fuse_conn *fc = get_fuse_conn_super(sb);
+	struct inode *inode;
+	struct dentry *entry;
+	int err = -ESTALE;
+
+	if (handle->nodeid == 0)
+		goto out_err;
+
+	inode = ilookup5(sb, handle->nodeid, fuse_inode_eq, &handle->nodeid);
+	if (!inode) {
+		struct fuse_entry_out outarg;
+		const struct qstr name = QSTR_INIT(".", 1);
+
+		if (!fc->export_support)
+			goto out_err;
+
+		err = fuse_lookup_name(sb, handle->nodeid, &name, &outarg,
+				       &inode);
+		if (err && err != -ENOENT)
+			goto out_err;
+		if (err || !inode) {
+			err = -ESTALE;
+			goto out_err;
+		}
+		err = -EIO;
+		if (get_node_id(inode) != handle->nodeid)
+			goto out_iput;
+	}
+	err = -ESTALE;
+	if (inode->i_generation != handle->generation)
+		goto out_iput;
+
+	entry = d_obtain_alias(inode);
+	if (!IS_ERR(entry) && get_node_id(inode) != FUSE_ROOT_ID)
+		fuse_invalidate_entry_cache(entry);
+
+	return entry;
+
+ out_iput:
+	iput(inode);
+ out_err:
+	return ERR_PTR(err);
+}
+
+static int fuse_encode_fh(struct inode *inode, u32 *fh, int *max_len,
+			   struct inode *parent)
+{
+	int len = parent ? 6 : 3;
+	u64 nodeid;
+	u32 generation;
+
+	if (*max_len < len) {
+		*max_len = len;
+		return  FILEID_INVALID;
+	}
+
+	nodeid = get_fuse_inode(inode)->nodeid;
+	generation = inode->i_generation;
+
+	fh[0] = (u32)(nodeid >> 32);
+	fh[1] = (u32)(nodeid & 0xffffffff);
+	fh[2] = generation;
+
+	if (parent) {
+		nodeid = get_fuse_inode(parent)->nodeid;
+		generation = parent->i_generation;
+
+		fh[3] = (u32)(nodeid >> 32);
+		fh[4] = (u32)(nodeid & 0xffffffff);
+		fh[5] = generation;
+	}
+
+	*max_len = len;
+	return parent ? 0x82 : 0x81;
+}
+
+static struct dentry *fuse_fh_to_dentry(struct super_block *sb,
+		struct fid *fid, int fh_len, int fh_type)
+{
+	struct fuse_inode_handle handle;
+
+	if ((fh_type != 0x81 && fh_type != 0x82) || fh_len < 3)
+		return NULL;
+
+	handle.nodeid = (u64) fid->raw[0] << 32;
+	handle.nodeid |= (u64) fid->raw[1];
+	handle.generation = fid->raw[2];
+	return fuse_get_dentry(sb, &handle);
+}
+
+static struct dentry *fuse_fh_to_parent(struct super_block *sb,
+		struct fid *fid, int fh_len, int fh_type)
+{
+	struct fuse_inode_handle parent;
+
+	if (fh_type != 0x82 || fh_len < 6)
+		return NULL;
+
+	parent.nodeid = (u64) fid->raw[3] << 32;
+	parent.nodeid |= (u64) fid->raw[4];
+	parent.generation = fid->raw[5];
+	return fuse_get_dentry(sb, &parent);
+}
+
+static struct dentry *fuse_get_parent(struct dentry *child)
+{
+	struct inode *child_inode = d_inode(child);
+	struct fuse_conn *fc = get_fuse_conn(child_inode);
+	struct inode *inode;
+	struct dentry *parent;
+	struct fuse_entry_out outarg;
+	const struct qstr name = QSTR_INIT("..", 2);
+	int err;
+
+	if (!fc->export_support)
+		return ERR_PTR(-ESTALE);
+
+	err = fuse_lookup_name(child_inode->i_sb, get_node_id(child_inode),
+			       &name, &outarg, &inode);
+	if (err) {
+		if (err == -ENOENT)
+			return ERR_PTR(-ESTALE);
+		return ERR_PTR(err);
+	}
+
+	parent = d_obtain_alias(inode);
+	if (!IS_ERR(parent) && get_node_id(inode) != FUSE_ROOT_ID)
+		fuse_invalidate_entry_cache(parent);
+
+	return parent;
+}
+
+static const struct export_operations fuse_export_operations = {
+	.fh_to_dentry	= fuse_fh_to_dentry,
+	.fh_to_parent	= fuse_fh_to_parent,
+	.encode_fh	= fuse_encode_fh,
+	.get_parent	= fuse_get_parent,
+};
+
+static const struct super_operations fuse_super_operations = {
+	.alloc_inode    = fuse_alloc_inode,
+	.free_inode     = fuse_free_inode,
+	.evict_inode	= fuse_evict_inode,
+	.write_inode	= fuse_write_inode,
+	.drop_inode	= generic_delete_inode,
+	.put_super	= fuse_put_super,
+	.umount_begin	= fuse_umount_begin,
+	.statfs		= fuse_statfs,
+	.show_options	= fuse_show_options,
+};
+
+static void sanitize_global_limit(unsigned *limit)
+{
+	/*
+	 * The default maximum number of async requests is calculated to consume
+	 * 1/2^13 of the total memory, assuming 392 bytes per request.
+	 */
+	if (*limit == 0)
+		*limit = ((totalram_pages() << PAGE_SHIFT) >> 13) / 392;
+
+	if (*limit >= 1 << 16)
+		*limit = (1 << 16) - 1;
+}
+
+static int set_global_limit(const char *val, const struct kernel_param *kp)
+{
+	int rv;
+
+	rv = param_set_uint(val, kp);
+	if (rv)
+		return rv;
+
+	sanitize_global_limit((unsigned *)kp->arg);
+
+	return 0;
+}
+
+static void process_init_limits(struct fuse_conn *fc, struct fuse_init_out *arg)
+{
+	int cap_sys_admin = capable(CAP_SYS_ADMIN);
+
+	if (arg->minor < 13)
+		return;
+
+	sanitize_global_limit(&max_user_bgreq);
+	sanitize_global_limit(&max_user_congthresh);
+
+	spin_lock(&fc->bg_lock);
+	if (arg->max_background) {
+		fc->max_background = arg->max_background;
+
+		if (!cap_sys_admin && fc->max_background > max_user_bgreq)
+			fc->max_background = max_user_bgreq;
+	}
+	if (arg->congestion_threshold) {
+		fc->congestion_threshold = arg->congestion_threshold;
+
+		if (!cap_sys_admin &&
+		    fc->congestion_threshold > max_user_congthresh)
+			fc->congestion_threshold = max_user_congthresh;
+	}
+	spin_unlock(&fc->bg_lock);
+}
+
+struct fuse_init_args {
+	struct fuse_args args;
+	struct fuse_init_in in;
+	struct fuse_init_out out;
+};
+
+static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
+			       int error)
+{
+	struct fuse_conn *fc = fm->fc;
+	struct fuse_init_args *ia = container_of(args, typeof(*ia), args);
+	struct fuse_init_out *arg = &ia->out;
+	bool ok = true;
+
+	if (error || arg->major != FUSE_KERNEL_VERSION)
+		ok = false;
+	else {
+		unsigned long ra_pages;
+
+		process_init_limits(fc, arg);
+
+		if (arg->minor >= 6) {
+			ra_pages = arg->max_readahead / PAGE_SIZE;
+			if (arg->flags & FUSE_ASYNC_READ)
+				fc->async_read = 1;
+			if (!(arg->flags & FUSE_POSIX_LOCKS))
+				fc->no_lock = 1;
+			if (arg->minor >= 17) {
+				if (!(arg->flags & FUSE_FLOCK_LOCKS))
+					fc->no_flock = 1;
+			} else {
+				if (!(arg->flags & FUSE_POSIX_LOCKS))
+					fc->no_flock = 1;
+			}
+			if (arg->flags & FUSE_ATOMIC_O_TRUNC)
+				fc->atomic_o_trunc = 1;
+			if (arg->minor >= 9) {
+				/* LOOKUP has dependency on proto version */
+				if (arg->flags & FUSE_EXPORT_SUPPORT)
+					fc->export_support = 1;
+			}
+			if (arg->flags & FUSE_BIG_WRITES)
+				fc->big_writes = 1;
+			if (arg->flags & FUSE_DONT_MASK)
+				fc->dont_mask = 1;
+			if (arg->flags & FUSE_AUTO_INVAL_DATA)
+				fc->auto_inval_data = 1;
+			else if (arg->flags & FUSE_EXPLICIT_INVAL_DATA)
+				fc->explicit_inval_data = 1;
+			if (arg->flags & FUSE_DO_READDIRPLUS) {
+				fc->do_readdirplus = 1;
+				if (arg->flags & FUSE_READDIRPLUS_AUTO)
+					fc->readdirplus_auto = 1;
+			}
+			if (arg->flags & FUSE_ASYNC_DIO)
+				fc->async_dio = 1;
+			if (arg->flags & FUSE_WRITEBACK_CACHE)
+				fc->writeback_cache = 1;
+			if (arg->flags & FUSE_PARALLEL_DIROPS)
+				fc->parallel_dirops = 1;
+			if (arg->flags & FUSE_HANDLE_KILLPRIV)
+				fc->handle_killpriv = 1;
+			if (arg->time_gran && arg->time_gran <= 1000000000)
+				fm->sb->s_time_gran = arg->time_gran;
+			if ((arg->flags & FUSE_POSIX_ACL)) {
+				fc->default_permissions = 1;
+				fc->posix_acl = 1;
+				fm->sb->s_xattr = fuse_acl_xattr_handlers;
+			}
+			if (arg->flags & FUSE_CACHE_SYMLINKS)
+				fc->cache_symlinks = 1;
+			if (arg->flags & FUSE_ABORT_ERROR)
+				fc->abort_err = 1;
+			if (arg->flags & FUSE_MAX_PAGES) {
+				fc->max_pages =
+					min_t(unsigned int, fc->max_pages_limit,
+					max_t(unsigned int, arg->max_pages, 1));
+			}
+			if (IS_ENABLED(CONFIG_FUSE_DAX) &&
+			    arg->flags & FUSE_MAP_ALIGNMENT &&
+			    !fuse_dax_check_alignment(fc, arg->map_alignment)) {
+				ok = false;
+			}
+		} else {
+			ra_pages = fc->max_read / PAGE_SIZE;
+			fc->no_lock = 1;
+			fc->no_flock = 1;
+		}
+
+		fm->sb->s_bdi->ra_pages =
+				min(fm->sb->s_bdi->ra_pages, ra_pages);
+		fc->minor = arg->minor;
+		fc->max_write = arg->minor < 5 ? 4096 : arg->max_write;
+		fc->max_write = max_t(unsigned, 4096, fc->max_write);
+		fc->conn_init = 1;
+	}
+	kfree(ia);
+
+	if (!ok) {
+		fc->conn_init = 0;
+		fc->conn_error = 1;
+	}
+
+	fuse_set_initialized(fc);
+	wake_up_all(&fc->blocked_waitq);
+}
+
+void fuse_send_init(struct fuse_mount *fm)
+{
+	struct fuse_init_args *ia;
+
+	ia = kzalloc(sizeof(*ia), GFP_KERNEL | __GFP_NOFAIL);
+
+	ia->in.major = FUSE_KERNEL_VERSION;
+	ia->in.minor = FUSE_KERNEL_MINOR_VERSION;
+	ia->in.max_readahead = fm->sb->s_bdi->ra_pages * PAGE_SIZE;
+	ia->in.flags |=
+		FUSE_ASYNC_READ | FUSE_POSIX_LOCKS | FUSE_ATOMIC_O_TRUNC |
+		FUSE_EXPORT_SUPPORT | FUSE_BIG_WRITES | FUSE_DONT_MASK |
+		FUSE_SPLICE_WRITE | FUSE_SPLICE_MOVE | FUSE_SPLICE_READ |
+		FUSE_FLOCK_LOCKS | FUSE_HAS_IOCTL_DIR | FUSE_AUTO_INVAL_DATA |
+		FUSE_DO_READDIRPLUS | FUSE_READDIRPLUS_AUTO | FUSE_ASYNC_DIO |
+		FUSE_WRITEBACK_CACHE | FUSE_NO_OPEN_SUPPORT |
+		FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |
+		FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
+		FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA;
+#ifdef CONFIG_FUSE_DAX
+	if (fm->fc->dax)
+		ia->in.flags |= FUSE_MAP_ALIGNMENT;
+#endif
+	if (fm->fc->auto_submounts)
+		ia->in.flags |= FUSE_SUBMOUNTS;
+
+	ia->args.opcode = FUSE_INIT;
+	ia->args.in_numargs = 1;
+	ia->args.in_args[0].size = sizeof(ia->in);
+	ia->args.in_args[0].value = &ia->in;
+	ia->args.out_numargs = 1;
+	/* Variable length argument used for backward compatibility
+	   with interface version < 7.5.  Rest of init_out is zeroed
+	   by do_get_request(), so a short reply is not a problem */
+	ia->args.out_argvar = true;
+	ia->args.out_args[0].size = sizeof(ia->out);
+	ia->args.out_args[0].value = &ia->out;
+	ia->args.force = true;
+	ia->args.nocreds = true;
+	ia->args.end = process_init_reply;
+
+	if (fuse_simple_background(fm, &ia->args, GFP_KERNEL) != 0)
+		process_init_reply(fm, &ia->args, -ENOTCONN);
+}
+EXPORT_SYMBOL_GPL(fuse_send_init);
+
+void fuse_free_conn(struct fuse_conn *fc)
+{
+	WARN_ON(!list_empty(&fc->devices));
+	kfree_rcu(fc, rcu);
+}
+EXPORT_SYMBOL_GPL(fuse_free_conn);
+
+static int fuse_bdi_init(struct fuse_conn *fc, struct super_block *sb)
+{
+	int err;
+	char *suffix = "";
+
+	if (sb->s_bdev) {
+		suffix = "-fuseblk";
+		/*
+		 * sb->s_bdi points to blkdev's bdi however we want to redirect
+		 * it to our private bdi...
+		 */
+		bdi_put(sb->s_bdi);
+		sb->s_bdi = &noop_backing_dev_info;
+	}
+	err = super_setup_bdi_name(sb, "%u:%u%s", MAJOR(fc->dev),
+				   MINOR(fc->dev), suffix);
+	if (err)
+		return err;
+
+	/* fuse does it's own writeback accounting */
+	sb->s_bdi->capabilities &= ~BDI_CAP_WRITEBACK_ACCT;
+	sb->s_bdi->capabilities |= BDI_CAP_STRICTLIMIT;
+
+	/*
+	 * For a single fuse filesystem use max 1% of dirty +
+	 * writeback threshold.
+	 *
+	 * This gives about 1M of write buffer for memory maps on a
+	 * machine with 1G and 10% dirty_ratio, which should be more
+	 * than enough.
+	 *
+	 * Privileged users can raise it by writing to
+	 *
+	 *    /sys/class/bdi/<bdi>/max_ratio
+	 */
+	bdi_set_max_ratio(sb->s_bdi, 1);
+
+	return 0;
+}
+
+struct fuse_dev *fuse_dev_alloc(void)
+{
+	struct fuse_dev *fud;
+	struct list_head *pq;
+
+	fud = kzalloc(sizeof(struct fuse_dev), GFP_KERNEL);
+	if (!fud)
+		return NULL;
+
+	pq = kcalloc(FUSE_PQ_HASH_SIZE, sizeof(struct list_head), GFP_KERNEL);
+	if (!pq) {
+		kfree(fud);
+		return NULL;
+	}
+
+	fud->pq.processing = pq;
+	fuse_pqueue_init(&fud->pq);
+
+	return fud;
+}
+EXPORT_SYMBOL_GPL(fuse_dev_alloc);
+
+void fuse_dev_install(struct fuse_dev *fud, struct fuse_conn *fc)
+{
+	fud->fc = fuse_conn_get(fc);
+	spin_lock(&fc->lock);
+	list_add_tail(&fud->entry, &fc->devices);
+	spin_unlock(&fc->lock);
+}
+EXPORT_SYMBOL_GPL(fuse_dev_install);
+
+struct fuse_dev *fuse_dev_alloc_install(struct fuse_conn *fc)
+{
+	struct fuse_dev *fud;
+
+	fud = fuse_dev_alloc();
+	if (!fud)
+		return NULL;
+
+	fuse_dev_install(fud, fc);
+	return fud;
+}
+EXPORT_SYMBOL_GPL(fuse_dev_alloc_install);
+
+void fuse_dev_free(struct fuse_dev *fud)
+{
+	struct fuse_conn *fc = fud->fc;
+
+	if (fc) {
+		spin_lock(&fc->lock);
+		list_del(&fud->entry);
+		spin_unlock(&fc->lock);
+
+		fuse_conn_put(fc);
+	}
+	kfree(fud->pq.processing);
+	kfree(fud);
+}
+EXPORT_SYMBOL_GPL(fuse_dev_free);
+
+static void fuse_fill_attr_from_inode(struct fuse_attr *attr,
+				      const struct fuse_inode *fi)
+{
+	*attr = (struct fuse_attr){
+		.ino		= fi->inode.i_ino,
+		.size		= fi->inode.i_size,
+		.blocks		= fi->inode.i_blocks,
+		.atime		= fi->inode.i_atime.tv_sec,
+		.mtime		= fi->inode.i_mtime.tv_sec,
+		.ctime		= fi->inode.i_ctime.tv_sec,
+		.atimensec	= fi->inode.i_atime.tv_nsec,
+		.mtimensec	= fi->inode.i_mtime.tv_nsec,
+		.ctimensec	= fi->inode.i_ctime.tv_nsec,
+		.mode		= fi->inode.i_mode,
+		.nlink		= fi->inode.i_nlink,
+		.uid		= fi->inode.i_uid.val,
+		.gid		= fi->inode.i_gid.val,
+		.rdev		= fi->inode.i_rdev,
+		.blksize	= 1u << fi->inode.i_blkbits,
+	};
+}
+
+static void fuse_sb_defaults(struct super_block *sb)
+{
+	sb->s_magic = FUSE_SUPER_MAGIC;
+	sb->s_op = &fuse_super_operations;
+	sb->s_xattr = fuse_xattr_handlers;
+	sb->s_maxbytes = MAX_LFS_FILESIZE;
+	sb->s_time_gran = 1;
+	sb->s_export_op = &fuse_export_operations;
+	sb->s_iflags |= SB_I_IMA_UNVERIFIABLE_SIGNATURE;
+	if (sb->s_user_ns != &init_user_ns)
+		sb->s_iflags |= SB_I_UNTRUSTED_MOUNTER;
+	sb->s_flags &= ~(SB_NOSEC | SB_I_VERSION);
+
+	/*
+	 * If we are not in the initial user namespace posix
+	 * acls must be translated.
+	 */
+	if (sb->s_user_ns != &init_user_ns)
+		sb->s_xattr = fuse_no_acl_xattr_handlers;
+}
+
+int fuse_fill_super_submount(struct super_block *sb,
+			     struct fuse_inode *parent_fi)
+{
+	struct fuse_mount *fm = get_fuse_mount_super(sb);
+	struct super_block *parent_sb = parent_fi->inode.i_sb;
+	struct fuse_attr root_attr;
+	struct inode *root;
+
+	fuse_sb_defaults(sb);
+	fm->sb = sb;
+
+	WARN_ON(sb->s_bdi != &noop_backing_dev_info);
+	sb->s_bdi = bdi_get(parent_sb->s_bdi);
+
+	sb->s_xattr = parent_sb->s_xattr;
+	sb->s_time_gran = parent_sb->s_time_gran;
+	sb->s_blocksize = parent_sb->s_blocksize;
+	sb->s_blocksize_bits = parent_sb->s_blocksize_bits;
+	sb->s_subtype = kstrdup(parent_sb->s_subtype, GFP_KERNEL);
+	if (parent_sb->s_subtype && !sb->s_subtype)
+		return -ENOMEM;
+
+	fuse_fill_attr_from_inode(&root_attr, parent_fi);
+	root = fuse_iget(sb, parent_fi->nodeid, 0, &root_attr, 0, 0);
+	/*
+	 * This inode is just a duplicate, so it is not looked up and
+	 * its nlookup should not be incremented.  fuse_iget() does
+	 * that, though, so undo it here.
+	 */
+	get_fuse_inode(root)->nlookup--;
+	sb->s_d_op = &fuse_dentry_operations;
+	sb->s_root = d_make_root(root);
+	if (!sb->s_root)
+		return -ENOMEM;
+
+	return 0;
+}
+
+int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
+{
+	struct fuse_dev *fud = NULL;
+	struct fuse_mount *fm = get_fuse_mount_super(sb);
+	struct fuse_conn *fc = fm->fc;
+	struct inode *root;
+	struct dentry *root_dentry;
+	int err;
+
+	err = -EINVAL;
+	if (sb->s_flags & SB_MANDLOCK)
+		goto err;
+
+	fuse_sb_defaults(sb);
+
+	if (ctx->is_bdev) {
+#ifdef CONFIG_BLOCK
+		err = -EINVAL;
+		if (!sb_set_blocksize(sb, ctx->blksize))
+			goto err;
+#endif
+	} else {
+		sb->s_blocksize = PAGE_SIZE;
+		sb->s_blocksize_bits = PAGE_SHIFT;
+	}
+
+	sb->s_subtype = ctx->subtype;
+	ctx->subtype = NULL;
+	if (IS_ENABLED(CONFIG_FUSE_DAX)) {
+		err = fuse_dax_conn_alloc(fc, ctx->dax_dev);
+		if (err)
+			goto err;
+	}
+
+	if (ctx->fudptr) {
+		err = -ENOMEM;
+		fud = fuse_dev_alloc_install(fc);
+		if (!fud)
+			goto err_free_dax;
+	}
+
+	fc->dev = sb->s_dev;
+	fm->sb = sb;
+	err = fuse_bdi_init(fc, sb);
+	if (err)
+		goto err_dev_free;
+
+	/* Handle umasking inside the fuse code */
+	if (sb->s_flags & SB_POSIXACL)
+		fc->dont_mask = 1;
+	sb->s_flags |= SB_POSIXACL;
+
+	fc->default_permissions = ctx->default_permissions;
+	fc->allow_other = ctx->allow_other;
+	fc->user_id = ctx->user_id;
+	fc->group_id = ctx->group_id;
+	fc->legacy_opts_show = ctx->legacy_opts_show;
+	fc->max_read = max_t(unsigned int, 4096, ctx->max_read);
+	fc->destroy = ctx->destroy;
+	fc->no_control = ctx->no_control;
+	fc->no_force_umount = ctx->no_force_umount;
+
+	err = -ENOMEM;
+	root = fuse_get_root_inode(sb, ctx->rootmode);
+	sb->s_d_op = &fuse_root_dentry_operations;
+	root_dentry = d_make_root(root);
+	if (!root_dentry)
+		goto err_dev_free;
+	/* Root dentry doesn't have .d_revalidate */
+	sb->s_d_op = &fuse_dentry_operations;
+
+	mutex_lock(&fuse_mutex);
+	err = -EINVAL;
+	if (ctx->fudptr && *ctx->fudptr)
+		goto err_unlock;
+
+	err = fuse_ctl_add_conn(fc);
+	if (err)
+		goto err_unlock;
+
+	list_add_tail(&fc->entry, &fuse_conn_list);
+	sb->s_root = root_dentry;
+	if (ctx->fudptr)
+		*ctx->fudptr = fud;
+	mutex_unlock(&fuse_mutex);
+	return 0;
+
+ err_unlock:
+	mutex_unlock(&fuse_mutex);
+	dput(root_dentry);
+ err_dev_free:
+	if (fud)
+		fuse_dev_free(fud);
+ err_free_dax:
+	if (IS_ENABLED(CONFIG_FUSE_DAX))
+		fuse_dax_conn_free(fc);
+ err:
+	return err;
+}
+EXPORT_SYMBOL_GPL(fuse_fill_super_common);
+
+static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
+{
+	struct fuse_fs_context *ctx = fsc->fs_private;
+	struct file *file;
+	int err;
+	struct fuse_conn *fc;
+	struct fuse_mount *fm;
+
+	err = -EINVAL;
+	file = fget(ctx->fd);
+	if (!file)
+		goto err;
+
+	/*
+	 * Require mount to happen from the same user namespace which
+	 * opened /dev/fuse to prevent potential attacks.
+	 */
+	if ((file->f_op != &fuse_dev_operations) ||
+	    (file->f_cred->user_ns != sb->s_user_ns))
+		goto err_fput;
+	ctx->fudptr = &file->private_data;
+
+	fc = kmalloc(sizeof(*fc), GFP_KERNEL);
+	err = -ENOMEM;
+	if (!fc)
+		goto err_fput;
+
+	fm = kzalloc(sizeof(*fm), GFP_KERNEL);
+	if (!fm) {
+		kfree(fc);
+		goto err_fput;
+	}
+
+	fuse_conn_init(fc, fm, sb->s_user_ns, &fuse_dev_fiq_ops, NULL);
+	fc->release = fuse_free_conn;
+
+	sb->s_fs_info = fm;
+
+	err = fuse_fill_super_common(sb, ctx);
+	if (err)
+		goto err_put_conn;
+	/*
+	 * atomic_dec_and_test() in fput() provides the necessary
+	 * memory barrier for file->private_data to be visible on all
+	 * CPUs after this
+	 */
+	fput(file);
+	fuse_send_init(get_fuse_mount_super(sb));
+	return 0;
+
+ err_put_conn:
+	fuse_mount_put(fm);
+	sb->s_fs_info = NULL;
+ err_fput:
+	fput(file);
+ err:
+	return err;
+}
+
+static int fuse_get_tree(struct fs_context *fc)
+{
+	struct fuse_fs_context *ctx = fc->fs_private;
+
+	if (!ctx->fd_present || !ctx->rootmode_present ||
+	    !ctx->user_id_present || !ctx->group_id_present)
+		return -EINVAL;
+
+#ifdef CONFIG_BLOCK
+	if (ctx->is_bdev)
+		return get_tree_bdev(fc, fuse_fill_super);
+#endif
+
+	return get_tree_nodev(fc, fuse_fill_super);
+}
+
+static const struct fs_context_operations fuse_context_ops = {
+	.free		= fuse_free_fc,
+	.parse_param	= fuse_parse_param,
+	.reconfigure	= fuse_reconfigure,
+	.get_tree	= fuse_get_tree,
+};
+
+/*
+ * Set up the filesystem mount context.
+ */
+static int fuse_init_fs_context(struct fs_context *fc)
+{
+	struct fuse_fs_context *ctx;
+
+	ctx = kzalloc(sizeof(struct fuse_fs_context), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->max_read = ~0;
+	ctx->blksize = FUSE_DEFAULT_BLKSIZE;
+	ctx->legacy_opts_show = true;
+
+#ifdef CONFIG_BLOCK
+	if (fc->fs_type == &fuseblk_fs_type) {
+		ctx->is_bdev = true;
+		ctx->destroy = true;
+	}
+#endif
+
+	fc->fs_private = ctx;
+	fc->ops = &fuse_context_ops;
+	return 0;
+}
+
+bool fuse_mount_remove(struct fuse_mount *fm)
+{
+	struct fuse_conn *fc = fm->fc;
+	bool last = false;
+
+	down_write(&fc->killsb);
+	list_del_init(&fm->fc_entry);
+	if (list_empty(&fc->mounts))
+		last = true;
+	up_write(&fc->killsb);
+
+	return last;
+}
+EXPORT_SYMBOL_GPL(fuse_mount_remove);
+
+void fuse_conn_destroy(struct fuse_mount *fm)
+{
+	struct fuse_conn *fc = fm->fc;
+
+	if (fc->destroy)
+		fuse_send_destroy(fm);
+
+	fuse_abort_conn(fc);
+	fuse_wait_aborted(fc);
+
+	if (!list_empty(&fc->entry)) {
+		mutex_lock(&fuse_mutex);
+		list_del(&fc->entry);
+		fuse_ctl_remove_conn(fc);
+		mutex_unlock(&fuse_mutex);
+	}
+}
+EXPORT_SYMBOL_GPL(fuse_conn_destroy);
+
+static void fuse_kill_sb_anon(struct super_block *sb)
+{
+	struct fuse_mount *fm = get_fuse_mount_super(sb);
+	bool last;
+
+	if (fm) {
+		last = fuse_mount_remove(fm);
+		if (last)
+			fuse_conn_destroy(fm);
+	}
+	kill_anon_super(sb);
+}
+
+static struct file_system_type fuse_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "fuse",
+	.fs_flags	= FS_HAS_SUBTYPE | FS_USERNS_MOUNT,
+	.init_fs_context = fuse_init_fs_context,
+	.parameters	= fuse_fs_parameters,
+	.kill_sb	= fuse_kill_sb_anon,
+};
+MODULE_ALIAS_FS("fuse");
+
+#ifdef CONFIG_BLOCK
+static void fuse_kill_sb_blk(struct super_block *sb)
+{
+	struct fuse_mount *fm = get_fuse_mount_super(sb);
+	bool last;
+
+	if (sb->s_root) {
+		last = fuse_mount_remove(fm);
+		if (last)
+			fuse_conn_destroy(fm);
+	}
+	kill_block_super(sb);
+}
+
+static struct file_system_type fuseblk_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "fuseblk",
+	.init_fs_context = fuse_init_fs_context,
+	.parameters	= fuse_fs_parameters,
+	.kill_sb	= fuse_kill_sb_blk,
+	.fs_flags	= FS_REQUIRES_DEV | FS_HAS_SUBTYPE,
+};
+MODULE_ALIAS_FS("fuseblk");
+
+static inline int register_fuseblk(void)
+{
+	return register_filesystem(&fuseblk_fs_type);
+}
+
+static inline void unregister_fuseblk(void)
+{
+	unregister_filesystem(&fuseblk_fs_type);
+}
+#else
+static inline int register_fuseblk(void)
+{
+	return 0;
+}
+
+static inline void unregister_fuseblk(void)
+{
+}
+#endif
+
+static void fuse_inode_init_once(void *foo)
+{
+	struct inode *inode = foo;
+
+	inode_init_once(inode);
+}
+
+static int __init fuse_fs_init(void)
+{
+	int err;
+
+	fuse_inode_cachep = kmem_cache_create("fuse_inode",
+			sizeof(struct fuse_inode), 0,
+			SLAB_HWCACHE_ALIGN|SLAB_ACCOUNT|SLAB_RECLAIM_ACCOUNT,
+			fuse_inode_init_once);
+	err = -ENOMEM;
+	if (!fuse_inode_cachep)
+		goto out;
+
+	err = register_fuseblk();
+	if (err)
+		goto out2;
+
+	err = register_filesystem(&fuse_fs_type);
+	if (err)
+		goto out3;
+
+	return 0;
+
+ out3:
+	unregister_fuseblk();
+ out2:
+	kmem_cache_destroy(fuse_inode_cachep);
+ out:
+	return err;
+}
+
+static void fuse_fs_cleanup(void)
+{
+	unregister_filesystem(&fuse_fs_type);
+	unregister_fuseblk();
+
+	/*
+	 * Make sure all delayed rcu free inodes are flushed before we
+	 * destroy cache.
+	 */
+	rcu_barrier();
+	kmem_cache_destroy(fuse_inode_cachep);
+}
+
+static struct kobject *fuse_kobj;
+
+static int fuse_sysfs_init(void)
+{
+	int err;
+
+	fuse_kobj = kobject_create_and_add("fuse", fs_kobj);
+	if (!fuse_kobj) {
+		err = -ENOMEM;
+		goto out_err;
+	}
+
+	err = sysfs_create_mount_point(fuse_kobj, "connections");
+	if (err)
+		goto out_fuse_unregister;
+
+	return 0;
+
+ out_fuse_unregister:
+	kobject_put(fuse_kobj);
+ out_err:
+	return err;
+}
+
+static void fuse_sysfs_cleanup(void)
+{
+	sysfs_remove_mount_point(fuse_kobj, "connections");
+	kobject_put(fuse_kobj);
+}
+
+static int __init fuse_init(void)
+{
+	int res;
+
+	pr_info("init (API version %i.%i)\n",
+		FUSE_KERNEL_VERSION, FUSE_KERNEL_MINOR_VERSION);
+
+	INIT_LIST_HEAD(&fuse_conn_list);
+	res = fuse_fs_init();
+	if (res)
+		goto err;
+
+	res = fuse_dev_init();
+	if (res)
+		goto err_fs_cleanup;
+
+	res = fuse_sysfs_init();
+	if (res)
+		goto err_dev_cleanup;
+
+	res = fuse_ctl_init();
+	if (res)
+		goto err_sysfs_cleanup;
+
+	sanitize_global_limit(&max_user_bgreq);
+	sanitize_global_limit(&max_user_congthresh);
+
+	return 0;
+
+ err_sysfs_cleanup:
+	fuse_sysfs_cleanup();
+ err_dev_cleanup:
+	fuse_dev_cleanup();
+ err_fs_cleanup:
+	fuse_fs_cleanup();
+ err:
+	return res;
+}
+
+static void __exit fuse_exit(void)
+{
+	pr_debug("exit\n");
+
+	fuse_ctl_cleanup();
+	fuse_sysfs_cleanup();
+	fuse_fs_cleanup();
+	fuse_dev_cleanup();
+}
+
+module_init(fuse_init);
+module_exit(fuse_exit);
diff --git a/fs/fuse/readdir.c b/fs/fuse/readdir.c
new file mode 100644
index 000000000..14e99ffa5
--- /dev/null
+++ b/fs/fuse/readdir.c
@@ -0,0 +1,604 @@
+/*
+  FUSE: Filesystem in Userspace
+  Copyright (C) 2001-2018  Miklos Szeredi <miklos@szeredi.hu>
+
+  This program can be distributed under the terms of the GNU GPL.
+  See the file COPYING.
+*/
+
+
+#include "fuse_i.h"
+#include <linux/iversion.h>
+#include <linux/posix_acl.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+
+static bool fuse_use_readdirplus(struct inode *dir, struct dir_context *ctx)
+{
+	struct fuse_conn *fc = get_fuse_conn(dir);
+	struct fuse_inode *fi = get_fuse_inode(dir);
+
+	if (!fc->do_readdirplus)
+		return false;
+	if (!fc->readdirplus_auto)
+		return true;
+	if (test_and_clear_bit(FUSE_I_ADVISE_RDPLUS, &fi->state))
+		return true;
+	if (ctx->pos == 0)
+		return true;
+	return false;
+}
+
+static void fuse_add_dirent_to_cache(struct file *file,
+				     struct fuse_dirent *dirent, loff_t pos)
+{
+	struct fuse_inode *fi = get_fuse_inode(file_inode(file));
+	size_t reclen = FUSE_DIRENT_SIZE(dirent);
+	pgoff_t index;
+	struct page *page;
+	loff_t size;
+	u64 version;
+	unsigned int offset;
+	void *addr;
+
+	spin_lock(&fi->rdc.lock);
+	/*
+	 * Is cache already completed?  Or this entry does not go at the end of
+	 * cache?
+	 */
+	if (fi->rdc.cached || pos != fi->rdc.pos) {
+		spin_unlock(&fi->rdc.lock);
+		return;
+	}
+	version = fi->rdc.version;
+	size = fi->rdc.size;
+	offset = size & ~PAGE_MASK;
+	index = size >> PAGE_SHIFT;
+	/* Dirent doesn't fit in current page?  Jump to next page. */
+	if (offset + reclen > PAGE_SIZE) {
+		index++;
+		offset = 0;
+	}
+	spin_unlock(&fi->rdc.lock);
+
+	if (offset) {
+		page = find_lock_page(file->f_mapping, index);
+	} else {
+		page = find_or_create_page(file->f_mapping, index,
+					   mapping_gfp_mask(file->f_mapping));
+	}
+	if (!page)
+		return;
+
+	spin_lock(&fi->rdc.lock);
+	/* Raced with another readdir */
+	if (fi->rdc.version != version || fi->rdc.size != size ||
+	    WARN_ON(fi->rdc.pos != pos))
+		goto unlock;
+
+	addr = kmap_atomic(page);
+	if (!offset) {
+		clear_page(addr);
+		SetPageUptodate(page);
+	}
+	memcpy(addr + offset, dirent, reclen);
+	kunmap_atomic(addr);
+	fi->rdc.size = (index << PAGE_SHIFT) + offset + reclen;
+	fi->rdc.pos = dirent->off;
+unlock:
+	spin_unlock(&fi->rdc.lock);
+	unlock_page(page);
+	put_page(page);
+}
+
+static void fuse_readdir_cache_end(struct file *file, loff_t pos)
+{
+	struct fuse_inode *fi = get_fuse_inode(file_inode(file));
+	loff_t end;
+
+	spin_lock(&fi->rdc.lock);
+	/* does cache end position match current position? */
+	if (fi->rdc.pos != pos) {
+		spin_unlock(&fi->rdc.lock);
+		return;
+	}
+
+	fi->rdc.cached = true;
+	end = ALIGN(fi->rdc.size, PAGE_SIZE);
+	spin_unlock(&fi->rdc.lock);
+
+	/* truncate unused tail of cache */
+	truncate_inode_pages(file->f_mapping, end);
+}
+
+static bool fuse_emit(struct file *file, struct dir_context *ctx,
+		      struct fuse_dirent *dirent)
+{
+	struct fuse_file *ff = file->private_data;
+
+	if (ff->open_flags & FOPEN_CACHE_DIR)
+		fuse_add_dirent_to_cache(file, dirent, ctx->pos);
+
+	return dir_emit(ctx, dirent->name, dirent->namelen, dirent->ino,
+			dirent->type);
+}
+
+static int parse_dirfile(char *buf, size_t nbytes, struct file *file,
+			 struct dir_context *ctx)
+{
+	while (nbytes >= FUSE_NAME_OFFSET) {
+		struct fuse_dirent *dirent = (struct fuse_dirent *) buf;
+		size_t reclen = FUSE_DIRENT_SIZE(dirent);
+		if (!dirent->namelen || dirent->namelen > FUSE_NAME_MAX)
+			return -EIO;
+		if (reclen > nbytes)
+			break;
+		if (memchr(dirent->name, '/', dirent->namelen) != NULL)
+			return -EIO;
+
+		if (!fuse_emit(file, ctx, dirent))
+			break;
+
+		buf += reclen;
+		nbytes -= reclen;
+		ctx->pos = dirent->off;
+	}
+
+	return 0;
+}
+
+static int fuse_direntplus_link(struct file *file,
+				struct fuse_direntplus *direntplus,
+				u64 attr_version)
+{
+	struct fuse_entry_out *o = &direntplus->entry_out;
+	struct fuse_dirent *dirent = &direntplus->dirent;
+	struct dentry *parent = file->f_path.dentry;
+	struct qstr name = QSTR_INIT(dirent->name, dirent->namelen);
+	struct dentry *dentry;
+	struct dentry *alias;
+	struct inode *dir = d_inode(parent);
+	struct fuse_conn *fc;
+	struct inode *inode;
+	DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
+
+	if (!o->nodeid) {
+		/*
+		 * Unlike in the case of fuse_lookup, zero nodeid does not mean
+		 * ENOENT. Instead, it only means the userspace filesystem did
+		 * not want to return attributes/handle for this entry.
+		 *
+		 * So do nothing.
+		 */
+		return 0;
+	}
+
+	if (name.name[0] == '.') {
+		/*
+		 * We could potentially refresh the attributes of the directory
+		 * and its parent?
+		 */
+		if (name.len == 1)
+			return 0;
+		if (name.name[1] == '.' && name.len == 2)
+			return 0;
+	}
+
+	if (invalid_nodeid(o->nodeid))
+		return -EIO;
+	if (fuse_invalid_attr(&o->attr))
+		return -EIO;
+
+	fc = get_fuse_conn(dir);
+
+	name.hash = full_name_hash(parent, name.name, name.len);
+	dentry = d_lookup(parent, &name);
+	if (!dentry) {
+retry:
+		dentry = d_alloc_parallel(parent, &name, &wq);
+		if (IS_ERR(dentry))
+			return PTR_ERR(dentry);
+	}
+	if (!d_in_lookup(dentry)) {
+		struct fuse_inode *fi;
+		inode = d_inode(dentry);
+		if (inode && get_node_id(inode) != o->nodeid)
+			inode = NULL;
+		if (!inode ||
+		    fuse_stale_inode(inode, o->generation, &o->attr)) {
+			if (inode)
+				fuse_make_bad(inode);
+			d_invalidate(dentry);
+			dput(dentry);
+			goto retry;
+		}
+		if (fuse_is_bad(inode)) {
+			dput(dentry);
+			return -EIO;
+		}
+
+		fi = get_fuse_inode(inode);
+		spin_lock(&fi->lock);
+		fi->nlookup++;
+		spin_unlock(&fi->lock);
+
+		forget_all_cached_acls(inode);
+		fuse_change_attributes(inode, &o->attr,
+				       entry_attr_timeout(o),
+				       attr_version);
+		/*
+		 * The other branch comes via fuse_iget()
+		 * which bumps nlookup inside
+		 */
+	} else {
+		inode = fuse_iget(dir->i_sb, o->nodeid, o->generation,
+				  &o->attr, entry_attr_timeout(o),
+				  attr_version);
+		if (!inode)
+			inode = ERR_PTR(-ENOMEM);
+
+		alias = d_splice_alias(inode, dentry);
+		d_lookup_done(dentry);
+		if (alias) {
+			dput(dentry);
+			dentry = alias;
+		}
+		if (IS_ERR(dentry)) {
+			if (!IS_ERR(inode)) {
+				struct fuse_inode *fi = get_fuse_inode(inode);
+
+				spin_lock(&fi->lock);
+				fi->nlookup--;
+				spin_unlock(&fi->lock);
+			}
+			return PTR_ERR(dentry);
+		}
+	}
+	if (fc->readdirplus_auto)
+		set_bit(FUSE_I_INIT_RDPLUS, &get_fuse_inode(inode)->state);
+	fuse_change_entry_timeout(dentry, o);
+
+	dput(dentry);
+	return 0;
+}
+
+static void fuse_force_forget(struct file *file, u64 nodeid)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	struct fuse_forget_in inarg;
+	FUSE_ARGS(args);
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.nlookup = 1;
+	args.opcode = FUSE_FORGET;
+	args.nodeid = nodeid;
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.force = true;
+	args.noreply = true;
+
+	fuse_simple_request(fm, &args);
+	/* ignore errors */
+}
+
+static int parse_dirplusfile(char *buf, size_t nbytes, struct file *file,
+			     struct dir_context *ctx, u64 attr_version)
+{
+	struct fuse_direntplus *direntplus;
+	struct fuse_dirent *dirent;
+	size_t reclen;
+	int over = 0;
+	int ret;
+
+	while (nbytes >= FUSE_NAME_OFFSET_DIRENTPLUS) {
+		direntplus = (struct fuse_direntplus *) buf;
+		dirent = &direntplus->dirent;
+		reclen = FUSE_DIRENTPLUS_SIZE(direntplus);
+
+		if (!dirent->namelen || dirent->namelen > FUSE_NAME_MAX)
+			return -EIO;
+		if (reclen > nbytes)
+			break;
+		if (memchr(dirent->name, '/', dirent->namelen) != NULL)
+			return -EIO;
+
+		if (!over) {
+			/* We fill entries into dstbuf only as much as
+			   it can hold. But we still continue iterating
+			   over remaining entries to link them. If not,
+			   we need to send a FORGET for each of those
+			   which we did not link.
+			*/
+			over = !fuse_emit(file, ctx, dirent);
+			if (!over)
+				ctx->pos = dirent->off;
+		}
+
+		buf += reclen;
+		nbytes -= reclen;
+
+		ret = fuse_direntplus_link(file, direntplus, attr_version);
+		if (ret)
+			fuse_force_forget(file, direntplus->entry_out.nodeid);
+	}
+
+	return 0;
+}
+
+static int fuse_readdir_uncached(struct file *file, struct dir_context *ctx)
+{
+	int plus;
+	ssize_t res;
+	struct page *page;
+	struct inode *inode = file_inode(file);
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	struct fuse_io_args ia = {};
+	struct fuse_args_pages *ap = &ia.ap;
+	struct fuse_page_desc desc = { .length = PAGE_SIZE };
+	u64 attr_version = 0;
+	bool locked;
+
+	page = alloc_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	plus = fuse_use_readdirplus(inode, ctx);
+	ap->args.out_pages = true;
+	ap->num_pages = 1;
+	ap->pages = &page;
+	ap->descs = &desc;
+	if (plus) {
+		attr_version = fuse_get_attr_version(fm->fc);
+		fuse_read_args_fill(&ia, file, ctx->pos, PAGE_SIZE,
+				    FUSE_READDIRPLUS);
+	} else {
+		fuse_read_args_fill(&ia, file, ctx->pos, PAGE_SIZE,
+				    FUSE_READDIR);
+	}
+	locked = fuse_lock_inode(inode);
+	res = fuse_simple_request(fm, &ap->args);
+	fuse_unlock_inode(inode, locked);
+	if (res >= 0) {
+		if (!res) {
+			struct fuse_file *ff = file->private_data;
+
+			if (ff->open_flags & FOPEN_CACHE_DIR)
+				fuse_readdir_cache_end(file, ctx->pos);
+		} else if (plus) {
+			res = parse_dirplusfile(page_address(page), res,
+						file, ctx, attr_version);
+		} else {
+			res = parse_dirfile(page_address(page), res, file,
+					    ctx);
+		}
+	}
+
+	__free_page(page);
+	fuse_invalidate_atime(inode);
+	return res;
+}
+
+enum fuse_parse_result {
+	FOUND_ERR = -1,
+	FOUND_NONE = 0,
+	FOUND_SOME,
+	FOUND_ALL,
+};
+
+static enum fuse_parse_result fuse_parse_cache(struct fuse_file *ff,
+					       void *addr, unsigned int size,
+					       struct dir_context *ctx)
+{
+	unsigned int offset = ff->readdir.cache_off & ~PAGE_MASK;
+	enum fuse_parse_result res = FOUND_NONE;
+
+	WARN_ON(offset >= size);
+
+	for (;;) {
+		struct fuse_dirent *dirent = addr + offset;
+		unsigned int nbytes = size - offset;
+		size_t reclen;
+
+		if (nbytes < FUSE_NAME_OFFSET || !dirent->namelen)
+			break;
+
+		reclen = FUSE_DIRENT_SIZE(dirent); /* derefs ->namelen */
+
+		if (WARN_ON(dirent->namelen > FUSE_NAME_MAX))
+			return FOUND_ERR;
+		if (WARN_ON(reclen > nbytes))
+			return FOUND_ERR;
+		if (WARN_ON(memchr(dirent->name, '/', dirent->namelen) != NULL))
+			return FOUND_ERR;
+
+		if (ff->readdir.pos == ctx->pos) {
+			res = FOUND_SOME;
+			if (!dir_emit(ctx, dirent->name, dirent->namelen,
+				      dirent->ino, dirent->type))
+				return FOUND_ALL;
+			ctx->pos = dirent->off;
+		}
+		ff->readdir.pos = dirent->off;
+		ff->readdir.cache_off += reclen;
+
+		offset += reclen;
+	}
+
+	return res;
+}
+
+static void fuse_rdc_reset(struct inode *inode)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	fi->rdc.cached = false;
+	fi->rdc.version++;
+	fi->rdc.size = 0;
+	fi->rdc.pos = 0;
+}
+
+#define UNCACHED 1
+
+static int fuse_readdir_cached(struct file *file, struct dir_context *ctx)
+{
+	struct fuse_file *ff = file->private_data;
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	enum fuse_parse_result res;
+	pgoff_t index;
+	unsigned int size;
+	struct page *page;
+	void *addr;
+
+	/* Seeked?  If so, reset the cache stream */
+	if (ff->readdir.pos != ctx->pos) {
+		ff->readdir.pos = 0;
+		ff->readdir.cache_off = 0;
+	}
+
+	/*
+	 * We're just about to start reading into the cache or reading the
+	 * cache; both cases require an up-to-date mtime value.
+	 */
+	if (!ctx->pos && fc->auto_inval_data) {
+		int err = fuse_update_attributes(inode, file);
+
+		if (err)
+			return err;
+	}
+
+retry:
+	spin_lock(&fi->rdc.lock);
+retry_locked:
+	if (!fi->rdc.cached) {
+		/* Starting cache? Set cache mtime. */
+		if (!ctx->pos && !fi->rdc.size) {
+			fi->rdc.mtime = inode->i_mtime;
+			fi->rdc.iversion = inode_query_iversion(inode);
+		}
+		spin_unlock(&fi->rdc.lock);
+		return UNCACHED;
+	}
+	/*
+	 * When at the beginning of the directory (i.e. just after opendir(3) or
+	 * rewinddir(3)), then need to check whether directory contents have
+	 * changed, and reset the cache if so.
+	 */
+	if (!ctx->pos) {
+		if (inode_peek_iversion(inode) != fi->rdc.iversion ||
+		    !timespec64_equal(&fi->rdc.mtime, &inode->i_mtime)) {
+			fuse_rdc_reset(inode);
+			goto retry_locked;
+		}
+	}
+
+	/*
+	 * If cache version changed since the last getdents() call, then reset
+	 * the cache stream.
+	 */
+	if (ff->readdir.version != fi->rdc.version) {
+		ff->readdir.pos = 0;
+		ff->readdir.cache_off = 0;
+	}
+	/*
+	 * If at the beginning of the cache, than reset version to
+	 * current.
+	 */
+	if (ff->readdir.pos == 0)
+		ff->readdir.version = fi->rdc.version;
+
+	WARN_ON(fi->rdc.size < ff->readdir.cache_off);
+
+	index = ff->readdir.cache_off >> PAGE_SHIFT;
+
+	if (index == (fi->rdc.size >> PAGE_SHIFT))
+		size = fi->rdc.size & ~PAGE_MASK;
+	else
+		size = PAGE_SIZE;
+	spin_unlock(&fi->rdc.lock);
+
+	/* EOF? */
+	if ((ff->readdir.cache_off & ~PAGE_MASK) == size)
+		return 0;
+
+	page = find_get_page_flags(file->f_mapping, index,
+				   FGP_ACCESSED | FGP_LOCK);
+	/* Page gone missing, then re-added to cache, but not initialized? */
+	if (page && !PageUptodate(page)) {
+		unlock_page(page);
+		put_page(page);
+		page = NULL;
+	}
+	spin_lock(&fi->rdc.lock);
+	if (!page) {
+		/*
+		 * Uh-oh: page gone missing, cache is useless
+		 */
+		if (fi->rdc.version == ff->readdir.version)
+			fuse_rdc_reset(inode);
+		goto retry_locked;
+	}
+
+	/* Make sure it's still the same version after getting the page. */
+	if (ff->readdir.version != fi->rdc.version) {
+		spin_unlock(&fi->rdc.lock);
+		unlock_page(page);
+		put_page(page);
+		goto retry;
+	}
+	spin_unlock(&fi->rdc.lock);
+
+	/*
+	 * Contents of the page are now protected against changing by holding
+	 * the page lock.
+	 */
+	addr = kmap(page);
+	res = fuse_parse_cache(ff, addr, size, ctx);
+	kunmap(page);
+	unlock_page(page);
+	put_page(page);
+
+	if (res == FOUND_ERR)
+		return -EIO;
+
+	if (res == FOUND_ALL)
+		return 0;
+
+	if (size == PAGE_SIZE) {
+		/* We hit end of page: skip to next page. */
+		ff->readdir.cache_off = ALIGN(ff->readdir.cache_off, PAGE_SIZE);
+		goto retry;
+	}
+
+	/*
+	 * End of cache reached.  If found position, then we are done, otherwise
+	 * need to fall back to uncached, since the position we were looking for
+	 * wasn't in the cache.
+	 */
+	return res == FOUND_SOME ? 0 : UNCACHED;
+}
+
+int fuse_readdir(struct file *file, struct dir_context *ctx)
+{
+	struct fuse_file *ff = file->private_data;
+	struct inode *inode = file_inode(file);
+	int err;
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	mutex_lock(&ff->readdir.lock);
+
+	err = UNCACHED;
+	if (ff->open_flags & FOPEN_CACHE_DIR)
+		err = fuse_readdir_cached(file, ctx);
+	if (err == UNCACHED)
+		err = fuse_readdir_uncached(file, ctx);
+
+	mutex_unlock(&ff->readdir.lock);
+
+	return err;
+}
diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
new file mode 100644
index 000000000..faadc8048
--- /dev/null
+++ b/fs/fuse/virtio_fs.c
@@ -0,0 +1,1556 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * virtio-fs: Virtio Filesystem
+ * Copyright (C) 2018 Red Hat, Inc.
+ */
+
+#include <linux/fs.h>
+#include <linux/dax.h>
+#include <linux/pci.h>
+#include <linux/pfn_t.h>
+#include <linux/module.h>
+#include <linux/virtio.h>
+#include <linux/virtio_fs.h>
+#include <linux/delay.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+#include <linux/highmem.h>
+#include <linux/uio.h>
+#include "fuse_i.h"
+
+/* Used to help calculate the FUSE connection's max_pages limit for a request's
+ * size. Parts of the struct fuse_req are sliced into scattergather lists in
+ * addition to the pages used, so this can help account for that overhead.
+ */
+#define FUSE_HEADER_OVERHEAD    4
+
+/* List of virtio-fs device instances and a lock for the list. Also provides
+ * mutual exclusion in device removal and mounting path
+ */
+static DEFINE_MUTEX(virtio_fs_mutex);
+static LIST_HEAD(virtio_fs_instances);
+
+enum {
+	VQ_HIPRIO,
+	VQ_REQUEST
+};
+
+#define VQ_NAME_LEN	24
+
+/* Per-virtqueue state */
+struct virtio_fs_vq {
+	spinlock_t lock;
+	struct virtqueue *vq;     /* protected by ->lock */
+	struct work_struct done_work;
+	struct list_head queued_reqs;
+	struct list_head end_reqs;	/* End these requests */
+	struct delayed_work dispatch_work;
+	struct fuse_dev *fud;
+	bool connected;
+	long in_flight;
+	struct completion in_flight_zero; /* No inflight requests */
+	char name[VQ_NAME_LEN];
+} ____cacheline_aligned_in_smp;
+
+/* A virtio-fs device instance */
+struct virtio_fs {
+	struct kref refcount;
+	struct list_head list;    /* on virtio_fs_instances */
+	char *tag;
+	struct virtio_fs_vq *vqs;
+	unsigned int nvqs;               /* number of virtqueues */
+	unsigned int num_request_queues; /* number of request queues */
+	struct dax_device *dax_dev;
+
+	/* DAX memory window where file contents are mapped */
+	void *window_kaddr;
+	phys_addr_t window_phys_addr;
+	size_t window_len;
+};
+
+struct virtio_fs_forget_req {
+	struct fuse_in_header ih;
+	struct fuse_forget_in arg;
+};
+
+struct virtio_fs_forget {
+	/* This request can be temporarily queued on virt queue */
+	struct list_head list;
+	struct virtio_fs_forget_req req;
+};
+
+struct virtio_fs_req_work {
+	struct fuse_req *req;
+	struct virtio_fs_vq *fsvq;
+	struct work_struct done_work;
+};
+
+static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
+				 struct fuse_req *req, bool in_flight);
+
+enum {
+	OPT_DAX,
+};
+
+static const struct fs_parameter_spec virtio_fs_parameters[] = {
+	fsparam_flag("dax", OPT_DAX),
+	{}
+};
+
+static int virtio_fs_parse_param(struct fs_context *fc,
+				 struct fs_parameter *param)
+{
+	struct fs_parse_result result;
+	struct fuse_fs_context *ctx = fc->fs_private;
+	int opt;
+
+	opt = fs_parse(fc, virtio_fs_parameters, param, &result);
+	if (opt < 0)
+		return opt;
+
+	switch (opt) {
+	case OPT_DAX:
+		ctx->dax = 1;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void virtio_fs_free_fc(struct fs_context *fc)
+{
+	struct fuse_fs_context *ctx = fc->fs_private;
+
+	kfree(ctx);
+}
+
+static inline struct virtio_fs_vq *vq_to_fsvq(struct virtqueue *vq)
+{
+	struct virtio_fs *fs = vq->vdev->priv;
+
+	return &fs->vqs[vq->index];
+}
+
+static inline struct fuse_pqueue *vq_to_fpq(struct virtqueue *vq)
+{
+	return &vq_to_fsvq(vq)->fud->pq;
+}
+
+/* Should be called with fsvq->lock held. */
+static inline void inc_in_flight_req(struct virtio_fs_vq *fsvq)
+{
+	fsvq->in_flight++;
+}
+
+/* Should be called with fsvq->lock held. */
+static inline void dec_in_flight_req(struct virtio_fs_vq *fsvq)
+{
+	WARN_ON(fsvq->in_flight <= 0);
+	fsvq->in_flight--;
+	if (!fsvq->in_flight)
+		complete(&fsvq->in_flight_zero);
+}
+
+static void release_virtio_fs_obj(struct kref *ref)
+{
+	struct virtio_fs *vfs = container_of(ref, struct virtio_fs, refcount);
+
+	kfree(vfs->vqs);
+	kfree(vfs);
+}
+
+/* Make sure virtiofs_mutex is held */
+static void virtio_fs_put(struct virtio_fs *fs)
+{
+	kref_put(&fs->refcount, release_virtio_fs_obj);
+}
+
+static void virtio_fs_fiq_release(struct fuse_iqueue *fiq)
+{
+	struct virtio_fs *vfs = fiq->priv;
+
+	mutex_lock(&virtio_fs_mutex);
+	virtio_fs_put(vfs);
+	mutex_unlock(&virtio_fs_mutex);
+}
+
+static void virtio_fs_drain_queue(struct virtio_fs_vq *fsvq)
+{
+	WARN_ON(fsvq->in_flight < 0);
+
+	/* Wait for in flight requests to finish.*/
+	spin_lock(&fsvq->lock);
+	if (fsvq->in_flight) {
+		/* We are holding virtio_fs_mutex. There should not be any
+		 * waiters waiting for completion.
+		 */
+		reinit_completion(&fsvq->in_flight_zero);
+		spin_unlock(&fsvq->lock);
+		wait_for_completion(&fsvq->in_flight_zero);
+	} else {
+		spin_unlock(&fsvq->lock);
+	}
+
+	flush_work(&fsvq->done_work);
+	flush_delayed_work(&fsvq->dispatch_work);
+}
+
+static void virtio_fs_drain_all_queues_locked(struct virtio_fs *fs)
+{
+	struct virtio_fs_vq *fsvq;
+	int i;
+
+	for (i = 0; i < fs->nvqs; i++) {
+		fsvq = &fs->vqs[i];
+		virtio_fs_drain_queue(fsvq);
+	}
+}
+
+static void virtio_fs_drain_all_queues(struct virtio_fs *fs)
+{
+	/* Provides mutual exclusion between ->remove and ->kill_sb
+	 * paths. We don't want both of these draining queue at the
+	 * same time. Current completion logic reinits completion
+	 * and that means there should not be any other thread
+	 * doing reinit or waiting for completion already.
+	 */
+	mutex_lock(&virtio_fs_mutex);
+	virtio_fs_drain_all_queues_locked(fs);
+	mutex_unlock(&virtio_fs_mutex);
+}
+
+static void virtio_fs_start_all_queues(struct virtio_fs *fs)
+{
+	struct virtio_fs_vq *fsvq;
+	int i;
+
+	for (i = 0; i < fs->nvqs; i++) {
+		fsvq = &fs->vqs[i];
+		spin_lock(&fsvq->lock);
+		fsvq->connected = true;
+		spin_unlock(&fsvq->lock);
+	}
+}
+
+/* Add a new instance to the list or return -EEXIST if tag name exists*/
+static int virtio_fs_add_instance(struct virtio_fs *fs)
+{
+	struct virtio_fs *fs2;
+	bool duplicate = false;
+
+	mutex_lock(&virtio_fs_mutex);
+
+	list_for_each_entry(fs2, &virtio_fs_instances, list) {
+		if (strcmp(fs->tag, fs2->tag) == 0)
+			duplicate = true;
+	}
+
+	if (!duplicate)
+		list_add_tail(&fs->list, &virtio_fs_instances);
+
+	mutex_unlock(&virtio_fs_mutex);
+
+	if (duplicate)
+		return -EEXIST;
+	return 0;
+}
+
+/* Return the virtio_fs with a given tag, or NULL */
+static struct virtio_fs *virtio_fs_find_instance(const char *tag)
+{
+	struct virtio_fs *fs;
+
+	mutex_lock(&virtio_fs_mutex);
+
+	list_for_each_entry(fs, &virtio_fs_instances, list) {
+		if (strcmp(fs->tag, tag) == 0) {
+			kref_get(&fs->refcount);
+			goto found;
+		}
+	}
+
+	fs = NULL; /* not found */
+
+found:
+	mutex_unlock(&virtio_fs_mutex);
+
+	return fs;
+}
+
+static void virtio_fs_free_devs(struct virtio_fs *fs)
+{
+	unsigned int i;
+
+	for (i = 0; i < fs->nvqs; i++) {
+		struct virtio_fs_vq *fsvq = &fs->vqs[i];
+
+		if (!fsvq->fud)
+			continue;
+
+		fuse_dev_free(fsvq->fud);
+		fsvq->fud = NULL;
+	}
+}
+
+/* Read filesystem name from virtio config into fs->tag (must kfree()). */
+static int virtio_fs_read_tag(struct virtio_device *vdev, struct virtio_fs *fs)
+{
+	char tag_buf[sizeof_field(struct virtio_fs_config, tag)];
+	char *end;
+	size_t len;
+
+	virtio_cread_bytes(vdev, offsetof(struct virtio_fs_config, tag),
+			   &tag_buf, sizeof(tag_buf));
+	end = memchr(tag_buf, '\0', sizeof(tag_buf));
+	if (end == tag_buf)
+		return -EINVAL; /* empty tag */
+	if (!end)
+		end = &tag_buf[sizeof(tag_buf)];
+
+	len = end - tag_buf;
+	fs->tag = devm_kmalloc(&vdev->dev, len + 1, GFP_KERNEL);
+	if (!fs->tag)
+		return -ENOMEM;
+	memcpy(fs->tag, tag_buf, len);
+	fs->tag[len] = '\0';
+	return 0;
+}
+
+/* Work function for hiprio completion */
+static void virtio_fs_hiprio_done_work(struct work_struct *work)
+{
+	struct virtio_fs_vq *fsvq = container_of(work, struct virtio_fs_vq,
+						 done_work);
+	struct virtqueue *vq = fsvq->vq;
+
+	/* Free completed FUSE_FORGET requests */
+	spin_lock(&fsvq->lock);
+	do {
+		unsigned int len;
+		void *req;
+
+		virtqueue_disable_cb(vq);
+
+		while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
+			kfree(req);
+			dec_in_flight_req(fsvq);
+		}
+	} while (!virtqueue_enable_cb(vq) && likely(!virtqueue_is_broken(vq)));
+	spin_unlock(&fsvq->lock);
+}
+
+static void virtio_fs_request_dispatch_work(struct work_struct *work)
+{
+	struct fuse_req *req;
+	struct virtio_fs_vq *fsvq = container_of(work, struct virtio_fs_vq,
+						 dispatch_work.work);
+	int ret;
+
+	pr_debug("virtio-fs: worker %s called.\n", __func__);
+	while (1) {
+		spin_lock(&fsvq->lock);
+		req = list_first_entry_or_null(&fsvq->end_reqs, struct fuse_req,
+					       list);
+		if (!req) {
+			spin_unlock(&fsvq->lock);
+			break;
+		}
+
+		list_del_init(&req->list);
+		spin_unlock(&fsvq->lock);
+		fuse_request_end(req);
+	}
+
+	/* Dispatch pending requests */
+	while (1) {
+		spin_lock(&fsvq->lock);
+		req = list_first_entry_or_null(&fsvq->queued_reqs,
+					       struct fuse_req, list);
+		if (!req) {
+			spin_unlock(&fsvq->lock);
+			return;
+		}
+		list_del_init(&req->list);
+		spin_unlock(&fsvq->lock);
+
+		ret = virtio_fs_enqueue_req(fsvq, req, true);
+		if (ret < 0) {
+			if (ret == -ENOMEM || ret == -ENOSPC) {
+				spin_lock(&fsvq->lock);
+				list_add_tail(&req->list, &fsvq->queued_reqs);
+				schedule_delayed_work(&fsvq->dispatch_work,
+						      msecs_to_jiffies(1));
+				spin_unlock(&fsvq->lock);
+				return;
+			}
+			req->out.h.error = ret;
+			spin_lock(&fsvq->lock);
+			dec_in_flight_req(fsvq);
+			spin_unlock(&fsvq->lock);
+			pr_err("virtio-fs: virtio_fs_enqueue_req() failed %d\n",
+			       ret);
+			fuse_request_end(req);
+		}
+	}
+}
+
+/*
+ * Returns 1 if queue is full and sender should wait a bit before sending
+ * next request, 0 otherwise.
+ */
+static int send_forget_request(struct virtio_fs_vq *fsvq,
+			       struct virtio_fs_forget *forget,
+			       bool in_flight)
+{
+	struct scatterlist sg;
+	struct virtqueue *vq;
+	int ret = 0;
+	bool notify;
+	struct virtio_fs_forget_req *req = &forget->req;
+
+	spin_lock(&fsvq->lock);
+	if (!fsvq->connected) {
+		if (in_flight)
+			dec_in_flight_req(fsvq);
+		kfree(forget);
+		goto out;
+	}
+
+	sg_init_one(&sg, req, sizeof(*req));
+	vq = fsvq->vq;
+	dev_dbg(&vq->vdev->dev, "%s\n", __func__);
+
+	ret = virtqueue_add_outbuf(vq, &sg, 1, forget, GFP_ATOMIC);
+	if (ret < 0) {
+		if (ret == -ENOMEM || ret == -ENOSPC) {
+			pr_debug("virtio-fs: Could not queue FORGET: err=%d. Will try later\n",
+				 ret);
+			list_add_tail(&forget->list, &fsvq->queued_reqs);
+			schedule_delayed_work(&fsvq->dispatch_work,
+					      msecs_to_jiffies(1));
+			if (!in_flight)
+				inc_in_flight_req(fsvq);
+			/* Queue is full */
+			ret = 1;
+		} else {
+			pr_debug("virtio-fs: Could not queue FORGET: err=%d. Dropping it.\n",
+				 ret);
+			kfree(forget);
+			if (in_flight)
+				dec_in_flight_req(fsvq);
+		}
+		goto out;
+	}
+
+	if (!in_flight)
+		inc_in_flight_req(fsvq);
+	notify = virtqueue_kick_prepare(vq);
+	spin_unlock(&fsvq->lock);
+
+	if (notify)
+		virtqueue_notify(vq);
+	return ret;
+out:
+	spin_unlock(&fsvq->lock);
+	return ret;
+}
+
+static void virtio_fs_hiprio_dispatch_work(struct work_struct *work)
+{
+	struct virtio_fs_forget *forget;
+	struct virtio_fs_vq *fsvq = container_of(work, struct virtio_fs_vq,
+						 dispatch_work.work);
+	pr_debug("virtio-fs: worker %s called.\n", __func__);
+	while (1) {
+		spin_lock(&fsvq->lock);
+		forget = list_first_entry_or_null(&fsvq->queued_reqs,
+					struct virtio_fs_forget, list);
+		if (!forget) {
+			spin_unlock(&fsvq->lock);
+			return;
+		}
+
+		list_del(&forget->list);
+		spin_unlock(&fsvq->lock);
+		if (send_forget_request(fsvq, forget, true))
+			return;
+	}
+}
+
+/* Allocate and copy args into req->argbuf */
+static int copy_args_to_argbuf(struct fuse_req *req)
+{
+	struct fuse_args *args = req->args;
+	unsigned int offset = 0;
+	unsigned int num_in;
+	unsigned int num_out;
+	unsigned int len;
+	unsigned int i;
+
+	num_in = args->in_numargs - args->in_pages;
+	num_out = args->out_numargs - args->out_pages;
+	len = fuse_len_args(num_in, (struct fuse_arg *) args->in_args) +
+	      fuse_len_args(num_out, args->out_args);
+
+	req->argbuf = kmalloc(len, GFP_ATOMIC);
+	if (!req->argbuf)
+		return -ENOMEM;
+
+	for (i = 0; i < num_in; i++) {
+		memcpy(req->argbuf + offset,
+		       args->in_args[i].value,
+		       args->in_args[i].size);
+		offset += args->in_args[i].size;
+	}
+
+	return 0;
+}
+
+/* Copy args out of and free req->argbuf */
+static void copy_args_from_argbuf(struct fuse_args *args, struct fuse_req *req)
+{
+	unsigned int remaining;
+	unsigned int offset;
+	unsigned int num_in;
+	unsigned int num_out;
+	unsigned int i;
+
+	remaining = req->out.h.len - sizeof(req->out.h);
+	num_in = args->in_numargs - args->in_pages;
+	num_out = args->out_numargs - args->out_pages;
+	offset = fuse_len_args(num_in, (struct fuse_arg *)args->in_args);
+
+	for (i = 0; i < num_out; i++) {
+		unsigned int argsize = args->out_args[i].size;
+
+		if (args->out_argvar &&
+		    i == args->out_numargs - 1 &&
+		    argsize > remaining) {
+			argsize = remaining;
+		}
+
+		memcpy(args->out_args[i].value, req->argbuf + offset, argsize);
+		offset += argsize;
+
+		if (i != args->out_numargs - 1)
+			remaining -= argsize;
+	}
+
+	/* Store the actual size of the variable-length arg */
+	if (args->out_argvar)
+		args->out_args[args->out_numargs - 1].size = remaining;
+
+	kfree(req->argbuf);
+	req->argbuf = NULL;
+}
+
+/* Work function for request completion */
+static void virtio_fs_request_complete(struct fuse_req *req,
+				       struct virtio_fs_vq *fsvq)
+{
+	struct fuse_pqueue *fpq = &fsvq->fud->pq;
+	struct fuse_args *args;
+	struct fuse_args_pages *ap;
+	unsigned int len, i, thislen;
+	struct page *page;
+
+	/*
+	 * TODO verify that server properly follows FUSE protocol
+	 * (oh.uniq, oh.len)
+	 */
+	args = req->args;
+	copy_args_from_argbuf(args, req);
+
+	if (args->out_pages && args->page_zeroing) {
+		len = args->out_args[args->out_numargs - 1].size;
+		ap = container_of(args, typeof(*ap), args);
+		for (i = 0; i < ap->num_pages; i++) {
+			thislen = ap->descs[i].length;
+			if (len < thislen) {
+				WARN_ON(ap->descs[i].offset);
+				page = ap->pages[i];
+				zero_user_segment(page, len, thislen);
+				len = 0;
+			} else {
+				len -= thislen;
+			}
+		}
+	}
+
+	spin_lock(&fpq->lock);
+	clear_bit(FR_SENT, &req->flags);
+	spin_unlock(&fpq->lock);
+
+	fuse_request_end(req);
+	spin_lock(&fsvq->lock);
+	dec_in_flight_req(fsvq);
+	spin_unlock(&fsvq->lock);
+}
+
+static void virtio_fs_complete_req_work(struct work_struct *work)
+{
+	struct virtio_fs_req_work *w =
+		container_of(work, typeof(*w), done_work);
+
+	virtio_fs_request_complete(w->req, w->fsvq);
+	kfree(w);
+}
+
+static void virtio_fs_requests_done_work(struct work_struct *work)
+{
+	struct virtio_fs_vq *fsvq = container_of(work, struct virtio_fs_vq,
+						 done_work);
+	struct fuse_pqueue *fpq = &fsvq->fud->pq;
+	struct virtqueue *vq = fsvq->vq;
+	struct fuse_req *req;
+	struct fuse_req *next;
+	unsigned int len;
+	LIST_HEAD(reqs);
+
+	/* Collect completed requests off the virtqueue */
+	spin_lock(&fsvq->lock);
+	do {
+		virtqueue_disable_cb(vq);
+
+		while ((req = virtqueue_get_buf(vq, &len)) != NULL) {
+			spin_lock(&fpq->lock);
+			list_move_tail(&req->list, &reqs);
+			spin_unlock(&fpq->lock);
+		}
+	} while (!virtqueue_enable_cb(vq) && likely(!virtqueue_is_broken(vq)));
+	spin_unlock(&fsvq->lock);
+
+	/* End requests */
+	list_for_each_entry_safe(req, next, &reqs, list) {
+		list_del_init(&req->list);
+
+		/* blocking async request completes in a worker context */
+		if (req->args->may_block) {
+			struct virtio_fs_req_work *w;
+
+			w = kzalloc(sizeof(*w), GFP_NOFS | __GFP_NOFAIL);
+			INIT_WORK(&w->done_work, virtio_fs_complete_req_work);
+			w->fsvq = fsvq;
+			w->req = req;
+			schedule_work(&w->done_work);
+		} else {
+			virtio_fs_request_complete(req, fsvq);
+		}
+	}
+}
+
+/* Virtqueue interrupt handler */
+static void virtio_fs_vq_done(struct virtqueue *vq)
+{
+	struct virtio_fs_vq *fsvq = vq_to_fsvq(vq);
+
+	dev_dbg(&vq->vdev->dev, "%s %s\n", __func__, fsvq->name);
+
+	schedule_work(&fsvq->done_work);
+}
+
+static void virtio_fs_init_vq(struct virtio_fs_vq *fsvq, char *name,
+			      int vq_type)
+{
+	strncpy(fsvq->name, name, VQ_NAME_LEN);
+	spin_lock_init(&fsvq->lock);
+	INIT_LIST_HEAD(&fsvq->queued_reqs);
+	INIT_LIST_HEAD(&fsvq->end_reqs);
+	init_completion(&fsvq->in_flight_zero);
+
+	if (vq_type == VQ_REQUEST) {
+		INIT_WORK(&fsvq->done_work, virtio_fs_requests_done_work);
+		INIT_DELAYED_WORK(&fsvq->dispatch_work,
+				  virtio_fs_request_dispatch_work);
+	} else {
+		INIT_WORK(&fsvq->done_work, virtio_fs_hiprio_done_work);
+		INIT_DELAYED_WORK(&fsvq->dispatch_work,
+				  virtio_fs_hiprio_dispatch_work);
+	}
+}
+
+/* Initialize virtqueues */
+static int virtio_fs_setup_vqs(struct virtio_device *vdev,
+			       struct virtio_fs *fs)
+{
+	struct virtqueue **vqs;
+	vq_callback_t **callbacks;
+	const char **names;
+	unsigned int i;
+	int ret = 0;
+
+	virtio_cread_le(vdev, struct virtio_fs_config, num_request_queues,
+			&fs->num_request_queues);
+	if (fs->num_request_queues == 0)
+		return -EINVAL;
+
+	fs->nvqs = VQ_REQUEST + fs->num_request_queues;
+	fs->vqs = kcalloc(fs->nvqs, sizeof(fs->vqs[VQ_HIPRIO]), GFP_KERNEL);
+	if (!fs->vqs)
+		return -ENOMEM;
+
+	vqs = kmalloc_array(fs->nvqs, sizeof(vqs[VQ_HIPRIO]), GFP_KERNEL);
+	callbacks = kmalloc_array(fs->nvqs, sizeof(callbacks[VQ_HIPRIO]),
+					GFP_KERNEL);
+	names = kmalloc_array(fs->nvqs, sizeof(names[VQ_HIPRIO]), GFP_KERNEL);
+	if (!vqs || !callbacks || !names) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/* Initialize the hiprio/forget request virtqueue */
+	callbacks[VQ_HIPRIO] = virtio_fs_vq_done;
+	virtio_fs_init_vq(&fs->vqs[VQ_HIPRIO], "hiprio", VQ_HIPRIO);
+	names[VQ_HIPRIO] = fs->vqs[VQ_HIPRIO].name;
+
+	/* Initialize the requests virtqueues */
+	for (i = VQ_REQUEST; i < fs->nvqs; i++) {
+		char vq_name[VQ_NAME_LEN];
+
+		snprintf(vq_name, VQ_NAME_LEN, "requests.%u", i - VQ_REQUEST);
+		virtio_fs_init_vq(&fs->vqs[i], vq_name, VQ_REQUEST);
+		callbacks[i] = virtio_fs_vq_done;
+		names[i] = fs->vqs[i].name;
+	}
+
+	ret = virtio_find_vqs(vdev, fs->nvqs, vqs, callbacks, names, NULL);
+	if (ret < 0)
+		goto out;
+
+	for (i = 0; i < fs->nvqs; i++)
+		fs->vqs[i].vq = vqs[i];
+
+	virtio_fs_start_all_queues(fs);
+out:
+	kfree(names);
+	kfree(callbacks);
+	kfree(vqs);
+	if (ret)
+		kfree(fs->vqs);
+	return ret;
+}
+
+/* Free virtqueues (device must already be reset) */
+static void virtio_fs_cleanup_vqs(struct virtio_device *vdev,
+				  struct virtio_fs *fs)
+{
+	vdev->config->del_vqs(vdev);
+}
+
+/* Map a window offset to a page frame number.  The window offset will have
+ * been produced by .iomap_begin(), which maps a file offset to a window
+ * offset.
+ */
+static long virtio_fs_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
+				    long nr_pages, void **kaddr, pfn_t *pfn)
+{
+	struct virtio_fs *fs = dax_get_private(dax_dev);
+	phys_addr_t offset = PFN_PHYS(pgoff);
+	size_t max_nr_pages = fs->window_len/PAGE_SIZE - pgoff;
+
+	if (kaddr)
+		*kaddr = fs->window_kaddr + offset;
+	if (pfn)
+		*pfn = phys_to_pfn_t(fs->window_phys_addr + offset,
+					PFN_DEV | PFN_MAP);
+	return nr_pages > max_nr_pages ? max_nr_pages : nr_pages;
+}
+
+static size_t virtio_fs_copy_from_iter(struct dax_device *dax_dev,
+				       pgoff_t pgoff, void *addr,
+				       size_t bytes, struct iov_iter *i)
+{
+	return copy_from_iter(addr, bytes, i);
+}
+
+static size_t virtio_fs_copy_to_iter(struct dax_device *dax_dev,
+				       pgoff_t pgoff, void *addr,
+				       size_t bytes, struct iov_iter *i)
+{
+	return copy_to_iter(addr, bytes, i);
+}
+
+static int virtio_fs_zero_page_range(struct dax_device *dax_dev,
+				     pgoff_t pgoff, size_t nr_pages)
+{
+	long rc;
+	void *kaddr;
+
+	rc = dax_direct_access(dax_dev, pgoff, nr_pages, &kaddr, NULL);
+	if (rc < 0)
+		return rc;
+	memset(kaddr, 0, nr_pages << PAGE_SHIFT);
+	dax_flush(dax_dev, kaddr, nr_pages << PAGE_SHIFT);
+	return 0;
+}
+
+static const struct dax_operations virtio_fs_dax_ops = {
+	.direct_access = virtio_fs_direct_access,
+	.copy_from_iter = virtio_fs_copy_from_iter,
+	.copy_to_iter = virtio_fs_copy_to_iter,
+	.zero_page_range = virtio_fs_zero_page_range,
+};
+
+static void virtio_fs_cleanup_dax(void *data)
+{
+	struct dax_device *dax_dev = data;
+
+	kill_dax(dax_dev);
+	put_dax(dax_dev);
+}
+
+static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
+{
+	struct virtio_shm_region cache_reg;
+	struct dev_pagemap *pgmap;
+	bool have_cache;
+
+	if (!IS_ENABLED(CONFIG_FUSE_DAX))
+		return 0;
+
+	/* Get cache region */
+	have_cache = virtio_get_shm_region(vdev, &cache_reg,
+					   (u8)VIRTIO_FS_SHMCAP_ID_CACHE);
+	if (!have_cache) {
+		dev_notice(&vdev->dev, "%s: No cache capability\n", __func__);
+		return 0;
+	}
+
+	if (!devm_request_mem_region(&vdev->dev, cache_reg.addr, cache_reg.len,
+				     dev_name(&vdev->dev))) {
+		dev_warn(&vdev->dev, "could not reserve region addr=0x%llx len=0x%llx\n",
+			 cache_reg.addr, cache_reg.len);
+		return -EBUSY;
+	}
+
+	dev_notice(&vdev->dev, "Cache len: 0x%llx @ 0x%llx\n", cache_reg.len,
+		   cache_reg.addr);
+
+	pgmap = devm_kzalloc(&vdev->dev, sizeof(*pgmap), GFP_KERNEL);
+	if (!pgmap)
+		return -ENOMEM;
+
+	pgmap->type = MEMORY_DEVICE_FS_DAX;
+
+	/* Ideally we would directly use the PCI BAR resource but
+	 * devm_memremap_pages() wants its own copy in pgmap.  So
+	 * initialize a struct resource from scratch (only the start
+	 * and end fields will be used).
+	 */
+	pgmap->range = (struct range) {
+		.start = (phys_addr_t) cache_reg.addr,
+		.end = (phys_addr_t) cache_reg.addr + cache_reg.len - 1,
+	};
+	pgmap->nr_range = 1;
+
+	fs->window_kaddr = devm_memremap_pages(&vdev->dev, pgmap);
+	if (IS_ERR(fs->window_kaddr))
+		return PTR_ERR(fs->window_kaddr);
+
+	fs->window_phys_addr = (phys_addr_t) cache_reg.addr;
+	fs->window_len = (phys_addr_t) cache_reg.len;
+
+	dev_dbg(&vdev->dev, "%s: window kaddr 0x%px phys_addr 0x%llx len 0x%llx\n",
+		__func__, fs->window_kaddr, cache_reg.addr, cache_reg.len);
+
+	fs->dax_dev = alloc_dax(fs, NULL, &virtio_fs_dax_ops, 0);
+	if (IS_ERR(fs->dax_dev))
+		return PTR_ERR(fs->dax_dev);
+
+	return devm_add_action_or_reset(&vdev->dev, virtio_fs_cleanup_dax,
+					fs->dax_dev);
+}
+
+static int virtio_fs_probe(struct virtio_device *vdev)
+{
+	struct virtio_fs *fs;
+	int ret;
+
+	fs = kzalloc(sizeof(*fs), GFP_KERNEL);
+	if (!fs)
+		return -ENOMEM;
+	kref_init(&fs->refcount);
+	vdev->priv = fs;
+
+	ret = virtio_fs_read_tag(vdev, fs);
+	if (ret < 0)
+		goto out;
+
+	ret = virtio_fs_setup_vqs(vdev, fs);
+	if (ret < 0)
+		goto out;
+
+	/* TODO vq affinity */
+
+	ret = virtio_fs_setup_dax(vdev, fs);
+	if (ret < 0)
+		goto out_vqs;
+
+	/* Bring the device online in case the filesystem is mounted and
+	 * requests need to be sent before we return.
+	 */
+	virtio_device_ready(vdev);
+
+	ret = virtio_fs_add_instance(fs);
+	if (ret < 0)
+		goto out_vqs;
+
+	return 0;
+
+out_vqs:
+	vdev->config->reset(vdev);
+	virtio_fs_cleanup_vqs(vdev, fs);
+	kfree(fs->vqs);
+
+out:
+	vdev->priv = NULL;
+	kfree(fs);
+	return ret;
+}
+
+static void virtio_fs_stop_all_queues(struct virtio_fs *fs)
+{
+	struct virtio_fs_vq *fsvq;
+	int i;
+
+	for (i = 0; i < fs->nvqs; i++) {
+		fsvq = &fs->vqs[i];
+		spin_lock(&fsvq->lock);
+		fsvq->connected = false;
+		spin_unlock(&fsvq->lock);
+	}
+}
+
+static void virtio_fs_remove(struct virtio_device *vdev)
+{
+	struct virtio_fs *fs = vdev->priv;
+
+	mutex_lock(&virtio_fs_mutex);
+	/* This device is going away. No one should get new reference */
+	list_del_init(&fs->list);
+	virtio_fs_stop_all_queues(fs);
+	virtio_fs_drain_all_queues_locked(fs);
+	vdev->config->reset(vdev);
+	virtio_fs_cleanup_vqs(vdev, fs);
+
+	vdev->priv = NULL;
+	/* Put device reference on virtio_fs object */
+	virtio_fs_put(fs);
+	mutex_unlock(&virtio_fs_mutex);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int virtio_fs_freeze(struct virtio_device *vdev)
+{
+	/* TODO need to save state here */
+	pr_warn("virtio-fs: suspend/resume not yet supported\n");
+	return -EOPNOTSUPP;
+}
+
+static int virtio_fs_restore(struct virtio_device *vdev)
+{
+	 /* TODO need to restore state here */
+	return 0;
+}
+#endif /* CONFIG_PM_SLEEP */
+
+static const struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_FS, VIRTIO_DEV_ANY_ID },
+	{},
+};
+
+static const unsigned int feature_table[] = {};
+
+static struct virtio_driver virtio_fs_driver = {
+	.driver.name		= KBUILD_MODNAME,
+	.driver.owner		= THIS_MODULE,
+	.id_table		= id_table,
+	.feature_table		= feature_table,
+	.feature_table_size	= ARRAY_SIZE(feature_table),
+	.probe			= virtio_fs_probe,
+	.remove			= virtio_fs_remove,
+#ifdef CONFIG_PM_SLEEP
+	.freeze			= virtio_fs_freeze,
+	.restore		= virtio_fs_restore,
+#endif
+};
+
+static void virtio_fs_wake_forget_and_unlock(struct fuse_iqueue *fiq)
+__releases(fiq->lock)
+{
+	struct fuse_forget_link *link;
+	struct virtio_fs_forget *forget;
+	struct virtio_fs_forget_req *req;
+	struct virtio_fs *fs;
+	struct virtio_fs_vq *fsvq;
+	u64 unique;
+
+	link = fuse_dequeue_forget(fiq, 1, NULL);
+	unique = fuse_get_unique(fiq);
+
+	fs = fiq->priv;
+	fsvq = &fs->vqs[VQ_HIPRIO];
+	spin_unlock(&fiq->lock);
+
+	/* Allocate a buffer for the request */
+	forget = kmalloc(sizeof(*forget), GFP_NOFS | __GFP_NOFAIL);
+	req = &forget->req;
+
+	req->ih = (struct fuse_in_header){
+		.opcode = FUSE_FORGET,
+		.nodeid = link->forget_one.nodeid,
+		.unique = unique,
+		.len = sizeof(*req),
+	};
+	req->arg = (struct fuse_forget_in){
+		.nlookup = link->forget_one.nlookup,
+	};
+
+	send_forget_request(fsvq, forget, false);
+	kfree(link);
+}
+
+static void virtio_fs_wake_interrupt_and_unlock(struct fuse_iqueue *fiq)
+__releases(fiq->lock)
+{
+	/*
+	 * TODO interrupts.
+	 *
+	 * Normal fs operations on a local filesystems aren't interruptible.
+	 * Exceptions are blocking lock operations; for example fcntl(F_SETLKW)
+	 * with shared lock between host and guest.
+	 */
+	spin_unlock(&fiq->lock);
+}
+
+/* Count number of scatter-gather elements required */
+static unsigned int sg_count_fuse_pages(struct fuse_page_desc *page_descs,
+				       unsigned int num_pages,
+				       unsigned int total_len)
+{
+	unsigned int i;
+	unsigned int this_len;
+
+	for (i = 0; i < num_pages && total_len; i++) {
+		this_len =  min(page_descs[i].length, total_len);
+		total_len -= this_len;
+	}
+
+	return i;
+}
+
+/* Return the number of scatter-gather list elements required */
+static unsigned int sg_count_fuse_req(struct fuse_req *req)
+{
+	struct fuse_args *args = req->args;
+	struct fuse_args_pages *ap = container_of(args, typeof(*ap), args);
+	unsigned int size, total_sgs = 1 /* fuse_in_header */;
+
+	if (args->in_numargs - args->in_pages)
+		total_sgs += 1;
+
+	if (args->in_pages) {
+		size = args->in_args[args->in_numargs - 1].size;
+		total_sgs += sg_count_fuse_pages(ap->descs, ap->num_pages,
+						 size);
+	}
+
+	if (!test_bit(FR_ISREPLY, &req->flags))
+		return total_sgs;
+
+	total_sgs += 1 /* fuse_out_header */;
+
+	if (args->out_numargs - args->out_pages)
+		total_sgs += 1;
+
+	if (args->out_pages) {
+		size = args->out_args[args->out_numargs - 1].size;
+		total_sgs += sg_count_fuse_pages(ap->descs, ap->num_pages,
+						 size);
+	}
+
+	return total_sgs;
+}
+
+/* Add pages to scatter-gather list and return number of elements used */
+static unsigned int sg_init_fuse_pages(struct scatterlist *sg,
+				       struct page **pages,
+				       struct fuse_page_desc *page_descs,
+				       unsigned int num_pages,
+				       unsigned int total_len)
+{
+	unsigned int i;
+	unsigned int this_len;
+
+	for (i = 0; i < num_pages && total_len; i++) {
+		sg_init_table(&sg[i], 1);
+		this_len =  min(page_descs[i].length, total_len);
+		sg_set_page(&sg[i], pages[i], this_len, page_descs[i].offset);
+		total_len -= this_len;
+	}
+
+	return i;
+}
+
+/* Add args to scatter-gather list and return number of elements used */
+static unsigned int sg_init_fuse_args(struct scatterlist *sg,
+				      struct fuse_req *req,
+				      struct fuse_arg *args,
+				      unsigned int numargs,
+				      bool argpages,
+				      void *argbuf,
+				      unsigned int *len_used)
+{
+	struct fuse_args_pages *ap = container_of(req->args, typeof(*ap), args);
+	unsigned int total_sgs = 0;
+	unsigned int len;
+
+	len = fuse_len_args(numargs - argpages, args);
+	if (len)
+		sg_init_one(&sg[total_sgs++], argbuf, len);
+
+	if (argpages)
+		total_sgs += sg_init_fuse_pages(&sg[total_sgs],
+						ap->pages, ap->descs,
+						ap->num_pages,
+						args[numargs - 1].size);
+
+	if (len_used)
+		*len_used = len;
+
+	return total_sgs;
+}
+
+/* Add a request to a virtqueue and kick the device */
+static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
+				 struct fuse_req *req, bool in_flight)
+{
+	/* requests need at least 4 elements */
+	struct scatterlist *stack_sgs[6];
+	struct scatterlist stack_sg[ARRAY_SIZE(stack_sgs)];
+	struct scatterlist **sgs = stack_sgs;
+	struct scatterlist *sg = stack_sg;
+	struct virtqueue *vq;
+	struct fuse_args *args = req->args;
+	unsigned int argbuf_used = 0;
+	unsigned int out_sgs = 0;
+	unsigned int in_sgs = 0;
+	unsigned int total_sgs;
+	unsigned int i;
+	int ret;
+	bool notify;
+	struct fuse_pqueue *fpq;
+
+	/* Does the sglist fit on the stack? */
+	total_sgs = sg_count_fuse_req(req);
+	if (total_sgs > ARRAY_SIZE(stack_sgs)) {
+		sgs = kmalloc_array(total_sgs, sizeof(sgs[0]), GFP_ATOMIC);
+		sg = kmalloc_array(total_sgs, sizeof(sg[0]), GFP_ATOMIC);
+		if (!sgs || !sg) {
+			ret = -ENOMEM;
+			goto out;
+		}
+	}
+
+	/* Use a bounce buffer since stack args cannot be mapped */
+	ret = copy_args_to_argbuf(req);
+	if (ret < 0)
+		goto out;
+
+	/* Request elements */
+	sg_init_one(&sg[out_sgs++], &req->in.h, sizeof(req->in.h));
+	out_sgs += sg_init_fuse_args(&sg[out_sgs], req,
+				     (struct fuse_arg *)args->in_args,
+				     args->in_numargs, args->in_pages,
+				     req->argbuf, &argbuf_used);
+
+	/* Reply elements */
+	if (test_bit(FR_ISREPLY, &req->flags)) {
+		sg_init_one(&sg[out_sgs + in_sgs++],
+			    &req->out.h, sizeof(req->out.h));
+		in_sgs += sg_init_fuse_args(&sg[out_sgs + in_sgs], req,
+					    args->out_args, args->out_numargs,
+					    args->out_pages,
+					    req->argbuf + argbuf_used, NULL);
+	}
+
+	WARN_ON(out_sgs + in_sgs != total_sgs);
+
+	for (i = 0; i < total_sgs; i++)
+		sgs[i] = &sg[i];
+
+	spin_lock(&fsvq->lock);
+
+	if (!fsvq->connected) {
+		spin_unlock(&fsvq->lock);
+		ret = -ENOTCONN;
+		goto out;
+	}
+
+	vq = fsvq->vq;
+	ret = virtqueue_add_sgs(vq, sgs, out_sgs, in_sgs, req, GFP_ATOMIC);
+	if (ret < 0) {
+		spin_unlock(&fsvq->lock);
+		goto out;
+	}
+
+	/* Request successfully sent. */
+	fpq = &fsvq->fud->pq;
+	spin_lock(&fpq->lock);
+	list_add_tail(&req->list, fpq->processing);
+	spin_unlock(&fpq->lock);
+	set_bit(FR_SENT, &req->flags);
+	/* matches barrier in request_wait_answer() */
+	smp_mb__after_atomic();
+
+	if (!in_flight)
+		inc_in_flight_req(fsvq);
+	notify = virtqueue_kick_prepare(vq);
+
+	spin_unlock(&fsvq->lock);
+
+	if (notify)
+		virtqueue_notify(vq);
+
+out:
+	if (ret < 0 && req->argbuf) {
+		kfree(req->argbuf);
+		req->argbuf = NULL;
+	}
+	if (sgs != stack_sgs) {
+		kfree(sgs);
+		kfree(sg);
+	}
+
+	return ret;
+}
+
+static void virtio_fs_wake_pending_and_unlock(struct fuse_iqueue *fiq)
+__releases(fiq->lock)
+{
+	unsigned int queue_id = VQ_REQUEST; /* TODO multiqueue */
+	struct virtio_fs *fs;
+	struct fuse_req *req;
+	struct virtio_fs_vq *fsvq;
+	int ret;
+
+	WARN_ON(list_empty(&fiq->pending));
+	req = list_last_entry(&fiq->pending, struct fuse_req, list);
+	clear_bit(FR_PENDING, &req->flags);
+	list_del_init(&req->list);
+	WARN_ON(!list_empty(&fiq->pending));
+	spin_unlock(&fiq->lock);
+
+	fs = fiq->priv;
+
+	pr_debug("%s: opcode %u unique %#llx nodeid %#llx in.len %u out.len %u\n",
+		  __func__, req->in.h.opcode, req->in.h.unique,
+		 req->in.h.nodeid, req->in.h.len,
+		 fuse_len_args(req->args->out_numargs, req->args->out_args));
+
+	fsvq = &fs->vqs[queue_id];
+	ret = virtio_fs_enqueue_req(fsvq, req, false);
+	if (ret < 0) {
+		if (ret == -ENOMEM || ret == -ENOSPC) {
+			/*
+			 * Virtqueue full. Retry submission from worker
+			 * context as we might be holding fc->bg_lock.
+			 */
+			spin_lock(&fsvq->lock);
+			list_add_tail(&req->list, &fsvq->queued_reqs);
+			inc_in_flight_req(fsvq);
+			schedule_delayed_work(&fsvq->dispatch_work,
+						msecs_to_jiffies(1));
+			spin_unlock(&fsvq->lock);
+			return;
+		}
+		req->out.h.error = ret;
+		pr_err("virtio-fs: virtio_fs_enqueue_req() failed %d\n", ret);
+
+		/* Can't end request in submission context. Use a worker */
+		spin_lock(&fsvq->lock);
+		list_add_tail(&req->list, &fsvq->end_reqs);
+		schedule_delayed_work(&fsvq->dispatch_work, 0);
+		spin_unlock(&fsvq->lock);
+		return;
+	}
+}
+
+static const struct fuse_iqueue_ops virtio_fs_fiq_ops = {
+	.wake_forget_and_unlock		= virtio_fs_wake_forget_and_unlock,
+	.wake_interrupt_and_unlock	= virtio_fs_wake_interrupt_and_unlock,
+	.wake_pending_and_unlock	= virtio_fs_wake_pending_and_unlock,
+	.release			= virtio_fs_fiq_release,
+};
+
+static inline void virtio_fs_ctx_set_defaults(struct fuse_fs_context *ctx)
+{
+	ctx->rootmode = S_IFDIR;
+	ctx->default_permissions = 1;
+	ctx->allow_other = 1;
+	ctx->max_read = UINT_MAX;
+	ctx->blksize = 512;
+	ctx->destroy = true;
+	ctx->no_control = true;
+	ctx->no_force_umount = true;
+}
+
+static int virtio_fs_fill_super(struct super_block *sb, struct fs_context *fsc)
+{
+	struct fuse_mount *fm = get_fuse_mount_super(sb);
+	struct fuse_conn *fc = fm->fc;
+	struct virtio_fs *fs = fc->iq.priv;
+	struct fuse_fs_context *ctx = fsc->fs_private;
+	unsigned int i;
+	int err;
+
+	virtio_fs_ctx_set_defaults(ctx);
+	mutex_lock(&virtio_fs_mutex);
+
+	/* After holding mutex, make sure virtiofs device is still there.
+	 * Though we are holding a reference to it, drive ->remove might
+	 * still have cleaned up virtual queues. In that case bail out.
+	 */
+	err = -EINVAL;
+	if (list_empty(&fs->list)) {
+		pr_info("virtio-fs: tag <%s> not found\n", fs->tag);
+		goto err;
+	}
+
+	err = -ENOMEM;
+	/* Allocate fuse_dev for hiprio and notification queues */
+	for (i = 0; i < fs->nvqs; i++) {
+		struct virtio_fs_vq *fsvq = &fs->vqs[i];
+
+		fsvq->fud = fuse_dev_alloc();
+		if (!fsvq->fud)
+			goto err_free_fuse_devs;
+	}
+
+	/* virtiofs allocates and installs its own fuse devices */
+	ctx->fudptr = NULL;
+	if (ctx->dax) {
+		if (!fs->dax_dev) {
+			err = -EINVAL;
+			pr_err("virtio-fs: dax can't be enabled as filesystem"
+			       " device does not support it.\n");
+			goto err_free_fuse_devs;
+		}
+		ctx->dax_dev = fs->dax_dev;
+	}
+	err = fuse_fill_super_common(sb, ctx);
+	if (err < 0)
+		goto err_free_fuse_devs;
+
+	for (i = 0; i < fs->nvqs; i++) {
+		struct virtio_fs_vq *fsvq = &fs->vqs[i];
+
+		fuse_dev_install(fsvq->fud, fc);
+	}
+
+	/* Previous unmount will stop all queues. Start these again */
+	virtio_fs_start_all_queues(fs);
+	fuse_send_init(fm);
+	mutex_unlock(&virtio_fs_mutex);
+	return 0;
+
+err_free_fuse_devs:
+	virtio_fs_free_devs(fs);
+err:
+	mutex_unlock(&virtio_fs_mutex);
+	return err;
+}
+
+static void virtio_fs_conn_destroy(struct fuse_mount *fm)
+{
+	struct fuse_conn *fc = fm->fc;
+	struct virtio_fs *vfs = fc->iq.priv;
+	struct virtio_fs_vq *fsvq = &vfs->vqs[VQ_HIPRIO];
+
+	/* Stop dax worker. Soon evict_inodes() will be called which
+	 * will free all memory ranges belonging to all inodes.
+	 */
+	if (IS_ENABLED(CONFIG_FUSE_DAX))
+		fuse_dax_cancel_work(fc);
+
+	/* Stop forget queue. Soon destroy will be sent */
+	spin_lock(&fsvq->lock);
+	fsvq->connected = false;
+	spin_unlock(&fsvq->lock);
+	virtio_fs_drain_all_queues(vfs);
+
+	fuse_conn_destroy(fm);
+
+	/* fuse_conn_destroy() must have sent destroy. Stop all queues
+	 * and drain one more time and free fuse devices. Freeing fuse
+	 * devices will drop their reference on fuse_conn and that in
+	 * turn will drop its reference on virtio_fs object.
+	 */
+	virtio_fs_stop_all_queues(vfs);
+	virtio_fs_drain_all_queues(vfs);
+	virtio_fs_free_devs(vfs);
+}
+
+static void virtio_kill_sb(struct super_block *sb)
+{
+	struct fuse_mount *fm = get_fuse_mount_super(sb);
+	bool last;
+
+	/* If mount failed, we can still be called without any fc */
+	if (sb->s_root) {
+		last = fuse_mount_remove(fm);
+		if (last)
+			virtio_fs_conn_destroy(fm);
+	}
+	kill_anon_super(sb);
+}
+
+static int virtio_fs_test_super(struct super_block *sb,
+				struct fs_context *fsc)
+{
+	struct fuse_mount *fsc_fm = fsc->s_fs_info;
+	struct fuse_mount *sb_fm = get_fuse_mount_super(sb);
+
+	return fsc_fm->fc->iq.priv == sb_fm->fc->iq.priv;
+}
+
+static int virtio_fs_set_super(struct super_block *sb,
+			       struct fs_context *fsc)
+{
+	int err;
+
+	err = get_anon_bdev(&sb->s_dev);
+	if (!err)
+		fuse_mount_get(fsc->s_fs_info);
+
+	return err;
+}
+
+static int virtio_fs_get_tree(struct fs_context *fsc)
+{
+	struct virtio_fs *fs;
+	struct super_block *sb;
+	struct fuse_conn *fc = NULL;
+	struct fuse_mount *fm;
+	unsigned int virtqueue_size;
+	int err = -EIO;
+
+	/* This gets a reference on virtio_fs object. This ptr gets installed
+	 * in fc->iq->priv. Once fuse_conn is going away, it calls ->put()
+	 * to drop the reference to this object.
+	 */
+	fs = virtio_fs_find_instance(fsc->source);
+	if (!fs) {
+		pr_info("virtio-fs: tag <%s> not found\n", fsc->source);
+		return -EINVAL;
+	}
+
+	virtqueue_size = virtqueue_get_vring_size(fs->vqs[VQ_REQUEST].vq);
+	if (WARN_ON(virtqueue_size <= FUSE_HEADER_OVERHEAD))
+		goto out_err;
+
+	err = -ENOMEM;
+	fc = kzalloc(sizeof(struct fuse_conn), GFP_KERNEL);
+	if (!fc)
+		goto out_err;
+
+	fm = kzalloc(sizeof(struct fuse_mount), GFP_KERNEL);
+	if (!fm)
+		goto out_err;
+
+	fuse_conn_init(fc, fm, fsc->user_ns, &virtio_fs_fiq_ops, fs);
+	fc->release = fuse_free_conn;
+	fc->delete_stale = true;
+	fc->auto_submounts = true;
+
+	/* Tell FUSE to split requests that exceed the virtqueue's size */
+	fc->max_pages_limit = min_t(unsigned int, fc->max_pages_limit,
+				    virtqueue_size - FUSE_HEADER_OVERHEAD);
+
+	fsc->s_fs_info = fm;
+	sb = sget_fc(fsc, virtio_fs_test_super, virtio_fs_set_super);
+	fuse_mount_put(fm);
+	if (IS_ERR(sb))
+		return PTR_ERR(sb);
+
+	if (!sb->s_root) {
+		err = virtio_fs_fill_super(sb, fsc);
+		if (err) {
+			fuse_mount_put(fm);
+			sb->s_fs_info = NULL;
+			deactivate_locked_super(sb);
+			return err;
+		}
+
+		sb->s_flags |= SB_ACTIVE;
+	}
+
+	WARN_ON(fsc->root);
+	fsc->root = dget(sb->s_root);
+	return 0;
+
+out_err:
+	kfree(fc);
+	mutex_lock(&virtio_fs_mutex);
+	virtio_fs_put(fs);
+	mutex_unlock(&virtio_fs_mutex);
+	return err;
+}
+
+static const struct fs_context_operations virtio_fs_context_ops = {
+	.free		= virtio_fs_free_fc,
+	.parse_param	= virtio_fs_parse_param,
+	.get_tree	= virtio_fs_get_tree,
+};
+
+static int virtio_fs_init_fs_context(struct fs_context *fsc)
+{
+	struct fuse_fs_context *ctx;
+
+	ctx = kzalloc(sizeof(struct fuse_fs_context), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+	fsc->fs_private = ctx;
+	fsc->ops = &virtio_fs_context_ops;
+	return 0;
+}
+
+static struct file_system_type virtio_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "virtiofs",
+	.init_fs_context = virtio_fs_init_fs_context,
+	.kill_sb	= virtio_kill_sb,
+};
+
+static int __init virtio_fs_init(void)
+{
+	int ret;
+
+	ret = register_virtio_driver(&virtio_fs_driver);
+	if (ret < 0)
+		return ret;
+
+	ret = register_filesystem(&virtio_fs_type);
+	if (ret < 0) {
+		unregister_virtio_driver(&virtio_fs_driver);
+		return ret;
+	}
+
+	return 0;
+}
+module_init(virtio_fs_init);
+
+static void __exit virtio_fs_exit(void)
+{
+	unregister_filesystem(&virtio_fs_type);
+	unregister_virtio_driver(&virtio_fs_driver);
+}
+module_exit(virtio_fs_exit);
+
+MODULE_AUTHOR("Stefan Hajnoczi <stefanha@redhat.com>");
+MODULE_DESCRIPTION("Virtio Filesystem");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_FS(KBUILD_MODNAME);
+MODULE_DEVICE_TABLE(virtio, id_table);
diff --git a/fs/fuse/xattr.c b/fs/fuse/xattr.c
new file mode 100644
index 000000000..cdea18de9
--- /dev/null
+++ b/fs/fuse/xattr.c
@@ -0,0 +1,263 @@
+/*
+ * FUSE: Filesystem in Userspace
+ * Copyright (C) 2001-2016  Miklos Szeredi <miklos@szeredi.hu>
+ *
+ * This program can be distributed under the terms of the GNU GPL.
+ * See the file COPYING.
+ */
+
+#include "fuse_i.h"
+
+#include <linux/xattr.h>
+#include <linux/posix_acl_xattr.h>
+
+int fuse_setxattr(struct inode *inode, const char *name, const void *value,
+		  size_t size, int flags)
+{
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+	struct fuse_setxattr_in inarg;
+	int err;
+
+	if (fm->fc->no_setxattr)
+		return -EOPNOTSUPP;
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.size = size;
+	inarg.flags = flags;
+	args.opcode = FUSE_SETXATTR;
+	args.nodeid = get_node_id(inode);
+	args.in_numargs = 3;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.in_args[1].size = strlen(name) + 1;
+	args.in_args[1].value = name;
+	args.in_args[2].size = size;
+	args.in_args[2].value = value;
+	err = fuse_simple_request(fm, &args);
+	if (err == -ENOSYS) {
+		fm->fc->no_setxattr = 1;
+		err = -EOPNOTSUPP;
+	}
+	if (!err) {
+		fuse_invalidate_attr(inode);
+		fuse_update_ctime(inode);
+	}
+	return err;
+}
+
+ssize_t fuse_getxattr(struct inode *inode, const char *name, void *value,
+		      size_t size)
+{
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+	struct fuse_getxattr_in inarg;
+	struct fuse_getxattr_out outarg;
+	ssize_t ret;
+
+	if (fm->fc->no_getxattr)
+		return -EOPNOTSUPP;
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.size = size;
+	args.opcode = FUSE_GETXATTR;
+	args.nodeid = get_node_id(inode);
+	args.in_numargs = 2;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	args.in_args[1].size = strlen(name) + 1;
+	args.in_args[1].value = name;
+	/* This is really two different operations rolled into one */
+	args.out_numargs = 1;
+	if (size) {
+		args.out_argvar = true;
+		args.out_args[0].size = size;
+		args.out_args[0].value = value;
+	} else {
+		args.out_args[0].size = sizeof(outarg);
+		args.out_args[0].value = &outarg;
+	}
+	ret = fuse_simple_request(fm, &args);
+	if (!ret && !size)
+		ret = min_t(ssize_t, outarg.size, XATTR_SIZE_MAX);
+	if (ret == -ENOSYS) {
+		fm->fc->no_getxattr = 1;
+		ret = -EOPNOTSUPP;
+	}
+	return ret;
+}
+
+static int fuse_verify_xattr_list(char *list, size_t size)
+{
+	size_t origsize = size;
+
+	while (size) {
+		size_t thislen = strnlen(list, size);
+
+		if (!thislen || thislen == size)
+			return -EIO;
+
+		size -= thislen + 1;
+		list += thislen + 1;
+	}
+
+	return origsize;
+}
+
+ssize_t fuse_listxattr(struct dentry *entry, char *list, size_t size)
+{
+	struct inode *inode = d_inode(entry);
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+	struct fuse_getxattr_in inarg;
+	struct fuse_getxattr_out outarg;
+	ssize_t ret;
+
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	if (!fuse_allow_current_process(fm->fc))
+		return -EACCES;
+
+	if (fm->fc->no_listxattr)
+		return -EOPNOTSUPP;
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.size = size;
+	args.opcode = FUSE_LISTXATTR;
+	args.nodeid = get_node_id(inode);
+	args.in_numargs = 1;
+	args.in_args[0].size = sizeof(inarg);
+	args.in_args[0].value = &inarg;
+	/* This is really two different operations rolled into one */
+	args.out_numargs = 1;
+	if (size) {
+		args.out_argvar = true;
+		args.out_args[0].size = size;
+		args.out_args[0].value = list;
+	} else {
+		args.out_args[0].size = sizeof(outarg);
+		args.out_args[0].value = &outarg;
+	}
+	ret = fuse_simple_request(fm, &args);
+	if (!ret && !size)
+		ret = min_t(ssize_t, outarg.size, XATTR_LIST_MAX);
+	if (ret > 0 && size)
+		ret = fuse_verify_xattr_list(list, ret);
+	if (ret == -ENOSYS) {
+		fm->fc->no_listxattr = 1;
+		ret = -EOPNOTSUPP;
+	}
+	return ret;
+}
+
+int fuse_removexattr(struct inode *inode, const char *name)
+{
+	struct fuse_mount *fm = get_fuse_mount(inode);
+	FUSE_ARGS(args);
+	int err;
+
+	if (fm->fc->no_removexattr)
+		return -EOPNOTSUPP;
+
+	args.opcode = FUSE_REMOVEXATTR;
+	args.nodeid = get_node_id(inode);
+	args.in_numargs = 1;
+	args.in_args[0].size = strlen(name) + 1;
+	args.in_args[0].value = name;
+	err = fuse_simple_request(fm, &args);
+	if (err == -ENOSYS) {
+		fm->fc->no_removexattr = 1;
+		err = -EOPNOTSUPP;
+	}
+	if (!err) {
+		fuse_invalidate_attr(inode);
+		fuse_update_ctime(inode);
+	}
+	return err;
+}
+
+static int fuse_xattr_get(const struct xattr_handler *handler,
+			 struct dentry *dentry, struct inode *inode,
+			 const char *name, void *value, size_t size)
+{
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	return fuse_getxattr(inode, name, value, size);
+}
+
+static int fuse_xattr_set(const struct xattr_handler *handler,
+			  struct dentry *dentry, struct inode *inode,
+			  const char *name, const void *value, size_t size,
+			  int flags)
+{
+	if (fuse_is_bad(inode))
+		return -EIO;
+
+	if (!value)
+		return fuse_removexattr(inode, name);
+
+	return fuse_setxattr(inode, name, value, size, flags);
+}
+
+static bool no_xattr_list(struct dentry *dentry)
+{
+	return false;
+}
+
+static int no_xattr_get(const struct xattr_handler *handler,
+			struct dentry *dentry, struct inode *inode,
+			const char *name, void *value, size_t size)
+{
+	return -EOPNOTSUPP;
+}
+
+static int no_xattr_set(const struct xattr_handler *handler,
+			struct dentry *dentry, struct inode *nodee,
+			const char *name, const void *value,
+			size_t size, int flags)
+{
+	return -EOPNOTSUPP;
+}
+
+static const struct xattr_handler fuse_xattr_handler = {
+	.prefix = "",
+	.get    = fuse_xattr_get,
+	.set    = fuse_xattr_set,
+};
+
+const struct xattr_handler *fuse_xattr_handlers[] = {
+	&fuse_xattr_handler,
+	NULL
+};
+
+const struct xattr_handler *fuse_acl_xattr_handlers[] = {
+	&posix_acl_access_xattr_handler,
+	&posix_acl_default_xattr_handler,
+	&fuse_xattr_handler,
+	NULL
+};
+
+static const struct xattr_handler fuse_no_acl_access_xattr_handler = {
+	.name  = XATTR_NAME_POSIX_ACL_ACCESS,
+	.flags = ACL_TYPE_ACCESS,
+	.list  = no_xattr_list,
+	.get   = no_xattr_get,
+	.set   = no_xattr_set,
+};
+
+static const struct xattr_handler fuse_no_acl_default_xattr_handler = {
+	.name  = XATTR_NAME_POSIX_ACL_DEFAULT,
+	.flags = ACL_TYPE_ACCESS,
+	.list  = no_xattr_list,
+	.get   = no_xattr_get,
+	.set   = no_xattr_set,
+};
+
+const struct xattr_handler *fuse_no_acl_xattr_handlers[] = {
+	&fuse_no_acl_access_xattr_handler,
+	&fuse_no_acl_default_xattr_handler,
+	&fuse_xattr_handler,
+	NULL
+};