Adding upstream version 5.10.209.upstream/5.10.209

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

1 files changed, 1767 insertions, 0 deletions

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);