Adding upstream version 4.19.249.upstream/4.19.249upstream

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

1 files changed, 2359 insertions, 0 deletions

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
new file mode 100644
index 000000000..a5144ecd5
--- /dev/null
+++ b/fs/fuse/dev.c
@@ -0,0 +1,2359 @@
+/*
+  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");
+
+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_req *req, struct page **pages,
+			      struct fuse_page_desc *page_descs,
+			      unsigned npages)
+{
+	memset(req, 0, sizeof(*req));
+	memset(pages, 0, sizeof(*pages) * npages);
+	memset(page_descs, 0, sizeof(*page_descs) * npages);
+	INIT_LIST_HEAD(&req->list);
+	INIT_LIST_HEAD(&req->intr_entry);
+	init_waitqueue_head(&req->waitq);
+	refcount_set(&req->count, 1);
+	req->pages = pages;
+	req->page_descs = page_descs;
+	req->max_pages = npages;
+	__set_bit(FR_PENDING, &req->flags);
+}
+
+static struct fuse_req *__fuse_request_alloc(unsigned npages, gfp_t flags)
+{
+	struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, flags);
+	if (req) {
+		struct page **pages;
+		struct fuse_page_desc *page_descs;
+
+		if (npages <= FUSE_REQ_INLINE_PAGES) {
+			pages = req->inline_pages;
+			page_descs = req->inline_page_descs;
+		} else {
+			pages = kmalloc_array(npages, sizeof(struct page *),
+					      flags);
+			page_descs =
+				kmalloc_array(npages,
+					      sizeof(struct fuse_page_desc),
+					      flags);
+		}
+
+		if (!pages || !page_descs) {
+			kfree(pages);
+			kfree(page_descs);
+			kmem_cache_free(fuse_req_cachep, req);
+			return NULL;
+		}
+
+		fuse_request_init(req, pages, page_descs, npages);
+	}
+	return req;
+}
+
+struct fuse_req *fuse_request_alloc(unsigned npages)
+{
+	return __fuse_request_alloc(npages, GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(fuse_request_alloc);
+
+struct fuse_req *fuse_request_alloc_nofs(unsigned npages)
+{
+	return __fuse_request_alloc(npages, GFP_NOFS);
+}
+
+void fuse_request_free(struct fuse_req *req)
+{
+	if (req->pages != req->inline_pages) {
+		kfree(req->pages);
+		kfree(req->page_descs);
+	}
+	kmem_cache_free(fuse_req_cachep, req);
+}
+
+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 struct fuse_req *__fuse_get_req(struct fuse_conn *fc, unsigned npages,
+				       bool for_background)
+{
+	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(npages);
+	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(fc, req);
+		return ERR_PTR(-EOVERFLOW);
+	}
+	return req;
+
+ out:
+	fuse_drop_waiting(fc);
+	return ERR_PTR(err);
+}
+
+struct fuse_req *fuse_get_req(struct fuse_conn *fc, unsigned npages)
+{
+	return __fuse_get_req(fc, npages, false);
+}
+EXPORT_SYMBOL_GPL(fuse_get_req);
+
+struct fuse_req *fuse_get_req_for_background(struct fuse_conn *fc,
+					     unsigned npages)
+{
+	return __fuse_get_req(fc, npages, true);
+}
+EXPORT_SYMBOL_GPL(fuse_get_req_for_background);
+
+/*
+ * Return request in fuse_file->reserved_req.  However that may
+ * currently be in use.  If that is the case, wait for it to become
+ * available.
+ */
+static struct fuse_req *get_reserved_req(struct fuse_conn *fc,
+					 struct file *file)
+{
+	struct fuse_req *req = NULL;
+	struct fuse_file *ff = file->private_data;
+
+	do {
+		wait_event(fc->reserved_req_waitq, ff->reserved_req);
+		spin_lock(&fc->lock);
+		if (ff->reserved_req) {
+			req = ff->reserved_req;
+			ff->reserved_req = NULL;
+			req->stolen_file = get_file(file);
+		}
+		spin_unlock(&fc->lock);
+	} while (!req);
+
+	return req;
+}
+
+/*
+ * Put stolen request back into fuse_file->reserved_req
+ */
+static void put_reserved_req(struct fuse_conn *fc, struct fuse_req *req)
+{
+	struct file *file = req->stolen_file;
+	struct fuse_file *ff = file->private_data;
+
+	spin_lock(&fc->lock);
+	fuse_request_init(req, req->pages, req->page_descs, req->max_pages);
+	BUG_ON(ff->reserved_req);
+	ff->reserved_req = req;
+	wake_up_all(&fc->reserved_req_waitq);
+	spin_unlock(&fc->lock);
+	fput(file);
+}
+
+/*
+ * Gets a requests for a file operation, always succeeds
+ *
+ * This is used for sending the FLUSH request, which must get to
+ * userspace, due to POSIX locks which may need to be unlocked.
+ *
+ * If allocation fails due to OOM, use the reserved request in
+ * fuse_file.
+ *
+ * This is very unlikely to deadlock accidentally, since the
+ * filesystem should not have it's own file open.  If deadlock is
+ * intentional, it can still be broken by "aborting" the filesystem.
+ */
+struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
+					     struct file *file)
+{
+	struct fuse_req *req;
+
+	atomic_inc(&fc->num_waiting);
+	wait_event(fc->blocked_waitq, fc->initialized);
+	/* Matches smp_wmb() in fuse_set_initialized() */
+	smp_rmb();
+	req = fuse_request_alloc(0);
+	if (!req)
+		req = get_reserved_req(fc, file);
+
+	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);
+
+	__set_bit(FR_WAITING, &req->flags);
+	__clear_bit(FR_BACKGROUND, &req->flags);
+	return req;
+}
+
+void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
+{
+	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->lock);
+			if (!fc->blocked)
+				wake_up(&fc->blocked_waitq);
+			spin_unlock(&fc->lock);
+		}
+
+		if (test_bit(FR_WAITING, &req->flags)) {
+			__clear_bit(FR_WAITING, &req->flags);
+			fuse_drop_waiting(fc);
+		}
+
+		if (req->stolen_file)
+			put_reserved_req(fc, req);
+		else
+			fuse_request_free(req);
+	}
+}
+EXPORT_SYMBOL_GPL(fuse_put_request);
+
+static unsigned len_args(unsigned numargs, struct fuse_arg *args)
+{
+	unsigned nbytes = 0;
+	unsigned i;
+
+	for (i = 0; i < numargs; i++)
+		nbytes += args[i].size;
+
+	return nbytes;
+}
+
+static u64 fuse_get_unique(struct fuse_iqueue *fiq)
+{
+	return ++fiq->reqctr;
+}
+
+static void queue_request(struct fuse_iqueue *fiq, struct fuse_req *req)
+{
+	req->in.h.len = sizeof(struct fuse_in_header) +
+		len_args(req->in.numargs, (struct fuse_arg *) req->in.args);
+	list_add_tail(&req->list, &fiq->pending);
+	wake_up(&fiq->waitq);
+	kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
+}
+
+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;
+		wake_up(&fiq->waitq);
+		kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
+	} else {
+		kfree(forget);
+	}
+	spin_unlock(&fiq->lock);
+}
+
+static void flush_bg_queue(struct fuse_conn *fc)
+{
+	while (fc->active_background < fc->max_background &&
+	       !list_empty(&fc->bg_queue)) {
+		struct fuse_req *req;
+		struct fuse_iqueue *fiq = &fc->iq;
+
+		req = list_entry(fc->bg_queue.next, 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(fiq, req);
+		spin_unlock(&fiq->lock);
+	}
+}
+
+/*
+ * 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
+ */
+static void request_end(struct fuse_conn *fc, struct fuse_req *req)
+{
+	struct fuse_iqueue *fiq = &fc->iq;
+
+	if (test_and_set_bit(FR_FINISHED, &req->flags))
+		goto put_request;
+
+	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->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 && fc->sb) {
+			clear_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC);
+			clear_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC);
+		}
+		fc->num_background--;
+		fc->active_background--;
+		flush_bg_queue(fc);
+		spin_unlock(&fc->lock);
+	}
+	wake_up(&req->waitq);
+	if (req->end)
+		req->end(fc, req);
+put_request:
+	fuse_put_request(fc, req);
+}
+
+static void queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req)
+{
+	spin_lock(&fiq->lock);
+	if (test_bit(FR_FINISHED, &req->flags)) {
+		spin_unlock(&fiq->lock);
+		return;
+	}
+	if (list_empty(&req->intr_entry)) {
+		list_add_tail(&req->intr_entry, &fiq->interrupts);
+		wake_up(&fiq->waitq);
+	}
+	spin_unlock(&fiq->lock);
+	kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
+}
+
+static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req)
+{
+	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(fiq, 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_conn *fc, struct fuse_req *req)
+{
+	struct fuse_iqueue *fiq = &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);
+		queue_request(fiq, req);
+		/* acquire extra reference, since request is still needed
+		   after request_end() */
+		__fuse_get_request(req);
+		spin_unlock(&fiq->lock);
+
+		request_wait_answer(fc, req);
+		/* Pairs with smp_wmb() in request_end() */
+		smp_rmb();
+	}
+}
+
+void fuse_request_send(struct fuse_conn *fc, struct fuse_req *req)
+{
+	__set_bit(FR_ISREPLY, &req->flags);
+	if (!test_bit(FR_WAITING, &req->flags)) {
+		__set_bit(FR_WAITING, &req->flags);
+		atomic_inc(&fc->num_waiting);
+	}
+	__fuse_request_send(fc, req);
+}
+EXPORT_SYMBOL_GPL(fuse_request_send);
+
+static void fuse_adjust_compat(struct fuse_conn *fc, struct fuse_args *args)
+{
+	if (fc->minor < 4 && args->in.h.opcode == FUSE_STATFS)
+		args->out.args[0].size = FUSE_COMPAT_STATFS_SIZE;
+
+	if (fc->minor < 9) {
+		switch (args->in.h.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->in.h.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;
+		}
+	}
+}
+
+ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args)
+{
+	struct fuse_req *req;
+	ssize_t ret;
+
+	req = fuse_get_req(fc, 0);
+	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);
+
+	req->in.h.opcode = args->in.h.opcode;
+	req->in.h.nodeid = args->in.h.nodeid;
+	req->in.numargs = args->in.numargs;
+	memcpy(req->in.args, args->in.args,
+	       args->in.numargs * sizeof(struct fuse_in_arg));
+	req->out.argvar = args->out.argvar;
+	req->out.numargs = args->out.numargs;
+	memcpy(req->out.args, args->out.args,
+	       args->out.numargs * sizeof(struct fuse_arg));
+	fuse_request_send(fc, req);
+	ret = req->out.h.error;
+	if (!ret && args->out.argvar) {
+		BUG_ON(args->out.numargs != 1);
+		ret = req->out.args[0].size;
+	}
+	fuse_put_request(fc, req);
+
+	return ret;
+}
+
+/*
+ * Called under fc->lock
+ *
+ * fc->connected must have been checked previously
+ */
+void fuse_request_send_background_locked(struct fuse_conn *fc,
+					 struct fuse_req *req)
+{
+	BUG_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);
+	fc->num_background++;
+	if (fc->num_background == fc->max_background)
+		fc->blocked = 1;
+	if (fc->num_background == fc->congestion_threshold && fc->sb) {
+		set_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC);
+		set_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC);
+	}
+	list_add_tail(&req->list, &fc->bg_queue);
+	flush_bg_queue(fc);
+}
+
+void fuse_request_send_background(struct fuse_conn *fc, struct fuse_req *req)
+{
+	BUG_ON(!req->end);
+	spin_lock(&fc->lock);
+	if (fc->connected) {
+		fuse_request_send_background_locked(fc, req);
+		spin_unlock(&fc->lock);
+	} else {
+		spin_unlock(&fc->lock);
+		req->out.h.error = -ENOTCONN;
+		req->end(fc, req);
+		fuse_put_request(fc, req);
+	}
+}
+EXPORT_SYMBOL_GPL(fuse_request_send_background);
+
+static int fuse_request_send_notify_reply(struct fuse_conn *fc,
+					  struct fuse_req *req, u64 unique)
+{
+	int err = -ENODEV;
+	struct fuse_iqueue *fiq = &fc->iq;
+
+	__clear_bit(FR_ISREPLY, &req->flags);
+	req->in.h.unique = unique;
+	spin_lock(&fiq->lock);
+	if (fiq->connected) {
+		queue_request(fiq, req);
+		err = 0;
+	}
+	spin_unlock(&fiq->lock);
+
+	return err;
+}
+
+void fuse_force_forget(struct file *file, u64 nodeid)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_req *req;
+	struct fuse_forget_in inarg;
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.nlookup = 1;
+	req = fuse_get_req_nofail_nopages(fc, file);
+	req->in.h.opcode = FUSE_FORGET;
+	req->in.h.nodeid = nodeid;
+	req->in.numargs = 1;
+	req->in.args[0].size = sizeof(inarg);
+	req->in.args[0].value = &inarg;
+	__clear_bit(FR_ISREPLY, &req->flags);
+	__fuse_request_send(fc, req);
+	/* ignore errors */
+	fuse_put_request(fc, req);
+}
+
+/*
+ * 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->buffers)
+				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_reclaim |
+	       1 << PG_waiters))) {
+		printk(KERN_WARNING "fuse: trying to steal weird page\n");
+		printk(KERN_WARNING "  page=%p index=%li flags=%08lx, count=%i, mapcount=%i, mapping=%p\n", page, page->index, page->flags, page_count(page), page_mapcount(page), page->mapping);
+		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_steal(cs->pipe, buf) != 0)
+		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_file(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->buffers)
+		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->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;
+
+	for (i = 0; i < req->num_pages && (nbytes || zeroing); i++) {
+		int err;
+		unsigned offset = req->page_descs[i].offset;
+		unsigned count = min(nbytes, req->page_descs[i].length);
+
+		err = fuse_copy_page(cs, &req->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);
+	req->intr_unique = fuse_get_unique(fiq);
+	memset(&ih, 0, sizeof(ih));
+	memset(&arg, 0, sizeof(arg));
+	ih.len = reqsize;
+	ih.opcode = FUSE_INTERRUPT;
+	ih.unique = req->intr_unique;
+	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;
+}
+
+static struct fuse_forget_link *dequeue_forget(struct fuse_iqueue *fiq,
+					       unsigned max,
+					       unsigned *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;
+}
+
+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 = 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 = 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
+ * 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_in *in;
+	unsigned reqsize;
+
+ 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 && fc->abort_err) ? -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);
+
+	in = &req->in;
+	reqsize = 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 (in->h.opcode == FUSE_SETXATTR)
+			req->out.h.error = -E2BIG;
+		request_end(fc, 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, &in->h, sizeof(in->h));
+	if (!err)
+		err = fuse_copy_args(cs, in->numargs, in->argpages,
+				     (struct fuse_arg *) in->args, 0);
+	fuse_copy_finish(cs);
+	spin_lock(&fpq->lock);
+	clear_bit(FR_LOCKED, &req->flags);
+	if (!fpq->connected) {
+		err = (fc->aborted && fc->abort_err) ? -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;
+	}
+	list_move_tail(&req->list, &fpq->processing);
+	__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(fiq, req);
+	fuse_put_request(fc, req);
+
+	return reqsize;
+
+out_end:
+	if (!test_bit(FR_PRIVATE, &req->flags))
+		list_del_init(&req->list);
+	spin_unlock(&fpq->lock);
+	request_end(fc, 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->buffers, 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->nrbufs + cs.nr_segs > pipe->buffers) {
+		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 = -ENOENT;
+	if (fc->sb) {
+		err = fuse_reverse_inval_inode(fc->sb, 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 = -ENOENT;
+	if (fc->sb)
+		err = fuse_reverse_inval_entry(fc->sb, 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 = -ENOENT;
+	if (fc->sb)
+		err = fuse_reverse_inval_entry(fc->sb, 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;
+	if (!fc->sb)
+		goto out_up_killsb;
+
+	inode = ilookup5(fc->sb, nodeid, fuse_inode_eq, &nodeid);
+	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;
+}
+
+static void fuse_retrieve_end(struct fuse_conn *fc, struct fuse_req *req)
+{
+	release_pages(req->pages, req->num_pages);
+}
+
+static int fuse_retrieve(struct fuse_conn *fc, struct inode *inode,
+			 struct fuse_notify_retrieve_out *outarg)
+{
+	int err;
+	struct address_space *mapping = inode->i_mapping;
+	struct fuse_req *req;
+	pgoff_t index;
+	loff_t file_size;
+	unsigned int num;
+	unsigned int offset;
+	size_t total_len = 0;
+	int num_pages;
+
+	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, FUSE_MAX_PAGES_PER_REQ);
+
+	req = fuse_get_req(fc, num_pages);
+	if (IS_ERR(req))
+		return PTR_ERR(req);
+
+	req->in.h.opcode = FUSE_NOTIFY_REPLY;
+	req->in.h.nodeid = outarg->nodeid;
+	req->in.numargs = 2;
+	req->in.argpages = 1;
+	req->end = fuse_retrieve_end;
+
+	index = outarg->offset >> PAGE_SHIFT;
+
+	while (num && req->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);
+		req->pages[req->num_pages] = page;
+		req->page_descs[req->num_pages].offset = offset;
+		req->page_descs[req->num_pages].length = this_num;
+		req->num_pages++;
+
+		offset = 0;
+		num -= this_num;
+		total_len += this_num;
+		index++;
+	}
+	req->misc.retrieve_in.offset = outarg->offset;
+	req->misc.retrieve_in.size = total_len;
+	req->in.args[0].size = sizeof(req->misc.retrieve_in);
+	req->in.args[0].value = &req->misc.retrieve_in;
+	req->in.args[1].size = total_len;
+
+	err = fuse_request_send_notify_reply(fc, req, outarg->notify_unique);
+	if (err) {
+		fuse_retrieve_end(fc, req);
+		fuse_put_request(fc, req);
+	}
+
+	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 inode *inode;
+	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;
+	if (fc->sb) {
+		u64 nodeid = outarg.nodeid;
+
+		inode = ilookup5(fc->sb, nodeid, fuse_inode_eq, &nodeid);
+		if (inode) {
+			err = fuse_retrieve(fc, 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)
+{
+	struct fuse_req *req;
+
+	list_for_each_entry(req, &fpq->processing, list) {
+		if (req->in.h.unique == unique || req->intr_unique == unique)
+			return req;
+	}
+	return NULL;
+}
+
+static int copy_out_args(struct fuse_copy_state *cs, struct fuse_out *out,
+			 unsigned nbytes)
+{
+	unsigned reqsize = sizeof(struct fuse_out_header);
+
+	if (out->h.error)
+		return nbytes != reqsize ? -EINVAL : 0;
+
+	reqsize += len_args(out->numargs, out->args);
+
+	if (reqsize < nbytes || (reqsize > nbytes && !out->argvar))
+		return -EINVAL;
+	else if (reqsize > nbytes) {
+		struct fuse_arg *lastarg = &out->args[out->numargs-1];
+		unsigned diffsize = reqsize - nbytes;
+		if (diffsize > lastarg->size)
+			return -EINVAL;
+		lastarg->size -= diffsize;
+	}
+	return fuse_copy_args(cs, out->numargs, out->argpages, out->args,
+			      out->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 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;
+
+	if (nbytes < sizeof(struct fuse_out_header))
+		return -EINVAL;
+
+	err = fuse_copy_one(cs, &oh, sizeof(oh));
+	if (err)
+		goto err_finish;
+
+	err = -EINVAL;
+	if (oh.len != nbytes)
+		goto err_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);
+		return err ? err : nbytes;
+	}
+
+	err = -EINVAL;
+	if (oh.error <= -512 || oh.error > 0)
+		goto err_finish;
+
+	spin_lock(&fpq->lock);
+	err = -ENOENT;
+	if (!fpq->connected)
+		goto err_unlock_pq;
+
+	req = request_find(fpq, oh.unique);
+	if (!req)
+		goto err_unlock_pq;
+
+	/* Is it an interrupt reply? */
+	if (req->intr_unique == oh.unique) {
+		__fuse_get_request(req);
+		spin_unlock(&fpq->lock);
+
+		err = -EINVAL;
+		if (nbytes != sizeof(struct fuse_out_header)) {
+			fuse_put_request(fc, req);
+			goto err_finish;
+		}
+
+		if (oh.error == -ENOSYS)
+			fc->no_interrupt = 1;
+		else if (oh.error == -EAGAIN)
+			queue_interrupt(&fc->iq, req);
+		fuse_put_request(fc, req);
+
+		fuse_copy_finish(cs);
+		return nbytes;
+	}
+
+	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->out.page_replace)
+		cs->move_pages = 0;
+
+	err = copy_out_args(cs, &req->out, 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);
+
+	request_end(fc, req);
+
+	return err ? err : nbytes;
+
+ err_unlock_pq:
+	spin_unlock(&fpq->lock);
+ err_finish:
+	fuse_copy_finish(cs);
+	return err;
+}
+
+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 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);
+
+	bufs = kvmalloc_array(pipe->nrbufs, sizeof(struct pipe_buffer),
+			      GFP_KERNEL);
+	if (!bufs) {
+		pipe_unlock(pipe);
+		return -ENOMEM;
+	}
+
+	nbuf = 0;
+	rem = 0;
+	for (idx = 0; idx < pipe->nrbufs && rem < len; idx++)
+		rem += pipe->bufs[(pipe->curbuf + idx) & (pipe->buffers - 1)].len;
+
+	ret = -EINVAL;
+	if (rem < len)
+		goto out_free;
+
+	rem = len;
+	while (rem) {
+		struct pipe_buffer *ibuf;
+		struct pipe_buffer *obuf;
+
+		BUG_ON(nbuf >= pipe->buffers);
+		BUG_ON(!pipe->nrbufs);
+		ibuf = &pipe->bufs[pipe->curbuf];
+		obuf = &bufs[nbuf];
+
+		if (rem >= ibuf->len) {
+			*obuf = *ibuf;
+			ibuf->ops = NULL;
+			pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
+			pipe->nrbufs--;
+		} 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)
+ *
+ * This function releases and reacquires fc->lock
+ */
+static void end_requests(struct fuse_conn *fc, 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);
+		request_end(fc, 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.txt).
+ *
+ * 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, bool is_abort)
+{
+	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);
+
+		fc->connected = 0;
+		fc->blocked = 0;
+		fc->aborted = is_abort;
+		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);
+			}
+			list_splice_tail_init(&fpq->processing, &to_end);
+			spin_unlock(&fpq->lock);
+		}
+		fc->max_background = UINT_MAX;
+		flush_bg_queue(fc);
+
+		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(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(fc, &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);
+
+		spin_lock(&fpq->lock);
+		WARN_ON(!list_empty(&fpq->io));
+		list_splice_init(&fpq->processing, &to_end);
+		spin_unlock(&fpq->lock);
+
+		end_requests(fc, &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, false);
+		}
+		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(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   = fuse_dev_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);
+}