Add the rt linux 4.1.3-rt3 as base

Import the rt linux 4.1.3-rt3 as OPNFV kvm base.

It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and
the base is:

commit 0917f823c59692d751951bf5ea699a2d1e2f26a2
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date:   Sat Jul 25 12:13:34 2015 +0200

    Prepare v4.1.3-rt3

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

We lose all the git history this way and it's not good. We
should apply another opnfv project repo in future.

Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>

1 files changed, 2994 insertions, 0 deletions

diff --git a/kernel/fs/fuse/file.c b/kernel/fs/fuse/file.c
new file mode 100644
index 000000000..5ef05b5c4
--- /dev/null
+++ b/kernel/fs/fuse/file.c
@@ -0,0 +1,2994 @@
+/*
+  FUSE: Filesystem in Userspace
+  Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>
+
+  This program can be distributed under the terms of the GNU GPL.
+  See the file COPYING.
+*/
+
+#include "fuse_i.h"
+
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+#include <linux/compat.h>
+#include <linux/swap.h>
+#include <linux/falloc.h>
+#include <linux/uio.h>
+
+static const struct file_operations fuse_direct_io_file_operations;
+
+static int fuse_send_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
+			  int opcode, struct fuse_open_out *outargp)
+{
+	struct fuse_open_in inarg;
+	FUSE_ARGS(args);
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.flags = file->f_flags & ~(O_CREAT | O_EXCL | O_NOCTTY);
+	if (!fc->atomic_o_trunc)
+		inarg.flags &= ~O_TRUNC;
+	args.in.h.opcode = opcode;
+	args.in.h.nodeid = nodeid;
+	args.in.numargs = 1;
+	args.in.args[0].size = sizeof(inarg);
+	args.in.args[0].value = &inarg;
+	args.out.numargs = 1;
+	args.out.args[0].size = sizeof(*outargp);
+	args.out.args[0].value = outargp;
+
+	return fuse_simple_request(fc, &args);
+}
+
+struct fuse_file *fuse_file_alloc(struct fuse_conn *fc)
+{
+	struct fuse_file *ff;
+
+	ff = kmalloc(sizeof(struct fuse_file), GFP_KERNEL);
+	if (unlikely(!ff))
+		return NULL;
+
+	ff->fc = fc;
+	ff->reserved_req = fuse_request_alloc(0);
+	if (unlikely(!ff->reserved_req)) {
+		kfree(ff);
+		return NULL;
+	}
+
+	INIT_LIST_HEAD(&ff->write_entry);
+	atomic_set(&ff->count, 0);
+	RB_CLEAR_NODE(&ff->polled_node);
+	init_waitqueue_head(&ff->poll_wait);
+
+	spin_lock(&fc->lock);
+	ff->kh = ++fc->khctr;
+	spin_unlock(&fc->lock);
+
+	return ff;
+}
+
+void fuse_file_free(struct fuse_file *ff)
+{
+	fuse_request_free(ff->reserved_req);
+	kfree(ff);
+}
+
+struct fuse_file *fuse_file_get(struct fuse_file *ff)
+{
+	atomic_inc(&ff->count);
+	return ff;
+}
+
+static void fuse_release_end(struct fuse_conn *fc, struct fuse_req *req)
+{
+	iput(req->misc.release.inode);
+}
+
+static void fuse_file_put(struct fuse_file *ff, bool sync)
+{
+	if (atomic_dec_and_test(&ff->count)) {
+		struct fuse_req *req = ff->reserved_req;
+
+		if (ff->fc->no_open) {
+			/*
+			 * Drop the release request when client does not
+			 * implement 'open'
+			 */
+			req->background = 0;
+			iput(req->misc.release.inode);
+			fuse_put_request(ff->fc, req);
+		} else if (sync) {
+			req->background = 0;
+			fuse_request_send(ff->fc, req);
+			iput(req->misc.release.inode);
+			fuse_put_request(ff->fc, req);
+		} else {
+			req->end = fuse_release_end;
+			req->background = 1;
+			fuse_request_send_background(ff->fc, req);
+		}
+		kfree(ff);
+	}
+}
+
+int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
+		 bool isdir)
+{
+	struct fuse_file *ff;
+	int opcode = isdir ? FUSE_OPENDIR : FUSE_OPEN;
+
+	ff = fuse_file_alloc(fc);
+	if (!ff)
+		return -ENOMEM;
+
+	ff->fh = 0;
+	ff->open_flags = FOPEN_KEEP_CACHE; /* Default for no-open */
+	if (!fc->no_open || isdir) {
+		struct fuse_open_out outarg;
+		int err;
+
+		err = fuse_send_open(fc, nodeid, file, opcode, &outarg);
+		if (!err) {
+			ff->fh = outarg.fh;
+			ff->open_flags = outarg.open_flags;
+
+		} else if (err != -ENOSYS || isdir) {
+			fuse_file_free(ff);
+			return err;
+		} else {
+			fc->no_open = 1;
+		}
+	}
+
+	if (isdir)
+		ff->open_flags &= ~FOPEN_DIRECT_IO;
+
+	ff->nodeid = nodeid;
+	file->private_data = fuse_file_get(ff);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fuse_do_open);
+
+static void fuse_link_write_file(struct file *file)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_file *ff = file->private_data;
+	/*
+	 * file may be written through mmap, so chain it onto the
+	 * inodes's write_file list
+	 */
+	spin_lock(&fc->lock);
+	if (list_empty(&ff->write_entry))
+		list_add(&ff->write_entry, &fi->write_files);
+	spin_unlock(&fc->lock);
+}
+
+void fuse_finish_open(struct inode *inode, struct file *file)
+{
+	struct fuse_file *ff = file->private_data;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	if (ff->open_flags & FOPEN_DIRECT_IO)
+		file->f_op = &fuse_direct_io_file_operations;
+	if (!(ff->open_flags & FOPEN_KEEP_CACHE))
+		invalidate_inode_pages2(inode->i_mapping);
+	if (ff->open_flags & FOPEN_NONSEEKABLE)
+		nonseekable_open(inode, file);
+	if (fc->atomic_o_trunc && (file->f_flags & O_TRUNC)) {
+		struct fuse_inode *fi = get_fuse_inode(inode);
+
+		spin_lock(&fc->lock);
+		fi->attr_version = ++fc->attr_version;
+		i_size_write(inode, 0);
+		spin_unlock(&fc->lock);
+		fuse_invalidate_attr(inode);
+		if (fc->writeback_cache)
+			file_update_time(file);
+	}
+	if ((file->f_mode & FMODE_WRITE) && fc->writeback_cache)
+		fuse_link_write_file(file);
+}
+
+int fuse_open_common(struct inode *inode, struct file *file, bool isdir)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	int err;
+	bool lock_inode = (file->f_flags & O_TRUNC) &&
+			  fc->atomic_o_trunc &&
+			  fc->writeback_cache;
+
+	err = generic_file_open(inode, file);
+	if (err)
+		return err;
+
+	if (lock_inode)
+		mutex_lock(&inode->i_mutex);
+
+	err = fuse_do_open(fc, get_node_id(inode), file, isdir);
+
+	if (!err)
+		fuse_finish_open(inode, file);
+
+	if (lock_inode)
+		mutex_unlock(&inode->i_mutex);
+
+	return err;
+}
+
+static void fuse_prepare_release(struct fuse_file *ff, int flags, int opcode)
+{
+	struct fuse_conn *fc = ff->fc;
+	struct fuse_req *req = ff->reserved_req;
+	struct fuse_release_in *inarg = &req->misc.release.in;
+
+	spin_lock(&fc->lock);
+	list_del(&ff->write_entry);
+	if (!RB_EMPTY_NODE(&ff->polled_node))
+		rb_erase(&ff->polled_node, &fc->polled_files);
+	spin_unlock(&fc->lock);
+
+	wake_up_interruptible_all(&ff->poll_wait);
+
+	inarg->fh = ff->fh;
+	inarg->flags = flags;
+	req->in.h.opcode = opcode;
+	req->in.h.nodeid = ff->nodeid;
+	req->in.numargs = 1;
+	req->in.args[0].size = sizeof(struct fuse_release_in);
+	req->in.args[0].value = inarg;
+}
+
+void fuse_release_common(struct file *file, int opcode)
+{
+	struct fuse_file *ff;
+	struct fuse_req *req;
+
+	ff = file->private_data;
+	if (unlikely(!ff))
+		return;
+
+	req = ff->reserved_req;
+	fuse_prepare_release(ff, file->f_flags, opcode);
+
+	if (ff->flock) {
+		struct fuse_release_in *inarg = &req->misc.release.in;
+		inarg->release_flags |= FUSE_RELEASE_FLOCK_UNLOCK;
+		inarg->lock_owner = fuse_lock_owner_id(ff->fc,
+						       (fl_owner_t) file);
+	}
+	/* Hold inode until release is finished */
+	req->misc.release.inode = igrab(file_inode(file));
+
+	/*
+	 * Normally this will send the RELEASE request, however if
+	 * some asynchronous READ or WRITE requests are outstanding,
+	 * the sending will be delayed.
+	 *
+	 * Make the release synchronous if this is a fuseblk mount,
+	 * synchronous RELEASE is allowed (and desirable) in this case
+	 * because the server can be trusted not to screw up.
+	 */
+	fuse_file_put(ff, ff->fc->destroy_req != NULL);
+}
+
+static int fuse_open(struct inode *inode, struct file *file)
+{
+	return fuse_open_common(inode, file, false);
+}
+
+static int fuse_release(struct inode *inode, struct file *file)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	/* see fuse_vma_close() for !writeback_cache case */
+	if (fc->writeback_cache)
+		write_inode_now(inode, 1);
+
+	fuse_release_common(file, FUSE_RELEASE);
+
+	/* return value is ignored by VFS */
+	return 0;
+}
+
+void fuse_sync_release(struct fuse_file *ff, int flags)
+{
+	WARN_ON(atomic_read(&ff->count) > 1);
+	fuse_prepare_release(ff, flags, FUSE_RELEASE);
+	ff->reserved_req->force = 1;
+	ff->reserved_req->background = 0;
+	fuse_request_send(ff->fc, ff->reserved_req);
+	fuse_put_request(ff->fc, ff->reserved_req);
+	kfree(ff);
+}
+EXPORT_SYMBOL_GPL(fuse_sync_release);
+
+/*
+ * Scramble the ID space with XTEA, so that the value of the files_struct
+ * pointer is not exposed to userspace.
+ */
+u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id)
+{
+	u32 *k = fc->scramble_key;
+	u64 v = (unsigned long) id;
+	u32 v0 = v;
+	u32 v1 = v >> 32;
+	u32 sum = 0;
+	int i;
+
+	for (i = 0; i < 32; i++) {
+		v0 += ((v1 << 4 ^ v1 >> 5) + v1) ^ (sum + k[sum & 3]);
+		sum += 0x9E3779B9;
+		v1 += ((v0 << 4 ^ v0 >> 5) + v0) ^ (sum + k[sum>>11 & 3]);
+	}
+
+	return (u64) v0 + ((u64) v1 << 32);
+}
+
+/*
+ * Check if any page in a range is under writeback
+ *
+ * This is currently done by walking the list of writepage requests
+ * for the inode, which can be pretty inefficient.
+ */
+static bool fuse_range_is_writeback(struct inode *inode, pgoff_t idx_from,
+				   pgoff_t idx_to)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_req *req;
+	bool found = false;
+
+	spin_lock(&fc->lock);
+	list_for_each_entry(req, &fi->writepages, writepages_entry) {
+		pgoff_t curr_index;
+
+		BUG_ON(req->inode != inode);
+		curr_index = req->misc.write.in.offset >> PAGE_CACHE_SHIFT;
+		if (idx_from < curr_index + req->num_pages &&
+		    curr_index <= idx_to) {
+			found = true;
+			break;
+		}
+	}
+	spin_unlock(&fc->lock);
+
+	return found;
+}
+
+static inline bool fuse_page_is_writeback(struct inode *inode, pgoff_t index)
+{
+	return fuse_range_is_writeback(inode, index, index);
+}
+
+/*
+ * Wait for page writeback to be completed.
+ *
+ * Since fuse doesn't rely on the VM writeback tracking, this has to
+ * use some other means.
+ */
+static int fuse_wait_on_page_writeback(struct inode *inode, pgoff_t index)
+{
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	wait_event(fi->page_waitq, !fuse_page_is_writeback(inode, index));
+	return 0;
+}
+
+/*
+ * Wait for all pending writepages on the inode to finish.
+ *
+ * This is currently done by blocking further writes with FUSE_NOWRITE
+ * and waiting for all sent writes to complete.
+ *
+ * This must be called under i_mutex, otherwise the FUSE_NOWRITE usage
+ * could conflict with truncation.
+ */
+static void fuse_sync_writes(struct inode *inode)
+{
+	fuse_set_nowrite(inode);
+	fuse_release_nowrite(inode);
+}
+
+static int fuse_flush(struct file *file, fl_owner_t id)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_file *ff = file->private_data;
+	struct fuse_req *req;
+	struct fuse_flush_in inarg;
+	int err;
+
+	if (is_bad_inode(inode))
+		return -EIO;
+
+	if (fc->no_flush)
+		return 0;
+
+	err = write_inode_now(inode, 1);
+	if (err)
+		return err;
+
+	mutex_lock(&inode->i_mutex);
+	fuse_sync_writes(inode);
+	mutex_unlock(&inode->i_mutex);
+
+	req = fuse_get_req_nofail_nopages(fc, file);
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.fh = ff->fh;
+	inarg.lock_owner = fuse_lock_owner_id(fc, id);
+	req->in.h.opcode = FUSE_FLUSH;
+	req->in.h.nodeid = get_node_id(inode);
+	req->in.numargs = 1;
+	req->in.args[0].size = sizeof(inarg);
+	req->in.args[0].value = &inarg;
+	req->force = 1;
+	fuse_request_send(fc, req);
+	err = req->out.h.error;
+	fuse_put_request(fc, req);
+	if (err == -ENOSYS) {
+		fc->no_flush = 1;
+		err = 0;
+	}
+	return err;
+}
+
+int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
+		      int datasync, int isdir)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_file *ff = file->private_data;
+	FUSE_ARGS(args);
+	struct fuse_fsync_in inarg;
+	int err;
+
+	if (is_bad_inode(inode))
+		return -EIO;
+
+	mutex_lock(&inode->i_mutex);
+
+	/*
+	 * Start writeback against all dirty pages of the inode, then
+	 * wait for all outstanding writes, before sending the FSYNC
+	 * request.
+	 */
+	err = filemap_write_and_wait_range(inode->i_mapping, start, end);
+	if (err)
+		goto out;
+
+	fuse_sync_writes(inode);
+	err = sync_inode_metadata(inode, 1);
+	if (err)
+		goto out;
+
+	if ((!isdir && fc->no_fsync) || (isdir && fc->no_fsyncdir))
+		goto out;
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.fh = ff->fh;
+	inarg.fsync_flags = datasync ? 1 : 0;
+	args.in.h.opcode = isdir ? FUSE_FSYNCDIR : FUSE_FSYNC;
+	args.in.h.nodeid = get_node_id(inode);
+	args.in.numargs = 1;
+	args.in.args[0].size = sizeof(inarg);
+	args.in.args[0].value = &inarg;
+	err = fuse_simple_request(fc, &args);
+	if (err == -ENOSYS) {
+		if (isdir)
+			fc->no_fsyncdir = 1;
+		else
+			fc->no_fsync = 1;
+		err = 0;
+	}
+out:
+	mutex_unlock(&inode->i_mutex);
+	return err;
+}
+
+static int fuse_fsync(struct file *file, loff_t start, loff_t end,
+		      int datasync)
+{
+	return fuse_fsync_common(file, start, end, datasync, 0);
+}
+
+void fuse_read_fill(struct fuse_req *req, struct file *file, loff_t pos,
+		    size_t count, int opcode)
+{
+	struct fuse_read_in *inarg = &req->misc.read.in;
+	struct fuse_file *ff = file->private_data;
+
+	inarg->fh = ff->fh;
+	inarg->offset = pos;
+	inarg->size = count;
+	inarg->flags = file->f_flags;
+	req->in.h.opcode = opcode;
+	req->in.h.nodeid = ff->nodeid;
+	req->in.numargs = 1;
+	req->in.args[0].size = sizeof(struct fuse_read_in);
+	req->in.args[0].value = inarg;
+	req->out.argvar = 1;
+	req->out.numargs = 1;
+	req->out.args[0].size = count;
+}
+
+static void fuse_release_user_pages(struct fuse_req *req, int write)
+{
+	unsigned i;
+
+	for (i = 0; i < req->num_pages; i++) {
+		struct page *page = req->pages[i];
+		if (write)
+			set_page_dirty_lock(page);
+		put_page(page);
+	}
+}
+
+static ssize_t fuse_get_res_by_io(struct fuse_io_priv *io)
+{
+	if (io->err)
+		return io->err;
+
+	if (io->bytes >= 0 && io->write)
+		return -EIO;
+
+	return io->bytes < 0 ? io->size : io->bytes;
+}
+
+/**
+ * In case of short read, the caller sets 'pos' to the position of
+ * actual end of fuse request in IO request. Otherwise, if bytes_requested
+ * == bytes_transferred or rw == WRITE, the caller sets 'pos' to -1.
+ *
+ * An example:
+ * User requested DIO read of 64K. It was splitted into two 32K fuse requests,
+ * both submitted asynchronously. The first of them was ACKed by userspace as
+ * fully completed (req->out.args[0].size == 32K) resulting in pos == -1. The
+ * second request was ACKed as short, e.g. only 1K was read, resulting in
+ * pos == 33K.
+ *
+ * Thus, when all fuse requests are completed, the minimal non-negative 'pos'
+ * will be equal to the length of the longest contiguous fragment of
+ * transferred data starting from the beginning of IO request.
+ */
+static void fuse_aio_complete(struct fuse_io_priv *io, int err, ssize_t pos)
+{
+	bool is_sync = is_sync_kiocb(io->iocb);
+	int left;
+
+	spin_lock(&io->lock);
+	if (err)
+		io->err = io->err ? : err;
+	else if (pos >= 0 && (io->bytes < 0 || pos < io->bytes))
+		io->bytes = pos;
+
+	left = --io->reqs;
+	if (!left && is_sync)
+		complete(io->done);
+	spin_unlock(&io->lock);
+
+	if (!left && !is_sync) {
+		ssize_t res = fuse_get_res_by_io(io);
+
+		if (res >= 0) {
+			struct inode *inode = file_inode(io->iocb->ki_filp);
+			struct fuse_conn *fc = get_fuse_conn(inode);
+			struct fuse_inode *fi = get_fuse_inode(inode);
+
+			spin_lock(&fc->lock);
+			fi->attr_version = ++fc->attr_version;
+			spin_unlock(&fc->lock);
+		}
+
+		io->iocb->ki_complete(io->iocb, res, 0);
+		kfree(io);
+	}
+}
+
+static void fuse_aio_complete_req(struct fuse_conn *fc, struct fuse_req *req)
+{
+	struct fuse_io_priv *io = req->io;
+	ssize_t pos = -1;
+
+	fuse_release_user_pages(req, !io->write);
+
+	if (io->write) {
+		if (req->misc.write.in.size != req->misc.write.out.size)
+			pos = req->misc.write.in.offset - io->offset +
+				req->misc.write.out.size;
+	} else {
+		if (req->misc.read.in.size != req->out.args[0].size)
+			pos = req->misc.read.in.offset - io->offset +
+				req->out.args[0].size;
+	}
+
+	fuse_aio_complete(io, req->out.h.error, pos);
+}
+
+static size_t fuse_async_req_send(struct fuse_conn *fc, struct fuse_req *req,
+		size_t num_bytes, struct fuse_io_priv *io)
+{
+	spin_lock(&io->lock);
+	io->size += num_bytes;
+	io->reqs++;
+	spin_unlock(&io->lock);
+
+	req->io = io;
+	req->end = fuse_aio_complete_req;
+
+	__fuse_get_request(req);
+	fuse_request_send_background(fc, req);
+
+	return num_bytes;
+}
+
+static size_t fuse_send_read(struct fuse_req *req, struct fuse_io_priv *io,
+			     loff_t pos, size_t count, fl_owner_t owner)
+{
+	struct file *file = io->file;
+	struct fuse_file *ff = file->private_data;
+	struct fuse_conn *fc = ff->fc;
+
+	fuse_read_fill(req, file, pos, count, FUSE_READ);
+	if (owner != NULL) {
+		struct fuse_read_in *inarg = &req->misc.read.in;
+
+		inarg->read_flags |= FUSE_READ_LOCKOWNER;
+		inarg->lock_owner = fuse_lock_owner_id(fc, owner);
+	}
+
+	if (io->async)
+		return fuse_async_req_send(fc, req, count, io);
+
+	fuse_request_send(fc, req);
+	return req->out.args[0].size;
+}
+
+static void fuse_read_update_size(struct inode *inode, loff_t size,
+				  u64 attr_ver)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	spin_lock(&fc->lock);
+	if (attr_ver == fi->attr_version && size < inode->i_size &&
+	    !test_bit(FUSE_I_SIZE_UNSTABLE, &fi->state)) {
+		fi->attr_version = ++fc->attr_version;
+		i_size_write(inode, size);
+	}
+	spin_unlock(&fc->lock);
+}
+
+static void fuse_short_read(struct fuse_req *req, struct inode *inode,
+			    u64 attr_ver)
+{
+	size_t num_read = req->out.args[0].size;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	if (fc->writeback_cache) {
+		/*
+		 * A hole in a file. Some data after the hole are in page cache,
+		 * but have not reached the client fs yet. So, the hole is not
+		 * present there.
+		 */
+		int i;
+		int start_idx = num_read >> PAGE_CACHE_SHIFT;
+		size_t off = num_read & (PAGE_CACHE_SIZE - 1);
+
+		for (i = start_idx; i < req->num_pages; i++) {
+			zero_user_segment(req->pages[i], off, PAGE_CACHE_SIZE);
+			off = 0;
+		}
+	} else {
+		loff_t pos = page_offset(req->pages[0]) + num_read;
+		fuse_read_update_size(inode, pos, attr_ver);
+	}
+}
+
+static int fuse_do_readpage(struct file *file, struct page *page)
+{
+	struct fuse_io_priv io = { .async = 0, .file = file };
+	struct inode *inode = page->mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_req *req;
+	size_t num_read;
+	loff_t pos = page_offset(page);
+	size_t count = PAGE_CACHE_SIZE;
+	u64 attr_ver;
+	int err;
+
+	/*
+	 * Page writeback can extend beyond the lifetime of the
+	 * page-cache page, so make sure we read a properly synced
+	 * page.
+	 */
+	fuse_wait_on_page_writeback(inode, page->index);
+
+	req = fuse_get_req(fc, 1);
+	if (IS_ERR(req))
+		return PTR_ERR(req);
+
+	attr_ver = fuse_get_attr_version(fc);
+
+	req->out.page_zeroing = 1;
+	req->out.argpages = 1;
+	req->num_pages = 1;
+	req->pages[0] = page;
+	req->page_descs[0].length = count;
+	num_read = fuse_send_read(req, &io, pos, count, NULL);
+	err = req->out.h.error;
+
+	if (!err) {
+		/*
+		 * Short read means EOF.  If file size is larger, truncate it
+		 */
+		if (num_read < count)
+			fuse_short_read(req, inode, attr_ver);
+
+		SetPageUptodate(page);
+	}
+
+	fuse_put_request(fc, req);
+
+	return err;
+}
+
+static int fuse_readpage(struct file *file, struct page *page)
+{
+	struct inode *inode = page->mapping->host;
+	int err;
+
+	err = -EIO;
+	if (is_bad_inode(inode))
+		goto out;
+
+	err = fuse_do_readpage(file, page);
+	fuse_invalidate_atime(inode);
+ out:
+	unlock_page(page);
+	return err;
+}
+
+static void fuse_readpages_end(struct fuse_conn *fc, struct fuse_req *req)
+{
+	int i;
+	size_t count = req->misc.read.in.size;
+	size_t num_read = req->out.args[0].size;
+	struct address_space *mapping = NULL;
+
+	for (i = 0; mapping == NULL && i < req->num_pages; i++)
+		mapping = req->pages[i]->mapping;
+
+	if (mapping) {
+		struct inode *inode = mapping->host;
+
+		/*
+		 * Short read means EOF. If file size is larger, truncate it
+		 */
+		if (!req->out.h.error && num_read < count)
+			fuse_short_read(req, inode, req->misc.read.attr_ver);
+
+		fuse_invalidate_atime(inode);
+	}
+
+	for (i = 0; i < req->num_pages; i++) {
+		struct page *page = req->pages[i];
+		if (!req->out.h.error)
+			SetPageUptodate(page);
+		else
+			SetPageError(page);
+		unlock_page(page);
+		page_cache_release(page);
+	}
+	if (req->ff)
+		fuse_file_put(req->ff, false);
+}
+
+static void fuse_send_readpages(struct fuse_req *req, struct file *file)
+{
+	struct fuse_file *ff = file->private_data;
+	struct fuse_conn *fc = ff->fc;
+	loff_t pos = page_offset(req->pages[0]);
+	size_t count = req->num_pages << PAGE_CACHE_SHIFT;
+
+	req->out.argpages = 1;
+	req->out.page_zeroing = 1;
+	req->out.page_replace = 1;
+	fuse_read_fill(req, file, pos, count, FUSE_READ);
+	req->misc.read.attr_ver = fuse_get_attr_version(fc);
+	if (fc->async_read) {
+		req->ff = fuse_file_get(ff);
+		req->end = fuse_readpages_end;
+		fuse_request_send_background(fc, req);
+	} else {
+		fuse_request_send(fc, req);
+		fuse_readpages_end(fc, req);
+		fuse_put_request(fc, req);
+	}
+}
+
+struct fuse_fill_data {
+	struct fuse_req *req;
+	struct file *file;
+	struct inode *inode;
+	unsigned nr_pages;
+};
+
+static int fuse_readpages_fill(void *_data, struct page *page)
+{
+	struct fuse_fill_data *data = _data;
+	struct fuse_req *req = data->req;
+	struct inode *inode = data->inode;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	fuse_wait_on_page_writeback(inode, page->index);
+
+	if (req->num_pages &&
+	    (req->num_pages == FUSE_MAX_PAGES_PER_REQ ||
+	     (req->num_pages + 1) * PAGE_CACHE_SIZE > fc->max_read ||
+	     req->pages[req->num_pages - 1]->index + 1 != page->index)) {
+		int nr_alloc = min_t(unsigned, data->nr_pages,
+				     FUSE_MAX_PAGES_PER_REQ);
+		fuse_send_readpages(req, data->file);
+		if (fc->async_read)
+			req = fuse_get_req_for_background(fc, nr_alloc);
+		else
+			req = fuse_get_req(fc, nr_alloc);
+
+		data->req = req;
+		if (IS_ERR(req)) {
+			unlock_page(page);
+			return PTR_ERR(req);
+		}
+	}
+
+	if (WARN_ON(req->num_pages >= req->max_pages)) {
+		fuse_put_request(fc, req);
+		return -EIO;
+	}
+
+	page_cache_get(page);
+	req->pages[req->num_pages] = page;
+	req->page_descs[req->num_pages].length = PAGE_SIZE;
+	req->num_pages++;
+	data->nr_pages--;
+	return 0;
+}
+
+static int fuse_readpages(struct file *file, struct address_space *mapping,
+			  struct list_head *pages, unsigned nr_pages)
+{
+	struct inode *inode = mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_fill_data data;
+	int err;
+	int nr_alloc = min_t(unsigned, nr_pages, FUSE_MAX_PAGES_PER_REQ);
+
+	err = -EIO;
+	if (is_bad_inode(inode))
+		goto out;
+
+	data.file = file;
+	data.inode = inode;
+	if (fc->async_read)
+		data.req = fuse_get_req_for_background(fc, nr_alloc);
+	else
+		data.req = fuse_get_req(fc, nr_alloc);
+	data.nr_pages = nr_pages;
+	err = PTR_ERR(data.req);
+	if (IS_ERR(data.req))
+		goto out;
+
+	err = read_cache_pages(mapping, pages, fuse_readpages_fill, &data);
+	if (!err) {
+		if (data.req->num_pages)
+			fuse_send_readpages(data.req, file);
+		else
+			fuse_put_request(fc, data.req);
+	}
+out:
+	return err;
+}
+
+static ssize_t fuse_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct inode *inode = iocb->ki_filp->f_mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	/*
+	 * In auto invalidate mode, always update attributes on read.
+	 * Otherwise, only update if we attempt to read past EOF (to ensure
+	 * i_size is up to date).
+	 */
+	if (fc->auto_inval_data ||
+	    (iocb->ki_pos + iov_iter_count(to) > i_size_read(inode))) {
+		int err;
+		err = fuse_update_attributes(inode, NULL, iocb->ki_filp, NULL);
+		if (err)
+			return err;
+	}
+
+	return generic_file_read_iter(iocb, to);
+}
+
+static void fuse_write_fill(struct fuse_req *req, struct fuse_file *ff,
+			    loff_t pos, size_t count)
+{
+	struct fuse_write_in *inarg = &req->misc.write.in;
+	struct fuse_write_out *outarg = &req->misc.write.out;
+
+	inarg->fh = ff->fh;
+	inarg->offset = pos;
+	inarg->size = count;
+	req->in.h.opcode = FUSE_WRITE;
+	req->in.h.nodeid = ff->nodeid;
+	req->in.numargs = 2;
+	if (ff->fc->minor < 9)
+		req->in.args[0].size = FUSE_COMPAT_WRITE_IN_SIZE;
+	else
+		req->in.args[0].size = sizeof(struct fuse_write_in);
+	req->in.args[0].value = inarg;
+	req->in.args[1].size = count;
+	req->out.numargs = 1;
+	req->out.args[0].size = sizeof(struct fuse_write_out);
+	req->out.args[0].value = outarg;
+}
+
+static size_t fuse_send_write(struct fuse_req *req, struct fuse_io_priv *io,
+			      loff_t pos, size_t count, fl_owner_t owner)
+{
+	struct file *file = io->file;
+	struct fuse_file *ff = file->private_data;
+	struct fuse_conn *fc = ff->fc;
+	struct fuse_write_in *inarg = &req->misc.write.in;
+
+	fuse_write_fill(req, ff, pos, count);
+	inarg->flags = file->f_flags;
+	if (owner != NULL) {
+		inarg->write_flags |= FUSE_WRITE_LOCKOWNER;
+		inarg->lock_owner = fuse_lock_owner_id(fc, owner);
+	}
+
+	if (io->async)
+		return fuse_async_req_send(fc, req, count, io);
+
+	fuse_request_send(fc, req);
+	return req->misc.write.out.size;
+}
+
+bool fuse_write_update_size(struct inode *inode, loff_t pos)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	bool ret = false;
+
+	spin_lock(&fc->lock);
+	fi->attr_version = ++fc->attr_version;
+	if (pos > inode->i_size) {
+		i_size_write(inode, pos);
+		ret = true;
+	}
+	spin_unlock(&fc->lock);
+
+	return ret;
+}
+
+static size_t fuse_send_write_pages(struct fuse_req *req, struct file *file,
+				    struct inode *inode, loff_t pos,
+				    size_t count)
+{
+	size_t res;
+	unsigned offset;
+	unsigned i;
+	struct fuse_io_priv io = { .async = 0, .file = file };
+
+	for (i = 0; i < req->num_pages; i++)
+		fuse_wait_on_page_writeback(inode, req->pages[i]->index);
+
+	res = fuse_send_write(req, &io, pos, count, NULL);
+
+	offset = req->page_descs[0].offset;
+	count = res;
+	for (i = 0; i < req->num_pages; i++) {
+		struct page *page = req->pages[i];
+
+		if (!req->out.h.error && !offset && count >= PAGE_CACHE_SIZE)
+			SetPageUptodate(page);
+
+		if (count > PAGE_CACHE_SIZE - offset)
+			count -= PAGE_CACHE_SIZE - offset;
+		else
+			count = 0;
+		offset = 0;
+
+		unlock_page(page);
+		page_cache_release(page);
+	}
+
+	return res;
+}
+
+static ssize_t fuse_fill_write_pages(struct fuse_req *req,
+			       struct address_space *mapping,
+			       struct iov_iter *ii, loff_t pos)
+{
+	struct fuse_conn *fc = get_fuse_conn(mapping->host);
+	unsigned offset = pos & (PAGE_CACHE_SIZE - 1);
+	size_t count = 0;
+	int err;
+
+	req->in.argpages = 1;
+	req->page_descs[0].offset = offset;
+
+	do {
+		size_t tmp;
+		struct page *page;
+		pgoff_t index = pos >> PAGE_CACHE_SHIFT;
+		size_t bytes = min_t(size_t, PAGE_CACHE_SIZE - offset,
+				     iov_iter_count(ii));
+
+		bytes = min_t(size_t, bytes, fc->max_write - count);
+
+ again:
+		err = -EFAULT;
+		if (iov_iter_fault_in_readable(ii, bytes))
+			break;
+
+		err = -ENOMEM;
+		page = grab_cache_page_write_begin(mapping, index, 0);
+		if (!page)
+			break;
+
+		if (mapping_writably_mapped(mapping))
+			flush_dcache_page(page);
+
+		tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes);
+		flush_dcache_page(page);
+
+		if (!tmp) {
+			unlock_page(page);
+			page_cache_release(page);
+			bytes = min(bytes, iov_iter_single_seg_count(ii));
+			goto again;
+		}
+
+		err = 0;
+		req->pages[req->num_pages] = page;
+		req->page_descs[req->num_pages].length = tmp;
+		req->num_pages++;
+
+		iov_iter_advance(ii, tmp);
+		count += tmp;
+		pos += tmp;
+		offset += tmp;
+		if (offset == PAGE_CACHE_SIZE)
+			offset = 0;
+
+		if (!fc->big_writes)
+			break;
+	} while (iov_iter_count(ii) && count < fc->max_write &&
+		 req->num_pages < req->max_pages && offset == 0);
+
+	return count > 0 ? count : err;
+}
+
+static inline unsigned fuse_wr_pages(loff_t pos, size_t len)
+{
+	return min_t(unsigned,
+		     ((pos + len - 1) >> PAGE_CACHE_SHIFT) -
+		     (pos >> PAGE_CACHE_SHIFT) + 1,
+		     FUSE_MAX_PAGES_PER_REQ);
+}
+
+static ssize_t fuse_perform_write(struct file *file,
+				  struct address_space *mapping,
+				  struct iov_iter *ii, loff_t pos)
+{
+	struct inode *inode = mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	int err = 0;
+	ssize_t res = 0;
+
+	if (is_bad_inode(inode))
+		return -EIO;
+
+	if (inode->i_size < pos + iov_iter_count(ii))
+		set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
+
+	do {
+		struct fuse_req *req;
+		ssize_t count;
+		unsigned nr_pages = fuse_wr_pages(pos, iov_iter_count(ii));
+
+		req = fuse_get_req(fc, nr_pages);
+		if (IS_ERR(req)) {
+			err = PTR_ERR(req);
+			break;
+		}
+
+		count = fuse_fill_write_pages(req, mapping, ii, pos);
+		if (count <= 0) {
+			err = count;
+		} else {
+			size_t num_written;
+
+			num_written = fuse_send_write_pages(req, file, inode,
+							    pos, count);
+			err = req->out.h.error;
+			if (!err) {
+				res += num_written;
+				pos += num_written;
+
+				/* break out of the loop on short write */
+				if (num_written != count)
+					err = -EIO;
+			}
+		}
+		fuse_put_request(fc, req);
+	} while (!err && iov_iter_count(ii));
+
+	if (res > 0)
+		fuse_write_update_size(inode, pos);
+
+	clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
+	fuse_invalidate_attr(inode);
+
+	return res > 0 ? res : err;
+}
+
+static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct address_space *mapping = file->f_mapping;
+	ssize_t written = 0;
+	ssize_t written_buffered = 0;
+	struct inode *inode = mapping->host;
+	ssize_t err;
+	loff_t endbyte = 0;
+
+	if (get_fuse_conn(inode)->writeback_cache) {
+		/* Update size (EOF optimization) and mode (SUID clearing) */
+		err = fuse_update_attributes(mapping->host, NULL, file, NULL);
+		if (err)
+			return err;
+
+		return generic_file_write_iter(iocb, from);
+	}
+
+	mutex_lock(&inode->i_mutex);
+
+	/* We can write back this queue in page reclaim */
+	current->backing_dev_info = inode_to_bdi(inode);
+
+	err = generic_write_checks(iocb, from);
+	if (err <= 0)
+		goto out;
+
+	err = file_remove_suid(file);
+	if (err)
+		goto out;
+
+	err = file_update_time(file);
+	if (err)
+		goto out;
+
+	if (iocb->ki_flags & IOCB_DIRECT) {
+		loff_t pos = iocb->ki_pos;
+		written = generic_file_direct_write(iocb, from, pos);
+		if (written < 0 || !iov_iter_count(from))
+			goto out;
+
+		pos += written;
+
+		written_buffered = fuse_perform_write(file, mapping, from, pos);
+		if (written_buffered < 0) {
+			err = written_buffered;
+			goto out;
+		}
+		endbyte = pos + written_buffered - 1;
+
+		err = filemap_write_and_wait_range(file->f_mapping, pos,
+						   endbyte);
+		if (err)
+			goto out;
+
+		invalidate_mapping_pages(file->f_mapping,
+					 pos >> PAGE_CACHE_SHIFT,
+					 endbyte >> PAGE_CACHE_SHIFT);
+
+		written += written_buffered;
+		iocb->ki_pos = pos + written_buffered;
+	} else {
+		written = fuse_perform_write(file, mapping, from, iocb->ki_pos);
+		if (written >= 0)
+			iocb->ki_pos += written;
+	}
+out:
+	current->backing_dev_info = NULL;
+	mutex_unlock(&inode->i_mutex);
+
+	return written ? written : err;
+}
+
+static inline void fuse_page_descs_length_init(struct fuse_req *req,
+		unsigned index, unsigned nr_pages)
+{
+	int i;
+
+	for (i = index; i < index + nr_pages; i++)
+		req->page_descs[i].length = PAGE_SIZE -
+			req->page_descs[i].offset;
+}
+
+static inline unsigned long fuse_get_user_addr(const struct iov_iter *ii)
+{
+	return (unsigned long)ii->iov->iov_base + ii->iov_offset;
+}
+
+static inline size_t fuse_get_frag_size(const struct iov_iter *ii,
+					size_t max_size)
+{
+	return min(iov_iter_single_seg_count(ii), max_size);
+}
+
+static int fuse_get_user_pages(struct fuse_req *req, struct iov_iter *ii,
+			       size_t *nbytesp, int write)
+{
+	size_t nbytes = 0;  /* # bytes already packed in req */
+
+	/* Special case for kernel I/O: can copy directly into the buffer */
+	if (ii->type & ITER_KVEC) {
+		unsigned long user_addr = fuse_get_user_addr(ii);
+		size_t frag_size = fuse_get_frag_size(ii, *nbytesp);
+
+		if (write)
+			req->in.args[1].value = (void *) user_addr;
+		else
+			req->out.args[0].value = (void *) user_addr;
+
+		iov_iter_advance(ii, frag_size);
+		*nbytesp = frag_size;
+		return 0;
+	}
+
+	while (nbytes < *nbytesp && req->num_pages < req->max_pages) {
+		unsigned npages;
+		size_t start;
+		ssize_t ret = iov_iter_get_pages(ii,
+					&req->pages[req->num_pages],
+					*nbytesp - nbytes,
+					req->max_pages - req->num_pages,
+					&start);
+		if (ret < 0)
+			return ret;
+
+		iov_iter_advance(ii, ret);
+		nbytes += ret;
+
+		ret += start;
+		npages = (ret + PAGE_SIZE - 1) / PAGE_SIZE;
+
+		req->page_descs[req->num_pages].offset = start;
+		fuse_page_descs_length_init(req, req->num_pages, npages);
+
+		req->num_pages += npages;
+		req->page_descs[req->num_pages - 1].length -=
+			(PAGE_SIZE - ret) & (PAGE_SIZE - 1);
+	}
+
+	if (write)
+		req->in.argpages = 1;
+	else
+		req->out.argpages = 1;
+
+	*nbytesp = nbytes;
+
+	return 0;
+}
+
+static inline int fuse_iter_npages(const struct iov_iter *ii_p)
+{
+	return iov_iter_npages(ii_p, FUSE_MAX_PAGES_PER_REQ);
+}
+
+ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
+		       loff_t *ppos, int flags)
+{
+	int write = flags & FUSE_DIO_WRITE;
+	int cuse = flags & FUSE_DIO_CUSE;
+	struct file *file = io->file;
+	struct inode *inode = file->f_mapping->host;
+	struct fuse_file *ff = file->private_data;
+	struct fuse_conn *fc = ff->fc;
+	size_t nmax = write ? fc->max_write : fc->max_read;
+	loff_t pos = *ppos;
+	size_t count = iov_iter_count(iter);
+	pgoff_t idx_from = pos >> PAGE_CACHE_SHIFT;
+	pgoff_t idx_to = (pos + count - 1) >> PAGE_CACHE_SHIFT;
+	ssize_t res = 0;
+	struct fuse_req *req;
+
+	if (io->async)
+		req = fuse_get_req_for_background(fc, fuse_iter_npages(iter));
+	else
+		req = fuse_get_req(fc, fuse_iter_npages(iter));
+	if (IS_ERR(req))
+		return PTR_ERR(req);
+
+	if (!cuse && fuse_range_is_writeback(inode, idx_from, idx_to)) {
+		if (!write)
+			mutex_lock(&inode->i_mutex);
+		fuse_sync_writes(inode);
+		if (!write)
+			mutex_unlock(&inode->i_mutex);
+	}
+
+	while (count) {
+		size_t nres;
+		fl_owner_t owner = current->files;
+		size_t nbytes = min(count, nmax);
+		int err = fuse_get_user_pages(req, iter, &nbytes, write);
+		if (err) {
+			res = err;
+			break;
+		}
+
+		if (write)
+			nres = fuse_send_write(req, io, pos, nbytes, owner);
+		else
+			nres = fuse_send_read(req, io, pos, nbytes, owner);
+
+		if (!io->async)
+			fuse_release_user_pages(req, !write);
+		if (req->out.h.error) {
+			if (!res)
+				res = req->out.h.error;
+			break;
+		} else if (nres > nbytes) {
+			res = -EIO;
+			break;
+		}
+		count -= nres;
+		res += nres;
+		pos += nres;
+		if (nres != nbytes)
+			break;
+		if (count) {
+			fuse_put_request(fc, req);
+			if (io->async)
+				req = fuse_get_req_for_background(fc,
+					fuse_iter_npages(iter));
+			else
+				req = fuse_get_req(fc, fuse_iter_npages(iter));
+			if (IS_ERR(req))
+				break;
+		}
+	}
+	if (!IS_ERR(req))
+		fuse_put_request(fc, req);
+	if (res > 0)
+		*ppos = pos;
+
+	return res;
+}
+EXPORT_SYMBOL_GPL(fuse_direct_io);
+
+static ssize_t __fuse_direct_read(struct fuse_io_priv *io,
+				  struct iov_iter *iter,
+				  loff_t *ppos)
+{
+	ssize_t res;
+	struct file *file = io->file;
+	struct inode *inode = file_inode(file);
+
+	if (is_bad_inode(inode))
+		return -EIO;
+
+	res = fuse_direct_io(io, iter, ppos, 0);
+
+	fuse_invalidate_attr(inode);
+
+	return res;
+}
+
+static ssize_t fuse_direct_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct fuse_io_priv io = { .async = 0, .file = iocb->ki_filp };
+	return __fuse_direct_read(&io, to, &iocb->ki_pos);
+}
+
+static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file_inode(file);
+	struct fuse_io_priv io = { .async = 0, .file = file };
+	ssize_t res;
+
+	if (is_bad_inode(inode))
+		return -EIO;
+
+	/* Don't allow parallel writes to the same file */
+	mutex_lock(&inode->i_mutex);
+	res = generic_write_checks(iocb, from);
+	if (res > 0)
+		res = fuse_direct_io(&io, from, &iocb->ki_pos, FUSE_DIO_WRITE);
+	fuse_invalidate_attr(inode);
+	if (res > 0)
+		fuse_write_update_size(inode, iocb->ki_pos);
+	mutex_unlock(&inode->i_mutex);
+
+	return res;
+}
+
+static void fuse_writepage_free(struct fuse_conn *fc, struct fuse_req *req)
+{
+	int i;
+
+	for (i = 0; i < req->num_pages; i++)
+		__free_page(req->pages[i]);
+
+	if (req->ff)
+		fuse_file_put(req->ff, false);
+}
+
+static void fuse_writepage_finish(struct fuse_conn *fc, struct fuse_req *req)
+{
+	struct inode *inode = req->inode;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct backing_dev_info *bdi = inode_to_bdi(inode);
+	int i;
+
+	list_del(&req->writepages_entry);
+	for (i = 0; i < req->num_pages; i++) {
+		dec_bdi_stat(bdi, BDI_WRITEBACK);
+		dec_zone_page_state(req->pages[i], NR_WRITEBACK_TEMP);
+		bdi_writeout_inc(bdi);
+	}
+	wake_up(&fi->page_waitq);
+}
+
+/* Called under fc->lock, may release and reacquire it */
+static void fuse_send_writepage(struct fuse_conn *fc, struct fuse_req *req,
+				loff_t size)
+__releases(fc->lock)
+__acquires(fc->lock)
+{
+	struct fuse_inode *fi = get_fuse_inode(req->inode);
+	struct fuse_write_in *inarg = &req->misc.write.in;
+	__u64 data_size = req->num_pages * PAGE_CACHE_SIZE;
+
+	if (!fc->connected)
+		goto out_free;
+
+	if (inarg->offset + data_size <= size) {
+		inarg->size = data_size;
+	} else if (inarg->offset < size) {
+		inarg->size = size - inarg->offset;
+	} else {
+		/* Got truncated off completely */
+		goto out_free;
+	}
+
+	req->in.args[1].size = inarg->size;
+	fi->writectr++;
+	fuse_request_send_background_locked(fc, req);
+	return;
+
+ out_free:
+	fuse_writepage_finish(fc, req);
+	spin_unlock(&fc->lock);
+	fuse_writepage_free(fc, req);
+	fuse_put_request(fc, req);
+	spin_lock(&fc->lock);
+}
+
+/*
+ * If fi->writectr is positive (no truncate or fsync going on) send
+ * all queued writepage requests.
+ *
+ * Called with fc->lock
+ */
+void fuse_flush_writepages(struct inode *inode)
+__releases(fc->lock)
+__acquires(fc->lock)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	size_t crop = i_size_read(inode);
+	struct fuse_req *req;
+
+	while (fi->writectr >= 0 && !list_empty(&fi->queued_writes)) {
+		req = list_entry(fi->queued_writes.next, struct fuse_req, list);
+		list_del_init(&req->list);
+		fuse_send_writepage(fc, req, crop);
+	}
+}
+
+static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_req *req)
+{
+	struct inode *inode = req->inode;
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	mapping_set_error(inode->i_mapping, req->out.h.error);
+	spin_lock(&fc->lock);
+	while (req->misc.write.next) {
+		struct fuse_conn *fc = get_fuse_conn(inode);
+		struct fuse_write_in *inarg = &req->misc.write.in;
+		struct fuse_req *next = req->misc.write.next;
+		req->misc.write.next = next->misc.write.next;
+		next->misc.write.next = NULL;
+		next->ff = fuse_file_get(req->ff);
+		list_add(&next->writepages_entry, &fi->writepages);
+
+		/*
+		 * Skip fuse_flush_writepages() to make it easy to crop requests
+		 * based on primary request size.
+		 *
+		 * 1st case (trivial): there are no concurrent activities using
+		 * fuse_set/release_nowrite.  Then we're on safe side because
+		 * fuse_flush_writepages() would call fuse_send_writepage()
+		 * anyway.
+		 *
+		 * 2nd case: someone called fuse_set_nowrite and it is waiting
+		 * now for completion of all in-flight requests.  This happens
+		 * rarely and no more than once per page, so this should be
+		 * okay.
+		 *
+		 * 3rd case: someone (e.g. fuse_do_setattr()) is in the middle
+		 * of fuse_set_nowrite..fuse_release_nowrite section.  The fact
+		 * that fuse_set_nowrite returned implies that all in-flight
+		 * requests were completed along with all of their secondary
+		 * requests.  Further primary requests are blocked by negative
+		 * writectr.  Hence there cannot be any in-flight requests and
+		 * no invocations of fuse_writepage_end() while we're in
+		 * fuse_set_nowrite..fuse_release_nowrite section.
+		 */
+		fuse_send_writepage(fc, next, inarg->offset + inarg->size);
+	}
+	fi->writectr--;
+	fuse_writepage_finish(fc, req);
+	spin_unlock(&fc->lock);
+	fuse_writepage_free(fc, req);
+}
+
+static struct fuse_file *__fuse_write_file_get(struct fuse_conn *fc,
+					       struct fuse_inode *fi)
+{
+	struct fuse_file *ff = NULL;
+
+	spin_lock(&fc->lock);
+	if (!list_empty(&fi->write_files)) {
+		ff = list_entry(fi->write_files.next, struct fuse_file,
+				write_entry);
+		fuse_file_get(ff);
+	}
+	spin_unlock(&fc->lock);
+
+	return ff;
+}
+
+static struct fuse_file *fuse_write_file_get(struct fuse_conn *fc,
+					     struct fuse_inode *fi)
+{
+	struct fuse_file *ff = __fuse_write_file_get(fc, fi);
+	WARN_ON(!ff);
+	return ff;
+}
+
+int fuse_write_inode(struct inode *inode, struct writeback_control *wbc)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_file *ff;
+	int err;
+
+	ff = __fuse_write_file_get(fc, fi);
+	err = fuse_flush_times(inode, ff);
+	if (ff)
+		fuse_file_put(ff, 0);
+
+	return err;
+}
+
+static int fuse_writepage_locked(struct page *page)
+{
+	struct address_space *mapping = page->mapping;
+	struct inode *inode = mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_req *req;
+	struct page *tmp_page;
+	int error = -ENOMEM;
+
+	set_page_writeback(page);
+
+	req = fuse_request_alloc_nofs(1);
+	if (!req)
+		goto err;
+
+	req->background = 1; /* writeback always goes to bg_queue */
+	tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
+	if (!tmp_page)
+		goto err_free;
+
+	error = -EIO;
+	req->ff = fuse_write_file_get(fc, fi);
+	if (!req->ff)
+		goto err_nofile;
+
+	fuse_write_fill(req, req->ff, page_offset(page), 0);
+
+	copy_highpage(tmp_page, page);
+	req->misc.write.in.write_flags |= FUSE_WRITE_CACHE;
+	req->misc.write.next = NULL;
+	req->in.argpages = 1;
+	req->num_pages = 1;
+	req->pages[0] = tmp_page;
+	req->page_descs[0].offset = 0;
+	req->page_descs[0].length = PAGE_SIZE;
+	req->end = fuse_writepage_end;
+	req->inode = inode;
+
+	inc_bdi_stat(inode_to_bdi(inode), BDI_WRITEBACK);
+	inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP);
+
+	spin_lock(&fc->lock);
+	list_add(&req->writepages_entry, &fi->writepages);
+	list_add_tail(&req->list, &fi->queued_writes);
+	fuse_flush_writepages(inode);
+	spin_unlock(&fc->lock);
+
+	end_page_writeback(page);
+
+	return 0;
+
+err_nofile:
+	__free_page(tmp_page);
+err_free:
+	fuse_request_free(req);
+err:
+	end_page_writeback(page);
+	return error;
+}
+
+static int fuse_writepage(struct page *page, struct writeback_control *wbc)
+{
+	int err;
+
+	if (fuse_page_is_writeback(page->mapping->host, page->index)) {
+		/*
+		 * ->writepages() should be called for sync() and friends.  We
+		 * should only get here on direct reclaim and then we are
+		 * allowed to skip a page which is already in flight
+		 */
+		WARN_ON(wbc->sync_mode == WB_SYNC_ALL);
+
+		redirty_page_for_writepage(wbc, page);
+		return 0;
+	}
+
+	err = fuse_writepage_locked(page);
+	unlock_page(page);
+
+	return err;
+}
+
+struct fuse_fill_wb_data {
+	struct fuse_req *req;
+	struct fuse_file *ff;
+	struct inode *inode;
+	struct page **orig_pages;
+};
+
+static void fuse_writepages_send(struct fuse_fill_wb_data *data)
+{
+	struct fuse_req *req = data->req;
+	struct inode *inode = data->inode;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	int num_pages = req->num_pages;
+	int i;
+
+	req->ff = fuse_file_get(data->ff);
+	spin_lock(&fc->lock);
+	list_add_tail(&req->list, &fi->queued_writes);
+	fuse_flush_writepages(inode);
+	spin_unlock(&fc->lock);
+
+	for (i = 0; i < num_pages; i++)
+		end_page_writeback(data->orig_pages[i]);
+}
+
+static bool fuse_writepage_in_flight(struct fuse_req *new_req,
+				     struct page *page)
+{
+	struct fuse_conn *fc = get_fuse_conn(new_req->inode);
+	struct fuse_inode *fi = get_fuse_inode(new_req->inode);
+	struct fuse_req *tmp;
+	struct fuse_req *old_req;
+	bool found = false;
+	pgoff_t curr_index;
+
+	BUG_ON(new_req->num_pages != 0);
+
+	spin_lock(&fc->lock);
+	list_del(&new_req->writepages_entry);
+	list_for_each_entry(old_req, &fi->writepages, writepages_entry) {
+		BUG_ON(old_req->inode != new_req->inode);
+		curr_index = old_req->misc.write.in.offset >> PAGE_CACHE_SHIFT;
+		if (curr_index <= page->index &&
+		    page->index < curr_index + old_req->num_pages) {
+			found = true;
+			break;
+		}
+	}
+	if (!found) {
+		list_add(&new_req->writepages_entry, &fi->writepages);
+		goto out_unlock;
+	}
+
+	new_req->num_pages = 1;
+	for (tmp = old_req; tmp != NULL; tmp = tmp->misc.write.next) {
+		BUG_ON(tmp->inode != new_req->inode);
+		curr_index = tmp->misc.write.in.offset >> PAGE_CACHE_SHIFT;
+		if (tmp->num_pages == 1 &&
+		    curr_index == page->index) {
+			old_req = tmp;
+		}
+	}
+
+	if (old_req->num_pages == 1 && (old_req->state == FUSE_REQ_INIT ||
+					old_req->state == FUSE_REQ_PENDING)) {
+		struct backing_dev_info *bdi = inode_to_bdi(page->mapping->host);
+
+		copy_highpage(old_req->pages[0], page);
+		spin_unlock(&fc->lock);
+
+		dec_bdi_stat(bdi, BDI_WRITEBACK);
+		dec_zone_page_state(page, NR_WRITEBACK_TEMP);
+		bdi_writeout_inc(bdi);
+		fuse_writepage_free(fc, new_req);
+		fuse_request_free(new_req);
+		goto out;
+	} else {
+		new_req->misc.write.next = old_req->misc.write.next;
+		old_req->misc.write.next = new_req;
+	}
+out_unlock:
+	spin_unlock(&fc->lock);
+out:
+	return found;
+}
+
+static int fuse_writepages_fill(struct page *page,
+		struct writeback_control *wbc, void *_data)
+{
+	struct fuse_fill_wb_data *data = _data;
+	struct fuse_req *req = data->req;
+	struct inode *inode = data->inode;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct page *tmp_page;
+	bool is_writeback;
+	int err;
+
+	if (!data->ff) {
+		err = -EIO;
+		data->ff = fuse_write_file_get(fc, get_fuse_inode(inode));
+		if (!data->ff)
+			goto out_unlock;
+	}
+
+	/*
+	 * Being under writeback is unlikely but possible.  For example direct
+	 * read to an mmaped fuse file will set the page dirty twice; once when
+	 * the pages are faulted with get_user_pages(), and then after the read
+	 * completed.
+	 */
+	is_writeback = fuse_page_is_writeback(inode, page->index);
+
+	if (req && req->num_pages &&
+	    (is_writeback || req->num_pages == FUSE_MAX_PAGES_PER_REQ ||
+	     (req->num_pages + 1) * PAGE_CACHE_SIZE > fc->max_write ||
+	     data->orig_pages[req->num_pages - 1]->index + 1 != page->index)) {
+		fuse_writepages_send(data);
+		data->req = NULL;
+	}
+	err = -ENOMEM;
+	tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
+	if (!tmp_page)
+		goto out_unlock;
+
+	/*
+	 * The page must not be redirtied until the writeout is completed
+	 * (i.e. userspace has sent a reply to the write request).  Otherwise
+	 * there could be more than one temporary page instance for each real
+	 * page.
+	 *
+	 * This is ensured by holding the page lock in page_mkwrite() while
+	 * checking fuse_page_is_writeback().  We already hold the page lock
+	 * since clear_page_dirty_for_io() and keep it held until we add the
+	 * request to the fi->writepages list and increment req->num_pages.
+	 * After this fuse_page_is_writeback() will indicate that the page is
+	 * under writeback, so we can release the page lock.
+	 */
+	if (data->req == NULL) {
+		struct fuse_inode *fi = get_fuse_inode(inode);
+
+		err = -ENOMEM;
+		req = fuse_request_alloc_nofs(FUSE_MAX_PAGES_PER_REQ);
+		if (!req) {
+			__free_page(tmp_page);
+			goto out_unlock;
+		}
+
+		fuse_write_fill(req, data->ff, page_offset(page), 0);
+		req->misc.write.in.write_flags |= FUSE_WRITE_CACHE;
+		req->misc.write.next = NULL;
+		req->in.argpages = 1;
+		req->background = 1;
+		req->num_pages = 0;
+		req->end = fuse_writepage_end;
+		req->inode = inode;
+
+		spin_lock(&fc->lock);
+		list_add(&req->writepages_entry, &fi->writepages);
+		spin_unlock(&fc->lock);
+
+		data->req = req;
+	}
+	set_page_writeback(page);
+
+	copy_highpage(tmp_page, page);
+	req->pages[req->num_pages] = tmp_page;
+	req->page_descs[req->num_pages].offset = 0;
+	req->page_descs[req->num_pages].length = PAGE_SIZE;
+
+	inc_bdi_stat(inode_to_bdi(inode), BDI_WRITEBACK);
+	inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP);
+
+	err = 0;
+	if (is_writeback && fuse_writepage_in_flight(req, page)) {
+		end_page_writeback(page);
+		data->req = NULL;
+		goto out_unlock;
+	}
+	data->orig_pages[req->num_pages] = page;
+
+	/*
+	 * Protected by fc->lock against concurrent access by
+	 * fuse_page_is_writeback().
+	 */
+	spin_lock(&fc->lock);
+	req->num_pages++;
+	spin_unlock(&fc->lock);
+
+out_unlock:
+	unlock_page(page);
+
+	return err;
+}
+
+static int fuse_writepages(struct address_space *mapping,
+			   struct writeback_control *wbc)
+{
+	struct inode *inode = mapping->host;
+	struct fuse_fill_wb_data data;
+	int err;
+
+	err = -EIO;
+	if (is_bad_inode(inode))
+		goto out;
+
+	data.inode = inode;
+	data.req = NULL;
+	data.ff = NULL;
+
+	err = -ENOMEM;
+	data.orig_pages = kcalloc(FUSE_MAX_PAGES_PER_REQ,
+				  sizeof(struct page *),
+				  GFP_NOFS);
+	if (!data.orig_pages)
+		goto out;
+
+	err = write_cache_pages(mapping, wbc, fuse_writepages_fill, &data);
+	if (data.req) {
+		/* Ignore errors if we can write at least one page */
+		BUG_ON(!data.req->num_pages);
+		fuse_writepages_send(&data);
+		err = 0;
+	}
+	if (data.ff)
+		fuse_file_put(data.ff, false);
+
+	kfree(data.orig_pages);
+out:
+	return err;
+}
+
+/*
+ * It's worthy to make sure that space is reserved on disk for the write,
+ * but how to implement it without killing performance need more thinking.
+ */
+static int fuse_write_begin(struct file *file, struct address_space *mapping,
+		loff_t pos, unsigned len, unsigned flags,
+		struct page **pagep, void **fsdata)
+{
+	pgoff_t index = pos >> PAGE_CACHE_SHIFT;
+	struct fuse_conn *fc = get_fuse_conn(file_inode(file));
+	struct page *page;
+	loff_t fsize;
+	int err = -ENOMEM;
+
+	WARN_ON(!fc->writeback_cache);
+
+	page = grab_cache_page_write_begin(mapping, index, flags);
+	if (!page)
+		goto error;
+
+	fuse_wait_on_page_writeback(mapping->host, page->index);
+
+	if (PageUptodate(page) || len == PAGE_CACHE_SIZE)
+		goto success;
+	/*
+	 * Check if the start this page comes after the end of file, in which
+	 * case the readpage can be optimized away.
+	 */
+	fsize = i_size_read(mapping->host);
+	if (fsize <= (pos & PAGE_CACHE_MASK)) {
+		size_t off = pos & ~PAGE_CACHE_MASK;
+		if (off)
+			zero_user_segment(page, 0, off);
+		goto success;
+	}
+	err = fuse_do_readpage(file, page);
+	if (err)
+		goto cleanup;
+success:
+	*pagep = page;
+	return 0;
+
+cleanup:
+	unlock_page(page);
+	page_cache_release(page);
+error:
+	return err;
+}
+
+static int fuse_write_end(struct file *file, struct address_space *mapping,
+		loff_t pos, unsigned len, unsigned copied,
+		struct page *page, void *fsdata)
+{
+	struct inode *inode = page->mapping->host;
+
+	if (!PageUptodate(page)) {
+		/* Zero any unwritten bytes at the end of the page */
+		size_t endoff = (pos + copied) & ~PAGE_CACHE_MASK;
+		if (endoff)
+			zero_user_segment(page, endoff, PAGE_CACHE_SIZE);
+		SetPageUptodate(page);
+	}
+
+	fuse_write_update_size(inode, pos + copied);
+	set_page_dirty(page);
+	unlock_page(page);
+	page_cache_release(page);
+
+	return copied;
+}
+
+static int fuse_launder_page(struct page *page)
+{
+	int err = 0;
+	if (clear_page_dirty_for_io(page)) {
+		struct inode *inode = page->mapping->host;
+		err = fuse_writepage_locked(page);
+		if (!err)
+			fuse_wait_on_page_writeback(inode, page->index);
+	}
+	return err;
+}
+
+/*
+ * Write back dirty pages now, because there may not be any suitable
+ * open files later
+ */
+static void fuse_vma_close(struct vm_area_struct *vma)
+{
+	filemap_write_and_wait(vma->vm_file->f_mapping);
+}
+
+/*
+ * Wait for writeback against this page to complete before allowing it
+ * to be marked dirty again, and hence written back again, possibly
+ * before the previous writepage completed.
+ *
+ * Block here, instead of in ->writepage(), so that the userspace fs
+ * can only block processes actually operating on the filesystem.
+ *
+ * Otherwise unprivileged userspace fs would be able to block
+ * unrelated:
+ *
+ * - page migration
+ * - sync(2)
+ * - try_to_free_pages() with order > PAGE_ALLOC_COSTLY_ORDER
+ */
+static int fuse_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+	struct page *page = vmf->page;
+	struct inode *inode = file_inode(vma->vm_file);
+
+	file_update_time(vma->vm_file);
+	lock_page(page);
+	if (page->mapping != inode->i_mapping) {
+		unlock_page(page);
+		return VM_FAULT_NOPAGE;
+	}
+
+	fuse_wait_on_page_writeback(inode, page->index);
+	return VM_FAULT_LOCKED;
+}
+
+static const struct vm_operations_struct fuse_file_vm_ops = {
+	.close		= fuse_vma_close,
+	.fault		= filemap_fault,
+	.map_pages	= filemap_map_pages,
+	.page_mkwrite	= fuse_page_mkwrite,
+};
+
+static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
+		fuse_link_write_file(file);
+
+	file_accessed(file);
+	vma->vm_ops = &fuse_file_vm_ops;
+	return 0;
+}
+
+static int fuse_direct_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	/* Can't provide the coherency needed for MAP_SHARED */
+	if (vma->vm_flags & VM_MAYSHARE)
+		return -ENODEV;
+
+	invalidate_inode_pages2(file->f_mapping);
+
+	return generic_file_mmap(file, vma);
+}
+
+static int convert_fuse_file_lock(const struct fuse_file_lock *ffl,
+				  struct file_lock *fl)
+{
+	switch (ffl->type) {
+	case F_UNLCK:
+		break;
+
+	case F_RDLCK:
+	case F_WRLCK:
+		if (ffl->start > OFFSET_MAX || ffl->end > OFFSET_MAX ||
+		    ffl->end < ffl->start)
+			return -EIO;
+
+		fl->fl_start = ffl->start;
+		fl->fl_end = ffl->end;
+		fl->fl_pid = ffl->pid;
+		break;
+
+	default:
+		return -EIO;
+	}
+	fl->fl_type = ffl->type;
+	return 0;
+}
+
+static void fuse_lk_fill(struct fuse_args *args, struct file *file,
+			 const struct file_lock *fl, int opcode, pid_t pid,
+			 int flock, struct fuse_lk_in *inarg)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_file *ff = file->private_data;
+
+	memset(inarg, 0, sizeof(*inarg));
+	inarg->fh = ff->fh;
+	inarg->owner = fuse_lock_owner_id(fc, fl->fl_owner);
+	inarg->lk.start = fl->fl_start;
+	inarg->lk.end = fl->fl_end;
+	inarg->lk.type = fl->fl_type;
+	inarg->lk.pid = pid;
+	if (flock)
+		inarg->lk_flags |= FUSE_LK_FLOCK;
+	args->in.h.opcode = opcode;
+	args->in.h.nodeid = get_node_id(inode);
+	args->in.numargs = 1;
+	args->in.args[0].size = sizeof(*inarg);
+	args->in.args[0].value = inarg;
+}
+
+static int fuse_getlk(struct file *file, struct file_lock *fl)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	FUSE_ARGS(args);
+	struct fuse_lk_in inarg;
+	struct fuse_lk_out outarg;
+	int err;
+
+	fuse_lk_fill(&args, file, fl, FUSE_GETLK, 0, 0, &inarg);
+	args.out.numargs = 1;
+	args.out.args[0].size = sizeof(outarg);
+	args.out.args[0].value = &outarg;
+	err = fuse_simple_request(fc, &args);
+	if (!err)
+		err = convert_fuse_file_lock(&outarg.lk, fl);
+
+	return err;
+}
+
+static int fuse_setlk(struct file *file, struct file_lock *fl, int flock)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	FUSE_ARGS(args);
+	struct fuse_lk_in inarg;
+	int opcode = (fl->fl_flags & FL_SLEEP) ? FUSE_SETLKW : FUSE_SETLK;
+	pid_t pid = fl->fl_type != F_UNLCK ? current->tgid : 0;
+	int err;
+
+	if (fl->fl_lmops && fl->fl_lmops->lm_grant) {
+		/* NLM needs asynchronous locks, which we don't support yet */
+		return -ENOLCK;
+	}
+
+	/* Unlock on close is handled by the flush method */
+	if (fl->fl_flags & FL_CLOSE)
+		return 0;
+
+	fuse_lk_fill(&args, file, fl, opcode, pid, flock, &inarg);
+	err = fuse_simple_request(fc, &args);
+
+	/* locking is restartable */
+	if (err == -EINTR)
+		err = -ERESTARTSYS;
+
+	return err;
+}
+
+static int fuse_file_lock(struct file *file, int cmd, struct file_lock *fl)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	int err;
+
+	if (cmd == F_CANCELLK) {
+		err = 0;
+	} else if (cmd == F_GETLK) {
+		if (fc->no_lock) {
+			posix_test_lock(file, fl);
+			err = 0;
+		} else
+			err = fuse_getlk(file, fl);
+	} else {
+		if (fc->no_lock)
+			err = posix_lock_file(file, fl, NULL);
+		else
+			err = fuse_setlk(file, fl, 0);
+	}
+	return err;
+}
+
+static int fuse_file_flock(struct file *file, int cmd, struct file_lock *fl)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	int err;
+
+	if (fc->no_flock) {
+		err = flock_lock_file_wait(file, fl);
+	} else {
+		struct fuse_file *ff = file->private_data;
+
+		/* emulate flock with POSIX locks */
+		ff->flock = true;
+		err = fuse_setlk(file, fl, 1);
+	}
+
+	return err;
+}
+
+static sector_t fuse_bmap(struct address_space *mapping, sector_t block)
+{
+	struct inode *inode = mapping->host;
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	FUSE_ARGS(args);
+	struct fuse_bmap_in inarg;
+	struct fuse_bmap_out outarg;
+	int err;
+
+	if (!inode->i_sb->s_bdev || fc->no_bmap)
+		return 0;
+
+	memset(&inarg, 0, sizeof(inarg));
+	inarg.block = block;
+	inarg.blocksize = inode->i_sb->s_blocksize;
+	args.in.h.opcode = FUSE_BMAP;
+	args.in.h.nodeid = get_node_id(inode);
+	args.in.numargs = 1;
+	args.in.args[0].size = sizeof(inarg);
+	args.in.args[0].value = &inarg;
+	args.out.numargs = 1;
+	args.out.args[0].size = sizeof(outarg);
+	args.out.args[0].value = &outarg;
+	err = fuse_simple_request(fc, &args);
+	if (err == -ENOSYS)
+		fc->no_bmap = 1;
+
+	return err ? 0 : outarg.block;
+}
+
+static loff_t fuse_file_llseek(struct file *file, loff_t offset, int whence)
+{
+	loff_t retval;
+	struct inode *inode = file_inode(file);
+
+	/* No i_mutex protection necessary for SEEK_CUR and SEEK_SET */
+	if (whence == SEEK_CUR || whence == SEEK_SET)
+		return generic_file_llseek(file, offset, whence);
+
+	mutex_lock(&inode->i_mutex);
+	retval = fuse_update_attributes(inode, NULL, file, NULL);
+	if (!retval)
+		retval = generic_file_llseek(file, offset, whence);
+	mutex_unlock(&inode->i_mutex);
+
+	return retval;
+}
+
+static int fuse_ioctl_copy_user(struct page **pages, struct iovec *iov,
+			unsigned int nr_segs, size_t bytes, bool to_user)
+{
+	struct iov_iter ii;
+	int page_idx = 0;
+
+	if (!bytes)
+		return 0;
+
+	iov_iter_init(&ii, to_user ? READ : WRITE, iov, nr_segs, bytes);
+
+	while (iov_iter_count(&ii)) {
+		struct page *page = pages[page_idx++];
+		size_t todo = min_t(size_t, PAGE_SIZE, iov_iter_count(&ii));
+		void *kaddr;
+
+		kaddr = kmap(page);
+
+		while (todo) {
+			char __user *uaddr = ii.iov->iov_base + ii.iov_offset;
+			size_t iov_len = ii.iov->iov_len - ii.iov_offset;
+			size_t copy = min(todo, iov_len);
+			size_t left;
+
+			if (!to_user)
+				left = copy_from_user(kaddr, uaddr, copy);
+			else
+				left = copy_to_user(uaddr, kaddr, copy);
+
+			if (unlikely(left))
+				return -EFAULT;
+
+			iov_iter_advance(&ii, copy);
+			todo -= copy;
+			kaddr += copy;
+		}
+
+		kunmap(page);
+	}
+
+	return 0;
+}
+
+/*
+ * CUSE servers compiled on 32bit broke on 64bit kernels because the
+ * ABI was defined to be 'struct iovec' which is different on 32bit
+ * and 64bit.  Fortunately we can determine which structure the server
+ * used from the size of the reply.
+ */
+static int fuse_copy_ioctl_iovec_old(struct iovec *dst, void *src,
+				     size_t transferred, unsigned count,
+				     bool is_compat)
+{
+#ifdef CONFIG_COMPAT
+	if (count * sizeof(struct compat_iovec) == transferred) {
+		struct compat_iovec *ciov = src;
+		unsigned i;
+
+		/*
+		 * With this interface a 32bit server cannot support
+		 * non-compat (i.e. ones coming from 64bit apps) ioctl
+		 * requests
+		 */
+		if (!is_compat)
+			return -EINVAL;
+
+		for (i = 0; i < count; i++) {
+			dst[i].iov_base = compat_ptr(ciov[i].iov_base);
+			dst[i].iov_len = ciov[i].iov_len;
+		}
+		return 0;
+	}
+#endif
+
+	if (count * sizeof(struct iovec) != transferred)
+		return -EIO;
+
+	memcpy(dst, src, transferred);
+	return 0;
+}
+
+/* Make sure iov_length() won't overflow */
+static int fuse_verify_ioctl_iov(struct iovec *iov, size_t count)
+{
+	size_t n;
+	u32 max = FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT;
+
+	for (n = 0; n < count; n++, iov++) {
+		if (iov->iov_len > (size_t) max)
+			return -ENOMEM;
+		max -= iov->iov_len;
+	}
+	return 0;
+}
+
+static int fuse_copy_ioctl_iovec(struct fuse_conn *fc, struct iovec *dst,
+				 void *src, size_t transferred, unsigned count,
+				 bool is_compat)
+{
+	unsigned i;
+	struct fuse_ioctl_iovec *fiov = src;
+
+	if (fc->minor < 16) {
+		return fuse_copy_ioctl_iovec_old(dst, src, transferred,
+						 count, is_compat);
+	}
+
+	if (count * sizeof(struct fuse_ioctl_iovec) != transferred)
+		return -EIO;
+
+	for (i = 0; i < count; i++) {
+		/* Did the server supply an inappropriate value? */
+		if (fiov[i].base != (unsigned long) fiov[i].base ||
+		    fiov[i].len != (unsigned long) fiov[i].len)
+			return -EIO;
+
+		dst[i].iov_base = (void __user *) (unsigned long) fiov[i].base;
+		dst[i].iov_len = (size_t) fiov[i].len;
+
+#ifdef CONFIG_COMPAT
+		if (is_compat &&
+		    (ptr_to_compat(dst[i].iov_base) != fiov[i].base ||
+		     (compat_size_t) dst[i].iov_len != fiov[i].len))
+			return -EIO;
+#endif
+	}
+
+	return 0;
+}
+
+
+/*
+ * For ioctls, there is no generic way to determine how much memory
+ * needs to be read and/or written.  Furthermore, ioctls are allowed
+ * to dereference the passed pointer, so the parameter requires deep
+ * copying but FUSE has no idea whatsoever about what to copy in or
+ * out.
+ *
+ * This is solved by allowing FUSE server to retry ioctl with
+ * necessary in/out iovecs.  Let's assume the ioctl implementation
+ * needs to read in the following structure.
+ *
+ * struct a {
+ *	char	*buf;
+ *	size_t	buflen;
+ * }
+ *
+ * On the first callout to FUSE server, inarg->in_size and
+ * inarg->out_size will be NULL; then, the server completes the ioctl
+ * with FUSE_IOCTL_RETRY set in out->flags, out->in_iovs set to 1 and
+ * the actual iov array to
+ *
+ * { { .iov_base = inarg.arg,	.iov_len = sizeof(struct a) } }
+ *
+ * which tells FUSE to copy in the requested area and retry the ioctl.
+ * On the second round, the server has access to the structure and
+ * from that it can tell what to look for next, so on the invocation,
+ * it sets FUSE_IOCTL_RETRY, out->in_iovs to 2 and iov array to
+ *
+ * { { .iov_base = inarg.arg,	.iov_len = sizeof(struct a)	},
+ *   { .iov_base = a.buf,	.iov_len = a.buflen		} }
+ *
+ * FUSE will copy both struct a and the pointed buffer from the
+ * process doing the ioctl and retry ioctl with both struct a and the
+ * buffer.
+ *
+ * This time, FUSE server has everything it needs and completes ioctl
+ * without FUSE_IOCTL_RETRY which finishes the ioctl call.
+ *
+ * Copying data out works the same way.
+ *
+ * Note that if FUSE_IOCTL_UNRESTRICTED is clear, the kernel
+ * automatically initializes in and out iovs by decoding @cmd with
+ * _IOC_* macros and the server is not allowed to request RETRY.  This
+ * limits ioctl data transfers to well-formed ioctls and is the forced
+ * behavior for all FUSE servers.
+ */
+long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
+		   unsigned int flags)
+{
+	struct fuse_file *ff = file->private_data;
+	struct fuse_conn *fc = ff->fc;
+	struct fuse_ioctl_in inarg = {
+		.fh = ff->fh,
+		.cmd = cmd,
+		.arg = arg,
+		.flags = flags
+	};
+	struct fuse_ioctl_out outarg;
+	struct fuse_req *req = NULL;
+	struct page **pages = NULL;
+	struct iovec *iov_page = NULL;
+	struct iovec *in_iov = NULL, *out_iov = NULL;
+	unsigned int in_iovs = 0, out_iovs = 0, num_pages = 0, max_pages;
+	size_t in_size, out_size, transferred;
+	int err;
+
+#if BITS_PER_LONG == 32
+	inarg.flags |= FUSE_IOCTL_32BIT;
+#else
+	if (flags & FUSE_IOCTL_COMPAT)
+		inarg.flags |= FUSE_IOCTL_32BIT;
+#endif
+
+	/* assume all the iovs returned by client always fits in a page */
+	BUILD_BUG_ON(sizeof(struct fuse_ioctl_iovec) * FUSE_IOCTL_MAX_IOV > PAGE_SIZE);
+
+	err = -ENOMEM;
+	pages = kcalloc(FUSE_MAX_PAGES_PER_REQ, sizeof(pages[0]), GFP_KERNEL);
+	iov_page = (struct iovec *) __get_free_page(GFP_KERNEL);
+	if (!pages || !iov_page)
+		goto out;
+
+	/*
+	 * If restricted, initialize IO parameters as encoded in @cmd.
+	 * RETRY from server is not allowed.
+	 */
+	if (!(flags & FUSE_IOCTL_UNRESTRICTED)) {
+		struct iovec *iov = iov_page;
+
+		iov->iov_base = (void __user *)arg;
+		iov->iov_len = _IOC_SIZE(cmd);
+
+		if (_IOC_DIR(cmd) & _IOC_WRITE) {
+			in_iov = iov;
+			in_iovs = 1;
+		}
+
+		if (_IOC_DIR(cmd) & _IOC_READ) {
+			out_iov = iov;
+			out_iovs = 1;
+		}
+	}
+
+ retry:
+	inarg.in_size = in_size = iov_length(in_iov, in_iovs);
+	inarg.out_size = out_size = iov_length(out_iov, out_iovs);
+
+	/*
+	 * Out data can be used either for actual out data or iovs,
+	 * make sure there always is at least one page.
+	 */
+	out_size = max_t(size_t, out_size, PAGE_SIZE);
+	max_pages = DIV_ROUND_UP(max(in_size, out_size), PAGE_SIZE);
+
+	/* make sure there are enough buffer pages and init request with them */
+	err = -ENOMEM;
+	if (max_pages > FUSE_MAX_PAGES_PER_REQ)
+		goto out;
+	while (num_pages < max_pages) {
+		pages[num_pages] = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
+		if (!pages[num_pages])
+			goto out;
+		num_pages++;
+	}
+
+	req = fuse_get_req(fc, num_pages);
+	if (IS_ERR(req)) {
+		err = PTR_ERR(req);
+		req = NULL;
+		goto out;
+	}
+	memcpy(req->pages, pages, sizeof(req->pages[0]) * num_pages);
+	req->num_pages = num_pages;
+	fuse_page_descs_length_init(req, 0, req->num_pages);
+
+	/* okay, let's send it to the client */
+	req->in.h.opcode = FUSE_IOCTL;
+	req->in.h.nodeid = ff->nodeid;
+	req->in.numargs = 1;
+	req->in.args[0].size = sizeof(inarg);
+	req->in.args[0].value = &inarg;
+	if (in_size) {
+		req->in.numargs++;
+		req->in.args[1].size = in_size;
+		req->in.argpages = 1;
+
+		err = fuse_ioctl_copy_user(pages, in_iov, in_iovs, in_size,
+					   false);
+		if (err)
+			goto out;
+	}
+
+	req->out.numargs = 2;
+	req->out.args[0].size = sizeof(outarg);
+	req->out.args[0].value = &outarg;
+	req->out.args[1].size = out_size;
+	req->out.argpages = 1;
+	req->out.argvar = 1;
+
+	fuse_request_send(fc, req);
+	err = req->out.h.error;
+	transferred = req->out.args[1].size;
+	fuse_put_request(fc, req);
+	req = NULL;
+	if (err)
+		goto out;
+
+	/* did it ask for retry? */
+	if (outarg.flags & FUSE_IOCTL_RETRY) {
+		void *vaddr;
+
+		/* no retry if in restricted mode */
+		err = -EIO;
+		if (!(flags & FUSE_IOCTL_UNRESTRICTED))
+			goto out;
+
+		in_iovs = outarg.in_iovs;
+		out_iovs = outarg.out_iovs;
+
+		/*
+		 * Make sure things are in boundary, separate checks
+		 * are to protect against overflow.
+		 */
+		err = -ENOMEM;
+		if (in_iovs > FUSE_IOCTL_MAX_IOV ||
+		    out_iovs > FUSE_IOCTL_MAX_IOV ||
+		    in_iovs + out_iovs > FUSE_IOCTL_MAX_IOV)
+			goto out;
+
+		vaddr = kmap_atomic(pages[0]);
+		err = fuse_copy_ioctl_iovec(fc, iov_page, vaddr,
+					    transferred, in_iovs + out_iovs,
+					    (flags & FUSE_IOCTL_COMPAT) != 0);
+		kunmap_atomic(vaddr);
+		if (err)
+			goto out;
+
+		in_iov = iov_page;
+		out_iov = in_iov + in_iovs;
+
+		err = fuse_verify_ioctl_iov(in_iov, in_iovs);
+		if (err)
+			goto out;
+
+		err = fuse_verify_ioctl_iov(out_iov, out_iovs);
+		if (err)
+			goto out;
+
+		goto retry;
+	}
+
+	err = -EIO;
+	if (transferred > inarg.out_size)
+		goto out;
+
+	err = fuse_ioctl_copy_user(pages, out_iov, out_iovs, transferred, true);
+ out:
+	if (req)
+		fuse_put_request(fc, req);
+	free_page((unsigned long) iov_page);
+	while (num_pages)
+		__free_page(pages[--num_pages]);
+	kfree(pages);
+
+	return err ? err : outarg.result;
+}
+EXPORT_SYMBOL_GPL(fuse_do_ioctl);
+
+long fuse_ioctl_common(struct file *file, unsigned int cmd,
+		       unsigned long arg, unsigned int flags)
+{
+	struct inode *inode = file_inode(file);
+	struct fuse_conn *fc = get_fuse_conn(inode);
+
+	if (!fuse_allow_current_process(fc))
+		return -EACCES;
+
+	if (is_bad_inode(inode))
+		return -EIO;
+
+	return fuse_do_ioctl(file, cmd, arg, flags);
+}
+
+static long fuse_file_ioctl(struct file *file, unsigned int cmd,
+			    unsigned long arg)
+{
+	return fuse_ioctl_common(file, cmd, arg, 0);
+}
+
+static long fuse_file_compat_ioctl(struct file *file, unsigned int cmd,
+				   unsigned long arg)
+{
+	return fuse_ioctl_common(file, cmd, arg, FUSE_IOCTL_COMPAT);
+}
+
+/*
+ * All files which have been polled are linked to RB tree
+ * fuse_conn->polled_files which is indexed by kh.  Walk the tree and
+ * find the matching one.
+ */
+static struct rb_node **fuse_find_polled_node(struct fuse_conn *fc, u64 kh,
+					      struct rb_node **parent_out)
+{
+	struct rb_node **link = &fc->polled_files.rb_node;
+	struct rb_node *last = NULL;
+
+	while (*link) {
+		struct fuse_file *ff;
+
+		last = *link;
+		ff = rb_entry(last, struct fuse_file, polled_node);
+
+		if (kh < ff->kh)
+			link = &last->rb_left;
+		else if (kh > ff->kh)
+			link = &last->rb_right;
+		else
+			return link;
+	}
+
+	if (parent_out)
+		*parent_out = last;
+	return link;
+}
+
+/*
+ * The file is about to be polled.  Make sure it's on the polled_files
+ * RB tree.  Note that files once added to the polled_files tree are
+ * not removed before the file is released.  This is because a file
+ * polled once is likely to be polled again.
+ */
+static void fuse_register_polled_file(struct fuse_conn *fc,
+				      struct fuse_file *ff)
+{
+	spin_lock(&fc->lock);
+	if (RB_EMPTY_NODE(&ff->polled_node)) {
+		struct rb_node **link, *uninitialized_var(parent);
+
+		link = fuse_find_polled_node(fc, ff->kh, &parent);
+		BUG_ON(*link);
+		rb_link_node(&ff->polled_node, parent, link);
+		rb_insert_color(&ff->polled_node, &fc->polled_files);
+	}
+	spin_unlock(&fc->lock);
+}
+
+unsigned fuse_file_poll(struct file *file, poll_table *wait)
+{
+	struct fuse_file *ff = file->private_data;
+	struct fuse_conn *fc = ff->fc;
+	struct fuse_poll_in inarg = { .fh = ff->fh, .kh = ff->kh };
+	struct fuse_poll_out outarg;
+	FUSE_ARGS(args);
+	int err;
+
+	if (fc->no_poll)
+		return DEFAULT_POLLMASK;
+
+	poll_wait(file, &ff->poll_wait, wait);
+	inarg.events = (__u32)poll_requested_events(wait);
+
+	/*
+	 * Ask for notification iff there's someone waiting for it.
+	 * The client may ignore the flag and always notify.
+	 */
+	if (waitqueue_active(&ff->poll_wait)) {
+		inarg.flags |= FUSE_POLL_SCHEDULE_NOTIFY;
+		fuse_register_polled_file(fc, ff);
+	}
+
+	args.in.h.opcode = FUSE_POLL;
+	args.in.h.nodeid = ff->nodeid;
+	args.in.numargs = 1;
+	args.in.args[0].size = sizeof(inarg);
+	args.in.args[0].value = &inarg;
+	args.out.numargs = 1;
+	args.out.args[0].size = sizeof(outarg);
+	args.out.args[0].value = &outarg;
+	err = fuse_simple_request(fc, &args);
+
+	if (!err)
+		return outarg.revents;
+	if (err == -ENOSYS) {
+		fc->no_poll = 1;
+		return DEFAULT_POLLMASK;
+	}
+	return POLLERR;
+}
+EXPORT_SYMBOL_GPL(fuse_file_poll);
+
+/*
+ * This is called from fuse_handle_notify() on FUSE_NOTIFY_POLL and
+ * wakes up the poll waiters.
+ */
+int fuse_notify_poll_wakeup(struct fuse_conn *fc,
+			    struct fuse_notify_poll_wakeup_out *outarg)
+{
+	u64 kh = outarg->kh;
+	struct rb_node **link;
+
+	spin_lock(&fc->lock);
+
+	link = fuse_find_polled_node(fc, kh, NULL);
+	if (*link) {
+		struct fuse_file *ff;
+
+		ff = rb_entry(*link, struct fuse_file, polled_node);
+		wake_up_interruptible_sync(&ff->poll_wait);
+	}
+
+	spin_unlock(&fc->lock);
+	return 0;
+}
+
+static void fuse_do_truncate(struct file *file)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct iattr attr;
+
+	attr.ia_valid = ATTR_SIZE;
+	attr.ia_size = i_size_read(inode);
+
+	attr.ia_file = file;
+	attr.ia_valid |= ATTR_FILE;
+
+	fuse_do_setattr(inode, &attr, file);
+}
+
+static inline loff_t fuse_round_up(loff_t off)
+{
+	return round_up(off, FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);
+}
+
+static ssize_t
+fuse_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t offset)
+{
+	DECLARE_COMPLETION_ONSTACK(wait);
+	ssize_t ret = 0;
+	struct file *file = iocb->ki_filp;
+	struct fuse_file *ff = file->private_data;
+	bool async_dio = ff->fc->async_dio;
+	loff_t pos = 0;
+	struct inode *inode;
+	loff_t i_size;
+	size_t count = iov_iter_count(iter);
+	struct fuse_io_priv *io;
+
+	pos = offset;
+	inode = file->f_mapping->host;
+	i_size = i_size_read(inode);
+
+	if ((iov_iter_rw(iter) == READ) && (offset > i_size))
+		return 0;
+
+	/* optimization for short read */
+	if (async_dio && iov_iter_rw(iter) != WRITE && offset + count > i_size) {
+		if (offset >= i_size)
+			return 0;
+		iov_iter_truncate(iter, fuse_round_up(i_size - offset));
+		count = iov_iter_count(iter);
+	}
+
+	io = kmalloc(sizeof(struct fuse_io_priv), GFP_KERNEL);
+	if (!io)
+		return -ENOMEM;
+	spin_lock_init(&io->lock);
+	io->reqs = 1;
+	io->bytes = -1;
+	io->size = 0;
+	io->offset = offset;
+	io->write = (iov_iter_rw(iter) == WRITE);
+	io->err = 0;
+	io->file = file;
+	/*
+	 * By default, we want to optimize all I/Os with async request
+	 * submission to the client filesystem if supported.
+	 */
+	io->async = async_dio;
+	io->iocb = iocb;
+
+	/*
+	 * We cannot asynchronously extend the size of a file. We have no method
+	 * to wait on real async I/O requests, so we must submit this request
+	 * synchronously.
+	 */
+	if (!is_sync_kiocb(iocb) && (offset + count > i_size) &&
+	    iov_iter_rw(iter) == WRITE)
+		io->async = false;
+
+	if (io->async && is_sync_kiocb(iocb))
+		io->done = &wait;
+
+	if (iov_iter_rw(iter) == WRITE) {
+		ret = fuse_direct_io(io, iter, &pos, FUSE_DIO_WRITE);
+		fuse_invalidate_attr(inode);
+	} else {
+		ret = __fuse_direct_read(io, iter, &pos);
+	}
+
+	if (io->async) {
+		fuse_aio_complete(io, ret < 0 ? ret : 0, -1);
+
+		/* we have a non-extending, async request, so return */
+		if (!is_sync_kiocb(iocb))
+			return -EIOCBQUEUED;
+
+		wait_for_completion(&wait);
+		ret = fuse_get_res_by_io(io);
+	}
+
+	kfree(io);
+
+	if (iov_iter_rw(iter) == WRITE) {
+		if (ret > 0)
+			fuse_write_update_size(inode, pos);
+		else if (ret < 0 && offset + count > i_size)
+			fuse_do_truncate(file);
+	}
+
+	return ret;
+}
+
+static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
+				loff_t length)
+{
+	struct fuse_file *ff = file->private_data;
+	struct inode *inode = file_inode(file);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+	struct fuse_conn *fc = ff->fc;
+	FUSE_ARGS(args);
+	struct fuse_fallocate_in inarg = {
+		.fh = ff->fh,
+		.offset = offset,
+		.length = length,
+		.mode = mode
+	};
+	int err;
+	bool lock_inode = !(mode & FALLOC_FL_KEEP_SIZE) ||
+			   (mode & FALLOC_FL_PUNCH_HOLE);
+
+	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
+		return -EOPNOTSUPP;
+
+	if (fc->no_fallocate)
+		return -EOPNOTSUPP;
+
+	if (lock_inode) {
+		mutex_lock(&inode->i_mutex);
+		if (mode & FALLOC_FL_PUNCH_HOLE) {
+			loff_t endbyte = offset + length - 1;
+			err = filemap_write_and_wait_range(inode->i_mapping,
+							   offset, endbyte);
+			if (err)
+				goto out;
+
+			fuse_sync_writes(inode);
+		}
+	}
+
+	if (!(mode & FALLOC_FL_KEEP_SIZE))
+		set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
+
+	args.in.h.opcode = FUSE_FALLOCATE;
+	args.in.h.nodeid = ff->nodeid;
+	args.in.numargs = 1;
+	args.in.args[0].size = sizeof(inarg);
+	args.in.args[0].value = &inarg;
+	err = fuse_simple_request(fc, &args);
+	if (err == -ENOSYS) {
+		fc->no_fallocate = 1;
+		err = -EOPNOTSUPP;
+	}
+	if (err)
+		goto out;
+
+	/* we could have extended the file */
+	if (!(mode & FALLOC_FL_KEEP_SIZE)) {
+		bool changed = fuse_write_update_size(inode, offset + length);
+
+		if (changed && fc->writeback_cache)
+			file_update_time(file);
+	}
+
+	if (mode & FALLOC_FL_PUNCH_HOLE)
+		truncate_pagecache_range(inode, offset, offset + length - 1);
+
+	fuse_invalidate_attr(inode);
+
+out:
+	if (!(mode & FALLOC_FL_KEEP_SIZE))
+		clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
+
+	if (lock_inode)
+		mutex_unlock(&inode->i_mutex);
+
+	return err;
+}
+
+static const struct file_operations fuse_file_operations = {
+	.llseek		= fuse_file_llseek,
+	.read_iter	= fuse_file_read_iter,
+	.write_iter	= fuse_file_write_iter,
+	.mmap		= fuse_file_mmap,
+	.open		= fuse_open,
+	.flush		= fuse_flush,
+	.release	= fuse_release,
+	.fsync		= fuse_fsync,
+	.lock		= fuse_file_lock,
+	.flock		= fuse_file_flock,
+	.splice_read	= generic_file_splice_read,
+	.unlocked_ioctl	= fuse_file_ioctl,
+	.compat_ioctl	= fuse_file_compat_ioctl,
+	.poll		= fuse_file_poll,
+	.fallocate	= fuse_file_fallocate,
+};
+
+static const struct file_operations fuse_direct_io_file_operations = {
+	.llseek		= fuse_file_llseek,
+	.read_iter	= fuse_direct_read_iter,
+	.write_iter	= fuse_direct_write_iter,
+	.mmap		= fuse_direct_mmap,
+	.open		= fuse_open,
+	.flush		= fuse_flush,
+	.release	= fuse_release,
+	.fsync		= fuse_fsync,
+	.lock		= fuse_file_lock,
+	.flock		= fuse_file_flock,
+	.unlocked_ioctl	= fuse_file_ioctl,
+	.compat_ioctl	= fuse_file_compat_ioctl,
+	.poll		= fuse_file_poll,
+	.fallocate	= fuse_file_fallocate,
+	/* no splice_read */
+};
+
+static const struct address_space_operations fuse_file_aops  = {
+	.readpage	= fuse_readpage,
+	.writepage	= fuse_writepage,
+	.writepages	= fuse_writepages,
+	.launder_page	= fuse_launder_page,
+	.readpages	= fuse_readpages,
+	.set_page_dirty	= __set_page_dirty_nobuffers,
+	.bmap		= fuse_bmap,
+	.direct_IO	= fuse_direct_IO,
+	.write_begin	= fuse_write_begin,
+	.write_end	= fuse_write_end,
+};
+
+void fuse_init_file_inode(struct inode *inode)
+{
+	inode->i_fop = &fuse_file_operations;
+	inode->i_data.a_ops = &fuse_file_aops;
+}