/*
    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>

  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;

  	struct fuse_req *req;
  	int err;

  	req = fuse_get_req(fc);
  	if (IS_ERR(req))
  		return PTR_ERR(req);

  
  	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;

  	req->in.h.opcode = opcode;
  	req->in.h.nodeid = nodeid;

  	req->in.numargs = 1;
  	req->in.args[0].size = sizeof(inarg);
  	req->in.args[0].value = &inarg;
  	req->out.numargs = 1;
  	req->out.args[0].size = sizeof(*outargp);
  	req->out.args[0].value = outargp;

  	fuse_request_send(fc, req);

  	err = req->out.h.error;
  	fuse_put_request(fc, req);
  
  	return err;
  }

  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();
  	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_async(struct work_struct *work)
  {
  	struct fuse_req *req;
  	struct fuse_conn *fc;
  	struct path path;
  
  	req = container_of(work, struct fuse_req, misc.release.work);
  	path = req->misc.release.path;
  	fc = get_fuse_conn(path.dentry->d_inode);
  
  	fuse_put_request(fc, req);
  	path_put(&path);
  }

  static void fuse_release_end(struct fuse_conn *fc, struct fuse_req *req)
  {

  	if (fc->destroy_req) {
  		/*
  		 * If this is a fuseblk mount, then it's possible that
  		 * releasing the path will result in releasing the
  		 * super block and sending the DESTROY request.  If
  		 * the server is single threaded, this would hang.
  		 * For this reason do the path_put() in a separate
  		 * thread.
  		 */
  		atomic_inc(&req->count);
  		INIT_WORK(&req->misc.release.work, fuse_release_async);
  		schedule_work(&req->misc.release.work);
  	} else {
  		path_put(&req->misc.release.path);
  	}

  }

  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 (sync) {
  			fuse_request_send(ff->fc, req);
  			path_put(&req->misc.release.path);
  			fuse_put_request(ff->fc, req);
  		} else {
  			req->end = fuse_release_end;
  			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_open_out outarg;
  	struct fuse_file *ff;
  	int err;
  	int opcode = isdir ? FUSE_OPENDIR : FUSE_OPEN;
  
  	ff = fuse_file_alloc(fc);
  	if (!ff)
  		return -ENOMEM;
  
  	err = fuse_send_open(fc, nodeid, file, opcode, &outarg);
  	if (err) {
  		fuse_file_free(ff);
  		return err;
  	}
  
  	if (isdir)
  		outarg.open_flags &= ~FOPEN_DIRECT_IO;
  
  	ff->fh = outarg.fh;
  	ff->nodeid = nodeid;
  	ff->open_flags = outarg.open_flags;
  	file->private_data = fuse_file_get(ff);
  
  	return 0;
  }

  EXPORT_SYMBOL_GPL(fuse_do_open);

  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);
  	}

  }

  int fuse_open_common(struct inode *inode, struct file *file, bool isdir)

  {

  	struct fuse_conn *fc = get_fuse_conn(inode);

  	int err;

  	/* VFS checks this, but only _after_ ->open() */
  	if (file->f_flags & O_DIRECT)
  		return -EINVAL;

  	err = generic_file_open(inode, file);
  	if (err)
  		return err;

  	err = fuse_do_open(fc, get_node_id(inode), file, isdir);

  	if (err)

  		return err;

  	fuse_finish_open(inode, file);
  
  	return 0;

  }

  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 vfsmount and dentry until release is finished */

  	path_get(&file->f_path);
  	req->misc.release.path = file->f_path;

  	/*
  	 * 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)
  {

  	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;
  	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 page 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_page_is_writeback(struct inode *inode, pgoff_t index)
  {
  	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 (curr_index == index) {
  			found = true;
  			break;
  		}
  	}
  	spin_unlock(&fc->lock);
  
  	return found;
  }
  
  /*
   * 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;
  }

  static int fuse_flush(struct file *file, fl_owner_t id)

  {

  	struct inode *inode = file->f_path.dentry->d_inode;

  	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;

  	req = fuse_get_req_nofail(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;
  }

  /*
   * 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);
  }

  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;
  	struct fuse_req *req;
  	struct fuse_fsync_in inarg;
  	int err;

  	if (is_bad_inode(inode))
  		return -EIO;

  	err = filemap_write_and_wait_range(inode->i_mapping, start, end);
  	if (err)
  		return err;

  	if ((!isdir && fc->no_fsync) || (isdir && fc->no_fsyncdir))

  		return 0;

  	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 = write_inode_now(inode, 0);
  	if (err)

  		goto out;

  
  	fuse_sync_writes(inode);

  	req = fuse_get_req(fc);

  	if (IS_ERR(req)) {
  		err = PTR_ERR(req);
  		goto out;
  	}

  
  	memset(&inarg, 0, sizeof(inarg));
  	inarg.fh = ff->fh;
  	inarg.fsync_flags = datasync ? 1 : 0;

  	req->in.h.opcode = isdir ? FUSE_FSYNCDIR : FUSE_FSYNC;

  	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;

  	fuse_request_send(fc, req);

  	err = req->out.h.error;
  	fuse_put_request(fc, req);
  	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 size_t fuse_send_read(struct fuse_req *req, struct file *file,

  			     loff_t pos, size_t count, fl_owner_t owner)

  {

  	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);
  	}

  	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) {
  		fi->attr_version = ++fc->attr_version;
  		i_size_write(inode, size);
  	}
  	spin_unlock(&fc->lock);
  }

  static int fuse_readpage(struct file *file, struct page *page)
  {
  	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;
  
  	err = -EIO;
  	if (is_bad_inode(inode))
  		goto out;

  	/*

  	 * 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);
  	err = PTR_ERR(req);
  	if (IS_ERR(req))

  		goto out;

  	attr_ver = fuse_get_attr_version(fc);

  	req->out.page_zeroing = 1;

  	req->out.argpages = 1;

  	req->num_pages = 1;
  	req->pages[0] = page;

  	num_read = fuse_send_read(req, file, pos, count, NULL);

  	err = req->out.h.error;
  	fuse_put_request(fc, req);

  
  	if (!err) {
  		/*
  		 * Short read means EOF.  If file size is larger, truncate it
  		 */
  		if (num_read < count)
  			fuse_read_update_size(inode, pos + num_read, attr_ver);

  		SetPageUptodate(page);

  	}

  	fuse_invalidate_attr(inode); /* atime changed */

   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) {
  			loff_t pos;
  
  			pos = page_offset(req->pages[0]) + num_read;
  			fuse_read_update_size(inode, pos,
  					      req->misc.read.attr_ver);
  		}
  		fuse_invalidate_attr(inode); /* atime changed */
  	}

  	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;
  };
  
  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)) {

  		fuse_send_readpages(req, data->file);

  		data->req = req = fuse_get_req(fc);
  		if (IS_ERR(req)) {

  			unlock_page(page);

  			return PTR_ERR(req);

  		}

  	}

  	page_cache_get(page);

  	req->pages[req->num_pages] = page;

  	req->num_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;

  	err = -EIO;

  	if (is_bad_inode(inode))

  		goto out;

  	data.file = file;

  	data.inode = inode;

  	data.req = fuse_get_req(fc);

  	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_aio_read(struct kiocb *iocb, const struct iovec *iov,
  				  unsigned long nr_segs, loff_t pos)
  {
  	struct inode *inode = iocb->ki_filp->f_mapping->host;
  
  	if (pos + iov_length(iov, nr_segs) > i_size_read(inode)) {
  		int err;
  		/*
  		 * If trying to read past EOF, make sure the i_size
  		 * attribute is up-to-date.
  		 */
  		err = fuse_update_attributes(inode, NULL, iocb->ki_filp, NULL);
  		if (err)
  			return err;
  	}
  
  	return generic_file_aio_read(iocb, iov, nr_segs, pos);
  }

  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 file *file,

  			      loff_t pos, size_t count, fl_owner_t owner)

  {

  	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);
  	}

  	fuse_request_send(fc, req);

  	return req->misc.write.out.size;

  }

  void 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);
  
  	spin_lock(&fc->lock);
  	fi->attr_version = ++fc->attr_version;
  	if (pos > inode->i_size)
  		i_size_write(inode, pos);
  	spin_unlock(&fc->lock);
  }

  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;
  
  	for (i = 0; i < req->num_pages; i++)
  		fuse_wait_on_page_writeback(inode, req->pages[i]->index);

  	res = fuse_send_write(req, file, pos, count, NULL);

  
  	offset = req->page_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_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);

  		pagefault_disable();
  		tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes);
  		pagefault_enable();
  		flush_dcache_page(page);

  		mark_page_accessed(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->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 < FUSE_MAX_PAGES_PER_REQ && offset == 0);
  
  	return count > 0 ? count : err;
  }
  
  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);
  	int err = 0;
  	ssize_t res = 0;
  
  	if (is_bad_inode(inode))
  		return -EIO;
  
  	do {
  		struct fuse_req *req;
  		ssize_t count;
  
  		req = fuse_get_req(fc);
  		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);
  
  	fuse_invalidate_attr(inode);
  
  	return res > 0 ? res : err;
  }
  
  static ssize_t fuse_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
  				   unsigned long nr_segs, loff_t pos)
  {
  	struct file *file = iocb->ki_filp;
  	struct address_space *mapping = file->f_mapping;
  	size_t count = 0;
  	ssize_t written = 0;
  	struct inode *inode = mapping->host;
  	ssize_t err;
  	struct iov_iter i;
  
  	WARN_ON(iocb->ki_pos != pos);
  
  	err = generic_segment_checks(iov, &nr_segs, &count, VERIFY_READ);
  	if (err)
  		return err;
  
  	mutex_lock(&inode->i_mutex);
  	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
  
  	/* We can write back this queue in page reclaim */
  	current->backing_dev_info = mapping->backing_dev_info;
  
  	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
  	if (err)
  		goto out;
  
  	if (count == 0)
  		goto out;

  	err = file_remove_suid(file);

  	if (err)
  		goto out;
  
  	file_update_time(file);
  
  	iov_iter_init(&i, iov, nr_segs, count, 0);
  	written = fuse_perform_write(file, mapping, &i, pos);
  	if (written >= 0)
  		iocb->ki_pos = pos + written;
  
  out:
  	current->backing_dev_info = NULL;
  	mutex_unlock(&inode->i_mutex);
  
  	return written ? written : err;
  }

  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 int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,

  			       size_t *nbytesp, int write)

  {

  	size_t nbytes = *nbytesp;

  	unsigned long user_addr = (unsigned long) buf;
  	unsigned offset = user_addr & ~PAGE_MASK;
  	int npages;

  	/* Special case for kernel I/O: can copy directly into the buffer */
  	if (segment_eq(get_fs(), KERNEL_DS)) {
  		if (write)
  			req->in.args[1].value = (void *) user_addr;
  		else
  			req->out.args[0].value = (void *) user_addr;
  
  		return 0;
  	}

  	nbytes = min_t(size_t, nbytes, FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);

  	npages = (nbytes + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;

  	npages = clamp(npages, 1, FUSE_MAX_PAGES_PER_REQ);

  	npages = get_user_pages_fast(user_addr, npages, !write, req->pages);

  	if (npages < 0)
  		return npages;
  
  	req->num_pages = npages;
  	req->page_offset = offset;

  
  	if (write)
  		req->in.argpages = 1;
  	else
  		req->out.argpages = 1;
  
  	nbytes = (req->num_pages << PAGE_SHIFT) - req->page_offset;
  	*nbytesp = min(*nbytesp, nbytes);

  	return 0;
  }

  ssize_t fuse_direct_io(struct file *file, const char __user *buf,
  		       size_t count, loff_t *ppos, int write)

  {

  	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;
  	ssize_t res = 0;

  	struct fuse_req *req;

  	req = fuse_get_req(fc);
  	if (IS_ERR(req))
  		return PTR_ERR(req);

  
  	while (count) {

  		size_t nres;

  		fl_owner_t owner = current->files;

  		size_t nbytes = min(count, nmax);
  		int err = fuse_get_user_pages(req, buf, &nbytes, write);

  		if (err) {
  			res = err;
  			break;
  		}

  		if (write)

  			nres = fuse_send_write(req, file, pos, nbytes, owner);

  		else

  			nres = fuse_send_read(req, file, pos, nbytes, owner);

  		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;
  		buf += nres;
  		if (nres != nbytes)
  			break;

  		if (count) {
  			fuse_put_request(fc, req);
  			req = fuse_get_req(fc);
  			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 file *file, char __user *buf,
  				     size_t count, loff_t *ppos)
  {

  	ssize_t res;
  	struct inode *inode = file->f_path.dentry->d_inode;
  
  	if (is_bad_inode(inode))
  		return -EIO;
  
  	res = fuse_direct_io(file, buf, count, ppos, 0);
  
  	fuse_invalidate_attr(inode);
  
  	return res;

  }
  
  static ssize_t fuse_direct_write(struct file *file, const char __user *buf,
  				 size_t count, loff_t *ppos)
  {

  	struct inode *inode = file->f_path.dentry->d_inode;

  	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(file, ppos, &count, 0);

  	if (!res) {

  		res = fuse_direct_io(file, buf, count, ppos, 1);

  		if (res > 0)
  			fuse_write_update_size(inode, *ppos);
  	}

  	mutex_unlock(&inode->i_mutex);

  
  	fuse_invalidate_attr(inode);

  	return res;
  }

  static void fuse_writepage_free(struct fuse_conn *fc, struct fuse_req *req)

  {

  	__free_page(req->pages[0]);

  	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->i_mapping->backing_dev_info;
  
  	list_del(&req->writepages_entry);
  	dec_bdi_stat(bdi, BDI_WRITEBACK);
  	dec_zone_page_state(req->pages[0], 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)

  __releases(fc->lock)
  __acquires(fc->lock)

  {
  	struct fuse_inode *fi = get_fuse_inode(req->inode);
  	loff_t size = i_size_read(req->inode);
  	struct fuse_write_in *inarg = &req->misc.write.in;
  
  	if (!fc->connected)
  		goto out_free;
  
  	if (inarg->offset + PAGE_CACHE_SIZE <= size) {
  		inarg->size = PAGE_CACHE_SIZE;
  	} else if (inarg->offset < size) {
  		inarg->size = size & (PAGE_CACHE_SIZE - 1);
  	} 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);
  	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);
  	}
  }
  
  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);
  	fi->writectr--;
  	fuse_writepage_finish(fc, req);
  	spin_unlock(&fc->lock);
  	fuse_writepage_free(fc, req);
  }
  
  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 fuse_file *ff;
  	struct page *tmp_page;
  
  	set_page_writeback(page);
  
  	req = fuse_request_alloc_nofs();
  	if (!req)
  		goto err;
  
  	tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
  	if (!tmp_page)
  		goto err_free;
  
  	spin_lock(&fc->lock);
  	BUG_ON(list_empty(&fi->write_files));
  	ff = list_entry(fi->write_files.next, struct fuse_file, write_entry);
  	req->ff = fuse_file_get(ff);
  	spin_unlock(&fc->lock);

  	fuse_write_fill(req, ff, page_offset(page), 0);

  
  	copy_highpage(tmp_page, page);

  	req->misc.write.in.write_flags |= FUSE_WRITE_CACHE;

  	req->in.argpages = 1;

  	req->num_pages = 1;
  	req->pages[0] = tmp_page;
  	req->page_offset = 0;
  	req->end = fuse_writepage_end;
  	req->inode = inode;
  
  	inc_bdi_stat(mapping->backing_dev_info, BDI_WRITEBACK);
  	inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP);
  	end_page_writeback(page);
  
  	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);
  
  	return 0;
  
  err_free:
  	fuse_request_free(req);
  err:
  	end_page_writeback(page);
  	return -ENOMEM;
  }
  
  static int fuse_writepage(struct page *page, struct writeback_control *wbc)
  {
  	int err;
  
  	err = fuse_writepage_locked(page);
  	unlock_page(page);
  
  	return err;
  }
  
  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;

  	/*
  	 * Don't use page->mapping as it may become NULL from a
  	 * concurrent truncate.
  	 */
  	struct inode *inode = vma->vm_file->f_mapping->host;
  
  	fuse_wait_on_page_writeback(inode, page->index);
  	return 0;
  }

  static const struct vm_operations_struct fuse_file_vm_ops = {

  	.close		= fuse_vma_close,
  	.fault		= filemap_fault,
  	.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)) {
  		struct inode *inode = file->f_dentry->d_inode;
  		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);
  	}
  	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_req *req, struct file *file,

  			 const struct file_lock *fl, int opcode, pid_t pid,
  			 int flock)

  {

  	struct inode *inode = file->f_path.dentry->d_inode;

  	struct fuse_conn *fc = get_fuse_conn(inode);

  	struct fuse_file *ff = file->private_data;
  	struct fuse_lk_in *arg = &req->misc.lk_in;
  
  	arg->fh = ff->fh;

  	arg->owner = fuse_lock_owner_id(fc, fl->fl_owner);

  	arg->lk.start = fl->fl_start;
  	arg->lk.end = fl->fl_end;
  	arg->lk.type = fl->fl_type;
  	arg->lk.pid = pid;

  	if (flock)
  		arg->lk_flags |= FUSE_LK_FLOCK;

  	req->in.h.opcode = opcode;
  	req->in.h.nodeid = get_node_id(inode);
  	req->in.numargs = 1;
  	req->in.args[0].size = sizeof(*arg);
  	req->in.args[0].value = arg;
  }
  
  static int fuse_getlk(struct file *file, struct file_lock *fl)
  {

  	struct inode *inode = file->f_path.dentry->d_inode;

  	struct fuse_conn *fc = get_fuse_conn(inode);
  	struct fuse_req *req;
  	struct fuse_lk_out outarg;
  	int err;
  
  	req = fuse_get_req(fc);
  	if (IS_ERR(req))
  		return PTR_ERR(req);

  	fuse_lk_fill(req, file, fl, FUSE_GETLK, 0, 0);

  	req->out.numargs = 1;
  	req->out.args[0].size = sizeof(outarg);
  	req->out.args[0].value = &outarg;

  	fuse_request_send(fc, req);

  	err = req->out.h.error;
  	fuse_put_request(fc, req);
  	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->f_path.dentry->d_inode;

  	struct fuse_conn *fc = get_fuse_conn(inode);
  	struct fuse_req *req;
  	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;
  
  	req = fuse_get_req(fc);
  	if (IS_ERR(req))
  		return PTR_ERR(req);

  	fuse_lk_fill(req, file, fl, opcode, pid, flock);

  	fuse_request_send(fc, req);

  	err = req->out.h.error;

  	/* locking is restartable */
  	if (err == -EINTR)
  		err = -ERESTARTSYS;

  	fuse_put_request(fc, req);
  	return err;
  }
  
  static int fuse_file_lock(struct file *file, int cmd, struct file_lock *fl)
  {

  	struct inode *inode = file->f_path.dentry->d_inode;

  	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->f_path.dentry->d_inode;
  	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 */
  		fl->fl_owner = (fl_owner_t) file;

  		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);
  	struct fuse_req *req;
  	struct fuse_bmap_in inarg;
  	struct fuse_bmap_out outarg;
  	int err;
  
  	if (!inode->i_sb->s_bdev || fc->no_bmap)
  		return 0;
  
  	req = fuse_get_req(fc);
  	if (IS_ERR(req))
  		return 0;
  
  	memset(&inarg, 0, sizeof(inarg));
  	inarg.block = block;
  	inarg.blocksize = inode->i_sb->s_blocksize;
  	req->in.h.opcode = FUSE_BMAP;
  	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->out.numargs = 1;
  	req->out.args[0].size = sizeof(outarg);
  	req->out.args[0].value = &outarg;

  	fuse_request_send(fc, req);

  	err = req->out.h.error;
  	fuse_put_request(fc, req);
  	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 origin)
  {
  	loff_t retval;
  	struct inode *inode = file->f_path.dentry->d_inode;

  	/* No i_mutex protection necessary for SEEK_CUR and SEEK_SET */
  	if (origin == SEEK_CUR || origin == SEEK_SET)
  		return generic_file_llseek(file, offset, origin);

  	mutex_lock(&inode->i_mutex);
  	retval = fuse_update_attributes(inode, NULL, file, NULL);
  	if (!retval)
  		retval = generic_file_llseek(file, offset, origin);

  	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, iov, nr_segs, bytes, 0);
  
  	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++) {
  		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);
  	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;
  
  	/* 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], KM_USER0);

  		err = fuse_copy_ioctl_iovec(fc, iov_page, vaddr,

  					    transferred, in_iovs + out_iovs,
  					    (flags & FUSE_IOCTL_COMPAT) != 0);

  		kunmap_atomic(vaddr, KM_USER0);

  		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->f_dentry->d_inode;
  	struct fuse_conn *fc = get_fuse_conn(inode);
  
  	if (!fuse_allow_task(fc, current))
  		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, *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;
  	struct fuse_req *req;
  	int err;
  
  	if (fc->no_poll)
  		return DEFAULT_POLLMASK;
  
  	poll_wait(file, &ff->poll_wait, 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);
  	}
  
  	req = fuse_get_req(fc);
  	if (IS_ERR(req))

  		return POLLERR;

  
  	req->in.h.opcode = FUSE_POLL;

  	req->in.h.nodeid = ff->nodeid;

  	req->in.numargs = 1;
  	req->in.args[0].size = sizeof(inarg);
  	req->in.args[0].value = &inarg;
  	req->out.numargs = 1;
  	req->out.args[0].size = sizeof(outarg);
  	req->out.args[0].value = &outarg;

  	fuse_request_send(fc, req);

  	err = req->out.h.error;
  	fuse_put_request(fc, req);
  
  	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 const struct file_operations fuse_file_operations = {

  	.llseek		= fuse_file_llseek,

  	.read		= do_sync_read,

  	.aio_read	= fuse_file_aio_read,

  	.write		= do_sync_write,

  	.aio_write	= fuse_file_aio_write,

  	.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,

  };

  static const struct file_operations fuse_direct_io_file_operations = {

  	.llseek		= fuse_file_llseek,

  	.read		= fuse_direct_read,
  	.write		= fuse_direct_write,

  	.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,

  	/* no splice_read */

  };

  static const struct address_space_operations fuse_file_aops  = {

  	.readpage	= fuse_readpage,

  	.writepage	= fuse_writepage,
  	.launder_page	= fuse_launder_page,

  	.readpages	= fuse_readpages,

  	.set_page_dirty	= __set_page_dirty_nobuffers,

  	.bmap		= fuse_bmap,

  };
  
  void fuse_init_file_inode(struct inode *inode)
  {

  	inode->i_fop = &fuse_file_operations;
  	inode->i_data.a_ops = &fuse_file_aops;

  }