/*
   * Copyright (C) 2007 Oracle.  All rights reserved.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public
   * License v2 as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public
   * License along with this program; if not, write to the
   * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   */

  #include <linux/fs.h>
  #include <linux/pagemap.h>
  #include <linux/highmem.h>
  #include <linux/time.h>
  #include <linux/init.h>
  #include <linux/string.h>

  #include <linux/backing-dev.h>
  #include <linux/mpage.h>

  #include <linux/falloc.h>

  #include <linux/swap.h>
  #include <linux/writeback.h>
  #include <linux/statfs.h>
  #include <linux/compat.h>

  #include <linux/slab.h>

  #include "ctree.h"
  #include "disk-io.h"
  #include "transaction.h"
  #include "btrfs_inode.h"
  #include "ioctl.h"
  #include "print-tree.h"

  #include "tree-log.h"
  #include "locking.h"

  #include "compat.h"

  /*
   * when auto defrag is enabled we
   * queue up these defrag structs to remember which
   * inodes need defragging passes
   */
  struct inode_defrag {
  	struct rb_node rb_node;
  	/* objectid */
  	u64 ino;
  	/*
  	 * transid where the defrag was added, we search for
  	 * extents newer than this
  	 */
  	u64 transid;
  
  	/* root objectid */
  	u64 root;
  
  	/* last offset we were able to defrag */
  	u64 last_offset;
  
  	/* if we've wrapped around back to zero once already */
  	int cycled;
  };
  
  /* pop a record for an inode into the defrag tree.  The lock
   * must be held already
   *
   * If you're inserting a record for an older transid than an
   * existing record, the transid already in the tree is lowered
   *
   * If an existing record is found the defrag item you
   * pass in is freed
   */

  static void __btrfs_add_inode_defrag(struct inode *inode,

  				    struct inode_defrag *defrag)
  {
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct inode_defrag *entry;
  	struct rb_node **p;
  	struct rb_node *parent = NULL;
  
  	p = &root->fs_info->defrag_inodes.rb_node;
  	while (*p) {
  		parent = *p;
  		entry = rb_entry(parent, struct inode_defrag, rb_node);
  
  		if (defrag->ino < entry->ino)
  			p = &parent->rb_left;
  		else if (defrag->ino > entry->ino)
  			p = &parent->rb_right;
  		else {
  			/* if we're reinserting an entry for
  			 * an old defrag run, make sure to
  			 * lower the transid of our existing record
  			 */
  			if (defrag->transid < entry->transid)
  				entry->transid = defrag->transid;
  			if (defrag->last_offset > entry->last_offset)
  				entry->last_offset = defrag->last_offset;
  			goto exists;
  		}
  	}
  	BTRFS_I(inode)->in_defrag = 1;
  	rb_link_node(&defrag->rb_node, parent, p);
  	rb_insert_color(&defrag->rb_node, &root->fs_info->defrag_inodes);

  	return;

  
  exists:
  	kfree(defrag);

  	return;

  
  }
  
  /*
   * insert a defrag record for this inode if auto defrag is
   * enabled
   */
  int btrfs_add_inode_defrag(struct btrfs_trans_handle *trans,
  			   struct inode *inode)
  {
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct inode_defrag *defrag;

  	u64 transid;
  
  	if (!btrfs_test_opt(root, AUTO_DEFRAG))
  		return 0;

  	if (btrfs_fs_closing(root->fs_info))

  		return 0;
  
  	if (BTRFS_I(inode)->in_defrag)
  		return 0;
  
  	if (trans)
  		transid = trans->transid;
  	else
  		transid = BTRFS_I(inode)->root->last_trans;
  
  	defrag = kzalloc(sizeof(*defrag), GFP_NOFS);
  	if (!defrag)
  		return -ENOMEM;

  	defrag->ino = btrfs_ino(inode);

  	defrag->transid = transid;
  	defrag->root = root->root_key.objectid;
  
  	spin_lock(&root->fs_info->defrag_inodes_lock);
  	if (!BTRFS_I(inode)->in_defrag)

  		__btrfs_add_inode_defrag(inode, defrag);

  	else
  		kfree(defrag);

  	spin_unlock(&root->fs_info->defrag_inodes_lock);

  	return 0;

  }
  
  /*
   * must be called with the defrag_inodes lock held
   */
  struct inode_defrag *btrfs_find_defrag_inode(struct btrfs_fs_info *info, u64 ino,
  					     struct rb_node **next)
  {
  	struct inode_defrag *entry = NULL;
  	struct rb_node *p;
  	struct rb_node *parent = NULL;
  
  	p = info->defrag_inodes.rb_node;
  	while (p) {
  		parent = p;
  		entry = rb_entry(parent, struct inode_defrag, rb_node);
  
  		if (ino < entry->ino)
  			p = parent->rb_left;
  		else if (ino > entry->ino)
  			p = parent->rb_right;
  		else
  			return entry;
  	}
  
  	if (next) {
  		while (parent && ino > entry->ino) {
  			parent = rb_next(parent);
  			entry = rb_entry(parent, struct inode_defrag, rb_node);
  		}
  		*next = parent;
  	}
  	return NULL;
  }
  
  /*
   * run through the list of inodes in the FS that need
   * defragging
   */
  int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info)
  {
  	struct inode_defrag *defrag;
  	struct btrfs_root *inode_root;
  	struct inode *inode;
  	struct rb_node *n;
  	struct btrfs_key key;
  	struct btrfs_ioctl_defrag_range_args range;
  	u64 first_ino = 0;
  	int num_defrag;
  	int defrag_batch = 1024;
  
  	memset(&range, 0, sizeof(range));
  	range.len = (u64)-1;
  
  	atomic_inc(&fs_info->defrag_running);
  	spin_lock(&fs_info->defrag_inodes_lock);
  	while(1) {
  		n = NULL;
  
  		/* find an inode to defrag */
  		defrag = btrfs_find_defrag_inode(fs_info, first_ino, &n);
  		if (!defrag) {
  			if (n)
  				defrag = rb_entry(n, struct inode_defrag, rb_node);
  			else if (first_ino) {
  				first_ino = 0;
  				continue;
  			} else {
  				break;
  			}
  		}
  
  		/* remove it from the rbtree */
  		first_ino = defrag->ino + 1;
  		rb_erase(&defrag->rb_node, &fs_info->defrag_inodes);

  		if (btrfs_fs_closing(fs_info))

  			goto next_free;
  
  		spin_unlock(&fs_info->defrag_inodes_lock);
  
  		/* get the inode */
  		key.objectid = defrag->root;
  		btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
  		key.offset = (u64)-1;
  		inode_root = btrfs_read_fs_root_no_name(fs_info, &key);
  		if (IS_ERR(inode_root))
  			goto next;
  
  		key.objectid = defrag->ino;
  		btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
  		key.offset = 0;
  
  		inode = btrfs_iget(fs_info->sb, &key, inode_root, NULL);
  		if (IS_ERR(inode))
  			goto next;
  
  		/* do a chunk of defrag */
  		BTRFS_I(inode)->in_defrag = 0;
  		range.start = defrag->last_offset;
  		num_defrag = btrfs_defrag_file(inode, NULL, &range, defrag->transid,
  					       defrag_batch);
  		/*
  		 * if we filled the whole defrag batch, there
  		 * must be more work to do.  Queue this defrag
  		 * again
  		 */
  		if (num_defrag == defrag_batch) {
  			defrag->last_offset = range.start;
  			__btrfs_add_inode_defrag(inode, defrag);
  			/*
  			 * we don't want to kfree defrag, we added it back to
  			 * the rbtree
  			 */
  			defrag = NULL;
  		} else if (defrag->last_offset && !defrag->cycled) {
  			/*
  			 * we didn't fill our defrag batch, but
  			 * we didn't start at zero.  Make sure we loop
  			 * around to the start of the file.
  			 */
  			defrag->last_offset = 0;
  			defrag->cycled = 1;
  			__btrfs_add_inode_defrag(inode, defrag);
  			defrag = NULL;
  		}
  
  		iput(inode);
  next:
  		spin_lock(&fs_info->defrag_inodes_lock);
  next_free:
  		kfree(defrag);
  	}
  	spin_unlock(&fs_info->defrag_inodes_lock);
  
  	atomic_dec(&fs_info->defrag_running);
  
  	/*
  	 * during unmount, we use the transaction_wait queue to
  	 * wait for the defragger to stop
  	 */
  	wake_up(&fs_info->transaction_wait);
  	return 0;
  }

  /* simple helper to fault in pages and copy.  This should go away
   * and be replaced with calls into generic code.
   */

  static noinline int btrfs_copy_from_user(loff_t pos, int num_pages,

  					 size_t write_bytes,

  					 struct page **prepared_pages,

  					 struct iov_iter *i)

  {

  	size_t copied = 0;

  	size_t total_copied = 0;

  	int pg = 0;

  	int offset = pos & (PAGE_CACHE_SIZE - 1);

  	while (write_bytes > 0) {

  		size_t count = min_t(size_t,
  				     PAGE_CACHE_SIZE - offset, write_bytes);

  		struct page *page = prepared_pages[pg];

  		/*
  		 * Copy data from userspace to the current page
  		 *
  		 * Disable pagefault to avoid recursive lock since
  		 * the pages are already locked
  		 */
  		pagefault_disable();
  		copied = iov_iter_copy_from_user_atomic(page, i, offset, count);
  		pagefault_enable();

  		/* Flush processor's dcache for this page */
  		flush_dcache_page(page);

  
  		/*
  		 * if we get a partial write, we can end up with
  		 * partially up to date pages.  These add
  		 * a lot of complexity, so make sure they don't
  		 * happen by forcing this copy to be retried.
  		 *
  		 * The rest of the btrfs_file_write code will fall
  		 * back to page at a time copies after we return 0.
  		 */
  		if (!PageUptodate(page) && copied < count)
  			copied = 0;

  		iov_iter_advance(i, copied);
  		write_bytes -= copied;

  		total_copied += copied;

  		/* Return to btrfs_file_aio_write to fault page */

  		if (unlikely(copied == 0))

  			break;

  
  		if (unlikely(copied < PAGE_CACHE_SIZE - offset)) {
  			offset += copied;
  		} else {
  			pg++;
  			offset = 0;
  		}

  	}

  	return total_copied;

  }

  /*
   * unlocks pages after btrfs_file_write is done with them
   */

  void btrfs_drop_pages(struct page **pages, size_t num_pages)

  {
  	size_t i;
  	for (i = 0; i < num_pages; i++) {

  		/* page checked is some magic around finding pages that
  		 * have been modified without going through btrfs_set_page_dirty
  		 * clear it here
  		 */

  		ClearPageChecked(pages[i]);

  		unlock_page(pages[i]);
  		mark_page_accessed(pages[i]);
  		page_cache_release(pages[i]);
  	}
  }

  /*
   * after copy_from_user, pages need to be dirtied and we need to make
   * sure holes are created between the current EOF and the start of
   * any next extents (if required).
   *
   * this also makes the decision about creating an inline extent vs
   * doing real data extents, marking pages dirty and delalloc as required.
   */

  int btrfs_dirty_pages(struct btrfs_root *root, struct inode *inode,
  		      struct page **pages, size_t num_pages,
  		      loff_t pos, size_t write_bytes,
  		      struct extent_state **cached)

  {

  	int err = 0;

  	int i;

  	u64 num_bytes;

  	u64 start_pos;
  	u64 end_of_last_block;
  	u64 end_pos = pos + write_bytes;
  	loff_t isize = i_size_read(inode);

  	start_pos = pos & ~((u64)root->sectorsize - 1);

  	num_bytes = (write_bytes + pos - start_pos +
  		    root->sectorsize - 1) & ~((u64)root->sectorsize - 1);

  	end_of_last_block = start_pos + num_bytes - 1;

  	err = btrfs_set_extent_delalloc(inode, start_pos, end_of_last_block,

  					cached);

  	if (err)
  		return err;

  	for (i = 0; i < num_pages; i++) {
  		struct page *p = pages[i];
  		SetPageUptodate(p);
  		ClearPageChecked(p);
  		set_page_dirty(p);

  	}

  
  	/*
  	 * we've only changed i_size in ram, and we haven't updated
  	 * the disk i_size.  There is no need to log the inode
  	 * at this time.
  	 */
  	if (end_pos > isize)

  		i_size_write(inode, end_pos);

  	return 0;

  }

  /*
   * this drops all the extents in the cache that intersect the range
   * [start, end].  Existing extents are split as required.
   */

  int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
  			    int skip_pinned)

  {
  	struct extent_map *em;

  	struct extent_map *split = NULL;
  	struct extent_map *split2 = NULL;

  	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;

  	u64 len = end - start + 1;

  	int ret;
  	int testend = 1;

  	unsigned long flags;

  	int compressed = 0;

  	WARN_ON(end < start);

  	if (end == (u64)-1) {

  		len = (u64)-1;

  		testend = 0;
  	}

  	while (1) {

  		if (!split)

  			split = alloc_extent_map();

  		if (!split2)

  			split2 = alloc_extent_map();

  		BUG_ON(!split || !split2);

  		write_lock(&em_tree->lock);

  		em = lookup_extent_mapping(em_tree, start, len);

  		if (!em) {

  			write_unlock(&em_tree->lock);

  			break;

  		}

  		flags = em->flags;
  		if (skip_pinned && test_bit(EXTENT_FLAG_PINNED, &em->flags)) {

  			if (testend && em->start + em->len >= start + len) {

  				free_extent_map(em);

  				write_unlock(&em_tree->lock);

  				break;
  			}

  			start = em->start + em->len;
  			if (testend)

  				len = start + len - (em->start + em->len);

  			free_extent_map(em);

  			write_unlock(&em_tree->lock);

  			continue;
  		}

  		compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);

  		clear_bit(EXTENT_FLAG_PINNED, &em->flags);

  		remove_extent_mapping(em_tree, em);

  
  		if (em->block_start < EXTENT_MAP_LAST_BYTE &&
  		    em->start < start) {
  			split->start = em->start;
  			split->len = start - em->start;

  			split->orig_start = em->orig_start;

  			split->block_start = em->block_start;

  
  			if (compressed)
  				split->block_len = em->block_len;
  			else
  				split->block_len = split->len;

  			split->bdev = em->bdev;

  			split->flags = flags;

  			split->compress_type = em->compress_type;

  			ret = add_extent_mapping(em_tree, split);
  			BUG_ON(ret);
  			free_extent_map(split);
  			split = split2;
  			split2 = NULL;
  		}
  		if (em->block_start < EXTENT_MAP_LAST_BYTE &&
  		    testend && em->start + em->len > start + len) {
  			u64 diff = start + len - em->start;
  
  			split->start = start + len;
  			split->len = em->start + em->len - (start + len);
  			split->bdev = em->bdev;

  			split->flags = flags;

  			split->compress_type = em->compress_type;

  			if (compressed) {
  				split->block_len = em->block_len;
  				split->block_start = em->block_start;

  				split->orig_start = em->orig_start;

  			} else {
  				split->block_len = split->len;
  				split->block_start = em->block_start + diff;

  				split->orig_start = split->start;

  			}

  
  			ret = add_extent_mapping(em_tree, split);
  			BUG_ON(ret);
  			free_extent_map(split);
  			split = NULL;
  		}

  		write_unlock(&em_tree->lock);

  		/* once for us */
  		free_extent_map(em);
  		/* once for the tree*/
  		free_extent_map(em);
  	}

  	if (split)
  		free_extent_map(split);
  	if (split2)
  		free_extent_map(split2);

  	return 0;
  }

  /*
   * this is very complex, but the basic idea is to drop all extents
   * in the range start - end.  hint_block is filled in with a block number
   * that would be a good hint to the block allocator for this file.
   *
   * If an extent intersects the range but is not entirely inside the range
   * it is either truncated or split.  Anything entirely inside the range
   * is deleted from the tree.
   */

  int btrfs_drop_extents(struct btrfs_trans_handle *trans, struct inode *inode,
  		       u64 start, u64 end, u64 *hint_byte, int drop_cache)

  {

  	struct btrfs_root *root = BTRFS_I(inode)->root;

  	struct extent_buffer *leaf;

  	struct btrfs_file_extent_item *fi;

  	struct btrfs_path *path;

  	struct btrfs_key key;

  	struct btrfs_key new_key;

  	u64 ino = btrfs_ino(inode);

  	u64 search_start = start;
  	u64 disk_bytenr = 0;
  	u64 num_bytes = 0;
  	u64 extent_offset = 0;
  	u64 extent_end = 0;
  	int del_nr = 0;
  	int del_slot = 0;
  	int extent_type;

  	int recow;

  	int ret;

  	if (drop_cache)
  		btrfs_drop_extent_cache(inode, start, end - 1, 0);

  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;

  	while (1) {

  		recow = 0;

  		ret = btrfs_lookup_file_extent(trans, root, path, ino,

  					       search_start, -1);
  		if (ret < 0)

  			break;
  		if (ret > 0 && path->slots[0] > 0 && search_start == start) {
  			leaf = path->nodes[0];
  			btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);

  			if (key.objectid == ino &&

  			    key.type == BTRFS_EXTENT_DATA_KEY)
  				path->slots[0]--;

  		}

  		ret = 0;

  next_slot:

  		leaf = path->nodes[0];

  		if (path->slots[0] >= btrfs_header_nritems(leaf)) {
  			BUG_ON(del_nr > 0);
  			ret = btrfs_next_leaf(root, path);
  			if (ret < 0)
  				break;
  			if (ret > 0) {
  				ret = 0;
  				break;

  			}

  			leaf = path->nodes[0];
  			recow = 1;
  		}
  
  		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);

  		if (key.objectid > ino ||

  		    key.type > BTRFS_EXTENT_DATA_KEY || key.offset >= end)
  			break;
  
  		fi = btrfs_item_ptr(leaf, path->slots[0],
  				    struct btrfs_file_extent_item);
  		extent_type = btrfs_file_extent_type(leaf, fi);
  
  		if (extent_type == BTRFS_FILE_EXTENT_REG ||
  		    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
  			disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
  			num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
  			extent_offset = btrfs_file_extent_offset(leaf, fi);
  			extent_end = key.offset +
  				btrfs_file_extent_num_bytes(leaf, fi);
  		} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
  			extent_end = key.offset +
  				btrfs_file_extent_inline_len(leaf, fi);

  		} else {

  			WARN_ON(1);

  			extent_end = search_start;

  		}

  		if (extent_end <= search_start) {
  			path->slots[0]++;

  			goto next_slot;

  		}

  		search_start = max(key.offset, start);
  		if (recow) {

  			btrfs_release_path(path);

  			continue;

  		}

  		/*
  		 *     | - range to drop - |
  		 *  | -------- extent -------- |
  		 */
  		if (start > key.offset && end < extent_end) {
  			BUG_ON(del_nr > 0);
  			BUG_ON(extent_type == BTRFS_FILE_EXTENT_INLINE);
  
  			memcpy(&new_key, &key, sizeof(new_key));
  			new_key.offset = start;
  			ret = btrfs_duplicate_item(trans, root, path,
  						   &new_key);
  			if (ret == -EAGAIN) {

  				btrfs_release_path(path);

  				continue;

  			}

  			if (ret < 0)
  				break;
  
  			leaf = path->nodes[0];
  			fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
  					    struct btrfs_file_extent_item);
  			btrfs_set_file_extent_num_bytes(leaf, fi,
  							start - key.offset);
  
  			fi = btrfs_item_ptr(leaf, path->slots[0],
  					    struct btrfs_file_extent_item);
  
  			extent_offset += start - key.offset;
  			btrfs_set_file_extent_offset(leaf, fi, extent_offset);
  			btrfs_set_file_extent_num_bytes(leaf, fi,
  							extent_end - start);
  			btrfs_mark_buffer_dirty(leaf);
  
  			if (disk_bytenr > 0) {

  				ret = btrfs_inc_extent_ref(trans, root,

  						disk_bytenr, num_bytes, 0,
  						root->root_key.objectid,
  						new_key.objectid,
  						start - extent_offset);

  				BUG_ON(ret);

  				*hint_byte = disk_bytenr;

  			}

  			key.offset = start;

  		}

  		/*
  		 *  | ---- range to drop ----- |
  		 *      | -------- extent -------- |
  		 */
  		if (start <= key.offset && end < extent_end) {
  			BUG_ON(extent_type == BTRFS_FILE_EXTENT_INLINE);

  			memcpy(&new_key, &key, sizeof(new_key));
  			new_key.offset = end;
  			btrfs_set_item_key_safe(trans, root, path, &new_key);

  			extent_offset += end - key.offset;
  			btrfs_set_file_extent_offset(leaf, fi, extent_offset);
  			btrfs_set_file_extent_num_bytes(leaf, fi,
  							extent_end - end);
  			btrfs_mark_buffer_dirty(leaf);
  			if (disk_bytenr > 0) {
  				inode_sub_bytes(inode, end - key.offset);
  				*hint_byte = disk_bytenr;

  			}

  			break;

  		}

  		search_start = extent_end;
  		/*
  		 *       | ---- range to drop ----- |
  		 *  | -------- extent -------- |
  		 */
  		if (start > key.offset && end >= extent_end) {
  			BUG_ON(del_nr > 0);
  			BUG_ON(extent_type == BTRFS_FILE_EXTENT_INLINE);

  			btrfs_set_file_extent_num_bytes(leaf, fi,
  							start - key.offset);
  			btrfs_mark_buffer_dirty(leaf);
  			if (disk_bytenr > 0) {
  				inode_sub_bytes(inode, extent_end - start);
  				*hint_byte = disk_bytenr;
  			}
  			if (end == extent_end)
  				break;

  			path->slots[0]++;
  			goto next_slot;

  		}

  		/*
  		 *  | ---- range to drop ----- |
  		 *    | ------ extent ------ |
  		 */
  		if (start <= key.offset && end >= extent_end) {
  			if (del_nr == 0) {
  				del_slot = path->slots[0];
  				del_nr = 1;
  			} else {
  				BUG_ON(del_slot + del_nr != path->slots[0]);
  				del_nr++;
  			}

  			if (extent_type == BTRFS_FILE_EXTENT_INLINE) {

  				inode_sub_bytes(inode,

  						extent_end - key.offset);
  				extent_end = ALIGN(extent_end,
  						   root->sectorsize);
  			} else if (disk_bytenr > 0) {

  				ret = btrfs_free_extent(trans, root,

  						disk_bytenr, num_bytes, 0,
  						root->root_key.objectid,

  						key.objectid, key.offset -

  						extent_offset);

  				BUG_ON(ret);

  				inode_sub_bytes(inode,
  						extent_end - key.offset);
  				*hint_byte = disk_bytenr;

  			}

  			if (end == extent_end)
  				break;
  
  			if (path->slots[0] + 1 < btrfs_header_nritems(leaf)) {
  				path->slots[0]++;
  				goto next_slot;
  			}
  
  			ret = btrfs_del_items(trans, root, path, del_slot,
  					      del_nr);
  			BUG_ON(ret);
  
  			del_nr = 0;
  			del_slot = 0;

  			btrfs_release_path(path);

  			continue;

  		}

  
  		BUG_ON(1);

  	}

  
  	if (del_nr > 0) {
  		ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
  		BUG_ON(ret);

  	}

  
  	btrfs_free_path(path);

  	return ret;
  }

  static int extent_mergeable(struct extent_buffer *leaf, int slot,

  			    u64 objectid, u64 bytenr, u64 orig_offset,
  			    u64 *start, u64 *end)

  {
  	struct btrfs_file_extent_item *fi;
  	struct btrfs_key key;
  	u64 extent_end;
  
  	if (slot < 0 || slot >= btrfs_header_nritems(leaf))
  		return 0;
  
  	btrfs_item_key_to_cpu(leaf, &key, slot);
  	if (key.objectid != objectid || key.type != BTRFS_EXTENT_DATA_KEY)
  		return 0;
  
  	fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
  	if (btrfs_file_extent_type(leaf, fi) != BTRFS_FILE_EXTENT_REG ||
  	    btrfs_file_extent_disk_bytenr(leaf, fi) != bytenr ||

  	    btrfs_file_extent_offset(leaf, fi) != key.offset - orig_offset ||

  	    btrfs_file_extent_compression(leaf, fi) ||
  	    btrfs_file_extent_encryption(leaf, fi) ||
  	    btrfs_file_extent_other_encoding(leaf, fi))
  		return 0;
  
  	extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
  	if ((*start && *start != key.offset) || (*end && *end != extent_end))
  		return 0;
  
  	*start = key.offset;
  	*end = extent_end;
  	return 1;
  }
  
  /*
   * Mark extent in the range start - end as written.
   *
   * This changes extent type from 'pre-allocated' to 'regular'. If only
   * part of extent is marked as written, the extent will be split into
   * two or three.
   */
  int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,

  			      struct inode *inode, u64 start, u64 end)
  {

  	struct btrfs_root *root = BTRFS_I(inode)->root;

  	struct extent_buffer *leaf;
  	struct btrfs_path *path;
  	struct btrfs_file_extent_item *fi;
  	struct btrfs_key key;

  	struct btrfs_key new_key;

  	u64 bytenr;
  	u64 num_bytes;
  	u64 extent_end;

  	u64 orig_offset;

  	u64 other_start;
  	u64 other_end;

  	u64 split;
  	int del_nr = 0;
  	int del_slot = 0;

  	int recow;

  	int ret;

  	u64 ino = btrfs_ino(inode);

  
  	btrfs_drop_extent_cache(inode, start, end - 1, 0);
  
  	path = btrfs_alloc_path();

  	if (!path)
  		return -ENOMEM;

  again:

  	recow = 0;

  	split = start;

  	key.objectid = ino;

  	key.type = BTRFS_EXTENT_DATA_KEY;

  	key.offset = split;

  
  	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);

  	if (ret < 0)
  		goto out;

  	if (ret > 0 && path->slots[0] > 0)
  		path->slots[0]--;
  
  	leaf = path->nodes[0];
  	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);

  	BUG_ON(key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY);

  	fi = btrfs_item_ptr(leaf, path->slots[0],
  			    struct btrfs_file_extent_item);

  	BUG_ON(btrfs_file_extent_type(leaf, fi) !=
  	       BTRFS_FILE_EXTENT_PREALLOC);

  	extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
  	BUG_ON(key.offset > start || extent_end < end);
  
  	bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
  	num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);

  	orig_offset = key.offset - btrfs_file_extent_offset(leaf, fi);

  	memcpy(&new_key, &key, sizeof(new_key));
  
  	if (start == key.offset && end < extent_end) {
  		other_start = 0;
  		other_end = start;
  		if (extent_mergeable(leaf, path->slots[0] - 1,

  				     ino, bytenr, orig_offset,

  				     &other_start, &other_end)) {
  			new_key.offset = end;
  			btrfs_set_item_key_safe(trans, root, path, &new_key);
  			fi = btrfs_item_ptr(leaf, path->slots[0],
  					    struct btrfs_file_extent_item);
  			btrfs_set_file_extent_num_bytes(leaf, fi,
  							extent_end - end);
  			btrfs_set_file_extent_offset(leaf, fi,
  						     end - orig_offset);
  			fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
  					    struct btrfs_file_extent_item);
  			btrfs_set_file_extent_num_bytes(leaf, fi,
  							end - other_start);
  			btrfs_mark_buffer_dirty(leaf);
  			goto out;
  		}
  	}
  
  	if (start > key.offset && end == extent_end) {
  		other_start = end;
  		other_end = 0;
  		if (extent_mergeable(leaf, path->slots[0] + 1,

  				     ino, bytenr, orig_offset,

  				     &other_start, &other_end)) {
  			fi = btrfs_item_ptr(leaf, path->slots[0],
  					    struct btrfs_file_extent_item);
  			btrfs_set_file_extent_num_bytes(leaf, fi,
  							start - key.offset);
  			path->slots[0]++;
  			new_key.offset = start;
  			btrfs_set_item_key_safe(trans, root, path, &new_key);
  
  			fi = btrfs_item_ptr(leaf, path->slots[0],
  					    struct btrfs_file_extent_item);
  			btrfs_set_file_extent_num_bytes(leaf, fi,
  							other_end - start);
  			btrfs_set_file_extent_offset(leaf, fi,
  						     start - orig_offset);
  			btrfs_mark_buffer_dirty(leaf);
  			goto out;
  		}
  	}

  	while (start > key.offset || end < extent_end) {
  		if (key.offset == start)
  			split = end;

  		new_key.offset = split;
  		ret = btrfs_duplicate_item(trans, root, path, &new_key);
  		if (ret == -EAGAIN) {

  			btrfs_release_path(path);

  			goto again;

  		}

  		BUG_ON(ret < 0);

  		leaf = path->nodes[0];
  		fi = btrfs_item_ptr(leaf, path->slots[0] - 1,

  				    struct btrfs_file_extent_item);

  		btrfs_set_file_extent_num_bytes(leaf, fi,

  						split - key.offset);
  
  		fi = btrfs_item_ptr(leaf, path->slots[0],
  				    struct btrfs_file_extent_item);
  
  		btrfs_set_file_extent_offset(leaf, fi, split - orig_offset);
  		btrfs_set_file_extent_num_bytes(leaf, fi,
  						extent_end - split);

  		btrfs_mark_buffer_dirty(leaf);

  		ret = btrfs_inc_extent_ref(trans, root, bytenr, num_bytes, 0,
  					   root->root_key.objectid,

  					   ino, orig_offset);

  		BUG_ON(ret);

  		if (split == start) {
  			key.offset = start;
  		} else {
  			BUG_ON(start != key.offset);

  			path->slots[0]--;

  			extent_end = end;

  		}

  		recow = 1;

  	}

  	other_start = end;
  	other_end = 0;

  	if (extent_mergeable(leaf, path->slots[0] + 1,

  			     ino, bytenr, orig_offset,

  			     &other_start, &other_end)) {
  		if (recow) {

  			btrfs_release_path(path);

  			goto again;
  		}

  		extent_end = other_end;
  		del_slot = path->slots[0] + 1;
  		del_nr++;
  		ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
  					0, root->root_key.objectid,

  					ino, orig_offset);

  		BUG_ON(ret);

  	}

  	other_start = 0;
  	other_end = start;

  	if (extent_mergeable(leaf, path->slots[0] - 1,

  			     ino, bytenr, orig_offset,

  			     &other_start, &other_end)) {
  		if (recow) {

  			btrfs_release_path(path);

  			goto again;
  		}

  		key.offset = other_start;
  		del_slot = path->slots[0];
  		del_nr++;
  		ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
  					0, root->root_key.objectid,

  					ino, orig_offset);

  		BUG_ON(ret);
  	}
  	if (del_nr == 0) {

  		fi = btrfs_item_ptr(leaf, path->slots[0],
  			   struct btrfs_file_extent_item);

  		btrfs_set_file_extent_type(leaf, fi,
  					   BTRFS_FILE_EXTENT_REG);
  		btrfs_mark_buffer_dirty(leaf);

  	} else {

  		fi = btrfs_item_ptr(leaf, del_slot - 1,
  			   struct btrfs_file_extent_item);

  		btrfs_set_file_extent_type(leaf, fi,
  					   BTRFS_FILE_EXTENT_REG);
  		btrfs_set_file_extent_num_bytes(leaf, fi,
  						extent_end - key.offset);
  		btrfs_mark_buffer_dirty(leaf);

  		ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
  		BUG_ON(ret);
  	}

  out:

  	btrfs_free_path(path);
  	return 0;
  }

  /*

   * on error we return an unlocked page and the error value
   * on success we return a locked page and 0
   */

  static int prepare_uptodate_page(struct page *page, u64 pos,
  				 bool force_uptodate)

  {
  	int ret = 0;

  	if (((pos & (PAGE_CACHE_SIZE - 1)) || force_uptodate) &&
  	    !PageUptodate(page)) {

  		ret = btrfs_readpage(NULL, page);
  		if (ret)
  			return ret;
  		lock_page(page);
  		if (!PageUptodate(page)) {
  			unlock_page(page);
  			return -EIO;
  		}
  	}
  	return 0;
  }
  
  /*

   * this gets pages into the page cache and locks them down, it also properly
   * waits for data=ordered extents to finish before allowing the pages to be
   * modified.

   */

  static noinline int prepare_pages(struct btrfs_root *root, struct file *file,

  			 struct page **pages, size_t num_pages,
  			 loff_t pos, unsigned long first_index,

  			 size_t write_bytes, bool force_uptodate)

  {

  	struct extent_state *cached_state = NULL;

  	int i;
  	unsigned long index = pos >> PAGE_CACHE_SHIFT;

  	struct inode *inode = fdentry(file)->d_inode;

  	gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);

  	int err = 0;

  	int faili = 0;

  	u64 start_pos;

  	u64 last_pos;

  	start_pos = pos & ~((u64)root->sectorsize - 1);

  	last_pos = ((u64)index + num_pages) << PAGE_CACHE_SHIFT;

  again:

  	for (i = 0; i < num_pages; i++) {

  		pages[i] = find_or_create_page(inode->i_mapping, index + i,

  					       mask | __GFP_WRITE);

  		if (!pages[i]) {

  			faili = i - 1;
  			err = -ENOMEM;
  			goto fail;
  		}
  
  		if (i == 0)

  			err = prepare_uptodate_page(pages[i], pos,
  						    force_uptodate);

  		if (i == num_pages - 1)
  			err = prepare_uptodate_page(pages[i],

  						    pos + write_bytes, false);

  		if (err) {
  			page_cache_release(pages[i]);
  			faili = i - 1;
  			goto fail;

  		}

  		wait_on_page_writeback(pages[i]);

  	}

  	err = 0;

  	if (start_pos < inode->i_size) {

  		struct btrfs_ordered_extent *ordered;

  		lock_extent_bits(&BTRFS_I(inode)->io_tree,
  				 start_pos, last_pos - 1, 0, &cached_state,
  				 GFP_NOFS);

  		ordered = btrfs_lookup_first_ordered_extent(inode,
  							    last_pos - 1);

  		if (ordered &&
  		    ordered->file_offset + ordered->len > start_pos &&
  		    ordered->file_offset < last_pos) {
  			btrfs_put_ordered_extent(ordered);

  			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
  					     start_pos, last_pos - 1,
  					     &cached_state, GFP_NOFS);

  			for (i = 0; i < num_pages; i++) {
  				unlock_page(pages[i]);
  				page_cache_release(pages[i]);
  			}
  			btrfs_wait_ordered_range(inode, start_pos,
  						 last_pos - start_pos);
  			goto again;
  		}
  		if (ordered)
  			btrfs_put_ordered_extent(ordered);

  		clear_extent_bit(&BTRFS_I(inode)->io_tree, start_pos,

  				  last_pos - 1, EXTENT_DIRTY | EXTENT_DELALLOC |

  				  EXTENT_DO_ACCOUNTING, 0, 0, &cached_state,

  				  GFP_NOFS);

  		unlock_extent_cached(&BTRFS_I(inode)->io_tree,
  				     start_pos, last_pos - 1, &cached_state,
  				     GFP_NOFS);

  	}

  	for (i = 0; i < num_pages; i++) {

  		if (clear_page_dirty_for_io(pages[i]))
  			account_page_redirty(pages[i]);

  		set_page_extent_mapped(pages[i]);
  		WARN_ON(!PageLocked(pages[i]));
  	}

  	return 0;

  fail:
  	while (faili >= 0) {
  		unlock_page(pages[faili]);
  		page_cache_release(pages[faili]);
  		faili--;
  	}
  	return err;

  }

  static noinline ssize_t __btrfs_buffered_write(struct file *file,
  					       struct iov_iter *i,
  					       loff_t pos)

  {

  	struct inode *inode = fdentry(file)->d_inode;
  	struct btrfs_root *root = BTRFS_I(inode)->root;

  	struct page **pages = NULL;

  	unsigned long first_index;

  	size_t num_written = 0;
  	int nrptrs;

  	int ret = 0;

  	bool force_page_uptodate = false;

  	nrptrs = min((iov_iter_count(i) + PAGE_CACHE_SIZE - 1) /

  		     PAGE_CACHE_SIZE, PAGE_CACHE_SIZE /
  		     (sizeof(struct page *)));

  	nrptrs = min(nrptrs, current->nr_dirtied_pause - current->nr_dirtied);
  	nrptrs = max(nrptrs, 8);

  	pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);

  	if (!pages)
  		return -ENOMEM;

  	first_index = pos >> PAGE_CACHE_SHIFT;

  	while (iov_iter_count(i) > 0) {

  		size_t offset = pos & (PAGE_CACHE_SIZE - 1);

  		size_t write_bytes = min(iov_iter_count(i),

  					 nrptrs * (size_t)PAGE_CACHE_SIZE -

  					 offset);

  		size_t num_pages = (write_bytes + offset +
  				    PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

  		size_t dirty_pages;
  		size_t copied;

  		WARN_ON(num_pages > nrptrs);

  		/*
  		 * Fault pages before locking them in prepare_pages
  		 * to avoid recursive lock
  		 */

  		if (unlikely(iov_iter_fault_in_readable(i, write_bytes))) {

  			ret = -EFAULT;

  			break;

  		}
  
  		ret = btrfs_delalloc_reserve_space(inode,
  					num_pages << PAGE_CACHE_SHIFT);

  		if (ret)

  			break;

  		/*
  		 * This is going to setup the pages array with the number of
  		 * pages we want, so we don't really need to worry about the
  		 * contents of pages from loop to loop
  		 */

  		ret = prepare_pages(root, file, pages, num_pages,

  				    pos, first_index, write_bytes,
  				    force_page_uptodate);

  		if (ret) {

  			btrfs_delalloc_release_space(inode,
  					num_pages << PAGE_CACHE_SHIFT);

  			break;

  		}

  		copied = btrfs_copy_from_user(pos, num_pages,

  					   write_bytes, pages, i);

  
  		/*
  		 * if we have trouble faulting in the pages, fall
  		 * back to one page at a time
  		 */
  		if (copied < write_bytes)
  			nrptrs = 1;

  		if (copied == 0) {
  			force_page_uptodate = true;

  			dirty_pages = 0;

  		} else {
  			force_page_uptodate = false;

  			dirty_pages = (copied + offset +
  				       PAGE_CACHE_SIZE - 1) >>
  				       PAGE_CACHE_SHIFT;

  		}

  		/*
  		 * If we had a short copy we need to release the excess delaloc
  		 * bytes we reserved.  We need to increment outstanding_extents
  		 * because btrfs_delalloc_release_space will decrement it, but
  		 * we still have an outstanding extent for the chunk we actually
  		 * managed to copy.
  		 */

  		if (num_pages > dirty_pages) {

  			if (copied > 0) {
  				spin_lock(&BTRFS_I(inode)->lock);
  				BTRFS_I(inode)->outstanding_extents++;
  				spin_unlock(&BTRFS_I(inode)->lock);
  			}

  			btrfs_delalloc_release_space(inode,
  					(num_pages - dirty_pages) <<
  					PAGE_CACHE_SHIFT);
  		}
  
  		if (copied > 0) {

  			ret = btrfs_dirty_pages(root, inode, pages,
  						dirty_pages, pos, copied,
  						NULL);

  			if (ret) {
  				btrfs_delalloc_release_space(inode,
  					dirty_pages << PAGE_CACHE_SHIFT);
  				btrfs_drop_pages(pages, num_pages);
  				break;
  			}

  		}

  		btrfs_drop_pages(pages, num_pages);

  		cond_resched();
  
  		balance_dirty_pages_ratelimited_nr(inode->i_mapping,
  						   dirty_pages);
  		if (dirty_pages < (root->leafsize >> PAGE_CACHE_SHIFT) + 1)
  			btrfs_btree_balance_dirty(root, 1);
  		btrfs_throttle(root);

  		pos += copied;
  		num_written += copied;

  	}

  	kfree(pages);
  
  	return num_written ? num_written : ret;
  }
  
  static ssize_t __btrfs_direct_write(struct kiocb *iocb,
  				    const struct iovec *iov,
  				    unsigned long nr_segs, loff_t pos,
  				    loff_t *ppos, size_t count, size_t ocount)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = fdentry(file)->d_inode;
  	struct iov_iter i;
  	ssize_t written;
  	ssize_t written_buffered;
  	loff_t endbyte;
  	int err;
  
  	written = generic_file_direct_write(iocb, iov, &nr_segs, pos, ppos,
  					    count, ocount);
  
  	/*
  	 * the generic O_DIRECT will update in-memory i_size after the
  	 * DIOs are done.  But our endio handlers that update the on
  	 * disk i_size never update past the in memory i_size.  So we
  	 * need one more update here to catch any additions to the
  	 * file
  	 */
  	if (inode->i_size != BTRFS_I(inode)->disk_i_size) {
  		btrfs_ordered_update_i_size(inode, inode->i_size, NULL);
  		mark_inode_dirty(inode);
  	}
  
  	if (written < 0 || written == count)
  		return written;
  
  	pos += written;
  	count -= written;
  	iov_iter_init(&i, iov, nr_segs, count, written);
  	written_buffered = __btrfs_buffered_write(file, &i, 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;
  	written += written_buffered;
  	*ppos = pos + written_buffered;
  	invalidate_mapping_pages(file->f_mapping, pos >> PAGE_CACHE_SHIFT,
  				 endbyte >> PAGE_CACHE_SHIFT);

  out:

  	return written ? written : err;
  }

  static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
  				    const struct iovec *iov,
  				    unsigned long nr_segs, loff_t pos)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = fdentry(file)->d_inode;
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	loff_t *ppos = &iocb->ki_pos;

  	u64 start_pos;

  	ssize_t num_written = 0;
  	ssize_t err = 0;
  	size_t count, ocount;
  
  	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
  
  	mutex_lock(&inode->i_mutex);
  
  	err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
  	if (err) {
  		mutex_unlock(&inode->i_mutex);
  		goto out;
  	}
  	count = ocount;
  
  	current->backing_dev_info = inode->i_mapping->backing_dev_info;
  	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
  	if (err) {
  		mutex_unlock(&inode->i_mutex);
  		goto out;
  	}
  
  	if (count == 0) {
  		mutex_unlock(&inode->i_mutex);
  		goto out;
  	}
  
  	err = file_remove_suid(file);
  	if (err) {
  		mutex_unlock(&inode->i_mutex);
  		goto out;
  	}
  
  	/*
  	 * If BTRFS flips readonly due to some impossible error
  	 * (fs_info->fs_state now has BTRFS_SUPER_FLAG_ERROR),
  	 * although we have opened a file as writable, we have
  	 * to stop this write operation to ensure FS consistency.
  	 */
  	if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR) {
  		mutex_unlock(&inode->i_mutex);
  		err = -EROFS;
  		goto out;
  	}

  	err = btrfs_update_time(file);
  	if (err) {
  		mutex_unlock(&inode->i_mutex);
  		goto out;
  	}

  	BTRFS_I(inode)->sequence++;

  	start_pos = round_down(pos, root->sectorsize);
  	if (start_pos > i_size_read(inode)) {
  		err = btrfs_cont_expand(inode, i_size_read(inode), start_pos);
  		if (err) {
  			mutex_unlock(&inode->i_mutex);
  			goto out;
  		}
  	}

  	if (unlikely(file->f_flags & O_DIRECT)) {
  		num_written = __btrfs_direct_write(iocb, iov, nr_segs,
  						   pos, ppos, count, ocount);
  	} else {
  		struct iov_iter i;
  
  		iov_iter_init(&i, iov, nr_segs, count, num_written);
  
  		num_written = __btrfs_buffered_write(file, &i, pos);
  		if (num_written > 0)
  			*ppos = pos + num_written;
  	}
  
  	mutex_unlock(&inode->i_mutex);

  	/*
  	 * we want to make sure fsync finds this change
  	 * but we haven't joined a transaction running right now.
  	 *
  	 * Later on, someone is sure to update the inode and get the
  	 * real transid recorded.
  	 *
  	 * We set last_trans now to the fs_info generation + 1,
  	 * this will either be one more than the running transaction
  	 * or the generation used for the next transaction if there isn't
  	 * one running right now.
  	 */
  	BTRFS_I(inode)->last_trans = root->fs_info->generation + 1;

  	if (num_written > 0 || num_written == -EIOCBQUEUED) {
  		err = generic_write_sync(file, pos, num_written);
  		if (err < 0 && num_written > 0)

  			num_written = err;
  	}

  out:

  	current->backing_dev_info = NULL;

  	return num_written ? num_written : err;
  }

  int btrfs_release_file(struct inode *inode, struct file *filp)

  {

  	/*
  	 * ordered_data_close is set by settattr when we are about to truncate
  	 * a file from a non-zero size to a zero size.  This tries to
  	 * flush down new bytes that may have been written if the
  	 * application were using truncate to replace a file in place.
  	 */
  	if (BTRFS_I(inode)->ordered_data_close) {
  		BTRFS_I(inode)->ordered_data_close = 0;
  		btrfs_add_ordered_operation(NULL, BTRFS_I(inode)->root, inode);
  		if (inode->i_size > BTRFS_ORDERED_OPERATIONS_FLUSH_LIMIT)
  			filemap_flush(inode->i_mapping);
  	}

  	if (filp->private_data)
  		btrfs_ioctl_trans_end(filp);

  	return 0;
  }

  /*
   * fsync call for both files and directories.  This logs the inode into
   * the tree log instead of forcing full commits whenever possible.
   *
   * It needs to call filemap_fdatawait so that all ordered extent updates are
   * in the metadata btree are up to date for copying to the log.
   *
   * It drops the inode mutex before doing the tree log commit.  This is an
   * important optimization for directories because holding the mutex prevents
   * new operations on the dir while we write to disk.
   */

  int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)

  {

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

  	struct inode *inode = dentry->d_inode;
  	struct btrfs_root *root = BTRFS_I(inode)->root;

  	int ret = 0;

  	struct btrfs_trans_handle *trans;

  	trace_btrfs_sync_file(file, datasync);

  	ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
  	if (ret)
  		return ret;
  	mutex_lock(&inode->i_mutex);

  	/* we wait first, since the writeback may change the inode */
  	root->log_batch++;

  	btrfs_wait_ordered_range(inode, 0, (u64)-1);
  	root->log_batch++;

  	/*

  	 * check the transaction that last modified this inode
  	 * and see if its already been committed

  	 */

  	if (!BTRFS_I(inode)->last_trans) {
  		mutex_unlock(&inode->i_mutex);

  		goto out;

  	}

  	/*
  	 * if the last transaction that changed this file was before
  	 * the current transaction, we can bail out now without any
  	 * syncing
  	 */

  	smp_mb();

  	if (BTRFS_I(inode)->last_trans <=
  	    root->fs_info->last_trans_committed) {
  		BTRFS_I(inode)->last_trans = 0;

  		mutex_unlock(&inode->i_mutex);

  		goto out;
  	}

  
  	/*

  	 * ok we haven't committed the transaction yet, lets do a commit
  	 */

  	if (file->private_data)

  		btrfs_ioctl_trans_end(file);

  	trans = btrfs_start_transaction(root, 0);
  	if (IS_ERR(trans)) {
  		ret = PTR_ERR(trans);

  		mutex_unlock(&inode->i_mutex);

  		goto out;
  	}

  	ret = btrfs_log_dentry_safe(trans, root, dentry);

  	if (ret < 0) {
  		mutex_unlock(&inode->i_mutex);

  		goto out;

  	}

  
  	/* we've logged all the items and now have a consistent
  	 * version of the file in the log.  It is possible that
  	 * someone will come in and modify the file, but that's
  	 * fine because the log is consistent on disk, and we
  	 * have references to all of the file's extents
  	 *
  	 * It is possible that someone will come in and log the
  	 * file again, but that will end up using the synchronization
  	 * inside btrfs_sync_log to keep things safe.
  	 */

  	mutex_unlock(&inode->i_mutex);

  	if (ret != BTRFS_NO_LOG_SYNC) {
  		if (ret > 0) {

  			ret = btrfs_commit_transaction(trans, root);

  		} else {
  			ret = btrfs_sync_log(trans, root);
  			if (ret == 0)
  				ret = btrfs_end_transaction(trans, root);
  			else
  				ret = btrfs_commit_transaction(trans, root);
  		}
  	} else {
  		ret = btrfs_end_transaction(trans, root);

  	}

  out:

  	return ret > 0 ? -EIO : ret;

  }

  static const struct vm_operations_struct btrfs_file_vm_ops = {

  	.fault		= filemap_fault,

  	.page_mkwrite	= btrfs_page_mkwrite,
  };
  
  static int btrfs_file_mmap(struct file	*filp, struct vm_area_struct *vma)
  {

  	struct address_space *mapping = filp->f_mapping;
  
  	if (!mapping->a_ops->readpage)
  		return -ENOEXEC;

  	file_accessed(filp);

  	vma->vm_ops = &btrfs_file_vm_ops;
  	vma->vm_flags |= VM_CAN_NONLINEAR;

  	return 0;
  }

  static long btrfs_fallocate(struct file *file, int mode,
  			    loff_t offset, loff_t len)
  {
  	struct inode *inode = file->f_path.dentry->d_inode;
  	struct extent_state *cached_state = NULL;
  	u64 cur_offset;
  	u64 last_byte;
  	u64 alloc_start;
  	u64 alloc_end;
  	u64 alloc_hint = 0;
  	u64 locked_end;
  	u64 mask = BTRFS_I(inode)->root->sectorsize - 1;
  	struct extent_map *em;
  	int ret;
  
  	alloc_start = offset & ~mask;
  	alloc_end =  (offset + len + mask) & ~mask;
  
  	/* We only support the FALLOC_FL_KEEP_SIZE mode */
  	if (mode & ~FALLOC_FL_KEEP_SIZE)
  		return -EOPNOTSUPP;
  
  	/*
  	 * wait for ordered IO before we have any locks.  We'll loop again
  	 * below with the locks held.
  	 */
  	btrfs_wait_ordered_range(inode, alloc_start, alloc_end - alloc_start);
  
  	mutex_lock(&inode->i_mutex);
  	ret = inode_newsize_ok(inode, alloc_end);
  	if (ret)
  		goto out;
  
  	if (alloc_start > inode->i_size) {

  		ret = btrfs_cont_expand(inode, i_size_read(inode),
  					alloc_start);

  		if (ret)
  			goto out;
  	}

  	locked_end = alloc_end - 1;
  	while (1) {
  		struct btrfs_ordered_extent *ordered;
  
  		/* the extent lock is ordered inside the running
  		 * transaction
  		 */
  		lock_extent_bits(&BTRFS_I(inode)->io_tree, alloc_start,
  				 locked_end, 0, &cached_state, GFP_NOFS);
  		ordered = btrfs_lookup_first_ordered_extent(inode,
  							    alloc_end - 1);
  		if (ordered &&
  		    ordered->file_offset + ordered->len > alloc_start &&
  		    ordered->file_offset < alloc_end) {
  			btrfs_put_ordered_extent(ordered);
  			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
  					     alloc_start, locked_end,
  					     &cached_state, GFP_NOFS);
  			/*
  			 * we can't wait on the range with the transaction
  			 * running or with the extent lock held
  			 */
  			btrfs_wait_ordered_range(inode, alloc_start,
  						 alloc_end - alloc_start);
  		} else {
  			if (ordered)
  				btrfs_put_ordered_extent(ordered);
  			break;
  		}
  	}
  
  	cur_offset = alloc_start;
  	while (1) {

  		u64 actual_end;

  		em = btrfs_get_extent(inode, NULL, 0, cur_offset,
  				      alloc_end - cur_offset, 0);

  		BUG_ON(IS_ERR_OR_NULL(em));

  		last_byte = min(extent_map_end(em), alloc_end);

  		actual_end = min_t(u64, extent_map_end(em), offset + len);

  		last_byte = (last_byte + mask) & ~mask;

  		if (em->block_start == EXTENT_MAP_HOLE ||
  		    (cur_offset >= inode->i_size &&
  		     !test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) {

  
  			/*
  			 * Make sure we have enough space before we do the
  			 * allocation.
  			 */
  			ret = btrfs_check_data_free_space(inode, last_byte -
  							  cur_offset);
  			if (ret) {
  				free_extent_map(em);
  				break;
  			}

  			ret = btrfs_prealloc_file_range(inode, mode, cur_offset,
  							last_byte - cur_offset,
  							1 << inode->i_blkbits,
  							offset + len,
  							&alloc_hint);

  
  			/* Let go of our reservation. */
  			btrfs_free_reserved_data_space(inode, last_byte -
  						       cur_offset);

  			if (ret < 0) {
  				free_extent_map(em);
  				break;
  			}

  		} else if (actual_end > inode->i_size &&
  			   !(mode & FALLOC_FL_KEEP_SIZE)) {
  			/*
  			 * We didn't need to allocate any more space, but we
  			 * still extended the size of the file so we need to
  			 * update i_size.
  			 */
  			inode->i_ctime = CURRENT_TIME;
  			i_size_write(inode, actual_end);
  			btrfs_ordered_update_i_size(inode, actual_end, NULL);

  		}
  		free_extent_map(em);
  
  		cur_offset = last_byte;
  		if (cur_offset >= alloc_end) {
  			ret = 0;
  			break;
  		}
  	}
  	unlock_extent_cached(&BTRFS_I(inode)->io_tree, alloc_start, locked_end,
  			     &cached_state, GFP_NOFS);

  out:
  	mutex_unlock(&inode->i_mutex);
  	return ret;
  }

  static int find_desired_extent(struct inode *inode, loff_t *offset, int origin)
  {
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct extent_map *em;
  	struct extent_state *cached_state = NULL;
  	u64 lockstart = *offset;
  	u64 lockend = i_size_read(inode);
  	u64 start = *offset;
  	u64 orig_start = *offset;
  	u64 len = i_size_read(inode);
  	u64 last_end = 0;
  	int ret = 0;
  
  	lockend = max_t(u64, root->sectorsize, lockend);
  	if (lockend <= lockstart)
  		lockend = lockstart + root->sectorsize;
  
  	len = lockend - lockstart + 1;
  
  	len = max_t(u64, len, root->sectorsize);
  	if (inode->i_size == 0)
  		return -ENXIO;
  
  	lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend, 0,
  			 &cached_state, GFP_NOFS);
  
  	/*
  	 * Delalloc is such a pain.  If we have a hole and we have pending
  	 * delalloc for a portion of the hole we will get back a hole that
  	 * exists for the entire range since it hasn't been actually written
  	 * yet.  So to take care of this case we need to look for an extent just
  	 * before the position we want in case there is outstanding delalloc
  	 * going on here.
  	 */
  	if (origin == SEEK_HOLE && start != 0) {
  		if (start <= root->sectorsize)
  			em = btrfs_get_extent_fiemap(inode, NULL, 0, 0,
  						     root->sectorsize, 0);
  		else
  			em = btrfs_get_extent_fiemap(inode, NULL, 0,
  						     start - root->sectorsize,
  						     root->sectorsize, 0);
  		if (IS_ERR(em)) {
  			ret = -ENXIO;
  			goto out;
  		}
  		last_end = em->start + em->len;
  		if (em->block_start == EXTENT_MAP_DELALLOC)
  			last_end = min_t(u64, last_end, inode->i_size);
  		free_extent_map(em);
  	}
  
  	while (1) {
  		em = btrfs_get_extent_fiemap(inode, NULL, 0, start, len, 0);
  		if (IS_ERR(em)) {
  			ret = -ENXIO;
  			break;
  		}
  
  		if (em->block_start == EXTENT_MAP_HOLE) {
  			if (test_bit(EXTENT_FLAG_VACANCY, &em->flags)) {
  				if (last_end <= orig_start) {
  					free_extent_map(em);
  					ret = -ENXIO;
  					break;
  				}
  			}
  
  			if (origin == SEEK_HOLE) {
  				*offset = start;
  				free_extent_map(em);
  				break;
  			}
  		} else {
  			if (origin == SEEK_DATA) {
  				if (em->block_start == EXTENT_MAP_DELALLOC) {
  					if (start >= inode->i_size) {
  						free_extent_map(em);
  						ret = -ENXIO;
  						break;
  					}
  				}
  
  				*offset = start;
  				free_extent_map(em);
  				break;
  			}
  		}
  
  		start = em->start + em->len;
  		last_end = em->start + em->len;
  
  		if (em->block_start == EXTENT_MAP_DELALLOC)
  			last_end = min_t(u64, last_end, inode->i_size);
  
  		if (test_bit(EXTENT_FLAG_VACANCY, &em->flags)) {
  			free_extent_map(em);
  			ret = -ENXIO;
  			break;
  		}
  		free_extent_map(em);
  		cond_resched();
  	}
  	if (!ret)
  		*offset = min(*offset, inode->i_size);
  out:
  	unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
  			     &cached_state, GFP_NOFS);
  	return ret;
  }
  
  static loff_t btrfs_file_llseek(struct file *file, loff_t offset, int origin)
  {
  	struct inode *inode = file->f_mapping->host;
  	int ret;
  
  	mutex_lock(&inode->i_mutex);
  	switch (origin) {
  	case SEEK_END:
  	case SEEK_CUR:

  		offset = generic_file_llseek(file, offset, origin);

  		goto out;
  	case SEEK_DATA:
  	case SEEK_HOLE:

  		if (offset >= i_size_read(inode)) {
  			mutex_unlock(&inode->i_mutex);
  			return -ENXIO;
  		}

  		ret = find_desired_extent(inode, &offset, origin);
  		if (ret) {
  			mutex_unlock(&inode->i_mutex);
  			return ret;
  		}
  	}

  	if (offset < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET)) {

  		offset = -EINVAL;

  		goto out;
  	}
  	if (offset > inode->i_sb->s_maxbytes) {

  		offset = -EINVAL;

  		goto out;
  	}

  
  	/* Special lock needed here? */
  	if (offset != file->f_pos) {
  		file->f_pos = offset;
  		file->f_version = 0;
  	}
  out:
  	mutex_unlock(&inode->i_mutex);
  	return offset;
  }

  const struct file_operations btrfs_file_operations = {

  	.llseek		= btrfs_file_llseek,

  	.read		= do_sync_read,

  	.write		= do_sync_write,

  	.aio_read       = generic_file_aio_read,

  	.splice_read	= generic_file_splice_read,

  	.aio_write	= btrfs_file_aio_write,

  	.mmap		= btrfs_file_mmap,

  	.open		= generic_file_open,

  	.release	= btrfs_release_file,

  	.fsync		= btrfs_sync_file,

  	.fallocate	= btrfs_fallocate,

  	.unlocked_ioctl	= btrfs_ioctl,

  #ifdef CONFIG_COMPAT

  	.compat_ioctl	= btrfs_ioctl,

  #endif
  };