text: /*
   * 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 <linux/btrfs.h>
  #include <linux/uio.h>
  #include "ctree.h"
  #include "disk-io.h"
  #include "transaction.h"
  #include "btrfs_inode.h"
  #include "print-tree.h"
  #include "tree-log.h"
  #include "locking.h"
  #include "volumes.h"
  #include "qgroup.h"
  
  static struct kmem_cache *btrfs_inode_defrag_cachep;
  /*
   * 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;
  };
  
  static int __compare_inode_defrag(struct inode_defrag *defrag1,
  				  struct inode_defrag *defrag2)
  {
  	if (defrag1->root > defrag2->root)
  		return 1;
  	else if (defrag1->root < defrag2->root)
  		return -1;
  	else if (defrag1->ino > defrag2->ino)
  		return 1;
  	else if (defrag1->ino < defrag2->ino)
  		return -1;
  	else
  		return 0;
  }
  
  /* 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 int __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;
  	int ret;
  
  	p = &root->fs_info->defrag_inodes.rb_node;
  	while (*p) {
  		parent = *p;
  		entry = rb_entry(parent, struct inode_defrag, rb_node);
  
  		ret = __compare_inode_defrag(defrag, entry);
  		if (ret < 0)
  			p = &parent->rb_left;
  		else if (ret > 0)
  			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;
  			return -EEXIST;
  		}
  	}
  	set_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags);
  	rb_link_node(&defrag->rb_node, parent, p);
  	rb_insert_color(&defrag->rb_node, &root->fs_info->defrag_inodes);
  	return 0;
  }
  
  static inline int __need_auto_defrag(struct btrfs_root *root)
  {
  	if (!btrfs_test_opt(root, AUTO_DEFRAG))
  		return 0;
  
  	if (btrfs_fs_closing(root->fs_info))
  		return 0;
  
  	return 1;
  }
  
  /*
   * 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;
  	int ret;
  
  	if (!__need_auto_defrag(root))
  		return 0;
  
  	if (test_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags))
  		return 0;
  
  	if (trans)
  		transid = trans->transid;
  	else
  		transid = BTRFS_I(inode)->root->last_trans;
  
  	defrag = kmem_cache_zalloc(btrfs_inode_defrag_cachep, 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 (!test_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags)) {
  		/*
  		 * If we set IN_DEFRAG flag and evict the inode from memory,
  		 * and then re-read this inode, this new inode doesn't have
  		 * IN_DEFRAG flag. At the case, we may find the existed defrag.
  		 */
  		ret = __btrfs_add_inode_defrag(inode, defrag);
  		if (ret)
  			kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
  	} else {
  		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
  	}
  	spin_unlock(&root->fs_info->defrag_inodes_lock);
  	return 0;
  }
  
  /*
   * Requeue the defrag object. If there is a defrag object that points to
   * the same inode in the tree, we will merge them together (by
   * __btrfs_add_inode_defrag()) and free the one that we want to requeue.
   */
  static void btrfs_requeue_inode_defrag(struct inode *inode,
  				       struct inode_defrag *defrag)
  {
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	int ret;
  
  	if (!__need_auto_defrag(root))
  		goto out;
  
  	/*
  	 * Here we don't check the IN_DEFRAG flag, because we need merge
  	 * them together.
  	 */
  	spin_lock(&root->fs_info->defrag_inodes_lock);
  	ret = __btrfs_add_inode_defrag(inode, defrag);
  	spin_unlock(&root->fs_info->defrag_inodes_lock);
  	if (ret)
  		goto out;
  	return;
  out:
  	kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
  }
  
  /*
   * pick the defragable inode that we want, if it doesn't exist, we will get
   * the next one.
   */
  static struct inode_defrag *
  btrfs_pick_defrag_inode(struct btrfs_fs_info *fs_info, u64 root, u64 ino)
  {
  	struct inode_defrag *entry = NULL;
  	struct inode_defrag tmp;
  	struct rb_node *p;
  	struct rb_node *parent = NULL;
  	int ret;
  
  	tmp.ino = ino;
  	tmp.root = root;
  
  	spin_lock(&fs_info->defrag_inodes_lock);
  	p = fs_info->defrag_inodes.rb_node;
  	while (p) {
  		parent = p;
  		entry = rb_entry(parent, struct inode_defrag, rb_node);
  
  		ret = __compare_inode_defrag(&tmp, entry);
  		if (ret < 0)
  			p = parent->rb_left;
  		else if (ret > 0)
  			p = parent->rb_right;
  		else
  			goto out;
  	}
  
  	if (parent && __compare_inode_defrag(&tmp, entry) > 0) {
  		parent = rb_next(parent);
  		if (parent)
  			entry = rb_entry(parent, struct inode_defrag, rb_node);
  		else
  			entry = NULL;
  	}
  out:
  	if (entry)
  		rb_erase(parent, &fs_info->defrag_inodes);
  	spin_unlock(&fs_info->defrag_inodes_lock);
  	return entry;
  }
  
  void btrfs_cleanup_defrag_inodes(struct btrfs_fs_info *fs_info)
  {
  	struct inode_defrag *defrag;
  	struct rb_node *node;
  
  	spin_lock(&fs_info->defrag_inodes_lock);
  	node = rb_first(&fs_info->defrag_inodes);
  	while (node) {
  		rb_erase(node, &fs_info->defrag_inodes);
  		defrag = rb_entry(node, struct inode_defrag, rb_node);
  		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
  
  		cond_resched_lock(&fs_info->defrag_inodes_lock);
  
  		node = rb_first(&fs_info->defrag_inodes);
  	}
  	spin_unlock(&fs_info->defrag_inodes_lock);
  }
  
  #define BTRFS_DEFRAG_BATCH	1024
  
  static int __btrfs_run_defrag_inode(struct btrfs_fs_info *fs_info,
  				    struct inode_defrag *defrag)
  {
  	struct btrfs_root *inode_root;
  	struct inode *inode;
  	struct btrfs_key key;
  	struct btrfs_ioctl_defrag_range_args range;
  	int num_defrag;
  	int index;
  	int ret;
  
  	/* get the inode */
  	key.objectid = defrag->root;
  	key.type = BTRFS_ROOT_ITEM_KEY;
  	key.offset = (u64)-1;
  
  	index = srcu_read_lock(&fs_info->subvol_srcu);
  
  	inode_root = btrfs_read_fs_root_no_name(fs_info, &key);
  	if (IS_ERR(inode_root)) {
  		ret = PTR_ERR(inode_root);
  		goto cleanup;
  	}
  
  	key.objectid = defrag->ino;
  	key.type = BTRFS_INODE_ITEM_KEY;
  	key.offset = 0;
  	inode = btrfs_iget(fs_info->sb, &key, inode_root, NULL);
  	if (IS_ERR(inode)) {
  		ret = PTR_ERR(inode);
  		goto cleanup;
  	}
  	srcu_read_unlock(&fs_info->subvol_srcu, index);
  
  	/* do a chunk of defrag */
  	clear_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags);
  	memset(&range, 0, sizeof(range));
  	range.len = (u64)-1;
  	range.start = defrag->last_offset;
  
  	sb_start_write(fs_info->sb);
  	num_defrag = btrfs_defrag_file(inode, NULL, &range, defrag->transid,
  				       BTRFS_DEFRAG_BATCH);
  	sb_end_write(fs_info->sb);
  	/*
  	 * if we filled the whole defrag batch, there
  	 * must be more work to do.  Queue this defrag
  	 * again
  	 */
  	if (num_defrag == BTRFS_DEFRAG_BATCH) {
  		defrag->last_offset = range.start;
  		btrfs_requeue_inode_defrag(inode, defrag);
  	} 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_requeue_inode_defrag(inode, defrag);
  	} else {
  		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
  	}
  
  	iput(inode);
  	return 0;
  cleanup:
  	srcu_read_unlock(&fs_info->subvol_srcu, index);
  	kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
  	return ret;
  }
  
  /*
   * 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;
  	u64 first_ino = 0;
  	u64 root_objectid = 0;
  
  	atomic_inc(&fs_info->defrag_running);
  	while (1) {
  		/* Pause the auto defragger. */
  		if (test_bit(BTRFS_FS_STATE_REMOUNTING,
  			     &fs_info->fs_state))
  			break;
  
  		if (!__need_auto_defrag(fs_info->tree_root))
  			break;
  
  		/* find an inode to defrag */
  		defrag = btrfs_pick_defrag_inode(fs_info, root_objectid,
  						 first_ino);
  		if (!defrag) {
  			if (root_objectid || first_ino) {
  				root_objectid = 0;
  				first_ino = 0;
  				continue;
  			} else {
  				break;
  			}
  		}
  
  		first_ino = defrag->ino + 1;
  		root_objectid = defrag->root;
  
  		__btrfs_run_defrag_inode(fs_info, defrag);
  	}
  	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
  		 */
  		copied = iov_iter_copy_from_user_atomic(page, i, offset, count);
  
  		/* 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_write_iter to fault page */
  		if (unlikely(copied == 0))
  			break;
  
  		if (copied < PAGE_CACHE_SIZE - offset) {
  			offset += copied;
  		} else {
  			pg++;
  			offset = 0;
  		}
  	}
  	return total_copied;
  }
  
  /*
   * unlocks pages after btrfs_file_write is done with them
   */
  static 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. There should be no need to mark the pages
  		 * accessed as prepare_pages should have marked them accessed
  		 * in prepare_pages via find_or_create_page()
  		 */
  		ClearPageChecked(pages[i]);
  		unlock_page(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 = ALIGN(write_bytes + pos - start_pos, root->sectorsize);
  
  	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.
   */
  void 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;
  	u64 gen;
  	int ret;
  	int testend = 1;
  	unsigned long flags;
  	int compressed = 0;
  	bool modified;
  
  	WARN_ON(end < start);
  	if (end == (u64)-1) {
  		len = (u64)-1;
  		testend = 0;
  	}
  	while (1) {
  		int no_splits = 0;
  
  		modified = false;
  		if (!split)
  			split = alloc_extent_map();
  		if (!split2)
  			split2 = alloc_extent_map();
  		if (!split || !split2)
  			no_splits = 1;
  
  		write_lock(&em_tree->lock);
  		em = lookup_extent_mapping(em_tree, start, len);
  		if (!em) {
  			write_unlock(&em_tree->lock);
  			break;
  		}
  		flags = em->flags;
  		gen = em->generation;
  		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);
  		clear_bit(EXTENT_FLAG_LOGGING, &flags);
  		modified = !list_empty(&em->list);
  		if (no_splits)
  			goto next;
  
  		if (em->start < start) {
  			split->start = em->start;
  			split->len = start - em->start;
  
  			if (em->block_start < EXTENT_MAP_LAST_BYTE) {
  				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->orig_block_len = max(split->block_len,
  						em->orig_block_len);
  				split->ram_bytes = em->ram_bytes;
  			} else {
  				split->orig_start = split->start;
  				split->block_len = 0;
  				split->block_start = em->block_start;
  				split->orig_block_len = 0;
  				split->ram_bytes = split->len;
  			}
  
  			split->generation = gen;
  			split->bdev = em->bdev;
  			split->flags = flags;
  			split->compress_type = em->compress_type;
  			replace_extent_mapping(em_tree, em, split, modified);
  			free_extent_map(split);
  			split = split2;
  			split2 = NULL;
  		}
  		if (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;
  			split->generation = gen;
  
  			if (em->block_start < EXTENT_MAP_LAST_BYTE) {
  				split->orig_block_len = max(em->block_len,
  						    em->orig_block_len);
  
  				split->ram_bytes = em->ram_bytes;
  				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 = em->orig_start;
  				}
  			} else {
  				split->ram_bytes = split->len;
  				split->orig_start = split->start;
  				split->block_len = 0;
  				split->block_start = em->block_start;
  				split->orig_block_len = 0;
  			}
  
  			if (extent_map_in_tree(em)) {
  				replace_extent_mapping(em_tree, em, split,
  						       modified);
  			} else {
  				ret = add_extent_mapping(em_tree, split,
  							 modified);
  				ASSERT(ret == 0); /* Logic error */
  			}
  			free_extent_map(split);
  			split = NULL;
  		}
  next:
  		if (extent_map_in_tree(em))
  			remove_extent_mapping(em_tree, em);
  		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);
  }
  
  /*
   * 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 btrfs_root *root, struct inode *inode,
  			 struct btrfs_path *path, u64 start, u64 end,
  			 u64 *drop_end, int drop_cache,
  			 int replace_extent,
  			 u32 extent_item_size,
  			 int *key_inserted)
  {
  	struct extent_buffer *leaf;
  	struct btrfs_file_extent_item *fi;
  	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;
  	int modify_tree = -1;
  	int update_refs;
  	int found = 0;
  	int leafs_visited = 0;
  
  	if (drop_cache)
  		btrfs_drop_extent_cache(inode, start, end - 1, 0);
  
  	if (start >= BTRFS_I(inode)->disk_i_size && !replace_extent)
  		modify_tree = 0;
  
  	update_refs = (test_bit(BTRFS_ROOT_REF_COWS, &root->state) ||
  		       root == root->fs_info->tree_root);
  	while (1) {
  		recow = 0;
  		ret = btrfs_lookup_file_extent(trans, root, path, ino,
  					       search_start, modify_tree);
  		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;
  		leafs_visited++;
  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;
  			}
  			leafs_visited++;
  			leaf = path->nodes[0];
  			recow = 1;
  		}
  
  		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
  
  		if (key.objectid > ino)
  			break;
  		if (WARN_ON_ONCE(key.objectid < ino) ||
  		    key.type < BTRFS_EXTENT_DATA_KEY) {
  			ASSERT(del_nr == 0);
  			path->slots[0]++;
  			goto next_slot;
  		}
  		if (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,
  						     path->slots[0], fi);
  		} else {
  			/* can't happen */
  			BUG();
  		}
  
  		/*
  		 * Don't skip extent items representing 0 byte lengths. They
  		 * used to be created (bug) if while punching holes we hit
  		 * -ENOSPC condition. So if we find one here, just ensure we
  		 * delete it, otherwise we would insert a new file extent item
  		 * with the same key (offset) as that 0 bytes length file
  		 * extent item in the call to setup_items_for_insert() later
  		 * in this function.
  		 */
  		if (extent_end == key.offset && extent_end >= search_start)
  			goto delete_extent_item;
  
  		if (extent_end <= search_start) {
  			path->slots[0]++;
  			goto next_slot;
  		}
  
  		found = 1;
  		search_start = max(key.offset, start);
  		if (recow || !modify_tree) {
  			modify_tree = -1;
  			btrfs_release_path(path);
  			continue;
  		}
  
  		/*
  		 *     | - range to drop - |
  		 *  | -------- extent -------- |
  		 */
  		if (start > key.offset && end < extent_end) {
  			BUG_ON(del_nr > 0);
  			if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
  				ret = -EOPNOTSUPP;
  				break;
  			}
  
  			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 (update_refs && 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); /* -ENOMEM */
  			}
  			key.offset = start;
  		}
  		/*
  		 *  | ---- range to drop ----- |
  		 *      | -------- extent -------- |
  		 */
  		if (start <= key.offset && end < extent_end) {
  			if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
  				ret = -EOPNOTSUPP;
  				break;
  			}
  
  			memcpy(&new_key, &key, sizeof(new_key));
  			new_key.offset = end;
  			btrfs_set_item_key_safe(root->fs_info, 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 (update_refs && disk_bytenr > 0)
  				inode_sub_bytes(inode, end - key.offset);
  			break;
  		}
  
  		search_start = extent_end;
  		/*
  		 *       | ---- range to drop ----- |
  		 *  | -------- extent -------- |
  		 */
  		if (start > key.offset && end >= extent_end) {
  			BUG_ON(del_nr > 0);
  			if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
  				ret = -EOPNOTSUPP;
  				break;
  			}
  
  			btrfs_set_file_extent_num_bytes(leaf, fi,
  							start - key.offset);
  			btrfs_mark_buffer_dirty(leaf);
  			if (update_refs && disk_bytenr > 0)
  				inode_sub_bytes(inode, extent_end - start);
  			if (end == extent_end)
  				break;
  
  			path->slots[0]++;
  			goto next_slot;
  		}
  
  		/*
  		 *  | ---- range to drop ----- |
  		 *    | ------ extent ------ |
  		 */
  		if (start <= key.offset && end >= extent_end) {
  delete_extent_item:
  			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 (update_refs &&
  			    extent_type == BTRFS_FILE_EXTENT_INLINE) {
  				inode_sub_bytes(inode,
  						extent_end - key.offset);
  				extent_end = ALIGN(extent_end,
  						   root->sectorsize);
  			} else if (update_refs && 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); /* -ENOMEM */
  				inode_sub_bytes(inode,
  						extent_end - key.offset);
  			}
  
  			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);
  			if (ret) {
  				btrfs_abort_transaction(trans, root, ret);
  				break;
  			}
  
  			del_nr = 0;
  			del_slot = 0;
  
  			btrfs_release_path(path);
  			continue;
  		}
  
  		BUG_ON(1);
  	}
  
  	if (!ret && del_nr > 0) {
  		/*
  		 * Set path->slots[0] to first slot, so that after the delete
  		 * if items are move off from our leaf to its immediate left or
  		 * right neighbor leafs, we end up with a correct and adjusted
  		 * path->slots[0] for our insertion (if replace_extent != 0).
  		 */
  		path->slots[0] = del_slot;
  		ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
  		if (ret)
  			btrfs_abort_transaction(trans, root, ret);
  	}
  
  	leaf = path->nodes[0];
  	/*
  	 * If btrfs_del_items() was called, it might have deleted a leaf, in
  	 * which case it unlocked our path, so check path->locks[0] matches a
  	 * write lock.
  	 */
  	if (!ret && replace_extent && leafs_visited == 1 &&
  	    (path->locks[0] == BTRFS_WRITE_LOCK_BLOCKING ||
  	     path->locks[0] == BTRFS_WRITE_LOCK) &&
  	    btrfs_leaf_free_space(root, leaf) >=
  	    sizeof(struct btrfs_item) + extent_item_size) {
  
  		key.objectid = ino;
  		key.type = BTRFS_EXTENT_DATA_KEY;
  		key.offset = start;
  		if (!del_nr && path->slots[0] < btrfs_header_nritems(leaf)) {
  			struct btrfs_key slot_key;
  
  			btrfs_item_key_to_cpu(leaf, &slot_key, path->slots[0]);
  			if (btrfs_comp_cpu_keys(&key, &slot_key) > 0)
  				path->slots[0]++;
  		}
  		setup_items_for_insert(root, path, &key,
  				       &extent_item_size,
  				       extent_item_size,
  				       sizeof(struct btrfs_item) +
  				       extent_item_size, 1);
  		*key_inserted = 1;
  	}
  
  	if (!replace_extent || !(*key_inserted))
  		btrfs_release_path(path);
  	if (drop_end)
  		*drop_end = found ? min(end, extent_end) : end;
  	return ret;
  }
  
  int btrfs_drop_extents(struct btrfs_trans_handle *trans,
  		       struct btrfs_root *root, struct inode *inode, u64 start,
  		       u64 end, int drop_cache)
  {
  	struct btrfs_path *path;
  	int ret;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  	ret = __btrfs_drop_extents(trans, root, inode, path, start, end, NULL,
  				   drop_cache, 0, 0, NULL);
  	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);
  
  	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(root->fs_info, path, &new_key);
  			fi = btrfs_item_ptr(leaf, path->slots[0],
  					    struct btrfs_file_extent_item);
  			btrfs_set_file_extent_generation(leaf, fi,
  							 trans->transid);
  			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_generation(leaf, fi,
  							 trans->transid);
  			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);
  			btrfs_set_file_extent_generation(leaf, fi,
  							 trans->transid);
  			path->slots[0]++;
  			new_key.offset = start;
  			btrfs_set_item_key_safe(root->fs_info, path, &new_key);
  
  			fi = btrfs_item_ptr(leaf, path->slots[0],
  					    struct btrfs_file_extent_item);
  			btrfs_set_file_extent_generation(leaf, fi,
  							 trans->transid);
  			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;
  		}
  		if (ret < 0) {
  			btrfs_abort_transaction(trans, root, ret);
  			goto out;
  		}
  
  		leaf = path->nodes[0];
  		fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
  				    struct btrfs_file_extent_item);
  		btrfs_set_file_extent_generation(leaf, fi, trans->transid);
  		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_generation(leaf, fi, trans->transid);
  		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); /* -ENOMEM */
  
  		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); /* -ENOMEM */
  	}
  	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); /* -ENOMEM */
  	}
  	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_set_file_extent_generation(leaf, fi, trans->transid);
  		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_generation(leaf, fi, trans->transid);
  		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);
  		if (ret < 0) {
  			btrfs_abort_transaction(trans, root, ret);
  			goto out;
  		}
  	}
  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 inode *inode,
  				 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;
  		}
  		if (page->mapping != inode->i_mapping) {
  			unlock_page(page);
  			return -EAGAIN;
  		}
  	}
  	return 0;
  }
  
  /*
   * this just gets pages into the page cache and locks them down.
   */
  static noinline int prepare_pages(struct inode *inode, struct page **pages,
  				  size_t num_pages, loff_t pos,
  				  size_t write_bytes, bool force_uptodate)
  {
  	int i;
  	unsigned long index = pos >> PAGE_CACHE_SHIFT;
  	gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
  	int err = 0;
  	int faili;
  
  	for (i = 0; i < num_pages; i++) {
  again:
  		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(inode, pages[i], pos,
  						    force_uptodate);
  		if (!err && i == num_pages - 1)
  			err = prepare_uptodate_page(inode, pages[i],
  						    pos + write_bytes, false);
  		if (err) {
  			page_cache_release(pages[i]);
  			if (err == -EAGAIN) {
  				err = 0;
  				goto again;
  			}
  			faili = i - 1;
  			goto fail;
  		}
  		wait_on_page_writeback(pages[i]);
  	}
  
  	return 0;
  fail:
  	while (faili >= 0) {
  		unlock_page(pages[faili]);
  		page_cache_release(pages[faili]);
  		faili--;
  	}
  	return err;
  
  }
  
  /*
   * This function locks the extent and properly waits for data=ordered extents
   * to finish before allowing the pages to be modified if need.
   *
   * The return value:
   * 1 - the extent is locked
   * 0 - the extent is not locked, and everything is OK
   * -EAGAIN - need re-prepare the pages
   * the other < 0 number - Something wrong happens
   */
  static noinline int
  lock_and_cleanup_extent_if_need(struct inode *inode, struct page **pages,
  				size_t num_pages, loff_t pos,
  				u64 *lockstart, u64 *lockend,
  				struct extent_state **cached_state)
  {
  	u64 start_pos;
  	u64 last_pos;
  	int i;
  	int ret = 0;
  
  	start_pos = pos & ~((u64)PAGE_CACHE_SIZE - 1);
  	last_pos = start_pos + ((u64)num_pages << PAGE_CACHE_SHIFT) - 1;
  
  	if (start_pos < inode->i_size) {
  		struct btrfs_ordered_extent *ordered;
  		lock_extent_bits(&BTRFS_I(inode)->io_tree,
  				 start_pos, last_pos, 0, cached_state);
  		ordered = btrfs_lookup_ordered_range(inode, start_pos,
  						     last_pos - start_pos + 1);
  		if (ordered &&
  		    ordered->file_offset + ordered->len > start_pos &&
  		    ordered->file_offset <= last_pos) {
  			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
  					     start_pos, last_pos,
  					     cached_state, GFP_NOFS);
  			for (i = 0; i < num_pages; i++) {
  				unlock_page(pages[i]);
  				page_cache_release(pages[i]);
  			}
  			btrfs_start_ordered_extent(inode, ordered, 1);
  			btrfs_put_ordered_extent(ordered);
  			return -EAGAIN;
  		}
  		if (ordered)
  			btrfs_put_ordered_extent(ordered);
  
  		clear_extent_bit(&BTRFS_I(inode)->io_tree, start_pos,
  				  last_pos, EXTENT_DIRTY | EXTENT_DELALLOC |
  				  EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG,
  				  0, 0, cached_state, GFP_NOFS);
  		*lockstart = start_pos;
  		*lockend = last_pos;
  		ret = 1;
  	}
  
  	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 ret;
  }
  
  static noinline int check_can_nocow(struct inode *inode, loff_t pos,
  				    size_t *write_bytes)
  {
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct btrfs_ordered_extent *ordered;
  	u64 lockstart, lockend;
  	u64 num_bytes;
  	int ret;
  
  	ret = btrfs_start_write_no_snapshoting(root);
  	if (!ret)
  		return -ENOSPC;
  
  	lockstart = round_down(pos, root->sectorsize);
  	lockend = round_up(pos + *write_bytes, root->sectorsize) - 1;
  
  	while (1) {
  		lock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend);
  		ordered = btrfs_lookup_ordered_range(inode, lockstart,
  						     lockend - lockstart + 1);
  		if (!ordered) {
  			break;
  		}
  		unlock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend);
  		btrfs_start_ordered_extent(inode, ordered, 1);
  		btrfs_put_ordered_extent(ordered);
  	}
  
  	num_bytes = lockend - lockstart + 1;
  	ret = can_nocow_extent(inode, lockstart, &num_bytes, NULL, NULL, NULL);
  	if (ret <= 0) {
  		ret = 0;
  		btrfs_end_write_no_snapshoting(root);
  	} else {
  		*write_bytes = min_t(size_t, *write_bytes ,
  				     num_bytes - pos + lockstart);
  	}
  
  	unlock_extent(&BTRFS_I(inode)->io_tree, lockstart, lockend);
  
  	return ret;
  }
  
  static noinline ssize_t __btrfs_buffered_write(struct file *file,
  					       struct iov_iter *i,
  					       loff_t pos)
  {
  	struct inode *inode = file_inode(file);
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct page **pages = NULL;
  	struct extent_state *cached_state = NULL;
  	u64 release_bytes = 0;
  	u64 lockstart;
  	u64 lockend;
  	size_t num_written = 0;
  	int nrptrs;
  	int ret = 0;
  	bool only_release_metadata = false;
  	bool force_page_uptodate = false;
  	bool need_unlock;
  
  	nrptrs = min(DIV_ROUND_UP(iov_iter_count(i), 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_array(nrptrs, sizeof(struct page *), GFP_KERNEL);
  	if (!pages)
  		return -ENOMEM;
  
  	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 = DIV_ROUND_UP(write_bytes + offset,
  						PAGE_CACHE_SIZE);
  		size_t reserve_bytes;
  		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;
  		}
  
  		reserve_bytes = num_pages << PAGE_CACHE_SHIFT;
  
  		if ((BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
  					      BTRFS_INODE_PREALLOC)) &&
  		    check_can_nocow(inode, pos, &write_bytes) > 0) {
  			/*
  			 * For nodata cow case, no need to reserve
  			 * data space.
  			 */
  			only_release_metadata = true;
  			/*
  			 * our prealloc extent may be smaller than
  			 * write_bytes, so scale down.
  			 */
  			num_pages = DIV_ROUND_UP(write_bytes + offset,
  						 PAGE_CACHE_SIZE);
  			reserve_bytes = num_pages << PAGE_CACHE_SHIFT;
  			goto reserve_metadata;
  		}
  
  		ret = btrfs_check_data_free_space(inode, pos, write_bytes);
  		if (ret < 0)
  			break;
  
  reserve_metadata:
  		ret = btrfs_delalloc_reserve_metadata(inode, reserve_bytes);
  		if (ret) {
  			if (!only_release_metadata)
  				btrfs_free_reserved_data_space(inode, pos,
  							       write_bytes);
  			else
  				btrfs_end_write_no_snapshoting(root);
  			break;
  		}
  
  		release_bytes = reserve_bytes;
  		need_unlock = false;
  again:
  		/*
  		 * 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(inode, pages, num_pages,
  				    pos, write_bytes,
  				    force_page_uptodate);
  		if (ret)
  			break;
  
  		ret = lock_and_cleanup_extent_if_need(inode, pages, num_pages,
  						      pos, &lockstart, &lockend,
  						      &cached_state);
  		if (ret < 0) {
  			if (ret == -EAGAIN)
  				goto again;
  			break;
  		} else if (ret > 0) {
  			need_unlock = true;
  			ret = 0;
  		}
  
  		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 = DIV_ROUND_UP(copied + offset,
  						   PAGE_CACHE_SIZE);
  		}
  
  		/*
  		 * 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) {
  			release_bytes = (num_pages - dirty_pages) <<
  				PAGE_CACHE_SHIFT;
  			if (copied > 0) {
  				spin_lock(&BTRFS_I(inode)->lock);
  				BTRFS_I(inode)->outstanding_extents++;
  				spin_unlock(&BTRFS_I(inode)->lock);
  			}
  			if (only_release_metadata) {
  				btrfs_delalloc_release_metadata(inode,
  								release_bytes);
  			} else {
  				u64 __pos;
  
  				__pos = round_down(pos, root->sectorsize) +
  					(dirty_pages << PAGE_CACHE_SHIFT);
  				btrfs_delalloc_release_space(inode, __pos,
  							     release_bytes);
  			}
  		}
  
  		release_bytes = dirty_pages << PAGE_CACHE_SHIFT;
  
  		if (copied > 0)
  			ret = btrfs_dirty_pages(root, inode, pages,
  						dirty_pages, pos, copied,
  						NULL);
  		if (need_unlock)
  			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
  					     lockstart, lockend, &cached_state,
  					     GFP_NOFS);
  		if (ret) {
  			btrfs_drop_pages(pages, num_pages);
  			break;
  		}
  
  		release_bytes = 0;
  		if (only_release_metadata)
  			btrfs_end_write_no_snapshoting(root);
  
  		if (only_release_metadata && copied > 0) {
  			lockstart = round_down(pos, root->sectorsize);
  			lockend = lockstart +
  				(dirty_pages << PAGE_CACHE_SHIFT) - 1;
  
  			set_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
  				       lockend, EXTENT_NORESERVE, NULL,
  				       NULL, GFP_NOFS);
  			only_release_metadata = false;
  		}
  
  		btrfs_drop_pages(pages, num_pages);
  
  		cond_resched();
  
  		balance_dirty_pages_ratelimited(inode->i_mapping);
  		if (dirty_pages < (root->nodesize >> PAGE_CACHE_SHIFT) + 1)
  			btrfs_btree_balance_dirty(root);
  
  		pos += copied;
  		num_written += copied;
  	}
  
  	kfree(pages);
  
  	if (release_bytes) {
  		if (only_release_metadata) {
  			btrfs_end_write_no_snapshoting(root);
  			btrfs_delalloc_release_metadata(inode, release_bytes);
  		} else {
  			btrfs_delalloc_release_space(inode, pos, release_bytes);
  		}
  	}
  
  	return num_written ? num_written : ret;
  }
  
  static ssize_t __btrfs_direct_write(struct kiocb *iocb,
  				    struct iov_iter *from,
  				    loff_t pos)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file_inode(file);
  	ssize_t written;
  	ssize_t written_buffered;
  	loff_t endbyte;
  	int err;
  
  	written = generic_file_direct_write(iocb, from, pos);
  
  	if (written < 0 || !iov_iter_count(from))
  		return written;
  
  	pos += written;
  	written_buffered = __btrfs_buffered_write(file, from, pos);
  	if (written_buffered < 0) {
  		err = written_buffered;
  		goto out;
  	}
  	/*
  	 * Ensure all data is persisted. We want the next direct IO read to be
  	 * able to read what was just written.
  	 */
  	endbyte = pos + written_buffered - 1;
  	err = btrfs_fdatawrite_range(inode, pos, endbyte);
  	if (err)
  		goto out;
  	err = filemap_fdatawait_range(inode->i_mapping, pos, endbyte);
  	if (err)
  		goto out;
  	written += written_buffered;
  	iocb->ki_pos = pos + written_buffered;
  	invalidate_mapping_pages(file->f_mapping, pos >> PAGE_CACHE_SHIFT,
  				 endbyte >> PAGE_CACHE_SHIFT);
  out:
  	return written ? written : err;
  }
  
  static void update_time_for_write(struct inode *inode)
  {
  	struct timespec now;
  
  	if (IS_NOCMTIME(inode))
  		return;
  
  	now = current_fs_time(inode->i_sb);
  	if (!timespec_equal(&inode->i_mtime, &now))
  		inode->i_mtime = now;
  
  	if (!timespec_equal(&inode->i_ctime, &now))
  		inode->i_ctime = now;
  
  	if (IS_I_VERSION(inode))
  		inode_inc_iversion(inode);
  }
  
  static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
  				    struct iov_iter *from)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file_inode(file);
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	u64 start_pos;
  	u64 end_pos;
  	ssize_t num_written = 0;
  	bool sync = (file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host);
  	ssize_t err;
  	loff_t pos;
  	size_t count;
  
  	mutex_lock(&inode->i_mutex);
  	err = generic_write_checks(iocb, from);
  	if (err <= 0) {
  		mutex_unlock(&inode->i_mutex);
  		return err;
  	}
  
  	current->backing_dev_info = inode_to_bdi(inode);
  	err = file_remove_privs(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 (test_bit(BTRFS_FS_STATE_ERROR, &root->fs_info->fs_state)) {
  		mutex_unlock(&inode->i_mutex);
  		err = -EROFS;
  		goto out;
  	}
  
  	/*
  	 * We reserve space for updating the inode when we reserve space for the
  	 * extent we are going to write, so we will enospc out there.  We don't
  	 * need to start yet another transaction to update the inode as we will
  	 * update the inode when we finish writing whatever data we write.
  	 */
  	update_time_for_write(inode);
  
  	pos = iocb->ki_pos;
  	count = iov_iter_count(from);
  	start_pos = round_down(pos, root->sectorsize);
  	if (start_pos > i_size_read(inode)) {
  		/* Expand hole size to cover write data, preventing empty gap */
  		end_pos = round_up(pos + count, root->sectorsize);
  		err = btrfs_cont_expand(inode, i_size_read(inode), end_pos);
  		if (err) {
  			mutex_unlock(&inode->i_mutex);
  			goto out;
  		}
  	}
  
  	if (sync)
  		atomic_inc(&BTRFS_I(inode)->sync_writers);
  
  	if (iocb->ki_flags & IOCB_DIRECT) {
  		num_written = __btrfs_direct_write(iocb, from, pos);
  	} else {
  		num_written = __btrfs_buffered_write(file, from, pos);
  		if (num_written > 0)
  			iocb->ki_pos = pos + num_written;
  	}
  
  	mutex_unlock(&inode->i_mutex);
  
  	/*
  	 * We also have to set last_sub_trans to the current log transid,
  	 * otherwise subsequent syncs to a file that's been synced in this
  	 * transaction will appear to have already occured.
  	 */
  	spin_lock(&BTRFS_I(inode)->lock);
  	BTRFS_I(inode)->last_sub_trans = root->log_transid;
  	spin_unlock(&BTRFS_I(inode)->lock);
  	if (num_written > 0) {
  		err = generic_write_sync(file, pos, num_written);
  		if (err < 0)
  			num_written = err;
  	}
  
  	if (sync)
  		atomic_dec(&BTRFS_I(inode)->sync_writers);
  out:
  	current->backing_dev_info = NULL;
  	return num_written ? num_written : err;
  }
  
  int btrfs_release_file(struct inode *inode, struct file *filp)
  {
  	if (filp->private_data)
  		btrfs_ioctl_trans_end(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 (test_and_clear_bit(BTRFS_INODE_ORDERED_DATA_CLOSE,
  			       &BTRFS_I(inode)->runtime_flags))
  			filemap_flush(inode->i_mapping);
  	return 0;
  }
  
  static int start_ordered_ops(struct inode *inode, loff_t start, loff_t end)
  {
  	int ret;
  
  	atomic_inc(&BTRFS_I(inode)->sync_writers);
  	ret = btrfs_fdatawrite_range(inode, start, end);
  	atomic_dec(&BTRFS_I(inode)->sync_writers);
  
  	return ret;
  }
  
  /*
   * 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_dentry(file);
  	struct inode *inode = d_inode(dentry);
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct btrfs_trans_handle *trans;
  	struct btrfs_log_ctx ctx;
  	int ret = 0;
  	bool full_sync = 0;
  	u64 len;
  
  	/*
  	 * The range length can be represented by u64, we have to do the typecasts
  	 * to avoid signed overflow if it's [0, LLONG_MAX] eg. from fsync()
  	 */
  	len = (u64)end - (u64)start + 1;
  	trace_btrfs_sync_file(file, datasync);
  
  	/*
  	 * We write the dirty pages in the range and wait until they complete
  	 * out of the ->i_mutex. If so, we can flush the dirty pages by
  	 * multi-task, and make the performance up.  See
  	 * btrfs_wait_ordered_range for an explanation of the ASYNC check.
  	 */
  	ret = start_ordered_ops(inode, start, end);
  	if (ret)
  		return ret;
  
  	mutex_lock(&inode->i_mutex);
  	atomic_inc(&root->log_batch);
  	full_sync = test_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
  			     &BTRFS_I(inode)->runtime_flags);
  	/*
  	 * We might have have had more pages made dirty after calling
  	 * start_ordered_ops and before acquiring the inode's i_mutex.
  	 */
  	if (full_sync) {
  		/*
  		 * For a full sync, we need to make sure any ordered operations
  		 * start and finish before we start logging the inode, so that
  		 * all extents are persisted and the respective file extent
  		 * items are in the fs/subvol btree.
  		 */
  		ret = btrfs_wait_ordered_range(inode, start, len);
  	} else {
  		/*
  		 * Start any new ordered operations before starting to log the
  		 * inode. We will wait for them to finish in btrfs_sync_log().
  		 *
  		 * Right before acquiring the inode's mutex, we might have new
  		 * writes dirtying pages, which won't immediately start the
  		 * respective ordered operations - that is done through the
  		 * fill_delalloc callbacks invoked from the writepage and
  		 * writepages address space operations. So make sure we start
  		 * all ordered operations before starting to log our inode. Not
  		 * doing this means that while logging the inode, writeback
  		 * could start and invoke writepage/writepages, which would call
  		 * the fill_delalloc callbacks (cow_file_range,
  		 * submit_compressed_extents). These callbacks add first an
  		 * extent map to the modified list of extents and then create
  		 * the respective ordered operation, which means in
  		 * tree-log.c:btrfs_log_inode() we might capture all existing
  		 * ordered operations (with btrfs_get_logged_extents()) before
  		 * the fill_delalloc callback adds its ordered operation, and by
  		 * the time we visit the modified list of extent maps (with
  		 * btrfs_log_changed_extents()), we see and process the extent
  		 * map they created. We then use the extent map to construct a
  		 * file extent item for logging without waiting for the
  		 * respective ordered operation to finish - this file extent
  		 * item points to a disk location that might not have yet been
  		 * written to, containing random data - so after a crash a log
  		 * replay will make our inode have file extent items that point
  		 * to disk locations containing invalid data, as we returned
  		 * success to userspace without waiting for the respective
  		 * ordered operation to finish, because it wasn't captured by
  		 * btrfs_get_logged_extents().
  		 */
  		ret = start_ordered_ops(inode, start, end);
  	}
  	if (ret) {
  		mutex_unlock(&inode->i_mutex);
  		goto out;
  	}
  	atomic_inc(&root->log_batch);
  
  	/*
  	 * If the last transaction that changed this file was before the current
  	 * transaction and we have the full sync flag set in our inode, we can
  	 * bail out now without any syncing.
  	 *
  	 * Note that we can't bail out if the full sync flag isn't set. This is
  	 * because when the full sync flag is set we start all ordered extents
  	 * and wait for them to fully complete - when they complete they update
  	 * the inode's last_trans field through:
  	 *
  	 *     btrfs_finish_ordered_io() ->
  	 *         btrfs_update_inode_fallback() ->
  	 *             btrfs_update_inode() ->
  	 *                 btrfs_set_inode_last_trans()
  	 *
  	 * So we are sure that last_trans is up to date and can do this check to
  	 * bail out safely. For the fast path, when the full sync flag is not
  	 * set in our inode, we can not do it because we start only our ordered
  	 * extents and don't wait for them to complete (that is when
  	 * btrfs_finish_ordered_io runs), so here at this point their last_trans
  	 * value might be less than or equals to fs_info->last_trans_committed,
  	 * and setting a speculative last_trans for an inode when a buffered
  	 * write is made (such as fs_info->generation + 1 for example) would not
  	 * be reliable since after setting the value and before fsync is called
  	 * any number of transactions can start and commit (transaction kthread
  	 * commits the current transaction periodically), and a transaction
  	 * commit does not start nor waits for ordered extents to complete.
  	 */
  	smp_mb();
  	if (btrfs_inode_in_log(inode, root->fs_info->generation) ||
  	    (BTRFS_I(inode)->last_trans <=
  	     root->fs_info->last_trans_committed &&
  	     (full_sync ||
  	      !btrfs_have_ordered_extents_in_range(inode, start, len)))) {
  		/*
  		 * We'v had everything committed since the last time we were
  		 * modified so clear this flag in case it was set for whatever
  		 * reason, it's no longer relevant.
  		 */
  		clear_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
  			  &BTRFS_I(inode)->runtime_flags);
  		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);
  
  	/*
  	 * We use start here because we will need to wait on the IO to complete
  	 * in btrfs_sync_log, which could require joining a transaction (for
  	 * example checking cross references in the nocow path).  If we use join
  	 * here we could get into a situation where we're waiting on IO to
  	 * happen that is blocked on a transaction trying to commit.  With start
  	 * we inc the extwriter counter, so we wait for all extwriters to exit
  	 * before we start blocking join'ers.  This comment is to keep somebody
  	 * from thinking they are super smart and changing this to
  	 * btrfs_join_transaction *cough*Josef*cough*.
  	 */
  	trans = btrfs_start_transaction(root, 0);
  	if (IS_ERR(trans)) {
  		ret = PTR_ERR(trans);
  		mutex_unlock(&inode->i_mutex);
  		goto out;
  	}
  	trans->sync = true;
  
  	btrfs_init_log_ctx(&ctx);
  
  	ret = btrfs_log_dentry_safe(trans, root, dentry, start, end, &ctx);
  	if (ret < 0) {
  		/* Fallthrough and commit/free transaction. */
  		ret = 1;
  	}
  
  	/* 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 any of the ordered extents had an error, just return it to user
  	 * space, so that the application knows some writes didn't succeed and
  	 * can take proper action (retry for e.g.). Blindly committing the
  	 * transaction in this case, would fool userspace that everything was
  	 * successful. And we also want to make sure our log doesn't contain
  	 * file extent items pointing to extents that weren't fully written to -
  	 * just like in the non fast fsync path, where we check for the ordered
  	 * operation's error flag before writing to the log tree and return -EIO
  	 * if any of them had this flag set (btrfs_wait_ordered_range) -
  	 * therefore we need to check for errors in the ordered operations,
  	 * which are indicated by ctx.io_err.
  	 */
  	if (ctx.io_err) {
  		btrfs_end_transaction(trans, root);
  		ret = ctx.io_err;
  		goto out;
  	}
  
  	if (ret != BTRFS_NO_LOG_SYNC) {
  		if (!ret) {
  			ret = btrfs_sync_log(trans, root, &ctx);
  			if (!ret) {
  				ret = btrfs_end_transaction(trans, root);
  				goto out;
  			}
  		}
  		if (!full_sync) {
  			ret = btrfs_wait_ordered_range(inode, start, len);
  			if (ret) {
  				btrfs_end_transaction(trans, root);
  				goto out;
  			}
  		}
  		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,
  	.map_pages	= filemap_map_pages,
  	.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;
  
  	return 0;
  }
  
  static int hole_mergeable(struct inode *inode, struct extent_buffer *leaf,
  			  int slot, u64 start, u64 end)
  {
  	struct btrfs_file_extent_item *fi;
  	struct btrfs_key key;
  
  	if (slot < 0 || slot >= btrfs_header_nritems(leaf))
  		return 0;
  
  	btrfs_item_key_to_cpu(leaf, &key, slot);
  	if (key.objectid != btrfs_ino(inode) ||
  	    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)
  		return 0;
  
  	if (btrfs_file_extent_disk_bytenr(leaf, fi))
  		return 0;
  
  	if (key.offset == end)
  		return 1;
  	if (key.offset + btrfs_file_extent_num_bytes(leaf, fi) == start)
  		return 1;
  	return 0;
  }
  
  static int fill_holes(struct btrfs_trans_handle *trans, struct inode *inode,
  		      struct btrfs_path *path, u64 offset, u64 end)
  {
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct extent_buffer *leaf;
  	struct btrfs_file_extent_item *fi;
  	struct extent_map *hole_em;
  	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
  	struct btrfs_key key;
  	int ret;
  
  	if (btrfs_fs_incompat(root->fs_info, NO_HOLES))
  		goto out;
  
  	key.objectid = btrfs_ino(inode);
  	key.type = BTRFS_EXTENT_DATA_KEY;
  	key.offset = offset;
  
  	ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
  	if (ret < 0)
  		return ret;
  	BUG_ON(!ret);
  
  	leaf = path->nodes[0];
  	if (hole_mergeable(inode, leaf, path->slots[0]-1, offset, end)) {
  		u64 num_bytes;
  
  		path->slots[0]--;
  		fi = btrfs_item_ptr(leaf, path->slots[0],
  				    struct btrfs_file_extent_item);
  		num_bytes = btrfs_file_extent_num_bytes(leaf, fi) +
  			end - offset;
  		btrfs_set_file_extent_num_bytes(leaf, fi, num_bytes);
  		btrfs_set_file_extent_ram_bytes(leaf, fi, num_bytes);
  		btrfs_set_file_extent_offset(leaf, fi, 0);
  		btrfs_mark_buffer_dirty(leaf);
  		goto out;
  	}
  
  	if (hole_mergeable(inode, leaf, path->slots[0], offset, end)) {
  		u64 num_bytes;
  
  		key.offset = offset;
  		btrfs_set_item_key_safe(root->fs_info, path, &key);
  		fi = btrfs_item_ptr(leaf, path->slots[0],
  				    struct btrfs_file_extent_item);
  		num_bytes = btrfs_file_extent_num_bytes(leaf, fi) + end -
  			offset;
  		btrfs_set_file_extent_num_bytes(leaf, fi, num_bytes);
  		btrfs_set_file_extent_ram_bytes(leaf, fi, num_bytes);
  		btrfs_set_file_extent_offset(leaf, fi, 0);
  		btrfs_mark_buffer_dirty(leaf);
  		goto out;
  	}
  	btrfs_release_path(path);
  
  	ret = btrfs_insert_file_extent(trans, root, btrfs_ino(inode), offset,
  				       0, 0, end - offset, 0, end - offset,
  				       0, 0, 0);
  	if (ret)
  		return ret;
  
  out:
  	btrfs_release_path(path);
  
  	hole_em = alloc_extent_map();
  	if (!hole_em) {
  		btrfs_drop_extent_cache(inode, offset, end - 1, 0);
  		set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
  			&BTRFS_I(inode)->runtime_flags);
  	} else {
  		hole_em->start = offset;
  		hole_em->len = end - offset;
  		hole_em->ram_bytes = hole_em->len;
  		hole_em->orig_start = offset;
  
  		hole_em->block_start = EXTENT_MAP_HOLE;
  		hole_em->block_len = 0;
  		hole_em->orig_block_len = 0;
  		hole_em->bdev = root->fs_info->fs_devices->latest_bdev;
  		hole_em->compress_type = BTRFS_COMPRESS_NONE;
  		hole_em->generation = trans->transid;
  
  		do {
  			btrfs_drop_extent_cache(inode, offset, end - 1, 0);
  			write_lock(&em_tree->lock);
  			ret = add_extent_mapping(em_tree, hole_em, 1);
  			write_unlock(&em_tree->lock);
  		} while (ret == -EEXIST);
  		free_extent_map(hole_em);
  		if (ret)
  			set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
  				&BTRFS_I(inode)->runtime_flags);
  	}
  
  	return 0;
  }
  
  /*
   * Find a hole extent on given inode and change start/len to the end of hole
   * extent.(hole/vacuum extent whose em->start <= start &&
   *	   em->start + em->len > start)
   * When a hole extent is found, return 1 and modify start/len.
   */
  static int find_first_non_hole(struct inode *inode, u64 *start, u64 *len)
  {
  	struct extent_map *em;
  	int ret = 0;
  
  	em = btrfs_get_extent(inode, NULL, 0, *start, *len, 0);
  	if (IS_ERR_OR_NULL(em)) {
  		if (!em)
  			ret = -ENOMEM;
  		else
  			ret = PTR_ERR(em);
  		return ret;
  	}
  
  	/* Hole or vacuum extent(only exists in no-hole mode) */
  	if (em->block_start == EXTENT_MAP_HOLE) {
  		ret = 1;
  		*len = em->start + em->len > *start + *len ?
  		       0 : *start + *len - em->start - em->len;
  		*start = em->start + em->len;
  	}
  	free_extent_map(em);
  	return ret;
  }
  
  static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
  {
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct extent_state *cached_state = NULL;
  	struct btrfs_path *path;
  	struct btrfs_block_rsv *rsv;
  	struct btrfs_trans_handle *trans;
  	u64 lockstart;
  	u64 lockend;
  	u64 tail_start;
  	u64 tail_len;
  	u64 orig_start = offset;
  	u64 cur_offset;
  	u64 min_size = btrfs_calc_trunc_metadata_size(root, 1);
  	u64 drop_end;
  	int ret = 0;
  	int err = 0;
  	unsigned int rsv_count;
  	bool same_page;
  	bool no_holes = btrfs_fs_incompat(root->fs_info, NO_HOLES);
  	u64 ino_size;
  	bool truncated_page = false;
  	bool updated_inode = false;
  
  	ret = btrfs_wait_ordered_range(inode, offset, len);
  	if (ret)
  		return ret;
  
  	mutex_lock(&inode->i_mutex);
  	ino_size = round_up(inode->i_size, PAGE_CACHE_SIZE);
  	ret = find_first_non_hole(inode, &offset, &len);
  	if (ret < 0)
  		goto out_only_mutex;
  	if (ret && !len) {
  		/* Already in a large hole */
  		ret = 0;
  		goto out_only_mutex;
  	}
  
  	lockstart = round_up(offset, BTRFS_I(inode)->root->sectorsize);
  	lockend = round_down(offset + len,
  			     BTRFS_I(inode)->root->sectorsize) - 1;
  	same_page = ((offset >> PAGE_CACHE_SHIFT) ==
  		    ((offset + len - 1) >> PAGE_CACHE_SHIFT));
  
  	/*
  	 * We needn't truncate any page which is beyond the end of the file
  	 * because we are sure there is no data there.
  	 */
  	/*
  	 * Only do this if we are in the same page and we aren't doing the
  	 * entire page.
  	 */
  	if (same_page && len < PAGE_CACHE_SIZE) {
  		if (offset < ino_size) {
  			truncated_page = true;
  			ret = btrfs_truncate_page(inode, offset, len, 0);
  		} else {
  			ret = 0;
  		}
  		goto out_only_mutex;
  	}
  
  	/* zero back part of the first page */
  	if (offset < ino_size) {
  		truncated_page = true;
  		ret = btrfs_truncate_page(inode, offset, 0, 0);
  		if (ret) {
  			mutex_unlock(&inode->i_mutex);
  			return ret;
  		}
  	}
  
  	/* Check the aligned pages after the first unaligned page,
  	 * if offset != orig_start, which means the first unaligned page
  	 * including serveral following pages are already in holes,
  	 * the extra check can be skipped */
  	if (offset == orig_start) {
  		/* after truncate page, check hole again */
  		len = offset + len - lockstart;
  		offset = lockstart;
  		ret = find_first_non_hole(inode, &offset, &len);
  		if (ret < 0)
  			goto out_only_mutex;
  		if (ret && !len) {
  			ret = 0;
  			goto out_only_mutex;
  		}
  		lockstart = offset;
  	}
  
  	/* Check the tail unaligned part is in a hole */
  	tail_start = lockend + 1;
  	tail_len = offset + len - tail_start;
  	if (tail_len) {
  		ret = find_first_non_hole(inode, &tail_start, &tail_len);
  		if (unlikely(ret < 0))
  			goto out_only_mutex;
  		if (!ret) {
  			/* zero the front end of the last page */
  			if (tail_start + tail_len < ino_size) {
  				truncated_page = true;
  				ret = btrfs_truncate_page(inode,
  						tail_start + tail_len, 0, 1);
  				if (ret)
  					goto out_only_mutex;
  			}
  		}
  	}
  
  	if (lockend < lockstart) {
  		ret = 0;
  		goto out_only_mutex;
  	}
  
  	while (1) {
  		struct btrfs_ordered_extent *ordered;
  
  		truncate_pagecache_range(inode, lockstart, lockend);
  
  		lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend,
  				 0, &cached_state);
  		ordered = btrfs_lookup_first_ordered_extent(inode, lockend);
  
  		/*
  		 * We need to make sure we have no ordered extents in this range
  		 * and nobody raced in and read a page in this range, if we did
  		 * we need to try again.
  		 */
  		if ((!ordered ||
  		    (ordered->file_offset + ordered->len <= lockstart ||
  		     ordered->file_offset > lockend)) &&
  		     !btrfs_page_exists_in_range(inode, lockstart, lockend)) {
  			if (ordered)
  				btrfs_put_ordered_extent(ordered);
  			break;
  		}
  		if (ordered)
  			btrfs_put_ordered_extent(ordered);
  		unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart,
  				     lockend, &cached_state, GFP_NOFS);
  		ret = btrfs_wait_ordered_range(inode, lockstart,
  					       lockend - lockstart + 1);
  		if (ret) {
  			mutex_unlock(&inode->i_mutex);
  			return ret;
  		}
  	}
  
  	path = btrfs_alloc_path();
  	if (!path) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	rsv = btrfs_alloc_block_rsv(root, BTRFS_BLOCK_RSV_TEMP);
  	if (!rsv) {
  		ret = -ENOMEM;
  		goto out_free;
  	}
  	rsv->size = btrfs_calc_trunc_metadata_size(root, 1);
  	rsv->failfast = 1;
  
  	/*
  	 * 1 - update the inode
  	 * 1 - removing the extents in the range
  	 * 1 - adding the hole extent if no_holes isn't set
  	 */
  	rsv_count = no_holes ? 2 : 3;
  	trans = btrfs_start_transaction(root, rsv_count);
  	if (IS_ERR(trans)) {
  		err = PTR_ERR(trans);
  		goto out_free;
  	}
  
  	ret = btrfs_block_rsv_migrate(&root->fs_info->trans_block_rsv, rsv,
  				      min_size);
  	BUG_ON(ret);
  	trans->block_rsv = rsv;
  
  	cur_offset = lockstart;
  	len = lockend - cur_offset;
  	while (cur_offset < lockend) {
  		ret = __btrfs_drop_extents(trans, root, inode, path,
  					   cur_offset, lockend + 1,
  					   &drop_end, 1, 0, 0, NULL);
  		if (ret != -ENOSPC)
  			break;
  
  		trans->block_rsv = &root->fs_info->trans_block_rsv;
  
  		if (cur_offset < ino_size) {
  			ret = fill_holes(trans, inode, path, cur_offset,
  					 drop_end);
  			if (ret) {
  				err = ret;
  				break;
  			}
  		}
  
  		cur_offset = drop_end;
  
  		ret = btrfs_update_inode(trans, root, inode);
  		if (ret) {
  			err = ret;
  			break;
  		}
  
  		btrfs_end_transaction(trans, root);
  		btrfs_btree_balance_dirty(root);
  
  		trans = btrfs_start_transaction(root, rsv_count);
  		if (IS_ERR(trans)) {
  			ret = PTR_ERR(trans);
  			trans = NULL;
  			break;
  		}
  
  		ret = btrfs_block_rsv_migrate(&root->fs_info->trans_block_rsv,
  					      rsv, min_size);
  		BUG_ON(ret);	/* shouldn't happen */
  		trans->block_rsv = rsv;
  
  		ret = find_first_non_hole(inode, &cur_offset, &len);
  		if (unlikely(ret < 0))
  			break;
  		if (ret && !len) {
  			ret = 0;
  			break;
  		}
  	}
  
  	if (ret) {
  		err = ret;
  		goto out_trans;
  	}
  
  	trans->block_rsv = &root->fs_info->trans_block_rsv;
  	/*
  	 * If we are using the NO_HOLES feature we might have had already an
  	 * hole that overlaps a part of the region [lockstart, lockend] and
  	 * ends at (or beyond) lockend. Since we have no file extent items to
  	 * represent holes, drop_end can be less than lockend and so we must
  	 * make sure we have an extent map representing the existing hole (the
  	 * call to __btrfs_drop_extents() might have dropped the existing extent
  	 * map representing the existing hole), otherwise the fast fsync path
  	 * will not record the existence of the hole region
  	 * [existing_hole_start, lockend].
  	 */
  	if (drop_end <= lockend)
  		drop_end = lockend + 1;
  	/*
  	 * Don't insert file hole extent item if it's for a range beyond eof
  	 * (because it's useless) or if it represents a 0 bytes range (when
  	 * cur_offset == drop_end).
  	 */
  	if (cur_offset < ino_size && cur_offset < drop_end) {
  		ret = fill_holes(trans, inode, path, cur_offset, drop_end);
  		if (ret) {
  			err = ret;
  			goto out_trans;
  		}
  	}
  
  out_trans:
  	if (!trans)
  		goto out_free;
  
  	inode_inc_iversion(inode);
  	inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  
  	trans->block_rsv = &root->fs_info->trans_block_rsv;
  	ret = btrfs_update_inode(trans, root, inode);
  	updated_inode = true;
  	btrfs_end_transaction(trans, root);
  	btrfs_btree_balance_dirty(root);
  out_free:
  	btrfs_free_path(path);
  	btrfs_free_block_rsv(root, rsv);
  out:
  	unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
  			     &cached_state, GFP_NOFS);
  out_only_mutex:
  	if (!updated_inode && truncated_page && !ret && !err) {
  		/*
  		 * If we only end up zeroing part of a page, we still need to
  		 * update the inode item, so that all the time fields are
  		 * updated as well as the necessary btrfs inode in memory fields
  		 * for detecting, at fsync time, if the inode isn't yet in the
  		 * log tree or it's there but not up to date.
  		 */
  		trans = btrfs_start_transaction(root, 1);
  		if (IS_ERR(trans)) {
  			err = PTR_ERR(trans);
  		} else {
  			err = btrfs_update_inode(trans, root, inode);
  			ret = btrfs_end_transaction(trans, root);
  		}
  	}
  	mutex_unlock(&inode->i_mutex);
  	if (ret && !err)
  		err = ret;
  	return err;
  }
  
  /* Helper structure to record which range is already reserved */
  struct falloc_range {
  	struct list_head list;
  	u64 start;
  	u64 len;
  };
  
  /*
   * Helper function to add falloc range
   *
   * Caller should have locked the larger range of extent containing
   * [start, len)
   */
  static int add_falloc_range(struct list_head *head, u64 start, u64 len)
  {
  	struct falloc_range *prev = NULL;
  	struct falloc_range *range = NULL;
  
  	if (list_empty(head))
  		goto insert;
  
  	/*
  	 * As fallocate iterate by bytenr order, we only need to check
  	 * the last range.
  	 */
  	prev = list_entry(head->prev, struct falloc_range, list);
  	if (prev->start + prev->len == start) {
  		prev->len += len;
  		return 0;
  	}
  insert:
  	range = kmalloc(sizeof(*range), GFP_NOFS);
  	if (!range)
  		return -ENOMEM;
  	range->start = start;
  	range->len = len;
  	list_add_tail(&range->list, head);
  	return 0;
  }
  
  static long btrfs_fallocate(struct file *file, int mode,
  			    loff_t offset, loff_t len)
  {
  	struct inode *inode = file_inode(file);
  	struct extent_state *cached_state = NULL;
  	struct falloc_range *range;
  	struct falloc_range *tmp;
  	struct list_head reserve_list;
  	u64 cur_offset;
  	u64 last_byte;
  	u64 alloc_start;
  	u64 alloc_end;
  	u64 alloc_hint = 0;
  	u64 locked_end;
  	u64 actual_end = 0;
  	struct extent_map *em;
  	int blocksize = BTRFS_I(inode)->root->sectorsize;
  	int ret;
  
  	alloc_start = round_down(offset, blocksize);
  	alloc_end = round_up(offset + len, blocksize);
  
  	/* Make sure we aren't being give some crap mode */
  	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
  		return -EOPNOTSUPP;
  
  	if (mode & FALLOC_FL_PUNCH_HOLE)
  		return btrfs_punch_hole(inode, offset, len);
  
  	/*
  	 * Only trigger disk allocation, don't trigger qgroup reserve
  	 *
  	 * For qgroup space, it will be checked later.
  	 */
  	ret = btrfs_alloc_data_chunk_ondemand(inode, alloc_end - alloc_start);
  	if (ret < 0)
  		return ret;
  
  	mutex_lock(&inode->i_mutex);
  	ret = inode_newsize_ok(inode, alloc_end);
  	if (ret)
  		goto out;
  
  	/*
  	 * TODO: Move these two operations after we have checked
  	 * accurate reserved space, or fallocate can still fail but
  	 * with page truncated or size expanded.
  	 *
  	 * But that's a minor problem and won't do much harm BTW.
  	 */
  	if (alloc_start > inode->i_size) {
  		ret = btrfs_cont_expand(inode, i_size_read(inode),
  					alloc_start);
  		if (ret)
  			goto out;
  	} else if (offset + len > inode->i_size) {
  		/*
  		 * If we are fallocating from the end of the file onward we
  		 * need to zero out the end of the page if i_size lands in the
  		 * middle of a page.
  		 */
  		ret = btrfs_truncate_page(inode, inode->i_size, 0, 0);
  		if (ret)
  			goto out;
  	}
  
  	/*
  	 * wait for ordered IO before we have any locks.  We'll loop again
  	 * below with the locks held.
  	 */
  	ret = btrfs_wait_ordered_range(inode, alloc_start,
  				       alloc_end - 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);
  		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
  			 */
  			ret = btrfs_wait_ordered_range(inode, alloc_start,
  						       alloc_end - alloc_start);
  			if (ret)
  				goto out;
  		} else {
  			if (ordered)
  				btrfs_put_ordered_extent(ordered);
  			break;
  		}
  	}
  
  	/* First, check if we exceed the qgroup limit */
  	INIT_LIST_HEAD(&reserve_list);
  	cur_offset = alloc_start;
  	while (1) {
  		em = btrfs_get_extent(inode, NULL, 0, cur_offset,
  				      alloc_end - cur_offset, 0);
  		if (IS_ERR_OR_NULL(em)) {
  			if (!em)
  				ret = -ENOMEM;
  			else
  				ret = PTR_ERR(em);
  			break;
  		}
  		last_byte = min(extent_map_end(em), alloc_end);
  		actual_end = min_t(u64, extent_map_end(em), offset + len);
  		last_byte = ALIGN(last_byte, blocksize);
  		if (em->block_start == EXTENT_MAP_HOLE ||
  		    (cur_offset >= inode->i_size &&
  		     !test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) {
  			ret = add_falloc_range(&reserve_list, cur_offset,
  					       last_byte - cur_offset);
  			if (ret < 0) {
  				free_extent_map(em);
  				break;
  			}
  			ret = btrfs_qgroup_reserve_data(inode, cur_offset,
  					last_byte - cur_offset);
  			if (ret < 0)
  				break;
  		}
  		free_extent_map(em);
  		cur_offset = last_byte;
  		if (cur_offset >= alloc_end)
  			break;
  	}
  
  	/*
  	 * If ret is still 0, means we're OK to fallocate.
  	 * Or just cleanup the list and exit.
  	 */
  	list_for_each_entry_safe(range, tmp, &reserve_list, list) {
  		if (!ret)
  			ret = btrfs_prealloc_file_range(inode, mode,
  					range->start,
  					range->len, 1 << inode->i_blkbits,
  					offset + len, &alloc_hint);
  		list_del(&range->list);
  		kfree(range);
  	}
  	if (ret < 0)
  		goto out_unlock;
  
  	if (actual_end > inode->i_size &&
  	    !(mode & FALLOC_FL_KEEP_SIZE)) {
  		struct btrfs_trans_handle *trans;
  		struct btrfs_root *root = BTRFS_I(inode)->root;
  
  		/*
  		 * 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 and the inode item.
  		 */
  		trans = btrfs_start_transaction(root, 1);
  		if (IS_ERR(trans)) {
  			ret = PTR_ERR(trans);
  		} else {
  			inode->i_ctime = CURRENT_TIME;
  			i_size_write(inode, actual_end);
  			btrfs_ordered_update_i_size(inode, actual_end, NULL);
  			ret = btrfs_update_inode(trans, root, inode);
  			if (ret)
  				btrfs_end_transaction(trans, root);
  			else
  				ret = btrfs_end_transaction(trans, root);
  		}
  	}
  out_unlock:
  	unlock_extent_cached(&BTRFS_I(inode)->io_tree, alloc_start, locked_end,
  			     &cached_state, GFP_NOFS);
  out:
  	/*
  	 * As we waited the extent range, the data_rsv_map must be empty
  	 * in the range, as written data range will be released from it.
  	 * And for prealloacted extent, it will also be released when
  	 * its metadata is written.
  	 * So this is completely used as cleanup.
  	 */
  	btrfs_qgroup_free_data(inode, alloc_start, alloc_end - alloc_start);
  	mutex_unlock(&inode->i_mutex);
  	/* Let go of our reservation. */
  	btrfs_free_reserved_data_space(inode, alloc_start,
  				       alloc_end - alloc_start);
  	return ret;
  }
  
  static int find_desired_extent(struct inode *inode, loff_t *offset, int whence)
  {
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct extent_map *em = NULL;
  	struct extent_state *cached_state = NULL;
  	u64 lockstart;
  	u64 lockend;
  	u64 start;
  	u64 len;
  	int ret = 0;
  
  	if (inode->i_size == 0)
  		return -ENXIO;
  
  	/*
  	 * *offset can be negative, in this case we start finding DATA/HOLE from
  	 * the very start of the file.
  	 */
  	start = max_t(loff_t, 0, *offset);
  
  	lockstart = round_down(start, root->sectorsize);
  	lockend = round_up(i_size_read(inode), root->sectorsize);
  	if (lockend <= lockstart)
  		lockend = lockstart + root->sectorsize;
  	lockend--;
  	len = lockend - lockstart + 1;
  
  	lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend, 0,
  			 &cached_state);
  
  	while (start < inode->i_size) {
  		em = btrfs_get_extent_fiemap(inode, NULL, 0, start, len, 0);
  		if (IS_ERR(em)) {
  			ret = PTR_ERR(em);
  			em = NULL;
  			break;
  		}
  
  		if (whence == SEEK_HOLE &&
  		    (em->block_start == EXTENT_MAP_HOLE ||
  		     test_bit(EXTENT_FLAG_PREALLOC, &em->flags)))
  			break;
  		else if (whence == SEEK_DATA &&
  			   (em->block_start != EXTENT_MAP_HOLE &&
  			    !test_bit(EXTENT_FLAG_PREALLOC, &em->flags)))
  			break;
  
  		start = em->start + em->len;
  		free_extent_map(em);
  		em = NULL;
  		cond_resched();
  	}
  	free_extent_map(em);
  	if (!ret) {
  		if (whence == SEEK_DATA && start >= inode->i_size)
  			ret = -ENXIO;
  		else
  			*offset = min_t(loff_t, start, inode->i_size);
  	}
  	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 whence)
  {
  	struct inode *inode = file->f_mapping->host;
  	int ret;
  
  	mutex_lock(&inode->i_mutex);
  	switch (whence) {
  	case SEEK_END:
  	case SEEK_CUR:
  		offset = generic_file_llseek(file, offset, whence);
  		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, whence);
  		if (ret) {
  			mutex_unlock(&inode->i_mutex);
  			return ret;
  		}
  	}
  
  	offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
  out:
  	mutex_unlock(&inode->i_mutex);
  	return offset;
  }
  
  const struct file_operations btrfs_file_operations = {
  	.llseek		= btrfs_file_llseek,
  	.read_iter      = generic_file_read_iter,
  	.splice_read	= generic_file_splice_read,
  	.write_iter	= btrfs_file_write_iter,
  	.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
  };
  
  void btrfs_auto_defrag_exit(void)
  {
  	if (btrfs_inode_defrag_cachep)
  		kmem_cache_destroy(btrfs_inode_defrag_cachep);
  }
  
  int btrfs_auto_defrag_init(void)
  {
  	btrfs_inode_defrag_cachep = kmem_cache_create("btrfs_inode_defrag",
  					sizeof(struct inode_defrag), 0,
  					SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
  					NULL);
  	if (!btrfs_inode_defrag_cachep)
  		return -ENOMEM;
  
  	return 0;
  }
  
  int btrfs_fdatawrite_range(struct inode *inode, loff_t start, loff_t end)
  {
  	int ret;
  
  	/*
  	 * So with compression we will find and lock a dirty page and clear the
  	 * first one as dirty, setup an async extent, and immediately return
  	 * with the entire range locked but with nobody actually marked with
  	 * writeback.  So we can't just filemap_write_and_wait_range() and
  	 * expect it to work since it will just kick off a thread to do the
  	 * actual work.  So we need to call filemap_fdatawrite_range _again_
  	 * since it will wait on the page lock, which won't be unlocked until
  	 * after the pages have been marked as writeback and so we're good to go
  	 * from there.  We have to do this otherwise we'll miss the ordered
  	 * extents and that results in badness.  Please Josef, do not think you
  	 * know better and pull this out at some point in the future, it is
  	 * right and you are wrong.
  	 */
  	ret = filemap_fdatawrite_range(inode->i_mapping, start, end);
  	if (!ret && test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
  			     &BTRFS_I(inode)->runtime_flags))
  		ret = filemap_fdatawrite_range(inode->i_mapping, start, end);
  
  	return ret;
  }
  