#include <linux/bitops.h>
  #include <linux/slab.h>
  #include <linux/bio.h>
  #include <linux/mm.h>

  #include <linux/pagemap.h>
  #include <linux/page-flags.h>

  #include <linux/spinlock.h>
  #include <linux/blkdev.h>
  #include <linux/swap.h>

  #include <linux/writeback.h>
  #include <linux/pagevec.h>

  #include <linux/prefetch.h>

  #include <linux/cleancache.h>

  #include "extent_io.h"
  #include "extent_map.h"

  #include "compat.h"

  #include "ctree.h"
  #include "btrfs_inode.h"

  #include "volumes.h"

  #include "check-integrity.h"

  #include "locking.h"

  #include "rcu-string.h"

  static struct kmem_cache *extent_state_cache;
  static struct kmem_cache *extent_buffer_cache;

  static struct bio_set *btrfs_bioset;

  #ifdef CONFIG_BTRFS_DEBUG

  static LIST_HEAD(buffers);
  static LIST_HEAD(states);

  static DEFINE_SPINLOCK(leak_lock);

  
  static inline
  void btrfs_leak_debug_add(struct list_head *new, struct list_head *head)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&leak_lock, flags);
  	list_add(new, head);
  	spin_unlock_irqrestore(&leak_lock, flags);
  }
  
  static inline
  void btrfs_leak_debug_del(struct list_head *entry)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&leak_lock, flags);
  	list_del(entry);
  	spin_unlock_irqrestore(&leak_lock, flags);
  }
  
  static inline
  void btrfs_leak_debug_check(void)
  {
  	struct extent_state *state;
  	struct extent_buffer *eb;
  
  	while (!list_empty(&states)) {
  		state = list_entry(states.next, struct extent_state, leak_list);
  		printk(KERN_ERR "btrfs state leak: start %llu end %llu "
  		       "state %lu in tree %p refs %d
  ",

  		       state->start, state->end, state->state, state->tree,
  		       atomic_read(&state->refs));

  		list_del(&state->leak_list);
  		kmem_cache_free(extent_state_cache, state);
  	}
  
  	while (!list_empty(&buffers)) {
  		eb = list_entry(buffers.next, struct extent_buffer, leak_list);
  		printk(KERN_ERR "btrfs buffer leak start %llu len %lu "

  		       "refs %d
  ",
  		       eb->start, eb->len, atomic_read(&eb->refs));

  		list_del(&eb->leak_list);
  		kmem_cache_free(extent_buffer_cache, eb);
  	}
  }

  
  #define btrfs_debug_check_extent_io_range(inode, start, end)		\
  	__btrfs_debug_check_extent_io_range(__func__, (inode), (start), (end))
  static inline void __btrfs_debug_check_extent_io_range(const char *caller,
  		struct inode *inode, u64 start, u64 end)
  {
  	u64 isize = i_size_read(inode);
  
  	if (end >= PAGE_SIZE && (end % 2) == 0 && end != isize - 1) {
  		printk_ratelimited(KERN_DEBUG
  		    "btrfs: %s: ino %llu isize %llu odd range [%llu,%llu]
  ",

  				caller, btrfs_ino(inode), isize, start, end);

  	}
  }

  #else
  #define btrfs_leak_debug_add(new, head)	do {} while (0)
  #define btrfs_leak_debug_del(entry)	do {} while (0)
  #define btrfs_leak_debug_check()	do {} while (0)

  #define btrfs_debug_check_extent_io_range(c, s, e)	do {} while (0)

  #endif

  #define BUFFER_LRU_MAX 64
  
  struct tree_entry {
  	u64 start;
  	u64 end;

  	struct rb_node rb_node;
  };
  
  struct extent_page_data {
  	struct bio *bio;
  	struct extent_io_tree *tree;
  	get_extent_t *get_extent;

  	unsigned long bio_flags;

  
  	/* tells writepage not to lock the state bits for this range
  	 * it still does the unlocking
  	 */

  	unsigned int extent_locked:1;
  
  	/* tells the submit_bio code to use a WRITE_SYNC */
  	unsigned int sync_io:1;

  };

  static noinline void flush_write_bio(void *data);

  static inline struct btrfs_fs_info *
  tree_fs_info(struct extent_io_tree *tree)
  {
  	return btrfs_sb(tree->mapping->host->i_sb);
  }

  int __init extent_io_init(void)
  {

  	extent_state_cache = kmem_cache_create("btrfs_extent_state",

  			sizeof(struct extent_state), 0,
  			SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);

  	if (!extent_state_cache)
  		return -ENOMEM;

  	extent_buffer_cache = kmem_cache_create("btrfs_extent_buffer",

  			sizeof(struct extent_buffer), 0,
  			SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);

  	if (!extent_buffer_cache)
  		goto free_state_cache;

  
  	btrfs_bioset = bioset_create(BIO_POOL_SIZE,
  				     offsetof(struct btrfs_io_bio, bio));
  	if (!btrfs_bioset)
  		goto free_buffer_cache;

  
  	if (bioset_integrity_create(btrfs_bioset, BIO_POOL_SIZE))
  		goto free_bioset;

  	return 0;

  free_bioset:
  	bioset_free(btrfs_bioset);
  	btrfs_bioset = NULL;

  free_buffer_cache:
  	kmem_cache_destroy(extent_buffer_cache);
  	extent_buffer_cache = NULL;

  free_state_cache:
  	kmem_cache_destroy(extent_state_cache);

  	extent_state_cache = NULL;

  	return -ENOMEM;
  }
  
  void extent_io_exit(void)
  {

  	btrfs_leak_debug_check();

  
  	/*
  	 * Make sure all delayed rcu free are flushed before we
  	 * destroy caches.
  	 */
  	rcu_barrier();

  	if (extent_state_cache)
  		kmem_cache_destroy(extent_state_cache);
  	if (extent_buffer_cache)
  		kmem_cache_destroy(extent_buffer_cache);

  	if (btrfs_bioset)
  		bioset_free(btrfs_bioset);

  }
  
  void extent_io_tree_init(struct extent_io_tree *tree,

  			 struct address_space *mapping)

  {

  	tree->state = RB_ROOT;

  	INIT_RADIX_TREE(&tree->buffer, GFP_ATOMIC);

  	tree->ops = NULL;
  	tree->dirty_bytes = 0;

  	spin_lock_init(&tree->lock);

  	spin_lock_init(&tree->buffer_lock);

  	tree->mapping = mapping;

  }

  static struct extent_state *alloc_extent_state(gfp_t mask)

  {
  	struct extent_state *state;

  
  	state = kmem_cache_alloc(extent_state_cache, mask);

  	if (!state)

  		return state;
  	state->state = 0;

  	state->private = 0;

  	state->tree = NULL;

  	btrfs_leak_debug_add(&state->leak_list, &states);

  	atomic_set(&state->refs, 1);
  	init_waitqueue_head(&state->wq);

  	trace_alloc_extent_state(state, mask, _RET_IP_);

  	return state;
  }

  void free_extent_state(struct extent_state *state)

  {

  	if (!state)
  		return;
  	if (atomic_dec_and_test(&state->refs)) {

  		WARN_ON(state->tree);

  		btrfs_leak_debug_del(&state->leak_list);

  		trace_free_extent_state(state, _RET_IP_);

  		kmem_cache_free(extent_state_cache, state);
  	}
  }

  
  static struct rb_node *tree_insert(struct rb_root *root, u64 offset,
  				   struct rb_node *node)
  {

  	struct rb_node **p = &root->rb_node;
  	struct rb_node *parent = NULL;

  	struct tree_entry *entry;

  	while (*p) {

  		parent = *p;
  		entry = rb_entry(parent, struct tree_entry, rb_node);
  
  		if (offset < entry->start)
  			p = &(*p)->rb_left;
  		else if (offset > entry->end)
  			p = &(*p)->rb_right;
  		else
  			return parent;
  	}

  	rb_link_node(node, parent, p);
  	rb_insert_color(node, root);
  	return NULL;
  }

  static struct rb_node *__etree_search(struct extent_io_tree *tree, u64 offset,

  				     struct rb_node **prev_ret,
  				     struct rb_node **next_ret)
  {

  	struct rb_root *root = &tree->state;

  	struct rb_node *n = root->rb_node;

  	struct rb_node *prev = NULL;
  	struct rb_node *orig_prev = NULL;
  	struct tree_entry *entry;
  	struct tree_entry *prev_entry = NULL;

  	while (n) {

  		entry = rb_entry(n, struct tree_entry, rb_node);
  		prev = n;
  		prev_entry = entry;
  
  		if (offset < entry->start)
  			n = n->rb_left;
  		else if (offset > entry->end)
  			n = n->rb_right;

  		else

  			return n;
  	}
  
  	if (prev_ret) {
  		orig_prev = prev;

  		while (prev && offset > prev_entry->end) {

  			prev = rb_next(prev);
  			prev_entry = rb_entry(prev, struct tree_entry, rb_node);
  		}
  		*prev_ret = prev;
  		prev = orig_prev;
  	}
  
  	if (next_ret) {
  		prev_entry = rb_entry(prev, struct tree_entry, rb_node);

  		while (prev && offset < prev_entry->start) {

  			prev = rb_prev(prev);
  			prev_entry = rb_entry(prev, struct tree_entry, rb_node);
  		}
  		*next_ret = prev;
  	}
  	return NULL;
  }

  static inline struct rb_node *tree_search(struct extent_io_tree *tree,
  					  u64 offset)

  {

  	struct rb_node *prev = NULL;

  	struct rb_node *ret;

  	ret = __etree_search(tree, offset, &prev, NULL);

  	if (!ret)

  		return prev;
  	return ret;
  }

  static void merge_cb(struct extent_io_tree *tree, struct extent_state *new,
  		     struct extent_state *other)
  {
  	if (tree->ops && tree->ops->merge_extent_hook)
  		tree->ops->merge_extent_hook(tree->mapping->host, new,
  					     other);
  }

  /*
   * utility function to look for merge candidates inside a given range.
   * Any extents with matching state are merged together into a single
   * extent in the tree.  Extents with EXTENT_IO in their state field
   * are not merged because the end_io handlers need to be able to do
   * operations on them without sleeping (or doing allocations/splits).
   *
   * This should be called with the tree lock held.
   */

  static void merge_state(struct extent_io_tree *tree,
  		        struct extent_state *state)

  {
  	struct extent_state *other;
  	struct rb_node *other_node;

  	if (state->state & (EXTENT_IOBITS | EXTENT_BOUNDARY))

  		return;

  
  	other_node = rb_prev(&state->rb_node);
  	if (other_node) {
  		other = rb_entry(other_node, struct extent_state, rb_node);
  		if (other->end == state->start - 1 &&
  		    other->state == state->state) {

  			merge_cb(tree, state, other);

  			state->start = other->start;

  			other->tree = NULL;

  			rb_erase(&other->rb_node, &tree->state);
  			free_extent_state(other);
  		}
  	}
  	other_node = rb_next(&state->rb_node);
  	if (other_node) {
  		other = rb_entry(other_node, struct extent_state, rb_node);
  		if (other->start == state->end + 1 &&
  		    other->state == state->state) {

  			merge_cb(tree, state, other);

  			state->end = other->end;
  			other->tree = NULL;
  			rb_erase(&other->rb_node, &tree->state);
  			free_extent_state(other);

  		}
  	}

  }

  static void set_state_cb(struct extent_io_tree *tree,

  			 struct extent_state *state, unsigned long *bits)

  {

  	if (tree->ops && tree->ops->set_bit_hook)
  		tree->ops->set_bit_hook(tree->mapping->host, state, bits);

  }
  
  static void clear_state_cb(struct extent_io_tree *tree,

  			   struct extent_state *state, unsigned long *bits)

  {

  	if (tree->ops && tree->ops->clear_bit_hook)
  		tree->ops->clear_bit_hook(tree->mapping->host, state, bits);

  }

  static void set_state_bits(struct extent_io_tree *tree,

  			   struct extent_state *state, unsigned long *bits);

  /*
   * insert an extent_state struct into the tree.  'bits' are set on the
   * struct before it is inserted.
   *
   * This may return -EEXIST if the extent is already there, in which case the
   * state struct is freed.
   *
   * The tree lock is not taken internally.  This is a utility function and
   * probably isn't what you want to call (see set/clear_extent_bit).
   */
  static int insert_state(struct extent_io_tree *tree,
  			struct extent_state *state, u64 start, u64 end,

  			unsigned long *bits)

  {
  	struct rb_node *node;

  	if (end < start)
  		WARN(1, KERN_ERR "btrfs end < start %llu %llu
  ",

  		       end, start);

  	state->start = start;
  	state->end = end;

  	set_state_bits(tree, state, bits);

  	node = tree_insert(&tree->state, end, &state->rb_node);
  	if (node) {
  		struct extent_state *found;
  		found = rb_entry(node, struct extent_state, rb_node);

  		printk(KERN_ERR "btrfs found node %llu %llu on insert of "

  		       "%llu %llu
  ",
  		       found->start, found->end, start, end);

  		return -EEXIST;
  	}

  	state->tree = tree;

  	merge_state(tree, state);
  	return 0;
  }

  static void split_cb(struct extent_io_tree *tree, struct extent_state *orig,

  		     u64 split)
  {
  	if (tree->ops && tree->ops->split_extent_hook)

  		tree->ops->split_extent_hook(tree->mapping->host, orig, split);

  }

  /*
   * split a given extent state struct in two, inserting the preallocated
   * struct 'prealloc' as the newly created second half.  'split' indicates an
   * offset inside 'orig' where it should be split.
   *
   * Before calling,
   * the tree has 'orig' at [orig->start, orig->end].  After calling, there
   * are two extent state structs in the tree:
   * prealloc: [orig->start, split - 1]
   * orig: [ split, orig->end ]
   *
   * The tree locks are not taken by this function. They need to be held
   * by the caller.
   */
  static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
  		       struct extent_state *prealloc, u64 split)
  {
  	struct rb_node *node;

  
  	split_cb(tree, orig, split);

  	prealloc->start = orig->start;
  	prealloc->end = split - 1;
  	prealloc->state = orig->state;
  	orig->start = split;
  
  	node = tree_insert(&tree->state, prealloc->end, &prealloc->rb_node);
  	if (node) {

  		free_extent_state(prealloc);
  		return -EEXIST;
  	}

  	prealloc->tree = tree;

  	return 0;
  }

  static struct extent_state *next_state(struct extent_state *state)
  {
  	struct rb_node *next = rb_next(&state->rb_node);
  	if (next)
  		return rb_entry(next, struct extent_state, rb_node);
  	else
  		return NULL;
  }

  /*
   * utility function to clear some bits in an extent state struct.

   * it will optionally wake up any one waiting on this state (wake == 1).

   *
   * If no bits are set on the state struct after clearing things, the
   * struct is freed and removed from the tree
   */

  static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
  					    struct extent_state *state,

  					    unsigned long *bits, int wake)

  {

  	struct extent_state *next;

  	unsigned long bits_to_clear = *bits & ~EXTENT_CTLBITS;

  	if ((bits_to_clear & EXTENT_DIRTY) && (state->state & EXTENT_DIRTY)) {

  		u64 range = state->end - state->start + 1;
  		WARN_ON(range > tree->dirty_bytes);
  		tree->dirty_bytes -= range;
  	}

  	clear_state_cb(tree, state, bits);

  	state->state &= ~bits_to_clear;

  	if (wake)
  		wake_up(&state->wq);

  	if (state->state == 0) {

  		next = next_state(state);

  		if (state->tree) {

  			rb_erase(&state->rb_node, &tree->state);

  			state->tree = NULL;

  			free_extent_state(state);
  		} else {
  			WARN_ON(1);
  		}
  	} else {
  		merge_state(tree, state);

  		next = next_state(state);

  	}

  	return next;

  }

  static struct extent_state *
  alloc_extent_state_atomic(struct extent_state *prealloc)
  {
  	if (!prealloc)
  		prealloc = alloc_extent_state(GFP_ATOMIC);
  
  	return prealloc;
  }

  static void extent_io_tree_panic(struct extent_io_tree *tree, int err)

  {
  	btrfs_panic(tree_fs_info(tree), err, "Locking error: "
  		    "Extent tree was modified by another "
  		    "thread while locked.");
  }

  /*
   * clear some bits on a range in the tree.  This may require splitting
   * or inserting elements in the tree, so the gfp mask is used to
   * indicate which allocations or sleeping are allowed.
   *
   * pass 'wake' == 1 to kick any sleepers, and 'delete' == 1 to remove
   * the given range from the tree regardless of state (ie for truncate).
   *
   * the range [start, end] is inclusive.
   *

   * This takes the tree lock, and returns 0 on success and < 0 on error.

   */
  int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,

  		     unsigned long bits, int wake, int delete,

  		     struct extent_state **cached_state,
  		     gfp_t mask)

  {
  	struct extent_state *state;

  	struct extent_state *cached;

  	struct extent_state *prealloc = NULL;
  	struct rb_node *node;

  	u64 last_end;

  	int err;

  	int clear = 0;

  	btrfs_debug_check_extent_io_range(tree->mapping->host, start, end);

  	if (bits & EXTENT_DELALLOC)
  		bits |= EXTENT_NORESERVE;

  	if (delete)
  		bits |= ~EXTENT_CTLBITS;
  	bits |= EXTENT_FIRST_DELALLOC;

  	if (bits & (EXTENT_IOBITS | EXTENT_BOUNDARY))
  		clear = 1;

  again:
  	if (!prealloc && (mask & __GFP_WAIT)) {
  		prealloc = alloc_extent_state(mask);
  		if (!prealloc)
  			return -ENOMEM;
  	}

  	spin_lock(&tree->lock);

  	if (cached_state) {
  		cached = *cached_state;

  
  		if (clear) {
  			*cached_state = NULL;
  			cached_state = NULL;
  		}

  		if (cached && cached->tree && cached->start <= start &&
  		    cached->end > start) {

  			if (clear)
  				atomic_dec(&cached->refs);

  			state = cached;

  			goto hit_next;

  		}

  		if (clear)
  			free_extent_state(cached);

  	}

  	/*
  	 * this search will find the extents that end after
  	 * our range starts
  	 */

  	node = tree_search(tree, start);

  	if (!node)
  		goto out;
  	state = rb_entry(node, struct extent_state, rb_node);

  hit_next:

  	if (state->start > end)
  		goto out;
  	WARN_ON(state->end < start);

  	last_end = state->end;

  	/* the state doesn't have the wanted bits, go ahead */

  	if (!(state->state & bits)) {
  		state = next_state(state);

  		goto next;

  	}

  	/*
  	 *     | ---- desired range ---- |
  	 *  | state | or
  	 *  | ------------- state -------------- |
  	 *
  	 * We need to split the extent we found, and may flip
  	 * bits on second half.
  	 *
  	 * If the extent we found extends past our range, we
  	 * just split and search again.  It'll get split again
  	 * the next time though.
  	 *
  	 * If the extent we found is inside our range, we clear
  	 * the desired bit on it.
  	 */
  
  	if (state->start < start) {

  		prealloc = alloc_extent_state_atomic(prealloc);
  		BUG_ON(!prealloc);

  		err = split_state(tree, state, prealloc, start);

  		if (err)
  			extent_io_tree_panic(tree, err);

  		prealloc = NULL;
  		if (err)
  			goto out;
  		if (state->end <= end) {

  			state = clear_state_bit(tree, state, &bits, wake);
  			goto next;

  		}
  		goto search_again;
  	}
  	/*
  	 * | ---- desired range ---- |
  	 *                        | state |
  	 * We need to split the extent, and clear the bit
  	 * on the first half
  	 */
  	if (state->start <= end && state->end > end) {

  		prealloc = alloc_extent_state_atomic(prealloc);
  		BUG_ON(!prealloc);

  		err = split_state(tree, state, prealloc, end + 1);

  		if (err)
  			extent_io_tree_panic(tree, err);

  		if (wake)
  			wake_up(&state->wq);

  		clear_state_bit(tree, prealloc, &bits, wake);

  		prealloc = NULL;
  		goto out;
  	}

  	state = clear_state_bit(tree, state, &bits, wake);

  next:

  	if (last_end == (u64)-1)
  		goto out;
  	start = last_end + 1;

  	if (start <= end && state && !need_resched())

  		goto hit_next;

  	goto search_again;
  
  out:

  	spin_unlock(&tree->lock);

  	if (prealloc)
  		free_extent_state(prealloc);

  	return 0;

  
  search_again:
  	if (start > end)
  		goto out;

  	spin_unlock(&tree->lock);

  	if (mask & __GFP_WAIT)
  		cond_resched();
  	goto again;
  }

  static void wait_on_state(struct extent_io_tree *tree,
  			  struct extent_state *state)

  		__releases(tree->lock)
  		__acquires(tree->lock)

  {
  	DEFINE_WAIT(wait);
  	prepare_to_wait(&state->wq, &wait, TASK_UNINTERRUPTIBLE);

  	spin_unlock(&tree->lock);

  	schedule();

  	spin_lock(&tree->lock);

  	finish_wait(&state->wq, &wait);

  }
  
  /*
   * waits for one or more bits to clear on a range in the state tree.
   * The range [start, end] is inclusive.
   * The tree lock is taken by this function
   */

  static void wait_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
  			    unsigned long bits)

  {
  	struct extent_state *state;
  	struct rb_node *node;

  	btrfs_debug_check_extent_io_range(tree->mapping->host, start, end);

  	spin_lock(&tree->lock);

  again:
  	while (1) {
  		/*
  		 * this search will find all the extents that end after
  		 * our range starts
  		 */

  		node = tree_search(tree, start);

  		if (!node)
  			break;
  
  		state = rb_entry(node, struct extent_state, rb_node);
  
  		if (state->start > end)
  			goto out;
  
  		if (state->state & bits) {
  			start = state->start;
  			atomic_inc(&state->refs);
  			wait_on_state(tree, state);
  			free_extent_state(state);
  			goto again;
  		}
  		start = state->end + 1;
  
  		if (start > end)
  			break;

  		cond_resched_lock(&tree->lock);

  	}
  out:

  	spin_unlock(&tree->lock);

  }

  static void set_state_bits(struct extent_io_tree *tree,

  			   struct extent_state *state,

  			   unsigned long *bits)

  {

  	unsigned long bits_to_set = *bits & ~EXTENT_CTLBITS;

  	set_state_cb(tree, state, bits);

  	if ((bits_to_set & EXTENT_DIRTY) && !(state->state & EXTENT_DIRTY)) {

  		u64 range = state->end - state->start + 1;
  		tree->dirty_bytes += range;
  	}

  	state->state |= bits_to_set;

  }

  static void cache_state(struct extent_state *state,
  			struct extent_state **cached_ptr)
  {
  	if (cached_ptr && !(*cached_ptr)) {
  		if (state->state & (EXTENT_IOBITS | EXTENT_BOUNDARY)) {
  			*cached_ptr = state;
  			atomic_inc(&state->refs);
  		}
  	}
  }

  /*

   * set some bits on a range in the tree.  This may require allocations or
   * sleeping, so the gfp mask is used to indicate what is allowed.

   *

   * If any of the exclusive bits are set, this will fail with -EEXIST if some
   * part of the range already has the desired bits set.  The start of the
   * existing range is returned in failed_start in this case.

   *

   * [start, end] is inclusive This takes the tree lock.

   */

  static int __must_check
  __set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,

  		 unsigned long bits, unsigned long exclusive_bits,
  		 u64 *failed_start, struct extent_state **cached_state,
  		 gfp_t mask)

  {
  	struct extent_state *state;
  	struct extent_state *prealloc = NULL;
  	struct rb_node *node;

  	int err = 0;

  	u64 last_start;
  	u64 last_end;

  	btrfs_debug_check_extent_io_range(tree->mapping->host, start, end);

  	bits |= EXTENT_FIRST_DELALLOC;

  again:
  	if (!prealloc && (mask & __GFP_WAIT)) {
  		prealloc = alloc_extent_state(mask);

  		BUG_ON(!prealloc);

  	}

  	spin_lock(&tree->lock);

  	if (cached_state && *cached_state) {
  		state = *cached_state;

  		if (state->start <= start && state->end > start &&
  		    state->tree) {

  			node = &state->rb_node;
  			goto hit_next;
  		}
  	}

  	/*
  	 * this search will find all the extents that end after
  	 * our range starts.
  	 */

  	node = tree_search(tree, start);

  	if (!node) {

  		prealloc = alloc_extent_state_atomic(prealloc);
  		BUG_ON(!prealloc);

  		err = insert_state(tree, prealloc, start, end, &bits);

  		if (err)
  			extent_io_tree_panic(tree, err);

  		prealloc = NULL;

  		goto out;
  	}

  	state = rb_entry(node, struct extent_state, rb_node);

  hit_next:

  	last_start = state->start;
  	last_end = state->end;
  
  	/*
  	 * | ---- desired range ---- |
  	 * | state |
  	 *
  	 * Just lock what we found and keep going
  	 */
  	if (state->start == start && state->end <= end) {

  		if (state->state & exclusive_bits) {

  			*failed_start = state->start;
  			err = -EEXIST;
  			goto out;
  		}

  		set_state_bits(tree, state, &bits);

  		cache_state(state, cached_state);

  		merge_state(tree, state);

  		if (last_end == (u64)-1)
  			goto out;
  		start = last_end + 1;

  		state = next_state(state);
  		if (start < end && state && state->start == start &&
  		    !need_resched())
  			goto hit_next;

  		goto search_again;
  	}
  
  	/*
  	 *     | ---- desired range ---- |
  	 * | state |
  	 *   or
  	 * | ------------- state -------------- |
  	 *
  	 * We need to split the extent we found, and may flip bits on
  	 * second half.
  	 *
  	 * If the extent we found extends past our
  	 * range, we just split and search again.  It'll get split
  	 * again the next time though.
  	 *
  	 * If the extent we found is inside our range, we set the
  	 * desired bit on it.
  	 */
  	if (state->start < start) {

  		if (state->state & exclusive_bits) {

  			*failed_start = start;
  			err = -EEXIST;
  			goto out;
  		}

  
  		prealloc = alloc_extent_state_atomic(prealloc);
  		BUG_ON(!prealloc);

  		err = split_state(tree, state, prealloc, start);

  		if (err)
  			extent_io_tree_panic(tree, err);

  		prealloc = NULL;
  		if (err)
  			goto out;
  		if (state->end <= end) {

  			set_state_bits(tree, state, &bits);

  			cache_state(state, cached_state);

  			merge_state(tree, state);

  			if (last_end == (u64)-1)
  				goto out;
  			start = last_end + 1;

  			state = next_state(state);
  			if (start < end && state && state->start == start &&
  			    !need_resched())
  				goto hit_next;

  		}
  		goto search_again;
  	}
  	/*
  	 * | ---- desired range ---- |
  	 *     | state | or               | state |
  	 *
  	 * There's a hole, we need to insert something in it and
  	 * ignore the extent we found.
  	 */
  	if (state->start > start) {
  		u64 this_end;
  		if (end < last_start)
  			this_end = end;
  		else

  			this_end = last_start - 1;

  
  		prealloc = alloc_extent_state_atomic(prealloc);
  		BUG_ON(!prealloc);

  
  		/*
  		 * Avoid to free 'prealloc' if it can be merged with
  		 * the later extent.
  		 */

  		err = insert_state(tree, prealloc, start, this_end,

  				   &bits);

  		if (err)
  			extent_io_tree_panic(tree, err);

  		cache_state(prealloc, cached_state);
  		prealloc = NULL;

  		start = this_end + 1;
  		goto search_again;
  	}
  	/*
  	 * | ---- desired range ---- |
  	 *                        | state |
  	 * We need to split the extent, and set the bit
  	 * on the first half
  	 */
  	if (state->start <= end && state->end > end) {

  		if (state->state & exclusive_bits) {

  			*failed_start = start;
  			err = -EEXIST;
  			goto out;
  		}

  
  		prealloc = alloc_extent_state_atomic(prealloc);
  		BUG_ON(!prealloc);

  		err = split_state(tree, state, prealloc, end + 1);

  		if (err)
  			extent_io_tree_panic(tree, err);

  		set_state_bits(tree, prealloc, &bits);

  		cache_state(prealloc, cached_state);

  		merge_state(tree, prealloc);
  		prealloc = NULL;
  		goto out;
  	}
  
  	goto search_again;
  
  out:

  	spin_unlock(&tree->lock);

  	if (prealloc)
  		free_extent_state(prealloc);
  
  	return err;
  
  search_again:
  	if (start > end)
  		goto out;

  	spin_unlock(&tree->lock);

  	if (mask & __GFP_WAIT)
  		cond_resched();
  	goto again;
  }

  int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
  		   unsigned long bits, u64 * failed_start,
  		   struct extent_state **cached_state, gfp_t mask)

  {
  	return __set_extent_bit(tree, start, end, bits, 0, failed_start,
  				cached_state, mask);
  }

  /**

   * convert_extent_bit - convert all bits in a given range from one bit to
   * 			another

   * @tree:	the io tree to search
   * @start:	the start offset in bytes
   * @end:	the end offset in bytes (inclusive)
   * @bits:	the bits to set in this range
   * @clear_bits:	the bits to clear in this range

   * @cached_state:	state that we're going to cache

   * @mask:	the allocation mask
   *
   * This will go through and set bits for the given range.  If any states exist
   * already in this range they are set with the given bit and cleared of the
   * clear_bits.  This is only meant to be used by things that are mergeable, ie
   * converting from say DELALLOC to DIRTY.  This is not meant to be used with
   * boundary bits like LOCK.
   */
  int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,

  		       unsigned long bits, unsigned long clear_bits,

  		       struct extent_state **cached_state, gfp_t mask)

  {
  	struct extent_state *state;
  	struct extent_state *prealloc = NULL;
  	struct rb_node *node;
  	int err = 0;
  	u64 last_start;
  	u64 last_end;

  	btrfs_debug_check_extent_io_range(tree->mapping->host, start, end);

  again:
  	if (!prealloc && (mask & __GFP_WAIT)) {
  		prealloc = alloc_extent_state(mask);
  		if (!prealloc)
  			return -ENOMEM;
  	}
  
  	spin_lock(&tree->lock);

  	if (cached_state && *cached_state) {
  		state = *cached_state;
  		if (state->start <= start && state->end > start &&
  		    state->tree) {
  			node = &state->rb_node;
  			goto hit_next;
  		}
  	}

  	/*
  	 * this search will find all the extents that end after
  	 * our range starts.
  	 */
  	node = tree_search(tree, start);
  	if (!node) {
  		prealloc = alloc_extent_state_atomic(prealloc);

  		if (!prealloc) {
  			err = -ENOMEM;
  			goto out;
  		}

  		err = insert_state(tree, prealloc, start, end, &bits);
  		prealloc = NULL;

  		if (err)
  			extent_io_tree_panic(tree, err);

  		goto out;
  	}
  	state = rb_entry(node, struct extent_state, rb_node);
  hit_next:
  	last_start = state->start;
  	last_end = state->end;
  
  	/*
  	 * | ---- desired range ---- |
  	 * | state |
  	 *
  	 * Just lock what we found and keep going
  	 */
  	if (state->start == start && state->end <= end) {

  		set_state_bits(tree, state, &bits);

  		cache_state(state, cached_state);

  		state = clear_state_bit(tree, state, &clear_bits, 0);

  		if (last_end == (u64)-1)
  			goto out;

  		start = last_end + 1;

  		if (start < end && state && state->start == start &&
  		    !need_resched())
  			goto hit_next;

  		goto search_again;
  	}
  
  	/*
  	 *     | ---- desired range ---- |
  	 * | state |
  	 *   or
  	 * | ------------- state -------------- |
  	 *
  	 * We need to split the extent we found, and may flip bits on
  	 * second half.
  	 *
  	 * If the extent we found extends past our
  	 * range, we just split and search again.  It'll get split
  	 * again the next time though.
  	 *
  	 * If the extent we found is inside our range, we set the
  	 * desired bit on it.
  	 */
  	if (state->start < start) {
  		prealloc = alloc_extent_state_atomic(prealloc);

  		if (!prealloc) {
  			err = -ENOMEM;
  			goto out;
  		}

  		err = split_state(tree, state, prealloc, start);

  		if (err)
  			extent_io_tree_panic(tree, err);

  		prealloc = NULL;
  		if (err)
  			goto out;
  		if (state->end <= end) {
  			set_state_bits(tree, state, &bits);

  			cache_state(state, cached_state);

  			state = clear_state_bit(tree, state, &clear_bits, 0);

  			if (last_end == (u64)-1)
  				goto out;
  			start = last_end + 1;

  			if (start < end && state && state->start == start &&
  			    !need_resched())
  				goto hit_next;

  		}
  		goto search_again;
  	}
  	/*
  	 * | ---- desired range ---- |
  	 *     | state | or               | state |
  	 *
  	 * There's a hole, we need to insert something in it and
  	 * ignore the extent we found.
  	 */
  	if (state->start > start) {
  		u64 this_end;
  		if (end < last_start)
  			this_end = end;
  		else
  			this_end = last_start - 1;
  
  		prealloc = alloc_extent_state_atomic(prealloc);

  		if (!prealloc) {
  			err = -ENOMEM;
  			goto out;
  		}

  
  		/*
  		 * Avoid to free 'prealloc' if it can be merged with
  		 * the later extent.
  		 */
  		err = insert_state(tree, prealloc, start, this_end,
  				   &bits);

  		if (err)
  			extent_io_tree_panic(tree, err);

  		cache_state(prealloc, cached_state);

  		prealloc = NULL;
  		start = this_end + 1;
  		goto search_again;
  	}
  	/*
  	 * | ---- desired range ---- |
  	 *                        | state |
  	 * We need to split the extent, and set the bit
  	 * on the first half
  	 */
  	if (state->start <= end && state->end > end) {
  		prealloc = alloc_extent_state_atomic(prealloc);

  		if (!prealloc) {
  			err = -ENOMEM;
  			goto out;
  		}

  
  		err = split_state(tree, state, prealloc, end + 1);

  		if (err)
  			extent_io_tree_panic(tree, err);

  
  		set_state_bits(tree, prealloc, &bits);

  		cache_state(prealloc, cached_state);

  		clear_state_bit(tree, prealloc, &clear_bits, 0);

  		prealloc = NULL;
  		goto out;
  	}
  
  	goto search_again;
  
  out:
  	spin_unlock(&tree->lock);
  	if (prealloc)
  		free_extent_state(prealloc);
  
  	return err;
  
  search_again:
  	if (start > end)
  		goto out;
  	spin_unlock(&tree->lock);
  	if (mask & __GFP_WAIT)
  		cond_resched();
  	goto again;
  }

  /* wrappers around set/clear extent bit */
  int set_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
  		     gfp_t mask)
  {

  	return set_extent_bit(tree, start, end, EXTENT_DIRTY, NULL,

  			      NULL, mask);

  }

  
  int set_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,

  		    unsigned long bits, gfp_t mask)

  {

  	return set_extent_bit(tree, start, end, bits, NULL,

  			      NULL, mask);

  }

  
  int clear_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,

  		      unsigned long bits, gfp_t mask)

  {

  	return clear_extent_bit(tree, start, end, bits, 0, 0, NULL, mask);

  }

  
  int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,

  			struct extent_state **cached_state, gfp_t mask)

  {
  	return set_extent_bit(tree, start, end,

  			      EXTENT_DELALLOC | EXTENT_UPTODATE,

  			      NULL, cached_state, mask);

  }

  int set_extent_defrag(struct extent_io_tree *tree, u64 start, u64 end,
  		      struct extent_state **cached_state, gfp_t mask)
  {
  	return set_extent_bit(tree, start, end,
  			      EXTENT_DELALLOC | EXTENT_UPTODATE | EXTENT_DEFRAG,
  			      NULL, cached_state, mask);
  }

  int clear_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
  		       gfp_t mask)
  {
  	return clear_extent_bit(tree, start, end,

  				EXTENT_DIRTY | EXTENT_DELALLOC |

  				EXTENT_DO_ACCOUNTING, 0, 0, NULL, mask);

  }

  
  int set_extent_new(struct extent_io_tree *tree, u64 start, u64 end,
  		     gfp_t mask)
  {

  	return set_extent_bit(tree, start, end, EXTENT_NEW, NULL,

  			      NULL, mask);

  }

  int set_extent_uptodate(struct extent_io_tree *tree, u64 start, u64 end,

  			struct extent_state **cached_state, gfp_t mask)

  {

  	return set_extent_bit(tree, start, end, EXTENT_UPTODATE, NULL,

  			      cached_state, mask);

  }

  int clear_extent_uptodate(struct extent_io_tree *tree, u64 start, u64 end,
  			  struct extent_state **cached_state, gfp_t mask)

  {

  	return clear_extent_bit(tree, start, end, EXTENT_UPTODATE, 0, 0,

  				cached_state, mask);

  }

  /*
   * either insert or lock state struct between start and end use mask to tell
   * us if waiting is desired.
   */

  int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,

  		     unsigned long bits, struct extent_state **cached_state)

  {
  	int err;
  	u64 failed_start;
  	while (1) {

  		err = __set_extent_bit(tree, start, end, EXTENT_LOCKED | bits,
  				       EXTENT_LOCKED, &failed_start,
  				       cached_state, GFP_NOFS);

  		if (err == -EEXIST) {

  			wait_extent_bit(tree, failed_start, end, EXTENT_LOCKED);
  			start = failed_start;

  		} else

  			break;

  		WARN_ON(start > end);
  	}
  	return err;
  }

  int lock_extent(struct extent_io_tree *tree, u64 start, u64 end)

  {

  	return lock_extent_bits(tree, start, end, 0, NULL);

  }

  int try_lock_extent(struct extent_io_tree *tree, u64 start, u64 end)

  {
  	int err;
  	u64 failed_start;

  	err = __set_extent_bit(tree, start, end, EXTENT_LOCKED, EXTENT_LOCKED,
  			       &failed_start, NULL, GFP_NOFS);

  	if (err == -EEXIST) {
  		if (failed_start > start)
  			clear_extent_bit(tree, start, failed_start - 1,

  					 EXTENT_LOCKED, 1, 0, NULL, GFP_NOFS);

  		return 0;

  	}

  	return 1;
  }

  int unlock_extent_cached(struct extent_io_tree *tree, u64 start, u64 end,
  			 struct extent_state **cached, gfp_t mask)
  {
  	return clear_extent_bit(tree, start, end, EXTENT_LOCKED, 1, 0, cached,
  				mask);
  }

  int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end)

  {

  	return clear_extent_bit(tree, start, end, EXTENT_LOCKED, 1, 0, NULL,

  				GFP_NOFS);

  }

  int extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end)
  {
  	unsigned long index = start >> PAGE_CACHE_SHIFT;
  	unsigned long end_index = end >> PAGE_CACHE_SHIFT;
  	struct page *page;
  
  	while (index <= end_index) {
  		page = find_get_page(inode->i_mapping, index);
  		BUG_ON(!page); /* Pages should be in the extent_io_tree */
  		clear_page_dirty_for_io(page);
  		page_cache_release(page);
  		index++;
  	}
  	return 0;
  }
  
  int extent_range_redirty_for_io(struct inode *inode, u64 start, u64 end)
  {
  	unsigned long index = start >> PAGE_CACHE_SHIFT;
  	unsigned long end_index = end >> PAGE_CACHE_SHIFT;
  	struct page *page;
  
  	while (index <= end_index) {
  		page = find_get_page(inode->i_mapping, index);
  		BUG_ON(!page); /* Pages should be in the extent_io_tree */
  		account_page_redirty(page);
  		__set_page_dirty_nobuffers(page);
  		page_cache_release(page);
  		index++;
  	}
  	return 0;
  }

  /*

   * helper function to set both pages and extents in the tree writeback
   */

  static int set_range_writeback(struct extent_io_tree *tree, u64 start, u64 end)

  {
  	unsigned long index = start >> PAGE_CACHE_SHIFT;
  	unsigned long end_index = end >> PAGE_CACHE_SHIFT;
  	struct page *page;
  
  	while (index <= end_index) {
  		page = find_get_page(tree->mapping, index);

  		BUG_ON(!page); /* Pages should be in the extent_io_tree */

  		set_page_writeback(page);
  		page_cache_release(page);
  		index++;
  	}

  	return 0;
  }

  /* find the first state struct with 'bits' set after 'start', and
   * return it.  tree->lock must be held.  NULL will returned if
   * nothing was found after 'start'
   */

  static struct extent_state *
  find_first_extent_bit_state(struct extent_io_tree *tree,

  			    u64 start, unsigned long bits)

  {
  	struct rb_node *node;
  	struct extent_state *state;
  
  	/*
  	 * this search will find all the extents that end after
  	 * our range starts.
  	 */
  	node = tree_search(tree, start);

  	if (!node)

  		goto out;

  	while (1) {

  		state = rb_entry(node, struct extent_state, rb_node);

  		if (state->end >= start && (state->state & bits))

  			return state;

  		node = rb_next(node);
  		if (!node)
  			break;
  	}
  out:
  	return NULL;
  }

  /*

   * find the first offset in the io tree with 'bits' set. zero is
   * returned if we find something, and *start_ret and *end_ret are
   * set to reflect the state struct that was found.
   *

   * If nothing was found, 1 is returned. If found something, return 0.

   */
  int find_first_extent_bit(struct extent_io_tree *tree, u64 start,

  			  u64 *start_ret, u64 *end_ret, unsigned long bits,

  			  struct extent_state **cached_state)

  {
  	struct extent_state *state;

  	struct rb_node *n;

  	int ret = 1;
  
  	spin_lock(&tree->lock);

  	if (cached_state && *cached_state) {
  		state = *cached_state;
  		if (state->end == start - 1 && state->tree) {
  			n = rb_next(&state->rb_node);
  			while (n) {
  				state = rb_entry(n, struct extent_state,
  						 rb_node);
  				if (state->state & bits)
  					goto got_it;
  				n = rb_next(n);
  			}
  			free_extent_state(*cached_state);
  			*cached_state = NULL;
  			goto out;
  		}
  		free_extent_state(*cached_state);
  		*cached_state = NULL;
  	}

  	state = find_first_extent_bit_state(tree, start, bits);

  got_it:

  	if (state) {

  		cache_state(state, cached_state);

  		*start_ret = state->start;
  		*end_ret = state->end;
  		ret = 0;
  	}

  out:

  	spin_unlock(&tree->lock);
  	return ret;
  }
  
  /*

   * find a contiguous range of bytes in the file marked as delalloc, not
   * more than 'max_bytes'.  start and end are used to return the range,
   *
   * 1 is returned if we find something, 0 if nothing was in the tree
   */

  static noinline u64 find_delalloc_range(struct extent_io_tree *tree,

  					u64 *start, u64 *end, u64 max_bytes,
  					struct extent_state **cached_state)

  {
  	struct rb_node *node;
  	struct extent_state *state;
  	u64 cur_start = *start;
  	u64 found = 0;
  	u64 total_bytes = 0;

  	spin_lock(&tree->lock);

  	/*
  	 * this search will find all the extents that end after
  	 * our range starts.
  	 */

  	node = tree_search(tree, cur_start);

  	if (!node) {

  		if (!found)
  			*end = (u64)-1;

  		goto out;
  	}

  	while (1) {

  		state = rb_entry(node, struct extent_state, rb_node);

  		if (found && (state->start != cur_start ||
  			      (state->state & EXTENT_BOUNDARY))) {

  			goto out;
  		}
  		if (!(state->state & EXTENT_DELALLOC)) {
  			if (!found)
  				*end = state->end;
  			goto out;
  		}

  		if (!found) {

  			*start = state->start;

  			*cached_state = state;
  			atomic_inc(&state->refs);
  		}

  		found++;
  		*end = state->end;
  		cur_start = state->end + 1;
  		node = rb_next(node);

  		total_bytes += state->end - state->start + 1;

  		if (total_bytes >= max_bytes)

  			break;

  		if (!node)

  			break;
  	}
  out:

  	spin_unlock(&tree->lock);

  	return found;
  }

  static noinline void __unlock_for_delalloc(struct inode *inode,
  					   struct page *locked_page,
  					   u64 start, u64 end)

  {
  	int ret;
  	struct page *pages[16];
  	unsigned long index = start >> PAGE_CACHE_SHIFT;
  	unsigned long end_index = end >> PAGE_CACHE_SHIFT;
  	unsigned long nr_pages = end_index - index + 1;
  	int i;
  
  	if (index == locked_page->index && end_index == index)

  		return;

  	while (nr_pages > 0) {

  		ret = find_get_pages_contig(inode->i_mapping, index,

  				     min_t(unsigned long, nr_pages,
  				     ARRAY_SIZE(pages)), pages);

  		for (i = 0; i < ret; i++) {
  			if (pages[i] != locked_page)
  				unlock_page(pages[i]);
  			page_cache_release(pages[i]);
  		}
  		nr_pages -= ret;
  		index += ret;
  		cond_resched();
  	}

  }
  
  static noinline int lock_delalloc_pages(struct inode *inode,
  					struct page *locked_page,
  					u64 delalloc_start,
  					u64 delalloc_end)
  {
  	unsigned long index = delalloc_start >> PAGE_CACHE_SHIFT;
  	unsigned long start_index = index;
  	unsigned long end_index = delalloc_end >> PAGE_CACHE_SHIFT;
  	unsigned long pages_locked = 0;
  	struct page *pages[16];
  	unsigned long nrpages;
  	int ret;
  	int i;
  
  	/* the caller is responsible for locking the start index */
  	if (index == locked_page->index && index == end_index)
  		return 0;
  
  	/* skip the page at the start index */
  	nrpages = end_index - index + 1;

  	while (nrpages > 0) {

  		ret = find_get_pages_contig(inode->i_mapping, index,

  				     min_t(unsigned long,
  				     nrpages, ARRAY_SIZE(pages)), pages);

  		if (ret == 0) {
  			ret = -EAGAIN;
  			goto done;
  		}
  		/* now we have an array of pages, lock them all */
  		for (i = 0; i < ret; i++) {
  			/*
  			 * the caller is taking responsibility for
  			 * locked_page
  			 */

  			if (pages[i] != locked_page) {

  				lock_page(pages[i]);

  				if (!PageDirty(pages[i]) ||
  				    pages[i]->mapping != inode->i_mapping) {

  					ret = -EAGAIN;
  					unlock_page(pages[i]);
  					page_cache_release(pages[i]);
  					goto done;
  				}
  			}

  			page_cache_release(pages[i]);

  			pages_locked++;

  		}

  		nrpages -= ret;
  		index += ret;
  		cond_resched();
  	}
  	ret = 0;
  done:
  	if (ret && pages_locked) {
  		__unlock_for_delalloc(inode, locked_page,
  			      delalloc_start,
  			      ((u64)(start_index + pages_locked - 1)) <<
  			      PAGE_CACHE_SHIFT);
  	}
  	return ret;
  }
  
  /*
   * find a contiguous range of bytes in the file marked as delalloc, not
   * more than 'max_bytes'.  start and end are used to return the range,
   *
   * 1 is returned if we find something, 0 if nothing was in the tree
   */
  static noinline u64 find_lock_delalloc_range(struct inode *inode,
  					     struct extent_io_tree *tree,
  					     struct page *locked_page,
  					     u64 *start, u64 *end,
  					     u64 max_bytes)
  {
  	u64 delalloc_start;
  	u64 delalloc_end;
  	u64 found;

  	struct extent_state *cached_state = NULL;

  	int ret;
  	int loops = 0;
  
  again:
  	/* step one, find a bunch of delalloc bytes starting at start */
  	delalloc_start = *start;
  	delalloc_end = 0;
  	found = find_delalloc_range(tree, &delalloc_start, &delalloc_end,

  				    max_bytes, &cached_state);

  	if (!found || delalloc_end <= *start) {

  		*start = delalloc_start;
  		*end = delalloc_end;

  		free_extent_state(cached_state);

  		return 0;

  	}
  
  	/*

  	 * start comes from the offset of locked_page.  We have to lock
  	 * pages in order, so we can't process delalloc bytes before
  	 * locked_page
  	 */

  	if (delalloc_start < *start)

  		delalloc_start = *start;

  
  	/*

  	 * make sure to limit the number of pages we try to lock down

  	 */

  	if (delalloc_end + 1 - delalloc_start > max_bytes)
  		delalloc_end = delalloc_start + max_bytes - 1;

  	/* step two, lock all the pages after the page that has start */
  	ret = lock_delalloc_pages(inode, locked_page,
  				  delalloc_start, delalloc_end);
  	if (ret == -EAGAIN) {
  		/* some of the pages are gone, lets avoid looping by
  		 * shortening the size of the delalloc range we're searching
  		 */

  		free_extent_state(cached_state);

  		cached_state = NULL;

  		if (!loops) {

  			max_bytes = PAGE_CACHE_SIZE;

  			loops = 1;
  			goto again;
  		} else {
  			found = 0;
  			goto out_failed;
  		}
  	}

  	BUG_ON(ret); /* Only valid values are 0 and -EAGAIN */

  
  	/* step three, lock the state bits for the whole range */

  	lock_extent_bits(tree, delalloc_start, delalloc_end, 0, &cached_state);

  
  	/* then test to make sure it is all still delalloc */
  	ret = test_range_bit(tree, delalloc_start, delalloc_end,

  			     EXTENT_DELALLOC, 1, cached_state);

  	if (!ret) {

  		unlock_extent_cached(tree, delalloc_start, delalloc_end,
  				     &cached_state, GFP_NOFS);

  		__unlock_for_delalloc(inode, locked_page,
  			      delalloc_start, delalloc_end);
  		cond_resched();
  		goto again;
  	}

  	free_extent_state(cached_state);

  	*start = delalloc_start;
  	*end = delalloc_end;
  out_failed:
  	return found;
  }

  int extent_clear_unlock_delalloc(struct inode *inode, u64 start, u64 end,
  				 struct page *locked_page,
  				 unsigned long clear_bits,
  				 unsigned long page_ops)

  {

  	struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;

  	int ret;
  	struct page *pages[16];
  	unsigned long index = start >> PAGE_CACHE_SHIFT;
  	unsigned long end_index = end >> PAGE_CACHE_SHIFT;
  	unsigned long nr_pages = end_index - index + 1;
  	int i;

  	clear_extent_bit(tree, start, end, clear_bits, 1, 0, NULL, GFP_NOFS);

  	if (page_ops == 0)

  		return 0;

  	while (nr_pages > 0) {

  		ret = find_get_pages_contig(inode->i_mapping, index,

  				     min_t(unsigned long,
  				     nr_pages, ARRAY_SIZE(pages)), pages);

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

  			if (page_ops & PAGE_SET_PRIVATE2)

  				SetPagePrivate2(pages[i]);

  			if (pages[i] == locked_page) {
  				page_cache_release(pages[i]);
  				continue;
  			}

  			if (page_ops & PAGE_CLEAR_DIRTY)

  				clear_page_dirty_for_io(pages[i]);

  			if (page_ops & PAGE_SET_WRITEBACK)

  				set_page_writeback(pages[i]);

  			if (page_ops & PAGE_END_WRITEBACK)

  				end_page_writeback(pages[i]);

  			if (page_ops & PAGE_UNLOCK)

  				unlock_page(pages[i]);

  			page_cache_release(pages[i]);
  		}
  		nr_pages -= ret;
  		index += ret;
  		cond_resched();
  	}
  	return 0;
  }

  /*
   * count the number of bytes in the tree that have a given bit(s)
   * set.  This can be fairly slow, except for EXTENT_DIRTY which is
   * cached.  The total number found is returned.
   */

  u64 count_range_bits(struct extent_io_tree *tree,
  		     u64 *start, u64 search_end, u64 max_bytes,

  		     unsigned long bits, int contig)

  {
  	struct rb_node *node;
  	struct extent_state *state;
  	u64 cur_start = *start;
  	u64 total_bytes = 0;

  	u64 last = 0;

  	int found = 0;
  
  	if (search_end <= cur_start) {

  		WARN_ON(1);
  		return 0;
  	}

  	spin_lock(&tree->lock);

  	if (cur_start == 0 && bits == EXTENT_DIRTY) {
  		total_bytes = tree->dirty_bytes;
  		goto out;
  	}
  	/*
  	 * this search will find all the extents that end after
  	 * our range starts.
  	 */

  	node = tree_search(tree, cur_start);

  	if (!node)

  		goto out;

  	while (1) {

  		state = rb_entry(node, struct extent_state, rb_node);
  		if (state->start > search_end)
  			break;

  		if (contig && found && state->start > last + 1)
  			break;
  		if (state->end >= cur_start && (state->state & bits) == bits) {

  			total_bytes += min(search_end, state->end) + 1 -
  				       max(cur_start, state->start);
  			if (total_bytes >= max_bytes)
  				break;
  			if (!found) {

  				*start = max(cur_start, state->start);

  				found = 1;
  			}

  			last = state->end;
  		} else if (contig && found) {
  			break;

  		}
  		node = rb_next(node);
  		if (!node)
  			break;
  	}
  out: