#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/module.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"

  static struct kmem_cache *extent_state_cache;
  static struct kmem_cache *extent_buffer_cache;
  
  static LIST_HEAD(buffers);
  static LIST_HEAD(states);

  #define LEAK_DEBUG 0

  #if LEAK_DEBUG

  static DEFINE_SPINLOCK(leak_lock);

  #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;

  
  	/* 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;

  };
  
  int __init extent_io_init(void)
  {

  	extent_state_cache = kmem_cache_create("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("extent_buffers",
  			sizeof(struct extent_buffer), 0,
  			SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);

  	if (!extent_buffer_cache)
  		goto free_state_cache;
  	return 0;
  
  free_state_cache:
  	kmem_cache_destroy(extent_state_cache);
  	return -ENOMEM;
  }
  
  void extent_io_exit(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
  ",
  		       (unsigned long long)state->start,
  		       (unsigned long long)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
  ", (unsigned long long)eb->start,
  		       eb->len, atomic_read(&eb->refs));

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

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

  #if LEAK_DEBUG

  	unsigned long flags;

  #endif

  
  	state = kmem_cache_alloc(extent_state_cache, mask);

  	if (!state)

  		return state;
  	state->state = 0;

  	state->private = 0;

  	state->tree = NULL;

  #if LEAK_DEBUG

  	spin_lock_irqsave(&leak_lock, flags);
  	list_add(&state->leak_list, &states);
  	spin_unlock_irqrestore(&leak_lock, flags);

  #endif

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

  void free_extent_state(struct extent_state *state)

  {

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

  #if LEAK_DEBUG

  		unsigned long flags;

  #endif

  		WARN_ON(state->tree);

  #if LEAK_DEBUG

  		spin_lock_irqsave(&leak_lock, flags);
  		list_del(&state->leak_list);
  		spin_unlock_irqrestore(&leak_lock, flags);

  #endif

  		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;
  	}
  
  	entry = rb_entry(node, struct tree_entry, rb_node);

  	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, int *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, int *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, int *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,

  			int *bits)

  {
  	struct rb_node *node;
  
  	if (end < start) {

  		printk(KERN_ERR "btrfs end < start %llu %llu
  ",
  		       (unsigned long long)end,
  		       (unsigned long long)start);

  		WARN_ON(1);
  	}

  	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
  ", (unsigned long long)found->start,
  		       (unsigned long long)found->end,
  		       (unsigned long long)start, (unsigned long long)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;
  }
  
  /*
   * utility function to clear some bits in an extent state struct.
   * it will optionally wake up any one waiting on this state (wake == 1), or
   * forcibly remove the state from the tree (delete == 1).
   *
   * If no bits are set on the state struct after clearing things, the
   * struct is freed and removed from the tree
   */
  static int clear_state_bit(struct extent_io_tree *tree,

  			    struct extent_state *state,
  			    int *bits, int wake)

  {

  	int bits_to_clear = *bits & ~EXTENT_CTLBITS;

  	int ret = state->state & bits_to_clear;

  	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) {

  		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);
  	}
  	return ret;
  }

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

  /*
   * 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 error, > 0 if any of the
   * bits were already set, or zero if none of the bits were already set.
   */
  int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,

  		     int 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 *next_node;

  	struct rb_node *node;

  	u64 last_end;

  	int err;
  	int set = 0;

  	int clear = 0;

  	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;

  
  	/*
  	 *     | ---- 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);
  		BUG_ON(err == -EEXIST);
  		prealloc = NULL;
  		if (err)
  			goto out;
  		if (state->end <= end) {

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

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

  		}
  		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);
  		BUG_ON(err == -EEXIST);

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

  		set |= clear_state_bit(tree, prealloc, &bits, wake);

  		prealloc = NULL;
  		goto out;
  	}

  	if (state->end < end && prealloc && !need_resched())
  		next_node = rb_next(&state->rb_node);
  	else
  		next_node = NULL;

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

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

  	if (start <= end && next_node) {
  		state = rb_entry(next_node, struct extent_state,
  				 rb_node);
  		if (state->start == start)
  			goto hit_next;
  	}

  	goto search_again;
  
  out:

  	spin_unlock(&tree->lock);

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

  	spin_unlock(&tree->lock);

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

  
  static int 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);
  	return 0;
  }
  
  /*
   * 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
   */
  int wait_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, int bits)
  {
  	struct extent_state *state;
  	struct rb_node *node;

  	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);

  	return 0;
  }

  static void set_state_bits(struct extent_io_tree *tree,

  			   struct extent_state *state,

  			   int *bits)

  {

  	int 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);
  		}
  	}
  }

  static void uncache_state(struct extent_state **cached_ptr)
  {
  	if (cached_ptr && (*cached_ptr)) {
  		struct extent_state *state = *cached_ptr;

  		*cached_ptr = NULL;
  		free_extent_state(state);

  	}
  }

  /*

   * 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.

   */

  int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
  		   int bits, int 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;

  	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);

  		prealloc = NULL;
  		BUG_ON(err == -EEXIST);
  		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) {

  		struct rb_node *next_node;

  		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;

  		next_node = rb_next(&state->rb_node);

  		if (next_node && start < end && prealloc && !need_resched()) {
  			state = rb_entry(next_node, struct extent_state,
  					 rb_node);
  			if (state->start == start)
  				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);
  		BUG_ON(err == -EEXIST);
  		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;

  		}
  		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);

  		BUG_ON(err == -EEXIST);

  		if (err) {

  			free_extent_state(prealloc);

  			prealloc = NULL;

  			goto out;

  		}
  		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);
  		BUG_ON(err == -EEXIST);

  		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;
  }

  /**
   * convert_extent - 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
   * @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,
  		       int bits, int clear_bits, 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;
  
  again:
  	if (!prealloc && (mask & __GFP_WAIT)) {
  		prealloc = alloc_extent_state(mask);
  		if (!prealloc)
  			return -ENOMEM;
  	}
  
  	spin_lock(&tree->lock);
  	/*
  	 * 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;
  		BUG_ON(err == -EEXIST);
  		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) {
  		struct rb_node *next_node;
  
  		set_state_bits(tree, state, &bits);
  		clear_state_bit(tree, state, &clear_bits, 0);
  
  		merge_state(tree, state);
  		if (last_end == (u64)-1)
  			goto out;
  
  		start = last_end + 1;
  		next_node = rb_next(&state->rb_node);
  		if (next_node && start < end && prealloc && !need_resched()) {
  			state = rb_entry(next_node, struct extent_state,
  					 rb_node);
  			if (state->start == start)
  				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);
  		BUG_ON(err == -EEXIST);
  		prealloc = NULL;
  		if (err)
  			goto out;
  		if (state->end <= end) {
  			set_state_bits(tree, state, &bits);
  			clear_state_bit(tree, state, &clear_bits, 0);
  			merge_state(tree, state);
  			if (last_end == (u64)-1)
  				goto out;
  			start = last_end + 1;
  		}
  		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);
  		BUG_ON(err == -EEXIST);
  		if (err) {
  			free_extent_state(prealloc);
  			prealloc = NULL;
  			goto out;
  		}
  		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);
  		BUG_ON(err == -EEXIST);
  
  		set_state_bits(tree, prealloc, &bits);
  		clear_state_bit(tree, prealloc, &clear_bits, 0);
  
  		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;
  }

  /* 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, 0, NULL,

  			      NULL, mask);

  }

  
  int set_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
  		    int bits, gfp_t mask)
  {
  	return set_extent_bit(tree, start, end, bits, 0, NULL,

  			      NULL, mask);

  }

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

  			      0, 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, 0, 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, 0,
  			      NULL, cached_state, mask);

  }

  static 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,

  		     int bits, struct extent_state **cached_state, gfp_t mask)

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

  		err = set_extent_bit(tree, start, end, EXTENT_LOCKED | bits,

  				     EXTENT_LOCKED, &failed_start,
  				     cached_state, mask);

  		if (err == -EEXIST && (mask & __GFP_WAIT)) {
  			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, gfp_t mask)
  {

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

  }

  int try_lock_extent(struct extent_io_tree *tree, u64 start, u64 end,
  		    gfp_t mask)
  {
  	int err;
  	u64 failed_start;

  	err = set_extent_bit(tree, start, end, EXTENT_LOCKED, EXTENT_LOCKED,
  			     &failed_start, NULL, mask);

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

  					 EXTENT_LOCKED, 1, 0, NULL, mask);

  		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, gfp_t mask)

  {

  	return clear_extent_bit(tree, start, end, EXTENT_LOCKED, 1, 0, NULL,
  				mask);

  }

  
  /*

   * 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);
  		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'
   */

  struct extent_state *find_first_extent_bit_state(struct extent_io_tree *tree,
  						 u64 start, int 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, < 0 on error
   */
  int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
  			  u64 *start_ret, u64 *end_ret, int bits)
  {
  	struct extent_state *state;
  	int ret = 1;
  
  	spin_lock(&tree->lock);
  	state = find_first_extent_bit_state(tree, start, bits);
  	if (state) {
  		*start_ret = state->start;
  		*end_ret = state->end;
  		ret = 0;
  	}
  	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);
  		if (!node)
  			break;
  		total_bytes += state->end - state->start + 1;
  		if (total_bytes >= max_bytes)
  			break;
  	}
  out:

  	spin_unlock(&tree->lock);

  	return found;
  }

  static noinline int __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 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 (pages[i] != locked_page)
  				unlock_page(pages[i]);
  			page_cache_release(pages[i]);
  		}
  		nr_pages -= ret;
  		index += ret;
  		cond_resched();
  	}
  	return 0;
  }
  
  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 found;
  	}
  
  	/*

  	 * 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 we're looping.
  	 */

  	if (delalloc_end + 1 - delalloc_start > max_bytes && loops)

  		delalloc_end = delalloc_start + PAGE_CACHE_SIZE - 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);

  		if (!loops) {
  			unsigned long offset = (*start) & (PAGE_CACHE_SIZE - 1);
  			max_bytes = PAGE_CACHE_SIZE - offset;
  			loops = 1;
  			goto again;
  		} else {
  			found = 0;
  			goto out_failed;
  		}
  	}
  	BUG_ON(ret);
  
  	/* step three, lock the state bits for the whole range */

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

  
  	/* 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,
  				struct extent_io_tree *tree,
  				u64 start, u64 end, struct page *locked_page,

  				unsigned long op)

  {
  	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;

  	int clear_bits = 0;

  	if (op & EXTENT_CLEAR_UNLOCK)

  		clear_bits |= EXTENT_LOCKED;

  	if (op & EXTENT_CLEAR_DIRTY)

  		clear_bits |= EXTENT_DIRTY;

  	if (op & EXTENT_CLEAR_DELALLOC)

  		clear_bits |= EXTENT_DELALLOC;

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

  	if (!(op & (EXTENT_CLEAR_UNLOCK_PAGE | EXTENT_CLEAR_DIRTY |
  		    EXTENT_SET_WRITEBACK | EXTENT_END_WRITEBACK |
  		    EXTENT_SET_PRIVATE2)))

  		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 (op & EXTENT_SET_PRIVATE2)

  				SetPagePrivate2(pages[i]);

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

  			if (op & EXTENT_CLEAR_DIRTY)

  				clear_page_dirty_for_io(pages[i]);

  			if (op & EXTENT_SET_WRITEBACK)

  				set_page_writeback(pages[i]);

  			if (op & EXTENT_END_WRITEBACK)

  				end_page_writeback(pages[i]);

  			if (op & EXTENT_CLEAR_UNLOCK_PAGE)

  				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:

  	spin_unlock(&tree->lock);

  	return total_bytes;
  }

  /*
   * set the private field for a given byte offset in the tree.  If there isn't
   * an extent_state there already, this does nothing.
   */

  int set_state_private(struct extent_io_tree *tree, u64 start, u64 private)
  {
  	struct rb_node *node;
  	struct extent_state *state;
  	int ret = 0;

  	spin_lock(&tree->lock);

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

  	node = tree_search(tree, start);

  	if (!node) {

  		ret = -ENOENT;
  		goto out;
  	}
  	state = rb_entry(node, struct extent_state, rb_node);
  	if (state->start != start) {
  		ret = -ENOENT;
  		goto out;
  	}
  	state->private = private;
  out:

  	spin_unlock(&tree->lock);

  	return ret;
  }
  
  int get_state_private(struct extent_io_tree *tree, u64 start, u64 *private)
  {
  	struct rb_node *node;
  	struct extent_state *state;
  	int ret = 0;

  	spin_lock(&tree->lock);

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

  	node = tree_search(tree, start);

  	if (!node) {

  		ret = -ENOENT;
  		goto out;
  	}
  	state = rb_entry(node, struct extent_state, rb_node);
  	if (state->start != start) {
  		ret = -ENOENT;
  		goto out;
  	}
  	*private = state->private;
  out:

  	spin_unlock(&tree->lock);

  	return ret;
  }
  
  /*
   * searches a range in the state tree for a given mask.

   * If 'filled' == 1, this returns 1 only if every extent in the tree

   * has the bits set.  Otherwise, 1 is returned if any bit in the
   * range is found set.
   */
  int test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,

  		   int bits, int filled, struct extent_state *cached)

  {
  	struct extent_state *state = NULL;
  	struct rb_node *node;
  	int bitset = 0;

  	spin_lock(&tree->lock);

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

  		node = &cached->rb_node;
  	else
  		node = tree_search(tree, start);

  	while (node && start <= end) {
  		state = rb_entry(node, struct extent_state, rb_node);
  
  		if (filled && state->start > start) {
  			bitset = 0;
  			break;
  		}
  
  		if (state->start > end)
  			break;
  
  		if (state->state & bits) {
  			bitset = 1;
  			if (!filled)
  				break;
  		} else if (filled) {
  			bitset = 0;
  			break;
  		}

  
  		if (state->end == (u64)-1)
  			break;

  		start = state->end + 1;
  		if (start > end)
  			break;
  		node = rb_next(node);
  		if (!node) {
  			if (filled)
  				bitset = 0;
  			break;
  		}
  	}

  	spin_unlock(&tree->lock);

  	return bitset;
  }

  
  /*
   * helper function to set a given page up to date if all the
   * extents in the tree for that page are up to date
   */
  static int check_page_uptodate(struct extent_io_tree *tree,
  			       struct page *page)
  {
  	u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
  	u64 end = start + PAGE_CACHE_SIZE - 1;

  	if (test_range_bit(tree, start, end, EXTENT_UPTODATE, 1, NULL))

  		SetPageUptodate(page);
  	return 0;
  }
  
  /*
   * helper function to unlock a page if all the extents in the tree
   * for that page are unlocked
   */
  static int check_page_locked(struct extent_io_tree *tree,
  			     struct page *page)
  {
  	u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
  	u64 end = start + PAGE_CACHE_SIZE - 1;

  	if (!test_range_bit(tree, start, end, EXTENT_LOCKED, 0, NULL))

  		unlock_page(page);
  	return 0;
  }
  
  /*
   * helper function to end page writeback if all the extents
   * in the tree for that page are done with writeback
   */
  static int check_page_writeback(struct extent_io_tree *tree,
  			     struct page *page)
  {

  	end_page_writeback(page);

  	return 0;
  }

  /*
   * When IO fails, either with EIO or csum verification fails, we
   * try other mirrors that might have a good copy of the data.  This
   * io_failure_record is used to record state as we go through all the
   * mirrors.  If another mirror has good data, the page is set up to date
   * and things continue.  If a good mirror can't be found, the original
   * bio end_io callback is called to indicate things have failed.
   */
  struct io_failure_record {
  	struct page *page;
  	u64 start;
  	u64 len;
  	u64 logical;
  	unsigned long bio_flags;
  	int this_mirror;
  	int failed_mirror;
  	int in_validation;
  };
  
  static int free_io_failure(struct inode *inode, struct io_failure_record *rec,
  				int did_repair)
  {
  	int ret;
  	int err = 0;
  	struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;
  
  	set_state_private(failure_tree, rec->start, 0);
  	ret = clear_extent_bits(failure_tree, rec->start,
  				rec->start + rec->len - 1,
  				EXTENT_LOCKED | EXTENT_DIRTY, GFP_NOFS);
  	if (ret)
  		err = ret;
  
  	if (did_repair) {
  		ret = clear_extent_bits(&BTRFS_I(inode)->io_tree, rec->start,
  					rec->start + rec->len - 1,
  					EXTENT_DAMAGED, GFP_NOFS);
  		if (ret && !err)
  			err = ret;
  	}
  
  	kfree(rec);
  	return err;
  }
  
  static void repair_io_failure_callback(struct bio *bio, int err)
  {
  	complete(bio->bi_private);
  }
  
  /*
   * this bypasses the standard btrfs submit functions deliberately, as
   * the standard behavior is to write all copies in a raid setup. here we only
   * want to write the one bad copy. so we do the mapping for ourselves and issue
   * submit_bio directly.
   * to avoid any synchonization issues, wait for the data after writing, which
   * actually prevents the read that triggered the error from finishing.
   * currently, there can be no more than two copies of every data bit. thus,
   * exactly one rewrite is required.
   */
  int repair_io_failure(struct btrfs_mapping_tree *map_tree, u64 start,
  			u64 length, u64 logical, struct page *page,
  			int mirror_num)
  {
  	struct bio *bio;
  	struct btrfs_device *dev;
  	DECLARE_COMPLETION_ONSTACK(compl);
  	u64 map_length = 0;
  	u64 sector;
  	struct btrfs_bio *bbio = NULL;
  	int ret;
  
  	BUG_ON(!mirror_num);
  
  	bio = bio_alloc(GFP_NOFS, 1);
  	if (!bio)
  		return -EIO;
  	bio->bi_private = &compl;
  	bio->bi_end_io = repair_io_failure_callback;
  	bio->bi_size = 0;
  	map_length = length;
  
  	ret = btrfs_map_block(map_tree, WRITE, logical,
  			      &map_length, &bbio, mirror_num);
  	if (ret) {
  		bio_put(bio);
  		return -EIO;
  	}
  	BUG_ON(mirror_num != bbio->mirror_num);
  	sector = bbio->stripes[mirror_num-1].physical >> 9;
  	bio->bi_sector = sector;
  	dev = bbio->stripes[mirror_num-1].dev;
  	kfree(bbio);
  	if (!dev || !dev->bdev || !dev->writeable) {
  		bio_put(bio);
  		return -EIO;
  	}
  	bio->bi_bdev = dev->bdev;
  	bio_add_page(bio, page, length, start-page_offset(page));
  	submit_bio(WRITE_SYNC, bio);
  	wait_for_completion(&compl);
  
  	if (!test_bit(BIO_UPTODATE, &bio->bi_flags)) {
  		/* try to remap that extent elsewhere? */
  		bio_put(bio);
  		return -EIO;
  	}
  
  	printk(KERN_INFO "btrfs read error corrected: ino %lu off %llu (dev %s "
  			"sector %llu)
  ", page->mapping->host->i_ino, start,
  			dev->name, sector);
  
  	bio_put(bio);
  	return 0;
  }
  
  /*
   * each time an IO finishes, we do a fast check in the IO failure tree
   * to see if we need to process or clean up an io_failure_record
   */
  static int clean_io_failure(u64 start, struct page *page)
  {
  	u64 private;
  	u64 private_failure;
  	struct io_failure_record *failrec;
  	struct btrfs_mapping_tree *map_tree;
  	struct extent_state *state;
  	int num_copies;
  	int did_repair = 0;
  	int ret;
  	struct inode *inode = page->mapping->host;
  
  	private = 0;
  	ret = count_range_bits(&BTRFS_I(inode)->io_failure_tree, &private,
  				(u64)-1, 1, EXTENT_DIRTY, 0);
  	if (!ret)
  		return 0;
  
  	ret = get_state_private(&BTRFS_I(inode)->io_failure_tree, start,
  				&private_failure);
  	if (ret)
  		return 0;
  
  	failrec = (struct io_failure_record *)(unsigned long) private_failure;
  	BUG_ON(!failrec->this_mirror);
  
  	if (failrec->in_validation) {
  		/* there was no real error, just free the record */
  		pr_debug("clean_io_failure: freeing dummy error at %llu
  ",
  			 failrec->start);
  		did_repair = 1;
  		goto out;
  	}
  
  	spin_lock(&BTRFS_I(inode)->io_tree.lock);
  	state = find_first_extent_bit_state(&BTRFS_I(inode)->io_tree,
  					    failrec->start,
  					    EXTENT_LOCKED);
  	spin_unlock(&BTRFS_I(inode)->io_tree.lock);
  
  	if (state && state->start == failrec->start) {
  		map_tree = &BTRFS_I(inode)->root->fs_info->mapping_tree;
  		num_copies = btrfs_num_copies(map_tree, failrec->logical,
  						failrec->len);
  		if (num_copies > 1)  {
  			ret = repair_io_failure(map_tree, start, failrec->len,
  						failrec->logical, page,
  						failrec->failed_mirror);
  			did_repair = !ret;
  		}
  	}
  
  out:
  	if (!ret)
  		ret = free_io_failure(inode, failrec, did_repair);
  
  	return ret;
  }
  
  /*
   * this is a generic handler for readpage errors (default
   * readpage_io_failed_hook). if other copies exist, read those and write back
   * good data to the failed position. does not investigate in remapping the
   * failed extent elsewhere, hoping the device will be smart enough to do this as
   * needed
   */
  
  static int bio_readpage_error(struct bio *failed_bio, struct page *page,
  				u64 start, u64 end, int failed_mirror,
  				struct extent_state *state)
  {
  	struct io_failure_record *failrec = NULL;
  	u64 private;
  	struct extent_map *em;
  	struct inode *inode = page->mapping->host;
  	struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;
  	struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
  	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
  	struct bio *bio;
  	int num_copies;
  	int ret;
  	int read_mode;
  	u64 logical;
  
  	BUG_ON(failed_bio->bi_rw & REQ_WRITE);
  
  	ret = get_state_private(failure_tree, start, &private);
  	if (ret) {
  		failrec = kzalloc(sizeof(*failrec), GFP_NOFS);
  		if (!failrec)
  			return -ENOMEM;
  		failrec->start = start;
  		failrec->len = end - start + 1;
  		failrec->this_mirror = 0;
  		failrec->bio_flags = 0;
  		failrec->in_validation = 0;
  
  		read_lock(&em_tree->lock);
  		em = lookup_extent_mapping(em_tree, start, failrec->len);
  		if (!em) {
  			read_unlock(&em_tree->lock);
  			kfree(failrec);
  			return -EIO;
  		}
  
  		if (em->start > start || em->start + em->len < start) {
  			free_extent_map(em);
  			em = NULL;
  		}
  		read_unlock(&em_tree->lock);
  
  		if (!em || IS_ERR(em)) {
  			kfree(failrec);
  			return -EIO;
  		}
  		logical = start - em->start;
  		logical = em->block_start + logical;
  		if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
  			logical = em->block_start;
  			failrec->bio_flags = EXTENT_BIO_COMPRESSED;
  			extent_set_compress_type(&failrec->bio_flags,
  						 em->compress_type);
  		}
  		pr_debug("bio_readpage_error: (new) logical=%llu, start=%llu, "
  			 "len=%llu
  ", logical, start, failrec->len);
  		failrec->logical = logical;
  		free_extent_map(em);
  
  		/* set the bits in the private failure tree */
  		ret = set_extent_bits(failure_tree, start, end,
  					EXTENT_LOCKED | EXTENT_DIRTY, GFP_NOFS);
  		if (ret >= 0)
  			ret = set_state_private(failure_tree, start,
  						(u64)(unsigned long)failrec);
  		/* set the bits in the inode's tree */
  		if (ret >= 0)
  			ret = set_extent_bits(tree, start, end, EXTENT_DAMAGED,
  						GFP_NOFS);
  		if (ret < 0) {
  			kfree(failrec);
  			return ret;
  		}
  	} else {
  		failrec = (struct io_failure_record *)(unsigned long)private;
  		pr_debug("bio_readpage_error: (found) logical=%llu, "
  			 "start=%llu, len=%llu, validation=%d
  ",
  			 failrec->logical, failrec->start, failrec->len,
  			 failrec->in_validation);
  		/*
  		 * when data can be on disk more than twice, add to failrec here
  		 * (e.g. with a list for failed_mirror) to make
  		 * clean_io_failure() clean all those errors at once.
  		 */
  	}
  	num_copies = btrfs_num_copies(
  			      &BTRFS_I(inode)->root->fs_info->mapping_tree,
  			      failrec->logical, failrec->len);
  	if (num_copies == 1) {
  		/*
  		 * we only have a single copy of the data, so don't bother with
  		 * all the retry and error correction code that follows. no
  		 * matter what the error is, it is very likely to persist.
  		 */
  		pr_debug("bio_readpage_error: cannot repair, num_copies == 1. "
  			 "state=%p, num_copies=%d, next_mirror %d, "
  			 "failed_mirror %d
  ", state, num_copies,
  			 failrec->this_mirror, failed_mirror);
  		free_io_failure(inode, failrec, 0);
  		return -EIO;
  	}
  
  	if (!state) {
  		spin_lock(&tree->lock);
  		state = find_first_extent_bit_state(tree, failrec->start,
  						    EXTENT_LOCKED);
  		if (state && state->start != failrec->start)
  			state = NULL;
  		spin_unlock(&tree->lock);
  	}
  
  	/*
  	 * there are two premises:
  	 *	a) deliver good data to the caller
  	 *	b) correct the bad sectors on disk
  	 */
  	if (failed_bio->bi_vcnt > 1) {
  		/*
  		 * to fulfill b), we need to know the exact failing sectors, as
  		 * we don't want to rewrite any more than the failed ones. thus,
  		 * we need separate read requests for the failed bio
  		 *
  		 * if the following BUG_ON triggers, our validation request got
  		 * merged. we need separate requests for our algorithm to work.
  		 */
  		BUG_ON(failrec->in_validation);
  		failrec->in_validation = 1;
  		failrec->this_mirror = failed_mirror;
  		read_mode = READ_SYNC | REQ_FAILFAST_DEV;
  	} else {
  		/*
  		 * we're ready to fulfill a) and b) alongside. get a good copy
  		 * of the failed sector and if we succeed, we have setup
  		 * everything for repair_io_failure to do the rest for us.
  		 */
  		if (failrec->in_validation) {
  			BUG_ON(failrec->this_mirror != failed_mirror);
  			failrec->in_validation = 0;
  			failrec->this_mirror = 0;
  		}
  		failrec->failed_mirror = failed_mirror;
  		failrec->this_mirror++;
  		if (failrec->this_mirror == failed_mirror)
  			failrec->this_mirror++;
  		read_mode = READ_SYNC;
  	}
  
  	if (!state || failrec->this_mirror > num_copies) {
  		pr_debug("bio_readpage_error: (fail) state=%p, num_copies=%d, "
  			 "next_mirror %d, failed_mirror %d
  ", state,
  			 num_copies, failrec->this_mirror, failed_mirror);
  		free_io_failure(inode, failrec, 0);
  		return -EIO;
  	}
  
  	bio = bio_alloc(GFP_NOFS, 1);
  	bio->bi_private = state;
  	bio->bi_end_io = failed_bio->bi_end_io;
  	bio->bi_sector = failrec->logical >> 9;
  	bio->bi_bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
  	bio->bi_size = 0;
  
  	bio_add_page(bio, page, failrec->len, start - page_offset(page));
  
  	pr_debug("bio_readpage_error: submitting new read[%#x] to "
  		 "this_mirror=%d, num_copies=%d, in_validation=%d
  ", read_mode,
  		 failrec->this_mirror, num_copies, failrec->in_validation);
  
  	tree->ops->submit_bio_hook(inode, read_mode, bio, failrec->this_mirror,
  					failrec->bio_flags, 0);
  	return 0;
  }

  /* lots and lots of room for performance fixes in the end_bio funcs */
  
  /*
   * after a writepage IO is done, we need to:
   * clear the uptodate bits on error
   * clear the writeback bits in the extent tree for this IO
   * end_page_writeback if the page has no more pending IO
   *
   * Scheduling is not allowed, so the extent state tree is expected
   * to have one and only one object corresponding to this IO.
   */

  static void end_bio_extent_writepage(struct bio *bio, int err)

  {

  	int uptodate = err == 0;

  	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;

  	struct extent_io_tree *tree;

  	u64 start;
  	u64 end;
  	int whole_page;

  	int ret;

  	do {
  		struct page *page = bvec->bv_page;

  		tree = &BTRFS_I(page->mapping->host)->io_tree;

  		start = ((u64)page->index << PAGE_CACHE_SHIFT) +
  			 bvec->bv_offset;
  		end = start + bvec->bv_len - 1;
  
  		if (bvec->bv_offset == 0 && bvec->bv_len == PAGE_CACHE_SIZE)
  			whole_page = 1;
  		else
  			whole_page = 0;
  
  		if (--bvec >= bio->bi_io_vec)
  			prefetchw(&bvec->bv_page->flags);

  		if (tree->ops && tree->ops->writepage_end_io_hook) {
  			ret = tree->ops->writepage_end_io_hook(page, start,

  						       end, NULL, uptodate);

  			if (ret)
  				uptodate = 0;
  		}
  
  		if (!uptodate && tree->ops &&
  		    tree->ops->writepage_io_failed_hook) {
  			ret = tree->ops->writepage_io_failed_hook(bio, page,

  							 start, end, NULL);

  			if (ret == 0) {

  				uptodate = (err == 0);
  				continue;
  			}
  		}

  		if (!uptodate) {

  			clear_extent_uptodate(tree, start, end, NULL, GFP_NOFS);

  			ClearPageUptodate(page);
  			SetPageError(page);
  		}

  		if (whole_page)
  			end_page_writeback(page);
  		else
  			check_page_writeback(tree, page);

  	} while (bvec >= bio->bi_io_vec);

  	bio_put(bio);

  }
  
  /*
   * after a readpage IO is done, we need to:
   * clear the uptodate bits on error
   * set the uptodate bits if things worked
   * set the page up to date if all extents in the tree are uptodate
   * clear the lock bit in the extent tree
   * unlock the page if there are no other extents locked for it
   *
   * Scheduling is not allowed, so the extent state tree is expected
   * to have one and only one object corresponding to this IO.
   */

  static void end_bio_extent_readpage(struct bio *bio, int err)

  {
  	int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);

  	struct bio_vec *bvec_end = bio->bi_io_vec + bio->bi_vcnt - 1;
  	struct bio_vec *bvec = bio->bi_io_vec;

  	struct extent_io_tree *tree;

  	u64 start;
  	u64 end;
  	int whole_page;
  	int ret;

  	if (err)
  		uptodate = 0;

  	do {
  		struct page *page = bvec->bv_page;

  		struct extent_state *cached = NULL;
  		struct extent_state *state;

  		pr_debug("end_bio_extent_readpage: bi_vcnt=%d, idx=%d, err=%d, "
  			 "mirror=%ld
  ", bio->bi_vcnt, bio->bi_idx, err,
  			 (long int)bio->bi_bdev);

  		tree = &BTRFS_I(page->mapping->host)->io_tree;

  		start = ((u64)page->index << PAGE_CACHE_SHIFT) +
  			bvec->bv_offset;
  		end = start + bvec->bv_len - 1;
  
  		if (bvec->bv_offset == 0 && bvec->bv_len == PAGE_CACHE_SIZE)
  			whole_page = 1;
  		else
  			whole_page = 0;

  		if (++bvec <= bvec_end)

  			prefetchw(&bvec->bv_page->flags);

  		spin_lock(&tree->lock);

  		state = find_first_extent_bit_state(tree, start, EXTENT_LOCKED);

  		if (state && state->start == start) {

  			/*
  			 * take a reference on the state, unlock will drop
  			 * the ref
  			 */
  			cache_state(state, &cached);
  		}
  		spin_unlock(&tree->lock);

  		if (uptodate && tree->ops && tree->ops->readpage_end_io_hook) {

  			ret = tree->ops->readpage_end_io_hook(page, start, end,

  							      state);

  			if (ret)
  				uptodate = 0;

  			else
  				clean_io_failure(start, page);

  		}

  		if (!uptodate) {

  			int failed_mirror;
  			failed_mirror = (int)(unsigned long)bio->bi_bdev;

  			/*
  			 * The generic bio_readpage_error handles errors the
  			 * following way: If possible, new read requests are
  			 * created and submitted and will end up in
  			 * end_bio_extent_readpage as well (if we're lucky, not
  			 * in the !uptodate case). In that case it returns 0 and
  			 * we just go on with the next page in our bio. If it
  			 * can't handle the error it will return -EIO and we
  			 * remain responsible for that page.
  			 */
  			ret = bio_readpage_error(bio, page, start, end,
  							failed_mirror, NULL);

  			if (ret == 0) {

  error_handled:

  				uptodate =
  					test_bit(BIO_UPTODATE, &bio->bi_flags);

  				if (err)
  					uptodate = 0;

  				uncache_state(&cached);

  				continue;
  			}

  			if (tree->ops && tree->ops->readpage_io_failed_hook) {
  				ret = tree->ops->readpage_io_failed_hook(
  							bio, page, start, end,
  							failed_mirror, state);
  				if (ret == 0)
  					goto error_handled;
  			}

  		}

  		if (uptodate) {

  			set_extent_uptodate(tree, start, end, &cached,

  					    GFP_ATOMIC);

  		}

  		unlock_extent_cached(tree, start, end, &cached, GFP_ATOMIC);

  		if (whole_page) {
  			if (uptodate) {
  				SetPageUptodate(page);
  			} else {
  				ClearPageUptodate(page);
  				SetPageError(page);
  			}

  			unlock_page(page);

  		} else {
  			if (uptodate) {
  				check_page_uptodate(tree, page);
  			} else {
  				ClearPageUptodate(page);
  				SetPageError(page);
  			}

  			check_page_locked(tree, page);

  		}

  	} while (bvec <= bvec_end);

  
  	bio_put(bio);

  }

  struct bio *
  btrfs_bio_alloc(struct block_device *bdev, u64 first_sector, int nr_vecs,
  		gfp_t gfp_flags)

  {
  	struct bio *bio;
  
  	bio = bio_alloc(gfp_flags, nr_vecs);
  
  	if (bio == NULL && (current->flags & PF_MEMALLOC)) {
  		while (!bio && (nr_vecs /= 2))
  			bio = bio_alloc(gfp_flags, nr_vecs);
  	}
  
  	if (bio) {

  		bio->bi_size = 0;

  		bio->bi_bdev = bdev;
  		bio->bi_sector = first_sector;
  	}
  	return bio;
  }

  static int submit_one_bio(int rw, struct bio *bio, int mirror_num,
  			  unsigned long bio_flags)

  {

  	int ret = 0;

  	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
  	struct page *page = bvec->bv_page;
  	struct extent_io_tree *tree = bio->bi_private;

  	u64 start;

  
  	start = ((u64)page->index << PAGE_CACHE_SHIFT) + bvec->bv_offset;

  	bio->bi_private = NULL;

  
  	bio_get(bio);

  	if (tree->ops && tree->ops->submit_bio_hook)

  		ret = tree->ops->submit_bio_hook(page->mapping->host, rw, bio,