Btrfs: Split the extent_map code into two parts

There is now extent_map for mapping offsets in the file to disk and
extent_io for state tracking, IO submission and extent_bufers.

The new extent_map code shifts from [start,end] pairs to [start,len], and
pushes the locking out into the caller.  This allows a few performance
optimizations and is easier to use.

A number of extent_map usage bugs were fixed, mostly with failing
to remove extent_map entries when changing the file.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 3089 insertions, 0 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
new file mode 100644
index 00000000000..15cc158a049
--- /dev/null
+++ b/fs/btrfs/extent_io.c
@@ -0,0 +1,3089 @@
+#include <linux/bitops.h>
+#include <linux/slab.h>
+#include <linux/bio.h>
+#include <linux/mm.h>
+#include <linux/gfp.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/version.h>
+#include <linux/writeback.h>
+#include <linux/pagevec.h>
+#include "extent_io.h"
+#include "extent_map.h"
+
+/* temporary define until extent_map moves out of btrfs */
+struct kmem_cache *btrfs_cache_create(const char *name, size_t size,
+				       unsigned long extra_flags,
+				       void (*ctor)(void *, struct kmem_cache *,
+						    unsigned long));
+
+static struct kmem_cache *extent_state_cache;
+static struct kmem_cache *extent_buffer_cache;
+
+static LIST_HEAD(buffers);
+static LIST_HEAD(states);
+
+static spinlock_t state_lock = SPIN_LOCK_UNLOCKED;
+#define BUFFER_LRU_MAX 64
+
+struct tree_entry {
+	u64 start;
+	u64 end;
+	int in_tree;
+	struct rb_node rb_node;
+};
+
+struct extent_page_data {
+	struct bio *bio;
+	struct extent_io_tree *tree;
+	get_extent_t *get_extent;
+};
+
+int __init extent_io_init(void)
+{
+	extent_state_cache = btrfs_cache_create("extent_state",
+					    sizeof(struct extent_state), 0,
+					    NULL);
+	if (!extent_state_cache)
+		return -ENOMEM;
+
+	extent_buffer_cache = btrfs_cache_create("extent_buffers",
+					    sizeof(struct extent_buffer), 0,
+					    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;
+
+	while (!list_empty(&states)) {
+		state = list_entry(states.next, struct extent_state, list);
+		printk("state leak: start %Lu end %Lu state %lu in tree %d refs %d\n", state->start, state->end, state->state, state->in_tree, atomic_read(&state->refs));
+		list_del(&state->list);
+		kmem_cache_free(extent_state_cache, state);
+
+	}
+
+	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, gfp_t mask)
+{
+	tree->state.rb_node = NULL;
+	tree->ops = NULL;
+	tree->dirty_bytes = 0;
+	rwlock_init(&tree->lock);
+	spin_lock_init(&tree->lru_lock);
+	tree->mapping = mapping;
+	INIT_LIST_HEAD(&tree->buffer_lru);
+	tree->lru_size = 0;
+}
+EXPORT_SYMBOL(extent_io_tree_init);
+
+void extent_io_tree_empty_lru(struct extent_io_tree *tree)
+{
+	struct extent_buffer *eb;
+	while(!list_empty(&tree->buffer_lru)) {
+		eb = list_entry(tree->buffer_lru.next, struct extent_buffer,
+				lru);
+		list_del_init(&eb->lru);
+		free_extent_buffer(eb);
+	}
+}
+EXPORT_SYMBOL(extent_io_tree_empty_lru);
+
+struct extent_state *alloc_extent_state(gfp_t mask)
+{
+	struct extent_state *state;
+	unsigned long flags;
+
+	state = kmem_cache_alloc(extent_state_cache, mask);
+	if (!state || IS_ERR(state))
+		return state;
+	state->state = 0;
+	state->in_tree = 0;
+	state->private = 0;
+
+	spin_lock_irqsave(&state_lock, flags);
+	list_add(&state->list, &states);
+	spin_unlock_irqrestore(&state_lock, flags);
+
+	atomic_set(&state->refs, 1);
+	init_waitqueue_head(&state->wq);
+	return state;
+}
+EXPORT_SYMBOL(alloc_extent_state);
+
+void free_extent_state(struct extent_state *state)
+{
+	unsigned long flags;
+	if (!state)
+		return;
+	if (atomic_dec_and_test(&state->refs)) {
+		WARN_ON(state->in_tree);
+		spin_lock_irqsave(&state_lock, flags);
+		list_del(&state->list);
+		spin_unlock_irqrestore(&state_lock, flags);
+		kmem_cache_free(extent_state_cache, state);
+	}
+}
+EXPORT_SYMBOL(free_extent_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);
+	entry->in_tree = 1;
+	rb_link_node(node, parent, p);
+	rb_insert_color(node, root);
+	return NULL;
+}
+
+static struct rb_node *__tree_search(struct rb_root *root, u64 offset,
+				     struct rb_node **prev_ret,
+				     struct rb_node **next_ret)
+{
+	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 rb_root *root, u64 offset)
+{
+	struct rb_node *prev;
+	struct rb_node *ret;
+	ret = __tree_search(root, offset, &prev, NULL);
+	if (!ret)
+		return prev;
+	return ret;
+}
+
+/*
+ * 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 int 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)
+		return 0;
+
+	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) {
+			state->start = other->start;
+			other->in_tree = 0;
+			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) {
+			other->start = state->start;
+			state->in_tree = 0;
+			rb_erase(&state->rb_node, &tree->state);
+			free_extent_state(state);
+		}
+	}
+	return 0;
+}
+
+/*
+ * 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("end < start %Lu %Lu\n", end, start);
+		WARN_ON(1);
+	}
+	if (bits & EXTENT_DIRTY)
+		tree->dirty_bytes += end - start + 1;
+	state->state |= bits;
+	state->start = start;
+	state->end = end;
+	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("found node %Lu %Lu on insert of %Lu %Lu\n", found->start, found->end, start, end);
+		free_extent_state(state);
+		return -EEXIST;
+	}
+	merge_state(tree, state);
+	return 0;
+}
+
+/*
+ * 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;
+	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) {
+		struct extent_state *found;
+		found = rb_entry(node, struct extent_state, rb_node);
+		printk("found node %Lu %Lu on insert of %Lu %Lu\n", found->start, found->end, prealloc->start, prealloc->end);
+		free_extent_state(prealloc);
+		return -EEXIST;
+	}
+	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 delete)
+{
+	int ret = state->state & bits;
+
+	if ((bits & EXTENT_DIRTY) && (state->state & EXTENT_DIRTY)) {
+		u64 range = state->end - state->start + 1;
+		WARN_ON(range > tree->dirty_bytes);
+		tree->dirty_bytes -= range;
+	}
+	state->state &= ~bits;
+	if (wake)
+		wake_up(&state->wq);
+	if (delete || state->state == 0) {
+		if (state->in_tree) {
+			rb_erase(&state->rb_node, &tree->state);
+			state->in_tree = 0;
+			free_extent_state(state);
+		} else {
+			WARN_ON(1);
+		}
+	} else {
+		merge_state(tree, state);
+	}
+	return ret;
+}
+
+/*
+ * 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, gfp_t mask)
+{
+	struct extent_state *state;
+	struct extent_state *prealloc = NULL;
+	struct rb_node *node;
+	unsigned long flags;
+	int err;
+	int set = 0;
+
+again:
+	if (!prealloc && (mask & __GFP_WAIT)) {
+		prealloc = alloc_extent_state(mask);
+		if (!prealloc)
+			return -ENOMEM;
+	}
+
+	write_lock_irqsave(&tree->lock, flags);
+	/*
+	 * this search will find the extents that end after
+	 * our range starts
+	 */
+	node = tree_search(&tree->state, start);
+	if (!node)
+		goto out;
+	state = rb_entry(node, struct extent_state, rb_node);
+	if (state->start > end)
+		goto out;
+	WARN_ON(state->end < start);
+
+	/*
+	 *     | ---- 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) {
+		err = split_state(tree, state, prealloc, start);
+		BUG_ON(err == -EEXIST);
+		prealloc = NULL;
+		if (err)
+			goto out;
+		if (state->end <= end) {
+			start = state->end + 1;
+			set |= clear_state_bit(tree, state, bits,
+					wake, delete);
+		} else {
+			start = state->start;
+		}
+		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) {
+		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, delete);
+		prealloc = NULL;
+		goto out;
+	}
+
+	start = state->end + 1;
+	set |= clear_state_bit(tree, state, bits, wake, delete);
+	goto search_again;
+
+out:
+	write_unlock_irqrestore(&tree->lock, flags);
+	if (prealloc)
+		free_extent_state(prealloc);
+
+	return set;
+
+search_again:
+	if (start > end)
+		goto out;
+	write_unlock_irqrestore(&tree->lock, flags);
+	if (mask & __GFP_WAIT)
+		cond_resched();
+	goto again;
+}
+EXPORT_SYMBOL(clear_extent_bit);
+
+static int wait_on_state(struct extent_io_tree *tree,
+			 struct extent_state *state)
+{
+	DEFINE_WAIT(wait);
+	prepare_to_wait(&state->wq, &wait, TASK_UNINTERRUPTIBLE);
+	read_unlock_irq(&tree->lock);
+	schedule();
+	read_lock_irq(&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;
+
+	read_lock_irq(&tree->lock);
+again:
+	while (1) {
+		/*
+		 * this search will find all the extents that end after
+		 * our range starts
+		 */
+		node = tree_search(&tree->state, 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;
+
+		if (need_resched()) {
+			read_unlock_irq(&tree->lock);
+			cond_resched();
+			read_lock_irq(&tree->lock);
+		}
+	}
+out:
+	read_unlock_irq(&tree->lock);
+	return 0;
+}
+EXPORT_SYMBOL(wait_extent_bit);
+
+static void set_state_bits(struct extent_io_tree *tree,
+			   struct extent_state *state,
+			   int bits)
+{
+	if ((bits & EXTENT_DIRTY) && !(state->state & EXTENT_DIRTY)) {
+		u64 range = state->end - state->start + 1;
+		tree->dirty_bytes += range;
+	}
+	state->state |= bits;
+}
+
+/*
+ * 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 'exclusive' == 1, 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, u64 *failed_start, gfp_t mask)
+{
+	struct extent_state *state;
+	struct extent_state *prealloc = NULL;
+	struct rb_node *node;
+	unsigned long flags;
+	int err = 0;
+	int set;
+	u64 last_start;
+	u64 last_end;
+again:
+	if (!prealloc && (mask & __GFP_WAIT)) {
+		prealloc = alloc_extent_state(mask);
+		if (!prealloc)
+			return -ENOMEM;
+	}
+
+	write_lock_irqsave(&tree->lock, flags);
+	/*
+	 * this search will find all the extents that end after
+	 * our range starts.
+	 */
+	node = tree_search(&tree->state, start);
+	if (!node) {
+		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);
+	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->state & bits;
+		if (set && exclusive) {
+			*failed_start = state->start;
+			err = -EEXIST;
+			goto out;
+		}
+		set_state_bits(tree, state, bits);
+		start = state->end + 1;
+		merge_state(tree, state);
+		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) {
+		set = state->state & bits;
+		if (exclusive && set) {
+			*failed_start = start;
+			err = -EEXIST;
+			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);
+			start = state->end + 1;
+			merge_state(tree, state);
+		} else {
+			start = state->start;
+		}
+		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;
+		err = insert_state(tree, prealloc, start, this_end,
+				   bits);
+		prealloc = NULL;
+		BUG_ON(err == -EEXIST);
+		if (err)
+			goto out;
+		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) {
+		set = state->state & bits;
+		if (exclusive && set) {
+			*failed_start = start;
+			err = -EEXIST;
+			goto out;
+		}
+		err = split_state(tree, state, prealloc, end + 1);
+		BUG_ON(err == -EEXIST);
+
+		set_state_bits(tree, prealloc, bits);
+		merge_state(tree, prealloc);
+		prealloc = NULL;
+		goto out;
+	}
+
+	goto search_again;
+
+out:
+	write_unlock_irqrestore(&tree->lock, flags);
+	if (prealloc)
+		free_extent_state(prealloc);
+
+	return err;
+
+search_again:
+	if (start > end)
+		goto out;
+	write_unlock_irqrestore(&tree->lock, flags);
+	if (mask & __GFP_WAIT)
+		cond_resched();
+	goto again;
+}
+EXPORT_SYMBOL(set_extent_bit);
+
+/* 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,
+			      mask);
+}
+EXPORT_SYMBOL(set_extent_dirty);
+
+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,
+			      mask);
+}
+EXPORT_SYMBOL(set_extent_bits);
+
+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, mask);
+}
+EXPORT_SYMBOL(clear_extent_bits);
+
+int set_extent_delalloc(struct extent_io_tree *tree, u64 start, u64 end,
+		     gfp_t mask)
+{
+	return set_extent_bit(tree, start, end,
+			      EXTENT_DELALLOC | EXTENT_DIRTY, 0, NULL,
+			      mask);
+}
+EXPORT_SYMBOL(set_extent_delalloc);
+
+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, 0, 0, mask);
+}
+EXPORT_SYMBOL(clear_extent_dirty);
+
+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,
+			      mask);
+}
+EXPORT_SYMBOL(set_extent_new);
+
+int clear_extent_new(struct extent_io_tree *tree, u64 start, u64 end,
+		       gfp_t mask)
+{
+	return clear_extent_bit(tree, start, end, EXTENT_NEW, 0, 0, mask);
+}
+EXPORT_SYMBOL(clear_extent_new);
+
+int set_extent_uptodate(struct extent_io_tree *tree, u64 start, u64 end,
+			gfp_t mask)
+{
+	return set_extent_bit(tree, start, end, EXTENT_UPTODATE, 0, NULL,
+			      mask);
+}
+EXPORT_SYMBOL(set_extent_uptodate);
+
+int clear_extent_uptodate(struct extent_io_tree *tree, u64 start, u64 end,
+			  gfp_t mask)
+{
+	return clear_extent_bit(tree, start, end, EXTENT_UPTODATE, 0, 0, mask);
+}
+EXPORT_SYMBOL(clear_extent_uptodate);
+
+int set_extent_writeback(struct extent_io_tree *tree, u64 start, u64 end,
+			 gfp_t mask)
+{
+	return set_extent_bit(tree, start, end, EXTENT_WRITEBACK,
+			      0, NULL, mask);
+}
+EXPORT_SYMBOL(set_extent_writeback);
+
+int clear_extent_writeback(struct extent_io_tree *tree, u64 start, u64 end,
+			   gfp_t mask)
+{
+	return clear_extent_bit(tree, start, end, EXTENT_WRITEBACK, 1, 0, mask);
+}
+EXPORT_SYMBOL(clear_extent_writeback);
+
+int wait_on_extent_writeback(struct extent_io_tree *tree, u64 start, u64 end)
+{
+	return wait_extent_bit(tree, start, end, EXTENT_WRITEBACK);
+}
+EXPORT_SYMBOL(wait_on_extent_writeback);
+
+/*
+ * locks a range in ascending order, waiting for any locked regions
+ * it hits on the way.  [start,end] are inclusive, and this will sleep.
+ */
+int lock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask)
+{
+	int err;
+	u64 failed_start;
+	while (1) {
+		err = set_extent_bit(tree, start, end, EXTENT_LOCKED, 1,
+				     &failed_start, 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;
+}
+EXPORT_SYMBOL(lock_extent);
+
+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, mask);
+}
+EXPORT_SYMBOL(unlock_extent);
+
+/*
+ * helper function to set pages and extents in the tree dirty
+ */
+int set_range_dirty(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_dirty_nobuffers(page);
+		page_cache_release(page);
+		index++;
+	}
+	set_extent_dirty(tree, start, end, GFP_NOFS);
+	return 0;
+}
+EXPORT_SYMBOL(set_range_dirty);
+
+/*
+ * helper function to set both pages and extents in the tree writeback
+ */
+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++;
+	}
+	set_extent_writeback(tree, start, end, GFP_NOFS);
+	return 0;
+}
+EXPORT_SYMBOL(set_range_writeback);
+
+int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
+			  u64 *start_ret, u64 *end_ret, int bits)
+{
+	struct rb_node *node;
+	struct extent_state *state;
+	int ret = 1;
+
+	read_lock_irq(&tree->lock);
+	/*
+	 * this search will find all the extents that end after
+	 * our range starts.
+	 */
+	node = tree_search(&tree->state, start);
+	if (!node || IS_ERR(node)) {
+		goto out;
+	}
+
+	while(1) {
+		state = rb_entry(node, struct extent_state, rb_node);
+		if (state->end >= start && (state->state & bits)) {
+			*start_ret = state->start;
+			*end_ret = state->end;
+			ret = 0;
+			break;
+		}
+		node = rb_next(node);
+		if (!node)
+			break;
+	}
+out:
+	read_unlock_irq(&tree->lock);
+	return ret;
+}
+EXPORT_SYMBOL(find_first_extent_bit);
+
+u64 find_lock_delalloc_range(struct extent_io_tree *tree,
+			     u64 *start, u64 *end, u64 max_bytes)
+{
+	struct rb_node *node;
+	struct extent_state *state;
+	u64 cur_start = *start;
+	u64 found = 0;
+	u64 total_bytes = 0;
+
+	write_lock_irq(&tree->lock);
+	/*
+	 * this search will find all the extents that end after
+	 * our range starts.
+	 */
+search_again:
+	node = tree_search(&tree->state, cur_start);
+	if (!node || IS_ERR(node)) {
+		*end = (u64)-1;
+		goto out;
+	}
+
+	while(1) {
+		state = rb_entry(node, struct extent_state, rb_node);
+		if (found && state->start != cur_start) {
+			goto out;
+		}
+		if (!(state->state & EXTENT_DELALLOC)) {
+			if (!found)
+				*end = state->end;
+			goto out;
+		}
+		if (!found) {
+			struct extent_state *prev_state;
+			struct rb_node *prev_node = node;
+			while(1) {
+				prev_node = rb_prev(prev_node);
+				if (!prev_node)
+					break;
+				prev_state = rb_entry(prev_node,
+						      struct extent_state,
+						      rb_node);
+				if (!(prev_state->state & EXTENT_DELALLOC))
+					break;
+				state = prev_state;
+				node = prev_node;
+			}
+		}
+		if (state->state & EXTENT_LOCKED) {
+			DEFINE_WAIT(wait);
+			atomic_inc(&state->refs);
+			prepare_to_wait(&state->wq, &wait,
+					TASK_UNINTERRUPTIBLE);
+			write_unlock_irq(&tree->lock);
+			schedule();
+			write_lock_irq(&tree->lock);
+			finish_wait(&state->wq, &wait);
+			free_extent_state(state);
+			goto search_again;
+		}
+		state->state |= EXTENT_LOCKED;
+		if (!found)
+			*start = state->start;
+		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:
+	write_unlock_irq(&tree->lock);
+	return found;
+}
+
+u64 count_range_bits(struct extent_io_tree *tree,
+		     u64 *start, u64 search_end, u64 max_bytes,
+		     unsigned long bits)
+{
+	struct rb_node *node;
+	struct extent_state *state;
+	u64 cur_start = *start;
+	u64 total_bytes = 0;
+	int found = 0;
+
+	if (search_end <= cur_start) {
+		printk("search_end %Lu start %Lu\n", search_end, cur_start);
+		WARN_ON(1);
+		return 0;
+	}
+
+	write_lock_irq(&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->state, cur_start);
+	if (!node || IS_ERR(node)) {
+		goto out;
+	}
+
+	while(1) {
+		state = rb_entry(node, struct extent_state, rb_node);
+		if (state->start > search_end)
+			break;
+		if (state->end >= cur_start && (state->state & bits)) {
+			total_bytes += min(search_end, state->end) + 1 -
+				       max(cur_start, state->start);
+			if (total_bytes >= max_bytes)
+				break;
+			if (!found) {
+				*start = state->start;
+				found = 1;
+			}
+		}
+		node = rb_next(node);
+		if (!node)
+			break;
+	}
+out:
+	write_unlock_irq(&tree->lock);
+	return total_bytes;
+}
+/*
+ * helper function to lock both pages and extents in the tree.
+ * pages must be locked first.
+ */
+int lock_range(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;
+	int err;
+
+	while (index <= end_index) {
+		page = grab_cache_page(tree->mapping, index);
+		if (!page) {
+			err = -ENOMEM;
+			goto failed;
+		}
+		if (IS_ERR(page)) {
+			err = PTR_ERR(page);
+			goto failed;
+		}
+		index++;
+	}
+	lock_extent(tree, start, end, GFP_NOFS);
+	return 0;
+
+failed:
+	/*
+	 * we failed above in getting the page at 'index', so we undo here
+	 * up to but not including the page at 'index'
+	 */
+	end_index = index;
+	index = start >> PAGE_CACHE_SHIFT;
+	while (index < end_index) {
+		page = find_get_page(tree->mapping, index);
+		unlock_page(page);
+		page_cache_release(page);
+		index++;
+	}
+	return err;
+}
+EXPORT_SYMBOL(lock_range);
+
+/*
+ * helper function to unlock both pages and extents in the tree.
+ */
+int unlock_range(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);
+		unlock_page(page);
+		page_cache_release(page);
+		index++;
+	}
+	unlock_extent(tree, start, end, GFP_NOFS);
+	return 0;
+}
+EXPORT_SYMBOL(unlock_range);
+
+int set_state_private(struct extent_io_tree *tree, u64 start, u64 private)
+{
+	struct rb_node *node;
+	struct extent_state *state;
+	int ret = 0;
+
+	write_lock_irq(&tree->lock);
+	/*
+	 * this search will find all the extents that end after
+	 * our range starts.
+	 */
+	node = tree_search(&tree->state, start);
+	if (!node || IS_ERR(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:
+	write_unlock_irq(&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;
+
+	read_lock_irq(&tree->lock);
+	/*
+	 * this search will find all the extents that end after
+	 * our range starts.
+	 */
+	node = tree_search(&tree->state, start);
+	if (!node || IS_ERR(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:
+	read_unlock_irq(&tree->lock);
+	return ret;
+}
+
+/*
+ * searches a range in the state tree for a given mask.
+ * If 'filled' == 1, this returns 1 only if ever 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 *state = NULL;
+	struct rb_node *node;
+	int bitset = 0;
+	unsigned long flags;
+
+	read_lock_irqsave(&tree->lock, flags);
+	node = tree_search(&tree->state, 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;
+		}
+		start = state->end + 1;
+		if (start > end)
+			break;
+		node = rb_next(node);
+		if (!node) {
+			if (filled)
+				bitset = 0;
+			break;
+		}
+	}
+	read_unlock_irqrestore(&tree->lock, flags);
+	return bitset;
+}
+EXPORT_SYMBOL(test_range_bit);
+
+/*
+ * 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))
+		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))
+		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)
+{
+	u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
+	u64 end = start + PAGE_CACHE_SIZE - 1;
+	if (!test_range_bit(tree, start, end, EXTENT_WRITEBACK, 0))
+		end_page_writeback(page);
+	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.
+ */
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,23)
+static void end_bio_extent_writepage(struct bio *bio, int err)
+#else
+static int end_bio_extent_writepage(struct bio *bio,
+				   unsigned int bytes_done, int err)
+#endif
+{
+	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+	struct extent_io_tree *tree = bio->bi_private;
+	u64 start;
+	u64 end;
+	int whole_page;
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,23)
+	if (bio->bi_size)
+		return 1;
+#endif
+
+	do {
+		struct page *page = bvec->bv_page;
+		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 (!uptodate) {
+			clear_extent_uptodate(tree, start, end, GFP_ATOMIC);
+			ClearPageUptodate(page);
+			SetPageError(page);
+		}
+		clear_extent_writeback(tree, start, end, GFP_ATOMIC);
+
+		if (whole_page)
+			end_page_writeback(page);
+		else
+			check_page_writeback(tree, page);
+		if (tree->ops && tree->ops->writepage_end_io_hook)
+			tree->ops->writepage_end_io_hook(page, start, end);
+	} while (bvec >= bio->bi_io_vec);
+
+	bio_put(bio);
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,23)
+	return 0;
+#endif
+}
+
+/*
+ * 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.
+ */
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,23)
+static void end_bio_extent_readpage(struct bio *bio, int err)
+#else
+static int end_bio_extent_readpage(struct bio *bio,
+				   unsigned int bytes_done, int err)
+#endif
+{
+	int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+	struct extent_io_tree *tree = bio->bi_private;
+	u64 start;
+	u64 end;
+	int whole_page;
+	int ret;
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,23)
+	if (bio->bi_size)
+		return 1;
+#endif
+
+	do {
+		struct page *page = bvec->bv_page;
+		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 (uptodate && tree->ops && tree->ops->readpage_end_io_hook) {
+			ret = tree->ops->readpage_end_io_hook(page, start, end);
+			if (ret)
+				uptodate = 0;
+		}
+		if (uptodate) {
+			set_extent_uptodate(tree, start, end, GFP_ATOMIC);
+			if (whole_page)
+				SetPageUptodate(page);
+			else
+				check_page_uptodate(tree, page);
+		} else {
+			ClearPageUptodate(page);
+			SetPageError(page);
+		}
+
+		unlock_extent(tree, start, end, GFP_ATOMIC);
+
+		if (whole_page)
+			unlock_page(page);
+		else
+			check_page_locked(tree, page);
+	} while (bvec >= bio->bi_io_vec);
+
+	bio_put(bio);
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,23)
+	return 0;
+#endif
+}
+
+/*
+ * IO done from prepare_write is pretty simple, we just unlock
+ * the structs in the extent tree when done, and set the uptodate bits
+ * as appropriate.
+ */
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,23)
+static void end_bio_extent_preparewrite(struct bio *bio, int err)
+#else
+static int end_bio_extent_preparewrite(struct bio *bio,
+				       unsigned int bytes_done, int err)
+#endif
+{
+	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+	struct extent_io_tree *tree = bio->bi_private;
+	u64 start;
+	u64 end;
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,23)
+	if (bio->bi_size)
+		return 1;
+#endif
+
+	do {
+		struct page *page = bvec->bv_page;
+		start = ((u64)page->index << PAGE_CACHE_SHIFT) +
+			bvec->bv_offset;
+		end = start + bvec->bv_len - 1;
+
+		if (--bvec >= bio->bi_io_vec)
+			prefetchw(&bvec->bv_page->flags);
+
+		if (uptodate) {
+			set_extent_uptodate(tree, start, end, GFP_ATOMIC);
+		} else {
+			ClearPageUptodate(page);
+			SetPageError(page);
+		}
+
+		unlock_extent(tree, start, end, GFP_ATOMIC);
+
+	} while (bvec >= bio->bi_io_vec);
+
+	bio_put(bio);
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,23)
+	return 0;
+#endif
+}
+
+static struct bio *
+extent_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_bdev = bdev;
+		bio->bi_sector = first_sector;
+	}
+	return bio;
+}
+
+static int submit_one_bio(int rw, struct bio *bio)
+{
+	u64 maxsector;
+	int ret = 0;
+
+	bio_get(bio);
+
+        maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
+	if (maxsector < bio->bi_sector) {
+		printk("sector too large max %Lu got %llu\n", maxsector,
+			(unsigned long long)bio->bi_sector);
+		WARN_ON(1);
+	}
+
+	submit_bio(rw, bio);
+	if (bio_flagged(bio, BIO_EOPNOTSUPP))
+		ret = -EOPNOTSUPP;
+	bio_put(bio);
+	return ret;
+}
+
+static int submit_extent_page(int rw, struct extent_io_tree *tree,
+			      struct page *page, sector_t sector,
+			      size_t size, unsigned long offset,
+			      struct block_device *bdev,
+			      struct bio **bio_ret,
+			      unsigned long max_pages,
+			      bio_end_io_t end_io_func)
+{
+	int ret = 0;
+	struct bio *bio;
+	int nr;
+
+	if (bio_ret && *bio_ret) {
+		bio = *bio_ret;
+		if (bio->bi_sector + (bio->bi_size >> 9) != sector ||
+		    bio_add_page(bio, page, size, offset) < size) {
+			ret = submit_one_bio(rw, bio);
+			bio = NULL;
+		} else {
+			return 0;
+		}
+	}
+	nr = min_t(int, max_pages, bio_get_nr_vecs(bdev));
+	bio = extent_bio_alloc(bdev, sector, nr, GFP_NOFS | __GFP_HIGH);
+	if (!bio) {
+		printk("failed to allocate bio nr %d\n", nr);
+	}
+	bio_add_page(bio, page, size, offset);
+	bio->bi_end_io = end_io_func;
+	bio->bi_private = tree;
+	if (bio_ret) {
+		*bio_ret = bio;
+	} else {
+		ret = submit_one_bio(rw, bio);
+	}
+
+	return ret;
+}
+
+void set_page_extent_mapped(struct page *page)
+{
+	if (!PagePrivate(page)) {
+		SetPagePrivate(page);
+		WARN_ON(!page->mapping->a_ops->invalidatepage);
+		set_page_private(page, EXTENT_PAGE_PRIVATE);
+		page_cache_get(page);
+	}
+}
+
+void set_page_extent_head(struct page *page, unsigned long len)
+{
+	set_page_private(page, EXTENT_PAGE_PRIVATE_FIRST_PAGE | len << 2);
+}
+
+/*
+ * basic readpage implementation.  Locked extent state structs are inserted
+ * into the tree that are removed when the IO is done (by the end_io
+ * handlers)
+ */
+static int __extent_read_full_page(struct extent_io_tree *tree,
+				   struct page *page,
+				   get_extent_t *get_extent,
+				   struct bio **bio)
+{
+	struct inode *inode = page->mapping->host;
+	u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
+	u64 page_end = start + PAGE_CACHE_SIZE - 1;
+	u64 end;
+	u64 cur = start;
+	u64 extent_offset;
+	u64 last_byte = i_size_read(inode);
+	u64 block_start;
+	u64 cur_end;
+	sector_t sector;
+	struct extent_map *em;
+	struct block_device *bdev;
+	int ret;
+	int nr = 0;
+	size_t page_offset = 0;
+	size_t iosize;
+	size_t blocksize = inode->i_sb->s_blocksize;
+
+	set_page_extent_mapped(page);
+
+	end = page_end;
+	lock_extent(tree, start, end, GFP_NOFS);
+
+	while (cur <= end) {
+		if (cur >= last_byte) {
+			char *userpage;
+			iosize = PAGE_CACHE_SIZE - page_offset;
+			userpage = kmap_atomic(page, KM_USER0);
+			memset(userpage + page_offset, 0, iosize);
+			flush_dcache_page(page);
+			kunmap_atomic(userpage, KM_USER0);
+			set_extent_uptodate(tree, cur, cur + iosize - 1,
+					    GFP_NOFS);
+			unlock_extent(tree, cur, cur + iosize - 1, GFP_NOFS);
+			break;
+		}
+		em = get_extent(inode, page, page_offset, cur,
+				end - cur + 1, 0);
+		if (IS_ERR(em) || !em) {
+			SetPageError(page);
+			unlock_extent(tree, cur, end, GFP_NOFS);
+			break;
+		}
+
+		extent_offset = cur - em->start;
+		BUG_ON(extent_map_end(em) <= cur);
+		BUG_ON(end < cur);
+
+		iosize = min(extent_map_end(em) - cur, end - cur + 1);
+		cur_end = min(extent_map_end(em) - 1, end);
+		iosize = (iosize + blocksize - 1) & ~((u64)blocksize - 1);
+		sector = (em->block_start + extent_offset) >> 9;
+		bdev = em->bdev;
+		block_start = em->block_start;
+		free_extent_map(em);
+		em = NULL;
+
+		/* we've found a hole, just zero and go on */
+		if (block_start == EXTENT_MAP_HOLE) {
+			char *userpage;
+			userpage = kmap_atomic(page, KM_USER0);
+			memset(userpage + page_offset, 0, iosize);
+			flush_dcache_page(page);
+			kunmap_atomic(userpage, KM_USER0);
+
+			set_extent_uptodate(tree, cur, cur + iosize - 1,
+					    GFP_NOFS);
+			unlock_extent(tree, cur, cur + iosize - 1, GFP_NOFS);
+			cur = cur + iosize;
+			page_offset += iosize;
+			continue;
+		}
+		/* the get_extent function already copied into the page */
+		if (test_range_bit(tree, cur, cur_end, EXTENT_UPTODATE, 1)) {
+			unlock_extent(tree, cur, cur + iosize - 1, GFP_NOFS);
+			cur = cur + iosize;
+			page_offset += iosize;
+			continue;
+		}
+
+		ret = 0;
+		if (tree->ops && tree->ops->readpage_io_hook) {
+			ret = tree->ops->readpage_io_hook(page, cur,
+							  cur + iosize - 1);
+		}
+		if (!ret) {
+			unsigned long nr = (last_byte >> PAGE_CACHE_SHIFT) + 1;
+			nr -= page->index;
+			ret = submit_extent_page(READ, tree, page,
+					 sector, iosize, page_offset,
+					 bdev, bio, nr,
+					 end_bio_extent_readpage);
+		}
+		if (ret)
+			SetPageError(page);
+		cur = cur + iosize;
+		page_offset += iosize;
+		nr++;
+	}
+	if (!nr) {
+		if (!PageError(page))
+			SetPageUptodate(page);
+		unlock_page(page);
+	}
+	return 0;
+}
+
+int extent_read_full_page(struct extent_io_tree *tree, struct page *page,
+			    get_extent_t *get_extent)
+{
+	struct bio *bio = NULL;
+	int ret;
+
+	ret = __extent_read_full_page(tree, page, get_extent, &bio);
+	if (bio)
+		submit_one_bio(READ, bio);
+	return ret;
+}
+EXPORT_SYMBOL(extent_read_full_page);
+
+/*
+ * the writepage semantics are similar to regular writepage.  extent
+ * records are inserted to lock ranges in the tree, and as dirty areas
+ * are found, they are marked writeback.  Then the lock bits are removed
+ * and the end_io handler clears the writeback ranges
+ */
+static int __extent_writepage(struct page *page, struct writeback_control *wbc,
+			      void *data)
+{
+	struct inode *inode = page->mapping->host;
+	struct extent_page_data *epd = data;
+	struct extent_io_tree *tree = epd->tree;
+	u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
+	u64 delalloc_start;
+	u64 page_end = start + PAGE_CACHE_SIZE - 1;
+	u64 end;
+	u64 cur = start;
+	u64 extent_offset;
+	u64 last_byte = i_size_read(inode);
+	u64 block_start;
+	u64 iosize;
+	sector_t sector;
+	struct extent_map *em;
+	struct block_device *bdev;
+	int ret;
+	int nr = 0;
+	size_t page_offset = 0;
+	size_t blocksize;
+	loff_t i_size = i_size_read(inode);
+	unsigned long end_index = i_size >> PAGE_CACHE_SHIFT;
+	u64 nr_delalloc;
+	u64 delalloc_end;
+
+	WARN_ON(!PageLocked(page));
+	if (page->index > end_index) {
+		clear_extent_dirty(tree, start, page_end, GFP_NOFS);
+		unlock_page(page);
+		return 0;
+	}
+
+	if (page->index == end_index) {
+		char *userpage;
+
+		size_t offset = i_size & (PAGE_CACHE_SIZE - 1);
+
+		userpage = kmap_atomic(page, KM_USER0);
+		memset(userpage + offset, 0, PAGE_CACHE_SIZE - offset);
+		flush_dcache_page(page);
+		kunmap_atomic(userpage, KM_USER0);
+	}
+
+	set_page_extent_mapped(page);
+
+	delalloc_start = start;
+	delalloc_end = 0;
+	while(delalloc_end < page_end) {
+		nr_delalloc = find_lock_delalloc_range(tree, &delalloc_start,
+						       &delalloc_end,
+						       128 * 1024 * 1024);
+		if (nr_delalloc == 0) {
+			delalloc_start = delalloc_end + 1;
+			continue;
+		}
+		tree->ops->fill_delalloc(inode, delalloc_start,
+					 delalloc_end);
+		clear_extent_bit(tree, delalloc_start,
+				 delalloc_end,
+				 EXTENT_LOCKED | EXTENT_DELALLOC,
+				 1, 0, GFP_NOFS);
+		delalloc_start = delalloc_end + 1;
+	}
+	lock_extent(tree, start, page_end, GFP_NOFS);
+
+	end = page_end;
+	if (test_range_bit(tree, start, page_end, EXTENT_DELALLOC, 0)) {
+		printk("found delalloc bits after lock_extent\n");
+	}
+
+	if (last_byte <= start) {
+		clear_extent_dirty(tree, start, page_end, GFP_NOFS);
+		goto done;
+	}
+
+	set_extent_uptodate(tree, start, page_end, GFP_NOFS);
+	blocksize = inode->i_sb->s_blocksize;
+
+	while (cur <= end) {
+		if (cur >= last_byte) {
+			clear_extent_dirty(tree, cur, page_end, GFP_NOFS);
+			break;
+		}
+		em = epd->get_extent(inode, page, page_offset, cur,
+				     end - cur + 1, 1);
+		if (IS_ERR(em) || !em) {
+			SetPageError(page);
+			break;
+		}
+
+		extent_offset = cur - em->start;
+		BUG_ON(extent_map_end(em) <= cur);
+		BUG_ON(end < cur);
+		iosize = min(extent_map_end(em) - cur, end - cur + 1);
+		iosize = (iosize + blocksize - 1) & ~((u64)blocksize - 1);
+		sector = (em->block_start + extent_offset) >> 9;
+		bdev = em->bdev;
+		block_start = em->block_start;
+		free_extent_map(em);
+		em = NULL;
+
+		if (block_start == EXTENT_MAP_HOLE ||
+		    block_start == EXTENT_MAP_INLINE) {
+			clear_extent_dirty(tree, cur,
+					   cur + iosize - 1, GFP_NOFS);
+			cur = cur + iosize;
+			page_offset += iosize;
+			continue;
+		}
+
+		/* leave this out until we have a page_mkwrite call */
+		if (0 && !test_range_bit(tree, cur, cur + iosize - 1,
+				   EXTENT_DIRTY, 0)) {
+			cur = cur + iosize;
+			page_offset += iosize;
+			continue;
+		}
+		clear_extent_dirty(tree, cur, cur + iosize - 1, GFP_NOFS);
+		if (tree->ops && tree->ops->writepage_io_hook) {
+			ret = tree->ops->writepage_io_hook(page, cur,
+						cur + iosize - 1);
+		} else {
+			ret = 0;
+		}
+		if (ret)
+			SetPageError(page);
+		else {
+			unsigned long max_nr = end_index + 1;
+			set_range_writeback(tree, cur, cur + iosize - 1);
+			if (!PageWriteback(page)) {
+				printk("warning page %lu not writeback, "
+				       "cur %llu end %llu\n", page->index,
+				       (unsigned long long)cur,
+				       (unsigned long long)end);
+			}
+
+			ret = submit_extent_page(WRITE, tree, page, sector,
+						 iosize, page_offset, bdev,
+						 &epd->bio, max_nr,
+						 end_bio_extent_writepage);
+			if (ret)
+				SetPageError(page);
+		}
+		cur = cur + iosize;
+		page_offset += iosize;
+		nr++;
+	}
+done:
+	if (nr == 0) {
+		/* make sure the mapping tag for page dirty gets cleared */
+		set_page_writeback(page);
+		end_page_writeback(page);
+	}
+	unlock_extent(tree, start, page_end, GFP_NOFS);
+	unlock_page(page);
+	return 0;
+}
+
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,18)
+
+/* Taken directly from 2.6.23 for 2.6.18 back port */
+typedef int (*writepage_t)(struct page *page, struct writeback_control *wbc,
+                                void *data);
+
+/**
+ * write_cache_pages - walk the list of dirty pages of the given address space
+ * and write all of them.
+ * @mapping: address space structure to write
+ * @wbc: subtract the number of written pages from *@wbc->nr_to_write
+ * @writepage: function called for each page
+ * @data: data passed to writepage function
+ *
+ * If a page is already under I/O, write_cache_pages() skips it, even
+ * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
+ * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()
+ * and msync() need to guarantee that all the data which was dirty at the time
+ * the call was made get new I/O started against them.  If wbc->sync_mode is
+ * WB_SYNC_ALL then we were called for data integrity and we must wait for
+ * existing IO to complete.
+ */
+static int write_cache_pages(struct address_space *mapping,
+		      struct writeback_control *wbc, writepage_t writepage,
+		      void *data)
+{
+	struct backing_dev_info *bdi = mapping->backing_dev_info;
+	int ret = 0;
+	int done = 0;
+	struct pagevec pvec;
+	int nr_pages;
+	pgoff_t index;
+	pgoff_t end;		/* Inclusive */
+	int scanned = 0;
+	int range_whole = 0;
+
+	if (wbc->nonblocking && bdi_write_congested(bdi)) {
+		wbc->encountered_congestion = 1;
+		return 0;
+	}
+
+	pagevec_init(&pvec, 0);
+	if (wbc->range_cyclic) {
+		index = mapping->writeback_index; /* Start from prev offset */
+		end = -1;
+	} else {
+		index = wbc->range_start >> PAGE_CACHE_SHIFT;
+		end = wbc->range_end >> PAGE_CACHE_SHIFT;
+		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
+			range_whole = 1;
+		scanned = 1;
+	}
+retry:
+	while (!done && (index <= end) &&
+	       (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
+					      PAGECACHE_TAG_DIRTY,
+					      min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) {
+		unsigned i;
+
+		scanned = 1;
+		for (i = 0; i < nr_pages; i++) {
+			struct page *page = pvec.pages[i];
+
+			/*
+			 * At this point we hold neither mapping->tree_lock nor
+			 * lock on the page itself: the page may be truncated or
+			 * invalidated (changing page->mapping to NULL), or even
+			 * swizzled back from swapper_space to tmpfs file
+			 * mapping
+			 */
+			lock_page(page);
+
+			if (unlikely(page->mapping != mapping)) {
+				unlock_page(page);
+				continue;
+			}
+
+			if (!wbc->range_cyclic && page->index > end) {
+				done = 1;
+				unlock_page(page);
+				continue;
+			}
+
+			if (wbc->sync_mode != WB_SYNC_NONE)
+				wait_on_page_writeback(page);
+
+			if (PageWriteback(page) ||
+			    !clear_page_dirty_for_io(page)) {
+				unlock_page(page);
+				continue;
+			}
+
+			ret = (*writepage)(page, wbc, data);
+
+			if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE)) {
+				unlock_page(page);
+				ret = 0;
+			}
+			if (ret || (--(wbc->nr_to_write) <= 0))
+				done = 1;
+			if (wbc->nonblocking && bdi_write_congested(bdi)) {
+				wbc->encountered_congestion = 1;
+				done = 1;
+			}
+		}
+		pagevec_release(&pvec);
+		cond_resched();
+	}
+	if (!scanned && !done) {
+		/*
+		 * We hit the last page and there is more work to be done: wrap
+		 * back to the start of the file
+		 */
+		scanned = 1;
+		index = 0;
+		goto retry;
+	}
+	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
+		mapping->writeback_index = index;
+	return ret;
+}
+#endif
+
+int extent_write_full_page(struct extent_io_tree *tree, struct page *page,
+			  get_extent_t *get_extent,
+			  struct writeback_control *wbc)
+{
+	int ret;
+	struct address_space *mapping = page->mapping;
+	struct extent_page_data epd = {
+		.bio = NULL,
+		.tree = tree,
+		.get_extent = get_extent,
+	};
+	struct writeback_control wbc_writepages = {
+		.bdi		= wbc->bdi,
+		.sync_mode	= WB_SYNC_NONE,
+		.older_than_this = NULL,
+		.nr_to_write	= 64,
+		.range_start	= page_offset(page) + PAGE_CACHE_SIZE,
+		.range_end	= (loff_t)-1,
+	};
+
+
+	ret = __extent_writepage(page, wbc, &epd);
+
+	write_cache_pages(mapping, &wbc_writepages, __extent_writepage, &epd);
+	if (epd.bio) {
+		submit_one_bio(WRITE, epd.bio);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(extent_write_full_page);
+
+
+int extent_writepages(struct extent_io_tree *tree,
+		      struct address_space *mapping,
+		      get_extent_t *get_extent,
+		      struct writeback_control *wbc)
+{
+	int ret = 0;
+	struct extent_page_data epd = {
+		.bio = NULL,
+		.tree = tree,
+		.get_extent = get_extent,
+	};
+
+	ret = write_cache_pages(mapping, wbc, __extent_writepage, &epd);
+	if (epd.bio) {
+		submit_one_bio(WRITE, epd.bio);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(extent_writepages);
+
+int extent_readpages(struct extent_io_tree *tree,
+		     struct address_space *mapping,
+		     struct list_head *pages, unsigned nr_pages,
+		     get_extent_t get_extent)
+{
+	struct bio *bio = NULL;
+	unsigned page_idx;
+	struct pagevec pvec;
+
+	pagevec_init(&pvec, 0);
+	for (page_idx = 0; page_idx < nr_pages; page_idx++) {
+		struct page *page = list_entry(pages->prev, struct page, lru);
+
+		prefetchw(&page->flags);
+		list_del(&page->lru);
+		/*
+		 * what we want to do here is call add_to_page_cache_lru,
+		 * but that isn't exported, so we reproduce it here
+		 */
+		if (!add_to_page_cache(page, mapping,
+					page->index, GFP_KERNEL)) {
+
+			/* open coding of lru_cache_add, also not exported */
+			page_cache_get(page);
+			if (!pagevec_add(&pvec, page))
+				__pagevec_lru_add(&pvec);
+			__extent_read_full_page(tree, page, get_extent, &bio);
+		}
+		page_cache_release(page);
+	}
+	if (pagevec_count(&pvec))
+		__pagevec_lru_add(&pvec);
+	BUG_ON(!list_empty(pages));
+	if (bio)
+		submit_one_bio(READ, bio);
+	return 0;
+}
+EXPORT_SYMBOL(extent_readpages);
+
+/*
+ * basic invalidatepage code, this waits on any locked or writeback
+ * ranges corresponding to the page, and then deletes any extent state
+ * records from the tree
+ */
+int extent_invalidatepage(struct extent_io_tree *tree,
+			  struct page *page, unsigned long offset)
+{
+	u64 start = ((u64)page->index << PAGE_CACHE_SHIFT);
+	u64 end = start + PAGE_CACHE_SIZE - 1;
+	size_t blocksize = page->mapping->host->i_sb->s_blocksize;
+
+	start += (offset + blocksize -1) & ~(blocksize - 1);
+	if (start > end)
+		return 0;
+
+	lock_extent(tree, start, end, GFP_NOFS);
+	wait_on_extent_writeback(tree, start, end);
+	clear_extent_bit(tree, start, end,
+			 EXTENT_LOCKED | EXTENT_DIRTY | EXTENT_DELALLOC,
+			 1, 1, GFP_NOFS);
+	return 0;
+}
+EXPORT_SYMBOL(extent_invalidatepage);
+
+/*
+ * simple commit_write call, set_range_dirty is used to mark both
+ * the pages and the extent records as dirty
+ */
+int extent_commit_write(struct extent_io_tree *tree,
+			struct inode *inode, struct page *page,
+			unsigned from, unsigned to)
+{
+	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
+
+	set_page_extent_mapped(page);
+	set_page_dirty(page);
+
+	if (pos > inode->i_size) {
+		i_size_write(inode, pos);
+		mark_inode_dirty(inode);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(extent_commit_write);
+
+int extent_prepare_write(struct extent_io_tree *tree,
+			 struct inode *inode, struct page *page,
+			 unsigned from, unsigned to, get_extent_t *get_extent)
+{
+	u64 page_start = (u64)page->index << PAGE_CACHE_SHIFT;
+	u64 page_end = page_start + PAGE_CACHE_SIZE - 1;
+	u64 block_start;
+	u64 orig_block_start;
+	u64 block_end;
+	u64 cur_end;
+	struct extent_map *em;
+	unsigned blocksize = 1 << inode->i_blkbits;
+	size_t page_offset = 0;
+	size_t block_off_start;
+	size_t block_off_end;
+	int err = 0;
+	int iocount = 0;
+	int ret = 0;
+	int isnew;
+
+	set_page_extent_mapped(page);
+
+	block_start = (page_start + from) & ~((u64)blocksize - 1);
+	block_end = (page_start + to - 1) | (blocksize - 1);
+	orig_block_start = block_start;
+
+	lock_extent(tree, page_start, page_end, GFP_NOFS);
+	while(block_start <= block_end) {
+		em = get_extent(inode, page, page_offset, block_start,
+				block_end - block_start + 1, 1);
+		if (IS_ERR(em) || !em) {
+			goto err;
+		}
+		cur_end = min(block_end, extent_map_end(em) - 1);
+		block_off_start = block_start & (PAGE_CACHE_SIZE - 1);
+		block_off_end = block_off_start + blocksize;
+		isnew = clear_extent_new(tree, block_start, cur_end, GFP_NOFS);
+
+		if (!PageUptodate(page) && isnew &&
+		    (block_off_end > to || block_off_start < from)) {
+			void *kaddr;
+
+			kaddr = kmap_atomic(page, KM_USER0);
+			if (block_off_end > to)
+				memset(kaddr + to, 0, block_off_end - to);
+			if (block_off_start < from)
+				memset(kaddr + block_off_start, 0,
+				       from - block_off_start);
+			flush_dcache_page(page);
+			kunmap_atomic(kaddr, KM_USER0);
+		}
+		if ((em->block_start != EXTENT_MAP_HOLE &&
+		     em->block_start != EXTENT_MAP_INLINE) &&
+		    !isnew && !PageUptodate(page) &&
+		    (block_off_end > to || block_off_start < from) &&
+		    !test_range_bit(tree, block_start, cur_end,
+				    EXTENT_UPTODATE, 1)) {
+			u64 sector;
+			u64 extent_offset = block_start - em->start;
+			size_t iosize;
+			sector = (em->block_start + extent_offset) >> 9;
+			iosize = (cur_end - block_start + blocksize) &
+				~((u64)blocksize - 1);
+			/*
+			 * we've already got the extent locked, but we
+			 * need to split the state such that our end_bio
+			 * handler can clear the lock.
+			 */
+			set_extent_bit(tree, block_start,
+				       block_start + iosize - 1,
+				       EXTENT_LOCKED, 0, NULL, GFP_NOFS);
+			ret = submit_extent_page(READ, tree, page,
+					 sector, iosize, page_offset, em->bdev,
+					 NULL, 1,
+					 end_bio_extent_preparewrite);
+			iocount++;
+			block_start = block_start + iosize;
+		} else {
+			set_extent_uptodate(tree, block_start, cur_end,
+					    GFP_NOFS);
+			unlock_extent(tree, block_start, cur_end, GFP_NOFS);
+			block_start = cur_end + 1;
+		}
+		page_offset = block_start & (PAGE_CACHE_SIZE - 1);
+		free_extent_map(em);
+	}
+	if (iocount) {
+		wait_extent_bit(tree, orig_block_start,
+				block_end, EXTENT_LOCKED);
+	}
+	check_page_uptodate(tree, page);
+err:
+	/* FIXME, zero out newly allocated blocks on error */
+	return err;
+}
+EXPORT_SYMBOL(extent_prepare_write);
+
+/*
+ * a helper for releasepage.  As long as there are no locked extents
+ * in the range corresponding to the page, both state records and extent
+ * map records are removed
+ */
+int try_release_extent_mapping(struct extent_map_tree *map,
+			       struct extent_io_tree *tree, struct page *page)
+{
+	struct extent_map *em;
+	u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
+	u64 end = start + PAGE_CACHE_SIZE - 1;
+	u64 orig_start = start;
+	int ret = 1;
+
+	while (start <= end) {
+		spin_lock(&map->lock);
+		em = lookup_extent_mapping(map, start, end);
+		if (!em || IS_ERR(em)) {
+			spin_unlock(&map->lock);
+			break;
+		}
+		if (!test_range_bit(tree, em->start, extent_map_end(em) - 1,
+				    EXTENT_LOCKED, 0)) {
+			remove_extent_mapping(map, em);
+			/* once for the rb tree */
+			free_extent_map(em);
+		}
+		start = extent_map_end(em);
+		spin_unlock(&map->lock);
+
+		/* once for us */
+		free_extent_map(em);
+	}
+	if (test_range_bit(tree, orig_start, end, EXTENT_LOCKED, 0))
+		ret = 0;
+	else
+		clear_extent_bit(tree, orig_start, end, EXTENT_UPTODATE,
+				 1, 1, GFP_NOFS);
+	return ret;
+}
+EXPORT_SYMBOL(try_release_extent_mapping);
+
+sector_t extent_bmap(struct address_space *mapping, sector_t iblock,
+		get_extent_t *get_extent)
+{
+	struct inode *inode = mapping->host;
+	u64 start = iblock << inode->i_blkbits;
+	sector_t sector = 0;
+	struct extent_map *em;
+
+	em = get_extent(inode, NULL, 0, start, (1 << inode->i_blkbits), 0);
+	if (!em || IS_ERR(em))
+		return 0;
+
+	if (em->block_start == EXTENT_MAP_INLINE ||
+	    em->block_start == EXTENT_MAP_HOLE)
+		goto out;
+
+	sector = (em->block_start + start - em->start) >> inode->i_blkbits;
+printk("bmap finds %Lu %Lu block %Lu\n", em->start, em->len, em->block_start);
+out:
+	free_extent_map(em);
+	return sector;
+}
+
+static int add_lru(struct extent_io_tree *tree, struct extent_buffer *eb)
+{
+	if (list_empty(&eb->lru)) {
+		extent_buffer_get(eb);
+		list_add(&eb->lru, &tree->buffer_lru);
+		tree->lru_size++;
+		if (tree->lru_size >= BUFFER_LRU_MAX) {
+			struct extent_buffer *rm;
+			rm = list_entry(tree->buffer_lru.prev,
+					struct extent_buffer, lru);
+			tree->lru_size--;
+			list_del_init(&rm->lru);
+			free_extent_buffer(rm);
+		}
+	} else
+		list_move(&eb->lru, &tree->buffer_lru);
+	return 0;
+}
+static struct extent_buffer *find_lru(struct extent_io_tree *tree,
+				      u64 start, unsigned long len)
+{
+	struct list_head *lru = &tree->buffer_lru;
+	struct list_head *cur = lru->next;
+	struct extent_buffer *eb;
+
+	if (list_empty(lru))
+		return NULL;
+
+	do {
+		eb = list_entry(cur, struct extent_buffer, lru);
+		if (eb->start == start && eb->len == len) {
+			extent_buffer_get(eb);
+			return eb;
+		}
+		cur = cur->next;
+	} while (cur != lru);
+	return NULL;
+}
+
+static inline unsigned long num_extent_pages(u64 start, u64 len)
+{
+	return ((start + len + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT) -
+		(start >> PAGE_CACHE_SHIFT);
+}
+
+static inline struct page *extent_buffer_page(struct extent_buffer *eb,
+					      unsigned long i)
+{
+	struct page *p;
+	struct address_space *mapping;
+
+	if (i == 0)
+		return eb->first_page;
+	i += eb->start >> PAGE_CACHE_SHIFT;
+	mapping = eb->first_page->mapping;
+	read_lock_irq(&mapping->tree_lock);
+	p = radix_tree_lookup(&mapping->page_tree, i);
+	read_unlock_irq(&mapping->tree_lock);
+	return p;
+}
+
+static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree,
+						   u64 start,
+						   unsigned long len,
+						   gfp_t mask)
+{
+	struct extent_buffer *eb = NULL;
+
+	spin_lock(&tree->lru_lock);
+	eb = find_lru(tree, start, len);
+	spin_unlock(&tree->lru_lock);
+	if (eb) {
+		return eb;
+	}
+
+	eb = kmem_cache_zalloc(extent_buffer_cache, mask);
+	INIT_LIST_HEAD(&eb->lru);
+	eb->start = start;
+	eb->len = len;
+	atomic_set(&eb->refs, 1);
+
+	return eb;
+}
+
+static void __free_extent_buffer(struct extent_buffer *eb)
+{
+	kmem_cache_free(extent_buffer_cache, eb);
+}
+
+struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
+					  u64 start, unsigned long len,
+					  struct page *page0,
+					  gfp_t mask)
+{
+	unsigned long num_pages = num_extent_pages(start, len);
+	unsigned long i;
+	unsigned long index = start >> PAGE_CACHE_SHIFT;
+	struct extent_buffer *eb;
+	struct page *p;
+	struct address_space *mapping = tree->mapping;
+	int uptodate = 1;
+
+	eb = __alloc_extent_buffer(tree, start, len, mask);
+	if (!eb || IS_ERR(eb))
+		return NULL;
+
+	if (eb->flags & EXTENT_BUFFER_FILLED)
+		goto lru_add;
+
+	if (page0) {
+		eb->first_page = page0;
+		i = 1;
+		index++;
+		page_cache_get(page0);
+		mark_page_accessed(page0);
+		set_page_extent_mapped(page0);
+		WARN_ON(!PageUptodate(page0));
+		set_page_extent_head(page0, len);
+	} else {
+		i = 0;
+	}
+	for (; i < num_pages; i++, index++) {
+		p = find_or_create_page(mapping, index, mask | __GFP_HIGHMEM);
+		if (!p) {
+			WARN_ON(1);
+			goto fail;
+		}
+		set_page_extent_mapped(p);
+		mark_page_accessed(p);
+		if (i == 0) {
+			eb->first_page = p;
+			set_page_extent_head(p, len);
+		} else {
+			set_page_private(p, EXTENT_PAGE_PRIVATE);
+		}
+		if (!PageUptodate(p))
+			uptodate = 0;
+		unlock_page(p);
+	}
+	if (uptodate)
+		eb->flags |= EXTENT_UPTODATE;
+	eb->flags |= EXTENT_BUFFER_FILLED;
+
+lru_add:
+	spin_lock(&tree->lru_lock);
+	add_lru(tree, eb);
+	spin_unlock(&tree->lru_lock);
+	return eb;
+
+fail:
+	spin_lock(&tree->lru_lock);
+	list_del_init(&eb->lru);
+	spin_unlock(&tree->lru_lock);
+	if (!atomic_dec_and_test(&eb->refs))
+		return NULL;
+	for (index = 1; index < i; index++) {
+		page_cache_release(extent_buffer_page(eb, index));
+	}
+	if (i > 0)
+		page_cache_release(extent_buffer_page(eb, 0));
+	__free_extent_buffer(eb);
+	return NULL;
+}
+EXPORT_SYMBOL(alloc_extent_buffer);
+
+struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree,
+					 u64 start, unsigned long len,
+					  gfp_t mask)
+{
+	unsigned long num_pages = num_extent_pages(start, len);
+	unsigned long i;
+	unsigned long index = start >> PAGE_CACHE_SHIFT;
+	struct extent_buffer *eb;
+	struct page *p;
+	struct address_space *mapping = tree->mapping;
+	int uptodate = 1;
+
+	eb = __alloc_extent_buffer(tree, start, len, mask);
+	if (!eb || IS_ERR(eb))
+		return NULL;
+
+	if (eb->flags & EXTENT_BUFFER_FILLED)
+		goto lru_add;
+
+	for (i = 0; i < num_pages; i++, index++) {
+		p = find_lock_page(mapping, index);
+		if (!p) {
+			goto fail;
+		}
+		set_page_extent_mapped(p);
+		mark_page_accessed(p);
+
+		if (i == 0) {
+			eb->first_page = p;
+			set_page_extent_head(p, len);
+		} else {
+			set_page_private(p, EXTENT_PAGE_PRIVATE);
+		}
+
+		if (!PageUptodate(p))
+			uptodate = 0;
+		unlock_page(p);
+	}
+	if (uptodate)
+		eb->flags |= EXTENT_UPTODATE;
+	eb->flags |= EXTENT_BUFFER_FILLED;
+
+lru_add:
+	spin_lock(&tree->lru_lock);
+	add_lru(tree, eb);
+	spin_unlock(&tree->lru_lock);
+	return eb;
+fail:
+	spin_lock(&tree->lru_lock);
+	list_del_init(&eb->lru);
+	spin_unlock(&tree->lru_lock);
+	if (!atomic_dec_and_test(&eb->refs))
+		return NULL;
+	for (index = 1; index < i; index++) {
+		page_cache_release(extent_buffer_page(eb, index));
+	}
+	if (i > 0)
+		page_cache_release(extent_buffer_page(eb, 0));
+	__free_extent_buffer(eb);
+	return NULL;
+}
+EXPORT_SYMBOL(find_extent_buffer);
+
+void free_extent_buffer(struct extent_buffer *eb)
+{
+	unsigned long i;
+	unsigned long num_pages;
+
+	if (!eb)
+		return;
+
+	if (!atomic_dec_and_test(&eb->refs))
+		return;
+
+	WARN_ON(!list_empty(&eb->lru));
+	num_pages = num_extent_pages(eb->start, eb->len);
+
+	for (i = 1; i < num_pages; i++) {
+		page_cache_release(extent_buffer_page(eb, i));
+	}
+	page_cache_release(extent_buffer_page(eb, 0));
+	__free_extent_buffer(eb);
+}
+EXPORT_SYMBOL(free_extent_buffer);
+
+int clear_extent_buffer_dirty(struct extent_io_tree *tree,
+			      struct extent_buffer *eb)
+{
+	int set;
+	unsigned long i;
+	unsigned long num_pages;
+	struct page *page;
+
+	u64 start = eb->start;
+	u64 end = start + eb->len - 1;
+
+	set = clear_extent_dirty(tree, start, end, GFP_NOFS);
+	num_pages = num_extent_pages(eb->start, eb->len);
+
+	for (i = 0; i < num_pages; i++) {
+		page = extent_buffer_page(eb, i);
+		lock_page(page);
+		if (i == 0)
+			set_page_extent_head(page, eb->len);
+		else
+			set_page_private(page, EXTENT_PAGE_PRIVATE);
+
+		/*
+		 * if we're on the last page or the first page and the
+		 * block isn't aligned on a page boundary, do extra checks
+		 * to make sure we don't clean page that is partially dirty
+		 */
+		if ((i == 0 && (eb->start & (PAGE_CACHE_SIZE - 1))) ||
+		    ((i == num_pages - 1) &&
+		     ((eb->start + eb->len) & (PAGE_CACHE_SIZE - 1)))) {
+			start = (u64)page->index << PAGE_CACHE_SHIFT;
+			end  = start + PAGE_CACHE_SIZE - 1;
+			if (test_range_bit(tree, start, end,
+					   EXTENT_DIRTY, 0)) {
+				unlock_page(page);
+				continue;
+			}
+		}
+		clear_page_dirty_for_io(page);
+		write_lock_irq(&page->mapping->tree_lock);
+		if (!PageDirty(page)) {
+			radix_tree_tag_clear(&page->mapping->page_tree,
+						page_index(page),
+						PAGECACHE_TAG_DIRTY);
+		}
+		write_unlock_irq(&page->mapping->tree_lock);
+		unlock_page(page);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(clear_extent_buffer_dirty);
+
+int wait_on_extent_buffer_writeback(struct extent_io_tree *tree,
+				    struct extent_buffer *eb)
+{
+	return wait_on_extent_writeback(tree, eb->start,
+					eb->start + eb->len - 1);
+}
+EXPORT_SYMBOL(wait_on_extent_buffer_writeback);
+
+int set_extent_buffer_dirty(struct extent_io_tree *tree,
+			     struct extent_buffer *eb)
+{
+	unsigned long i;
+	unsigned long num_pages;
+
+	num_pages = num_extent_pages(eb->start, eb->len);
+	for (i = 0; i < num_pages; i++) {
+		struct page *page = extent_buffer_page(eb, i);
+		/* writepage may need to do something special for the
+		 * first page, we have to make sure page->private is
+		 * properly set.  releasepage may drop page->private
+		 * on us if the page isn't already dirty.
+		 */
+		if (i == 0) {
+			lock_page(page);
+			set_page_extent_head(page, eb->len);
+		} else if (PagePrivate(page) &&
+			   page->private != EXTENT_PAGE_PRIVATE) {
+			lock_page(page);
+			set_page_extent_mapped(page);
+			unlock_page(page);
+		}
+		__set_page_dirty_nobuffers(extent_buffer_page(eb, i));
+		if (i == 0)
+			unlock_page(page);
+	}
+	return set_extent_dirty(tree, eb->start,
+				eb->start + eb->len - 1, GFP_NOFS);
+}
+EXPORT_SYMBOL(set_extent_buffer_dirty);
+
+int set_extent_buffer_uptodate(struct extent_io_tree *tree,
+				struct extent_buffer *eb)
+{
+	unsigned long i;
+	struct page *page;
+	unsigned long num_pages;
+
+	num_pages = num_extent_pages(eb->start, eb->len);
+
+	set_extent_uptodate(tree, eb->start, eb->start + eb->len - 1,
+			    GFP_NOFS);
+	for (i = 0; i < num_pages; i++) {
+		page = extent_buffer_page(eb, i);
+		if ((i == 0 && (eb->start & (PAGE_CACHE_SIZE - 1))) ||
+		    ((i == num_pages - 1) &&
+		     ((eb->start + eb->len) & (PAGE_CACHE_SIZE - 1)))) {
+			check_page_uptodate(tree, page);
+			continue;
+		}
+		SetPageUptodate(page);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(set_extent_buffer_uptodate);
+
+int extent_buffer_uptodate(struct extent_io_tree *tree,
+			     struct extent_buffer *eb)
+{
+	if (eb->flags & EXTENT_UPTODATE)
+		return 1;
+	return test_range_bit(tree, eb->start, eb->start + eb->len - 1,
+			   EXTENT_UPTODATE, 1);
+}
+EXPORT_SYMBOL(extent_buffer_uptodate);
+
+int read_extent_buffer_pages(struct extent_io_tree *tree,
+			     struct extent_buffer *eb,
+			     u64 start,
+			     int wait)
+{
+	unsigned long i;
+	unsigned long start_i;
+	struct page *page;
+	int err;
+	int ret = 0;
+	unsigned long num_pages;
+
+	if (eb->flags & EXTENT_UPTODATE)
+		return 0;
+
+	if (0 && test_range_bit(tree, eb->start, eb->start + eb->len - 1,
+			   EXTENT_UPTODATE, 1)) {
+		return 0;
+	}
+
+	if (start) {
+		WARN_ON(start < eb->start);
+		start_i = (start >> PAGE_CACHE_SHIFT) -
+			(eb->start >> PAGE_CACHE_SHIFT);
+	} else {
+		start_i = 0;
+	}
+
+	num_pages = num_extent_pages(eb->start, eb->len);
+	for (i = start_i; i < num_pages; i++) {
+		page = extent_buffer_page(eb, i);
+		if (PageUptodate(page)) {
+			continue;
+		}
+		if (!wait) {
+			if (TestSetPageLocked(page)) {
+				continue;
+			}
+		} else {
+			lock_page(page);
+		}
+		if (!PageUptodate(page)) {
+			err = page->mapping->a_ops->readpage(NULL, page);
+			if (err) {
+				ret = err;
+			}
+		} else {
+			unlock_page(page);
+		}
+	}
+
+	if (ret || !wait) {
+		return ret;
+	}
+
+	for (i = start_i; i < num_pages; i++) {
+		page = extent_buffer_page(eb, i);
+		wait_on_page_locked(page);
+		if (!PageUptodate(page)) {
+			ret = -EIO;
+		}
+	}
+	if (!ret)
+		eb->flags |= EXTENT_UPTODATE;
+	return ret;
+}
+EXPORT_SYMBOL(read_extent_buffer_pages);
+
+void read_extent_buffer(struct extent_buffer *eb, void *dstv,
+			unsigned long start,
+			unsigned long len)
+{
+	size_t cur;
+	size_t offset;
+	struct page *page;
+	char *kaddr;
+	char *dst = (char *)dstv;
+	size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
+	unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
+	unsigned long num_pages = num_extent_pages(eb->start, eb->len);
+
+	WARN_ON(start > eb->len);
+	WARN_ON(start + len > eb->start + eb->len);
+
+	offset = (start_offset + start) & ((unsigned long)PAGE_CACHE_SIZE - 1);
+
+	while(len > 0) {
+		page = extent_buffer_page(eb, i);
+		if (!PageUptodate(page)) {
+			printk("page %lu not up to date i %lu, total %lu, len %lu\n", page->index, i, num_pages, eb->len);
+			WARN_ON(1);
+		}
+		WARN_ON(!PageUptodate(page));
+
+		cur = min(len, (PAGE_CACHE_SIZE - offset));
+		kaddr = kmap_atomic(page, KM_USER1);
+		memcpy(dst, kaddr + offset, cur);
+		kunmap_atomic(kaddr, KM_USER1);
+
+		dst += cur;
+		len -= cur;
+		offset = 0;
+		i++;
+	}
+}
+EXPORT_SYMBOL(read_extent_buffer);
+
+int map_private_extent_buffer(struct extent_buffer *eb, unsigned long start,
+			       unsigned long min_len, char **token, char **map,
+			       unsigned long *map_start,
+			       unsigned long *map_len, int km)
+{
+	size_t offset = start & (PAGE_CACHE_SIZE - 1);
+	char *kaddr;
+	struct page *p;
+	size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
+	unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
+	unsigned long end_i = (start_offset + start + min_len - 1) >>
+		PAGE_CACHE_SHIFT;
+
+	if (i != end_i)
+		return -EINVAL;
+
+	if (i == 0) {
+		offset = start_offset;
+		*map_start = 0;
+	} else {
+		offset = 0;
+		*map_start = ((u64)i << PAGE_CACHE_SHIFT) - start_offset;
+	}
+	if (start + min_len > eb->len) {
+printk("bad mapping eb start %Lu len %lu, wanted %lu %lu\n", eb->start, eb->len, start, min_len);
+		WARN_ON(1);
+	}
+
+	p = extent_buffer_page(eb, i);
+	WARN_ON(!PageUptodate(p));
+	kaddr = kmap_atomic(p, km);
+	*token = kaddr;
+	*map = kaddr + offset;
+	*map_len = PAGE_CACHE_SIZE - offset;
+	return 0;
+}
+EXPORT_SYMBOL(map_private_extent_buffer);
+
+int map_extent_buffer(struct extent_buffer *eb, unsigned long start,
+		      unsigned long min_len,
+		      char **token, char **map,
+		      unsigned long *map_start,
+		      unsigned long *map_len, int km)
+{
+	int err;
+	int save = 0;
+	if (eb->map_token) {
+		unmap_extent_buffer(eb, eb->map_token, km);
+		eb->map_token = NULL;
+		save = 1;
+	}
+	err = map_private_extent_buffer(eb, start, min_len, token, map,
+				       map_start, map_len, km);
+	if (!err && save) {
+		eb->map_token = *token;
+		eb->kaddr = *map;
+		eb->map_start = *map_start;
+		eb->map_len = *map_len;
+	}
+	return err;
+}
+EXPORT_SYMBOL(map_extent_buffer);
+
+void unmap_extent_buffer(struct extent_buffer *eb, char *token, int km)
+{
+	kunmap_atomic(token, km);
+}
+EXPORT_SYMBOL(unmap_extent_buffer);
+
+int memcmp_extent_buffer(struct extent_buffer *eb, const void *ptrv,
+			  unsigned long start,
+			  unsigned long len)
+{
+	size_t cur;
+	size_t offset;
+	struct page *page;
+	char *kaddr;
+	char *ptr = (char *)ptrv;
+	size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
+	unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
+	int ret = 0;
+
+	WARN_ON(start > eb->len);
+	WARN_ON(start + len > eb->start + eb->len);
+
+	offset = (start_offset + start) & ((unsigned long)PAGE_CACHE_SIZE - 1);
+
+	while(len > 0) {
+		page = extent_buffer_page(eb, i);
+		WARN_ON(!PageUptodate(page));
+
+		cur = min(len, (PAGE_CACHE_SIZE - offset));
+
+		kaddr = kmap_atomic(page, KM_USER0);
+		ret = memcmp(ptr, kaddr + offset, cur);
+		kunmap_atomic(kaddr, KM_USER0);
+		if (ret)
+			break;
+
+		ptr += cur;
+		len -= cur;
+		offset = 0;
+		i++;
+	}
+	return ret;
+}
+EXPORT_SYMBOL(memcmp_extent_buffer);
+
+void write_extent_buffer(struct extent_buffer *eb, const void *srcv,
+			 unsigned long start, unsigned long len)
+{
+	size_t cur;
+	size_t offset;
+	struct page *page;
+	char *kaddr;
+	char *src = (char *)srcv;
+	size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
+	unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
+
+	WARN_ON(start > eb->len);
+	WARN_ON(start + len > eb->start + eb->len);
+
+	offset = (start_offset + start) & ((unsigned long)PAGE_CACHE_SIZE - 1);
+
+	while(len > 0) {
+		page = extent_buffer_page(eb, i);
+		WARN_ON(!PageUptodate(page));
+
+		cur = min(len, PAGE_CACHE_SIZE - offset);
+		kaddr = kmap_atomic(page, KM_USER1);
+		memcpy(kaddr + offset, src, cur);
+		kunmap_atomic(kaddr, KM_USER1);
+
+		src += cur;
+		len -= cur;
+		offset = 0;
+		i++;
+	}
+}
+EXPORT_SYMBOL(write_extent_buffer);
+
+void memset_extent_buffer(struct extent_buffer *eb, char c,
+			  unsigned long start, unsigned long len)
+{
+	size_t cur;
+	size_t offset;
+	struct page *page;
+	char *kaddr;
+	size_t start_offset = eb->start & ((u64)PAGE_CACHE_SIZE - 1);
+	unsigned long i = (start_offset + start) >> PAGE_CACHE_SHIFT;
+
+	WARN_ON(start > eb->len);
+	WARN_ON(start + len > eb->start + eb->len);
+
+	offset = (start_offset + start) & ((unsigned long)PAGE_CACHE_SIZE - 1);
+
+	while(len > 0) {
+		page = extent_buffer_page(eb, i);
+		WARN_ON(!PageUptodate(page));
+
+		cur = min(len, PAGE_CACHE_SIZE - offset);
+		kaddr = kmap_atomic(page, KM_USER0);
+		memset(kaddr + offset, c, cur);
+		kunmap_atomic(kaddr, KM_USER0);
+
+		len -= cur;
+		offset = 0;
+		i++;
+	}
+}
+EXPORT_SYMBOL(memset_extent_buffer);
+
+void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src,
+			unsigned long dst_offset, unsigned long src_offset,
+			unsigned long len)
+{
+	u64 dst_len = dst->len;
+	size_t cur;
+	size_t offset;
+	struct page *page;
+	char *kaddr;
+	size_t start_offset = dst->start & ((u64)PAGE_CACHE_SIZE - 1);
+	unsigned long i = (start_offset + dst_offset) >> PAGE_CACHE_SHIFT;
+
+	WARN_ON(src->len != dst_len);
+
+	offset = (start_offset + dst_offset) &
+		((unsigned long)PAGE_CACHE_SIZE - 1);
+
+	while(len > 0) {
+		page = extent_buffer_page(dst, i);
+		WARN_ON(!PageUptodate(page));
+
+		cur = min(len, (unsigned long)(PAGE_CACHE_SIZE - offset));
+
+		kaddr = kmap_atomic(page, KM_USER0);
+		read_extent_buffer(src, kaddr + offset, src_offset, cur);
+		kunmap_atomic(kaddr, KM_USER0);
+
+		src_offset += cur;
+		len -= cur;
+		offset = 0;
+		i++;
+	}
+}
+EXPORT_SYMBOL(copy_extent_buffer);
+
+static void move_pages(struct page *dst_page, struct page *src_page,
+		       unsigned long dst_off, unsigned long src_off,
+		       unsigned long len)
+{
+	char *dst_kaddr = kmap_atomic(dst_page, KM_USER0);
+	if (dst_page == src_page) {
+		memmove(dst_kaddr + dst_off, dst_kaddr + src_off, len);
+	} else {
+		char *src_kaddr = kmap_atomic(src_page, KM_USER1);
+		char *p = dst_kaddr + dst_off + len;
+		char *s = src_kaddr + src_off + len;
+
+		while (len--)
+			*--p = *--s;
+
+		kunmap_atomic(src_kaddr, KM_USER1);
+	}
+	kunmap_atomic(dst_kaddr, KM_USER0);
+}
+
+static void copy_pages(struct page *dst_page, struct page *src_page,
+		       unsigned long dst_off, unsigned long src_off,
+		       unsigned long len)
+{
+	char *dst_kaddr = kmap_atomic(dst_page, KM_USER0);
+	char *src_kaddr;
+
+	if (dst_page != src_page)
+		src_kaddr = kmap_atomic(src_page, KM_USER1);
+	else
+		src_kaddr = dst_kaddr;
+
+	memcpy(dst_kaddr + dst_off, src_kaddr + src_off, len);
+	kunmap_atomic(dst_kaddr, KM_USER0);
+	if (dst_page != src_page)
+		kunmap_atomic(src_kaddr, KM_USER1);
+}
+
+void memcpy_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
+			   unsigned long src_offset, unsigned long len)
+{
+	size_t cur;
+	size_t dst_off_in_page;
+	size_t src_off_in_page;
+	size_t start_offset = dst->start & ((u64)PAGE_CACHE_SIZE - 1);
+	unsigned long dst_i;
+	unsigned long src_i;
+
+	if (src_offset + len > dst->len) {
+		printk("memmove bogus src_offset %lu move len %lu len %lu\n",
+		       src_offset, len, dst->len);
+		BUG_ON(1);
+	}
+	if (dst_offset + len > dst->len) {
+		printk("memmove bogus dst_offset %lu move len %lu len %lu\n",
+		       dst_offset, len, dst->len);
+		BUG_ON(1);
+	}
+
+	while(len > 0) {
+		dst_off_in_page = (start_offset + dst_offset) &
+			((unsigned long)PAGE_CACHE_SIZE - 1);
+		src_off_in_page = (start_offset + src_offset) &
+			((unsigned long)PAGE_CACHE_SIZE - 1);
+
+		dst_i = (start_offset + dst_offset) >> PAGE_CACHE_SHIFT;
+		src_i = (start_offset + src_offset) >> PAGE_CACHE_SHIFT;
+
+		cur = min(len, (unsigned long)(PAGE_CACHE_SIZE -
+					       src_off_in_page));
+		cur = min_t(unsigned long, cur,
+			(unsigned long)(PAGE_CACHE_SIZE - dst_off_in_page));
+
+		copy_pages(extent_buffer_page(dst, dst_i),
+			   extent_buffer_page(dst, src_i),
+			   dst_off_in_page, src_off_in_page, cur);
+
+		src_offset += cur;
+		dst_offset += cur;
+		len -= cur;
+	}
+}
+EXPORT_SYMBOL(memcpy_extent_buffer);
+
+void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
+			   unsigned long src_offset, unsigned long len)
+{
+	size_t cur;
+	size_t dst_off_in_page;
+	size_t src_off_in_page;
+	unsigned long dst_end = dst_offset + len - 1;
+	unsigned long src_end = src_offset + len - 1;
+	size_t start_offset = dst->start & ((u64)PAGE_CACHE_SIZE - 1);
+	unsigned long dst_i;
+	unsigned long src_i;
+
+	if (src_offset + len > dst->len) {
+		printk("memmove bogus src_offset %lu move len %lu len %lu\n",
+		       src_offset, len, dst->len);
+		BUG_ON(1);
+	}
+	if (dst_offset + len > dst->len) {
+		printk("memmove bogus dst_offset %lu move len %lu len %lu\n",
+		       dst_offset, len, dst->len);
+		BUG_ON(1);
+	}
+	if (dst_offset < src_offset) {
+		memcpy_extent_buffer(dst, dst_offset, src_offset, len);
+		return;
+	}
+	while(len > 0) {
+		dst_i = (start_offset + dst_end) >> PAGE_CACHE_SHIFT;
+		src_i = (start_offset + src_end) >> PAGE_CACHE_SHIFT;
+
+		dst_off_in_page = (start_offset + dst_end) &
+			((unsigned long)PAGE_CACHE_SIZE - 1);
+		src_off_in_page = (start_offset + src_end) &
+			((unsigned long)PAGE_CACHE_SIZE - 1);
+
+		cur = min_t(unsigned long, len, src_off_in_page + 1);
+		cur = min(cur, dst_off_in_page + 1);
+		move_pages(extent_buffer_page(dst, dst_i),
+			   extent_buffer_page(dst, src_i),
+			   dst_off_in_page - cur + 1,
+			   src_off_in_page - cur + 1, cur);
+
+		dst_end -= cur;
+		src_end -= cur;
+		len -= cur;
+	}
+}
+EXPORT_SYMBOL(memmove_extent_buffer);