Btrfs: Extent based page cache code. This uses an rbtree of extents and tests

instead of buffer heads.

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

9 files changed, 2203 insertions, 669 deletions

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 9321438..ea7a228 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -4,7 +4,8 @@ ifneq ($(KERNELRELEASE),)
 obj-m  := btrfs.o
 btrfs-y := super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
 	   hash.o file-item.o inode-item.o inode-map.o disk-io.o \
-	   transaction.o bit-radix.o inode.o file.o tree-defrag.o
+	   transaction.o bit-radix.o inode.o file.o tree-defrag.o \
+	   extent_map.o
 
 #btrfs-y := ctree.o disk-io.o radix-tree.o extent-tree.o print-tree.o \
 #	  root-tree.o dir-item.o hash.o file-item.o inode-item.o \
diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index f446f16..d1d5af4 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -19,11 +19,14 @@
 #ifndef __BTRFS_I__
 #define __BTRFS_I__
 
+#include "extent_map.h"
+
 /* in memory btrfs inode */
 struct btrfs_inode {
 	struct btrfs_root *root;
 	struct btrfs_block_group_cache *block_group;
 	struct btrfs_key location;
+	struct extent_map_tree extent_tree;
 	struct inode vfs_inode;
 
 	/*
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index c7f5161..947f061 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1176,7 +1176,14 @@ int btrfs_commit_write(struct file *file, struct page *page,
 		       unsigned from, unsigned to);
 int btrfs_get_block(struct inode *inode, sector_t iblock,
 		    struct buffer_head *result, int create);
+struct extent_map *btrfs_get_extent(struct inode *inode, struct page *page,
+				    size_t page_offset, u64 start, u64 end,
+				    int create);
+int btrfs_update_inode(struct btrfs_trans_handle *trans,
+			      struct btrfs_root *root,
+			      struct inode *inode);
 /* file.c */
+int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end);
 extern struct file_operations btrfs_file_operations;
 int btrfs_drop_extents(struct btrfs_trans_handle *trans,
 		       struct btrfs_root *root, struct inode *inode,
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 81fd18c..5261733 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -77,7 +77,6 @@ int btrfs_insert_dev_radix(struct btrfs_root *root,
 			   u64 num_blocks);
 int btrfs_map_bh_to_logical(struct btrfs_root *root, struct buffer_head *bh,
 			     u64 logical);
-int btrfs_releasepage(struct page *page, gfp_t flags);
 void btrfs_btree_balance_dirty(struct btrfs_root *root);
 int btrfs_free_fs_root(struct btrfs_fs_info *fs_info, struct btrfs_root *root);
 void btrfs_mark_buffer_dirty(struct buffer_head *bh);
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
new file mode 100644
index 0000000..d378edf
--- /dev/null
+++ b/fs/btrfs/extent_map.c
@@ -0,0 +1,1656 @@
+#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 "extent_map.h"
+
+static struct kmem_cache *extent_map_cache;
+static struct kmem_cache *extent_state_cache;
+
+struct tree_entry {
+	u64 start;
+	u64 end;
+	int in_tree;
+	struct rb_node rb_node;
+};
+
+/* bits for the extent state */
+#define EXTENT_DIRTY 1
+#define EXTENT_WRITEBACK (1 << 1)
+#define EXTENT_UPTODATE (1 << 2)
+#define EXTENT_LOCKED (1 << 3)
+#define EXTENT_NEW (1 << 4)
+#define EXTENT_DELALLOC (1 << 5)
+
+#define EXTENT_IOBITS (EXTENT_LOCKED | EXTENT_WRITEBACK)
+
+static LIST_HEAD(all_states);
+spinlock_t state_lock = SPIN_LOCK_UNLOCKED;
+
+void __init extent_map_init(void)
+{
+	extent_map_cache = kmem_cache_create("extent_map",
+					    sizeof(struct extent_map), 0,
+					    SLAB_RECLAIM_ACCOUNT |
+					    SLAB_DESTROY_BY_RCU,
+					    NULL);
+	extent_state_cache = kmem_cache_create("extent_state",
+					    sizeof(struct extent_state), 0,
+					    SLAB_RECLAIM_ACCOUNT |
+					    SLAB_DESTROY_BY_RCU,
+					    NULL);
+}
+
+void __exit extent_map_exit(void)
+{
+	while(!list_empty(&all_states)) {
+		struct extent_state *state;
+		struct list_head *cur = all_states.next;
+		state = list_entry(cur, struct extent_state, list);
+		printk("found leaked state %Lu %Lu state %d in_tree %d\n",
+		       state->start, state->end, state->state, state->in_tree);
+		list_del(&state->list);
+		kfree(state);
+	}
+	if (extent_map_cache)
+		kmem_cache_destroy(extent_map_cache);
+	if (extent_state_cache)
+		kmem_cache_destroy(extent_state_cache);
+}
+
+void extent_map_tree_init(struct extent_map_tree *tree,
+			  struct address_space *mapping, gfp_t mask)
+{
+	tree->map.rb_node = NULL;
+	tree->state.rb_node = NULL;
+	rwlock_init(&tree->lock);
+	tree->mapping = mapping;
+}
+EXPORT_SYMBOL(extent_map_tree_init);
+
+struct extent_map *alloc_extent_map(gfp_t mask)
+{
+	struct extent_map *em;
+	em = kmem_cache_alloc(extent_map_cache, mask);
+	if (!em || IS_ERR(em))
+		return em;
+	em->in_tree = 0;
+	atomic_set(&em->refs, 1);
+	return em;
+}
+EXPORT_SYMBOL(alloc_extent_map);
+
+void free_extent_map(struct extent_map *em)
+{
+	if (atomic_dec_and_test(&em->refs)) {
+		WARN_ON(em->in_tree);
+		kmem_cache_free(extent_map_cache, em);
+	}
+}
+EXPORT_SYMBOL(free_extent_map);
+
+
+struct extent_state *alloc_extent_state(gfp_t mask)
+{
+	struct extent_state *state;
+	state = kmem_cache_alloc(extent_state_cache, mask);
+	if (!state || IS_ERR(state))
+		return state;
+	state->state = 0;
+	state->in_tree = 0;
+	atomic_set(&state->refs, 1);
+	init_waitqueue_head(&state->wq);
+	spin_lock_irq(&state_lock);
+	list_add(&state->list, &all_states);
+	spin_unlock_irq(&state_lock);
+	return state;
+}
+EXPORT_SYMBOL(alloc_extent_state);
+
+void free_extent_state(struct extent_state *state)
+{
+	if (atomic_dec_and_test(&state->refs)) {
+		WARN_ON(state->in_tree);
+		spin_lock_irq(&state_lock);
+		list_del_init(&state->list);
+		spin_unlock_irq(&state_lock);
+		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 * n = root->rb_node;
+	struct rb_node *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)
+		return NULL;
+	while(prev && offset > prev_entry->end) {
+		prev = rb_next(prev);
+		prev_entry = rb_entry(prev, struct tree_entry, rb_node);
+	}
+	*prev_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);
+	if (!ret)
+		return prev;
+	return ret;
+}
+
+static int tree_delete(struct rb_root *root, u64 offset)
+{
+	struct rb_node *node;
+	struct tree_entry *entry;
+
+	node = __tree_search(root, offset, NULL);
+	if (!node)
+		return -ENOENT;
+	entry = rb_entry(node, struct tree_entry, rb_node);
+	entry->in_tree = 0;
+	rb_erase(node, root);
+	return 0;
+}
+
+/*
+ * add_extent_mapping tries a simple backward merge with existing
+ * mappings.  The extent_map struct passed in will be inserted into
+ * the tree directly (no copies made, just a reference taken).
+ */
+int add_extent_mapping(struct extent_map_tree *tree,
+		       struct extent_map *em)
+{
+	int ret = 0;
+	struct extent_map *prev = NULL;
+	struct rb_node *rb;
+
+	write_lock_irq(&tree->lock);
+	rb = tree_insert(&tree->map, em->end, &em->rb_node);
+	if (rb) {
+		prev = rb_entry(rb, struct extent_map, rb_node);
+		printk("found extent map %Lu %Lu on insert of %Lu %Lu\n", prev->start, prev->end, em->start, em->end);
+		ret = -EEXIST;
+		goto out;
+	}
+	atomic_inc(&em->refs);
+	if (em->start != 0) {
+		rb = rb_prev(&em->rb_node);
+		if (rb)
+			prev = rb_entry(rb, struct extent_map, rb_node);
+		if (prev && prev->end + 1 == em->start &&
+		    ((em->block_start == 0 && prev->block_start == 0) ||
+			     (em->block_start == prev->block_end + 1))) {
+			em->start = prev->start;
+			em->block_start = prev->block_start;
+			rb_erase(&prev->rb_node, &tree->map);
+			prev->in_tree = 0;
+			free_extent_map(prev);
+		}
+	 }
+out:
+	write_unlock_irq(&tree->lock);
+	return ret;
+}
+EXPORT_SYMBOL(add_extent_mapping);
+
+/*
+ * lookup_extent_mapping returns the first extent_map struct in the
+ * tree that intersects the [start, end] (inclusive) range.  There may
+ * be additional objects in the tree that intersect, so check the object
+ * returned carefully to make sure you don't need additional lookups.
+ */
+struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
+					 u64 start, u64 end)
+{
+	struct extent_map *em;
+	struct rb_node *rb_node;
+
+	read_lock_irq(&tree->lock);
+	rb_node = tree_search(&tree->map, start);
+	if (!rb_node) {
+		em = NULL;
+		goto out;
+	}
+	if (IS_ERR(rb_node)) {
+		em = ERR_PTR(PTR_ERR(rb_node));
+		goto out;
+	}
+	em = rb_entry(rb_node, struct extent_map, rb_node);
+	if (em->end < start || em->start > end) {
+		em = NULL;
+		goto out;
+	}
+	atomic_inc(&em->refs);
+out:
+	read_unlock_irq(&tree->lock);
+	return em;
+}
+EXPORT_SYMBOL(lookup_extent_mapping);
+
+/*
+ * removes an extent_map struct from the tree.  No reference counts are
+ * dropped, and no checks are done to  see if the range is in use
+ */
+int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em)
+{
+	int ret;
+
+	write_lock_irq(&tree->lock);
+	ret = tree_delete(&tree->map, em->end);
+	write_unlock_irq(&tree->lock);
+	return ret;
+}
+EXPORT_SYMBOL(remove_extent_mapping);
+
+/*
+ * 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_map_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_map_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);
+	}
+	state->state |= bits;
+	state->start = start;
+	state->end = end;
+	if ((end & 4095) == 0) {
+		printk("insert state %Lu %Lu strange end\n", start, end);
+		WARN_ON(1);
+	}
+	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_map_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;
+	if ((prealloc->end & 4095) == 0) {
+		printk("insert state %Lu %Lu strange end\n", prealloc->start,
+		       prealloc->end);
+		WARN_ON(1);
+	}
+	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_map_tree *tree,
+			    struct extent_state *state, int bits, int wake,
+			    int delete)
+{
+	int ret = state->state & bits;
+	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_map_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;
+	int err;
+	int set = 0;
+
+again:
+	if (!prealloc && (mask & __GFP_WAIT)) {
+		prealloc = alloc_extent_state(mask);
+		if (!prealloc)
+			return -ENOMEM;
+	}
+
+	write_lock_irq(&tree->lock);
+	/*
+	 * 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_irq(&tree->lock);
+	if (prealloc)
+		free_extent_state(prealloc);
+
+	return set;
+
+search_again:
+	if (start >= end)
+		goto out;
+	write_unlock_irq(&tree->lock);
+	if (mask & __GFP_WAIT)
+		cond_resched();
+	goto again;
+}
+EXPORT_SYMBOL(clear_extent_bit);
+
+static int wait_on_state(struct extent_map_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_map_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);
+
+/*
+ * 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_map_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;
+	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_irq(&tree->lock);
+	/*
+	 * 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;
+		}
+		state->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) {
+			state->state |= bits;
+			start = state->end + 1;
+			merge_state(tree, state);
+		} else {
+			start = state->start;
+		}
+		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);
+
+		prealloc->state |= bits;
+		merge_state(tree, prealloc);
+		prealloc = NULL;
+		goto out;
+	}
+
+	/*
+	 * | ---- 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;
+	}
+	goto search_again;
+
+out:
+	write_unlock_irq(&tree->lock);
+	if (prealloc)
+		free_extent_state(prealloc);
+
+	return err;
+
+search_again:
+	if (start > end)
+		goto out;
+	write_unlock_irq(&tree->lock);
+	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_map_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 clear_extent_dirty(struct extent_map_tree *tree, u64 start, u64 end,
+		       gfp_t mask)
+{
+	return clear_extent_bit(tree, start, end, EXTENT_DIRTY, 0, 0, mask);
+}
+EXPORT_SYMBOL(clear_extent_dirty);
+
+int set_extent_new(struct extent_map_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_map_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_map_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_map_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_map_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_map_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_map_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_map_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_map_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_map_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_map_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);
+
+/*
+ * helper function to lock both pages and extents in the tree.
+ * pages must be locked first.
+ */
+int lock_range(struct extent_map_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_map_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);
+
+/*
+ * 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.
+ */
+static int test_range_bit(struct extent_map_tree *tree, u64 start, u64 end,
+			  int bits, int filled)
+{
+	struct extent_state *state = NULL;
+	struct rb_node *node;
+	int bitset = 0;
+
+	read_lock_irq(&tree->lock);
+	node = tree_search(&tree->state, start);
+	while (node && start <= end) {
+		state = rb_entry(node, struct extent_state, rb_node);
+		if (state->start > end)
+			break;
+
+		if (filled && state->start > start) {
+			bitset = 0;
+			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);
+	}
+	read_unlock_irq(&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_map_tree *tree,
+			       struct page *page)
+{
+	u64 start = 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_map_tree *tree,
+			     struct page *page)
+{
+	u64 start = 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_map_tree *tree,
+			     struct page *page)
+{
+	u64 start = 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.
+ */
+static int end_bio_extent_writepage(struct bio *bio,
+				   unsigned int bytes_done, int err)
+{
+	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+	struct extent_map_tree *tree = bio->bi_private;
+	u64 start;
+	u64 end;
+	int whole_page;
+
+	if (bio->bi_size)
+		return 1;
+
+	do {
+		struct page *page = bvec->bv_page;
+		start = (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);
+	} while (bvec >= bio->bi_io_vec);
+
+	bio_put(bio);
+	return 0;
+}
+
+/*
+ * 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 int end_bio_extent_readpage(struct bio *bio,
+				   unsigned int bytes_done, int err)
+{
+	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+	struct extent_map_tree *tree = bio->bi_private;
+	u64 start;
+	u64 end;
+	int whole_page;
+
+	if (bio->bi_size)
+		return 1;
+
+	do {
+		struct page *page = bvec->bv_page;
+		start = (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) {
+			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);
+	return 0;
+}
+
+/*
+ * 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.
+ */
+static int end_bio_extent_preparewrite(struct bio *bio,
+				       unsigned int bytes_done, int err)
+{
+	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
+	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+	struct extent_map_tree *tree = bio->bi_private;
+	u64 start;
+	u64 end;
+
+	if (bio->bi_size)
+		return 1;
+
+	do {
+		struct page *page = bvec->bv_page;
+		start = (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);
+	return 0;
+}
+
+static int submit_extent_page(int rw, struct extent_map_tree *tree,
+			      struct page *page, sector_t sector,
+			      size_t size, unsigned long offset,
+			      struct block_device *bdev,
+			      bio_end_io_t end_io_func)
+{
+	struct bio *bio;
+	int ret = 0;
+
+	bio = bio_alloc(GFP_NOIO, 1);
+
+	bio->bi_sector = sector;
+	bio->bi_bdev = bdev;
+	bio->bi_io_vec[0].bv_page = page;
+	bio->bi_io_vec[0].bv_len = size;
+	bio->bi_io_vec[0].bv_offset = offset;
+
+	bio->bi_vcnt = 1;
+	bio->bi_idx = 0;
+	bio->bi_size = size;
+
+	bio->bi_end_io = end_io_func;
+	bio->bi_private = tree;
+
+	bio_get(bio);
+	submit_bio(rw, bio);
+
+	if (bio_flagged(bio, BIO_EOPNOTSUPP))
+		ret = -EOPNOTSUPP;
+
+	bio_put(bio);
+	return ret;
+}
+
+/*
+ * 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)
+ */
+int extent_read_full_page(struct extent_map_tree *tree, struct page *page,
+			  get_extent_t *get_extent)
+{
+	struct inode *inode = page->mapping->host;
+	u64 start = 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;
+
+	if (!PagePrivate(page)) {
+		SetPagePrivate(page);
+		set_page_private(page, 1);
+		page_cache_get(page);
+	}
+
+	end = page_end;
+	lock_extent(tree, start, end, GFP_NOFS);
+
+	while (cur <= end) {
+		if (cur >= last_byte) {
+			iosize = PAGE_CACHE_SIZE - page_offset;
+			zero_user_page(page, page_offset, iosize, 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, 0);
+		if (IS_ERR(em) || !em) {
+			SetPageError(page);
+			unlock_extent(tree, cur, end, GFP_NOFS);
+			break;
+		}
+
+		extent_offset = cur - em->start;
+		BUG_ON(em->end < cur);
+		BUG_ON(end < cur);
+
+		iosize = min(em->end - cur, end - cur) + 1;
+		cur_end = min(em->end, 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 == 0) {
+			zero_user_page(page, page_offset, iosize, 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 = submit_extent_page(READ, tree, page,
+					 sector, iosize, page_offset, bdev,
+					 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;
+}
+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
+ */
+int extent_write_full_page(struct extent_map_tree *tree, struct page *page,
+			  get_extent_t *get_extent,
+			  struct writeback_control *wbc)
+{
+	struct inode *inode = page->mapping->host;
+	u64 start = 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;
+	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;
+	loff_t i_size = i_size_read(inode);
+	unsigned long end_index = i_size >> PAGE_CACHE_SHIFT;
+
+	if (page->index > end_index) {
+		clear_extent_dirty(tree, start, page_end, GFP_NOFS);
+		unlock_page(page);
+		return 0;
+	}
+
+	if (page->index == end_index) {
+		size_t offset = i_size & (PAGE_CACHE_SIZE - 1);
+		zero_user_page(page, offset,
+			       PAGE_CACHE_SIZE - offset, KM_USER0);
+	}
+
+	if (!PagePrivate(page)) {
+		SetPagePrivate(page);
+		set_page_private(page, 1);
+		page_cache_get(page);
+	}
+
+	end = page_end;
+	lock_extent(tree, start, page_end, GFP_NOFS);
+
+	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 = get_extent(inode, page, page_offset, cur, end, 1);
+		if (IS_ERR(em) || !em) {
+			SetPageError(page);
+			break;
+		}
+
+		extent_offset = cur - em->start;
+		BUG_ON(em->end < cur);
+		BUG_ON(end < cur);
+		iosize = min(em->end - 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 == 0 || 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);
+		set_range_writeback(tree, cur, cur + iosize - 1);
+		ret = submit_extent_page(WRITE, tree, page,
+					 sector, iosize, page_offset, bdev,
+					 end_bio_extent_writepage);
+		if (ret)
+			SetPageError(page);
+		cur = cur + iosize;
+		page_offset += iosize;
+		nr++;
+	}
+done:
+	WARN_ON(test_range_bit(tree, start, page_end, EXTENT_DIRTY, 0));
+	unlock_extent(tree, start, page_end, GFP_NOFS);
+	unlock_page(page);
+	return 0;
+}
+EXPORT_SYMBOL(extent_write_full_page);
+
+/*
+ * 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_map_tree *tree,
+			  struct page *page, unsigned long offset)
+{
+	u64 start = (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,
+			 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_map_tree *tree,
+			struct inode *inode, struct page *page,
+			unsigned from, unsigned to)
+{
+	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
+
+	if (!PagePrivate(page)) {
+		SetPagePrivate(page);
+		set_page_private(page, 1);
+		page_cache_get(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_map_tree *tree,
+			 struct inode *inode, struct page *page,
+			 unsigned from, unsigned to, get_extent_t *get_extent)
+{
+	u64 page_start = 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;
+
+	if (!PagePrivate(page)) {
+		SetPagePrivate(page);
+		set_page_private(page, 1);
+		page_cache_get(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, 1);
+		if (IS_ERR(em) || !em) {
+			goto err;
+		}
+		cur_end = min(block_end, em->end);
+		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 (!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 - 1) &
+				~((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,
+					 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 *tree, struct page *page)
+{
+	struct extent_map *em;
+	u64 start = page->index << PAGE_CACHE_SHIFT;
+	u64 end = start + PAGE_CACHE_SIZE - 1;
+	u64 orig_start = start;
+
+	while (start <= end) {
+		em = lookup_extent_mapping(tree, start, end);
+		if (!em || IS_ERR(em))
+			break;
+		if (test_range_bit(tree, em->start, em->end,
+				   EXTENT_LOCKED, 0)) {
+			free_extent_map(em);
+			start = em->end + 1;
+printk("range still locked %Lu %Lu\n", em->start, em->end);
+			break;
+		}
+		remove_extent_mapping(tree, em);
+		start = em->end + 1;
+		/* once for the rb tree */
+		free_extent_map(em);
+		/* once for us */
+		free_extent_map(em);
+	}
+	WARN_ON(test_range_bit(tree, orig_start, end, EXTENT_WRITEBACK, 0));
+	clear_extent_bit(tree, orig_start, end, EXTENT_UPTODATE,
+			 1, 1, GFP_NOFS);
+	return 1;
+}
+EXPORT_SYMBOL(try_release_extent_mapping);
+
diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
new file mode 100644
index 0000000..108944a
--- /dev/null
+++ b/fs/btrfs/extent_map.h
@@ -0,0 +1,89 @@
+#ifndef __EXTENTMAP__
+#define __EXTENTMAP__
+
+#include <linux/rbtree.h>
+
+#define EXTENT_MAP_INLINE (u64)-2
+#define EXTENT_MAP_DELALLOC (u64)-1
+
+struct extent_map_tree {
+	struct rb_root map;
+	struct rb_root state;
+	struct address_space *mapping;
+	rwlock_t lock;
+};
+
+/* note, this must start with the same fields as fs/extent_map.c:tree_entry */
+struct extent_map {
+	u64 start;
+	u64 end; /* inclusive */
+	int in_tree;
+	struct rb_node rb_node;
+	/* block_start and block_end are in bytes */
+	u64 block_start;
+	u64 block_end; /* inclusive */
+	struct block_device *bdev;
+	atomic_t refs;
+};
+
+/* note, this must start with the same fields as fs/extent_map.c:tree_entry */
+struct extent_state {
+	u64 start;
+	u64 end; /* inclusive */
+	int in_tree;
+	struct rb_node rb_node;
+	wait_queue_head_t wq;
+	atomic_t refs;
+	unsigned long state;
+	struct list_head list;
+};
+
+struct extent_buffer {
+	u64 start;
+	u64 end; /* inclusive */
+	char *addr;
+	struct page *pages[];
+};
+
+typedef struct extent_map *(get_extent_t)(struct inode *inode,
+					  struct page *page,
+					  size_t page_offset,
+					  u64 start, u64 end,
+					  int create);
+
+void extent_map_tree_init(struct extent_map_tree *tree,
+			  struct address_space *mapping, gfp_t mask);
+struct extent_map *lookup_extent_mapping(struct extent_map_tree *tree,
+					 u64 start, u64 end);
+int add_extent_mapping(struct extent_map_tree *tree,
+		       struct extent_map *em);
+int remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em);
+int try_release_extent_mapping(struct extent_map_tree *tree, struct page *page);
+int lock_extent(struct extent_map_tree *tree, u64 start, u64 end, gfp_t mask);
+int unlock_extent(struct extent_map_tree *tree, u64 start, u64 end, gfp_t mask);
+struct extent_map *alloc_extent_map(gfp_t mask);
+void free_extent_map(struct extent_map *em);
+int extent_read_full_page(struct extent_map_tree *tree, struct page *page,
+			  get_extent_t *get_extent);
+void __init extent_map_init(void);
+void __exit extent_map_exit(void);
+int extent_clean_all_trees(struct extent_map_tree *tree);
+int set_extent_uptodate(struct extent_map_tree *tree, u64 start, u64 end,
+			gfp_t mask);
+int set_extent_new(struct extent_map_tree *tree, u64 start, u64 end,
+		   gfp_t mask);
+int set_extent_dirty(struct extent_map_tree *tree, u64 start, u64 end,
+		     gfp_t mask);
+int extent_invalidatepage(struct extent_map_tree *tree,
+			  struct page *page, unsigned long offset);
+int extent_write_full_page(struct extent_map_tree *tree, struct page *page,
+			  get_extent_t *get_extent,
+			  struct writeback_control *wbc);
+int extent_prepare_write(struct extent_map_tree *tree,
+			 struct inode *inode, struct page *page,
+			 unsigned from, unsigned to, get_extent_t *get_extent);
+int extent_commit_write(struct extent_map_tree *tree,
+			struct inode *inode, struct page *page,
+			unsigned from, unsigned to);
+int set_range_dirty(struct extent_map_tree *tree, u64 start, u64 end);
+#endif
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 6933ab1..71a4818 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -81,14 +81,14 @@ static void btrfs_drop_pages(struct page **pages, size_t num_pages)
 	}
 }
 
-static int insert_inline_extent(struct btrfs_root *root, struct inode *inode,
+static int insert_inline_extent(struct btrfs_trans_handle *trans,
+				struct btrfs_root *root, struct inode *inode,
 				u64 offset, ssize_t size,
-				struct buffer_head *bh)
+				struct page *page, size_t page_offset)
 {
 	struct btrfs_key key;
 	struct btrfs_path *path;
 	char *ptr, *kaddr;
-	struct btrfs_trans_handle *trans;
 	struct btrfs_file_extent_item *ei;
 	u32 datasize;
 	int err = 0;
@@ -98,8 +98,6 @@ static int insert_inline_extent(struct btrfs_root *root, struct inode *inode,
 	if (!path)
 		return -ENOMEM;
 
-	mutex_lock(&root->fs_info->fs_mutex);
-	trans = btrfs_start_transaction(root, 1);
 	btrfs_set_trans_block_group(trans, inode);
 
 	key.objectid = inode->i_ino;
@@ -122,18 +120,13 @@ static int insert_inline_extent(struct btrfs_root *root, struct inode *inode,
 				   BTRFS_FILE_EXTENT_INLINE);
 	ptr = btrfs_file_extent_inline_start(ei);
 
-	kaddr = kmap_atomic(bh->b_page, KM_USER0);
+	kaddr = kmap_atomic(page, KM_USER0);
 	btrfs_memcpy(root, path->nodes[0]->b_data,
-		     ptr, kaddr + bh_offset(bh),
-		     size);
+		     ptr, kaddr + page_offset, size);
 	kunmap_atomic(kaddr, KM_USER0);
 	btrfs_mark_buffer_dirty(path->nodes[0]);
 fail:
 	btrfs_free_path(path);
-	ret = btrfs_end_transaction(trans, root);
-	if (ret && !err)
-		err = ret;
-	mutex_unlock(&root->fs_info->fs_mutex);
 	return err;
 }
 
@@ -145,45 +138,143 @@ static int dirty_and_release_pages(struct btrfs_trans_handle *trans,
 				   loff_t pos,
 				   size_t write_bytes)
 {
-	int i;
-	int offset;
 	int err = 0;
-	int ret;
-	int this_write;
+	int i;
 	struct inode *inode = file->f_path.dentry->d_inode;
-	struct buffer_head *bh;
+	struct extent_map *em;
+	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+	struct btrfs_key ins;
+	u64 hint_block;
+	u64 num_blocks;
+	u64 start_pos;
+	u64 end_of_last_block;
+	u64 end_pos = pos + write_bytes;
+	loff_t isize = i_size_read(inode);
 
-	for (i = 0; i < num_pages; i++) {
-		offset = pos & (PAGE_CACHE_SIZE -1);
-		this_write = min((size_t)PAGE_CACHE_SIZE - offset, write_bytes);
+	em = alloc_extent_map(GFP_NOFS);
+	if (!em)
+		return -ENOMEM;
 
-		/* FIXME, one block at a time */
-		bh = page_buffers(pages[i]);
+	em->bdev = inode->i_sb->s_bdev;
 
-		if (buffer_mapped(bh) && bh->b_blocknr == 0) {
-			ret = insert_inline_extent(root, inode,
-					pages[i]->index << PAGE_CACHE_SHIFT,
-					offset + this_write, bh);
-			if (ret) {
-				err = ret;
-				goto failed;
-			}
-		}
+	start_pos = pos & ~((u64)root->blocksize - 1);
+	num_blocks = (write_bytes + pos - start_pos + root->blocksize - 1) >>
+			inode->i_blkbits;
 
-		ret = btrfs_commit_write(file, pages[i], offset,
-					 offset + this_write);
-		pos += this_write;
-		if (ret) {
-			err = ret;
+	end_of_last_block = start_pos + (num_blocks << inode->i_blkbits) - 1;
+	mutex_lock(&root->fs_info->fs_mutex);
+	trans = btrfs_start_transaction(root, 1);
+	if (!trans) {
+		err = -ENOMEM;
+		goto out_unlock;
+	}
+	btrfs_set_trans_block_group(trans, inode);
+	inode->i_blocks += num_blocks << 3;
+	hint_block = 0;
+
+	if ((end_of_last_block & 4095) == 0) {
+		printk("strange end of last %Lu %lu %Lu\n", start_pos, write_bytes, end_of_last_block);
+	}
+	set_extent_uptodate(em_tree, start_pos, end_of_last_block, GFP_NOFS);
+
+	/* FIXME...EIEIO, ENOSPC and more */
+
+	/* step one, delete the existing extents in this range */
+	/* FIXME blocksize != pagesize */
+	if (start_pos < inode->i_size) {
+		err = btrfs_drop_extents(trans, root, inode,
+			 start_pos, (pos + write_bytes + root->blocksize -1) &
+			 ~((u64)root->blocksize - 1), &hint_block);
+		if (err)
+			goto failed;
+	}
+
+	/* insert any holes we need to create */
+	if (inode->i_size < start_pos) {
+		u64 last_pos_in_file;
+		u64 hole_size;
+		u64 mask = root->blocksize - 1;
+		last_pos_in_file = (isize + mask) & ~mask;
+		hole_size = (start_pos - last_pos_in_file + mask) & ~mask;
+		hole_size >>= inode->i_blkbits;
+		if (last_pos_in_file < start_pos) {
+			err = btrfs_insert_file_extent(trans, root,
+						       inode->i_ino,
+						       last_pos_in_file,
+						       0, 0, hole_size);
+		}
+		if (err)
 			goto failed;
+	}
+
+	/*
+	 * either allocate an extent for the new bytes or setup the key
+	 * to show we are doing inline data in the extent
+	 */
+	if (isize >= PAGE_CACHE_SIZE || pos + write_bytes < inode->i_size ||
+	    pos + write_bytes - start_pos > BTRFS_MAX_INLINE_DATA_SIZE(root)) {
+		err = btrfs_alloc_extent(trans, root, inode->i_ino,
+					 num_blocks, 0, hint_block, (u64)-1,
+					 &ins, 1);
+		BUG_ON(err);
+		err = btrfs_insert_file_extent(trans, root, inode->i_ino,
+				       start_pos, ins.objectid, ins.offset,
+				       ins.offset);
+		BUG_ON(err);
+		em->start = start_pos;
+		em->end = end_of_last_block;
+		em->block_start = ins.objectid << inode->i_blkbits;
+		em->block_end = em->block_start +
+			(ins.offset << inode->i_blkbits) - 1;
+		set_extent_dirty(em_tree, start_pos, end_of_last_block,
+				 GFP_NOFS);
+		err = add_extent_mapping(em_tree, em);
+		for (i = 0; i < num_pages; i++) {
+			struct page *p = pages[i];
+			SetPageUptodate(p);
+			__set_page_dirty_nobuffers(p);
 		}
-		WARN_ON(this_write > write_bytes);
-		write_bytes -= this_write;
+	} else {
+		struct page *p = pages[0];
+		err = insert_inline_extent(trans, root, inode, start_pos,
+					   end_pos - start_pos, p, 0);
+		BUG_ON(err);
+		em->start = start_pos;
+		em->end = end_pos;
+		em->block_start = EXTENT_MAP_INLINE;
+		em->block_end = EXTENT_MAP_INLINE;
+		add_extent_mapping(em_tree, em);
+	}
+	if (end_pos > isize) {
+		i_size_write(inode, end_pos);
+		btrfs_update_inode(trans, root, inode);
 	}
 failed:
+	err = btrfs_end_transaction(trans, root);
+out_unlock:
+	mutex_unlock(&root->fs_info->fs_mutex);
+	free_extent_map(em);
 	return err;
 }
 
+int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end)
+{
+	struct extent_map *em;
+	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+
+	while(1) {
+		em = lookup_extent_mapping(em_tree, start, end);
+		if (!em)
+			break;
+		remove_extent_mapping(em_tree, em);
+		/* once for us */
+		free_extent_map(em);
+		/* once for the tree*/
+		free_extent_map(em);
+	}
+	return 0;
+}
+
 /*
  * this is very complex, but the basic idea is to drop all extents
  * in the range start - end.  hint_block is filled in with a block number
@@ -213,6 +304,8 @@ int btrfs_drop_extents(struct btrfs_trans_handle *trans,
 	int found_inline;
 	int recow;
 
+	btrfs_drop_extent_cache(inode, start, end - 1);
+
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
@@ -434,18 +527,9 @@ static int prepare_pages(struct btrfs_root *root,
 	int i;
 	unsigned long index = pos >> PAGE_CACHE_SHIFT;
 	struct inode *inode = file->f_path.dentry->d_inode;
-	int offset;
 	int err = 0;
-	int this_write;
-	struct buffer_head *bh;
-	struct buffer_head *head;
-	loff_t isize = i_size_read(inode);
-	struct btrfs_trans_handle *trans;
-	u64 hint_block;
 	u64 num_blocks;
-	u64 alloc_extent_start;
 	u64 start_pos;
-	struct btrfs_key ins;
 
 	start_pos = pos & ~((u64)PAGE_CACHE_SIZE - 1);
 	num_blocks = (write_bytes + pos - start_pos + root->blocksize - 1) >>
@@ -457,119 +541,17 @@ static int prepare_pages(struct btrfs_root *root,
 		pages[i] = grab_cache_page(inode->i_mapping, index + i);
 		if (!pages[i]) {
 			err = -ENOMEM;
-			goto failed_release;
+			BUG_ON(1);
 		}
 		cancel_dirty_page(pages[i], PAGE_CACHE_SIZE);
 		wait_on_page_writeback(pages[i]);
-	}
-
-	mutex_lock(&root->fs_info->fs_mutex);
-	trans = btrfs_start_transaction(root, 1);
-	if (!trans) {
-		err = -ENOMEM;
-		mutex_unlock(&root->fs_info->fs_mutex);
-		goto out_unlock;
-	}
-	btrfs_set_trans_block_group(trans, inode);
-	/* FIXME blocksize != 4096 */
-	inode->i_blocks += num_blocks << 3;
-	hint_block = 0;
-
-	/* FIXME...EIEIO, ENOSPC and more */
-
-	/* step one, delete the existing extents in this range */
-	/* FIXME blocksize != pagesize */
-	if (start_pos < inode->i_size) {
-		err = btrfs_drop_extents(trans, root, inode,
-			 start_pos, (pos + write_bytes + root->blocksize -1) &
-			 ~((u64)root->blocksize - 1), &hint_block);
-		if (err)
-			goto failed_release;
-	}
-
-	/* insert any holes we need to create */
-	if (inode->i_size < start_pos) {
-		u64 last_pos_in_file;
-		u64 hole_size;
-		u64 mask = root->blocksize - 1;
-		last_pos_in_file = (isize + mask) & ~mask;
-		hole_size = (start_pos - last_pos_in_file + mask) & ~mask;
-		hole_size >>= inode->i_blkbits;
-		if (last_pos_in_file < start_pos) {
-			err = btrfs_insert_file_extent(trans, root,
-						       inode->i_ino,
-						       last_pos_in_file,
-						       0, 0, hole_size);
-		}
-		if (err)
-			goto failed_release;
-	}
-
-	/*
-	 * either allocate an extent for the new bytes or setup the key
-	 * to show we are doing inline data in the extent
-	 */
-	if (isize >= PAGE_CACHE_SIZE || pos + write_bytes < inode->i_size ||
-	    pos + write_bytes - start_pos > BTRFS_MAX_INLINE_DATA_SIZE(root)) {
-		err = btrfs_alloc_extent(trans, root, inode->i_ino,
-					 num_blocks, 0, hint_block, (u64)-1,
-					 &ins, 1);
-		if (err)
-			goto failed_truncate;
-		err = btrfs_insert_file_extent(trans, root, inode->i_ino,
-				       start_pos, ins.objectid, ins.offset,
-				       ins.offset);
-		if (err)
-			goto failed_truncate;
-	} else {
-		ins.offset = 0;
-		ins.objectid = 0;
-	}
-	BUG_ON(err);
-	alloc_extent_start = ins.objectid;
-	err = btrfs_end_transaction(trans, root);
-	mutex_unlock(&root->fs_info->fs_mutex);
-
-	for (i = 0; i < num_pages; i++) {
-		offset = pos & (PAGE_CACHE_SIZE -1);
-		this_write = min((size_t)PAGE_CACHE_SIZE - offset, write_bytes);
-		if (!page_has_buffers(pages[i])) {
-			create_empty_buffers(pages[i],
-					     root->fs_info->sb->s_blocksize,
-					     (1 << BH_Uptodate));
+		if (!PagePrivate(pages[i])) {
+			SetPagePrivate(pages[i]);
+			set_page_private(pages[i], 1);
+			page_cache_get(pages[i]);
 		}
-		head = page_buffers(pages[i]);
-		bh = head;
-		do {
-			err = btrfs_map_bh_to_logical(root, bh,
-						      alloc_extent_start);
-			BUG_ON(err);
-			if (err)
-				goto failed_truncate;
-			bh = bh->b_this_page;
-			if (alloc_extent_start)
-				alloc_extent_start++;
-		} while (bh != head);
-		pos += this_write;
-		WARN_ON(this_write > write_bytes);
-		write_bytes -= this_write;
 	}
 	return 0;
-
-failed_release:
-	btrfs_drop_pages(pages, num_pages);
-	return err;
-
-failed_truncate:
-	btrfs_drop_pages(pages, num_pages);
-	if (pos > isize)
-		vmtruncate(inode, isize);
-	return err;
-
-out_unlock:
-	mutex_unlock(&root->fs_info->fs_mutex);
-	goto failed_release;
-
 }
 
 static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
@@ -685,7 +667,6 @@ out:
 		page_cache_release(pinned[1]);
 	*ppos = pos;
 	current->backing_dev_info = NULL;
-	mark_inode_dirty(inode);
 	return num_written ? num_written : err;
 }
 
@@ -714,8 +695,8 @@ static int btrfs_sync_file(struct file *file,
 	mutex_unlock(&root->fs_info->trans_mutex);
 
 	/*
- 	 * ok we haven't committed the transaction yet, lets do a commit
- 	 */
+	 * ok we haven't committed the transaction yet, lets do a commit
+	 */
 	trans = btrfs_start_transaction(root, 1);
 	if (!trans) {
 		ret = -ENOMEM;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 504d37d..fd4cb65 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -121,6 +121,8 @@ void btrfs_read_locked_inode(struct inode *inode)
 	switch (inode->i_mode & S_IFMT) {
 	case S_IFREG:
 		inode->i_mapping->a_ops = &btrfs_aops;
+		extent_map_tree_init(&BTRFS_I(inode)->extent_tree,
+				     inode->i_mapping, GFP_NOFS);
 		inode->i_fop = &btrfs_file_operations;
 		inode->i_op = &btrfs_file_inode_operations;
 		break;
@@ -169,7 +171,7 @@ static void fill_inode_item(struct btrfs_inode_item *item,
 				    BTRFS_I(inode)->block_group->key.objectid);
 }
 
-static int btrfs_update_inode(struct btrfs_trans_handle *trans,
+int btrfs_update_inode(struct btrfs_trans_handle *trans,
 			      struct btrfs_root *root,
 			      struct inode *inode)
 {
@@ -400,6 +402,7 @@ static int btrfs_truncate_in_trans(struct btrfs_trans_handle *trans,
 	int found_extent;
 	int del_item;
 
+	btrfs_drop_extent_cache(inode, inode->i_size, (u64)-1);
 	path = btrfs_alloc_path();
 	path->reada = -1;
 	BUG_ON(!path);
@@ -511,6 +514,50 @@ error:
 	return ret;
 }
 
+static int btrfs_cow_one_page(struct btrfs_trans_handle *trans,
+			      struct inode *inode, struct page *page,
+			      size_t zero_start)
+{
+	char *kaddr;
+	int ret = 0;
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	u64 alloc_hint = 0;
+	u64 page_start = page->index << PAGE_CACHE_SHIFT;
+	struct btrfs_key ins;
+
+	if (!PagePrivate(page)) {
+		SetPagePrivate(page);
+		set_page_private(page, 1);
+		page_cache_get(page);
+	}
+
+	btrfs_set_trans_block_group(trans, inode);
+
+	ret = btrfs_drop_extents(trans, root, inode,
+				 page_start, page_start + PAGE_CACHE_SIZE,
+				 &alloc_hint);
+	if (ret)
+		goto out;
+	ret = btrfs_alloc_extent(trans, root, inode->i_ino, 1, 0,
+				 alloc_hint, (u64)-1, &ins, 1);
+	if (ret)
+		goto out;
+	ret = btrfs_insert_file_extent(trans, root, inode->i_ino,
+				       page_start, ins.objectid, 1, 1);
+	if (ret)
+		goto out;
+	SetPageChecked(page);
+	kaddr = kmap(page);
+	if (zero_start != PAGE_CACHE_SIZE) {
+		memset(kaddr + zero_start, 0, PAGE_CACHE_SIZE - zero_start);
+		flush_dcache_page(page);
+	}
+	kunmap(page);
+
+out:
+	return ret;
+}
+
 /*
  * taken from block_truncate_page, but does cow as it zeros out
  * any bytes left in the last page in the file.
@@ -518,16 +565,14 @@ error:
 static int btrfs_truncate_page(struct address_space *mapping, loff_t from)
 {
 	struct inode *inode = mapping->host;
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct btrfs_trans_handle *trans;
 	unsigned blocksize = 1 << inode->i_blkbits;
 	pgoff_t index = from >> PAGE_CACHE_SHIFT;
 	unsigned offset = from & (PAGE_CACHE_SIZE-1);
 	struct page *page;
-	char *kaddr;
 	int ret = 0;
-	struct btrfs_root *root = BTRFS_I(inode)->root;
-	u64 alloc_hint = 0;
-	struct btrfs_key ins;
-	struct btrfs_trans_handle *trans;
+	u64 page_start;
 
 	if ((offset & (blocksize - 1)) == 0)
 		goto out;
@@ -536,7 +581,6 @@ static int btrfs_truncate_page(struct address_space *mapping, loff_t from)
 	page = grab_cache_page(mapping, index);
 	if (!page)
 		goto out;
-
 	if (!PageUptodate(page)) {
 		ret = btrfs_readpage(NULL, page);
 		lock_page(page);
@@ -545,37 +589,24 @@ static int btrfs_truncate_page(struct address_space *mapping, loff_t from)
 			goto out;
 		}
 	}
+	page_start = page->index << PAGE_CACHE_SHIFT;
+
 	mutex_lock(&root->fs_info->fs_mutex);
 	trans = btrfs_start_transaction(root, 1);
-	btrfs_set_trans_block_group(trans, inode);
-
-	ret = btrfs_drop_extents(trans, root, inode,
-				 page->index << PAGE_CACHE_SHIFT,
-				 (page->index + 1) << PAGE_CACHE_SHIFT,
-				 &alloc_hint);
-	if (ret)
-		goto out;
-	ret = btrfs_alloc_extent(trans, root, inode->i_ino, 1, 0,
-				 alloc_hint, (u64)-1, &ins, 1);
-	if (ret)
-		goto out;
-	ret = btrfs_insert_file_extent(trans, root, inode->i_ino,
-				       page->index << PAGE_CACHE_SHIFT,
-				       ins.objectid, 1, 1);
-	if (ret)
-		goto out;
-	SetPageChecked(page);
-	kaddr = kmap(page);
-	memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
-	flush_dcache_page(page);
-	ret = btrfs_csum_file_block(trans, root, inode->i_ino,
-			      page->index << PAGE_CACHE_SHIFT,
-			      kaddr, PAGE_CACHE_SIZE);
-	kunmap(page);
+	ret = btrfs_cow_one_page(trans, inode, page, offset);
+	if (!ret) {
+		char *kaddr = kmap(page);
+		ret = btrfs_csum_file_block(trans, root, inode->i_ino,
+					    page_start, kaddr, PAGE_CACHE_SIZE);
+		kunmap(page);
+	}
+	set_extent_dirty(&BTRFS_I(inode)->extent_tree,
+			 page_start, page_start + PAGE_CACHE_SIZE - 1,
+			 GFP_NOFS);
+	set_page_dirty(page);
 	btrfs_end_transaction(trans, root);
 	mutex_unlock(&root->fs_info->fs_mutex);
 
-	set_page_dirty(page);
 	unlock_page(page);
 	page_cache_release(page);
 out:
@@ -1095,6 +1126,8 @@ static int btrfs_create(struct inode *dir, struct dentry *dentry,
 		inode->i_mapping->a_ops = &btrfs_aops;
 		inode->i_fop = &btrfs_file_operations;
 		inode->i_op = &btrfs_file_inode_operations;
+		extent_map_tree_init(&BTRFS_I(inode)->extent_tree,
+				     inode->i_mapping, GFP_NOFS);
 	}
 	dir->i_sb->s_dirt = 1;
 	btrfs_update_inode_block_group(trans, inode);
@@ -1238,6 +1271,182 @@ out_unlock:
 	return err;
 }
 
+struct extent_map *btrfs_get_extent(struct inode *inode, struct page *page,
+				    size_t page_offset, u64 start, u64 end,
+				    int create)
+{
+	int ret;
+	int err = 0;
+	u64 blocknr;
+	u64 extent_start = 0;
+	u64 extent_end = 0;
+	u64 objectid = inode->i_ino;
+	u32 found_type;
+	int failed_insert = 0;
+	struct btrfs_path *path;
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct btrfs_file_extent_item *item;
+	struct btrfs_leaf *leaf;
+	struct btrfs_disk_key *found_key;
+	struct extent_map *em = NULL;
+	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+	struct btrfs_trans_handle *trans = NULL;
+
+	path = btrfs_alloc_path();
+	BUG_ON(!path);
+	mutex_lock(&root->fs_info->fs_mutex);
+
+again:
+	em = lookup_extent_mapping(em_tree, start, end);
+	if (em) {
+		goto out;
+	}
+	if (!em) {
+		em = alloc_extent_map(GFP_NOFS);
+		if (!em) {
+			err = -ENOMEM;
+			goto out;
+		}
+		em->start = 0;
+		em->end = 0;
+	}
+	em->bdev = inode->i_sb->s_bdev;
+	ret = btrfs_lookup_file_extent(NULL, root, path,
+				       objectid, start, 0);
+	if (ret < 0) {
+		err = ret;
+		goto out;
+	}
+
+	if (ret != 0) {
+		if (path->slots[0] == 0)
+			goto not_found;
+		path->slots[0]--;
+	}
+
+	item = btrfs_item_ptr(btrfs_buffer_leaf(path->nodes[0]), path->slots[0],
+			      struct btrfs_file_extent_item);
+	leaf = btrfs_buffer_leaf(path->nodes[0]);
+	blocknr = btrfs_file_extent_disk_blocknr(item);
+	blocknr += btrfs_file_extent_offset(item);
+
+	/* are we inside the extent that was found? */
+	found_key = &leaf->items[path->slots[0]].key;
+	found_type = btrfs_disk_key_type(found_key);
+	if (btrfs_disk_key_objectid(found_key) != objectid ||
+	    found_type != BTRFS_EXTENT_DATA_KEY) {
+		goto not_found;
+	}
+
+	found_type = btrfs_file_extent_type(item);
+	extent_start = btrfs_disk_key_offset(&leaf->items[path->slots[0]].key);
+	if (found_type == BTRFS_FILE_EXTENT_REG) {
+		extent_end = extent_start +
+		       (btrfs_file_extent_num_blocks(item) << inode->i_blkbits);
+		err = 0;
+		if (start < extent_start || start > extent_end) {
+			em->start = start;
+			if (start < extent_start) {
+				em->end = extent_end - 1;
+			} else {
+				em->end = end;
+			}
+			goto not_found_em;
+		}
+		if (btrfs_file_extent_disk_blocknr(item) == 0) {
+			em->start = extent_start;
+			em->end = extent_end - 1;
+			em->block_start = 0;
+			em->block_end = 0;
+			goto insert;
+		}
+		em->block_start = blocknr << inode->i_blkbits;
+		em->block_end = em->block_start +
+			(btrfs_file_extent_num_blocks(item) <<
+			 inode->i_blkbits) - 1;
+		em->start = extent_start;
+		em->end = extent_end - 1;
+		goto insert;
+	} else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
+		char *ptr;
+		char *map;
+		u32 size;
+
+		size = btrfs_file_extent_inline_len(leaf->items +
+						    path->slots[0]);
+		extent_end = extent_start + size;
+		if (start < extent_start || start > extent_end) {
+			em->start = start;
+			if (start < extent_start) {
+				em->end = extent_end - 1;
+			} else {
+				em->end = end;
+			}
+			goto not_found_em;
+		}
+		em->block_start = EXTENT_MAP_INLINE;
+		em->block_end = EXTENT_MAP_INLINE;
+		em->start = extent_start;
+		em->end = extent_end - 1;
+		if (!page) {
+			goto insert;
+		}
+		ptr = btrfs_file_extent_inline_start(item);
+		map = kmap(page);
+		memcpy(map + page_offset, ptr, size);
+		flush_dcache_page(result->b_page);
+		kunmap(page);
+		set_extent_uptodate(em_tree, extent_start,
+				    extent_end, GFP_NOFS);
+		goto insert;
+	} else {
+		printk("unkknown found_type %d\n", found_type);
+		WARN_ON(1);
+	}
+not_found:
+	em->start = start;
+	em->end = end;
+not_found_em:
+	em->block_start = 0;
+	em->block_end = 0;
+insert:
+	btrfs_release_path(root, path);
+	if (em->start > start || em->end < start) {
+		printk("bad extent! %Lu %Lu start %Lu end %Lu\n", em->start, em->end, start, end);
+		WARN_ON(1);
+		err = -EIO;
+		goto out;
+	}
+	ret = add_extent_mapping(em_tree, em);
+	if (ret == -EEXIST) {
+		free_extent_map(em);
+		failed_insert++;
+		if (failed_insert > 5) {
+			printk("failing to insert %Lu %Lu\n", start, end);
+			err = -EIO;
+			goto out;
+		}
+		em = NULL;
+		goto again;
+	}
+	err = 0;
+out:
+	btrfs_free_path(path);
+	if (trans) {
+		ret = btrfs_end_transaction(trans, root);
+		if (!err)
+			err = ret;
+	}
+	mutex_unlock(&root->fs_info->fs_mutex);
+	if (err) {
+		free_extent_map(em);
+		WARN_ON(1);
+		return ERR_PTR(err);
+	}
+	return em;
+}
+
+
 /*
  * FIBMAP and others want to pass in a fake buffer head.  They need to
  * use BTRFS_GET_BLOCK_NO_DIRECT to make sure we don't try to memcpy
@@ -1398,46 +1607,22 @@ int btrfs_get_block(struct inode *inode, sector_t iblock,
 	return err;
 }
 
-static int btrfs_get_block_csum(struct inode *inode, sector_t iblock,
-				struct buffer_head *result, int create)
-{
-	int ret;
-	struct btrfs_root *root = BTRFS_I(inode)->root;
-	struct page *page = result->b_page;
-	u64 offset = (page->index << PAGE_CACHE_SHIFT) + bh_offset(result);
-	struct btrfs_csum_item *item;
-	struct btrfs_path *path = NULL;
-
-	mutex_lock(&root->fs_info->fs_mutex);
-	ret = btrfs_get_block_lock(inode, iblock, result, create);
-	if (ret)
-		goto out;
-
-	path = btrfs_alloc_path();
-	item = btrfs_lookup_csum(NULL, root, path, inode->i_ino, offset, 0);
-	if (IS_ERR(item)) {
-		ret = PTR_ERR(item);
-		/* a csum that isn't present is a preallocated region. */
-		if (ret == -ENOENT || ret == -EFBIG)
-			ret = 0;
-		result->b_private = NULL;
-		goto out;
-	}
-	memcpy((char *)&result->b_private, &item->csum, BTRFS_CRC32_SIZE);
-out:
-	if (path)
-		btrfs_free_path(path);
-	mutex_unlock(&root->fs_info->fs_mutex);
-	return ret;
-}
-
 static int btrfs_get_block_bmap(struct inode *inode, sector_t iblock,
 			   struct buffer_head *result, int create)
 {
 	struct btrfs_root *root = BTRFS_I(inode)->root;
-	mutex_lock(&root->fs_info->fs_mutex);
-	btrfs_get_block_lock(inode, iblock, result, BTRFS_GET_BLOCK_NO_DIRECT);
-	mutex_unlock(&root->fs_info->fs_mutex);
+	u64 start = iblock << inode->i_blkbits;
+	u64 end = start + root->blocksize -1;
+	struct extent_map *em;
+
+	em = btrfs_get_extent(inode, NULL, 0, start, end, 0);
+	if (em && !IS_ERR(em) && em->block_start != EXTENT_MAP_INLINE &&
+	    em->block_start != 0) {
+		u64 offset;
+		offset = start - em->start;
+		start = (em->block_start + offset) >> inode->i_blkbits;
+		btrfs_map_bh_to_logical(root, result, start);
+	}
 	return 0;
 }
 
@@ -1449,442 +1634,50 @@ static sector_t btrfs_bmap(struct address_space *as, sector_t block)
 static int btrfs_prepare_write(struct file *file, struct page *page,
 			       unsigned from, unsigned to)
 {
-	return block_prepare_write(page, from, to, btrfs_get_block);
+	return extent_prepare_write(&BTRFS_I(page->mapping->host)->extent_tree,
+				    page->mapping->host, page, from, to,
+				    btrfs_get_extent);
 }
 
-static void buffer_io_error(struct buffer_head *bh)
+int btrfs_readpage(struct file *file, struct page *page)
 {
-	char b[BDEVNAME_SIZE];
-
-	printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
-			bdevname(bh->b_bdev, b),
-			(unsigned long long)bh->b_blocknr);
+	struct extent_map_tree *tree;
+	tree = &BTRFS_I(page->mapping->host)->extent_tree;
+	return extent_read_full_page(tree, page, btrfs_get_extent);
 }
-
-/*
- * I/O completion handler for block_read_full_page() - pages
- * which come unlocked at the end of I/O.
- */
-static void btrfs_end_buffer_async_read(struct buffer_head *bh, int uptodate)
+static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
 {
-	unsigned long flags;
-	struct buffer_head *first;
-	struct buffer_head *tmp;
-	struct page *page;
-	int page_uptodate = 1;
-	struct inode *inode;
-	int ret;
-
-	BUG_ON(!buffer_async_read(bh));
-
-	page = bh->b_page;
-	inode = page->mapping->host;
-	if (uptodate) {
-		void *kaddr;
-		struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
-		if (bh->b_private) {
-			char csum[BTRFS_CRC32_SIZE];
-			kaddr = kmap_atomic(page, KM_IRQ0);
-			ret = btrfs_csum_data(root, kaddr + bh_offset(bh),
-					      bh->b_size, csum);
-			BUG_ON(ret);
-			if (memcmp(csum, &bh->b_private, BTRFS_CRC32_SIZE)) {
-				u64 offset;
-				offset = (page->index << PAGE_CACHE_SHIFT) +
-					bh_offset(bh);
-				printk("btrfs csum failed ino %lu off %llu\n",
-				       page->mapping->host->i_ino,
-				       (unsigned long long)offset);
-				memset(kaddr + bh_offset(bh), 1, bh->b_size);
-				flush_dcache_page(page);
-			}
-			kunmap_atomic(kaddr, KM_IRQ0);
-		}
-		set_buffer_uptodate(bh);
-	} else {
-		clear_buffer_uptodate(bh);
-		if (printk_ratelimit())
-			buffer_io_error(bh);
-		SetPageError(page);
-	}
-
-	/*
-	 * Be _very_ careful from here on. Bad things can happen if
-	 * two buffer heads end IO at almost the same time and both
-	 * decide that the page is now completely done.
-	 */
-	first = page_buffers(page);
-	local_irq_save(flags);
-	bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
-	clear_buffer_async_read(bh);
-	unlock_buffer(bh);
-	tmp = bh;
-	do {
-		if (!buffer_uptodate(tmp))
-			page_uptodate = 0;
-		if (buffer_async_read(tmp)) {
-			BUG_ON(!buffer_locked(tmp));
-			goto still_busy;
-		}
-		tmp = tmp->b_this_page;
-	} while (tmp != bh);
-	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
-	local_irq_restore(flags);
-
-	/*
-	 * If none of the buffers had errors and they are all
-	 * uptodate then we can set the page uptodate.
-	 */
-	if (page_uptodate && !PageError(page))
-		SetPageUptodate(page);
-	unlock_page(page);
-	return;
-
-still_busy:
-	bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
-	local_irq_restore(flags);
-	return;
+	struct extent_map_tree *tree;
+	tree = &BTRFS_I(page->mapping->host)->extent_tree;
+	return extent_write_full_page(tree, page, btrfs_get_extent, wbc);
 }
 
-/*
- * Generic "read page" function for block devices that have the normal
- * get_block functionality. This is most of the block device filesystems.
- * Reads the page asynchronously --- the unlock_buffer() and
- * set/clear_buffer_uptodate() functions propagate buffer state into the
- * page struct once IO has completed.
- */
-int btrfs_readpage(struct file *file, struct page *page)
+static int btrfs_releasepage(struct page *page, gfp_t unused_gfp_flags)
 {
-	struct inode *inode = page->mapping->host;
-	sector_t iblock, lblock;
-	struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
-	unsigned int blocksize;
-	int nr, i;
-	int fully_mapped = 1;
-
-	BUG_ON(!PageLocked(page));
-	blocksize = 1 << inode->i_blkbits;
-	if (!page_has_buffers(page))
-		create_empty_buffers(page, blocksize, 0);
-	head = page_buffers(page);
-
-	iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
-	lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
-	bh = head;
-	nr = 0;
-	i = 0;
-
-	do {
-		if (buffer_uptodate(bh))
-			continue;
-
-		if (!buffer_mapped(bh)) {
-			int err = 0;
-
-			fully_mapped = 0;
-			if (iblock < lblock) {
-				WARN_ON(bh->b_size != blocksize);
-				err = btrfs_get_block_csum(inode, iblock,
-							   bh, 0);
-				if (err)
-					SetPageError(page);
-			}
-			if (!buffer_mapped(bh)) {
-				void *kaddr = kmap_atomic(page, KM_USER0);
-				memset(kaddr + i * blocksize, 0, blocksize);
-				flush_dcache_page(page);
-				kunmap_atomic(kaddr, KM_USER0);
-				if (!err)
-					set_buffer_uptodate(bh);
-				continue;
-			}
-			/*
-			 * get_block() might have updated the buffer
-			 * synchronously
-			 */
-			if (buffer_uptodate(bh))
-				continue;
-		}
-		arr[nr++] = bh;
-	} while (i++, iblock++, (bh = bh->b_this_page) != head);
-
-	if (fully_mapped)
-		SetPageMappedToDisk(page);
-
-	if (!nr) {
-		/*
-		 * All buffers are uptodate - we can set the page uptodate
-		 * as well. But not if get_block() returned an error.
-		 */
-		if (!PageError(page))
-			SetPageUptodate(page);
-		unlock_page(page);
-		return 0;
-	}
-
-	/* Stage two: lock the buffers */
-	for (i = 0; i < nr; i++) {
-		bh = arr[i];
-		lock_buffer(bh);
-		bh->b_end_io = btrfs_end_buffer_async_read;
-		set_buffer_async_read(bh);
-	}
-
-	/*
-	 * Stage 3: start the IO.  Check for uptodateness
-	 * inside the buffer lock in case another process reading
-	 * the underlying blockdev brought it uptodate (the sct fix).
-	 */
-	for (i = 0; i < nr; i++) {
-		bh = arr[i];
-		if (buffer_uptodate(bh))
-			btrfs_end_buffer_async_read(bh, 1);
-		else
-			submit_bh(READ, bh);
-	}
-	return 0;
-}
-
-/*
- * Aside from a tiny bit of packed file data handling, this is the
- * same as the generic code.
- *
- * While block_write_full_page is writing back the dirty buffers under
- * the page lock, whoever dirtied the buffers may decide to clean them
- * again at any time.  We handle that by only looking at the buffer
- * state inside lock_buffer().
- *
- * If block_write_full_page() is called for regular writeback
- * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
- * locked buffer.   This only can happen if someone has written the buffer
- * directly, with submit_bh().  At the address_space level PageWriteback
- * prevents this contention from occurring.
- */
-static int __btrfs_write_full_page(struct inode *inode, struct page *page,
-				   struct writeback_control *wbc)
-{
-	int err;
-	sector_t block;
-	sector_t last_block;
-	struct buffer_head *bh, *head;
-	const unsigned blocksize = 1 << inode->i_blkbits;
-	int nr_underway = 0;
-	struct btrfs_root *root = BTRFS_I(inode)->root;
-
-	BUG_ON(!PageLocked(page));
-
-	last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
-
-	/* no csumming allowed when from PF_MEMALLOC */
-	if (current->flags & PF_MEMALLOC) {
-		redirty_page_for_writepage(wbc, page);
-		unlock_page(page);
-		return 0;
-	}
+	struct extent_map_tree *tree;
+	int ret;
 
-	if (!page_has_buffers(page)) {
-		create_empty_buffers(page, blocksize,
-					(1 << BH_Dirty)|(1 << BH_Uptodate));
+	if (page->private != 1) {
+		WARN_ON(1);
+		return try_to_free_buffers(page);
 	}
-
-	/*
-	 * Be very careful.  We have no exclusion from __set_page_dirty_buffers
-	 * here, and the (potentially unmapped) buffers may become dirty at
-	 * any time.  If a buffer becomes dirty here after we've inspected it
-	 * then we just miss that fact, and the page stays dirty.
-	 *
-	 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
-	 * handle that here by just cleaning them.
-	 */
-
-	block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
-	head = page_buffers(page);
-	bh = head;
-
-	/*
-	 * Get all the dirty buffers mapped to disk addresses and
-	 * handle any aliases from the underlying blockdev's mapping.
-	 */
-	do {
-		if (block > last_block) {
-			/*
-			 * mapped buffers outside i_size will occur, because
-			 * this page can be outside i_size when there is a
-			 * truncate in progress.
-			 */
-			/*
-			 * The buffer was zeroed by block_write_full_page()
-			 */
-			clear_buffer_dirty(bh);
-			set_buffer_uptodate(bh);
-		} else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
-			WARN_ON(bh->b_size != blocksize);
-			err = btrfs_get_block(inode, block, bh, 0);
-			if (err) {
-				goto recover;
-			}
-			if (buffer_new(bh)) {
-				/* blockdev mappings never come here */
-				clear_buffer_new(bh);
-			}
-		}
-		bh = bh->b_this_page;
-		block++;
-	} while (bh != head);
-
-	do {
-		if (!buffer_mapped(bh))
-			continue;
-		/*
-		 * If it's a fully non-blocking write attempt and we cannot
-		 * lock the buffer then redirty the page.  Note that this can
-		 * potentially cause a busy-wait loop from pdflush and kswapd
-		 * activity, but those code paths have their own higher-level
-		 * throttling.
-		 */
-		if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
-			lock_buffer(bh);
-		} else if (test_set_buffer_locked(bh)) {
-			redirty_page_for_writepage(wbc, page);
-			continue;
-		}
-		if (test_clear_buffer_dirty(bh) && bh->b_blocknr != 0) {
-			struct btrfs_trans_handle *trans;
-			int ret;
-			u64 off = page->index << PAGE_CACHE_SHIFT;
-			char *kaddr;
-
-			off += bh_offset(bh);
-			mutex_lock(&root->fs_info->fs_mutex);
-			trans = btrfs_start_transaction(root, 1);
-			btrfs_set_trans_block_group(trans, inode);
-			kaddr = kmap(page);
-			btrfs_csum_file_block(trans, root, inode->i_ino,
-						    off, kaddr + bh_offset(bh),
-						    bh->b_size);
-			kunmap(page);
-			ret = btrfs_end_transaction(trans, root);
-			BUG_ON(ret);
-			mutex_unlock(&root->fs_info->fs_mutex);
-			mark_buffer_async_write(bh);
-		} else {
-			unlock_buffer(bh);
-		}
-	} while ((bh = bh->b_this_page) != head);
-
-	/*
-	 * The page and its buffers are protected by PageWriteback(), so we can
-	 * drop the bh refcounts early.
-	 */
-	BUG_ON(PageWriteback(page));
-	set_page_writeback(page);
-
-	do {
-		struct buffer_head *next = bh->b_this_page;
-		if (buffer_async_write(bh)) {
-			submit_bh(WRITE, bh);
-			nr_underway++;
-		}
-		bh = next;
-	} while (bh != head);
-	unlock_page(page);
-
-	err = 0;
-done:
-	if (nr_underway == 0) {
-		/*
-		 * The page was marked dirty, but the buffers were
-		 * clean.  Someone wrote them back by hand with
-		 * ll_rw_block/submit_bh.  A rare case.
-		 */
-		int uptodate = 1;
-		do {
-			if (!buffer_uptodate(bh)) {
-				uptodate = 0;
-				break;
-			}
-			bh = bh->b_this_page;
-		} while (bh != head);
-		if (uptodate)
-			SetPageUptodate(page);
-		end_page_writeback(page);
+	tree = &BTRFS_I(page->mapping->host)->extent_tree;
+	ret = try_release_extent_mapping(tree, page);
+	if (ret == 1) {
+		ClearPagePrivate(page);
+		set_page_private(page, 0);
+		page_cache_release(page);
 	}
-	return err;
-
-recover:
-	/*
-	 * ENOSPC, or some other error.  We may already have added some
-	 * blocks to the file, so we need to write these out to avoid
-	 * exposing stale data.
-	 * The page is currently locked and not marked for writeback
-	 */
-	bh = head;
-	/* Recovery: lock and submit the mapped buffers */
-	do {
-		if (buffer_mapped(bh) && buffer_dirty(bh)) {
-			lock_buffer(bh);
-			mark_buffer_async_write(bh);
-		} else {
-			/*
-			 * The buffer may have been set dirty during
-			 * attachment to a dirty page.
-			 */
-			clear_buffer_dirty(bh);
-		}
-	} while ((bh = bh->b_this_page) != head);
-	SetPageError(page);
-	BUG_ON(PageWriteback(page));
-	set_page_writeback(page);
-	do {
-		struct buffer_head *next = bh->b_this_page;
-		if (buffer_async_write(bh)) {
-			clear_buffer_dirty(bh);
-			submit_bh(WRITE, bh);
-			nr_underway++;
-		}
-		bh = next;
-	} while (bh != head);
-	unlock_page(page);
-	goto done;
+	return ret;
 }
 
-static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
+static void btrfs_invalidatepage(struct page *page, unsigned long offset)
 {
-	struct inode * const inode = page->mapping->host;
-	loff_t i_size = i_size_read(inode);
-	const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
-	unsigned offset;
-	void *kaddr;
-
-	/* Is the page fully inside i_size? */
-	if (page->index < end_index)
-		return __btrfs_write_full_page(inode, page, wbc);
-
-	/* Is the page fully outside i_size? (truncate in progress) */
-	offset = i_size & (PAGE_CACHE_SIZE-1);
-	if (page->index >= end_index+1 || !offset) {
-		/*
-		 * The page may have dirty, unmapped buffers.  For example,
-		 * they may have been added in ext3_writepage().  Make them
-		 * freeable here, so the page does not leak.
-		 */
-		block_invalidatepage(page, 0);
-		unlock_page(page);
-		return 0; /* don't care */
-	}
+	struct extent_map_tree *tree;
 
-	/*
-	 * The page straddles i_size.  It must be zeroed out on each and every
-	 * writepage invokation because it may be mmapped.  "A file is mapped
-	 * in multiples of the page size.  For a file that is not a multiple of
-	 * the  page size, the remaining memory is zeroed when mapped, and
-	 * writes to that region are not written out to the file."
-	 */
-	kaddr = kmap_atomic(page, KM_USER0);
-	memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
-	flush_dcache_page(page);
-	kunmap_atomic(kaddr, KM_USER0);
-	return __btrfs_write_full_page(inode, page, wbc);
+	tree = &BTRFS_I(page->mapping->host)->extent_tree;
+	extent_invalidatepage(tree, page, offset);
+	btrfs_releasepage(page, GFP_NOFS);
 }
 
 /*
@@ -1905,28 +1698,39 @@ static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
 int btrfs_page_mkwrite(struct vm_area_struct *vma, struct page *page)
 {
 	struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct btrfs_trans_handle *trans;
 	unsigned long end;
 	loff_t size;
 	int ret = -EINVAL;
+	u64 page_start;
 
 	lock_page(page);
 	wait_on_page_writeback(page);
 	size = i_size_read(inode);
+	page_start = page->index << PAGE_CACHE_SHIFT;
+
 	if ((page->mapping != inode->i_mapping) ||
-	    ((page->index << PAGE_CACHE_SHIFT) > size)) {
+	    (page_start > size)) {
 		/* page got truncated out from underneath us */
 		goto out_unlock;
 	}
 
 	/* page is wholly or partially inside EOF */
-	if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
+	if (page_start + PAGE_CACHE_SIZE > size)
 		end = size & ~PAGE_CACHE_MASK;
 	else
 		end = PAGE_CACHE_SIZE;
 
-	ret = btrfs_prepare_write(NULL, page, 0, end);
-	if (!ret)
-		ret = btrfs_commit_write(NULL, page, 0, end);
+	mutex_lock(&root->fs_info->fs_mutex);
+	trans = btrfs_start_transaction(root, 1);
+	ret = btrfs_cow_one_page(trans, inode, page, end);
+	btrfs_end_transaction(trans, root);
+	mutex_unlock(&root->fs_info->fs_mutex);
+	set_extent_dirty(&BTRFS_I(inode)->extent_tree,
+			 page_start, page_start + PAGE_CACHE_SIZE - 1,
+			 GFP_NOFS);
+	set_page_dirty(page);
 
 out_unlock:
 	unlock_page(page);
@@ -1962,21 +1766,8 @@ static void btrfs_truncate(struct inode *inode)
 int btrfs_commit_write(struct file *file, struct page *page,
 		       unsigned from, unsigned to)
 {
-	struct inode *inode = page->mapping->host;
-	struct buffer_head *bh;
-	loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
-
-	SetPageUptodate(page);
-	bh = page_buffers(page);
-	set_buffer_uptodate(bh);
-	if (buffer_mapped(bh) && bh->b_blocknr != 0) {
-		set_page_dirty(page);
-	}
-	if (pos > inode->i_size) {
-		i_size_write(inode, pos);
-		mark_inode_dirty(inode);
-	}
-	return 0;
+	return extent_commit_write(&BTRFS_I(page->mapping->host)->extent_tree,
+				   page->mapping->host, page, from, to);
 }
 
 static int create_subvol(struct btrfs_root *root, char *name, int namelen)
@@ -2471,6 +2262,8 @@ static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
 		inode->i_mapping->a_ops = &btrfs_aops;
 		inode->i_fop = &btrfs_file_operations;
 		inode->i_op = &btrfs_file_inode_operations;
+		extent_map_tree_init(&BTRFS_I(inode)->extent_tree,
+				     inode->i_mapping, GFP_NOFS);
 	}
 	dir->i_sb->s_dirt = 1;
 	btrfs_update_inode_block_group(trans, inode);
@@ -2553,6 +2346,9 @@ static struct address_space_operations btrfs_aops = {
 	.prepare_write	= btrfs_prepare_write,
 	.commit_write	= btrfs_commit_write,
 	.bmap		= btrfs_bmap,
+	.invalidatepage = btrfs_invalidatepage,
+	.releasepage	= btrfs_releasepage,
+	.set_page_dirty	= __set_page_dirty_nobuffers,
 };
 
 static struct address_space_operations btrfs_symlink_aops = {
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 74f3de4..7b7c32c 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -185,6 +185,7 @@ static int __init init_btrfs_fs(void)
 	err = btrfs_init_cachep();
 	if (err)
 		return err;
+	extent_map_init();
 	return register_filesystem(&btrfs_fs_type);
 }
 
@@ -192,6 +193,7 @@ static void __exit exit_btrfs_fs(void)
 {
 	btrfs_exit_transaction_sys();
 	btrfs_destroy_cachep();
+	extent_map_exit();
 	unregister_filesystem(&btrfs_fs_type);
 }