Btrfs: Fix extent replacment race

[linux-2.6-block.git] / fs / btrfs / extent_map.c

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 72e9fa3c31f5f132a8d477f7a1ef741a22594460..5bc7a0d325e7f6a00849c74c794cb168b12c4b4c 100644 (file)
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -198,6 +198,56 @@ static int mergable_maps(struct extent_map *prev, struct extent_map *next)
        return 0;
 }
 
+int unpin_extent_cache(struct extent_map_tree *tree, u64 start, u64 len)
+{
+       int ret = 0;
+       struct extent_map *merge = NULL;
+       struct rb_node *rb;
+       struct extent_map *em;
+
+       write_lock(&tree->lock);
+       em = lookup_extent_mapping(tree, start, len);
+
+       WARN_ON(em->start != start || !em);
+
+       if (!em)
+               goto out;
+
+       clear_bit(EXTENT_FLAG_PINNED, &em->flags);
+
+       if (em->start != 0) {
+               rb = rb_prev(&em->rb_node);
+               if (rb)
+                       merge = rb_entry(rb, struct extent_map, rb_node);
+               if (rb && mergable_maps(merge, em)) {
+                       em->start = merge->start;
+                       em->len += merge->len;
+                       em->block_len += merge->block_len;
+                       em->block_start = merge->block_start;
+                       merge->in_tree = 0;
+                       rb_erase(&merge->rb_node, &tree->map);
+                       free_extent_map(merge);
+               }
+       }
+
+       rb = rb_next(&em->rb_node);
+       if (rb)
+               merge = rb_entry(rb, struct extent_map, rb_node);
+       if (rb && mergable_maps(em, merge)) {
+               em->len += merge->len;
+               em->block_len += merge->len;
+               rb_erase(&merge->rb_node, &tree->map);
+               merge->in_tree = 0;
+               free_extent_map(merge);
+       }
+
+       free_extent_map(em);
+out:
+       write_unlock(&tree->lock);
+       return ret;
+
+}
+
 /**
  * add_extent_mapping - add new extent map to the extent tree
  * @tree:      tree to insert new map in