Btrfs: search for an allocation hint while filling file COW

[pandora-kernel.git] / fs / btrfs / extent_map.c

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 5bc7a0d..2c726b7 100644 (file)
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -366,6 +366,54 @@ out:
        return em;
 }
 
+/**
+ * search_extent_mapping - find a nearby extent map
+ * @tree:      tree to lookup in
+ * @start:     byte offset to start the search
+ * @len:       length of the lookup range
+ *
+ * Find and return the first extent_map struct in @tree that intersects the
+ * [start, len] range.
+ *
+ * If one can't be found, any nearby extent may be returned
+ */
+struct extent_map *search_extent_mapping(struct extent_map_tree *tree,
+                                        u64 start, u64 len)
+{
+       struct extent_map *em;
+       struct rb_node *rb_node;
+       struct rb_node *prev = NULL;
+       struct rb_node *next = NULL;
+
+       rb_node = __tree_search(&tree->map, start, &prev, &next);
+       if (!rb_node && prev) {
+               em = rb_entry(prev, struct extent_map, rb_node);
+               goto found;
+       }
+       if (!rb_node && next) {
+               em = rb_entry(next, struct extent_map, rb_node);
+               goto found;
+       }
+       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);
+       goto found;
+
+       em = NULL;
+       goto out;
+
+found:
+       atomic_inc(&em->refs);
+out:
+       return em;
+}
+
 /**
  * remove_extent_mapping - removes an extent_map from the extent tree
  * @tree:      extent tree to remove from