1 files changed, 48 insertions, 0 deletions

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 5bc7a0d325e7..2c726b7b9faa 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -367,6 +367,54 @@ out:
 }
 
 /**
+ * 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
  * @em:         extent map beeing removed