1 files changed, 30 insertions, 1 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 47e91184fff3..b38c3e92f0c8 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -940,7 +940,6 @@ static int find_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
         int wrapped = 0;
         u64 limit;
 
-        path = btrfs_alloc_path();
         ins->flags = 0;
         btrfs_set_key_type(ins, BTRFS_EXTENT_ITEM_KEY);
 
@@ -974,6 +973,8 @@ static int find_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root
                                                      data, 1);
         }
 
+        path = btrfs_alloc_path();
+
 check_failed:
         if (!block_group->data)
                 search_start = find_search_start(root, &block_group,
@@ -1355,6 +1356,28 @@ static int drop_leaf_ref(struct btrfs_trans_handle *trans,
         return 0;
 }
 
+static void reada_walk_down(struct btrfs_root *root,
+                            struct btrfs_node *node)
+{
+        int i;
+        u32 nritems;
+        u64 blocknr;
+        int ret;
+        u32 refs;
+
+        nritems = btrfs_header_nritems(&node->header);
+        for (i = 0; i < nritems; i++) {
+                blocknr = btrfs_node_blockptr(node, i);
+                ret = lookup_extent_ref(NULL, root, blocknr, 1, &refs);
+                BUG_ON(ret);
+                if (refs != 1)
+                        continue;
+                ret = readahead_tree_block(root, blocknr);
+                if (ret)
+                        break;
+        }
+}
+
 /*
  * helper function for drop_snapshot, this walks down the tree dropping ref
  * counts as it goes.
@@ -1375,6 +1398,7 @@ static int walk_down_tree(struct btrfs_trans_handle *trans, struct btrfs_root
         BUG_ON(ret);
         if (refs > 1)
                 goto out;
+
         /*
          * walk down to the last node level and free all the leaves
          */
@@ -1382,8 +1406,13 @@ static int walk_down_tree(struct btrfs_trans_handle *trans, struct btrfs_root
                 WARN_ON(*level < 0);
                 WARN_ON(*level >= BTRFS_MAX_LEVEL);
                 cur = path->nodes[*level];
+
+                if (*level > 0 && path->slots[*level] == 0)
+                        reada_walk_down(root, btrfs_buffer_node(cur));
+
                 if (btrfs_header_level(btrfs_buffer_header(cur)) != *level)
                         WARN_ON(1);
+
                 if (path->slots[*level] >=
                     btrfs_header_nritems(btrfs_buffer_header(cur)))
                         break;