Call btrfs_cow_block while lowering tree level.

When freeing root block of a tree,  btrfs_free_extent' parameter
'ref_generation' is from root block itseft.  When freeing non-root
block,  'ref_generation' is from its parent. so when converting a
non-root block to root block, we must guarantee its generation is
equal to its parent's generation.

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

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index cf32651876bf970abb78bb963ff3f8b522eb7554..ef8809c1e69c3896655a64ee43d6713f7fc1f3ab 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -720,6 +720,9 @@ static int balance_level(struct btrfs_trans_handle *trans,
                /* promote the child to a root */
                child = read_node_slot(root, mid, 0);
                BUG_ON(!child);
+               ret = btrfs_cow_block(trans, root, child, mid, 0, &child);
+               BUG_ON(ret);
+
                root->node = child;
                path->nodes[level] = NULL;
                clean_tree_block(trans, root, mid);