Btrfs: Fix oopsen when dropping empty tree.

When dropping a empty tree, walk_down_tree() skips checking
extent information for the tree root. This will triggers a
BUG_ON in walk_up_proc().

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 432a2da4641ec55d0d2f963b2f9b276beb61aba1..559f72489b3bf02b4477369da854bf371cbbd0e4 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5402,10 +5402,6 @@ static noinline int walk_down_tree(struct btrfs_trans_handle *trans,
        int ret;
 
        while (level >= 0) {
-               if (path->slots[level] >=
-                   btrfs_header_nritems(path->nodes[level]))
-                       break;
-
                ret = walk_down_proc(trans, root, path, wc, lookup_info);
                if (ret > 0)
                        break;
@@ -5413,6 +5409,10 @@ static noinline int walk_down_tree(struct btrfs_trans_handle *trans,
                if (level == 0)
                        break;
 
+               if (path->slots[level] >=
+                   btrfs_header_nritems(path->nodes[level]))
+                       break;
+
                ret = do_walk_down(trans, root, path, wc, &lookup_info);
                if (ret > 0) {
                        path->slots[level]++;