btrfs: Error handle for get_ref_objectid_v0() in relocate_block_group()

We need error checking code for get_ref_objectid_v0() in
relocate_block_group(), to avoid unpredictable result, especially
for accessing uninitialized value(when function failed) after
this line.

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 52fe55a..1659c94 100644 (file)
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3976,6 +3976,10 @@ restart:
                               sizeof(struct btrfs_extent_item_v0));
                        ret = get_ref_objectid_v0(rc, path, &key, &ref_owner,
                                                  &path_change);
+                       if (ret < 0) {
+                               err = ret;
+                               break;
+                       }
                        if (ref_owner < BTRFS_FIRST_FREE_OBJECTID)
                                flags = BTRFS_EXTENT_FLAG_TREE_BLOCK;
                        else