Btrfs: check return value of lookup_extent_mapping() correctly

[firefly-linux-kernel-4.4.55.git] / fs / btrfs / volumes.c

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index d8f282b5baa993b881cc6a91506d666825b34b96..cd040bf3fd87134bd36c76e40b29d7d0eab46b1d 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1954,7 +1954,7 @@ static int btrfs_relocate_chunk(struct btrfs_root *root,
        em = lookup_extent_mapping(em_tree, chunk_offset, 1);
        read_unlock(&em_tree->lock);
 
-       BUG_ON(em->start > chunk_offset ||
+       BUG_ON(!em || em->start > chunk_offset ||
               em->start + em->len < chunk_offset);
        map = (struct map_lookup *)em->bdev;