Btrfs: check return value of lookup_extent_mapping() correctly
This patch corrects error checking of lookup_extent_mapping().
Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index d8f282b..cd040bf 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1954,7 +1954,7 @@
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;