Btrfs: check for NULL pointer in updating reloc roots

Add a check for NULL pointer to avoid invalid reference.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index ba5a3210da9a..16e0c6fbdbed 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -1269,6 +1269,8 @@ static int __update_reloc_root(struct btrfs_root *root, int del)
         }
         spin_unlock(&rc->reloc_root_tree.lock);
 
+        if (!node)
+                return 0;
         BUG_ON((struct btrfs_root *)node->data != root);
 
         if (!del) {