Btrfs: Fix NULL block groups on reading the inode

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f6a2011..3c7bf3b 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -402,6 +402,10 @@
 	BTRFS_I(inode)->block_group = btrfs_lookup_block_group(root->fs_info,
 						       alloc_group_block);
 
+	if (!BTRFS_I(inode)->block_group) {
+		BTRFS_I(inode)->block_group = btrfs_find_block_group(root,
+						         NULL, 0, 0, 0);
+	}
 	btrfs_free_path(path);
 	inode_item = NULL;