Btrfs: Various small fixes.

This trivial patch contains two locking fixes and a off by one fix.

---

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
index a5c0e98..3672669 100644
--- a/fs/btrfs/root-tree.c
+++ b/fs/btrfs/root-tree.c
@@ -209,8 +209,7 @@
 			goto err;
 		}
 
-		ret = btrfs_add_dead_root(dead_root, latest,
-					  &root->fs_info->dead_roots);
+		ret = btrfs_add_dead_root(dead_root, latest);
 		if (ret)
 			goto err;
 		goto again;