[PATCH RFC 03/16] fs: add assert for move_mount()

[Christian Brauner <brauner@kernel.org>]

After we've attached a detached mount tree the anonymous mount namespace
must be empty. Add an assert and make this assumption explicit.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/namespace.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 1d3b524ef878..7d0fa8ef8674 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3421,10 +3421,13 @@ static int do_move_mount(struct path *old_path, struct path *new_path,
 out:
 	unlock_mount(mp);
 	if (!err) {
-		if (attached)
+		if (attached) {
 			mntput_no_expire(parent);
-		else
+		} else {
+			/* Make sure we notice when we leak mounts. */
+			VFS_WARN_ON_ONCE(!mnt_ns_empty(ns));
 			free_mnt_ns(ns);
+		}
 	}
 	return err;
 }

-- 
2.47.2