[dm-devel] [PATCH] fix writing to the filesystem after unmount

[Al Viro]

On Wed, Sep 06, 2023 at 06:01:06PM +0200, Mikulas Patocka wrote:

> Perhaps we could distinguish between FIFREEZE-initiated freezes and 
> device-mapper initiated freezes as well. And we could change the logic to 
> return -EBUSY if the freeze was initiated by FIFREEZE and to wait for 
> unfreeze if it was initiated by the device-mapper.

By the time you get to cleanup_mnt() it's far too late to return -EBUSY.