Re: [PATCH 00/17] VFS: Filesystem information and notifications [ver #17]

[Al Viro]

On Fri, Mar 06, 2020 at 08:37:05PM +0000, Al Viro wrote:

> You are misreading mntput_no_expire(), BTW - your get_mount() can
> bloody well race with umount(2), hitting the moment when we are done
> figuring out whether it's busy but hadn't cleaned ->mnt_ns (let alone
> set MNT_DOOMED) yet.  If somebody calls umount(2) on a filesystem that
> is not mounted anywhere else, they are not supposed to see the sucker
> return 0 until the filesystem is shut down.  You break that.

While we are at it, d_alloc_parallel() requires i_rwsem on parent held
at least shared.