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

Miklos Szeredi
2020-03-06T20:51:28Z

On Fri, Mar 6, 2020 at 9:45 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Fri, Mar 06, 2020 at 08:38:44PM +0000, Al Viro wrote:
> > 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.

Ah, good point.

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

Okay.

> Egads... Let me see if I got it right - you are providing procfs symlinks
> to objects on the internal mount of that thing. And those objects happen
> to be directories, so one can get to their parent that way. Or am I misreading
> that thing?

Yes.

Thanks,
Miklos