Re: [PATCH 12/13] loop: remove lo_refcount and avoid lo_mutex in ->open / ->release

[Jan Kara <jack@suse.cz>]

On Tue 29-03-22 08:39:21, Christoph Hellwig wrote:
> On Mon, Mar 28, 2022 at 10:30:45AM +0200, Jan Kara wrote:
> > On Fri 25-03-22 17:23:31, Christoph Hellwig wrote:
> > > On Fri, Mar 25, 2022 at 07:54:15PM +0900, Tetsuo Handa wrote:
> > > > > But for now I'd really prefer to stop moving the goalpost further and
> > > > > further.
> > > > 
> > > > Then, why not kill this code?
> > > 
> > > I think we should eventually do that, and I've indeed tested a patch
> > > that is only cosmetically different.  I wasn't really convinced we
> > > should do it in this series, but if there is consensus that we should
> > > do it now I can respin the series with a patch like this included.
> > 
> > I'd defer it to a separate patchset. Because as much as the change to
> > disallow LOOP_CLR_FD ioctl for used loop device makes sense, I'm not sure
> > there isn't some framework using loop devices somewhere which relies on
> > this just getting magically translated to setting LO_AUTOCLEAR flag. So IMO
> > this has a big potential of userspace visible regression and as such I'd
> > prefer doing it separately from the bugfixes.
> 
> At least my idea would not be to disallow LOOP_CLR_FD on a used block
> devices as that would go back to the udev problems before Dave turned
> it into a magic LO_AUTOCLEAR.  But to remove the lo_refcnt check
> entirely, as loop_clr_fd now is safe against concurrent users - it
> has to anyway as there can be other users even without an open.

Ah, OK, so you'd always set LO_AUTOCLEAR and leave cleanup to happen
from lo_release()? That makes sense to me.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR