Re: [PATCH 2/2] cdrom: gdrom: update gendisk capacity on open

[Florian Fuchs]

On 06 Apr 11:21, Adrian McMenamin wrote:
> On Mon, 6 Apr 2026 at 11:00, Adrian McMenamin <adrianmcmenamin@xxxxxxxxx> wrote:
> >
> > Florian,
> >
> > On Mon, 6 Apr 2026 at 10:20, Florian Fuchs <fuchsfl@xxxxxxxxx> wrote:
> >
> >
> > >
> > > You mean, because one of the functions in the call tree of
> > > gdrom_update_capacity() wants to get the mutex gdrom_mutex or s_umount?
> > > I checked the locally called functions, but don't see that one tries to
> > > aquire a lock.
> > >
> > > I don't understand the exact potential of the race condition, maybe you
> > > can elaborate, where I should look.
> > >
> >
> >
> > Actually, having looked at the code path in detail too I agree that
> > this won't recreate the problem the earlier patch addressed, so this
> > looks good to me.
> 
> 
> Sorry - a further thought. This rechecking for capacity is only truly
> necessary if there has been a change of medium - is that right? So we
> can take the result of the earlier disk_check_media_change and if that
> returns true update the capacity? Is that not correct?

The problem is, that disk_check_media_change(disk) is false on initial
gdrom_bdops_open() when the CD is already in it. It gets true there, if I
swap the disc while running the DC.

So right now, it would check capacity on every gdrom_bdops_open() -
which is mostly on every mount, instead of only if the disk was really
changed in between two mounts.

Regards
Florian