Re: [PATCH v2] scsi: sr: get rid of sr global mutex

[Christoph Hellwig]

On Tue, Feb 18, 2020 at 09:20:28AM -0800, James Bottomley wrote:
> > > Replace the global mutex with per-sr-device mutex.
> > 
> > Do we actually need the lock at all?  What is protected by it?
> 
> We do at least for cdrom_open.  It modifies the cdi structure with no
> other protection and concurrent modification would at least screw up
> the use counter which is not atomic.  Same reasoning for cdrom_release.

Wouldn't the right fix to add locking to cdrom_open/release instead of
having an undocumented requirement for the callers?