Re: [PATCH] md: Prevent IO hold during accessing to failed raid5 array

["Obitotskiy, Aleksey" <aleksey.obitotskiy@intel.com>]

Hello,

I would like to know what the status of this patch.
Maybe I should provide more info about?

Regards,
Aleksey

On Tue, 2016-07-19 at 15:46 -0700, Shaohua Li wrote:
> On Fri, Jul 15, 2016 at 03:24:27PM +0200, Alexey Obitotskiy wrote:
> > 
> > After array enters in failed state (e.g. number of failed drives
> > becomes more then accepted for raid5 level) it sets error flags
> > (one of this flags is MD_CHANGE_PENDING). This flag prevents to
> > finish all new or non-finished IOs to array and hold them in
> > pending state. In some cases this can leads to deadlock situation.
> > 
> > For example udev handle array state changes (drives becomes faulty)
> > and blkid started but unable to finish reads due to IO hold.
> > At the same time we unable to get exclusive access to array
> > (to stop array in our case) because another external application
> > still use this array (blkid in our case).
> > 
> > Fix makes possible to return IO with errors immediately.
> > So external application can finish working with array and
> > give exclusive access to other applications.
> > 
> > Signed-off-by: Alexey Obitotskiy <aleksey.obitotskiy@intel.com>
> > ---
> >  drivers/md/raid5.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> > index 6c1149d..99471b6 100644
> > --- a/drivers/md/raid5.c
> > +++ b/drivers/md/raid5.c
> > @@ -4692,7 +4692,9 @@ finish:
> >  	}
> >  
> >  	if (!bio_list_empty(&s.return_bi)) {
> > -		if (test_bit(MD_CHANGE_PENDING, &conf->mddev-
> > >flags)) {
> > +		if (test_bit(MD_CHANGE_PENDING, &conf->mddev-
> > >flags) &&
> > +				(s.failed <= conf->max_degraded ||
> > +					conf->mddev->external ==
> > 0)) {
> >  			spin_lock_irq(&conf->device_lock);
> >  			bio_list_merge(&conf->return_bi,
> > &s.return_bi);
> >  			spin_unlock_irq(&conf->device_lock);