Re: [PATCH v2 05/11] md: export helpers to stop sync_thread

[Yu Kuai]

Hi,

在 2024/01/25 15:57, Yu Kuai 写道:
> Hi,
>
> 在 2024/01/25 15:51, Xiao Ni 写道:
> > On Wed, Jan 24, 2024 at 5:19 PM Yu Kuai <yukuai3@xxxxxxxxxx> wrote:
> > > The new heleprs will be used in dm-raid in later patches to fix
> > > regressions and prevent calling md_reap_sync_thread() directly.
> > >
> > > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> > > ---
> > >   drivers/md/md.c | 41 +++++++++++++++++++++++++++++++++++++----
> > >   drivers/md/md.h |  3 +++
> > >   2 files changed, 40 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > > index 6c5d0a372927..90cf31b53804 100644
> > > --- a/drivers/md/md.c
> > > +++ b/drivers/md/md.c
> > > @@ -4915,30 +4915,63 @@ static void stop_sync_thread(struct mddev 
> > > *mddev, bool locked, bool check_seq)
> > >                  mddev_lock_nointr(mddev);
> > >   }
> > >
> > > -static void idle_sync_thread(struct mddev *mddev)
> > > +void md_idle_sync_thread(struct mddev *mddev)
> > >   {
> > > +       lockdep_assert_held(mddev->reconfig_mutex);
> > > +
> >
> > Hi Kuai
> >
> > There is a building error. It should give a pointer to
> > lockdep_assert_held. And same with the other two places in this patch.
>
> Yes, I forgot that I disabled all the debug config in order to let tests
> finish quickly.

I enabled these debuging conifg, and turns out this patch has some
problem, see below.
> Thanks for the notince, will fix this in v3.
>
> Thanks,
> Kuai
>
> > Regards
> > Xiao
> >
> > >          mutex_lock(&mddev->sync_mutex);
> > >          clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > > +       stop_sync_thread(mddev, true, true);
> > > +       mutex_unlock(&mddev->sync_mutex);
> > > +}
> > > +EXPORT_SYMBOL_GPL(md_idle_sync_thread);
> > > +
> > > +void md_frozen_sync_thread(struct mddev *mddev)
> > > +{
> > > +       lockdep_assert_held(mddev->reconfig_mutex);
> > > +
> > > +       mutex_lock(&mddev->sync_mutex);
> > > +       set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > > +       stop_sync_thread(mddev, true, false);

stop_sync_thread() may release 'reconfig_mutex' and grab it again, hence
it's not right to grab 'sync_mutex' before 'reconfig_mutex'.

Since 'sync_mutex' is introduced to serialize sysfs api 'sync_action'
writers, while is not involved for dm-raid. I'll remove 'sync_mutex' for
the new helper in v3.

Thanks,
Kuai

> > > +       mutex_unlock(&mddev->sync_mutex);
> > > +}
> > > +EXPORT_SYMBOL_GPL(md_frozen_sync_thread);
> > >
> > > +void md_unfrozen_sync_thread(struct mddev *mddev)
> > > +{
> > > +       lockdep_assert_held(mddev->reconfig_mutex);
> > > +
> > > +       mutex_lock(&mddev->sync_mutex);
> > > +       clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > > +       set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
> > > +       md_wakeup_thread(mddev->thread);
> > > +       sysfs_notify_dirent_safe(mddev->sysfs_action);
> > > +       mutex_unlock(&mddev->sync_mutex);
> > > +}
> > > +EXPORT_SYMBOL_GPL(md_unfrozen_sync_thread);
> > > +
> > > +static void idle_sync_thread(struct mddev *mddev)
> > > +{
> > >          if (mddev_lock(mddev)) {
> > >                  mutex_unlock(&mddev->sync_mutex);
> > >                  return;
> > >          }
> > >
> > > +       mutex_lock(&mddev->sync_mutex);
> > > +       clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > >          stop_sync_thread(mddev, false, true);
> > >          mutex_unlock(&mddev->sync_mutex);
> > >   }
> > >
> > >   static void frozen_sync_thread(struct mddev *mddev)
> > >   {
> > > -       mutex_lock(&mddev->sync_mutex);
> > > -       set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > > -
> > >          if (mddev_lock(mddev)) {
> > >                  mutex_unlock(&mddev->sync_mutex);
> > >                  return;
> > >          }
> > >
> > > +       mutex_lock(&mddev->sync_mutex);
> > > +       set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
> > >          stop_sync_thread(mddev, false, false);
> > >          mutex_unlock(&mddev->sync_mutex);
> > >   }
> > > diff --git a/drivers/md/md.h b/drivers/md/md.h
> > > index 8d881cc59799..437ab70ce79b 100644
> > > --- a/drivers/md/md.h
> > > +++ b/drivers/md/md.h
> > > @@ -781,6 +781,9 @@ extern void md_rdev_clear(struct md_rdev *rdev);
> > >   extern void md_handle_request(struct mddev *mddev, struct bio *bio);
> > >   extern int mddev_suspend(struct mddev *mddev, bool interruptible);
> > >   extern void mddev_resume(struct mddev *mddev);
> > > +extern void md_idle_sync_thread(struct mddev *mddev);
> > > +extern void md_frozen_sync_thread(struct mddev *mddev);
> > > +extern void md_unfrozen_sync_thread(struct mddev *mddev);
> > >
> > >   extern void md_reload_sb(struct mddev *mddev, int raid_disk);
> > >   extern void md_update_sb(struct mddev *mddev, int force);
> > > --
> > > 2.39.2
> >
> > .
>
> .