Re: [PATCH v2 1/2] md: factor out a new helper to put mddev

[Yu Kuai]

Hi,

在 2023/09/27 8:15, Song Liu 写道:
> On Mon, Sep 25, 2023 at 8:04 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote:
> > From: Yu Kuai <yukuai3@xxxxxxxxxx>
> >
> > There are no functional changes, the new helper will still hold
> > 'all_mddevs_lock' after putting mddev, and it will be used to simplify
> > md_seq_ops.
> >
> > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> > ---
> >   drivers/md/md.c | 18 +++++++++++++++---
> >   1 file changed, 15 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > index 10cb4dfbf4ae..a5ef6f7da8ec 100644
> > --- a/drivers/md/md.c
> > +++ b/drivers/md/md.c
> > @@ -616,10 +616,15 @@ static inline struct mddev *mddev_get(struct mddev *mddev)
> >
> >   static void mddev_delayed_delete(struct work_struct *ws);
> >
> > -void mddev_put(struct mddev *mddev)
> > +static void __mddev_put(struct mddev *mddev, bool locked)
> >   {
> > -       if (!atomic_dec_and_lock(&mddev->active, &all_mddevs_lock))
> > +       if (locked) {
> > +               spin_lock(&all_mddevs_lock);
> > +               if (!atomic_dec_and_test(&mddev->active))
> > +                       return;
> > +       } else if (!atomic_dec_and_lock(&mddev->active, &all_mddevs_lock))
> >                  return;
> > +
>
> This condition is indeed very confusing. No matter whether we call the
> flag "locked" or "do_lock", it is not really accurate.
>
> How about we factor out a helper with the following logic:
>
>          if (!mddev->raid_disks && list_empty(&mddev->disks) &&
>              mddev->ctime == 0 && !mddev->hold_active) {
>                  /* Array is not configured at all, and not held active,
>                   * so destroy it */
>                  set_bit(MD_DELETED, &mddev->flags);
>
>                  /*
>                   * Call queue_work inside the spinlock so that
>                   * flush_workqueue() after mddev_find will succeed in waiting
>                   * for the work to be done.
>                   */
>                  queue_work(md_misc_wq, &mddev->del_work);
>          }
>
> and then use it at the two callers?
>
> Does this make sense?

Yes, that sounds great. I'll do this in v3.

Thanks,
Kuai

> Thanks,
> Song
> .