Re: [PATCH -next v3 4/7] md: factor out a helper rdev_removeable() from remove_and_add_spares()

[Yu Kuai <yukuai1@xxxxxxxxxxxxxxx>]

Hi,

在 2023/08/22 18:19, Xiao Ni 写道:
> On Sun, Aug 20, 2023 at 5:13 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote:
> > From: Yu Kuai <yukuai3@xxxxxxxxxx>
> >
> > There are no functional changes, just to make the code simpler and
> > prepare to delay remove_and_add_spares() to md_start_sync().
> >
> > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> > ---
> >   drivers/md/md.c | 33 +++++++++++++++++++--------------
> >   1 file changed, 19 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > index 561cac13ff96..ceace5ffadd6 100644
> > --- a/drivers/md/md.c
> > +++ b/drivers/md/md.c
> > @@ -9153,6 +9153,22 @@ void md_do_sync(struct md_thread *thread)
> >   }
> >   EXPORT_SYMBOL_GPL(md_do_sync);
> >
> > +static bool rdev_removeable(struct md_rdev *rdev)
> > +{
> > +       if (rdev->raid_disk < 0 || test_bit(Blocked, &rdev->flags) ||
> > +           atomic_read(&rdev->nr_pending))
> > +               return false;
> > +
> > +       if (test_bit(RemoveSynchronized, &rdev->flags))
> > +               return true;
> > +
> > +       if (test_bit(In_sync, &rdev->flags) ||
> > +           test_bit(Journal, &rdev->flags))
> > +               return false;
> > +
> > +       return true;
> > +}
> > +
> >   static int remove_and_add_spares(struct mddev *mddev,
> >                                   struct md_rdev *this)
> >   {
> > @@ -9166,11 +9182,7 @@ static int remove_and_add_spares(struct mddev *mddev,
> >                  return 0;
> >
> >          rdev_for_each(rdev, mddev) {
> > -               if ((this == NULL || rdev == this) &&
> > -                   rdev->raid_disk >= 0 &&
> > -                   !test_bit(Blocked, &rdev->flags) &&
> > -                   test_bit(Faulty, &rdev->flags) &&
> > -                   atomic_read(&rdev->nr_pending)==0) {
> > +               if ((this == NULL || rdev == this) && rdev_removeable(rdev)) {
>
> There is a small change with the original method. Before this patch,
> it checks the Faulty flag when setting RemoveSynchronized and it
> checks RemoveSynchronized and "!In_sync && !Journal". I'm not sure if
> it's right or not.

Yes, there is a small change. After a second thought, I think it's OK
to leave the code to set RemoveSynchronized where it is for now, because
it'll be removed later. I don't need to bother factor out a common code
to set RemoveSynchronized and call hot_remove_disk().

By the way, once refactor of mddev_suspend() is done, then access to
rdev from fastpath will be replaced from:

rcu_read_lock()
...
rcu_read_unlock()

to:

md_array_enter()
// grab 'active_io', 'active_io' will probably be renamed
...
md_array_exit()

That's why I said RemoveSynchronized will be removed.

Thanks,
Kuai

> >                          /* Faulty non-Blocked devices with nr_pending == 0
> >                           * never get nr_pending incremented,
> >                           * never get Faulty cleared, and never get Blocked set.
> > @@ -9185,19 +9197,12 @@ static int remove_and_add_spares(struct mddev *mddev,
> >                  synchronize_rcu();
> >          rdev_for_each(rdev, mddev) {
> >                  if ((this == NULL || rdev == this) &&
> > -                   rdev->raid_disk >= 0 &&
> > -                   !test_bit(Blocked, &rdev->flags) &&
> > -                   ((test_bit(RemoveSynchronized, &rdev->flags) ||
> > -                    (!test_bit(In_sync, &rdev->flags) &&
> > -                     !test_bit(Journal, &rdev->flags))) &&
> > -                   atomic_read(&rdev->nr_pending)==0)) {
> > -                       if (mddev->pers->hot_remove_disk(
> > -                                   mddev, rdev) == 0) {
> > +                   rdev_removeable(rdev) &&
> > +                   mddev->pers->hot_remove_disk(mddev, rdev) == 0) {
> >                                  sysfs_unlink_rdev(mddev, rdev);
> >                                  rdev->saved_raid_disk = rdev->raid_disk;
> >                                  rdev->raid_disk = -1;
> >                                  removed++;
> > -                       }
> >                  }
> >                  if (remove_some && test_bit(RemoveSynchronized, &rdev->flags))
> >                          clear_bit(RemoveSynchronized, &rdev->flags);
> > --
> > 2.39.2
>
> .