Re: [PATCH v3 2/2] md: don't account sync_io if iostats of the disk is disabled

[Li Nan]

在 2024/1/3 11:16, Yu Kuai 写道:
> 在 2023/12/23 11:37, linan666@xxxxxxxxxxxxxxx 写道:
> > From: Li Nan <linan122@xxxxxxxxxx>
> >
> > If iostats is disabled, disk_stats will not be updated and
> > part_stat_read_accum() only returns a constant value. In this case,
> > continuing to count sync_io and to check is_mddev_idle() is no longer
> > meaningful.
> >
> > Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
> > ---
> >   drivers/md/md.h | 3 ++-
> >   drivers/md/md.c | 4 ++++
> >   2 files changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/md/md.h b/drivers/md/md.h
> > index 1a4f976951c1..e2d03a7a858c 100644
> > --- a/drivers/md/md.h
> > +++ b/drivers/md/md.h
> > @@ -584,7 +584,8 @@ extern void mddev_unlock(struct mddev *mddev);
> >   static inline void md_sync_acct(struct block_device *bdev, unsigned 
> > long nr_sectors)
> >   {
> > -    atomic64_add(nr_sectors, &bdev->bd_disk->sync_io);
> > +    if (blk_queue_io_stat(bdev->bd_disk->queue))
> > +        atomic64_add(nr_sectors, &bdev->bd_disk->sync_io);
> >   }
> >   static inline void md_sync_acct_bio(struct bio *bio, unsigned long 
> > nr_sectors)
> > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > index a6829ea5b560..b56614eae8dc 100644
> > --- a/drivers/md/md.c
> > +++ b/drivers/md/md.c
> > @@ -8502,6 +8502,10 @@ static int is_mddev_idle(struct mddev *mddev, 
> > int init)
> >       rcu_read_lock();
> >       rdev_for_each_rcu(rdev, mddev) {
> >           struct gendisk *disk = rdev->bdev->bd_disk;
> > +
> > +        if (!blk_queue_io_stat(disk->queue))
> > +            continue;
>
> Consider that the queue flag can be set/cleared through sysfs, let's
> keep set rdev->last_events in the case 'init'. To prevent a false
> positive(althrough highly unlikely) if iostat is enabled during
> md_do_sync().

Thanks for your review, I will add checks of 'init' in next version.

> Thanks,
> Kuai
>
> > +
> >           curr_events =
> >               (long long)part_stat_read_accum(disk->part0, sectors) -
> >               atomic64_read(&disk->sync_io);

--
Thanks,
Nan