Re: [PATCH v2 2/2] md: don't account sync_io if iostats of the disk is disabled

[Li Nan]

在 2023/12/15 17:08, Song Liu 写道:
> On Thu, Dec 14, 2023 at 5:41 PM <linan666@xxxxxxxxxxxxxxx> wrote:
> > 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..75f5c5d04e71 100644
> > --- a/drivers/md/md.h
> > +++ b/drivers/md/md.h
> > @@ -589,7 +589,8 @@ static inline void md_sync_acct(struct block_device *bdev, unsigned long nr_sect
> >
> >   static inline void md_sync_acct_bio(struct bio *bio, unsigned long nr_sectors)
> >   {
> > -       md_sync_acct(bio->bi_bdev, nr_sectors);
> > +       if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
> > +               md_sync_acct(bio->bi_bdev, nr_sectors);
>
> Do we need the same check for md_sync_acct()?
>
> >   }
> >
> >   struct md_personality
> > diff --git a/drivers/md/md.c b/drivers/md/md.c
> > index 1d71b2a9af03..18bbceb0ffd6 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(mddev->queue))
> > +                       continue;
>
> This looks weird. Do you mean
>
>     if (!blk_queue_io_stat(disk->queue))
>
> Note that I changed two things here: 1) add "!"; 2) check disk, not mddev.
>
> Did I miss something?
>
> Thanks,
> Song

Yeah... It's my bad. I will fix it in v3.

> > +
> >                  curr_events =
> >                          (long long)part_stat_read_accum(disk->part0, sectors) -
> >                                atomic64_read(&disk->sync_io);
> > --
> > 2.39.2
>
> .

--
Thanks,
Nan