Re: [PATCH] md/raid10: Only check QUEUE_FLAG_IO_STAT when issuing io

[Li Nan]

在 2023/6/10 10:32, Yu Kuai 写道:
> Hi,
>
> 在 2023/06/09 17:43, linan666@xxxxxxxxxxxxxxx 写道:
> > From: Li Nan <linan122@xxxxxxxxxx>
> >
> > /sys/block/[device]/queue/iostats is used to control whether to count io
> > stat. Write 0 to it will clear queue_flags QUEUE_FLAG_IO_STAT which means
> > iostats is disabled. If we disable iostats and later endable it, the io
> > issued during this period will be counted incorrectly, inflight will be
> > decreased to -1.
> >
> >    //T1 set iostats
> >    echo 0 > /sys/block/md0/queue/iostats
> >     clear QUEUE_FLAG_IO_STAT
> >
> >             //T2 issue io
> >             if (QUEUE_FLAG_IO_STAT) -> false
> >              bio_start_io_acct
> >               inflight++
> >
> >    echo 1 > /sys/block/md0/queue/iostats
> >     set QUEUE_FLAG_IO_STAT
> >
> >                     //T3 io end
> >                     if (QUEUE_FLAG_IO_STAT) -> true
> >                      bio_end_io_acct
> >                       inflight--    -> -1
> >
> > Also, if iostats is enabled while issuing io but disabled while io end,
> > inflight will never be decreased.
> >
> > Fix it by checking start_time when io end. Only check QUEUE_FLAG_IO_STAT
> > while issuing io, just like request based devices.
> >
> > Fixes: 528bc2cf2fcc ("md/raid10: enable io accounting")
> > Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
> > ---
> >   drivers/md/raid10.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> > index 381c21f7fb06..bf9dca5c25c3 100644
> > --- a/drivers/md/raid10.c
> > +++ b/drivers/md/raid10.c
> > @@ -325,7 +325,7 @@ static void raid_end_bio_io(struct r10bio *r10_bio)
> >       if (!test_bit(R10BIO_Uptodate, &r10_bio->state))
> >           bio->bi_status = BLK_STS_IOERR;
> > -    if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
> > +    if (r10_bio->start_time)
> >           bio_end_io_acct(bio, r10_bio->start_time);
>
> This patch LGTM, can you change this for raid1 as well? raid0 and
> raid456 is using md_account_bio(), and they don't have such problem.

OK, I will fix raid1 later. Thanks for suggestion.

> Thanks,
> Kuai
--
Thanks,
Nan