Re: [PATCH -next] raid10: fix leak of io accounting

[Yu Kuai]

Hi,

在 2023/03/09 14:36, Guoqing Jiang 写道:
> Hi,
>
> What do you mean 'leak' here?

I try to mean that inflight counting is leaked, because it's increased
twice for one io.
> On 3/4/23 15:01, Yu Kuai wrote:
> > From: Yu Kuai <yukuai3@xxxxxxxxxx>
> >
> > handle_read_error() will resumit r10_bio by raid10_read_request(), which
> > will call bio_start_io_acct() again, while bio_end_io_acct() will only
> > be called once.
> >
> > Fix the problem by don't account io again from handle_read_error().
>
> My understanding is it caused inaccurate io stats for bio which had a read
> error.
>
> > Fixes: 528bc2cf2fcc ("md/raid10: enable io accounting")
> > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> > ---
> >   drivers/md/raid10.c | 8 ++++----
> >   1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> > index 6c66357f92f5..4f8edb6ea3e2 100644
> > --- a/drivers/md/raid10.c
> > +++ b/drivers/md/raid10.c
> > @@ -1173,7 +1173,7 @@ static bool regular_request_wait(struct mddev 
> > *mddev, struct r10conf *conf,
> >   }
> >   static void raid10_read_request(struct mddev *mddev, struct bio *bio,
> > -                struct r10bio *r10_bio)
> > +                struct r10bio *r10_bio, bool handle_error)
> >   {
> >       struct r10conf *conf = mddev->private;
> >       struct bio *read_bio;
> > @@ -1244,7 +1244,7 @@ static void raid10_read_request(struct mddev 
> > *mddev, struct bio *bio,
> >       }
> >       slot = r10_bio->read_slot;
> > -    if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
> > +    if (!handle_error && 
> > blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
> >           r10_bio->start_time = bio_start_io_acct(bio);
>
> I think a simpler way is just check R10BIO_ReadError here.

No, I'm afraid this is incorrect because handle_read_error clears the
state before resubmiting the r10bio.

Thanks,
Kuai
> Thanks,
> Guoqing
> .