linux-kernel - Re: [PATCH v2 1/6] md/raid10: don't call bio_start_io_acct twice for bio which experienced read error

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Message-ID: <CAPhsuW5nw0tgVmm-iB++_x2K=dBNSyHNtfpLyKBArn6YZVoteA@mail.gmail.com>
Date:   Mon, 13 Mar 2023 15:08:36 -0700
From:   Song Liu <song@...nel.org>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     guoqing.jiang@...ux.dev, jgq516@...il.com, neilb@...e.de,
        shli@...com, lzhong@...e.com, linux-raid@...r.kernel.org,
        linux-kernel@...r.kernel.org, yukuai3@...wei.com,
        yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH v2 1/6] md/raid10: don't call bio_start_io_acct twice for
 bio which experienced read error

On Thu, Mar 9, 2023 at 11:39 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> From: Yu Kuai <yukuai3@...wei.com>
>
> 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().
>
> Fixes: 528bc2cf2fcc ("md/raid10: enable io accounting")
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> Acked-by: Guoqing Jiang <guoqing.jiang@...ux.dev>

I would rather keep same argument lists for raid10_read_request
and raid10_write_request. How about we do something like this
instead?

diff --git i/drivers/md/raid10.c w/drivers/md/raid10.c
index 6b39e6c7ada3..13f33a8a8fe8 100644
--- i/drivers/md/raid10.c
+++ w/drivers/md/raid10.c
@@ -1248,7 +1248,8 @@ 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 (!r10_bio->start_time &&
+           blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
                r10_bio->start_time = bio_start_io_acct(bio);
        read_bio = bio_alloc_clone(rdev->bdev, bio, gfp, &mddev->bio_set);

@@ -1578,6 +1579,7 @@ static void __make_request(struct mddev *mddev,
struct bio *bio, int sectors)
        r10_bio->sector = bio->bi_iter.bi_sector;
        r10_bio->state = 0;
        r10_bio->read_slot = -1;
+       r10_bio->start_time = 0;
        memset(r10_bio->devs, 0, sizeof(r10_bio->devs[0]) *
                        conf->geo.raid_disks);

Thanks,
Song

> ---
>  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);
>         read_bio = bio_alloc_clone(rdev->bdev, bio, gfp, &mddev->bio_set);
>
> @@ -1578,7 +1578,7 @@ static void __make_request(struct mddev *mddev, struct bio *bio, int sectors)
>                         conf->geo.raid_disks);
>
>         if (bio_data_dir(bio) == READ)
> -               raid10_read_request(mddev, bio, r10_bio);
> +               raid10_read_request(mddev, bio, r10_bio, false);
>         else
>                 raid10_write_request(mddev, bio, r10_bio);
>  }
> @@ -2980,7 +2980,7 @@ static void handle_read_error(struct mddev *mddev, struct r10bio *r10_bio)
>         rdev_dec_pending(rdev, mddev);
>         allow_barrier(conf);
>         r10_bio->state = 0;
> -       raid10_read_request(mddev, r10_bio->master_bio, r10_bio);
> +       raid10_read_request(mddev, r10_bio->master_bio, r10_bio, true);
>  }
>
>  static void handle_write_completed(struct r10conf *conf, struct r10bio *r10_bio)
> --
> 2.31.1
>