linux-kernel - Re: [PATCH -next 4/8] md/raid1: switch to use md_account

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Date:   Tue, 20 Jun 2023 17:07:43 +0800
From:   Xiao Ni <xni@...hat.com>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     song@...nel.org, linux-raid@...r.kernel.org,
        linux-kernel@...r.kernel.org, yukuai3@...wei.com,
        yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH -next 4/8] md/raid1: switch to use md_account_bio() for io accounting

On Mon, Jun 19, 2023 at 8:49 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> From: Yu Kuai <yukuai3@...wei.com>
>
> Two problems can be fixed this way:
>
> 1) 'active_io' will represent inflight io instead of io that is
> dispatching.
>
> 2) If io accounting is enabled or disabled while io is still inflight,
> bio_start_io_acct() and bio_end_io_acct() is not balanced and io
> inflight counter will be leaked.
>
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
>  drivers/md/raid1.c | 14 ++++++--------
>  drivers/md/raid1.h |  1 -
>  2 files changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index dd25832eb045..06fa1580501f 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -304,8 +304,6 @@ static void call_bio_endio(struct r1bio *r1_bio)
>         if (!test_bit(R1BIO_Uptodate, &r1_bio->state))
>                 bio->bi_status = BLK_STS_IOERR;
>
> -       if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
> -               bio_end_io_acct(bio, r1_bio->start_time);
>         bio_endio(bio);
>  }
>
> @@ -1303,10 +1301,10 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
>         }
>
>         r1_bio->read_disk = rdisk;
> -
> -       if (!r1bio_existed && blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
> -               r1_bio->start_time = bio_start_io_acct(bio);
> -
> +       if (!r1bio_existed) {
> +               md_account_bio(mddev, &bio);
> +               r1_bio->master_bio = bio;
> +       }
>         read_bio = bio_alloc_clone(mirror->rdev->bdev, bio, gfp,
>                                    &mddev->bio_set);
>
> @@ -1500,8 +1498,8 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
>                 r1_bio->sectors = max_sectors;
>         }
>
> -       if (blk_queue_io_stat(bio->bi_bdev->bd_disk->queue))
> -               r1_bio->start_time = bio_start_io_acct(bio);
> +       md_account_bio(mddev, &bio);
> +       r1_bio->master_bio = bio;
>         atomic_set(&r1_bio->remaining, 1);
>         atomic_set(&r1_bio->behind_remaining, 0);
>
> diff --git a/drivers/md/raid1.h b/drivers/md/raid1.h
> index 468f189da7a0..14d4211a123a 100644
> --- a/drivers/md/raid1.h
> +++ b/drivers/md/raid1.h
> @@ -157,7 +157,6 @@ struct r1bio {
>         sector_t                sector;
>         int                     sectors;
>         unsigned long           state;
> -       unsigned long           start_time;
>         struct mddev            *mddev;
>         /*
>          * original bio going to /dev/mdx
> --
> 2.39.2
>

Hi Kuai

After this patch, raid1 will have one more memory allocation in the
I/O path. Not sure if it can affect performance. Beside this, the
patch is good for me.

Reviewed-by: Xiao Ni <xni@...hat.com>