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From:   Song Liu <song@kernel.org>
Date:   Tue, 26 Jan 2021 23:22:01 -0800
Message-ID: <CAPhsuW6sVtB-baGn46_o6NVynuxQfy9_FuhC2ZK0cKu5cQHWDg@mail.gmail.com>
Subject: Re: [PATCH 12/17] md: simplify sync_page_io
To:     Christoph Hellwig <hch@lst.de>
Cc:     Jens Axboe <axboe@kernel.dk>, Jaegeuk Kim <jaegeuk@kernel.org>,
        Chao Yu <chao@kernel.org>,
        Philipp Reisner <philipp.reisner@linbit.com>,
        Lars Ellenberg <lars.ellenberg@linbit.com>,
        Coly Li <colyli@suse.de>, Mike Snitzer <snitzer@redhat.com>,
        Josef Bacik <josef@toxicpanda.com>,
        David Sterba <dsterba@suse.com>,
        Damien Le Moal <damien.lemoal@wdc.com>,
        Naohiro Aota <naohiro.aota@wdc.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ryusuke Konishi <konishi.ryusuke@gmail.com>,
        linux-nilfs@vger.kernel.org, dm-devel@redhat.com,
        linux-f2fs-devel@lists.sourceforge.net,
        linux-block@vger.kernel.org, drbd-dev@lists.linbit.com,
        linux-bcache@vger.kernel.org,
        linux-raid <linux-raid@vger.kernel.org>,
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        Linux-MM <linux-mm@kvack.org>
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On Tue, Jan 26, 2021 at 7:14 AM Christoph Hellwig <hch@lst.de> wrote:
>
> Use an on-stack bio and biovec for the single page synchronous I/O.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Acked-by: Song Liu <song@kernel.org>

> ---
>  drivers/md/md.c | 26 +++++++++++++-------------
>  1 file changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index e2b9dbb6e888f6..6a27f52007c871 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -1021,29 +1021,29 @@ int md_super_wait(struct mddev *mddev)
>  int sync_page_io(struct md_rdev *rdev, sector_t sector, int size,
>                  struct page *page, int op, int op_flags, bool metadata_op)
>  {
> -       struct bio *bio = md_bio_alloc_sync(rdev->mddev);
> -       int ret;
> +       struct bio bio;
> +       struct bio_vec bvec;
> +
> +       bio_init(&bio, &bvec, 1);
>
>         if (metadata_op && rdev->meta_bdev)
> -               bio_set_dev(bio, rdev->meta_bdev);
> +               bio_set_dev(&bio, rdev->meta_bdev);
>         else
> -               bio_set_dev(bio, rdev->bdev);
> -       bio_set_op_attrs(bio, op, op_flags);
> +               bio_set_dev(&bio, rdev->bdev);
> +       bio.bi_opf = op | op_flags;
>         if (metadata_op)
> -               bio->bi_iter.bi_sector = sector + rdev->sb_start;
> +               bio.bi_iter.bi_sector = sector + rdev->sb_start;
>         else if (rdev->mddev->reshape_position != MaxSector &&
>                  (rdev->mddev->reshape_backwards ==
>                   (sector >= rdev->mddev->reshape_position)))
> -               bio->bi_iter.bi_sector = sector + rdev->new_data_offset;
> +               bio.bi_iter.bi_sector = sector + rdev->new_data_offset;
>         else
> -               bio->bi_iter.bi_sector = sector + rdev->data_offset;
> -       bio_add_page(bio, page, size, 0);
> +               bio.bi_iter.bi_sector = sector + rdev->data_offset;
> +       bio_add_page(&bio, page, size, 0);
>
> -       submit_bio_wait(bio);
> +       submit_bio_wait(&bio);
>
> -       ret = !bio->bi_status;
> -       bio_put(bio);
> -       return ret;
> +       return !bio.bi_status;
>  }
>  EXPORT_SYMBOL_GPL(sync_page_io);
>
> --
> 2.29.2
>