Re: [PATCH 14/17] md/raid6: refactor raid5_read_one_chunk

[Song Liu <song@kernel.org>]

On Tue, Jan 26, 2021 at 7:19 AM Christoph Hellwig <hch@lst.de> wrote:
>
> Refactor raid5_read_one_chunk so that all simple checks are done
> before allocating the bio.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

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

Thanks for the clean-up!


> ---
>  drivers/md/raid5.c | 108 +++++++++++++++++++--------------------------
>  1 file changed, 45 insertions(+), 63 deletions(-)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index f411b9e5c332f4..a348b2adf2a9f9 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -5393,90 +5393,72 @@ static void raid5_align_endio(struct bio *bi)
>  static int raid5_read_one_chunk(struct mddev *mddev, struct bio *raid_bio)
>  {
>         struct r5conf *conf = mddev->private;
> -       int dd_idx;
> -       struct bio* align_bi;
> +       struct bio *align_bio;
>         struct md_rdev *rdev;
> -       sector_t end_sector;
> +       sector_t sector, end_sector, first_bad;
> +       int bad_sectors, dd_idx;
>
>         if (!in_chunk_boundary(mddev, raid_bio)) {
>                 pr_debug("%s: non aligned\n", __func__);
>                 return 0;
>         }
> -       /*
> -        * use bio_clone_fast to make a copy of the bio
> -        */
> -       align_bi = bio_clone_fast(raid_bio, GFP_NOIO, &mddev->bio_set);
> -       if (!align_bi)
> -               return 0;
> -       /*
> -        *   set bi_end_io to a new function, and set bi_private to the
> -        *     original bio.
> -        */
> -       align_bi->bi_end_io  = raid5_align_endio;
> -       align_bi->bi_private = raid_bio;
> -       /*
> -        *      compute position
> -        */
> -       align_bi->bi_iter.bi_sector =
> -               raid5_compute_sector(conf, raid_bio->bi_iter.bi_sector,
> -                                    0, &dd_idx, NULL);
>
> -       end_sector = bio_end_sector(align_bi);
> +       sector = raid5_compute_sector(conf, raid_bio->bi_iter.bi_sector, 0,
> +                                     &dd_idx, NULL);
> +       end_sector = bio_end_sector(raid_bio);
> +
>         rcu_read_lock();
> +       if (r5c_big_stripe_cached(conf, sector))
> +               goto out_rcu_unlock;
> +
>         rdev = rcu_dereference(conf->disks[dd_idx].replacement);
>         if (!rdev || test_bit(Faulty, &rdev->flags) ||
>             rdev->recovery_offset < end_sector) {
>                 rdev = rcu_dereference(conf->disks[dd_idx].rdev);
> -               if (rdev &&
> -                   (test_bit(Faulty, &rdev->flags) ||
> +               if (!rdev)
> +                       goto out_rcu_unlock;
> +               if (test_bit(Faulty, &rdev->flags) ||
>                     !(test_bit(In_sync, &rdev->flags) ||
> -                     rdev->recovery_offset >= end_sector)))
> -                       rdev = NULL;
> +                     rdev->recovery_offset >= end_sector))
> +                       goto out_rcu_unlock;
>         }
>
> -       if (r5c_big_stripe_cached(conf, align_bi->bi_iter.bi_sector)) {
> -               rcu_read_unlock();
> -               bio_put(align_bi);
> +       atomic_inc(&rdev->nr_pending);
> +       rcu_read_unlock();
> +
> +       align_bio = bio_clone_fast(raid_bio, GFP_NOIO, &mddev->bio_set);
> +       bio_set_dev(align_bio, rdev->bdev);
> +       align_bio->bi_end_io = raid5_align_endio;
> +       align_bio->bi_private = raid_bio;
> +       align_bio->bi_iter.bi_sector = sector;
> +
> +       raid_bio->bi_next = (void *)rdev;
> +
> +       if (is_badblock(rdev, sector, bio_sectors(align_bio), &first_bad,
> +                       &bad_sectors)) {
> +               bio_put(align_bio);
> +               rdev_dec_pending(rdev, mddev);
>                 return 0;
>         }
>
> -       if (rdev) {
> -               sector_t first_bad;
> -               int bad_sectors;
> -
> -               atomic_inc(&rdev->nr_pending);
> -               rcu_read_unlock();
> -               raid_bio->bi_next = (void*)rdev;
> -               bio_set_dev(align_bi, rdev->bdev);
> -
> -               if (is_badblock(rdev, align_bi->bi_iter.bi_sector,
> -                               bio_sectors(align_bi),
> -                               &first_bad, &bad_sectors)) {
> -                       bio_put(align_bi);
> -                       rdev_dec_pending(rdev, mddev);
> -                       return 0;
> -               }
> +       /* No reshape active, so we can trust rdev->data_offset */
> +       align_bio->bi_iter.bi_sector += rdev->data_offset;
>
> -               /* No reshape active, so we can trust rdev->data_offset */
> -               align_bi->bi_iter.bi_sector += rdev->data_offset;
> +       spin_lock_irq(&conf->device_lock);
> +       wait_event_lock_irq(conf->wait_for_quiescent, conf->quiesce == 0,
> +                           conf->device_lock);
> +       atomic_inc(&conf->active_aligned_reads);
> +       spin_unlock_irq(&conf->device_lock);
>
> -               spin_lock_irq(&conf->device_lock);
> -               wait_event_lock_irq(conf->wait_for_quiescent,
> -                                   conf->quiesce == 0,
> -                                   conf->device_lock);
> -               atomic_inc(&conf->active_aligned_reads);
> -               spin_unlock_irq(&conf->device_lock);
> +       if (mddev->gendisk)
> +               trace_block_bio_remap(align_bio, disk_devt(mddev->gendisk),
> +                                     raid_bio->bi_iter.bi_sector);
> +       submit_bio_noacct(align_bio);
> +       return 1;
>
> -               if (mddev->gendisk)
> -                       trace_block_bio_remap(align_bi, disk_devt(mddev->gendisk),
> -                                             raid_bio->bi_iter.bi_sector);
> -               submit_bio_noacct(align_bi);
> -               return 1;
> -       } else {
> -               rcu_read_unlock();
> -               bio_put(align_bi);
> -               return 0;
> -       }
> +out_rcu_unlock:
> +       rcu_read_unlock();
> +       return 0;
>  }
>
>  static struct bio *chunk_aligned_read(struct mddev *mddev, struct bio *raid_bio)
> --
> 2.29.2
>