linux-kernel - Re: [PATCH -next 1/5] md/raid5: don't allow replacement while reshape is not done

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Date:   Fri, 19 May 2023 16:33:59 -0700
From:   Song Liu <song@...nel.org>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     logang@...tatee.com, reddunur@...ine.de, jovetoo@...il.com,
        dgilmour76@...il.com, linux-raid@...r.kernel.org,
        linux-kernel@...r.kernel.org, yukuai3@...wei.com,
        yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH -next 1/5] md/raid5: don't allow replacement while reshape
 is not done

On Thu, May 11, 2023 at 6:59 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> From: Yu Kuai <yukuai3@...wei.com>
>
> Set rdev replacement has but not only two conditions:
>
> 1) MD_RECOVERY_RUNNING is not set;
> 2) rdev nr_pending is 0;

The above is confusing. I updated it and applied the set to md-next.
Please let me know if it looks good.

Thanks,
Song

>
> If reshape is interrupted(for example, echo frozen to sync_action), then
> rdev replacement can be set. It's safe because reshape is always prior to
> resync in md_check_recovery(). However, if system reboots, then kernel will
> complain cannot handle concurrent replacement and reshape and this array
> is not able to assemble anymore.
>
> Fix this problem by don't allow replacement until reshape is done.
>
> Reported-by: Peter Neuwirth <reddunur@...ine.de>
> Link: https://lore.kernel.org/linux-raid/e2f96772-bfbc-f43b-6da1-f520e5164536@online.de/
> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
>  drivers/md/raid5.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index a58507a4345d..bd3b535c0739 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -8378,6 +8378,7 @@ static int raid5_add_disk(struct mddev *mddev, struct md_rdev *rdev)
>                 p = conf->disks + disk;
>                 tmp = rdev_mdlock_deref(mddev, p->rdev);
>                 if (test_bit(WantReplacement, &tmp->flags) &&
> +                   mddev->reshape_position == MaxSector &&
>                     p->replacement == NULL) {
>                         clear_bit(In_sync, &rdev->flags);
>                         set_bit(Replacement, &rdev->flags);
> --
> 2.39.2
>