linux-kernel - Re: [PATCH -next] md/raid5: don't allow concurrent reshape with recovery

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Message-ID: <6074a7aa-bb9c-6803-dd94-bba208d47ba0@molgen.mpg.de>
Date:   Mon, 29 May 2023 08:44:06 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
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] md/raid5: don't allow concurrent reshape with
 recovery

Dear Yu,


Thank you for your patch. As always some minor commons, you can also ignore.

Am 29.05.23 um 05:10 schrieb Yu Kuai:
> From: Yu Kuai <yukuai3@...wei.com>
> 
> commit 0aecb06e2249 ("md/raid5: don't allow replacement while reshape

I’d start with a capital letter: Commit …

> is in progress") fix that replacement can be set if reshape is

fixes

> interrupted, which will cause that array can't be assemebled.

assembled

> There is a similar on the other side, if recovery is interrupted, then

similar *problem*?

> reshape can start, which will cause the same problem.
> 
> Fix the prblem by don't start reshape is recovery is still in progress.

•  problem
•  … by not starting to reshape while recovery is still in progress

> Signed-off-by: Yu Kuai <yukuai3@...wei.com>
> ---
>   drivers/md/raid5.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 64865f9dd3f5..6db783ca71b7 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -8500,6 +8500,7 @@ static int raid5_start_reshape(struct mddev *mddev)
>   	struct r5conf *conf = mddev->private;
>   	struct md_rdev *rdev;
>   	int spares = 0;
> +	int i;

It won’t make a difference for the code I believe, but as the count 
variable can’t be negative, I’d use `unsigned int`.

>   	unsigned long flags;
>   
>   	if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
> @@ -8511,6 +8512,13 @@ static int raid5_start_reshape(struct mddev *mddev)
>   	if (has_failed(conf))
>   		return -EINVAL;
>   
> +	/* raid5 can't handle concurrent reshape and recovery */
> +	if (mddev->recovery_cp < MaxSector)
> +		return -EBUSY;
> +	for (i = 0; i < conf->raid_disks; i++)
> +		if (rdev_mdlock_deref(mddev, conf->disks[i].replacement))
> +			return -EBUSY;
> +
>   	rdev_for_each(rdev, mddev) {
>   		if (!test_bit(In_sync, &rdev->flags)
>   		    && !test_bit(Faulty, &rdev->flags))


Kind regards,

Paul