linux-kernel - Re: [PATCH v2 4/5] md/raid1: Atomic write support

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Message-ID: <d4d9d0cf-08ff-6494-172a-44694b6d13f9@huaweicloud.com>
Date: Thu, 31 Oct 2024 09:57:37 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: John Garry <john.g.garry@...cle.com>, axboe@...nel.dk, song@...nel.org,
 hch@....de
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-raid@...r.kernel.org, martin.petersen@...cle.com,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v2 4/5] md/raid1: Atomic write support

Hi,

在 2024/10/30 17:49, John Garry 写道:
> Set BLK_FEAT_ATOMIC_WRITES_STACKED to enable atomic writes.
> 
> For an attempt to atomic write to a region which has bad blocks, error
> the write as we just cannot do this. It is unlikely to find devices which
> support atomic writes and bad blocks.
> 
> Signed-off-by: John Garry <john.g.garry@...cle.com>
> ---
>   drivers/md/raid1.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index a10018282629..b57f69e3e8a7 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -1524,6 +1524,13 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
>   				blocked_rdev = rdev;
>   				break;
>   			}
> +
> +			if (is_bad && bio->bi_opf & REQ_ATOMIC) {
> +				/* We just cannot atomically write this ... */
> +				error = -EFAULT;
> +				goto err_handle;
> +			}

One nit here. If the write range are all badblocks, then this rdev is
skipped, and bio won't be splited, so I think atomic write is still fine
in this case. Perhaps move this conditon below?

Same for raid10.

Thanks,
Kuai

> +
>   			if (is_bad && first_bad <= r1_bio->sector) {
>   				/* Cannot write here at all */
>   				bad_sectors -= (r1_bio->sector - first_bad);
> @@ -3220,6 +3227,7 @@ static int raid1_set_limits(struct mddev *mddev)
>   
>   	md_init_stacking_limits(&lim);
>   	lim.max_write_zeroes_sectors = 0;
> +	lim.features |= BLK_FEAT_ATOMIC_WRITES_STACKED;
>   	err = mddev_stack_rdev_limits(mddev, &lim, MDDEV_STACK_INTEGRITY);
>   	if (err) {
>   		queue_limits_cancel_update(mddev->gendisk->queue);
>