linux-kernel - Re: [PATCH] md/raid1,raid10: strip REQ

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Message-ID: <8d4fd6e0-ebaf-4351-be17-5be24de8b2af@molgen.mpg.de>
Date: Wed, 2 Jul 2025 13:02:32 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Zheng Qixing <zhengqixing@...weicloud.com>
Cc: song@...nel.org, yukuai3@...wei.com, linux-raid@...r.kernel.org,
 linux-kernel@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com,
 houtao1@...wei.com, zhengqixing@...wei.com
Subject: Re: [PATCH] md/raid1,raid10: strip REQ_NOWAIT from member bios

Dear Qixing,


Thank you for your patch.


Am 02.07.25 um 12:23 schrieb Zheng Qixing:
> From: Zheng Qixing <zhengqixing@...wei.com>
> 
> RAID layers don't implement proper non-blocking semantics for
> REQ_NOWAIT, making the flag potentially misleading when propagated
> to member disks.
> 
> This patch clear REQ_NOWAIT from cloned bios in raid1/raid10. Retain
> original bio's REQ_NOWAIT flag for upper layer error handling.

clear*s* or just Clear REQ_NOWAIT …

> Maybe we can implement non-blocking I/O handling mechanisms within
> RAID in future work.

Excuse my ignorance. Is this going to cause a regression for people 
depending on this feature, despite not working reliably?

Also, is there a reproducer to check, that it’s not misleading anymore?

> Signed-off-by: Zheng Qixing <zhengqixing@...wei.com>
> ---
>   drivers/md/raid1.c  | 3 ++-
>   drivers/md/raid10.c | 2 ++
>   2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index 19c5a0ce5a40..213ad5b7e20b 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -1399,7 +1399,7 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
>   	}
>   	read_bio = bio_alloc_clone(mirror->rdev->bdev, bio, gfp,
>   				   &mddev->bio_set);
> -
> +	read_bio->bi_opf &= ~REQ_NOWAIT;
>   	r1_bio->bios[rdisk] = read_bio;
>   
>   	read_bio->bi_iter.bi_sector = r1_bio->sector +
> @@ -1649,6 +1649,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
>   				wait_for_serialization(rdev, r1_bio);
>   		}
>   
> +		mbio->bi_opf &= ~REQ_NOWAIT;
>   		r1_bio->bios[i] = mbio;
>   
>   		mbio->bi_iter.bi_sector	= (r1_bio->sector + rdev->data_offset);
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index b74780af4c22..951b9b443cd1 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -1221,6 +1221,7 @@ static void raid10_read_request(struct mddev *mddev, struct bio *bio,
>   		r10_bio->master_bio = bio;
>   	}
>   	read_bio = bio_alloc_clone(rdev->bdev, bio, gfp, &mddev->bio_set);
> +	read_bio->bi_opf &= ~REQ_NOWAIT;
>   
>   	r10_bio->devs[slot].bio = read_bio;
>   	r10_bio->devs[slot].rdev = rdev;
> @@ -1256,6 +1257,7 @@ static void raid10_write_one_disk(struct mddev *mddev, struct r10bio *r10_bio,
>   			     conf->mirrors[devnum].rdev;
>   
>   	mbio = bio_alloc_clone(rdev->bdev, bio, GFP_NOIO, &mddev->bio_set);
> +	mbio->bi_opf &= ~REQ_NOWAIT;
>   	if (replacement)
>   		r10_bio->devs[n_copy].repl_bio = mbio;
>   	else


Kind regards,

Paul