linux-kernel - Re: [PATCH v4 7/9] md/raid10: fix failfast read error not rescheduled

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Message-ID: <e7031446-88be-cd4d-ca00-7ce95da5f55a@huaweicloud.com>
Date: Thu, 18 Sep 2025 15:38:57 +0800
From: Li Nan <linan666@...weicloud.com>
To: Kenta Akagi <k@...l.me>, Song Liu <song@...nel.org>,
 Yu Kuai <yukuai3@...wei.com>, Mariusz Tkaczyk <mtkaczyk@...nel.org>,
 Shaohua Li <shli@...com>, Guoqing Jiang <jgq516@...il.com>
Cc: linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 7/9] md/raid10: fix failfast read error not rescheduled



在 2025/9/15 11:42, Kenta Akagi 写道:
> raid10_end_read_request lacks a path to retry when a FailFast IO fails.
> As a result, when Failfast Read IOs fail on all rdevs, the upper layer
> receives EIO, without read rescheduled.
> 
> Looking at the two commits below, it seems only raid10_end_read_request
> lacks the failfast read retry handling, while raid1_end_read_request has
> it. In RAID1, the retry works as expected.
> * commit 8d3ca83dcf9c ("md/raid10: add failfast handling for reads.")
> * commit 2e52d449bcec ("md/raid1: add failfast handling for reads.")
> 
> I don't know why raid10_end_read_request lacks this, but it is probably
> just a simple oversight.

Agreed, these two lines can be removed.

Other than that, LGTM.

Reviewed-by: Li Nan <linan122@...wei.com>

> 
> This commit will make the failfast read bio for the last rdev in raid10
> retry if it fails.
> 
> Fixes: 8d3ca83dcf9c ("md/raid10: add failfast handling for reads.")
> Signed-off-by: Kenta Akagi <k@...l.me>
> ---
>   drivers/md/raid10.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 92cf3047dce6..86c0eacd37cb 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -399,6 +399,11 @@ static void raid10_end_read_request(struct bio *bio)
>   		 * wait for the 'master' bio.
>   		 */
>   		set_bit(R10BIO_Uptodate, &r10_bio->state);
> +	} else if (test_bit(FailFast, &rdev->flags) &&
> +		 test_bit(R10BIO_FailFast, &r10_bio->state)) {
> +		/* This was a fail-fast read so we definitely
> +		 * want to retry */
> +		;
>   	} else if (!raid1_should_handle_error(bio)) {
>   		uptodate = 1;
>   	} else {

-- 
Thanks,
Nan