linux-kernel - Re: [PATCH] md/raid5: Fix a deadlock of reshape and suspend

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Message-Id: <13706e9e-541a-4c09-b104-2d7272d0a2fa@fnnas.com>
Date: Thu, 25 Dec 2025 15:32:17 +0800
From: "Yu Kuai" <yukuai@...as.com>
To: <linan666@...weicloud.com>, <song@...nel.org>
Cc: <linux-raid@...r.kernel.org>, <linux-kernel@...r.kernel.org>, 
	<yangerkun@...wei.com>, <yi.zhang@...wei.com>, <yukuai@...as.com>
Subject: Re: [PATCH] md/raid5: Fix a deadlock of reshape and suspend

Hi,

在 2025/11/24 16:45, linan666@...weicloud.com 写道:
> From: Li Nan <linan122@...wei.com>
>
> Commit 868bba54a3bc ("md/raid5: fix a deadlock in the case that reshape is
> interrupted") fixed a raid deadlock of reshape, but a similar issue is hit
> by mdadm test 25raid456-reshape-deadlock.
>
>    INFO: task (udev-worker):63822 blocked for more than 122 seconds.
>          Not tainted 6.18.0-rc2-g0555b5424915-dirty #153
>    "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>    __schedule
>    schedule
>    schedule_timeout
>    wait_woken
>    raid5_make_request
>    md_handle_request
>    md_submit_bio
>    [...]
>    blkdev_read_iter
>    vfs_read
>    ksys_read
>    __x64_sys_read
>
> It is triggered by:
> 1) normal IO waits for reshape to progress
> 2) user sets ACTION_FROZEN via ioctl
> 3) reshape is interrupted and cannot restart
> 4) users try to suspend array while active IO waits reshape
>
> Following Kuai's previous fix, such IOs should fail in
> make_stripe_request(). Thus, set a timeout for wait_woken() to fix
> the deadlock, and blocked IO will fail in the next cycle.
>
> Signed-off-by: Li Nan <linan122@...wei.com>
> ---
>   drivers/md/raid5.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index cdbc7eba5c54..957e712d2be9 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -6185,7 +6185,7 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
>   			}
>   
>   			wait_woken(&wait, TASK_UNINTERRUPTIBLE,
> -				   MAX_SCHEDULE_TIMEOUT);
> +				   msecs_to_jiffies(10000));

Instead of this change to wake up every 10s unconditionally, can you fix this by wake up
synchronously when array is frozen or suspended that reshape can't continue.

>   			continue;
>   		}
>   

-- 
Thansk,
Kuai