linux-kernel - Re: [PATCH] md: Don't clear MD_CLOSING when the raid is about to stop

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Date:   Mon, 11 Dec 2023 10:56:20 +0100
From:   Mariusz Tkaczyk <mariusz.tkaczyk@...ux.intel.com>
To:     linan666@...weicloud.com
Cc:     song@...nel.org, zlliu@...e.com, neilb@...e.com, shli@...com,
        linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        yukuai3@...wei.com, yi.zhang@...wei.com, houtao1@...wei.com,
        yangerkun@...wei.com
Subject: Re: [PATCH] md: Don't clear MD_CLOSING when the raid is about to
 stop

On Mon, 11 Dec 2023 16:17:14 +0800
linan666@...weicloud.com wrote:

> From: Li Nan <linan122@...wei.com>
> 
> The raid should not be opened anymore when it is about to be stopped.
> However, other processes can open it again if the flag MD_CLOSING is
> cleared before exiting. From now on, this flag will not be cleared when
> the raid will be stopped.
> 
> Fixes: 065e519e71b2 ("md: MD_CLOSING needs to be cleared after called
> md_set_readonly or do_md_stop") Signed-off-by: Li Nan <linan122@...wei.com>

Hello Li Nan,
I was there when I needed to fix this:
https://git.kernel.org/pub/scm/linux/kernel/git/song/md.git/commit/?h=md-next&id=c8870379a21fbd9ad14ca36204ccfbe9d25def43

For sure, you have to consider applying same solution for array_store "clear".
Minor nit below.

Thanks,
Mariusz

> ---
>  drivers/md/md.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 4e9fe5cbeedc..ebdfc9068a60 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -6238,7 +6238,6 @@ static void md_clean(struct mddev *mddev)
>  	mddev->persistent = 0;
>  	mddev->level = LEVEL_NONE;
>  	mddev->clevel[0] = 0;
> -	mddev->flags = 0;

I recommend (safety recommendation):
	mddev->flags = MD_CLOSING;

Unless you can prove that other flags cannot race.

>  	mddev->sb_flags = 0;
>  	mddev->ro = MD_RDWR;
>  	mddev->metadata_type[0] = 0;