linux-kernel - Re: [PATCH v4 1/4] md: Don't clear MD_CLOSING when the raid is about to stop

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Date: Sat, 27 Jan 2024 16:38:03 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: linan666@...weicloud.com, song@...nel.org, neilb@...e.com, shli@...com,
 mariusz.tkaczyk@...ux.intel.com
Cc: linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
 yi.zhang@...wei.com, houtao1@...wei.com, yangerkun@...wei.com,
 "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v4 1/4] md: Don't clear MD_CLOSING when the raid is about
 to stop

Hi,

在 2024/01/26 17:22, linan666@...weicloud.com 写道:
> 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.

This patch looks good, just one nit below:
> 
> 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>
> Acked-by: Mariusz Tkaczyk <mariusz.tkaczyk@...ux.intel.com>
> ---
>   drivers/md/md.c | 22 ++++++++++++++++++----
>   1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 9bdd57324c37..06550fe34aa1 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -6254,7 +6254,15 @@ static void md_clean(struct mddev *mddev)
>   	mddev->persistent = 0;
>   	mddev->level = LEVEL_NONE;
>   	mddev->clevel[0] = 0;
> -	mddev->flags = 0;
> +	/*
> +	 * Don't clear MD_CLOSING, or mddev can be opened again.
> +	 * 'hold_active != 0' means mddev is still in the creation
> +	 * process and will be used later.
> +	 */
> +	if (mddev->hold_active)
> +		mddev->flags = 0;
> +	else
> +		mddev->flags &= BIT_ULL_MASK(MD_CLOSING);
>   	mddev->sb_flags = 0;
>   	mddev->ro = MD_RDWR;
>   	mddev->metadata_type[0] = 0;
> @@ -7600,7 +7608,7 @@ static int md_ioctl(struct block_device *bdev, blk_mode_t mode,
>   	int err = 0;
>   	void __user *argp = (void __user *)arg;
>   	struct mddev *mddev = NULL;
> -	bool did_set_md_closing = false;
> +	bool clear_md_closing = false;
>   
>   	if (!md_ioctl_valid(cmd))
>   		return -ENOTTY;
> @@ -7684,7 +7692,7 @@ static int md_ioctl(struct block_device *bdev, blk_mode_t mode,
>   			err = -EBUSY;
>   			goto out;
>   		}
> -		did_set_md_closing = true;
> +		clear_md_closing = true;
>   		mutex_unlock(&mddev->open_mutex);
>   		sync_blockdev(bdev);
>   	}
> @@ -7728,6 +7736,12 @@ static int md_ioctl(struct block_device *bdev, blk_mode_t mode,
>   
>   	case STOP_ARRAY:
>   		err = do_md_stop(mddev, 0, bdev);
> +		if (!err)
> +			/*
> +			 * mddev has been stopped, keep the flag
> +			 * MD_CLOSING to prevent reuse.
> +			 */
> +			clear_md_closing = false;
>   		goto unlock;
>   
>   	case STOP_ARRAY_RO:
> @@ -7826,7 +7840,7 @@ static int md_ioctl(struct block_device *bdev, blk_mode_t mode,
>   				     mddev_unlock(mddev);
>   
>   out:
> -	if(did_set_md_closing)
> +	if (clear_md_closing)

I think code will be simplier if we just remove this local variable, and
replace this with:
if (test_bit(MD_CLOSING, &mddev->flags) && (err || cmd == STOP_ARRAY_RO))

And the same for patch 3.

Thanks,
Kuai

>   		clear_bit(MD_CLOSING, &mddev->flags);
>   	return err;
>   }
>