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Message-ID: <fefca89d-2bf3-b732-4812-5341203c0818@molgen.mpg.de>
Date:   Fri, 28 Jul 2023 09:21:31 +0200
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Subject: Re: [PATCH -next] md:ensure mddev->reconfig_mutex is hold when try to
 get mddev->sync_thread
To:     Li Lingfeng <lilingfeng@huaweicloud.com>
Cc:     song@kernel.org, linux-raid@vger.kernel.org,
        linux-kernel@vger.kernel.org, yukuai3@huawei.com,
        linan122@huawei.com, yi.zhang@huawei.com, yangerkun@huawei.com,
        lilingfeng3@huawei.com
References: <20230727072047.389637-1-lilingfeng@huaweicloud.com>
Content-Language: en-US
From:   Paul Menzel <pmenzel@molgen.mpg.de>
In-Reply-To: <20230727072047.389637-1-lilingfeng@huaweicloud.com>
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Dear Li,


Thank you for your patch.

I notice two minor things in the summary:

1.  Please add a space after the colon
2.  “is hold” should be “is held”.

Maybe even shorter:

md: Hold mddev->reconfig_mutex when trying to get mddev->sync_thread

Am 27.07.23 um 09:20 schrieb Li Lingfeng:
> Commit ba9d9f1a707f ("Revert "md: unlock mddev before reap sync_thread in
> action_store"") removed the scenario of calling md_unregister_thread()
> without holding mddev->reconfig_mutex, so add a lock holding check before
> acquiring mddev->sync_thread.

Maybe also mention, that this is done by passing `mdev` to 
`md_unregister_thread()`.

Plesae add a Fixes: tag.

> Signed-off-by: Li Lingfeng <lilingfeng@huaweicloud.com>
> ---
>   drivers/md/md-cluster.c  | 8 ++++----
>   drivers/md/md.c          | 9 +++++----
>   drivers/md/md.h          | 2 +-
>   drivers/md/raid1.c       | 4 ++--
>   drivers/md/raid10.c      | 2 +-
>   drivers/md/raid5-cache.c | 2 +-
>   drivers/md/raid5.c       | 2 +-
>   7 files changed, 15 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
> index 3d9fd74233df..1e26eb223349 100644
> --- a/drivers/md/md-cluster.c
> +++ b/drivers/md/md-cluster.c
> @@ -952,8 +952,8 @@ static int join(struct mddev *mddev, int nodes)
>   	return 0;
>   err:
>   	set_bit(MD_CLUSTER_HOLDING_MUTEX_FOR_RECVD, &cinfo->state);
> -	md_unregister_thread(&cinfo->recovery_thread);
> -	md_unregister_thread(&cinfo->recv_thread);
> +	md_unregister_thread(mddev, &cinfo->recovery_thread);
> +	md_unregister_thread(mddev, &cinfo->recv_thread);
>   	lockres_free(cinfo->message_lockres);
>   	lockres_free(cinfo->token_lockres);
>   	lockres_free(cinfo->ack_lockres);
> @@ -1015,8 +1015,8 @@ static int leave(struct mddev *mddev)
>   		resync_bitmap(mddev);
>   
>   	set_bit(MD_CLUSTER_HOLDING_MUTEX_FOR_RECVD, &cinfo->state);
> -	md_unregister_thread(&cinfo->recovery_thread);
> -	md_unregister_thread(&cinfo->recv_thread);
> +	md_unregister_thread(mddev, &cinfo->recovery_thread);
> +	md_unregister_thread(mddev, &cinfo->recv_thread);
>   	lockres_free(cinfo->message_lockres);
>   	lockres_free(cinfo->token_lockres);
>   	lockres_free(cinfo->ack_lockres);
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index a3d98273b295..5c3c19b8d509 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -6258,7 +6258,7 @@ static void mddev_detach(struct mddev *mddev)
>   		mddev->pers->quiesce(mddev, 1);
>   		mddev->pers->quiesce(mddev, 0);
>   	}
> -	md_unregister_thread(&mddev->thread);
> +	md_unregister_thread(mddev, &mddev->thread);
>   	if (mddev->queue)
>   		blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
>   }
> @@ -7990,9 +7990,10 @@ struct md_thread *md_register_thread(void (*run) (struct md_thread *),
>   }
>   EXPORT_SYMBOL(md_register_thread);
>   
> -void md_unregister_thread(struct md_thread __rcu **threadp)
> +void md_unregister_thread(struct mddev *mddev, struct md_thread __rcu **threadp)
>   {
> -	struct md_thread *thread = rcu_dereference_protected(*threadp, true);
> +	struct md_thread *thread = rcu_dereference_protected(*threadp,
> +					lockdep_is_held(&mddev->reconfig_mutex));
>   
>   	if (!thread)
>   		return;
> @@ -9484,7 +9485,7 @@ void md_reap_sync_thread(struct mddev *mddev)
>   	bool is_reshaped = false;
>   
>   	/* resync has finished, collect result */
> -	md_unregister_thread(&mddev->sync_thread);
> +	md_unregister_thread(mddev, &mddev->sync_thread);
>   	atomic_inc(&mddev->sync_seq);
>   
>   	if (!test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
> diff --git a/drivers/md/md.h b/drivers/md/md.h
> index 8ae957480976..9bcb77bca963 100644
> --- a/drivers/md/md.h
> +++ b/drivers/md/md.h
> @@ -761,7 +761,7 @@ extern struct md_thread *md_register_thread(
>   	void (*run)(struct md_thread *thread),
>   	struct mddev *mddev,
>   	const char *name);
> -extern void md_unregister_thread(struct md_thread __rcu **threadp);
> +extern void md_unregister_thread(struct mddev *mddev, struct md_thread __rcu **threadp);
>   extern void md_wakeup_thread(struct md_thread __rcu *thread);
>   extern void md_check_recovery(struct mddev *mddev);
>   extern void md_reap_sync_thread(struct mddev *mddev);
> diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> index 23d211969565..581dfbdfca89 100644
> --- a/drivers/md/raid1.c
> +++ b/drivers/md/raid1.c
> @@ -3152,7 +3152,7 @@ static int raid1_run(struct mddev *mddev)
>   	 * RAID1 needs at least one disk in active
>   	 */
>   	if (conf->raid_disks - mddev->degraded < 1) {
> -		md_unregister_thread(&conf->thread);
> +		md_unregister_thread(mddev, &conf->thread);
>   		ret = -EINVAL;
>   		goto abort;
>   	}
> @@ -3179,7 +3179,7 @@ static int raid1_run(struct mddev *mddev)
>   
>   	ret = md_integrity_register(mddev);
>   	if (ret) {
> -		md_unregister_thread(&mddev->thread);
> +		md_unregister_thread(mddev, &mddev->thread);
>   		goto abort;
>   	}
>   	return 0;
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 16aa9d735880..6188b71186f4 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -4320,7 +4320,7 @@ static int raid10_run(struct mddev *mddev)
>   	return 0;
>   
>   out_free_conf:
> -	md_unregister_thread(&mddev->thread);
> +	md_unregister_thread(mddev, &mddev->thread);
>   	raid10_free_conf(conf);
>   	mddev->private = NULL;
>   out:
> diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
> index 47ba7d9e81e1..ce9b42fd54b9 100644
> --- a/drivers/md/raid5-cache.c
> +++ b/drivers/md/raid5-cache.c
> @@ -3171,7 +3171,7 @@ void r5l_exit_log(struct r5conf *conf)
>   	/* Ensure disable_writeback_work wakes up and exits */
>   	wake_up(&conf->mddev->sb_wait);
>   	flush_work(&log->disable_writeback_work);
> -	md_unregister_thread(&log->reclaim_thread);
> +	md_unregister_thread(conf->mddev, &log->reclaim_thread);
>   
>   	conf->log = NULL;
>   
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 4cdb35e54251..f41f9b712d3d 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -8107,7 +8107,7 @@ static int raid5_run(struct mddev *mddev)
>   
>   	return 0;
>   abort:
> -	md_unregister_thread(&mddev->thread);
> +	md_unregister_thread(mddev, &mddev->thread);
>   	print_raid5_conf(conf);
>   	free_conf(conf);
>   	mddev->private = NULL;