linux-kernel - Re: [RFC PATCH v3 2/3] blk-mq: Freeze and quiesce all queues for tagset in elevator

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 5 Mar 2021 20:32:24 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     John Garry <john.garry@...wei.com>, hare@...e.de,
        ming.lei@...hat.com, axboe@...nel.dk, hch@....de
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        pragalla@...eaurora.org, kashyap.desai@...adcom.com,
        yuyufen@...wei.com
Subject: Re: [RFC PATCH v3 2/3] blk-mq: Freeze and quiesce all queues for
 tagset in elevator_exit()

On 3/5/21 7:14 AM, John Garry wrote:
> diff --git a/block/blk.h b/block/blk.h
> index 3b53e44b967e..1a948bfd91e4 100644
> --- a/block/blk.h
> +++ b/block/blk.h
> @@ -201,10 +201,29 @@ void elv_unregister_queue(struct request_queue *q);
>  static inline void elevator_exit(struct request_queue *q,
>  		struct elevator_queue *e)
>  {
> +	struct blk_mq_tag_set *set = q->tag_set;
> +	struct request_queue *tmp;
> +
>  	lockdep_assert_held(&q->sysfs_lock);
>  
> +	mutex_lock(&set->tag_list_lock);
> +	list_for_each_entry(tmp, &set->tag_list, tag_set_list) {
> +		if (tmp == q)
> +			continue;
> +		blk_mq_freeze_queue(tmp);
> +		blk_mq_quiesce_queue(tmp);
> +	}
> +
>  	blk_mq_sched_free_requests(q);
>  	__elevator_exit(q, e);
> +
> +	list_for_each_entry(tmp, &set->tag_list, tag_set_list) {
> +		if (tmp == q)
> +			continue;
> +		blk_mq_unquiesce_queue(tmp);
> +		blk_mq_unfreeze_queue(tmp);
> +	}
> +	mutex_unlock(&set->tag_list_lock);
>  }

This patch introduces nesting of tag_list_lock inside sysfs_lock. The
latter is per request queue while the former can be shared across
multiple request queues. Has it been analyzed whether this is safe?

Thanks,

Bart.