From: Hannes Reinecke <hare@suse.de>
To: Daniel Wagner <dwagner@suse.de>, Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
Ming Lei <ming.lei@redhat.com>
Subject: Re: [PATCH] block: Use non _rcu version of list functions for tag_set_list
Date: Tue, 28 Jul 2020 16:13:13 +0200 [thread overview]
Message-ID: <e9e63b09-c077-edb9-ea28-cbbc96b99261@suse.de> (raw)
In-Reply-To: <20200728132951.29459-1-dwagner@suse.de>
On 7/28/20 3:29 PM, Daniel Wagner wrote:
> tag_set_list is only accessed under the tag_set_lock lock. There is
> no need for using the _rcu list functions.
>
> The _rcu list function were introduced to allow read access to the
> tag_set_list protected under RCU, see 705cda97ee3a ("blk-mq: Make it
> safe to use RCU to iterate over blk_mq_tag_set.tag_list") and
> 05b79413946d ("Revert "blk-mq: don't handle TAG_SHARED in restart"").
> Those changes got reverted later but the cleanup commit missed a
> couple of places to undo the changes.
>
> Fixes: 97889f9ac24f ("blk-mq: remove synchronize_rcu() from blk_mq_del_queue_tag_set()"
> Cc: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: Daniel Wagner <dwagner@suse.de>
> ---
> block/blk-mq.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index e32cb0217135..14ee7506f32f 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -2792,7 +2792,7 @@ static void blk_mq_del_queue_tag_set(struct request_queue *q)
> struct blk_mq_tag_set *set = q->tag_set;
>
> mutex_lock(&set->tag_list_lock);
> - list_del_rcu(&q->tag_set_list);
> + list_del(&q->tag_set_list);
> if (list_is_singular(&set->tag_list)) {
> /* just transitioned to unshared */
> set->flags &= ~BLK_MQ_F_TAG_SHARED;
> @@ -2819,7 +2819,7 @@ static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
> }
> if (set->flags & BLK_MQ_F_TAG_SHARED)
> queue_set_hctx_shared(q, true);
> - list_add_tail_rcu(&q->tag_set_list, &set->tag_list);
> + list_add_tail(&q->tag_set_list, &set->tag_list);
>
> mutex_unlock(&set->tag_list_lock);
> }
>
Indeed.
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
hare@suse.de +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer
next prev parent reply other threads:[~2020-07-28 14:13 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-28 13:29 [PATCH] block: Use non _rcu version of list functions for tag_set_list Daniel Wagner
2020-07-28 14:13 ` Hannes Reinecke [this message]
2020-07-28 15:37 ` Jens Axboe
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