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Date: Tue, 3 Nov 2015 09:12:16 +0800 From: Ming Lei <tom.leiming@...il.com> To: Jeff Moyer <jmoyer@...hat.com> Cc: Jens Axboe <axboe@...nel.dk>, Jason Luo <zhangqing.luo@...cle.com>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Guru Anbalagane <guru.anbalagane@...cle.com>, Feng Jin <joe.jin@...cle.com>, Tejun Heo <tj@...nel.org> Subject: Re: [patch, v2] blk-mq: avoid excessive boot delays with large lun counts On Mon, Nov 2, 2015 at 10:04 PM, Jeff Moyer <jmoyer@...hat.com> wrote: > Ming Lei <tom.leiming@...il.com> writes: > >> You can add >> Reviewed-by: Ming Lei <ming.lei@...onical.com> >> if the following trivial issues(especially the 2nd one) are addressed. > > [snip] > >>> @@ -1891,7 +1890,12 @@ static void blk_mq_del_queue_tag_set(struct request_queue *q) >>> >>> mutex_lock(&set->tag_list_lock); >>> list_del_init(&q->tag_set_list); >>> - blk_mq_update_tag_set_depth(set); >>> + if (set->tag_list.next == set->tag_list.prev) { >> >> list_is_singular() should be better. > > Didn't even know that existed. Thanks. > >>> + /* just transitioned to unshared */ >>> + set->flags &= ~BLK_MQ_F_TAG_SHARED; >>> + /* update existing queue */ >>> + blk_mq_update_tag_set_depth(set, false); >>> + } >>> mutex_unlock(&set->tag_list_lock); >>> } >>> >>> @@ -1901,8 +1905,17 @@ static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set, >>> q->tag_set = set; >>> >>> mutex_lock(&set->tag_list_lock); >>> + >>> + /* Check to see if we're transitioning to shared (from 1 to 2 queues). */ >>> + if (!list_empty(&set->tag_list) && !(set->flags & BLK_MQ_F_TAG_SHARED)) { >>> + set->flags |= BLK_MQ_F_TAG_SHARED; >>> + /* update existing queue */ >>> + blk_mq_update_tag_set_depth(set, true); >>> + } >>> + if (set->flags & BLK_MQ_F_TAG_SHARED) >> >> The above should be 'else if', otherwise the current queue will be set >> twice. > > I moved the list add below this to avoid that very issue. See: > >>> + queue_set_hctx_shared(q, true); >>> list_add_tail(&q->tag_set_list, &set->tag_list); > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > This seemed the cleanest way to structure the code to avoid the double > walking of the hctx list for the current q. OK, it is correct, then v1 is fine. Reviewed-by: Ming Lei <ming.lei@...onical.com> > > -Jeff > >>> - blk_mq_update_tag_set_depth(set); >>> + >>> mutex_unlock(&set->tag_list_lock); >>> } >>> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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