From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 19B51C3A5A9 for ; Wed, 4 Sep 2019 09:05:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F1A6C22CF7 for ; Wed, 4 Sep 2019 09:05:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729379AbfIDJFj (ORCPT ); Wed, 4 Sep 2019 05:05:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:65055 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728878AbfIDJFj (ORCPT ); Wed, 4 Sep 2019 05:05:39 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 76A778980EA; Wed, 4 Sep 2019 09:05:38 +0000 (UTC) Received: from ming.t460p (ovpn-8-23.pek2.redhat.com [10.72.8.23]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9CA4B60606; Wed, 4 Sep 2019 09:05:32 +0000 (UTC) Date: Wed, 4 Sep 2019 17:05:27 +0800 From: Ming Lei To: Damien Le Moal Cc: linux-block@vger.kernel.org, Jens Axboe , linux-scsi@vger.kernel.org, "Martin K . Petersen" Subject: Re: [PATCH v3 2/7] block: Change elevator_init_mq() to always succeed Message-ID: <20190904090526.GE7578@ming.t460p> References: <20190904084247.23338-1-damien.lemoal@wdc.com> <20190904084247.23338-3-damien.lemoal@wdc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190904084247.23338-3-damien.lemoal@wdc.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.67]); Wed, 04 Sep 2019 09:05:38 +0000 (UTC) Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Wed, Sep 04, 2019 at 05:42:42PM +0900, Damien Le Moal wrote: > If the default elevator chosen is mq-deadline, elevator_init_mq() may > return an error if mq-deadline initialization fails, leading to > blk_mq_init_allocated_queue() returning an error, which in turn will > cause the block device initialization to fail and the device not being > exposed. > > Instead of taking such extreme measure, handle mq-deadline > initialization failures in the same manner as when mq-deadline is not > available (no module to load), that is, default to the "none" scheduler. > With this change, elevator_init_mq() return type can be changed to void. > > Signed-off-by: Damien Le Moal > Reviewed-by: Johannes Thumshirn > Reviewed-by: Christoph Hellwig > --- > block/blk-mq.c | 8 +------- > block/blk.h | 2 +- > block/elevator.c | 23 ++++++++++++----------- > 3 files changed, 14 insertions(+), 19 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 13923630e00a..ee4caf0c0807 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2842,8 +2842,6 @@ static unsigned int nr_hw_queues(struct blk_mq_tag_set *set) > struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, > struct request_queue *q) > { > - int ret = -ENOMEM; > - > /* mark the queue as mq asap */ > q->mq_ops = set->ops; > > @@ -2904,14 +2902,10 @@ struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set, > blk_mq_add_queue_tag_set(set, q); > blk_mq_map_swqueue(q); > > - ret = elevator_init_mq(q); > - if (ret) > - goto err_tag_set; > + elevator_init_mq(q); > > return q; > > -err_tag_set: > - blk_mq_del_queue_tag_set(q); > err_hctxs: > kfree(q->queue_hw_ctx); > q->nr_hw_queues = 0; > diff --git a/block/blk.h b/block/blk.h > index e4619fc5c99a..ed347f7a97b1 100644 > --- a/block/blk.h > +++ b/block/blk.h > @@ -184,7 +184,7 @@ void blk_account_io_done(struct request *req, u64 now); > > void blk_insert_flush(struct request *rq); > > -int elevator_init_mq(struct request_queue *q); > +void elevator_init_mq(struct request_queue *q); > int elevator_switch_mq(struct request_queue *q, > struct elevator_type *new_e); > void __elevator_exit(struct request_queue *, struct elevator_queue *); > diff --git a/block/elevator.c b/block/elevator.c > index 4721834815bb..2944c129760c 100644 > --- a/block/elevator.c > +++ b/block/elevator.c > @@ -628,34 +628,35 @@ static inline bool elv_support_iosched(struct request_queue *q) > > /* > * For blk-mq devices supporting IO scheduling, we default to using mq-deadline, > - * if available, for single queue devices. If deadline isn't available OR we > - * have multiple queues, default to "none". > + * if available, for single queue devices. If deadline isn't available OR > + * deadline initialization fails OR we have multiple queues, default to "none". > */ > -int elevator_init_mq(struct request_queue *q) > +void elevator_init_mq(struct request_queue *q) > { > struct elevator_type *e; > - int err = 0; > + int err; > > if (!elv_support_iosched(q)) > - return 0; > + return; > > if (q->nr_hw_queues != 1) > - return 0; > + return; > > WARN_ON_ONCE(test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags)); > > if (unlikely(q->elevator)) > - goto out; > + return; > > e = elevator_get(q, "mq-deadline", false); > if (!e) > - goto out; > + return; > > err = blk_mq_init_sched(q, e); > - if (err) > + if (err) { > + pr_warn("\"%s\" elevator initialization failed, " > + "falling back to \"none\"\n", e->elevator_name); > elevator_put(e); > -out: > - return err; > + } > } Looks fine: Reviewed-by: Ming Lei BTW, blk_mq_init_sched()'s failure patch should have restored q->nr_request. And that could be done in another standalone patch. -- Ming