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Petersen" , dm-devel@redhat.com, Mike Snitzer Cc: Ming Lei Subject: [PATCH v5 2/7] block: Change elevator_init_mq() to always succeed Date: Thu, 5 Sep 2019 18:51:30 +0900 Message-Id: <20190905095135.26026-3-damien.lemoal@wdc.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190905095135.26026-1-damien.lemoal@wdc.com> References: <20190905095135.26026-1-damien.lemoal@wdc.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org 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; + } } -- 2.21.0