From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig Cc: Bart Van Assche , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, Omar Sandoval , John Garry , Ming Lei Subject: [PATCH 2/2] blk-mq: don't handle TAG_SHARED in restart Date: Tue, 17 Oct 2017 13:04:18 +0800 Message-Id: <20171017050418.22555-3-ming.lei@redhat.com> In-Reply-To: <20171017050418.22555-1-ming.lei@redhat.com> References: <20171017050418.22555-1-ming.lei@redhat.com> Sender: linux-scsi-owner@vger.kernel.org List-ID: Now restart is used in the following cases, and TAG_SHARED is for SCSI only. 1) .get_budget() returns BLK_STS_RESOURCE - if resource in target/host level isn't satistifed, this SCSI device will be added in shost->starved_list, and the whole queue will be rerun (via SCSI's built-in RESTART) in scsi_end_request() after any request initiated from this host/targe is completed. Forget to mention, host level resource is always respected by blk-mq before running .queue_rq(). - the same is true if resource in the queue level isn't satisfied. - if there isn't outstanding request on this queue, then SCSI's RESTART can't work(blk-mq's can't work too), and the queue will be run after SCSI_QUEUE_DELAY, and finally all starved sdevs will be handled by SCSI's RESTART when this request is finished 2) scsi_dispatch_cmd() returns BLK_STS_RESOURCE - if there isn't onprogressing request on this queue, the queue will be run after SCSI_QUEUE_DELAY - otherwise, SCSI's RESTART covers the rerun. 3) blk_mq_get_driver_tag() failed - BLK_MQ_S_TAG_WAITING covers the cross-queue RESTART for driver allocation. In one word, SCSI's built-in RESTART is enough to cover itself. So we don't need to pay special attention to TAG_SHARED wrt. restart. Signed-off-by: Ming Lei --- block/blk-mq-sched.c | 78 +++------------------------------------------------- 1 file changed, 4 insertions(+), 74 deletions(-) diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index df8581bb0a37..daab27feb653 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -68,25 +68,17 @@ static void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx) set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state); } -static bool blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx) +void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx) { if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) - return false; - - if (hctx->flags & BLK_MQ_F_TAG_SHARED) { - struct request_queue *q = hctx->queue; + return; - if (test_and_clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) - atomic_dec(&q->shared_hctx_restart); - } else - clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state); + clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state); if (blk_mq_hctx_has_pending(hctx)) { blk_mq_run_hw_queue(hctx, true); - return true; + return; } - - return false; } /* return true if hctx need to run again */ @@ -385,68 +377,6 @@ static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx, return true; } -/** - * list_for_each_entry_rcu_rr - iterate in a round-robin fashion over rcu list - * @pos: loop cursor. - * @skip: the list element that will not be examined. Iteration starts at - * @skip->next. - * @head: head of the list to examine. This list must have at least one - * element, namely @skip. - * @member: name of the list_head structure within typeof(*pos). - */ -#define list_for_each_entry_rcu_rr(pos, skip, head, member) \ - for ((pos) = (skip); \ - (pos = (pos)->member.next != (head) ? list_entry_rcu( \ - (pos)->member.next, typeof(*pos), member) : \ - list_entry_rcu((pos)->member.next->next, typeof(*pos), member)), \ - (pos) != (skip); ) - -/* - * Called after a driver tag has been freed to check whether a hctx needs to - * be restarted. Restarts @hctx if its tag set is not shared. Restarts hardware - * queues in a round-robin fashion if the tag set of @hctx is shared with other - * hardware queues. - */ -void blk_mq_sched_restart(struct blk_mq_hw_ctx *const hctx) -{ - struct blk_mq_tags *const tags = hctx->tags; - struct blk_mq_tag_set *const set = hctx->queue->tag_set; - struct request_queue *const queue = hctx->queue, *q; - struct blk_mq_hw_ctx *hctx2; - unsigned int i, j; - - if (set->flags & BLK_MQ_F_TAG_SHARED) { - /* - * If this is 0, then we know that no hardware queues - * have RESTART marked. We're done. - */ - if (!atomic_read(&queue->shared_hctx_restart)) - return; - - rcu_read_lock(); - list_for_each_entry_rcu_rr(q, queue, &set->tag_list, - tag_set_list) { - queue_for_each_hw_ctx(q, hctx2, i) - if (hctx2->tags == tags && - blk_mq_sched_restart_hctx(hctx2)) - goto done; - } - j = hctx->queue_num + 1; - for (i = 0; i < queue->nr_hw_queues; i++, j++) { - if (j == queue->nr_hw_queues) - j = 0; - hctx2 = queue->queue_hw_ctx[j]; - if (hctx2->tags == tags && - blk_mq_sched_restart_hctx(hctx2)) - break; - } -done: - rcu_read_unlock(); - } else { - blk_mq_sched_restart_hctx(hctx); - } -} - /* * Add flush/fua to the queue. If we fail getting a driver tag, then * punt to the requeue list. Requeue will re-invoke us from a context -- 2.9.5