From patchwork Thu Sep 13 12:15:44 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 10599403 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 495D8112B for ; Thu, 13 Sep 2018 12:17:19 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 387942AABC for ; Thu, 13 Sep 2018 12:17:19 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2C2CB2AACA; Thu, 13 Sep 2018 12:17:19 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 103722AABC for ; Thu, 13 Sep 2018 12:17:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727796AbeIMR03 (ORCPT ); Thu, 13 Sep 2018 13:26:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38064 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727300AbeIMR02 (ORCPT ); Thu, 13 Sep 2018 13:26:28 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id CE627308403C; Thu, 13 Sep 2018 12:17:15 +0000 (UTC) Received: from localhost (ovpn-8-34.pek2.redhat.com [10.72.8.34]) by smtp.corp.redhat.com (Postfix) with ESMTP id CED7C5D6B3; Thu, 13 Sep 2018 12:17:11 +0000 (UTC) From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, Ming Lei , Alan Stern , Christoph Hellwig , Bart Van Assche , Jianchao Wang , Hannes Reinecke , Johannes Thumshirn , Adrian Hunter , "James E.J. Bottomley" , "Martin K. Petersen" , linux-scsi@vger.kernel.org Subject: [PATCH V3 15/17] SCSI: use admin queue to implement queue QUIESCE Date: Thu, 13 Sep 2018 20:15:44 +0800 Message-Id: <20180913121546.5710-16-ming.lei@redhat.com> In-Reply-To: <20180913121546.5710-1-ming.lei@redhat.com> References: <20180913121546.5710-1-ming.lei@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Thu, 13 Sep 2018 12:17:16 +0000 (UTC) Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP All admin commands are sent via per-host admin queue, so we can simply freeze the IO queue for quiescing scsi device. Also the current SCSI stack guarantees that any request originated from admin queue won't be called back to block layer via the associated IO queue, and it is always dealt with by the admin queue. So it is safe to submit admin request via admin queue when the associated IO queue is frozen, and this way matches the PREEMPT flag perfectly. Finally, we can remove the preempt_only approach for supporting SCSI quiesce, then the code in block fast path is simplified a lot. Cc: Alan Stern Cc: Christoph Hellwig Cc: Bart Van Assche Cc: Jianchao Wang Cc: Hannes Reinecke Cc: Johannes Thumshirn Cc: Adrian Hunter Cc: "James E.J. Bottomley" Cc: "Martin K. Petersen" Cc: linux-scsi@vger.kernel.org Signed-off-by: Ming Lei --- block/blk-core.c | 44 ++------------------------------------------ block/blk-mq-debugfs.c | 1 - drivers/scsi/scsi_lib.c | 29 +++-------------------------- include/linux/blkdev.h | 6 ------ include/scsi/scsi_device.h | 1 - 5 files changed, 5 insertions(+), 76 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index 4dbc93f43b38..f51c19b381e3 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -421,26 +421,6 @@ void blk_sync_queue(struct request_queue *q) EXPORT_SYMBOL(blk_sync_queue); /** - * blk_set_preempt_only - set QUEUE_FLAG_PREEMPT_ONLY - * @q: request queue pointer - * - * Returns the previous value of the PREEMPT_ONLY flag - 0 if the flag was not - * set and 1 if the flag was already set. - */ -int blk_set_preempt_only(struct request_queue *q) -{ - return blk_queue_flag_test_and_set(QUEUE_FLAG_PREEMPT_ONLY, q); -} -EXPORT_SYMBOL_GPL(blk_set_preempt_only); - -void blk_clear_preempt_only(struct request_queue *q) -{ - blk_queue_flag_clear(QUEUE_FLAG_PREEMPT_ONLY, q); - wake_up_all(&q->mq_freeze_wq); -} -EXPORT_SYMBOL_GPL(blk_clear_preempt_only); - -/** * __blk_run_queue_uncond - run a queue whether or not it has been stopped * @q: The queue to run * @@ -917,27 +897,8 @@ EXPORT_SYMBOL(blk_alloc_queue); */ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags) { - const bool preempt = flags & BLK_MQ_REQ_PREEMPT; - while (true) { - bool success = false; - - rcu_read_lock(); - if (percpu_ref_tryget_live(&q->q_usage_counter)) { - /* - * The code that sets the PREEMPT_ONLY flag is - * responsible for ensuring that that flag is globally - * visible before the queue is unfrozen. - */ - if (preempt || !blk_queue_preempt_only(q)) { - success = true; - } else { - percpu_ref_put(&q->q_usage_counter); - } - } - rcu_read_unlock(); - - if (success) + if (percpu_ref_tryget_live(&q->q_usage_counter)) return 0; if (flags & BLK_MQ_REQ_NOWAIT) @@ -953,8 +914,7 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags) smp_rmb(); wait_event(q->mq_freeze_wq, - (atomic_read(&q->mq_freeze_depth) == 0 && - (preempt || !blk_queue_preempt_only(q))) || + atomic_read(&q->mq_freeze_depth) == 0 || blk_queue_dying(q)); if (blk_queue_dying(q)) return -ENODEV; diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c index 8df013e9f242..82df43ec322f 100644 --- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -132,7 +132,6 @@ static const char *const blk_queue_flag_name[] = { QUEUE_FLAG_NAME(REGISTERED), QUEUE_FLAG_NAME(SCSI_PASSTHROUGH), QUEUE_FLAG_NAME(QUIESCED), - QUEUE_FLAG_NAME(PREEMPT_ONLY), QUEUE_FLAG_NAME(ADMIN), }; #undef QUEUE_FLAG_NAME diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 1e75515cc7ba..85fed8d96c8a 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -3180,34 +3180,12 @@ static void scsi_wait_for_queuecommand(struct scsi_device *sdev) int scsi_device_quiesce(struct scsi_device *sdev) { - struct request_queue *q = sdev->request_queue; int err; - /* - * It is allowed to call scsi_device_quiesce() multiple times from - * the same context but concurrent scsi_device_quiesce() calls are - * not allowed. - */ - WARN_ON_ONCE(sdev->quiesced_by && sdev->quiesced_by != current); - - blk_set_preempt_only(q); - - blk_mq_freeze_queue(q); - /* - * Ensure that the effect of blk_set_preempt_only() will be visible - * for percpu_ref_tryget() callers that occur after the queue - * unfreeze even if the queue was already frozen before this function - * was called. See also https://lwn.net/Articles/573497/. - */ - synchronize_rcu(); - blk_mq_unfreeze_queue(q); + blk_mq_freeze_queue(sdev->request_queue); mutex_lock(&sdev->state_mutex); err = scsi_device_set_state(sdev, SDEV_QUIESCE); - if (err == 0) - sdev->quiesced_by = current; - else - blk_clear_preempt_only(q); mutex_unlock(&sdev->state_mutex); return err; @@ -3230,12 +3208,11 @@ void scsi_device_resume(struct scsi_device *sdev) * device deleted during suspend) */ mutex_lock(&sdev->state_mutex); - WARN_ON_ONCE(!sdev->quiesced_by); - sdev->quiesced_by = NULL; - blk_clear_preempt_only(sdev->request_queue); if (sdev->sdev_state == SDEV_QUIESCE) scsi_device_set_state(sdev, SDEV_RUNNING); mutex_unlock(&sdev->state_mutex); + + blk_mq_unfreeze_queue(sdev->request_queue); } EXPORT_SYMBOL(scsi_device_resume); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 2dbc7524a169..1bd4f02d11c0 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -698,7 +698,6 @@ struct request_queue { #define QUEUE_FLAG_REGISTERED 26 /* queue has been registered to a disk */ #define QUEUE_FLAG_SCSI_PASSTHROUGH 27 /* queue supports SCSI commands */ #define QUEUE_FLAG_QUIESCED 28 /* queue has been quiesced */ -#define QUEUE_FLAG_PREEMPT_ONLY 29 /* only process REQ_PREEMPT requests */ #define QUEUE_FLAG_ADMIN 30 /* admin queue */ #define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \ @@ -740,14 +739,9 @@ bool blk_queue_flag_test_and_clear(unsigned int flag, struct request_queue *q); ((rq)->cmd_flags & (REQ_FAILFAST_DEV|REQ_FAILFAST_TRANSPORT| \ REQ_FAILFAST_DRIVER)) #define blk_queue_quiesced(q) test_bit(QUEUE_FLAG_QUIESCED, &(q)->queue_flags) -#define blk_queue_preempt_only(q) \ - test_bit(QUEUE_FLAG_PREEMPT_ONLY, &(q)->queue_flags) #define blk_queue_fua(q) test_bit(QUEUE_FLAG_FUA, &(q)->queue_flags) #define blk_queue_admin(q) test_bit(QUEUE_FLAG_ADMIN, &(q)->queue_flags) -extern int blk_set_preempt_only(struct request_queue *q); -extern void blk_clear_preempt_only(struct request_queue *q); - static inline int queue_in_flight(struct request_queue *q) { return q->in_flight[0] + q->in_flight[1]; diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h index f6820da1dc37..666b58799cec 100644 --- a/include/scsi/scsi_device.h +++ b/include/scsi/scsi_device.h @@ -226,7 +226,6 @@ struct scsi_device { unsigned char access_state; struct mutex state_mutex; enum scsi_device_state sdev_state; - struct task_struct *quiesced_by; atomic_t nr_admin_pending; wait_queue_head_t admin_wq;