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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham 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 F052CC4360C for ; Mon, 14 Oct 2019 01:51:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C8AE920650 for ; Mon, 14 Oct 2019 01:51:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729698AbfJNBvE (ORCPT ); Sun, 13 Oct 2019 21:51:04 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54798 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729630AbfJNBvE (ORCPT ); Sun, 13 Oct 2019 21:51:04 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 81B7A308FC22; Mon, 14 Oct 2019 01:51:03 +0000 (UTC) Received: from localhost (ovpn-8-17.pek2.redhat.com [10.72.8.17]) by smtp.corp.redhat.com (Postfix) with ESMTP id 43CEC60BE0; Mon, 14 Oct 2019 01:51:01 +0000 (UTC) From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, Ming Lei , John Garry , Bart Van Assche , Hannes Reinecke , Christoph Hellwig , Thomas Gleixner , Keith Busch Subject: [PATCH V4 2/5] blk-mq: prepare for draining IO when hctx's all CPUs are offline Date: Mon, 14 Oct 2019 09:50:40 +0800 Message-Id: <20191014015043.25029-3-ming.lei@redhat.com> In-Reply-To: <20191014015043.25029-1-ming.lei@redhat.com> References: <20191014015043.25029-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Mon, 14 Oct 2019 01:51:03 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Most of blk-mq drivers depend on managed IRQ's auto-affinity to setup up queue mapping. Thomas mentioned the following point[1]: " That was the constraint of managed interrupts from the very beginning: The driver/subsystem has to quiesce the interrupt line and the associated queue _before_ it gets shutdown in CPU unplug and not fiddle with it until it's restarted by the core when the CPU is plugged in again. " However, current blk-mq implementation doesn't quiesce hw queue before the last CPU in the hctx is shutdown. Even worse, CPUHP_BLK_MQ_DEAD is one cpuhp state handled after the CPU is down, so there isn't any chance to quiesce hctx for blk-mq wrt. CPU hotplug. Add new cpuhp state of CPUHP_AP_BLK_MQ_ONLINE for blk-mq to stop queues and wait for completion of in-flight requests. We will stop hw queue and wait for completion of in-flight requests when one hctx is becoming dead in the following patch. This way may cause dead-lock for some stacking blk-mq drivers, such as dm-rq and loop. Add blk-mq flag of BLK_MQ_F_NO_MANAGED_IRQ and mark it for dm-rq and loop, so we needn't to wait for completion of in-flight requests from dm-rq & loop, then the potential dead-lock can be avoided. [1] https://lore.kernel.org/linux-block/alpine.DEB.2.21.1904051331270.1802@nanos.tec.linutronix.de/ Cc: John Garry Cc: Bart Van Assche Cc: Hannes Reinecke Cc: Christoph Hellwig Cc: Thomas Gleixner Cc: Keith Busch Signed-off-by: Ming Lei --- block/blk-mq-debugfs.c | 1 + block/blk-mq.c | 13 +++++++++++++ drivers/block/loop.c | 2 +- drivers/md/dm-rq.c | 2 +- include/linux/blk-mq.h | 2 ++ include/linux/cpuhotplug.h | 1 + 6 files changed, 19 insertions(+), 2 deletions(-) diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c index af40a02c46ee..24fff8c90942 100644 --- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -240,6 +240,7 @@ static const char *const hctx_flag_name[] = { HCTX_FLAG_NAME(TAG_SHARED), HCTX_FLAG_NAME(BLOCKING), HCTX_FLAG_NAME(NO_SCHED), + HCTX_FLAG_NAME(NO_MANAGED_IRQ), }; #undef HCTX_FLAG_NAME diff --git a/block/blk-mq.c b/block/blk-mq.c index ec791156e9cc..a664f196782a 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2225,6 +2225,11 @@ int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags, return -ENOMEM; } +static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node) +{ + return 0; +} + /* * 'cpu' is going away. splice any existing rq_list entries from this * software queue to the hw queue dispatch list, and ensure that it @@ -2261,6 +2266,9 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node) static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx) { + if (!(hctx->flags & BLK_MQ_F_NO_MANAGED_IRQ)) + cpuhp_state_remove_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE, + &hctx->cpuhp_online); cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead); } @@ -2320,6 +2328,9 @@ static int blk_mq_init_hctx(struct request_queue *q, { hctx->queue_num = hctx_idx; + if (!(hctx->flags & BLK_MQ_F_NO_MANAGED_IRQ)) + cpuhp_state_add_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE, + &hctx->cpuhp_online); cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead); hctx->tags = set->tags[hctx_idx]; @@ -3547,6 +3558,8 @@ static int __init blk_mq_init(void) { cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL, blk_mq_hctx_notify_dead); + cpuhp_setup_state_multi(CPUHP_AP_BLK_MQ_ONLINE, "block/mq:online", + NULL, blk_mq_hctx_notify_online); return 0; } subsys_initcall(blk_mq_init); diff --git a/drivers/block/loop.c b/drivers/block/loop.c index f6f77eaa7217..751a28a1d4b0 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1999,7 +1999,7 @@ static int loop_add(struct loop_device **l, int i) lo->tag_set.queue_depth = 128; lo->tag_set.numa_node = NUMA_NO_NODE; lo->tag_set.cmd_size = sizeof(struct loop_cmd); - lo->tag_set.flags = BLK_MQ_F_SHOULD_MERGE; + lo->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_NO_MANAGED_IRQ; lo->tag_set.driver_data = lo; err = blk_mq_alloc_tag_set(&lo->tag_set); diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c index 3f8577e2c13b..5f1ff70ac029 100644 --- a/drivers/md/dm-rq.c +++ b/drivers/md/dm-rq.c @@ -547,7 +547,7 @@ int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t) md->tag_set->ops = &dm_mq_ops; md->tag_set->queue_depth = dm_get_blk_mq_queue_depth(); md->tag_set->numa_node = md->numa_node_id; - md->tag_set->flags = BLK_MQ_F_SHOULD_MERGE; + md->tag_set->flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_NO_MANAGED_IRQ; md->tag_set->nr_hw_queues = dm_get_blk_mq_nr_hw_queues(); md->tag_set->driver_data = md; diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 079c282e4471..a345f2cf920d 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -58,6 +58,7 @@ struct blk_mq_hw_ctx { atomic_t nr_active; + struct hlist_node cpuhp_online; struct hlist_node cpuhp_dead; struct kobject kobj; @@ -226,6 +227,7 @@ struct blk_mq_ops { enum { BLK_MQ_F_SHOULD_MERGE = 1 << 0, BLK_MQ_F_TAG_SHARED = 1 << 1, + BLK_MQ_F_NO_MANAGED_IRQ = 1 << 2, BLK_MQ_F_BLOCKING = 1 << 5, BLK_MQ_F_NO_SCHED = 1 << 6, BLK_MQ_F_ALLOC_POLICY_START_BIT = 8, diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index 068793a619ca..bb80f52040cb 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -147,6 +147,7 @@ enum cpuhp_state { CPUHP_AP_SMPBOOT_THREADS, CPUHP_AP_X86_VDSO_VMA_ONLINE, CPUHP_AP_IRQ_AFFINITY_ONLINE, + CPUHP_AP_BLK_MQ_ONLINE, CPUHP_AP_ARM_MVEBU_SYNC_CLOCKS, CPUHP_AP_X86_INTEL_EPB_ONLINE, CPUHP_AP_PERF_ONLINE, -- 2.20.1