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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 A0604C33CB1 for ; Wed, 15 Jan 2020 11:45:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6921622522 for ; Wed, 15 Jan 2020 11:45:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="M5qhpW5G" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729961AbgAOLpm (ORCPT ); Wed, 15 Jan 2020 06:45:42 -0500 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:42251 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729841AbgAOLpl (ORCPT ); Wed, 15 Jan 2020 06:45:41 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579088740; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ajIlPESgBrh1KWK3hts6HUKkW3AJfbbvRA8AzJsWt5c=; b=M5qhpW5GppyHV5iSXn+pj500ITTkl+EXBXnx1hvq3JjFBrcnOiOTlMQYKgGXUMm0GKOvTO D+V5tdo1ka8quUFmqpN7qKsRl3PcZHk/yF20Rn6xu+7PhLOoAzMkq7bnRBq6/KaXgGqv8R 9Cb3tfgrzf143gotYM4P8Tfrl+HRxLg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-211-7eYry7NhPxSttv1jW0H-4w-1; Wed, 15 Jan 2020 06:45:36 -0500 X-MC-Unique: 7eYry7NhPxSttv1jW0H-4w-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0CF421005512; Wed, 15 Jan 2020 11:45:35 +0000 (UTC) Received: from localhost (ovpn-8-17.pek2.redhat.com [10.72.8.17]) by smtp.corp.redhat.com (Postfix) with ESMTP id E60CF5C1D6; Wed, 15 Jan 2020 11:45:31 +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 2/6] blk-mq: prepare for draining IO when hctx's all CPUs are offline Date: Wed, 15 Jan 2020 19:44:05 +0800 Message-Id: <20200115114409.28895-3-ming.lei@redhat.com> In-Reply-To: <20200115114409.28895-1-ming.lei@redhat.com> References: <20200115114409.28895-1-ming.lei@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Content-Transfer-Encoding: quoted-printable 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 associat= ed 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.2.21.1904051331270.180= 2@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 | 3 +++ include/linux/cpuhotplug.h | 1 + 6 files changed, 20 insertions(+), 2 deletions(-) diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c index d6de4f7f38cb..b62390918ca5 100644 --- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -240,6 +240,7 @@ static const char *const hctx_flag_name[] =3D { HCTX_FLAG_NAME(TAG_SHARED), HCTX_FLAG_NAME(BLOCKING), HCTX_FLAG_NAME(NO_SCHED), + HCTX_FLAG_NAME(NO_MANAGED_IRQ), }; #undef HCTX_FLAG_NAME =20 diff --git a/block/blk-mq.c b/block/blk-mq.c index a12b1763508d..0f55bb92b16f 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2244,6 +2244,11 @@ int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, s= truct blk_mq_tags *tags, return -ENOMEM; } =20 +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 @@ -2280,6 +2285,9 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu= , struct hlist_node *node) =20 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); } @@ -2339,6 +2347,9 @@ static int blk_mq_init_hctx(struct request_queue *q= , { hctx->queue_num =3D hctx_idx; =20 + 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); =20 hctx->tags =3D set->tags[hctx_idx]; @@ -3585,6 +3596,8 @@ 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 739b372a5112..651dadd9be12 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -2012,7 +2012,7 @@ static int loop_add(struct loop_device **l, int i) lo->tag_set.queue_depth =3D 128; lo->tag_set.numa_node =3D NUMA_NO_NODE; lo->tag_set.cmd_size =3D sizeof(struct loop_cmd); - lo->tag_set.flags =3D BLK_MQ_F_SHOULD_MERGE; + lo->tag_set.flags =3D BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_NO_MANAGED_IRQ; lo->tag_set.driver_data =3D lo; =20 err =3D 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 =3D &dm_mq_ops; md->tag_set->queue_depth =3D dm_get_blk_mq_queue_depth(); md->tag_set->numa_node =3D md->numa_node_id; - md->tag_set->flags =3D BLK_MQ_F_SHOULD_MERGE; + md->tag_set->flags =3D BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_NO_MANAGED_IRQ; md->tag_set->nr_hw_queues =3D dm_get_blk_mq_nr_hw_queues(); md->tag_set->driver_data =3D md; =20 diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index b669e776d4cb..ca2201435a48 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -140,6 +140,8 @@ struct blk_mq_hw_ctx { */ atomic_t nr_active; =20 + /** @cpuhp_online: List to store request if CPU is going to die */ + struct hlist_node cpuhp_online; /** @cpuhp_dead: List to store request if some CPU die. */ struct hlist_node cpuhp_dead; /** @kobj: Kernel object for sysfs. */ @@ -388,6 +390,7 @@ struct blk_mq_ops { enum { BLK_MQ_F_SHOULD_MERGE =3D 1 << 0, BLK_MQ_F_TAG_SHARED =3D 1 << 1, + BLK_MQ_F_NO_MANAGED_IRQ =3D 1 << 2, BLK_MQ_F_BLOCKING =3D 1 << 5, BLK_MQ_F_NO_SCHED =3D 1 << 6, BLK_MQ_F_ALLOC_POLICY_START_BIT =3D 8, diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index e51ee772b9f5..48b7cb04224a 100644 --- a/include/linux/cpuhotplug.h +++ b/include/linux/cpuhotplug.h @@ -149,6 +149,7 @@ 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, --=20 2.20.1