From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CFCC01C6FF7 for ; Thu, 24 Apr 2025 15:23:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745508187; cv=none; b=Vz8FoYnl2Mbud8cRALF+wj0fT9EcDReeYHaOnkjJ0Dn8PJoJzREUEcTkBrq4MYA79kPky1m5eZQC4Jg8WUIcE9FbkRrXaBFtAgVgztTkncOG8nnJdULR0uVDIGwNea1NgXsyLPL6mWSFfzPfSK4t5FPwssbT8m1YNqwX3hGC2u0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745508187; c=relaxed/simple; bh=sxml3vmjVXlDnQy+FiUm8/IF6ngN+SqCUh7bGI0XY6Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nabCtTsOSbwJ+K/KuPXi5Hu6guBCRoCJXY5uJbIPNFB/AHNore78y80UTwPUXehMHQFj9CYjzFK5CY6pt9VTHJWf9pd8CAK8Y5gTUVeR6Po824MPaF/Q62UPrDkYKelhzngiIwUQy4rl/8/FS9b6w8YqikSegeEUq4nB4ZraDi8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=cIzv0az0; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cIzv0az0" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1745508184; 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=z0rJg75dF/Nq6pypbJXQHR4zU+/dGmHZTO4mhHqhlLc=; b=cIzv0az0XgCcLZixwyNAxFDEy/o2VS5ghwUCL/KXzDqzMB7fxOgtjeHSrpUpBQMyqdXRNd ZCSGJ//3JTeGvGYtlSqPwNLAMAt1sv6czdImJEagBDRS0XllRJdzXxn7CmJSxJS0tvfEkL HjWBM/cmQi2ZzzUDwYhXFP9HIRg6INo= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-453--EpnAtCEMVm3xTYmEwWzyw-1; Thu, 24 Apr 2025 11:23:00 -0400 X-MC-Unique: -EpnAtCEMVm3xTYmEwWzyw-1 X-Mimecast-MFC-AGG-ID: -EpnAtCEMVm3xTYmEwWzyw_1745508178 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D217719560BB; Thu, 24 Apr 2025 15:22:58 +0000 (UTC) Received: from localhost (unknown [10.72.116.90]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id B849618001D5; Thu, 24 Apr 2025 15:22:57 +0000 (UTC) From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org Cc: Nilay Shroff , Shinichiro Kawasaki , =?UTF-8?q?Thomas=20Hellstr=C3=B6m?= , Christoph Hellwig , Ming Lei Subject: [PATCH V3 16/20] block: move elv_register[unregister]_queue out of elevator_lock Date: Thu, 24 Apr 2025 23:21:39 +0800 Message-ID: <20250424152148.1066220-17-ming.lei@redhat.com> In-Reply-To: <20250424152148.1066220-1-ming.lei@redhat.com> References: <20250424152148.1066220-1-ming.lei@redhat.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Move elv_register[unregister]_queue out of ->elevator_lock & queue freezing, so we can kill many lockdep warnings. elv_register[unregister]_queue() is serialized, and just dealing with sysfs/ debugfs things, no need to be done with queue frozen. With this change, elevator's ->exit() is called before calling elv_unregister_queue, then user may call into ->show()/store() of elevator's sysfs attributes, and we have covered this issue by adding `ELEVATOR_FLAG_DYNG`. For blk-mq debugfs, hctx->sched_tags is always checked with ->elevator_lock by debugfs code, meantime hctx->sched_tags is updated with ->elevator_lock, so there isn't such issue. Signed-off-by: Ming Lei --- block/blk-mq.c | 3 +- block/elevator.c | 80 ++++++++++++++++++++++++++++++++++++------------ 2 files changed, 62 insertions(+), 21 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 3afcddd21586..3ecbf73773ea 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -4997,11 +4997,10 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, blk_mq_debugfs_register_hctxs(q); } + /* elv_update_nr_hw_queues() unfreeze queue for us */ list_for_each_entry(q, &set->tag_list, tag_set_list) elv_update_nr_hw_queues(q); - list_for_each_entry(q, &set->tag_list, tag_set_list) - blk_mq_unfreeze_queue_nomemrestore(q); memalloc_noio_restore(memflags); /* Free the excess tags when nr_hw_queues shrink. */ diff --git a/block/elevator.c b/block/elevator.c index 48f2f202af98..aec8081a6be3 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -50,6 +50,11 @@ struct elv_change_ctx { const char *name; bool uevent; bool init; + + /* for unregistering old elevator */ + struct elevator_queue *old; + /* for registering new elevator */ + struct elevator_queue *new; }; static DEFINE_SPINLOCK(elv_list_lock); @@ -155,18 +160,18 @@ static void elevator_release(struct kobject *kobj) kfree(e); } -static void elevator_exit(struct request_queue *q) +static void __elevator_exit(struct request_queue *q) { struct elevator_queue *e = q->elevator; + lockdep_assert_held(&q->elevator_lock); + ioc_clear_queue(q); blk_mq_sched_free_rqs(q); mutex_lock(&e->sysfs_lock); blk_mq_exit_sched(q, e); mutex_unlock(&e->sysfs_lock); - - kobject_put(&e->kobj); } static inline void __elv_rqhash_del(struct request *rq) @@ -471,8 +476,6 @@ static int elv_register_queue(struct request_queue *q, { int error; - lockdep_assert_held(&q->elevator_lock); - error = kobject_add(&e->kobj, &q->disk->queue_kobj, "iosched"); if (!error) { const struct elv_fs_entry *attr = e->type->elevator_attrs; @@ -499,8 +502,6 @@ static int elv_register_queue(struct request_queue *q, static void elv_unregister_queue(struct request_queue *q, struct elevator_queue *e) { - lockdep_assert_held(&q->elevator_lock); - if (e && test_and_clear_bit(ELEVATOR_FLAG_REGISTERED, &e->flags)) { kobject_uevent(&e->kobj, KOBJ_REMOVE); kobject_del(&e->kobj); @@ -601,19 +602,15 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e, blk_mq_quiesce_queue(q); if (q->elevator) { - elv_unregister_queue(q, q->elevator); - elevator_exit(q); + ctx->old = q->elevator; + __elevator_exit(q); } ret = blk_mq_init_sched(q, new_e); if (ret) goto out_unfreeze; - ret = elv_register_queue(q, q->elevator, ctx->uevent); - if (ret) { - elevator_exit(q); - goto out_unfreeze; - } + ctx->new = q->elevator; blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name); out_unfreeze: @@ -627,15 +624,16 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e, return ret; } -static void elevator_disable(struct request_queue *q) +static void elevator_disable(struct request_queue *q, + struct elv_change_ctx *ctx) { WARN_ON_ONCE(q->mq_freeze_depth == 0); lockdep_assert_held(&q->elevator_lock); blk_mq_quiesce_queue(q); - elv_unregister_queue(q, q->elevator); - elevator_exit(q); + ctx->old = q->elevator; + __elevator_exit(q); blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q); q->elevator = NULL; q->nr_requests = q->tag_set->queue_depth; @@ -644,6 +642,38 @@ static void elevator_disable(struct request_queue *q) blk_mq_unquiesce_queue(q); } +static void elv_exit_and_release(struct request_queue *q) +{ + struct elevator_queue *e; + unsigned memflags; + + memflags = blk_mq_freeze_queue(q); + mutex_lock(&q->elevator_lock); + e = q->elevator; + __elevator_exit(q); + mutex_unlock(&q->elevator_lock); + blk_mq_unfreeze_queue(q, memflags); + if (e) + kobject_put(&e->kobj); +} + +static int elevator_change_done(struct request_queue *q, + struct elv_change_ctx *ctx) +{ + int ret = 0; + + if (ctx->old) { + elv_unregister_queue(q, ctx->old); + kobject_put(&ctx->old->kobj); + } + if (ctx->new) { + ret = elv_register_queue(q, ctx->new, ctx->uevent); + if (ret) + elv_exit_and_release(q); + } + return ret; +} + /* * Switch this queue to the given IO scheduler. */ @@ -662,7 +692,7 @@ static int __elevator_change(struct request_queue *q, if (!strncmp(elevator_name, "none", 4)) { if (q->elevator) - elevator_disable(q); + elevator_disable(q, ctx); return 0; } @@ -696,6 +726,9 @@ static int elevator_change(struct request_queue *q, ret = __elevator_change(q, ctx); mutex_unlock(&q->elevator_lock); blk_mq_unfreeze_queue(q, memflags); + if (!ret) + ret = elevator_change_done(q, ctx); + return ret; } @@ -745,6 +778,8 @@ void elevator_set_none(struct request_queue *q) /* * The I/O scheduler depends on the number of hardware queues, this forces a * reattachment when nr_hw_queues changes. + * + * Note that this unfreezes the passed in queue. */ void elv_update_nr_hw_queues(struct request_queue *q) { @@ -752,12 +787,19 @@ void elv_update_nr_hw_queues(struct request_queue *q) .name = "none", .uevent = true, }; + int ret = -ENODEV; + + WARN_ON_ONCE(q->mq_freeze_depth == 0); mutex_lock(&q->elevator_lock); if (q->elevator && !blk_queue_dying(q)) ctx.name = q->elevator->type->elevator_name; - __elevator_change(q, &ctx); + ret = __elevator_change(q, &ctx); mutex_unlock(&q->elevator_lock); + blk_mq_unfreeze_queue_nomemrestore(q); + + if (!ret) + WARN_ON_ONCE(elevator_change_done(q, &ctx)); } static void elv_iosched_load_module(const char *elevator_name) -- 2.47.0