From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 1EB5115D1 for ; Wed, 30 Apr 2025 04:36:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745987817; cv=none; b=b7ktP7eaTxFZuuFAWeaRXWshPgSUrzZ7863jqRdcvSKGUrdlDvfXDRAN3MEfj+EabRIQsQFAhjSYGDWVZUQzNdG82aLrw2sGvc+Ufg99EUtJCLvbiNdsxJpQVJsHf6EF1GqaCRzeMvYADFgxYSJg2mCrNThfcRAYqmzYdjtzSJs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745987817; c=relaxed/simple; bh=XrgMtXVsnnsFS9sXNFad5tmLgF2Pb/JWuUS9wlEju4w=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=k0WqOGb7dZBgBM/Q6IJIqjru9KbyyhjvTefuNUWf7WUAE9p+cEWMcL0wayiTSVy1EHhGs5g0xSLtFCpe+Rh0NzWpBuHICanvddsrHNZHmIq9oX0/0oewvfLSO2O69hA1dCSx82zomtm3wjd0+ziWomQ9XHFJNBshNsSDRgYMVYU= 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=VK0+BHqu; arc=none smtp.client-ip=170.10.133.124 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="VK0+BHqu" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1745987815; 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=/8m7upFyXaZdofvMdef15ajuRZR9u7rQ3+1fxbtymJI=; b=VK0+BHquJu1qiFRhTdIfYafiD5MgTSHCY+K7FNb+AX/Wm0pEVkbPJzLE5M3M8e7NKGJzT+ FA9yo2HuH25Fd3nmxuRsxt1yIj0wjebQdzzZvtPn74S/QEDhGFHm3qy5i5zY8Sz6qCBHf1 Pbg52B87NDQ2ocT2/TtAQnLLQzIyzKU= Received: from mx-prod-mc-01.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-248-RLYunwnFPaKehSDUmhko7g-1; Wed, 30 Apr 2025 00:36:53 -0400 X-MC-Unique: RLYunwnFPaKehSDUmhko7g-1 X-Mimecast-MFC-AGG-ID: RLYunwnFPaKehSDUmhko7g_1745987812 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3844D195608C; Wed, 30 Apr 2025 04:36:52 +0000 (UTC) Received: from localhost (unknown [10.72.116.48]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 3BA2F1800367; Wed, 30 Apr 2025 04:36:50 +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 , Hannes Reinecke Subject: [PATCH V4 20/24] block: move elv_register[unregister]_queue out of elevator_lock Date: Wed, 30 Apr 2025 12:35:22 +0800 Message-ID: <20250430043529.1950194-21-ming.lei@redhat.com> In-Reply-To: <20250430043529.1950194-1-ming.lei@redhat.com> References: <20250430043529.1950194-1-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 10.30.177.93 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: - when it is called from adding disk, elevator switch isn't possible because ->queue_kobj isn't added yet - when it is called from deleting disk, disable_elv_switch() is responsible for preventing new elevator switch and draining old elevator switch. - when it is called from blk_mq_update_nr_hw_queues(), adding/removing disk and elevator switch can't be allowed or in-progress 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. Reviewed-by: Hannes Reinecke Signed-off-by: Ming Lei --- block/blk-mq.c | 3 +-- block/elevator.c | 63 ++++++++++++++++++++++++++++++++++++++---------- block/genhd.c | 6 +++++ 3 files changed, 57 insertions(+), 15 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index b920eaedbaa9..a4bcfce4c4b9 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 98a754f58de5..492a593160ae 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -49,6 +49,11 @@ struct elv_change_ctx { const char *name; bool no_uevent; + + /* for unregistering old elevator */ + struct elevator_queue *old; + /* for registering new elevator */ + struct elevator_queue *new; }; static DEFINE_SPINLOCK(elv_list_lock); @@ -158,14 +163,14 @@ 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) @@ -466,8 +471,6 @@ 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; @@ -494,8 +497,6 @@ 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); @@ -586,7 +587,7 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx) blk_mq_quiesce_queue(q); if (q->elevator) { - elv_unregister_queue(q, q->elevator); + ctx->old = q->elevator; elevator_exit(q); } @@ -594,11 +595,7 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx) ret = blk_mq_init_sched(q, new_e); if (ret) goto out_unfreeze; - ret = elv_register_queue(q, q->elevator, !ctx->no_uevent); - if (ret) { - elevator_exit(q); - goto out_unfreeze; - } + ctx->new = q->elevator; } else { blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q); q->elevator = NULL; @@ -619,6 +616,38 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx) return ret; } +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->no_uevent); + if (ret) + elv_exit_and_release(q); + } + return ret; +} + /* * Switch this queue to the given IO scheduler. */ @@ -645,6 +674,9 @@ static int elevator_change(struct request_queue *q, struct elv_change_ctx *ctx) ret = elevator_switch(q, ctx); mutex_unlock(&q->elevator_lock); blk_mq_unfreeze_queue(q, memflags); + if (!ret) + ret = elevator_change_done(q, ctx); + return ret; } @@ -657,6 +689,7 @@ void elv_update_nr_hw_queues(struct request_queue *q) struct elv_change_ctx ctx = { .name = "none", }; + int ret = -ENODEV; WARN_ON_ONCE(q->mq_freeze_depth == 0); @@ -664,8 +697,12 @@ void elv_update_nr_hw_queues(struct request_queue *q) if (q->elevator && !blk_queue_dying(q) && !blk_queue_registered(q)) ctx.name = q->elevator->type->elevator_name; /* force to reattach elevator after nr_hw_queue is updated */ - elevator_switch(q, &ctx); + ret = elevator_switch(q, &ctx); mutex_unlock(&q->elevator_lock); + blk_mq_unfreeze_queue_nomemrestore(q); + + if (!ret) + WARN_ON_ONCE(elevator_change_done(q, &ctx)); } /* diff --git a/block/genhd.c b/block/genhd.c index 0e64e7400fb4..59d9febd8c14 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -751,11 +751,17 @@ static void __del_gendisk(struct gendisk *disk) static void disable_elv_switch(struct request_queue *q) { + struct blk_mq_tag_set *set = q->tag_set; + WARN_ON_ONCE(!queue_is_mq(q)); mutex_lock(&q->elevator_lock); blk_queue_flag_set(QUEUE_FLAG_NO_ELV_SWITCH, q); mutex_unlock(&q->elevator_lock); + + /* wait until in-progress elevator switch is done */ + down_write(&set->update_nr_hwq_lock); + up_write(&set->update_nr_hwq_lock); } /** -- 2.47.0