From patchwork Mon Oct 21 22:42:56 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bart Van Assche X-Patchwork-Id: 11203135 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 39D6013BD for ; Mon, 21 Oct 2019 22:43:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 22DAE20B7C for ; Mon, 21 Oct 2019 22:43:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730203AbfJUWnI (ORCPT ); Mon, 21 Oct 2019 18:43:08 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:38427 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727264AbfJUWnI (ORCPT ); Mon, 21 Oct 2019 18:43:08 -0400 Received: by mail-pg1-f196.google.com with SMTP id w3so8686743pgt.5 for ; Mon, 21 Oct 2019 15:43:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=kH6arMtNKhExAQtmx+B/ga34kxbYtksoL7+f/odhzAo=; b=k3vk8cZREe6Y5YF9OM62KK8nARXffDtkvOMx6R9xPJqBA6wyo+CObuAuRF/kKfxnhs jc0mINEo5rVnMOt5isCOxjMPytkBn9hqZfresHHdKZJcmR50w0oxLe+x4RedBUrKyyNK jQRo2ZgnXwPYNXGDuHMNlm/ZnsF65vqpfN2HCLuggncUSrxtAbVamvvUvAdNg1iM1wtz aDYviEN6Df06Zy5bx5Mkh3oibVQBm12VeVQO7xoEJ8xSxYcs4/ROe5Nq9xmcrBG6Ooe1 PTHA6j7kmKR72ihRwW6Tj3R+RhuycaCr7lixaebxY0AuAYnkGABf1UECAhwFB8r2gGuo wW+Q== X-Gm-Message-State: APjAAAWh7kWxsY9k06TZwu0e8Xl5LHqf1PPWm9/NyQ+LUMclEBwAYBwT 4DxY8R7nXy9vkMal7k+QvQ0= X-Google-Smtp-Source: APXvYqxu22ftwVOeFHXKBFRqIfeISWgt//PMqeTzZsrK/3ofmcaUADIAD3+TZ3Nj2rWoV2MjIDXqkg== X-Received: by 2002:a62:38d5:: with SMTP id f204mr470676pfa.75.1571697787688; Mon, 21 Oct 2019 15:43:07 -0700 (PDT) Received: from desktop-bart.svl.corp.google.com ([2620:15c:2cd:202:4308:52a3:24b6:2c60]) by smtp.gmail.com with ESMTPSA id u9sm15944763pjb.4.2019.10.21.15.43.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Oct 2019 15:43:06 -0700 (PDT) From: Bart Van Assche To: Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Bart Van Assche , Christoph Hellwig , Ming Lei , Hannes Reinecke , Johannes Thumshirn Subject: [PATCH 1/4] block: Remove the synchronize_rcu() call from __blk_mq_update_nr_hw_queues() Date: Mon, 21 Oct 2019 15:42:56 -0700 Message-Id: <20191021224259.209542-2-bvanassche@acm.org> X-Mailer: git-send-email 2.23.0.866.gb869b98d4c-goog In-Reply-To: <20191021224259.209542-1-bvanassche@acm.org> References: <20191021224259.209542-1-bvanassche@acm.org> MIME-Version: 1.0 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Since the blk_mq_{,un}freeze_queue() calls in __blk_mq_update_nr_hw_queues() already serialize __blk_mq_update_nr_hw_queues() against blk_mq_queue_tag_busy_iter(), the synchronize_rcu() call in __blk_mq_update_nr_hw_queues() is not necessary. Hence remove it. Note: the synchronize_rcu() call in __blk_mq_update_nr_hw_queues() was introduced by commit f5bbbbe4d635 ("blk-mq: sync the update nr_hw_queues with blk_mq_queue_tag_busy_iter"). Commit 530ca2c9bd69 ("blk-mq: Allow blocking queue tag iter callbacks") removed the rcu_read_{,un}lock() calls that correspond to the synchronize_rcu() call in __blk_mq_update_nr_hw_queues(). Cc: Christoph Hellwig Cc: Ming Lei Cc: Hannes Reinecke Cc: Johannes Thumshirn Signed-off-by: Bart Van Assche Reviewed-by: Ming Lei --- block/blk-mq.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 8538dc415499..7528678ef41f 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -3242,10 +3242,6 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, list_for_each_entry(q, &set->tag_list, tag_set_list) blk_mq_freeze_queue(q); - /* - * Sync with blk_mq_queue_tag_busy_iter. - */ - synchronize_rcu(); /* * Switch IO scheduler to 'none', cleaning up the data associated * with the previous scheduler. We will switch back once we are done