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=-1.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_MED 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 50858C4321D for ; Mon, 20 Aug 2018 14:45:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0704B21722 for ; Mon, 20 Aug 2018 14:45:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="ZdxqcvB+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0704B21722 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727159AbeHTSBZ (ORCPT ); Mon, 20 Aug 2018 14:01:25 -0400 Received: from mail-it0-f68.google.com ([209.85.214.68]:53918 "EHLO mail-it0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726293AbeHTSBZ (ORCPT ); Mon, 20 Aug 2018 14:01:25 -0400 Received: by mail-it0-f68.google.com with SMTP id 72-v6so20911469itw.3 for ; Mon, 20 Aug 2018 07:45:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=Nvghb6d1UHIvwtIvS1HDDKmjGbMeRZK9ngrHRje7tPY=; b=ZdxqcvB+NNIlglD02DYgzJ6WAc9jkjCW9bQe+4wWpUKcQEoh/l72Y2e/JTqc2n/n3v iqWlCiu43z2e6eyNImYS0Q3vL61n42qdGEZWZkUpGLgQ2P113LpA50q9hOMkW+tg4PUK 4wQPfg1+mnnE3bs87eRuEZXZzTn3Li6zxLALcI11ndBQ4QdgTuam0dZUdCIKgsQWoKAf Ai2i4kpc2eAqmNGvsrWq2YMFJyHRcKQce/EmzEjsHDyjnLALm2WaFgpUAKtpbwv5d6bV dBngNMenVgkRq5exHGEfINFrkH/IyQFCisbLDLRaHyxzVj0ULXXOP6YCNVpHtyidhdvp L6fA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=Nvghb6d1UHIvwtIvS1HDDKmjGbMeRZK9ngrHRje7tPY=; b=VqdoeRsGRyodSzVm8ZvmkS72wSB7T1w5ZQXmYzxt644YyEw0jF3IeZeE4g+LbKev9i 75fKsRloRRP4QjXRw+mCe9kPcwDeDvqb2h/SkZbT0ISkhDATPWn2GETFMy5TqKrIO4fe XaeJcefXqtsRFTkr6GlqniDKX1v8KsUA/l7FxPsUBURDXfoxQhUtQTE4W0dfO5pQUDZK zAil6j4SgfHusb83DQLVvMxPBXT7Vo44sd2e0dOXWnPwmbB5LfnucjjwnzG7AdjLB2CP pYXy7o9ogrPe8zMEPQzqVfivmF5YmyZ7hDSwBM/mdEX2TrrZfpC74kxaTFwflslZhMN5 Ho7g== X-Gm-Message-State: AOUpUlEbvVDrgzzFFxjgCXBjCgBNSgwiuxXrZi5mi0B882Xx3cecUQUc AoRYPTOuMERO8ojUmHD4pZ24amU4m6s= X-Google-Smtp-Source: AA+uWPwwdSxsLLKaVff8X/vv6x3MurMts4QU4+kpkhCz2FC0aJD/NRVSZOaz5h67amXyVSZkSB+m+Q== X-Received: by 2002:a24:3901:: with SMTP id l1-v6mr12597063ita.88.1534776328786; Mon, 20 Aug 2018 07:45:28 -0700 (PDT) Received: from [192.168.1.56] ([216.160.245.98]) by smtp.gmail.com with ESMTPSA id h71-v6sm5416155ith.9.2018.08.20.07.45.27 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 20 Aug 2018 07:45:27 -0700 (PDT) Subject: Re: [PATCH V3 1/2] blk-mq: init hctx sched after update ctx and hctx mapping To: Jianchao Wang Cc: tom.leiming@gmail.com, bart.vanassche@wdc.com, keith.busch@linux.intel.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <1534749606-7311-1-git-send-email-jianchao.w.wang@oracle.com> <1534749606-7311-2-git-send-email-jianchao.w.wang@oracle.com> From: Jens Axboe Message-ID: <048cdf08-6c9e-f54a-1e5c-f1d40fb2ecdb@kernel.dk> Date: Mon, 20 Aug 2018 08:45:26 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <1534749606-7311-2-git-send-email-jianchao.w.wang@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/20/18 1:20 AM, Jianchao Wang wrote: > @@ -2913,6 +2906,29 @@ 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); > > + /* > + * switch io scheduler to NULL to clean up the data in it. > + * will get it back after update mapping between cpu and hw queues. > + */ "Switch IO scheduler to 'none', cleaning up the data associated with the previous scheduler. We'll switch back once we're done updating the new sw to hw queue mappings. > + list_for_each_entry(q, &set->tag_list, tag_set_list) { > + if (!q->elevator) { > + q->elv_type = NULL; > + continue; > + } > + q->elv_type = q->elevator->type; > + mutex_lock(&q->sysfs_lock); > + /* > + * After elevator_switch_mq, the previous elevator_queue will be > + * released by elevator_release. The reference of the io scheduler > + * module get by elevator_get will also be put. So we need to get > + * a reference of the io scheduler module here to prevent it to be > + * removed. > + */ > + __module_get(q->elv_type->elevator_owner); > + elevator_switch_mq(q, NULL); > + mutex_unlock(&q->sysfs_lock); > + } I don't hate this, but I also find it pretty annoying to put local state into the queue itself. It would be much nicer _not_ to have ->elv_type in the queue itself. That would need an allocation, however... Apart from those two things, looks fine to me. -- Jens Axboe