From patchwork Mon Oct 24 11:32:25 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 9037 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a5d:6687:0:0:0:0:0 with SMTP id l7csp442023wru; Mon, 24 Oct 2022 06:06:49 -0700 (PDT) X-Google-Smtp-Source: AMsMyM5mrgAgP072Tuof6vrF6RbtVTgB6a6WtBWZzibJQqWPM1Hxrt4qMHNMHQHflYB7Fk+dapDI X-Received: by 2002:a65:5886:0:b0:439:8dd3:18d4 with SMTP id d6-20020a655886000000b004398dd318d4mr28063675pgu.430.1666616809177; Mon, 24 Oct 2022 06:06:49 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1666616809; cv=none; d=google.com; s=arc-20160816; b=UXBC2KnFV4Rnr4+2MjscSOBEPPv8orpkUwB6mXn4p64c4tiWiqFg6gQ7UFkLDs3pQy lI8nChxK7jMEsgx2GVhA6kouw9plt3q8GVsqU2JaRzm2OcvbXoGE5FoxPlpvatnIvabX W1AvFtPWb+tWnYFph6StJxWzS3Lep2zbLPKLSgRpOTxQhLtVMNwV5wQP3vLUQ6yI/maX MGZV3Mb+ITtdN7dB9i3yBeoUgeMKzpdap+FQaG8ixBVPBMl67J5IfIGmQas6WB2aGUKF XKrXCjbJHnWpxN9ycHaL+HxFrE8cOTyOkcJEmSCtrOlE5hdHMvs3glogNsPUP2H1b9o6 B3Jg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :user-agent:references:in-reply-to:message-id:date:subject:cc:to :from:dkim-signature; bh=Y3lKKUJF8DYuQZiIe9FwJeWW5oEL/3qeoorv+p43kDg=; b=vic4TEZfh1eeV7pNySCpYxDHn1fD78/HgxFlLeJjmR8c4DKK8Ur5avkyuyf7IXHYxH bUsXR8Wgphau1U4I6UFLtNOmNu6jsRJ4YGOxDEPhBjkyepg5fSTcfv9mmJ2J6Ua3RIC5 g+OgDug9AOcJ6B/HPBCk+/kO2gIlfqcUNy7hxoGx0PUf6CGIFihsqdidscN5rlkKoQrB nQ4jBAk5qL+SnENTpAPSKHoquZs91dtiUPw9PxL/q+hz/SlB5YCbJasp01DFSjKh0+GB +Fn1n22J4uYqpuo+XuCN9+Ve0zIRSbiQCGU/mwFYn30bahObipIRh2fI4af8kPr4wlkJ 9uRQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@linuxfoundation.org header.s=korg header.b=Zc6Jkkr1; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linuxfoundation.org Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id b5-20020a170902e94500b00174ab1a7deasi32856610pll.316.2022.10.24.06.06.31; Mon, 24 Oct 2022 06:06:49 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@linuxfoundation.org header.s=korg header.b=Zc6Jkkr1; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linuxfoundation.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235336AbiJXNGB (ORCPT + 99 others); Mon, 24 Oct 2022 09:06:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44998 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235192AbiJXNDS (ORCPT ); Mon, 24 Oct 2022 09:03:18 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3A22842D48; Mon, 24 Oct 2022 05:20:09 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id B3182B815DF; Mon, 24 Oct 2022 12:14:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 14E85C433C1; Mon, 24 Oct 2022 12:14:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666613695; bh=/IDR0zTm2lJPM0MK7UW3XnXItapXnLnqvTqAjER0wR0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Zc6Jkkr1uDcT3rD+29DtrQMDh5IiJpRf7EeP2/oTmpjUq14cEJLPBkYc/qJV7IlQx bz9Npyup3aP5Nr/WiFoEaEPrJPC59eIM8i7qemdU833GLpvAYuRTBRngWA8crn2fAA yCWR3irbOEI2kAjVKSS8CBHw5eMTMe2YEmr739NU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mingzhe Zou , Coly Li , Jens Axboe , Sasha Levin Subject: [PATCH 5.4 235/255] bcache: fix set_at_max_writeback_rate() for multiple attached devices Date: Mon, 24 Oct 2022 13:32:25 +0200 Message-Id: <20221024113011.010431941@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221024113002.471093005@linuxfoundation.org> References: <20221024113002.471093005@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 X-Spam-Status: No, score=-7.6 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747574387095967466?= X-GMAIL-MSGID: =?utf-8?q?1747574387095967466?= From: Coly Li [ Upstream commit d2d05b88035d2d51a5bb6c5afec88a0880c73df4 ] Inside set_at_max_writeback_rate() the calculation in following if() check is wrong, if (atomic_inc_return(&c->idle_counter) < atomic_read(&c->attached_dev_nr) * 6) Because each attached backing device has its own writeback thread running and increasing c->idle_counter, the counter increates much faster than expected. The correct calculation should be, (counter / dev_nr) < dev_nr * 6 which equals to, counter < dev_nr * dev_nr * 6 This patch fixes the above mistake with correct calculation, and helper routine idle_counter_exceeded() is added to make code be more clear. Reported-by: Mingzhe Zou Signed-off-by: Coly Li Acked-by: Mingzhe Zou Link: https://lore.kernel.org/r/20220919161647.81238-6-colyli@suse.de Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- drivers/md/bcache/writeback.c | 73 +++++++++++++++++++++++++---------- 1 file changed, 52 insertions(+), 21 deletions(-) diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c index 0b02210ab435..5767ff6c13e3 100644 --- a/drivers/md/bcache/writeback.c +++ b/drivers/md/bcache/writeback.c @@ -119,27 +119,61 @@ static void __update_writeback_rate(struct cached_dev *dc) dc->writeback_rate_target = target; } +static bool idle_counter_exceeded(struct cache_set *c) +{ + int counter, dev_nr; + + /* + * If c->idle_counter is overflow (idel for really long time), + * reset as 0 and not set maximum rate this time for code + * simplicity. + */ + counter = atomic_inc_return(&c->idle_counter); + if (counter <= 0) { + atomic_set(&c->idle_counter, 0); + return false; + } + + dev_nr = atomic_read(&c->attached_dev_nr); + if (dev_nr == 0) + return false; + + /* + * c->idle_counter is increased by writeback thread of all + * attached backing devices, in order to represent a rough + * time period, counter should be divided by dev_nr. + * Otherwise the idle time cannot be larger with more backing + * device attached. + * The following calculation equals to checking + * (counter / dev_nr) < (dev_nr * 6) + */ + if (counter < (dev_nr * dev_nr * 6)) + return false; + + return true; +} + +/* + * Idle_counter is increased every time when update_writeback_rate() is + * called. If all backing devices attached to the same cache set have + * identical dc->writeback_rate_update_seconds values, it is about 6 + * rounds of update_writeback_rate() on each backing device before + * c->at_max_writeback_rate is set to 1, and then max wrteback rate set + * to each dc->writeback_rate.rate. + * In order to avoid extra locking cost for counting exact dirty cached + * devices number, c->attached_dev_nr is used to calculate the idle + * throushold. It might be bigger if not all cached device are in write- + * back mode, but it still works well with limited extra rounds of + * update_writeback_rate(). + */ static bool set_at_max_writeback_rate(struct cache_set *c, struct cached_dev *dc) { /* Don't set max writeback rate if gc is running */ if (!c->gc_mark_valid) return false; - /* - * Idle_counter is increased everytime when update_writeback_rate() is - * called. If all backing devices attached to the same cache set have - * identical dc->writeback_rate_update_seconds values, it is about 6 - * rounds of update_writeback_rate() on each backing device before - * c->at_max_writeback_rate is set to 1, and then max wrteback rate set - * to each dc->writeback_rate.rate. - * In order to avoid extra locking cost for counting exact dirty cached - * devices number, c->attached_dev_nr is used to calculate the idle - * throushold. It might be bigger if not all cached device are in write- - * back mode, but it still works well with limited extra rounds of - * update_writeback_rate(). - */ - if (atomic_inc_return(&c->idle_counter) < - atomic_read(&c->attached_dev_nr) * 6) + + if (!idle_counter_exceeded(c)) return false; if (atomic_read(&c->at_max_writeback_rate) != 1) @@ -153,13 +187,10 @@ static bool set_at_max_writeback_rate(struct cache_set *c, dc->writeback_rate_change = 0; /* - * Check c->idle_counter and c->at_max_writeback_rate agagain in case - * new I/O arrives during before set_at_max_writeback_rate() returns. - * Then the writeback rate is set to 1, and its new value should be - * decided via __update_writeback_rate(). + * In case new I/O arrives during before + * set_at_max_writeback_rate() returns. */ - if ((atomic_read(&c->idle_counter) < - atomic_read(&c->attached_dev_nr) * 6) || + if (!idle_counter_exceeded(c) || !atomic_read(&c->at_max_writeback_rate)) return false;