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=-5.6 required=3.0 tests=DATE_IN_PAST_06_12, DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 02A4DC76194 for ; Thu, 25 Jul 2019 05:48:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C615420657 for ; Thu, 25 Jul 2019 05:48:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564033682; bh=2FTCZ8GaL62WVSaOP6GV+yF95ekypWreRV9cXFynotM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=HXK7c7u84/O5+RsKqbAw+PV97V3udPYOzR0dJHX2zcbjRnx52Q1MDGwpj0rql6Rpe hmUTV46bZVyhtb+enyZyRdFcs1Xvzd5uc2mYaDumnvvE/+QCTdzkjoxWJN34Itsi4d c77VVcYjI54+64Qi3BqjGURkbnIh7PctIUTU+WX8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729037AbfGYFqs (ORCPT ); Thu, 25 Jul 2019 01:46:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:34538 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729015AbfGYFqp (ORCPT ); Thu, 25 Jul 2019 01:46:45 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4DD9E22BEB; Thu, 25 Jul 2019 05:46:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564033604; bh=2FTCZ8GaL62WVSaOP6GV+yF95ekypWreRV9cXFynotM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JHpKHA3nn2dnj7MEMGcew1cMke3VH3KeYES6CR+715SW3FGSzx5at/q9dOxCl++1q VT5rUQFv5NoZvLo16mrBw4JR10mLgHACSs7+EMmVjkD4yZdlrqw7+414JlNKd0zOWU obo6EKDd1fQhOOEslwYRuaU98vX/Jj/VBH/x/j7U= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Konstantin Khlebnikov , Jens Axboe Subject: [PATCH 4.19 266/271] blk-throttle: fix zero wait time for iops throttled group Date: Wed, 24 Jul 2019 21:22:15 +0200 Message-Id: <20190724191718.027335460@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190724191655.268628197@linuxfoundation.org> References: <20190724191655.268628197@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Konstantin Khlebnikov commit 3a10f999ffd464d01c5a05592a15470a3c4bbc36 upstream. After commit 991f61fe7e1d ("Blk-throttle: reduce tail io latency when iops limit is enforced") wait time could be zero even if group is throttled and cannot issue requests right now. As a result throtl_select_dispatch() turns into busy-loop under irq-safe queue spinlock. Fix is simple: always round up target time to the next throttle slice. Fixes: 991f61fe7e1d ("Blk-throttle: reduce tail io latency when iops limit is enforced") Signed-off-by: Konstantin Khlebnikov Cc: stable@vger.kernel.org # v4.19+ Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-throttle.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -892,13 +892,10 @@ static bool tg_with_in_iops_limit(struct unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; u64 tmp; - jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; + jiffy_elapsed = jiffies - tg->slice_start[rw]; - /* Slice has just started. Consider one slice interval */ - if (!jiffy_elapsed) - jiffy_elapsed_rnd = tg->td->throtl_slice; - - jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice); + /* Round up to the next throttle slice, wait time must be nonzero */ + jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice); /* * jiffy_elapsed_rnd should not be a big value as minimum iops can be