From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753215AbdECO5M (ORCPT ); Wed, 3 May 2017 10:57:12 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:53478 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751118AbdECO5A (ORCPT ); Wed, 3 May 2017 10:57:00 -0400 Authentication-Results: suse.de; dkim=none (message not signed) header.d=none;suse.de; dmarc=none action=none header.from=fb.com; Subject: Re: [PATCH] btrfs: always write superblocks synchronously To: Jan Kara , Davidlohr Bueso References: <20170502162813.4299-1-dave@stgolabs.net> <20170503083615.GC10084@quack2.suse.cz> CC: , , , , Jan Kara , Davidlohr Bueso From: Chris Mason Message-ID: <4614b613-8cc6-1f58-09e1-066e97fc638a@fb.com> Date: Wed, 3 May 2017 10:55:44 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20170503083615.GC10084@quack2.suse.cz> Content-Type: text/plain; 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This was seen to cause performance hits up >> to 90% regression in disk IO related benchmarks such as reaim and >> dbench[1]. >> >> Fix the problem by making sure the first superblock write is also >> treated as synchronous since they can block progress of the >> journalling (commit, log syncs) machinery and thus the whole filesystem. >> >> >> Fixes: b685d3d65ac (block: treat REQ_FUA and REQ_PREFLUSH as synchronous) >> Cc: stable >> Cc: Jan Kara >> Signed-off-by: Davidlohr Bueso > > I wasn't patient enough and already sent the fix as part of my series > fixing other filesystems [1]. It also fixes one more place in btrfs that > needs REQ_SYNC to return to the original behavior. > Thanks guys. -chris