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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 9809BC433E9 for ; Thu, 18 Mar 2021 19:42:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6EF0464E81 for ; Thu, 18 Mar 2021 19:42:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233061AbhCRTmW (ORCPT ); Thu, 18 Mar 2021 15:42:22 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:34835 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S233162AbhCRTmR (ORCPT ); Thu, 18 Mar 2021 15:42:17 -0400 Received: from cwcc.thunk.org (pool-72-74-133-215.bstnma.fios.verizon.net [72.74.133.215]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 12IJfx16022967 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 18 Mar 2021 15:41:59 -0400 Received: by cwcc.thunk.org (Postfix, from userid 15806) id DB89715C39CA; Thu, 18 Mar 2021 15:41:58 -0400 (EDT) Date: Thu, 18 Mar 2021 15:41:58 -0400 From: "Theodore Ts'o" To: Eric Whitney Cc: linux-ext4@vger.kernel.org, willy@infradead.org Subject: Re: generic/418 regression seen on 5.12-rc3 Message-ID: References: <20210318181613.GA13891@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210318181613.GA13891@localhost.localdomain> Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Thu, Mar 18, 2021 at 02:16:13PM -0400, Eric Whitney wrote: > As mentioned in today's ext4 concall, I've seen generic/418 fail from time to > time when run on 5.12-rc3 and 5.12-rc1 kernels. This first occurred when > running the 1k test case using kvm-xfstests. I was then able to bisect the > failure to a patch landed in the -rc1 merge window: > > (bd8a1f3655a7) mm/filemap: support readpage splitting a page > > Typical test output resulting from a failure looks like: > > QA output created by 418 > +cmpbuf: offset 0: Expected: 0x1, got 0x0 > +[6:0] FAIL - comparison failed, offset 3072 > +diotest -w -b 512 -n 8 -i 4 failed at loop 0 > Silence is golden > ... > > I've also been able to reproduce the failure on -rc3 in the 4k test case as > well. The failure frequency there was 10 out of 100 runs. It was anywhere > from 2 to 8 failures out of 100 runs in the 1k case. FWIW, testing on a kernel which is -rc2 based (ext4.git's tip) I wasn't able to see a failure using gce-xfstests using the ext4/4k, ext4/1k, and xfs/1k test scenarios. This may be because of the I/O timing for the persistent disk block device in GCE, or differences in the number of CPU's or amount of memory available --- or in the kernel configuration that was used to build it. I'm currently retrying with -rc3, with and without the kernel debug configs, to see if that makes any difference... - Ted