From patchwork Fri Jan 11 13:31:24 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Brian Foster X-Patchwork-Id: 10758019 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8EB151390 for ; Fri, 11 Jan 2019 13:31:27 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7CCAD29BC7 for ; Fri, 11 Jan 2019 13:31:27 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7B20F29B3A; Fri, 11 Jan 2019 13:31:27 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E657F29BFB for ; Fri, 11 Jan 2019 13:31:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729273AbfAKNb0 (ORCPT ); Fri, 11 Jan 2019 08:31:26 -0500 Received: from mx1.redhat.com ([209.132.183.28]:54274 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728853AbfAKNb0 (ORCPT ); Fri, 11 Jan 2019 08:31:26 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A88ACA0BF9; Fri, 11 Jan 2019 13:31:25 +0000 (UTC) Received: from bfoster.bos.redhat.com (dhcp-41-2.bos.redhat.com [10.18.41.2]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4886A60BF6; Fri, 11 Jan 2019 13:31:25 +0000 (UTC) From: Brian Foster To: fstests@vger.kernel.org Cc: linux-xfs@vger.kernel.org Subject: [PATCH] tests/generic: test writepage cached mapping validity Date: Fri, 11 Jan 2019 08:31:24 -0500 Message-Id: <20190111133124.31879-1-bfoster@redhat.com> In-Reply-To: <20190111123032.31538-1-bfoster@redhat.com> References: <20190111123032.31538-1-bfoster@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Fri, 11 Jan 2019 13:31:25 +0000 (UTC) Sender: fstests-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: fstests@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP XFS has a bug where page writeback can end up sending data to the wrong location due to a stale, cached file mapping. Add a test to trigger this problem by racing background writeback with a truncate/rewrite of the final page of the file. Signed-off-by: Brian Foster --- Hi all, This is a resend of an old post[1] that never quite made it upstream. It wasn't a big deal at the time because we didn't really have a proper fix for the problem. I'm resending now because there is a proposed fix[2]. I've verified that this still reproduces the problem and no longer fails with the fix applied (in hundreds of iters). Note that reproduction may require many iterations. It took me anywhere from 5 to 30 or so on the box I tested, which I think is reasonable for the tradeoff of a fairly quick test. There was some discussion on the original post around making the test run longer for a more reliable reproducer, but I'm not sure how valuable that is given this is a targeted regression test. Thoughts appreciated. Brian [1] https://marc.info/?l=fstests&m=150902929900510&w=2 [2] https://marc.info/?l=linux-xfs&m=154721212321112&w=2 tests/generic/999 | 94 +++++++++++++++++++++++++++++++++++++++++++ tests/generic/999.out | 2 + tests/generic/group | 1 + 3 files changed, 97 insertions(+) create mode 100755 tests/generic/999 create mode 100644 tests/generic/999.out diff --git a/tests/generic/999 b/tests/generic/999 new file mode 100755 index 00000000..9e56a1e0 --- /dev/null +++ b/tests/generic/999 @@ -0,0 +1,94 @@ +#! /bin/bash +# FS QA Test 999 +# +# Test XFS page writeback code for races with the cached file mapping. XFS +# caches the file -> block mapping for a full extent once it is initially looked +# up. The cached mapping is used for all subsequent pages in the same writeback +# cycle that cover the associated extent. Under certain conditions, it is +# possible for concurrent operations on the file to invalidate the cached +# mapping without the knowledge of writeback. Writeback ends up sending I/O to a +# partly stale mapping and potentially leaving delalloc blocks in the current +# mapping unconverted. +# +#----------------------------------------------------------------------- +# Copyright (c) 2017 Red Hat, Inc. All Rights Reserved. +# +# This program is free software; you can redistribute it and/or +# modify it under the terms of the GNU General Public License as +# published by the Free Software Foundation. +# +# This program is distributed in the hope that it would be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program; if not, write the Free Software Foundation, +# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA +#----------------------------------------------------------------------- +# + +seq=`basename $0` +seqres=$RESULT_DIR/$seq +echo "QA output created by $seq" + +here=`pwd` +tmp=/tmp/$$ +status=1 # failure is the default! +trap "_cleanup; exit \$status" 0 1 2 3 15 + +_cleanup() +{ + cd / + rm -f $tmp.* +} + +# get standard environment, filters and checks +. ./common/rc + +# remove previous $seqres.full before test +rm -f $seqres.full + +# real QA test starts here + +# Modify as appropriate. +_supported_fs generic +_supported_os Linux +_require_scratch +_require_test_program "feature" + +_scratch_mkfs >> $seqres.full 2>&1 || _fail "mkfs failed" +_scratch_mount || _fail "mount failed" + +file=$SCRATCH_MNT/file +filesize=$((1024 * 1024 * 32)) +pagesize=`src/feature -s` +truncsize=$((filesize - pagesize)) + +for i in $(seq 0 15); do + # Truncate the file and fsync to persist the final size on-disk. This is + # required so the subsequent truncate will not wait on writeback. + $XFS_IO_PROG -fc "truncate 0" $file + $XFS_IO_PROG -c "truncate $filesize" -c fsync $file + + # create a small enough delalloc extent to likely be contiguous + $XFS_IO_PROG -c "pwrite 0 $filesize" $file >> $seqres.full 2>&1 + + # Start writeback and a racing truncate and rewrite of the final page. + $XFS_IO_PROG -c "sync_range -w 0 0" $file & + sync_pid=$! + $XFS_IO_PROG -c "truncate $truncsize" \ + -c "pwrite $truncsize $pagesize" $file >> $seqres.full 2>&1 + + # If the test fails, the most likely outcome is an sb_fdblocks mismatch + # and/or an associated delalloc assert failure on inode reclaim. Cycle + # the mount to trigger detection. + wait $sync_pid + _scratch_cycle_mount || _fail "mount failed" +done + +echo Silence is golden + +# success, all done +status=0 +exit diff --git a/tests/generic/999.out b/tests/generic/999.out new file mode 100644 index 00000000..3b276ca8 --- /dev/null +++ b/tests/generic/999.out @@ -0,0 +1,2 @@ +QA output created by 999 +Silence is golden diff --git a/tests/generic/group b/tests/generic/group index ea5aa7aa..ce165981 100644 --- a/tests/generic/group +++ b/tests/generic/group @@ -525,3 +525,4 @@ 520 auto quick log 521 soak long_rw 522 soak long_rw +999 auto quick