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Date:   Thu, 19 Aug 2021 14:06:36 +0800
From:   Eryu Guan <eguan@linux.alibaba.com>
To:     Boyang Xue <bxue@redhat.com>
Cc:     fstests@vger.kernel.org, Jan Kara <jack@suse.cz>,
        linux-ext4@vger.kernel.org, Zirong Lang <zlang@redhat.com>
Subject: Re: [PATCH] ext4: regression test for "tune2fs -l" after ext4
 shutdown
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On Thu, Aug 19, 2021 at 01:48:55PM +0800, Boyang Xue wrote:
> Zorro,
> 
> Please check my reply inline below.
> 
> On Thu, Aug 19, 2021 at 12:47 AM Zorro Lang <zlang@redhat.com> wrote:
> >
> > On Wed, Aug 18, 2021 at 09:20:44PM +0800, Boyang Xue wrote:
> > > Hi Zorro,
> > >
> > > On Wed, Aug 18, 2021 at 7:32 PM Zorro Lang <zlang@redhat.com> wrote:
> > > >
> > > > On Wed, Aug 18, 2021 at 04:40:56PM +0800, bxue@redhat.com wrote:
> > > > > From: Boyang Xue <bxue@redhat.com>
> > > > >
> > > > > Regression test for:
> > > > >
> > > > > ext4: Fix tune2fs checksum failure for mounted filesystem
> > > >
> > > > Better to specify the commit id number. I saw Ted has applied that patch:
> > > >
> > > > https://lore.kernel.org/linux-ext4/162895105421.460437.8931255765382647790.b4-ty@mit.edu/
> > >
> > > Thanks. I see the commit id e905fbe3fd0fdb90052f6efdf88f50a78833cfe7
> > > in the above URL. I didn't add it since I'm not sure if this id will
> > > be the final id when the commit is finally merged to the mainline
> > > kernel (Linus tree)?
> > >
> > > >
> > > > And maybe you can describe *a little* more in commit log.
> > >
> > > Yes I can add a few words in the commit log, but actually I expect the
> > > reader of this test reads the commit message of the mentioned commit
> > > "ext4: Fix tune2fs checksum failure for mounted filesystem", which I
> > > think is more precise.
> > >
> > > >
> > > > >
> > > > > Signed-off-by: Boyang Xue <bxue@redhat.com>
> > > > > ---
> > > > > Hi,
> > > > >
> > > > > This is a new regression test for the patch
> > > > >
> > > > > ```
> > > > > ext4: Fix tune2fs checksum failure for mounted filesystem
> > > > >
> > > > > Commit 81414b4dd48 ("ext4: remove redundant sb checksum recomputation")
> > > > > removed checksum recalculation after updating superblock free space /
> > > > > inode counters in ext4_fill_super() based on the fact that we will
> > > > > recalculate the checksum on superblock writeout. That is correct
> > > > > assumption but until the writeout happens (which can take a long time)
> > > > > the checksum is incorrect in the buffer cache and if tune2fs is called
> > > > > in that time window it will complain. So return back the checksum
> > > > > recalculation and add a comment explaining the tune2fs peculiarity.
> > > > >
> > > > > Fixes: 81414b4dd48f ("ext4: remove redundant sb checksum recomputation")
> > > > > Reported-by: Boyang Xue <bxue@xxxxxxxxxx>
> > > > > Signed-off-by: Jan Kara <jack@xxxxxxx>
> > > > > ```
> > > > >
> > > > > It's expected to fail on kernels from the kernel-5.11-rc1 to the latest
> > > > > version, where tune2fs fails with:
> > > > >
> > > > > ```
> > > > > tune2fs 1.46.2 (28-Feb-2021)
> > > > > tune2fs: Superblock checksum does not match superblock while trying to
> > > > > open /dev/loop0
> > > > > Couldn't find valid filesystem superblock.
> > > > > ```
> > > > >
> > > > > Please help review this test, Thanks!
> > > > >
> > > > > -Boyang
> > > > >
> > > > >  tests/ext4/309     | 42 ++++++++++++++++++++++++++++++++++++++++++
> > > > >  tests/ext4/309.out |  2 ++
> > > > >  2 files changed, 44 insertions(+)
> > > > >  create mode 100755 tests/ext4/309
> > > > >  create mode 100644 tests/ext4/309.out
> > > > >
> > > > > diff --git a/tests/ext4/309 b/tests/ext4/309
> > > > > new file mode 100755
> > > > > index 00000000..ae335617
> > > > > --- /dev/null
> > > > > +++ b/tests/ext4/309
> > > > > @@ -0,0 +1,42 @@
> > > > > +#! /bin/bash
> > > > > +# SPDX-License-Identifier: GPL-2.0
> > > > > +# Copyright (c) 2021 YOUR NAME HERE.  All Rights Reserved.
> > > >                         ^^^^^^^^^^^^^^
> > > >                        Write your copyright
> > >
> > > I will correct it in the next version. Thanks.
> > >
> > > >
> > > > > +#
> > > > > +# FS QA Test 309
> > > > > +#
> > > > > +# Test that tune2fs doesn't fail after ext4 shutdown
> > > > > +# Regression test for commit:
> > > > > +# ext4: Fix tune2fs checksum failure for mounted filesystem
> > > > > +#
> > > > > +. ./common/preamble
> > > > > +_begin_fstest auto rw quick
> > > > > +
> > > > > +_cleanup()
> > > > > +{
> > > > > +     _scratch_unmount
> > > > > +}
> > > >
> > > > I think the umount isn't necessary, so the specific _cleanup isn't
> > > > needed either.
> > >
> > > The $SCRATCH_DEV was still mounted before this _cleanup(), so I'm
> > > wondering why we shouldn't do _scratch_unmount here? And I see at
> > > least another similar structured test ext4/306 do _scratch_unmount in
> > > _cleanup().
> >
> > The SCRATCH_DEV will be umounted, don't need to do that in the end of each
> > test cases, except you need to do something on the unmounted SCRATCH_DEV
> > in the end.
> >
> > I don't know why ext4/306 has that, maybe due to old reason, or we didn't
> > notice/care that when we reviewed it? And it's not worth sending a patch
> > just for removing this "not wrong but just redundant" line now. Except a
> > patch trys to cleanup all _cleanup().
> 
> OK. I will remove the _cleanup() in my next version, unless someone
> else has other opinions.
> 
> >
> > >
> > > >
> > > > > +
> > > > > +# Import common functions.
> > > > > +. ./common/filter
> > > >
> > > > Do you use any filter helpers below?
> > >
> > > No. I will remove this line in my next version.
> > >
> > > >
> > > > > +
> > > > > +# real QA test starts here
> > > > > +_supported_fs ext4
> > > >
> > > > I'm wondering if this case can be a generic case, there's nothing
> > > > ext4 specified operations, except this line:
> > > >
> > > > "$TUNE2FS_PROG -l $SCRATCH_DEV"
> > > >
> > > > Hmm... if we can change this line to something likes _get_fs_super(),
> > > > it might help to make this test to be a generic test.
> > >
> > > I think this bug is heavily related to "tune2fs", ext4 only. So I
> > > guess an ext4 only test is enough?
> >
> > Just checking. That's fine for me to keep this case as an ext4 only case.
> >
> > >
> > > >
> > > > > +_require_scratch
> > > > > +_require_scratch_shutdown
> > > > > +_require_command "$TUNE2FS_PROG" tune2fs
> > > > > +
> > > > > +echo "Silence is golden"
> > > > > +
> > > > > +_scratch_mkfs >/dev/null 2>&1
> > > > > +_scratch_mount
> > > > > +echo "ext4/309" > $SCRATCH_MNT/309.tmp
> > > >
> > > > It's sure this case will be "ext4/309", although you use "309" won't
> > > > affect anything.
> > >
> > > Yes I can rename it to something like ext4-309.tmp if it looks better.
> >
> > I think something likes: echo "This is a test" > $SCRATCH_MNT/testfile
> > is good enough, don't need the "ext4" or "309" things.
> 
> OK. I will modify it to
> 
> echo "This is a test" > $SCRATCH_MNT/testfile
> 
> Unless someone else has other preferences.
> 
> >
> > >
> > > >
> > > > > +_scratch_shutdown
> > > > > +_scratch_cycle_mount
> > > > > +$TUNE2FS_PROG -l $SCRATCH_DEV >> $seqres.full 2>&1
> > > > > +if [ $? -eq 0 ]; then
> > > > > +     status=0
> > > > > +else
> > > > > +     status=1
> > > > > +fi
> > > >
> > > > Don't need to change the status value, how about write as:
> > > >
> > > > $TUNE2FS_PROG -l $SCRATCH_DEV >/dev/null
> > > >
> > > > The error output will break the golden image directly.
> > >
> > > How did you test that? The error output didn't break the "golden
> > > image" in my test.
> >
> > [root@xx-xxxx-xx xfstests-dev]# ./check ext4/309
> > FSTYP         -- ext4
> > PLATFORM      -- Linux/x86_64 xx-xxxx-xx 5.14.0-rc4-xfs #14 SMP Thu Aug 12 00:56:07 CST 2021
> > MKFS_OPTIONS  -- /dev/mapper/testvg-scratchdev
> > MOUNT_OPTIONS -- -o acl,user_xattr -o context=system_u:object_r:root_t:s0 /dev/mapper/testvg-scratchdev /mnt/scratch
> >
> > ext4/309 5s ... - output mismatch (see /root/git/xfstests-dev/results//ext4/309.out.bad)
> >     --- tests/ext4/309.out      2021-08-18 18:17:15.925427714 +0800
> >     +++ /root/git/xfstests-dev/results//ext4/309.out.bad        2021-08-19 00:17:57.001648868 +0800
> >     @@ -1,2 +1,4 @@
> >      QA output created by 309
> >      Silence is golden
> >     +/usr/sbin/tune2fs: Superblock checksum does not match superblock while trying to open /dev/mapper/testvg-scratchdev
> >     +Couldn't find valid filesystem superblock.
> >     ...
> >     (Run 'diff -u /root/git/xfstests-dev/tests/ext4/309.out /root/git/xfstests-dev/results//ext4/309.out.bad'  to see the entire diff)
> > Ran: ext4/309
> > Failures: ext4/309
> > Failed 1 of 1 tests
> >
> > [root@xx-xxxx-xx xfstests-dev]# git diff
> > ...
> >  _scratch_mkfs >/dev/null 2>&1
> >  _scratch_mount
> > -echo "ext4/309" > $SCRATCH_MNT/309.tmp
> > +echo "This is a test" > $SCRATCH_MNT/testfile
> >  _scratch_shutdown
> > -_scratch_cycle_mount
> > -$TUNE2FS_PROG -l $SCRATCH_DEV >> $seqres.full 2>&1
> > -if [ $? -eq 0 ]; then
> > -       status=0
> > -else
> > -       status=1
> > -fi
> > +_scratch_cycle_mount
> > +$TUNE2FS_PROG -l $SCRATCH_DEV >/dev/null
> >
> > +status=0
> >  exit
> 
> Unless I missed something, I would say that, tune2fs' error output
> went to .out.bad just because you had modified the tune2fs line from
> mine:
> 
> $TUNE2FS_PROG -l $SCRATCH_DEV >> $seqres.full 2>&1
> 
> to yours:
> 
> $TUNE2FS_PROG -l $SCRATCH_DEV >/dev/null

I think what Zorro is suggesting is that *when test fails* just dump
stderr and let the error message break golden image to fail the test, so
there's no need to set exit status.

> 
> My original version redirecting stderr and stdout both to $seqres.full
> doesn't break the "golden output". Test log:
> ```
> [root@kvm102 repo_xfstests]# ./check ext4/309
> FSTYP         -- ext4
> PLATFORM      -- Linux/x86_64 kvm102 5.14.0-0.rc4.35.xx.x86_64 #1 SMP
> Tue Aug 3 13:02:44 EDT 2021
> MKFS_OPTIONS  -- -b 1024 /dev/vda3
> MOUNT_OPTIONS -- -o acl,user_xattr -o
> context=system_u:object_r:root_t:s0 /dev/vda3 /scratch
> 
> ext4/309        [failed, exit status 1]

And this failure doesn't give any clues why it failed, you must check
$seqres.full file to find out.

With stderr breaking golden image, you'll see what fails more easily,
e.g.


  QA output created by 309
  Silence is golden
 +/usr/sbin/tune2fs: Superblock checksum does not match superblock while trying to open /dev/mapper/testvg-scratchdev
 +Couldn't find valid filesystem superblock.
 ...
 (Run 'diff -u /root/git/xfstests-dev/tests/ext4/309.out /root/git/xfstests-dev/results//ext4/309.out.bad'  to see the entire diff)

Thanks,
Eryu