Date:   Thu, 19 Aug 2021 13:48:55 +0800
From:   Boyang Xue <bxue@...hat.com>
To:     Boyang Xue <bxue@...hat.com>, fstests@...r.kernel.org,
        Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org,
        Zirong Lang <zlang@...hat.com>
Subject: Re: [PATCH] ext4: regression test for "tune2fs -l" after ext4 shutdown

Zorro,

Please check my reply inline below.

On Thu, Aug 19, 2021 at 12:47 AM Zorro Lang <zlang@...hat.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@...hat.com> wrote:
> > >
> > > On Wed, Aug 18, 2021 at 04:40:56PM +0800, bxue@...hat.com wrote:
> > > > From: Boyang Xue <bxue@...hat.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@...hat.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@...xxxxxxx>
> > > > Signed-off-by: Jan Kara <jack@...xxxx>
> > > > ```
> > > >
> > > > 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@...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@...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

My original version redirecting stderr and stdout both to $seqres.full
doesn't break the "golden output". Test log:
```
[root@...102 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]
Ran: ext4/309
Failures: ext4/309
Failed 1 of 1 tests
[root@...102 repo_xfstests]# cat results/ext4/309.full
/usr/sbin/tune2fs: Superblock checksum does not match superblock while
trying to open /dev/vda3
Couldn't find valid filesystem superblock.
tune2fs 1.46.2 (28-Feb-2021)
[root@...102 repo_xfstests]# ls results/ext4/309.out.bad
ls: cannot access 'results/ext4/309.out.bad': No such file or directory
```

As far as I can understand, there're at least two approaches to mark a
test pass or fail in xfstests:
1) Compare the output of the test with the "golden output" (i.e.
309.out), I guess this is the approach you mentioned.
2) Exit the test with the value of $status (i.e. status=0 - pass,
status=non-zero - fail)

I'm using the 2) here, not using 1) with the output of tune2fs
compared with the 309.out, because the output of tune2fs can be
different in different runs. An example output of a successful tune2fs
run is like (sorry for this long paste):
```
[root@...101 repo_xfstests]# cat results/ext4/309.full
tune2fs 1.45.6 (20-Mar-2020)
Filesystem volume name:   <none>
Last mounted on:          /scratch
Filesystem UUID:          22975090-96d7-49ee-9b4f-ee6afe046219
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal ext_attr resize_inode dir_index
filetype needs_recovery extent 64bit flex_bg sparse_super large_file
huge_file dir_nlink extra_isize metadata_csum
Filesystem flags:         signed_directory_hash
Default mount options:    user_xattr acl
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              720896
Block count:              11534336
Reserved block count:     576716
Free blocks:              11280570
Free inodes:              720884
First block:              1
Block size:               1024
Fragment size:            1024
Group descriptor size:    64
Reserved GDT blocks:      256
Blocks per group:         8192
Fragments per group:      8192
Inodes per group:         512
Inode blocks per group:   128
Flex block group size:    16
Filesystem created:       Thu Aug 19 05:45:26 2021
Last mount time:          Thu Aug 19 05:45:26 2021
Last write time:          Thu Aug 19 05:45:26 2021
Mount count:              2
Maximum mount count:      -1
Last checked:             Thu Aug 19 05:45:26 2021
Check interval:           0 (<none>)
Lifetime writes:          462 kB
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:               256
Required extra isize:     32
Desired extra isize:      32
Journal inode:            8
Default directory hash:   half_md4
Directory Hash Seed:      f5af5862-d415-460b-9a6b-97584578600f
Journal backup:           inode blocks
Checksum type:            crc32c
Checksum:                 0x0f5b9c13
```

Thanks,
Boyang

>
>
> Thanks,
> Zorro
>
> >
> > >
> > > ( cc ext4 mailist, to get more review)
> > >
> > > Thanks,
> > > Zorro
> >
> > Thanks for review!
> >
> > -Boyang
> >
> > >
> > > > +
> > > > +exit
> > > > diff --git a/tests/ext4/309.out b/tests/ext4/309.out
> > > > new file mode 100644
> > > > index 00000000..56330d65
> > > > --- /dev/null
> > > > +++ b/tests/ext4/309.out
> > > > @@ -0,0 +1,2 @@
> > > > +QA output created by 309
> > > > +Silence is golden
> > > > --
> > > > 2.27.0
> > > >
> > >
> >
>

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