[PATCH] fstests: ext4: regression test for fsync transaction ids initialization

[PATCH] fstests: ext4: regression test for fsync transaction ids initialization

[Wang Xiaoguang]

Commit 688f869 fixed this bug:
    ext4: ext4: Initialize fsync transaction ids in ext4_new_inode()

We manually modify jbd2 journal_superblock_s.s_sequence to be a very large
number, which will greatly reduce the time taken to trigger this bug, though
it seems some too hacked.

Signed-off-by: Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>
---
 tests/ext4/021     | 117 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/ext4/021.out |   2 +
 tests/ext4/group   |   1 +
 3 files changed, 120 insertions(+)
 create mode 100755 tests/ext4/021
 create mode 100644 tests/ext4/021.out

diff --git a/tests/ext4/021 b/tests/ext4/021
new file mode 100755
index 0000000..cdc1524
--- /dev/null
+++ b/tests/ext4/021
@@ -0,0 +1,117 @@
+#! /bin/bash
+# FS QA Test 021
+#
+# Regression test for commit:
+# 688f869 ext4: Initialize fsync transaction ids in ext4_new_inode()
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2016 Fujitsu.  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/$$
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+	rm -f $tmp.*
+	$UMOUNT_PROG $loop_mnt
+	_destroy_loop_device $loop_dev1
+	_destroy_loop_device $loop_dev2
+	rm -rf $loop_mnt
+	rm -f $fs_img1 $fs_img2
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+_supported_fs ext4
+_supported_os Linux
+_require_test
+_require_loop
+
+BLOCKSIZE=1024
+loop_mnt=$TEST_DIR/$seq.$$.mnt
+fs_img1=$TEST_DIR/$seq.$$.img1
+fs_img2=$TEST_DIR/$seq.$$.img2
+mkdir $loop_mnt
+$XFS_IO_PROG -f -c "truncate 128m" $fs_img1 >>$seqres.full 2>&1
+$XFS_IO_PROG -f -c "truncate 16m" $fs_img2 >>$seqres.full 2>&1
+
+loop_dev1=`_create_loop_device $fs_img1`
+loop_dev2=`_create_loop_device $fs_img2`
+
+_mkfs_dev -b $BLOCKSIZE -O journal_dev $loop_dev2 >>$seqres.full 2>&1
+_mkfs_dev -b $BLOCKSIZE -J device=$loop_dev2 $loop_dev1 >>$seqres.full 2>&1
+
+# Below command will modify jbd2 journal transaction id to be 2178000000,
+# which will reduce the time taken to trigger this bug. When ext4 fs block
+# size is 1024, journal superblock will start at offset 2048, and
+# journal_superblock_s.s_sequence will start at offset 2072. After this
+# modification, jbd2 will will start to run with a initial transaction id
+# 2178000000.
+echo 81d1a480 | xxd -r -ps | dd of=$loop_dev2 bs=4 count=1 seek=518 >/dev/null 2>&1
+
+trans_id=$(dumpe2fs $loop_dev2 2>/dev/null | grep "Journal sequence" | \
+  awk -F ":" '{print $2}')
+trans_id=$((trans_id))
+if [ $trans_id -ne 2178000000 ]; then
+	echo "fail to set initial transaction id to 2178000000"
+	exit
+fi
+echo "Initial transaction id is $trans_id"
+
+_mount $loop_dev1 $loop_mnt
+cd $loop_mnt
+
+cat >do_fdatasync.c <<EOF
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+void main(void)
+{
+	int fd;
+
+	fd = open("testfile", O_RDWR | O_CREAT | O_EXCL);
+	while (1)
+		fdatasync(fd);
+}
+EOF
+gcc -o do_fdatasync do_fdatasync.c >> $seqres.full 2>&1 || \
+  _notrun "Could not compile test program (see end of $seqres.full)"
+
+./do_fdatasync &
+child_process=$!
+
+sleep 60
+kill $child_process >/dev/null 2>&1
+
+# success, all done
+status=0
+exit
diff --git a/tests/ext4/021.out b/tests/ext4/021.out
new file mode 100644
index 0000000..ee3e81d
--- /dev/null
+++ b/tests/ext4/021.out
@@ -0,0 +1,2 @@
+QA output created by 021
+Initial transaction id is 2178000000
diff --git a/tests/ext4/group b/tests/ext4/group
index 9e28159..7736da1 100644
--- a/tests/ext4/group
+++ b/tests/ext4/group
@@ -23,6 +23,7 @@
 018 fuzzers
 019 fuzzers
 020 auto quick ioctl rw
+021 auto
 271 auto rw quick
 301 aio auto ioctl rw stress
 302 aio auto ioctl rw stress
-- 
2.5.0

Re: [PATCH] fstests: ext4: regression test for fsync transaction ids initialization

[Eryu Guan]

On Wed, Jun 08, 2016 at 11:02:25AM +0800, Wang Xiaoguang wrote:
> Commit 688f869 fixed this bug:
>     ext4: ext4: Initialize fsync transaction ids in ext4_new_inode()

Double "ext4: " here :)

And the "fstests: " prefix in summary can be dropped, "ext4: " prefix is
Okay.

> 
> We manually modify jbd2 journal_superblock_s.s_sequence to be a very large
> number, which will greatly reduce the time taken to trigger this bug, though
> it seems some too hacked.
> 
> Signed-off-by: Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>
> ---
>  tests/ext4/021     | 117 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/ext4/021.out |   2 +
>  tests/ext4/group   |   1 +
>  3 files changed, 120 insertions(+)
>  create mode 100755 tests/ext4/021
>  create mode 100644 tests/ext4/021.out
> 
> diff --git a/tests/ext4/021 b/tests/ext4/021
> new file mode 100755
> index 0000000..cdc1524
> --- /dev/null
> +++ b/tests/ext4/021
> @@ -0,0 +1,117 @@
> +#! /bin/bash
> +# FS QA Test 021
> +#
> +# Regression test for commit:
> +# 688f869 ext4: Initialize fsync transaction ids in ext4_new_inode()
> +#
> +#-----------------------------------------------------------------------
> +# Copyright (c) 2016 Fujitsu.  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/$$
> +status=1	# failure is the default!
> +trap "_cleanup; exit \$status" 0 1 2 3 15
> +
> +_cleanup()
> +{
> +	cd /
> +	rm -f $tmp.*
> +	$UMOUNT_PROG $loop_mnt
> +	_destroy_loop_device $loop_dev1
> +	_destroy_loop_device $loop_dev2
> +	rm -rf $loop_mnt
> +	rm -f $fs_img1 $fs_img2
> +}
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +
> +# remove previous $seqres.full before test
> +rm -f $seqres.full
> +
> +# real QA test starts here
> +_supported_fs ext4
> +_supported_os Linux
> +_require_test
> +_require_loop
> +
> +BLOCKSIZE=1024
> +loop_mnt=$TEST_DIR/$seq.$$.mnt
> +fs_img1=$TEST_DIR/$seq.$$.img1
> +fs_img2=$TEST_DIR/$seq.$$.img2
> +mkdir $loop_mnt
> +$XFS_IO_PROG -f -c "truncate 128m" $fs_img1 >>$seqres.full 2>&1
> +$XFS_IO_PROG -f -c "truncate 16m" $fs_img2 >>$seqres.full 2>&1
> +
> +loop_dev1=`_create_loop_device $fs_img1`
> +loop_dev2=`_create_loop_device $fs_img2`

You're using two loop devices and one is used as external journal
device, I think test on SCRATCH_DEV should be fine, e.g.

_scratch_mkfs_sized a 8M ext4 filesystem, then use a script to find the
journal superblock on disk, then modify the journal.s_sequence according
to the location of journal superblock and the offset of s_sequence to
it. I use the following script to do all this:

#/bin/bash
dev=$1
mkfs -t ext4 $dev 8M
blocksize=`dumpe2fs -h $dev 2>/dev/null | grep "Block size" | awk '{print $3}'`
offset=0
found=0
# this is the jbd2 journal superblock magic number on disk, in big endian
magic="c0 3b 39 98"

# 8M in bytes
filesize=$((8 * 1024 * 1024))
while [ $offset -lt $filesize ]; do
        if od -j $offset -N 4 -t x1 $dev | grep -i "$magic";then
                echo "Found journal: $offset"
                found=1
                break
        fi
        offset=$((offset + blocksize))
done

# Overwrite journal.s_squence to 0x 81d1a480
# 0x81d1a480 is hex form of 2178000000, and jbd2 journal is big endian on
# disk, the s_squence offset to the beginning of journal superblock is 24
xfs_io  -c "pwrite -S 0x81 $((offset+24)) 1" \
        -c "pwrite -S 0xd1 $((offset+25)) 1" \
        -c "pwrite -S 0xa4 $((offset+26)) 1" \
        -c "pwrite -S 0x80 $((offset+27)) 1" $dev


This way, we don't have to use loop device nor external journal device,
and don't have to test on fixed block size ext4, SCRATCH_DEV just works.

> +
> +_mkfs_dev -b $BLOCKSIZE -O journal_dev $loop_dev2 >>$seqres.full 2>&1
> +_mkfs_dev -b $BLOCKSIZE -J device=$loop_dev2 $loop_dev1 >>$seqres.full 2>&1
> +
> +# Below command will modify jbd2 journal transaction id to be 2178000000,
> +# which will reduce the time taken to trigger this bug. When ext4 fs block
> +# size is 1024, journal superblock will start at offset 2048, and
> +# journal_superblock_s.s_sequence will start at offset 2072. After this
> +# modification, jbd2 will will start to run with a initial transaction id
> +# 2178000000.
> +echo 81d1a480 | xxd -r -ps | dd of=$loop_dev2 bs=4 count=1 seek=518 >/dev/null 2>&1
> +
> +trans_id=$(dumpe2fs $loop_dev2 2>/dev/null | grep "Journal sequence" | \
> +  awk -F ":" '{print $2}')
> +trans_id=$((trans_id))

I think this is unnecessary, just print the hex form.

> +if [ $trans_id -ne 2178000000 ]; then
> +	echo "fail to set initial transaction id to 2178000000"
> +	exit
> +fi

This is not needed, because..

> +echo "Initial transaction id is $trans_id"

You have this in golden output, when trans_id goes wrong, it will be
caught by golden image.

> +
> +_mount $loop_dev1 $loop_mnt
> +cd $loop_mnt
> +
> +cat >do_fdatasync.c <<EOF
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <sys/types.h>
> +
> +void main(void)
> +{
> +	int fd;
> +
> +	fd = open("testfile", O_RDWR | O_CREAT | O_EXCL);
> +	while (1)
> +		fdatasync(fd);
> +}
> +EOF
> +gcc -o do_fdatasync do_fdatasync.c >> $seqres.full 2>&1 || \
> +  _notrun "Could not compile test program (see end of $seqres.full)"
> +
> +./do_fdatasync &
> +child_process=$!

No need to write a temporary c program, calling xfs_io -c "fdatasync" in
a loop is good enough.

> +
> +sleep 60
> +kill $child_process >/dev/null 2>&1

In my test, the test triggers WARNINGs (seems not panic every time)
almost as soon as the fdatasync loop runs. I think 10s is long enough.

> +
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/ext4/021.out b/tests/ext4/021.out
> new file mode 100644
> index 0000000..ee3e81d
> --- /dev/null
> +++ b/tests/ext4/021.out
> @@ -0,0 +1,2 @@
> +QA output created by 021
> +Initial transaction id is 2178000000
> diff --git a/tests/ext4/group b/tests/ext4/group
> index 9e28159..7736da1 100644
> --- a/tests/ext4/group
> +++ b/tests/ext4/group
> @@ -23,6 +23,7 @@
>  018 fuzzers
>  019 fuzzers
>  020 auto quick ioctl rw
> +021 auto

If it runs for 10s, quick group can be added.

Thanks,
Eryu

>  271 auto rw quick
>  301 aio auto ioctl rw stress
>  302 aio auto ioctl rw stress
> -- 
> 2.5.0
> 
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe fstests" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] fstests: ext4: regression test for fsync transaction ids initialization

[Wang Xiaoguang]

Hello,

Thanks for reviewing.

On 06/08/2016 04:55 PM, Eryu Guan wrote:
> On Wed, Jun 08, 2016 at 11:02:25AM +0800, Wang Xiaoguang wrote:
>> Commit 688f869 fixed this bug:
>>      ext4: ext4: Initialize fsync transaction ids in ext4_new_inode()
> Double "ext4: " here :)
>
> And the "fstests: " prefix in summary can be dropped, "ext4: " prefix is
> Okay.
>
>> We manually modify jbd2 journal_superblock_s.s_sequence to be a very large
>> number, which will greatly reduce the time taken to trigger this bug, though
>> it seems some too hacked.
>>
>> Signed-off-by: Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>
>> ---
>>   tests/ext4/021     | 117 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   tests/ext4/021.out |   2 +
>>   tests/ext4/group   |   1 +
>>   3 files changed, 120 insertions(+)
>>   create mode 100755 tests/ext4/021
>>   create mode 100644 tests/ext4/021.out
>>
>> diff --git a/tests/ext4/021 b/tests/ext4/021
>> new file mode 100755
>> index 0000000..cdc1524
>> --- /dev/null
>> +++ b/tests/ext4/021
>> @@ -0,0 +1,117 @@
>> +#! /bin/bash
>> +# FS QA Test 021
>> +#
>> +# Regression test for commit:
>> +# 688f869 ext4: Initialize fsync transaction ids in ext4_new_inode()
>> +#
>> +#-----------------------------------------------------------------------
>> +# Copyright (c) 2016 Fujitsu.  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/$$
>> +status=1	# failure is the default!
>> +trap "_cleanup; exit \$status" 0 1 2 3 15
>> +
>> +_cleanup()
>> +{
>> +	cd /
>> +	rm -f $tmp.*
>> +	$UMOUNT_PROG $loop_mnt
>> +	_destroy_loop_device $loop_dev1
>> +	_destroy_loop_device $loop_dev2
>> +	rm -rf $loop_mnt
>> +	rm -f $fs_img1 $fs_img2
>> +}
>> +
>> +# get standard environment, filters and checks
>> +. ./common/rc
>> +
>> +# remove previous $seqres.full before test
>> +rm -f $seqres.full
>> +
>> +# real QA test starts here
>> +_supported_fs ext4
>> +_supported_os Linux
>> +_require_test
>> +_require_loop
>> +
>> +BLOCKSIZE=1024
>> +loop_mnt=$TEST_DIR/$seq.$$.mnt
>> +fs_img1=$TEST_DIR/$seq.$$.img1
>> +fs_img2=$TEST_DIR/$seq.$$.img2
>> +mkdir $loop_mnt
>> +$XFS_IO_PROG -f -c "truncate 128m" $fs_img1 >>$seqres.full 2>&1
>> +$XFS_IO_PROG -f -c "truncate 16m" $fs_img2 >>$seqres.full 2>&1
>> +
>> +loop_dev1=`_create_loop_device $fs_img1`
>> +loop_dev2=`_create_loop_device $fs_img2`
> You're using two loop devices and one is used as external journal
> device, I think test on SCRATCH_DEV should be fine, e.g.
>
> _scratch_mkfs_sized a 8M ext4 filesystem, then use a script to find the
> journal superblock on disk, then modify the journal.s_sequence according
> to the location of journal superblock and the offset of s_sequence to
> it. I use the following script to do all this:
>
> #/bin/bash
> dev=$1
> mkfs -t ext4 $dev 8M
> blocksize=`dumpe2fs -h $dev 2>/dev/null | grep "Block size" | awk '{print $3}'`
> offset=0
> found=0
> # this is the jbd2 journal superblock magic number on disk, in big endian
> magic="c0 3b 39 98"
>
> # 8M in bytes
> filesize=$((8 * 1024 * 1024))
> while [ $offset -lt $filesize ]; do
>          if  | grep -i "$magic";then
>                  echo "Found journal: $offset"
>                  found=1
>                  break
>          fi
>          offset=$((offset + blocksize))
> done
Thanks for your script, but I wonder whether there will be some other
metadata which would have the same magic number "c0 3b 39 98", such
as ext4 super_block or block_group_description.

Regards,
Xiaoguang Wang


>
> # Overwrite journal.s_squence to 0x 81d1a480
> # 0x81d1a480 is hex form of 2178000000, and jbd2 journal is big endian on
> # disk, the s_squence offset to the beginning of journal superblock is 24
> xfs_io  -c "pwrite -S 0x81 $((offset+24)) 1" \
>          -c "pwrite -S 0xd1 $((offset+25)) 1" \
>          -c "pwrite -S 0xa4 $((offset+26)) 1" \
>          -c "pwrite -S 0x80 $((offset+27)) 1" $dev
>
>
> This way, we don't have to use loop device nor external journal device,
> and don't have to test on fixed block size ext4, SCRATCH_DEV just works.
>
>> +
>> +_mkfs_dev -b $BLOCKSIZE -O journal_dev $loop_dev2 >>$seqres.full 2>&1
>> +_mkfs_dev -b $BLOCKSIZE -J device=$loop_dev2 $loop_dev1 >>$seqres.full 2>&1
>> +
>> +# Below command will modify jbd2 journal transaction id to be 2178000000,
>> +# which will reduce the time taken to trigger this bug. When ext4 fs block
>> +# size is 1024, journal superblock will start at offset 2048, and
>> +# journal_superblock_s.s_sequence will start at offset 2072. After this
>> +# modification, jbd2 will will start to run with a initial transaction id
>> +# 2178000000.
>> +echo 81d1a480 | xxd -r -ps | dd of=$loop_dev2 bs=4 count=1 seek=518 >/dev/null 2>&1
>> +
>> +trans_id=$(dumpe2fs $loop_dev2 2>/dev/null | grep "Journal sequence" | \
>> +  awk -F ":" '{print $2}')
>> +trans_id=$((trans_id))
> I think this is unnecessary, just print the hex form.
>
>> +if [ $trans_id -ne 2178000000 ]; then
>> +	echo "fail to set initial transaction id to 2178000000"
>> +	exit
>> +fi
> This is not needed, because..
>
>> +echo "Initial transaction id is $trans_id"
> You have this in golden output, when trans_id goes wrong, it will be
> caught by golden image.
>
>> +
>> +_mount $loop_dev1 $loop_mnt
>> +cd $loop_mnt
>> +
>> +cat >do_fdatasync.c <<EOF
>> +#include <sys/stat.h>
>> +#include <fcntl.h>
>> +#include <unistd.h>
>> +#include <sys/types.h>
>> +
>> +void main(void)
>> +{
>> +	int fd;
>> +
>> +	fd = open("testfile", O_RDWR | O_CREAT | O_EXCL);
>> +	while (1)
>> +		fdatasync(fd);
>> +}
>> +EOF
>> +gcc -o do_fdatasync do_fdatasync.c >> $seqres.full 2>&1 || \
>> +  _notrun "Could not compile test program (see end of $seqres.full)"
>> +
>> +./do_fdatasync &
>> +child_process=$!
> No need to write a temporary c program, calling xfs_io -c "fdatasync" in
> a loop is good enough.
>
>> +
>> +sleep 60
>> +kill $child_process >/dev/null 2>&1
> In my test, the test triggers WARNINGs (seems not panic every time)
> almost as soon as the fdatasync loop runs. I think 10s is long enough.
>
>> +
>> +# success, all done
>> +status=0
>> +exit
>> diff --git a/tests/ext4/021.out b/tests/ext4/021.out
>> new file mode 100644
>> index 0000000..ee3e81d
>> --- /dev/null
>> +++ b/tests/ext4/021.out
>> @@ -0,0 +1,2 @@
>> +QA output created by 021
>> +Initial transaction id is 2178000000
>> diff --git a/tests/ext4/group b/tests/ext4/group
>> index 9e28159..7736da1 100644
>> --- a/tests/ext4/group
>> +++ b/tests/ext4/group
>> @@ -23,6 +23,7 @@
>>   018 fuzzers
>>   019 fuzzers
>>   020 auto quick ioctl rw
>> +021 auto
> If it runs for 10s, quick group can be added.
>
> Thanks,
> Eryu
>
>>   271 auto rw quick
>>   301 aio auto ioctl rw stress
>>   302 aio auto ioctl rw stress
>> -- 
>> 2.5.0
>>
>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe fstests" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Re: [PATCH] fstests: ext4: regression test for fsync transaction ids initialization

[Eryu Guan]

On Tue, Jun 14, 2016 at 10:37:16AM +0800, Wang Xiaoguang wrote:
> Hello,
> 
> Thanks for reviewing.
> 
> On 06/08/2016 04:55 PM, Eryu Guan wrote:
[snip]
> >>+
> >>+loop_dev1=`_create_loop_device $fs_img1`
> >>+loop_dev2=`_create_loop_device $fs_img2`
> >You're using two loop devices and one is used as external journal
> >device, I think test on SCRATCH_DEV should be fine, e.g.
> >
> >_scratch_mkfs_sized a 8M ext4 filesystem, then use a script to find the
> >journal superblock on disk, then modify the journal.s_sequence according
> >to the location of journal superblock and the offset of s_sequence to
> >it. I use the following script to do all this:
> >
> >#/bin/bash
> >dev=$1
> >mkfs -t ext4 $dev 8M
> >blocksize=`dumpe2fs -h $dev 2>/dev/null | grep "Block size" | awk '{print $3}'`
> >offset=0
> >found=0
> ># this is the jbd2 journal superblock magic number on disk, in big endian
> >magic="c0 3b 39 98"
> >
> ># 8M in bytes
> >filesize=$((8 * 1024 * 1024))
> >while [ $offset -lt $filesize ]; do
> >         if  | grep -i "$magic";then
> >                 echo "Found journal: $offset"
> >                 found=1
> >                 break
> >         fi
> >         offset=$((offset + blocksize))
> >done
> Thanks for your script, but I wonder whether there will be some other
> metadata which would have the same magic number "c0 3b 39 98", such
> as ext4 super_block or block_group_description.

I don't think so. If they have the same magic number, it looks like a
bug to me.

Thanks,
Eryu

[PATCH v2] ext4: regression test for fsync transaction ids initialization

[Wang Xiaoguang]

Commit 688f869 fixed this bug:
    ext4: Initialize fsync transaction ids in ext4_new_inode()

We manually modify jbd2 journal_superblock_s.s_sequence to be a very large
number, which will greatly reduce the time taken to trigger this bug, though
it seems some too hacked.

Signed-off-by: Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>
---
v2:
- don't use loop devices, use scratch device directly. And use
Eryu Guan's script to find jbd2 journal superblock's offset.
---
 tests/ext4/021     | 106 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/ext4/021.out |   2 +
 tests/ext4/group   |   1 +
 3 files changed, 109 insertions(+)
 create mode 100755 tests/ext4/021
 create mode 100644 tests/ext4/021.out

diff --git a/tests/ext4/021 b/tests/ext4/021
new file mode 100755
index 0000000..2e13142
--- /dev/null
+++ b/tests/ext4/021
@@ -0,0 +1,106 @@
+#! /bin/bash
+# FS QA Test 021
+#
+# Regression test for commit:
+# 688f869 ext4: Initialize fsync transaction ids in ext4_new_inode()
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2016 Fujitsu.  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
+_supported_fs ext4
+_supported_os Linux
+_require_scratch
+_require_dumpe2fs
+
+_scratch_mkfs_sized $((8 * 1024 * 1024)) >> $seqres.full 2>&1
+
+blocksize=`$DUMPE2FS_PROG -h $SCRATCH_DEV 2>/dev/null | grep "Block size" | \
+	awk '{print $3}'`
+offset=0
+found=0
+# this is the jbd2 journal superblock magic number on disk, in big endian
+magic="c0 3b 39 98"
+
+# 8M in bytes
+filesize=$((8 * 1024 * 1024))
+while [ $offset -lt $filesize ]; do
+	if od -j $offset -N 4 -t x1 $SCRATCH_DEV | \
+	   grep -i "$magic" >/dev/null; then
+		echo "Found journal: $offset" >> $seqres.full
+		found=1
+		break
+	fi
+	offset=$((offset + blocksize))
+done
+if [ $found -ne 1 ]; then
+	echo "Found no journal"
+	exit
+fi
+
+# Overwrite journal.s_squence to 0x 81d1a480
+# 0x81d1a480 is hex form of 2178000000, and jbd2 journal is big endian on
+# disk, the s_squence offset to the beginning of journal superblock is 24
+# we do this to let jbd2 start to run with a initial big transaction id,
+# which will reduce the time taken to trigger this bug.
+xfs_io  -c "pwrite -S 0x81 $((offset+24)) 1" \
+	-c "pwrite -S 0xd1 $((offset+25)) 1" \
+	-c "pwrite -S 0xa4 $((offset+26)) 1" \
+	-c "pwrite -S 0x80 $((offset+27)) 1" $SCRATCH_DEV >> $seqres.full 2>&1
+
+trans_id=`$DUMPE2FS_PROG $SCRATCH_DEV 2>/dev/null | grep "Journal sequence" | \
+	awk '{print $NF}'`
+echo "Initial transaction id is $trans_id"
+_scratch_mount
+
+do_fdatasync_work()
+{
+	while [ 1 ]; do
+		$XFS_IO_PROG -f -c "fdatasync" $SCRATCH_MNT/testfile
+	done
+}
+
+do_fdatasync_work &
+datasync_work_pid=$!
+sleep 10
+kill $datasync_work_pid >/dev/null 2>&1
+
+# success, all done
+status=0
+exit
diff --git a/tests/ext4/021.out b/tests/ext4/021.out
new file mode 100644
index 0000000..9e504e2
--- /dev/null
+++ b/tests/ext4/021.out
@@ -0,0 +1,2 @@
+QA output created by 021
+Initial transaction id is 0x81d1a480
diff --git a/tests/ext4/group b/tests/ext4/group
index 9e28159..bbdbe1d 100644
--- a/tests/ext4/group
+++ b/tests/ext4/group
@@ -23,6 +23,7 @@
 018 fuzzers
 019 fuzzers
 020 auto quick ioctl rw
+021 auto quick
 271 auto rw quick
 301 aio auto ioctl rw stress
 302 aio auto ioctl rw stress
-- 
2.5.0