Re: [PATCH 1/2] ext4: check mount's handling for very large s_first_meta_bg

[Xiao Yang <yangx.jy@cn.fujitsu.com>]

On 2017/04/24 12:47, Eryu Guan wrote:
> On Fri, Apr 21, 2017 at 06:10:39PM +0800, Xiao Yang wrote:
>> On ext4 filesystem, the kernel carshes at mount time when
>> s_first_meta_bg's value exceeds the largest possible meta_bg
>> number.  This kernel bug has been fixed in:
>>
>> 3a4b77c ext4: validate s_first_meta_bg at mount time
>>
>> Signed-off-by: Xiao Yang<yangx.jy@cn.fujitsu.com>
>> ---
>>   tests/ext4/025     | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   tests/ext4/025.out |  4 ++++
>>   tests/ext4/group   |  1 +
>>   3 files changed, 74 insertions(+)
>>   create mode 100755 tests/ext4/025
>>   create mode 100644 tests/ext4/025.out
>>
>> diff --git a/tests/ext4/025 b/tests/ext4/025
>> new file mode 100755
>> index 0000000..085c52f
>> --- /dev/null
>> +++ b/tests/ext4/025
>> @@ -0,0 +1,69 @@
>> +#! /bin/bash
>> +# FS QA Test ext4/025
>> +#
>> +# Regression test for commit:
>> +# 3a4b77c ("ext4: validate s_first_meta_bg at mount time").
>> +#
>> +#-----------------------------------------------------------------------
>> +# Copyright (c) 2017 Fujitsu.  All Rights Reserved.
>> +# Author: Xiao Yang<yangx.jy@cn.fujitsu.com>
>> +#
>> +# 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"
>> +
>> +tmp=/tmp/$$
>> +status=1	# failure is the default!
>> +trap "_cleanup; exit \$status" 0 1 2 3 15
>> +
>> +_cleanup()
>> +{
>> +	rm -f $tmp.*
>> +}
>> +
>> +# get standard environment and checks
>> +. ./common/rc
>> +. ./common/filter
>> +
>> +# remove previous $seqres.full before test
>> +rm -f $seqres.full
>> +
>> +# real QA test starts here
>> +_supported_fs ext4
>> +_supported_os Linux
>> +_require_scratch
>> +_require_scratch_nocheck
> _require_scratch_nocheck is sufficient, don't need _require_scratch
>
Hi Eryu

Agreed. :-)
>> +_require_command "$DEBUGFS_PROG" debugfs
>> +_require_ext4_mkfs_feature "bigalloc,meta_bg,^resize_inode"
>> +
>> +echo "Create ext4 fs and modify first_meta_bg's value"
>> +$MKFS_EXT4_PROG -F -b 4096 -O bigalloc,meta_bg,^resize_inode $SCRATCH_DEV 16m>>  $seqres.full 2>&1 \
>> +	|| _notrun "Could not create ext4 filesystem"
> _scratch_mkfs "-O bigalloc,meta_bg,^resize_inode">>  $seqres.full 2>&1
>
> should be fine, if there're conflicts between MKFS_OPTIONS and these
> extra mkfs options _scratch_mkfs will mkfs again only with test-provided
> mkfs options.
>
I will use _scratch_mkfs as you said.  However, i still specify 4096 as 
block size, because debugfs can't set first_meta_bg
to 842150400 on RHEL7 when default block size is 1024.   Please see the 
following e2fsprogs bug:

commit d36b957b345ee6e4b529be99b8fdc8d3e70ccdc1
Author: Darrick J. Wong <darrick.wong@oracle.com>
Date:   Sat Jan 11 13:58:15 2014 -0500

     libext2fs: don't always read backup group descriptors on a 1k-block 
meta_bg fs
>> +
>> +$DEBUGFS_PROG -w -R "ssv first_meta_bg 842150400" $SCRATCH_DEV>>  $seqres.full 2>&1
>> +
>> +# check whether debugfs succeeds to set first_meta_bg to 842150400 or not
>> +$DEBUGFS_PROG -R "show_super_stats" $SCRATCH_DEV 2>&1 | grep -q "First meta block group:   842150400" \
>> +	|| _notrun "Could not set first_meta_bg to 842150400 successfully, skip test."
>> +
>> +echo "Try to mount a modified ext4 fs"
>> +_scratch_mount>>  $seqres.full 2>&1 || echo "Fail to mount ext4 fs expectedly"
>> +
>> +# success, all done
>> +status=0
>> +exit
>> diff --git a/tests/ext4/025.out b/tests/ext4/025.out
>> new file mode 100644
>> index 0000000..f9a76bb
>> --- /dev/null
>> +++ b/tests/ext4/025.out
>> @@ -0,0 +1,4 @@
>> +QA output created by 025
>> +Create ext4 fs and modify first_meta_bg's value
>> +Try to mount a modified ext4 fs
>> +Fail to mount ext4 fs expectedly
>> diff --git a/tests/ext4/group b/tests/ext4/group
>> index cac5aa5..c42a4d5 100644
>> --- a/tests/ext4/group
>> +++ b/tests/ext4/group
>> @@ -27,6 +27,7 @@
>>   022 auto quick attr dangerous
>>   023 auto quick scrub
>>   024 auto quick encrypt dangerous
>> +025 auto quick dangerous
> Can be in fuzzers group too.
>
I will add it. :-)

Thanks,
Xiao Yang.
> Thanks,
> Eryu
>>   271 auto rw quick
>>   301 aio auto ioctl rw stress defrag
>>   302 aio auto ioctl rw stress defrag
>> -- 
>> 1.8.3.1
>>
>>
>>
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