Re: [PATCH] fstests: generic: Check if cycle mount and sleep can affect fiemap result

Qu Wenruo
2017-04-05T02:42:45Z

At 04/05/2017 10:35 AM, Eryu Guan wrote:
> On Mon, Apr 03, 2017 at 03:09:23PM +0800, Qu Wenruo wrote:
>> As long as we don't modify the on-disk data, fiemap result should always
>> be constant.
>>
>> Operation like cycle mount and sleep should not affect fiemap result.
>> While unfortunately, btrfs doesn't follow that behavior.
>>
>> Btrfs fiemap sometimes return merged result, while after cycle mount, it
>> returns split result. Furthermore after a snap, btrfs returns merged
>> result again.
>>
>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
>
> Test fails with ext3/2 when driving with ext4 driver, fiemap changed
> after umount/mount cycle, then changed back to original result after
> sleeping some time. An ext4 bug? (cc'ed linux-ext4 list.)

It's good to know this test case can already detect hidden bug of other fs.

>
> === Fiemap after dsync write and sleep ===
> /vda6/file:
> EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
> 0: [0..127]: 12288..12415 128 0x1000
> 1: [128..255]: 12160..12287 128 0x1000
> 2: [256..511]: 16384..16639 256 0x1000
> 3: [512..2047]: 16896..18431 1536 0x1000
> 4: [2048..4095]: 19456..21503 2048 0x1001
> === Fiemap after cycle mount ===
> /vda6/file:
> EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
> 0: [0..95]: 12288..12383 96 0x1000
> 1: [96..127]: 12384..12415 32 0x1000
>
> [0-127] was split to two extents
>
> 2: [128..255]: 12160..12287 128 0x1000
> 3: [256..511]: 16384..16639 256 0x1000
> 4: [512..2047]: 16896..18431 1536 0x1000
> 5: [2048..4095]: 19456..21503 2048 0x1001
> === Fiemap after cycle mount and sleep ===
> /vda6/file:
> EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
> 0: [0..127]: 12288..12415 128 0x1000
> 1: [128..255]: 12160..12287 128 0x1000
> 2: [256..511]: 16384..16639 256 0x1000
> 3: [512..2047]: 16896..18431 1536 0x1000
> 4: [2048..4095]: 19456..21503 2048 0x1001
>
>> ---
>> tests/generic/422 | 127 ++++++++++++++++++++++++++++++++++++++++++++++++++
>> tests/generic/422.out | 2 +
>> tests/generic/group | 1 +
>> 3 files changed, 130 insertions(+)
>> create mode 100755 tests/generic/422
>> create mode 100644 tests/generic/422.out
>>
>> diff --git a/tests/generic/422 b/tests/generic/422
>> new file mode 100755
>> index 0000000..4ca4476
>> --- /dev/null
>> +++ b/tests/generic/422
>> @@ -0,0 +1,127 @@
>> +#! /bin/bash
>> +# FS QA Test 422
>> +#
>> +# Test if a file system returns constant fiemap result after remount and
>> +# fiemap.
>> +# Unfortunately, btrfs doesn't follow this behavior.
>> +#
>> +#-----------------------------------------------------------------------
>> +# Copyright (c) 2017 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
>> +. ./common/filter
>> +
>> +# remove previous $seqres.full before test
>> +rm -f $seqres.full
>> +
>> +# real QA test starts here
>> +
>> +# Modify as appropriate.
>> +_supported_fs generic
>> +_supported_os IRIX Linux
>> +_require_scratch
>
> Need _require_fiemap
>
>> +
>> +block_size=$((64 * 1024))
>> +block_count=32
>> +dst=$SCRATCH_MNT/file
>> +sleeptime=3
>> +
>> +# It's almost 100% for btrfs to trigger inconstant fiemap result
>
> Trailing whitespace in above line.
>
>> +# just in case
>> +runtime=$((2 * $LOAD_FACTOR))
>
> I don't think this loop is necessary, as the comments state, it's almost
> 100% reproducible for btrfs (and for ext2/3 in my testing).

In fact, the uncertainty lies in the time of sleep.

In my test environment, if only sleeps for 1 second, the fiemap result
won't change for btrfs. (although cycle mount still changes the fiemap
result)

So it's better to keep the runtime (will be renamed to loop_counts in
next version), just as stated, in case.

>
>> +
>> +# record fiemap as checkpoint, and output the hash of fiemap result
>> +# to stdout
>> +fiemap_checkpoint()
>> +{
>> + local number=$1
>> + local message=$2
>> +
>> + echo "=== $message ===" >> $seqres.full
>> + $XFS_IO_PROG -c "fiemap -v" $dst > ${tmp}.cp$number
>> + cat ${tmp}.cp${number} >> $seqres.full
>> +
>> + md5sum ${tmp}.cp${number} | cut -d ' ' -f 1
>> +}
>> +
>> +do_test()
>> +{
>> + local number=$1
>> +
>> + # Use 16 times of file size to ensure we have enough space
>> + _scratch_mkfs_sized $((16 * $block_size * $block_count)) \
>
> Use _require_fs_space for required space. Not all filesystems have
> _scratch_mkfs_sized support so this could potentially reduce the
> filesystem coverage.

As most tester won't use a disk smaller than 32M as SCRATCH_DEV, I'm OK
to remove it.

Thanks,
Qu
>
>> + > /dev/null 2>&1
>> + _scratch_mount
>
> Trailing whitespace issue.
>
> Thanks,
> Eryu
>
>> +
>> + echo "====== Loop $number ======" >> $seqres.full
>> + touch $dst
>> + # Xfsprogs 4.9.0 still has a bug that xfs_io "open" with O_SYNC command
>> + # doesn't work well with "pwrite", although it gets fixed in v4.10.0,
>> + # use dd here to avoid it won't hurt for non-xfs developers
>> + dd if=/dev/zero of=$dst bs=$block_size count=$block_count oflag=dsync \
>> + status=none 2>&1
>> +
>> + hash1=$(fiemap_checkpoint 1 "Fiemap just after dsync write")
>> +
>> + # Sleep should not modify fiemap result
>> + sleep $sleeptime
>> +
>> + hash2=$(fiemap_checkpoint 2 "Fiemap after dsync write and sleep")
>> +
>> + # cycle mount should not modify fiemap result
>> + _scratch_cycle_mount
>> +
>> + hash3=$(fiemap_checkpoint 3 "Fiemap after cycle mount")
>> +
>> + # Sleep should not modify fiemap result
>> + sleep $sleeptime
>> +
>> + hash4=$(fiemap_checkpoint 4 "Fiemap after cycle mount and sleep")
>> +
>> + _scratch_unmount
>> +
>> + if [ $hash1 != $hash2 -o $hash2 != $hash3 -o $hash3 != $hash4 ]; then
>> + echo "Inconstant fiemap result detected"
>> + fi
>> + echo >> $seqres.full
>> +}
>> +
>> +for i in $(seq 1 $runtime); do
>> + do_test $i
>> +done
>> +
>> +echo "Silence is golden"
>> +# success, all done
>> +status=0
>> +exit
>> diff --git a/tests/generic/422.out b/tests/generic/422.out
>> new file mode 100644
>> index 0000000..f70693f
>> --- /dev/null
>> +++ b/tests/generic/422.out
>> @@ -0,0 +1,2 @@
>> +QA output created by 422
>> +Silence is golden
>> diff --git a/tests/generic/group b/tests/generic/group
>> index 3c7c5e4..86d2325 100644
>> --- a/tests/generic/group
>> +++ b/tests/generic/group
>> @@ -424,3 +424,4 @@
>> 419 auto quick encrypt
>> 420 auto quick punch
>> 421 auto quick encrypt dangerous
>> +422 auto
>> --
>> 2.9.3
>>
>>
>>
>> --
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>
>