Re: [PATCH] fstests: btrfs: Test fiemap ioctl on completely deduped file

Qu Wenruo
2016-05-12T00:46:41Z

Darrick J. Wong wrote on 2016/05/11 17:23 -0700:
> On Wed, May 11, 2016 at 10:14:42AM +0800, Qu Wenruo wrote:
>>
>>
>> Filipe Manana wrote on 2016/05/10 11:01 +0100:
>>> On Tue, May 10, 2016 at 9:39 AM, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
>>>> For a completely deduped file, which means all its file extent are
>>>> pointing to one bytenr, if calling fiemap on it, btrfs will cause soft
>>>> hang up or just takes years long.
>>>>
>>>> This bug can be reproduced even without any in-band or out-of-band
>>>> dedupe, normal clone_file_range() call can create such situation.
>>>>
>>>> This test case will detect it.
>>>
>>> Why isn't this a generic test?
>>> There's nothing btrfs specific anymore...
>>>
>>> Thanks.
>>
>> I'm OK to move it to generic, just as original planned.
>
> Thank you!
>
>> BTW, does other fs support reflink file range?
>
> As Christoph said, future-XFS and NFS.
>
>> I found a lot xfs test cases using reflink, but I still can't reflink a file
>> range inside the same inode
>> ---
>> $ xfs_io -c "reflink test.file 0 128k 128k" test.file
>> XFS_IOC_CLONE_RANGE: Operation not supported
>
> <shrug> It should work...
>
> ...and currently works for me (4.6-rc7) on both btrfs and xfs:

Oh, I'm using 4.5-rc6, which is current btrfs for-linus branch.

Thanks for your kind info!
I'll try mainline kernel.

>
> # rm -rf a ; dd if=/dev/zero of=a bs=131072 count=1 ; xfs_io -c 'reflink a 0 128k 128k' a ; filefrag -v a ; grep $PWD /proc/mounts
> 1+0 records in
> 1+0 records out
> 131072 bytes (131 kB, 128 KiB) copied, 0.000539818 s, 243 MB/s
> linked 131072/131072 bytes at offset 131072
> 128 KiB, 1 ops; 0.0000 sec (120.077 MiB/sec and 960.6148 ops/sec)
> Filesystem type is: 9123683e
> File size of a is 262144 (64 blocks of 4096 bytes)
> ext: logical_offset: physical_offset: length: expected: flags:
> 0: 0.. 31: 3088.. 3119: 32:
> 1: 32.. 63: 3088.. 3119: 32: 3120: last,eof
> a: 2 extents found
> /dev/sda /mnt btrfs rw,relatime,space_cache,subvolid=5,subvol=/ 0 0
> # cd /opt
> # rm -rf a ; dd if=/dev/zero of=a bs=131072 count=1 ; xfs_io -c 'reflink a 0 128k 128k' a ; filefrag -v a ; grep $PWD /proc/mounts
> 1+0 records in
> 1+0 records out
> 131072 bytes (131 kB, 128 KiB) copied, 0.00237377 s, 55.2 MB/s
> linked 131072/131072 bytes at offset 131072
> 128 KiB, 1 ops; 0.0000 sec (87.047 MiB/sec and 696.3788 ops/sec)
> Filesystem type is: 58465342
> File size of a is 262144 (64 blocks of 4096 bytes)
> ext: logical_offset: physical_offset: length: expected: flags:
> 0: 0.. 31: 24.. 55: 32: shared
> 1: 32.. 63: 24.. 55: 32: 56: last,shared,eof

Also the "shared" flag is different from btrfs, where btrfs is wrong,
and the btrfs routine to check shared extent caused the soft lockup.

I originally planned to check "shared" flag, but the soft lockup is more
important, and 8000+ output seems not suitable as golden output.

Thanks,
Qu

> a: 2 extents found
> /dev/sdb /opt xfs rw,relatime,attr2,inode64,noquota 0 0
>
> That said, I haven't checked with latest xfsprogs master.
>
> --D
>
>> ---
>>
>>>
>>>>
>>>> Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
>>>> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
>>>> ---
>>>> tests/btrfs/028 | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>> tests/btrfs/028.out | 3 +++
>>>> tests/btrfs/group | 1 +
>>>> 3 files changed, 82 insertions(+)
>>>> create mode 100755 tests/btrfs/028
>>>> create mode 100644 tests/btrfs/028.out
>>>>
>>>> diff --git a/tests/btrfs/028 b/tests/btrfs/028
>>>> new file mode 100755
>>>> index 0000000..62bcc9d
>>>> --- /dev/null
>>>> +++ b/tests/btrfs/028
>>>> @@ -0,0 +1,78 @@
>>>> +#! /bin/bash
>>>> +# FS QA Test 028
>>>> +#
>>>> +# Test fiemap ioctl on heavily deduped file.
>>>> +#
>>>> +# This test will cause btrfs to soft hang up or takes years long to finish
>>>
>>> Haven't tried it, but I doubt it will take years...
>>> Are you sure that the soft lookup, which is what makes the test fail
>>> due to the dmesg warning, is triggered on very fast machines as well?
>>> I.e. this may not be reliable on better hardware.
>>
>> On a fast test server too, using the same test case, but your concern is
>> valid.
>>
>> The reporter initially triggered the bug on a even faster server with
>> similar file layout with 100% possibility, but with nr set to 8192.
>>
>> I reduced the nr from 8192 (which is always reproducible) to 4096 to save
>> some time creating file, but considering the scale of loops, considering the
>> loop scale (at least n^3), the halved nr seems to hugely reduce the time.
>>
>> The know loop scale is n^3 ~ n^4:
>> 1. Loop all file extents (* 4096)
>> 2. Loop all backrefs of one extent (* 4096)
>> 3. Loop each backref in __merge_refs(list_for_each_entry_safe_continue) (*
>> 4096)
>> 4. Loop to the list end in "while(eie & eie->next) {eie=eie->next}" (*4096)
>>
>> What about change nr to (8192 * $LOAD_FACTOR)?
>>
>> Thanks,
>> Qu
>>
>>
>> Thanks,
>> Qu
>>
>>>
>>>
>>>> +#
>>>> +#-----------------------------------------------------------------------
>>>> +# 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
>>>> +. ./common/filter
>>>> +. ./common/reflink
>>>> +
>>>> +# remove previous $seqres.full before test
>>>> +rm -f $seqres.full
>>>> +
>>>> +# real QA test starts here
>>>> +
>>>> +# Modify as appropriate.
>>>> +_supported_fs btrfs
>>>> +_supported_os Linux
>>>> +_require_scratch_reflink
>>>> +
>>>> +blocksize=$(( 128 * 1024 ))
>>>> +nr=4096
>>>> +file="$SCRATCH_MNT/tmp"
>>>> +
>>>> +_scratch_mkfs
>>>> +_scratch_mount
>>>> +
>>>> +# write the initial block for later reflink
>>>> +$XFS_IO_PROG -f -c "pwrite 0 $blocksize" -c "fsync" $file | _filter_xfs_io
>>>> +
>>>> +# use reflink to create the rest of the file, whose all extents are all
>>>> +# pointing to the first extent
>>>> +for i in $(seq 1 $nr); do
>>>> + $XFS_IO_PROG -c "reflink $file 0 $(( $i * $blocksize )) $blocksize" \
>>>> + $SCRATCH_MNT/tmp > /dev/null || _fail "reflink failed"
>>>> +done
>>>> +
>>>> +# then call fiemap on that file, which shouldn't hang the fs by all means
>>>> +$XFS_IO_PROG -c "fiemap" $file >> $seqres.full
>>>> +
>>>> +# success, all done
>>>> +status=0
>>>> +exit
>>>> diff --git a/tests/btrfs/028.out b/tests/btrfs/028.out
>>>> new file mode 100644
>>>> index 0000000..2b5a9a5
>>>> --- /dev/null
>>>> +++ b/tests/btrfs/028.out
>>>> @@ -0,0 +1,3 @@
>>>> +QA output created by 028
>>>> +wrote 131072/131072 bytes at offset 0
>>>> +XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>>>> diff --git a/tests/btrfs/group b/tests/btrfs/group
>>>> index da0e27f..8f6f877 100644
>>>> --- a/tests/btrfs/group
>>>> +++ b/tests/btrfs/group
>>>> @@ -30,6 +30,7 @@
>>>> 025 auto quick send clone
>>>> 026 auto quick compress prealloc
>>>> 027 auto replace
>>>> +028 auto clone
>>>> 029 auto quick clone
>>>> 030 auto quick send
>>>> 031 auto quick subvol clone
>>>> --
>>>> 2.5.5
>>>>
>>>>
>>>>
>>>> --
>>>> 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
>>>
>>>
>>>
>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>