fstests: generic test for fsync after fallocate
diff mbox

Message ID 20180408020754.GA2932@desktop
State New
Headers show

Commit Message

Eryu Guan April 8, 2018, 2:07 a.m. UTC
On Thu, Apr 05, 2018 at 10:56:14PM +0100, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> Test that fsync operations preserve extents allocated with fallocate(2)
> that are placed beyond a file's size.
> 
> This test is motivated by a bug found in btrfs where unwritten extents
> beyond the inode's i_size were not preserved after a fsync and power
> failure. The btrfs bug is fixed by the following patch for the linux
> kernel:
> 
>  "Btrfs: fix loss of prealloc extents past i_size after fsync log replay"
> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>

Hmm, xfs fails this test, while ext4 passes.

# diff -u tests/generic/483.out /root/workspace/xfstests/results//xfs_4k_crc/generic/483.out.bad

I'm not sure what the problem is yet, but IMHO controlling on-disk
layout of a file from userspace is hard and should be avoided if
possible.

Why not dumping md5sum to .out file like other dmflakey tests? I've
checked the md5sum of all the three test files, and they're the same on
xfs as on ext4, so the files are not corrupted on xfs.

Thanks,
Eryu

> ---
>  tests/generic/482     | 118 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/482.out |  10 +++++
>  tests/generic/group   |   1 +
>  3 files changed, 129 insertions(+)
>  create mode 100755 tests/generic/482
>  create mode 100644 tests/generic/482.out
> 
> diff --git a/tests/generic/482 b/tests/generic/482
> new file mode 100755
> index 00000000..43bbc913
> --- /dev/null
> +++ b/tests/generic/482
> @@ -0,0 +1,118 @@
> +#! /bin/bash
> +# FSQA Test No. 482
> +#
> +# Test that fsync operations preserve extents allocated with fallocate(2) that
> +# are placed beyond a file's size.
> +#
> +#-----------------------------------------------------------------------
> +#
> +# Copyright (C) 2018 SUSE Linux Products GmbH. All Rights Reserved.
> +# Author: Filipe Manana <fdmanana@suse.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()
> +{
> +	_cleanup_flakey
> +	cd /
> +	rm -f $tmp.*
> +}
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter
> +. ./common/dmflakey
> +. ./common/punch
> +
> +# real QA test starts here
> +_supported_fs generic
> +_supported_os Linux
> +_require_scratch
> +_require_dm_target flakey
> +_require_xfs_io_command "falloc" "-k"
> +_require_xfs_io_command "fiemap"
> +
> +rm -f $seqres.full
> +
> +_scratch_mkfs >>$seqres.full 2>&1
> +_require_metadata_journaling $SCRATCH_DEV
> +_init_flakey
> +_mount_flakey
> +
> +# Create our test files.
> +$XFS_IO_PROG -f -c "pwrite -S 0xea 0 256K" $SCRATCH_MNT/foo >/dev/null
> +
> +# Create a file with many extents. We later want to shrink truncate it and
> +# add a prealloc extent beyond its new size.
> +for ((i = 1; i <= 500; i++)); do
> +	offset=$(((i - 1) * 4 * 1024))
> +	$XFS_IO_PROG -f -s -c "pwrite -S 0xcf $offset 4K" \
> +		$SCRATCH_MNT/bar >/dev/null
> +done
> +
> +# A file which already has a prealloc extent beyond its size.
> +# The fsync done on it is motivated by differences in the btrfs implementation
> +# of fsync (first fsync has different logic from subsequent fsyncs).
> +$XFS_IO_PROG -f -c "pwrite -S 0xf1 0 256K" \
> +	     -c "falloc -k 256K 768K" \
> +	     -c "fsync" \
> +	     $SCRATCH_MNT/baz >/dev/null
> +
> +# Make sure everything done so far is durably persisted.
> +sync
> +
> +# Allocate an extent beyond the size of the first test file and fsync it.
> +$XFS_IO_PROG -c "falloc -k 256K 1M"\
> +	     -c "fsync" \
> +	     $SCRATCH_MNT/foo
> +
> +# Do a shrinking truncate of our test file, add a prealloc extent to it after
> +# its new size and fsync it.
> +$XFS_IO_PROG -c "truncate 256K" \
> +	     -c "falloc -k 256K 1M"\
> +	     -c "fsync" \
> +	     $SCRATCH_MNT/bar
> +
> +# Allocate another extent beyond the size of file baz.
> +$XFS_IO_PROG -c "falloc -k 1M 2M"\
> +	     -c "fsync" \
> +	     $SCRATCH_MNT/baz
> +
> +# Simulate a power failure and mount the filesystem to check that the extents
> +# previously allocated were not lost.
> +_flakey_drop_and_remount
> +
> +echo "File foo fiemap:"
> +$XFS_IO_PROG -c "fiemap -v" $SCRATCH_MNT/foo | _filter_fiemap
> +
> +echo "File bar fiemap:"
> +$XFS_IO_PROG -c "fiemap -v" $SCRATCH_MNT/bar | _filter_fiemap
> +
> +echo "File baz fiemap:"
> +$XFS_IO_PROG -c "fiemap -v" $SCRATCH_MNT/baz | _filter_fiemap
> +
> +_unmount_flakey
> +_cleanup_flakey
> +
> +status=0
> +exit
> diff --git a/tests/generic/482.out b/tests/generic/482.out
> new file mode 100644
> index 00000000..7e3ed139
> --- /dev/null
> +++ b/tests/generic/482.out
> @@ -0,0 +1,10 @@
> +QA output created by 482
> +File foo fiemap:
> +0: [0..511]: data
> +1: [512..2559]: unwritten
> +File bar fiemap:
> +0: [0..511]: data
> +1: [512..2559]: unwritten
> +File baz fiemap:
> +0: [0..511]: data
> +1: [512..6143]: unwritten
> diff --git a/tests/generic/group b/tests/generic/group
> index e8676062..58ac1f00 100644
> --- a/tests/generic/group
> +++ b/tests/generic/group
> @@ -484,3 +484,4 @@
>  479 auto quick metadata
>  480 auto quick metadata
>  481 auto quick log metadata
> +482 auto quick log metadata
> -- 
> 2.11.0
> 
> --
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Comments

Filipe Manana April 8, 2018, 8:53 a.m. UTC | #1
On Sun, Apr 8, 2018 at 3:07 AM, Eryu Guan <guaneryu@gmail.com> wrote:
> On Thu, Apr 05, 2018 at 10:56:14PM +0100, fdmanana@kernel.org wrote:
>> From: Filipe Manana <fdmanana@suse.com>
>>
>> Test that fsync operations preserve extents allocated with fallocate(2)
>> that are placed beyond a file's size.
>>
>> This test is motivated by a bug found in btrfs where unwritten extents
>> beyond the inode's i_size were not preserved after a fsync and power
>> failure. The btrfs bug is fixed by the following patch for the linux
>> kernel:
>>
>>  "Btrfs: fix loss of prealloc extents past i_size after fsync log replay"
>>
>> Signed-off-by: Filipe Manana <fdmanana@suse.com>
>
> Hmm, xfs fails this test, while ext4 passes.
>
> # diff -u tests/generic/483.out /root/workspace/xfstests/results//xfs_4k_crc/generic/483.out.bad
> --- tests/generic/483.out       2018-04-07 23:35:00.555555511 +0800
> +++ /root/workspace/xfstests/results//xfs_4k_crc/generic/483.out.bad    2018-04-07 23:39:48.780659707 +0800
> @@ -6,5 +6,5 @@
>  0: [0..511]: data
>  1: [512..2559]: unwritten
>  File baz fiemap:
> -0: [0..511]: data
> -1: [512..6143]: unwritten
> +0: [0..895]: data
> +1: [896..6143]: unwritten
>
> I'm not sure what the problem is yet, but IMHO controlling on-disk
> layout of a file from userspace is hard and should be avoided if
> possible.

Well, both ext4 and f2fs give the same result, which makes sense, if
userspace has only written to the first 256K of the file, only blocks
0..511 should be reported as written.
However xfs decides to report more than that was written (448K), seems
like a bug to me.
The goal of fallocate(), specifically here, is precisely to create
unwritten extents beyond eof.

>
> Why not dumping md5sum to .out file like other dmflakey tests? I've
> checked the md5sum of all the three test files, and they're the same on
> xfs as on ext4, so the files are not corrupted on xfs.

Nop, that won't work. Because userspace can't read extents beyond eof.
That would make unpatched btrfs succeed the test (or any fs with
similar bug persisting prealloc extents beyond eof).
Without fiemap, how can one check that unwritten extents beyond eof exist?

>
> Thanks,
> Eryu
>
>> ---
>>  tests/generic/482     | 118 ++++++++++++++++++++++++++++++++++++++++++++++++++
>>  tests/generic/482.out |  10 +++++
>>  tests/generic/group   |   1 +
>>  3 files changed, 129 insertions(+)
>>  create mode 100755 tests/generic/482
>>  create mode 100644 tests/generic/482.out
>>
>> diff --git a/tests/generic/482 b/tests/generic/482
>> new file mode 100755
>> index 00000000..43bbc913
>> --- /dev/null
>> +++ b/tests/generic/482
>> @@ -0,0 +1,118 @@
>> +#! /bin/bash
>> +# FSQA Test No. 482
>> +#
>> +# Test that fsync operations preserve extents allocated with fallocate(2) that
>> +# are placed beyond a file's size.
>> +#
>> +#-----------------------------------------------------------------------
>> +#
>> +# Copyright (C) 2018 SUSE Linux Products GmbH. All Rights Reserved.
>> +# Author: Filipe Manana <fdmanana@suse.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()
>> +{
>> +     _cleanup_flakey
>> +     cd /
>> +     rm -f $tmp.*
>> +}
>> +
>> +# get standard environment, filters and checks
>> +. ./common/rc
>> +. ./common/filter
>> +. ./common/dmflakey
>> +. ./common/punch
>> +
>> +# real QA test starts here
>> +_supported_fs generic
>> +_supported_os Linux
>> +_require_scratch
>> +_require_dm_target flakey
>> +_require_xfs_io_command "falloc" "-k"
>> +_require_xfs_io_command "fiemap"
>> +
>> +rm -f $seqres.full
>> +
>> +_scratch_mkfs >>$seqres.full 2>&1
>> +_require_metadata_journaling $SCRATCH_DEV
>> +_init_flakey
>> +_mount_flakey
>> +
>> +# Create our test files.
>> +$XFS_IO_PROG -f -c "pwrite -S 0xea 0 256K" $SCRATCH_MNT/foo >/dev/null
>> +
>> +# Create a file with many extents. We later want to shrink truncate it and
>> +# add a prealloc extent beyond its new size.
>> +for ((i = 1; i <= 500; i++)); do
>> +     offset=$(((i - 1) * 4 * 1024))
>> +     $XFS_IO_PROG -f -s -c "pwrite -S 0xcf $offset 4K" \
>> +             $SCRATCH_MNT/bar >/dev/null
>> +done
>> +
>> +# A file which already has a prealloc extent beyond its size.
>> +# The fsync done on it is motivated by differences in the btrfs implementation
>> +# of fsync (first fsync has different logic from subsequent fsyncs).
>> +$XFS_IO_PROG -f -c "pwrite -S 0xf1 0 256K" \
>> +          -c "falloc -k 256K 768K" \
>> +          -c "fsync" \
>> +          $SCRATCH_MNT/baz >/dev/null
>> +
>> +# Make sure everything done so far is durably persisted.
>> +sync
>> +
>> +# Allocate an extent beyond the size of the first test file and fsync it.
>> +$XFS_IO_PROG -c "falloc -k 256K 1M"\
>> +          -c "fsync" \
>> +          $SCRATCH_MNT/foo
>> +
>> +# Do a shrinking truncate of our test file, add a prealloc extent to it after
>> +# its new size and fsync it.
>> +$XFS_IO_PROG -c "truncate 256K" \
>> +          -c "falloc -k 256K 1M"\
>> +          -c "fsync" \
>> +          $SCRATCH_MNT/bar
>> +
>> +# Allocate another extent beyond the size of file baz.
>> +$XFS_IO_PROG -c "falloc -k 1M 2M"\
>> +          -c "fsync" \
>> +          $SCRATCH_MNT/baz
>> +
>> +# Simulate a power failure and mount the filesystem to check that the extents
>> +# previously allocated were not lost.
>> +_flakey_drop_and_remount
>> +
>> +echo "File foo fiemap:"
>> +$XFS_IO_PROG -c "fiemap -v" $SCRATCH_MNT/foo | _filter_fiemap
>> +
>> +echo "File bar fiemap:"
>> +$XFS_IO_PROG -c "fiemap -v" $SCRATCH_MNT/bar | _filter_fiemap
>> +
>> +echo "File baz fiemap:"
>> +$XFS_IO_PROG -c "fiemap -v" $SCRATCH_MNT/baz | _filter_fiemap
>> +
>> +_unmount_flakey
>> +_cleanup_flakey
>> +
>> +status=0
>> +exit
>> diff --git a/tests/generic/482.out b/tests/generic/482.out
>> new file mode 100644
>> index 00000000..7e3ed139
>> --- /dev/null
>> +++ b/tests/generic/482.out
>> @@ -0,0 +1,10 @@
>> +QA output created by 482
>> +File foo fiemap:
>> +0: [0..511]: data
>> +1: [512..2559]: unwritten
>> +File bar fiemap:
>> +0: [0..511]: data
>> +1: [512..2559]: unwritten
>> +File baz fiemap:
>> +0: [0..511]: data
>> +1: [512..6143]: unwritten
>> diff --git a/tests/generic/group b/tests/generic/group
>> index e8676062..58ac1f00 100644
>> --- a/tests/generic/group
>> +++ b/tests/generic/group
>> @@ -484,3 +484,4 @@
>>  479 auto quick metadata
>>  480 auto quick metadata
>>  481 auto quick log metadata
>> +482 auto quick log metadata
>> --
>> 2.11.0
>>
>> --
>> 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
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Dave Chinner April 9, 2018, 9:51 a.m. UTC | #2
On Sun, Apr 08, 2018 at 10:07:54AM +0800, Eryu Guan wrote:
> On Thu, Apr 05, 2018 at 10:56:14PM +0100, fdmanana@kernel.org wrote:
> > From: Filipe Manana <fdmanana@suse.com>
> > 
> > Test that fsync operations preserve extents allocated with fallocate(2)
> > that are placed beyond a file's size.
> > 
> > This test is motivated by a bug found in btrfs where unwritten extents
> > beyond the inode's i_size were not preserved after a fsync and power
> > failure. The btrfs bug is fixed by the following patch for the linux
> > kernel:
> > 
> >  "Btrfs: fix loss of prealloc extents past i_size after fsync log replay"
> > 
> > Signed-off-by: Filipe Manana <fdmanana@suse.com>
> 
> Hmm, xfs fails this test, while ext4 passes.
> 
> # diff -u tests/generic/483.out /root/workspace/xfstests/results//xfs_4k_crc/generic/483.out.bad
> --- tests/generic/483.out       2018-04-07 23:35:00.555555511 +0800
> +++ /root/workspace/xfstests/results//xfs_4k_crc/generic/483.out.bad    2018-04-07 23:39:48.780659707 +0800
> @@ -6,5 +6,5 @@
>  0: [0..511]: data
>  1: [512..2559]: unwritten
>  File baz fiemap:
> -0: [0..511]: data
> -1: [512..6143]: unwritten
> +0: [0..895]: data
> +1: [896..6143]: unwritten

Perfectly valid result from the test.

> > +# A file which already has a prealloc extent beyond its size.
> > +# The fsync done on it is motivated by differences in the btrfs implementation
> > +# of fsync (first fsync has different logic from subsequent fsyncs).
> > +$XFS_IO_PROG -f -c "pwrite -S 0xf1 0 256K" \
> > +	     -c "falloc -k 256K 768K" \
> > +	     -c "fsync" \
> > +	     $SCRATCH_MNT/baz >/dev/null

Delayed allocation extending the file to 256k means we'll have
speculative prealloc of data beyond 256k - it should be somewhere
around 448k IIRC.

Now, falloc doesn't guarantee unwritten extents are allocated - it
just guarantees space is allocated. unwritten extents are an
optimisation to avoid needing to zero the extents pre-allocated
within EOF. i.e. we can quite safely allocate data extents beyond
EOF rather than unwritten extents, and this is not a bug.

In this case, the delalloc extent is completely allocated as written
data, but nothing is written beyond EOF @ 256k.  Hence it reports as
a data extent, not an unwritten extent, and this is a perfectly
valid thing to do.

> > +# Allocate another extent beyond the size of file baz.
> > +$XFS_IO_PROG -c "falloc -k 1M 2M"\
> > +	     -c "fsync" \
> > +	     $SCRATCH_MNT/baz

You also cannot assume that two separate preallocations beyond EOF
are going to be contiguous (i.e. it could be two separate extents.

What you should just be checking is that there are extents allocated
covering EOF to 3MB, not the exactly size, shape and type of extents
are allocated.

Cheers,

Dave.
Filipe Manana April 9, 2018, 10 a.m. UTC | #3
On Mon, Apr 9, 2018 at 10:51 AM, Dave Chinner <david@fromorbit.com> wrote:
> On Sun, Apr 08, 2018 at 10:07:54AM +0800, Eryu Guan wrote:
>> On Thu, Apr 05, 2018 at 10:56:14PM +0100, fdmanana@kernel.org wrote:
>> > From: Filipe Manana <fdmanana@suse.com>
>> >
>> > Test that fsync operations preserve extents allocated with fallocate(2)
>> > that are placed beyond a file's size.
>> >
>> > This test is motivated by a bug found in btrfs where unwritten extents
>> > beyond the inode's i_size were not preserved after a fsync and power
>> > failure. The btrfs bug is fixed by the following patch for the linux
>> > kernel:
>> >
>> >  "Btrfs: fix loss of prealloc extents past i_size after fsync log replay"
>> >
>> > Signed-off-by: Filipe Manana <fdmanana@suse.com>
>>
>> Hmm, xfs fails this test, while ext4 passes.
>>
>> # diff -u tests/generic/483.out /root/workspace/xfstests/results//xfs_4k_crc/generic/483.out.bad
>> --- tests/generic/483.out       2018-04-07 23:35:00.555555511 +0800
>> +++ /root/workspace/xfstests/results//xfs_4k_crc/generic/483.out.bad    2018-04-07 23:39:48.780659707 +0800
>> @@ -6,5 +6,5 @@
>>  0: [0..511]: data
>>  1: [512..2559]: unwritten
>>  File baz fiemap:
>> -0: [0..511]: data
>> -1: [512..6143]: unwritten
>> +0: [0..895]: data
>> +1: [896..6143]: unwritten
>
> Perfectly valid result from the test.

Still very surprising without knowing specifics about xfs (as you
describe below).

>
>> > +# A file which already has a prealloc extent beyond its size.
>> > +# The fsync done on it is motivated by differences in the btrfs implementation
>> > +# of fsync (first fsync has different logic from subsequent fsyncs).
>> > +$XFS_IO_PROG -f -c "pwrite -S 0xf1 0 256K" \
>> > +        -c "falloc -k 256K 768K" \
>> > +        -c "fsync" \
>> > +        $SCRATCH_MNT/baz >/dev/null
>
> Delayed allocation extending the file to 256k means we'll have
> speculative prealloc of data beyond 256k - it should be somewhere
> around 448k IIRC.
>
> Now, falloc doesn't guarantee unwritten extents are allocated - it
> just guarantees space is allocated. unwritten extents are an
> optimisation to avoid needing to zero the extents pre-allocated
> within EOF. i.e. we can quite safely allocate data extents beyond
> EOF rather than unwritten extents, and this is not a bug.
>
> In this case, the delalloc extent is completely allocated as written
> data, but nothing is written beyond EOF @ 256k.  Hence it reports as
> a data extent, not an unwritten extent, and this is a perfectly
> valid thing to do.
>
>> > +# Allocate another extent beyond the size of file baz.
>> > +$XFS_IO_PROG -c "falloc -k 1M 2M"\
>> > +        -c "fsync" \
>> > +        $SCRATCH_MNT/baz
>
> You also cannot assume that two separate preallocations beyond EOF
> are going to be contiguous (i.e. it could be two separate extents.

I really don't care about that.
Just want to check that allocated space is not lost, don't care if
that space is covered by 1, 2 or more extents, or whether they are
contiguous or not.
>
> What you should just be checking is that there are extents allocated
> covering EOF to 3MB, not the exactly size, shape and type of extents
> are allocated.

How to do such check, for a generic test, without using fiemap?

thanks

>
> Cheers,
>
> Dave.
> --
> Dave Chinner
> david@fromorbit.com
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Dave Chinner April 9, 2018, 10:32 a.m. UTC | #4
On Mon, Apr 09, 2018 at 11:00:52AM +0100, Filipe Manana wrote:
> On Mon, Apr 9, 2018 at 10:51 AM, Dave Chinner <david@fromorbit.com> wrote:
> > On Sun, Apr 08, 2018 at 10:07:54AM +0800, Eryu Guan wrote:
> >> On Thu, Apr 05, 2018 at 10:56:14PM +0100, fdmanana@kernel.org wrote:
> > You also cannot assume that two separate preallocations beyond EOF
> > are going to be contiguous (i.e. it could be two separate extents.
> 
> I really don't care about that.
> Just want to check that allocated space is not lost, don't care if
> that space is covered by 1, 2 or more extents, or whether they are
> contiguous or not.

Sure, but that's not what the test does :/

> > What you should just be checking is that there are extents allocated
> > covering EOF to 3MB, not the exactly size, shape and type of extents
> > are allocated.
> 
> How to do such check, for a generic test, without using fiemap?

We already do such checks using fiemap, yes?

i.e. there's a bunch of _filter*fiemap() functions in common/punch
which should show you exactly how to do this i.e. filter all the
unwritten/data extents to be the same name, then they coalesce into
single ranges....

Cheers,

Dave.

Patch
diff mbox

--- tests/generic/483.out       2018-04-07 23:35:00.555555511 +0800
+++ /root/workspace/xfstests/results//xfs_4k_crc/generic/483.out.bad    2018-04-07 23:39:48.780659707 +0800
@@ -6,5 +6,5 @@ 
 0: [0..511]: data
 1: [512..2559]: unwritten
 File baz fiemap:
-0: [0..511]: data
-1: [512..6143]: unwritten
+0: [0..895]: data
+1: [896..6143]: unwritten