Re: [PATCH v2] generic/391: check inode metadata on f{data}sync after power-cut

[Jaegeuk Kim <jaegeuk@kernel.org>]

On Fri, Nov 18, 2016 at 07:42:17PM -0500, Brian Foster wrote:
> On Fri, Nov 18, 2016 at 11:44:42AM -0800, Jaegeuk Kim wrote:
> > On Fri, Nov 18, 2016 at 02:39:43PM +0800, Eryu Guan wrote:
> > > On Thu, Nov 17, 2016 at 11:20:51AM -0800, Jaegeuk Kim wrote:
> > > > This patch adds tests/generic/391 to test fsync and fdatasync with power-cuts.
> > > > 
> > > > The rule to check is:
> > > > 1) fsync should guarantee all the inode metadata after power-cut,
> > > > 2) fdatasync should guarantee i_size and i_blocks at least after power-cut.
> > > > 
> > > > Suggested-by: Chao Yu <yuchao0@huawei.com>
> > > > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > > > ---
> > > >  tests/generic/391     | 136 ++++++++++++++++++++++++++++++++++++++++++++++++++
> > > >  tests/generic/391.out |  11 ++++
> > > >  tests/generic/group   |   1 +
> > > >  3 files changed, 148 insertions(+)
> > > >  create mode 100644 tests/generic/391
> > > >  create mode 100644 tests/generic/391.out
> > > > 
> > > > diff --git a/tests/generic/391 b/tests/generic/391
> > > > new file mode 100644
> > > > index 0000000..2b95151
> > > > --- /dev/null
> > > > +++ b/tests/generic/391
> > > > @@ -0,0 +1,136 @@
> > > > +#! /bin/bash
> > > > +# FS QA Test 391
> > > > +#
> > > > +# Test inode's metadata after fsync or fdatasync calls.
> > > > +# In the case of fsync, filesystem should recover all the inode metadata, while
> > > > +# recovering i_blocks and i_size at least for fdatasync.
> > > > +#
> > > > +#-----------------------------------------------------------------------
> > > > +# Copyright (c) 2016 Jaegeuk Kim.  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/punch
> > > > +
> > > > +# real QA test starts here
> > > > +_supported_fs generic
> > > > +_supported_os Linux
> > > > +
> > > > +rm -f $seqres.full
> > > > +_require_scratch
> > > > +_require_scratch_shutdown
> > > > +_require_xfs_io_command "fpunch"
> > > > +
> > > > +_scratch_mkfs >/dev/null 2>&1
> > > > +_scratch_mount
> > > > +
> > > > +testfile=$SCRATCH_MNT/testfile
> > > > +
> > > > +# check inode metadata after shutdown
> > > > +check_inode_metadata()
> > > > +{
> > > > +	$XFS_IO_PROG -r -c "stat -v" $1 >$tmp.before
> > > > +	src/godown $SCRATCH_MNT >> $seqres.full
> > > > +	_scratch_cycle_mount
> > > > +	$XFS_IO_PROG -r -c "stat -v" $1 >$tmp.after
> > > > +
> > > > +	if [ $FSTYP = xfs ]; then
> > > > +		sed -i '/stat.blocks/d' $tmp.before
> > > > +		sed -i '/stat.blocks/d' $tmp.after
> > > > +	fi
> > > 
> > > Blacklist some fs "randomly" seems not easy to maintain, at least we
> > > need some comments to explain why we do this.
> > > 
> > > I prefer the other way Brian suggested, i.e. truncate the file to
> > > correct size before the real fsync/fdatasync to remove any preallocated
> > > blocks past eof. I made the following update and test passed on XFS
> > > without problems, what do you think?
> > 
> > I don't think that is a right way, since it breaks the existing IO behavior.
> > I tested a little bit, and it seems the key is to call fclose to truncate
> > out-of-eof blocks. Indeed, I could get the expected i_blocks by adding open and
> > close after shutdown->remount; please check v3.
> > 
> 
> I'm not sure what you mean by truncate breaking existing behavior. FWIW,

What I mean is this testcase was intended to check inode's metadata, and
if we do truncate the file before fsync, I believe that would become just
another testcase, when treating filesystem as a black box.

> you can probably get similar behavior by issuing the fsync in a
> subsequent xfs_io call rather than adding the '-c fsync' to the same
> xfs_io call that issues the write. This is because in most cases XFS
> cleans up such preallocation on file close. Do note however that if a
> file is repeatedly open-write-closed, the preallocation can stick around
> longer.

Oh, right. Indeed, that is a better choice which makes sence to me. Also, I put
$testfile deletion in each iteration.

> > BTW, does it make sense user needs to do fclose after power-cut to reclaim such
> > the preallocated blocks? I feel that XFS must reclaim them during recovery on
> > mount.
> > 
> 
> I'm not sure there's much we can do about this, particularly since XFS
> uses physical style logging and thus it's not straightforward to tell
> when log recovery is extending the bmap of a file beyond i_size. Even
> then, there are cases where we can't free post-eof blocks even if we
> know they exist, such as when an inode has explicit (fallocate)
> preallocation.

Okay, I see. Thank you for the explanation.

Thanks,

> 
> Brian
> 
> > Thanks,
> > 
> > > 
> > > --- a/tests/generic/391
> > > +++ b/tests/generic/391
> > > @@ -65,10 +65,6 @@ check_inode_metadata()
> > >         _scratch_cycle_mount
> > >         $XFS_IO_PROG -r -c "stat -v" $1 >$tmp.after
> > >  
> > > -       if [ $FSTYP = xfs ]; then
> > > -               sed -i '/stat.blocks/d' $tmp.before
> > > -               sed -i '/stat.blocks/d' $tmp.after
> > > -       fi
> > >         diff $tmp.before $tmp.after >$tmp.diff
> > >  
> > >         if [ "$2" = "fdatasync" ]; then
> > > @@ -82,13 +78,19 @@ check_inode_metadata()
> > >  }
> > >  
> > >  # append XX KB with f{data}sync, followed by power-cut
> > > +# truncate file to the current size to avoid post-eof preallocated
> > > +# blocks on XFS
> > >  test_i_size()
> > >  {
> > > +       local len=$2
> > > +       local base_len=$((4 * 1024 * 1024))
> > > +       local new_len=$((base_len + len))
> > >         echo "==== i_size $2 test with $1 ====" | tee -a $seqres.full
> > > -       $XFS_IO_PROG -f -c "pwrite 0 4M"        \
> > > -                       -c "fsync"              \
> > > -                       -c "pwrite 4M $2"       \
> > > -                       -c "$1"                 \
> > > +       $XFS_IO_PROG -f -c "pwrite 0 $base_len"         \
> > > +                       -c "fsync"                      \
> > > +                       -c "pwrite $base_len $len"      \
> > > +                       -c "truncate $new_len"          \
> > > +                       -c "$1"                         \
> > >                         $testfile >/dev/null
> > >         check_inode_metadata $testfile $1
> > >  }
> > > @@ -108,12 +110,15 @@ test_i_time()
> > >  }
> > >  
> > >  # punch XX KB with f{data}sync, followed by power-cut
> > > +# truncate file to the current size to avoid post-eof preallocated
> > > +# blocks on XFS
> > >  test_punch()
> > >  {
> > >         echo "==== fpunch $2 test with $1 ====" | tee -a $seqres.full
> > >         $XFS_IO_PROG -f -c "pwrite 0 4202496"   \
> > >                         -c "fsync"              \
> > > -                       -c "fpunch 4194304 $2"\
> > > +                       -c "fpunch 4194304 $2"  \
> > > +                       -c "truncate 4202496"   \
> > >                         -c "$1"                 \
> > >                         $testfile >/dev/null
> > >  
> > > Thanks,
> > > Eryu
> > --
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