Re: [PATCH v2] generic: test cloning large exents to a file with many small extents

[Eryu Guan <guaneryu@gmail.com>]

On Fri, Jul 05, 2019 at 11:09:38AM +0100, Filipe Manana wrote:
> On Fri, Jul 5, 2019 at 8:43 AM Eryu Guan <guaneryu@gmail.com> wrote:
> >
> > On Fri, Jun 28, 2019 at 11:08:36PM +0100, fdmanana@kernel.org wrote:
> > > From: Filipe Manana <fdmanana@suse.com>
> > >
> > > Test that if we clone a file with some large extents into a file that has
> > > many small extents, when the fs is nearly full, the clone operation does
> > > not fail and produces the correct result.
> > >
> > > This is motivated by a bug found in btrfs wich is fixed by the following
> > > patches for the linux kernel:
> > >
> > >  [PATCH 1/2] Btrfs: factor out extent dropping code from hole punch handler
> > >  [PATCH 2/2] Btrfs: fix ENOSPC errors, leading to transaction aborts, when
> > >              cloning extents
> > >
> > > The test currently passes on xfs.
> > >
> > > Signed-off-by: Filipe Manana <fdmanana@suse.com>
> > > ---
> > >
> > > V2: Use _scratch_cycle_mount instead of _scratch_remount, as we want to see
> > >     if the operation was durably persisted (otherwise we are seeing content
> > >     from the page cache).
> > >     Use _reflink instead of calling xfs_io with the reflink command.
> > >     Make the comment before filling the filesystem more clear about why it
> > >     is done the way it is instead of using _fill_fs.
> > >
> > >  tests/generic/558     | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++
> > >  tests/generic/558.out |  5 ++++
> > >  tests/generic/group   |  1 +
> > >  3 files changed, 86 insertions(+)
> > >  create mode 100755 tests/generic/558
> > >  create mode 100644 tests/generic/558.out
> > >
> > > diff --git a/tests/generic/558 b/tests/generic/558
> > > new file mode 100755
> > > index 00000000..f982930d
> > > --- /dev/null
> > > +++ b/tests/generic/558
> > > @@ -0,0 +1,80 @@
> > > +#! /bin/bash
> > > +# SPDX-License-Identifier: GPL-2.0
> > > +# Copyright (C) 2019 SUSE Linux Products GmbH. All Rights Reserved.
> > > +#
> > > +# FSQA Test No. 558
> > > +#
> > > +# Test that if we clone a file with some large extents into a file that has
> > > +# many small extents, when the fs is nearly full, the clone operation does
> > > +# not fail and produces the correct result.
> > > +#
> > > +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()
> > > +{
> > > +     cd /
> > > +     rm -f $tmp.*
> > > +}
> > > +
> > > +# get standard environment, filters and checks
> > > +. ./common/rc
> > > +. ./common/filter
> > > +. ./common/reflink
> > > +
> > > +# real QA test starts here
> > > +_supported_fs generic
> > > +_supported_os Linux
> > > +_require_scratch_reflink
> > > +
> > > +rm -f $seqres.full
> > > +
> > > +_scratch_mkfs_sized $((512 * 1024 * 1024)) >>$seqres.full 2>&1
> > > +_scratch_mount
> > > +
> > > +file_size=$(( 128 * 1024 * 1024 )) # 128Mb
> > > +extent_size=4096
> > > +num_extents=$(( $file_size / $extent_size ))
> > > +
> > > +# Create a file with many small extents.
> > > +for ((i = 0; i < $num_extents; i++)); do
> > > +     offset=$(( $i * $extent_size ))
> > > +     $XFS_IO_PROG -f -s -c "pwrite -S 0xe5 $offset $extent_size" \
> > > +             $SCRATCH_MNT/foo >>/dev/null
> > > +done
> >
> > This is taking too long time (1000+s) to finish when testing on XFS.
> 
> Hum, for on 5.2-rc, debug kernel (lockdep, plenty of other debug stuff
> enabled that slows things down), it takes about 350 seconds for me.
> 
> > I'm
> > wondering if we could take use of src/punch-alternating to punch out
> > every other block to create a file with many small extents.
> 
> That's fine, I didn't remember about that.
> 
> >
> > i.e. with the following diffs, test runs & passes with XFS within 90s
> > while still reproduces the btrfs bug (note that I have to increase the
> > file_size to 200M to reproduce the btrfs bug, while 256M seems bring
> > test time back to 1000+s). Would you please check if this works for you?
> 
> It does, thanks!
> And, because of the holes, it uncovered a bug in my fix (second patch).

That's great :)

> 
> Now it takes ~15 seconds on btrfs instead of ~300s and ~100s on xfs for me.

Sounds good!

> 
> >
> > Thanks,
> > Eryu
> >
> >
> > diff --git a/tests/generic/558 b/tests/generic/558
> > index f982930d65a2..40f8a7a98d3f 100755
> > --- a/tests/generic/558
> > +++ b/tests/generic/558
> > @@ -30,22 +30,22 @@ _cleanup()
> >  _supported_fs generic
> >  _supported_os Linux
> >  _require_scratch_reflink
> > +_require_test_program "punch-alternating"
> > +_require_xfs_io_command "fpunch"
> >
> >  rm -f $seqres.full
> >
> >  _scratch_mkfs_sized $((512 * 1024 * 1024)) >>$seqres.full 2>&1
> >  _scratch_mount
> >
> > -file_size=$(( 128 * 1024 * 1024 )) # 128Mb
> > +file_size=$(( 200 * 1024 * 1024 )) # 200MB
> >  extent_size=4096
> >  num_extents=$(( $file_size / $extent_size ))
> 
> These two variables, extent_size and num_extents, are no longer needed.
> 
> Do you want me to send another version of the patch or can you apply
> this patch on top of it?

I can fix the patch on commit. Thanks for the confirmation!

Eryu

> 
> Thanks.
> 
> >
> >  # Create a file with many small extents.
> > -for ((i = 0; i < $num_extents; i++)); do
> > -       offset=$(( $i * $extent_size ))
> > -       $XFS_IO_PROG -f -s -c "pwrite -S 0xe5 $offset $extent_size" \
> > -               $SCRATCH_MNT/foo >>/dev/null
> > -done
> > +$XFS_IO_PROG -f -c "pwrite -S 0xe5 -b $file_size 0 $file_size" \
> > +       $SCRATCH_MNT/foo >>/dev/null
> > +$here/src/punch-alternating $SCRATCH_MNT/foo >> $seqres.full
> >
> >  # Create file bar with the same size that file foo has but with large extents.
> >  $XFS_IO_PROG -f -c "pwrite -S 0xc7 -b $file_size 0 $file_size" \
> > diff --git a/tests/generic/558.out b/tests/generic/558.out
> > index d1e8e70f5b79..00cb5a9744aa 100644
> > --- a/tests/generic/558.out
> > +++ b/tests/generic/558.out
> > @@ -2,4 +2,4 @@ QA output created by 558
> >  File foo data after cloning and remount:
> >  0000000 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7
> >  *
> > -134217728
> > +209715200
> >
> > > +
> > > +# Create file bar with the same size that file foo has but with large extents.
> > > +$XFS_IO_PROG -f -c "pwrite -S 0xc7 -b $file_size 0 $file_size" \
> > > +     $SCRATCH_MNT/bar >>/dev/null
> > > +
> > > +# Fill the fs (For btrfs we are interested in filling all unallocated space
> > > +# and most of the existing metadata block group(s), so that after this there
> > > +# will be no unallocated space and metadata space will be mostly full but with
> > > +# more than enough free space for the clone operation below to succeed, we
> > > +# create files with 2Kb because that results in extents inlined in the metadata
> > > +# (btree leafs) and it's the fastest way to fill metadata space on btrfs, by
> > > +# default btrfs inlines up to 2Kb of data).
> > > +i=1
> > > +while true; do
> > > +     $XFS_IO_PROG -f -c "pwrite 0 2K" $SCRATCH_MNT/filler_$i &> /dev/null
> > > +     [ $? -ne 0 ] && break
> > > +     i=$(( i + 1 ))
> > > +done
> > > +
> > > +# Now clone file bar into file foo. This is supposed to succeed and not fail
> > > +# with ENOSPC for example.
> > > +_reflink $SCRATCH_MNT/bar $SCRATCH_MNT/foo >>$seqres.full
> > > +
> > > +# Unmount and mount the filesystem again to verify the operation was durably
> > > +# persisted.
> > > +_scratch_cycle_mount
> > > +
> > > +echo "File foo data after cloning and remount:"
> > > +od -A d -t x1 $SCRATCH_MNT/foo
> > > +
> > > +status=0
> > > +exit
> > > diff --git a/tests/generic/558.out b/tests/generic/558.out
> > > new file mode 100644
> > > index 00000000..d1e8e70f
> > > --- /dev/null
> > > +++ b/tests/generic/558.out
> > > @@ -0,0 +1,5 @@
> > > +QA output created by 558
> > > +File foo data after cloning and remount:
> > > +0000000 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7 c7
> > > +*
> > > +134217728
> > > diff --git a/tests/generic/group b/tests/generic/group
> > > index 543c0627..c06c1cd1 100644
> > > --- a/tests/generic/group
> > > +++ b/tests/generic/group
> > > @@ -560,3 +560,4 @@
> > >  555 auto quick cap
> > >  556 auto quick casefold
> > >  557 auto quick log
> > > +558 auto clone
> > > --
> > > 2.11.0
> > >