Re: [PATCH] xfs: new EOF fragmentation tests

Darrick J. Wong
2024-10-02T14:57:16Z

On Wed, Oct 02, 2024 at 10:35:55AM -0400, Brian Foster wrote:
> On Wed, Oct 02, 2024 at 09:38:00PM +0800, Zorro Lang wrote:
> > On Tue, Oct 01, 2024 at 07:59:44AM -0700, Darrick J. Wong wrote:
> > > On Tue, Sep 24, 2024 at 10:45:48AM +0200, Christoph Hellwig wrote:
> > > > From: Dave Chinner <dchinner@redhat.com>
> > > >
> > > > These tests create substantial file fragmentation as a result of
> > > > application actions that defeat post-EOF preallocation
> > > > optimisations. They are intended to replicate known vectors for
> > > > these problems, and provide a check that the fragmentation levels
> > > > have been controlled. The mitigations we make may not completely
> > > > remove fragmentation (e.g. they may demonstrate speculative delalloc
> > > > related extent size growth) so the checks don't assume we'll end up
> > > > with perfect layouts and hence check for an exceptable level of
> > > > fragmentation rather than none.
> > > >
> > > > Signed-off-by: Dave Chinner <dchinner@redhat.com>
> > > > [move to different test number, update to current xfstest APIs]
> > > > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > > > ---
> > > > tests/xfs/1500 | 66 +++++++++++++++++++++++++++++++++++++++
> > > > tests/xfs/1500.out | 9 ++++++
> > > > tests/xfs/1501 | 68 ++++++++++++++++++++++++++++++++++++++++
> > > > tests/xfs/1501.out | 9 ++++++
> > > > tests/xfs/1502 | 68 ++++++++++++++++++++++++++++++++++++++++
> > > > tests/xfs/1502.out | 9 ++++++
> > > > tests/xfs/1503 | 77 ++++++++++++++++++++++++++++++++++++++++++++++
> > > > tests/xfs/1503.out | 33 ++++++++++++++++++++
> > > > 8 files changed, 339 insertions(+)
> > > > create mode 100755 tests/xfs/1500
> > > > create mode 100644 tests/xfs/1500.out
> > > > create mode 100755 tests/xfs/1501
> > > > create mode 100644 tests/xfs/1501.out
> > > > create mode 100755 tests/xfs/1502
> > > > create mode 100644 tests/xfs/1502.out
> > > > create mode 100755 tests/xfs/1503
> > > > create mode 100644 tests/xfs/1503.out
> > > >
> > > > diff --git a/tests/xfs/1500 b/tests/xfs/1500
> > > > new file mode 100755
> > > > index 000000000..de0e1df62
> > > > --- /dev/null
> > > > +++ b/tests/xfs/1500
> > > > @@ -0,0 +1,66 @@
> > > > +#! /bin/bash
> > > > +# SPDX-License-Identifier: GPL-2.0
> > > > +# Copyright (c) 2019 Red Hat, Inc. All Rights Reserved.
> > > > +#
> > > > +# FS QA Test xfs/500
> > > > +#
> > > > +# Post-EOF preallocation defeat test for O_SYNC buffered I/O.
> > > > +#
> > > > +
> > > > +. ./common/preamble
> > > > +_begin_fstest auto quick prealloc rw
> > > > +
> > > > +. ./common/rc
> > > > +. ./common/filter
> > > > +
> > > > +_require_scratch
> > > > +
> > > > +_cleanup()
> > > > +{
> > > > + # try to kill all background processes
> > > > + wait
> > > > + cd /
> > > > + rm -r -f $tmp.*
> > > > +}
> > > > +
> > > > +_scratch_mkfs > "$seqres.full" 2>&1
> > > > +_scratch_mount
> > > > +
> > > > +# Write multiple files in parallel using synchronous buffered writes. Aim is to
> > > > +# interleave allocations to fragment the files. Synchronous writes defeat the
> > > > +# open/write/close heuristics in xfs_file_release() that prevent EOF block
> > > > +# removal, so this should fragment badly. Typical problematic behaviour shows
> > > > +# per-file extent counts of >900 (almost worse case) whilst fixed behaviour
> > > > +# typically shows extent counts in the low 20s.
> > >
> > > Now that these are in for-next, I've noticed that these new tests
> > > consistently fail in the above-documented manner on various configs --
> > > fsdax, always_cow, rtextsize > 1fsb, and sometimes 1k fsblock size.
> > >
> > > I'm not sure why this happens, but it probably needs to be looked at
> > > along with all the FALLOC_FL_UNSHARE_RANGE brokenness that's also been
> > > exposed by fstests that /does/ need to be fixed.
> >
> > Yes, some fsx tests fail on xfs, after the FALLOC_FL_UNSHARE_RANGE supporting.
> > e.g. g/091, g/127, g/263, g/363 and g/616. I thought they're known issues as
> > you known. If they're not, better to check. Hi Brian, are these failures as you
> > known?
> >
>
> So I'm aware of two fundamental issues that fsx unshare range support
> uncovers. First is the XFS data loss issue that is addressed here[1],
> second is the iomap unshare range warning/error splat that Julian Sun
> has been working on (last version posted here[2] I believe).
>
> My initial testing of the fsx unshare range patch was to run fsx
> directly on the fs until I could run for some notable number of
> operations without triggering a failure (probably at least 1m+, but I
> don't recall exactly). I was initially able to do that with the patches
> from [1] plus a local hack to trim to i_size in iomap_unshare_range(),
> so based on that I _think_ these are the only two outstanding issues
> with unshare range.
>
> [1] https://lore.kernel.org/linux-xfs/20240906114051.120743-1-bfoster@redhat.com/
> [2] https://lore.kernel.org/linux-fsdevel/20240927065344.2628691-1-sunjunchao2870@gmail.com/
>
> The patches at [1] have been reviewed, but I'm not really sure where
> they stand in terms of the XFS pipeline. Carlos?
>
> It looks like the fix associated with [2] is still under
> development/review. In any event, I just ran the set of tests noted by
> Zorro above (w/ unshare range support) and they all fail on my distro
> kernel, but all but generic/363 pass on current master (6.12.0-rc1+)
> plus [1]. The generic/363 failure produces the iomap error associated
> with [2], so I suspect that all of these test failures can be
> categorized into one of those two known issues.

Yep. [1] fixes a lot of the splats, and the rest of the splats can be
fixed by a couple of other patches that I'll send out today.

Those same fsx tests above are still broken on fsdax though, so
something is still wrong. :(

--D

> Brian
>
> > Thanks,
> > Zorro
> >
> > >
> > > --D
> > >
> > > > +# Failure is determined by golden output mismatch from _within_tolerance().
> > > > +
> > > > +workfile=$SCRATCH_MNT/file
> > > > +nfiles=8
> > > > +wsize=4096
> > > > +wcnt=1000
> > > > +
> > > > +write_sync_file()
> > > > +{
> > > > + idx=$1
> > > > +
> > > > + for ((cnt=0; cnt<$wcnt; cnt++)); do
> > > > + $XFS_IO_PROG -f -s -c "pwrite $((cnt * wsize)) $wsize" $workfile.$idx
> > > > + done
> > > > +}
> > > > +
> > > > +rm -f $workfile*
> > > > +for ((n=0; n<$nfiles; n++)); do
> > > > + write_sync_file $n > /dev/null 2>&1 &
> > > > +done
> > > > +wait
> > > > +sync
> > > > +
> > > > +for ((n=0; n<$nfiles; n++)); do
> > > > + count=$(_count_extents $workfile.$n)
> > > > + # Acceptible extent count range is 1-40
> > > > + _within_tolerance "file.$n extent count" $count 21 19 -v
> > > > +done
> > > > +
> > > > +status=0
> > > > +exit
> > > > diff --git a/tests/xfs/1500.out b/tests/xfs/1500.out
> > > > new file mode 100644
> > > > index 000000000..414df87ed
> > > > --- /dev/null
> > > > +++ b/tests/xfs/1500.out
> > > > @@ -0,0 +1,9 @@
> > > > +QA output created by 1500
> > > > +file.0 extent count is in range
> > > > +file.1 extent count is in range
> > > > +file.2 extent count is in range
> > > > +file.3 extent count is in range
> > > > +file.4 extent count is in range
> > > > +file.5 extent count is in range
> > > > +file.6 extent count is in range
> > > > +file.7 extent count is in range
> > > > diff --git a/tests/xfs/1501 b/tests/xfs/1501
> > > > new file mode 100755
> > > > index 000000000..cf3cbf8b5
> > > > --- /dev/null
> > > > +++ b/tests/xfs/1501
> > > > @@ -0,0 +1,68 @@
> > > > +#! /bin/bash
> > > > +# SPDX-License-Identifier: GPL-2.0
> > > > +# Copyright (c) 2019 Red Hat, Inc. All Rights Reserved.
> > > > +#
> > > > +# FS QA Test xfs/501
> > > > +#
> > > > +# Post-EOF preallocation defeat test for buffered I/O with extent size hints.
> > > > +#
> > > > +
> > > > +. ./common/preamble
> > > > +_begin_fstest auto quick prealloc rw
> > > > +
> > > > +. ./common/rc
> > > > +. ./common/filter
> > > > +
> > > > +_require_scratch
> > > > +
> > > > +_cleanup()
> > > > +{
> > > > + # try to kill all background processes
> > > > + wait
> > > > + cd /
> > > > + rm -r -f $tmp.*
> > > > +}
> > > > +
> > > > +_scratch_mkfs > "$seqres.full" 2>&1
> > > > +_scratch_mount
> > > > +
> > > > +# Write multiple files in parallel using buffered writes with extent size hints.
> > > > +# Aim is to interleave allocations to fragment the files. Writes w/ extent size
> > > > +# hints set defeat the open/write/close heuristics in xfs_file_release() that
> > > > +# prevent EOF block removal, so this should fragment badly. Typical problematic
> > > > +# behaviour shows per-file extent counts of 1000 (worst case!) whilst
> > > > +# fixed behaviour should show very few extents (almost best case).
> > > > +#
> > > > +# Failure is determined by golden output mismatch from _within_tolerance().
> > > > +
> > > > +workfile=$SCRATCH_MNT/file
> > > > +nfiles=8
> > > > +wsize=4096
> > > > +wcnt=1000
> > > > +extent_size=16m
> > > > +
> > > > +write_extsz_file()
> > > > +{
> > > > + idx=$1
> > > > +
> > > > + $XFS_IO_PROG -f -c "extsize $extent_size" $workfile.$idx
> > > > + for ((cnt=0; cnt<$wcnt; cnt++)); do
> > > > + $XFS_IO_PROG -f -c "pwrite $((cnt * wsize)) $wsize" $workfile.$idx
> > > > + done
> > > > +}
> > > > +
> > > > +rm -f $workfile*
> > > > +for ((n=0; n<$nfiles; n++)); do
> > > > + write_extsz_file $n > /dev/null 2>&1 &
> > > > +done
> > > > +wait
> > > > +sync
> > > > +
> > > > +for ((n=0; n<$nfiles; n++)); do
> > > > + count=$(_count_extents $workfile.$n)
> > > > + # Acceptible extent count range is 1-10
> > > > + _within_tolerance "file.$n extent count" $count 2 1 8 -v
> > > > +done
> > > > +
> > > > +status=0
> > > > +exit
> > > > diff --git a/tests/xfs/1501.out b/tests/xfs/1501.out
> > > > new file mode 100644
> > > > index 000000000..a266ef74b
> > > > --- /dev/null
> > > > +++ b/tests/xfs/1501.out
> > > > @@ -0,0 +1,9 @@
> > > > +QA output created by 1501
> > > > +file.0 extent count is in range
> > > > +file.1 extent count is in range
> > > > +file.2 extent count is in range
> > > > +file.3 extent count is in range
> > > > +file.4 extent count is in range
> > > > +file.5 extent count is in range
> > > > +file.6 extent count is in range
> > > > +file.7 extent count is in range
> > > > diff --git a/tests/xfs/1502 b/tests/xfs/1502
> > > > new file mode 100755
> > > > index 000000000..f4228667a
> > > > --- /dev/null
> > > > +++ b/tests/xfs/1502
> > > > @@ -0,0 +1,68 @@
> > > > +#! /bin/bash
> > > > +# SPDX-License-Identifier: GPL-2.0
> > > > +# Copyright (c) 2019 Red Hat, Inc. All Rights Reserved.
> > > > +#
> > > > +# FS QA Test xfs/502
> > > > +#
> > > > +# Post-EOF preallocation defeat test for direct I/O with extent size hints.
> > > > +#
> > > > +
> > > > +. ./common/preamble
> > > > +_begin_fstest auto quick prealloc rw
> > > > +
> > > > +. ./common/rc
> > > > +. ./common/filter
> > > > +
> > > > +_require_scratch
> > > > +
> > > > +_cleanup()
> > > > +{
> > > > + # try to kill all background processes
> > > > + wait
> > > > + cd /
> > > > + rm -r -f $tmp.*
> > > > +}
> > > > +
> > > > +_scratch_mkfs > "$seqres.full" 2>&1
> > > > +_scratch_mount
> > > > +
> > > > +# Write multiple files in parallel using O_DIRECT writes w/ extent size hints.
> > > > +# Aim is to interleave allocations to fragment the files. O_DIRECT writes defeat
> > > > +# the open/write/close heuristics in xfs_file_release() that prevent EOF block
> > > > +# removal, so this should fragment badly. Typical problematic behaviour shows
> > > > +# per-file extent counts of ~1000 (worst case) whilst fixed behaviour typically
> > > > +# shows extent counts in the low single digits (almost best case)
> > > > +#
> > > > +# Failure is determined by golden output mismatch from _within_tolerance().
> > > > +
> > > > +workfile=$SCRATCH_MNT/file
> > > > +nfiles=8
> > > > +wsize=4096
> > > > +wcnt=1000
> > > > +extent_size=16m
> > > > +
> > > > +write_direct_file()
> > > > +{
> > > > + idx=$1
> > > > +
> > > > + $XFS_IO_PROG -f -c "extsize $extent_size" $workfile.$idx
> > > > + for ((cnt=0; cnt<$wcnt; cnt++)); do
> > > > + $XFS_IO_PROG -f -d -c "pwrite $((cnt * wsize)) $wsize" $workfile.$idx
> > > > + done
> > > > +}
> > > > +
> > > > +rm -f $workfile*
> > > > +for ((n=0; n<$nfiles; n++)); do
> > > > + write_direct_file $n > /dev/null 2>&1 &
> > > > +done
> > > > +wait
> > > > +sync
> > > > +
> > > > +for ((n=0; n<$nfiles; n++)); do
> > > > + count=$(_count_extents $workfile.$n)
> > > > + # Acceptible extent count range is 1-10
> > > > + _within_tolerance "file.$n extent count" $count 2 1 8 -v
> > > > +done
> > > > +
> > > > +status=0
> > > > +exit
> > > > diff --git a/tests/xfs/1502.out b/tests/xfs/1502.out
> > > > new file mode 100644
> > > > index 000000000..82c8760a3
> > > > --- /dev/null
> > > > +++ b/tests/xfs/1502.out
> > > > @@ -0,0 +1,9 @@
> > > > +QA output created by 1502
> > > > +file.0 extent count is in range
> > > > +file.1 extent count is in range
> > > > +file.2 extent count is in range
> > > > +file.3 extent count is in range
> > > > +file.4 extent count is in range
> > > > +file.5 extent count is in range
> > > > +file.6 extent count is in range
> > > > +file.7 extent count is in range
> > > > diff --git a/tests/xfs/1503 b/tests/xfs/1503
> > > > new file mode 100755
> > > > index 000000000..9002f87e6
> > > > --- /dev/null
> > > > +++ b/tests/xfs/1503
> > > > @@ -0,0 +1,77 @@
> > > > +#! /bin/bash
> > > > +# SPDX-License-Identifier: GPL-2.0
> > > > +# Copyright (c) 2019 Red Hat, Inc. All Rights Reserved.
> > > > +#
> > > > +# FS QA Test xfs/503
> > > > +#
> > > > +# Post-EOF preallocation defeat test with O_SYNC buffered I/O that repeatedly
> > > > +# closes and reopens the files.
> > > > +#
> > > > +
> > > > +. ./common/preamble
> > > > +_begin_fstest auto prealloc rw
> > > > +
> > > > +. ./common/rc
> > > > +. ./common/filter
> > > > +
> > > > +_require_scratch
> > > > +
> > > > +_cleanup()
> > > > +{
> > > > + # try to kill all background processes
> > > > + wait
> > > > + cd /
> > > > + rm -r -f $tmp.*
> > > > +}
> > > > +
> > > > +_scratch_mkfs > "$seqres.full" 2>&1
> > > > +_scratch_mount
> > > > +
> > > > +# Write multiple files in parallel using synchronous buffered writes that
> > > > +# repeatedly close and reopen the fails. Aim is to interleave allocations to
> > > > +# fragment the files. Assuming we've fixed the synchronous write defeat, we can
> > > > +# still trigger the same issue with a open/read/close on O_RDONLY files. We
> > > > +# should not be triggering EOF preallocation removal on files we don't have
> > > > +# permission to write, so until this is fixed it should fragment badly. Typical
> > > > +# problematic behaviour shows per-file extent counts of 50-350 whilst fixed
> > > > +# behaviour typically demonstrates post-eof speculative delalloc growth in
> > > > +# extent size (~6 extents for 50MB file).
> > > > +#
> > > > +# Failure is determined by golden output mismatch from _within_tolerance().
> > > > +
> > > > +workfile=$SCRATCH_MNT/file
> > > > +nfiles=32
> > > > +wsize=4096
> > > > +wcnt=1000
> > > > +
> > > > +write_file()
> > > > +{
> > > > + idx=$1
> > > > +
> > > > + $XFS_IO_PROG -f -s -c "pwrite -b 64k 0 50m" $workfile.$idx
> > > > +}
> > > > +
> > > > +read_file()
> > > > +{
> > > > + idx=$1
> > > > +
> > > > + for ((cnt=0; cnt<$wcnt; cnt++)); do
> > > > + $XFS_IO_PROG -f -r -c "pread 0 28" $workfile.$idx
> > > > + done
> > > > +}
> > > > +
> > > > +rm -f $workdir/file*
> > > > +for ((n=0; n<$((nfiles)); n++)); do
> > > > + write_file $n > /dev/null 2>&1 &
> > > > + read_file $n > /dev/null 2>&1 &
> > > > +done
> > > > +wait
> > > > +
> > > > +for ((n=0; n<$nfiles; n++)); do
> > > > + count=$(_count_extents $workfile.$n)
> > > > + # Acceptible extent count range is 1-40
> > > > + _within_tolerance "file.$n extent count" $count 6 5 10 -v
> > > > +done
> > > > +
> > > > +status=0
> > > > +exit
> > > > diff --git a/tests/xfs/1503.out b/tests/xfs/1503.out
> > > > new file mode 100644
> > > > index 000000000..1780b16df
> > > > --- /dev/null
> > > > +++ b/tests/xfs/1503.out
> > > > @@ -0,0 +1,33 @@
> > > > +QA output created by 1503
> > > > +file.0 extent count is in range
> > > > +file.1 extent count is in range
> > > > +file.2 extent count is in range
> > > > +file.3 extent count is in range
> > > > +file.4 extent count is in range
> > > > +file.5 extent count is in range
> > > > +file.6 extent count is in range
> > > > +file.7 extent count is in range
> > > > +file.8 extent count is in range
> > > > +file.9 extent count is in range
> > > > +file.10 extent count is in range
> > > > +file.11 extent count is in range
> > > > +file.12 extent count is in range
> > > > +file.13 extent count is in range
> > > > +file.14 extent count is in range
> > > > +file.15 extent count is in range
> > > > +file.16 extent count is in range
> > > > +file.17 extent count is in range
> > > > +file.18 extent count is in range
> > > > +file.19 extent count is in range
> > > > +file.20 extent count is in range
> > > > +file.21 extent count is in range
> > > > +file.22 extent count is in range
> > > > +file.23 extent count is in range
> > > > +file.24 extent count is in range
> > > > +file.25 extent count is in range
> > > > +file.26 extent count is in range
> > > > +file.27 extent count is in range
> > > > +file.28 extent count is in range
> > > > +file.29 extent count is in range
> > > > +file.30 extent count is in range
> > > > +file.31 extent count is in range
> > > > --
> > > > 2.45.2
> > > >
> > > >
> > >
> >
>
>