[PATCH v5 0/3] xfs: testcases for shrinking free space in the last AG

[PATCH v5 0/3] xfs: testcases for shrinking free space in the last AG

[Gao Xiang]

Hi,

This adds testcases for shrinking free space in the last AG in the upstream.
This version mainly addresses Darrick's previous comments.
(and I've checked with "512m logdev with USE_EXTERNAL and SCRATCH_LOGDEV
 without issues)

changes since v4 (Darrick):
 - [1/3] check xfs_growfs output instead;
 - [2/3] fix a typo;
 - [2/3] echo statements rather than fail out;
 - [3/3] avoid unncessary scale due to _scale_fsstress_args;
 - [3/3] inject a bit randomness to decsize;
 - [3/3] use '_scratch_xfs_repair -n' instead.

Thanks,
Gao Xiang

Gao Xiang (3):
  common/xfs: add _require_xfs_scratch_shrink helper
  xfs: basic functionality test for shrinking free space in the last AG
  xfs: stress test for shrinking free space in the last AG

 common/xfs        |  20 ++++++++
 tests/xfs/990     |  73 ++++++++++++++++++++++++++++
 tests/xfs/990.out |  12 +++++
 tests/xfs/991     | 120 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/xfs/991.out |   8 ++++
 tests/xfs/group   |   2 +
 6 files changed, 235 insertions(+)
 create mode 100755 tests/xfs/990
 create mode 100644 tests/xfs/990.out
 create mode 100755 tests/xfs/991
 create mode 100644 tests/xfs/991.out

-- 
2.27.0

[PATCH v5 1/3] common/xfs: add _require_xfs_scratch_shrink helper

[Gao Xiang]

In order to detect whether the current kernel supports XFS shrinking.

Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
---
 common/xfs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/common/xfs b/common/xfs
index 69f76d6e..184aa01e 100644
--- a/common/xfs
+++ b/common/xfs
@@ -766,6 +766,26 @@ _require_xfs_mkfs_without_validation()
 	fi
 }
 
+_require_xfs_scratch_shrink()
+{
+	_require_scratch
+	_require_command "$XFS_GROWFS_PROG" xfs_growfs
+
+	_scratch_mkfs_xfs | _filter_mkfs 2>$tmp.mkfs >/dev/null
+	. $tmp.mkfs
+	_scratch_mount
+	# here just to check if kernel supports, no need do more extra work
+	errmsg=$($XFS_GROWFS_PROG -D$((dblocks-1)) "$SCRATCH_MNT" 2>&1)
+	if [ "$?" -ne 0 ]; then
+		echo "$errmsg" | grep 'XFS_IOC_FSGROWFSDATA xfsctl failed: Invalid argument' && \
+			_notrun "kernel does not support shrinking"
+		echo "$errmsg" | grep 'data size .* too small, old size is ' && \
+			_notrun "xfsprogs does not support shrinking"
+		_fail "$XFS_GROWFS_PROG failed unexpectedly"
+	fi
+	_scratch_unmount
+}
+
 # XFS ability to change UUIDs on V5/CRC filesystems
 #
 _require_meta_uuid()
-- 
2.27.0

Re: [PATCH v5 1/3] common/xfs: add _require_xfs_scratch_shrink helper

[Darrick J. Wong]

On Tue, May 11, 2021 at 03:39:43PM +0800, Gao Xiang wrote:
> In order to detect whether the current kernel supports XFS shrinking.
> 
> Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
> ---
>  common/xfs | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/common/xfs b/common/xfs
> index 69f76d6e..184aa01e 100644
> --- a/common/xfs
> +++ b/common/xfs
> @@ -766,6 +766,26 @@ _require_xfs_mkfs_without_validation()
>  	fi
>  }
>  
> +_require_xfs_scratch_shrink()
> +{
> +	_require_scratch
> +	_require_command "$XFS_GROWFS_PROG" xfs_growfs
> +
> +	_scratch_mkfs_xfs | _filter_mkfs 2>$tmp.mkfs >/dev/null
> +	. $tmp.mkfs
> +	_scratch_mount
> +	# here just to check if kernel supports, no need do more extra work
> +	errmsg=$($XFS_GROWFS_PROG -D$((dblocks-1)) "$SCRATCH_MNT" 2>&1)
> +	if [ "$?" -ne 0 ]; then
> +		echo "$errmsg" | grep 'XFS_IOC_FSGROWFSDATA xfsctl failed: Invalid argument' && \
> +			_notrun "kernel does not support shrinking"
> +		echo "$errmsg" | grep 'data size .* too small, old size is ' && \
> +			_notrun "xfsprogs does not support shrinking"
> +		_fail "$XFS_GROWFS_PROG failed unexpectedly"

Silly nit: why not print $errmsg in the fail string?

With that fixed,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> +	fi
> +	_scratch_unmount
> +}
> +
>  # XFS ability to change UUIDs on V5/CRC filesystems
>  #
>  _require_meta_uuid()
> -- 
> 2.27.0
> 

[PATCH v5 2/3] xfs: basic functionality test for shrinking free space in the last AG

[Gao Xiang]

Add basic test to make sure the functionality works as expected.

Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
---
 tests/xfs/990     | 73 +++++++++++++++++++++++++++++++++++++++++++++++
 tests/xfs/990.out | 12 ++++++++
 tests/xfs/group   |  1 +
 3 files changed, 86 insertions(+)
 create mode 100755 tests/xfs/990
 create mode 100644 tests/xfs/990.out

diff --git a/tests/xfs/990 b/tests/xfs/990
new file mode 100755
index 00000000..ec2592f6
--- /dev/null
+++ b/tests/xfs/990
@@ -0,0 +1,73 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2021 Red Hat, Inc.  All Rights Reserved.
+#
+# FS QA Test 990
+#
+# XFS shrinkfs basic functionality test
+#
+# This test attempts to shrink with a small size (512K), half AG size and
+# an out-of-bound size (agsize + 1) to observe if it works as expected.
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1    # failure is the default!
+trap "rm -f $tmp.*; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+test_shrink()
+{
+	$XFS_GROWFS_PROG -D"$1" $SCRATCH_MNT >> $seqres.full 2>&1
+	ret=$?
+
+	_scratch_unmount
+	_check_scratch_fs
+	_scratch_mount
+
+	$XFS_INFO_PROG $SCRATCH_MNT 2>&1 | _filter_mkfs 2>$tmp.growfs >/dev/null
+	. $tmp.growfs
+	[ $ret -eq 0 -a $1 -eq $dblocks ]
+}
+
+# real QA test starts here
+_supported_fs xfs
+_require_xfs_scratch_shrink
+
+rm -f $seqres.full
+echo "Format and mount"
+
+# agcount = 1 is forbidden on purpose, and need to ensure shrinking to
+# 2 AGs isn't feasible yet. So agcount = 3 is the minimum number now.
+_scratch_mkfs -dsize="$((512 * 1024 * 1024))" -dagcount=3 2>&1 | \
+	tee -a $seqres.full | _filter_mkfs 2>$tmp.mkfs
+. $tmp.mkfs
+t_dblocks=$dblocks
+_scratch_mount >> $seqres.full
+
+echo "Shrink fs (small size)"
+test_shrink $((t_dblocks-512*1024/dbsize)) || \
+	echo "Shrink fs (small size) failure"
+
+echo "Shrink fs (half AG)"
+test_shrink $((t_dblocks-agsize/2)) || \
+	echo "Shrink fs (half AG) failure"
+
+echo "Shrink fs (out-of-bound)"
+test_shrink $((t_dblocks-agsize-1)) && \
+	echo "Shrink fs (out-of-bound) failure"
+[ $dblocks -ne $((t_dblocks-agsize/2)) ] && \
+	echo "dblocks changed after shrinking failure"
+
+$XFS_INFO_PROG $SCRATCH_MNT >> $seqres.full
+echo "*** done"
+
+# success, all done
+status=0
+exit
diff --git a/tests/xfs/990.out b/tests/xfs/990.out
new file mode 100644
index 00000000..812f89ef
--- /dev/null
+++ b/tests/xfs/990.out
@@ -0,0 +1,12 @@
+QA output created by 990
+Format and mount
+meta-data=DDEV isize=XXX agcount=N, agsize=XXX blks
+data     = bsize=XXX blocks=XXX, imaxpct=PCT
+         = sunit=XXX swidth=XXX, unwritten=X
+naming   =VERN bsize=XXX
+log      =LDEV bsize=XXX blocks=XXX
+realtime =RDEV extsz=XXX blocks=XXX, rtextents=XXX
+Shrink fs (small size)
+Shrink fs (half AG)
+Shrink fs (out-of-bound)
+*** done
diff --git a/tests/xfs/group b/tests/xfs/group
index fe83f82d..472c8f9a 100644
--- a/tests/xfs/group
+++ b/tests/xfs/group
@@ -520,3 +520,4 @@
 537 auto quick
 538 auto stress
 539 auto quick mount
+990 auto quick growfs shrinkfs
-- 
2.27.0

Re: [PATCH v5 2/3] xfs: basic functionality test for shrinking free space in the last AG

[Darrick J. Wong]

On Tue, May 11, 2021 at 03:39:44PM +0800, Gao Xiang wrote:
> Add basic test to make sure the functionality works as expected.
> 
> Signed-off-by: Gao Xiang <hsiangkao@redhat.com>

Looks fine now,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  tests/xfs/990     | 73 +++++++++++++++++++++++++++++++++++++++++++++++
>  tests/xfs/990.out | 12 ++++++++
>  tests/xfs/group   |  1 +
>  3 files changed, 86 insertions(+)
>  create mode 100755 tests/xfs/990
>  create mode 100644 tests/xfs/990.out
> 
> diff --git a/tests/xfs/990 b/tests/xfs/990
> new file mode 100755
> index 00000000..ec2592f6
> --- /dev/null
> +++ b/tests/xfs/990
> @@ -0,0 +1,73 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2021 Red Hat, Inc.  All Rights Reserved.
> +#
> +# FS QA Test 990
> +#
> +# XFS shrinkfs basic functionality test
> +#
> +# This test attempts to shrink with a small size (512K), half AG size and
> +# an out-of-bound size (agsize + 1) to observe if it works as expected.
> +#
> +seq=`basename $0`
> +seqres=$RESULT_DIR/$seq
> +echo "QA output created by $seq"
> +
> +here=`pwd`
> +tmp=/tmp/$$
> +status=1    # failure is the default!
> +trap "rm -f $tmp.*; exit \$status" 0 1 2 3 15
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter
> +
> +test_shrink()
> +{
> +	$XFS_GROWFS_PROG -D"$1" $SCRATCH_MNT >> $seqres.full 2>&1
> +	ret=$?
> +
> +	_scratch_unmount
> +	_check_scratch_fs
> +	_scratch_mount
> +
> +	$XFS_INFO_PROG $SCRATCH_MNT 2>&1 | _filter_mkfs 2>$tmp.growfs >/dev/null
> +	. $tmp.growfs
> +	[ $ret -eq 0 -a $1 -eq $dblocks ]
> +}
> +
> +# real QA test starts here
> +_supported_fs xfs
> +_require_xfs_scratch_shrink
> +
> +rm -f $seqres.full
> +echo "Format and mount"
> +
> +# agcount = 1 is forbidden on purpose, and need to ensure shrinking to
> +# 2 AGs isn't feasible yet. So agcount = 3 is the minimum number now.
> +_scratch_mkfs -dsize="$((512 * 1024 * 1024))" -dagcount=3 2>&1 | \
> +	tee -a $seqres.full | _filter_mkfs 2>$tmp.mkfs
> +. $tmp.mkfs
> +t_dblocks=$dblocks
> +_scratch_mount >> $seqres.full
> +
> +echo "Shrink fs (small size)"
> +test_shrink $((t_dblocks-512*1024/dbsize)) || \
> +	echo "Shrink fs (small size) failure"
> +
> +echo "Shrink fs (half AG)"
> +test_shrink $((t_dblocks-agsize/2)) || \
> +	echo "Shrink fs (half AG) failure"
> +
> +echo "Shrink fs (out-of-bound)"
> +test_shrink $((t_dblocks-agsize-1)) && \
> +	echo "Shrink fs (out-of-bound) failure"
> +[ $dblocks -ne $((t_dblocks-agsize/2)) ] && \
> +	echo "dblocks changed after shrinking failure"
> +
> +$XFS_INFO_PROG $SCRATCH_MNT >> $seqres.full
> +echo "*** done"
> +
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/xfs/990.out b/tests/xfs/990.out
> new file mode 100644
> index 00000000..812f89ef
> --- /dev/null
> +++ b/tests/xfs/990.out
> @@ -0,0 +1,12 @@
> +QA output created by 990
> +Format and mount
> +meta-data=DDEV isize=XXX agcount=N, agsize=XXX blks
> +data     = bsize=XXX blocks=XXX, imaxpct=PCT
> +         = sunit=XXX swidth=XXX, unwritten=X
> +naming   =VERN bsize=XXX
> +log      =LDEV bsize=XXX blocks=XXX
> +realtime =RDEV extsz=XXX blocks=XXX, rtextents=XXX
> +Shrink fs (small size)
> +Shrink fs (half AG)
> +Shrink fs (out-of-bound)
> +*** done
> diff --git a/tests/xfs/group b/tests/xfs/group
> index fe83f82d..472c8f9a 100644
> --- a/tests/xfs/group
> +++ b/tests/xfs/group
> @@ -520,3 +520,4 @@
>  537 auto quick
>  538 auto stress
>  539 auto quick mount
> +990 auto quick growfs shrinkfs
> -- 
> 2.27.0
> 

[PATCH v5 3/3] xfs: stress test for shrinking free space in the last AG

[Gao Xiang]

This adds a stress testcase to shrink free space as much as
possible in the last AG with background fsstress workload.

The expectation is that no crash happens with expected output.

Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
---
 tests/xfs/991     | 120 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/xfs/991.out |   8 ++++
 tests/xfs/group   |   1 +
 3 files changed, 129 insertions(+)
 create mode 100755 tests/xfs/991
 create mode 100644 tests/xfs/991.out

diff --git a/tests/xfs/991 b/tests/xfs/991
new file mode 100755
index 00000000..3561bfab
--- /dev/null
+++ b/tests/xfs/991
@@ -0,0 +1,120 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2020-2021 Red Hat, Inc.  All Rights Reserved.
+#
+# FS QA Test 991
+#
+# XFS online shrinkfs stress test
+#
+# This test attempts to shrink unused space as much as possible with
+# background fsstress workload. It will decrease the shrink size if
+# larger size fails. And totally repeat 2 * TIME_FACTOR times.
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "rm -f $tmp.*; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+create_scratch()
+{
+	_scratch_mkfs_xfs $@ | tee -a $seqres.full | \
+		_filter_mkfs 2>$tmp.mkfs >/dev/null
+	. $tmp.mkfs
+
+	_scratch_mount
+	# fix the reserve block pool to a known size so that the enospc
+	# calculations work out correctly.
+	_scratch_resvblks 1024 > /dev/null 2>&1
+}
+
+fill_scratch()
+{
+	$XFS_IO_PROG -f -c "falloc 0 $1" $SCRATCH_MNT/resvfile
+}
+
+stress_scratch()
+{
+	local procs=3
+	local nops=1000
+	# -w ensures that the only ops are ones which cause write I/O
+	local FSSTRESS_ARGS=`_scale_fsstress_args -d $SCRATCH_MNT -w \
+		-p $procs -n $nops $FSSTRESS_AVOID`
+	$FSSTRESS_PROG $FSSTRESS_ARGS >> $seqres.full 2>&1
+}
+
+# real QA test starts here
+_supported_fs xfs
+_require_xfs_scratch_shrink
+_require_xfs_io_command "falloc"
+
+rm -f $seqres.full
+_scratch_mkfs_xfs | tee -a $seqres.full | _filter_mkfs 2>$tmp.mkfs
+. $tmp.mkfs	# extract blocksize and data size for scratch device
+
+endsize=`expr 125 \* 1048576`	# stop after shrinking this big
+[ `expr $endsize / $dbsize` -lt $dblocks ] || _notrun "Scratch device too small"
+
+nags=2
+totalcount=$((2 * TIME_FACTOR))
+
+while [ $totalcount -gt 0 ]; do
+	size=`expr 1010 \* 1048576`	# 1010 megabytes initially
+	logblks=$(_scratch_find_xfs_min_logblocks -dsize=${size} -dagcount=${nags})
+
+	create_scratch -lsize=${logblks}b -dsize=${size} -dagcount=${nags}
+
+	for i in `seq 125 -1 90`; do
+		fillsize=`expr $i \* 1048576`
+		out="$(fill_scratch $fillsize 2>&1)"
+		echo "$out" | grep -q 'No space left on device' && continue
+		test -n "${out}" && echo "$out"
+		break
+	done
+
+	# shrink in chunks of this size at most
+	decsize=`expr  41 \* 1048576 + 1 + $RANDOM \* $RANDOM % 1048576`
+
+	while [ $size -gt $endsize ]; do
+		stress_scratch &
+		sleep 1
+
+		decb=`expr $decsize / $dbsize`    # in data blocks
+		while [ $decb -gt 0 ]; do
+			sizeb=`expr $size / $dbsize - $decb`
+
+			$XFS_GROWFS_PROG -D ${sizeb} $SCRATCH_MNT \
+				>> $seqres.full 2>&1 && break
+
+			[ $decb -gt 100 ] && decb=`expr $decb + $RANDOM % 10`
+			decb=`expr $decb / 2`
+		done
+
+		wait
+		[ $decb -eq 0 ] && break
+
+		# get latest dblocks
+		$XFS_INFO_PROG $SCRATCH_MNT 2>&1 | _filter_mkfs 2>$tmp.growfs >/dev/null
+		. $tmp.growfs
+
+		size=`expr $dblocks \* $dbsize`
+		_scratch_unmount
+		_scratch_xfs_repair -n >> $seqres.full 2>&1 || _fail "xfs_repair failed"
+		_scratch_mount
+	done
+
+	_scratch_unmount
+	_scratch_xfs_repair -n >> $seqres.full 2>&1 || _fail "xfs_repair failed"
+	totalcount=`expr $totalcount - 1`
+done
+
+echo "*** done"
+status=0
+exit
diff --git a/tests/xfs/991.out b/tests/xfs/991.out
new file mode 100644
index 00000000..e8209672
--- /dev/null
+++ b/tests/xfs/991.out
@@ -0,0 +1,8 @@
+QA output created by 991
+meta-data=DDEV isize=XXX agcount=N, agsize=XXX blks
+data     = bsize=XXX blocks=XXX, imaxpct=PCT
+         = sunit=XXX swidth=XXX, unwritten=X
+naming   =VERN bsize=XXX
+log      =LDEV bsize=XXX blocks=XXX
+realtime =RDEV extsz=XXX blocks=XXX, rtextents=XXX
+*** done
diff --git a/tests/xfs/group b/tests/xfs/group
index 472c8f9a..53e68bea 100644
--- a/tests/xfs/group
+++ b/tests/xfs/group
@@ -521,3 +521,4 @@
 538 auto stress
 539 auto quick mount
 990 auto quick growfs shrinkfs
+991 auto growfs shrinkfs ioctl prealloc stress
-- 
2.27.0

Re: [PATCH v5 3/3] xfs: stress test for shrinking free space in the last AG

[Darrick J. Wong]

On Tue, May 11, 2021 at 03:39:45PM +0800, Gao Xiang wrote:
> This adds a stress testcase to shrink free space as much as
> possible in the last AG with background fsstress workload.
> 
> The expectation is that no crash happens with expected output.
> 
> Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
> ---
>  tests/xfs/991     | 120 ++++++++++++++++++++++++++++++++++++++++++++++
>  tests/xfs/991.out |   8 ++++
>  tests/xfs/group   |   1 +
>  3 files changed, 129 insertions(+)
>  create mode 100755 tests/xfs/991
>  create mode 100644 tests/xfs/991.out
> 
> diff --git a/tests/xfs/991 b/tests/xfs/991
> new file mode 100755
> index 00000000..3561bfab
> --- /dev/null
> +++ b/tests/xfs/991
> @@ -0,0 +1,120 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2020-2021 Red Hat, Inc.  All Rights Reserved.
> +#
> +# FS QA Test 991
> +#
> +# XFS online shrinkfs stress test
> +#
> +# This test attempts to shrink unused space as much as possible with
> +# background fsstress workload. It will decrease the shrink size if
> +# larger size fails. And totally repeat 2 * TIME_FACTOR times.
> +#
> +seq=`basename $0`
> +seqres=$RESULT_DIR/$seq
> +echo "QA output created by $seq"
> +
> +here=`pwd`
> +tmp=/tmp/$$
> +status=1	# failure is the default!
> +trap "rm -f $tmp.*; exit \$status" 0 1 2 3 15
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter
> +
> +create_scratch()
> +{
> +	_scratch_mkfs_xfs $@ | tee -a $seqres.full | \
> +		_filter_mkfs 2>$tmp.mkfs >/dev/null
> +	. $tmp.mkfs
> +
> +	_scratch_mount
> +	# fix the reserve block pool to a known size so that the enospc
> +	# calculations work out correctly.
> +	_scratch_resvblks 1024 > /dev/null 2>&1
> +}
> +
> +fill_scratch()
> +{
> +	$XFS_IO_PROG -f -c "falloc 0 $1" $SCRATCH_MNT/resvfile
> +}
> +
> +stress_scratch()
> +{
> +	local procs=3
> +	local nops=1000
> +	# -w ensures that the only ops are ones which cause write I/O
> +	local FSSTRESS_ARGS=`_scale_fsstress_args -d $SCRATCH_MNT -w \
> +		-p $procs -n $nops $FSSTRESS_AVOID`
> +	$FSSTRESS_PROG $FSSTRESS_ARGS >> $seqres.full 2>&1
> +}
> +
> +# real QA test starts here
> +_supported_fs xfs
> +_require_xfs_scratch_shrink
> +_require_xfs_io_command "falloc"
> +
> +rm -f $seqres.full
> +_scratch_mkfs_xfs | tee -a $seqres.full | _filter_mkfs 2>$tmp.mkfs
> +. $tmp.mkfs	# extract blocksize and data size for scratch device
> +
> +endsize=`expr 125 \* 1048576`	# stop after shrinking this big
> +[ `expr $endsize / $dbsize` -lt $dblocks ] || _notrun "Scratch device too small"
> +
> +nags=2
> +totalcount=$((2 * TIME_FACTOR))
> +
> +while [ $totalcount -gt 0 ]; do
> +	size=`expr 1010 \* 1048576`	# 1010 megabytes initially
> +	logblks=$(_scratch_find_xfs_min_logblocks -dsize=${size} -dagcount=${nags})
> +
> +	create_scratch -lsize=${logblks}b -dsize=${size} -dagcount=${nags}
> +
> +	for i in `seq 125 -1 90`; do
> +		fillsize=`expr $i \* 1048576`
> +		out="$(fill_scratch $fillsize 2>&1)"
> +		echo "$out" | grep -q 'No space left on device' && continue
> +		test -n "${out}" && echo "$out"
> +		break
> +	done
> +
> +	# shrink in chunks of this size at most
> +	decsize=`expr  41 \* 1048576 + 1 + $RANDOM \* $RANDOM % 1048576`
> +
> +	while [ $size -gt $endsize ]; do
> +		stress_scratch &
> +		sleep 1
> +
> +		decb=`expr $decsize / $dbsize`    # in data blocks
> +		while [ $decb -gt 0 ]; do
> +			sizeb=`expr $size / $dbsize - $decb`
> +
> +			$XFS_GROWFS_PROG -D ${sizeb} $SCRATCH_MNT \
> +				>> $seqres.full 2>&1 && break
> +
> +			[ $decb -gt 100 ] && decb=`expr $decb + $RANDOM % 10`
> +			decb=`expr $decb / 2`
> +		done
> +
> +		wait
> +		[ $decb -eq 0 ] && break
> +
> +		# get latest dblocks
> +		$XFS_INFO_PROG $SCRATCH_MNT 2>&1 | _filter_mkfs 2>$tmp.growfs >/dev/null
> +		. $tmp.growfs
> +
> +		size=`expr $dblocks \* $dbsize`
> +		_scratch_unmount
> +		_scratch_xfs_repair -n >> $seqres.full 2>&1 || _fail "xfs_repair failed"

Might be nice to print $sizeb with the error message so that one can
correlate with tracepoints/growfs output without having to dig through
$seqres.full...

With that changed, I'd say:
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> +		_scratch_mount
> +	done
> +
> +	_scratch_unmount
> +	_scratch_xfs_repair -n >> $seqres.full 2>&1 || _fail "xfs_repair failed"
> +	totalcount=`expr $totalcount - 1`
> +done
> +
> +echo "*** done"
> +status=0
> +exit
> diff --git a/tests/xfs/991.out b/tests/xfs/991.out
> new file mode 100644
> index 00000000..e8209672
> --- /dev/null
> +++ b/tests/xfs/991.out
> @@ -0,0 +1,8 @@
> +QA output created by 991
> +meta-data=DDEV isize=XXX agcount=N, agsize=XXX blks
> +data     = bsize=XXX blocks=XXX, imaxpct=PCT
> +         = sunit=XXX swidth=XXX, unwritten=X
> +naming   =VERN bsize=XXX
> +log      =LDEV bsize=XXX blocks=XXX
> +realtime =RDEV extsz=XXX blocks=XXX, rtextents=XXX
> +*** done
> diff --git a/tests/xfs/group b/tests/xfs/group
> index 472c8f9a..53e68bea 100644
> --- a/tests/xfs/group
> +++ b/tests/xfs/group
> @@ -521,3 +521,4 @@
>  538 auto stress
>  539 auto quick mount
>  990 auto quick growfs shrinkfs
> +991 auto growfs shrinkfs ioctl prealloc stress
> -- 
> 2.27.0
>