[PATCH v2 2/2] fstests: btrfs: Introduce stress test for deadlock between snapshot delete and other read-write operations

[PATCH v2 2/2] fstests: btrfs: Introduce stress test for deadlock between snapshot delete and other read-write operations

[Qu Wenruo]

Commit fb235dc06fac ("btrfs: qgroup: Move half of the qgroup accounting
time out of commit trans") could cause ABBA deadlock between backref
lookup with write lock hold (subvolume deletion) and other read/write
operations.

It's going to be fixed by "btrfs: qgroup: Don't trigger backref walk at
delayed ref insert time".

This test will generate pwrite background workload, along with
constant subvolume creation and deletion to trigger the bug.

It needs some time to generate enough files to bump the tree height to
trigger the bug.
In my test environment, with 'unsafe' cache mode for the VM, it triggers
the bug at around 70~90 seconds. So I leave the default runtime to 120s
to make sure the bug will be triggered.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
changelog:
v2:
- Commit message grammar fix.
- Remove unnecessary comment about how the bug is triggered.
- Use better signal handle to avoid -EBUSY at umount.
---
 tests/btrfs/179     | 116 ++++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/179.out |   2 +
 tests/btrfs/group   |   1 +
 3 files changed, 119 insertions(+)
 create mode 100755 tests/btrfs/179
 create mode 100644 tests/btrfs/179.out

diff --git a/tests/btrfs/179 b/tests/btrfs/179
new file mode 100755
index 000000000000..4a24ea419a7e
--- /dev/null
+++ b/tests/btrfs/179
@@ -0,0 +1,116 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2019 SUSE Linux Products GmbH. All Rights Reserved.
+#
+# FS QA Test 179
+#
+# Test if btrfs will lockup at subvolume deletion when qgroups are enabled.
+#
+# This bug is going to be fixed by a patch for the kernel titled
+# "btrfs: qgroup: Don't trigger backref walk at delayed ref insert time".
+#
+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
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs btrfs
+_supported_os Linux
+_require_scratch
+
+# default sleep interval
+sleep_time=1
+
+# stress test runtime
+runtime=120
+
+_scratch_mkfs > /dev/null 2>&1
+_scratch_mount
+
+mkdir -p "$SCRATCH_MNT/snapshots"
+$BTRFS_UTIL_PROG subvolume create "$SCRATCH_MNT/src" > /dev/null
+$BTRFS_UTIL_PROG quota enable "$SCRATCH_MNT" > /dev/null
+$BTRFS_UTIL_PROG quota rescan -w "$SCRATCH_MNT" > /dev/null
+
+fill_workload()
+{
+	trap "wait; exit" SIGTERM
+	local i=0
+	while true; do
+		_pwrite_byte 0xcd 0 8K "$SCRATCH_MNT/src/large_$i" > /dev/null
+		_pwrite_byte 0xcd 0 2K "$SCRATCH_MNT/src/inline_$i" > /dev/null
+
+		# Randomly remove some files for every 5 loop
+		if [ $(( $i % 5 )) -eq 0 ]; then
+			victim=$(ls "$SCRATCH_MNT/src" | sort -R | head -n1)
+			rm "$SCRATCH_MNT/src/$victim"
+		fi
+		i=$((i + 1))
+	done
+}
+
+snapshot_workload()
+{
+	trap "wait; exit" SIGTERM
+	local i=0
+	while true; do
+		sleep $sleep_time
+		$BTRFS_UTIL_PROG subvolume snapshot "$SCRATCH_MNT/src" \
+			"$SCRATCH_MNT/snapshots/$i" > /dev/null
+		i=$((i + 1))
+	done
+}
+
+delete_workload()
+{
+	trap "wait; exit" SIGTERM
+	while true; do
+		sleep $((sleep_time * 2))
+		victim=$(ls "$SCRATCH_MNT/snapshots" | sort -R | head -n1)
+		$BTRFS_UTIL_PROG subvolume delete \
+			"$SCRATCH_MNT/snapshots/$victim" > /dev/null
+	done
+}
+
+fill_workload &
+fill_pid=$!
+
+sleep $((sleep_time * 2))
+snapshot_workload &
+snapshot_pid=$!
+delete_workload &
+delete_pid=$!
+
+sleep $runtime
+kill $fill_pid
+wait $fill_pid
+kill $snapshot_pid
+wait $snapshot_pid
+kill $delete_pid
+wait $delete_pid
+
+# success, all done
+echo "Silence is golden"
+
+status=0
+exit
diff --git a/tests/btrfs/179.out b/tests/btrfs/179.out
new file mode 100644
index 000000000000..cb9eba3d34b1
--- /dev/null
+++ b/tests/btrfs/179.out
@@ -0,0 +1,2 @@
+QA output created by 179
+Silence is golden
diff --git a/tests/btrfs/group b/tests/btrfs/group
index 04c0254aa4bf..46dd3c9523c2 100644
--- a/tests/btrfs/group
+++ b/tests/btrfs/group
@@ -181,3 +181,4 @@
 176 auto quick swap volume
 177 auto quick swap balance
 178 auto quick send
+179 auto qgroup dangerous
-- 
2.20.1

Re: [PATCH v2 2/2] fstests: btrfs: Introduce stress test for deadlock between snapshot delete and other read-write operations

[Filipe Manana]

On Fri, Jan 11, 2019 at 5:38 AM Qu Wenruo <wqu@suse.com> wrote:
>
> Commit fb235dc06fac ("btrfs: qgroup: Move half of the qgroup accounting
> time out of commit trans") could cause ABBA deadlock between backref
> lookup with write lock hold (subvolume deletion) and other read/write
> operations.
>
> It's going to be fixed by "btrfs: qgroup: Don't trigger backref walk at
> delayed ref insert time".
>
> This test will generate pwrite background workload, along with
> constant subvolume creation and deletion to trigger the bug.
>
> It needs some time to generate enough files to bump the tree height to
> trigger the bug.
> In my test environment, with 'unsafe' cache mode for the VM, it triggers
> the bug at around 70~90 seconds. So I leave the default runtime to 120s
> to make sure the bug will be triggered.
>
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Reviewed-by: Filipe Manana <fdmanana@suse.com>

Thanks.

> ---
> changelog:
> v2:
> - Commit message grammar fix.
> - Remove unnecessary comment about how the bug is triggered.
> - Use better signal handle to avoid -EBUSY at umount.
> ---
>  tests/btrfs/179     | 116 ++++++++++++++++++++++++++++++++++++++++++++
>  tests/btrfs/179.out |   2 +
>  tests/btrfs/group   |   1 +
>  3 files changed, 119 insertions(+)
>  create mode 100755 tests/btrfs/179
>  create mode 100644 tests/btrfs/179.out
>
> diff --git a/tests/btrfs/179 b/tests/btrfs/179
> new file mode 100755
> index 000000000000..4a24ea419a7e
> --- /dev/null
> +++ b/tests/btrfs/179
> @@ -0,0 +1,116 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (C) 2019 SUSE Linux Products GmbH. All Rights Reserved.
> +#
> +# FS QA Test 179
> +#
> +# Test if btrfs will lockup at subvolume deletion when qgroups are enabled.
> +#
> +# This bug is going to be fixed by a patch for the kernel titled
> +# "btrfs: qgroup: Don't trigger backref walk at delayed ref insert time".
> +#
> +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
> +
> +# remove previous $seqres.full before test
> +rm -f $seqres.full
> +
> +# real QA test starts here
> +
> +# Modify as appropriate.
> +_supported_fs btrfs
> +_supported_os Linux
> +_require_scratch
> +
> +# default sleep interval
> +sleep_time=1
> +
> +# stress test runtime
> +runtime=120
> +
> +_scratch_mkfs > /dev/null 2>&1
> +_scratch_mount
> +
> +mkdir -p "$SCRATCH_MNT/snapshots"
> +$BTRFS_UTIL_PROG subvolume create "$SCRATCH_MNT/src" > /dev/null
> +$BTRFS_UTIL_PROG quota enable "$SCRATCH_MNT" > /dev/null
> +$BTRFS_UTIL_PROG quota rescan -w "$SCRATCH_MNT" > /dev/null
> +
> +fill_workload()
> +{
> +       trap "wait; exit" SIGTERM
> +       local i=0
> +       while true; do
> +               _pwrite_byte 0xcd 0 8K "$SCRATCH_MNT/src/large_$i" > /dev/null
> +               _pwrite_byte 0xcd 0 2K "$SCRATCH_MNT/src/inline_$i" > /dev/null
> +
> +               # Randomly remove some files for every 5 loop
> +               if [ $(( $i % 5 )) -eq 0 ]; then
> +                       victim=$(ls "$SCRATCH_MNT/src" | sort -R | head -n1)
> +                       rm "$SCRATCH_MNT/src/$victim"
> +               fi
> +               i=$((i + 1))
> +       done
> +}
> +
> +snapshot_workload()
> +{
> +       trap "wait; exit" SIGTERM
> +       local i=0
> +       while true; do
> +               sleep $sleep_time
> +               $BTRFS_UTIL_PROG subvolume snapshot "$SCRATCH_MNT/src" \
> +                       "$SCRATCH_MNT/snapshots/$i" > /dev/null
> +               i=$((i + 1))
> +       done
> +}
> +
> +delete_workload()
> +{
> +       trap "wait; exit" SIGTERM
> +       while true; do
> +               sleep $((sleep_time * 2))
> +               victim=$(ls "$SCRATCH_MNT/snapshots" | sort -R | head -n1)
> +               $BTRFS_UTIL_PROG subvolume delete \
> +                       "$SCRATCH_MNT/snapshots/$victim" > /dev/null
> +       done
> +}
> +
> +fill_workload &
> +fill_pid=$!
> +
> +sleep $((sleep_time * 2))
> +snapshot_workload &
> +snapshot_pid=$!
> +delete_workload &
> +delete_pid=$!
> +
> +sleep $runtime
> +kill $fill_pid
> +wait $fill_pid
> +kill $snapshot_pid
> +wait $snapshot_pid
> +kill $delete_pid
> +wait $delete_pid
> +
> +# success, all done
> +echo "Silence is golden"
> +
> +status=0
> +exit
> diff --git a/tests/btrfs/179.out b/tests/btrfs/179.out
> new file mode 100644
> index 000000000000..cb9eba3d34b1
> --- /dev/null
> +++ b/tests/btrfs/179.out
> @@ -0,0 +1,2 @@
> +QA output created by 179
> +Silence is golden
> diff --git a/tests/btrfs/group b/tests/btrfs/group
> index 04c0254aa4bf..46dd3c9523c2 100644
> --- a/tests/btrfs/group
> +++ b/tests/btrfs/group
> @@ -181,3 +181,4 @@
>  176 auto quick swap volume
>  177 auto quick swap balance
>  178 auto quick send
> +179 auto qgroup dangerous
> --
> 2.20.1
>


-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”

Re: [PATCH v2 2/2] fstests: btrfs: Introduce stress test for deadlock between snapshot delete and other read-write operations

[Qu Wenruo]

[-- Attachment #1.1: Type: text/plain, Size: 3460 bytes --]



On 2019/1/11 下午1:01, Qu Wenruo wrote:
[snip]
> +# FS QA Test 179
> +#
> +# Test if btrfs will lockup at subvolume deletion when qgroups are enabled.
> +#
> +# This bug is going to be fixed by a patch for the kernel titled
> +# "btrfs: qgroup: Don't trigger backref walk at delayed ref insert time".

Although the test case is already merged, btrfs community is going to
use a much better fix than this.

Should I update the patch in this test case after the fix get merged
upstream?

Thanks,
Qu

> +#
> +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
> +
> +# remove previous $seqres.full before test
> +rm -f $seqres.full
> +
> +# real QA test starts here
> +
> +# Modify as appropriate.
> +_supported_fs btrfs
> +_supported_os Linux
> +_require_scratch
> +
> +# default sleep interval
> +sleep_time=1
> +
> +# stress test runtime
> +runtime=120
> +
> +_scratch_mkfs > /dev/null 2>&1
> +_scratch_mount
> +
> +mkdir -p "$SCRATCH_MNT/snapshots"
> +$BTRFS_UTIL_PROG subvolume create "$SCRATCH_MNT/src" > /dev/null
> +$BTRFS_UTIL_PROG quota enable "$SCRATCH_MNT" > /dev/null
> +$BTRFS_UTIL_PROG quota rescan -w "$SCRATCH_MNT" > /dev/null
> +
> +fill_workload()
> +{
> +	trap "wait; exit" SIGTERM
> +	local i=0
> +	while true; do
> +		_pwrite_byte 0xcd 0 8K "$SCRATCH_MNT/src/large_$i" > /dev/null
> +		_pwrite_byte 0xcd 0 2K "$SCRATCH_MNT/src/inline_$i" > /dev/null
> +
> +		# Randomly remove some files for every 5 loop
> +		if [ $(( $i % 5 )) -eq 0 ]; then
> +			victim=$(ls "$SCRATCH_MNT/src" | sort -R | head -n1)
> +			rm "$SCRATCH_MNT/src/$victim"
> +		fi
> +		i=$((i + 1))
> +	done
> +}
> +
> +snapshot_workload()
> +{
> +	trap "wait; exit" SIGTERM
> +	local i=0
> +	while true; do
> +		sleep $sleep_time
> +		$BTRFS_UTIL_PROG subvolume snapshot "$SCRATCH_MNT/src" \
> +			"$SCRATCH_MNT/snapshots/$i" > /dev/null
> +		i=$((i + 1))
> +	done
> +}
> +
> +delete_workload()
> +{
> +	trap "wait; exit" SIGTERM
> +	while true; do
> +		sleep $((sleep_time * 2))
> +		victim=$(ls "$SCRATCH_MNT/snapshots" | sort -R | head -n1)
> +		$BTRFS_UTIL_PROG subvolume delete \
> +			"$SCRATCH_MNT/snapshots/$victim" > /dev/null
> +	done
> +}
> +
> +fill_workload &
> +fill_pid=$!
> +
> +sleep $((sleep_time * 2))
> +snapshot_workload &
> +snapshot_pid=$!
> +delete_workload &
> +delete_pid=$!
> +
> +sleep $runtime
> +kill $fill_pid
> +wait $fill_pid
> +kill $snapshot_pid
> +wait $snapshot_pid
> +kill $delete_pid
> +wait $delete_pid
> +
> +# success, all done
> +echo "Silence is golden"
> +
> +status=0
> +exit
> diff --git a/tests/btrfs/179.out b/tests/btrfs/179.out
> new file mode 100644
> index 000000000000..cb9eba3d34b1
> --- /dev/null
> +++ b/tests/btrfs/179.out
> @@ -0,0 +1,2 @@
> +QA output created by 179
> +Silence is golden
> diff --git a/tests/btrfs/group b/tests/btrfs/group
> index 04c0254aa4bf..46dd3c9523c2 100644
> --- a/tests/btrfs/group
> +++ b/tests/btrfs/group
> @@ -181,3 +181,4 @@
>  176 auto quick swap volume
>  177 auto quick swap balance
>  178 auto quick send
> +179 auto qgroup dangerous
> 


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

Re: [PATCH v2 2/2] fstests: btrfs: Introduce stress test for deadlock between snapshot delete and other read-write operations

[Filipe Manana]

On Tue, Feb 12, 2019 at 5:14 AM Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:
>
>
>
> On 2019/1/11 下午1:01, Qu Wenruo wrote:
> [snip]
> > +# FS QA Test 179
> > +#
> > +# Test if btrfs will lockup at subvolume deletion when qgroups are enabled.
> > +#
> > +# This bug is going to be fixed by a patch for the kernel titled
> > +# "btrfs: qgroup: Don't trigger backref walk at delayed ref insert time".
>
> Although the test case is already merged, btrfs community is going to
> use a much better fix than this.
>
> Should I update the patch in this test case after the fix get merged
> upstream?

Yes please. Why shouldn't it be updated? It makes no sense to leave a
stale comment.

>
> Thanks,
> Qu
>
> > +#
> > +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
> > +
> > +# remove previous $seqres.full before test
> > +rm -f $seqres.full
> > +
> > +# real QA test starts here
> > +
> > +# Modify as appropriate.
> > +_supported_fs btrfs
> > +_supported_os Linux
> > +_require_scratch
> > +
> > +# default sleep interval
> > +sleep_time=1
> > +
> > +# stress test runtime
> > +runtime=120
> > +
> > +_scratch_mkfs > /dev/null 2>&1
> > +_scratch_mount
> > +
> > +mkdir -p "$SCRATCH_MNT/snapshots"
> > +$BTRFS_UTIL_PROG subvolume create "$SCRATCH_MNT/src" > /dev/null
> > +$BTRFS_UTIL_PROG quota enable "$SCRATCH_MNT" > /dev/null
> > +$BTRFS_UTIL_PROG quota rescan -w "$SCRATCH_MNT" > /dev/null
> > +
> > +fill_workload()
> > +{
> > +     trap "wait; exit" SIGTERM
> > +     local i=0
> > +     while true; do
> > +             _pwrite_byte 0xcd 0 8K "$SCRATCH_MNT/src/large_$i" > /dev/null
> > +             _pwrite_byte 0xcd 0 2K "$SCRATCH_MNT/src/inline_$i" > /dev/null
> > +
> > +             # Randomly remove some files for every 5 loop
> > +             if [ $(( $i % 5 )) -eq 0 ]; then
> > +                     victim=$(ls "$SCRATCH_MNT/src" | sort -R | head -n1)
> > +                     rm "$SCRATCH_MNT/src/$victim"
> > +             fi
> > +             i=$((i + 1))
> > +     done
> > +}
> > +
> > +snapshot_workload()
> > +{
> > +     trap "wait; exit" SIGTERM
> > +     local i=0
> > +     while true; do
> > +             sleep $sleep_time
> > +             $BTRFS_UTIL_PROG subvolume snapshot "$SCRATCH_MNT/src" \
> > +                     "$SCRATCH_MNT/snapshots/$i" > /dev/null
> > +             i=$((i + 1))
> > +     done
> > +}
> > +
> > +delete_workload()
> > +{
> > +     trap "wait; exit" SIGTERM
> > +     while true; do
> > +             sleep $((sleep_time * 2))
> > +             victim=$(ls "$SCRATCH_MNT/snapshots" | sort -R | head -n1)
> > +             $BTRFS_UTIL_PROG subvolume delete \
> > +                     "$SCRATCH_MNT/snapshots/$victim" > /dev/null
> > +     done
> > +}
> > +
> > +fill_workload &
> > +fill_pid=$!
> > +
> > +sleep $((sleep_time * 2))
> > +snapshot_workload &
> > +snapshot_pid=$!
> > +delete_workload &
> > +delete_pid=$!
> > +
> > +sleep $runtime
> > +kill $fill_pid
> > +wait $fill_pid
> > +kill $snapshot_pid
> > +wait $snapshot_pid
> > +kill $delete_pid
> > +wait $delete_pid
> > +
> > +# success, all done
> > +echo "Silence is golden"
> > +
> > +status=0
> > +exit
> > diff --git a/tests/btrfs/179.out b/tests/btrfs/179.out
> > new file mode 100644
> > index 000000000000..cb9eba3d34b1
> > --- /dev/null
> > +++ b/tests/btrfs/179.out
> > @@ -0,0 +1,2 @@
> > +QA output created by 179
> > +Silence is golden
> > diff --git a/tests/btrfs/group b/tests/btrfs/group
> > index 04c0254aa4bf..46dd3c9523c2 100644
> > --- a/tests/btrfs/group
> > +++ b/tests/btrfs/group
> > @@ -181,3 +181,4 @@
> >  176 auto quick swap volume
> >  177 auto quick swap balance
> >  178 auto quick send
> > +179 auto qgroup dangerous
> >
>


-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”