[PATCH] fstests/generic: cgroup aware writeback accounting test

[Brian Foster <bfoster@redhat.com>]

A test to perform reads/writes under various cgroups and verify that
I/Os are accounted properly according to cgroup aware writeback.
This is a generic test, but not all commonly used local filesystems
support cgroup aware writeback at the moment (i.e., XFS). Therefore,
this test currently requires ext4 or btrfs for the time being.

The common/cgroup2 file is copied from a separate cgroup related
patch from Shaohua Li that never made it upstream.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Shaohua Li <shli@fb.com>
---

This is a test I had lying around from previous cgawb on XFS discussions
that I never got back to finishing off. This currently passes on
ext4/btrfs, fails on upstream XFS and survives XFS with the old cgawb
enablement patch applied.

Shaohua's patch referenced in the commit log is available here[1].

Brian

[1] https://marc.info/?l=fstests&m=152175327503759&w=2

 common/cgroup2        |  15 +++++
 tests/generic/999     | 141 ++++++++++++++++++++++++++++++++++++++++++
 tests/generic/999.out |  14 +++++
 tests/generic/group   |   1 +
 4 files changed, 171 insertions(+)
 create mode 100644 common/cgroup2
 create mode 100755 tests/generic/999
 create mode 100644 tests/generic/999.out

diff --git a/common/cgroup2 b/common/cgroup2
new file mode 100644
index 00000000..f89825e2
--- /dev/null
+++ b/common/cgroup2
@@ -0,0 +1,15 @@
+# cgroup2 specific common functions
+
+export CGROUP2_PATH="${CGROUP2_PATH:-/sys/fs/cgroup}"
+
+_require_cgroup2()
+{
+	if [ ! -f "${CGROUP2_PATH}/cgroup.subtree_control" ]; then
+		_notrun "Test requires cgroup2 enabled"
+	fi
+	if [[ ! $(cat ${CGROUP2_PATH}/cgroup.controllers) =~ $1 ]]; then
+		_notrun "Cgroup2 doesn't support $1 controller $1"
+	fi
+}
+
+/bin/true
diff --git a/tests/generic/999 b/tests/generic/999
new file mode 100755
index 00000000..1664da60
--- /dev/null
+++ b/tests/generic/999
@@ -0,0 +1,141 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2019 Red Hat, Inc.  All Rights Reserved.
+#
+# FS QA Test 999
+#
+# This test verifies that cgroup aware writeback properly accounts I/Os in
+# various scenarios. We perform reads/writes from different combinations of
+# cgroups and verify that pages are accounted against the group that brought
+# them into cache.
+#
+
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+	rm -f $tmp.*
+
+	echo $$ > $cgdir/cgroup.procs
+	rmdir $cgdir/$seq-cg* > /dev/null 2>&1
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+. ./common/cgroup2
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs ext4 btrfs
+_supported_os Linux
+_require_scratch
+_require_cgroup2 io
+
+smajor=$((0x`stat -L -c %t $SCRATCH_DEV`))
+sminor=$((0x`stat -L -c %T $SCRATCH_DEV`))
+cgdir=$CGROUP2_PATH
+
+iosize=$((1024 * 1024 * 8))
+
+# Check cgroup read/write charges against expected values. Allow for some
+# tolerance as different filesystems seem to account slightly differently.
+check_cg()
+{
+	cgroot=$1
+	cgname=$(basename $cgroot)
+	expectedread=$2
+	expectedwrite=$3
+	rbytes=0
+	wbytes=0
+
+	iobytes=`cat $cgroot/io.stat | grep $smajor:$sminor`
+	if [ $? == 0 ]; then
+		rbytes=`echo $iobytes | awk '{ print $2 }' | \
+			awk -F = '{ print $2 }'`
+		wbytes=`echo $iobytes | awk '{ print $3 }' | \
+			awk -F = '{ print $2 }'`
+	fi
+
+	_within_tolerance "read" $rbytes $expectedread 5% -v
+	_within_tolerance "write" $wbytes $expectedwrite 5% -v
+}
+
+# Move current process to another cgroup.
+switch_cg()
+{
+	mkdir -p $1
+	echo $$ > $1/cgroup.procs
+}
+
+# Reset cgroup state for a new test.
+reset()
+{
+	echo $$ > $cgdir/cgroup.procs
+	rmdir $cgdir/$seq-cg* > /dev/null 2>&1
+	$XFS_IO_PROG -fc "pwrite 0 $iosize" $SCRATCH_MNT/file \
+		>> $seqres.full 2>&1
+	_scratch_cycle_mount || _fail "mount failed"
+	stat $SCRATCH_MNT/file > /dev/null
+}
+
+_scratch_mkfs >> $seqres.full 2>&1
+_scratch_mount
+
+echo "+io" > $cgdir/cgroup.subtree_control || _fail "subtree control"
+
+# Read and write from a single group.
+echo "read/write"
+reset
+switch_cg $cgdir/$seq-cg
+$XFS_IO_PROG -c "pread 0 $iosize" -c "pwrite 0 $iosize" -c fsync \
+	$SCRATCH_MNT/file >> $seqres.full 2>&1
+switch_cg $cgdir
+$XFS_IO_PROG -c fsync $SCRATCH_MNT/file
+check_cg $cgdir/$seq-cg $iosize $iosize
+
+# Write from one cgroup then read and write from a second. Writes are charged to
+# the first group and nothing to the second.
+echo "write -> read/write"
+reset
+switch_cg $cgdir/$seq-cg
+$XFS_IO_PROG -c "pwrite 0 $iosize" $SCRATCH_MNT/file >> $seqres.full 2>&1
+switch_cg $cgdir/$seq-cg-2
+$XFS_IO_PROG -c "pread 0 $iosize" -c "pwrite 0 $iosize" $SCRATCH_MNT/file \
+	>> $seqres.full 2>&1
+switch_cg $cgdir
+$XFS_IO_PROG -c fsync $SCRATCH_MNT/file
+check_cg $cgdir/$seq-cg 0 $iosize
+check_cg $cgdir/$seq-cg-2 0 0
+
+# Read from one cgroup, read & write from a second. Both reads and writes are
+# charged to the first group and nothing to the second.
+echo "read -> read/write"
+reset
+switch_cg $cgdir/$seq-cg
+$XFS_IO_PROG -c "pread 0 $iosize" $SCRATCH_MNT/file >> $seqres.full 2>&1
+switch_cg $cgdir/$seq-cg-2
+$XFS_IO_PROG -c "pread 0 $iosize" -c "pwrite 0 $iosize" $SCRATCH_MNT/file \
+	>> $seqres.full 2>&1
+switch_cg $cgdir
+$XFS_IO_PROG -c fsync $SCRATCH_MNT/file
+check_cg $cgdir/$seq-cg $iosize $iosize
+check_cg $cgdir/$seq-cg-2 0 0
+
+echo "-io" > $cgdir/cgroup.subtree_control || _fail "subtree control"
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/999.out b/tests/generic/999.out
new file mode 100644
index 00000000..d93b7089
--- /dev/null
+++ b/tests/generic/999.out
@@ -0,0 +1,14 @@
+QA output created by 999
+read/write
+read is in range
+write is in range
+write -> read/write
+read is in range
+write is in range
+read is in range
+write is in range
+read -> read/write
+read is in range
+write is in range
+read is in range
+write is in range
diff --git a/tests/generic/group b/tests/generic/group
index cfd003d3..9d7d7613 100644
--- a/tests/generic/group
+++ b/tests/generic/group
@@ -528,3 +528,4 @@
 523 auto quick attr
 524 auto quick
 525 auto quick rw
+999 auto quick
-- 
2.17.2