[PATCH] xfstests: add a CGROUP configuration option

[Josef Bacik <josef@toxicpanda.com>]

I want to add some extended statistic gathering for xfstests, but it's
tricky to isolate xfstests from the rest of the host applications.  The
most straightforward way to do this is to run every test inside of it's
own cgroup.  From there we can monitor the activity of tasks in the
specific cgroup using BPF.

The support for this is pretty simple, allow users to specify
CGROUP=/path/to/cgroup.  We will create the path if it doesn't already
exist, and validate we can add things to cgroup.procs.  If we cannot
it'll be disabled, otherwise we will use this when we do _run_seq by
echo'ing the bash pid into cgroup.procs, which will cause any children
to run under that cgroup.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 README |  3 +++
 check  | 17 ++++++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/README b/README
index 593c1052..722dc170 100644
--- a/README
+++ b/README
@@ -102,6 +102,9 @@ Preparing system for tests:
              - set USE_KMEMLEAK=yes to scan for memory leaks in the kernel
                after every test, if the kernel supports kmemleak.
              - set KEEP_DMESG=yes to keep dmesg log after test
+             - set CGROUP=/path/to/cgroup to create a cgroup to run tests inside
+               of.  The main check will run outside of the cgroup, only the test
+               itself and any child processes will run under the cgroup.
 
         - or add a case to the switch in common/config assigning
           these variables based on the hostname of your test
diff --git a/check b/check
index 2e148e57..07a0e251 100755
--- a/check
+++ b/check
@@ -509,11 +509,23 @@ _expunge_test()
 OOM_SCORE_ADJ="/proc/self/oom_score_adj"
 test -w ${OOM_SCORE_ADJ} && echo -1000 > ${OOM_SCORE_ADJ}
 
+# Initialize the cgroup path if it doesn't already exist
+if [ ! -z "$CGROUP" ]; then
+	mkdir -p ${CGROUP}
+
+	# If we can't write to cgroup.procs then unset cgroup
+	test -w ${CGROUP}/cgroup.procs || unset CGROUP
+fi
+
 # ...and make the tests themselves somewhat more attractive to it, so that if
 # the system runs out of memory it'll be the test that gets killed and not the
 # test framework.
 _run_seq() {
-	bash -c "test -w ${OOM_SCORE_ADJ} && echo 250 > ${OOM_SCORE_ADJ}; exec ./$seq"
+	_extra="test -w ${OOM_SCORE_ADJ} && echo 250 > ${OOM_SCORE_ADJ};"
+	if [ ! -z "$CGROUP" ]; then
+		_extra+="echo $$ > ${CGROUP}/cgroup.procs;"
+	fi
+	bash -c "${_extra} exec ./$seq"
 }
 
 _detect_kmemleak
@@ -615,6 +627,9 @@ for section in $HOST_OPTIONS_SECTIONS; do
 	  echo "MKFS_OPTIONS  -- `_scratch_mkfs_options`"
 	  echo "MOUNT_OPTIONS -- `_scratch_mount_options`"
 	fi
+	if [ ! -z "$CGROUP" ]; then
+	  echo "CGROUP        -- ${CGROUP}"
+	fi
 	echo
 	needwrap=true
 
-- 
2.24.1