[LTP] [PATCH] controllers: detect previous test failure on cgroup mounts

[Krzysztof Kozlowski]

The failure of memcg_stress_test.sh cleanup went unnoticed (except
echo message) and caused further cgroup_fj and memcg_control_test
failures because of unclean cgroups. Flow is usually like:

1. memcg_stress_test succeeds but actually the /dev/memcg was not
   cleaned up. Notice lack of any error message due to 2>/dev/null.

     memcg_stress_test 1 TINFO: Testing 150 cgroups, using 1273 MB, interval 5
     memcg_stress_test 1 TINFO: Starting cgroups
     memcg_stress_test 1 TINFO: Testing cgroups for 900s
     memcg_stress_test 1 TINFO: Killing groups
     tag=memcg_stress stime=1626770787 dur=903 exit=exited stat=2 core=no cu=19 cs=12

2. memcg_control_test has false-positive. It succeeds but actually no
   test was done due to /dev/memcg pollution from previous test:

     mkdir: cannot create directory ‘/tmp/ltp-q8DjShPJeB/mnt/1’: File exists
     memcg_control    0  TINFO  :  Test #1: Checking if the memory usage limit imposed by the topmost group is enforced
     sh: echo: I/O error
     /opt/ltp/testcases/bin/memcg_control_test.sh: 86: /opt/ltp/testcases/bin/memcg_control_test.sh: cannot create /tmp/ltp-q8DjShPJeB/mnt/1/memory.memsw.limit_in_bytes:
     Permission denied
     rmdir: failed to remove 'sub': Device or resource busy
     rmdir: failed to remove '/tmp/ltp-q8DjShPJeB/mnt/1': Device or resource busy
     memcg_control    1  TPASS  :  memcg_control: passed
     tag=memcg_control stime=1626771695 dur=6 exit=exited stat=0 core=no cu=2 cs=1

3. cgroup_fj_function2_memory fails with a cryptic message of mounting a
   path with new line (because /dev/memcg was not cleaned up before):

     cgroup_fj_function2_memory 1 TINFO: Subsystem memory is mounted at /sys/fs/cgroup/memory
     /dev/memcg
     mkdir: cannot create directory ‘/sys/fs/cgroup/memory’: File exists
     cgroup_fj_function2_memory 1 TBROK: mkdir /sys/fs/cgroup/memory
     /dev/memcg/ltp failed
     cgroup_fj_function2_memory 1 TINFO: Removing all ltp subgroups...
     find: ‘/sys/fs/cgroup/memory\n/dev/memcg/ltp/’: No such file or directory

The actual failure was in memcg_stress_test executed before other tests,
however it went unnoticed.  Debugging such failures is difficult as
result of failing test depends on running another which did not fail.
Instead, detect unclean cgroups mounts and explicitly test it.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
---
 .../kernel/controllers/cgroup_fj/cgroup_fj_common.sh   |  4 ++--
 .../controllers/memcg/control/memcg_control_test.sh    | 10 ++++++----
 .../controllers/memcg/stress/memcg_stress_test.sh      |  8 ++++----
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/testcases/kernel/controllers/cgroup_fj/cgroup_fj_common.sh b/testcases/kernel/controllers/cgroup_fj/cgroup_fj_common.sh
index 5594fe9de426..53ab637e8910 100755
--- a/testcases/kernel/controllers/cgroup_fj/cgroup_fj_common.sh
+++ b/testcases/kernel/controllers/cgroup_fj/cgroup_fj_common.sh
@@ -123,10 +123,10 @@ cleanup()
     fi
 
     if grep -q "$mount_point" /proc/mounts; then
-        umount "$mount_point"
+        EXPECT_PASS umount "$mount_point"
     fi
 
     if [ -e "$mount_point" ]; then
-        rmdir "$mount_point"
+        EXPECT_PASS rmdir "$mount_point"
     fi
 }
diff --git a/testcases/kernel/controllers/memcg/control/memcg_control_test.sh b/testcases/kernel/controllers/memcg/control/memcg_control_test.sh
index 4d9f1bb5d586..626f5e676831 100644
--- a/testcases/kernel/controllers/memcg/control/memcg_control_test.sh
+++ b/testcases/kernel/controllers/memcg/control/memcg_control_test.sh
@@ -53,6 +53,8 @@ STATUS_PIPE="$TMP/status_pipe"
 PASS=0
 FAIL=1
 
+. test.sh
+
 # Check if the test process is killed on crossing boundary
 test_proc_kill()
 {
@@ -118,8 +120,8 @@ result()
 cleanup()
 {
 	if [ -e $TST_PATH/mnt ]; then
-		umount $TST_PATH/mnt 2> /dev/null
-		rm -rf $TST_PATH/mnt
+		EXPECT_PASS umount $TST_PATH/mnt
+		EXPECT_PASS rm -rf $TST_PATH/mnt
 	fi
 }
 
@@ -127,8 +129,8 @@ do_mount()
 {
 	cleanup
 
-	mkdir $TST_PATH/mnt
-	mount -t cgroup -o memory cgroup $TST_PATH/mnt 2> /dev/null
+	EXPECT_PASS mkdir $TST_PATH/mnt
+	EXPECT_PASS mount -t cgroup -o memory cgroup $TST_PATH/mnt 2> /dev/null
 	if [ $? -ne 0 ]; then
 		tst_brkm TBROK NULL "Mounting cgroup to temp dir failed"
 		rmdir $TST_PATH/mnt
diff --git a/testcases/kernel/controllers/memcg/stress/memcg_stress_test.sh b/testcases/kernel/controllers/memcg/stress/memcg_stress_test.sh
index c2501e164018..8f7a0eb9dc37 100755
--- a/testcases/kernel/controllers/memcg/stress/memcg_stress_test.sh
+++ b/testcases/kernel/controllers/memcg/stress/memcg_stress_test.sh
@@ -44,8 +44,8 @@ setup()
 cleanup()
 {
 	if [ -e /dev/memcg ]; then
-		umount /dev/memcg 2> /dev/null
-		rmdir /dev/memcg 2> /dev/null
+		EXPECT_PASS umount /dev/memcg
+		EXPECT_PASS rmdir /dev/memcg
 	fi
 }
 
@@ -53,8 +53,8 @@ do_mount()
 {
 	cleanup
 
-	mkdir /dev/memcg 2> /dev/null
-	mount -t cgroup -omemory memcg /dev/memcg
+	EXPECT_PASS mkdir /dev/memcg
+	EXPECT_PASS mount -t cgroup -omemory memcg /dev/memcg
 }
 
 # $1 Number of cgroups
-- 
2.27.0