[LTP] Failing test on failing shell commands

[Krzysztof Kozlowski]

Hi all,

I have a failing memcg_use_hierarchy_test (in
testcases/kernel/controllers/memcg/functional/) which hits unexpected
OOM on one of earlier commands, already in the test:

 18         echo 1 > memory.use_hierarchy
 19         echo $PAGESIZE > memory.limit_in_bytes
 20 
 21         mkdir subgroup  
mkdir: cannot create directory ‘subgroup’: Cannot allocate memory
/home/ubuntu/ltp-install/testcases/bin/memcg_use_hierarchy_test.sh: 22: cd: can't cd to subgroup

The command did not fail, as there is no "set -e" and test fails later.
However there could be a case where such failure does not trigger later
issue and test is a false-positive.

What is the practice for LTP shell tests to handle kind of preparation
commands? Maybe this should be something like:

--------

diff --git a/testcases/kernel/controllers/memcg/functional/memcg_use_hierarchy_test.sh b/testcases/kernel/controllers/memcg/functional/memcg_use_hierarchy_test.sh
index 8be342499ece..f8dd8946f80b 100755
--- a/testcases/kernel/controllers/memcg/functional/memcg_use_hierarchy_test.sh
+++ b/testcases/kernel/controllers/memcg/functional/memcg_use_hierarchy_test.sh
@@ -18,8 +18,8 @@ test1()
        echo 1 > memory.use_hierarchy
        echo $PAGESIZE > memory.limit_in_bytes
 
-       mkdir subgroup
-       cd subgroup
+       EXPECT_PASS mkdir subgroup
+       EXPECT_PASS cd subgroup
        test_proc_kill $((PAGESIZE * 3)) "--mmap-lock1" $((PAGESIZE * 2)) 0
 
        cd ..

Best regards,
Krzysztof