selftests: memfd: return Kselftest Skip code for skipped tests

When memfd test is skipped because of unmet dependencies and/or unsupported configuration, it returns non-zero value which is treated as a fail by the Kselftest framework. This leads to false negative result even when the test could not be run.

Change it to return kselftest skip code when a test gets skipped to clearly report that the test could not be run.

Added an explicit check for root user at the start of memfd hugetlbfs test and return skip code if a non-root user attempts to run it.

In addition, return skip code when not enough huge pages are available to run the test.

Kselftest framework SKIP code is 4 and the framework prints appropriate messages to indicate that the test is skipped.

Signed-off-by Shuah Khan (Samsung OSG) <shuah at kernel.org>

---

Changes since v1:
-- addressed review comments on v1
-- Fixed a regression in v1 that changed the behavior to require root
for all tests not just the hugetlbfs test.

 tools/testing/selftests/memfd/run_tests.sh | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

tools/testing/selftests/memfd/run_tests.sh +8 -4

index c2d41ed81b24..2013f195e623 100755
@@ -1,6 +1,9 @@
 #!/bin/bash
 # please run as root
 
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
 #
 # Normal tests requiring no special resources
 #

@@ -29,12 +32,13 @@ if [ -n "$freepgs" ] && [ $freepgs -lt $hpages_test ]; then
 	nr_hugepgs=`cat /proc/sys/vm/nr_hugepages`
 	hpages_needed=`expr $hpages_test - $freepgs`
 
+	if [ $UID != 0 ]; then
+		echo "Please run memfd with hugetlbfs test as root"
+		exit $ksft_skip
+	fi
+
 	echo 3 > /proc/sys/vm/drop_caches
 	echo $(( $hpages_needed + $nr_hugepgs )) > /proc/sys/vm/nr_hugepages
-	if [ $? -ne 0 ]; then
-		echo "Please run this test as root"
-		exit 1
-	fi
 	while read name size unit; do
 		if [ "$name" = "HugePages_Free:" ]; then
 			freepgs=$size