selftests/mm: allow tests to run with no huge pages support

JIRA: https://issues.redhat.com/browse/RHEL-130531
Conflicts:
  - Missing commit 3a103b5 ("selftest: mm: Test if hugepage does not get
    leaked during bio_release_pages()"), so lack the hugetlb_dio line,
    manually applied.
  - Missing commit fc4d182 ("mm: huge_memory: enable debugfs to split
    huge pages to any order"), so removed the 'split_huge_page_test' chunk.

commit 85968b6
Author: Mark Brown <broonie@kernel.org>
Date:   Wed Feb 12 17:44:26 2025 +0000

    selftests/mm: allow tests to run with no huge pages support

    Currently the mm selftests refuse to run if huge pages are not available
    in the current system but this is an optional feature and not all the
    tests actually require them.  Change the test during startup to be
    non-fatal and skip or omit tests which actually rely on having huge pages,
    allowing the other tests to be run.

    The gup_test does support using madvise() to configure huge pages but it
    ignores the error code so we just let it run.

    Link: https://lkml.kernel.org/r/20250212-kselftest-mm-no-hugepages-v1-2-44702f538522@kernel.org
    Signed-off-by: Mark Brown <broonie@kernel.org>
    Reviewed-by: Nico Pache <npache@redhat.com>
    Cc: Mariano Pache <npache@redhat.com>
    Cc: Shuah Khan <shuah@kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Chunyu Hu <chuhu@redhat.com>

Author: Chunyu-Hu

tools/testing/selftests/mm/run_vmtests.sh

@@ -181,9 +181,10 @@ if [ -n "$freepgs" ] && [ -n "$hpgsize_KB" ]; then
 		printf "Not enough huge pages available (%d < %d)\n" \
 		       "$freepgs" "$needpgs"
 	fi
+	HAVE_HUGEPAGES=1
 else
 	echo "no hugetlbfs support in kernel?"
-	exit 1
+	HAVE_HUGEPAGES=0
 fi
 
 # filter 64bit architectures
@@ -212,22 +213,33 @@ pretty_name() {
 # Usage: run_test [test binary] [arbitrary test arguments...]
 run_test() {
 	if test_selected ${CATEGORY}; then
+		local skip=0
+
 		# On memory constrainted systems some tests can fail to allocate hugepages.
 		# perform some cleanup before the test for a higher success rate.
 		if [ ${CATEGORY} == "thp" -o ${CATEGORY} == "hugetlb" ]; then
-			echo 3 > /proc/sys/vm/drop_caches
-			sleep 2
-			echo 1 > /proc/sys/vm/compact_memory
-			sleep 2
+			if [ "${HAVE_HUGEPAGES}" = "1" ]; then
+				echo 3 > /proc/sys/vm/drop_caches
+				sleep 2
+				echo 1 > /proc/sys/vm/compact_memory
+				sleep 2
+			else
+				echo "hugepages not supported" | tap_prefix
+				skip=1
+			fi
 		fi
 
 		local test=$(pretty_name "$*")
 		local title="running $*"
 		local sep=$(echo -n "$title" | tr "[:graph:][:space:]" -)
 		printf "%s\n%s\n%s\n" "$sep" "$title" "$sep" | tap_prefix
 
-		("$@" 2>&1) | tap_prefix
-		local ret=${PIPESTATUS[0]}
+		if [ "${skip}" != "1" ]; then
+			("$@" 2>&1) | tap_prefix
+			local ret=${PIPESTATUS[0]}
+		else
+			local ret=$ksft_skip
+		fi
 		count_total=$(( count_total + 1 ))
 		if [ $ret -eq 0 ]; then
 			count_pass=$(( count_pass + 1 ))
@@ -264,13 +276,15 @@ CATEGORY="hugetlb" run_test ./hugepage-mremap
 CATEGORY="hugetlb" run_test ./hugepage-vmemmap
 CATEGORY="hugetlb" run_test ./hugetlb-madvise 
 
-nr_hugepages_tmp=$(cat /proc/sys/vm/nr_hugepages)
-# For this test, we need one and just one huge page
-echo 1 > /proc/sys/vm/nr_hugepages
-CATEGORY="hugetlb" run_test ./hugetlb_fault_after_madv
-CATEGORY="hugetlb" run_test ./hugetlb_madv_vs_map
-# Restore the previous number of huge pages, since further tests rely on it
-echo "$nr_hugepages_tmp" > /proc/sys/vm/nr_hugepages
+if [ "${HAVE_HUGEPAGES}" = "1" ]; then
+	nr_hugepages_tmp=$(cat /proc/sys/vm/nr_hugepages)
+	# For this test, we need one and just one huge page
+	echo 1 > /proc/sys/vm/nr_hugepages
+	CATEGORY="hugetlb" run_test ./hugetlb_fault_after_madv
+	CATEGORY="hugetlb" run_test ./hugetlb_madv_vs_map
+	# Restore the previous number of huge pages, since further tests rely on it
+	echo "$nr_hugepages_tmp" > /proc/sys/vm/nr_hugepages
+fi
 
 if test_selected "hugetlb"; then
 	echo "NOTE: These hugetlb tests provide minimal coverage.  Use"	  | tap_prefix
@@ -370,7 +384,9 @@ CATEGORY="madv_populate" run_test ./madv_populate
 CATEGORY="memfd_secret" run_test ./memfd_secret
 
 # KSM KSM_MERGE_TIME_HUGE_PAGES test with size of 100
-CATEGORY="ksm" run_test ./ksm_tests -H -s 100
+if [ "${HAVE_HUGEPAGES}" = "1" ]; then
+	CATEGORY="ksm" run_test ./ksm_tests -H -s 100
+fi
 # KSM KSM_MERGE_TIME test with size of 100
 CATEGORY="ksm" run_test ./ksm_tests -P -s 100
 # KSM MADV_MERGEABLE test with 10 identical pages