linux-kernel - [PATCH 1/2] selftests/mm: fix hugepages cleanup too early

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Message-ID: <20250827075209.2347015-2-chuhu@redhat.com>
Date: Wed, 27 Aug 2025 15:52:08 +0800
From: Chunyu Hu <chuhu@...hat.com>
To: akpm@...ux-foundation.org,
	david@...hat.com,
	shuah@...nel.org,
	linux-mm@...ck.org
Cc: linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lorenzo.stoakes@...cle.com,
	Liam.Howlett@...cle.com,
	vbabka@...e.cz,
	rppt@...nel.org,
	surenb@...gle.com,
	mhocko@...e.com,
	chuhu@...hat.com
Subject: [PATCH 1/2] selftests/mm: fix hugepages cleanup too early

The nr_hugepgs variable is used to keep the original nr_hugepages at the
hugepage setup step at test beginning. After userfaultfd test, a cleaup is
executed, both /sys/kernel/mm/hugepages/hugepages-*/nr_hugepages and
/proc/sys//vm/nr_hugepages are reset to 'original' value before userfaultfd
test starts.

Issue here is the value used to restore /proc/sys/vm/nr_hugepages is
nr_hugepgs which is the initial value before the vm_runtests.sh runs, not
the value before userfaultfd test starts. 'va_high_addr_swith.sh' tests
runs after that will possibly see no hugepages available for test, and got
EINVAL when mmap(HUGETLB), making the result invalid.

And before pkey tests, nr_hugepgs is changed to be used as a temp variable
to save nr_hugepages before pkey test, and restore it after pkey tests
finish. The original nr_hugepages value is not tracked anymore, so no way
to restore it after all tests finish.

Add a new variable nr_hugepgs_origin to save the original nr_hugepages, and
and restore it to nr_hugepages after all tests finish. And change to use
the nr_hugepgs variable to save the /proc/sys/vm/nr_hugeages after hugepage
setup, it's also the value before userfaultfd test starts, and the correct
value to be restored after userfaultfd finishes. The va_high_addr_switch.sh
broken will be resolved.

Signed-off-by: Chunyu Hu <chuhu@...hat.com>
---
 tools/testing/selftests/mm/run_vmtests.sh | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index 471e539d82b8..f1a7ad3ec6a7 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -172,13 +172,13 @@ fi

 # set proper nr_hugepages
 if [ -n "$freepgs" ] && [ -n "$hpgsize_KB" ]; then
-	nr_hugepgs=$(cat /proc/sys/vm/nr_hugepages)
+	nr_hugepgs_origin=$(cat /proc/sys/vm/nr_hugepages)
 	needpgs=$((needmem_KB / hpgsize_KB))
 	tries=2
 	while [ "$tries" -gt 0 ] && [ "$freepgs" -lt "$needpgs" ]; do
 		lackpgs=$((needpgs - freepgs))
 		echo 3 > /proc/sys/vm/drop_caches
-		if ! echo $((lackpgs + nr_hugepgs)) > /proc/sys/vm/nr_hugepages; then
+		if ! echo $((lackpgs + nr_hugepgs_origin)) > /proc/sys/vm/nr_hugepages; then
 			echo "Please run this test as root"
 			exit $ksft_skip
 		fi
@@ -189,6 +189,7 @@ if [ -n "$freepgs" ] && [ -n "$hpgsize_KB" ]; then
 		done < /proc/meminfo
 		tries=$((tries - 1))
 	done
+	nr_hugepgs=$(cat /proc/sys/vm/nr_hugepages)
 	if [ "$freepgs" -lt "$needpgs" ]; then
 		printf "Not enough huge pages available (%d < %d)\n" \
 		       "$freepgs" "$needpgs"
@@ -532,6 +533,10 @@ CATEGORY="page_frag" run_test ./test_page_frag.sh aligned

 CATEGORY="page_frag" run_test ./test_page_frag.sh nonaligned

+if [ "${HAVE_HUGEPAGES}" = 1 ]; then
+	echo "$nr_hugepgs_origin" > /proc/sys/vm/nr_hugepages
+fi
+
 echo "SUMMARY: PASS=${count_pass} SKIP=${count_skip} FAIL=${count_fail}" | tap_prefix
 echo "1..${count_total}" | tap_output

-- 
2.49.0