@@ -1,3 +1,4 @@
# SPDX-License-Identifier: GPL-2.0-only
huge_count_read_write
debugfs_target_ids_read_before_terminate_race
+debugfs_target_ids_pid_leak
@@ -3,6 +3,7 @@
TEST_GEN_FILES += huge_count_read_write
TEST_GEN_FILES += debugfs_target_ids_read_before_terminate_race
+TEST_GEN_FILES += debugfs_target_ids_pid_leak
TEST_GEN_FILES += access_memory
TEST_FILES = _chk_dependency.sh _debugfs_common.sh
@@ -11,6 +12,7 @@ TEST_PROGS += debugfs_empty_targets.sh debugfs_huge_count_read_write.sh
TEST_PROGS += debugfs_duplicate_context_creation.sh
TEST_PROGS += debugfs_rm_non_contexts.sh
TEST_PROGS += debugfs_target_ids_read_before_terminate_race.sh
+TEST_PROGS += debugfs_target_ids_pid_leak.sh
TEST_PROGS += sysfs.sh sysfs_update_removed_scheme_dir.sh
TEST_PROGS += sysfs_update_schemes_tried_regions_hang.py
TEST_PROGS += sysfs_update_schemes_tried_regions_wss_estimation.py
new file mode 100644
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Author: SeongJae Park <sj@kernel.org>
+ */
+
+#define _GNU_SOURCE
+
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#define DBGFS_TARGET_IDS "/sys/kernel/debug/damon/target_ids"
+
+static void write_targetid_exit(void)
+{
+ int target_ids_fd = open(DBGFS_TARGET_IDS, O_RDWR);
+ char pid_str[128];
+
+ snprintf(pid_str, sizeof(pid_str), "%d", getpid());
+ write(target_ids_fd, pid_str, sizeof(pid_str));
+ close(target_ids_fd);
+ exit(0);
+}
+
+unsigned long msec_timestamp(void)
+{
+ struct timeval tv;
+
+ gettimeofday(&tv, NULL);
+ return tv.tv_sec * 1000UL + tv.tv_usec / 1000;
+}
+
+int main(int argc, char *argv[])
+{
+ unsigned long start_ms;
+ int time_to_run, nr_forks = 0;
+
+ if (argc != 2) {
+ fprintf(stderr, "Usage: %s <msecs to run>\n", argv[0]);
+ exit(1);
+ }
+ time_to_run = atoi(argv[1]);
+
+ start_ms = msec_timestamp();
+ while (true) {
+ int pid = fork();
+
+ if (pid < 0) {
+ fprintf(stderr, "fork() failed\n");
+ exit(1);
+ }
+ if (pid == 0)
+ write_targetid_exit();
+ wait(NULL);
+ nr_forks++;
+
+ if (msec_timestamp() - start_ms > time_to_run)
+ break;
+ }
+ printf("%d\n", nr_forks);
+ return 0;
+}
new file mode 100755
@@ -0,0 +1,22 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+before=$(grep "^pid " /proc/slabinfo | awk '{print $2}')
+
+nr_leaks=$(./debugfs_target_ids_pid_leak 1000)
+expected_after_max=$((before + nr_leaks / 2))
+
+after=$(grep "^pid " /proc/slabinfo | awk '{print $2}')
+
+echo > /sys/kernel/debug/damon/target_ids
+
+echo "tried $nr_leaks pid leak"
+echo "number of active pid slabs: $before -> $after"
+echo "(up to $expected_after_max expected)"
+if [ $after -gt $expected_after_max ]
+then
+ echo "maybe pids are leaking"
+ exit 1
+else
+ exit 0
+fi
Commit ebb3f994dd92 ("mm/damon/dbgfs: fix 'struct pid' leaks in 'dbgfs_target_ids_write()'") fixes a pid leak bug in DAMON debugfs interface, namely dbgfs_target_ids_write() function. Add a selftest for the issue to prevent the problem from mistakenly recurring. Signed-off-by: SeongJae Park <sj@kernel.org> --- tools/testing/selftests/damon/.gitignore | 1 + tools/testing/selftests/damon/Makefile | 2 + .../damon/debugfs_target_ids_pid_leak.c | 68 +++++++++++++++++++ .../damon/debugfs_target_ids_pid_leak.sh | 22 ++++++ 4 files changed, 93 insertions(+) create mode 100644 tools/testing/selftests/damon/debugfs_target_ids_pid_leak.c create mode 100755 tools/testing/selftests/damon/debugfs_target_ids_pid_leak.sh