1 files changed, 34 insertions, 21 deletions

diff --git a/tools/testing/selftests/mm/droppable.c b/tools/testing/selftests/mm/droppable.c
index 44940f75c461..57e1b6fc5569 100644
--- a/tools/testing/selftests/mm/droppable.c
+++ b/tools/testing/selftests/mm/droppable.c
@@ -17,37 +17,50 @@
 
 int main(int argc, char *argv[])
 {
-	size_t alloc_size = 134217728;
-	size_t page_size = getpagesize();
+	const size_t alloc_size = 2 * 1024 * 1024;
+	int retry_count = 10;
+	bool dropped;
 	void *alloc;
-	pid_t child;
 
 	ksft_print_header();
 	ksft_set_plan(1);
 
 	alloc = mmap(0, alloc_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_DROPPABLE, -1, 0);
-	assert(alloc != MAP_FAILED);
-	memset(alloc, 'A', alloc_size);
-	for (size_t i = 0; i < alloc_size; i += page_size)
-		assert(*(uint8_t *)(alloc + i));
-
-	child = fork();
-	assert(child >= 0);
-	if (!child) {
-		for (;;)
-			*(char *)malloc(page_size) = 'B';
+	if (alloc == MAP_FAILED) {
+		if ((errno == EOPNOTSUPP) || (errno == EINVAL)) {
+			ksft_test_result_skip("MAP_DROPPABLE not supported\n");
+			exit(KSFT_SKIP);
+		}
+		ksft_test_result_fail("mmap error: %s\n", strerror(errno));
+		exit(KSFT_FAIL);
 	}
+	memset(alloc, 'A', alloc_size);
 
-	for (bool done = false; !done;) {
-		for (size_t i = 0; i < alloc_size; i += page_size) {
-			if (!*(uint8_t *)(alloc + i)) {
-				done = true;
-				break;
+	while (retry_count--) {
+		if (madvise(alloc, alloc_size, MADV_PAGEOUT)) {
+			if (errno == EINVAL) {
+				ksft_test_result_skip("madvise(MADV_PAGEOUT) not supported\n");
+				exit(KSFT_SKIP);
 			}
+			ksft_test_result_fail("madvise(MADV_PAGEOUT) error: %s\n", strerror(errno));
+			exit(KSFT_FAIL);
 		}
+
+		dropped = memchr(alloc, 'A', alloc_size) == NULL;
+
+		/*
+		 * Speculative reference can temporarily prevent some
+		 * pages from getting dropped. So sleep and retry.
+		 *
+		 * If a page is not droppable for 10s, something
+		 * is seriously messed up and we want to fail.
+		 */
+		if (dropped)
+			break;
+		sleep(1);
 	}
-	kill(child, SIGTERM);
 
-	ksft_test_result_pass("MAP_DROPPABLE: PASS\n");
-	exit(KSFT_PASS);
+	ksft_test_result(dropped, "madvise(MADV_PAGEOUT) behavior\n");
+
+	ksft_finished();
 }