[PATCH 1/2] selftests: mincore: fix tmpfs mincore test failure

[Baolin Wang <baolin.wang@linux.alibaba.com>]

When running mincore test cases, I encountered the following failures:

"
mincore_selftest.c:359:check_tmpfs_mmap:Expected ra_pages (511) == 0 (0)
mincore_selftest.c:360:check_tmpfs_mmap:Read-ahead pages found in memory
check_tmpfs_mmap: Test terminated by assertion
          FAIL  global.check_tmpfs_mmap
not ok 5 global.check_tmpfs_mmap
FAILED: 4 / 5 tests passed
"

The reason for the test case failure is that my system automatically enabled
tmpfs large folio allocation by adding the 'transparent_hugepage_tmpfs=always'
cmdline. However, the test case still expects the tmpfs mounted on /dev/shm to
allocate small folios, which leads to assertion failures when verifying readahead
pages.

To fix this issue, remount tmpfs to a new test directory and set the 'huge=never'
parameter to avoid allocating large folios, which can pass the test.

Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
 .../selftests/mincore/mincore_selftest.c      | 25 +++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/mincore/mincore_selftest.c b/tools/testing/selftests/mincore/mincore_selftest.c
index e949a43a6145..e8d7a3a4739f 100644
--- a/tools/testing/selftests/mincore/mincore_selftest.c
+++ b/tools/testing/selftests/mincore/mincore_selftest.c
@@ -12,6 +12,7 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <sys/mman.h>
+#include <sys/mount.h>
 #include <string.h>
 #include <fcntl.h>
 
@@ -283,7 +284,7 @@ TEST(check_file_mmap)
 	free(vec);
 }
 
-
+#define INPUT_MAX 80
 /*
  * Test mincore() behavior on a page backed by a tmpfs file.  This test
  * performs the same steps as the previous one. However, we don't expect
@@ -291,6 +292,9 @@ TEST(check_file_mmap)
  */
 TEST(check_tmpfs_mmap)
 {
+	char tmpfs_template[] = "/tmp/check_tmpfs_XXXXXX";
+	const char *tmpfs_loc = mkdtemp(tmpfs_template);
+	char testfile[INPUT_MAX];
 	unsigned char *vec;
 	int vec_size;
 	char *addr;
@@ -300,6 +304,10 @@ TEST(check_tmpfs_mmap)
 	int i;
 	int ra_pages = 0;
 
+	ASSERT_NE(NULL, tmpfs_loc) {
+		TH_LOG("Can't mkdir tmpfs dentry\n");
+	}
+
 	page_size = sysconf(_SC_PAGESIZE);
 	vec_size = FILE_SIZE / page_size;
 	if (FILE_SIZE % page_size)
@@ -311,7 +319,18 @@ TEST(check_tmpfs_mmap)
 	}
 
 	errno = 0;
-	fd = open("/dev/shm", O_TMPFILE | O_RDWR, 0600);
+	/* Do not use large folios for tmpfs mincore testing */
+	retval = mount("tmpfs", tmpfs_loc, "tmpfs", 0, "huge=never,size=4M");
+	ASSERT_EQ(0, retval) {
+		TH_LOG("Unable to mount tmpfs for testing\n");
+	}
+
+	retval = snprintf(testfile, INPUT_MAX, "%s/test_file", tmpfs_loc);
+	ASSERT_GE(INPUT_MAX, retval) {
+		TH_LOG("Unable to create a tmpfs for testing\n");
+	}
+
+	fd = open(testfile, O_CREAT|O_RDWR, 0664);
 	ASSERT_NE(-1, fd) {
 		TH_LOG("Can't create temporary file: %s",
 			strerror(errno));
@@ -363,6 +382,8 @@ TEST(check_tmpfs_mmap)
 	munmap(addr, FILE_SIZE);
 	close(fd);
 	free(vec);
+	umount(tmpfs_loc);
+	rmdir(tmpfs_loc);
 }
 
 TEST_HARNESS_MAIN
-- 
2.43.5