selftests/mm: pagemap_scan ioctl: add PFN ZERO test cases

Add test cases to test the correctness of PFN ZERO flag of pagemap_scan
ioctl.  Test with normal pages backed memory and huge pages backed memory.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Muhammad Usama Anjum <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Muhammad Usama Anjum <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 23 insertions, 0 deletions

diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index 1d434772fa54..9dafa7669ef9 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c
@@ -532,3 +532,26 @@ void *sys_mremap(void *old_address, unsigned long old_size,
 			       old_size, new_size, flags,
 			       (unsigned long)new_address);
 }
+
+bool detect_huge_zeropage(void)
+{
+	int fd = open("/sys/kernel/mm/transparent_hugepage/use_zero_page",
+		      O_RDONLY);
+	bool enabled = 0;
+	char buf[15];
+	int ret;
+
+	if (fd < 0)
+		return 0;
+
+	ret = pread(fd, buf, sizeof(buf), 0);
+	if (ret > 0 && ret < sizeof(buf)) {
+		buf[ret] = 0;
+
+		if (strtoul(buf, NULL, 10) == 1)
+			enabled = 1;
+	}
+
+	close(fd);
+	return enabled;
+}