The hugepage-mremap selftest uses a default mapping size of 10MB
when no argument is provided. This size is not guaranteed to be
aligned to the system hugepage size, which can cause munmap() to fail
and mremap() to succeed where a failure is expected.

Align the mapping length to the runtime hugepage size using
default_huge_page_size() to ensure the mapping is properly
aligned. Also handle the case where
default_huge_page_size() returns 0 by skipping the test.

Before patch:
  running ./hugepage-mremap
  ------------------------------
  TAP version 13
  1..1
  Map haddr: Returned address is 0x7eaa40000000
  Map daddr: Returned address is 0x7daa40000000
  Map vaddr: Returned address is 0x7faa40000000
  Address returned by mmap() = 0x7fffaa600000
  Mremap: Returned address is 0x7faa40000000
  First hex is 0
  First hex is 3020100
  Bail out! mremap: Expected failure, but call succeeded
  Planned tests != run tests (1 != 0)
  Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
  [FAIL]
not ok 1 hugepage-mremap # exit=1

After patch:
  running ./hugepage-mremap
  -------------------------
  TAP version 13
  1..1
  Map haddr: Returned address is 0x7eaa40000000
  Map daddr: Returned address is 0x7daa40000000
  Map vaddr: Returned address is 0x7faa40000000
  Address returned by mmap() = 0x7fff13000000
  Mremap: Returned address is 0x7faa40000000
  First hex is 0
  First hex is 3020100
  ok 1 Read same data
  Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
  [PASS]
ok 1 hugepage-mremap

Fixes: f77a286de48c ("mm, hugepages: make memory size variable in hugepage-mremap selftest")
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
---
 tools/testing/selftests/mm/hugepage-mremap.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/testing/selftests/mm/hugepage-mremap.c b/tools/testing/selftests/mm/hugepage-mremap.c
index b8f7d92e5a35..f66e4d806477 100644
--- a/tools/testing/selftests/mm/hugepage-mremap.c
+++ b/tools/testing/selftests/mm/hugepage-mremap.c
@@ -32,6 +32,7 @@
 
 #define PROTECTION (PROT_READ | PROT_WRITE | PROT_EXEC)
 #define FLAGS (MAP_SHARED | MAP_ANONYMOUS)
+#define ALIGN(x, a) (((x) + ((a) - 1)) & ~((a) - 1))
 
 static void check_bytes(char *addr)
 {
@@ -110,6 +111,7 @@ int main(int argc, char *argv[])
 {
 	size_t length = 0;
 	int ret = 0, fd;
+	size_t hpage_size;
 
 	ksft_print_header();
 	ksft_set_plan(1);
@@ -126,6 +128,14 @@ int main(int argc, char *argv[])
 		length = DEFAULT_LENGTH_MB;
 
 	length = MB_TO_BYTES(length);
+
+	hpage_size = default_huge_page_size();
+	if (!hpage_size)
+		ksft_exit_skip("Unable to determine huge page size\n");
+
+	/* Ensure length is hugepage aligned */
+	length = ALIGN(length, hpage_size);
+
 	fd = memfd_create(argv[0], MFD_HUGETLB);
 	if (fd < 0)
 		ksft_exit_fail_msg("Open failed: %s\n", strerror(errno));
-- 
2.52.0