mm, selftests: test return value of munmap for MAP_HUGETLB memory

When MAP_HUGETLB memory is unmapped, the length must be hugepage aligned,
otherwise it fails with -EINVAL.

All tests currently behave correctly, but it's better to explcitly test
the return value for completeness and document the requirement, especially
if users copy map_hugetlb.c as a sample implementation.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Joern Engel <joern@logfs.org>
Cc: Jianguo Wu <wujianguo@huawei.com>
Cc: Eric B Munson <emunson@akamai.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 14 insertions, 4 deletions

diff --git a/tools/testing/selftests/powerpc/mm/hugetlb_vs_thp_test.c b/tools/testing/selftests/powerpc/mm/hugetlb_vs_thp_test.c
index 3d8e5b033e1d..49003674de4f 100644
--- a/tools/testing/selftests/powerpc/mm/hugetlb_vs_thp_test.c
+++ b/tools/testing/selftests/powerpc/mm/hugetlb_vs_thp_test.c
@@ -21,9 +21,13 @@ static int test_body(void)
                  * Typically the mmap will fail because no huge pages are
                  * allocated on the system. But if there are huge pages
                  * allocated the mmap will succeed. That's fine too, we just
-                 * munmap here before continuing.
+                 * munmap here before continuing.  munmap() length of
+                 * MAP_HUGETLB memory must be hugepage aligned.
                  */
-                munmap(addr, SIZE);
+                if (munmap(addr, SIZE)) {
+                        perror("munmap");
+                        return 1;
+                }
         }
 
         p = mmap(addr, SIZE, PROT_READ | PROT_WRITE,
diff --git a/tools/testing/selftests/vm/hugetlbfstest.c b/tools/testing/selftests/vm/hugetlbfstest.c
index ea40ff8c2391..02e1072ec187 100644
--- a/tools/testing/selftests/vm/hugetlbfstest.c
+++ b/tools/testing/selftests/vm/hugetlbfstest.c
@@ -34,6 +34,7 @@ static void do_mmap(int fd, int extra_flags, int unmap)
         int *p;
         int flags = MAP_PRIVATE | MAP_POPULATE | extra_flags;
         u64 before, after;
+        int ret;
 
         before = read_rss();
         p = mmap(NULL, length, PROT_READ | PROT_WRITE, flags, fd, 0);
@@ -44,7 +45,8 @@ static void do_mmap(int fd, int extra_flags, int unmap)
                         !"rss didn't grow as expected");
         if (!unmap)
                 return;
-        munmap(p, length);
+        ret = munmap(p, length);
+        assert(!ret || !"munmap returned an unexpected error");
         after = read_rss();
         assert(llabs(after - before) < 0x40000 ||
                         !"rss didn't shrink as expected");
diff --git a/tools/testing/selftests/vm/map_hugetlb.c b/tools/testing/selftests/vm/map_hugetlb.c
index ac56639dd4a9..addcd6fc1ecc 100644
--- a/tools/testing/selftests/vm/map_hugetlb.c
+++ b/tools/testing/selftests/vm/map_hugetlb.c
@@ -73,7 +73,11 @@ int main(void)
         write_bytes(addr);
         ret = read_bytes(addr);
 
-        munmap(addr, LENGTH);
+        /* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
+        if (munmap(addr, LENGTH)) {
+                perror("munmap");
+                exit(1);
+        }
 
         return ret;
 }