[PATCH 6.1 170/197] selftests/mm: ksm_tests should only MADV_HUGEPAGE valid memory

Greg Kroah-Hartman
2024-02-20T21:08:22Z

From: Ryan Roberts <ryan.roberts@arm.com>

[ Upstream commit d021b442cf312664811783e92b3d5e4548e92a53 ]

ksm_tests was previously mmapping a region of memory, aligning the
returned pointer to a PMD boundary, then setting MADV_HUGEPAGE, but was
setting it past the end of the mmapped area due to not taking the pointer
alignment into consideration. Fix this behaviour.

Up until commit efa7df3e3bb5 ("mm: align larger anonymous mappings on THP
boundaries"), this buggy behavior was (usually) masked because the
alignment difference was always less than PMD-size. But since the
mentioned commit, `ksm_tests -H -s 100` started failing.

Link: https://lkml.kernel.org/r/20240122120554.3108022-1-ryan.roberts@arm.com
Fixes: 325254899684 ("selftests: vm: add KSM huge pages merging time test")
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: Pedro Demarchi Gomes <pedrodemargomes@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/testing/selftests/vm/ksm_tests.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
index 0d85be2350fa..a81165930785 100644
--- a/tools/testing/selftests/vm/ksm_tests.c
+++ b/tools/testing/selftests/vm/ksm_tests.c
@@ -470,7 +470,7 @@ static int ksm_merge_hugepages_time(int mapping, int prot, int timeout, size_t m
if (map_ptr_orig == MAP_FAILED)
err(2, "initial mmap");

- if (madvise(map_ptr, len + HPAGE_SIZE, MADV_HUGEPAGE))
+ if (madvise(map_ptr, len, MADV_HUGEPAGE))
err(2, "MADV_HUGEPAGE");

pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
--
2.43.0