Re: [PATCH v1 2/3] selftests/ksm: ksm_functional_tests: add prctl unmerge test

Stefan Roesch
2023-04-20T21:31:41Z

David Hildenbrand <david@redhat.com> writes:

> Let's test whether setting PR_SET_MEMORY_MERGE to 0 after setting it to
> 1 will unmerge pages, similar to how setting MADV_UNMERGEABLE after setting
> MADV_MERGEABLE would.
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> .../selftests/mm/ksm_functional_tests.c | 46 ++++++++++++++++---
> 1 file changed, 40 insertions(+), 6 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c
> index 7bc9fc17c9f0..26853badae70 100644
> --- a/tools/testing/selftests/mm/ksm_functional_tests.c
> +++ b/tools/testing/selftests/mm/ksm_functional_tests.c
> @@ -91,9 +91,10 @@ static int ksm_merge(void)
> return 0;
> }
>
> -static char *mmap_and_merge_range(char val, unsigned long size)
> +static char *mmap_and_merge_range(char val, unsigned long size, bool use_prctl)
> {
> char *map;
> + int ret;
>
> map = mmap(NULL, size, PROT_READ|PROT_WRITE,
> MAP_PRIVATE|MAP_ANON, -1, 0);
> @@ -110,7 +111,17 @@ static char *mmap_and_merge_range(char val, unsigned long size)
>
> /* Make sure each page contains the same values to merge them. */
> memset(map, val, size);
> - if (madvise(map, size, MADV_MERGEABLE)) {
> +
> + if (use_prctl) {
> + ret = prctl(PR_SET_MEMORY_MERGE, 1, 0, 0, 0);
> + if (ret < 0 && errno == EINVAL) {
> + ksft_test_result_skip("PR_SET_MEMORY_MERGE not supported\n");
> + goto unmap;
> + } else if (ret) {
> + ksft_test_result_fail("PR_SET_MEMORY_MERGE=1 failed\n");
> + goto unmap;
> + }
> + } else if (madvise(map, size, MADV_MERGEABLE)) {
> ksft_test_result_fail("MADV_MERGEABLE failed\n");
> goto unmap;
> }
> @@ -133,7 +144,7 @@ static void test_unmerge(void)
>
> ksft_print_msg("[RUN] %s\n", __func__);
>
> - map = mmap_and_merge_range(0xcf, size);
> + map = mmap_and_merge_range(0xcf, size, false);
> if (map == MAP_FAILED)
> return;
>
> @@ -155,7 +166,7 @@ static void test_unmerge_discarded(void)
>
> ksft_print_msg("[RUN] %s\n", __func__);
>
> - map = mmap_and_merge_range(0xcf, size);
> + map = mmap_and_merge_range(0xcf, size, false);
> if (map == MAP_FAILED)
> return;
>
> @@ -187,7 +198,7 @@ static void test_unmerge_uffd_wp(void)
>
> ksft_print_msg("[RUN] %s\n", __func__);
>
> - map = mmap_and_merge_range(0xcf, size);
> + map = mmap_and_merge_range(0xcf, size, false);
> if (map == MAP_FAILED)
> return;
>
> @@ -323,9 +334,31 @@ static void test_prctl_fork(void)
> ksft_test_result_pass("PR_SET_MEMORY_MERGE value is inherited\n");
> }
>
> +static void test_prctl_unmerge(void)
> +{
> + const unsigned int size = 2 * MiB;
> + char *map;
> +
> + ksft_print_msg("[RUN] %s\n", __func__);
> +
> + map = mmap_and_merge_range(0xcf, size, true);
> + if (map == MAP_FAILED)
> + return;
> +
> + if (prctl(PR_SET_MEMORY_MERGE, 0, 0, 0, 0)) {
> + ksft_test_result_fail("PR_SET_MEMORY_MERGE=0 failed\n");
> + goto unmap;
> + }
> +
> + ksft_test_result(!range_maps_duplicates(map, size),
> + "Pages were unmerged\n");
> +unmap:
> + munmap(map, size);
> +}
> +
> int main(int argc, char **argv)
> {
> - unsigned int tests = 4;
> + unsigned int tests = 5;
> int err;
>
> #ifdef __NR_userfaultfd
> @@ -355,6 +388,7 @@ int main(int argc, char **argv)
>
> test_prctl();
> test_prctl_fork();
> + test_prctl_unmerge();
>
> err = ksft_get_fail_cnt();
> if (err)

Acked-by: Stefan Roesch <shr@devkernel.io>