* Aboorva Devarajan <aboor...@linux.ibm.com> [250616 12:07]:
> From: Donet Tom <donet...@linux.ibm.com>
>
> This patch fixed 2 issues.
>
> 1)After fork() in test_prctl_fork, the child process uses the file
> descriptors from the parent process to read ksm_stat and
> ksm_merging_pages. This results in incorrect values being read (parent
> process ksm_stat and ksm_merge_pages will be read in child), causing
> the test to fail.
>
> This patch calls init_global_file_handles() in the child process to
> ensure that the current process's file descriptors are used to read
> ksm_stat and ksm_merging_pages.
>
> 2) All tests currently call ksm_merge to trigger page merging.
> To ensure the system remains in a consistent state for subsequent
> tests, it is better to call ksm_unmerge during the test cleanup phase
>
> In the test_prctl_fork test, after a fork(), reading ksm_merging_pages
> in the child process returns a non-zero value because a previous test
> performed a merge, and the child's memory state is inherited from the
> parent.
>
> Although the child process calls ksm_unmerge, the ksm_merging_pages
> counter in the parent is reset to zero, while the child's counter
> remains unchanged. This discrepancy causes the test to fail.
>
> To avoid this issue, each test should call ksm_unmerge during cleanup
> to ensure the counter is reset and the system is in a clean state for
> subsequent tests.
>
Fixes: ?
> Signed-off-by: Donet Tom <donet...@linux.ibm.com>
> Signed-off-by: Aboorva Devarajan <aboor...@linux.ibm.com>
> ---
> tools/testing/selftests/mm/ksm_functional_tests.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c
> b/tools/testing/selftests/mm/ksm_functional_tests.c
> index b61803e36d1c..d7d3c22c077a 100644
> --- a/tools/testing/selftests/mm/ksm_functional_tests.c
> +++ b/tools/testing/selftests/mm/ksm_functional_tests.c
> @@ -46,6 +46,8 @@ static int ksm_use_zero_pages_fd;
> static int pagemap_fd;
> static size_t pagesize;
>
> +static void init_global_file_handles(void);
> +
> static bool range_maps_duplicates(char *addr, unsigned long size)
> {
> unsigned long offs_a, offs_b, pfn_a, pfn_b;
> @@ -274,6 +276,7 @@ static void test_unmerge(void)
> ksft_test_result(!range_maps_duplicates(map, size),
> "Pages were unmerged\n");
> unmap:
> + ksm_unmerge();
> munmap(map, size);
> }
>
> @@ -338,6 +341,7 @@ static void test_unmerge_zero_pages(void)
> ksft_test_result(!range_maps_duplicates(map, size),
> "KSM zero pages were unmerged\n");
> unmap:
> + ksm_unmerge();
> munmap(map, size);
> }
>
> @@ -366,6 +370,7 @@ static void test_unmerge_discarded(void)
> ksft_test_result(!range_maps_duplicates(map, size),
> "Pages were unmerged\n");
> unmap:
> + ksm_unmerge();
> munmap(map, size);
> }
>
> @@ -428,6 +433,7 @@ static void test_unmerge_uffd_wp(void)
> close_uffd:
> close(uffd);
> unmap:
> + ksm_unmerge();
> munmap(map, size);
> }
> #endif
> @@ -491,6 +497,7 @@ static int test_child_ksm(void)
> else if (map == MAP_MERGE_SKIP)
> return -3;
>
> + ksm_unmerge();
> munmap(map, size);
> return 0;
> }
> @@ -524,6 +531,7 @@ static void test_prctl_fork(void)
>
> child_pid = fork();
> if (!child_pid) {
> + init_global_file_handles();
> exit(test_child_ksm());
> } else if (child_pid < 0) {
> ksft_test_result_fail("fork() failed\n");
> @@ -620,6 +628,7 @@ static void test_prctl_unmerge(void)
> ksft_test_result(!range_maps_duplicates(map, size),
> "Pages were unmerged\n");
> unmap:
> + ksm_unmerge();
> munmap(map, size);
> }
>
> @@ -653,6 +662,7 @@ static void test_prot_none(void)
> ksft_test_result(!range_maps_duplicates(map, size),
> "Pages were unmerged\n");
> unmap:
> + ksm_unmerge();
> munmap(map, size);
> }
>
> --
> 2.43.5
>
>
