From: Donet Tom donettom@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.
Signed-off-by: Donet Tom donettom@linux.ibm.com Signed-off-by: Aboorva Devarajan aboorvad@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); }