selftest: add testing unsharing and counting ksm zero page

Add a function test_unmerge_zero_page() to test the functionality on
unsharing and counting ksm-placed zero pages and counting of this patch
series.

test_unmerge_zero_page() actually contains three subjct test objects:
	1) whether the count of ksm zero page can react correctly to cow
	   (copy on write);
	2) whether the count of ksm zero page can react correctly to unmerge;
	3) whether ksm zero pages are really unmerged.

Link: https://lkml.kernel.org/r/202212300918477352037@zte.com.cn
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Reviewed-by: Xiaokai Ran <ran.xiaokai@zte.com.cn>
Reviewed-by: Yang Yang <yang.yang29@zte.com.cn>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Xuexin Jiang <jiang.xuexin@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c b/tools/testing/selftests/mm/ksm_functional_tests.c
index d8b5b49304121ef06bd9ebcd03feb3b3e9e5afa4..6acbd08e73e7bbd75f84e4cd6c05ba0b67bac051 100644 (file)
--- a/tools/testing/selftests/mm/ksm_functional_tests.c
+++ b/tools/testing/selftests/mm/ksm_functional_tests.c
@@ -27,6 +27,8 @@
 
 static int ksm_fd;
 static int ksm_full_scans_fd;
+static int ksm_zero_pages_fd;
+static int ksm_use_zero_pages_fd;
 static int pagemap_fd;
 static size_t pagesize;
 
@@ -57,6 +59,22 @@ static bool range_maps_duplicates(char *addr, unsigned long size)
        return false;
 }
 
+static bool check_ksm_zero_pages_count(unsigned long zero_size)
+{
+       unsigned long pages_expected = zero_size / (4 * KiB);
+       char buf[20];
+       ssize_t read_size;
+       unsigned long ksm_zero_pages;
+
+       read_size = pread(ksm_zero_pages_fd, buf, sizeof(buf) - 1, 0);
+       if (read_size < 0)
+               return -errno;
+       buf[read_size] = 0;
+       ksm_zero_pages = strtol(buf, NULL, 10);
+
+       return ksm_zero_pages == pages_expected;
+}
+
 static long ksm_get_full_scans(void)
 {
        char buf[10];
@@ -70,15 +88,12 @@ static long ksm_get_full_scans(void)
        return strtol(buf, NULL, 10);
 }
 
-static int ksm_merge(void)
+static int wait_two_full_scans(void)
 {
        long start_scans, end_scans;
 
-       /* Wait for two full scans such that any possible merging happened. */
        start_scans = ksm_get_full_scans();
        if (start_scans < 0)
-               return start_scans;
-       if (write(ksm_fd, "1", 1) != 1)
                return -errno;
        do {
                end_scans = ksm_get_full_scans();
@@ -89,6 +104,34 @@ static int ksm_merge(void)
        return 0;
 }
 
+static inline int ksm_merge(void)
+{
+       /* Wait for two full scans such that any possible merging happened. */
+       if (write(ksm_fd, "1", 1) != 1)
+               return -errno;
+       return wait_two_full_scans();
+}
+
+static inline int make_cow(char *map, char val, unsigned long size)
+{
+
+       memset(map, val, size);
+       return wait_two_full_scans();
+}
+
+static int unmerge_zero_page(char *start, unsigned long size)
+{
+       int ret;
+
+       ret = madvise(start, size, MADV_UNMERGEABLE);
+       if (ret) {
+               ksft_test_result_fail("MADV_UNMERGEABLE failed\n");
+               return ret;
+       }
+
+       return wait_two_full_scans();
+}
+
 static char *mmap_and_merge_range(char val, unsigned long size)
 {
        char *map;
@@ -146,6 +189,56 @@ unmap:
        munmap(map, size);
 }
 
+static void test_unmerge_zero_pages(void)
+{
+       const unsigned int size = 2 * MiB;
+       char *map;
+
+       ksft_print_msg("[RUN] %s\n", __func__);
+
+       /* Confirm the interfaces*/
+       ksm_zero_pages_fd = open("/sys/kernel/mm/ksm/zero_pages_sharing", O_RDONLY);
+       if (ksm_zero_pages_fd < 0) {
+               ksft_test_result_skip("open(\"/sys/kernel/mm/ksm/zero_pages_sharing\") failed\n");
+               return;
+       }
+       ksm_use_zero_pages_fd = open("/sys/kernel/mm/ksm/use_zero_pages", O_RDWR);
+       if (ksm_use_zero_pages_fd < 0) {
+               ksft_test_result_skip("open \"/sys/kernel/mm/ksm/use_zero_pages\" failed\n");
+               return;
+       }
+       if (write(ksm_use_zero_pages_fd, "1", 1) != 1) {
+               ksft_test_result_skip("write \"/sys/kernel/mm/ksm/use_zero_pages\" failed\n");
+               return;
+       }
+
+       /* Mmap zero pages*/
+       map = mmap_and_merge_range(0x00, size);
+
+       /* Case 1: make Writing on ksm zero pages (COW) */
+       if (make_cow(map, 0xcf, size / 2)) {
+               ksft_test_result_fail("COW failed\n");
+               goto unmap;
+       }
+       ksft_test_result(check_ksm_zero_pages_count(size / 2),
+                                               "zero page count react to cow\n");
+
+       /* Case 2: Call madvise(xxx, MADV_UNMERGEABLE)*/
+       if (unmerge_zero_page(map + size / 2, size / 4)) {
+               ksft_test_result_fail("unmerge_zero_page failed\n");
+               goto unmap;
+       }
+       ksft_test_result(check_ksm_zero_pages_count(size / 4),
+                                               "zero page count react to unmerge\n");
+
+       /*Check if ksm pages are really unmerged */
+       ksft_test_result(!range_maps_duplicates(map + size / 2, size / 4),
+                                               "KSM zero pages were unmerged\n");
+
+unmap:
+       munmap(map, size);
+}
+
 static void test_unmerge_discarded(void)
 {
        const unsigned int size = 2 * MiB;
@@ -261,11 +354,13 @@ int main(int argc, char **argv)
        ksm_full_scans_fd = open("/sys/kernel/mm/ksm/full_scans", O_RDONLY);
        if (ksm_full_scans_fd < 0)
                ksft_exit_skip("open(\"/sys/kernel/mm/ksm/full_scans\") failed\n");
+
        pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
        if (pagemap_fd < 0)
                ksft_exit_skip("open(\"/proc/self/pagemap\") failed\n");
 
        test_unmerge();
+       test_unmerge_zero_pages();
        test_unmerge_discarded();
 #ifdef __NR_userfaultfd
        test_unmerge_uffd_wp();