[PATCH 3/3] selftests/mm: test splitting file-backed THP to any lower order.

[Zi Yan <ziy@nvidia.com>]

Now split_huge_page*() supports shmem THP split to any lower order.
Test it.

The test now reads file content out after split to check if the split
corrupts the file data.

Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
 .../selftests/mm/split_huge_page_test.c       | 32 ++++++++++++++-----
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
index 8e15fc9dce3a..13ad5ac7d178 100644
--- a/tools/testing/selftests/mm/split_huge_page_test.c
+++ b/tools/testing/selftests/mm/split_huge_page_test.c
@@ -261,14 +261,16 @@ void split_pte_mapped_thp(void)
 	close(kpageflags_fd);
 }
 
-void split_file_backed_thp(void)
+void split_file_backed_thp(int order)
 {
 	int status;
 	int fd, shmem_sysctl_fd;
 	ssize_t num_written, num_read;
 	char tmpfs_template[] = "/tmp/thp_split_XXXXXX";
 	const char *tmpfs_loc = mkdtemp(tmpfs_template);
-	char testfile[INPUT_MAX], sysctl_buf[INPUT_MAX] = {0};
+	char testfile[INPUT_MAX];
+	char sysctl_buf[INPUT_MAX] = {0};
+	char file_buf[INPUT_MAX] = {0};
 	uint64_t pgoff_start = 0, pgoff_end = 1024;
 	const char *shmem_sysctl = "/sys/kernel/mm/transparent_hugepage/shmem_enabled";
 	char *opt1, *opt2;
@@ -314,7 +316,7 @@ void split_file_backed_thp(void)
 		ksft_exit_fail_msg("Fail to create file-backed THP split testing file\n");
 	}
 
-	fd = open(testfile, O_CREAT|O_WRONLY, 0664);
+	fd = open(testfile, O_CREAT|O_RDWR, 0664);
 	if (fd == -1) {
 		ksft_perror("Cannot open testing file");
 		goto cleanup;
@@ -322,7 +324,6 @@ void split_file_backed_thp(void)
 
 	/* write something to the file, so a file-backed THP can be allocated */
 	num_written = write(fd, tmpfs_loc, strlen(tmpfs_loc) + 1);
-	close(fd);
 
 	if (num_written < 1) {
 		ksft_perror("Fail to write data to testing file");
@@ -330,8 +331,22 @@ void split_file_backed_thp(void)
 	}
 
 	/* split the file-backed THP */
-	write_debugfs(PATH_FMT, testfile, pgoff_start, pgoff_end, 0);
+	write_debugfs(PATH_FMT, testfile, pgoff_start, pgoff_end, order);
+
+	/* check file content after split */
+	num_read = lseek(fd, 0, SEEK_SET);
+	if (num_read == -1) {
+		ksft_perror("Cannot lseek file");
+		goto cleanup;
+	}
 
+	num_read = read(fd, file_buf, num_written);
+	if (num_read < 1 || strncmp(file_buf, tmpfs_loc, num_read)) {
+		ksft_print_msg("File content changed, origin: %s, now: %s\n", tmpfs_loc, file_buf);
+		goto cleanup;
+	}
+
+	close(fd);
 	status = unlink(testfile);
 	if (status) {
 		ksft_perror("Cannot remove testing file");
@@ -354,7 +369,7 @@ void split_file_backed_thp(void)
 
 	close(shmem_sysctl_fd);
 	ksft_print_msg("Please check dmesg for more information\n");
-	ksft_test_result_pass("File-backed THP split test done\n");
+	ksft_test_result_pass("File-backed THP split to order %d test done\n", order);
 	return;
 
 cleanup:
@@ -523,7 +538,7 @@ int main(int argc, char **argv)
 	if (argc > 1)
 		optional_xfs_path = argv[1];
 
-	ksft_set_plan(1+8+2+9);
+	ksft_set_plan(1+8+1+9+9);
 
 	pagesize = getpagesize();
 	pageshift = ffs(pagesize) - 1;
@@ -540,7 +555,8 @@ int main(int argc, char **argv)
 			split_pmd_thp_to_order(i);
 
 	split_pte_mapped_thp();
-	split_file_backed_thp();
+	for (i = 0; i < 9; i++)
+		split_file_backed_thp(i);
 
 	created_tmp = prepare_thp_fs(optional_xfs_path, fs_loc_template,
 			&fs_loc);
-- 
2.45.2