[PATCH v4 10/10] selftests/mm: add tests for folio_split(), buddy allocator like split.

[Zi Yan <ziy@nvidia.com>]

It splits page cache folios to orders from 0 to 8 at different in-folio
offset.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
 .../selftests/mm/split_huge_page_test.c       | 29 ++++++++++++++-----
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
index 5bb159ebc83d..1af8d6fa4465 100644
--- a/tools/testing/selftests/mm/split_huge_page_test.c
+++ b/tools/testing/selftests/mm/split_huge_page_test.c
@@ -14,6 +14,7 @@
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <sys/mount.h>
+#include <sys/param.h>
 #include <malloc.h>
 #include <stdbool.h>
 #include <time.h>
@@ -420,7 +421,8 @@ int create_pagecache_thp_and_fd(const char *testfile, size_t fd_size, int *fd,
 	return -1;
 }
 
-void split_thp_in_pagecache_to_order(size_t fd_size, int order, const char *fs_loc)
+void split_thp_in_pagecache_to_order_at(size_t fd_size, const char *fs_loc,
+		int order, int offset)
 {
 	int fd;
 	char *addr;
@@ -438,7 +440,12 @@ void split_thp_in_pagecache_to_order(size_t fd_size, int order, const char *fs_l
 		return;
 	err = 0;
 
-	write_debugfs(PID_FMT, getpid(), (uint64_t)addr, (uint64_t)addr + fd_size, order);
+	if (offset == -1)
+		write_debugfs(PID_FMT, getpid(), (uint64_t)addr,
+			      (uint64_t)addr + fd_size, order);
+	else
+		write_debugfs(PID_FMT, getpid(), (uint64_t)addr,
+			      (uint64_t)addr + fd_size, order, offset);
 
 	for (i = 0; i < fd_size; i++)
 		if (*(addr + i) != (char)i) {
@@ -458,8 +465,8 @@ void split_thp_in_pagecache_to_order(size_t fd_size, int order, const char *fs_l
 	close(fd);
 	unlink(testfile);
 	if (err)
-		ksft_exit_fail_msg("Split PMD-mapped pagecache folio to order %d failed\n", order);
-	ksft_test_result_pass("Split PMD-mapped pagecache folio to order %d passed\n", order);
+		ksft_exit_fail_msg("Split PMD-mapped pagecache folio to order %d at in-folio offset %d failed\n", order, offset);
+	ksft_test_result_pass("Split PMD-mapped pagecache folio to order %d at in-folio offset %d passed\n", order, offset);
 }
 
 int main(int argc, char **argv)
@@ -470,6 +477,7 @@ int main(int argc, char **argv)
 	char fs_loc_template[] = "/tmp/thp_fs_XXXXXX";
 	const char *fs_loc;
 	bool created_tmp;
+	int offset;
 
 	ksft_print_header();
 
@@ -481,7 +489,7 @@ int main(int argc, char **argv)
 	if (argc > 1)
 		optional_xfs_path = argv[1];
 
-	ksft_set_plan(1+9+2+9);
+	ksft_set_plan(1+8+2+9+8*4+2);
 
 	pagesize = getpagesize();
 	pageshift = ffs(pagesize) - 1;
@@ -494,7 +502,8 @@ int main(int argc, char **argv)
 	split_pmd_zero_pages();
 
 	for (i = 0; i < 9; i++)
-		split_pmd_thp_to_order(i);
+		if (i != 1)
+			split_pmd_thp_to_order(i);
 
 	split_pte_mapped_thp();
 	split_file_backed_thp();
@@ -502,7 +511,13 @@ int main(int argc, char **argv)
 	created_tmp = prepare_thp_fs(optional_xfs_path, fs_loc_template,
 			&fs_loc);
 	for (i = 8; i >= 0; i--)
-		split_thp_in_pagecache_to_order(fd_size, i, fs_loc);
+		split_thp_in_pagecache_to_order_at(fd_size, fs_loc, i, -1);
+
+	for (i = 0; i < 9; i++)
+		for (offset = 0;
+		     offset < pmd_pagesize / pagesize;
+		     offset += MAX(pmd_pagesize / pagesize / 4, 1 << i))
+			split_thp_in_pagecache_to_order_at(fd_size, fs_loc, i, offset);
 	cleanup_thp_fs(fs_loc, created_tmp);
 
 	ksft_finished();
-- 
2.45.2