selftests/mm: add tests for folio_split(), buddy allocator like split

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

Link: https://lkml.kernel.org/r/20250307174001.242794-9-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Kirill A. Shuemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Kairui Song <kasong@tencent.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 27 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 e0304046b1a0..719c5e2a6624 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>
@@ -456,7 +457,8 @@ err_out_unlink:
 	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;
@@ -474,7 +476,12 @@ 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) {
@@ -493,9 +500,15 @@ out:
 	munmap(addr, fd_size);
 	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);
+	if (offset == -1) {
+		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);
+	} else {
+		if (err)
+			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)
@@ -506,6 +519,7 @@ 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();
 
@@ -517,7 +531,7 @@ int main(int argc, char **argv)
 	if (argc > 1)
 		optional_xfs_path = argv[1];
 
-	ksft_set_plan(1+8+1+9+9);
+	ksft_set_plan(1+8+1+9+9+8*4+2);
 
 	pagesize = getpagesize();
 	pageshift = ffs(pagesize) - 1;
@@ -540,7 +554,13 @@ 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();