BACKPORT: selftests/mm: add separate UFFDIO_MOVE test for PMD splitting

Add a test for UFFDIO_MOVE ioctl operating on a hugepage which has to be
split because destination is marked with MADV_NOHUGEPAGE.  With this we
cover all 3 cases: normal page move, hugepage move, hugepage splitting
before move.

Link: https://lkml.kernel.org/r/20231230025636.2477429-1-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Nicolas Geoffray <ngeoffray@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: ZhangPeng <zhangpeng362@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

(cherry picked from commit a5b7620bab81f16e8bbb04f4aea94c4c7feb0d77)
Conflicts:
	tools/testing/selftests/mm/uffd-unit-tests.c
	tools/testing/selftests/vm/userfaultfd.c

1. Add request_src_hugepages() to enable THP on src
2. Add madvise() to enable THP on dst in request_hugepages()
3. Add request_split_hugepages() to enable THP on src and disable on dst
4. Change return type of uffd_move_pmd_split_test() to int

Bug: 274911254
Change-Id: I21147a5b7f3e8bbe2befa8bff536e62826e9f6e3
Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>

tools/testing/selftests/vm/userfaultfd.c

@@ -1255,7 +1255,7 @@ static void prevent_hugepages()
 	}
 }
 
-static void request_hugepages()
+static void request_src_hugepages()
 {
 	/* This should be done before source area is populated */
 	if (madvise(area_src, nr_pages * page_size, MADV_HUGEPAGE)) {
@@ -1266,6 +1266,20 @@ static void request_hugepages()
 	}
 }
 
+static void request_hugepages()
+{
+	request_src_hugepages();
+	if (madvise(area_dst, nr_pages * page_size, MADV_HUGEPAGE))
+		err("madvise(MADV_HUGEPAGE) failure");
+}
+
+static void request_split_hugepages()
+{
+	request_src_hugepages();
+	if (madvise(area_dst, nr_pages * page_size, MADV_NOHUGEPAGE))
+		err("madvise(MADV_NOHUGEPAGE) failure");
+}
+
 struct uffd_test_case_ops uffd_move_test_case_ops = {
 	.post_alloc = prevent_hugepages,
 };
@@ -1274,6 +1288,10 @@ struct uffd_test_case_ops uffd_move_test_pmd_case_ops = {
 	.post_alloc = request_hugepages,
 };
 
+struct uffd_test_case_ops uffd_move_test_pmd_split_case_ops = {
+	.post_alloc = request_split_hugepages,
+};
+
 static void
 uffd_move_handle_fault_common(struct uffd_msg *msg, struct uffd_stats *args,
 			      unsigned long len)
@@ -1420,6 +1438,14 @@ static int uffd_move_pmd_test(void)
 				     uffd_move_pmd_handle_fault);
 }
 
+static int uffd_move_pmd_split_test(void)
+{
+	printf("move-pmd-split ");
+	return uffd_move_test_common(&uffd_move_test_pmd_split_case_ops,
+				     read_pmd_pagesize(),
+				     uffd_move_pmd_handle_fault);
+}
+
 static int userfaultfd_move_test(void)
 {
 	int ret;
@@ -1430,7 +1456,8 @@ static int userfaultfd_move_test(void)
 	printf("testing UFFDIO_MOVE: ");
 	fflush(stdout);
 
-	ret = uffd_move_test() || uffd_move_pmd_test();
+	ret = uffd_move_test() || uffd_move_pmd_test()
+		|| uffd_move_pmd_split_test();
 
 	printf("done.\n");
 	return ret;