linux-kernel - [PATCH 09/11] tools/testing/selftests: have CoW self test use MREMAP_RELOCATE

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Message-ID: <0cbe373c1d14270f5fcaf3ba8734d50d761796c0.1749473726.git.lorenzo.stoakes@oracle.com>
Date: Mon,  9 Jun 2025 14:26:43 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>, Pedro Falcato <pfalcato@...e.de>,
        Rik van Riel <riel@...riel.com>, Harry Yoo <harry.yoo@...cle.com>,
        Zi Yan <ziy@...dia.com>, Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Nico Pache <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
        Dev Jain <dev.jain@....com>, Jakub Matena <matenajakub@...il.com>,
        Wei Yang <richard.weiyang@...il.com>, Barry Song <baohua@...nel.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH 09/11] tools/testing/selftests: have CoW self test use MREMAP_RELOCATE_ANON

It is useful to have the CoW self-test invoke MREMAP_RELOCATE_ANON on
partial THP mappings, as this triggers folio split code paths and asserts
that this behaves correctly.

Add an additional set of tests to explicitly do so.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 tools/testing/selftests/mm/cow.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
index dbbcc5eb3dce..c483bfd4269e 100644
--- a/tools/testing/selftests/mm/cow.c
+++ b/tools/testing/selftests/mm/cow.c
@@ -845,13 +845,14 @@ enum thp_run {
 	THP_RUN_SINGLE_PTE,
 	THP_RUN_SINGLE_PTE_SWAPOUT,
 	THP_RUN_PARTIAL_MREMAP,
+	THP_RUN_PARTIAL_MREMAP_RELOCATE_ANON,
 	THP_RUN_PARTIAL_SHARED,
 };
 
 static void do_run_with_thp(test_fn fn, enum thp_run thp_run, size_t thpsize)
 {
 	char *mem, *mmap_mem, *tmp, *mremap_mem = MAP_FAILED;
-	size_t size, mmap_size, mremap_size;
+	size_t size, mmap_size, mremap_size, mremap_flags;
 	int ret;
 
 	/* For alignment purposes, we need twice the thp size. */
@@ -927,6 +928,7 @@ static void do_run_with_thp(test_fn fn, enum thp_run thp_run, size_t thpsize)
 		size = pagesize;
 		break;
 	case THP_RUN_PARTIAL_MREMAP:
+	case THP_RUN_PARTIAL_MREMAP_RELOCATE_ANON:
 		/*
 		 * Remap half of the THP. We need some new memory location
 		 * for that.
@@ -939,8 +941,13 @@ static void do_run_with_thp(test_fn fn, enum thp_run thp_run, size_t thpsize)
 			log_test_result(KSFT_FAIL);
 			goto munmap;
 		}
-		tmp = mremap(mem + mremap_size, mremap_size, mremap_size,
-			     MREMAP_MAYMOVE | MREMAP_FIXED, mremap_mem);
+
+		mremap_flags = MREMAP_MAYMOVE | MREMAP_FIXED;
+		if (thp_run == THP_RUN_PARTIAL_MREMAP_RELOCATE_ANON)
+			mremap_flags |= MREMAP_RELOCATE_ANON;
+
+		tmp = sys_mremap(mem + mremap_size, mremap_size, mremap_size,
+				 mremap_flags, mremap_mem);
 		if (tmp != mremap_mem) {
 			ksft_perror("mremap() failed");
 			log_test_result(KSFT_FAIL);
@@ -1052,6 +1059,13 @@ static void run_with_partial_mremap_thp(test_fn fn, const char *desc, size_t siz
 	do_run_with_thp(fn, THP_RUN_PARTIAL_MREMAP, size);
 }
 
+static void run_with_partial_mremap_relocate_anon_thp(test_fn fn, const char *desc, size_t size)
+{
+	ksft_print_msg("[RUN] %s ... with partially mremap(MREMAP_RELOCATE_ANON)'ed THP (%zu kB)\n",
+		desc, size / 1024);
+	do_run_with_thp(fn, THP_RUN_PARTIAL_MREMAP_RELOCATE_ANON, size);
+}
+
 static void run_with_partial_shared_thp(test_fn fn, const char *desc, size_t size)
 {
 	log_test_start("%s ... with partially shared THP (%zu kB)",
@@ -1247,6 +1261,7 @@ static void run_anon_test_case(struct test_case const *test_case)
 		run_with_single_pte_of_thp(test_case->fn, test_case->desc, size);
 		run_with_single_pte_of_thp_swap(test_case->fn, test_case->desc, size);
 		run_with_partial_mremap_thp(test_case->fn, test_case->desc, size);
+		run_with_partial_mremap_relocate_anon_thp(test_case->fn, test_case->desc, size);
 		run_with_partial_shared_thp(test_case->fn, test_case->desc, size);
 
 		thp_pop_settings();
@@ -1270,7 +1285,7 @@ static int tests_per_anon_test_case(void)
 {
 	int tests = 2 + nr_hugetlbsizes;
 
-	tests += 6 * nr_thpsizes;
+	tests += 7 * nr_thpsizes;
 	if (pmdsize)
 		tests += 2;
 	return tests;
-- 
2.49.0