linux-kernel - [PATCH v3 1/2] selftests/mm: gup_test: stop testing FOLL

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Message-ID: <20251117154012.197499-1-peng8420.li@gmail.com>
Date: Mon, 17 Nov 2025 23:40:11 +0800
From: Peng Li <peng8420.li@...il.com>
To: linux-mm@...ck.org,
	akpm@...ux-foundation.org
Cc: david@...hat.com,
	osalvador@...e.de,
	jgg@...pe.ca,
	jhubbard@...dia.com,
	peterx@...hat.com,
	linux-kernel@...r.kernel.org,
	dan.j.williams@...el.com,
	Peng Li <peng8420.li@...il.com>,
	David Hildenbrand <david@...nel.org>
Subject: [PATCH v3 1/2] selftests/mm: gup_test: stop testing FOLL_TOUCH

From: Peng Li <peng8420.li@...il.com>

commit 0f20bba1688b ("mm/gup: explicitly define and check internal GUP
flags, disallow FOLL_TOUCH") marked FOLL_TOUCH as a GUP-internal flag.

This causes a warning to fire when running gup_test, for example:

    $ ./gup_test -L -r 100 -z

dmesg:
    WARNING: CPU: 1 PID: 117 at mm/gup.c:2512 is_valid_gup_args+0x66/0x8c

Therefore, remove the "FOLL_TOUCH" test code from gup_test.c.

Signed-off-by: Peng Li <peng8420.li@...il.com>
Reviewed-by: John Hubbard <jhubbard@...dia.com>
Reviewed-by: David Hildenbrand (Red Hat) <david@...nel.org>
---
 tools/testing/selftests/mm/gup_test.c | 22 ++++------------------
 1 file changed, 4 insertions(+), 18 deletions(-)

diff --git a/tools/testing/selftests/mm/gup_test.c b/tools/testing/selftests/mm/gup_test.c
index 8900b840c17a..75f7134d529d 100644
--- a/tools/testing/selftests/mm/gup_test.c
+++ b/tools/testing/selftests/mm/gup_test.c
@@ -19,7 +19,6 @@
 
 /* Just the flags we need, copied from mm.h: */
 #define FOLL_WRITE	0x01	/* check pte is writable */
-#define FOLL_TOUCH	0x02	/* mark page accessed */
 
 #define GUP_TEST_FILE "/sys/kernel/debug/gup_test"
 
@@ -93,7 +92,7 @@ int main(int argc, char **argv)
 {
 	struct gup_test gup = { 0 };
 	int filed, i, opt, nr_pages = 1, thp = -1, write = 1, nthreads = 1, ret;
-	int flags = MAP_PRIVATE, touch = 0;
+	int flags = MAP_PRIVATE;
 	char *file = "/dev/zero";
 	pthread_t *tid;
 	char *p;
@@ -170,10 +169,6 @@ int main(int argc, char **argv)
 		case 'H':
 			flags |= (MAP_HUGETLB | MAP_ANONYMOUS);
 			break;
-		case 'z':
-			/* fault pages in gup, do not fault in userland */
-			touch = 1;
-			break;
 		default:
 			ksft_exit_fail_msg("Wrong argument\n");
 		}
@@ -244,18 +239,9 @@ int main(int argc, char **argv)
 	else if (thp == 0)
 		madvise(p, size, MADV_NOHUGEPAGE);
 
-	/*
-	 * FOLL_TOUCH, in gup_test, is used as an either/or case: either
-	 * fault pages in from the kernel via FOLL_TOUCH, or fault them
-	 * in here, from user space. This allows comparison of performance
-	 * between those two cases.
-	 */
-	if (touch) {
-		gup.gup_flags |= FOLL_TOUCH;
-	} else {
-		for (; (unsigned long)p < gup.addr + size; p += psize())
-			p[0] = 0;
-	}
+	/* Fault them in here, from user space. */
+	for (; (unsigned long)p < gup.addr + size; p += psize())
+		p[0] = 0;
 
 	tid = malloc(sizeof(pthread_t) * nthreads);
 	assert(tid);
-- 
2.43.0