linux-kernel - [PATCH 1/2] Remove the "FOLL_TOUCH" test code from gup

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Message-ID: <20251114085038.191031-1-peng8420.li@gmail.com>
Date: Fri, 14 Nov 2025 16:50:37 +0800
From: 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,
	"peng8420.li" <peng8420.li@...il.com>
Subject: [PATCH 1/2] Remove the "FOLL_TOUCH" test code from gup_test.c.

From: "peng8420.li" <peng8420.li@...il.com>

>From submission 0f20bba1688bdf3b32df0162511a67d4eda15790, we know that "FOLL_TOUCH" is only for internal scope use;

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

Otherwise, executing the test command "./gup_test -L -r 100 -z" will report the following warning log:
TAP version 13
1..1
ENCHMARK: Time: [   39.363371] WARNING: CPU: 1 PID: 117 at mm/gup.c:2512 is_valid_gup_args+0x66/0x8c
get:2818 put:46 [   39.364043] Modules linked in:
us# , truncated [   39.364311] CPU: 1 UID: 0 PID: 117 Comm: gup_test Not tainted 6.18.0-rc5-00324-gd09eaf415c87 #29 NONE
(size: 0)#
[   39.364434] Hardware name: riscv-virtio,qemu (DT)
[   39.364546] epc : is_valid_gup_args+0x66/0x8c
[   39.364596]  ra : pin_user_pages+0x38/0x78
[   39.364630] epc : ffffffff802079e6 ra : ffffffff8020c214 sp : ff2000000041bd20
[   39.364650]  gp : ffffffff81a26068 tp : ff60000080b3b000 t0 : ff2000000041bdf8
[   39.364678]  t1 : 000000000000001e t2 : 0000000000000000 s0 : ff2000000041bd30
[   39.364697]  s1 : ff60000081300000 a0 : ff60000081300000 a1 : 0000000000000000
[   39.364714]  a2 : ff2000000041bd3c a3 : 0000000000080000 a4 : 0000000000000001
[   39.364731]  a5 : 0000000000010101 a6 : 0000000000000001 a7 : 0000000000000000
[   39.364747]  s2 : 00007fff7eeed000 s3 : 0000000000000001 s4 : 00007fff7eeee000
[   39.364761]  s5 : 00007fff7eeeb838 s6 : 0000000000000000 s7 : 00007fff7eeed000
[   39.364825]  s8 : ff60000081300000 s9 : 0000000000000000 s10: 0000000000000002
[   39.364842]  s11: 000000092869bfdc t3 : 2152ffffffffffc0 t4 : 00000000001fffff
[   39.364855]  t5 : ffffffffffffffff t6 : 0000000000000000
[   39.364867] status: 0000000200000120 badaddr: ffffffff802079e6 cause: 0000000000000003
[   39.364949] [<ffffffff802079e6>] is_valid_gup_args+0x66/0x8c
[   39.365036] [<ffffffff8020c214>] pin_user_pages+0x38/0x78
[   39.365049] [<ffffffff80278f78>] gup_test_ioctl+0x2b4/0xc08
[   39.365060] [<ffffffff80297da6>] __riscv_sys_ioctl+0xba/0xc4
[   39.365072] [<ffffffff80b93f96>] do_trap_ecall_u+0x296/0x370
[   39.365093] [<ffffffff80b9ef06>] handle_exception+0x146/0x152
[   39.365220] ---[ end trace 0000000000000000 ]---
ok 1 ioctl status 0

Signed-off-by: peng8420.li <peng8420.li@...il.com>
---
 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