linux-kernel - [PATCH v2] selftest/mm: fix pointer comparison in mremap

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Message-ID: <20251108161829.25105-1-ankitkhushwaha.linux@gmail.com>
Date: Sat,  8 Nov 2025 21:48:29 +0530
From: Ankit Khushwaha <ankitkhushwaha.linux@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...nel.org>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Mike Rapoport <rppt@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	Shuah Khan <shuah@...nel.org>,
	linux-mm@...ck.org,
	linux-kselftest@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Ankit Khushwaha <ankitkhushwaha.linux@...il.com>
Subject: [PATCH v2] selftest/mm: fix pointer comparison in mremap_test

Pointer arthemitic with 'void * addr' and 'ulong dest_alignment'
triggers following warning:

mremap_test.c:1035:31: warning: pointer comparison always evaluates to
false [-Wtautological-compare]
 1035 |                 if (addr + c.dest_alignment < addr) {
      |                                             ^

this warning is raised from clang version 20.1.8 (Fedora 20.1.8-4.fc42).

use 'void *tmp_addr' to do the pointer arthemitic.

Signed-off-by: Ankit Khushwaha <ankitkhushwaha.linux@...il.com>
---
Changelog:
v2:
- use 'void *tmp_addr' for pointer arthemitic instead of typecasting
'addr' to 'unsigned long long' as suggested by Andrew.

v1: https://lore.kernel.org/linux-kselftest/20251106104917.39890-1-ankitkhushwaha.linux@gmail.com/
---
 tools/testing/selftests/mm/mremap_test.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selftests/mm/mremap_test.c
index a95c0663a011..308576437228 100644
--- a/tools/testing/selftests/mm/mremap_test.c
+++ b/tools/testing/selftests/mm/mremap_test.c
@@ -994,7 +994,7 @@ static void mremap_move_multi_invalid_vmas(FILE *maps_fp, unsigned long page_siz
 static long long remap_region(struct config c, unsigned int threshold_mb,
 			      char *rand_addr)
 {
-	void *addr, *src_addr, *dest_addr, *dest_preamble_addr = NULL;
+	void *addr, *tmp_addr, *src_addr, *dest_addr, *dest_preamble_addr = NULL;
 	unsigned long long t, d;
 	struct timespec t_start = {0, 0}, t_end = {0, 0};
 	long long  start_ns, end_ns, align_mask, ret, offset;
@@ -1032,7 +1032,8 @@ static long long remap_region(struct config c, unsigned int threshold_mb,
 	/* Don't destroy existing mappings unless expected to overlap */
 	while (!is_remap_region_valid(addr, c.region_size) && !c.overlapping) {
 		/* Check for unsigned overflow */
-		if (addr + c.dest_alignment < addr) {
+		tmp_addr = addr + c.dest_alignment;
+		if (tmp_addr < addr) {
 			ksft_print_msg("Couldn't find a valid region to remap to\n");
 			ret = -1;
 			goto clean_up_src;
--
2.51.1