linux-kernel - [PATCH] mm/selftests: Fix -Wtautological-compare warning in mremap

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Message-ID: <20251110175155.1314757-1-wakel@google.com>
Date: Tue, 11 Nov 2025 01:51:55 +0800
From: Wake Liu <wakel@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>, David Hildenbrand <david@...hat.com>, 
	Shuah Khan <shuah@...nel.org>, linux-mm@...ck.org, linux-kselftest@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Cc: 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>, 
	Wake Liu <wakel@...gle.com>
Subject: [PATCH] mm/selftests: Fix -Wtautological-compare warning in mremap_test.c

The compiler warns about a tautological comparison in mremap_test.c:
"pointer comparison always evaluates to false [-Wtautological-compare]"

This occurs when checking for unsigned overflow:
  if (addr + c.dest_alignment < addr)

Cast 'addr' to 'unsigned long long' to ensure the comparison is performed
with a wider type, correctly detecting potential overflow and resolving
the warning.

Signed-off-by: Wake Liu <wakel@...gle.com>
---
 tools/testing/selftests/mm/mremap_test.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/mremap_test.c b/tools/testing/selftests/mm/mremap_test.c
index bf2863b102e3..c4933f4cbd48 100644
--- a/tools/testing/selftests/mm/mremap_test.c
+++ b/tools/testing/selftests/mm/mremap_test.c
@@ -1032,7 +1032,7 @@ 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) {
+		if ((unsigned long long)addr + c.dest_alignment < (unsigned long long)addr) {
 			ksft_print_msg("Couldn't find a valid region to remap to\n");
 			ret = -1;
 			goto clean_up_src;
-- 
2.51.2.1041.gc1ab5b90ca-goog