linux-kernel - [PATCH 3/7 6.12.y] minmax.h: reduce the #define expansion of min(), max() and clamp()

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Message-ID: <20250922103123.14538-4-farbere@amazon.com>
Date: Mon, 22 Sep 2025 10:31:19 +0000
From: Eliav Farber <farbere@...zon.com>
To: <farbere@...zon.com>, <akpm@...ux-foundation.org>,
	<David.Laight@...LAB.COM>, <arnd@...nel.org>, <linux-kernel@...r.kernel.org>,
	<stable@...r.kernel.org>
CC: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Christoph Hellwig
	<hch@...radead.org>, Dan Carpenter <dan.carpenter@...aro.org>, "Jason A.
 Donenfeld" <Jason@...c4.com>, Jens Axboe <axboe@...nel.dk>, Lorenzo Stoakes
	<lorenzo.stoakes@...cle.com>, Mateusz Guzik <mjguzik@...il.com>, "Matthew
 Wilcox" <willy@...radead.org>, Pedro Falcato <pedro.falcato@...il.com>
Subject: [PATCH 3/7 6.12.y] minmax.h: reduce the #define expansion of min(), max() and clamp()

From: David Laight <David.Laight@...LAB.COM>

[ Upstream commit b280bb27a9f7c91ddab730e1ad91a9c18a051f41 ]

Since the test for signed values being non-negative only relies on
__builtion_constant_p() (not is_constexpr()) it can use the 'ux' variable
instead of the caller supplied expression.  This means that the #define
parameters are only expanded twice.  Once in the code and once quoted in
the error message.

Link: https://lkml.kernel.org/r/051afc171806425da991908ed8688a98@AcuMS.aculab.com
Signed-off-by: David Laight <david.laight@...lab.com>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Arnd Bergmann <arnd@...nel.org>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Jason A. Donenfeld <Jason@...c4.com>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Mateusz Guzik <mjguzik@...il.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Pedro Falcato <pedro.falcato@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Eliav Farber <farbere@...zon.com>
---
 include/linux/minmax.h | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/include/linux/minmax.h b/include/linux/minmax.h
index 24e4b372649a..6f7ea669d305 100644
--- a/include/linux/minmax.h
+++ b/include/linux/minmax.h
@@ -46,10 +46,10 @@
  * comparison, and these expressions only need to be careful to not cause
  * warnings for pointer use.
  */
-#define __signed_type_use(x, ux) (2 + __is_nonneg(x, ux))
-#define __unsigned_type_use(x, ux) (1 + 2 * (sizeof(ux) < 4))
-#define __sign_use(x, ux) (is_signed_type(typeof(ux)) ? \
-	__signed_type_use(x, ux) : __unsigned_type_use(x, ux))
+#define __signed_type_use(ux) (2 + __is_nonneg(ux))
+#define __unsigned_type_use(ux) (1 + 2 * (sizeof(ux) < 4))
+#define __sign_use(ux) (is_signed_type(typeof(ux)) ? \
+	__signed_type_use(ux) : __unsigned_type_use(ux))
 
 /*
  * Check whether a signed value is always non-negative.
@@ -71,13 +71,13 @@
 #else
   #define __signed_type(ux) typeof(__builtin_choose_expr(sizeof(ux) > 4, 1LL, 1L))
 #endif
-#define __is_nonneg(x, ux) statically_true((__signed_type(ux))(x) >= 0)
+#define __is_nonneg(ux) statically_true((__signed_type(ux))(ux) >= 0)
 
-#define __types_ok(x, y, ux, uy) \
-	(__sign_use(x, ux) & __sign_use(y, uy))
+#define __types_ok(ux, uy) \
+	(__sign_use(ux) & __sign_use(uy))
 
-#define __types_ok3(x, y, z, ux, uy, uz) \
-	(__sign_use(x, ux) & __sign_use(y, uy) & __sign_use(z, uz))
+#define __types_ok3(ux, uy, uz) \
+	(__sign_use(ux) & __sign_use(uy) & __sign_use(uz))
 
 #define __cmp_op_min <
 #define __cmp_op_max >
@@ -92,7 +92,7 @@
 
 #define __careful_cmp_once(op, x, y, ux, uy) ({		\
 	__auto_type ux = (x); __auto_type uy = (y);	\
-	BUILD_BUG_ON_MSG(!__types_ok(x, y, ux, uy),	\
+	BUILD_BUG_ON_MSG(!__types_ok(ux, uy),		\
 		#op"("#x", "#y") signedness error");	\
 	__cmp(op, ux, uy); })
 
@@ -109,7 +109,7 @@
 	static_assert(__builtin_choose_expr(__is_constexpr((lo) > (hi)), 	\
 			(lo) <= (hi), true),					\
 		"clamp() low limit " #lo " greater than high limit " #hi);	\
-	BUILD_BUG_ON_MSG(!__types_ok3(val, lo, hi, uval, ulo, uhi),		\
+	BUILD_BUG_ON_MSG(!__types_ok3(uval, ulo, uhi),				\
 		"clamp("#val", "#lo", "#hi") signedness error");		\
 	__clamp(uval, ulo, uhi); })
 
@@ -149,7 +149,7 @@
 
 #define __careful_op3(op, x, y, z, ux, uy, uz) ({			\
 	__auto_type ux = (x); __auto_type uy = (y);__auto_type uz = (z);\
-	BUILD_BUG_ON_MSG(!__types_ok3(x, y, z, ux, uy, uz),		\
+	BUILD_BUG_ON_MSG(!__types_ok3(ux, uy, uz),			\
 		#op"3("#x", "#y", "#z") signedness error");		\
 	__cmp(op, ux, __cmp(op, uy, uz)); })
 
-- 
2.47.3