netdev - [PATCH hotfix 6.11 v2 2/3] minmax: reduce min/max macro expansion in skbuff

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Message-ID: <a32131084038312529243bc22b06f0ee64c95fb6.1726074904.git.lorenzo.stoakes@oracle.com>
Date: Wed, 11 Sep 2024 18:51:10 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Richard Narron <richard@...zen.com>, Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Marcin Wojtas <marcin.s.wojtas@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Arnd Bergmann <arnd@...nel.org>,
        Linus Torvalds <torvalds@...uxfoundation.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-staging@...ts.linux.dev, linux-mm@...ck.org,
        Andrew Lunn <andrew@...n.ch>, Dan Carpenter <dan.carpenter@...aro.org>,
        stable@...r.kernel.org
Subject: [PATCH hotfix 6.11 v2 2/3] minmax: reduce min/max macro expansion in skbuff

Avoid unnecessary nested min()/max() which reults in egregious macro
expansion.

The nesting occurs when NET_SKB_PAD is used in a min() or max() invocation,
for instance, various ethernet drivers wrap it in a max().

Not doing so results in an impact on build times.

Cc: stable@...r.kernel.org
Fixes: 867046cc7027 ("minmax: relax check to allow comparison between unsigned arguments and signed constants")
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 include/linux/skbuff.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 29c3ea5b6e93..d53b296df504 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3164,7 +3164,11 @@ static inline int pskb_network_may_pull(struct sk_buff *skb, unsigned int len)
  * NET_IP_ALIGN(2) + ethernet_header(14) + IP_header(20/40) + ports(8)
  */
 #ifndef NET_SKB_PAD
-#define NET_SKB_PAD	max(32, L1_CACHE_BYTES)
+#if L1_CACHE_BYTES < 32
+#define NET_SKB_PAD	32
+#else
+#define NET_SKB_PAD	L1_CACHE_BYTES
+#endif
 #endif

 int ___pskb_trim(struct sk_buff *skb, unsigned int len);
--
2.46.0