linux-kernel - [PATCH] slab : allow SLAB_RED_ZONE and SLAB_STORE

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Date:	Tue, 16 Oct 2012 13:17:11 +0200
From:	Matthieu CASTET <matthieu.castet@...rot.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	'linux-arm-kernel' <linux-arm-kernel@...ts.infradead.org>
Cc:	Matthieu CASTET <castet.matthieu@...e.fr>,
	Matthieu Castet <matthieu.castet@...rot.com>,
	Russell King <rmk@....linux.org.uk>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: [PATCH] slab : allow SLAB_RED_ZONE and SLAB_STORE_USER to work on arm

From: Matthieu CASTET <castet.matthieu@...e.fr>

on cortexA8 (omap3) ralign is 64 and __alignof__(unsigned long long) is 8.
So we always disable debug.

This patch is based on 5c5e3b33b7cb959a401f823707bee006caadd76e, but fix
case were align < sizeof(unsigned long long).

Signed-off-by: Matthieu Castet <matthieu.castet@...rot.com>
CC: Russell King <rmk@....linux.org.uk>
CC: Pekka Enberg <penberg@...helsinki.fi>
---
 mm/slab.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index c685475..8427901 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2462,9 +2462,6 @@ __kmem_cache_create (const char *name, size_t size, size_t align,
 	if (ralign < align) {
 		ralign = align;
 	}
-	/* disable debug if necessary */
-	if (ralign > __alignof__(unsigned long long))
-		flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
 	/*
 	 * 4) Store it.
 	 */
@@ -2491,8 +2488,9 @@ __kmem_cache_create (const char *name, size_t size, size_t align,
 	 */
 	if (flags & SLAB_RED_ZONE) {
 		/* add space for red zone words */
-		cachep->obj_offset += sizeof(unsigned long long);
-		size += 2 * sizeof(unsigned long long);
+		int offset = max(align, sizeof(unsigned long long));
+		cachep->obj_offset += offset;
+		size += offset + sizeof(unsigned long long);
 	}
 	if (flags & SLAB_STORE_USER) {
 		/* user store requires one word storage behind the end of
-- 
1.7.10.4

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