From 922d566cdcb7166c729ff67bb15ff5f93a3774b6 Mon Sep 17 00:00:00 2001
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Date: Thu, 17 Mar 2016 14:17:53 -0700
Subject: [PATCH] mm/slub: query dynamic DEBUG_PAGEALLOC setting

We can disable debug_pagealloc processing even if the code is compiled
with CONFIG_DEBUG_PAGEALLOC.  This patch changes the code to query
whether it is enabled or not in runtime.

[akpm@linux-foundation.org: clean up code, per Christian]
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Takashi Iwai <tiwai@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/slub.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 712d53474082..2f2f04d39104 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -254,11 +254,10 @@ static inline void *get_freepointer_safe(struct kmem_cache *s, void *object)
 {
 	void *p;
 
-#ifdef CONFIG_DEBUG_PAGEALLOC
+	if (!debug_pagealloc_enabled())
+		return get_freepointer(s, object);
+
 	probe_kernel_read(&p, (void **)(object + s->offset), sizeof(p));
-#else
-	p = get_freepointer(s, object);
-#endif
 	return p;
 }