linux-kernel - [PATCH review for 4.9 24/50] slub: do not merge cache if slub

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Message-ID: <20170925011225.10029-24-alexander.levin@verizon.com>
Date:   Mon, 25 Sep 2017 01:12:50 +0000
From:   "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Grygorii Maistrenko <grygoriimkd@...il.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
Subject: [PATCH review for 4.9 24/50] slub: do not merge cache if slub_debug
 contains a never-merge flag

From: Grygorii Maistrenko <grygoriimkd@...il.com>

[ Upstream commit c6e28895a4372992961888ffaadc9efc643b5bfe ]

In case CONFIG_SLUB_DEBUG_ON=n, find_mergeable() gets debug features from
commandline but never checks if there are features from the
SLAB_NEVER_MERGE set.

As a result selected by slub_debug caches are always mergeable if they
have been created without a custom constructor set or without one of the
SLAB_* debug features on.

This moves the SLAB_NEVER_MERGE check below the flags update from
commandline to make sure it won't merge the slab cache if one of the debug
features is on.

Link: http://lkml.kernel.org/r/20170101124451.GA4740@lp-laptop-d
Signed-off-by: Grygorii Maistrenko <grygoriimkd@...il.com>
Reviewed-by: Pekka Enberg <penberg@...nel.org>
Acked-by: David Rientjes <rientjes@...gle.com>
Acked-by: Christoph Lameter <cl@...ux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 mm/slab_common.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 5d2f24fbafc5..622f6b6ae844 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -255,7 +255,7 @@ struct kmem_cache *find_mergeable(size_t size, size_t align,
 {
 	struct kmem_cache *s;
 
-	if (slab_nomerge || (flags & SLAB_NEVER_MERGE))
+	if (slab_nomerge)
 		return NULL;
 
 	if (ctor)
@@ -266,6 +266,9 @@ struct kmem_cache *find_mergeable(size_t size, size_t align,
 	size = ALIGN(size, align);
 	flags = kmem_cache_flags(size, flags, name, NULL);
 
+	if (flags & SLAB_NEVER_MERGE)
+		return NULL;
+
 	list_for_each_entry_reverse(s, &slab_caches, list) {
 		if (slab_unmergeable(s))
 			continue;
-- 
2.11.0