Commit 076a6220 authored Feb 22, 2017 by Grygorii Maistrenko Committed by Greg Kroah-Hartman Oct 21, 2017

slub: do not merge cache if slub_debug contains a never-merge flag


[ 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@gmail.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 2ada592f

mm/slab_common.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -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;