[PATCH v2] slub: do not merge cache if slub_debug contains a never-merge flag

[Grygorii Maistrenko <grygoriimkd@gmail.com>]

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.

Signed-off-by: Grygorii Maistrenko <grygoriimkd@gmail.com>
---
 mm/slab_common.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

New in v2:
	- (flags & SLAB_NEVER_MERGE) check is moved down below the flags update
	  as suggested by Christoph Lameter

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 329b03843863..a85a01439490 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

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