[PATCH v4 3/3] mm: memcg/slab: Disable cache merging for KMALLOC_NORMAL caches

[Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

The KMALLOC_NORMAL (kmalloc-<n>) caches are for unaccounted objects only
when CONFIG_MEMCG_KMEM is enabled. To make sure that this condition
remains true, we will have to prevent KMALOC_NORMAL caches to merge
with other kmem caches. This is now done by setting its refcount to -1
right after its creation.

Suggested-by: Roman Gushchin <guro-b10kYP2dOMg@public.gmane.org>
Signed-off-by: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
---
 mm/slab_common.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index bbaf41a7c77e..a0ff8e1d8b67 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -841,6 +841,13 @@ new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
 					kmalloc_info[idx].name[type],
 					kmalloc_info[idx].size, flags, 0,
 					kmalloc_info[idx].size);
+
+	/*
+	 * If CONFIG_MEMCG_KMEM is enabled, disable cache merging for
+	 * KMALLOC_NORMAL caches.
+	 */
+	if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_NORMAL))
+		kmalloc_caches[type][idx]->refcount = -1;
 }
 
 /*
-- 
2.18.1