mm: memcg/slab: disable cache merging for KMALLOC_NORMAL caches

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.

Link: https://lkml.kernel.org/r/20210505200610.13943-4-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Suggested-by: Roman Gushchin <guro@fb.com>
Acked-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/slab_common.c b/mm/slab_common.c
index db3f356..c126e6f 100644 (file)
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -856,6 +856,13 @@ 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;
 }
 
 /*