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/[email protected]
Signed-off-by: Waiman Long <[email protected]>
Suggested-by: Roman Gushchin <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Reviewed-by: Shakeel Butt <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 7 insertions, 0 deletions

diff --git a/mm/slab_common.c b/mm/slab_common.c
index db3f356bf725..c126e6f6b5a5 100644
--- 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;
 }
 
 /*