slab: add SLAB_ACCOUNT flag

Currently, if we want to account all objects of a particular kmem cache,
we have to pass __GFP_ACCOUNT to each kmem_cache_alloc call, which is
inconvenient.  This patch introduces SLAB_ACCOUNT flag which if passed
to kmem_cache_create will force accounting for every allocation from
this cache even if __GFP_ACCOUNT is not passed.

This patch does not make any of the existing caches use this flag - it
will be done later in the series.

Note, a cache with SLAB_ACCOUNT cannot be merged with a cache w/o
SLAB_ACCOUNT, because merged caches share the same kmem_cache struct and
hence cannot have different sets of SLAB_* flags.  Thus using this flag
will probably reduce the number of merged slabs even if kmem accounting
is not used (only compiled in).

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Suggested-by: Tejun Heo <tj@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.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>

1 files changed, 7 insertions, 1 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 14cb1db4c52b..4bd6c4513393 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2356,7 +2356,7 @@ static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
  * Can't be called in interrupt context or from kernel threads.
  * This function needs to be called with rcu_read_lock() held.
  */
-struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep)
+struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep, gfp_t gfp)
 {
         struct mem_cgroup *memcg;
         struct kmem_cache *memcg_cachep;
@@ -2364,6 +2364,12 @@ struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep)
 
         VM_BUG_ON(!is_root_cache(cachep));
 
+        if (cachep->flags & SLAB_ACCOUNT)
+                gfp |= __GFP_ACCOUNT;
+
+        if (!(gfp & __GFP_ACCOUNT))
+                return cachep;
+
         if (current->memcg_kmem_skip_account)
                 return cachep;