[PATCH -mm] memcg: zap memcg_can_account_kmem

From: Vladimir Davydov
Date: Wed Sep 24 2014 - 10:52:59 EST

memcg_can_account_kmem() returns true iff

!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg) &&

To begin with the !mem_cgroup_is_root(memcg) check is useless, because
one can't enable kmem accounting for the root cgroup (mem_cgroup_write()
returns EINVAL on an attempt to set the limit on the root cgroup).

Furthermore, the !mem_cgroup_disabled() check also seems to be
redundant. The point is memcg_can_account_kmem() is called from three
places: mem_cgroup_salbinfo_read(), __memcg_kmem_get_cache(), and
__memcg_kmem_newpage_charge(). The latter two functions are only invoked
if memcg_kmem_enabled() returns true, which implies that the memory
cgroup subsystem is enabled. And mem_cgroup_slabinfo_read() shows the
output of memory.kmem.slabinfo, which won't exist if the memory cgroup
is completely disabled.

So let's substitute all the calls to memcg_can_account_kmem() with plain
memcg_kmem_is_active(), and kill the former.

Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
mm/memcontrol.c | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1ec22bf380d0..63d58d79470d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2786,12 +2786,6 @@ static DEFINE_MUTEX(memcg_slab_mutex);

static DEFINE_MUTEX(activate_kmem_mutex);

-static inline bool memcg_can_account_kmem(struct mem_cgroup *memcg)
- return !mem_cgroup_disabled() && !mem_cgroup_is_root(memcg) &&
- memcg_kmem_is_active(memcg);
* This is a bit cumbersome, but it is rarely used and avoids a backpointer
* in the memcg_cache_params struct.
@@ -2811,7 +2805,7 @@ static int mem_cgroup_slabinfo_read(struct seq_file *m, void *v)
struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
struct memcg_cache_params *params;

- if (!memcg_can_account_kmem(memcg))
+ if (!memcg_kmem_is_active(memcg))
return -EIO;

@@ -3188,7 +3182,7 @@ struct kmem_cache *__memcg_kmem_get_cache(struct kmem_cache *cachep,
memcg = mem_cgroup_from_task(rcu_dereference(current->mm->owner));

- if (!memcg_can_account_kmem(memcg))
+ if (!memcg_kmem_is_active(memcg))
goto out;

memcg_cachep = cache_from_memcg_idx(cachep, memcg_cache_id(memcg));
@@ -3273,7 +3267,7 @@ __memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **_memcg, int order)

memcg = get_mem_cgroup_from_mm(current->mm);

- if (!memcg_can_account_kmem(memcg)) {
+ if (!memcg_kmem_is_active(memcg)) {
return true;

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