memcg: only check memcg_kmem_skip_account in __memcg_kmem_get_cache

__memcg_kmem_get_cache can recurse if it calls kmalloc (which it does if
the cgroup's kmem cache doesn't exist), because kmalloc may call
__memcg_kmem_get_cache internally again.  To avoid the recursion, we use
the task_struct->memcg_kmem_skip_account flag.

However, there's no need checking the flag in memcg_kmem_newpage_charge,
because there's no way how this function could result in recursion, if
called from memcg_kmem_get_cache.  So let's remove the redundant code.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 28 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index bb8c237026cc..d9fab72da52e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2905,34 +2905,6 @@ __memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **_memcg, int order)
 
         *_memcg = NULL;
 
-        /*
-         * Disabling accounting is only relevant for some specific memcg
-         * internal allocations. Therefore we would initially not have such
-         * check here, since direct calls to the page allocator that are
-         * accounted to kmemcg (alloc_kmem_pages and friends) only happen
-         * outside memcg core. We are mostly concerned with cache allocations,
-         * and by having this test at memcg_kmem_get_cache, we are already able
-         * to relay the allocation to the root cache and bypass the memcg cache
-         * altogether.
-         *
-         * There is one exception, though: the SLUB allocator does not create
-         * large order caches, but rather service large kmallocs directly from
-         * the page allocator. Therefore, the following sequence when backed by
-         * the SLUB allocator:
-         *
-         *      memcg_stop_kmem_account();
-         *      kmalloc(<large_number>)
-         *      memcg_resume_kmem_account();
-         *
-         * would effectively ignore the fact that we should skip accounting,
-         * since it will drive us directly to this function without passing
-         * through the cache selector memcg_kmem_get_cache. Such large
-         * allocations are extremely rare but can happen, for instance, for the
-         * cache arrays. We bring this test here.
-         */
-        if (current->memcg_kmem_skip_account)
-                return true;
-
         memcg = get_mem_cgroup_from_mm(current->mm);
 
         if (!memcg_kmem_is_active(memcg)) {