memcg: remove memcg_kmem_skip_account

The flag memcg_kmem_skip_account was added during the era of opt-out kmem
accounting.  There is no need for such flag in the opt-in world as there
aren't any __GFP_ACCOUNT allocations within memcg_create_cache_enqueue().

Link: http://lkml.kernel.org/r/20180919004501.178023-1-shakeelb@google.com
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/sched.h

@@ -724,9 +724,6 @@ struct task_struct {
 #endif
 #ifdef CONFIG_MEMCG
 	unsigned			in_user_fault:1;
-#ifdef CONFIG_MEMCG_KMEM
-	unsigned			memcg_kmem_skip_account:1;
-#endif
 #endif
 #ifdef CONFIG_COMPAT_BRK
 	unsigned			brk_randomized:1;

mm/memcontrol.c

@@ -2460,7 +2460,7 @@ static void memcg_kmem_cache_create_func(struct work_struct *w)
 /*
  * Enqueue the creation of a per-memcg kmem_cache.
  */
-static void __memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
+static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
 					       struct kmem_cache *cachep)
 {
 	struct memcg_kmem_cache_create_work *cw;
@@ -2478,25 +2478,6 @@ static void __memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
 	queue_work(memcg_kmem_cache_wq, &cw->work);
 }
 
-static void memcg_schedule_kmem_cache_create(struct mem_cgroup *memcg,
-					     struct kmem_cache *cachep)
-{
-	/*
-	 * We need to stop accounting when we kmalloc, because if the
-	 * corresponding kmalloc cache is not yet created, the first allocation
-	 * in __memcg_schedule_kmem_cache_create will recurse.
-	 *
-	 * However, it is better to enclose the whole function. Depending on
-	 * the debugging options enabled, INIT_WORK(), for instance, can
-	 * trigger an allocation. This too, will make us recurse. Because at
-	 * this point we can't allow ourselves back into memcg_kmem_get_cache,
-	 * the safest choice is to do it like this, wrapping the whole function.
-	 */
-	current->memcg_kmem_skip_account = 1;
-	__memcg_schedule_kmem_cache_create(memcg, cachep);
-	current->memcg_kmem_skip_account = 0;
-}
-
 static inline bool memcg_kmem_bypass(void)
 {
 	if (in_interrupt() || !current->mm || (current->flags & PF_KTHREAD))
@@ -2531,9 +2512,6 @@ struct kmem_cache *memcg_kmem_get_cache(struct kmem_cache *cachep)
 	if (memcg_kmem_bypass())
 		return cachep;
 
-	if (current->memcg_kmem_skip_account)
-		return cachep;
-
 	memcg = get_mem_cgroup_from_current();
 	kmemcg_id = READ_ONCE(memcg->kmemcg_id);
 	if (kmemcg_id < 0)