[PATCH 4/5] mm: memcontrol: move remote memcg charging APIs to CONFIG_MEMCG_KMEM

[Muchun Song <songmuchun@bytedance.com>]

The remote memcg charing APIs is a mechanism to charge kernel memory
to a given memcg. So we can move the infrastructure to the scope of
the CONFIG_MEMCG_KMEM.

As a bonus, on !CONFIG_MEMCG_KMEM build some functions and variables
can be compiled out.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 include/linux/sched.h    | 2 ++
 include/linux/sched/mm.h | 2 +-
 kernel/fork.c            | 2 +-
 mm/memcontrol.c          | 4 ++++
 4 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index ee46f5cab95b..c2d488eddf85 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1314,7 +1314,9 @@ struct task_struct {
 
 	/* Number of pages to reclaim on returning to userland: */
 	unsigned int			memcg_nr_pages_over_high;
+#endif
 
+#ifdef CONFIG_MEMCG_KMEM
 	/* Used by memcontrol for targeted memcg charge: */
 	struct mem_cgroup		*active_memcg;
 #endif
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 1ae08b8462a4..64a72975270e 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -294,7 +294,7 @@ static inline void memalloc_nocma_restore(unsigned int flags)
 }
 #endif
 
-#ifdef CONFIG_MEMCG
+#ifdef CONFIG_MEMCG_KMEM
 DECLARE_PER_CPU(struct mem_cgroup *, int_active_memcg);
 /**
  * set_active_memcg - Starts the remote memcg charging scope.
diff --git a/kernel/fork.c b/kernel/fork.c
index d66cd1014211..d66718bc82d5 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -942,7 +942,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 	tsk->use_memdelay = 0;
 #endif
 
-#ifdef CONFIG_MEMCG
+#ifdef CONFIG_MEMCG_KMEM
 	tsk->active_memcg = NULL;
 #endif
 	return tsk;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 39cb8c5bf8b2..092dc4588b43 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -76,8 +76,10 @@ EXPORT_SYMBOL(memory_cgrp_subsys);
 
 struct mem_cgroup *root_mem_cgroup __read_mostly;
 
+#ifdef CONFIG_MEMCG_KMEM
 /* Active memory cgroup to use from an interrupt context */
 DEFINE_PER_CPU(struct mem_cgroup *, int_active_memcg);
+#endif
 
 /* Socket memory accounting disabled? */
 static bool cgroup_memory_nosocket;
@@ -1054,6 +1056,7 @@ struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
 }
 EXPORT_SYMBOL(get_mem_cgroup_from_mm);
 
+#ifdef CONFIG_MEMCG_KMEM
 static __always_inline struct mem_cgroup *active_memcg(void)
 {
 	if (in_interrupt())
@@ -1074,6 +1077,7 @@ static __always_inline bool memcg_kmem_bypass(void)
 
 	return false;
 }
+#endif
 
 /**
  * mem_cgroup_iter - iterate over memory cgroup hierarchy
-- 
2.11.0