[PATCH rfc 9/9] mm: memcg: put cgroup v1-related members of task_struct under config option

[Roman Gushchin <roman.gushchin@linux.dev>]

Guard cgroup v1-related members of task_struct under the CONFIG_MEMCG_V1
config option, so that users who adopted cgroup v2 don't have to waste
the memory for fields which are never accessed.

Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
---
 include/linux/memcontrol.h | 11 ++++++++++-
 include/linux/sched.h      |  5 ++++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 4347d6889fa0..8005d749f8fc 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -944,6 +944,7 @@ void mem_cgroup_print_oom_context(struct mem_cgroup *memcg,
 
 void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg);
 
+#ifdef CONFIG_MEMCG_V1
 static inline void mem_cgroup_enter_user_fault(void)
 {
 	WARN_ON(current->in_user_fault);
@@ -961,9 +962,17 @@ static inline bool task_in_memcg_oom(struct task_struct *p)
 	return p->memcg_in_oom;
 }
 
-#ifdef CONFIG_MEMCG_V1
 bool mem_cgroup_oom_synchronize(bool wait);
 #else
+static inline void mem_cgroup_enter_user_fault(void) {}
+
+static inline void mem_cgroup_exit_user_fault(void) {}
+
+static inline bool task_in_memcg_oom(struct task_struct *p)
+{
+	return false;
+}
+
 static inline bool mem_cgroup_oom_synchronize(bool wait)
 {
 	return false;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4118b3f959c3..2ecdeb7588e3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1446,11 +1446,14 @@ struct task_struct {
 	unsigned int			kcov_softirq;
 #endif
 
-#ifdef CONFIG_MEMCG
+
+#ifdef CONFIG_MEMCG_V1
 	struct mem_cgroup		*memcg_in_oom;
 	gfp_t				memcg_oom_gfp_mask;
 	int				memcg_oom_order;
+#endif
 
+#ifdef CONFIG_MEMCG
 	/* Number of pages to reclaim on returning to userland: */
 	unsigned int			memcg_nr_pages_over_high;
 
-- 
2.43.2