mm: memcg: put struct task_struct::in_user_fault under CONFIG_MEMCG_V1

The struct task_struct's in_user_fault member is not used by the cgroup
v2's memory controller, so it can be put under the CONFIG_MEMCG_V1 config
option.  To do so, mem_cgroup_enter_user_fault() and
mem_cgroup_exit_user_fault() are moved under the CONFIG_MEMCG_V1 option as
well.

Link: https://lkml.kernel.org/r/20240628210317.272856-10-roman.gushchin@linux.devSigned-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/memcontrol.h

@@ -943,18 +943,6 @@ void mem_cgroup_print_oom_context(struct mem_cgroup *memcg,
 
 void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg);
 
-static inline void mem_cgroup_enter_user_fault(void)
-{
-	WARN_ON(current->in_user_fault);
-	current->in_user_fault = 1;
-}
-
-static inline void mem_cgroup_exit_user_fault(void)
-{
-	WARN_ON(!current->in_user_fault);
-	current->in_user_fault = 0;
-}
-
 struct mem_cgroup *mem_cgroup_get_oom_group(struct task_struct *victim,
 					    struct mem_cgroup *oom_domain);
 void mem_cgroup_print_oom_group(struct mem_cgroup *memcg);
@@ -1402,14 +1390,6 @@ static inline void mem_cgroup_handle_over_high(gfp_t gfp_mask)
 {
 }
 
-static inline void mem_cgroup_enter_user_fault(void)
-{
-}
-
-static inline void mem_cgroup_exit_user_fault(void)
-{
-}
-
 static inline struct mem_cgroup *mem_cgroup_get_oom_group(
 	struct task_struct *victim, struct mem_cgroup *oom_domain)
 {
@@ -1890,6 +1870,18 @@ static inline void mem_cgroup_unlock_pages(void)
 	rcu_read_unlock();
 }
 
+static inline void mem_cgroup_enter_user_fault(void)
+{
+	WARN_ON(current->in_user_fault);
+	current->in_user_fault = 1;
+}
+
+static inline void mem_cgroup_exit_user_fault(void)
+{
+	WARN_ON(!current->in_user_fault);
+	current->in_user_fault = 0;
+}
+
 #else /* CONFIG_MEMCG_V1 */
 static inline
 unsigned long memcg1_soft_limit_reclaim(pg_data_t *pgdat, int order,
@@ -1929,6 +1921,14 @@ static inline bool mem_cgroup_oom_synchronize(bool wait)
 	return false;
 }
 
+static inline void mem_cgroup_enter_user_fault(void)
+{
+}
+
+static inline void mem_cgroup_exit_user_fault(void)
+{
+}
+
 #endif /* CONFIG_MEMCG_V1 */
 
 #endif /* _LINUX_MEMCONTROL_H */

include/linux/sched.h

@@ -934,7 +934,7 @@ struct task_struct {
 #ifndef TIF_RESTORE_SIGMASK
 	unsigned			restore_sigmask:1;
 #endif
-#ifdef CONFIG_MEMCG
+#ifdef CONFIG_MEMCG_V1
 	unsigned			in_user_fault:1;
 #endif
 #ifdef CONFIG_LRU_GEN