[PATCH v2 -next 10/11] cgroup/cpuset: guard cpuset-v1 code under CONFIG_CPUSETS_V1

[Chen Ridong <chenridong@huawei.com>]

This patch introduces CONFIG_CPUSETS_V1 and guard cpuset-v1 code under
CONFIG_CPUSETS_V1. The default value of CONFIG_CPUSETS_V1 is N, so that
user who adopted v2 don't have 'pay' for cpuset v1.

Signed-off-by: Chen Ridong <chenridong@huawei.com>
---
 include/linux/cpuset.h          |  4 ++++
 init/Kconfig                    | 13 +++++++++++++
 kernel/cgroup/Makefile          |  3 ++-
 kernel/cgroup/cpuset-internal.h | 13 +++++++++++++
 kernel/cgroup/cpuset.c          |  2 ++
 5 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 2a6981eeebf8..835e7b793f6a 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -99,6 +99,7 @@ static inline bool cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask)
 extern int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
 					  const struct task_struct *tsk2);
 
+#ifdef CONFIG_CPUSETS_V1
 #define cpuset_memory_pressure_bump() 				\
 	do {							\
 		if (cpuset_memory_pressure_enabled)		\
@@ -106,6 +107,9 @@ extern int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
 	} while (0)
 extern int cpuset_memory_pressure_enabled;
 extern void __cpuset_memory_pressure_bump(void);
+#else
+static inline void cpuset_memory_pressure_bump(void) { }
+#endif
 
 extern void cpuset_task_status_allowed(struct seq_file *m,
 					struct task_struct *task);
diff --git a/init/Kconfig b/init/Kconfig
index a465ea9525bd..8bf091354bea 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1143,6 +1143,19 @@ config CPUSETS
 
 	  Say N if unsure.
 
+config CPUSETS_V1
+	bool "Legacy cgroup v1 cpusets controller"
+	depends on CPUSETS
+	default n
+	help
+	  Legacy cgroup v1 cpusets controller which has been deprecated by
+	  cgroup v2 implementation. The v1 is there for legacy applications
+	  which haven't migrated to the new cgroup v2 interface yet. If you
+	  do not have any such application then you are completely fine leaving
+	  this option disabled.
+
+	  Say N if unsure.
+
 config PROC_PID_CPUSET
 	bool "Include legacy /proc/<pid>/cpuset file"
 	depends on CPUSETS
diff --git a/kernel/cgroup/Makefile b/kernel/cgroup/Makefile
index 005ac4c675cb..a5c9359d516f 100644
--- a/kernel/cgroup/Makefile
+++ b/kernel/cgroup/Makefile
@@ -4,6 +4,7 @@ obj-y := cgroup.o rstat.o namespace.o cgroup-v1.o freezer.o
 obj-$(CONFIG_CGROUP_FREEZER) += legacy_freezer.o
 obj-$(CONFIG_CGROUP_PIDS) += pids.o
 obj-$(CONFIG_CGROUP_RDMA) += rdma.o
-obj-$(CONFIG_CPUSETS) += cpuset.o cpuset-v1.o
+obj-$(CONFIG_CPUSETS) += cpuset.o
+obj-$(CONFIG_CPUSETS_V1) += cpuset-v1.o
 obj-$(CONFIG_CGROUP_MISC) += misc.o
 obj-$(CONFIG_CGROUP_DEBUG) += debug.o
diff --git a/kernel/cgroup/cpuset-internal.h b/kernel/cgroup/cpuset-internal.h
index a6c71c86e58d..7ec702dff877 100644
--- a/kernel/cgroup/cpuset-internal.h
+++ b/kernel/cgroup/cpuset-internal.h
@@ -279,6 +279,7 @@ int cpuset_common_seq_show(struct seq_file *sf, void *v);
 /*
  * cpuset-v1.c
  */
+#ifdef CONFIG_CPUSETS_V1
 extern struct cftype legacy_files[];
 void fmeter_init(struct fmeter *fmp);
 void cpuset_update_task_spread_flags(struct cpuset *cs,
@@ -289,4 +290,16 @@ void hotplug_update_tasks_legacy(struct cpuset *cs,
 			    bool cpus_updated, bool mems_updated);
 int validate_change_legacy(struct cpuset *cur, struct cpuset *trial);
 
+#else
+static inline void fmeter_init(struct fmeter *fmp) {}
+static inline void cpuset_update_task_spread_flags(struct cpuset *cs,
+					struct task_struct *tsk) {}
+static inline void update_tasks_flags(struct cpuset *cs) {}
+static inline void hotplug_update_tasks_legacy(struct cpuset *cs,
+			    struct cpumask *new_cpus, nodemask_t *new_mems,
+			    bool cpus_updated, bool mems_updated) {}
+static inline int validate_change_legacy(struct cpuset *cur,
+				struct cpuset *trial) { return 0; }
+
+#endif /* CONFIG_CPUSETS_V1 */
 #endif /* __CPUSET_INTERNAL_H */
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 2f52fe488f3a..2cefeaaff742 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3617,7 +3617,9 @@ struct cgroup_subsys cpuset_cgrp_subsys = {
 	.can_fork	= cpuset_can_fork,
 	.cancel_fork	= cpuset_cancel_fork,
 	.fork		= cpuset_fork,
+#ifdef CONFIG_CPUSETS_V1
 	.legacy_cftypes	= legacy_files,
+#endif
 	.dfl_cftypes	= dfl_files,
 	.early_init	= true,
 	.threaded	= true,
-- 
2.34.1