cgroup: move cgroup v1 specific code to kernel/cgroup/cgroup-v1.c

cgroup.c is getting too unwieldy.  Let's move out cgroup v1 specific
code along with the debug controller into kernel/cgroup/cgroup-v1.c.

v2: cgroup_mutex and css_set_lock made available in cgroup-internal.h
    regardless of CONFIG_PROVE_RCU.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Acked-by: Zefan Li <lizefan@huawei.com>

kernel/cgroup/Makefile

-obj-y := cgroup.o
+obj-y := cgroup.o cgroup-v1.o
 
 obj-$(CONFIG_CGROUP_FREEZER) += freezer.o
 obj-$(CONFIG_CGROUP_PIDS) += pids.o

kernel/cgroup/cgroup-internal.h

+#ifndef __CGROUP_INTERNAL_H
+#define __CGROUP_INTERNAL_H
+
+#include <linux/cgroup.h>
+#include <linux/kernfs.h>
+#include <linux/workqueue.h>
+#include <linux/list.h>
+
+/*
+ * A cgroup can be associated with multiple css_sets as different tasks may
+ * belong to different cgroups on different hierarchies.  In the other
+ * direction, a css_set is naturally associated with multiple cgroups.
+ * This M:N relationship is represented by the following link structure
+ * which exists for each association and allows traversing the associations
+ * from both sides.
+ */
+struct cgrp_cset_link {
+	/* the cgroup and css_set this link associates */
+	struct cgroup		*cgrp;
+	struct css_set		*cset;
+
+	/* list of cgrp_cset_links anchored at cgrp->cset_links */
+	struct list_head	cset_link;
+
+	/* list of cgrp_cset_links anchored at css_set->cgrp_links */
+	struct list_head	cgrp_link;
+};
+
+extern struct mutex cgroup_mutex;
+extern spinlock_t css_set_lock;
+extern struct cgroup_subsys *cgroup_subsys[];
+extern struct list_head cgroup_roots;
+extern struct file_system_type cgroup_fs_type;
+
+/* iterate across the hierarchies */
+#define for_each_root(root)						\
+	list_for_each_entry((root), &cgroup_roots, root_list)
+
+/**
+ * for_each_subsys - iterate all enabled cgroup subsystems
+ * @ss: the iteration cursor
+ * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
+ */
+#define for_each_subsys(ss, ssid)					\
+	for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT &&		\
+	     (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
+
+static inline bool cgroup_is_dead(const struct cgroup *cgrp)
+{
+	return !(cgrp->self.flags & CSS_ONLINE);
+}
+
+static inline bool notify_on_release(const struct cgroup *cgrp)
+{
+	return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
+}
+
+bool cgroup_ssid_enabled(int ssid);
+bool cgroup_on_dfl(const struct cgroup *cgrp);
+
+struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root);
+struct cgroup *task_cgroup_from_root(struct task_struct *task,
+				     struct cgroup_root *root);
+struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn, bool drain_offline);
+void cgroup_kn_unlock(struct kernfs_node *kn);
+int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
+			  struct cgroup_namespace *ns);
+
+int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask);
+
+bool cgroup_may_migrate_to(struct cgroup *dst_cgrp);
+void cgroup_migrate_finish(struct list_head *preloaded_csets);
+void cgroup_migrate_add_src(struct css_set *src_cset,
+			    struct cgroup *dst_cgrp,
+			    struct list_head *preloaded_csets);
+int cgroup_migrate_prepare_dst(struct list_head *preloaded_csets);
+int cgroup_migrate(struct task_struct *leader, bool threadgroup,
+		   struct cgroup_root *root);
+
+int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
+		       bool threadgroup);
+ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
+			     size_t nbytes, loff_t off, bool threadgroup);
+ssize_t cgroup_procs_write(struct kernfs_open_file *of, char *buf, size_t nbytes,
+			   loff_t off);
+
+void cgroup_lock_and_drain_offline(struct cgroup *cgrp);
+
+/*
+ * cgroup-v1.c
+ */
+extern spinlock_t release_agent_path_lock;
+extern struct cftype cgroup_legacy_base_files[];
+extern const struct file_operations proc_cgroupstats_operations;
+
+bool cgroup_ssid_no_v1(int ssid);
+void cgroup_pidlist_destroy_all(struct cgroup *cgrp);
+int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
+		  const char *new_name_str);
+void cgroup_release_agent(struct work_struct *work);
+void check_for_release(struct cgroup *cgrp);
+
+#endif /* __CGROUP_INTERNAL_H */