cgroup: separate out cgroup1_kf_syscall_ops

Currently, cgroup_kf_syscall_ops is shared by v1 and v2 and the
specific methods test the version and take different actions.  Split
out v1 functions and put them in cgroup1_kf_syscall_ops and remove the
now unnecessary explicit branches in specific methods.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Acked-by: Zefan Li <lizefan@huawei.com>

kernel/cgroup/cgroup-internal.h

@@ -95,7 +95,7 @@ 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,
+int cgroup1_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);

kernel/cgroup/cgroup-v1.c

@@ -800,7 +800,7 @@ void cgroup_release_agent(struct work_struct *work)
 /*
  * cgroup_rename - Only allow simple rename of directories in place.
  */
-int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
+int cgroup1_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
 		   const char *new_name_str)
 {
 	struct cgroup *cgrp = kn->priv;
@@ -811,13 +811,6 @@ int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
 	if (kn->parent != new_parent)
 		return -EIO;
 
-	/*
-	 * This isn't a proper migration and its usefulness is very
-	 * limited.  Disallow on the default hierarchy.
-	 */
-	if (cgroup_on_dfl(cgrp))
-		return -EPERM;
-
 	/*
 	 * We're gonna grab cgroup_mutex which nests outside kernfs
 	 * active_ref.  kernfs_rename() doesn't require active_ref

kernel/cgroup/cgroup.c

@@ -1232,6 +1232,7 @@ struct cgroup *task_cgroup_from_root(struct task_struct *task,
  * update of a tasks cgroup pointer by cgroup_attach_task()
  */
 
+static struct kernfs_syscall_ops cgroup1_kf_syscall_ops;
 static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
 
 static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
@@ -1566,13 +1567,12 @@ static int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
 	return len;
 }
 
-static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
+static int cgroup1_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
 {
 	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
 	struct cgroup_subsys *ss;
 	int ssid;
 
-	if (root != &cgrp_dfl_root)
 	for_each_subsys(ss, ssid)
 		if (root->subsys_mask & (1 << ssid))
 			seq_show_option(seq, ss->legacy_name, NULL);
@@ -1736,18 +1736,13 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
 	return 0;
 }
 
-static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
+static int cgroup1_remount(struct kernfs_root *kf_root, int *flags, char *data)
 {
 	int ret = 0;
 	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
 	struct cgroup_sb_opts opts;
 	u16 added_mask, removed_mask;
 
-	if (root == &cgrp_dfl_root) {
-		pr_err("remount is not allowed\n");
-		return -EINVAL;
-	}
-
 	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
 
 	/* See what subsystems are wanted */
@@ -1798,6 +1793,12 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
 	return ret;
 }
 
+static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
+{
+	pr_err("remount is not allowed\n");
+	return -EINVAL;
+}
+
 /*
  * To reduce the fork() overhead for systems that are not actually using
  * their cgroups capability, we don't maintain the lists running through
@@ -1900,6 +1901,7 @@ static int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
 {
 	LIST_HEAD(tmp_links);
 	struct cgroup *root_cgrp = &root->cgrp;
+	struct kernfs_syscall_ops *kf_sops;
 	struct css_set *cset;
 	int i, ret;
 
@@ -1931,7 +1933,10 @@ static int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
 	if (ret)
 		goto cancel_ref;
 
-	root->kf_root = kernfs_create_root(&cgroup_kf_syscall_ops,
+	kf_sops = root == &cgrp_dfl_root ?
+		&cgroup_kf_syscall_ops : &cgroup1_kf_syscall_ops;
+
+	root->kf_root = kernfs_create_root(kf_sops,
 					   KERNFS_ROOT_CREATE_DEACTIVATED,
 					   root_cgrp);
 	if (IS_ERR(root->kf_root)) {
@@ -4813,12 +4818,19 @@ static int cgroup_rmdir(struct kernfs_node *kn)
 	return ret;
 }
 
+static struct kernfs_syscall_ops cgroup1_kf_syscall_ops = {
+	.remount_fs		= cgroup1_remount,
+	.show_options		= cgroup1_show_options,
+	.rename			= cgroup1_rename,
+	.mkdir			= cgroup_mkdir,
+	.rmdir			= cgroup_rmdir,
+	.show_path		= cgroup_show_path,
+};
+
 static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
 	.remount_fs		= cgroup_remount,
-	.show_options		= cgroup_show_options,
 	.mkdir			= cgroup_mkdir,
 	.rmdir			= cgroup_rmdir,
-	.rename			= cgroup_rename,
 	.show_path		= cgroup_show_path,
 };