proc: introduce proc_create_single{,_data}

Variants of proc_create{,_data} that directly take a seq_file show
callback and drastically reduces the boilerplate code in the callers.

All trivial callers converted over.

Signed-off-by: Christoph Hellwig <hch@lst.de>

kernel/cgroup/cgroup-internal.h

@@ -218,9 +218,9 @@ extern const struct proc_ns_operations cgroupns_operations;
  * cgroup-v1.c
  */
 extern struct cftype cgroup1_base_files[];
-extern const struct file_operations proc_cgroupstats_operations;
 extern struct kernfs_syscall_ops cgroup1_kf_syscall_ops;
 
+int proc_cgroupstats_show(struct seq_file *m, void *v);
 bool cgroup1_ssid_disabled(int ssid);
 void cgroup1_pidlist_destroy_all(struct cgroup *cgrp);
 void cgroup1_release_agent(struct work_struct *work);

kernel/cgroup/cgroup-v1.c

@@ -682,7 +682,7 @@ struct cftype cgroup1_base_files[] = {
 };
 
 /* Display information about each subsystem and each hierarchy */
-static int proc_cgroupstats_show(struct seq_file *m, void *v)
+int proc_cgroupstats_show(struct seq_file *m, void *v)
 {
 	struct cgroup_subsys *ss;
 	int i;
@@ -705,18 +705,6 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v)
 	return 0;
 }
 
-static int cgroupstats_open(struct inode *inode, struct file *file)
-{
-	return single_open(file, proc_cgroupstats_show, NULL);
-}
-
-const struct file_operations proc_cgroupstats_operations = {
-	.open = cgroupstats_open,
-	.read = seq_read,
-	.llseek = seq_lseek,
-	.release = single_release,
-};
-
 /**
  * cgroupstats_build - build and fill cgroupstats
  * @stats: cgroupstats to fill information into

kernel/cgroup/cgroup.c

@@ -5335,7 +5335,7 @@ int __init cgroup_init(void)
 	WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup"));
 	WARN_ON(register_filesystem(&cgroup_fs_type));
 	WARN_ON(register_filesystem(&cgroup2_fs_type));
-	WARN_ON(!proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations));
+	WARN_ON(!proc_create_single("cgroups", 0, NULL, proc_cgroupstats_show));
 
 	return 0;
 }