fs/proc: use __ro_after_init

/proc/self inode numbers, value of proc_inode_cache and st_nlink of
/proc/$TGID are fixed constants.

Link: http://lkml.kernel.org/r/20180103184707.GA31849@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/base.c

@@ -75,6 +75,7 @@
 #include <linux/ptrace.h>
 #include <linux/tracehook.h>
 #include <linux/printk.h>
+#include <linux/cache.h>
 #include <linux/cgroup.h>
 #include <linux/cpuset.h>
 #include <linux/audit.h>
@@ -112,8 +113,8 @@
  *	in /proc for a task before it execs a suid executable.
  */
 
-static u8 nlink_tid;
-static u8 nlink_tgid;
+static u8 nlink_tid __ro_after_init;
+static u8 nlink_tgid __ro_after_init;
 
 struct pid_entry {
 	const char *name;

fs/proc/inode.c

@@ -5,6 +5,7 @@
  *  Copyright (C) 1991, 1992  Linus Torvalds
  */
 
+#include <linux/cache.h>
 #include <linux/time.h>
 #include <linux/proc_fs.h>
 #include <linux/kernel.h>
@@ -52,7 +53,7 @@ static void proc_evict_inode(struct inode *inode)
 	}
 }
 
-static struct kmem_cache * proc_inode_cachep;
+static struct kmem_cache *proc_inode_cachep __ro_after_init;
 
 static struct inode *proc_alloc_inode(struct super_block *sb)
 {

fs/proc/self.c

@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
+#include <linux/cache.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/pid_namespace.h>
@@ -30,7 +31,7 @@ static const struct inode_operations proc_self_inode_operations = {
 	.get_link	= proc_self_get_link,
 };
 
-static unsigned self_inum;
+static unsigned self_inum __ro_after_init;
 
 int proc_setup_self(struct super_block *s)
 {

fs/proc/thread_self.c

@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
+#include <linux/cache.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/pid_namespace.h>
@@ -30,7 +31,7 @@ static const struct inode_operations proc_thread_self_inode_operations = {
 	.get_link	= proc_thread_self_get_link,
 };
 
-static unsigned thread_self_inum;
+static unsigned thread_self_inum __ro_after_init;
 
 int proc_setup_thread_self(struct super_block *s)
 {