proc: constify seq_operations

proc_uid_seq_operations, proc_gid_seq_operations and
proc_projid_seq_operations are only called in proc_id_map_open with
seq_open as const struct seq_operations so we can constify the 3
structures and update proc_id_map_open prototype.

   text    data     bss     dec     hex filename
   6817     404    1984    9205    23f5 kernel/user_namespace.o-before
   6913     308    1984    9205    23f5 kernel/user_namespace.o-after

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/base.c

@@ -2449,7 +2449,7 @@ static int proc_tgid_io_accounting(struct task_struct *task, char *buffer)
 
 #ifdef CONFIG_USER_NS
 static int proc_id_map_open(struct inode *inode, struct file *file,
-	struct seq_operations *seq_ops)
+	const struct seq_operations *seq_ops)
 {
 	struct user_namespace *ns = NULL;
 	struct task_struct *task;

include/linux/user_namespace.h

@@ -57,9 +57,9 @@ static inline void put_user_ns(struct user_namespace *ns)
 }
 
 struct seq_operations;
-extern struct seq_operations proc_uid_seq_operations;
-extern struct seq_operations proc_gid_seq_operations;
-extern struct seq_operations proc_projid_seq_operations;
+extern const struct seq_operations proc_uid_seq_operations;
+extern const struct seq_operations proc_gid_seq_operations;
+extern const struct seq_operations proc_projid_seq_operations;
 extern ssize_t proc_uid_map_write(struct file *, const char __user *, size_t, loff_t *);
 extern ssize_t proc_gid_map_write(struct file *, const char __user *, size_t, loff_t *);
 extern ssize_t proc_projid_map_write(struct file *, const char __user *, size_t, loff_t *);

kernel/user_namespace.c

@@ -526,21 +526,21 @@ static void m_stop(struct seq_file *seq, void *v)
 	return;
 }
 
-struct seq_operations proc_uid_seq_operations = {
+const struct seq_operations proc_uid_seq_operations = {
 	.start = uid_m_start,
 	.stop = m_stop,
 	.next = m_next,
 	.show = uid_m_show,
 };
 
-struct seq_operations proc_gid_seq_operations = {
+const struct seq_operations proc_gid_seq_operations = {
 	.start = gid_m_start,
 	.stop = m_stop,
 	.next = m_next,
 	.show = gid_m_show,
 };
 
-struct seq_operations proc_projid_seq_operations = {
+const struct seq_operations proc_projid_seq_operations = {
 	.start = projid_m_start,
 	.stop = m_stop,
 	.next = m_next,