Rework /proc/locks via seq_files and seq_list helpers

Currently /proc/locks is shown with a proc_read function, but its behavior
is rather complex as it has to manually handle current offset and buffer
length.  On the other hand, files that show objects from lists can be
easily reimplemented using the sequential files and the seq_list_XXX()
helpers.

This saves (as usually) 16 lines of code and more than 200 from
the .text section.

[akpm@linux-foundation.org: no externs in C]
[akpm@linux-foundation.org: warning fixes]
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f5075e0..4f1e8ce 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -883,6 +883,7 @@
 extern int lease_modify(struct file_lock **, int);
 extern int lock_may_read(struct inode *, loff_t start, unsigned long count);
 extern int lock_may_write(struct inode *, loff_t start, unsigned long count);
+extern struct seq_operations locks_seq_operations;
 
 struct fasync_struct {
 	int	magic;