[PATCH] reduce sizeof(struct file)

Now that RCU applied on 'struct file' seems stable, we can place f_rcuhead
in a memory location that is not anymore used at call_rcu(&f->f_rcuhead,
file_free_rcu) time, to reduce the size of this critical kernel object.

The trick I used is to move f_rcuhead and f_list in an union called f_u

The callers are changed so that f_rcuhead becomes f_u.fu_rcuhead and f_list
becomes f_u.f_list

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index 7a387fe..fdc3823 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -914,7 +914,7 @@
 
 	file_list_lock();
 	list_for_each(p, &sb->s_files) {
-		struct file * filp = list_entry(p, struct file, f_list);
+		struct file * filp = list_entry(p, struct file, f_u.fu_list);
 		struct dentry * dentry = filp->f_dentry;
 
 		if (dentry->d_parent != de) {