[PATCH] Add lockless helpers for remove_suid()

Right now users have to grab i_mutex before calling remove_suid(), in the
unlikely event that a call to ->setattr() may be needed. Split up the
function in two parts:

- One to check if we need to remove suid
- One to actually remove it

The first we can call lockless.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d695ba2..2fe6e3f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1712,6 +1712,8 @@
 extern void clear_inode(struct inode *);
 extern void destroy_inode(struct inode *);
 extern struct inode *new_inode(struct super_block *);
+extern int __remove_suid(struct dentry *, int);
+extern int should_remove_suid(struct dentry *);
 extern int remove_suid(struct dentry *);
 extern void remove_dquot_ref(struct super_block *, int, struct list_head *);