- use nonseekable_open() instead of messing with

	if (*ppos != file->f_pos)
		return -EISPIPE

   in ->write() (->read is NULL).

 - trivial __user annotations
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>