Switched to use of sys_pread64()/sys_pwrite64() rather than keep duplicating
their guts; among the little things that had been missing there were such as
	ret = security_file_permission (file, MAY_READ);
Gotta love the LSM robustness, right?

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