is non-NULL. Note that link body isn't available anymore, so if you need it,
store it as cookie.
--
-[mandatory]
- __fd_install() & fd_install() can now sleep. Callers should not
- hold a spinlock or other resources that do not allow a schedule.
---
[mandatory]
any symlink that might use page_follow_link_light/page_put_link() must
have inode_nohighmem(inode) called before anything might start playing with