This commit pulls those portions of the kernel implementation of
delayed refs which are necessary to have them working in user-space.
I've done the following modifications:
1. Replaced all kmem_cache_alloc calls to kmalloc.
2. Removed all locking-related code, since we are single threaded in
3. Removed code which deals with data refs - delayed refs in user space
are going to be used only for cowonly trees.
Signed-off-by: Nikolay Borisov <firstname.lastname@example.org>
Signed-off-by: David Sterba <email@example.com>