Still digesting the algorithmic changes, but a few nitpicks below:
> /*
> + * BLock allocation algorithm and data structures.
I think the upper case L is a typo.
> +struct xfs_alloc_btree_cur {
> + struct xfs_btree_cur *cur; /* cursor */
> + bool active; /* cursor active flag */
> +};
Can't we move the active flag inside the btree_cur, more specically
into enum xfs_btree_cur_private?
Or maybe we should byte the bullet and make xfs_btree_cur a structure
embedded into the type specific structures and use container_of.
But I certainly don't want to burden that on you and this series..
