Function vdev_get_min_asize

freebsd/contrib/openzfs/module/zfs/vdev.c:284–304

* Get the minimum allocatable size. We define the allocatable size as * the vdev's asize rounded to the nearest metaslab. This allows us to * replace or attach devices which don't have the same physical size but * can still satisfy the same number of allocations. */

 * can still satisfy the same number of allocations.
 */
uint64_t
vdev_get_min_asize(vdev_t *vd)
{
	vdev_t *pvd = vd->vdev_parent;

	/*
	 * If our parent is NULL (inactive spare or cache) or is the root,
	 * just return our own asize.
	 */
	if (pvd == NULL)
		return (vd->vdev_asize);

	/*
	 * The top-level vdev just returns the allocatable size rounded
	 * to the nearest metaslab.
	 */
	if (vd == vd->vdev_top)
		return (P2ALIGN(vd->vdev_asize, 1ULL << vd->vdev_ms_shift));

	return (pvd->vdev_ops->vdev_op_min_asize(pvd));
}

void
vdev_set_min_asize(vdev_t *vd)