Function vdev_xlate

freebsd/contrib/openzfs/module/zfs/vdev.c:5108–5147

* Translate a logical range to the first contiguous physical range for the * specified vdev_t. This function is initially called with a leaf vdev and * will walk each parent vdev until it reaches a top-level vdev. Once the * top-level is reached the physical range is initialized and the recursive * function begins to unwind. As it unwinds it calls the parent's vdev * specific translation fun

 * specific translation function to do the real conversion.
 */
void
vdev_xlate(vdev_t *vd, const range_seg64_t *logical_rs,
    range_seg64_t *physical_rs, range_seg64_t *remain_rs)
{
	/*
	 * Walk up the vdev tree
	 */
	if (vd != vd->vdev_top) {
		vdev_xlate(vd->vdev_parent, logical_rs, physical_rs,
		    remain_rs);
	} else {
		/*
		 * We've reached the top-level vdev, initialize the physical
		 * range to the logical range and set an empty remaining
		 * range then start to unwind.
		 */
		physical_rs->rs_start = logical_rs->rs_start;
		physical_rs->rs_end = logical_rs->rs_end;

		remain_rs->rs_start = logical_rs->rs_start;
		remain_rs->rs_end = logical_rs->rs_start;

		return;
	}

	vdev_t *pvd = vd->vdev_parent;
	ASSERT3P(pvd, !=, NULL);
	ASSERT3P(pvd->vdev_ops->vdev_op_xlate, !=, NULL);

	/*
	 * As this recursive function unwinds, translate the logical
	 * range into its physical and any remaining components by calling
	 * the vdev specific translate function.
	 */
	range_seg64_t intermediate = { 0 };
	pvd->vdev_ops->vdev_op_xlate(vd, physical_rs, &intermediate, remain_rs);

	physical_rs->rs_start = intermediate.rs_start;
	physical_rs->rs_end = intermediate.rs_end;
}

void
vdev_xlate_walk(vdev_t *vd, const range_seg64_t *logical_rs,