Function vdev_mirror_io_start

freebsd/contrib/openzfs/module/zfs/vdev_mirror.c:624–702

}

static void
vdev_mirror_io_start(zio_t *zio)
{
	mirror_map_t *mm;
	mirror_child_t *mc;
	int c, children;

	mm = vdev_mirror_map_init(zio);

	if (mm == NULL) {
		ASSERT(!spa_trust_config(zio->io_spa));
		ASSERT(zio->io_type == ZIO_TYPE_READ);
		zio_execute(zio);
		return;
	}

	if (zio->io_type == ZIO_TYPE_READ) {
		if (zio->io_bp != NULL &&
		    (zio->io_flags & ZIO_FLAG_SCRUB) && !mm->mm_resilvering) {
			/*
			 * For scrubbing reads (if we can verify the
			 * checksum here, as indicated by io_bp being
			 * non-NULL) we need to allocate a read buffer for
			 * each child and issue reads to all children.  If
			 * any child succeeds, it will copy its data into
			 * zio->io_data in vdev_mirror_scrub_done.
			 */
			for (c = 0; c < mm->mm_children; c++) {
				mc = &mm->mm_child[c];
				zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
				    mc->mc_vd, mc->mc_offset,
				    abd_alloc_sametype(zio->io_abd,
				    zio->io_size), zio->io_size,
				    zio->io_type, zio->io_priority, 0,
				    vdev_mirror_scrub_done, mc));
			}
			zio_execute(zio);
			return;
		}
		/*
		 * For normal reads just pick one child.
		 */
		c = vdev_mirror_child_select(zio);
		children = (c >= 0);
	} else {
		ASSERT(zio->io_type == ZIO_TYPE_WRITE);

		/*
		 * Writes go to all children.
		 */
		c = 0;
		children = mm->mm_children;
	}

	while (children--) {
		mc = &mm->mm_child[c];
		c++;