diff --git a/include/sys/spa.h b/include/sys/spa.h
index 12321c6562..3998f5a6de 100644
--- a/include/sys/spa.h
+++ b/include/sys/spa.h
@@ -1049,8 +1049,7 @@ extern metaslab_class_t *spa_log_class(spa_t *spa);
 extern metaslab_class_t *spa_embedded_log_class(spa_t *spa);
 extern metaslab_class_t *spa_special_class(spa_t *spa);
 extern metaslab_class_t *spa_dedup_class(spa_t *spa);
-extern metaslab_class_t *spa_preferred_class(spa_t *spa, uint64_t size,
-    dmu_object_type_t objtype, uint_t level, uint_t special_smallblk);
+extern metaslab_class_t *spa_preferred_class(spa_t *spa, const zio_t *zio);
 extern boolean_t spa_special_has_ddt(spa_t *spa);
 
 extern void spa_evicting_os_register(spa_t *, objset_t *os);
diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
index 439e56f0d0..c9ee36c0f9 100644
--- a/module/zfs/spa_misc.c
+++ b/module/zfs/spa_misc.c
@@ -2007,9 +2007,11 @@ spa_special_has_ddt(spa_t *spa)
  * Locate an appropriate allocation class
  */
 metaslab_class_t *
-spa_preferred_class(spa_t *spa, uint64_t size, dmu_object_type_t objtype,
-    uint_t level, uint_t special_smallblk)
+spa_preferred_class(spa_t *spa, const zio_t *zio)
 {
+	const zio_prop_t *zp = &zio->io_prop;
+	dmu_object_type_t objtype = zp->zp_type;
+
 	/*
 	 * ZIL allocations determine their class in zio_alloc_zil().
 	 */
@@ -2027,14 +2029,15 @@ spa_preferred_class(spa_t *spa, uint64_t size, dmu_object_type_t objtype,
 	}
 
 	/* Indirect blocks for user data can land in special if allowed */
-	if (level > 0 && (DMU_OT_IS_FILE(objtype) || objtype == DMU_OT_ZVOL)) {
+	if (zp->zp_level > 0 &&
+	    (DMU_OT_IS_FILE(objtype) || objtype == DMU_OT_ZVOL)) {
 		if (has_special_class && zfs_user_indirect_is_special)
 			return (spa_special_class(spa));
 		else
 			return (spa_normal_class(spa));
 	}
 
-	if (DMU_OT_IS_METADATA(objtype) || level > 0) {
+	if (DMU_OT_IS_METADATA(objtype) || zp->zp_level > 0) {
 		if (has_special_class)
 			return (spa_special_class(spa));
 		else
@@ -2047,7 +2050,7 @@ spa_preferred_class(spa_t *spa, uint64_t size, dmu_object_type_t objtype,
 	 * zfs_special_class_metadata_reserve_pct exclusively for metadata.
 	 */
 	if (DMU_OT_IS_FILE(objtype) &&
-	    has_special_class && size <= special_smallblk) {
+	    has_special_class && zio->io_size <= zp->zp_zpl_smallblk) {
 		metaslab_class_t *special = spa_special_class(spa);
 		uint64_t alloc = metaslab_class_get_alloc(special);
 		uint64_t space = metaslab_class_get_space(special);
diff --git a/module/zfs/zio.c b/module/zfs/zio.c
index bc5a3c9b70..7810113737 100644
--- a/module/zfs/zio.c
+++ b/module/zfs/zio.c
@@ -3637,8 +3637,7 @@ zio_dva_throttle(zio_t *zio)
 	metaslab_class_t *mc;
 
 	/* locate an appropriate allocation class */
-	mc = spa_preferred_class(spa, zio->io_size, zio->io_prop.zp_type,
-	    zio->io_prop.zp_level, zio->io_prop.zp_zpl_smallblk);
+	mc = spa_preferred_class(spa, zio);
 
 	if (zio->io_priority == ZIO_PRIORITY_SYNC_WRITE ||
 	    !mc->mc_alloc_throttle_enabled ||
@@ -3710,9 +3709,7 @@ zio_dva_allocate(zio_t *zio)
 	 */
 	mc = zio->io_metaslab_class;
 	if (mc == NULL) {
-		mc = spa_preferred_class(spa, zio->io_size,
-		    zio->io_prop.zp_type, zio->io_prop.zp_level,
-		    zio->io_prop.zp_zpl_smallblk);
+		mc = spa_preferred_class(spa, zio);
 		zio->io_metaslab_class = mc;
 	}