Index: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_queue.c
===================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_queue.c
+++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_queue.c
@@ -670,6 +670,7 @@
 vdev_queue_aggregate(vdev_queue_t *vq, zio_t *zio)
 {
 	zio_t *first, *last, *aio, *dio, *mandatory, *nio;
+	zio_link_t *zl = NULL;
 	uint64_t maxgap = 0;
 	uint64_t size;
 	boolean_t stretch;
@@ -813,9 +814,18 @@
 
 		zio_add_child(dio, aio);
 		vdev_queue_io_remove(vq, dio);
+	} while (dio != last);
+
+	/*
+	 * We need to drop the vdev queue's lock to avoid a deadlock that we
+	 * could encounter since this I/O will complete immediately.
+	 */
+	mutex_exit(&vq->vq_lock);
+	while ((dio = zio_walk_parents(aio, &zl)) != NULL) {
 		zio_vdev_io_bypass(dio);
 		zio_execute(dio);
-	} while (dio != last);
+	}
+	mutex_enter(&vq->vq_lock);
 
 	return (aio);
 }