--- a/usr/src/uts/common/fs/zfs/zvol.c	Thu Apr 29 15:27:29 2010 -0400
+++ b/usr/src/uts/common/fs/zfs/zvol.c	Thu Apr 29 13:37:53 2010 -0700
@@ -949,7 +949,8 @@
 	} else {
 		size = zv->zv_volblocksize;
 		offset = P2ALIGN(offset, size);
-		error = dmu_buf_hold(os, object, offset, zgd, &db);
+		error = dmu_buf_hold(os, object, offset, zgd, &db,
+		    DMU_READ_NO_PREFETCH);
 		if (error == 0) {
 			zgd->zgd_db = db;
 			zgd->zgd_bp = bp;