--- a/usr/src/uts/common/fs/zfs/zfs_vfsops.c	Wed Jun 02 14:57:52 2010 +0800
+++ b/usr/src/uts/common/fs/zfs/zfs_vfsops.c	Wed Jun 02 05:25:10 2010 -0600
@@ -1175,6 +1175,7 @@
 			goto out;
 		xattr_changed_cb(zfsvfs, pval);
 		zfsvfs->z_issnap = B_TRUE;
+		zfsvfs->z_os->os_sync = ZFS_SYNC_DISABLED;
 
 		mutex_enter(&zfsvfs->z_os->os_user_ptr_lock);
 		dmu_objset_set_user(zfsvfs->z_os, zfsvfs);