ZFS Ignore fsflush

ZFS ignores the fsflush. Here's a snippet of the code in zfs_sync():

/*
* SYNC_ATTR is used by fsflush() to force old filesystems like UFS
* to sync metadata, which they would otherwise cache indefinitely.
* Semantically, the only requirement is that the sync be initiated.
* The DMU syncs out txgs frequently, so there's nothing to do.
*/
if (flag & SYNC_ATTR)
return (0);

However, for a user initiated sync(1m) and sync(2) ZFS does force
all outstanding data/transactions synchronously to disk .
This goes beyond the requirement of sync(2) which says IO is inititiated
but not waited on (ie asynchronous).