Re: BIO_FLUSH on twe driver. Why is it not there?

Artem Kuchin wrote:
> 7-BETA1
> gjournal complained that BIO_FLUSH is not supported by the driver. That 
> is twe driver.
> However, twe is working via scsi subsystem and the authour of  gjournal 
> said somewhere that he
> has had implemeneted BIO_FLISH for scsi and he specifically mentioned 
> that he has tested twe and twa and they both support BIO_FLUSH.
> Then why BIO_FLISH is not supported now?
> 

The twe driver does NOT operate under the SCSI subsystem.  As for
flush semantics in SCSI, they are much better done with ordered tags,
not explicit SYNC_CACHE commands.  That's not to say that SYNC_CACHE
won't work (well, except for random devices that will hang with it in
unpredictable ways, but no one seems to care about that little detail).
Unfortunately, BIO_ORDERED was removed from the FreeBSD block layer
several years ago.

Scott