Re: [PATCH] 2.4.x write barriers (updated for ext3)

James Bottomley
2002-03-04T14:48:40Z

phillips@bonn-fries.net said:
> I've been following the thread, I hope I haven't missed anything
> fundamental. A better long term solution is to have ordered tags work
> as designed. It's not broken by design is it, just implementation?

There is actually one hole in the design: A scsi device may accept a command
with an ordered tag, disconnect and at a later time reconnect and return a
QUEUE FULL status indicating that the tag must be retried. In the time
between the disconnect and reconnect, the standard doesn't require that no
other tags be accepted, so if the local flow control conditions abate, the
device is allowed to accept and execute a tag sent down in between the
disconnect and reconnect.

I think this would introduce a very minor deviation where one tag could
overtake another, but we may still get a useable implementation even with this.

James