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

[James Bottomley <James.Bottomley@SteelEye.com>]

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