Re: requeuing a Scsi_Cmnd?

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

On Sun, 2003-05-11 at 15:25, Jeff Garzik wrote:
> This question applies to 2.4 as well as 2.5 (I believe the strategies 
> are different for the two?)
> 
> Suppose I am passed several Scsi_Cmnd structures via ->queuecommand. 
> TCQ depth is >1.  An event causes the entire queue to be aborted, but I 
> know that the majority of the queue was actually ok.  So, my LLD would 
> need to requeue and resend most of the recently-aborted Scsi_Cmnds.

You keep finding these unhandled condidions, sigh.  The correct thing to
do (since this is a situation identical to QErr set) is to return a
check condition to the failing command and to return a status of TASK
ABORTED for all the others (SPC3).  Of course, the SCSI-2 behaviour was
just to expect all tasks to be silently aborted on QErr=1.  Neither of
these, of course, is coded into the mid-layer.

> How do I tell the SCSI layer to requeue and resend a Scsi_Cmnd [almost] 
> immediately?

Probably the best thing to do is to return DID_BUS_BUSY which will force
a fast retry.  Note, that's the driver return, *not* the status BUSY,
which will force a requeue and take longer---DID_BUS_BUSY will retry
immediately from the SCSI tasklet.

James