Re: SCSI EH tidbit

[Jeff Garzik <jgarzik@pobox.com>]

Tejun Heo wrote:
> 
>  Hi, Jeff.
> 
> Jeff Garzik wrote:
> 
>>
>> I'm thinking that __scsi_done() might be more appropriate than 
>> scsi_finish_command(), for use in completing commands in the EH path. 
>> There may need to be some timer-related mods somewhere to make that 
>> work, though.
> 
> 
>  Can you elaborate on why you think that would be a good idea?  I see 
> cons but not many pros.  My cons are...
> 
> * SCSI EH uses scsi_finish_command()
> 
> * iodone/err counters will be incremented twice
> 
> * has possibility of looping


scsi_finish_command unconditionally completes the command, rather than 
running it through scsi_decide_disposition() decision tree again.  That 
prevents us from using the standard command-retry path, for PCI/ATA bus 
errors where we want to resubmit the command.

There would be no loop, as __scsi_done() simply raises a softirq.  There 
are just a few details to consider in case you're in the error handler.

	Jeff