Re: [PATCH 4/5] convert st to use scsi_execte_async

[Mike Christie <michaelc@cs.wisc.edu>]

Kai Makisara wrote:
> The command triggering these problems is a 6-byte read of 10240 bytes. It 
> should not a this point return anything but finish with some sense data.
> 
> I am debugging the problem but it is going slowly because the system disk 
> is a SCSI disk. I have to be careful with the debugging output and changes 
> outside st.c require a reboot ;-) So far I have found out that 
> scsi_check_sense() is called correctly and returns SUCCESS as it should. 
> What happens after that is a mystery.
> 

If we sent the command as multiple segments then since scsi_generic_done 
just does this

scsi_io_completion(cmd, cmd->result == 0 ? cmd->bufflen : 0, 0);

we could up gettting here in scsi_io_completion() (or depding on the 
sense we could get retired further up in that function).


/*
  * Mark a single buffer as not uptodate.  Queue the remainder.
  * We sometimes get this cruft in the event that a medium error
  * isn't properly reported.
  */
block_bytes = req->hard_cur_sectors << 9;
if (!block_bytes)
	block_bytes = req->data_len;
scsi_end_request(cmd, 0, block_bytes, 1);


and if this command has multiple segments we only partially complete the 
command and the rest gets retried.