Re: eh_abort_handler and calling scsi_done

[Christof Schmitt <christof.schmitt@de.ibm.com>]

On Tue, Mar 24, 2009 at 10:46:09AM -0700, Mike Anderson wrote:
> Brian King <brking@linux.vnet.ibm.com> wrote:
> > Your assessment sounds correct to me. The other caveat to note is that
> > if for some reason in your eh_abort_handler you don't think the command
> > is still outstanding, you should return SUCCESS for this as well.
> > 
> > -Brian
> > 
> > Christof Schmitt wrote:
> > > I am investigating what is required from a LLD when SCSI commands time
> > > out and the SCSI EH calls the eh_abort_handler. The documentation in
> > > scsi_eh.txt states:
> > > 
> > >     <<scsi_eh_abort_cmds>>
> > > 
> > > 	This action is taken for each timed out command.
> > > 	hostt->eh_abort_handler() is invoked for each scmd.  The
> > > 	handler returns SUCCESS if it has succeeded to make LLDD and
> > > 	all related hardware forget about the scmd.
> > > 
> > > From this and from looking at the code, i would conclude:
> > > 
> > > 1) If the LLD returns FAILED from the eh_abort_handler, then the
> > >    command is still allowed to be active in the LLD and the LLD can
> > >    call scsi_done any time later (probably latest when the
> > >    eh_host_reset_handler flushes everything that is still pending).
> > > 
> > > 2) While the abort is pending, but before returning SUCCESS from
> > >    eh_abort_handler, the LLD can still call scsi_done for the SCSI
> > >    command to be aborted (the SCSI command might be returned with a
> > >    status "aborted" if the abort succeeds, or "good" if it was
> > >    completed just before the abort reached the storage system).
> > > 
> 
> In cases 1 and 2 above calling scsi_done can be done but will cause
> the request to be stopped in blk_complete_request
> (scsi_done->blk_complete_request) as the timed out handler has
> already taken ownership of the command.

I am not too familiar with the blk completion handling. Would calling
scsi_done for the cases above cause any problems? If there are reasons
not to call scsi_done here, then this could be mentioned in the scsi
documentation file.

--
Christof Schmitt