On Sat, 2010-09-18 at 12:58 -0700, Nicholas A. Bellinger wrote:
> On Fri, 2010-09-17 at 21:45 -0500, Mike Christie wrote:
> > On 09/17/2010 02:03 PM, Joe Eykholt wrote:
> > >
> > > How about instead of adding use_serial_number, let's just have the
> > > drivers that want a serial number call scsi_cmd_get_serial()
> >
> > I think this sounds better.
> >
>
> In that case I will go ahead and add explict scsi_cmd_get_serial() calls
> to the LLDs that use struct scsi_cmnd->serial_number in anything beyond
> an obvious and simple informational purpose.
>
> > You could also convert drivers to the host tagging if you needed a
> > unique id for each command sent to a host.
>
> Hmmm, what does this entail again..?
>
> >
> > > and stop calling it from scsi_dispatch_cmd()? AFAICT, it's only
> > > used in debug messages in some drivers. I didn't find other usages
> > > but didn't do an exhaustive search.
> >
> > The comments for serial_number say that it is only supposed to be used
> > for debugging printks and most drivers use it for that.
>
> So I would suppose it would be OK for those drivers to continue to
> printk serial_number to show the internal serial_number allocation is
> now disabled by default.
>
> > However, it looks like mpt and dpt_i2o are using it for error handling
> > and/or lookup type of operations. I think the mpt* uses are not needed
> > in the abort checks.
> >
>
> In that case, then adding an explict scsi_cmd_get_serial() call in mpt*
> and dpt_i20 ->queuecommand() callers would be a good first step.
>
> > And eata is using it for ordering and tracking or something. It could
> > probably be converted to the host tagging if or what you suggested if it
> > needs the uniqueue id.
>
> Adding an explict scsi_cmd_get_serial() for eata for now, and we can
> consider LLD canidates for host tag conversion as a future step.
>
> >
> > zfcp looks like it copies it. It does not look like the driver needs it.
> >
>
> Ok, I will look at removing it's usage in zfcp or if necessary add an
> the explict scsi_cmd_get_serial() call.
>
> > scsi_error.c uses it in scsi_try_to_abort_cmd to check if a command has
> > completed, but I think that can be done by checking if REQ_ATOM_COMPLETE
> > is set.
>
> Hmmm, good catch here. Jejb and hch, does this item work for you..?
>
> If so then I will take another peek for any ML uses of a struct
> scsi_cmnd->serial_number that need to be addressed, and include Joe's
> and Mike's recommendations into a v3 series.
>
Greetings Mike and Co,
I was doing some followup on these items for a v3 series and started
with a patch following mnc's recommendations for dropping the
scsi_error.c codes depending upon struct scsi_cmnd->serial_number:
diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
index 1de30eb..f35c127 100644
--- a/drivers/scsi/scsi_error.c
+++ b/drivers/scsi/scsi_error.c
@@ -644,11 +644,7 @@ static int __scsi_try_to_abort_cmd(struct scsi_cmnd *scmd)
*/
static int scsi_try_to_abort_cmd(struct scsi_cmnd *scmd)
{
- /*
- * scsi_done was called just after the command timed out and before
- * we had a chance to process it. (db)
- */
- if (scmd->serial_number == 0)
+ if (test_bit(REQ_ATOM_COMPLETE, &scmd->request->atomic_flags))
return SUCCESS;
return __scsi_try_to_abort_cmd(scmd);
}
and while building I noticed that the simple single enum REQ_ATOM_COMPLETE=0 is
currently located in block/blk.h and along with blk_mark_rq_complete() and
blk_clear_rq_complete() for setting this bit within struct request->atomic_flags.
jens, hch, tejun, and co, do you guys have a preference how this should be handled
so that scsi_try_to_abort_cmd() can use proper atomic struct request bits here and
we can get rid of this (racy..?) method of using struct scsi_cmnd->serial_number
for anything wrt to per struct scsi_cmnd context timeout handling.
Thanks!
--nab
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