Re: [PATCH 9/9] scsi_error: do not display kernel pointer in message logs

[Ewan Milne <emilne@redhat.com>]

On Mon, 2015-01-12 at 09:57 -0500, Ewan Milne wrote:
> On Mon, 2015-01-12 at 14:29 +0100, Hannes Reinecke wrote:
> > On 01/12/2015 02:12 PM, Ewan Milne wrote:
> > > On Thu, 2015-01-08 at 07:43 +0100, Hannes Reinecke wrote:
> > >> It is not good practice to display the kernel pointer
> > >> in any message logs, and it doesn't display any additional
> > >> information. And as we know have block-layer assigned tags
> > >> we can use them to differentiate the messages.
> > >> So remove any pointer references from the displayed messages.
> > >>
> > > 
> > > I'd actually be sad to see this go -- I have found it useful
> > > in the past when debugging crash dumps from customer sites
> > > to be able to look in the kernel messages and see that a
> > > particular scsi_cmnd had been aborted just before the crash
> > > (and then later completed).
> > > 
> > But that's precisely why we've prefixed the scmd messages with the
> > tag number; with that you'll be able to extract the same information.
> > 
> > And now that hch separated out the block layer tagging from SCSI-2
> > TCQ we should have the tag number available for any command, not
> > just those from drivers which use TCQ.
> > 
> > Let me know if that isn't the case; this patch indeed only makes
> > sense if the tag number is always available.
> 
> Ah, yes, I think you may be right -- I ran into this when debugging some
> double completion panics, so my concern is whether the tag field
> remains valid after it completes the first time.  I'll check.

Looks like if the scmd completes twice, the req could be getting reused,
so scmd->request->tag might be different.  However, for crash analysis,
scmd->tag gets a copy of the request tag so that would be good enough
to match up with an earlier logged abort message.

Reviewed-by: Ewan D. Milne <emilne@redhat.com>