Re: [PATCH v2 01/11] scsi: Convert struct Scsi_Host->cmd_serial_number to atomic_t

["Nicholas A. Bellinger" <nab@linux-iscsi.org>]

On Mon, 2010-09-27 at 16:05 +0200, Christof Schmitt wrote:
> On Sat, Sep 18, 2010 at 12:57:58PM -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.
> > 

<SNIP>

> > > 
> > > 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.
> 
> In zfcp, the serial_number is only accessed for writing it to debug
> traces. With the change that the driver has to request the serial
> number through use_serial_number, simply remove the serial number from
> zfcp.

Hi Christof,

So since the use of struct scsi_cmnd->serial_number is purely
informational for some LLDs (including zfcp) , I have been putting the
conversion of these LLDs as a low priority ATM.   I would happily accept
a patch to remove these.  8-)

Best,

--nab