Re: [PATCH, RFC] scsi: use host wide tags by default

[Christoph Hellwig <hch@lst.de>]

On Fri, Apr 17, 2015 at 02:42:40PM -0700, James Bottomley wrote:
> >  		if(hostdata->msgin[1] == A_SIMPLE_TAG_MSG) {
> > -			struct scsi_cmnd *SCp = scsi_find_tag(SDp, hostdata->msgin[2]);
> > +			struct scsi_cmnd *SCp;
> > +
> > +			SCp = scsi_find_tag(SDp->host, hostdata->msgin[2]);
> 
> This (and the following) is a stylistic modification and doesn't really
> belong here.

Both split lines that would grow beyond 80 lines.

> This lock/unlock is a nasty global sync point which can be eliminated:
> we can rely on the architectural atomicity of 32 bit writes (might need
> to make sdev->queue_depth a u32 because I seem to remember 16 bit writes
> had to be done as two byte stores on some architectures).

It's much more easy to understand than the barrier magic we'd otherwise
have to do, and this is a slow path.  Nevermind that it would be an
unrelated change even if we had a good argument for it.