Re: [PATCH] Promise 'stex' driver

From: Jens Axboe
Date: Thu Jul 20 2006 - 21:05:32 EST

On Thu, Jul 20 2006, Jeff Garzik wrote:
> James Bottomley wrote:
> >On Thu, 2006-07-20 at 17:27 -0400, Jeff Garzik wrote:
> >>Since _no individual SCSI driver_ uses the block layer
> >>tagging, it is likely that some instability and core kernel
> >>development
> >>will occur, in order to make that work.
> >
> >That's not quite true: 53c700 and tmscsim both use it ... I could with
> >the usage were wider, but at least 53c700 has pretty regular and
> >constant usage ... enough I think to validate the block tag code (it's
> >been using it for the last three years).
> Not for the case being discussed in this thread, adapter-wide tags.

That just means the map is shared, otherwise there should be little if
any difference.

> AFAICS, no file in include/scsi/* or drivers/scsi/* ever calls
> blk_queue_init_tags() with a non-NULL third arg.

grpe again, it's in scsi_tcq.h.

> The block tagging capability being discussed here is poorly validated
> due to overall underuse, and its never been used in SCSI AFAIK.

It has and is, James uses it every day!

Jens Axboe

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