Ran into a couple small issues with the patch. First,
blk_queue_resize_tags wasn't getting exported, so I sent Jens a patch to
fix this, which he has now sent upstream. Second, the comment above
blk_queue_resize_tags says the queue_lock must be held when calling this
routine. Attached is an updated patch that grabs the lock. Other than
that, it looks good.

James Bottomley wrote:
> On Tue, 2004-08-03 at 10:50, Brian King wrote:
>>Currently, it is possible to call scsi_activate_tcq with a small queue depth,
>>then later call scsi_adjust_queue_depth with a larger queue depth. This results
>>in the scsi layer having a larger queue depth than the block layer knows about.
>>This results in these additional commands being issued as untagged ops rather than
>>tagged ops. This patch changes scsi_activate_tcq to call blk_queue_init_tags with
>>the maximum supported number of tags so this cannot occur.
>
>
> Sorry, been away at conferences with not enough time to remember what
> went on here.
>
> The reason it looks the way it does is historical...when the blk layer
> tcq interfaces were created, there was no way to resize the queue.  Jens
> later added resize (for me) and I forgot to incorporate it into the
> code.
>
> Another small point is that the max number of tags can be greater than
> 256.  256 is a SPI limit only (and even the qla1280, a SPI card which
> could use the tag as its global queue index would take > 256).  The
> limit in scsi_adjust_queue_depth has long since been obsoleted by our
> dynamic command allocation.
>
> I think the attached should work correctly (as long as it compiles...I
> coded it up on the flight home).
Signed-off-by: Brian King <brking@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>