Re: [PATCH v2] nvme-pci: Support shared tags across queues for Apple 2018 controllers

[Benjamin Herrenschmidt]

On Fri, 2019-07-19 at 05:01 +0000, Damien Le Moal wrote:
> > I suppose that would work and be simpler. I honestly don't know much
> > about the block layer and tag allocation so I stayed away from it :-)
> > 
> > I'll dig, but a hint would be welcome :)
> 
> Uuuh.. Never played with the tag management code directly myself either. A quick
> look seem to indicate that blk_mq_get/put_tag() is what you should be using. But
> further looking, struct blk_mq_tags has the field nr_reserved_tags which is used
> as an offset start point for searching free tags, which is exactly what you
> would need.

Yup. I was getting there, it's just that we use the tagset mess which I
had to untangle a bit first :-)

Cheers,
Ben.