[PATCHv2 1/3] block: introduce rq_list_for_each_safe macro

[Keith Busch]

On Thu, Dec 30, 2021 at 04:38:57PM +0200, Max Gurtovoy wrote:
> 
> On 12/29/2021 10:57 PM, Keith Busch wrote:
> > On Wed, Dec 29, 2021 at 06:39:02PM +0100, Christoph Hellwig wrote:
> > > (except for the fact that it, just like the other rq_list helpers
> > > really should go into blk-mq.h, where all request related bits moved
> > > early in this cycle)
> > Agreed, I just put it here because it's where the other macros live. But
> > 'struct request' doesn't exist in this header, so it does seem out of
> > place.  For v3, I'll add a preceding patch to move them all to blk-mq.h.
> 
> Did you see the discussion I had with Jens ?

I did, yes. That's when I noticed the error handling wasn't right, and
doing it correctly was a bit clunky. This series was supposed to make it
easier for drivers to use the new interface.
 
> Seems it works only for non-shared tagsets and it means that it will work
> only for NVMe devices that have 1 namespace and will not work for NVMf
> drivers.

I am aware shared tags don't get to use the batched queueing, but that's
orthogonal to this series.

Most PCIe NVMe SSDs only have 1 namespace, so it generally works out for
those. 

> Unless, we'll do some changes in the block layer and/or remove this
> condition.

I think it just may work if we export blk_mq_get_driver_tag().