[PATCHv5 1/8] blk-mq-dma: introduce blk_map_iter

[Keith Busch]

On Sun, Aug 10, 2025 at 04:04:48PM +0200, Christoph Hellwig wrote:
> > +struct blk_map_iter {
> > +	phys_addr_t			paddr;
> > +	u32				len;
> > +	struct bvec_iter		iter;
> > +	struct bio			*bio;
> > +};
> 
> This now mixes the output previous in the phys_vec, and instead
> of keeping it private to the implementation exposes it to all the
> callers.  I could not find an explanation in the commit log, nor
> something that makes use of it later in the series.
> 
> If possible I'd like to keep these separate and the output isolated
> in blk-mq-dma.c.  But if there's a good reason to merge them, please
> add it to the commit log, and also clearly document the usage of the
> fields in the (public) structure.  Especially the len member could
> very easily confuse.

Perhaps I misunderstood the assignment:

  https://lore.kernel.org/linux-block/20250722055339.GB13634@lst.de/

I thought you were saying you wanted the lower (bvec pages -> phys
addrs) and upper part (phys -> dma) available as an API rather than
keeping the lower part private to blk-dma. This patch helps move towards
that, and in the next patch provides a common place to stash the bvec
array that's being iterated.