Subject: Re: [PATCH v4 14/16] block-dma: migrate to dma_map_phys instead of map_page

From: Keith Busch <[email-masked]>
Date: Tue, 2 Sep 2025 15:59:37 -0600

On Tue, Sep 02, 2025 at 10:49:48PM +0200, Marek Szyprowski wrote:
> On 19.08.2025 19:36, Leon Romanovsky wrote:
> > @@ -87,8 +87,8 @@ static bool blk_dma_map_bus(struct blk_dma_iter *iter, struct phys_vec *vec)
> >   static bool blk_dma_map_direct(struct request *req, struct device *dma_dev,
> >   		struct blk_dma_iter *iter, struct phys_vec *vec)
> >   {
> > -	iter->addr = dma_map_page(dma_dev, phys_to_page(vec->paddr),
> > -			offset_in_page(vec->paddr), vec->len, rq_dma_dir(req));
> > +	iter->addr = dma_map_phys(dma_dev, vec->paddr, vec->len,
> > +			rq_dma_dir(req), 0);
> >   	if (dma_mapping_error(dma_dev, iter->addr)) {
> >   		iter->status = BLK_STS_RESOURCE;
> >   		return false;
> 
> I wonder where is the corresponding dma_unmap_page() call and its change 
> to dma_unmap_phys()...

You can't do that in the generic layer, so it's up to the caller. The
dma addrs that blk_dma_iter yield are used in a caller specific
structure. For example, for NVMe, it goes into an NVMe PRP. The generic
layer doesn't know what that is, so the driver has to provide the
unmapping.