On Mon, Jun 23, 2025 at 04:12:28PM +0200, Christoph Hellwig wrote: > Use the blk_rq_dma_map API to DMA map requests instead of scatterlists. > This removes the need to allocate a scatterlist covering every segment, > and thus the overall transfer length limit based on the scatterlist > allocation. > > Instead the DMA mapping is done by iterating the bio_vec chain in the > request directly. The unmap is handled differently depending on how > we mapped: > > - when using an IOMMU only a single IOVA is used, and it is stored in > iova_state > - for direct mappings that don't use swiotlb and are cache coherent, > unmap is not needed at all > - for direct mappings that are not cache coherent or use swiotlb, the > physical addresses are rebuild from the PRPs or SGL segments > > The latter unfortunately adds a fair amount of code to the driver, but > it is code not used in the fast path. > > The conversion only covers the data mapping path, and still uses a > scatterlist for the multi-segment metadata case. I plan to convert that > as soon as we have good test coverage for the multi-segment metadata > path. Looks good. Reviewed-by: Keith Busch <kbusch@xxxxxxxxxx>
