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7ce3c1dd78
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. Thanks to Chaitanya Kulkarni for an initial attempt at a new DMA API conversion for nvme-pci, Kanchan Joshi for bringing back the single segment optimization, Leon Romanovsky for shepherding this through a gazillion rebases and Nitesh Shetty for various improvements. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Keith Busch <kbusch@kernel.org> Reviewed-by: Leon Romanovsky <leonro@nvidia.com> Link: https://lore.kernel.org/r/20250625113531.522027-7-hch@lst.de Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.