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SubjectRe: [PATCH 21/26] iommu/dma: Refactor iommu_dma_get_sgtable
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On 22/04/2019 18:59, Christoph Hellwig wrote:
> Inline __iommu_dma_get_sgtable_page into the main function, and use the
> fact that __iommu_dma_get_pages return NULL for remapped contigous
> allocations to simplify the code flow a bit.

Yeah, even I was a bit dubious about the readability of "if (page)...
else if (pages)..." that my attempt ended up with, so I don't really
have anything to complain about here.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> drivers/iommu/dma-iommu.c | 45 +++++++++++++++------------------------
> 1 file changed, 17 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index acdfe866cb29..138b85e675c8 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -1070,42 +1070,31 @@ static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
> return __iommu_dma_mmap(pages, size, vma);
> }
>
> -static int __iommu_dma_get_sgtable_page(struct sg_table *sgt, struct page *page,
> - size_t size)
> -{
> - int ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
> -
> - if (!ret)
> - sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
> - return ret;
> -}
> -
> static int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
> void *cpu_addr, dma_addr_t dma_addr, size_t size,
> unsigned long attrs)
> {
> - unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> - struct page **pages;
> + struct page *page;
> + int ret;
>
> - if (!is_vmalloc_addr(cpu_addr)) {
> - struct page *page = virt_to_page(cpu_addr);
> - return __iommu_dma_get_sgtable_page(sgt, page, size);
> - }
> + if (is_vmalloc_addr(cpu_addr)) {
> + struct page **pages = __iommu_dma_get_pages(cpu_addr);
>
> - if (attrs & DMA_ATTR_FORCE_CONTIGUOUS) {
> - /*
> - * DMA_ATTR_FORCE_CONTIGUOUS allocations are always remapped,
> - * hence in the vmalloc space.
> - */
> - struct page *page = vmalloc_to_page(cpu_addr);
> - return __iommu_dma_get_sgtable_page(sgt, page, size);
> + if (pages) {
> + return sg_alloc_table_from_pages(sgt, pages,
> + PAGE_ALIGN(size) >> PAGE_SHIFT,
> + 0, size, GFP_KERNEL);
> + }
> +
> + page = vmalloc_to_page(cpu_addr);
> + } else {
> + page = virt_to_page(cpu_addr);
> }
>
> - pages = __iommu_dma_get_pages(cpu_addr);
> - if (WARN_ON_ONCE(!pages))
> - return -ENXIO;
> - return sg_alloc_table_from_pages(sgt, pages, count, 0, size,
> - GFP_KERNEL);
> + ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
> + if (!ret)
> + sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
> + return ret;
> }
>
> static const struct dma_map_ops iommu_dma_ops = {
>

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