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SubjectRe: [PATCH 14/26] iommu/dma: Refactor iommu_dma_free
On Mon, Apr 29, 2019 at 09:03:48PM +0200, Christoph Hellwig wrote:
> On Mon, Apr 29, 2019 at 02:59:43PM +0100, Robin Murphy wrote:
> > Hmm, I do still prefer my original flow with the dma_common_free_remap()
> > call right out of the way at the end rather than being a special case in
> > the middle of all the page-freeing (which is the kind of existing
> > complexity I was trying to eliminate). I guess you've done this to avoid
> > having "if (!dma_release_from_contiguous(...))..." twice like I ended up
> > with, which is fair enough I suppose - once we manage to solve the new
> > dma_{alloc,free}_contiguous() interface that may tip the balance so I can
> > always revisit this then.
>
> Ok, I'll try to accomodate that with a minor rework.

Does this look reasonable?

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 5b2a2bf44078..f884d22b1388 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -921,7 +921,7 @@ static void iommu_dma_free(struct device *dev, size_t size, void *cpu_addr,
{
size_t alloc_size = PAGE_ALIGN(size);
int count = alloc_size >> PAGE_SHIFT;
- struct page *page = NULL;
+ struct page *page = NULL, **pages = NULL;

__iommu_dma_unmap(dev, handle, size);

@@ -934,19 +934,17 @@ static void iommu_dma_free(struct device *dev, size_t size, void *cpu_addr,
* If it the address is remapped, then it's either non-coherent
* or highmem CMA, or an iommu_dma_alloc_remap() construction.
*/
- struct page **pages = __iommu_dma_get_pages(cpu_addr);
-
- if (pages)
- __iommu_dma_free_pages(pages, count);
- else
+ pages = __iommu_dma_get_pages(cpu_addr);
+ if (!pages)
page = vmalloc_to_page(cpu_addr);
-
dma_common_free_remap(cpu_addr, alloc_size, VM_USERMAP);
} else {
/* Lowmem means a coherent atomic or CMA allocation */
page = virt_to_page(cpu_addr);
}

+ if (pages)
+ __iommu_dma_free_pages(pages, count);
if (page && !dma_release_from_contiguous(dev, page, count))
__free_pages(page, get_order(alloc_size));
}
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