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dma-contiguous: add dma_{alloc,free}_contiguous() helpers

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Both dma_alloc_from_contiguous() and dma_release_from_contiguous() are
very simply implemented, but requiring callers to pass certain
parameters like count and align, and taking a boolean parameter to check
__GFP_NOWARN in the allocation flags. So every function call duplicates
similar work:

	unsigned long order = get_order(size);
	size_t count = size >> PAGE_SHIFT;

	page = dma_alloc_from_contiguous(dev, count, order,
			gfp & __GFP_NOWARN);

	[...]

	dma_release_from_contiguous(dev, page, size >> PAGE_SHIFT);

Additionally, as CMA can be used only in the context which permits
sleeping, most of callers do a gfpflags_allow_blocking() check and a
corresponding fallback allocation of normal pages upon any false result:

	if (gfpflags_allow_blocking(flag))
		page = dma_alloc_from_contiguous();
	if (!page)
		page = alloc_pages();

	[...]

	if (!dma_release_from_contiguous(dev, page, count))
		__free_pages(page, get_order(size));

So this patch simplifies those function calls by abstracting these
operations into the two new functions: dma_{alloc,free}_contiguous.

As some callers of dma_{alloc,release}_from_contiguous() might be
complicated, this patch just implements these two new functions to
kernel/dma/direct.c only as an initial step.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Tested-by: dann frazier <dann.frazier@canonical.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Nicolin Chen
2019-05-23 21:06:32 -07:00
committed by Christoph Hellwig
parent 1b96142315
commit b1d2dc009d
3 changed files with 64 additions and 20 deletions
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13
include/linux/dma-contiguous.h
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@@ -111,6 +111,8 @@ struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
unsigned int order, bool no_warn);
bool dma_release_from_contiguous(struct device *dev, struct page *pages,
int count);
struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp);
void dma_free_contiguous(struct device *dev, struct page *page, size_t size);
#else
@@ -153,6 +155,17 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages,
return false;
}
static inline struct page *dma_alloc_contiguous(struct device *dev, size_t size,
gfp_t gfp)
{
return NULL;
}
static inline void dma_free_contiguous(struct device *dev, struct page *page,
size_t size)
{
}
#endif
#endif