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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
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

13
include/linux/dma-contiguous.h
View file

@ -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

47
kernel/dma/contiguous.c
View file

@ -214,6 +214,53 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages,
return cma_release(dev_get_cma_area(dev), pages, count);
}
/**
* dma_alloc_contiguous() - allocate contiguous pages
* @dev: Pointer to device for which the allocation is performed.
* @size: Requested allocation size.
* @gfp: Allocation flags.
*
* This function allocates contiguous memory buffer for specified device. It
* first tries to use device specific contiguous memory area if available or
* the default global one, then tries a fallback allocation of normal pages.
*/
struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
{
int node = dev ? dev_to_node(dev) : NUMA_NO_NODE;
size_t count = PAGE_ALIGN(size) >> PAGE_SHIFT;
size_t align = get_order(PAGE_ALIGN(size));
struct cma *cma = dev_get_cma_area(dev);
struct page *page = NULL;
/* CMA can be used only in the context which permits sleeping */
if (cma && gfpflags_allow_blocking(gfp)) {
align = min_t(size_t, align, CONFIG_CMA_ALIGNMENT);
page = cma_alloc(cma, count, align, gfp & __GFP_NOWARN);
}
/* Fallback allocation of normal pages */
if (!page)
page = alloc_pages_node(node, gfp, align);
return page;
}
/**
* dma_free_contiguous() - release allocated pages
* @dev: Pointer to device for which the pages were allocated.
* @page: Pointer to the allocated pages.
* @size: Size of allocated pages.
*
* This function releases memory allocated by dma_alloc_contiguous(). As the
* cma_release returns false when provided pages do not belong to contiguous
* area and true otherwise, this function then does a fallback __free_pages()
* upon a false-return.
*/
void dma_free_contiguous(struct device *dev, struct page *page, size_t size)
{
if (!cma_release(dev_get_cma_area(dev), page, size >> PAGE_SHIFT))
__free_pages(page, get_order(size));
}
/*
* Support for reserved memory regions defined in device tree
*/

24
kernel/dma/direct.c
View file

@ -96,8 +96,6 @@ static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
{
unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
int page_order = get_order(size);
struct page *page = NULL;
u64 phys_mask;
@ -109,20 +107,9 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
gfp |= __dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
&phys_mask);
again:
/* CMA can be used only in the context which permits sleeping */
if (gfpflags_allow_blocking(gfp)) {
page = dma_alloc_from_contiguous(dev, count, page_order,
gfp & __GFP_NOWARN);
if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
dma_release_from_contiguous(dev, page, count);
page = NULL;
}
}
if (!page)
page = alloc_pages_node(dev_to_node(dev), gfp, page_order);
page = dma_alloc_contiguous(dev, size, gfp);
if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
__free_pages(page, page_order);
dma_free_contiguous(dev, page, size);
page = NULL;
if (IS_ENABLED(CONFIG_ZONE_DMA32) &&
@ -154,7 +141,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
if (PageHighMem(page)) {
/*
* Depending on the cma= arguments and per-arch setup
* dma_alloc_from_contiguous could return highmem pages.
* dma_alloc_contiguous could return highmem pages.
* Without remapping there is no way to return them here,
* so log an error and fail.
*/
@ -176,10 +163,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
void __dma_direct_free_pages(struct device *dev, size_t size, struct page *page)
{
unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
if (!dma_release_from_contiguous(dev, page, count))
__free_pages(page, get_order(size));
dma_free_contiguous(dev, page, size);
}
void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr,