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SubjectRe: [PATCH] cma: use unsigned type for count argument
On Wed, 19 Dec 2012 18:44:40 +0100
Michal Nazarewicz <mpn@google.com> wrote:

> From: Michal Nazarewicz <mina86@mina86.com>
>
> Specifying negative size of buffer makes no sense and thus this commit
> changes the type of the count argument to unsigned.
>
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1038,9 +1038,9 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size,
> gfp_t gfp, struct dma_attrs *attrs)
> {
> struct page **pages;
> - int count = size >> PAGE_SHIFT;
> - int array_size = count * sizeof(struct page *);
> - int i = 0;
> + unsigned int count = size >> PAGE_SHIFT;
> + unsigned int array_size = count * sizeof(struct page *);
> + unsigned int i = 0;

C programmers expect a variable called `i' to have type `int'. It
would be clearer to find a new name for this. `idx', perhaps.

Also, we later do

int j;
..
pages[i + j] ...

So `j' should also be converted to unsigned. And perhaps renamed, but
`j' isn't as egregious as `i'.

> if (array_size <= PAGE_SIZE)
> pages = kzalloc(array_size, gfp);
> @@ -1102,9 +1102,9 @@ error:
> static int __iommu_free_buffer(struct device *dev, struct page **pages,
> size_t size, struct dma_attrs *attrs)
> {
> - int count = size >> PAGE_SHIFT;
> - int array_size = count * sizeof(struct page *);
> - int i;
> + unsigned int count = size >> PAGE_SHIFT;
> + unsigned int array_size = count * sizeof(struct page *);
> + unsigned int i;

ditto.


--- a/arch/arm/mm/dma-mapping.c~cma-use-unsigned-type-for-count-argument-fix
+++ a/arch/arm/mm/dma-mapping.c
@@ -1040,7 +1040,7 @@ static struct page **__iommu_alloc_buffe
struct page **pages;
unsigned int count = size >> PAGE_SHIFT;
unsigned int array_size = count * sizeof(struct page *);
- unsigned int i = 0;
+ unsigned int idx = 0;

if (array_size <= PAGE_SIZE)
pages = kzalloc(array_size, gfp);
@@ -1049,8 +1049,7 @@ static struct page **__iommu_alloc_buffe
if (!pages)
return NULL;

- if (dma_get_attr(DMA_ATTR_FORCE_CONTIGUOUS, attrs))
- {
+ if (dma_get_attr(DMA_ATTR_FORCE_CONTIGUOUS, attrs)) {
unsigned long order = get_order(size);
struct page *page;

@@ -1060,38 +1059,39 @@ static struct page **__iommu_alloc_buffe

__dma_clear_buffer(page, size);

- for (i = 0; i < count; i++)
- pages[i] = page + i;
+ for (idx = 0; idx < count; idx++)
+ pages[i] = page + idx;

return pages;
}

while (count) {
- int j, order = __fls(count);
+ unsigned int j;
+ unnsigned int order = __fls(count);

- pages[i] = alloc_pages(gfp | __GFP_NOWARN, order);
- while (!pages[i] && order)
- pages[i] = alloc_pages(gfp | __GFP_NOWARN, --order);
- if (!pages[i])
+ pages[idx] = alloc_pages(gfp | __GFP_NOWARN, order);
+ while (!pages[idx] && order)
+ pages[idx] = alloc_pages(gfp | __GFP_NOWARN, --order);
+ if (!pages[idx])
goto error;

if (order) {
- split_page(pages[i], order);
+ split_page(pages[idx], order);
j = 1 << order;
while (--j)
- pages[i + j] = pages[i] + j;
+ pages[idx + j] = pages[idx] + j;
}

- __dma_clear_buffer(pages[i], PAGE_SIZE << order);
- i += 1 << order;
+ __dma_clear_buffer(pages[idx], PAGE_SIZE << order);
+ idx += 1 << order;
count -= 1 << order;
}

return pages;
error:
- while (i--)
- if (pages[i])
- __free_pages(pages[i], 0);
+ while (idx--)
+ if (pages[idx])
+ __free_pages(pages[idx], 0);
if (array_size <= PAGE_SIZE)
kfree(pages);
else
@@ -1104,14 +1104,15 @@ static int __iommu_free_buffer(struct de
{
unsigned int count = size >> PAGE_SHIFT;
unsigned int array_size = count * sizeof(struct page *);
- unsigned int i;

if (dma_get_attr(DMA_ATTR_FORCE_CONTIGUOUS, attrs)) {
dma_release_from_contiguous(dev, pages[0], count);
} else {
- for (i = 0; i < count; i++)
- if (pages[i])
- __free_pages(pages[i], 0);
+ unsigned int idx;
+
+ for (idx = 0; idx < count; idx++)
+ if (pages[idx])
+ __free_pages(pages[idx], 0);
}

if (array_size <= PAGE_SIZE)
diff -puN drivers/base/dma-contiguous.c~cma-use-unsigned-type-for-count-argument-fix drivers/base/dma-contiguous.c
diff -puN include/linux/dma-contiguous.h~cma-use-unsigned-type-for-count-argument-fix include/linux/dma-contiguous.h
_


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