[v2 4/4] ARM: dma-mapping: IOMMU allocates pages from atomic_pool with GFP_ATOMIC
From: m.szyprowski@samsung.com (Marek Szyprowski)
Date: 2012-08-23 07:33:28
Also in:
linux-mm, lkml
Hi Hiroshi, On Thursday, August 23, 2012 8:10 AM Hiroshi Doyu wrote:
quoted hunk ↗ jump to hunk
Makes use of the same atomic pool from DMA, and skips kernel page mapping which can involve sleep'able operations at allocating a kernel page table. Signed-off-by: Hiroshi Doyu <redacted> --- arch/arm/mm/dma-mapping.c | 30 +++++++++++++++++++++++++----- 1 files changed, 25 insertions(+), 5 deletions(-)diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 7ab016b..433312a 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c@@ -1063,7 +1063,6 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_tsize, struct page **pages; int count = size >> PAGE_SHIFT; int array_size = count * sizeof(struct page *); - int err; if ((array_size <= PAGE_SIZE) || (gfp & GFP_ATOMIC)) pages = kzalloc(array_size, gfp);@@ -1072,9 +1071,20 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_tsize, if (!pages) return NULL; - err = __alloc_fill_pages(&pages, count, gfp); - if (err) - goto error + if (gfp & GFP_ATOMIC) { + struct page *page; + int i; + void *addr = __alloc_from_pool(size, &page); + if (!addr) + goto error; + + for (i = 0; i < count; i++) + pages[i] = page + i; + } else { + int err = __alloc_fill_pages(&pages, count, gfp); + if (err) + goto error; + } return pages;@@ -1091,9 +1101,15 @@ static int __iommu_free_buffer(struct device *dev, struct page **pages,size_t s int count = size >> PAGE_SHIFT; int array_size = count * sizeof(struct page *); int i; + + if (__free_from_pool(page_address(pages[0]), size)) + goto out; + for (i = 0; i < count; i++) if (pages[i]) __free_pages(pages[i], 0); + +out: if ((array_size <= PAGE_SIZE) || __in_atomic_pool(page_address(pages[0]), size)) kfree(pages);@@ -1221,6 +1237,9 @@ static void *arm_iommu_alloc_attrs(struct device *dev, size_t size, if (*handle == DMA_ERROR_CODE) goto err_buffer; + if (gfp & GFP_ATOMIC) + return page_address(pages[0]); + if (dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING, attrs)) return pages;
I've read the whole code and it looks that it starts to become a little spaghetti - there are too
many places altered by those atomic changes and it is hard to follow the logic at the first sight.
IMHO it will be better to add a following function:
static void *__iommu_alloc_atomic(struct device *dev, size_t size,
dma_addr_t *handle)
{
struct page *page, **pages;
int count = size >> PAGE_SHIFT;
int array_size = count * sizeof(struct page *);
void *addr;
int i;
pages = kzalloc(array_size, gfp);
if (!pages)
return NULL;
addr = __alloc_from_pool(size, &page);
if (!addr)
goto err_pool;
for (i = 0; i < count; i++)
pages[i] = page + i;
*handle = __iommu_create_mapping(dev, pages, size);
if (*handle == DMA_ERROR_CODE)
goto err_mapping;
return addr;
err_mapping:
__free_from_pool(addr, size);
err_pool:
kfree(pages);
return NULL;
}
and then call it@the beginning of the arm_iommu_alloc_attrs():
if (gfp & GFP_ATOMIC)
return __iommu_alloc_atomic(dev, size, handle);
You should also add support for the allocation from atomic_pool to __iommu_get_pages() function
to get dma_mmap() and dma_get_sgtable() working correctly.
quoted hunk ↗ jump to hunk
@@ -1279,7 +1298,8 @@ void arm_iommu_free_attrs(struct device *dev, size_t size, void*cpu_addr, return; } - if (!dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING, attrs)) { + if (!dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING, attrs) || + !__in_atomic_pool(cpu_addr, size)) { unmap_kernel_range((unsigned long)cpu_addr, size); vunmap(cpu_addr); }
Are you sure this one works? __iommu_get_pages() won't find pages array, because atomic allocations don't get their separate vm_struct area, so this check will be never reached. Maybe a __iommu_free_atomic() function would also make it safer and easier to understand. Best regards -- Marek Szyprowski Samsung Poland R&D Center