Marek Szyprowski [off-list ref] wrote @ Wed, 22 Aug 2012 14:29:47 +0200:

Hello,

On Wednesday, August 22, 2012 12:20 PM Hiroshi Doyu wrote:

quoted

Makes use of the same atomic pool from DMA, and skips kernel page
mapping which can involves sleep'able operation at allocating a kernel
page table.

Signed-off-by: Hiroshi Doyu <redacted>
---
 arch/arm/mm/dma-mapping.c |   22 ++++++++++++++++++----
 1 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index aec0c06..9260107 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c

@@ -1028,7 +1028,6 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t

size,
 	struct page **pages;
 	int count = size >> PAGE_SHIFT;
 	int array_size = count * sizeof(struct page *);
-	int err;

 	if (array_size <= PAGE_SIZE)
 		pages = kzalloc(array_size, gfp);

@@ -1037,9 +1036,20 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t

size,
 	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 err_out;
+
+		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;
 error:

@@ -1055,6 +1065,10 @@ 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))
+		return 0;

You leak memory here. pages array should be also freed.

Right, I'll fix as below:

	Modified arch/arm/mm/dma-mapping.c

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 47c4978..4656c0f 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c

@@ -1121,11 +1121,12 @@ static int __iommu_free_buffer(struct device *dev, struct page **pages, size_t s
 	int i;
 
 	if (__free_from_pool(page_address(pages[0]), size))
-		return 0;
+		goto out;
 
 	for (i = 0; i < count; i++)
 		if (pages[i])
 			__free_pages(pages[i], 0);
+out:
 	if (array_size <= PAGE_SIZE)
 		kfree(pages);
 	else

--

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