linux-kernel - Re: [PATCH 6/6] scatterlist: use sg

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Date:	Sat, 8 Aug 2015 13:23:58 +0000
From:	"Williams, Dan J" <dan.j.williams@...el.com>
To:	"hch@....de" <hch@....de>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"joro@...tes.org" <joro@...tes.org>,
	"linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
	"Julia.Lawall@...6.fr" <Julia.Lawall@...6.fr>,
	"axboe@...nel.dk" <axboe@...nel.dk>,
	"herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>
Subject: Re: [PATCH 6/6] scatterlist: use sg_phys()

On Fri, 2015-08-07 at 18:15 +0200, Christoph Hellwig wrote:
[..]
> - page_to_phys(sg_page(sg))
> + sg_phys(sg) - sg->offset

Here's a replacement using PAGE_MASK instead of subtracting sg->offset
and a fixup for the awkward whitespace in dma_direct_map_sg().

8<-----
Subject: scatterlist: use sg_phys()

From: Dan Williams <dan.j.williams@...el.com>

Coccinelle cleanup to replace open coded sg to physical address
translations.  This is in preparation for introducing scatterlists that
reference __pfn_t.

// sg_phys.cocci: convert usage page_to_phys(sg_page(sg)) to sg_phys(sg)
// usage: make coccicheck COCCI=sg_phys.cocci MODE=patch

virtual patch

@@
struct scatterlist *sg;
@@

- page_to_phys(sg_page(sg)) + sg->offset
+ sg_phys(sg)

@@
struct scatterlist *sg;
@@

- page_to_phys(sg_page(sg))
+ sg_phys(sg) & PAGE_MASK

Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 arch/arm/mm/dma-mapping.c                    |    2 +-
 arch/microblaze/kernel/dma.c                 |    3 +--
 drivers/iommu/intel-iommu.c                  |    4 ++--
 drivers/iommu/iommu.c                        |    2 +-
 drivers/staging/android/ion/ion_chunk_heap.c |    4 ++--
 5 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index cba12f34ff77..3d3d6aa60c87 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1520,7 +1520,7 @@ static int __map_sg_chunk(struct device *dev, struct scatterlist *sg,
 		return -ENOMEM;
 
 	for (count = 0, s = sg; count < (size >> PAGE_SHIFT); s = sg_next(s)) {
-		phys_addr_t phys = page_to_phys(sg_page(s));
+		phys_addr_t phys = sg_phys(s) & PAGE_MASK;
 		unsigned int len = PAGE_ALIGN(s->offset + s->length);
 
 		if (!is_coherent &&
diff --git a/arch/microblaze/kernel/dma.c b/arch/microblaze/kernel/dma.c
index bf4dec229437..c89da6312954 100644
--- a/arch/microblaze/kernel/dma.c
+++ b/arch/microblaze/kernel/dma.c
@@ -61,8 +61,7 @@ static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl,
 	/* FIXME this part of code is untested */
 	for_each_sg(sgl, sg, nents, i) {
 		sg->dma_address = sg_phys(sg);
-		__dma_sync(page_to_phys(sg_page(sg)) + sg->offset,
-							sg->length, direction);
+		__dma_sync(sg_phys(sg), sg->length, direction);
 	}
 
 	return nents;
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 5852df8cc50f..7b6c5b63ece7 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -2098,7 +2098,7 @@ static int __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn,
 			sg_res = aligned_nrpages(sg->offset, sg->length);
 			sg->dma_address = ((dma_addr_t)iov_pfn << VTD_PAGE_SHIFT) + sg->offset;
 			sg->dma_length = sg->length;
-			pteval = page_to_phys(sg_page(sg)) | prot;
+			pteval = (sg_phys(sg) & PAGE_MASK) | prot;
 			phys_pfn = pteval >> VTD_PAGE_SHIFT;
 		}
 
@@ -3625,7 +3625,7 @@ static int intel_nontranslate_map_sg(struct device *hddev,
 
 	for_each_sg(sglist, sg, nelems, i) {
 		BUG_ON(!sg_page(sg));
-		sg->dma_address = page_to_phys(sg_page(sg)) + sg->offset;
+		sg->dma_address = sg_phys(sg);
 		sg->dma_length = sg->length;
 	}
 	return nelems;
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index f286090931cc..049df495c274 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1408,7 +1408,7 @@ size_t default_iommu_map_sg(struct iommu_domain *domain, unsigned long iova,
 	min_pagesz = 1 << __ffs(domain->ops->pgsize_bitmap);
 
 	for_each_sg(sg, s, nents, i) {
-		phys_addr_t phys = page_to_phys(sg_page(s)) + s->offset;
+		phys_addr_t phys = sg_phys(s);
 
 		/*
 		 * We are mapping on IOMMU page boundaries, so offset within
diff --git a/drivers/staging/android/ion/ion_chunk_heap.c b/drivers/staging/android/ion/ion_chunk_heap.c
index 54746157d799..f7b6ef991cd0 100644
--- a/drivers/staging/android/ion/ion_chunk_heap.c
+++ b/drivers/staging/android/ion/ion_chunk_heap.c
@@ -81,7 +81,7 @@ static int ion_chunk_heap_allocate(struct ion_heap *heap,
 err:
 	sg = table->sgl;
 	for (i -= 1; i >= 0; i--) {
-		gen_pool_free(chunk_heap->pool, page_to_phys(sg_page(sg)),
+		gen_pool_free(chunk_heap->pool, sg_phys(sg) & PAGE_MASK,
 			      sg->length);
 		sg = sg_next(sg);
 	}
@@ -109,7 +109,7 @@ static void ion_chunk_heap_free(struct ion_buffer *buffer)
 							DMA_BIDIRECTIONAL);
 
 	for_each_sg(table->sgl, sg, table->nents, i) {
-		gen_pool_free(chunk_heap->pool, page_to_phys(sg_page(sg)),
+		gen_pool_free(chunk_heap->pool, sg_phys(sg) & PAGE_MASK,
 			      sg->length);
 	}
 	chunk_heap->allocated -= allocated_size;