[PATCH 07/19] dma-iommu: fix and refactor iommu_dma_get_sgtable

[Christoph Hellwig]

The current iommu_dma_get_sgtable code does not properly handle memory
from the page allocator that hasn't been remapped, which can happen in
the rare case of allocations for a coherent device that aren't allowed
to block.

Fix this by replacing iommu_dma_get_sgtable with a slightly tweaked copy
of dma_common_get_sgtable with special handling for the remapped array
of pages allocated from __iommu_dma_alloc.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 drivers/iommu/dma-iommu.c | 49 +++++++++++++++++++--------------------
 1 file changed, 24 insertions(+), 25 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 26f479d49103..8f3dc6ab3da1 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -620,6 +620,18 @@ static int iommu_dma_mmap_remap(void *cpu_addr, size_t size,
 	return ret;
 }
 
+static int iommu_dma_get_sgtable_remap(struct sg_table *sgt, void *cpu_addr,
+		size_t size)
+{
+	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+	struct vm_struct *area = find_vm_area(cpu_addr);
+
+	if (WARN_ON(!area || !area->pages))
+		return -ENXIO;
+	return sg_alloc_table_from_pages(sgt, area->pages, count, 0, size,
+			GFP_KERNEL);
+}
+
 static void iommu_dma_sync_single_for_cpu(struct device *dev,
 		dma_addr_t dma_handle, size_t size, enum dma_data_direction dir)
 {
@@ -1080,37 +1092,24 @@ static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
 			user_count << PAGE_SHIFT, vma->vm_page_prot);
 }
 
-static int __iommu_dma_get_sgtable_page(struct sg_table *sgt, struct page *page,
-		size_t size)
-{
-	int ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
-
-	if (!ret)
-		sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
-	return ret;
-}
-
 static int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
 		void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		unsigned long attrs)
 {
-	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
-	struct vm_struct *area = find_vm_area(cpu_addr);
-
-	if (attrs & DMA_ATTR_FORCE_CONTIGUOUS) {
-		/*
-		 * DMA_ATTR_FORCE_CONTIGUOUS allocations are always remapped,
-		 * hence in the vmalloc space.
-		 */
-		struct page *page = vmalloc_to_page(cpu_addr);
-		return __iommu_dma_get_sgtable_page(sgt, page, size);
-	}
+	struct page *page;
+	int ret;
 
-	if (WARN_ON(!area || !area->pages))
-		return -ENXIO;
+	if (is_vmalloc_addr(cpu_addr)) {
+		if (!(attrs & DMA_ATTR_FORCE_CONTIGUOUS))
+			return iommu_dma_get_sgtable_remap(sgt, cpu_addr, size);
+		page = vmalloc_to_page(cpu_addr);
+	} else
+		page = virt_to_page(cpu_addr);
 
-	return sg_alloc_table_from_pages(sgt, area->pages, count, 0, size,
-					 GFP_KERNEL);
+	ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
+	if (!ret)
+		sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
+	return ret;
 }
 
 static const struct dma_map_ops iommu_dma_ops = {
-- 
2.20.1