dma-mapping: introduce a dma_common_find_pages helper

A helper to find the backing page array based on a virtual address.
This also ensures we do the same vm_flags check everywhere instead
of slightly different or missing ones in a few places.
Signed-off-by: Christoph Hellwig <hch@lst.de>

arch/arm/mm/dma-mapping.c

@@ -1439,18 +1439,13 @@ static struct page **__atomic_get_pages(void *addr)
 
 static struct page **__iommu_get_pages(void *cpu_addr, unsigned long attrs)
 {
-	struct vm_struct *area;
-
 	if (__in_atomic_pool(cpu_addr, PAGE_SIZE))
 		return __atomic_get_pages(cpu_addr);
 
 	if (attrs & DMA_ATTR_NO_KERNEL_MAPPING)
 		return cpu_addr;
 
-	area = find_vm_area(cpu_addr);
-	if (area && (area->flags & VM_DMA_COHERENT))
-		return area->pages;
-	return NULL;
+	return dma_common_find_pages(cpu_addr);
 }
 
 static void *__iommu_alloc_simple(struct device *dev, size_t size, gfp_t gfp,

drivers/iommu/dma-iommu.c

@@ -541,15 +541,6 @@ static struct page **__iommu_dma_alloc_pages(struct device *dev,
 	return pages;
 }
 
-static struct page **__iommu_dma_get_pages(void *cpu_addr)
-{
-	struct vm_struct *area = find_vm_area(cpu_addr);
-
-	if (!area || !area->pages)
-		return NULL;
-	return area->pages;
-}
-
 /**
  * iommu_dma_alloc_remap - Allocate and map a buffer contiguous in IOVA space
  * @dev: Device to allocate memory for. Must be a real device
@@ -938,7 +929,7 @@ static void __iommu_dma_free(struct device *dev, size_t size, void *cpu_addr)
 		 * If it the address is remapped, then it's either non-coherent
 		 * or highmem CMA, or an iommu_dma_alloc_remap() construction.
 		 */
-		pages = __iommu_dma_get_pages(cpu_addr);
+		pages = dma_common_find_pages(cpu_addr);
 		if (!pages)
 			page = vmalloc_to_page(cpu_addr);
 		dma_common_free_remap(cpu_addr, alloc_size);
@@ -1045,7 +1036,7 @@ static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
 		return -ENXIO;
 
 	if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) {
-		struct page **pages = __iommu_dma_get_pages(cpu_addr);
+		struct page **pages = dma_common_find_pages(cpu_addr);
 
 		if (pages)
 			return __iommu_dma_mmap(pages, size, vma);
@@ -1067,7 +1058,7 @@ static int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
 	int ret;
 
 	if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) {
-		struct page **pages = __iommu_dma_get_pages(cpu_addr);
+		struct page **pages = dma_common_find_pages(cpu_addr);
 
 		if (pages) {
 			return sg_alloc_table_from_pages(sgt, pages,

include/linux/dma-mapping.h

@@ -626,6 +626,7 @@ extern int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 		void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		unsigned long attrs);
 
+struct page **dma_common_find_pages(void *cpu_addr);
 void *dma_common_contiguous_remap(struct page *page, size_t size,
 			pgprot_t prot, const void *caller);
 

kernel/dma/remap.c

@@ -11,6 +11,15 @@
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 
+struct page **dma_common_find_pages(void *cpu_addr)
+{
+	struct vm_struct *area = find_vm_area(cpu_addr);
+
+	if (!area || area->flags != VM_DMA_COHERENT)
+		return NULL;
+	return area->pages;
+}
+
 static struct vm_struct *__dma_common_pages_remap(struct page **pages,
 			size_t size, pgprot_t prot, const void *caller)
 {
@@ -78,9 +87,9 @@ void *dma_common_contiguous_remap(struct page *page, size_t size,
  */
 void dma_common_free_remap(void *cpu_addr, size_t size)
 {
-	struct vm_struct *area = find_vm_area(cpu_addr);
+	struct page **pages = dma_common_find_pages(cpu_addr);
 
-	if (!area || area->flags != VM_DMA_COHERENT) {
+	if (!pages) {
 		WARN(1, "trying to free invalid coherent area: %p\n", cpu_addr);
 		return;
 	}