cleanup vmap usage in the dma-mapping layer

cleanup vmap usage in the dma-mapping layer

[Christoph Hellwig]

Hi all,

the common DMA remapping code uses the vmalloc/vmap code to create
page table entries for DMA mappings.  This series lifts the currently
arm specific VM_* flag for that into common code, and also exposes
it to userspace in procfs to better understand the mappings, and cleans
up a couple helpers in this area.
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[PATCH 1/3] vmalloc: lift the arm flag for coherent mappings to common code

[Christoph Hellwig]

The arm architecture had a VM_ARM_DMA_CONSISTENT flag to mark DMA
coherent remapping for a while.  Lift this flag to common code so
that we can use it generically.  We also check it in the only place
VM_USERMAP is directly check so that we can entirely replace that
flag as well (although I'm not even sure why we'd want to allow
remapping DMA appings, but I'd rather not change behavior).

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/arm/mm/dma-mapping.c | 22 +++++++---------------
 arch/arm/mm/mm.h          |  3 ---
 include/linux/vmalloc.h   |  2 ++
 mm/vmalloc.c              |  5 ++++-
 4 files changed, 13 insertions(+), 19 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 0a75058c11f3..e197b028e341 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -360,19 +360,13 @@ static void *
 __dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
 	const void *caller)
 {
-	/*
-	 * DMA allocation can be mapped to user space, so lets
-	 * set VM_USERMAP flags too.
-	 */
-	return dma_common_contiguous_remap(page, size,
-			VM_ARM_DMA_CONSISTENT | VM_USERMAP,
+	return dma_common_contiguous_remap(page, size, VM_DMA_COHERENT,
 			prot, caller);
 }
 
 static void __dma_free_remap(void *cpu_addr, size_t size)
 {
-	dma_common_free_remap(cpu_addr, size,
-			VM_ARM_DMA_CONSISTENT | VM_USERMAP);
+	dma_common_free_remap(cpu_addr, size, VM_DMA_COHERENT);
 }
 
 #define DEFAULT_DMA_COHERENT_POOL_SIZE	SZ_256K
@@ -1387,8 +1381,8 @@ static void *
 __iommu_alloc_remap(struct page **pages, size_t size, gfp_t gfp, pgprot_t prot,
 		    const void *caller)
 {
-	return dma_common_pages_remap(pages, size,
-			VM_ARM_DMA_CONSISTENT | VM_USERMAP, prot, caller);
+	return dma_common_pages_remap(pages, size, VM_DMA_COHERENT, prot,
+			caller);
 }
 
 /*
@@ -1472,7 +1466,7 @@ static struct page **__iommu_get_pages(void *cpu_addr, unsigned long attrs)
 		return cpu_addr;
 
 	area = find_vm_area(cpu_addr);
-	if (area && (area->flags & VM_ARM_DMA_CONSISTENT))
+	if (area && (area->flags & VM_DMA_COHERENT))
 		return area->pages;
 	return NULL;
 }
@@ -1630,10 +1624,8 @@ void __arm_iommu_free_attrs(struct device *dev, size_t size, void *cpu_addr,
 		return;
 	}
 
-	if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0) {
-		dma_common_free_remap(cpu_addr, size,
-			VM_ARM_DMA_CONSISTENT | VM_USERMAP);
-	}
+	if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0)
+		dma_common_free_remap(cpu_addr, size, VM_DMA_COHERENT);
 
 	__iommu_remove_mapping(dev, handle, size);
 	__iommu_free_buffer(dev, pages, size, attrs);
diff --git a/arch/arm/mm/mm.h b/arch/arm/mm/mm.h
index 6b045c6653ea..6ec48188ef9f 100644
--- a/arch/arm/mm/mm.h
+++ b/arch/arm/mm/mm.h
@@ -68,9 +68,6 @@ extern void __flush_dcache_page(struct address_space *mapping, struct page *page
 #define VM_ARM_MTYPE(mt)		((mt) << 20)
 #define VM_ARM_MTYPE_MASK	(0x1f << 20)
 
-/* consistent regions used by dma_alloc_attrs() */
-#define VM_ARM_DMA_CONSISTENT	0x20000000
-
 
 struct static_vm {
 	struct vm_struct vm;
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 51e131245379..500fa4fb06f0 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -18,6 +18,7 @@ struct notifier_block;		/* in notifier.h */
 #define VM_ALLOC		0x00000002	/* vmalloc() */
 #define VM_MAP			0x00000004	/* vmap()ed pages */
 #define VM_USERMAP		0x00000008	/* suitable for remap_vmalloc_range */
+#define VM_DMA_COHERENT		0x00000010	/* dma_alloc_coherent */
 #define VM_UNINITIALIZED	0x00000020	/* vm_struct is not fully initialized */
 #define VM_NO_GUARD		0x00000040      /* don't add guard page */
 #define VM_KASAN		0x00000080      /* has allocated kasan shadow memory */
@@ -26,6 +27,7 @@ struct notifier_block;		/* in notifier.h */
  * vfree_atomic().
  */
 #define VM_FLUSH_RESET_PERMS	0x00000100      /* Reset direct map and flush TLB on unmap */
+
 /* bits [20..32] reserved for arch specific ioremap internals */
 
 /*
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 233af6936c93..c4b5784bccc1 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2948,7 +2948,7 @@ int remap_vmalloc_range_partial(struct vm_area_struct *vma, unsigned long uaddr,
 	if (!area)
 		return -EINVAL;
 
-	if (!(area->flags & VM_USERMAP))
+	if (!(area->flags & (VM_USERMAP | VM_DMA_COHERENT)))
 		return -EINVAL;
 
 	if (kaddr + size > area->addr + get_vm_area_size(area))
@@ -3438,6 +3438,9 @@ static int s_show(struct seq_file *m, void *p)
 	if (v->flags & VM_USERMAP)
 		seq_puts(m, " user");
 
+	if (v->flags & VM_DMA_COHERENT)
+		seq_puts(m, " dma-coherent");
+
 	if (is_vmalloc_addr(v->pages))
 		seq_puts(m, " vpages");
 
-- 
2.20.1

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[PATCH 2/3] dma-mapping: always use VM_DMA_COHERENT for generic DMA remap

[Christoph Hellwig]

Currently the generic dma remap allocator gets a vm_flags passed by
the caller that is a little confusing.  We just introduced a generic
vmalloc-level flag to identify the dma coherent allocations, so use
that everywhere and remove the now pointless argument.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/arm/mm/dma-mapping.c    | 37 +++++++-----------------------------
 arch/xtensa/kernel/pci-dma.c |  4 ++--
 drivers/iommu/dma-iommu.c    |  6 +++---
 include/linux/dma-mapping.h  |  6 ++----
 kernel/dma/remap.c           | 25 +++++++++++-------------
 5 files changed, 25 insertions(+), 53 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index e197b028e341..647fd25d2aba 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -356,19 +356,6 @@ static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
 				 pgprot_t prot, struct page **ret_page,
 				 const void *caller, bool want_vaddr);
 
-static void *
-__dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
-	const void *caller)
-{
-	return dma_common_contiguous_remap(page, size, VM_DMA_COHERENT,
-			prot, caller);
-}
-
-static void __dma_free_remap(void *cpu_addr, size_t size)
-{
-	dma_common_free_remap(cpu_addr, size, VM_DMA_COHERENT);
-}
-
 #define DEFAULT_DMA_COHERENT_POOL_SIZE	SZ_256K
 static struct gen_pool *atomic_pool __ro_after_init;
 
@@ -525,7 +512,7 @@ static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
 	if (!want_vaddr)
 		goto out;
 
-	ptr = __dma_alloc_remap(page, size, gfp, prot, caller);
+	ptr = dma_common_contiguous_remap(page, size, gfp, prot, caller);
 	if (!ptr) {
 		__dma_free_buffer(page, size);
 		return NULL;
@@ -592,7 +579,8 @@ static void *__alloc_from_contiguous(struct device *dev, size_t size,
 		goto out;
 
 	if (PageHighMem(page)) {
-		ptr = __dma_alloc_remap(page, size, GFP_KERNEL, prot, caller);
+		ptr = dma_common_contiguous_remap(page, size, GFP_KERNEL, prot,
+				caller);
 		if (!ptr) {
 			dma_release_from_contiguous(dev, page, count);
 			return NULL;
@@ -612,7 +600,7 @@ static void __free_from_contiguous(struct device *dev, struct page *page,
 {
 	if (want_vaddr) {
 		if (PageHighMem(page))
-			__dma_free_remap(cpu_addr, size);
+			dma_common_free_remap(cpu_addr, size);
 		else
 			__dma_remap(page, size, PAGE_KERNEL);
 	}
@@ -704,7 +692,7 @@ static void *remap_allocator_alloc(struct arm_dma_alloc_args *args,
 static void remap_allocator_free(struct arm_dma_free_args *args)
 {
 	if (args->want_vaddr)
-		__dma_free_remap(args->cpu_addr, args->size);
+		dma_common_free_remap(args->cpu_addr, args->size);
 
 	__dma_free_buffer(args->page, args->size);
 }
@@ -1374,17 +1362,6 @@ static int __iommu_free_buffer(struct device *dev, struct page **pages,
 	return 0;
 }
 
-/*
- * Create a CPU mapping for a specified pages
- */
-static void *
-__iommu_alloc_remap(struct page **pages, size_t size, gfp_t gfp, pgprot_t prot,
-		    const void *caller)
-{
-	return dma_common_pages_remap(pages, size, VM_DMA_COHERENT, prot,
-			caller);
-}
-
 /*
  * Create a mapping in device IO address space for specified pages
  */
@@ -1541,7 +1518,7 @@ static void *__arm_iommu_alloc_attrs(struct device *dev, size_t size,
 	if (attrs & DMA_ATTR_NO_KERNEL_MAPPING)
 		return pages;
 
-	addr = __iommu_alloc_remap(pages, size, gfp, prot,
+	addr = dma_common_pages_remap(pages, size, gfp, prot,
 				   __builtin_return_address(0));
 	if (!addr)
 		goto err_mapping;
@@ -1625,7 +1602,7 @@ void __arm_iommu_free_attrs(struct device *dev, size_t size, void *cpu_addr,
 	}
 
 	if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0)
-		dma_common_free_remap(cpu_addr, size, VM_DMA_COHERENT);
+		dma_common_free_remap(cpu_addr, size);
 
 	__iommu_remove_mapping(dev, handle, size);
 	__iommu_free_buffer(dev, pages, size, attrs);
diff --git a/arch/xtensa/kernel/pci-dma.c b/arch/xtensa/kernel/pci-dma.c
index 9171bff76fc4..81c1def6b5a2 100644
--- a/arch/xtensa/kernel/pci-dma.c
+++ b/arch/xtensa/kernel/pci-dma.c
@@ -175,7 +175,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 	if (PageHighMem(page)) {
 		void *p;
 
-		p = dma_common_contiguous_remap(page, size, VM_MAP,
+		p = dma_common_contiguous_remap(page, size,
 						pgprot_noncached(PAGE_KERNEL),
 						__builtin_return_address(0));
 		if (!p) {
@@ -202,7 +202,7 @@ void arch_dma_free(struct device *dev, size_t size, void *vaddr,
 		page = virt_to_page(platform_vaddr_to_cached(vaddr));
 	} else {
 #ifdef CONFIG_MMU
-		dma_common_free_remap(vaddr, size, VM_MAP);
+		dma_common_free_remap(vaddr, size);
 #endif
 		page = pfn_to_page(PHYS_PFN(dma_to_phys(dev, dma_handle)));
 	}
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 0dee374fc64a..cea561897086 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -619,7 +619,7 @@ static void *iommu_dma_alloc_remap(struct device *dev, size_t size,
 			< size)
 		goto out_free_sg;
 
-	vaddr = dma_common_pages_remap(pages, size, VM_USERMAP, prot,
+	vaddr = dma_common_pages_remap(pages, size, prot,
 			__builtin_return_address(0));
 	if (!vaddr)
 		goto out_unmap;
@@ -943,7 +943,7 @@ static void __iommu_dma_free(struct device *dev, size_t size, void *cpu_addr)
 		pages = __iommu_dma_get_pages(cpu_addr);
 		if (!pages)
 			page = vmalloc_to_page(cpu_addr);
-		dma_common_free_remap(cpu_addr, alloc_size, VM_USERMAP);
+		dma_common_free_remap(cpu_addr, alloc_size);
 	} else {
 		/* Lowmem means a coherent atomic or CMA allocation */
 		page = virt_to_page(cpu_addr);
@@ -983,7 +983,7 @@ static void *iommu_dma_alloc_pages(struct device *dev, size_t size,
 		pgprot_t prot = arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs);
 
 		cpu_addr = dma_common_contiguous_remap(page, alloc_size,
-				VM_USERMAP, prot, __builtin_return_address(0));
+				prot, __builtin_return_address(0));
 		if (!cpu_addr)
 			goto out_free_pages;
 
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 6309a721394b..ac320b7cacfd 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -616,13 +616,11 @@ extern int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 		unsigned long attrs);
 
 void *dma_common_contiguous_remap(struct page *page, size_t size,
-			unsigned long vm_flags,
 			pgprot_t prot, const void *caller);
 
 void *dma_common_pages_remap(struct page **pages, size_t size,
-			unsigned long vm_flags, pgprot_t prot,
-			const void *caller);
-void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags);
+			pgprot_t prot, const void *caller);
+void dma_common_free_remap(void *cpu_addr, size_t size);
 
 int __init dma_atomic_pool_init(gfp_t gfp, pgprot_t prot);
 bool dma_in_atomic_pool(void *start, size_t size);
diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
index 7a723194ecbe..51958d21c810 100644
--- a/kernel/dma/remap.c
+++ b/kernel/dma/remap.c
@@ -12,12 +12,11 @@
 #include <linux/vmalloc.h>
 
 static struct vm_struct *__dma_common_pages_remap(struct page **pages,
-			size_t size, unsigned long vm_flags, pgprot_t prot,
-			const void *caller)
+			size_t size, pgprot_t prot, const void *caller)
 {
 	struct vm_struct *area;
 
-	area = get_vm_area_caller(size, vm_flags, caller);
+	area = get_vm_area_caller(size, VM_DMA_COHERENT, caller);
 	if (!area)
 		return NULL;
 
@@ -34,12 +33,11 @@ static struct vm_struct *__dma_common_pages_remap(struct page **pages,
  * Cannot be used in non-sleeping contexts
  */
 void *dma_common_pages_remap(struct page **pages, size_t size,
-			unsigned long vm_flags, pgprot_t prot,
-			const void *caller)
+			 pgprot_t prot, const void *caller)
 {
 	struct vm_struct *area;
 
-	area = __dma_common_pages_remap(pages, size, vm_flags, prot, caller);
+	area = __dma_common_pages_remap(pages, size, prot, caller);
 	if (!area)
 		return NULL;
 
@@ -53,7 +51,6 @@ void *dma_common_pages_remap(struct page **pages, size_t size,
  * Cannot be used in non-sleeping contexts
  */
 void *dma_common_contiguous_remap(struct page *page, size_t size,
-			unsigned long vm_flags,
 			pgprot_t prot, const void *caller)
 {
 	int i;
@@ -67,7 +64,7 @@ void *dma_common_contiguous_remap(struct page *page, size_t size,
 	for (i = 0; i < (size >> PAGE_SHIFT); i++)
 		pages[i] = nth_page(page, i);
 
-	area = __dma_common_pages_remap(pages, size, vm_flags, prot, caller);
+	area = __dma_common_pages_remap(pages, size, prot, caller);
 
 	kfree(pages);
 
@@ -79,11 +76,11 @@ void *dma_common_contiguous_remap(struct page *page, size_t size,
 /*
  * Unmaps a range previously mapped by dma_common_*_remap
  */
-void dma_common_free_remap(void *cpu_addr, size_t size, unsigned long vm_flags)
+void dma_common_free_remap(void *cpu_addr, size_t size)
 {
 	struct vm_struct *area = find_vm_area(cpu_addr);
 
-	if (!area || (area->flags & vm_flags) != vm_flags) {
+	if (!area || area->flags != VM_DMA_COHERENT) {
 		WARN(1, "trying to free invalid coherent area: %p\n", cpu_addr);
 		return;
 	}
@@ -127,8 +124,8 @@ int __init dma_atomic_pool_init(gfp_t gfp, pgprot_t prot)
 	if (!atomic_pool)
 		goto free_page;
 
-	addr = dma_common_contiguous_remap(page, atomic_pool_size, VM_USERMAP,
-					   prot, __builtin_return_address(0));
+	addr = dma_common_contiguous_remap(page, atomic_pool_size, prot,
+					   __builtin_return_address(0));
 	if (!addr)
 		goto destroy_genpool;
 
@@ -143,7 +140,7 @@ int __init dma_atomic_pool_init(gfp_t gfp, pgprot_t prot)
 	return 0;
 
 remove_mapping:
-	dma_common_free_remap(addr, atomic_pool_size, VM_USERMAP);
+	dma_common_free_remap(addr, atomic_pool_size);
 destroy_genpool:
 	gen_pool_destroy(atomic_pool);
 	atomic_pool = NULL;
@@ -220,7 +217,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 	}
 
 	/* create a coherent mapping */
-	ret = dma_common_contiguous_remap(page, size, VM_USERMAP,
+	ret = dma_common_contiguous_remap(page, size,
 			arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs),
 			__builtin_return_address(0));
 	if (!ret) {
-- 
2.20.1

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[PATCH 3/3] dma-mapping: introduce a dma_common_find_pages helper

[Christoph Hellwig]

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   |  7 +------
 drivers/iommu/dma-iommu.c   | 15 +++------------
 include/linux/dma-mapping.h |  1 +
 kernel/dma/remap.c          | 13 +++++++++++--
 4 files changed, 16 insertions(+), 20 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 647fd25d2aba..7620d4f55e92 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1434,18 +1434,13 @@ 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,
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index cea561897086..002d3bb6254a 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -543,15 +543,6 @@ 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
@@ -940,7 +931,7 @@ 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);
@@ -1050,7 +1041,7 @@ 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);
@@ -1072,7 +1063,7 @@ 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,
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index ac320b7cacfd..cb07d1388d66 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -615,6 +615,7 @@ 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);
 
diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
index 51958d21c810..52cdca386de0 100644
--- a/kernel/dma/remap.c
+++ b/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;
 	}
-- 
2.20.1

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cleanup vmap usage in the dma-mapping layer

[Christoph Hellwig]

Hi all,

the common DMA remapping code uses the vmalloc/vmap code to create
page table entries for DMA mappings.  This series lifts the currently
arm specific VM_* flag for that into common code, and also exposes
it to userspace in procfs to better understand the mappings.
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