Do not waste vmalloc space on allocations that do not require a mapping
into the kernel address space.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
  kernel/dma/remap.c | 11 +++++++++--
  1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
index 8f1fca34b894..10a545126b0b 100644
--- a/kernel/dma/remap.c
+++ b/kernel/dma/remap.c

@@ -200,7 +200,8 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
  
  	size = PAGE_ALIGN(size);
  
-	if (!gfpflags_allow_blocking(flags)) {
+	if (!gfpflags_allow_blocking(flags) &&
+	    !(attrs & DMA_ATTR_NO_KERNEL_MAPPING)) {
  		ret = dma_alloc_from_pool(size, &page, flags);
  		if (!ret)
  			return NULL;

@@ -215,6 +216,9 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
  	/* remove any dirty cache lines on the kernel alias */
  	arch_dma_prep_coherent(page, size);
  
+	if (attrs & DMA_ATTR_NO_KERNEL_MAPPING)
+		return page; /* opaqueue cookie */

+
  	/* create a coherent mapping */
  	ret = dma_common_contiguous_remap(page, size, VM_USERMAP,
  			arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs),

@@ -227,7 +231,10 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
  void arch_dma_free(struct device *dev, size_t size, void *vaddr,
  		dma_addr_t dma_handle, unsigned long attrs)
  {
-	if (!dma_free_from_pool(vaddr, PAGE_ALIGN(size))) {
+	if (attrs & DMA_ATTR_NO_KERNEL_MAPPING) {
+		/* vaddr is a struct page cookie, not a kernel address */
+		__dma_direct_free_pages(dev, size, vaddr);
+	} else if (!dma_free_from_pool(vaddr, PAGE_ALIGN(size))) {
  		phys_addr_t phys = dma_to_phys(dev, dma_handle);
  		struct page *page = pfn_to_page(__phys_to_pfn(phys));