dma-remap: support DMA_ATTR_NO_KERNEL_MAPPING

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>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>

diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
index dcc82dd668f841cd5cde4527bda65f40bcbdeb33..68a64e3ff6a15f3c8b201e73a5b27b72d569d0f6 100644 (file)
--- 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; /* opaque 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));