dma-direct: fix zone selection after an unaddressable CMA allocation

The new dma_alloc_contiguous hides if we allocate CMA or regular
pages, and thus fails to retry a ZONE_NORMAL allocation if the CMA
allocation succeeds but isn't addressable.  That means we either fail
outright or dip into a small zone that might not succeed either.

Thanks to Hillf Danton for debugging this issue.

Fixes: b1d2dc00 ("dma-contiguous: add dma_{alloc,free}_contiguous() helpers")
Reported-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>

drivers/iommu/dma-iommu.c

@@ -965,10 +965,13 @@ static void *iommu_dma_alloc_pages(struct device *dev, size_t size,
 {
 	bool coherent = dev_is_dma_coherent(dev);
 	size_t alloc_size = PAGE_ALIGN(size);
+	int node = dev_to_node(dev);
 	struct page *page = NULL;
 	void *cpu_addr;
 
 	page = dma_alloc_contiguous(dev, alloc_size, gfp);
+	if (!page)
+		page = alloc_pages_node(node, gfp, get_order(alloc_size));
 	if (!page)
 		return NULL;
 

include/linux/dma-contiguous.h

@@ -160,10 +160,7 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages,
 static inline struct page *dma_alloc_contiguous(struct device *dev, size_t size,
 		gfp_t gfp)
 {
-	int node = dev ? dev_to_node(dev) : NUMA_NO_NODE;
-	size_t align = get_order(PAGE_ALIGN(size));
-
-	return alloc_pages_node(node, gfp, align);
+	return NULL;
 }
 
 static inline void dma_free_contiguous(struct device *dev, struct page *page,

kernel/dma/contiguous.c

@@ -230,9 +230,7 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages,
  */
 struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
 {
-	int node = dev ? dev_to_node(dev) : NUMA_NO_NODE;
-	size_t count = PAGE_ALIGN(size) >> PAGE_SHIFT;
-	size_t align = get_order(PAGE_ALIGN(size));
+	size_t count = size >> PAGE_SHIFT;
 	struct page *page = NULL;
 	struct cma *cma = NULL;
 
@@ -243,14 +241,12 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
 
 	/* CMA can be used only in the context which permits sleeping */
 	if (cma && gfpflags_allow_blocking(gfp)) {
+		size_t align = get_order(size);
 		size_t cma_align = min_t(size_t, align, CONFIG_CMA_ALIGNMENT);
 
 		page = cma_alloc(cma, count, cma_align, gfp & __GFP_NOWARN);
 	}
 
-	/* Fallback allocation of normal pages */
-	if (!page)
-		page = alloc_pages_node(node, gfp, align);
 	return page;
 }
 

kernel/dma/direct.c

@@ -85,6 +85,8 @@ static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
 struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
 		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
 {
+	size_t alloc_size = PAGE_ALIGN(size);
+	int node = dev_to_node(dev);
 	struct page *page = NULL;
 	u64 phys_mask;
 
@@ -95,8 +97,14 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
 	gfp &= ~__GFP_ZERO;
 	gfp |= __dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
 			&phys_mask);
+	page = dma_alloc_contiguous(dev, alloc_size, gfp);
+	if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
+		dma_free_contiguous(dev, page, alloc_size);
+		page = NULL;
+	}
 again:
-	page = dma_alloc_contiguous(dev, size, gfp);
+	if (!page)
+		page = alloc_pages_node(node, gfp, get_order(alloc_size));
 	if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
 		dma_free_contiguous(dev, page, size);
 		page = NULL;