drm/nouveau: remove allocations from gart populate() hook

Since some somewhat questionable changes a while back, TTM provides a
completely empty array of struct dma_address that stays around for the
entire lifetime of the TTM object.

Lets use this array, *always*, rather than wasting yet more memory on
another array who's purpose is identical, as well as yet another bool array
of the same size saying *which* of the previous two arrays to use...

This change will also solve the high order allocation failures seen by
some people while using nouveau.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_sgdma.c

@@ -12,8 +12,8 @@ struct nouveau_sgdma_be {
 	struct drm_device *dev;
 
 	dma_addr_t *pages;
-	bool *ttm_alloced;
 	unsigned nr_pages;
+	bool unmap_pages;
 
 	u64 offset;
 	bool bound;
@@ -26,43 +26,28 @@ nouveau_sgdma_populate(struct ttm_backend *be, unsigned long num_pages,
 {
 	struct nouveau_sgdma_be *nvbe = (struct nouveau_sgdma_be *)be;
 	struct drm_device *dev = nvbe->dev;
+	int i;
 
 	NV_DEBUG(nvbe->dev, "num_pages = %ld\n", num_pages);
 
-	if (nvbe->pages)
-		return -EINVAL;
-
-	nvbe->pages = kmalloc(sizeof(dma_addr_t) * num_pages, GFP_KERNEL);
-	if (!nvbe->pages)
-		return -ENOMEM;
+	nvbe->pages = dma_addrs;
+	nvbe->nr_pages = num_pages;
+	nvbe->unmap_pages = true;
 
-	nvbe->ttm_alloced = kmalloc(sizeof(bool) * num_pages, GFP_KERNEL);
-	if (!nvbe->ttm_alloced) {
-		kfree(nvbe->pages);
-		nvbe->pages = NULL;
-		return -ENOMEM;
+	/* this code path isn't called and is incorrect anyways */
+	if (0) { /* dma_addrs[0] != DMA_ERROR_CODE) { */
+		nvbe->unmap_pages = false;
+		return 0;
 	}
 
-	nvbe->nr_pages = 0;
-	while (num_pages--) {
-		/* this code path isn't called and is incorrect anyways */
-		if (0) { /*dma_addrs[nvbe->nr_pages] != DMA_ERROR_CODE)*/
-			nvbe->pages[nvbe->nr_pages] =
-					dma_addrs[nvbe->nr_pages];
-		 	nvbe->ttm_alloced[nvbe->nr_pages] = true;
-		} else {
-			nvbe->pages[nvbe->nr_pages] =
-				pci_map_page(dev->pdev, pages[nvbe->nr_pages], 0,
-				     PAGE_SIZE, PCI_DMA_BIDIRECTIONAL);
-			if (pci_dma_mapping_error(dev->pdev,
-						  nvbe->pages[nvbe->nr_pages])) {
-				be->func->clear(be);
-				return -EFAULT;
-			}
-			nvbe->ttm_alloced[nvbe->nr_pages] = false;
+	for (i = 0; i < num_pages; i++) {
+		nvbe->pages[i] = pci_map_page(dev->pdev, pages[i], 0,
+					      PAGE_SIZE, PCI_DMA_BIDIRECTIONAL);
+		if (pci_dma_mapping_error(dev->pdev, nvbe->pages[i])) {
+			nvbe->nr_pages = --i;
+			be->func->clear(be);
+			return -EFAULT;
 		}
-
-		nvbe->nr_pages++;
 	}
 
 	return 0;
@@ -72,25 +57,16 @@ static void
 nouveau_sgdma_clear(struct ttm_backend *be)
 {
 	struct nouveau_sgdma_be *nvbe = (struct nouveau_sgdma_be *)be;
-	struct drm_device *dev;
-
-	if (nvbe && nvbe->pages) {
-		dev = nvbe->dev;
-		NV_DEBUG(dev, "\n");
+	struct drm_device *dev = nvbe->dev;
 
-		if (nvbe->bound)
-			be->func->unbind(be);
+	if (nvbe->bound)
+		be->func->unbind(be);
 
+	if (nvbe->unmap_pages) {
 		while (nvbe->nr_pages--) {
-			if (!nvbe->ttm_alloced[nvbe->nr_pages])
-				pci_unmap_page(dev->pdev, nvbe->pages[nvbe->nr_pages],
+			pci_unmap_page(dev->pdev, nvbe->pages[nvbe->nr_pages],
 				       PAGE_SIZE, PCI_DMA_BIDIRECTIONAL);
 		}
-		kfree(nvbe->pages);
-		kfree(nvbe->ttm_alloced);
-		nvbe->pages = NULL;
-		nvbe->ttm_alloced = NULL;
-		nvbe->nr_pages = 0;
 	}
 }