iommu/dma: Remove broken huge page handling

The attempt to handle huge page allocations was originally added since
the comments around stripping __GFP_COMP in other implementations were
nonsensical, and we naively assumed that split_huge_page() could simply
be called equivalently to split_page(). It turns out that this doesn't
actually work correctly, so just get rid of it - there's little point
going to the effort of allocating huge pages if we're only going to
split them anyway.

Reported-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/e287dbe69aa0933abafd97c80631940fd188ddd1.1599132844.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 3afd076e9f3665b566f0a6a699705471a62108cf..79b4d1073dcb991ef66f06ce23f233046c9e84b9 100644 (file)
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -524,6 +524,9 @@ static struct page **__iommu_dma_alloc_pages(struct device *dev,
        /* IOMMU can map any pages, so himem can also be used here */
        gfp |= __GFP_NOWARN | __GFP_HIGHMEM;
 
+       /* It makes no sense to muck about with huge pages */
+       gfp &= ~__GFP_COMP;
+
        while (count) {
                struct page *page = NULL;
                unsigned int order_size;
@@ -544,15 +547,9 @@ static struct page **__iommu_dma_alloc_pages(struct device *dev,
                        page = alloc_pages_node(nid, alloc_flags, order);
                        if (!page)
                                continue;
-                       if (!order)
-                               break;
-                       if (!PageCompound(page)) {
+                       if (order)
                                split_page(page, order);
-                               break;
-                       } else if (!split_huge_page(page)) {
-                               break;
-                       }
-                       __free_pages(page, order);
+                       break;
                }
                if (!page) {
                        __iommu_dma_free_pages(pages, i);