From ffcb754584603adf7039d7972564fbf6febdc542 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 9 Nov 2022 08:37:17 +0100 Subject: dma-mapping: reject __GFP_COMP in dma_alloc_attrs DMA allocations can never be turned back into a page pointer, so requesting compound pages doesn't make sense and it can't even be supported at all by various backends. Reject __GFP_COMP with a warning in dma_alloc_attrs, and stop clearing the flag in the arm dma ops and dma-iommu. Signed-off-by: Christoph Hellwig Acked-by: Marek Szyprowski --- kernel/dma/mapping.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'kernel/dma') diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c index 33437d620644..c026a5a5e046 100644 --- a/kernel/dma/mapping.c +++ b/kernel/dma/mapping.c @@ -498,6 +498,14 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle, WARN_ON_ONCE(!dev->coherent_dma_mask); + /* + * DMA allocations can never be turned back into a page pointer, so + * requesting compound pages doesn't make sense (and can't even be + * supported at all by various backends). + */ + if (WARN_ON_ONCE(flag & __GFP_COMP)) + return NULL; + if (dma_alloc_from_dev_coherent(dev, size, dma_handle, &cpu_addr)) return cpu_addr; -- cgit v1.2.3