[PATCH 5.15.y 03/10] dma-direct: fail allocations that can't be made coherent

[Sasha Levin <sashal@kernel.org>]

From: Christoph Hellwig <hch@lst.de>

[ Upstream commit 955f58f7406ad912825fc344c7825fd904b124a0 ]

If the architecture can't remap or set an address uncached there is no way
to fullfill a request for a coherent allocation.  Return NULL in that case.
Note that this case currently does not happen, so this is a theoretical
fixup and/or a preparation for eventually supporting platforms that
can't support coherent allocations with the generic code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Stable-dep-of: 94a04ad732c9 ("dma-direct: return struct page from dma_direct_alloc_from_pool()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/dma/direct.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 517ca0e61a57c..0d6467b6553b7 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -236,8 +236,9 @@ void *dma_direct_alloc(struct device *dev, size_t size,
 				return dma_direct_alloc_from_pool(dev, size,
 						dma_handle, gfp);
 		} else {
-			if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED))
-				set_uncached = true;
+			if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED))
+				return NULL;
+			set_uncached = true;
 		}
 	}
 
-- 
2.53.0