linux-kernel - [PATCH 1/2] dma-direct: Don't repeat allocation for no-op GFP

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Date:   Sun, 15 Apr 2018 11:08:07 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Christoph Hellwig <hch@....de>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] dma-direct: Don't repeat allocation for no-op GFP_DMA

When an allocation with lower dma_coherent mask fails,
dma_direct_alloc() retries the allocation with GFP_DMA.  But, it's
useless for architectures that has no ZONE_DMA, obviously.

Fix it by adding the check of CONFIG_ZONE_DMA before retrying the
allocation.

Fixes: 95f183916d4b ("dma-direct: retry allocations using GFP_DMA for small masks")
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 lib/dma-direct.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index c0bba30fef0a..bbfb229aa067 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c
@@ -84,7 +84,8 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		__free_pages(page, page_order);
 		page = NULL;
 
-		if (dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
+		if (IS_ENABLED(CONFIG_ZONE_DMA) &&
+		    dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
 		    !(gfp & GFP_DMA)) {
 			gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
 			goto again;
-- 
2.16.3