linux-kernel - [PATCH] swiotlb: remove panic for alloc

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Message-Id: <20081023184032F.fujita.tomonori@lab.ntt.co.jp>
Date:	Thu, 23 Oct 2008 18:42:03 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, tony.luck@...el.com, tiwai@...e.de
Subject: [PATCH] swiotlb: remove panic for alloc_coherent failure

swiotlb_alloc_coherent calls panic() when allocated swiotlb pages is
not fit for a device's dma mask. However, alloc_coherent failure is
not a disaster at all. AFAIK, none of other x86 and IA64 IOMMU
implementations don't crash in case of alloc_coherent failure.

There are some drivers that don't check alloc_coherent failure but not
many (about ten and I've already started to fix some of
them). alloc_coherent returns NULL in case of failure so it's likely
that these guilty drivers crash immediately. So swiotlb doesn't need
to call panic() just for them.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
---
 lib/swiotlb.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index f8eebd4..78330c3 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -497,8 +497,10 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size,
 		printk("hwdev DMA mask = 0x%016Lx, dev_addr = 0x%016Lx\n",
 		       (unsigned long long)*hwdev->dma_mask,
 		       (unsigned long long)dev_addr);
-		panic("swiotlb_alloc_coherent: allocated memory is out of "
-		      "range for device");
+
+		/* DMA_TO_DEVICE to avoid memcpy in unmap_single */
+		unmap_single(hwdev, ret, size, DMA_TO_DEVICE);
+		return NULL;
 	}
 	*dma_handle = dev_addr;
 	return ret;
-- 
1.5.5.GIT

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