linux-kernel - [PATCH 21/28] x86: retry allocation if failed

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Date:	Tue,  8 Apr 2008 13:21:03 -0300
From:	Glauber Costa <gcosta@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...ux-foundation.org, glommer@...il.com, mingo@...e.hu,
	tglx@...utronix.de, kvm-devel@...ts.sourceforge.net,
	amit.shah@...ranet.com, avi@...ranet.com,
	Glauber Costa <gcosta@...hat.com>
Subject: [PATCH 21/28] x86: retry allocation if failed

This patch puts in the code to retry allocation in case it fails. By its
own, it does not make much sense but making the code look like x86_64.
But later patches in this series will make we try to allocate from
zones other than DMA first, which will possibly fail.

Signed-off-by: Glauber Costa <gcosta@...hat.com>
---
 arch/x86/kernel/pci-dma_32.c |   34 +++++++++++++++++++++++++++++-----
 1 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/pci-dma_32.c b/arch/x86/kernel/pci-dma_32.c
index 0d630ae..f6cf434 100644
--- a/arch/x86/kernel/pci-dma_32.c
+++ b/arch/x86/kernel/pci-dma_32.c
@@ -66,6 +66,8 @@ void *dma_alloc_coherent(struct device *dev, size_t size,
 	struct page *page;
 	dma_addr_t bus;
 	int order = get_order(size);
+	unsigned long dma_mask = 0;
+
 	/* ignore region specifiers */
 	gfp &= ~(__GFP_DMA | __GFP_HIGHMEM);
 
@@ -75,15 +77,37 @@ void *dma_alloc_coherent(struct device *dev, size_t size,
 	if (dev == NULL || (dev->coherent_dma_mask < 0xffffffff))
 		gfp |= GFP_DMA;
 
+	dma_mask = dev->coherent_dma_mask;
+	if (dma_mask == 0)
+		dma_mask = DMA_32BIT_MASK;
+
+ again:
 	page = dma_alloc_pages(dev, gfp, order);
 	if (page == NULL)
 		return NULL;
 
-	ret = page_address(page);
-	bus = page_to_phys(page);
-
-	memset(ret, 0, size);
-	*dma_handle = bus;
+	{
+		int high, mmu;
+		bus = page_to_phys(page);
+		ret = page_address(page);
+		high = (bus + size) >= dma_mask;
+		mmu = high;
+		if (force_iommu && !(gfp & GFP_DMA))
+			mmu = 1;
+		else if (high) {
+			free_pages((unsigned long)ret,
+				   get_order(size));
+
+			/* Don't use the 16MB ZONE_DMA unless absolutely
+			   needed. It's better to use remapping first. */
+			if (dma_mask < DMA_32BIT_MASK && !(gfp & GFP_DMA)) {
+				gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
+				goto again;
+			}
+		}
+		memset(ret, 0, size);
+		*dma_handle = bus;
+	}
 
 	return ret;
 }
-- 
1.5.0.6

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