linux-kernel - [PATCH v3] x86: dma-mapping: fix GFP

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Date:	Tue, 11 Feb 2014 09:38:59 +0100
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	linux-kernel@...r.kernel.org, x86@...nel.org
Cc:	Marek Szyprowski <m.szyprowski@...sung.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Whitcroft <apw@...onical.com>, stable@...r.kernel.org
Subject: [PATCH v3] x86: dma-mapping: fix GFP_ATOMIC macro usage

GFP_ATOMIC is not a single gfp flag, but a macro which expands to the other
flags, where meaningful is the LACK of __GFP_WAIT flag. To check if caller
wants to perform an atomic allocation, the code must test for a lack of the
__GFP_WAIT flag. This patch fixes the issue introduced in v3.5-rc1.

CC: stable@...r.kernel.org
Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
---
Changelog:

v3:
- fixed spelling issues

v2:
- added more comments in the code to explain for _GFP_WAIT test

v1:
- initial version

---
 arch/x86/kernel/pci-dma.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 872079a..3519a78 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -100,8 +100,10 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size,
 	flag |= __GFP_ZERO;
 again:
 	page = NULL;
-	if (!(flag & GFP_ATOMIC))
+	/* CMA can be used only in the context which permits sleeping */
+	if (flag & __GFP_WAIT)
 		page = dma_alloc_from_contiguous(dev, count, get_order(size));
+	/* fallback */
 	if (!page)
 		page = alloc_pages_node(dev_to_node(dev), flag, get_order(size));
 	if (!page)
-- 
1.7.9.5

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