Re: [PATCH] x86: dma-mapping: fix GFP_ATOMIC macro usage
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From: Andy Whitcroft <apw@canonical.com>
Date: 2014-01-17 10:49:46
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On Fri, Jan 17, 2014 at 8:46 AM, Marek Szyprowski [off-list ref] wrote:
quoted hunk ↗ jump to hunk
GFP_ATOMIC is not a single gfp flag, but a macro which expands to the other flags and LACK of __GFP_WAIT flag. To check if caller wanted to perform an atomic allocation, the code must test __GFP_WAIT flag presence. This patch fixes the issue introduced in v3.5-rc1 CC: stable@vger.kernel.org Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> --- arch/x86/kernel/pci-dma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index 872079a..32a81c9 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c@@ -100,7 +100,7 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size, flag |= __GFP_ZERO; again: page = NULL; - if (!(flag & GFP_ATOMIC)) + if (flag & __GFP_WAIT)
From that description should this not actually be:
if (!(flag & (GFP_ATOMIC|__GFP_WAIT) == GFP_ATOMIC))
Else we will start using this pool for more than __GFP_HIGH allocations?
That said, it is possible this is right and the intent was to allow
__GFP_HIGH allocations (in general) to use this contigious pool, but I
will let someone more intimate with the code comment to that. I would
have hoped the code would have been as below in that case:
if (!(flag & __GFP_HIGH))
Either way once this is resolved a nice comment should be added to
make it really clear:
-apw