Richard Zhao <linuxzsc@xxxxxxxxx> wrote @ Thu, 20 Jun 2013 15:40:50 +0200:
> >> + /*
> >> + * Following is a work-around (a.k.a. hack) to prevent pages
> >> + * with __GFP_COMP being passed to split_page() which cannot
> >> + * handle them. The real problem is that this flag probably
> >> + * should be 0 on ARM as it is not supported on this
> >> + * platform; see CONFIG_HUGETLBFS.
> >> + */
> >> + gfp &= ~(__GFP_COMP);
> >
> >
> > Hm, what exactly is the sense you meant in using ()?
>
> It's copy/paste from elsewhere in this file. At least it's consistent? :)
I almost sent the exact same one, actually it was under internal reivew;)
This patch is similar but is the iommu version of:
commit ea2e7057c0234cfb8b09467d8f137760d371fc72
Author: Sumit Bhattacharya <sumitb@xxxxxxxxxx>
Date: Thu Nov 24 00:47:12 2011 +0100
ARM: 7172/1: dma: Drop GFP_COMP for DMA memory allocations
dma_alloc_coherent wants to split pages after allocation in order to
reduce the memory footprint. This does not work well with GFP_COMP
pages, so drop this flag before allocation.
This patch is ported from arch/avr32
(commit 3611553ef985ef7c5863c8a94641738addd04cff).
[swarren: s/HUGETLB_PAGE/HUGETLBFS/ in comment, minor comment cleanup]
Signed-off-by: Sumit Bhattacharya <sumitb@xxxxxxxxxx>
Tested-by: Varun Colbert <vcolbert@xxxxxxxxxx>
Signed-off-by: Stephen Warren <swarren@xxxxxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index ab58456..1aa664a 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -332,6 +332,15 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
struct page *page;
void *addr;
+ /*
+ * Following is a work-around (a.k.a. hack) to prevent pages
+ * with __GFP_COMP being passed to split_page() which cannot
+ * handle them. The real problem is that this flag probably
+ * should be 0 on ARM as it is not supported on this
+ * platform; see CONFIG_HUGETLBFS.
+ */
+ gfp &= ~(__GFP_COMP);
+
*handle = ~0;
size = PAGE_ALIGN(size);
--
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