Messages in this thread Patch in this message | | | Date | Fri, 13 Feb 2015 14:13:31 +0900 | From | Alexandre Courbot <> | Subject | Re: [PATCH RESEND] ARM: DMA: Fix kzalloc flags in __iommu_alloc_buffer() |
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On 02/13/2015 12:32 PM, Will Deacon wrote: > On Wed, Feb 11, 2015 at 09:01:41AM +0000, Alexandre Courbot wrote: >> There doesn't seem to be any valid reason to allocate the pages array >> with the same flags as the buffer itself. Doing so can eventually lead >> to the following safeguard in mm/slab.c to be hit: >> >> BUG_ON(flags & GFP_SLAB_BUG_MASK); > > nit: I can't actually spot this BUG_ON in the kernel.
I have been trying to push this patch for so long that the line in question changed in the meantime. :) It is now
if (unlikely(flags & GFP_SLAB_BUG_MASK)) { pr_emerg("gfp: %u\n", flags & GFP_SLAB_BUG_MASK); BUG(); }
in cache_grow, line 2593 of mm/slab.c.
> >> This happens when buffers are allocated with __GFP_DMA32 or >> __GFP_HIGHMEM. >> >> Fix this by allocating the pages array with GFP_KERNEL to follow what is >> done elsewhere in this file. Using GFP_KERNEL in __iommu_alloc_buffer() >> is safe because atomic allocations are handled by __iommu_alloc_atomic(). >> >> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com> >> Cc: Arnd Bergmann <arnd@arndb.de> >> Cc: Marek Szyprowski <m.szyprowski@samsung.com> >> Cc: Russell King <linux@arm.linux.org.uk> >> Acked-by: Marek Szyprowski <m.szyprowski@samsung.com> >> --- >> arch/arm/mm/dma-mapping.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c >> index 903dba0..170a116 100644 >> --- a/arch/arm/mm/dma-mapping.c >> +++ b/arch/arm/mm/dma-mapping.c >> @@ -1106,7 +1106,7 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size, >> int i = 0; >> >> if (array_size <= PAGE_SIZE) >> - pages = kzalloc(array_size, gfp); >> + pages = kzalloc(array_size, GFP_KERNEL); >> else >> pages = vzalloc(array_size); >> if (!pages) >> -- >> 2.3.0 > > Looks sensible to me: > > Acked-by: Will Deacon <will.deacon@arm.com>
Thanks! I will amend the commit message and resend.
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