Re: [PATCH RESEND] ARM: DMA: Fix kzalloc flags in __iommu_alloc_buffer()

[Will Deacon <will.deacon@arm.com>]

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.

> 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>

Will