linux-kernel - Re: [PATCH 2/2] iommu/dma: use __GFP_NOWARN only for high-order allocations

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Date:   Tue, 27 Jun 2017 12:05:22 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Tomasz Figa <tfiga@...omium.org>, iommu@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org, Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH 2/2] iommu/dma: use __GFP_NOWARN only for high-order
 allocations

On 27/06/17 08:28, Tomasz Figa wrote:
> Memory allocation routines are expected to report allocation errors to
> kernel log. However, current implementation of __iommu_dma_alloc_pages()
> adds __GFP_NOWARN for all calls to alloc_pages(), which completely
> disables any logging.
> 
> Fix it by adding __GFP_NOWARN only to high order allocation attempts,
> which are not critical.

Makes sense to me.

Reviewed-by: Robin Murphy <robin.murphy@....com>

> Signed-off-by: Tomasz Figa <tfiga@...omium.org>
> ---
>  drivers/iommu/dma-iommu.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 29965a092a69..8507987eed90 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -433,6 +433,7 @@ static struct page **__iommu_dma_alloc_pages(unsigned int count,
>  {
>  	struct page **pages;
>  	unsigned int i = 0, array_size = count * sizeof(*pages);
> +	const gfp_t high_order_gfp = __GFP_NOWARN | __GFP_NORETRY;
>  
>  	order_mask &= (2U << MAX_ORDER) - 1;
>  	if (!order_mask)
> @@ -452,8 +453,6 @@ static struct page **__iommu_dma_alloc_pages(unsigned int count,
>  	if (!(gfp & (__GFP_DMA | __GFP_DMA32)))
>  		gfp |= __GFP_HIGHMEM;
>  
> -	gfp |= __GFP_NOWARN;
> -
>  	while (count) {
>  		struct page *page = NULL;
>  		unsigned int order_size;
> @@ -469,7 +468,7 @@ static struct page **__iommu_dma_alloc_pages(unsigned int count,
>  
>  			order_size = 1U << order;
>  			page = alloc_pages((order_mask - order_size) ?
> -					   gfp | __GFP_NORETRY : gfp, order);
> +					   gfp | high_order_gfp : gfp, order);
>  			if (!page)
>  				continue;
>  			if (!order)
>