linux-kernel - Re: [PATCH 1/4] dma-iommu: add kalloc gfp flag to alloc helper

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Date:   Thu, 8 Jul 2021 18:22:17 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     David Stevens <stevensd@...omium.org>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        iommu@...ts.linux-foundation.org, Christoph Hellwig <hch@....de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] dma-iommu: add kalloc gfp flag to alloc helper

On 2021-07-07 08:55, David Stevens wrote:
> From: David Stevens <stevensd@...omium.org>
> 
> Add gfp flag for kalloc calls within __iommu_dma_alloc_pages, so the
> function can be called from atomic contexts.

Why bother? If you need GFP_ATOMIC for allocating the pages array, then 
you don't not need it for allocating the pages themselves. It's hardly 
rocket science to infer one from the other.

Robin.

> Signed-off-by: David Stevens <stevensd@...omium.org>
> ---
>   drivers/iommu/dma-iommu.c | 13 +++++++------
>   1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 614f0dd86b08..00993b56c977 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -593,7 +593,8 @@ static void __iommu_dma_free_pages(struct page **pages, int count)
>   }
>   
>   static struct page **__iommu_dma_alloc_pages(struct device *dev,
> -		unsigned int count, unsigned long order_mask, gfp_t gfp)
> +		unsigned int count, unsigned long order_mask,
> +		gfp_t page_gfp, gfp_t kalloc_gfp)
>   {
>   	struct page **pages;
>   	unsigned int i = 0, nid = dev_to_node(dev);
> @@ -602,15 +603,15 @@ static struct page **__iommu_dma_alloc_pages(struct device *dev,
>   	if (!order_mask)
>   		return NULL;
>   
> -	pages = kvzalloc(count * sizeof(*pages), GFP_KERNEL);
> +	pages = kvzalloc(count * sizeof(*pages), kalloc_gfp);
>   	if (!pages)
>   		return NULL;
>   
>   	/* IOMMU can map any pages, so himem can also be used here */
> -	gfp |= __GFP_NOWARN | __GFP_HIGHMEM;
> +	page_gfp |= __GFP_NOWARN | __GFP_HIGHMEM;
>   
>   	/* It makes no sense to muck about with huge pages */
> -	gfp &= ~__GFP_COMP;
> +	page_gfp &= ~__GFP_COMP;
>   
>   	while (count) {
>   		struct page *page = NULL;
> @@ -624,7 +625,7 @@ static struct page **__iommu_dma_alloc_pages(struct device *dev,
>   		for (order_mask &= (2U << __fls(count)) - 1;
>   		     order_mask; order_mask &= ~order_size) {
>   			unsigned int order = __fls(order_mask);
> -			gfp_t alloc_flags = gfp;
> +			gfp_t alloc_flags = page_gfp;
>   
>   			order_size = 1U << order;
>   			if (order_mask > order_size)
> @@ -680,7 +681,7 @@ static struct page **__iommu_dma_alloc_noncontiguous(struct device *dev,
>   
>   	count = PAGE_ALIGN(size) >> PAGE_SHIFT;
>   	pages = __iommu_dma_alloc_pages(dev, count, alloc_sizes >> PAGE_SHIFT,
> -					gfp);
> +					gfp, GFP_KERNEL);
>   	if (!pages)
>   		return NULL;
>   
>