From: Joerg Roedel <joro@8bytes.org>
To: Tomasz Figa <tfiga@chromium.org>
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
Robin Murphy <robin.murphy@arm.com>
Subject: Re: [PATCH v2 2/2] iommu/dma: Use __GFP_NOWARN only for high-order allocations
Date: Wed, 26 Jul 2017 11:24:11 +0200 [thread overview]
Message-ID: <20170726092411.GD15833@8bytes.org> (raw)
In-Reply-To: <20170704135556.21704-2-tfiga@chromium.org>
On Tue, Jul 04, 2017 at 10:55:56PM +0900, Tomasz Figa wrote:
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index bf23989b5158..6ed8c8f941d8 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;
> -
Okay, so a warning should be there if allocation fails, independent of
what the allocation order is. So either this function prints a message
in case of allocation failure or we remove __GFP_NOWARN for all
allocation attempts.
Adding __GFP_NOWARN only makes sense when there is another fall-back in
case allocation fails anyway, which is not the case here.
> 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);
Why does it specify __GFP_NORETRY at all? The alloc-routines in the
DMA-API don't need to be atomic.
Joerg
next prev parent reply other threads:[~2017-07-26 9:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-04 13:55 [PATCH v2 1/2] iommu/dma: Respect __GFP_DMA and __GFP_DMA32 in incoming GFP flags Tomasz Figa
2017-07-04 13:55 ` [PATCH v2 2/2] iommu/dma: Use __GFP_NOWARN only for high-order allocations Tomasz Figa
2017-07-26 9:24 ` Joerg Roedel [this message]
2017-07-26 9:29 ` Tomasz Figa
2017-07-26 9:15 ` [PATCH v2 1/2] iommu/dma: Respect __GFP_DMA and __GFP_DMA32 in incoming GFP flags Joerg Roedel
2017-07-26 9:26 ` Tomasz Figa
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