linux-kernel - Re: [PATCH RFC] dma-direct: Try reallocation with GFP

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Date:   Fri, 20 Apr 2018 11:47:02 +0200
From:   Christoph Hellwig <hch@....de>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Christoph Hellwig <hch@....de>, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC] dma-direct: Try reallocation with GFP_DMA32 if
        possible

On Mon, Apr 16, 2018 at 05:18:19PM +0200, Takashi Iwai wrote:
> As the recent swiotlb bug revealed, we seem to have given up the
> direct DMA allocation too early and felt back to swiotlb allocation.
> The reason is that swiotlb allocator expected that dma_direct_alloc()
> would try harder to get pages even below 64bit DMA mask with
> GFP_DMA32, but the function doesn't do that but only deals with
> GFP_DMA case.
> 
> This patch adds a similar fallback reallocation with GFP_DMA32 as
> we've done with GFP_DMA.  The condition is that the coherent mask is
> smaller than 64bit (i.e. some address limitation), and neither GFP_DMA
> nor GFP_DMA32 is set beforehand.
> 
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> 
> ---
> 
> This is a resend of a test patch included in the previous thread
> ("swiotlb: Fix unexpected swiotlb_alloc_coherent() failures").

I like the patch, but as-is it doesn't apply.  Can you resend it against
latest Linus' tree?