Messages in this thread Patch in this message | | | Date | Thu, 4 Jan 2018 10:02:51 +0100 | From | Christoph Hellwig <> | Subject | Re: [PATCH 30/67] dma-direct: retry allocations using GFP_DMA for small masks |
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On Tue, Jan 02, 2018 at 04:43:15PM +0000, Vladimir Murzin wrote: > On 29/12/17 08:18, Christoph Hellwig wrote: > > If we got back an allocation that wasn't inside the support coherent mask, > > retry the allocation using GFP_DMA. > > > > Based on the x86 code. > > > > Signed-off-by: Christoph Hellwig <hch@lst.de> > > --- > > lib/dma-direct.c | 25 ++++++++++++++++++++++++- > > 1 file changed, 24 insertions(+), 1 deletion(-) > > > > diff --git a/lib/dma-direct.c b/lib/dma-direct.c > > index ab81de3ac1d3..f8467cb3d89a 100644 > > --- a/lib/dma-direct.c > > +++ b/lib/dma-direct.c > > @@ -28,6 +28,11 @@ check_addr(struct device *dev, dma_addr_t dma_addr, size_t size, > > return true; > > } > > > > +static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size) > > +{ > > + return phys_to_dma(dev, phys) + size <= dev->coherent_dma_mask; > > Shouldn't it be: phys_to_dma(dev, phys) + size - 1 <= dev->coherent_dma_mask ?
Yes, I think it should. The existing code was blindly copy and pasted from x86.
> > + if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) { > > + __free_pages(page, page_order); > > + page = NULL; > > + > > + if (dev->coherent_dma_mask < DMA_BIT_MASK(32) && > > + !(gfp & GFP_DMA)) { > > + gfp = (gfp & ~GFP_DMA32) | GFP_DMA; > > + goto again; > > Shouldn't we limit number of attempts?
We only retty once anyway, due to the !GFP_DMA check first and then ORing in GFP_DMA.
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