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Groups > linux.kernel > #1287431
| From | Mel Gorman <mgorman@techsingularity.net> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] MIPS: Fix DMA contiguous allocation |
| Date | 2015-12-09 12:40 +0100 |
| Message-ID | <qDLge-7LW-5@gated-at.bofh.it> (permalink) |
| References | <qDnxg-Xg-5@gated-at.bofh.it> <qDyM2-89u-9@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Tue, Dec 08, 2015 at 02:19:39PM -0800, Andrew Morton wrote: > On Tue, 8 Dec 2015 10:18:50 +0000 Qais Yousef <qais.yousef@imgtec.com> wrote: > > > Recent changes to how GFP_ATOMIC is defined seems to have broken the condition > > to use mips_alloc_from_contiguous() in mips_dma_alloc_coherent(). > > > > I couldn't bottom out the exact change but I think it's this one > > > > d0164adc89f6 (mm, page_alloc: distinguish between being unable to sleep, > > unwilling to sleep and avoiding waking kswapd) > > > > >From what I see GFP_ATOMIC has multiple bits set and the check for !(gfp > > & GFP_ATOMIC) isn't enough. To verify if the flag is atomic we need to make > > sure that (gfp & GFP_ATOMIC) == GFP_ATOMIC to verify that all bits rquired to > > satisfy GFP_ATOMIC condition are set. > > > > ... > > > > --- a/arch/mips/mm/dma-default.c > > +++ b/arch/mips/mm/dma-default.c > > @@ -145,7 +145,7 @@ static void *mips_dma_alloc_coherent(struct device *dev, size_t size, > > > > gfp = massage_gfp_flags(dev, gfp); > > > > - if (IS_ENABLED(CONFIG_DMA_CMA) && !(gfp & GFP_ATOMIC)) > > + if (IS_ENABLED(CONFIG_DMA_CMA) && ((gfp & GFP_ATOMIC) != GFP_ATOMIC)) > > page = dma_alloc_from_contiguous(dev, > > count, get_order(size)); > > if (!page) > > hm. It seems that the code is asking "can I do a potentially-sleeping > memory allocation"? > > The way to do that under the new regime is > > if (IS_ENABLED(CONFIG_DMA_CMA) && gfpflags_allow_blocking(gfp)) > > Mel, can you please confirm? Yes, this is the correct way it should be checked. The full flags cover watermark and kswapd treatment which potentially could be altered by the caller. -- Mel Gorman SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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[PATCH] MIPS: Fix DMA contiguous allocation Qais Yousef <qais.yousef@imgtec.com> - 2015-12-08 11:20 +0100
Re: [PATCH] MIPS: Fix DMA contiguous allocation Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> - 2015-12-08 13:20 +0100
Re: [PATCH] MIPS: Fix DMA contiguous allocation Andrew Morton <akpm@linux-foundation.org> - 2015-12-08 23:20 +0100
Re: [PATCH] MIPS: Fix DMA contiguous allocation Mel Gorman <mgorman@techsingularity.net> - 2015-12-09 12:40 +0100
Re: [PATCH] MIPS: Fix DMA contiguous allocation Qais Yousef <qais.yousef@imgtec.com> - 2015-12-09 15:40 +0100
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