x86, pci-dma.c: don't always add __GFP_NORETRY to gfp (b7f09ae5) · Commits · 戴 / test

Currently arch/x86/kernel/pci-dma.c always adds __GFP_NORETRY to the allocation flags, because it wants to be reasonably sure not to deadlock when calling alloc_pages(). But really that should only be done in two cases: - when allocating memory in the lower 16 MB DMA zone. If there's no free memory there, waiting or OOM killing is of no use - when optimistically trying an allocation in the DMA32 zone when dma_mask < DMA_32BIT_MASK hoping that the allocation happens to fall within the limits of the dma_mask Also blindly adding __GFP_NORETRY to the the gfp variable might not be a good idea since we then also use it when calling dma_ops->alloc_coherent(). Clearing it might also not be a good idea, dma_alloc_coherent()'s caller might have set it on purpose. The gfp variable should not be clobbered. [ mingo@elte.hu: converted to delta patch ontop of previous version. ] Signed-off-by:

Miquel van Smoorenburg <miquels@cistron.nl> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/pci-dma.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -378,6 +378,7 @@ dma_alloc_coherent(struct device dev, size_t size, dma_addr_t dma_handle,
		struct page *page;
		unsigned long dma_mask = 0;
		dma_addr_t bus;
		int noretry = 0;

		/* ignore region specifiers */
		gfp &= ~(__GFP_DMA \| __GFP_HIGHMEM \| __GFP_DMA32);
		@@ -397,19 +398,25 @@ dma_alloc_coherent(struct device dev, size_t size, dma_addr_t dma_handle,
		if (dev->dma_mask == NULL)
		return NULL;

		/* Don't invoke OOM killer or retry in lower 16MB DMA zone */
		if (gfp & __GFP_DMA)
		noretry = 1;

		#ifdef CONFIG_X86_64
		/* Why <=? Even when the mask is smaller than 4GB it is often
		larger than 16MB and in this case we have a chance of
		finding fitting memory in the next higher zone first. If
		not retry with true GFP_DMA. -AK */
		if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA))
		if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA)) {
		gfp \|= GFP_DMA32;
		if (dma_mask < DMA_32BIT_MASK)
		noretry = 1;
		}
		#endif

		again:
		/* Don't invoke OOM killer or retry in lower 16MB DMA zone */
		page = dma_alloc_pages(dev,
		(gfp & GFP_DMA) ? gfp \| __GFP_NORETRY : gfp, get_order(size));
		noretry ? gfp \| __GFP_NORETRY : gfp, get_order(size));
		if (page == NULL)
		return NULL;

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