dma-mapping: Don't clear GFP_ZERO in dma_alloc_attrs (e89f5b37) · Commits · 戴 / test

Revert the clearing of __GFP_ZERO in dma_alloc_attrs and move it to dma_direct_alloc for now. While most common architectures always zero dma cohereny allocations (and x86 did so since day one) this is not documented and at least arc and s390 do not zero without the explicit __GFP_ZERO argument. Fixes: ("dma-mapping: clear harmful GFP_* flags in common code") Reported-by:

Evgeniy Didin <Evgeniy.Didin@synopsys.com> Reported-by:

Sebastian Ott <sebott@linux.vnet.ibm.com> Signed-off-by:

Christoph Hellwig <hch@lst.de> Signed-off-by:

Thomas Gleixner <tglx@linutronix.de> Tested-by:

Evgeniy Didin <Evgeniy.Didin@synopsys.com> Cc: iommu@lists.linux-foundation.org Link: https://lkml.kernel.org/r/20180328133535.17302-2-hch@lst.de

include/linux/dma-mapping.h

+2 −6

Original line number	Diff line number	Diff line
		@@ -518,12 +518,8 @@ static inline void dma_alloc_attrs(struct device dev, size_t size,
		if (dma_alloc_from_dev_coherent(dev, size, dma_handle, &cpu_addr))
		return cpu_addr;

		/*
		* Let the implementation decide on the zone to allocate from, and
		* decide on the way of zeroing the memory given that the memory
		* returned should always be zeroed.
		*/
		flag &= ~(__GFP_DMA \| __GFP_DMA32 \| __GFP_HIGHMEM \| __GFP_ZERO);
		/* let the implementation decide on the zone to allocate from: */
		flag &= ~(__GFP_DMA \| __GFP_DMA32 \| __GFP_HIGHMEM);

		if (!arch_dma_alloc_attrs(&dev, &flag))
		return NULL;

lib/dma-direct.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -59,6 +59,9 @@ void dma_direct_alloc(struct device dev, size_t size, dma_addr_t *dma_handle,
		struct page *page = NULL;
		void *ret;

		/* we always manually zero the memory once we are done: */
		gfp &= ~__GFP_ZERO;

		/* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
		if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
		gfp \|= GFP_DMA;

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