Messages in this thread | | | Subject | Re: [PATCH] ARM: DMA: Fix kzalloc flags in __dma_alloc | From | Alexandre Courbot <> | Date | Fri, 18 Mar 2016 18:25:04 +0900 |
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On 03/18/2016 05:05 PM, Rabin Vincent wrote: > On Fri, Mar 18, 2016 at 11:12:26AM +0900, Alexandre Courbot wrote: >> Commit 19e6e5e5392b ("ARM: 8547/1: dma-mapping: store buffer >> information") allocates a structure meant for internal buffer management >> with the GFP flags of the buffer itself. This can trigger the following >> safeguard in the slab/slub allocator: >> >> if (unlikely(flags & GFP_SLAB_BUG_MASK)) { >> pr_emerg("gfp: %u\n", flags & GFP_SLAB_BUG_MASK); >> BUG(); >> } >> >> Fix this by allocating the structure with GFP_KERNEL, as it is meant to >> be used by the kernel and not for DMA. > > We can't use GFP_KERNEL here. The caller may have passed in gfp flags > which indicate that we can't sleep, and we need to respect that. What we can > do is mask out the region specifiers in the gfp flags that we pass to > kzalloc(). This is what the other architectures do in their dma > allocation functions: > > arch/mips/cavium-octeon/dma-octeon.c: gfp &= ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM); > arch/mips/loongson64/common/dma-swiotlb.c: gfp &= ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM); > arch/mips/mm/dma-default.c: gfp &= ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM); > arch/mips/netlogic/common/nlm-dma.c: gfp &= ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM); > arch/x86/kernel/pci-dma.c: *gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
Makes sense. Too bad GFP_SLAB_BUG_MASK is private, otherwise we could have used it directly.
Your comment reminded me that I have applied the same "fix" to __iommu_alloc_buffer() last year:
if (array_size <= PAGE_SIZE) pages = kzalloc(array_size, GFP_KERNEL);
... but that one is followed by this, which exists since 2012:
else pages = vzalloc(array_size);
So I guess we are not too worried about sleeping in that particular function.
Anyway, I will fix as you suggested and resend.
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