Messages in this thread |  | | Date | Fri, 26 Jul 2019 08:28:49 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH 1/2] dma-contiguous: do not overwrite align in dma_alloc_contiguous() |
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On Thu, Jul 25, 2019 at 04:39:58PM -0700, Nicolin Chen wrote: > The dma_alloc_contiguous() limits align at CONFIG_CMA_ALIGNMENT for > cma_alloc() however it does not restore it for the fallback routine. > This will result in a size mismatch between the allocation and free > when running in the fallback routines, if the align is larger than > CONFIG_CMA_ALIGNMENT. > > This patch adds a cma_align to take care of cma_alloc() and prevent > the align from being overwritten. > > Fixes: fdaeec198ada ("dma-contiguous: add dma_{alloc,free}_contiguous() helpers") > Reported-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com> > Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com> > --- > kernel/dma/contiguous.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c > index bfc0c17f2a3d..fa8cd0f0512e 100644 > --- a/kernel/dma/contiguous.c > +++ b/kernel/dma/contiguous.c > @@ -233,6 +233,7 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp) > int node = dev ? dev_to_node(dev) : NUMA_NO_NODE; > size_t count = PAGE_ALIGN(size) >> PAGE_SHIFT; > size_t align = get_order(PAGE_ALIGN(size)); > + size_t cma_align = CONFIG_CMA_ALIGNMENT; > struct page *page = NULL; > struct cma *cma = NULL; > > @@ -241,11 +242,11 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp) > else if (count > 1) > cma = dma_contiguous_default_area; > > + cma_align = min_t(size_t, align, cma_align); > + > /* CMA can be used only in the context which permits sleeping */ > - if (cma && gfpflags_allow_blocking(gfp)) { > - align = min_t(size_t, align, CONFIG_CMA_ALIGNMENT); > - page = cma_alloc(cma, count, align, gfp & __GFP_NOWARN); > - } > + if (cma && gfpflags_allow_blocking(gfp)) > + page = cma_alloc(cma, count, cma_align, gfp & __GFP_NOWARN);
Shouldn't cma_align be confined to the block guarded by "if (cma && gfpflags_allow_blocking(gfp))" so that we can optimize it away for configurations that do not support CMA?
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