On Sun, Sep 28, 2014 at 01:44:15AM +0100, Miles MH Chen wrote: > On Sat, Sep 27, 2014 at 11:13 PM, Catalin Marinas > <catalin.mari...@arm.com> wrote: > > On 27 Sep 2014, at 16:09, Miles MH Chen <orca.c...@gmail.com> wrote: > >> Signed-off-by: Min-Hua Chen <orca.c...@gmail.com> > >> --- > >> arch/arm64/mm/dma-mapping.c | 3 ++- > >> 1 file changed, 2 insertions(+), 1 deletion(-) > >> > >> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c > >> index 4164c5a..273cf6d 100644 > >> --- a/arch/arm64/mm/dma-mapping.c > >> +++ b/arch/arm64/mm/dma-mapping.c > >> @@ -103,7 +103,8 @@ static void *__dma_alloc_noncoherent(struct device > >> *dev, size_t size, > >> ptr = __dma_alloc_coherent(dev, size, dma_handle, flags, attrs); > >> if (!ptr) > >> goto no_mem; > >> - map = kmalloc(sizeof(struct page *) << order, flags & ~GFP_DMA); > >> + map = kmalloc(sizeof(struct page *) << order, > >> + flags & ~(GFP_DMA | GFP_DMA32)); > > > > Do you have an explanation on why this is needed (and such explanation > > should also be included in the commit log)? We don’t use ZONE_DMA32 on > > arm64 (we did initially but it was for the wrong reasons). > > If GFP_DMA32 is passed to dma_alloc_coherent, the flag will go to kmalloc and > trigger a BUG_ON check in slab allocator: > > __dma_alloc_noncoherent > kmalloc > new_slab BUG_ON(flags & GFP_SLAB_BUG_MASK); > > It can be avoided this by removing GFP_DMA32 before passing it to kmalloc > or we should block GFP_DMA32 flag earlier in arch/arm64/dma-mapping.c if > GFP_DMA32 is not allowed in arch/arm64/dma-mapping.c.
With commit d4932f9e81ae (arm64: add atomic pool for non-coherent and CMA allocations), this fix is no longer needed. Prior to this we could simply use GFP_KERNEL rather than masking out bits as we don't care about atomic contexts prior to the commit I mentioned. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
