From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Thu, 04 Jan 2018 10:03:01 +0100 (CET) Received: from verein.lst.de ([213.95.11.211]:38010 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S23990418AbeADJCxLfxFB (ORCPT ); Thu, 4 Jan 2018 10:02:53 +0100 Received: by newverein.lst.de (Postfix, from userid 2407) id B237668C8A; Thu, 4 Jan 2018 10:02:51 +0100 (CET) Date: Thu, 4 Jan 2018 10:02:51 +0100 From: Christoph Hellwig To: Vladimir Murzin Cc: Christoph Hellwig , iommu@lists.linux-foundation.org, linux-mips@linux-mips.org, linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, Guan Xuetao , linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, linux-c6x-dev@linux-c6x.org, linux-hexagon@vger.kernel.org, x86@kernel.org, linux-snps-arc@lists.infradead.org, adi-buildroot-devel@lists.sourceforge.net, linux-m68k@lists.linux-m68k.org, patches@groups.riscv.org, linux-metag@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Michal Simek , linux-parisc@vger.kernel.org, linux-cris-kernel@axis.com, linux-kernel@vger.kernel.org, linux-alpha@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 30/67] dma-direct: retry allocations using GFP_DMA for small masks Message-ID: <20180104090251.GE3251@lst.de> References: <20171229081911.2802-1-hch@lst.de> <20171229081911.2802-31-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 61899 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: hch@lst.de Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips On Tue, Jan 02, 2018 at 04:43:15PM +0000, Vladimir Murzin wrote: > On 29/12/17 08:18, Christoph Hellwig wrote: > > If we got back an allocation that wasn't inside the support coherent mask, > > retry the allocation using GFP_DMA. > > > > Based on the x86 code. > > > > Signed-off-by: Christoph Hellwig > > --- > > lib/dma-direct.c | 25 ++++++++++++++++++++++++- > > 1 file changed, 24 insertions(+), 1 deletion(-) > > > > diff --git a/lib/dma-direct.c b/lib/dma-direct.c > > index ab81de3ac1d3..f8467cb3d89a 100644 > > --- a/lib/dma-direct.c > > +++ b/lib/dma-direct.c > > @@ -28,6 +28,11 @@ check_addr(struct device *dev, dma_addr_t dma_addr, size_t size, > > return true; > > } > > > > +static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size) > > +{ > > + return phys_to_dma(dev, phys) + size <= dev->coherent_dma_mask; > > Shouldn't it be: phys_to_dma(dev, phys) + size - 1 <= dev->coherent_dma_mask ? Yes, I think it should. The existing code was blindly copy and pasted from x86. > > + if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) { > > + __free_pages(page, page_order); > > + page = NULL; > > + > > + if (dev->coherent_dma_mask < DMA_BIT_MASK(32) && > > + !(gfp & GFP_DMA)) { > > + gfp = (gfp & ~GFP_DMA32) | GFP_DMA; > > + goto again; > > Shouldn't we limit number of attempts? We only retty once anyway, due to the !GFP_DMA check first and then ORing in GFP_DMA.