From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 82460C7618B for ; Fri, 26 Jul 2019 06:28:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 586AE217D4 for ; Fri, 26 Jul 2019 06:28:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726109AbfGZG2y (ORCPT ); Fri, 26 Jul 2019 02:28:54 -0400 Received: from verein.lst.de ([213.95.11.211]:41795 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725867AbfGZG2x (ORCPT ); Fri, 26 Jul 2019 02:28:53 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id CA18068B02; Fri, 26 Jul 2019 08:28:49 +0200 (CEST) Date: Fri, 26 Jul 2019 08:28:49 +0200 From: Christoph Hellwig To: Nicolin Chen Cc: dafna.hirschfeld@collabora.com, hch@lst.de, m.szyprowski@samsung.com, robin.murphy@arm.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] dma-contiguous: do not overwrite align in dma_alloc_contiguous() Message-ID: <20190726062849.GE22881@lst.de> References: <20190725233959.15129-1-nicoleotsuka@gmail.com> <20190725233959.15129-2-nicoleotsuka@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190725233959.15129-2-nicoleotsuka@gmail.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > Signed-off-by: Nicolin Chen > --- > 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?