From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758956Ab3APKcn (ORCPT ); Wed, 16 Jan 2013 05:32:43 -0500 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:53730 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758752Ab3APKcl (ORCPT ); Wed, 16 Jan 2013 05:32:41 -0500 Message-ID: <1358332355.2384.11.camel@dabdike.int.hansenpartnership.com> Subject: Re: [PATCH v2 1/1] block: blk-merge: don't merge the pages with non-contiguous descriptors From: James Bottomley To: Subhash Jadavani Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-mmc@vger.kernel.org, linux-arm-msm@vger.kernel.org, martin.petersen@oracle.com, asias@redhat.com, tj@kernel.org, linux-arm-kernel@lists.infradead.org, Russell King Date: Wed, 16 Jan 2013 10:32:35 +0000 In-Reply-To: <50F64AC1.3040304@codeaurora.org> References: <1358265681-25671-1-git-send-email-subhashj@codeaurora.org> <1358266794.10591.8.camel@dabdike.int.hansenpartnership.com> <50F64AC1.3040304@codeaurora.org> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.6.2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2013-01-16 at 12:07 +0530, Subhash Jadavani wrote: > Now consider this call stack from MMC block driver (this is on the ARmv7 > based board): > [ 98.918174] [] (v7_dma_inv_range+0x30/0x48) from > [] (dma_cache_maint_page+0x1c4/0x24c) > [ 98.927819] [] (dma_cache_maint_page+0x1c4/0x24c) from > [] (___dma_page_cpu_to_dev+0x14/0x1c) > [ 98.937982] [] (___dma_page_cpu_to_dev+0x14/0x1c) from > [] (dma_map_sg+0x3c/0x114) OK, so this is showing that ARM itself is making the assumption that the pages are contiguous in the page offset map. Fix this by doing the increment via the pfn, which will do the right thing whatever the memory model. Signed-off-by: James Bottomley --- diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 6b2fb87..ab88c5b 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -809,7 +809,7 @@ static void dma_cache_maint_page(struct page *page, unsigned long offset, op(vaddr, len, dir); } offset = 0; - page++; + page = pfn_to_page(page_to_pfn(page) + 1); left -= len; } while (left); }