From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id 968846B0038 for ; Thu, 16 Nov 2017 21:45:06 -0500 (EST) Received: by mail-wr0-f199.google.com with SMTP id f9so643144wra.2 for ; Thu, 16 Nov 2017 18:45:06 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id a14si2109898wrf.227.2017.11.16.18.45.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 16 Nov 2017 18:45:05 -0800 (PST) Date: Thu, 16 Nov 2017 18:45:01 -0800 From: Andrew Morton Subject: Re: [PATCH v4] dma-debug: fix incorrect pfn calculation Message-Id: <20171116184501.8c83e100fa14721e459907e0@linux-foundation.org> In-Reply-To: <1510881798.3024.43.camel@mtkswgap22> References: <1510872972-23919-1-git-send-email-miles.chen@mediatek.com> <20171116161350.3b8bd1fbcaae8e032441d3e7@linux-foundation.org> <1510881798.3024.43.camel@mtkswgap22> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Miles Chen Cc: Christoph Hellwig , Robin Murphy , linux-kernel@vger.kernel.org, linux-mm@kvack.org, wsd_upstream@mediatek.com, linux-mediatek@lists.infradead.org, iommu@lists.linux-foundation.org, Christoph Hellwig On Fri, 17 Nov 2017 09:23:18 +0800 Miles Chen wrote: > On Thu, 2017-11-16 at 16:13 -0800, Andrew Morton wrote: > > On Fri, 17 Nov 2017 06:56:12 +0800 wrote: > > > > > From: Miles Chen > > > > > > dma-debug reports the following warning: > > > > > > [name:panic&]WARNING: CPU: 3 PID: 298 at kernel-4.4/lib/dma-debug.c:604 > > > debug _dma_assert_idle+0x1a8/0x230() > > > DMA-API: cpu touching an active dma mapped cacheline [cln=0x00000882300] > > > CPU: 3 PID: 298 Comm: vold Tainted: G W O 4.4.22+ #1 > > > Hardware name: MT6739 (DT) > > > Call trace: > > > [] dump_backtrace+0x0/0x1d4 > > > [] show_stack+0x14/0x1c > > > [] dump_stack+0xa8/0xe0 > > > [] warn_slowpath_common+0xf4/0x11c > > > [] warn_slowpath_fmt+0x60/0x80 > > > [] debug_dma_assert_idle+0x1a8/0x230 > > > [] wp_page_copy.isra.96+0x118/0x520 > > > [] do_wp_page+0x4fc/0x534 > > > [] handle_mm_fault+0xd4c/0x1310 > > > [] do_page_fault+0x1c8/0x394 > > > [] do_mem_abort+0x50/0xec > > > > > > I found that debug_dma_alloc_coherent() and debug_dma_free_coherent() > > > assume that dma_alloc_coherent() always returns a linear address. However > > > it's possible that dma_alloc_coherent() returns a non-linear address. In > > > this case, page_to_pfn(virt_to_page(virt)) will return an incorrect pfn. > > > If the pfn is valid and mapped as a COW page, we will hit the warning when > > > doing wp_page_copy(). > > > > > > Fix this by calculating pfn for linear and non-linear addresses. > > > > > > > It's a shame you didn't Cc Christoph, who was the sole reviewer of the > > earlier version. > > > > And it's a shame you didn't capture the result of that review > > discussion in the v3 changelog. > > > > And it's a shame that you didn't describe how this patch differs from > > earlier versions. > > > I am truly sorry about this. I was not sure if I can submit a patch > based on a linux-next patch, so I submit a new patch based on the latest > mainline kernel again. > > I know how to do this now. I will do it correctly next time. > > Is there anyway to fix this? (send another patch with v3 discussion and > the difference from earlier versions to the commit message). A complete resend is perfectly OK - I will handle the changelog modifications, etc. My point is that the Cc: line was incomplete and that the changelog is missing information, as described above. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org