Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753720Ab3JaWtn (ORCPT ); Thu, 31 Oct 2013 18:49:43 -0400 Received: from filtteri6.pp.htv.fi ([213.243.153.189]:51091 "EHLO filtteri6.pp.htv.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751766Ab3JaWtl (ORCPT ); Thu, 31 Oct 2013 18:49:41 -0400 Date: Fri, 1 Nov 2013 00:49:27 +0200 From: Aaro Koskinen To: Andrew Morton Cc: Ming Lei , linux-kernel@vger.kernel.org, Russell King - ARM Linux , linux-arm-kernel@lists.infradead.org, Simon Baatz , Will Deacon , Catalin Marinas , FUJITA Tomonori , Tejun Heo , "James E.J. Bottomley" , Jens Axboe Subject: Re: [PATCH] lib/scatterlist.c: don't flush_kernel_dcache_page on slab page Message-ID: <20131031224927.GK17447@blackmetal.musicnaut.iki.fi> References: <1382977205-26268-1-git-send-email-ming.lei@canonical.com> <20131031152745.821d2b5dbe93e2ca69d45264@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131031152745.821d2b5dbe93e2ca69d45264@linux-foundation.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1805 Lines: 43 Hi, On Thu, Oct 31, 2013 at 03:27:45PM -0700, Andrew Morton wrote: > On Tue, 29 Oct 2013 00:20:05 +0800 Ming Lei wrote: > > > Commit b1adaf65ba03([SCSI] block: add sg buffer copy helper functions) > > introduces two sg buffer copy helpers, and calls flush_kernel_dcache_page() > > on pages in SG list after these pages are written to. > > > > Unfortunately, the commit may introduce a potential bug: > > > > - Before sending some SCSI commands, kmalloc() buffer may be > > passed to block layper, so flush_kernel_dcache_page() can > > see a slab page finally > > > > - According to cachetlb.txt, flush_kernel_dcache_page() is > > only called on "a user page", which surely can't be a slab page. > > > > - ARCH's implementation of flush_kernel_dcache_page() may > > use page mapping information to do optimization so page_mapping() > > will see the slab page, then VM_BUG_ON() is triggered. > > > > Aaro Koskinen reported the bug on ARM/kirkwood when DEBUG_VM is enabled, > > and this patch fixes the bug by adding test of '!PageSlab(miter->page)' > > before calling flush_kernel_dcache_page(). > > We should work out which kernel(s) need this patch. b1adaf65ba03 was > merged in 2008, so presumably some more recent patch has exposed the > problem, but I don't know what one that was. > > Help me out here? On ARM, this problem started to appear after 1bc39742aab09248169ef9d3727c9def3528b3f3 (ARM: 7755/1: handle user space mapped pages in flush_kernel_dcache_page) and that was tagged for 3.2+ stable kernels. A. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/