Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755207Ab3J2M5o (ORCPT ); Tue, 29 Oct 2013 08:57:44 -0400 Received: from mail-ee0-f47.google.com ([74.125.83.47]:34463 "EHLO mail-ee0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754668Ab3J2M5m (ORCPT ); Tue, 29 Oct 2013 08:57:42 -0400 Date: Tue, 29 Oct 2013 13:57:37 +0100 From: Simon Baatz To: Ming Lei Cc: linux-kernel@vger.kernel.org, Andrew Morton , Russell King - ARM Linux , linux-arm-kernel@lists.infradead.org, Will Deacon , Aaro Koskinen , 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: <20131029125737.GA3643@schnuecks.de> References: <1382977205-26268-1-git-send-email-ming.lei@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1382977205-26268-1-git-send-email-ming.lei@canonical.com> 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: 2580 Lines: 67 On Tue, Oct 29, 2013 at 12:20:05AM +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(). > > Reported-by: Aaro Koskinen > Cc: Russell King - ARM Linux > Cc: linux-arm-kernel@lists.infradead.org > Cc: Simon Baatz > Cc: Will Deacon > Cc: Aaro Koskinen > Cc: Catalin Marinas > Cc: Andrew Morton > Cc: FUJITA Tomonori > Cc: Tejun Heo > Cc: "James E.J. Bottomley" > Cc: Jens Axboe > Signed-off-by: Ming Lei > --- > lib/scatterlist.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/lib/scatterlist.c b/lib/scatterlist.c > index a685c8a..d16fa29 100644 > --- a/lib/scatterlist.c > +++ b/lib/scatterlist.c > @@ -577,7 +577,8 @@ void sg_miter_stop(struct sg_mapping_iter *miter) > miter->__offset += miter->consumed; > miter->__remaining -= miter->consumed; > > - if (miter->__flags & SG_MITER_TO_SG) > + if ((miter->__flags & SG_MITER_TO_SG) && > + !PageSlab(miter->page)) > flush_kernel_dcache_page(miter->page); > > if (miter->__flags & SG_MITER_ATOMIC) { > -- > 1.7.9.5 > Tested-by: Simon Baatz on top of 3.12-rc7 on Kirkwood with DEBUG_VM enabled. - Simon -- 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/