From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753043Ab3KPUH3 (ORCPT ); Sat, 16 Nov 2013 15:07:29 -0500 Received: from mail-ee0-f48.google.com ([74.125.83.48]:53174 "EHLO mail-ee0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751901Ab3KPUHV (ORCPT ); Sat, 16 Nov 2013 15:07:21 -0500 Date: Sat, 16 Nov 2013 21:07:18 +0100 From: Simon Baatz To: James Bottomley Cc: Helge Deller , Benjamin LaHaise , linux-aio@kvack.org, linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org Subject: Re: [PATCH] aio: fix D-cache aliasing issues Message-ID: <20131116200717.GA18939@schnuecks.de> References: <20131115220529.GA3160@ls3530.box> <1384555325.2003.39.camel@dabdike.int.hansenpartnership.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1384555325.2003.39.camel@dabdike.int.hansenpartnership.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 On Fri, Nov 15, 2013 at 02:42:05PM -0800, James Bottomley wrote: > On Fri, 2013-11-15 at 23:05 +0100, Helge Deller wrote: > > When a user page mapping is released via kunmap*() functions, the D-cache needs > > to be flushed via flush_dcache_page() to avoid D-cache aliasing issues. > > > > This patch fixes aio on the parisc platform (and probably others). > > This should be flush_kernel_dcache_page(). flush_dcache_page() is for > full coherency but for unmap, we know the page was coherent going in and > may have been modified by the kernel, so only the kernel view needs to > be sync'd. Technically, by the kernel API, the flush should be done > *before* unmapping. This would have mattered on parisc until we did > flush via tmpalias which means we no-longer care if the mapping for the > flush exists or not because we always recreate it via the tmpalias > pages. On ARM, flush_kernel_dcache_page() actually assumes that the page is mapped. It avoids double flushing of highmem pages by not flushing in those cases where kunmap_atomic() already takes care of flushing. - Simon