Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758678AbYFKEr0 (ORCPT ); Wed, 11 Jun 2008 00:47:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751327AbYFKErT (ORCPT ); Wed, 11 Jun 2008 00:47:19 -0400 Received: from cantor2.suse.de ([195.135.220.15]:52672 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751236AbYFKErS (ORCPT ); Wed, 11 Jun 2008 00:47:18 -0400 Date: Wed, 11 Jun 2008 06:47:16 +0200 From: Nick Piggin To: Christoph Lameter Cc: akpm@linux-foundation.org, torvalds@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, benh@kernel.crashing.org, paulus@samba.org Subject: Re: [patch 7/7] powerpc: lockless get_user_pages_fast Message-ID: <20080611044716.GA11545@wotan.suse.de> References: <20080605094300.295184000@nick.local0.net> <20080605094826.128415000@nick.local0.net> <20080611031822.GA8228@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1232 Lines: 26 On Tue, Jun 10, 2008 at 09:40:25PM -0700, Christoph Lameter wrote: > On Wed, 11 Jun 2008, Nick Piggin wrote: > > > > This is reversing the modification to make get_page_unless_zero() usable > > > with compound page heads. Will break the slab defrag patchset. > > > > Is the slab defrag patchset in -mm? Because you ignored my comment about > > this change that assertions should not be weakened until required by the > > actual patchset. I wanted to have these assertions be as strong as > > possible for the lockless pagecache patchset. > > So you are worried about accidentally using get_page_unless_zero on a > compound page? What would be wrong about that? Unexpected. Compound pages should have no such races that require get_page_unless_zero that we very carefully use in page reclaim. If you don't actually know whether you have a reference to the thing or not before trying to operate on it, then you're almost definitely got refcount wrong. How does slab defrag use it? -- 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/