From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762626AbYG3O4a (ORCPT ); Wed, 30 Jul 2008 10:56:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759713AbYG3Oz4 (ORCPT ); Wed, 30 Jul 2008 10:55:56 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:46482 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757057AbYG3Ozz (ORCPT ); Wed, 30 Jul 2008 10:55:55 -0400 Message-ID: <48907F49.7020101@linux-foundation.org> Date: Wed, 30 Jul 2008 09:48:41 -0500 From: Christoph Lameter User-Agent: Thunderbird 2.0.0.14 (Windows/20080421) MIME-Version: 1.0 To: Pekka Enberg CC: Eric Sandeen , Andrew Morton , linux-kernel@vger.kernel.org, mhalcrow@us.ibm.com, stable@kernel.org Subject: Re: [PATCH] eCryptfs - use page_alloc not kmalloc to get a page of memory References: <488DF00F.3080809@redhat.com> <20080728133504.156f438f.akpm@linux-foundation.org> <84144f020807281342t2e1a3dc3id01314ac01de406f@mail.gmail.com> <488E3414.8020506@redhat.com> <488E3643.8000300@cs.helsinki.fi> In-Reply-To: <488E3643.8000300@cs.helsinki.fi> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Pekka Enberg wrote: >> For whatever reason, I did see non-page-aligned memory returned from >> kmalloc(PAGE_CACHE_SIZE), and I think this is what caused the problem >> once virt_to_page() was used to get hold of a page to pass around in the >> ecryptfs/crypto code... > > With SLUB? I can't see how that's possible. I can see this with SLAB, > though, for 4K pages. It possible because PAGE_CACHE_SIZE is still handled by SLUB and if debugging is on then kmalloc may return non page aligned objects. The handoff to the page allocator only occurs for objects > 4k. We used to do this also for 4k objects but then we got performance regressions in tbench. > In any case, the patch, of course, make sense as kmalloc() behavior > varies between allocators. > > Pekka