From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CCDA5C433F4 for ; Fri, 21 Sep 2018 15:00:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7A3A2206B6 for ; Fri, 21 Sep 2018 15:00:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="ZfJTFzoL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7A3A2206B6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390324AbeIUUtu (ORCPT ); Fri, 21 Sep 2018 16:49:50 -0400 Received: from mail-io1-f68.google.com ([209.85.166.68]:37348 "EHLO mail-io1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390164AbeIUUtt (ORCPT ); Fri, 21 Sep 2018 16:49:49 -0400 Received: by mail-io1-f68.google.com with SMTP id v14-v6so12543184iob.4 for ; Fri, 21 Sep 2018 08:00:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=xe7Q8DIiNcGuVcVOhi5q07ExrmVZrXiLuYUV2fXfkrI=; b=ZfJTFzoLni/h+Q8mgzFuqksFDlyl7LarsJIw97uKZ7emYfCXzhJpMN0hIm55kVl5o3 Z81jJCca1JFJJnwfEviYMYkqrzFC7TVCO4CIozMAPW7FWeEOMgBFvxvZbKkD/cxEZv9w 9aPJMhH0k+qLh6ScKlozBlNUHDj1n5y+31gix33KOg9/ikruNdiUhCJhz9kbcpC5Pzbk CYBsoFvWTdS9i7yC6Jy4dLvRkb9nbc9yBwYssTtIqSf//VM4LbyGly9rCMieEUcl8Nhv pz0xjDvWGAA4sZTta4USSxD4mR43ksoENgQaRXRNCAdc6oCI5P6eBjAcU1vpGXeY/TF2 D+vw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=xe7Q8DIiNcGuVcVOhi5q07ExrmVZrXiLuYUV2fXfkrI=; b=f1blF7LFz1poF9qwFHH2J+To1Pb9wKd4n54NdK+vlDlyLtdzWHMLUD0spAbbF3yJA6 rv4DsWlcufHxToWJNGD0/1eMTVK72eGL9TV6dj1scF7e0UYs+s5AsPsReEFKwRidmura H6UJpiNY89O35QkDZ6uorI5jVJjm+l6vZ6+/Hz97hkq4zTki7XfP9rCNj5XPU6DvRYJm i2CGPMbLGL9NY2jU0PTh2WFfXAkZaMKlmL6o5VXWx0A+hIxjA4APWdROevziyE8I5QLT 3CC/Oki1TwFPNk4Ieeksfw8ZsFBOmMFYPLRAQpGYTjQ9M+F9993vMpqTkwrXvCOIr5c9 ou1A== X-Gm-Message-State: APzg51BIM9/KQV6CEfVpxV1mf50el6QseUgFrWTizaMkzvQ2s3RQAkg1 TyGJmgmMd1OArm88ZDHLI2ShQA== X-Google-Smtp-Source: ACcGV62stjqul3nA9NSHW7Sy5UFUjlDw6rpgRTU7MbRTxk1GHmetjh9GpjB+iaXu1xOVE/CwxlchbQ== X-Received: by 2002:a6b:9142:: with SMTP id t63-v6mr13369415iod.123.1537542033550; Fri, 21 Sep 2018 08:00:33 -0700 (PDT) Received: from [192.168.1.56] ([216.160.245.98]) by smtp.gmail.com with ESMTPSA id m123-v6sm2385210itg.29.2018.09.21.08.00.31 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 21 Sep 2018 08:00:32 -0700 (PDT) Subject: Re: block: DMA alignment of IO buffer allocated from slab To: Christoph Hellwig , Vitaly Kuznetsov Cc: Ming Lei , linux-block , linux-mm , Linux FS Devel , "open list:XFS FILESYSTEM" , Dave Chinner , Linux Kernel Mailing List , Ming Lei , Christoph Lameter References: <20180920063129.GB12913@lst.de> <87h8ij0zot.fsf@vitty.brq.redhat.com> <20180921130504.GA22551@lst.de> From: Jens Axboe Message-ID: <98996e39-7d29-354c-9009-d4b1a1bbdeb0@kernel.dk> Date: Fri, 21 Sep 2018 09:00:31 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <20180921130504.GA22551@lst.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/21/18 7:05 AM, Christoph Hellwig wrote: > On Fri, Sep 21, 2018 at 03:04:18PM +0200, Vitaly Kuznetsov wrote: >> Christoph Hellwig writes: >> >>> On Wed, Sep 19, 2018 at 05:15:43PM +0800, Ming Lei wrote: >>>> 1) does kmalloc-N slab guarantee to return N-byte aligned buffer? If >>>> yes, is it a stable rule? >>> >>> This is the assumption in a lot of the kernel, so I think if somethings >>> breaks this we are in a lot of pain. >> >> It seems that SLUB debug breaks this assumption. Kernel built with >> >> CONFIG_SLUB_DEBUG=y >> CONFIG_SLUB=y >> CONFIG_SLUB_DEBUG_ON=y > > Looks like we should fix SLUB debug then.. Fully agree, it's such a fundamental property. -- Jens Axboe