From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=4ISz=MC=vger.kernel.org=linux-kernel-owner@kernel.org>
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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 9673EC433F4
	for <linux-kernel@archiver.kernel.org>; Thu, 20 Sep 2018 06:31:31 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
	by mail.kernel.org (Postfix) with ESMTP id 5ACE22146E
	for <linux-kernel@archiver.kernel.org>; Thu, 20 Sep 2018 06:31:31 +0000 (UTC)
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5ACE22146E
Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de
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 S1732159AbeITMNT (ORCPT
        <rfc822;linux-kernel@archiver.kernel.org>);
        Thu, 20 Sep 2018 08:13:19 -0400
Received: from verein.lst.de ([213.95.11.211]:57797 "EHLO newverein.lst.de"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1731851AbeITMNT (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 20 Sep 2018 08:13:19 -0400
Received: by newverein.lst.de (Postfix, from userid 2407)
        id F04E368D62; Thu, 20 Sep 2018 08:31:29 +0200 (CEST)
Date:   Thu, 20 Sep 2018 08:31:29 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Ming Lei <tom.leiming@gmail.com>
Cc:     linux-block <linux-block@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        Linux FS Devel <linux-fsdevel@vger.kernel.org>,
        "open list:XFS FILESYSTEM" <linux-xfs@vger.kernel.org>,
        Dave Chinner <dchinner@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        Ming Lei <ming.lei@redhat.com>
Subject: Re: block: DMA alignment of IO buffer allocated from slab
Message-ID: <20180920063129.GB12913@lst.de>
References: <CACVXFVOBq3L_EjSTCoiqUL1PH=HMR5EuNNQV0hNndFpGxmUK6g@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CACVXFVOBq3L_EjSTCoiqUL1PH=HMR5EuNNQV0hNndFpGxmUK6g@mail.gmail.com>
User-Agent: Mutt/1.5.17 (2007-11-01)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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.