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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, 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 EFC85C43382 for ; Tue, 25 Sep 2018 04:44:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A61CD20858 for ; Tue, 25 Sep 2018 04:44:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="tLv15Ytr" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A61CD20858 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org 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 S1726864AbeIYKuF (ORCPT ); Tue, 25 Sep 2018 06:50:05 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:53200 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725926AbeIYKuF (ORCPT ); Tue, 25 Sep 2018 06:50:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=wDvpu8H3Ikr//X/klTD2dMiWhainW0pREkRQNoQ66N0=; b=tLv15YtrA5V5wNI2oroTMSsKR r7FVBluvimuMza1U8nmsZyDPd6KJPR9rT0F6bbLxepa0lIAauI6Ks6bUkDUMgNoPYG06nXOHzm75S JIR6NjhHqlzuZNfOzmoURGCOR77f+7GpbupWaWV3H9UeCctfTGlpbG2QQe6RFDOwB9J4IbukF2IYH 6SZg9/XWENDsCiDQR9iFJD7UN76mI6NHznYmoFF8my08NOodaF332x/DP+9WSvzaBYz8LMG4/ox+x uMIAqqE4oS8tskLDG9oi8D2IqJMkNC2s5WM2ilktAWkeAIiYZKAURY6vv9o+q50WVwZEHl4O/Qurm 2q2xe7uNQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1g4fCv-0004Q8-GD; Tue, 25 Sep 2018 04:44:21 +0000 Date: Mon, 24 Sep 2018 21:44:21 -0700 From: Matthew Wilcox To: Bart Van Assche Cc: Ming Lei , Andrey Ryabinin , Vitaly Kuznetsov , Christoph Hellwig , Ming Lei , linux-block , linux-mm , Linux FS Devel , "open list:XFS FILESYSTEM" , Dave Chinner , Linux Kernel Mailing List , Jens Axboe , Christoph Lameter , Linus Torvalds , Greg Kroah-Hartman Subject: Re: block: DMA alignment of IO buffer allocated from slab Message-ID: <20180925044421.GA11163@bombadil.infradead.org> References: <12eee877-affa-c822-c9d5-fda3aa0a50da@virtuozzo.com> <1537801706.195115.7.camel@acm.org> <1537804720.195115.9.camel@acm.org> <10c706fd-2252-f11b-312e-ae0d97d9a538@virtuozzo.com> <1537805984.195115.14.camel@acm.org> <20180924185753.GA32269@bombadil.infradead.org> <20180925001615.GA14386@ming.t460p> <20180925032826.GA4110@bombadil.infradead.org> <4a19ac2f-82c1-db55-9b93-4005ace5e2fe@acm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4a19ac2f-82c1-db55-9b93-4005ace5e2fe@acm.org> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 24, 2018 at 09:10:43PM -0700, Bart Van Assche wrote: > On 9/24/18 8:28 PM, Matthew Wilcox wrote: > > [ ... ] Because if we have to > > round all allocations below 64 bytes up to 64 bytes, [ ... ] > Have you noticed that in another e-mail in this thread it has been explained > why it is not necessary on x86 to align buffers allocated by kmalloc() on a > 64-byte boundary even if these buffers are used for DMA? Oh, so drivers which do this only break on !x86. Yes, that'll work out great.