From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1754194AbbHJIIs (ORCPT <rfc822;w@1wt.eu>);
	Mon, 10 Aug 2015 04:08:48 -0400
Received: from bombadil.infradead.org ([198.137.202.9]:60608 "EHLO
	bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752830AbbHJIIo (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 10 Aug 2015 04:08:44 -0400
Date: Mon, 10 Aug 2015 01:08:40 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Ming Lei <ming.lei@canonical.com>
Cc: Dave Chinner <david@fromorbit.com>, Christoph Hellwig <hch@infradead.org>,
        Jens Axboe <axboe@kernel.dk>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Dave Kleikamp <dave.kleikamp@oracle.com>, Zach Brown <zab@zabbo.net>,
        Maxim Patlasov <mpatlasov@parallels.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>, Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH v9 6/6] block: loop: support DIO & AIO
Message-ID: <20150810080840.GA2293@infradead.org>
References: <1438850538-15682-1-git-send-email-ming.lei@canonical.com>
 <1438850538-15682-7-git-send-email-ming.lei@canonical.com>
 <20150807074342.GA30547@infradead.org>
 <CACVXFVOyVi8hyxU5yv=heSy2SpjGAY9MKi3kow_gweFn8_tL-A@mail.gmail.com>
 <20150809064439.GC2436@infradead.org>
 <CACVXFVO9Wpa+9QWCzMOVQOramd1KsfvtC=vcf-EsCQum-9Omuw@mail.gmail.com>
 <20150809134404.GA7190@infradead.org>
 <CACVXFVOdc5GYrgUXGarosc5AGNvJbsGG+i=R5o+NDKkQHGwFoQ@mail.gmail.com>
 <20150809234126.GA906@dastard>
 <CACVXFVMBqNQAb6iCm8TOWDyFmgPnjvACFJ9wvWEeCaKiZAB22g@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CACVXFVMBqNQAb6iCm8TOWDyFmgPnjvACFJ9wvWEeCaKiZAB22g@mail.gmail.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
X-SRS-Rewrite: SMTP reverse-path rewritten from <hch@infradead.org> by bombadil.infradead.org
	See http://www.infradead.org/rpr.html
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Sun, Aug 09, 2015 at 10:50:41PM -0400, Ming Lei wrote:
> Christoph, could you share your idea again about this approch?
> 
> If you still don't think it is good to switch between buffered I/O
> and direct I/O, I will not do that in next post.

If we epxose a 512 byte block size to the loop device people will use
it, for example mkfs.xfs might do smaller I/O, extN will default to
small blocksize for small devices, etc.

If you are using a loop devices on a 4k sector backing device and care
about performance (which current loop users generally don't..) just
make sure to set the loop block size to 4k, which Hannes' series will
allow us to do easily.