Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752028AbcDKDa5 (ORCPT ); Sun, 10 Apr 2016 23:30:57 -0400 Received: from mail-yw0-f196.google.com ([209.85.161.196]:32796 "EHLO mail-yw0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751269AbcDKDaz (ORCPT ); Sun, 10 Apr 2016 23:30:55 -0400 MIME-Version: 1.0 In-Reply-To: References: <1459857443-20611-1-git-send-email-tom.leiming@gmail.com> <1459857443-20611-9-git-send-email-tom.leiming@gmail.com> <20160405130109.GB32576@infradead.org> <20160410144145.GA24062@infradead.org> Date: Mon, 11 Apr 2016 11:30:54 +0800 Message-ID: Subject: Re: [PATCH 08/27] staging: lustre: avoid to use bio->bi_vcnt directly From: Ming Lei To: James Simmons Cc: Christoph Hellwig , Jens Axboe , Linux Kernel Mailing List , linux-block@vger.kernel.org, Boaz Harrosh , Oleg Drokin , Andreas Dilger , Greg Kroah-Hartman , "John L. Hammond" , Frank Zago , Mike Rapoport , Kent Overstreet , Julia Lawall , Al Viro , "moderated list:STAGING - LUSTRE PARALLEL FILESYSTEM" , "open list:STAGING SUBSYSTEM" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1736 Lines: 36 On Mon, Apr 11, 2016 at 12:02 AM, James Simmons wrote: > >> On Sun, Apr 10, 2016 at 03:37:42PM +0100, James Simmons wrote: >> > >> > > The lloop driver should be removed entirely - use the loop driver >> > > instead. >> > >> > I talked with Andreas last week at our annual Lustre users group meeting >> > about this. The reason I was told for existance is that some users were >> > using files on a Lustre file system with the loop back device. The >> > performance was really bad at the time so a lloop was developed to >> > overcome those limitations. Its been a long time so perhaps its time >> > to look at the default loop driver again to see if can perform now. If >> > it doesn't we will go the route of reworking the lloop driver in the >> > spirit of the cryptoloop device. >> >> The loop driver now supports using AIO/DIO on any file systems that >> implements ->read_iter and ->write_iter. If lustre doesn't support >> those or doesn't have proper performance using them it should be >> addressed in the file system. >> >> Note that the dio mode in the loop device is not the default and you >> need to manually enabled it, keep that in mind when testing. > > This is excellent news. The only sad thing is that most lustre users > are running distros that use kernels before the AIO/DIO enhancements > were landed :-( We will have to keep a copy around for those guys. But > first I need to test the performance of the loop back driver this > week before this can be dropped. Considered that this cleanup patch for lustre loop is quite simple and straightforward, I suggest to keep this cleanup patch as so and do the dropping in another patchset. Christoph, are you OK with that? Thanks, Ming Lei