From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cn.fujitsu.com ([222.73.24.84]:1792 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752520AbaACAnD (ORCPT ); Thu, 2 Jan 2014 19:43:03 -0500 Message-ID: <52C607CA.6000105@cn.fujitsu.com> Date: Fri, 03 Jan 2014 08:43:54 +0800 From: Qu Wenruo MIME-Version: 1.0 To: dsterba@suse.cz, linux-btrfs@vger.kernel.org Subject: Re: [PATCH] btrfs: Add "barrier" option to support "-o remount,barrier" References: <1388040310-25092-1-git-send-email-quwenruo@cn.fujitsu.com> <20140102154103.GL6498@twin.jikos.cz> In-Reply-To: <20140102154103.GL6498@twin.jikos.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Thu, 2 Jan 2014 16:41:03 +0100, David Sterba wrote: > On Thu, Dec 26, 2013 at 02:45:10PM +0800, Qu Wenruo wrote: >> Btrfs can be remounted without barrier, but there is no "barrier" option >> so nobody can remount btrfs back with barrier on. Only umount and >> mount again can re-enable barrier.(Quite awkward) > Ok for adding the mount option. > >> Reported-by: Daniel Blueman >> Signed-off-by: Qu Wenruo >> --- >> Documentation/filesystems/btrfs.txt | 6 ++++++ >> fs/btrfs/super.c | 8 +++++++- >> 2 files changed, 13 insertions(+), 1 deletion(-) >> >> diff --git a/Documentation/filesystems/btrfs.txt b/Documentation/filesystems/btrfs.txt >> index 5dd282d..f6f71d6 100644 >> --- a/Documentation/filesystems/btrfs.txt >> +++ b/Documentation/filesystems/btrfs.txt >> @@ -51,6 +51,12 @@ Unless otherwise specified, all options default to off. >> defrag process. Works best for small files; Not well suited for >> large database workloads. >> >> + barrier >> + Enable the use of block layer write barriers. Write barriers ensure >> + that certain IOs make it through the device cache and are on persistent >> + storage. >> + Barriers are enabled by default. > There's the 'nobarrier' option already, I think it's better to keep the > pairing option documentation at one place and mark the default one with (*). > > Related to that, there should imho be a pairing option for every mount > option where it makes sense, so all the combinations work through > remount. > > The defaults do not need to be listed via btrfs_show_options, ie. keep > the output same as it is now. > > > david > Thanks for pointing out these problem. This makes sense.Like space_cache and nospace_cache follows the way you mentioned, but most other options just followed the alphabet order, and a lot of pairing is missing. I'll try to add all the missingpairing and unify mount options in the document. Qu