From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dmitry Monakhov <dmonakhov@openvz.org>
Subject: Re: [RFC] vfs generic subtree support
Date: Tue, 16 Feb 2010 18:00:32 +0300
Message-ID: <87hbphns33.fsf@openvz.org>
References: <87tythtptw.fsf@openvz.org>
	<20100216122029.GC30031@ZenIV.linux.org.uk>
	<87bpfpcq55.fsf@openvz.org>
	<20100216133836.GD30031@ZenIV.linux.org.uk>
	<87mxz9nutb.fsf@openvz.org>
	<20100216142154.GE30031@ZenIV.linux.org.uk>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: linux-fsdevel@vger.kernel.org
To: Al Viro <viro@ZenIV.linux.org.uk>
Return-path: <linux-fsdevel-owner@vger.kernel.org>
Received: from mail-bw0-f219.google.com ([209.85.218.219]:39047 "EHLO
	mail-bw0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S932201Ab0BPPAi (ORCPT
	<rfc822;linux-fsdevel@vger.kernel.org>);
	Tue, 16 Feb 2010 10:00:38 -0500
Received: by bwz19 with SMTP id 19so4425208bwz.28
        for <linux-fsdevel@vger.kernel.org>; Tue, 16 Feb 2010 07:00:35 -0800 (PST)
In-Reply-To: <20100216142154.GE30031@ZenIV.linux.org.uk> (Al Viro's message of
	"Tue, 16 Feb 2010 14:21:54 +0000")
Sender: linux-fsdevel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>

Al Viro <viro@ZenIV.linux.org.uk> writes:

> On Tue, Feb 16, 2010 at 05:01:36PM +0300, Dmitry Monakhov wrote:
>
>> Let's call it "metagroup" id. If you know better (more descriptive) word
>> for this purpose i please make your suggestion.
>> 
>> - Such metagroup may be assigned to inode. And this id is stored on
>>   inode.
>> - It may be inherent from parent, if corresponding flag is set 
>>   on parent dir.
- if inherent flag is not set, then inherent metagroup id
  from mnt_root 
>> - metagroup id may be used by generic quota.
>
> I would probably like to see example with fewer "may" and more details ;-)
> Seriously, what kind of rules and uses for it do you have in mind?  More
> specific example would be nice...
Use-cases:
*Assing maximum disc space consumption for some hierarchy *

  1) Create chroot environment
    # tar  xf chroot_env.tar /var/xxx/chroot
  2) Assign some metagroup id to the chroot content (via not yet
     existent ./metagroup cmd-tool)
    # find /var/xxx/chroot  | xargs ./metagroup --set 1000

  3) Setup quota limits
    # quota-set --type metagroup --blk_soft=1024M blk_hard=1024M /var

  4) Export this tree (it may be more complex)
    # mount /var/xxx/chroot /mnt/chroot -obound

  5)Now we may use this /mnt/chroot as:
    5A) A regular chroot envirement, user is unable to exceed metagroup
        quota, regardless to real available space on /var/
    5B) As a container's (namespace) root. 
    5C) export this /mnt/chroot to nfs server and nfs client can not
        overcome given metagroup quota limit.