From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [PATCH v3 36/39] ubifs: implement ubifs_get_qsize to get quota size in ubifs Date: Mon, 21 Sep 2015 11:13:55 +0200 Message-ID: <20150921091355.GA9028@quack.suse.cz> References: <1442307754-13233-1-git-send-email-yangds.fnst@cn.fujitsu.com> <1442307754-13233-37-git-send-email-yangds.fnst@cn.fujitsu.com> <20150916100007.GD13325@quack.suse.cz> <55FA6A5F.1010702@cn.fujitsu.com> <20150917120044.GC32280@quack.suse.cz> <55FBABD8.9030002@cn.fujitsu.com> <20150918112006.GA16306@quack.suse.cz> <55FF88F5.5070703@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , viro@ZenIV.linux.org.uk, dedekind1@gmail.com, richard.weinberger@gmail.com, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org To: Dongsheng Yang Return-path: Received: from mx2.suse.de ([195.135.220.15]:32858 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753733AbbIUJN6 (ORCPT ); Mon, 21 Sep 2015 05:13:58 -0400 Content-Disposition: inline In-Reply-To: <55FF88F5.5070703@cn.fujitsu.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon 21-09-15 12:35:01, Dongsheng Yang wrote: > On 09/18/2015 07:20 PM, Jan Kara wrote: > >>.... TBH, there is a little different with other filesystems. I did not > >>use the "disk" space, but the file space in ubifs quota, although dquot > >>means disk quota. Same with btrfs quota. If we use disk space for quota, > >>the most common problem from user is that: why I did not reach the limit > >>but I can not write any byte. COW in btrfs or out-place-updating in > >>ubifs makes this problem much worse. > >> > >>So I choose file space here for ubifs. > > > >OK, so these are really two separate questions. I understand your choice of > >using file space as the amount of space to account for quota purposes and > >I'm fine with that choice. Another thing is that regardless of how you > >decide to do quota accounting, you must maintain i_blocks / i_bytes to > >contain proper value because dquot_transfer() uses that information to update > >quota usage when inode owner is changed. > > But if we don't use i_blocks to get qsize, what we care only in > dquot_transter() is dquot->dq_dqb. That means, even if the i_blocks > is not correct in dquot_transfer() in ubifs, that's okey, because we > will never use this value, right? dquot_transfer() will use the value - when file F changes owner from user A to user B, then you need to decrement amount of space used by F from A's quota usage and add that amount to B's quota usage. And the amount of space is obtained via inode_get_bytes() which uses i_blocks and i_bytes. See __dquot_transfer() in fs/quota/dquot.c for details. Honza -- Jan Kara SUSE Labs, CR