linux-ext4 - Re: quota: dqio

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Date:   Thu, 03 Aug 2017 15:24:05 +0300
From:   Andrew Perepechko <anserper@...dex.ru>
To:     Wang Shilong <wangshilong1991@...il.com>
Cc:     Shuichi Ihara <sihara@....com>, Wang Shilong <wshilong@....com>,
        Li Xi <lixi@....com>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        Jan Kara <jack@...e.cz>, linux-fsdevel@...r.kernel.org
Subject: Re: quota: dqio_mutex design

> 
> I don't think this is right, as far as i understand, journal quota need go
> together with quota space change update inside same transaction, this will
> break consistency if power off or RO happen.
> 

Hello Wang!

There is no transaction change in this case because all callers of this
function have open handles for the same transaction.

If you enter that DQ_MOD_B check, you are guaranteed to reference
the SAME transaction as the thread that's in between of mark_dirty
and clear_dirty.

Thank you,
Andrew