linux-ext4 - Re: [PATCH] ext4: Automatic setting of {INODE,BLOCK}

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Message-ID: <alpine.LFD.2.00.1210251555310.14460@dhcp-1-104.brq.redhat.com>
Date:	Thu, 25 Oct 2012 15:59:38 +0200 (CEST)
From:	Lukáš Czerner <lczerner@...hat.com>
To:	Zheng Liu <gnehzuil.liu@...il.com>
cc:	Yongqiang Yang <xiaoqiangnk@...il.com>,
	Lukáš Czerner <lczerner@...hat.com>,
	Tomas Racek <tracek@...hat.com>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4: Automatic setting of {INODE,BLOCK}_UNINIT flags

On Thu, 25 Oct 2012, Zheng Liu wrote:

> Date: Thu, 25 Oct 2012 20:54:09 +0800
> From: Zheng Liu <gnehzuil.liu@...il.com>
> To: Yongqiang Yang <xiaoqiangnk@...il.com>
> Cc: Lukáš Czerner <lczerner@...hat.com>, Tomas Racek <tracek@...hat.com>,
>     linux-ext4@...r.kernel.org
> Subject: Re: [PATCH] ext4: Automatic setting of {INODE,BLOCK}_UNINIT flags
> 
> On Thu, Oct 25, 2012 at 07:39:06PM +0800, Yongqiang Yang wrote:
> > >
> > > So my question is, why do you think this might not make sense in no
> > > journal mode ? Maybe I am missing something.
> > Yep, advantage is obvious, in no journal mode, if we delete a file
> > which is the last inode in a block group, and the uninit flag of inode
> > bitmap is flused to disk and directory referring the inode is not
> > flushed,  I don't know how fsck handles the situation currently.  If
> > fsck handles the situation, everything is ok. I meant maybe we should
> > check fsck too.
> 
> Hi Yongqiang,
> 
> It seems that it couldn't happen whether it is in no journal mode or
> journal mode.  When a file is deleted, the dir entry will be updated
> firstly, and then the block will be freed.  So the block is freed after
> the dir entry is updated.  So when the last inode is freed, the dir
> entry must be flushed to the disk.  Am I missing something?

I think you're right. Doing this the other way around would be a bug
regardless on this patch.

Thanks!
-Lukas

> 
> Regards,
> Zheng
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