linux-ext4 - RE: [PATCH 09/25] misc: zero s_jnl_blocks when removing internal journal

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Message-ID: <BAY179-W471384B15AB594C29D96F9FDCD0@phx.gbl>
Date:	Fri, 12 Sep 2014 15:06:23 -0400
From:	TR Reardon <thomas_reardon@...mail.com>
To:	"Darrick J. Wong" <darrick.wong@...cle.com>
CC:	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: RE: [PATCH 09/25] misc: zero s_jnl_blocks when removing internal
 journal

If the change from journal_inode to journal_dev is/was made prior to the recent change, the s_jnl_blocks will have whatever it last had.  So if it started with journal_inode and then switched to journal_dev (again, prior to your fix) or no journal, the s_jnl_blocks will have the old journal_inode info, and adding/removing journal_dev does no clear it out.  For a new fs with created only with journal_dev, there is no issue.  I'm just arguing that *adding* journal_dev should also zero this out.

+Reardon

----------------------------------------
> Date: Fri, 12 Sep 2014 09:43:42 -0700
> From: darrick.wong@...cle.com
> To: thomas_reardon@...mail.com
> CC: linux-ext4@...r.kernel.org
> Subject: Re: [PATCH 09/25] misc: zero s_jnl_blocks when removing internal journal
>
> [cc linux-ext4]
>
> On Fri, Sep 12, 2014 at 10:09:55AM -0400, TR Reardon wrote:
>> Note that this only works (zeroes out) when removing inode journal. Removing
>> an existing journal_dev leaves s_jnl_blocks untouched. To be absolutely
>> clean, perhaps it should be wiped in all removal cases?
>
> s_jnl_blocks shouldn't be set if an external journal is in use.
>
> (Unless it is somehow?)
>
> --D

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