linux-ext4 - Re: xt4 - True Readonly mount [WAS - Re: [Bug 14354] Bad corruption with 2.6.32-rc1 and upwards]

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Message-ID: <e9e943910910301043n3e5e8816y74286b0c159a8a78@mail.gmail.com>
Date:	Fri, 30 Oct 2009 17:43:14 +0000
From:	Duane Griffin <duaneg@...da.com>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	Alexey Fisher <bug-track@...her-privat.net>,
	Greg Freemyer <greg.freemyer@...il.com>,
	Ted Augustine <taugustine@...hpathways.com>,
	linux-ext4@...r.kernel.org
Subject: Re: xt4 - True Readonly mount [WAS - Re: [Bug 14354] Bad corruption 
	with 2.6.32-rc1 and upwards]

2009/10/30 Eric Sandeen <sandeen@...hat.com>:
> Alexey Fisher wrote:
>> Hmm... bdev. any chance to do temporary recovery and load it as external
>> journal if ro used? Anyway, you already pointed me to hdparm, so i can
>> use it too.
>
> There were patches floated to in-ram recovery for those blocks so that you
> could have a consistent fs w/o touching the disk but it didn't seem to get
> far.

Those were mine, I think. I got stuck at the point of needing to
handle escaped blocks -- I couldn't find any way of reliably and
efficiently getting hold of a buffer after it had been read from disk
but before anybody else had a chance to access it. I think if I could
have cracked that then I could have got it working. The only other
missing piece of functionality was handling the transition from
read-only (unrecovered) to read-write.

It would have needed a very thorough audit of the places where ext3
was doing ll_rw_block and such like, though.

Cheers,
Duane.

-- 
"I never could learn to drink that blood and call it wine" - Bob Dylan
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