linux-ext4 - Re: zero out blocks of freed user data for operation a virtual machine environment

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Message-ID: <87ab51qq91.fsf@frosties.localdomain>
Date:	Mon, 25 May 2009 15:14:02 +0200
From:	Goswin von Brederlow <goswin-v-b@....de>
To:	Thomas Glanzmann <thomas@...nzmann.de>
Cc:	Theodore Tso <tytso@....edu>,
	Arjan van de Ven <arjan@...radead.org>, tytso@...nk.org,
	LKML <linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org
Subject: Re: zero out blocks of freed user data for operation a virtual machine environment

Thomas Glanzmann <thomas@...nzmann.de> writes:

> Hello Ted,
>
>> Yes, it does, sb_issue_discard().  So if you wanted to hook into this
>> routine with a function which issued calls to zero out blocks, it
>> would be easy to create a private patch.
>
> that sounds good because it wouldn't only target the most used
> filesystem but every other filesystem that uses the interface as well.
> Do you think that a tunable or configurable patch has a chance to hit
> upstream as well?
>
>         Thomas

I could imagine a device mapper target that eats TRIM commands and
writes out zeroes instead. That should be easy to maintain outside or
inside the upstream kernel source.

MfG
        Goswin
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