linux-ext4 - Re: persistent preallocation

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Message-ID: <4C584315.6060701@redhat.com>
Date:	Tue, 03 Aug 2010 11:25:57 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Dmitry Monakhov <dmonakhov@...nvz.org>
CC:	Bo Brantén <bosse@....umu.se>,
	linux-ext4@...r.kernel.org
Subject: Re: persistent preallocation

On 08/03/2010 06:18 AM, Dmitry Monakhov wrote:
> Bo Brantén <bosse@....umu.se> writes:
> 
>> Hello,
>>
>> I have a question on the implementation of persistent preallocation,
>> the reason to not return the disk block is because it can contain old
>> data but I wonder if an implementation has to return zeros instead or
> Please look at fallocate(2) syscall.
>> if it could return any garbage as long as it is not _that_ garbage?
> Off course it is not a garbage, it is old user's data which may be
> very very useful (old passwords, cookies, and etc)for person who has
> time to analyze it :)

I think the question was, could the implementation return 0xFF rather
than what is actually on disk (and rather than 0's) when reading a
preallocated block.

You could certainly write it that way, but I don't know why you would
want to...

IOW it wouldn't be posix_fallocate() or fallocate(), it'd be
junk_preallocate() or something.

-Eric

>>
>> Bo Branten
>>
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