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To: ric@emc.com
Cc: Tomasz Torcz <zdzichu@irc.pl>,
       Thomas Glanzmann <sithglan@stud.uni-erlangen.de>,
       "Theodore Ts'o" <tytso@mit.edu>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: ext4 features
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From: Krzysztof Halasa <khc@pm.waw.pl>
Date: Thu, 06 Jul 2006 19:05:48 +0200
In-Reply-To: <44AD286F.3030507@emc.com> (Ric Wheeler's message of "Thu, 06 Jul 2006 11:12:47 -0400")
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Ric Wheeler <ric@emc.com> writes:

> Having a checksum (or even a digital signature on a file) that lets us
> detect corruption is very useful since, in many cases, it allows us to
> flag the file as corrupt before it gets used.

We can't have that. Sector/block/etc. checksums - yes.

A checksum, signature, hash etc. of the whole file would require
actually reading the whole file. It can be done by tripwire or
backup, and even by fsck, but not by the filesystem in normal
operation.
-- 
Krzysztof Halasa