From: Tvrtko Ursulin <tvrtko.ursulin@sophos.com>
Organization: Sophos Plc
To: Jens Axboe <jens.axboe@oracle.com>
Subject: Re: [PATCH] loop: Update mtime when writing using aops
Date: Thu, 8 Apr 2010 15:15:55 +0100
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CC: Nikanth Karthikesan <knikanth@suse.de>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <201004081551.37824.knikanth@suse.de> <20100408124539.GM10103@kernel.dk>
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On Thursday 08 April 2010 13:45:39 Jens Axboe wrote:
> On Thu, Apr 08 2010, Nikanth Karthikesan wrote:
> > Update mtime when writing to backing filesystem using the address space
> > operations write_begin and write_end.
>
> You forgot to include a 'why' :-)
>
> Not that I disagree with the patch, just curious what made you make the
> change.

You mean how the bug was found? I originally reported this problem against
openSUSE 11.2 kernel, where when you have a dm-crypt loop filesystem the
container file modification time does not get updated with use. Consequence
of that is that backup runs would miss the fact container has changed.

Maybe one could argue it is a security feature in this scenario :), but as the
problem turns out to be unrelated to the crypto case, rather contained in the
loop driver itself, it looks like that would not hold.

Tvrtko

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