From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com>
Subject: Re: Snapshots
Date: Fri, 21 Dec 2007 20:28:05 -0500
Message-ID: <476C6825.7070701@ce.jp.nec.com>
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Phillip Susi wrote:
> Jun'ichi Nomura wrote:
>> So, you have to put the linear mapping *before* that.
>> Then, the top-level block device will be locked but you can
>> still change the underlying mappings.
> 
> So using a disk device as a dm target locks it.  DM won't use a disk
> device as a target if it is locked.

If a device is locked by a DM device on top of it,
other DM device can still use the device as a target.

Also, even if a DM device is locked by mount, you can still change
the table of the DM device.

> Are you saying that dm can use
> another dm device as a target, even if it is already locked by being
> used as another dm target?

I'm not sure if I understand your last sentence correctly.
Does the above comment answer to your question?

Thanks,
-- 
Jun'ichi Nomura, NEC Corporation of America