From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ted Ts'o <tytso@mit.edu>
Subject: Re: [dm-devel] linux-next - WARNING: at fs/block_dev.c:824
 bd_link_disk_holder+0x92/0x1ac()
Date: Thu, 13 Jan 2011 15:41:45 -0500
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Cc: Tejun Heo <tj@kernel.org>, Milan Broz <mbroz@redhat.com>,
	Karel Zak <kzak@redhat.com>,
	device-mapper development <dm-devel@redhat.com>,
	Jun'ichi Nomura <j-nomura@ce.jp.nec.com>,
	Valdis.Kletnieks@vt.edu, linux-kernel@vger.kernel.org,
	linux-raid@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org, Kay Sievers <kay.sievers@vrfy.org>
To: NeilBrown <neilb@suse.de>
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On Fri, Jan 14, 2011 at 07:18:58AM +1100, NeilBrown wrote:
> 
> open(O_EXCL) will fail on a block device if it is being used by anything else
> - a filesystem or a dm target or an md array or ....
> 
> So if the *only* thing you want is "is this currently an active part of
> something else", then O_EXCL works since 2.6.0 (I think).

Unfortunately, that won't distinguish between a currently active file
system, and a device which is being used by a dm target, which is what
we want to do.

						- Ted