Date: Tue, 31 May 2005 11:04:14 +0000
From: Andy Smith <andy@strugglers.net>
Message-ID: <20050531110414.GP686@strugglers.net>
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Subject: [linux-lvm] deadlock on snapshot creation;
	any way out without a reboot?
Reply-To: LVM general discussion and development <linux-lvm@redhat.com>
To: linux-lvm@redhat.com


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Hello,

One of my LVs has just become unusable and I am hoping there is a
way to fix it without rebooting.

I am not sure exactly what happened, but it is possible that an
attempt was made to create a snapshot of the LV while in another
window someone had an lvremove of the same-named snapshot LV waiting
at the 'y/n' prompt.

Anyway the end result is no snapshot LV, and a source LV that
deadlocks whenever there is any attempt made to access it.

An fsck looks like this:

$ sudo e2fsck -f /dev/mainvg/admindata
e2fsck 1.37 (21-Mar-2005)

and then nothing, the e2fsck is now in state D, and has been for
half an hour or so.  top shows machine in 100% iowait, and the
e2fsck process is unkillable.

My question really is, is there any known way to get out of this
sort of situation without having to reboot?  If I reboot it means
downtime and it's not guranteed that the server will actually
complete a reboot since it may hang due to this very problem.  I may
then not be able to do anything even over serial, and there is no
remote power switch.

I'm more concerned about getting out of the 100% iowait situation
than preserving the contents of the LV, since I have backups.

debian sarge, LVM2, kernel 2.6.11.  And yes I am aware that snapshots
are experimental. :)

Thanks,
Andy

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