From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <52028170.1010000@pse-consulting.de>
Date: Wed, 07 Aug 2013 19:18:40 +0200
From: Andreas Pflug <pgadmin@pse-consulting.de>
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	<520211BB.2040301@pse-consulting.de> <5202164B.5010302@redhat.com>
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Subject: Re: [linux-lvm] Missing error handling in lv_snapshot_remove
Reply-To: LVM general discussion and development <linux-lvm@redhat.com>
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To: Zdenek Kabelac <zkabelac@redhat.com>
Cc: LVM general discussion and development <linux-lvm@redhat.com>

On 08/07/13 11:41, Zdenek Kabelac wrote:
> Dne 7.8.2013 11:22, Andreas Pflug napsal(a):
>> Am 06.08.13 19:37, schrieb Bastian Blank:
>>> Hi
>>>
>>> I tried to tackle a particular bug that shows up in Debian for some 
>>> time
>>> now. Some blamed the udev rules and I still can't completely rule them
>>> out. But this triggers a much worse bug in the error cleanup of the
>>> snapshot remove. I reproduced this with Debian/Linux 3.2.46/LVM 2.02.99
>>> without udevd running and Fedora 19/LVM 2.02.98-10.fc19.
>>>
>>> On snapshot removal, LVM first converts the device into a regular LV
>>> (lv_remove_snapshot) and in a second step removes this LV
>>> (lv_remove_single). Is there a reason for this two step removal? An
>>> error during removal leaves a non-snapshot LV behind.
>> Ah, this explains why sometimes my backup stops: I take a snapshot,
>> rsync the stuff and remove the snapshot with a daily cron job, but I
>> observed twice that a non-snapshot volume named like a backup snapshot
>> was lingering around, preventing the script to work. So this is no
>> exotic corner case, but happens in real life.
>>
>> I observe this since I dist-upgraded to wheezy.
>>
>
> Because Debian is using non-upstream udev rules.
>
> With upstream udev rules with standard real-life use, this situation
> cannot happen - since these rules are constructed to play better with
> udev WATCH rule.

Hm, does udev play a role on this at all? Without having dived the code, 
I'd assume udev has only to do with creation and deletion of 
/dev/mapper/... and/or /dev/vgname/... devices (upon lvchange -aX), but 
not with lvm metadata manipulation.

Regards
Andreas