[linux-lvm] Can't remove snapshot at first

[linux-lvm] Can't remove snapshot at first

[Alexander Skwar]

Hi.

I noticed, that rather often, I'm unable to remove an unused
snapshot volume at first command execution. See this:

--($ ~)-- sudo /sbin/lvremove /dev/Sys/Home-Backup_Snapshot 
  Can't remove open logical volume "Home-Backup_Snapshot"

--($ ~)-- sudo /sbin/lvremove /dev/Sys/Home-Backup_Snapshot 
Do you really want to remove active logical volume Home-Backup_Snapshot? [y/n]: 

Between those two commands, I did not do anything at all! I ran the
commands directly after each other in like 5 seconds or so.

Why's that so?

--($ ~)-- sudo /sbin/lvm version
  LVM version:     2.02.70(2) (2010-07-06)
  Library version: 1.02.52 (2010-07-06)
  Driver version:  4.17.0

--($ ~)-- uname -a
Linux winnb000546 2.6.35-ARCH #1 SMP PREEMPT Sat Aug 21 07:23:08 UTC 2010 i686
Intel(R) Core(TM)2 Duo CPU T7300 @ 2.00GHz GenuineIntel GNU/Linux

This is a Arch Linux system.

Thanks,
Alexander

Re: [linux-lvm] Can't remove snapshot at first

[Peter Rajnoha]

On 08/25/2010 10:12 AM +0100, Alexander Skwar wrote:
> --($ ~)-- sudo /sbin/lvremove /dev/Sys/Home-Backup_Snapshot 
>   Can't remove open logical volume "Home-Backup_Snapshot"
> 
> --($ ~)-- sudo /sbin/lvremove /dev/Sys/Home-Backup_Snapshot 
> Do you really want to remove active logical volume Home-Backup_Snapshot? [y/n]: 
> 
> Between those two commands, I did not do anything at all! I ran the
> commands directly after each other in like 5 seconds or so.
> 
> Why's that so?
> 

Do you have "udisks" installed? There's a problem we track already and
this seems to be the same:

  https://bugzilla.redhat.com/show_bug.cgi?id=577798

Peter

Re: [linux-lvm] Can't remove snapshot at first

[Alexander Skwar]

Hi.

2010/8/25 Peter Rajnoha <prajnoha@redhat.com>
>
> On 08/25/2010 10:12 AM +0100, Alexander Skwar wrote:
> > --($ ~)-- sudo /sbin/lvremove /dev/Sys/Home-Backup_Snapshot
> >   Can't remove open logical volume "Home-Backup_Snapshot"
> >
> > --($ ~)-- sudo /sbin/lvremove /dev/Sys/Home-Backup_Snapshot
> > Do you really want to remove active logical volume Home-Backup_Snapshot? [y/n]:
> >
> > Between those two commands, I did not do anything at all! I ran the
> > commands directly after each other in like 5 seconds or so.
> >
> > Why's that so?
> >
>
> Do you have "udisks" installed?

TBH, I don't know what udisks is, but, yes, it's installed.

--($ /.backup/lib)-- pacman -Q udisks
udisks 1.0.1-5

And it's running as well...

root      9604  0.0  0.1  13708  3088 ?        Sl   07:47   0:10
/usr/lib/udisks/udisks-daemon


> There's a problem we track already and
> this seems to be the same:
>
>  https://bugzilla.redhat.com/show_bug.cgi?id=577798

I removed that line from the udev rule, and now the problem seems
to be gone.

Alexander
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Re: [linux-lvm] Can't remove snapshot at first

[Milan Broz]

On 08/25/2010 10:12 AM, Alexander Skwar wrote:
> I noticed, that rather often, I'm unable to remove an unused
> snapshot volume at first command execution. See this:
> 
> --($ ~)-- sudo /sbin/lvremove /dev/Sys/Home-Backup_Snapshot 
>   Can't remove open logical volume "Home-Backup_Snapshot"
> 
> --($ ~)-- sudo /sbin/lvremove /dev/Sys/Home-Backup_Snapshot 
> Do you really want to remove active logical volume Home-Backup_Snapshot? [y/n]: 
> 
> Between those two commands, I did not do anything at all! I ran the
> commands directly after each other in like 5 seconds or so.

I t is possible that udev run some async scan in reaction to even (during snap manipulation).

Distro maintainers should probably update lvm udev rules
(and possibly udisks rules etc) to work relieably.

Upstream lvm2 with combination of recent udev and udisks package
should have this fixed (hopefully).

Milan

Re: [linux-lvm] Can't remove snapshot at first

[Alexander Skwar]

Hello!

2010/8/25 Milan Broz <mbroz@redhat.com>:
> On 08/25/2010 10:12 AM, Alexander Skwar wrote:
>> I noticed, that rather often, I'm unable to remove an unused
>> snapshot volume at first command execution. See this:
>>
>> --($ ~)-- sudo /sbin/lvremove /dev/Sys/Home-Backup_Snapshot
>>   Can't remove open logical volume "Home-Backup_Snapshot"
>>
>> --($ ~)-- sudo /sbin/lvremove /dev/Sys/Home-Backup_Snapshot
>> Do you really want to remove active logical volume Home-Backup_Snapshot? [y/n]:
>>
>> Between those two commands, I did not do anything at all! I ran the
>> commands directly after each other in like 5 seconds or so.
>
> I t is possible that udev run some async scan in reaction to even (during snap manipulation).
>
> Distro maintainers should probably update lvm udev rules
> (and possibly udisks rules etc) to work relieably.

Guess so.

> Upstream lvm2 with combination of recent udev and udisks package
> should have this fixed (hopefully).

Hm. I have udisks 1.0.1 installed.
http://cgit.freedesktop.org/DeviceKit/DeviceKit-disks/
lists 1.0.1 as the most recent, so what should Arch Linux do in this
case?

Same for udev - http://www.kernel.org/pub/linux/utils/kernel/hotplug/?C=M;O=D
lists udev-161 as the latest and I do have udev-161 installed.

But LVM2 is indeed out of date - I've got 2.02.70. Would've .71 or .73 have
fixed this?

BTW: I'm on kernel 2.6.35.3-1. Well, I guess that should be 2.6.35.3,
but should the
uname -a output show 2.6.35.3?

Alexander
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Re: [linux-lvm] Can't remove snapshot at first

[Peter Rajnoha]

On 08/25/2010 01:30 PM +0100, Milan Broz wrote:
> On 08/25/2010 10:12 AM, Alexander Skwar wrote:
>> --($ ~)-- sudo /sbin/lvremove /dev/Sys/Home-Backup_Snapshot 
>>   Can't remove open logical volume "Home-Backup_Snapshot"
>>
> Upstream lvm2 with combination of recent udev and udisks package
> should have this fixed (hopefully).

Well, not completely in this exact case. It's hard to cover this
situation with "nowatch"/dm udev flags here because someone could
change the contents of the volume and so the snapshot volume and
original volume can differ.

Anyone scanning for those changes in udev rules could miss the
change of a symlink name based on some changed attribute or some
other call that notifies about changes in general.

We can rule out the mirror's _mimage, snapshot's -cow/-real etc.
scanning, but the top-level snapshot - unfortunately not.

So for now, it would be better to just try to comment out that
watch rule in udisks udev rules so we can see that is the case.

If yes, we can make our argument that this really causes problems
even stronger and try to persuade people who use the watch rule
to be inclined to some other alternative solution that is less
problematic to support.

Peter

Re: [linux-lvm] Can't remove snapshot at first

[Alexander Skwar]

Hi.

2010/8/25 Peter Rajnoha <prajnoha@redhat.com>:

> So for now, it would be better to just try to comment out that
> watch rule in udisks udev rules so we can see that is the case.

Sorry, I guess I was "a bit" too hasty, when I said that removing
the line helped... I'm still getting the error in my OP.

Alexander
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