Debian Bug report logs - #285979
can't create snapshots of frozen xfs file system

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Package: lvm2; Maintainer for lvm2 is Debian LVM Team <pkg-lvm-maintainers@lists.alioth.debian.org>; Source for lvm2 is src:lvm2.

Reported by: Steve Feehan <sfeehan@sbb.uvm.edu>

Date: Thu, 16 Dec 2004 18:18:07 UTC

Severity: normal

Found in version 2.00.24-1

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Report forwarded to debian-bugs-dist@lists.debian.org, Patrick Caulfield <patrick@debian.org>:
Bug#285979; Package lvm2. Full text and rfc822 format available.

Acknowledgement sent to Steve Feehan <sfeehan@sbb.uvm.edu>:
New Bug report received and forwarded. Copy sent to Patrick Caulfield <patrick@debian.org>. Full text and rfc822 format available.

Message #5 received at submit@bugs.debian.org (full text, mbox):

From: Steve Feehan <sfeehan@sbb.uvm.edu>
To: submit@bugs.debian.org
Subject: can't create snapshots of frozen xfs file system
Date: Thu, 16 Dec 2004 13:05:45 -0500
Package: lvm2
Version: 2.00.24-1

When I try to create an LVM snapshot of a frozen XFS file system,
lvcreate blocks:

  xfs_freeze -f /home
  lvcreate --snap --size 100M --name home_snap /dev/vg0/home

 .. blocking ..

If I switch to a second terminal and unfreeze /home:

  xfs_freeze -u /home

Then the lvcreate command immediatly completes and the snapshot
is created.

You can see an strace of the lvcreate command up to the point
it blocks at:

http://sbb.uvm.edu/~sfeehan/debian-bugs/lvm2/20041216/lvcreate-part1

And the continuation of the trace after the file system is unfrozen:

http://sbb.uvm.edu/~sfeehan/debian-bugs/lvm2/20041216/lvcreate-part2

Other packages/versions of interest:
  
  xfsprogs                      2.6.20-1
  kernel-image-2.6.8-1-386      2.6.8-10

If there is any additional information I can provide, please 
let me know.

-- 
Steve Feehan



Information forwarded to debian-bugs-dist@lists.debian.org, Patrick Caulfield <patrick@debian.org>:
Bug#285979; Package lvm2. Full text and rfc822 format available.

Acknowledgement sent to Alasdair G Kergon <agk@redhat.com>:
Extra info received and forwarded to list. Copy sent to Patrick Caulfield <patrick@debian.org>. Full text and rfc822 format available.

Message #10 received at 285979@bugs.debian.org (full text, mbox):

From: Alasdair G Kergon <agk@redhat.com>
To: Steve Feehan <sfeehan@sbb.uvm.edu>, 285979@bugs.debian.org
Subject: Re: Bug#285979: can't create snapshots of frozen xfs file system
Date: Sat, 18 Dec 2004 20:03:40 +0000
On Thu, Dec 16, 2004 at 01:05:45PM -0500, Steve Feehan wrote:
> Then the lvcreate command immediatly completes and the snapshot
> is created.
 
Try without freezing it explictly and leave lvm to do it: maybe 
xfs doesn't cope with multiple freezes?

Alasdair
-- 
agk@redhat.com



Information forwarded to debian-bugs-dist@lists.debian.org, Patrick Caulfield <patrick@debian.org>:
Bug#285979; Package lvm2. Full text and rfc822 format available.

Acknowledgement sent to Steve Feehan <sfeehan@sbb.uvm.edu>:
Extra info received and forwarded to list. Copy sent to Patrick Caulfield <patrick@debian.org>. Full text and rfc822 format available.

Message #15 received at 285979@bugs.debian.org (full text, mbox):

From: Steve Feehan <sfeehan@sbb.uvm.edu>
To: Alasdair G Kergon <agk@redhat.com>
Cc: Steve Feehan <sfeehan@sbb.uvm.edu>, 285979@bugs.debian.org
Subject: Re: Bug#285979: can't create snapshots of frozen xfs file system
Date: Sat, 18 Dec 2004 15:30:18 -0500
On Sat, Dec 18, 2004 at 08:03:40PM +0000, Alasdair G Kergon wrote:
> On Thu, Dec 16, 2004 at 01:05:45PM -0500, Steve Feehan wrote:
> > Then the lvcreate command immediatly completes and the snapshot
> > is created.
>  
> Try without freezing it explictly and leave lvm to do it: maybe 
> xfs doesn't cope with multiple freezes?
> 
> Alasdair
> -- 
> agk@redhat.com

It works fine if the file system is not frozen, but this is a
regression. I have created snapshots of frozen XFS file systems
in the past. There are quite a few references on the web that
this is the suggested procedure. Ie.

xfs_freeze -f /home
.. create snapshot ..
xfs_freeze -u /home

A few references:

http://howtos.linux.com/howtos/LVM-HOWTO/snapshots_backup.shtml
http://adumont.hopto.org/~adumont/xfs_lvm_snapshot.txt
http://www.hccfl.edu/pollock/AUnix1/LVM.htm

This procedure worked about a month ago (last time I did a
backup of my home computer). I don't know which packages
changed during that time. Probably quite a few since my
computer is using the testing distribution. Perhaps the
bug is not in the LVM2 software (kernel or userland), 
but I didn't know which package to file the bug against.

If there is more information I can provide to help narrow
down the problem, please let me know.

Thanks.

-- 
Steve Feehan



Information forwarded to debian-bugs-dist@lists.debian.org, Patrick Caulfield <patrick@debian.org>:
Bug#285979; Package lvm2. Full text and rfc822 format available.

Acknowledgement sent to Alasdair G Kergon <agk@redhat.com>:
Extra info received and forwarded to list. Copy sent to Patrick Caulfield <patrick@debian.org>. Full text and rfc822 format available.

Message #20 received at 285979@bugs.debian.org (full text, mbox):

From: Alasdair G Kergon <agk@redhat.com>
To: Steve Feehan <sfeehan@sbb.uvm.edu>
Cc: Alasdair G Kergon <agk@redhat.com>, 285979@bugs.debian.org
Subject: Re: Bug#285979: can't create snapshots of frozen xfs file system
Date: Sat, 18 Dec 2004 20:38:56 +0000
On Sat, Dec 18, 2004 at 03:30:18PM -0500, Steve Feehan wrote:
> It works fine if the file system is not frozen, but this is a
> regression. I have created snapshots of frozen XFS file systems
> in the past. There are quite a few references on the web that
> this is the suggested procedure. Ie.
 
> xfs_freeze -f /home
> .. create snapshot ..
> xfs_freeze -u /home
 
I'm guessing XFS is locking up if it's asked to freeze
while it's already frozen, instead of returning 
success (or a failure code that indicates it's already
frozen).

I know GFS handles this situation OK.

Will try to check things from the device-mapper / VFS point-of-view
in the New Year.

BTW What happens if you run xfs_freeze -f twice?

Alasdair
-- 
agk@redhat.com



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