[linux-lvm] kernel errors from a merging snapshot

[Lentes, Bernd]

Mike wrote:


> -----Ursprüngliche Nachricht-----
> Von: Mike Snitzer [mailto:snitzer at redhat.com]
> Gesendet: Dienstag, 14. Oktober 2014 23:07
> An: Lentes, Bernd
> Cc: LVM general discussion and development
> Betreff: Re: kernel errors from a merging snapshot
>
> On Tue, Oct 14 2014 at  2:08pm -0400,
> Lentes, Bernd <bernd.lentes at helmholtz-muenchen.de> wrote:
>
> > Hi,
> >
> > i have a /-filesystem residing on a lv. I also had a snapshot of that lv
> because I tried some software. After testing the software I merged the
> snapshot into the origin, by rebooting. It seemed to went fine.
> > Btw: how do I know when merging is finished ? Where can I see results
> from the merging ?
>
> You can use lvm to see the merge in progress (via lvs).  Or you can have a
> look at the "How to determine when a merging is complete" section of the
> kernel's Documentation/device-mapper/snapshot.txt
>
> > But in /var/log/messages I have error messages about a block device:
> >
> > Oct 14 16:22:45 vm59093-4 kernel: [    7.580247] Buffer I/O error on device
> dm-3, logical block 0
> > Oct 14 16:22:45 vm59093-4 kernel: [    7.580254] Buffer I/O error on device
> dm-3, logical block 1
> > Oct 14 16:22:45 vm59093-4 kernel: [    7.580258] Buffer I/O error on device
> dm-3, logical block 2
> > Oct 14 16:22:45 vm59093-4 kernel: [    7.580261] Buffer I/O error on device
> dm-3, logical block 3
> > Oct 14 16:22:45 vm59093-4 kernel: [    7.580264] Buffer I/O error on device
> dm-3, logical block 0
> > Oct 14 16:22:45 vm59093-4 kernel: [    7.580271] Buffer I/O error on device
> dm-3, logical block 9961471
> > Oct 14 16:22:45 vm59093-4 kernel: [    7.580274] Buffer I/O error on device
> dm-3, logical block 9961471
> > Oct 14 16:22:45 vm59093-4 kernel: [    7.580341] Buffer I/O error on device
> dm-3, logical block 0
> > Oct 14 16:22:45 vm59093-4 kernel: [    7.580345] Buffer I/O error on device
> dm-3, logical block 1
> >
> > Dm-3 is the snapshot I merged (although I named it root-snapshot while
> creating, not root--snapshot !):
> >
> > Dmsetup info says:
> >
> > ...
> > Name:              vg_1-root--snapshot
> > State:             ACTIVE
> > Read Ahead:        1024
> > Tables present:    LIVE
> > Open count:        0
> > Event number:      0
> > Major, minor:      252, 3
> > Number of targets: 1
> > UUID:
> > LVM-
> ZfsXYr9bkOt1d9bMNpcrn7MxH2aX6H0bhELCnywHd7rbddry6f63xtkk1vqs1hv
> v
> > ...
> >
> > The errors appeared during the reboot. Is that normal ?
>
> We replace the device that is being merged with the "error" target.  So any
> IO directly to the merging device will get errored out.  But IIRC that was fixed
> with an updated lvm2 (libdm) change to hide the device from udev (udev
> rules were trying to read labels from the device via blkid, etc).
>
> Which distro and kernel are you using?

SLES 11 SP3 64bit, kernel 3.0.76-0.11-default


Bernd

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