[lvm-devel] a bug in snapshots

[Mike Snitzer]

On Tue, Feb 09 2010 at  7:07pm -0500,
Mikulas Patocka <mpatocka at redhat.com> wrote:

> Hi
> 
> Try to make a snapshot that is so big that it spans more than one physical 
> volume. Then, type "lvs" command. You get these errors:
> 
> [slunicko:/usr/src/LVM2.2.02.60]# lvs
>   Number of segments in active LV lvol1 does not match metadata
>   Number of segments in active LV lvol1 does not match metadata
>   Number of segments in active LV lvol1 does not match metadata
>   Number of segments in active LV lvol1 does not match metadata
>   LV    VG   Attr   LSize  Origin Snap%  Move Log Copy%  Convert
>   lvol0 vg1  owi-a- 16.00m
>   lvol1 vg1  Swi-I- 60.00m lvol0  100.00
>   m     vg1  -wi-a- 64.00m
> 
> This bug was introduced in LVM2.2.02.59 with this change:
> 
> --- ./LVM2.2.02.58/lib/activate/dev_manager.c   2010-01-13 
> 02:55:44.000000000 +0100
> +++ ./LVM2.2.02.59/lib/activate/dev_manager.c   2010-01-15 
> 23:58:25.000000000 +0100
> @@ -584,7 +593,7 @@ int dev_manager_snapshot_percent(struct
>          * Try and get some info on this device.
>          */
>         log_debug("Getting device status percentage for %s", name);
> -       if (!(_percent(dm, name, dlid, "snapshot", 0, NULL, percent,
> +       if (!(_percent(dm, name, dlid, "snapshot", 0, lv, percent,
>                        percent_range, NULL)))
>                 return_0;
> 

That change was part of this commit:
http://sources.redhat.com/git/?p=lvm2.git;a=commit;h=13713bc147

I'm not seeing how this commit has any functional change for anything
other than snapshot-merge related snapshots.

All I did was pass lv into _percent() (and then _percent_run()) so that
I could inspect it to know if lv_is_merging_origin().

The vg1/lvol1's flags indicate the snapshot is set to merge and it is
also invalid.  Can you detail your testcase a bit more please?

Are you certain there isn't some other reason your test case is failing?

Mike