[PATCH 2/2] Fix lv-seg relationship on layer removal

[PATCH 2/2] Fix lv-seg relationship on layer removal

[Jun'ichi Nomura]

When a layer is removed, a linear-mapping segment of its parent
is discarded and segments of the layer are moved to the parent LV.

To discard the linear-mapping layer properly,
we need to call lv_empty() for the parent to release the layer.
Otherwise, the layer LV still has the discarded linear segment
in its segs_using_this_lv list.
(Though it might not have any visible effect because the layer
 is eventually removed.)

Thanks Milan Broz for finding this bug.

Thanks,
-- 
Jun'ichi Nomura, NEC Corporation of America
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[PATCH 2/2] Fix lv-seg relationship on layer removal

[Jim Meyering]

"Jun'ichi Nomura" <j-nomura@ce.jp.nec.com> wrote:
> When removing a layer, segments are moved from the layer LV to
> the original LV (parent).
> Before doing that, call lv_empty() to cleanup the parent and
> any relationships.
>
> Without this, the relationship between the layer_lv and parent remains
> and lvconvert will fail, for example:
>
> # lvconvert -m-1 vg/lvol0
>   LV lvol0_mimagetmp_2 used by LV lvol0:0-511, but is not listed in LV lvol0 segments list.
>   Internal error: LV segments corrupted in lvol0_mimagetmp_2.
>   intermediate VG write failed.

Hi Jun'ichi,

Would you please consider writing (or just outlining) a test case
that fails without yesterday's change, but succeeds with it?

Future maintainers will be grateful :-)