[linux-lvm] Possible bug in expanding thinpool: lvextend doens't expand the top-level dm-linear device

[M.H. Tsai]

Hi,

Sorry, what's the purpose of commit cd8e95d9337207a8f87a6f68dc9b1db7e3828bbf ?

Another issue is, the current code suspends the first thin volume
(just the first one!)
while extending a thinpool, which is unnecessary and also harms IO performance.

Also, If the top-level "fake" pool device is unimportant, why not
remove it, or simply
make tp1 as a thin-pool target? It seems that the commit 00a45ca4 want
to do this,
it removes the -tpool layer while activating a new thinpool. But if
there are thin
volumes, the -tpool layer back again. This make me confused -- Do we really need
layers?


Thanks,
Ming-Hung Tsai

2015-12-24 17:04 GMT+08:00 Zdenek Kabelac <zkabelac at redhat.com>:
> Dne 23.12.2015 v 10:50 M.H. Tsai napsal(a):
>
>> After running lvextend, the table of vg1-tp1_tdata and vg1-tp1-tpool
>> are expanded, but the dm-linear table of vg1-tp1 remains unchanged.
>>
>> I think that the function _lv_update_and_reload() erroneously operates
>> on the holder of of tp1, that is, lvol0. This might be caused by
>> commit fa64823, hence the subsequent actions runs on the lock_lv. The
>> verbose output also shows that the tree_action() is running on lvol0,
>> not tp1.
>>
>> Creating PRELOAD tree for vg1/lvol0.
>> Creating SUSPEND tree for vg1/lvol0.
>> Creating ACTIVATE tree for vg1/lvol0.
>> Creating CLEAN tree for vg1/lvol0.
>>
>> Is that a bug?
>>
>>
>> Thanks,
>> Ming-Hung Tsai
>
>
> Hi
>
> Please check with commit cd8e95d9337207a8f87a6f68dc9b1db7e3828bbf included
> (2.02.139).
>
> It's been known issue, the size of top-level 'fake' pool device is however
> not really important - no one should be actually using it and the size could
> have been artificial.
>
> In fact - I do plan to rework this 'pool' device 'faking' to avoid need
> of this 'extra' device - but it's 'a little bit' complex - so it will take
> some time (I've even fix to correct the size of fake device - but then I've
> realized it would be actually much better without it)
>
> So do not worry about the size of this device - the only device which does
> matter is -tpool.
>
> Regards
>
> Zdenek
>
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