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Date: Wed, 14 Oct 2015 14:18:41 -0600
From: Chris Friesen <chris.friesen@windriver.com>
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Subject: [linux-lvm] unexpected behaviour of "lvresize" with sparse volumes
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To: LVM general discussion and development <linux-lvm@redhat.com>

Hi,

I'm running the 3.14 kernel with lvm 2.02.98 and I ran into something unexpected 
with lvresize.

I created a sparse volume:

lvcreate -L 25M -V 50M -n sparsevol myvg


This gives output in lvdisplay like this:
   LV Size                52.00 MiB
   Current LE             13
   COW-table size         28.00 MiB
   COW-table LE           7

I then resized the volume with lvresize:

lvresize -L 200M myvg/sparsevol


This seems to resize the COW-table, but not the volume itself.  Now lvdisplay shows:

   LV Size                52.00 MiB
   Current LE             13
   COW-table size         200.00 MiB
   COW-table LE           50


At this point I've got 200MiB of backing store and running "lvs" shows an LSize 
of "200m" but I can only write 52MiB worth of data to the volume before it 
complains.

Is there a way to expand the "LV Size" shown in lvdisplay so that I can write 
the resized amount of data to the volume?

Thanks,
Chris