bug? shrink lv by specifying pv extent to be removed does not behave as expected

[Roland <devzero@xxxxxx>]

hi,

we can extend a logical volume by arbitrary pv extends like this :


root@s740:~# lvresize mytestVG/blocks_allocated -l +1 /dev/sdb:5
  Size of logical volume mytestVG/blocks_allocated changed from 1.00 
MiB (1 extents) to 2.00 MiB (2 extents).
  Logical volume mytestVG/blocks_allocated successfully resized.

root@s740:~# lvresize mytestVG/blocks_allocated -l +1 /dev/sdb:10
  Size of logical volume mytestVG/blocks_allocated changed from 2.00 
MiB (2 extents) to 3.00 MiB (3 extents).
  Logical volume mytestVG/blocks_allocated successfully resized.

root@s740:~# lvresize mytestVG/blocks_allocated -l +1 /dev/sdb:15
  Size of logical volume mytestVG/blocks_allocated changed from 3.00 
MiB (3 extents) to 4.00 MiB (4 extents).
  Logical volume mytestVG/blocks_allocated successfully resized.

root@s740:~# lvresize mytestVG/blocks_allocated -l +1 /dev/sdb:20
  Size of logical volume mytestVG/blocks_allocated changed from 4.00 
MiB (4 extents) to 5.00 MiB (5 extents).
  Logical volume mytestVG/blocks_allocated successfully resized.

root@s740:~# pvs --segments 
-olv_name,seg_start_pe,seg_size_pe,pvseg_start  -O pvseg_start
  LV               Start SSize  Start
  blocks_allocated     0      1     0
                       0      4     1
  blocks_allocated     1      1     5
                       0      4     6
  blocks_allocated     2      1    10
                       0      4    11
  blocks_allocated     3      1    15
                       0      4    16
  blocks_allocated     4      1    20
                       0 476917    21


how can i do this in reverse ?

when i specify the physical extend to be added, it works - but when is 
specifcy the physical extent to be removed,
the last one is being removed but not the specified one.

see here for example - i wanted to remove extent number 10 like i did 
add it, but instead extent number 20
is being removed

root@s740:~# lvresize mytestVG/blocks_allocated -l -1 /dev/sdb:10
  Ignoring PVs on command line when reducing.
  WARNING: Reducing active logical volume to 4.00 MiB.
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce mytestVG/blocks_allocated? [y/n]: y
  Size of logical volume mytestVG/blocks_allocated changed from 5.00 
MiB (5 extents) to 4.00 MiB (4 extents).
  Logical volume mytestVG/blocks_allocated successfully resized.

root@s740:~# pvs --segments 
-olv_name,seg_start_pe,seg_size_pe,pvseg_start  -O pvseg_start
  LV               Start SSize  Start
  blocks_allocated     0      1     0
                       0      4     1
  blocks_allocated     1      1     5
                       0      4     6
  blocks_allocated     2      1    10
                       0      4    11
  blocks_allocated     3      1    15
                       0 476922    16


how can i remove extent number 10 ?

is this a bug ?

regards
roland

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