[linux-lvm] bug? shrink lv by specifying pv extent to be removed does not behave as expected

[Roland]

hi,

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


root at 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 at 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 at 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 at 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 at 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 at 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 at 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