Description of problem:
When converting a mirrored LV to linear using "lvconvert -m0", if the PV to
remove is specified on the command line and that PV is completely allocated,
lvconvert fails with "No free extents on physical volume".

Version-Release number of selected component (if applicable):
lvm2-2.02.27-2.el4, upstream CVS

How reproducible:
100%

Steps to Reproduce:
1. lvcreate -l <PV SIZE> -n l0 -m1 mvg0 /dev/pv0 /dev/pv1 /dev/pv2:0
2. lvconvert -m0 mvg0/l0 /dev/pv0

  
Actual results:
# lvconvert -m0 mvg0/m0 /dev/pv0
  No free extents on physical volume "/dev/pv0"
  No specified PVs have space available


Expected results:
# lvconvert -m0 mvg0/m0 /dev/pv0
  Logical volume m0 converted.


Additional info:
Looked into this with Marco and we found that this is happening here:

The problem is caused by this check in _create_pv_entry() function
./tools/toollib.c:_create_pv_entry():

       if (allocatable_only &&
           (pvl->pv->pe_count == pvl->pv->pe_alloc_count)) {
               log_err("No free extents on physical volume "%s"", pvname);
               return 1;
       }

Since converting to a linear volume does not require any new extent allocations
this check is invalid.

Forcing allocatable=0 in the debugger allows the command to complete without
error and produces the expected result.

Marco checked with Nick who couldn't see a problem with making this change -
patch from Marco attached.