[PATCH LVM2] set stripes = 0 for the log device only allocation

[PATCH LVM2] set stripes = 0 for the log device only allocation

[Jun'ichi Nomura]

Hi,

This patch fixes the allocation failure at adding mirror log
if there is only one PV available.


In lib/metadata/lv_manip.c:_allocate(), the number of stripes
is used for calculation of the number of necessary PVs.
    if (areas_size < ah->area_count + ah->log_count) {

On the other hand, lvconvert gives stripes = 1 even if the
allocation request is for log device only.

As a result, the check above will fail if there is only one
PV available and the command will fail as followings:
  Not enough PVs with free space available for parallel allocation.

even though the log device should be allocated from the free PV
without problem.

For log-only allocation, don't give stripes = 1 to the allocator.
The stripes value is considered to be the number of stripes
for which the allocation is requested. (i.e. ah->area_count)


Patch applicable to LVM2 2.02.16.
The patch depends on safe-area_multiple.patch for correct handling
of stripes = 0 by the allocator.

Shell script to reproduce the problem and the sample metadata
is attached for reference.
You can reproduce the problem with just executing the script
without additional parameters.

Thanks,
-- 
Jun'ichi Nomura, NEC Corporation of America
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