[libvirt] directory storage pools reported available space

[Ryan Harper]

We recently had an issue with not being able to allocate the full
capacity of a directory based storage pool.  The reported value via
pool-info was larger than what was available to the image creator.

Looking at the storage code, in virStorageBackendFileSystemRefresh()
we're using statvfs, and reporting back 

   pool->def->available = ((unsigned long long)sb.f_bfree *
                          (unsigned long long)sb.f_bsize);

Which is the amount of blocks available, including any root reservation
if present on the filesystem.

This does't line up with df output , which at least on RHEL5 and 6
systems reports the available space from f_bavail, which excludes
and reserved space.

Is it reasonable to have the available value line up with output from df
and not report reserved space?

-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh at us.ibm.com