Description of problem:
In LVM based storage, create a volume and dump info, found the capacity and allocation values are more bigger than the defined values.

Version-Release number of selected component (if applicable):
# uname -a
Linux dhcp-65-85.nay.redhat.com 2.6.32-99.el6.x86_64 #1 SMP Fri Jan 14 10:46:00
EST 2011 x86_64 x86_64 x86_64 GNU/Linux

libvirt-0.8.7-4.el6.x86_64
kernel-2.6.32-99.el6.x86_64
qemu-kvm-0.12.1.2-2.132.el6.x86_64

How reproducible:
Always

Steps to Reproduce:
1. Create a LVM storage pool
# cat test.xml 
     <pool type='logical'>
       <name>test</name>
       <source>
         <name>test</name>
         <format type='lvm2'/>
         <device path='/dev/sda5'/>
       </source>
       <target>
         <path>/dev/test</path>
       </target>
     </pool>

# virsh pool-define test.xml 
Pool test defined from test.xml

# virsh pool-build test
Pool test built

# virsh pool-start test
Pool test started

# virsh pool-list 
Name                 State      Autostart 
-----------------------------------------
default              active     yes       
test                 active     no        

2. Create a volume in this storage
# cat vol1.xml 
<volume>
            <name>vol1</name>
            <capacity>2147484672</capacity>
            <allocation>2147484672</allocation>
            <target>
                <format type='raw'/>
            </target>
        </volume>

# virsh vol-create test vol1.xml 
Vol vol1 created from vol1.xml

# virsh vol-dumpxml --pool test vol1
<volume>
  <name>vol1</name>
  <key>5IDQQg-Lhfg-z9iA-jau4-I2GF-vuK8-XBSdAG</key>
  <source>
    <device path='/dev/sda5'>
      <extent start='2151677952' end='4303355904'/>
    </device>
  </source>
  <capacity>2151677952</capacity>
  <allocation>2151677952</allocation>
  <target>
    <path>/dev/test/vol1</path>
    <permissions>
      <mode>0600</mode>
      <owner>0</owner>
      <group>6</group>
      <label>system_u:object_r:fixed_disk_device_t:s0</label>
    </permissions>
  </target>
</volume>


3. Some debug info about actual allocated sizes:
....
Jan 29 00:15:35 dhcp-65-85 libvirtd: 00:15:35.822: 26681: warning : storageVolumeCreateXML:1301 :  voldef->capacity: 2147484672
Jan 29 00:15:35 dhcp-65-85 libvirtd: 00:15:35.822: 26681: warning : virStorageBackendLogicalCreateVol:607 :  vol->capacity: 2147484672
Jan 29 00:15:35 dhcp-65-85 libvirtd: 00:15:35.822: 26681: warning : virStorageBackendLogicalCreateVol:612 :  capacity: 2097153
....

  
Actual results:
2151677952 / 1024= 2101248 kb display in volume dumpxml which is much bigger than 2097153 kb. 

Expected results:
The expected result in volume dumpxml should be as debug info: 2147484672 /1024=2097153 kb.

Additional info:

This bug can also be reproduced with following xml with different size 2147483649.

# cat vol.xml 
    <volume>
            <name>vol</name>
            <capacity>2147483649</capacity>
            <allocation>2147483649</allocation>
            <target>
                <format type='raw'/>
            </target>
        </volume>

# virsh vol-create test vol.xml 
Vol vol created from vol.xml

# virsh vol-dumpxml --pool test vol
<volume>
  <name>vol</name>
  <key>rf2n5V-GkuP-N3p5-ddUQ-21q5-y9TH-dFA6Y0</key>
  <source>
    <device path='/dev/sda5'>
      <extent start='0' end='2151677952'/>
    </device>
  </source>
  <capacity>2151677952</capacity>
  <allocation>2151677952</allocation>
  <target>
    <path>/dev/test/vol</path>
    <permissions>
      <mode>0600</mode>
      <owner>0</owner>
      <group>6</group>
      <label>system_u:object_r:fixed_disk_device_t:s0</label>
    </permissions>
  </target>
</volume>