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Bug 670529 - LVM storage pool creates smaller-than-expected volume
Summary: LVM storage pool creates smaller-than-expected volume
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: libvirt
Version: 6.1
Hardware: Unspecified
OS: Unspecified
low
medium
Target Milestone: rc
: ---
Assignee: Osier Yang
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2011-01-18 15:39 UTC by Matthew Booth
Modified: 2011-05-19 13:25 UTC (History)
7 users (show)

Fixed In Version: libvirt-0.8.7-4.el6
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2011-05-19 13:25:47 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2011:0596 0 normal SHIPPED_LIVE libvirt bug fix and enhancement update 2011-05-18 17:56:36 UTC

Description Matthew Booth 2011-01-18 15:39:12 UTC 
Description of problem:
I have some code which creates a volume with:
        <volume>
            <name>$name</name>
            <capacity>$size</capacity>
            <allocation>$allocation</allocation>
            <target>
                <format type='$format'/>
            </target>
        </volume>

When the storage pool is LVM-backed, and size is 2147483649 bytes, the volume is created successfully, but the size is 2147483648 bytes (1 byte too small). This results in an error when I try to write 2147483649 bytes to the newly created volume.

danpb points out the offending code does:
  snprintf(size, sizeof(size)-1, "%lluK", vol->capacity/1024);

The rounding is due to the 1k granularity of an LVM volume. However, this code rounds down. It would be safer if it rounded up.

Version-Release number of selected component (if applicable):
Actually reproduced in libvirt-0.8.3-2.fc14.x86_64, but present in RHEL 6.
Comment 2 Osier Yang 2011-01-22 11:18:52 UTC 
http://www.redhat.com/archives/libvir-list/2011-January/msg00932.html

patch posted to upstream.
Comment 3 Osier Yang 2011-01-27 09:20:41 UTC 
http://post-office.corp.redhat.com/archives/rhvirt-patches/2011-January/msg01409.html

patch sent to rhvirt-patches
Comment 6 Min Zhan 2011-01-28 09:57:36 UTC 
Verified with Passed with below environment:
# 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

Steps:
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 --all
Name                 State      Autostart 
-----------------------------------------
default              active     yes       
pool-mpath           inactive   no        
test                 active     no  

# virsh pool-dumpxml test
<pool type='logical'>
  <name>test</name>
  <uuid>d54b19d3-339c-112c-27f8-11fff54381e1</uuid>
  <capacity>31448891392</capacity>
  <allocation>0</allocation>
  <available>31448891392</available>
  <source>
    <device path='/dev/sda5'/>
    <name>test</name>
    <format type='lvm2'/>
  </source>
  <target>
    <path>/dev/test</path>
    <permissions>
      <mode>0700</mode>
      <owner>-1</owner>
      <group>-1</group>
    </permissions>
  </target>
</pool>

2. Create a volume in lvm pool.
# 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

[root@dhcp-65-85 ~]# virsh vol-dumpxml --pool test vol
<volume>
  <name>vol</name>
  <key>wQ7Ilp-unr9-ED1J-LqmN-3Bm5-5rYF-iTOlfC</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>

3. According to this bug description, 2147483649 / 1024= 2097152.0009 kb, it should round up,so correct capacity and allocation should be 2097153 kb, that is 2097153*1024=2147484672.

I also have some debug info below that the allocated size is correct, 2097153. So I thinks the patch fixed the bug. 

....
Jan 29 00:15:35 dhcp-65-85 libvirtd: 00:15:35.822: 26681: warning : storageVolumeCreateXML:1301 :  voldef->capacity: 2147483649
Jan 29 00:15:35 dhcp-65-85 libvirtd: 00:15:35.822: 26681: warning : virStorageBackendLogicalCreateVol:607 :  vol->capacity: 2147483649
Jan 29 00:15:35 dhcp-65-85 libvirtd: 00:15:35.822: 26681: warning : virStorageBackendLogicalCreateVol:612 :  capacity: 2097153
....

But as we see in volume dumpxml, the actual allocation number display as 2151677952 / 1024= 2101248 kb, which is much bigger than the expected 2097153 kb. About the incorrect display problem I will file a new bug 673455 for this .


----------------
Also, I can reproduce this bug 670529 with libvirt-0.8.1-27.el6.x86_64,libvirt-0.8.7-3.el6.x86_64. When I use # virsh vol-dumpxml, the capacity and allocation are both 2147483648.

# virsh vol-dumpxml --pool test vol
<volume>
  <name>vol</name>
  <key>vIbXY1-LTcK-1zY7-kumN-KOm7-3UAQ-BZ1N8x</key>
  <source>
    <device path='/dev/sda5'>
      <extent start='0' end='2147483648'/>
    </device>
  </source>
  <capacity>2147483648</capacity>
  <allocation>2147483648</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>
Comment 9 errata-xmlrpc 2011-05-19 13:25:47 UTC 
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHBA-2011-0596.html
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