qcow2 [virtio-scsi] devices when mapped to the guest shows as 0MB irrespective of the volume size

[chandrashekar shastri]

qcow2 [virtio-scsi] devices when mapped to the guest shows as 0MB irrespective of the volume size.

Kernel Version: 3.10.0-rc5+

Libvirt Version: 1.0.6

Qemu Version: 1.5.50

Steps to reproduce the issue:

1. Create a qcow2 voulme using the command qemu-img create -f qcow2 virtio-scsi11.img 10G
2. Add the virtio-scsi controller

 <controller type='scsi' index='0' model='virtio-scsi'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </controller>

3. Attach the qcow2 device to the guest, virsh attach-disk rhel64-64 /home/images/virtio-scsi11.img --persistent sdr --cache writethrough

4. Run the scan commnad echo ' - - - ' > /sys/class/scsi_host/host#/scan, if the attached volume doesn't get recognize.

5. Check the dmesg for the added volume.

6. Run fdisk -l command

Disk /dev/sdl: 0 MB, 197120 bytes
1 heads, 1 sectors/track, 385 cylinders, total 385 sectors
Units = cylinders of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

And observe that the 10G qcow2 volume shows as 0MB.

This is not seen with the raw image.

Disk /dev/sdm: 10.7 GB, 10737418240 bytes
64 heads, 32 sectors/track, 10240 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Expected Result:

The volume size for the qcow2 volumes should be shown correctly inside the guest to avoid confusion.

Guest XML:
virsh dumpxml rhel64-64
<domain type='kvm' id='4'>
  <name>rhel64-64</name>
  <uuid>48deb0e1-0c23-9be9-da12-2ead34864de2</uuid>
  <memory unit='KiB'>4096000</memory>
  <currentMemory unit='KiB'>4096000</currentMemory>
  <vcpu placement='static'>1</vcpu>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64' machine='pc-i440fx-1.5'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/local/bin/qemu-system-x86_64</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='none'/>
      <source file='/home/images/rhel64-64.qcow2'/>
      <target dev='hda' bus='ide'/>
      <alias name='ide0-0-0'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source file='/home/upstream/autotest/virt-test/shared/data/isos/RHEL-6.4-x86_64-DVD.iso'/>
      <target dev='hdb' bus='ide'/>
      <readonly/>
      <alias name='ide0-0-1'/>
      <address type='drive' controller='0' bus='0' target='0' unit='1'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi11.img'/>
      <target dev='sda' bus='scsi'/>
      <alias name='scsi0-0-0-0'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi1.img'/>
      <target dev='sdf' bus='scsi'/>
      <alias name='scsi0-0-0-5'/>
      <address type='drive' controller='0' bus='0' target='0' unit='5'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi9.img'/>
      <target dev='sdg' bus='scsi'/>
      <alias name='scsi0-0-0-6'/>
      <address type='drive' controller='0' bus='0' target='0' unit='6'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi8.img'/>
      <target dev='sdh' bus='scsi'/>
      <alias name='scsi1-0-0'/>
      <address type='drive' controller='1' bus='0' target='0' unit='0'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi10.img'/>
      <target dev='sdi' bus='scsi'/>
      <alias name='scsi1-0-1'/>
      <address type='drive' controller='1' bus='0' target='0' unit='1'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi7.img'/>
      <target dev='sdk' bus='scsi'/>
      <alias name='scsi1-0-3'/>
      <address type='drive' controller='1' bus='0' target='0' unit='3'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi6.img'/>
      <target dev='sdl' bus='scsi'/>
      <alias name='scsi1-0-4'/>
      <address type='drive' controller='1' bus='0' target='0' unit='4'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi5.img'/>
      <target dev='sdm' bus='scsi'/>
      <alias name='scsi1-0-5'/>
      <address type='drive' controller='1' bus='0' target='0' unit='5'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi12.img'/>
      <target dev='sdn' bus='scsi'/>
      <alias name='scsi1-0-6'/>
      <address type='drive' controller='1' bus='0' target='0' unit='6'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi11.img'/>
      <target dev='sdr' bus='scsi'/>
      <alias name='scsi2-0-3'/>
      <address type='drive' controller='2' bus='0' target='0' unit='3'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi2.img'/>
      <target dev='sdx' bus='scsi'/>
      <alias name='scsi3-0-2'/>
      <address type='drive' controller='3' bus='0' target='0' unit='2'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi4.img'/>
      <target dev='sdy' bus='scsi'/>
      <alias name='scsi3-0-3'/>
      <address type='drive' controller='3' bus='0' target='0' unit='3'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi3.img'/>
      <target dev='sdz' bus='scsi'/>
      <alias name='scsi3-0-4'/>
      <address type='drive' controller='3' bus='0' target='0' unit='4'/>
    </disk>
    <controller type='usb' index='0'>
      <alias name='usb0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
    </controller>
    <controller type='ide' index='0'>
      <alias name='ide0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
    </controller>
    <controller type='pci' index='0' model='pci-root'>
      <alias name='pci0'/>
    </controller>
    <controller type='scsi' index='0' model='virtio-scsi'>
      <alias name='scsi0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </controller>
    <controller type='scsi' index='1'>
      <alias name='scsi1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    </controller>
    <controller type='scsi' index='2'>
      <alias name='scsi2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </controller>
    <controller type='scsi' index='3'>
      <alias name='scsi3'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
    </controller>
    <interface type='network'>
      <mac address='52:54:00:9d:cf:bb'/>
      <source network='default'/>
      <target dev='vnet0'/>
      <model type='rtl8139'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/1'/>
      <target port='0'/>
      <alias name='serial0'/>
    </serial>
    <console type='pty' tty='/dev/pts/1'>
      <source path='/dev/pts/1'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    </console>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='5900' autoport='yes' listen='127.0.0.1'>
      <listen type='address' address='127.0.0.1'/>
    </graphics>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    </video>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
    </memballoon>
  </devices>
  <seclabel type='none' model='selinux'/>
</domain>

[chandrashekar shastri (cshastri)]

I tried booting with the qemu and observed the same thing.

qemu-system-x86_64 /home/images/rhel64-64.qcow2 -drive if=none,id=hd,file=/home/images/virtio-scsi11.img -device virtio-scsi-pci,id=scsi --enable-kvm -device scsi-hd,drive=hd -m 2000

After creating the filesystem tried running the iozone and noticed disk out of space issue.

[Stefan Hajnoczi (stefanha)]

On Thu, Jul 4, 2013 at 9:07 AM, chandrashekar shastri
<email address hidden> wrote:
> Public bug reported:
>
> qcow2 [virtio-scsi] devices when mapped to the guest shows as 0MB
> irrespective of the volume size.

qemu-system-x86_64 -enable-kvm -m 1024 -cpu host,+x2apic \
    -device virtio-scsi-pci,id=virtio-scsi0 \
    -drive if=none,cache=none,file=test2.qcow2,format=qcow2,id=drive0 \
    -device scsi-hd,drive=drive0 \
    -cdrom rhel64_live.iso

Works fine in qemu.git/master with a RHEL6.4 guest.

What happens when you run "blockdev --getsize64 /dev/sdb" in your guest?

Please also post the output of "qemu-img info
/home/images/virtio-scsi11.img" on the host.

Stefan

[chandrashekar shastri (cshastri)]

Guest output:
-------------------

[root@redhat ~]# ls -lrt /dev/sd
sda sda1 sda2 sdb
[root@redhat ~]# ls -lrt /dev/sd
sda sda1 sda2 sdb
[root@redhat ~]# ls -lrt /dev/sdb
brw-rw----. 1 root disk 8, 16 Jul 4 21:58 /dev/sdb
[root@redhat ~]# blockdev --getsize64 /dev/sdb
197120
[root@redhat ~]# fdisk -l /dev/sdb

Disk /dev/sdb: 0 MB, 197120 bytes
1 heads, 1 sectors/track, 385 cylinders, total 385 sectors
Units = cylinders of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

[root@redhat ~]#

Host Output:
------------------
qemu-img info virtio-scsi23.img
image: virtio-scsi23.img
file format: qcow2
virtual size: 15G (16106127360 bytes)
disk size: 196K
cluster_size: 65536

XML Output:
-----------------

<disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='writethrough'/>
      <source file='/home/images/virtio-scsi23.img'/>
      <target dev='sdz' bus='scsi'/>
      <address type='drive' controller='3' bus='0' target='0' unit='4'/>
    </disk>

[Stefan Hajnoczi (stefanha)]

<driver name='qemu' type='raw' cache='writethrough'/>
<source file='/home/images/virtio-scsi23.img'/>

You created a qcow2 file but told libvirt it's type='raw'. Therefore the guest sees a raw file and not a qcow2 file. The qcow2 file is only 196 KB on disk (qemu-img output shows this), this matches with the blocksize --getsize64 output inside the guest.

Change type='raw' to type='qcow2' in your XML and the issue will be resolved.

[chandrashekar shastri (cshastri)]

Thanks Stefanha.

If we use the commad virsh attach-disk rhel64-64 /home/images/virtio-scsi11.img --persistent sdr --cache writethrough the qcow2 images will also gets added as raw which is by default. Hence we should use

"virsh attach-disk rhel64-64 /home/images/virtio-scsi11.img --persistent sdr --cache writethrough --sourcetype file --driver qemu --subdriver qcow2".