[Qemu-devel] Block format 'raw' does not support the option 'locking' when disable image locking with option locking=off

[Qemu-devel] Block format 'raw' does not support the option 'locking' when disable image locking with option locking=off

[Changlimin]

Hi,
When running Oracle RAC, one image is shared between multiple vms, so I want to disable locking with option locking=off, But Block format 'raw' does not support the option 'locking'.
How to disable locking?

The version is git e822e81e350825dd94f41ee2538ff1432b812eb9

The command line is
-drive file=/var/lib/libvirt/images/r0605-share.img,format=raw,if=none,id=drive-virtio-disk1,cache=directsync,aio=native,locking=off \
-device virtio-blk-pci,scsi=off,bus=pci.0,addr=0xa,drive=drive-virtio-disk1,id=virtio-disk1 \

The error message is
-drive file=/var/lib/libvirt/images/r0605-share.img,format=raw,if=none,id=drive-virtio-disk1,cache=directsync,aio=native,locking=off: Block format 'raw' does not support the option 'locking'

BR
Chang Limin

Re: [Qemu-devel] Block format 'raw' does not support the option 'locking' when disable image locking with option locking=off

[Fam Zheng]

On Wed, 10/25 08:15, Changlimin wrote:
> Hi,
> When running Oracle RAC, one image is shared between multiple vms, so I want to disable locking with option locking=off, But Block format 'raw' does not support the option 'locking'.
> How to disable locking?
> 
> The version is git e822e81e350825dd94f41ee2538ff1432b812eb9
> 
> The command line is
> -drive file=/var/lib/libvirt/images/r0605-share.img,format=raw,if=none,id=drive-virtio-disk1,cache=directsync,aio=native,locking=off \
> -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0xa,drive=drive-virtio-disk1,id=virtio-disk1 \

Hi, in this case you probably want to use share-rw=on:

 -device virtio-blk-pci,share-rw=on,scsi=off,...

The -drive option is the same. This is more semantically correct than
locking=off as it means "the device can share the image with other QEMUs".

But for really disabling locking with "locking=off", the right syntax is:

 -drive file.filename=/var/lib/...,file.locking=off \

or alternatively:

 -drive driver=file,filename=/var/lib/...,locking=off \

Fam

Re: [Qemu-devel] Block format 'raw' does not support the option 'locking' when disable image locking with option locking=off

[Changlimin]

share-rw=on is good for raw format file, but bad for qcow2 format file:

Failed to get "write" lock
Is another process using the image?

Is this intented?

BR
Chang Limin

-----Original Message-----
From: Fam Zheng [mailto:famz@redhat.com] 
Sent: Wednesday, October 25, 2017 9:31 PM
To: changlimin 00148 (Cloud)
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] Block format 'raw' does not support the option 'locking' when disable image locking with option locking=off

On Wed, 10/25 08:15, Changlimin wrote:
> Hi,
> When running Oracle RAC, one image is shared between multiple vms, so I want to disable locking with option locking=off, But Block format 'raw' does not support the option 'locking'.
> How to disable locking?
> 
> The version is git e822e81e350825dd94f41ee2538ff1432b812eb9
> 
> The command line is
> -drive 
> file=/var/lib/libvirt/images/r0605-share.img,format=raw,if=none,id=dri
> ve-virtio-disk1,cache=directsync,aio=native,locking=off \ -device 
> virtio-blk-pci,scsi=off,bus=pci.0,addr=0xa,drive=drive-virtio-disk1,id
> =virtio-disk1 \

Hi, in this case you probably want to use share-rw=on:

 -device virtio-blk-pci,share-rw=on,scsi=off,...

The -drive option is the same. This is more semantically correct than locking=off as it means "the device can share the image with other QEMUs".

But for really disabling locking with "locking=off", the right syntax is:

 -drive file.filename=/var/lib/...,file.locking=off \

or alternatively:

 -drive driver=file,filename=/var/lib/...,locking=off \

Fam

Re: [Qemu-devel] Block format 'raw' does not support the option 'locking' when disable image locking with option locking=off

[Max Reitz]

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On 2017-10-26 03:06, Changlimin wrote:
> share-rw=on is good for raw format file, but bad for qcow2 format file:
> 
> Failed to get "write" lock
> Is another process using the image?
> 
> Is this intented?

Yes, because you can never share qcow2 image files between VMs.  The
qcow2 format itself does not support this, as it may lead to metadata
corruption.

Max


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Re: [Qemu-devel] Block format 'raw' does not support the option 'locking' when disable image locking with option locking=off

[Changlimin]

If the qcow2 file is created with preallocation=full, I think metadata will not corrupt when it is shared between two vms? Snapshot is not required. 

Is this right?

BR
Chang limin

-----Original Message-----
From: Max Reitz [mailto:mreitz@redhat.com] 
Sent: Thursday, October 26, 2017 3:12 PM
To: changlimin 00148 (Cloud); Fam Zheng
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] Block format 'raw' does not support the option 'locking' when disable image locking with option locking=off

On 2017-10-26 03:06, Changlimin wrote:
> share-rw=on is good for raw format file, but bad for qcow2 format file:
> 
> Failed to get "write" lock
> Is another process using the image?
> 
> Is this intented?

Yes, because you can never share qcow2 image files between VMs.  The
qcow2 format itself does not support this, as it may lead to metadata corruption.

Max

Re: [Qemu-devel] Block format 'raw' does not support the option 'locking' when disable image locking with option locking=off

[Max Reitz]

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On 2017-10-26 09:18, Changlimin wrote:
> If the qcow2 file is created with preallocation=full, I think metadata will not corrupt when it is shared between two vms? Snapshot is not required. 
> 
> Is this right?

I wouldn't count on it.

If you really want to take the risk, you can probably use the
file.locking=off option again.

Max


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Re: [Qemu-devel] Block format 'raw' does not support the option 'locking' when disable image locking with option locking=off

[Changlimin]

I tried locking=off, it supports qcow2

-drive file.filename=r 0605-share.img,format=qcow2,if=none,id=drive-virtio-disk1,cache=directsync,aio=native,file.locking=off 

Thank you very much.

BR
Chang Limin

-----Original Message-----
From: Max Reitz [mailto:mreitz@redhat.com] 
Sent: Thursday, October 26, 2017 3:33 PM
To: changlimin 00148 (Cloud); Fam Zheng
Cc: qemu-devel@nongnu.org; Qemu-block
Subject: Re: [Qemu-devel] Block format 'raw' does not support the option 'locking' when disable image locking with option locking=off

On 2017-10-26 09:18, Changlimin wrote:
> If the qcow2 file is created with preallocation=full, I think metadata will not corrupt when it is shared between two vms? Snapshot is not required. 
> 
> Is this right?

I wouldn't count on it.

If you really want to take the risk, you can probably use the file.locking=off option again.

Max

Re: [Qemu-devel] Block format 'raw' does not support the option 'locking' when disable image locking with option locking=off

[John Snow]

On 10/26/2017 03:18 AM, Changlimin wrote:
> If the qcow2 file is created with preallocation=full, I think metadata will not corrupt when it is shared between two vms? Snapshot is not required. 
> 
> Is this right?
> 

You can only share images read-only in this way. If you are asking to
share one qcow2 as r/w across two VMs, that's not going to work
regardless of how you allocate them, or the image format you are using.

--js

> BR
> Chang limin
>