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Re: [libvirt] [PATCH 23/23] Change the default QEMU lock manager to 'lockd'



On 08/09/2012 09:20 AM, Daniel P. Berrange wrote:
> From: "Daniel P. Berrange" <berrange redhat com>
> 
> The current default QEMU lock manager is the 'nop' lock manager,
> which obviously does not perform any locking. The new virtlockd
> daemon is able to work out of the box with zero configuration
> in single-host only mode. Enable this as the default lock manager
> for all QEMU guests

Question - can virtlockd also be made to work in multi-host mode for
shared file systems that support fcntl locking, possibly by adding some
non-default configuration?

> 
> * src/qemu/qemu.conf: Update docs for lock_driver parameter
> * src/qemu/qemu_conf.c: Change default lock manager to 'lockd'
> 
> Signed-off-by: Daniel P. Berrange <berrange redhat com>
> ---
>  src/qemu/qemu.conf                 | 17 ++++++++++-------
>  src/qemu/qemu_conf.c               |  2 +-
>  src/qemu/test_libvirtd_qemu.aug.in |  2 +-
>  3 files changed, 12 insertions(+), 9 deletions(-)

Missing documentation in docs/locking.html.in on how to use virtlockd
instead of sanlock, and any tips on setting up multi-box environments
(if those are indeed possible).

> 
> diff --git a/src/qemu/qemu.conf b/src/qemu/qemu.conf
> index ed4683c..b232762 100644
> --- a/src/qemu/qemu.conf
> +++ b/src/qemu/qemu.conf
> @@ -318,14 +318,17 @@
>  #
>  #allow_disk_format_probing = 1
>  
> -
> -# To enable 'Sanlock' project based locking of the file
> -# content (to prevent two VMs writing to the same
> -# disk), uncomment this
> +# By default the QEMU driver talks to the 'virtlockd'

Is the config setting 'virtlockd'...

> +# daemon to acquire exclusive locks for all guest disk
> +# images associated with a running VM.
>  #
> -#lock_manager = "sanlock"
> -
> -
> +# To revert to behaviour of previous releases which did
> +# not acquire any locks, set this to 'nop'.
> +#
> +# To enable use of the external 'sanlock' locking
> +# daemon, change this to 'sanlock'.
> +#
> +#lock_manager = "lockd"

...or 'lockd'?  This needs to be consistent.  Maybe call out:

This defaults to 'lockd' to use the virtlockd(8) daemon...

Hmm, that means an earlier patch is also missing a virtlockd.8 man page.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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