[libvirt] [PATCH v3 19/28] qemu_conf: Introduce metadata_lock_manager

[John Ferlan]

On 08/27/2018 04:08 AM, Michal Privoznik wrote:
> This config option allows users to set and enable lock manager
> for domain metadata. The lock manager is going to be used by
> security drivers to serialize each other when changing a file
> ownership or changing the SELinux label. The only supported lock
> manager is 'lockd' for now.
> 
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
>  src/qemu/libvirtd_qemu.aug         |  1 +
>  src/qemu/qemu.conf                 |  6 ++++++
>  src/qemu/qemu_conf.c               | 13 +++++++++++++
>  src/qemu/qemu_conf.h               |  1 +
>  src/qemu/test_libvirtd_qemu.aug.in |  1 +
>  5 files changed, 22 insertions(+)
> 
> diff --git a/src/qemu/libvirtd_qemu.aug b/src/qemu/libvirtd_qemu.aug
> index ddc4bbfd1d..42e325d4fb 100644
> --- a/src/qemu/libvirtd_qemu.aug
> +++ b/src/qemu/libvirtd_qemu.aug
> @@ -98,6 +98,7 @@ module Libvirtd_qemu =
>                   | bool_entry "relaxed_acs_check"
>                   | bool_entry "allow_disk_format_probing"
>                   | str_entry "lock_manager"
> +                 | str_entry "metadata_lock_manager"
>  
>     let rpc_entry = int_entry "max_queued"
>                   | int_entry "keepalive_interval"
> diff --git a/src/qemu/qemu.conf b/src/qemu/qemu.conf
> index cd57b3cc69..06caa39232 100644
> --- a/src/qemu/qemu.conf
> +++ b/src/qemu/qemu.conf
> @@ -659,6 +659,12 @@
>  #lock_manager = "lockd"
>  
>  
> +# To serialize two daemons trying to change metadata on a file,

Just two? ;-)

> +# libvirt offers a locking mechanism. Currently, only "lockd" is
> +# supported (or no locking at all if unset).
> +#
> +#metadata_lock_manager = "lockd"
> +

Should we state that the domain locking is independent of the metadata
daemon locking? I know it's obvious to the author (and now the
reviewer), but for the first time reader of the config file.

And of course that leaves the question on the table for the consumer
about what is meant by multiple daemons. As in, which daemons...  That
little factoid would be lost in the commit message.

Assuming some beefed up text,

Reviewed-by: John Ferlan <jferlan at redhat.com>

John

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