Re: [libvirt RFCv4 06/20] libvirt: introduce virDomainSaveParametersFlags public API

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On Wed, Apr 27, 2022 at 11:13:25PM +0200, Claudio Fontana wrote:
> add new API in order to be able to extend parameters to the domain
> save operation. We will use it to fit the existing arguments of
> VirDomainSaveFlags, and then add parallel saves functionality.
> 
> Signed-off-by: Claudio Fontana <cfontana@xxxxxxx>
> ---
>  include/libvirt/libvirt-domain.h | 45 ++++++++++++++++++++++++++++
>  src/driver-hypervisor.h          |  7 +++++
>  src/libvirt-domain.c             | 51 ++++++++++++++++++++++++++++++++
>  src/libvirt_public.syms          |  5 ++++
>  4 files changed, 108 insertions(+)
> 
> diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-domain.h
> index 9aa214f3df..b870a73b64 100644
> --- a/include/libvirt/libvirt-domain.h
> +++ b/include/libvirt/libvirt-domain.h
> @@ -1481,6 +1481,8 @@ typedef enum {
>      VIR_DOMAIN_SAVE_RUNNING      = 1 << 1, /* Favor running over paused */
>      VIR_DOMAIN_SAVE_PAUSED       = 1 << 2, /* Favor paused over running */
>      VIR_DOMAIN_SAVE_RESET_NVRAM  = 1 << 3, /* Re-initialize NVRAM from template */
> +    /** Since: v8.3.0 */
> +    VIR_DOMAIN_SAVE_PARALLEL     = 1 << 4, /* Parallel Save/Restore to multiple files */
>  } virDomainSaveRestoreFlags;
>  
>  int                     virDomainSave           (virDomainPtr domain,
> @@ -1489,6 +1491,10 @@ int                     virDomainSaveFlags      (virDomainPtr domain,
>                                                   const char *to,
>                                                   const char *dxml,
>                                                   unsigned int flags);
> +int                     virDomainSaveParametersFlags (virDomainPtr domain,
> +                                                      virTypedParameterPtr params,
> +                                                      int nparams,
> +                                                      unsigned int flags);

BTW, we don't need 'Flags' as a suffix here.  We only add 'Flags' suffixes
when we had an existing API that was missing flags and need a new unique
name. I'd also probably shorten to 'Params', eg in this case, it is
sufficient to have  virDomainSaveParams and virDomainRestoreParams.

>  int                     virDomainRestore        (virConnectPtr conn,
>                                                   const char *from);
>  int                     virDomainRestoreFlags   (virConnectPtr conn,
> @@ -1496,6 +1502,45 @@ int                     virDomainRestoreFlags   (virConnectPtr conn,
>                                                   const char *dxml,
>                                                   unsigned int flags);
>  
> +/**
> + * VIR_SAVE_PARAM_FILE:
> + *
> + * the parameter used to specify the savestate file to save to or restore from.
> + * For parallel saves, this is the main file, with the extra connections adding suffix
> + * .1 .2 .3 ... up to VIR_SAVE_PARAM_PARALLEL_CONNECTIONS.
> + *
> + * Since: v8.3.0
> + */
> +# define VIR_SAVE_PARAM_FILE                     "file"
> +
> +/**
> + * VIR_SAVE_PARAM_DXML:
> + *
> + * an optional parameter used to adjust guest xml on restore.
> + * If the hypervisor supports it, it can be used to alter
> + * host-specific portions of the domain XML that will be used when
> + * restoring an image.  For example, it is possible to alter the
> + * device while the domain is stopped.
> + *
> + * Since: v8.3.0
> + */
> +# define VIR_SAVE_PARAM_DXML                     "dxml"
> +
> +/**
> + * VIR_SAVE_PARAM_PARALLEL_CONNECTIONS:
> + *
> + * this optional parameter mirrors the migration parameter
> + * VIR_MIGRATE_PARAM_PARALLEL_CONNECTIONS.
> + *
> + * This parameter is used when saving or restoring state files
> + * in parallel using the flag VIR_DOMAIN_SAVE_PARALLEL .
> + * It specifies the number of extra files to save/restore
> + * using parallel connections.
> + *
> + * Since: v8.3.0
> + */
> +# define VIR_SAVE_PARAM_PARALLEL_CONNECTIONS     "parallel.connections"
> +
>  /* See below for virDomainSaveImageXMLFlags */
>  char *          virDomainSaveImageGetXMLDesc    (virConnectPtr conn,
>                                                   const char *file,
> diff --git a/src/driver-hypervisor.h b/src/driver-hypervisor.h
> index 4423eb0885..a4e1d21e76 100644
> --- a/src/driver-hypervisor.h
> +++ b/src/driver-hypervisor.h
> @@ -240,6 +240,12 @@ typedef int
>                           const char *dxml,
>                           unsigned int flags);
>  
> +typedef int
> +(*virDrvDomainSaveParametersFlags)(virDomainPtr domain,
> +                                   virTypedParameterPtr params,
> +                                   int nparams,
> +                                   unsigned int flags);
> +
>  typedef int
>  (*virDrvDomainRestore)(virConnectPtr conn,
>                         const char *from);
> @@ -1489,6 +1495,7 @@ struct _virHypervisorDriver {
>      virDrvDomainGetControlInfo domainGetControlInfo;
>      virDrvDomainSave domainSave;
>      virDrvDomainSaveFlags domainSaveFlags;
> +    virDrvDomainSaveParametersFlags domainSaveParametersFlags;
>      virDrvDomainRestore domainRestore;
>      virDrvDomainRestoreFlags domainRestoreFlags;
>      virDrvDomainSaveImageGetXMLDesc domainSaveImageGetXMLDesc;
> diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
> index cbd7902d2d..9e4fcfd022 100644
> --- a/src/libvirt-domain.c
> +++ b/src/libvirt-domain.c
> @@ -959,6 +959,57 @@ virDomainSaveFlags(virDomainPtr domain, const char *to,
>      return -1;
>  }
>  
> +/**
> + * virDomainSaveParametersFlags:
> + * @domain: a domain object
> + * @params: save parameters
> + * @nparams: number of save parameters
> + * @flags: bitwise-OR of virDomainSaveRestoreFlags
> + *
> + * This method extends virDomainSaveFlags by adding parameters to Save.
> + *
> + * If @flags includes VIR_DOMAIN_SAVE_PARALLEL, then libvirt will
> + * attempt to trigger a parallel transfer to multiple files,
> + * where the number of extra files is determined by the parameter
> + * VIR_SAVE_PARAM_PARALLEL_CONNECTIONS.
> + *
> + * Returns 0 in case of success and -1 in case of failure.
> + */
> +int
> +virDomainSaveParametersFlags(virDomainPtr domain,
> +                             virTypedParameterPtr params, int nparams,
> +                             unsigned int flags)
> +{
> +    virConnectPtr conn;
> +
> +    VIR_DOMAIN_DEBUG(domain, "params=%p, nparams=%d, flags=0x%x",
> +                     params, nparams, flags);
> +    VIR_TYPED_PARAMS_DEBUG(params, nparams);
> +
> +    virResetLastError();
> +
> +    virCheckDomainReturn(domain, -1);
> +    conn = domain->conn;
> +
> +    virCheckReadOnlyGoto(conn->flags, error);
> +
> +    VIR_EXCLUSIVE_FLAGS_GOTO(VIR_DOMAIN_SAVE_RUNNING,
> +                             VIR_DOMAIN_SAVE_PAUSED,
> +                             error);
> +
> +    if (conn->driver->domainSaveParametersFlags) {
> +        if (conn->driver->domainSaveParametersFlags(domain, params, nparams, flags) < 0)
> +            goto error;
> +        return 0;
> +    }
> +
> +    virReportUnsupportedError();
> +
> + error:
> +    virDispatchError(domain->conn);
> +    return -1;
> +}
> +
>  
>  /**
>   * virDomainRestore:
> diff --git a/src/libvirt_public.syms b/src/libvirt_public.syms
> index f93692c427..eb3a7afb75 100644
> --- a/src/libvirt_public.syms
> +++ b/src/libvirt_public.syms
> @@ -916,4 +916,9 @@ LIBVIRT_8.0.0 {
>          virDomainSetLaunchSecurityState;
>  } LIBVIRT_7.8.0;
>  
> +LIBVIRT_8.3.0 {
> +    global:
> +        virDomainSaveParametersFlags;
> +} LIBVIRT_8.0.0;
> +
>  # .... define new API here using predicted next version number ....
> -- 
> 2.34.1
> 

With regards,
Daniel
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