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

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On 4/28/22 11:05 AM, Daniel P. Berrangé wrote:
> 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.
> 
> Regardless of my thoughts on the parallel save to multiple files,
> I think this API is conceptually a benefit, given it is more
> extensible long term. Likewise for the restore counterpart.
> 
> Could you split off the new save/restore APIs into a standalone
> patch series, that simply wires them up with the existing
> functionality. That way we can get the APIs merged without being
> blocked on any ongoing parallel save design debate.
> 
> IOW, this patch and the next 5 that follow could be merged
> fairly easily, if the VIR_DOMAIN_SAVE_PARALLEL flag is added
> in a later patch.

Absolutely, will work on it.

> 
>>
>> 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);
>>  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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