Re: [RFC 5/6] migration: Deprecate block migration

[Stefan Hajnoczi]

On Mon, Jun 12, 2023 at 09:33:43PM +0200, Juan Quintela wrote:
> It is obsolete.  It is better to use driver_mirror+NBD instead.
> 
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Eric Blake <eblake@redhat.com>
> CC: Stefan Hajnoczi <stefanha@redhat.com>
> CC: Hanna Czenczek <hreitz@redhat.com>
> 
> Signed-off-by: Juan Quintela <quintela@redhat.com>
> 
> ---
> 
> Can any of you give one example of how to use driver_mirror+NBD for
> deprecated.rst?

Please see "QMP invocation for live storage migration with
``drive-mirror`` + NBD" in docs/interop/live-block-operations.rst for a
detailed explanation.

> 
> Thanks, Juan.
> ---
>  docs/about/deprecated.rst |  6 ++++++
>  qapi/migration.json       | 29 +++++++++++++++++++++++++----
>  migration/block.c         |  2 ++
>  migration/options.c       |  7 +++++++
>  4 files changed, 40 insertions(+), 4 deletions(-)
> 
> diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
> index 518672722d..173c5ba5cb 100644
> --- a/docs/about/deprecated.rst
> +++ b/docs/about/deprecated.rst
> @@ -454,3 +454,9 @@ Everything except ``-incoming defer`` are deprecated.  
> This allows to
>  setup parameters before launching the proper migration with
>  ``migrate-incoming uri``.
>  
> +block migration (since 8.1)
> +'''''''''''''''''''''''''''
> +
> +Block migration is too inflexible.  It needs to migrate all block
> +devices or none.  Use driver_mirror+NBD instead.

blockdev-mirror with NBD

> +
> diff --git a/qapi/migration.json b/qapi/migration.json
> index b71e00737e..a8497de48d 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -258,11 +258,16 @@
>  #     blocked.  Present and non-empty when migration is blocked.
>  #     (since 6.0)
>  #
> +# Features:
> +#
> +# @deprecated: @disk migration is deprecated.  Use driver_mirror+NBD

blockdev-mirror with NBD

> +#     instead.
> +#
>  # Since: 0.14
>  ##
>  { 'struct': 'MigrationInfo',
>    'data': {'*status': 'MigrationStatus', '*ram': 'MigrationStats',
> -           '*disk': 'MigrationStats',
> +           '*disk': { 'type': 'MigrationStats', 'features': ['deprecated'] },
>             '*vfio': 'VfioStats',
>             '*xbzrle-cache': 'XBZRLECacheStats',
>             '*total-time': 'int',
> @@ -497,6 +502,9 @@
>  #
>  # Features:
>  #
> +# @deprecated: @block migration is deprecated.  Use driver_mirror+NBD

blockdev-mirror with NBD

> +#     instead.
> +#
>  # @unstable: Members @x-colo and @x-ignore-shared are experimental.
>  #
>  # Since: 1.2
> @@ -506,7 +514,8 @@
>             'compress', 'events', 'postcopy-ram',
>             { 'name': 'x-colo', 'features': [ 'unstable' ] },
>             'release-ram',
> -           'block', 'return-path', 'pause-before-switchover', 'multifd',
> +           { 'name': 'block', 'features': [ 'deprecated' ] },
> +           'return-path', 'pause-before-switchover', 'multifd',
>             'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate',
>             { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] },
>             'validate-uuid', 'background-snapshot',
> @@ -789,6 +798,9 @@
>  #
>  # Features:
>  #
> +# @deprecated: Member @block-incremental is obsolete. Use
> +#     driver_mirror+NBD instead.

blockdev-mirror with NBD

> +#
>  # @unstable: Member @x-checkpoint-delay is experimental.
>  #
>  # Since: 2.4
> @@ -803,7 +815,7 @@
>             'tls-creds', 'tls-hostname', 'tls-authz', 'max-bandwidth',
>             'downtime-limit',
>             { 'name': 'x-checkpoint-delay', 'features': [ 'unstable' ] },
> -           'block-incremental',
> +           { 'name': 'block-incremental', 'features': [ 'deprecated' ] },
>             'multifd-channels',
>             'xbzrle-cache-size', 'max-postcopy-bandwidth',
>             'max-cpu-throttle', 'multifd-compression',
> @@ -945,6 +957,9 @@
>  #
>  # Features:
>  #
> +# @deprecated: Member @block-incremental is obsolete. Use
> +#     driver_mirror+NBD instead.

blockdev-mirror with NBD

> +#
>  # @unstable: Member @x-checkpoint-delay is experimental.
>  #
>  # TODO: either fuse back into MigrationParameters, or make
> @@ -972,7 +987,8 @@
>              '*downtime-limit': 'uint64',
>              '*x-checkpoint-delay': { 'type': 'uint32',
>                                       'features': [ 'unstable' ] },
> -            '*block-incremental': 'bool',
> +            '*block-incremental': { 'type': 'bool',
> +                                    'features': [ 'deprecated' ] },
>              '*multifd-channels': 'uint8',
>              '*xbzrle-cache-size': 'size',
>              '*max-postcopy-bandwidth': 'size',
> @@ -1137,6 +1153,9 @@
>  #
>  # Features:
>  #
> +# @deprecated: Member @block-incremental is obsolete. Use
> +#     driver_mirror+NBD instead.

blockdev-mirror with NBD

> +#
>  # @unstable: Member @x-checkpoint-delay is experimental.
>  #
>  # Since: 2.4
> @@ -1161,6 +1180,8 @@
>              '*downtime-limit': 'uint64',
>              '*x-checkpoint-delay': { 'type': 'uint32',
>                                       'features': [ 'unstable' ] },
> +            '*block-incremental': { 'type': 'bool',
> +                                    'features': [ 'deprecated' ] },
>              '*block-incremental': 'bool',
>              '*multifd-channels': 'uint8',
>              '*xbzrle-cache-size': 'size',
> diff --git a/migration/block.c b/migration/block.c
> index b9580a6c7e..2521a22269 100644
> --- a/migration/block.c
> +++ b/migration/block.c
> @@ -722,6 +722,8 @@ static int block_save_setup(QEMUFile *f, void *opaque)
>      trace_migration_block_save("setup", block_mig_state.submitted,
>                                 block_mig_state.transferred);
>  
> +    warn_report("block migration is deprecated.  Use mirror jobs instead.");

blockdev-mirror with NBD

> +
>      qemu_mutex_lock_iothread();
>      ret = init_blk_migration(f);
>      if (ret < 0) {
> diff --git a/migration/options.c b/migration/options.c
> index b62ab30cd5..374dc0767e 100644
> --- a/migration/options.c
> +++ b/migration/options.c
> @@ -12,6 +12,7 @@
>   */
>  
>  #include "qemu/osdep.h"
> +#include "qemu/error-report.h"
>  #include "exec/target_page.h"
>  #include "qapi/clone-visitor.h"
>  #include "qapi/error.h"
> @@ -437,6 +438,10 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, 
> Error **errp)
>          return false;
>      }
>  #endif
> +    if (new_caps[MIGRATION_CAPABILITY_BLOCK]) {
> +        warn_report("Block migration is deprecated. "
> +                    "Use driver_mirror+NBD instead.");

blockdev-mirror with NBD

> +    }
>  
>  #ifndef CONFIG_REPLICATION
>      if (new_caps[MIGRATION_CAPABILITY_X_COLO]) {
> @@ -1257,6 +1262,8 @@ static void migrate_params_apply(MigrateSetParameters 
> *params, Error **errp)
>      }
>  
>      if (params->has_block_incremental) {
> +        warn_report("Block migration is deprecated. "
> +                    "Use driver_mirror+NBD instead.");

blockdev-mirror with NBD

>          s->parameters.block_incremental = params->block_incremental;
>      }
>      if (params->has_multifd_channels) {
> -- 
> 2.40.1
>

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