Re: [Qemu-devel] [RFC PATCH COLO v2 04/13] Add new block driver interfaces to control block replication

[Fam Zheng]

On Wed, 03/25 17:36, Wen Congyang wrote:
> Signed-off-by: Wen Congyang <address@hidden>
> Signed-off-by: zhanghailiang <address@hidden>
> Signed-off-by: Gonglei <address@hidden>
> Cc: Luiz Capitulino <address@hidden>
> Cc: Michael Roth <address@hidden>
> ---
>  block.c                   | 39 +++++++++++++++++++++++++++++++++++++++
>  include/block/block.h     |  4 ++++
>  include/block/block_int.h | 11 +++++++++++
>  qapi/block.json           | 16 ++++++++++++++++
>  4 files changed, 70 insertions(+)
> 
> diff --git a/block.c b/block.c
> index 0fe97de..0ff5cf8 100644
> --- a/block.c
> +++ b/block.c
> @@ -6196,3 +6196,42 @@ BlockAcctStats *bdrv_get_stats(BlockDriverState *bs)
>  {
>      return &bs->stats;
>  }
> +
> +void bdrv_start_replication(BlockDriverState *bs, COLOMode mode, Error 
> **errp)
> +{
> +    BlockDriver *drv = bs->drv;
> +
> +    if (drv && drv->bdrv_start_replication) {
> +        drv->bdrv_start_replication(bs, mode, errp);
> +    } else if (bs->file) {
> +        bdrv_start_replication(bs->file, mode, errp);
> +    } else {
> +        error_set(errp, QERR_UNSUPPORTED);

I think we should use error_setg in new code? (The same to following ones)

> +    }
> +}
> +
> +void bdrv_do_checkpoint(BlockDriverState *bs, Error **errp)
> +{
> +    BlockDriver *drv = bs->drv;
> +
> +    if (drv && drv->bdrv_do_checkpoint) {
> +        drv->bdrv_do_checkpoint(bs, errp);
> +    } else if (bs->file) {
> +        bdrv_do_checkpoint(bs->file, errp);
> +    } else {
> +        error_set(errp, QERR_UNSUPPORTED);
> +    }
> +}
> +
> +void bdrv_stop_replication(BlockDriverState *bs, Error **errp)
> +{
> +    BlockDriver *drv = bs->drv;
> +
> +    if (drv && drv->bdrv_stop_replication) {
> +        drv->bdrv_stop_replication(bs, errp);
> +    } else if (bs->file) {
> +        bdrv_stop_replication(bs->file, errp);
> +    } else {
> +        error_set(errp, QERR_UNSUPPORTED);
> +    }
> +}
> diff --git a/include/block/block.h b/include/block/block.h
> index 4c57d63..68f3b1a 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -569,4 +569,8 @@ void bdrv_flush_io_queue(BlockDriverState *bs);
>  
>  BlockAcctStats *bdrv_get_stats(BlockDriverState *bs);
>  
> +void bdrv_start_replication(BlockDriverState *bs, COLOMode mode, Error 
> **errp);
> +void bdrv_do_checkpoint(BlockDriverState *bs, Error **errp);
> +void bdrv_stop_replication(BlockDriverState *bs, Error **errp);
> +
>  #endif
> diff --git a/include/block/block_int.h b/include/block/block_int.h
> index dccb092..08dd8ba 100644
> --- a/include/block/block_int.h
> +++ b/include/block/block_int.h
> @@ -290,6 +290,17 @@ struct BlockDriver {
>       */
>      int (*bdrv_probe_geometry)(BlockDriverState *bs, HDGeometry *geo);
>  
> +
> +    void (*bdrv_start_replication)(BlockDriverState *bs, COLOMode mode,
> +                                   Error **errp);

Need some documentation, but I have a generic question:

Why is a single interface with modes better than different functions for each
mode (bdrv_start_replication_{primary,secondary}? Asking because the behavior
is very different between them, and I don't see much sharing -- you implement
primary operation in quorum, and secondary in qcow2+colo.

> +    /* Drop Disk buffer when doing checkpoint. */
> +    void (*bdrv_do_checkpoint)(BlockDriverState *bs, Error **errp);
> +    /*
> +     * After failover, we should flush Disk buffer into secondary disk
> +     * and stop block replication.
> +     */
> +    void (*bdrv_stop_replication)(BlockDriverState *bs, Error **errp);
> +
>      QLIST_ENTRY(BlockDriver) list;
>  };
>  
> diff --git a/qapi/block.json b/qapi/block.json
> index e313465..e640566 100644
> --- a/qapi/block.json
> +++ b/qapi/block.json
> @@ -40,6 +40,22 @@
>    'data': ['auto', 'none', 'lba', 'large', 'rechs']}
>  
>  ##
> +# @COLOMode
> +#
> +# An enumeration of COLO mode.
> +#
> +# @unprotected: COLO is not started or after failover
> +#
> +# @primary: Primary mode, the vm's state will be sent to secondary QEMU.
> +#
> +# @secondary: Secondary mode, receive the vm's state from primary QEMU.
> +#
> +# Since: 2.4
> +##
> +{ 'enum' : 'COLOMode',
> +  'data' : ['unprotected', 'primary', 'secondary']}

If split bdrv_start_replication, do we still need an enum? I can't find the
usage in QMP interface, is it in some other series?

Fam

> +
> +##
>  # @BlockdevSnapshotInternal
>  #
>  # @device: the name of the device to generate the snapshot from
> -- 
> 2.1.0
>