Re: [Xen-devel] [PATCH v8 --for 4.6 COLO 07/25] tools/libxl: add back channel support to read stream

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 15/07/15 10:18, Yang Hongyang wrote:
> This is used by primay to read records sent by secondary.
>
> Signed-off-by: Yang Hongyang <yanghy@xxxxxxxxxxxxxx>
> ---
>  tools/libxl/libxl_create.c      |  1 +
>  tools/libxl/libxl_internal.h    |  1 +
>  tools/libxl/libxl_stream_read.c | 17 +++++++++++++++++
>  3 files changed, 19 insertions(+)
>
> diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
> index 1d4b13b..1af7103 100644
> --- a/tools/libxl/libxl_create.c
> +++ b/tools/libxl/libxl_create.c
> @@ -978,6 +978,7 @@ static void domcreate_bootloader_done(libxl__egc *egc,
>      dcs->srs.dcs = dcs;
>      dcs->srs.fd = restore_fd;
>      dcs->srs.legacy = (dcs->restore_params.stream_version == 1);
> +    dcs->srs.back_channel = false;
>      dcs->srs.completion_callback = domcreate_stream_done;
>  
>      libxl__stream_read_start(egc, &dcs->srs);
> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> index 2634836..05cee04 100644
> --- a/tools/libxl/libxl_internal.h
> +++ b/tools/libxl/libxl_internal.h
> @@ -3358,6 +3358,7 @@ struct libxl__stream_read_state {
>      libxl__domain_create_state *dcs;
>      int fd;
>      bool legacy;
> +    bool back_channel;
>      void (*completion_callback)(libxl__egc *egc,
>                                  libxl__stream_read_state *srs,
>                                  int rc);
> diff --git a/tools/libxl/libxl_stream_read.c b/tools/libxl/libxl_stream_read.c
> index 2d17403..b924f05 100644
> --- a/tools/libxl/libxl_stream_read.c
> +++ b/tools/libxl/libxl_stream_read.c
> @@ -104,6 +104,15 @@
>   * Depending on the contents of the stream, there are likely to be several
>   * parallel tasks being managed.  check_all_finished() is used to join all
>   * tasks in both success and error cases.
> + *
> + * For back channel stream:
> + * - libxl__stream_read_start()
> + *    - Set up the stream to running state
> + *
> + * - libxl__stream_read_continue()
> + *     - Set up reading the next record from a started stream.
> + *       Add some codes to process_record() to handle the record.
> + *       Then call stream->checkpoint_callback() to return.
>   */
>  
>  /* Success/error/cleanup handling. */
> @@ -200,6 +209,9 @@ void libxl__stream_read_start(libxl__egc *egc,
>      stream->running = true;
>      stream->phase   = SRS_PHASE_NORMAL;
>  
> +    if (stream->back_channel)
> +        return;
> +
>      if (stream->legacy) {
>          /* Convert the legacy stream. */
>          libxl__conversion_helper_state *chs = &stream->chs;
> @@ -700,6 +712,11 @@ static void stream_done(libxl__egc *egc,
>      assert(!stream->in_checkpoint);
>      stream->running = false;
>  
> +    if (stream->back_channel) {
> +        stream->completion_callback(egc, stream, stream->rc);
> +        return;
> +    }
> +

This should be in stream_complete() not stream_done().  stream_done() is
strictly called once, and cleans stuff up.

~Andrew

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