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

[Yang Hongyang <yanghy@xxxxxxxxxxxxxx>]

On 07/16/2015 01:38 AM, Andrew Cooper wrote:
> 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.
Ok, will look into the code closely.

> ~Andrew
> .
--
Thanks,
Yang.

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