Re: [Xen-devel] [PATCH v3 COLOPre 17/26] tools/libx{l, c}: introduce should_checkpoint callback

[Yang Hongyang <yanghy@xxxxxxxxxxxxxx>]

On 06/30/2015 06:19 PM, Ian Campbell wrote:
> On Thu, 2015-06-25 at 14:25 +0800, Yang Hongyang wrote:
> > Under COLO, we are doing checkpoint on demand, if this
> > callback returns 1, we will take another checkpoint.
> > 0 indicates unexpected error.
> Is this checkpoint therefore expected to be blocking until another
> checkpoint is desired (or an error occurs)?
Right.

> > Signed-off-by: Yang Hongyang <yanghy@xxxxxxxxxxxxxx>
> > ---
> >   tools/libxc/include/xenguest.h     | 18 ++++++++++++++++++
> >   tools/libxl/libxl_save_msgs_gen.pl |  7 ++++---
> >   2 files changed, 22 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/libxc/include/xenguest.h b/tools/libxc/include/xenguest.h
> > index 3e48a97..e804a1d 100644
> > --- a/tools/libxc/include/xenguest.h
> > +++ b/tools/libxc/include/xenguest.h
> > @@ -63,6 +63,15 @@ struct save_callbacks {
> >        * 1: take another checkpoint */
> >       int (*checkpoint)(void* data);
> >
> > +    /*
> > +     * Called after the checkpoint callback.
> > +     *
> > +     * returns:
> > +     * 0: terminate checkpointing gracefully
> The commit message describes this as an "unexpected error" which this
> seems more like the desired response to such an error.
>
> And what would gracefully involve in this context, resuming on sender or
> receiver?
It depends on the error. If it indicates a failover on restore side, we will
resuming the receiver. I will make the comment clearer next version.

> > +     * 1: take another checkpoint
> > +     */
> > +    int (*should_checkpoint)(void* data);
> > +
> >       /* Enable qemu-dm logging dirty pages to xen */
> >       int (*switch_qemu_logdirty)(int domid, unsigned enable, void *data); /* 
> > HVM only */
> >
> > @@ -108,6 +117,15 @@ struct restore_callbacks {
> >       /* A checkpoint record has been found in the stream */
> >       int (*checkpoint)(void* data);
> >
> > +    /*
> > +     * Called after the checkpoint callback.
> > +     *
> > +     * returns:
> > +     * 0: terminate checkpointing gracefully
> Again.
>
> > +     * 1: take another checkpoint
> > +     */
> > +    int (*should_checkpoint)(void* data);
> > +
> >       /* to be provided as the last argument to each callback function */
> >       void* data;
> >   };
> > diff --git a/tools/libxl/libxl_save_msgs_gen.pl 
> > b/tools/libxl/libxl_save_msgs_gen.pl
> > index dc17c6b..7284975 100755
> > --- a/tools/libxl/libxl_save_msgs_gen.pl
> > +++ b/tools/libxl/libxl_save_msgs_gen.pl
> > @@ -26,11 +26,12 @@ our @msgs = (
> >       [  3, 'scxA',   "suspend", [] ],
> >       [  4, 'scxA',   "postcopy", [] ],
> >       [  5, 'srcxA',   "checkpoint", [] ],
> > -    [  6, 'scxA',   "switch_qemu_logdirty",  [qw(int domid
> > +    [  6, 'srcxA',  "should_checkpoint", [] ],
> > +    [  7, 'scxA',   "switch_qemu_logdirty",  [qw(int domid
> >                                                 unsigned enable)] ],
> > -    [  7, 'r',      "restore_results",       ['unsigned long', 'store_mfn',
> > +    [  8, 'r',      "restore_results",       ['unsigned long', 'store_mfn',
> >                                                 'unsigned long', 'console_mfn'] 
> > ],
> > -    [  8, 'srW',    "complete",              [qw(int retval
> > +    [  9, 'srW',    "complete",              [qw(int retval
> >                                                    int errnoval)] ],
> >   );
>
> .
--
Thanks,
Yang.

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