Re: [Qemu-devel] [PATCH RFC v7 5/9] migration: fix the multifd code when sending less channels

[Fei Li]

On 11/02/2018 10:37 AM, Peter Xu wrote:
> On Thu, Nov 01, 2018 at 06:17:11PM +0800, Fei Li wrote:
> > Set the migration state to "failed" instead of "setup" when failing
> > to send packet via some channel.
> Could you please provide more information in the commit message?
> E.g., what will happen if without this patch?  Will it crash the
> source or stall the source migration or others?  Otherwise it's a bit
> hard for me to understand what's this patch for.
Sorry for the inadequate description , I was intended to say that when 
failing
to do the live migration using multifd, e.g. sending less channels, the src
status displays "setup" when running `info migrate`. I assume we should tell
users that the "Migration status" is "failed" now (and along with the 
failure reason).

The current src status when failed inmultifd_new_send_channel_async()：


(qemu) migrate_set_capability x-multifd on
(qemu) migrate_set_parameter x-multifd-channels 4
(qemu) migrate -d tcp:192.168.190.98:4444
(qemu) qemu-system-x86_64: failed in multifd_new_send_channel_async due 
to ...
(qemu) info migrate
globals:
store-global-state: on
only-migratable: off
send-configuration: on
send-section-footer: on
decompress-error-check: on
capabilities: xbzrle: off rdma-pin-all: off auto-converge: off 
zero-blocks: off compress: off events: off postcopy-ram: off x-colo: off 
release-ram: off block: off return-path: off pause-before-switchover: 
off x-multifd: on dirty-bitmaps: off postcopy-blocktime: off 
late-block-activate: off
Migration status: setup
total time: 0 milliseconds

> Normally I would prefer to not touch global states in feature specific
> code path, but I'd like to know the problem more first...
>
> Thanks,
>
> > Cc: Peter Xu <address@hidden>
> > Signed-off-by: Fei Li <address@hidden>
> > ---
> >   migration/ram.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/migration/ram.c b/migration/ram.c
> > index 4db3b3e8f4..c84d164fc8 100644
> > --- a/migration/ram.c
> > +++ b/migration/ram.c
> > @@ -1072,6 +1072,7 @@ out:
> >   static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque)
> >   {
> >       MultiFDSendParams *p = opaque;
> > +    MigrationState *s = migrate_get_current();
> >       QIOChannel *sioc = QIO_CHANNEL(qio_task_get_source(task));
> >       Error *local_err = NULL;
> >   
> > @@ -1083,6 +1084,7 @@ static void multifd_new_send_channel_async(QIOTask *task, gpointer opaque)
> >           if (multifd_save_cleanup(&local_err) != 0) {
> >               migrate_set_error(migrate_get_current(), local_err);
> >           }
> > +        migrate_set_state(&s->state, s->state, MIGRATION_STATUS_FAILED);
> >       } else {
> >           p->c = QIO_CHANNEL(sioc);
> >           qio_channel_set_delay(p->c, false);
> > --
> > 2.13.7
> Regards,