Re: [PATCH v5 03/14] migration: Simplify migration_iteration_run()

[Avihai Horon]

On 06/01/2023 19:56, Alex Williamson wrote:
> External email: Use caution opening links or attachments
>
>
> On Thu, 29 Dec 2022 13:03:34 +0200
> Avihai Horon <avihaih@nvidia.com> wrote:
>
> > From: Juan Quintela <quintela@redhat.com>
> IMHO, there should always be a commit log description.  Why is this a
> simplification?

Yes. It just rephrases the condition so we can drop the else {}.

>    What does it allow us to do?  Nothing later obviously
> depends on this, why is it part of this series?

Right.
This is part of Juan's RFC [1].
Eventually we didn't need the RFC because of the new MIG_DATA_SIZE ioctl.
Since Juan already did this work, I thought I might as well take some of 
these patches.

I will simply drop it in next version.
If a real need to simplify this if else condition arises in the future, 
it can be done then.

Thanks.

[1] 
https://lore.kernel.org/qemu-devel/20221003031600.20084-1-quintela@redhat.com/

>    Thanks,
>
> Alex
>
> > Signed-off-by: Juan Quintela <quintela@redhat.com>
> > Signed-off-by: Avihai Horon <avihaih@nvidia.com>
> > ---
> >   migration/migration.c | 25 +++++++++++++------------
> >   1 file changed, 13 insertions(+), 12 deletions(-)
> >
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 9795d0ec5c..61b9ce0fe8 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -3758,23 +3758,24 @@ static MigIterateState 
> > migration_iteration_run(MigrationState *s)
> >       trace_migrate_pending(pending_size, s->threshold_size,
> >                             pend_pre, pend_compat, pend_post);
> >
> > -    if (pending_size && pending_size >= s->threshold_size) {
> > -        /* Still a significant amount to transfer */
> > -        if (!in_postcopy && pend_pre <= s->threshold_size &&
> > -            qatomic_read(&s->start_postcopy)) {
> > -            if (postcopy_start(s)) {
> > -                error_report("%s: postcopy failed to start", __func__);
> > -            }
> > -            return MIG_ITERATE_SKIP;
> > -        }
> > -        /* Just another iteration step */
> > -        qemu_savevm_state_iterate(s->to_dst_file, in_postcopy);
> > -    } else {
> > +
> > +    if (!pending_size || pending_size < s->threshold_size) {
> >           trace_migration_thread_low_pending(pending_size);
> >           migration_completion(s);
> >           return MIG_ITERATE_BREAK;
> >       }
> >
> > +    /* Still a significant amount to transfer */
> > +    if (!in_postcopy && pend_pre <= s->threshold_size &&
> > +        qatomic_read(&s->start_postcopy)) {
> > +        if (postcopy_start(s)) {
> > +            error_report("%s: postcopy failed to start", __func__);
> > +        }
> > +        return MIG_ITERATE_SKIP;
> > +    }
> > +
> > +    /* Just another iteration step */
> > +    qemu_savevm_state_iterate(s->to_dst_file, in_postcopy);
> >       return MIG_ITERATE_RESUME;
> >   }