Re: [PATCH v5 4/5] migration: process_incoming_migration_co(): rework error reporting

[Vladimir Sementsov-Ogievskiy]

On 29.04.24 22:39, Peter Xu wrote:
> On Mon, Apr 29, 2024 at 10:14:25PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> > Unify error reporting in the function. This simplifies the following
> > commit, which will not-exit-on-error behavior variant to the function.
> >
> > Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> > Reviewed-by: Fabiano Rosas <farosas@suse.de>
> > ---
> >   migration/migration.c | 17 ++++++++++-------
> >   1 file changed, 10 insertions(+), 7 deletions(-)
> >
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 58fd5819bc..5489ff96df 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -748,11 +748,12 @@ process_incoming_migration_co(void *opaque)
> >       MigrationIncomingState *mis = migration_incoming_get_current();
> >       PostcopyState ps;
> >       int ret;
> > +    Error *local_err = NULL;
> >   
> >       assert(mis->from_src_file);
> >   
> >       if (compress_threads_load_setup(mis->from_src_file)) {
> > -        error_report("Failed to setup decompress threads");
> > +        error_setg(&local_err, "Failed to setup decompress threads");
> >           goto fail;
> >       }
> >   
> > @@ -789,16 +790,12 @@ process_incoming_migration_co(void *opaque)
> >       }
> >   
> >       if (ret < 0) {
> > -        if (migrate_has_error(s)) {
> > -            WITH_QEMU_LOCK_GUARD(&s->error_mutex) {
> > -                error_report_err(error_copy(s->error));
> > -            }
> > -        }
> > -        error_report("load of migration failed: %s", strerror(-ret));
> > +        error_setg(&local_err, "load of migration failed: %s", strerror(-ret));
> >           goto fail;
> >       }
> >   
> >       if (colo_incoming_co() < 0) {
> > +        error_setg(&local_err, "colo incoming failed");
> >           goto fail;
> >       }
> >   
> > @@ -809,6 +806,12 @@ fail:
> >                         MIGRATION_STATUS_FAILED);
> >       migration_incoming_state_destroy();
> >   
> > +    if (migrate_has_error(s)) {
> > +        WITH_QEMU_LOCK_GUARD(&s->error_mutex) {
> > +            error_report_err(error_copy(s->error));
> > +        }
> > +    }
> > +    error_report_err(local_err);
>
> Here migrate_has_error() will always return true?  If so we can drop it.
>
> Meanwhile, IMHO it's easier we simply always keep the earliest error we see
> and report that only, local_err is just one of the errors and whoever
> reaches first will be reported.  Something like:
>
>    migrate_set_error(local_err);
>    WITH_QEMU_LOCK_GUARD(&s->error_mutex) {
>        error_report_err(error_copy(s->error));
>    }
>    exit(EXIT_FAILURE);
>
> Then when with the exit-on-error thing:
>
>    migrate_set_error(local_err);
>    if (exit_on_error) {
>      WITH_QEMU_LOCK_GUARD(&s->error_mutex) {
>        error_report_err(error_copy(s->error));
>      }
>      exit(EXIT_FAILURE);
>    }
>
> Would this looks slightly cleaner?

Yes, looks better, will do so

--
Best regards,
Vladimir