Re: [PATCH] migration/rdma: rdma_accept_incoming_migration fix error handling

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Peter Xu (peterx@redhat.com) wrote:
> On Mon, Feb 10, 2020 at 07:44:59PM +0000, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > 
> > rdma_accept_incoming_migration is called from an fd handler and
> > can't return an Error * anywhere.
> > Currently it's leaking Error's in errp/local_err - there's
> > no point putting them in there unless we can report them.
> > 
> > Turn most into fprintf's, and the last into an error_reportf_err
> > where it's coming up from another function.
> > 
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >  migration/rdma.c | 11 +++++++----
> >  1 file changed, 7 insertions(+), 4 deletions(-)
> > 
> > diff --git a/migration/rdma.c b/migration/rdma.c
> > index 2379b8345b..f67161c98f 100644
> > --- a/migration/rdma.c
> > +++ b/migration/rdma.c
> > @@ -3980,13 +3980,13 @@ static void rdma_accept_incoming_migration(void *opaque)
> >      RDMAContext *rdma = opaque;
> >      int ret;
> >      QEMUFile *f;
> > -    Error *local_err = NULL, **errp = &local_err;
> > +    Error *local_err = NULL;
> >  
> >      trace_qemu_rdma_accept_incoming_migration();
> >      ret = qemu_rdma_accept(rdma);
> >  
> >      if (ret) {
> > -        ERROR(errp, "RDMA Migration initialization failed!");
> > +        fprintf(stderr, "RDMA ERROR: Migration initialization failed");
> 
> Is there any reason to explictly use stderr instead of the
> error_reportf_err() below (then we simply jump to that for error
> paths)?  The only difference of error_reportf_err() and stderr should
> be when there's one HMP, while shall we always suggest to use
> error_reportf_err() rather than stderr?

Because the error_reportf_err is taking an Error* (from an error
reported by migration_fd_process_incoming) where as we don't have an
Error* at the earlier points.

Dave

> Thanks,
> 
> >          return;
> >      }
> >  
> > @@ -3998,13 +3998,16 @@ static void rdma_accept_incoming_migration(void *opaque)
> >  
> >      f = qemu_fopen_rdma(rdma, "rb");
> >      if (f == NULL) {
> > -        ERROR(errp, "could not qemu_fopen_rdma!");
> > +        fprintf(stderr, "RDMA ERROR: could not qemu_fopen_rdma");
> >          qemu_rdma_cleanup(rdma);
> >          return;
> >      }
> >  
> >      rdma->migration_started_on_destination = 1;
> > -    migration_fd_process_incoming(f, errp);
> > +    migration_fd_process_incoming(f, &local_err);
> > +    if (local_err) {
> > +        error_reportf_err(local_err, "RDMA ERROR:");
> > +    }
> >  }
> >  
> >  void rdma_start_incoming_migration(const char *host_port, Error **errp)
> > -- 
> > 2.24.1
> > 
> 
> -- 
> Peter Xu
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK