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

[Peter Xu <peterx@redhat.com>]

On Tue, Feb 11, 2020 at 09:22:00AM +0000, Dr. David Alan Gilbert wrote:
> * 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.

The ERROR() macro in rdma.c created them?  Though it also prints to
stderr so if we also use the same error_reportf_err() then we can
remove that prints to stderr too.

-- 
Peter Xu