Re: [PATCH 01/33] migration: push Error **errp into qemu_loadvm_state()

[Daniel P . Berrangé]

On Fri, Feb 05, 2021 at 10:35:28AM +0100, Philippe Mathieu-Daudé wrote:
> On Fri, Feb 5, 2021 at 10:33 AM Daniel P. Berrangé <berrange@redhat.com> 
> wrote:
> > On Thu, Feb 04, 2021 at 10:57:20PM +0100, Philippe Mathieu-Daudé wrote:
> > > On 2/4/21 6:18 PM, Daniel P. Berrangé wrote:
> > > > This is an incremental step in converting vmstate loading code to report
> > > > via Error objects instead of printing directly to the console/monitor.
> > > >
> > > > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > > > ---
> > > >  migration/migration.c |  4 ++--
> > > >  migration/savevm.c    | 36 ++++++++++++++++++++----------------
> > > >  migration/savevm.h    |  2 +-
> > > >  3 files changed, 23 insertions(+), 19 deletions(-)
> > > ...
> > >
> > > > diff --git a/migration/savevm.c b/migration/savevm.c
> > > > index 6b320423c7..c8d93eee1e 100644
> > > > --- a/migration/savevm.c
> > > > +++ b/migration/savevm.c
> > > > @@ -2638,40 +2638,49 @@ out:
> > > >      return ret;
> > > >  }
> > > >
> > > > -int qemu_loadvm_state(QEMUFile *f)
> > > > +int qemu_loadvm_state(QEMUFile *f, Error **errp)
> > > >  {
> > > >      MigrationIncomingState *mis = migration_incoming_get_current();
> > > > -    Error *local_err = NULL;
> > > >      int ret;
> > > >
> > > > -    if (qemu_savevm_state_blocked(&local_err)) {
> > > > -        error_report_err(local_err);
> > > > -        return -EINVAL;
> > > > +    if (qemu_savevm_state_blocked(errp)) {
> > > > +        return -1;
> > > >      }
> > > >
> > > >      ret = qemu_loadvm_state_header(f);
> > > >      if (ret) {
> > > > -        return ret;
> > > > +        error_setg(errp, "Error %d while loading VM state", ret);
> > >
> > > Using error_setg_errno() instead (multiple occurences):
> >
> > I don't think we want todo that in general, because the code is
> > already not reliable at actually returning an errno value, sometimes
> > returning just "-1". At the end of this series it will almost always
> > be returning "-1", not an errno.  There are some places where an
> > errno is relevant though - specificially qemu_get_file_error calls.
> 
> Fair. Ignore my other same comments in this. R-b tag stands.

On further investigation you are right. Not using error_setg_errno
has caused a regression in error quality as shown by Dave in a later
patch in this series.

Regards,
Daniel
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