Re: [Qemu-devel] [PATCH] block: do_commit() does not pass along error messages for all errors

[Luiz Capitulino <lcapitulino@redhat.com>]

On Thu, 17 Jan 2013 08:49:38 +0100
Markus Armbruster <armbru@redhat.com> wrote:

> [Cc: Luiz for error stuff]
> 
> Jeff Cody <jcody@redhat.com> writes:
> 
> > The non-live bdrv_commit() function may return one of the following
> > errors: -ENOTSUP, -EBUSY, -EACCES, -EIO.  The only error that is
> > checked in the HMP handler is -EBUSY, so the monitor command 'commit'
> > silently fails for all error cases other than 'Device is in use'.
> >
> > This patch adds the appropriate error messages for the errors
> > explicitely returned by bdrv_commit().
> >
> > Signed-off-by: Jeff Cody <jcody@redhat.com>
> > ---
> >  blockdev.c | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> >
> > diff --git a/blockdev.c b/blockdev.c
> > index d724e2d..7db7d8e 100644
> > --- a/blockdev.c
> > +++ b/blockdev.c
> > @@ -657,6 +657,20 @@ void do_commit(Monitor *mon, const QDict *qdict)
> >              qerror_report(QERR_DEVICE_IN_USE, device);
> >              return;
> >          }
> > +        if (ret == -EACCES) {
> > +            qerror_report(QERR_DEVICE_IS_READ_ONLY, device);
> > +            return;
> > +        }
> > +        if (ret == -EIO) {
> > +            qerror_report(QERR_IO_ERROR);
> > +            return;
> > +        }
> > +        if (ret == -ENOTSUP) {
> > +            const char *format = bdrv_get_format_name(bs);
> > +            qerror_report(QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,
> > +                          format ? format : "NULL", device, "commit");
> > +
> > +        }
> >      }
> >  }
> 
> A switch could be more obvious than the if cascade.  Matter of taste.
> 
> We're trying to avoid QERR_ in new code.  This case isn't bad, because
> it doesn't add new QERR_ defines.  Should we convert the function to
> error_setg() instead?  Perhaps a few cases could be collapsed into a
> single error_setg_errno() then.

I'd suggest to convert do_commit() to the qapi. However, we already
have block-commit in QMP. So I'm not sure this is a good idea.

If it isn't, then maybe we could drop all qerro_report() calls and
use monitor_printf() instead (building the error message with
strerror()), as do_commit() seems to be used only from HMP.