On (Tue) Mar 16 2010 [17:37:39], Michael S. Tsirkin wrote: > On Mon, Mar 08, 2010 at 11:50:23AM +0530, Amit Shah wrote: > > On (Sat) Mar 06 2010 [21:06:35], Michael S. Tsirkin wrote: > > > > > > > > + r = vhost_virtqueue_set_addr(dev, vq, idx, dev->log_enabled); > > > > > + if (r < 0) { > > > > > + r = -errno; > > > > > + goto fail_alloc; > > > > > + } > > > > > + if (!vdev->binding->guest_notifier || > > > > > !vdev->binding->host_notifier) { > > > > > + fprintf(stderr, "binding does not support irqfd/queuefd\n"); > > > > > + r = -ENOSYS; > > > > > + goto fail_alloc; > > > > > + } > > > > > > > > This could be checked much earlier on in the function; so that we avoid > > > > doing all that stuff above and the cleanup. > > > > > > Whatever order we put checks in, we'll have to undo stuff > > > done beforehand on error. > > > > Not if you do this check before any ioctls or allocations. > > !vdev->binding->guest_notifier is not dependent on anything you do above > > it in this function, so just checking for this first thing in the > > function will not need any cleanup. > > Yes, but I think it's clearer to do check function just before > calling it. No?
The good thing about doing it before is that we can check for whatever conditions are not met first and exit instead of doing N things and undoing them later and then exiting -- faster and more efficient in the case when vhost is not being used. Amit -- http://log.amitshah.net/