Re: [Virtio-fs] [PATCH 3/3] virtio-fs: Waiting for pending forget requests to finish

[Vivek Goyal <vgoyal@redhat.com>]

On Wed, Jun 05, 2019 at 11:26:07AM -0700, Liu Bo wrote:

[..]
> > +static void virtio_fs_flush_hiprio_queue(struct virtio_fs_vq *fsvq)
> > +{
> > +	struct virtio_fs_forget *forget;
> > +
> > +	WARN_ON(fsvq->in_flight < 0);
> > +
> > +	/* Go through pending forget reuests and free them */
> > +	spin_lock(&fsvq->lock);
> > +	while(1) {
> > +		forget = list_first_entry_or_null(&fsvq->queued_reqs,
> > +					struct virtio_fs_forget, list);
> > +		if (!forget)
> > +			break;
> > +		kfree(forget);
> > +	}
> > +
> > +	spin_unlock(&fsvq->lock);
> > +
> > +	/* Wait for in flight requests to finish.*/
> > +	while (1) {
> > +		spin_lock(&fsvq->lock);
> > +		if (!fsvq->in_flight) {
> > +			spin_unlock(&fsvq->lock);
> > +			break;
> > +		}
> > +		spin_unlock(&fsvq->lock);
> > +		usleep_range(1000, 2000);
> > +	}
> 
> why not a wait_queue for fsvq->in_flight == 0?

It was much simpler to do busy wait as I am not expecting this wait to
be long. But if this turns out to be issue later, we can switch to
wait queue.

Vivek