On Mon, Apr 09, 2018 at 09:52:13AM -0700, Linus Torvalds wrote:
> On Mon, Apr 9, 2018 at 6:10 AM, Stefan Hajnoczi <stefanha@xxxxxxxxxx> wrote:
> > @@ -1246,7 +1246,7 @@ int vhost_vq_access_ok(struct vhost_virtqueue *vq)
> > {
> > int ret = vq_log_access_ok(vq, vq->log_base);
> >
> > - if (ret || vq->iotlb)
> > + if (!ret || vq->iotlb)
> > return ret;
>
> That logic is still very non-obvious.
>
> This code already had one bug because of an odd illegible test
> sequence. Let's not keep the crazy code.
>
> Why not just do the *obvious* thing, and get rid of "ret" entirely,
> and make the damn thing return a boolean, and then just write it all
> as
>
> /* Caller should have vq mutex and device mutex */
> bool vhost_vq_access_ok(struct vhost_virtqueue *vq)
> {
> if (!vq_log_access_ok(vq, vq->log_base))
> return false;
>
> if (vq->iotlb || vq_access_ok(vq, vq->num, vq->desc,
> vq->avail, vq->used);
> }
>
> which makes the logic obvious: if vq_log_access_ok() fails, then then
> vhost_vq_access_ok() fails unconditionally.
>
> Otherwise, we need to have an iotlb, or a successful vq_access_ok() check.
>
> Doesn't that all make more sense, and avoid the insane "ret" value use
> that is really quite subtle?
>
> Linus
I agree it's cleaner.
Stefan, I reposted your patch on netdev (since the breakage got applied
there too).
Would you like to self-nak it and post v2? Pls remember to CC netdev.
--
MST
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