nouveau_fence_sync
ret = nouveau_fence_sync(old_bo, chan, false, false);
ret = nouveau_fence_sync(new_bo, chan, false, true);
ret = nouveau_fence_sync(nouveau_bo(bo), chan, true, ctx->interruptible);
int nouveau_fence_sync(struct nouveau_bo *, struct nouveau_channel *, bool exclusive, bool intr);
ret = nouveau_fence_sync(nvbo, chan, !!b->write_domains, true);