Re: [PATCH] vhost/net: Replace wait_queue with completion in ubufs reference

Yes, if multiple waiters call vhost_net_ubuf_put_and_wait() concurrently we
are screwed. Furthermore, it was not the case before this patch. While it
was explicitly mentioned in the commit message, now I changed my mind,
because amount of vhost_net_ubuf_put_and_wait() users may change when this
patch will be backported to older LTSes. In 6.6+ kernels there are
only two put_and_wait() callers, both are ensuring that there
is only one thread calling put_and_wait() at a time.

I think its better to preserve thread-safety of vhost_net_ubuf_put_and_wait()
and move reinit_completion() call to vhost_net_flush(). We don't need
reinit on free'ing path anyway.

I will send v2 with the fix. Thank you for noticing this.