Re: [Xen-devel] [PATCH v1 07/13] xen/pvcalls: implement accept command

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 24 Jul 2017, Juergen Gross wrote:
> On 22/07/17 02:11, Stefano Stabellini wrote:
> > Send PVCALLS_ACCEPT to the backend. Allocate a new active socket. Make
> > sure that only one accept command is executed at any given time by
> > setting PVCALLS_FLAG_ACCEPT_INFLIGHT and waiting on the
> > inflight_accept_req waitqueue.
> > 
> > sock->sk->sk_send_head is not used for ip sockets: reuse the field to
> > store a pointer to the struct sock_mapping corresponding to the socket.
> > 
> > Convert the new struct socket pointer into an uint64_t and use it as id
> > for the new socket to pass to the backend.
> > 
> > Signed-off-by: Stefano Stabellini <stefano@xxxxxxxxxxx>
> > CC: boris.ostrovsky@xxxxxxxxxx
> > CC: jgross@xxxxxxxx
> > ---
> >  drivers/xen/pvcalls-front.c | 79 
> > +++++++++++++++++++++++++++++++++++++++++++++
> >  drivers/xen/pvcalls-front.h |  3 ++
> >  2 files changed, 82 insertions(+)
> > 
> > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> > index 80fd5fb..f3a04a2 100644
> > --- a/drivers/xen/pvcalls-front.c
> > +++ b/drivers/xen/pvcalls-front.c
> > @@ -410,6 +410,85 @@ int pvcalls_front_listen(struct socket *sock, int 
> > backlog)
> >     return ret;
> >  }
> >  
> > +int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int 
> > flags)
> > +{
> > +   struct pvcalls_bedata *bedata;
> > +   struct sock_mapping *map;
> > +   struct sock_mapping *map2 = NULL;
> > +   struct xen_pvcalls_request *req;
> > +   int notify, req_id, ret, evtchn;
> > +
> > +   if (!pvcalls_front_dev)
> > +           return -ENOTCONN;
> > +   bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> > +
> > +   map = (struct sock_mapping *) READ_ONCE(sock->sk->sk_send_head);
> > +   if (!map)
> > +           return -ENOTSOCK;
> > +
> > +   if (map->passive.status != PVCALLS_STATUS_LISTEN)
> > +           return -EINVAL;
> > +
> > +   /*
> > +    * Backend only supports 1 inflight accept request, will return
> > +    * errors for the others
> > +    */
> > +   if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> > +                        (void *)&map->passive.flags)) {
> > +           if (wait_event_interruptible(map->passive.inflight_accept_req,
> > +                   !test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> > +                                     (void *)&map->passive.flags))
> > +                   != 0)
> > +                   return -EINTR;
> > +   }
> > +
> > +
> > +   newsock->sk = kzalloc(sizeof(*newsock->sk), GFP_KERNEL);
> > +   if (newsock->sk == NULL)
> > +           return -ENOMEM;
> > +
> > +   spin_lock(&bedata->pvcallss_lock);
> > +   req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
> > +   BUG_ON(req_id >= PVCALLS_NR_REQ_PER_RING);
> 
> BUG_ON()?
> 
> > +   if (RING_FULL(&bedata->ring) ||
> > +       READ_ONCE(bedata->rsp[req_id].req_id) != PVCALLS_INVALID_ID) {
> > +           spin_unlock(&bedata->pvcallss_lock);
> > +           return -EAGAIN;
> 
> Leaking newsock->sk?

I'll fix


> > +   }
> > +
> > +   map2 = create_active(&evtchn);
> > +
> > +   req = RING_GET_REQUEST(&bedata->ring, req_id);
> > +   req->req_id = req_id;
> > +   req->cmd = PVCALLS_ACCEPT;
> > +   req->u.accept.id = (uint64_t) sock;
> > +   req->u.accept.ref = map2->active.ref;
> > +   req->u.accept.id_new = (uint64_t) newsock;
> > +   req->u.accept.evtchn = evtchn;
> > +
> > +   list_add_tail(&map2->list, &bedata->socket_mappings);
> > +   WRITE_ONCE(newsock->sk->sk_send_head, (void *)map2);
> > +   map2->sock = newsock;
> > +
> > +   bedata->ring.req_prod_pvt++;
> > +   RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
> > +   spin_unlock(&bedata->pvcallss_lock);
> > +   if (notify)
> > +           notify_remote_via_irq(bedata->irq);
> > +
> > +   wait_event(bedata->inflight_req,
> > +              READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
> > +
> > +   clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
> > +   wake_up(&map->passive.inflight_accept_req);
> > +
> > +   ret = bedata->rsp[req_id].ret;
> > +   /* read ret, then set this rsp slot to be reused */
> > +   smp_mb();
> > +   WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
> > +   return ret;
> > +}
> > +
> >  static const struct xenbus_device_id pvcalls_front_ids[] = {
> >     { "pvcalls" },
> >     { "" }
> > diff --git a/drivers/xen/pvcalls-front.h b/drivers/xen/pvcalls-front.h
> > index aa8fe10..ab4f1da 100644
> > --- a/drivers/xen/pvcalls-front.h
> > +++ b/drivers/xen/pvcalls-front.h
> > @@ -10,5 +10,8 @@ int pvcalls_front_bind(struct socket *sock,
> >                    struct sockaddr *addr,
> >                    int addr_len);
> >  int pvcalls_front_listen(struct socket *sock, int backlog);
> > +int pvcalls_front_accept(struct socket *sock,
> > +                    struct socket *newsock,
> > +                    int flags);
> >  
> >  #endif
> > 
> 

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