Re: [Xen-devel] [PATCH v1 05/13] xen/pvcalls: implement bind command

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 24 Jul 2017, Juergen Gross wrote:
> On 22/07/17 02:11, Stefano Stabellini wrote:
> > Send PVCALLS_BIND to the backend. Introduce a new structure, part of
> > struct sock_mapping, to store information specific to passive sockets.
> > 
> > Introduce a status field to keep track of the status of the passive
> > socket.
> > 
> > Introduce a waitqueue for the "accept" command (see the accept command
> > implementation): it is used to allow only one outstanding accept
> > command at any given time and to implement polling on the passive
> > socket. Introduce a flags field to keep track of in-flight accept and
> > poll commands.
> > 
> > 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 struct socket pointer into an uint64_t and use it as id for
> > the 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 | 74 
> > +++++++++++++++++++++++++++++++++++++++++++++
> >  drivers/xen/pvcalls-front.h |  3 ++
> >  2 files changed, 77 insertions(+)
> > 
> > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> > index 0d305e0..71619bc 100644
> > --- a/drivers/xen/pvcalls-front.c
> > +++ b/drivers/xen/pvcalls-front.c
> > @@ -57,6 +57,23 @@ struct sock_mapping {
> >  
> >                     wait_queue_head_t inflight_conn_req;
> >             } active;
> > +           struct {
> > +           /* Socket status */
> > +#define PVCALLS_STATUS_UNINITALIZED  0
> > +#define PVCALLS_STATUS_BIND          1
> > +#define PVCALLS_STATUS_LISTEN        2
> > +                   uint8_t status;
> > +           /*
> > +            * Internal state-machine flags.
> > +            * Only one accept operation can be inflight for a socket.
> > +            * Only one poll operation can be inflight for a given socket.
> > +            */
> > +#define PVCALLS_FLAG_ACCEPT_INFLIGHT 0
> > +#define PVCALLS_FLAG_POLL_INFLIGHT   1
> > +#define PVCALLS_FLAG_POLL_RET        2
> > +                   uint8_t flags;
> > +                   wait_queue_head_t inflight_accept_req;
> > +           } passive;
> >     };
> >  };
> >  
> > @@ -287,6 +304,63 @@ int pvcalls_front_connect(struct socket *sock, struct 
> > sockaddr *addr,
> >     return ret;
> >  }
> >  
> > +int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int 
> > addr_len)
> > +{
> > +   struct pvcalls_bedata *bedata;
> > +   struct sock_mapping *map = NULL;
> > +   struct xen_pvcalls_request *req;
> > +   int notify, req_id, ret;
> > +
> > +   if (!pvcalls_front_dev)
> > +           return -ENOTCONN;
> > +   if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
> > +           return -ENOTSUPP;
> > +   bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> > +
> > +   map = kzalloc(sizeof(*map), GFP_KERNEL);
> > +   if (map == 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() isn't appropriate here. The system can still be used.

Yes, and checkpatch.pl also told me the same. Basically, this condition
cannot happen, I'll just remove the BUG_ON.


> > +   if (RING_FULL(&bedata->ring) ||
> > +       READ_ONCE(bedata->rsp[req_id].req_id) != PVCALLS_INVALID_ID) {
> > +           kfree(map);
> > +           spin_unlock(&bedata->pvcallss_lock);
> > +           return -EAGAIN;
> > +   }
> > +   req = RING_GET_REQUEST(&bedata->ring, req_id);
> > +   req->req_id = req_id;
> > +   map->sock = sock;
> > +   req->cmd = PVCALLS_BIND;
> > +   req->u.bind.id = (uint64_t) sock;
> > +   memcpy(req->u.bind.addr, addr, sizeof(*addr));
> > +   req->u.bind.len = addr_len;
> > +
> > +   init_waitqueue_head(&map->passive.inflight_accept_req);
> > +
> > +   list_add_tail(&map->list, &bedata->socketpass_mappings);
> > +   WRITE_ONCE(sock->sk->sk_send_head, (void *)map);
> > +   map->active_socket = false;
> > +
> > +   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);
> > +
> > +   map->passive.status = PVCALLS_STATUS_BIND;
> > +   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 0;
> > +}
> > +
> >  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 63b0417..8b0a274 100644
> > --- a/drivers/xen/pvcalls-front.h
> > +++ b/drivers/xen/pvcalls-front.h
> > @@ -6,5 +6,8 @@
> >  int pvcalls_front_socket(struct socket *sock);
> >  int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
> >                       int addr_len, int flags);
> > +int pvcalls_front_bind(struct socket *sock,
> > +                  struct sockaddr *addr,
> > +                  int addr_len);
> >  
> >  #endif
> > 
> 

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