On Mon, 12 Feb 2018, Juergen Gross wrote:
> On 05/02/18 23:51, Stefano Stabellini wrote:
> > Introduce a per sock_mapping refcount, in addition to the existing
> > global refcount. Thanks to the sock_mapping refcount, we can safely wait
> > for it to be 1 in pvcalls_front_release before freeing an active socket,
> > instead of waiting for the global refcount to be 1.
> > 
> > Signed-off-by: Stefano Stabellini <stef...@aporeto.com>
> > ---
> >  drivers/xen/pvcalls-front.c | 190 
> > ++++++++++++++++++--------------------------
> >  1 file changed, 78 insertions(+), 112 deletions(-)
> > 
> > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> > index 4c789e6..164d3ad 100644
> > --- a/drivers/xen/pvcalls-front.c
> > +++ b/drivers/xen/pvcalls-front.c
> > @@ -60,6 +60,7 @@ struct sock_mapping {
> >     bool active_socket;
> >     struct list_head list;
> >     struct socket *sock;
> > +   atomic_t refcount;
> >     union {
> >             struct {
> >                     int irq;
> > @@ -93,6 +94,33 @@ struct sock_mapping {
> >     };
> >  };
> >  
> > +static inline struct sock_mapping *pvcalls_enter_sock(struct socket *sock)
> > +{
> > +   struct sock_mapping *map = NULL;
> > +
> > +   if (!pvcalls_front_dev || &pvcalls_front_dev->dev == NULL)
> 
> Did you mean:
>         if (!pvcalls_front_dev || !pvcalls_front_dev->dev)

I actually meant:

if (!pvcalls_front_dev || dev_get_drvdata(&pvcalls_front_dev->dev) == NULL)

 
> > +           return ERR_PTR(-ENOTCONN);
> > +
> > +   pvcalls_enter();
> > +   map = (struct sock_mapping *) sock->sk->sk_send_head;
> 
> Style: no blank after the cast, please (multiple times).

OK, I'll fix them all


> > +   if (map == NULL) {
> > +           pvcalls_exit()
> > +           return ERR_PTR(-ENOTSOCK);
> > +   }
> > +
> > +   atomic_inc(&map->refcount);
> > +   return map;
> > +}
> > +
> > +static inline void pvcalls_exit_sock(struct socket *sock)
> > +{
> > +   struct sock_mapping *map = NULL;
> > +
> > +   map = (struct sock_mapping *) sock->sk->sk_send_head;
> > +   atomic_dec(&map->refcount);
> > +   pvcalls_exit();
> > +}
> > +
> >  static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
> >  {
> >     *req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
> > @@ -369,31 +397,23 @@ int pvcalls_front_connect(struct socket *sock, struct 
> > sockaddr *addr,
> >     if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
> >             return -EOPNOTSUPP;
> >  
> > -   pvcalls_enter();
> > -   if (!pvcalls_front_dev) {
> > -           pvcalls_exit();
> > -           return -ENOTCONN;
> > -   }
> > +   map = pvcalls_enter_sock(sock);
> > +   if (IS_ERR(map))
> > +           return PTR_ERR(map);
> >  
> >     bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> >  
> > -   map = (struct sock_mapping *)sock->sk->sk_send_head;
> > -   if (!map) {
> > -           pvcalls_exit();
> > -           return -ENOTSOCK;
> > -   }
> > -
> >     spin_lock(&bedata->socket_lock);
> >     ret = get_request(bedata, &req_id);
> >     if (ret < 0) {
> >             spin_unlock(&bedata->socket_lock);
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return ret;
> >     }
> >     ret = create_active(map, &evtchn);
> >     if (ret < 0) {
> >             spin_unlock(&bedata->socket_lock);
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return ret;
> >     }
> >  
> > @@ -423,7 +443,7 @@ int pvcalls_front_connect(struct socket *sock, struct 
> > sockaddr *addr,
> >     smp_rmb();
> >     ret = bedata->rsp[req_id].ret;
> >     bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
> > -   pvcalls_exit();
> > +   pvcalls_exit_sock(sock);
> >     return ret;
> >  }
> >  
> > @@ -488,23 +508,15 @@ int pvcalls_front_sendmsg(struct socket *sock, struct 
> > msghdr *msg,
> >     if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
> >             return -EOPNOTSUPP;
> >  
> > -   pvcalls_enter();
> > -   if (!pvcalls_front_dev) {
> > -           pvcalls_exit();
> > -           return -ENOTCONN;
> > -   }
> > +   map = pvcalls_enter_sock(sock);
> > +   if (IS_ERR(map))
> > +           return PTR_ERR(map);
> >     bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> >  
> > -   map = (struct sock_mapping *) sock->sk->sk_send_head;
> > -   if (!map) {
> > -           pvcalls_exit();
> > -           return -ENOTSOCK;
> > -   }
> > -
> >     mutex_lock(&map->active.out_mutex);
> >     if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
> >             mutex_unlock(&map->active.out_mutex);
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return -EAGAIN;
> >     }
> >     if (len > INT_MAX)
> > @@ -526,7 +538,7 @@ int pvcalls_front_sendmsg(struct socket *sock, struct 
> > msghdr *msg,
> >             tot_sent = sent;
> >  
> >     mutex_unlock(&map->active.out_mutex);
> > -   pvcalls_exit();
> > +   pvcalls_exit_sock(sock);
> >     return tot_sent;
> >  }
> >  
> > @@ -591,19 +603,11 @@ int pvcalls_front_recvmsg(struct socket *sock, struct 
> > msghdr *msg, size_t len,
> >     if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
> >             return -EOPNOTSUPP;
> >  
> > -   pvcalls_enter();
> > -   if (!pvcalls_front_dev) {
> > -           pvcalls_exit();
> > -           return -ENOTCONN;
> > -   }
> > +   map = pvcalls_enter_sock(sock);
> > +   if (IS_ERR(map))
> > +           return PTR_ERR(map);
> >     bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> >  
> > -   map = (struct sock_mapping *) sock->sk->sk_send_head;
> > -   if (!map) {
> > -           pvcalls_exit();
> > -           return -ENOTSOCK;
> > -   }
> > -
> >     mutex_lock(&map->active.in_mutex);
> >     if (len > XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER))
> >             len = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
> > @@ -623,7 +627,7 @@ int pvcalls_front_recvmsg(struct socket *sock, struct 
> > msghdr *msg, size_t len,
> >             ret = 0;
> >  
> >     mutex_unlock(&map->active.in_mutex);
> > -   pvcalls_exit();
> > +   pvcalls_exit_sock(sock);
> >     return ret;
> >  }
> >  
> > @@ -637,24 +641,16 @@ int pvcalls_front_bind(struct socket *sock, struct 
> > sockaddr *addr, int addr_len)
> >     if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
> >             return -EOPNOTSUPP;
> >  
> > -   pvcalls_enter();
> > -   if (!pvcalls_front_dev) {
> > -           pvcalls_exit();
> > -           return -ENOTCONN;
> > -   }
> > +   map = pvcalls_enter_sock(sock);
> > +   if (IS_ERR(map))
> > +           return PTR_ERR(map);
> >     bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> >  
> > -   map = (struct sock_mapping *) sock->sk->sk_send_head;
> > -   if (map == NULL) {
> > -           pvcalls_exit();
> > -           return -ENOTSOCK;
> > -   }
> > -
> >     spin_lock(&bedata->socket_lock);
> >     ret = get_request(bedata, &req_id);
> >     if (ret < 0) {
> >             spin_unlock(&bedata->socket_lock);
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return ret;
> >     }
> >     req = RING_GET_REQUEST(&bedata->ring, req_id);
> > @@ -684,7 +680,7 @@ int pvcalls_front_bind(struct socket *sock, struct 
> > sockaddr *addr, int addr_len)
> >     bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
> >  
> >     map->passive.status = PVCALLS_STATUS_BIND;
> > -   pvcalls_exit();
> > +   pvcalls_exit_sock(sock);
> >     return 0;
> >  }
> >  
> > @@ -695,21 +691,13 @@ int pvcalls_front_listen(struct socket *sock, int 
> > backlog)
> >     struct xen_pvcalls_request *req;
> >     int notify, req_id, ret;
> >  
> > -   pvcalls_enter();
> > -   if (!pvcalls_front_dev) {
> > -           pvcalls_exit();
> > -           return -ENOTCONN;
> > -   }
> > +   map = pvcalls_enter_sock(sock);
> > +   if (IS_ERR(map))
> > +           return PTR_ERR(map);
> >     bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> >  
> > -   map = (struct sock_mapping *) sock->sk->sk_send_head;
> > -   if (!map) {
> > -           pvcalls_exit();
> > -           return -ENOTSOCK;
> > -   }
> > -
> >     if (map->passive.status != PVCALLS_STATUS_BIND) {
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return -EOPNOTSUPP;
> >     }
> >  
> > @@ -717,7 +705,7 @@ int pvcalls_front_listen(struct socket *sock, int 
> > backlog)
> >     ret = get_request(bedata, &req_id);
> >     if (ret < 0) {
> >             spin_unlock(&bedata->socket_lock);
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return ret;
> >     }
> >     req = RING_GET_REQUEST(&bedata->ring, req_id);
> > @@ -741,7 +729,7 @@ int pvcalls_front_listen(struct socket *sock, int 
> > backlog)
> >     bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
> >  
> >     map->passive.status = PVCALLS_STATUS_LISTEN;
> > -   pvcalls_exit();
> > +   pvcalls_exit_sock(sock);
> >     return ret;
> >  }
> >  
> > @@ -753,21 +741,13 @@ int pvcalls_front_accept(struct socket *sock, struct 
> > socket *newsock, int flags)
> >     struct xen_pvcalls_request *req;
> >     int notify, req_id, ret, evtchn, nonblock;
> >  
> > -   pvcalls_enter();
> > -   if (!pvcalls_front_dev) {
> > -           pvcalls_exit();
> > -           return -ENOTCONN;
> > -   }
> > +   map = pvcalls_enter_sock(sock);
> > +   if (IS_ERR(map))
> > +           return PTR_ERR(map);
> >     bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> >  
> > -   map = (struct sock_mapping *) sock->sk->sk_send_head;
> > -   if (!map) {
> > -           pvcalls_exit();
> > -           return -ENOTSOCK;
> > -   }
> > -
> >     if (map->passive.status != PVCALLS_STATUS_LISTEN) {
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return -EINVAL;
> >     }
> >  
> > @@ -785,13 +765,13 @@ int pvcalls_front_accept(struct socket *sock, struct 
> > socket *newsock, int flags)
> >                     goto received;
> >             }
> >             if (nonblock) {
> > -                   pvcalls_exit();
> > +                   pvcalls_exit_sock(sock);
> >                     return -EAGAIN;
> >             }
> >             if (wait_event_interruptible(map->passive.inflight_accept_req,
> >                     !test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> >                                       (void *)&map->passive.flags))) {
> > -                   pvcalls_exit();
> > +                   pvcalls_exit_sock(sock);
> >                     return -EINTR;
> >             }
> >     }
> > @@ -802,7 +782,7 @@ int pvcalls_front_accept(struct socket *sock, struct 
> > socket *newsock, int flags)
> >             clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> >                       (void *)&map->passive.flags);
> >             spin_unlock(&bedata->socket_lock);
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return ret;
> >     }
> >     map2 = kzalloc(sizeof(*map2), GFP_ATOMIC);
> > @@ -810,7 +790,7 @@ int pvcalls_front_accept(struct socket *sock, struct 
> > socket *newsock, int flags)
> >             clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> >                       (void *)&map->passive.flags);
> >             spin_unlock(&bedata->socket_lock);
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return -ENOMEM;
> >     }
> >     ret = create_active(map2, &evtchn);
> > @@ -819,7 +799,7 @@ int pvcalls_front_accept(struct socket *sock, struct 
> > socket *newsock, int flags)
> >             clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> >                       (void *)&map->passive.flags);
> >             spin_unlock(&bedata->socket_lock);
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return ret;
> >     }
> >     list_add_tail(&map2->list, &bedata->socket_mappings);
> > @@ -841,13 +821,13 @@ int pvcalls_front_accept(struct socket *sock, struct 
> > socket *newsock, int flags)
> >     /* We could check if we have received a response before returning. */
> >     if (nonblock) {
> >             WRITE_ONCE(map->passive.inflight_req_id, req_id);
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return -EAGAIN;
> >     }
> >  
> >     if (wait_event_interruptible(bedata->inflight_req,
> >             READ_ONCE(bedata->rsp[req_id].req_id) == req_id)) {
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return -EINTR;
> >     }
> >     /* read req_id, then the content */
> > @@ -862,7 +842,7 @@ int pvcalls_front_accept(struct socket *sock, struct 
> > socket *newsock, int flags)
> >             clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> >                       (void *)&map->passive.flags);
> >             pvcalls_front_free_map(bedata, map2);
> > -           pvcalls_exit();
> > +           pvcalls_exit_sock(sock);
> >             return -ENOMEM;
> >     }
> >     newsock->sk->sk_send_head = (void *)map2;
> > @@ -874,7 +854,7 @@ int pvcalls_front_accept(struct socket *sock, struct 
> > socket *newsock, int flags)
> >     clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
> >     wake_up(&map->passive.inflight_accept_req);
> >  
> > -   pvcalls_exit();
> > +   pvcalls_exit_sock(sock);
> >     return ret;
> >  }
> >  
> > @@ -965,23 +945,16 @@ unsigned int pvcalls_front_poll(struct file *file, 
> > struct socket *sock,
> >     struct sock_mapping *map;
> >     int ret;
> >  
> > -   pvcalls_enter();
> > -   if (!pvcalls_front_dev) {
> > -           pvcalls_exit();
> > +   map = pvcalls_enter_sock(sock);
> > +   if (IS_ERR(map))
> >             return POLLNVAL;
> > -   }
> >     bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> >  
> > -   map = (struct sock_mapping *) sock->sk->sk_send_head;
> > -   if (!map) {
> > -           pvcalls_exit();
> > -           return POLLNVAL;
> > -   }
> >     if (map->active_socket)
> >             ret = pvcalls_front_poll_active(file, bedata, map, wait);
> >     else
> >             ret = pvcalls_front_poll_passive(file, bedata, map, wait);
> > -   pvcalls_exit();
> > +   pvcalls_exit_sock(sock);
> >     return ret;
> >  }
> >  
> > @@ -995,25 +968,18 @@ int pvcalls_front_release(struct socket *sock)
> >     if (sock->sk == NULL)
> >             return 0;
> >  
> > -   pvcalls_enter();
> > -   if (!pvcalls_front_dev) {
> > -           pvcalls_exit();
> > +   map = pvcalls_enter_sock(sock);
> > +   if (IS_ERR(map) && PTR_ERR(map) == -ENOTCONN)
> >             return -EIO;
> > -   }
> > -
> > -   bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> > -
> > -   map = (struct sock_mapping *) sock->sk->sk_send_head;
> > -   if (map == NULL) {
> > -           pvcalls_exit();
> > +   if (IS_ERR(map) && PTR_ERR(map) == -ENOTSOCK)
> >             return 0;
> 
> Hmm, what about:
> 
> if (IS_ERR(map)) {
>     if (PTR_ERR(map) == -ENOTCONN)
>         return -EIO;
>     else
>         return 0;
> }

Sounds good.

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