[rfc] sk_write_space() for atm

[chas williams <chas@xxxxxxxxxxxxxxxx>]

i am thinking about the following for the atm protocol.
the writable for atm has always been when you have enough
space to send the next pdu.  i suppose this should be 
preserved to be completely compat, but it might not be the
best choice.  poll is interesting also.  it seems to me
that vcc->reply should be atleast copied, since it could
change during the poll function (or so i imagine).  its
probably a better idea to just change WAITING to be a bit
inside vcc->flags and remove vcc->error in favor of sk->sk_err.

===== net/atm/common.c 1.41 vs edited =====
--- 1.41/net/atm/common.c       Mon Jun 23 10:57:01 2003
+++ edited/net/atm/common.c     Tue Jun 24 11:58:16 2003
@@ -243,6 +243,29 @@
                wake_up(sk->sk_sleep);
        read_unlock(&sk->sk_callback_lock);
 }
+
+static inline int vcc_writable(struct sock *sk)
+{
+       struct atm_vcc *vcc = atm_sk(sk);
+
+       return (vcc->qos.txtp.max_sdu +
+               atomic_read(&sk->sk_wmem_alloc)) <= sk->sk_sndbuf;
+}
+
+static void vcc_write_space(struct sock *sk)
+{       
+       read_lock(&sk->sk_callback_lock);
+
+       if (vcc_writable(sk)) {
+               if (sk->sk_sleep && waitqueue_active(sk->sk_sleep))
+                       wake_up_interruptible(sk->sk_sleep);
+
+               sk_wake_async(sk, 2, POLL_OUT);
+       }
+
+       read_unlock(&sk->sk_callback_lock);
+}
+
  
 int vcc_create(struct socket *sock, int protocol, int family)
 {
@@ -257,6 +280,7 @@
                return -ENOMEM;
        sock_init_data(sock, sk);
        sk->sk_state_change = vcc_def_wakeup;
+       sk->sk_write_space = vcc_write_space;
 
        vcc = atm_sk(sk) = kmalloc(sizeof(*vcc), GFP_KERNEL);
        if (!vcc) {
@@ -617,29 +641,39 @@
 }
 
 
-unsigned int atm_poll(struct file *file,struct socket *sock,poll_table *wait)
+unsigned int vcc_poll(struct file *file, struct socket *sock, poll_table *wait)
 {
+       struct sock *sk = sock->sk;
        struct atm_vcc *vcc;
+       volatile int reply;
        unsigned int mask;
 
-       vcc = ATM_SD(sock);
-       poll_wait(file, vcc->sk->sk_sleep, wait);
+       poll_wait(file, sk->sk_sleep, wait);
        mask = 0;
-       if (skb_peek(&vcc->sk->sk_receive_queue))
-               mask |= POLLIN | POLLRDNORM;
-       if (test_bit(ATM_VF_RELEASED,&vcc->flags) ||
-           test_bit(ATM_VF_CLOSE,&vcc->flags))
+
+       vcc = ATM_SD(sock);
+       reply = vcc->reply;
+
+       /* exceptional events */
+       if (sk->sk_err || (reply && reply != WAITING))
+               mask = POLLERR;
+
+       if (test_bit(ATM_VF_RELEASED, &vcc->flags) ||
+           test_bit(ATM_VF_CLOSE, &vcc->flags))
                mask |= POLLHUP;
-       if (sock->state != SS_CONNECTING) {
-               if (vcc->qos.txtp.traffic_class != ATM_NONE &&
-                   vcc->qos.txtp.max_sdu +
-                   atomic_read(&vcc->sk->sk_wmem_alloc) <= vcc->sk->sk_sndbuf)
-                       mask |= POLLOUT | POLLWRNORM;
-       }
-       else if (vcc->reply != WAITING) {
-                       mask |= POLLOUT | POLLWRNORM;
-                       if (vcc->reply) mask |= POLLERR;
-               }
+
+       /* readable? */
+       if (!skb_queue_empty(&sk->sk_receive_queue))
+               mask |= POLLIN | POLLRDNORM;
+
+       /* writable? */
+       if (sock->state == SS_CONNECTING && reply == WAITING)
+               return mask;
+
+       if (vcc->qos.txtp.traffic_class != ATM_NONE &&
+           vcc_writable(vcc->sk))
+               mask |= POLLOUT | POLLWRNORM | POLLWRBAND;
+
        return mask;
 }
 
===== net/atm/common.h 1.15 vs edited =====
--- 1.15/net/atm/common.h       Mon Jun 23 10:51:10 2003
+++ edited/net/atm/common.h     Mon Jun 23 11:04:38 2003
@@ -17,7 +17,7 @@
                int size, int flags);
 int vcc_sendmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *m,
                int total_len);
-unsigned int atm_poll(struct file *file,struct socket *sock,poll_table *wait);
+unsigned int vcc_poll(struct file *file, struct socket *sock, poll_table 
*wait);
 int vcc_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg);
 int vcc_setsockopt(struct socket *sock, int level, int optname, char *optval,
                   int optlen);
===== net/atm/pvc.c 1.17 vs edited =====
--- 1.17/net/atm/pvc.c  Fri Jun 20 17:33:02 2003
+++ edited/net/atm/pvc.c        Mon Jun 23 11:05:07 2003
@@ -111,7 +111,7 @@
        .socketpair =   sock_no_socketpair,
        .accept =       sock_no_accept,
        .getname =      pvc_getname,
-       .poll =         atm_poll,
+       .poll =         vcc_poll,
        .ioctl =        vcc_ioctl,
        .listen =       sock_no_listen,
        .shutdown =     pvc_shutdown,
===== net/atm/raw.c 1.6 vs edited =====
--- 1.6/net/atm/raw.c   Mon Jun 23 10:57:02 2003
+++ edited/net/atm/raw.c        Mon Jun 23 11:06:57 2003
@@ -40,7 +40,7 @@
                skb->truesize);
        atomic_sub(skb->truesize, &vcc->sk->sk_wmem_alloc);
        dev_kfree_skb_any(skb);
-       wake_up(vcc->sk->sk_sleep);
+       vcc->sk->sk_write_space(vcc->sk);
 }
 
 
===== net/atm/svc.c 1.21 vs edited =====
--- 1.21/net/atm/svc.c  Mon Jun 23 10:45:54 2003
+++ edited/net/atm/svc.c        Mon Jun 23 11:05:17 2003
@@ -519,7 +519,7 @@
        .socketpair =   sock_no_socketpair,
        .accept =       svc_accept,
        .getname =      svc_getname,
-       .poll =         atm_poll,
+       .poll =         vcc_poll,
        .ioctl =        vcc_ioctl,
        .listen =       svc_listen,
        .shutdown =     svc_shutdown,