fs: dlm: introduce con_next_wq helper

This patch introduce a function to determine if something is ready to
being send in the writequeue. It's not just that the writequeue is not
empty additional the first entry need to have a valid length field.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 1bdd24bce7097da5790c4187111bd2caba81c137..9d21a8b9e9fbe41ce473ab2b16f7231d47b29d9c 100644 (file)
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -175,6 +175,22 @@ static void sctp_connect_to_sock(struct connection *con);
 static void tcp_connect_to_sock(struct connection *con);
 static void dlm_tcp_shutdown(struct connection *con);
 
+/* need to held writequeue_lock */
+static struct writequeue_entry *con_next_wq(struct connection *con)
+{
+       struct writequeue_entry *e;
+
+       if (list_empty(&con->writequeue))
+               return NULL;
+
+       e = list_first_entry(&con->writequeue, struct writequeue_entry,
+                            list);
+       if (e->len == 0)
+               return NULL;
+
+       return e;
+}
+
 static struct connection *__find_con(int nodeid, int r)
 {
        struct connection *con;
@@ -1646,10 +1662,9 @@ int dlm_lowcomms_resend_msg(struct dlm_msg *msg)
 /* Send a message */
 static void send_to_sock(struct connection *con)
 {
-       int ret = 0;
        const int msg_flags = MSG_DONTWAIT | MSG_NOSIGNAL;
        struct writequeue_entry *e;
-       int len, offset;
+       int len, offset, ret;
        int count = 0;
 
        mutex_lock(&con->sock_mutex);
@@ -1658,7 +1673,8 @@ static void send_to_sock(struct connection *con)
 
        spin_lock(&con->writequeue_lock);
        for (;;) {
-               if (list_empty(&con->writequeue))
+               e = con_next_wq(con);
+               if (!e)
                        break;
 
                e = list_first_entry(&con->writequeue, struct writequeue_entry, list);
@@ -1667,25 +1683,22 @@ static void send_to_sock(struct connection *con)
                BUG_ON(len == 0 && e->users == 0);
                spin_unlock(&con->writequeue_lock);
 
-               ret = 0;
-               if (len) {
-                       ret = kernel_sendpage(con->sock, e->page, offset, len,
-                                             msg_flags);
-                       if (ret == -EAGAIN || ret == 0) {
-                               if (ret == -EAGAIN &&
-                                   test_bit(SOCKWQ_ASYNC_NOSPACE, &con->sock->flags) &&
-                                   !test_and_set_bit(CF_APP_LIMITED, &con->flags)) {
-                                       /* Notify TCP that we're limited by the
-                                        * application window size.
-                                        */
-                                       set_bit(SOCK_NOSPACE, &con->sock->flags);
-                                       con->sock->sk->sk_write_pending++;
-                               }
-                               cond_resched();
-                               goto out;
-                       } else if (ret < 0)
-                               goto out;
-               }
+               ret = kernel_sendpage(con->sock, e->page, offset, len,
+                                     msg_flags);
+               if (ret == -EAGAIN || ret == 0) {
+                       if (ret == -EAGAIN &&
+                           test_bit(SOCKWQ_ASYNC_NOSPACE, &con->sock->flags) &&
+                           !test_and_set_bit(CF_APP_LIMITED, &con->flags)) {
+                               /* Notify TCP that we're limited by the
+                                * application window size.
+                                */
+                               set_bit(SOCK_NOSPACE, &con->sock->flags);
+                               con->sock->sk->sk_write_pending++;
+                       }
+                       cond_resched();
+                       goto out;
+               } else if (ret < 0)
+                       goto out;
 
                /* Don't starve people filling buffers */
                if (++count >= MAX_SEND_MSG_COUNT) {