Experimental optimization. Suppose that if sock_recvmsg() returned less data than...

git-svn-id: https://scst.svn.sourceforge.net/svnroot/scst/trunk@1236 d57e44dd-8a1f-0410-8b47-8ef2f437770f

diff --git a/iscsi-scst/kernel/nthread.c b/iscsi-scst/kernel/nthread.c
index 31e2bfc..9f4aab2 100644 (file)
--- a/iscsi-scst/kernel/nthread.c
+++ b/iscsi-scst/kernel/nthread.c
@@ -647,68 +647,71 @@ static struct iscsi_cmnd *iscsi_get_send_cmnd(struct iscsi_conn *conn)
 static int do_recv(struct iscsi_conn *conn)
 {
        int res;
+       mm_segment_t oldfs;
+       struct msghdr msg;
+       int first_len;
 
        EXTRACHECKS_BUG_ON(conn->read_cmnd == NULL);
 
-       do {
-               mm_segment_t oldfs;
-               struct msghdr msg;
-               int first_len;
+       if (unlikely(conn->closing)) {
+               res = -EIO;
+               goto out;
+       }
 
-               if (unlikely(conn->closing)) {
-                       res = -EIO;
-                       goto out;
-               }
+       /*
+        * We suppose that if sock_recvmsg() returned less data than requested,
+        * then next time it will return -EAGAIN, so there's no point to call
+        * it again.
+        */
 
-               memset(&msg, 0, sizeof(msg));
-               msg.msg_iov = conn->read_msg.msg_iov;
-               msg.msg_iovlen = conn->read_msg.msg_iovlen;
-               first_len = msg.msg_iov->iov_len;
+restart:
+       memset(&msg, 0, sizeof(msg));
+       msg.msg_iov = conn->read_msg.msg_iov;
+       msg.msg_iovlen = conn->read_msg.msg_iovlen;
+       first_len = msg.msg_iov->iov_len;
 
-               oldfs = get_fs();
-               set_fs(get_ds());
-               res = sock_recvmsg(conn->sock, &msg, conn->read_size,
-                                  MSG_DONTWAIT | MSG_NOSIGNAL);
-               set_fs(oldfs);
+       oldfs = get_fs();
+       set_fs(get_ds());
+       res = sock_recvmsg(conn->sock, &msg, conn->read_size,
+                          MSG_DONTWAIT | MSG_NOSIGNAL);
+       set_fs(oldfs);
 
-               if (res > 0) {
-                       /*
-                        * To save some considerable effort and CPU power we
-                        * suppose that TCP functions adjust
-                        * conn->read_msg.msg_iov and conn->read_msg.msg_iovlen
-                        * on amount of copied data. This BUG_ON is intended
-                        * to catch if it is changed in the future.
-                        */
-                       sBUG_ON((res >= first_len) &&
-                               (conn->read_msg.msg_iov->iov_len != 0));
-                       conn->read_size -= res;
-                       if (conn->read_size != 0) {
-                               if (res >= first_len) {
-                                       int done = 1 + ((res - first_len) >> PAGE_SHIFT);
-                                       conn->read_msg.msg_iov += done;
-                                       conn->read_msg.msg_iovlen -= done;
-                               }
+       if (res > 0) {
+               /*
+                * To save some considerable effort and CPU power we
+                * suppose that TCP functions adjust
+                * conn->read_msg.msg_iov and conn->read_msg.msg_iovlen
+                * on amount of copied data. This BUG_ON is intended
+                * to catch if it is changed in the future.
+                */
+               sBUG_ON((res >= first_len) &&
+                       (conn->read_msg.msg_iov->iov_len != 0));
+               conn->read_size -= res;
+               if (conn->read_size != 0) {
+                       if (res >= first_len) {
+                               int done = 1 + ((res - first_len) >> PAGE_SHIFT);
+                               conn->read_msg.msg_iov += done;
+                               conn->read_msg.msg_iovlen -= done;
                        }
+               }
+               res = conn->read_size;
+       } else {
+               switch (res) {
+               case -EAGAIN:
+                       TRACE_DBG("EAGAIN received for conn %p", conn);
                        res = conn->read_size;
-               } else {
-                       switch (res) {
-                       case -EAGAIN:
-                               TRACE_DBG("EAGAIN received for conn %p", conn);
-                               res = conn->read_size;
-                               break;
-                       case -ERESTARTSYS:
-                               TRACE_DBG("ERESTARTSYS received for conn %p", conn);
-                               continue;
-                       default:
-                               PRINT_ERROR("sock_recvmsg() failed: %d", res);
-                               mark_conn_closed(conn);
-                               if (res == 0)
-                                       res = -EIO;
-                               break;
-                       }
+                       break;
+               case -ERESTARTSYS:
+                       TRACE_DBG("ERESTARTSYS received for conn %p", conn);
+                       goto restart;
+               default:
+                       PRINT_ERROR("sock_recvmsg() failed: %d", res);
+                       mark_conn_closed(conn);
+                       if (res == 0)
+                               res = -EIO;
                        break;
                }
-       } while (res > 0);
+       }
 
 out:
        TRACE_EXIT_RES(res);