rio fdset target: handle short writes.

While the socket is set in blocking mode, we still can get short writes
writing to a socket.

src/rdb.c

@@ -1347,6 +1347,8 @@ void backgroundSaveDoneHandlerSocket(int exitcode, int bysignal) {
                 redisLog(REDIS_WARNING,
                 "Slave %llu correctly received the streamed RDB file.",
                 slave->id);
+                /* Restore the socket as non-blocking. */
+                anetNonBlock(NULL,slave->fd);
             }
         }
     }
@@ -1408,6 +1410,10 @@ int rdbSaveToSlavesSockets(void) {
             clientids[numfds] = slave->id;
             fds[numfds++] = slave->fd;
             slave->replstate = REDIS_REPL_WAIT_BGSAVE_END;
+            /* Put the socket in non-blocking mode to simplify RDB transfer.
+             * We'll restore it when the children returns (since duped socket
+             * will share the O_NONBLOCK attribute with the parent). */
+            anetBlock(NULL,slave->fd);
         }
     }
 

src/replication.c

@@ -888,6 +888,7 @@ void readSyncBulkPayload(aeEventLoop *el, int fd, void *privdata, int mask) {
     }
 
     nread = read(fd,buf,readlen);
+    printf("NREAD %d (%d)\n", (int)nread, (int)readlen);
     if (nread <= 0) {
         redisLog(REDIS_WARNING,"I/O error trying to sync with MASTER: %s",
             (nread == -1) ? strerror(errno) : "connection lost");

src/rio.c

@@ -197,8 +197,17 @@ static size_t rioFdsetWrite(rio *r, const void *buf, size_t len) {
                 broken++;
                 continue;
             }
-            retval = write(r->io.fdset.fds[j],p,count);
-            if (retval != count) {
+
+            /* Make sure to write 'count' bytes to the socket regardless
+             * of short writes. */
+            size_t nwritten = 0;
+            while(nwritten != count) {
+                retval = write(r->io.fdset.fds[j],p+nwritten,count-nwritten);
+                if (retval <= 0) break;
+                nwritten += retval;
+            }
+
+            if (nwritten != count) {
                 /* Mark this FD as broken. */
                 r->io.fdset.state[j] = errno;
                 if (r->io.fdset.state[j] == 0) r->io.fdset.state[j] = EIO;