ctdb: calculate queue input buffer size correctly

The queue's input buffer is calculated in an iterative way.
This can result in a few back and forth jumping and
a few memory allocations and mem-free cycles.
This is very time consuming and not required, because the required
memory size can be calculated right away.

Signed-off-by: Swen Schillig <swen@vnet.ibm.com>
Reviewed-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Sat Aug 18 04:58:05 CEST 2018 on sn-devel-144

diff --git a/ctdb/common/ctdb_io.c b/ctdb/common/ctdb_io.c
index 698febd08475fab8919df3a08fb1b3ed499a2c53..32d8fc753a643f4d2525fad3d8cdac52320a40c7 100644 (file)
--- a/ctdb/common/ctdb_io.c
+++ b/ctdb/common/ctdb_io.c
@@ -43,7 +43,6 @@ struct ctdb_buffer {
        uint8_t *data;
        uint32_t length;
        uint32_t size;
-       uint32_t extend;
 };
 
 struct ctdb_queue_pkt {
@@ -102,16 +101,15 @@ static void queue_process(struct ctdb_queue *queue)
                return;
        }
 
+       /* Did we at least read the size into the buffer */
        pkt_size = *(uint32_t *)queue->buffer.data;
        if (pkt_size == 0) {
                DEBUG(DEBUG_CRIT, ("Invalid packet of length 0\n"));
                goto failed;
        }
 
+       /* the buffer doesn't contain the full packet, return to get the rest */
        if (queue->buffer.length < pkt_size) {
-               if (pkt_size > queue->buffer_size) {
-                       queue->buffer.extend = pkt_size;
-               }
                return;
        }
 
@@ -158,6 +156,7 @@ failed:
 static void queue_io_read(struct ctdb_queue *queue)
 {
        int num_ready = 0;
+       uint32_t pkt_size;
        ssize_t nread;
        uint8_t *data;
 
@@ -183,18 +182,28 @@ static void queue_io_read(struct ctdb_queue *queue)
                        goto failed;
                }
                queue->buffer.size = queue->buffer_size;
-       } else if (queue->buffer.extend > 0) {
-               /* extending buffer */
-               data = talloc_realloc_size(queue, queue->buffer.data, queue->buffer.extend);
+               goto data_read;
+       }
+
+       if (queue->buffer.length < sizeof(pkt_size)) {
+               /* data read is not sufficient to gather message size */
+               goto data_read;
+       }
+
+       pkt_size = *(uint32_t *)queue->buffer.data;
+       if (pkt_size > queue->buffer.size) {
+               data = talloc_realloc_size(queue,
+                                          queue->buffer.data,
+                                          pkt_size);
                if (data == NULL) {
-                       DEBUG(DEBUG_ERR, ("read error realloc failed for %u\n", queue->buffer.extend));
+                       DBG_ERR("read error realloc failed for %u\n", pkt_size);
                        goto failed;
                }
                queue->buffer.data = data;
-               queue->buffer.size = queue->buffer.extend;
-               queue->buffer.extend = 0;
+               queue->buffer.size = pkt_size;
        }
 
+data_read:
        num_ready = MIN(num_ready, queue->buffer.size - queue->buffer.length);
 
        if (num_ready > 0) {