osd/OSD: rewrite build_incremental_map_msg()

* use lambda to maintain size limits.
* avoid copying by std::move the bl into the message.

Signed-off-by: Matan Breizman <[email protected]>

Author: Matan-B

src/osd/OSD.cc

@@ -1377,6 +1377,19 @@ void OSDService::got_stop_ack()
 MOSDMap *OSDService::build_incremental_map_msg(epoch_t since, epoch_t to,
                                                OSDSuperblock& sblock)
 {
+  auto get_map_and_adjust_counters = [] (
+    bufferlist& bl,
+    int& max,
+    ssize_t& max_bytes,
+    std::function<bool()> map_getter) {
+      if (!map_getter()) {
+        return false;
+      }
+      max--;
+      max_bytes -= bl.length();
+      return true;
+  };
+
   MOSDMap *m = new MOSDMap(monc->get_fsid(),
 			   osdmap->get_encoding_features());
   m->cluster_osdmap_trim_lower_bound = sblock.cluster_osdmap_trim_lower_bound;
@@ -1388,36 +1401,34 @@ MOSDMap *OSDService::build_incremental_map_msg(epoch_t since, epoch_t to,
   if (since < m->cluster_osdmap_trim_lower_bound) {
     // we don't have the next map the target wants, so start with a
     // full map.
-    bufferlist bl;
     dout(10) << __func__ << " cluster osdmap lower bound "
              << sblock.cluster_osdmap_trim_lower_bound
              << " > since " << since << ", starting with full map"
              << dendl;
     since = m->cluster_osdmap_trim_lower_bound;
-    if (!get_map_bl(since, bl)) {
-      derr << __func__ << " missing full map " << since << dendl;
+    if (bufferlist bl;
+        get_map_and_adjust_counters(bl, max, max_bytes, [&] { return get_map_bl(since, bl);})) {
+      m->maps[since] = std::move(bl);
+      ++since;
+    } else {
+      derr << __func__ << " missing full map after map gap " << since << dendl;
       goto panic;
     }
-    max--;
-    max_bytes -= bl.length();
-    m->maps[since] = std::move(bl);
   }
-  for (epoch_t e = since; e <= to; ++e) {
-    bufferlist bl;
-    if (get_inc_map_bl(e, bl)) {
-      m->incremental_maps[e] = bl;
+
+  for (epoch_t e = since; e <= to && max > 0 && max_bytes > 0; ++e) {
+    if (bufferlist bl;
+        get_map_and_adjust_counters(bl, max, max_bytes, [&] { return get_inc_map_bl(e, bl);})) {
+        m->incremental_maps[e] = std::move(bl);
     } else {
       dout(10) << __func__ << " missing incremental map " << e << dendl;
-      if (!get_map_bl(e, bl)) {
-	derr << __func__ << " also missing full map " << e << dendl;
-	goto panic;
+      if (bufferlist bl;
+          get_map_and_adjust_counters(bl, max, max_bytes, [&] { return get_map_bl(e, bl);})) {
+        m->maps[e] = std::move(bl);
+      } else {
+        derr << __func__ << " also missing full map " << e << dendl;
+        goto panic;
       }
-      m->maps[e] = bl;
-    }
-    max--;
-    max_bytes -= bl.length();
-    if (max <= 0 || max_bytes <= 0) {
-      break;
     }
   }
   return m;