Handle memory allocation failure when open vnode

This patch fixes a few error handling of memory allocation
failure while opening vnodes.

bonus fix: also add a new error code to indicate failure
of opening vnode. Before the patch, the function would simply
return -1 when vnode open fails.

src/dnode/src/dnodeVnodes.c

@@ -127,9 +127,20 @@ int32_t dnodeInitVnodes() {
   int32_t threadNum = tsNumOfCores;
   int32_t vnodesPerThread = numOfVnodes / threadNum + 1;
   SOpenVnodeThread *threads = calloc(threadNum, sizeof(SOpenVnodeThread));
+
+  if (threads == NULL) {
+    return TSDB_CODE_DND_OUT_OF_MEMORY;
+  }
+
   for (int32_t t = 0; t < threadNum; ++t) {
     threads[t].threadIndex = t;
     threads[t].vnodeList = calloc(vnodesPerThread, sizeof(int32_t));
+
+    if (threads[t].vnodeList == NULL) {
+      dError("vnodeList allocation failed");
+      status = TSDB_CODE_DND_OUT_OF_MEMORY;
+      goto DNODE_INIT_VNODES_OUT;
+    }
   }
 
   for (int32_t v = 0; v < numOfVnodes; ++v) {
@@ -163,18 +174,24 @@ int32_t dnodeInitVnodes() {
     }
     openVnodes += pThread->opened;
     failedVnodes += pThread->failed;
-    free(pThread->vnodeList);
   }
 
-  free(threads);
   dInfo("there are total vnodes:%d, opened:%d", numOfVnodes, openVnodes);
 
   if (failedVnodes != 0) {
     dError("there are total vnodes:%d, failed:%d", numOfVnodes, failedVnodes);
-    return -1;
+    status = TSDB_CODE_DND_VNODE_OPEN_FAILED;
   }
 
-  return TSDB_CODE_SUCCESS;
+DNODE_INIT_VNODES_OUT:
+
+  for (int32_t t = 0; t < threadNum; ++t) {
+    SOpenVnodeThread *pThread = &threads[t];
+    free(pThread->vnodeList);
+  }
+  free(threads);
+
+  return status;
 }
 
 void dnodeCleanupVnodes() {

src/inc/taoserror.h

@@ -224,6 +224,7 @@ int32_t* taosGetErrno();
 #define TSDB_CODE_DND_ACTION_IN_PROGRESS        TAOS_DEF_ERROR_CODE(0, 0x0404)  //"Action in progress")
 #define TSDB_CODE_DND_TOO_MANY_VNODES           TAOS_DEF_ERROR_CODE(0, 0x0405)  //"Too many vnode directories")
 #define TSDB_CODE_DND_EXITING                   TAOS_DEF_ERROR_CODE(0, 0x0406)  //"Dnode is exiting"
+#define TSDB_CODE_DND_VNODE_OPEN_FAILED         TAOS_DEF_ERROR_CODE(0, 0x0407)  //"Vnode open failed
 
 // vnode
 #define TSDB_CODE_VND_ACTION_IN_PROGRESS        TAOS_DEF_ERROR_CODE(0, 0x0500)  //"Action in progress")