fix that wrong dir is creaed when using mult-dirs storage (apache#3901)

Co-authored-by: dengzhiwen1 <dengzhiwen1@xiaomi.com>

store/src/main/java/org/apache/rocketmq/store/MappedFile.java

@@ -39,6 +39,7 @@
 import org.apache.rocketmq.common.message.MessageExtBatch;
 import org.apache.rocketmq.store.CommitLog.PutMessageContext;
 import org.apache.rocketmq.store.config.FlushDiskType;
+import org.apache.rocketmq.store.config.MessageStoreConfig;
 import org.apache.rocketmq.store.util.LibC;
 import sun.nio.ch.DirectBuffer;
 
@@ -80,14 +81,25 @@ public MappedFile(final String fileName, final int fileSize,
 
     public static void ensureDirOK(final String dirName) {
         if (dirName != null) {
-            File f = new File(dirName);
-            if (!f.exists()) {
-                boolean result = f.mkdirs();
-                log.info(dirName + " mkdir " + (result ? "OK" : "Failed"));
+            if (dirName.contains(MessageStoreConfig.MULTI_PATH_SPLITTER)) {
+                String[] dirs = dirName.trim().split(MessageStoreConfig.MULTI_PATH_SPLITTER);
+                for (String dir : dirs) {
+                    createDirIfNotExist(dir);
+                }
+            } else {
+                createDirIfNotExist(dirName);
             }
         }
     }
 
+    private static void  createDirIfNotExist(String dirName) {
+        File f = new File(dirName);
+        if (!f.exists()) {
+            boolean result = f.mkdirs();
+            log.info(dirName + " mkdir " + (result ? "OK" : "Failed"));
+        }
+    }
+
     public static void clean(final ByteBuffer buffer) {
         if (buffer == null || !buffer.isDirect() || buffer.capacity() == 0)
             return;