Make pending buffer processing safe for CLIENT_MASTER client.

Related to #5305.

src/blocked.c

@@ -126,7 +126,7 @@ void processUnblockedClients(void) {
          * the code is conceptually more correct this way. */
         if (!(c->flags & CLIENT_BLOCKED)) {
             if (c->querybuf && sdslen(c->querybuf) > 0) {
-                processInputBuffer(c);
+                processInputBufferAndReplicate(c);
             }
         }
     }

src/networking.c

@@ -1425,6 +1425,25 @@ void processInputBuffer(client *c) {
     server.current_client = NULL;
 }
 
+/* This is a wrapper for processInputBuffer that also cares about handling
+ * the replication forwarding to the sub-slaves, in case the client 'c'
+ * is flagged as master. Usually you want to call this instead of the
+ * raw processInputBuffer(). */
+void processInputBufferAndReplicate(client *c) {
+    if (!(c->flags & CLIENT_MASTER)) {
+        processInputBuffer(c);
+    } else {
+        size_t prev_offset = c->reploff;
+        processInputBuffer(c);
+        size_t applied = c->reploff - prev_offset;
+        if (applied) {
+            replicationFeedSlavesFromMasterStream(server.slaves,
+                    c->pending_querybuf, applied);
+            sdsrange(c->pending_querybuf,applied,-1);
+        }
+    }
+}
+
 void readQueryFromClient(aeEventLoop *el, int fd, void *privdata, int mask) {
     client *c = (client*) privdata;
     int nread, readlen;
@@ -1492,18 +1511,7 @@ void readQueryFromClient(aeEventLoop *el, int fd, void *privdata, int mask) {
      * was actually applied to the master state: this quantity, and its
      * corresponding part of the replication stream, will be propagated to
      * the sub-slaves and to the replication backlog. */
-    if (!(c->flags & CLIENT_MASTER)) {
+    processInputBufferAndReplicate(c);
-        processInputBuffer(c);
-    } else {
-        size_t prev_offset = c->reploff;
-        processInputBuffer(c);
-        size_t applied = c->reploff - prev_offset;
-        if (applied) {
-            replicationFeedSlavesFromMasterStream(server.slaves,
-                    c->pending_querybuf, applied);
-            sdsrange(c->pending_querybuf,applied,-1);
-        }
-    }
 }
 
 void getClientsMaxBuffers(unsigned long *longest_output_list,

src/server.h

@@ -1418,6 +1418,7 @@ void sendReplyToClient(aeEventLoop *el, int fd, void *privdata, int mask);
 void *addDeferredMultiBulkLength(client *c);
 void setDeferredMultiBulkLength(client *c, void *node, long length);
 void processInputBuffer(client *c);
+void processInputBufferAndReplicate(client *c);
 void acceptHandler(aeEventLoop *el, int fd, void *privdata, int mask);
 void acceptTcpHandler(aeEventLoop *el, int fd, void *privdata, int mask);
 void acceptUnixHandler(aeEventLoop *el, int fd, void *privdata, int mask);