freeMemoryIfNeeded() small refactoring.

Related to issue #5686 and PR #5689.

src/config.c

@@ -1248,7 +1248,7 @@ void configSetCommand(client *c) {
             if (server.maxmemory < zmalloc_used_memory()) {
                 serverLog(LL_WARNING,"WARNING: the new maxmemory value set via CONFIG SET is smaller than the current memory usage. This will result in key eviction and/or the inability to accept new write commands depending on the maxmemory-policy.");
             }
-            freeMemoryIfNeeded();
+            freeMemoryIfNeededAndSafe();
         }
     } config_set_memory_field(
       "proto-max-bulk-len",server.proto_max_bulk_len) {

src/evict.c

@@ -445,14 +445,8 @@ int getMaxmemoryState(size_t *total, size_t *logical, size_t *tofree, float *lev
  * was freed to return back under the limit, the function returns C_ERR. */
 int freeMemoryIfNeeded(void) {
     /* By default replicas should ignore maxmemory
-     * and just be masters exact copies.
-     *
-     * And don't care about mem if loading. */
-    if (server.loading ||
-        (server.masterhost && server.repl_slave_ignore_maxmemory))
-    {
-        return C_OK;
-    }
+     * and just be masters exact copies. */
+    if (server.masterhost && server.repl_slave_ignore_maxmemory) return C_OK;
 
     size_t mem_reported, mem_tofree, mem_freed;
     mstime_t latency, eviction_latency;
@@ -628,3 +622,14 @@ cant_free:
     return C_ERR;
 }
 
+/* This is a wrapper for freeMemoryIfNeeded() that only really calls the
+ * function if right now there are the conditions to do so safely:
+ *
+ * - There must be no script in timeout condition.
+ * - Nor we are loading data right now.
+ *
+ */
+int freeMemoryIfNeededAndSafe(void) {
+    if (server.lua_timedout || server.loading) return C_OK;
+    return freeMemoryIfNeeded();
+}

src/server.c

@@ -2613,7 +2613,7 @@ int processCommand(client *c) {
      * condition, to avoid mixing the propagation of scripts with the
      * propagation of DELs due to eviction. */
     if (server.maxmemory && !server.lua_timedout) {
-        int out_of_memory = freeMemoryIfNeeded() == C_ERR;
+        int out_of_memory = freeMemoryIfNeededAndSafe() == C_ERR;
         /* freeMemoryIfNeeded may flush slave output buffers. This may result
          * into a slave, that may be the active client, to be freed. */
         if (server.current_client == NULL) return C_ERR;

src/server.h

@@ -1702,6 +1702,7 @@ int zslLexValueLteMax(sds value, zlexrangespec *spec);
 int getMaxmemoryState(size_t *total, size_t *logical, size_t *tofree, float *level);
 size_t freeMemoryGetNotCountedMemory();
 int freeMemoryIfNeeded(void);
+int freeMemoryIfNeededAndSafe(void);
 int processCommand(client *c);
 void setupSignalHandlers(void);
 struct redisCommand *lookupCommand(sds name);