Warn the user that will try to enable VM that VM sucks. But still allows him...

Warn the user that will try to enable VM that VM sucks. But still allows him to enable VM with a special option.

src/config.c

@@ -30,6 +30,7 @@ void loadServerConfig(char *filename) {
     char buf[REDIS_CONFIGLINE_MAX+1], *err = NULL;
     int linenum = 0;
     sds line = NULL;
+    int really_use_vm = 0;
 
     if (filename[0] == '-' && filename[1] == '\0')
         fp = stdin;
@@ -243,6 +244,10 @@ void loadServerConfig(char *filename) {
             if ((server.vm_enabled = yesnotoi(argv[1])) == -1) {
                 err = "argument must be 'yes' or 'no'"; goto loaderr;
             }
+        } else if (!strcasecmp(argv[0],"really-use-vm") && argc == 2) {
+            if ((really_use_vm = yesnotoi(argv[1])) == -1) {
+                err = "argument must be 'yes' or 'no'"; goto loaderr;
+            }
         } else if (!strcasecmp(argv[0],"vm-swap-file") && argc == 2) {
             zfree(server.vm_swap_file);
             server.vm_swap_file = zstrdup(argv[1]);
@@ -303,6 +308,7 @@ void loadServerConfig(char *filename) {
         sdsfree(line);
     }
     if (fp != stdin) fclose(fp);
+    if (server.vm_enabled && !really_use_vm) goto vm_warning;
     return;
 
 loaderr:
@@ -311,6 +317,15 @@ loaderr:
     fprintf(stderr, ">>> '%s'\n", line);
     fprintf(stderr, "%s\n", err);
     exit(1);
+
+vm_warning:
+    fprintf(stderr, "\nARE YOU SURE YOU WANT TO USE VM?\n\n");
+    fprintf(stderr, "Redis Virtual Memory is going to be deprecated soon,\n");
+    fprintf(stderr, "we think you should NOT use it, but use Redis only if\n");
+    fprintf(stderr, "your data is suitable for an in-memory database.\n");
+    fprintf(stderr, "If you *really* want VM add this in the config file:\n");
+    fprintf(stderr, "\n    really-use-vm yes\n\n");
+    exit(1);
 }
 
 /*-----------------------------------------------------------------------------