dedup-tool: add options for operating usability

Daemonization is used for background execution of crawler.
Iterative execution makes crawler threads wake up at each period.

[usage]
  ceph_dedup_tool --op sample-dedup --pool POOL --chunk-pool POOL \
    --iterative --daemonize

src/tools/ceph_dedup_tool.cc

@@ -160,6 +160,8 @@ void usage()
   cout << "   --chunk-dedup-threshold <number>" << std::endl;
   cout << "   --sampling-ratio <percentile>" << std::endl;
   cout << "   --shallow-crawling" << std::endl;
+  cout << "   --daemon" << std::endl;
+  cout << "   --iterative" << std::endl;
   cout << "explanations: " << std::endl;
   cout << "   chunk-dedup performs deduplication using a chunk generated by given source" << std::endl;
   cout << "   offset and length. object-dedup deduplicates the entire object, not a chunk" << std::endl;
@@ -1758,6 +1760,28 @@ int make_dedup_object(const std::map < std::string, std::string > &opts,
 
 int make_crawling_daemon(const map<string, string> &opts,
   vector<const char*> &nargs) {
+
+  map<string, string>::const_iterator i = opts.find("daemon");
+  if (i != opts.end()) {
+    pid_t pid = fork();
+    if (pid < 0) {
+      cerr << "daemon process creation failed\n";
+      return -EINVAL;
+    }
+
+    if (pid != 0) {
+      return 0;
+    }
+    signal(SIGHUP, SIG_IGN);
+    close(STDIN_FILENO);
+    close(STDOUT_FILENO);
+  }
+
+  i = opts.find("iterative");
+  bool iterative = false;
+  if (i != opts.end()) {
+    iterative = true;
+  }
   string base_pool_name;
   auto i = opts.find("pool");
   if (i != opts.end()) {
@@ -1840,6 +1864,13 @@ int make_crawling_daemon(const map<string, string> &opts,
     cerr << "couldn't connect to cluster: " << cpp_strerror(ret) << std::endl;
     return -EINVAL;
   }
+  uint32_t wakeup_period = 100;
+  i = opts.find("wakeup-period");
+  if (i != opts.end()) {
+    if (rados_sistrtoll(i, &wakeup_period)) {
+      return -EINVAL;
+    }
+  }
 
   std::string fp_algo;
   i = opts.find("fingerprint-algorithm");
@@ -1950,7 +1981,12 @@ int make_crawling_daemon(const map<string, string> &opts,
     for (auto &p : estimate_threads) {
       p->join();
     }
-    break;
+
+    if (iterative) {
+     sleep(wakeup_period);
+    } else {
+      break;
+    }
   }
 
   return 0;
@@ -2028,6 +2064,12 @@ int main(int argc, const char **argv)
       opts["object-dedup-threshold"] = val;
     } else if (ceph_argparse_witharg(args, i, &val, "--chunk-dedup-threshold", (char*)NULL)) {
       opts["chunk-dedup-threshold"] = val;
+    } else if (ceph_argparse_witharg(args, i, &val, "--wakeup-period", (char*)NULL)) {
+      opts["wakeup-period"] = val;
+    } else if (ceph_argparse_flag(args, i, "--daemon", (char*)NULL)) {
+      opts["daemon"] = "true";
+    } else if (ceph_argparse_flag(args, i, "--iterative", (char*)NULL)) {
+      opts["iterative"] = "true";
     } else if (ceph_argparse_flag(args, i, "--shallow-crawling", (char*)NULL)) {
       opts["shallow-crawling"] = true;
     } else if (ceph_argparse_flag(args, i, "--debug", (char*)NULL)) {