Find device-dependent disk stats file, and skip disk stats if not available.

metrics_daemon_main.cc

Index: metrics_daemon_main.cc
diff --git a/metrics_daemon_main.cc b/metrics_daemon_main.cc
index 899256cffccbd6948d2699b4b12ebbfbff5951fc..2d3628a3cce4070075d9abdb1fe6f2138e7211ff 100644
--- a/metrics_daemon_main.cc
+++ b/metrics_daemon_main.cc
@@ -3,20 +3,38 @@
 // found in the LICENSE file.
 
 
+#include <base/logging.h>
 #include <gflags/gflags.h>
+#include <rootdev/rootdev.h>
 
 #include "metrics_daemon.h"
 
 DEFINE_bool(daemon, true, "run as daemon (use -nodaemon for debugging)");
 
-// Path to disk stats.  This may be system dependent.
-const char kMetricsMainDiskStatsPath[] = "/sys/class/block/sda/stat";
+// Return the path to the disk stats in the sysfs.
+static
+const std::string MetricsMainDiskStatsPath() {
+  char dev_path[PATH_MAX];
+  int ret = rootdev(dev_path, sizeof(dev_path), true, true);
+  if (ret != 0) {
+    LOG(WARNING) << "error " << ret << " determining root device";
+    return "";
+  }
+  if (strcmp(dev_path, "/dev/sda") == 0) {

[petkov, 2011/02/18 04:52:00]

this is probably ok as is... just a suggestion though:

why not check for and strip "/dev/" prefix and then check for the existence of
"/sys/class/block/" + suffix + "/stat"? it will be a tiny bit more generic and
somewhat more robust.

+    return "/sys/class/block/sda/stat";
+  } else if (strcmp(dev_path, "/dev/mmcblk0") == 0) {
+    return "/sys/class/block/mmcblk0/stat";
+  } else {
+    LOG(WARNING) << "unknown root device " << dev_path;
+    return "";
+  }
+}
 
 int main(int argc, char** argv) {
   google::ParseCommandLineFlags(&argc, &argv, true);
   MetricsLibrary metrics_lib;
   metrics_lib.Init();
   MetricsDaemon daemon;
-  daemon.Init(false, &metrics_lib, kMetricsMainDiskStatsPath);
+  daemon.Init(false, &metrics_lib, MetricsMainDiskStatsPath());
   daemon.Run(FLAGS_daemon);
 }