arc: Abort booting ARC if the device is critically low on disk space.

chromeos/dbus/cryptohome_client.cc

Index: chromeos/dbus/cryptohome_client.cc
diff --git a/chromeos/dbus/cryptohome_client.cc b/chromeos/dbus/cryptohome_client.cc
index 86fe5b7e65ab7ff67ad86c151812aee85abde460..2608496e47528afbf972afb4f54266fab0303c17 100644
--- a/chromeos/dbus/cryptohome_client.cc
+++ b/chromeos/dbus/cryptohome_client.cc
@@ -168,6 +168,15 @@ class CryptohomeClientImpl : public CryptohomeClient {
   }
 
   // CryptohomeClient override.
+  void GetFreeDiskSpace(const GetFreeDiskSpaceCallback& callback) override {
+    dbus::MethodCall method_call(cryptohome::kCryptohomeInterface,
+                                 cryptohome::kCryptohomeGetFreeDiskSpace);
+    proxy_->CallMethod(&method_call, kTpmDBusTimeoutMs,
+                       base::Bind(&CryptohomeClientImpl::OnGetFreeDiskSpace,
+                                  weak_ptr_factory_.GetWeakPtr(), callback));
+  }
+
+  // CryptohomeClient override.
   void GetSystemSalt(const GetSystemSaltCallback& callback) override {
     dbus::MethodCall method_call(cryptohome::kCryptohomeInterface,
                                  cryptohome::kCryptohomeGetSystemSalt);
@@ -973,6 +982,22 @@ class CryptohomeClientImpl : public CryptohomeClient {
     callback.Run(async_id);
   }
 
+  // Handles the result of GetFreeDiskSpace().
+  void OnGetFreeDiskSpace(const GetFreeDiskSpaceCallback& callback,
+                          dbus::Response* response) {
+    if (!response) {
+      callback.Run(DBUS_METHOD_CALL_FAILURE, 0);
+      return;
+    }
+    dbus::MessageReader reader(response);
+    uint64_t disk_free_bytes = 0;
+    if (!reader.PopUint64(&disk_free_bytes)) {
+      LOG(ERROR) << "Invalid response: " << response->ToString();
+      return;

[hidehiko, 2016/07/14 07:39:40]

isn't it necessary to invoke callback.Run(FAILURE, ...); ?
Some methods around here do, and some other don't.
I cannot figure out the difference of them, though...

[Shuhei Takahashi, 2016/07/14 08:44:27]

Yup, I think that's good to call failure callback. Done.

+    }
+    callback.Run(DBUS_METHOD_CALL_SUCCESS, disk_free_bytes);
+  }
+
   // Handles the result of GetSystemSalt().
   void OnGetSystemSalt(const GetSystemSaltCallback& callback,
                        dbus::Response* response) {