update_engine resize dynamic partitions during OTA.

update_engine uses device mapper to resize dynamic partitions
before opening the devices to apply the update.

* DeltaPerformer calls BootControlInterface::InitPartitionMetadata
  when parsing the update manifest. The implementation for
  BootControlAndroid::InitPartitionMetadata does the following
  if sizes for dynamic partitions are incorrect (assuming updating
  from slot A to B):
  * Load metadata from metadata slot A
  * Delete all extents of partitions at slot B (with _b suffix)
  * Add extents for partitions at slot B
  * Write metadata to metadata slot B
  * Re-map all partitions at slot B using metadata slot B with
    force_writable = true
* BootControlAndroid::GetPartitionDevice() checks device-mapper
  before returning static partitions.
* PostinstallRunnerAction::Cleanup calls BootControlInterface::Cleanup
  which unmaps all partitions at slot B.

A partition "foo" is considered dynamic if foo_a exists as a dynamic
partition OR foo_b does NOT exist as a static partition.

Bug: 110717529

Test: manual ota
Test: update_engine_unittests --gtest_filter=*BootControlAndroid*
Change-Id: I50f410b486a874242663624801c3694151bdda18
diff --git a/dynamic_partition_control_android.h b/dynamic_partition_control_android.h
new file mode 100644
index 0000000..945954d
--- /dev/null
+++ b/dynamic_partition_control_android.h
@@ -0,0 +1,61 @@
+//
+// Copyright (C) 2018 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef UPDATE_ENGINE_DYNAMIC_PARTITION_CONTROL_ANDROID_H_
+#define UPDATE_ENGINE_DYNAMIC_PARTITION_CONTROL_ANDROID_H_
+
+#include "update_engine/dynamic_partition_control_interface.h"
+
+#include <memory>
+#include <set>
+#include <string>
+
+namespace chromeos_update_engine {
+
+class DynamicPartitionControlAndroid : public DynamicPartitionControlInterface {
+ public:
+  DynamicPartitionControlAndroid() = default;
+  ~DynamicPartitionControlAndroid();
+  bool IsDynamicPartitionsEnabled() override;
+  bool MapPartitionOnDeviceMapper(const std::string& super_device,
+                                  const std::string& target_partition_name,
+                                  uint32_t slot,
+                                  std::string* path) override;
+  bool UnmapPartitionOnDeviceMapper(const std::string& target_partition_name,
+                                    bool wait) override;
+  void Cleanup() override;
+  bool DeviceExists(const std::string& path) override;
+  android::dm::DmDeviceState GetState(const std::string& name) override;
+  bool GetDmDevicePathByName(const std::string& name,
+                             std::string* path) override;
+  std::unique_ptr<android::fs_mgr::MetadataBuilder> LoadMetadataBuilder(
+      const std::string& super_device, uint32_t source_slot) override;
+  bool StoreMetadata(const std::string& super_device,
+                     android::fs_mgr::MetadataBuilder* builder,
+                     uint32_t target_slot) override;
+  bool GetDeviceDir(std::string* path) override;
+
+ private:
+  std::set<std::string> mapped_devices_;
+
+  void CleanupInternal(bool wait);
+
+  DISALLOW_COPY_AND_ASSIGN(DynamicPartitionControlAndroid);
+};
+
+}  // namespace chromeos_update_engine
+
+#endif  // UPDATE_ENGINE_DYNAMIC_PARTITION_CONTROL_ANDROID_H_