三、Storage框架整理

转自：http://blog.sina.com.cn/s/blog_6100a4f10101ee40.html

一 storage功能相关模块

• MountService.java

              base/services/java/com/android/server/MountService.java

• PackageManagerService.java

              base/services/java/com/android/server/pm/PackageManagerService.java

• StorageManager.java

              base/core/java/android/os/storage/StorageManager.java

• DefaultContainerService.java

              base/packages/DefaultContainerService/src/com/android/defcontainer/DefaultContainerService.java

• Settings—storage/application

              packages/apps/Settings/src/com/android/settings

• Vold框架

              system/vold

• Kernel

二 StorageManager

2.1 方法/类/变量

package                                                                                                   

   android.os.storage  

 class                                                                                                     

   StorageManager                                                                                           

   MountServiceBinderListener [StorageManager]                                                             

   ObbActionListener [StorageManager]                                                                       

   ObbListenerDelegate [StorageManager]                                                                    

   ObbStateChangedStorageEvent [StorageManager]                                                            

   StorageEvent [StorageManager]                                                                           

   UmsConnectionChangedStorageEvent [StorageManager]                                                       

   StorageStateChangedStorageEvent [StorageManager]                                                        

   ListenerDelegate [StorageManager]                                                                       

  field                                                                                                     

   TAG [StorageManager]                                                                                    

   PROP_SD_DEFAULT_PATH [StorageManager]                                                                   

   PROP_SD_INTERNAL_PATH [StorageManager]                                                                  

   PROP_SD_EXTERNAL_PATH [StorageManager]                                                                   

   ICS_STORAGE_PATH_SD1 [StorageManager]                                                                   

   ICS_STORAGE_PATH_SD2 [StorageManager]                                                                    

   STORAGE_PATH_SD1 [StorageManager]                                                                       

   STORAGE_PATH_SD2 [StorageManager]                                                                       

   mMTKExternalCacheDir [StorageManager]                                                                   

   mMountService [StorageManager]                                                                          

   mTgtLooper [StorageManager]                                                                              

   mBinderListener [StorageManager] 

   mListeners [StorageManager]                                                                             

   mNextNonce [StorageManager]                                                                              

   mObbActionListener [StorageManager]                                                                     

   mListeners [StorageManager.ObbActionListener]                                                            

   mObbEventListenerRef [StorageManager.ObbListenerDelegate]                                               

   mHandler [StorageManager.ObbListenerDelegate]                                                           

   nonce [StorageManager.ObbListenerDelegate]                                                              

   path [StorageManager.ObbStateChangedStorageEvent]                                                       

   state [StorageManager.ObbStateChangedStorageEvent]                                                       

   EVENT_UMS_CONNECTION_CHANGED [StorageManager.StorageEvent]                                              

   EVENT_STORAGE_STATE_CHANGED [StorageManager.StorageEvent]                                                

   EVENT_OBB_STATE_CHANGED [StorageManager.StorageEvent]                                                   

   mMessage [StorageManager.StorageEvent]                                                                  

   available [StorageManager.UmsConnectionChangedStorageEvent]                                             

   path [StorageManager.StorageStateChangedStorageEvent]                                                   

   oldState [StorageManager.StorageStateChangedStorageEvent]                                                

   newState [StorageManager.StorageStateChangedStorageEvent]                                               

   mStorageEventListener [StorageManager.ListenerDelegate]                                                  

   mHandler [StorageManager.ListenerDelegate]                                                              

                                                                                                           

 method                                                                                                     

   onUsbMassStorageConnectionChanged [StorageManager.MountServiceBinderListener]                           

   onStorageStateChanged [StorageManager.MountServiceBinderListener]                                       

   onObbResult [StorageManager.ObbActionListener]                                                          

   addListener [StorageManager.ObbActionListener]                                                           

   getNextNonce [StorageManager]                                                                           

   ObbListenerDelegate [StorageManager.ObbListenerDelegate]                                                

   getListener [StorageManager.ObbListenerDelegate]                                                        

   sendObbStateChanged [StorageManager.ObbListenerDelegate]                                                

   ObbStateChangedStorageEvent [StorageManager.ObbStateChangedStorageEvent]

StorageEvent [StorageManager.StorageEvent]                                                                 

   getMessage [StorageManager.StorageEvent]                                                                

   UmsConnectionChangedStorageEvent [StorageManager.UmsConnectionChangedStorageEvent]                      

   StorageStateChangedStorageEvent [StorageManager.StorageStateChangedStorageEvent]                        

   ListenerDelegate [StorageManager.ListenerDelegate]                                                       

   getListener [StorageManager.ListenerDelegate]                                                           

   sendShareAvailabilityChanged [StorageManager.ListenerDelegate]                                          

   sendStorageStateChanged [StorageManager.ListenerDelegate]                                               

   from [StorageManager]                                                                                   

   StorageManager [StorageManager]                                                                          

   registerListener [StorageManager]                                                                       

   unregisterListener [StorageManager]                                                                      

   enableUsbMassStorage [StorageManager]                                                                   

   disableUsbMassStorage [StorageManager]                                                                  

   isUsbMassStorageConnected [StorageManager]                                                              

   isUsbMassStorageEnabled [StorageManager]                                                                

   mountObb [StorageManager]                                                                                

   unmountObb [StorageManager]                                                                             

   isObbMounted [StorageManager]                                                                            

   getMountedObbPath [StorageManager]                                                                      

   getVolumeState [StorageManager]                                                                         

   getVolumeList [StorageManager]                                                                          

   getVolumePaths [StorageManager]                                                                         

   getPrimaryVolume [StorageManager]                                                                        

   getPrimaryVolume [StorageManager]                                                                       

   getDefaultPath [StorageManager]                                                                          

   setDefaultPath [StorageManager]                                                                         

   getMTKExternalCacheDir [StorageManager]                                                                 

   getExternalStoragePath [StorageManager]                                                                 

   getInternalStoragePath [StorageManager]         

 

2.2 工作流程

应用PhoneStatusBarPolicy.java

frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/PhoneStatusBarPolicy.java

调用StorageManager的监听注册函数，将监听的StorageEventListener注册到StorageManager中，当有状态变化时，会调用该类的对应函数。通常在具体需要storage状态变化的场景会定义一个新类，继承于StorageEventListener。下面注册到StorageManager的listener就是继承于StorageEventListener。

// storage

mStorageManager=(StorageManager) context.getSystemService(Context.STORAGE_SERVICE);

mStorageManager.registerListener(new com.android.systemui.usb.StorageNotification(context));

com.android.systemui.usb.StorageNotification就是继承于StorageEventListener。

1)      registerListener

    public void registerListener(StorageEventListener listener) {

        if (listener == null) {

            return;

        }

        synchronized (mListeners) {

            if (mBinderListener == null ) {

                try {

                    mBinderListener = new MountServiceBinderListener();

                    mMountService.registerListener(mBinderListener);

                } catch (RemoteException rex) {

                    Log.e(TAG, "Register mBinderListener failed");

                    return;

                }

            }

            mListeners.add(new ListenerDelegate(listener));

        }

    }

2)      StorageManager的registerListener有两个功能，一个是接收其他应用过来的申请，将他们的StorageEventListener，转换成ListenerDelegate 对象，然后保存在mListeners 这个数组中。

     private List<ListenerDelegate> mListeners = new ArrayList<ListenerDelegate>();

mListeners.add(new ListenerDelegate(listener));

       另外一个功能就是向mountService注册listener，StorageManager也是个中间者，拿不到一手信息，需要从上线拿到资源，所以它需要向mountService注册listener。

                    mBinderListener = new MountServiceBinderListener();

                    mMountService.registerListener(mBinderListener);

       注册进去的类型为MountServiceBinderListener，是MountServiceListener的实现。

       特别注意：在mountService中，对注册进来的MountServiceBinderListener又做了一层处理，恶心的是两个类是同一个名字。

MountServiceBinderListener bl = new MountServiceBinderListener(listener);

参数listener的类型是上面蓝色的，从StorageManager传过来，红色的是mountService中的类，类似于StorageManager中的ListenerDelegate。实现如下:

    private final class MountServiceBinderListener implements IBinder.DeathRecipient {

        final IMountServiceListener mListener;

        MountServiceBinderListener(IMountServiceListener listener) {

            mListener = listener;

        }

StorageManager和MountService都有一个用来记录外边注册进来的listener的数组mListeners，但是使用的类型都是自己包中定义的类，都对传进来的进行了处理。

3)      从底向上的触发

MountService的onEvent会收到底层的调用，进而触发相应的动作，例如调用updatePublicVolumeState，这里边就会调用注册进来的listener的成员函数; bl.mListener.onStorageStateChanged。这样就进入到了StorageManager，其中的listener，MountServiceBinderListener的onStorageStateChanged会被触发。进而依次触发每一个注册到StorageManager的listener，sendStorageStateChanged，发出EVENT_STORAGE_STATE_CHANGED消息。在每个listener注册到StorageManager时，通过ListenerDelegate进行过一次打包，在其构造函数中对每个listener创建了一个handler，不停的接收消息并处理。当接收到EVENT_STORAGE_STATE_CHANGED后就调用注册进来的listener的onStorageStateChanged方法。如上即为com.android.systemui.usb.StorageNotification的onStorageStateChanged函数，所以该类的onStorageStateChanged方法需要重载。

以上内容参考了这篇文章：usb状态相关处理

2.3 功能调用

上面介绍的是上层如何获取系统及底层信息的中断通知的方式，除了这种被动通知状态改变的行为以外，更多的则是应用主动的获取系统的storage信息。这个功能就相对简单、直白了，可以直接调用StorageManager的成员方法。

       1) ums功能的使能/禁能/状态查询

       2)obb的挂载/卸载及查询

       3)获取分区的所有信息:分区列表/挂载点状态/主分区路径等

4) 应用的默认存储路径的管理及内外置卡的路径获取

       JB的挂载路径较ics做了更新:

    private static final String ICS_STORAGE_PATH_SD1 = "/mnt/sdcard";

    private static final String ICS_STORAGE_PATH_SD2 = "/mnt/sdcard2";

    private static final String STORAGE_PATH_SD1 = "/storage/sdcard0";

    private static final String STORAGE_PATH_SD2 = "/storage/sdcard1";

       JB版本以后，为了兼容ICS，将/mnt/sdcard链接到/storage/sdcard0。

2.4 使用方法

mStorageManager=(StorageManager) context.getSystemService(Context.STORAGE_SERVICE);

mStorageManager.functions;

2.5 StorageManager总结

如果外界需要知道系统的storage信息,直接调用StorageManager的方法。那么如果需要实时的知道状态的改变，就需要派一个信使驻扎在StorageManager家里，当有状态变化时，StorageManager会通知驻扎在他家的信使，listener。这就是为什么要安排驻京人员，能够及时的拿到一手信息。

三 MountService

3.1 MountService与StorageManager的交互   

紧接上面的StorageManager,MountService是为framework层和StorageManager服务的，StorageManager为应用程序服务。

-----------------------下面来自网友总结

MountService是运行在SystemService这个进程中，所以上层应用无法直接访问，StorageManager就是提供给应用层来访问存储服务的，它通过Binder机制与MountService所在进程进行通信，将使用者的请求转发进MountService中进行处理。目前StorageManager中支持的方法有enableUsbMassStorage，disableUsbMassStorage，isUsbMassStorageConnected，isUsbMassStorageConnected。在StorageManager的构造函数中，还通过调用MountService中的registerListener函数来注册listener到MountService，同时，它自己也提供了registerListener函数供其它应用来注册listener，这样，当MountService知道存储设备状态变更时，会调用StorageManager中listener的方法，而StorageManager又会继续回调上去，上层应用也就可以做相应的操作，比如图示的更新等。

MountService是一个服务类，在ServiceManager中注册为系统服务，提供对外部存储设备的管理、查询等服务，并在存储设备状态变更时发出通知。MountService起到了一个承上启下的作用，向上公开方法供上层对存储设备进行操作（enable/disable/mount…），并在存储设备状态变更时发出通知。向下接收Vold发来的事件（设备状态变更，设备插入，设备移除等），同时也会将命令发送给Vold，进行更底层的操作。

------------------

3.2 工作流程

工作流程有几个:首先是构造函数的准备工作、一些接口的被调用、以及监听回调。

1)      构造函数

Mediatek/custom/mt8389_tablet_a3v2/resource_overlay/generic/frameworks/base/core/res/res/xml/

<StorageList xmlns:android="http://schemas./apk/res/android">

    <!-- removable is not set in nosdcard product -->

    <storage android:mountPoint="/storage/sdcard0"

             android:storageDescription="@string/storage_usb"

           android:allowMassStorage="true"

           android:mtpReserve="10485760"

             android:primary="true" />

    <storage android:mountPoint="/storage/sdcard1"

             android:storageDescription="@string/storage_sd_card"

             android:removable="true"

           android:allowMassStorage="true"

           android:mtpReserve="10485760"

             android:primary="false" />

<storage android:mountPoint="/mnt/usbotg"

             android:storageDescription="@string/storage_external_usb"

             android:removable="true"

             android:primary="false" />                                                                                      

</StorageList>

但是vold 中关于外部存储器的挂载路径是在

mediatek /config/mt8389_tablet_a3v2/vold.fstab文件中指定的，

 dev_mount sdcard /storage/sdcard0 emmc@fat /devices/platform/goldfish_mmc.0

                                                               /devices/platform/mtk-msdc.0/mmc_host

  dev_mount sdcard2 /storage/sdcard1 auto /devices/platform/goldfish_mmc.1

                                                               /devices/platform/mtk-msdc.1/mmc_host

dev_mount usbotg /mnt/usbotg auto /devices/platform/mt_usb

                                                               /devices/platform/musbfsh_hdrc

       所以这个xml和vold.fstab的路径必须统一。

readStorageList函数通过解析xml，丰富了系统的分区信息。mVolumes、mVolumeMap和mPrimaryVolume。 

2)      intent 接收处理

private final BroadcastReceiver mBroadcastReceiver = new BroadcastReceiver() {

            String action = intent.getAction();

通过在构造函数中注册intentfilter，接收系统发出的intent，执行相应的动作。

       3) Callback from NativeDaemonConnector

MountService注册到NativeDaemonConnector 的两个回调函数:onDaemonConnected和onEvent。在构造函数创建NativeDaemonConnector时，将MountService植入进了NativeDaemonConnector。

onDaemonConnected在NativeDaemonConnector线程开始运行，创建socket监听时，执行一次。onEvent是在listenToSocket每次读取socket信息，然后通过mCallbackHandler发送消息，随后在handleMessage中调用onEvent。

当vold发生动作时，通过NativeDaemonConnector完成向上的通知。

NativeDaemonConnector和vold使用的是socket连接，大概使用流程如下:

{

LocalSocket socket = null;

socket = new LocalSocket();//创建socket

//创建目的地的socket地址

LocalSocketAddress address = new LocalSocketAddress(mSocket,

LocalSocketAddress.Namespace.RESERVED);//mSocketà "vold"

socket.connect(address);//连接目的socket

InputStream inputStream = socket.getInputStream()//获取inputStream

inputStream.read(buffer, start, BUFFER_SIZE - start);//读取socket数据

}

在init.rc中，vold服务启动时，创建与framework通讯的socket

service vold /system/bin/vold

    class core

    socket vold stream 0660 root mount                                                                                      

    ioprio be 2

3)功能调用

              如setUsbMassStorageEnabled，有其他功能直接调用。

mountVolume----àdoMountVolume-------àmConnector.execute(cmd);

3.3 使用方法

1)定义变量

private IMountService mMountService;

2)获取实例

mMountService = IMountService.Stub.asInterface(ServiceManager.getService("mount"));

    3)调用功能

mMountService.registerListener(mBinderListener);

3.4 MountService总结

MountService是一个核心处理功能，承上启下。他的具体功能通过他提供的各种方法来体现。如何工作上面的工作流程已经涵盖。

四 volume demo

参考文档:

http://terryblog.blog.51cto.com/1764499/826656

android系统vold透析

这两篇文章已经讲的很好，下面只是部分功能点的说明。

         4.1 vold/kernel简介

----------网友

kernel层能检测到有新的设备接入，加载相应的驱动，但如何通知用户层呢？这就是sysfs的工作，内核中的sysfs机制要求当有新的驱动加载时给用户层发送相应的event.但这些event只尽告知的义务，具体怎么处理，这就是vold的事了。

uevent由内核发出，通过netlink sokect来传递给vold，在kobject被创建的时候，就会发生uevent的传递。对于未传递的uevent，会在kset下产生uevent文件，这是供用户态触发uevent使用的，通过向uevent档写入action（add，remove等），可以触发一个uevent，这些uevent可以被vold捕获，从而完成未完成的vold处理。在系统启动的时候，vold未启动的时候，这些uevent写入了uevent档，vold启动后，会扫描sys目录查找uevent，然后触发它们，来完成之前未完成的事宜。uevent文件的内容，就是uevent事件的数据。

Vold.fstab文件中的设备路径是设备在sys下的路径，并不是kernel为该设备创建的节点:

dev_mount sdcard /storage/sdcard0 emmc@fat /devices/platform/goldfish_mmc.0

                                                               /devices/platform/mtk-msdc.0/mmc_host

#######################

## Regular device mount

##

## Format: dev_mount <label> <mount_point> <part> <sysfs_path1...>

## label        - Label for the volume

## mount_point  - Where the volume will be mounted

## part         - Partition # (1 based), or 'auto' for first usable partition.

## <sysfs_path> - List of sysfs paths to source devices

######################

Kernel 创建完设备节点后又再sys下创建了相关的内容，进而发出了uevent，让vold中的socket,NetLinkManager.cpp来处理，进而根据vold.fstab的配置挂载到指定的目录。那么kernel是如何将sys下创建的目录对象和具体的设备对应起来的呢？todo:sys

4.2 vold 代码流程

       1)入口:System/vold/main.c

              a)创建3个vold框架使用的对象

VolumeManager *vm;

    CommandListener *cl; 接收上层MountService的命令，分析后转给volumeManager，处理后返给MountService或者交给volume执行具体操作。

NetlinkManager *nm; 创建与内核通讯的socket，接收底层的信息，交给volumeManager

b)解析/etc/vold.fstab

       process_config

2)netlinkManager

3)commandListener

4)volumeManager

分区管理类，volume.cpp代理人。真正的分区动作都在volume.cpp来完成。

5)其他文件

Fat.cpp/bicr.cpp/Ext4.cpp

        这些都是volume等配套的具体功能文件，最后一个环节。 

2013-7-31: vold和kernel配合工作的流程：首先vold在开始执行时，通过解析vold.fstab得知了该设备用户层最终需要管理的存储设备分区信息，针对需要挂载的分区信息，创建对应的DirectVolume，放入VolumeManager中进行管理。解析vold.fstab时如果是emmc是要从/proc/emmc中获取信息的，以防止vold.fstab写的信息有误。所以上面这部分工作只是准备工作，意思是当有对应的分区设备在内核空间出现时，用户空间应该如何去处理，挂载还是不挂载，挂载点是哪里。那么当内核空间的设备创建时通过uevent机制传递到netlinkManager时，会调用到netlinkHandler.cpp的onEvent，进入调用VolumeManager的handleBlockEvent，意思是处理块设备变化，由于开始时已经将vold.fstab中的分区信息创建对应的DirectVolume添加到了VolumeManager容器中，然后找出容器中的某个DirectVolume执行handleBlockEvent。