android存儲3--初始化.unlock事件的處理

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android版本：android-11.0.0_r21
http://aospxref.com/android-11.0.0_r21

概述：SystemServiceManager收到unlock事件后，遍歷service鏈表，執(zhí)行各個service的onUserUnlocking。對于存儲service，執(zhí)行的是StorageManagerService$Lifecycle中的onUserUnlocking，在這個方法中，存儲的StorageSessionController、vold、storaged模塊進行各自初始化操作。

一、SystemServiceManager處理unlock事件

設備解鎖后，loop線程處理unlock消息，最終會執(zhí)行到存儲的StorageManagerService$Lifecycle中的onUserUnlocking方法，整個流程如下：

loop() //android.os.Looper
|
|-->msg.target.dispatchMessage(msg) //android.os.Handler
   |
   |--mCallback.handleMessage(msg) //com.android.server.am.UserController
      |
      |--case USER_UNLOCK_MSG:
                mInjector.getSystemServiceManager().unlockUser(userId) //com.android.server.SystemServiceManager
                |
               ①|(zhì)--onUser(UNLOCKING, userHandle) //com.android.server.SystemServiceManager
                  |
                 ②|--onUser(TimingsTraceAndSlog.newAsyncLog(), onWhat, userHandle) //com.android.server.SystemServiceManager 
                       |
                      ③|--onUser(t, onWhat, userHandle, UserHandle.USER_NULL) //com.android.server.SystemServiceManager
                          |
                          |--case UNLOCKING:
                                    service.onUserUnlocking(curUser) //com.android.server.SystemService
                                    |
                                    |--onUnlockUser(user.getUserInfo()) //com.android.server.SystemService
                                       |
                                       |--onUnlockUser(userInfo.id) //com.android.server.StorageManagerService$Lifecycle

1）loop線程處理Android消息隊列中的消息和事件，從隊列中獲取事件，將unlock事件通知其他系統(tǒng)服務。

2）系統(tǒng)服務UserController管理用戶和用戶操作，接收到USER_UNLOCK_MSG消息后執(zhí)行SystemServiceManager中的unlockUser方法。

3）unlockUser方法經(jīng)過幾次轉(zhuǎn)換（①②③見下，只是做了參數(shù)轉(zhuǎn)換。參數(shù)差異見下）。

SystemServiceManager::(final @UserIdInt int userHandle)
    -->?onUser(@NonNull String onWhat, @UserIdInt int userHandle)  ①
        -->?onUser(@NonNull TimingsTraceAndSlog t, @NonNull String onWhat,
? ? ? ? ? ?        @UserIdInt int userHandle)  ②
             ???????-->onUser(@NonNull TimingsTraceAndSlog t, @NonNull String onWhat,
? ? ? ? ? ?        @UserIdInt int curUserId, @UserIdInt int prevUserId)  ③
(如果未寫明方法所屬class，默認所屬class與前面相同，所以這些onUser方法都是SystemServiceManager類中實現(xiàn)的)

UserController收到USER_UNLOCK_MSG后的處理細節(jié)見其他文章。

最終③處的onUser會遍歷mServices鏈表，執(zhí)行各個service的?onUserUnlocking，簡化后的代碼如下：
http://aospxref.com/android-11.0.0_r21/xref/frameworks/base/services/core/java/com/android/server/SystemServiceManager.java#onUser

//frameworks/base/services/core/java/com/android/server/SystemServiceManager.java

private void onUser(@NonNull TimingsTraceAndSlog t, @NonNull String onWhat,
            @UserIdInt int curUserId, @UserIdInt int prevUserId) {

        final TargetUser curUser = new TargetUser(getUserInfo(curUserId));

        final int serviceLen = mServices.size();

        // 遍歷系統(tǒng)服務，執(zhí)行每個servie的onUserUnlocking方法
        for (int i = 0; i < serviceLen; i++) {
            final SystemService service = mServices.get(i);
            final String serviceName = service.getClass().getName();

            try {
                switch (onWhat) {
 
                    case UNLOCKING:
                        	service.onUserUnlocking(curUser);  // ④，存儲的sevice是"StorageManagerService$Lifecycle"
                        break;
                     ……
                }
            } 
    }

《android存儲2--初始化.存儲service的啟動》中“mount service”一節(jié)已經(jīng)闡述了StorageManagerService$Lifecycle發(fā)布的流程，所以上面代碼執(zhí)行for循環(huán)時，SystemService service = mServices.get(i)將會獲取到StorageManagerService$Lifecycle。在④處，service.onUserUnlocking(curUser)將會執(zhí)行StorageManagerService$Lifecycle中的onUserUnlocking方法。

二、存儲模塊處理unlock事件

2.1? StorageManagerService$Lifecycle::onUserUnlocking

StorageManagerService中定義了靜態(tài)內(nèi)部類StorageManagerService$Lifecycle，這個內(nèi)部類用來控制StorageManagerService的Lifecycle，代碼見下：http://aospxref.com/android-11.0.0_r21/xref/frameworks/base/services/core/java/com/android/server/StorageManagerService.java#246

public class StorageManagerService extends IStorageManager.Stub
        implements Watchdog.Monitor, ScreenObserver {

        public static class Lifecycle extends SystemService {
                protected StorageManagerService mStorageManagerService;

                @Override
                public void onUnlockUser(int userHandle) {
                    mStorageManagerService.onUnlockUser(userHandle);
                }
                ……
            }
}

從StorageManagerService$Lifecycle函數(shù)可知道：

Lifecycle繼承自SystemService抽象類
???????子類Lifecycle覆寫了父類SystemService的onUnlockUser方法，但沒有覆寫onUserUnlocking

上文④處service.onUserUnlocking(curUser)調(diào)用的是父類SystemService::onUserUnlocking方法（因為StorageManagerService$Lifecycle沒有覆寫onUserUnlocking），見下。

http://aospxref.com/android-11.0.0_r21/xref/frameworks/base/services/core/java/com/android/server/SystemService.java#onUserUnlocking

// SystemService類中的實現(xiàn)

public void onUserUnlocking(@NonNull TargetUser user) {
    onUnlockUser(user.getUserInfo());
}

onUnlockUser(user.getUserInfo())執(zhí)行SystemService::onUnlockUser(@NonNull UserInfo userInfo)方法（注意重載參數(shù)類型）。

http://aospxref.com/android-11.0.0_r21/xref/frameworks/base/services/core/java/com/android/server/SystemService.java#onUnlockUser

// SystemService類中的實現(xiàn)

public void onUnlockUser(@NonNull UserInfo userInfo) {
    onUnlockUser(userInfo.id);
}

onUnlockUser(userInfo.id)執(zhí)行的是被StorageManagerService$Lifecycle覆寫后的方法:

http://aospxref.com/android-11.0.0_r21/xref/frameworks/base/services/core/java/com/android/server/StorageManagerService.java#onUnlockUser

//StorageManagerService$Lifecycle類中的實現(xiàn)

@Override
public void onUnlockUser(int userHandle) {
    mStorageManagerService.onUnlockUser(userHandle);
}

mStorageManagerService.onUnlockUser代碼：

http://aospxref.com/android-11.0.0_r21/xref/frameworks/base/services/core/java/com/android/server/StorageManagerService.java#1162

//StorageManagerService類中的實現(xiàn)

1162      private void onUnlockUser(int userId) {
1163          Slog.d(TAG, "onUnlockUser " + userId);
1164  
1165          // We purposefully block here to make sure that user-specific
1166          // staging area is ready so it's ready for zygote-forked apps to
1167          // bind mount against.
1168          try {
1169              mStorageSessionController.onUnlockUser(userId); // ⑤
1170              mVold.onUserStarted(userId); // ⑥
1171              mStoraged.onUserStarted(userId); // ⑦
1172          } catch (Exception e) {
1173              Slog.wtf(TAG, e);
1174          }
1175  
1176          mHandler.obtainMessage(H_COMPLETE_UNLOCK_USER, userId).sendToTarget();
1177      }

http://aospxref.com/android-11.0.0_r21/xref/frameworks/base/services/core/java/com/android/server/StorageManagerService.java#1162即StorageManagerService$Lifecycle中的onUserUnlocking方法最終執(zhí)行到StorageManagerService::onUnlockUser方法。⑤⑥⑦是存儲內(nèi)部各模塊處理unlock user后的邏輯，后面分段分析。

2.2??⑤處代碼mStorageSessionController.onUnlockUser分析

StorageManagerService::onUnlockUser中，mStorageManagerService.onUnlockUser執(zhí)行的是StorageSessionController::onUnlockUser：

// 初始化?mExternalStorageServiceComponent變量（ComponentName類型）
StorageManagerService::onUnlockUser
    -->?StorageSessionController::initExternalStorageServiceComponent

mExternalStorageServiceComponent用于提供外部存儲服務，初始化后mExternalStorageServiceComponent的信息如下：

mExternalStorageServiceComponent.getPackageName()
值為：com.android.providers.media.module

mExternalStorageServiceComponent.getClassName()
值為：com.android.providers.media.fuse.ExternalStorageServiceImpl

ComponentName
值為：com.android.providers.media.module/com.android.providers.media.fuse.ExternalStorageServiceImpl

⑤處代碼很簡單，就是初始化了mExternalStorageServiceComponent變量。

附上mExternalStorageServiceComponent是何時使用的：

StorageSessionController::getExternalStorageServiceComponentName獲取mExternalStorageServiceComponent，即com.android.providers.media.module/com.android.providers.media.fuse.ExternalStorageServiceImpl。這個服務是在provider/media/fuse目錄實現(xiàn)的：

http://aospxref.com/android-11.0.0_r21/xref/packages/providers/MediaProvider/src/com/android/providers/media/fuse/

mExternalStorageServiceComponent在mount emulated 存儲時，用于連接ExternalStorageServiceImpl服務，流程如下：

StorageManagerService::mount
   --> mStorageSessionController.onVolumeMount(pfd, vol) // StorageSessionController::onVolumeMount
         // sessionId: emulated;0
         // deviceFd代表的文件：/dev/fuse
         // vol.getPath().getPath()對應upperPath，值為：/storage/emulated
         // vol.getInternalPath().getPath()對應lowerPath，值為：/data/media
         -->?connection.startSession(sessionId, deviceFd, vol.getPath().getPath(),
                    vol.getInternalPath().getPath())  // StorageUserConnection::startSession
               // sessionId, upperPath, lowerPath封裝進session
               --> session = new Session(sessionId, upperPath, lowerPath)
               --> mActiveConnection.startSession(session, pfd)  // StorageUserConnection$ActiveConnection::startSession
                      // fd代表的文件：/dev/fuse
                      -->  waitForAsync((service, callback) -> service.startSession(session.sessionId,
                        FLAG_SESSION_TYPE_FUSE | FLAG_SESSION_ATTRIBUTE_INDEXABLE,
                        fd, session.upperPath, session.lowerPath, callback))
                            --> serviceFuture = connectIfNeeded()
                                   //獲取外部存儲組件名稱com.android.providers.media.module/com.android.providers.media.fuse.ExternalStorageServiceImpl
                                   --> name = mSessionController.getExternalStorageServiceComponentName()
                                   --> mContext.bindServiceAsUser(new Intent().setComponent(name),
                                mServiceConnection,
                                Context.BIND_AUTO_CREATE | Context.BIND_IMPORTANT,
                                mHandlerThread.getThreadHandler(),
                                UserHandle.of(mUserId))) // ContextImpl::bindServiceAsUser
                                         --> bindServiceCommon(service, conn, flags, null, handler, null, user) // ContextImpl::bindServiceCommon
                                                 --> ActivityManager.getService().bindIsolatedService(
                mMainThread.getApplicationThread(), getActivityToken(), service,
                service.resolveTypeIfNeeded(getContentResolver())

MediaProvider::openFile -->?openFileCommon -->?openFileAndEnforcePathPermissionsHelper中：

// MediaProvider.java  openFileAndEnforcePathPermissionsHelper函數(shù)

 // 通過ExternalStorageServiceImpl.getFuseDaemon獲取daemon
 daemon = getFuseDaemonForFile(file);

 boolean shouldOpenWithFuse = daemon != null
           && daemon.shouldOpenWithFuse(filePath, true /* forRead */, 
 lowerFsFd.getFd());

 if (SystemProperties.getBoolean(PROP_FUSE, false) && shouldOpenWithFuse) {
        // 走fuse流程
        pfd = FileUtils.openSafely(getFuseFile(file), modeBits);
        try {
               lowerFsFd.close();
         } 
   } else {
         // 繞過fuse，直接走底層文件系統(tǒng)
         Log.i(TAG, "Using lower FS for " + filePath);
    }

2.3? ⑥處代碼mVold.onUserStarted(userId)分析

StorageManagerService::onUnlockUser中，mVold.onUserStarted(userId)是核心代碼，比較復雜。這篇文章簡單說一下mVold.onUserStarted功能，它主要是為外部存儲創(chuàng)建、掛載相關目錄，以主用戶0為例，掛載視圖如下：

android存儲3--初始化.unlock事件的處理

?注意，圖中⑦⑧⑨?處在代碼中bind mount掛載的分別是：
⑦：/mnt/runtime/default/emulated/0/Android/data??on? /mnt/user/0/emulated/0/Android/data
⑧：/mnt/runtime/default/emulated/0/Android/obb??on? /mnt/user/0/emulated/0/Android/obb
⑨：/mnt/runtime/write/emulated/0/Android/obb? on? /mnt/installer/0/emulated/0/Android/obb
?：/mnt/runtime/full/emulated??on? /mnt/pass_through/0/emulated
但mount命令看到的卻是/data/media目錄被bind mount到其他目錄：
/data/media on /mnt/user/0/emulated/0/Android/data?
/data/media on /mnt/user/0/emulated/0/Android/obb
……

流程在下一篇文章中講解。

2.4? StorageManagerService::onUnlockUser⑦處代碼mStoraged.onUserStarted(userId)分析

StorageManagerService::onUnlockUser中，mStoraged.onUserStarted(userId）功能比較簡單，為storaged加載/data/misc_ce/0/storaged.proto文件。

storaged周期地將統(tǒng)計結(jié)果寫入/data/misc_ce/0/storaged.proto（默認1小時更新一次，見DEFAULT_PERIODIC_CHORES_INTERVAL_FLUSH_PROTO宏），這個文件按照system/core/storaged/storaged.proto格式編碼。執(zhí)行storaged -p命令時從/data/misc_ce/0/storaged.proto讀取數(shù)據(jù)輸出到終端上。示例如下：

cp15:/data/misc_ce/0/storaged # ls
storaged.proto
cp15:/data/misc_ce/0/storaged # storaged -p

I/O perf history (KB/s) :  most_recent  <---------  least_recent
last 24 hours : 66468 33941 44126 35316 45839 37312
last 7 days   : 0 0 0 0 0 0 0
last 52 weeks : 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
cp15:/data/misc_ce/0/storaged #

下一篇文章分析mVold.onUserStarted為外部存儲掛載目錄的流程。文章來源地址http://www.zghlxwxcb.cn/news/detail-496915.html

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