Android5.0挂载子系统

logcat -s Vold MountService DirectVolume

虚拟SD卡相关：

Android虚拟SD卡

一、启动过程分析

1.应用程序API

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

2.MountService

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

frameworks/base/services/core/java/com/android/server/storage/

public MountService(Context context) {  mConnector = new NativeDaemonConnector(this, "vold", MAX_CONTAINERS * 2, VOLD_TAG, 25,                null);  //vold的socket,与CommandListener通信}

3.vold进程

system/vold/main.cpp

int main() {  VolumeManager *vm;  //管理挂载  CommandListener *cl;  //与Android的MountService通信  NetlinkManager *nm;    //与Linux的Kernel通信  cl = new CommandListener();  vm->setBroadcaster((SocketListener *) cl); //VolumeManager可以与MountService通信  nm->setBroadcaster((SocketListener *) cl); //NetlinkManager可以与MountService通信}

二、U盘挂载分析

1.vold进程获取内核U盘接入事件

system/core/libsysutils/src/SocketListener.cpp

void SocketListener::runListener() {  if (!onDataAvailable(c)) {    release(c, false);  }}/*system/core/include/sysutils/NetlinkListener.hclass NetlinkListener : public SocketListener {  }*/

system/core/libsysutils/src/NetlinkListener.cpp

bool NetlinkListener::onDataAvailable(SocketClient *cli){  int socket = cli->getSocket();  NetlinkEvent *evt = new NetlinkEvent();  if (evt->decode(mBuffer, count, mFormat)) {    onEvent(evt);  } else if (mFormat != NETLINK_FORMAT_BINARY) {      // Don't complain if parseBinaryNetlinkMessage returns false. That can      // just mean that the buffer contained no messages we're interested in.      SLOGE("Error decoding NetlinkEvent");  }}/*system/vold/NetlinkHandler.hclass NetlinkHandler: public NetlinkListener {}*/

system/vold/NetlinkHandler.cpp

void NetlinkHandler::onEvent(NetlinkEvent *evt) {    VolumeManager *vm = VolumeManager::Instance();    const char *subsys = evt->getSubsystem();    if (!subsys) {        SLOGW("No subsystem found in netlink event");        return;    }    if (!strcmp(subsys, "block")) {        vm->handleBlockEvent(evt);    }else if(!strcmp(subsys, "usb")) {        vm->handleHidEvent(evt);    }}

system/vold/VolumeManager.cpp

void VolumeManager::handleBlockEvent(NetlinkEvent *evt) {  for (it = mVolumes->begin(); it != mVolumes->end(); ++it) {    (*it)->handleBlockEvent(evt);  }  volume = new DirectVolume(this, &rec, flags);  addVolume(volume);  if ( volume->handleBlockEvent(evt) !=0 ) {    SLOGD("New add volume fail to handle the event of %s",devpath);  }}

2.向Android的MountServer发送U盘接入消息

system/vold/DirectVolume.cpp

int DirectVolume::handleBlockEvent(NetlinkEvent *evt) {  handleDiskAdded(dp, evt);}void DirectVolume::handleDiskAdded(const char * /*devpath*/,                                   NetlinkEvent *evt) {  mVm->getBroadcaster()->sendBroadcast(ResponseCode::VolumeDiskInserted,                                             msg, false);}/*system/vold/DirectVolume.hclass DirectVolume : public Volume { VolumeManager *mVm;}*/

system/vold/VolumeManager.h

class VolumeManager {  void setBroadcaster(SocketListener *sl) { mBroadcaster = sl; }  /*  system/vold/main.cpp  int main() {    VolumeManager *vm;    CommandListener *cl;    NetlinkManager *nm;    cl = new CommandListener();    vm->setBroadcaster((SocketListener *) cl);    nm->setBroadcaster((SocketListener *) cl);  }  */  SocketListener *getBroadcaster() { return mBroadcaster; }}

system/vold/CommandListener.h

class CommandListener : public FrameworkListener {  }/*system/core/include/sysutils/FrameworkListener.hclass FrameworkListener : public SocketListener {}*/

system/core/libsysutils/src/SocketListener.cpp

void SocketListener::sendBroadcast(int code, const char *msg, bool addErrno) {  if (c->sendMsg(code, msg, addErrno, false)) {    SLOGW("Error sending broadcast (%s)", strerror(errno));  }}

3.Android的MountServer接收到VolumeDiskInserted消息后处理

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

public boolean onEvent(int code, String raw, String[] cooked) {  if ((rc = doMountVolume(path)) != StorageResultCode.OperationSucceeded) {    Slog.w(TAG, String.format("Insertion mount failed (%d)", rc));  }}private int doMountVolume(String path) {  mConnector.execute("volume", "mount", path);  /*  mConnector = new NativeDaemonConnector(this, "vold", MAX_CONTAINERS * 2, VOLD_TAG, 25,                null);  */}

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

public NativeDaemonEvent execute(String cmd, Object... args)            throws NativeDaemonConnectorException {  final NativeDaemonEvent[] events = executeForList(cmd, args);}public NativeDaemonEvent[] executeForList(String cmd, Object... args)            throws NativeDaemonConnectorException {  return execute(DEFAULT_TIMEOUT, cmd, args);}public NativeDaemonEvent[] execute(int timeout, String cmd, Object... args)           throws NativeDaemonConnectorException {  NativeDaemonEvent event = null;  events.add(event);}public void add(int cmdNum, NativeDaemonEvent response) {  found = new PendingCmd(cmdNum, null);  mPendingCmds.add(found);}

4.vold进程接收Android的MountServer进程的volume的mount命令

system/core/libsysutils/src/SocketListener.cpp

void SocketListener::runListener() {  if (!onDataAvailable(c)) {    release(c, false);  }}

system/core/libsysutils/src/FrameworkListener.cpp

bool FrameworkListener::onDataAvailable(SocketClient *c) {  dispatchCommand(c, buffer + offset);}void FrameworkListener::dispatchCommand(SocketClient *cli, char *data) {  for (i = mCommands->begin(); i != mCommands->end(); ++i) {    FrameworkCommand *c = *i;    /*    void FrameworkListener::registerCmd(FrameworkCommand *cmd) {      mCommands->push_back(cmd);    }    system/core/include/sysutils/FrameworkListener.h    class FrameworkListener : public SocketListener {    }    system/vold/CommandListener.h    class CommandListener : public FrameworkListener {      }    system/vold/CommandListener.cpp    CommandListener::CommandListener() :                 FrameworkListener("vold", true) {      registerCmd(new DumpCmd());      registerCmd(new VolumeCmd());  //volume的mount命令      registerCmd(new AsecCmd());      registerCmd(new ObbCmd());    }    */    if (c->runCommand(cli, argc, argv)) {      SLOGW("Handler '%s' error (%s)", c->getCommand(), strerror(errno));    }  }}

system/vold/CommandListener.cpp

int CommandListener::VolumeCmd::runCommand(SocketClient *cli,                                           int argc, char **argv) {  VolumeManager *vm = VolumeManager::Instance();  else if (!strcmp(argv[1], "mount")) {    rc = vm->mountVolume(argv[2]);  }}

system/vold/VolumeManager.cpp

int VolumeManager::mountVolume(const char *label) {  Volume *v = lookupVolume(label);  return v->mountVol();}

/system/vold/Volume.cpp

int Volume::mountVol() {  if (isNtfsFS) {    if (Ntfs::doMount(devicePath, getMountpoint(), false, false, AID_MEDIA_RW, AID_MEDIA_RW, permMask)) { //实际调用Linux系统调用挂载      SLOGE("%s failed to mount via NTFS (%s)\n", devicePath, strerror(errno));      isNtfsFS = false;    } else {      isFatFs = false;      isExtFs = false;      isExfatFs = false;    }  }  setState(Volume::State_Mounted);}void Volume::setState(int state) {  mVm->getBroadcaster()->sendBroadcast(ResponseCode::VolumeStateChange,                                         msg, false); //同之前消息发送，不做分析；MountServer会收到VolumeStateChange消息}

5.Android的MountServer收到VolumeStateChange消息通知应用

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

public boolean onEvent(int code, String raw, String[] cooked) {  if (code == VoldResponseCode.VolumeStateChange) {    notifyVolumeStateChange(                    cooked[2], cooked[3], Integer.parseInt(cooked[7]),                            Integer.parseInt(cooked[10]));  }}private void notifyVolumeStateChange(String label, String path, int oldState, int newState) {  else if (newState == VolumeState.Mounted) {    if (DEBUG_EVENTS) Slog.i(TAG, "updating volume state mounted");    updatePublicVolumeState(volume, Environment.MEDIA_MOUNTED); //广播通知应用挂载完毕    action = Intent.ACTION_MEDIA_MOUNTED;  }  if (action != null) {    sendStorageIntent(action, volume, UserHandle.ALL);  }}

三、项目问题

Android下开机启动后U盘经常不能自动挂载

Android媒体应用下不能将两个U盘间文件复制

Android5.0挂载NTFS为只读问题

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