作者:gzshun. 原创作品,转载请标明出处!
上篇文章分析到了handleBlockEvent函数,该函数包含了以下6个处理函数:
void handleDiskAdded(const char *devpath, NetlinkEvent *evt); void handleDiskRemoved(const char *devpath, NetlinkEvent *evt); void handleDiskChanged(const char *devpath, NetlinkEvent *evt); void handlePartitionAdded(const char *devpath, NetlinkEvent *evt); void handlePartitionRemoved(const char *devpath, NetlinkEvent *evt); void handlePartitionChanged(const char *devpath, NetlinkEvent *evt);
if (action == NetlinkEvent::NlActionAdd) { ... if (!strcmp(devtype, "disk")) { handleDiskAdded(dp, evt); } else { handlePartitionAdded(dp, evt); } } else if (action == NetlinkEvent::NlActionRemove) { if (!strcmp(devtype, "disk")) { handleDiskRemoved(dp, evt); } else { handlePartitionRemoved(dp, evt); } } else if (action == NetlinkEvent::NlActionChange) { if (!strcmp(devtype, "disk")) { handleDiskChanged(dp, evt); } else { handlePartitionChanged(dp, evt); } }
void DirectVolume::handleDiskAdded(const char *devpath, NetlinkEvent *evt) { mDiskMajor = atoi(evt->findParam("MAJOR")); mDiskMinor = atoi(evt->findParam("MINOR")); const char *tmp = evt->findParam("NPARTS"); if (tmp) { mDiskNumParts = atoi(tmp); } else { SLOGW("Kernel block uevent missing 'NPARTS'"); mDiskNumParts = 0; } /********************************************************************************** **mPendingPartsCount是一个全局变量,用来保存该存储设备的分区数量;这里需要说明一个 **存储设备识别的顺序: **当插入一块5个分区的硬盘,首先会调用handleDiskAdded函数获取该存储设备的事件信息, **随后会调用若干次handlePartitionAdded函数来识别该存储设备的多个分区的事件信息, **当然,一般5个分区的硬盘肯定有一个扩展节点(因为mbr最多支持4个主分区); **调用顺序是这样: **handleDiskAdded函数调用1次; **handlePartitionAdded函数调用6次; **该变量的作用是这样:插入一块硬盘,此时mPendingPartsCount变量为分区数量, **开始用handlePartitionAdded函数识别分区,每识别一个分区, **mPendingPartsCount自减一次,当mPendingPartsCount==0时,结束该存储设备事件的捕获。 **********************************************************************************/ mPendingPartsCount = mDiskNumParts; if (mDiskNumParts == 0) { /********************************************************************************** **broadcastDiskAdded函数的作用是通知framework,系统插入一块存储设备,源码如下: void DirectVolume::broadcastDiskAdded() { setState(Volume::State_Idle); char msg[255]; snprintf(msg, sizeof(msg), "Volume %s %s disk inserted (%d:%d)", getLabel(), getMountpoint(), mDiskMajor, mDiskMinor); mVm->getBroadcaster()->sendBroadcast(ResponseCode::VolumeDiskInserted, msg, false); } **********************************************************************************/ broadcastDiskAdded(); } else { /********************************************************************************** **setState函数起到的作用很大,相当于一只信鸽,每次sd卡发现状态改变,该函数马上就将 **最新的状态广播给framework,后面会详细介绍该函数与framework的通信。 **********************************************************************************/ setState(Volume::State_Pending); } }
void DirectVolume::handlePartitionAdded(const char *devpath, NetlinkEvent *evt) { int major = atoi(evt->findParam("MAJOR")); int minor = atoi(evt->findParam("MINOR")); int part_num; const char *tmp = evt->findParam("PARTN"); if (tmp) { part_num = atoi(tmp); } else { SLOGW("Kernel block uevent missing 'PARTN'"); part_num = 1; } if (part_num > mDiskNumParts) { mDiskNumParts = part_num; } if (major != mDiskMajor) { SLOGE("Partition '%s' has a different major than its disk!", devpath); return; } /********************************************************************************** **上面就是做一下其他的判断,不重要; **MAX_PARTITIONS定义在system/vold/DirectVolume.h文件中,声明如下: static const int MAX_PARTITIONS = 4; Android系统支持太有限,谷歌太懒,呵呵,最多就识别4个分区,当然如果有些厂商想多实现 **分区的识别数量,需要修改源码; **我觉得,Android系统是做得不错,但磁盘管理方面不太完善,自从分析修改了vold源码, **vold支持得太少,也许谷歌以前只想到应用于手机,要是哥想识别一块10个分区的硬盘, **咋办?修改源码咯。。。 **********************************************************************************/ if (part_num > MAX_PARTITIONS) { SLOGE("Dv:partAdd: ignoring part_num = %d (max: %d)\n", part_num, MAX_PARTITIONS); } else { /*全局数组,用来存放磁盘分区的此设备号*/ mPartMinors[part_num -1] = minor; } /*看到了吧,上面那个函数说到mPendingPartsCount每识别一个分区要自减一次,就在这里*/ --mPendingPartsCount; /*这里就在判断mPendingPartsCount变量了,如果mPendingPartsCount==0时,再向framework广播 一次该设备的插入,所以framework总共需要收到磁盘的插入广播2次,才会下发操作命令。*/ if (!mPendingPartsCount) { /*判断了磁盘的状态,如果正在格式化,将不做操作*/ if (getState() != Volume::State_Formatting) { broadcastDiskAdded(); } } else { } }
void DirectVolume::handleDiskChanged(const char *devpath, NetlinkEvent *evt) { int major = atoi(evt->findParam("MAJOR")); int minor = atoi(evt->findParam("MINOR")); if ((major != mDiskMajor) || (minor != mDiskMinor)) { return; } SLOGI("Volume %s disk has changed", getLabel()); const char *tmp = evt->findParam("NPARTS"); if (tmp) { mDiskNumParts = atoi(tmp); } else { SLOGW("Kernel block uevent missing 'NPARTS'"); mDiskNumParts = 0; } mPendingPartsCount = mDiskNumParts; if (getState() != Volume::State_Formatting) { if (mDiskNumParts == 0) { /*这里类似于fdisk将删除存储设备的所有分区,这样存储设备的分区数量mDiskNumParts 就等于0,此时广播磁盘的空闲状态*/ setState(Volume::State_Idle); } else { setState(Volume::State_Pending); } } }
void DirectVolume::handlePartitionChanged(const char *devpath, NetlinkEvent *evt) { int major = atoi(evt->findParam("MAJOR")); int minor = atoi(evt->findParam("MINOR")); SLOGD("Volume %s %s partition %d:%d changed\n", getLabel(), getMountpoint(), major, minor); }
void DirectVolume::handleDiskRemoved(const char *devpath, NetlinkEvent *evt) { int major = atoi(evt->findParam("MAJOR")); int minor = atoi(evt->findParam("MINOR")); char msg[255]; SLOGD("Volume %s %s disk %d:%d removed\n", getLabel(), getMountpoint(), major, minor); snprintf(msg, sizeof(msg), "Volume %s %s disk removed (%d:%d)", getLabel(), getMountpoint(), major, minor); mVm->getBroadcaster()->sendBroadcast(ResponseCode::VolumeDiskRemoved, msg, false); /*设备移除后,广播通知framework*/ setState(Volume::State_NoMedia); }
void DirectVolume::handlePartitionRemoved(const char *devpath, NetlinkEvent *evt) { int major = atoi(evt->findParam("MAJOR")); int minor = atoi(evt->findParam("MINOR")); char msg[255]; int state; SLOGD("Volume %s %s partition %d:%d removed\n", getLabel(), getMountpoint(), major, minor); state = getState(); if (state != Volume::State_Mounted && state != Volume::State_Shared) { return; } if ((dev_t) MKDEV(major, minor) == mCurrentlyMountedKdev) { snprintf(msg, sizeof(msg), "Volume %s %s bad removal (%d:%d)", getLabel(), getMountpoint(), major, minor); /*mCurrentlyMountedKdev变量保存着目前正挂载在系统的存储设备的设备号, 这里的判断是这样:如果目前正在移除的分区等于挂载的存储设备的设备号,说明 该存储设备没有被安全删除,也就是没有先卸载后移除*/ mVm->getBroadcaster()->sendBroadcast(ResponseCode::VolumeBadRemoval, msg, false); /*卸载挂载在asec目录的分区*/ if (mVm->cleanupAsec(this, true)) { SLOGE("Failed to cleanup ASEC - unmount will probably fail!"); } /*卸载该分区挂载的所有挂载点,这里为什么用所有来形容了,因为Android 系统挂载一个分区的期间,重复挂载在好几个目录,将分区挂载在/mnt/asec目录,也挂载 在/mnt/secure/asec目录,也挂载在/mnt/sdcard目录下,总共三次挂载,谷歌不知为什么搞这么复杂? 待深究。。*/ if (Volume::unmountVol(true)) { SLOGE("Failed to unmount volume on bad removal (%s)", strerror(errno)); } else { SLOGD("Crisis averted"); } } else if (state == Volume::State_Shared) { snprintf(msg, sizeof(msg), "Volume %s bad removal (%d:%d)", getLabel(), major, minor); mVm->getBroadcaster()->sendBroadcast(ResponseCode::VolumeBadRemoval, msg, false); /*这种情况是这样:如果手机跟电脑连接在一起,电脑正在使用sd卡,你把sd卡取出, 就会广播该错误信息给framework*/ if (mVm->unshareVolume(getLabel(), "ums")) { SLOGE("Failed to unshare volume on bad removal (%s)", strerror(errno)); } else { SLOGD("Crisis averted"); } } }