3. VolumeManager::Instance() 和 VolumeManager::start()
system/vold/VolumeManager.cpp
3.1 Instance()没啥好说的 非常简单
cpp
112 VolumeManager* VolumeManager::Instance() {
113 if (!sInstance) sInstance = new VolumeManager();
114 return sInstance;
115 }
116
117 VolumeManager::VolumeManager() {
118 mDebug = false;
119 mNextObbId = 0;
120 mNextStubId = 0;
121 // For security reasons, assume that a secure keyguard is
122 // showing until we hear otherwise
123 mSecureKeyguardShowing = true;
124 }3.2 VolumeManager::start()
cpp
174 int VolumeManager::start() {
175 ATRACE_NAME("VolumeManager::start");
176
177 // Always start from a clean slate by unmounting everything in
178 // directories that we own, in case we crashed.
179 unmountAll(); -----> 全部 unmount ， 这里的unmount似乎并不是全部所有分区， 全部的话那还了得
180
181 Loop::destroyAll();
182
183 // Assume that we always have an emulated volume on internal
184 // storage; the framework will decide if it should be mounted.
185 CHECK(mInternalEmulatedVolumes.empty());
186
187 auto vol = std::shared_ptr<android::vold::VolumeBase>(
188 new android::vold::EmulatedVolume("/data/media", 0)); ---> 创建 EmulatedVolume
189 vol->setMountUserId(0);
190 vol->create();
191 mInternalEmulatedVolumes.push_back(vol);
192
193 // Consider creating a virtual disk
194 updateVirtualDisk();
195
196 return 0;
197 }4. NetlinkManger::Instance() 和 NetlinkManger::start()
system/vold/NetlinkManager.cpp
4.1 NetlinkManger::Instance() 很简单 不需要赘述
cpp
36 NetlinkManager* NetlinkManager::Instance() {
37 if (!sInstance) sInstance = new NetlinkManager();
38 return sInstance;
39 }
40
41 NetlinkManager::NetlinkManager() {
42 mBroadcaster = NULL;
43 }4.2 NetlinkManger::start()
cpp
47 int NetlinkManager::start() {
48 struct sockaddr_nl nladdr;
49 int sz = 64 * 1024;
50 int on = 1;
51
52 memset(&nladdr, 0, sizeof(nladdr));
53 nladdr.nl_family = AF_NETLINK;
54 nladdr.nl_pid = getpid();
55 nladdr.nl_groups = 0xffffffff;
56
57 if ((mSock = socket(PF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_KOBJECT_UEVENT)) < 0) { ---> 创建socket client
58 PLOG(ERROR) << "Unable to create uevent socket";
59 return -1;
60 }
61
62 // When running in a net/user namespace, SO_RCVBUFFORCE will fail because
63 // it will check for the CAP_NET_ADMIN capability in the root namespace.
64 // Try using SO_RCVBUF if that fails.
65 if ((setsockopt(mSock, SOL_SOCKET, SO_RCVBUFFORCE, &sz, sizeof(sz)) < 0) &&
66 (setsockopt(mSock, SOL_SOCKET, SO_RCVBUF, &sz, sizeof(sz)) < 0)) {
67 PLOG(ERROR) << "Unable to set uevent socket SO_RCVBUF/SO_RCVBUFFORCE option";
68 goto out;
69 }
70
71 if (setsockopt(mSock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)) < 0) {
72 PLOG(ERROR) << "Unable to set uevent socket SO_PASSCRED option";
73 goto out;
74 }
75
76 if (bind(mSock, (struct sockaddr*)&nladdr, sizeof(nladdr)) < 0) { --> socket bind
77 PLOG(ERROR) << "Unable to bind uevent socket";
78 goto out;
79 }
80
81 mHandler = new NetlinkHandler(mSock); --> 创建 new NetlinkHandler
82 if (mHandler->start()) { --> 创建 new NetlinkHandler.start() 见4.3
83 PLOG(ERROR) << "Unable to start NetlinkHandler";
84 goto out;
85 }
86
87 return 0;
88
89 out:
90 close(mSock);
91 return -1;
92 }4.3 new NetlinkHandler and start()
这有个继承关系NetlinkHandler : NetlinkListener : SocketListener
cpp
2 int NetlinkHandler::start() {
33 return this->startListener(); ------> 实际就是SocketListener poll监听，是否有POLLIN 产生, onDataAvailable -> onEvent
34 }
35
36 void NetlinkHandler::onEvent(NetlinkEvent* evt) { ---> 收到了uevent
37 VolumeManager* vm = VolumeManager::Instance();
38 const char* subsys = evt->getSubsystem();
39
40 if (!subsys) {
41 LOG(WARNING) << "No subsystem found in netlink event";
42 return;
43 }
44
45 if (std::string(subsys) == "block") { ------> 只有uevent的subsys是block才会处理的
46 vm->handleBlockEvent(evt); ------> VolumeManager处理 block device uevent 见 4.4
47 }
48 }4.4 VolumeManager::handleBlockEvent()
cpp
199 void VolumeManager::handleBlockEvent(NetlinkEvent* evt) {
200 std::lock_guard<std::mutex> lock(mLock);
201
202 if (mDebug) {
203 LOG(DEBUG) << "----------------";
204 LOG(DEBUG) << "handleBlockEvent with action " << (int)evt->getAction(); ---> 这里是vold.debug控制的，打印具体的action
205 evt->dump();
206 }
207
208 std::string eventPath(evt->findParam("DEVPATH") ? evt->findParam("DEVPATH") : "");
209 std::string devType(evt->findParam("DEVTYPE") ? evt->findParam("DEVTYPE") : "");
210
211 if (devType != "disk") return; ---> devType不是disk还不处理， 真是牛逼哄哄
212
213 int major = std::stoi(evt->findParam("MAJOR"));
214 int minor = std::stoi(evt->findParam("MINOR"));
215 dev_t device = makedev(major, minor); ---> 创建block device组合
216
217 switch (evt->getAction()) {
218 case NetlinkEvent::Action::kAdd: { ---> uevent action为add 具体见4.5
219 for (const auto& source : mDiskSources) { ---> 之前添加的两个disksource，还记得吗，只支持sd卡和U盘
220 if (source->matches(eventPath)) {
221 // For now, assume that MMC and virtio-blk (the latter is
222 // specific to virtual platforms; see Utils.cpp for details)
223 // devices are SD, and that everything else is USB
224 int flags = source->getFlags();
225 if (major == kMajorBlockMmc || IsVirtioBlkDevice(major)) {
226 flags |= android::vold::Disk::Flags::kSd; ---> SD卡
227 } else {
228 flags |= android::vold::Disk::Flags::kUsb; ---> usb storage, 通过otg插入的
229 }
230
231 auto disk =
232 new android::vold::Disk(eventPath, device, source->getNickname(), flags); ---> 创建一个disk设备节点mknod
233 handleDiskAdded(std::shared_ptr<android::vold::Disk>(disk)); --> 真正的处理
234 break;
235 }
236 }
237 break;
238 }
239 case NetlinkEvent::Action::kChange: { --> uevent action为add 具体见4.6
240 LOG(VERBOSE) << "Disk at " << major << ":" << minor << " changed";
241 handleDiskChanged(device);
242 break;
243 }
244 case NetlinkEvent::Action::kRemove: { --> uevent action为add 具体见4.7
245 handleDiskRemoved(device);
246 break;
247 }
248 default: {
249 LOG(WARNING) << "Unexpected block event action " << (int)evt->getAction();
250 break;
251 }
252 }
253 }4.5 new android::vold::Disk()和handleDiskAdded()
system/vold/model/Disk.cpp
4.5.1 new android::vold::Disk()
cpp
Disk::Disk(const std::string& eventPath, dev_t device, const std::string& nickname, int flags)
95 : mDevice(device),
96 mSize(-1),
97 mNickname(nickname),
98 mFlags(flags),
99 mCreated(false),
100 mJustPartitioned(false) {
101 mId = StringPrintf("disk:%u,%u", major(device), minor(device));
102 mEventPath = eventPath;
103 mSysPath = StringPrintf("/sys/%s", eventPath.c_str());
104 mDevPath = StringPrintf("/dev/block/vold/%s", mId.c_str());
105 CreateDeviceNode(mDevPath, mDevice); ---------> 创建block device 的设备节点mknod
106 }4.5.2 handleDiskAdded()
cpp
255 void VolumeManager::handleDiskAdded(const std::shared_ptr<android::vold::Disk>& disk) {
256 // For security reasons, if secure keyguard is showing, wait
257 // until the user unlocks the device to actually touch it
258 // Additionally, wait until user 0 is actually started, since we need
259 // the user to be up before we can mount a FUSE daemon to handle the disk.
260 bool userZeroStarted = mStartedUsers.find(0) != mStartedUsers.end();
261 if (mSecureKeyguardShowing) {
262 LOG(INFO) << "Found disk at " << disk->getEventPath()
263 << " but delaying scan due to secure keyguard";
264 mPendingDisks.push_back(disk);
265 } else if (!userZeroStarted) {
266 LOG(INFO) << "Found disk at " << disk->getEventPath()
267 << " but delaying scan due to user zero not having started";
268 mPendingDisks.push_back(disk);
269 } else {
270 disk->create(); ---------> disk->create()
271 mDisks.push_back(disk);
272 }
273 }
146 status_t Disk::create() {
147 CHECK(!mCreated);
148 mCreated = true;
149
150 auto listener = VolumeManager::Instance()->getListener(); ---------> StorageManaerService通信
151 if (listener) listener->onDiskCreated(getId(), mFlags); ------> StorageManaerService->onDiskCreated()
152
153 if (isStub()) {
154 createStubVolume();
155 return OK;
156 }
157 readMetadata(); --------> listener->onDiskMetadataChanged(getId(), mSize, mLabel, mSysPath);
158 readPartitions(); --------> Disk::createPublicVolume() listener->onVolumeCreated()and listener->onDiskScanned()
159 return OK;
160 }思考， vold比mount service启动的早，那开机时vold获取到的listener为空，也就是说虽然disk创建了但是不会mount，那什么时候才会mount呢？ 我们下一篇文章解答