Android系统如何创建/storage/self/primary目录？

Question

我注意到 android 目录按如下符号链接组织：

lrwxrwxrwx 1 root root 21 1970-01-01 08:00 /sdcard -> /storage/self/primary 
lrwxrwxrwx 1 root root 19 1972-12-17 02:19 /storage/self/primary -> /mnt/user/0/primary
lrwxrwxrwx 1 root root 19 2020-02-21 10:31 /mnt/user/0/primary -> /storage/emulated/0

我搜索了一些 android 文档，发现：

/sdcard -> /storage/self/primary是由system/core/rootdir/init.rc中的命令创建的：

symlink /storage/self/primary /sdcard

/storage/self/和/mnt/user/0/挂载在system/vold/VolumeManager.cpp:

            std::string storageSource;
            if (mode == "default") {
                storageSource = "/mnt/runtime/default";
            } else if (mode == "read") {
                storageSource = "/mnt/runtime/read";
            } else if (mode == "write") {
                storageSource = "/mnt/runtime/write";
            } else if (mode == "full") {
                storageSource = "/mnt/runtime/full";
            } else {
                // Sane default of no storage visible
                _exit(0);
            }
            if (TEMP_FAILURE_RETRY(
                    mount(storageSource.c_str(), "/storage", NULL, MS_BIND | MS_REC, NULL)) == -1) {
                PLOG(ERROR) << "Failed to mount " << storageSource << " for " << de->d_name;
                _exit(1);
            }
            if (TEMP_FAILURE_RETRY(mount(NULL, "/storage", NULL, MS_REC | MS_SLAVE, NULL)) == -1) {
                PLOG(ERROR) << "Failed to set MS_SLAVE to /storage for " << de->d_name;
                _exit(1);
            }

            // Mount user-specific symlink helper into place
            userid_t user_id = multiuser_get_user_id(uid);
            std::string userSource(StringPrintf("/mnt/user/%d", user_id));
            if (TEMP_FAILURE_RETRY(
                    mount(userSource.c_str(), "/storage/self", NULL, MS_BIND, NULL)) == -1) {
                PLOG(ERROR) << "Failed to mount " << userSource << " for " << de->d_name;
                _exit(1);
            }

但是，我没有找到Android系统何时何地在/storage/self或/mnt/user/0/self中创建了一个primary目录。你能帮我解决这个问题吗？非常感谢！

Answer 1

或许可以参考VolumeManager.cpp中的函数"linkPrimary"。它将创建链接器 /mnt/user/0/primary -> /storage/emulated/0

Android系统如何创建/storage/self/primary目录？

How does the Android system create the /storage/self/primary directory?

android

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