Merge "Changes of root storage space unmounting time on Zygote Process"

core/java/com/android/internal/os/Zygote.java

@@ -149,6 +149,12 @@ public final class Zygote {
     native private static int nativeForkSystemServer(int uid, int gid, int[] gids, int debugFlags,
             int[][] rlimits, long permittedCapabilities, long effectiveCapabilities);
 
+    /**
+     * Zygote unmount storage space on initializing.
+     * This method is called once.
+     */
+    native protected static void nativeUnmountStorageOnInit();
+
     private static void callPostForkChildHooks(int debugFlags, boolean isSystemServer,
             String instructionSet) {
         VM_HOOKS.postForkChild(debugFlags, isSystemServer, instructionSet);

core/java/com/android/internal/os/ZygoteInit.java

@@ -621,6 +621,9 @@ public class ZygoteInit {
             // Zygote.
             Trace.setTracingEnabled(false);
 
+            // Zygote process unmounts root storage spaces.
+            Zygote.nativeUnmountStorageOnInit();
+
             if (startSystemServer) {
                 startSystemServer(abiList, socketName);
             }

core/jni/com_android_internal_os_Zygote.cpp

@@ -302,9 +302,6 @@ static bool MountEmulatedStorage(uid_t uid, jint mount_mode,
         return false;
     }
 
-    // Unmount storage provided by root namespace and mount requested view
-    UnmountTree("/storage");
-
     String8 storageSource;
     if (mount_mode == MOUNT_EXTERNAL_DEFAULT) {
         storageSource = "/mnt/runtime/default";
@@ -663,12 +660,24 @@ static jint com_android_internal_os_Zygote_nativeForkSystemServer(
   return pid;
 }
 
+static void com_android_internal_os_Zygote_nativeUnmountStorageOnInit(JNIEnv* env, jclass) {
+    // Zygote process unmount root storage space initially before every child processes are forked.
+    // Every forked child processes (include SystemServer) only mount their own root storage space
+    // And no need unmount storage operation in MountEmulatedStorage method.
+    // Zygote process does not utilize root storage spaces and unshared its mount namespace from the ART.
+
+    UnmountTree("/storage");
+    return;
+}
+
 static const JNINativeMethod gMethods[] = {
     { "nativeForkAndSpecialize",
       "(II[II[[IILjava/lang/String;Ljava/lang/String;[ILjava/lang/String;Ljava/lang/String;)I",
       (void *) com_android_internal_os_Zygote_nativeForkAndSpecialize },
     { "nativeForkSystemServer", "(II[II[[IJJ)I",
-      (void *) com_android_internal_os_Zygote_nativeForkSystemServer }
+      (void *) com_android_internal_os_Zygote_nativeForkSystemServer },
+    { "nativeUnmountStorageOnInit", "()V",
+      (void *) com_android_internal_os_Zygote_nativeUnmountStorageOnInit }
 };
 
 int register_com_android_internal_os_Zygote(JNIEnv* env) {