vold: implement resetCheckpoint

It will be used by userspace reboot to reset checkpoint state, to make
sure that when /data is remounted, it will be remounted in checkpointing
if a checkpoint was requested beforee userspace reboot.

Test: /system/bin/vdc startCheckpoint 1
      /system/bin/vdc needsCheckpoint (returns 0)
      /system/bin/vdc resetCheckpoint
      /system/bin/vdc needsCheckpoint (returns 1)

Bug: 135984674
Change-Id: Ia29238686289b4eed93e2fb936a8b3d894b94dc9

Checkpoint.cpp

@@ -145,8 +145,10 @@ namespace {
 
 volatile bool isCheckpointing = false;
 
-// Protects isCheckpointing and code that makes decisions based on status of
+volatile bool needsCheckpointWasCalled = false;
-// isCheckpointing
+
+// Protects isCheckpointing, needsCheckpointWasCalled and code that makes decisions based on status
+// of isCheckpointing
 std::mutex isCheckpointingLock;
 }
 
@@ -263,16 +265,16 @@ bool cp_needsRollback() {
 }
 
 bool cp_needsCheckpoint() {
+    std::lock_guard<std::mutex> lock(isCheckpointingLock);
+
     // Make sure we only return true during boot. See b/138952436 for discussion
-    static bool called_once = false;
+    if (needsCheckpointWasCalled) return isCheckpointing;
-    if (called_once) return isCheckpointing;
+    needsCheckpointWasCalled = true;
-    called_once = true;
 
     bool ret;
     std::string content;
     sp<IBootControl> module = IBootControl::getService();
 
-    std::lock_guard<std::mutex> lock(isCheckpointingLock);
     if (isCheckpointing) return isCheckpointing;
 
     if (module && module->isSlotMarkedSuccessful(module->getCurrentSlot()) == BoolResult::FALSE) {
@@ -727,5 +729,10 @@ Status cp_markBootAttempt() {
     return Status::ok();
 }
 
+void cp_resetCheckpoint() {
+    std::lock_guard<std::mutex> lock(isCheckpointingLock);
+    needsCheckpointWasCalled = false;
+}
+
 }  // namespace vold
 }  // namespace android

Checkpoint.h

@@ -45,6 +45,7 @@ android::binder::Status cp_restoreCheckpoint(const std::string& mountPoint, int
 
 android::binder::Status cp_markBootAttempt();
 
+void cp_resetCheckpoint();
 }  // namespace vold
 }  // namespace android
 

VoldNativeService.cpp

@@ -907,5 +907,13 @@ binder::Status VoldNativeService::supportsFileCheckpoint(bool* _aidl_return) {
     return cp_supportsFileCheckpoint(*_aidl_return);
 }
 
+binder::Status VoldNativeService::resetCheckpoint() {
+    ENFORCE_UID(AID_SYSTEM);
+    ACQUIRE_LOCK;
+
+    cp_resetCheckpoint();
+    return ok();
+}
+
 }  // namespace vold
 }  // namespace android

VoldNativeService.h

@@ -140,6 +140,7 @@ class VoldNativeService : public BinderService<VoldNativeService>, public os::Bn
     binder::Status supportsCheckpoint(bool* _aidl_return);
     binder::Status supportsBlockCheckpoint(bool* _aidl_return);
     binder::Status supportsFileCheckpoint(bool* _aidl_return);
+    binder::Status resetCheckpoint();
 };
 
 }  // namespace vold

binder/android/os/IVold.aidl

@@ -116,6 +116,7 @@ interface IVold {
     boolean supportsCheckpoint();
     boolean supportsBlockCheckpoint();
     boolean supportsFileCheckpoint();
+    void resetCheckpoint();
 
     @utf8InCpp String createStubVolume(@utf8InCpp String sourcePath,
             @utf8InCpp String mountPath, @utf8InCpp String fsType,

vdc.cpp

@@ -147,6 +147,8 @@ int main(int argc, char** argv) {
         int retry;
         if (!android::base::ParseInt(args[2], &retry)) exit(EINVAL);
         checkStatus(args, vold->abortChanges(args[2], retry != 0));
+    } else if (args[0] == "checkpoint" && args[1] == "resetCheckpoint") {
+        checkStatus(args, vold->resetCheckpoint());
     } else {
         LOG(ERROR) << "Raw commands are no longer supported";
         exit(EINVAL);