Add an isCheckpointing() binder call for adb remount.

This is needed so "adb remount" can avoid writing to /data during a
checkpoint.

Bug: 157540389
Test: manual test
Change-Id: I33a691da3b99343acfc1e8ddf68a14504c3bfbe1

Checkpoint.cpp

@@ -294,6 +294,10 @@ bool cp_needsCheckpoint() {
     return false;
 }
 
+bool cp_isCheckpointing() {
+    return isCheckpointing;
+}
+
 namespace {
 const std::string kSleepTimeProp = "ro.sys.cp_msleeptime";
 const uint32_t msleeptime_default = 1000;  // 1 s

Checkpoint.h

@@ -39,6 +39,8 @@ bool cp_needsRollback();
 
 bool cp_needsCheckpoint();
 
+bool cp_isCheckpointing();
+
 android::binder::Status cp_prepareCheckpoint();
 
 android::binder::Status cp_restoreCheckpoint(const std::string& mountPoint, int count = 0);

VoldNativeService.cpp

@@ -778,6 +778,14 @@ binder::Status VoldNativeService::needsCheckpoint(bool* _aidl_return) {
     return Ok();
 }
 
+binder::Status VoldNativeService::isCheckpointing(bool* _aidl_return) {
+    ENFORCE_SYSTEM_OR_ROOT;
+    ACQUIRE_LOCK;
+
+    *_aidl_return = cp_isCheckpointing();
+    return Ok();
+}
+
 binder::Status VoldNativeService::commitChanges() {
     ENFORCE_SYSTEM_OR_ROOT;
     ACQUIRE_LOCK;

VoldNativeService.h

@@ -133,6 +133,7 @@ class VoldNativeService : public BinderService<VoldNativeService>, public os::Bn
     binder::Status startCheckpoint(int32_t retry);
     binder::Status needsCheckpoint(bool* _aidl_return);
     binder::Status needsRollback(bool* _aidl_return);
+    binder::Status isCheckpointing(bool* _aidl_return);
     binder::Status commitChanges();
     binder::Status prepareCheckpoint();
     binder::Status restoreCheckpoint(const std::string& mountPoint);

binder/android/os/IVold.aidl

@@ -110,6 +110,7 @@ interface IVold {
     void startCheckpoint(int retry);
     boolean needsCheckpoint();
     boolean needsRollback();
+    boolean isCheckpointing();
     void abortChanges(in @utf8InCpp String device, boolean retry);
     void commitChanges();
     void prepareCheckpoint();