If we fail to persist the current settings and fall back to the back settings file
when reading settings in PackageManager, we might rename the corrupted settings to
backup(in case of power failure between the earlier write failure and file deletion)
and end up loosing both files.
So just clear up the corrupted current settings file if we have backup.
The backup wouldn't exist if everything went well with persisting the earlier settings.
We do this in both read and write just in case.
diff --git a/services/java/com/android/server/PackageManagerService.java b/services/java/com/android/server/PackageManagerService.java
index 66e7ecd..5f30b3d 100644
--- a/services/java/com/android/server/PackageManagerService.java
+++ b/services/java/com/android/server/PackageManagerService.java
@@ -6440,12 +6440,17 @@
// Keep the old settings around until we know the new ones have
// been successfully written.
if (mSettingsFilename.exists()) {
- if (mBackupSettingsFilename.exists()) {
- mBackupSettingsFilename.delete();
- }
- if (!mSettingsFilename.renameTo(mBackupSettingsFilename)) {
- Log.w(TAG, "Unable to backup package manager settings, current changes will be lost at reboot");
- return;
+ // Presence of backup settings file indicates that we failed
+ // to persist settings earlier. So preserve the older
+ // backup for future reference since the current settings
+ // might have been corrupted.
+ if (!mBackupSettingsFilename.exists()) {
+ if (!mSettingsFilename.renameTo(mBackupSettingsFilename)) {
+ Log.w(TAG, "Unable to backup package manager settings, current changes will be lost at reboot");
+ return;
+ }
+ } else {
+ Log.w(TAG, "Preserving older settings backup");
}
}
@@ -6712,6 +6717,13 @@
str = new FileInputStream(mBackupSettingsFilename);
mReadMessages.append("Reading from backup settings file\n");
Log.i(TAG, "Reading from backup settings file!");
+ if (mSettingsFilename.exists()) {
+ // If both the backup and settings file exist, we
+ // ignore the settings since it might have been
+ // corrupted.
+ Log.w(TAG, "Cleaning up settings file " + mSettingsFilename);
+ mSettingsFilename.delete();
+ }
} catch (java.io.IOException e) {
// We'll try for the normal settings file.
}