[FELIX-4195] Sync on a Preference doesn't do a OS side sync

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: prefs-1.0.6
• Component/s: Preferences Service
• Environment: Angstroem Embedded Linux; UBIFS on a flash drive
• Assignee: Unassigned
• Reporter: Matt Wiselka
• Created: 16/Aug/13 05:34
• Updated: 16/Aug/13 07:21

Description

I ran in to the following problem using the Preferences Service on an embedded device with a flash memory:
When a preference is changed the sync method is called to persist it. A sudden power loss occurs. On restart the preference file in the bundle cache is empty and causes a BackingStoreException: Could not load preference.

It seems to me as that the OS is caching the write to the flash drive and the change is not actually persisted. I was able to fix this issue by performing a sync on the FileDescriptor of the OutputStream in the store method of the DataFileBackingStoreImpl

try {
final FileOutputStream os = (FileOutputStream) this.getOutputStream(root.getDescription());
this.write(root, os);
os.getFD().sync();
os.close();
}
catch (IOException ioe) {
throw new BackingStoreException("Unable to store preferences.", ioe);
}