commit c5375f2f23f0ae4813c35502b4a4989815605d2d
author JW Wang <wangchun@google.com> Thu Sep 09 16:05:57 2021 +0800
committer JW Wang <wangchun@google.com> Fri Sep 10 11:22:17 2021 +0000
tree 7e2887cce23b085018a6d5111648c3d603fa279d
parent 5ced92cac555c340faa5beef0e499f53b001a64d

Fix that the file is not correctly flushed to the disk

Fix a bug where rollback is corrupted when system_server crasshes
and reboots into RAMDUMP mode.

AtomicFile.finishWrite() calls FileUtils.sync() on the stream internally
which requires the stream is flushed but not yet closed.

pw.close() will close the stream which conflicts the use of
AtomicFile.finishWrite().

Let's remove the use of PrintWriter and flush the stream before calling
AtomicFile.finishWrite() so the file is correctly persisted to the disk.

Bug: 199124163
Test: atest RollbackManagerHostTest#testNativeWatchdogTriggersRollback
      and check no "AtomicFile: Failed to sync file output stream"
      appears in the log messages.
Test: atest CtsRootRollbackManagerHostTestCases \
            CtsRollbackManagerHostTestCases \
            CtsRollbackManagerTestCases

Change-Id: I6c93f20949f6103a7fe28fa2955155cd19df018a

services/core/java/com/android/server/rollback/RollbackStore.java

diff --git a/services/core/java/com/android/server/rollback/RollbackStore.java b/services/core/java/com/android/server/rollback/RollbackStore.java
index 2cfc785..f973f5c 100644
--- a/services/core/java/com/android/server/rollback/RollbackStore.java
+++ b/services/core/java/com/android/server/rollback/RollbackStore.java
@@ -43,7 +43,6 @@
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
-import java.io.PrintWriter;
 import java.nio.file.Files;
 import java.text.ParseException;
 import java.time.Instant;
@@ -323,9 +322,8 @@
                     "extensionVersions", extensionVersionsToJson(rollback.getExtensionVersions()));
 
             fos = file.startWrite();
-            PrintWriter pw = new PrintWriter(fos);
-            pw.println(dataJson.toString());
-            pw.close();
+            fos.write(dataJson.toString().getBytes());
+            fos.flush();
             file.finishWrite(fos);
         } catch (JSONException | IOException e) {
             Slog.e(TAG, "Unable to save rollback for: " + rollback.info.getRollbackId(), e);