jbd: don't write superblock when unmounting an ro filesystem

This sequence: results in an IO error when unmounting the RO filesystem. The bug was introduced by: commit 9754e39 Author: Jan Kara <[email protected]> Date: Sat Apr 7 12:33:03 2012 +0200 jbd: Split updating of journal superblock and marking journal empty which lost some of the magic in journal_update_superblock() which used to test for a journal with no outstanding transactions. This is a port of a jbd2 fix by Eric Sandeen. CC: <[email protected]> # 3.4.x Signed-off-by: Jan Kara <[email protected]>
tong646591 · Aug 15, 2012 · 2e84f26 · 2e84f26
1 parent 48d1788
commit 2e84f26
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
@@ -1113,6 +1113,11 @@ static void mark_journal_empty(journal_t *journal)
 
 	BUG_ON(!mutex_is_locked(&journal->j_checkpoint_mutex));
 	spin_lock(&journal->j_state_lock);
+	/* Is it already empty? */
+	if (sb->s_start == 0) {
+		spin_unlock(&journal->j_state_lock);
+		return;
+	}
 	jbd_debug(1, "JBD: Marking journal as empty (seq %d)\n",
         	  journal->j_tail_sequence);