1 files changed, 31 insertions, 12 deletions

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index a0512700542f..bfc70f57900f 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1727,6 +1727,21 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
 	if (!jh)
 		goto zap_buffer_no_jh;
 
+	/*
+	 * We cannot remove the buffer from checkpoint lists until the
+	 * transaction adding inode to orphan list (let's call it T)
+	 * is committed.  Otherwise if the transaction changing the
+	 * buffer would be cleaned from the journal before T is
+	 * committed, a crash will cause that the correct contents of
+	 * the buffer will be lost.  On the other hand we have to
+	 * clear the buffer dirty bit at latest at the moment when the
+	 * transaction marking the buffer as freed in the filesystem
+	 * structures is committed because from that moment on the
+	 * buffer can be reallocated and used by a different page.
+	 * Since the block hasn't been freed yet but the inode has
+	 * already been added to orphan list, it is safe for us to add
+	 * the buffer to BJ_Forget list of the newest transaction.
+	 */
 	transaction = jh->b_transaction;
 	if (transaction == NULL) {
 		/* First case: not on any transaction.  If it
@@ -1783,16 +1798,15 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
 	} else if (transaction == journal->j_committing_transaction) {
 		JBUFFER_TRACE(jh, "on committing transaction");
 		/*
-		 * If it is committing, we simply cannot touch it.  We
-		 * can remove it's next_transaction pointer from the
-		 * running transaction if that is set, but nothing
-		 * else. */
+		 * The buffer is committing, we simply cannot touch
+		 * it. So we just set j_next_transaction to the
+		 * running transaction (if there is one) and mark
+		 * buffer as freed so that commit code knows it should
+		 * clear dirty bits when it is done with the buffer.
+		 */
 		set_buffer_freed(bh);
-		if (jh->b_next_transaction) {
-			J_ASSERT(jh->b_next_transaction ==
-					journal->j_running_transaction);
-			jh->b_next_transaction = NULL;
-		}
+		if (journal->j_running_transaction && buffer_jbddirty(bh))
+			jh->b_next_transaction = journal->j_running_transaction;
 		jbd2_journal_put_journal_head(jh);
 		spin_unlock(&journal->j_list_lock);
 		jbd_unlock_bh_state(bh);
@@ -1969,7 +1983,7 @@ void jbd2_journal_file_buffer(struct journal_head *jh,
  */
 void __jbd2_journal_refile_buffer(struct journal_head *jh)
 {
-	int was_dirty;
+	int was_dirty, jlist;
 	struct buffer_head *bh = jh2bh(jh);
 
 	J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
@@ -1991,8 +2005,13 @@ void __jbd2_journal_refile_buffer(struct journal_head *jh)
 	__jbd2_journal_temp_unlink_buffer(jh);
 	jh->b_transaction = jh->b_next_transaction;
 	jh->b_next_transaction = NULL;
-	__jbd2_journal_file_buffer(jh, jh->b_transaction,
-				jh->b_modified ? BJ_Metadata : BJ_Reserved);
+	if (buffer_freed(bh))
+		jlist = BJ_Forget;
+	else if (jh->b_modified)
+		jlist = BJ_Metadata;
+	else
+		jlist = BJ_Reserved;
+	__jbd2_journal_file_buffer(jh, jh->b_transaction, jlist);
 	J_ASSERT_JH(jh, jh->b_transaction->t_state == T_RUNNING);
 
 	if (was_dirty)