jbd2: Don't call __bforget() unnecessarily

jbd2_journal_forget() jumps to 'not_jbd' branch which calls __bforget()
in cases where the buffer is clean which is pointless. In case of failed
assertion, it can be even argued that it is safer not to touch buffer's
dirty bits. Also logically it makes more sense to just jump to 'drop'
and that will make logic also simpler when we switch bh_state_lock to a
spinlock.

Signed-off-by: Jan Kara <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Theodore Ts'o <[e-mail]>

fs/jbd2/transaction.c

···
 	if (!J_EXPECT_JH(jh, !jh->b_committed_data,
 			 "inconsistent data on disk")) {
 		err = -EIO;
-		goto not_jbd;
+		goto drop;
 	}
 
 	/* keep track of whether or not this transaction modified us */
···
 		if (!jh->b_cp_transaction) {
 			JBUFFER_TRACE(jh, "belongs to none transaction");
 			spin_unlock(&journal->j_list_lock);
-			goto not_jbd;
+			goto drop;
 		}
 
 		/*
···
 		if (!buffer_dirty(bh)) {
 			__jbd2_journal_remove_checkpoint(jh);
 			spin_unlock(&journal->j_list_lock);
-			goto not_jbd;
+			goto drop;
 		}
 
 		/*
···
 		__jbd2_journal_file_buffer(jh, transaction, BJ_Forget);
 		spin_unlock(&journal->j_list_lock);
 	}
-
+drop:
 	jbd_unlock_bh_state(bh);
 	__brelse(bh);
-drop:
 	if (drop_reserve) {
 		/* no need to reserve log space for this block -bzzz */
 		handle->h_buffer_credits++;