[PATCH] jbd: avoid kfree(NULL)

There are a couple of places where JBD has to check to see whether an unneeded
memory allocation was performed.  Usually it _was_ needed, so we end up
calling kfree(NULL).  We can micro-optimise that by checking the pointer
before calling kfree().

Thanks to Steven Rostedt <rostedt@goodmis.org> for identifying this.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/jbd/transaction.c

@@ -227,7 +227,8 @@ static int start_this_handle(journal_t *journal, handle_t *handle)
 	spin_unlock(&transaction->t_handle_lock);
 	spin_unlock(&journal->j_state_lock);
 out:
-	kfree(new_transaction);
+	if (unlikely(new_transaction))		/* It's usually NULL */
+		kfree(new_transaction);
 	return ret;
 }
 
@@ -724,7 +725,8 @@ do_get_write_access(handle_t *handle, struct journal_head *jh,
 	journal_cancel_revoke(handle, jh);
 
 out:
-	kfree(frozen_buffer);
+	if (unlikely(frozen_buffer))	/* It's usually NULL */
+		kfree(frozen_buffer);
 
 	JBUFFER_TRACE(jh, "exit");
 	return error;
@@ -903,7 +905,8 @@ int journal_get_undo_access(handle_t *handle, struct buffer_head *bh)
 	jbd_unlock_bh_state(bh);
 out:
 	journal_put_journal_head(jh);
-	kfree(committed_data);
+	if (unlikely(committed_data))
+		kfree(committed_data);
 	return err;
 }