[PATCH] cfq-iosched: tighten allow merge criteria

	pid_t key;

	/*

	 * If bio is async or a write, always allow merge

	 * Disallow merge, if bio and rq aren't both sync or async

	 */

	if (!bio_sync(bio) || rw == WRITE)

		return 1;

	/*

	 * bio is sync. if request is not, disallow.

	 */

	if (!rq_is_sync(rq))

	if (!!bio_sync(bio) != !!rq_is_sync(rq))

		return 0;

	/*

	 * Ok, both bio and request are sync. Allow merge if they are

	 * from the same queue.

	 * Lookup the cfqq that this bio will be queued with. Allow

	 * merge only if rq is queued there.

	 */

	key = cfq_queue_pid(current, rw, 1);

	key = cfq_queue_pid(current, rw, bio_sync(bio));

	cfqq = cfq_find_cfq_hash(cfqd, key, current->ioprio);

	if (cfqq != RQ_CFQQ(rq))

		return 0;

	if (cfqq == RQ_CFQQ(rq))

		return 1;

	return 1;

}