Commit 9c2c38a1 authored by Jens Axboe's avatar Jens Axboe Committed by Linus Torvalds
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[PATCH] cfq-iosched.c: minor fixes 



One critical fix and two minor fixes for 2.6.13-rc7:

- Max depth must currently be 2 to allow barriers to function on SCSI
- Prefer sync request over async in choosing the next request
- Never allow async request to preempt or disturb the "anticipation" for
  a single cfq process context. This is as-designed, the code right now
  is buggy in that area.

Signed-off-by: default avatarJens Axboe <axboe@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 41290c14

drivers/block/cfq-iosched.c

+21 −10
Original line number Diff line number Diff line
@@ -47,7 +47,7 @@ static int cfq_slice_idle = HZ / 100; 
/*

 * disable queueing at the driver/hardware level

 */

static int cfq_max_depth = 1;

static int cfq_max_depth = 2;



/*

 * for the hash of cfqq inside the cfqd
@@ -385,9 +385,15 @@ cfq_choose_req(struct cfq_data *cfqd, struct cfq_rq *crq1, struct cfq_rq *crq2) 
		return crq2;

	if (crq2 == NULL)

		return crq1;

	if (cfq_crq_requeued(crq1))



	if (cfq_crq_requeued(crq1) && !cfq_crq_requeued(crq2))

		return crq1;

	else if (cfq_crq_requeued(crq2) && !cfq_crq_requeued(crq1))

		return crq2;



	if (cfq_crq_is_sync(crq1) && !cfq_crq_is_sync(crq2))

		return crq1;

	if (cfq_crq_requeued(crq2))

	else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1))

		return crq2;



	s1 = crq1->request->sector;
@@ -1769,18 +1775,23 @@ static void 
cfq_crq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,

		 struct cfq_rq *crq)

{

	const int sync = cfq_crq_is_sync(crq);

	struct cfq_io_context *cic;



	cfqq->next_crq = cfq_choose_req(cfqd, cfqq->next_crq, crq);



	if (sync) {

		struct cfq_io_context *cic = crq->io_context;

	/*

	 * we never wait for an async request and we don't allow preemption

	 * of an async request. so just return early

	 */

	if (!cfq_crq_is_sync(crq))

		return;



	cic = crq->io_context;



	cfq_update_io_thinktime(cfqd, cic);

	cfq_update_idle_window(cfqd, cfqq, cic);



	cic->last_queue = jiffies;

	}



	if (cfqq == cfqd->active_queue) {

		/*

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