[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: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/block/cfq-iosched.c b/drivers/block/cfq-iosched.c
index 2435a7c..cd056e7 100644
--- a/drivers/block/cfq-iosched.c
+++ b/drivers/block/cfq-iosched.c
@@ -47,7 +47,7 @@
/*
* 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 @@
return crq2;
if (crq2 == NULL)
return crq1;
- if (cfq_crq_requeued(crq1))
+
+ if (cfq_crq_requeued(crq1) && !cfq_crq_requeued(crq2))
return crq1;
- if (cfq_crq_requeued(crq2))
+ 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;
+ else if (cfq_crq_is_sync(crq2) && !cfq_crq_is_sync(crq1))
return crq2;
s1 = crq1->request->sector;
@@ -1769,18 +1775,23 @@
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;
- cfq_update_io_thinktime(cfqd, cic);
- cfq_update_idle_window(cfqd, cfqq, cic);
+ cic = crq->io_context;
- cic->last_queue = jiffies;
- }
+ cfq_update_io_thinktime(cfqd, cic);
+ cfq_update_idle_window(cfqd, cfqq, cic);
+
+ cic->last_queue = jiffies;
if (cfqq == cfqd->active_queue) {
/*