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authorJan Kara <jack@suse.com>2016-01-12 16:24:16 +0100
committerJens Axboe <axboe@fb.com>2016-02-04 09:50:12 -0700
commit6c80731c75bd3289d35b89a21a4e317cbcb306e3 (patch)
tree6436e8e33ca1f8cd62a46c900547bab559504384
parente795421e40b39bf874c5ed9434365fb4a4b6c5d1 (diff)
cfq-iosched: Reorder checks in cfq_should_preempt()
Move check for preemption by rt class up. There is no functional change but it makes arguing about conditions simpler since we can be sure both cfq queues are from the same ioprio class. Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jan Kara <jack@suse.com> Signed-off-by: Jens Axboe <axboe@fb.com>
-rw-r--r--block/cfq-iosched.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 0a6a70a9bca8..2544c219c00c 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -3959,6 +3959,13 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
if (cfq_slice_used(cfqq))
return true;
+ /*
+ * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
+ */
+ if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
+ return true;
+
+ WARN_ON_ONCE(cfqq->ioprio_class != new_cfqq->ioprio_class);
/* Allow preemption only if we are idling on sync-noidle tree */
if (cfqd->serving_wl_type == SYNC_NOIDLE_WORKLOAD &&
cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
@@ -3973,12 +3980,6 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
if ((rq->cmd_flags & REQ_PRIO) && !cfqq->prio_pending)
return true;
- /*
- * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
- */
- if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
- return true;
-
/* An idle queue should not be idle now for some reason */
if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))
return true;