blkio: Provide some isolation between groups

o Do not allow following three operations across groups for isolation.
	- selection of co-operating queues
	- preemtpions across groups
	- request merging across groups.

o Async queues are currently global and not per group. Allow preemption of
  an async queue if a sync queue in other group gets backlogged.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 20 insertions, 10 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 7d345e772d88..3a62ce95daec 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1461,6 +1461,9 @@ static int cfq_allow_merge(struct request_queue *q, struct request *rq,
         struct cfq_io_context *cic;
         struct cfq_queue *cfqq;
 
+        /* Deny merge if bio and rq don't belong to same cfq group */
+        if ((RQ_CFQQ(rq))->cfqg != cfq_get_cfqg(cfqd, 0))
+                return false;
         /*
          * Disallow merge of a sync bio into an async request.
          */
@@ -1698,6 +1701,10 @@ static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
         if (!cfqq)
                 return NULL;
 
+        /* If new queue belongs to different cfq_group, don't choose it */
+        if (cur_cfqq->cfqg != cfqq->cfqg)
+                return NULL;
+
         /*
          * It only makes sense to merge sync queues.
          */
@@ -2950,22 +2957,12 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
         if (!cfqq)
                 return false;
 
-        if (cfq_slice_used(cfqq))
-                return true;
-
         if (cfq_class_idle(new_cfqq))
                 return false;
 
         if (cfq_class_idle(cfqq))
                 return true;
 
-        /* Allow preemption only if we are idling on sync-noidle tree */
-        if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
-            cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
-            new_cfqq->service_tree->count == 2 &&
-            RB_EMPTY_ROOT(&cfqq->sort_list))
-                return true;
-
         /*
          * if the new request is sync, but the currently running queue is
          * not, let the sync request have priority.
@@ -2973,6 +2970,19 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
         if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
                 return true;
 
+        if (new_cfqq->cfqg != cfqq->cfqg)
+                return false;
+
+        if (cfq_slice_used(cfqq))
+                return true;
+
+        /* Allow preemption only if we are idling on sync-noidle tree */
+        if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
+            cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
+            new_cfqq->service_tree->count == 2 &&
+            RB_EMPTY_ROOT(&cfqq->sort_list))
+                return true;
+
         /*
          * So both queues are sync. Let the new request get disk time if
          * it's a metadata request and the current queue is doing regular IO.