[PATCH 12/16] blkio: Provide some isolation between groups

[Vivek Goyal <vgoyal@redhat.com>]

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

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 block/cfq-iosched.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 4e1c673..21121ce 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1449,6 +1449,9 @@ 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.
 	 */
@@ -1694,6 +1697,10 @@ 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.
 	 */
@@ -2962,6 +2969,9 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
 	if (!cfqq)
 		return false;
 
+	if (new_cfqq->cfqg != cfqq->cfqg)
+		return false;
+
 	if (cfq_slice_used(cfqq))
 		return true;
 
-- 
1.6.2.5