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Subject[PATCH 15/16] blkio: Drop the reference to queue once the task changes cgroup
Date
o If a task changes cgroup, drop reference to the cfqq associated with io
context and set cfqq pointer stored in ioc to NULL so that upon next request
arrival we will allocate a new queue in new group.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
block/cfq-iosched.c | 39 +++++++++++++++++++++++++++++++++++++++
1 files changed, 39 insertions(+), 0 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 3f7a350..34f029c 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2648,6 +2648,41 @@ static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
cfqq->pid = pid;
}

+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
+{
+ struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
+ struct cfq_data *cfqd = cic->key;
+ unsigned long flags;
+ struct request_queue *q;
+
+ if (unlikely(!cfqd))
+ return;
+
+ q = cfqd->queue;
+
+ spin_lock_irqsave(q->queue_lock, flags);
+
+ if (sync_cfqq) {
+ /*
+ * Drop reference to sync queue. A new sync queue will be
+ * assigned in new group upon arrival of a fresh request.
+ */
+ cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
+ cic_set_cfqq(cic, NULL, 1);
+ cfq_put_queue(sync_cfqq);
+ }
+
+ spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+static void cfq_ioc_set_cgroup(struct io_context *ioc)
+{
+ call_for_each_cic(ioc, changed_cgroup);
+ ioc->cgroup_changed = 0;
+}
+#endif /* CONFIG_CFQ_GROUP_IOSCHED */
+
static struct cfq_queue *
cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
struct io_context *ioc, gfp_t gfp_mask)
@@ -2880,6 +2915,10 @@ out:
if (unlikely(ioc->ioprio_changed))
cfq_ioc_set_ioprio(ioc);

+#ifdef CONFIG_CFQ_GROUP_IOSCHED
+ if (unlikely(ioc->cgroup_changed))
+ cfq_ioc_set_cgroup(ioc);
+#endif
return cic;
err_free:
cfq_cic_free(cic);
--
1.6.2.5


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