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authorTejun Heo <tj@kernel.org>2014-11-04 13:52:27 -0500
committerJens Axboe <axboe@fb.com>2014-11-04 14:49:31 -0700
commitf3af020b9a8d298022b811a19719df0cf461efa5 (patch)
tree7468b9e6077738b941c89433d491662c7b8da8b4 /block
parentece9c72accdc45c3a9484dacb1125ce572647288 (diff)
blk-mq: make mq_queue_reinit_notify() freeze queues in parallel
q->mq_usage_counter is a percpu_ref which is killed and drained when the queue is frozen. On a CPU hotplug event, blk_mq_queue_reinit() which involves freezing the queue is invoked on all existing queues. Because percpu_ref killing and draining involve a RCU grace period, doing the above on one queue after another may take a long time if there are many queues on the system. This patch splits out initiation of freezing and waiting for its completion, and updates blk_mq_queue_reinit_notify() so that the queues are frozen in parallel instead of one after another. Note that freezing and unfreezing are moved from blk_mq_queue_reinit() to blk_mq_queue_reinit_notify(). Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Christian Borntraeger <borntraeger@de.ibm.com> Tested-by: Christian Borntraeger <borntraeger@de.ibm.com> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block')
-rw-r--r--block/blk-mq.c41
1 files changed, 33 insertions, 8 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 68929bad9a6a..1d016fc9a8b6 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -107,11 +107,7 @@ static void blk_mq_usage_counter_release(struct percpu_ref *ref)
wake_up_all(&q->mq_freeze_wq);
}
-/*
- * Guarantee no request is in use, so we can change any data structure of
- * the queue afterward.
- */
-void blk_mq_freeze_queue(struct request_queue *q)
+static void blk_mq_freeze_queue_start(struct request_queue *q)
{
bool freeze;
@@ -123,9 +119,23 @@ void blk_mq_freeze_queue(struct request_queue *q)
percpu_ref_kill(&q->mq_usage_counter);
blk_mq_run_queues(q, false);
}
+}
+
+static void blk_mq_freeze_queue_wait(struct request_queue *q)
+{
wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->mq_usage_counter));
}
+/*
+ * Guarantee no request is in use, so we can change any data structure of
+ * the queue afterward.
+ */
+void blk_mq_freeze_queue(struct request_queue *q)
+{
+ blk_mq_freeze_queue_start(q);
+ blk_mq_freeze_queue_wait(q);
+}
+
static void blk_mq_unfreeze_queue(struct request_queue *q)
{
bool wake;
@@ -1921,7 +1931,7 @@ void blk_mq_free_queue(struct request_queue *q)
/* Basically redo blk_mq_init_queue with queue frozen */
static void blk_mq_queue_reinit(struct request_queue *q)
{
- blk_mq_freeze_queue(q);
+ WARN_ON_ONCE(!q->mq_freeze_depth);
blk_mq_sysfs_unregister(q);
@@ -1936,8 +1946,6 @@ static void blk_mq_queue_reinit(struct request_queue *q)
blk_mq_map_swqueue(q);
blk_mq_sysfs_register(q);
-
- blk_mq_unfreeze_queue(q);
}
static int blk_mq_queue_reinit_notify(struct notifier_block *nb,
@@ -1956,8 +1964,25 @@ static int blk_mq_queue_reinit_notify(struct notifier_block *nb,
return NOTIFY_OK;
mutex_lock(&all_q_mutex);
+
+ /*
+ * We need to freeze and reinit all existing queues. Freezing
+ * involves synchronous wait for an RCU grace period and doing it
+ * one by one may take a long time. Start freezing all queues in
+ * one swoop and then wait for the completions so that freezing can
+ * take place in parallel.
+ */
+ list_for_each_entry(q, &all_q_list, all_q_node)
+ blk_mq_freeze_queue_start(q);
+ list_for_each_entry(q, &all_q_list, all_q_node)
+ blk_mq_freeze_queue_wait(q);
+
list_for_each_entry(q, &all_q_list, all_q_node)
blk_mq_queue_reinit(q);
+
+ list_for_each_entry(q, &all_q_list, all_q_node)
+ blk_mq_unfreeze_queue(q);
+
mutex_unlock(&all_q_mutex);
return NOTIFY_OK;
}