From 6c7e8cee6a9128eeb7f83c3ad1cb243f77f5cb16 Mon Sep 17 00:00:00 2001
From: Jens Axboe <jens.axboe@oracle.com>
Date: Fri, 27 Mar 2009 10:30:47 +0100
Subject: [PATCH] block: elevator quiescing helpers
Simple helper functions to quiesce the request queue. These are
currently only used for switching IO schedulers on-the-fly, but
we can use them to properly switch IO accounting on and off as well.
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
block/blk.h | 4 ++++
block/elevator.c | 40 +++++++++++++++++++++++++++-------------
2 files changed, 31 insertions(+), 13 deletions(-)
diff --git a/block/blk.h b/block/blk.h
index 3ee94358b43d..22043c2886c7 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -70,6 +70,10 @@ void blk_queue_congestion_threshold(struct request_queue *q);
int blk_dev_init(void);
+void elv_quisce_start(struct request_queue *q);
+void elv_quisce_end(struct request_queue *q);
+
+
/*
* Return the threshold (number of used requests) at which the queue is
* considered to be congested. It include a little hysteresis to keep the
diff --git a/block/elevator.c b/block/elevator.c
index ca6788a0195a..c6744913ff4a 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -587,6 +587,31 @@ static void elv_drain_elevator(struct request_queue *q)
}
}
+/*
+ * Call with queue lock held, interrupts disabled
+ */
+void elv_quisce_start(struct request_queue *q)
+{
+ queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
+
+ /*
+ * make sure we don't have any requests in flight
+ */
+ elv_drain_elevator(q);
+ while (q->rq.elvpriv) {
+ blk_start_queueing(q);
+ spin_unlock_irq(q->queue_lock);
+ msleep(10);
+ spin_lock_irq(q->queue_lock);
+ elv_drain_elevator(q);
+ }
+}
+
+void elv_quisce_end(struct request_queue *q)
+{
+ queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
+}
+
void elv_insert(struct request_queue *q, struct request *rq, int where)
{
struct list_head *pos;
@@ -1101,18 +1126,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
* Turn on BYPASS and drain all requests w/ elevator private data
*/
spin_lock_irq(q->queue_lock);
-
- queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
-
- elv_drain_elevator(q);
-
- while (q->rq.elvpriv) {
- blk_start_queueing(q);
- spin_unlock_irq(q->queue_lock);
- msleep(10);
- spin_lock_irq(q->queue_lock);
- elv_drain_elevator(q);
- }
+ elv_quisce_start(q);
/*
* Remember old elevator.
@@ -1136,7 +1150,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
*/
elevator_exit(old_elevator);
spin_lock_irq(q->queue_lock);
- queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
+ elv_quisce_end(q);
spin_unlock_irq(q->queue_lock);
blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
--
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