From 6c7e8cee6a9128eeb7f83c3ad1cb243f77f5cb16 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 27 Mar 2009 10:30:47 +0100 Subject: 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 Signed-off-by: Jens Axboe --- 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); -- cgit v1.2.2