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block: reorganize queue draining

Reorganize queue draining related code in preparation of queue exit
changes.

* Factor out actual draining from elv_quiesce_start() to
  blk_drain_queue().

* Make elv_quiesce_start/end() responsible for their own locking.

* Replace open-coded ELVSWITCH clearing in elevator_switch() with
  elv_quiesce_end().

This patch doesn't cause any visible functional difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
master
Tejun Heo 10 years ago
committed by Jens Axboe
parent
commit
e3c78ca524
  1. 28
      block/blk-core.c
  2. 1
      block/blk.h
  3. 37
      block/elevator.c

28
block/blk-core.c

@ -28,6 +28,7 @@
#include <linux/task_io_accounting_ops.h>
#include <linux/fault-inject.h>
#include <linux/list_sort.h>
#include <linux/delay.h>
#define CREATE_TRACE_POINTS
#include <trace/events/block.h>
@ -345,6 +346,33 @@ void blk_put_queue(struct request_queue *q)
}
EXPORT_SYMBOL(blk_put_queue);
/**
* blk_drain_queue - drain requests from request_queue
* @q: queue to drain
*
* Drain ELV_PRIV requests from @q. The caller is responsible for ensuring
* that no new requests which need to be drained are queued.
*/
void blk_drain_queue(struct request_queue *q)
{
while (true) {
int nr_rqs;
spin_lock_irq(q->queue_lock);
elv_drain_elevator(q);
__blk_run_queue(q);
nr_rqs = q->rq.elvpriv;
spin_unlock_irq(q->queue_lock);
if (!nr_rqs)
break;
msleep(10);
}
}
/*
* Note: If a driver supplied the queue lock, it is disconnected
* by this function. The actual state of the lock doesn't matter

1
block/blk.h

@ -15,6 +15,7 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
struct bio *bio);
int blk_rq_append_bio(struct request_queue *q, struct request *rq,
struct bio *bio);
void blk_drain_queue(struct request_queue *q);
void blk_dequeue_request(struct request *rq);
void __blk_queue_free_tags(struct request_queue *q);
bool __blk_end_bidi_request(struct request *rq, int error,

37
block/elevator.c

@ -31,7 +31,6 @@
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/compiler.h>
#include <linux/delay.h>
#include <linux/blktrace_api.h>
#include <linux/hash.h>
#include <linux/uaccess.h>
@ -606,43 +605,35 @@ void elv_requeue_request(struct request_queue *q, struct request *rq)
void elv_drain_elevator(struct request_queue *q)
{
static int printed;
lockdep_assert_held(q->queue_lock);
while (q->elevator->ops->elevator_dispatch_fn(q, 1))
;
if (q->nr_sorted == 0)
return;
if (printed++ < 10) {
if (q->nr_sorted && printed++ < 10) {
printk(KERN_ERR "%s: forced dispatching is broken "
"(nr_sorted=%u), please report this\n",
q->elevator->elevator_type->elevator_name, q->nr_sorted);
}
}
/*
* Call with queue lock held, interrupts disabled
*/
void elv_quiesce_start(struct request_queue *q)
{
if (!q->elevator)
return;
spin_lock_irq(q->queue_lock);
queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
spin_unlock_irq(q->queue_lock);
/*
* make sure we don't have any requests in flight
*/
elv_drain_elevator(q);
while (q->rq.elvpriv) {
__blk_run_queue(q);
spin_unlock_irq(q->queue_lock);
msleep(10);
spin_lock_irq(q->queue_lock);
elv_drain_elevator(q);
}
blk_drain_queue(q);
}
void elv_quiesce_end(struct request_queue *q)
{
spin_lock_irq(q->queue_lock);
queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
spin_unlock_irq(q->queue_lock);
}
void __elv_add_request(struct request_queue *q, struct request *rq, int where)
@ -972,7 +963,6 @@ 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);
elv_quiesce_start(q);
/*
@ -983,8 +973,8 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
/*
* attach and start new elevator
*/
spin_lock_irq(q->queue_lock);
elevator_attach(q, e, data);
spin_unlock_irq(q->queue_lock);
if (old_elevator->registered) {
@ -999,9 +989,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
* finally exit old elevator and turn off BYPASS.
*/
elevator_exit(old_elevator);
spin_lock_irq(q->queue_lock);
elv_quiesce_end(q);
spin_unlock_irq(q->queue_lock);
blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
@ -1015,10 +1003,7 @@ fail_register:
elevator_exit(e);
q->elevator = old_elevator;
elv_register_queue(q);
spin_lock_irq(q->queue_lock);
queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
spin_unlock_irq(q->queue_lock);
elv_quiesce_end(q);
return err;
}

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