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block: only call ->request_fn when the queue is not stopped

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Callers should use either blk_run_queue/__blk_run_queue, or
blk_start_queueing() to invoke request handling instead of calling
->request_fn() directly as that does not take the queue stopped
flag into account.

Also add appropriate comments on the above functions to detail
their usage.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe 2008-10-14 09:51:06 +02:00
parent ee2e992cc2
commit 80a4b58e36
2 changed files with 20 additions and 6 deletions
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19
block/blk-core.c
View file

@ -325,6 +325,9 @@ EXPORT_SYMBOL(blk_unplug);
static void blk_invoke_request_fn(struct request_queue *q)
{
if (unlikely(blk_queue_stopped(q)))
return;
/*
* one level of recursion is ok and is much faster than kicking
* the unplug handling
@ -399,8 +402,13 @@ void blk_sync_queue(struct request_queue *q)
EXPORT_SYMBOL(blk_sync_queue);
/**
* blk_run_queue - run a single device queue
* __blk_run_queue - run a single device queue
* @q: The queue to run
*
* Description:
* See @blk_run_queue. This variant must be called with the queue lock
* held and interrupts disabled.
*
*/
void __blk_run_queue(struct request_queue *q)
{
@ -418,6 +426,12 @@ EXPORT_SYMBOL(__blk_run_queue);
/**
* blk_run_queue - run a single device queue
* @q: The queue to run
*
* Description:
* Invoke request handling on this queue, if it has pending work to do.
* May be used to restart queueing when a request has completed. Also
* See @blk_start_queueing.
*
*/
void blk_run_queue(struct request_queue *q)
{
@ -884,7 +898,8 @@ EXPORT_SYMBOL(blk_get_request);
*
* This is basically a helper to remove the need to know whether a queue
* is plugged or not if someone just wants to initiate dispatch of requests
* for this queue.
* for this queue. Should be used to start queueing on a device outside
* of ->request_fn() context. Also see @blk_run_queue.
*
* The queue lock must be held with interrupts disabled.
*/

7
block/elevator.c
View file

@ -612,7 +612,7 @@ void elv_insert(struct request_queue *q, struct request *rq, int where)
* processing.
*/
blk_remove_plug(q);
q->request_fn(q);
blk_start_queueing(q);
break;
case ELEVATOR_INSERT_SORT:
@ -950,7 +950,7 @@ void elv_completed_request(struct request_queue *q, struct request *rq)
blk_ordered_cur_seq(q) == QUEUE_ORDSEQ_DRAIN &&
blk_ordered_req_seq(first_rq) > QUEUE_ORDSEQ_DRAIN) {
blk_ordered_complete_seq(q, QUEUE_ORDSEQ_DRAIN, 0);
q->request_fn(q);
blk_start_queueing(q);
}
}
}
@ -1109,8 +1109,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
elv_drain_elevator(q);
while (q->rq.elvpriv) {
blk_remove_plug(q);
q->request_fn(q);
blk_start_queueing(q);
spin_unlock_irq(q->queue_lock);
msleep(10);
spin_lock_irq(q->queue_lock);