block: only call ->request_fn when the queue is not stopped
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>
diff --git a/block/blk-core.c b/block/blk-core.c
index 2d053b5..91532f2 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -325,6 +325,9 @@
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 @@
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 @@
/**
* 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 @@
*
* 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.
*/
diff --git a/block/elevator.c b/block/elevator.c
index 9482ffa..59173a6 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -612,7 +612,7 @@
* processing.
*/
blk_remove_plug(q);
- q->request_fn(q);
+ blk_start_queueing(q);
break;
case ELEVATOR_INSERT_SORT:
@@ -950,7 +950,7 @@
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 @@
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);