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authorJens Axboe <jens.axboe@oracle.com>2008-10-14 09:51:06 +0200
committerJens Axboe <jens.axboe@oracle.com>2008-10-17 08:46:57 +0200
commit80a4b58e36b63d7b0b592beb1bd6410aadeeb63c (patch)
treea37df7feb2db67254cc8927730828e87706b2205 /block
parentee2e992cc28553f6c4dd1ab5483c8733c393626b (diff)
downloadconfigs-80a4b58e36b63d7b0b592beb1bd6410aadeeb63c.tar.gz
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>
Diffstat (limited to 'block')
-rw-r--r--block/blk-core.c19
-rw-r--r--block/elevator.c7
2 files changed, 20 insertions, 6 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index 2d053b58441..91532f2d2fa 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -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.
*/
diff --git a/block/elevator.c b/block/elevator.c
index 9482ffa1aae..59173a69ebd 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -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);