blk-mq: unify hctx delay_work and run_work
The only difference between ->run_work and ->delay_work, is that
the latter is used to defer running a queue. This is done by
marking the queue stopped, and scheduling ->delay_work to run
sometime in the future. While the queue is stopped, direct runs
or runs through ->run_work will not run the queue.
If we combine the handlers, then we need to handle two things:
1) If a delayed/stopped run is scheduled, then we should not run
the queue before that has been completed.
2) If a queue is delayed/stopped, the handler needs to restart
the queue. Normally a run of a queue with the stopped bit set
would be a no-op.
Case 1 is handled by modifying a currently pending queue run
to the deadline set by the caller of blk_mq_delay_queue().
Subsequent attempts to queue a queue run will find the work
item already pending, and direct runs will see a stopped queue
as before.
Case 2 is handled by adding a new bit, BLK_MQ_S_START_ON_RUN,
that tells the work handler that it should clear a stopped
queue and run the handler.
Reviewed-by: Bart Van Assche <Bart.VanAssche@sandisk.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-core.c b/block/blk-core.c
index 64b6e58..24886b6 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -268,10 +268,8 @@
struct blk_mq_hw_ctx *hctx;
int i;
- queue_for_each_hw_ctx(q, hctx, i) {
+ queue_for_each_hw_ctx(q, hctx, i)
cancel_delayed_work_sync(&hctx->run_work);
- cancel_delayed_work_sync(&hctx->delay_work);
- }
} else {
cancel_delayed_work_sync(&q->delay_work);
}
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5c68fce..a0bdf63 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1221,7 +1221,6 @@
void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)
{
cancel_delayed_work_sync(&hctx->run_work);
- cancel_delayed_work(&hctx->delay_work);
set_bit(BLK_MQ_S_STOPPED, &hctx->state);
}
EXPORT_SYMBOL(blk_mq_stop_hw_queue);
@@ -1279,27 +1278,39 @@
struct blk_mq_hw_ctx *hctx;
hctx = container_of(work, struct blk_mq_hw_ctx, run_work.work);
+
+ /*
+ * If we are stopped, don't run the queue. The exception is if
+ * BLK_MQ_S_START_ON_RUN is set. For that case, we auto-clear
+ * the STOPPED bit and run it.
+ */
+ if (test_bit(BLK_MQ_S_STOPPED, &hctx->state)) {
+ if (!test_bit(BLK_MQ_S_START_ON_RUN, &hctx->state))
+ return;
+
+ clear_bit(BLK_MQ_S_START_ON_RUN, &hctx->state);
+ clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
+ }
+
__blk_mq_run_hw_queue(hctx);
}
-static void blk_mq_delay_work_fn(struct work_struct *work)
-{
- struct blk_mq_hw_ctx *hctx;
-
- hctx = container_of(work, struct blk_mq_hw_ctx, delay_work.work);
-
- if (test_and_clear_bit(BLK_MQ_S_STOPPED, &hctx->state))
- __blk_mq_run_hw_queue(hctx);
-}
void blk_mq_delay_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
{
if (unlikely(!blk_mq_hw_queue_mapped(hctx)))
return;
+ /*
+ * Stop the hw queue, then modify currently delayed work.
+ * This should prevent us from running the queue prematurely.
+ * Mark the queue as auto-clearing STOPPED when it runs.
+ */
blk_mq_stop_hw_queue(hctx);
- kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
- &hctx->delay_work, msecs_to_jiffies(msecs));
+ set_bit(BLK_MQ_S_START_ON_RUN, &hctx->state);
+ kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
+ &hctx->run_work,
+ msecs_to_jiffies(msecs));
}
EXPORT_SYMBOL(blk_mq_delay_queue);
@@ -1885,7 +1896,6 @@
node = hctx->numa_node = set->numa_node;
INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);
- INIT_DELAYED_WORK(&hctx->delay_work, blk_mq_delay_work_fn);
spin_lock_init(&hctx->lock);
INIT_LIST_HEAD(&hctx->dispatch);
hctx->queue = q;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index c7cc903..f3e5e1d 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -51,8 +51,6 @@
atomic_t nr_active;
- struct delayed_work delay_work;
-
struct hlist_node cpuhp_dead;
struct kobject kobj;
@@ -168,6 +166,7 @@
BLK_MQ_S_TAG_ACTIVE = 1,
BLK_MQ_S_SCHED_RESTART = 2,
BLK_MQ_S_TAG_WAITING = 3,
+ BLK_MQ_S_START_ON_RUN = 4,
BLK_MQ_MAX_DEPTH = 10240,