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blk-mq: unify hctx delay_work and run_work

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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>
This commit is contained in:
Jens Axboe 2017-04-10 09:54:56 -06:00
parent 818cd1cbaa
commit 21c6e939a9
3 changed files with 25 additions and 18 deletions
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3
include/linux/blk-mq.h
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@ -51,8 +51,6 @@ struct blk_mq_hw_ctx {
atomic_t nr_active;
struct delayed_work delay_work;
struct hlist_node cpuhp_dead;
struct kobject kobj;
@ -168,6 +166,7 @@ enum {
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,