block: implement runtime pm strategy

When a request is added:
    If device is suspended or is suspending and the request is not a
    PM request, resume the device.

When the last request finishes:
    Call pm_runtime_mark_last_busy().

When pick a request:
    If device is resuming/suspending, then only PM request is allowed
    to go.

The idea and API is designed by Alan Stern and described here:
http://marc.info/?l=linux-scsi&m=133727953625963&w=2

Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 26 insertions, 0 deletions

diff --git a/block/elevator.c b/block/elevator.c
index a0ffdd943c98..eba5b04c29b1 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -34,6 +34,7 @@
 #include <linux/blktrace_api.h>
 #include <linux/hash.h>
 #include <linux/uaccess.h>
+#include <linux/pm_runtime.h>
 
 #include <trace/events/block.h>
 
@@ -536,6 +537,27 @@ void elv_bio_merged(struct request_queue *q, struct request *rq,
                 e->type->ops.elevator_bio_merged_fn(q, rq, bio);
 }
 
+#ifdef CONFIG_PM_RUNTIME
+static void blk_pm_requeue_request(struct request *rq)
+{
+        if (rq->q->dev && !(rq->cmd_flags & REQ_PM))
+                rq->q->nr_pending--;
+}
+
+static void blk_pm_add_request(struct request_queue *q, struct request *rq)
+{
+        if (q->dev && !(rq->cmd_flags & REQ_PM) && q->nr_pending++ == 0 &&
+            (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
+                pm_request_resume(q->dev);
+}
+#else
+static inline void blk_pm_requeue_request(struct request *rq) {}
+static inline void blk_pm_add_request(struct request_queue *q,
+                                      struct request *rq)
+{
+}
+#endif
+
 void elv_requeue_request(struct request_queue *q, struct request *rq)
 {
         /*
@@ -550,6 +572,8 @@ void elv_requeue_request(struct request_queue *q, struct request *rq)
 
         rq->cmd_flags &= ~REQ_STARTED;
 
+        blk_pm_requeue_request(rq);
+
         __elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
 }
 
@@ -572,6 +596,8 @@ void __elv_add_request(struct request_queue *q, struct request *rq, int where)
 {
         trace_block_rq_insert(q, rq);
 
+        blk_pm_add_request(q, rq);
+
         rq->q = q;
 
         if (rq->cmd_flags & REQ_SOFTBARRIER) {