block: blk-mq: support draining mq queue

blk_mq_drain_queue() is introduced so that we can drain
mq queue inside blk_cleanup_queue().

Also don't accept new requests any more if queue is marked
as dying.

Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

4 files changed, 40 insertions, 18 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 5da8e900d3b1..accb7fc6ec94 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -38,6 +38,7 @@
 
 #include "blk.h"
 #include "blk-cgroup.h"
+#include "blk-mq.h"
 
 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
 EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
@@ -497,8 +498,13 @@ void blk_cleanup_queue(struct request_queue *q)
          * Drain all requests queued before DYING marking. Set DEAD flag to
          * prevent that q->request_fn() gets invoked after draining finished.
          */
-        spin_lock_irq(lock);
-        __blk_drain_queue(q, true);
+        if (q->mq_ops) {
+                blk_mq_drain_queue(q);
+                spin_lock_irq(lock);
+        } else {
+                spin_lock_irq(lock);
+                __blk_drain_queue(q, true);
+        }
         queue_flag_set(QUEUE_FLAG_DEAD, q);
         spin_unlock_irq(lock);
 
diff --git a/block/blk-exec.c b/block/blk-exec.c
index c3edf9dff566..bbfc072a79c2 100644
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -60,6 +60,10 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
         rq->rq_disk = bd_disk;
         rq->end_io = done;
 
+        /*
+         * don't check dying flag for MQ because the request won't
+         * be resued after dying flag is set
+         */
         if (q->mq_ops) {
                 blk_mq_insert_request(q, rq, true);
                 return;
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 3929f43d0b03..e2f811cba417 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -106,10 +106,13 @@ static int blk_mq_queue_enter(struct request_queue *q)
 
         spin_lock_irq(q->queue_lock);
         ret = wait_event_interruptible_lock_irq(q->mq_freeze_wq,
-                !blk_queue_bypass(q), *q->queue_lock);
+                !blk_queue_bypass(q) || blk_queue_dying(q),
+                *q->queue_lock);
         /* inc usage with lock hold to avoid freeze_queue runs here */
-        if (!ret)
+        if (!ret && !blk_queue_dying(q))
                 __percpu_counter_add(&q->mq_usage_counter, 1, 1000000);
+        else if (blk_queue_dying(q))
+                ret = -ENODEV;
         spin_unlock_irq(q->queue_lock);
 
         return ret;
@@ -120,6 +123,22 @@ static void blk_mq_queue_exit(struct request_queue *q)
         __percpu_counter_add(&q->mq_usage_counter, -1, 1000000);
 }
 
+static void __blk_mq_drain_queue(struct request_queue *q)
+{
+        while (true) {
+                s64 count;
+
+                spin_lock_irq(q->queue_lock);
+                count = percpu_counter_sum(&q->mq_usage_counter);
+                spin_unlock_irq(q->queue_lock);
+
+                if (count == 0)
+                        break;
+                blk_mq_run_queues(q, false);
+                msleep(10);
+        }
+}
+
 /*
  * Guarantee no request is in use, so we can change any data structure of
  * the queue afterward.
@@ -133,21 +152,13 @@ static void blk_mq_freeze_queue(struct request_queue *q)
         queue_flag_set(QUEUE_FLAG_BYPASS, q);
         spin_unlock_irq(q->queue_lock);
 
-        if (!drain)
-                return;
-
-        while (true) {
-                s64 count;
-
-                spin_lock_irq(q->queue_lock);
-                count = percpu_counter_sum(&q->mq_usage_counter);
-                spin_unlock_irq(q->queue_lock);
+        if (drain)
+                __blk_mq_drain_queue(q);
+}
 
-                if (count == 0)
-                        break;
-                blk_mq_run_queues(q, false);
-                msleep(10);
-        }
+void blk_mq_drain_queue(struct request_queue *q)
+{
+        __blk_mq_drain_queue(q);
 }
 
 static void blk_mq_unfreeze_queue(struct request_queue *q)
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 52bf1f96a2c2..caa614f24409 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -27,6 +27,7 @@ void blk_mq_complete_request(struct request *rq, int error);
 void blk_mq_run_request(struct request *rq, bool run_queue, bool async);
 void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);
 void blk_mq_init_flush(struct request_queue *q);
+void blk_mq_drain_queue(struct request_queue *q);
 
 /*
  * CPU hotplug helpers