diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index bcba2742cfba3785d994abd1ead7dbe9b8d55378..c804e44b9455bf908c0900404d3e362f3af6b4f0 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -1102,6 +1102,7 @@ struct drbd_conf {
 	struct fifo_buffer rs_plan_s; /* correction values of resync planer */
 	int rs_in_flight; /* resync sectors in flight (to proxy, in proxy and from proxy) */
 	int rs_planed;    /* resync sectors already planed */
+	atomic_t ap_in_flight; /* App sectors in flight (waiting for ack) */
 };
 
 static inline struct drbd_conf *minor_to_mdev(unsigned int minor)
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 9d9c2ed31e9afcb6af2b1136dd84c0e626936a8b..e81d009dd0612d37c06b507265e33f8cc0d07db0 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2799,6 +2799,7 @@ void drbd_init_set_defaults(struct drbd_conf *mdev)
 	atomic_set(&mdev->pp_in_use_by_net, 0);
 	atomic_set(&mdev->rs_sect_in, 0);
 	atomic_set(&mdev->rs_sect_ev, 0);
+	atomic_set(&mdev->ap_in_flight, 0);
 
 	mutex_init(&mdev->md_io_mutex);
 	mutex_init(&mdev->data.mutex);
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 08f53ce9b88f07687bd5cf3c4557f7eedc19ae3e..5c60d77d447ceb0266db94feba948feb6f84c118 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -558,6 +558,9 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
 	case handed_over_to_network:
 		/* assert something? */
+		if (bio_data_dir(req->master_bio) == WRITE)
+			atomic_add(req->size>>9, &mdev->ap_in_flight);
+
 		if (bio_data_dir(req->master_bio) == WRITE &&
 		    mdev->net_conf->wire_protocol == DRBD_PROT_A) {
 			/* this is what is dangerous about protocol A:
@@ -591,6 +594,9 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 			dec_ap_pending(mdev);
 		req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
 		req->rq_state |= RQ_NET_DONE;
+		if (req->rq_state & RQ_NET_SENT && req->rq_state & RQ_WRITE)
+			atomic_sub(req->size>>9, &mdev->ap_in_flight);
+
 		/* if it is still queued, we may not complete it here.
 		 * it will be canceled soon. */
 		if (!(req->rq_state & RQ_NET_QUEUED))
@@ -628,14 +634,17 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		req->rq_state |= RQ_NET_OK;
 		D_ASSERT(req->rq_state & RQ_NET_PENDING);
 		dec_ap_pending(mdev);
+		atomic_sub(req->size>>9, &mdev->ap_in_flight);
 		req->rq_state &= ~RQ_NET_PENDING;
 		_req_may_be_done_not_susp(req, m);
 		break;
 
 	case neg_acked:
 		/* assert something? */
-		if (req->rq_state & RQ_NET_PENDING)
+		if (req->rq_state & RQ_NET_PENDING) {
 			dec_ap_pending(mdev);
+			atomic_sub(req->size>>9, &mdev->ap_in_flight);
+		}
 		req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
 
 		req->rq_state |= RQ_NET_DONE;
@@ -692,6 +701,8 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 		}
 		D_ASSERT(req->rq_state & RQ_NET_SENT);
 		req->rq_state |= RQ_NET_DONE;
+		if (mdev->net_conf->wire_protocol == DRBD_PROT_A)
+			atomic_sub(req->size>>9, &mdev->ap_in_flight);
 		_req_may_be_done(req, m); /* Allowed while state.susp */
 		break;
 
diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
index ab2bd09d54b4bfc9fbf7bf74c2e46dbbeb389db5..69d350fe7c1e6ef1e42d4426ddc1c298d16428e5 100644
--- a/drivers/block/drbd/drbd_req.h
+++ b/drivers/block/drbd/drbd_req.h
@@ -338,19 +338,21 @@ static inline int _req_mod(struct drbd_request *req, enum drbd_req_event what)
 	return rv;
 }
 
-/* completion of master bio is outside of spinlock.
- * If you need it irqsave, do it your self!
- * Which means: don't use from bio endio callback. */
+/* completion of master bio is outside of our spinlock.
+ * We still may or may not be inside some irqs disabled section
+ * of the lower level driver completion callback, so we need to
+ * spin_lock_irqsave here. */
 static inline int req_mod(struct drbd_request *req,
 		enum drbd_req_event what)
 {
+	unsigned long flags;
 	struct drbd_conf *mdev = req->mdev;
 	struct bio_and_error m;
 	int rv;
 
-	spin_lock_irq(&mdev->req_lock);
+	spin_lock_irqsave(&mdev->req_lock, flags);
 	rv = __req_mod(req, what, &m);
-	spin_unlock_irq(&mdev->req_lock);
+	spin_unlock_irqrestore(&mdev->req_lock, flags);
 
 	if (m.bio)
 		complete_master_bio(mdev, &m);