1 files changed, 23 insertions, 120 deletions

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index b7e3c8653414..30bb8f905733 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -538,8 +538,6 @@ struct bfq_data {
 
 	/* bfq_queue in service */
 	struct bfq_queue *in_service_queue;
-	/* bfq_io_cq (bic) associated with the @in_service_queue */
-	struct bfq_io_cq *in_service_bic;
 
 	/* on-disk position of the last served request */
 	sector_t last_position;
@@ -704,15 +702,6 @@ struct bfq_data {
 	struct bfq_io_cq *bio_bic;
 	/* bfqq associated with the task issuing current bio for merging */
 	struct bfq_queue *bio_bfqq;
-
-	/*
-	 * io context to put right after bfqd->lock is released. This
-	 * filed is used to perform put_io_context, when needed, to
-	 * after the scheduler lock has been released, and thus
-	 * prevent an ioc->lock from being possibly taken while the
-	 * scheduler lock is being held.
-	 */
-	struct io_context *ioc_to_put;
 };
 
 enum bfqq_state_flags {
@@ -1148,34 +1137,6 @@ static void bfq_schedule_dispatch(struct bfq_data *bfqd)
 	}
 }
 
-/*
- * Next two functions release bfqd->lock and put the io context
- * pointed by bfqd->ioc_to_put. This delayed put is used to not risk
- * to take an ioc->lock while the scheduler lock is being held.
- */
-static void bfq_unlock_put_ioc(struct bfq_data *bfqd)
-{
-	struct io_context *ioc_to_put = bfqd->ioc_to_put;
-
-	bfqd->ioc_to_put = NULL;
-	spin_unlock_irq(&bfqd->lock);
-
-	if (ioc_to_put)
-		put_io_context(ioc_to_put);
-}
-
-static void bfq_unlock_put_ioc_restore(struct bfq_data *bfqd,
-				       unsigned long flags)
-{
-	struct io_context *ioc_to_put = bfqd->ioc_to_put;
-
-	bfqd->ioc_to_put = NULL;
-	spin_unlock_irqrestore(&bfqd->lock, flags);
-
-	if (ioc_to_put)
-		put_io_context(ioc_to_put);
-}
-
 /**
  * bfq_gt - compare two timestamps.
  * @a: first ts.
@@ -2684,18 +2645,6 @@ static void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd)
 	struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity;
 	struct bfq_entity *entity = in_serv_entity;
 
-	if (bfqd->in_service_bic) {
-		/*
-		 * Schedule the release of a reference to
-		 * bfqd->in_service_bic->icq.ioc to right after the
-		 * scheduler lock is released. This ioc is not
-		 * released immediately, to not risk to possibly take
-		 * an ioc->lock while holding the scheduler lock.
-		 */
-		bfqd->ioc_to_put = bfqd->in_service_bic->icq.ioc;
-		bfqd->in_service_bic = NULL;
-	}
-
 	bfq_clear_bfqq_wait_request(in_serv_bfqq);
 	hrtimer_try_to_cancel(&bfqd->idle_slice_timer);
 	bfqd->in_service_queue = NULL;
@@ -3495,7 +3444,7 @@ static void bfq_pd_offline(struct blkg_policy_data *pd)
 	__bfq_deactivate_entity(entity, false);
 	bfq_put_async_queues(bfqd, bfqg);
 
-	bfq_unlock_put_ioc_restore(bfqd, flags);
+	spin_unlock_irqrestore(&bfqd->lock, flags);
 	/*
 	 * @blkg is going offline and will be ignored by
 	 * blkg_[rw]stat_recursive_sum().  Transfer stats to the parent so
@@ -5472,20 +5421,18 @@ bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
 	 * first time that the requests of some process are redirected to
 	 * it.
 	 *
-	 * We redirect bfqq to new_bfqq and not the opposite, because we
-	 * are in the context of the process owning bfqq, hence we have
-	 * the io_cq of this process. So we can immediately configure this
-	 * io_cq to redirect the requests of the process to new_bfqq.
+	 * We redirect bfqq to new_bfqq and not the opposite, because
+	 * we are in the context of the process owning bfqq, thus we
+	 * have the io_cq of this process. So we can immediately
+	 * configure this io_cq to redirect the requests of the
+	 * process to new_bfqq. In contrast, the io_cq of new_bfqq is
+	 * not available any more (new_bfqq->bic == NULL).
 	 *
-	 * NOTE, even if new_bfqq coincides with the in-service queue, the
-	 * io_cq of new_bfqq is not available, because, if the in-service
-	 * queue is shared, bfqd->in_service_bic may not point to the
-	 * io_cq of the in-service queue.
-	 * Redirecting the requests of the process owning bfqq to the
-	 * currently in-service queue is in any case the best option, as
-	 * we feed the in-service queue with new requests close to the
-	 * last request served and, by doing so, hopefully increase the
-	 * throughput.
+	 * Anyway, even in case new_bfqq coincides with the in-service
+	 * queue, redirecting requests the in-service queue is the
+	 * best option, as we feed the in-service queue with new
+	 * requests close to the last request served and, by doing so,
+	 * are likely to increase the throughput.
 	 */
 	bfqq->new_bfqq = new_bfqq;
 	new_bfqq->ref += process_refs;
@@ -5577,8 +5524,8 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
 
 	in_service_bfqq = bfqd->in_service_queue;
 
-	if (!in_service_bfqq || in_service_bfqq == bfqq ||
-	    !bfqd->in_service_bic || wr_from_too_long(in_service_bfqq) ||
+	if (!in_service_bfqq || in_service_bfqq == bfqq
+	    || wr_from_too_long(in_service_bfqq) ||
 	    unlikely(in_service_bfqq == &bfqd->oom_bfqq))
 		goto check_scheduled;
 
@@ -5629,16 +5576,6 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
 	bic->saved_wr_cur_max_time = bfqq->wr_cur_max_time;
 }
 
-static void bfq_get_bic_reference(struct bfq_queue *bfqq)
-{
-	/*
-	 * If bfqq->bic has a non-NULL value, the bic to which it belongs
-	 * is about to begin using a shared bfq_queue.
-	 */
-	if (bfqq->bic)
-		atomic_long_inc(&bfqq->bic->icq.ioc->refcount);
-}
-
 static void
 bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic,
 		struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
@@ -5683,12 +5620,6 @@ bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic,
 		     bfqd->wr_busy_queues);
 
 	/*
-	 * Grab a reference to the bic, to prevent it from being destroyed
-	 * before being possibly touched by a bfq_split_bfqq().
-	 */
-	bfq_get_bic_reference(bfqq);
-	bfq_get_bic_reference(new_bfqq);
-	/*
 	 * Merge queues (that is, let bic redirect its requests to new_bfqq)
 	 */
 	bic_set_bfqq(bic, new_bfqq, 1);
@@ -5853,14 +5784,8 @@ static struct bfq_queue *bfq_set_in_service_queue(struct bfq_data *bfqd)
 static void bfq_arm_slice_timer(struct bfq_data *bfqd)
 {
 	struct bfq_queue *bfqq = bfqd->in_service_queue;
-	struct bfq_io_cq *bic;
 	u32 sl;
 
-	/* Processes have exited, don't wait. */
-	bic = bfqd->in_service_bic;
-	if (!bic || atomic_read(&bic->icq.ioc->active_ref) == 0)
-		return;
-
 	bfq_mark_bfqq_wait_request(bfqq);
 
 	/*
@@ -7147,11 +7072,6 @@ static struct request *bfq_dispatch_rq_from_bfqq(struct bfq_data *bfqd,
 	 */
 	bfq_update_wr_data(bfqd, bfqq);
 
-	if (!bfqd->in_service_bic) {
-		atomic_long_inc(&RQ_BIC(rq)->icq.ioc->refcount);
-		bfqd->in_service_bic = RQ_BIC(rq);
-	}
-
 	/*
 	 * Expire bfqq, pretending that its budget expired, if bfqq
 	 * belongs to CLASS_IDLE and other queues are waiting for
@@ -7272,7 +7192,7 @@ static struct request *bfq_dispatch_request(struct blk_mq_hw_ctx *hctx)
 	spin_lock_irq(&bfqd->lock);
 
 	rq = __bfq_dispatch_request(hctx);
-	bfq_unlock_put_ioc(bfqd);
+	spin_unlock_irq(&bfqd->lock);
 
 	return rq;
 }
@@ -7360,20 +7280,9 @@ static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync)
 		unsigned long flags;
 
 		spin_lock_irqsave(&bfqd->lock, flags);
-		/*
-		 * If the bic is using a shared queue, put the
-		 * reference taken on the io_context when the bic
-		 * started using a shared bfq_queue. This put cannot
-		 * make ioc->ref_count reach 0, then no ioc->lock
-		 * risks to be taken (leading to possible deadlock
-		 * scenarios).
-		 */
-		if (is_sync && bfq_bfqq_coop(bfqq))
-			put_io_context(bic->icq.ioc);
-
 		bfq_exit_bfqq(bfqd, bfqq);
 		bic_set_bfqq(bic, NULL, is_sync);
-		bfq_unlock_put_ioc_restore(bfqd, flags);
+		spin_unlock_irqrestore(&bfqd->lock, flags);
 	}
 }
 
@@ -7808,7 +7717,7 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
 		}
 	}
 
-	bfq_unlock_put_ioc(bfqd);
+	spin_unlock_irq(&bfqd->lock);
 }
 
 static void bfq_insert_requests(struct blk_mq_hw_ctx *hctx,
@@ -7962,7 +7871,7 @@ static void bfq_put_rq_private(struct request_queue *q, struct request *rq)
 		bfq_completed_request(bfqq, bfqd);
 		bfq_put_rq_priv_body(bfqq);
 
-		bfq_unlock_put_ioc_restore(bfqd, flags);
+		spin_unlock_irqrestore(&bfqd->lock, flags);
 	} else {
 		/*
 		 * Request rq may be still/already in the scheduler,
@@ -8055,6 +7964,7 @@ static int bfq_get_rq_private(struct request_queue *q, struct request *rq,
 	const int is_sync = rq_is_sync(rq);
 	struct bfq_queue *bfqq;
 	bool new_queue = false;
+	bool split = false;
 
 	spin_lock_irq(&bfqd->lock);
 
@@ -8078,14 +7988,7 @@ static int bfq_get_rq_private(struct request_queue *q, struct request *rq,
 				bic->saved_in_large_burst = true;
 
 			bfqq = bfq_split_bfqq(bic, bfqq);
-			/*
-			 * A reference to bic->icq.ioc needs to be
-			 * released after a queue split. Do not do it
-			 * immediately, to not risk to possibly take
-			 * an ioc->lock while holding the scheduler
-			 * lock.
-			 */
-			bfqd->ioc_to_put = bic->icq.ioc;
+			split = true;
 
 			if (!bfqq)
 				bfqq = bfq_get_bfqq_handle_split(bfqd, bic, bio,
@@ -8110,7 +8013,7 @@ static int bfq_get_rq_private(struct request_queue *q, struct request *rq,
 	 */
 	if (likely(bfqq != &bfqd->oom_bfqq) && bfqq_process_refs(bfqq) == 1) {
 		bfqq->bic = bic;
-		if (bfqd->ioc_to_put) { /* if true, there has been a split */
+		if (split) {
 			/*
 			 * The queue has just been split from a shared
 			 * queue: restore the idle window and the
@@ -8123,7 +8026,7 @@ static int bfq_get_rq_private(struct request_queue *q, struct request *rq,
 	if (unlikely(bfq_bfqq_just_created(bfqq)))
 		bfq_handle_burst(bfqd, bfqq);
 
-	bfq_unlock_put_ioc(bfqd);
+	spin_unlock_irq(&bfqd->lock);
 
 	return 0;
 
@@ -8168,7 +8071,7 @@ static void bfq_idle_slice_timer_body(struct bfq_queue *bfqq)
 	bfq_bfqq_expire(bfqd, bfqq, true, reason);
 
 schedule_dispatch:
-	bfq_unlock_put_ioc_restore(bfqd, flags);
+	spin_unlock_irqrestore(&bfqd->lock, flags);
 	bfq_schedule_dispatch(bfqd);
 }