Merge tag 'for-linus-20181207' of git://git.kernel.dk/linux-block

Pull block fixes from Jens Axboe:
 "Let's try this again...

  We're finally happy with the DM livelock issue, and it's also passed
  overnight testing and the corruption regression test. The end result
  is much nicer now too, which is great.

  Outside of that fix, there's a pull request for NVMe with two small
  fixes, and a regression fix for BFQ from this merge window. The BFQ
  fix looks bigger than it is, it's 90% comment updates"

* tag 'for-linus-20181207' of git://git.kernel.dk/linux-block:
  blk-mq: punt failed direct issue to dispatch list
  nvmet-rdma: fix response use after free
  nvme: validate controller state before rescheduling keep alive
  block, bfq: fix decrement of num_active_groups

6 files changed, 123 insertions, 55 deletions

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 3a27d31fcda6..97337214bec4 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -638,7 +638,7 @@ static bool bfq_varied_queue_weights_or_active_groups(struct bfq_data *bfqd)
 		 bfqd->queue_weights_tree.rb_node->rb_right)
 #ifdef CONFIG_BFQ_GROUP_IOSCHED
 	       ) ||
-		(bfqd->num_active_groups > 0
+		(bfqd->num_groups_with_pending_reqs > 0
 #endif
 	       );
 }
@@ -802,7 +802,21 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd,
 			 */
 			break;
 		}
-		bfqd->num_active_groups--;
+
+		/*
+		 * The decrement of num_groups_with_pending_reqs is
+		 * not performed immediately upon the deactivation of
+		 * entity, but it is delayed to when it also happens
+		 * that the first leaf descendant bfqq of entity gets
+		 * all its pending requests completed. The following
+		 * instructions perform this delayed decrement, if
+		 * needed. See the comments on
+		 * num_groups_with_pending_reqs for details.
+		 */
+		if (entity->in_groups_with_pending_reqs) {
+			entity->in_groups_with_pending_reqs = false;
+			bfqd->num_groups_with_pending_reqs--;
+		}
 	}
 }
 
@@ -3529,27 +3543,44 @@ static bool bfq_better_to_idle(struct bfq_queue *bfqq)
 	 * fact, if there are active groups, then, for condition (i)
 	 * to become false, it is enough that an active group contains
 	 * more active processes or sub-groups than some other active
-	 * group. We address this issue with the following bi-modal
-	 * behavior, implemented in the function
+	 * group. More precisely, for condition (i) to hold because of
+	 * such a group, it is not even necessary that the group is
+	 * (still) active: it is sufficient that, even if the group
+	 * has become inactive, some of its descendant processes still
+	 * have some request already dispatched but still waiting for
+	 * completion. In fact, requests have still to be guaranteed
+	 * their share of the throughput even after being
+	 * dispatched. In this respect, it is easy to show that, if a
+	 * group frequently becomes inactive while still having
+	 * in-flight requests, and if, when this happens, the group is
+	 * not considered in the calculation of whether the scenario
+	 * is asymmetric, then the group may fail to be guaranteed its
+	 * fair share of the throughput (basically because idling may
+	 * not be performed for the descendant processes of the group,
+	 * but it had to be).  We address this issue with the
+	 * following bi-modal behavior, implemented in the function
 	 * bfq_symmetric_scenario().
 	 *
-	 * If there are active groups, then the scenario is tagged as
+	 * If there are groups with requests waiting for completion
+	 * (as commented above, some of these groups may even be
+	 * already inactive), then the scenario is tagged as
 	 * asymmetric, conservatively, without checking any of the
 	 * conditions (i) and (ii). So the device is idled for bfqq.
 	 * This behavior matches also the fact that groups are created
-	 * exactly if controlling I/O (to preserve bandwidth and
-	 * latency guarantees) is a primary concern.
+	 * exactly if controlling I/O is a primary concern (to
+	 * preserve bandwidth and latency guarantees).
 	 *
-	 * On the opposite end, if there are no active groups, then
-	 * only condition (i) is actually controlled, i.e., provided
-	 * that condition (i) holds, idling is not performed,
-	 * regardless of whether condition (ii) holds. In other words,
-	 * only if condition (i) does not hold, then idling is
-	 * allowed, and the device tends to be prevented from queueing
-	 * many requests, possibly of several processes. Since there
-	 * are no active groups, then, to control condition (i) it is
-	 * enough to check whether all active queues have the same
-	 * weight.
+	 * On the opposite end, if there are no groups with requests
+	 * waiting for completion, then only condition (i) is actually
+	 * controlled, i.e., provided that condition (i) holds, idling
+	 * is not performed, regardless of whether condition (ii)
+	 * holds. In other words, only if condition (i) does not hold,
+	 * then idling is allowed, and the device tends to be
+	 * prevented from queueing many requests, possibly of several
+	 * processes. Since there are no groups with requests waiting
+	 * for completion, then, to control condition (i) it is enough
+	 * to check just whether all the queues with requests waiting
+	 * for completion also have the same weight.
 	 *
 	 * Not checking condition (ii) evidently exposes bfqq to the
 	 * risk of getting less throughput than its fair share.
@@ -3607,10 +3638,11 @@ static bool bfq_better_to_idle(struct bfq_queue *bfqq)
 	 * bfqq is weight-raised is checked explicitly here. More
 	 * precisely, the compound condition below takes into account
 	 * also the fact that, even if bfqq is being weight-raised,
-	 * the scenario is still symmetric if all active queues happen
-	 * to be weight-raised. Actually, we should be even more
-	 * precise here, and differentiate between interactive weight
-	 * raising and soft real-time weight raising.
+	 * the scenario is still symmetric if all queues with requests
+	 * waiting for completion happen to be
+	 * weight-raised. Actually, we should be even more precise
+	 * here, and differentiate between interactive weight raising
+	 * and soft real-time weight raising.
 	 *
 	 * As a side note, it is worth considering that the above
 	 * device-idling countermeasures may however fail in the
@@ -5417,7 +5449,7 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
 	bfqd->idle_slice_timer.function = bfq_idle_slice_timer;
 
 	bfqd->queue_weights_tree = RB_ROOT;
-	bfqd->num_active_groups = 0;
+	bfqd->num_groups_with_pending_reqs = 0;
 
 	INIT_LIST_HEAD(&bfqd->active_list);
 	INIT_LIST_HEAD(&bfqd->idle_list);
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 77651d817ecd..0b02bf302de0 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -196,6 +196,9 @@ struct bfq_entity {
 
 	/* flag, set to request a weight, ioprio or ioprio_class change  */
 	int prio_changed;
+
+	/* flag, set if the entity is counted in groups_with_pending_reqs */
+	bool in_groups_with_pending_reqs;
 };
 
 struct bfq_group;
@@ -448,10 +451,54 @@ struct bfq_data {
 	 * bfq_weights_tree_[add|remove] for further details).
 	 */
 	struct rb_root queue_weights_tree;
+
 	/*
-	 * number of groups with requests still waiting for completion
+	 * Number of groups with at least one descendant process that
+	 * has at least one request waiting for completion. Note that
+	 * this accounts for also requests already dispatched, but not
+	 * yet completed. Therefore this number of groups may differ
+	 * (be larger) than the number of active groups, as a group is
+	 * considered active only if its corresponding entity has
+	 * descendant queues with at least one request queued. This
+	 * number is used to decide whether a scenario is symmetric.
+	 * For a detailed explanation see comments on the computation
+	 * of the variable asymmetric_scenario in the function
+	 * bfq_better_to_idle().
+	 *
+	 * However, it is hard to compute this number exactly, for
+	 * groups with multiple descendant processes. Consider a group
+	 * that is inactive, i.e., that has no descendant process with
+	 * pending I/O inside BFQ queues. Then suppose that
+	 * num_groups_with_pending_reqs is still accounting for this
+	 * group, because the group has descendant processes with some
+	 * I/O request still in flight. num_groups_with_pending_reqs
+	 * should be decremented when the in-flight request of the
+	 * last descendant process is finally completed (assuming that
+	 * nothing else has changed for the group in the meantime, in
+	 * terms of composition of the group and active/inactive state of child
+	 * groups and processes). To accomplish this, an additional
+	 * pending-request counter must be added to entities, and must
+	 * be updated correctly. To avoid this additional field and operations,
+	 * we resort to the following tradeoff between simplicity and
+	 * accuracy: for an inactive group that is still counted in
+	 * num_groups_with_pending_reqs, we decrement
+	 * num_groups_with_pending_reqs when the first descendant
+	 * process of the group remains with no request waiting for
+	 * completion.
+	 *
+	 * Even this simpler decrement strategy requires a little
+	 * carefulness: to avoid multiple decrements, we flag a group,
+	 * more precisely an entity representing a group, as still
+	 * counted in num_groups_with_pending_reqs when it becomes
+	 * inactive. Then, when the first descendant queue of the
+	 * entity remains with no request waiting for completion,
+	 * num_groups_with_pending_reqs is decremented, and this flag
+	 * is reset. After this flag is reset for the entity,
+	 * num_groups_with_pending_reqs won't be decremented any
+	 * longer in case a new descendant queue of the entity remains
+	 * with no request waiting for completion.
 	 */
-	unsigned int num_active_groups;
+	unsigned int num_groups_with_pending_reqs;
 
 	/*
 	 * Number of bfq_queues containing requests (including the
diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
index 4b0d5fb69160..63e0f12be7c9 100644
--- a/block/bfq-wf2q.c
+++ b/block/bfq-wf2q.c
@@ -1012,7 +1012,10 @@ static void __bfq_activate_entity(struct bfq_entity *entity,
 			container_of(entity, struct bfq_group, entity);
 		struct bfq_data *bfqd = bfqg->bfqd;
 
-		bfqd->num_active_groups++;
+		if (!entity->in_groups_with_pending_reqs) {
+			entity->in_groups_with_pending_reqs = true;
+			bfqd->num_groups_with_pending_reqs++;
+		}
 	}
 #endif
 
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 3262d83b9e07..6a7566244de3 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1715,15 +1715,6 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
 		break;
 	case BLK_STS_RESOURCE:
 	case BLK_STS_DEV_RESOURCE:
-		/*
-		 * If direct dispatch fails, we cannot allow any merging on
-		 * this IO. Drivers (like SCSI) may have set up permanent state
-		 * for this request, like SG tables and mappings, and if we
-		 * merge to it later on then we'll still only do IO to the
-		 * original part.
-		 */
-		rq->cmd_flags |= REQ_NOMERGE;
-
 		blk_mq_update_dispatch_busy(hctx, true);
 		__blk_mq_requeue_request(rq);
 		break;
@@ -1736,18 +1727,6 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
 	return ret;
 }
 
-/*
- * Don't allow direct dispatch of anything but regular reads/writes,
- * as some of the other commands can potentially share request space
- * with data we need for the IO scheduler. If we attempt a direct dispatch
- * on those and fail, we can't safely add it to the scheduler afterwards
- * without potentially overwriting data that the driver has already written.
- */
-static bool blk_rq_can_direct_dispatch(struct request *rq)
-{
-	return req_op(rq) == REQ_OP_READ || req_op(rq) == REQ_OP_WRITE;
-}
-
 static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 						struct request *rq,
 						blk_qc_t *cookie,
@@ -1769,7 +1748,7 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 		goto insert;
 	}
 
-	if (!blk_rq_can_direct_dispatch(rq) || (q->elevator && !bypass_insert))
+	if (q->elevator && !bypass_insert)
 		goto insert;
 
 	if (!blk_mq_get_dispatch_budget(hctx))
@@ -1785,7 +1764,7 @@ insert:
 	if (bypass_insert)
 		return BLK_STS_RESOURCE;
 
-	blk_mq_sched_insert_request(rq, false, run_queue, false);
+	blk_mq_request_bypass_insert(rq, run_queue);
 	return BLK_STS_OK;
 }
 
@@ -1801,7 +1780,7 @@ static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 
 	ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false);
 	if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
-		blk_mq_sched_insert_request(rq, false, true, false);
+		blk_mq_request_bypass_insert(rq, true);
 	else if (ret != BLK_STS_OK)
 		blk_mq_end_request(rq, ret);
 
@@ -1831,15 +1810,13 @@ void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
 		struct request *rq = list_first_entry(list, struct request,
 				queuelist);
 
-		if (!blk_rq_can_direct_dispatch(rq))
-			break;
-
 		list_del_init(&rq->queuelist);
 		ret = blk_mq_request_issue_directly(rq);
 		if (ret != BLK_STS_OK) {
 			if (ret == BLK_STS_RESOURCE ||
 					ret == BLK_STS_DEV_RESOURCE) {
-				list_add(&rq->queuelist, list);
+				blk_mq_request_bypass_insert(rq,
+							list_empty(list));
 				break;
 			}
 			blk_mq_end_request(rq, ret);
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 3cf1b773158e..962012135b62 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -831,6 +831,8 @@ static int nvme_submit_user_cmd(struct request_queue *q,
 static void nvme_keep_alive_end_io(struct request *rq, blk_status_t status)
 {
 	struct nvme_ctrl *ctrl = rq->end_io_data;
+	unsigned long flags;
+	bool startka = false;
 
 	blk_mq_free_request(rq);
 
@@ -841,7 +843,13 @@ static void nvme_keep_alive_end_io(struct request *rq, blk_status_t status)
 		return;
 	}
 
-	schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);
+	spin_lock_irqsave(&ctrl->lock, flags);
+	if (ctrl->state == NVME_CTRL_LIVE ||
+	    ctrl->state == NVME_CTRL_CONNECTING)
+		startka = true;
+	spin_unlock_irqrestore(&ctrl->lock, flags);
+	if (startka)
+		schedule_delayed_work(&ctrl->ka_work, ctrl->kato * HZ);
 }
 
 static int nvme_keep_alive(struct nvme_ctrl *ctrl)
diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
index 3f7971d3706d..583086dd9cb9 100644
--- a/drivers/nvme/target/rdma.c
+++ b/drivers/nvme/target/rdma.c
@@ -529,6 +529,7 @@ static void nvmet_rdma_send_done(struct ib_cq *cq, struct ib_wc *wc)
 {
 	struct nvmet_rdma_rsp *rsp =
 		container_of(wc->wr_cqe, struct nvmet_rdma_rsp, send_cqe);
+	struct nvmet_rdma_queue *queue = cq->cq_context;
 
 	nvmet_rdma_release_rsp(rsp);
 
@@ -536,7 +537,7 @@ static void nvmet_rdma_send_done(struct ib_cq *cq, struct ib_wc *wc)
 		     wc->status != IB_WC_WR_FLUSH_ERR)) {
 		pr_err("SEND for CQE 0x%p failed with status %s (%d).\n",
 			wc->wr_cqe, ib_wc_status_msg(wc->status), wc->status);
-		nvmet_rdma_error_comp(rsp->queue);
+		nvmet_rdma_error_comp(queue);
 	}
 }