Merge branch 'next' into for-linus

Prepare first round of input updates for 3.20.

1 files changed, 292 insertions, 225 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index df8e1e09dd17..da1ab5641227 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -20,6 +20,7 @@
 #include <linux/cache.h>
 #include <linux/sched/sysctl.h>
 #include <linux/delay.h>
+#include <linux/crash_dump.h>
 
 #include <trace/events/block.h>
 
@@ -106,11 +107,7 @@ static void blk_mq_usage_counter_release(struct percpu_ref *ref)
 	wake_up_all(&q->mq_freeze_wq);
 }
 
-/*
- * Guarantee no request is in use, so we can change any data structure of
- * the queue afterward.
- */
-void blk_mq_freeze_queue(struct request_queue *q)
+static void blk_mq_freeze_queue_start(struct request_queue *q)
 {
 	bool freeze;
 
@@ -119,21 +116,26 @@ void blk_mq_freeze_queue(struct request_queue *q)
 	spin_unlock_irq(q->queue_lock);
 
 	if (freeze) {
-		/*
-		 * XXX: Temporary kludge to work around SCSI blk-mq stall.
-		 * SCSI synchronously creates and destroys many queues
-		 * back-to-back during probe leading to lengthy stalls.
-		 * This will be fixed by keeping ->mq_usage_counter in
-		 * atomic mode until genhd registration, but, for now,
-		 * let's work around using expedited synchronization.
-		 */
-		__percpu_ref_kill_expedited(&q->mq_usage_counter);
-
+		percpu_ref_kill(&q->mq_usage_counter);
 		blk_mq_run_queues(q, false);
 	}
+}
+
+static void blk_mq_freeze_queue_wait(struct request_queue *q)
+{
 	wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->mq_usage_counter));
 }
 
+/*
+ * Guarantee no request is in use, so we can change any data structure of
+ * the queue afterward.
+ */
+void blk_mq_freeze_queue(struct request_queue *q)
+{
+	blk_mq_freeze_queue_start(q);
+	blk_mq_freeze_queue_wait(q);
+}
+
 static void blk_mq_unfreeze_queue(struct request_queue *q)
 {
 	bool wake;
@@ -232,9 +234,11 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp,
 	struct blk_mq_hw_ctx *hctx;
 	struct request *rq;
 	struct blk_mq_alloc_data alloc_data;
+	int ret;
 
-	if (blk_mq_queue_enter(q))
-		return NULL;
+	ret = blk_mq_queue_enter(q);
+	if (ret)
+		return ERR_PTR(ret);
 
 	ctx = blk_mq_get_ctx(q);
 	hctx = q->mq_ops->map_queue(q, ctx->cpu);
@@ -254,6 +258,8 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp,
 		ctx = alloc_data.ctx;
 	}
 	blk_mq_put_ctx(ctx);
+	if (!rq)
+		return ERR_PTR(-EWOULDBLOCK);
 	return rq;
 }
 EXPORT_SYMBOL(blk_mq_alloc_request);
@@ -273,39 +279,27 @@ static void __blk_mq_free_request(struct blk_mq_hw_ctx *hctx,
 	blk_mq_queue_exit(q);
 }
 
-void blk_mq_free_request(struct request *rq)
+void blk_mq_free_hctx_request(struct blk_mq_hw_ctx *hctx, struct request *rq)
 {
 	struct blk_mq_ctx *ctx = rq->mq_ctx;
-	struct blk_mq_hw_ctx *hctx;
-	struct request_queue *q = rq->q;
 
 	ctx->rq_completed[rq_is_sync(rq)]++;
-
-	hctx = q->mq_ops->map_queue(q, ctx->cpu);
 	__blk_mq_free_request(hctx, ctx, rq);
+
 }
+EXPORT_SYMBOL_GPL(blk_mq_free_hctx_request);
 
-/*
- * Clone all relevant state from a request that has been put on hold in
- * the flush state machine into the preallocated flush request that hangs
- * off the request queue.
- *
- * For a driver the flush request should be invisible, that's why we are
- * impersonating the original request here.
- */
-void blk_mq_clone_flush_request(struct request *flush_rq,
-		struct request *orig_rq)
+void blk_mq_free_request(struct request *rq)
 {
-	struct blk_mq_hw_ctx *hctx =
-		orig_rq->q->mq_ops->map_queue(orig_rq->q, orig_rq->mq_ctx->cpu);
+	struct blk_mq_hw_ctx *hctx;
+	struct request_queue *q = rq->q;
 
-	flush_rq->mq_ctx = orig_rq->mq_ctx;
-	flush_rq->tag = orig_rq->tag;
-	memcpy(blk_mq_rq_to_pdu(flush_rq), blk_mq_rq_to_pdu(orig_rq),
-		hctx->cmd_size);
+	hctx = q->mq_ops->map_queue(q, rq->mq_ctx->cpu);
+	blk_mq_free_hctx_request(hctx, rq);
 }
+EXPORT_SYMBOL_GPL(blk_mq_free_request);
 
-inline void __blk_mq_end_io(struct request *rq, int error)
+inline void __blk_mq_end_request(struct request *rq, int error)
 {
 	blk_account_io_done(rq);
 
@@ -317,15 +311,15 @@ inline void __blk_mq_end_io(struct request *rq, int error)
 		blk_mq_free_request(rq);
 	}
 }
-EXPORT_SYMBOL(__blk_mq_end_io);
+EXPORT_SYMBOL(__blk_mq_end_request);
 
-void blk_mq_end_io(struct request *rq, int error)
+void blk_mq_end_request(struct request *rq, int error)
 {
 	if (blk_update_request(rq, error, blk_rq_bytes(rq)))
 		BUG();
-	__blk_mq_end_io(rq, error);
+	__blk_mq_end_request(rq, error);
 }
-EXPORT_SYMBOL(blk_mq_end_io);
+EXPORT_SYMBOL(blk_mq_end_request);
 
 static void __blk_mq_complete_request_remote(void *data)
 {
@@ -365,7 +359,7 @@ void __blk_mq_complete_request(struct request *rq)
 	struct request_queue *q = rq->q;
 
 	if (!q->softirq_done_fn)
-		blk_mq_end_io(rq, rq->errors);
+		blk_mq_end_request(rq, rq->errors);
 	else
 		blk_mq_ipi_complete_request(rq);
 }
@@ -389,7 +383,7 @@ void blk_mq_complete_request(struct request *rq)
 }
 EXPORT_SYMBOL(blk_mq_complete_request);
 
-static void blk_mq_start_request(struct request *rq, bool last)
+void blk_mq_start_request(struct request *rq)
 {
 	struct request_queue *q = rq->q;
 
@@ -426,35 +420,24 @@ static void blk_mq_start_request(struct request *rq, bool last)
 		 */
 		rq->nr_phys_segments++;
 	}
-
-	/*
-	 * Flag the last request in the series so that drivers know when IO
-	 * should be kicked off, if they don't do it on a per-request basis.
-	 *
-	 * Note: the flag isn't the only condition drivers should do kick off.
-	 * If drive is busy, the last request might not have the bit set.
-	 */
-	if (last)
-		rq->cmd_flags |= REQ_END;
 }
+EXPORT_SYMBOL(blk_mq_start_request);
 
 static void __blk_mq_requeue_request(struct request *rq)
 {
 	struct request_queue *q = rq->q;
 
 	trace_block_rq_requeue(q, rq);
-	clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
-
-	rq->cmd_flags &= ~REQ_END;
 
-	if (q->dma_drain_size && blk_rq_bytes(rq))
-		rq->nr_phys_segments--;
+	if (test_and_clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags)) {
+		if (q->dma_drain_size && blk_rq_bytes(rq))
+			rq->nr_phys_segments--;
+	}
 }
 
 void blk_mq_requeue_request(struct request *rq)
 {
 	__blk_mq_requeue_request(rq);
-	blk_clear_rq_complete(rq);
 
 	BUG_ON(blk_queued_rq(rq));
 	blk_mq_add_to_requeue_list(rq, true);
@@ -523,78 +506,35 @@ void blk_mq_kick_requeue_list(struct request_queue *q)
 }
 EXPORT_SYMBOL(blk_mq_kick_requeue_list);
 
-static inline bool is_flush_request(struct request *rq, unsigned int tag)
+static inline bool is_flush_request(struct request *rq,
+		struct blk_flush_queue *fq, unsigned int tag)
 {
 	return ((rq->cmd_flags & REQ_FLUSH_SEQ) &&
-			rq->q->flush_rq->tag == tag);
+			fq->flush_rq->tag == tag);
 }
 
 struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
 {
 	struct request *rq = tags->rqs[tag];
+	/* mq_ctx of flush rq is always cloned from the corresponding req */
+	struct blk_flush_queue *fq = blk_get_flush_queue(rq->q, rq->mq_ctx);
 
-	if (!is_flush_request(rq, tag))
+	if (!is_flush_request(rq, fq, tag))
 		return rq;
 
-	return rq->q->flush_rq;
+	return fq->flush_rq;
 }
 EXPORT_SYMBOL(blk_mq_tag_to_rq);
 
 struct blk_mq_timeout_data {
-	struct blk_mq_hw_ctx *hctx;
-	unsigned long *next;
-	unsigned int *next_set;
+	unsigned long next;
+	unsigned int next_set;
 };
 
-static void blk_mq_timeout_check(void *__data, unsigned long *free_tags)
+void blk_mq_rq_timed_out(struct request *req, bool reserved)
 {
-	struct blk_mq_timeout_data *data = __data;
-	struct blk_mq_hw_ctx *hctx = data->hctx;
-	unsigned int tag;
-
-	 /* It may not be in flight yet (this is where
-	 * the REQ_ATOMIC_STARTED flag comes in). The requests are
-	 * statically allocated, so we know it's always safe to access the
-	 * memory associated with a bit offset into ->rqs[].
-	 */
-	tag = 0;
-	do {
-		struct request *rq;
-
-		tag = find_next_zero_bit(free_tags, hctx->tags->nr_tags, tag);
-		if (tag >= hctx->tags->nr_tags)
-			break;
-
-		rq = blk_mq_tag_to_rq(hctx->tags, tag++);
-		if (rq->q != hctx->queue)
-			continue;
-		if (!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))
-			continue;
-
-		blk_rq_check_expired(rq, data->next, data->next_set);
-	} while (1);
-}
-
-static void blk_mq_hw_ctx_check_timeout(struct blk_mq_hw_ctx *hctx,
-					unsigned long *next,
-					unsigned int *next_set)
-{
-	struct blk_mq_timeout_data data = {
-		.hctx		= hctx,
-		.next		= next,
-		.next_set	= next_set,
-	};
-
-	/*
-	 * Ask the tagging code to iterate busy requests, so we can
-	 * check them for timeout.
-	 */
-	blk_mq_tag_busy_iter(hctx->tags, blk_mq_timeout_check, &data);
-}
-
-static enum blk_eh_timer_return blk_mq_rq_timed_out(struct request *rq)
-{
-	struct request_queue *q = rq->q;
+	struct blk_mq_ops *ops = req->q->mq_ops;
+	enum blk_eh_timer_return ret = BLK_EH_RESET_TIMER;
 
 	/*
 	 * We know that complete is set at this point. If STARTED isn't set
@@ -605,36 +545,69 @@ static enum blk_eh_timer_return blk_mq_rq_timed_out(struct request *rq)
 	 * we both flags will get cleared. So check here again, and ignore
 	 * a timeout event with a request that isn't active.
 	 */
-	if (!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))
-		return BLK_EH_NOT_HANDLED;
+	if (!test_bit(REQ_ATOM_STARTED, &req->atomic_flags))
+		return;
 
-	if (!q->mq_ops->timeout)
-		return BLK_EH_RESET_TIMER;
+	if (ops->timeout)
+		ret = ops->timeout(req, reserved);
+
+	switch (ret) {
+	case BLK_EH_HANDLED:
+		__blk_mq_complete_request(req);
+		break;
+	case BLK_EH_RESET_TIMER:
+		blk_add_timer(req);
+		blk_clear_rq_complete(req);
+		break;
+	case BLK_EH_NOT_HANDLED:
+		break;
+	default:
+		printk(KERN_ERR "block: bad eh return: %d\n", ret);
+		break;
+	}
+}
+		
+static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
+		struct request *rq, void *priv, bool reserved)
+{
+	struct blk_mq_timeout_data *data = priv;
 
-	return q->mq_ops->timeout(rq);
+	if (!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))
+		return;
+
+	if (time_after_eq(jiffies, rq->deadline)) {
+		if (!blk_mark_rq_complete(rq))
+			blk_mq_rq_timed_out(rq, reserved);
+	} else if (!data->next_set || time_after(data->next, rq->deadline)) {
+		data->next = rq->deadline;
+		data->next_set = 1;
+	}
 }
 
-static void blk_mq_rq_timer(unsigned long data)
+static void blk_mq_rq_timer(unsigned long priv)
 {
-	struct request_queue *q = (struct request_queue *) data;
+	struct request_queue *q = (struct request_queue *)priv;
+	struct blk_mq_timeout_data data = {
+		.next		= 0,
+		.next_set	= 0,
+	};
 	struct blk_mq_hw_ctx *hctx;
-	unsigned long next = 0;
-	int i, next_set = 0;
+	int i;
 
 	queue_for_each_hw_ctx(q, hctx, i) {
 		/*
 		 * If not software queues are currently mapped to this
 		 * hardware queue, there's nothing to check
 		 */
-		if (!hctx->nr_ctx || !hctx->tags)
+		if (!blk_mq_hw_queue_mapped(hctx))
 			continue;
 
-		blk_mq_hw_ctx_check_timeout(hctx, &next, &next_set);
+		blk_mq_tag_busy_iter(hctx, blk_mq_check_expired, &data);
 	}
 
-	if (next_set) {
-		next = blk_rq_timeout(round_jiffies_up(next));
-		mod_timer(&q->timeout, next);
+	if (data.next_set) {
+		data.next = blk_rq_timeout(round_jiffies_up(data.next));
+		mod_timer(&q->timeout, data.next);
 	} else {
 		queue_for_each_hw_ctx(q, hctx, i)
 			blk_mq_tag_idle(hctx);
@@ -725,6 +698,8 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
 	struct request_queue *q = hctx->queue;
 	struct request *rq;
 	LIST_HEAD(rq_list);
+	LIST_HEAD(driver_list);
+	struct list_head *dptr;
 	int queued;
 
 	WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask));
@@ -751,18 +726,27 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
 	}
 
 	/*
+	 * Start off with dptr being NULL, so we start the first request
+	 * immediately, even if we have more pending.
+	 */
+	dptr = NULL;
+
+	/*
 	 * Now process all the entries, sending them to the driver.
 	 */
 	queued = 0;
 	while (!list_empty(&rq_list)) {
+		struct blk_mq_queue_data bd;
 		int ret;
 
 		rq = list_first_entry(&rq_list, struct request, queuelist);
 		list_del_init(&rq->queuelist);
 
-		blk_mq_start_request(rq, list_empty(&rq_list));
+		bd.rq = rq;
+		bd.list = dptr;
+		bd.last = list_empty(&rq_list);
 
-		ret = q->mq_ops->queue_rq(hctx, rq);
+		ret = q->mq_ops->queue_rq(hctx, &bd);
 		switch (ret) {
 		case BLK_MQ_RQ_QUEUE_OK:
 			queued++;
@@ -775,12 +759,19 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
 			pr_err("blk-mq: bad return on queue: %d\n", ret);
 		case BLK_MQ_RQ_QUEUE_ERROR:
 			rq->errors = -EIO;
-			blk_mq_end_io(rq, rq->errors);
+			blk_mq_end_request(rq, rq->errors);
 			break;
 		}
 
 		if (ret == BLK_MQ_RQ_QUEUE_BUSY)
 			break;
+
+		/*
+		 * We've done the first request. If we have more than 1
+		 * left in the list, set dptr to defer issue.
+		 */
+		if (!dptr && rq_list.next != rq_list.prev)
+			dptr = &driver_list;
 	}
 
 	if (!queued)
@@ -807,10 +798,11 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
  */
 static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
 {
-	int cpu = hctx->next_cpu;
+	if (hctx->queue->nr_hw_queues == 1)
+		return WORK_CPU_UNBOUND;
 
 	if (--hctx->next_cpu_batch <= 0) {
-		int next_cpu;
+		int cpu = hctx->next_cpu, next_cpu;
 
 		next_cpu = cpumask_next(hctx->next_cpu, hctx->cpumask);
 		if (next_cpu >= nr_cpu_ids)
@@ -818,26 +810,32 @@ static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
 
 		hctx->next_cpu = next_cpu;
 		hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
+
+		return cpu;
 	}
 
-	return cpu;
+	return hctx->next_cpu;
 }
 
 void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
 {
-	if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state)))
+	if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state) ||
+	    !blk_mq_hw_queue_mapped(hctx)))
 		return;
 
-	if (!async && cpumask_test_cpu(smp_processor_id(), hctx->cpumask))
-		__blk_mq_run_hw_queue(hctx);
-	else if (hctx->queue->nr_hw_queues == 1)
-		kblockd_schedule_delayed_work(&hctx->run_work, 0);
-	else {
-		unsigned int cpu;
+	if (!async) {
+		int cpu = get_cpu();
+		if (cpumask_test_cpu(cpu, hctx->cpumask)) {
+			__blk_mq_run_hw_queue(hctx);
+			put_cpu();
+			return;
+		}
 
-		cpu = blk_mq_hctx_next_cpu(hctx);
-		kblockd_schedule_delayed_work_on(cpu, &hctx->run_work, 0);
+		put_cpu();
 	}
+
+	kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
+			&hctx->run_work, 0);
 }
 
 void blk_mq_run_queues(struct request_queue *q, bool async)
@@ -851,9 +849,7 @@ void blk_mq_run_queues(struct request_queue *q, bool async)
 		    test_bit(BLK_MQ_S_STOPPED, &hctx->state))
 			continue;
 
-		preempt_disable();
 		blk_mq_run_hw_queue(hctx, async);
-		preempt_enable();
 	}
 }
 EXPORT_SYMBOL(blk_mq_run_queues);
@@ -880,9 +876,7 @@ void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)
 {
 	clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
 
-	preempt_disable();
 	blk_mq_run_hw_queue(hctx, false);
-	preempt_enable();
 }
 EXPORT_SYMBOL(blk_mq_start_hw_queue);
 
@@ -907,9 +901,7 @@ void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)
 			continue;
 
 		clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
-		preempt_disable();
 		blk_mq_run_hw_queue(hctx, async);
-		preempt_enable();
 	}
 }
 EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues);
@@ -935,16 +927,11 @@ static void blk_mq_delay_work_fn(struct work_struct *work)
 
 void blk_mq_delay_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
 {
-	unsigned long tmo = msecs_to_jiffies(msecs);
-
-	if (hctx->queue->nr_hw_queues == 1)
-		kblockd_schedule_delayed_work(&hctx->delay_work, tmo);
-	else {
-		unsigned int cpu;
+	if (unlikely(!blk_mq_hw_queue_mapped(hctx)))
+		return;
 
-		cpu = blk_mq_hctx_next_cpu(hctx);
-		kblockd_schedule_delayed_work_on(cpu, &hctx->delay_work, tmo);
-	}
+	kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
+			&hctx->delay_work, msecs_to_jiffies(msecs));
 }
 EXPORT_SYMBOL(blk_mq_delay_queue);
 
@@ -1199,18 +1186,27 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
 		goto run_queue;
 	}
 
-	if (is_sync) {
+	/*
+	 * If the driver supports defer issued based on 'last', then
+	 * queue it up like normal since we can potentially save some
+	 * CPU this way.
+	 */
+	if (is_sync && !(data.hctx->flags & BLK_MQ_F_DEFER_ISSUE)) {
+		struct blk_mq_queue_data bd = {
+			.rq = rq,
+			.list = NULL,
+			.last = 1
+		};
 		int ret;
 
 		blk_mq_bio_to_request(rq, bio);
-		blk_mq_start_request(rq, true);
 
 		/*
 		 * For OK queue, we are done. For error, kill it. Any other
 		 * error (busy), just add it to our list as we previously
 		 * would have done
 		 */
-		ret = q->mq_ops->queue_rq(data.hctx, rq);
+		ret = q->mq_ops->queue_rq(data.hctx, &bd);
 		if (ret == BLK_MQ_RQ_QUEUE_OK)
 			goto done;
 		else {
@@ -1218,7 +1214,7 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
 
 			if (ret == BLK_MQ_RQ_QUEUE_ERROR) {
 				rq->errors = -EIO;
-				blk_mq_end_io(rq, rq->errors);
+				blk_mq_end_request(rq, rq->errors);
 				goto done;
 			}
 		}
@@ -1540,6 +1536,28 @@ static int blk_mq_hctx_notify(void *data, unsigned long action,
 	return NOTIFY_OK;
 }
 
+static void blk_mq_exit_hctx(struct request_queue *q,
+		struct blk_mq_tag_set *set,
+		struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
+{
+	unsigned flush_start_tag = set->queue_depth;
+
+	blk_mq_tag_idle(hctx);
+
+	if (set->ops->exit_request)
+		set->ops->exit_request(set->driver_data,
+				       hctx->fq->flush_rq, hctx_idx,
+				       flush_start_tag + hctx_idx);
+
+	if (set->ops->exit_hctx)
+		set->ops->exit_hctx(hctx, hctx_idx);
+
+	blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
+	blk_free_flush_queue(hctx->fq);
+	kfree(hctx->ctxs);
+	blk_mq_free_bitmap(&hctx->ctx_map);
+}
+
 static void blk_mq_exit_hw_queues(struct request_queue *q,
 		struct blk_mq_tag_set *set, int nr_queue)
 {
@@ -1549,17 +1567,8 @@ static void blk_mq_exit_hw_queues(struct request_queue *q,
 	queue_for_each_hw_ctx(q, hctx, i) {
 		if (i == nr_queue)
 			break;
-
-		blk_mq_tag_idle(hctx);
-
-		if (set->ops->exit_hctx)
-			set->ops->exit_hctx(hctx, i);
-
-		blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
-		kfree(hctx->ctxs);
-		blk_mq_free_bitmap(&hctx->ctx_map);
+		blk_mq_exit_hctx(q, set, hctx, i);
 	}
-
 }
 
 static void blk_mq_free_hw_queues(struct request_queue *q,
@@ -1574,53 +1583,88 @@ static void blk_mq_free_hw_queues(struct request_queue *q,
 	}
 }
 
-static int blk_mq_init_hw_queues(struct request_queue *q,
-		struct blk_mq_tag_set *set)
+static int blk_mq_init_hctx(struct request_queue *q,
+		struct blk_mq_tag_set *set,
+		struct blk_mq_hw_ctx *hctx, unsigned hctx_idx)
 {
-	struct blk_mq_hw_ctx *hctx;
-	unsigned int i;
+	int node;
+	unsigned flush_start_tag = set->queue_depth;
+
+	node = hctx->numa_node;
+	if (node == NUMA_NO_NODE)
+		node = hctx->numa_node = set->numa_node;
+
+	INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);
+	INIT_DELAYED_WORK(&hctx->delay_work, blk_mq_delay_work_fn);
+	spin_lock_init(&hctx->lock);
+	INIT_LIST_HEAD(&hctx->dispatch);
+	hctx->queue = q;
+	hctx->queue_num = hctx_idx;
+	hctx->flags = set->flags;
+	hctx->cmd_size = set->cmd_size;
+
+	blk_mq_init_cpu_notifier(&hctx->cpu_notifier,
+					blk_mq_hctx_notify, hctx);
+	blk_mq_register_cpu_notifier(&hctx->cpu_notifier);
+
+	hctx->tags = set->tags[hctx_idx];
 
 	/*
-	 * Initialize hardware queues
+	 * Allocate space for all possible cpus to avoid allocation at
+	 * runtime
 	 */
-	queue_for_each_hw_ctx(q, hctx, i) {
-		int node;
+	hctx->ctxs = kmalloc_node(nr_cpu_ids * sizeof(void *),
+					GFP_KERNEL, node);
+	if (!hctx->ctxs)
+		goto unregister_cpu_notifier;
 
-		node = hctx->numa_node;
-		if (node == NUMA_NO_NODE)
-			node = hctx->numa_node = set->numa_node;
+	if (blk_mq_alloc_bitmap(&hctx->ctx_map, node))
+		goto free_ctxs;
 
-		INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);
-		INIT_DELAYED_WORK(&hctx->delay_work, blk_mq_delay_work_fn);
-		spin_lock_init(&hctx->lock);
-		INIT_LIST_HEAD(&hctx->dispatch);
-		hctx->queue = q;
-		hctx->queue_num = i;
-		hctx->flags = set->flags;
-		hctx->cmd_size = set->cmd_size;
+	hctx->nr_ctx = 0;
 
-		blk_mq_init_cpu_notifier(&hctx->cpu_notifier,
-						blk_mq_hctx_notify, hctx);
-		blk_mq_register_cpu_notifier(&hctx->cpu_notifier);
+	if (set->ops->init_hctx &&
+	    set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
+		goto free_bitmap;
 
-		hctx->tags = set->tags[i];
+	hctx->fq = blk_alloc_flush_queue(q, hctx->numa_node, set->cmd_size);
+	if (!hctx->fq)
+		goto exit_hctx;
 
-		/*
-		 * Allocate space for all possible cpus to avoid allocation at
-		 * runtime
-		 */
-		hctx->ctxs = kmalloc_node(nr_cpu_ids * sizeof(void *),
-						GFP_KERNEL, node);
-		if (!hctx->ctxs)
-			break;
+	if (set->ops->init_request &&
+	    set->ops->init_request(set->driver_data,
+				   hctx->fq->flush_rq, hctx_idx,
+				   flush_start_tag + hctx_idx, node))
+		goto free_fq;
 
-		if (blk_mq_alloc_bitmap(&hctx->ctx_map, node))
-			break;
+	return 0;
 
-		hctx->nr_ctx = 0;
+ free_fq:
+	kfree(hctx->fq);
+ exit_hctx:
+	if (set->ops->exit_hctx)
+		set->ops->exit_hctx(hctx, hctx_idx);
+ free_bitmap:
+	blk_mq_free_bitmap(&hctx->ctx_map);
+ free_ctxs:
+	kfree(hctx->ctxs);
+ unregister_cpu_notifier:
+	blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier);
 
-		if (set->ops->init_hctx &&
-		    set->ops->init_hctx(hctx, set->driver_data, i))
+	return -1;
+}
+
+static int blk_mq_init_hw_queues(struct request_queue *q,
+		struct blk_mq_tag_set *set)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned int i;
+
+	/*
+	 * Initialize hardware queues
+	 */
+	queue_for_each_hw_ctx(q, hctx, i) {
+		if (blk_mq_init_hctx(q, set, hctx, i))
 			break;
 	}
 
@@ -1792,7 +1836,8 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
 		if (!hctxs[i])
 			goto err_hctxs;
 
-		if (!zalloc_cpumask_var(&hctxs[i]->cpumask, GFP_KERNEL))
+		if (!zalloc_cpumask_var_node(&hctxs[i]->cpumask, GFP_KERNEL,
+						node))
 			goto err_hctxs;
 
 		atomic_set(&hctxs[i]->nr_active, 0);
@@ -1804,7 +1849,12 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
 	if (!q)
 		goto err_hctxs;
 
-	if (percpu_ref_init(&q->mq_usage_counter, blk_mq_usage_counter_release))
+	/*
+	 * Init percpu_ref in atomic mode so that it's faster to shutdown.
+	 * See blk_register_queue() for details.
+	 */
+	if (percpu_ref_init(&q->mq_usage_counter, blk_mq_usage_counter_release,
+			    PERCPU_REF_INIT_ATOMIC, GFP_KERNEL))
 		goto err_map;
 
 	setup_timer(&q->timeout, blk_mq_rq_timer, (unsigned long) q);
@@ -1834,7 +1884,6 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
 	else
 		blk_queue_make_request(q, blk_sq_make_request);
 
-	blk_queue_rq_timed_out(q, blk_mq_rq_timed_out);
 	if (set->timeout)
 		blk_queue_rq_timeout(q, set->timeout);
 
@@ -1846,17 +1895,10 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
 	if (set->ops->complete)
 		blk_queue_softirq_done(q, set->ops->complete);
 
-	blk_mq_init_flush(q);
 	blk_mq_init_cpu_queues(q, set->nr_hw_queues);
 
-	q->flush_rq = kzalloc(round_up(sizeof(struct request) +
-				set->cmd_size, cache_line_size()),
-				GFP_KERNEL);
-	if (!q->flush_rq)
-		goto err_hw;
-
 	if (blk_mq_init_hw_queues(q, set))
-		goto err_flush_rq;
+		goto err_hw;
 
 	mutex_lock(&all_q_mutex);
 	list_add_tail(&q->all_q_node, &all_q_list);
@@ -1868,8 +1910,6 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
 
 	return q;
 
-err_flush_rq:
-	kfree(q->flush_rq);
 err_hw:
 	blk_cleanup_queue(q);
 err_hctxs:
@@ -1915,7 +1955,7 @@ void blk_mq_free_queue(struct request_queue *q)
 /* Basically redo blk_mq_init_queue with queue frozen */
 static void blk_mq_queue_reinit(struct request_queue *q)
 {
-	blk_mq_freeze_queue(q);
+	WARN_ON_ONCE(!q->mq_freeze_depth);
 
 	blk_mq_sysfs_unregister(q);
 
@@ -1930,8 +1970,6 @@ static void blk_mq_queue_reinit(struct request_queue *q)
 	blk_mq_map_swqueue(q);
 
 	blk_mq_sysfs_register(q);
-
-	blk_mq_unfreeze_queue(q);
 }
 
 static int blk_mq_queue_reinit_notify(struct notifier_block *nb,
@@ -1950,8 +1988,25 @@ static int blk_mq_queue_reinit_notify(struct notifier_block *nb,
 		return NOTIFY_OK;
 
 	mutex_lock(&all_q_mutex);
+
+	/*
+	 * We need to freeze and reinit all existing queues.  Freezing
+	 * involves synchronous wait for an RCU grace period and doing it
+	 * one by one may take a long time.  Start freezing all queues in
+	 * one swoop and then wait for the completions so that freezing can
+	 * take place in parallel.
+	 */
+	list_for_each_entry(q, &all_q_list, all_q_node)
+		blk_mq_freeze_queue_start(q);
+	list_for_each_entry(q, &all_q_list, all_q_node)
+		blk_mq_freeze_queue_wait(q);
+
 	list_for_each_entry(q, &all_q_list, all_q_node)
 		blk_mq_queue_reinit(q);
+
+	list_for_each_entry(q, &all_q_list, all_q_node)
+		blk_mq_unfreeze_queue(q);
+
 	mutex_unlock(&all_q_mutex);
 	return NOTIFY_OK;
 }
@@ -2018,6 +2073,8 @@ static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
  */
 int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
 {
+	BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);
+
 	if (!set->nr_hw_queues)
 		return -EINVAL;
 	if (!set->queue_depth)
@@ -2034,6 +2091,16 @@ int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
 		set->queue_depth = BLK_MQ_MAX_DEPTH;
 	}
 
+	/*
+	 * If a crashdump is active, then we are potentially in a very
+	 * memory constrained environment. Limit us to 1 queue and
+	 * 64 tags to prevent using too much memory.
+	 */
+	if (is_kdump_kernel()) {
+		set->nr_hw_queues = 1;
+		set->queue_depth = min(64U, set->queue_depth);
+	}
+
 	set->tags = kmalloc_node(set->nr_hw_queues *
 				 sizeof(struct blk_mq_tags *),
 				 GFP_KERNEL, set->numa_node);