ms_block: convert to blk-mq

Straight forward conversion, room for optimization in how everything
is punted to a work queue. Also looks plenty racy all over the map,
with the state changes. I fixed a bunch of them up while doing the
conversion, but there are surely more.

Cc: Maxim Levitsky <maximlevitsky@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Tested-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/memstick/core/ms_block.c

@@ -15,7 +15,7 @@
 #define pr_fmt(fmt) DRIVER_NAME ": " fmt
 
 #include <linux/module.h>
-#include <linux/blkdev.h>
+#include <linux/blk-mq.h>
 #include <linux/memstick.h>
 #include <linux/idr.h>
 #include <linux/hdreg.h>
@@ -1873,69 +1873,65 @@ static void msb_io_work(struct work_struct *work)
 	struct msb_data *msb = container_of(work, struct msb_data, io_work);
 	int page, error, len;
 	sector_t lba;
-	unsigned long flags;
 	struct scatterlist *sg = msb->prealloc_sg;
+	struct request *req;
 
 	dbg_verbose("IO: work started");
 
 	while (1) {
-		spin_lock_irqsave(&msb->q_lock, flags);
+		spin_lock_irq(&msb->q_lock);
 
 		if (msb->need_flush_cache) {
 			msb->need_flush_cache = false;
-			spin_unlock_irqrestore(&msb->q_lock, flags);
+			spin_unlock_irq(&msb->q_lock);
 			msb_cache_flush(msb);
 			continue;
 		}
 
-		if (!msb->req) {
-			msb->req = blk_fetch_request(msb->queue);
-			if (!msb->req) {
-				dbg_verbose("IO: no more requests exiting");
-				spin_unlock_irqrestore(&msb->q_lock, flags);
-				return;
-			}
+		req = msb->req;
+		if (!req) {
+			dbg_verbose("IO: no more requests exiting");
+			spin_unlock_irq(&msb->q_lock);
+			return;
 		}
 
-		spin_unlock_irqrestore(&msb->q_lock, flags);
-
-		/* If card was removed meanwhile */
-		if (!msb->req)
-			return;
+		spin_unlock_irq(&msb->q_lock);
 
 		/* process the request */
 		dbg_verbose("IO: processing new request");
-		blk_rq_map_sg(msb->queue, msb->req, sg);
+		blk_rq_map_sg(msb->queue, req, sg);
 
-		lba = blk_rq_pos(msb->req);
+		lba = blk_rq_pos(req);
 
 		sector_div(lba, msb->page_size / 512);
 		page = sector_div(lba, msb->pages_in_block);
 
 		if (rq_data_dir(msb->req) == READ)
 			error = msb_do_read_request(msb, lba, page, sg,
-				blk_rq_bytes(msb->req), &len);
+				blk_rq_bytes(req), &len);
 		else
 			error = msb_do_write_request(msb, lba, page, sg,
-				blk_rq_bytes(msb->req), &len);
+				blk_rq_bytes(req), &len);
 
-		spin_lock_irqsave(&msb->q_lock, flags);
-
-		if (len)
-			if (!__blk_end_request(msb->req, BLK_STS_OK, len))
-				msb->req = NULL;
+		if (len && !blk_update_request(req, BLK_STS_OK, len)) {
+			__blk_mq_end_request(req, BLK_STS_OK);
+			spin_lock_irq(&msb->q_lock);
+			msb->req = NULL;
+			spin_unlock_irq(&msb->q_lock);
+		}
 
 		if (error && msb->req) {
 			blk_status_t ret = errno_to_blk_status(error);
+
 			dbg_verbose("IO: ending one sector of the request with error");
-			if (!__blk_end_request(msb->req, ret, msb->page_size))
-				msb->req = NULL;
+			blk_mq_end_request(req, ret);
+			spin_lock_irq(&msb->q_lock);
+			msb->req = NULL;
+			spin_unlock_irq(&msb->q_lock);
 		}
 
 		if (msb->req)
 			dbg_verbose("IO: request still pending");
-
-		spin_unlock_irqrestore(&msb->q_lock, flags);
 	}
 }
 
@@ -2002,29 +1998,40 @@ static int msb_bd_getgeo(struct block_device *bdev,
 	return 0;
 }
 
-static void msb_submit_req(struct request_queue *q)
+static blk_status_t msb_queue_rq(struct blk_mq_hw_ctx *hctx,
+				 const struct blk_mq_queue_data *bd)
 {
-	struct memstick_dev *card = q->queuedata;
+	struct memstick_dev *card = hctx->queue->queuedata;
 	struct msb_data *msb = memstick_get_drvdata(card);
-	struct request *req = NULL;
+	struct request *req = bd->rq;
 
 	dbg_verbose("Submit request");
 
+	spin_lock_irq(&msb->q_lock);
+
 	if (msb->card_dead) {
 		dbg("Refusing requests on removed card");
 
 		WARN_ON(!msb->io_queue_stopped);
 
-		while ((req = blk_fetch_request(q)) != NULL)
-			__blk_end_request_all(req, BLK_STS_IOERR);
-		return;
+		spin_unlock_irq(&msb->q_lock);
+		blk_mq_start_request(req);
+		return BLK_STS_IOERR;
 	}
 
-	if (msb->req)
-		return;
+	if (msb->req) {
+		spin_unlock_irq(&msb->q_lock);
+		return BLK_STS_DEV_RESOURCE;
+	}
+
+	blk_mq_start_request(req);
+	msb->req = req;
 
 	if (!msb->io_queue_stopped)
 		queue_work(msb->io_queue, &msb->io_work);
+
+	spin_unlock_irq(&msb->q_lock);
+	return BLK_STS_OK;
 }
 
 static int msb_check_card(struct memstick_dev *card)
@@ -2040,21 +2047,20 @@ static void msb_stop(struct memstick_dev *card)
 
 	dbg("Stopping all msblock IO");
 
+	blk_mq_stop_hw_queues(msb->queue);
 	spin_lock_irqsave(&msb->q_lock, flags);
-	blk_stop_queue(msb->queue);
 	msb->io_queue_stopped = true;
 	spin_unlock_irqrestore(&msb->q_lock, flags);
 
 	del_timer_sync(&msb->cache_flush_timer);
 	flush_workqueue(msb->io_queue);
 
+	spin_lock_irqsave(&msb->q_lock, flags);
 	if (msb->req) {
-		spin_lock_irqsave(&msb->q_lock, flags);
-		blk_requeue_request(msb->queue, msb->req);
+		blk_mq_requeue_request(msb->req, false);
 		msb->req = NULL;
-		spin_unlock_irqrestore(&msb->q_lock, flags);
 	}
-
+	spin_unlock_irqrestore(&msb->q_lock, flags);
 }
 
 static void msb_start(struct memstick_dev *card)
@@ -2077,9 +2083,7 @@ static void msb_start(struct memstick_dev *card)
 	msb->need_flush_cache = true;
 	msb->io_queue_stopped = false;
 
-	spin_lock_irqsave(&msb->q_lock, flags);
-	blk_start_queue(msb->queue);
-	spin_unlock_irqrestore(&msb->q_lock, flags);
+	blk_mq_start_hw_queues(msb->queue);
 
 	queue_work(msb->io_queue, &msb->io_work);
 
@@ -2092,10 +2096,15 @@ static const struct block_device_operations msb_bdops = {
 	.owner   = THIS_MODULE
 };
 
+static const struct blk_mq_ops msb_mq_ops = {
+	.queue_rq	= msb_queue_rq,
+};
+
 /* Registers the block device */
 static int msb_init_disk(struct memstick_dev *card)
 {
 	struct msb_data *msb = memstick_get_drvdata(card);
+	struct blk_mq_tag_set *set = NULL;
 	int rc;
 	unsigned long capacity;
 
@@ -2112,9 +2121,11 @@ static int msb_init_disk(struct memstick_dev *card)
 		goto out_release_id;
 	}
 
-	msb->queue = blk_init_queue(msb_submit_req, &msb->q_lock);
-	if (!msb->queue) {
-		rc = -ENOMEM;
+	msb->queue = blk_mq_init_sq_queue(&msb->tag_set, &msb_mq_ops, 2,
+						BLK_MQ_F_SHOULD_MERGE);
+	if (IS_ERR(msb->queue)) {
+		rc = PTR_ERR(msb->queue);
+		msb->queue = NULL;
 		goto out_put_disk;
 	}
 
@@ -2202,12 +2213,13 @@ static void msb_remove(struct memstick_dev *card)
 	/* Take care of unhandled + new requests from now on */
 	spin_lock_irqsave(&msb->q_lock, flags);
 	msb->card_dead = true;
-	blk_start_queue(msb->queue);
 	spin_unlock_irqrestore(&msb->q_lock, flags);
+	blk_mq_start_hw_queues(msb->queue);
 
 	/* Remove the disk */
 	del_gendisk(msb->disk);
 	blk_cleanup_queue(msb->queue);
+	blk_mq_free_tag_set(&msb->tag_set);
 	msb->queue = NULL;
 
 	mutex_lock(&msb_disk_lock);

drivers/memstick/core/ms_block.h

@@ -152,6 +152,7 @@ struct msb_data {
 	struct gendisk			*disk;
 	struct request_queue		*queue;
 	spinlock_t			q_lock;
+	struct blk_mq_tag_set		tag_set;
 	struct hd_geometry		geometry;
 	struct attribute_group		attr_group;
 	struct request			*req;