skd: Introduce skd_process_request()

The only functional change in this patch is that the skd_fitmsg_context
in which requests are accumulated is changed from a local variable into
a member of struct skd_device. This patch will make the blk-mq conversion
easier.
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/skd_main.c

@@ -232,6 +232,7 @@ struct skd_device {
 	spinlock_t lock;
 	struct gendisk *disk;
 	struct request_queue *queue;
+	struct skd_fitmsg_context *skmsg;
 	struct device *class_dev;
 	int gendisk_on;
 	int sync_done;
@@ -492,56 +493,30 @@ static bool skd_fail_all(struct request_queue *q)
 	}
 }
 
-static void skd_request_fn(struct request_queue *q)
+static void skd_process_request(struct request *req)
 {
+	struct request_queue *const q = req->q;
 	struct skd_device *skdev = q->queuedata;
-	struct skd_fitmsg_context *skmsg = NULL;
-	struct fit_msg_hdr *fmh = NULL;
-	struct skd_request_context *skreq;
-	struct request *req = NULL;
+	struct skd_fitmsg_context *skmsg;
+	struct fit_msg_hdr *fmh;
+	const u32 tag = blk_mq_unique_tag(req);
+	struct skd_request_context *const skreq = &skdev->skreq_table[tag];
 	struct skd_scsi_request *scsi_req;
 	unsigned long io_flags;
 	u32 lba;
 	u32 count;
 	int data_dir;
 	__be64 be_dmaa;
-	u64 cmdctxt;
 	u32 timo_slot;
 	int flush, fua;
-	u32 tag;
-
-	if (skdev->state != SKD_DRVR_STATE_ONLINE) {
-		if (skd_fail_all(q))
-			skd_fail_all_pending(skdev);
-		return;
-	}
-
-	if (blk_queue_stopped(skdev->queue)) {
-		if (atomic_read(&skdev->in_flight) >=
-		    skdev->queue_low_water_mark)
-			/* There is still some kind of shortage */
-			return;
 
-		queue_flag_clear(QUEUE_FLAG_STOPPED, skdev->queue);
-	}
+	WARN_ONCE(tag >= skd_max_queue_depth, "%#x > %#x (nr_requests = %lu)\n",
+		  tag, skd_max_queue_depth, q->nr_requests);
 
-	/*
-	 * Stop conditions:
-	 *  - There are no more native requests
-	 *  - There are already the maximum number of requests in progress
-	 *  - There are no more skd_request_context entries
-	 *  - There are no more FIT msg buffers
-	 */
-	for (;; ) {
+	SKD_ASSERT(skreq->state == SKD_REQ_STATE_IDLE);
 
 	flush = fua = 0;
 
-		req = blk_peek_request(q);
-
-		/* Are there any native requests to start? */
-		if (req == NULL)
-			break;
-
 	lba = (u32)blk_rq_pos(req);
 	count = blk_rq_sectors(req);
 	data_dir = rq_data_dir(req);
@@ -554,37 +529,8 @@ static void skd_request_fn(struct request_queue *q)
 		fua++;
 
 	dev_dbg(&skdev->pdev->dev,
-			"new req=%p lba=%u(0x%x) count=%u(0x%x) dir=%d\n",
-			req, lba, lba, count, count, data_dir);
-
-		/* At this point we know there is a request */
-
-		/* Are too many requets already in progress? */
-		if (atomic_read(&skdev->in_flight) >=
-		    skdev->cur_max_queue_depth) {
-			dev_dbg(&skdev->pdev->dev, "qdepth %d, limit %d\n",
-				atomic_read(&skdev->in_flight),
-				skdev->cur_max_queue_depth);
-			break;
-		}
-
-		/*
-		 * OK to now dequeue request from q.
-		 *
-		 * At this point we are comitted to either start or reject
-		 * the native request. Note that skd_request_context is
-		 * available but is still at the head of the free list.
-		 */
-		WARN_ON_ONCE(blk_queue_start_tag(q, req));
-
-		tag = blk_mq_unique_tag(req);
-		WARN_ONCE(tag >= skd_max_queue_depth,
-			  "%#x > %#x (nr_requests = %lu)\n", tag,
-			  skd_max_queue_depth, q->nr_requests);
-
-		skreq = &skdev->skreq_table[tag];
-		SKD_ASSERT(skreq->state == SKD_REQ_STATE_IDLE);
-		SKD_ASSERT((skreq->id & SKD_ID_INCR) == 0);
+		"new req=%p lba=%u(0x%x) count=%u(0x%x) dir=%d\n", req, lba,
+		lba, count, count, data_dir);
 
 	skreq->id = tag + SKD_ID_RW_REQUEST;
 	skreq->flush_cmd = 0;
@@ -594,36 +540,37 @@ static void skd_request_fn(struct request_queue *q)
 	skreq->req = req;
 	skreq->fitmsg_id = 0;
 
-		skreq->data_dir = data_dir == READ ? DMA_FROM_DEVICE :
-			DMA_TO_DEVICE;
+	skreq->data_dir = data_dir == READ ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
 
 	if (req->bio && !skd_preop_sg_list(skdev, skreq)) {
 		dev_dbg(&skdev->pdev->dev, "error Out\n");
 		skd_end_request(skdev, skreq->req, BLK_STS_RESOURCE);
-			continue;
+		return;
 	}
 
 	/* Either a FIT msg is in progress or we have to start one. */
-		if (skmsg == NULL) {
+	skmsg = skdev->skmsg;
+	if (!skmsg) {
 		skmsg = &skdev->skmsg_table[tag];
+		skdev->skmsg = skmsg;
 
 		/* Initialize the FIT msg header */
 		fmh = &skmsg->msg_buf->fmh;
 		memset(fmh, 0, sizeof(*fmh));
 		fmh->protocol_id = FIT_PROTOCOL_ID_SOFIT;
 		skmsg->length = sizeof(*fmh);
+	} else {
+		fmh = &skmsg->msg_buf->fmh;
 	}
 
 	skreq->fitmsg_id = skmsg->id;
 
-		scsi_req =
-			&skmsg->msg_buf->scsi[fmh->num_protocol_cmds_coalesced];
+	scsi_req = &skmsg->msg_buf->scsi[fmh->num_protocol_cmds_coalesced];
 	memset(scsi_req, 0, sizeof(*scsi_req));
 
 	be_dmaa = cpu_to_be64(skreq->sksg_dma_address);
-		cmdctxt = skreq->id + SKD_ID_INCR;
 
-		scsi_req->hdr.tag = cmdctxt;
+	scsi_req->hdr.tag = skreq->id;
 	scsi_req->hdr.sg_list_dma_address = be_dmaa;
 
 	if (flush == SKD_FLUSH_ZERO_SIZE_FIRST) {
@@ -636,12 +583,10 @@ static void skd_request_fn(struct request_queue *q)
 	if (fua)
 		scsi_req->cdb[1] |= SKD_FUA_NV;
 
-		scsi_req->hdr.sg_list_len_bytes =
-			cpu_to_be32(skreq->sg_byte_count);
+	scsi_req->hdr.sg_list_len_bytes = cpu_to_be32(skreq->sg_byte_count);
 
 	/* Complete resource allocations. */
 	skreq->state = SKD_REQ_STATE_BUSY;
-		skreq->id += SKD_ID_INCR;
 
 	skmsg->length += sizeof(struct skd_scsi_request);
 	fmh->num_protocol_cmds_coalesced++;
@@ -662,17 +607,73 @@ static void skd_request_fn(struct request_queue *q)
 	 */
 	if (fmh->num_protocol_cmds_coalesced >= skd_max_req_per_msg) {
 		skd_send_fitmsg(skdev, skmsg);
-			skmsg = NULL;
-			fmh = NULL;
+		skdev->skmsg = NULL;
+	}
+}
+
+static void skd_request_fn(struct request_queue *q)
+{
+	struct skd_device *skdev = q->queuedata;
+	struct request *req;
+
+	if (skdev->state != SKD_DRVR_STATE_ONLINE) {
+		if (skd_fail_all(q))
+			skd_fail_all_pending(skdev);
+		return;
+	}
+
+	if (blk_queue_stopped(skdev->queue)) {
+		if (atomic_read(&skdev->in_flight) >=
+		    skdev->queue_low_water_mark)
+			/* There is still some kind of shortage */
+			return;
+
+		queue_flag_clear(QUEUE_FLAG_STOPPED, skdev->queue);
+	}
+
+	/*
+	 * Stop conditions:
+	 *  - There are no more native requests
+	 *  - There are already the maximum number of requests in progress
+	 *  - There are no more skd_request_context entries
+	 *  - There are no more FIT msg buffers
+	 */
+	for (;; ) {
+		req = blk_peek_request(q);
+
+		/* Are there any native requests to start? */
+		if (req == NULL)
+			break;
+
+		/* At this point we know there is a request */
+
+		/* Are too many requets already in progress? */
+		if (atomic_read(&skdev->in_flight) >=
+		    skdev->cur_max_queue_depth) {
+			dev_dbg(&skdev->pdev->dev, "qdepth %d, limit %d\n",
+				atomic_read(&skdev->in_flight),
+				skdev->cur_max_queue_depth);
+			break;
 		}
+
+		/*
+		 * OK to now dequeue request from q.
+		 *
+		 * At this point we are comitted to either start or reject
+		 * the native request. Note that skd_request_context is
+		 * available but is still at the head of the free list.
+		 */
+		WARN_ON_ONCE(blk_queue_start_tag(q, req));
+		skd_process_request(req);
 	}
 
 	/* If the FIT msg buffer is not empty send what we got. */
-	if (skmsg) {
+	if (skdev->skmsg) {
+		struct fit_msg_hdr *fmh = &skdev->skmsg->msg_buf->fmh;
+
 		WARN_ON_ONCE(!fmh->num_protocol_cmds_coalesced);
-		skd_send_fitmsg(skdev, skmsg);
-		skmsg = NULL;
-		fmh = NULL;
+		skd_send_fitmsg(skdev, skdev->skmsg);
+		skdev->skmsg = NULL;
 	}
 
 	/*