block: add a rq_list type

Replace the semi-open coded request list helpers with a proper rq_list
type that mirrors the bio_list and has head and tail pointers.  Besides
better type safety this actually allows to insert at the tail of the
list, which will be useful soon.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241113152050.157179-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

4 files changed, 18 insertions, 21 deletions

diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 2f0431e42c49..3c3d8d200abb 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -1638,10 +1638,9 @@ static blk_status_t null_queue_rq(struct blk_mq_hw_ctx *hctx,
 	return BLK_STS_OK;
 }
 
-static void null_queue_rqs(struct request **rqlist)
+static void null_queue_rqs(struct rq_list *rqlist)
 {
-	struct request *requeue_list = NULL;
-	struct request **requeue_lastp = &requeue_list;
+	struct rq_list requeue_list = {};
 	struct blk_mq_queue_data bd = { };
 	blk_status_t ret;
 
@@ -1651,8 +1650,8 @@ static void null_queue_rqs(struct request **rqlist)
 		bd.rq = rq;
 		ret = null_queue_rq(rq->mq_hctx, &bd);
 		if (ret != BLK_STS_OK)
-			rq_list_add_tail(&requeue_lastp, rq);
-	} while (!rq_list_empty(*rqlist));
+			rq_list_add_tail(&requeue_list, rq);
+	} while (!rq_list_empty(rqlist));
 
 	*rqlist = requeue_list;
 }
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index b25f7c06a28e..a19f24c19140 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -472,7 +472,7 @@ static bool virtblk_prep_rq_batch(struct request *req)
 }
 
 static void virtblk_add_req_batch(struct virtio_blk_vq *vq,
-					struct request **rqlist)
+		struct rq_list *rqlist)
 {
 	struct request *req;
 	unsigned long flags;
@@ -499,11 +499,10 @@ static void virtblk_add_req_batch(struct virtio_blk_vq *vq,
 		virtqueue_notify(vq->vq);
 }
 
-static void virtio_queue_rqs(struct request **rqlist)
+static void virtio_queue_rqs(struct rq_list *rqlist)
 {
-	struct request *submit_list = NULL;
-	struct request *requeue_list = NULL;
-	struct request **requeue_lastp = &requeue_list;
+	struct rq_list submit_list = { };
+	struct rq_list requeue_list = { };
 	struct virtio_blk_vq *vq = NULL;
 	struct request *req;
 
@@ -515,9 +514,9 @@ static void virtio_queue_rqs(struct request **rqlist)
 		vq = this_vq;
 
 		if (virtblk_prep_rq_batch(req))
-			rq_list_add(&submit_list, req); /* reverse order */
+			rq_list_add_head(&submit_list, req); /* reverse order */
 		else
-			rq_list_add_tail(&requeue_lastp, req);
+			rq_list_add_tail(&requeue_list, req);
 	}
 
 	if (vq)
diff --git a/drivers/nvme/host/apple.c b/drivers/nvme/host/apple.c
index b1387dc459a3..7cd1102a8d2c 100644
--- a/drivers/nvme/host/apple.c
+++ b/drivers/nvme/host/apple.c
@@ -649,7 +649,7 @@ static bool apple_nvme_handle_cq(struct apple_nvme_queue *q, bool force)
 
 	found = apple_nvme_poll_cq(q, &iob);
 
-	if (!rq_list_empty(iob.req_list))
+	if (!rq_list_empty(&iob.req_list))
 		apple_nvme_complete_batch(&iob);
 
 	return found;
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index ec1c44c75d92..707dbe8be6a2 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -904,7 +904,7 @@ static blk_status_t nvme_queue_rq(struct blk_mq_hw_ctx *hctx,
 	return BLK_STS_OK;
 }
 
-static void nvme_submit_cmds(struct nvme_queue *nvmeq, struct request **rqlist)
+static void nvme_submit_cmds(struct nvme_queue *nvmeq, struct rq_list *rqlist)
 {
 	struct request *req;
 
@@ -932,11 +932,10 @@ static bool nvme_prep_rq_batch(struct nvme_queue *nvmeq, struct request *req)
 	return nvme_prep_rq(nvmeq->dev, req) == BLK_STS_OK;
 }
 
-static void nvme_queue_rqs(struct request **rqlist)
+static void nvme_queue_rqs(struct rq_list *rqlist)
 {
-	struct request *submit_list = NULL;
-	struct request *requeue_list = NULL;
-	struct request **requeue_lastp = &requeue_list;
+	struct rq_list submit_list = { };
+	struct rq_list requeue_list = { };
 	struct nvme_queue *nvmeq = NULL;
 	struct request *req;
 
@@ -946,9 +945,9 @@ static void nvme_queue_rqs(struct request **rqlist)
 		nvmeq = req->mq_hctx->driver_data;
 
 		if (nvme_prep_rq_batch(nvmeq, req))
-			rq_list_add(&submit_list, req); /* reverse order */
+			rq_list_add_head(&submit_list, req); /* reverse order */
 		else
-			rq_list_add_tail(&requeue_lastp, req);
+			rq_list_add_tail(&requeue_list, req);
 	}
 
 	if (nvmeq)
@@ -1080,7 +1079,7 @@ static irqreturn_t nvme_irq(int irq, void *data)
 	DEFINE_IO_COMP_BATCH(iob);
 
 	if (nvme_poll_cq(nvmeq, &iob)) {
-		if (!rq_list_empty(iob.req_list))
+		if (!rq_list_empty(&iob.req_list))
 			nvme_pci_complete_batch(&iob);
 		return IRQ_HANDLED;
 	}