ublk: factor out ublk_start_io() helper

In preparation for calling it from outside ublk_dispatch_req(), factor
out the code responsible for setting up an incoming ublk I/O request.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250430225234.2676781-7-csander@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 31 insertions, 23 deletions

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index dcde38b39a82..b4c64779c4fd 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1152,13 +1152,41 @@ static inline void __ublk_abort_rq(struct ublk_queue *ubq,
 		blk_mq_end_request(rq, BLK_STS_IOERR);
 }
 
+static bool ublk_start_io(const struct ublk_queue *ubq, struct request *req,
+			  struct ublk_io *io)
+{
+	unsigned mapped_bytes = ublk_map_io(ubq, req, io);
+
+	/* partially mapped, update io descriptor */
+	if (unlikely(mapped_bytes != blk_rq_bytes(req))) {
+		/*
+		 * Nothing mapped, retry until we succeed.
+		 *
+		 * We may never succeed in mapping any bytes here because
+		 * of OOM. TODO: reserve one buffer with single page pinned
+		 * for providing forward progress guarantee.
+		 */
+		if (unlikely(!mapped_bytes)) {
+			blk_mq_requeue_request(req, false);
+			blk_mq_delay_kick_requeue_list(req->q,
+					UBLK_REQUEUE_DELAY_MS);
+			return false;
+		}
+
+		ublk_get_iod(ubq, req->tag)->nr_sectors =
+			mapped_bytes >> 9;
+	}
+
+	ublk_init_req_ref(ubq, req);
+	return true;
+}
+
 static void ublk_dispatch_req(struct ublk_queue *ubq,
 			      struct request *req,
 			      unsigned int issue_flags)
 {
 	int tag = req->tag;
 	struct ublk_io *io = &ubq->ios[tag];
-	unsigned int mapped_bytes;
 
 	pr_devel("%s: complete: qid %d tag %d io_flags %x addr %llx\n",
 			__func__, ubq->q_id, req->tag, io->flags,
@@ -1205,29 +1233,9 @@ static void ublk_dispatch_req(struct ublk_queue *ubq,
 				ublk_get_iod(ubq, req->tag)->addr);
 	}
 
-	mapped_bytes = ublk_map_io(ubq, req, io);
-
-	/* partially mapped, update io descriptor */
-	if (unlikely(mapped_bytes != blk_rq_bytes(req))) {
-		/*
-		 * Nothing mapped, retry until we succeed.
-		 *
-		 * We may never succeed in mapping any bytes here because
-		 * of OOM. TODO: reserve one buffer with single page pinned
-		 * for providing forward progress guarantee.
-		 */
-		if (unlikely(!mapped_bytes)) {
-			blk_mq_requeue_request(req, false);
-			blk_mq_delay_kick_requeue_list(req->q,
-					UBLK_REQUEUE_DELAY_MS);
-			return;
-		}
-
-		ublk_get_iod(ubq, req->tag)->nr_sectors =
-			mapped_bytes >> 9;
-	}
+	if (!ublk_start_io(ubq, req, io))
+		return;
 
-	ublk_init_req_ref(ubq, req);
 	ublk_complete_io_cmd(io, UBLK_IO_RES_OK, issue_flags);
 }