ublk: add parameter struct io_uring_cmd * to ublk_prep_auto_buf_reg()

Add parameter `struct io_uring_cmd *` to ublk_prep_auto_buf_reg() and
prepare for reusing this helper for the coming UBLK_BATCH_IO feature,
which can fetch & commit one batch of io commands via single uring_cmd.

Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Ming Lei

drivers/block/ublk_drv.c

@@ -1176,11 +1176,12 @@ ublk_auto_buf_reg_fallback(const struct ublk_queue *ubq, struct ublk_io *io)
 }
 
 static bool ublk_auto_buf_reg(const struct ublk_queue *ubq, struct request *req,
-			      struct ublk_io *io, unsigned int issue_flags)
+			      struct ublk_io *io, struct io_uring_cmd *cmd,
+			      unsigned int issue_flags)
 {
 	int ret;
 
-	ret = io_buffer_register_bvec(io->cmd, req, ublk_io_release,
+	ret = io_buffer_register_bvec(cmd, req, ublk_io_release,
 				      io->buf.index, issue_flags);
 	if (ret) {
 		if (io->buf.flags & UBLK_AUTO_BUF_REG_FALLBACK) {
@@ -1192,18 +1193,19 @@ static bool ublk_auto_buf_reg(const struct ublk_queue *ubq, struct request *req,
 	}
 
 	io->task_registered_buffers = 1;
-	io->buf_ctx_handle = io_uring_cmd_ctx_handle(io->cmd);
+	io->buf_ctx_handle = io_uring_cmd_ctx_handle(cmd);
 	io->flags |= UBLK_IO_FLAG_AUTO_BUF_REG;
 	return true;
 }
 
 static bool ublk_prep_auto_buf_reg(struct ublk_queue *ubq,
 				   struct request *req, struct ublk_io *io,
+				   struct io_uring_cmd *cmd,
 				   unsigned int issue_flags)
 {
 	ublk_init_req_ref(ubq, io);
 	if (ublk_support_auto_buf_reg(ubq) && ublk_rq_has_data(req))
-		return ublk_auto_buf_reg(ubq, req, io, issue_flags);
+		return ublk_auto_buf_reg(ubq, req, io, cmd, issue_flags);
 
 	return true;
 }
@@ -1278,7 +1280,7 @@ static void ublk_dispatch_req(struct ublk_queue *ubq,
 	if (!ublk_start_io(ubq, req, io))
 		return;
 
-	if (ublk_prep_auto_buf_reg(ubq, req, io, issue_flags))
+	if (ublk_prep_auto_buf_reg(ubq, req, io, io->cmd, issue_flags))
 		ublk_complete_io_cmd(io, req, UBLK_IO_RES_OK, issue_flags);
 }