scsi: move the nr_phys_segments assert into scsi_init_io

commit 635d98b1 upstream.

scsi_init_io should only be called for requests that transfer data,
so move the assert that a request has segments from the callers into
scsi_init_io.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Willy Tarreau <w@1wt.eu>

drivers/scsi/scsi_lib.c

@@ -1009,8 +1009,11 @@ static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb,
 int scsi_init_io(struct scsi_cmnd *cmd, gfp_t gfp_mask)
 {
 	struct request *rq = cmd->request;
+	int error;
 
-	int error = scsi_init_sgtable(rq, &cmd->sdb, gfp_mask);
+	BUG_ON(!rq->nr_phys_segments);
+
+	error = scsi_init_sgtable(rq, &cmd->sdb, gfp_mask);
 	if (error)
 		goto err_exit;
 
@@ -1102,11 +1105,7 @@ int scsi_setup_blk_pc_cmnd(struct scsi_device *sdev, struct request *req)
 	 * submit a request without an attached bio.
 	 */
 	if (req->bio) {
-		int ret;
-
-		BUG_ON(!req->nr_phys_segments);
-
-		ret = scsi_init_io(cmd, GFP_ATOMIC);
+		int ret = scsi_init_io(cmd, GFP_ATOMIC);
 		if (unlikely(ret))
 			return ret;
 	} else {
@@ -1150,11 +1149,6 @@ int scsi_setup_fs_cmnd(struct scsi_device *sdev, struct request *req)
 			return ret;
 	}
 
-	/*
-	 * Filesystem requests must transfer data.
-	 */
-	BUG_ON(!req->nr_phys_segments);
-
 	cmd = scsi_get_cmd_from_req(sdev, req);
 	if (unlikely(!cmd))
 		return BLKPREP_DEFER;