bsg: split handling of SCSI CDBs vs transport requeues

The current BSG design tries to shoe-horn the transport-specific
passthrough commands into the overall framework for SCSI passthrough
requests.  This has a couple problems:

 - each passthrough queue has to set the QUEUE_FLAG_SCSI_PASSTHROUGH flag
   despite not dealing with SCSI commands at all.  Because of that these
   queues could also incorrectly accept SCSI commands from in-kernel
   users or through the legacy SCSI_IOCTL_SEND_COMMAND ioctl.
 - the real SCSI bsg queues also incorrectly accept bsg requests of the
   BSG_SUB_PROTOCOL_SCSI_TRANSPORT type
 - the bsg transport code is almost unredable because it tries to reuse
   different SCSI concepts for its own purpose.

This patch instead adds a new bsg_ops structure to handle the two cases
differently, and thus solves all of the above problems.  Another side
effect is that the bsg-lib queues also don't need to embedd a
struct scsi_request anymore.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 22 insertions, 13 deletions

diff --git a/include/linux/bsg.h b/include/linux/bsg.h
index 2a202e41a3af..0c7dd9ceb139 100644
--- a/include/linux/bsg.h
+++ b/include/linux/bsg.h
@@ -1,34 +1,43 @@
 /* SPDX-License-Identifier: GPL-2.0 */
-#ifndef BSG_H
-#define BSG_H
+#ifndef _LINUX_BSG_H
+#define _LINUX_BSG_H
 
 #include <uapi/linux/bsg.h>
 
+struct request;
+
+#ifdef CONFIG_BLK_DEV_BSG
+struct bsg_ops {
+	int	(*check_proto)(struct sg_io_v4 *hdr);
+	int	(*fill_hdr)(struct request *rq, struct sg_io_v4 *hdr,
+				fmode_t mode);
+	int	(*complete_rq)(struct request *rq, struct sg_io_v4 *hdr);
+	void	(*free_rq)(struct request *rq);
+};
 
-#if defined(CONFIG_BLK_DEV_BSG)
 struct bsg_class_device {
 	struct device *class_dev;
 	struct device *parent;
 	int minor;
 	struct request_queue *queue;
 	struct kref ref;
+	const struct bsg_ops *ops;
 	void (*release)(struct device *);
 };
 
-extern int bsg_register_queue(struct request_queue *q,
-			      struct device *parent, const char *name,
-			      void (*release)(struct device *));
-extern void bsg_unregister_queue(struct request_queue *);
+int bsg_register_queue(struct request_queue *q, struct device *parent,
+		const char *name, const struct bsg_ops *ops,
+		void (*release)(struct device *));
+int bsg_scsi_register_queue(struct request_queue *q, struct device *parent);
+void bsg_unregister_queue(struct request_queue *q);
 #else
-static inline int bsg_register_queue(struct request_queue *q,
-				     struct device *parent, const char *name,
-				     void (*release)(struct device *))
+static inline int bsg_scsi_register_queue(struct request_queue *q,
+		struct device *parent)
 {
 	return 0;
 }
 static inline void bsg_unregister_queue(struct request_queue *q)
 {
 }
-#endif
-
-#endif
+#endif /* CONFIG_BLK_DEV_BSG */
+#endif /* _LINUX_BSG_H */