scsi: don't use disk->private_data to find the scsi_driver

Requiring every ULP to have the scsi_drive as first member of the
private data is rather fragile and not necessary anyway.  Just use
the driver hanging off the SCSI device instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220308055200.735835-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Christoph Hellwig

drivers/scsi/sd.c

@@ -3515,7 +3515,6 @@ static int sd_probe(struct device *dev)
 	}
 
 	sdkp->device = sdp;
-	sdkp->driver = &sd_template;
 	sdkp->disk = gd;
 	sdkp->index = index;
 	sdkp->max_retries = SD_MAX_RETRIES;
@@ -3548,7 +3547,7 @@ static int sd_probe(struct device *dev)
 	gd->minors = SD_MINORS;
 
 	gd->fops = &sd_fops;
-	gd->private_data = &sdkp->driver;
+	gd->private_data = sdkp;
 
 	/* defaults, until the device tells us otherwise */
 	sdp->sector_size = 512;

drivers/scsi/sd.h

@@ -68,7 +68,6 @@ enum {
 };
 
 struct scsi_disk {
-	struct scsi_driver *driver;	/* always &sd_template */
 	struct scsi_device *device;
 	struct device	dev;
 	struct gendisk	*disk;
@@ -131,7 +130,7 @@ struct scsi_disk {
 
 static inline struct scsi_disk *scsi_disk(struct gendisk *disk)
 {
-	return container_of(disk->private_data, struct scsi_disk, driver);
+	return disk->private_data;
 }
 
 #define sd_printk(prefix, sdsk, fmt, a...)				\

drivers/scsi/sr.c

@@ -147,7 +147,7 @@ static void sr_kref_release(struct kref *kref);
 
 static inline struct scsi_cd *scsi_cd(struct gendisk *disk)
 {
-	return container_of(disk->private_data, struct scsi_cd, driver);
+	return disk->private_data;
 }
 
 static int sr_runtime_suspend(struct device *dev)
@@ -692,7 +692,6 @@ static int sr_probe(struct device *dev)
 
 	cd->device = sdev;
 	cd->disk = disk;
-	cd->driver = &sr_template;
 	cd->capacity = 0x1fffff;
 	cd->device->changed = 1;	/* force recheck CD type */
 	cd->media_present = 1;
@@ -713,7 +712,7 @@ static int sr_probe(struct device *dev)
 	sr_vendor_init(cd);
 
 	set_capacity(disk, cd->capacity);
-	disk->private_data = &cd->driver;
+	disk->private_data = cd;
 
 	if (register_cdrom(disk, &cd->cdi))
 		goto fail_minor;

drivers/scsi/sr.h

@@ -32,7 +32,6 @@ struct scsi_device;
 
 
 typedef struct scsi_cd {
-	struct scsi_driver *driver;
 	unsigned capacity;	/* size in blocks                       */
 	struct scsi_device *device;
 	unsigned int vendor;	/* vendor code, see sr_vendor.c         */

drivers/scsi/st.c

@@ -4276,7 +4276,6 @@ static int st_probe(struct device *dev)
 		goto out_buffer_free;
 	}
 	kref_init(&tpnt->kref);
-	tpnt->driver = &st_template;
 
 	tpnt->device = SDp;
 	if (SDp->scsi_level <= 2)

drivers/scsi/st.h

@@ -117,7 +117,6 @@ struct scsi_tape_stats {
 
 /* The tape drive descriptor */
 struct scsi_tape {
-	struct scsi_driver *driver;
 	struct scsi_device *device;
 	struct mutex lock;	/* For serialization */
 	struct completion wait;	/* For SCSI commands */

include/scsi/scsi_cmnd.h

@@ -13,7 +13,6 @@
 #include <scsi/scsi_request.h>
 
 struct Scsi_Host;
-struct scsi_driver;
 
 /*
  * MAX_COMMAND_SIZE is:
@@ -159,14 +158,6 @@ static inline void *scsi_cmd_priv(struct scsi_cmnd *cmd)
 	return cmd + 1;
 }
 
-/* make sure not to use it with passthrough commands */
-static inline struct scsi_driver *scsi_cmd_to_driver(struct scsi_cmnd *cmd)
-{
-	struct request *rq = scsi_cmd_to_rq(cmd);
-
-	return *(struct scsi_driver **)rq->q->disk->private_data;
-}
-
 void scsi_done(struct scsi_cmnd *cmd);
 
 extern void scsi_finish_command(struct scsi_cmnd *cmd);

include/scsi/scsi_driver.h

@@ -4,11 +4,10 @@
 
 #include <linux/blk_types.h>
 #include <linux/device.h>
+#include <scsi/scsi_cmnd.h>
 
 struct module;
 struct request;
-struct scsi_cmnd;
-struct scsi_device;
 
 struct scsi_driver {
 	struct device_driver	gendrv;
@@ -31,4 +30,10 @@ extern int scsi_register_interface(struct class_interface *);
 #define scsi_unregister_interface(intf) \
 	class_interface_unregister(intf)
 
+/* make sure not to use it with passthrough commands */
+static inline struct scsi_driver *scsi_cmd_to_driver(struct scsi_cmnd *cmd)
+{
+	return to_scsi_driver(cmd->device->sdev_gendev.driver);
+}
+
 #endif /* _SCSI_SCSI_DRIVER_H */