scsi: core: Put hot fields of scsi_host_template in one cacheline

The following three fields of scsi_host_template are referenced in the SCSI
I/O submission hot path. Put them together in one cacheline:

 - cmd_size

 - queuecommand

 - commit_rqs

Link: https://lore.kernel.org/r/20210122023317.687987-10-ming.lei@redhat.com
Cc: Omar Sandoval <osandov@fb.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Tested-by: Sumanesh Samanta <sumanesh.samanta@broadcom.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

include/scsi/scsi_host.h

@@ -30,40 +30,15 @@ struct scsi_transport_template;
 #define MODE_TARGET 0x02
 
 struct scsi_host_template {
-	struct module *module;
-	const char *name;
-
 	/*
-	 * The info function will return whatever useful information the
-	 * developer sees fit.  If not provided, then the name field will
-	 * be used instead.
-	 *
-	 * Status: OPTIONAL
+	 * Put fields referenced in IO submission path together in
+	 * same cacheline
 	 */
-	const char *(* info)(struct Scsi_Host *);
 
 	/*
-	 * Ioctl interface
-	 *
-	 * Status: OPTIONAL
-	 */
-	int (*ioctl)(struct scsi_device *dev, unsigned int cmd,
-		     void __user *arg);
-
-
-#ifdef CONFIG_COMPAT
-	/* 
-	 * Compat handler. Handle 32bit ABI.
-	 * When unknown ioctl is passed return -ENOIOCTLCMD.
-	 *
-	 * Status: OPTIONAL
+	 * Additional per-command data allocated for the driver.
 	 */
-	int (*compat_ioctl)(struct scsi_device *dev, unsigned int cmd,
-			    void __user *arg);
-#endif
-
-	int (*init_cmd_priv)(struct Scsi_Host *shost, struct scsi_cmnd *cmd);
-	int (*exit_cmd_priv)(struct Scsi_Host *shost, struct scsi_cmnd *cmd);
+	unsigned int cmd_size;
 
 	/*
 	 * The queuecommand function is used to queue up a scsi
@@ -111,6 +86,41 @@ struct scsi_host_template {
 	 */
 	void (*commit_rqs)(struct Scsi_Host *, u16);
 
+	struct module *module;
+	const char *name;
+
+	/*
+	 * The info function will return whatever useful information the
+	 * developer sees fit.  If not provided, then the name field will
+	 * be used instead.
+	 *
+	 * Status: OPTIONAL
+	 */
+	const char *(*info)(struct Scsi_Host *);
+
+	/*
+	 * Ioctl interface
+	 *
+	 * Status: OPTIONAL
+	 */
+	int (*ioctl)(struct scsi_device *dev, unsigned int cmd,
+		     void __user *arg);
+
+
+#ifdef CONFIG_COMPAT
+	/*
+	 * Compat handler. Handle 32bit ABI.
+	 * When unknown ioctl is passed return -ENOIOCTLCMD.
+	 *
+	 * Status: OPTIONAL
+	 */
+	int (*compat_ioctl)(struct scsi_device *dev, unsigned int cmd,
+			    void __user *arg);
+#endif
+
+	int (*init_cmd_priv)(struct Scsi_Host *shost, struct scsi_cmnd *cmd);
+	int (*exit_cmd_priv)(struct Scsi_Host *shost, struct scsi_cmnd *cmd);
+
 	/*
 	 * This is an error handling strategy routine.  You don't need to
 	 * define one of these if you don't want to - there is a default
@@ -484,10 +494,6 @@ struct scsi_host_template {
 	 */
 	u64 vendor_id;
 
-	/*
-	 * Additional per-command data allocated for the driver.
-	 */
-	unsigned int cmd_size;
 	struct scsi_host_cmd_pool *cmd_pool;
 
 	/* Delay for runtime autosuspend */