[SCSI] hpsa: allow user to disable accelerated i/o path

Allow SSD Smart Path for a controller to be disabled by
the user, regardless of settings in controller firmware
or array configuration.

To disable: echo 0 > /sys/class/scsi_host/host<id>/acciopath_status
To re-enable: echo 1 > /sys/class/scsi_host/host<id>/acciopath_status
To check state: cat /sys/class/scsi_host/host<id>/acciopath_status

Signed-off-by: Scott Teel <[e-mail]>
Signed-off-by: Stephen M. Cameron <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

Documentation/ABI/testing/sysfs-class-scsi_host

···
 		guaranteed.  The 'isci_id' attribute unambiguously identifies
 		the controller index: '0' for the first controller,
 		'1' for the second.
+
+What:		/sys/class/scsi_host/hostX/acciopath_status
+Date:		November 2013
+Contact:	Stephen M. Cameron <[e-mail]>
+Description:	This file contains the current status of the "SSD Smart Path"
+		feature of HP Smart Array RAID controllers using the hpsa
+		driver.  SSD Smart Path, when enabled permits the driver to
+		send i/o requests directly to physical devices that are part
+		of a logical drive, bypassing the controllers firmware RAID
+		stack for a performance advantage when possible.  A value of
+		'1' indicates the feature is enabled, and the controller may
+		use the direct i/o path to physical devices.  A value of zero
+		means the feature is disabled and the controller may not use
+		the direct i/o path to physical devices.  This setting is
+		controller wide, affecting all configured logical drives on the
+		controller.  This file is readable and writable.

drivers/scsi/hpsa.c

···
 	return 1;
 }
 
+static ssize_t host_store_hp_ssd_smart_path_status(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t count)
+{
+	int status, len;
+	struct ctlr_info *h;
+	struct Scsi_Host *shost = class_to_shost(dev);
+	char tmpbuf[10];
+
+	if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
+		return -EACCES;
+	len = count > sizeof(tmpbuf) - 1 ? sizeof(tmpbuf) - 1 : count;
+	strncpy(tmpbuf, buf, len);
+	tmpbuf[len] = '\0';
+	if (sscanf(tmpbuf, "%d", &status) != 1)
+		return -EINVAL;
+	h = shost_to_hba(shost);
+	h->acciopath_status = !!status;
+	dev_warn(&h->pdev->dev,
+		"hpsa: HP SSD Smart Path %s via sysfs update.\n",
+		h->acciopath_status ? "enabled" : "disabled");
+	return count;
+}
+
 static ssize_t host_store_rescan(struct device *dev,
 				 struct device_attribute *attr,
 				 const char *buf, size_t count)
···
 	return snprintf(buf, 20, "%s\n",
 		h->transMethod & CFGTBL_Trans_Performant ?
 			"performant" : "simple");
+}
+
+static ssize_t host_show_hp_ssd_smart_path_status(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct ctlr_info *h;
+	struct Scsi_Host *shost = class_to_shost(dev);
+
+	h = shost_to_hba(shost);
+	return snprintf(buf, 30, "HP SSD Smart Path %s\n",
+		(h->acciopath_status == 1) ?  "enabled" : "disabled");
 }
 
 /* List of controllers which cannot be hard reset on kexec with reset_devices */
···
 static DEVICE_ATTR(rescan, S_IWUSR, NULL, host_store_rescan);
 static DEVICE_ATTR(hp_ssd_smart_path_enabled, S_IRUGO,
 			host_show_hp_ssd_smart_path_enabled, NULL);
+static DEVICE_ATTR(hp_ssd_smart_path_status, S_IWUSR|S_IRUGO|S_IROTH,
+		host_show_hp_ssd_smart_path_status,
+		host_store_hp_ssd_smart_path_status);
 static DEVICE_ATTR(firmware_revision, S_IRUGO,
 	host_show_firmware_revision, NULL);
 static DEVICE_ATTR(commands_outstanding, S_IRUGO,
···
 	&dev_attr_commands_outstanding,
 	&dev_attr_transport_mode,
 	&dev_attr_resettable,
+	&dev_attr_hp_ssd_smart_path_status,
 	NULL,
 };
 
···
 	 * Retries always go down the normal I/O path.
 	 */
 	if (likely(cmd->retries == 0 &&
-		cmd->request->cmd_type == REQ_TYPE_FS)) {
+		cmd->request->cmd_type == REQ_TYPE_FS &&
+		h->acciopath_status)) {
 		if (dev->offload_enabled) {
 			rc = hpsa_scsi_ioaccel_raid_map(h, c);
 			if (rc == 0)
···
 
 		goto reinit_after_soft_reset;
 	}
+
+	/* Enable Accelerated IO path at driver layer */
+	h->acciopath_status = 1;
 
 	/* Turn the interrupts on so we can service requests */
 	h->access.set_intr_mask(h, HPSA_INTR_ON);

drivers/scsi/hpsa.h

···
 #define HPSATMF_LOG_QRY_TSET    (1 << 24)
 #define HPSATMF_LOG_QRY_ASYNC   (1 << 25)
 	u32 events;
+	int	acciopath_status;
 };
 #define HPSA_ABORT_MSG 0
 #define HPSA_DEVICE_RESET_MSG 1