text: /*
   *  scsi_error.c Copyright (C) 1997 Eric Youngdale
   *
   *  SCSI error/timeout handling
   *      Initial versions: Eric Youngdale.  Based upon conversations with
   *                        Leonard Zubkoff and David Miller at Linux Expo,
   *                        ideas originating from all over the place.
   *
   *	Restructured scsi_unjam_host and associated functions.
   *	September 04, 2002 Mike Anderson (andmike@us.ibm.com)
   *
   *	Forward port of Russell King's (rmk@arm.linux.org.uk) changes and
   *	minor cleanups.
   *	September 30, 2002 Mike Anderson (andmike@us.ibm.com)
   */
  
  #include <linux/module.h>
  #include <linux/sched.h>
  #include <linux/gfp.h>
  #include <linux/timer.h>
  #include <linux/string.h>
  #include <linux/kernel.h>
  #include <linux/freezer.h>
  #include <linux/kthread.h>
  #include <linux/interrupt.h>
  #include <linux/blkdev.h>
  #include <linux/delay.h>
  #include <linux/jiffies.h>
  
  #include <scsi/scsi.h>
  #include <scsi/scsi_cmnd.h>
  #include <scsi/scsi_dbg.h>
  #include <scsi/scsi_device.h>
  #include <scsi/scsi_driver.h>
  #include <scsi/scsi_eh.h>
  #include <scsi/scsi_common.h>
  #include <scsi/scsi_transport.h>
  #include <scsi/scsi_host.h>
  #include <scsi/scsi_ioctl.h>
  #include <scsi/scsi_dh.h>
  #include <scsi/sg.h>
  
  #include "scsi_priv.h"
  #include "scsi_logging.h"
  #include "scsi_transport_api.h"
  
  #include <trace/events/scsi.h>
  
  static void scsi_eh_done(struct scsi_cmnd *scmd);
  
  /*
   * These should *probably* be handled by the host itself.
   * Since it is allowed to sleep, it probably should.
   */
  #define BUS_RESET_SETTLE_TIME   (10)
  #define HOST_RESET_SETTLE_TIME  (10)
  
  static int scsi_eh_try_stu(struct scsi_cmnd *scmd);
  static int scsi_try_to_abort_cmd(struct scsi_host_template *,
  				 struct scsi_cmnd *);
  
  /* called with shost->host_lock held */
  void scsi_eh_wakeup(struct Scsi_Host *shost)
  {
  	if (atomic_read(&shost->host_busy) == shost->host_failed) {
  		trace_scsi_eh_wakeup(shost);
  		wake_up_process(shost->ehandler);
  		SCSI_LOG_ERROR_RECOVERY(5, shost_printk(KERN_INFO, shost,
  			"Waking error handler thread\n"));
  	}
  }
  
  /**
   * scsi_schedule_eh - schedule EH for SCSI host
   * @shost:	SCSI host to invoke error handling on.
   *
   * Schedule SCSI EH without scmd.
   */
  void scsi_schedule_eh(struct Scsi_Host *shost)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(shost->host_lock, flags);
  
  	if (scsi_host_set_state(shost, SHOST_RECOVERY) == 0 ||
  	    scsi_host_set_state(shost, SHOST_CANCEL_RECOVERY) == 0) {
  		shost->host_eh_scheduled++;
  		scsi_eh_wakeup(shost);
  	}
  
  	spin_unlock_irqrestore(shost->host_lock, flags);
  }
  EXPORT_SYMBOL_GPL(scsi_schedule_eh);
  
  static int scsi_host_eh_past_deadline(struct Scsi_Host *shost)
  {
  	if (!shost->last_reset || shost->eh_deadline == -1)
  		return 0;
  
  	/*
  	 * 32bit accesses are guaranteed to be atomic
  	 * (on all supported architectures), so instead
  	 * of using a spinlock we can as well double check
  	 * if eh_deadline has been set to 'off' during the
  	 * time_before call.
  	 */
  	if (time_before(jiffies, shost->last_reset + shost->eh_deadline) &&
  	    shost->eh_deadline > -1)
  		return 0;
  
  	return 1;
  }
  
  /**
   * scmd_eh_abort_handler - Handle command aborts
   * @work:	command to be aborted.
   */
  void
  scmd_eh_abort_handler(struct work_struct *work)
  {
  	struct scsi_cmnd *scmd =
  		container_of(work, struct scsi_cmnd, abort_work.work);
  	struct scsi_device *sdev = scmd->device;
  	int rtn;
  
  	if (scsi_host_eh_past_deadline(sdev->host)) {
  		SCSI_LOG_ERROR_RECOVERY(3,
  			scmd_printk(KERN_INFO, scmd,
  				    "eh timeout, not aborting\n"));
  	} else {
  		SCSI_LOG_ERROR_RECOVERY(3,
  			scmd_printk(KERN_INFO, scmd,
  				    "aborting command\n"));
  		rtn = scsi_try_to_abort_cmd(sdev->host->hostt, scmd);
  		if (rtn == SUCCESS) {
  			set_host_byte(scmd, DID_TIME_OUT);
  			if (scsi_host_eh_past_deadline(sdev->host)) {
  				SCSI_LOG_ERROR_RECOVERY(3,
  					scmd_printk(KERN_INFO, scmd,
  						    "eh timeout, not retrying "
  						    "aborted command\n"));
  			} else if (!scsi_noretry_cmd(scmd) &&
  			    (++scmd->retries <= scmd->allowed)) {
  				SCSI_LOG_ERROR_RECOVERY(3,
  					scmd_printk(KERN_WARNING, scmd,
  						    "retry aborted command\n"));
  				scsi_queue_insert(scmd, SCSI_MLQUEUE_EH_RETRY);
  				return;
  			} else {
  				SCSI_LOG_ERROR_RECOVERY(3,
  					scmd_printk(KERN_WARNING, scmd,
  						    "finish aborted command\n"));
  				scsi_finish_command(scmd);
  				return;
  			}
  		} else {
  			SCSI_LOG_ERROR_RECOVERY(3,
  				scmd_printk(KERN_INFO, scmd,
  					    "cmd abort %s\n",
  					    (rtn == FAST_IO_FAIL) ?
  					    "not send" : "failed"));
  		}
  	}
  
  	if (!scsi_eh_scmd_add(scmd, 0)) {
  		SCSI_LOG_ERROR_RECOVERY(3,
  			scmd_printk(KERN_WARNING, scmd,
  				    "terminate aborted command\n"));
  		set_host_byte(scmd, DID_TIME_OUT);
  		scsi_finish_command(scmd);
  	}
  }
  
  /**
   * scsi_abort_command - schedule a command abort
   * @scmd:	scmd to abort.
   *
   * We only need to abort commands after a command timeout
   */
  static int
  scsi_abort_command(struct scsi_cmnd *scmd)
  {
  	struct scsi_device *sdev = scmd->device;
  	struct Scsi_Host *shost = sdev->host;
  	unsigned long flags;
  
  	if (scmd->eh_eflags & SCSI_EH_ABORT_SCHEDULED) {
  		/*
  		 * Retry after abort failed, escalate to next level.
  		 */
  		scmd->eh_eflags &= ~SCSI_EH_ABORT_SCHEDULED;
  		SCSI_LOG_ERROR_RECOVERY(3,
  			scmd_printk(KERN_INFO, scmd,
  				    "previous abort failed\n"));
  		BUG_ON(delayed_work_pending(&scmd->abort_work));
  		return FAILED;
  	}
  
  	/*
  	 * Do not try a command abort if
  	 * SCSI EH has already started.
  	 */
  	spin_lock_irqsave(shost->host_lock, flags);
  	if (scsi_host_in_recovery(shost)) {
  		spin_unlock_irqrestore(shost->host_lock, flags);
  		SCSI_LOG_ERROR_RECOVERY(3,
  			scmd_printk(KERN_INFO, scmd,
  				    "not aborting, host in recovery\n"));
  		return FAILED;
  	}
  
  	if (shost->eh_deadline != -1 && !shost->last_reset)
  		shost->last_reset = jiffies;
  	spin_unlock_irqrestore(shost->host_lock, flags);
  
  	scmd->eh_eflags |= SCSI_EH_ABORT_SCHEDULED;
  	SCSI_LOG_ERROR_RECOVERY(3,
  		scmd_printk(KERN_INFO, scmd, "abort scheduled\n"));
  	queue_delayed_work(shost->tmf_work_q, &scmd->abort_work, HZ / 100);
  	return SUCCESS;
  }
  
  /**
   * scsi_eh_scmd_add - add scsi cmd to error handling.
   * @scmd:	scmd to run eh on.
   * @eh_flag:	optional SCSI_EH flag.
   *
   * Return value:
   *	0 on failure.
   */
  int scsi_eh_scmd_add(struct scsi_cmnd *scmd, int eh_flag)
  {
  	struct Scsi_Host *shost = scmd->device->host;
  	unsigned long flags;
  	int ret = 0;
  
  	if (!shost->ehandler)
  		return 0;
  
  	spin_lock_irqsave(shost->host_lock, flags);
  	if (scsi_host_set_state(shost, SHOST_RECOVERY))
  		if (scsi_host_set_state(shost, SHOST_CANCEL_RECOVERY))
  			goto out_unlock;
  
  	if (shost->eh_deadline != -1 && !shost->last_reset)
  		shost->last_reset = jiffies;
  
  	ret = 1;
  	if (scmd->eh_eflags & SCSI_EH_ABORT_SCHEDULED)
  		eh_flag &= ~SCSI_EH_CANCEL_CMD;
  	scmd->eh_eflags |= eh_flag;
  	list_add_tail(&scmd->eh_entry, &shost->eh_cmd_q);
  	shost->host_failed++;
  	scsi_eh_wakeup(shost);
   out_unlock:
  	spin_unlock_irqrestore(shost->host_lock, flags);
  	return ret;
  }
  
  /**
   * scsi_times_out - Timeout function for normal scsi commands.
   * @req:	request that is timing out.
   *
   * Notes:
   *     We do not need to lock this.  There is the potential for a race
   *     only in that the normal completion handling might run, but if the
   *     normal completion function determines that the timer has already
   *     fired, then it mustn't do anything.
   */
  enum blk_eh_timer_return scsi_times_out(struct request *req)
  {
  	struct scsi_cmnd *scmd = req->special;
  	enum blk_eh_timer_return rtn = BLK_EH_NOT_HANDLED;
  	struct Scsi_Host *host = scmd->device->host;
  
  	trace_scsi_dispatch_cmd_timeout(scmd);
  	scsi_log_completion(scmd, TIMEOUT_ERROR);
  
  	if (host->eh_deadline != -1 && !host->last_reset)
  		host->last_reset = jiffies;
  
  	if (host->transportt->eh_timed_out)
  		rtn = host->transportt->eh_timed_out(scmd);
  	else if (host->hostt->eh_timed_out)
  		rtn = host->hostt->eh_timed_out(scmd);
  
  	if (rtn == BLK_EH_NOT_HANDLED) {
  		if (!host->hostt->no_async_abort &&
  		    scsi_abort_command(scmd) == SUCCESS)
  			return BLK_EH_NOT_HANDLED;
  
  		set_host_byte(scmd, DID_TIME_OUT);
  		if (!scsi_eh_scmd_add(scmd, SCSI_EH_CANCEL_CMD))
  			rtn = BLK_EH_HANDLED;
  	}
  
  	return rtn;
  }
  
  /**
   * scsi_block_when_processing_errors - Prevent cmds from being queued.
   * @sdev:	Device on which we are performing recovery.
   *
   * Description:
   *     We block until the host is out of error recovery, and then check to
   *     see whether the host or the device is offline.
   *
   * Return value:
   *     0 when dev was taken offline by error recovery. 1 OK to proceed.
   */
  int scsi_block_when_processing_errors(struct scsi_device *sdev)
  {
  	int online;
  
  	wait_event(sdev->host->host_wait, !scsi_host_in_recovery(sdev->host));
  
  	online = scsi_device_online(sdev);
  
  	SCSI_LOG_ERROR_RECOVERY(5, sdev_printk(KERN_INFO, sdev,
  		"%s: rtn: %d\n", __func__, online));
  
  	return online;
  }
  EXPORT_SYMBOL(scsi_block_when_processing_errors);
  
  #ifdef CONFIG_SCSI_LOGGING
  /**
   * scsi_eh_prt_fail_stats - Log info on failures.
   * @shost:	scsi host being recovered.
   * @work_q:	Queue of scsi cmds to process.
   */
  static inline void scsi_eh_prt_fail_stats(struct Scsi_Host *shost,
  					  struct list_head *work_q)
  {
  	struct scsi_cmnd *scmd;
  	struct scsi_device *sdev;
  	int total_failures = 0;
  	int cmd_failed = 0;
  	int cmd_cancel = 0;
  	int devices_failed = 0;
  
  	shost_for_each_device(sdev, shost) {
  		list_for_each_entry(scmd, work_q, eh_entry) {
  			if (scmd->device == sdev) {
  				++total_failures;
  				if (scmd->eh_eflags & SCSI_EH_CANCEL_CMD)
  					++cmd_cancel;
  				else
  					++cmd_failed;
  			}
  		}
  
  		if (cmd_cancel || cmd_failed) {
  			SCSI_LOG_ERROR_RECOVERY(3,
  				shost_printk(KERN_INFO, shost,
  					    "%s: cmds failed: %d, cancel: %d\n",
  					    __func__, cmd_failed,
  					    cmd_cancel));
  			cmd_cancel = 0;
  			cmd_failed = 0;
  			++devices_failed;
  		}
  	}
  
  	SCSI_LOG_ERROR_RECOVERY(2, shost_printk(KERN_INFO, shost,
  				   "Total of %d commands on %d"
  				   " devices require eh work\n",
  				   total_failures, devices_failed));
  }
  #endif
  
   /**
   * scsi_report_lun_change - Set flag on all *other* devices on the same target
   *                          to indicate that a UNIT ATTENTION is expected.
   * @sdev:	Device reporting the UNIT ATTENTION
   */
  static void scsi_report_lun_change(struct scsi_device *sdev)
  {
  	sdev->sdev_target->expecting_lun_change = 1;
  }
  
  /**
   * scsi_report_sense - Examine scsi sense information and log messages for
   *		       certain conditions, also issue uevents for some of them.
   * @sdev:	Device reporting the sense code
   * @sshdr:	sshdr to be examined
   */
  static void scsi_report_sense(struct scsi_device *sdev,
  			      struct scsi_sense_hdr *sshdr)
  {
  	enum scsi_device_event evt_type = SDEV_EVT_MAXBITS;	/* i.e. none */
  
  	if (sshdr->sense_key == UNIT_ATTENTION) {
  		if (sshdr->asc == 0x3f && sshdr->ascq == 0x03) {
  			evt_type = SDEV_EVT_INQUIRY_CHANGE_REPORTED;
  			sdev_printk(KERN_WARNING, sdev,
  				    "Inquiry data has changed");
  		} else if (sshdr->asc == 0x3f && sshdr->ascq == 0x0e) {
  			evt_type = SDEV_EVT_LUN_CHANGE_REPORTED;
  			scsi_report_lun_change(sdev);
  			sdev_printk(KERN_WARNING, sdev,
  				    "Warning! Received an indication that the "
  				    "LUN assignments on this target have "
  				    "changed. The Linux SCSI layer does not "
  				    "automatically remap LUN assignments.\n");
  		} else if (sshdr->asc == 0x3f)
  			sdev_printk(KERN_WARNING, sdev,
  				    "Warning! Received an indication that the "
  				    "operating parameters on this target have "
  				    "changed. The Linux SCSI layer does not "
  				    "automatically adjust these parameters.\n");
  
  		if (sshdr->asc == 0x38 && sshdr->ascq == 0x07) {
  			evt_type = SDEV_EVT_SOFT_THRESHOLD_REACHED_REPORTED;
  			sdev_printk(KERN_WARNING, sdev,
  				    "Warning! Received an indication that the "
  				    "LUN reached a thin provisioning soft "
  				    "threshold.\n");
  		}
  
  		if (sshdr->asc == 0x2a && sshdr->ascq == 0x01) {
  			evt_type = SDEV_EVT_MODE_PARAMETER_CHANGE_REPORTED;
  			sdev_printk(KERN_WARNING, sdev,
  				    "Mode parameters changed");
  		} else if (sshdr->asc == 0x2a && sshdr->ascq == 0x06) {
  			evt_type = SDEV_EVT_ALUA_STATE_CHANGE_REPORTED;
  			sdev_printk(KERN_WARNING, sdev,
  				    "Asymmetric access state changed");
  		} else if (sshdr->asc == 0x2a && sshdr->ascq == 0x09) {
  			evt_type = SDEV_EVT_CAPACITY_CHANGE_REPORTED;
  			sdev_printk(KERN_WARNING, sdev,
  				    "Capacity data has changed");
  		} else if (sshdr->asc == 0x2a)
  			sdev_printk(KERN_WARNING, sdev,
  				    "Parameters changed");
  	}
  
  	if (evt_type != SDEV_EVT_MAXBITS) {
  		set_bit(evt_type, sdev->pending_events);
  		schedule_work(&sdev->event_work);
  	}
  }
  
  /**
   * scsi_check_sense - Examine scsi cmd sense
   * @scmd:	Cmd to have sense checked.
   *
   * Return value:
   *	SUCCESS or FAILED or NEEDS_RETRY or ADD_TO_MLQUEUE
   *
   * Notes:
   *	When a deferred error is detected the current command has
   *	not been executed and needs retrying.
   */
  static int scsi_check_sense(struct scsi_cmnd *scmd)
  {
  	struct scsi_device *sdev = scmd->device;
  	struct scsi_sense_hdr sshdr;
  
  	if (! scsi_command_normalize_sense(scmd, &sshdr))
  		return FAILED;	/* no valid sense data */
  
  	scsi_report_sense(sdev, &sshdr);
  
  	if (scsi_sense_is_deferred(&sshdr))
  		return NEEDS_RETRY;
  
  	if (sdev->handler && sdev->handler->check_sense) {
  		int rc;
  
  		rc = sdev->handler->check_sense(sdev, &sshdr);
  		if (rc != SCSI_RETURN_NOT_HANDLED)
  			return rc;
  		/* handler does not care. Drop down to default handling */
  	}
  
  	if (scmd->cmnd[0] == TEST_UNIT_READY && scmd->scsi_done != scsi_eh_done)
  		/*
  		 * nasty: for mid-layer issued TURs, we need to return the
  		 * actual sense data without any recovery attempt.  For eh
  		 * issued ones, we need to try to recover and interpret
  		 */
  		return SUCCESS;
  
  	/*
  	 * Previous logic looked for FILEMARK, EOM or ILI which are
  	 * mainly associated with tapes and returned SUCCESS.
  	 */
  	if (sshdr.response_code == 0x70) {
  		/* fixed format */
  		if (scmd->sense_buffer[2] & 0xe0)
  			return SUCCESS;
  	} else {
  		/*
  		 * descriptor format: look for "stream commands sense data
  		 * descriptor" (see SSC-3). Assume single sense data
  		 * descriptor. Ignore ILI from SBC-2 READ LONG and WRITE LONG.
  		 */
  		if ((sshdr.additional_length > 3) &&
  		    (scmd->sense_buffer[8] == 0x4) &&
  		    (scmd->sense_buffer[11] & 0xe0))
  			return SUCCESS;
  	}
  
  	switch (sshdr.sense_key) {
  	case NO_SENSE:
  		return SUCCESS;
  	case RECOVERED_ERROR:
  		return /* soft_error */ SUCCESS;
  
  	case ABORTED_COMMAND:
  		if (sshdr.asc == 0x10) /* DIF */
  			return SUCCESS;
  
  		return NEEDS_RETRY;
  	case NOT_READY:
  	case UNIT_ATTENTION:
  		/*
  		 * if we are expecting a cc/ua because of a bus reset that we
  		 * performed, treat this just as a retry.  otherwise this is
  		 * information that we should pass up to the upper-level driver
  		 * so that we can deal with it there.
  		 */
  		if (scmd->device->expecting_cc_ua) {
  			/*
  			 * Because some device does not queue unit
  			 * attentions correctly, we carefully check
  			 * additional sense code and qualifier so as
  			 * not to squash media change unit attention.
  			 */
  			if (sshdr.asc != 0x28 || sshdr.ascq != 0x00) {
  				scmd->device->expecting_cc_ua = 0;
  				return NEEDS_RETRY;
  			}
  		}
  		/*
  		 * we might also expect a cc/ua if another LUN on the target
  		 * reported a UA with an ASC/ASCQ of 3F 0E -
  		 * REPORTED LUNS DATA HAS CHANGED.
  		 */
  		if (scmd->device->sdev_target->expecting_lun_change &&
  		    sshdr.asc == 0x3f && sshdr.ascq == 0x0e)
  			return NEEDS_RETRY;
  		/*
  		 * if the device is in the process of becoming ready, we
  		 * should retry.
  		 */
  		if ((sshdr.asc == 0x04) && (sshdr.ascq == 0x01))
  			return NEEDS_RETRY;
  		/*
  		 * if the device is not started, we need to wake
  		 * the error handler to start the motor
  		 */
  		if (scmd->device->allow_restart &&
  		    (sshdr.asc == 0x04) && (sshdr.ascq == 0x02))
  			return FAILED;
  		/*
  		 * Pass the UA upwards for a determination in the completion
  		 * functions.
  		 */
  		return SUCCESS;
  
  		/* these are not supported */
  	case DATA_PROTECT:
  		if (sshdr.asc == 0x27 && sshdr.ascq == 0x07) {
  			/* Thin provisioning hard threshold reached */
  			set_host_byte(scmd, DID_ALLOC_FAILURE);
  			return SUCCESS;
  		}
  	case COPY_ABORTED:
  	case VOLUME_OVERFLOW:
  	case MISCOMPARE:
  	case BLANK_CHECK:
  		set_host_byte(scmd, DID_TARGET_FAILURE);
  		return SUCCESS;
  
  	case MEDIUM_ERROR:
  		if (sshdr.asc == 0x11 || /* UNRECOVERED READ ERR */
  		    sshdr.asc == 0x13 || /* AMNF DATA FIELD */
  		    sshdr.asc == 0x14) { /* RECORD NOT FOUND */
  			set_host_byte(scmd, DID_MEDIUM_ERROR);
  			return SUCCESS;
  		}
  		return NEEDS_RETRY;
  
  	case HARDWARE_ERROR:
  		if (scmd->device->retry_hwerror)
  			return ADD_TO_MLQUEUE;
  		else
  			set_host_byte(scmd, DID_TARGET_FAILURE);
  
  	case ILLEGAL_REQUEST:
  		if (sshdr.asc == 0x20 || /* Invalid command operation code */
  		    sshdr.asc == 0x21 || /* Logical block address out of range */
  		    sshdr.asc == 0x24 || /* Invalid field in cdb */
  		    sshdr.asc == 0x26) { /* Parameter value invalid */
  			set_host_byte(scmd, DID_TARGET_FAILURE);
  		}
  		return SUCCESS;
  
  	default:
  		return SUCCESS;
  	}
  }
  
  static void scsi_handle_queue_ramp_up(struct scsi_device *sdev)
  {
  	struct scsi_host_template *sht = sdev->host->hostt;
  	struct scsi_device *tmp_sdev;
  
  	if (!sht->track_queue_depth ||
  	    sdev->queue_depth >= sdev->max_queue_depth)
  		return;
  
  	if (time_before(jiffies,
  	    sdev->last_queue_ramp_up + sdev->queue_ramp_up_period))
  		return;
  
  	if (time_before(jiffies,
  	    sdev->last_queue_full_time + sdev->queue_ramp_up_period))
  		return;
  
  	/*
  	 * Walk all devices of a target and do
  	 * ramp up on them.
  	 */
  	shost_for_each_device(tmp_sdev, sdev->host) {
  		if (tmp_sdev->channel != sdev->channel ||
  		    tmp_sdev->id != sdev->id ||
  		    tmp_sdev->queue_depth == sdev->max_queue_depth)
  			continue;
  
  		scsi_change_queue_depth(tmp_sdev, tmp_sdev->queue_depth + 1);
  		sdev->last_queue_ramp_up = jiffies;
  	}
  }
  
  static void scsi_handle_queue_full(struct scsi_device *sdev)
  {
  	struct scsi_host_template *sht = sdev->host->hostt;
  	struct scsi_device *tmp_sdev;
  
  	if (!sht->track_queue_depth)
  		return;
  
  	shost_for_each_device(tmp_sdev, sdev->host) {
  		if (tmp_sdev->channel != sdev->channel ||
  		    tmp_sdev->id != sdev->id)
  			continue;
  		/*
  		 * We do not know the number of commands that were at
  		 * the device when we got the queue full so we start
  		 * from the highest possible value and work our way down.
  		 */
  		scsi_track_queue_full(tmp_sdev, tmp_sdev->queue_depth - 1);
  	}
  }
  
  /**
   * scsi_eh_completed_normally - Disposition a eh cmd on return from LLD.
   * @scmd:	SCSI cmd to examine.
   *
   * Notes:
   *    This is *only* called when we are examining the status of commands
   *    queued during error recovery.  the main difference here is that we
   *    don't allow for the possibility of retries here, and we are a lot
   *    more restrictive about what we consider acceptable.
   */
  static int scsi_eh_completed_normally(struct scsi_cmnd *scmd)
  {
  	/*
  	 * first check the host byte, to see if there is anything in there
  	 * that would indicate what we need to do.
  	 */
  	if (host_byte(scmd->result) == DID_RESET) {
  		/*
  		 * rats.  we are already in the error handler, so we now
  		 * get to try and figure out what to do next.  if the sense
  		 * is valid, we have a pretty good idea of what to do.
  		 * if not, we mark it as FAILED.
  		 */
  		return scsi_check_sense(scmd);
  	}
  	if (host_byte(scmd->result) != DID_OK)
  		return FAILED;
  
  	/*
  	 * next, check the message byte.
  	 */
  	if (msg_byte(scmd->result) != COMMAND_COMPLETE)
  		return FAILED;
  
  	/*
  	 * now, check the status byte to see if this indicates
  	 * anything special.
  	 */
  	switch (status_byte(scmd->result)) {
  	case GOOD:
  		scsi_handle_queue_ramp_up(scmd->device);
  	case COMMAND_TERMINATED:
  		return SUCCESS;
  	case CHECK_CONDITION:
  		return scsi_check_sense(scmd);
  	case CONDITION_GOOD:
  	case INTERMEDIATE_GOOD:
  	case INTERMEDIATE_C_GOOD:
  		/*
  		 * who knows?  FIXME(eric)
  		 */
  		return SUCCESS;
  	case RESERVATION_CONFLICT:
  		if (scmd->cmnd[0] == TEST_UNIT_READY)
  			/* it is a success, we probed the device and
  			 * found it */
  			return SUCCESS;
  		/* otherwise, we failed to send the command */
  		return FAILED;
  	case QUEUE_FULL:
  		scsi_handle_queue_full(scmd->device);
  		/* fall through */
  	case BUSY:
  		return NEEDS_RETRY;
  	default:
  		return FAILED;
  	}
  	return FAILED;
  }
  
  /**
   * scsi_eh_done - Completion function for error handling.
   * @scmd:	Cmd that is done.
   */
  static void scsi_eh_done(struct scsi_cmnd *scmd)
  {
  	struct completion *eh_action;
  
  	SCSI_LOG_ERROR_RECOVERY(3, scmd_printk(KERN_INFO, scmd,
  			"%s result: %x\n", __func__, scmd->result));
  
  	eh_action = scmd->device->host->eh_action;
  	if (eh_action)
  		complete(eh_action);
  }
  
  /**
   * scsi_try_host_reset - ask host adapter to reset itself
   * @scmd:	SCSI cmd to send host reset.
   */
  static int scsi_try_host_reset(struct scsi_cmnd *scmd)
  {
  	unsigned long flags;
  	int rtn;
  	struct Scsi_Host *host = scmd->device->host;
  	struct scsi_host_template *hostt = host->hostt;
  
  	SCSI_LOG_ERROR_RECOVERY(3,
  		shost_printk(KERN_INFO, host, "Snd Host RST\n"));
  
  	if (!hostt->eh_host_reset_handler)
  		return FAILED;
  
  	rtn = hostt->eh_host_reset_handler(scmd);
  
  	if (rtn == SUCCESS) {
  		if (!hostt->skip_settle_delay)
  			ssleep(HOST_RESET_SETTLE_TIME);
  		spin_lock_irqsave(host->host_lock, flags);
  		scsi_report_bus_reset(host, scmd_channel(scmd));
  		spin_unlock_irqrestore(host->host_lock, flags);
  	}
  
  	return rtn;
  }
  
  /**
   * scsi_try_bus_reset - ask host to perform a bus reset
   * @scmd:	SCSI cmd to send bus reset.
   */
  static int scsi_try_bus_reset(struct scsi_cmnd *scmd)
  {
  	unsigned long flags;
  	int rtn;
  	struct Scsi_Host *host = scmd->device->host;
  	struct scsi_host_template *hostt = host->hostt;
  
  	SCSI_LOG_ERROR_RECOVERY(3, scmd_printk(KERN_INFO, scmd,
  		"%s: Snd Bus RST\n", __func__));
  
  	if (!hostt->eh_bus_reset_handler)
  		return FAILED;
  
  	rtn = hostt->eh_bus_reset_handler(scmd);
  
  	if (rtn == SUCCESS) {
  		if (!hostt->skip_settle_delay)
  			ssleep(BUS_RESET_SETTLE_TIME);
  		spin_lock_irqsave(host->host_lock, flags);
  		scsi_report_bus_reset(host, scmd_channel(scmd));
  		spin_unlock_irqrestore(host->host_lock, flags);
  	}
  
  	return rtn;
  }
  
  static void __scsi_report_device_reset(struct scsi_device *sdev, void *data)
  {
  	sdev->was_reset = 1;
  	sdev->expecting_cc_ua = 1;
  }
  
  /**
   * scsi_try_target_reset - Ask host to perform a target reset
   * @scmd:	SCSI cmd used to send a target reset
   *
   * Notes:
   *    There is no timeout for this operation.  if this operation is
   *    unreliable for a given host, then the host itself needs to put a
   *    timer on it, and set the host back to a consistent state prior to
   *    returning.
   */
  static int scsi_try_target_reset(struct scsi_cmnd *scmd)
  {
  	unsigned long flags;
  	int rtn;
  	struct Scsi_Host *host = scmd->device->host;
  	struct scsi_host_template *hostt = host->hostt;
  
  	if (!hostt->eh_target_reset_handler)
  		return FAILED;
  
  	rtn = hostt->eh_target_reset_handler(scmd);
  	if (rtn == SUCCESS) {
  		spin_lock_irqsave(host->host_lock, flags);
  		__starget_for_each_device(scsi_target(scmd->device), NULL,
  					  __scsi_report_device_reset);
  		spin_unlock_irqrestore(host->host_lock, flags);
  	}
  
  	return rtn;
  }
  
  /**
   * scsi_try_bus_device_reset - Ask host to perform a BDR on a dev
   * @scmd:	SCSI cmd used to send BDR
   *
   * Notes:
   *    There is no timeout for this operation.  if this operation is
   *    unreliable for a given host, then the host itself needs to put a
   *    timer on it, and set the host back to a consistent state prior to
   *    returning.
   */
  static int scsi_try_bus_device_reset(struct scsi_cmnd *scmd)
  {
  	int rtn;
  	struct scsi_host_template *hostt = scmd->device->host->hostt;
  
  	if (!hostt->eh_device_reset_handler)
  		return FAILED;
  
  	rtn = hostt->eh_device_reset_handler(scmd);
  	if (rtn == SUCCESS)
  		__scsi_report_device_reset(scmd->device, NULL);
  	return rtn;
  }
  
  /**
   * scsi_try_to_abort_cmd - Ask host to abort a SCSI command
   * @hostt:	SCSI driver host template
   * @scmd:	SCSI cmd used to send a target reset
   *
   * Return value:
   *	SUCCESS, FAILED, or FAST_IO_FAIL
   *
   * Notes:
   *    SUCCESS does not necessarily indicate that the command
   *    has been aborted; it only indicates that the LLDDs
   *    has cleared all references to that command.
   *    LLDDs should return FAILED only if an abort was required
   *    but could not be executed. LLDDs should return FAST_IO_FAIL
   *    if the device is temporarily unavailable (eg due to a
   *    link down on FibreChannel)
   */
  static int scsi_try_to_abort_cmd(struct scsi_host_template *hostt,
  				 struct scsi_cmnd *scmd)
  {
  	if (!hostt->eh_abort_handler)
  		return FAILED;
  
  	return hostt->eh_abort_handler(scmd);
  }
  
  static void scsi_abort_eh_cmnd(struct scsi_cmnd *scmd)
  {
  	if (scsi_try_to_abort_cmd(scmd->device->host->hostt, scmd) != SUCCESS)
  		if (scsi_try_bus_device_reset(scmd) != SUCCESS)
  			if (scsi_try_target_reset(scmd) != SUCCESS)
  				if (scsi_try_bus_reset(scmd) != SUCCESS)
  					scsi_try_host_reset(scmd);
  }
  
  /**
   * scsi_eh_prep_cmnd  - Save a scsi command info as part of error recovery
   * @scmd:       SCSI command structure to hijack
   * @ses:        structure to save restore information
   * @cmnd:       CDB to send. Can be NULL if no new cmnd is needed
   * @cmnd_size:  size in bytes of @cmnd (must be <= BLK_MAX_CDB)
   * @sense_bytes: size of sense data to copy. or 0 (if != 0 @cmnd is ignored)
   *
   * This function is used to save a scsi command information before re-execution
   * as part of the error recovery process.  If @sense_bytes is 0 the command
   * sent must be one that does not transfer any data.  If @sense_bytes != 0
   * @cmnd is ignored and this functions sets up a REQUEST_SENSE command
   * and cmnd buffers to read @sense_bytes into @scmd->sense_buffer.
   */
  void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd, struct scsi_eh_save *ses,
  			unsigned char *cmnd, int cmnd_size, unsigned sense_bytes)
  {
  	struct scsi_device *sdev = scmd->device;
  
  	/*
  	 * We need saved copies of a number of fields - this is because
  	 * error handling may need to overwrite these with different values
  	 * to run different commands, and once error handling is complete,
  	 * we will need to restore these values prior to running the actual
  	 * command.
  	 */
  	ses->cmd_len = scmd->cmd_len;
  	ses->cmnd = scmd->cmnd;
  	ses->data_direction = scmd->sc_data_direction;
  	ses->sdb = scmd->sdb;
  	ses->next_rq = scmd->request->next_rq;
  	ses->result = scmd->result;
  	ses->underflow = scmd->underflow;
  	ses->prot_op = scmd->prot_op;
  
  	scmd->prot_op = SCSI_PROT_NORMAL;
  	scmd->eh_eflags = 0;
  	scmd->cmnd = ses->eh_cmnd;
  	memset(scmd->cmnd, 0, BLK_MAX_CDB);
  	memset(&scmd->sdb, 0, sizeof(scmd->sdb));
  	scmd->request->next_rq = NULL;
  	scmd->result = 0;
  
  	if (sense_bytes) {
  		scmd->sdb.length = min_t(unsigned, SCSI_SENSE_BUFFERSIZE,
  					 sense_bytes);
  		sg_init_one(&ses->sense_sgl, scmd->sense_buffer,
  			    scmd->sdb.length);
  		scmd->sdb.table.sgl = &ses->sense_sgl;
  		scmd->sc_data_direction = DMA_FROM_DEVICE;
  		scmd->sdb.table.nents = scmd->sdb.table.orig_nents = 1;
  		scmd->cmnd[0] = REQUEST_SENSE;
  		scmd->cmnd[4] = scmd->sdb.length;
  		scmd->cmd_len = COMMAND_SIZE(scmd->cmnd[0]);
  	} else {
  		scmd->sc_data_direction = DMA_NONE;
  		if (cmnd) {
  			BUG_ON(cmnd_size > BLK_MAX_CDB);
  			memcpy(scmd->cmnd, cmnd, cmnd_size);
  			scmd->cmd_len = COMMAND_SIZE(scmd->cmnd[0]);
  		}
  	}
  
  	scmd->underflow = 0;
  
  	if (sdev->scsi_level <= SCSI_2 && sdev->scsi_level != SCSI_UNKNOWN)
  		scmd->cmnd[1] = (scmd->cmnd[1] & 0x1f) |
  			(sdev->lun << 5 & 0xe0);
  
  	/*
  	 * Zero the sense buffer.  The scsi spec mandates that any
  	 * untransferred sense data should be interpreted as being zero.
  	 */
  	memset(scmd->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE);
  }
  EXPORT_SYMBOL(scsi_eh_prep_cmnd);
  
  /**
   * scsi_eh_restore_cmnd  - Restore a scsi command info as part of error recovery
   * @scmd:       SCSI command structure to restore
   * @ses:        saved information from a coresponding call to scsi_eh_prep_cmnd
   *
   * Undo any damage done by above scsi_eh_prep_cmnd().
   */
  void scsi_eh_restore_cmnd(struct scsi_cmnd* scmd, struct scsi_eh_save *ses)
  {
  	/*
  	 * Restore original data
  	 */
  	scmd->cmd_len = ses->cmd_len;
  	scmd->cmnd = ses->cmnd;
  	scmd->sc_data_direction = ses->data_direction;
  	scmd->sdb = ses->sdb;
  	scmd->request->next_rq = ses->next_rq;
  	scmd->result = ses->result;
  	scmd->underflow = ses->underflow;
  	scmd->prot_op = ses->prot_op;
  }
  EXPORT_SYMBOL(scsi_eh_restore_cmnd);
  
  /**
   * scsi_send_eh_cmnd  - submit a scsi command as part of error recovery
   * @scmd:       SCSI command structure to hijack
   * @cmnd:       CDB to send
   * @cmnd_size:  size in bytes of @cmnd
   * @timeout:    timeout for this request
   * @sense_bytes: size of sense data to copy or 0
   *
   * This function is used to send a scsi command down to a target device
   * as part of the error recovery process. See also scsi_eh_prep_cmnd() above.
   *
   * Return value:
   *    SUCCESS or FAILED or NEEDS_RETRY
   */
  static int scsi_send_eh_cmnd(struct scsi_cmnd *scmd, unsigned char *cmnd,
  			     int cmnd_size, int timeout, unsigned sense_bytes)
  {
  	struct scsi_device *sdev = scmd->device;
  	struct Scsi_Host *shost = sdev->host;
  	DECLARE_COMPLETION_ONSTACK(done);
  	unsigned long timeleft = timeout;
  	struct scsi_eh_save ses;
  	const unsigned long stall_for = msecs_to_jiffies(100);
  	int rtn;
  
  retry:
  	scsi_eh_prep_cmnd(scmd, &ses, cmnd, cmnd_size, sense_bytes);
  	shost->eh_action = &done;
  
  	scsi_log_send(scmd);
  	scmd->scsi_done = scsi_eh_done;
  	rtn = shost->hostt->queuecommand(shost, scmd);
  	if (rtn) {
  		if (timeleft > stall_for) {
  			scsi_eh_restore_cmnd(scmd, &ses);
  			timeleft -= stall_for;
  			msleep(jiffies_to_msecs(stall_for));
  			goto retry;
  		}
  		/* signal not to enter either branch of the if () below */
  		timeleft = 0;
  		rtn = FAILED;
  	} else {
  		timeleft = wait_for_completion_timeout(&done, timeout);
  		rtn = SUCCESS;
  	}
  
  	shost->eh_action = NULL;
  
  	scsi_log_completion(scmd, rtn);
  
  	SCSI_LOG_ERROR_RECOVERY(3, scmd_printk(KERN_INFO, scmd,
  			"%s timeleft: %ld\n",
  			__func__, timeleft));
  
  	/*
  	 * If there is time left scsi_eh_done got called, and we will examine
  	 * the actual status codes to see whether the command actually did
  	 * complete normally, else if we have a zero return and no time left,
  	 * the command must still be pending, so abort it and return FAILED.
  	 * If we never actually managed to issue the command, because
  	 * ->queuecommand() kept returning non zero, use the rtn = FAILED
  	 * value above (so don't execute either branch of the if)
  	 */
  	if (timeleft) {
  		rtn = scsi_eh_completed_normally(scmd);
  		SCSI_LOG_ERROR_RECOVERY(3, scmd_printk(KERN_INFO, scmd,
  			"%s: scsi_eh_completed_normally %x\n", __func__, rtn));
  
  		switch (rtn) {
  		case SUCCESS:
  		case NEEDS_RETRY:
  		case FAILED:
  			break;
  		case ADD_TO_MLQUEUE:
  			rtn = NEEDS_RETRY;
  			break;
  		default:
  			rtn = FAILED;
  			break;
  		}
  	} else if (rtn != FAILED) {
  		scsi_abort_eh_cmnd(scmd);
  		rtn = FAILED;
  	}
  
  	scsi_eh_restore_cmnd(scmd, &ses);
  
  	return rtn;
  }
  
  /**
   * scsi_request_sense - Request sense data from a particular target.
   * @scmd:	SCSI cmd for request sense.
   *
   * Notes:
   *    Some hosts automatically obtain this information, others require
   *    that we obtain it on our own. This function will *not* return until
   *    the command either times out, or it completes.
   */
  static int scsi_request_sense(struct scsi_cmnd *scmd)
  {
  	return scsi_send_eh_cmnd(scmd, NULL, 0, scmd->device->eh_timeout, ~0);
  }
  
  static int scsi_eh_action(struct scsi_cmnd *scmd, int rtn)
  {
  	if (scmd->request->cmd_type != REQ_TYPE_BLOCK_PC) {
  		struct scsi_driver *sdrv = scsi_cmd_to_driver(scmd);
  		if (sdrv->eh_action)
  			rtn = sdrv->eh_action(scmd, rtn);
  	}
  	return rtn;
  }
  
  /**
   * scsi_eh_finish_cmd - Handle a cmd that eh is finished with.
   * @scmd:	Original SCSI cmd that eh has finished.
   * @done_q:	Queue for processed commands.
   *
   * Notes:
   *    We don't want to use the normal command completion while we are are
   *    still handling errors - it may cause other commands to be queued,
   *    and that would disturb what we are doing.  Thus we really want to
   *    keep a list of pending commands for final completion, and once we
   *    are ready to leave error handling we handle completion for real.
   */
  void scsi_eh_finish_cmd(struct scsi_cmnd *scmd, struct list_head *done_q)
  {
  	scmd->device->host->host_failed--;
  	scmd->eh_eflags = 0;
  	list_move_tail(&scmd->eh_entry, done_q);
  }
  EXPORT_SYMBOL(scsi_eh_finish_cmd);
  
  /**
   * scsi_eh_get_sense - Get device sense data.
   * @work_q:	Queue of commands to process.
   * @done_q:	Queue of processed commands.
   *
   * Description:
   *    See if we need to request sense information.  if so, then get it
   *    now, so we have a better idea of what to do.
   *
   * Notes:
   *    This has the unfortunate side effect that if a shost adapter does
   *    not automatically request sense information, we end up shutting
   *    it down before we request it.
   *
   *    All drivers should request sense information internally these days,
   *    so for now all I have to say is tough noogies if you end up in here.
   *
   *    XXX: Long term this code should go away, but that needs an audit of
   *         all LLDDs first.
   */
  int scsi_eh_get_sense(struct list_head *work_q,
  		      struct list_head *done_q)
  {
  	struct scsi_cmnd *scmd, *next;
  	struct Scsi_Host *shost;
  	int rtn;
  
  	/*
  	 * If SCSI_EH_ABORT_SCHEDULED has been set, it is timeout IO,
  	 * should not get sense.
  	 */
  	list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
  		if ((scmd->eh_eflags & SCSI_EH_CANCEL_CMD) ||
  		    (scmd->eh_eflags & SCSI_EH_ABORT_SCHEDULED) ||
  		    SCSI_SENSE_VALID(scmd))
  			continue;
  
  		shost = scmd->device->host;
  		if (scsi_host_eh_past_deadline(shost)) {
  			SCSI_LOG_ERROR_RECOVERY(3,
  				scmd_printk(KERN_INFO, scmd,
  					    "%s: skip request sense, past eh deadline\n",
  					     current->comm));
  			break;
  		}
  		if (status_byte(scmd->result) != CHECK_CONDITION)
  			/*
  			 * don't request sense if there's no check condition
  			 * status because the error we're processing isn't one
  			 * that has a sense code (and some devices get
  			 * confused by sense requests out of the blue)
  			 */
  			continue;
  
  		SCSI_LOG_ERROR_RECOVERY(2, scmd_printk(KERN_INFO, scmd,
  						  "%s: requesting sense\n",
  						  current->comm));
  		rtn = scsi_request_sense(scmd);
  		if (rtn != SUCCESS)
  			continue;
  
  		SCSI_LOG_ERROR_RECOVERY(3, scmd_printk(KERN_INFO, scmd,
  			"sense requested, result %x\n", scmd->result));
  		SCSI_LOG_ERROR_RECOVERY(3, scsi_print_sense(scmd));
  
  		rtn = scsi_decide_disposition(scmd);
  
  		/*
  		 * if the result was normal, then just pass it along to the
  		 * upper level.
  		 */
  		if (rtn == SUCCESS)
  			/* we don't want this command reissued, just
  			 * finished with the sense data, so set
  			 * retries to the max allowed to ensure it
  			 * won't get reissued */
  			scmd->retries = scmd->allowed;
  		else if (rtn != NEEDS_RETRY)
  			continue;
  
  		scsi_eh_finish_cmd(scmd, done_q);
  	}
  
  	return list_empty(work_q);
  }
  EXPORT_SYMBOL_GPL(scsi_eh_get_sense);
  
  /**
   * scsi_eh_tur - Send TUR to device.
   * @scmd:	&scsi_cmnd to send TUR
   *
   * Return value:
   *    0 - Device is ready. 1 - Device NOT ready.
   */
  static int scsi_eh_tur(struct scsi_cmnd *scmd)
  {
  	static unsigned char tur_command[6] = {TEST_UNIT_READY, 0, 0, 0, 0, 0};
  	int retry_cnt = 1, rtn;
  
  retry_tur:
  	rtn = scsi_send_eh_cmnd(scmd, tur_command, 6,
  				scmd->device->eh_timeout, 0);
  
  	SCSI_LOG_ERROR_RECOVERY(3, scmd_printk(KERN_INFO, scmd,
  		"%s return: %x\n", __func__, rtn));
  
  	switch (rtn) {
  	case NEEDS_RETRY:
  		if (retry_cnt--)
  			goto retry_tur;
  		/*FALLTHRU*/
  	case SUCCESS:
  		return 0;
  	default:
  		return 1;
  	}
  }
  
  /**
   * scsi_eh_test_devices - check if devices are responding from error recovery.
   * @cmd_list:	scsi commands in error recovery.
   * @work_q:	queue for commands which still need more error recovery
   * @done_q:	queue for commands which are finished
   * @try_stu:	boolean on if a STU command should be tried in addition to TUR.
   *
   * Decription:
   *    Tests if devices are in a working state.  Commands to devices now in
   *    a working state are sent to the done_q while commands to devices which
   *    are still failing to respond are returned to the work_q for more
   *    processing.
   **/
  static int scsi_eh_test_devices(struct list_head *cmd_list,
  				struct list_head *work_q,
  				struct list_head *done_q, int try_stu)
  {
  	struct scsi_cmnd *scmd, *next;
  	struct scsi_device *sdev;
  	int finish_cmds;
  
  	while (!list_empty(cmd_list)) {
  		scmd = list_entry(cmd_list->next, struct scsi_cmnd, eh_entry);
  		sdev = scmd->device;
  
  		if (!try_stu) {
  			if (scsi_host_eh_past_deadline(sdev->host)) {
  				/* Push items back onto work_q */
  				list_splice_init(cmd_list, work_q);
  				SCSI_LOG_ERROR_RECOVERY(3,
  					sdev_printk(KERN_INFO, sdev,
  						    "%s: skip test device, past eh deadline",
  						    current->comm));
  				break;
  			}
  		}
  
  		finish_cmds = !scsi_device_online(scmd->device) ||
  			(try_stu && !scsi_eh_try_stu(scmd) &&
  			 !scsi_eh_tur(scmd)) ||
  			!scsi_eh_tur(scmd);
  
  		list_for_each_entry_safe(scmd, next, cmd_list, eh_entry)
  			if (scmd->device == sdev) {
  				if (finish_cmds &&
  				    (try_stu ||
  				     scsi_eh_action(scmd, SUCCESS) == SUCCESS))
  					scsi_eh_finish_cmd(scmd, done_q);
  				else
  					list_move_tail(&scmd->eh_entry, work_q);
  			}
  	}
  	return list_empty(work_q);
  }
  
  
  /**
   * scsi_eh_abort_cmds - abort pending commands.
   * @work_q:	&list_head for pending commands.
   * @done_q:	&list_head for processed commands.
   *
   * Decription:
   *    Try and see whether or not it makes sense to try and abort the
   *    running command.  This only works out to be the case if we have one
   *    command that has timed out.  If the command simply failed, it makes
   *    no sense to try and abort the command, since as far as the shost
   *    adapter is concerned, it isn't running.
   */
  static int scsi_eh_abort_cmds(struct list_head *work_q,
  			      struct list_head *done_q)
  {
  	struct scsi_cmnd *scmd, *next;
  	LIST_HEAD(check_list);
  	int rtn;
  	struct Scsi_Host *shost;
  
  	list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
  		if (!(scmd->eh_eflags & SCSI_EH_CANCEL_CMD))
  			continue;
  		shost = scmd->device->host;
  		if (scsi_host_eh_past_deadline(shost)) {
  			list_splice_init(&check_list, work_q);
  			SCSI_LOG_ERROR_RECOVERY(3,
  				scmd_printk(KERN_INFO, scmd,
  					    "%s: skip aborting cmd, past eh deadline\n",
  					    current->comm));
  			return list_empty(work_q);
  		}
  		SCSI_LOG_ERROR_RECOVERY(3,
  			scmd_printk(KERN_INFO, scmd,
  				     "%s: aborting cmd\n", current->comm));
  		rtn = scsi_try_to_abort_cmd(shost->hostt, scmd);
  		if (rtn == FAILED) {
  			SCSI_LOG_ERROR_RECOVERY(3,
  				scmd_printk(KERN_INFO, scmd,
  					    "%s: aborting cmd failed\n",
  					     current->comm));
  			list_splice_init(&check_list, work_q);
  			return list_empty(work_q);
  		}
  		scmd->eh_eflags &= ~SCSI_EH_CANCEL_CMD;
  		if (rtn == FAST_IO_FAIL)
  			scsi_eh_finish_cmd(scmd, done_q);
  		else
  			list_move_tail(&scmd->eh_entry, &check_list);
  	}
  
  	return scsi_eh_test_devices(&check_list, work_q, done_q, 0);
  }
  
  /**
   * scsi_eh_try_stu - Send START_UNIT to device.
   * @scmd:	&scsi_cmnd to send START_UNIT
   *
   * Return value:
   *    0 - Device is ready. 1 - Device NOT ready.
   */
  static int scsi_eh_try_stu(struct scsi_cmnd *scmd)
  {
  	static unsigned char stu_command[6] = {START_STOP, 0, 0, 0, 1, 0};
  
  	if (scmd->device->allow_restart) {
  		int i, rtn = NEEDS_RETRY;
  
  		for (i = 0; rtn == NEEDS_RETRY && i < 2; i++)
  			rtn = scsi_send_eh_cmnd(scmd, stu_command, 6, scmd->device->request_queue->rq_timeout, 0);
  
  		if (rtn == SUCCESS)
  			return 0;
  	}
  
  	return 1;
  }
  
   /**
   * scsi_eh_stu - send START_UNIT if needed
   * @shost:	&scsi host being recovered.
   * @work_q:	&list_head for pending commands.
   * @done_q:	&list_head for processed commands.
   *
   * Notes:
   *    If commands are failing due to not ready, initializing command required,
   *	try revalidating the device, which will end up sending a start unit.
   */
  static int scsi_eh_stu(struct Scsi_Host *shost,
  			      struct list_head *work_q,
  			      struct list_head *done_q)
  {
  	struct scsi_cmnd *scmd, *stu_scmd, *next;
  	struct scsi_device *sdev;
  
  	shost_for_each_device(sdev, shost) {
  		if (scsi_host_eh_past_deadline(shost)) {
  			SCSI_LOG_ERROR_RECOVERY(3,
  				sdev_printk(KERN_INFO, sdev,
  					    "%s: skip START_UNIT, past eh deadline\n",
  					    current->comm));
  			break;
  		}
  		stu_scmd = NULL;
  		list_for_each_entry(scmd, work_q, eh_entry)
  			if (scmd->device == sdev && SCSI_SENSE_VALID(scmd) &&
  			    scsi_check_sense(scmd) == FAILED ) {
  				stu_scmd = scmd;
  				break;
  			}
  
  		if (!stu_scmd)
  			continue;
  
  		SCSI_LOG_ERROR_RECOVERY(3,
  			sdev_printk(KERN_INFO, sdev,
  				     "%s: Sending START_UNIT\n",
  				    current->comm));
  
  		if (!scsi_eh_try_stu(stu_scmd)) {
  			if (!scsi_device_online(sdev) ||
  			    !scsi_eh_tur(stu_scmd)) {
  				list_for_each_entry_safe(scmd, next,
  							  work_q, eh_entry) {
  					if (scmd->device == sdev &&
  					    scsi_eh_action(scmd, SUCCESS) == SUCCESS)
  						scsi_eh_finish_cmd(scmd, done_q);
  				}
  			}
  		} else {
  			SCSI_LOG_ERROR_RECOVERY(3,
  				sdev_printk(KERN_INFO, sdev,
  					    "%s: START_UNIT failed\n",
  					    current->comm));
  		}
  	}
  
  	return list_empty(work_q);
  }
  
  
  /**
   * scsi_eh_bus_device_reset - send bdr if needed
   * @shost:	scsi host being recovered.
   * @work_q:	&list_head for pending commands.
   * @done_q:	&list_head for processed commands.
   *
   * Notes:
   *    Try a bus device reset.  Still, look to see whether we have multiple
   *    devices that are jammed or not - if we have multiple devices, it
   *    makes no sense to try bus_device_reset - we really would need to try
   *    a bus_reset instead.
   */
  static int scsi_eh_bus_device_reset(struct Scsi_Host *shost,
  				    struct list_head *work_q,
  				    struct list_head *done_q)
  {
  	struct scsi_cmnd *scmd, *bdr_scmd, *next;
  	struct scsi_device *sdev;
  	int rtn;
  
  	shost_for_each_device(sdev, shost) {
  		if (scsi_host_eh_past_deadline(shost)) {
  			SCSI_LOG_ERROR_RECOVERY(3,
  				sdev_printk(KERN_INFO, sdev,
  					    "%s: skip BDR, past eh deadline\n",
  					     current->comm));
  			break;
  		}
  		bdr_scmd = NULL;
  		list_for_each_entry(scmd, work_q, eh_entry)
  			if (scmd->device == sdev) {
  				bdr_scmd = scmd;
  				break;
  			}
  
  		if (!bdr_scmd)
  			continue;
  
  		SCSI_LOG_ERROR_RECOVERY(3,
  			sdev_printk(KERN_INFO, sdev,
  				     "%s: Sending BDR\n", current->comm));
  		rtn = scsi_try_bus_device_reset(bdr_scmd);
  		if (rtn == SUCCESS || rtn == FAST_IO_FAIL) {
  			if (!scsi_device_online(sdev) ||
  			    rtn == FAST_IO_FAIL ||
  			    !scsi_eh_tur(bdr_scmd)) {
  				list_for_each_entry_safe(scmd, next,
  							 work_q, eh_entry) {
  					if (scmd->device == sdev &&
  					    scsi_eh_action(scmd, rtn) != FAILED)
  						scsi_eh_finish_cmd(scmd,
  								   done_q);
  				}
  			}
  		} else {
  			SCSI_LOG_ERROR_RECOVERY(3,
  				sdev_printk(KERN_INFO, sdev,
  					    "%s: BDR failed\n", current->comm));
  		}
  	}
  
  	return list_empty(work_q);
  }
  
  /**
   * scsi_eh_target_reset - send target reset if needed
   * @shost:	scsi host being recovered.
   * @work_q:	&list_head for pending commands.
   * @done_q:	&list_head for processed commands.
   *
   * Notes:
   *    Try a target reset.
   */
  static int scsi_eh_target_reset(struct Scsi_Host *shost,
  				struct list_head *work_q,
  				struct list_head *done_q)
  {
  	LIST_HEAD(tmp_list);
  	LIST_HEAD(check_list);
  
  	list_splice_init(work_q, &tmp_list);
  
  	while (!list_empty(&tmp_list)) {
  		struct scsi_cmnd *next, *scmd;
  		int rtn;
  		unsigned int id;
  
  		if (scsi_host_eh_past_deadline(shost)) {
  			/* push back on work queue for further processing */
  			list_splice_init(&check_list, work_q);
  			list_splice_init(&tmp_list, work_q);
  			SCSI_LOG_ERROR_RECOVERY(3,
  				shost_printk(KERN_INFO, shost,
  					    "%s: Skip target reset, past eh deadline\n",
  					     current->comm));
  			return list_empty(work_q);
  		}
  
  		scmd = list_entry(tmp_list.next, struct scsi_cmnd, eh_entry);
  		id = scmd_id(scmd);
  
  		SCSI_LOG_ERROR_RECOVERY(3,
  			shost_printk(KERN_INFO, shost,
  				     "%s: Sending target reset to target %d\n",
  				     current->comm, id));
  		rtn = scsi_try_target_reset(scmd);
  		if (rtn != SUCCESS && rtn != FAST_IO_FAIL)
  			SCSI_LOG_ERROR_RECOVERY(3,
  				shost_printk(KERN_INFO, shost,
  					     "%s: Target reset failed"
  					     " target: %d\n",
  					     current->comm, id));
  		list_for_each_entry_safe(scmd, next, &tmp_list, eh_entry) {
  			if (scmd_id(scmd) != id)
  				continue;
  
  			if (rtn == SUCCESS)
  				list_move_tail(&scmd->eh_entry, &check_list);
  			else if (rtn == FAST_IO_FAIL)
  				scsi_eh_finish_cmd(scmd, done_q);
  			else
  				/* push back on work queue for further processing */
  				list_move(&scmd->eh_entry, work_q);
  		}
  	}
  
  	return scsi_eh_test_devices(&check_list, work_q, done_q, 0);
  }
  
  /**
   * scsi_eh_bus_reset - send a bus reset
   * @shost:	&scsi host being recovered.
   * @work_q:	&list_head for pending commands.
   * @done_q:	&list_head for processed commands.
   */
  static int scsi_eh_bus_reset(struct Scsi_Host *shost,
  			     struct list_head *work_q,
  			     struct list_head *done_q)
  {
  	struct scsi_cmnd *scmd, *chan_scmd, *next;
  	LIST_HEAD(check_list);
  	unsigned int channel;
  	int rtn;
  
  	/*
  	 * we really want to loop over the various channels, and do this on
  	 * a channel by channel basis.  we should also check to see if any
  	 * of the failed commands are on soft_reset devices, and if so, skip
  	 * the reset.
  	 */
  
  	for (channel = 0; channel <= shost->max_channel; channel++) {
  		if (scsi_host_eh_past_deadline(shost)) {
  			list_splice_init(&check_list, work_q);
  			SCSI_LOG_ERROR_RECOVERY(3,
  				shost_printk(KERN_INFO, shost,
  					    "%s: skip BRST, past eh deadline\n",
  					     current->comm));
  			return list_empty(work_q);
  		}
  
  		chan_scmd = NULL;
  		list_for_each_entry(scmd, work_q, eh_entry) {
  			if (channel == scmd_channel(scmd)) {
  				chan_scmd = scmd;
  				break;
  				/*
  				 * FIXME add back in some support for
  				 * soft_reset devices.
  				 */
  			}
  		}
  
  		if (!chan_scmd)
  			continue;
  		SCSI_LOG_ERROR_RECOVERY(3,
  			shost_printk(KERN_INFO, shost,
  				     "%s: Sending BRST chan: %d\n",
  				     current->comm, channel));
  		rtn = scsi_try_bus_reset(chan_scmd);
  		if (rtn == SUCCESS || rtn == FAST_IO_FAIL) {
  			list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
  				if (channel == scmd_channel(scmd)) {
  					if (rtn == FAST_IO_FAIL)
  						scsi_eh_finish_cmd(scmd,
  								   done_q);
  					else
  						list_move_tail(&scmd->eh_entry,
  							       &check_list);
  				}
  			}
  		} else {
  			SCSI_LOG_ERROR_RECOVERY(3,
  				shost_printk(KERN_INFO, shost,
  					     "%s: BRST failed chan: %d\n",
  					     current->comm, channel));
  		}
  	}
  	return scsi_eh_test_devices(&check_list, work_q, done_q, 0);
  }
  
  /**
   * scsi_eh_host_reset - send a host reset
   * @shost:	host to be reset.
   * @work_q:	&list_head for pending commands.
   * @done_q:	&list_head for processed commands.
   */
  static int scsi_eh_host_reset(struct Scsi_Host *shost,
  			      struct list_head *work_q,
  			      struct list_head *done_q)
  {
  	struct scsi_cmnd *scmd, *next;
  	LIST_HEAD(check_list);
  	int rtn;
  
  	if (!list_empty(work_q)) {
  		scmd = list_entry(work_q->next,
  				  struct scsi_cmnd, eh_entry);
  
  		SCSI_LOG_ERROR_RECOVERY(3,
  			shost_printk(KERN_INFO, shost,
  				     "%s: Sending HRST\n",
  				     current->comm));
  
  		rtn = scsi_try_host_reset(scmd);
  		if (rtn == SUCCESS) {
  			list_splice_init(work_q, &check_list);
  		} else if (rtn == FAST_IO_FAIL) {
  			list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
  					scsi_eh_finish_cmd(scmd, done_q);
  			}
  		} else {
  			SCSI_LOG_ERROR_RECOVERY(3,
  				shost_printk(KERN_INFO, shost,
  					     "%s: HRST failed\n",
  					     current->comm));
  		}
  	}
  	return scsi_eh_test_devices(&check_list, work_q, done_q, 1);
  }
  
  /**
   * scsi_eh_offline_sdevs - offline scsi devices that fail to recover
   * @work_q:	&list_head for pending commands.
   * @done_q:	&list_head for processed commands.
   */
  static void scsi_eh_offline_sdevs(struct list_head *work_q,
  				  struct list_head *done_q)
  {
  	struct scsi_cmnd *scmd, *next;
  
  	list_for_each_entry_safe(scmd, next, work_q, eh_entry) {
  		sdev_printk(KERN_INFO, scmd->device, "Device offlined - "
  			    "not ready after error recovery\n");
  		scsi_device_set_state(scmd->device, SDEV_OFFLINE);
  		if (scmd->eh_eflags & SCSI_EH_CANCEL_CMD) {
  			/*
  			 * FIXME: Handle lost cmds.
  			 */
  		}
  		scsi_eh_finish_cmd(scmd, done_q);
  	}
  	return;
  }
  
  /**
   * scsi_noretry_cmd - determine if command should be failed fast
   * @scmd:	SCSI cmd to examine.
   */
  int scsi_noretry_cmd(struct scsi_cmnd *scmd)
  {
  	switch (host_byte(scmd->result)) {
  	case DID_OK:
  		break;
  	case DID_TIME_OUT:
  		goto check_type;
  	case DID_BUS_BUSY:
  		return (scmd->request->cmd_flags & REQ_FAILFAST_TRANSPORT);
  	case DID_PARITY:
  		return (scmd->request->cmd_flags & REQ_FAILFAST_DEV);
  	case DID_ERROR:
  		if (msg_byte(scmd->result) == COMMAND_COMPLETE &&
  		    status_byte(scmd->result) == RESERVATION_CONFLICT)
  			return 0;
  		/* fall through */
  	case DID_SOFT_ERROR:
  		return (scmd->request->cmd_flags & REQ_FAILFAST_DRIVER);
  	}
  
  	if (status_byte(scmd->result) != CHECK_CONDITION)
  		return 0;
  
  check_type:
  	/*
  	 * assume caller has checked sense and determined
  	 * the check condition was retryable.
  	 */
  	if (scmd->request->cmd_flags & REQ_FAILFAST_DEV ||
  	    scmd->request->cmd_type == REQ_TYPE_BLOCK_PC)
  		return 1;
  	else
  		return 0;
  }
  
  /**
   * scsi_decide_disposition - Disposition a cmd on return from LLD.
   * @scmd:	SCSI cmd to examine.
   *
   * Notes:
   *    This is *only* called when we are examining the status after sending
   *    out the actual data command.  any commands that are queued for error
   *    recovery (e.g. test_unit_ready) do *not* come through here.
   *
   *    When this routine returns failed, it means the error handler thread
   *    is woken.  In cases where the error code indicates an error that
   *    doesn't require the error handler read (i.e. we don't need to
   *    abort/reset), this function should return SUCCESS.
   */
  int scsi_decide_disposition(struct scsi_cmnd *scmd)
  {
  	int rtn;
  
  	/*
  	 * if the device is offline, then we clearly just pass the result back
  	 * up to the top level.
  	 */
  	if (!scsi_device_online(scmd->device)) {
  		SCSI_LOG_ERROR_RECOVERY(5, scmd_printk(KERN_INFO, scmd,
  			"%s: device offline - report as SUCCESS\n", __func__));
  		return SUCCESS;
  	}
  
  	/*
  	 * first check the host byte, to see if there is anything in there
  	 * that would indicate what we need to do.
  	 */
  	switch (host_byte(scmd->result)) {
  	case DID_PASSTHROUGH:
  		/*
  		 * no matter what, pass this through to the upper layer.
  		 * nuke this special code so that it looks like we are saying
  		 * did_ok.
  		 */
  		scmd->result &= 0xff00ffff;
  		return SUCCESS;
  	case DID_OK:
  		/*
  		 * looks good.  drop through, and check the next byte.
  		 */
  		break;
  	case DID_ABORT:
  		if (scmd->eh_eflags & SCSI_EH_ABORT_SCHEDULED) {
  			set_host_byte(scmd, DID_TIME_OUT);
  			return SUCCESS;
  		}
  	case DID_NO_CONNECT:
  	case DID_BAD_TARGET:
  		/*
  		 * note - this means that we just report the status back
  		 * to the top level driver, not that we actually think
  		 * that it indicates SUCCESS.
  		 */
  		return SUCCESS;
  		/*
  		 * when the low level driver returns did_soft_error,
  		 * it is responsible for keeping an internal retry counter
  		 * in order to avoid endless loops (db)
  		 *
  		 * actually this is a bug in this function here.  we should
  		 * be mindful of the maximum number of retries specified
  		 * and not get stuck in a loop.
  		 */
  	case DID_SOFT_ERROR:
  		goto maybe_retry;
  	case DID_IMM_RETRY:
  		return NEEDS_RETRY;
  
  	case DID_REQUEUE:
  		return ADD_TO_MLQUEUE;
  	case DID_TRANSPORT_DISRUPTED:
  		/*
  		 * LLD/transport was disrupted during processing of the IO.
  		 * The transport class is now blocked/blocking,
  		 * and the transport will decide what to do with the IO
  		 * based on its timers and recovery capablilities if
  		 * there are enough retries.
  		 */
  		goto maybe_retry;
  	case DID_TRANSPORT_FAILFAST:
  		/*
  		 * The transport decided to failfast the IO (most likely
  		 * the fast io fail tmo fired), so send IO directly upwards.
  		 */
  		return SUCCESS;
  	case DID_ERROR:
  		if (msg_byte(scmd->result) == COMMAND_COMPLETE &&
  		    status_byte(scmd->result) == RESERVATION_CONFLICT)
  			/*
  			 * execute reservation conflict processing code
  			 * lower down
  			 */
  			break;
  		/* fallthrough */
  	case DID_BUS_BUSY:
  	case DID_PARITY:
  		goto maybe_retry;
  	case DID_TIME_OUT:
  		/*
  		 * when we scan the bus, we get timeout messages for
  		 * these commands if there is no device available.
  		 * other hosts report did_no_connect for the same thing.
  		 */
  		if ((scmd->cmnd[0] == TEST_UNIT_READY ||
  		     scmd->cmnd[0] == INQUIRY)) {
  			return SUCCESS;
  		} else {
  			return FAILED;
  		}
  	case DID_RESET:
  		return SUCCESS;
  	default:
  		return FAILED;
  	}
  
  	/*
  	 * next, check the message byte.
  	 */
  	if (msg_byte(scmd->result) != COMMAND_COMPLETE)
  		return FAILED;
  
  	/*
  	 * check the status byte to see if this indicates anything special.
  	 */
  	switch (status_byte(scmd->result)) {
  	case QUEUE_FULL:
  		scsi_handle_queue_full(scmd->device);
  		/*
  		 * the case of trying to send too many commands to a
  		 * tagged queueing device.
  		 */
  	case BUSY:
  		/*
  		 * device can't talk to us at the moment.  Should only
  		 * occur (SAM-3) when the task queue is empty, so will cause
  		 * the empty queue handling to trigger a stall in the
  		 * device.
  		 */
  		return ADD_TO_MLQUEUE;
  	case GOOD:
  		if (scmd->cmnd[0] == REPORT_LUNS)
  			scmd->device->sdev_target->expecting_lun_change = 0;
  		scsi_handle_queue_ramp_up(scmd->device);
  	case COMMAND_TERMINATED:
  		return SUCCESS;
  	case TASK_ABORTED:
  		goto maybe_retry;
  	case CHECK_CONDITION:
  		rtn = scsi_check_sense(scmd);
  		if (rtn == NEEDS_RETRY)
  			goto maybe_retry;
  		/* if rtn == FAILED, we have no sense information;
  		 * returning FAILED will wake the error handler thread
  		 * to collect the sense and redo the decide
  		 * disposition */
  		return rtn;
  	case CONDITION_GOOD:
  	case INTERMEDIATE_GOOD:
  	case INTERMEDIATE_C_GOOD:
  	case ACA_ACTIVE:
  		/*
  		 * who knows?  FIXME(eric)
  		 */
  		return SUCCESS;
  
  	case RESERVATION_CONFLICT:
  		sdev_printk(KERN_INFO, scmd->device,
  			    "reservation conflict\n");
  		set_host_byte(scmd, DID_NEXUS_FAILURE);
  		return SUCCESS; /* causes immediate i/o error */
  	default:
  		return FAILED;
  	}
  	return FAILED;
  
        maybe_retry:
  
  	/* we requeue for retry because the error was retryable, and
  	 * the request was not marked fast fail.  Note that above,
  	 * even if the request is marked fast fail, we still requeue
  	 * for queue congestion conditions (QUEUE_FULL or BUSY) */
  	if ((++scmd->retries) <= scmd->allowed
  	    && !scsi_noretry_cmd(scmd)) {
  		return NEEDS_RETRY;
  	} else {
  		/*
  		 * no more retries - report this one back to upper level.
  		 */
  		return SUCCESS;
  	}
  }
  
  static void eh_lock_door_done(struct request *req, int uptodate)
  {
  	__blk_put_request(req->q, req);
  }
  
  /**
   * scsi_eh_lock_door - Prevent medium removal for the specified device
   * @sdev:	SCSI device to prevent medium removal
   *
   * Locking:
   * 	We must be called from process context.
   *
   * Notes:
   * 	We queue up an asynchronous "ALLOW MEDIUM REMOVAL" request on the
   * 	head of the devices request queue, and continue.
   */
  static void scsi_eh_lock_door(struct scsi_device *sdev)
  {
  	struct request *req;
  
  	/*
  	 * blk_get_request with GFP_KERNEL (__GFP_WAIT) sleeps until a
  	 * request becomes available
  	 */
  	req = blk_get_request(sdev->request_queue, READ, GFP_KERNEL);
  	if (IS_ERR(req))
  		return;
  
  	blk_rq_set_block_pc(req);
  
  	req->cmd[0] = ALLOW_MEDIUM_REMOVAL;
  	req->cmd[1] = 0;
  	req->cmd[2] = 0;
  	req->cmd[3] = 0;
  	req->cmd[4] = SCSI_REMOVAL_PREVENT;
  	req->cmd[5] = 0;
  
  	req->cmd_len = COMMAND_SIZE(req->cmd[0]);
  
  	req->cmd_flags |= REQ_QUIET;
  	req->timeout = 10 * HZ;
  	req->retries = 5;
  
  	blk_execute_rq_nowait(req->q, NULL, req, 1, eh_lock_door_done);
  }
  
  /**
   * scsi_restart_operations - restart io operations to the specified host.
   * @shost:	Host we are restarting.
   *
   * Notes:
   *    When we entered the error handler, we blocked all further i/o to
   *    this device.  we need to 'reverse' this process.
   */
  static void scsi_restart_operations(struct Scsi_Host *shost)
  {
  	struct scsi_device *sdev;
  	unsigned long flags;
  
  	/*
  	 * If the door was locked, we need to insert a door lock request
  	 * onto the head of the SCSI request queue for the device.  There
  	 * is no point trying to lock the door of an off-line device.
  	 */
  	shost_for_each_device(sdev, shost) {
  		if (scsi_device_online(sdev) && sdev->was_reset && sdev->locked) {
  			scsi_eh_lock_door(sdev);
  			sdev->was_reset = 0;
  		}
  	}
  
  	/*
  	 * next free up anything directly waiting upon the host.  this
  	 * will be requests for character device operations, and also for
  	 * ioctls to queued block devices.
  	 */
  	SCSI_LOG_ERROR_RECOVERY(3,
  		shost_printk(KERN_INFO, shost, "waking up host to restart\n"));
  
  	spin_lock_irqsave(shost->host_lock, flags);
  	if (scsi_host_set_state(shost, SHOST_RUNNING))
  		if (scsi_host_set_state(shost, SHOST_CANCEL))
  			BUG_ON(scsi_host_set_state(shost, SHOST_DEL));
  	spin_unlock_irqrestore(shost->host_lock, flags);
  
  	wake_up(&shost->host_wait);
  
  	/*
  	 * finally we need to re-initiate requests that may be pending.  we will
  	 * have had everything blocked while error handling is taking place, and
  	 * now that error recovery is done, we will need to ensure that these
  	 * requests are started.
  	 */
  	scsi_run_host_queues(shost);
  
  	/*
  	 * if eh is active and host_eh_scheduled is pending we need to re-run
  	 * recovery.  we do this check after scsi_run_host_queues() to allow
  	 * everything pent up since the last eh run a chance to make forward
  	 * progress before we sync again.  Either we'll immediately re-run
  	 * recovery or scsi_device_unbusy() will wake us again when these
  	 * pending commands complete.
  	 */
  	spin_lock_irqsave(shost->host_lock, flags);
  	if (shost->host_eh_scheduled)
  		if (scsi_host_set_state(shost, SHOST_RECOVERY))
  			WARN_ON(scsi_host_set_state(shost, SHOST_CANCEL_RECOVERY));
  	spin_unlock_irqrestore(shost->host_lock, flags);
  }
  
  /**
   * scsi_eh_ready_devs - check device ready state and recover if not.
   * @shost:	host to be recovered.
   * @work_q:	&list_head for pending commands.
   * @done_q:	&list_head for processed commands.
   */
  void scsi_eh_ready_devs(struct Scsi_Host *shost,
  			struct list_head *work_q,
  			struct list_head *done_q)
  {
  	if (!scsi_eh_stu(shost, work_q, done_q))
  		if (!scsi_eh_bus_device_reset(shost, work_q, done_q))
  			if (!scsi_eh_target_reset(shost, work_q, done_q))
  				if (!scsi_eh_bus_reset(shost, work_q, done_q))
  					if (!scsi_eh_host_reset(shost, work_q, done_q))
  						scsi_eh_offline_sdevs(work_q,
  								      done_q);
  }
  EXPORT_SYMBOL_GPL(scsi_eh_ready_devs);
  
  /**
   * scsi_eh_flush_done_q - finish processed commands or retry them.
   * @done_q:	list_head of processed commands.
   */
  void scsi_eh_flush_done_q(struct list_head *done_q)
  {
  	struct scsi_cmnd *scmd, *next;
  
  	list_for_each_entry_safe(scmd, next, done_q, eh_entry) {
  		list_del_init(&scmd->eh_entry);
  		if (scsi_device_online(scmd->device) &&
  		    !scsi_noretry_cmd(scmd) &&
  		    (++scmd->retries <= scmd->allowed)) {
  			SCSI_LOG_ERROR_RECOVERY(3,
  				scmd_printk(KERN_INFO, scmd,
  					     "%s: flush retry cmd\n",
  					     current->comm));
  				scsi_queue_insert(scmd, SCSI_MLQUEUE_EH_RETRY);
  		} else {
  			/*
  			 * If just we got sense for the device (called
  			 * scsi_eh_get_sense), scmd->result is already
  			 * set, do not set DRIVER_TIMEOUT.
  			 */
  			if (!scmd->result)
  				scmd->result |= (DRIVER_TIMEOUT << 24);
  			SCSI_LOG_ERROR_RECOVERY(3,
  				scmd_printk(KERN_INFO, scmd,
  					     "%s: flush finish cmd\n",
  					     current->comm));
  			scsi_finish_command(scmd);
  		}
  	}
  }
  EXPORT_SYMBOL(scsi_eh_flush_done_q);
  
  /**
   * scsi_unjam_host - Attempt to fix a host which has a cmd that failed.
   * @shost:	Host to unjam.
   *
   * Notes:
   *    When we come in here, we *know* that all commands on the bus have
   *    either completed, failed or timed out.  we also know that no further
   *    commands are being sent to the host, so things are relatively quiet
   *    and we have freedom to fiddle with things as we wish.
   *
   *    This is only the *default* implementation.  it is possible for
   *    individual drivers to supply their own version of this function, and
   *    if the maintainer wishes to do this, it is strongly suggested that
   *    this function be taken as a template and modified.  this function
   *    was designed to correctly handle problems for about 95% of the
   *    different cases out there, and it should always provide at least a
   *    reasonable amount of error recovery.
   *
   *    Any command marked 'failed' or 'timeout' must eventually have
   *    scsi_finish_cmd() called for it.  we do all of the retry stuff
   *    here, so when we restart the host after we return it should have an
   *    empty queue.
   */
  static void scsi_unjam_host(struct Scsi_Host *shost)
  {
  	unsigned long flags;
  	LIST_HEAD(eh_work_q);
  	LIST_HEAD(eh_done_q);
  
  	spin_lock_irqsave(shost->host_lock, flags);
  	list_splice_init(&shost->eh_cmd_q, &eh_work_q);
  	spin_unlock_irqrestore(shost->host_lock, flags);
  
  	SCSI_LOG_ERROR_RECOVERY(1, scsi_eh_prt_fail_stats(shost, &eh_work_q));
  
  	if (!scsi_eh_get_sense(&eh_work_q, &eh_done_q))
  		if (!scsi_eh_abort_cmds(&eh_work_q, &eh_done_q))
  			scsi_eh_ready_devs(shost, &eh_work_q, &eh_done_q);
  
  	spin_lock_irqsave(shost->host_lock, flags);
  	if (shost->eh_deadline != -1)
  		shost->last_reset = 0;
  	spin_unlock_irqrestore(shost->host_lock, flags);
  	scsi_eh_flush_done_q(&eh_done_q);
  }
  
  /**
   * scsi_error_handler - SCSI error handler thread
   * @data:	Host for which we are running.
   *
   * Notes:
   *    This is the main error handling loop.  This is run as a kernel thread
   *    for every SCSI host and handles all error handling activity.
   */
  int scsi_error_handler(void *data)
  {
  	struct Scsi_Host *shost = data;
  
  	/*
  	 * We use TASK_INTERRUPTIBLE so that the thread is not
  	 * counted against the load average as a running process.
  	 * We never actually get interrupted because kthread_run
  	 * disables signal delivery for the created thread.
  	 */
  	while (true) {
  		/*
  		 * The sequence in kthread_stop() sets the stop flag first
  		 * then wakes the process.  To avoid missed wakeups, the task
  		 * should always be in a non running state before the stop
  		 * flag is checked
  		 */
  		set_current_state(TASK_INTERRUPTIBLE);
  		if (kthread_should_stop())
  			break;
  
  		if ((shost->host_failed == 0 && shost->host_eh_scheduled == 0) ||
  		    shost->host_failed != atomic_read(&shost->host_busy)) {
  			SCSI_LOG_ERROR_RECOVERY(1,
  				shost_printk(KERN_INFO, shost,
  					     "scsi_eh_%d: sleeping\n",
  					     shost->host_no));
  			schedule();
  			continue;
  		}
  
  		__set_current_state(TASK_RUNNING);
  		SCSI_LOG_ERROR_RECOVERY(1,
  			shost_printk(KERN_INFO, shost,
  				     "scsi_eh_%d: waking up %d/%d/%d\n",
  				     shost->host_no, shost->host_eh_scheduled,
  				     shost->host_failed,
  				     atomic_read(&shost->host_busy)));
  
  		/*
  		 * We have a host that is failing for some reason.  Figure out
  		 * what we need to do to get it up and online again (if we can).
  		 * If we fail, we end up taking the thing offline.
  		 */
  		if (!shost->eh_noresume && scsi_autopm_get_host(shost) != 0) {
  			SCSI_LOG_ERROR_RECOVERY(1,
  				shost_printk(KERN_ERR, shost,
  					     "scsi_eh_%d: unable to autoresume\n",
  					     shost->host_no));
  			continue;
  		}
  
  		if (shost->transportt->eh_strategy_handler)
  			shost->transportt->eh_strategy_handler(shost);
  		else
  			scsi_unjam_host(shost);
  
  		/*
  		 * Note - if the above fails completely, the action is to take
  		 * individual devices offline and flush the queue of any
  		 * outstanding requests that may have been pending.  When we
  		 * restart, we restart any I/O to any other devices on the bus
  		 * which are still online.
  		 */
  		scsi_restart_operations(shost);
  		if (!shost->eh_noresume)
  			scsi_autopm_put_host(shost);
  	}
  	__set_current_state(TASK_RUNNING);
  
  	SCSI_LOG_ERROR_RECOVERY(1,
  		shost_printk(KERN_INFO, shost,
  			     "Error handler scsi_eh_%d exiting\n",
  			     shost->host_no));
  	shost->ehandler = NULL;
  	return 0;
  }
  
  /*
   * Function:    scsi_report_bus_reset()
   *
   * Purpose:     Utility function used by low-level drivers to report that
   *		they have observed a bus reset on the bus being handled.
   *
   * Arguments:   shost       - Host in question
   *		channel     - channel on which reset was observed.
   *
   * Returns:     Nothing
   *
   * Lock status: Host lock must be held.
   *
   * Notes:       This only needs to be called if the reset is one which
   *		originates from an unknown location.  Resets originated
   *		by the mid-level itself don't need to call this, but there
   *		should be no harm.
   *
   *		The main purpose of this is to make sure that a CHECK_CONDITION
   *		is properly treated.
   */
  void scsi_report_bus_reset(struct Scsi_Host *shost, int channel)
  {
  	struct scsi_device *sdev;
  
  	__shost_for_each_device(sdev, shost) {
  		if (channel == sdev_channel(sdev))
  			__scsi_report_device_reset(sdev, NULL);
  	}
  }
  EXPORT_SYMBOL(scsi_report_bus_reset);
  
  /*
   * Function:    scsi_report_device_reset()
   *
   * Purpose:     Utility function used by low-level drivers to report that
   *		they have observed a device reset on the device being handled.
   *
   * Arguments:   shost       - Host in question
   *		channel     - channel on which reset was observed
   *		target	    - target on which reset was observed
   *
   * Returns:     Nothing
   *
   * Lock status: Host lock must be held
   *
   * Notes:       This only needs to be called if the reset is one which
   *		originates from an unknown location.  Resets originated
   *		by the mid-level itself don't need to call this, but there
   *		should be no harm.
   *
   *		The main purpose of this is to make sure that a CHECK_CONDITION
   *		is properly treated.
   */
  void scsi_report_device_reset(struct Scsi_Host *shost, int channel, int target)
  {
  	struct scsi_device *sdev;
  
  	__shost_for_each_device(sdev, shost) {
  		if (channel == sdev_channel(sdev) &&
  		    target == sdev_id(sdev))
  			__scsi_report_device_reset(sdev, NULL);
  	}
  }
  EXPORT_SYMBOL(scsi_report_device_reset);
  
  static void
  scsi_reset_provider_done_command(struct scsi_cmnd *scmd)
  {
  }
  
  /**
   * scsi_ioctl_reset: explicitly reset a host/bus/target/device
   * @dev:	scsi_device to operate on
   * @arg:	reset type (see sg.h)
   */
  int
  scsi_ioctl_reset(struct scsi_device *dev, int __user *arg)
  {
  	struct scsi_cmnd *scmd;
  	struct Scsi_Host *shost = dev->host;
  	struct request req;
  	unsigned long flags;
  	int error = 0, rtn, val;
  
  	if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
  		return -EACCES;
  
  	error = get_user(val, arg);
  	if (error)
  		return error;
  
  	if (scsi_autopm_get_host(shost) < 0)
  		return -EIO;
  
  	error = -EIO;
  	scmd = scsi_get_command(dev, GFP_KERNEL);
  	if (!scmd)
  		goto out_put_autopm_host;
  
  	blk_rq_init(NULL, &req);
  	scmd->request = &req;
  
  	scmd->cmnd = req.cmd;
  
  	scmd->scsi_done		= scsi_reset_provider_done_command;
  	memset(&scmd->sdb, 0, sizeof(scmd->sdb));
  
  	scmd->cmd_len			= 0;
  
  	scmd->sc_data_direction		= DMA_BIDIRECTIONAL;
  
  	spin_lock_irqsave(shost->host_lock, flags);
  	shost->tmf_in_progress = 1;
  	spin_unlock_irqrestore(shost->host_lock, flags);
  
  	switch (val & ~SG_SCSI_RESET_NO_ESCALATE) {
  	case SG_SCSI_RESET_NOTHING:
  		rtn = SUCCESS;
  		break;
  	case SG_SCSI_RESET_DEVICE:
  		rtn = scsi_try_bus_device_reset(scmd);
  		if (rtn == SUCCESS || (val & SG_SCSI_RESET_NO_ESCALATE))
  			break;
  		/* FALLTHROUGH */
  	case SG_SCSI_RESET_TARGET:
  		rtn = scsi_try_target_reset(scmd);
  		if (rtn == SUCCESS || (val & SG_SCSI_RESET_NO_ESCALATE))
  			break;
  		/* FALLTHROUGH */
  	case SG_SCSI_RESET_BUS:
  		rtn = scsi_try_bus_reset(scmd);
  		if (rtn == SUCCESS || (val & SG_SCSI_RESET_NO_ESCALATE))
  			break;
  		/* FALLTHROUGH */
  	case SG_SCSI_RESET_HOST:
  		rtn = scsi_try_host_reset(scmd);
  		if (rtn == SUCCESS)
  			break;
  	default:
  		/* FALLTHROUGH */
  		rtn = FAILED;
  		break;
  	}
  
  	error = (rtn == SUCCESS) ? 0 : -EIO;
  
  	spin_lock_irqsave(shost->host_lock, flags);
  	shost->tmf_in_progress = 0;
  	spin_unlock_irqrestore(shost->host_lock, flags);
  
  	/*
  	 * be sure to wake up anyone who was sleeping or had their queue
  	 * suspended while we performed the TMF.
  	 */
  	SCSI_LOG_ERROR_RECOVERY(3,
  		shost_printk(KERN_INFO, shost,
  			     "waking up host to restart after TMF\n"));
  
  	wake_up(&shost->host_wait);
  	scsi_run_host_queues(shost);
  
  	scsi_put_command(scmd);
  
  out_put_autopm_host:
  	scsi_autopm_put_host(shost);
  	return error;
  }
  EXPORT_SYMBOL(scsi_ioctl_reset);
  
  bool scsi_command_normalize_sense(const struct scsi_cmnd *cmd,
  				  struct scsi_sense_hdr *sshdr)
  {
  	return scsi_normalize_sense(cmd->sense_buffer,
  			SCSI_SENSE_BUFFERSIZE, sshdr);
  }
  EXPORT_SYMBOL(scsi_command_normalize_sense);
  
  /**
   * scsi_get_sense_info_fld - get information field from sense data (either fixed or descriptor format)
   * @sense_buffer:	byte array of sense data
   * @sb_len:		number of valid bytes in sense_buffer
   * @info_out:		pointer to 64 integer where 8 or 4 byte information
   *			field will be placed if found.
   *
   * Return value:
   *	1 if information field found, 0 if not found.
   */
  int scsi_get_sense_info_fld(const u8 * sense_buffer, int sb_len,
  			    u64 * info_out)
  {
  	int j;
  	const u8 * ucp;
  	u64 ull;
  
  	if (sb_len < 7)
  		return 0;
  	switch (sense_buffer[0] & 0x7f) {
  	case 0x70:
  	case 0x71:
  		if (sense_buffer[0] & 0x80) {
  			*info_out = (sense_buffer[3] << 24) +
  				    (sense_buffer[4] << 16) +
  				    (sense_buffer[5] << 8) + sense_buffer[6];
  			return 1;
  		} else
  			return 0;
  	case 0x72:
  	case 0x73:
  		ucp = scsi_sense_desc_find(sense_buffer, sb_len,
  					   0 /* info desc */);
  		if (ucp && (0xa == ucp[1])) {
  			ull = 0;
  			for (j = 0; j < 8; ++j) {
  				if (j > 0)
  					ull <<= 8;
  				ull |= ucp[4 + j];
  			}
  			*info_out = ull;
  			return 1;
  		} else
  			return 0;
  	default:
  		return 0;
  	}
  }
  EXPORT_SYMBOL(scsi_get_sense_info_fld);
  