scsi_error.c

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		 * 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_BUS_BUSY:
	case DID_PARITY:
	case DID_ERROR:
		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 ((SCpnt->cmnd[0] == TEST_UNIT_READY ||
		     SCpnt->cmnd[0] == INQUIRY)) {
			return SUCCESS;
		} else {
			return FAILED;
		}
	case DID_RESET:
		/*
		 * In the normal case where we haven't initiated a reset, this is
		 * a failure.
		 */
		if (SCpnt->flags & IS_RESETTING) {
			SCpnt->flags &= ~IS_RESETTING;
			goto maybe_retry;
		}
		/*
		 * Examine the sense data to figure out how to proceed from here.
		 * If there is no sense data, we will be forced into the error
		 * handler thread, where we get to examine the thing in a lot more
		 * detail.
		 */
		return scsi_check_sense(SCpnt);
	default:
		return FAILED;
	}

	/*
	 * Next, check the message byte.
	 */
	if (msg_byte(SCpnt->result) != COMMAND_COMPLETE) {
		return FAILED;
	}
	/*
	 * Now, check the status byte to see if this indicates anything special.
	 */
	switch (status_byte(SCpnt->result)) {
	case QUEUE_FULL:
		/*
		 * The case of trying to send too many commands to a tagged queueing
		 * device.
		 */
		return ADD_TO_MLQUEUE;
	case GOOD:
	case COMMAND_TERMINATED:
		return SUCCESS;
	case CHECK_CONDITION:
		rtn = scsi_check_sense(SCpnt);
		if (rtn == NEEDS_RETRY) {
			goto maybe_retry;
		}
		return rtn;
	case CONDITION_GOOD:
	case INTERMEDIATE_GOOD:
	case INTERMEDIATE_C_GOOD:
		/*
		 * Who knows?  FIXME(eric)
		 */
		return SUCCESS;
	case BUSY:
	case RESERVATION_CONFLICT:
		goto maybe_retry;
	default:
		return FAILED;
	}
	return FAILED;

      maybe_retry:

	if ((++SCpnt->retries) < SCpnt->allowed) {
		return NEEDS_RETRY;
	} else {
                /*
                 * No more retries - report this one back to upper level.
                 */
		return SUCCESS;
	}
}

/*
 * Function:  scsi_eh_completed_normally
 *
 * Purpose:     Examine a command block that has come back from the low-level
 *              and figure out what to do next.
 *
 * Returns:     SUCCESS         - pass on to upper level.
 *              FAILED          - pass on to error handler thread.
 *              RETRY           - command should be retried.
 *              SOFTERR         - command succeeded, but we need to log
 *                                a soft error.
 *
 * 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(Scsi_Cmnd * SCpnt)
{
	int rtn;
	/*
	 * First check the host byte, to see if there is anything in there
	 * that would indicate what we need to do.
	 */
	if (host_byte(SCpnt->result) == DID_RESET) {
		if (SCpnt->flags & IS_RESETTING) {
			/*
			 * OK, this is normal.  We don't know whether in fact the
			 * command in question really needs to be rerun or not - 
			 * if this was the original data command then the answer is yes,
			 * otherwise we just flag it as success.
			 */
			SCpnt->flags &= ~IS_RESETTING;
			return NEEDS_RETRY;
		}
		/*
		 * 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(SCpnt);
	}
	if (host_byte(SCpnt->result) != DID_OK) {
		return FAILED;
	}
	/*
	 * Next, check the message byte.
	 */
	if (msg_byte(SCpnt->result) != COMMAND_COMPLETE) {
		return FAILED;
	}
	/*
	 * Now, check the status byte to see if this indicates anything special.
	 */
	switch (status_byte(SCpnt->result)) {
	case GOOD:
	case COMMAND_TERMINATED:
		return SUCCESS;
	case CHECK_CONDITION:
		rtn = scsi_check_sense(SCpnt);
		if (rtn == NEEDS_RETRY) {
			return FAILED;
		}
		return rtn;
	case CONDITION_GOOD:
	case INTERMEDIATE_GOOD:
	case INTERMEDIATE_C_GOOD:
		/*
		 * Who knows?  FIXME(eric)
		 */
		return SUCCESS;
	case BUSY:
	case QUEUE_FULL:
	case RESERVATION_CONFLICT:
	default:
		return FAILED;
	}
	return FAILED;
}

/*
 * Function:  scsi_check_sense
 *
 * Purpose:     Examine sense information - give suggestion as to what
 *              we should do with it.
 */
STATIC int scsi_check_sense(Scsi_Cmnd * SCpnt)
{
	if (!scsi_sense_valid(SCpnt)) {
		return FAILED;
	}
	if (SCpnt->sense_buffer[2] & 0xe0)
		return SUCCESS;

	switch (SCpnt->sense_buffer[2] & 0xf) {
	case NO_SENSE:
		return SUCCESS;
	case RECOVERED_ERROR:
		return /* SOFT_ERROR */ SUCCESS;

	case ABORTED_COMMAND:
		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 (SCpnt->device->expecting_cc_ua) {
			SCpnt->device->expecting_cc_ua = 0;
			return NEEDS_RETRY;
		}
		return SUCCESS;

		/* these three are not supported */
	case COPY_ABORTED:
	case VOLUME_OVERFLOW:
	case MISCOMPARE:
		return SUCCESS;

	case MEDIUM_ERROR:
		return NEEDS_RETRY;

	case ILLEGAL_REQUEST:
	case BLANK_CHECK:
	case DATA_PROTECT:
	case HARDWARE_ERROR:
	default:
		return SUCCESS;
	}
}


/*
 * Function:  scsi_restart_operations
 *
 * Purpose:     Restart IO operations to the specified host.
 *
 * Arguments:   host  - host that we are restarting
 *
 * Lock status: Assumed that locks are not held upon entry.
 *
 * Returns:     Nothing
 *
 * 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 *host)
{
	Scsi_Device *SDpnt;
	unsigned long flags;

	ASSERT_LOCK(&io_request_lock, 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(5, printk("scsi_error.c: Waking up host to restart\n"));

	wake_up(&host->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.
	 */
	spin_lock_irqsave(&io_request_lock, flags);
	for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
		request_queue_t *q;
		if ((host->can_queue > 0 && (host->host_busy >= host->can_queue))
		    || (host->host_blocked)
		    || (host->host_self_blocked)
		    || (SDpnt->device_blocked)) {
			break;
		}
		q = &SDpnt->request_queue;
		q->request_fn(q);
	}
	spin_unlock_irqrestore(&io_request_lock, flags);
}

/*
 * Function:  scsi_unjam_host
 *
 * Purpose:     Attempt to fix a host which has a command that failed for
 *              some reason.
 *
 * Arguments:   host    - host that needs unjamming.
 * 
 * Returns:     Nothing
 *
 * 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.
 *
 * Additional note:  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.
 *
 * Note3:       Any command marked 'FAILED' or 'TIMEOUT' must eventually
 *              have scsi_finish_command() 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 int scsi_unjam_host(struct Scsi_Host *host)
{
	int devices_failed;
	int numfailed;
	int ourrtn;
	int rtn = FALSE;
	int result;
	Scsi_Cmnd *SCloop;
	Scsi_Cmnd *SCpnt;
	Scsi_Device *SDpnt;
	Scsi_Device *SDloop;
	Scsi_Cmnd *SCdone;
	int timed_out;

	ASSERT_LOCK(&io_request_lock, 0);

	SCdone = NULL;

	/*
	 * First, protect against any sort of race condition.  If any of the outstanding
	 * commands are in states that indicate that we are not yet blocked (i.e. we are
	 * not in a quiet state) then we got woken up in error.  If we ever end up here,
	 * we need to re-examine some of the assumptions.
	 */
	for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
		for (SCpnt = SDpnt->device_queue; SCpnt; SCpnt = SCpnt->next) {
			if (SCpnt->state == SCSI_STATE_FAILED
			    || SCpnt->state == SCSI_STATE_TIMEOUT
			    || SCpnt->state == SCSI_STATE_INITIALIZING
			    || SCpnt->state == SCSI_STATE_UNUSED) {
				continue;
			}
			/*
			 * Rats.  Something is still floating around out there.  This could
			 * be the result of the fact that the upper level drivers are still frobbing
			 * commands that might have succeeded.  There are two outcomes.  One is that
			 * the command block will eventually be freed, and the other one is that
			 * the command will be queued and will be finished along the way.
			 */
			SCSI_LOG_ERROR_RECOVERY(1, printk("Error handler prematurely woken - commands still active (%p %x %d)\n", SCpnt, SCpnt->state, SCpnt->target));

/*
 *        panic("SCSI Error handler woken too early\n");
 *
 * This is no longer a problem, since now the code cares only about
 * SCSI_STATE_TIMEOUT and SCSI_STATE_FAILED.
 * Other states are useful only to release active commands when devices are
 * set offline. If (host->host_active == host->host_busy) we can safely assume
 * that there are no commands in state other then TIMEOUT od FAILED. (DB)
 *
 * FIXME:
 * It is not easy to release correctly commands according to their state when 
 * devices are set offline, when the state is neither TIMEOUT nor FAILED.
 * When a device is set offline, we can have some command with
 * rq_status=RQ_SCSY_BUSY, owner=SCSI_STATE_HIGHLEVEL, 
 * state=SCSI_STATE_INITIALIZING and the driver module cannot be released.
 * (DB, 17 May 1998)
 */
		}
	}

	/*
	 * Next, see if we need to request sense information.  if so,
	 * then get it now, so we have a better idea of what to do.
	 * FIXME(eric) this has the unfortunate side effect that if a host
	 * adapter does not automatically request sense information, that we end
	 * up shutting it down before we request it.  All hosts should be doing this
	 * anyways, so for now all I have to say is tough noogies if you end up in here.
	 * On second thought, this is probably a good idea.  We *really* want to give
	 * authors an incentive to automatically request this.
	 */
	SCSI_LOG_ERROR_RECOVERY(3, printk("scsi_unjam_host: Checking to see if we need to request sense\n"));

	for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
		for (SCpnt = SDpnt->device_queue; SCpnt; SCpnt = SCpnt->next) {
			if (SCpnt->state != SCSI_STATE_FAILED || scsi_sense_valid(SCpnt)) {
				continue;
			}
			SCSI_LOG_ERROR_RECOVERY(2, printk("scsi_unjam_host: Requesting sense for %d\n",
							  SCpnt->target));
			rtn = scsi_request_sense(SCpnt);
			if (rtn != SUCCESS) {
				continue;
			}
			SCSI_LOG_ERROR_RECOVERY(3, printk("Sense requested for %p - result %x\n",
						  SCpnt, SCpnt->result));
			SCSI_LOG_ERROR_RECOVERY(3, print_sense("bh", SCpnt));

			result = scsi_decide_disposition(SCpnt);

			/*
			 * If the result was normal, then just pass it along to the
			 * upper level.
			 */
			if (result == SUCCESS) {
				SCpnt->host->host_failed--;
				scsi_eh_finish_command(&SCdone, SCpnt);
			}
			if (result != NEEDS_RETRY) {
				continue;
			}
			/* 
			 * We only come in here if we want to retry a
			 * command.  The test to see whether the command
			 * should be retried should be keeping track of the
			 * number of tries, so we don't end up looping, of
			 * course.  
			 */
			SCpnt->state = NEEDS_RETRY;
			rtn = scsi_eh_retry_command(SCpnt);
			if (rtn != SUCCESS) {
				continue;
			}
			/*
			 * We eventually hand this one back to the top level.
			 */
			SCpnt->host->host_failed--;
			scsi_eh_finish_command(&SCdone, SCpnt);
		}
	}

	/*
	 * Go through the list of commands and figure out where we stand and how bad things
	 * really are.
	 */
	numfailed = 0;
	timed_out = 0;
	devices_failed = 0;
	for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
		unsigned int device_error = 0;

		for (SCpnt = SDpnt->device_queue; SCpnt; SCpnt = SCpnt->next) {
			if (SCpnt->state == SCSI_STATE_FAILED) {
				SCSI_LOG_ERROR_RECOVERY(5, printk("Command to ID %d failed\n",
							 SCpnt->target));
				numfailed++;
				device_error++;
			}
			if (SCpnt->state == SCSI_STATE_TIMEOUT) {
				SCSI_LOG_ERROR_RECOVERY(5, printk("Command to ID %d timedout\n",
							 SCpnt->target));
				timed_out++;
				device_error++;
			}
		}
		if (device_error > 0) {
			devices_failed++;
		}
	}

	SCSI_LOG_ERROR_RECOVERY(2, printk("Total of %d+%d commands on %d devices require eh work\n",
				  numfailed, timed_out, devices_failed));

	if (host->host_failed == 0) {
		ourrtn = TRUE;
		goto leave;
	}
	/*
	 * Next, 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
	 * host adapter is concerned, it isn't running.
	 */

	SCSI_LOG_ERROR_RECOVERY(3, printk("scsi_unjam_host: Checking to see if we want to try abort\n"));

	for (SDpnt = host->host_queue; SDpnt; SDpnt = SDpnt->next) {
		for (SCloop = SDpnt->device_queue; SCloop; SCloop = SCloop->next) {
			if (SCloop->state != SCSI_STATE_TIMEOUT) {
				continue;
			}
			rtn = scsi_try_to_abort_command(SCloop, ABORT_TIMEOUT);
			if (rtn == SUCCESS) {
				rtn = scsi_test_unit_ready(SCloop);

				if (rtn == SUCCESS && scsi_unit_is_ready(SCloop)) {
					rtn = scsi_eh_retry_command(SCloop);

					if (rtn == SUCCESS) {
						SCloop->host->host_failed--;
						scsi_eh_finish_command(&SCdone, SCloop);
					}
				}
			}