drivers/scsi/device_handler/scsi_dh_alua.c - kernel/msm-4.19 - Gitiles

 /*
  * Generic SCSI-3 ALUA SCSI Device Handler
  *
  * Copyright (C) 2007-2010 Hannes Reinecke, SUSE Linux Products GmbH.
  * All rights reserved.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  *
  */
 #include <linux/slab.h>
 #include <linux/delay.h>
 #include <linux/module.h>
 #include <asm/unaligned.h>
 #include <scsi/scsi.h>
 #include <scsi/scsi_dbg.h>
 #include <scsi/scsi_eh.h>
 #include <scsi/scsi_dh.h>

 #define ALUA_DH_NAME "alua"
 #define ALUA_DH_VER "1.3"

 #define TPGS_STATE_OPTIMIZED		0x0
 #define TPGS_STATE_NONOPTIMIZED		0x1
 #define TPGS_STATE_STANDBY		0x2
 #define TPGS_STATE_UNAVAILABLE		0x3
 #define TPGS_STATE_LBA_DEPENDENT	0x4
 #define TPGS_STATE_OFFLINE		0xe
 #define TPGS_STATE_TRANSITIONING	0xf

 #define TPGS_SUPPORT_NONE		0x00
 #define TPGS_SUPPORT_OPTIMIZED		0x01
 #define TPGS_SUPPORT_NONOPTIMIZED	0x02
 #define TPGS_SUPPORT_STANDBY		0x04
 #define TPGS_SUPPORT_UNAVAILABLE	0x08
 #define TPGS_SUPPORT_LBA_DEPENDENT	0x10
 #define TPGS_SUPPORT_OFFLINE		0x40
 #define TPGS_SUPPORT_TRANSITION		0x80

 #define RTPG_FMT_MASK			0x70
 #define RTPG_FMT_EXT_HDR		0x10

 #define TPGS_MODE_UNINITIALIZED		 -1
 #define TPGS_MODE_NONE			0x0
 #define TPGS_MODE_IMPLICIT		0x1
 #define TPGS_MODE_EXPLICIT		0x2

 #define ALUA_INQUIRY_SIZE		36
 #define ALUA_FAILOVER_TIMEOUT		60
 #define ALUA_FAILOVER_RETRIES		5

 /* device handler flags */
 #define ALUA_OPTIMIZE_STPG		1
 #define ALUA_RTPG_EXT_HDR_UNSUPP	2

 struct alua_dh_data {
 	int			group_id;
 	int			rel_port;
 	int			tpgs;
 	int			state;
 	int			pref;
 	unsigned		flags; /* used for optimizing STPG */
 	unsigned char		inq[ALUA_INQUIRY_SIZE];
 	unsigned char		*buff;
 	int			bufflen;
 	unsigned char		transition_tmo;
 	unsigned char		sense[SCSI_SENSE_BUFFERSIZE];
 	struct scsi_device	*sdev;
 	activate_complete	callback_fn;
 	void			*callback_data;
 };

 #define ALUA_POLICY_SWITCH_CURRENT	0
 #define ALUA_POLICY_SWITCH_ALL		1

 static char print_alua_state(int);

 static int realloc_buffer(struct alua_dh_data *h, unsigned len)
 {
 	if (h->buff && h->buff != h->inq)
 		kfree(h->buff);

 	h->buff = kmalloc(len, GFP_NOIO);
 	if (!h->buff) {
 		h->buff = h->inq;
 		h->bufflen = ALUA_INQUIRY_SIZE;
 		return 1;
 	}
 	h->bufflen = len;
 	return 0;
 }

 static struct request *get_alua_req(struct scsi_device *sdev,
 				    void *buffer, unsigned buflen, int rw)
 {
 	struct request *rq;
 	struct request_queue *q = sdev->request_queue;

 	rq = blk_get_request(q, rw, GFP_NOIO);

 	if (IS_ERR(rq)) {
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: blk_get_request failed\n", __func__);
 		return NULL;
 	}
 	blk_rq_set_block_pc(rq);

 	if (buflen && blk_rq_map_kern(q, rq, buffer, buflen, GFP_NOIO)) {
 		blk_put_request(rq);
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: blk_rq_map_kern failed\n", __func__);
 		return NULL;
 	}

 	rq->cmd_flags |= REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 			 REQ_FAILFAST_DRIVER;
 	rq->retries = ALUA_FAILOVER_RETRIES;
 	rq->timeout = ALUA_FAILOVER_TIMEOUT * HZ;

 	return rq;
 }

 /*
  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
  * @sdev: sdev the command should be sent to
  */
 static unsigned submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
 			    int bufflen, unsigned char *sense, int flags)
 {
 	struct request *rq;
 	int err = 0;

 	rq = get_alua_req(sdev, buff, bufflen, READ);
 	if (!rq) {
 		err = DRIVER_BUSY << 24;
 		goto done;
 	}

 	/* Prepare the command. */
 	rq->cmd[0] = MAINTENANCE_IN;
 	if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
 		rq->cmd[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
 	else
 		rq->cmd[1] = MI_REPORT_TARGET_PGS;
 	put_unaligned_be32(bufflen, &rq->cmd[6]);
 	rq->cmd_len = COMMAND_SIZE(MAINTENANCE_IN);

 	rq->sense = sense;
 	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
 	rq->sense_len = 0;

 	blk_execute_rq(rq->q, NULL, rq, 1);
 	if (rq->errors)
 		err = rq->errors;
 	blk_put_request(rq);
 done:
 	return err;
 }

 /*
  * submit_stpg - Issue a SET TARGET PORT GROUP command
  *
  * Currently we're only setting the current target port group state
  * to 'active/optimized' and let the array firmware figure out
  * the states of the remaining groups.
  */
 static unsigned submit_stpg(struct scsi_device *sdev, int group_id,
 			    unsigned char *sense)
 {
 	struct request *rq;
 	unsigned char stpg_data[8];
 	int stpg_len = 8;
 	int err = 0;

 	/* Prepare the data buffer */
 	memset(stpg_data, 0, stpg_len);
 	stpg_data[4] = TPGS_STATE_OPTIMIZED & 0x0f;
 	put_unaligned_be16(group_id, &stpg_data[6]);

 	rq = get_alua_req(sdev, stpg_data, stpg_len, WRITE);
 	if (!rq)
 		return DRIVER_BUSY << 24;

 	/* Prepare the command. */
 	rq->cmd[0] = MAINTENANCE_OUT;
 	rq->cmd[1] = MO_SET_TARGET_PGS;
 	put_unaligned_be32(stpg_len, &rq->cmd[6]);
 	rq->cmd_len = COMMAND_SIZE(MAINTENANCE_OUT);

 	rq->sense = sense;
 	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
 	rq->sense_len = 0;

 	blk_execute_rq(rq->q, NULL, rq, 1);
 	if (rq->errors)
 		err = rq->errors;

 	blk_put_request(rq);

 	return err;
 }

 /*
  * alua_check_tpgs - Evaluate TPGS setting
  * @sdev: device to be checked
  *
  * Examine the TPGS setting of the sdev to find out if ALUA
  * is supported.
  */
 static int alua_check_tpgs(struct scsi_device *sdev)
 {
 	int tpgs = TPGS_MODE_NONE;

 	/*
 	 * ALUA support for non-disk devices is fraught with
 	 * difficulties, so disable it for now.
 	 */
 	if (sdev->type != TYPE_DISK) {
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: disable for non-disk devices\n",
 			    ALUA_DH_NAME);
 		return tpgs;
 	}

 	tpgs = scsi_device_tpgs(sdev);
 	switch (tpgs) {
 	case TPGS_MODE_EXPLICIT|TPGS_MODE_IMPLICIT:
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: supports implicit and explicit TPGS\n",
 			    ALUA_DH_NAME);
 		break;
 	case TPGS_MODE_EXPLICIT:
 		sdev_printk(KERN_INFO, sdev, "%s: supports explicit TPGS\n",
 			    ALUA_DH_NAME);
 		break;
 	case TPGS_MODE_IMPLICIT:
 		sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n",
 			    ALUA_DH_NAME);
 		break;
 	case TPGS_MODE_NONE:
 		sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
 			    ALUA_DH_NAME);
 		break;
 	default:
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: unsupported TPGS setting %d\n",
 			    ALUA_DH_NAME, tpgs);
 		tpgs = TPGS_MODE_NONE;
 		break;
 	}

 	return tpgs;
 }

 /*
  * alua_check_vpd - Evaluate INQUIRY vpd page 0x83
  * @sdev: device to be checked
  *
  * Extract the relative target port and the target port group
  * descriptor from the list of identificators.
  */
 static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h)
 {
 	int rel_port = -1, group_id;

 	group_id = scsi_vpd_tpg_id(sdev, &rel_port);
 	if (group_id < 0) {
 		/*
 		 * Internal error; TPGS supported but required
 		 * VPD identification descriptors not present.
 		 * Disable ALUA support
 		 */
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: No target port descriptors found\n",
 			    ALUA_DH_NAME);
 		return SCSI_DH_DEV_UNSUPP;
 	}
 	h->state = TPGS_STATE_OPTIMIZED;
 	h->group_id = group_id;

 	sdev_printk(KERN_INFO, sdev,
 		    "%s: port group %02x rel port %02x\n",
 		    ALUA_DH_NAME, h->group_id, h->rel_port);

 	return 0;
 }

 static char print_alua_state(int state)
 {
 	switch (state) {
 	case TPGS_STATE_OPTIMIZED:
 		return 'A';
 	case TPGS_STATE_NONOPTIMIZED:
 		return 'N';
 	case TPGS_STATE_STANDBY:
 		return 'S';
 	case TPGS_STATE_UNAVAILABLE:
 		return 'U';
 	case TPGS_STATE_LBA_DEPENDENT:
 		return 'L';
 	case TPGS_STATE_OFFLINE:
 		return 'O';
 	case TPGS_STATE_TRANSITIONING:
 		return 'T';
 	default:
 		return 'X';
 	}
 }

 static int alua_check_sense(struct scsi_device *sdev,
 			    struct scsi_sense_hdr *sense_hdr)
 {
 	switch (sense_hdr->sense_key) {
 	case NOT_READY:
 		if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a)
 			/*
 			 * LUN Not Accessible - ALUA state transition
 			 */
 			return ADD_TO_MLQUEUE;
 		break;
 	case UNIT_ATTENTION:
 		if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00)
 			/*
 			 * Power On, Reset, or Bus Device Reset, just retry.
 			 */
 			return ADD_TO_MLQUEUE;
 		if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
 			/*
 			 * Device internal reset
 			 */
 			return ADD_TO_MLQUEUE;
 		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
 			/*
 			 * Mode Parameters Changed
 			 */
 			return ADD_TO_MLQUEUE;
 		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06)
 			/*
 			 * ALUA state changed
 			 */
 			return ADD_TO_MLQUEUE;
 		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07)
 			/*
 			 * Implicit ALUA state transition failed
 			 */
 			return ADD_TO_MLQUEUE;
 		if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
 			/*
 			 * Inquiry data has changed
 			 */
 			return ADD_TO_MLQUEUE;
 		if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x0e)
 			/*
 			 * REPORTED_LUNS_DATA_HAS_CHANGED is reported
 			 * when switching controllers on targets like
 			 * Intel Multi-Flex. We can just retry.
 			 */
 			return ADD_TO_MLQUEUE;
 		break;
 	}

 	return SCSI_RETURN_NOT_HANDLED;
 }

 /*
  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
  * @sdev: the device to be evaluated.
  * @wait_for_transition: if nonzero, wait ALUA_FAILOVER_TIMEOUT seconds for device to exit transitioning state
  *
  * Evaluate the Target Port Group State.
  * Returns SCSI_DH_DEV_OFFLINED if the path is
  * found to be unusable.
  */
 static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h, int wait_for_transition)
 {
 	struct scsi_sense_hdr sense_hdr;
 	int len, k, off, valid_states = 0;
 	unsigned char *ucp;
 	unsigned err, retval;
 	unsigned long expiry, interval = 0;
 	unsigned int tpg_desc_tbl_off;
 	unsigned char orig_transition_tmo;

 	if (!h->transition_tmo)
 		expiry = round_jiffies_up(jiffies + ALUA_FAILOVER_TIMEOUT * HZ);
 	else
 		expiry = round_jiffies_up(jiffies + h->transition_tmo * HZ);

  retry:
 	retval = submit_rtpg(sdev, h->buff, h->bufflen, h->sense, h->flags);
 	if (retval) {
 		if (!scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
 					  &sense_hdr)) {
 			sdev_printk(KERN_INFO, sdev,
 				    "%s: rtpg failed, result %d\n",
 				    ALUA_DH_NAME, retval);
 			if (driver_byte(retval) == DRIVER_BUSY)
 				return SCSI_DH_DEV_TEMP_BUSY;
 			return SCSI_DH_IO;
 		}

 		/*
 		 * submit_rtpg() has failed on existing arrays
 		 * when requesting extended header info, and
 		 * the array doesn't support extended headers,
 		 * even though it shouldn't according to T10.
 		 * The retry without rtpg_ext_hdr_req set
 		 * handles this.
 		 */
 		if (!(h->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
 		    sense_hdr.sense_key == ILLEGAL_REQUEST &&
 		    sense_hdr.asc == 0x24 && sense_hdr.ascq == 0) {
 			h->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
 			goto retry;
 		}
 		/*
 		 * Retry on ALUA state transition or if any
 		 * UNIT ATTENTION occurred.
 		 */
 		if (sense_hdr.sense_key == NOT_READY &&
 		    sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
 			err = SCSI_DH_RETRY;
 		else if (sense_hdr.sense_key == UNIT_ATTENTION)
 			err = SCSI_DH_RETRY;
 		if (err == SCSI_DH_RETRY && time_before(jiffies, expiry)) {
 			sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
 				    ALUA_DH_NAME);
 			scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 			goto retry;
 		}
 		sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
 			    ALUA_DH_NAME);
 		scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 		return SCSI_DH_IO;
 	}

 	len = get_unaligned_be32(&h->buff[0]) + 4;

 	if (len > h->bufflen) {
 		/* Resubmit with the correct length */
 		if (realloc_buffer(h, len)) {
 			sdev_printk(KERN_WARNING, sdev,
 				    "%s: kmalloc buffer failed\n",__func__);
 			/* Temporary failure, bypass */
 			return SCSI_DH_DEV_TEMP_BUSY;
 		}
 		goto retry;
 	}

 	orig_transition_tmo = h->transition_tmo;
 	if ((h->buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && h->buff[5] != 0)
 		h->transition_tmo = h->buff[5];
 	else
 		h->transition_tmo = ALUA_FAILOVER_TIMEOUT;

 	if (wait_for_transition && (orig_transition_tmo != h->transition_tmo)) {
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: transition timeout set to %d seconds\n",
 			    ALUA_DH_NAME, h->transition_tmo);
 		expiry = jiffies + h->transition_tmo * HZ;
 	}

 	if ((h->buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
 		tpg_desc_tbl_off = 8;
 	else
 		tpg_desc_tbl_off = 4;

 	for (k = tpg_desc_tbl_off, ucp = h->buff + tpg_desc_tbl_off;
 	     k < len;
 	     k += off, ucp += off) {

 		if (h->group_id == get_unaligned_be16(&ucp[2])) {
 			h->state = ucp[0] & 0x0f;
 			h->pref = ucp[0] >> 7;
 			valid_states = ucp[1];
 		}
 		off = 8 + (ucp[7] * 4);
 	}

 	sdev_printk(KERN_INFO, sdev,
 		    "%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
 		    ALUA_DH_NAME, h->group_id, print_alua_state(h->state),
 		    h->pref ? "preferred" : "non-preferred",
 		    valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
 		    valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
 		    valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
 		    valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
 		    valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
 		    valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
 		    valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');

 	switch (h->state) {
 	case TPGS_STATE_TRANSITIONING:
 		if (wait_for_transition) {
 			if (time_before(jiffies, expiry)) {
 				/* State transition, retry */
 				interval += 2000;
 				msleep(interval);
 				goto retry;
 			}
 			err = SCSI_DH_RETRY;
 		} else {
 			err = SCSI_DH_OK;
 		}

 		/* Transitioning time exceeded, set port to standby */
 		h->state = TPGS_STATE_STANDBY;
 		break;
 	case TPGS_STATE_OFFLINE:
 		/* Path unusable */
 		err = SCSI_DH_DEV_OFFLINED;
 		break;
 	default:
 		/* Useable path if active */
 		err = SCSI_DH_OK;
 		break;
 	}
 	return err;
 }

 /*
  * alua_stpg - Issue a SET TARGET PORT GROUP command
  *
  * Issue a SET TARGET PORT GROUP command and evaluate the
  * response. Returns SCSI_DH_RETRY per default to trigger
  * a re-evaluation of the target group state or SCSI_DH_OK
  * if no further action needs to be taken.
  */
 static unsigned alua_stpg(struct scsi_device *sdev, struct alua_dh_data *h)
 {
 	int retval;
 	struct scsi_sense_hdr sense_hdr;

 	if (!(h->tpgs & TPGS_MODE_EXPLICIT)) {
 		/* Only implicit ALUA supported, retry */
 		return SCSI_DH_RETRY;
 	}
 	switch (h->state) {
 	case TPGS_STATE_OPTIMIZED:
 		return SCSI_DH_OK;
 	case TPGS_STATE_NONOPTIMIZED:
 		if ((h->flags & ALUA_OPTIMIZE_STPG) &&
 		    !h->pref &&
 		    (h->tpgs & TPGS_MODE_IMPLICIT))
 			return SCSI_DH_OK;
 		break;
 	case TPGS_STATE_STANDBY:
 	case TPGS_STATE_UNAVAILABLE:
 		break;
 	case TPGS_STATE_OFFLINE:
 		return SCSI_DH_IO;
 	case TPGS_STATE_TRANSITIONING:
 		break;
 	default:
 		sdev_printk(KERN_INFO, sdev,
 			    "%s: stpg failed, unhandled TPGS state %d",
 			    ALUA_DH_NAME, h->state);
 		return SCSI_DH_NOSYS;
 	}
 	retval = submit_stpg(sdev, h->group_id, h->sense);

 	if (retval) {
 		if (!scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
 					  &sense_hdr)) {
 			sdev_printk(KERN_INFO, sdev,
 				    "%s: stpg failed, result %d",
 				    ALUA_DH_NAME, retval);
 			if (driver_byte(retval) == DRIVER_BUSY)
 				return SCSI_DH_DEV_TEMP_BUSY;
 		} else {
 			sdev_printk(KERN_INFO, h->sdev, "%s: stpg failed\n",
 				    ALUA_DH_NAME);
 			scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 		}
 	}
 	/* Retry RTPG */
 	return SCSI_DH_RETRY;
 }

 /*
  * alua_initialize - Initialize ALUA state
  * @sdev: the device to be initialized
  *
  * For the prep_fn to work correctly we have
  * to initialize the ALUA state for the device.
  */
 static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 {
 	int err = SCSI_DH_DEV_UNSUPP;

 	h->tpgs = alua_check_tpgs(sdev);
 	if (h->tpgs == TPGS_MODE_NONE)
 		goto out;

 	err = alua_check_vpd(sdev, h);
 	if (err != SCSI_DH_OK)
 		goto out;

 	err = alua_rtpg(sdev, h, 0);
 	if (err != SCSI_DH_OK)
 		goto out;

 out:
 	return err;
 }
 /*
  * alua_set_params - set/unset the optimize flag
  * @sdev: device on the path to be activated
  * params - parameters in the following format
  *      "no_of_params\0param1\0param2\0param3\0...\0"
  * For example, to set the flag pass the following parameters
  * from multipath.conf
  *     hardware_handler        "2 alua 1"
  */
 static int alua_set_params(struct scsi_device *sdev, const char *params)
 {
 	struct alua_dh_data *h = sdev->handler_data;
 	unsigned int optimize = 0, argc;
 	const char *p = params;
 	int result = SCSI_DH_OK;

 	if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
 		return -EINVAL;

 	while (*p++)
 		;
 	if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
 		return -EINVAL;

 	if (optimize)
 		h->flags |= ALUA_OPTIMIZE_STPG;
 	else
 		h->flags &= ~ALUA_OPTIMIZE_STPG;

 	return result;
 }

 static uint optimize_stpg;
 module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
 MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized path, rather than sending a STPG, when implicit TPGS is supported (0=No,1=Yes). Default is 0.");

 /*
  * alua_activate - activate a path
  * @sdev: device on the path to be activated
  *
  * We're currently switching the port group to be activated only and
  * let the array figure out the rest.
  * There may be other arrays which require us to switch all port groups
  * based on a certain policy. But until we actually encounter them it
  * should be okay.
  */
 static int alua_activate(struct scsi_device *sdev,
 			activate_complete fn, void *data)
 {
 	struct alua_dh_data *h = sdev->handler_data;
 	int err = SCSI_DH_OK;

 	err = alua_rtpg(sdev, h, 1);
 	if (err != SCSI_DH_OK)
 		goto out;

 	if (optimize_stpg)
 		h->flags |= ALUA_OPTIMIZE_STPG;

 	err = alua_stpg(sdev, h);
 out:
 	if (fn)
 		fn(data, err);
 	return 0;
 }

 /*
  * alua_prep_fn - request callback
  *
  * Fail I/O to all paths not in state
  * active/optimized or active/non-optimized.
  */
 static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
 {
 	struct alua_dh_data *h = sdev->handler_data;
 	int ret = BLKPREP_OK;

 	if (h->state == TPGS_STATE_TRANSITIONING)
 		ret = BLKPREP_DEFER;
 	else if (h->state != TPGS_STATE_OPTIMIZED &&
 		 h->state != TPGS_STATE_NONOPTIMIZED &&
 		 h->state != TPGS_STATE_LBA_DEPENDENT) {
 		ret = BLKPREP_KILL;
 		req->cmd_flags |= REQ_QUIET;
 	}
 	return ret;

 }

 /*
  * alua_bus_attach - Attach device handler
  * @sdev: device to be attached to
  */
 static int alua_bus_attach(struct scsi_device *sdev)
 {
 	struct alua_dh_data *h;
 	int err;

 	h = kzalloc(sizeof(*h) , GFP_KERNEL);
 	if (!h)
 		return -ENOMEM;
 	h->tpgs = TPGS_MODE_UNINITIALIZED;
 	h->state = TPGS_STATE_OPTIMIZED;
 	h->group_id = -1;
 	h->rel_port = -1;
 	h->buff = h->inq;
 	h->bufflen = ALUA_INQUIRY_SIZE;
 	h->sdev = sdev;

 	err = alua_initialize(sdev, h);
 	if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
 		goto failed;

 	sdev->handler_data = h;
 	return 0;
 failed:
 	kfree(h);
 	return -EINVAL;
 }

 /*
  * alua_bus_detach - Detach device handler
  * @sdev: device to be detached from
  */
 static void alua_bus_detach(struct scsi_device *sdev)
 {
 	struct alua_dh_data *h = sdev->handler_data;

 	if (h->buff && h->inq != h->buff)
 		kfree(h->buff);
 	sdev->handler_data = NULL;
 	kfree(h);
 }

 static struct scsi_device_handler alua_dh = {
 	.name = ALUA_DH_NAME,
 	.module = THIS_MODULE,
 	.attach = alua_bus_attach,
 	.detach = alua_bus_detach,
 	.prep_fn = alua_prep_fn,
 	.check_sense = alua_check_sense,
 	.activate = alua_activate,
 	.set_params = alua_set_params,
 };

 static int __init alua_init(void)
 {
 	int r;

 	r = scsi_register_device_handler(&alua_dh);
 	if (r != 0)
 		printk(KERN_ERR "%s: Failed to register scsi device handler",
 			ALUA_DH_NAME);
 	return r;
 }

 static void __exit alua_exit(void)
 {
 	scsi_unregister_device_handler(&alua_dh);
 }

 module_init(alua_init);
 module_exit(alua_exit);

 MODULE_DESCRIPTION("DM Multipath ALUA support");
 MODULE_AUTHOR("Hannes Reinecke <hare@suse.de>");
 MODULE_LICENSE("GPL");
 MODULE_VERSION(ALUA_DH_VER);
	/*
	* Generic SCSI-3 ALUA SCSI Device Handler
	*
	* Copyright (C) 2007-2010 Hannes Reinecke, SUSE Linux Products GmbH.
	* All rights reserved.
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	*
	*/
	#include <linux/slab.h>
	#include <linux/delay.h>
	#include <linux/module.h>
	#include <asm/unaligned.h>
	#include <scsi/scsi.h>
	#include <scsi/scsi_dbg.h>
	#include <scsi/scsi_eh.h>
	#include <scsi/scsi_dh.h>

	#define ALUA_DH_NAME "alua"
	#define ALUA_DH_VER "1.3"

	#define TPGS_STATE_OPTIMIZED 0x0
	#define TPGS_STATE_NONOPTIMIZED 0x1
	#define TPGS_STATE_STANDBY 0x2
	#define TPGS_STATE_UNAVAILABLE 0x3
	#define TPGS_STATE_LBA_DEPENDENT 0x4
	#define TPGS_STATE_OFFLINE 0xe
	#define TPGS_STATE_TRANSITIONING 0xf

	#define TPGS_SUPPORT_NONE 0x00
	#define TPGS_SUPPORT_OPTIMIZED 0x01
	#define TPGS_SUPPORT_NONOPTIMIZED 0x02
	#define TPGS_SUPPORT_STANDBY 0x04
	#define TPGS_SUPPORT_UNAVAILABLE 0x08
	#define TPGS_SUPPORT_LBA_DEPENDENT 0x10
	#define TPGS_SUPPORT_OFFLINE 0x40
	#define TPGS_SUPPORT_TRANSITION 0x80

	#define RTPG_FMT_MASK 0x70
	#define RTPG_FMT_EXT_HDR 0x10

	#define TPGS_MODE_UNINITIALIZED -1
	#define TPGS_MODE_NONE 0x0
	#define TPGS_MODE_IMPLICIT 0x1
	#define TPGS_MODE_EXPLICIT 0x2

	#define ALUA_INQUIRY_SIZE 36
	#define ALUA_FAILOVER_TIMEOUT 60
	#define ALUA_FAILOVER_RETRIES 5

	/* device handler flags */
	#define ALUA_OPTIMIZE_STPG 1
	#define ALUA_RTPG_EXT_HDR_UNSUPP 2

	struct alua_dh_data {
	int group_id;
	int rel_port;
	int tpgs;
	int state;
	int pref;
	unsigned flags; /* used for optimizing STPG */
	unsigned char inq[ALUA_INQUIRY_SIZE];
	unsigned char *buff;
	int bufflen;
	unsigned char transition_tmo;
	unsigned char sense[SCSI_SENSE_BUFFERSIZE];
	struct scsi_device *sdev;
	activate_complete callback_fn;
	void *callback_data;
	};

	#define ALUA_POLICY_SWITCH_CURRENT 0
	#define ALUA_POLICY_SWITCH_ALL 1

	static char print_alua_state(int);

	static int realloc_buffer(struct alua_dh_data *h, unsigned len)
	{
	if (h->buff && h->buff != h->inq)
	kfree(h->buff);

	h->buff = kmalloc(len, GFP_NOIO);
	if (!h->buff) {
	h->buff = h->inq;
	h->bufflen = ALUA_INQUIRY_SIZE;
	return 1;
	}
	h->bufflen = len;
	return 0;
	}

	static struct request get_alua_req(struct scsi_device sdev,
	void *buffer, unsigned buflen, int rw)
	{
	struct request *rq;
	struct request_queue *q = sdev->request_queue;

	rq = blk_get_request(q, rw, GFP_NOIO);

	if (IS_ERR(rq)) {
	sdev_printk(KERN_INFO, sdev,
	"%s: blk_get_request failed\n", __func__);
	return NULL;
	}
	blk_rq_set_block_pc(rq);

	if (buflen && blk_rq_map_kern(q, rq, buffer, buflen, GFP_NOIO)) {
	blk_put_request(rq);
	sdev_printk(KERN_INFO, sdev,
	"%s: blk_rq_map_kern failed\n", __func__);
	return NULL;
	}

	rq->cmd_flags \|= REQ_FAILFAST_DEV \| REQ_FAILFAST_TRANSPORT \|
	REQ_FAILFAST_DRIVER;
	rq->retries = ALUA_FAILOVER_RETRIES;
	rq->timeout = ALUA_FAILOVER_TIMEOUT * HZ;

	return rq;
	}

	/*
	* submit_rtpg - Issue a REPORT TARGET GROUP STATES command
	* @sdev: sdev the command should be sent to
	*/
	static unsigned submit_rtpg(struct scsi_device sdev, unsigned char buff,
	int bufflen, unsigned char *sense, int flags)
	{
	struct request *rq;
	int err = 0;

	rq = get_alua_req(sdev, buff, bufflen, READ);
	if (!rq) {
	err = DRIVER_BUSY << 24;
	goto done;
	}

	/* Prepare the command. */
	rq->cmd[0] = MAINTENANCE_IN;
	if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
	rq->cmd[1] = MI_REPORT_TARGET_PGS \| MI_EXT_HDR_PARAM_FMT;
	else
	rq->cmd[1] = MI_REPORT_TARGET_PGS;
	put_unaligned_be32(bufflen, &rq->cmd[6]);
	rq->cmd_len = COMMAND_SIZE(MAINTENANCE_IN);

	rq->sense = sense;
	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
	rq->sense_len = 0;

	blk_execute_rq(rq->q, NULL, rq, 1);
	if (rq->errors)
	err = rq->errors;
	blk_put_request(rq);
	done:
	return err;
	}

	/*
	* submit_stpg - Issue a SET TARGET PORT GROUP command
	*
	* Currently we're only setting the current target port group state
	* to 'active/optimized' and let the array firmware figure out
	* the states of the remaining groups.
	*/
	static unsigned submit_stpg(struct scsi_device *sdev, int group_id,
	unsigned char *sense)
	{
	struct request *rq;
	unsigned char stpg_data[8];
	int stpg_len = 8;
	int err = 0;

	/* Prepare the data buffer */
	memset(stpg_data, 0, stpg_len);
	stpg_data[4] = TPGS_STATE_OPTIMIZED & 0x0f;
	put_unaligned_be16(group_id, &stpg_data[6]);

	rq = get_alua_req(sdev, stpg_data, stpg_len, WRITE);
	if (!rq)
	return DRIVER_BUSY << 24;

	/* Prepare the command. */
	rq->cmd[0] = MAINTENANCE_OUT;
	rq->cmd[1] = MO_SET_TARGET_PGS;
	put_unaligned_be32(stpg_len, &rq->cmd[6]);
	rq->cmd_len = COMMAND_SIZE(MAINTENANCE_OUT);

	rq->sense = sense;
	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
	rq->sense_len = 0;

	blk_execute_rq(rq->q, NULL, rq, 1);
	if (rq->errors)
	err = rq->errors;

	blk_put_request(rq);

	return err;
	}

	/*
	* alua_check_tpgs - Evaluate TPGS setting
	* @sdev: device to be checked
	*
	* Examine the TPGS setting of the sdev to find out if ALUA
	* is supported.
	*/
	static int alua_check_tpgs(struct scsi_device *sdev)
	{
	int tpgs = TPGS_MODE_NONE;

	/*
	* ALUA support for non-disk devices is fraught with
	* difficulties, so disable it for now.
	*/
	if (sdev->type != TYPE_DISK) {
	sdev_printk(KERN_INFO, sdev,
	"%s: disable for non-disk devices\n",
	ALUA_DH_NAME);
	return tpgs;
	}

	tpgs = scsi_device_tpgs(sdev);
	switch (tpgs) {
	case TPGS_MODE_EXPLICIT\|TPGS_MODE_IMPLICIT:
	sdev_printk(KERN_INFO, sdev,
	"%s: supports implicit and explicit TPGS\n",
	ALUA_DH_NAME);
	break;
	case TPGS_MODE_EXPLICIT:
	sdev_printk(KERN_INFO, sdev, "%s: supports explicit TPGS\n",
	ALUA_DH_NAME);
	break;
	case TPGS_MODE_IMPLICIT:
	sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n",
	ALUA_DH_NAME);
	break;
	case TPGS_MODE_NONE:
	sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
	ALUA_DH_NAME);
	break;
	default:
	sdev_printk(KERN_INFO, sdev,
	"%s: unsupported TPGS setting %d\n",
	ALUA_DH_NAME, tpgs);
	tpgs = TPGS_MODE_NONE;
	break;
	}

	return tpgs;
	}

	/*
	* alua_check_vpd - Evaluate INQUIRY vpd page 0x83
	* @sdev: device to be checked
	*
	* Extract the relative target port and the target port group
	* descriptor from the list of identificators.
	*/
	static int alua_check_vpd(struct scsi_device sdev, struct alua_dh_data h)
	{
	int rel_port = -1, group_id;

	group_id = scsi_vpd_tpg_id(sdev, &rel_port);
	if (group_id < 0) {
	/*
	* Internal error; TPGS supported but required
	* VPD identification descriptors not present.
	* Disable ALUA support
	*/
	sdev_printk(KERN_INFO, sdev,
	"%s: No target port descriptors found\n",
	ALUA_DH_NAME);
	return SCSI_DH_DEV_UNSUPP;
	}
	h->state = TPGS_STATE_OPTIMIZED;
	h->group_id = group_id;

	sdev_printk(KERN_INFO, sdev,
	"%s: port group %02x rel port %02x\n",
	ALUA_DH_NAME, h->group_id, h->rel_port);

	return 0;
	}

	static char print_alua_state(int state)
	{
	switch (state) {
	case TPGS_STATE_OPTIMIZED:
	return 'A';
	case TPGS_STATE_NONOPTIMIZED:
	return 'N';
	case TPGS_STATE_STANDBY:
	return 'S';
	case TPGS_STATE_UNAVAILABLE:
	return 'U';
	case TPGS_STATE_LBA_DEPENDENT:
	return 'L';
	case TPGS_STATE_OFFLINE:
	return 'O';
	case TPGS_STATE_TRANSITIONING:
	return 'T';
	default:
	return 'X';
	}
	}

	static int alua_check_sense(struct scsi_device *sdev,
	struct scsi_sense_hdr *sense_hdr)
	{
	switch (sense_hdr->sense_key) {
	case NOT_READY:
	if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a)
	/*
	* LUN Not Accessible - ALUA state transition
	*/
	return ADD_TO_MLQUEUE;
	break;
	case UNIT_ATTENTION:
	if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00)
	/*
	* Power On, Reset, or Bus Device Reset, just retry.
	*/
	return ADD_TO_MLQUEUE;
	if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
	/*
	* Device internal reset
	*/
	return ADD_TO_MLQUEUE;
	if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
	/*
	* Mode Parameters Changed
	*/
	return ADD_TO_MLQUEUE;
	if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06)
	/*
	* ALUA state changed
	*/
	return ADD_TO_MLQUEUE;
	if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07)
	/*
	* Implicit ALUA state transition failed
	*/
	return ADD_TO_MLQUEUE;
	if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
	/*
	* Inquiry data has changed
	*/
	return ADD_TO_MLQUEUE;
	if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x0e)
	/*
	* REPORTED_LUNS_DATA_HAS_CHANGED is reported
	* when switching controllers on targets like
	* Intel Multi-Flex. We can just retry.
	*/
	return ADD_TO_MLQUEUE;
	break;
	}

	return SCSI_RETURN_NOT_HANDLED;
	}

	/*
	* alua_rtpg - Evaluate REPORT TARGET GROUP STATES
	* @sdev: the device to be evaluated.
	* @wait_for_transition: if nonzero, wait ALUA_FAILOVER_TIMEOUT seconds for device to exit transitioning state
	*
	* Evaluate the Target Port Group State.
	* Returns SCSI_DH_DEV_OFFLINED if the path is
	* found to be unusable.
	*/
	static int alua_rtpg(struct scsi_device sdev, struct alua_dh_data h, int wait_for_transition)
	{
	struct scsi_sense_hdr sense_hdr;
	int len, k, off, valid_states = 0;
	unsigned char *ucp;
	unsigned err, retval;
	unsigned long expiry, interval = 0;
	unsigned int tpg_desc_tbl_off;
	unsigned char orig_transition_tmo;

	if (!h->transition_tmo)
	expiry = round_jiffies_up(jiffies + ALUA_FAILOVER_TIMEOUT * HZ);
	else
	expiry = round_jiffies_up(jiffies + h->transition_tmo * HZ);

	retry:
	retval = submit_rtpg(sdev, h->buff, h->bufflen, h->sense, h->flags);
	if (retval) {
	if (!scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
	&sense_hdr)) {
	sdev_printk(KERN_INFO, sdev,
	"%s: rtpg failed, result %d\n",
	ALUA_DH_NAME, retval);
	if (driver_byte(retval) == DRIVER_BUSY)
	return SCSI_DH_DEV_TEMP_BUSY;
	return SCSI_DH_IO;
	}

	/*
	* submit_rtpg() has failed on existing arrays
	* when requesting extended header info, and
	* the array doesn't support extended headers,
	* even though it shouldn't according to T10.
	* The retry without rtpg_ext_hdr_req set
	* handles this.
	*/
	if (!(h->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
	sense_hdr.sense_key == ILLEGAL_REQUEST &&
	sense_hdr.asc == 0x24 && sense_hdr.ascq == 0) {
	h->flags \|= ALUA_RTPG_EXT_HDR_UNSUPP;
	goto retry;
	}
	/*
	* Retry on ALUA state transition or if any
	* UNIT ATTENTION occurred.
	*/
	if (sense_hdr.sense_key == NOT_READY &&
	sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
	err = SCSI_DH_RETRY;
	else if (sense_hdr.sense_key == UNIT_ATTENTION)
	err = SCSI_DH_RETRY;
	if (err == SCSI_DH_RETRY && time_before(jiffies, expiry)) {
	sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
	ALUA_DH_NAME);
	scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
	goto retry;
	}
	sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
	ALUA_DH_NAME);
	scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
	return SCSI_DH_IO;
	}

	len = get_unaligned_be32(&h->buff[0]) + 4;

	if (len > h->bufflen) {
	/* Resubmit with the correct length */
	if (realloc_buffer(h, len)) {
	sdev_printk(KERN_WARNING, sdev,
	"%s: kmalloc buffer failed\n",__func__);
	/* Temporary failure, bypass */
	return SCSI_DH_DEV_TEMP_BUSY;
	}
	goto retry;
	}

	orig_transition_tmo = h->transition_tmo;
	if ((h->buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && h->buff[5] != 0)
	h->transition_tmo = h->buff[5];
	else
	h->transition_tmo = ALUA_FAILOVER_TIMEOUT;

	if (wait_for_transition && (orig_transition_tmo != h->transition_tmo)) {
	sdev_printk(KERN_INFO, sdev,
	"%s: transition timeout set to %d seconds\n",
	ALUA_DH_NAME, h->transition_tmo);
	expiry = jiffies + h->transition_tmo * HZ;
	}

	if ((h->buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
	tpg_desc_tbl_off = 8;
	else
	tpg_desc_tbl_off = 4;

	for (k = tpg_desc_tbl_off, ucp = h->buff + tpg_desc_tbl_off;
	k < len;
	k += off, ucp += off) {

	if (h->group_id == get_unaligned_be16(&ucp[2])) {
	h->state = ucp[0] & 0x0f;
	h->pref = ucp[0] >> 7;
	valid_states = ucp[1];
	}
	off = 8 + (ucp[7] * 4);
	}

	sdev_printk(KERN_INFO, sdev,
	"%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
	ALUA_DH_NAME, h->group_id, print_alua_state(h->state),
	h->pref ? "preferred" : "non-preferred",
	valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
	valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
	valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
	valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
	valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
	valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
	valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');

	switch (h->state) {
	case TPGS_STATE_TRANSITIONING:
	if (wait_for_transition) {
	if (time_before(jiffies, expiry)) {
	/* State transition, retry */
	interval += 2000;
	msleep(interval);
	goto retry;
	}
	err = SCSI_DH_RETRY;
	} else {
	err = SCSI_DH_OK;
	}

	/* Transitioning time exceeded, set port to standby */
	h->state = TPGS_STATE_STANDBY;
	break;
	case TPGS_STATE_OFFLINE:
	/* Path unusable */
	err = SCSI_DH_DEV_OFFLINED;
	break;
	default:
	/* Useable path if active */
	err = SCSI_DH_OK;
	break;
	}
	return err;
	}

	/*
	* alua_stpg - Issue a SET TARGET PORT GROUP command
	*
	* Issue a SET TARGET PORT GROUP command and evaluate the
	* response. Returns SCSI_DH_RETRY per default to trigger
	* a re-evaluation of the target group state or SCSI_DH_OK
	* if no further action needs to be taken.
	*/
	static unsigned alua_stpg(struct scsi_device sdev, struct alua_dh_data h)
	{
	int retval;
	struct scsi_sense_hdr sense_hdr;

	if (!(h->tpgs & TPGS_MODE_EXPLICIT)) {
	/* Only implicit ALUA supported, retry */
	return SCSI_DH_RETRY;
	}
	switch (h->state) {
	case TPGS_STATE_OPTIMIZED:
	return SCSI_DH_OK;
	case TPGS_STATE_NONOPTIMIZED:
	if ((h->flags & ALUA_OPTIMIZE_STPG) &&
	!h->pref &&
	(h->tpgs & TPGS_MODE_IMPLICIT))
	return SCSI_DH_OK;
	break;
	case TPGS_STATE_STANDBY:
	case TPGS_STATE_UNAVAILABLE:
	break;
	case TPGS_STATE_OFFLINE:
	return SCSI_DH_IO;
	case TPGS_STATE_TRANSITIONING:
	break;
	default:
	sdev_printk(KERN_INFO, sdev,
	"%s: stpg failed, unhandled TPGS state %d",
	ALUA_DH_NAME, h->state);
	return SCSI_DH_NOSYS;
	}
	retval = submit_stpg(sdev, h->group_id, h->sense);

	if (retval) {
	if (!scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
	&sense_hdr)) {
	sdev_printk(KERN_INFO, sdev,
	"%s: stpg failed, result %d",
	ALUA_DH_NAME, retval);
	if (driver_byte(retval) == DRIVER_BUSY)
	return SCSI_DH_DEV_TEMP_BUSY;
	} else {
	sdev_printk(KERN_INFO, h->sdev, "%s: stpg failed\n",
	ALUA_DH_NAME);
	scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
	}
	}
	/* Retry RTPG */
	return SCSI_DH_RETRY;
	}

	/*
	* alua_initialize - Initialize ALUA state
	* @sdev: the device to be initialized
	*
	* For the prep_fn to work correctly we have
	* to initialize the ALUA state for the device.
	*/
	static int alua_initialize(struct scsi_device sdev, struct alua_dh_data h)
	{
	int err = SCSI_DH_DEV_UNSUPP;

	h->tpgs = alua_check_tpgs(sdev);
	if (h->tpgs == TPGS_MODE_NONE)
	goto out;

	err = alua_check_vpd(sdev, h);
	if (err != SCSI_DH_OK)
	goto out;

	err = alua_rtpg(sdev, h, 0);
	if (err != SCSI_DH_OK)
	goto out;

	out:
	return err;
	}
	/*
	* alua_set_params - set/unset the optimize flag
	* @sdev: device on the path to be activated
	* params - parameters in the following format
	* "no_of_params\0param1\0param2\0param3\0...\0"
	* For example, to set the flag pass the following parameters
	* from multipath.conf
	* hardware_handler "2 alua 1"
	*/
	static int alua_set_params(struct scsi_device sdev, const char params)
	{
	struct alua_dh_data *h = sdev->handler_data;
	unsigned int optimize = 0, argc;
	const char *p = params;
	int result = SCSI_DH_OK;

	if ((sscanf(params, "%u", &argc) != 1) \|\| (argc != 1))
	return -EINVAL;

	while (*p++)
	;
	if ((sscanf(p, "%u", &optimize) != 1) \|\| (optimize > 1))
	return -EINVAL;

	if (optimize)
	h->flags \|= ALUA_OPTIMIZE_STPG;
	else
	h->flags &= ~ALUA_OPTIMIZE_STPG;

	return result;
	}

	static uint optimize_stpg;
	module_param(optimize_stpg, uint, S_IRUGO\|S_IWUSR);
	MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized path, rather than sending a STPG, when implicit TPGS is supported (0=No,1=Yes). Default is 0.");

	/*
	* alua_activate - activate a path
	* @sdev: device on the path to be activated
	*
	* We're currently switching the port group to be activated only and
	* let the array figure out the rest.
	* There may be other arrays which require us to switch all port groups
	* based on a certain policy. But until we actually encounter them it
	* should be okay.
	*/
	static int alua_activate(struct scsi_device *sdev,
	activate_complete fn, void *data)
	{
	struct alua_dh_data *h = sdev->handler_data;
	int err = SCSI_DH_OK;

	err = alua_rtpg(sdev, h, 1);
	if (err != SCSI_DH_OK)
	goto out;

	if (optimize_stpg)
	h->flags \|= ALUA_OPTIMIZE_STPG;

	err = alua_stpg(sdev, h);
	out:
	if (fn)
	fn(data, err);
	return 0;
	}

	/*
	* alua_prep_fn - request callback
	*
	* Fail I/O to all paths not in state
	* active/optimized or active/non-optimized.
	*/
	static int alua_prep_fn(struct scsi_device sdev, struct request req)
	{
	struct alua_dh_data *h = sdev->handler_data;
	int ret = BLKPREP_OK;

	if (h->state == TPGS_STATE_TRANSITIONING)
	ret = BLKPREP_DEFER;
	else if (h->state != TPGS_STATE_OPTIMIZED &&
	h->state != TPGS_STATE_NONOPTIMIZED &&
	h->state != TPGS_STATE_LBA_DEPENDENT) {
	ret = BLKPREP_KILL;
	req->cmd_flags \|= REQ_QUIET;
	}
	return ret;

	}

	/*
	* alua_bus_attach - Attach device handler
	* @sdev: device to be attached to
	*/
	static int alua_bus_attach(struct scsi_device *sdev)
	{
	struct alua_dh_data *h;
	int err;

	h = kzalloc(sizeof(*h) , GFP_KERNEL);
	if (!h)
	return -ENOMEM;
	h->tpgs = TPGS_MODE_UNINITIALIZED;
	h->state = TPGS_STATE_OPTIMIZED;
	h->group_id = -1;
	h->rel_port = -1;
	h->buff = h->inq;
	h->bufflen = ALUA_INQUIRY_SIZE;
	h->sdev = sdev;

	err = alua_initialize(sdev, h);
	if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
	goto failed;

	sdev->handler_data = h;
	return 0;
	failed:
	kfree(h);
	return -EINVAL;
	}

	/*
	* alua_bus_detach - Detach device handler
	* @sdev: device to be detached from
	*/
	static void alua_bus_detach(struct scsi_device *sdev)
	{
	struct alua_dh_data *h = sdev->handler_data;

	if (h->buff && h->inq != h->buff)
	kfree(h->buff);
	sdev->handler_data = NULL;
	kfree(h);
	}

	static struct scsi_device_handler alua_dh = {
	.name = ALUA_DH_NAME,
	.module = THIS_MODULE,
	.attach = alua_bus_attach,
	.detach = alua_bus_detach,
	.prep_fn = alua_prep_fn,
	.check_sense = alua_check_sense,
	.activate = alua_activate,
	.set_params = alua_set_params,
	};

	static int __init alua_init(void)
	{
	int r;

	r = scsi_register_device_handler(&alua_dh);
	if (r != 0)
	printk(KERN_ERR "%s: Failed to register scsi device handler",
	ALUA_DH_NAME);
	return r;
	}

	static void __exit alua_exit(void)
	{
	scsi_unregister_device_handler(&alua_dh);
	}

	module_init(alua_init);
	module_exit(alua_exit);

	MODULE_DESCRIPTION("DM Multipath ALUA support");
	MODULE_AUTHOR("Hannes Reinecke <hare@suse.de>");
	MODULE_LICENSE("GPL");
	MODULE_VERSION(ALUA_DH_VER);