[SCSI] scsi_dh: add generic SPC-3 alua handler

Signed-off-by: Hannes Reinecke <[e-mail]>
Signed-off-by: Chandra Seetharaman <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/device_handler/Kconfig

···
 	depends on SCSI_DH
 	help
 	If you have a EMC CLARiiON select y. Otherwise, say N.
+
+config SCSI_DH_ALUA
+	tristate "SPC-3 ALUA Device Handler (EXPERIMENTAL)"
+	depends on SCSI_DH && EXPERIMENTAL
+	help
+	  SCSI Device handler for generic SPC-3 Asymmetric Logical Unit
+	  Access (ALUA).
+

drivers/scsi/device_handler/Makefile

···
 obj-$(CONFIG_SCSI_DH_RDAC)	+= scsi_dh_rdac.o
 obj-$(CONFIG_SCSI_DH_HP_SW)	+= scsi_dh_hp_sw.o
 obj-$(CONFIG_SCSI_DH_EMC)	+= scsi_dh_emc.o
+obj-$(CONFIG_SCSI_DH_ALUA)	+= scsi_dh_alua.o

drivers/scsi/device_handler/scsi_dh_alua.c

···
+/*
+ * Generic SCSI-3 ALUA SCSI Device Handler
+ *
+ * Copyright (C) 2007, 2008 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 <scsi/scsi.h>
+#include <scsi/scsi_eh.h>
+#include <scsi/scsi_dh.h>
+
+#define ALUA_DH_NAME "alua"
+#define ALUA_DH_VER "1.2"
+
+#define TPGS_STATE_OPTIMIZED		0x0
+#define TPGS_STATE_NONOPTIMIZED		0x1
+#define TPGS_STATE_STANDBY		0x2
+#define TPGS_STATE_UNAVAILABLE		0x3
+#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_OFFLINE		0x40
+#define TPGS_SUPPORT_TRANSITION		0x80
+
+#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 * HZ)
+#define ALUA_FAILOVER_RETRIES		5
+
+struct alua_dh_data {
+	int			group_id;
+	int			rel_port;
+	int			tpgs;
+	int			state;
+	unsigned char		inq[ALUA_INQUIRY_SIZE];
+	unsigned char		*buff;
+	int			bufflen;
+	unsigned char		sense[SCSI_SENSE_BUFFERSIZE];
+	int			senselen;
+};
+
+#define ALUA_POLICY_SWITCH_CURRENT	0
+#define ALUA_POLICY_SWITCH_ALL		1
+
+static inline struct alua_dh_data *get_alua_data(struct scsi_device *sdev)
+{
+	struct scsi_dh_data *scsi_dh_data = sdev->scsi_dh_data;
+	BUG_ON(scsi_dh_data == NULL);
+	return ((struct alua_dh_data *) scsi_dh_data->buf);
+}
+
+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 (!rq) {
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: blk_get_request failed\n", __FUNCTION__);
+		return NULL;
+	}
+
+	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", __FUNCTION__);
+		return NULL;
+	}
+
+	rq->cmd_type = REQ_TYPE_BLOCK_PC;
+	rq->cmd_flags |= REQ_FAILFAST | REQ_NOMERGE;
+	rq->retries = ALUA_FAILOVER_RETRIES;
+	rq->timeout = ALUA_FAILOVER_TIMEOUT;
+
+	return rq;
+}
+
+/*
+ * submit_std_inquiry - Issue a standard INQUIRY command
+ * @sdev: sdev the command should be send to
+ */
+static int submit_std_inquiry(struct scsi_device *sdev, struct alua_dh_data *h)
+{
+	struct request *rq;
+	int err = SCSI_DH_RES_TEMP_UNAVAIL;
+
+	rq = get_alua_req(sdev, h->inq, ALUA_INQUIRY_SIZE, READ);
+	if (!rq)
+		goto done;
+
+	/* Prepare the command. */
+	rq->cmd[0] = INQUIRY;
+	rq->cmd[1] = 0;
+	rq->cmd[2] = 0;
+	rq->cmd[4] = ALUA_INQUIRY_SIZE;
+	rq->cmd_len = COMMAND_SIZE(INQUIRY);
+
+	rq->sense = h->sense;
+	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
+	rq->sense_len = h->senselen = 0;
+
+	err = blk_execute_rq(rq->q, NULL, rq, 1);
+	if (err == -EIO) {
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: std inquiry failed with %x\n",
+			    ALUA_DH_NAME, rq->errors);
+		h->senselen = rq->sense_len;
+		err = SCSI_DH_IO;
+	}
+	blk_put_request(rq);
+done:
+	return err;
+}
+
+/*
+ * submit_vpd_inquiry - Issue an INQUIRY VPD page 0x83 command
+ * @sdev: sdev the command should be sent to
+ */
+static int submit_vpd_inquiry(struct scsi_device *sdev, struct alua_dh_data *h)
+{
+	struct request *rq;
+	int err = SCSI_DH_RES_TEMP_UNAVAIL;
+
+	rq = get_alua_req(sdev, h->buff, h->bufflen, READ);
+	if (!rq)
+		goto done;
+
+	/* Prepare the command. */
+	rq->cmd[0] = INQUIRY;
+	rq->cmd[1] = 1;
+	rq->cmd[2] = 0x83;
+	rq->cmd[4] = h->bufflen;
+	rq->cmd_len = COMMAND_SIZE(INQUIRY);
+
+	rq->sense = h->sense;
+	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
+	rq->sense_len = h->senselen = 0;
+
+	err = blk_execute_rq(rq->q, NULL, rq, 1);
+	if (err == -EIO) {
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: evpd inquiry failed with %x\n",
+			    ALUA_DH_NAME, rq->errors);
+		h->senselen = rq->sense_len;
+		err = SCSI_DH_IO;
+	}
+	blk_put_request(rq);
+done:
+	return err;
+}
+
+/*
+ * 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, struct alua_dh_data *h)
+{
+	struct request *rq;
+	int err = SCSI_DH_RES_TEMP_UNAVAIL;
+
+	rq = get_alua_req(sdev, h->buff, h->bufflen, READ);
+	if (!rq)
+		goto done;
+
+	/* Prepare the command. */
+	rq->cmd[0] = MAINTENANCE_IN;
+	rq->cmd[1] = MI_REPORT_TARGET_PGS;
+	rq->cmd[6] = (h->bufflen >> 24) & 0xff;
+	rq->cmd[7] = (h->bufflen >> 16) & 0xff;
+	rq->cmd[8] = (h->bufflen >>  8) & 0xff;
+	rq->cmd[9] = h->bufflen & 0xff;
+	rq->cmd_len = COMMAND_SIZE(MAINTENANCE_IN);
+
+	rq->sense = h->sense;
+	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
+	rq->sense_len = h->senselen = 0;
+
+	err = blk_execute_rq(rq->q, NULL, rq, 1);
+	if (err == -EIO) {
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: rtpg failed with %x\n",
+			    ALUA_DH_NAME, rq->errors);
+		h->senselen = rq->sense_len;
+		err = SCSI_DH_IO;
+	}
+	blk_put_request(rq);
+done:
+	return err;
+}
+
+/*
+ * submit_stpg - Issue a SET TARGET GROUP STATES command
+ * @sdev: sdev the command should be sent to
+ *
+ * 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, struct alua_dh_data *h)
+{
+	struct request *rq;
+	int err = SCSI_DH_RES_TEMP_UNAVAIL;
+	int stpg_len = 8;
+
+	/* Prepare the data buffer */
+	memset(h->buff, 0, stpg_len);
+	h->buff[4] = TPGS_STATE_OPTIMIZED & 0x0f;
+	h->buff[6] = (h->group_id >> 8) & 0x0f;
+	h->buff[7] = h->group_id & 0x0f;
+
+	rq = get_alua_req(sdev, h->buff, stpg_len, WRITE);
+	if (!rq)
+		goto done;
+
+	/* Prepare the command. */
+	rq->cmd[0] = MAINTENANCE_OUT;
+	rq->cmd[1] = MO_SET_TARGET_PGS;
+	rq->cmd[6] = (stpg_len >> 24) & 0xff;
+	rq->cmd[7] = (stpg_len >> 16) & 0xff;
+	rq->cmd[8] = (stpg_len >>  8) & 0xff;
+	rq->cmd[9] = stpg_len & 0xff;
+	rq->cmd_len = COMMAND_SIZE(MAINTENANCE_OUT);
+
+	rq->sense = h->sense;
+	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
+	rq->sense_len = h->senselen = 0;
+
+	err = blk_execute_rq(rq->q, NULL, rq, 1);
+	if (err == -EIO) {
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: stpg failed with %x\n",
+			    ALUA_DH_NAME, rq->errors);
+		h->senselen = rq->sense_len;
+		err = SCSI_DH_IO;
+	}
+	blk_put_request(rq);
+done:
+	return err;
+}
+
+/*
+ * alua_std_inquiry - Evaluate standard INQUIRY command
+ * @sdev: device to be checked
+ *
+ * Just extract the TPGS setting to find out if ALUA
+ * is supported.
+ */
+static int alua_std_inquiry(struct scsi_device *sdev, struct alua_dh_data *h)
+{
+	int err;
+
+	err = submit_std_inquiry(sdev, h);
+
+	if (err != SCSI_DH_OK)
+		return err;
+
+	/* Check TPGS setting */
+	h->tpgs = (h->inq[5] >> 4) & 0x3;
+	switch (h->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;
+	default:
+		h->tpgs = TPGS_MODE_NONE;
+		sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
+			    ALUA_DH_NAME);
+		err = SCSI_DH_DEV_UNSUPP;
+		break;
+	}
+
+	return err;
+}
+
+/*
+ * alua_vpd_inquiry - 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_vpd_inquiry(struct scsi_device *sdev, struct alua_dh_data *h)
+{
+	int len;
+	unsigned err;
+	unsigned char *d;
+
+ retry:
+	err = submit_vpd_inquiry(sdev, h);
+
+	if (err != SCSI_DH_OK)
+		return err;
+
+	/* Check if vpd page exceeds initial buffer */
+	len = (h->buff[2] << 8) + h->buff[3] + 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",
+				    ALUA_DH_NAME);
+			/* Temporary failure, bypass */
+			return SCSI_DH_DEV_TEMP_BUSY;
+		}
+		goto retry;
+	}
+
+	/*
+	 * Now look for the correct descriptor.
+	 */
+	d = h->buff + 4;
+	while (d < h->buff + len) {
+		switch (d[1] & 0xf) {
+		case 0x4:
+			/* Relative target port */
+			h->rel_port = (d[6] << 8) + d[7];
+			break;
+		case 0x5:
+			/* Target port group */
+			h->group_id = (d[6] << 8) + d[7];
+			break;
+		default:
+			break;
+		}
+		d += d[3] + 4;
+	}
+
+	if (h->group_id == -1) {
+		/*
+		 * 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);
+		h->state = TPGS_STATE_OPTIMIZED;
+		h->tpgs = TPGS_MODE_NONE;
+		err = SCSI_DH_DEV_UNSUPP;
+	} else {
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: port group %02x rel port %02x\n",
+			    ALUA_DH_NAME, h->group_id, h->rel_port);
+	}
+
+	return err;
+}
+
+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_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 NEEDS_RETRY;
+		if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0b)
+			/*
+			 * LUN Not Accessible -- Target port in standby state
+			 */
+			return SUCCESS;
+		if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0c)
+			/*
+			 * LUN Not Accessible -- Target port in unavailable state
+			 */
+			return SUCCESS;
+		if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x12)
+			/*
+			 * LUN Not Ready -- Offline
+			 */
+			return SUCCESS;
+		break;
+	case UNIT_ATTENTION:
+		if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00)
+			/*
+			 * Power On, Reset, or Bus Device Reset, just retry.
+			 */
+			return NEEDS_RETRY;
+		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
+			/*
+			 * ALUA state changed
+			 */
+			return NEEDS_RETRY;
+		}
+		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
+			/*
+			 * Implicit ALUA state transition failed
+			 */
+			return NEEDS_RETRY;
+		}
+		break;
+	}
+
+	return SCSI_RETURN_NOT_HANDLED;
+}
+
+/*
+ * alua_stpg - Evaluate SET TARGET GROUP STATES
+ * @sdev: the device to be evaluated
+ * @state: the new target group state
+ *
+ * Send a SET TARGET GROUP STATES command to the device.
+ * We only have to test here if we should resubmit the command;
+ * any other error is assumed as a failure.
+ */
+static int alua_stpg(struct scsi_device *sdev, int state,
+		     struct alua_dh_data *h)
+{
+	struct scsi_sense_hdr sense_hdr;
+	unsigned err;
+	int retry = ALUA_FAILOVER_RETRIES;
+
+ retry:
+	err = submit_stpg(sdev, h);
+	if (err == SCSI_DH_IO && h->senselen > 0) {
+		err = scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
+					   &sense_hdr);
+		if (!err)
+			return SCSI_DH_IO;
+		err = alua_check_sense(sdev, &sense_hdr);
+		if (retry > 0 && err == NEEDS_RETRY) {
+			retry--;
+			goto retry;
+		}
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: stpg sense code: %02x/%02x/%02x\n",
+			    ALUA_DH_NAME, sense_hdr.sense_key,
+			    sense_hdr.asc, sense_hdr.ascq);
+		err = SCSI_DH_IO;
+	}
+	if (err == SCSI_DH_OK) {
+		h->state = state;
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: port group %02x switched to state %c\n",
+			    ALUA_DH_NAME, h->group_id,
+			    print_alua_state(h->state) );
+	}
+	return err;
+}
+
+/*
+ * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
+ * @sdev: the device to be evaluated.
+ *
+ * Evaluate the Target Port Group State.
+ * Returns SCSI_DH_DEV_OFFLINED if the path is
+ * found to be unuseable.
+ */
+static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
+{
+	struct scsi_sense_hdr sense_hdr;
+	int len, k, off, valid_states = 0;
+	char *ucp;
+	unsigned err;
+
+ retry:
+	err = submit_rtpg(sdev, h);
+
+	if (err == SCSI_DH_IO && h->senselen > 0) {
+		err = scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
+					   &sense_hdr);
+		if (!err)
+			return SCSI_DH_IO;
+
+		err = alua_check_sense(sdev, &sense_hdr);
+		if (err == NEEDS_RETRY)
+			goto retry;
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: rtpg sense code %02x/%02x/%02x\n",
+			    ALUA_DH_NAME, sense_hdr.sense_key,
+			    sense_hdr.asc, sense_hdr.ascq);
+		err = SCSI_DH_IO;
+	}
+	if (err != SCSI_DH_OK)
+		return err;
+
+	len = (h->buff[0] << 24) + (h->buff[1] << 16) +
+		(h->buff[2] << 8) + h->buff[3] + 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",__FUNCTION__);
+			/* Temporary failure, bypass */
+			return SCSI_DH_DEV_TEMP_BUSY;
+		}
+		goto retry;
+	}
+
+	for (k = 4, ucp = h->buff + 4; k < len; k += off, ucp += off) {
+		if (h->group_id == (ucp[2] << 8) + ucp[3]) {
+			h->state = ucp[0] & 0x0f;
+			valid_states = ucp[1];
+		}
+		off = 8 + (ucp[7] * 4);
+	}
+
+	sdev_printk(KERN_INFO, sdev,
+		    "%s: port group %02x state %c supports %c%c%c%c%c%c\n",
+		    ALUA_DH_NAME, h->group_id, print_alua_state(h->state),
+		    valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
+		    valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
+		    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');
+
+	if (h->tpgs & TPGS_MODE_EXPLICIT) {
+		switch (h->state) {
+		case TPGS_STATE_TRANSITIONING:
+			/* State transition, retry */
+			goto retry;
+			break;
+		case TPGS_STATE_OFFLINE:
+			/* Path is offline, fail */
+			err = SCSI_DH_DEV_OFFLINED;
+			break;
+		default:
+			break;
+		}
+	} else {
+		/* Only Implicit ALUA support */
+		if (h->state == TPGS_STATE_OPTIMIZED ||
+		    h->state == TPGS_STATE_NONOPTIMIZED ||
+		    h->state == TPGS_STATE_STANDBY)
+			/* Useable path if active */
+			err = SCSI_DH_OK;
+		else
+			/* Path unuseable for unavailable/offline */
+			err = SCSI_DH_DEV_OFFLINED;
+	}
+	return err;
+}
+
+/*
+ * 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;
+
+	err = alua_std_inquiry(sdev, h);
+	if (err != SCSI_DH_OK)
+		goto out;
+
+	err = alua_vpd_inquiry(sdev, h);
+	if (err != SCSI_DH_OK)
+		goto out;
+
+	err = alua_rtpg(sdev, h);
+	if (err != SCSI_DH_OK)
+		goto out;
+
+out:
+	return err;
+}
+
+/*
+ * 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)
+{
+	struct alua_dh_data *h = get_alua_data(sdev);
+	int err = SCSI_DH_OK;
+
+	if (h->group_id != -1) {
+		err = alua_rtpg(sdev, h);
+		if (err != SCSI_DH_OK)
+			goto out;
+	}
+
+	if (h->tpgs == TPGS_MODE_EXPLICIT && h->state != TPGS_STATE_OPTIMIZED)
+		err = alua_stpg(sdev, TPGS_STATE_OPTIMIZED, h);
+
+out:
+	return err;
+}
+
+/*
+ * 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 = get_alua_data(sdev);
+	int ret = BLKPREP_OK;
+
+	if (h->state != TPGS_STATE_OPTIMIZED &&
+	    h->state != TPGS_STATE_NONOPTIMIZED) {
+		ret = BLKPREP_KILL;
+		req->cmd_flags |= REQ_QUIET;
+	}
+	return ret;
+
+}
+
+const struct scsi_dh_devlist alua_dev_list[] = {
+	{"HP", "MSA VOLUME" },
+	{"HP", "HSV101" },
+	{"HP", "HSV111" },
+	{"HP", "HSV200" },
+	{"HP", "HSV210" },
+	{"HP", "HSV300" },
+	{"IBM", "2107900" },
+	{"IBM", "2145" },
+	{"Pillar", "Axiom" },
+	{NULL, NULL}
+};
+
+static int alua_bus_attach(struct scsi_device *sdev);
+static void alua_bus_detach(struct scsi_device *sdev);
+
+static struct scsi_device_handler alua_dh = {
+	.name = ALUA_DH_NAME,
+	.module = THIS_MODULE,
+	.devlist = alua_dev_list,
+	.attach = alua_bus_attach,
+	.detach = alua_bus_detach,
+	.prep_fn = alua_prep_fn,
+	.check_sense = alua_check_sense,
+	.activate = alua_activate,
+};
+
+/*
+ * alua_bus_attach - Attach device handler
+ * @sdev: device to be attached to
+ */
+static int alua_bus_attach(struct scsi_device *sdev)
+{
+	struct scsi_dh_data *scsi_dh_data;
+	struct alua_dh_data *h;
+	unsigned long flags;
+	int err = SCSI_DH_OK;
+
+	scsi_dh_data = kzalloc(sizeof(struct scsi_device_handler *)
+			       + sizeof(*h) , GFP_KERNEL);
+	if (!scsi_dh_data) {
+		sdev_printk(KERN_ERR, sdev, "%s: Attach failed\n",
+			    ALUA_DH_NAME);
+		return -ENOMEM;
+	}
+
+	scsi_dh_data->scsi_dh = &alua_dh;
+	h = (struct alua_dh_data *) scsi_dh_data->buf;
+	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;
+
+	err = alua_initialize(sdev, h);
+	if (err != SCSI_DH_OK)
+		goto failed;
+
+	if (!try_module_get(THIS_MODULE))
+		goto failed;
+
+	spin_lock_irqsave(sdev->request_queue->queue_lock, flags);
+	sdev->scsi_dh_data = scsi_dh_data;
+	spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
+
+	return 0;
+
+failed:
+	kfree(scsi_dh_data);
+	sdev_printk(KERN_ERR, sdev, "%s: not attached\n", ALUA_DH_NAME);
+	return -EINVAL;
+}
+
+/*
+ * alua_bus_detach - Detach device handler
+ * @sdev: device to be detached from
+ */
+static void alua_bus_detach(struct scsi_device *sdev)
+{
+	struct scsi_dh_data *scsi_dh_data;
+	struct alua_dh_data *h;
+	unsigned long flags;
+
+	spin_lock_irqsave(sdev->request_queue->queue_lock, flags);
+	scsi_dh_data = sdev->scsi_dh_data;
+	sdev->scsi_dh_data = NULL;
+	spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags);
+
+	h = (struct alua_dh_data *) scsi_dh_data->buf;
+	if (h->buff && h->inq != h->buff)
+		kfree(h->buff);
+	kfree(scsi_dh_data);
+	module_put(THIS_MODULE);
+	sdev_printk(KERN_NOTICE, sdev, "%s: Detached\n", ALUA_DH_NAME);
+}
+
+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 <[e-mail]>");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(ALUA_DH_VER);

include/scsi/scsi.h

···
 #define VARIABLE_LENGTH_CMD   0x7f
 #define REPORT_LUNS           0xa0
 #define MAINTENANCE_IN        0xa3
+#define MAINTENANCE_OUT       0xa4
 #define MOVE_MEDIUM           0xa5
 #define EXCHANGE_MEDIUM       0xa6
 #define READ_12               0xa8
···
 #define	SAI_READ_CAPACITY_16  0x10
 /* values for maintenance in */
 #define MI_REPORT_TARGET_PGS  0x0a
+/* values for maintenance out */
+#define MO_SET_TARGET_PGS     0x0a
 
 /* Values for T10/04-262r7 */
 #define	ATA_16		      0x85	/* 16-byte pass-thru */