dm mpath: rdac

This patch supports LSI/Engenio devices in RDAC mode. Like dm-emc
it requires userspace support. In your multipath.conf file you must have:

path_checker            rdac
hardware_handler        "1 rdac"
prio_callout		"/sbin/mpath_prio_tpc /dev/%n"

And you also then must have a updated multipath tools release which
has rdac support.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/md/Kconfig

@@ -262,6 +262,12 @@ config DM_MULTIPATH_EMC
 	---help---
 	  Multipath support for EMC CX/AX series hardware.
 
+config DM_MULTIPATH_RDAC
+	tristate "LSI/Engenio RDAC multipath support (EXPERIMENTAL)"
+	depends on DM_MULTIPATH && BLK_DEV_DM && EXPERIMENTAL
+	---help---
+	  Multipath support for LSI/Engenio RDAC.
+
 config DM_DELAY
 	tristate "I/O delaying target (EXPERIMENTAL)"
 	depends on BLK_DEV_DM && EXPERIMENTAL

drivers/md/Makefile

@@ -7,6 +7,7 @@ dm-mod-objs	:= dm.o dm-table.o dm-target.o dm-linear.o dm-stripe.o \
 dm-multipath-objs := dm-hw-handler.o dm-path-selector.o dm-mpath.o
 dm-snapshot-objs := dm-snap.o dm-exception-store.o
 dm-mirror-objs	:= dm-log.o dm-raid1.o
+dm-rdac-objs	:= dm-mpath-rdac.o
 md-mod-objs     := md.o bitmap.o
 raid456-objs	:= raid5.o raid6algos.o raid6recov.o raid6tables.o \
 		   raid6int1.o raid6int2.o raid6int4.o \
@@ -34,6 +35,7 @@ obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o
 obj-$(CONFIG_DM_DELAY)		+= dm-delay.o
 obj-$(CONFIG_DM_MULTIPATH)	+= dm-multipath.o dm-round-robin.o
 obj-$(CONFIG_DM_MULTIPATH_EMC)	+= dm-emc.o
+obj-$(CONFIG_DM_MULTIPATH_RDAC)	+= dm-rdac.o
 obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
 obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o
 obj-$(CONFIG_DM_ZERO)		+= dm-zero.o

drivers/md/dm-mpath-rdac.c

@@ -0,0 +1,700 @@
+/*
+ * Engenio/LSI RDAC DM HW handler
+ *
+ * Copyright (C) 2005 Mike Christie. All rights reserved.
+ * Copyright (C) Chandra Seetharaman, IBM Corp. 2007
+ *
+ * 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_cmnd.h>
+#include <scsi/scsi_eh.h>
+
+#define DM_MSG_PREFIX "multipath rdac"
+
+#include "dm.h"
+#include "dm-hw-handler.h"
+
+#define RDAC_DM_HWH_NAME "rdac"
+#define RDAC_DM_HWH_VER "0.4"
+
+/*
+ * LSI mode page stuff
+ *
+ * These struct definitions and the forming of the
+ * mode page were taken from the LSI RDAC 2.4 GPL'd
+ * driver, and then converted to Linux conventions.
+ */
+#define RDAC_QUIESCENCE_TIME 20;
+/*
+ * Page Codes
+ */
+#define RDAC_PAGE_CODE_REDUNDANT_CONTROLLER 0x2c
+
+/*
+ * Controller modes definitions
+ */
+#define RDAC_MODE_TRANSFER_ALL_LUNS		0x01
+#define RDAC_MODE_TRANSFER_SPECIFIED_LUNS	0x02
+
+/*
+ * RDAC Options field
+ */
+#define RDAC_FORCED_QUIESENCE 0x02
+
+#define RDAC_FAILOVER_TIMEOUT (60 * HZ)
+
+struct rdac_mode_6_hdr {
+	u8	data_len;
+	u8	medium_type;
+	u8	device_params;
+	u8	block_desc_len;
+};
+
+struct rdac_mode_10_hdr {
+	u16	data_len;
+	u8	medium_type;
+	u8	device_params;
+	u16	reserved;
+	u16	block_desc_len;
+};
+
+struct rdac_mode_common {
+	u8	controller_serial[16];
+	u8	alt_controller_serial[16];
+	u8	rdac_mode[2];
+	u8	alt_rdac_mode[2];
+	u8	quiescence_timeout;
+	u8	rdac_options;
+};
+
+struct rdac_pg_legacy {
+	struct rdac_mode_6_hdr hdr;
+	u8	page_code;
+	u8	page_len;
+	struct rdac_mode_common common;
+#define MODE6_MAX_LUN	32
+	u8	lun_table[MODE6_MAX_LUN];
+	u8	reserved2[32];
+	u8	reserved3;
+	u8	reserved4;
+};
+
+struct rdac_pg_expanded {
+	struct rdac_mode_10_hdr hdr;
+	u8	page_code;
+	u8	subpage_code;
+	u8	page_len[2];
+	struct rdac_mode_common common;
+	u8	lun_table[256];
+	u8	reserved3;
+	u8	reserved4;
+};
+
+struct c9_inquiry {
+	u8	peripheral_info;
+	u8	page_code;	/* 0xC9 */
+	u8	reserved1;
+	u8	page_len;
+	u8	page_id[4];	/* "vace" */
+	u8	avte_cvp;
+	u8	path_prio;
+	u8	reserved2[38];
+};
+
+#define SUBSYS_ID_LEN	16
+#define SLOT_ID_LEN	2
+
+struct c4_inquiry {
+	u8	peripheral_info;
+	u8	page_code;	/* 0xC4 */
+	u8	reserved1;
+	u8	page_len;
+	u8	page_id[4];	/* "subs" */
+	u8	subsys_id[SUBSYS_ID_LEN];
+	u8	revision[4];
+	u8	slot_id[SLOT_ID_LEN];
+	u8	reserved[2];
+};
+
+struct rdac_controller {
+	u8			subsys_id[SUBSYS_ID_LEN];
+	u8			slot_id[SLOT_ID_LEN];
+	int			use_10_ms;
+	struct kref		kref;
+	struct list_head	node; /* list of all controllers */
+	spinlock_t		lock;
+	int			submitted;
+	struct list_head	cmd_list; /* list of commands to be submitted */
+	union			{
+		struct rdac_pg_legacy legacy;
+		struct rdac_pg_expanded expanded;
+	} mode_select;
+};
+struct c8_inquiry {
+	u8	peripheral_info;
+	u8	page_code; /* 0xC8 */
+	u8	reserved1;
+	u8	page_len;
+	u8	page_id[4]; /* "edid" */
+	u8	reserved2[3];
+	u8	vol_uniq_id_len;
+	u8	vol_uniq_id[16];
+	u8	vol_user_label_len;
+	u8	vol_user_label[60];
+	u8	array_uniq_id_len;
+	u8	array_unique_id[16];
+	u8	array_user_label_len;
+	u8	array_user_label[60];
+	u8	lun[8];
+};
+
+struct c2_inquiry {
+	u8	peripheral_info;
+	u8	page_code;	/* 0xC2 */
+	u8	reserved1;
+	u8	page_len;
+	u8	page_id[4];	/* "swr4" */
+	u8	sw_version[3];
+	u8	sw_date[3];
+	u8	features_enabled;
+	u8	max_lun_supported;
+	u8	partitions[239]; /* Total allocation length should be 0xFF */
+};
+
+struct rdac_handler {
+	struct list_head	entry; /* list waiting to submit MODE SELECT */
+	unsigned		timeout;
+	struct rdac_controller	*ctlr;
+#define UNINITIALIZED_LUN	(1 << 8)
+	unsigned		lun;
+	unsigned char		sense[SCSI_SENSE_BUFFERSIZE];
+	struct dm_path		*path;
+	struct work_struct	work;
+#define	SEND_C2_INQUIRY		1
+#define	SEND_C4_INQUIRY		2
+#define	SEND_C8_INQUIRY		3
+#define	SEND_C9_INQUIRY		4
+#define	SEND_MODE_SELECT	5
+	int			cmd_to_send;
+	union			{
+		struct c2_inquiry c2;
+		struct c4_inquiry c4;
+		struct c8_inquiry c8;
+		struct c9_inquiry c9;
+	} inq;
+};
+
+static LIST_HEAD(ctlr_list);
+static DEFINE_SPINLOCK(list_lock);
+static struct workqueue_struct *rdac_wkqd;
+
+static inline int had_failures(struct request *req, int error)
+{
+	return (error || host_byte(req->errors) != DID_OK ||
+			msg_byte(req->errors) != COMMAND_COMPLETE);
+}
+
+static void rdac_resubmit_all(struct rdac_handler *h)
+{
+	struct rdac_controller *ctlr = h->ctlr;
+	struct rdac_handler *tmp, *h1;
+
+	spin_lock(&ctlr->lock);
+	list_for_each_entry_safe(h1, tmp, &ctlr->cmd_list, entry) {
+		h1->cmd_to_send = SEND_C9_INQUIRY;
+		queue_work(rdac_wkqd, &h1->work);
+		list_del(&h1->entry);
+	}
+	ctlr->submitted = 0;
+	spin_unlock(&ctlr->lock);
+}
+
+static void mode_select_endio(struct request *req, int error)
+{
+	struct rdac_handler *h = req->end_io_data;
+	struct scsi_sense_hdr sense_hdr;
+	int sense = 0, fail = 0;
+
+	if (had_failures(req, error)) {
+		fail = 1;
+		goto failed;
+	}
+
+	if (status_byte(req->errors) == CHECK_CONDITION) {
+		scsi_normalize_sense(req->sense, SCSI_SENSE_BUFFERSIZE,
+				&sense_hdr);
+		sense = (sense_hdr.sense_key << 16) | (sense_hdr.asc << 8) |
+				sense_hdr.ascq;
+		/* If it is retryable failure, submit the c9 inquiry again */
+		if (sense == 0x59136 || sense == 0x68b02 || sense == 0xb8b02 ||
+		    sense == 0x62900) {
+			/* 0x59136    - Command lock contention
+			 * 0x[6b]8b02 - Quiesense in progress or achieved
+			 * 0x62900    - Power On, Reset, or Bus Device Reset
+			 */
+			h->cmd_to_send = SEND_C9_INQUIRY;
+			queue_work(rdac_wkqd, &h->work);
+			goto done;
+		}
+		if (sense)
+			DMINFO("MODE_SELECT failed on %s with sense 0x%x",
+						h->path->dev->name, sense);
+ 	}
+failed:
+	if (fail || sense)
+		dm_pg_init_complete(h->path, MP_FAIL_PATH);
+	else
+		dm_pg_init_complete(h->path, 0);
+
+done:
+	rdac_resubmit_all(h);
+	__blk_put_request(req->q, req);
+}
+
+static struct request *get_rdac_req(struct rdac_handler *h,
+			void *buffer, unsigned buflen, int rw)
+{
+	struct request *rq;
+	struct request_queue *q = bdev_get_queue(h->path->dev->bdev);
+
+	rq = blk_get_request(q, rw, GFP_KERNEL);
+
+	if (!rq) {
+		DMINFO("get_rdac_req: blk_get_request failed");
+		return NULL;
+	}
+
+	if (buflen && blk_rq_map_kern(q, rq, buffer, buflen, GFP_KERNEL)) {
+		blk_put_request(rq);
+		DMINFO("get_rdac_req: blk_rq_map_kern failed");
+		return NULL;
+	}
+
+ 	memset(&rq->cmd, 0, BLK_MAX_CDB);
+	rq->sense = h->sense;
+	memset(rq->sense, 0, SCSI_SENSE_BUFFERSIZE);
+	rq->sense_len = 0;
+
+	rq->end_io_data = h;
+	rq->timeout = h->timeout;
+	rq->cmd_type = REQ_TYPE_BLOCK_PC;
+	rq->cmd_flags = REQ_FAILFAST | REQ_NOMERGE;
+	return rq;
+}
+
+static struct request *rdac_failover_get(struct rdac_handler *h)
+{
+	struct request *rq;
+	struct rdac_mode_common *common;
+	unsigned data_size;
+
+	if (h->ctlr->use_10_ms) {
+		struct rdac_pg_expanded *rdac_pg;
+
+		data_size = sizeof(struct rdac_pg_expanded);
+		rdac_pg = &h->ctlr->mode_select.expanded;
+		memset(rdac_pg, 0, data_size);
+		common = &rdac_pg->common;
+		rdac_pg->page_code = RDAC_PAGE_CODE_REDUNDANT_CONTROLLER + 0x40;
+		rdac_pg->subpage_code = 0x1;
+		rdac_pg->page_len[0] = 0x01;
+		rdac_pg->page_len[1] = 0x28;
+		rdac_pg->lun_table[h->lun] = 0x81;
+	} else {
+		struct rdac_pg_legacy *rdac_pg;
+
+		data_size = sizeof(struct rdac_pg_legacy);
+		rdac_pg = &h->ctlr->mode_select.legacy;
+		memset(rdac_pg, 0, data_size);
+		common = &rdac_pg->common;
+		rdac_pg->page_code = RDAC_PAGE_CODE_REDUNDANT_CONTROLLER;
+		rdac_pg->page_len = 0x68;
+		rdac_pg->lun_table[h->lun] = 0x81;
+	}
+	common->rdac_mode[1] = RDAC_MODE_TRANSFER_SPECIFIED_LUNS;
+	common->quiescence_timeout = RDAC_QUIESCENCE_TIME;
+	common->rdac_options = RDAC_FORCED_QUIESENCE;
+
+	/* get request for block layer packet command */
+	rq = get_rdac_req(h, &h->ctlr->mode_select, data_size, WRITE);
+	if (!rq) {
+		DMERR("rdac_failover_get: no rq");
+		return NULL;
+	}
+
+	/* Prepare the command. */
+	if (h->ctlr->use_10_ms) {
+		rq->cmd[0] = MODE_SELECT_10;
+		rq->cmd[7] = data_size >> 8;
+		rq->cmd[8] = data_size & 0xff;
+	} else {
+		rq->cmd[0] = MODE_SELECT;
+		rq->cmd[4] = data_size;
+	}
+	rq->cmd_len = COMMAND_SIZE(rq->cmd[0]);
+
+	return rq;
+}
+
+/* Acquires h->ctlr->lock */
+static void submit_mode_select(struct rdac_handler *h)
+{
+	struct request *rq;
+	struct request_queue *q = bdev_get_queue(h->path->dev->bdev);
+
+	spin_lock(&h->ctlr->lock);
+	if (h->ctlr->submitted) {
+		list_add(&h->entry, &h->ctlr->cmd_list);
+		goto drop_lock;
+	}
+
+	if (!q) {
+		DMINFO("submit_mode_select: no queue");
+		goto fail_path;
+	}
+
+	rq = rdac_failover_get(h);
+	if (!rq) {
+		DMERR("submit_mode_select: no rq");
+		goto fail_path;
+	}
+
+	DMINFO("queueing MODE_SELECT command on %s", h->path->dev->name);
+
+	blk_execute_rq_nowait(q, NULL, rq, 1, mode_select_endio);
+	h->ctlr->submitted = 1;
+	goto drop_lock;
+fail_path:
+	dm_pg_init_complete(h->path, MP_FAIL_PATH);
+drop_lock:
+	spin_unlock(&h->ctlr->lock);
+}
+
+static void release_ctlr(struct kref *kref)
+{
+	struct rdac_controller *ctlr;
+	ctlr = container_of(kref, struct rdac_controller, kref);
+
+	spin_lock(&list_lock);
+	list_del(&ctlr->node);
+	spin_unlock(&list_lock);
+	kfree(ctlr);
+}
+
+static struct rdac_controller *get_controller(u8 *subsys_id, u8 *slot_id)
+{
+	struct rdac_controller *ctlr, *tmp;
+
+	spin_lock(&list_lock);
+
+	list_for_each_entry(tmp, &ctlr_list, node) {
+		if ((memcmp(tmp->subsys_id, subsys_id, SUBSYS_ID_LEN) == 0) &&
+			  (memcmp(tmp->slot_id, slot_id, SLOT_ID_LEN) == 0)) {
+			kref_get(&tmp->kref);
+			spin_unlock(&list_lock);
+			return tmp;
+		}
+	}
+	ctlr = kmalloc(sizeof(*ctlr), GFP_ATOMIC);
+	if (!ctlr)
+		goto done;
+
+	/* initialize fields of controller */
+	memcpy(ctlr->subsys_id, subsys_id, SUBSYS_ID_LEN);
+	memcpy(ctlr->slot_id, slot_id, SLOT_ID_LEN);
+	kref_init(&ctlr->kref);
+	spin_lock_init(&ctlr->lock);
+	ctlr->submitted = 0;
+	ctlr->use_10_ms = -1;
+	INIT_LIST_HEAD(&ctlr->cmd_list);
+	list_add(&ctlr->node, &ctlr_list);
+done:
+	spin_unlock(&list_lock);
+	return ctlr;
+}
+
+static void c4_endio(struct request *req, int error)
+{
+	struct rdac_handler *h = req->end_io_data;
+	struct c4_inquiry *sp;
+
+	if (had_failures(req, error)) {
+		dm_pg_init_complete(h->path, MP_FAIL_PATH);
+		goto done;
+	}
+
+	sp = &h->inq.c4;
+
+	h->ctlr = get_controller(sp->subsys_id, sp->slot_id);
+
+	if (h->ctlr) {
+		h->cmd_to_send = SEND_C9_INQUIRY;
+		queue_work(rdac_wkqd, &h->work);
+	} else
+		dm_pg_init_complete(h->path, MP_FAIL_PATH);
+done:
+	__blk_put_request(req->q, req);
+}
+
+static void c2_endio(struct request *req, int error)
+{
+	struct rdac_handler *h = req->end_io_data;
+	struct c2_inquiry *sp;
+
+	if (had_failures(req, error)) {
+		dm_pg_init_complete(h->path, MP_FAIL_PATH);
+		goto done;
+	}
+
+	sp = &h->inq.c2;
+
+	/* If more than MODE6_MAX_LUN luns are supported, use mode select 10 */
+	if (sp->max_lun_supported >= MODE6_MAX_LUN)
+		h->ctlr->use_10_ms = 1;
+	else
+		h->ctlr->use_10_ms = 0;
+
+	h->cmd_to_send = SEND_MODE_SELECT;
+	queue_work(rdac_wkqd, &h->work);
+done:
+	__blk_put_request(req->q, req);
+}
+
+static void c9_endio(struct request *req, int error)
+{
+	struct rdac_handler *h = req->end_io_data;
+	struct c9_inquiry *sp;
+
+	if (had_failures(req, error)) {
+		dm_pg_init_complete(h->path, MP_FAIL_PATH);
+		goto done;
+	}
+
+	/* We need to look at the sense keys here to take clear action.
+	 * For now simple logic: If the host is in AVT mode or if controller
+	 * owns the lun, return dm_pg_init_complete(), otherwise submit
+	 * MODE SELECT.
+	 */
+	sp = &h->inq.c9;
+
+	/* If in AVT mode, return success */
+	if ((sp->avte_cvp >> 7) == 0x1) {
+		dm_pg_init_complete(h->path, 0);
+		goto done;
+	}
+
+	/* If the controller on this path owns the LUN, return success */
+	if (sp->avte_cvp & 0x1) {
+		dm_pg_init_complete(h->path, 0);
+		goto done;
+	}
+
+	if (h->ctlr) {
+		if (h->ctlr->use_10_ms == -1)
+			h->cmd_to_send = SEND_C2_INQUIRY;
+		else
+			h->cmd_to_send = SEND_MODE_SELECT;
+	} else
+		h->cmd_to_send = SEND_C4_INQUIRY;
+	queue_work(rdac_wkqd, &h->work);
+done:
+	__blk_put_request(req->q, req);
+}
+
+static void c8_endio(struct request *req, int error)
+{
+	struct rdac_handler *h = req->end_io_data;
+	struct c8_inquiry *sp;
+
+	if (had_failures(req, error)) {
+		dm_pg_init_complete(h->path, MP_FAIL_PATH);
+		goto done;
+	}
+
+	/* We need to look at the sense keys here to take clear action.
+	 * For now simple logic: Get the lun from the inquiry page.
+	 */
+	sp = &h->inq.c8;
+	h->lun = sp->lun[7]; /* currently it uses only one byte */
+	h->cmd_to_send = SEND_C9_INQUIRY;
+	queue_work(rdac_wkqd, &h->work);
+done:
+	__blk_put_request(req->q, req);
+}
+
+static void submit_inquiry(struct rdac_handler *h, int page_code,
+		unsigned int len, rq_end_io_fn endio)
+{
+	struct request *rq;
+	struct request_queue *q = bdev_get_queue(h->path->dev->bdev);
+
+	if (!q)
+		goto fail_path;
+
+	rq = get_rdac_req(h, &h->inq, len, READ);
+	if (!rq)
+		goto fail_path;
+
+	/* Prepare the command. */
+	rq->cmd[0] = INQUIRY;
+	rq->cmd[1] = 1;
+	rq->cmd[2] = page_code;
+	rq->cmd[4] = len;
+	rq->cmd_len = COMMAND_SIZE(INQUIRY);
+	blk_execute_rq_nowait(q, NULL, rq, 1, endio);
+	return;
+
+fail_path:
+	dm_pg_init_complete(h->path, MP_FAIL_PATH);
+}
+
+static void service_wkq(struct work_struct *work)
+{
+	struct rdac_handler *h = container_of(work, struct rdac_handler, work);
+
+	switch (h->cmd_to_send) {
+	case SEND_C2_INQUIRY:
+		submit_inquiry(h, 0xC2, sizeof(struct c2_inquiry), c2_endio);
+		break;
+	case SEND_C4_INQUIRY:
+		submit_inquiry(h, 0xC4, sizeof(struct c4_inquiry), c4_endio);
+		break;
+	case SEND_C8_INQUIRY:
+		submit_inquiry(h, 0xC8, sizeof(struct c8_inquiry), c8_endio);
+		break;
+	case SEND_C9_INQUIRY:
+		submit_inquiry(h, 0xC9, sizeof(struct c9_inquiry), c9_endio);
+		break;
+	case SEND_MODE_SELECT:
+		submit_mode_select(h);
+		break;
+	default:
+		BUG();
+	}
+}
+/*
+ * only support subpage2c until we confirm that this is just a matter of
+ * of updating firmware or not, and RDAC (basic AVT works already) for now
+ * but we can add these in in when we get time and testers
+ */
+static int rdac_create(struct hw_handler *hwh, unsigned argc, char **argv)
+{
+	struct rdac_handler *h;
+	unsigned timeout;
+
+	if (argc == 0) {
+		/* No arguments: use defaults */
+		timeout = RDAC_FAILOVER_TIMEOUT;
+	} else if (argc != 1) {
+		DMWARN("incorrect number of arguments");
+		return -EINVAL;
+	} else {
+		if (sscanf(argv[1], "%u", &timeout) != 1) {
+			DMWARN("invalid timeout value");
+			return -EINVAL;
+		}
+	}
+
+	h = kzalloc(sizeof(*h), GFP_KERNEL);
+	if (!h)
+		return -ENOMEM;
+
+	hwh->context = h;
+	h->timeout = timeout;
+	h->lun = UNINITIALIZED_LUN;
+	INIT_WORK(&h->work, service_wkq);
+	DMWARN("using RDAC command with timeout %u", h->timeout);
+
+	return 0;
+}
+
+static void rdac_destroy(struct hw_handler *hwh)
+{
+	struct rdac_handler *h = hwh->context;
+
+	if (h->ctlr)
+		kref_put(&h->ctlr->kref, release_ctlr);
+	kfree(h);
+	hwh->context = NULL;
+}
+
+static unsigned rdac_error(struct hw_handler *hwh, struct bio *bio)
+{
+	/* Try default handler */
+	return dm_scsi_err_handler(hwh, bio);
+}
+
+static void rdac_pg_init(struct hw_handler *hwh, unsigned bypassed,
+			struct dm_path *path)
+{
+	struct rdac_handler *h = hwh->context;
+
+	h->path = path;
+	switch (h->lun) {
+	case UNINITIALIZED_LUN:
+		submit_inquiry(h, 0xC8, sizeof(struct c8_inquiry), c8_endio);
+		break;
+	default:
+		submit_inquiry(h, 0xC9, sizeof(struct c9_inquiry), c9_endio);
+	}
+}
+
+static struct hw_handler_type rdac_handler = {
+	.name = RDAC_DM_HWH_NAME,
+	.module = THIS_MODULE,
+	.create = rdac_create,
+	.destroy = rdac_destroy,
+	.pg_init = rdac_pg_init,
+	.error = rdac_error,
+};
+
+static int __init rdac_init(void)
+{
+	int r = dm_register_hw_handler(&rdac_handler);
+
+	if (r < 0) {
+		DMERR("%s: register failed %d", RDAC_DM_HWH_NAME, r);
+		return r;
+	}
+
+	rdac_wkqd = create_singlethread_workqueue("rdac_wkqd");
+	if (!rdac_wkqd) {
+		DMERR("Failed to create workqueue rdac_wkqd.");
+		dm_unregister_hw_handler(&rdac_handler);
+		return -ENOMEM;
+	}
+
+	DMINFO("%s: version %s loaded", RDAC_DM_HWH_NAME, RDAC_DM_HWH_VER);
+	return 0;
+}
+
+static void __exit rdac_exit(void)
+{
+	int r = dm_unregister_hw_handler(&rdac_handler);
+
+	destroy_workqueue(rdac_wkqd);
+	if (r < 0)
+		DMERR("%s: unregister failed %d", RDAC_DM_HWH_NAME, r);
+}
+
+module_init(rdac_init);
+module_exit(rdac_exit);
+
+MODULE_DESCRIPTION("DM Multipath LSI/Engenio RDAC support");
+MODULE_AUTHOR("Mike Christie, Chandra Seetharaman");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(RDAC_DM_HWH_VER);