1 files changed, 943 insertions, 534 deletions

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index 68adb8955d2d..6fd89ae33059 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -1,41 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * 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 <linux/unaligned.h>
 #include <scsi/scsi.h>
+#include <scsi/scsi_proto.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 ALUA_DH_VER "2.0"
 
 #define TPGS_SUPPORT_NONE		0x00
 #define TPGS_SUPPORT_OPTIMIZED		0x01
@@ -45,6 +26,7 @@
 #define TPGS_SUPPORT_LBA_DEPENDENT	0x10
 #define TPGS_SUPPORT_OFFLINE		0x40
 #define TPGS_SUPPORT_TRANSITION		0x80
+#define TPGS_SUPPORT_ALL		0xdf
 
 #define RTPG_FMT_MASK			0x70
 #define RTPG_FMT_EXT_HDR		0x10
@@ -54,27 +36,63 @@
 #define TPGS_MODE_IMPLICIT		0x1
 #define TPGS_MODE_EXPLICIT		0x2
 
-#define ALUA_INQUIRY_SIZE		36
+#define ALUA_RTPG_SIZE			128
 #define ALUA_FAILOVER_TIMEOUT		60
 #define ALUA_FAILOVER_RETRIES		5
+#define ALUA_RTPG_DELAY_MSECS		5
+#define ALUA_RTPG_RETRY_DELAY		2
 
-/* flags passed from user level */
-#define ALUA_OPTIMIZE_STPG		1
+/* device handler flags */
+#define ALUA_OPTIMIZE_STPG		0x01
+#define ALUA_RTPG_EXT_HDR_UNSUPP	0x02
+/* State machine flags */
+#define ALUA_PG_RUN_RTPG		0x10
+#define ALUA_PG_RUN_STPG		0x20
+#define ALUA_PG_RUNNING			0x40
 
-struct alua_dh_data {
+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.");
+
+static LIST_HEAD(port_group_list);
+static DEFINE_SPINLOCK(port_group_lock);
+static struct workqueue_struct *kaluad_wq;
+
+struct alua_port_group {
+	struct kref		kref;
+	struct rcu_head		rcu;
+	struct list_head	node;
+	struct list_head	dh_list;
+	unsigned char		device_id_str[256];
+	int			device_id_len;
 	int			group_id;
-	int			rel_port;
 	int			tpgs;
 	int			state;
 	int			pref;
+	int			valid_states;
 	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];
-	int			senselen;
+	unsigned long		expiry;
+	unsigned long		interval;
+	struct delayed_work	rtpg_work;
+	spinlock_t		lock;
+	struct list_head	rtpg_list;
+	struct scsi_device	*rtpg_sdev;
+};
+
+struct alua_dh_data {
+	struct list_head	node;
+	struct alua_port_group __rcu *pg;
+	int			group_id;
+	spinlock_t		pg_lock;
 	struct scsi_device	*sdev;
+	int			init_error;
+	struct mutex		init_mutex;
+	bool			disabled;
+};
+
+struct alua_queue_data {
+	struct list_head	entry;
 	activate_complete	callback_fn;
 	void			*callback_data;
 };
@@ -82,238 +100,168 @@ struct alua_dh_data {
 #define ALUA_POLICY_SWITCH_CURRENT	0
 #define ALUA_POLICY_SWITCH_ALL		1
 
-static char print_alua_state(int);
-static int alua_check_sense(struct scsi_device *, struct scsi_sense_hdr *);
-
-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 void alua_rtpg_work(struct work_struct *work);
+static bool alua_rtpg_queue(struct alua_port_group *pg,
+			    struct scsi_device *sdev,
+			    struct alua_queue_data *qdata, bool force);
+static void alua_check(struct scsi_device *sdev, bool force);
 
-static struct request *get_alua_req(struct scsi_device *sdev,
-				    void *buffer, unsigned buflen, int rw)
+static void release_port_group(struct kref *kref)
 {
-	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", __func__);
-		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", __func__);
-		return NULL;
-	}
-
-	rq->cmd_type = REQ_TYPE_BLOCK_PC;
-	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;
+	struct alua_port_group *pg;
+
+	pg = container_of(kref, struct alua_port_group, kref);
+	if (pg->rtpg_sdev)
+		flush_delayed_work(&pg->rtpg_work);
+	spin_lock(&port_group_lock);
+	list_del(&pg->node);
+	spin_unlock(&port_group_lock);
+	kfree_rcu(pg, rcu);
 }
 
 /*
- * submit_vpd_inquiry - Issue an INQUIRY VPD page 0x83 command
+ * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
  * @sdev: sdev the command should be sent to
  */
-static int submit_vpd_inquiry(struct scsi_device *sdev, struct alua_dh_data *h)
+static int submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
+		       int bufflen, struct scsi_sense_hdr *sshdr, int flags)
 {
-	struct request *rq;
-	int err = SCSI_DH_RES_TEMP_UNAVAIL;
-
-	rq = get_alua_req(sdev, h->buff, h->bufflen, READ);
-	if (!rq)
-		goto done;
+	u8 cdb[MAX_COMMAND_SIZE];
+	blk_opf_t opf = REQ_OP_DRV_IN | REQ_FAILFAST_DEV |
+				REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER;
+	const struct scsi_exec_args exec_args = {
+		.sshdr = sshdr,
+	};
 
 	/* 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;
+	memset(cdb, 0x0, MAX_COMMAND_SIZE);
+	cdb[0] = MAINTENANCE_IN;
+	if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
+		cdb[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
+	else
+		cdb[1] = MI_REPORT_TARGET_PGS;
+	put_unaligned_be32(bufflen, &cdb[6]);
+
+	return scsi_execute_cmd(sdev, cdb, opf, buff, bufflen,
+				ALUA_FAILOVER_TIMEOUT * HZ,
+				ALUA_FAILOVER_RETRIES, &exec_args);
 }
 
 /*
- * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
- * @sdev: sdev the command should be sent to
+ * 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_rtpg(struct scsi_device *sdev, struct alua_dh_data *h,
-			    bool rtpg_ext_hdr_req)
+static int submit_stpg(struct scsi_device *sdev, int group_id,
+		       struct scsi_sense_hdr *sshdr)
 {
-	struct request *rq;
-	int err = SCSI_DH_RES_TEMP_UNAVAIL;
+	u8 cdb[MAX_COMMAND_SIZE];
+	unsigned char stpg_data[8];
+	int stpg_len = 8;
+	blk_opf_t opf = REQ_OP_DRV_OUT | REQ_FAILFAST_DEV |
+				REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER;
+	const struct scsi_exec_args exec_args = {
+		.sshdr = sshdr,
+	};
 
-	rq = get_alua_req(sdev, h->buff, h->bufflen, READ);
-	if (!rq)
-		goto done;
+	/* Prepare the data buffer */
+	memset(stpg_data, 0, stpg_len);
+	stpg_data[4] = SCSI_ACCESS_STATE_OPTIMAL;
+	put_unaligned_be16(group_id, &stpg_data[6]);
 
 	/* Prepare the command. */
-	rq->cmd[0] = MAINTENANCE_IN;
-	if (rtpg_ext_hdr_req)
-		rq->cmd[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
-	else
-		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;
+	memset(cdb, 0x0, MAX_COMMAND_SIZE);
+	cdb[0] = MAINTENANCE_OUT;
+	cdb[1] = MO_SET_TARGET_PGS;
+	put_unaligned_be32(stpg_len, &cdb[6]);
+
+	return scsi_execute_cmd(sdev, cdb, opf, stpg_data,
+				stpg_len, ALUA_FAILOVER_TIMEOUT * HZ,
+				ALUA_FAILOVER_RETRIES, &exec_args);
 }
 
-/*
- * 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 void stpg_endio(struct request *req, int error)
+static struct alua_port_group *alua_find_get_pg(char *id_str, size_t id_size,
+						int group_id)
 {
-	struct alua_dh_data *h = req->end_io_data;
-	struct scsi_sense_hdr sense_hdr;
-	unsigned err = SCSI_DH_OK;
+	struct alua_port_group *pg;
 
-	if (host_byte(req->errors) != DID_OK ||
-	    msg_byte(req->errors) != COMMAND_COMPLETE) {
-		err = SCSI_DH_IO;
-		goto done;
-	}
+	if (!id_str || !id_size || !strlen(id_str))
+		return NULL;
 
-	if (req->sense_len > 0) {
-		err = scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
-					   &sense_hdr);
-		if (!err) {
-			err = SCSI_DH_IO;
-			goto done;
-		}
-		err = alua_check_sense(h->sdev, &sense_hdr);
-		if (err == ADD_TO_MLQUEUE) {
-			err = SCSI_DH_RETRY;
-			goto done;
-		}
-		sdev_printk(KERN_INFO, h->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;
-	} else if (error)
-		err = SCSI_DH_IO;
-
-	if (err == SCSI_DH_OK) {
-		h->state = TPGS_STATE_OPTIMIZED;
-		sdev_printk(KERN_INFO, h->sdev,
-			    "%s: port group %02x switched to state %c\n",
-			    ALUA_DH_NAME, h->group_id,
-			    print_alua_state(h->state));
-	}
-done:
-	req->end_io_data = NULL;
-	__blk_put_request(req->q, req);
-	if (h->callback_fn) {
-		h->callback_fn(h->callback_data, err);
-		h->callback_fn = h->callback_data = NULL;
+	list_for_each_entry(pg, &port_group_list, node) {
+		if (pg->group_id != group_id)
+			continue;
+		if (!pg->device_id_len || pg->device_id_len != id_size)
+			continue;
+		if (strncmp(pg->device_id_str, id_str, id_size))
+			continue;
+		if (!kref_get_unless_zero(&pg->kref))
+			continue;
+		return pg;
 	}
-	return;
+
+	return NULL;
 }
 
 /*
- * submit_stpg - Issue a SET TARGET GROUP STATES command
+ * alua_alloc_pg - Allocate a new port_group structure
+ * @sdev: scsi device
+ * @group_id: port group id
+ * @tpgs: target port group settings
  *
- * 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.
+ * Allocate a new port_group structure for a given
+ * device.
  */
-static unsigned submit_stpg(struct alua_dh_data *h)
+static struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
+					     int group_id, int tpgs)
 {
-	struct request *rq;
-	int stpg_len = 8;
-	struct scsi_device *sdev = h->sdev;
+	struct alua_port_group *pg, *tmp_pg;
 
-	/* Prepare the data buffer */
-	memset(h->buff, 0, stpg_len);
-	h->buff[4] = TPGS_STATE_OPTIMIZED & 0x0f;
-	h->buff[6] = (h->group_id >> 8) & 0xff;
-	h->buff[7] = h->group_id & 0xff;
+	pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL);
+	if (!pg)
+		return ERR_PTR(-ENOMEM);
 
-	rq = get_alua_req(sdev, h->buff, stpg_len, WRITE);
-	if (!rq)
-		return SCSI_DH_RES_TEMP_UNAVAIL;
+	pg->device_id_len = scsi_vpd_lun_id(sdev, pg->device_id_str,
+					    sizeof(pg->device_id_str));
+	if (pg->device_id_len <= 0) {
+		/*
+		 * TPGS supported but no device identification found.
+		 * Generate private device identification.
+		 */
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: No device descriptors found\n",
+			    ALUA_DH_NAME);
+		pg->device_id_str[0] = '\0';
+		pg->device_id_len = 0;
+	}
+	pg->group_id = group_id;
+	pg->tpgs = tpgs;
+	pg->state = SCSI_ACCESS_STATE_OPTIMAL;
+	pg->valid_states = TPGS_SUPPORT_ALL;
+	if (optimize_stpg)
+		pg->flags |= ALUA_OPTIMIZE_STPG;
+	kref_init(&pg->kref);
+	INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
+	INIT_LIST_HEAD(&pg->rtpg_list);
+	INIT_LIST_HEAD(&pg->node);
+	INIT_LIST_HEAD(&pg->dh_list);
+	spin_lock_init(&pg->lock);
+
+	spin_lock(&port_group_lock);
+	tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
+				  group_id);
+	if (tmp_pg) {
+		spin_unlock(&port_group_lock);
+		kfree(pg);
+		return tmp_pg;
+	}
 
-	/* 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;
-	rq->end_io_data = h;
-
-	blk_execute_rq_nowait(rq->q, NULL, rq, 1, stpg_endio);
-	return SCSI_DH_OK;
+	list_add(&pg->node, &port_group_list);
+	spin_unlock(&port_group_lock);
+
+	return pg;
 }
 
 /*
@@ -323,12 +271,23 @@ static unsigned submit_stpg(struct alua_dh_data *h)
  * Examine the TPGS setting of the sdev to find out if ALUA
  * is supported.
  */
-static int alua_check_tpgs(struct scsi_device *sdev, struct alua_dh_data *h)
+static int alua_check_tpgs(struct scsi_device *sdev)
 {
-	int err = SCSI_DH_OK;
+	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;
+	}
 
-	h->tpgs = scsi_device_tpgs(sdev);
-	switch (h->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",
@@ -342,71 +301,38 @@ static int alua_check_tpgs(struct scsi_device *sdev, struct alua_dh_data *h)
 		sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n",
 			    ALUA_DH_NAME);
 		break;
-	default:
-		h->tpgs = TPGS_MODE_NONE;
+	case TPGS_MODE_NONE:
 		sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
 			    ALUA_DH_NAME);
-		err = SCSI_DH_DEV_UNSUPP;
+		break;
+	default:
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: unsupported TPGS setting %d\n",
+			    ALUA_DH_NAME, tpgs);
+		tpgs = TPGS_MODE_NONE;
 		break;
 	}
 
-	return err;
+	return tpgs;
 }
 
 /*
- * alua_vpd_inquiry - Evaluate INQUIRY vpd page 0x83
+ * 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_vpd_inquiry(struct scsi_device *sdev, struct alua_dh_data *h)
+static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
+			  int tpgs)
 {
-	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;
-	}
+	int rel_port = -1, group_id;
+	struct alua_port_group *pg, *old_pg = NULL;
+	bool pg_updated = false;
+	unsigned long flags;
 
-	if (h->group_id == -1) {
+	group_id = scsi_vpd_tpg_id(sdev, &rel_port);
+	if (group_id < 0) {
 		/*
 		 * Internal error; TPGS supported but required
 		 * VPD identification descriptors not present.
@@ -415,70 +341,125 @@ static int alua_vpd_inquiry(struct scsi_device *sdev, struct alua_dh_data *h)
 		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 {
+		return SCSI_DH_DEV_UNSUPP;
+	}
+
+	pg = alua_alloc_pg(sdev, group_id, tpgs);
+	if (IS_ERR(pg)) {
+		if (PTR_ERR(pg) == -ENOMEM)
+			return SCSI_DH_NOMEM;
+		return SCSI_DH_DEV_UNSUPP;
+	}
+	if (pg->device_id_len)
 		sdev_printk(KERN_INFO, sdev,
-			    "%s: port group %02x rel port %02x\n",
-			    ALUA_DH_NAME, h->group_id, h->rel_port);
+			    "%s: device %s port group %x rel port %x\n",
+			    ALUA_DH_NAME, pg->device_id_str,
+			    group_id, rel_port);
+	else
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: port group %x rel port %x\n",
+			    ALUA_DH_NAME, group_id, rel_port);
+
+	kref_get(&pg->kref);
+
+	/* Check for existing port group references */
+	spin_lock(&h->pg_lock);
+	old_pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
+	if (old_pg != pg) {
+		/* port group has changed. Update to new port group */
+		if (h->pg) {
+			spin_lock_irqsave(&old_pg->lock, flags);
+			list_del_rcu(&h->node);
+			spin_unlock_irqrestore(&old_pg->lock, flags);
+		}
+		rcu_assign_pointer(h->pg, pg);
+		pg_updated = true;
 	}
 
-	return err;
+	spin_lock_irqsave(&pg->lock, flags);
+	if (pg_updated)
+		list_add_rcu(&h->node, &pg->dh_list);
+	spin_unlock_irqrestore(&pg->lock, flags);
+
+	spin_unlock(&h->pg_lock);
+
+	alua_rtpg_queue(pg, sdev, NULL, true);
+	kref_put(&pg->kref, release_port_group);
+
+	if (old_pg)
+		kref_put(&old_pg->kref, release_port_group);
+
+	return SCSI_DH_OK;
 }
 
-static char print_alua_state(int state)
+static char print_alua_state(unsigned char state)
 {
 	switch (state) {
-	case TPGS_STATE_OPTIMIZED:
+	case SCSI_ACCESS_STATE_OPTIMAL:
 		return 'A';
-	case TPGS_STATE_NONOPTIMIZED:
+	case SCSI_ACCESS_STATE_ACTIVE:
 		return 'N';
-	case TPGS_STATE_STANDBY:
+	case SCSI_ACCESS_STATE_STANDBY:
 		return 'S';
-	case TPGS_STATE_UNAVAILABLE:
+	case SCSI_ACCESS_STATE_UNAVAILABLE:
 		return 'U';
-	case TPGS_STATE_LBA_DEPENDENT:
+	case SCSI_ACCESS_STATE_LBA:
 		return 'L';
-	case TPGS_STATE_OFFLINE:
+	case SCSI_ACCESS_STATE_OFFLINE:
 		return 'O';
-	case TPGS_STATE_TRANSITIONING:
+	case SCSI_ACCESS_STATE_TRANSITIONING:
 		return 'T';
 	default:
 		return 'X';
 	}
 }
 
-static int alua_check_sense(struct scsi_device *sdev,
-			    struct scsi_sense_hdr *sense_hdr)
+static void alua_handle_state_transition(struct scsi_device *sdev)
+{
+	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg;
+
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (pg)
+		pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
+	rcu_read_unlock();
+	alua_check(sdev, false);
+}
+
+static enum scsi_disposition 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)
+		if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
 			/*
 			 * LUN Not Accessible - ALUA state transition
 			 */
-			return ADD_TO_MLQUEUE;
-		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)
+			alua_handle_state_transition(sdev);
+			return NEEDS_RETRY;
+		}
+		break;
+	case UNIT_ATTENTION:
+		if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
 			/*
-			 * LUN Not Accessible -- Target port in unavailable state
+			 * LUN Not Accessible - ALUA state transition
 			 */
-			return SUCCESS;
-		if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x12)
+			alua_handle_state_transition(sdev);
+			return NEEDS_RETRY;
+		}
+		if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
 			/*
-			 * LUN Not Ready -- Offline
+			 * Power On, Reset, or Bus Device Reset.
+			 * Might have obscured a state transition,
+			 * so schedule a recheck.
 			 */
-			return SUCCESS;
-		break;
-	case UNIT_ATTENTION:
-		if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00)
+			alua_check(sdev, true);
+			return ADD_TO_MLQUEUE;
+		}
+		if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
 			/*
-			 * Power On, Reset, or Bus Device Reset, just retry.
+			 * Device internal reset
 			 */
 			return ADD_TO_MLQUEUE;
 		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
@@ -486,16 +467,20 @@ static int alua_check_sense(struct scsi_device *sdev,
 			 * Mode Parameters Changed
 			 */
 			return ADD_TO_MLQUEUE;
-		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06)
+		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
 			/*
 			 * ALUA state changed
 			 */
+			alua_check(sdev, true);
 			return ADD_TO_MLQUEUE;
-		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07)
+		}
+		if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
 			/*
 			 * Implicit ALUA state transition failed
 			 */
+			alua_check(sdev, true);
 			return ADD_TO_MLQUEUE;
+		}
 		if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
 			/*
 			 * Inquiry data has changed
@@ -515,6 +500,31 @@ static int alua_check_sense(struct scsi_device *sdev,
 }
 
 /*
+ * alua_tur - Send a TEST UNIT READY
+ * @sdev: device to which the TEST UNIT READY command should be send
+ *
+ * Send a TEST UNIT READY to @sdev to figure out the device state
+ * Returns SCSI_DH_RETRY if the sense code is NOT READY/ALUA TRANSITIONING,
+ * SCSI_DH_OK if no error occurred, and SCSI_DH_IO otherwise.
+ */
+static int alua_tur(struct scsi_device *sdev)
+{
+	struct scsi_sense_hdr sense_hdr;
+	int retval;
+
+	retval = scsi_test_unit_ready(sdev, ALUA_FAILOVER_TIMEOUT * HZ,
+				      ALUA_FAILOVER_RETRIES, &sense_hdr);
+	if ((sense_hdr.sense_key == NOT_READY ||
+	     sense_hdr.sense_key == UNIT_ATTENTION) &&
+	    sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
+		return SCSI_DH_RETRY;
+	else if (retval)
+		return SCSI_DH_IO;
+	else
+		return SCSI_DH_OK;
+}
+
+/*
  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
  * @sdev: the device to be evaluated.
  *
@@ -522,30 +532,70 @@ static int alua_check_sense(struct scsi_device *sdev,
  * 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)
+static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 {
 	struct scsi_sense_hdr sense_hdr;
-	int len, k, off, valid_states = 0;
-	unsigned char *ucp;
+	struct alua_port_group *tmp_pg;
+	int len, k, off, bufflen = ALUA_RTPG_SIZE;
+	int group_id_old, state_old, pref_old, valid_states_old;
+	unsigned char *desc, *buff;
 	unsigned err;
-	bool rtpg_ext_hdr_req = 1;
-	unsigned long expiry, interval = 0;
+	int retval;
 	unsigned int tpg_desc_tbl_off;
 	unsigned char orig_transition_tmo;
+	unsigned long flags;
+	bool transitioning_sense = false;
 
-	if (!h->transition_tmo)
-		expiry = round_jiffies_up(jiffies + ALUA_FAILOVER_TIMEOUT * HZ);
-	else
-		expiry = round_jiffies_up(jiffies + h->transition_tmo * HZ);
+	group_id_old = pg->group_id;
+	state_old = pg->state;
+	pref_old = pg->pref;
+	valid_states_old = pg->valid_states;
+
+	if (!pg->expiry) {
+		unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
+
+		if (pg->transition_tmo)
+			transition_tmo = pg->transition_tmo * HZ;
+
+		pg->expiry = round_jiffies_up(jiffies + transition_tmo);
+	}
+
+	buff = kzalloc(bufflen, GFP_KERNEL);
+	if (!buff)
+		return SCSI_DH_DEV_TEMP_BUSY;
 
  retry:
-	err = submit_rtpg(sdev, h, rtpg_ext_hdr_req);
+	err = 0;
+	retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
 
-	if (err == SCSI_DH_IO && h->senselen > 0) {
-		err = scsi_normalize_sense(h->sense, SCSI_SENSE_BUFFERSIZE,
-					   &sense_hdr);
-		if (!err)
+	if (retval) {
+		/*
+		 * Some (broken) implementations have a habit of returning
+		 * an error during things like firmware update etc.
+		 * But if the target only supports active/optimized there's
+		 * not much we can do; it's not that we can switch paths
+		 * or anything.
+		 * So ignore any errors to avoid spurious failures during
+		 * path failover.
+		 */
+		if ((pg->valid_states & ~TPGS_SUPPORT_OPTIMIZED) == 0) {
+			sdev_printk(KERN_INFO, sdev,
+				    "%s: ignoring rtpg result %d\n",
+				    ALUA_DH_NAME, retval);
+			kfree(buff);
+			return SCSI_DH_OK;
+		}
+		if (retval < 0 || !scsi_sense_valid(&sense_hdr)) {
+			sdev_printk(KERN_INFO, sdev,
+				    "%s: rtpg failed, result %d\n",
+				    ALUA_DH_NAME, retval);
+			kfree(buff);
+			if (retval < 0)
+				return SCSI_DH_DEV_TEMP_BUSY;
+			if (host_byte(retval) == DID_NO_CONNECT)
+				return SCSI_DH_RES_TEMP_UNAVAIL;
 			return SCSI_DH_IO;
+		}
 
 		/*
 		 * submit_rtpg() has failed on existing arrays
@@ -554,107 +604,459 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
 		 * even though it shouldn't according to T10.
 		 * The retry without rtpg_ext_hdr_req set
 		 * handles this.
+		 * Note:  some arrays return a sense key of ILLEGAL_REQUEST
+		 * with ASC 00h if they don't support the extended header.
 		 */
-		if (rtpg_ext_hdr_req == 1 &&
-		    sense_hdr.sense_key == ILLEGAL_REQUEST &&
-		    sense_hdr.asc == 0x24 && sense_hdr.ascq == 0) {
-			rtpg_ext_hdr_req = 0;
+		if (!(pg->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
+		    sense_hdr.sense_key == ILLEGAL_REQUEST) {
+			pg->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
 			goto retry;
 		}
-
-		err = alua_check_sense(sdev, &sense_hdr);
-		if (err == ADD_TO_MLQUEUE && time_before(jiffies, expiry))
-			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 the array returns with 'ALUA state transition'
+		 * sense code here it cannot return RTPG data during
+		 * transition. So set the state to 'transitioning' directly.
+		 */
+		if (sense_hdr.sense_key == NOT_READY &&
+		    sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a) {
+			transitioning_sense = true;
+			goto skip_rtpg;
+		}
+		/*
+		 * Retry on any other UNIT ATTENTION occurred.
+		 */
+		if (sense_hdr.sense_key == UNIT_ATTENTION)
+			err = SCSI_DH_RETRY;
+		if (err == SCSI_DH_RETRY &&
+		    pg->expiry != 0 && time_before(jiffies, pg->expiry)) {
+			sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
+				    ALUA_DH_NAME);
+			scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
+			kfree(buff);
+			return err;
+		}
+		sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
+			    ALUA_DH_NAME);
+		scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
+		kfree(buff);
+		pg->expiry = 0;
+		return 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;
+	len = get_unaligned_be32(&buff[0]) + 4;
 
-	if (len > h->bufflen) {
+	if (len > bufflen) {
 		/* Resubmit with the correct length */
-		if (realloc_buffer(h, len)) {
+		kfree(buff);
+		bufflen = len;
+		buff = kmalloc(bufflen, GFP_KERNEL);
+		if (!buff) {
 			sdev_printk(KERN_WARNING, sdev,
 				    "%s: kmalloc buffer failed\n",__func__);
 			/* Temporary failure, bypass */
+			pg->expiry = 0;
 			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];
+	orig_transition_tmo = pg->transition_tmo;
+	if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0)
+		pg->transition_tmo = buff[5];
 	else
-		h->transition_tmo = ALUA_FAILOVER_TIMEOUT;
+		pg->transition_tmo = ALUA_FAILOVER_TIMEOUT;
 
-	if (orig_transition_tmo != h->transition_tmo) {
+	if (orig_transition_tmo != pg->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;
+			    ALUA_DH_NAME, pg->transition_tmo);
+		pg->expiry = jiffies + pg->transition_tmo * HZ;
 	}
 
-	if ((h->buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
+	if ((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;
+	for (k = tpg_desc_tbl_off, desc = buff + tpg_desc_tbl_off;
 	     k < len;
-	     k += off, ucp += off) {
-
-		if (h->group_id == (ucp[2] << 8) + ucp[3]) {
-			h->state = ucp[0] & 0x0f;
-			h->pref = ucp[0] >> 7;
-			valid_states = ucp[1];
+	     k += off, desc += off) {
+		u16 group_id = get_unaligned_be16(&desc[2]);
+
+		spin_lock_irqsave(&port_group_lock, flags);
+		tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
+					  group_id);
+		spin_unlock_irqrestore(&port_group_lock, flags);
+		if (tmp_pg) {
+			if (spin_trylock_irqsave(&tmp_pg->lock, flags)) {
+				if ((tmp_pg == pg) ||
+				    !(tmp_pg->flags & ALUA_PG_RUNNING)) {
+					struct alua_dh_data *h;
+
+					tmp_pg->state = desc[0] & 0x0f;
+					tmp_pg->pref = desc[0] >> 7;
+					rcu_read_lock();
+					list_for_each_entry_rcu(h,
+						&tmp_pg->dh_list, node) {
+						if (!h->sdev)
+							continue;
+						h->sdev->access_state = desc[0];
+					}
+					rcu_read_unlock();
+				}
+				if (tmp_pg == pg)
+					tmp_pg->valid_states = desc[1];
+				spin_unlock_irqrestore(&tmp_pg->lock, flags);
+			}
+			kref_put(&tmp_pg->kref, release_port_group);
 		}
-		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 (time_before(jiffies, expiry)) {
+		off = 8 + (desc[7] * 4);
+	}
+
+ skip_rtpg:
+	spin_lock_irqsave(&pg->lock, flags);
+	if (transitioning_sense)
+		pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
+
+	if (group_id_old != pg->group_id || state_old != pg->state ||
+		pref_old != pg->pref || valid_states_old != pg->valid_states)
+		sdev_printk(KERN_INFO, sdev,
+			"%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
+			ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state),
+			pg->pref ? "preferred" : "non-preferred",
+			pg->valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
+			pg->valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
+			pg->valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
+			pg->valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
+			pg->valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
+			pg->valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
+			pg->valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
+
+	switch (pg->state) {
+	case SCSI_ACCESS_STATE_TRANSITIONING:
+		if (time_before(jiffies, pg->expiry)) {
 			/* State transition, retry */
-			interval += 2000;
-			msleep(interval);
-			goto retry;
+			pg->interval = ALUA_RTPG_RETRY_DELAY;
+			err = SCSI_DH_RETRY;
+		} else {
+			struct alua_dh_data *h;
+
+			/* Transitioning time exceeded, set port to standby */
+			err = SCSI_DH_IO;
+			pg->state = SCSI_ACCESS_STATE_STANDBY;
+			pg->expiry = 0;
+			rcu_read_lock();
+			list_for_each_entry_rcu(h, &pg->dh_list, node) {
+				if (!h->sdev)
+					continue;
+				h->sdev->access_state =
+					(pg->state & SCSI_ACCESS_STATE_MASK);
+				if (pg->pref)
+					h->sdev->access_state |=
+						SCSI_ACCESS_STATE_PREFERRED;
+			}
+			rcu_read_unlock();
 		}
-		/* Transitioning time exceeded, set port to standby */
-		err = SCSI_DH_RETRY;
-		h->state = TPGS_STATE_STANDBY;
 		break;
-	case TPGS_STATE_OFFLINE:
+	case SCSI_ACCESS_STATE_OFFLINE:
 		/* Path unusable */
 		err = SCSI_DH_DEV_OFFLINED;
+		pg->expiry = 0;
 		break;
 	default:
 		/* Useable path if active */
 		err = SCSI_DH_OK;
+		pg->expiry = 0;
 		break;
 	}
+	spin_unlock_irqrestore(&pg->lock, flags);
+	kfree(buff);
 	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_port_group *pg)
+{
+	int retval;
+	struct scsi_sense_hdr sense_hdr;
+
+	if (!(pg->tpgs & TPGS_MODE_EXPLICIT)) {
+		/* Only implicit ALUA supported, retry */
+		return SCSI_DH_RETRY;
+	}
+	switch (pg->state) {
+	case SCSI_ACCESS_STATE_OPTIMAL:
+		return SCSI_DH_OK;
+	case SCSI_ACCESS_STATE_ACTIVE:
+		if ((pg->flags & ALUA_OPTIMIZE_STPG) &&
+		    !pg->pref &&
+		    (pg->tpgs & TPGS_MODE_IMPLICIT))
+			return SCSI_DH_OK;
+		break;
+	case SCSI_ACCESS_STATE_STANDBY:
+	case SCSI_ACCESS_STATE_UNAVAILABLE:
+		break;
+	case SCSI_ACCESS_STATE_OFFLINE:
+		return SCSI_DH_IO;
+	case SCSI_ACCESS_STATE_TRANSITIONING:
+		break;
+	default:
+		sdev_printk(KERN_INFO, sdev,
+			    "%s: stpg failed, unhandled TPGS state %d",
+			    ALUA_DH_NAME, pg->state);
+		return SCSI_DH_NOSYS;
+	}
+	retval = submit_stpg(sdev, pg->group_id, &sense_hdr);
+
+	if (retval) {
+		if (retval < 0 || !scsi_sense_valid(&sense_hdr)) {
+			sdev_printk(KERN_INFO, sdev,
+				    "%s: stpg failed, result %d",
+				    ALUA_DH_NAME, retval);
+			if (retval < 0)
+				return SCSI_DH_DEV_TEMP_BUSY;
+		} else {
+			sdev_printk(KERN_INFO, sdev, "%s: stpg failed\n",
+				    ALUA_DH_NAME);
+			scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
+		}
+	}
+	/* Retry RTPG */
+	return SCSI_DH_RETRY;
+}
+
+/*
+ * The caller must call scsi_device_put() on the returned pointer if it is not
+ * NULL.
+ */
+static struct scsi_device * __must_check
+alua_rtpg_select_sdev(struct alua_port_group *pg)
+{
+	struct alua_dh_data *h;
+	struct scsi_device *sdev = NULL, *prev_sdev;
+
+	lockdep_assert_held(&pg->lock);
+	if (WARN_ON(!pg->rtpg_sdev))
+		return NULL;
+
+	/*
+	 * RCU protection isn't necessary for dh_list here
+	 * as we hold pg->lock, but for access to h->pg.
+	 */
+	rcu_read_lock();
+	list_for_each_entry_rcu(h, &pg->dh_list, node) {
+		if (!h->sdev)
+			continue;
+		if (h->sdev == pg->rtpg_sdev) {
+			h->disabled = true;
+			continue;
+		}
+		if (rcu_dereference(h->pg) == pg &&
+		    !h->disabled &&
+		    !scsi_device_get(h->sdev)) {
+			sdev = h->sdev;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	if (!sdev) {
+		pr_warn("%s: no device found for rtpg\n",
+			(pg->device_id_len ?
+			 (char *)pg->device_id_str : "(nameless PG)"));
+		return NULL;
+	}
+
+	sdev_printk(KERN_INFO, sdev, "rtpg retry on different device\n");
+
+	prev_sdev = pg->rtpg_sdev;
+	pg->rtpg_sdev = sdev;
+
+	return prev_sdev;
+}
+
+static void alua_rtpg_work(struct work_struct *work)
+{
+	struct alua_port_group *pg =
+		container_of(work, struct alua_port_group, rtpg_work.work);
+	struct scsi_device *sdev, *prev_sdev = NULL;
+	LIST_HEAD(qdata_list);
+	int err = SCSI_DH_OK;
+	struct alua_queue_data *qdata, *tmp;
+	struct alua_dh_data *h;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pg->lock, flags);
+	sdev = pg->rtpg_sdev;
+	if (!sdev) {
+		WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
+		WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
+		spin_unlock_irqrestore(&pg->lock, flags);
+		kref_put(&pg->kref, release_port_group);
+		return;
+	}
+	pg->flags |= ALUA_PG_RUNNING;
+	if (pg->flags & ALUA_PG_RUN_RTPG) {
+		int state = pg->state;
+
+		pg->flags &= ~ALUA_PG_RUN_RTPG;
+		spin_unlock_irqrestore(&pg->lock, flags);
+		if (state == SCSI_ACCESS_STATE_TRANSITIONING) {
+			if (alua_tur(sdev) == SCSI_DH_RETRY) {
+				spin_lock_irqsave(&pg->lock, flags);
+				pg->flags &= ~ALUA_PG_RUNNING;
+				pg->flags |= ALUA_PG_RUN_RTPG;
+				if (!pg->interval)
+					pg->interval = ALUA_RTPG_RETRY_DELAY;
+				spin_unlock_irqrestore(&pg->lock, flags);
+				queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+						   pg->interval * HZ);
+				return;
+			}
+			/* Send RTPG on failure or if TUR indicates SUCCESS */
+		}
+		err = alua_rtpg(sdev, pg);
+		spin_lock_irqsave(&pg->lock, flags);
+
+		/* If RTPG failed on the current device, try using another */
+		if (err == SCSI_DH_RES_TEMP_UNAVAIL &&
+		    (prev_sdev = alua_rtpg_select_sdev(pg)))
+			err = SCSI_DH_IMM_RETRY;
+
+		if (err == SCSI_DH_RETRY || err == SCSI_DH_IMM_RETRY ||
+		    pg->flags & ALUA_PG_RUN_RTPG) {
+			pg->flags &= ~ALUA_PG_RUNNING;
+			if (err == SCSI_DH_IMM_RETRY)
+				pg->interval = 0;
+			else if (!pg->interval && !(pg->flags & ALUA_PG_RUN_RTPG))
+				pg->interval = ALUA_RTPG_RETRY_DELAY;
+			pg->flags |= ALUA_PG_RUN_RTPG;
+			spin_unlock_irqrestore(&pg->lock, flags);
+			goto queue_rtpg;
+		}
+		if (err != SCSI_DH_OK)
+			pg->flags &= ~ALUA_PG_RUN_STPG;
+	}
+	if (pg->flags & ALUA_PG_RUN_STPG) {
+		pg->flags &= ~ALUA_PG_RUN_STPG;
+		spin_unlock_irqrestore(&pg->lock, flags);
+		err = alua_stpg(sdev, pg);
+		spin_lock_irqsave(&pg->lock, flags);
+		if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
+			pg->flags |= ALUA_PG_RUN_RTPG;
+			pg->interval = 0;
+			pg->flags &= ~ALUA_PG_RUNNING;
+			spin_unlock_irqrestore(&pg->lock, flags);
+			goto queue_rtpg;
+		}
+	}
+
+	list_splice_init(&pg->rtpg_list, &qdata_list);
+	/*
+	 * We went through an RTPG, for good or bad.
+	 * Re-enable all devices for the next attempt.
+	 */
+	list_for_each_entry(h, &pg->dh_list, node)
+		h->disabled = false;
+	pg->rtpg_sdev = NULL;
+	spin_unlock_irqrestore(&pg->lock, flags);
+
+	if (prev_sdev)
+		scsi_device_put(prev_sdev);
+
+	list_for_each_entry_safe(qdata, tmp, &qdata_list, entry) {
+		list_del(&qdata->entry);
+		if (qdata->callback_fn)
+			qdata->callback_fn(qdata->callback_data, err);
+		kfree(qdata);
+	}
+	spin_lock_irqsave(&pg->lock, flags);
+	pg->flags &= ~ALUA_PG_RUNNING;
+	spin_unlock_irqrestore(&pg->lock, flags);
+	scsi_device_put(sdev);
+	kref_put(&pg->kref, release_port_group);
+	return;
+
+queue_rtpg:
+	if (prev_sdev)
+		scsi_device_put(prev_sdev);
+	queue_delayed_work(kaluad_wq, &pg->rtpg_work, pg->interval * HZ);
+}
+
+/**
+ * alua_rtpg_queue() - cause RTPG to be submitted asynchronously
+ * @pg: ALUA port group associated with @sdev.
+ * @sdev: SCSI device for which to submit an RTPG.
+ * @qdata: Information about the callback to invoke after the RTPG.
+ * @force: Whether or not to submit an RTPG if a work item that will submit an
+ *         RTPG already has been scheduled.
+ *
+ * Returns true if and only if alua_rtpg_work() will be called asynchronously.
+ * That function is responsible for calling @qdata->fn().
+ *
+ * Context: may be called from atomic context (alua_check()) only if the caller
+ *	holds an sdev reference.
+ */
+static bool alua_rtpg_queue(struct alua_port_group *pg,
+			    struct scsi_device *sdev,
+			    struct alua_queue_data *qdata, bool force)
+{
+	int start_queue = 0;
+	unsigned long flags;
+
+	if (WARN_ON_ONCE(!pg) || scsi_device_get(sdev))
+		return false;
+
+	spin_lock_irqsave(&pg->lock, flags);
+	if (qdata) {
+		list_add_tail(&qdata->entry, &pg->rtpg_list);
+		pg->flags |= ALUA_PG_RUN_STPG;
+		force = true;
+	}
+	if (pg->rtpg_sdev == NULL) {
+		struct alua_dh_data *h = sdev->handler_data;
+
+		rcu_read_lock();
+		if (h && rcu_dereference(h->pg) == pg) {
+			pg->interval = 0;
+			pg->flags |= ALUA_PG_RUN_RTPG;
+			kref_get(&pg->kref);
+			pg->rtpg_sdev = sdev;
+			start_queue = 1;
+		}
+		rcu_read_unlock();
+	} else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {
+		pg->flags |= ALUA_PG_RUN_RTPG;
+		/* Do not queue if the worker is already running */
+		if (!(pg->flags & ALUA_PG_RUNNING)) {
+			kref_get(&pg->kref);
+			start_queue = 1;
+		}
+	}
+
+	spin_unlock_irqrestore(&pg->lock, flags);
+
+	if (start_queue) {
+		if (queue_delayed_work(kaluad_wq, &pg->rtpg_work,
+				msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS)))
+			sdev = NULL;
+		else
+			kref_put(&pg->kref, release_port_group);
+	}
+	if (sdev)
+		scsi_device_put(sdev);
+
+	return true;
+}
+
+/*
  * alua_initialize - Initialize ALUA state
  * @sdev: the device to be initialized
  *
@@ -663,21 +1065,15 @@ static int alua_rtpg(struct scsi_device *sdev, struct alua_dh_data *h)
  */
 static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 {
-	int err;
-
-	err = alua_check_tpgs(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:
+	int err = SCSI_DH_DEV_UNSUPP, tpgs;
+
+	mutex_lock(&h->init_mutex);
+	h->disabled = false;
+	tpgs = alua_check_tpgs(sdev);
+	if (tpgs != TPGS_MODE_NONE)
+		err = alua_check_vpd(sdev, h, tpgs);
+	h->init_error = err;
+	mutex_unlock(&h->init_mutex);
 	return err;
 }
 /*
@@ -691,10 +1087,12 @@ out:
  */
 static int alua_set_params(struct scsi_device *sdev, const char *params)
 {
-	struct alua_dh_data *h = get_alua_data(sdev);
+	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg = NULL;
 	unsigned int optimize = 0, argc;
 	const char *p = params;
 	int result = SCSI_DH_OK;
+	unsigned long flags;
 
 	if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
 		return -EINVAL;
@@ -704,18 +1102,23 @@ static int alua_set_params(struct scsi_device *sdev, const char *params)
 	if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
 		return -EINVAL;
 
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (!pg) {
+		rcu_read_unlock();
+		return -ENXIO;
+	}
+	spin_lock_irqsave(&pg->lock, flags);
 	if (optimize)
-		h->flags |= ALUA_OPTIMIZE_STPG;
+		pg->flags |= ALUA_OPTIMIZE_STPG;
 	else
-		h->flags &= ~ALUA_OPTIMIZE_STPG;
+		pg->flags &= ~ALUA_OPTIMIZE_STPG;
+	spin_unlock_irqrestore(&pg->lock, flags);
+	rcu_read_unlock();
 
 	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
@@ -729,50 +1132,39 @@ MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized path, rather than
 static int alua_activate(struct scsi_device *sdev,
 			activate_complete fn, void *data)
 {
-	struct alua_dh_data *h = get_alua_data(sdev);
+	struct alua_dh_data *h = sdev->handler_data;
 	int err = SCSI_DH_OK;
-	int stpg = 0;
+	struct alua_queue_data *qdata;
+	struct alua_port_group *pg;
 
-	err = alua_rtpg(sdev, h);
-	if (err != SCSI_DH_OK)
+	qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
+	if (!qdata) {
+		err = SCSI_DH_RES_TEMP_UNAVAIL;
 		goto out;
-
-	if (optimize_stpg)
-		h->flags |= ALUA_OPTIMIZE_STPG;
-
-	if (h->tpgs & TPGS_MODE_EXPLICIT) {
-		switch (h->state) {
-		case TPGS_STATE_NONOPTIMIZED:
-			stpg = 1;
-			if ((h->flags & ALUA_OPTIMIZE_STPG) &&
-			    (!h->pref) &&
-			    (h->tpgs & TPGS_MODE_IMPLICIT))
-				stpg = 0;
-			break;
-		case TPGS_STATE_STANDBY:
-		case TPGS_STATE_UNAVAILABLE:
-			stpg = 1;
-			break;
-		case TPGS_STATE_OFFLINE:
-			err = SCSI_DH_IO;
-			break;
-		case TPGS_STATE_TRANSITIONING:
-			err = SCSI_DH_RETRY;
-			break;
-		default:
-			break;
-		}
 	}
-
-	if (stpg) {
-		h->callback_fn = fn;
-		h->callback_data = data;
-		err = submit_stpg(h);
-		if (err == SCSI_DH_OK)
-			return 0;
-		h->callback_fn = h->callback_data = NULL;
+	qdata->callback_fn = fn;
+	qdata->callback_data = data;
+
+	mutex_lock(&h->init_mutex);
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (!pg || !kref_get_unless_zero(&pg->kref)) {
+		rcu_read_unlock();
+		kfree(qdata);
+		err = h->init_error;
+		mutex_unlock(&h->init_mutex);
+		goto out;
 	}
+	rcu_read_unlock();
+	mutex_unlock(&h->init_mutex);
 
+	if (alua_rtpg_queue(pg, sdev, qdata, true)) {
+		fn = NULL;
+	} else {
+		kfree(qdata);
+		err = SCSI_DH_DEV_OFFLINED;
+	}
+	kref_put(&pg->kref, release_port_group);
 out:
 	if (fn)
 		fn(data, err);
@@ -780,47 +1172,63 @@ out:
 }
 
 /*
+ * alua_check - check path status
+ * @sdev: device on the path to be checked
+ *
+ * Check the device status
+ */
+static void alua_check(struct scsi_device *sdev, bool force)
+{
+	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg;
+
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (!pg || !kref_get_unless_zero(&pg->kref)) {
+		rcu_read_unlock();
+		return;
+	}
+	rcu_read_unlock();
+	alua_rtpg_queue(pg, sdev, NULL, force);
+	kref_put(&pg->kref, release_port_group);
+}
+
+/*
  * 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)
+static blk_status_t alua_prep_fn(struct scsi_device *sdev, struct request *req)
 {
-	struct alua_dh_data *h = get_alua_data(sdev);
-	int ret = BLKPREP_OK;
+	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg;
+	unsigned char state = SCSI_ACCESS_STATE_OPTIMAL;
 
-	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;
+	rcu_read_lock();
+	pg = rcu_dereference(h->pg);
+	if (pg)
+		state = pg->state;
+	rcu_read_unlock();
 
+	switch (state) {
+	case SCSI_ACCESS_STATE_OPTIMAL:
+	case SCSI_ACCESS_STATE_ACTIVE:
+	case SCSI_ACCESS_STATE_LBA:
+	case SCSI_ACCESS_STATE_TRANSITIONING:
+		return BLK_STS_OK;
+	default:
+		req->rq_flags |= RQF_QUIET;
+		return BLK_STS_IOERR;
+	}
 }
 
-static bool alua_match(struct scsi_device *sdev)
+static void alua_rescan(struct scsi_device *sdev)
 {
-	return (scsi_device_tpgs(sdev) != 0);
-}
-
-static int alua_bus_attach(struct scsi_device *sdev);
-static void alua_bus_detach(struct scsi_device *sdev);
+	struct alua_dh_data *h = sdev->handler_data;
 
-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,
-	.match = alua_match,
-};
+	alua_initialize(sdev, h);
+}
 
 /*
  * alua_bus_attach - Attach device handler
@@ -828,47 +1236,28 @@ static struct scsi_device_handler alua_dh = {
  */
 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(*scsi_dh_data)
-			       + sizeof(*h) , GFP_KERNEL);
-	if (!scsi_dh_data) {
-		sdev_printk(KERN_ERR, sdev, "%s: Attach failed\n",
-			    ALUA_DH_NAME);
-		return -ENOMEM;
-	}
+	int err;
 
-	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;
+	h = kzalloc(sizeof(*h) , GFP_KERNEL);
+	if (!h)
+		return SCSI_DH_NOMEM;
+	spin_lock_init(&h->pg_lock);
+	rcu_assign_pointer(h->pg, NULL);
+	h->init_error = SCSI_DH_OK;
 	h->sdev = sdev;
+	INIT_LIST_HEAD(&h->node);
 
+	mutex_init(&h->init_mutex);
 	err = alua_initialize(sdev, h);
-	if ((err != SCSI_DH_OK) && (err != SCSI_DH_DEV_OFFLINED))
-		goto failed;
-
-	if (!try_module_get(THIS_MODULE))
+	if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
 		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);
-	sdev_printk(KERN_NOTICE, sdev, "%s: Attached\n", ALUA_DH_NAME);
-
-	return 0;
-
+	sdev->handler_data = h;
+	return SCSI_DH_OK;
 failed:
-	kfree(scsi_dh_data);
-	sdev_printk(KERN_ERR, sdev, "%s: not attached\n", ALUA_DH_NAME);
-	return -EINVAL;
+	kfree(h);
+	return err;
 }
 
 /*
@@ -877,37 +1266,57 @@ failed:
  */
 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);
+	struct alua_dh_data *h = sdev->handler_data;
+	struct alua_port_group *pg;
+
+	spin_lock(&h->pg_lock);
+	pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
+	rcu_assign_pointer(h->pg, NULL);
+	spin_unlock(&h->pg_lock);
+	if (pg) {
+		spin_lock_irq(&pg->lock);
+		list_del_rcu(&h->node);
+		spin_unlock_irq(&pg->lock);
+		kref_put(&pg->kref, release_port_group);
+	}
+	sdev->handler_data = NULL;
+	synchronize_rcu();
+	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,
+	.rescan = alua_rescan,
+	.set_params = alua_set_params,
+};
+
 static int __init alua_init(void)
 {
 	int r;
 
+	kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM | WQ_PERCPU, 0);
+	if (!kaluad_wq)
+		return -ENOMEM;
+
 	r = scsi_register_device_handler(&alua_dh);
-	if (r != 0)
+	if (r != 0) {
 		printk(KERN_ERR "%s: Failed to register scsi device handler",
 			ALUA_DH_NAME);
+		destroy_workqueue(kaluad_wq);
+	}
 	return r;
 }
 
 static void __exit alua_exit(void)
 {
 	scsi_unregister_device_handler(&alua_dh);
+	destroy_workqueue(kaluad_wq);
 }
 
 module_init(alua_init);