drivers/scsi/device_handler/scsi_dh_alua.c

   1 /*
   2  * Generic SCSI-3 ALUA SCSI Device Handler
   3  *
   4  * Copyright (C) 2007-2010 Hannes Reinecke, SUSE Linux Products GmbH.
   5  * All rights reserved.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  20  *
  21  */
  22 #include <linux/slab.h>
  23 #include <linux/delay.h>
  24 #include <linux/module.h>
  25 #include <asm/unaligned.h>
  26 #include <scsi/scsi.h>
  27 #include <scsi/scsi_proto.h>
  28 #include <scsi/scsi_dbg.h>
  29 #include <scsi/scsi_eh.h>
  30 #include <scsi/scsi_dh.h>
  31
  32 #define ALUA_DH_NAME "alua"
  33 #define ALUA_DH_VER "2.0"
  34
  35 #define TPGS_SUPPORT_NONE               0x00
  36 #define TPGS_SUPPORT_OPTIMIZED          0x01
  37 #define TPGS_SUPPORT_NONOPTIMIZED       0x02
  38 #define TPGS_SUPPORT_STANDBY            0x04
  39 #define TPGS_SUPPORT_UNAVAILABLE        0x08
  40 #define TPGS_SUPPORT_LBA_DEPENDENT      0x10
  41 #define TPGS_SUPPORT_OFFLINE            0x40
  42 #define TPGS_SUPPORT_TRANSITION         0x80
  43
  44 #define RTPG_FMT_MASK                   0x70
  45 #define RTPG_FMT_EXT_HDR                0x10
  46
  47 #define TPGS_MODE_UNINITIALIZED          -1
  48 #define TPGS_MODE_NONE                  0x0
  49 #define TPGS_MODE_IMPLICIT              0x1
  50 #define TPGS_MODE_EXPLICIT              0x2
  51
  52 #define ALUA_RTPG_SIZE                  128
  53 #define ALUA_FAILOVER_TIMEOUT           60
  54 #define ALUA_FAILOVER_RETRIES           5
  55 #define ALUA_RTPG_DELAY_MSECS           5
  56
  57 /* device handler flags */
  58 #define ALUA_OPTIMIZE_STPG              0x01
  59 #define ALUA_RTPG_EXT_HDR_UNSUPP        0x02
  60 #define ALUA_SYNC_STPG                  0x04
  61 /* State machine flags */
  62 #define ALUA_PG_RUN_RTPG                0x10
  63 #define ALUA_PG_RUN_STPG                0x20
  64 #define ALUA_PG_RUNNING                 0x40
  65
  66 static uint optimize_stpg;
  67 module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
  68 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.");
  69
  70 static LIST_HEAD(port_group_list);
  71 static DEFINE_SPINLOCK(port_group_lock);
  72 static struct workqueue_struct *kaluad_wq;
  73 static struct workqueue_struct *kaluad_sync_wq;
  74
  75 struct alua_port_group {
  76         struct kref             kref;
  77         struct rcu_head         rcu;
  78         struct list_head        node;
  79         struct list_head        dh_list;
  80         unsigned char           device_id_str[256];
  81         int                     device_id_len;
  82         int                     group_id;
  83         int                     tpgs;
  84         int                     state;
  85         int                     pref;
  86         unsigned                flags; /* used for optimizing STPG */
  87         unsigned char           transition_tmo;
  88         unsigned long           expiry;
  89         unsigned long           interval;
  90         struct delayed_work     rtpg_work;
  91         spinlock_t              lock;
  92         struct list_head        rtpg_list;
  93         struct scsi_device      *rtpg_sdev;
  94 };
  95
  96 struct alua_dh_data {
  97         struct list_head        node;
  98         struct alua_port_group __rcu *pg;
  99         int                     group_id;
 100         spinlock_t              pg_lock;
 101         struct scsi_device      *sdev;
 102         int                     init_error;
 103         struct mutex            init_mutex;
 104 };
 105
 106 struct alua_queue_data {
 107         struct list_head        entry;
 108         activate_complete       callback_fn;
 109         void                    *callback_data;
 110 };
 111
 112 #define ALUA_POLICY_SWITCH_CURRENT      0
 113 #define ALUA_POLICY_SWITCH_ALL          1
 114
 115 static void alua_rtpg_work(struct work_struct *work);
 116 static bool alua_rtpg_queue(struct alua_port_group *pg,
 117                             struct scsi_device *sdev,
 118                             struct alua_queue_data *qdata, bool force);
 119 static void alua_check(struct scsi_device *sdev, bool force);
 120
 121 static void release_port_group(struct kref *kref)
 122 {
 123         struct alua_port_group *pg;
 124
 125         pg = container_of(kref, struct alua_port_group, kref);
 126         if (pg->rtpg_sdev)
 127                 flush_delayed_work(&pg->rtpg_work);
 128         spin_lock(&port_group_lock);
 129         list_del(&pg->node);
 130         spin_unlock(&port_group_lock);
 131         kfree_rcu(pg, rcu);
 132 }
 133
 134 /*
 135  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
 136  * @sdev: sdev the command should be sent to
 137  */
 138 static int submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
 139                        int bufflen, struct scsi_sense_hdr *sshdr, int flags)
 140 {
 141         u8 cdb[COMMAND_SIZE(MAINTENANCE_IN)];
 142         int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 143                 REQ_FAILFAST_DRIVER;
 144
 145         /* Prepare the command. */
 146         memset(cdb, 0x0, COMMAND_SIZE(MAINTENANCE_IN));
 147         cdb[0] = MAINTENANCE_IN;
 148         if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
 149                 cdb[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
 150         else
 151                 cdb[1] = MI_REPORT_TARGET_PGS;
 152         put_unaligned_be32(bufflen, &cdb[6]);
 153
 154         return scsi_execute(sdev, cdb, DMA_FROM_DEVICE, buff, bufflen, NULL,
 155                         sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
 156                         ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
 157 }
 158
 159 /*
 160  * submit_stpg - Issue a SET TARGET PORT GROUP command
 161  *
 162  * Currently we're only setting the current target port group state
 163  * to 'active/optimized' and let the array firmware figure out
 164  * the states of the remaining groups.
 165  */
 166 static int submit_stpg(struct scsi_device *sdev, int group_id,
 167                        struct scsi_sense_hdr *sshdr)
 168 {
 169         u8 cdb[COMMAND_SIZE(MAINTENANCE_OUT)];
 170         unsigned char stpg_data[8];
 171         int stpg_len = 8;
 172         int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 173                 REQ_FAILFAST_DRIVER;
 174
 175         /* Prepare the data buffer */
 176         memset(stpg_data, 0, stpg_len);
 177         stpg_data[4] = SCSI_ACCESS_STATE_OPTIMAL;
 178         put_unaligned_be16(group_id, &stpg_data[6]);
 179
 180         /* Prepare the command. */
 181         memset(cdb, 0x0, COMMAND_SIZE(MAINTENANCE_OUT));
 182         cdb[0] = MAINTENANCE_OUT;
 183         cdb[1] = MO_SET_TARGET_PGS;
 184         put_unaligned_be32(stpg_len, &cdb[6]);
 185
 186         return scsi_execute(sdev, cdb, DMA_TO_DEVICE, stpg_data, stpg_len, NULL,
 187                         sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
 188                         ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
 189 }
 190
 191 static struct alua_port_group *alua_find_get_pg(char *id_str, size_t id_size,
 192                                                 int group_id)
 193 {
 194         struct alua_port_group *pg;
 195
 196         if (!id_str || !id_size || !strlen(id_str))
 197                 return NULL;
 198
 199         list_for_each_entry(pg, &port_group_list, node) {
 200                 if (pg->group_id != group_id)
 201                         continue;
 202                 if (!pg->device_id_len || pg->device_id_len != id_size)
 203                         continue;
 204                 if (strncmp(pg->device_id_str, id_str, id_size))
 205                         continue;
 206                 if (!kref_get_unless_zero(&pg->kref))
 207                         continue;
 208                 return pg;
 209         }
 210
 211         return NULL;
 212 }
 213
 214 /*
 215  * alua_alloc_pg - Allocate a new port_group structure
 216  * @sdev: scsi device
 217  * @h: alua device_handler data
 218  * @group_id: port group id
 219  *
 220  * Allocate a new port_group structure for a given
 221  * device.
 222  */
 223 static struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
 224                                              int group_id, int tpgs)
 225 {
 226         struct alua_port_group *pg, *tmp_pg;
 227
 228         pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL);
 229         if (!pg)
 230                 return ERR_PTR(-ENOMEM);
 231
 232         pg->device_id_len = scsi_vpd_lun_id(sdev, pg->device_id_str,
 233                                             sizeof(pg->device_id_str));
 234         if (pg->device_id_len <= 0) {
 235                 /*
 236                  * TPGS supported but no device identification found.
 237                  * Generate private device identification.
 238                  */
 239                 sdev_printk(KERN_INFO, sdev,
 240                             "%s: No device descriptors found\n",
 241                             ALUA_DH_NAME);
 242                 pg->device_id_str[0] = '\0';
 243                 pg->device_id_len = 0;
 244         }
 245         pg->group_id = group_id;
 246         pg->tpgs = tpgs;
 247         pg->state = SCSI_ACCESS_STATE_OPTIMAL;
 248         if (optimize_stpg)
 249                 pg->flags |= ALUA_OPTIMIZE_STPG;
 250         kref_init(&pg->kref);
 251         INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
 252         INIT_LIST_HEAD(&pg->rtpg_list);
 253         INIT_LIST_HEAD(&pg->node);
 254         INIT_LIST_HEAD(&pg->dh_list);
 255         spin_lock_init(&pg->lock);
 256
 257         spin_lock(&port_group_lock);
 258         tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 259                                   group_id);
 260         if (tmp_pg) {
 261                 spin_unlock(&port_group_lock);
 262                 kfree(pg);
 263                 return tmp_pg;
 264         }
 265
 266         list_add(&pg->node, &port_group_list);
 267         spin_unlock(&port_group_lock);
 268
 269         return pg;
 270 }
 271
 272 /*
 273  * alua_check_tpgs - Evaluate TPGS setting
 274  * @sdev: device to be checked
 275  *
 276  * Examine the TPGS setting of the sdev to find out if ALUA
 277  * is supported.
 278  */
 279 static int alua_check_tpgs(struct scsi_device *sdev)
 280 {
 281         int tpgs = TPGS_MODE_NONE;
 282
 283         /*
 284          * ALUA support for non-disk devices is fraught with
 285          * difficulties, so disable it for now.
 286          */
 287         if (sdev->type != TYPE_DISK) {
 288                 sdev_printk(KERN_INFO, sdev,
 289                             "%s: disable for non-disk devices\n",
 290                             ALUA_DH_NAME);
 291                 return tpgs;
 292         }
 293
 294         tpgs = scsi_device_tpgs(sdev);
 295         switch (tpgs) {
 296         case TPGS_MODE_EXPLICIT|TPGS_MODE_IMPLICIT:
 297                 sdev_printk(KERN_INFO, sdev,
 298                             "%s: supports implicit and explicit TPGS\n",
 299                             ALUA_DH_NAME);
 300                 break;
 301         case TPGS_MODE_EXPLICIT:
 302                 sdev_printk(KERN_INFO, sdev, "%s: supports explicit TPGS\n",
 303                             ALUA_DH_NAME);
 304                 break;
 305         case TPGS_MODE_IMPLICIT:
 306                 sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n",
 307                             ALUA_DH_NAME);
 308                 break;
 309         case TPGS_MODE_NONE:
 310                 sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
 311                             ALUA_DH_NAME);
 312                 break;
 313         default:
 314                 sdev_printk(KERN_INFO, sdev,
 315                             "%s: unsupported TPGS setting %d\n",
 316                             ALUA_DH_NAME, tpgs);
 317                 tpgs = TPGS_MODE_NONE;
 318                 break;
 319         }
 320
 321         return tpgs;
 322 }
 323
 324 /*
 325  * alua_check_vpd - Evaluate INQUIRY vpd page 0x83
 326  * @sdev: device to be checked
 327  *
 328  * Extract the relative target port and the target port group
 329  * descriptor from the list of identificators.
 330  */
 331 static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 332                           int tpgs)
 333 {
 334         int rel_port = -1, group_id;
 335         struct alua_port_group *pg, *old_pg = NULL;
 336         bool pg_updated = false;
 337         unsigned long flags;
 338
 339         group_id = scsi_vpd_tpg_id(sdev, &rel_port);
 340         if (group_id < 0) {
 341                 /*
 342                  * Internal error; TPGS supported but required
 343                  * VPD identification descriptors not present.
 344                  * Disable ALUA support
 345                  */
 346                 sdev_printk(KERN_INFO, sdev,
 347                             "%s: No target port descriptors found\n",
 348                             ALUA_DH_NAME);
 349                 return SCSI_DH_DEV_UNSUPP;
 350         }
 351
 352         pg = alua_alloc_pg(sdev, group_id, tpgs);
 353         if (IS_ERR(pg)) {
 354                 if (PTR_ERR(pg) == -ENOMEM)
 355                         return SCSI_DH_NOMEM;
 356                 return SCSI_DH_DEV_UNSUPP;
 357         }
 358         if (pg->device_id_len)
 359                 sdev_printk(KERN_INFO, sdev,
 360                             "%s: device %s port group %x rel port %x\n",
 361                             ALUA_DH_NAME, pg->device_id_str,
 362                             group_id, rel_port);
 363         else
 364                 sdev_printk(KERN_INFO, sdev,
 365                             "%s: port group %x rel port %x\n",
 366                             ALUA_DH_NAME, group_id, rel_port);
 367
 368         /* Check for existing port group references */
 369         spin_lock(&h->pg_lock);
 370         old_pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
 371         if (old_pg != pg) {
 372                 /* port group has changed. Update to new port group */
 373                 if (h->pg) {
 374                         spin_lock_irqsave(&old_pg->lock, flags);
 375                         list_del_rcu(&h->node);
 376                         spin_unlock_irqrestore(&old_pg->lock, flags);
 377                 }
 378                 rcu_assign_pointer(h->pg, pg);
 379                 pg_updated = true;
 380         }
 381
 382         spin_lock_irqsave(&pg->lock, flags);
 383         if (sdev->synchronous_alua)
 384                 pg->flags |= ALUA_SYNC_STPG;
 385         if (pg_updated)
 386                 list_add_rcu(&h->node, &pg->dh_list);
 387         spin_unlock_irqrestore(&pg->lock, flags);
 388
 389         alua_rtpg_queue(rcu_dereference_protected(h->pg,
 390                                                   lockdep_is_held(&h->pg_lock)),
 391                         sdev, NULL, true);
 392         spin_unlock(&h->pg_lock);
 393
 394         if (old_pg)
 395                 kref_put(&old_pg->kref, release_port_group);
 396
 397         return SCSI_DH_OK;
 398 }
 399
 400 static char print_alua_state(unsigned char state)
 401 {
 402         switch (state) {
 403         case SCSI_ACCESS_STATE_OPTIMAL:
 404                 return 'A';
 405         case SCSI_ACCESS_STATE_ACTIVE:
 406                 return 'N';
 407         case SCSI_ACCESS_STATE_STANDBY:
 408                 return 'S';
 409         case SCSI_ACCESS_STATE_UNAVAILABLE:
 410                 return 'U';
 411         case SCSI_ACCESS_STATE_LBA:
 412                 return 'L';
 413         case SCSI_ACCESS_STATE_OFFLINE:
 414                 return 'O';
 415         case SCSI_ACCESS_STATE_TRANSITIONING:
 416                 return 'T';
 417         default:
 418                 return 'X';
 419         }
 420 }
 421
 422 static int alua_check_sense(struct scsi_device *sdev,
 423                             struct scsi_sense_hdr *sense_hdr)
 424 {
 425         switch (sense_hdr->sense_key) {
 426         case NOT_READY:
 427                 if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
 428                         /*
 429                          * LUN Not Accessible - ALUA state transition
 430                          */
 431                         alua_check(sdev, false);
 432                         return NEEDS_RETRY;
 433                 }
 434                 break;
 435         case UNIT_ATTENTION:
 436                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
 437                         /*
 438                          * Power On, Reset, or Bus Device Reset.
 439                          * Might have obscured a state transition,
 440                          * so schedule a recheck.
 441                          */
 442                         alua_check(sdev, true);
 443                         return ADD_TO_MLQUEUE;
 444                 }
 445                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
 446                         /*
 447                          * Device internal reset
 448                          */
 449                         return ADD_TO_MLQUEUE;
 450                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
 451                         /*
 452                          * Mode Parameters Changed
 453                          */
 454                         return ADD_TO_MLQUEUE;
 455                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
 456                         /*
 457                          * ALUA state changed
 458                          */
 459                         alua_check(sdev, true);
 460                         return ADD_TO_MLQUEUE;
 461                 }
 462                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
 463                         /*
 464                          * Implicit ALUA state transition failed
 465                          */
 466                         alua_check(sdev, true);
 467                         return ADD_TO_MLQUEUE;
 468                 }
 469                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
 470                         /*
 471                          * Inquiry data has changed
 472                          */
 473                         return ADD_TO_MLQUEUE;
 474                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x0e)
 475                         /*
 476                          * REPORTED_LUNS_DATA_HAS_CHANGED is reported
 477                          * when switching controllers on targets like
 478                          * Intel Multi-Flex. We can just retry.
 479                          */
 480                         return ADD_TO_MLQUEUE;
 481                 break;
 482         }
 483
 484         return SCSI_RETURN_NOT_HANDLED;
 485 }
 486
 487 /*
 488  * alua_tur - Send a TEST UNIT READY
 489  * @sdev: device to which the TEST UNIT READY command should be send
 490  *
 491  * Send a TEST UNIT READY to @sdev to figure out the device state
 492  * Returns SCSI_DH_RETRY if the sense code is NOT READY/ALUA TRANSITIONING,
 493  * SCSI_DH_OK if no error occurred, and SCSI_DH_IO otherwise.
 494  */
 495 static int alua_tur(struct scsi_device *sdev)
 496 {
 497         struct scsi_sense_hdr sense_hdr;
 498         int retval;
 499
 500         retval = scsi_test_unit_ready(sdev, ALUA_FAILOVER_TIMEOUT * HZ,
 501                                       ALUA_FAILOVER_RETRIES, &sense_hdr);
 502         if (sense_hdr.sense_key == NOT_READY &&
 503             sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
 504                 return SCSI_DH_RETRY;
 505         else if (retval)
 506                 return SCSI_DH_IO;
 507         else
 508                 return SCSI_DH_OK;
 509 }
 510
 511 /*
 512  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
 513  * @sdev: the device to be evaluated.
 514  *
 515  * Evaluate the Target Port Group State.
 516  * Returns SCSI_DH_DEV_OFFLINED if the path is
 517  * found to be unusable.
 518  */
 519 static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 520 {
 521         struct scsi_sense_hdr sense_hdr;
 522         struct alua_port_group *tmp_pg;
 523         int len, k, off, valid_states = 0, bufflen = ALUA_RTPG_SIZE;
 524         unsigned char *desc, *buff;
 525         unsigned err, retval;
 526         unsigned int tpg_desc_tbl_off;
 527         unsigned char orig_transition_tmo;
 528         unsigned long flags;
 529
 530         if (!pg->expiry) {
 531                 unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
 532
 533                 if (pg->transition_tmo)
 534                         transition_tmo = pg->transition_tmo * HZ;
 535
 536                 pg->expiry = round_jiffies_up(jiffies + transition_tmo);
 537         }
 538
 539         buff = kzalloc(bufflen, GFP_KERNEL);
 540         if (!buff)
 541                 return SCSI_DH_DEV_TEMP_BUSY;
 542
 543  retry:
 544         err = 0;
 545         retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
 546
 547         if (retval) {
 548                 if (!scsi_sense_valid(&sense_hdr)) {
 549                         sdev_printk(KERN_INFO, sdev,
 550                                     "%s: rtpg failed, result %d\n",
 551                                     ALUA_DH_NAME, retval);
 552                         kfree(buff);
 553                         if (driver_byte(retval) == DRIVER_ERROR)
 554                                 return SCSI_DH_DEV_TEMP_BUSY;
 555                         return SCSI_DH_IO;
 556                 }
 557
 558                 /*
 559                  * submit_rtpg() has failed on existing arrays
 560                  * when requesting extended header info, and
 561                  * the array doesn't support extended headers,
 562                  * even though it shouldn't according to T10.
 563                  * The retry without rtpg_ext_hdr_req set
 564                  * handles this.
 565                  */
 566                 if (!(pg->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
 567                     sense_hdr.sense_key == ILLEGAL_REQUEST &&
 568                     sense_hdr.asc == 0x24 && sense_hdr.ascq == 0) {
 569                         pg->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
 570                         goto retry;
 571                 }
 572                 /*
 573                  * Retry on ALUA state transition or if any
 574                  * UNIT ATTENTION occurred.
 575                  */
 576                 if (sense_hdr.sense_key == NOT_READY &&
 577                     sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
 578                         err = SCSI_DH_RETRY;
 579                 else if (sense_hdr.sense_key == UNIT_ATTENTION)
 580                         err = SCSI_DH_RETRY;
 581                 if (err == SCSI_DH_RETRY &&
 582                     pg->expiry != 0 && time_before(jiffies, pg->expiry)) {
 583                         sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
 584                                     ALUA_DH_NAME);
 585                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 586                         kfree(buff);
 587                         return err;
 588                 }
 589                 sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
 590                             ALUA_DH_NAME);
 591                 scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 592                 kfree(buff);
 593                 pg->expiry = 0;
 594                 return SCSI_DH_IO;
 595         }
 596
 597         len = get_unaligned_be32(&buff[0]) + 4;
 598
 599         if (len > bufflen) {
 600                 /* Resubmit with the correct length */
 601                 kfree(buff);
 602                 bufflen = len;
 603                 buff = kmalloc(bufflen, GFP_KERNEL);
 604                 if (!buff) {
 605                         sdev_printk(KERN_WARNING, sdev,
 606                                     "%s: kmalloc buffer failed\n",__func__);
 607                         /* Temporary failure, bypass */
 608                         pg->expiry = 0;
 609                         return SCSI_DH_DEV_TEMP_BUSY;
 610                 }
 611                 goto retry;
 612         }
 613
 614         orig_transition_tmo = pg->transition_tmo;
 615         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0)
 616                 pg->transition_tmo = buff[5];
 617         else
 618                 pg->transition_tmo = ALUA_FAILOVER_TIMEOUT;
 619
 620         if (orig_transition_tmo != pg->transition_tmo) {
 621                 sdev_printk(KERN_INFO, sdev,
 622                             "%s: transition timeout set to %d seconds\n",
 623                             ALUA_DH_NAME, pg->transition_tmo);
 624                 pg->expiry = jiffies + pg->transition_tmo * HZ;
 625         }
 626
 627         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
 628                 tpg_desc_tbl_off = 8;
 629         else
 630                 tpg_desc_tbl_off = 4;
 631
 632         for (k = tpg_desc_tbl_off, desc = buff + tpg_desc_tbl_off;
 633              k < len;
 634              k += off, desc += off) {
 635                 u16 group_id = get_unaligned_be16(&desc[2]);
 636
 637                 spin_lock_irqsave(&port_group_lock, flags);
 638                 tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 639                                           group_id);
 640                 spin_unlock_irqrestore(&port_group_lock, flags);
 641                 if (tmp_pg) {
 642                         if (spin_trylock_irqsave(&tmp_pg->lock, flags)) {
 643                                 if ((tmp_pg == pg) ||
 644                                     !(tmp_pg->flags & ALUA_PG_RUNNING)) {
 645                                         struct alua_dh_data *h;
 646
 647                                         tmp_pg->state = desc[0] & 0x0f;
 648                                         tmp_pg->pref = desc[0] >> 7;
 649                                         rcu_read_lock();
 650                                         list_for_each_entry_rcu(h,
 651                                                 &tmp_pg->dh_list, node) {
 652                                                 /* h->sdev should always be valid */
 653                                                 BUG_ON(!h->sdev);
 654                                                 h->sdev->access_state = desc[0];
 655                                         }
 656                                         rcu_read_unlock();
 657                                 }
 658                                 if (tmp_pg == pg)
 659                                         valid_states = desc[1];
 660                                 spin_unlock_irqrestore(&tmp_pg->lock, flags);
 661                         }
 662                         kref_put(&tmp_pg->kref, release_port_group);
 663                 }
 664                 off = 8 + (desc[7] * 4);
 665         }
 666
 667         spin_lock_irqsave(&pg->lock, flags);
 668         sdev_printk(KERN_INFO, sdev,
 669                     "%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
 670                     ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state),
 671                     pg->pref ? "preferred" : "non-preferred",
 672                     valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
 673                     valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
 674                     valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
 675                     valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
 676                     valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
 677                     valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
 678                     valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
 679
 680         switch (pg->state) {
 681         case SCSI_ACCESS_STATE_TRANSITIONING:
 682                 if (time_before(jiffies, pg->expiry)) {
 683                         /* State transition, retry */
 684                         pg->interval = 2;
 685                         err = SCSI_DH_RETRY;
 686                 } else {
 687                         struct alua_dh_data *h;
 688
 689                         /* Transitioning time exceeded, set port to standby */
 690                         err = SCSI_DH_IO;
 691                         pg->state = SCSI_ACCESS_STATE_STANDBY;
 692                         pg->expiry = 0;
 693                         rcu_read_lock();
 694                         list_for_each_entry_rcu(h, &pg->dh_list, node) {
 695                                 BUG_ON(!h->sdev);
 696                                 h->sdev->access_state =
 697                                         (pg->state & SCSI_ACCESS_STATE_MASK);
 698                                 if (pg->pref)
 699                                         h->sdev->access_state |=
 700                                                 SCSI_ACCESS_STATE_PREFERRED;
 701                         }
 702                         rcu_read_unlock();
 703                 }
 704                 break;
 705         case SCSI_ACCESS_STATE_OFFLINE:
 706                 /* Path unusable */
 707                 err = SCSI_DH_DEV_OFFLINED;
 708                 pg->expiry = 0;
 709                 break;
 710         default:
 711                 /* Useable path if active */
 712                 err = SCSI_DH_OK;
 713                 pg->expiry = 0;
 714                 break;
 715         }
 716         spin_unlock_irqrestore(&pg->lock, flags);
 717         kfree(buff);
 718         return err;
 719 }
 720
 721 /*
 722  * alua_stpg - Issue a SET TARGET PORT GROUP command
 723  *
 724  * Issue a SET TARGET PORT GROUP command and evaluate the
 725  * response. Returns SCSI_DH_RETRY per default to trigger
 726  * a re-evaluation of the target group state or SCSI_DH_OK
 727  * if no further action needs to be taken.
 728  */
 729 static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg)
 730 {
 731         int retval;
 732         struct scsi_sense_hdr sense_hdr;
 733
 734         if (!(pg->tpgs & TPGS_MODE_EXPLICIT)) {
 735                 /* Only implicit ALUA supported, retry */
 736                 return SCSI_DH_RETRY;
 737         }
 738         switch (pg->state) {
 739         case SCSI_ACCESS_STATE_OPTIMAL:
 740                 return SCSI_DH_OK;
 741         case SCSI_ACCESS_STATE_ACTIVE:
 742                 if ((pg->flags & ALUA_OPTIMIZE_STPG) &&
 743                     !pg->pref &&
 744                     (pg->tpgs & TPGS_MODE_IMPLICIT))
 745                         return SCSI_DH_OK;
 746                 break;
 747         case SCSI_ACCESS_STATE_STANDBY:
 748         case SCSI_ACCESS_STATE_UNAVAILABLE:
 749                 break;
 750         case SCSI_ACCESS_STATE_OFFLINE:
 751                 return SCSI_DH_IO;
 752         case SCSI_ACCESS_STATE_TRANSITIONING:
 753                 break;
 754         default:
 755                 sdev_printk(KERN_INFO, sdev,
 756                             "%s: stpg failed, unhandled TPGS state %d",
 757                             ALUA_DH_NAME, pg->state);
 758                 return SCSI_DH_NOSYS;
 759         }
 760         retval = submit_stpg(sdev, pg->group_id, &sense_hdr);
 761
 762         if (retval) {
 763                 if (!scsi_sense_valid(&sense_hdr)) {
 764                         sdev_printk(KERN_INFO, sdev,
 765                                     "%s: stpg failed, result %d",
 766                                     ALUA_DH_NAME, retval);
 767                         if (driver_byte(retval) == DRIVER_ERROR)
 768                                 return SCSI_DH_DEV_TEMP_BUSY;
 769                 } else {
 770                         sdev_printk(KERN_INFO, sdev, "%s: stpg failed\n",
 771                                     ALUA_DH_NAME);
 772                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 773                 }
 774         }
 775         /* Retry RTPG */
 776         return SCSI_DH_RETRY;
 777 }
 778
 779 static void alua_rtpg_work(struct work_struct *work)
 780 {
 781         struct alua_port_group *pg =
 782                 container_of(work, struct alua_port_group, rtpg_work.work);
 783         struct scsi_device *sdev;
 784         LIST_HEAD(qdata_list);
 785         int err = SCSI_DH_OK;
 786         struct alua_queue_data *qdata, *tmp;
 787         unsigned long flags;
 788         struct workqueue_struct *alua_wq = kaluad_wq;
 789
 790         spin_lock_irqsave(&pg->lock, flags);
 791         sdev = pg->rtpg_sdev;
 792         if (!sdev) {
 793                 WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
 794                 WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
 795                 spin_unlock_irqrestore(&pg->lock, flags);
 796                 kref_put(&pg->kref, release_port_group);
 797                 return;
 798         }
 799         if (pg->flags & ALUA_SYNC_STPG)
 800                 alua_wq = kaluad_sync_wq;
 801         pg->flags |= ALUA_PG_RUNNING;
 802         if (pg->flags & ALUA_PG_RUN_RTPG) {
 803                 int state = pg->state;
 804
 805                 pg->flags &= ~ALUA_PG_RUN_RTPG;
 806                 spin_unlock_irqrestore(&pg->lock, flags);
 807                 if (state == SCSI_ACCESS_STATE_TRANSITIONING) {
 808                         if (alua_tur(sdev) == SCSI_DH_RETRY) {
 809                                 spin_lock_irqsave(&pg->lock, flags);
 810                                 pg->flags &= ~ALUA_PG_RUNNING;
 811                                 pg->flags |= ALUA_PG_RUN_RTPG;
 812                                 spin_unlock_irqrestore(&pg->lock, flags);
 813                                 queue_delayed_work(alua_wq, &pg->rtpg_work,
 814                                                    pg->interval * HZ);
 815                                 return;
 816                         }
 817                         /* Send RTPG on failure or if TUR indicates SUCCESS */
 818                 }
 819                 err = alua_rtpg(sdev, pg);
 820                 spin_lock_irqsave(&pg->lock, flags);
 821                 if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 822                         pg->flags &= ~ALUA_PG_RUNNING;
 823                         pg->flags |= ALUA_PG_RUN_RTPG;
 824                         spin_unlock_irqrestore(&pg->lock, flags);
 825                         queue_delayed_work(alua_wq, &pg->rtpg_work,
 826                                            pg->interval * HZ);
 827                         return;
 828                 }
 829                 if (err != SCSI_DH_OK)
 830                         pg->flags &= ~ALUA_PG_RUN_STPG;
 831         }
 832         if (pg->flags & ALUA_PG_RUN_STPG) {
 833                 pg->flags &= ~ALUA_PG_RUN_STPG;
 834                 spin_unlock_irqrestore(&pg->lock, flags);
 835                 err = alua_stpg(sdev, pg);
 836                 spin_lock_irqsave(&pg->lock, flags);
 837                 if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 838                         pg->flags |= ALUA_PG_RUN_RTPG;
 839                         pg->interval = 0;
 840                         pg->flags &= ~ALUA_PG_RUNNING;
 841                         spin_unlock_irqrestore(&pg->lock, flags);
 842                         queue_delayed_work(alua_wq, &pg->rtpg_work,
 843                                            pg->interval * HZ);
 844                         return;
 845                 }
 846         }
 847
 848         list_splice_init(&pg->rtpg_list, &qdata_list);
 849         pg->rtpg_sdev = NULL;
 850         spin_unlock_irqrestore(&pg->lock, flags);
 851
 852         list_for_each_entry_safe(qdata, tmp, &qdata_list, entry) {
 853                 list_del(&qdata->entry);
 854                 if (qdata->callback_fn)
 855                         qdata->callback_fn(qdata->callback_data, err);
 856                 kfree(qdata);
 857         }
 858         spin_lock_irqsave(&pg->lock, flags);
 859         pg->flags &= ~ALUA_PG_RUNNING;
 860         spin_unlock_irqrestore(&pg->lock, flags);
 861         scsi_device_put(sdev);
 862         kref_put(&pg->kref, release_port_group);
 863 }
 864
 865 /**
 866  * alua_rtpg_queue() - cause RTPG to be submitted asynchronously
 867  *
 868  * Returns true if and only if alua_rtpg_work() will be called asynchronously.
 869  * That function is responsible for calling @qdata->fn().
 870  */
 871 static bool alua_rtpg_queue(struct alua_port_group *pg,
 872                             struct scsi_device *sdev,
 873                             struct alua_queue_data *qdata, bool force)
 874 {
 875         int start_queue = 0;
 876         unsigned long flags;
 877         struct workqueue_struct *alua_wq = kaluad_wq;
 878
 879         if (WARN_ON_ONCE(!pg) || scsi_device_get(sdev))
 880                 return false;
 881
 882         spin_lock_irqsave(&pg->lock, flags);
 883         if (qdata) {
 884                 list_add_tail(&qdata->entry, &pg->rtpg_list);
 885                 pg->flags |= ALUA_PG_RUN_STPG;
 886                 force = true;
 887         }
 888         if (pg->rtpg_sdev == NULL) {
 889                 pg->interval = 0;
 890                 pg->flags |= ALUA_PG_RUN_RTPG;
 891                 kref_get(&pg->kref);
 892                 pg->rtpg_sdev = sdev;
 893                 start_queue = 1;
 894         } else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {
 895                 pg->flags |= ALUA_PG_RUN_RTPG;
 896                 /* Do not queue if the worker is already running */
 897                 if (!(pg->flags & ALUA_PG_RUNNING)) {
 898                         kref_get(&pg->kref);
 899                         start_queue = 1;
 900                 }
 901         }
 902
 903         if (pg->flags & ALUA_SYNC_STPG)
 904                 alua_wq = kaluad_sync_wq;
 905         spin_unlock_irqrestore(&pg->lock, flags);
 906
 907         if (start_queue) {
 908                 if (queue_delayed_work(alua_wq, &pg->rtpg_work,
 909                                 msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS)))
 910                         sdev = NULL;
 911                 else
 912                         kref_put(&pg->kref, release_port_group);
 913         }
 914         if (sdev)
 915                 scsi_device_put(sdev);
 916
 917         return true;
 918 }
 919
 920 /*
 921  * alua_initialize - Initialize ALUA state
 922  * @sdev: the device to be initialized
 923  *
 924  * For the prep_fn to work correctly we have
 925  * to initialize the ALUA state for the device.
 926  */
 927 static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 928 {
 929         int err = SCSI_DH_DEV_UNSUPP, tpgs;
 930
 931         mutex_lock(&h->init_mutex);
 932         tpgs = alua_check_tpgs(sdev);
 933         if (tpgs != TPGS_MODE_NONE)
 934                 err = alua_check_vpd(sdev, h, tpgs);
 935         h->init_error = err;
 936         mutex_unlock(&h->init_mutex);
 937         return err;
 938 }
 939 /*
 940  * alua_set_params - set/unset the optimize flag
 941  * @sdev: device on the path to be activated
 942  * params - parameters in the following format
 943  *      "no_of_params\0param1\0param2\0param3\0...\0"
 944  * For example, to set the flag pass the following parameters
 945  * from multipath.conf
 946  *     hardware_handler        "2 alua 1"
 947  */
 948 static int alua_set_params(struct scsi_device *sdev, const char *params)
 949 {
 950         struct alua_dh_data *h = sdev->handler_data;
 951         struct alua_port_group *pg = NULL;
 952         unsigned int optimize = 0, argc;
 953         const char *p = params;
 954         int result = SCSI_DH_OK;
 955         unsigned long flags;
 956
 957         if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
 958                 return -EINVAL;
 959
 960         while (*p++)
 961                 ;
 962         if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
 963                 return -EINVAL;
 964
 965         rcu_read_lock();
 966         pg = rcu_dereference(h->pg);
 967         if (!pg) {
 968                 rcu_read_unlock();
 969                 return -ENXIO;
 970         }
 971         spin_lock_irqsave(&pg->lock, flags);
 972         if (optimize)
 973                 pg->flags |= ALUA_OPTIMIZE_STPG;
 974         else
 975                 pg->flags &= ~ALUA_OPTIMIZE_STPG;
 976         spin_unlock_irqrestore(&pg->lock, flags);
 977         rcu_read_unlock();
 978
 979         return result;
 980 }
 981
 982 /*
 983  * alua_activate - activate a path
 984  * @sdev: device on the path to be activated
 985  *
 986  * We're currently switching the port group to be activated only and
 987  * let the array figure out the rest.
 988  * There may be other arrays which require us to switch all port groups
 989  * based on a certain policy. But until we actually encounter them it
 990  * should be okay.
 991  */
 992 static int alua_activate(struct scsi_device *sdev,
 993                         activate_complete fn, void *data)
 994 {
 995         struct alua_dh_data *h = sdev->handler_data;
 996         int err = SCSI_DH_OK;
 997         struct alua_queue_data *qdata;
 998         struct alua_port_group *pg;
 999
1000         qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
1001         if (!qdata) {
1002                 err = SCSI_DH_RES_TEMP_UNAVAIL;
1003                 goto out;
1004         }
1005         qdata->callback_fn = fn;
1006         qdata->callback_data = data;
1007
1008         mutex_lock(&h->init_mutex);
1009         rcu_read_lock();
1010         pg = rcu_dereference(h->pg);
1011         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1012                 rcu_read_unlock();
1013                 kfree(qdata);
1014                 err = h->init_error;
1015                 mutex_unlock(&h->init_mutex);
1016                 goto out;
1017         }
1018         rcu_read_unlock();
1019         mutex_unlock(&h->init_mutex);
1020
1021         if (alua_rtpg_queue(pg, sdev, qdata, true))
1022                 fn = NULL;
1023         else
1024                 err = SCSI_DH_DEV_OFFLINED;
1025         kref_put(&pg->kref, release_port_group);
1026 out:
1027         if (fn)
1028                 fn(data, err);
1029         return 0;
1030 }
1031
1032 /*
1033  * alua_check - check path status
1034  * @sdev: device on the path to be checked
1035  *
1036  * Check the device status
1037  */
1038 static void alua_check(struct scsi_device *sdev, bool force)
1039 {
1040         struct alua_dh_data *h = sdev->handler_data;
1041         struct alua_port_group *pg;
1042
1043         rcu_read_lock();
1044         pg = rcu_dereference(h->pg);
1045         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1046                 rcu_read_unlock();
1047                 return;
1048         }
1049         rcu_read_unlock();
1050
1051         alua_rtpg_queue(pg, sdev, NULL, force);
1052         kref_put(&pg->kref, release_port_group);
1053 }
1054
1055 /*
1056  * alua_prep_fn - request callback
1057  *
1058  * Fail I/O to all paths not in state
1059  * active/optimized or active/non-optimized.
1060  */
1061 static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
1062 {
1063         struct alua_dh_data *h = sdev->handler_data;
1064         struct alua_port_group *pg;
1065         unsigned char state = SCSI_ACCESS_STATE_OPTIMAL;
1066         int ret = BLKPREP_OK;
1067
1068         rcu_read_lock();
1069         pg = rcu_dereference(h->pg);
1070         if (pg)
1071                 state = pg->state;
1072         rcu_read_unlock();
1073         if (state == SCSI_ACCESS_STATE_TRANSITIONING)
1074                 ret = BLKPREP_DEFER;
1075         else if (state != SCSI_ACCESS_STATE_OPTIMAL &&
1076                  state != SCSI_ACCESS_STATE_ACTIVE &&
1077                  state != SCSI_ACCESS_STATE_LBA) {
1078                 ret = BLKPREP_KILL;
1079                 req->rq_flags |= RQF_QUIET;
1080         }
1081         return ret;
1082
1083 }
1084
1085 static void alua_rescan(struct scsi_device *sdev)
1086 {
1087         struct alua_dh_data *h = sdev->handler_data;
1088
1089         alua_initialize(sdev, h);
1090 }
1091
1092 /*
1093  * alua_bus_attach - Attach device handler
1094  * @sdev: device to be attached to
1095  */
1096 static int alua_bus_attach(struct scsi_device *sdev)
1097 {
1098         struct alua_dh_data *h;
1099         int err, ret = -EINVAL;
1100
1101         h = kzalloc(sizeof(*h) , GFP_KERNEL);
1102         if (!h)
1103                 return -ENOMEM;
1104         spin_lock_init(&h->pg_lock);
1105         rcu_assign_pointer(h->pg, NULL);
1106         h->init_error = SCSI_DH_OK;
1107         h->sdev = sdev;
1108         INIT_LIST_HEAD(&h->node);
1109
1110         mutex_init(&h->init_mutex);
1111         err = alua_initialize(sdev, h);
1112         if (err == SCSI_DH_NOMEM)
1113                 ret = -ENOMEM;
1114         if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
1115                 goto failed;
1116
1117         sdev->handler_data = h;
1118         return 0;
1119 failed:
1120         kfree(h);
1121         return ret;
1122 }
1123
1124 /*
1125  * alua_bus_detach - Detach device handler
1126  * @sdev: device to be detached from
1127  */
1128 static void alua_bus_detach(struct scsi_device *sdev)
1129 {
1130         struct alua_dh_data *h = sdev->handler_data;
1131         struct alua_port_group *pg;
1132
1133         spin_lock(&h->pg_lock);
1134         pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
1135         rcu_assign_pointer(h->pg, NULL);
1136         h->sdev = NULL;
1137         spin_unlock(&h->pg_lock);
1138         if (pg) {
1139                 spin_lock_irq(&pg->lock);
1140                 list_del_rcu(&h->node);
1141                 spin_unlock_irq(&pg->lock);
1142                 kref_put(&pg->kref, release_port_group);
1143         }
1144         sdev->handler_data = NULL;
1145         kfree(h);
1146 }
1147
1148 static struct scsi_device_handler alua_dh = {
1149         .name = ALUA_DH_NAME,
1150         .module = THIS_MODULE,
1151         .attach = alua_bus_attach,
1152         .detach = alua_bus_detach,
1153         .prep_fn = alua_prep_fn,
1154         .check_sense = alua_check_sense,
1155         .activate = alua_activate,
1156         .rescan = alua_rescan,
1157         .set_params = alua_set_params,
1158 };
1159
1160 static int __init alua_init(void)
1161 {
1162         int r;
1163
1164         kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM, 0);
1165         if (!kaluad_wq) {
1166                 /* Temporary failure, bypass */
1167                 return SCSI_DH_DEV_TEMP_BUSY;
1168         }
1169         kaluad_sync_wq = create_workqueue("kaluad_sync");
1170         if (!kaluad_sync_wq) {
1171                 destroy_workqueue(kaluad_wq);
1172                 return SCSI_DH_DEV_TEMP_BUSY;
1173         }
1174         r = scsi_register_device_handler(&alua_dh);
1175         if (r != 0) {
1176                 printk(KERN_ERR "%s: Failed to register scsi device handler",
1177                         ALUA_DH_NAME);
1178                 destroy_workqueue(kaluad_sync_wq);
1179                 destroy_workqueue(kaluad_wq);
1180         }
1181         return r;
1182 }
1183
1184 static void __exit alua_exit(void)
1185 {
1186         scsi_unregister_device_handler(&alua_dh);
1187         destroy_workqueue(kaluad_sync_wq);
1188         destroy_workqueue(kaluad_wq);
1189 }
1190
1191 module_init(alua_init);
1192 module_exit(alua_exit);
1193
1194 MODULE_DESCRIPTION("DM Multipath ALUA support");
1195 MODULE_AUTHOR("Hannes Reinecke <hare@suse.de>");
1196 MODULE_LICENSE("GPL");
1197 MODULE_VERSION(ALUA_DH_VER);