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 #define ALUA_RTPG_RETRY_DELAY           2
  57
  58 /* device handler flags */
  59 #define ALUA_OPTIMIZE_STPG              0x01
  60 #define ALUA_RTPG_EXT_HDR_UNSUPP        0x02
  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
  74 struct alua_port_group {
  75         struct kref             kref;
  76         struct rcu_head         rcu;
  77         struct list_head        node;
  78         struct list_head        dh_list;
  79         unsigned char           device_id_str[256];
  80         int                     device_id_len;
  81         int                     group_id;
  82         int                     tpgs;
  83         int                     state;
  84         int                     pref;
  85         unsigned                flags; /* used for optimizing STPG */
  86         unsigned char           transition_tmo;
  87         unsigned long           expiry;
  88         unsigned long           interval;
  89         struct delayed_work     rtpg_work;
  90         spinlock_t              lock;
  91         struct list_head        rtpg_list;
  92         struct scsi_device      *rtpg_sdev;
  93 };
  94
  95 struct alua_dh_data {
  96         struct list_head        node;
  97         struct alua_port_group __rcu *pg;
  98         int                     group_id;
  99         spinlock_t              pg_lock;
 100         struct scsi_device      *sdev;
 101         int                     init_error;
 102         struct mutex            init_mutex;
 103 };
 104
 105 struct alua_queue_data {
 106         struct list_head        entry;
 107         activate_complete       callback_fn;
 108         void                    *callback_data;
 109 };
 110
 111 #define ALUA_POLICY_SWITCH_CURRENT      0
 112 #define ALUA_POLICY_SWITCH_ALL          1
 113
 114 static void alua_rtpg_work(struct work_struct *work);
 115 static bool alua_rtpg_queue(struct alua_port_group *pg,
 116                             struct scsi_device *sdev,
 117                             struct alua_queue_data *qdata, bool force);
 118 static void alua_check(struct scsi_device *sdev, bool force);
 119
 120 static void release_port_group(struct kref *kref)
 121 {
 122         struct alua_port_group *pg;
 123
 124         pg = container_of(kref, struct alua_port_group, kref);
 125         if (pg->rtpg_sdev)
 126                 flush_delayed_work(&pg->rtpg_work);
 127         spin_lock(&port_group_lock);
 128         list_del(&pg->node);
 129         spin_unlock(&port_group_lock);
 130         kfree_rcu(pg, rcu);
 131 }
 132
 133 /*
 134  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
 135  * @sdev: sdev the command should be sent to
 136  */
 137 static int submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
 138                        int bufflen, struct scsi_sense_hdr *sshdr, int flags)
 139 {
 140         u8 cdb[COMMAND_SIZE(MAINTENANCE_IN)];
 141         int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 142                 REQ_FAILFAST_DRIVER;
 143
 144         /* Prepare the command. */
 145         memset(cdb, 0x0, COMMAND_SIZE(MAINTENANCE_IN));
 146         cdb[0] = MAINTENANCE_IN;
 147         if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
 148                 cdb[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
 149         else
 150                 cdb[1] = MI_REPORT_TARGET_PGS;
 151         put_unaligned_be32(bufflen, &cdb[6]);
 152
 153         return scsi_execute(sdev, cdb, DMA_FROM_DEVICE, buff, bufflen, NULL,
 154                         sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
 155                         ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
 156 }
 157
 158 /*
 159  * submit_stpg - Issue a SET TARGET PORT GROUP command
 160  *
 161  * Currently we're only setting the current target port group state
 162  * to 'active/optimized' and let the array firmware figure out
 163  * the states of the remaining groups.
 164  */
 165 static int submit_stpg(struct scsi_device *sdev, int group_id,
 166                        struct scsi_sense_hdr *sshdr)
 167 {
 168         u8 cdb[COMMAND_SIZE(MAINTENANCE_OUT)];
 169         unsigned char stpg_data[8];
 170         int stpg_len = 8;
 171         int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 172                 REQ_FAILFAST_DRIVER;
 173
 174         /* Prepare the data buffer */
 175         memset(stpg_data, 0, stpg_len);
 176         stpg_data[4] = SCSI_ACCESS_STATE_OPTIMAL;
 177         put_unaligned_be16(group_id, &stpg_data[6]);
 178
 179         /* Prepare the command. */
 180         memset(cdb, 0x0, COMMAND_SIZE(MAINTENANCE_OUT));
 181         cdb[0] = MAINTENANCE_OUT;
 182         cdb[1] = MO_SET_TARGET_PGS;
 183         put_unaligned_be32(stpg_len, &cdb[6]);
 184
 185         return scsi_execute(sdev, cdb, DMA_TO_DEVICE, stpg_data, stpg_len, NULL,
 186                         sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
 187                         ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
 188 }
 189
 190 static struct alua_port_group *alua_find_get_pg(char *id_str, size_t id_size,
 191                                                 int group_id)
 192 {
 193         struct alua_port_group *pg;
 194
 195         if (!id_str || !id_size || !strlen(id_str))
 196                 return NULL;
 197
 198         list_for_each_entry(pg, &port_group_list, node) {
 199                 if (pg->group_id != group_id)
 200                         continue;
 201                 if (!pg->device_id_len || pg->device_id_len != id_size)
 202                         continue;
 203                 if (strncmp(pg->device_id_str, id_str, id_size))
 204                         continue;
 205                 if (!kref_get_unless_zero(&pg->kref))
 206                         continue;
 207                 return pg;
 208         }
 209
 210         return NULL;
 211 }
 212
 213 /*
 214  * alua_alloc_pg - Allocate a new port_group structure
 215  * @sdev: scsi device
 216  * @h: alua device_handler data
 217  * @group_id: port group id
 218  *
 219  * Allocate a new port_group structure for a given
 220  * device.
 221  */
 222 static struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
 223                                              int group_id, int tpgs)
 224 {
 225         struct alua_port_group *pg, *tmp_pg;
 226
 227         pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL);
 228         if (!pg)
 229                 return ERR_PTR(-ENOMEM);
 230
 231         pg->device_id_len = scsi_vpd_lun_id(sdev, pg->device_id_str,
 232                                             sizeof(pg->device_id_str));
 233         if (pg->device_id_len <= 0) {
 234                 /*
 235                  * TPGS supported but no device identification found.
 236                  * Generate private device identification.
 237                  */
 238                 sdev_printk(KERN_INFO, sdev,
 239                             "%s: No device descriptors found\n",
 240                             ALUA_DH_NAME);
 241                 pg->device_id_str[0] = '\0';
 242                 pg->device_id_len = 0;
 243         }
 244         pg->group_id = group_id;
 245         pg->tpgs = tpgs;
 246         pg->state = SCSI_ACCESS_STATE_OPTIMAL;
 247         if (optimize_stpg)
 248                 pg->flags |= ALUA_OPTIMIZE_STPG;
 249         kref_init(&pg->kref);
 250         INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
 251         INIT_LIST_HEAD(&pg->rtpg_list);
 252         INIT_LIST_HEAD(&pg->node);
 253         INIT_LIST_HEAD(&pg->dh_list);
 254         spin_lock_init(&pg->lock);
 255
 256         spin_lock(&port_group_lock);
 257         tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 258                                   group_id);
 259         if (tmp_pg) {
 260                 spin_unlock(&port_group_lock);
 261                 kfree(pg);
 262                 return tmp_pg;
 263         }
 264
 265         list_add(&pg->node, &port_group_list);
 266         spin_unlock(&port_group_lock);
 267
 268         return pg;
 269 }
 270
 271 /*
 272  * alua_check_tpgs - Evaluate TPGS setting
 273  * @sdev: device to be checked
 274  *
 275  * Examine the TPGS setting of the sdev to find out if ALUA
 276  * is supported.
 277  */
 278 static int alua_check_tpgs(struct scsi_device *sdev)
 279 {
 280         int tpgs = TPGS_MODE_NONE;
 281
 282         /*
 283          * ALUA support for non-disk devices is fraught with
 284          * difficulties, so disable it for now.
 285          */
 286         if (sdev->type != TYPE_DISK) {
 287                 sdev_printk(KERN_INFO, sdev,
 288                             "%s: disable for non-disk devices\n",
 289                             ALUA_DH_NAME);
 290                 return tpgs;
 291         }
 292
 293         tpgs = scsi_device_tpgs(sdev);
 294         switch (tpgs) {
 295         case TPGS_MODE_EXPLICIT|TPGS_MODE_IMPLICIT:
 296                 sdev_printk(KERN_INFO, sdev,
 297                             "%s: supports implicit and explicit TPGS\n",
 298                             ALUA_DH_NAME);
 299                 break;
 300         case TPGS_MODE_EXPLICIT:
 301                 sdev_printk(KERN_INFO, sdev, "%s: supports explicit TPGS\n",
 302                             ALUA_DH_NAME);
 303                 break;
 304         case TPGS_MODE_IMPLICIT:
 305                 sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n",
 306                             ALUA_DH_NAME);
 307                 break;
 308         case TPGS_MODE_NONE:
 309                 sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
 310                             ALUA_DH_NAME);
 311                 break;
 312         default:
 313                 sdev_printk(KERN_INFO, sdev,
 314                             "%s: unsupported TPGS setting %d\n",
 315                             ALUA_DH_NAME, tpgs);
 316                 tpgs = TPGS_MODE_NONE;
 317                 break;
 318         }
 319
 320         return tpgs;
 321 }
 322
 323 /*
 324  * alua_check_vpd - Evaluate INQUIRY vpd page 0x83
 325  * @sdev: device to be checked
 326  *
 327  * Extract the relative target port and the target port group
 328  * descriptor from the list of identificators.
 329  */
 330 static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 331                           int tpgs)
 332 {
 333         int rel_port = -1, group_id;
 334         struct alua_port_group *pg, *old_pg = NULL;
 335         bool pg_updated = false;
 336         unsigned long flags;
 337
 338         group_id = scsi_vpd_tpg_id(sdev, &rel_port);
 339         if (group_id < 0) {
 340                 /*
 341                  * Internal error; TPGS supported but required
 342                  * VPD identification descriptors not present.
 343                  * Disable ALUA support
 344                  */
 345                 sdev_printk(KERN_INFO, sdev,
 346                             "%s: No target port descriptors found\n",
 347                             ALUA_DH_NAME);
 348                 return SCSI_DH_DEV_UNSUPP;
 349         }
 350
 351         pg = alua_alloc_pg(sdev, group_id, tpgs);
 352         if (IS_ERR(pg)) {
 353                 if (PTR_ERR(pg) == -ENOMEM)
 354                         return SCSI_DH_NOMEM;
 355                 return SCSI_DH_DEV_UNSUPP;
 356         }
 357         if (pg->device_id_len)
 358                 sdev_printk(KERN_INFO, sdev,
 359                             "%s: device %s port group %x rel port %x\n",
 360                             ALUA_DH_NAME, pg->device_id_str,
 361                             group_id, rel_port);
 362         else
 363                 sdev_printk(KERN_INFO, sdev,
 364                             "%s: port group %x rel port %x\n",
 365                             ALUA_DH_NAME, group_id, rel_port);
 366
 367         /* Check for existing port group references */
 368         spin_lock(&h->pg_lock);
 369         old_pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
 370         if (old_pg != pg) {
 371                 /* port group has changed. Update to new port group */
 372                 if (h->pg) {
 373                         spin_lock_irqsave(&old_pg->lock, flags);
 374                         list_del_rcu(&h->node);
 375                         spin_unlock_irqrestore(&old_pg->lock, flags);
 376                 }
 377                 rcu_assign_pointer(h->pg, pg);
 378                 pg_updated = true;
 379         }
 380
 381         spin_lock_irqsave(&pg->lock, flags);
 382         if (pg_updated)
 383                 list_add_rcu(&h->node, &pg->dh_list);
 384         spin_unlock_irqrestore(&pg->lock, flags);
 385
 386         alua_rtpg_queue(rcu_dereference_protected(h->pg,
 387                                                   lockdep_is_held(&h->pg_lock)),
 388                         sdev, NULL, true);
 389         spin_unlock(&h->pg_lock);
 390
 391         if (old_pg)
 392                 kref_put(&old_pg->kref, release_port_group);
 393
 394         return SCSI_DH_OK;
 395 }
 396
 397 static char print_alua_state(unsigned char state)
 398 {
 399         switch (state) {
 400         case SCSI_ACCESS_STATE_OPTIMAL:
 401                 return 'A';
 402         case SCSI_ACCESS_STATE_ACTIVE:
 403                 return 'N';
 404         case SCSI_ACCESS_STATE_STANDBY:
 405                 return 'S';
 406         case SCSI_ACCESS_STATE_UNAVAILABLE:
 407                 return 'U';
 408         case SCSI_ACCESS_STATE_LBA:
 409                 return 'L';
 410         case SCSI_ACCESS_STATE_OFFLINE:
 411                 return 'O';
 412         case SCSI_ACCESS_STATE_TRANSITIONING:
 413                 return 'T';
 414         default:
 415                 return 'X';
 416         }
 417 }
 418
 419 static int alua_check_sense(struct scsi_device *sdev,
 420                             struct scsi_sense_hdr *sense_hdr)
 421 {
 422         switch (sense_hdr->sense_key) {
 423         case NOT_READY:
 424                 if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
 425                         /*
 426                          * LUN Not Accessible - ALUA state transition
 427                          */
 428                         alua_check(sdev, false);
 429                         return NEEDS_RETRY;
 430                 }
 431                 break;
 432         case UNIT_ATTENTION:
 433                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
 434                         /*
 435                          * Power On, Reset, or Bus Device Reset.
 436                          * Might have obscured a state transition,
 437                          * so schedule a recheck.
 438                          */
 439                         alua_check(sdev, true);
 440                         return ADD_TO_MLQUEUE;
 441                 }
 442                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
 443                         /*
 444                          * Device internal reset
 445                          */
 446                         return ADD_TO_MLQUEUE;
 447                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
 448                         /*
 449                          * Mode Parameters Changed
 450                          */
 451                         return ADD_TO_MLQUEUE;
 452                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
 453                         /*
 454                          * ALUA state changed
 455                          */
 456                         alua_check(sdev, true);
 457                         return ADD_TO_MLQUEUE;
 458                 }
 459                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
 460                         /*
 461                          * Implicit ALUA state transition failed
 462                          */
 463                         alua_check(sdev, true);
 464                         return ADD_TO_MLQUEUE;
 465                 }
 466                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
 467                         /*
 468                          * Inquiry data has changed
 469                          */
 470                         return ADD_TO_MLQUEUE;
 471                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x0e)
 472                         /*
 473                          * REPORTED_LUNS_DATA_HAS_CHANGED is reported
 474                          * when switching controllers on targets like
 475                          * Intel Multi-Flex. We can just retry.
 476                          */
 477                         return ADD_TO_MLQUEUE;
 478                 break;
 479         }
 480
 481         return SCSI_RETURN_NOT_HANDLED;
 482 }
 483
 484 /*
 485  * alua_tur - Send a TEST UNIT READY
 486  * @sdev: device to which the TEST UNIT READY command should be send
 487  *
 488  * Send a TEST UNIT READY to @sdev to figure out the device state
 489  * Returns SCSI_DH_RETRY if the sense code is NOT READY/ALUA TRANSITIONING,
 490  * SCSI_DH_OK if no error occurred, and SCSI_DH_IO otherwise.
 491  */
 492 static int alua_tur(struct scsi_device *sdev)
 493 {
 494         struct scsi_sense_hdr sense_hdr;
 495         int retval;
 496
 497         retval = scsi_test_unit_ready(sdev, ALUA_FAILOVER_TIMEOUT * HZ,
 498                                       ALUA_FAILOVER_RETRIES, &sense_hdr);
 499         if (sense_hdr.sense_key == NOT_READY &&
 500             sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
 501                 return SCSI_DH_RETRY;
 502         else if (retval)
 503                 return SCSI_DH_IO;
 504         else
 505                 return SCSI_DH_OK;
 506 }
 507
 508 /*
 509  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
 510  * @sdev: the device to be evaluated.
 511  *
 512  * Evaluate the Target Port Group State.
 513  * Returns SCSI_DH_DEV_OFFLINED if the path is
 514  * found to be unusable.
 515  */
 516 static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 517 {
 518         struct scsi_sense_hdr sense_hdr;
 519         struct alua_port_group *tmp_pg;
 520         int len, k, off, valid_states = 0, bufflen = ALUA_RTPG_SIZE;
 521         unsigned char *desc, *buff;
 522         unsigned err, retval;
 523         unsigned int tpg_desc_tbl_off;
 524         unsigned char orig_transition_tmo;
 525         unsigned long flags;
 526         bool transitioning_sense = false;
 527
 528         if (!pg->expiry) {
 529                 unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
 530
 531                 if (pg->transition_tmo)
 532                         transition_tmo = pg->transition_tmo * HZ;
 533
 534                 pg->expiry = round_jiffies_up(jiffies + transition_tmo);
 535         }
 536
 537         buff = kzalloc(bufflen, GFP_KERNEL);
 538         if (!buff)
 539                 return SCSI_DH_DEV_TEMP_BUSY;
 540
 541  retry:
 542         err = 0;
 543         retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
 544
 545         if (retval) {
 546                 if (!scsi_sense_valid(&sense_hdr)) {
 547                         sdev_printk(KERN_INFO, sdev,
 548                                     "%s: rtpg failed, result %d\n",
 549                                     ALUA_DH_NAME, retval);
 550                         kfree(buff);
 551                         if (driver_byte(retval) == DRIVER_ERROR)
 552                                 return SCSI_DH_DEV_TEMP_BUSY;
 553                         return SCSI_DH_IO;
 554                 }
 555
 556                 /*
 557                  * submit_rtpg() has failed on existing arrays
 558                  * when requesting extended header info, and
 559                  * the array doesn't support extended headers,
 560                  * even though it shouldn't according to T10.
 561                  * The retry without rtpg_ext_hdr_req set
 562                  * handles this.
 563                  * Note:  some arrays return a sense key of ILLEGAL_REQUEST
 564                  * with ASC 00h if they don't support the extended header.
 565                  */
 566                 if (!(pg->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
 567                     sense_hdr.sense_key == ILLEGAL_REQUEST) {
 568                         pg->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
 569                         goto retry;
 570                 }
 571                 /*
 572                  * If the array returns with 'ALUA state transition'
 573                  * sense code here it cannot return RTPG data during
 574                  * transition. So set the state to 'transitioning' directly.
 575                  */
 576                 if (sense_hdr.sense_key == NOT_READY &&
 577                     sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a) {
 578                         transitioning_sense = true;
 579                         goto skip_rtpg;
 580                 }
 581                 /*
 582                  * Retry on any other UNIT ATTENTION occurred.
 583                  */
 584                 if (sense_hdr.sense_key == UNIT_ATTENTION)
 585                         err = SCSI_DH_RETRY;
 586                 if (err == SCSI_DH_RETRY &&
 587                     pg->expiry != 0 && time_before(jiffies, pg->expiry)) {
 588                         sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
 589                                     ALUA_DH_NAME);
 590                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 591                         kfree(buff);
 592                         return err;
 593                 }
 594                 sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
 595                             ALUA_DH_NAME);
 596                 scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 597                 kfree(buff);
 598                 pg->expiry = 0;
 599                 return SCSI_DH_IO;
 600         }
 601
 602         len = get_unaligned_be32(&buff[0]) + 4;
 603
 604         if (len > bufflen) {
 605                 /* Resubmit with the correct length */
 606                 kfree(buff);
 607                 bufflen = len;
 608                 buff = kmalloc(bufflen, GFP_KERNEL);
 609                 if (!buff) {
 610                         sdev_printk(KERN_WARNING, sdev,
 611                                     "%s: kmalloc buffer failed\n",__func__);
 612                         /* Temporary failure, bypass */
 613                         pg->expiry = 0;
 614                         return SCSI_DH_DEV_TEMP_BUSY;
 615                 }
 616                 goto retry;
 617         }
 618
 619         orig_transition_tmo = pg->transition_tmo;
 620         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0)
 621                 pg->transition_tmo = buff[5];
 622         else
 623                 pg->transition_tmo = ALUA_FAILOVER_TIMEOUT;
 624
 625         if (orig_transition_tmo != pg->transition_tmo) {
 626                 sdev_printk(KERN_INFO, sdev,
 627                             "%s: transition timeout set to %d seconds\n",
 628                             ALUA_DH_NAME, pg->transition_tmo);
 629                 pg->expiry = jiffies + pg->transition_tmo * HZ;
 630         }
 631
 632         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
 633                 tpg_desc_tbl_off = 8;
 634         else
 635                 tpg_desc_tbl_off = 4;
 636
 637         for (k = tpg_desc_tbl_off, desc = buff + tpg_desc_tbl_off;
 638              k < len;
 639              k += off, desc += off) {
 640                 u16 group_id = get_unaligned_be16(&desc[2]);
 641
 642                 spin_lock_irqsave(&port_group_lock, flags);
 643                 tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 644                                           group_id);
 645                 spin_unlock_irqrestore(&port_group_lock, flags);
 646                 if (tmp_pg) {
 647                         if (spin_trylock_irqsave(&tmp_pg->lock, flags)) {
 648                                 if ((tmp_pg == pg) ||
 649                                     !(tmp_pg->flags & ALUA_PG_RUNNING)) {
 650                                         struct alua_dh_data *h;
 651
 652                                         tmp_pg->state = desc[0] & 0x0f;
 653                                         tmp_pg->pref = desc[0] >> 7;
 654                                         rcu_read_lock();
 655                                         list_for_each_entry_rcu(h,
 656                                                 &tmp_pg->dh_list, node) {
 657                                                 if (!h->sdev)
 658                                                         continue;
 659                                                 h->sdev->access_state = desc[0];
 660                                         }
 661                                         rcu_read_unlock();
 662                                 }
 663                                 if (tmp_pg == pg)
 664                                         valid_states = desc[1];
 665                                 spin_unlock_irqrestore(&tmp_pg->lock, flags);
 666                         }
 667                         kref_put(&tmp_pg->kref, release_port_group);
 668                 }
 669                 off = 8 + (desc[7] * 4);
 670         }
 671
 672  skip_rtpg:
 673         spin_lock_irqsave(&pg->lock, flags);
 674         if (transitioning_sense)
 675                 pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
 676
 677         sdev_printk(KERN_INFO, sdev,
 678                     "%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
 679                     ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state),
 680                     pg->pref ? "preferred" : "non-preferred",
 681                     valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
 682                     valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
 683                     valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
 684                     valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
 685                     valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
 686                     valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
 687                     valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
 688
 689         switch (pg->state) {
 690         case SCSI_ACCESS_STATE_TRANSITIONING:
 691                 if (time_before(jiffies, pg->expiry)) {
 692                         /* State transition, retry */
 693                         pg->interval = ALUA_RTPG_RETRY_DELAY;
 694                         err = SCSI_DH_RETRY;
 695                 } else {
 696                         struct alua_dh_data *h;
 697
 698                         /* Transitioning time exceeded, set port to standby */
 699                         err = SCSI_DH_IO;
 700                         pg->state = SCSI_ACCESS_STATE_STANDBY;
 701                         pg->expiry = 0;
 702                         rcu_read_lock();
 703                         list_for_each_entry_rcu(h, &pg->dh_list, node) {
 704                                 if (!h->sdev)
 705                                         continue;
 706                                 h->sdev->access_state =
 707                                         (pg->state & SCSI_ACCESS_STATE_MASK);
 708                                 if (pg->pref)
 709                                         h->sdev->access_state |=
 710                                                 SCSI_ACCESS_STATE_PREFERRED;
 711                         }
 712                         rcu_read_unlock();
 713                 }
 714                 break;
 715         case SCSI_ACCESS_STATE_OFFLINE:
 716                 /* Path unusable */
 717                 err = SCSI_DH_DEV_OFFLINED;
 718                 pg->expiry = 0;
 719                 break;
 720         default:
 721                 /* Useable path if active */
 722                 err = SCSI_DH_OK;
 723                 pg->expiry = 0;
 724                 break;
 725         }
 726         spin_unlock_irqrestore(&pg->lock, flags);
 727         kfree(buff);
 728         return err;
 729 }
 730
 731 /*
 732  * alua_stpg - Issue a SET TARGET PORT GROUP command
 733  *
 734  * Issue a SET TARGET PORT GROUP command and evaluate the
 735  * response. Returns SCSI_DH_RETRY per default to trigger
 736  * a re-evaluation of the target group state or SCSI_DH_OK
 737  * if no further action needs to be taken.
 738  */
 739 static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg)
 740 {
 741         int retval;
 742         struct scsi_sense_hdr sense_hdr;
 743
 744         if (!(pg->tpgs & TPGS_MODE_EXPLICIT)) {
 745                 /* Only implicit ALUA supported, retry */
 746                 return SCSI_DH_RETRY;
 747         }
 748         switch (pg->state) {
 749         case SCSI_ACCESS_STATE_OPTIMAL:
 750                 return SCSI_DH_OK;
 751         case SCSI_ACCESS_STATE_ACTIVE:
 752                 if ((pg->flags & ALUA_OPTIMIZE_STPG) &&
 753                     !pg->pref &&
 754                     (pg->tpgs & TPGS_MODE_IMPLICIT))
 755                         return SCSI_DH_OK;
 756                 break;
 757         case SCSI_ACCESS_STATE_STANDBY:
 758         case SCSI_ACCESS_STATE_UNAVAILABLE:
 759                 break;
 760         case SCSI_ACCESS_STATE_OFFLINE:
 761                 return SCSI_DH_IO;
 762         case SCSI_ACCESS_STATE_TRANSITIONING:
 763                 break;
 764         default:
 765                 sdev_printk(KERN_INFO, sdev,
 766                             "%s: stpg failed, unhandled TPGS state %d",
 767                             ALUA_DH_NAME, pg->state);
 768                 return SCSI_DH_NOSYS;
 769         }
 770         retval = submit_stpg(sdev, pg->group_id, &sense_hdr);
 771
 772         if (retval) {
 773                 if (!scsi_sense_valid(&sense_hdr)) {
 774                         sdev_printk(KERN_INFO, sdev,
 775                                     "%s: stpg failed, result %d",
 776                                     ALUA_DH_NAME, retval);
 777                         if (driver_byte(retval) == DRIVER_ERROR)
 778                                 return SCSI_DH_DEV_TEMP_BUSY;
 779                 } else {
 780                         sdev_printk(KERN_INFO, sdev, "%s: stpg failed\n",
 781                                     ALUA_DH_NAME);
 782                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 783                 }
 784         }
 785         /* Retry RTPG */
 786         return SCSI_DH_RETRY;
 787 }
 788
 789 static void alua_rtpg_work(struct work_struct *work)
 790 {
 791         struct alua_port_group *pg =
 792                 container_of(work, struct alua_port_group, rtpg_work.work);
 793         struct scsi_device *sdev;
 794         LIST_HEAD(qdata_list);
 795         int err = SCSI_DH_OK;
 796         struct alua_queue_data *qdata, *tmp;
 797         unsigned long flags;
 798
 799         spin_lock_irqsave(&pg->lock, flags);
 800         sdev = pg->rtpg_sdev;
 801         if (!sdev) {
 802                 WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
 803                 WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
 804                 spin_unlock_irqrestore(&pg->lock, flags);
 805                 kref_put(&pg->kref, release_port_group);
 806                 return;
 807         }
 808         pg->flags |= ALUA_PG_RUNNING;
 809         if (pg->flags & ALUA_PG_RUN_RTPG) {
 810                 int state = pg->state;
 811
 812                 pg->flags &= ~ALUA_PG_RUN_RTPG;
 813                 spin_unlock_irqrestore(&pg->lock, flags);
 814                 if (state == SCSI_ACCESS_STATE_TRANSITIONING) {
 815                         if (alua_tur(sdev) == SCSI_DH_RETRY) {
 816                                 spin_lock_irqsave(&pg->lock, flags);
 817                                 pg->flags &= ~ALUA_PG_RUNNING;
 818                                 pg->flags |= ALUA_PG_RUN_RTPG;
 819                                 if (!pg->interval)
 820                                         pg->interval = ALUA_RTPG_RETRY_DELAY;
 821                                 spin_unlock_irqrestore(&pg->lock, flags);
 822                                 queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 823                                                    pg->interval * HZ);
 824                                 return;
 825                         }
 826                         /* Send RTPG on failure or if TUR indicates SUCCESS */
 827                 }
 828                 err = alua_rtpg(sdev, pg);
 829                 spin_lock_irqsave(&pg->lock, flags);
 830                 if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 831                         pg->flags &= ~ALUA_PG_RUNNING;
 832                         if (!pg->interval && !(pg->flags & ALUA_PG_RUN_RTPG))
 833                                 pg->interval = ALUA_RTPG_RETRY_DELAY;
 834                         pg->flags |= ALUA_PG_RUN_RTPG;
 835                         spin_unlock_irqrestore(&pg->lock, flags);
 836                         queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 837                                            pg->interval * HZ);
 838                         return;
 839                 }
 840                 if (err != SCSI_DH_OK)
 841                         pg->flags &= ~ALUA_PG_RUN_STPG;
 842         }
 843         if (pg->flags & ALUA_PG_RUN_STPG) {
 844                 pg->flags &= ~ALUA_PG_RUN_STPG;
 845                 spin_unlock_irqrestore(&pg->lock, flags);
 846                 err = alua_stpg(sdev, pg);
 847                 spin_lock_irqsave(&pg->lock, flags);
 848                 if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 849                         pg->flags |= ALUA_PG_RUN_RTPG;
 850                         pg->interval = 0;
 851                         pg->flags &= ~ALUA_PG_RUNNING;
 852                         spin_unlock_irqrestore(&pg->lock, flags);
 853                         queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 854                                            pg->interval * HZ);
 855                         return;
 856                 }
 857         }
 858
 859         list_splice_init(&pg->rtpg_list, &qdata_list);
 860         pg->rtpg_sdev = NULL;
 861         spin_unlock_irqrestore(&pg->lock, flags);
 862
 863         list_for_each_entry_safe(qdata, tmp, &qdata_list, entry) {
 864                 list_del(&qdata->entry);
 865                 if (qdata->callback_fn)
 866                         qdata->callback_fn(qdata->callback_data, err);
 867                 kfree(qdata);
 868         }
 869         spin_lock_irqsave(&pg->lock, flags);
 870         pg->flags &= ~ALUA_PG_RUNNING;
 871         spin_unlock_irqrestore(&pg->lock, flags);
 872         scsi_device_put(sdev);
 873         kref_put(&pg->kref, release_port_group);
 874 }
 875
 876 /**
 877  * alua_rtpg_queue() - cause RTPG to be submitted asynchronously
 878  *
 879  * Returns true if and only if alua_rtpg_work() will be called asynchronously.
 880  * That function is responsible for calling @qdata->fn().
 881  */
 882 static bool alua_rtpg_queue(struct alua_port_group *pg,
 883                             struct scsi_device *sdev,
 884                             struct alua_queue_data *qdata, bool force)
 885 {
 886         int start_queue = 0;
 887         unsigned long flags;
 888         if (WARN_ON_ONCE(!pg) || scsi_device_get(sdev))
 889                 return false;
 890
 891         spin_lock_irqsave(&pg->lock, flags);
 892         if (qdata) {
 893                 list_add_tail(&qdata->entry, &pg->rtpg_list);
 894                 pg->flags |= ALUA_PG_RUN_STPG;
 895                 force = true;
 896         }
 897         if (pg->rtpg_sdev == NULL) {
 898                 pg->interval = 0;
 899                 pg->flags |= ALUA_PG_RUN_RTPG;
 900                 kref_get(&pg->kref);
 901                 pg->rtpg_sdev = sdev;
 902                 start_queue = 1;
 903         } else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {
 904                 pg->flags |= ALUA_PG_RUN_RTPG;
 905                 /* Do not queue if the worker is already running */
 906                 if (!(pg->flags & ALUA_PG_RUNNING)) {
 907                         kref_get(&pg->kref);
 908                         start_queue = 1;
 909                 }
 910         }
 911
 912         spin_unlock_irqrestore(&pg->lock, flags);
 913
 914         if (start_queue) {
 915                 if (queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 916                                 msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS)))
 917                         sdev = NULL;
 918                 else
 919                         kref_put(&pg->kref, release_port_group);
 920         }
 921         if (sdev)
 922                 scsi_device_put(sdev);
 923
 924         return true;
 925 }
 926
 927 /*
 928  * alua_initialize - Initialize ALUA state
 929  * @sdev: the device to be initialized
 930  *
 931  * For the prep_fn to work correctly we have
 932  * to initialize the ALUA state for the device.
 933  */
 934 static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 935 {
 936         int err = SCSI_DH_DEV_UNSUPP, tpgs;
 937
 938         mutex_lock(&h->init_mutex);
 939         tpgs = alua_check_tpgs(sdev);
 940         if (tpgs != TPGS_MODE_NONE)
 941                 err = alua_check_vpd(sdev, h, tpgs);
 942         h->init_error = err;
 943         mutex_unlock(&h->init_mutex);
 944         return err;
 945 }
 946 /*
 947  * alua_set_params - set/unset the optimize flag
 948  * @sdev: device on the path to be activated
 949  * params - parameters in the following format
 950  *      "no_of_params\0param1\0param2\0param3\0...\0"
 951  * For example, to set the flag pass the following parameters
 952  * from multipath.conf
 953  *     hardware_handler        "2 alua 1"
 954  */
 955 static int alua_set_params(struct scsi_device *sdev, const char *params)
 956 {
 957         struct alua_dh_data *h = sdev->handler_data;
 958         struct alua_port_group *pg = NULL;
 959         unsigned int optimize = 0, argc;
 960         const char *p = params;
 961         int result = SCSI_DH_OK;
 962         unsigned long flags;
 963
 964         if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
 965                 return -EINVAL;
 966
 967         while (*p++)
 968                 ;
 969         if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
 970                 return -EINVAL;
 971
 972         rcu_read_lock();
 973         pg = rcu_dereference(h->pg);
 974         if (!pg) {
 975                 rcu_read_unlock();
 976                 return -ENXIO;
 977         }
 978         spin_lock_irqsave(&pg->lock, flags);
 979         if (optimize)
 980                 pg->flags |= ALUA_OPTIMIZE_STPG;
 981         else
 982                 pg->flags &= ~ALUA_OPTIMIZE_STPG;
 983         spin_unlock_irqrestore(&pg->lock, flags);
 984         rcu_read_unlock();
 985
 986         return result;
 987 }
 988
 989 /*
 990  * alua_activate - activate a path
 991  * @sdev: device on the path to be activated
 992  *
 993  * We're currently switching the port group to be activated only and
 994  * let the array figure out the rest.
 995  * There may be other arrays which require us to switch all port groups
 996  * based on a certain policy. But until we actually encounter them it
 997  * should be okay.
 998  */
 999 static int alua_activate(struct scsi_device *sdev,
1000                         activate_complete fn, void *data)
1001 {
1002         struct alua_dh_data *h = sdev->handler_data;
1003         int err = SCSI_DH_OK;
1004         struct alua_queue_data *qdata;
1005         struct alua_port_group *pg;
1006
1007         qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
1008         if (!qdata) {
1009                 err = SCSI_DH_RES_TEMP_UNAVAIL;
1010                 goto out;
1011         }
1012         qdata->callback_fn = fn;
1013         qdata->callback_data = data;
1014
1015         mutex_lock(&h->init_mutex);
1016         rcu_read_lock();
1017         pg = rcu_dereference(h->pg);
1018         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1019                 rcu_read_unlock();
1020                 kfree(qdata);
1021                 err = h->init_error;
1022                 mutex_unlock(&h->init_mutex);
1023                 goto out;
1024         }
1025         rcu_read_unlock();
1026         mutex_unlock(&h->init_mutex);
1027
1028         if (alua_rtpg_queue(pg, sdev, qdata, true))
1029                 fn = NULL;
1030         else
1031                 err = SCSI_DH_DEV_OFFLINED;
1032         kref_put(&pg->kref, release_port_group);
1033 out:
1034         if (fn)
1035                 fn(data, err);
1036         return 0;
1037 }
1038
1039 /*
1040  * alua_check - check path status
1041  * @sdev: device on the path to be checked
1042  *
1043  * Check the device status
1044  */
1045 static void alua_check(struct scsi_device *sdev, bool force)
1046 {
1047         struct alua_dh_data *h = sdev->handler_data;
1048         struct alua_port_group *pg;
1049
1050         rcu_read_lock();
1051         pg = rcu_dereference(h->pg);
1052         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1053                 rcu_read_unlock();
1054                 return;
1055         }
1056         rcu_read_unlock();
1057
1058         alua_rtpg_queue(pg, sdev, NULL, force);
1059         kref_put(&pg->kref, release_port_group);
1060 }
1061
1062 /*
1063  * alua_prep_fn - request callback
1064  *
1065  * Fail I/O to all paths not in state
1066  * active/optimized or active/non-optimized.
1067  */
1068 static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
1069 {
1070         struct alua_dh_data *h = sdev->handler_data;
1071         struct alua_port_group *pg;
1072         unsigned char state = SCSI_ACCESS_STATE_OPTIMAL;
1073         int ret = BLKPREP_OK;
1074
1075         rcu_read_lock();
1076         pg = rcu_dereference(h->pg);
1077         if (pg)
1078                 state = pg->state;
1079         rcu_read_unlock();
1080         if (state == SCSI_ACCESS_STATE_TRANSITIONING)
1081                 ret = BLKPREP_DEFER;
1082         else if (state != SCSI_ACCESS_STATE_OPTIMAL &&
1083                  state != SCSI_ACCESS_STATE_ACTIVE &&
1084                  state != SCSI_ACCESS_STATE_LBA) {
1085                 ret = BLKPREP_KILL;
1086                 req->rq_flags |= RQF_QUIET;
1087         }
1088         return ret;
1089
1090 }
1091
1092 static void alua_rescan(struct scsi_device *sdev)
1093 {
1094         struct alua_dh_data *h = sdev->handler_data;
1095
1096         alua_initialize(sdev, h);
1097 }
1098
1099 /*
1100  * alua_bus_attach - Attach device handler
1101  * @sdev: device to be attached to
1102  */
1103 static int alua_bus_attach(struct scsi_device *sdev)
1104 {
1105         struct alua_dh_data *h;
1106         int err, ret = -EINVAL;
1107
1108         h = kzalloc(sizeof(*h) , GFP_KERNEL);
1109         if (!h)
1110                 return -ENOMEM;
1111         spin_lock_init(&h->pg_lock);
1112         rcu_assign_pointer(h->pg, NULL);
1113         h->init_error = SCSI_DH_OK;
1114         h->sdev = sdev;
1115         INIT_LIST_HEAD(&h->node);
1116
1117         mutex_init(&h->init_mutex);
1118         err = alua_initialize(sdev, h);
1119         if (err == SCSI_DH_NOMEM)
1120                 ret = -ENOMEM;
1121         if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
1122                 goto failed;
1123
1124         sdev->handler_data = h;
1125         return 0;
1126 failed:
1127         kfree(h);
1128         return ret;
1129 }
1130
1131 /*
1132  * alua_bus_detach - Detach device handler
1133  * @sdev: device to be detached from
1134  */
1135 static void alua_bus_detach(struct scsi_device *sdev)
1136 {
1137         struct alua_dh_data *h = sdev->handler_data;
1138         struct alua_port_group *pg;
1139
1140         spin_lock(&h->pg_lock);
1141         pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
1142         rcu_assign_pointer(h->pg, NULL);
1143         spin_unlock(&h->pg_lock);
1144         if (pg) {
1145                 spin_lock_irq(&pg->lock);
1146                 list_del_rcu(&h->node);
1147                 spin_unlock_irq(&pg->lock);
1148                 kref_put(&pg->kref, release_port_group);
1149         }
1150         sdev->handler_data = NULL;
1151         synchronize_rcu();
1152         kfree(h);
1153 }
1154
1155 static struct scsi_device_handler alua_dh = {
1156         .name = ALUA_DH_NAME,
1157         .module = THIS_MODULE,
1158         .attach = alua_bus_attach,
1159         .detach = alua_bus_detach,
1160         .prep_fn = alua_prep_fn,
1161         .check_sense = alua_check_sense,
1162         .activate = alua_activate,
1163         .rescan = alua_rescan,
1164         .set_params = alua_set_params,
1165 };
1166
1167 static int __init alua_init(void)
1168 {
1169         int r;
1170
1171         kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM, 0);
1172         if (!kaluad_wq)
1173                 return -ENOMEM;
1174
1175         r = scsi_register_device_handler(&alua_dh);
1176         if (r != 0) {
1177                 printk(KERN_ERR "%s: Failed to register scsi device handler",
1178                         ALUA_DH_NAME);
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_wq);
1188 }
1189
1190 module_init(alua_init);
1191 module_exit(alua_exit);
1192
1193 MODULE_DESCRIPTION("DM Multipath ALUA support");
1194 MODULE_AUTHOR("Hannes Reinecke <hare@suse.de>");
1195 MODULE_LICENSE("GPL");
1196 MODULE_VERSION(ALUA_DH_VER);