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