drivers/scsi/device_handler/scsi_dh_alua.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Generic SCSI-3 ALUA SCSI Device Handler
   4  *
   5  * Copyright (C) 2007-2010 Hannes Reinecke, SUSE Linux Products GmbH.
   6  * All rights reserved.
   7  */
   8 #include <linux/slab.h>
   9 #include <linux/delay.h>
  10 #include <linux/module.h>
  11 #include <asm/unaligned.h>
  12 #include <scsi/scsi.h>
  13 #include <scsi/scsi_proto.h>
  14 #include <scsi/scsi_dbg.h>
  15 #include <scsi/scsi_eh.h>
  16 #include <scsi/scsi_dh.h>
  17
  18 #define ALUA_DH_NAME "alua"
  19 #define ALUA_DH_VER "2.0"
  20
  21 #define TPGS_SUPPORT_NONE               0x00
  22 #define TPGS_SUPPORT_OPTIMIZED          0x01
  23 #define TPGS_SUPPORT_NONOPTIMIZED       0x02
  24 #define TPGS_SUPPORT_STANDBY            0x04
  25 #define TPGS_SUPPORT_UNAVAILABLE        0x08
  26 #define TPGS_SUPPORT_LBA_DEPENDENT      0x10
  27 #define TPGS_SUPPORT_OFFLINE            0x40
  28 #define TPGS_SUPPORT_TRANSITION         0x80
  29 #define TPGS_SUPPORT_ALL                0xdf
  30
  31 #define RTPG_FMT_MASK                   0x70
  32 #define RTPG_FMT_EXT_HDR                0x10
  33
  34 #define TPGS_MODE_UNINITIALIZED          -1
  35 #define TPGS_MODE_NONE                  0x0
  36 #define TPGS_MODE_IMPLICIT              0x1
  37 #define TPGS_MODE_EXPLICIT              0x2
  38
  39 #define ALUA_RTPG_SIZE                  128
  40 #define ALUA_FAILOVER_TIMEOUT           60
  41 #define ALUA_FAILOVER_RETRIES           5
  42 #define ALUA_RTPG_DELAY_MSECS           5
  43 #define ALUA_RTPG_RETRY_DELAY           2
  44
  45 /* device handler flags */
  46 #define ALUA_OPTIMIZE_STPG              0x01
  47 #define ALUA_RTPG_EXT_HDR_UNSUPP        0x02
  48 /* State machine flags */
  49 #define ALUA_PG_RUN_RTPG                0x10
  50 #define ALUA_PG_RUN_STPG                0x20
  51 #define ALUA_PG_RUNNING                 0x40
  52
  53 static uint optimize_stpg;
  54 module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
  55 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.");
  56
  57 static LIST_HEAD(port_group_list);
  58 static DEFINE_SPINLOCK(port_group_lock);
  59 static struct workqueue_struct *kaluad_wq;
  60
  61 struct alua_port_group {
  62         struct kref             kref;
  63         struct rcu_head         rcu;
  64         struct list_head        node;
  65         struct list_head        dh_list;
  66         unsigned char           device_id_str[256];
  67         int                     device_id_len;
  68         int                     group_id;
  69         int                     tpgs;
  70         int                     state;
  71         int                     pref;
  72         int                     valid_states;
  73         unsigned                flags; /* used for optimizing STPG */
  74         unsigned char           transition_tmo;
  75         unsigned long           expiry;
  76         unsigned long           interval;
  77         struct delayed_work     rtpg_work;
  78         spinlock_t              lock;
  79         struct list_head        rtpg_list;
  80         struct scsi_device      *rtpg_sdev;
  81 };
  82
  83 struct alua_dh_data {
  84         struct list_head        node;
  85         struct alua_port_group __rcu *pg;
  86         int                     group_id;
  87         spinlock_t              pg_lock;
  88         struct scsi_device      *sdev;
  89         int                     init_error;
  90         struct mutex            init_mutex;
  91 };
  92
  93 struct alua_queue_data {
  94         struct list_head        entry;
  95         activate_complete       callback_fn;
  96         void                    *callback_data;
  97 };
  98
  99 #define ALUA_POLICY_SWITCH_CURRENT      0
 100 #define ALUA_POLICY_SWITCH_ALL          1
 101
 102 static void alua_rtpg_work(struct work_struct *work);
 103 static bool alua_rtpg_queue(struct alua_port_group *pg,
 104                             struct scsi_device *sdev,
 105                             struct alua_queue_data *qdata, bool force);
 106 static void alua_check(struct scsi_device *sdev, bool force);
 107
 108 static void release_port_group(struct kref *kref)
 109 {
 110         struct alua_port_group *pg;
 111
 112         pg = container_of(kref, struct alua_port_group, kref);
 113         if (pg->rtpg_sdev)
 114                 flush_delayed_work(&pg->rtpg_work);
 115         spin_lock(&port_group_lock);
 116         list_del(&pg->node);
 117         spin_unlock(&port_group_lock);
 118         kfree_rcu(pg, rcu);
 119 }
 120
 121 /*
 122  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
 123  * @sdev: sdev the command should be sent to
 124  */
 125 static int submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
 126                        int bufflen, struct scsi_sense_hdr *sshdr, int flags)
 127 {
 128         u8 cdb[MAX_COMMAND_SIZE];
 129         int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 130                 REQ_FAILFAST_DRIVER;
 131
 132         /* Prepare the command. */
 133         memset(cdb, 0x0, MAX_COMMAND_SIZE);
 134         cdb[0] = MAINTENANCE_IN;
 135         if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
 136                 cdb[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
 137         else
 138                 cdb[1] = MI_REPORT_TARGET_PGS;
 139         put_unaligned_be32(bufflen, &cdb[6]);
 140
 141         return scsi_execute(sdev, cdb, DMA_FROM_DEVICE, buff, bufflen, NULL,
 142                         sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
 143                         ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
 144 }
 145
 146 /*
 147  * submit_stpg - Issue a SET TARGET PORT GROUP command
 148  *
 149  * Currently we're only setting the current target port group state
 150  * to 'active/optimized' and let the array firmware figure out
 151  * the states of the remaining groups.
 152  */
 153 static int submit_stpg(struct scsi_device *sdev, int group_id,
 154                        struct scsi_sense_hdr *sshdr)
 155 {
 156         u8 cdb[MAX_COMMAND_SIZE];
 157         unsigned char stpg_data[8];
 158         int stpg_len = 8;
 159         int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 160                 REQ_FAILFAST_DRIVER;
 161
 162         /* Prepare the data buffer */
 163         memset(stpg_data, 0, stpg_len);
 164         stpg_data[4] = SCSI_ACCESS_STATE_OPTIMAL;
 165         put_unaligned_be16(group_id, &stpg_data[6]);
 166
 167         /* Prepare the command. */
 168         memset(cdb, 0x0, MAX_COMMAND_SIZE);
 169         cdb[0] = MAINTENANCE_OUT;
 170         cdb[1] = MO_SET_TARGET_PGS;
 171         put_unaligned_be32(stpg_len, &cdb[6]);
 172
 173         return scsi_execute(sdev, cdb, DMA_TO_DEVICE, stpg_data, stpg_len, NULL,
 174                         sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
 175                         ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
 176 }
 177
 178 static struct alua_port_group *alua_find_get_pg(char *id_str, size_t id_size,
 179                                                 int group_id)
 180 {
 181         struct alua_port_group *pg;
 182
 183         if (!id_str || !id_size || !strlen(id_str))
 184                 return NULL;
 185
 186         list_for_each_entry(pg, &port_group_list, node) {
 187                 if (pg->group_id != group_id)
 188                         continue;
 189                 if (!pg->device_id_len || pg->device_id_len != id_size)
 190                         continue;
 191                 if (strncmp(pg->device_id_str, id_str, id_size))
 192                         continue;
 193                 if (!kref_get_unless_zero(&pg->kref))
 194                         continue;
 195                 return pg;
 196         }
 197
 198         return NULL;
 199 }
 200
 201 /*
 202  * alua_alloc_pg - Allocate a new port_group structure
 203  * @sdev: scsi device
 204  * @group_id: port group id
 205  * @tpgs: target port group settings
 206  *
 207  * Allocate a new port_group structure for a given
 208  * device.
 209  */
 210 static struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
 211                                              int group_id, int tpgs)
 212 {
 213         struct alua_port_group *pg, *tmp_pg;
 214
 215         pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL);
 216         if (!pg)
 217                 return ERR_PTR(-ENOMEM);
 218
 219         pg->device_id_len = scsi_vpd_lun_id(sdev, pg->device_id_str,
 220                                             sizeof(pg->device_id_str));
 221         if (pg->device_id_len <= 0) {
 222                 /*
 223                  * TPGS supported but no device identification found.
 224                  * Generate private device identification.
 225                  */
 226                 sdev_printk(KERN_INFO, sdev,
 227                             "%s: No device descriptors found\n",
 228                             ALUA_DH_NAME);
 229                 pg->device_id_str[0] = '\0';
 230                 pg->device_id_len = 0;
 231         }
 232         pg->group_id = group_id;
 233         pg->tpgs = tpgs;
 234         pg->state = SCSI_ACCESS_STATE_OPTIMAL;
 235         pg->valid_states = TPGS_SUPPORT_ALL;
 236         if (optimize_stpg)
 237                 pg->flags |= ALUA_OPTIMIZE_STPG;
 238         kref_init(&pg->kref);
 239         INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
 240         INIT_LIST_HEAD(&pg->rtpg_list);
 241         INIT_LIST_HEAD(&pg->node);
 242         INIT_LIST_HEAD(&pg->dh_list);
 243         spin_lock_init(&pg->lock);
 244
 245         spin_lock(&port_group_lock);
 246         tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 247                                   group_id);
 248         if (tmp_pg) {
 249                 spin_unlock(&port_group_lock);
 250                 kfree(pg);
 251                 return tmp_pg;
 252         }
 253
 254         list_add(&pg->node, &port_group_list);
 255         spin_unlock(&port_group_lock);
 256
 257         return pg;
 258 }
 259
 260 /*
 261  * alua_check_tpgs - Evaluate TPGS setting
 262  * @sdev: device to be checked
 263  *
 264  * Examine the TPGS setting of the sdev to find out if ALUA
 265  * is supported.
 266  */
 267 static int alua_check_tpgs(struct scsi_device *sdev)
 268 {
 269         int tpgs = TPGS_MODE_NONE;
 270
 271         /*
 272          * ALUA support for non-disk devices is fraught with
 273          * difficulties, so disable it for now.
 274          */
 275         if (sdev->type != TYPE_DISK) {
 276                 sdev_printk(KERN_INFO, sdev,
 277                             "%s: disable for non-disk devices\n",
 278                             ALUA_DH_NAME);
 279                 return tpgs;
 280         }
 281
 282         tpgs = scsi_device_tpgs(sdev);
 283         switch (tpgs) {
 284         case TPGS_MODE_EXPLICIT|TPGS_MODE_IMPLICIT:
 285                 sdev_printk(KERN_INFO, sdev,
 286                             "%s: supports implicit and explicit TPGS\n",
 287                             ALUA_DH_NAME);
 288                 break;
 289         case TPGS_MODE_EXPLICIT:
 290                 sdev_printk(KERN_INFO, sdev, "%s: supports explicit TPGS\n",
 291                             ALUA_DH_NAME);
 292                 break;
 293         case TPGS_MODE_IMPLICIT:
 294                 sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n",
 295                             ALUA_DH_NAME);
 296                 break;
 297         case TPGS_MODE_NONE:
 298                 sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
 299                             ALUA_DH_NAME);
 300                 break;
 301         default:
 302                 sdev_printk(KERN_INFO, sdev,
 303                             "%s: unsupported TPGS setting %d\n",
 304                             ALUA_DH_NAME, tpgs);
 305                 tpgs = TPGS_MODE_NONE;
 306                 break;
 307         }
 308
 309         return tpgs;
 310 }
 311
 312 /*
 313  * alua_check_vpd - Evaluate INQUIRY vpd page 0x83
 314  * @sdev: device to be checked
 315  *
 316  * Extract the relative target port and the target port group
 317  * descriptor from the list of identificators.
 318  */
 319 static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 320                           int tpgs)
 321 {
 322         int rel_port = -1, group_id;
 323         struct alua_port_group *pg, *old_pg = NULL;
 324         bool pg_updated = false;
 325         unsigned long flags;
 326
 327         group_id = scsi_vpd_tpg_id(sdev, &rel_port);
 328         if (group_id < 0) {
 329                 /*
 330                  * Internal error; TPGS supported but required
 331                  * VPD identification descriptors not present.
 332                  * Disable ALUA support
 333                  */
 334                 sdev_printk(KERN_INFO, sdev,
 335                             "%s: No target port descriptors found\n",
 336                             ALUA_DH_NAME);
 337                 return SCSI_DH_DEV_UNSUPP;
 338         }
 339
 340         pg = alua_alloc_pg(sdev, group_id, tpgs);
 341         if (IS_ERR(pg)) {
 342                 if (PTR_ERR(pg) == -ENOMEM)
 343                         return SCSI_DH_NOMEM;
 344                 return SCSI_DH_DEV_UNSUPP;
 345         }
 346         if (pg->device_id_len)
 347                 sdev_printk(KERN_INFO, sdev,
 348                             "%s: device %s port group %x rel port %x\n",
 349                             ALUA_DH_NAME, pg->device_id_str,
 350                             group_id, rel_port);
 351         else
 352                 sdev_printk(KERN_INFO, sdev,
 353                             "%s: port group %x rel port %x\n",
 354                             ALUA_DH_NAME, group_id, rel_port);
 355
 356         /* Check for existing port group references */
 357         spin_lock(&h->pg_lock);
 358         old_pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
 359         if (old_pg != pg) {
 360                 /* port group has changed. Update to new port group */
 361                 if (h->pg) {
 362                         spin_lock_irqsave(&old_pg->lock, flags);
 363                         list_del_rcu(&h->node);
 364                         spin_unlock_irqrestore(&old_pg->lock, flags);
 365                 }
 366                 rcu_assign_pointer(h->pg, pg);
 367                 pg_updated = true;
 368         }
 369
 370         spin_lock_irqsave(&pg->lock, flags);
 371         if (pg_updated)
 372                 list_add_rcu(&h->node, &pg->dh_list);
 373         spin_unlock_irqrestore(&pg->lock, flags);
 374
 375         alua_rtpg_queue(rcu_dereference_protected(h->pg,
 376                                                   lockdep_is_held(&h->pg_lock)),
 377                         sdev, NULL, true);
 378         spin_unlock(&h->pg_lock);
 379
 380         if (old_pg)
 381                 kref_put(&old_pg->kref, release_port_group);
 382
 383         return SCSI_DH_OK;
 384 }
 385
 386 static char print_alua_state(unsigned char state)
 387 {
 388         switch (state) {
 389         case SCSI_ACCESS_STATE_OPTIMAL:
 390                 return 'A';
 391         case SCSI_ACCESS_STATE_ACTIVE:
 392                 return 'N';
 393         case SCSI_ACCESS_STATE_STANDBY:
 394                 return 'S';
 395         case SCSI_ACCESS_STATE_UNAVAILABLE:
 396                 return 'U';
 397         case SCSI_ACCESS_STATE_LBA:
 398                 return 'L';
 399         case SCSI_ACCESS_STATE_OFFLINE:
 400                 return 'O';
 401         case SCSI_ACCESS_STATE_TRANSITIONING:
 402                 return 'T';
 403         default:
 404                 return 'X';
 405         }
 406 }
 407
 408 static int alua_check_sense(struct scsi_device *sdev,
 409                             struct scsi_sense_hdr *sense_hdr)
 410 {
 411         switch (sense_hdr->sense_key) {
 412         case NOT_READY:
 413                 if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
 414                         /*
 415                          * LUN Not Accessible - ALUA state transition
 416                          */
 417                         alua_check(sdev, false);
 418                         return NEEDS_RETRY;
 419                 }
 420                 break;
 421         case UNIT_ATTENTION:
 422                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
 423                         /*
 424                          * Power On, Reset, or Bus Device Reset.
 425                          * Might have obscured a state transition,
 426                          * so schedule a recheck.
 427                          */
 428                         alua_check(sdev, true);
 429                         return ADD_TO_MLQUEUE;
 430                 }
 431                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
 432                         /*
 433                          * Device internal reset
 434                          */
 435                         return ADD_TO_MLQUEUE;
 436                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
 437                         /*
 438                          * Mode Parameters Changed
 439                          */
 440                         return ADD_TO_MLQUEUE;
 441                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
 442                         /*
 443                          * ALUA state changed
 444                          */
 445                         alua_check(sdev, true);
 446                         return ADD_TO_MLQUEUE;
 447                 }
 448                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
 449                         /*
 450                          * Implicit ALUA state transition failed
 451                          */
 452                         alua_check(sdev, true);
 453                         return ADD_TO_MLQUEUE;
 454                 }
 455                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
 456                         /*
 457                          * Inquiry data has changed
 458                          */
 459                         return ADD_TO_MLQUEUE;
 460                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x0e)
 461                         /*
 462                          * REPORTED_LUNS_DATA_HAS_CHANGED is reported
 463                          * when switching controllers on targets like
 464                          * Intel Multi-Flex. We can just retry.
 465                          */
 466                         return ADD_TO_MLQUEUE;
 467                 break;
 468         }
 469
 470         return SCSI_RETURN_NOT_HANDLED;
 471 }
 472
 473 /*
 474  * alua_tur - Send a TEST UNIT READY
 475  * @sdev: device to which the TEST UNIT READY command should be send
 476  *
 477  * Send a TEST UNIT READY to @sdev to figure out the device state
 478  * Returns SCSI_DH_RETRY if the sense code is NOT READY/ALUA TRANSITIONING,
 479  * SCSI_DH_OK if no error occurred, and SCSI_DH_IO otherwise.
 480  */
 481 static int alua_tur(struct scsi_device *sdev)
 482 {
 483         struct scsi_sense_hdr sense_hdr;
 484         int retval;
 485
 486         retval = scsi_test_unit_ready(sdev, ALUA_FAILOVER_TIMEOUT * HZ,
 487                                       ALUA_FAILOVER_RETRIES, &sense_hdr);
 488         if (sense_hdr.sense_key == NOT_READY &&
 489             sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
 490                 return SCSI_DH_RETRY;
 491         else if (retval)
 492                 return SCSI_DH_IO;
 493         else
 494                 return SCSI_DH_OK;
 495 }
 496
 497 /*
 498  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
 499  * @sdev: the device to be evaluated.
 500  *
 501  * Evaluate the Target Port Group State.
 502  * Returns SCSI_DH_DEV_OFFLINED if the path is
 503  * found to be unusable.
 504  */
 505 static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 506 {
 507         struct scsi_sense_hdr sense_hdr;
 508         struct alua_port_group *tmp_pg;
 509         int len, k, off, bufflen = ALUA_RTPG_SIZE;
 510         unsigned char *desc, *buff;
 511         unsigned err, retval;
 512         unsigned int tpg_desc_tbl_off;
 513         unsigned char orig_transition_tmo;
 514         unsigned long flags;
 515         bool transitioning_sense = false;
 516
 517         if (!pg->expiry) {
 518                 unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
 519
 520                 if (pg->transition_tmo)
 521                         transition_tmo = pg->transition_tmo * HZ;
 522
 523                 pg->expiry = round_jiffies_up(jiffies + transition_tmo);
 524         }
 525
 526         buff = kzalloc(bufflen, GFP_KERNEL);
 527         if (!buff)
 528                 return SCSI_DH_DEV_TEMP_BUSY;
 529
 530  retry:
 531         err = 0;
 532         retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
 533
 534         if (retval) {
 535                 /*
 536                  * Some (broken) implementations have a habit of returning
 537                  * an error during things like firmware update etc.
 538                  * But if the target only supports active/optimized there's
 539                  * not much we can do; it's not that we can switch paths
 540                  * or anything.
 541                  * So ignore any errors to avoid spurious failures during
 542                  * path failover.
 543                  */
 544                 if ((pg->valid_states & ~TPGS_SUPPORT_OPTIMIZED) == 0) {
 545                         sdev_printk(KERN_INFO, sdev,
 546                                     "%s: ignoring rtpg result %d\n",
 547                                     ALUA_DH_NAME, retval);
 548                         kfree(buff);
 549                         return SCSI_DH_OK;
 550                 }
 551                 if (!scsi_sense_valid(&sense_hdr)) {
 552                         sdev_printk(KERN_INFO, sdev,
 553                                     "%s: rtpg failed, result %d\n",
 554                                     ALUA_DH_NAME, retval);
 555                         kfree(buff);
 556                         if (driver_byte(retval) == DRIVER_ERROR)
 557                                 return SCSI_DH_DEV_TEMP_BUSY;
 558                         return SCSI_DH_IO;
 559                 }
 560
 561                 /*
 562                  * submit_rtpg() has failed on existing arrays
 563                  * when requesting extended header info, and
 564                  * the array doesn't support extended headers,
 565                  * even though it shouldn't according to T10.
 566                  * The retry without rtpg_ext_hdr_req set
 567                  * handles this.
 568                  */
 569                 if (!(pg->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
 570                     sense_hdr.sense_key == ILLEGAL_REQUEST &&
 571                     sense_hdr.asc == 0x24 && sense_hdr.ascq == 0) {
 572                         pg->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
 573                         goto retry;
 574                 }
 575                 /*
 576                  * If the array returns with 'ALUA state transition'
 577                  * sense code here it cannot return RTPG data during
 578                  * transition. So set the state to 'transitioning' directly.
 579                  */
 580                 if (sense_hdr.sense_key == NOT_READY &&
 581                     sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a) {
 582                         transitioning_sense = true;
 583                         goto skip_rtpg;
 584                 }
 585                 /*
 586                  * Retry on any other UNIT ATTENTION occurred.
 587                  */
 588                 if (sense_hdr.sense_key == UNIT_ATTENTION)
 589                         err = SCSI_DH_RETRY;
 590                 if (err == SCSI_DH_RETRY &&
 591                     pg->expiry != 0 && time_before(jiffies, pg->expiry)) {
 592                         sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
 593                                     ALUA_DH_NAME);
 594                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 595                         kfree(buff);
 596                         return err;
 597                 }
 598                 sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
 599                             ALUA_DH_NAME);
 600                 scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 601                 kfree(buff);
 602                 pg->expiry = 0;
 603                 return SCSI_DH_IO;
 604         }
 605
 606         len = get_unaligned_be32(&buff[0]) + 4;
 607
 608         if (len > bufflen) {
 609                 /* Resubmit with the correct length */
 610                 kfree(buff);
 611                 bufflen = len;
 612                 buff = kmalloc(bufflen, GFP_KERNEL);
 613                 if (!buff) {
 614                         sdev_printk(KERN_WARNING, sdev,
 615                                     "%s: kmalloc buffer failed\n",__func__);
 616                         /* Temporary failure, bypass */
 617                         pg->expiry = 0;
 618                         return SCSI_DH_DEV_TEMP_BUSY;
 619                 }
 620                 goto retry;
 621         }
 622
 623         orig_transition_tmo = pg->transition_tmo;
 624         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0)
 625                 pg->transition_tmo = buff[5];
 626         else
 627                 pg->transition_tmo = ALUA_FAILOVER_TIMEOUT;
 628
 629         if (orig_transition_tmo != pg->transition_tmo) {
 630                 sdev_printk(KERN_INFO, sdev,
 631                             "%s: transition timeout set to %d seconds\n",
 632                             ALUA_DH_NAME, pg->transition_tmo);
 633                 pg->expiry = jiffies + pg->transition_tmo * HZ;
 634         }
 635
 636         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
 637                 tpg_desc_tbl_off = 8;
 638         else
 639                 tpg_desc_tbl_off = 4;
 640
 641         for (k = tpg_desc_tbl_off, desc = buff + tpg_desc_tbl_off;
 642              k < len;
 643              k += off, desc += off) {
 644                 u16 group_id = get_unaligned_be16(&desc[2]);
 645
 646                 spin_lock_irqsave(&port_group_lock, flags);
 647                 tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 648                                           group_id);
 649                 spin_unlock_irqrestore(&port_group_lock, flags);
 650                 if (tmp_pg) {
 651                         if (spin_trylock_irqsave(&tmp_pg->lock, flags)) {
 652                                 if ((tmp_pg == pg) ||
 653                                     !(tmp_pg->flags & ALUA_PG_RUNNING)) {
 654                                         struct alua_dh_data *h;
 655
 656                                         tmp_pg->state = desc[0] & 0x0f;
 657                                         tmp_pg->pref = desc[0] >> 7;
 658                                         rcu_read_lock();
 659                                         list_for_each_entry_rcu(h,
 660                                                 &tmp_pg->dh_list, node) {
 661                                                 /* h->sdev should always be valid */
 662                                                 BUG_ON(!h->sdev);
 663                                                 h->sdev->access_state = desc[0];
 664                                         }
 665                                         rcu_read_unlock();
 666                                 }
 667                                 if (tmp_pg == pg)
 668                                         tmp_pg->valid_states = desc[1];
 669                                 spin_unlock_irqrestore(&tmp_pg->lock, flags);
 670                         }
 671                         kref_put(&tmp_pg->kref, release_port_group);
 672                 }
 673                 off = 8 + (desc[7] * 4);
 674         }
 675
 676  skip_rtpg:
 677         spin_lock_irqsave(&pg->lock, flags);
 678         if (transitioning_sense)
 679                 pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
 680
 681         sdev_printk(KERN_INFO, sdev,
 682                     "%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
 683                     ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state),
 684                     pg->pref ? "preferred" : "non-preferred",
 685                     pg->valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
 686                     pg->valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
 687                     pg->valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
 688                     pg->valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
 689                     pg->valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
 690                     pg->valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
 691                     pg->valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
 692
 693         switch (pg->state) {
 694         case SCSI_ACCESS_STATE_TRANSITIONING:
 695                 if (time_before(jiffies, pg->expiry)) {
 696                         /* State transition, retry */
 697                         pg->interval = ALUA_RTPG_RETRY_DELAY;
 698                         err = SCSI_DH_RETRY;
 699                 } else {
 700                         struct alua_dh_data *h;
 701
 702                         /* Transitioning time exceeded, set port to standby */
 703                         err = SCSI_DH_IO;
 704                         pg->state = SCSI_ACCESS_STATE_STANDBY;
 705                         pg->expiry = 0;
 706                         rcu_read_lock();
 707                         list_for_each_entry_rcu(h, &pg->dh_list, node) {
 708                                 BUG_ON(!h->sdev);
 709                                 h->sdev->access_state =
 710                                         (pg->state & SCSI_ACCESS_STATE_MASK);
 711                                 if (pg->pref)
 712                                         h->sdev->access_state |=
 713                                                 SCSI_ACCESS_STATE_PREFERRED;
 714                         }
 715                         rcu_read_unlock();
 716                 }
 717                 break;
 718         case SCSI_ACCESS_STATE_OFFLINE:
 719                 /* Path unusable */
 720                 err = SCSI_DH_DEV_OFFLINED;
 721                 pg->expiry = 0;
 722                 break;
 723         default:
 724                 /* Useable path if active */
 725                 err = SCSI_DH_OK;
 726                 pg->expiry = 0;
 727                 break;
 728         }
 729         spin_unlock_irqrestore(&pg->lock, flags);
 730         kfree(buff);
 731         return err;
 732 }
 733
 734 /*
 735  * alua_stpg - Issue a SET TARGET PORT GROUP command
 736  *
 737  * Issue a SET TARGET PORT GROUP command and evaluate the
 738  * response. Returns SCSI_DH_RETRY per default to trigger
 739  * a re-evaluation of the target group state or SCSI_DH_OK
 740  * if no further action needs to be taken.
 741  */
 742 static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg)
 743 {
 744         int retval;
 745         struct scsi_sense_hdr sense_hdr;
 746
 747         if (!(pg->tpgs & TPGS_MODE_EXPLICIT)) {
 748                 /* Only implicit ALUA supported, retry */
 749                 return SCSI_DH_RETRY;
 750         }
 751         switch (pg->state) {
 752         case SCSI_ACCESS_STATE_OPTIMAL:
 753                 return SCSI_DH_OK;
 754         case SCSI_ACCESS_STATE_ACTIVE:
 755                 if ((pg->flags & ALUA_OPTIMIZE_STPG) &&
 756                     !pg->pref &&
 757                     (pg->tpgs & TPGS_MODE_IMPLICIT))
 758                         return SCSI_DH_OK;
 759                 break;
 760         case SCSI_ACCESS_STATE_STANDBY:
 761         case SCSI_ACCESS_STATE_UNAVAILABLE:
 762                 break;
 763         case SCSI_ACCESS_STATE_OFFLINE:
 764                 return SCSI_DH_IO;
 765         case SCSI_ACCESS_STATE_TRANSITIONING:
 766                 break;
 767         default:
 768                 sdev_printk(KERN_INFO, sdev,
 769                             "%s: stpg failed, unhandled TPGS state %d",
 770                             ALUA_DH_NAME, pg->state);
 771                 return SCSI_DH_NOSYS;
 772         }
 773         retval = submit_stpg(sdev, pg->group_id, &sense_hdr);
 774
 775         if (retval) {
 776                 if (!scsi_sense_valid(&sense_hdr)) {
 777                         sdev_printk(KERN_INFO, sdev,
 778                                     "%s: stpg failed, result %d",
 779                                     ALUA_DH_NAME, retval);
 780                         if (driver_byte(retval) == DRIVER_ERROR)
 781                                 return SCSI_DH_DEV_TEMP_BUSY;
 782                 } else {
 783                         sdev_printk(KERN_INFO, sdev, "%s: stpg failed\n",
 784                                     ALUA_DH_NAME);
 785                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 786                 }
 787         }
 788         /* Retry RTPG */
 789         return SCSI_DH_RETRY;
 790 }
 791
 792 static void alua_rtpg_work(struct work_struct *work)
 793 {
 794         struct alua_port_group *pg =
 795                 container_of(work, struct alua_port_group, rtpg_work.work);
 796         struct scsi_device *sdev;
 797         LIST_HEAD(qdata_list);
 798         int err = SCSI_DH_OK;
 799         struct alua_queue_data *qdata, *tmp;
 800         unsigned long flags;
 801
 802         spin_lock_irqsave(&pg->lock, flags);
 803         sdev = pg->rtpg_sdev;
 804         if (!sdev) {
 805                 WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
 806                 WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
 807                 spin_unlock_irqrestore(&pg->lock, flags);
 808                 kref_put(&pg->kref, release_port_group);
 809                 return;
 810         }
 811         pg->flags |= ALUA_PG_RUNNING;
 812         if (pg->flags & ALUA_PG_RUN_RTPG) {
 813                 int state = pg->state;
 814
 815                 pg->flags &= ~ALUA_PG_RUN_RTPG;
 816                 spin_unlock_irqrestore(&pg->lock, flags);
 817                 if (state == SCSI_ACCESS_STATE_TRANSITIONING) {
 818                         if (alua_tur(sdev) == SCSI_DH_RETRY) {
 819                                 spin_lock_irqsave(&pg->lock, flags);
 820                                 pg->flags &= ~ALUA_PG_RUNNING;
 821                                 pg->flags |= ALUA_PG_RUN_RTPG;
 822                                 if (!pg->interval)
 823                                         pg->interval = ALUA_RTPG_RETRY_DELAY;
 824                                 spin_unlock_irqrestore(&pg->lock, flags);
 825                                 queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 826                                                    pg->interval * HZ);
 827                                 return;
 828                         }
 829                         /* Send RTPG on failure or if TUR indicates SUCCESS */
 830                 }
 831                 err = alua_rtpg(sdev, pg);
 832                 spin_lock_irqsave(&pg->lock, flags);
 833                 if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 834                         pg->flags &= ~ALUA_PG_RUNNING;
 835                         if (!pg->interval && !(pg->flags & ALUA_PG_RUN_RTPG))
 836                                 pg->interval = ALUA_RTPG_RETRY_DELAY;
 837                         pg->flags |= ALUA_PG_RUN_RTPG;
 838                         spin_unlock_irqrestore(&pg->lock, flags);
 839                         queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 840                                            pg->interval * HZ);
 841                         return;
 842                 }
 843                 if (err != SCSI_DH_OK)
 844                         pg->flags &= ~ALUA_PG_RUN_STPG;
 845         }
 846         if (pg->flags & ALUA_PG_RUN_STPG) {
 847                 pg->flags &= ~ALUA_PG_RUN_STPG;
 848                 spin_unlock_irqrestore(&pg->lock, flags);
 849                 err = alua_stpg(sdev, pg);
 850                 spin_lock_irqsave(&pg->lock, flags);
 851                 if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 852                         pg->flags |= ALUA_PG_RUN_RTPG;
 853                         pg->interval = 0;
 854                         pg->flags &= ~ALUA_PG_RUNNING;
 855                         spin_unlock_irqrestore(&pg->lock, flags);
 856                         queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 857                                            pg->interval * HZ);
 858                         return;
 859                 }
 860         }
 861
 862         list_splice_init(&pg->rtpg_list, &qdata_list);
 863         pg->rtpg_sdev = NULL;
 864         spin_unlock_irqrestore(&pg->lock, flags);
 865
 866         list_for_each_entry_safe(qdata, tmp, &qdata_list, entry) {
 867                 list_del(&qdata->entry);
 868                 if (qdata->callback_fn)
 869                         qdata->callback_fn(qdata->callback_data, err);
 870                 kfree(qdata);
 871         }
 872         spin_lock_irqsave(&pg->lock, flags);
 873         pg->flags &= ~ALUA_PG_RUNNING;
 874         spin_unlock_irqrestore(&pg->lock, flags);
 875         scsi_device_put(sdev);
 876         kref_put(&pg->kref, release_port_group);
 877 }
 878
 879 /**
 880  * alua_rtpg_queue() - cause RTPG to be submitted asynchronously
 881  * @pg: ALUA port group associated with @sdev.
 882  * @sdev: SCSI device for which to submit an RTPG.
 883  * @qdata: Information about the callback to invoke after the RTPG.
 884  * @force: Whether or not to submit an RTPG if a work item that will submit an
 885  *         RTPG already has been scheduled.
 886  *
 887  * Returns true if and only if alua_rtpg_work() will be called asynchronously.
 888  * That function is responsible for calling @qdata->fn().
 889  */
 890 static bool alua_rtpg_queue(struct alua_port_group *pg,
 891                             struct scsi_device *sdev,
 892                             struct alua_queue_data *qdata, bool force)
 893 {
 894         int start_queue = 0;
 895         unsigned long flags;
 896         if (WARN_ON_ONCE(!pg) || scsi_device_get(sdev))
 897                 return false;
 898
 899         spin_lock_irqsave(&pg->lock, flags);
 900         if (qdata) {
 901                 list_add_tail(&qdata->entry, &pg->rtpg_list);
 902                 pg->flags |= ALUA_PG_RUN_STPG;
 903                 force = true;
 904         }
 905         if (pg->rtpg_sdev == NULL) {
 906                 pg->interval = 0;
 907                 pg->flags |= ALUA_PG_RUN_RTPG;
 908                 kref_get(&pg->kref);
 909                 pg->rtpg_sdev = sdev;
 910                 start_queue = 1;
 911         } else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {
 912                 pg->flags |= ALUA_PG_RUN_RTPG;
 913                 /* Do not queue if the worker is already running */
 914                 if (!(pg->flags & ALUA_PG_RUNNING)) {
 915                         kref_get(&pg->kref);
 916                         start_queue = 1;
 917                 }
 918         }
 919
 920         spin_unlock_irqrestore(&pg->lock, flags);
 921
 922         if (start_queue) {
 923                 if (queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 924                                 msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS)))
 925                         sdev = NULL;
 926                 else
 927                         kref_put(&pg->kref, release_port_group);
 928         }
 929         if (sdev)
 930                 scsi_device_put(sdev);
 931
 932         return true;
 933 }
 934
 935 /*
 936  * alua_initialize - Initialize ALUA state
 937  * @sdev: the device to be initialized
 938  *
 939  * For the prep_fn to work correctly we have
 940  * to initialize the ALUA state for the device.
 941  */
 942 static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 943 {
 944         int err = SCSI_DH_DEV_UNSUPP, tpgs;
 945
 946         mutex_lock(&h->init_mutex);
 947         tpgs = alua_check_tpgs(sdev);
 948         if (tpgs != TPGS_MODE_NONE)
 949                 err = alua_check_vpd(sdev, h, tpgs);
 950         h->init_error = err;
 951         mutex_unlock(&h->init_mutex);
 952         return err;
 953 }
 954 /*
 955  * alua_set_params - set/unset the optimize flag
 956  * @sdev: device on the path to be activated
 957  * params - parameters in the following format
 958  *      "no_of_params\0param1\0param2\0param3\0...\0"
 959  * For example, to set the flag pass the following parameters
 960  * from multipath.conf
 961  *     hardware_handler        "2 alua 1"
 962  */
 963 static int alua_set_params(struct scsi_device *sdev, const char *params)
 964 {
 965         struct alua_dh_data *h = sdev->handler_data;
 966         struct alua_port_group *pg = NULL;
 967         unsigned int optimize = 0, argc;
 968         const char *p = params;
 969         int result = SCSI_DH_OK;
 970         unsigned long flags;
 971
 972         if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
 973                 return -EINVAL;
 974
 975         while (*p++)
 976                 ;
 977         if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
 978                 return -EINVAL;
 979
 980         rcu_read_lock();
 981         pg = rcu_dereference(h->pg);
 982         if (!pg) {
 983                 rcu_read_unlock();
 984                 return -ENXIO;
 985         }
 986         spin_lock_irqsave(&pg->lock, flags);
 987         if (optimize)
 988                 pg->flags |= ALUA_OPTIMIZE_STPG;
 989         else
 990                 pg->flags &= ~ALUA_OPTIMIZE_STPG;
 991         spin_unlock_irqrestore(&pg->lock, flags);
 992         rcu_read_unlock();
 993
 994         return result;
 995 }
 996
 997 /*
 998  * alua_activate - activate a path
 999  * @sdev: device on the path to be activated
1000  *
1001  * We're currently switching the port group to be activated only and
1002  * let the array figure out the rest.
1003  * There may be other arrays which require us to switch all port groups
1004  * based on a certain policy. But until we actually encounter them it
1005  * should be okay.
1006  */
1007 static int alua_activate(struct scsi_device *sdev,
1008                         activate_complete fn, void *data)
1009 {
1010         struct alua_dh_data *h = sdev->handler_data;
1011         int err = SCSI_DH_OK;
1012         struct alua_queue_data *qdata;
1013         struct alua_port_group *pg;
1014
1015         qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
1016         if (!qdata) {
1017                 err = SCSI_DH_RES_TEMP_UNAVAIL;
1018                 goto out;
1019         }
1020         qdata->callback_fn = fn;
1021         qdata->callback_data = data;
1022
1023         mutex_lock(&h->init_mutex);
1024         rcu_read_lock();
1025         pg = rcu_dereference(h->pg);
1026         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1027                 rcu_read_unlock();
1028                 kfree(qdata);
1029                 err = h->init_error;
1030                 mutex_unlock(&h->init_mutex);
1031                 goto out;
1032         }
1033         rcu_read_unlock();
1034         mutex_unlock(&h->init_mutex);
1035
1036         if (alua_rtpg_queue(pg, sdev, qdata, true))
1037                 fn = NULL;
1038         else
1039                 err = SCSI_DH_DEV_OFFLINED;
1040         kref_put(&pg->kref, release_port_group);
1041 out:
1042         if (fn)
1043                 fn(data, err);
1044         return 0;
1045 }
1046
1047 /*
1048  * alua_check - check path status
1049  * @sdev: device on the path to be checked
1050  *
1051  * Check the device status
1052  */
1053 static void alua_check(struct scsi_device *sdev, bool force)
1054 {
1055         struct alua_dh_data *h = sdev->handler_data;
1056         struct alua_port_group *pg;
1057
1058         rcu_read_lock();
1059         pg = rcu_dereference(h->pg);
1060         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1061                 rcu_read_unlock();
1062                 return;
1063         }
1064         rcu_read_unlock();
1065
1066         alua_rtpg_queue(pg, sdev, NULL, force);
1067         kref_put(&pg->kref, release_port_group);
1068 }
1069
1070 /*
1071  * alua_prep_fn - request callback
1072  *
1073  * Fail I/O to all paths not in state
1074  * active/optimized or active/non-optimized.
1075  */
1076 static blk_status_t alua_prep_fn(struct scsi_device *sdev, struct request *req)
1077 {
1078         struct alua_dh_data *h = sdev->handler_data;
1079         struct alua_port_group *pg;
1080         unsigned char state = SCSI_ACCESS_STATE_OPTIMAL;
1081
1082         rcu_read_lock();
1083         pg = rcu_dereference(h->pg);
1084         if (pg)
1085                 state = pg->state;
1086         rcu_read_unlock();
1087
1088         switch (state) {
1089         case SCSI_ACCESS_STATE_OPTIMAL:
1090         case SCSI_ACCESS_STATE_ACTIVE:
1091         case SCSI_ACCESS_STATE_LBA:
1092                 return BLK_STS_OK;
1093         case SCSI_ACCESS_STATE_TRANSITIONING:
1094                 return BLK_STS_RESOURCE;
1095         default:
1096                 req->rq_flags |= RQF_QUIET;
1097                 return BLK_STS_IOERR;
1098         }
1099 }
1100
1101 static void alua_rescan(struct scsi_device *sdev)
1102 {
1103         struct alua_dh_data *h = sdev->handler_data;
1104
1105         alua_initialize(sdev, h);
1106 }
1107
1108 /*
1109  * alua_bus_attach - Attach device handler
1110  * @sdev: device to be attached to
1111  */
1112 static int alua_bus_attach(struct scsi_device *sdev)
1113 {
1114         struct alua_dh_data *h;
1115         int err;
1116
1117         h = kzalloc(sizeof(*h) , GFP_KERNEL);
1118         if (!h)
1119                 return SCSI_DH_NOMEM;
1120         spin_lock_init(&h->pg_lock);
1121         rcu_assign_pointer(h->pg, NULL);
1122         h->init_error = SCSI_DH_OK;
1123         h->sdev = sdev;
1124         INIT_LIST_HEAD(&h->node);
1125
1126         mutex_init(&h->init_mutex);
1127         err = alua_initialize(sdev, h);
1128         if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
1129                 goto failed;
1130
1131         sdev->handler_data = h;
1132         return SCSI_DH_OK;
1133 failed:
1134         kfree(h);
1135         return err;
1136 }
1137
1138 /*
1139  * alua_bus_detach - Detach device handler
1140  * @sdev: device to be detached from
1141  */
1142 static void alua_bus_detach(struct scsi_device *sdev)
1143 {
1144         struct alua_dh_data *h = sdev->handler_data;
1145         struct alua_port_group *pg;
1146
1147         spin_lock(&h->pg_lock);
1148         pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
1149         rcu_assign_pointer(h->pg, NULL);
1150         h->sdev = NULL;
1151         spin_unlock(&h->pg_lock);
1152         if (pg) {
1153                 spin_lock_irq(&pg->lock);
1154                 list_del_rcu(&h->node);
1155                 spin_unlock_irq(&pg->lock);
1156                 kref_put(&pg->kref, release_port_group);
1157         }
1158         sdev->handler_data = NULL;
1159         kfree(h);
1160 }
1161
1162 static struct scsi_device_handler alua_dh = {
1163         .name = ALUA_DH_NAME,
1164         .module = THIS_MODULE,
1165         .attach = alua_bus_attach,
1166         .detach = alua_bus_detach,
1167         .prep_fn = alua_prep_fn,
1168         .check_sense = alua_check_sense,
1169         .activate = alua_activate,
1170         .rescan = alua_rescan,
1171         .set_params = alua_set_params,
1172 };
1173
1174 static int __init alua_init(void)
1175 {
1176         int r;
1177
1178         kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM, 0);
1179         if (!kaluad_wq)
1180                 return -ENOMEM;
1181
1182         r = scsi_register_device_handler(&alua_dh);
1183         if (r != 0) {
1184                 printk(KERN_ERR "%s: Failed to register scsi device handler",
1185                         ALUA_DH_NAME);
1186                 destroy_workqueue(kaluad_wq);
1187         }
1188         return r;
1189 }
1190
1191 static void __exit alua_exit(void)
1192 {
1193         scsi_unregister_device_handler(&alua_dh);
1194         destroy_workqueue(kaluad_wq);
1195 }
1196
1197 module_init(alua_init);
1198 module_exit(alua_exit);
1199
1200 MODULE_DESCRIPTION("DM Multipath ALUA support");
1201 MODULE_AUTHOR("Hannes Reinecke <hare@suse.de>");
1202 MODULE_LICENSE("GPL");
1203 MODULE_VERSION(ALUA_DH_VER);