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