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 #define ALUA_RTPG_RETRY_DELAY           2
  58
  59 /* device handler flags */
  60 #define ALUA_OPTIMIZE_STPG              0x01
  61 #define ALUA_RTPG_EXT_HDR_UNSUPP        0x02
  62 /* State machine flags */
  63 #define ALUA_PG_RUN_RTPG                0x10
  64 #define ALUA_PG_RUN_STPG                0x20
  65 #define ALUA_PG_RUNNING                 0x40
  66
  67 static uint optimize_stpg;
  68 module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
  69 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.");
  70
  71 static LIST_HEAD(port_group_list);
  72 static DEFINE_SPINLOCK(port_group_lock);
  73 static struct workqueue_struct *kaluad_wq;
  74
  75 struct alua_port_group {
  76         struct kref             kref;
  77         struct rcu_head         rcu;
  78         struct list_head        node;
  79         struct list_head        dh_list;
  80         unsigned char           device_id_str[256];
  81         int                     device_id_len;
  82         int                     group_id;
  83         int                     tpgs;
  84         int                     state;
  85         int                     pref;
  86         int                     valid_states;
  87         unsigned                flags; /* used for optimizing STPG */
  88         unsigned char           transition_tmo;
  89         unsigned long           expiry;
  90         unsigned long           interval;
  91         struct delayed_work     rtpg_work;
  92         spinlock_t              lock;
  93         struct list_head        rtpg_list;
  94         struct scsi_device      *rtpg_sdev;
  95 };
  96
  97 struct alua_dh_data {
  98         struct list_head        node;
  99         struct alua_port_group __rcu *pg;
 100         int                     group_id;
 101         spinlock_t              pg_lock;
 102         struct scsi_device      *sdev;
 103         int                     init_error;
 104         struct mutex            init_mutex;
 105 };
 106
 107 struct alua_queue_data {
 108         struct list_head        entry;
 109         activate_complete       callback_fn;
 110         void                    *callback_data;
 111 };
 112
 113 #define ALUA_POLICY_SWITCH_CURRENT      0
 114 #define ALUA_POLICY_SWITCH_ALL          1
 115
 116 static void alua_rtpg_work(struct work_struct *work);
 117 static bool alua_rtpg_queue(struct alua_port_group *pg,
 118                             struct scsi_device *sdev,
 119                             struct alua_queue_data *qdata, bool force);
 120 static void alua_check(struct scsi_device *sdev, bool force);
 121
 122 static void release_port_group(struct kref *kref)
 123 {
 124         struct alua_port_group *pg;
 125
 126         pg = container_of(kref, struct alua_port_group, kref);
 127         if (pg->rtpg_sdev)
 128                 flush_delayed_work(&pg->rtpg_work);
 129         spin_lock(&port_group_lock);
 130         list_del(&pg->node);
 131         spin_unlock(&port_group_lock);
 132         kfree_rcu(pg, rcu);
 133 }
 134
 135 /*
 136  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
 137  * @sdev: sdev the command should be sent to
 138  */
 139 static int submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
 140                        int bufflen, struct scsi_sense_hdr *sshdr, int flags)
 141 {
 142         u8 cdb[MAX_COMMAND_SIZE];
 143         int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 144                 REQ_FAILFAST_DRIVER;
 145
 146         /* Prepare the command. */
 147         memset(cdb, 0x0, MAX_COMMAND_SIZE);
 148         cdb[0] = MAINTENANCE_IN;
 149         if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
 150                 cdb[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
 151         else
 152                 cdb[1] = MI_REPORT_TARGET_PGS;
 153         put_unaligned_be32(bufflen, &cdb[6]);
 154
 155         return scsi_execute(sdev, cdb, DMA_FROM_DEVICE, buff, bufflen, NULL,
 156                         sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
 157                         ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
 158 }
 159
 160 /*
 161  * submit_stpg - Issue a SET TARGET PORT GROUP command
 162  *
 163  * Currently we're only setting the current target port group state
 164  * to 'active/optimized' and let the array firmware figure out
 165  * the states of the remaining groups.
 166  */
 167 static int submit_stpg(struct scsi_device *sdev, int group_id,
 168                        struct scsi_sense_hdr *sshdr)
 169 {
 170         u8 cdb[MAX_COMMAND_SIZE];
 171         unsigned char stpg_data[8];
 172         int stpg_len = 8;
 173         int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 174                 REQ_FAILFAST_DRIVER;
 175
 176         /* Prepare the data buffer */
 177         memset(stpg_data, 0, stpg_len);
 178         stpg_data[4] = SCSI_ACCESS_STATE_OPTIMAL;
 179         put_unaligned_be16(group_id, &stpg_data[6]);
 180
 181         /* Prepare the command. */
 182         memset(cdb, 0x0, MAX_COMMAND_SIZE);
 183         cdb[0] = MAINTENANCE_OUT;
 184         cdb[1] = MO_SET_TARGET_PGS;
 185         put_unaligned_be32(stpg_len, &cdb[6]);
 186
 187         return scsi_execute(sdev, cdb, DMA_TO_DEVICE, stpg_data, stpg_len, NULL,
 188                         sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
 189                         ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
 190 }
 191
 192 static struct alua_port_group *alua_find_get_pg(char *id_str, size_t id_size,
 193                                                 int group_id)
 194 {
 195         struct alua_port_group *pg;
 196
 197         if (!id_str || !id_size || !strlen(id_str))
 198                 return NULL;
 199
 200         list_for_each_entry(pg, &port_group_list, node) {
 201                 if (pg->group_id != group_id)
 202                         continue;
 203                 if (!pg->device_id_len || pg->device_id_len != id_size)
 204                         continue;
 205                 if (strncmp(pg->device_id_str, id_str, id_size))
 206                         continue;
 207                 if (!kref_get_unless_zero(&pg->kref))
 208                         continue;
 209                 return pg;
 210         }
 211
 212         return NULL;
 213 }
 214
 215 /*
 216  * alua_alloc_pg - Allocate a new port_group structure
 217  * @sdev: scsi device
 218  * @group_id: port group id
 219  * @tpgs: target port group settings
 220  *
 221  * Allocate a new port_group structure for a given
 222  * device.
 223  */
 224 static struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
 225                                              int group_id, int tpgs)
 226 {
 227         struct alua_port_group *pg, *tmp_pg;
 228
 229         pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL);
 230         if (!pg)
 231                 return ERR_PTR(-ENOMEM);
 232
 233         pg->device_id_len = scsi_vpd_lun_id(sdev, pg->device_id_str,
 234                                             sizeof(pg->device_id_str));
 235         if (pg->device_id_len <= 0) {
 236                 /*
 237                  * TPGS supported but no device identification found.
 238                  * Generate private device identification.
 239                  */
 240                 sdev_printk(KERN_INFO, sdev,
 241                             "%s: No device descriptors found\n",
 242                             ALUA_DH_NAME);
 243                 pg->device_id_str[0] = '\0';
 244                 pg->device_id_len = 0;
 245         }
 246         pg->group_id = group_id;
 247         pg->tpgs = tpgs;
 248         pg->state = SCSI_ACCESS_STATE_OPTIMAL;
 249         pg->valid_states = TPGS_SUPPORT_ALL;
 250         if (optimize_stpg)
 251                 pg->flags |= ALUA_OPTIMIZE_STPG;
 252         kref_init(&pg->kref);
 253         INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
 254         INIT_LIST_HEAD(&pg->rtpg_list);
 255         INIT_LIST_HEAD(&pg->node);
 256         INIT_LIST_HEAD(&pg->dh_list);
 257         spin_lock_init(&pg->lock);
 258
 259         spin_lock(&port_group_lock);
 260         tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 261                                   group_id);
 262         if (tmp_pg) {
 263                 spin_unlock(&port_group_lock);
 264                 kfree(pg);
 265                 return tmp_pg;
 266         }
 267
 268         list_add(&pg->node, &port_group_list);
 269         spin_unlock(&port_group_lock);
 270
 271         return pg;
 272 }
 273
 274 /*
 275  * alua_check_tpgs - Evaluate TPGS setting
 276  * @sdev: device to be checked
 277  *
 278  * Examine the TPGS setting of the sdev to find out if ALUA
 279  * is supported.
 280  */
 281 static int alua_check_tpgs(struct scsi_device *sdev)
 282 {
 283         int tpgs = TPGS_MODE_NONE;
 284
 285         /*
 286          * ALUA support for non-disk devices is fraught with
 287          * difficulties, so disable it for now.
 288          */
 289         if (sdev->type != TYPE_DISK) {
 290                 sdev_printk(KERN_INFO, sdev,
 291                             "%s: disable for non-disk devices\n",
 292                             ALUA_DH_NAME);
 293                 return tpgs;
 294         }
 295
 296         tpgs = scsi_device_tpgs(sdev);
 297         switch (tpgs) {
 298         case TPGS_MODE_EXPLICIT|TPGS_MODE_IMPLICIT:
 299                 sdev_printk(KERN_INFO, sdev,
 300                             "%s: supports implicit and explicit TPGS\n",
 301                             ALUA_DH_NAME);
 302                 break;
 303         case TPGS_MODE_EXPLICIT:
 304                 sdev_printk(KERN_INFO, sdev, "%s: supports explicit TPGS\n",
 305                             ALUA_DH_NAME);
 306                 break;
 307         case TPGS_MODE_IMPLICIT:
 308                 sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n",
 309                             ALUA_DH_NAME);
 310                 break;
 311         case TPGS_MODE_NONE:
 312                 sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
 313                             ALUA_DH_NAME);
 314                 break;
 315         default:
 316                 sdev_printk(KERN_INFO, sdev,
 317                             "%s: unsupported TPGS setting %d\n",
 318                             ALUA_DH_NAME, tpgs);
 319                 tpgs = TPGS_MODE_NONE;
 320                 break;
 321         }
 322
 323         return tpgs;
 324 }
 325
 326 /*
 327  * alua_check_vpd - Evaluate INQUIRY vpd page 0x83
 328  * @sdev: device to be checked
 329  *
 330  * Extract the relative target port and the target port group
 331  * descriptor from the list of identificators.
 332  */
 333 static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 334                           int tpgs)
 335 {
 336         int rel_port = -1, group_id;
 337         struct alua_port_group *pg, *old_pg = NULL;
 338         bool pg_updated = false;
 339         unsigned long flags;
 340
 341         group_id = scsi_vpd_tpg_id(sdev, &rel_port);
 342         if (group_id < 0) {
 343                 /*
 344                  * Internal error; TPGS supported but required
 345                  * VPD identification descriptors not present.
 346                  * Disable ALUA support
 347                  */
 348                 sdev_printk(KERN_INFO, sdev,
 349                             "%s: No target port descriptors found\n",
 350                             ALUA_DH_NAME);
 351                 return SCSI_DH_DEV_UNSUPP;
 352         }
 353
 354         pg = alua_alloc_pg(sdev, group_id, tpgs);
 355         if (IS_ERR(pg)) {
 356                 if (PTR_ERR(pg) == -ENOMEM)
 357                         return SCSI_DH_NOMEM;
 358                 return SCSI_DH_DEV_UNSUPP;
 359         }
 360         if (pg->device_id_len)
 361                 sdev_printk(KERN_INFO, sdev,
 362                             "%s: device %s port group %x rel port %x\n",
 363                             ALUA_DH_NAME, pg->device_id_str,
 364                             group_id, rel_port);
 365         else
 366                 sdev_printk(KERN_INFO, sdev,
 367                             "%s: port group %x rel port %x\n",
 368                             ALUA_DH_NAME, group_id, rel_port);
 369
 370         /* Check for existing port group references */
 371         spin_lock(&h->pg_lock);
 372         old_pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
 373         if (old_pg != pg) {
 374                 /* port group has changed. Update to new port group */
 375                 if (h->pg) {
 376                         spin_lock_irqsave(&old_pg->lock, flags);
 377                         list_del_rcu(&h->node);
 378                         spin_unlock_irqrestore(&old_pg->lock, flags);
 379                 }
 380                 rcu_assign_pointer(h->pg, pg);
 381                 pg_updated = true;
 382         }
 383
 384         spin_lock_irqsave(&pg->lock, flags);
 385         if (pg_updated)
 386                 list_add_rcu(&h->node, &pg->dh_list);
 387         spin_unlock_irqrestore(&pg->lock, flags);
 388
 389         alua_rtpg_queue(rcu_dereference_protected(h->pg,
 390                                                   lockdep_is_held(&h->pg_lock)),
 391                         sdev, NULL, true);
 392         spin_unlock(&h->pg_lock);
 393
 394         if (old_pg)
 395                 kref_put(&old_pg->kref, release_port_group);
 396
 397         return SCSI_DH_OK;
 398 }
 399
 400 static char print_alua_state(unsigned char state)
 401 {
 402         switch (state) {
 403         case SCSI_ACCESS_STATE_OPTIMAL:
 404                 return 'A';
 405         case SCSI_ACCESS_STATE_ACTIVE:
 406                 return 'N';
 407         case SCSI_ACCESS_STATE_STANDBY:
 408                 return 'S';
 409         case SCSI_ACCESS_STATE_UNAVAILABLE:
 410                 return 'U';
 411         case SCSI_ACCESS_STATE_LBA:
 412                 return 'L';
 413         case SCSI_ACCESS_STATE_OFFLINE:
 414                 return 'O';
 415         case SCSI_ACCESS_STATE_TRANSITIONING:
 416                 return 'T';
 417         default:
 418                 return 'X';
 419         }
 420 }
 421
 422 static int alua_check_sense(struct scsi_device *sdev,
 423                             struct scsi_sense_hdr *sense_hdr)
 424 {
 425         switch (sense_hdr->sense_key) {
 426         case NOT_READY:
 427                 if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
 428                         /*
 429                          * LUN Not Accessible - ALUA state transition
 430                          */
 431                         alua_check(sdev, false);
 432                         return NEEDS_RETRY;
 433                 }
 434                 break;
 435         case UNIT_ATTENTION:
 436                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
 437                         /*
 438                          * Power On, Reset, or Bus Device Reset.
 439                          * Might have obscured a state transition,
 440                          * so schedule a recheck.
 441                          */
 442                         alua_check(sdev, true);
 443                         return ADD_TO_MLQUEUE;
 444                 }
 445                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
 446                         /*
 447                          * Device internal reset
 448                          */
 449                         return ADD_TO_MLQUEUE;
 450                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
 451                         /*
 452                          * Mode Parameters Changed
 453                          */
 454                         return ADD_TO_MLQUEUE;
 455                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
 456                         /*
 457                          * ALUA state changed
 458                          */
 459                         alua_check(sdev, true);
 460                         return ADD_TO_MLQUEUE;
 461                 }
 462                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
 463                         /*
 464                          * Implicit ALUA state transition failed
 465                          */
 466                         alua_check(sdev, true);
 467                         return ADD_TO_MLQUEUE;
 468                 }
 469                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
 470                         /*
 471                          * Inquiry data has changed
 472                          */
 473                         return ADD_TO_MLQUEUE;
 474                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x0e)
 475                         /*
 476                          * REPORTED_LUNS_DATA_HAS_CHANGED is reported
 477                          * when switching controllers on targets like
 478                          * Intel Multi-Flex. We can just retry.
 479                          */
 480                         return ADD_TO_MLQUEUE;
 481                 break;
 482         }
 483
 484         return SCSI_RETURN_NOT_HANDLED;
 485 }
 486
 487 /*
 488  * alua_tur - Send a TEST UNIT READY
 489  * @sdev: device to which the TEST UNIT READY command should be send
 490  *
 491  * Send a TEST UNIT READY to @sdev to figure out the device state
 492  * Returns SCSI_DH_RETRY if the sense code is NOT READY/ALUA TRANSITIONING,
 493  * SCSI_DH_OK if no error occurred, and SCSI_DH_IO otherwise.
 494  */
 495 static int alua_tur(struct scsi_device *sdev)
 496 {
 497         struct scsi_sense_hdr sense_hdr;
 498         int retval;
 499
 500         retval = scsi_test_unit_ready(sdev, ALUA_FAILOVER_TIMEOUT * HZ,
 501                                       ALUA_FAILOVER_RETRIES, &sense_hdr);
 502         if (sense_hdr.sense_key == NOT_READY &&
 503             sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
 504                 return SCSI_DH_RETRY;
 505         else if (retval)
 506                 return SCSI_DH_IO;
 507         else
 508                 return SCSI_DH_OK;
 509 }
 510
 511 /*
 512  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
 513  * @sdev: the device to be evaluated.
 514  *
 515  * Evaluate the Target Port Group State.
 516  * Returns SCSI_DH_DEV_OFFLINED if the path is
 517  * found to be unusable.
 518  */
 519 static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 520 {
 521         struct scsi_sense_hdr sense_hdr;
 522         struct alua_port_group *tmp_pg;
 523         int len, k, off, bufflen = ALUA_RTPG_SIZE;
 524         unsigned char *desc, *buff;
 525         unsigned err;
 526         int retval;
 527         unsigned int tpg_desc_tbl_off;
 528         unsigned char orig_transition_tmo;
 529         unsigned long flags;
 530         bool transitioning_sense = false;
 531
 532         if (!pg->expiry) {
 533                 unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
 534
 535                 if (pg->transition_tmo)
 536                         transition_tmo = pg->transition_tmo * HZ;
 537
 538                 pg->expiry = round_jiffies_up(jiffies + transition_tmo);
 539         }
 540
 541         buff = kzalloc(bufflen, GFP_KERNEL);
 542         if (!buff)
 543                 return SCSI_DH_DEV_TEMP_BUSY;
 544
 545  retry:
 546         err = 0;
 547         retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
 548
 549         if (retval) {
 550                 /*
 551                  * Some (broken) implementations have a habit of returning
 552                  * an error during things like firmware update etc.
 553                  * But if the target only supports active/optimized there's
 554                  * not much we can do; it's not that we can switch paths
 555                  * or anything.
 556                  * So ignore any errors to avoid spurious failures during
 557                  * path failover.
 558                  */
 559                 if ((pg->valid_states & ~TPGS_SUPPORT_OPTIMIZED) == 0) {
 560                         sdev_printk(KERN_INFO, sdev,
 561                                     "%s: ignoring rtpg result %d\n",
 562                                     ALUA_DH_NAME, retval);
 563                         kfree(buff);
 564                         return SCSI_DH_OK;
 565                 }
 566                 if (retval < 0 || !scsi_sense_valid(&sense_hdr)) {
 567                         sdev_printk(KERN_INFO, sdev,
 568                                     "%s: rtpg failed, result %d\n",
 569                                     ALUA_DH_NAME, retval);
 570                         kfree(buff);
 571                         if (retval < 0)
 572                                 return SCSI_DH_DEV_TEMP_BUSY;
 573                         return SCSI_DH_IO;
 574                 }
 575
 576                 /*
 577                  * submit_rtpg() has failed on existing arrays
 578                  * when requesting extended header info, and
 579                  * the array doesn't support extended headers,
 580                  * even though it shouldn't according to T10.
 581                  * The retry without rtpg_ext_hdr_req set
 582                  * handles this.
 583                  * Note:  some arrays return a sense key of ILLEGAL_REQUEST
 584                  * with ASC 00h if they don't support the extended header.
 585                  */
 586                 if (!(pg->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
 587                     sense_hdr.sense_key == ILLEGAL_REQUEST) {
 588                         pg->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
 589                         goto retry;
 590                 }
 591                 /*
 592                  * If the array returns with 'ALUA state transition'
 593                  * sense code here it cannot return RTPG data during
 594                  * transition. So set the state to 'transitioning' directly.
 595                  */
 596                 if (sense_hdr.sense_key == NOT_READY &&
 597                     sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a) {
 598                         transitioning_sense = true;
 599                         goto skip_rtpg;
 600                 }
 601                 /*
 602                  * Retry on any other UNIT ATTENTION occurred.
 603                  */
 604                 if (sense_hdr.sense_key == UNIT_ATTENTION)
 605                         err = SCSI_DH_RETRY;
 606                 if (err == SCSI_DH_RETRY &&
 607                     pg->expiry != 0 && time_before(jiffies, pg->expiry)) {
 608                         sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
 609                                     ALUA_DH_NAME);
 610                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 611                         kfree(buff);
 612                         return err;
 613                 }
 614                 sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
 615                             ALUA_DH_NAME);
 616                 scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 617                 kfree(buff);
 618                 pg->expiry = 0;
 619                 return SCSI_DH_IO;
 620         }
 621
 622         len = get_unaligned_be32(&buff[0]) + 4;
 623
 624         if (len > bufflen) {
 625                 /* Resubmit with the correct length */
 626                 kfree(buff);
 627                 bufflen = len;
 628                 buff = kmalloc(bufflen, GFP_KERNEL);
 629                 if (!buff) {
 630                         sdev_printk(KERN_WARNING, sdev,
 631                                     "%s: kmalloc buffer failed\n",__func__);
 632                         /* Temporary failure, bypass */
 633                         pg->expiry = 0;
 634                         return SCSI_DH_DEV_TEMP_BUSY;
 635                 }
 636                 goto retry;
 637         }
 638
 639         orig_transition_tmo = pg->transition_tmo;
 640         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0)
 641                 pg->transition_tmo = buff[5];
 642         else
 643                 pg->transition_tmo = ALUA_FAILOVER_TIMEOUT;
 644
 645         if (orig_transition_tmo != pg->transition_tmo) {
 646                 sdev_printk(KERN_INFO, sdev,
 647                             "%s: transition timeout set to %d seconds\n",
 648                             ALUA_DH_NAME, pg->transition_tmo);
 649                 pg->expiry = jiffies + pg->transition_tmo * HZ;
 650         }
 651
 652         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
 653                 tpg_desc_tbl_off = 8;
 654         else
 655                 tpg_desc_tbl_off = 4;
 656
 657         for (k = tpg_desc_tbl_off, desc = buff + tpg_desc_tbl_off;
 658              k < len;
 659              k += off, desc += off) {
 660                 u16 group_id = get_unaligned_be16(&desc[2]);
 661
 662                 spin_lock_irqsave(&port_group_lock, flags);
 663                 tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 664                                           group_id);
 665                 spin_unlock_irqrestore(&port_group_lock, flags);
 666                 if (tmp_pg) {
 667                         if (spin_trylock_irqsave(&tmp_pg->lock, flags)) {
 668                                 if ((tmp_pg == pg) ||
 669                                     !(tmp_pg->flags & ALUA_PG_RUNNING)) {
 670                                         struct alua_dh_data *h;
 671
 672                                         tmp_pg->state = desc[0] & 0x0f;
 673                                         tmp_pg->pref = desc[0] >> 7;
 674                                         rcu_read_lock();
 675                                         list_for_each_entry_rcu(h,
 676                                                 &tmp_pg->dh_list, node) {
 677                                                 if (!h->sdev)
 678                                                         continue;
 679                                                 h->sdev->access_state = desc[0];
 680                                         }
 681                                         rcu_read_unlock();
 682                                 }
 683                                 if (tmp_pg == pg)
 684                                         tmp_pg->valid_states = desc[1];
 685                                 spin_unlock_irqrestore(&tmp_pg->lock, flags);
 686                         }
 687                         kref_put(&tmp_pg->kref, release_port_group);
 688                 }
 689                 off = 8 + (desc[7] * 4);
 690         }
 691
 692  skip_rtpg:
 693         spin_lock_irqsave(&pg->lock, flags);
 694         if (transitioning_sense)
 695                 pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
 696
 697         sdev_printk(KERN_INFO, sdev,
 698                     "%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
 699                     ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state),
 700                     pg->pref ? "preferred" : "non-preferred",
 701                     pg->valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
 702                     pg->valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
 703                     pg->valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
 704                     pg->valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
 705                     pg->valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
 706                     pg->valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
 707                     pg->valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
 708
 709         switch (pg->state) {
 710         case SCSI_ACCESS_STATE_TRANSITIONING:
 711                 if (time_before(jiffies, pg->expiry)) {
 712                         /* State transition, retry */
 713                         pg->interval = ALUA_RTPG_RETRY_DELAY;
 714                         err = SCSI_DH_RETRY;
 715                 } else {
 716                         struct alua_dh_data *h;
 717
 718                         /* Transitioning time exceeded, set port to standby */
 719                         err = SCSI_DH_IO;
 720                         pg->state = SCSI_ACCESS_STATE_STANDBY;
 721                         pg->expiry = 0;
 722                         rcu_read_lock();
 723                         list_for_each_entry_rcu(h, &pg->dh_list, node) {
 724                                 if (!h->sdev)
 725                                         continue;
 726                                 h->sdev->access_state =
 727                                         (pg->state & SCSI_ACCESS_STATE_MASK);
 728                                 if (pg->pref)
 729                                         h->sdev->access_state |=
 730                                                 SCSI_ACCESS_STATE_PREFERRED;
 731                         }
 732                         rcu_read_unlock();
 733                 }
 734                 break;
 735         case SCSI_ACCESS_STATE_OFFLINE:
 736                 /* Path unusable */
 737                 err = SCSI_DH_DEV_OFFLINED;
 738                 pg->expiry = 0;
 739                 break;
 740         default:
 741                 /* Useable path if active */
 742                 err = SCSI_DH_OK;
 743                 pg->expiry = 0;
 744                 break;
 745         }
 746         spin_unlock_irqrestore(&pg->lock, flags);
 747         kfree(buff);
 748         return err;
 749 }
 750
 751 /*
 752  * alua_stpg - Issue a SET TARGET PORT GROUP command
 753  *
 754  * Issue a SET TARGET PORT GROUP command and evaluate the
 755  * response. Returns SCSI_DH_RETRY per default to trigger
 756  * a re-evaluation of the target group state or SCSI_DH_OK
 757  * if no further action needs to be taken.
 758  */
 759 static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg)
 760 {
 761         int retval;
 762         struct scsi_sense_hdr sense_hdr;
 763
 764         if (!(pg->tpgs & TPGS_MODE_EXPLICIT)) {
 765                 /* Only implicit ALUA supported, retry */
 766                 return SCSI_DH_RETRY;
 767         }
 768         switch (pg->state) {
 769         case SCSI_ACCESS_STATE_OPTIMAL:
 770                 return SCSI_DH_OK;
 771         case SCSI_ACCESS_STATE_ACTIVE:
 772                 if ((pg->flags & ALUA_OPTIMIZE_STPG) &&
 773                     !pg->pref &&
 774                     (pg->tpgs & TPGS_MODE_IMPLICIT))
 775                         return SCSI_DH_OK;
 776                 break;
 777         case SCSI_ACCESS_STATE_STANDBY:
 778         case SCSI_ACCESS_STATE_UNAVAILABLE:
 779                 break;
 780         case SCSI_ACCESS_STATE_OFFLINE:
 781                 return SCSI_DH_IO;
 782         case SCSI_ACCESS_STATE_TRANSITIONING:
 783                 break;
 784         default:
 785                 sdev_printk(KERN_INFO, sdev,
 786                             "%s: stpg failed, unhandled TPGS state %d",
 787                             ALUA_DH_NAME, pg->state);
 788                 return SCSI_DH_NOSYS;
 789         }
 790         retval = submit_stpg(sdev, pg->group_id, &sense_hdr);
 791
 792         if (retval) {
 793                 if (retval < 0 || !scsi_sense_valid(&sense_hdr)) {
 794                         sdev_printk(KERN_INFO, sdev,
 795                                     "%s: stpg failed, result %d",
 796                                     ALUA_DH_NAME, retval);
 797                         if (retval < 0)
 798                                 return SCSI_DH_DEV_TEMP_BUSY;
 799                 } else {
 800                         sdev_printk(KERN_INFO, sdev, "%s: stpg failed\n",
 801                                     ALUA_DH_NAME);
 802                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 803                 }
 804         }
 805         /* Retry RTPG */
 806         return SCSI_DH_RETRY;
 807 }
 808
 809 static void alua_rtpg_work(struct work_struct *work)
 810 {
 811         struct alua_port_group *pg =
 812                 container_of(work, struct alua_port_group, rtpg_work.work);
 813         struct scsi_device *sdev;
 814         LIST_HEAD(qdata_list);
 815         int err = SCSI_DH_OK;
 816         struct alua_queue_data *qdata, *tmp;
 817         unsigned long flags;
 818
 819         spin_lock_irqsave(&pg->lock, flags);
 820         sdev = pg->rtpg_sdev;
 821         if (!sdev) {
 822                 WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
 823                 WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
 824                 spin_unlock_irqrestore(&pg->lock, flags);
 825                 kref_put(&pg->kref, release_port_group);
 826                 return;
 827         }
 828         pg->flags |= ALUA_PG_RUNNING;
 829         if (pg->flags & ALUA_PG_RUN_RTPG) {
 830                 int state = pg->state;
 831
 832                 pg->flags &= ~ALUA_PG_RUN_RTPG;
 833                 spin_unlock_irqrestore(&pg->lock, flags);
 834                 if (state == SCSI_ACCESS_STATE_TRANSITIONING) {
 835                         if (alua_tur(sdev) == SCSI_DH_RETRY) {
 836                                 spin_lock_irqsave(&pg->lock, flags);
 837                                 pg->flags &= ~ALUA_PG_RUNNING;
 838                                 pg->flags |= ALUA_PG_RUN_RTPG;
 839                                 if (!pg->interval)
 840                                         pg->interval = ALUA_RTPG_RETRY_DELAY;
 841                                 spin_unlock_irqrestore(&pg->lock, flags);
 842                                 queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 843                                                    pg->interval * HZ);
 844                                 return;
 845                         }
 846                         /* Send RTPG on failure or if TUR indicates SUCCESS */
 847                 }
 848                 err = alua_rtpg(sdev, pg);
 849                 spin_lock_irqsave(&pg->lock, flags);
 850                 if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 851                         pg->flags &= ~ALUA_PG_RUNNING;
 852                         if (!pg->interval && !(pg->flags & ALUA_PG_RUN_RTPG))
 853                                 pg->interval = ALUA_RTPG_RETRY_DELAY;
 854                         pg->flags |= ALUA_PG_RUN_RTPG;
 855                         spin_unlock_irqrestore(&pg->lock, flags);
 856                         queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 857                                            pg->interval * HZ);
 858                         return;
 859                 }
 860                 if (err != SCSI_DH_OK)
 861                         pg->flags &= ~ALUA_PG_RUN_STPG;
 862         }
 863         if (pg->flags & ALUA_PG_RUN_STPG) {
 864                 pg->flags &= ~ALUA_PG_RUN_STPG;
 865                 spin_unlock_irqrestore(&pg->lock, flags);
 866                 err = alua_stpg(sdev, pg);
 867                 spin_lock_irqsave(&pg->lock, flags);
 868                 if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 869                         pg->flags |= ALUA_PG_RUN_RTPG;
 870                         pg->interval = 0;
 871                         pg->flags &= ~ALUA_PG_RUNNING;
 872                         spin_unlock_irqrestore(&pg->lock, flags);
 873                         queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 874                                            pg->interval * HZ);
 875                         return;
 876                 }
 877         }
 878
 879         list_splice_init(&pg->rtpg_list, &qdata_list);
 880         pg->rtpg_sdev = NULL;
 881         spin_unlock_irqrestore(&pg->lock, flags);
 882
 883         list_for_each_entry_safe(qdata, tmp, &qdata_list, entry) {
 884                 list_del(&qdata->entry);
 885                 if (qdata->callback_fn)
 886                         qdata->callback_fn(qdata->callback_data, err);
 887                 kfree(qdata);
 888         }
 889         spin_lock_irqsave(&pg->lock, flags);
 890         pg->flags &= ~ALUA_PG_RUNNING;
 891         spin_unlock_irqrestore(&pg->lock, flags);
 892         scsi_device_put(sdev);
 893         kref_put(&pg->kref, release_port_group);
 894 }
 895
 896 /**
 897  * alua_rtpg_queue() - cause RTPG to be submitted asynchronously
 898  * @pg: ALUA port group associated with @sdev.
 899  * @sdev: SCSI device for which to submit an RTPG.
 900  * @qdata: Information about the callback to invoke after the RTPG.
 901  * @force: Whether or not to submit an RTPG if a work item that will submit an
 902  *         RTPG already has been scheduled.
 903  *
 904  * Returns true if and only if alua_rtpg_work() will be called asynchronously.
 905  * That function is responsible for calling @qdata->fn().
 906  */
 907 static bool alua_rtpg_queue(struct alua_port_group *pg,
 908                             struct scsi_device *sdev,
 909                             struct alua_queue_data *qdata, bool force)
 910 {
 911         int start_queue = 0;
 912         unsigned long flags;
 913         if (WARN_ON_ONCE(!pg) || scsi_device_get(sdev))
 914                 return false;
 915
 916         spin_lock_irqsave(&pg->lock, flags);
 917         if (qdata) {
 918                 list_add_tail(&qdata->entry, &pg->rtpg_list);
 919                 pg->flags |= ALUA_PG_RUN_STPG;
 920                 force = true;
 921         }
 922         if (pg->rtpg_sdev == NULL) {
 923                 pg->interval = 0;
 924                 pg->flags |= ALUA_PG_RUN_RTPG;
 925                 kref_get(&pg->kref);
 926                 pg->rtpg_sdev = sdev;
 927                 start_queue = 1;
 928         } else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {
 929                 pg->flags |= ALUA_PG_RUN_RTPG;
 930                 /* Do not queue if the worker is already running */
 931                 if (!(pg->flags & ALUA_PG_RUNNING)) {
 932                         kref_get(&pg->kref);
 933                         start_queue = 1;
 934                 }
 935         }
 936
 937         spin_unlock_irqrestore(&pg->lock, flags);
 938
 939         if (start_queue) {
 940                 if (queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 941                                 msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS)))
 942                         sdev = NULL;
 943                 else
 944                         kref_put(&pg->kref, release_port_group);
 945         }
 946         if (sdev)
 947                 scsi_device_put(sdev);
 948
 949         return true;
 950 }
 951
 952 /*
 953  * alua_initialize - Initialize ALUA state
 954  * @sdev: the device to be initialized
 955  *
 956  * For the prep_fn to work correctly we have
 957  * to initialize the ALUA state for the device.
 958  */
 959 static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 960 {
 961         int err = SCSI_DH_DEV_UNSUPP, tpgs;
 962
 963         mutex_lock(&h->init_mutex);
 964         tpgs = alua_check_tpgs(sdev);
 965         if (tpgs != TPGS_MODE_NONE)
 966                 err = alua_check_vpd(sdev, h, tpgs);
 967         h->init_error = err;
 968         mutex_unlock(&h->init_mutex);
 969         return err;
 970 }
 971 /*
 972  * alua_set_params - set/unset the optimize flag
 973  * @sdev: device on the path to be activated
 974  * params - parameters in the following format
 975  *      "no_of_params\0param1\0param2\0param3\0...\0"
 976  * For example, to set the flag pass the following parameters
 977  * from multipath.conf
 978  *     hardware_handler        "2 alua 1"
 979  */
 980 static int alua_set_params(struct scsi_device *sdev, const char *params)
 981 {
 982         struct alua_dh_data *h = sdev->handler_data;
 983         struct alua_port_group *pg = NULL;
 984         unsigned int optimize = 0, argc;
 985         const char *p = params;
 986         int result = SCSI_DH_OK;
 987         unsigned long flags;
 988
 989         if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
 990                 return -EINVAL;
 991
 992         while (*p++)
 993                 ;
 994         if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
 995                 return -EINVAL;
 996
 997         rcu_read_lock();
 998         pg = rcu_dereference(h->pg);
 999         if (!pg) {
1000                 rcu_read_unlock();
1001                 return -ENXIO;
1002         }
1003         spin_lock_irqsave(&pg->lock, flags);
1004         if (optimize)
1005                 pg->flags |= ALUA_OPTIMIZE_STPG;
1006         else
1007                 pg->flags &= ~ALUA_OPTIMIZE_STPG;
1008         spin_unlock_irqrestore(&pg->lock, flags);
1009         rcu_read_unlock();
1010
1011         return result;
1012 }
1013
1014 /*
1015  * alua_activate - activate a path
1016  * @sdev: device on the path to be activated
1017  *
1018  * We're currently switching the port group to be activated only and
1019  * let the array figure out the rest.
1020  * There may be other arrays which require us to switch all port groups
1021  * based on a certain policy. But until we actually encounter them it
1022  * should be okay.
1023  */
1024 static int alua_activate(struct scsi_device *sdev,
1025                         activate_complete fn, void *data)
1026 {
1027         struct alua_dh_data *h = sdev->handler_data;
1028         int err = SCSI_DH_OK;
1029         struct alua_queue_data *qdata;
1030         struct alua_port_group *pg;
1031
1032         qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
1033         if (!qdata) {
1034                 err = SCSI_DH_RES_TEMP_UNAVAIL;
1035                 goto out;
1036         }
1037         qdata->callback_fn = fn;
1038         qdata->callback_data = data;
1039
1040         mutex_lock(&h->init_mutex);
1041         rcu_read_lock();
1042         pg = rcu_dereference(h->pg);
1043         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1044                 rcu_read_unlock();
1045                 kfree(qdata);
1046                 err = h->init_error;
1047                 mutex_unlock(&h->init_mutex);
1048                 goto out;
1049         }
1050         rcu_read_unlock();
1051         mutex_unlock(&h->init_mutex);
1052
1053         if (alua_rtpg_queue(pg, sdev, qdata, true)) {
1054                 fn = NULL;
1055         } else {
1056                 kfree(qdata);
1057                 err = SCSI_DH_DEV_OFFLINED;
1058         }
1059         kref_put(&pg->kref, release_port_group);
1060 out:
1061         if (fn)
1062                 fn(data, err);
1063         return 0;
1064 }
1065
1066 /*
1067  * alua_check - check path status
1068  * @sdev: device on the path to be checked
1069  *
1070  * Check the device status
1071  */
1072 static void alua_check(struct scsi_device *sdev, bool force)
1073 {
1074         struct alua_dh_data *h = sdev->handler_data;
1075         struct alua_port_group *pg;
1076
1077         rcu_read_lock();
1078         pg = rcu_dereference(h->pg);
1079         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1080                 rcu_read_unlock();
1081                 return;
1082         }
1083         rcu_read_unlock();
1084
1085         alua_rtpg_queue(pg, sdev, NULL, force);
1086         kref_put(&pg->kref, release_port_group);
1087 }
1088
1089 /*
1090  * alua_prep_fn - request callback
1091  *
1092  * Fail I/O to all paths not in state
1093  * active/optimized or active/non-optimized.
1094  */
1095 static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
1096 {
1097         struct alua_dh_data *h = sdev->handler_data;
1098         struct alua_port_group *pg;
1099         unsigned char state = SCSI_ACCESS_STATE_OPTIMAL;
1100         int ret = BLKPREP_OK;
1101
1102         rcu_read_lock();
1103         pg = rcu_dereference(h->pg);
1104         if (pg)
1105                 state = pg->state;
1106         rcu_read_unlock();
1107         if (state == SCSI_ACCESS_STATE_TRANSITIONING)
1108                 ret = BLKPREP_DEFER;
1109         else if (state != SCSI_ACCESS_STATE_OPTIMAL &&
1110                  state != SCSI_ACCESS_STATE_ACTIVE &&
1111                  state != SCSI_ACCESS_STATE_LBA) {
1112                 ret = BLKPREP_KILL;
1113                 req->rq_flags |= RQF_QUIET;
1114         }
1115         return ret;
1116
1117 }
1118
1119 static void alua_rescan(struct scsi_device *sdev)
1120 {
1121         struct alua_dh_data *h = sdev->handler_data;
1122
1123         alua_initialize(sdev, h);
1124 }
1125
1126 /*
1127  * alua_bus_attach - Attach device handler
1128  * @sdev: device to be attached to
1129  */
1130 static int alua_bus_attach(struct scsi_device *sdev)
1131 {
1132         struct alua_dh_data *h;
1133         int err;
1134
1135         h = kzalloc(sizeof(*h) , GFP_KERNEL);
1136         if (!h)
1137                 return SCSI_DH_NOMEM;
1138         spin_lock_init(&h->pg_lock);
1139         rcu_assign_pointer(h->pg, NULL);
1140         h->init_error = SCSI_DH_OK;
1141         h->sdev = sdev;
1142         INIT_LIST_HEAD(&h->node);
1143
1144         mutex_init(&h->init_mutex);
1145         err = alua_initialize(sdev, h);
1146         if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
1147                 goto failed;
1148
1149         sdev->handler_data = h;
1150         return SCSI_DH_OK;
1151 failed:
1152         kfree(h);
1153         return err;
1154 }
1155
1156 /*
1157  * alua_bus_detach - Detach device handler
1158  * @sdev: device to be detached from
1159  */
1160 static void alua_bus_detach(struct scsi_device *sdev)
1161 {
1162         struct alua_dh_data *h = sdev->handler_data;
1163         struct alua_port_group *pg;
1164
1165         spin_lock(&h->pg_lock);
1166         pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
1167         rcu_assign_pointer(h->pg, NULL);
1168         spin_unlock(&h->pg_lock);
1169         if (pg) {
1170                 spin_lock_irq(&pg->lock);
1171                 list_del_rcu(&h->node);
1172                 spin_unlock_irq(&pg->lock);
1173                 kref_put(&pg->kref, release_port_group);
1174         }
1175         sdev->handler_data = NULL;
1176         synchronize_rcu();
1177         kfree(h);
1178 }
1179
1180 static struct scsi_device_handler alua_dh = {
1181         .name = ALUA_DH_NAME,
1182         .module = THIS_MODULE,
1183         .attach = alua_bus_attach,
1184         .detach = alua_bus_detach,
1185         .prep_fn = alua_prep_fn,
1186         .check_sense = alua_check_sense,
1187         .activate = alua_activate,
1188         .rescan = alua_rescan,
1189         .set_params = alua_set_params,
1190 };
1191
1192 static int __init alua_init(void)
1193 {
1194         int r;
1195
1196         kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM, 0);
1197         if (!kaluad_wq)
1198                 return -ENOMEM;
1199
1200         r = scsi_register_device_handler(&alua_dh);
1201         if (r != 0) {
1202                 printk(KERN_ERR "%s: Failed to register scsi device handler",
1203                         ALUA_DH_NAME);
1204                 destroy_workqueue(kaluad_wq);
1205         }
1206         return r;
1207 }
1208
1209 static void __exit alua_exit(void)
1210 {
1211         scsi_unregister_device_handler(&alua_dh);
1212         destroy_workqueue(kaluad_wq);
1213 }
1214
1215 module_init(alua_init);
1216 module_exit(alua_exit);
1217
1218 MODULE_DESCRIPTION("DM Multipath ALUA support");
1219 MODULE_AUTHOR("Hannes Reinecke <hare@suse.de>");
1220 MODULE_LICENSE("GPL");
1221 MODULE_VERSION(ALUA_DH_VER);