drivers/scsi/device_handler/scsi_dh_alua.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Generic SCSI-3 ALUA SCSI Device Handler
   4  *
   5  * Copyright (C) 2007-2010 Hannes Reinecke, SUSE Linux Products GmbH.
   6  * All rights reserved.
   7  */
   8 #include <linux/slab.h>
   9 #include <linux/delay.h>
  10 #include <linux/module.h>
  11 #include <asm/unaligned.h>
  12 #include <scsi/scsi.h>
  13 #include <scsi/scsi_proto.h>
  14 #include <scsi/scsi_dbg.h>
  15 #include <scsi/scsi_eh.h>
  16 #include <scsi/scsi_dh.h>
  17
  18 #define ALUA_DH_NAME "alua"
  19 #define ALUA_DH_VER "2.0"
  20
  21 #define TPGS_SUPPORT_NONE               0x00
  22 #define TPGS_SUPPORT_OPTIMIZED          0x01
  23 #define TPGS_SUPPORT_NONOPTIMIZED       0x02
  24 #define TPGS_SUPPORT_STANDBY            0x04
  25 #define TPGS_SUPPORT_UNAVAILABLE        0x08
  26 #define TPGS_SUPPORT_LBA_DEPENDENT      0x10
  27 #define TPGS_SUPPORT_OFFLINE            0x40
  28 #define TPGS_SUPPORT_TRANSITION         0x80
  29 #define TPGS_SUPPORT_ALL                0xdf
  30
  31 #define RTPG_FMT_MASK                   0x70
  32 #define RTPG_FMT_EXT_HDR                0x10
  33
  34 #define TPGS_MODE_UNINITIALIZED          -1
  35 #define TPGS_MODE_NONE                  0x0
  36 #define TPGS_MODE_IMPLICIT              0x1
  37 #define TPGS_MODE_EXPLICIT              0x2
  38
  39 #define ALUA_RTPG_SIZE                  128
  40 #define ALUA_FAILOVER_TIMEOUT           60
  41 #define ALUA_FAILOVER_RETRIES           5
  42 #define ALUA_RTPG_DELAY_MSECS           5
  43 #define ALUA_RTPG_RETRY_DELAY           2
  44
  45 /* device handler flags */
  46 #define ALUA_OPTIMIZE_STPG              0x01
  47 #define ALUA_RTPG_EXT_HDR_UNSUPP        0x02
  48 /* State machine flags */
  49 #define ALUA_PG_RUN_RTPG                0x10
  50 #define ALUA_PG_RUN_STPG                0x20
  51 #define ALUA_PG_RUNNING                 0x40
  52
  53 static uint optimize_stpg;
  54 module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
  55 MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized path, rather than sending a STPG, when implicit TPGS is supported (0=No,1=Yes). Default is 0.");
  56
  57 static LIST_HEAD(port_group_list);
  58 static DEFINE_SPINLOCK(port_group_lock);
  59 static struct workqueue_struct *kaluad_wq;
  60
  61 struct alua_port_group {
  62         struct kref             kref;
  63         struct rcu_head         rcu;
  64         struct list_head        node;
  65         struct list_head        dh_list;
  66         unsigned char           device_id_str[256];
  67         int                     device_id_len;
  68         int                     group_id;
  69         int                     tpgs;
  70         int                     state;
  71         int                     pref;
  72         int                     valid_states;
  73         unsigned                flags; /* used for optimizing STPG */
  74         unsigned char           transition_tmo;
  75         unsigned long           expiry;
  76         unsigned long           interval;
  77         struct delayed_work     rtpg_work;
  78         spinlock_t              lock;
  79         struct list_head        rtpg_list;
  80         struct scsi_device      *rtpg_sdev;
  81 };
  82
  83 struct alua_dh_data {
  84         struct list_head        node;
  85         struct alua_port_group __rcu *pg;
  86         int                     group_id;
  87         spinlock_t              pg_lock;
  88         struct scsi_device      *sdev;
  89         int                     init_error;
  90         struct mutex            init_mutex;
  91         bool                    disabled;
  92 };
  93
  94 struct alua_queue_data {
  95         struct list_head        entry;
  96         activate_complete       callback_fn;
  97         void                    *callback_data;
  98 };
  99
 100 #define ALUA_POLICY_SWITCH_CURRENT      0
 101 #define ALUA_POLICY_SWITCH_ALL          1
 102
 103 static void alua_rtpg_work(struct work_struct *work);
 104 static bool alua_rtpg_queue(struct alua_port_group *pg,
 105                             struct scsi_device *sdev,
 106                             struct alua_queue_data *qdata, bool force);
 107 static void alua_check(struct scsi_device *sdev, bool force);
 108
 109 static void release_port_group(struct kref *kref)
 110 {
 111         struct alua_port_group *pg;
 112
 113         pg = container_of(kref, struct alua_port_group, kref);
 114         if (pg->rtpg_sdev)
 115                 flush_delayed_work(&pg->rtpg_work);
 116         spin_lock(&port_group_lock);
 117         list_del(&pg->node);
 118         spin_unlock(&port_group_lock);
 119         kfree_rcu(pg, rcu);
 120 }
 121
 122 /*
 123  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
 124  * @sdev: sdev the command should be sent to
 125  */
 126 static int submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
 127                        int bufflen, struct scsi_sense_hdr *sshdr, int flags)
 128 {
 129         u8 cdb[MAX_COMMAND_SIZE];
 130         blk_opf_t req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 131                 REQ_FAILFAST_DRIVER;
 132
 133         /* Prepare the command. */
 134         memset(cdb, 0x0, MAX_COMMAND_SIZE);
 135         cdb[0] = MAINTENANCE_IN;
 136         if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
 137                 cdb[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
 138         else
 139                 cdb[1] = MI_REPORT_TARGET_PGS;
 140         put_unaligned_be32(bufflen, &cdb[6]);
 141
 142         return scsi_execute(sdev, cdb, DMA_FROM_DEVICE, buff, bufflen, NULL,
 143                         sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
 144                         ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
 145 }
 146
 147 /*
 148  * submit_stpg - Issue a SET TARGET PORT GROUP command
 149  *
 150  * Currently we're only setting the current target port group state
 151  * to 'active/optimized' and let the array firmware figure out
 152  * the states of the remaining groups.
 153  */
 154 static int submit_stpg(struct scsi_device *sdev, int group_id,
 155                        struct scsi_sense_hdr *sshdr)
 156 {
 157         u8 cdb[MAX_COMMAND_SIZE];
 158         unsigned char stpg_data[8];
 159         int stpg_len = 8;
 160         blk_opf_t req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 161                 REQ_FAILFAST_DRIVER;
 162
 163         /* Prepare the data buffer */
 164         memset(stpg_data, 0, stpg_len);
 165         stpg_data[4] = SCSI_ACCESS_STATE_OPTIMAL;
 166         put_unaligned_be16(group_id, &stpg_data[6]);
 167
 168         /* Prepare the command. */
 169         memset(cdb, 0x0, MAX_COMMAND_SIZE);
 170         cdb[0] = MAINTENANCE_OUT;
 171         cdb[1] = MO_SET_TARGET_PGS;
 172         put_unaligned_be32(stpg_len, &cdb[6]);
 173
 174         return scsi_execute(sdev, cdb, DMA_TO_DEVICE, stpg_data, stpg_len, NULL,
 175                         sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
 176                         ALUA_FAILOVER_RETRIES, req_flags, 0, NULL);
 177 }
 178
 179 static struct alua_port_group *alua_find_get_pg(char *id_str, size_t id_size,
 180                                                 int group_id)
 181 {
 182         struct alua_port_group *pg;
 183
 184         if (!id_str || !id_size || !strlen(id_str))
 185                 return NULL;
 186
 187         list_for_each_entry(pg, &port_group_list, node) {
 188                 if (pg->group_id != group_id)
 189                         continue;
 190                 if (!pg->device_id_len || pg->device_id_len != id_size)
 191                         continue;
 192                 if (strncmp(pg->device_id_str, id_str, id_size))
 193                         continue;
 194                 if (!kref_get_unless_zero(&pg->kref))
 195                         continue;
 196                 return pg;
 197         }
 198
 199         return NULL;
 200 }
 201
 202 /*
 203  * alua_alloc_pg - Allocate a new port_group structure
 204  * @sdev: scsi device
 205  * @group_id: port group id
 206  * @tpgs: target port group settings
 207  *
 208  * Allocate a new port_group structure for a given
 209  * device.
 210  */
 211 static struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
 212                                              int group_id, int tpgs)
 213 {
 214         struct alua_port_group *pg, *tmp_pg;
 215
 216         pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL);
 217         if (!pg)
 218                 return ERR_PTR(-ENOMEM);
 219
 220         pg->device_id_len = scsi_vpd_lun_id(sdev, pg->device_id_str,
 221                                             sizeof(pg->device_id_str));
 222         if (pg->device_id_len <= 0) {
 223                 /*
 224                  * TPGS supported but no device identification found.
 225                  * Generate private device identification.
 226                  */
 227                 sdev_printk(KERN_INFO, sdev,
 228                             "%s: No device descriptors found\n",
 229                             ALUA_DH_NAME);
 230                 pg->device_id_str[0] = '\0';
 231                 pg->device_id_len = 0;
 232         }
 233         pg->group_id = group_id;
 234         pg->tpgs = tpgs;
 235         pg->state = SCSI_ACCESS_STATE_OPTIMAL;
 236         pg->valid_states = TPGS_SUPPORT_ALL;
 237         if (optimize_stpg)
 238                 pg->flags |= ALUA_OPTIMIZE_STPG;
 239         kref_init(&pg->kref);
 240         INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
 241         INIT_LIST_HEAD(&pg->rtpg_list);
 242         INIT_LIST_HEAD(&pg->node);
 243         INIT_LIST_HEAD(&pg->dh_list);
 244         spin_lock_init(&pg->lock);
 245
 246         spin_lock(&port_group_lock);
 247         tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 248                                   group_id);
 249         if (tmp_pg) {
 250                 spin_unlock(&port_group_lock);
 251                 kfree(pg);
 252                 return tmp_pg;
 253         }
 254
 255         list_add(&pg->node, &port_group_list);
 256         spin_unlock(&port_group_lock);
 257
 258         return pg;
 259 }
 260
 261 /*
 262  * alua_check_tpgs - Evaluate TPGS setting
 263  * @sdev: device to be checked
 264  *
 265  * Examine the TPGS setting of the sdev to find out if ALUA
 266  * is supported.
 267  */
 268 static int alua_check_tpgs(struct scsi_device *sdev)
 269 {
 270         int tpgs = TPGS_MODE_NONE;
 271
 272         /*
 273          * ALUA support for non-disk devices is fraught with
 274          * difficulties, so disable it for now.
 275          */
 276         if (sdev->type != TYPE_DISK) {
 277                 sdev_printk(KERN_INFO, sdev,
 278                             "%s: disable for non-disk devices\n",
 279                             ALUA_DH_NAME);
 280                 return tpgs;
 281         }
 282
 283         tpgs = scsi_device_tpgs(sdev);
 284         switch (tpgs) {
 285         case TPGS_MODE_EXPLICIT|TPGS_MODE_IMPLICIT:
 286                 sdev_printk(KERN_INFO, sdev,
 287                             "%s: supports implicit and explicit TPGS\n",
 288                             ALUA_DH_NAME);
 289                 break;
 290         case TPGS_MODE_EXPLICIT:
 291                 sdev_printk(KERN_INFO, sdev, "%s: supports explicit TPGS\n",
 292                             ALUA_DH_NAME);
 293                 break;
 294         case TPGS_MODE_IMPLICIT:
 295                 sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n",
 296                             ALUA_DH_NAME);
 297                 break;
 298         case TPGS_MODE_NONE:
 299                 sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
 300                             ALUA_DH_NAME);
 301                 break;
 302         default:
 303                 sdev_printk(KERN_INFO, sdev,
 304                             "%s: unsupported TPGS setting %d\n",
 305                             ALUA_DH_NAME, tpgs);
 306                 tpgs = TPGS_MODE_NONE;
 307                 break;
 308         }
 309
 310         return tpgs;
 311 }
 312
 313 /*
 314  * alua_check_vpd - Evaluate INQUIRY vpd page 0x83
 315  * @sdev: device to be checked
 316  *
 317  * Extract the relative target port and the target port group
 318  * descriptor from the list of identificators.
 319  */
 320 static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 321                           int tpgs)
 322 {
 323         int rel_port = -1, group_id;
 324         struct alua_port_group *pg, *old_pg = NULL;
 325         bool pg_updated = false;
 326         unsigned long flags;
 327
 328         group_id = scsi_vpd_tpg_id(sdev, &rel_port);
 329         if (group_id < 0) {
 330                 /*
 331                  * Internal error; TPGS supported but required
 332                  * VPD identification descriptors not present.
 333                  * Disable ALUA support
 334                  */
 335                 sdev_printk(KERN_INFO, sdev,
 336                             "%s: No target port descriptors found\n",
 337                             ALUA_DH_NAME);
 338                 return SCSI_DH_DEV_UNSUPP;
 339         }
 340
 341         pg = alua_alloc_pg(sdev, group_id, tpgs);
 342         if (IS_ERR(pg)) {
 343                 if (PTR_ERR(pg) == -ENOMEM)
 344                         return SCSI_DH_NOMEM;
 345                 return SCSI_DH_DEV_UNSUPP;
 346         }
 347         if (pg->device_id_len)
 348                 sdev_printk(KERN_INFO, sdev,
 349                             "%s: device %s port group %x rel port %x\n",
 350                             ALUA_DH_NAME, pg->device_id_str,
 351                             group_id, rel_port);
 352         else
 353                 sdev_printk(KERN_INFO, sdev,
 354                             "%s: port group %x rel port %x\n",
 355                             ALUA_DH_NAME, group_id, rel_port);
 356
 357         kref_get(&pg->kref);
 358
 359         /* Check for existing port group references */
 360         spin_lock(&h->pg_lock);
 361         old_pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
 362         if (old_pg != pg) {
 363                 /* port group has changed. Update to new port group */
 364                 if (h->pg) {
 365                         spin_lock_irqsave(&old_pg->lock, flags);
 366                         list_del_rcu(&h->node);
 367                         spin_unlock_irqrestore(&old_pg->lock, flags);
 368                 }
 369                 rcu_assign_pointer(h->pg, pg);
 370                 pg_updated = true;
 371         }
 372
 373         spin_lock_irqsave(&pg->lock, flags);
 374         if (pg_updated)
 375                 list_add_rcu(&h->node, &pg->dh_list);
 376         spin_unlock_irqrestore(&pg->lock, flags);
 377
 378         spin_unlock(&h->pg_lock);
 379
 380         alua_rtpg_queue(pg, sdev, NULL, true);
 381         kref_put(&pg->kref, release_port_group);
 382
 383         if (old_pg)
 384                 kref_put(&old_pg->kref, release_port_group);
 385
 386         return SCSI_DH_OK;
 387 }
 388
 389 static char print_alua_state(unsigned char state)
 390 {
 391         switch (state) {
 392         case SCSI_ACCESS_STATE_OPTIMAL:
 393                 return 'A';
 394         case SCSI_ACCESS_STATE_ACTIVE:
 395                 return 'N';
 396         case SCSI_ACCESS_STATE_STANDBY:
 397                 return 'S';
 398         case SCSI_ACCESS_STATE_UNAVAILABLE:
 399                 return 'U';
 400         case SCSI_ACCESS_STATE_LBA:
 401                 return 'L';
 402         case SCSI_ACCESS_STATE_OFFLINE:
 403                 return 'O';
 404         case SCSI_ACCESS_STATE_TRANSITIONING:
 405                 return 'T';
 406         default:
 407                 return 'X';
 408         }
 409 }
 410
 411 static enum scsi_disposition alua_check_sense(struct scsi_device *sdev,
 412                                               struct scsi_sense_hdr *sense_hdr)
 413 {
 414         struct alua_dh_data *h = sdev->handler_data;
 415         struct alua_port_group *pg;
 416
 417         switch (sense_hdr->sense_key) {
 418         case NOT_READY:
 419                 if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
 420                         /*
 421                          * LUN Not Accessible - ALUA state transition
 422                          */
 423                         rcu_read_lock();
 424                         pg = rcu_dereference(h->pg);
 425                         if (pg)
 426                                 pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
 427                         rcu_read_unlock();
 428                         alua_check(sdev, false);
 429                         return NEEDS_RETRY;
 430                 }
 431                 break;
 432         case UNIT_ATTENTION:
 433                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
 434                         /*
 435                          * Power On, Reset, or Bus Device Reset.
 436                          * Might have obscured a state transition,
 437                          * so schedule a recheck.
 438                          */
 439                         alua_check(sdev, true);
 440                         return ADD_TO_MLQUEUE;
 441                 }
 442                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
 443                         /*
 444                          * Device internal reset
 445                          */
 446                         return ADD_TO_MLQUEUE;
 447                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
 448                         /*
 449                          * Mode Parameters Changed
 450                          */
 451                         return ADD_TO_MLQUEUE;
 452                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
 453                         /*
 454                          * ALUA state changed
 455                          */
 456                         alua_check(sdev, true);
 457                         return ADD_TO_MLQUEUE;
 458                 }
 459                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
 460                         /*
 461                          * Implicit ALUA state transition failed
 462                          */
 463                         alua_check(sdev, true);
 464                         return ADD_TO_MLQUEUE;
 465                 }
 466                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
 467                         /*
 468                          * Inquiry data has changed
 469                          */
 470                         return ADD_TO_MLQUEUE;
 471                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x0e)
 472                         /*
 473                          * REPORTED_LUNS_DATA_HAS_CHANGED is reported
 474                          * when switching controllers on targets like
 475                          * Intel Multi-Flex. We can just retry.
 476                          */
 477                         return ADD_TO_MLQUEUE;
 478                 break;
 479         }
 480
 481         return SCSI_RETURN_NOT_HANDLED;
 482 }
 483
 484 /*
 485  * alua_tur - Send a TEST UNIT READY
 486  * @sdev: device to which the TEST UNIT READY command should be send
 487  *
 488  * Send a TEST UNIT READY to @sdev to figure out the device state
 489  * Returns SCSI_DH_RETRY if the sense code is NOT READY/ALUA TRANSITIONING,
 490  * SCSI_DH_OK if no error occurred, and SCSI_DH_IO otherwise.
 491  */
 492 static int alua_tur(struct scsi_device *sdev)
 493 {
 494         struct scsi_sense_hdr sense_hdr;
 495         int retval;
 496
 497         retval = scsi_test_unit_ready(sdev, ALUA_FAILOVER_TIMEOUT * HZ,
 498                                       ALUA_FAILOVER_RETRIES, &sense_hdr);
 499         if (sense_hdr.sense_key == NOT_READY &&
 500             sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
 501                 return SCSI_DH_RETRY;
 502         else if (retval)
 503                 return SCSI_DH_IO;
 504         else
 505                 return SCSI_DH_OK;
 506 }
 507
 508 /*
 509  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
 510  * @sdev: the device to be evaluated.
 511  *
 512  * Evaluate the Target Port Group State.
 513  * Returns SCSI_DH_DEV_OFFLINED if the path is
 514  * found to be unusable.
 515  */
 516 static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 517 {
 518         struct scsi_sense_hdr sense_hdr;
 519         struct alua_port_group *tmp_pg;
 520         int len, k, off, bufflen = ALUA_RTPG_SIZE;
 521         int group_id_old, state_old, pref_old, valid_states_old;
 522         unsigned char *desc, *buff;
 523         unsigned err;
 524         int retval;
 525         unsigned int tpg_desc_tbl_off;
 526         unsigned char orig_transition_tmo;
 527         unsigned long flags;
 528         bool transitioning_sense = false;
 529
 530         group_id_old = pg->group_id;
 531         state_old = pg->state;
 532         pref_old = pg->pref;
 533         valid_states_old = pg->valid_states;
 534
 535         if (!pg->expiry) {
 536                 unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
 537
 538                 if (pg->transition_tmo)
 539                         transition_tmo = pg->transition_tmo * HZ;
 540
 541                 pg->expiry = round_jiffies_up(jiffies + transition_tmo);
 542         }
 543
 544         buff = kzalloc(bufflen, GFP_KERNEL);
 545         if (!buff)
 546                 return SCSI_DH_DEV_TEMP_BUSY;
 547
 548  retry:
 549         err = 0;
 550         retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
 551
 552         if (retval) {
 553                 /*
 554                  * Some (broken) implementations have a habit of returning
 555                  * an error during things like firmware update etc.
 556                  * But if the target only supports active/optimized there's
 557                  * not much we can do; it's not that we can switch paths
 558                  * or anything.
 559                  * So ignore any errors to avoid spurious failures during
 560                  * path failover.
 561                  */
 562                 if ((pg->valid_states & ~TPGS_SUPPORT_OPTIMIZED) == 0) {
 563                         sdev_printk(KERN_INFO, sdev,
 564                                     "%s: ignoring rtpg result %d\n",
 565                                     ALUA_DH_NAME, retval);
 566                         kfree(buff);
 567                         return SCSI_DH_OK;
 568                 }
 569                 if (retval < 0 || !scsi_sense_valid(&sense_hdr)) {
 570                         sdev_printk(KERN_INFO, sdev,
 571                                     "%s: rtpg failed, result %d\n",
 572                                     ALUA_DH_NAME, retval);
 573                         kfree(buff);
 574                         if (retval < 0)
 575                                 return SCSI_DH_DEV_TEMP_BUSY;
 576                         if (host_byte(retval) == DID_NO_CONNECT)
 577                                 return SCSI_DH_RES_TEMP_UNAVAIL;
 578                         return SCSI_DH_IO;
 579                 }
 580
 581                 /*
 582                  * submit_rtpg() has failed on existing arrays
 583                  * when requesting extended header info, and
 584                  * the array doesn't support extended headers,
 585                  * even though it shouldn't according to T10.
 586                  * The retry without rtpg_ext_hdr_req set
 587                  * handles this.
 588                  * Note:  some arrays return a sense key of ILLEGAL_REQUEST
 589                  * with ASC 00h if they don't support the extended header.
 590                  */
 591                 if (!(pg->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
 592                     sense_hdr.sense_key == ILLEGAL_REQUEST) {
 593                         pg->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
 594                         goto retry;
 595                 }
 596                 /*
 597                  * If the array returns with 'ALUA state transition'
 598                  * sense code here it cannot return RTPG data during
 599                  * transition. So set the state to 'transitioning' directly.
 600                  */
 601                 if (sense_hdr.sense_key == NOT_READY &&
 602                     sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a) {
 603                         transitioning_sense = true;
 604                         goto skip_rtpg;
 605                 }
 606                 /*
 607                  * Retry on any other UNIT ATTENTION occurred.
 608                  */
 609                 if (sense_hdr.sense_key == UNIT_ATTENTION)
 610                         err = SCSI_DH_RETRY;
 611                 if (err == SCSI_DH_RETRY &&
 612                     pg->expiry != 0 && time_before(jiffies, pg->expiry)) {
 613                         sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
 614                                     ALUA_DH_NAME);
 615                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 616                         kfree(buff);
 617                         return err;
 618                 }
 619                 sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
 620                             ALUA_DH_NAME);
 621                 scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 622                 kfree(buff);
 623                 pg->expiry = 0;
 624                 return SCSI_DH_IO;
 625         }
 626
 627         len = get_unaligned_be32(&buff[0]) + 4;
 628
 629         if (len > bufflen) {
 630                 /* Resubmit with the correct length */
 631                 kfree(buff);
 632                 bufflen = len;
 633                 buff = kmalloc(bufflen, GFP_KERNEL);
 634                 if (!buff) {
 635                         sdev_printk(KERN_WARNING, sdev,
 636                                     "%s: kmalloc buffer failed\n",__func__);
 637                         /* Temporary failure, bypass */
 638                         pg->expiry = 0;
 639                         return SCSI_DH_DEV_TEMP_BUSY;
 640                 }
 641                 goto retry;
 642         }
 643
 644         orig_transition_tmo = pg->transition_tmo;
 645         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0)
 646                 pg->transition_tmo = buff[5];
 647         else
 648                 pg->transition_tmo = ALUA_FAILOVER_TIMEOUT;
 649
 650         if (orig_transition_tmo != pg->transition_tmo) {
 651                 sdev_printk(KERN_INFO, sdev,
 652                             "%s: transition timeout set to %d seconds\n",
 653                             ALUA_DH_NAME, pg->transition_tmo);
 654                 pg->expiry = jiffies + pg->transition_tmo * HZ;
 655         }
 656
 657         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
 658                 tpg_desc_tbl_off = 8;
 659         else
 660                 tpg_desc_tbl_off = 4;
 661
 662         for (k = tpg_desc_tbl_off, desc = buff + tpg_desc_tbl_off;
 663              k < len;
 664              k += off, desc += off) {
 665                 u16 group_id = get_unaligned_be16(&desc[2]);
 666
 667                 spin_lock_irqsave(&port_group_lock, flags);
 668                 tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 669                                           group_id);
 670                 spin_unlock_irqrestore(&port_group_lock, flags);
 671                 if (tmp_pg) {
 672                         if (spin_trylock_irqsave(&tmp_pg->lock, flags)) {
 673                                 if ((tmp_pg == pg) ||
 674                                     !(tmp_pg->flags & ALUA_PG_RUNNING)) {
 675                                         struct alua_dh_data *h;
 676
 677                                         tmp_pg->state = desc[0] & 0x0f;
 678                                         tmp_pg->pref = desc[0] >> 7;
 679                                         rcu_read_lock();
 680                                         list_for_each_entry_rcu(h,
 681                                                 &tmp_pg->dh_list, node) {
 682                                                 if (!h->sdev)
 683                                                         continue;
 684                                                 h->sdev->access_state = desc[0];
 685                                         }
 686                                         rcu_read_unlock();
 687                                 }
 688                                 if (tmp_pg == pg)
 689                                         tmp_pg->valid_states = desc[1];
 690                                 spin_unlock_irqrestore(&tmp_pg->lock, flags);
 691                         }
 692                         kref_put(&tmp_pg->kref, release_port_group);
 693                 }
 694                 off = 8 + (desc[7] * 4);
 695         }
 696
 697  skip_rtpg:
 698         spin_lock_irqsave(&pg->lock, flags);
 699         if (transitioning_sense)
 700                 pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
 701
 702         if (group_id_old != pg->group_id || state_old != pg->state ||
 703                 pref_old != pg->pref || valid_states_old != pg->valid_states)
 704                 sdev_printk(KERN_INFO, sdev,
 705                         "%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
 706                         ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state),
 707                         pg->pref ? "preferred" : "non-preferred",
 708                         pg->valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
 709                         pg->valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
 710                         pg->valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
 711                         pg->valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
 712                         pg->valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
 713                         pg->valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
 714                         pg->valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
 715
 716         switch (pg->state) {
 717         case SCSI_ACCESS_STATE_TRANSITIONING:
 718                 if (time_before(jiffies, pg->expiry)) {
 719                         /* State transition, retry */
 720                         pg->interval = ALUA_RTPG_RETRY_DELAY;
 721                         err = SCSI_DH_RETRY;
 722                 } else {
 723                         struct alua_dh_data *h;
 724
 725                         /* Transitioning time exceeded, set port to standby */
 726                         err = SCSI_DH_IO;
 727                         pg->state = SCSI_ACCESS_STATE_STANDBY;
 728                         pg->expiry = 0;
 729                         rcu_read_lock();
 730                         list_for_each_entry_rcu(h, &pg->dh_list, node) {
 731                                 if (!h->sdev)
 732                                         continue;
 733                                 h->sdev->access_state =
 734                                         (pg->state & SCSI_ACCESS_STATE_MASK);
 735                                 if (pg->pref)
 736                                         h->sdev->access_state |=
 737                                                 SCSI_ACCESS_STATE_PREFERRED;
 738                         }
 739                         rcu_read_unlock();
 740                 }
 741                 break;
 742         case SCSI_ACCESS_STATE_OFFLINE:
 743                 /* Path unusable */
 744                 err = SCSI_DH_DEV_OFFLINED;
 745                 pg->expiry = 0;
 746                 break;
 747         default:
 748                 /* Useable path if active */
 749                 err = SCSI_DH_OK;
 750                 pg->expiry = 0;
 751                 break;
 752         }
 753         spin_unlock_irqrestore(&pg->lock, flags);
 754         kfree(buff);
 755         return err;
 756 }
 757
 758 /*
 759  * alua_stpg - Issue a SET TARGET PORT GROUP command
 760  *
 761  * Issue a SET TARGET PORT GROUP command and evaluate the
 762  * response. Returns SCSI_DH_RETRY per default to trigger
 763  * a re-evaluation of the target group state or SCSI_DH_OK
 764  * if no further action needs to be taken.
 765  */
 766 static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg)
 767 {
 768         int retval;
 769         struct scsi_sense_hdr sense_hdr;
 770
 771         if (!(pg->tpgs & TPGS_MODE_EXPLICIT)) {
 772                 /* Only implicit ALUA supported, retry */
 773                 return SCSI_DH_RETRY;
 774         }
 775         switch (pg->state) {
 776         case SCSI_ACCESS_STATE_OPTIMAL:
 777                 return SCSI_DH_OK;
 778         case SCSI_ACCESS_STATE_ACTIVE:
 779                 if ((pg->flags & ALUA_OPTIMIZE_STPG) &&
 780                     !pg->pref &&
 781                     (pg->tpgs & TPGS_MODE_IMPLICIT))
 782                         return SCSI_DH_OK;
 783                 break;
 784         case SCSI_ACCESS_STATE_STANDBY:
 785         case SCSI_ACCESS_STATE_UNAVAILABLE:
 786                 break;
 787         case SCSI_ACCESS_STATE_OFFLINE:
 788                 return SCSI_DH_IO;
 789         case SCSI_ACCESS_STATE_TRANSITIONING:
 790                 break;
 791         default:
 792                 sdev_printk(KERN_INFO, sdev,
 793                             "%s: stpg failed, unhandled TPGS state %d",
 794                             ALUA_DH_NAME, pg->state);
 795                 return SCSI_DH_NOSYS;
 796         }
 797         retval = submit_stpg(sdev, pg->group_id, &sense_hdr);
 798
 799         if (retval) {
 800                 if (retval < 0 || !scsi_sense_valid(&sense_hdr)) {
 801                         sdev_printk(KERN_INFO, sdev,
 802                                     "%s: stpg failed, result %d",
 803                                     ALUA_DH_NAME, retval);
 804                         if (retval < 0)
 805                                 return SCSI_DH_DEV_TEMP_BUSY;
 806                 } else {
 807                         sdev_printk(KERN_INFO, sdev, "%s: stpg failed\n",
 808                                     ALUA_DH_NAME);
 809                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 810                 }
 811         }
 812         /* Retry RTPG */
 813         return SCSI_DH_RETRY;
 814 }
 815
 816 /*
 817  * The caller must call scsi_device_put() on the returned pointer if it is not
 818  * NULL.
 819  */
 820 static struct scsi_device * __must_check
 821 alua_rtpg_select_sdev(struct alua_port_group *pg)
 822 {
 823         struct alua_dh_data *h;
 824         struct scsi_device *sdev = NULL, *prev_sdev;
 825
 826         lockdep_assert_held(&pg->lock);
 827         if (WARN_ON(!pg->rtpg_sdev))
 828                 return NULL;
 829
 830         /*
 831          * RCU protection isn't necessary for dh_list here
 832          * as we hold pg->lock, but for access to h->pg.
 833          */
 834         rcu_read_lock();
 835         list_for_each_entry_rcu(h, &pg->dh_list, node) {
 836                 if (!h->sdev)
 837                         continue;
 838                 if (h->sdev == pg->rtpg_sdev) {
 839                         h->disabled = true;
 840                         continue;
 841                 }
 842                 if (rcu_dereference(h->pg) == pg &&
 843                     !h->disabled &&
 844                     !scsi_device_get(h->sdev)) {
 845                         sdev = h->sdev;
 846                         break;
 847                 }
 848         }
 849         rcu_read_unlock();
 850
 851         if (!sdev) {
 852                 pr_warn("%s: no device found for rtpg\n",
 853                         (pg->device_id_len ?
 854                          (char *)pg->device_id_str : "(nameless PG)"));
 855                 return NULL;
 856         }
 857
 858         sdev_printk(KERN_INFO, sdev, "rtpg retry on different device\n");
 859
 860         prev_sdev = pg->rtpg_sdev;
 861         pg->rtpg_sdev = sdev;
 862
 863         return prev_sdev;
 864 }
 865
 866 static void alua_rtpg_work(struct work_struct *work)
 867 {
 868         struct alua_port_group *pg =
 869                 container_of(work, struct alua_port_group, rtpg_work.work);
 870         struct scsi_device *sdev, *prev_sdev = NULL;
 871         LIST_HEAD(qdata_list);
 872         int err = SCSI_DH_OK;
 873         struct alua_queue_data *qdata, *tmp;
 874         struct alua_dh_data *h;
 875         unsigned long flags;
 876
 877         spin_lock_irqsave(&pg->lock, flags);
 878         sdev = pg->rtpg_sdev;
 879         if (!sdev) {
 880                 WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
 881                 WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
 882                 spin_unlock_irqrestore(&pg->lock, flags);
 883                 kref_put(&pg->kref, release_port_group);
 884                 return;
 885         }
 886         pg->flags |= ALUA_PG_RUNNING;
 887         if (pg->flags & ALUA_PG_RUN_RTPG) {
 888                 int state = pg->state;
 889
 890                 pg->flags &= ~ALUA_PG_RUN_RTPG;
 891                 spin_unlock_irqrestore(&pg->lock, flags);
 892                 if (state == SCSI_ACCESS_STATE_TRANSITIONING) {
 893                         if (alua_tur(sdev) == SCSI_DH_RETRY) {
 894                                 spin_lock_irqsave(&pg->lock, flags);
 895                                 pg->flags &= ~ALUA_PG_RUNNING;
 896                                 pg->flags |= ALUA_PG_RUN_RTPG;
 897                                 if (!pg->interval)
 898                                         pg->interval = ALUA_RTPG_RETRY_DELAY;
 899                                 spin_unlock_irqrestore(&pg->lock, flags);
 900                                 queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 901                                                    pg->interval * HZ);
 902                                 return;
 903                         }
 904                         /* Send RTPG on failure or if TUR indicates SUCCESS */
 905                 }
 906                 err = alua_rtpg(sdev, pg);
 907                 spin_lock_irqsave(&pg->lock, flags);
 908
 909                 /* If RTPG failed on the current device, try using another */
 910                 if (err == SCSI_DH_RES_TEMP_UNAVAIL &&
 911                     (prev_sdev = alua_rtpg_select_sdev(pg)))
 912                         err = SCSI_DH_IMM_RETRY;
 913
 914                 if (err == SCSI_DH_RETRY || err == SCSI_DH_IMM_RETRY ||
 915                     pg->flags & ALUA_PG_RUN_RTPG) {
 916                         pg->flags &= ~ALUA_PG_RUNNING;
 917                         if (err == SCSI_DH_IMM_RETRY)
 918                                 pg->interval = 0;
 919                         else if (!pg->interval && !(pg->flags & ALUA_PG_RUN_RTPG))
 920                                 pg->interval = ALUA_RTPG_RETRY_DELAY;
 921                         pg->flags |= ALUA_PG_RUN_RTPG;
 922                         spin_unlock_irqrestore(&pg->lock, flags);
 923                         goto queue_rtpg;
 924                 }
 925                 if (err != SCSI_DH_OK)
 926                         pg->flags &= ~ALUA_PG_RUN_STPG;
 927         }
 928         if (pg->flags & ALUA_PG_RUN_STPG) {
 929                 pg->flags &= ~ALUA_PG_RUN_STPG;
 930                 spin_unlock_irqrestore(&pg->lock, flags);
 931                 err = alua_stpg(sdev, pg);
 932                 spin_lock_irqsave(&pg->lock, flags);
 933                 if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 934                         pg->flags |= ALUA_PG_RUN_RTPG;
 935                         pg->interval = 0;
 936                         pg->flags &= ~ALUA_PG_RUNNING;
 937                         spin_unlock_irqrestore(&pg->lock, flags);
 938                         goto queue_rtpg;
 939                 }
 940         }
 941
 942         list_splice_init(&pg->rtpg_list, &qdata_list);
 943         /*
 944          * We went through an RTPG, for good or bad.
 945          * Re-enable all devices for the next attempt.
 946          */
 947         list_for_each_entry(h, &pg->dh_list, node)
 948                 h->disabled = false;
 949         pg->rtpg_sdev = NULL;
 950         spin_unlock_irqrestore(&pg->lock, flags);
 951
 952         if (prev_sdev)
 953                 scsi_device_put(prev_sdev);
 954
 955         list_for_each_entry_safe(qdata, tmp, &qdata_list, entry) {
 956                 list_del(&qdata->entry);
 957                 if (qdata->callback_fn)
 958                         qdata->callback_fn(qdata->callback_data, err);
 959                 kfree(qdata);
 960         }
 961         spin_lock_irqsave(&pg->lock, flags);
 962         pg->flags &= ~ALUA_PG_RUNNING;
 963         spin_unlock_irqrestore(&pg->lock, flags);
 964         scsi_device_put(sdev);
 965         kref_put(&pg->kref, release_port_group);
 966         return;
 967
 968 queue_rtpg:
 969         if (prev_sdev)
 970                 scsi_device_put(prev_sdev);
 971         queue_delayed_work(kaluad_wq, &pg->rtpg_work, pg->interval * HZ);
 972 }
 973
 974 /**
 975  * alua_rtpg_queue() - cause RTPG to be submitted asynchronously
 976  * @pg: ALUA port group associated with @sdev.
 977  * @sdev: SCSI device for which to submit an RTPG.
 978  * @qdata: Information about the callback to invoke after the RTPG.
 979  * @force: Whether or not to submit an RTPG if a work item that will submit an
 980  *         RTPG already has been scheduled.
 981  *
 982  * Returns true if and only if alua_rtpg_work() will be called asynchronously.
 983  * That function is responsible for calling @qdata->fn().
 984  *
 985  * Context: may be called from atomic context (alua_check()) only if the caller
 986  *      holds an sdev reference.
 987  */
 988 static bool alua_rtpg_queue(struct alua_port_group *pg,
 989                             struct scsi_device *sdev,
 990                             struct alua_queue_data *qdata, bool force)
 991 {
 992         int start_queue = 0;
 993         unsigned long flags;
 994
 995         if (WARN_ON_ONCE(!pg) || scsi_device_get(sdev))
 996                 return false;
 997
 998         spin_lock_irqsave(&pg->lock, flags);
 999         if (qdata) {
1000                 list_add_tail(&qdata->entry, &pg->rtpg_list);
1001                 pg->flags |= ALUA_PG_RUN_STPG;
1002                 force = true;
1003         }
1004         if (pg->rtpg_sdev == NULL) {
1005                 struct alua_dh_data *h = sdev->handler_data;
1006
1007                 rcu_read_lock();
1008                 if (h && rcu_dereference(h->pg) == pg) {
1009                         pg->interval = 0;
1010                         pg->flags |= ALUA_PG_RUN_RTPG;
1011                         kref_get(&pg->kref);
1012                         pg->rtpg_sdev = sdev;
1013                         start_queue = 1;
1014                 }
1015                 rcu_read_unlock();
1016         } else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {
1017                 pg->flags |= ALUA_PG_RUN_RTPG;
1018                 /* Do not queue if the worker is already running */
1019                 if (!(pg->flags & ALUA_PG_RUNNING)) {
1020                         kref_get(&pg->kref);
1021                         start_queue = 1;
1022                 }
1023         }
1024
1025         spin_unlock_irqrestore(&pg->lock, flags);
1026
1027         if (start_queue) {
1028                 if (queue_delayed_work(kaluad_wq, &pg->rtpg_work,
1029                                 msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS)))
1030                         sdev = NULL;
1031                 else
1032                         kref_put(&pg->kref, release_port_group);
1033         }
1034         if (sdev)
1035                 scsi_device_put(sdev);
1036
1037         return true;
1038 }
1039
1040 /*
1041  * alua_initialize - Initialize ALUA state
1042  * @sdev: the device to be initialized
1043  *
1044  * For the prep_fn to work correctly we have
1045  * to initialize the ALUA state for the device.
1046  */
1047 static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
1048 {
1049         int err = SCSI_DH_DEV_UNSUPP, tpgs;
1050
1051         mutex_lock(&h->init_mutex);
1052         h->disabled = false;
1053         tpgs = alua_check_tpgs(sdev);
1054         if (tpgs != TPGS_MODE_NONE)
1055                 err = alua_check_vpd(sdev, h, tpgs);
1056         h->init_error = err;
1057         mutex_unlock(&h->init_mutex);
1058         return err;
1059 }
1060 /*
1061  * alua_set_params - set/unset the optimize flag
1062  * @sdev: device on the path to be activated
1063  * params - parameters in the following format
1064  *      "no_of_params\0param1\0param2\0param3\0...\0"
1065  * For example, to set the flag pass the following parameters
1066  * from multipath.conf
1067  *     hardware_handler        "2 alua 1"
1068  */
1069 static int alua_set_params(struct scsi_device *sdev, const char *params)
1070 {
1071         struct alua_dh_data *h = sdev->handler_data;
1072         struct alua_port_group *pg = NULL;
1073         unsigned int optimize = 0, argc;
1074         const char *p = params;
1075         int result = SCSI_DH_OK;
1076         unsigned long flags;
1077
1078         if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
1079                 return -EINVAL;
1080
1081         while (*p++)
1082                 ;
1083         if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
1084                 return -EINVAL;
1085
1086         rcu_read_lock();
1087         pg = rcu_dereference(h->pg);
1088         if (!pg) {
1089                 rcu_read_unlock();
1090                 return -ENXIO;
1091         }
1092         spin_lock_irqsave(&pg->lock, flags);
1093         if (optimize)
1094                 pg->flags |= ALUA_OPTIMIZE_STPG;
1095         else
1096                 pg->flags &= ~ALUA_OPTIMIZE_STPG;
1097         spin_unlock_irqrestore(&pg->lock, flags);
1098         rcu_read_unlock();
1099
1100         return result;
1101 }
1102
1103 /*
1104  * alua_activate - activate a path
1105  * @sdev: device on the path to be activated
1106  *
1107  * We're currently switching the port group to be activated only and
1108  * let the array figure out the rest.
1109  * There may be other arrays which require us to switch all port groups
1110  * based on a certain policy. But until we actually encounter them it
1111  * should be okay.
1112  */
1113 static int alua_activate(struct scsi_device *sdev,
1114                         activate_complete fn, void *data)
1115 {
1116         struct alua_dh_data *h = sdev->handler_data;
1117         int err = SCSI_DH_OK;
1118         struct alua_queue_data *qdata;
1119         struct alua_port_group *pg;
1120
1121         qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
1122         if (!qdata) {
1123                 err = SCSI_DH_RES_TEMP_UNAVAIL;
1124                 goto out;
1125         }
1126         qdata->callback_fn = fn;
1127         qdata->callback_data = data;
1128
1129         mutex_lock(&h->init_mutex);
1130         rcu_read_lock();
1131         pg = rcu_dereference(h->pg);
1132         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1133                 rcu_read_unlock();
1134                 kfree(qdata);
1135                 err = h->init_error;
1136                 mutex_unlock(&h->init_mutex);
1137                 goto out;
1138         }
1139         rcu_read_unlock();
1140         mutex_unlock(&h->init_mutex);
1141
1142         if (alua_rtpg_queue(pg, sdev, qdata, true))
1143                 fn = NULL;
1144         else
1145                 err = SCSI_DH_DEV_OFFLINED;
1146         kref_put(&pg->kref, release_port_group);
1147 out:
1148         if (fn)
1149                 fn(data, err);
1150         return 0;
1151 }
1152
1153 /*
1154  * alua_check - check path status
1155  * @sdev: device on the path to be checked
1156  *
1157  * Check the device status
1158  */
1159 static void alua_check(struct scsi_device *sdev, bool force)
1160 {
1161         struct alua_dh_data *h = sdev->handler_data;
1162         struct alua_port_group *pg;
1163
1164         rcu_read_lock();
1165         pg = rcu_dereference(h->pg);
1166         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1167                 rcu_read_unlock();
1168                 return;
1169         }
1170         rcu_read_unlock();
1171         alua_rtpg_queue(pg, sdev, NULL, force);
1172         kref_put(&pg->kref, release_port_group);
1173 }
1174
1175 /*
1176  * alua_prep_fn - request callback
1177  *
1178  * Fail I/O to all paths not in state
1179  * active/optimized or active/non-optimized.
1180  */
1181 static blk_status_t alua_prep_fn(struct scsi_device *sdev, struct request *req)
1182 {
1183         struct alua_dh_data *h = sdev->handler_data;
1184         struct alua_port_group *pg;
1185         unsigned char state = SCSI_ACCESS_STATE_OPTIMAL;
1186
1187         rcu_read_lock();
1188         pg = rcu_dereference(h->pg);
1189         if (pg)
1190                 state = pg->state;
1191         rcu_read_unlock();
1192
1193         switch (state) {
1194         case SCSI_ACCESS_STATE_OPTIMAL:
1195         case SCSI_ACCESS_STATE_ACTIVE:
1196         case SCSI_ACCESS_STATE_LBA:
1197         case SCSI_ACCESS_STATE_TRANSITIONING:
1198                 return BLK_STS_OK;
1199         default:
1200                 req->rq_flags |= RQF_QUIET;
1201                 return BLK_STS_IOERR;
1202         }
1203 }
1204
1205 static void alua_rescan(struct scsi_device *sdev)
1206 {
1207         struct alua_dh_data *h = sdev->handler_data;
1208
1209         alua_initialize(sdev, h);
1210 }
1211
1212 /*
1213  * alua_bus_attach - Attach device handler
1214  * @sdev: device to be attached to
1215  */
1216 static int alua_bus_attach(struct scsi_device *sdev)
1217 {
1218         struct alua_dh_data *h;
1219         int err;
1220
1221         h = kzalloc(sizeof(*h) , GFP_KERNEL);
1222         if (!h)
1223                 return SCSI_DH_NOMEM;
1224         spin_lock_init(&h->pg_lock);
1225         rcu_assign_pointer(h->pg, NULL);
1226         h->init_error = SCSI_DH_OK;
1227         h->sdev = sdev;
1228         INIT_LIST_HEAD(&h->node);
1229
1230         mutex_init(&h->init_mutex);
1231         err = alua_initialize(sdev, h);
1232         if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
1233                 goto failed;
1234
1235         sdev->handler_data = h;
1236         return SCSI_DH_OK;
1237 failed:
1238         kfree(h);
1239         return err;
1240 }
1241
1242 /*
1243  * alua_bus_detach - Detach device handler
1244  * @sdev: device to be detached from
1245  */
1246 static void alua_bus_detach(struct scsi_device *sdev)
1247 {
1248         struct alua_dh_data *h = sdev->handler_data;
1249         struct alua_port_group *pg;
1250
1251         spin_lock(&h->pg_lock);
1252         pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
1253         rcu_assign_pointer(h->pg, NULL);
1254         spin_unlock(&h->pg_lock);
1255         if (pg) {
1256                 spin_lock_irq(&pg->lock);
1257                 list_del_rcu(&h->node);
1258                 spin_unlock_irq(&pg->lock);
1259                 kref_put(&pg->kref, release_port_group);
1260         }
1261         sdev->handler_data = NULL;
1262         synchronize_rcu();
1263         kfree(h);
1264 }
1265
1266 static struct scsi_device_handler alua_dh = {
1267         .name = ALUA_DH_NAME,
1268         .module = THIS_MODULE,
1269         .attach = alua_bus_attach,
1270         .detach = alua_bus_detach,
1271         .prep_fn = alua_prep_fn,
1272         .check_sense = alua_check_sense,
1273         .activate = alua_activate,
1274         .rescan = alua_rescan,
1275         .set_params = alua_set_params,
1276 };
1277
1278 static int __init alua_init(void)
1279 {
1280         int r;
1281
1282         kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM, 0);
1283         if (!kaluad_wq)
1284                 return -ENOMEM;
1285
1286         r = scsi_register_device_handler(&alua_dh);
1287         if (r != 0) {
1288                 printk(KERN_ERR "%s: Failed to register scsi device handler",
1289                         ALUA_DH_NAME);
1290                 destroy_workqueue(kaluad_wq);
1291         }
1292         return r;
1293 }
1294
1295 static void __exit alua_exit(void)
1296 {
1297         scsi_unregister_device_handler(&alua_dh);
1298         destroy_workqueue(kaluad_wq);
1299 }
1300
1301 module_init(alua_init);
1302 module_exit(alua_exit);
1303
1304 MODULE_DESCRIPTION("DM Multipath ALUA support");
1305 MODULE_AUTHOR("Hannes Reinecke <hare@suse.de>");
1306 MODULE_LICENSE("GPL");
1307 MODULE_VERSION(ALUA_DH_VER);