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 opf = REQ_OP_DRV_IN | REQ_FAILFAST_DEV |
 131                                 REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER;
 132         const struct scsi_exec_args exec_args = {
 133                 .sshdr = sshdr,
 134         };
 135
 136         /* Prepare the command. */
 137         memset(cdb, 0x0, MAX_COMMAND_SIZE);
 138         cdb[0] = MAINTENANCE_IN;
 139         if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
 140                 cdb[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
 141         else
 142                 cdb[1] = MI_REPORT_TARGET_PGS;
 143         put_unaligned_be32(bufflen, &cdb[6]);
 144
 145         return scsi_execute_cmd(sdev, cdb, opf, buff, bufflen,
 146                                 ALUA_FAILOVER_TIMEOUT * HZ,
 147                                 ALUA_FAILOVER_RETRIES, &exec_args);
 148 }
 149
 150 /*
 151  * submit_stpg - Issue a SET TARGET PORT GROUP command
 152  *
 153  * Currently we're only setting the current target port group state
 154  * to 'active/optimized' and let the array firmware figure out
 155  * the states of the remaining groups.
 156  */
 157 static int submit_stpg(struct scsi_device *sdev, int group_id,
 158                        struct scsi_sense_hdr *sshdr)
 159 {
 160         u8 cdb[MAX_COMMAND_SIZE];
 161         unsigned char stpg_data[8];
 162         int stpg_len = 8;
 163         blk_opf_t opf = REQ_OP_DRV_OUT | REQ_FAILFAST_DEV |
 164                                 REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER;
 165         const struct scsi_exec_args exec_args = {
 166                 .sshdr = sshdr,
 167         };
 168
 169         /* Prepare the data buffer */
 170         memset(stpg_data, 0, stpg_len);
 171         stpg_data[4] = SCSI_ACCESS_STATE_OPTIMAL;
 172         put_unaligned_be16(group_id, &stpg_data[6]);
 173
 174         /* Prepare the command. */
 175         memset(cdb, 0x0, MAX_COMMAND_SIZE);
 176         cdb[0] = MAINTENANCE_OUT;
 177         cdb[1] = MO_SET_TARGET_PGS;
 178         put_unaligned_be32(stpg_len, &cdb[6]);
 179
 180         return scsi_execute_cmd(sdev, cdb, opf, stpg_data,
 181                                 stpg_len, ALUA_FAILOVER_TIMEOUT * HZ,
 182                                 ALUA_FAILOVER_RETRIES, &exec_args);
 183 }
 184
 185 static struct alua_port_group *alua_find_get_pg(char *id_str, size_t id_size,
 186                                                 int group_id)
 187 {
 188         struct alua_port_group *pg;
 189
 190         if (!id_str || !id_size || !strlen(id_str))
 191                 return NULL;
 192
 193         list_for_each_entry(pg, &port_group_list, node) {
 194                 if (pg->group_id != group_id)
 195                         continue;
 196                 if (!pg->device_id_len || pg->device_id_len != id_size)
 197                         continue;
 198                 if (strncmp(pg->device_id_str, id_str, id_size))
 199                         continue;
 200                 if (!kref_get_unless_zero(&pg->kref))
 201                         continue;
 202                 return pg;
 203         }
 204
 205         return NULL;
 206 }
 207
 208 /*
 209  * alua_alloc_pg - Allocate a new port_group structure
 210  * @sdev: scsi device
 211  * @group_id: port group id
 212  * @tpgs: target port group settings
 213  *
 214  * Allocate a new port_group structure for a given
 215  * device.
 216  */
 217 static struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
 218                                              int group_id, int tpgs)
 219 {
 220         struct alua_port_group *pg, *tmp_pg;
 221
 222         pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL);
 223         if (!pg)
 224                 return ERR_PTR(-ENOMEM);
 225
 226         pg->device_id_len = scsi_vpd_lun_id(sdev, pg->device_id_str,
 227                                             sizeof(pg->device_id_str));
 228         if (pg->device_id_len <= 0) {
 229                 /*
 230                  * TPGS supported but no device identification found.
 231                  * Generate private device identification.
 232                  */
 233                 sdev_printk(KERN_INFO, sdev,
 234                             "%s: No device descriptors found\n",
 235                             ALUA_DH_NAME);
 236                 pg->device_id_str[0] = '\0';
 237                 pg->device_id_len = 0;
 238         }
 239         pg->group_id = group_id;
 240         pg->tpgs = tpgs;
 241         pg->state = SCSI_ACCESS_STATE_OPTIMAL;
 242         pg->valid_states = TPGS_SUPPORT_ALL;
 243         if (optimize_stpg)
 244                 pg->flags |= ALUA_OPTIMIZE_STPG;
 245         kref_init(&pg->kref);
 246         INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
 247         INIT_LIST_HEAD(&pg->rtpg_list);
 248         INIT_LIST_HEAD(&pg->node);
 249         INIT_LIST_HEAD(&pg->dh_list);
 250         spin_lock_init(&pg->lock);
 251
 252         spin_lock(&port_group_lock);
 253         tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 254                                   group_id);
 255         if (tmp_pg) {
 256                 spin_unlock(&port_group_lock);
 257                 kfree(pg);
 258                 return tmp_pg;
 259         }
 260
 261         list_add(&pg->node, &port_group_list);
 262         spin_unlock(&port_group_lock);
 263
 264         return pg;
 265 }
 266
 267 /*
 268  * alua_check_tpgs - Evaluate TPGS setting
 269  * @sdev: device to be checked
 270  *
 271  * Examine the TPGS setting of the sdev to find out if ALUA
 272  * is supported.
 273  */
 274 static int alua_check_tpgs(struct scsi_device *sdev)
 275 {
 276         int tpgs = TPGS_MODE_NONE;
 277
 278         /*
 279          * ALUA support for non-disk devices is fraught with
 280          * difficulties, so disable it for now.
 281          */
 282         if (sdev->type != TYPE_DISK) {
 283                 sdev_printk(KERN_INFO, sdev,
 284                             "%s: disable for non-disk devices\n",
 285                             ALUA_DH_NAME);
 286                 return tpgs;
 287         }
 288
 289         tpgs = scsi_device_tpgs(sdev);
 290         switch (tpgs) {
 291         case TPGS_MODE_EXPLICIT|TPGS_MODE_IMPLICIT:
 292                 sdev_printk(KERN_INFO, sdev,
 293                             "%s: supports implicit and explicit TPGS\n",
 294                             ALUA_DH_NAME);
 295                 break;
 296         case TPGS_MODE_EXPLICIT:
 297                 sdev_printk(KERN_INFO, sdev, "%s: supports explicit TPGS\n",
 298                             ALUA_DH_NAME);
 299                 break;
 300         case TPGS_MODE_IMPLICIT:
 301                 sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n",
 302                             ALUA_DH_NAME);
 303                 break;
 304         case TPGS_MODE_NONE:
 305                 sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
 306                             ALUA_DH_NAME);
 307                 break;
 308         default:
 309                 sdev_printk(KERN_INFO, sdev,
 310                             "%s: unsupported TPGS setting %d\n",
 311                             ALUA_DH_NAME, tpgs);
 312                 tpgs = TPGS_MODE_NONE;
 313                 break;
 314         }
 315
 316         return tpgs;
 317 }
 318
 319 /*
 320  * alua_check_vpd - Evaluate INQUIRY vpd page 0x83
 321  * @sdev: device to be checked
 322  *
 323  * Extract the relative target port and the target port group
 324  * descriptor from the list of identificators.
 325  */
 326 static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 327                           int tpgs)
 328 {
 329         int rel_port = -1, group_id;
 330         struct alua_port_group *pg, *old_pg = NULL;
 331         bool pg_updated = false;
 332         unsigned long flags;
 333
 334         group_id = scsi_vpd_tpg_id(sdev, &rel_port);
 335         if (group_id < 0) {
 336                 /*
 337                  * Internal error; TPGS supported but required
 338                  * VPD identification descriptors not present.
 339                  * Disable ALUA support
 340                  */
 341                 sdev_printk(KERN_INFO, sdev,
 342                             "%s: No target port descriptors found\n",
 343                             ALUA_DH_NAME);
 344                 return SCSI_DH_DEV_UNSUPP;
 345         }
 346
 347         pg = alua_alloc_pg(sdev, group_id, tpgs);
 348         if (IS_ERR(pg)) {
 349                 if (PTR_ERR(pg) == -ENOMEM)
 350                         return SCSI_DH_NOMEM;
 351                 return SCSI_DH_DEV_UNSUPP;
 352         }
 353         if (pg->device_id_len)
 354                 sdev_printk(KERN_INFO, sdev,
 355                             "%s: device %s port group %x rel port %x\n",
 356                             ALUA_DH_NAME, pg->device_id_str,
 357                             group_id, rel_port);
 358         else
 359                 sdev_printk(KERN_INFO, sdev,
 360                             "%s: port group %x rel port %x\n",
 361                             ALUA_DH_NAME, group_id, rel_port);
 362
 363         kref_get(&pg->kref);
 364
 365         /* Check for existing port group references */
 366         spin_lock(&h->pg_lock);
 367         old_pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
 368         if (old_pg != pg) {
 369                 /* port group has changed. Update to new port group */
 370                 if (h->pg) {
 371                         spin_lock_irqsave(&old_pg->lock, flags);
 372                         list_del_rcu(&h->node);
 373                         spin_unlock_irqrestore(&old_pg->lock, flags);
 374                 }
 375                 rcu_assign_pointer(h->pg, pg);
 376                 pg_updated = true;
 377         }
 378
 379         spin_lock_irqsave(&pg->lock, flags);
 380         if (pg_updated)
 381                 list_add_rcu(&h->node, &pg->dh_list);
 382         spin_unlock_irqrestore(&pg->lock, flags);
 383
 384         spin_unlock(&h->pg_lock);
 385
 386         alua_rtpg_queue(pg, sdev, NULL, true);
 387         kref_put(&pg->kref, release_port_group);
 388
 389         if (old_pg)
 390                 kref_put(&old_pg->kref, release_port_group);
 391
 392         return SCSI_DH_OK;
 393 }
 394
 395 static char print_alua_state(unsigned char state)
 396 {
 397         switch (state) {
 398         case SCSI_ACCESS_STATE_OPTIMAL:
 399                 return 'A';
 400         case SCSI_ACCESS_STATE_ACTIVE:
 401                 return 'N';
 402         case SCSI_ACCESS_STATE_STANDBY:
 403                 return 'S';
 404         case SCSI_ACCESS_STATE_UNAVAILABLE:
 405                 return 'U';
 406         case SCSI_ACCESS_STATE_LBA:
 407                 return 'L';
 408         case SCSI_ACCESS_STATE_OFFLINE:
 409                 return 'O';
 410         case SCSI_ACCESS_STATE_TRANSITIONING:
 411                 return 'T';
 412         default:
 413                 return 'X';
 414         }
 415 }
 416
 417 static enum scsi_disposition alua_check_sense(struct scsi_device *sdev,
 418                                               struct scsi_sense_hdr *sense_hdr)
 419 {
 420         struct alua_dh_data *h = sdev->handler_data;
 421         struct alua_port_group *pg;
 422
 423         switch (sense_hdr->sense_key) {
 424         case NOT_READY:
 425                 if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
 426                         /*
 427                          * LUN Not Accessible - ALUA state transition
 428                          */
 429                         rcu_read_lock();
 430                         pg = rcu_dereference(h->pg);
 431                         if (pg)
 432                                 pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
 433                         rcu_read_unlock();
 434                         alua_check(sdev, false);
 435                         return NEEDS_RETRY;
 436                 }
 437                 break;
 438         case UNIT_ATTENTION:
 439                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
 440                         /*
 441                          * Power On, Reset, or Bus Device Reset.
 442                          * Might have obscured a state transition,
 443                          * so schedule a recheck.
 444                          */
 445                         alua_check(sdev, true);
 446                         return ADD_TO_MLQUEUE;
 447                 }
 448                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
 449                         /*
 450                          * Device internal reset
 451                          */
 452                         return ADD_TO_MLQUEUE;
 453                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
 454                         /*
 455                          * Mode Parameters Changed
 456                          */
 457                         return ADD_TO_MLQUEUE;
 458                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
 459                         /*
 460                          * ALUA state changed
 461                          */
 462                         alua_check(sdev, true);
 463                         return ADD_TO_MLQUEUE;
 464                 }
 465                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
 466                         /*
 467                          * Implicit ALUA state transition failed
 468                          */
 469                         alua_check(sdev, true);
 470                         return ADD_TO_MLQUEUE;
 471                 }
 472                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
 473                         /*
 474                          * Inquiry data has changed
 475                          */
 476                         return ADD_TO_MLQUEUE;
 477                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x0e)
 478                         /*
 479                          * REPORTED_LUNS_DATA_HAS_CHANGED is reported
 480                          * when switching controllers on targets like
 481                          * Intel Multi-Flex. We can just retry.
 482                          */
 483                         return ADD_TO_MLQUEUE;
 484                 break;
 485         }
 486
 487         return SCSI_RETURN_NOT_HANDLED;
 488 }
 489
 490 /*
 491  * alua_tur - Send a TEST UNIT READY
 492  * @sdev: device to which the TEST UNIT READY command should be send
 493  *
 494  * Send a TEST UNIT READY to @sdev to figure out the device state
 495  * Returns SCSI_DH_RETRY if the sense code is NOT READY/ALUA TRANSITIONING,
 496  * SCSI_DH_OK if no error occurred, and SCSI_DH_IO otherwise.
 497  */
 498 static int alua_tur(struct scsi_device *sdev)
 499 {
 500         struct scsi_sense_hdr sense_hdr;
 501         int retval;
 502
 503         retval = scsi_test_unit_ready(sdev, ALUA_FAILOVER_TIMEOUT * HZ,
 504                                       ALUA_FAILOVER_RETRIES, &sense_hdr);
 505         if (sense_hdr.sense_key == NOT_READY &&
 506             sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
 507                 return SCSI_DH_RETRY;
 508         else if (retval)
 509                 return SCSI_DH_IO;
 510         else
 511                 return SCSI_DH_OK;
 512 }
 513
 514 /*
 515  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
 516  * @sdev: the device to be evaluated.
 517  *
 518  * Evaluate the Target Port Group State.
 519  * Returns SCSI_DH_DEV_OFFLINED if the path is
 520  * found to be unusable.
 521  */
 522 static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 523 {
 524         struct scsi_sense_hdr sense_hdr;
 525         struct alua_port_group *tmp_pg;
 526         int len, k, off, bufflen = ALUA_RTPG_SIZE;
 527         int group_id_old, state_old, pref_old, valid_states_old;
 528         unsigned char *desc, *buff;
 529         unsigned err;
 530         int retval;
 531         unsigned int tpg_desc_tbl_off;
 532         unsigned char orig_transition_tmo;
 533         unsigned long flags;
 534         bool transitioning_sense = false;
 535
 536         group_id_old = pg->group_id;
 537         state_old = pg->state;
 538         pref_old = pg->pref;
 539         valid_states_old = pg->valid_states;
 540
 541         if (!pg->expiry) {
 542                 unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
 543
 544                 if (pg->transition_tmo)
 545                         transition_tmo = pg->transition_tmo * HZ;
 546
 547                 pg->expiry = round_jiffies_up(jiffies + transition_tmo);
 548         }
 549
 550         buff = kzalloc(bufflen, GFP_KERNEL);
 551         if (!buff)
 552                 return SCSI_DH_DEV_TEMP_BUSY;
 553
 554  retry:
 555         err = 0;
 556         retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
 557
 558         if (retval) {
 559                 /*
 560                  * Some (broken) implementations have a habit of returning
 561                  * an error during things like firmware update etc.
 562                  * But if the target only supports active/optimized there's
 563                  * not much we can do; it's not that we can switch paths
 564                  * or anything.
 565                  * So ignore any errors to avoid spurious failures during
 566                  * path failover.
 567                  */
 568                 if ((pg->valid_states & ~TPGS_SUPPORT_OPTIMIZED) == 0) {
 569                         sdev_printk(KERN_INFO, sdev,
 570                                     "%s: ignoring rtpg result %d\n",
 571                                     ALUA_DH_NAME, retval);
 572                         kfree(buff);
 573                         return SCSI_DH_OK;
 574                 }
 575                 if (retval < 0 || !scsi_sense_valid(&sense_hdr)) {
 576                         sdev_printk(KERN_INFO, sdev,
 577                                     "%s: rtpg failed, result %d\n",
 578                                     ALUA_DH_NAME, retval);
 579                         kfree(buff);
 580                         if (retval < 0)
 581                                 return SCSI_DH_DEV_TEMP_BUSY;
 582                         if (host_byte(retval) == DID_NO_CONNECT)
 583                                 return SCSI_DH_RES_TEMP_UNAVAIL;
 584                         return SCSI_DH_IO;
 585                 }
 586
 587                 /*
 588                  * submit_rtpg() has failed on existing arrays
 589                  * when requesting extended header info, and
 590                  * the array doesn't support extended headers,
 591                  * even though it shouldn't according to T10.
 592                  * The retry without rtpg_ext_hdr_req set
 593                  * handles this.
 594                  * Note:  some arrays return a sense key of ILLEGAL_REQUEST
 595                  * with ASC 00h if they don't support the extended header.
 596                  */
 597                 if (!(pg->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
 598                     sense_hdr.sense_key == ILLEGAL_REQUEST) {
 599                         pg->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
 600                         goto retry;
 601                 }
 602                 /*
 603                  * If the array returns with 'ALUA state transition'
 604                  * sense code here it cannot return RTPG data during
 605                  * transition. So set the state to 'transitioning' directly.
 606                  */
 607                 if (sense_hdr.sense_key == NOT_READY &&
 608                     sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a) {
 609                         transitioning_sense = true;
 610                         goto skip_rtpg;
 611                 }
 612                 /*
 613                  * Retry on any other UNIT ATTENTION occurred.
 614                  */
 615                 if (sense_hdr.sense_key == UNIT_ATTENTION)
 616                         err = SCSI_DH_RETRY;
 617                 if (err == SCSI_DH_RETRY &&
 618                     pg->expiry != 0 && time_before(jiffies, pg->expiry)) {
 619                         sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
 620                                     ALUA_DH_NAME);
 621                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 622                         kfree(buff);
 623                         return err;
 624                 }
 625                 sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
 626                             ALUA_DH_NAME);
 627                 scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 628                 kfree(buff);
 629                 pg->expiry = 0;
 630                 return SCSI_DH_IO;
 631         }
 632
 633         len = get_unaligned_be32(&buff[0]) + 4;
 634
 635         if (len > bufflen) {
 636                 /* Resubmit with the correct length */
 637                 kfree(buff);
 638                 bufflen = len;
 639                 buff = kmalloc(bufflen, GFP_KERNEL);
 640                 if (!buff) {
 641                         sdev_printk(KERN_WARNING, sdev,
 642                                     "%s: kmalloc buffer failed\n",__func__);
 643                         /* Temporary failure, bypass */
 644                         pg->expiry = 0;
 645                         return SCSI_DH_DEV_TEMP_BUSY;
 646                 }
 647                 goto retry;
 648         }
 649
 650         orig_transition_tmo = pg->transition_tmo;
 651         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0)
 652                 pg->transition_tmo = buff[5];
 653         else
 654                 pg->transition_tmo = ALUA_FAILOVER_TIMEOUT;
 655
 656         if (orig_transition_tmo != pg->transition_tmo) {
 657                 sdev_printk(KERN_INFO, sdev,
 658                             "%s: transition timeout set to %d seconds\n",
 659                             ALUA_DH_NAME, pg->transition_tmo);
 660                 pg->expiry = jiffies + pg->transition_tmo * HZ;
 661         }
 662
 663         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
 664                 tpg_desc_tbl_off = 8;
 665         else
 666                 tpg_desc_tbl_off = 4;
 667
 668         for (k = tpg_desc_tbl_off, desc = buff + tpg_desc_tbl_off;
 669              k < len;
 670              k += off, desc += off) {
 671                 u16 group_id = get_unaligned_be16(&desc[2]);
 672
 673                 spin_lock_irqsave(&port_group_lock, flags);
 674                 tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 675                                           group_id);
 676                 spin_unlock_irqrestore(&port_group_lock, flags);
 677                 if (tmp_pg) {
 678                         if (spin_trylock_irqsave(&tmp_pg->lock, flags)) {
 679                                 if ((tmp_pg == pg) ||
 680                                     !(tmp_pg->flags & ALUA_PG_RUNNING)) {
 681                                         struct alua_dh_data *h;
 682
 683                                         tmp_pg->state = desc[0] & 0x0f;
 684                                         tmp_pg->pref = desc[0] >> 7;
 685                                         rcu_read_lock();
 686                                         list_for_each_entry_rcu(h,
 687                                                 &tmp_pg->dh_list, node) {
 688                                                 if (!h->sdev)
 689                                                         continue;
 690                                                 h->sdev->access_state = desc[0];
 691                                         }
 692                                         rcu_read_unlock();
 693                                 }
 694                                 if (tmp_pg == pg)
 695                                         tmp_pg->valid_states = desc[1];
 696                                 spin_unlock_irqrestore(&tmp_pg->lock, flags);
 697                         }
 698                         kref_put(&tmp_pg->kref, release_port_group);
 699                 }
 700                 off = 8 + (desc[7] * 4);
 701         }
 702
 703  skip_rtpg:
 704         spin_lock_irqsave(&pg->lock, flags);
 705         if (transitioning_sense)
 706                 pg->state = SCSI_ACCESS_STATE_TRANSITIONING;
 707
 708         if (group_id_old != pg->group_id || state_old != pg->state ||
 709                 pref_old != pg->pref || valid_states_old != pg->valid_states)
 710                 sdev_printk(KERN_INFO, sdev,
 711                         "%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
 712                         ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state),
 713                         pg->pref ? "preferred" : "non-preferred",
 714                         pg->valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
 715                         pg->valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
 716                         pg->valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
 717                         pg->valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
 718                         pg->valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
 719                         pg->valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
 720                         pg->valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
 721
 722         switch (pg->state) {
 723         case SCSI_ACCESS_STATE_TRANSITIONING:
 724                 if (time_before(jiffies, pg->expiry)) {
 725                         /* State transition, retry */
 726                         pg->interval = ALUA_RTPG_RETRY_DELAY;
 727                         err = SCSI_DH_RETRY;
 728                 } else {
 729                         struct alua_dh_data *h;
 730
 731                         /* Transitioning time exceeded, set port to standby */
 732                         err = SCSI_DH_IO;
 733                         pg->state = SCSI_ACCESS_STATE_STANDBY;
 734                         pg->expiry = 0;
 735                         rcu_read_lock();
 736                         list_for_each_entry_rcu(h, &pg->dh_list, node) {
 737                                 if (!h->sdev)
 738                                         continue;
 739                                 h->sdev->access_state =
 740                                         (pg->state & SCSI_ACCESS_STATE_MASK);
 741                                 if (pg->pref)
 742                                         h->sdev->access_state |=
 743                                                 SCSI_ACCESS_STATE_PREFERRED;
 744                         }
 745                         rcu_read_unlock();
 746                 }
 747                 break;
 748         case SCSI_ACCESS_STATE_OFFLINE:
 749                 /* Path unusable */
 750                 err = SCSI_DH_DEV_OFFLINED;
 751                 pg->expiry = 0;
 752                 break;
 753         default:
 754                 /* Useable path if active */
 755                 err = SCSI_DH_OK;
 756                 pg->expiry = 0;
 757                 break;
 758         }
 759         spin_unlock_irqrestore(&pg->lock, flags);
 760         kfree(buff);
 761         return err;
 762 }
 763
 764 /*
 765  * alua_stpg - Issue a SET TARGET PORT GROUP command
 766  *
 767  * Issue a SET TARGET PORT GROUP command and evaluate the
 768  * response. Returns SCSI_DH_RETRY per default to trigger
 769  * a re-evaluation of the target group state or SCSI_DH_OK
 770  * if no further action needs to be taken.
 771  */
 772 static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg)
 773 {
 774         int retval;
 775         struct scsi_sense_hdr sense_hdr;
 776
 777         if (!(pg->tpgs & TPGS_MODE_EXPLICIT)) {
 778                 /* Only implicit ALUA supported, retry */
 779                 return SCSI_DH_RETRY;
 780         }
 781         switch (pg->state) {
 782         case SCSI_ACCESS_STATE_OPTIMAL:
 783                 return SCSI_DH_OK;
 784         case SCSI_ACCESS_STATE_ACTIVE:
 785                 if ((pg->flags & ALUA_OPTIMIZE_STPG) &&
 786                     !pg->pref &&
 787                     (pg->tpgs & TPGS_MODE_IMPLICIT))
 788                         return SCSI_DH_OK;
 789                 break;
 790         case SCSI_ACCESS_STATE_STANDBY:
 791         case SCSI_ACCESS_STATE_UNAVAILABLE:
 792                 break;
 793         case SCSI_ACCESS_STATE_OFFLINE:
 794                 return SCSI_DH_IO;
 795         case SCSI_ACCESS_STATE_TRANSITIONING:
 796                 break;
 797         default:
 798                 sdev_printk(KERN_INFO, sdev,
 799                             "%s: stpg failed, unhandled TPGS state %d",
 800                             ALUA_DH_NAME, pg->state);
 801                 return SCSI_DH_NOSYS;
 802         }
 803         retval = submit_stpg(sdev, pg->group_id, &sense_hdr);
 804
 805         if (retval) {
 806                 if (retval < 0 || !scsi_sense_valid(&sense_hdr)) {
 807                         sdev_printk(KERN_INFO, sdev,
 808                                     "%s: stpg failed, result %d",
 809                                     ALUA_DH_NAME, retval);
 810                         if (retval < 0)
 811                                 return SCSI_DH_DEV_TEMP_BUSY;
 812                 } else {
 813                         sdev_printk(KERN_INFO, sdev, "%s: stpg failed\n",
 814                                     ALUA_DH_NAME);
 815                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 816                 }
 817         }
 818         /* Retry RTPG */
 819         return SCSI_DH_RETRY;
 820 }
 821
 822 /*
 823  * The caller must call scsi_device_put() on the returned pointer if it is not
 824  * NULL.
 825  */
 826 static struct scsi_device * __must_check
 827 alua_rtpg_select_sdev(struct alua_port_group *pg)
 828 {
 829         struct alua_dh_data *h;
 830         struct scsi_device *sdev = NULL, *prev_sdev;
 831
 832         lockdep_assert_held(&pg->lock);
 833         if (WARN_ON(!pg->rtpg_sdev))
 834                 return NULL;
 835
 836         /*
 837          * RCU protection isn't necessary for dh_list here
 838          * as we hold pg->lock, but for access to h->pg.
 839          */
 840         rcu_read_lock();
 841         list_for_each_entry_rcu(h, &pg->dh_list, node) {
 842                 if (!h->sdev)
 843                         continue;
 844                 if (h->sdev == pg->rtpg_sdev) {
 845                         h->disabled = true;
 846                         continue;
 847                 }
 848                 if (rcu_dereference(h->pg) == pg &&
 849                     !h->disabled &&
 850                     !scsi_device_get(h->sdev)) {
 851                         sdev = h->sdev;
 852                         break;
 853                 }
 854         }
 855         rcu_read_unlock();
 856
 857         if (!sdev) {
 858                 pr_warn("%s: no device found for rtpg\n",
 859                         (pg->device_id_len ?
 860                          (char *)pg->device_id_str : "(nameless PG)"));
 861                 return NULL;
 862         }
 863
 864         sdev_printk(KERN_INFO, sdev, "rtpg retry on different device\n");
 865
 866         prev_sdev = pg->rtpg_sdev;
 867         pg->rtpg_sdev = sdev;
 868
 869         return prev_sdev;
 870 }
 871
 872 static void alua_rtpg_work(struct work_struct *work)
 873 {
 874         struct alua_port_group *pg =
 875                 container_of(work, struct alua_port_group, rtpg_work.work);
 876         struct scsi_device *sdev, *prev_sdev = NULL;
 877         LIST_HEAD(qdata_list);
 878         int err = SCSI_DH_OK;
 879         struct alua_queue_data *qdata, *tmp;
 880         struct alua_dh_data *h;
 881         unsigned long flags;
 882
 883         spin_lock_irqsave(&pg->lock, flags);
 884         sdev = pg->rtpg_sdev;
 885         if (!sdev) {
 886                 WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
 887                 WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
 888                 spin_unlock_irqrestore(&pg->lock, flags);
 889                 kref_put(&pg->kref, release_port_group);
 890                 return;
 891         }
 892         pg->flags |= ALUA_PG_RUNNING;
 893         if (pg->flags & ALUA_PG_RUN_RTPG) {
 894                 int state = pg->state;
 895
 896                 pg->flags &= ~ALUA_PG_RUN_RTPG;
 897                 spin_unlock_irqrestore(&pg->lock, flags);
 898                 if (state == SCSI_ACCESS_STATE_TRANSITIONING) {
 899                         if (alua_tur(sdev) == SCSI_DH_RETRY) {
 900                                 spin_lock_irqsave(&pg->lock, flags);
 901                                 pg->flags &= ~ALUA_PG_RUNNING;
 902                                 pg->flags |= ALUA_PG_RUN_RTPG;
 903                                 if (!pg->interval)
 904                                         pg->interval = ALUA_RTPG_RETRY_DELAY;
 905                                 spin_unlock_irqrestore(&pg->lock, flags);
 906                                 queue_delayed_work(kaluad_wq, &pg->rtpg_work,
 907                                                    pg->interval * HZ);
 908                                 return;
 909                         }
 910                         /* Send RTPG on failure or if TUR indicates SUCCESS */
 911                 }
 912                 err = alua_rtpg(sdev, pg);
 913                 spin_lock_irqsave(&pg->lock, flags);
 914
 915                 /* If RTPG failed on the current device, try using another */
 916                 if (err == SCSI_DH_RES_TEMP_UNAVAIL &&
 917                     (prev_sdev = alua_rtpg_select_sdev(pg)))
 918                         err = SCSI_DH_IMM_RETRY;
 919
 920                 if (err == SCSI_DH_RETRY || err == SCSI_DH_IMM_RETRY ||
 921                     pg->flags & ALUA_PG_RUN_RTPG) {
 922                         pg->flags &= ~ALUA_PG_RUNNING;
 923                         if (err == SCSI_DH_IMM_RETRY)
 924                                 pg->interval = 0;
 925                         else if (!pg->interval && !(pg->flags & ALUA_PG_RUN_RTPG))
 926                                 pg->interval = ALUA_RTPG_RETRY_DELAY;
 927                         pg->flags |= ALUA_PG_RUN_RTPG;
 928                         spin_unlock_irqrestore(&pg->lock, flags);
 929                         goto queue_rtpg;
 930                 }
 931                 if (err != SCSI_DH_OK)
 932                         pg->flags &= ~ALUA_PG_RUN_STPG;
 933         }
 934         if (pg->flags & ALUA_PG_RUN_STPG) {
 935                 pg->flags &= ~ALUA_PG_RUN_STPG;
 936                 spin_unlock_irqrestore(&pg->lock, flags);
 937                 err = alua_stpg(sdev, pg);
 938                 spin_lock_irqsave(&pg->lock, flags);
 939                 if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 940                         pg->flags |= ALUA_PG_RUN_RTPG;
 941                         pg->interval = 0;
 942                         pg->flags &= ~ALUA_PG_RUNNING;
 943                         spin_unlock_irqrestore(&pg->lock, flags);
 944                         goto queue_rtpg;
 945                 }
 946         }
 947
 948         list_splice_init(&pg->rtpg_list, &qdata_list);
 949         /*
 950          * We went through an RTPG, for good or bad.
 951          * Re-enable all devices for the next attempt.
 952          */
 953         list_for_each_entry(h, &pg->dh_list, node)
 954                 h->disabled = false;
 955         pg->rtpg_sdev = NULL;
 956         spin_unlock_irqrestore(&pg->lock, flags);
 957
 958         if (prev_sdev)
 959                 scsi_device_put(prev_sdev);
 960
 961         list_for_each_entry_safe(qdata, tmp, &qdata_list, entry) {
 962                 list_del(&qdata->entry);
 963                 if (qdata->callback_fn)
 964                         qdata->callback_fn(qdata->callback_data, err);
 965                 kfree(qdata);
 966         }
 967         spin_lock_irqsave(&pg->lock, flags);
 968         pg->flags &= ~ALUA_PG_RUNNING;
 969         spin_unlock_irqrestore(&pg->lock, flags);
 970         scsi_device_put(sdev);
 971         kref_put(&pg->kref, release_port_group);
 972         return;
 973
 974 queue_rtpg:
 975         if (prev_sdev)
 976                 scsi_device_put(prev_sdev);
 977         queue_delayed_work(kaluad_wq, &pg->rtpg_work, pg->interval * HZ);
 978 }
 979
 980 /**
 981  * alua_rtpg_queue() - cause RTPG to be submitted asynchronously
 982  * @pg: ALUA port group associated with @sdev.
 983  * @sdev: SCSI device for which to submit an RTPG.
 984  * @qdata: Information about the callback to invoke after the RTPG.
 985  * @force: Whether or not to submit an RTPG if a work item that will submit an
 986  *         RTPG already has been scheduled.
 987  *
 988  * Returns true if and only if alua_rtpg_work() will be called asynchronously.
 989  * That function is responsible for calling @qdata->fn().
 990  *
 991  * Context: may be called from atomic context (alua_check()) only if the caller
 992  *      holds an sdev reference.
 993  */
 994 static bool alua_rtpg_queue(struct alua_port_group *pg,
 995                             struct scsi_device *sdev,
 996                             struct alua_queue_data *qdata, bool force)
 997 {
 998         int start_queue = 0;
 999         unsigned long flags;
1000
1001         if (WARN_ON_ONCE(!pg) || scsi_device_get(sdev))
1002                 return false;
1003
1004         spin_lock_irqsave(&pg->lock, flags);
1005         if (qdata) {
1006                 list_add_tail(&qdata->entry, &pg->rtpg_list);
1007                 pg->flags |= ALUA_PG_RUN_STPG;
1008                 force = true;
1009         }
1010         if (pg->rtpg_sdev == NULL) {
1011                 struct alua_dh_data *h = sdev->handler_data;
1012
1013                 rcu_read_lock();
1014                 if (h && rcu_dereference(h->pg) == pg) {
1015                         pg->interval = 0;
1016                         pg->flags |= ALUA_PG_RUN_RTPG;
1017                         kref_get(&pg->kref);
1018                         pg->rtpg_sdev = sdev;
1019                         start_queue = 1;
1020                 }
1021                 rcu_read_unlock();
1022         } else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {
1023                 pg->flags |= ALUA_PG_RUN_RTPG;
1024                 /* Do not queue if the worker is already running */
1025                 if (!(pg->flags & ALUA_PG_RUNNING)) {
1026                         kref_get(&pg->kref);
1027                         start_queue = 1;
1028                 }
1029         }
1030
1031         spin_unlock_irqrestore(&pg->lock, flags);
1032
1033         if (start_queue) {
1034                 if (queue_delayed_work(kaluad_wq, &pg->rtpg_work,
1035                                 msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS)))
1036                         sdev = NULL;
1037                 else
1038                         kref_put(&pg->kref, release_port_group);
1039         }
1040         if (sdev)
1041                 scsi_device_put(sdev);
1042
1043         return true;
1044 }
1045
1046 /*
1047  * alua_initialize - Initialize ALUA state
1048  * @sdev: the device to be initialized
1049  *
1050  * For the prep_fn to work correctly we have
1051  * to initialize the ALUA state for the device.
1052  */
1053 static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
1054 {
1055         int err = SCSI_DH_DEV_UNSUPP, tpgs;
1056
1057         mutex_lock(&h->init_mutex);
1058         h->disabled = false;
1059         tpgs = alua_check_tpgs(sdev);
1060         if (tpgs != TPGS_MODE_NONE)
1061                 err = alua_check_vpd(sdev, h, tpgs);
1062         h->init_error = err;
1063         mutex_unlock(&h->init_mutex);
1064         return err;
1065 }
1066 /*
1067  * alua_set_params - set/unset the optimize flag
1068  * @sdev: device on the path to be activated
1069  * params - parameters in the following format
1070  *      "no_of_params\0param1\0param2\0param3\0...\0"
1071  * For example, to set the flag pass the following parameters
1072  * from multipath.conf
1073  *     hardware_handler        "2 alua 1"
1074  */
1075 static int alua_set_params(struct scsi_device *sdev, const char *params)
1076 {
1077         struct alua_dh_data *h = sdev->handler_data;
1078         struct alua_port_group *pg = NULL;
1079         unsigned int optimize = 0, argc;
1080         const char *p = params;
1081         int result = SCSI_DH_OK;
1082         unsigned long flags;
1083
1084         if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
1085                 return -EINVAL;
1086
1087         while (*p++)
1088                 ;
1089         if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
1090                 return -EINVAL;
1091
1092         rcu_read_lock();
1093         pg = rcu_dereference(h->pg);
1094         if (!pg) {
1095                 rcu_read_unlock();
1096                 return -ENXIO;
1097         }
1098         spin_lock_irqsave(&pg->lock, flags);
1099         if (optimize)
1100                 pg->flags |= ALUA_OPTIMIZE_STPG;
1101         else
1102                 pg->flags &= ~ALUA_OPTIMIZE_STPG;
1103         spin_unlock_irqrestore(&pg->lock, flags);
1104         rcu_read_unlock();
1105
1106         return result;
1107 }
1108
1109 /*
1110  * alua_activate - activate a path
1111  * @sdev: device on the path to be activated
1112  *
1113  * We're currently switching the port group to be activated only and
1114  * let the array figure out the rest.
1115  * There may be other arrays which require us to switch all port groups
1116  * based on a certain policy. But until we actually encounter them it
1117  * should be okay.
1118  */
1119 static int alua_activate(struct scsi_device *sdev,
1120                         activate_complete fn, void *data)
1121 {
1122         struct alua_dh_data *h = sdev->handler_data;
1123         int err = SCSI_DH_OK;
1124         struct alua_queue_data *qdata;
1125         struct alua_port_group *pg;
1126
1127         qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
1128         if (!qdata) {
1129                 err = SCSI_DH_RES_TEMP_UNAVAIL;
1130                 goto out;
1131         }
1132         qdata->callback_fn = fn;
1133         qdata->callback_data = data;
1134
1135         mutex_lock(&h->init_mutex);
1136         rcu_read_lock();
1137         pg = rcu_dereference(h->pg);
1138         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1139                 rcu_read_unlock();
1140                 kfree(qdata);
1141                 err = h->init_error;
1142                 mutex_unlock(&h->init_mutex);
1143                 goto out;
1144         }
1145         rcu_read_unlock();
1146         mutex_unlock(&h->init_mutex);
1147
1148         if (alua_rtpg_queue(pg, sdev, qdata, true)) {
1149                 fn = NULL;
1150         } else {
1151                 kfree(qdata);
1152                 err = SCSI_DH_DEV_OFFLINED;
1153         }
1154         kref_put(&pg->kref, release_port_group);
1155 out:
1156         if (fn)
1157                 fn(data, err);
1158         return 0;
1159 }
1160
1161 /*
1162  * alua_check - check path status
1163  * @sdev: device on the path to be checked
1164  *
1165  * Check the device status
1166  */
1167 static void alua_check(struct scsi_device *sdev, bool force)
1168 {
1169         struct alua_dh_data *h = sdev->handler_data;
1170         struct alua_port_group *pg;
1171
1172         rcu_read_lock();
1173         pg = rcu_dereference(h->pg);
1174         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1175                 rcu_read_unlock();
1176                 return;
1177         }
1178         rcu_read_unlock();
1179         alua_rtpg_queue(pg, sdev, NULL, force);
1180         kref_put(&pg->kref, release_port_group);
1181 }
1182
1183 /*
1184  * alua_prep_fn - request callback
1185  *
1186  * Fail I/O to all paths not in state
1187  * active/optimized or active/non-optimized.
1188  */
1189 static blk_status_t alua_prep_fn(struct scsi_device *sdev, struct request *req)
1190 {
1191         struct alua_dh_data *h = sdev->handler_data;
1192         struct alua_port_group *pg;
1193         unsigned char state = SCSI_ACCESS_STATE_OPTIMAL;
1194
1195         rcu_read_lock();
1196         pg = rcu_dereference(h->pg);
1197         if (pg)
1198                 state = pg->state;
1199         rcu_read_unlock();
1200
1201         switch (state) {
1202         case SCSI_ACCESS_STATE_OPTIMAL:
1203         case SCSI_ACCESS_STATE_ACTIVE:
1204         case SCSI_ACCESS_STATE_LBA:
1205         case SCSI_ACCESS_STATE_TRANSITIONING:
1206                 return BLK_STS_OK;
1207         default:
1208                 req->rq_flags |= RQF_QUIET;
1209                 return BLK_STS_IOERR;
1210         }
1211 }
1212
1213 static void alua_rescan(struct scsi_device *sdev)
1214 {
1215         struct alua_dh_data *h = sdev->handler_data;
1216
1217         alua_initialize(sdev, h);
1218 }
1219
1220 /*
1221  * alua_bus_attach - Attach device handler
1222  * @sdev: device to be attached to
1223  */
1224 static int alua_bus_attach(struct scsi_device *sdev)
1225 {
1226         struct alua_dh_data *h;
1227         int err;
1228
1229         h = kzalloc(sizeof(*h) , GFP_KERNEL);
1230         if (!h)
1231                 return SCSI_DH_NOMEM;
1232         spin_lock_init(&h->pg_lock);
1233         rcu_assign_pointer(h->pg, NULL);
1234         h->init_error = SCSI_DH_OK;
1235         h->sdev = sdev;
1236         INIT_LIST_HEAD(&h->node);
1237
1238         mutex_init(&h->init_mutex);
1239         err = alua_initialize(sdev, h);
1240         if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
1241                 goto failed;
1242
1243         sdev->handler_data = h;
1244         return SCSI_DH_OK;
1245 failed:
1246         kfree(h);
1247         return err;
1248 }
1249
1250 /*
1251  * alua_bus_detach - Detach device handler
1252  * @sdev: device to be detached from
1253  */
1254 static void alua_bus_detach(struct scsi_device *sdev)
1255 {
1256         struct alua_dh_data *h = sdev->handler_data;
1257         struct alua_port_group *pg;
1258
1259         spin_lock(&h->pg_lock);
1260         pg = rcu_dereference_protected(h->pg, lockdep_is_held(&h->pg_lock));
1261         rcu_assign_pointer(h->pg, NULL);
1262         spin_unlock(&h->pg_lock);
1263         if (pg) {
1264                 spin_lock_irq(&pg->lock);
1265                 list_del_rcu(&h->node);
1266                 spin_unlock_irq(&pg->lock);
1267                 kref_put(&pg->kref, release_port_group);
1268         }
1269         sdev->handler_data = NULL;
1270         synchronize_rcu();
1271         kfree(h);
1272 }
1273
1274 static struct scsi_device_handler alua_dh = {
1275         .name = ALUA_DH_NAME,
1276         .module = THIS_MODULE,
1277         .attach = alua_bus_attach,
1278         .detach = alua_bus_detach,
1279         .prep_fn = alua_prep_fn,
1280         .check_sense = alua_check_sense,
1281         .activate = alua_activate,
1282         .rescan = alua_rescan,
1283         .set_params = alua_set_params,
1284 };
1285
1286 static int __init alua_init(void)
1287 {
1288         int r;
1289
1290         kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM, 0);
1291         if (!kaluad_wq)
1292                 return -ENOMEM;
1293
1294         r = scsi_register_device_handler(&alua_dh);
1295         if (r != 0) {
1296                 printk(KERN_ERR "%s: Failed to register scsi device handler",
1297                         ALUA_DH_NAME);
1298                 destroy_workqueue(kaluad_wq);
1299         }
1300         return r;
1301 }
1302
1303 static void __exit alua_exit(void)
1304 {
1305         scsi_unregister_device_handler(&alua_dh);
1306         destroy_workqueue(kaluad_wq);
1307 }
1308
1309 module_init(alua_init);
1310 module_exit(alua_exit);
1311
1312 MODULE_DESCRIPTION("DM Multipath ALUA support");
1313 MODULE_AUTHOR("Hannes Reinecke <hare@suse.de>");
1314 MODULE_LICENSE("GPL");
1315 MODULE_VERSION(ALUA_DH_VER);