drivers/scsi/device_handler/scsi_dh_alua.c

   1 /*
   2  * Generic SCSI-3 ALUA SCSI Device Handler
   3  *
   4  * Copyright (C) 2007-2010 Hannes Reinecke, SUSE Linux Products GmbH.
   5  * All rights reserved.
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  20  *
  21  */
  22 #include <linux/slab.h>
  23 #include <linux/delay.h>
  24 #include <linux/module.h>
  25 #include <asm/unaligned.h>
  26 #include <scsi/scsi.h>
  27 #include <scsi/scsi_proto.h>
  28 #include <scsi/scsi_dbg.h>
  29 #include <scsi/scsi_eh.h>
  30 #include <scsi/scsi_dh.h>
  31
  32 #define ALUA_DH_NAME "alua"
  33 #define ALUA_DH_VER "2.0"
  34
  35 #define TPGS_SUPPORT_NONE               0x00
  36 #define TPGS_SUPPORT_OPTIMIZED          0x01
  37 #define TPGS_SUPPORT_NONOPTIMIZED       0x02
  38 #define TPGS_SUPPORT_STANDBY            0x04
  39 #define TPGS_SUPPORT_UNAVAILABLE        0x08
  40 #define TPGS_SUPPORT_LBA_DEPENDENT      0x10
  41 #define TPGS_SUPPORT_OFFLINE            0x40
  42 #define TPGS_SUPPORT_TRANSITION         0x80
  43
  44 #define RTPG_FMT_MASK                   0x70
  45 #define RTPG_FMT_EXT_HDR                0x10
  46
  47 #define TPGS_MODE_UNINITIALIZED          -1
  48 #define TPGS_MODE_NONE                  0x0
  49 #define TPGS_MODE_IMPLICIT              0x1
  50 #define TPGS_MODE_EXPLICIT              0x2
  51
  52 #define ALUA_RTPG_SIZE                  128
  53 #define ALUA_FAILOVER_TIMEOUT           60
  54 #define ALUA_FAILOVER_RETRIES           5
  55 #define ALUA_RTPG_DELAY_MSECS           5
  56
  57 /* device handler flags */
  58 #define ALUA_OPTIMIZE_STPG              0x01
  59 #define ALUA_RTPG_EXT_HDR_UNSUPP        0x02
  60 #define ALUA_SYNC_STPG                  0x04
  61 /* State machine flags */
  62 #define ALUA_PG_RUN_RTPG                0x10
  63 #define ALUA_PG_RUN_STPG                0x20
  64 #define ALUA_PG_RUNNING                 0x40
  65
  66 static uint optimize_stpg;
  67 module_param(optimize_stpg, uint, S_IRUGO|S_IWUSR);
  68 MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized path, rather than sending a STPG, when implicit TPGS is supported (0=No,1=Yes). Default is 0.");
  69
  70 static LIST_HEAD(port_group_list);
  71 static DEFINE_SPINLOCK(port_group_lock);
  72 static struct workqueue_struct *kaluad_wq;
  73 static struct workqueue_struct *kaluad_sync_wq;
  74
  75 struct alua_port_group {
  76         struct kref             kref;
  77         struct rcu_head         rcu;
  78         struct list_head        node;
  79         struct list_head        dh_list;
  80         unsigned char           device_id_str[256];
  81         int                     device_id_len;
  82         int                     group_id;
  83         int                     tpgs;
  84         int                     state;
  85         int                     pref;
  86         unsigned                flags; /* used for optimizing STPG */
  87         unsigned char           transition_tmo;
  88         unsigned long           expiry;
  89         unsigned long           interval;
  90         struct delayed_work     rtpg_work;
  91         spinlock_t              lock;
  92         struct list_head        rtpg_list;
  93         struct scsi_device      *rtpg_sdev;
  94 };
  95
  96 struct alua_dh_data {
  97         struct list_head        node;
  98         struct alua_port_group  *pg;
  99         int                     group_id;
 100         spinlock_t              pg_lock;
 101         struct scsi_device      *sdev;
 102         int                     init_error;
 103         struct mutex            init_mutex;
 104 };
 105
 106 struct alua_queue_data {
 107         struct list_head        entry;
 108         activate_complete       callback_fn;
 109         void                    *callback_data;
 110 };
 111
 112 #define ALUA_POLICY_SWITCH_CURRENT      0
 113 #define ALUA_POLICY_SWITCH_ALL          1
 114
 115 static void alua_rtpg_work(struct work_struct *work);
 116 static void alua_rtpg_queue(struct alua_port_group *pg,
 117                             struct scsi_device *sdev,
 118                             struct alua_queue_data *qdata, bool force);
 119 static void alua_check(struct scsi_device *sdev, bool force);
 120
 121 static void release_port_group(struct kref *kref)
 122 {
 123         struct alua_port_group *pg;
 124
 125         pg = container_of(kref, struct alua_port_group, kref);
 126         if (pg->rtpg_sdev)
 127                 flush_delayed_work(&pg->rtpg_work);
 128         spin_lock(&port_group_lock);
 129         list_del(&pg->node);
 130         spin_unlock(&port_group_lock);
 131         kfree_rcu(pg, rcu);
 132 }
 133
 134 /*
 135  * submit_rtpg - Issue a REPORT TARGET GROUP STATES command
 136  * @sdev: sdev the command should be sent to
 137  */
 138 static int submit_rtpg(struct scsi_device *sdev, unsigned char *buff,
 139                        int bufflen, struct scsi_sense_hdr *sshdr, int flags)
 140 {
 141         u8 cdb[COMMAND_SIZE(MAINTENANCE_IN)];
 142         int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 143                 REQ_FAILFAST_DRIVER;
 144
 145         /* Prepare the command. */
 146         memset(cdb, 0x0, COMMAND_SIZE(MAINTENANCE_IN));
 147         cdb[0] = MAINTENANCE_IN;
 148         if (!(flags & ALUA_RTPG_EXT_HDR_UNSUPP))
 149                 cdb[1] = MI_REPORT_TARGET_PGS | MI_EXT_HDR_PARAM_FMT;
 150         else
 151                 cdb[1] = MI_REPORT_TARGET_PGS;
 152         put_unaligned_be32(bufflen, &cdb[6]);
 153
 154         return scsi_execute_req_flags(sdev, cdb, DMA_FROM_DEVICE,
 155                                       buff, bufflen, sshdr,
 156                                       ALUA_FAILOVER_TIMEOUT * HZ,
 157                                       ALUA_FAILOVER_RETRIES, NULL, req_flags);
 158 }
 159
 160 /*
 161  * submit_stpg - Issue a SET TARGET PORT GROUP command
 162  *
 163  * Currently we're only setting the current target port group state
 164  * to 'active/optimized' and let the array firmware figure out
 165  * the states of the remaining groups.
 166  */
 167 static int submit_stpg(struct scsi_device *sdev, int group_id,
 168                        struct scsi_sense_hdr *sshdr)
 169 {
 170         u8 cdb[COMMAND_SIZE(MAINTENANCE_OUT)];
 171         unsigned char stpg_data[8];
 172         int stpg_len = 8;
 173         int req_flags = REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT |
 174                 REQ_FAILFAST_DRIVER;
 175
 176         /* Prepare the data buffer */
 177         memset(stpg_data, 0, stpg_len);
 178         stpg_data[4] = SCSI_ACCESS_STATE_OPTIMAL;
 179         put_unaligned_be16(group_id, &stpg_data[6]);
 180
 181         /* Prepare the command. */
 182         memset(cdb, 0x0, COMMAND_SIZE(MAINTENANCE_OUT));
 183         cdb[0] = MAINTENANCE_OUT;
 184         cdb[1] = MO_SET_TARGET_PGS;
 185         put_unaligned_be32(stpg_len, &cdb[6]);
 186
 187         return scsi_execute_req_flags(sdev, cdb, DMA_TO_DEVICE,
 188                                       stpg_data, stpg_len,
 189                                       sshdr, ALUA_FAILOVER_TIMEOUT * HZ,
 190                                       ALUA_FAILOVER_RETRIES, NULL, req_flags);
 191 }
 192
 193 static struct alua_port_group *alua_find_get_pg(char *id_str, size_t id_size,
 194                                                 int group_id)
 195 {
 196         struct alua_port_group *pg;
 197
 198         if (!id_str || !id_size || !strlen(id_str))
 199                 return NULL;
 200
 201         list_for_each_entry(pg, &port_group_list, node) {
 202                 if (pg->group_id != group_id)
 203                         continue;
 204                 if (!pg->device_id_len || pg->device_id_len != id_size)
 205                         continue;
 206                 if (strncmp(pg->device_id_str, id_str, id_size))
 207                         continue;
 208                 if (!kref_get_unless_zero(&pg->kref))
 209                         continue;
 210                 return pg;
 211         }
 212
 213         return NULL;
 214 }
 215
 216 /*
 217  * alua_alloc_pg - Allocate a new port_group structure
 218  * @sdev: scsi device
 219  * @h: alua device_handler data
 220  * @group_id: port group id
 221  *
 222  * Allocate a new port_group structure for a given
 223  * device.
 224  */
 225 static struct alua_port_group *alua_alloc_pg(struct scsi_device *sdev,
 226                                              int group_id, int tpgs)
 227 {
 228         struct alua_port_group *pg, *tmp_pg;
 229
 230         pg = kzalloc(sizeof(struct alua_port_group), GFP_KERNEL);
 231         if (!pg)
 232                 return ERR_PTR(-ENOMEM);
 233
 234         pg->device_id_len = scsi_vpd_lun_id(sdev, pg->device_id_str,
 235                                             sizeof(pg->device_id_str));
 236         if (pg->device_id_len <= 0) {
 237                 /*
 238                  * TPGS supported but no device identification found.
 239                  * Generate private device identification.
 240                  */
 241                 sdev_printk(KERN_INFO, sdev,
 242                             "%s: No device descriptors found\n",
 243                             ALUA_DH_NAME);
 244                 pg->device_id_str[0] = '\0';
 245                 pg->device_id_len = 0;
 246         }
 247         pg->group_id = group_id;
 248         pg->tpgs = tpgs;
 249         pg->state = SCSI_ACCESS_STATE_OPTIMAL;
 250         if (optimize_stpg)
 251                 pg->flags |= ALUA_OPTIMIZE_STPG;
 252         kref_init(&pg->kref);
 253         INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work);
 254         INIT_LIST_HEAD(&pg->rtpg_list);
 255         INIT_LIST_HEAD(&pg->node);
 256         INIT_LIST_HEAD(&pg->dh_list);
 257         spin_lock_init(&pg->lock);
 258
 259         spin_lock(&port_group_lock);
 260         tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 261                                   group_id);
 262         if (tmp_pg) {
 263                 spin_unlock(&port_group_lock);
 264                 kfree(pg);
 265                 return tmp_pg;
 266         }
 267
 268         list_add(&pg->node, &port_group_list);
 269         spin_unlock(&port_group_lock);
 270
 271         return pg;
 272 }
 273
 274 /*
 275  * alua_check_tpgs - Evaluate TPGS setting
 276  * @sdev: device to be checked
 277  *
 278  * Examine the TPGS setting of the sdev to find out if ALUA
 279  * is supported.
 280  */
 281 static int alua_check_tpgs(struct scsi_device *sdev)
 282 {
 283         int tpgs = TPGS_MODE_NONE;
 284
 285         /*
 286          * ALUA support for non-disk devices is fraught with
 287          * difficulties, so disable it for now.
 288          */
 289         if (sdev->type != TYPE_DISK) {
 290                 sdev_printk(KERN_INFO, sdev,
 291                             "%s: disable for non-disk devices\n",
 292                             ALUA_DH_NAME);
 293                 return tpgs;
 294         }
 295
 296         tpgs = scsi_device_tpgs(sdev);
 297         switch (tpgs) {
 298         case TPGS_MODE_EXPLICIT|TPGS_MODE_IMPLICIT:
 299                 sdev_printk(KERN_INFO, sdev,
 300                             "%s: supports implicit and explicit TPGS\n",
 301                             ALUA_DH_NAME);
 302                 break;
 303         case TPGS_MODE_EXPLICIT:
 304                 sdev_printk(KERN_INFO, sdev, "%s: supports explicit TPGS\n",
 305                             ALUA_DH_NAME);
 306                 break;
 307         case TPGS_MODE_IMPLICIT:
 308                 sdev_printk(KERN_INFO, sdev, "%s: supports implicit TPGS\n",
 309                             ALUA_DH_NAME);
 310                 break;
 311         case TPGS_MODE_NONE:
 312                 sdev_printk(KERN_INFO, sdev, "%s: not supported\n",
 313                             ALUA_DH_NAME);
 314                 break;
 315         default:
 316                 sdev_printk(KERN_INFO, sdev,
 317                             "%s: unsupported TPGS setting %d\n",
 318                             ALUA_DH_NAME, tpgs);
 319                 tpgs = TPGS_MODE_NONE;
 320                 break;
 321         }
 322
 323         return tpgs;
 324 }
 325
 326 /*
 327  * alua_check_vpd - Evaluate INQUIRY vpd page 0x83
 328  * @sdev: device to be checked
 329  *
 330  * Extract the relative target port and the target port group
 331  * descriptor from the list of identificators.
 332  */
 333 static int alua_check_vpd(struct scsi_device *sdev, struct alua_dh_data *h,
 334                           int tpgs)
 335 {
 336         int rel_port = -1, group_id;
 337         struct alua_port_group *pg, *old_pg = NULL;
 338         bool pg_updated = false;
 339         unsigned long flags;
 340
 341         group_id = scsi_vpd_tpg_id(sdev, &rel_port);
 342         if (group_id < 0) {
 343                 /*
 344                  * Internal error; TPGS supported but required
 345                  * VPD identification descriptors not present.
 346                  * Disable ALUA support
 347                  */
 348                 sdev_printk(KERN_INFO, sdev,
 349                             "%s: No target port descriptors found\n",
 350                             ALUA_DH_NAME);
 351                 return SCSI_DH_DEV_UNSUPP;
 352         }
 353
 354         pg = alua_alloc_pg(sdev, group_id, tpgs);
 355         if (IS_ERR(pg)) {
 356                 if (PTR_ERR(pg) == -ENOMEM)
 357                         return SCSI_DH_NOMEM;
 358                 return SCSI_DH_DEV_UNSUPP;
 359         }
 360         if (pg->device_id_len)
 361                 sdev_printk(KERN_INFO, sdev,
 362                             "%s: device %s port group %x rel port %x\n",
 363                             ALUA_DH_NAME, pg->device_id_str,
 364                             group_id, rel_port);
 365         else
 366                 sdev_printk(KERN_INFO, sdev,
 367                             "%s: port group %x rel port %x\n",
 368                             ALUA_DH_NAME, group_id, rel_port);
 369
 370         /* Check for existing port group references */
 371         spin_lock(&h->pg_lock);
 372         old_pg = h->pg;
 373         if (old_pg != pg) {
 374                 /* port group has changed. Update to new port group */
 375                 if (h->pg) {
 376                         spin_lock_irqsave(&old_pg->lock, flags);
 377                         list_del_rcu(&h->node);
 378                         spin_unlock_irqrestore(&old_pg->lock, flags);
 379                 }
 380                 rcu_assign_pointer(h->pg, pg);
 381                 pg_updated = true;
 382         }
 383
 384         spin_lock_irqsave(&pg->lock, flags);
 385         if (sdev->synchronous_alua)
 386                 pg->flags |= ALUA_SYNC_STPG;
 387         if (pg_updated)
 388                 list_add_rcu(&h->node, &pg->dh_list);
 389         spin_unlock_irqrestore(&pg->lock, flags);
 390
 391         alua_rtpg_queue(h->pg, sdev, NULL, true);
 392         spin_unlock(&h->pg_lock);
 393
 394         if (old_pg)
 395                 kref_put(&old_pg->kref, release_port_group);
 396
 397         return SCSI_DH_OK;
 398 }
 399
 400 static char print_alua_state(unsigned char state)
 401 {
 402         switch (state) {
 403         case SCSI_ACCESS_STATE_OPTIMAL:
 404                 return 'A';
 405         case SCSI_ACCESS_STATE_ACTIVE:
 406                 return 'N';
 407         case SCSI_ACCESS_STATE_STANDBY:
 408                 return 'S';
 409         case SCSI_ACCESS_STATE_UNAVAILABLE:
 410                 return 'U';
 411         case SCSI_ACCESS_STATE_LBA:
 412                 return 'L';
 413         case SCSI_ACCESS_STATE_OFFLINE:
 414                 return 'O';
 415         case SCSI_ACCESS_STATE_TRANSITIONING:
 416                 return 'T';
 417         default:
 418                 return 'X';
 419         }
 420 }
 421
 422 static int alua_check_sense(struct scsi_device *sdev,
 423                             struct scsi_sense_hdr *sense_hdr)
 424 {
 425         switch (sense_hdr->sense_key) {
 426         case NOT_READY:
 427                 if (sense_hdr->asc == 0x04 && sense_hdr->ascq == 0x0a) {
 428                         /*
 429                          * LUN Not Accessible - ALUA state transition
 430                          */
 431                         alua_check(sdev, false);
 432                         return NEEDS_RETRY;
 433                 }
 434                 break;
 435         case UNIT_ATTENTION:
 436                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x00) {
 437                         /*
 438                          * Power On, Reset, or Bus Device Reset.
 439                          * Might have obscured a state transition,
 440                          * so schedule a recheck.
 441                          */
 442                         alua_check(sdev, true);
 443                         return ADD_TO_MLQUEUE;
 444                 }
 445                 if (sense_hdr->asc == 0x29 && sense_hdr->ascq == 0x04)
 446                         /*
 447                          * Device internal reset
 448                          */
 449                         return ADD_TO_MLQUEUE;
 450                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x01)
 451                         /*
 452                          * Mode Parameters Changed
 453                          */
 454                         return ADD_TO_MLQUEUE;
 455                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x06) {
 456                         /*
 457                          * ALUA state changed
 458                          */
 459                         alua_check(sdev, true);
 460                         return ADD_TO_MLQUEUE;
 461                 }
 462                 if (sense_hdr->asc == 0x2a && sense_hdr->ascq == 0x07) {
 463                         /*
 464                          * Implicit ALUA state transition failed
 465                          */
 466                         alua_check(sdev, true);
 467                         return ADD_TO_MLQUEUE;
 468                 }
 469                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x03)
 470                         /*
 471                          * Inquiry data has changed
 472                          */
 473                         return ADD_TO_MLQUEUE;
 474                 if (sense_hdr->asc == 0x3f && sense_hdr->ascq == 0x0e)
 475                         /*
 476                          * REPORTED_LUNS_DATA_HAS_CHANGED is reported
 477                          * when switching controllers on targets like
 478                          * Intel Multi-Flex. We can just retry.
 479                          */
 480                         return ADD_TO_MLQUEUE;
 481                 break;
 482         }
 483
 484         return SCSI_RETURN_NOT_HANDLED;
 485 }
 486
 487 /*
 488  * alua_tur - Send a TEST UNIT READY
 489  * @sdev: device to which the TEST UNIT READY command should be send
 490  *
 491  * Send a TEST UNIT READY to @sdev to figure out the device state
 492  * Returns SCSI_DH_RETRY if the sense code is NOT READY/ALUA TRANSITIONING,
 493  * SCSI_DH_OK if no error occurred, and SCSI_DH_IO otherwise.
 494  */
 495 static int alua_tur(struct scsi_device *sdev)
 496 {
 497         struct scsi_sense_hdr sense_hdr;
 498         int retval;
 499
 500         retval = scsi_test_unit_ready(sdev, ALUA_FAILOVER_TIMEOUT * HZ,
 501                                       ALUA_FAILOVER_RETRIES, &sense_hdr);
 502         if (sense_hdr.sense_key == NOT_READY &&
 503             sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
 504                 return SCSI_DH_RETRY;
 505         else if (retval)
 506                 return SCSI_DH_IO;
 507         else
 508                 return SCSI_DH_OK;
 509 }
 510
 511 /*
 512  * alua_rtpg - Evaluate REPORT TARGET GROUP STATES
 513  * @sdev: the device to be evaluated.
 514  *
 515  * Evaluate the Target Port Group State.
 516  * Returns SCSI_DH_DEV_OFFLINED if the path is
 517  * found to be unusable.
 518  */
 519 static int alua_rtpg(struct scsi_device *sdev, struct alua_port_group *pg)
 520 {
 521         struct scsi_sense_hdr sense_hdr;
 522         struct alua_port_group *tmp_pg;
 523         int len, k, off, valid_states = 0, bufflen = ALUA_RTPG_SIZE;
 524         unsigned char *desc, *buff;
 525         unsigned err, retval;
 526         unsigned int tpg_desc_tbl_off;
 527         unsigned char orig_transition_tmo;
 528         unsigned long flags;
 529
 530         if (!pg->expiry) {
 531                 unsigned long transition_tmo = ALUA_FAILOVER_TIMEOUT * HZ;
 532
 533                 if (pg->transition_tmo)
 534                         transition_tmo = pg->transition_tmo * HZ;
 535
 536                 pg->expiry = round_jiffies_up(jiffies + transition_tmo);
 537         }
 538
 539         buff = kzalloc(bufflen, GFP_KERNEL);
 540         if (!buff)
 541                 return SCSI_DH_DEV_TEMP_BUSY;
 542
 543  retry:
 544         err = 0;
 545         retval = submit_rtpg(sdev, buff, bufflen, &sense_hdr, pg->flags);
 546
 547         if (retval) {
 548                 if (!scsi_sense_valid(&sense_hdr)) {
 549                         sdev_printk(KERN_INFO, sdev,
 550                                     "%s: rtpg failed, result %d\n",
 551                                     ALUA_DH_NAME, retval);
 552                         kfree(buff);
 553                         if (driver_byte(retval) == DRIVER_ERROR)
 554                                 return SCSI_DH_DEV_TEMP_BUSY;
 555                         return SCSI_DH_IO;
 556                 }
 557
 558                 /*
 559                  * submit_rtpg() has failed on existing arrays
 560                  * when requesting extended header info, and
 561                  * the array doesn't support extended headers,
 562                  * even though it shouldn't according to T10.
 563                  * The retry without rtpg_ext_hdr_req set
 564                  * handles this.
 565                  */
 566                 if (!(pg->flags & ALUA_RTPG_EXT_HDR_UNSUPP) &&
 567                     sense_hdr.sense_key == ILLEGAL_REQUEST &&
 568                     sense_hdr.asc == 0x24 && sense_hdr.ascq == 0) {
 569                         pg->flags |= ALUA_RTPG_EXT_HDR_UNSUPP;
 570                         goto retry;
 571                 }
 572                 /*
 573                  * Retry on ALUA state transition or if any
 574                  * UNIT ATTENTION occurred.
 575                  */
 576                 if (sense_hdr.sense_key == NOT_READY &&
 577                     sense_hdr.asc == 0x04 && sense_hdr.ascq == 0x0a)
 578                         err = SCSI_DH_RETRY;
 579                 else if (sense_hdr.sense_key == UNIT_ATTENTION)
 580                         err = SCSI_DH_RETRY;
 581                 if (err == SCSI_DH_RETRY &&
 582                     pg->expiry != 0 && time_before(jiffies, pg->expiry)) {
 583                         sdev_printk(KERN_ERR, sdev, "%s: rtpg retry\n",
 584                                     ALUA_DH_NAME);
 585                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 586                         kfree(buff);
 587                         return err;
 588                 }
 589                 sdev_printk(KERN_ERR, sdev, "%s: rtpg failed\n",
 590                             ALUA_DH_NAME);
 591                 scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 592                 kfree(buff);
 593                 pg->expiry = 0;
 594                 return SCSI_DH_IO;
 595         }
 596
 597         len = get_unaligned_be32(&buff[0]) + 4;
 598
 599         if (len > bufflen) {
 600                 /* Resubmit with the correct length */
 601                 kfree(buff);
 602                 bufflen = len;
 603                 buff = kmalloc(bufflen, GFP_KERNEL);
 604                 if (!buff) {
 605                         sdev_printk(KERN_WARNING, sdev,
 606                                     "%s: kmalloc buffer failed\n",__func__);
 607                         /* Temporary failure, bypass */
 608                         pg->expiry = 0;
 609                         return SCSI_DH_DEV_TEMP_BUSY;
 610                 }
 611                 goto retry;
 612         }
 613
 614         orig_transition_tmo = pg->transition_tmo;
 615         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR && buff[5] != 0)
 616                 pg->transition_tmo = buff[5];
 617         else
 618                 pg->transition_tmo = ALUA_FAILOVER_TIMEOUT;
 619
 620         if (orig_transition_tmo != pg->transition_tmo) {
 621                 sdev_printk(KERN_INFO, sdev,
 622                             "%s: transition timeout set to %d seconds\n",
 623                             ALUA_DH_NAME, pg->transition_tmo);
 624                 pg->expiry = jiffies + pg->transition_tmo * HZ;
 625         }
 626
 627         if ((buff[4] & RTPG_FMT_MASK) == RTPG_FMT_EXT_HDR)
 628                 tpg_desc_tbl_off = 8;
 629         else
 630                 tpg_desc_tbl_off = 4;
 631
 632         for (k = tpg_desc_tbl_off, desc = buff + tpg_desc_tbl_off;
 633              k < len;
 634              k += off, desc += off) {
 635                 u16 group_id = get_unaligned_be16(&desc[2]);
 636
 637                 spin_lock_irqsave(&port_group_lock, flags);
 638                 tmp_pg = alua_find_get_pg(pg->device_id_str, pg->device_id_len,
 639                                           group_id);
 640                 spin_unlock_irqrestore(&port_group_lock, flags);
 641                 if (tmp_pg) {
 642                         if (spin_trylock_irqsave(&tmp_pg->lock, flags)) {
 643                                 if ((tmp_pg == pg) ||
 644                                     !(tmp_pg->flags & ALUA_PG_RUNNING)) {
 645                                         struct alua_dh_data *h;
 646
 647                                         tmp_pg->state = desc[0] & 0x0f;
 648                                         tmp_pg->pref = desc[0] >> 7;
 649                                         rcu_read_lock();
 650                                         list_for_each_entry_rcu(h,
 651                                                 &tmp_pg->dh_list, node) {
 652                                                 /* h->sdev should always be valid */
 653                                                 BUG_ON(!h->sdev);
 654                                                 h->sdev->access_state = desc[0];
 655                                         }
 656                                         rcu_read_unlock();
 657                                 }
 658                                 if (tmp_pg == pg)
 659                                         valid_states = desc[1];
 660                                 spin_unlock_irqrestore(&tmp_pg->lock, flags);
 661                         }
 662                         kref_put(&tmp_pg->kref, release_port_group);
 663                 }
 664                 off = 8 + (desc[7] * 4);
 665         }
 666
 667         spin_lock_irqsave(&pg->lock, flags);
 668         sdev_printk(KERN_INFO, sdev,
 669                     "%s: port group %02x state %c %s supports %c%c%c%c%c%c%c\n",
 670                     ALUA_DH_NAME, pg->group_id, print_alua_state(pg->state),
 671                     pg->pref ? "preferred" : "non-preferred",
 672                     valid_states&TPGS_SUPPORT_TRANSITION?'T':'t',
 673                     valid_states&TPGS_SUPPORT_OFFLINE?'O':'o',
 674                     valid_states&TPGS_SUPPORT_LBA_DEPENDENT?'L':'l',
 675                     valid_states&TPGS_SUPPORT_UNAVAILABLE?'U':'u',
 676                     valid_states&TPGS_SUPPORT_STANDBY?'S':'s',
 677                     valid_states&TPGS_SUPPORT_NONOPTIMIZED?'N':'n',
 678                     valid_states&TPGS_SUPPORT_OPTIMIZED?'A':'a');
 679
 680         switch (pg->state) {
 681         case SCSI_ACCESS_STATE_TRANSITIONING:
 682                 if (time_before(jiffies, pg->expiry)) {
 683                         /* State transition, retry */
 684                         pg->interval = 2;
 685                         err = SCSI_DH_RETRY;
 686                 } else {
 687                         struct alua_dh_data *h;
 688
 689                         /* Transitioning time exceeded, set port to standby */
 690                         err = SCSI_DH_IO;
 691                         pg->state = SCSI_ACCESS_STATE_STANDBY;
 692                         pg->expiry = 0;
 693                         rcu_read_lock();
 694                         list_for_each_entry_rcu(h, &pg->dh_list, node) {
 695                                 BUG_ON(!h->sdev);
 696                                 h->sdev->access_state =
 697                                         (pg->state & SCSI_ACCESS_STATE_MASK);
 698                                 if (pg->pref)
 699                                         h->sdev->access_state |=
 700                                                 SCSI_ACCESS_STATE_PREFERRED;
 701                         }
 702                         rcu_read_unlock();
 703                 }
 704                 break;
 705         case SCSI_ACCESS_STATE_OFFLINE:
 706                 /* Path unusable */
 707                 err = SCSI_DH_DEV_OFFLINED;
 708                 pg->expiry = 0;
 709                 break;
 710         default:
 711                 /* Useable path if active */
 712                 err = SCSI_DH_OK;
 713                 pg->expiry = 0;
 714                 break;
 715         }
 716         spin_unlock_irqrestore(&pg->lock, flags);
 717         kfree(buff);
 718         return err;
 719 }
 720
 721 /*
 722  * alua_stpg - Issue a SET TARGET PORT GROUP command
 723  *
 724  * Issue a SET TARGET PORT GROUP command and evaluate the
 725  * response. Returns SCSI_DH_RETRY per default to trigger
 726  * a re-evaluation of the target group state or SCSI_DH_OK
 727  * if no further action needs to be taken.
 728  */
 729 static unsigned alua_stpg(struct scsi_device *sdev, struct alua_port_group *pg)
 730 {
 731         int retval;
 732         struct scsi_sense_hdr sense_hdr;
 733
 734         if (!(pg->tpgs & TPGS_MODE_EXPLICIT)) {
 735                 /* Only implicit ALUA supported, retry */
 736                 return SCSI_DH_RETRY;
 737         }
 738         switch (pg->state) {
 739         case SCSI_ACCESS_STATE_OPTIMAL:
 740                 return SCSI_DH_OK;
 741         case SCSI_ACCESS_STATE_ACTIVE:
 742                 if ((pg->flags & ALUA_OPTIMIZE_STPG) &&
 743                     !pg->pref &&
 744                     (pg->tpgs & TPGS_MODE_IMPLICIT))
 745                         return SCSI_DH_OK;
 746                 break;
 747         case SCSI_ACCESS_STATE_STANDBY:
 748         case SCSI_ACCESS_STATE_UNAVAILABLE:
 749                 break;
 750         case SCSI_ACCESS_STATE_OFFLINE:
 751                 return SCSI_DH_IO;
 752         case SCSI_ACCESS_STATE_TRANSITIONING:
 753                 break;
 754         default:
 755                 sdev_printk(KERN_INFO, sdev,
 756                             "%s: stpg failed, unhandled TPGS state %d",
 757                             ALUA_DH_NAME, pg->state);
 758                 return SCSI_DH_NOSYS;
 759         }
 760         retval = submit_stpg(sdev, pg->group_id, &sense_hdr);
 761
 762         if (retval) {
 763                 if (!scsi_sense_valid(&sense_hdr)) {
 764                         sdev_printk(KERN_INFO, sdev,
 765                                     "%s: stpg failed, result %d",
 766                                     ALUA_DH_NAME, retval);
 767                         if (driver_byte(retval) == DRIVER_ERROR)
 768                                 return SCSI_DH_DEV_TEMP_BUSY;
 769                 } else {
 770                         sdev_printk(KERN_INFO, sdev, "%s: stpg failed\n",
 771                                     ALUA_DH_NAME);
 772                         scsi_print_sense_hdr(sdev, ALUA_DH_NAME, &sense_hdr);
 773                 }
 774         }
 775         /* Retry RTPG */
 776         return SCSI_DH_RETRY;
 777 }
 778
 779 static void alua_rtpg_work(struct work_struct *work)
 780 {
 781         struct alua_port_group *pg =
 782                 container_of(work, struct alua_port_group, rtpg_work.work);
 783         struct scsi_device *sdev;
 784         LIST_HEAD(qdata_list);
 785         int err = SCSI_DH_OK;
 786         struct alua_queue_data *qdata, *tmp;
 787         unsigned long flags;
 788         struct workqueue_struct *alua_wq = kaluad_wq;
 789
 790         spin_lock_irqsave(&pg->lock, flags);
 791         sdev = pg->rtpg_sdev;
 792         if (!sdev) {
 793                 WARN_ON(pg->flags & ALUA_PG_RUN_RTPG);
 794                 WARN_ON(pg->flags & ALUA_PG_RUN_STPG);
 795                 spin_unlock_irqrestore(&pg->lock, flags);
 796                 return;
 797         }
 798         if (pg->flags & ALUA_SYNC_STPG)
 799                 alua_wq = kaluad_sync_wq;
 800         pg->flags |= ALUA_PG_RUNNING;
 801         if (pg->flags & ALUA_PG_RUN_RTPG) {
 802                 int state = pg->state;
 803
 804                 pg->flags &= ~ALUA_PG_RUN_RTPG;
 805                 spin_unlock_irqrestore(&pg->lock, flags);
 806                 if (state == SCSI_ACCESS_STATE_TRANSITIONING) {
 807                         if (alua_tur(sdev) == SCSI_DH_RETRY) {
 808                                 spin_lock_irqsave(&pg->lock, flags);
 809                                 pg->flags &= ~ALUA_PG_RUNNING;
 810                                 pg->flags |= ALUA_PG_RUN_RTPG;
 811                                 spin_unlock_irqrestore(&pg->lock, flags);
 812                                 queue_delayed_work(alua_wq, &pg->rtpg_work,
 813                                                    pg->interval * HZ);
 814                                 return;
 815                         }
 816                         /* Send RTPG on failure or if TUR indicates SUCCESS */
 817                 }
 818                 err = alua_rtpg(sdev, pg);
 819                 spin_lock_irqsave(&pg->lock, flags);
 820                 if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 821                         pg->flags &= ~ALUA_PG_RUNNING;
 822                         pg->flags |= ALUA_PG_RUN_RTPG;
 823                         spin_unlock_irqrestore(&pg->lock, flags);
 824                         queue_delayed_work(alua_wq, &pg->rtpg_work,
 825                                            pg->interval * HZ);
 826                         return;
 827                 }
 828                 if (err != SCSI_DH_OK)
 829                         pg->flags &= ~ALUA_PG_RUN_STPG;
 830         }
 831         if (pg->flags & ALUA_PG_RUN_STPG) {
 832                 pg->flags &= ~ALUA_PG_RUN_STPG;
 833                 spin_unlock_irqrestore(&pg->lock, flags);
 834                 err = alua_stpg(sdev, pg);
 835                 spin_lock_irqsave(&pg->lock, flags);
 836                 if (err == SCSI_DH_RETRY || pg->flags & ALUA_PG_RUN_RTPG) {
 837                         pg->flags |= ALUA_PG_RUN_RTPG;
 838                         pg->interval = 0;
 839                         pg->flags &= ~ALUA_PG_RUNNING;
 840                         spin_unlock_irqrestore(&pg->lock, flags);
 841                         queue_delayed_work(alua_wq, &pg->rtpg_work,
 842                                            pg->interval * HZ);
 843                         return;
 844                 }
 845         }
 846
 847         list_splice_init(&pg->rtpg_list, &qdata_list);
 848         pg->rtpg_sdev = NULL;
 849         spin_unlock_irqrestore(&pg->lock, flags);
 850
 851         list_for_each_entry_safe(qdata, tmp, &qdata_list, entry) {
 852                 list_del(&qdata->entry);
 853                 if (qdata->callback_fn)
 854                         qdata->callback_fn(qdata->callback_data, err);
 855                 kfree(qdata);
 856         }
 857         spin_lock_irqsave(&pg->lock, flags);
 858         pg->flags &= ~ALUA_PG_RUNNING;
 859         spin_unlock_irqrestore(&pg->lock, flags);
 860         scsi_device_put(sdev);
 861         kref_put(&pg->kref, release_port_group);
 862 }
 863
 864 static void alua_rtpg_queue(struct alua_port_group *pg,
 865                             struct scsi_device *sdev,
 866                             struct alua_queue_data *qdata, bool force)
 867 {
 868         int start_queue = 0;
 869         unsigned long flags;
 870         struct workqueue_struct *alua_wq = kaluad_wq;
 871
 872         if (!pg)
 873                 return;
 874
 875         spin_lock_irqsave(&pg->lock, flags);
 876         if (qdata) {
 877                 list_add_tail(&qdata->entry, &pg->rtpg_list);
 878                 pg->flags |= ALUA_PG_RUN_STPG;
 879                 force = true;
 880         }
 881         if (pg->rtpg_sdev == NULL) {
 882                 pg->interval = 0;
 883                 pg->flags |= ALUA_PG_RUN_RTPG;
 884                 kref_get(&pg->kref);
 885                 pg->rtpg_sdev = sdev;
 886                 scsi_device_get(sdev);
 887                 start_queue = 1;
 888         } else if (!(pg->flags & ALUA_PG_RUN_RTPG) && force) {
 889                 pg->flags |= ALUA_PG_RUN_RTPG;
 890                 /* Do not queue if the worker is already running */
 891                 if (!(pg->flags & ALUA_PG_RUNNING)) {
 892                         kref_get(&pg->kref);
 893                         start_queue = 1;
 894                 }
 895         }
 896
 897         if (pg->flags & ALUA_SYNC_STPG)
 898                 alua_wq = kaluad_sync_wq;
 899         spin_unlock_irqrestore(&pg->lock, flags);
 900
 901         if (start_queue &&
 902             !queue_delayed_work(alua_wq, &pg->rtpg_work,
 903                                 msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS))) {
 904                 scsi_device_put(sdev);
 905                 kref_put(&pg->kref, release_port_group);
 906         }
 907 }
 908
 909 /*
 910  * alua_initialize - Initialize ALUA state
 911  * @sdev: the device to be initialized
 912  *
 913  * For the prep_fn to work correctly we have
 914  * to initialize the ALUA state for the device.
 915  */
 916 static int alua_initialize(struct scsi_device *sdev, struct alua_dh_data *h)
 917 {
 918         int err = SCSI_DH_DEV_UNSUPP, tpgs;
 919
 920         mutex_lock(&h->init_mutex);
 921         tpgs = alua_check_tpgs(sdev);
 922         if (tpgs != TPGS_MODE_NONE)
 923                 err = alua_check_vpd(sdev, h, tpgs);
 924         h->init_error = err;
 925         mutex_unlock(&h->init_mutex);
 926         return err;
 927 }
 928 /*
 929  * alua_set_params - set/unset the optimize flag
 930  * @sdev: device on the path to be activated
 931  * params - parameters in the following format
 932  *      "no_of_params\0param1\0param2\0param3\0...\0"
 933  * For example, to set the flag pass the following parameters
 934  * from multipath.conf
 935  *     hardware_handler        "2 alua 1"
 936  */
 937 static int alua_set_params(struct scsi_device *sdev, const char *params)
 938 {
 939         struct alua_dh_data *h = sdev->handler_data;
 940         struct alua_port_group __rcu *pg = NULL;
 941         unsigned int optimize = 0, argc;
 942         const char *p = params;
 943         int result = SCSI_DH_OK;
 944         unsigned long flags;
 945
 946         if ((sscanf(params, "%u", &argc) != 1) || (argc != 1))
 947                 return -EINVAL;
 948
 949         while (*p++)
 950                 ;
 951         if ((sscanf(p, "%u", &optimize) != 1) || (optimize > 1))
 952                 return -EINVAL;
 953
 954         rcu_read_lock();
 955         pg = rcu_dereference(h->pg);
 956         if (!pg) {
 957                 rcu_read_unlock();
 958                 return -ENXIO;
 959         }
 960         spin_lock_irqsave(&pg->lock, flags);
 961         if (optimize)
 962                 pg->flags |= ALUA_OPTIMIZE_STPG;
 963         else
 964                 pg->flags &= ~ALUA_OPTIMIZE_STPG;
 965         spin_unlock_irqrestore(&pg->lock, flags);
 966         rcu_read_unlock();
 967
 968         return result;
 969 }
 970
 971 /*
 972  * alua_activate - activate a path
 973  * @sdev: device on the path to be activated
 974  *
 975  * We're currently switching the port group to be activated only and
 976  * let the array figure out the rest.
 977  * There may be other arrays which require us to switch all port groups
 978  * based on a certain policy. But until we actually encounter them it
 979  * should be okay.
 980  */
 981 static int alua_activate(struct scsi_device *sdev,
 982                         activate_complete fn, void *data)
 983 {
 984         struct alua_dh_data *h = sdev->handler_data;
 985         int err = SCSI_DH_OK;
 986         struct alua_queue_data *qdata;
 987         struct alua_port_group __rcu *pg;
 988
 989         qdata = kzalloc(sizeof(*qdata), GFP_KERNEL);
 990         if (!qdata) {
 991                 err = SCSI_DH_RES_TEMP_UNAVAIL;
 992                 goto out;
 993         }
 994         qdata->callback_fn = fn;
 995         qdata->callback_data = data;
 996
 997         mutex_lock(&h->init_mutex);
 998         rcu_read_lock();
 999         pg = rcu_dereference(h->pg);
1000         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1001                 rcu_read_unlock();
1002                 kfree(qdata);
1003                 err = h->init_error;
1004                 mutex_unlock(&h->init_mutex);
1005                 goto out;
1006         }
1007         fn = NULL;
1008         rcu_read_unlock();
1009         mutex_unlock(&h->init_mutex);
1010
1011         alua_rtpg_queue(pg, sdev, qdata, true);
1012         kref_put(&pg->kref, release_port_group);
1013 out:
1014         if (fn)
1015                 fn(data, err);
1016         return 0;
1017 }
1018
1019 /*
1020  * alua_check - check path status
1021  * @sdev: device on the path to be checked
1022  *
1023  * Check the device status
1024  */
1025 static void alua_check(struct scsi_device *sdev, bool force)
1026 {
1027         struct alua_dh_data *h = sdev->handler_data;
1028         struct alua_port_group *pg;
1029
1030         rcu_read_lock();
1031         pg = rcu_dereference(h->pg);
1032         if (!pg || !kref_get_unless_zero(&pg->kref)) {
1033                 rcu_read_unlock();
1034                 return;
1035         }
1036         rcu_read_unlock();
1037
1038         alua_rtpg_queue(pg, sdev, NULL, force);
1039         kref_put(&pg->kref, release_port_group);
1040 }
1041
1042 /*
1043  * alua_prep_fn - request callback
1044  *
1045  * Fail I/O to all paths not in state
1046  * active/optimized or active/non-optimized.
1047  */
1048 static int alua_prep_fn(struct scsi_device *sdev, struct request *req)
1049 {
1050         struct alua_dh_data *h = sdev->handler_data;
1051         struct alua_port_group __rcu *pg;
1052         unsigned char state = SCSI_ACCESS_STATE_OPTIMAL;
1053         int ret = BLKPREP_OK;
1054
1055         rcu_read_lock();
1056         pg = rcu_dereference(h->pg);
1057         if (pg)
1058                 state = pg->state;
1059         rcu_read_unlock();
1060         if (state == SCSI_ACCESS_STATE_TRANSITIONING)
1061                 ret = BLKPREP_DEFER;
1062         else if (state != SCSI_ACCESS_STATE_OPTIMAL &&
1063                  state != SCSI_ACCESS_STATE_ACTIVE &&
1064                  state != SCSI_ACCESS_STATE_LBA) {
1065                 ret = BLKPREP_KILL;
1066                 req->cmd_flags |= REQ_QUIET;
1067         }
1068         return ret;
1069
1070 }
1071
1072 static void alua_rescan(struct scsi_device *sdev)
1073 {
1074         struct alua_dh_data *h = sdev->handler_data;
1075
1076         alua_initialize(sdev, h);
1077 }
1078
1079 /*
1080  * alua_bus_attach - Attach device handler
1081  * @sdev: device to be attached to
1082  */
1083 static int alua_bus_attach(struct scsi_device *sdev)
1084 {
1085         struct alua_dh_data *h;
1086         int err, ret = -EINVAL;
1087
1088         h = kzalloc(sizeof(*h) , GFP_KERNEL);
1089         if (!h)
1090                 return -ENOMEM;
1091         spin_lock_init(&h->pg_lock);
1092         rcu_assign_pointer(h->pg, NULL);
1093         h->init_error = SCSI_DH_OK;
1094         h->sdev = sdev;
1095         INIT_LIST_HEAD(&h->node);
1096
1097         mutex_init(&h->init_mutex);
1098         err = alua_initialize(sdev, h);
1099         if (err == SCSI_DH_NOMEM)
1100                 ret = -ENOMEM;
1101         if (err != SCSI_DH_OK && err != SCSI_DH_DEV_OFFLINED)
1102                 goto failed;
1103
1104         sdev->handler_data = h;
1105         return 0;
1106 failed:
1107         kfree(h);
1108         return ret;
1109 }
1110
1111 /*
1112  * alua_bus_detach - Detach device handler
1113  * @sdev: device to be detached from
1114  */
1115 static void alua_bus_detach(struct scsi_device *sdev)
1116 {
1117         struct alua_dh_data *h = sdev->handler_data;
1118         struct alua_port_group *pg;
1119
1120         spin_lock(&h->pg_lock);
1121         pg = h->pg;
1122         rcu_assign_pointer(h->pg, NULL);
1123         h->sdev = NULL;
1124         spin_unlock(&h->pg_lock);
1125         if (pg) {
1126                 spin_lock_irq(&pg->lock);
1127                 list_del_rcu(&h->node);
1128                 spin_unlock_irq(&pg->lock);
1129                 kref_put(&pg->kref, release_port_group);
1130         }
1131         sdev->handler_data = NULL;
1132         kfree(h);
1133 }
1134
1135 static struct scsi_device_handler alua_dh = {
1136         .name = ALUA_DH_NAME,
1137         .module = THIS_MODULE,
1138         .attach = alua_bus_attach,
1139         .detach = alua_bus_detach,
1140         .prep_fn = alua_prep_fn,
1141         .check_sense = alua_check_sense,
1142         .activate = alua_activate,
1143         .rescan = alua_rescan,
1144         .set_params = alua_set_params,
1145 };
1146
1147 static int __init alua_init(void)
1148 {
1149         int r;
1150
1151         kaluad_wq = alloc_workqueue("kaluad", WQ_MEM_RECLAIM, 0);
1152         if (!kaluad_wq) {
1153                 /* Temporary failure, bypass */
1154                 return SCSI_DH_DEV_TEMP_BUSY;
1155         }
1156         kaluad_sync_wq = create_workqueue("kaluad_sync");
1157         if (!kaluad_sync_wq) {
1158                 destroy_workqueue(kaluad_wq);
1159                 return SCSI_DH_DEV_TEMP_BUSY;
1160         }
1161         r = scsi_register_device_handler(&alua_dh);
1162         if (r != 0) {
1163                 printk(KERN_ERR "%s: Failed to register scsi device handler",
1164                         ALUA_DH_NAME);
1165                 destroy_workqueue(kaluad_sync_wq);
1166                 destroy_workqueue(kaluad_wq);
1167         }
1168         return r;
1169 }
1170
1171 static void __exit alua_exit(void)
1172 {
1173         scsi_unregister_device_handler(&alua_dh);
1174         destroy_workqueue(kaluad_sync_wq);
1175         destroy_workqueue(kaluad_wq);
1176 }
1177
1178 module_init(alua_init);
1179 module_exit(alua_exit);
1180
1181 MODULE_DESCRIPTION("DM Multipath ALUA support");
1182 MODULE_AUTHOR("Hannes Reinecke <hare@suse.de>");
1183 MODULE_LICENSE("GPL");
1184 MODULE_VERSION(ALUA_DH_VER);