drivers/md/dm-mpath.c

   1 /*
   2  * Copyright (C) 2003 Sistina Software Limited.
   3  * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
   4  *
   5  * This file is released under the GPL.
   6  */
   7
   8 #include "dm.h"
   9 #include "dm-path-selector.h"
  10 #include "dm-bio-list.h"
  11 #include "dm-bio-record.h"
  12 #include "dm-uevent.h"
  13
  14 #include <linux/ctype.h>
  15 #include <linux/init.h>
  16 #include <linux/mempool.h>
  17 #include <linux/module.h>
  18 #include <linux/pagemap.h>
  19 #include <linux/slab.h>
  20 #include <linux/time.h>
  21 #include <linux/workqueue.h>
  22 #include <scsi/scsi_dh.h>
  23 #include <asm/atomic.h>
  24
  25 #define DM_MSG_PREFIX "multipath"
  26 #define MESG_STR(x) x, sizeof(x)
  27
  28 /* Path properties */
  29 struct pgpath {
  30         struct list_head list;
  31
  32         struct priority_group *pg;      /* Owning PG */
  33         unsigned fail_count;            /* Cumulative failure count */
  34
  35         struct dm_path path;
  36         struct work_struct deactivate_path;
  37 };
  38
  39 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  40
  41 /*
  42  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  43  * Each has a path selector which controls which path gets used.
  44  */
  45 struct priority_group {
  46         struct list_head list;
  47
  48         struct multipath *m;            /* Owning multipath instance */
  49         struct path_selector ps;
  50
  51         unsigned pg_num;                /* Reference number */
  52         unsigned bypassed;              /* Temporarily bypass this PG? */
  53
  54         unsigned nr_pgpaths;            /* Number of paths in PG */
  55         struct list_head pgpaths;
  56 };
  57
  58 /* Multipath context */
  59 struct multipath {
  60         struct list_head list;
  61         struct dm_target *ti;
  62
  63         spinlock_t lock;
  64
  65         const char *hw_handler_name;
  66         struct work_struct activate_path;
  67         struct pgpath *pgpath_to_activate;
  68         unsigned nr_priority_groups;
  69         struct list_head priority_groups;
  70         unsigned pg_init_required;      /* pg_init needs calling? */
  71         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  72
  73         unsigned nr_valid_paths;        /* Total number of usable paths */
  74         struct pgpath *current_pgpath;
  75         struct priority_group *current_pg;
  76         struct priority_group *next_pg; /* Switch to this PG if set */
  77         unsigned repeat_count;          /* I/Os left before calling PS again */
  78
  79         unsigned queue_io;              /* Must we queue all I/O? */
  80         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
  81         unsigned saved_queue_if_no_path;/* Saved state during suspension */
  82         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  83         unsigned pg_init_count;         /* Number of times pg_init called */
  84
  85         struct work_struct process_queued_ios;
  86         struct bio_list queued_ios;
  87         unsigned queue_size;
  88
  89         struct work_struct trigger_event;
  90
  91         /*
  92          * We must use a mempool of dm_mpath_io structs so that we
  93          * can resubmit bios on error.
  94          */
  95         mempool_t *mpio_pool;
  96 };
  97
  98 /*
  99  * Context information attached to each bio we process.
 100  */
 101 struct dm_mpath_io {
 102         struct pgpath *pgpath;
 103         struct dm_bio_details details;
 104 };
 105
 106 typedef int (*action_fn) (struct pgpath *pgpath);
 107
 108 #define MIN_IOS 256     /* Mempool size */
 109
 110 static struct kmem_cache *_mpio_cache;
 111
 112 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 113 static void process_queued_ios(struct work_struct *work);
 114 static void trigger_event(struct work_struct *work);
 115 static void activate_path(struct work_struct *work);
 116 static void deactivate_path(struct work_struct *work);
 117
 118
 119 /*-----------------------------------------------
 120  * Allocation routines
 121  *-----------------------------------------------*/
 122
 123 static struct pgpath *alloc_pgpath(void)
 124 {
 125         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 126
 127         if (pgpath) {
 128                 pgpath->path.is_active = 1;
 129                 INIT_WORK(&pgpath->deactivate_path, deactivate_path);
 130         }
 131
 132         return pgpath;
 133 }
 134
 135 static void free_pgpath(struct pgpath *pgpath)
 136 {
 137         kfree(pgpath);
 138 }
 139
 140 static void deactivate_path(struct work_struct *work)
 141 {
 142         struct pgpath *pgpath =
 143                 container_of(work, struct pgpath, deactivate_path);
 144
 145         blk_abort_queue(pgpath->path.dev->bdev->bd_disk->queue);
 146 }
 147
 148 static struct priority_group *alloc_priority_group(void)
 149 {
 150         struct priority_group *pg;
 151
 152         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 153
 154         if (pg)
 155                 INIT_LIST_HEAD(&pg->pgpaths);
 156
 157         return pg;
 158 }
 159
 160 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 161 {
 162         unsigned long flags;
 163         struct pgpath *pgpath, *tmp;
 164         struct multipath *m = ti->private;
 165
 166         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 167                 list_del(&pgpath->list);
 168                 if (m->hw_handler_name)
 169                         scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 170                 dm_put_device(ti, pgpath->path.dev);
 171                 spin_lock_irqsave(&m->lock, flags);
 172                 if (m->pgpath_to_activate == pgpath)
 173                         m->pgpath_to_activate = NULL;
 174                 spin_unlock_irqrestore(&m->lock, flags);
 175                 free_pgpath(pgpath);
 176         }
 177 }
 178
 179 static void free_priority_group(struct priority_group *pg,
 180                                 struct dm_target *ti)
 181 {
 182         struct path_selector *ps = &pg->ps;
 183
 184         if (ps->type) {
 185                 ps->type->destroy(ps);
 186                 dm_put_path_selector(ps->type);
 187         }
 188
 189         free_pgpaths(&pg->pgpaths, ti);
 190         kfree(pg);
 191 }
 192
 193 static struct multipath *alloc_multipath(struct dm_target *ti)
 194 {
 195         struct multipath *m;
 196
 197         m = kzalloc(sizeof(*m), GFP_KERNEL);
 198         if (m) {
 199                 INIT_LIST_HEAD(&m->priority_groups);
 200                 spin_lock_init(&m->lock);
 201                 m->queue_io = 1;
 202                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
 203                 INIT_WORK(&m->trigger_event, trigger_event);
 204                 INIT_WORK(&m->activate_path, activate_path);
 205                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 206                 if (!m->mpio_pool) {
 207                         kfree(m);
 208                         return NULL;
 209                 }
 210                 m->ti = ti;
 211                 ti->private = m;
 212         }
 213
 214         return m;
 215 }
 216
 217 static void free_multipath(struct multipath *m)
 218 {
 219         struct priority_group *pg, *tmp;
 220
 221         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 222                 list_del(&pg->list);
 223                 free_priority_group(pg, m->ti);
 224         }
 225
 226         kfree(m->hw_handler_name);
 227         mempool_destroy(m->mpio_pool);
 228         kfree(m);
 229 }
 230
 231
 232 /*-----------------------------------------------
 233  * Path selection
 234  *-----------------------------------------------*/
 235
 236 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 237 {
 238         m->current_pg = pgpath->pg;
 239
 240         /* Must we initialise the PG first, and queue I/O till it's ready? */
 241         if (m->hw_handler_name) {
 242                 m->pg_init_required = 1;
 243                 m->queue_io = 1;
 244         } else {
 245                 m->pg_init_required = 0;
 246                 m->queue_io = 0;
 247         }
 248
 249         m->pg_init_count = 0;
 250 }
 251
 252 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg)
 253 {
 254         struct dm_path *path;
 255
 256         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count);
 257         if (!path)
 258                 return -ENXIO;
 259
 260         m->current_pgpath = path_to_pgpath(path);
 261
 262         if (m->current_pg != pg)
 263                 __switch_pg(m, m->current_pgpath);
 264
 265         return 0;
 266 }
 267
 268 static void __choose_pgpath(struct multipath *m)
 269 {
 270         struct priority_group *pg;
 271         unsigned bypassed = 1;
 272
 273         if (!m->nr_valid_paths)
 274                 goto failed;
 275
 276         /* Were we instructed to switch PG? */
 277         if (m->next_pg) {
 278                 pg = m->next_pg;
 279                 m->next_pg = NULL;
 280                 if (!__choose_path_in_pg(m, pg))
 281                         return;
 282         }
 283
 284         /* Don't change PG until it has no remaining paths */
 285         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg))
 286                 return;
 287
 288         /*
 289          * Loop through priority groups until we find a valid path.
 290          * First time we skip PGs marked 'bypassed'.
 291          * Second time we only try the ones we skipped.
 292          */
 293         do {
 294                 list_for_each_entry(pg, &m->priority_groups, list) {
 295                         if (pg->bypassed == bypassed)
 296                                 continue;
 297                         if (!__choose_path_in_pg(m, pg))
 298                                 return;
 299                 }
 300         } while (bypassed--);
 301
 302 failed:
 303         m->current_pgpath = NULL;
 304         m->current_pg = NULL;
 305 }
 306
 307 /*
 308  * Check whether bios must be queued in the device-mapper core rather
 309  * than here in the target.
 310  *
 311  * m->lock must be held on entry.
 312  *
 313  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 314  * same value then we are not between multipath_presuspend()
 315  * and multipath_resume() calls and we have no need to check
 316  * for the DMF_NOFLUSH_SUSPENDING flag.
 317  */
 318 static int __must_push_back(struct multipath *m)
 319 {
 320         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 321                 dm_noflush_suspending(m->ti));
 322 }
 323
 324 static int map_io(struct multipath *m, struct bio *bio,
 325                   struct dm_mpath_io *mpio, unsigned was_queued)
 326 {
 327         int r = DM_MAPIO_REMAPPED;
 328         unsigned long flags;
 329         struct pgpath *pgpath;
 330
 331         spin_lock_irqsave(&m->lock, flags);
 332
 333         /* Do we need to select a new pgpath? */
 334         if (!m->current_pgpath ||
 335             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 336                 __choose_pgpath(m);
 337
 338         pgpath = m->current_pgpath;
 339
 340         if (was_queued)
 341                 m->queue_size--;
 342
 343         if ((pgpath && m->queue_io) ||
 344             (!pgpath && m->queue_if_no_path)) {
 345                 /* Queue for the daemon to resubmit */
 346                 bio_list_add(&m->queued_ios, bio);
 347                 m->queue_size++;
 348                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 349                     !m->queue_io)
 350                         queue_work(kmultipathd, &m->process_queued_ios);
 351                 pgpath = NULL;
 352                 r = DM_MAPIO_SUBMITTED;
 353         } else if (pgpath)
 354                 bio->bi_bdev = pgpath->path.dev->bdev;
 355         else if (__must_push_back(m))
 356                 r = DM_MAPIO_REQUEUE;
 357         else
 358                 r = -EIO;       /* Failed */
 359
 360         mpio->pgpath = pgpath;
 361
 362         spin_unlock_irqrestore(&m->lock, flags);
 363
 364         return r;
 365 }
 366
 367 /*
 368  * If we run out of usable paths, should we queue I/O or error it?
 369  */
 370 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 371                             unsigned save_old_value)
 372 {
 373         unsigned long flags;
 374
 375         spin_lock_irqsave(&m->lock, flags);
 376
 377         if (save_old_value)
 378                 m->saved_queue_if_no_path = m->queue_if_no_path;
 379         else
 380                 m->saved_queue_if_no_path = queue_if_no_path;
 381         m->queue_if_no_path = queue_if_no_path;
 382         if (!m->queue_if_no_path && m->queue_size)
 383                 queue_work(kmultipathd, &m->process_queued_ios);
 384
 385         spin_unlock_irqrestore(&m->lock, flags);
 386
 387         return 0;
 388 }
 389
 390 /*-----------------------------------------------------------------
 391  * The multipath daemon is responsible for resubmitting queued ios.
 392  *---------------------------------------------------------------*/
 393
 394 static void dispatch_queued_ios(struct multipath *m)
 395 {
 396         int r;
 397         unsigned long flags;
 398         struct bio *bio = NULL, *next;
 399         struct dm_mpath_io *mpio;
 400         union map_info *info;
 401
 402         spin_lock_irqsave(&m->lock, flags);
 403         bio = bio_list_get(&m->queued_ios);
 404         spin_unlock_irqrestore(&m->lock, flags);
 405
 406         while (bio) {
 407                 next = bio->bi_next;
 408                 bio->bi_next = NULL;
 409
 410                 info = dm_get_mapinfo(bio);
 411                 mpio = info->ptr;
 412
 413                 r = map_io(m, bio, mpio, 1);
 414                 if (r < 0)
 415                         bio_endio(bio, r);
 416                 else if (r == DM_MAPIO_REMAPPED)
 417                         generic_make_request(bio);
 418                 else if (r == DM_MAPIO_REQUEUE)
 419                         bio_endio(bio, -EIO);
 420
 421                 bio = next;
 422         }
 423 }
 424
 425 static void process_queued_ios(struct work_struct *work)
 426 {
 427         struct multipath *m =
 428                 container_of(work, struct multipath, process_queued_ios);
 429         struct pgpath *pgpath = NULL;
 430         unsigned init_required = 0, must_queue = 1;
 431         unsigned long flags;
 432
 433         spin_lock_irqsave(&m->lock, flags);
 434
 435         if (!m->queue_size)
 436                 goto out;
 437
 438         if (!m->current_pgpath)
 439                 __choose_pgpath(m);
 440
 441         pgpath = m->current_pgpath;
 442         m->pgpath_to_activate = m->current_pgpath;
 443
 444         if ((pgpath && !m->queue_io) ||
 445             (!pgpath && !m->queue_if_no_path))
 446                 must_queue = 0;
 447
 448         if (m->pg_init_required && !m->pg_init_in_progress) {
 449                 m->pg_init_count++;
 450                 m->pg_init_required = 0;
 451                 m->pg_init_in_progress = 1;
 452                 init_required = 1;
 453         }
 454
 455 out:
 456         spin_unlock_irqrestore(&m->lock, flags);
 457
 458         if (init_required)
 459                 queue_work(kmpath_handlerd, &m->activate_path);
 460
 461         if (!must_queue)
 462                 dispatch_queued_ios(m);
 463 }
 464
 465 /*
 466  * An event is triggered whenever a path is taken out of use.
 467  * Includes path failure and PG bypass.
 468  */
 469 static void trigger_event(struct work_struct *work)
 470 {
 471         struct multipath *m =
 472                 container_of(work, struct multipath, trigger_event);
 473
 474         dm_table_event(m->ti->table);
 475 }
 476
 477 /*-----------------------------------------------------------------
 478  * Constructor/argument parsing:
 479  * <#multipath feature args> [<arg>]*
 480  * <#hw_handler args> [hw_handler [<arg>]*]
 481  * <#priority groups>
 482  * <initial priority group>
 483  *     [<selector> <#selector args> [<arg>]*
 484  *      <#paths> <#per-path selector args>
 485  *         [<path> [<arg>]* ]+ ]+
 486  *---------------------------------------------------------------*/
 487 struct param {
 488         unsigned min;
 489         unsigned max;
 490         char *error;
 491 };
 492
 493 static int read_param(struct param *param, char *str, unsigned *v, char **error)
 494 {
 495         if (!str ||
 496             (sscanf(str, "%u", v) != 1) ||
 497             (*v < param->min) ||
 498             (*v > param->max)) {
 499                 *error = param->error;
 500                 return -EINVAL;
 501         }
 502
 503         return 0;
 504 }
 505
 506 struct arg_set {
 507         unsigned argc;
 508         char **argv;
 509 };
 510
 511 static char *shift(struct arg_set *as)
 512 {
 513         char *r;
 514
 515         if (as->argc) {
 516                 as->argc--;
 517                 r = *as->argv;
 518                 as->argv++;
 519                 return r;
 520         }
 521
 522         return NULL;
 523 }
 524
 525 static void consume(struct arg_set *as, unsigned n)
 526 {
 527         BUG_ON (as->argc < n);
 528         as->argc -= n;
 529         as->argv += n;
 530 }
 531
 532 static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
 533                                struct dm_target *ti)
 534 {
 535         int r;
 536         struct path_selector_type *pst;
 537         unsigned ps_argc;
 538
 539         static struct param _params[] = {
 540                 {0, 1024, "invalid number of path selector args"},
 541         };
 542
 543         pst = dm_get_path_selector(shift(as));
 544         if (!pst) {
 545                 ti->error = "unknown path selector type";
 546                 return -EINVAL;
 547         }
 548
 549         r = read_param(_params, shift(as), &ps_argc, &ti->error);
 550         if (r) {
 551                 dm_put_path_selector(pst);
 552                 return -EINVAL;
 553         }
 554
 555         r = pst->create(&pg->ps, ps_argc, as->argv);
 556         if (r) {
 557                 dm_put_path_selector(pst);
 558                 ti->error = "path selector constructor failed";
 559                 return r;
 560         }
 561
 562         pg->ps.type = pst;
 563         consume(as, ps_argc);
 564
 565         return 0;
 566 }
 567
 568 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
 569                                struct dm_target *ti)
 570 {
 571         int r;
 572         struct pgpath *p;
 573         struct multipath *m = ti->private;
 574
 575         /* we need at least a path arg */
 576         if (as->argc < 1) {
 577                 ti->error = "no device given";
 578                 return NULL;
 579         }
 580
 581         p = alloc_pgpath();
 582         if (!p)
 583                 return NULL;
 584
 585         r = dm_get_device(ti, shift(as), ti->begin, ti->len,
 586                           dm_table_get_mode(ti->table), &p->path.dev);
 587         if (r) {
 588                 ti->error = "error getting device";
 589                 goto bad;
 590         }
 591
 592         if (m->hw_handler_name) {
 593                 r = scsi_dh_attach(bdev_get_queue(p->path.dev->bdev),
 594                                    m->hw_handler_name);
 595                 if (r < 0) {
 596                         dm_put_device(ti, p->path.dev);
 597                         goto bad;
 598                 }
 599         }
 600
 601         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 602         if (r) {
 603                 dm_put_device(ti, p->path.dev);
 604                 goto bad;
 605         }
 606
 607         return p;
 608
 609  bad:
 610         free_pgpath(p);
 611         return NULL;
 612 }
 613
 614 static struct priority_group *parse_priority_group(struct arg_set *as,
 615                                                    struct multipath *m)
 616 {
 617         static struct param _params[] = {
 618                 {1, 1024, "invalid number of paths"},
 619                 {0, 1024, "invalid number of selector args"}
 620         };
 621
 622         int r;
 623         unsigned i, nr_selector_args, nr_params;
 624         struct priority_group *pg;
 625         struct dm_target *ti = m->ti;
 626
 627         if (as->argc < 2) {
 628                 as->argc = 0;
 629                 ti->error = "not enough priority group aruments";
 630                 return NULL;
 631         }
 632
 633         pg = alloc_priority_group();
 634         if (!pg) {
 635                 ti->error = "couldn't allocate priority group";
 636                 return NULL;
 637         }
 638         pg->m = m;
 639
 640         r = parse_path_selector(as, pg, ti);
 641         if (r)
 642                 goto bad;
 643
 644         /*
 645          * read the paths
 646          */
 647         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
 648         if (r)
 649                 goto bad;
 650
 651         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
 652         if (r)
 653                 goto bad;
 654
 655         nr_params = 1 + nr_selector_args;
 656         for (i = 0; i < pg->nr_pgpaths; i++) {
 657                 struct pgpath *pgpath;
 658                 struct arg_set path_args;
 659
 660                 if (as->argc < nr_params) {
 661                         ti->error = "not enough path parameters";
 662                         goto bad;
 663                 }
 664
 665                 path_args.argc = nr_params;
 666                 path_args.argv = as->argv;
 667
 668                 pgpath = parse_path(&path_args, &pg->ps, ti);
 669                 if (!pgpath)
 670                         goto bad;
 671
 672                 pgpath->pg = pg;
 673                 list_add_tail(&pgpath->list, &pg->pgpaths);
 674                 consume(as, nr_params);
 675         }
 676
 677         return pg;
 678
 679  bad:
 680         free_priority_group(pg, ti);
 681         return NULL;
 682 }
 683
 684 static int parse_hw_handler(struct arg_set *as, struct multipath *m)
 685 {
 686         unsigned hw_argc;
 687         struct dm_target *ti = m->ti;
 688
 689         static struct param _params[] = {
 690                 {0, 1024, "invalid number of hardware handler args"},
 691         };
 692
 693         if (read_param(_params, shift(as), &hw_argc, &ti->error))
 694                 return -EINVAL;
 695
 696         if (!hw_argc)
 697                 return 0;
 698
 699         m->hw_handler_name = kstrdup(shift(as), GFP_KERNEL);
 700         request_module("scsi_dh_%s", m->hw_handler_name);
 701         if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
 702                 ti->error = "unknown hardware handler type";
 703                 kfree(m->hw_handler_name);
 704                 m->hw_handler_name = NULL;
 705                 return -EINVAL;
 706         }
 707         consume(as, hw_argc - 1);
 708
 709         return 0;
 710 }
 711
 712 static int parse_features(struct arg_set *as, struct multipath *m)
 713 {
 714         int r;
 715         unsigned argc;
 716         struct dm_target *ti = m->ti;
 717         const char *param_name;
 718
 719         static struct param _params[] = {
 720                 {0, 3, "invalid number of feature args"},
 721                 {1, 50, "pg_init_retries must be between 1 and 50"},
 722         };
 723
 724         r = read_param(_params, shift(as), &argc, &ti->error);
 725         if (r)
 726                 return -EINVAL;
 727
 728         if (!argc)
 729                 return 0;
 730
 731         do {
 732                 param_name = shift(as);
 733                 argc--;
 734
 735                 if (!strnicmp(param_name, MESG_STR("queue_if_no_path"))) {
 736                         r = queue_if_no_path(m, 1, 0);
 737                         continue;
 738                 }
 739
 740                 if (!strnicmp(param_name, MESG_STR("pg_init_retries")) &&
 741                     (argc >= 1)) {
 742                         r = read_param(_params + 1, shift(as),
 743                                        &m->pg_init_retries, &ti->error);
 744                         argc--;
 745                         continue;
 746                 }
 747
 748                 ti->error = "Unrecognised multipath feature request";
 749                 r = -EINVAL;
 750         } while (argc && !r);
 751
 752         return r;
 753 }
 754
 755 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 756                          char **argv)
 757 {
 758         /* target parameters */
 759         static struct param _params[] = {
 760                 {1, 1024, "invalid number of priority groups"},
 761                 {1, 1024, "invalid initial priority group number"},
 762         };
 763
 764         int r;
 765         struct multipath *m;
 766         struct arg_set as;
 767         unsigned pg_count = 0;
 768         unsigned next_pg_num;
 769
 770         as.argc = argc;
 771         as.argv = argv;
 772
 773         m = alloc_multipath(ti);
 774         if (!m) {
 775                 ti->error = "can't allocate multipath";
 776                 return -EINVAL;
 777         }
 778
 779         r = parse_features(&as, m);
 780         if (r)
 781                 goto bad;
 782
 783         r = parse_hw_handler(&as, m);
 784         if (r)
 785                 goto bad;
 786
 787         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
 788         if (r)
 789                 goto bad;
 790
 791         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
 792         if (r)
 793                 goto bad;
 794
 795         /* parse the priority groups */
 796         while (as.argc) {
 797                 struct priority_group *pg;
 798
 799                 pg = parse_priority_group(&as, m);
 800                 if (!pg) {
 801                         r = -EINVAL;
 802                         goto bad;
 803                 }
 804
 805                 m->nr_valid_paths += pg->nr_pgpaths;
 806                 list_add_tail(&pg->list, &m->priority_groups);
 807                 pg_count++;
 808                 pg->pg_num = pg_count;
 809                 if (!--next_pg_num)
 810                         m->next_pg = pg;
 811         }
 812
 813         if (pg_count != m->nr_priority_groups) {
 814                 ti->error = "priority group count mismatch";
 815                 r = -EINVAL;
 816                 goto bad;
 817         }
 818
 819         return 0;
 820
 821  bad:
 822         free_multipath(m);
 823         return r;
 824 }
 825
 826 static void multipath_dtr(struct dm_target *ti)
 827 {
 828         struct multipath *m = (struct multipath *) ti->private;
 829
 830         flush_workqueue(kmpath_handlerd);
 831         flush_workqueue(kmultipathd);
 832         free_multipath(m);
 833 }
 834
 835 /*
 836  * Map bios, recording original fields for later in case we have to resubmit
 837  */
 838 static int multipath_map(struct dm_target *ti, struct bio *bio,
 839                          union map_info *map_context)
 840 {
 841         int r;
 842         struct dm_mpath_io *mpio;
 843         struct multipath *m = (struct multipath *) ti->private;
 844
 845         mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
 846         dm_bio_record(&mpio->details, bio);
 847
 848         map_context->ptr = mpio;
 849         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
 850         r = map_io(m, bio, mpio, 0);
 851         if (r < 0 || r == DM_MAPIO_REQUEUE)
 852                 mempool_free(mpio, m->mpio_pool);
 853
 854         return r;
 855 }
 856
 857 /*
 858  * Take a path out of use.
 859  */
 860 static int fail_path(struct pgpath *pgpath)
 861 {
 862         unsigned long flags;
 863         struct multipath *m = pgpath->pg->m;
 864
 865         spin_lock_irqsave(&m->lock, flags);
 866
 867         if (!pgpath->path.is_active)
 868                 goto out;
 869
 870         DMWARN("Failing path %s.", pgpath->path.dev->name);
 871
 872         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 873         pgpath->path.is_active = 0;
 874         pgpath->fail_count++;
 875
 876         m->nr_valid_paths--;
 877
 878         if (pgpath == m->current_pgpath)
 879                 m->current_pgpath = NULL;
 880
 881         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
 882                       pgpath->path.dev->name, m->nr_valid_paths);
 883
 884         queue_work(kmultipathd, &m->trigger_event);
 885         queue_work(kmultipathd, &pgpath->deactivate_path);
 886
 887 out:
 888         spin_unlock_irqrestore(&m->lock, flags);
 889
 890         return 0;
 891 }
 892
 893 /*
 894  * Reinstate a previously-failed path
 895  */
 896 static int reinstate_path(struct pgpath *pgpath)
 897 {
 898         int r = 0;
 899         unsigned long flags;
 900         struct multipath *m = pgpath->pg->m;
 901
 902         spin_lock_irqsave(&m->lock, flags);
 903
 904         if (pgpath->path.is_active)
 905                 goto out;
 906
 907         if (!pgpath->pg->ps.type->reinstate_path) {
 908                 DMWARN("Reinstate path not supported by path selector %s",
 909                        pgpath->pg->ps.type->name);
 910                 r = -EINVAL;
 911                 goto out;
 912         }
 913
 914         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
 915         if (r)
 916                 goto out;
 917
 918         pgpath->path.is_active = 1;
 919
 920         m->current_pgpath = NULL;
 921         if (!m->nr_valid_paths++ && m->queue_size)
 922                 queue_work(kmultipathd, &m->process_queued_ios);
 923
 924         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
 925                       pgpath->path.dev->name, m->nr_valid_paths);
 926
 927         queue_work(kmultipathd, &m->trigger_event);
 928
 929 out:
 930         spin_unlock_irqrestore(&m->lock, flags);
 931
 932         return r;
 933 }
 934
 935 /*
 936  * Fail or reinstate all paths that match the provided struct dm_dev.
 937  */
 938 static int action_dev(struct multipath *m, struct dm_dev *dev,
 939                       action_fn action)
 940 {
 941         int r = 0;
 942         struct pgpath *pgpath;
 943         struct priority_group *pg;
 944
 945         list_for_each_entry(pg, &m->priority_groups, list) {
 946                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
 947                         if (pgpath->path.dev == dev)
 948                                 r = action(pgpath);
 949                 }
 950         }
 951
 952         return r;
 953 }
 954
 955 /*
 956  * Temporarily try to avoid having to use the specified PG
 957  */
 958 static void bypass_pg(struct multipath *m, struct priority_group *pg,
 959                       int bypassed)
 960 {
 961         unsigned long flags;
 962
 963         spin_lock_irqsave(&m->lock, flags);
 964
 965         pg->bypassed = bypassed;
 966         m->current_pgpath = NULL;
 967         m->current_pg = NULL;
 968
 969         spin_unlock_irqrestore(&m->lock, flags);
 970
 971         queue_work(kmultipathd, &m->trigger_event);
 972 }
 973
 974 /*
 975  * Switch to using the specified PG from the next I/O that gets mapped
 976  */
 977 static int switch_pg_num(struct multipath *m, const char *pgstr)
 978 {
 979         struct priority_group *pg;
 980         unsigned pgnum;
 981         unsigned long flags;
 982
 983         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
 984             (pgnum > m->nr_priority_groups)) {
 985                 DMWARN("invalid PG number supplied to switch_pg_num");
 986                 return -EINVAL;
 987         }
 988
 989         spin_lock_irqsave(&m->lock, flags);
 990         list_for_each_entry(pg, &m->priority_groups, list) {
 991                 pg->bypassed = 0;
 992                 if (--pgnum)
 993                         continue;
 994
 995                 m->current_pgpath = NULL;
 996                 m->current_pg = NULL;
 997                 m->next_pg = pg;
 998         }
 999         spin_unlock_irqrestore(&m->lock, flags);
1000
1001         queue_work(kmultipathd, &m->trigger_event);
1002         return 0;
1003 }
1004
1005 /*
1006  * Set/clear bypassed status of a PG.
1007  * PGs are numbered upwards from 1 in the order they were declared.
1008  */
1009 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1010 {
1011         struct priority_group *pg;
1012         unsigned pgnum;
1013
1014         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1015             (pgnum > m->nr_priority_groups)) {
1016                 DMWARN("invalid PG number supplied to bypass_pg");
1017                 return -EINVAL;
1018         }
1019
1020         list_for_each_entry(pg, &m->priority_groups, list) {
1021                 if (!--pgnum)
1022                         break;
1023         }
1024
1025         bypass_pg(m, pg, bypassed);
1026         return 0;
1027 }
1028
1029 /*
1030  * Should we retry pg_init immediately?
1031  */
1032 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1033 {
1034         unsigned long flags;
1035         int limit_reached = 0;
1036
1037         spin_lock_irqsave(&m->lock, flags);
1038
1039         if (m->pg_init_count <= m->pg_init_retries)
1040                 m->pg_init_required = 1;
1041         else
1042                 limit_reached = 1;
1043
1044         spin_unlock_irqrestore(&m->lock, flags);
1045
1046         return limit_reached;
1047 }
1048
1049 static void pg_init_done(struct dm_path *path, int errors)
1050 {
1051         struct pgpath *pgpath = path_to_pgpath(path);
1052         struct priority_group *pg = pgpath->pg;
1053         struct multipath *m = pg->m;
1054         unsigned long flags;
1055
1056         /* device or driver problems */
1057         switch (errors) {
1058         case SCSI_DH_OK:
1059                 break;
1060         case SCSI_DH_NOSYS:
1061                 if (!m->hw_handler_name) {
1062                         errors = 0;
1063                         break;
1064                 }
1065                 DMERR("Cannot failover device because scsi_dh_%s was not "
1066                       "loaded.", m->hw_handler_name);
1067                 /*
1068                  * Fail path for now, so we do not ping pong
1069                  */
1070                 fail_path(pgpath);
1071                 break;
1072         case SCSI_DH_DEV_TEMP_BUSY:
1073                 /*
1074                  * Probably doing something like FW upgrade on the
1075                  * controller so try the other pg.
1076                  */
1077                 bypass_pg(m, pg, 1);
1078                 break;
1079         /* TODO: For SCSI_DH_RETRY we should wait a couple seconds */
1080         case SCSI_DH_RETRY:
1081         case SCSI_DH_IMM_RETRY:
1082         case SCSI_DH_RES_TEMP_UNAVAIL:
1083                 if (pg_init_limit_reached(m, pgpath))
1084                         fail_path(pgpath);
1085                 errors = 0;
1086                 break;
1087         default:
1088                 /*
1089                  * We probably do not want to fail the path for a device
1090                  * error, but this is what the old dm did. In future
1091                  * patches we can do more advanced handling.
1092                  */
1093                 fail_path(pgpath);
1094         }
1095
1096         spin_lock_irqsave(&m->lock, flags);
1097         if (errors) {
1098                 DMERR("Could not failover device. Error %d.", errors);
1099                 m->current_pgpath = NULL;
1100                 m->current_pg = NULL;
1101         } else if (!m->pg_init_required) {
1102                 m->queue_io = 0;
1103                 pg->bypassed = 0;
1104         }
1105
1106         m->pg_init_in_progress = 0;
1107         queue_work(kmultipathd, &m->process_queued_ios);
1108         spin_unlock_irqrestore(&m->lock, flags);
1109 }
1110
1111 static void activate_path(struct work_struct *work)
1112 {
1113         int ret;
1114         struct multipath *m =
1115                 container_of(work, struct multipath, activate_path);
1116         struct dm_path *path;
1117         unsigned long flags;
1118
1119         spin_lock_irqsave(&m->lock, flags);
1120         path = &m->pgpath_to_activate->path;
1121         m->pgpath_to_activate = NULL;
1122         spin_unlock_irqrestore(&m->lock, flags);
1123         if (!path)
1124                 return;
1125         ret = scsi_dh_activate(bdev_get_queue(path->dev->bdev));
1126         pg_init_done(path, ret);
1127 }
1128
1129 /*
1130  * end_io handling
1131  */
1132 static int do_end_io(struct multipath *m, struct bio *bio,
1133                      int error, struct dm_mpath_io *mpio)
1134 {
1135         unsigned long flags;
1136
1137         if (!error)
1138                 return 0;       /* I/O complete */
1139
1140         if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
1141                 return error;
1142
1143         if (error == -EOPNOTSUPP)
1144                 return error;
1145
1146         spin_lock_irqsave(&m->lock, flags);
1147         if (!m->nr_valid_paths) {
1148                 if (__must_push_back(m)) {
1149                         spin_unlock_irqrestore(&m->lock, flags);
1150                         return DM_ENDIO_REQUEUE;
1151                 } else if (!m->queue_if_no_path) {
1152                         spin_unlock_irqrestore(&m->lock, flags);
1153                         return -EIO;
1154                 } else {
1155                         spin_unlock_irqrestore(&m->lock, flags);
1156                         goto requeue;
1157                 }
1158         }
1159         spin_unlock_irqrestore(&m->lock, flags);
1160
1161         if (mpio->pgpath)
1162                 fail_path(mpio->pgpath);
1163
1164       requeue:
1165         dm_bio_restore(&mpio->details, bio);
1166
1167         /* queue for the daemon to resubmit or fail */
1168         spin_lock_irqsave(&m->lock, flags);
1169         bio_list_add(&m->queued_ios, bio);
1170         m->queue_size++;
1171         if (!m->queue_io)
1172                 queue_work(kmultipathd, &m->process_queued_ios);
1173         spin_unlock_irqrestore(&m->lock, flags);
1174
1175         return DM_ENDIO_INCOMPLETE;     /* io not complete */
1176 }
1177
1178 static int multipath_end_io(struct dm_target *ti, struct bio *bio,
1179                             int error, union map_info *map_context)
1180 {
1181         struct multipath *m = ti->private;
1182         struct dm_mpath_io *mpio = map_context->ptr;
1183         struct pgpath *pgpath = mpio->pgpath;
1184         struct path_selector *ps;
1185         int r;
1186
1187         r  = do_end_io(m, bio, error, mpio);
1188         if (pgpath) {
1189                 ps = &pgpath->pg->ps;
1190                 if (ps->type->end_io)
1191                         ps->type->end_io(ps, &pgpath->path);
1192         }
1193         if (r != DM_ENDIO_INCOMPLETE)
1194                 mempool_free(mpio, m->mpio_pool);
1195
1196         return r;
1197 }
1198
1199 /*
1200  * Suspend can't complete until all the I/O is processed so if
1201  * the last path fails we must error any remaining I/O.
1202  * Note that if the freeze_bdev fails while suspending, the
1203  * queue_if_no_path state is lost - userspace should reset it.
1204  */
1205 static void multipath_presuspend(struct dm_target *ti)
1206 {
1207         struct multipath *m = (struct multipath *) ti->private;
1208
1209         queue_if_no_path(m, 0, 1);
1210 }
1211
1212 /*
1213  * Restore the queue_if_no_path setting.
1214  */
1215 static void multipath_resume(struct dm_target *ti)
1216 {
1217         struct multipath *m = (struct multipath *) ti->private;
1218         unsigned long flags;
1219
1220         spin_lock_irqsave(&m->lock, flags);
1221         m->queue_if_no_path = m->saved_queue_if_no_path;
1222         spin_unlock_irqrestore(&m->lock, flags);
1223 }
1224
1225 /*
1226  * Info output has the following format:
1227  * num_multipath_feature_args [multipath_feature_args]*
1228  * num_handler_status_args [handler_status_args]*
1229  * num_groups init_group_number
1230  *            [A|D|E num_ps_status_args [ps_status_args]*
1231  *             num_paths num_selector_args
1232  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1233  *
1234  * Table output has the following format (identical to the constructor string):
1235  * num_feature_args [features_args]*
1236  * num_handler_args hw_handler [hw_handler_args]*
1237  * num_groups init_group_number
1238  *     [priority selector-name num_ps_args [ps_args]*
1239  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1240  */
1241 static int multipath_status(struct dm_target *ti, status_type_t type,
1242                             char *result, unsigned int maxlen)
1243 {
1244         int sz = 0;
1245         unsigned long flags;
1246         struct multipath *m = (struct multipath *) ti->private;
1247         struct priority_group *pg;
1248         struct pgpath *p;
1249         unsigned pg_num;
1250         char state;
1251
1252         spin_lock_irqsave(&m->lock, flags);
1253
1254         /* Features */
1255         if (type == STATUSTYPE_INFO)
1256                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1257         else {
1258                 DMEMIT("%u ", m->queue_if_no_path +
1259                               (m->pg_init_retries > 0) * 2);
1260                 if (m->queue_if_no_path)
1261                         DMEMIT("queue_if_no_path ");
1262                 if (m->pg_init_retries)
1263                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1264         }
1265
1266         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1267                 DMEMIT("0 ");
1268         else
1269                 DMEMIT("1 %s ", m->hw_handler_name);
1270
1271         DMEMIT("%u ", m->nr_priority_groups);
1272
1273         if (m->next_pg)
1274                 pg_num = m->next_pg->pg_num;
1275         else if (m->current_pg)
1276                 pg_num = m->current_pg->pg_num;
1277         else
1278                         pg_num = 1;
1279
1280         DMEMIT("%u ", pg_num);
1281
1282         switch (type) {
1283         case STATUSTYPE_INFO:
1284                 list_for_each_entry(pg, &m->priority_groups, list) {
1285                         if (pg->bypassed)
1286                                 state = 'D';    /* Disabled */
1287                         else if (pg == m->current_pg)
1288                                 state = 'A';    /* Currently Active */
1289                         else
1290                                 state = 'E';    /* Enabled */
1291
1292                         DMEMIT("%c ", state);
1293
1294                         if (pg->ps.type->status)
1295                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1296                                                           result + sz,
1297                                                           maxlen - sz);
1298                         else
1299                                 DMEMIT("0 ");
1300
1301                         DMEMIT("%u %u ", pg->nr_pgpaths,
1302                                pg->ps.type->info_args);
1303
1304                         list_for_each_entry(p, &pg->pgpaths, list) {
1305                                 DMEMIT("%s %s %u ", p->path.dev->name,
1306                                        p->path.is_active ? "A" : "F",
1307                                        p->fail_count);
1308                                 if (pg->ps.type->status)
1309                                         sz += pg->ps.type->status(&pg->ps,
1310                                               &p->path, type, result + sz,
1311                                               maxlen - sz);
1312                         }
1313                 }
1314                 break;
1315
1316         case STATUSTYPE_TABLE:
1317                 list_for_each_entry(pg, &m->priority_groups, list) {
1318                         DMEMIT("%s ", pg->ps.type->name);
1319
1320                         if (pg->ps.type->status)
1321                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1322                                                           result + sz,
1323                                                           maxlen - sz);
1324                         else
1325                                 DMEMIT("0 ");
1326
1327                         DMEMIT("%u %u ", pg->nr_pgpaths,
1328                                pg->ps.type->table_args);
1329
1330                         list_for_each_entry(p, &pg->pgpaths, list) {
1331                                 DMEMIT("%s ", p->path.dev->name);
1332                                 if (pg->ps.type->status)
1333                                         sz += pg->ps.type->status(&pg->ps,
1334                                               &p->path, type, result + sz,
1335                                               maxlen - sz);
1336                         }
1337                 }
1338                 break;
1339         }
1340
1341         spin_unlock_irqrestore(&m->lock, flags);
1342
1343         return 0;
1344 }
1345
1346 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1347 {
1348         int r;
1349         struct dm_dev *dev;
1350         struct multipath *m = (struct multipath *) ti->private;
1351         action_fn action;
1352
1353         if (argc == 1) {
1354                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path")))
1355                         return queue_if_no_path(m, 1, 0);
1356                 else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path")))
1357                         return queue_if_no_path(m, 0, 0);
1358         }
1359
1360         if (argc != 2)
1361                 goto error;
1362
1363         if (!strnicmp(argv[0], MESG_STR("disable_group")))
1364                 return bypass_pg_num(m, argv[1], 1);
1365         else if (!strnicmp(argv[0], MESG_STR("enable_group")))
1366                 return bypass_pg_num(m, argv[1], 0);
1367         else if (!strnicmp(argv[0], MESG_STR("switch_group")))
1368                 return switch_pg_num(m, argv[1]);
1369         else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1370                 action = reinstate_path;
1371         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1372                 action = fail_path;
1373         else
1374                 goto error;
1375
1376         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
1377                           dm_table_get_mode(ti->table), &dev);
1378         if (r) {
1379                 DMWARN("message: error getting device %s",
1380                        argv[1]);
1381                 return -EINVAL;
1382         }
1383
1384         r = action_dev(m, dev, action);
1385
1386         dm_put_device(ti, dev);
1387
1388         return r;
1389
1390 error:
1391         DMWARN("Unrecognised multipath message received.");
1392         return -EINVAL;
1393 }
1394
1395 static int multipath_ioctl(struct dm_target *ti, struct inode *inode,
1396                            struct file *filp, unsigned int cmd,
1397                            unsigned long arg)
1398 {
1399         struct multipath *m = (struct multipath *) ti->private;
1400         struct block_device *bdev = NULL;
1401         unsigned long flags;
1402         struct file fake_file = {};
1403         struct dentry fake_dentry = {};
1404         int r = 0;
1405
1406         fake_file.f_path.dentry = &fake_dentry;
1407
1408         spin_lock_irqsave(&m->lock, flags);
1409
1410         if (!m->current_pgpath)
1411                 __choose_pgpath(m);
1412
1413         if (m->current_pgpath) {
1414                 bdev = m->current_pgpath->path.dev->bdev;
1415                 fake_dentry.d_inode = bdev->bd_inode;
1416                 fake_file.f_mode = m->current_pgpath->path.dev->mode;
1417         }
1418
1419         if (m->queue_io)
1420                 r = -EAGAIN;
1421         else if (!bdev)
1422                 r = -EIO;
1423
1424         spin_unlock_irqrestore(&m->lock, flags);
1425
1426         return r ? : blkdev_driver_ioctl(bdev->bd_inode, &fake_file,
1427                                          bdev->bd_disk, cmd, arg);
1428 }
1429
1430 /*-----------------------------------------------------------------
1431  * Module setup
1432  *---------------------------------------------------------------*/
1433 static struct target_type multipath_target = {
1434         .name = "multipath",
1435         .version = {1, 0, 5},
1436         .module = THIS_MODULE,
1437         .ctr = multipath_ctr,
1438         .dtr = multipath_dtr,
1439         .map = multipath_map,
1440         .end_io = multipath_end_io,
1441         .presuspend = multipath_presuspend,
1442         .resume = multipath_resume,
1443         .status = multipath_status,
1444         .message = multipath_message,
1445         .ioctl  = multipath_ioctl,
1446 };
1447
1448 static int __init dm_multipath_init(void)
1449 {
1450         int r;
1451
1452         /* allocate a slab for the dm_ios */
1453         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1454         if (!_mpio_cache)
1455                 return -ENOMEM;
1456
1457         r = dm_register_target(&multipath_target);
1458         if (r < 0) {
1459                 DMERR("register failed %d", r);
1460                 kmem_cache_destroy(_mpio_cache);
1461                 return -EINVAL;
1462         }
1463
1464         kmultipathd = create_workqueue("kmpathd");
1465         if (!kmultipathd) {
1466                 DMERR("failed to create workqueue kmpathd");
1467                 dm_unregister_target(&multipath_target);
1468                 kmem_cache_destroy(_mpio_cache);
1469                 return -ENOMEM;
1470         }
1471
1472         /*
1473          * A separate workqueue is used to handle the device handlers
1474          * to avoid overloading existing workqueue. Overloading the
1475          * old workqueue would also create a bottleneck in the
1476          * path of the storage hardware device activation.
1477          */
1478         kmpath_handlerd = create_singlethread_workqueue("kmpath_handlerd");
1479         if (!kmpath_handlerd) {
1480                 DMERR("failed to create workqueue kmpath_handlerd");
1481                 destroy_workqueue(kmultipathd);
1482                 dm_unregister_target(&multipath_target);
1483                 kmem_cache_destroy(_mpio_cache);
1484                 return -ENOMEM;
1485         }
1486
1487         DMINFO("version %u.%u.%u loaded",
1488                multipath_target.version[0], multipath_target.version[1],
1489                multipath_target.version[2]);
1490
1491         return r;
1492 }
1493
1494 static void __exit dm_multipath_exit(void)
1495 {
1496         int r;
1497
1498         destroy_workqueue(kmpath_handlerd);
1499         destroy_workqueue(kmultipathd);
1500
1501         r = dm_unregister_target(&multipath_target);
1502         if (r < 0)
1503                 DMERR("target unregister failed %d", r);
1504         kmem_cache_destroy(_mpio_cache);
1505 }
1506
1507 module_init(dm_multipath_init);
1508 module_exit(dm_multipath_exit);
1509
1510 MODULE_DESCRIPTION(DM_NAME " multipath target");
1511 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1512 MODULE_LICENSE("GPL");