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