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