drivers/md/dm-mpath.c

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