drivers/md/dm-mpath.c

   1 /*
   2  * Copyright (C) 2003 Sistina Software Limited.
   3  * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
   4  *
   5  * This file is released under the GPL.
   6  */
   7
   8 #include <linux/device-mapper.h>
   9
  10 #include "dm-path-selector.h"
  11 #include "dm-bio-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         struct work_struct deactivate_path;
  38 };
  39
  40 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  41
  42 /*
  43  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  44  * Each has a path selector which controls which path gets used.
  45  */
  46 struct priority_group {
  47         struct list_head list;
  48
  49         struct multipath *m;            /* Owning multipath instance */
  50         struct path_selector ps;
  51
  52         unsigned pg_num;                /* Reference number */
  53         unsigned bypassed;              /* Temporarily bypass this PG? */
  54
  55         unsigned nr_pgpaths;            /* Number of paths in PG */
  56         struct list_head pgpaths;
  57 };
  58
  59 /* Multipath context */
  60 struct multipath {
  61         struct list_head list;
  62         struct dm_target *ti;
  63
  64         spinlock_t lock;
  65
  66         const char *hw_handler_name;
  67         struct work_struct activate_path;
  68         struct pgpath *pgpath_to_activate;
  69         unsigned nr_priority_groups;
  70         struct list_head priority_groups;
  71         unsigned pg_init_required;      /* pg_init needs calling? */
  72         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  73
  74         unsigned nr_valid_paths;        /* Total number of usable paths */
  75         struct pgpath *current_pgpath;
  76         struct priority_group *current_pg;
  77         struct priority_group *next_pg; /* Switch to this PG if set */
  78         unsigned repeat_count;          /* I/Os left before calling PS again */
  79
  80         unsigned queue_io;              /* Must we queue all I/O? */
  81         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
  82         unsigned saved_queue_if_no_path;/* Saved state during suspension */
  83         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  84         unsigned pg_init_count;         /* Number of times pg_init called */
  85
  86         struct work_struct process_queued_ios;
  87         struct bio_list queued_ios;
  88         unsigned queue_size;
  89
  90         struct work_struct trigger_event;
  91
  92         /*
  93          * We must use a mempool of dm_mpath_io structs so that we
  94          * can resubmit bios on error.
  95          */
  96         mempool_t *mpio_pool;
  97 };
  98
  99 /*
 100  * Context information attached to each bio we process.
 101  */
 102 struct dm_mpath_io {
 103         struct pgpath *pgpath;
 104         struct dm_bio_details details;
 105 };
 106
 107 typedef int (*action_fn) (struct pgpath *pgpath);
 108
 109 #define MIN_IOS 256     /* Mempool size */
 110
 111 static struct kmem_cache *_mpio_cache;
 112
 113 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 114 static void process_queued_ios(struct work_struct *work);
 115 static void trigger_event(struct work_struct *work);
 116 static void activate_path(struct work_struct *work);
 117 static void deactivate_path(struct work_struct *work);
 118
 119
 120 /*-----------------------------------------------
 121  * Allocation routines
 122  *-----------------------------------------------*/
 123
 124 static struct pgpath *alloc_pgpath(void)
 125 {
 126         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 127
 128         if (pgpath) {
 129                 pgpath->is_active = 1;
 130                 INIT_WORK(&pgpath->deactivate_path, deactivate_path);
 131         }
 132
 133         return pgpath;
 134 }
 135
 136 static void free_pgpath(struct pgpath *pgpath)
 137 {
 138         kfree(pgpath);
 139 }
 140
 141 static void deactivate_path(struct work_struct *work)
 142 {
 143         struct pgpath *pgpath =
 144                 container_of(work, struct pgpath, deactivate_path);
 145
 146         blk_abort_queue(pgpath->path.dev->bdev->bd_disk->queue);
 147 }
 148
 149 static struct priority_group *alloc_priority_group(void)
 150 {
 151         struct priority_group *pg;
 152
 153         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 154
 155         if (pg)
 156                 INIT_LIST_HEAD(&pg->pgpaths);
 157
 158         return pg;
 159 }
 160
 161 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 162 {
 163         unsigned long flags;
 164         struct pgpath *pgpath, *tmp;
 165         struct multipath *m = ti->private;
 166
 167         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 168                 list_del(&pgpath->list);
 169                 if (m->hw_handler_name)
 170                         scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 171                 dm_put_device(ti, pgpath->path.dev);
 172                 spin_lock_irqsave(&m->lock, flags);
 173                 if (m->pgpath_to_activate == pgpath)
 174                         m->pgpath_to_activate = NULL;
 175                 spin_unlock_irqrestore(&m->lock, flags);
 176                 free_pgpath(pgpath);
 177         }
 178 }
 179
 180 static void free_priority_group(struct priority_group *pg,
 181                                 struct dm_target *ti)
 182 {
 183         struct path_selector *ps = &pg->ps;
 184
 185         if (ps->type) {
 186                 ps->type->destroy(ps);
 187                 dm_put_path_selector(ps->type);
 188         }
 189
 190         free_pgpaths(&pg->pgpaths, ti);
 191         kfree(pg);
 192 }
 193
 194 static struct multipath *alloc_multipath(struct dm_target *ti)
 195 {
 196         struct multipath *m;
 197
 198         m = kzalloc(sizeof(*m), GFP_KERNEL);
 199         if (m) {
 200                 INIT_LIST_HEAD(&m->priority_groups);
 201                 spin_lock_init(&m->lock);
 202                 m->queue_io = 1;
 203                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
 204                 INIT_WORK(&m->trigger_event, trigger_event);
 205                 INIT_WORK(&m->activate_path, activate_path);
 206                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 207                 if (!m->mpio_pool) {
 208                         kfree(m);
 209                         return NULL;
 210                 }
 211                 m->ti = ti;
 212                 ti->private = m;
 213         }
 214
 215         return m;
 216 }
 217
 218 static void free_multipath(struct multipath *m)
 219 {
 220         struct priority_group *pg, *tmp;
 221
 222         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 223                 list_del(&pg->list);
 224                 free_priority_group(pg, m->ti);
 225         }
 226
 227         kfree(m->hw_handler_name);
 228         mempool_destroy(m->mpio_pool);
 229         kfree(m);
 230 }
 231
 232
 233 /*-----------------------------------------------
 234  * Path selection
 235  *-----------------------------------------------*/
 236
 237 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 238 {
 239         m->current_pg = pgpath->pg;
 240
 241         /* Must we initialise the PG first, and queue I/O till it's ready? */
 242         if (m->hw_handler_name) {
 243                 m->pg_init_required = 1;
 244                 m->queue_io = 1;
 245         } else {
 246                 m->pg_init_required = 0;
 247                 m->queue_io = 0;
 248         }
 249
 250         m->pg_init_count = 0;
 251 }
 252
 253 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg)
 254 {
 255         struct dm_path *path;
 256
 257         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count);
 258         if (!path)
 259                 return -ENXIO;
 260
 261         m->current_pgpath = path_to_pgpath(path);
 262
 263         if (m->current_pg != pg)
 264                 __switch_pg(m, m->current_pgpath);
 265
 266         return 0;
 267 }
 268
 269 static void __choose_pgpath(struct multipath *m)
 270 {
 271         struct priority_group *pg;
 272         unsigned bypassed = 1;
 273
 274         if (!m->nr_valid_paths)
 275                 goto failed;
 276
 277         /* Were we instructed to switch PG? */
 278         if (m->next_pg) {
 279                 pg = m->next_pg;
 280                 m->next_pg = NULL;
 281                 if (!__choose_path_in_pg(m, pg))
 282                         return;
 283         }
 284
 285         /* Don't change PG until it has no remaining paths */
 286         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg))
 287                 return;
 288
 289         /*
 290          * Loop through priority groups until we find a valid path.
 291          * First time we skip PGs marked 'bypassed'.
 292          * Second time we only try the ones we skipped.
 293          */
 294         do {
 295                 list_for_each_entry(pg, &m->priority_groups, list) {
 296                         if (pg->bypassed == bypassed)
 297                                 continue;
 298                         if (!__choose_path_in_pg(m, pg))
 299                                 return;
 300                 }
 301         } while (bypassed--);
 302
 303 failed:
 304         m->current_pgpath = NULL;
 305         m->current_pg = NULL;
 306 }
 307
 308 /*
 309  * Check whether bios must be queued in the device-mapper core rather
 310  * than here in the target.
 311  *
 312  * m->lock must be held on entry.
 313  *
 314  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 315  * same value then we are not between multipath_presuspend()
 316  * and multipath_resume() calls and we have no need to check
 317  * for the DMF_NOFLUSH_SUSPENDING flag.
 318  */
 319 static int __must_push_back(struct multipath *m)
 320 {
 321         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 322                 dm_noflush_suspending(m->ti));
 323 }
 324
 325 static int map_io(struct multipath *m, struct bio *bio,
 326                   struct dm_mpath_io *mpio, unsigned was_queued)
 327 {
 328         int r = DM_MAPIO_REMAPPED;
 329         unsigned long flags;
 330         struct pgpath *pgpath;
 331
 332         spin_lock_irqsave(&m->lock, flags);
 333
 334         /* Do we need to select a new pgpath? */
 335         if (!m->current_pgpath ||
 336             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 337                 __choose_pgpath(m);
 338
 339         pgpath = m->current_pgpath;
 340
 341         if (was_queued)
 342                 m->queue_size--;
 343
 344         if ((pgpath && m->queue_io) ||
 345             (!pgpath && m->queue_if_no_path)) {
 346                 /* Queue for the daemon to resubmit */
 347                 bio_list_add(&m->queued_ios, bio);
 348                 m->queue_size++;
 349                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 350                     !m->queue_io)
 351                         queue_work(kmultipathd, &m->process_queued_ios);
 352                 pgpath = NULL;
 353                 r = DM_MAPIO_SUBMITTED;
 354         } else if (pgpath)
 355                 bio->bi_bdev = pgpath->path.dev->bdev;
 356         else if (__must_push_back(m))
 357                 r = DM_MAPIO_REQUEUE;
 358         else
 359                 r = -EIO;       /* Failed */
 360
 361         mpio->pgpath = pgpath;
 362
 363         spin_unlock_irqrestore(&m->lock, flags);
 364
 365         return r;
 366 }
 367
 368 /*
 369  * If we run out of usable paths, should we queue I/O or error it?
 370  */
 371 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 372                             unsigned save_old_value)
 373 {
 374         unsigned long flags;
 375
 376         spin_lock_irqsave(&m->lock, flags);
 377
 378         if (save_old_value)
 379                 m->saved_queue_if_no_path = m->queue_if_no_path;
 380         else
 381                 m->saved_queue_if_no_path = queue_if_no_path;
 382         m->queue_if_no_path = queue_if_no_path;
 383         if (!m->queue_if_no_path && m->queue_size)
 384                 queue_work(kmultipathd, &m->process_queued_ios);
 385
 386         spin_unlock_irqrestore(&m->lock, flags);
 387
 388         return 0;
 389 }
 390
 391 /*-----------------------------------------------------------------
 392  * The multipath daemon is responsible for resubmitting queued ios.
 393  *---------------------------------------------------------------*/
 394
 395 static void dispatch_queued_ios(struct multipath *m)
 396 {
 397         int r;
 398         unsigned long flags;
 399         struct bio *bio = NULL, *next;
 400         struct dm_mpath_io *mpio;
 401         union map_info *info;
 402
 403         spin_lock_irqsave(&m->lock, flags);
 404         bio = bio_list_get(&m->queued_ios);
 405         spin_unlock_irqrestore(&m->lock, flags);
 406
 407         while (bio) {
 408                 next = bio->bi_next;
 409                 bio->bi_next = NULL;
 410
 411                 info = dm_get_mapinfo(bio);
 412                 mpio = info->ptr;
 413
 414                 r = map_io(m, bio, mpio, 1);
 415                 if (r < 0)
 416                         bio_endio(bio, r);
 417                 else if (r == DM_MAPIO_REMAPPED)
 418                         generic_make_request(bio);
 419                 else if (r == DM_MAPIO_REQUEUE)
 420                         bio_endio(bio, -EIO);
 421
 422                 bio = next;
 423         }
 424 }
 425
 426 static void process_queued_ios(struct work_struct *work)
 427 {
 428         struct multipath *m =
 429                 container_of(work, struct multipath, process_queued_ios);
 430         struct pgpath *pgpath = NULL;
 431         unsigned init_required = 0, must_queue = 1;
 432         unsigned long flags;
 433
 434         spin_lock_irqsave(&m->lock, flags);
 435
 436         if (!m->queue_size)
 437                 goto out;
 438
 439         if (!m->current_pgpath)
 440                 __choose_pgpath(m);
 441
 442         pgpath = m->current_pgpath;
 443
 444         if ((pgpath && !m->queue_io) ||
 445             (!pgpath && !m->queue_if_no_path))
 446                 must_queue = 0;
 447
 448         if (m->pg_init_required && !m->pg_init_in_progress && pgpath) {
 449                 m->pgpath_to_activate = pgpath;
 450                 m->pg_init_count++;
 451                 m->pg_init_required = 0;
 452                 m->pg_init_in_progress = 1;
 453                 init_required = 1;
 454         }
 455
 456 out:
 457         spin_unlock_irqrestore(&m->lock, flags);
 458
 459         if (init_required)
 460                 queue_work(kmpath_handlerd, &m->activate_path);
 461
 462         if (!must_queue)
 463                 dispatch_queued_ios(m);
 464 }
 465
 466 /*
 467  * An event is triggered whenever a path is taken out of use.
 468  * Includes path failure and PG bypass.
 469  */
 470 static void trigger_event(struct work_struct *work)
 471 {
 472         struct multipath *m =
 473                 container_of(work, struct multipath, trigger_event);
 474
 475         dm_table_event(m->ti->table);
 476 }
 477
 478 /*-----------------------------------------------------------------
 479  * Constructor/argument parsing:
 480  * <#multipath feature args> [<arg>]*
 481  * <#hw_handler args> [hw_handler [<arg>]*]
 482  * <#priority groups>
 483  * <initial priority group>
 484  *     [<selector> <#selector args> [<arg>]*
 485  *      <#paths> <#per-path selector args>
 486  *         [<path> [<arg>]* ]+ ]+
 487  *---------------------------------------------------------------*/
 488 struct param {
 489         unsigned min;
 490         unsigned max;
 491         char *error;
 492 };
 493
 494 static int read_param(struct param *param, char *str, unsigned *v, char **error)
 495 {
 496         if (!str ||
 497             (sscanf(str, "%u", v) != 1) ||
 498             (*v < param->min) ||
 499             (*v > param->max)) {
 500                 *error = param->error;
 501                 return -EINVAL;
 502         }
 503
 504         return 0;
 505 }
 506
 507 struct arg_set {
 508         unsigned argc;
 509         char **argv;
 510 };
 511
 512 static char *shift(struct arg_set *as)
 513 {
 514         char *r;
 515
 516         if (as->argc) {
 517                 as->argc--;
 518                 r = *as->argv;
 519                 as->argv++;
 520                 return r;
 521         }
 522
 523         return NULL;
 524 }
 525
 526 static void consume(struct arg_set *as, unsigned n)
 527 {
 528         BUG_ON (as->argc < n);
 529         as->argc -= n;
 530         as->argv += n;
 531 }
 532
 533 static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
 534                                struct dm_target *ti)
 535 {
 536         int r;
 537         struct path_selector_type *pst;
 538         unsigned ps_argc;
 539
 540         static struct param _params[] = {
 541                 {0, 1024, "invalid number of path selector args"},
 542         };
 543
 544         pst = dm_get_path_selector(shift(as));
 545         if (!pst) {
 546                 ti->error = "unknown path selector type";
 547                 return -EINVAL;
 548         }
 549
 550         r = read_param(_params, shift(as), &ps_argc, &ti->error);
 551         if (r) {
 552                 dm_put_path_selector(pst);
 553                 return -EINVAL;
 554         }
 555
 556         if (ps_argc > as->argc) {
 557                 dm_put_path_selector(pst);
 558                 ti->error = "not enough arguments for path selector";
 559                 return -EINVAL;
 560         }
 561
 562         r = pst->create(&pg->ps, ps_argc, as->argv);
 563         if (r) {
 564                 dm_put_path_selector(pst);
 565                 ti->error = "path selector constructor failed";
 566                 return r;
 567         }
 568
 569         pg->ps.type = pst;
 570         consume(as, ps_argc);
 571
 572         return 0;
 573 }
 574
 575 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
 576                                struct dm_target *ti)
 577 {
 578         int r;
 579         struct pgpath *p;
 580         struct multipath *m = ti->private;
 581
 582         /* we need at least a path arg */
 583         if (as->argc < 1) {
 584                 ti->error = "no device given";
 585                 return ERR_PTR(-EINVAL);
 586         }
 587
 588         p = alloc_pgpath();
 589         if (!p)
 590                 return ERR_PTR(-ENOMEM);
 591
 592         r = dm_get_device(ti, shift(as), ti->begin, ti->len,
 593                           dm_table_get_mode(ti->table), &p->path.dev);
 594         if (r) {
 595                 ti->error = "error getting device";
 596                 goto bad;
 597         }
 598
 599         if (m->hw_handler_name) {
 600                 struct request_queue *q = bdev_get_queue(p->path.dev->bdev);
 601
 602                 r = scsi_dh_attach(q, m->hw_handler_name);
 603                 if (r == -EBUSY) {
 604                         /*
 605                          * Already attached to different hw_handler,
 606                          * try to reattach with correct one.
 607                          */
 608                         scsi_dh_detach(q);
 609                         r = scsi_dh_attach(q, m->hw_handler_name);
 610                 }
 611
 612                 if (r < 0) {
 613                         ti->error = "error attaching hardware handler";
 614                         dm_put_device(ti, p->path.dev);
 615                         goto bad;
 616                 }
 617         }
 618
 619         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 620         if (r) {
 621                 dm_put_device(ti, p->path.dev);
 622                 goto bad;
 623         }
 624
 625         return p;
 626
 627  bad:
 628         free_pgpath(p);
 629         return ERR_PTR(r);
 630 }
 631
 632 static struct priority_group *parse_priority_group(struct arg_set *as,
 633                                                    struct multipath *m)
 634 {
 635         static struct param _params[] = {
 636                 {1, 1024, "invalid number of paths"},
 637                 {0, 1024, "invalid number of selector args"}
 638         };
 639
 640         int r;
 641         unsigned i, nr_selector_args, nr_params;
 642         struct priority_group *pg;
 643         struct dm_target *ti = m->ti;
 644
 645         if (as->argc < 2) {
 646                 as->argc = 0;
 647                 ti->error = "not enough priority group arguments";
 648                 return ERR_PTR(-EINVAL);
 649         }
 650
 651         pg = alloc_priority_group();
 652         if (!pg) {
 653                 ti->error = "couldn't allocate priority group";
 654                 return ERR_PTR(-ENOMEM);
 655         }
 656         pg->m = m;
 657
 658         r = parse_path_selector(as, pg, ti);
 659         if (r)
 660                 goto bad;
 661
 662         /*
 663          * read the paths
 664          */
 665         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
 666         if (r)
 667                 goto bad;
 668
 669         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
 670         if (r)
 671                 goto bad;
 672
 673         nr_params = 1 + nr_selector_args;
 674         for (i = 0; i < pg->nr_pgpaths; i++) {
 675                 struct pgpath *pgpath;
 676                 struct arg_set path_args;
 677
 678                 if (as->argc < nr_params) {
 679                         ti->error = "not enough path parameters";
 680                         goto bad;
 681                 }
 682
 683                 path_args.argc = nr_params;
 684                 path_args.argv = as->argv;
 685
 686                 pgpath = parse_path(&path_args, &pg->ps, ti);
 687                 if (IS_ERR(pgpath)) {
 688                         r = PTR_ERR(pgpath);
 689                         goto bad;
 690                 }
 691
 692                 pgpath->pg = pg;
 693                 list_add_tail(&pgpath->list, &pg->pgpaths);
 694                 consume(as, nr_params);
 695         }
 696
 697         return pg;
 698
 699  bad:
 700         free_priority_group(pg, ti);
 701         return ERR_PTR(r);
 702 }
 703
 704 static int parse_hw_handler(struct arg_set *as, struct multipath *m)
 705 {
 706         unsigned hw_argc;
 707         struct dm_target *ti = m->ti;
 708
 709         static struct param _params[] = {
 710                 {0, 1024, "invalid number of hardware handler args"},
 711         };
 712
 713         if (read_param(_params, shift(as), &hw_argc, &ti->error))
 714                 return -EINVAL;
 715
 716         if (!hw_argc)
 717                 return 0;
 718
 719         if (hw_argc > as->argc) {
 720                 ti->error = "not enough arguments for hardware handler";
 721                 return -EINVAL;
 722         }
 723
 724         m->hw_handler_name = kstrdup(shift(as), GFP_KERNEL);
 725         request_module("scsi_dh_%s", m->hw_handler_name);
 726         if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
 727                 ti->error = "unknown hardware handler type";
 728                 kfree(m->hw_handler_name);
 729                 m->hw_handler_name = NULL;
 730                 return -EINVAL;
 731         }
 732
 733         if (hw_argc > 1)
 734                 DMWARN("Ignoring user-specified arguments for "
 735                        "hardware handler \"%s\"", m->hw_handler_name);
 736         consume(as, hw_argc - 1);
 737
 738         return 0;
 739 }
 740
 741 static int parse_features(struct arg_set *as, struct multipath *m)
 742 {
 743         int r;
 744         unsigned argc;
 745         struct dm_target *ti = m->ti;
 746         const char *param_name;
 747
 748         static struct param _params[] = {
 749                 {0, 3, "invalid number of feature args"},
 750                 {1, 50, "pg_init_retries must be between 1 and 50"},
 751         };
 752
 753         r = read_param(_params, shift(as), &argc, &ti->error);
 754         if (r)
 755                 return -EINVAL;
 756
 757         if (!argc)
 758                 return 0;
 759
 760         do {
 761                 param_name = shift(as);
 762                 argc--;
 763
 764                 if (!strnicmp(param_name, MESG_STR("queue_if_no_path"))) {
 765                         r = queue_if_no_path(m, 1, 0);
 766                         continue;
 767                 }
 768
 769                 if (!strnicmp(param_name, MESG_STR("pg_init_retries")) &&
 770                     (argc >= 1)) {
 771                         r = read_param(_params + 1, shift(as),
 772                                        &m->pg_init_retries, &ti->error);
 773                         argc--;
 774                         continue;
 775                 }
 776
 777                 ti->error = "Unrecognised multipath feature request";
 778                 r = -EINVAL;
 779         } while (argc && !r);
 780
 781         return r;
 782 }
 783
 784 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 785                          char **argv)
 786 {
 787         /* target parameters */
 788         static struct param _params[] = {
 789                 {1, 1024, "invalid number of priority groups"},
 790                 {1, 1024, "invalid initial priority group number"},
 791         };
 792
 793         int r;
 794         struct multipath *m;
 795         struct arg_set as;
 796         unsigned pg_count = 0;
 797         unsigned next_pg_num;
 798
 799         as.argc = argc;
 800         as.argv = argv;
 801
 802         m = alloc_multipath(ti);
 803         if (!m) {
 804                 ti->error = "can't allocate multipath";
 805                 return -EINVAL;
 806         }
 807
 808         r = parse_features(&as, m);
 809         if (r)
 810                 goto bad;
 811
 812         r = parse_hw_handler(&as, m);
 813         if (r)
 814                 goto bad;
 815
 816         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
 817         if (r)
 818                 goto bad;
 819
 820         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
 821         if (r)
 822                 goto bad;
 823
 824         /* parse the priority groups */
 825         while (as.argc) {
 826                 struct priority_group *pg;
 827
 828                 pg = parse_priority_group(&as, m);
 829                 if (IS_ERR(pg)) {
 830                         r = PTR_ERR(pg);
 831                         goto bad;
 832                 }
 833
 834                 m->nr_valid_paths += pg->nr_pgpaths;
 835                 list_add_tail(&pg->list, &m->priority_groups);
 836                 pg_count++;
 837                 pg->pg_num = pg_count;
 838                 if (!--next_pg_num)
 839                         m->next_pg = pg;
 840         }
 841
 842         if (pg_count != m->nr_priority_groups) {
 843                 ti->error = "priority group count mismatch";
 844                 r = -EINVAL;
 845                 goto bad;
 846         }
 847
 848         return 0;
 849
 850  bad:
 851         free_multipath(m);
 852         return r;
 853 }
 854
 855 static void multipath_dtr(struct dm_target *ti)
 856 {
 857         struct multipath *m = (struct multipath *) ti->private;
 858
 859         flush_workqueue(kmpath_handlerd);
 860         flush_workqueue(kmultipathd);
 861         free_multipath(m);
 862 }
 863
 864 /*
 865  * Map bios, recording original fields for later in case we have to resubmit
 866  */
 867 static int multipath_map(struct dm_target *ti, struct bio *bio,
 868                          union map_info *map_context)
 869 {
 870         int r;
 871         struct dm_mpath_io *mpio;
 872         struct multipath *m = (struct multipath *) ti->private;
 873
 874         mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
 875         dm_bio_record(&mpio->details, bio);
 876
 877         map_context->ptr = mpio;
 878         bio->bi_rw |= (1 << BIO_RW_FAILFAST_TRANSPORT);
 879         r = map_io(m, bio, mpio, 0);
 880         if (r < 0 || r == DM_MAPIO_REQUEUE)
 881                 mempool_free(mpio, m->mpio_pool);
 882
 883         return r;
 884 }
 885
 886 /*
 887  * Take a path out of use.
 888  */
 889 static int fail_path(struct pgpath *pgpath)
 890 {
 891         unsigned long flags;
 892         struct multipath *m = pgpath->pg->m;
 893
 894         spin_lock_irqsave(&m->lock, flags);
 895
 896         if (!pgpath->is_active)
 897                 goto out;
 898
 899         DMWARN("Failing path %s.", pgpath->path.dev->name);
 900
 901         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 902         pgpath->is_active = 0;
 903         pgpath->fail_count++;
 904
 905         m->nr_valid_paths--;
 906
 907         if (pgpath == m->current_pgpath)
 908                 m->current_pgpath = NULL;
 909
 910         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
 911                       pgpath->path.dev->name, m->nr_valid_paths);
 912
 913         schedule_work(&m->trigger_event);
 914         queue_work(kmultipathd, &pgpath->deactivate_path);
 915
 916 out:
 917         spin_unlock_irqrestore(&m->lock, flags);
 918
 919         return 0;
 920 }
 921
 922 /*
 923  * Reinstate a previously-failed path
 924  */
 925 static int reinstate_path(struct pgpath *pgpath)
 926 {
 927         int r = 0;
 928         unsigned long flags;
 929         struct multipath *m = pgpath->pg->m;
 930
 931         spin_lock_irqsave(&m->lock, flags);
 932
 933         if (pgpath->is_active)
 934                 goto out;
 935
 936         if (!pgpath->pg->ps.type->reinstate_path) {
 937                 DMWARN("Reinstate path not supported by path selector %s",
 938                        pgpath->pg->ps.type->name);
 939                 r = -EINVAL;
 940                 goto out;
 941         }
 942
 943         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
 944         if (r)
 945                 goto out;
 946
 947         pgpath->is_active = 1;
 948
 949         m->current_pgpath = NULL;
 950         if (!m->nr_valid_paths++ && m->queue_size)
 951                 queue_work(kmultipathd, &m->process_queued_ios);
 952
 953         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
 954                       pgpath->path.dev->name, m->nr_valid_paths);
 955
 956         schedule_work(&m->trigger_event);
 957
 958 out:
 959         spin_unlock_irqrestore(&m->lock, flags);
 960
 961         return r;
 962 }
 963
 964 /*
 965  * Fail or reinstate all paths that match the provided struct dm_dev.
 966  */
 967 static int action_dev(struct multipath *m, struct dm_dev *dev,
 968                       action_fn action)
 969 {
 970         int r = 0;
 971         struct pgpath *pgpath;
 972         struct priority_group *pg;
 973
 974         list_for_each_entry(pg, &m->priority_groups, list) {
 975                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
 976                         if (pgpath->path.dev == dev)
 977                                 r = action(pgpath);
 978                 }
 979         }
 980
 981         return r;
 982 }
 983
 984 /*
 985  * Temporarily try to avoid having to use the specified PG
 986  */
 987 static void bypass_pg(struct multipath *m, struct priority_group *pg,
 988                       int bypassed)
 989 {
 990         unsigned long flags;
 991
 992         spin_lock_irqsave(&m->lock, flags);
 993
 994         pg->bypassed = bypassed;
 995         m->current_pgpath = NULL;
 996         m->current_pg = NULL;
 997
 998         spin_unlock_irqrestore(&m->lock, flags);
 999
1000         schedule_work(&m->trigger_event);
1001 }
1002
1003 /*
1004  * Switch to using the specified PG from the next I/O that gets mapped
1005  */
1006 static int switch_pg_num(struct multipath *m, const char *pgstr)
1007 {
1008         struct priority_group *pg;
1009         unsigned pgnum;
1010         unsigned long flags;
1011
1012         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1013             (pgnum > m->nr_priority_groups)) {
1014                 DMWARN("invalid PG number supplied to switch_pg_num");
1015                 return -EINVAL;
1016         }
1017
1018         spin_lock_irqsave(&m->lock, flags);
1019         list_for_each_entry(pg, &m->priority_groups, list) {
1020                 pg->bypassed = 0;
1021                 if (--pgnum)
1022                         continue;
1023
1024                 m->current_pgpath = NULL;
1025                 m->current_pg = NULL;
1026                 m->next_pg = pg;
1027         }
1028         spin_unlock_irqrestore(&m->lock, flags);
1029
1030         schedule_work(&m->trigger_event);
1031         return 0;
1032 }
1033
1034 /*
1035  * Set/clear bypassed status of a PG.
1036  * PGs are numbered upwards from 1 in the order they were declared.
1037  */
1038 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1039 {
1040         struct priority_group *pg;
1041         unsigned pgnum;
1042
1043         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1044             (pgnum > m->nr_priority_groups)) {
1045                 DMWARN("invalid PG number supplied to bypass_pg");
1046                 return -EINVAL;
1047         }
1048
1049         list_for_each_entry(pg, &m->priority_groups, list) {
1050                 if (!--pgnum)
1051                         break;
1052         }
1053
1054         bypass_pg(m, pg, bypassed);
1055         return 0;
1056 }
1057
1058 /*
1059  * Should we retry pg_init immediately?
1060  */
1061 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1062 {
1063         unsigned long flags;
1064         int limit_reached = 0;
1065
1066         spin_lock_irqsave(&m->lock, flags);
1067
1068         if (m->pg_init_count <= m->pg_init_retries)
1069                 m->pg_init_required = 1;
1070         else
1071                 limit_reached = 1;
1072
1073         spin_unlock_irqrestore(&m->lock, flags);
1074
1075         return limit_reached;
1076 }
1077
1078 static void pg_init_done(struct dm_path *path, int errors)
1079 {
1080         struct pgpath *pgpath = path_to_pgpath(path);
1081         struct priority_group *pg = pgpath->pg;
1082         struct multipath *m = pg->m;
1083         unsigned long flags;
1084
1085         /* device or driver problems */
1086         switch (errors) {
1087         case SCSI_DH_OK:
1088                 break;
1089         case SCSI_DH_NOSYS:
1090                 if (!m->hw_handler_name) {
1091                         errors = 0;
1092                         break;
1093                 }
1094                 DMERR("Cannot failover device because scsi_dh_%s was not "
1095                       "loaded.", m->hw_handler_name);
1096                 /*
1097                  * Fail path for now, so we do not ping pong
1098                  */
1099                 fail_path(pgpath);
1100                 break;
1101         case SCSI_DH_DEV_TEMP_BUSY:
1102                 /*
1103                  * Probably doing something like FW upgrade on the
1104                  * controller so try the other pg.
1105                  */
1106                 bypass_pg(m, pg, 1);
1107                 break;
1108         /* TODO: For SCSI_DH_RETRY we should wait a couple seconds */
1109         case SCSI_DH_RETRY:
1110         case SCSI_DH_IMM_RETRY:
1111         case SCSI_DH_RES_TEMP_UNAVAIL:
1112                 if (pg_init_limit_reached(m, pgpath))
1113                         fail_path(pgpath);
1114                 errors = 0;
1115                 break;
1116         default:
1117                 /*
1118                  * We probably do not want to fail the path for a device
1119                  * error, but this is what the old dm did. In future
1120                  * patches we can do more advanced handling.
1121                  */
1122                 fail_path(pgpath);
1123         }
1124
1125         spin_lock_irqsave(&m->lock, flags);
1126         if (errors) {
1127                 DMERR("Could not failover device. Error %d.", errors);
1128                 m->current_pgpath = NULL;
1129                 m->current_pg = NULL;
1130         } else if (!m->pg_init_required) {
1131                 m->queue_io = 0;
1132                 pg->bypassed = 0;
1133         }
1134
1135         m->pg_init_in_progress = 0;
1136         queue_work(kmultipathd, &m->process_queued_ios);
1137         spin_unlock_irqrestore(&m->lock, flags);
1138 }
1139
1140 static void activate_path(struct work_struct *work)
1141 {
1142         int ret;
1143         struct multipath *m =
1144                 container_of(work, struct multipath, activate_path);
1145         struct dm_path *path;
1146         unsigned long flags;
1147
1148         spin_lock_irqsave(&m->lock, flags);
1149         path = &m->pgpath_to_activate->path;
1150         m->pgpath_to_activate = NULL;
1151         spin_unlock_irqrestore(&m->lock, flags);
1152         if (!path)
1153                 return;
1154         ret = scsi_dh_activate(bdev_get_queue(path->dev->bdev));
1155         pg_init_done(path, ret);
1156 }
1157
1158 /*
1159  * end_io handling
1160  */
1161 static int do_end_io(struct multipath *m, struct bio *bio,
1162                      int error, struct dm_mpath_io *mpio)
1163 {
1164         unsigned long flags;
1165
1166         if (!error)
1167                 return 0;       /* I/O complete */
1168
1169         if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
1170                 return error;
1171
1172         if (error == -EOPNOTSUPP)
1173                 return error;
1174
1175         spin_lock_irqsave(&m->lock, flags);
1176         if (!m->nr_valid_paths) {
1177                 if (__must_push_back(m)) {
1178                         spin_unlock_irqrestore(&m->lock, flags);
1179                         return DM_ENDIO_REQUEUE;
1180                 } else if (!m->queue_if_no_path) {
1181                         spin_unlock_irqrestore(&m->lock, flags);
1182                         return -EIO;
1183                 } else {
1184                         spin_unlock_irqrestore(&m->lock, flags);
1185                         goto requeue;
1186                 }
1187         }
1188         spin_unlock_irqrestore(&m->lock, flags);
1189
1190         if (mpio->pgpath)
1191                 fail_path(mpio->pgpath);
1192
1193       requeue:
1194         dm_bio_restore(&mpio->details, bio);
1195
1196         /* queue for the daemon to resubmit or fail */
1197         spin_lock_irqsave(&m->lock, flags);
1198         bio_list_add(&m->queued_ios, bio);
1199         m->queue_size++;
1200         if (!m->queue_io)
1201                 queue_work(kmultipathd, &m->process_queued_ios);
1202         spin_unlock_irqrestore(&m->lock, flags);
1203
1204         return DM_ENDIO_INCOMPLETE;     /* io not complete */
1205 }
1206
1207 static int multipath_end_io(struct dm_target *ti, struct bio *bio,
1208                             int error, union map_info *map_context)
1209 {
1210         struct multipath *m = ti->private;
1211         struct dm_mpath_io *mpio = map_context->ptr;
1212         struct pgpath *pgpath = mpio->pgpath;
1213         struct path_selector *ps;
1214         int r;
1215
1216         r  = do_end_io(m, bio, error, mpio);
1217         if (pgpath) {
1218                 ps = &pgpath->pg->ps;
1219                 if (ps->type->end_io)
1220                         ps->type->end_io(ps, &pgpath->path);
1221         }
1222         if (r != DM_ENDIO_INCOMPLETE)
1223                 mempool_free(mpio, m->mpio_pool);
1224
1225         return r;
1226 }
1227
1228 /*
1229  * Suspend can't complete until all the I/O is processed so if
1230  * the last path fails we must error any remaining I/O.
1231  * Note that if the freeze_bdev fails while suspending, the
1232  * queue_if_no_path state is lost - userspace should reset it.
1233  */
1234 static void multipath_presuspend(struct dm_target *ti)
1235 {
1236         struct multipath *m = (struct multipath *) ti->private;
1237
1238         queue_if_no_path(m, 0, 1);
1239 }
1240
1241 /*
1242  * Restore the queue_if_no_path setting.
1243  */
1244 static void multipath_resume(struct dm_target *ti)
1245 {
1246         struct multipath *m = (struct multipath *) ti->private;
1247         unsigned long flags;
1248
1249         spin_lock_irqsave(&m->lock, flags);
1250         m->queue_if_no_path = m->saved_queue_if_no_path;
1251         spin_unlock_irqrestore(&m->lock, flags);
1252 }
1253
1254 /*
1255  * Info output has the following format:
1256  * num_multipath_feature_args [multipath_feature_args]*
1257  * num_handler_status_args [handler_status_args]*
1258  * num_groups init_group_number
1259  *            [A|D|E num_ps_status_args [ps_status_args]*
1260  *             num_paths num_selector_args
1261  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1262  *
1263  * Table output has the following format (identical to the constructor string):
1264  * num_feature_args [features_args]*
1265  * num_handler_args hw_handler [hw_handler_args]*
1266  * num_groups init_group_number
1267  *     [priority selector-name num_ps_args [ps_args]*
1268  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1269  */
1270 static int multipath_status(struct dm_target *ti, status_type_t type,
1271                             char *result, unsigned int maxlen)
1272 {
1273         int sz = 0;
1274         unsigned long flags;
1275         struct multipath *m = (struct multipath *) ti->private;
1276         struct priority_group *pg;
1277         struct pgpath *p;
1278         unsigned pg_num;
1279         char state;
1280
1281         spin_lock_irqsave(&m->lock, flags);
1282
1283         /* Features */
1284         if (type == STATUSTYPE_INFO)
1285                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1286         else {
1287                 DMEMIT("%u ", m->queue_if_no_path +
1288                               (m->pg_init_retries > 0) * 2);
1289                 if (m->queue_if_no_path)
1290                         DMEMIT("queue_if_no_path ");
1291                 if (m->pg_init_retries)
1292                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1293         }
1294
1295         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1296                 DMEMIT("0 ");
1297         else
1298                 DMEMIT("1 %s ", m->hw_handler_name);
1299
1300         DMEMIT("%u ", m->nr_priority_groups);
1301
1302         if (m->next_pg)
1303                 pg_num = m->next_pg->pg_num;
1304         else if (m->current_pg)
1305                 pg_num = m->current_pg->pg_num;
1306         else
1307                         pg_num = 1;
1308
1309         DMEMIT("%u ", pg_num);
1310
1311         switch (type) {
1312         case STATUSTYPE_INFO:
1313                 list_for_each_entry(pg, &m->priority_groups, list) {
1314                         if (pg->bypassed)
1315                                 state = 'D';    /* Disabled */
1316                         else if (pg == m->current_pg)
1317                                 state = 'A';    /* Currently Active */
1318                         else
1319                                 state = 'E';    /* Enabled */
1320
1321                         DMEMIT("%c ", state);
1322
1323                         if (pg->ps.type->status)
1324                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1325                                                           result + sz,
1326                                                           maxlen - sz);
1327                         else
1328                                 DMEMIT("0 ");
1329
1330                         DMEMIT("%u %u ", pg->nr_pgpaths,
1331                                pg->ps.type->info_args);
1332
1333                         list_for_each_entry(p, &pg->pgpaths, list) {
1334                                 DMEMIT("%s %s %u ", p->path.dev->name,
1335                                        p->is_active ? "A" : "F",
1336                                        p->fail_count);
1337                                 if (pg->ps.type->status)
1338                                         sz += pg->ps.type->status(&pg->ps,
1339                                               &p->path, type, result + sz,
1340                                               maxlen - sz);
1341                         }
1342                 }
1343                 break;
1344
1345         case STATUSTYPE_TABLE:
1346                 list_for_each_entry(pg, &m->priority_groups, list) {
1347                         DMEMIT("%s ", pg->ps.type->name);
1348
1349                         if (pg->ps.type->status)
1350                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1351                                                           result + sz,
1352                                                           maxlen - sz);
1353                         else
1354                                 DMEMIT("0 ");
1355
1356                         DMEMIT("%u %u ", pg->nr_pgpaths,
1357                                pg->ps.type->table_args);
1358
1359                         list_for_each_entry(p, &pg->pgpaths, list) {
1360                                 DMEMIT("%s ", p->path.dev->name);
1361                                 if (pg->ps.type->status)
1362                                         sz += pg->ps.type->status(&pg->ps,
1363                                               &p->path, type, result + sz,
1364                                               maxlen - sz);
1365                         }
1366                 }
1367                 break;
1368         }
1369
1370         spin_unlock_irqrestore(&m->lock, flags);
1371
1372         return 0;
1373 }
1374
1375 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1376 {
1377         int r;
1378         struct dm_dev *dev;
1379         struct multipath *m = (struct multipath *) ti->private;
1380         action_fn action;
1381
1382         if (argc == 1) {
1383                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path")))
1384                         return queue_if_no_path(m, 1, 0);
1385                 else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path")))
1386                         return queue_if_no_path(m, 0, 0);
1387         }
1388
1389         if (argc != 2)
1390                 goto error;
1391
1392         if (!strnicmp(argv[0], MESG_STR("disable_group")))
1393                 return bypass_pg_num(m, argv[1], 1);
1394         else if (!strnicmp(argv[0], MESG_STR("enable_group")))
1395                 return bypass_pg_num(m, argv[1], 0);
1396         else if (!strnicmp(argv[0], MESG_STR("switch_group")))
1397                 return switch_pg_num(m, argv[1]);
1398         else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1399                 action = reinstate_path;
1400         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1401                 action = fail_path;
1402         else
1403                 goto error;
1404
1405         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
1406                           dm_table_get_mode(ti->table), &dev);
1407         if (r) {
1408                 DMWARN("message: error getting device %s",
1409                        argv[1]);
1410                 return -EINVAL;
1411         }
1412
1413         r = action_dev(m, dev, action);
1414
1415         dm_put_device(ti, dev);
1416
1417         return r;
1418
1419 error:
1420         DMWARN("Unrecognised multipath message received.");
1421         return -EINVAL;
1422 }
1423
1424 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1425                            unsigned long arg)
1426 {
1427         struct multipath *m = (struct multipath *) ti->private;
1428         struct block_device *bdev = NULL;
1429         fmode_t mode = 0;
1430         unsigned long flags;
1431         int r = 0;
1432
1433         spin_lock_irqsave(&m->lock, flags);
1434
1435         if (!m->current_pgpath)
1436                 __choose_pgpath(m);
1437
1438         if (m->current_pgpath) {
1439                 bdev = m->current_pgpath->path.dev->bdev;
1440                 mode = m->current_pgpath->path.dev->mode;
1441         }
1442
1443         if (m->queue_io)
1444                 r = -EAGAIN;
1445         else if (!bdev)
1446                 r = -EIO;
1447
1448         spin_unlock_irqrestore(&m->lock, flags);
1449
1450         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1451 }
1452
1453 /*-----------------------------------------------------------------
1454  * Module setup
1455  *---------------------------------------------------------------*/
1456 static struct target_type multipath_target = {
1457         .name = "multipath",
1458         .version = {1, 0, 5},
1459         .module = THIS_MODULE,
1460         .ctr = multipath_ctr,
1461         .dtr = multipath_dtr,
1462         .map = multipath_map,
1463         .end_io = multipath_end_io,
1464         .presuspend = multipath_presuspend,
1465         .resume = multipath_resume,
1466         .status = multipath_status,
1467         .message = multipath_message,
1468         .ioctl  = multipath_ioctl,
1469 };
1470
1471 static int __init dm_multipath_init(void)
1472 {
1473         int r;
1474
1475         /* allocate a slab for the dm_ios */
1476         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1477         if (!_mpio_cache)
1478                 return -ENOMEM;
1479
1480         r = dm_register_target(&multipath_target);
1481         if (r < 0) {
1482                 DMERR("register failed %d", r);
1483                 kmem_cache_destroy(_mpio_cache);
1484                 return -EINVAL;
1485         }
1486
1487         kmultipathd = create_workqueue("kmpathd");
1488         if (!kmultipathd) {
1489                 DMERR("failed to create workqueue kmpathd");
1490                 dm_unregister_target(&multipath_target);
1491                 kmem_cache_destroy(_mpio_cache);
1492                 return -ENOMEM;
1493         }
1494
1495         /*
1496          * A separate workqueue is used to handle the device handlers
1497          * to avoid overloading existing workqueue. Overloading the
1498          * old workqueue would also create a bottleneck in the
1499          * path of the storage hardware device activation.
1500          */
1501         kmpath_handlerd = create_singlethread_workqueue("kmpath_handlerd");
1502         if (!kmpath_handlerd) {
1503                 DMERR("failed to create workqueue kmpath_handlerd");
1504                 destroy_workqueue(kmultipathd);
1505                 dm_unregister_target(&multipath_target);
1506                 kmem_cache_destroy(_mpio_cache);
1507                 return -ENOMEM;
1508         }
1509
1510         DMINFO("version %u.%u.%u loaded",
1511                multipath_target.version[0], multipath_target.version[1],
1512                multipath_target.version[2]);
1513
1514         return r;
1515 }
1516
1517 static void __exit dm_multipath_exit(void)
1518 {
1519         destroy_workqueue(kmpath_handlerd);
1520         destroy_workqueue(kmultipathd);
1521
1522         dm_unregister_target(&multipath_target);
1523         kmem_cache_destroy(_mpio_cache);
1524 }
1525
1526 module_init(dm_multipath_init);
1527 module_exit(dm_multipath_exit);
1528
1529 MODULE_DESCRIPTION(DM_NAME " multipath target");
1530 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1531 MODULE_LICENSE("GPL");