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