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-rq.h"
  11 #include "dm-bio-record.h"
  12 #include "dm-path-selector.h"
  13 #include "dm-uevent.h"
  14
  15 #include <linux/blkdev.h>
  16 #include <linux/ctype.h>
  17 #include <linux/init.h>
  18 #include <linux/mempool.h>
  19 #include <linux/module.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/slab.h>
  22 #include <linux/time.h>
  23 #include <linux/workqueue.h>
  24 #include <linux/delay.h>
  25 #include <scsi/scsi_dh.h>
  26 #include <linux/atomic.h>
  27 #include <linux/blk-mq.h>
  28
  29 #define DM_MSG_PREFIX "multipath"
  30 #define DM_PG_INIT_DELAY_MSECS 2000
  31 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  32
  33 /* Path properties */
  34 struct pgpath {
  35         struct list_head list;
  36
  37         struct priority_group *pg;      /* Owning PG */
  38         unsigned fail_count;            /* Cumulative failure count */
  39
  40         struct dm_path path;
  41         struct delayed_work activate_path;
  42
  43         bool is_active:1;               /* Path status */
  44 };
  45
  46 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  47
  48 /*
  49  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  50  * Each has a path selector which controls which path gets used.
  51  */
  52 struct priority_group {
  53         struct list_head list;
  54
  55         struct multipath *m;            /* Owning multipath instance */
  56         struct path_selector ps;
  57
  58         unsigned pg_num;                /* Reference number */
  59         unsigned nr_pgpaths;            /* Number of paths in PG */
  60         struct list_head pgpaths;
  61
  62         bool bypassed:1;                /* Temporarily bypass this PG? */
  63 };
  64
  65 /* Multipath context */
  66 struct multipath {
  67         struct list_head list;
  68         struct dm_target *ti;
  69
  70         const char *hw_handler_name;
  71         char *hw_handler_params;
  72
  73         spinlock_t lock;
  74
  75         unsigned nr_priority_groups;
  76         struct list_head priority_groups;
  77
  78         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  79
  80         struct pgpath *current_pgpath;
  81         struct priority_group *current_pg;
  82         struct priority_group *next_pg; /* Switch to this PG if set */
  83
  84         unsigned long flags;            /* Multipath state flags */
  85
  86         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  87         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  88
  89         atomic_t nr_valid_paths;        /* Total number of usable paths */
  90         atomic_t pg_init_in_progress;   /* Only one pg_init allowed at once */
  91         atomic_t pg_init_count;         /* Number of times pg_init called */
  92
  93         enum dm_queue_mode queue_mode;
  94
  95         struct mutex work_mutex;
  96         struct work_struct trigger_event;
  97
  98         struct work_struct process_queued_bios;
  99         struct bio_list queued_bios;
 100 };
 101
 102 /*
 103  * Context information attached to each io we process.
 104  */
 105 struct dm_mpath_io {
 106         struct pgpath *pgpath;
 107         size_t nr_bytes;
 108 };
 109
 110 typedef int (*action_fn) (struct pgpath *pgpath);
 111
 112 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 113 static void trigger_event(struct work_struct *work);
 114 static void activate_or_offline_path(struct pgpath *pgpath);
 115 static void activate_path_work(struct work_struct *work);
 116 static void process_queued_bios(struct work_struct *work);
 117
 118 /*-----------------------------------------------
 119  * Multipath state flags.
 120  *-----------------------------------------------*/
 121
 122 #define MPATHF_QUEUE_IO 0                       /* Must we queue all I/O? */
 123 #define MPATHF_QUEUE_IF_NO_PATH 1               /* Queue I/O if last path fails? */
 124 #define MPATHF_SAVED_QUEUE_IF_NO_PATH 2         /* Saved state during suspension */
 125 #define MPATHF_RETAIN_ATTACHED_HW_HANDLER 3     /* If there's already a hw_handler present, don't change it. */
 126 #define MPATHF_PG_INIT_DISABLED 4               /* pg_init is not currently allowed */
 127 #define MPATHF_PG_INIT_REQUIRED 5               /* pg_init needs calling? */
 128 #define MPATHF_PG_INIT_DELAY_RETRY 6            /* Delay pg_init retry? */
 129
 130 /*-----------------------------------------------
 131  * Allocation routines
 132  *-----------------------------------------------*/
 133
 134 static struct pgpath *alloc_pgpath(void)
 135 {
 136         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 137
 138         if (pgpath) {
 139                 pgpath->is_active = true;
 140                 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path_work);
 141         }
 142
 143         return pgpath;
 144 }
 145
 146 static void free_pgpath(struct pgpath *pgpath)
 147 {
 148         kfree(pgpath);
 149 }
 150
 151 static struct priority_group *alloc_priority_group(void)
 152 {
 153         struct priority_group *pg;
 154
 155         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 156
 157         if (pg)
 158                 INIT_LIST_HEAD(&pg->pgpaths);
 159
 160         return pg;
 161 }
 162
 163 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 164 {
 165         struct pgpath *pgpath, *tmp;
 166
 167         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 168                 list_del(&pgpath->list);
 169                 dm_put_device(ti, pgpath->path.dev);
 170                 free_pgpath(pgpath);
 171         }
 172 }
 173
 174 static void free_priority_group(struct priority_group *pg,
 175                                 struct dm_target *ti)
 176 {
 177         struct path_selector *ps = &pg->ps;
 178
 179         if (ps->type) {
 180                 ps->type->destroy(ps);
 181                 dm_put_path_selector(ps->type);
 182         }
 183
 184         free_pgpaths(&pg->pgpaths, ti);
 185         kfree(pg);
 186 }
 187
 188 static struct multipath *alloc_multipath(struct dm_target *ti)
 189 {
 190         struct multipath *m;
 191
 192         m = kzalloc(sizeof(*m), GFP_KERNEL);
 193         if (m) {
 194                 INIT_LIST_HEAD(&m->priority_groups);
 195                 spin_lock_init(&m->lock);
 196                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 197                 atomic_set(&m->nr_valid_paths, 0);
 198                 atomic_set(&m->pg_init_in_progress, 0);
 199                 atomic_set(&m->pg_init_count, 0);
 200                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 201                 INIT_WORK(&m->trigger_event, trigger_event);
 202                 init_waitqueue_head(&m->pg_init_wait);
 203                 mutex_init(&m->work_mutex);
 204
 205                 m->queue_mode = DM_TYPE_NONE;
 206
 207                 m->ti = ti;
 208                 ti->private = m;
 209         }
 210
 211         return m;
 212 }
 213
 214 static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
 215 {
 216         if (m->queue_mode == DM_TYPE_NONE) {
 217                 /*
 218                  * Default to request-based.
 219                  */
 220                 if (dm_use_blk_mq(dm_table_get_md(ti->table)))
 221                         m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
 222                 else
 223                         m->queue_mode = DM_TYPE_REQUEST_BASED;
 224         } else if (m->queue_mode == DM_TYPE_BIO_BASED) {
 225                 INIT_WORK(&m->process_queued_bios, process_queued_bios);
 226                 /*
 227                  * bio-based doesn't support any direct scsi_dh management;
 228                  * it just discovers if a scsi_dh is attached.
 229                  */
 230                 set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 231         }
 232
 233         dm_table_set_type(ti->table, m->queue_mode);
 234
 235         return 0;
 236 }
 237
 238 static void free_multipath(struct multipath *m)
 239 {
 240         struct priority_group *pg, *tmp;
 241
 242         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 243                 list_del(&pg->list);
 244                 free_priority_group(pg, m->ti);
 245         }
 246
 247         kfree(m->hw_handler_name);
 248         kfree(m->hw_handler_params);
 249         kfree(m);
 250 }
 251
 252 static struct dm_mpath_io *get_mpio(union map_info *info)
 253 {
 254         return info->ptr;
 255 }
 256
 257 static size_t multipath_per_bio_data_size(void)
 258 {
 259         return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
 260 }
 261
 262 static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
 263 {
 264         return dm_per_bio_data(bio, multipath_per_bio_data_size());
 265 }
 266
 267 static struct dm_bio_details *get_bio_details_from_bio(struct bio *bio)
 268 {
 269         /* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
 270         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 271         void *bio_details = mpio + 1;
 272
 273         return bio_details;
 274 }
 275
 276 static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p,
 277                                         struct dm_bio_details **bio_details_p)
 278 {
 279         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 280         struct dm_bio_details *bio_details = get_bio_details_from_bio(bio);
 281
 282         memset(mpio, 0, sizeof(*mpio));
 283         memset(bio_details, 0, sizeof(*bio_details));
 284         dm_bio_record(bio_details, bio);
 285
 286         if (mpio_p)
 287                 *mpio_p = mpio;
 288         if (bio_details_p)
 289                 *bio_details_p = bio_details;
 290 }
 291
 292 /*-----------------------------------------------
 293  * Path selection
 294  *-----------------------------------------------*/
 295
 296 static int __pg_init_all_paths(struct multipath *m)
 297 {
 298         struct pgpath *pgpath;
 299         unsigned long pg_init_delay = 0;
 300
 301         lockdep_assert_held(&m->lock);
 302
 303         if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
 304                 return 0;
 305
 306         atomic_inc(&m->pg_init_count);
 307         clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 308
 309         /* Check here to reset pg_init_required */
 310         if (!m->current_pg)
 311                 return 0;
 312
 313         if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
 314                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 315                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 316         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 317                 /* Skip failed paths */
 318                 if (!pgpath->is_active)
 319                         continue;
 320                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 321                                        pg_init_delay))
 322                         atomic_inc(&m->pg_init_in_progress);
 323         }
 324         return atomic_read(&m->pg_init_in_progress);
 325 }
 326
 327 static int pg_init_all_paths(struct multipath *m)
 328 {
 329         int ret;
 330         unsigned long flags;
 331
 332         spin_lock_irqsave(&m->lock, flags);
 333         ret = __pg_init_all_paths(m);
 334         spin_unlock_irqrestore(&m->lock, flags);
 335
 336         return ret;
 337 }
 338
 339 static void __switch_pg(struct multipath *m, struct priority_group *pg)
 340 {
 341         m->current_pg = pg;
 342
 343         /* Must we initialise the PG first, and queue I/O till it's ready? */
 344         if (m->hw_handler_name) {
 345                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 346                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 347         } else {
 348                 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 349                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 350         }
 351
 352         atomic_set(&m->pg_init_count, 0);
 353 }
 354
 355 static struct pgpath *choose_path_in_pg(struct multipath *m,
 356                                         struct priority_group *pg,
 357                                         size_t nr_bytes)
 358 {
 359         unsigned long flags;
 360         struct dm_path *path;
 361         struct pgpath *pgpath;
 362
 363         path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 364         if (!path)
 365                 return ERR_PTR(-ENXIO);
 366
 367         pgpath = path_to_pgpath(path);
 368
 369         if (unlikely(lockless_dereference(m->current_pg) != pg)) {
 370                 /* Only update current_pgpath if pg changed */
 371                 spin_lock_irqsave(&m->lock, flags);
 372                 m->current_pgpath = pgpath;
 373                 __switch_pg(m, pg);
 374                 spin_unlock_irqrestore(&m->lock, flags);
 375         }
 376
 377         return pgpath;
 378 }
 379
 380 static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 381 {
 382         unsigned long flags;
 383         struct priority_group *pg;
 384         struct pgpath *pgpath;
 385         unsigned bypassed = 1;
 386
 387         if (!atomic_read(&m->nr_valid_paths)) {
 388                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 389                 goto failed;
 390         }
 391
 392         /* Were we instructed to switch PG? */
 393         if (lockless_dereference(m->next_pg)) {
 394                 spin_lock_irqsave(&m->lock, flags);
 395                 pg = m->next_pg;
 396                 if (!pg) {
 397                         spin_unlock_irqrestore(&m->lock, flags);
 398                         goto check_current_pg;
 399                 }
 400                 m->next_pg = NULL;
 401                 spin_unlock_irqrestore(&m->lock, flags);
 402                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 403                 if (!IS_ERR_OR_NULL(pgpath))
 404                         return pgpath;
 405         }
 406
 407         /* Don't change PG until it has no remaining paths */
 408 check_current_pg:
 409         pg = lockless_dereference(m->current_pg);
 410         if (pg) {
 411                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 412                 if (!IS_ERR_OR_NULL(pgpath))
 413                         return pgpath;
 414         }
 415
 416         /*
 417          * Loop through priority groups until we find a valid path.
 418          * First time we skip PGs marked 'bypassed'.
 419          * Second time we only try the ones we skipped, but set
 420          * pg_init_delay_retry so we do not hammer controllers.
 421          */
 422         do {
 423                 list_for_each_entry(pg, &m->priority_groups, list) {
 424                         if (pg->bypassed == !!bypassed)
 425                                 continue;
 426                         pgpath = choose_path_in_pg(m, pg, nr_bytes);
 427                         if (!IS_ERR_OR_NULL(pgpath)) {
 428                                 if (!bypassed)
 429                                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 430                                 return pgpath;
 431                         }
 432                 }
 433         } while (bypassed--);
 434
 435 failed:
 436         spin_lock_irqsave(&m->lock, flags);
 437         m->current_pgpath = NULL;
 438         m->current_pg = NULL;
 439         spin_unlock_irqrestore(&m->lock, flags);
 440
 441         return NULL;
 442 }
 443
 444 /*
 445  * dm_report_EIO() is a macro instead of a function to make pr_debug()
 446  * report the function name and line number of the function from which
 447  * it has been invoked.
 448  */
 449 #define dm_report_EIO(m)                                                \
 450 do {                                                                    \
 451         struct mapped_device *md = dm_table_get_md((m)->ti->table);     \
 452                                                                         \
 453         pr_debug("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d\n", \
 454                  dm_device_name(md),                                    \
 455                  test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),        \
 456                  test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags),  \
 457                  dm_noflush_suspending((m)->ti));                       \
 458 } while (0)
 459
 460 /*
 461  * Map cloned requests (request-based multipath)
 462  */
 463 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 464                                    union map_info *map_context,
 465                                    struct request **__clone)
 466 {
 467         struct multipath *m = ti->private;
 468         size_t nr_bytes = blk_rq_bytes(rq);
 469         struct pgpath *pgpath;
 470         struct block_device *bdev;
 471         struct dm_mpath_io *mpio = get_mpio(map_context);
 472         struct request_queue *q;
 473         struct request *clone;
 474
 475         /* Do we need to select a new pgpath? */
 476         pgpath = lockless_dereference(m->current_pgpath);
 477         if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
 478                 pgpath = choose_pgpath(m, nr_bytes);
 479
 480         if (!pgpath) {
 481                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
 482                         return DM_MAPIO_DELAY_REQUEUE;
 483                 dm_report_EIO(m);       /* Failed */
 484                 return DM_MAPIO_KILL;
 485         } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
 486                    test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
 487                 if (pg_init_all_paths(m))
 488                         return DM_MAPIO_DELAY_REQUEUE;
 489                 return DM_MAPIO_REQUEUE;
 490         }
 491
 492         memset(mpio, 0, sizeof(*mpio));
 493         mpio->pgpath = pgpath;
 494         mpio->nr_bytes = nr_bytes;
 495
 496         bdev = pgpath->path.dev->bdev;
 497         q = bdev_get_queue(bdev);
 498         clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE, GFP_ATOMIC);
 499         if (IS_ERR(clone)) {
 500                 /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 501                 bool queue_dying = blk_queue_dying(q);
 502                 DMERR_LIMIT("blk_get_request() returned %ld%s - requeuing",
 503                             PTR_ERR(clone), queue_dying ? " (path offline)" : "");
 504                 if (queue_dying) {
 505                         atomic_inc(&m->pg_init_in_progress);
 506                         activate_or_offline_path(pgpath);
 507                         return DM_MAPIO_REQUEUE;
 508                 }
 509                 return DM_MAPIO_DELAY_REQUEUE;
 510         }
 511         clone->bio = clone->biotail = NULL;
 512         clone->rq_disk = bdev->bd_disk;
 513         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 514         *__clone = clone;
 515
 516         if (pgpath->pg->ps.type->start_io)
 517                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 518                                               &pgpath->path,
 519                                               nr_bytes);
 520         return DM_MAPIO_REMAPPED;
 521 }
 522
 523 static void multipath_release_clone(struct request *clone)
 524 {
 525         blk_put_request(clone);
 526 }
 527
 528 /*
 529  * Map cloned bios (bio-based multipath)
 530  */
 531 static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_mpath_io *mpio)
 532 {
 533         size_t nr_bytes = bio->bi_iter.bi_size;
 534         struct pgpath *pgpath;
 535         unsigned long flags;
 536         bool queue_io;
 537
 538         /* Do we need to select a new pgpath? */
 539         pgpath = lockless_dereference(m->current_pgpath);
 540         queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
 541         if (!pgpath || !queue_io)
 542                 pgpath = choose_pgpath(m, nr_bytes);
 543
 544         if ((pgpath && queue_io) ||
 545             (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
 546                 /* Queue for the daemon to resubmit */
 547                 spin_lock_irqsave(&m->lock, flags);
 548                 bio_list_add(&m->queued_bios, bio);
 549                 spin_unlock_irqrestore(&m->lock, flags);
 550                 /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
 551                 if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
 552                         pg_init_all_paths(m);
 553                 else if (!queue_io)
 554                         queue_work(kmultipathd, &m->process_queued_bios);
 555                 return DM_MAPIO_SUBMITTED;
 556         }
 557
 558         if (!pgpath) {
 559                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
 560                         return DM_MAPIO_REQUEUE;
 561                 dm_report_EIO(m);
 562                 return DM_MAPIO_KILL;
 563         }
 564
 565         mpio->pgpath = pgpath;
 566         mpio->nr_bytes = nr_bytes;
 567
 568         bio->bi_status = 0;
 569         bio->bi_bdev = pgpath->path.dev->bdev;
 570         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 571
 572         if (pgpath->pg->ps.type->start_io)
 573                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 574                                               &pgpath->path,
 575                                               nr_bytes);
 576         return DM_MAPIO_REMAPPED;
 577 }
 578
 579 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 580 {
 581         struct multipath *m = ti->private;
 582         struct dm_mpath_io *mpio = NULL;
 583
 584         multipath_init_per_bio_data(bio, &mpio, NULL);
 585
 586         return __multipath_map_bio(m, bio, mpio);
 587 }
 588
 589 static void process_queued_io_list(struct multipath *m)
 590 {
 591         if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
 592                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 593         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 594                 queue_work(kmultipathd, &m->process_queued_bios);
 595 }
 596
 597 static void process_queued_bios(struct work_struct *work)
 598 {
 599         int r;
 600         unsigned long flags;
 601         struct bio *bio;
 602         struct bio_list bios;
 603         struct blk_plug plug;
 604         struct multipath *m =
 605                 container_of(work, struct multipath, process_queued_bios);
 606
 607         bio_list_init(&bios);
 608
 609         spin_lock_irqsave(&m->lock, flags);
 610
 611         if (bio_list_empty(&m->queued_bios)) {
 612                 spin_unlock_irqrestore(&m->lock, flags);
 613                 return;
 614         }
 615
 616         bio_list_merge(&bios, &m->queued_bios);
 617         bio_list_init(&m->queued_bios);
 618
 619         spin_unlock_irqrestore(&m->lock, flags);
 620
 621         blk_start_plug(&plug);
 622         while ((bio = bio_list_pop(&bios))) {
 623                 r = __multipath_map_bio(m, bio, get_mpio_from_bio(bio));
 624                 switch (r) {
 625                 case DM_MAPIO_KILL:
 626                         bio->bi_status = BLK_STS_IOERR;
 627                         bio_endio(bio);
 628                         break;
 629                 case DM_MAPIO_REQUEUE:
 630                         bio->bi_status = BLK_STS_DM_REQUEUE;
 631                         bio_endio(bio);
 632                         break;
 633                 case DM_MAPIO_REMAPPED:
 634                         generic_make_request(bio);
 635                         break;
 636                 }
 637         }
 638         blk_finish_plug(&plug);
 639 }
 640
 641 static void assign_bit(bool value, long nr, unsigned long *addr)
 642 {
 643         if (value)
 644                 set_bit(nr, addr);
 645         else
 646                 clear_bit(nr, addr);
 647 }
 648
 649 /*
 650  * If we run out of usable paths, should we queue I/O or error it?
 651  */
 652 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 653                             bool save_old_value)
 654 {
 655         unsigned long flags;
 656
 657         spin_lock_irqsave(&m->lock, flags);
 658         assign_bit((save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
 659                    (!save_old_value && queue_if_no_path),
 660                    MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 661         assign_bit(queue_if_no_path || dm_noflush_suspending(m->ti),
 662                    MPATHF_QUEUE_IF_NO_PATH, &m->flags);
 663         spin_unlock_irqrestore(&m->lock, flags);
 664
 665         if (!queue_if_no_path) {
 666                 dm_table_run_md_queue_async(m->ti->table);
 667                 process_queued_io_list(m);
 668         }
 669
 670         return 0;
 671 }
 672
 673 /*
 674  * An event is triggered whenever a path is taken out of use.
 675  * Includes path failure and PG bypass.
 676  */
 677 static void trigger_event(struct work_struct *work)
 678 {
 679         struct multipath *m =
 680                 container_of(work, struct multipath, trigger_event);
 681
 682         dm_table_event(m->ti->table);
 683 }
 684
 685 /*-----------------------------------------------------------------
 686  * Constructor/argument parsing:
 687  * <#multipath feature args> [<arg>]*
 688  * <#hw_handler args> [hw_handler [<arg>]*]
 689  * <#priority groups>
 690  * <initial priority group>
 691  *     [<selector> <#selector args> [<arg>]*
 692  *      <#paths> <#per-path selector args>
 693  *         [<path> [<arg>]* ]+ ]+
 694  *---------------------------------------------------------------*/
 695 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 696                                struct dm_target *ti)
 697 {
 698         int r;
 699         struct path_selector_type *pst;
 700         unsigned ps_argc;
 701
 702         static struct dm_arg _args[] = {
 703                 {0, 1024, "invalid number of path selector args"},
 704         };
 705
 706         pst = dm_get_path_selector(dm_shift_arg(as));
 707         if (!pst) {
 708                 ti->error = "unknown path selector type";
 709                 return -EINVAL;
 710         }
 711
 712         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 713         if (r) {
 714                 dm_put_path_selector(pst);
 715                 return -EINVAL;
 716         }
 717
 718         r = pst->create(&pg->ps, ps_argc, as->argv);
 719         if (r) {
 720                 dm_put_path_selector(pst);
 721                 ti->error = "path selector constructor failed";
 722                 return r;
 723         }
 724
 725         pg->ps.type = pst;
 726         dm_consume_args(as, ps_argc);
 727
 728         return 0;
 729 }
 730
 731 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 732                                struct dm_target *ti)
 733 {
 734         int r;
 735         struct pgpath *p;
 736         struct multipath *m = ti->private;
 737         struct request_queue *q = NULL;
 738         const char *attached_handler_name;
 739
 740         /* we need at least a path arg */
 741         if (as->argc < 1) {
 742                 ti->error = "no device given";
 743                 return ERR_PTR(-EINVAL);
 744         }
 745
 746         p = alloc_pgpath();
 747         if (!p)
 748                 return ERR_PTR(-ENOMEM);
 749
 750         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 751                           &p->path.dev);
 752         if (r) {
 753                 ti->error = "error getting device";
 754                 goto bad;
 755         }
 756
 757         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) || m->hw_handler_name)
 758                 q = bdev_get_queue(p->path.dev->bdev);
 759
 760         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 761 retain:
 762                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 763                 if (attached_handler_name) {
 764                         /*
 765                          * Clear any hw_handler_params associated with a
 766                          * handler that isn't already attached.
 767                          */
 768                         if (m->hw_handler_name && strcmp(attached_handler_name, m->hw_handler_name)) {
 769                                 kfree(m->hw_handler_params);
 770                                 m->hw_handler_params = NULL;
 771                         }
 772
 773                         /*
 774                          * Reset hw_handler_name to match the attached handler
 775                          *
 776                          * NB. This modifies the table line to show the actual
 777                          * handler instead of the original table passed in.
 778                          */
 779                         kfree(m->hw_handler_name);
 780                         m->hw_handler_name = attached_handler_name;
 781                 }
 782         }
 783
 784         if (m->hw_handler_name) {
 785                 r = scsi_dh_attach(q, m->hw_handler_name);
 786                 if (r == -EBUSY) {
 787                         char b[BDEVNAME_SIZE];
 788
 789                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 790                                 bdevname(p->path.dev->bdev, b));
 791                         goto retain;
 792                 }
 793                 if (r < 0) {
 794                         ti->error = "error attaching hardware handler";
 795                         dm_put_device(ti, p->path.dev);
 796                         goto bad;
 797                 }
 798
 799                 if (m->hw_handler_params) {
 800                         r = scsi_dh_set_params(q, m->hw_handler_params);
 801                         if (r < 0) {
 802                                 ti->error = "unable to set hardware "
 803                                                         "handler parameters";
 804                                 dm_put_device(ti, p->path.dev);
 805                                 goto bad;
 806                         }
 807                 }
 808         }
 809
 810         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 811         if (r) {
 812                 dm_put_device(ti, p->path.dev);
 813                 goto bad;
 814         }
 815
 816         return p;
 817
 818  bad:
 819         free_pgpath(p);
 820         return ERR_PTR(r);
 821 }
 822
 823 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 824                                                    struct multipath *m)
 825 {
 826         static struct dm_arg _args[] = {
 827                 {1, 1024, "invalid number of paths"},
 828                 {0, 1024, "invalid number of selector args"}
 829         };
 830
 831         int r;
 832         unsigned i, nr_selector_args, nr_args;
 833         struct priority_group *pg;
 834         struct dm_target *ti = m->ti;
 835
 836         if (as->argc < 2) {
 837                 as->argc = 0;
 838                 ti->error = "not enough priority group arguments";
 839                 return ERR_PTR(-EINVAL);
 840         }
 841
 842         pg = alloc_priority_group();
 843         if (!pg) {
 844                 ti->error = "couldn't allocate priority group";
 845                 return ERR_PTR(-ENOMEM);
 846         }
 847         pg->m = m;
 848
 849         r = parse_path_selector(as, pg, ti);
 850         if (r)
 851                 goto bad;
 852
 853         /*
 854          * read the paths
 855          */
 856         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 857         if (r)
 858                 goto bad;
 859
 860         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 861         if (r)
 862                 goto bad;
 863
 864         nr_args = 1 + nr_selector_args;
 865         for (i = 0; i < pg->nr_pgpaths; i++) {
 866                 struct pgpath *pgpath;
 867                 struct dm_arg_set path_args;
 868
 869                 if (as->argc < nr_args) {
 870                         ti->error = "not enough path parameters";
 871                         r = -EINVAL;
 872                         goto bad;
 873                 }
 874
 875                 path_args.argc = nr_args;
 876                 path_args.argv = as->argv;
 877
 878                 pgpath = parse_path(&path_args, &pg->ps, ti);
 879                 if (IS_ERR(pgpath)) {
 880                         r = PTR_ERR(pgpath);
 881                         goto bad;
 882                 }
 883
 884                 pgpath->pg = pg;
 885                 list_add_tail(&pgpath->list, &pg->pgpaths);
 886                 dm_consume_args(as, nr_args);
 887         }
 888
 889         return pg;
 890
 891  bad:
 892         free_priority_group(pg, ti);
 893         return ERR_PTR(r);
 894 }
 895
 896 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 897 {
 898         unsigned hw_argc;
 899         int ret;
 900         struct dm_target *ti = m->ti;
 901
 902         static struct dm_arg _args[] = {
 903                 {0, 1024, "invalid number of hardware handler args"},
 904         };
 905
 906         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 907                 return -EINVAL;
 908
 909         if (!hw_argc)
 910                 return 0;
 911
 912         if (m->queue_mode == DM_TYPE_BIO_BASED) {
 913                 dm_consume_args(as, hw_argc);
 914                 DMERR("bio-based multipath doesn't allow hardware handler args");
 915                 return 0;
 916         }
 917
 918         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 919         if (!m->hw_handler_name)
 920                 return -EINVAL;
 921
 922         if (hw_argc > 1) {
 923                 char *p;
 924                 int i, j, len = 4;
 925
 926                 for (i = 0; i <= hw_argc - 2; i++)
 927                         len += strlen(as->argv[i]) + 1;
 928                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 929                 if (!p) {
 930                         ti->error = "memory allocation failed";
 931                         ret = -ENOMEM;
 932                         goto fail;
 933                 }
 934                 j = sprintf(p, "%d", hw_argc - 1);
 935                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 936                         j = sprintf(p, "%s", as->argv[i]);
 937         }
 938         dm_consume_args(as, hw_argc - 1);
 939
 940         return 0;
 941 fail:
 942         kfree(m->hw_handler_name);
 943         m->hw_handler_name = NULL;
 944         return ret;
 945 }
 946
 947 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 948 {
 949         int r;
 950         unsigned argc;
 951         struct dm_target *ti = m->ti;
 952         const char *arg_name;
 953
 954         static struct dm_arg _args[] = {
 955                 {0, 8, "invalid number of feature args"},
 956                 {1, 50, "pg_init_retries must be between 1 and 50"},
 957                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 958         };
 959
 960         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 961         if (r)
 962                 return -EINVAL;
 963
 964         if (!argc)
 965                 return 0;
 966
 967         do {
 968                 arg_name = dm_shift_arg(as);
 969                 argc--;
 970
 971                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 972                         r = queue_if_no_path(m, true, false);
 973                         continue;
 974                 }
 975
 976                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
 977                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 978                         continue;
 979                 }
 980
 981                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 982                     (argc >= 1)) {
 983                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
 984                         argc--;
 985                         continue;
 986                 }
 987
 988                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
 989                     (argc >= 1)) {
 990                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
 991                         argc--;
 992                         continue;
 993                 }
 994
 995                 if (!strcasecmp(arg_name, "queue_mode") &&
 996                     (argc >= 1)) {
 997                         const char *queue_mode_name = dm_shift_arg(as);
 998
 999                         if (!strcasecmp(queue_mode_name, "bio"))
1000                                 m->queue_mode = DM_TYPE_BIO_BASED;
1001                         else if (!strcasecmp(queue_mode_name, "rq"))
1002                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1003                         else if (!strcasecmp(queue_mode_name, "mq"))
1004                                 m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
1005                         else {
1006                                 ti->error = "Unknown 'queue_mode' requested";
1007                                 r = -EINVAL;
1008                         }
1009                         argc--;
1010                         continue;
1011                 }
1012
1013                 ti->error = "Unrecognised multipath feature request";
1014                 r = -EINVAL;
1015         } while (argc && !r);
1016
1017         return r;
1018 }
1019
1020 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1021 {
1022         /* target arguments */
1023         static struct dm_arg _args[] = {
1024                 {0, 1024, "invalid number of priority groups"},
1025                 {0, 1024, "invalid initial priority group number"},
1026         };
1027
1028         int r;
1029         struct multipath *m;
1030         struct dm_arg_set as;
1031         unsigned pg_count = 0;
1032         unsigned next_pg_num;
1033
1034         as.argc = argc;
1035         as.argv = argv;
1036
1037         m = alloc_multipath(ti);
1038         if (!m) {
1039                 ti->error = "can't allocate multipath";
1040                 return -EINVAL;
1041         }
1042
1043         r = parse_features(&as, m);
1044         if (r)
1045                 goto bad;
1046
1047         r = alloc_multipath_stage2(ti, m);
1048         if (r)
1049                 goto bad;
1050
1051         r = parse_hw_handler(&as, m);
1052         if (r)
1053                 goto bad;
1054
1055         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1056         if (r)
1057                 goto bad;
1058
1059         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1060         if (r)
1061                 goto bad;
1062
1063         if ((!m->nr_priority_groups && next_pg_num) ||
1064             (m->nr_priority_groups && !next_pg_num)) {
1065                 ti->error = "invalid initial priority group";
1066                 r = -EINVAL;
1067                 goto bad;
1068         }
1069
1070         /* parse the priority groups */
1071         while (as.argc) {
1072                 struct priority_group *pg;
1073                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1074
1075                 pg = parse_priority_group(&as, m);
1076                 if (IS_ERR(pg)) {
1077                         r = PTR_ERR(pg);
1078                         goto bad;
1079                 }
1080
1081                 nr_valid_paths += pg->nr_pgpaths;
1082                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1083
1084                 list_add_tail(&pg->list, &m->priority_groups);
1085                 pg_count++;
1086                 pg->pg_num = pg_count;
1087                 if (!--next_pg_num)
1088                         m->next_pg = pg;
1089         }
1090
1091         if (pg_count != m->nr_priority_groups) {
1092                 ti->error = "priority group count mismatch";
1093                 r = -EINVAL;
1094                 goto bad;
1095         }
1096
1097         ti->num_flush_bios = 1;
1098         ti->num_discard_bios = 1;
1099         ti->num_write_same_bios = 1;
1100         ti->num_write_zeroes_bios = 1;
1101         if (m->queue_mode == DM_TYPE_BIO_BASED)
1102                 ti->per_io_data_size = multipath_per_bio_data_size();
1103         else
1104                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1105
1106         return 0;
1107
1108  bad:
1109         free_multipath(m);
1110         return r;
1111 }
1112
1113 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1114 {
1115         DEFINE_WAIT(wait);
1116
1117         while (1) {
1118                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1119
1120                 if (!atomic_read(&m->pg_init_in_progress))
1121                         break;
1122
1123                 io_schedule();
1124         }
1125         finish_wait(&m->pg_init_wait, &wait);
1126 }
1127
1128 static void flush_multipath_work(struct multipath *m)
1129 {
1130         set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1131         smp_mb__after_atomic();
1132
1133         flush_workqueue(kmpath_handlerd);
1134         multipath_wait_for_pg_init_completion(m);
1135         flush_workqueue(kmultipathd);
1136         flush_work(&m->trigger_event);
1137
1138         clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1139         smp_mb__after_atomic();
1140 }
1141
1142 static void multipath_dtr(struct dm_target *ti)
1143 {
1144         struct multipath *m = ti->private;
1145
1146         flush_multipath_work(m);
1147         free_multipath(m);
1148 }
1149
1150 /*
1151  * Take a path out of use.
1152  */
1153 static int fail_path(struct pgpath *pgpath)
1154 {
1155         unsigned long flags;
1156         struct multipath *m = pgpath->pg->m;
1157
1158         spin_lock_irqsave(&m->lock, flags);
1159
1160         if (!pgpath->is_active)
1161                 goto out;
1162
1163         DMWARN("Failing path %s.", pgpath->path.dev->name);
1164
1165         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1166         pgpath->is_active = false;
1167         pgpath->fail_count++;
1168
1169         atomic_dec(&m->nr_valid_paths);
1170
1171         if (pgpath == m->current_pgpath)
1172                 m->current_pgpath = NULL;
1173
1174         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1175                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1176
1177         schedule_work(&m->trigger_event);
1178
1179 out:
1180         spin_unlock_irqrestore(&m->lock, flags);
1181
1182         return 0;
1183 }
1184
1185 /*
1186  * Reinstate a previously-failed path
1187  */
1188 static int reinstate_path(struct pgpath *pgpath)
1189 {
1190         int r = 0, run_queue = 0;
1191         unsigned long flags;
1192         struct multipath *m = pgpath->pg->m;
1193         unsigned nr_valid_paths;
1194
1195         spin_lock_irqsave(&m->lock, flags);
1196
1197         if (pgpath->is_active)
1198                 goto out;
1199
1200         DMWARN("Reinstating path %s.", pgpath->path.dev->name);
1201
1202         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1203         if (r)
1204                 goto out;
1205
1206         pgpath->is_active = true;
1207
1208         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1209         if (nr_valid_paths == 1) {
1210                 m->current_pgpath = NULL;
1211                 run_queue = 1;
1212         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1213                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1214                         atomic_inc(&m->pg_init_in_progress);
1215         }
1216
1217         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1218                        pgpath->path.dev->name, nr_valid_paths);
1219
1220         schedule_work(&m->trigger_event);
1221
1222 out:
1223         spin_unlock_irqrestore(&m->lock, flags);
1224         if (run_queue) {
1225                 dm_table_run_md_queue_async(m->ti->table);
1226                 process_queued_io_list(m);
1227         }
1228
1229         return r;
1230 }
1231
1232 /*
1233  * Fail or reinstate all paths that match the provided struct dm_dev.
1234  */
1235 static int action_dev(struct multipath *m, struct dm_dev *dev,
1236                       action_fn action)
1237 {
1238         int r = -EINVAL;
1239         struct pgpath *pgpath;
1240         struct priority_group *pg;
1241
1242         list_for_each_entry(pg, &m->priority_groups, list) {
1243                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1244                         if (pgpath->path.dev == dev)
1245                                 r = action(pgpath);
1246                 }
1247         }
1248
1249         return r;
1250 }
1251
1252 /*
1253  * Temporarily try to avoid having to use the specified PG
1254  */
1255 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1256                       bool bypassed)
1257 {
1258         unsigned long flags;
1259
1260         spin_lock_irqsave(&m->lock, flags);
1261
1262         pg->bypassed = bypassed;
1263         m->current_pgpath = NULL;
1264         m->current_pg = NULL;
1265
1266         spin_unlock_irqrestore(&m->lock, flags);
1267
1268         schedule_work(&m->trigger_event);
1269 }
1270
1271 /*
1272  * Switch to using the specified PG from the next I/O that gets mapped
1273  */
1274 static int switch_pg_num(struct multipath *m, const char *pgstr)
1275 {
1276         struct priority_group *pg;
1277         unsigned pgnum;
1278         unsigned long flags;
1279         char dummy;
1280
1281         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1282             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1283                 DMWARN("invalid PG number supplied to switch_pg_num");
1284                 return -EINVAL;
1285         }
1286
1287         spin_lock_irqsave(&m->lock, flags);
1288         list_for_each_entry(pg, &m->priority_groups, list) {
1289                 pg->bypassed = false;
1290                 if (--pgnum)
1291                         continue;
1292
1293                 m->current_pgpath = NULL;
1294                 m->current_pg = NULL;
1295                 m->next_pg = pg;
1296         }
1297         spin_unlock_irqrestore(&m->lock, flags);
1298
1299         schedule_work(&m->trigger_event);
1300         return 0;
1301 }
1302
1303 /*
1304  * Set/clear bypassed status of a PG.
1305  * PGs are numbered upwards from 1 in the order they were declared.
1306  */
1307 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1308 {
1309         struct priority_group *pg;
1310         unsigned pgnum;
1311         char dummy;
1312
1313         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1314             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1315                 DMWARN("invalid PG number supplied to bypass_pg");
1316                 return -EINVAL;
1317         }
1318
1319         list_for_each_entry(pg, &m->priority_groups, list) {
1320                 if (!--pgnum)
1321                         break;
1322         }
1323
1324         bypass_pg(m, pg, bypassed);
1325         return 0;
1326 }
1327
1328 /*
1329  * Should we retry pg_init immediately?
1330  */
1331 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1332 {
1333         unsigned long flags;
1334         bool limit_reached = false;
1335
1336         spin_lock_irqsave(&m->lock, flags);
1337
1338         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1339             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1340                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1341         else
1342                 limit_reached = true;
1343
1344         spin_unlock_irqrestore(&m->lock, flags);
1345
1346         return limit_reached;
1347 }
1348
1349 static void pg_init_done(void *data, int errors)
1350 {
1351         struct pgpath *pgpath = data;
1352         struct priority_group *pg = pgpath->pg;
1353         struct multipath *m = pg->m;
1354         unsigned long flags;
1355         bool delay_retry = false;
1356
1357         /* device or driver problems */
1358         switch (errors) {
1359         case SCSI_DH_OK:
1360                 break;
1361         case SCSI_DH_NOSYS:
1362                 if (!m->hw_handler_name) {
1363                         errors = 0;
1364                         break;
1365                 }
1366                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1367                       "Error %d.", m->hw_handler_name, errors);
1368                 /*
1369                  * Fail path for now, so we do not ping pong
1370                  */
1371                 fail_path(pgpath);
1372                 break;
1373         case SCSI_DH_DEV_TEMP_BUSY:
1374                 /*
1375                  * Probably doing something like FW upgrade on the
1376                  * controller so try the other pg.
1377                  */
1378                 bypass_pg(m, pg, true);
1379                 break;
1380         case SCSI_DH_RETRY:
1381                 /* Wait before retrying. */
1382                 delay_retry = 1;
1383         case SCSI_DH_IMM_RETRY:
1384         case SCSI_DH_RES_TEMP_UNAVAIL:
1385                 if (pg_init_limit_reached(m, pgpath))
1386                         fail_path(pgpath);
1387                 errors = 0;
1388                 break;
1389         case SCSI_DH_DEV_OFFLINED:
1390         default:
1391                 /*
1392                  * We probably do not want to fail the path for a device
1393                  * error, but this is what the old dm did. In future
1394                  * patches we can do more advanced handling.
1395                  */
1396                 fail_path(pgpath);
1397         }
1398
1399         spin_lock_irqsave(&m->lock, flags);
1400         if (errors) {
1401                 if (pgpath == m->current_pgpath) {
1402                         DMERR("Could not failover device. Error %d.", errors);
1403                         m->current_pgpath = NULL;
1404                         m->current_pg = NULL;
1405                 }
1406         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1407                 pg->bypassed = false;
1408
1409         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1410                 /* Activations of other paths are still on going */
1411                 goto out;
1412
1413         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1414                 if (delay_retry)
1415                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1416                 else
1417                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1418
1419                 if (__pg_init_all_paths(m))
1420                         goto out;
1421         }
1422         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1423
1424         process_queued_io_list(m);
1425
1426         /*
1427          * Wake up any thread waiting to suspend.
1428          */
1429         wake_up(&m->pg_init_wait);
1430
1431 out:
1432         spin_unlock_irqrestore(&m->lock, flags);
1433 }
1434
1435 static void activate_or_offline_path(struct pgpath *pgpath)
1436 {
1437         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1438
1439         if (pgpath->is_active && !blk_queue_dying(q))
1440                 scsi_dh_activate(q, pg_init_done, pgpath);
1441         else
1442                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1443 }
1444
1445 static void activate_path_work(struct work_struct *work)
1446 {
1447         struct pgpath *pgpath =
1448                 container_of(work, struct pgpath, activate_path.work);
1449
1450         activate_or_offline_path(pgpath);
1451 }
1452
1453 static int noretry_error(blk_status_t error)
1454 {
1455         switch (error) {
1456         case BLK_STS_NOTSUPP:
1457         case BLK_STS_NOSPC:
1458         case BLK_STS_TARGET:
1459         case BLK_STS_NEXUS:
1460         case BLK_STS_MEDIUM:
1461         case BLK_STS_RESOURCE:
1462                 return 1;
1463         }
1464
1465         /* Anything else could be a path failure, so should be retried */
1466         return 0;
1467 }
1468
1469 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1470                             blk_status_t error, union map_info *map_context)
1471 {
1472         struct dm_mpath_io *mpio = get_mpio(map_context);
1473         struct pgpath *pgpath = mpio->pgpath;
1474         int r = DM_ENDIO_DONE;
1475
1476         /*
1477          * We don't queue any clone request inside the multipath target
1478          * during end I/O handling, since those clone requests don't have
1479          * bio clones.  If we queue them inside the multipath target,
1480          * we need to make bio clones, that requires memory allocation.
1481          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1482          *  don't have bio clones.)
1483          * Instead of queueing the clone request here, we queue the original
1484          * request into dm core, which will remake a clone request and
1485          * clone bios for it and resubmit it later.
1486          */
1487         if (error && !noretry_error(error)) {
1488                 struct multipath *m = ti->private;
1489
1490                 r = DM_ENDIO_REQUEUE;
1491
1492                 if (pgpath)
1493                         fail_path(pgpath);
1494
1495                 if (atomic_read(&m->nr_valid_paths) == 0 &&
1496                     !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1497                         if (error == BLK_STS_IOERR)
1498                                 dm_report_EIO(m);
1499                         /* complete with the original error */
1500                         r = DM_ENDIO_DONE;
1501                 }
1502         }
1503
1504         if (pgpath) {
1505                 struct path_selector *ps = &pgpath->pg->ps;
1506
1507                 if (ps->type->end_io)
1508                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1509         }
1510
1511         return r;
1512 }
1513
1514 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1515                 blk_status_t *error)
1516 {
1517         struct multipath *m = ti->private;
1518         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1519         struct pgpath *pgpath = mpio->pgpath;
1520         unsigned long flags;
1521         int r = DM_ENDIO_DONE;
1522
1523         if (!*error || noretry_error(*error))
1524                 goto done;
1525
1526         if (pgpath)
1527                 fail_path(pgpath);
1528
1529         if (atomic_read(&m->nr_valid_paths) == 0 &&
1530             !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1531                 dm_report_EIO(m);
1532                 *error = BLK_STS_IOERR;
1533                 goto done;
1534         }
1535
1536         /* Queue for the daemon to resubmit */
1537         dm_bio_restore(get_bio_details_from_bio(clone), clone);
1538
1539         spin_lock_irqsave(&m->lock, flags);
1540         bio_list_add(&m->queued_bios, clone);
1541         spin_unlock_irqrestore(&m->lock, flags);
1542         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1543                 queue_work(kmultipathd, &m->process_queued_bios);
1544
1545         r = DM_ENDIO_INCOMPLETE;
1546 done:
1547         if (pgpath) {
1548                 struct path_selector *ps = &pgpath->pg->ps;
1549
1550                 if (ps->type->end_io)
1551                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1552         }
1553
1554         return r;
1555 }
1556
1557 /*
1558  * Suspend can't complete until all the I/O is processed so if
1559  * the last path fails we must error any remaining I/O.
1560  * Note that if the freeze_bdev fails while suspending, the
1561  * queue_if_no_path state is lost - userspace should reset it.
1562  */
1563 static void multipath_presuspend(struct dm_target *ti)
1564 {
1565         struct multipath *m = ti->private;
1566
1567         queue_if_no_path(m, false, true);
1568 }
1569
1570 static void multipath_postsuspend(struct dm_target *ti)
1571 {
1572         struct multipath *m = ti->private;
1573
1574         mutex_lock(&m->work_mutex);
1575         flush_multipath_work(m);
1576         mutex_unlock(&m->work_mutex);
1577 }
1578
1579 /*
1580  * Restore the queue_if_no_path setting.
1581  */
1582 static void multipath_resume(struct dm_target *ti)
1583 {
1584         struct multipath *m = ti->private;
1585         unsigned long flags;
1586
1587         spin_lock_irqsave(&m->lock, flags);
1588         assign_bit(test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags),
1589                    MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1590         spin_unlock_irqrestore(&m->lock, flags);
1591 }
1592
1593 /*
1594  * Info output has the following format:
1595  * num_multipath_feature_args [multipath_feature_args]*
1596  * num_handler_status_args [handler_status_args]*
1597  * num_groups init_group_number
1598  *            [A|D|E num_ps_status_args [ps_status_args]*
1599  *             num_paths num_selector_args
1600  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1601  *
1602  * Table output has the following format (identical to the constructor string):
1603  * num_feature_args [features_args]*
1604  * num_handler_args hw_handler [hw_handler_args]*
1605  * num_groups init_group_number
1606  *     [priority selector-name num_ps_args [ps_args]*
1607  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1608  */
1609 static void multipath_status(struct dm_target *ti, status_type_t type,
1610                              unsigned status_flags, char *result, unsigned maxlen)
1611 {
1612         int sz = 0;
1613         unsigned long flags;
1614         struct multipath *m = ti->private;
1615         struct priority_group *pg;
1616         struct pgpath *p;
1617         unsigned pg_num;
1618         char state;
1619
1620         spin_lock_irqsave(&m->lock, flags);
1621
1622         /* Features */
1623         if (type == STATUSTYPE_INFO)
1624                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1625                        atomic_read(&m->pg_init_count));
1626         else {
1627                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1628                               (m->pg_init_retries > 0) * 2 +
1629                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1630                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1631                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1632
1633                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1634                         DMEMIT("queue_if_no_path ");
1635                 if (m->pg_init_retries)
1636                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1637                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1638                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1639                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1640                         DMEMIT("retain_attached_hw_handler ");
1641                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1642                         switch(m->queue_mode) {
1643                         case DM_TYPE_BIO_BASED:
1644                                 DMEMIT("queue_mode bio ");
1645                                 break;
1646                         case DM_TYPE_MQ_REQUEST_BASED:
1647                                 DMEMIT("queue_mode mq ");
1648                                 break;
1649                         default:
1650                                 WARN_ON_ONCE(true);
1651                                 break;
1652                         }
1653                 }
1654         }
1655
1656         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1657                 DMEMIT("0 ");
1658         else
1659                 DMEMIT("1 %s ", m->hw_handler_name);
1660
1661         DMEMIT("%u ", m->nr_priority_groups);
1662
1663         if (m->next_pg)
1664                 pg_num = m->next_pg->pg_num;
1665         else if (m->current_pg)
1666                 pg_num = m->current_pg->pg_num;
1667         else
1668                 pg_num = (m->nr_priority_groups ? 1 : 0);
1669
1670         DMEMIT("%u ", pg_num);
1671
1672         switch (type) {
1673         case STATUSTYPE_INFO:
1674                 list_for_each_entry(pg, &m->priority_groups, list) {
1675                         if (pg->bypassed)
1676                                 state = 'D';    /* Disabled */
1677                         else if (pg == m->current_pg)
1678                                 state = 'A';    /* Currently Active */
1679                         else
1680                                 state = 'E';    /* Enabled */
1681
1682                         DMEMIT("%c ", state);
1683
1684                         if (pg->ps.type->status)
1685                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1686                                                           result + sz,
1687                                                           maxlen - sz);
1688                         else
1689                                 DMEMIT("0 ");
1690
1691                         DMEMIT("%u %u ", pg->nr_pgpaths,
1692                                pg->ps.type->info_args);
1693
1694                         list_for_each_entry(p, &pg->pgpaths, list) {
1695                                 DMEMIT("%s %s %u ", p->path.dev->name,
1696                                        p->is_active ? "A" : "F",
1697                                        p->fail_count);
1698                                 if (pg->ps.type->status)
1699                                         sz += pg->ps.type->status(&pg->ps,
1700                                               &p->path, type, result + sz,
1701                                               maxlen - sz);
1702                         }
1703                 }
1704                 break;
1705
1706         case STATUSTYPE_TABLE:
1707                 list_for_each_entry(pg, &m->priority_groups, list) {
1708                         DMEMIT("%s ", pg->ps.type->name);
1709
1710                         if (pg->ps.type->status)
1711                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1712                                                           result + sz,
1713                                                           maxlen - sz);
1714                         else
1715                                 DMEMIT("0 ");
1716
1717                         DMEMIT("%u %u ", pg->nr_pgpaths,
1718                                pg->ps.type->table_args);
1719
1720                         list_for_each_entry(p, &pg->pgpaths, list) {
1721                                 DMEMIT("%s ", p->path.dev->name);
1722                                 if (pg->ps.type->status)
1723                                         sz += pg->ps.type->status(&pg->ps,
1724                                               &p->path, type, result + sz,
1725                                               maxlen - sz);
1726                         }
1727                 }
1728                 break;
1729         }
1730
1731         spin_unlock_irqrestore(&m->lock, flags);
1732 }
1733
1734 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1735 {
1736         int r = -EINVAL;
1737         struct dm_dev *dev;
1738         struct multipath *m = ti->private;
1739         action_fn action;
1740
1741         mutex_lock(&m->work_mutex);
1742
1743         if (dm_suspended(ti)) {
1744                 r = -EBUSY;
1745                 goto out;
1746         }
1747
1748         if (argc == 1) {
1749                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1750                         r = queue_if_no_path(m, true, false);
1751                         goto out;
1752                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1753                         r = queue_if_no_path(m, false, false);
1754                         goto out;
1755                 }
1756         }
1757
1758         if (argc != 2) {
1759                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1760                 goto out;
1761         }
1762
1763         if (!strcasecmp(argv[0], "disable_group")) {
1764                 r = bypass_pg_num(m, argv[1], true);
1765                 goto out;
1766         } else if (!strcasecmp(argv[0], "enable_group")) {
1767                 r = bypass_pg_num(m, argv[1], false);
1768                 goto out;
1769         } else if (!strcasecmp(argv[0], "switch_group")) {
1770                 r = switch_pg_num(m, argv[1]);
1771                 goto out;
1772         } else if (!strcasecmp(argv[0], "reinstate_path"))
1773                 action = reinstate_path;
1774         else if (!strcasecmp(argv[0], "fail_path"))
1775                 action = fail_path;
1776         else {
1777                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1778                 goto out;
1779         }
1780
1781         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1782         if (r) {
1783                 DMWARN("message: error getting device %s",
1784                        argv[1]);
1785                 goto out;
1786         }
1787
1788         r = action_dev(m, dev, action);
1789
1790         dm_put_device(ti, dev);
1791
1792 out:
1793         mutex_unlock(&m->work_mutex);
1794         return r;
1795 }
1796
1797 static int multipath_prepare_ioctl(struct dm_target *ti,
1798                 struct block_device **bdev, fmode_t *mode)
1799 {
1800         struct multipath *m = ti->private;
1801         struct pgpath *current_pgpath;
1802         int r;
1803
1804         current_pgpath = lockless_dereference(m->current_pgpath);
1805         if (!current_pgpath)
1806                 current_pgpath = choose_pgpath(m, 0);
1807
1808         if (current_pgpath) {
1809                 if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1810                         *bdev = current_pgpath->path.dev->bdev;
1811                         *mode = current_pgpath->path.dev->mode;
1812                         r = 0;
1813                 } else {
1814                         /* pg_init has not started or completed */
1815                         r = -ENOTCONN;
1816                 }
1817         } else {
1818                 /* No path is available */
1819                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1820                         r = -ENOTCONN;
1821                 else
1822                         r = -EIO;
1823         }
1824
1825         if (r == -ENOTCONN) {
1826                 if (!lockless_dereference(m->current_pg)) {
1827                         /* Path status changed, redo selection */
1828                         (void) choose_pgpath(m, 0);
1829                 }
1830                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1831                         pg_init_all_paths(m);
1832                 dm_table_run_md_queue_async(m->ti->table);
1833                 process_queued_io_list(m);
1834         }
1835
1836         /*
1837          * Only pass ioctls through if the device sizes match exactly.
1838          */
1839         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1840                 return 1;
1841         return r;
1842 }
1843
1844 static int multipath_iterate_devices(struct dm_target *ti,
1845                                      iterate_devices_callout_fn fn, void *data)
1846 {
1847         struct multipath *m = ti->private;
1848         struct priority_group *pg;
1849         struct pgpath *p;
1850         int ret = 0;
1851
1852         list_for_each_entry(pg, &m->priority_groups, list) {
1853                 list_for_each_entry(p, &pg->pgpaths, list) {
1854                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1855                         if (ret)
1856                                 goto out;
1857                 }
1858         }
1859
1860 out:
1861         return ret;
1862 }
1863
1864 static int pgpath_busy(struct pgpath *pgpath)
1865 {
1866         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1867
1868         return blk_lld_busy(q);
1869 }
1870
1871 /*
1872  * We return "busy", only when we can map I/Os but underlying devices
1873  * are busy (so even if we map I/Os now, the I/Os will wait on
1874  * the underlying queue).
1875  * In other words, if we want to kill I/Os or queue them inside us
1876  * due to map unavailability, we don't return "busy".  Otherwise,
1877  * dm core won't give us the I/Os and we can't do what we want.
1878  */
1879 static int multipath_busy(struct dm_target *ti)
1880 {
1881         bool busy = false, has_active = false;
1882         struct multipath *m = ti->private;
1883         struct priority_group *pg, *next_pg;
1884         struct pgpath *pgpath;
1885
1886         /* pg_init in progress */
1887         if (atomic_read(&m->pg_init_in_progress))
1888                 return true;
1889
1890         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
1891         if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1892                 return (m->queue_mode != DM_TYPE_MQ_REQUEST_BASED);
1893
1894         /* Guess which priority_group will be used at next mapping time */
1895         pg = lockless_dereference(m->current_pg);
1896         next_pg = lockless_dereference(m->next_pg);
1897         if (unlikely(!lockless_dereference(m->current_pgpath) && next_pg))
1898                 pg = next_pg;
1899
1900         if (!pg) {
1901                 /*
1902                  * We don't know which pg will be used at next mapping time.
1903                  * We don't call choose_pgpath() here to avoid to trigger
1904                  * pg_init just by busy checking.
1905                  * So we don't know whether underlying devices we will be using
1906                  * at next mapping time are busy or not. Just try mapping.
1907                  */
1908                 return busy;
1909         }
1910
1911         /*
1912          * If there is one non-busy active path at least, the path selector
1913          * will be able to select it. So we consider such a pg as not busy.
1914          */
1915         busy = true;
1916         list_for_each_entry(pgpath, &pg->pgpaths, list) {
1917                 if (pgpath->is_active) {
1918                         has_active = true;
1919                         if (!pgpath_busy(pgpath)) {
1920                                 busy = false;
1921                                 break;
1922                         }
1923                 }
1924         }
1925
1926         if (!has_active) {
1927                 /*
1928                  * No active path in this pg, so this pg won't be used and
1929                  * the current_pg will be changed at next mapping time.
1930                  * We need to try mapping to determine it.
1931                  */
1932                 busy = false;
1933         }
1934
1935         return busy;
1936 }
1937
1938 /*-----------------------------------------------------------------
1939  * Module setup
1940  *---------------------------------------------------------------*/
1941 static struct target_type multipath_target = {
1942         .name = "multipath",
1943         .version = {1, 12, 0},
1944         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
1945         .module = THIS_MODULE,
1946         .ctr = multipath_ctr,
1947         .dtr = multipath_dtr,
1948         .clone_and_map_rq = multipath_clone_and_map,
1949         .release_clone_rq = multipath_release_clone,
1950         .rq_end_io = multipath_end_io,
1951         .map = multipath_map_bio,
1952         .end_io = multipath_end_io_bio,
1953         .presuspend = multipath_presuspend,
1954         .postsuspend = multipath_postsuspend,
1955         .resume = multipath_resume,
1956         .status = multipath_status,
1957         .message = multipath_message,
1958         .prepare_ioctl = multipath_prepare_ioctl,
1959         .iterate_devices = multipath_iterate_devices,
1960         .busy = multipath_busy,
1961 };
1962
1963 static int __init dm_multipath_init(void)
1964 {
1965         int r;
1966
1967         r = dm_register_target(&multipath_target);
1968         if (r < 0) {
1969                 DMERR("request-based register failed %d", r);
1970                 r = -EINVAL;
1971                 goto bad_register_target;
1972         }
1973
1974         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1975         if (!kmultipathd) {
1976                 DMERR("failed to create workqueue kmpathd");
1977                 r = -ENOMEM;
1978                 goto bad_alloc_kmultipathd;
1979         }
1980
1981         /*
1982          * A separate workqueue is used to handle the device handlers
1983          * to avoid overloading existing workqueue. Overloading the
1984          * old workqueue would also create a bottleneck in the
1985          * path of the storage hardware device activation.
1986          */
1987         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1988                                                   WQ_MEM_RECLAIM);
1989         if (!kmpath_handlerd) {
1990                 DMERR("failed to create workqueue kmpath_handlerd");
1991                 r = -ENOMEM;
1992                 goto bad_alloc_kmpath_handlerd;
1993         }
1994
1995         return 0;
1996
1997 bad_alloc_kmpath_handlerd:
1998         destroy_workqueue(kmultipathd);
1999 bad_alloc_kmultipathd:
2000         dm_unregister_target(&multipath_target);
2001 bad_register_target:
2002         return r;
2003 }
2004
2005 static void __exit dm_multipath_exit(void)
2006 {
2007         destroy_workqueue(kmpath_handlerd);
2008         destroy_workqueue(kmultipathd);
2009
2010         dm_unregister_target(&multipath_target);
2011 }
2012
2013 module_init(dm_multipath_init);
2014 module_exit(dm_multipath_exit);
2015
2016 MODULE_DESCRIPTION(DM_NAME " multipath target");
2017 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2018 MODULE_LICENSE("GPL");