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(READ_ONCE(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 (READ_ONCE(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 = READ_ONCE(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 = READ_ONCE(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                 if (queue_dying) {
 503                         atomic_inc(&m->pg_init_in_progress);
 504                         activate_or_offline_path(pgpath);
 505                 }
 506                 return DM_MAPIO_DELAY_REQUEUE;
 507         }
 508         clone->bio = clone->biotail = NULL;
 509         clone->rq_disk = bdev->bd_disk;
 510         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 511         *__clone = clone;
 512
 513         if (pgpath->pg->ps.type->start_io)
 514                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 515                                               &pgpath->path,
 516                                               nr_bytes);
 517         return DM_MAPIO_REMAPPED;
 518 }
 519
 520 static void multipath_release_clone(struct request *clone)
 521 {
 522         blk_put_request(clone);
 523 }
 524
 525 /*
 526  * Map cloned bios (bio-based multipath)
 527  */
 528 static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_mpath_io *mpio)
 529 {
 530         size_t nr_bytes = bio->bi_iter.bi_size;
 531         struct pgpath *pgpath;
 532         unsigned long flags;
 533         bool queue_io;
 534
 535         /* Do we need to select a new pgpath? */
 536         pgpath = READ_ONCE(m->current_pgpath);
 537         queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
 538         if (!pgpath || !queue_io)
 539                 pgpath = choose_pgpath(m, nr_bytes);
 540
 541         if ((pgpath && queue_io) ||
 542             (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
 543                 /* Queue for the daemon to resubmit */
 544                 spin_lock_irqsave(&m->lock, flags);
 545                 bio_list_add(&m->queued_bios, bio);
 546                 spin_unlock_irqrestore(&m->lock, flags);
 547                 /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
 548                 if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
 549                         pg_init_all_paths(m);
 550                 else if (!queue_io)
 551                         queue_work(kmultipathd, &m->process_queued_bios);
 552                 return DM_MAPIO_SUBMITTED;
 553         }
 554
 555         if (!pgpath) {
 556                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
 557                         return DM_MAPIO_REQUEUE;
 558                 dm_report_EIO(m);
 559                 return DM_MAPIO_KILL;
 560         }
 561
 562         mpio->pgpath = pgpath;
 563         mpio->nr_bytes = nr_bytes;
 564
 565         bio->bi_status = 0;
 566         bio_set_dev(bio, pgpath->path.dev->bdev);
 567         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 568
 569         if (pgpath->pg->ps.type->start_io)
 570                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 571                                               &pgpath->path,
 572                                               nr_bytes);
 573         return DM_MAPIO_REMAPPED;
 574 }
 575
 576 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 577 {
 578         struct multipath *m = ti->private;
 579         struct dm_mpath_io *mpio = NULL;
 580
 581         multipath_init_per_bio_data(bio, &mpio, NULL);
 582
 583         return __multipath_map_bio(m, bio, mpio);
 584 }
 585
 586 static void process_queued_io_list(struct multipath *m)
 587 {
 588         if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
 589                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 590         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 591                 queue_work(kmultipathd, &m->process_queued_bios);
 592 }
 593
 594 static void process_queued_bios(struct work_struct *work)
 595 {
 596         int r;
 597         unsigned long flags;
 598         struct bio *bio;
 599         struct bio_list bios;
 600         struct blk_plug plug;
 601         struct multipath *m =
 602                 container_of(work, struct multipath, process_queued_bios);
 603
 604         bio_list_init(&bios);
 605
 606         spin_lock_irqsave(&m->lock, flags);
 607
 608         if (bio_list_empty(&m->queued_bios)) {
 609                 spin_unlock_irqrestore(&m->lock, flags);
 610                 return;
 611         }
 612
 613         bio_list_merge(&bios, &m->queued_bios);
 614         bio_list_init(&m->queued_bios);
 615
 616         spin_unlock_irqrestore(&m->lock, flags);
 617
 618         blk_start_plug(&plug);
 619         while ((bio = bio_list_pop(&bios))) {
 620                 r = __multipath_map_bio(m, bio, get_mpio_from_bio(bio));
 621                 switch (r) {
 622                 case DM_MAPIO_KILL:
 623                         bio->bi_status = BLK_STS_IOERR;
 624                         bio_endio(bio);
 625                         break;
 626                 case DM_MAPIO_REQUEUE:
 627                         bio->bi_status = BLK_STS_DM_REQUEUE;
 628                         bio_endio(bio);
 629                         break;
 630                 case DM_MAPIO_REMAPPED:
 631                         generic_make_request(bio);
 632                         break;
 633                 case 0:
 634                         break;
 635                 default:
 636                         WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 637                 }
 638         }
 639         blk_finish_plug(&plug);
 640 }
 641
 642 static void assign_bit(bool value, long nr, unsigned long *addr)
 643 {
 644         if (value)
 645                 set_bit(nr, addr);
 646         else
 647                 clear_bit(nr, addr);
 648 }
 649
 650 /*
 651  * If we run out of usable paths, should we queue I/O or error it?
 652  */
 653 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 654                             bool save_old_value)
 655 {
 656         unsigned long flags;
 657
 658         spin_lock_irqsave(&m->lock, flags);
 659         assign_bit((save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
 660                    (!save_old_value && queue_if_no_path),
 661                    MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 662         assign_bit(queue_if_no_path || dm_noflush_suspending(m->ti),
 663                    MPATHF_QUEUE_IF_NO_PATH, &m->flags);
 664         spin_unlock_irqrestore(&m->lock, flags);
 665
 666         if (!queue_if_no_path) {
 667                 dm_table_run_md_queue_async(m->ti->table);
 668                 process_queued_io_list(m);
 669         }
 670
 671         return 0;
 672 }
 673
 674 /*
 675  * An event is triggered whenever a path is taken out of use.
 676  * Includes path failure and PG bypass.
 677  */
 678 static void trigger_event(struct work_struct *work)
 679 {
 680         struct multipath *m =
 681                 container_of(work, struct multipath, trigger_event);
 682
 683         dm_table_event(m->ti->table);
 684 }
 685
 686 /*-----------------------------------------------------------------
 687  * Constructor/argument parsing:
 688  * <#multipath feature args> [<arg>]*
 689  * <#hw_handler args> [hw_handler [<arg>]*]
 690  * <#priority groups>
 691  * <initial priority group>
 692  *     [<selector> <#selector args> [<arg>]*
 693  *      <#paths> <#per-path selector args>
 694  *         [<path> [<arg>]* ]+ ]+
 695  *---------------------------------------------------------------*/
 696 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 697                                struct dm_target *ti)
 698 {
 699         int r;
 700         struct path_selector_type *pst;
 701         unsigned ps_argc;
 702
 703         static const struct dm_arg _args[] = {
 704                 {0, 1024, "invalid number of path selector args"},
 705         };
 706
 707         pst = dm_get_path_selector(dm_shift_arg(as));
 708         if (!pst) {
 709                 ti->error = "unknown path selector type";
 710                 return -EINVAL;
 711         }
 712
 713         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 714         if (r) {
 715                 dm_put_path_selector(pst);
 716                 return -EINVAL;
 717         }
 718
 719         r = pst->create(&pg->ps, ps_argc, as->argv);
 720         if (r) {
 721                 dm_put_path_selector(pst);
 722                 ti->error = "path selector constructor failed";
 723                 return r;
 724         }
 725
 726         pg->ps.type = pst;
 727         dm_consume_args(as, ps_argc);
 728
 729         return 0;
 730 }
 731
 732 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 733                                struct dm_target *ti)
 734 {
 735         int r;
 736         struct pgpath *p;
 737         struct multipath *m = ti->private;
 738         struct request_queue *q = NULL;
 739         const char *attached_handler_name;
 740
 741         /* we need at least a path arg */
 742         if (as->argc < 1) {
 743                 ti->error = "no device given";
 744                 return ERR_PTR(-EINVAL);
 745         }
 746
 747         p = alloc_pgpath();
 748         if (!p)
 749                 return ERR_PTR(-ENOMEM);
 750
 751         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 752                           &p->path.dev);
 753         if (r) {
 754                 ti->error = "error getting device";
 755                 goto bad;
 756         }
 757
 758         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) || m->hw_handler_name)
 759                 q = bdev_get_queue(p->path.dev->bdev);
 760
 761         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 762 retain:
 763                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 764                 if (attached_handler_name) {
 765                         /*
 766                          * Clear any hw_handler_params associated with a
 767                          * handler that isn't already attached.
 768                          */
 769                         if (m->hw_handler_name && strcmp(attached_handler_name, m->hw_handler_name)) {
 770                                 kfree(m->hw_handler_params);
 771                                 m->hw_handler_params = NULL;
 772                         }
 773
 774                         /*
 775                          * Reset hw_handler_name to match the attached handler
 776                          *
 777                          * NB. This modifies the table line to show the actual
 778                          * handler instead of the original table passed in.
 779                          */
 780                         kfree(m->hw_handler_name);
 781                         m->hw_handler_name = attached_handler_name;
 782                 }
 783         }
 784
 785         if (m->hw_handler_name) {
 786                 r = scsi_dh_attach(q, m->hw_handler_name);
 787                 if (r == -EBUSY) {
 788                         char b[BDEVNAME_SIZE];
 789
 790                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 791                                 bdevname(p->path.dev->bdev, b));
 792                         goto retain;
 793                 }
 794                 if (r < 0) {
 795                         ti->error = "error attaching hardware handler";
 796                         dm_put_device(ti, p->path.dev);
 797                         goto bad;
 798                 }
 799
 800                 if (m->hw_handler_params) {
 801                         r = scsi_dh_set_params(q, m->hw_handler_params);
 802                         if (r < 0) {
 803                                 ti->error = "unable to set hardware "
 804                                                         "handler parameters";
 805                                 dm_put_device(ti, p->path.dev);
 806                                 goto bad;
 807                         }
 808                 }
 809         }
 810
 811         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 812         if (r) {
 813                 dm_put_device(ti, p->path.dev);
 814                 goto bad;
 815         }
 816
 817         return p;
 818
 819  bad:
 820         free_pgpath(p);
 821         return ERR_PTR(r);
 822 }
 823
 824 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 825                                                    struct multipath *m)
 826 {
 827         static const struct dm_arg _args[] = {
 828                 {1, 1024, "invalid number of paths"},
 829                 {0, 1024, "invalid number of selector args"}
 830         };
 831
 832         int r;
 833         unsigned i, nr_selector_args, nr_args;
 834         struct priority_group *pg;
 835         struct dm_target *ti = m->ti;
 836
 837         if (as->argc < 2) {
 838                 as->argc = 0;
 839                 ti->error = "not enough priority group arguments";
 840                 return ERR_PTR(-EINVAL);
 841         }
 842
 843         pg = alloc_priority_group();
 844         if (!pg) {
 845                 ti->error = "couldn't allocate priority group";
 846                 return ERR_PTR(-ENOMEM);
 847         }
 848         pg->m = m;
 849
 850         r = parse_path_selector(as, pg, ti);
 851         if (r)
 852                 goto bad;
 853
 854         /*
 855          * read the paths
 856          */
 857         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 858         if (r)
 859                 goto bad;
 860
 861         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 862         if (r)
 863                 goto bad;
 864
 865         nr_args = 1 + nr_selector_args;
 866         for (i = 0; i < pg->nr_pgpaths; i++) {
 867                 struct pgpath *pgpath;
 868                 struct dm_arg_set path_args;
 869
 870                 if (as->argc < nr_args) {
 871                         ti->error = "not enough path parameters";
 872                         r = -EINVAL;
 873                         goto bad;
 874                 }
 875
 876                 path_args.argc = nr_args;
 877                 path_args.argv = as->argv;
 878
 879                 pgpath = parse_path(&path_args, &pg->ps, ti);
 880                 if (IS_ERR(pgpath)) {
 881                         r = PTR_ERR(pgpath);
 882                         goto bad;
 883                 }
 884
 885                 pgpath->pg = pg;
 886                 list_add_tail(&pgpath->list, &pg->pgpaths);
 887                 dm_consume_args(as, nr_args);
 888         }
 889
 890         return pg;
 891
 892  bad:
 893         free_priority_group(pg, ti);
 894         return ERR_PTR(r);
 895 }
 896
 897 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 898 {
 899         unsigned hw_argc;
 900         int ret;
 901         struct dm_target *ti = m->ti;
 902
 903         static const struct dm_arg _args[] = {
 904                 {0, 1024, "invalid number of hardware handler args"},
 905         };
 906
 907         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 908                 return -EINVAL;
 909
 910         if (!hw_argc)
 911                 return 0;
 912
 913         if (m->queue_mode == DM_TYPE_BIO_BASED) {
 914                 dm_consume_args(as, hw_argc);
 915                 DMERR("bio-based multipath doesn't allow hardware handler args");
 916                 return 0;
 917         }
 918
 919         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 920         if (!m->hw_handler_name)
 921                 return -EINVAL;
 922
 923         if (hw_argc > 1) {
 924                 char *p;
 925                 int i, j, len = 4;
 926
 927                 for (i = 0; i <= hw_argc - 2; i++)
 928                         len += strlen(as->argv[i]) + 1;
 929                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 930                 if (!p) {
 931                         ti->error = "memory allocation failed";
 932                         ret = -ENOMEM;
 933                         goto fail;
 934                 }
 935                 j = sprintf(p, "%d", hw_argc - 1);
 936                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 937                         j = sprintf(p, "%s", as->argv[i]);
 938         }
 939         dm_consume_args(as, hw_argc - 1);
 940
 941         return 0;
 942 fail:
 943         kfree(m->hw_handler_name);
 944         m->hw_handler_name = NULL;
 945         return ret;
 946 }
 947
 948 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 949 {
 950         int r;
 951         unsigned argc;
 952         struct dm_target *ti = m->ti;
 953         const char *arg_name;
 954
 955         static const struct dm_arg _args[] = {
 956                 {0, 8, "invalid number of feature args"},
 957                 {1, 50, "pg_init_retries must be between 1 and 50"},
 958                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 959         };
 960
 961         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 962         if (r)
 963                 return -EINVAL;
 964
 965         if (!argc)
 966                 return 0;
 967
 968         do {
 969                 arg_name = dm_shift_arg(as);
 970                 argc--;
 971
 972                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 973                         r = queue_if_no_path(m, true, false);
 974                         continue;
 975                 }
 976
 977                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
 978                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 979                         continue;
 980                 }
 981
 982                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 983                     (argc >= 1)) {
 984                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
 985                         argc--;
 986                         continue;
 987                 }
 988
 989                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
 990                     (argc >= 1)) {
 991                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
 992                         argc--;
 993                         continue;
 994                 }
 995
 996                 if (!strcasecmp(arg_name, "queue_mode") &&
 997                     (argc >= 1)) {
 998                         const char *queue_mode_name = dm_shift_arg(as);
 999
1000                         if (!strcasecmp(queue_mode_name, "bio"))
1001                                 m->queue_mode = DM_TYPE_BIO_BASED;
1002                         else if (!strcasecmp(queue_mode_name, "rq"))
1003                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1004                         else if (!strcasecmp(queue_mode_name, "mq"))
1005                                 m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
1006                         else {
1007                                 ti->error = "Unknown 'queue_mode' requested";
1008                                 r = -EINVAL;
1009                         }
1010                         argc--;
1011                         continue;
1012                 }
1013
1014                 ti->error = "Unrecognised multipath feature request";
1015                 r = -EINVAL;
1016         } while (argc && !r);
1017
1018         return r;
1019 }
1020
1021 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1022 {
1023         /* target arguments */
1024         static const struct dm_arg _args[] = {
1025                 {0, 1024, "invalid number of priority groups"},
1026                 {0, 1024, "invalid initial priority group number"},
1027         };
1028
1029         int r;
1030         struct multipath *m;
1031         struct dm_arg_set as;
1032         unsigned pg_count = 0;
1033         unsigned next_pg_num;
1034
1035         as.argc = argc;
1036         as.argv = argv;
1037
1038         m = alloc_multipath(ti);
1039         if (!m) {
1040                 ti->error = "can't allocate multipath";
1041                 return -EINVAL;
1042         }
1043
1044         r = parse_features(&as, m);
1045         if (r)
1046                 goto bad;
1047
1048         r = alloc_multipath_stage2(ti, m);
1049         if (r)
1050                 goto bad;
1051
1052         r = parse_hw_handler(&as, m);
1053         if (r)
1054                 goto bad;
1055
1056         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1057         if (r)
1058                 goto bad;
1059
1060         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1061         if (r)
1062                 goto bad;
1063
1064         if ((!m->nr_priority_groups && next_pg_num) ||
1065             (m->nr_priority_groups && !next_pg_num)) {
1066                 ti->error = "invalid initial priority group";
1067                 r = -EINVAL;
1068                 goto bad;
1069         }
1070
1071         /* parse the priority groups */
1072         while (as.argc) {
1073                 struct priority_group *pg;
1074                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1075
1076                 pg = parse_priority_group(&as, m);
1077                 if (IS_ERR(pg)) {
1078                         r = PTR_ERR(pg);
1079                         goto bad;
1080                 }
1081
1082                 nr_valid_paths += pg->nr_pgpaths;
1083                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1084
1085                 list_add_tail(&pg->list, &m->priority_groups);
1086                 pg_count++;
1087                 pg->pg_num = pg_count;
1088                 if (!--next_pg_num)
1089                         m->next_pg = pg;
1090         }
1091
1092         if (pg_count != m->nr_priority_groups) {
1093                 ti->error = "priority group count mismatch";
1094                 r = -EINVAL;
1095                 goto bad;
1096         }
1097
1098         ti->num_flush_bios = 1;
1099         ti->num_discard_bios = 1;
1100         ti->num_write_same_bios = 1;
1101         ti->num_write_zeroes_bios = 1;
1102         if (m->queue_mode == DM_TYPE_BIO_BASED)
1103                 ti->per_io_data_size = multipath_per_bio_data_size();
1104         else
1105                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1106
1107         return 0;
1108
1109  bad:
1110         free_multipath(m);
1111         return r;
1112 }
1113
1114 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1115 {
1116         DEFINE_WAIT(wait);
1117
1118         while (1) {
1119                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1120
1121                 if (!atomic_read(&m->pg_init_in_progress))
1122                         break;
1123
1124                 io_schedule();
1125         }
1126         finish_wait(&m->pg_init_wait, &wait);
1127 }
1128
1129 static void flush_multipath_work(struct multipath *m)
1130 {
1131         set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1132         smp_mb__after_atomic();
1133
1134         flush_workqueue(kmpath_handlerd);
1135         multipath_wait_for_pg_init_completion(m);
1136         flush_workqueue(kmultipathd);
1137         flush_work(&m->trigger_event);
1138
1139         clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1140         smp_mb__after_atomic();
1141 }
1142
1143 static void multipath_dtr(struct dm_target *ti)
1144 {
1145         struct multipath *m = ti->private;
1146
1147         flush_multipath_work(m);
1148         free_multipath(m);
1149 }
1150
1151 /*
1152  * Take a path out of use.
1153  */
1154 static int fail_path(struct pgpath *pgpath)
1155 {
1156         unsigned long flags;
1157         struct multipath *m = pgpath->pg->m;
1158
1159         spin_lock_irqsave(&m->lock, flags);
1160
1161         if (!pgpath->is_active)
1162                 goto out;
1163
1164         DMWARN("Failing path %s.", pgpath->path.dev->name);
1165
1166         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1167         pgpath->is_active = false;
1168         pgpath->fail_count++;
1169
1170         atomic_dec(&m->nr_valid_paths);
1171
1172         if (pgpath == m->current_pgpath)
1173                 m->current_pgpath = NULL;
1174
1175         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1176                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1177
1178         schedule_work(&m->trigger_event);
1179
1180 out:
1181         spin_unlock_irqrestore(&m->lock, flags);
1182
1183         return 0;
1184 }
1185
1186 /*
1187  * Reinstate a previously-failed path
1188  */
1189 static int reinstate_path(struct pgpath *pgpath)
1190 {
1191         int r = 0, run_queue = 0;
1192         unsigned long flags;
1193         struct multipath *m = pgpath->pg->m;
1194         unsigned nr_valid_paths;
1195
1196         spin_lock_irqsave(&m->lock, flags);
1197
1198         if (pgpath->is_active)
1199                 goto out;
1200
1201         DMWARN("Reinstating path %s.", pgpath->path.dev->name);
1202
1203         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1204         if (r)
1205                 goto out;
1206
1207         pgpath->is_active = true;
1208
1209         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1210         if (nr_valid_paths == 1) {
1211                 m->current_pgpath = NULL;
1212                 run_queue = 1;
1213         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1214                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1215                         atomic_inc(&m->pg_init_in_progress);
1216         }
1217
1218         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1219                        pgpath->path.dev->name, nr_valid_paths);
1220
1221         schedule_work(&m->trigger_event);
1222
1223 out:
1224         spin_unlock_irqrestore(&m->lock, flags);
1225         if (run_queue) {
1226                 dm_table_run_md_queue_async(m->ti->table);
1227                 process_queued_io_list(m);
1228         }
1229
1230         return r;
1231 }
1232
1233 /*
1234  * Fail or reinstate all paths that match the provided struct dm_dev.
1235  */
1236 static int action_dev(struct multipath *m, struct dm_dev *dev,
1237                       action_fn action)
1238 {
1239         int r = -EINVAL;
1240         struct pgpath *pgpath;
1241         struct priority_group *pg;
1242
1243         list_for_each_entry(pg, &m->priority_groups, list) {
1244                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1245                         if (pgpath->path.dev == dev)
1246                                 r = action(pgpath);
1247                 }
1248         }
1249
1250         return r;
1251 }
1252
1253 /*
1254  * Temporarily try to avoid having to use the specified PG
1255  */
1256 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1257                       bool bypassed)
1258 {
1259         unsigned long flags;
1260
1261         spin_lock_irqsave(&m->lock, flags);
1262
1263         pg->bypassed = bypassed;
1264         m->current_pgpath = NULL;
1265         m->current_pg = NULL;
1266
1267         spin_unlock_irqrestore(&m->lock, flags);
1268
1269         schedule_work(&m->trigger_event);
1270 }
1271
1272 /*
1273  * Switch to using the specified PG from the next I/O that gets mapped
1274  */
1275 static int switch_pg_num(struct multipath *m, const char *pgstr)
1276 {
1277         struct priority_group *pg;
1278         unsigned pgnum;
1279         unsigned long flags;
1280         char dummy;
1281
1282         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1283             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1284                 DMWARN("invalid PG number supplied to switch_pg_num");
1285                 return -EINVAL;
1286         }
1287
1288         spin_lock_irqsave(&m->lock, flags);
1289         list_for_each_entry(pg, &m->priority_groups, list) {
1290                 pg->bypassed = false;
1291                 if (--pgnum)
1292                         continue;
1293
1294                 m->current_pgpath = NULL;
1295                 m->current_pg = NULL;
1296                 m->next_pg = pg;
1297         }
1298         spin_unlock_irqrestore(&m->lock, flags);
1299
1300         schedule_work(&m->trigger_event);
1301         return 0;
1302 }
1303
1304 /*
1305  * Set/clear bypassed status of a PG.
1306  * PGs are numbered upwards from 1 in the order they were declared.
1307  */
1308 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1309 {
1310         struct priority_group *pg;
1311         unsigned pgnum;
1312         char dummy;
1313
1314         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1315             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1316                 DMWARN("invalid PG number supplied to bypass_pg");
1317                 return -EINVAL;
1318         }
1319
1320         list_for_each_entry(pg, &m->priority_groups, list) {
1321                 if (!--pgnum)
1322                         break;
1323         }
1324
1325         bypass_pg(m, pg, bypassed);
1326         return 0;
1327 }
1328
1329 /*
1330  * Should we retry pg_init immediately?
1331  */
1332 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1333 {
1334         unsigned long flags;
1335         bool limit_reached = false;
1336
1337         spin_lock_irqsave(&m->lock, flags);
1338
1339         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1340             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1341                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1342         else
1343                 limit_reached = true;
1344
1345         spin_unlock_irqrestore(&m->lock, flags);
1346
1347         return limit_reached;
1348 }
1349
1350 static void pg_init_done(void *data, int errors)
1351 {
1352         struct pgpath *pgpath = data;
1353         struct priority_group *pg = pgpath->pg;
1354         struct multipath *m = pg->m;
1355         unsigned long flags;
1356         bool delay_retry = false;
1357
1358         /* device or driver problems */
1359         switch (errors) {
1360         case SCSI_DH_OK:
1361                 break;
1362         case SCSI_DH_NOSYS:
1363                 if (!m->hw_handler_name) {
1364                         errors = 0;
1365                         break;
1366                 }
1367                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1368                       "Error %d.", m->hw_handler_name, errors);
1369                 /*
1370                  * Fail path for now, so we do not ping pong
1371                  */
1372                 fail_path(pgpath);
1373                 break;
1374         case SCSI_DH_DEV_TEMP_BUSY:
1375                 /*
1376                  * Probably doing something like FW upgrade on the
1377                  * controller so try the other pg.
1378                  */
1379                 bypass_pg(m, pg, true);
1380                 break;
1381         case SCSI_DH_RETRY:
1382                 /* Wait before retrying. */
1383                 delay_retry = 1;
1384                 /* fall through */
1385         case SCSI_DH_IMM_RETRY:
1386         case SCSI_DH_RES_TEMP_UNAVAIL:
1387                 if (pg_init_limit_reached(m, pgpath))
1388                         fail_path(pgpath);
1389                 errors = 0;
1390                 break;
1391         case SCSI_DH_DEV_OFFLINED:
1392         default:
1393                 /*
1394                  * We probably do not want to fail the path for a device
1395                  * error, but this is what the old dm did. In future
1396                  * patches we can do more advanced handling.
1397                  */
1398                 fail_path(pgpath);
1399         }
1400
1401         spin_lock_irqsave(&m->lock, flags);
1402         if (errors) {
1403                 if (pgpath == m->current_pgpath) {
1404                         DMERR("Could not failover device. Error %d.", errors);
1405                         m->current_pgpath = NULL;
1406                         m->current_pg = NULL;
1407                 }
1408         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1409                 pg->bypassed = false;
1410
1411         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1412                 /* Activations of other paths are still on going */
1413                 goto out;
1414
1415         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1416                 if (delay_retry)
1417                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1418                 else
1419                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1420
1421                 if (__pg_init_all_paths(m))
1422                         goto out;
1423         }
1424         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1425
1426         process_queued_io_list(m);
1427
1428         /*
1429          * Wake up any thread waiting to suspend.
1430          */
1431         wake_up(&m->pg_init_wait);
1432
1433 out:
1434         spin_unlock_irqrestore(&m->lock, flags);
1435 }
1436
1437 static void activate_or_offline_path(struct pgpath *pgpath)
1438 {
1439         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1440
1441         if (pgpath->is_active && !blk_queue_dying(q))
1442                 scsi_dh_activate(q, pg_init_done, pgpath);
1443         else
1444                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1445 }
1446
1447 static void activate_path_work(struct work_struct *work)
1448 {
1449         struct pgpath *pgpath =
1450                 container_of(work, struct pgpath, activate_path.work);
1451
1452         activate_or_offline_path(pgpath);
1453 }
1454
1455 static int noretry_error(blk_status_t error)
1456 {
1457         switch (error) {
1458         case BLK_STS_NOTSUPP:
1459         case BLK_STS_NOSPC:
1460         case BLK_STS_TARGET:
1461         case BLK_STS_NEXUS:
1462         case BLK_STS_MEDIUM:
1463                 return 1;
1464         }
1465
1466         /* Anything else could be a path failure, so should be retried */
1467         return 0;
1468 }
1469
1470 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1471                             blk_status_t error, union map_info *map_context)
1472 {
1473         struct dm_mpath_io *mpio = get_mpio(map_context);
1474         struct pgpath *pgpath = mpio->pgpath;
1475         int r = DM_ENDIO_DONE;
1476
1477         /*
1478          * We don't queue any clone request inside the multipath target
1479          * during end I/O handling, since those clone requests don't have
1480          * bio clones.  If we queue them inside the multipath target,
1481          * we need to make bio clones, that requires memory allocation.
1482          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1483          *  don't have bio clones.)
1484          * Instead of queueing the clone request here, we queue the original
1485          * request into dm core, which will remake a clone request and
1486          * clone bios for it and resubmit it later.
1487          */
1488         if (error && !noretry_error(error)) {
1489                 struct multipath *m = ti->private;
1490
1491                 r = DM_ENDIO_REQUEUE;
1492
1493                 if (pgpath)
1494                         fail_path(pgpath);
1495
1496                 if (atomic_read(&m->nr_valid_paths) == 0 &&
1497                     !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1498                         if (error == BLK_STS_IOERR)
1499                                 dm_report_EIO(m);
1500                         /* complete with the original error */
1501                         r = DM_ENDIO_DONE;
1502                 }
1503         }
1504
1505         if (pgpath) {
1506                 struct path_selector *ps = &pgpath->pg->ps;
1507
1508                 if (ps->type->end_io)
1509                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1510         }
1511
1512         return r;
1513 }
1514
1515 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1516                 blk_status_t *error)
1517 {
1518         struct multipath *m = ti->private;
1519         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1520         struct pgpath *pgpath = mpio->pgpath;
1521         unsigned long flags;
1522         int r = DM_ENDIO_DONE;
1523
1524         if (!*error || noretry_error(*error))
1525                 goto done;
1526
1527         if (pgpath)
1528                 fail_path(pgpath);
1529
1530         if (atomic_read(&m->nr_valid_paths) == 0 &&
1531             !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1532                 dm_report_EIO(m);
1533                 *error = BLK_STS_IOERR;
1534                 goto done;
1535         }
1536
1537         /* Queue for the daemon to resubmit */
1538         dm_bio_restore(get_bio_details_from_bio(clone), clone);
1539
1540         spin_lock_irqsave(&m->lock, flags);
1541         bio_list_add(&m->queued_bios, clone);
1542         spin_unlock_irqrestore(&m->lock, flags);
1543         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1544                 queue_work(kmultipathd, &m->process_queued_bios);
1545
1546         r = DM_ENDIO_INCOMPLETE;
1547 done:
1548         if (pgpath) {
1549                 struct path_selector *ps = &pgpath->pg->ps;
1550
1551                 if (ps->type->end_io)
1552                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1553         }
1554
1555         return r;
1556 }
1557
1558 /*
1559  * Suspend can't complete until all the I/O is processed so if
1560  * the last path fails we must error any remaining I/O.
1561  * Note that if the freeze_bdev fails while suspending, the
1562  * queue_if_no_path state is lost - userspace should reset it.
1563  */
1564 static void multipath_presuspend(struct dm_target *ti)
1565 {
1566         struct multipath *m = ti->private;
1567
1568         queue_if_no_path(m, false, true);
1569 }
1570
1571 static void multipath_postsuspend(struct dm_target *ti)
1572 {
1573         struct multipath *m = ti->private;
1574
1575         mutex_lock(&m->work_mutex);
1576         flush_multipath_work(m);
1577         mutex_unlock(&m->work_mutex);
1578 }
1579
1580 /*
1581  * Restore the queue_if_no_path setting.
1582  */
1583 static void multipath_resume(struct dm_target *ti)
1584 {
1585         struct multipath *m = ti->private;
1586         unsigned long flags;
1587
1588         spin_lock_irqsave(&m->lock, flags);
1589         assign_bit(test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags),
1590                    MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1591         spin_unlock_irqrestore(&m->lock, flags);
1592 }
1593
1594 /*
1595  * Info output has the following format:
1596  * num_multipath_feature_args [multipath_feature_args]*
1597  * num_handler_status_args [handler_status_args]*
1598  * num_groups init_group_number
1599  *            [A|D|E num_ps_status_args [ps_status_args]*
1600  *             num_paths num_selector_args
1601  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1602  *
1603  * Table output has the following format (identical to the constructor string):
1604  * num_feature_args [features_args]*
1605  * num_handler_args hw_handler [hw_handler_args]*
1606  * num_groups init_group_number
1607  *     [priority selector-name num_ps_args [ps_args]*
1608  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1609  */
1610 static void multipath_status(struct dm_target *ti, status_type_t type,
1611                              unsigned status_flags, char *result, unsigned maxlen)
1612 {
1613         int sz = 0;
1614         unsigned long flags;
1615         struct multipath *m = ti->private;
1616         struct priority_group *pg;
1617         struct pgpath *p;
1618         unsigned pg_num;
1619         char state;
1620
1621         spin_lock_irqsave(&m->lock, flags);
1622
1623         /* Features */
1624         if (type == STATUSTYPE_INFO)
1625                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1626                        atomic_read(&m->pg_init_count));
1627         else {
1628                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1629                               (m->pg_init_retries > 0) * 2 +
1630                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1631                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1632                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1633
1634                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1635                         DMEMIT("queue_if_no_path ");
1636                 if (m->pg_init_retries)
1637                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1638                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1639                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1640                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1641                         DMEMIT("retain_attached_hw_handler ");
1642                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1643                         switch(m->queue_mode) {
1644                         case DM_TYPE_BIO_BASED:
1645                                 DMEMIT("queue_mode bio ");
1646                                 break;
1647                         case DM_TYPE_MQ_REQUEST_BASED:
1648                                 DMEMIT("queue_mode mq ");
1649                                 break;
1650                         default:
1651                                 WARN_ON_ONCE(true);
1652                                 break;
1653                         }
1654                 }
1655         }
1656
1657         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1658                 DMEMIT("0 ");
1659         else
1660                 DMEMIT("1 %s ", m->hw_handler_name);
1661
1662         DMEMIT("%u ", m->nr_priority_groups);
1663
1664         if (m->next_pg)
1665                 pg_num = m->next_pg->pg_num;
1666         else if (m->current_pg)
1667                 pg_num = m->current_pg->pg_num;
1668         else
1669                 pg_num = (m->nr_priority_groups ? 1 : 0);
1670
1671         DMEMIT("%u ", pg_num);
1672
1673         switch (type) {
1674         case STATUSTYPE_INFO:
1675                 list_for_each_entry(pg, &m->priority_groups, list) {
1676                         if (pg->bypassed)
1677                                 state = 'D';    /* Disabled */
1678                         else if (pg == m->current_pg)
1679                                 state = 'A';    /* Currently Active */
1680                         else
1681                                 state = 'E';    /* Enabled */
1682
1683                         DMEMIT("%c ", state);
1684
1685                         if (pg->ps.type->status)
1686                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1687                                                           result + sz,
1688                                                           maxlen - sz);
1689                         else
1690                                 DMEMIT("0 ");
1691
1692                         DMEMIT("%u %u ", pg->nr_pgpaths,
1693                                pg->ps.type->info_args);
1694
1695                         list_for_each_entry(p, &pg->pgpaths, list) {
1696                                 DMEMIT("%s %s %u ", p->path.dev->name,
1697                                        p->is_active ? "A" : "F",
1698                                        p->fail_count);
1699                                 if (pg->ps.type->status)
1700                                         sz += pg->ps.type->status(&pg->ps,
1701                                               &p->path, type, result + sz,
1702                                               maxlen - sz);
1703                         }
1704                 }
1705                 break;
1706
1707         case STATUSTYPE_TABLE:
1708                 list_for_each_entry(pg, &m->priority_groups, list) {
1709                         DMEMIT("%s ", pg->ps.type->name);
1710
1711                         if (pg->ps.type->status)
1712                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1713                                                           result + sz,
1714                                                           maxlen - sz);
1715                         else
1716                                 DMEMIT("0 ");
1717
1718                         DMEMIT("%u %u ", pg->nr_pgpaths,
1719                                pg->ps.type->table_args);
1720
1721                         list_for_each_entry(p, &pg->pgpaths, list) {
1722                                 DMEMIT("%s ", p->path.dev->name);
1723                                 if (pg->ps.type->status)
1724                                         sz += pg->ps.type->status(&pg->ps,
1725                                               &p->path, type, result + sz,
1726                                               maxlen - sz);
1727                         }
1728                 }
1729                 break;
1730         }
1731
1732         spin_unlock_irqrestore(&m->lock, flags);
1733 }
1734
1735 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1736 {
1737         int r = -EINVAL;
1738         struct dm_dev *dev;
1739         struct multipath *m = ti->private;
1740         action_fn action;
1741
1742         mutex_lock(&m->work_mutex);
1743
1744         if (dm_suspended(ti)) {
1745                 r = -EBUSY;
1746                 goto out;
1747         }
1748
1749         if (argc == 1) {
1750                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1751                         r = queue_if_no_path(m, true, false);
1752                         goto out;
1753                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1754                         r = queue_if_no_path(m, false, false);
1755                         goto out;
1756                 }
1757         }
1758
1759         if (argc != 2) {
1760                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1761                 goto out;
1762         }
1763
1764         if (!strcasecmp(argv[0], "disable_group")) {
1765                 r = bypass_pg_num(m, argv[1], true);
1766                 goto out;
1767         } else if (!strcasecmp(argv[0], "enable_group")) {
1768                 r = bypass_pg_num(m, argv[1], false);
1769                 goto out;
1770         } else if (!strcasecmp(argv[0], "switch_group")) {
1771                 r = switch_pg_num(m, argv[1]);
1772                 goto out;
1773         } else if (!strcasecmp(argv[0], "reinstate_path"))
1774                 action = reinstate_path;
1775         else if (!strcasecmp(argv[0], "fail_path"))
1776                 action = fail_path;
1777         else {
1778                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1779                 goto out;
1780         }
1781
1782         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1783         if (r) {
1784                 DMWARN("message: error getting device %s",
1785                        argv[1]);
1786                 goto out;
1787         }
1788
1789         r = action_dev(m, dev, action);
1790
1791         dm_put_device(ti, dev);
1792
1793 out:
1794         mutex_unlock(&m->work_mutex);
1795         return r;
1796 }
1797
1798 static int multipath_prepare_ioctl(struct dm_target *ti,
1799                 struct block_device **bdev, fmode_t *mode)
1800 {
1801         struct multipath *m = ti->private;
1802         struct pgpath *current_pgpath;
1803         int r;
1804
1805         current_pgpath = READ_ONCE(m->current_pgpath);
1806         if (!current_pgpath)
1807                 current_pgpath = choose_pgpath(m, 0);
1808
1809         if (current_pgpath) {
1810                 if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1811                         *bdev = current_pgpath->path.dev->bdev;
1812                         *mode = current_pgpath->path.dev->mode;
1813                         r = 0;
1814                 } else {
1815                         /* pg_init has not started or completed */
1816                         r = -ENOTCONN;
1817                 }
1818         } else {
1819                 /* No path is available */
1820                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1821                         r = -ENOTCONN;
1822                 else
1823                         r = -EIO;
1824         }
1825
1826         if (r == -ENOTCONN) {
1827                 if (!READ_ONCE(m->current_pg)) {
1828                         /* Path status changed, redo selection */
1829                         (void) choose_pgpath(m, 0);
1830                 }
1831                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1832                         pg_init_all_paths(m);
1833                 dm_table_run_md_queue_async(m->ti->table);
1834                 process_queued_io_list(m);
1835         }
1836
1837         /*
1838          * Only pass ioctls through if the device sizes match exactly.
1839          */
1840         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1841                 return 1;
1842         return r;
1843 }
1844
1845 static int multipath_iterate_devices(struct dm_target *ti,
1846                                      iterate_devices_callout_fn fn, void *data)
1847 {
1848         struct multipath *m = ti->private;
1849         struct priority_group *pg;
1850         struct pgpath *p;
1851         int ret = 0;
1852
1853         list_for_each_entry(pg, &m->priority_groups, list) {
1854                 list_for_each_entry(p, &pg->pgpaths, list) {
1855                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1856                         if (ret)
1857                                 goto out;
1858                 }
1859         }
1860
1861 out:
1862         return ret;
1863 }
1864
1865 static int pgpath_busy(struct pgpath *pgpath)
1866 {
1867         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1868
1869         return blk_lld_busy(q);
1870 }
1871
1872 /*
1873  * We return "busy", only when we can map I/Os but underlying devices
1874  * are busy (so even if we map I/Os now, the I/Os will wait on
1875  * the underlying queue).
1876  * In other words, if we want to kill I/Os or queue them inside us
1877  * due to map unavailability, we don't return "busy".  Otherwise,
1878  * dm core won't give us the I/Os and we can't do what we want.
1879  */
1880 static int multipath_busy(struct dm_target *ti)
1881 {
1882         bool busy = false, has_active = false;
1883         struct multipath *m = ti->private;
1884         struct priority_group *pg, *next_pg;
1885         struct pgpath *pgpath;
1886
1887         /* pg_init in progress */
1888         if (atomic_read(&m->pg_init_in_progress))
1889                 return true;
1890
1891         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
1892         if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1893                 return (m->queue_mode != DM_TYPE_MQ_REQUEST_BASED);
1894
1895         /* Guess which priority_group will be used at next mapping time */
1896         pg = READ_ONCE(m->current_pg);
1897         next_pg = READ_ONCE(m->next_pg);
1898         if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
1899                 pg = next_pg;
1900
1901         if (!pg) {
1902                 /*
1903                  * We don't know which pg will be used at next mapping time.
1904                  * We don't call choose_pgpath() here to avoid to trigger
1905                  * pg_init just by busy checking.
1906                  * So we don't know whether underlying devices we will be using
1907                  * at next mapping time are busy or not. Just try mapping.
1908                  */
1909                 return busy;
1910         }
1911
1912         /*
1913          * If there is one non-busy active path at least, the path selector
1914          * will be able to select it. So we consider such a pg as not busy.
1915          */
1916         busy = true;
1917         list_for_each_entry(pgpath, &pg->pgpaths, list) {
1918                 if (pgpath->is_active) {
1919                         has_active = true;
1920                         if (!pgpath_busy(pgpath)) {
1921                                 busy = false;
1922                                 break;
1923                         }
1924                 }
1925         }
1926
1927         if (!has_active) {
1928                 /*
1929                  * No active path in this pg, so this pg won't be used and
1930                  * the current_pg will be changed at next mapping time.
1931                  * We need to try mapping to determine it.
1932                  */
1933                 busy = false;
1934         }
1935
1936         return busy;
1937 }
1938
1939 /*-----------------------------------------------------------------
1940  * Module setup
1941  *---------------------------------------------------------------*/
1942 static struct target_type multipath_target = {
1943         .name = "multipath",
1944         .version = {1, 12, 0},
1945         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
1946         .module = THIS_MODULE,
1947         .ctr = multipath_ctr,
1948         .dtr = multipath_dtr,
1949         .clone_and_map_rq = multipath_clone_and_map,
1950         .release_clone_rq = multipath_release_clone,
1951         .rq_end_io = multipath_end_io,
1952         .map = multipath_map_bio,
1953         .end_io = multipath_end_io_bio,
1954         .presuspend = multipath_presuspend,
1955         .postsuspend = multipath_postsuspend,
1956         .resume = multipath_resume,
1957         .status = multipath_status,
1958         .message = multipath_message,
1959         .prepare_ioctl = multipath_prepare_ioctl,
1960         .iterate_devices = multipath_iterate_devices,
1961         .busy = multipath_busy,
1962 };
1963
1964 static int __init dm_multipath_init(void)
1965 {
1966         int r;
1967
1968         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1969         if (!kmultipathd) {
1970                 DMERR("failed to create workqueue kmpathd");
1971                 r = -ENOMEM;
1972                 goto bad_alloc_kmultipathd;
1973         }
1974
1975         /*
1976          * A separate workqueue is used to handle the device handlers
1977          * to avoid overloading existing workqueue. Overloading the
1978          * old workqueue would also create a bottleneck in the
1979          * path of the storage hardware device activation.
1980          */
1981         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1982                                                   WQ_MEM_RECLAIM);
1983         if (!kmpath_handlerd) {
1984                 DMERR("failed to create workqueue kmpath_handlerd");
1985                 r = -ENOMEM;
1986                 goto bad_alloc_kmpath_handlerd;
1987         }
1988
1989         r = dm_register_target(&multipath_target);
1990         if (r < 0) {
1991                 DMERR("request-based register failed %d", r);
1992                 r = -EINVAL;
1993                 goto bad_register_target;
1994         }
1995
1996         return 0;
1997
1998 bad_register_target:
1999         destroy_workqueue(kmpath_handlerd);
2000 bad_alloc_kmpath_handlerd:
2001         destroy_workqueue(kmultipathd);
2002 bad_alloc_kmultipathd:
2003         return r;
2004 }
2005
2006 static void __exit dm_multipath_exit(void)
2007 {
2008         destroy_workqueue(kmpath_handlerd);
2009         destroy_workqueue(kmultipathd);
2010
2011         dm_unregister_target(&multipath_target);
2012 }
2013
2014 module_init(dm_multipath_init);
2015 module_exit(dm_multipath_exit);
2016
2017 MODULE_DESCRIPTION(DM_NAME " multipath target");
2018 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2019 MODULE_LICENSE("GPL");