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