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