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         unsigned long flags;            /* Multipath state flags */
  68
  69         spinlock_t lock;
  70         enum dm_queue_mode queue_mode;
  71
  72         struct pgpath *current_pgpath;
  73         struct priority_group *current_pg;
  74         struct priority_group *next_pg; /* Switch to this PG if set */
  75
  76         atomic_t nr_valid_paths;        /* Total number of usable paths */
  77         unsigned nr_priority_groups;
  78         struct list_head priority_groups;
  79
  80         const char *hw_handler_name;
  81         char *hw_handler_params;
  82         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  83         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  84         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  85         atomic_t pg_init_in_progress;   /* Only one pg_init allowed at once */
  86         atomic_t pg_init_count;         /* Number of times pg_init called */
  87
  88         struct mutex work_mutex;
  89         struct work_struct trigger_event;
  90         struct dm_target *ti;
  91
  92         struct work_struct process_queued_bios;
  93         struct bio_list queued_bios;
  94 };
  95
  96 /*
  97  * Context information attached to each io we process.
  98  */
  99 struct dm_mpath_io {
 100         struct pgpath *pgpath;
 101         size_t nr_bytes;
 102 };
 103
 104 typedef int (*action_fn) (struct pgpath *pgpath);
 105
 106 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 107 static void trigger_event(struct work_struct *work);
 108 static void activate_or_offline_path(struct pgpath *pgpath);
 109 static void activate_path_work(struct work_struct *work);
 110 static void process_queued_bios(struct work_struct *work);
 111
 112 /*-----------------------------------------------
 113  * Multipath state flags.
 114  *-----------------------------------------------*/
 115
 116 #define MPATHF_QUEUE_IO 0                       /* Must we queue all I/O? */
 117 #define MPATHF_QUEUE_IF_NO_PATH 1               /* Queue I/O if last path fails? */
 118 #define MPATHF_SAVED_QUEUE_IF_NO_PATH 2         /* Saved state during suspension */
 119 #define MPATHF_RETAIN_ATTACHED_HW_HANDLER 3     /* If there's already a hw_handler present, don't change it. */
 120 #define MPATHF_PG_INIT_DISABLED 4               /* pg_init is not currently allowed */
 121 #define MPATHF_PG_INIT_REQUIRED 5               /* pg_init needs calling? */
 122 #define MPATHF_PG_INIT_DELAY_RETRY 6            /* Delay pg_init retry? */
 123
 124 /*-----------------------------------------------
 125  * Allocation routines
 126  *-----------------------------------------------*/
 127
 128 static struct pgpath *alloc_pgpath(void)
 129 {
 130         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 131
 132         if (!pgpath)
 133                 return NULL;
 134
 135         pgpath->is_active = true;
 136
 137         return pgpath;
 138 }
 139
 140 static void free_pgpath(struct pgpath *pgpath)
 141 {
 142         kfree(pgpath);
 143 }
 144
 145 static struct priority_group *alloc_priority_group(void)
 146 {
 147         struct priority_group *pg;
 148
 149         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 150
 151         if (pg)
 152                 INIT_LIST_HEAD(&pg->pgpaths);
 153
 154         return pg;
 155 }
 156
 157 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 158 {
 159         struct pgpath *pgpath, *tmp;
 160
 161         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 162                 list_del(&pgpath->list);
 163                 dm_put_device(ti, pgpath->path.dev);
 164                 free_pgpath(pgpath);
 165         }
 166 }
 167
 168 static void free_priority_group(struct priority_group *pg,
 169                                 struct dm_target *ti)
 170 {
 171         struct path_selector *ps = &pg->ps;
 172
 173         if (ps->type) {
 174                 ps->type->destroy(ps);
 175                 dm_put_path_selector(ps->type);
 176         }
 177
 178         free_pgpaths(&pg->pgpaths, ti);
 179         kfree(pg);
 180 }
 181
 182 static struct multipath *alloc_multipath(struct dm_target *ti)
 183 {
 184         struct multipath *m;
 185
 186         m = kzalloc(sizeof(*m), GFP_KERNEL);
 187         if (m) {
 188                 INIT_LIST_HEAD(&m->priority_groups);
 189                 spin_lock_init(&m->lock);
 190                 atomic_set(&m->nr_valid_paths, 0);
 191                 INIT_WORK(&m->trigger_event, trigger_event);
 192                 mutex_init(&m->work_mutex);
 193
 194                 m->queue_mode = DM_TYPE_NONE;
 195
 196                 m->ti = ti;
 197                 ti->private = m;
 198         }
 199
 200         return m;
 201 }
 202
 203 static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
 204 {
 205         if (m->queue_mode == DM_TYPE_NONE) {
 206                 m->queue_mode = DM_TYPE_REQUEST_BASED;
 207         } else if (m->queue_mode == DM_TYPE_BIO_BASED) {
 208                 INIT_WORK(&m->process_queued_bios, process_queued_bios);
 209                 /*
 210                  * bio-based doesn't support any direct scsi_dh management;
 211                  * it just discovers if a scsi_dh is attached.
 212                  */
 213                 set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 214         }
 215
 216         dm_table_set_type(ti->table, m->queue_mode);
 217
 218         /*
 219          * Init fields that are only used when a scsi_dh is attached
 220          * - must do this unconditionally (really doesn't hurt non-SCSI uses)
 221          */
 222         set_bit(MPATHF_QUEUE_IO, &m->flags);
 223         atomic_set(&m->pg_init_in_progress, 0);
 224         atomic_set(&m->pg_init_count, 0);
 225         m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 226         init_waitqueue_head(&m->pg_init_wait);
 227
 228         return 0;
 229 }
 230
 231 static void free_multipath(struct multipath *m)
 232 {
 233         struct priority_group *pg, *tmp;
 234
 235         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 236                 list_del(&pg->list);
 237                 free_priority_group(pg, m->ti);
 238         }
 239
 240         kfree(m->hw_handler_name);
 241         kfree(m->hw_handler_params);
 242         mutex_destroy(&m->work_mutex);
 243         kfree(m);
 244 }
 245
 246 static struct dm_mpath_io *get_mpio(union map_info *info)
 247 {
 248         return info->ptr;
 249 }
 250
 251 static size_t multipath_per_bio_data_size(void)
 252 {
 253         return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
 254 }
 255
 256 static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
 257 {
 258         return dm_per_bio_data(bio, multipath_per_bio_data_size());
 259 }
 260
 261 static struct dm_bio_details *get_bio_details_from_mpio(struct dm_mpath_io *mpio)
 262 {
 263         /* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
 264         void *bio_details = mpio + 1;
 265         return bio_details;
 266 }
 267
 268 static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p)
 269 {
 270         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 271         struct dm_bio_details *bio_details = get_bio_details_from_mpio(mpio);
 272
 273         mpio->nr_bytes = bio->bi_iter.bi_size;
 274         mpio->pgpath = NULL;
 275         *mpio_p = mpio;
 276
 277         dm_bio_record(bio_details, bio);
 278 }
 279
 280 /*-----------------------------------------------
 281  * Path selection
 282  *-----------------------------------------------*/
 283
 284 static int __pg_init_all_paths(struct multipath *m)
 285 {
 286         struct pgpath *pgpath;
 287         unsigned long pg_init_delay = 0;
 288
 289         lockdep_assert_held(&m->lock);
 290
 291         if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
 292                 return 0;
 293
 294         atomic_inc(&m->pg_init_count);
 295         clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 296
 297         /* Check here to reset pg_init_required */
 298         if (!m->current_pg)
 299                 return 0;
 300
 301         if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
 302                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 303                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 304         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 305                 /* Skip failed paths */
 306                 if (!pgpath->is_active)
 307                         continue;
 308                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 309                                        pg_init_delay))
 310                         atomic_inc(&m->pg_init_in_progress);
 311         }
 312         return atomic_read(&m->pg_init_in_progress);
 313 }
 314
 315 static int pg_init_all_paths(struct multipath *m)
 316 {
 317         int ret;
 318         unsigned long flags;
 319
 320         spin_lock_irqsave(&m->lock, flags);
 321         ret = __pg_init_all_paths(m);
 322         spin_unlock_irqrestore(&m->lock, flags);
 323
 324         return ret;
 325 }
 326
 327 static void __switch_pg(struct multipath *m, struct priority_group *pg)
 328 {
 329         m->current_pg = pg;
 330
 331         /* Must we initialise the PG first, and queue I/O till it's ready? */
 332         if (m->hw_handler_name) {
 333                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 334                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 335         } else {
 336                 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 337                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 338         }
 339
 340         atomic_set(&m->pg_init_count, 0);
 341 }
 342
 343 static struct pgpath *choose_path_in_pg(struct multipath *m,
 344                                         struct priority_group *pg,
 345                                         size_t nr_bytes)
 346 {
 347         unsigned long flags;
 348         struct dm_path *path;
 349         struct pgpath *pgpath;
 350
 351         path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 352         if (!path)
 353                 return ERR_PTR(-ENXIO);
 354
 355         pgpath = path_to_pgpath(path);
 356
 357         if (unlikely(READ_ONCE(m->current_pg) != pg)) {
 358                 /* Only update current_pgpath if pg changed */
 359                 spin_lock_irqsave(&m->lock, flags);
 360                 m->current_pgpath = pgpath;
 361                 __switch_pg(m, pg);
 362                 spin_unlock_irqrestore(&m->lock, flags);
 363         }
 364
 365         return pgpath;
 366 }
 367
 368 static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 369 {
 370         unsigned long flags;
 371         struct priority_group *pg;
 372         struct pgpath *pgpath;
 373         unsigned bypassed = 1;
 374
 375         if (!atomic_read(&m->nr_valid_paths)) {
 376                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 377                 goto failed;
 378         }
 379
 380         /* Were we instructed to switch PG? */
 381         if (READ_ONCE(m->next_pg)) {
 382                 spin_lock_irqsave(&m->lock, flags);
 383                 pg = m->next_pg;
 384                 if (!pg) {
 385                         spin_unlock_irqrestore(&m->lock, flags);
 386                         goto check_current_pg;
 387                 }
 388                 m->next_pg = NULL;
 389                 spin_unlock_irqrestore(&m->lock, flags);
 390                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 391                 if (!IS_ERR_OR_NULL(pgpath))
 392                         return pgpath;
 393         }
 394
 395         /* Don't change PG until it has no remaining paths */
 396 check_current_pg:
 397         pg = READ_ONCE(m->current_pg);
 398         if (pg) {
 399                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 400                 if (!IS_ERR_OR_NULL(pgpath))
 401                         return pgpath;
 402         }
 403
 404         /*
 405          * Loop through priority groups until we find a valid path.
 406          * First time we skip PGs marked 'bypassed'.
 407          * Second time we only try the ones we skipped, but set
 408          * pg_init_delay_retry so we do not hammer controllers.
 409          */
 410         do {
 411                 list_for_each_entry(pg, &m->priority_groups, list) {
 412                         if (pg->bypassed == !!bypassed)
 413                                 continue;
 414                         pgpath = choose_path_in_pg(m, pg, nr_bytes);
 415                         if (!IS_ERR_OR_NULL(pgpath)) {
 416                                 if (!bypassed)
 417                                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 418                                 return pgpath;
 419                         }
 420                 }
 421         } while (bypassed--);
 422
 423 failed:
 424         spin_lock_irqsave(&m->lock, flags);
 425         m->current_pgpath = NULL;
 426         m->current_pg = NULL;
 427         spin_unlock_irqrestore(&m->lock, flags);
 428
 429         return NULL;
 430 }
 431
 432 /*
 433  * dm_report_EIO() is a macro instead of a function to make pr_debug()
 434  * report the function name and line number of the function from which
 435  * it has been invoked.
 436  */
 437 #define dm_report_EIO(m)                                                \
 438 do {                                                                    \
 439         struct mapped_device *md = dm_table_get_md((m)->ti->table);     \
 440                                                                         \
 441         pr_debug("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d\n", \
 442                  dm_device_name(md),                                    \
 443                  test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),        \
 444                  test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags),  \
 445                  dm_noflush_suspending((m)->ti));                       \
 446 } while (0)
 447
 448 /*
 449  * Check whether bios must be queued in the device-mapper core rather
 450  * than here in the target.
 451  *
 452  * If MPATHF_QUEUE_IF_NO_PATH and MPATHF_SAVED_QUEUE_IF_NO_PATH hold
 453  * the same value then we are not between multipath_presuspend()
 454  * and multipath_resume() calls and we have no need to check
 455  * for the DMF_NOFLUSH_SUSPENDING flag.
 456  */
 457 static bool __must_push_back(struct multipath *m, unsigned long flags)
 458 {
 459         return ((test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) !=
 460                  test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &flags)) &&
 461                 dm_noflush_suspending(m->ti));
 462 }
 463
 464 /*
 465  * Following functions use READ_ONCE to get atomic access to
 466  * all m->flags to avoid taking spinlock
 467  */
 468 static bool must_push_back_rq(struct multipath *m)
 469 {
 470         unsigned long flags = READ_ONCE(m->flags);
 471         return test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) || __must_push_back(m, flags);
 472 }
 473
 474 static bool must_push_back_bio(struct multipath *m)
 475 {
 476         unsigned long flags = READ_ONCE(m->flags);
 477         return __must_push_back(m, flags);
 478 }
 479
 480 /*
 481  * Map cloned requests (request-based multipath)
 482  */
 483 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 484                                    union map_info *map_context,
 485                                    struct request **__clone)
 486 {
 487         struct multipath *m = ti->private;
 488         size_t nr_bytes = blk_rq_bytes(rq);
 489         struct pgpath *pgpath;
 490         struct block_device *bdev;
 491         struct dm_mpath_io *mpio = get_mpio(map_context);
 492         struct request_queue *q;
 493         struct request *clone;
 494
 495         /* Do we need to select a new pgpath? */
 496         pgpath = READ_ONCE(m->current_pgpath);
 497         if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
 498                 pgpath = choose_pgpath(m, nr_bytes);
 499
 500         if (!pgpath) {
 501                 if (must_push_back_rq(m))
 502                         return DM_MAPIO_DELAY_REQUEUE;
 503                 dm_report_EIO(m);       /* Failed */
 504                 return DM_MAPIO_KILL;
 505         } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
 506                    test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
 507                 pg_init_all_paths(m);
 508                 return DM_MAPIO_DELAY_REQUEUE;
 509         }
 510
 511         mpio->pgpath = pgpath;
 512         mpio->nr_bytes = nr_bytes;
 513
 514         bdev = pgpath->path.dev->bdev;
 515         q = bdev_get_queue(bdev);
 516         clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE,
 517                         BLK_MQ_REQ_NOWAIT);
 518         if (IS_ERR(clone)) {
 519                 /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 520                 if (blk_queue_dying(q)) {
 521                         atomic_inc(&m->pg_init_in_progress);
 522                         activate_or_offline_path(pgpath);
 523                         return DM_MAPIO_DELAY_REQUEUE;
 524                 }
 525
 526                 /*
 527                  * blk-mq's SCHED_RESTART can cover this requeue, so we
 528                  * needn't deal with it by DELAY_REQUEUE. More importantly,
 529                  * we have to return DM_MAPIO_REQUEUE so that blk-mq can
 530                  * get the queue busy feedback (via BLK_STS_RESOURCE),
 531                  * otherwise I/O merging can suffer.
 532                  */
 533                 return DM_MAPIO_REQUEUE;
 534         }
 535         clone->bio = clone->biotail = NULL;
 536         clone->rq_disk = bdev->bd_disk;
 537         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 538         *__clone = clone;
 539
 540         if (pgpath->pg->ps.type->start_io)
 541                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 542                                               &pgpath->path,
 543                                               nr_bytes);
 544         return DM_MAPIO_REMAPPED;
 545 }
 546
 547 static void multipath_release_clone(struct request *clone)
 548 {
 549         blk_put_request(clone);
 550 }
 551
 552 /*
 553  * Map cloned bios (bio-based multipath)
 554  */
 555
 556 static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
 557 {
 558         struct pgpath *pgpath;
 559         unsigned long flags;
 560         bool queue_io;
 561
 562         /* Do we need to select a new pgpath? */
 563         pgpath = READ_ONCE(m->current_pgpath);
 564         queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
 565         if (!pgpath || !queue_io)
 566                 pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 567
 568         if ((pgpath && queue_io) ||
 569             (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
 570                 /* Queue for the daemon to resubmit */
 571                 spin_lock_irqsave(&m->lock, flags);
 572                 bio_list_add(&m->queued_bios, bio);
 573                 spin_unlock_irqrestore(&m->lock, flags);
 574
 575                 /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
 576                 if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
 577                         pg_init_all_paths(m);
 578                 else if (!queue_io)
 579                         queue_work(kmultipathd, &m->process_queued_bios);
 580
 581                 return ERR_PTR(-EAGAIN);
 582         }
 583
 584         return pgpath;
 585 }
 586
 587 static struct pgpath *__map_bio_fast(struct multipath *m, struct bio *bio)
 588 {
 589         struct pgpath *pgpath;
 590         unsigned long flags;
 591
 592         /* Do we need to select a new pgpath? */
 593         /*
 594          * FIXME: currently only switching path if no path (due to failure, etc)
 595          * - which negates the point of using a path selector
 596          */
 597         pgpath = READ_ONCE(m->current_pgpath);
 598         if (!pgpath)
 599                 pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 600
 601         if (!pgpath) {
 602                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 603                         /* Queue for the daemon to resubmit */
 604                         spin_lock_irqsave(&m->lock, flags);
 605                         bio_list_add(&m->queued_bios, bio);
 606                         spin_unlock_irqrestore(&m->lock, flags);
 607                         queue_work(kmultipathd, &m->process_queued_bios);
 608
 609                         return ERR_PTR(-EAGAIN);
 610                 }
 611                 return NULL;
 612         }
 613
 614         return pgpath;
 615 }
 616
 617 static int __multipath_map_bio(struct multipath *m, struct bio *bio,
 618                                struct dm_mpath_io *mpio)
 619 {
 620         struct pgpath *pgpath;
 621
 622         if (!m->hw_handler_name)
 623                 pgpath = __map_bio_fast(m, bio);
 624         else
 625                 pgpath = __map_bio(m, bio);
 626
 627         if (IS_ERR(pgpath))
 628                 return DM_MAPIO_SUBMITTED;
 629
 630         if (!pgpath) {
 631                 if (must_push_back_bio(m))
 632                         return DM_MAPIO_REQUEUE;
 633                 dm_report_EIO(m);
 634                 return DM_MAPIO_KILL;
 635         }
 636
 637         mpio->pgpath = pgpath;
 638
 639         bio->bi_status = 0;
 640         bio_set_dev(bio, pgpath->path.dev->bdev);
 641         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 642
 643         if (pgpath->pg->ps.type->start_io)
 644                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 645                                               &pgpath->path,
 646                                               mpio->nr_bytes);
 647         return DM_MAPIO_REMAPPED;
 648 }
 649
 650 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 651 {
 652         struct multipath *m = ti->private;
 653         struct dm_mpath_io *mpio = NULL;
 654
 655         multipath_init_per_bio_data(bio, &mpio);
 656         return __multipath_map_bio(m, bio, mpio);
 657 }
 658
 659 static void process_queued_io_list(struct multipath *m)
 660 {
 661         if (m->queue_mode == DM_TYPE_REQUEST_BASED)
 662                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 663         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 664                 queue_work(kmultipathd, &m->process_queued_bios);
 665 }
 666
 667 static void process_queued_bios(struct work_struct *work)
 668 {
 669         int r;
 670         unsigned long flags;
 671         struct bio *bio;
 672         struct bio_list bios;
 673         struct blk_plug plug;
 674         struct multipath *m =
 675                 container_of(work, struct multipath, process_queued_bios);
 676
 677         bio_list_init(&bios);
 678
 679         spin_lock_irqsave(&m->lock, flags);
 680
 681         if (bio_list_empty(&m->queued_bios)) {
 682                 spin_unlock_irqrestore(&m->lock, flags);
 683                 return;
 684         }
 685
 686         bio_list_merge(&bios, &m->queued_bios);
 687         bio_list_init(&m->queued_bios);
 688
 689         spin_unlock_irqrestore(&m->lock, flags);
 690
 691         blk_start_plug(&plug);
 692         while ((bio = bio_list_pop(&bios))) {
 693                 struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 694                 dm_bio_restore(get_bio_details_from_mpio(mpio), bio);
 695                 r = __multipath_map_bio(m, bio, mpio);
 696                 switch (r) {
 697                 case DM_MAPIO_KILL:
 698                         bio->bi_status = BLK_STS_IOERR;
 699                         bio_endio(bio);
 700                         break;
 701                 case DM_MAPIO_REQUEUE:
 702                         bio->bi_status = BLK_STS_DM_REQUEUE;
 703                         bio_endio(bio);
 704                         break;
 705                 case DM_MAPIO_REMAPPED:
 706                         generic_make_request(bio);
 707                         break;
 708                 case DM_MAPIO_SUBMITTED:
 709                         break;
 710                 default:
 711                         WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 712                 }
 713         }
 714         blk_finish_plug(&plug);
 715 }
 716
 717 /*
 718  * If we run out of usable paths, should we queue I/O or error it?
 719  */
 720 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 721                             bool save_old_value)
 722 {
 723         unsigned long flags;
 724
 725         spin_lock_irqsave(&m->lock, flags);
 726         assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags,
 727                    (save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
 728                    (!save_old_value && queue_if_no_path));
 729         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);
 730         spin_unlock_irqrestore(&m->lock, flags);
 731
 732         if (!queue_if_no_path) {
 733                 dm_table_run_md_queue_async(m->ti->table);
 734                 process_queued_io_list(m);
 735         }
 736
 737         return 0;
 738 }
 739
 740 /*
 741  * An event is triggered whenever a path is taken out of use.
 742  * Includes path failure and PG bypass.
 743  */
 744 static void trigger_event(struct work_struct *work)
 745 {
 746         struct multipath *m =
 747                 container_of(work, struct multipath, trigger_event);
 748
 749         dm_table_event(m->ti->table);
 750 }
 751
 752 /*-----------------------------------------------------------------
 753  * Constructor/argument parsing:
 754  * <#multipath feature args> [<arg>]*
 755  * <#hw_handler args> [hw_handler [<arg>]*]
 756  * <#priority groups>
 757  * <initial priority group>
 758  *     [<selector> <#selector args> [<arg>]*
 759  *      <#paths> <#per-path selector args>
 760  *         [<path> [<arg>]* ]+ ]+
 761  *---------------------------------------------------------------*/
 762 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 763                                struct dm_target *ti)
 764 {
 765         int r;
 766         struct path_selector_type *pst;
 767         unsigned ps_argc;
 768
 769         static const struct dm_arg _args[] = {
 770                 {0, 1024, "invalid number of path selector args"},
 771         };
 772
 773         pst = dm_get_path_selector(dm_shift_arg(as));
 774         if (!pst) {
 775                 ti->error = "unknown path selector type";
 776                 return -EINVAL;
 777         }
 778
 779         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 780         if (r) {
 781                 dm_put_path_selector(pst);
 782                 return -EINVAL;
 783         }
 784
 785         r = pst->create(&pg->ps, ps_argc, as->argv);
 786         if (r) {
 787                 dm_put_path_selector(pst);
 788                 ti->error = "path selector constructor failed";
 789                 return r;
 790         }
 791
 792         pg->ps.type = pst;
 793         dm_consume_args(as, ps_argc);
 794
 795         return 0;
 796 }
 797
 798 static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
 799                          const char **attached_handler_name, char **error)
 800 {
 801         struct request_queue *q = bdev_get_queue(bdev);
 802         int r;
 803
 804         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 805 retain:
 806                 if (*attached_handler_name) {
 807                         /*
 808                          * Clear any hw_handler_params associated with a
 809                          * handler that isn't already attached.
 810                          */
 811                         if (m->hw_handler_name && strcmp(*attached_handler_name, m->hw_handler_name)) {
 812                                 kfree(m->hw_handler_params);
 813                                 m->hw_handler_params = NULL;
 814                         }
 815
 816                         /*
 817                          * Reset hw_handler_name to match the attached handler
 818                          *
 819                          * NB. This modifies the table line to show the actual
 820                          * handler instead of the original table passed in.
 821                          */
 822                         kfree(m->hw_handler_name);
 823                         m->hw_handler_name = *attached_handler_name;
 824                         *attached_handler_name = NULL;
 825                 }
 826         }
 827
 828         if (m->hw_handler_name) {
 829                 r = scsi_dh_attach(q, m->hw_handler_name);
 830                 if (r == -EBUSY) {
 831                         char b[BDEVNAME_SIZE];
 832
 833                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 834                                bdevname(bdev, b));
 835                         goto retain;
 836                 }
 837                 if (r < 0) {
 838                         *error = "error attaching hardware handler";
 839                         return r;
 840                 }
 841
 842                 if (m->hw_handler_params) {
 843                         r = scsi_dh_set_params(q, m->hw_handler_params);
 844                         if (r < 0) {
 845                                 *error = "unable to set hardware handler parameters";
 846                                 return r;
 847                         }
 848                 }
 849         }
 850
 851         return 0;
 852 }
 853
 854 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 855                                  struct dm_target *ti)
 856 {
 857         int r;
 858         struct pgpath *p;
 859         struct multipath *m = ti->private;
 860         struct request_queue *q;
 861         const char *attached_handler_name = NULL;
 862
 863         /* we need at least a path arg */
 864         if (as->argc < 1) {
 865                 ti->error = "no device given";
 866                 return ERR_PTR(-EINVAL);
 867         }
 868
 869         p = alloc_pgpath();
 870         if (!p)
 871                 return ERR_PTR(-ENOMEM);
 872
 873         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 874                           &p->path.dev);
 875         if (r) {
 876                 ti->error = "error getting device";
 877                 goto bad;
 878         }
 879
 880         q = bdev_get_queue(p->path.dev->bdev);
 881         attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 882         if (attached_handler_name || m->hw_handler_name) {
 883                 INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
 884                 r = setup_scsi_dh(p->path.dev->bdev, m, &attached_handler_name, &ti->error);
 885                 if (r) {
 886                         dm_put_device(ti, p->path.dev);
 887                         goto bad;
 888                 }
 889         }
 890
 891         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 892         if (r) {
 893                 dm_put_device(ti, p->path.dev);
 894                 goto bad;
 895         }
 896
 897         return p;
 898  bad:
 899         kfree(attached_handler_name);
 900         free_pgpath(p);
 901         return ERR_PTR(r);
 902 }
 903
 904 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 905                                                    struct multipath *m)
 906 {
 907         static const struct dm_arg _args[] = {
 908                 {1, 1024, "invalid number of paths"},
 909                 {0, 1024, "invalid number of selector args"}
 910         };
 911
 912         int r;
 913         unsigned i, nr_selector_args, nr_args;
 914         struct priority_group *pg;
 915         struct dm_target *ti = m->ti;
 916
 917         if (as->argc < 2) {
 918                 as->argc = 0;
 919                 ti->error = "not enough priority group arguments";
 920                 return ERR_PTR(-EINVAL);
 921         }
 922
 923         pg = alloc_priority_group();
 924         if (!pg) {
 925                 ti->error = "couldn't allocate priority group";
 926                 return ERR_PTR(-ENOMEM);
 927         }
 928         pg->m = m;
 929
 930         r = parse_path_selector(as, pg, ti);
 931         if (r)
 932                 goto bad;
 933
 934         /*
 935          * read the paths
 936          */
 937         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 938         if (r)
 939                 goto bad;
 940
 941         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 942         if (r)
 943                 goto bad;
 944
 945         nr_args = 1 + nr_selector_args;
 946         for (i = 0; i < pg->nr_pgpaths; i++) {
 947                 struct pgpath *pgpath;
 948                 struct dm_arg_set path_args;
 949
 950                 if (as->argc < nr_args) {
 951                         ti->error = "not enough path parameters";
 952                         r = -EINVAL;
 953                         goto bad;
 954                 }
 955
 956                 path_args.argc = nr_args;
 957                 path_args.argv = as->argv;
 958
 959                 pgpath = parse_path(&path_args, &pg->ps, ti);
 960                 if (IS_ERR(pgpath)) {
 961                         r = PTR_ERR(pgpath);
 962                         goto bad;
 963                 }
 964
 965                 pgpath->pg = pg;
 966                 list_add_tail(&pgpath->list, &pg->pgpaths);
 967                 dm_consume_args(as, nr_args);
 968         }
 969
 970         return pg;
 971
 972  bad:
 973         free_priority_group(pg, ti);
 974         return ERR_PTR(r);
 975 }
 976
 977 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 978 {
 979         unsigned hw_argc;
 980         int ret;
 981         struct dm_target *ti = m->ti;
 982
 983         static const struct dm_arg _args[] = {
 984                 {0, 1024, "invalid number of hardware handler args"},
 985         };
 986
 987         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 988                 return -EINVAL;
 989
 990         if (!hw_argc)
 991                 return 0;
 992
 993         if (m->queue_mode == DM_TYPE_BIO_BASED) {
 994                 dm_consume_args(as, hw_argc);
 995                 DMERR("bio-based multipath doesn't allow hardware handler args");
 996                 return 0;
 997         }
 998
 999         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
1000         if (!m->hw_handler_name)
1001                 return -EINVAL;
1002
1003         if (hw_argc > 1) {
1004                 char *p;
1005                 int i, j, len = 4;
1006
1007                 for (i = 0; i <= hw_argc - 2; i++)
1008                         len += strlen(as->argv[i]) + 1;
1009                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1010                 if (!p) {
1011                         ti->error = "memory allocation failed";
1012                         ret = -ENOMEM;
1013                         goto fail;
1014                 }
1015                 j = sprintf(p, "%d", hw_argc - 1);
1016                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
1017                         j = sprintf(p, "%s", as->argv[i]);
1018         }
1019         dm_consume_args(as, hw_argc - 1);
1020
1021         return 0;
1022 fail:
1023         kfree(m->hw_handler_name);
1024         m->hw_handler_name = NULL;
1025         return ret;
1026 }
1027
1028 static int parse_features(struct dm_arg_set *as, struct multipath *m)
1029 {
1030         int r;
1031         unsigned argc;
1032         struct dm_target *ti = m->ti;
1033         const char *arg_name;
1034
1035         static const struct dm_arg _args[] = {
1036                 {0, 8, "invalid number of feature args"},
1037                 {1, 50, "pg_init_retries must be between 1 and 50"},
1038                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1039         };
1040
1041         r = dm_read_arg_group(_args, as, &argc, &ti->error);
1042         if (r)
1043                 return -EINVAL;
1044
1045         if (!argc)
1046                 return 0;
1047
1048         do {
1049                 arg_name = dm_shift_arg(as);
1050                 argc--;
1051
1052                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
1053                         r = queue_if_no_path(m, true, false);
1054                         continue;
1055                 }
1056
1057                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1058                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1059                         continue;
1060                 }
1061
1062                 if (!strcasecmp(arg_name, "pg_init_retries") &&
1063                     (argc >= 1)) {
1064                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1065                         argc--;
1066                         continue;
1067                 }
1068
1069                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1070                     (argc >= 1)) {
1071                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1072                         argc--;
1073                         continue;
1074                 }
1075
1076                 if (!strcasecmp(arg_name, "queue_mode") &&
1077                     (argc >= 1)) {
1078                         const char *queue_mode_name = dm_shift_arg(as);
1079
1080                         if (!strcasecmp(queue_mode_name, "bio"))
1081                                 m->queue_mode = DM_TYPE_BIO_BASED;
1082                         else if (!strcasecmp(queue_mode_name, "rq") ||
1083                                  !strcasecmp(queue_mode_name, "mq"))
1084                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1085                         else {
1086                                 ti->error = "Unknown 'queue_mode' requested";
1087                                 r = -EINVAL;
1088                         }
1089                         argc--;
1090                         continue;
1091                 }
1092
1093                 ti->error = "Unrecognised multipath feature request";
1094                 r = -EINVAL;
1095         } while (argc && !r);
1096
1097         return r;
1098 }
1099
1100 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1101 {
1102         /* target arguments */
1103         static const struct dm_arg _args[] = {
1104                 {0, 1024, "invalid number of priority groups"},
1105                 {0, 1024, "invalid initial priority group number"},
1106         };
1107
1108         int r;
1109         struct multipath *m;
1110         struct dm_arg_set as;
1111         unsigned pg_count = 0;
1112         unsigned next_pg_num;
1113
1114         as.argc = argc;
1115         as.argv = argv;
1116
1117         m = alloc_multipath(ti);
1118         if (!m) {
1119                 ti->error = "can't allocate multipath";
1120                 return -EINVAL;
1121         }
1122
1123         r = parse_features(&as, m);
1124         if (r)
1125                 goto bad;
1126
1127         r = alloc_multipath_stage2(ti, m);
1128         if (r)
1129                 goto bad;
1130
1131         r = parse_hw_handler(&as, m);
1132         if (r)
1133                 goto bad;
1134
1135         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1136         if (r)
1137                 goto bad;
1138
1139         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1140         if (r)
1141                 goto bad;
1142
1143         if ((!m->nr_priority_groups && next_pg_num) ||
1144             (m->nr_priority_groups && !next_pg_num)) {
1145                 ti->error = "invalid initial priority group";
1146                 r = -EINVAL;
1147                 goto bad;
1148         }
1149
1150         /* parse the priority groups */
1151         while (as.argc) {
1152                 struct priority_group *pg;
1153                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1154
1155                 pg = parse_priority_group(&as, m);
1156                 if (IS_ERR(pg)) {
1157                         r = PTR_ERR(pg);
1158                         goto bad;
1159                 }
1160
1161                 nr_valid_paths += pg->nr_pgpaths;
1162                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1163
1164                 list_add_tail(&pg->list, &m->priority_groups);
1165                 pg_count++;
1166                 pg->pg_num = pg_count;
1167                 if (!--next_pg_num)
1168                         m->next_pg = pg;
1169         }
1170
1171         if (pg_count != m->nr_priority_groups) {
1172                 ti->error = "priority group count mismatch";
1173                 r = -EINVAL;
1174                 goto bad;
1175         }
1176
1177         ti->num_flush_bios = 1;
1178         ti->num_discard_bios = 1;
1179         ti->num_write_same_bios = 1;
1180         ti->num_write_zeroes_bios = 1;
1181         if (m->queue_mode == DM_TYPE_BIO_BASED)
1182                 ti->per_io_data_size = multipath_per_bio_data_size();
1183         else
1184                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1185
1186         return 0;
1187
1188  bad:
1189         free_multipath(m);
1190         return r;
1191 }
1192
1193 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1194 {
1195         DEFINE_WAIT(wait);
1196
1197         while (1) {
1198                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1199
1200                 if (!atomic_read(&m->pg_init_in_progress))
1201                         break;
1202
1203                 io_schedule();
1204         }
1205         finish_wait(&m->pg_init_wait, &wait);
1206 }
1207
1208 static void flush_multipath_work(struct multipath *m)
1209 {
1210         if (m->hw_handler_name) {
1211                 set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1212                 smp_mb__after_atomic();
1213
1214                 flush_workqueue(kmpath_handlerd);
1215                 multipath_wait_for_pg_init_completion(m);
1216
1217                 clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1218                 smp_mb__after_atomic();
1219         }
1220
1221         flush_workqueue(kmultipathd);
1222         flush_work(&m->trigger_event);
1223 }
1224
1225 static void multipath_dtr(struct dm_target *ti)
1226 {
1227         struct multipath *m = ti->private;
1228
1229         flush_multipath_work(m);
1230         free_multipath(m);
1231 }
1232
1233 /*
1234  * Take a path out of use.
1235  */
1236 static int fail_path(struct pgpath *pgpath)
1237 {
1238         unsigned long flags;
1239         struct multipath *m = pgpath->pg->m;
1240
1241         spin_lock_irqsave(&m->lock, flags);
1242
1243         if (!pgpath->is_active)
1244                 goto out;
1245
1246         DMWARN("Failing path %s.", pgpath->path.dev->name);
1247
1248         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1249         pgpath->is_active = false;
1250         pgpath->fail_count++;
1251
1252         atomic_dec(&m->nr_valid_paths);
1253
1254         if (pgpath == m->current_pgpath)
1255                 m->current_pgpath = NULL;
1256
1257         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1258                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1259
1260         schedule_work(&m->trigger_event);
1261
1262 out:
1263         spin_unlock_irqrestore(&m->lock, flags);
1264
1265         return 0;
1266 }
1267
1268 /*
1269  * Reinstate a previously-failed path
1270  */
1271 static int reinstate_path(struct pgpath *pgpath)
1272 {
1273         int r = 0, run_queue = 0;
1274         unsigned long flags;
1275         struct multipath *m = pgpath->pg->m;
1276         unsigned nr_valid_paths;
1277
1278         spin_lock_irqsave(&m->lock, flags);
1279
1280         if (pgpath->is_active)
1281                 goto out;
1282
1283         DMWARN("Reinstating path %s.", pgpath->path.dev->name);
1284
1285         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1286         if (r)
1287                 goto out;
1288
1289         pgpath->is_active = true;
1290
1291         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1292         if (nr_valid_paths == 1) {
1293                 m->current_pgpath = NULL;
1294                 run_queue = 1;
1295         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1296                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1297                         atomic_inc(&m->pg_init_in_progress);
1298         }
1299
1300         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1301                        pgpath->path.dev->name, nr_valid_paths);
1302
1303         schedule_work(&m->trigger_event);
1304
1305 out:
1306         spin_unlock_irqrestore(&m->lock, flags);
1307         if (run_queue) {
1308                 dm_table_run_md_queue_async(m->ti->table);
1309                 process_queued_io_list(m);
1310         }
1311
1312         return r;
1313 }
1314
1315 /*
1316  * Fail or reinstate all paths that match the provided struct dm_dev.
1317  */
1318 static int action_dev(struct multipath *m, struct dm_dev *dev,
1319                       action_fn action)
1320 {
1321         int r = -EINVAL;
1322         struct pgpath *pgpath;
1323         struct priority_group *pg;
1324
1325         list_for_each_entry(pg, &m->priority_groups, list) {
1326                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1327                         if (pgpath->path.dev == dev)
1328                                 r = action(pgpath);
1329                 }
1330         }
1331
1332         return r;
1333 }
1334
1335 /*
1336  * Temporarily try to avoid having to use the specified PG
1337  */
1338 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1339                       bool bypassed)
1340 {
1341         unsigned long flags;
1342
1343         spin_lock_irqsave(&m->lock, flags);
1344
1345         pg->bypassed = bypassed;
1346         m->current_pgpath = NULL;
1347         m->current_pg = NULL;
1348
1349         spin_unlock_irqrestore(&m->lock, flags);
1350
1351         schedule_work(&m->trigger_event);
1352 }
1353
1354 /*
1355  * Switch to using the specified PG from the next I/O that gets mapped
1356  */
1357 static int switch_pg_num(struct multipath *m, const char *pgstr)
1358 {
1359         struct priority_group *pg;
1360         unsigned pgnum;
1361         unsigned long flags;
1362         char dummy;
1363
1364         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1365             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1366                 DMWARN("invalid PG number supplied to switch_pg_num");
1367                 return -EINVAL;
1368         }
1369
1370         spin_lock_irqsave(&m->lock, flags);
1371         list_for_each_entry(pg, &m->priority_groups, list) {
1372                 pg->bypassed = false;
1373                 if (--pgnum)
1374                         continue;
1375
1376                 m->current_pgpath = NULL;
1377                 m->current_pg = NULL;
1378                 m->next_pg = pg;
1379         }
1380         spin_unlock_irqrestore(&m->lock, flags);
1381
1382         schedule_work(&m->trigger_event);
1383         return 0;
1384 }
1385
1386 /*
1387  * Set/clear bypassed status of a PG.
1388  * PGs are numbered upwards from 1 in the order they were declared.
1389  */
1390 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1391 {
1392         struct priority_group *pg;
1393         unsigned pgnum;
1394         char dummy;
1395
1396         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1397             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1398                 DMWARN("invalid PG number supplied to bypass_pg");
1399                 return -EINVAL;
1400         }
1401
1402         list_for_each_entry(pg, &m->priority_groups, list) {
1403                 if (!--pgnum)
1404                         break;
1405         }
1406
1407         bypass_pg(m, pg, bypassed);
1408         return 0;
1409 }
1410
1411 /*
1412  * Should we retry pg_init immediately?
1413  */
1414 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1415 {
1416         unsigned long flags;
1417         bool limit_reached = false;
1418
1419         spin_lock_irqsave(&m->lock, flags);
1420
1421         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1422             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1423                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1424         else
1425                 limit_reached = true;
1426
1427         spin_unlock_irqrestore(&m->lock, flags);
1428
1429         return limit_reached;
1430 }
1431
1432 static void pg_init_done(void *data, int errors)
1433 {
1434         struct pgpath *pgpath = data;
1435         struct priority_group *pg = pgpath->pg;
1436         struct multipath *m = pg->m;
1437         unsigned long flags;
1438         bool delay_retry = false;
1439
1440         /* device or driver problems */
1441         switch (errors) {
1442         case SCSI_DH_OK:
1443                 break;
1444         case SCSI_DH_NOSYS:
1445                 if (!m->hw_handler_name) {
1446                         errors = 0;
1447                         break;
1448                 }
1449                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1450                       "Error %d.", m->hw_handler_name, errors);
1451                 /*
1452                  * Fail path for now, so we do not ping pong
1453                  */
1454                 fail_path(pgpath);
1455                 break;
1456         case SCSI_DH_DEV_TEMP_BUSY:
1457                 /*
1458                  * Probably doing something like FW upgrade on the
1459                  * controller so try the other pg.
1460                  */
1461                 bypass_pg(m, pg, true);
1462                 break;
1463         case SCSI_DH_RETRY:
1464                 /* Wait before retrying. */
1465                 delay_retry = 1;
1466                 /* fall through */
1467         case SCSI_DH_IMM_RETRY:
1468         case SCSI_DH_RES_TEMP_UNAVAIL:
1469                 if (pg_init_limit_reached(m, pgpath))
1470                         fail_path(pgpath);
1471                 errors = 0;
1472                 break;
1473         case SCSI_DH_DEV_OFFLINED:
1474         default:
1475                 /*
1476                  * We probably do not want to fail the path for a device
1477                  * error, but this is what the old dm did. In future
1478                  * patches we can do more advanced handling.
1479                  */
1480                 fail_path(pgpath);
1481         }
1482
1483         spin_lock_irqsave(&m->lock, flags);
1484         if (errors) {
1485                 if (pgpath == m->current_pgpath) {
1486                         DMERR("Could not failover device. Error %d.", errors);
1487                         m->current_pgpath = NULL;
1488                         m->current_pg = NULL;
1489                 }
1490         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1491                 pg->bypassed = false;
1492
1493         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1494                 /* Activations of other paths are still on going */
1495                 goto out;
1496
1497         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1498                 if (delay_retry)
1499                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1500                 else
1501                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1502
1503                 if (__pg_init_all_paths(m))
1504                         goto out;
1505         }
1506         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1507
1508         process_queued_io_list(m);
1509
1510         /*
1511          * Wake up any thread waiting to suspend.
1512          */
1513         wake_up(&m->pg_init_wait);
1514
1515 out:
1516         spin_unlock_irqrestore(&m->lock, flags);
1517 }
1518
1519 static void activate_or_offline_path(struct pgpath *pgpath)
1520 {
1521         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1522
1523         if (pgpath->is_active && !blk_queue_dying(q))
1524                 scsi_dh_activate(q, pg_init_done, pgpath);
1525         else
1526                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1527 }
1528
1529 static void activate_path_work(struct work_struct *work)
1530 {
1531         struct pgpath *pgpath =
1532                 container_of(work, struct pgpath, activate_path.work);
1533
1534         activate_or_offline_path(pgpath);
1535 }
1536
1537 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1538                             blk_status_t error, union map_info *map_context)
1539 {
1540         struct dm_mpath_io *mpio = get_mpio(map_context);
1541         struct pgpath *pgpath = mpio->pgpath;
1542         int r = DM_ENDIO_DONE;
1543
1544         /*
1545          * We don't queue any clone request inside the multipath target
1546          * during end I/O handling, since those clone requests don't have
1547          * bio clones.  If we queue them inside the multipath target,
1548          * we need to make bio clones, that requires memory allocation.
1549          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1550          *  don't have bio clones.)
1551          * Instead of queueing the clone request here, we queue the original
1552          * request into dm core, which will remake a clone request and
1553          * clone bios for it and resubmit it later.
1554          */
1555         if (error && blk_path_error(error)) {
1556                 struct multipath *m = ti->private;
1557
1558                 if (error == BLK_STS_RESOURCE)
1559                         r = DM_ENDIO_DELAY_REQUEUE;
1560                 else
1561                         r = DM_ENDIO_REQUEUE;
1562
1563                 if (pgpath)
1564                         fail_path(pgpath);
1565
1566                 if (atomic_read(&m->nr_valid_paths) == 0 &&
1567                     !must_push_back_rq(m)) {
1568                         if (error == BLK_STS_IOERR)
1569                                 dm_report_EIO(m);
1570                         /* complete with the original error */
1571                         r = DM_ENDIO_DONE;
1572                 }
1573         }
1574
1575         if (pgpath) {
1576                 struct path_selector *ps = &pgpath->pg->ps;
1577
1578                 if (ps->type->end_io)
1579                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1580         }
1581
1582         return r;
1583 }
1584
1585 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1586                                 blk_status_t *error)
1587 {
1588         struct multipath *m = ti->private;
1589         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1590         struct pgpath *pgpath = mpio->pgpath;
1591         unsigned long flags;
1592         int r = DM_ENDIO_DONE;
1593
1594         if (!*error || !blk_path_error(*error))
1595                 goto done;
1596
1597         if (pgpath)
1598                 fail_path(pgpath);
1599
1600         if (atomic_read(&m->nr_valid_paths) == 0 &&
1601             !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1602                 if (must_push_back_bio(m)) {
1603                         r = DM_ENDIO_REQUEUE;
1604                 } else {
1605                         dm_report_EIO(m);
1606                         *error = BLK_STS_IOERR;
1607                 }
1608                 goto done;
1609         }
1610
1611         spin_lock_irqsave(&m->lock, flags);
1612         bio_list_add(&m->queued_bios, clone);
1613         spin_unlock_irqrestore(&m->lock, flags);
1614         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1615                 queue_work(kmultipathd, &m->process_queued_bios);
1616
1617         r = DM_ENDIO_INCOMPLETE;
1618 done:
1619         if (pgpath) {
1620                 struct path_selector *ps = &pgpath->pg->ps;
1621
1622                 if (ps->type->end_io)
1623                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1624         }
1625
1626         return r;
1627 }
1628
1629 /*
1630  * Suspend can't complete until all the I/O is processed so if
1631  * the last path fails we must error any remaining I/O.
1632  * Note that if the freeze_bdev fails while suspending, the
1633  * queue_if_no_path state is lost - userspace should reset it.
1634  */
1635 static void multipath_presuspend(struct dm_target *ti)
1636 {
1637         struct multipath *m = ti->private;
1638
1639         queue_if_no_path(m, false, true);
1640 }
1641
1642 static void multipath_postsuspend(struct dm_target *ti)
1643 {
1644         struct multipath *m = ti->private;
1645
1646         mutex_lock(&m->work_mutex);
1647         flush_multipath_work(m);
1648         mutex_unlock(&m->work_mutex);
1649 }
1650
1651 /*
1652  * Restore the queue_if_no_path setting.
1653  */
1654 static void multipath_resume(struct dm_target *ti)
1655 {
1656         struct multipath *m = ti->private;
1657         unsigned long flags;
1658
1659         spin_lock_irqsave(&m->lock, flags);
1660         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags,
1661                    test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1662         spin_unlock_irqrestore(&m->lock, flags);
1663 }
1664
1665 /*
1666  * Info output has the following format:
1667  * num_multipath_feature_args [multipath_feature_args]*
1668  * num_handler_status_args [handler_status_args]*
1669  * num_groups init_group_number
1670  *            [A|D|E num_ps_status_args [ps_status_args]*
1671  *             num_paths num_selector_args
1672  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1673  *
1674  * Table output has the following format (identical to the constructor string):
1675  * num_feature_args [features_args]*
1676  * num_handler_args hw_handler [hw_handler_args]*
1677  * num_groups init_group_number
1678  *     [priority selector-name num_ps_args [ps_args]*
1679  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1680  */
1681 static void multipath_status(struct dm_target *ti, status_type_t type,
1682                              unsigned status_flags, char *result, unsigned maxlen)
1683 {
1684         int sz = 0;
1685         unsigned long flags;
1686         struct multipath *m = ti->private;
1687         struct priority_group *pg;
1688         struct pgpath *p;
1689         unsigned pg_num;
1690         char state;
1691
1692         spin_lock_irqsave(&m->lock, flags);
1693
1694         /* Features */
1695         if (type == STATUSTYPE_INFO)
1696                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1697                        atomic_read(&m->pg_init_count));
1698         else {
1699                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1700                               (m->pg_init_retries > 0) * 2 +
1701                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1702                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1703                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1704
1705                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1706                         DMEMIT("queue_if_no_path ");
1707                 if (m->pg_init_retries)
1708                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1709                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1710                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1711                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1712                         DMEMIT("retain_attached_hw_handler ");
1713                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1714                         switch(m->queue_mode) {
1715                         case DM_TYPE_BIO_BASED:
1716                                 DMEMIT("queue_mode bio ");
1717                                 break;
1718                         default:
1719                                 WARN_ON_ONCE(true);
1720                                 break;
1721                         }
1722                 }
1723         }
1724
1725         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1726                 DMEMIT("0 ");
1727         else
1728                 DMEMIT("1 %s ", m->hw_handler_name);
1729
1730         DMEMIT("%u ", m->nr_priority_groups);
1731
1732         if (m->next_pg)
1733                 pg_num = m->next_pg->pg_num;
1734         else if (m->current_pg)
1735                 pg_num = m->current_pg->pg_num;
1736         else
1737                 pg_num = (m->nr_priority_groups ? 1 : 0);
1738
1739         DMEMIT("%u ", pg_num);
1740
1741         switch (type) {
1742         case STATUSTYPE_INFO:
1743                 list_for_each_entry(pg, &m->priority_groups, list) {
1744                         if (pg->bypassed)
1745                                 state = 'D';    /* Disabled */
1746                         else if (pg == m->current_pg)
1747                                 state = 'A';    /* Currently Active */
1748                         else
1749                                 state = 'E';    /* Enabled */
1750
1751                         DMEMIT("%c ", state);
1752
1753                         if (pg->ps.type->status)
1754                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1755                                                           result + sz,
1756                                                           maxlen - sz);
1757                         else
1758                                 DMEMIT("0 ");
1759
1760                         DMEMIT("%u %u ", pg->nr_pgpaths,
1761                                pg->ps.type->info_args);
1762
1763                         list_for_each_entry(p, &pg->pgpaths, list) {
1764                                 DMEMIT("%s %s %u ", p->path.dev->name,
1765                                        p->is_active ? "A" : "F",
1766                                        p->fail_count);
1767                                 if (pg->ps.type->status)
1768                                         sz += pg->ps.type->status(&pg->ps,
1769                                               &p->path, type, result + sz,
1770                                               maxlen - sz);
1771                         }
1772                 }
1773                 break;
1774
1775         case STATUSTYPE_TABLE:
1776                 list_for_each_entry(pg, &m->priority_groups, list) {
1777                         DMEMIT("%s ", pg->ps.type->name);
1778
1779                         if (pg->ps.type->status)
1780                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1781                                                           result + sz,
1782                                                           maxlen - sz);
1783                         else
1784                                 DMEMIT("0 ");
1785
1786                         DMEMIT("%u %u ", pg->nr_pgpaths,
1787                                pg->ps.type->table_args);
1788
1789                         list_for_each_entry(p, &pg->pgpaths, list) {
1790                                 DMEMIT("%s ", p->path.dev->name);
1791                                 if (pg->ps.type->status)
1792                                         sz += pg->ps.type->status(&pg->ps,
1793                                               &p->path, type, result + sz,
1794                                               maxlen - sz);
1795                         }
1796                 }
1797                 break;
1798         }
1799
1800         spin_unlock_irqrestore(&m->lock, flags);
1801 }
1802
1803 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv,
1804                              char *result, unsigned maxlen)
1805 {
1806         int r = -EINVAL;
1807         struct dm_dev *dev;
1808         struct multipath *m = ti->private;
1809         action_fn action;
1810
1811         mutex_lock(&m->work_mutex);
1812
1813         if (dm_suspended(ti)) {
1814                 r = -EBUSY;
1815                 goto out;
1816         }
1817
1818         if (argc == 1) {
1819                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1820                         r = queue_if_no_path(m, true, false);
1821                         goto out;
1822                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1823                         r = queue_if_no_path(m, false, false);
1824                         goto out;
1825                 }
1826         }
1827
1828         if (argc != 2) {
1829                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1830                 goto out;
1831         }
1832
1833         if (!strcasecmp(argv[0], "disable_group")) {
1834                 r = bypass_pg_num(m, argv[1], true);
1835                 goto out;
1836         } else if (!strcasecmp(argv[0], "enable_group")) {
1837                 r = bypass_pg_num(m, argv[1], false);
1838                 goto out;
1839         } else if (!strcasecmp(argv[0], "switch_group")) {
1840                 r = switch_pg_num(m, argv[1]);
1841                 goto out;
1842         } else if (!strcasecmp(argv[0], "reinstate_path"))
1843                 action = reinstate_path;
1844         else if (!strcasecmp(argv[0], "fail_path"))
1845                 action = fail_path;
1846         else {
1847                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1848                 goto out;
1849         }
1850
1851         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1852         if (r) {
1853                 DMWARN("message: error getting device %s",
1854                        argv[1]);
1855                 goto out;
1856         }
1857
1858         r = action_dev(m, dev, action);
1859
1860         dm_put_device(ti, dev);
1861
1862 out:
1863         mutex_unlock(&m->work_mutex);
1864         return r;
1865 }
1866
1867 static int multipath_prepare_ioctl(struct dm_target *ti,
1868                                    struct block_device **bdev)
1869 {
1870         struct multipath *m = ti->private;
1871         struct pgpath *current_pgpath;
1872         int r;
1873
1874         current_pgpath = READ_ONCE(m->current_pgpath);
1875         if (!current_pgpath)
1876                 current_pgpath = choose_pgpath(m, 0);
1877
1878         if (current_pgpath) {
1879                 if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1880                         *bdev = current_pgpath->path.dev->bdev;
1881                         r = 0;
1882                 } else {
1883                         /* pg_init has not started or completed */
1884                         r = -ENOTCONN;
1885                 }
1886         } else {
1887                 /* No path is available */
1888                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1889                         r = -ENOTCONN;
1890                 else
1891                         r = -EIO;
1892         }
1893
1894         if (r == -ENOTCONN) {
1895                 if (!READ_ONCE(m->current_pg)) {
1896                         /* Path status changed, redo selection */
1897                         (void) choose_pgpath(m, 0);
1898                 }
1899                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1900                         pg_init_all_paths(m);
1901                 dm_table_run_md_queue_async(m->ti->table);
1902                 process_queued_io_list(m);
1903         }
1904
1905         /*
1906          * Only pass ioctls through if the device sizes match exactly.
1907          */
1908         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1909                 return 1;
1910         return r;
1911 }
1912
1913 static int multipath_iterate_devices(struct dm_target *ti,
1914                                      iterate_devices_callout_fn fn, void *data)
1915 {
1916         struct multipath *m = ti->private;
1917         struct priority_group *pg;
1918         struct pgpath *p;
1919         int ret = 0;
1920
1921         list_for_each_entry(pg, &m->priority_groups, list) {
1922                 list_for_each_entry(p, &pg->pgpaths, list) {
1923                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1924                         if (ret)
1925                                 goto out;
1926                 }
1927         }
1928
1929 out:
1930         return ret;
1931 }
1932
1933 static int pgpath_busy(struct pgpath *pgpath)
1934 {
1935         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1936
1937         return blk_lld_busy(q);
1938 }
1939
1940 /*
1941  * We return "busy", only when we can map I/Os but underlying devices
1942  * are busy (so even if we map I/Os now, the I/Os will wait on
1943  * the underlying queue).
1944  * In other words, if we want to kill I/Os or queue them inside us
1945  * due to map unavailability, we don't return "busy".  Otherwise,
1946  * dm core won't give us the I/Os and we can't do what we want.
1947  */
1948 static int multipath_busy(struct dm_target *ti)
1949 {
1950         bool busy = false, has_active = false;
1951         struct multipath *m = ti->private;
1952         struct priority_group *pg, *next_pg;
1953         struct pgpath *pgpath;
1954
1955         /* pg_init in progress */
1956         if (atomic_read(&m->pg_init_in_progress))
1957                 return true;
1958
1959         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
1960         if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1961                 return (m->queue_mode != DM_TYPE_REQUEST_BASED);
1962
1963         /* Guess which priority_group will be used at next mapping time */
1964         pg = READ_ONCE(m->current_pg);
1965         next_pg = READ_ONCE(m->next_pg);
1966         if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
1967                 pg = next_pg;
1968
1969         if (!pg) {
1970                 /*
1971                  * We don't know which pg will be used at next mapping time.
1972                  * We don't call choose_pgpath() here to avoid to trigger
1973                  * pg_init just by busy checking.
1974                  * So we don't know whether underlying devices we will be using
1975                  * at next mapping time are busy or not. Just try mapping.
1976                  */
1977                 return busy;
1978         }
1979
1980         /*
1981          * If there is one non-busy active path at least, the path selector
1982          * will be able to select it. So we consider such a pg as not busy.
1983          */
1984         busy = true;
1985         list_for_each_entry(pgpath, &pg->pgpaths, list) {
1986                 if (pgpath->is_active) {
1987                         has_active = true;
1988                         if (!pgpath_busy(pgpath)) {
1989                                 busy = false;
1990                                 break;
1991                         }
1992                 }
1993         }
1994
1995         if (!has_active) {
1996                 /*
1997                  * No active path in this pg, so this pg won't be used and
1998                  * the current_pg will be changed at next mapping time.
1999                  * We need to try mapping to determine it.
2000                  */
2001                 busy = false;
2002         }
2003
2004         return busy;
2005 }
2006
2007 /*-----------------------------------------------------------------
2008  * Module setup
2009  *---------------------------------------------------------------*/
2010 static struct target_type multipath_target = {
2011         .name = "multipath",
2012         .version = {1, 13, 0},
2013         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE |
2014                     DM_TARGET_PASSES_INTEGRITY,
2015         .module = THIS_MODULE,
2016         .ctr = multipath_ctr,
2017         .dtr = multipath_dtr,
2018         .clone_and_map_rq = multipath_clone_and_map,
2019         .release_clone_rq = multipath_release_clone,
2020         .rq_end_io = multipath_end_io,
2021         .map = multipath_map_bio,
2022         .end_io = multipath_end_io_bio,
2023         .presuspend = multipath_presuspend,
2024         .postsuspend = multipath_postsuspend,
2025         .resume = multipath_resume,
2026         .status = multipath_status,
2027         .message = multipath_message,
2028         .prepare_ioctl = multipath_prepare_ioctl,
2029         .iterate_devices = multipath_iterate_devices,
2030         .busy = multipath_busy,
2031 };
2032
2033 static int __init dm_multipath_init(void)
2034 {
2035         int r;
2036
2037         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2038         if (!kmultipathd) {
2039                 DMERR("failed to create workqueue kmpathd");
2040                 r = -ENOMEM;
2041                 goto bad_alloc_kmultipathd;
2042         }
2043
2044         /*
2045          * A separate workqueue is used to handle the device handlers
2046          * to avoid overloading existing workqueue. Overloading the
2047          * old workqueue would also create a bottleneck in the
2048          * path of the storage hardware device activation.
2049          */
2050         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2051                                                   WQ_MEM_RECLAIM);
2052         if (!kmpath_handlerd) {
2053                 DMERR("failed to create workqueue kmpath_handlerd");
2054                 r = -ENOMEM;
2055                 goto bad_alloc_kmpath_handlerd;
2056         }
2057
2058         r = dm_register_target(&multipath_target);
2059         if (r < 0) {
2060                 DMERR("request-based register failed %d", r);
2061                 r = -EINVAL;
2062                 goto bad_register_target;
2063         }
2064
2065         return 0;
2066
2067 bad_register_target:
2068         destroy_workqueue(kmpath_handlerd);
2069 bad_alloc_kmpath_handlerd:
2070         destroy_workqueue(kmultipathd);
2071 bad_alloc_kmultipathd:
2072         return r;
2073 }
2074
2075 static void __exit dm_multipath_exit(void)
2076 {
2077         destroy_workqueue(kmpath_handlerd);
2078         destroy_workqueue(kmultipathd);
2079
2080         dm_unregister_target(&multipath_target);
2081 }
2082
2083 module_init(dm_multipath_init);
2084 module_exit(dm_multipath_exit);
2085
2086 MODULE_DESCRIPTION(DM_NAME " multipath target");
2087 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2088 MODULE_LICENSE("GPL");