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                                     union map_info *map_context)
 549 {
 550         if (unlikely(map_context)) {
 551                 /*
 552                  * non-NULL map_context means caller is still map
 553                  * method; must undo multipath_clone_and_map()
 554                  */
 555                 struct dm_mpath_io *mpio = get_mpio(map_context);
 556                 struct pgpath *pgpath = mpio->pgpath;
 557
 558                 if (pgpath && pgpath->pg->ps.type->end_io)
 559                         pgpath->pg->ps.type->end_io(&pgpath->pg->ps,
 560                                                     &pgpath->path,
 561                                                     mpio->nr_bytes);
 562         }
 563
 564         blk_put_request(clone);
 565 }
 566
 567 /*
 568  * Map cloned bios (bio-based multipath)
 569  */
 570
 571 static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
 572 {
 573         struct pgpath *pgpath;
 574         unsigned long flags;
 575         bool queue_io;
 576
 577         /* Do we need to select a new pgpath? */
 578         pgpath = READ_ONCE(m->current_pgpath);
 579         queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
 580         if (!pgpath || !queue_io)
 581                 pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 582
 583         if ((pgpath && queue_io) ||
 584             (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
 585                 /* Queue for the daemon to resubmit */
 586                 spin_lock_irqsave(&m->lock, flags);
 587                 bio_list_add(&m->queued_bios, bio);
 588                 spin_unlock_irqrestore(&m->lock, flags);
 589
 590                 /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
 591                 if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
 592                         pg_init_all_paths(m);
 593                 else if (!queue_io)
 594                         queue_work(kmultipathd, &m->process_queued_bios);
 595
 596                 return ERR_PTR(-EAGAIN);
 597         }
 598
 599         return pgpath;
 600 }
 601
 602 static struct pgpath *__map_bio_fast(struct multipath *m, struct bio *bio)
 603 {
 604         struct pgpath *pgpath;
 605         unsigned long flags;
 606
 607         /* Do we need to select a new pgpath? */
 608         /*
 609          * FIXME: currently only switching path if no path (due to failure, etc)
 610          * - which negates the point of using a path selector
 611          */
 612         pgpath = READ_ONCE(m->current_pgpath);
 613         if (!pgpath)
 614                 pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 615
 616         if (!pgpath) {
 617                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 618                         /* Queue for the daemon to resubmit */
 619                         spin_lock_irqsave(&m->lock, flags);
 620                         bio_list_add(&m->queued_bios, bio);
 621                         spin_unlock_irqrestore(&m->lock, flags);
 622                         queue_work(kmultipathd, &m->process_queued_bios);
 623
 624                         return ERR_PTR(-EAGAIN);
 625                 }
 626                 return NULL;
 627         }
 628
 629         return pgpath;
 630 }
 631
 632 static int __multipath_map_bio(struct multipath *m, struct bio *bio,
 633                                struct dm_mpath_io *mpio)
 634 {
 635         struct pgpath *pgpath;
 636
 637         if (!m->hw_handler_name)
 638                 pgpath = __map_bio_fast(m, bio);
 639         else
 640                 pgpath = __map_bio(m, bio);
 641
 642         if (IS_ERR(pgpath))
 643                 return DM_MAPIO_SUBMITTED;
 644
 645         if (!pgpath) {
 646                 if (must_push_back_bio(m))
 647                         return DM_MAPIO_REQUEUE;
 648                 dm_report_EIO(m);
 649                 return DM_MAPIO_KILL;
 650         }
 651
 652         mpio->pgpath = pgpath;
 653
 654         bio->bi_status = 0;
 655         bio_set_dev(bio, pgpath->path.dev->bdev);
 656         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 657
 658         if (pgpath->pg->ps.type->start_io)
 659                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 660                                               &pgpath->path,
 661                                               mpio->nr_bytes);
 662         return DM_MAPIO_REMAPPED;
 663 }
 664
 665 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 666 {
 667         struct multipath *m = ti->private;
 668         struct dm_mpath_io *mpio = NULL;
 669
 670         multipath_init_per_bio_data(bio, &mpio);
 671         return __multipath_map_bio(m, bio, mpio);
 672 }
 673
 674 static void process_queued_io_list(struct multipath *m)
 675 {
 676         if (m->queue_mode == DM_TYPE_REQUEST_BASED)
 677                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 678         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 679                 queue_work(kmultipathd, &m->process_queued_bios);
 680 }
 681
 682 static void process_queued_bios(struct work_struct *work)
 683 {
 684         int r;
 685         unsigned long flags;
 686         struct bio *bio;
 687         struct bio_list bios;
 688         struct blk_plug plug;
 689         struct multipath *m =
 690                 container_of(work, struct multipath, process_queued_bios);
 691
 692         bio_list_init(&bios);
 693
 694         spin_lock_irqsave(&m->lock, flags);
 695
 696         if (bio_list_empty(&m->queued_bios)) {
 697                 spin_unlock_irqrestore(&m->lock, flags);
 698                 return;
 699         }
 700
 701         bio_list_merge(&bios, &m->queued_bios);
 702         bio_list_init(&m->queued_bios);
 703
 704         spin_unlock_irqrestore(&m->lock, flags);
 705
 706         blk_start_plug(&plug);
 707         while ((bio = bio_list_pop(&bios))) {
 708                 struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 709                 dm_bio_restore(get_bio_details_from_mpio(mpio), bio);
 710                 r = __multipath_map_bio(m, bio, mpio);
 711                 switch (r) {
 712                 case DM_MAPIO_KILL:
 713                         bio->bi_status = BLK_STS_IOERR;
 714                         bio_endio(bio);
 715                         break;
 716                 case DM_MAPIO_REQUEUE:
 717                         bio->bi_status = BLK_STS_DM_REQUEUE;
 718                         bio_endio(bio);
 719                         break;
 720                 case DM_MAPIO_REMAPPED:
 721                         generic_make_request(bio);
 722                         break;
 723                 case DM_MAPIO_SUBMITTED:
 724                         break;
 725                 default:
 726                         WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 727                 }
 728         }
 729         blk_finish_plug(&plug);
 730 }
 731
 732 /*
 733  * If we run out of usable paths, should we queue I/O or error it?
 734  */
 735 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 736                             bool save_old_value)
 737 {
 738         unsigned long flags;
 739
 740         spin_lock_irqsave(&m->lock, flags);
 741         assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags,
 742                    (save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
 743                    (!save_old_value && queue_if_no_path));
 744         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);
 745         spin_unlock_irqrestore(&m->lock, flags);
 746
 747         if (!queue_if_no_path) {
 748                 dm_table_run_md_queue_async(m->ti->table);
 749                 process_queued_io_list(m);
 750         }
 751
 752         return 0;
 753 }
 754
 755 /*
 756  * An event is triggered whenever a path is taken out of use.
 757  * Includes path failure and PG bypass.
 758  */
 759 static void trigger_event(struct work_struct *work)
 760 {
 761         struct multipath *m =
 762                 container_of(work, struct multipath, trigger_event);
 763
 764         dm_table_event(m->ti->table);
 765 }
 766
 767 /*-----------------------------------------------------------------
 768  * Constructor/argument parsing:
 769  * <#multipath feature args> [<arg>]*
 770  * <#hw_handler args> [hw_handler [<arg>]*]
 771  * <#priority groups>
 772  * <initial priority group>
 773  *     [<selector> <#selector args> [<arg>]*
 774  *      <#paths> <#per-path selector args>
 775  *         [<path> [<arg>]* ]+ ]+
 776  *---------------------------------------------------------------*/
 777 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 778                                struct dm_target *ti)
 779 {
 780         int r;
 781         struct path_selector_type *pst;
 782         unsigned ps_argc;
 783
 784         static const struct dm_arg _args[] = {
 785                 {0, 1024, "invalid number of path selector args"},
 786         };
 787
 788         pst = dm_get_path_selector(dm_shift_arg(as));
 789         if (!pst) {
 790                 ti->error = "unknown path selector type";
 791                 return -EINVAL;
 792         }
 793
 794         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 795         if (r) {
 796                 dm_put_path_selector(pst);
 797                 return -EINVAL;
 798         }
 799
 800         r = pst->create(&pg->ps, ps_argc, as->argv);
 801         if (r) {
 802                 dm_put_path_selector(pst);
 803                 ti->error = "path selector constructor failed";
 804                 return r;
 805         }
 806
 807         pg->ps.type = pst;
 808         dm_consume_args(as, ps_argc);
 809
 810         return 0;
 811 }
 812
 813 static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
 814                          const char **attached_handler_name, char **error)
 815 {
 816         struct request_queue *q = bdev_get_queue(bdev);
 817         int r;
 818
 819         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 820 retain:
 821                 if (*attached_handler_name) {
 822                         /*
 823                          * Clear any hw_handler_params associated with a
 824                          * handler that isn't already attached.
 825                          */
 826                         if (m->hw_handler_name && strcmp(*attached_handler_name, m->hw_handler_name)) {
 827                                 kfree(m->hw_handler_params);
 828                                 m->hw_handler_params = NULL;
 829                         }
 830
 831                         /*
 832                          * Reset hw_handler_name to match the attached handler
 833                          *
 834                          * NB. This modifies the table line to show the actual
 835                          * handler instead of the original table passed in.
 836                          */
 837                         kfree(m->hw_handler_name);
 838                         m->hw_handler_name = *attached_handler_name;
 839                         *attached_handler_name = NULL;
 840                 }
 841         }
 842
 843         if (m->hw_handler_name) {
 844                 r = scsi_dh_attach(q, m->hw_handler_name);
 845                 if (r == -EBUSY) {
 846                         char b[BDEVNAME_SIZE];
 847
 848                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 849                                bdevname(bdev, b));
 850                         goto retain;
 851                 }
 852                 if (r < 0) {
 853                         *error = "error attaching hardware handler";
 854                         return r;
 855                 }
 856
 857                 if (m->hw_handler_params) {
 858                         r = scsi_dh_set_params(q, m->hw_handler_params);
 859                         if (r < 0) {
 860                                 *error = "unable to set hardware handler parameters";
 861                                 return r;
 862                         }
 863                 }
 864         }
 865
 866         return 0;
 867 }
 868
 869 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 870                                  struct dm_target *ti)
 871 {
 872         int r;
 873         struct pgpath *p;
 874         struct multipath *m = ti->private;
 875         struct request_queue *q;
 876         const char *attached_handler_name = NULL;
 877
 878         /* we need at least a path arg */
 879         if (as->argc < 1) {
 880                 ti->error = "no device given";
 881                 return ERR_PTR(-EINVAL);
 882         }
 883
 884         p = alloc_pgpath();
 885         if (!p)
 886                 return ERR_PTR(-ENOMEM);
 887
 888         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 889                           &p->path.dev);
 890         if (r) {
 891                 ti->error = "error getting device";
 892                 goto bad;
 893         }
 894
 895         q = bdev_get_queue(p->path.dev->bdev);
 896         attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 897         if (attached_handler_name || m->hw_handler_name) {
 898                 INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
 899                 r = setup_scsi_dh(p->path.dev->bdev, m, &attached_handler_name, &ti->error);
 900                 kfree(attached_handler_name);
 901                 if (r) {
 902                         dm_put_device(ti, p->path.dev);
 903                         goto bad;
 904                 }
 905         }
 906
 907         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 908         if (r) {
 909                 dm_put_device(ti, p->path.dev);
 910                 goto bad;
 911         }
 912
 913         return p;
 914  bad:
 915         free_pgpath(p);
 916         return ERR_PTR(r);
 917 }
 918
 919 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 920                                                    struct multipath *m)
 921 {
 922         static const struct dm_arg _args[] = {
 923                 {1, 1024, "invalid number of paths"},
 924                 {0, 1024, "invalid number of selector args"}
 925         };
 926
 927         int r;
 928         unsigned i, nr_selector_args, nr_args;
 929         struct priority_group *pg;
 930         struct dm_target *ti = m->ti;
 931
 932         if (as->argc < 2) {
 933                 as->argc = 0;
 934                 ti->error = "not enough priority group arguments";
 935                 return ERR_PTR(-EINVAL);
 936         }
 937
 938         pg = alloc_priority_group();
 939         if (!pg) {
 940                 ti->error = "couldn't allocate priority group";
 941                 return ERR_PTR(-ENOMEM);
 942         }
 943         pg->m = m;
 944
 945         r = parse_path_selector(as, pg, ti);
 946         if (r)
 947                 goto bad;
 948
 949         /*
 950          * read the paths
 951          */
 952         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 953         if (r)
 954                 goto bad;
 955
 956         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 957         if (r)
 958                 goto bad;
 959
 960         nr_args = 1 + nr_selector_args;
 961         for (i = 0; i < pg->nr_pgpaths; i++) {
 962                 struct pgpath *pgpath;
 963                 struct dm_arg_set path_args;
 964
 965                 if (as->argc < nr_args) {
 966                         ti->error = "not enough path parameters";
 967                         r = -EINVAL;
 968                         goto bad;
 969                 }
 970
 971                 path_args.argc = nr_args;
 972                 path_args.argv = as->argv;
 973
 974                 pgpath = parse_path(&path_args, &pg->ps, ti);
 975                 if (IS_ERR(pgpath)) {
 976                         r = PTR_ERR(pgpath);
 977                         goto bad;
 978                 }
 979
 980                 pgpath->pg = pg;
 981                 list_add_tail(&pgpath->list, &pg->pgpaths);
 982                 dm_consume_args(as, nr_args);
 983         }
 984
 985         return pg;
 986
 987  bad:
 988         free_priority_group(pg, ti);
 989         return ERR_PTR(r);
 990 }
 991
 992 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 993 {
 994         unsigned hw_argc;
 995         int ret;
 996         struct dm_target *ti = m->ti;
 997
 998         static const struct dm_arg _args[] = {
 999                 {0, 1024, "invalid number of hardware handler args"},
1000         };
1001
1002         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
1003                 return -EINVAL;
1004
1005         if (!hw_argc)
1006                 return 0;
1007
1008         if (m->queue_mode == DM_TYPE_BIO_BASED) {
1009                 dm_consume_args(as, hw_argc);
1010                 DMERR("bio-based multipath doesn't allow hardware handler args");
1011                 return 0;
1012         }
1013
1014         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
1015         if (!m->hw_handler_name)
1016                 return -EINVAL;
1017
1018         if (hw_argc > 1) {
1019                 char *p;
1020                 int i, j, len = 4;
1021
1022                 for (i = 0; i <= hw_argc - 2; i++)
1023                         len += strlen(as->argv[i]) + 1;
1024                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1025                 if (!p) {
1026                         ti->error = "memory allocation failed";
1027                         ret = -ENOMEM;
1028                         goto fail;
1029                 }
1030                 j = sprintf(p, "%d", hw_argc - 1);
1031                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
1032                         j = sprintf(p, "%s", as->argv[i]);
1033         }
1034         dm_consume_args(as, hw_argc - 1);
1035
1036         return 0;
1037 fail:
1038         kfree(m->hw_handler_name);
1039         m->hw_handler_name = NULL;
1040         return ret;
1041 }
1042
1043 static int parse_features(struct dm_arg_set *as, struct multipath *m)
1044 {
1045         int r;
1046         unsigned argc;
1047         struct dm_target *ti = m->ti;
1048         const char *arg_name;
1049
1050         static const struct dm_arg _args[] = {
1051                 {0, 8, "invalid number of feature args"},
1052                 {1, 50, "pg_init_retries must be between 1 and 50"},
1053                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1054         };
1055
1056         r = dm_read_arg_group(_args, as, &argc, &ti->error);
1057         if (r)
1058                 return -EINVAL;
1059
1060         if (!argc)
1061                 return 0;
1062
1063         do {
1064                 arg_name = dm_shift_arg(as);
1065                 argc--;
1066
1067                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
1068                         r = queue_if_no_path(m, true, false);
1069                         continue;
1070                 }
1071
1072                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1073                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1074                         continue;
1075                 }
1076
1077                 if (!strcasecmp(arg_name, "pg_init_retries") &&
1078                     (argc >= 1)) {
1079                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1080                         argc--;
1081                         continue;
1082                 }
1083
1084                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1085                     (argc >= 1)) {
1086                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1087                         argc--;
1088                         continue;
1089                 }
1090
1091                 if (!strcasecmp(arg_name, "queue_mode") &&
1092                     (argc >= 1)) {
1093                         const char *queue_mode_name = dm_shift_arg(as);
1094
1095                         if (!strcasecmp(queue_mode_name, "bio"))
1096                                 m->queue_mode = DM_TYPE_BIO_BASED;
1097                         else if (!strcasecmp(queue_mode_name, "rq") ||
1098                                  !strcasecmp(queue_mode_name, "mq"))
1099                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1100                         else {
1101                                 ti->error = "Unknown 'queue_mode' requested";
1102                                 r = -EINVAL;
1103                         }
1104                         argc--;
1105                         continue;
1106                 }
1107
1108                 ti->error = "Unrecognised multipath feature request";
1109                 r = -EINVAL;
1110         } while (argc && !r);
1111
1112         return r;
1113 }
1114
1115 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1116 {
1117         /* target arguments */
1118         static const struct dm_arg _args[] = {
1119                 {0, 1024, "invalid number of priority groups"},
1120                 {0, 1024, "invalid initial priority group number"},
1121         };
1122
1123         int r;
1124         struct multipath *m;
1125         struct dm_arg_set as;
1126         unsigned pg_count = 0;
1127         unsigned next_pg_num;
1128
1129         as.argc = argc;
1130         as.argv = argv;
1131
1132         m = alloc_multipath(ti);
1133         if (!m) {
1134                 ti->error = "can't allocate multipath";
1135                 return -EINVAL;
1136         }
1137
1138         r = parse_features(&as, m);
1139         if (r)
1140                 goto bad;
1141
1142         r = alloc_multipath_stage2(ti, m);
1143         if (r)
1144                 goto bad;
1145
1146         r = parse_hw_handler(&as, m);
1147         if (r)
1148                 goto bad;
1149
1150         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1151         if (r)
1152                 goto bad;
1153
1154         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1155         if (r)
1156                 goto bad;
1157
1158         if ((!m->nr_priority_groups && next_pg_num) ||
1159             (m->nr_priority_groups && !next_pg_num)) {
1160                 ti->error = "invalid initial priority group";
1161                 r = -EINVAL;
1162                 goto bad;
1163         }
1164
1165         /* parse the priority groups */
1166         while (as.argc) {
1167                 struct priority_group *pg;
1168                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1169
1170                 pg = parse_priority_group(&as, m);
1171                 if (IS_ERR(pg)) {
1172                         r = PTR_ERR(pg);
1173                         goto bad;
1174                 }
1175
1176                 nr_valid_paths += pg->nr_pgpaths;
1177                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1178
1179                 list_add_tail(&pg->list, &m->priority_groups);
1180                 pg_count++;
1181                 pg->pg_num = pg_count;
1182                 if (!--next_pg_num)
1183                         m->next_pg = pg;
1184         }
1185
1186         if (pg_count != m->nr_priority_groups) {
1187                 ti->error = "priority group count mismatch";
1188                 r = -EINVAL;
1189                 goto bad;
1190         }
1191
1192         ti->num_flush_bios = 1;
1193         ti->num_discard_bios = 1;
1194         ti->num_write_same_bios = 1;
1195         ti->num_write_zeroes_bios = 1;
1196         if (m->queue_mode == DM_TYPE_BIO_BASED)
1197                 ti->per_io_data_size = multipath_per_bio_data_size();
1198         else
1199                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1200
1201         return 0;
1202
1203  bad:
1204         free_multipath(m);
1205         return r;
1206 }
1207
1208 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1209 {
1210         DEFINE_WAIT(wait);
1211
1212         while (1) {
1213                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1214
1215                 if (!atomic_read(&m->pg_init_in_progress))
1216                         break;
1217
1218                 io_schedule();
1219         }
1220         finish_wait(&m->pg_init_wait, &wait);
1221 }
1222
1223 static void flush_multipath_work(struct multipath *m)
1224 {
1225         if (m->hw_handler_name) {
1226                 set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1227                 smp_mb__after_atomic();
1228
1229                 if (atomic_read(&m->pg_init_in_progress))
1230                         flush_workqueue(kmpath_handlerd);
1231                 multipath_wait_for_pg_init_completion(m);
1232
1233                 clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1234                 smp_mb__after_atomic();
1235         }
1236
1237         if (m->queue_mode == DM_TYPE_BIO_BASED)
1238                 flush_work(&m->process_queued_bios);
1239         flush_work(&m->trigger_event);
1240 }
1241
1242 static void multipath_dtr(struct dm_target *ti)
1243 {
1244         struct multipath *m = ti->private;
1245
1246         flush_multipath_work(m);
1247         free_multipath(m);
1248 }
1249
1250 /*
1251  * Take a path out of use.
1252  */
1253 static int fail_path(struct pgpath *pgpath)
1254 {
1255         unsigned long flags;
1256         struct multipath *m = pgpath->pg->m;
1257
1258         spin_lock_irqsave(&m->lock, flags);
1259
1260         if (!pgpath->is_active)
1261                 goto out;
1262
1263         DMWARN("Failing path %s.", pgpath->path.dev->name);
1264
1265         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1266         pgpath->is_active = false;
1267         pgpath->fail_count++;
1268
1269         atomic_dec(&m->nr_valid_paths);
1270
1271         if (pgpath == m->current_pgpath)
1272                 m->current_pgpath = NULL;
1273
1274         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1275                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1276
1277         schedule_work(&m->trigger_event);
1278
1279 out:
1280         spin_unlock_irqrestore(&m->lock, flags);
1281
1282         return 0;
1283 }
1284
1285 /*
1286  * Reinstate a previously-failed path
1287  */
1288 static int reinstate_path(struct pgpath *pgpath)
1289 {
1290         int r = 0, run_queue = 0;
1291         unsigned long flags;
1292         struct multipath *m = pgpath->pg->m;
1293         unsigned nr_valid_paths;
1294
1295         spin_lock_irqsave(&m->lock, flags);
1296
1297         if (pgpath->is_active)
1298                 goto out;
1299
1300         DMWARN("Reinstating path %s.", pgpath->path.dev->name);
1301
1302         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1303         if (r)
1304                 goto out;
1305
1306         pgpath->is_active = true;
1307
1308         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1309         if (nr_valid_paths == 1) {
1310                 m->current_pgpath = NULL;
1311                 run_queue = 1;
1312         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1313                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1314                         atomic_inc(&m->pg_init_in_progress);
1315         }
1316
1317         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1318                        pgpath->path.dev->name, nr_valid_paths);
1319
1320         schedule_work(&m->trigger_event);
1321
1322 out:
1323         spin_unlock_irqrestore(&m->lock, flags);
1324         if (run_queue) {
1325                 dm_table_run_md_queue_async(m->ti->table);
1326                 process_queued_io_list(m);
1327         }
1328
1329         return r;
1330 }
1331
1332 /*
1333  * Fail or reinstate all paths that match the provided struct dm_dev.
1334  */
1335 static int action_dev(struct multipath *m, struct dm_dev *dev,
1336                       action_fn action)
1337 {
1338         int r = -EINVAL;
1339         struct pgpath *pgpath;
1340         struct priority_group *pg;
1341
1342         list_for_each_entry(pg, &m->priority_groups, list) {
1343                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1344                         if (pgpath->path.dev == dev)
1345                                 r = action(pgpath);
1346                 }
1347         }
1348
1349         return r;
1350 }
1351
1352 /*
1353  * Temporarily try to avoid having to use the specified PG
1354  */
1355 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1356                       bool bypassed)
1357 {
1358         unsigned long flags;
1359
1360         spin_lock_irqsave(&m->lock, flags);
1361
1362         pg->bypassed = bypassed;
1363         m->current_pgpath = NULL;
1364         m->current_pg = NULL;
1365
1366         spin_unlock_irqrestore(&m->lock, flags);
1367
1368         schedule_work(&m->trigger_event);
1369 }
1370
1371 /*
1372  * Switch to using the specified PG from the next I/O that gets mapped
1373  */
1374 static int switch_pg_num(struct multipath *m, const char *pgstr)
1375 {
1376         struct priority_group *pg;
1377         unsigned pgnum;
1378         unsigned long flags;
1379         char dummy;
1380
1381         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1382             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1383                 DMWARN("invalid PG number supplied to switch_pg_num");
1384                 return -EINVAL;
1385         }
1386
1387         spin_lock_irqsave(&m->lock, flags);
1388         list_for_each_entry(pg, &m->priority_groups, list) {
1389                 pg->bypassed = false;
1390                 if (--pgnum)
1391                         continue;
1392
1393                 m->current_pgpath = NULL;
1394                 m->current_pg = NULL;
1395                 m->next_pg = pg;
1396         }
1397         spin_unlock_irqrestore(&m->lock, flags);
1398
1399         schedule_work(&m->trigger_event);
1400         return 0;
1401 }
1402
1403 /*
1404  * Set/clear bypassed status of a PG.
1405  * PGs are numbered upwards from 1 in the order they were declared.
1406  */
1407 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1408 {
1409         struct priority_group *pg;
1410         unsigned pgnum;
1411         char dummy;
1412
1413         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1414             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1415                 DMWARN("invalid PG number supplied to bypass_pg");
1416                 return -EINVAL;
1417         }
1418
1419         list_for_each_entry(pg, &m->priority_groups, list) {
1420                 if (!--pgnum)
1421                         break;
1422         }
1423
1424         bypass_pg(m, pg, bypassed);
1425         return 0;
1426 }
1427
1428 /*
1429  * Should we retry pg_init immediately?
1430  */
1431 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1432 {
1433         unsigned long flags;
1434         bool limit_reached = false;
1435
1436         spin_lock_irqsave(&m->lock, flags);
1437
1438         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1439             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1440                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1441         else
1442                 limit_reached = true;
1443
1444         spin_unlock_irqrestore(&m->lock, flags);
1445
1446         return limit_reached;
1447 }
1448
1449 static void pg_init_done(void *data, int errors)
1450 {
1451         struct pgpath *pgpath = data;
1452         struct priority_group *pg = pgpath->pg;
1453         struct multipath *m = pg->m;
1454         unsigned long flags;
1455         bool delay_retry = false;
1456
1457         /* device or driver problems */
1458         switch (errors) {
1459         case SCSI_DH_OK:
1460                 break;
1461         case SCSI_DH_NOSYS:
1462                 if (!m->hw_handler_name) {
1463                         errors = 0;
1464                         break;
1465                 }
1466                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1467                       "Error %d.", m->hw_handler_name, errors);
1468                 /*
1469                  * Fail path for now, so we do not ping pong
1470                  */
1471                 fail_path(pgpath);
1472                 break;
1473         case SCSI_DH_DEV_TEMP_BUSY:
1474                 /*
1475                  * Probably doing something like FW upgrade on the
1476                  * controller so try the other pg.
1477                  */
1478                 bypass_pg(m, pg, true);
1479                 break;
1480         case SCSI_DH_RETRY:
1481                 /* Wait before retrying. */
1482                 delay_retry = 1;
1483                 /* fall through */
1484         case SCSI_DH_IMM_RETRY:
1485         case SCSI_DH_RES_TEMP_UNAVAIL:
1486                 if (pg_init_limit_reached(m, pgpath))
1487                         fail_path(pgpath);
1488                 errors = 0;
1489                 break;
1490         case SCSI_DH_DEV_OFFLINED:
1491         default:
1492                 /*
1493                  * We probably do not want to fail the path for a device
1494                  * error, but this is what the old dm did. In future
1495                  * patches we can do more advanced handling.
1496                  */
1497                 fail_path(pgpath);
1498         }
1499
1500         spin_lock_irqsave(&m->lock, flags);
1501         if (errors) {
1502                 if (pgpath == m->current_pgpath) {
1503                         DMERR("Could not failover device. Error %d.", errors);
1504                         m->current_pgpath = NULL;
1505                         m->current_pg = NULL;
1506                 }
1507         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1508                 pg->bypassed = false;
1509
1510         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1511                 /* Activations of other paths are still on going */
1512                 goto out;
1513
1514         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1515                 if (delay_retry)
1516                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1517                 else
1518                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1519
1520                 if (__pg_init_all_paths(m))
1521                         goto out;
1522         }
1523         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1524
1525         process_queued_io_list(m);
1526
1527         /*
1528          * Wake up any thread waiting to suspend.
1529          */
1530         wake_up(&m->pg_init_wait);
1531
1532 out:
1533         spin_unlock_irqrestore(&m->lock, flags);
1534 }
1535
1536 static void activate_or_offline_path(struct pgpath *pgpath)
1537 {
1538         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1539
1540         if (pgpath->is_active && !blk_queue_dying(q))
1541                 scsi_dh_activate(q, pg_init_done, pgpath);
1542         else
1543                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1544 }
1545
1546 static void activate_path_work(struct work_struct *work)
1547 {
1548         struct pgpath *pgpath =
1549                 container_of(work, struct pgpath, activate_path.work);
1550
1551         activate_or_offline_path(pgpath);
1552 }
1553
1554 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1555                             blk_status_t error, union map_info *map_context)
1556 {
1557         struct dm_mpath_io *mpio = get_mpio(map_context);
1558         struct pgpath *pgpath = mpio->pgpath;
1559         int r = DM_ENDIO_DONE;
1560
1561         /*
1562          * We don't queue any clone request inside the multipath target
1563          * during end I/O handling, since those clone requests don't have
1564          * bio clones.  If we queue them inside the multipath target,
1565          * we need to make bio clones, that requires memory allocation.
1566          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1567          *  don't have bio clones.)
1568          * Instead of queueing the clone request here, we queue the original
1569          * request into dm core, which will remake a clone request and
1570          * clone bios for it and resubmit it later.
1571          */
1572         if (error && blk_path_error(error)) {
1573                 struct multipath *m = ti->private;
1574
1575                 if (error == BLK_STS_RESOURCE)
1576                         r = DM_ENDIO_DELAY_REQUEUE;
1577                 else
1578                         r = DM_ENDIO_REQUEUE;
1579
1580                 if (pgpath)
1581                         fail_path(pgpath);
1582
1583                 if (atomic_read(&m->nr_valid_paths) == 0 &&
1584                     !must_push_back_rq(m)) {
1585                         if (error == BLK_STS_IOERR)
1586                                 dm_report_EIO(m);
1587                         /* complete with the original error */
1588                         r = DM_ENDIO_DONE;
1589                 }
1590         }
1591
1592         if (pgpath) {
1593                 struct path_selector *ps = &pgpath->pg->ps;
1594
1595                 if (ps->type->end_io)
1596                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1597         }
1598
1599         return r;
1600 }
1601
1602 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1603                                 blk_status_t *error)
1604 {
1605         struct multipath *m = ti->private;
1606         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1607         struct pgpath *pgpath = mpio->pgpath;
1608         unsigned long flags;
1609         int r = DM_ENDIO_DONE;
1610
1611         if (!*error || !blk_path_error(*error))
1612                 goto done;
1613
1614         if (pgpath)
1615                 fail_path(pgpath);
1616
1617         if (atomic_read(&m->nr_valid_paths) == 0 &&
1618             !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1619                 if (must_push_back_bio(m)) {
1620                         r = DM_ENDIO_REQUEUE;
1621                 } else {
1622                         dm_report_EIO(m);
1623                         *error = BLK_STS_IOERR;
1624                 }
1625                 goto done;
1626         }
1627
1628         spin_lock_irqsave(&m->lock, flags);
1629         bio_list_add(&m->queued_bios, clone);
1630         spin_unlock_irqrestore(&m->lock, flags);
1631         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1632                 queue_work(kmultipathd, &m->process_queued_bios);
1633
1634         r = DM_ENDIO_INCOMPLETE;
1635 done:
1636         if (pgpath) {
1637                 struct path_selector *ps = &pgpath->pg->ps;
1638
1639                 if (ps->type->end_io)
1640                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1641         }
1642
1643         return r;
1644 }
1645
1646 /*
1647  * Suspend can't complete until all the I/O is processed so if
1648  * the last path fails we must error any remaining I/O.
1649  * Note that if the freeze_bdev fails while suspending, the
1650  * queue_if_no_path state is lost - userspace should reset it.
1651  */
1652 static void multipath_presuspend(struct dm_target *ti)
1653 {
1654         struct multipath *m = ti->private;
1655
1656         queue_if_no_path(m, false, true);
1657 }
1658
1659 static void multipath_postsuspend(struct dm_target *ti)
1660 {
1661         struct multipath *m = ti->private;
1662
1663         mutex_lock(&m->work_mutex);
1664         flush_multipath_work(m);
1665         mutex_unlock(&m->work_mutex);
1666 }
1667
1668 /*
1669  * Restore the queue_if_no_path setting.
1670  */
1671 static void multipath_resume(struct dm_target *ti)
1672 {
1673         struct multipath *m = ti->private;
1674         unsigned long flags;
1675
1676         spin_lock_irqsave(&m->lock, flags);
1677         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags,
1678                    test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1679         spin_unlock_irqrestore(&m->lock, flags);
1680 }
1681
1682 /*
1683  * Info output has the following format:
1684  * num_multipath_feature_args [multipath_feature_args]*
1685  * num_handler_status_args [handler_status_args]*
1686  * num_groups init_group_number
1687  *            [A|D|E num_ps_status_args [ps_status_args]*
1688  *             num_paths num_selector_args
1689  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1690  *
1691  * Table output has the following format (identical to the constructor string):
1692  * num_feature_args [features_args]*
1693  * num_handler_args hw_handler [hw_handler_args]*
1694  * num_groups init_group_number
1695  *     [priority selector-name num_ps_args [ps_args]*
1696  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1697  */
1698 static void multipath_status(struct dm_target *ti, status_type_t type,
1699                              unsigned status_flags, char *result, unsigned maxlen)
1700 {
1701         int sz = 0;
1702         unsigned long flags;
1703         struct multipath *m = ti->private;
1704         struct priority_group *pg;
1705         struct pgpath *p;
1706         unsigned pg_num;
1707         char state;
1708
1709         spin_lock_irqsave(&m->lock, flags);
1710
1711         /* Features */
1712         if (type == STATUSTYPE_INFO)
1713                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1714                        atomic_read(&m->pg_init_count));
1715         else {
1716                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1717                               (m->pg_init_retries > 0) * 2 +
1718                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1719                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1720                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1721
1722                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1723                         DMEMIT("queue_if_no_path ");
1724                 if (m->pg_init_retries)
1725                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1726                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1727                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1728                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1729                         DMEMIT("retain_attached_hw_handler ");
1730                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1731                         switch(m->queue_mode) {
1732                         case DM_TYPE_BIO_BASED:
1733                                 DMEMIT("queue_mode bio ");
1734                                 break;
1735                         default:
1736                                 WARN_ON_ONCE(true);
1737                                 break;
1738                         }
1739                 }
1740         }
1741
1742         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1743                 DMEMIT("0 ");
1744         else
1745                 DMEMIT("1 %s ", m->hw_handler_name);
1746
1747         DMEMIT("%u ", m->nr_priority_groups);
1748
1749         if (m->next_pg)
1750                 pg_num = m->next_pg->pg_num;
1751         else if (m->current_pg)
1752                 pg_num = m->current_pg->pg_num;
1753         else
1754                 pg_num = (m->nr_priority_groups ? 1 : 0);
1755
1756         DMEMIT("%u ", pg_num);
1757
1758         switch (type) {
1759         case STATUSTYPE_INFO:
1760                 list_for_each_entry(pg, &m->priority_groups, list) {
1761                         if (pg->bypassed)
1762                                 state = 'D';    /* Disabled */
1763                         else if (pg == m->current_pg)
1764                                 state = 'A';    /* Currently Active */
1765                         else
1766                                 state = 'E';    /* Enabled */
1767
1768                         DMEMIT("%c ", state);
1769
1770                         if (pg->ps.type->status)
1771                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1772                                                           result + sz,
1773                                                           maxlen - sz);
1774                         else
1775                                 DMEMIT("0 ");
1776
1777                         DMEMIT("%u %u ", pg->nr_pgpaths,
1778                                pg->ps.type->info_args);
1779
1780                         list_for_each_entry(p, &pg->pgpaths, list) {
1781                                 DMEMIT("%s %s %u ", p->path.dev->name,
1782                                        p->is_active ? "A" : "F",
1783                                        p->fail_count);
1784                                 if (pg->ps.type->status)
1785                                         sz += pg->ps.type->status(&pg->ps,
1786                                               &p->path, type, result + sz,
1787                                               maxlen - sz);
1788                         }
1789                 }
1790                 break;
1791
1792         case STATUSTYPE_TABLE:
1793                 list_for_each_entry(pg, &m->priority_groups, list) {
1794                         DMEMIT("%s ", pg->ps.type->name);
1795
1796                         if (pg->ps.type->status)
1797                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1798                                                           result + sz,
1799                                                           maxlen - sz);
1800                         else
1801                                 DMEMIT("0 ");
1802
1803                         DMEMIT("%u %u ", pg->nr_pgpaths,
1804                                pg->ps.type->table_args);
1805
1806                         list_for_each_entry(p, &pg->pgpaths, list) {
1807                                 DMEMIT("%s ", p->path.dev->name);
1808                                 if (pg->ps.type->status)
1809                                         sz += pg->ps.type->status(&pg->ps,
1810                                               &p->path, type, result + sz,
1811                                               maxlen - sz);
1812                         }
1813                 }
1814                 break;
1815         }
1816
1817         spin_unlock_irqrestore(&m->lock, flags);
1818 }
1819
1820 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv,
1821                              char *result, unsigned maxlen)
1822 {
1823         int r = -EINVAL;
1824         struct dm_dev *dev;
1825         struct multipath *m = ti->private;
1826         action_fn action;
1827
1828         mutex_lock(&m->work_mutex);
1829
1830         if (dm_suspended(ti)) {
1831                 r = -EBUSY;
1832                 goto out;
1833         }
1834
1835         if (argc == 1) {
1836                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1837                         r = queue_if_no_path(m, true, false);
1838                         goto out;
1839                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1840                         r = queue_if_no_path(m, false, false);
1841                         goto out;
1842                 }
1843         }
1844
1845         if (argc != 2) {
1846                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1847                 goto out;
1848         }
1849
1850         if (!strcasecmp(argv[0], "disable_group")) {
1851                 r = bypass_pg_num(m, argv[1], true);
1852                 goto out;
1853         } else if (!strcasecmp(argv[0], "enable_group")) {
1854                 r = bypass_pg_num(m, argv[1], false);
1855                 goto out;
1856         } else if (!strcasecmp(argv[0], "switch_group")) {
1857                 r = switch_pg_num(m, argv[1]);
1858                 goto out;
1859         } else if (!strcasecmp(argv[0], "reinstate_path"))
1860                 action = reinstate_path;
1861         else if (!strcasecmp(argv[0], "fail_path"))
1862                 action = fail_path;
1863         else {
1864                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1865                 goto out;
1866         }
1867
1868         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1869         if (r) {
1870                 DMWARN("message: error getting device %s",
1871                        argv[1]);
1872                 goto out;
1873         }
1874
1875         r = action_dev(m, dev, action);
1876
1877         dm_put_device(ti, dev);
1878
1879 out:
1880         mutex_unlock(&m->work_mutex);
1881         return r;
1882 }
1883
1884 static int multipath_prepare_ioctl(struct dm_target *ti,
1885                                    struct block_device **bdev)
1886 {
1887         struct multipath *m = ti->private;
1888         struct pgpath *current_pgpath;
1889         int r;
1890
1891         current_pgpath = READ_ONCE(m->current_pgpath);
1892         if (!current_pgpath)
1893                 current_pgpath = choose_pgpath(m, 0);
1894
1895         if (current_pgpath) {
1896                 if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1897                         *bdev = current_pgpath->path.dev->bdev;
1898                         r = 0;
1899                 } else {
1900                         /* pg_init has not started or completed */
1901                         r = -ENOTCONN;
1902                 }
1903         } else {
1904                 /* No path is available */
1905                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1906                         r = -ENOTCONN;
1907                 else
1908                         r = -EIO;
1909         }
1910
1911         if (r == -ENOTCONN) {
1912                 if (!READ_ONCE(m->current_pg)) {
1913                         /* Path status changed, redo selection */
1914                         (void) choose_pgpath(m, 0);
1915                 }
1916                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1917                         pg_init_all_paths(m);
1918                 dm_table_run_md_queue_async(m->ti->table);
1919                 process_queued_io_list(m);
1920         }
1921
1922         /*
1923          * Only pass ioctls through if the device sizes match exactly.
1924          */
1925         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1926                 return 1;
1927         return r;
1928 }
1929
1930 static int multipath_iterate_devices(struct dm_target *ti,
1931                                      iterate_devices_callout_fn fn, void *data)
1932 {
1933         struct multipath *m = ti->private;
1934         struct priority_group *pg;
1935         struct pgpath *p;
1936         int ret = 0;
1937
1938         list_for_each_entry(pg, &m->priority_groups, list) {
1939                 list_for_each_entry(p, &pg->pgpaths, list) {
1940                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1941                         if (ret)
1942                                 goto out;
1943                 }
1944         }
1945
1946 out:
1947         return ret;
1948 }
1949
1950 static int pgpath_busy(struct pgpath *pgpath)
1951 {
1952         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1953
1954         return blk_lld_busy(q);
1955 }
1956
1957 /*
1958  * We return "busy", only when we can map I/Os but underlying devices
1959  * are busy (so even if we map I/Os now, the I/Os will wait on
1960  * the underlying queue).
1961  * In other words, if we want to kill I/Os or queue them inside us
1962  * due to map unavailability, we don't return "busy".  Otherwise,
1963  * dm core won't give us the I/Os and we can't do what we want.
1964  */
1965 static int multipath_busy(struct dm_target *ti)
1966 {
1967         bool busy = false, has_active = false;
1968         struct multipath *m = ti->private;
1969         struct priority_group *pg, *next_pg;
1970         struct pgpath *pgpath;
1971
1972         /* pg_init in progress */
1973         if (atomic_read(&m->pg_init_in_progress))
1974                 return true;
1975
1976         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
1977         if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1978                 return (m->queue_mode != DM_TYPE_REQUEST_BASED);
1979
1980         /* Guess which priority_group will be used at next mapping time */
1981         pg = READ_ONCE(m->current_pg);
1982         next_pg = READ_ONCE(m->next_pg);
1983         if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
1984                 pg = next_pg;
1985
1986         if (!pg) {
1987                 /*
1988                  * We don't know which pg will be used at next mapping time.
1989                  * We don't call choose_pgpath() here to avoid to trigger
1990                  * pg_init just by busy checking.
1991                  * So we don't know whether underlying devices we will be using
1992                  * at next mapping time are busy or not. Just try mapping.
1993                  */
1994                 return busy;
1995         }
1996
1997         /*
1998          * If there is one non-busy active path at least, the path selector
1999          * will be able to select it. So we consider such a pg as not busy.
2000          */
2001         busy = true;
2002         list_for_each_entry(pgpath, &pg->pgpaths, list) {
2003                 if (pgpath->is_active) {
2004                         has_active = true;
2005                         if (!pgpath_busy(pgpath)) {
2006                                 busy = false;
2007                                 break;
2008                         }
2009                 }
2010         }
2011
2012         if (!has_active) {
2013                 /*
2014                  * No active path in this pg, so this pg won't be used and
2015                  * the current_pg will be changed at next mapping time.
2016                  * We need to try mapping to determine it.
2017                  */
2018                 busy = false;
2019         }
2020
2021         return busy;
2022 }
2023
2024 /*-----------------------------------------------------------------
2025  * Module setup
2026  *---------------------------------------------------------------*/
2027 static struct target_type multipath_target = {
2028         .name = "multipath",
2029         .version = {1, 13, 0},
2030         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE |
2031                     DM_TARGET_PASSES_INTEGRITY,
2032         .module = THIS_MODULE,
2033         .ctr = multipath_ctr,
2034         .dtr = multipath_dtr,
2035         .clone_and_map_rq = multipath_clone_and_map,
2036         .release_clone_rq = multipath_release_clone,
2037         .rq_end_io = multipath_end_io,
2038         .map = multipath_map_bio,
2039         .end_io = multipath_end_io_bio,
2040         .presuspend = multipath_presuspend,
2041         .postsuspend = multipath_postsuspend,
2042         .resume = multipath_resume,
2043         .status = multipath_status,
2044         .message = multipath_message,
2045         .prepare_ioctl = multipath_prepare_ioctl,
2046         .iterate_devices = multipath_iterate_devices,
2047         .busy = multipath_busy,
2048 };
2049
2050 static int __init dm_multipath_init(void)
2051 {
2052         int r;
2053
2054         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2055         if (!kmultipathd) {
2056                 DMERR("failed to create workqueue kmpathd");
2057                 r = -ENOMEM;
2058                 goto bad_alloc_kmultipathd;
2059         }
2060
2061         /*
2062          * A separate workqueue is used to handle the device handlers
2063          * to avoid overloading existing workqueue. Overloading the
2064          * old workqueue would also create a bottleneck in the
2065          * path of the storage hardware device activation.
2066          */
2067         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2068                                                   WQ_MEM_RECLAIM);
2069         if (!kmpath_handlerd) {
2070                 DMERR("failed to create workqueue kmpath_handlerd");
2071                 r = -ENOMEM;
2072                 goto bad_alloc_kmpath_handlerd;
2073         }
2074
2075         r = dm_register_target(&multipath_target);
2076         if (r < 0) {
2077                 DMERR("request-based register failed %d", r);
2078                 r = -EINVAL;
2079                 goto bad_register_target;
2080         }
2081
2082         return 0;
2083
2084 bad_register_target:
2085         destroy_workqueue(kmpath_handlerd);
2086 bad_alloc_kmpath_handlerd:
2087         destroy_workqueue(kmultipathd);
2088 bad_alloc_kmultipathd:
2089         return r;
2090 }
2091
2092 static void __exit dm_multipath_exit(void)
2093 {
2094         destroy_workqueue(kmpath_handlerd);
2095         destroy_workqueue(kmultipathd);
2096
2097         dm_unregister_target(&multipath_target);
2098 }
2099
2100 module_init(dm_multipath_init);
2101 module_exit(dm_multipath_exit);
2102
2103 MODULE_DESCRIPTION(DM_NAME " multipath target");
2104 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2105 MODULE_LICENSE("GPL");