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/timer.h>
  24 #include <linux/workqueue.h>
  25 #include <linux/delay.h>
  26 #include <scsi/scsi_dh.h>
  27 #include <linux/atomic.h>
  28 #include <linux/blk-mq.h>
  29
  30 #define DM_MSG_PREFIX "multipath"
  31 #define DM_PG_INIT_DELAY_MSECS 2000
  32 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  33 #define QUEUE_IF_NO_PATH_TIMEOUT_DEFAULT 0
  34
  35 static unsigned long queue_if_no_path_timeout_secs = QUEUE_IF_NO_PATH_TIMEOUT_DEFAULT;
  36
  37 /* Path properties */
  38 struct pgpath {
  39         struct list_head list;
  40
  41         struct priority_group *pg;      /* Owning PG */
  42         unsigned fail_count;            /* Cumulative failure count */
  43
  44         struct dm_path path;
  45         struct delayed_work activate_path;
  46
  47         bool is_active:1;               /* Path status */
  48 };
  49
  50 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  51
  52 /*
  53  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  54  * Each has a path selector which controls which path gets used.
  55  */
  56 struct priority_group {
  57         struct list_head list;
  58
  59         struct multipath *m;            /* Owning multipath instance */
  60         struct path_selector ps;
  61
  62         unsigned pg_num;                /* Reference number */
  63         unsigned nr_pgpaths;            /* Number of paths in PG */
  64         struct list_head pgpaths;
  65
  66         bool bypassed:1;                /* Temporarily bypass this PG? */
  67 };
  68
  69 /* Multipath context */
  70 struct multipath {
  71         unsigned long flags;            /* Multipath state flags */
  72
  73         spinlock_t lock;
  74         enum dm_queue_mode queue_mode;
  75
  76         struct pgpath *current_pgpath;
  77         struct priority_group *current_pg;
  78         struct priority_group *next_pg; /* Switch to this PG if set */
  79
  80         atomic_t nr_valid_paths;        /* Total number of usable paths */
  81         unsigned nr_priority_groups;
  82         struct list_head priority_groups;
  83
  84         const char *hw_handler_name;
  85         char *hw_handler_params;
  86         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  87         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  88         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  89         atomic_t pg_init_in_progress;   /* Only one pg_init allowed at once */
  90         atomic_t pg_init_count;         /* Number of times pg_init called */
  91
  92         struct mutex work_mutex;
  93         struct work_struct trigger_event;
  94         struct dm_target *ti;
  95
  96         struct work_struct process_queued_bios;
  97         struct bio_list queued_bios;
  98
  99         struct timer_list nopath_timer; /* Timeout for queue_if_no_path */
 100 };
 101
 102 /*
 103  * Context information attached to each io we process.
 104  */
 105 struct dm_mpath_io {
 106         struct pgpath *pgpath;
 107         size_t nr_bytes;
 108 };
 109
 110 typedef int (*action_fn) (struct pgpath *pgpath);
 111
 112 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 113 static void trigger_event(struct work_struct *work);
 114 static void activate_or_offline_path(struct pgpath *pgpath);
 115 static void activate_path_work(struct work_struct *work);
 116 static void process_queued_bios(struct work_struct *work);
 117 static void queue_if_no_path_timeout_work(struct timer_list *t);
 118
 119 /*-----------------------------------------------
 120  * Multipath state flags.
 121  *-----------------------------------------------*/
 122
 123 #define MPATHF_QUEUE_IO 0                       /* Must we queue all I/O? */
 124 #define MPATHF_QUEUE_IF_NO_PATH 1               /* Queue I/O if last path fails? */
 125 #define MPATHF_SAVED_QUEUE_IF_NO_PATH 2         /* Saved state during suspension */
 126 #define MPATHF_RETAIN_ATTACHED_HW_HANDLER 3     /* If there's already a hw_handler present, don't change it. */
 127 #define MPATHF_PG_INIT_DISABLED 4               /* pg_init is not currently allowed */
 128 #define MPATHF_PG_INIT_REQUIRED 5               /* pg_init needs calling? */
 129 #define MPATHF_PG_INIT_DELAY_RETRY 6            /* Delay pg_init retry? */
 130
 131 /*-----------------------------------------------
 132  * Allocation routines
 133  *-----------------------------------------------*/
 134
 135 static struct pgpath *alloc_pgpath(void)
 136 {
 137         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 138
 139         if (!pgpath)
 140                 return NULL;
 141
 142         pgpath->is_active = true;
 143
 144         return pgpath;
 145 }
 146
 147 static void free_pgpath(struct pgpath *pgpath)
 148 {
 149         kfree(pgpath);
 150 }
 151
 152 static struct priority_group *alloc_priority_group(void)
 153 {
 154         struct priority_group *pg;
 155
 156         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 157
 158         if (pg)
 159                 INIT_LIST_HEAD(&pg->pgpaths);
 160
 161         return pg;
 162 }
 163
 164 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 165 {
 166         struct pgpath *pgpath, *tmp;
 167
 168         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 169                 list_del(&pgpath->list);
 170                 dm_put_device(ti, pgpath->path.dev);
 171                 free_pgpath(pgpath);
 172         }
 173 }
 174
 175 static void free_priority_group(struct priority_group *pg,
 176                                 struct dm_target *ti)
 177 {
 178         struct path_selector *ps = &pg->ps;
 179
 180         if (ps->type) {
 181                 ps->type->destroy(ps);
 182                 dm_put_path_selector(ps->type);
 183         }
 184
 185         free_pgpaths(&pg->pgpaths, ti);
 186         kfree(pg);
 187 }
 188
 189 static struct multipath *alloc_multipath(struct dm_target *ti)
 190 {
 191         struct multipath *m;
 192
 193         m = kzalloc(sizeof(*m), GFP_KERNEL);
 194         if (m) {
 195                 INIT_LIST_HEAD(&m->priority_groups);
 196                 spin_lock_init(&m->lock);
 197                 atomic_set(&m->nr_valid_paths, 0);
 198                 INIT_WORK(&m->trigger_event, trigger_event);
 199                 mutex_init(&m->work_mutex);
 200
 201                 m->queue_mode = DM_TYPE_NONE;
 202
 203                 m->ti = ti;
 204                 ti->private = m;
 205
 206                 timer_setup(&m->nopath_timer, queue_if_no_path_timeout_work, 0);
 207         }
 208
 209         return m;
 210 }
 211
 212 static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
 213 {
 214         if (m->queue_mode == DM_TYPE_NONE) {
 215                 m->queue_mode = DM_TYPE_REQUEST_BASED;
 216         } else if (m->queue_mode == DM_TYPE_BIO_BASED) {
 217                 INIT_WORK(&m->process_queued_bios, process_queued_bios);
 218                 /*
 219                  * bio-based doesn't support any direct scsi_dh management;
 220                  * it just discovers if a scsi_dh is attached.
 221                  */
 222                 set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 223         }
 224
 225         dm_table_set_type(ti->table, m->queue_mode);
 226
 227         /*
 228          * Init fields that are only used when a scsi_dh is attached
 229          * - must do this unconditionally (really doesn't hurt non-SCSI uses)
 230          */
 231         set_bit(MPATHF_QUEUE_IO, &m->flags);
 232         atomic_set(&m->pg_init_in_progress, 0);
 233         atomic_set(&m->pg_init_count, 0);
 234         m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 235         init_waitqueue_head(&m->pg_init_wait);
 236
 237         return 0;
 238 }
 239
 240 static void free_multipath(struct multipath *m)
 241 {
 242         struct priority_group *pg, *tmp;
 243
 244         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 245                 list_del(&pg->list);
 246                 free_priority_group(pg, m->ti);
 247         }
 248
 249         kfree(m->hw_handler_name);
 250         kfree(m->hw_handler_params);
 251         mutex_destroy(&m->work_mutex);
 252         kfree(m);
 253 }
 254
 255 static struct dm_mpath_io *get_mpio(union map_info *info)
 256 {
 257         return info->ptr;
 258 }
 259
 260 static size_t multipath_per_bio_data_size(void)
 261 {
 262         return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
 263 }
 264
 265 static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
 266 {
 267         return dm_per_bio_data(bio, multipath_per_bio_data_size());
 268 }
 269
 270 static struct dm_bio_details *get_bio_details_from_mpio(struct dm_mpath_io *mpio)
 271 {
 272         /* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
 273         void *bio_details = mpio + 1;
 274         return bio_details;
 275 }
 276
 277 static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p)
 278 {
 279         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 280         struct dm_bio_details *bio_details = get_bio_details_from_mpio(mpio);
 281
 282         mpio->nr_bytes = bio->bi_iter.bi_size;
 283         mpio->pgpath = NULL;
 284         *mpio_p = mpio;
 285
 286         dm_bio_record(bio_details, bio);
 287 }
 288
 289 /*-----------------------------------------------
 290  * Path selection
 291  *-----------------------------------------------*/
 292
 293 static int __pg_init_all_paths(struct multipath *m)
 294 {
 295         struct pgpath *pgpath;
 296         unsigned long pg_init_delay = 0;
 297
 298         lockdep_assert_held(&m->lock);
 299
 300         if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
 301                 return 0;
 302
 303         atomic_inc(&m->pg_init_count);
 304         clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 305
 306         /* Check here to reset pg_init_required */
 307         if (!m->current_pg)
 308                 return 0;
 309
 310         if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
 311                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 312                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 313         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 314                 /* Skip failed paths */
 315                 if (!pgpath->is_active)
 316                         continue;
 317                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 318                                        pg_init_delay))
 319                         atomic_inc(&m->pg_init_in_progress);
 320         }
 321         return atomic_read(&m->pg_init_in_progress);
 322 }
 323
 324 static int pg_init_all_paths(struct multipath *m)
 325 {
 326         int ret;
 327         unsigned long flags;
 328
 329         spin_lock_irqsave(&m->lock, flags);
 330         ret = __pg_init_all_paths(m);
 331         spin_unlock_irqrestore(&m->lock, flags);
 332
 333         return ret;
 334 }
 335
 336 static void __switch_pg(struct multipath *m, struct priority_group *pg)
 337 {
 338         m->current_pg = pg;
 339
 340         /* Must we initialise the PG first, and queue I/O till it's ready? */
 341         if (m->hw_handler_name) {
 342                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 343                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 344         } else {
 345                 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 346                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 347         }
 348
 349         atomic_set(&m->pg_init_count, 0);
 350 }
 351
 352 static struct pgpath *choose_path_in_pg(struct multipath *m,
 353                                         struct priority_group *pg,
 354                                         size_t nr_bytes)
 355 {
 356         unsigned long flags;
 357         struct dm_path *path;
 358         struct pgpath *pgpath;
 359
 360         path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 361         if (!path)
 362                 return ERR_PTR(-ENXIO);
 363
 364         pgpath = path_to_pgpath(path);
 365
 366         if (unlikely(READ_ONCE(m->current_pg) != pg)) {
 367                 /* Only update current_pgpath if pg changed */
 368                 spin_lock_irqsave(&m->lock, flags);
 369                 m->current_pgpath = pgpath;
 370                 __switch_pg(m, pg);
 371                 spin_unlock_irqrestore(&m->lock, flags);
 372         }
 373
 374         return pgpath;
 375 }
 376
 377 static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 378 {
 379         unsigned long flags;
 380         struct priority_group *pg;
 381         struct pgpath *pgpath;
 382         unsigned bypassed = 1;
 383
 384         if (!atomic_read(&m->nr_valid_paths)) {
 385                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 386                 goto failed;
 387         }
 388
 389         /* Were we instructed to switch PG? */
 390         if (READ_ONCE(m->next_pg)) {
 391                 spin_lock_irqsave(&m->lock, flags);
 392                 pg = m->next_pg;
 393                 if (!pg) {
 394                         spin_unlock_irqrestore(&m->lock, flags);
 395                         goto check_current_pg;
 396                 }
 397                 m->next_pg = NULL;
 398                 spin_unlock_irqrestore(&m->lock, flags);
 399                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 400                 if (!IS_ERR_OR_NULL(pgpath))
 401                         return pgpath;
 402         }
 403
 404         /* Don't change PG until it has no remaining paths */
 405 check_current_pg:
 406         pg = READ_ONCE(m->current_pg);
 407         if (pg) {
 408                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 409                 if (!IS_ERR_OR_NULL(pgpath))
 410                         return pgpath;
 411         }
 412
 413         /*
 414          * Loop through priority groups until we find a valid path.
 415          * First time we skip PGs marked 'bypassed'.
 416          * Second time we only try the ones we skipped, but set
 417          * pg_init_delay_retry so we do not hammer controllers.
 418          */
 419         do {
 420                 list_for_each_entry(pg, &m->priority_groups, list) {
 421                         if (pg->bypassed == !!bypassed)
 422                                 continue;
 423                         pgpath = choose_path_in_pg(m, pg, nr_bytes);
 424                         if (!IS_ERR_OR_NULL(pgpath)) {
 425                                 if (!bypassed)
 426                                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 427                                 return pgpath;
 428                         }
 429                 }
 430         } while (bypassed--);
 431
 432 failed:
 433         spin_lock_irqsave(&m->lock, flags);
 434         m->current_pgpath = NULL;
 435         m->current_pg = NULL;
 436         spin_unlock_irqrestore(&m->lock, flags);
 437
 438         return NULL;
 439 }
 440
 441 /*
 442  * dm_report_EIO() is a macro instead of a function to make pr_debug_ratelimited()
 443  * report the function name and line number of the function from which
 444  * it has been invoked.
 445  */
 446 #define dm_report_EIO(m)                                                \
 447 do {                                                                    \
 448         struct mapped_device *md = dm_table_get_md((m)->ti->table);     \
 449                                                                         \
 450         DMDEBUG_LIMIT("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d", \
 451                       dm_device_name(md),                               \
 452                       test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),   \
 453                       test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags), \
 454                       dm_noflush_suspending((m)->ti));                  \
 455 } while (0)
 456
 457 /*
 458  * Check whether bios must be queued in the device-mapper core rather
 459  * than here in the target.
 460  */
 461 static bool __must_push_back(struct multipath *m)
 462 {
 463         return dm_noflush_suspending(m->ti);
 464 }
 465
 466 static bool must_push_back_rq(struct multipath *m)
 467 {
 468         return test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) || __must_push_back(m);
 469 }
 470
 471 /*
 472  * Map cloned requests (request-based multipath)
 473  */
 474 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 475                                    union map_info *map_context,
 476                                    struct request **__clone)
 477 {
 478         struct multipath *m = ti->private;
 479         size_t nr_bytes = blk_rq_bytes(rq);
 480         struct pgpath *pgpath;
 481         struct block_device *bdev;
 482         struct dm_mpath_io *mpio = get_mpio(map_context);
 483         struct request_queue *q;
 484         struct request *clone;
 485
 486         /* Do we need to select a new pgpath? */
 487         pgpath = READ_ONCE(m->current_pgpath);
 488         if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
 489                 pgpath = choose_pgpath(m, nr_bytes);
 490
 491         if (!pgpath) {
 492                 if (must_push_back_rq(m))
 493                         return DM_MAPIO_DELAY_REQUEUE;
 494                 dm_report_EIO(m);       /* Failed */
 495                 return DM_MAPIO_KILL;
 496         } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
 497                    test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
 498                 pg_init_all_paths(m);
 499                 return DM_MAPIO_DELAY_REQUEUE;
 500         }
 501
 502         mpio->pgpath = pgpath;
 503         mpio->nr_bytes = nr_bytes;
 504
 505         bdev = pgpath->path.dev->bdev;
 506         q = bdev_get_queue(bdev);
 507         clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE,
 508                         BLK_MQ_REQ_NOWAIT);
 509         if (IS_ERR(clone)) {
 510                 /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 511                 if (blk_queue_dying(q)) {
 512                         atomic_inc(&m->pg_init_in_progress);
 513                         activate_or_offline_path(pgpath);
 514                         return DM_MAPIO_DELAY_REQUEUE;
 515                 }
 516
 517                 /*
 518                  * blk-mq's SCHED_RESTART can cover this requeue, so we
 519                  * needn't deal with it by DELAY_REQUEUE. More importantly,
 520                  * we have to return DM_MAPIO_REQUEUE so that blk-mq can
 521                  * get the queue busy feedback (via BLK_STS_RESOURCE),
 522                  * otherwise I/O merging can suffer.
 523                  */
 524                 return DM_MAPIO_REQUEUE;
 525         }
 526         clone->bio = clone->biotail = NULL;
 527         clone->rq_disk = bdev->bd_disk;
 528         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 529         *__clone = clone;
 530
 531         if (pgpath->pg->ps.type->start_io)
 532                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 533                                               &pgpath->path,
 534                                               nr_bytes);
 535         return DM_MAPIO_REMAPPED;
 536 }
 537
 538 static void multipath_release_clone(struct request *clone,
 539                                     union map_info *map_context)
 540 {
 541         if (unlikely(map_context)) {
 542                 /*
 543                  * non-NULL map_context means caller is still map
 544                  * method; must undo multipath_clone_and_map()
 545                  */
 546                 struct dm_mpath_io *mpio = get_mpio(map_context);
 547                 struct pgpath *pgpath = mpio->pgpath;
 548
 549                 if (pgpath && pgpath->pg->ps.type->end_io)
 550                         pgpath->pg->ps.type->end_io(&pgpath->pg->ps,
 551                                                     &pgpath->path,
 552                                                     mpio->nr_bytes,
 553                                                     clone->io_start_time_ns);
 554         }
 555
 556         blk_put_request(clone);
 557 }
 558
 559 /*
 560  * Map cloned bios (bio-based multipath)
 561  */
 562
 563 static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
 564 {
 565         struct pgpath *pgpath;
 566         unsigned long flags;
 567         bool queue_io;
 568
 569         /* Do we need to select a new pgpath? */
 570         pgpath = READ_ONCE(m->current_pgpath);
 571         if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
 572                 pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 573
 574         /* MPATHF_QUEUE_IO might have been cleared by choose_pgpath. */
 575         queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
 576
 577         if ((pgpath && queue_io) ||
 578             (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
 579                 /* Queue for the daemon to resubmit */
 580                 spin_lock_irqsave(&m->lock, flags);
 581                 bio_list_add(&m->queued_bios, bio);
 582                 spin_unlock_irqrestore(&m->lock, flags);
 583
 584                 /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
 585                 if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
 586                         pg_init_all_paths(m);
 587                 else if (!queue_io)
 588                         queue_work(kmultipathd, &m->process_queued_bios);
 589
 590                 return ERR_PTR(-EAGAIN);
 591         }
 592
 593         return pgpath;
 594 }
 595
 596 static int __multipath_map_bio(struct multipath *m, struct bio *bio,
 597                                struct dm_mpath_io *mpio)
 598 {
 599         struct pgpath *pgpath = __map_bio(m, bio);
 600
 601         if (IS_ERR(pgpath))
 602                 return DM_MAPIO_SUBMITTED;
 603
 604         if (!pgpath) {
 605                 if (__must_push_back(m))
 606                         return DM_MAPIO_REQUEUE;
 607                 dm_report_EIO(m);
 608                 return DM_MAPIO_KILL;
 609         }
 610
 611         mpio->pgpath = pgpath;
 612
 613         bio->bi_status = 0;
 614         bio_set_dev(bio, pgpath->path.dev->bdev);
 615         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 616
 617         if (pgpath->pg->ps.type->start_io)
 618                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 619                                               &pgpath->path,
 620                                               mpio->nr_bytes);
 621         return DM_MAPIO_REMAPPED;
 622 }
 623
 624 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 625 {
 626         struct multipath *m = ti->private;
 627         struct dm_mpath_io *mpio = NULL;
 628
 629         multipath_init_per_bio_data(bio, &mpio);
 630         return __multipath_map_bio(m, bio, mpio);
 631 }
 632
 633 static void process_queued_io_list(struct multipath *m)
 634 {
 635         if (m->queue_mode == DM_TYPE_REQUEST_BASED)
 636                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 637         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 638                 queue_work(kmultipathd, &m->process_queued_bios);
 639 }
 640
 641 static void process_queued_bios(struct work_struct *work)
 642 {
 643         int r;
 644         unsigned long flags;
 645         struct bio *bio;
 646         struct bio_list bios;
 647         struct blk_plug plug;
 648         struct multipath *m =
 649                 container_of(work, struct multipath, process_queued_bios);
 650
 651         bio_list_init(&bios);
 652
 653         spin_lock_irqsave(&m->lock, flags);
 654
 655         if (bio_list_empty(&m->queued_bios)) {
 656                 spin_unlock_irqrestore(&m->lock, flags);
 657                 return;
 658         }
 659
 660         bio_list_merge(&bios, &m->queued_bios);
 661         bio_list_init(&m->queued_bios);
 662
 663         spin_unlock_irqrestore(&m->lock, flags);
 664
 665         blk_start_plug(&plug);
 666         while ((bio = bio_list_pop(&bios))) {
 667                 struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 668                 dm_bio_restore(get_bio_details_from_mpio(mpio), bio);
 669                 r = __multipath_map_bio(m, bio, mpio);
 670                 switch (r) {
 671                 case DM_MAPIO_KILL:
 672                         bio->bi_status = BLK_STS_IOERR;
 673                         bio_endio(bio);
 674                         break;
 675                 case DM_MAPIO_REQUEUE:
 676                         bio->bi_status = BLK_STS_DM_REQUEUE;
 677                         bio_endio(bio);
 678                         break;
 679                 case DM_MAPIO_REMAPPED:
 680                         generic_make_request(bio);
 681                         break;
 682                 case DM_MAPIO_SUBMITTED:
 683                         break;
 684                 default:
 685                         WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 686                 }
 687         }
 688         blk_finish_plug(&plug);
 689 }
 690
 691 /*
 692  * If we run out of usable paths, should we queue I/O or error it?
 693  */
 694 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 695                             bool save_old_value, const char *caller)
 696 {
 697         unsigned long flags;
 698         bool queue_if_no_path_bit, saved_queue_if_no_path_bit;
 699         const char *dm_dev_name = dm_device_name(dm_table_get_md(m->ti->table));
 700
 701         DMDEBUG("%s: %s caller=%s queue_if_no_path=%d save_old_value=%d",
 702                 dm_dev_name, __func__, caller, queue_if_no_path, save_old_value);
 703
 704         spin_lock_irqsave(&m->lock, flags);
 705
 706         queue_if_no_path_bit = test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
 707         saved_queue_if_no_path_bit = test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 708
 709         if (save_old_value) {
 710                 if (unlikely(!queue_if_no_path_bit && saved_queue_if_no_path_bit)) {
 711                         DMERR("%s: QIFNP disabled but saved as enabled, saving again loses state, not saving!",
 712                               dm_dev_name);
 713                 } else
 714                         assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path_bit);
 715         } else if (!queue_if_no_path && saved_queue_if_no_path_bit) {
 716                 /* due to "fail_if_no_path" message, need to honor it. */
 717                 clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 718         }
 719         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);
 720
 721         DMDEBUG("%s: after %s changes; QIFNP = %d; SQIFNP = %d; DNFS = %d",
 722                 dm_dev_name, __func__,
 723                 test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
 724                 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags),
 725                 dm_noflush_suspending(m->ti));
 726
 727         spin_unlock_irqrestore(&m->lock, flags);
 728
 729         if (!queue_if_no_path) {
 730                 dm_table_run_md_queue_async(m->ti->table);
 731                 process_queued_io_list(m);
 732         }
 733
 734         return 0;
 735 }
 736
 737 /*
 738  * If the queue_if_no_path timeout fires, turn off queue_if_no_path and
 739  * process any queued I/O.
 740  */
 741 static void queue_if_no_path_timeout_work(struct timer_list *t)
 742 {
 743         struct multipath *m = from_timer(m, t, nopath_timer);
 744         struct mapped_device *md = dm_table_get_md(m->ti->table);
 745
 746         DMWARN("queue_if_no_path timeout on %s, failing queued IO", dm_device_name(md));
 747         queue_if_no_path(m, false, false, __func__);
 748 }
 749
 750 /*
 751  * Enable the queue_if_no_path timeout if necessary.
 752  * Called with m->lock held.
 753  */
 754 static void enable_nopath_timeout(struct multipath *m)
 755 {
 756         unsigned long queue_if_no_path_timeout =
 757                 READ_ONCE(queue_if_no_path_timeout_secs) * HZ;
 758
 759         lockdep_assert_held(&m->lock);
 760
 761         if (queue_if_no_path_timeout > 0 &&
 762             atomic_read(&m->nr_valid_paths) == 0 &&
 763             test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 764                 mod_timer(&m->nopath_timer,
 765                           jiffies + queue_if_no_path_timeout);
 766         }
 767 }
 768
 769 static void disable_nopath_timeout(struct multipath *m)
 770 {
 771         del_timer_sync(&m->nopath_timer);
 772 }
 773
 774 /*
 775  * An event is triggered whenever a path is taken out of use.
 776  * Includes path failure and PG bypass.
 777  */
 778 static void trigger_event(struct work_struct *work)
 779 {
 780         struct multipath *m =
 781                 container_of(work, struct multipath, trigger_event);
 782
 783         dm_table_event(m->ti->table);
 784 }
 785
 786 /*-----------------------------------------------------------------
 787  * Constructor/argument parsing:
 788  * <#multipath feature args> [<arg>]*
 789  * <#hw_handler args> [hw_handler [<arg>]*]
 790  * <#priority groups>
 791  * <initial priority group>
 792  *     [<selector> <#selector args> [<arg>]*
 793  *      <#paths> <#per-path selector args>
 794  *         [<path> [<arg>]* ]+ ]+
 795  *---------------------------------------------------------------*/
 796 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 797                                struct dm_target *ti)
 798 {
 799         int r;
 800         struct path_selector_type *pst;
 801         unsigned ps_argc;
 802
 803         static const struct dm_arg _args[] = {
 804                 {0, 1024, "invalid number of path selector args"},
 805         };
 806
 807         pst = dm_get_path_selector(dm_shift_arg(as));
 808         if (!pst) {
 809                 ti->error = "unknown path selector type";
 810                 return -EINVAL;
 811         }
 812
 813         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 814         if (r) {
 815                 dm_put_path_selector(pst);
 816                 return -EINVAL;
 817         }
 818
 819         r = pst->create(&pg->ps, ps_argc, as->argv);
 820         if (r) {
 821                 dm_put_path_selector(pst);
 822                 ti->error = "path selector constructor failed";
 823                 return r;
 824         }
 825
 826         pg->ps.type = pst;
 827         dm_consume_args(as, ps_argc);
 828
 829         return 0;
 830 }
 831
 832 static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
 833                          const char **attached_handler_name, char **error)
 834 {
 835         struct request_queue *q = bdev_get_queue(bdev);
 836         int r;
 837
 838         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 839 retain:
 840                 if (*attached_handler_name) {
 841                         /*
 842                          * Clear any hw_handler_params associated with a
 843                          * handler that isn't already attached.
 844                          */
 845                         if (m->hw_handler_name && strcmp(*attached_handler_name, m->hw_handler_name)) {
 846                                 kfree(m->hw_handler_params);
 847                                 m->hw_handler_params = NULL;
 848                         }
 849
 850                         /*
 851                          * Reset hw_handler_name to match the attached handler
 852                          *
 853                          * NB. This modifies the table line to show the actual
 854                          * handler instead of the original table passed in.
 855                          */
 856                         kfree(m->hw_handler_name);
 857                         m->hw_handler_name = *attached_handler_name;
 858                         *attached_handler_name = NULL;
 859                 }
 860         }
 861
 862         if (m->hw_handler_name) {
 863                 r = scsi_dh_attach(q, m->hw_handler_name);
 864                 if (r == -EBUSY) {
 865                         char b[BDEVNAME_SIZE];
 866
 867                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 868                                bdevname(bdev, b));
 869                         goto retain;
 870                 }
 871                 if (r < 0) {
 872                         *error = "error attaching hardware handler";
 873                         return r;
 874                 }
 875
 876                 if (m->hw_handler_params) {
 877                         r = scsi_dh_set_params(q, m->hw_handler_params);
 878                         if (r < 0) {
 879                                 *error = "unable to set hardware handler parameters";
 880                                 return r;
 881                         }
 882                 }
 883         }
 884
 885         return 0;
 886 }
 887
 888 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 889                                  struct dm_target *ti)
 890 {
 891         int r;
 892         struct pgpath *p;
 893         struct multipath *m = ti->private;
 894         struct request_queue *q;
 895         const char *attached_handler_name = NULL;
 896
 897         /* we need at least a path arg */
 898         if (as->argc < 1) {
 899                 ti->error = "no device given";
 900                 return ERR_PTR(-EINVAL);
 901         }
 902
 903         p = alloc_pgpath();
 904         if (!p)
 905                 return ERR_PTR(-ENOMEM);
 906
 907         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 908                           &p->path.dev);
 909         if (r) {
 910                 ti->error = "error getting device";
 911                 goto bad;
 912         }
 913
 914         q = bdev_get_queue(p->path.dev->bdev);
 915         attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 916         if (attached_handler_name || m->hw_handler_name) {
 917                 INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
 918                 r = setup_scsi_dh(p->path.dev->bdev, m, &attached_handler_name, &ti->error);
 919                 kfree(attached_handler_name);
 920                 if (r) {
 921                         dm_put_device(ti, p->path.dev);
 922                         goto bad;
 923                 }
 924         }
 925
 926         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 927         if (r) {
 928                 dm_put_device(ti, p->path.dev);
 929                 goto bad;
 930         }
 931
 932         return p;
 933  bad:
 934         free_pgpath(p);
 935         return ERR_PTR(r);
 936 }
 937
 938 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 939                                                    struct multipath *m)
 940 {
 941         static const struct dm_arg _args[] = {
 942                 {1, 1024, "invalid number of paths"},
 943                 {0, 1024, "invalid number of selector args"}
 944         };
 945
 946         int r;
 947         unsigned i, nr_selector_args, nr_args;
 948         struct priority_group *pg;
 949         struct dm_target *ti = m->ti;
 950
 951         if (as->argc < 2) {
 952                 as->argc = 0;
 953                 ti->error = "not enough priority group arguments";
 954                 return ERR_PTR(-EINVAL);
 955         }
 956
 957         pg = alloc_priority_group();
 958         if (!pg) {
 959                 ti->error = "couldn't allocate priority group";
 960                 return ERR_PTR(-ENOMEM);
 961         }
 962         pg->m = m;
 963
 964         r = parse_path_selector(as, pg, ti);
 965         if (r)
 966                 goto bad;
 967
 968         /*
 969          * read the paths
 970          */
 971         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 972         if (r)
 973                 goto bad;
 974
 975         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 976         if (r)
 977                 goto bad;
 978
 979         nr_args = 1 + nr_selector_args;
 980         for (i = 0; i < pg->nr_pgpaths; i++) {
 981                 struct pgpath *pgpath;
 982                 struct dm_arg_set path_args;
 983
 984                 if (as->argc < nr_args) {
 985                         ti->error = "not enough path parameters";
 986                         r = -EINVAL;
 987                         goto bad;
 988                 }
 989
 990                 path_args.argc = nr_args;
 991                 path_args.argv = as->argv;
 992
 993                 pgpath = parse_path(&path_args, &pg->ps, ti);
 994                 if (IS_ERR(pgpath)) {
 995                         r = PTR_ERR(pgpath);
 996                         goto bad;
 997                 }
 998
 999                 pgpath->pg = pg;
1000                 list_add_tail(&pgpath->list, &pg->pgpaths);
1001                 dm_consume_args(as, nr_args);
1002         }
1003
1004         return pg;
1005
1006  bad:
1007         free_priority_group(pg, ti);
1008         return ERR_PTR(r);
1009 }
1010
1011 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
1012 {
1013         unsigned hw_argc;
1014         int ret;
1015         struct dm_target *ti = m->ti;
1016
1017         static const struct dm_arg _args[] = {
1018                 {0, 1024, "invalid number of hardware handler args"},
1019         };
1020
1021         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
1022                 return -EINVAL;
1023
1024         if (!hw_argc)
1025                 return 0;
1026
1027         if (m->queue_mode == DM_TYPE_BIO_BASED) {
1028                 dm_consume_args(as, hw_argc);
1029                 DMERR("bio-based multipath doesn't allow hardware handler args");
1030                 return 0;
1031         }
1032
1033         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
1034         if (!m->hw_handler_name)
1035                 return -EINVAL;
1036
1037         if (hw_argc > 1) {
1038                 char *p;
1039                 int i, j, len = 4;
1040
1041                 for (i = 0; i <= hw_argc - 2; i++)
1042                         len += strlen(as->argv[i]) + 1;
1043                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1044                 if (!p) {
1045                         ti->error = "memory allocation failed";
1046                         ret = -ENOMEM;
1047                         goto fail;
1048                 }
1049                 j = sprintf(p, "%d", hw_argc - 1);
1050                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
1051                         j = sprintf(p, "%s", as->argv[i]);
1052         }
1053         dm_consume_args(as, hw_argc - 1);
1054
1055         return 0;
1056 fail:
1057         kfree(m->hw_handler_name);
1058         m->hw_handler_name = NULL;
1059         return ret;
1060 }
1061
1062 static int parse_features(struct dm_arg_set *as, struct multipath *m)
1063 {
1064         int r;
1065         unsigned argc;
1066         struct dm_target *ti = m->ti;
1067         const char *arg_name;
1068
1069         static const struct dm_arg _args[] = {
1070                 {0, 8, "invalid number of feature args"},
1071                 {1, 50, "pg_init_retries must be between 1 and 50"},
1072                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1073         };
1074
1075         r = dm_read_arg_group(_args, as, &argc, &ti->error);
1076         if (r)
1077                 return -EINVAL;
1078
1079         if (!argc)
1080                 return 0;
1081
1082         do {
1083                 arg_name = dm_shift_arg(as);
1084                 argc--;
1085
1086                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
1087                         r = queue_if_no_path(m, true, false, __func__);
1088                         continue;
1089                 }
1090
1091                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1092                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1093                         continue;
1094                 }
1095
1096                 if (!strcasecmp(arg_name, "pg_init_retries") &&
1097                     (argc >= 1)) {
1098                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1099                         argc--;
1100                         continue;
1101                 }
1102
1103                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1104                     (argc >= 1)) {
1105                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1106                         argc--;
1107                         continue;
1108                 }
1109
1110                 if (!strcasecmp(arg_name, "queue_mode") &&
1111                     (argc >= 1)) {
1112                         const char *queue_mode_name = dm_shift_arg(as);
1113
1114                         if (!strcasecmp(queue_mode_name, "bio"))
1115                                 m->queue_mode = DM_TYPE_BIO_BASED;
1116                         else if (!strcasecmp(queue_mode_name, "rq") ||
1117                                  !strcasecmp(queue_mode_name, "mq"))
1118                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1119                         else {
1120                                 ti->error = "Unknown 'queue_mode' requested";
1121                                 r = -EINVAL;
1122                         }
1123                         argc--;
1124                         continue;
1125                 }
1126
1127                 ti->error = "Unrecognised multipath feature request";
1128                 r = -EINVAL;
1129         } while (argc && !r);
1130
1131         return r;
1132 }
1133
1134 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1135 {
1136         /* target arguments */
1137         static const struct dm_arg _args[] = {
1138                 {0, 1024, "invalid number of priority groups"},
1139                 {0, 1024, "invalid initial priority group number"},
1140         };
1141
1142         int r;
1143         struct multipath *m;
1144         struct dm_arg_set as;
1145         unsigned pg_count = 0;
1146         unsigned next_pg_num;
1147         unsigned long flags;
1148
1149         as.argc = argc;
1150         as.argv = argv;
1151
1152         m = alloc_multipath(ti);
1153         if (!m) {
1154                 ti->error = "can't allocate multipath";
1155                 return -EINVAL;
1156         }
1157
1158         r = parse_features(&as, m);
1159         if (r)
1160                 goto bad;
1161
1162         r = alloc_multipath_stage2(ti, m);
1163         if (r)
1164                 goto bad;
1165
1166         r = parse_hw_handler(&as, m);
1167         if (r)
1168                 goto bad;
1169
1170         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1171         if (r)
1172                 goto bad;
1173
1174         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1175         if (r)
1176                 goto bad;
1177
1178         if ((!m->nr_priority_groups && next_pg_num) ||
1179             (m->nr_priority_groups && !next_pg_num)) {
1180                 ti->error = "invalid initial priority group";
1181                 r = -EINVAL;
1182                 goto bad;
1183         }
1184
1185         /* parse the priority groups */
1186         while (as.argc) {
1187                 struct priority_group *pg;
1188                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1189
1190                 pg = parse_priority_group(&as, m);
1191                 if (IS_ERR(pg)) {
1192                         r = PTR_ERR(pg);
1193                         goto bad;
1194                 }
1195
1196                 nr_valid_paths += pg->nr_pgpaths;
1197                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1198
1199                 list_add_tail(&pg->list, &m->priority_groups);
1200                 pg_count++;
1201                 pg->pg_num = pg_count;
1202                 if (!--next_pg_num)
1203                         m->next_pg = pg;
1204         }
1205
1206         if (pg_count != m->nr_priority_groups) {
1207                 ti->error = "priority group count mismatch";
1208                 r = -EINVAL;
1209                 goto bad;
1210         }
1211
1212         spin_lock_irqsave(&m->lock, flags);
1213         enable_nopath_timeout(m);
1214         spin_unlock_irqrestore(&m->lock, flags);
1215
1216         ti->num_flush_bios = 1;
1217         ti->num_discard_bios = 1;
1218         ti->num_write_same_bios = 1;
1219         ti->num_write_zeroes_bios = 1;
1220         if (m->queue_mode == DM_TYPE_BIO_BASED)
1221                 ti->per_io_data_size = multipath_per_bio_data_size();
1222         else
1223                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1224
1225         return 0;
1226
1227  bad:
1228         free_multipath(m);
1229         return r;
1230 }
1231
1232 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1233 {
1234         DEFINE_WAIT(wait);
1235
1236         while (1) {
1237                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1238
1239                 if (!atomic_read(&m->pg_init_in_progress))
1240                         break;
1241
1242                 io_schedule();
1243         }
1244         finish_wait(&m->pg_init_wait, &wait);
1245 }
1246
1247 static void flush_multipath_work(struct multipath *m)
1248 {
1249         if (m->hw_handler_name) {
1250                 set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1251                 smp_mb__after_atomic();
1252
1253                 if (atomic_read(&m->pg_init_in_progress))
1254                         flush_workqueue(kmpath_handlerd);
1255                 multipath_wait_for_pg_init_completion(m);
1256
1257                 clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1258                 smp_mb__after_atomic();
1259         }
1260
1261         if (m->queue_mode == DM_TYPE_BIO_BASED)
1262                 flush_work(&m->process_queued_bios);
1263         flush_work(&m->trigger_event);
1264 }
1265
1266 static void multipath_dtr(struct dm_target *ti)
1267 {
1268         struct multipath *m = ti->private;
1269
1270         disable_nopath_timeout(m);
1271         flush_multipath_work(m);
1272         free_multipath(m);
1273 }
1274
1275 /*
1276  * Take a path out of use.
1277  */
1278 static int fail_path(struct pgpath *pgpath)
1279 {
1280         unsigned long flags;
1281         struct multipath *m = pgpath->pg->m;
1282
1283         spin_lock_irqsave(&m->lock, flags);
1284
1285         if (!pgpath->is_active)
1286                 goto out;
1287
1288         DMWARN("%s: Failing path %s.",
1289                dm_device_name(dm_table_get_md(m->ti->table)),
1290                pgpath->path.dev->name);
1291
1292         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1293         pgpath->is_active = false;
1294         pgpath->fail_count++;
1295
1296         atomic_dec(&m->nr_valid_paths);
1297
1298         if (pgpath == m->current_pgpath)
1299                 m->current_pgpath = NULL;
1300
1301         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1302                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1303
1304         schedule_work(&m->trigger_event);
1305
1306         enable_nopath_timeout(m);
1307
1308 out:
1309         spin_unlock_irqrestore(&m->lock, flags);
1310
1311         return 0;
1312 }
1313
1314 /*
1315  * Reinstate a previously-failed path
1316  */
1317 static int reinstate_path(struct pgpath *pgpath)
1318 {
1319         int r = 0, run_queue = 0;
1320         unsigned long flags;
1321         struct multipath *m = pgpath->pg->m;
1322         unsigned nr_valid_paths;
1323
1324         spin_lock_irqsave(&m->lock, flags);
1325
1326         if (pgpath->is_active)
1327                 goto out;
1328
1329         DMWARN("%s: Reinstating path %s.",
1330                dm_device_name(dm_table_get_md(m->ti->table)),
1331                pgpath->path.dev->name);
1332
1333         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1334         if (r)
1335                 goto out;
1336
1337         pgpath->is_active = true;
1338
1339         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1340         if (nr_valid_paths == 1) {
1341                 m->current_pgpath = NULL;
1342                 run_queue = 1;
1343         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1344                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1345                         atomic_inc(&m->pg_init_in_progress);
1346         }
1347
1348         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1349                        pgpath->path.dev->name, nr_valid_paths);
1350
1351         schedule_work(&m->trigger_event);
1352
1353 out:
1354         spin_unlock_irqrestore(&m->lock, flags);
1355         if (run_queue) {
1356                 dm_table_run_md_queue_async(m->ti->table);
1357                 process_queued_io_list(m);
1358         }
1359
1360         if (pgpath->is_active)
1361                 disable_nopath_timeout(m);
1362
1363         return r;
1364 }
1365
1366 /*
1367  * Fail or reinstate all paths that match the provided struct dm_dev.
1368  */
1369 static int action_dev(struct multipath *m, struct dm_dev *dev,
1370                       action_fn action)
1371 {
1372         int r = -EINVAL;
1373         struct pgpath *pgpath;
1374         struct priority_group *pg;
1375
1376         list_for_each_entry(pg, &m->priority_groups, list) {
1377                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1378                         if (pgpath->path.dev == dev)
1379                                 r = action(pgpath);
1380                 }
1381         }
1382
1383         return r;
1384 }
1385
1386 /*
1387  * Temporarily try to avoid having to use the specified PG
1388  */
1389 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1390                       bool bypassed)
1391 {
1392         unsigned long flags;
1393
1394         spin_lock_irqsave(&m->lock, flags);
1395
1396         pg->bypassed = bypassed;
1397         m->current_pgpath = NULL;
1398         m->current_pg = NULL;
1399
1400         spin_unlock_irqrestore(&m->lock, flags);
1401
1402         schedule_work(&m->trigger_event);
1403 }
1404
1405 /*
1406  * Switch to using the specified PG from the next I/O that gets mapped
1407  */
1408 static int switch_pg_num(struct multipath *m, const char *pgstr)
1409 {
1410         struct priority_group *pg;
1411         unsigned pgnum;
1412         unsigned long flags;
1413         char dummy;
1414
1415         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1416             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1417                 DMWARN("invalid PG number supplied to switch_pg_num");
1418                 return -EINVAL;
1419         }
1420
1421         spin_lock_irqsave(&m->lock, flags);
1422         list_for_each_entry(pg, &m->priority_groups, list) {
1423                 pg->bypassed = false;
1424                 if (--pgnum)
1425                         continue;
1426
1427                 m->current_pgpath = NULL;
1428                 m->current_pg = NULL;
1429                 m->next_pg = pg;
1430         }
1431         spin_unlock_irqrestore(&m->lock, flags);
1432
1433         schedule_work(&m->trigger_event);
1434         return 0;
1435 }
1436
1437 /*
1438  * Set/clear bypassed status of a PG.
1439  * PGs are numbered upwards from 1 in the order they were declared.
1440  */
1441 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1442 {
1443         struct priority_group *pg;
1444         unsigned pgnum;
1445         char dummy;
1446
1447         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1448             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1449                 DMWARN("invalid PG number supplied to bypass_pg");
1450                 return -EINVAL;
1451         }
1452
1453         list_for_each_entry(pg, &m->priority_groups, list) {
1454                 if (!--pgnum)
1455                         break;
1456         }
1457
1458         bypass_pg(m, pg, bypassed);
1459         return 0;
1460 }
1461
1462 /*
1463  * Should we retry pg_init immediately?
1464  */
1465 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1466 {
1467         unsigned long flags;
1468         bool limit_reached = false;
1469
1470         spin_lock_irqsave(&m->lock, flags);
1471
1472         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1473             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1474                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1475         else
1476                 limit_reached = true;
1477
1478         spin_unlock_irqrestore(&m->lock, flags);
1479
1480         return limit_reached;
1481 }
1482
1483 static void pg_init_done(void *data, int errors)
1484 {
1485         struct pgpath *pgpath = data;
1486         struct priority_group *pg = pgpath->pg;
1487         struct multipath *m = pg->m;
1488         unsigned long flags;
1489         bool delay_retry = false;
1490
1491         /* device or driver problems */
1492         switch (errors) {
1493         case SCSI_DH_OK:
1494                 break;
1495         case SCSI_DH_NOSYS:
1496                 if (!m->hw_handler_name) {
1497                         errors = 0;
1498                         break;
1499                 }
1500                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1501                       "Error %d.", m->hw_handler_name, errors);
1502                 /*
1503                  * Fail path for now, so we do not ping pong
1504                  */
1505                 fail_path(pgpath);
1506                 break;
1507         case SCSI_DH_DEV_TEMP_BUSY:
1508                 /*
1509                  * Probably doing something like FW upgrade on the
1510                  * controller so try the other pg.
1511                  */
1512                 bypass_pg(m, pg, true);
1513                 break;
1514         case SCSI_DH_RETRY:
1515                 /* Wait before retrying. */
1516                 delay_retry = true;
1517                 /* fall through */
1518         case SCSI_DH_IMM_RETRY:
1519         case SCSI_DH_RES_TEMP_UNAVAIL:
1520                 if (pg_init_limit_reached(m, pgpath))
1521                         fail_path(pgpath);
1522                 errors = 0;
1523                 break;
1524         case SCSI_DH_DEV_OFFLINED:
1525         default:
1526                 /*
1527                  * We probably do not want to fail the path for a device
1528                  * error, but this is what the old dm did. In future
1529                  * patches we can do more advanced handling.
1530                  */
1531                 fail_path(pgpath);
1532         }
1533
1534         spin_lock_irqsave(&m->lock, flags);
1535         if (errors) {
1536                 if (pgpath == m->current_pgpath) {
1537                         DMERR("Could not failover device. Error %d.", errors);
1538                         m->current_pgpath = NULL;
1539                         m->current_pg = NULL;
1540                 }
1541         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1542                 pg->bypassed = false;
1543
1544         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1545                 /* Activations of other paths are still on going */
1546                 goto out;
1547
1548         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1549                 if (delay_retry)
1550                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1551                 else
1552                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1553
1554                 if (__pg_init_all_paths(m))
1555                         goto out;
1556         }
1557         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1558
1559         process_queued_io_list(m);
1560
1561         /*
1562          * Wake up any thread waiting to suspend.
1563          */
1564         wake_up(&m->pg_init_wait);
1565
1566 out:
1567         spin_unlock_irqrestore(&m->lock, flags);
1568 }
1569
1570 static void activate_or_offline_path(struct pgpath *pgpath)
1571 {
1572         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1573
1574         if (pgpath->is_active && !blk_queue_dying(q))
1575                 scsi_dh_activate(q, pg_init_done, pgpath);
1576         else
1577                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1578 }
1579
1580 static void activate_path_work(struct work_struct *work)
1581 {
1582         struct pgpath *pgpath =
1583                 container_of(work, struct pgpath, activate_path.work);
1584
1585         activate_or_offline_path(pgpath);
1586 }
1587
1588 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1589                             blk_status_t error, union map_info *map_context)
1590 {
1591         struct dm_mpath_io *mpio = get_mpio(map_context);
1592         struct pgpath *pgpath = mpio->pgpath;
1593         int r = DM_ENDIO_DONE;
1594
1595         /*
1596          * We don't queue any clone request inside the multipath target
1597          * during end I/O handling, since those clone requests don't have
1598          * bio clones.  If we queue them inside the multipath target,
1599          * we need to make bio clones, that requires memory allocation.
1600          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1601          *  don't have bio clones.)
1602          * Instead of queueing the clone request here, we queue the original
1603          * request into dm core, which will remake a clone request and
1604          * clone bios for it and resubmit it later.
1605          */
1606         if (error && blk_path_error(error)) {
1607                 struct multipath *m = ti->private;
1608
1609                 if (error == BLK_STS_RESOURCE)
1610                         r = DM_ENDIO_DELAY_REQUEUE;
1611                 else
1612                         r = DM_ENDIO_REQUEUE;
1613
1614                 if (pgpath)
1615                         fail_path(pgpath);
1616
1617                 if (atomic_read(&m->nr_valid_paths) == 0 &&
1618                     !must_push_back_rq(m)) {
1619                         if (error == BLK_STS_IOERR)
1620                                 dm_report_EIO(m);
1621                         /* complete with the original error */
1622                         r = DM_ENDIO_DONE;
1623                 }
1624         }
1625
1626         if (pgpath) {
1627                 struct path_selector *ps = &pgpath->pg->ps;
1628
1629                 if (ps->type->end_io)
1630                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1631                                          clone->io_start_time_ns);
1632         }
1633
1634         return r;
1635 }
1636
1637 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1638                                 blk_status_t *error)
1639 {
1640         struct multipath *m = ti->private;
1641         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1642         struct pgpath *pgpath = mpio->pgpath;
1643         unsigned long flags;
1644         int r = DM_ENDIO_DONE;
1645
1646         if (!*error || !blk_path_error(*error))
1647                 goto done;
1648
1649         if (pgpath)
1650                 fail_path(pgpath);
1651
1652         if (atomic_read(&m->nr_valid_paths) == 0 &&
1653             !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1654                 if (__must_push_back(m)) {
1655                         r = DM_ENDIO_REQUEUE;
1656                 } else {
1657                         dm_report_EIO(m);
1658                         *error = BLK_STS_IOERR;
1659                 }
1660                 goto done;
1661         }
1662
1663         spin_lock_irqsave(&m->lock, flags);
1664         bio_list_add(&m->queued_bios, clone);
1665         spin_unlock_irqrestore(&m->lock, flags);
1666         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1667                 queue_work(kmultipathd, &m->process_queued_bios);
1668
1669         r = DM_ENDIO_INCOMPLETE;
1670 done:
1671         if (pgpath) {
1672                 struct path_selector *ps = &pgpath->pg->ps;
1673
1674                 if (ps->type->end_io)
1675                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1676                                          dm_start_time_ns_from_clone(clone));
1677         }
1678
1679         return r;
1680 }
1681
1682 /*
1683  * Suspend with flush can't complete until all the I/O is processed
1684  * so if the last path fails we must error any remaining I/O.
1685  * - Note that if the freeze_bdev fails while suspending, the
1686  *   queue_if_no_path state is lost - userspace should reset it.
1687  * Otherwise, during noflush suspend, queue_if_no_path will not change.
1688  */
1689 static void multipath_presuspend(struct dm_target *ti)
1690 {
1691         struct multipath *m = ti->private;
1692
1693         /* FIXME: bio-based shouldn't need to always disable queue_if_no_path */
1694         if (m->queue_mode == DM_TYPE_BIO_BASED || !dm_noflush_suspending(m->ti))
1695                 queue_if_no_path(m, false, true, __func__);
1696 }
1697
1698 static void multipath_postsuspend(struct dm_target *ti)
1699 {
1700         struct multipath *m = ti->private;
1701
1702         mutex_lock(&m->work_mutex);
1703         flush_multipath_work(m);
1704         mutex_unlock(&m->work_mutex);
1705 }
1706
1707 /*
1708  * Restore the queue_if_no_path setting.
1709  */
1710 static void multipath_resume(struct dm_target *ti)
1711 {
1712         struct multipath *m = ti->private;
1713         unsigned long flags;
1714
1715         spin_lock_irqsave(&m->lock, flags);
1716         if (test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) {
1717                 set_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1718                 clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
1719         }
1720
1721         DMDEBUG("%s: %s finished; QIFNP = %d; SQIFNP = %d",
1722                 dm_device_name(dm_table_get_md(m->ti->table)), __func__,
1723                 test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
1724                 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1725
1726         spin_unlock_irqrestore(&m->lock, flags);
1727 }
1728
1729 /*
1730  * Info output has the following format:
1731  * num_multipath_feature_args [multipath_feature_args]*
1732  * num_handler_status_args [handler_status_args]*
1733  * num_groups init_group_number
1734  *            [A|D|E num_ps_status_args [ps_status_args]*
1735  *             num_paths num_selector_args
1736  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1737  *
1738  * Table output has the following format (identical to the constructor string):
1739  * num_feature_args [features_args]*
1740  * num_handler_args hw_handler [hw_handler_args]*
1741  * num_groups init_group_number
1742  *     [priority selector-name num_ps_args [ps_args]*
1743  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1744  */
1745 static void multipath_status(struct dm_target *ti, status_type_t type,
1746                              unsigned status_flags, char *result, unsigned maxlen)
1747 {
1748         int sz = 0;
1749         unsigned long flags;
1750         struct multipath *m = ti->private;
1751         struct priority_group *pg;
1752         struct pgpath *p;
1753         unsigned pg_num;
1754         char state;
1755
1756         spin_lock_irqsave(&m->lock, flags);
1757
1758         /* Features */
1759         if (type == STATUSTYPE_INFO)
1760                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1761                        atomic_read(&m->pg_init_count));
1762         else {
1763                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1764                               (m->pg_init_retries > 0) * 2 +
1765                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1766                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1767                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1768
1769                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1770                         DMEMIT("queue_if_no_path ");
1771                 if (m->pg_init_retries)
1772                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1773                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1774                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1775                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1776                         DMEMIT("retain_attached_hw_handler ");
1777                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1778                         switch(m->queue_mode) {
1779                         case DM_TYPE_BIO_BASED:
1780                                 DMEMIT("queue_mode bio ");
1781                                 break;
1782                         default:
1783                                 WARN_ON_ONCE(true);
1784                                 break;
1785                         }
1786                 }
1787         }
1788
1789         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1790                 DMEMIT("0 ");
1791         else
1792                 DMEMIT("1 %s ", m->hw_handler_name);
1793
1794         DMEMIT("%u ", m->nr_priority_groups);
1795
1796         if (m->next_pg)
1797                 pg_num = m->next_pg->pg_num;
1798         else if (m->current_pg)
1799                 pg_num = m->current_pg->pg_num;
1800         else
1801                 pg_num = (m->nr_priority_groups ? 1 : 0);
1802
1803         DMEMIT("%u ", pg_num);
1804
1805         switch (type) {
1806         case STATUSTYPE_INFO:
1807                 list_for_each_entry(pg, &m->priority_groups, list) {
1808                         if (pg->bypassed)
1809                                 state = 'D';    /* Disabled */
1810                         else if (pg == m->current_pg)
1811                                 state = 'A';    /* Currently Active */
1812                         else
1813                                 state = 'E';    /* Enabled */
1814
1815                         DMEMIT("%c ", state);
1816
1817                         if (pg->ps.type->status)
1818                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1819                                                           result + sz,
1820                                                           maxlen - sz);
1821                         else
1822                                 DMEMIT("0 ");
1823
1824                         DMEMIT("%u %u ", pg->nr_pgpaths,
1825                                pg->ps.type->info_args);
1826
1827                         list_for_each_entry(p, &pg->pgpaths, list) {
1828                                 DMEMIT("%s %s %u ", p->path.dev->name,
1829                                        p->is_active ? "A" : "F",
1830                                        p->fail_count);
1831                                 if (pg->ps.type->status)
1832                                         sz += pg->ps.type->status(&pg->ps,
1833                                               &p->path, type, result + sz,
1834                                               maxlen - sz);
1835                         }
1836                 }
1837                 break;
1838
1839         case STATUSTYPE_TABLE:
1840                 list_for_each_entry(pg, &m->priority_groups, list) {
1841                         DMEMIT("%s ", pg->ps.type->name);
1842
1843                         if (pg->ps.type->status)
1844                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1845                                                           result + sz,
1846                                                           maxlen - sz);
1847                         else
1848                                 DMEMIT("0 ");
1849
1850                         DMEMIT("%u %u ", pg->nr_pgpaths,
1851                                pg->ps.type->table_args);
1852
1853                         list_for_each_entry(p, &pg->pgpaths, list) {
1854                                 DMEMIT("%s ", p->path.dev->name);
1855                                 if (pg->ps.type->status)
1856                                         sz += pg->ps.type->status(&pg->ps,
1857                                               &p->path, type, result + sz,
1858                                               maxlen - sz);
1859                         }
1860                 }
1861                 break;
1862         }
1863
1864         spin_unlock_irqrestore(&m->lock, flags);
1865 }
1866
1867 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv,
1868                              char *result, unsigned maxlen)
1869 {
1870         int r = -EINVAL;
1871         struct dm_dev *dev;
1872         struct multipath *m = ti->private;
1873         action_fn action;
1874         unsigned long flags;
1875
1876         mutex_lock(&m->work_mutex);
1877
1878         if (dm_suspended(ti)) {
1879                 r = -EBUSY;
1880                 goto out;
1881         }
1882
1883         if (argc == 1) {
1884                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1885                         r = queue_if_no_path(m, true, false, __func__);
1886                         spin_lock_irqsave(&m->lock, flags);
1887                         enable_nopath_timeout(m);
1888                         spin_unlock_irqrestore(&m->lock, flags);
1889                         goto out;
1890                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1891                         r = queue_if_no_path(m, false, false, __func__);
1892                         disable_nopath_timeout(m);
1893                         goto out;
1894                 }
1895         }
1896
1897         if (argc != 2) {
1898                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1899                 goto out;
1900         }
1901
1902         if (!strcasecmp(argv[0], "disable_group")) {
1903                 r = bypass_pg_num(m, argv[1], true);
1904                 goto out;
1905         } else if (!strcasecmp(argv[0], "enable_group")) {
1906                 r = bypass_pg_num(m, argv[1], false);
1907                 goto out;
1908         } else if (!strcasecmp(argv[0], "switch_group")) {
1909                 r = switch_pg_num(m, argv[1]);
1910                 goto out;
1911         } else if (!strcasecmp(argv[0], "reinstate_path"))
1912                 action = reinstate_path;
1913         else if (!strcasecmp(argv[0], "fail_path"))
1914                 action = fail_path;
1915         else {
1916                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1917                 goto out;
1918         }
1919
1920         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1921         if (r) {
1922                 DMWARN("message: error getting device %s",
1923                        argv[1]);
1924                 goto out;
1925         }
1926
1927         r = action_dev(m, dev, action);
1928
1929         dm_put_device(ti, dev);
1930
1931 out:
1932         mutex_unlock(&m->work_mutex);
1933         return r;
1934 }
1935
1936 static int multipath_prepare_ioctl(struct dm_target *ti,
1937                                    struct block_device **bdev)
1938 {
1939         struct multipath *m = ti->private;
1940         struct pgpath *current_pgpath;
1941         int r;
1942
1943         current_pgpath = READ_ONCE(m->current_pgpath);
1944         if (!current_pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
1945                 current_pgpath = choose_pgpath(m, 0);
1946
1947         if (current_pgpath) {
1948                 if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1949                         *bdev = current_pgpath->path.dev->bdev;
1950                         r = 0;
1951                 } else {
1952                         /* pg_init has not started or completed */
1953                         r = -ENOTCONN;
1954                 }
1955         } else {
1956                 /* No path is available */
1957                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1958                         r = -ENOTCONN;
1959                 else
1960                         r = -EIO;
1961         }
1962
1963         if (r == -ENOTCONN) {
1964                 if (!READ_ONCE(m->current_pg)) {
1965                         /* Path status changed, redo selection */
1966                         (void) choose_pgpath(m, 0);
1967                 }
1968                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1969                         pg_init_all_paths(m);
1970                 dm_table_run_md_queue_async(m->ti->table);
1971                 process_queued_io_list(m);
1972         }
1973
1974         /*
1975          * Only pass ioctls through if the device sizes match exactly.
1976          */
1977         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1978                 return 1;
1979         return r;
1980 }
1981
1982 static int multipath_iterate_devices(struct dm_target *ti,
1983                                      iterate_devices_callout_fn fn, void *data)
1984 {
1985         struct multipath *m = ti->private;
1986         struct priority_group *pg;
1987         struct pgpath *p;
1988         int ret = 0;
1989
1990         list_for_each_entry(pg, &m->priority_groups, list) {
1991                 list_for_each_entry(p, &pg->pgpaths, list) {
1992                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1993                         if (ret)
1994                                 goto out;
1995                 }
1996         }
1997
1998 out:
1999         return ret;
2000 }
2001
2002 static int pgpath_busy(struct pgpath *pgpath)
2003 {
2004         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
2005
2006         return blk_lld_busy(q);
2007 }
2008
2009 /*
2010  * We return "busy", only when we can map I/Os but underlying devices
2011  * are busy (so even if we map I/Os now, the I/Os will wait on
2012  * the underlying queue).
2013  * In other words, if we want to kill I/Os or queue them inside us
2014  * due to map unavailability, we don't return "busy".  Otherwise,
2015  * dm core won't give us the I/Os and we can't do what we want.
2016  */
2017 static int multipath_busy(struct dm_target *ti)
2018 {
2019         bool busy = false, has_active = false;
2020         struct multipath *m = ti->private;
2021         struct priority_group *pg, *next_pg;
2022         struct pgpath *pgpath;
2023
2024         /* pg_init in progress */
2025         if (atomic_read(&m->pg_init_in_progress))
2026                 return true;
2027
2028         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
2029         if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
2030                 return (m->queue_mode != DM_TYPE_REQUEST_BASED);
2031
2032         /* Guess which priority_group will be used at next mapping time */
2033         pg = READ_ONCE(m->current_pg);
2034         next_pg = READ_ONCE(m->next_pg);
2035         if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
2036                 pg = next_pg;
2037
2038         if (!pg) {
2039                 /*
2040                  * We don't know which pg will be used at next mapping time.
2041                  * We don't call choose_pgpath() here to avoid to trigger
2042                  * pg_init just by busy checking.
2043                  * So we don't know whether underlying devices we will be using
2044                  * at next mapping time are busy or not. Just try mapping.
2045                  */
2046                 return busy;
2047         }
2048
2049         /*
2050          * If there is one non-busy active path at least, the path selector
2051          * will be able to select it. So we consider such a pg as not busy.
2052          */
2053         busy = true;
2054         list_for_each_entry(pgpath, &pg->pgpaths, list) {
2055                 if (pgpath->is_active) {
2056                         has_active = true;
2057                         if (!pgpath_busy(pgpath)) {
2058                                 busy = false;
2059                                 break;
2060                         }
2061                 }
2062         }
2063
2064         if (!has_active) {
2065                 /*
2066                  * No active path in this pg, so this pg won't be used and
2067                  * the current_pg will be changed at next mapping time.
2068                  * We need to try mapping to determine it.
2069                  */
2070                 busy = false;
2071         }
2072
2073         return busy;
2074 }
2075
2076 /*-----------------------------------------------------------------
2077  * Module setup
2078  *---------------------------------------------------------------*/
2079 static struct target_type multipath_target = {
2080         .name = "multipath",
2081         .version = {1, 14, 0},
2082         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE |
2083                     DM_TARGET_PASSES_INTEGRITY,
2084         .module = THIS_MODULE,
2085         .ctr = multipath_ctr,
2086         .dtr = multipath_dtr,
2087         .clone_and_map_rq = multipath_clone_and_map,
2088         .release_clone_rq = multipath_release_clone,
2089         .rq_end_io = multipath_end_io,
2090         .map = multipath_map_bio,
2091         .end_io = multipath_end_io_bio,
2092         .presuspend = multipath_presuspend,
2093         .postsuspend = multipath_postsuspend,
2094         .resume = multipath_resume,
2095         .status = multipath_status,
2096         .message = multipath_message,
2097         .prepare_ioctl = multipath_prepare_ioctl,
2098         .iterate_devices = multipath_iterate_devices,
2099         .busy = multipath_busy,
2100 };
2101
2102 static int __init dm_multipath_init(void)
2103 {
2104         int r;
2105
2106         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2107         if (!kmultipathd) {
2108                 DMERR("failed to create workqueue kmpathd");
2109                 r = -ENOMEM;
2110                 goto bad_alloc_kmultipathd;
2111         }
2112
2113         /*
2114          * A separate workqueue is used to handle the device handlers
2115          * to avoid overloading existing workqueue. Overloading the
2116          * old workqueue would also create a bottleneck in the
2117          * path of the storage hardware device activation.
2118          */
2119         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2120                                                   WQ_MEM_RECLAIM);
2121         if (!kmpath_handlerd) {
2122                 DMERR("failed to create workqueue kmpath_handlerd");
2123                 r = -ENOMEM;
2124                 goto bad_alloc_kmpath_handlerd;
2125         }
2126
2127         r = dm_register_target(&multipath_target);
2128         if (r < 0) {
2129                 DMERR("request-based register failed %d", r);
2130                 r = -EINVAL;
2131                 goto bad_register_target;
2132         }
2133
2134         return 0;
2135
2136 bad_register_target:
2137         destroy_workqueue(kmpath_handlerd);
2138 bad_alloc_kmpath_handlerd:
2139         destroy_workqueue(kmultipathd);
2140 bad_alloc_kmultipathd:
2141         return r;
2142 }
2143
2144 static void __exit dm_multipath_exit(void)
2145 {
2146         destroy_workqueue(kmpath_handlerd);
2147         destroy_workqueue(kmultipathd);
2148
2149         dm_unregister_target(&multipath_target);
2150 }
2151
2152 module_init(dm_multipath_init);
2153 module_exit(dm_multipath_exit);
2154
2155 module_param_named(queue_if_no_path_timeout_secs,
2156                    queue_if_no_path_timeout_secs, ulong, S_IRUGO | S_IWUSR);
2157 MODULE_PARM_DESC(queue_if_no_path_timeout_secs, "No available paths queue IO timeout in seconds");
2158
2159 MODULE_DESCRIPTION(DM_NAME " multipath target");
2160 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2161 MODULE_LICENSE("GPL");