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 static bool mpath_double_check_test_bit(int MPATHF_bit, struct multipath *m)
 132 {
 133         bool r = test_bit(MPATHF_bit, &m->flags);
 134
 135         if (r) {
 136                 unsigned long flags;
 137                 spin_lock_irqsave(&m->lock, flags);
 138                 r = test_bit(MPATHF_bit, &m->flags);
 139                 spin_unlock_irqrestore(&m->lock, flags);
 140         }
 141
 142         return r;
 143 }
 144
 145 /*-----------------------------------------------
 146  * Allocation routines
 147  *-----------------------------------------------*/
 148
 149 static struct pgpath *alloc_pgpath(void)
 150 {
 151         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 152
 153         if (!pgpath)
 154                 return NULL;
 155
 156         pgpath->is_active = true;
 157
 158         return pgpath;
 159 }
 160
 161 static void free_pgpath(struct pgpath *pgpath)
 162 {
 163         kfree(pgpath);
 164 }
 165
 166 static struct priority_group *alloc_priority_group(void)
 167 {
 168         struct priority_group *pg;
 169
 170         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 171
 172         if (pg)
 173                 INIT_LIST_HEAD(&pg->pgpaths);
 174
 175         return pg;
 176 }
 177
 178 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 179 {
 180         struct pgpath *pgpath, *tmp;
 181
 182         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 183                 list_del(&pgpath->list);
 184                 dm_put_device(ti, pgpath->path.dev);
 185                 free_pgpath(pgpath);
 186         }
 187 }
 188
 189 static void free_priority_group(struct priority_group *pg,
 190                                 struct dm_target *ti)
 191 {
 192         struct path_selector *ps = &pg->ps;
 193
 194         if (ps->type) {
 195                 ps->type->destroy(ps);
 196                 dm_put_path_selector(ps->type);
 197         }
 198
 199         free_pgpaths(&pg->pgpaths, ti);
 200         kfree(pg);
 201 }
 202
 203 static struct multipath *alloc_multipath(struct dm_target *ti)
 204 {
 205         struct multipath *m;
 206
 207         m = kzalloc(sizeof(*m), GFP_KERNEL);
 208         if (m) {
 209                 INIT_LIST_HEAD(&m->priority_groups);
 210                 spin_lock_init(&m->lock);
 211                 atomic_set(&m->nr_valid_paths, 0);
 212                 INIT_WORK(&m->trigger_event, trigger_event);
 213                 mutex_init(&m->work_mutex);
 214
 215                 m->queue_mode = DM_TYPE_NONE;
 216
 217                 m->ti = ti;
 218                 ti->private = m;
 219
 220                 timer_setup(&m->nopath_timer, queue_if_no_path_timeout_work, 0);
 221         }
 222
 223         return m;
 224 }
 225
 226 static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
 227 {
 228         if (m->queue_mode == DM_TYPE_NONE) {
 229                 m->queue_mode = DM_TYPE_REQUEST_BASED;
 230         } else if (m->queue_mode == DM_TYPE_BIO_BASED) {
 231                 INIT_WORK(&m->process_queued_bios, process_queued_bios);
 232                 /*
 233                  * bio-based doesn't support any direct scsi_dh management;
 234                  * it just discovers if a scsi_dh is attached.
 235                  */
 236                 set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 237         }
 238
 239         dm_table_set_type(ti->table, m->queue_mode);
 240
 241         /*
 242          * Init fields that are only used when a scsi_dh is attached
 243          * - must do this unconditionally (really doesn't hurt non-SCSI uses)
 244          */
 245         set_bit(MPATHF_QUEUE_IO, &m->flags);
 246         atomic_set(&m->pg_init_in_progress, 0);
 247         atomic_set(&m->pg_init_count, 0);
 248         m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 249         init_waitqueue_head(&m->pg_init_wait);
 250
 251         return 0;
 252 }
 253
 254 static void free_multipath(struct multipath *m)
 255 {
 256         struct priority_group *pg, *tmp;
 257
 258         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 259                 list_del(&pg->list);
 260                 free_priority_group(pg, m->ti);
 261         }
 262
 263         kfree(m->hw_handler_name);
 264         kfree(m->hw_handler_params);
 265         mutex_destroy(&m->work_mutex);
 266         kfree(m);
 267 }
 268
 269 static struct dm_mpath_io *get_mpio(union map_info *info)
 270 {
 271         return info->ptr;
 272 }
 273
 274 static size_t multipath_per_bio_data_size(void)
 275 {
 276         return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
 277 }
 278
 279 static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
 280 {
 281         return dm_per_bio_data(bio, multipath_per_bio_data_size());
 282 }
 283
 284 static struct dm_bio_details *get_bio_details_from_mpio(struct dm_mpath_io *mpio)
 285 {
 286         /* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
 287         void *bio_details = mpio + 1;
 288         return bio_details;
 289 }
 290
 291 static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p)
 292 {
 293         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 294         struct dm_bio_details *bio_details = get_bio_details_from_mpio(mpio);
 295
 296         mpio->nr_bytes = bio->bi_iter.bi_size;
 297         mpio->pgpath = NULL;
 298         *mpio_p = mpio;
 299
 300         dm_bio_record(bio_details, bio);
 301 }
 302
 303 /*-----------------------------------------------
 304  * Path selection
 305  *-----------------------------------------------*/
 306
 307 static int __pg_init_all_paths(struct multipath *m)
 308 {
 309         struct pgpath *pgpath;
 310         unsigned long pg_init_delay = 0;
 311
 312         lockdep_assert_held(&m->lock);
 313
 314         if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
 315                 return 0;
 316
 317         atomic_inc(&m->pg_init_count);
 318         clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 319
 320         /* Check here to reset pg_init_required */
 321         if (!m->current_pg)
 322                 return 0;
 323
 324         if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
 325                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 326                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 327         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 328                 /* Skip failed paths */
 329                 if (!pgpath->is_active)
 330                         continue;
 331                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 332                                        pg_init_delay))
 333                         atomic_inc(&m->pg_init_in_progress);
 334         }
 335         return atomic_read(&m->pg_init_in_progress);
 336 }
 337
 338 static int pg_init_all_paths(struct multipath *m)
 339 {
 340         int ret;
 341         unsigned long flags;
 342
 343         spin_lock_irqsave(&m->lock, flags);
 344         ret = __pg_init_all_paths(m);
 345         spin_unlock_irqrestore(&m->lock, flags);
 346
 347         return ret;
 348 }
 349
 350 static void __switch_pg(struct multipath *m, struct priority_group *pg)
 351 {
 352         lockdep_assert_held(&m->lock);
 353
 354         m->current_pg = pg;
 355
 356         /* Must we initialise the PG first, and queue I/O till it's ready? */
 357         if (m->hw_handler_name) {
 358                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 359                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 360         } else {
 361                 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 362                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 363         }
 364
 365         atomic_set(&m->pg_init_count, 0);
 366 }
 367
 368 static struct pgpath *choose_path_in_pg(struct multipath *m,
 369                                         struct priority_group *pg,
 370                                         size_t nr_bytes)
 371 {
 372         unsigned long flags;
 373         struct dm_path *path;
 374         struct pgpath *pgpath;
 375
 376         path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 377         if (!path)
 378                 return ERR_PTR(-ENXIO);
 379
 380         pgpath = path_to_pgpath(path);
 381
 382         if (unlikely(READ_ONCE(m->current_pg) != pg)) {
 383                 /* Only update current_pgpath if pg changed */
 384                 spin_lock_irqsave(&m->lock, flags);
 385                 m->current_pgpath = pgpath;
 386                 __switch_pg(m, pg);
 387                 spin_unlock_irqrestore(&m->lock, flags);
 388         }
 389
 390         return pgpath;
 391 }
 392
 393 static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 394 {
 395         unsigned long flags;
 396         struct priority_group *pg;
 397         struct pgpath *pgpath;
 398         unsigned bypassed = 1;
 399
 400         if (!atomic_read(&m->nr_valid_paths)) {
 401                 spin_lock_irqsave(&m->lock, flags);
 402                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 403                 spin_unlock_irqrestore(&m->lock, flags);
 404                 goto failed;
 405         }
 406
 407         /* Were we instructed to switch PG? */
 408         if (READ_ONCE(m->next_pg)) {
 409                 spin_lock_irqsave(&m->lock, flags);
 410                 pg = m->next_pg;
 411                 if (!pg) {
 412                         spin_unlock_irqrestore(&m->lock, flags);
 413                         goto check_current_pg;
 414                 }
 415                 m->next_pg = NULL;
 416                 spin_unlock_irqrestore(&m->lock, flags);
 417                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 418                 if (!IS_ERR_OR_NULL(pgpath))
 419                         return pgpath;
 420         }
 421
 422         /* Don't change PG until it has no remaining paths */
 423 check_current_pg:
 424         pg = READ_ONCE(m->current_pg);
 425         if (pg) {
 426                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 427                 if (!IS_ERR_OR_NULL(pgpath))
 428                         return pgpath;
 429         }
 430
 431         /*
 432          * Loop through priority groups until we find a valid path.
 433          * First time we skip PGs marked 'bypassed'.
 434          * Second time we only try the ones we skipped, but set
 435          * pg_init_delay_retry so we do not hammer controllers.
 436          */
 437         do {
 438                 list_for_each_entry(pg, &m->priority_groups, list) {
 439                         if (pg->bypassed == !!bypassed)
 440                                 continue;
 441                         pgpath = choose_path_in_pg(m, pg, nr_bytes);
 442                         if (!IS_ERR_OR_NULL(pgpath)) {
 443                                 if (!bypassed) {
 444                                         spin_lock_irqsave(&m->lock, flags);
 445                                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 446                                         spin_unlock_irqrestore(&m->lock, flags);
 447                                 }
 448                                 return pgpath;
 449                         }
 450                 }
 451         } while (bypassed--);
 452
 453 failed:
 454         spin_lock_irqsave(&m->lock, flags);
 455         m->current_pgpath = NULL;
 456         m->current_pg = NULL;
 457         spin_unlock_irqrestore(&m->lock, flags);
 458
 459         return NULL;
 460 }
 461
 462 /*
 463  * dm_report_EIO() is a macro instead of a function to make pr_debug_ratelimited()
 464  * report the function name and line number of the function from which
 465  * it has been invoked.
 466  */
 467 #define dm_report_EIO(m)                                                \
 468 do {                                                                    \
 469         DMDEBUG_LIMIT("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d", \
 470                       dm_table_device_name((m)->ti->table),             \
 471                       test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),   \
 472                       test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags), \
 473                       dm_noflush_suspending((m)->ti));                  \
 474 } while (0)
 475
 476 /*
 477  * Check whether bios must be queued in the device-mapper core rather
 478  * than here in the target.
 479  */
 480 static bool __must_push_back(struct multipath *m)
 481 {
 482         return dm_noflush_suspending(m->ti);
 483 }
 484
 485 static bool must_push_back_rq(struct multipath *m)
 486 {
 487         unsigned long flags;
 488         bool ret;
 489
 490         spin_lock_irqsave(&m->lock, flags);
 491         ret = (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) || __must_push_back(m));
 492         spin_unlock_irqrestore(&m->lock, flags);
 493
 494         return ret;
 495 }
 496
 497 /*
 498  * Map cloned requests (request-based multipath)
 499  */
 500 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 501                                    union map_info *map_context,
 502                                    struct request **__clone)
 503 {
 504         struct multipath *m = ti->private;
 505         size_t nr_bytes = blk_rq_bytes(rq);
 506         struct pgpath *pgpath;
 507         struct block_device *bdev;
 508         struct dm_mpath_io *mpio = get_mpio(map_context);
 509         struct request_queue *q;
 510         struct request *clone;
 511
 512         /* Do we need to select a new pgpath? */
 513         pgpath = READ_ONCE(m->current_pgpath);
 514         if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
 515                 pgpath = choose_pgpath(m, nr_bytes);
 516
 517         if (!pgpath) {
 518                 if (must_push_back_rq(m))
 519                         return DM_MAPIO_DELAY_REQUEUE;
 520                 dm_report_EIO(m);       /* Failed */
 521                 return DM_MAPIO_KILL;
 522         } else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
 523                    mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
 524                 pg_init_all_paths(m);
 525                 return DM_MAPIO_DELAY_REQUEUE;
 526         }
 527
 528         mpio->pgpath = pgpath;
 529         mpio->nr_bytes = nr_bytes;
 530
 531         bdev = pgpath->path.dev->bdev;
 532         q = bdev_get_queue(bdev);
 533         clone = blk_mq_alloc_request(q, rq->cmd_flags | REQ_NOMERGE,
 534                         BLK_MQ_REQ_NOWAIT);
 535         if (IS_ERR(clone)) {
 536                 /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 537                 if (blk_queue_dying(q)) {
 538                         atomic_inc(&m->pg_init_in_progress);
 539                         activate_or_offline_path(pgpath);
 540                         return DM_MAPIO_DELAY_REQUEUE;
 541                 }
 542
 543                 /*
 544                  * blk-mq's SCHED_RESTART can cover this requeue, so we
 545                  * needn't deal with it by DELAY_REQUEUE. More importantly,
 546                  * we have to return DM_MAPIO_REQUEUE so that blk-mq can
 547                  * get the queue busy feedback (via BLK_STS_RESOURCE),
 548                  * otherwise I/O merging can suffer.
 549                  */
 550                 return DM_MAPIO_REQUEUE;
 551         }
 552         clone->bio = clone->biotail = NULL;
 553         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 554         *__clone = clone;
 555
 556         if (pgpath->pg->ps.type->start_io)
 557                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 558                                               &pgpath->path,
 559                                               nr_bytes);
 560         return DM_MAPIO_REMAPPED;
 561 }
 562
 563 static void multipath_release_clone(struct request *clone,
 564                                     union map_info *map_context)
 565 {
 566         if (unlikely(map_context)) {
 567                 /*
 568                  * non-NULL map_context means caller is still map
 569                  * method; must undo multipath_clone_and_map()
 570                  */
 571                 struct dm_mpath_io *mpio = get_mpio(map_context);
 572                 struct pgpath *pgpath = mpio->pgpath;
 573
 574                 if (pgpath && pgpath->pg->ps.type->end_io)
 575                         pgpath->pg->ps.type->end_io(&pgpath->pg->ps,
 576                                                     &pgpath->path,
 577                                                     mpio->nr_bytes,
 578                                                     clone->io_start_time_ns);
 579         }
 580
 581         blk_mq_free_request(clone);
 582 }
 583
 584 /*
 585  * Map cloned bios (bio-based multipath)
 586  */
 587
 588 static void __multipath_queue_bio(struct multipath *m, struct bio *bio)
 589 {
 590         /* Queue for the daemon to resubmit */
 591         bio_list_add(&m->queued_bios, bio);
 592         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
 593                 queue_work(kmultipathd, &m->process_queued_bios);
 594 }
 595
 596 static void multipath_queue_bio(struct multipath *m, struct bio *bio)
 597 {
 598         unsigned long flags;
 599
 600         spin_lock_irqsave(&m->lock, flags);
 601         __multipath_queue_bio(m, bio);
 602         spin_unlock_irqrestore(&m->lock, flags);
 603 }
 604
 605 static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
 606 {
 607         struct pgpath *pgpath;
 608         unsigned long flags;
 609
 610         /* Do we need to select a new pgpath? */
 611         pgpath = READ_ONCE(m->current_pgpath);
 612         if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
 613                 pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 614
 615         if (!pgpath) {
 616                 spin_lock_irqsave(&m->lock, flags);
 617                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 618                         __multipath_queue_bio(m, bio);
 619                         pgpath = ERR_PTR(-EAGAIN);
 620                 }
 621                 spin_unlock_irqrestore(&m->lock, flags);
 622
 623         } else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
 624                    mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
 625                 multipath_queue_bio(m, bio);
 626                 pg_init_all_paths(m);
 627                 return ERR_PTR(-EAGAIN);
 628         }
 629
 630         return pgpath;
 631 }
 632
 633 static int __multipath_map_bio(struct multipath *m, struct bio *bio,
 634                                struct dm_mpath_io *mpio)
 635 {
 636         struct pgpath *pgpath = __map_bio(m, bio);
 637
 638         if (IS_ERR(pgpath))
 639                 return DM_MAPIO_SUBMITTED;
 640
 641         if (!pgpath) {
 642                 if (__must_push_back(m))
 643                         return DM_MAPIO_REQUEUE;
 644                 dm_report_EIO(m);
 645                 return DM_MAPIO_KILL;
 646         }
 647
 648         mpio->pgpath = pgpath;
 649
 650         bio->bi_status = 0;
 651         bio_set_dev(bio, pgpath->path.dev->bdev);
 652         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 653
 654         if (pgpath->pg->ps.type->start_io)
 655                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 656                                               &pgpath->path,
 657                                               mpio->nr_bytes);
 658         return DM_MAPIO_REMAPPED;
 659 }
 660
 661 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 662 {
 663         struct multipath *m = ti->private;
 664         struct dm_mpath_io *mpio = NULL;
 665
 666         multipath_init_per_bio_data(bio, &mpio);
 667         return __multipath_map_bio(m, bio, mpio);
 668 }
 669
 670 static void process_queued_io_list(struct multipath *m)
 671 {
 672         if (m->queue_mode == DM_TYPE_REQUEST_BASED)
 673                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 674         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 675                 queue_work(kmultipathd, &m->process_queued_bios);
 676 }
 677
 678 static void process_queued_bios(struct work_struct *work)
 679 {
 680         int r;
 681         unsigned long flags;
 682         struct bio *bio;
 683         struct bio_list bios;
 684         struct blk_plug plug;
 685         struct multipath *m =
 686                 container_of(work, struct multipath, process_queued_bios);
 687
 688         bio_list_init(&bios);
 689
 690         spin_lock_irqsave(&m->lock, flags);
 691
 692         if (bio_list_empty(&m->queued_bios)) {
 693                 spin_unlock_irqrestore(&m->lock, flags);
 694                 return;
 695         }
 696
 697         bio_list_merge(&bios, &m->queued_bios);
 698         bio_list_init(&m->queued_bios);
 699
 700         spin_unlock_irqrestore(&m->lock, flags);
 701
 702         blk_start_plug(&plug);
 703         while ((bio = bio_list_pop(&bios))) {
 704                 struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 705                 dm_bio_restore(get_bio_details_from_mpio(mpio), bio);
 706                 r = __multipath_map_bio(m, bio, mpio);
 707                 switch (r) {
 708                 case DM_MAPIO_KILL:
 709                         bio->bi_status = BLK_STS_IOERR;
 710                         bio_endio(bio);
 711                         break;
 712                 case DM_MAPIO_REQUEUE:
 713                         bio->bi_status = BLK_STS_DM_REQUEUE;
 714                         bio_endio(bio);
 715                         break;
 716                 case DM_MAPIO_REMAPPED:
 717                         submit_bio_noacct(bio);
 718                         break;
 719                 case DM_MAPIO_SUBMITTED:
 720                         break;
 721                 default:
 722                         WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 723                 }
 724         }
 725         blk_finish_plug(&plug);
 726 }
 727
 728 /*
 729  * If we run out of usable paths, should we queue I/O or error it?
 730  */
 731 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 732                             bool save_old_value, const char *caller)
 733 {
 734         unsigned long flags;
 735         bool queue_if_no_path_bit, saved_queue_if_no_path_bit;
 736         const char *dm_dev_name = dm_table_device_name(m->ti->table);
 737
 738         DMDEBUG("%s: %s caller=%s queue_if_no_path=%d save_old_value=%d",
 739                 dm_dev_name, __func__, caller, queue_if_no_path, save_old_value);
 740
 741         spin_lock_irqsave(&m->lock, flags);
 742
 743         queue_if_no_path_bit = test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
 744         saved_queue_if_no_path_bit = test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 745
 746         if (save_old_value) {
 747                 if (unlikely(!queue_if_no_path_bit && saved_queue_if_no_path_bit)) {
 748                         DMERR("%s: QIFNP disabled but saved as enabled, saving again loses state, not saving!",
 749                               dm_dev_name);
 750                 } else
 751                         assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path_bit);
 752         } else if (!queue_if_no_path && saved_queue_if_no_path_bit) {
 753                 /* due to "fail_if_no_path" message, need to honor it. */
 754                 clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 755         }
 756         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);
 757
 758         DMDEBUG("%s: after %s changes; QIFNP = %d; SQIFNP = %d; DNFS = %d",
 759                 dm_dev_name, __func__,
 760                 test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
 761                 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags),
 762                 dm_noflush_suspending(m->ti));
 763
 764         spin_unlock_irqrestore(&m->lock, flags);
 765
 766         if (!queue_if_no_path) {
 767                 dm_table_run_md_queue_async(m->ti->table);
 768                 process_queued_io_list(m);
 769         }
 770
 771         return 0;
 772 }
 773
 774 /*
 775  * If the queue_if_no_path timeout fires, turn off queue_if_no_path and
 776  * process any queued I/O.
 777  */
 778 static void queue_if_no_path_timeout_work(struct timer_list *t)
 779 {
 780         struct multipath *m = from_timer(m, t, nopath_timer);
 781
 782         DMWARN("queue_if_no_path timeout on %s, failing queued IO",
 783                dm_table_device_name(m->ti->table));
 784         queue_if_no_path(m, false, false, __func__);
 785 }
 786
 787 /*
 788  * Enable the queue_if_no_path timeout if necessary.
 789  * Called with m->lock held.
 790  */
 791 static void enable_nopath_timeout(struct multipath *m)
 792 {
 793         unsigned long queue_if_no_path_timeout =
 794                 READ_ONCE(queue_if_no_path_timeout_secs) * HZ;
 795
 796         lockdep_assert_held(&m->lock);
 797
 798         if (queue_if_no_path_timeout > 0 &&
 799             atomic_read(&m->nr_valid_paths) == 0 &&
 800             test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 801                 mod_timer(&m->nopath_timer,
 802                           jiffies + queue_if_no_path_timeout);
 803         }
 804 }
 805
 806 static void disable_nopath_timeout(struct multipath *m)
 807 {
 808         del_timer_sync(&m->nopath_timer);
 809 }
 810
 811 /*
 812  * An event is triggered whenever a path is taken out of use.
 813  * Includes path failure and PG bypass.
 814  */
 815 static void trigger_event(struct work_struct *work)
 816 {
 817         struct multipath *m =
 818                 container_of(work, struct multipath, trigger_event);
 819
 820         dm_table_event(m->ti->table);
 821 }
 822
 823 /*-----------------------------------------------------------------
 824  * Constructor/argument parsing:
 825  * <#multipath feature args> [<arg>]*
 826  * <#hw_handler args> [hw_handler [<arg>]*]
 827  * <#priority groups>
 828  * <initial priority group>
 829  *     [<selector> <#selector args> [<arg>]*
 830  *      <#paths> <#per-path selector args>
 831  *         [<path> [<arg>]* ]+ ]+
 832  *---------------------------------------------------------------*/
 833 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 834                                struct dm_target *ti)
 835 {
 836         int r;
 837         struct path_selector_type *pst;
 838         unsigned ps_argc;
 839
 840         static const struct dm_arg _args[] = {
 841                 {0, 1024, "invalid number of path selector args"},
 842         };
 843
 844         pst = dm_get_path_selector(dm_shift_arg(as));
 845         if (!pst) {
 846                 ti->error = "unknown path selector type";
 847                 return -EINVAL;
 848         }
 849
 850         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 851         if (r) {
 852                 dm_put_path_selector(pst);
 853                 return -EINVAL;
 854         }
 855
 856         r = pst->create(&pg->ps, ps_argc, as->argv);
 857         if (r) {
 858                 dm_put_path_selector(pst);
 859                 ti->error = "path selector constructor failed";
 860                 return r;
 861         }
 862
 863         pg->ps.type = pst;
 864         dm_consume_args(as, ps_argc);
 865
 866         return 0;
 867 }
 868
 869 static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
 870                          const char **attached_handler_name, char **error)
 871 {
 872         struct request_queue *q = bdev_get_queue(bdev);
 873         int r;
 874
 875         if (mpath_double_check_test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, m)) {
 876 retain:
 877                 if (*attached_handler_name) {
 878                         /*
 879                          * Clear any hw_handler_params associated with a
 880                          * handler that isn't already attached.
 881                          */
 882                         if (m->hw_handler_name && strcmp(*attached_handler_name, m->hw_handler_name)) {
 883                                 kfree(m->hw_handler_params);
 884                                 m->hw_handler_params = NULL;
 885                         }
 886
 887                         /*
 888                          * Reset hw_handler_name to match the attached handler
 889                          *
 890                          * NB. This modifies the table line to show the actual
 891                          * handler instead of the original table passed in.
 892                          */
 893                         kfree(m->hw_handler_name);
 894                         m->hw_handler_name = *attached_handler_name;
 895                         *attached_handler_name = NULL;
 896                 }
 897         }
 898
 899         if (m->hw_handler_name) {
 900                 r = scsi_dh_attach(q, m->hw_handler_name);
 901                 if (r == -EBUSY) {
 902                         char b[BDEVNAME_SIZE];
 903
 904                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 905                                bdevname(bdev, b));
 906                         goto retain;
 907                 }
 908                 if (r < 0) {
 909                         *error = "error attaching hardware handler";
 910                         return r;
 911                 }
 912
 913                 if (m->hw_handler_params) {
 914                         r = scsi_dh_set_params(q, m->hw_handler_params);
 915                         if (r < 0) {
 916                                 *error = "unable to set hardware handler parameters";
 917                                 return r;
 918                         }
 919                 }
 920         }
 921
 922         return 0;
 923 }
 924
 925 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 926                                  struct dm_target *ti)
 927 {
 928         int r;
 929         struct pgpath *p;
 930         struct multipath *m = ti->private;
 931         struct request_queue *q;
 932         const char *attached_handler_name = NULL;
 933
 934         /* we need at least a path arg */
 935         if (as->argc < 1) {
 936                 ti->error = "no device given";
 937                 return ERR_PTR(-EINVAL);
 938         }
 939
 940         p = alloc_pgpath();
 941         if (!p)
 942                 return ERR_PTR(-ENOMEM);
 943
 944         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 945                           &p->path.dev);
 946         if (r) {
 947                 ti->error = "error getting device";
 948                 goto bad;
 949         }
 950
 951         q = bdev_get_queue(p->path.dev->bdev);
 952         attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 953         if (attached_handler_name || m->hw_handler_name) {
 954                 INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
 955                 r = setup_scsi_dh(p->path.dev->bdev, m, &attached_handler_name, &ti->error);
 956                 kfree(attached_handler_name);
 957                 if (r) {
 958                         dm_put_device(ti, p->path.dev);
 959                         goto bad;
 960                 }
 961         }
 962
 963         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 964         if (r) {
 965                 dm_put_device(ti, p->path.dev);
 966                 goto bad;
 967         }
 968
 969         return p;
 970  bad:
 971         free_pgpath(p);
 972         return ERR_PTR(r);
 973 }
 974
 975 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 976                                                    struct multipath *m)
 977 {
 978         static const struct dm_arg _args[] = {
 979                 {1, 1024, "invalid number of paths"},
 980                 {0, 1024, "invalid number of selector args"}
 981         };
 982
 983         int r;
 984         unsigned i, nr_selector_args, nr_args;
 985         struct priority_group *pg;
 986         struct dm_target *ti = m->ti;
 987
 988         if (as->argc < 2) {
 989                 as->argc = 0;
 990                 ti->error = "not enough priority group arguments";
 991                 return ERR_PTR(-EINVAL);
 992         }
 993
 994         pg = alloc_priority_group();
 995         if (!pg) {
 996                 ti->error = "couldn't allocate priority group";
 997                 return ERR_PTR(-ENOMEM);
 998         }
 999         pg->m = m;
1000
1001         r = parse_path_selector(as, pg, ti);
1002         if (r)
1003                 goto bad;
1004
1005         /*
1006          * read the paths
1007          */
1008         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
1009         if (r)
1010                 goto bad;
1011
1012         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
1013         if (r)
1014                 goto bad;
1015
1016         nr_args = 1 + nr_selector_args;
1017         for (i = 0; i < pg->nr_pgpaths; i++) {
1018                 struct pgpath *pgpath;
1019                 struct dm_arg_set path_args;
1020
1021                 if (as->argc < nr_args) {
1022                         ti->error = "not enough path parameters";
1023                         r = -EINVAL;
1024                         goto bad;
1025                 }
1026
1027                 path_args.argc = nr_args;
1028                 path_args.argv = as->argv;
1029
1030                 pgpath = parse_path(&path_args, &pg->ps, ti);
1031                 if (IS_ERR(pgpath)) {
1032                         r = PTR_ERR(pgpath);
1033                         goto bad;
1034                 }
1035
1036                 pgpath->pg = pg;
1037                 list_add_tail(&pgpath->list, &pg->pgpaths);
1038                 dm_consume_args(as, nr_args);
1039         }
1040
1041         return pg;
1042
1043  bad:
1044         free_priority_group(pg, ti);
1045         return ERR_PTR(r);
1046 }
1047
1048 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
1049 {
1050         unsigned hw_argc;
1051         int ret;
1052         struct dm_target *ti = m->ti;
1053
1054         static const struct dm_arg _args[] = {
1055                 {0, 1024, "invalid number of hardware handler args"},
1056         };
1057
1058         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
1059                 return -EINVAL;
1060
1061         if (!hw_argc)
1062                 return 0;
1063
1064         if (m->queue_mode == DM_TYPE_BIO_BASED) {
1065                 dm_consume_args(as, hw_argc);
1066                 DMERR("bio-based multipath doesn't allow hardware handler args");
1067                 return 0;
1068         }
1069
1070         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
1071         if (!m->hw_handler_name)
1072                 return -EINVAL;
1073
1074         if (hw_argc > 1) {
1075                 char *p;
1076                 int i, j, len = 4;
1077
1078                 for (i = 0; i <= hw_argc - 2; i++)
1079                         len += strlen(as->argv[i]) + 1;
1080                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1081                 if (!p) {
1082                         ti->error = "memory allocation failed";
1083                         ret = -ENOMEM;
1084                         goto fail;
1085                 }
1086                 j = sprintf(p, "%d", hw_argc - 1);
1087                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
1088                         j = sprintf(p, "%s", as->argv[i]);
1089         }
1090         dm_consume_args(as, hw_argc - 1);
1091
1092         return 0;
1093 fail:
1094         kfree(m->hw_handler_name);
1095         m->hw_handler_name = NULL;
1096         return ret;
1097 }
1098
1099 static int parse_features(struct dm_arg_set *as, struct multipath *m)
1100 {
1101         int r;
1102         unsigned argc;
1103         struct dm_target *ti = m->ti;
1104         const char *arg_name;
1105
1106         static const struct dm_arg _args[] = {
1107                 {0, 8, "invalid number of feature args"},
1108                 {1, 50, "pg_init_retries must be between 1 and 50"},
1109                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1110         };
1111
1112         r = dm_read_arg_group(_args, as, &argc, &ti->error);
1113         if (r)
1114                 return -EINVAL;
1115
1116         if (!argc)
1117                 return 0;
1118
1119         do {
1120                 arg_name = dm_shift_arg(as);
1121                 argc--;
1122
1123                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
1124                         r = queue_if_no_path(m, true, false, __func__);
1125                         continue;
1126                 }
1127
1128                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1129                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1130                         continue;
1131                 }
1132
1133                 if (!strcasecmp(arg_name, "pg_init_retries") &&
1134                     (argc >= 1)) {
1135                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1136                         argc--;
1137                         continue;
1138                 }
1139
1140                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1141                     (argc >= 1)) {
1142                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1143                         argc--;
1144                         continue;
1145                 }
1146
1147                 if (!strcasecmp(arg_name, "queue_mode") &&
1148                     (argc >= 1)) {
1149                         const char *queue_mode_name = dm_shift_arg(as);
1150
1151                         if (!strcasecmp(queue_mode_name, "bio"))
1152                                 m->queue_mode = DM_TYPE_BIO_BASED;
1153                         else if (!strcasecmp(queue_mode_name, "rq") ||
1154                                  !strcasecmp(queue_mode_name, "mq"))
1155                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1156                         else {
1157                                 ti->error = "Unknown 'queue_mode' requested";
1158                                 r = -EINVAL;
1159                         }
1160                         argc--;
1161                         continue;
1162                 }
1163
1164                 ti->error = "Unrecognised multipath feature request";
1165                 r = -EINVAL;
1166         } while (argc && !r);
1167
1168         return r;
1169 }
1170
1171 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1172 {
1173         /* target arguments */
1174         static const struct dm_arg _args[] = {
1175                 {0, 1024, "invalid number of priority groups"},
1176                 {0, 1024, "invalid initial priority group number"},
1177         };
1178
1179         int r;
1180         struct multipath *m;
1181         struct dm_arg_set as;
1182         unsigned pg_count = 0;
1183         unsigned next_pg_num;
1184         unsigned long flags;
1185
1186         as.argc = argc;
1187         as.argv = argv;
1188
1189         m = alloc_multipath(ti);
1190         if (!m) {
1191                 ti->error = "can't allocate multipath";
1192                 return -EINVAL;
1193         }
1194
1195         r = parse_features(&as, m);
1196         if (r)
1197                 goto bad;
1198
1199         r = alloc_multipath_stage2(ti, m);
1200         if (r)
1201                 goto bad;
1202
1203         r = parse_hw_handler(&as, m);
1204         if (r)
1205                 goto bad;
1206
1207         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1208         if (r)
1209                 goto bad;
1210
1211         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1212         if (r)
1213                 goto bad;
1214
1215         if ((!m->nr_priority_groups && next_pg_num) ||
1216             (m->nr_priority_groups && !next_pg_num)) {
1217                 ti->error = "invalid initial priority group";
1218                 r = -EINVAL;
1219                 goto bad;
1220         }
1221
1222         /* parse the priority groups */
1223         while (as.argc) {
1224                 struct priority_group *pg;
1225                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1226
1227                 pg = parse_priority_group(&as, m);
1228                 if (IS_ERR(pg)) {
1229                         r = PTR_ERR(pg);
1230                         goto bad;
1231                 }
1232
1233                 nr_valid_paths += pg->nr_pgpaths;
1234                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1235
1236                 list_add_tail(&pg->list, &m->priority_groups);
1237                 pg_count++;
1238                 pg->pg_num = pg_count;
1239                 if (!--next_pg_num)
1240                         m->next_pg = pg;
1241         }
1242
1243         if (pg_count != m->nr_priority_groups) {
1244                 ti->error = "priority group count mismatch";
1245                 r = -EINVAL;
1246                 goto bad;
1247         }
1248
1249         spin_lock_irqsave(&m->lock, flags);
1250         enable_nopath_timeout(m);
1251         spin_unlock_irqrestore(&m->lock, flags);
1252
1253         ti->num_flush_bios = 1;
1254         ti->num_discard_bios = 1;
1255         ti->num_write_same_bios = 1;
1256         ti->num_write_zeroes_bios = 1;
1257         if (m->queue_mode == DM_TYPE_BIO_BASED)
1258                 ti->per_io_data_size = multipath_per_bio_data_size();
1259         else
1260                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1261
1262         return 0;
1263
1264  bad:
1265         free_multipath(m);
1266         return r;
1267 }
1268
1269 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1270 {
1271         DEFINE_WAIT(wait);
1272
1273         while (1) {
1274                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1275
1276                 if (!atomic_read(&m->pg_init_in_progress))
1277                         break;
1278
1279                 io_schedule();
1280         }
1281         finish_wait(&m->pg_init_wait, &wait);
1282 }
1283
1284 static void flush_multipath_work(struct multipath *m)
1285 {
1286         if (m->hw_handler_name) {
1287                 unsigned long flags;
1288
1289                 if (!atomic_read(&m->pg_init_in_progress))
1290                         goto skip;
1291
1292                 spin_lock_irqsave(&m->lock, flags);
1293                 if (atomic_read(&m->pg_init_in_progress) &&
1294                     !test_and_set_bit(MPATHF_PG_INIT_DISABLED, &m->flags)) {
1295                         spin_unlock_irqrestore(&m->lock, flags);
1296
1297                         flush_workqueue(kmpath_handlerd);
1298                         multipath_wait_for_pg_init_completion(m);
1299
1300                         spin_lock_irqsave(&m->lock, flags);
1301                         clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1302                 }
1303                 spin_unlock_irqrestore(&m->lock, flags);
1304         }
1305 skip:
1306         if (m->queue_mode == DM_TYPE_BIO_BASED)
1307                 flush_work(&m->process_queued_bios);
1308         flush_work(&m->trigger_event);
1309 }
1310
1311 static void multipath_dtr(struct dm_target *ti)
1312 {
1313         struct multipath *m = ti->private;
1314
1315         disable_nopath_timeout(m);
1316         flush_multipath_work(m);
1317         free_multipath(m);
1318 }
1319
1320 /*
1321  * Take a path out of use.
1322  */
1323 static int fail_path(struct pgpath *pgpath)
1324 {
1325         unsigned long flags;
1326         struct multipath *m = pgpath->pg->m;
1327
1328         spin_lock_irqsave(&m->lock, flags);
1329
1330         if (!pgpath->is_active)
1331                 goto out;
1332
1333         DMWARN("%s: Failing path %s.",
1334                dm_table_device_name(m->ti->table),
1335                pgpath->path.dev->name);
1336
1337         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1338         pgpath->is_active = false;
1339         pgpath->fail_count++;
1340
1341         atomic_dec(&m->nr_valid_paths);
1342
1343         if (pgpath == m->current_pgpath)
1344                 m->current_pgpath = NULL;
1345
1346         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1347                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1348
1349         schedule_work(&m->trigger_event);
1350
1351         enable_nopath_timeout(m);
1352
1353 out:
1354         spin_unlock_irqrestore(&m->lock, flags);
1355
1356         return 0;
1357 }
1358
1359 /*
1360  * Reinstate a previously-failed path
1361  */
1362 static int reinstate_path(struct pgpath *pgpath)
1363 {
1364         int r = 0, run_queue = 0;
1365         unsigned long flags;
1366         struct multipath *m = pgpath->pg->m;
1367         unsigned nr_valid_paths;
1368
1369         spin_lock_irqsave(&m->lock, flags);
1370
1371         if (pgpath->is_active)
1372                 goto out;
1373
1374         DMWARN("%s: Reinstating path %s.",
1375                dm_table_device_name(m->ti->table),
1376                pgpath->path.dev->name);
1377
1378         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1379         if (r)
1380                 goto out;
1381
1382         pgpath->is_active = true;
1383
1384         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1385         if (nr_valid_paths == 1) {
1386                 m->current_pgpath = NULL;
1387                 run_queue = 1;
1388         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1389                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1390                         atomic_inc(&m->pg_init_in_progress);
1391         }
1392
1393         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1394                        pgpath->path.dev->name, nr_valid_paths);
1395
1396         schedule_work(&m->trigger_event);
1397
1398 out:
1399         spin_unlock_irqrestore(&m->lock, flags);
1400         if (run_queue) {
1401                 dm_table_run_md_queue_async(m->ti->table);
1402                 process_queued_io_list(m);
1403         }
1404
1405         if (pgpath->is_active)
1406                 disable_nopath_timeout(m);
1407
1408         return r;
1409 }
1410
1411 /*
1412  * Fail or reinstate all paths that match the provided struct dm_dev.
1413  */
1414 static int action_dev(struct multipath *m, struct dm_dev *dev,
1415                       action_fn action)
1416 {
1417         int r = -EINVAL;
1418         struct pgpath *pgpath;
1419         struct priority_group *pg;
1420
1421         list_for_each_entry(pg, &m->priority_groups, list) {
1422                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1423                         if (pgpath->path.dev == dev)
1424                                 r = action(pgpath);
1425                 }
1426         }
1427
1428         return r;
1429 }
1430
1431 /*
1432  * Temporarily try to avoid having to use the specified PG
1433  */
1434 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1435                       bool bypassed)
1436 {
1437         unsigned long flags;
1438
1439         spin_lock_irqsave(&m->lock, flags);
1440
1441         pg->bypassed = bypassed;
1442         m->current_pgpath = NULL;
1443         m->current_pg = NULL;
1444
1445         spin_unlock_irqrestore(&m->lock, flags);
1446
1447         schedule_work(&m->trigger_event);
1448 }
1449
1450 /*
1451  * Switch to using the specified PG from the next I/O that gets mapped
1452  */
1453 static int switch_pg_num(struct multipath *m, const char *pgstr)
1454 {
1455         struct priority_group *pg;
1456         unsigned pgnum;
1457         unsigned long flags;
1458         char dummy;
1459
1460         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1461             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1462                 DMWARN("invalid PG number supplied to switch_pg_num");
1463                 return -EINVAL;
1464         }
1465
1466         spin_lock_irqsave(&m->lock, flags);
1467         list_for_each_entry(pg, &m->priority_groups, list) {
1468                 pg->bypassed = false;
1469                 if (--pgnum)
1470                         continue;
1471
1472                 m->current_pgpath = NULL;
1473                 m->current_pg = NULL;
1474                 m->next_pg = pg;
1475         }
1476         spin_unlock_irqrestore(&m->lock, flags);
1477
1478         schedule_work(&m->trigger_event);
1479         return 0;
1480 }
1481
1482 /*
1483  * Set/clear bypassed status of a PG.
1484  * PGs are numbered upwards from 1 in the order they were declared.
1485  */
1486 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1487 {
1488         struct priority_group *pg;
1489         unsigned pgnum;
1490         char dummy;
1491
1492         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1493             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1494                 DMWARN("invalid PG number supplied to bypass_pg");
1495                 return -EINVAL;
1496         }
1497
1498         list_for_each_entry(pg, &m->priority_groups, list) {
1499                 if (!--pgnum)
1500                         break;
1501         }
1502
1503         bypass_pg(m, pg, bypassed);
1504         return 0;
1505 }
1506
1507 /*
1508  * Should we retry pg_init immediately?
1509  */
1510 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1511 {
1512         unsigned long flags;
1513         bool limit_reached = false;
1514
1515         spin_lock_irqsave(&m->lock, flags);
1516
1517         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1518             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1519                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1520         else
1521                 limit_reached = true;
1522
1523         spin_unlock_irqrestore(&m->lock, flags);
1524
1525         return limit_reached;
1526 }
1527
1528 static void pg_init_done(void *data, int errors)
1529 {
1530         struct pgpath *pgpath = data;
1531         struct priority_group *pg = pgpath->pg;
1532         struct multipath *m = pg->m;
1533         unsigned long flags;
1534         bool delay_retry = false;
1535
1536         /* device or driver problems */
1537         switch (errors) {
1538         case SCSI_DH_OK:
1539                 break;
1540         case SCSI_DH_NOSYS:
1541                 if (!m->hw_handler_name) {
1542                         errors = 0;
1543                         break;
1544                 }
1545                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1546                       "Error %d.", m->hw_handler_name, errors);
1547                 /*
1548                  * Fail path for now, so we do not ping pong
1549                  */
1550                 fail_path(pgpath);
1551                 break;
1552         case SCSI_DH_DEV_TEMP_BUSY:
1553                 /*
1554                  * Probably doing something like FW upgrade on the
1555                  * controller so try the other pg.
1556                  */
1557                 bypass_pg(m, pg, true);
1558                 break;
1559         case SCSI_DH_RETRY:
1560                 /* Wait before retrying. */
1561                 delay_retry = true;
1562                 fallthrough;
1563         case SCSI_DH_IMM_RETRY:
1564         case SCSI_DH_RES_TEMP_UNAVAIL:
1565                 if (pg_init_limit_reached(m, pgpath))
1566                         fail_path(pgpath);
1567                 errors = 0;
1568                 break;
1569         case SCSI_DH_DEV_OFFLINED:
1570         default:
1571                 /*
1572                  * We probably do not want to fail the path for a device
1573                  * error, but this is what the old dm did. In future
1574                  * patches we can do more advanced handling.
1575                  */
1576                 fail_path(pgpath);
1577         }
1578
1579         spin_lock_irqsave(&m->lock, flags);
1580         if (errors) {
1581                 if (pgpath == m->current_pgpath) {
1582                         DMERR("Could not failover device. Error %d.", errors);
1583                         m->current_pgpath = NULL;
1584                         m->current_pg = NULL;
1585                 }
1586         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1587                 pg->bypassed = false;
1588
1589         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1590                 /* Activations of other paths are still on going */
1591                 goto out;
1592
1593         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1594                 if (delay_retry)
1595                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1596                 else
1597                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1598
1599                 if (__pg_init_all_paths(m))
1600                         goto out;
1601         }
1602         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1603
1604         process_queued_io_list(m);
1605
1606         /*
1607          * Wake up any thread waiting to suspend.
1608          */
1609         wake_up(&m->pg_init_wait);
1610
1611 out:
1612         spin_unlock_irqrestore(&m->lock, flags);
1613 }
1614
1615 static void activate_or_offline_path(struct pgpath *pgpath)
1616 {
1617         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1618
1619         if (pgpath->is_active && !blk_queue_dying(q))
1620                 scsi_dh_activate(q, pg_init_done, pgpath);
1621         else
1622                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1623 }
1624
1625 static void activate_path_work(struct work_struct *work)
1626 {
1627         struct pgpath *pgpath =
1628                 container_of(work, struct pgpath, activate_path.work);
1629
1630         activate_or_offline_path(pgpath);
1631 }
1632
1633 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1634                             blk_status_t error, union map_info *map_context)
1635 {
1636         struct dm_mpath_io *mpio = get_mpio(map_context);
1637         struct pgpath *pgpath = mpio->pgpath;
1638         int r = DM_ENDIO_DONE;
1639
1640         /*
1641          * We don't queue any clone request inside the multipath target
1642          * during end I/O handling, since those clone requests don't have
1643          * bio clones.  If we queue them inside the multipath target,
1644          * we need to make bio clones, that requires memory allocation.
1645          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1646          *  don't have bio clones.)
1647          * Instead of queueing the clone request here, we queue the original
1648          * request into dm core, which will remake a clone request and
1649          * clone bios for it and resubmit it later.
1650          */
1651         if (error && blk_path_error(error)) {
1652                 struct multipath *m = ti->private;
1653
1654                 if (error == BLK_STS_RESOURCE)
1655                         r = DM_ENDIO_DELAY_REQUEUE;
1656                 else
1657                         r = DM_ENDIO_REQUEUE;
1658
1659                 if (pgpath)
1660                         fail_path(pgpath);
1661
1662                 if (!atomic_read(&m->nr_valid_paths) &&
1663                     !must_push_back_rq(m)) {
1664                         if (error == BLK_STS_IOERR)
1665                                 dm_report_EIO(m);
1666                         /* complete with the original error */
1667                         r = DM_ENDIO_DONE;
1668                 }
1669         }
1670
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                                          clone->io_start_time_ns);
1677         }
1678
1679         return r;
1680 }
1681
1682 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1683                                 blk_status_t *error)
1684 {
1685         struct multipath *m = ti->private;
1686         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1687         struct pgpath *pgpath = mpio->pgpath;
1688         unsigned long flags;
1689         int r = DM_ENDIO_DONE;
1690
1691         if (!*error || !blk_path_error(*error))
1692                 goto done;
1693
1694         if (pgpath)
1695                 fail_path(pgpath);
1696
1697         if (!atomic_read(&m->nr_valid_paths)) {
1698                 spin_lock_irqsave(&m->lock, flags);
1699                 if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1700                         if (__must_push_back(m)) {
1701                                 r = DM_ENDIO_REQUEUE;
1702                         } else {
1703                                 dm_report_EIO(m);
1704                                 *error = BLK_STS_IOERR;
1705                         }
1706                         spin_unlock_irqrestore(&m->lock, flags);
1707                         goto done;
1708                 }
1709                 spin_unlock_irqrestore(&m->lock, flags);
1710         }
1711
1712         multipath_queue_bio(m, clone);
1713         r = DM_ENDIO_INCOMPLETE;
1714 done:
1715         if (pgpath) {
1716                 struct path_selector *ps = &pgpath->pg->ps;
1717
1718                 if (ps->type->end_io)
1719                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1720                                          dm_start_time_ns_from_clone(clone));
1721         }
1722
1723         return r;
1724 }
1725
1726 /*
1727  * Suspend with flush can't complete until all the I/O is processed
1728  * so if the last path fails we must error any remaining I/O.
1729  * - Note that if the freeze_bdev fails while suspending, the
1730  *   queue_if_no_path state is lost - userspace should reset it.
1731  * Otherwise, during noflush suspend, queue_if_no_path will not change.
1732  */
1733 static void multipath_presuspend(struct dm_target *ti)
1734 {
1735         struct multipath *m = ti->private;
1736
1737         /* FIXME: bio-based shouldn't need to always disable queue_if_no_path */
1738         if (m->queue_mode == DM_TYPE_BIO_BASED || !dm_noflush_suspending(m->ti))
1739                 queue_if_no_path(m, false, true, __func__);
1740 }
1741
1742 static void multipath_postsuspend(struct dm_target *ti)
1743 {
1744         struct multipath *m = ti->private;
1745
1746         mutex_lock(&m->work_mutex);
1747         flush_multipath_work(m);
1748         mutex_unlock(&m->work_mutex);
1749 }
1750
1751 /*
1752  * Restore the queue_if_no_path setting.
1753  */
1754 static void multipath_resume(struct dm_target *ti)
1755 {
1756         struct multipath *m = ti->private;
1757         unsigned long flags;
1758
1759         spin_lock_irqsave(&m->lock, flags);
1760         if (test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) {
1761                 set_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1762                 clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
1763         }
1764
1765         DMDEBUG("%s: %s finished; QIFNP = %d; SQIFNP = %d",
1766                 dm_table_device_name(m->ti->table), __func__,
1767                 test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
1768                 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1769
1770         spin_unlock_irqrestore(&m->lock, flags);
1771 }
1772
1773 /*
1774  * Info output has the following format:
1775  * num_multipath_feature_args [multipath_feature_args]*
1776  * num_handler_status_args [handler_status_args]*
1777  * num_groups init_group_number
1778  *            [A|D|E num_ps_status_args [ps_status_args]*
1779  *             num_paths num_selector_args
1780  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1781  *
1782  * Table output has the following format (identical to the constructor string):
1783  * num_feature_args [features_args]*
1784  * num_handler_args hw_handler [hw_handler_args]*
1785  * num_groups init_group_number
1786  *     [priority selector-name num_ps_args [ps_args]*
1787  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1788  */
1789 static void multipath_status(struct dm_target *ti, status_type_t type,
1790                              unsigned status_flags, char *result, unsigned maxlen)
1791 {
1792         int sz = 0, pg_counter, pgpath_counter;
1793         unsigned long flags;
1794         struct multipath *m = ti->private;
1795         struct priority_group *pg;
1796         struct pgpath *p;
1797         unsigned pg_num;
1798         char state;
1799
1800         spin_lock_irqsave(&m->lock, flags);
1801
1802         /* Features */
1803         if (type == STATUSTYPE_INFO)
1804                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1805                        atomic_read(&m->pg_init_count));
1806         else {
1807                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1808                               (m->pg_init_retries > 0) * 2 +
1809                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1810                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1811                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1812
1813                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1814                         DMEMIT("queue_if_no_path ");
1815                 if (m->pg_init_retries)
1816                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1817                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1818                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1819                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1820                         DMEMIT("retain_attached_hw_handler ");
1821                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1822                         switch(m->queue_mode) {
1823                         case DM_TYPE_BIO_BASED:
1824                                 DMEMIT("queue_mode bio ");
1825                                 break;
1826                         default:
1827                                 WARN_ON_ONCE(true);
1828                                 break;
1829                         }
1830                 }
1831         }
1832
1833         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1834                 DMEMIT("0 ");
1835         else
1836                 DMEMIT("1 %s ", m->hw_handler_name);
1837
1838         DMEMIT("%u ", m->nr_priority_groups);
1839
1840         if (m->next_pg)
1841                 pg_num = m->next_pg->pg_num;
1842         else if (m->current_pg)
1843                 pg_num = m->current_pg->pg_num;
1844         else
1845                 pg_num = (m->nr_priority_groups ? 1 : 0);
1846
1847         DMEMIT("%u ", pg_num);
1848
1849         switch (type) {
1850         case STATUSTYPE_INFO:
1851                 list_for_each_entry(pg, &m->priority_groups, list) {
1852                         if (pg->bypassed)
1853                                 state = 'D';    /* Disabled */
1854                         else if (pg == m->current_pg)
1855                                 state = 'A';    /* Currently Active */
1856                         else
1857                                 state = 'E';    /* Enabled */
1858
1859                         DMEMIT("%c ", state);
1860
1861                         if (pg->ps.type->status)
1862                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1863                                                           result + sz,
1864                                                           maxlen - sz);
1865                         else
1866                                 DMEMIT("0 ");
1867
1868                         DMEMIT("%u %u ", pg->nr_pgpaths,
1869                                pg->ps.type->info_args);
1870
1871                         list_for_each_entry(p, &pg->pgpaths, list) {
1872                                 DMEMIT("%s %s %u ", p->path.dev->name,
1873                                        p->is_active ? "A" : "F",
1874                                        p->fail_count);
1875                                 if (pg->ps.type->status)
1876                                         sz += pg->ps.type->status(&pg->ps,
1877                                               &p->path, type, result + sz,
1878                                               maxlen - sz);
1879                         }
1880                 }
1881                 break;
1882
1883         case STATUSTYPE_TABLE:
1884                 list_for_each_entry(pg, &m->priority_groups, list) {
1885                         DMEMIT("%s ", pg->ps.type->name);
1886
1887                         if (pg->ps.type->status)
1888                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1889                                                           result + sz,
1890                                                           maxlen - sz);
1891                         else
1892                                 DMEMIT("0 ");
1893
1894                         DMEMIT("%u %u ", pg->nr_pgpaths,
1895                                pg->ps.type->table_args);
1896
1897                         list_for_each_entry(p, &pg->pgpaths, list) {
1898                                 DMEMIT("%s ", p->path.dev->name);
1899                                 if (pg->ps.type->status)
1900                                         sz += pg->ps.type->status(&pg->ps,
1901                                               &p->path, type, result + sz,
1902                                               maxlen - sz);
1903                         }
1904                 }
1905                 break;
1906
1907         case STATUSTYPE_IMA:
1908                 sz = 0; /*reset the result pointer*/
1909
1910                 DMEMIT_TARGET_NAME_VERSION(ti->type);
1911                 DMEMIT(",nr_priority_groups=%u", m->nr_priority_groups);
1912
1913                 pg_counter = 0;
1914                 list_for_each_entry(pg, &m->priority_groups, list) {
1915                         if (pg->bypassed)
1916                                 state = 'D';    /* Disabled */
1917                         else if (pg == m->current_pg)
1918                                 state = 'A';    /* Currently Active */
1919                         else
1920                                 state = 'E';    /* Enabled */
1921                         DMEMIT(",pg_state_%d=%c", pg_counter, state);
1922                         DMEMIT(",nr_pgpaths_%d=%u", pg_counter, pg->nr_pgpaths);
1923                         DMEMIT(",path_selector_name_%d=%s", pg_counter, pg->ps.type->name);
1924
1925                         pgpath_counter = 0;
1926                         list_for_each_entry(p, &pg->pgpaths, list) {
1927                                 DMEMIT(",path_name_%d_%d=%s,is_active_%d_%d=%c,fail_count_%d_%d=%u",
1928                                        pg_counter, pgpath_counter, p->path.dev->name,
1929                                        pg_counter, pgpath_counter, p->is_active ? 'A' : 'F',
1930                                        pg_counter, pgpath_counter, p->fail_count);
1931                                 if (pg->ps.type->status) {
1932                                         DMEMIT(",path_selector_status_%d_%d=",
1933                                                pg_counter, pgpath_counter);
1934                                         sz += pg->ps.type->status(&pg->ps, &p->path,
1935                                                                   type, result + sz,
1936                                                                   maxlen - sz);
1937                                 }
1938                                 pgpath_counter++;
1939                         }
1940                         pg_counter++;
1941                 }
1942                 DMEMIT(";");
1943                 break;
1944         }
1945
1946         spin_unlock_irqrestore(&m->lock, flags);
1947 }
1948
1949 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv,
1950                              char *result, unsigned maxlen)
1951 {
1952         int r = -EINVAL;
1953         struct dm_dev *dev;
1954         struct multipath *m = ti->private;
1955         action_fn action;
1956         unsigned long flags;
1957
1958         mutex_lock(&m->work_mutex);
1959
1960         if (dm_suspended(ti)) {
1961                 r = -EBUSY;
1962                 goto out;
1963         }
1964
1965         if (argc == 1) {
1966                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1967                         r = queue_if_no_path(m, true, false, __func__);
1968                         spin_lock_irqsave(&m->lock, flags);
1969                         enable_nopath_timeout(m);
1970                         spin_unlock_irqrestore(&m->lock, flags);
1971                         goto out;
1972                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1973                         r = queue_if_no_path(m, false, false, __func__);
1974                         disable_nopath_timeout(m);
1975                         goto out;
1976                 }
1977         }
1978
1979         if (argc != 2) {
1980                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1981                 goto out;
1982         }
1983
1984         if (!strcasecmp(argv[0], "disable_group")) {
1985                 r = bypass_pg_num(m, argv[1], true);
1986                 goto out;
1987         } else if (!strcasecmp(argv[0], "enable_group")) {
1988                 r = bypass_pg_num(m, argv[1], false);
1989                 goto out;
1990         } else if (!strcasecmp(argv[0], "switch_group")) {
1991                 r = switch_pg_num(m, argv[1]);
1992                 goto out;
1993         } else if (!strcasecmp(argv[0], "reinstate_path"))
1994                 action = reinstate_path;
1995         else if (!strcasecmp(argv[0], "fail_path"))
1996                 action = fail_path;
1997         else {
1998                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1999                 goto out;
2000         }
2001
2002         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
2003         if (r) {
2004                 DMWARN("message: error getting device %s",
2005                        argv[1]);
2006                 goto out;
2007         }
2008
2009         r = action_dev(m, dev, action);
2010
2011         dm_put_device(ti, dev);
2012
2013 out:
2014         mutex_unlock(&m->work_mutex);
2015         return r;
2016 }
2017
2018 static int multipath_prepare_ioctl(struct dm_target *ti,
2019                                    struct block_device **bdev)
2020 {
2021         struct multipath *m = ti->private;
2022         struct pgpath *pgpath;
2023         unsigned long flags;
2024         int r;
2025
2026         pgpath = READ_ONCE(m->current_pgpath);
2027         if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
2028                 pgpath = choose_pgpath(m, 0);
2029
2030         if (pgpath) {
2031                 if (!mpath_double_check_test_bit(MPATHF_QUEUE_IO, m)) {
2032                         *bdev = pgpath->path.dev->bdev;
2033                         r = 0;
2034                 } else {
2035                         /* pg_init has not started or completed */
2036                         r = -ENOTCONN;
2037                 }
2038         } else {
2039                 /* No path is available */
2040                 r = -EIO;
2041                 spin_lock_irqsave(&m->lock, flags);
2042                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
2043                         r = -ENOTCONN;
2044                 spin_unlock_irqrestore(&m->lock, flags);
2045         }
2046
2047         if (r == -ENOTCONN) {
2048                 if (!READ_ONCE(m->current_pg)) {
2049                         /* Path status changed, redo selection */
2050                         (void) choose_pgpath(m, 0);
2051                 }
2052                 spin_lock_irqsave(&m->lock, flags);
2053                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
2054                         (void) __pg_init_all_paths(m);
2055                 spin_unlock_irqrestore(&m->lock, flags);
2056                 dm_table_run_md_queue_async(m->ti->table);
2057                 process_queued_io_list(m);
2058         }
2059
2060         /*
2061          * Only pass ioctls through if the device sizes match exactly.
2062          */
2063         if (!r && ti->len != bdev_nr_sectors((*bdev)))
2064                 return 1;
2065         return r;
2066 }
2067
2068 static int multipath_iterate_devices(struct dm_target *ti,
2069                                      iterate_devices_callout_fn fn, void *data)
2070 {
2071         struct multipath *m = ti->private;
2072         struct priority_group *pg;
2073         struct pgpath *p;
2074         int ret = 0;
2075
2076         list_for_each_entry(pg, &m->priority_groups, list) {
2077                 list_for_each_entry(p, &pg->pgpaths, list) {
2078                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
2079                         if (ret)
2080                                 goto out;
2081                 }
2082         }
2083
2084 out:
2085         return ret;
2086 }
2087
2088 static int pgpath_busy(struct pgpath *pgpath)
2089 {
2090         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
2091
2092         return blk_lld_busy(q);
2093 }
2094
2095 /*
2096  * We return "busy", only when we can map I/Os but underlying devices
2097  * are busy (so even if we map I/Os now, the I/Os will wait on
2098  * the underlying queue).
2099  * In other words, if we want to kill I/Os or queue them inside us
2100  * due to map unavailability, we don't return "busy".  Otherwise,
2101  * dm core won't give us the I/Os and we can't do what we want.
2102  */
2103 static int multipath_busy(struct dm_target *ti)
2104 {
2105         bool busy = false, has_active = false;
2106         struct multipath *m = ti->private;
2107         struct priority_group *pg, *next_pg;
2108         struct pgpath *pgpath;
2109
2110         /* pg_init in progress */
2111         if (atomic_read(&m->pg_init_in_progress))
2112                 return true;
2113
2114         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
2115         if (!atomic_read(&m->nr_valid_paths)) {
2116                 unsigned long flags;
2117                 spin_lock_irqsave(&m->lock, flags);
2118                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
2119                         spin_unlock_irqrestore(&m->lock, flags);
2120                         return (m->queue_mode != DM_TYPE_REQUEST_BASED);
2121                 }
2122                 spin_unlock_irqrestore(&m->lock, flags);
2123         }
2124
2125         /* Guess which priority_group will be used at next mapping time */
2126         pg = READ_ONCE(m->current_pg);
2127         next_pg = READ_ONCE(m->next_pg);
2128         if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
2129                 pg = next_pg;
2130
2131         if (!pg) {
2132                 /*
2133                  * We don't know which pg will be used at next mapping time.
2134                  * We don't call choose_pgpath() here to avoid to trigger
2135                  * pg_init just by busy checking.
2136                  * So we don't know whether underlying devices we will be using
2137                  * at next mapping time are busy or not. Just try mapping.
2138                  */
2139                 return busy;
2140         }
2141
2142         /*
2143          * If there is one non-busy active path at least, the path selector
2144          * will be able to select it. So we consider such a pg as not busy.
2145          */
2146         busy = true;
2147         list_for_each_entry(pgpath, &pg->pgpaths, list) {
2148                 if (pgpath->is_active) {
2149                         has_active = true;
2150                         if (!pgpath_busy(pgpath)) {
2151                                 busy = false;
2152                                 break;
2153                         }
2154                 }
2155         }
2156
2157         if (!has_active) {
2158                 /*
2159                  * No active path in this pg, so this pg won't be used and
2160                  * the current_pg will be changed at next mapping time.
2161                  * We need to try mapping to determine it.
2162                  */
2163                 busy = false;
2164         }
2165
2166         return busy;
2167 }
2168
2169 /*-----------------------------------------------------------------
2170  * Module setup
2171  *---------------------------------------------------------------*/
2172 static struct target_type multipath_target = {
2173         .name = "multipath",
2174         .version = {1, 14, 0},
2175         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE |
2176                     DM_TARGET_PASSES_INTEGRITY,
2177         .module = THIS_MODULE,
2178         .ctr = multipath_ctr,
2179         .dtr = multipath_dtr,
2180         .clone_and_map_rq = multipath_clone_and_map,
2181         .release_clone_rq = multipath_release_clone,
2182         .rq_end_io = multipath_end_io,
2183         .map = multipath_map_bio,
2184         .end_io = multipath_end_io_bio,
2185         .presuspend = multipath_presuspend,
2186         .postsuspend = multipath_postsuspend,
2187         .resume = multipath_resume,
2188         .status = multipath_status,
2189         .message = multipath_message,
2190         .prepare_ioctl = multipath_prepare_ioctl,
2191         .iterate_devices = multipath_iterate_devices,
2192         .busy = multipath_busy,
2193 };
2194
2195 static int __init dm_multipath_init(void)
2196 {
2197         int r;
2198
2199         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2200         if (!kmultipathd) {
2201                 DMERR("failed to create workqueue kmpathd");
2202                 r = -ENOMEM;
2203                 goto bad_alloc_kmultipathd;
2204         }
2205
2206         /*
2207          * A separate workqueue is used to handle the device handlers
2208          * to avoid overloading existing workqueue. Overloading the
2209          * old workqueue would also create a bottleneck in the
2210          * path of the storage hardware device activation.
2211          */
2212         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2213                                                   WQ_MEM_RECLAIM);
2214         if (!kmpath_handlerd) {
2215                 DMERR("failed to create workqueue kmpath_handlerd");
2216                 r = -ENOMEM;
2217                 goto bad_alloc_kmpath_handlerd;
2218         }
2219
2220         r = dm_register_target(&multipath_target);
2221         if (r < 0) {
2222                 DMERR("request-based register failed %d", r);
2223                 r = -EINVAL;
2224                 goto bad_register_target;
2225         }
2226
2227         return 0;
2228
2229 bad_register_target:
2230         destroy_workqueue(kmpath_handlerd);
2231 bad_alloc_kmpath_handlerd:
2232         destroy_workqueue(kmultipathd);
2233 bad_alloc_kmultipathd:
2234         return r;
2235 }
2236
2237 static void __exit dm_multipath_exit(void)
2238 {
2239         destroy_workqueue(kmpath_handlerd);
2240         destroy_workqueue(kmultipathd);
2241
2242         dm_unregister_target(&multipath_target);
2243 }
2244
2245 module_init(dm_multipath_init);
2246 module_exit(dm_multipath_exit);
2247
2248 module_param_named(queue_if_no_path_timeout_secs,
2249                    queue_if_no_path_timeout_secs, ulong, S_IRUGO | S_IWUSR);
2250 MODULE_PARM_DESC(queue_if_no_path_timeout_secs, "No available paths queue IO timeout in seconds");
2251
2252 MODULE_DESCRIPTION(DM_NAME " multipath target");
2253 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2254 MODULE_LICENSE("GPL");