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         struct mapped_device *md = dm_table_get_md((m)->ti->table);     \
 470                                                                         \
 471         DMDEBUG_LIMIT("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d", \
 472                       dm_device_name(md),                               \
 473                       test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),   \
 474                       test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags), \
 475                       dm_noflush_suspending((m)->ti));                  \
 476 } while (0)
 477
 478 /*
 479  * Check whether bios must be queued in the device-mapper core rather
 480  * than here in the target.
 481  */
 482 static bool __must_push_back(struct multipath *m)
 483 {
 484         return dm_noflush_suspending(m->ti);
 485 }
 486
 487 static bool must_push_back_rq(struct multipath *m)
 488 {
 489         unsigned long flags;
 490         bool ret;
 491
 492         spin_lock_irqsave(&m->lock, flags);
 493         ret = (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) || __must_push_back(m));
 494         spin_unlock_irqrestore(&m->lock, flags);
 495
 496         return ret;
 497 }
 498
 499 /*
 500  * Map cloned requests (request-based multipath)
 501  */
 502 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 503                                    union map_info *map_context,
 504                                    struct request **__clone)
 505 {
 506         struct multipath *m = ti->private;
 507         size_t nr_bytes = blk_rq_bytes(rq);
 508         struct pgpath *pgpath;
 509         struct block_device *bdev;
 510         struct dm_mpath_io *mpio = get_mpio(map_context);
 511         struct request_queue *q;
 512         struct request *clone;
 513
 514         /* Do we need to select a new pgpath? */
 515         pgpath = READ_ONCE(m->current_pgpath);
 516         if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
 517                 pgpath = choose_pgpath(m, nr_bytes);
 518
 519         if (!pgpath) {
 520                 if (must_push_back_rq(m))
 521                         return DM_MAPIO_DELAY_REQUEUE;
 522                 dm_report_EIO(m);       /* Failed */
 523                 return DM_MAPIO_KILL;
 524         } else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
 525                    mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
 526                 pg_init_all_paths(m);
 527                 return DM_MAPIO_DELAY_REQUEUE;
 528         }
 529
 530         mpio->pgpath = pgpath;
 531         mpio->nr_bytes = nr_bytes;
 532
 533         bdev = pgpath->path.dev->bdev;
 534         q = bdev_get_queue(bdev);
 535         clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE,
 536                         BLK_MQ_REQ_NOWAIT);
 537         if (IS_ERR(clone)) {
 538                 /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 539                 if (blk_queue_dying(q)) {
 540                         atomic_inc(&m->pg_init_in_progress);
 541                         activate_or_offline_path(pgpath);
 542                         return DM_MAPIO_DELAY_REQUEUE;
 543                 }
 544
 545                 /*
 546                  * blk-mq's SCHED_RESTART can cover this requeue, so we
 547                  * needn't deal with it by DELAY_REQUEUE. More importantly,
 548                  * we have to return DM_MAPIO_REQUEUE so that blk-mq can
 549                  * get the queue busy feedback (via BLK_STS_RESOURCE),
 550                  * otherwise I/O merging can suffer.
 551                  */
 552                 return DM_MAPIO_REQUEUE;
 553         }
 554         clone->bio = clone->biotail = NULL;
 555         clone->rq_disk = bdev->bd_disk;
 556         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 557         *__clone = clone;
 558
 559         if (pgpath->pg->ps.type->start_io)
 560                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 561                                               &pgpath->path,
 562                                               nr_bytes);
 563         return DM_MAPIO_REMAPPED;
 564 }
 565
 566 static void multipath_release_clone(struct request *clone,
 567                                     union map_info *map_context)
 568 {
 569         if (unlikely(map_context)) {
 570                 /*
 571                  * non-NULL map_context means caller is still map
 572                  * method; must undo multipath_clone_and_map()
 573                  */
 574                 struct dm_mpath_io *mpio = get_mpio(map_context);
 575                 struct pgpath *pgpath = mpio->pgpath;
 576
 577                 if (pgpath && pgpath->pg->ps.type->end_io)
 578                         pgpath->pg->ps.type->end_io(&pgpath->pg->ps,
 579                                                     &pgpath->path,
 580                                                     mpio->nr_bytes,
 581                                                     clone->io_start_time_ns);
 582         }
 583
 584         blk_put_request(clone);
 585 }
 586
 587 /*
 588  * Map cloned bios (bio-based multipath)
 589  */
 590
 591 static void __multipath_queue_bio(struct multipath *m, struct bio *bio)
 592 {
 593         /* Queue for the daemon to resubmit */
 594         bio_list_add(&m->queued_bios, bio);
 595         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
 596                 queue_work(kmultipathd, &m->process_queued_bios);
 597 }
 598
 599 static void multipath_queue_bio(struct multipath *m, struct bio *bio)
 600 {
 601         unsigned long flags;
 602
 603         spin_lock_irqsave(&m->lock, flags);
 604         __multipath_queue_bio(m, bio);
 605         spin_unlock_irqrestore(&m->lock, flags);
 606 }
 607
 608 static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
 609 {
 610         struct pgpath *pgpath;
 611         unsigned long flags;
 612
 613         /* Do we need to select a new pgpath? */
 614         pgpath = READ_ONCE(m->current_pgpath);
 615         if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
 616                 pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 617
 618         if (!pgpath) {
 619                 spin_lock_irqsave(&m->lock, flags);
 620                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 621                         __multipath_queue_bio(m, bio);
 622                         pgpath = ERR_PTR(-EAGAIN);
 623                 }
 624                 spin_unlock_irqrestore(&m->lock, flags);
 625
 626         } else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
 627                    mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
 628                 multipath_queue_bio(m, bio);
 629                 pg_init_all_paths(m);
 630                 return ERR_PTR(-EAGAIN);
 631         }
 632
 633         return pgpath;
 634 }
 635
 636 static int __multipath_map_bio(struct multipath *m, struct bio *bio,
 637                                struct dm_mpath_io *mpio)
 638 {
 639         struct pgpath *pgpath = __map_bio(m, bio);
 640
 641         if (IS_ERR(pgpath))
 642                 return DM_MAPIO_SUBMITTED;
 643
 644         if (!pgpath) {
 645                 if (__must_push_back(m))
 646                         return DM_MAPIO_REQUEUE;
 647                 dm_report_EIO(m);
 648                 return DM_MAPIO_KILL;
 649         }
 650
 651         mpio->pgpath = pgpath;
 652
 653         bio->bi_status = 0;
 654         bio_set_dev(bio, pgpath->path.dev->bdev);
 655         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 656
 657         if (pgpath->pg->ps.type->start_io)
 658                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 659                                               &pgpath->path,
 660                                               mpio->nr_bytes);
 661         return DM_MAPIO_REMAPPED;
 662 }
 663
 664 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 665 {
 666         struct multipath *m = ti->private;
 667         struct dm_mpath_io *mpio = NULL;
 668
 669         multipath_init_per_bio_data(bio, &mpio);
 670         return __multipath_map_bio(m, bio, mpio);
 671 }
 672
 673 static void process_queued_io_list(struct multipath *m)
 674 {
 675         if (m->queue_mode == DM_TYPE_REQUEST_BASED)
 676                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 677         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 678                 queue_work(kmultipathd, &m->process_queued_bios);
 679 }
 680
 681 static void process_queued_bios(struct work_struct *work)
 682 {
 683         int r;
 684         unsigned long flags;
 685         struct bio *bio;
 686         struct bio_list bios;
 687         struct blk_plug plug;
 688         struct multipath *m =
 689                 container_of(work, struct multipath, process_queued_bios);
 690
 691         bio_list_init(&bios);
 692
 693         spin_lock_irqsave(&m->lock, flags);
 694
 695         if (bio_list_empty(&m->queued_bios)) {
 696                 spin_unlock_irqrestore(&m->lock, flags);
 697                 return;
 698         }
 699
 700         bio_list_merge(&bios, &m->queued_bios);
 701         bio_list_init(&m->queued_bios);
 702
 703         spin_unlock_irqrestore(&m->lock, flags);
 704
 705         blk_start_plug(&plug);
 706         while ((bio = bio_list_pop(&bios))) {
 707                 struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 708                 dm_bio_restore(get_bio_details_from_mpio(mpio), bio);
 709                 r = __multipath_map_bio(m, bio, mpio);
 710                 switch (r) {
 711                 case DM_MAPIO_KILL:
 712                         bio->bi_status = BLK_STS_IOERR;
 713                         bio_endio(bio);
 714                         break;
 715                 case DM_MAPIO_REQUEUE:
 716                         bio->bi_status = BLK_STS_DM_REQUEUE;
 717                         bio_endio(bio);
 718                         break;
 719                 case DM_MAPIO_REMAPPED:
 720                         submit_bio_noacct(bio);
 721                         break;
 722                 case DM_MAPIO_SUBMITTED:
 723                         break;
 724                 default:
 725                         WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 726                 }
 727         }
 728         blk_finish_plug(&plug);
 729 }
 730
 731 /*
 732  * If we run out of usable paths, should we queue I/O or error it?
 733  */
 734 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 735                             bool save_old_value, const char *caller)
 736 {
 737         unsigned long flags;
 738         bool queue_if_no_path_bit, saved_queue_if_no_path_bit;
 739         const char *dm_dev_name = dm_device_name(dm_table_get_md(m->ti->table));
 740
 741         DMDEBUG("%s: %s caller=%s queue_if_no_path=%d save_old_value=%d",
 742                 dm_dev_name, __func__, caller, queue_if_no_path, save_old_value);
 743
 744         spin_lock_irqsave(&m->lock, flags);
 745
 746         queue_if_no_path_bit = test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
 747         saved_queue_if_no_path_bit = test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 748
 749         if (save_old_value) {
 750                 if (unlikely(!queue_if_no_path_bit && saved_queue_if_no_path_bit)) {
 751                         DMERR("%s: QIFNP disabled but saved as enabled, saving again loses state, not saving!",
 752                               dm_dev_name);
 753                 } else
 754                         assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path_bit);
 755         } else if (!queue_if_no_path && saved_queue_if_no_path_bit) {
 756                 /* due to "fail_if_no_path" message, need to honor it. */
 757                 clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 758         }
 759         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);
 760
 761         DMDEBUG("%s: after %s changes; QIFNP = %d; SQIFNP = %d; DNFS = %d",
 762                 dm_dev_name, __func__,
 763                 test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
 764                 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags),
 765                 dm_noflush_suspending(m->ti));
 766
 767         spin_unlock_irqrestore(&m->lock, flags);
 768
 769         if (!queue_if_no_path) {
 770                 dm_table_run_md_queue_async(m->ti->table);
 771                 process_queued_io_list(m);
 772         }
 773
 774         return 0;
 775 }
 776
 777 /*
 778  * If the queue_if_no_path timeout fires, turn off queue_if_no_path and
 779  * process any queued I/O.
 780  */
 781 static void queue_if_no_path_timeout_work(struct timer_list *t)
 782 {
 783         struct multipath *m = from_timer(m, t, nopath_timer);
 784         struct mapped_device *md = dm_table_get_md(m->ti->table);
 785
 786         DMWARN("queue_if_no_path timeout on %s, failing queued IO", dm_device_name(md));
 787         queue_if_no_path(m, false, false, __func__);
 788 }
 789
 790 /*
 791  * Enable the queue_if_no_path timeout if necessary.
 792  * Called with m->lock held.
 793  */
 794 static void enable_nopath_timeout(struct multipath *m)
 795 {
 796         unsigned long queue_if_no_path_timeout =
 797                 READ_ONCE(queue_if_no_path_timeout_secs) * HZ;
 798
 799         lockdep_assert_held(&m->lock);
 800
 801         if (queue_if_no_path_timeout > 0 &&
 802             atomic_read(&m->nr_valid_paths) == 0 &&
 803             test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 804                 mod_timer(&m->nopath_timer,
 805                           jiffies + queue_if_no_path_timeout);
 806         }
 807 }
 808
 809 static void disable_nopath_timeout(struct multipath *m)
 810 {
 811         del_timer_sync(&m->nopath_timer);
 812 }
 813
 814 /*
 815  * An event is triggered whenever a path is taken out of use.
 816  * Includes path failure and PG bypass.
 817  */
 818 static void trigger_event(struct work_struct *work)
 819 {
 820         struct multipath *m =
 821                 container_of(work, struct multipath, trigger_event);
 822
 823         dm_table_event(m->ti->table);
 824 }
 825
 826 /*-----------------------------------------------------------------
 827  * Constructor/argument parsing:
 828  * <#multipath feature args> [<arg>]*
 829  * <#hw_handler args> [hw_handler [<arg>]*]
 830  * <#priority groups>
 831  * <initial priority group>
 832  *     [<selector> <#selector args> [<arg>]*
 833  *      <#paths> <#per-path selector args>
 834  *         [<path> [<arg>]* ]+ ]+
 835  *---------------------------------------------------------------*/
 836 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 837                                struct dm_target *ti)
 838 {
 839         int r;
 840         struct path_selector_type *pst;
 841         unsigned ps_argc;
 842
 843         static const struct dm_arg _args[] = {
 844                 {0, 1024, "invalid number of path selector args"},
 845         };
 846
 847         pst = dm_get_path_selector(dm_shift_arg(as));
 848         if (!pst) {
 849                 ti->error = "unknown path selector type";
 850                 return -EINVAL;
 851         }
 852
 853         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 854         if (r) {
 855                 dm_put_path_selector(pst);
 856                 return -EINVAL;
 857         }
 858
 859         r = pst->create(&pg->ps, ps_argc, as->argv);
 860         if (r) {
 861                 dm_put_path_selector(pst);
 862                 ti->error = "path selector constructor failed";
 863                 return r;
 864         }
 865
 866         pg->ps.type = pst;
 867         dm_consume_args(as, ps_argc);
 868
 869         return 0;
 870 }
 871
 872 static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
 873                          const char **attached_handler_name, char **error)
 874 {
 875         struct request_queue *q = bdev_get_queue(bdev);
 876         int r;
 877
 878         if (mpath_double_check_test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, m)) {
 879 retain:
 880                 if (*attached_handler_name) {
 881                         /*
 882                          * Clear any hw_handler_params associated with a
 883                          * handler that isn't already attached.
 884                          */
 885                         if (m->hw_handler_name && strcmp(*attached_handler_name, m->hw_handler_name)) {
 886                                 kfree(m->hw_handler_params);
 887                                 m->hw_handler_params = NULL;
 888                         }
 889
 890                         /*
 891                          * Reset hw_handler_name to match the attached handler
 892                          *
 893                          * NB. This modifies the table line to show the actual
 894                          * handler instead of the original table passed in.
 895                          */
 896                         kfree(m->hw_handler_name);
 897                         m->hw_handler_name = *attached_handler_name;
 898                         *attached_handler_name = NULL;
 899                 }
 900         }
 901
 902         if (m->hw_handler_name) {
 903                 r = scsi_dh_attach(q, m->hw_handler_name);
 904                 if (r == -EBUSY) {
 905                         char b[BDEVNAME_SIZE];
 906
 907                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 908                                bdevname(bdev, b));
 909                         goto retain;
 910                 }
 911                 if (r < 0) {
 912                         *error = "error attaching hardware handler";
 913                         return r;
 914                 }
 915
 916                 if (m->hw_handler_params) {
 917                         r = scsi_dh_set_params(q, m->hw_handler_params);
 918                         if (r < 0) {
 919                                 *error = "unable to set hardware handler parameters";
 920                                 return r;
 921                         }
 922                 }
 923         }
 924
 925         return 0;
 926 }
 927
 928 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 929                                  struct dm_target *ti)
 930 {
 931         int r;
 932         struct pgpath *p;
 933         struct multipath *m = ti->private;
 934         struct request_queue *q;
 935         const char *attached_handler_name = NULL;
 936
 937         /* we need at least a path arg */
 938         if (as->argc < 1) {
 939                 ti->error = "no device given";
 940                 return ERR_PTR(-EINVAL);
 941         }
 942
 943         p = alloc_pgpath();
 944         if (!p)
 945                 return ERR_PTR(-ENOMEM);
 946
 947         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 948                           &p->path.dev);
 949         if (r) {
 950                 ti->error = "error getting device";
 951                 goto bad;
 952         }
 953
 954         q = bdev_get_queue(p->path.dev->bdev);
 955         attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 956         if (attached_handler_name || m->hw_handler_name) {
 957                 INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
 958                 r = setup_scsi_dh(p->path.dev->bdev, m, &attached_handler_name, &ti->error);
 959                 kfree(attached_handler_name);
 960                 if (r) {
 961                         dm_put_device(ti, p->path.dev);
 962                         goto bad;
 963                 }
 964         }
 965
 966         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 967         if (r) {
 968                 dm_put_device(ti, p->path.dev);
 969                 goto bad;
 970         }
 971
 972         return p;
 973  bad:
 974         free_pgpath(p);
 975         return ERR_PTR(r);
 976 }
 977
 978 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 979                                                    struct multipath *m)
 980 {
 981         static const struct dm_arg _args[] = {
 982                 {1, 1024, "invalid number of paths"},
 983                 {0, 1024, "invalid number of selector args"}
 984         };
 985
 986         int r;
 987         unsigned i, nr_selector_args, nr_args;
 988         struct priority_group *pg;
 989         struct dm_target *ti = m->ti;
 990
 991         if (as->argc < 2) {
 992                 as->argc = 0;
 993                 ti->error = "not enough priority group arguments";
 994                 return ERR_PTR(-EINVAL);
 995         }
 996
 997         pg = alloc_priority_group();
 998         if (!pg) {
 999                 ti->error = "couldn't allocate priority group";
1000                 return ERR_PTR(-ENOMEM);
1001         }
1002         pg->m = m;
1003
1004         r = parse_path_selector(as, pg, ti);
1005         if (r)
1006                 goto bad;
1007
1008         /*
1009          * read the paths
1010          */
1011         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
1012         if (r)
1013                 goto bad;
1014
1015         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
1016         if (r)
1017                 goto bad;
1018
1019         nr_args = 1 + nr_selector_args;
1020         for (i = 0; i < pg->nr_pgpaths; i++) {
1021                 struct pgpath *pgpath;
1022                 struct dm_arg_set path_args;
1023
1024                 if (as->argc < nr_args) {
1025                         ti->error = "not enough path parameters";
1026                         r = -EINVAL;
1027                         goto bad;
1028                 }
1029
1030                 path_args.argc = nr_args;
1031                 path_args.argv = as->argv;
1032
1033                 pgpath = parse_path(&path_args, &pg->ps, ti);
1034                 if (IS_ERR(pgpath)) {
1035                         r = PTR_ERR(pgpath);
1036                         goto bad;
1037                 }
1038
1039                 pgpath->pg = pg;
1040                 list_add_tail(&pgpath->list, &pg->pgpaths);
1041                 dm_consume_args(as, nr_args);
1042         }
1043
1044         return pg;
1045
1046  bad:
1047         free_priority_group(pg, ti);
1048         return ERR_PTR(r);
1049 }
1050
1051 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
1052 {
1053         unsigned hw_argc;
1054         int ret;
1055         struct dm_target *ti = m->ti;
1056
1057         static const struct dm_arg _args[] = {
1058                 {0, 1024, "invalid number of hardware handler args"},
1059         };
1060
1061         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
1062                 return -EINVAL;
1063
1064         if (!hw_argc)
1065                 return 0;
1066
1067         if (m->queue_mode == DM_TYPE_BIO_BASED) {
1068                 dm_consume_args(as, hw_argc);
1069                 DMERR("bio-based multipath doesn't allow hardware handler args");
1070                 return 0;
1071         }
1072
1073         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
1074         if (!m->hw_handler_name)
1075                 return -EINVAL;
1076
1077         if (hw_argc > 1) {
1078                 char *p;
1079                 int i, j, len = 4;
1080
1081                 for (i = 0; i <= hw_argc - 2; i++)
1082                         len += strlen(as->argv[i]) + 1;
1083                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1084                 if (!p) {
1085                         ti->error = "memory allocation failed";
1086                         ret = -ENOMEM;
1087                         goto fail;
1088                 }
1089                 j = sprintf(p, "%d", hw_argc - 1);
1090                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
1091                         j = sprintf(p, "%s", as->argv[i]);
1092         }
1093         dm_consume_args(as, hw_argc - 1);
1094
1095         return 0;
1096 fail:
1097         kfree(m->hw_handler_name);
1098         m->hw_handler_name = NULL;
1099         return ret;
1100 }
1101
1102 static int parse_features(struct dm_arg_set *as, struct multipath *m)
1103 {
1104         int r;
1105         unsigned argc;
1106         struct dm_target *ti = m->ti;
1107         const char *arg_name;
1108
1109         static const struct dm_arg _args[] = {
1110                 {0, 8, "invalid number of feature args"},
1111                 {1, 50, "pg_init_retries must be between 1 and 50"},
1112                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1113         };
1114
1115         r = dm_read_arg_group(_args, as, &argc, &ti->error);
1116         if (r)
1117                 return -EINVAL;
1118
1119         if (!argc)
1120                 return 0;
1121
1122         do {
1123                 arg_name = dm_shift_arg(as);
1124                 argc--;
1125
1126                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
1127                         r = queue_if_no_path(m, true, false, __func__);
1128                         continue;
1129                 }
1130
1131                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1132                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1133                         continue;
1134                 }
1135
1136                 if (!strcasecmp(arg_name, "pg_init_retries") &&
1137                     (argc >= 1)) {
1138                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1139                         argc--;
1140                         continue;
1141                 }
1142
1143                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1144                     (argc >= 1)) {
1145                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1146                         argc--;
1147                         continue;
1148                 }
1149
1150                 if (!strcasecmp(arg_name, "queue_mode") &&
1151                     (argc >= 1)) {
1152                         const char *queue_mode_name = dm_shift_arg(as);
1153
1154                         if (!strcasecmp(queue_mode_name, "bio"))
1155                                 m->queue_mode = DM_TYPE_BIO_BASED;
1156                         else if (!strcasecmp(queue_mode_name, "rq") ||
1157                                  !strcasecmp(queue_mode_name, "mq"))
1158                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1159                         else {
1160                                 ti->error = "Unknown 'queue_mode' requested";
1161                                 r = -EINVAL;
1162                         }
1163                         argc--;
1164                         continue;
1165                 }
1166
1167                 ti->error = "Unrecognised multipath feature request";
1168                 r = -EINVAL;
1169         } while (argc && !r);
1170
1171         return r;
1172 }
1173
1174 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1175 {
1176         /* target arguments */
1177         static const struct dm_arg _args[] = {
1178                 {0, 1024, "invalid number of priority groups"},
1179                 {0, 1024, "invalid initial priority group number"},
1180         };
1181
1182         int r;
1183         struct multipath *m;
1184         struct dm_arg_set as;
1185         unsigned pg_count = 0;
1186         unsigned next_pg_num;
1187         unsigned long flags;
1188
1189         as.argc = argc;
1190         as.argv = argv;
1191
1192         m = alloc_multipath(ti);
1193         if (!m) {
1194                 ti->error = "can't allocate multipath";
1195                 return -EINVAL;
1196         }
1197
1198         r = parse_features(&as, m);
1199         if (r)
1200                 goto bad;
1201
1202         r = alloc_multipath_stage2(ti, m);
1203         if (r)
1204                 goto bad;
1205
1206         r = parse_hw_handler(&as, m);
1207         if (r)
1208                 goto bad;
1209
1210         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1211         if (r)
1212                 goto bad;
1213
1214         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1215         if (r)
1216                 goto bad;
1217
1218         if ((!m->nr_priority_groups && next_pg_num) ||
1219             (m->nr_priority_groups && !next_pg_num)) {
1220                 ti->error = "invalid initial priority group";
1221                 r = -EINVAL;
1222                 goto bad;
1223         }
1224
1225         /* parse the priority groups */
1226         while (as.argc) {
1227                 struct priority_group *pg;
1228                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1229
1230                 pg = parse_priority_group(&as, m);
1231                 if (IS_ERR(pg)) {
1232                         r = PTR_ERR(pg);
1233                         goto bad;
1234                 }
1235
1236                 nr_valid_paths += pg->nr_pgpaths;
1237                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1238
1239                 list_add_tail(&pg->list, &m->priority_groups);
1240                 pg_count++;
1241                 pg->pg_num = pg_count;
1242                 if (!--next_pg_num)
1243                         m->next_pg = pg;
1244         }
1245
1246         if (pg_count != m->nr_priority_groups) {
1247                 ti->error = "priority group count mismatch";
1248                 r = -EINVAL;
1249                 goto bad;
1250         }
1251
1252         spin_lock_irqsave(&m->lock, flags);
1253         enable_nopath_timeout(m);
1254         spin_unlock_irqrestore(&m->lock, flags);
1255
1256         ti->num_flush_bios = 1;
1257         ti->num_discard_bios = 1;
1258         ti->num_write_same_bios = 1;
1259         ti->num_write_zeroes_bios = 1;
1260         if (m->queue_mode == DM_TYPE_BIO_BASED)
1261                 ti->per_io_data_size = multipath_per_bio_data_size();
1262         else
1263                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1264
1265         return 0;
1266
1267  bad:
1268         free_multipath(m);
1269         return r;
1270 }
1271
1272 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1273 {
1274         DEFINE_WAIT(wait);
1275
1276         while (1) {
1277                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1278
1279                 if (!atomic_read(&m->pg_init_in_progress))
1280                         break;
1281
1282                 io_schedule();
1283         }
1284         finish_wait(&m->pg_init_wait, &wait);
1285 }
1286
1287 static void flush_multipath_work(struct multipath *m)
1288 {
1289         if (m->hw_handler_name) {
1290                 set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1291                 smp_mb__after_atomic();
1292
1293                 if (atomic_read(&m->pg_init_in_progress))
1294                         flush_workqueue(kmpath_handlerd);
1295                 multipath_wait_for_pg_init_completion(m);
1296
1297                 clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1298                 smp_mb__after_atomic();
1299         }
1300
1301         if (m->queue_mode == DM_TYPE_BIO_BASED)
1302                 flush_work(&m->process_queued_bios);
1303         flush_work(&m->trigger_event);
1304 }
1305
1306 static void multipath_dtr(struct dm_target *ti)
1307 {
1308         struct multipath *m = ti->private;
1309
1310         disable_nopath_timeout(m);
1311         flush_multipath_work(m);
1312         free_multipath(m);
1313 }
1314
1315 /*
1316  * Take a path out of use.
1317  */
1318 static int fail_path(struct pgpath *pgpath)
1319 {
1320         unsigned long flags;
1321         struct multipath *m = pgpath->pg->m;
1322
1323         spin_lock_irqsave(&m->lock, flags);
1324
1325         if (!pgpath->is_active)
1326                 goto out;
1327
1328         DMWARN("%s: Failing path %s.",
1329                dm_device_name(dm_table_get_md(m->ti->table)),
1330                pgpath->path.dev->name);
1331
1332         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1333         pgpath->is_active = false;
1334         pgpath->fail_count++;
1335
1336         atomic_dec(&m->nr_valid_paths);
1337
1338         if (pgpath == m->current_pgpath)
1339                 m->current_pgpath = NULL;
1340
1341         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1342                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1343
1344         schedule_work(&m->trigger_event);
1345
1346         enable_nopath_timeout(m);
1347
1348 out:
1349         spin_unlock_irqrestore(&m->lock, flags);
1350
1351         return 0;
1352 }
1353
1354 /*
1355  * Reinstate a previously-failed path
1356  */
1357 static int reinstate_path(struct pgpath *pgpath)
1358 {
1359         int r = 0, run_queue = 0;
1360         unsigned long flags;
1361         struct multipath *m = pgpath->pg->m;
1362         unsigned nr_valid_paths;
1363
1364         spin_lock_irqsave(&m->lock, flags);
1365
1366         if (pgpath->is_active)
1367                 goto out;
1368
1369         DMWARN("%s: Reinstating path %s.",
1370                dm_device_name(dm_table_get_md(m->ti->table)),
1371                pgpath->path.dev->name);
1372
1373         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1374         if (r)
1375                 goto out;
1376
1377         pgpath->is_active = true;
1378
1379         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1380         if (nr_valid_paths == 1) {
1381                 m->current_pgpath = NULL;
1382                 run_queue = 1;
1383         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1384                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1385                         atomic_inc(&m->pg_init_in_progress);
1386         }
1387
1388         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1389                        pgpath->path.dev->name, nr_valid_paths);
1390
1391         schedule_work(&m->trigger_event);
1392
1393 out:
1394         spin_unlock_irqrestore(&m->lock, flags);
1395         if (run_queue) {
1396                 dm_table_run_md_queue_async(m->ti->table);
1397                 process_queued_io_list(m);
1398         }
1399
1400         if (pgpath->is_active)
1401                 disable_nopath_timeout(m);
1402
1403         return r;
1404 }
1405
1406 /*
1407  * Fail or reinstate all paths that match the provided struct dm_dev.
1408  */
1409 static int action_dev(struct multipath *m, struct dm_dev *dev,
1410                       action_fn action)
1411 {
1412         int r = -EINVAL;
1413         struct pgpath *pgpath;
1414         struct priority_group *pg;
1415
1416         list_for_each_entry(pg, &m->priority_groups, list) {
1417                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1418                         if (pgpath->path.dev == dev)
1419                                 r = action(pgpath);
1420                 }
1421         }
1422
1423         return r;
1424 }
1425
1426 /*
1427  * Temporarily try to avoid having to use the specified PG
1428  */
1429 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1430                       bool bypassed)
1431 {
1432         unsigned long flags;
1433
1434         spin_lock_irqsave(&m->lock, flags);
1435
1436         pg->bypassed = bypassed;
1437         m->current_pgpath = NULL;
1438         m->current_pg = NULL;
1439
1440         spin_unlock_irqrestore(&m->lock, flags);
1441
1442         schedule_work(&m->trigger_event);
1443 }
1444
1445 /*
1446  * Switch to using the specified PG from the next I/O that gets mapped
1447  */
1448 static int switch_pg_num(struct multipath *m, const char *pgstr)
1449 {
1450         struct priority_group *pg;
1451         unsigned pgnum;
1452         unsigned long flags;
1453         char dummy;
1454
1455         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1456             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1457                 DMWARN("invalid PG number supplied to switch_pg_num");
1458                 return -EINVAL;
1459         }
1460
1461         spin_lock_irqsave(&m->lock, flags);
1462         list_for_each_entry(pg, &m->priority_groups, list) {
1463                 pg->bypassed = false;
1464                 if (--pgnum)
1465                         continue;
1466
1467                 m->current_pgpath = NULL;
1468                 m->current_pg = NULL;
1469                 m->next_pg = pg;
1470         }
1471         spin_unlock_irqrestore(&m->lock, flags);
1472
1473         schedule_work(&m->trigger_event);
1474         return 0;
1475 }
1476
1477 /*
1478  * Set/clear bypassed status of a PG.
1479  * PGs are numbered upwards from 1 in the order they were declared.
1480  */
1481 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1482 {
1483         struct priority_group *pg;
1484         unsigned pgnum;
1485         char dummy;
1486
1487         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1488             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1489                 DMWARN("invalid PG number supplied to bypass_pg");
1490                 return -EINVAL;
1491         }
1492
1493         list_for_each_entry(pg, &m->priority_groups, list) {
1494                 if (!--pgnum)
1495                         break;
1496         }
1497
1498         bypass_pg(m, pg, bypassed);
1499         return 0;
1500 }
1501
1502 /*
1503  * Should we retry pg_init immediately?
1504  */
1505 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1506 {
1507         unsigned long flags;
1508         bool limit_reached = false;
1509
1510         spin_lock_irqsave(&m->lock, flags);
1511
1512         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1513             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1514                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1515         else
1516                 limit_reached = true;
1517
1518         spin_unlock_irqrestore(&m->lock, flags);
1519
1520         return limit_reached;
1521 }
1522
1523 static void pg_init_done(void *data, int errors)
1524 {
1525         struct pgpath *pgpath = data;
1526         struct priority_group *pg = pgpath->pg;
1527         struct multipath *m = pg->m;
1528         unsigned long flags;
1529         bool delay_retry = false;
1530
1531         /* device or driver problems */
1532         switch (errors) {
1533         case SCSI_DH_OK:
1534                 break;
1535         case SCSI_DH_NOSYS:
1536                 if (!m->hw_handler_name) {
1537                         errors = 0;
1538                         break;
1539                 }
1540                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1541                       "Error %d.", m->hw_handler_name, errors);
1542                 /*
1543                  * Fail path for now, so we do not ping pong
1544                  */
1545                 fail_path(pgpath);
1546                 break;
1547         case SCSI_DH_DEV_TEMP_BUSY:
1548                 /*
1549                  * Probably doing something like FW upgrade on the
1550                  * controller so try the other pg.
1551                  */
1552                 bypass_pg(m, pg, true);
1553                 break;
1554         case SCSI_DH_RETRY:
1555                 /* Wait before retrying. */
1556                 delay_retry = true;
1557                 /* fall through */
1558         case SCSI_DH_IMM_RETRY:
1559         case SCSI_DH_RES_TEMP_UNAVAIL:
1560                 if (pg_init_limit_reached(m, pgpath))
1561                         fail_path(pgpath);
1562                 errors = 0;
1563                 break;
1564         case SCSI_DH_DEV_OFFLINED:
1565         default:
1566                 /*
1567                  * We probably do not want to fail the path for a device
1568                  * error, but this is what the old dm did. In future
1569                  * patches we can do more advanced handling.
1570                  */
1571                 fail_path(pgpath);
1572         }
1573
1574         spin_lock_irqsave(&m->lock, flags);
1575         if (errors) {
1576                 if (pgpath == m->current_pgpath) {
1577                         DMERR("Could not failover device. Error %d.", errors);
1578                         m->current_pgpath = NULL;
1579                         m->current_pg = NULL;
1580                 }
1581         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1582                 pg->bypassed = false;
1583
1584         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1585                 /* Activations of other paths are still on going */
1586                 goto out;
1587
1588         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1589                 if (delay_retry)
1590                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1591                 else
1592                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1593
1594                 if (__pg_init_all_paths(m))
1595                         goto out;
1596         }
1597         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1598
1599         process_queued_io_list(m);
1600
1601         /*
1602          * Wake up any thread waiting to suspend.
1603          */
1604         wake_up(&m->pg_init_wait);
1605
1606 out:
1607         spin_unlock_irqrestore(&m->lock, flags);
1608 }
1609
1610 static void activate_or_offline_path(struct pgpath *pgpath)
1611 {
1612         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1613
1614         if (pgpath->is_active && !blk_queue_dying(q))
1615                 scsi_dh_activate(q, pg_init_done, pgpath);
1616         else
1617                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1618 }
1619
1620 static void activate_path_work(struct work_struct *work)
1621 {
1622         struct pgpath *pgpath =
1623                 container_of(work, struct pgpath, activate_path.work);
1624
1625         activate_or_offline_path(pgpath);
1626 }
1627
1628 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1629                             blk_status_t error, union map_info *map_context)
1630 {
1631         struct dm_mpath_io *mpio = get_mpio(map_context);
1632         struct pgpath *pgpath = mpio->pgpath;
1633         int r = DM_ENDIO_DONE;
1634
1635         /*
1636          * We don't queue any clone request inside the multipath target
1637          * during end I/O handling, since those clone requests don't have
1638          * bio clones.  If we queue them inside the multipath target,
1639          * we need to make bio clones, that requires memory allocation.
1640          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1641          *  don't have bio clones.)
1642          * Instead of queueing the clone request here, we queue the original
1643          * request into dm core, which will remake a clone request and
1644          * clone bios for it and resubmit it later.
1645          */
1646         if (error && blk_path_error(error)) {
1647                 struct multipath *m = ti->private;
1648
1649                 if (error == BLK_STS_RESOURCE)
1650                         r = DM_ENDIO_DELAY_REQUEUE;
1651                 else
1652                         r = DM_ENDIO_REQUEUE;
1653
1654                 if (pgpath)
1655                         fail_path(pgpath);
1656
1657                 if (!atomic_read(&m->nr_valid_paths) &&
1658                     !must_push_back_rq(m)) {
1659                         if (error == BLK_STS_IOERR)
1660                                 dm_report_EIO(m);
1661                         /* complete with the original error */
1662                         r = DM_ENDIO_DONE;
1663                 }
1664         }
1665
1666         if (pgpath) {
1667                 struct path_selector *ps = &pgpath->pg->ps;
1668
1669                 if (ps->type->end_io)
1670                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1671                                          clone->io_start_time_ns);
1672         }
1673
1674         return r;
1675 }
1676
1677 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1678                                 blk_status_t *error)
1679 {
1680         struct multipath *m = ti->private;
1681         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1682         struct pgpath *pgpath = mpio->pgpath;
1683         unsigned long flags;
1684         int r = DM_ENDIO_DONE;
1685
1686         if (!*error || !blk_path_error(*error))
1687                 goto done;
1688
1689         if (pgpath)
1690                 fail_path(pgpath);
1691
1692         if (!atomic_read(&m->nr_valid_paths)) {
1693                 spin_lock_irqsave(&m->lock, flags);
1694                 if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1695                         if (__must_push_back(m)) {
1696                                 r = DM_ENDIO_REQUEUE;
1697                         } else {
1698                                 dm_report_EIO(m);
1699                                 *error = BLK_STS_IOERR;
1700                         }
1701                         spin_unlock_irqrestore(&m->lock, flags);
1702                         goto done;
1703                 }
1704                 spin_unlock_irqrestore(&m->lock, flags);
1705         }
1706
1707         multipath_queue_bio(m, clone);
1708         r = DM_ENDIO_INCOMPLETE;
1709 done:
1710         if (pgpath) {
1711                 struct path_selector *ps = &pgpath->pg->ps;
1712
1713                 if (ps->type->end_io)
1714                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1715                                          dm_start_time_ns_from_clone(clone));
1716         }
1717
1718         return r;
1719 }
1720
1721 /*
1722  * Suspend with flush can't complete until all the I/O is processed
1723  * so if the last path fails we must error any remaining I/O.
1724  * - Note that if the freeze_bdev fails while suspending, the
1725  *   queue_if_no_path state is lost - userspace should reset it.
1726  * Otherwise, during noflush suspend, queue_if_no_path will not change.
1727  */
1728 static void multipath_presuspend(struct dm_target *ti)
1729 {
1730         struct multipath *m = ti->private;
1731
1732         /* FIXME: bio-based shouldn't need to always disable queue_if_no_path */
1733         if (m->queue_mode == DM_TYPE_BIO_BASED || !dm_noflush_suspending(m->ti))
1734                 queue_if_no_path(m, false, true, __func__);
1735 }
1736
1737 static void multipath_postsuspend(struct dm_target *ti)
1738 {
1739         struct multipath *m = ti->private;
1740
1741         mutex_lock(&m->work_mutex);
1742         flush_multipath_work(m);
1743         mutex_unlock(&m->work_mutex);
1744 }
1745
1746 /*
1747  * Restore the queue_if_no_path setting.
1748  */
1749 static void multipath_resume(struct dm_target *ti)
1750 {
1751         struct multipath *m = ti->private;
1752         unsigned long flags;
1753
1754         spin_lock_irqsave(&m->lock, flags);
1755         if (test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) {
1756                 set_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1757                 clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
1758         }
1759
1760         DMDEBUG("%s: %s finished; QIFNP = %d; SQIFNP = %d",
1761                 dm_device_name(dm_table_get_md(m->ti->table)), __func__,
1762                 test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
1763                 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1764
1765         spin_unlock_irqrestore(&m->lock, flags);
1766 }
1767
1768 /*
1769  * Info output has the following format:
1770  * num_multipath_feature_args [multipath_feature_args]*
1771  * num_handler_status_args [handler_status_args]*
1772  * num_groups init_group_number
1773  *            [A|D|E num_ps_status_args [ps_status_args]*
1774  *             num_paths num_selector_args
1775  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1776  *
1777  * Table output has the following format (identical to the constructor string):
1778  * num_feature_args [features_args]*
1779  * num_handler_args hw_handler [hw_handler_args]*
1780  * num_groups init_group_number
1781  *     [priority selector-name num_ps_args [ps_args]*
1782  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1783  */
1784 static void multipath_status(struct dm_target *ti, status_type_t type,
1785                              unsigned status_flags, char *result, unsigned maxlen)
1786 {
1787         int sz = 0;
1788         unsigned long flags;
1789         struct multipath *m = ti->private;
1790         struct priority_group *pg;
1791         struct pgpath *p;
1792         unsigned pg_num;
1793         char state;
1794
1795         spin_lock_irqsave(&m->lock, flags);
1796
1797         /* Features */
1798         if (type == STATUSTYPE_INFO)
1799                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1800                        atomic_read(&m->pg_init_count));
1801         else {
1802                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1803                               (m->pg_init_retries > 0) * 2 +
1804                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1805                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1806                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1807
1808                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1809                         DMEMIT("queue_if_no_path ");
1810                 if (m->pg_init_retries)
1811                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1812                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1813                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1814                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1815                         DMEMIT("retain_attached_hw_handler ");
1816                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1817                         switch(m->queue_mode) {
1818                         case DM_TYPE_BIO_BASED:
1819                                 DMEMIT("queue_mode bio ");
1820                                 break;
1821                         default:
1822                                 WARN_ON_ONCE(true);
1823                                 break;
1824                         }
1825                 }
1826         }
1827
1828         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1829                 DMEMIT("0 ");
1830         else
1831                 DMEMIT("1 %s ", m->hw_handler_name);
1832
1833         DMEMIT("%u ", m->nr_priority_groups);
1834
1835         if (m->next_pg)
1836                 pg_num = m->next_pg->pg_num;
1837         else if (m->current_pg)
1838                 pg_num = m->current_pg->pg_num;
1839         else
1840                 pg_num = (m->nr_priority_groups ? 1 : 0);
1841
1842         DMEMIT("%u ", pg_num);
1843
1844         switch (type) {
1845         case STATUSTYPE_INFO:
1846                 list_for_each_entry(pg, &m->priority_groups, list) {
1847                         if (pg->bypassed)
1848                                 state = 'D';    /* Disabled */
1849                         else if (pg == m->current_pg)
1850                                 state = 'A';    /* Currently Active */
1851                         else
1852                                 state = 'E';    /* Enabled */
1853
1854                         DMEMIT("%c ", state);
1855
1856                         if (pg->ps.type->status)
1857                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1858                                                           result + sz,
1859                                                           maxlen - sz);
1860                         else
1861                                 DMEMIT("0 ");
1862
1863                         DMEMIT("%u %u ", pg->nr_pgpaths,
1864                                pg->ps.type->info_args);
1865
1866                         list_for_each_entry(p, &pg->pgpaths, list) {
1867                                 DMEMIT("%s %s %u ", p->path.dev->name,
1868                                        p->is_active ? "A" : "F",
1869                                        p->fail_count);
1870                                 if (pg->ps.type->status)
1871                                         sz += pg->ps.type->status(&pg->ps,
1872                                               &p->path, type, result + sz,
1873                                               maxlen - sz);
1874                         }
1875                 }
1876                 break;
1877
1878         case STATUSTYPE_TABLE:
1879                 list_for_each_entry(pg, &m->priority_groups, list) {
1880                         DMEMIT("%s ", pg->ps.type->name);
1881
1882                         if (pg->ps.type->status)
1883                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1884                                                           result + sz,
1885                                                           maxlen - sz);
1886                         else
1887                                 DMEMIT("0 ");
1888
1889                         DMEMIT("%u %u ", pg->nr_pgpaths,
1890                                pg->ps.type->table_args);
1891
1892                         list_for_each_entry(p, &pg->pgpaths, list) {
1893                                 DMEMIT("%s ", p->path.dev->name);
1894                                 if (pg->ps.type->status)
1895                                         sz += pg->ps.type->status(&pg->ps,
1896                                               &p->path, type, result + sz,
1897                                               maxlen - sz);
1898                         }
1899                 }
1900                 break;
1901         }
1902
1903         spin_unlock_irqrestore(&m->lock, flags);
1904 }
1905
1906 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv,
1907                              char *result, unsigned maxlen)
1908 {
1909         int r = -EINVAL;
1910         struct dm_dev *dev;
1911         struct multipath *m = ti->private;
1912         action_fn action;
1913         unsigned long flags;
1914
1915         mutex_lock(&m->work_mutex);
1916
1917         if (dm_suspended(ti)) {
1918                 r = -EBUSY;
1919                 goto out;
1920         }
1921
1922         if (argc == 1) {
1923                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1924                         r = queue_if_no_path(m, true, false, __func__);
1925                         spin_lock_irqsave(&m->lock, flags);
1926                         enable_nopath_timeout(m);
1927                         spin_unlock_irqrestore(&m->lock, flags);
1928                         goto out;
1929                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1930                         r = queue_if_no_path(m, false, false, __func__);
1931                         disable_nopath_timeout(m);
1932                         goto out;
1933                 }
1934         }
1935
1936         if (argc != 2) {
1937                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1938                 goto out;
1939         }
1940
1941         if (!strcasecmp(argv[0], "disable_group")) {
1942                 r = bypass_pg_num(m, argv[1], true);
1943                 goto out;
1944         } else if (!strcasecmp(argv[0], "enable_group")) {
1945                 r = bypass_pg_num(m, argv[1], false);
1946                 goto out;
1947         } else if (!strcasecmp(argv[0], "switch_group")) {
1948                 r = switch_pg_num(m, argv[1]);
1949                 goto out;
1950         } else if (!strcasecmp(argv[0], "reinstate_path"))
1951                 action = reinstate_path;
1952         else if (!strcasecmp(argv[0], "fail_path"))
1953                 action = fail_path;
1954         else {
1955                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1956                 goto out;
1957         }
1958
1959         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1960         if (r) {
1961                 DMWARN("message: error getting device %s",
1962                        argv[1]);
1963                 goto out;
1964         }
1965
1966         r = action_dev(m, dev, action);
1967
1968         dm_put_device(ti, dev);
1969
1970 out:
1971         mutex_unlock(&m->work_mutex);
1972         return r;
1973 }
1974
1975 static int multipath_prepare_ioctl(struct dm_target *ti,
1976                                    struct block_device **bdev)
1977 {
1978         struct multipath *m = ti->private;
1979         struct pgpath *pgpath;
1980         unsigned long flags;
1981         int r;
1982
1983         pgpath = READ_ONCE(m->current_pgpath);
1984         if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
1985                 pgpath = choose_pgpath(m, 0);
1986
1987         if (pgpath) {
1988                 if (!mpath_double_check_test_bit(MPATHF_QUEUE_IO, m)) {
1989                         *bdev = pgpath->path.dev->bdev;
1990                         r = 0;
1991                 } else {
1992                         /* pg_init has not started or completed */
1993                         r = -ENOTCONN;
1994                 }
1995         } else {
1996                 /* No path is available */
1997                 r = -EIO;
1998                 spin_lock_irqsave(&m->lock, flags);
1999                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
2000                         r = -ENOTCONN;
2001                 spin_unlock_irqrestore(&m->lock, flags);
2002         }
2003
2004         if (r == -ENOTCONN) {
2005                 if (!READ_ONCE(m->current_pg)) {
2006                         /* Path status changed, redo selection */
2007                         (void) choose_pgpath(m, 0);
2008                 }
2009                 spin_lock_irqsave(&m->lock, flags);
2010                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
2011                         (void) __pg_init_all_paths(m);
2012                 spin_unlock_irqrestore(&m->lock, flags);
2013                 dm_table_run_md_queue_async(m->ti->table);
2014                 process_queued_io_list(m);
2015         }
2016
2017         /*
2018          * Only pass ioctls through if the device sizes match exactly.
2019          */
2020         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
2021                 return 1;
2022         return r;
2023 }
2024
2025 static int multipath_iterate_devices(struct dm_target *ti,
2026                                      iterate_devices_callout_fn fn, void *data)
2027 {
2028         struct multipath *m = ti->private;
2029         struct priority_group *pg;
2030         struct pgpath *p;
2031         int ret = 0;
2032
2033         list_for_each_entry(pg, &m->priority_groups, list) {
2034                 list_for_each_entry(p, &pg->pgpaths, list) {
2035                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
2036                         if (ret)
2037                                 goto out;
2038                 }
2039         }
2040
2041 out:
2042         return ret;
2043 }
2044
2045 static int pgpath_busy(struct pgpath *pgpath)
2046 {
2047         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
2048
2049         return blk_lld_busy(q);
2050 }
2051
2052 /*
2053  * We return "busy", only when we can map I/Os but underlying devices
2054  * are busy (so even if we map I/Os now, the I/Os will wait on
2055  * the underlying queue).
2056  * In other words, if we want to kill I/Os or queue them inside us
2057  * due to map unavailability, we don't return "busy".  Otherwise,
2058  * dm core won't give us the I/Os and we can't do what we want.
2059  */
2060 static int multipath_busy(struct dm_target *ti)
2061 {
2062         bool busy = false, has_active = false;
2063         struct multipath *m = ti->private;
2064         struct priority_group *pg, *next_pg;
2065         struct pgpath *pgpath;
2066
2067         /* pg_init in progress */
2068         if (atomic_read(&m->pg_init_in_progress))
2069                 return true;
2070
2071         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
2072         if (!atomic_read(&m->nr_valid_paths)) {
2073                 unsigned long flags;
2074                 spin_lock_irqsave(&m->lock, flags);
2075                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
2076                         spin_unlock_irqrestore(&m->lock, flags);
2077                         return (m->queue_mode != DM_TYPE_REQUEST_BASED);
2078                 }
2079                 spin_unlock_irqrestore(&m->lock, flags);
2080         }
2081
2082         /* Guess which priority_group will be used at next mapping time */
2083         pg = READ_ONCE(m->current_pg);
2084         next_pg = READ_ONCE(m->next_pg);
2085         if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
2086                 pg = next_pg;
2087
2088         if (!pg) {
2089                 /*
2090                  * We don't know which pg will be used at next mapping time.
2091                  * We don't call choose_pgpath() here to avoid to trigger
2092                  * pg_init just by busy checking.
2093                  * So we don't know whether underlying devices we will be using
2094                  * at next mapping time are busy or not. Just try mapping.
2095                  */
2096                 return busy;
2097         }
2098
2099         /*
2100          * If there is one non-busy active path at least, the path selector
2101          * will be able to select it. So we consider such a pg as not busy.
2102          */
2103         busy = true;
2104         list_for_each_entry(pgpath, &pg->pgpaths, list) {
2105                 if (pgpath->is_active) {
2106                         has_active = true;
2107                         if (!pgpath_busy(pgpath)) {
2108                                 busy = false;
2109                                 break;
2110                         }
2111                 }
2112         }
2113
2114         if (!has_active) {
2115                 /*
2116                  * No active path in this pg, so this pg won't be used and
2117                  * the current_pg will be changed at next mapping time.
2118                  * We need to try mapping to determine it.
2119                  */
2120                 busy = false;
2121         }
2122
2123         return busy;
2124 }
2125
2126 /*-----------------------------------------------------------------
2127  * Module setup
2128  *---------------------------------------------------------------*/
2129 static struct target_type multipath_target = {
2130         .name = "multipath",
2131         .version = {1, 14, 0},
2132         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE |
2133                     DM_TARGET_PASSES_INTEGRITY,
2134         .module = THIS_MODULE,
2135         .ctr = multipath_ctr,
2136         .dtr = multipath_dtr,
2137         .clone_and_map_rq = multipath_clone_and_map,
2138         .release_clone_rq = multipath_release_clone,
2139         .rq_end_io = multipath_end_io,
2140         .map = multipath_map_bio,
2141         .end_io = multipath_end_io_bio,
2142         .presuspend = multipath_presuspend,
2143         .postsuspend = multipath_postsuspend,
2144         .resume = multipath_resume,
2145         .status = multipath_status,
2146         .message = multipath_message,
2147         .prepare_ioctl = multipath_prepare_ioctl,
2148         .iterate_devices = multipath_iterate_devices,
2149         .busy = multipath_busy,
2150 };
2151
2152 static int __init dm_multipath_init(void)
2153 {
2154         int r;
2155
2156         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2157         if (!kmultipathd) {
2158                 DMERR("failed to create workqueue kmpathd");
2159                 r = -ENOMEM;
2160                 goto bad_alloc_kmultipathd;
2161         }
2162
2163         /*
2164          * A separate workqueue is used to handle the device handlers
2165          * to avoid overloading existing workqueue. Overloading the
2166          * old workqueue would also create a bottleneck in the
2167          * path of the storage hardware device activation.
2168          */
2169         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2170                                                   WQ_MEM_RECLAIM);
2171         if (!kmpath_handlerd) {
2172                 DMERR("failed to create workqueue kmpath_handlerd");
2173                 r = -ENOMEM;
2174                 goto bad_alloc_kmpath_handlerd;
2175         }
2176
2177         r = dm_register_target(&multipath_target);
2178         if (r < 0) {
2179                 DMERR("request-based register failed %d", r);
2180                 r = -EINVAL;
2181                 goto bad_register_target;
2182         }
2183
2184         return 0;
2185
2186 bad_register_target:
2187         destroy_workqueue(kmpath_handlerd);
2188 bad_alloc_kmpath_handlerd:
2189         destroy_workqueue(kmultipathd);
2190 bad_alloc_kmultipathd:
2191         return r;
2192 }
2193
2194 static void __exit dm_multipath_exit(void)
2195 {
2196         destroy_workqueue(kmpath_handlerd);
2197         destroy_workqueue(kmultipathd);
2198
2199         dm_unregister_target(&multipath_target);
2200 }
2201
2202 module_init(dm_multipath_init);
2203 module_exit(dm_multipath_exit);
2204
2205 module_param_named(queue_if_no_path_timeout_secs,
2206                    queue_if_no_path_timeout_secs, ulong, S_IRUGO | S_IWUSR);
2207 MODULE_PARM_DESC(queue_if_no_path_timeout_secs, "No available paths queue IO timeout in seconds");
2208
2209 MODULE_DESCRIPTION(DM_NAME " multipath target");
2210 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2211 MODULE_LICENSE("GPL");