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.h"
  11 #include "dm-path-selector.h"
  12 #include "dm-uevent.h"
  13
  14 #include <linux/blkdev.h>
  15 #include <linux/ctype.h>
  16 #include <linux/init.h>
  17 #include <linux/mempool.h>
  18 #include <linux/module.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/slab.h>
  21 #include <linux/time.h>
  22 #include <linux/workqueue.h>
  23 #include <linux/delay.h>
  24 #include <scsi/scsi_dh.h>
  25 #include <linux/atomic.h>
  26
  27 #define DM_MSG_PREFIX "multipath"
  28 #define DM_PG_INIT_DELAY_MSECS 2000
  29 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  30
  31 /* Path properties */
  32 struct pgpath {
  33         struct list_head list;
  34
  35         struct priority_group *pg;      /* Owning PG */
  36         unsigned is_active;             /* Path status */
  37         unsigned fail_count;            /* Cumulative failure count */
  38
  39         struct dm_path path;
  40         struct delayed_work activate_path;
  41 };
  42
  43 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  44
  45 /*
  46  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  47  * Each has a path selector which controls which path gets used.
  48  */
  49 struct priority_group {
  50         struct list_head list;
  51
  52         struct multipath *m;            /* Owning multipath instance */
  53         struct path_selector ps;
  54
  55         unsigned pg_num;                /* Reference number */
  56         unsigned bypassed;              /* Temporarily bypass this PG? */
  57
  58         unsigned nr_pgpaths;            /* Number of paths in PG */
  59         struct list_head pgpaths;
  60 };
  61
  62 /* Multipath context */
  63 struct multipath {
  64         struct list_head list;
  65         struct dm_target *ti;
  66
  67         const char *hw_handler_name;
  68         char *hw_handler_params;
  69
  70         spinlock_t lock;
  71
  72         unsigned nr_priority_groups;
  73         struct list_head priority_groups;
  74
  75         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  76
  77         unsigned pg_init_required;      /* pg_init needs calling? */
  78         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  79         unsigned pg_init_delay_retry;   /* Delay pg_init retry? */
  80
  81         unsigned nr_valid_paths;        /* Total number of usable paths */
  82         struct pgpath *current_pgpath;
  83         struct priority_group *current_pg;
  84         struct priority_group *next_pg; /* Switch to this PG if set */
  85         unsigned repeat_count;          /* I/Os left before calling PS again */
  86
  87         unsigned queue_io:1;            /* Must we queue all I/O? */
  88         unsigned queue_if_no_path:1;    /* Queue I/O if last path fails? */
  89         unsigned saved_queue_if_no_path:1; /* Saved state during suspension */
  90         unsigned retain_attached_hw_handler:1; /* If there's already a hw_handler present, don't change it. */
  91         unsigned pg_init_disabled:1;    /* pg_init is not currently allowed */
  92
  93         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  94         unsigned pg_init_count;         /* Number of times pg_init called */
  95         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  96
  97         struct work_struct trigger_event;
  98
  99         /*
 100          * We must use a mempool of dm_mpath_io structs so that we
 101          * can resubmit bios on error.
 102          */
 103         mempool_t *mpio_pool;
 104
 105         struct mutex work_mutex;
 106 };
 107
 108 /*
 109  * Context information attached to each bio we process.
 110  */
 111 struct dm_mpath_io {
 112         struct pgpath *pgpath;
 113         size_t nr_bytes;
 114 };
 115
 116 typedef int (*action_fn) (struct pgpath *pgpath);
 117
 118 static struct kmem_cache *_mpio_cache;
 119
 120 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 121 static void trigger_event(struct work_struct *work);
 122 static void activate_path(struct work_struct *work);
 123 static int __pgpath_busy(struct pgpath *pgpath);
 124
 125
 126 /*-----------------------------------------------
 127  * Allocation routines
 128  *-----------------------------------------------*/
 129
 130 static struct pgpath *alloc_pgpath(void)
 131 {
 132         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 133
 134         if (pgpath) {
 135                 pgpath->is_active = 1;
 136                 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);
 137         }
 138
 139         return pgpath;
 140 }
 141
 142 static void free_pgpath(struct pgpath *pgpath)
 143 {
 144         kfree(pgpath);
 145 }
 146
 147 static struct priority_group *alloc_priority_group(void)
 148 {
 149         struct priority_group *pg;
 150
 151         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 152
 153         if (pg)
 154                 INIT_LIST_HEAD(&pg->pgpaths);
 155
 156         return pg;
 157 }
 158
 159 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 160 {
 161         struct pgpath *pgpath, *tmp;
 162
 163         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 164                 list_del(&pgpath->list);
 165                 dm_put_device(ti, pgpath->path.dev);
 166                 free_pgpath(pgpath);
 167         }
 168 }
 169
 170 static void free_priority_group(struct priority_group *pg,
 171                                 struct dm_target *ti)
 172 {
 173         struct path_selector *ps = &pg->ps;
 174
 175         if (ps->type) {
 176                 ps->type->destroy(ps);
 177                 dm_put_path_selector(ps->type);
 178         }
 179
 180         free_pgpaths(&pg->pgpaths, ti);
 181         kfree(pg);
 182 }
 183
 184 static struct multipath *alloc_multipath(struct dm_target *ti, bool use_blk_mq)
 185 {
 186         struct multipath *m;
 187
 188         m = kzalloc(sizeof(*m), GFP_KERNEL);
 189         if (m) {
 190                 INIT_LIST_HEAD(&m->priority_groups);
 191                 spin_lock_init(&m->lock);
 192                 m->queue_io = 1;
 193                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 194                 INIT_WORK(&m->trigger_event, trigger_event);
 195                 init_waitqueue_head(&m->pg_init_wait);
 196                 mutex_init(&m->work_mutex);
 197
 198                 m->mpio_pool = NULL;
 199                 if (!use_blk_mq) {
 200                         unsigned min_ios = dm_get_reserved_rq_based_ios();
 201
 202                         m->mpio_pool = mempool_create_slab_pool(min_ios, _mpio_cache);
 203                         if (!m->mpio_pool) {
 204                                 kfree(m);
 205                                 return NULL;
 206                         }
 207                 }
 208
 209                 m->ti = ti;
 210                 ti->private = m;
 211         }
 212
 213         return m;
 214 }
 215
 216 static void free_multipath(struct multipath *m)
 217 {
 218         struct priority_group *pg, *tmp;
 219
 220         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 221                 list_del(&pg->list);
 222                 free_priority_group(pg, m->ti);
 223         }
 224
 225         kfree(m->hw_handler_name);
 226         kfree(m->hw_handler_params);
 227         mempool_destroy(m->mpio_pool);
 228         kfree(m);
 229 }
 230
 231 static struct dm_mpath_io *get_mpio(union map_info *info)
 232 {
 233         return info->ptr;
 234 }
 235
 236 static struct dm_mpath_io *set_mpio(struct multipath *m, union map_info *info)
 237 {
 238         struct dm_mpath_io *mpio;
 239
 240         if (!m->mpio_pool) {
 241                 /* Use blk-mq pdu memory requested via per_io_data_size */
 242                 mpio = get_mpio(info);
 243                 memset(mpio, 0, sizeof(*mpio));
 244                 return mpio;
 245         }
 246
 247         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 248         if (!mpio)
 249                 return NULL;
 250
 251         memset(mpio, 0, sizeof(*mpio));
 252         info->ptr = mpio;
 253
 254         return mpio;
 255 }
 256
 257 static void clear_request_fn_mpio(struct multipath *m, union map_info *info)
 258 {
 259         /* Only needed for non blk-mq (.request_fn) multipath */
 260         if (m->mpio_pool) {
 261                 struct dm_mpath_io *mpio = info->ptr;
 262
 263                 info->ptr = NULL;
 264                 mempool_free(mpio, m->mpio_pool);
 265         }
 266 }
 267
 268 /*-----------------------------------------------
 269  * Path selection
 270  *-----------------------------------------------*/
 271
 272 static int __pg_init_all_paths(struct multipath *m)
 273 {
 274         struct pgpath *pgpath;
 275         unsigned long pg_init_delay = 0;
 276
 277         if (m->pg_init_in_progress || m->pg_init_disabled)
 278                 return 0;
 279
 280         m->pg_init_count++;
 281         m->pg_init_required = 0;
 282
 283         /* Check here to reset pg_init_required */
 284         if (!m->current_pg)
 285                 return 0;
 286
 287         if (m->pg_init_delay_retry)
 288                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 289                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 290         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 291                 /* Skip failed paths */
 292                 if (!pgpath->is_active)
 293                         continue;
 294                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 295                                        pg_init_delay))
 296                         m->pg_init_in_progress++;
 297         }
 298         return m->pg_init_in_progress;
 299 }
 300
 301 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 302 {
 303         m->current_pg = pgpath->pg;
 304
 305         /* Must we initialise the PG first, and queue I/O till it's ready? */
 306         if (m->hw_handler_name) {
 307                 m->pg_init_required = 1;
 308                 m->queue_io = 1;
 309         } else {
 310                 m->pg_init_required = 0;
 311                 m->queue_io = 0;
 312         }
 313
 314         m->pg_init_count = 0;
 315 }
 316
 317 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 318                                size_t nr_bytes)
 319 {
 320         struct dm_path *path;
 321
 322         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 323         if (!path)
 324                 return -ENXIO;
 325
 326         m->current_pgpath = path_to_pgpath(path);
 327
 328         if (m->current_pg != pg)
 329                 __switch_pg(m, m->current_pgpath);
 330
 331         return 0;
 332 }
 333
 334 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 335 {
 336         struct priority_group *pg;
 337         unsigned bypassed = 1;
 338
 339         if (!m->nr_valid_paths) {
 340                 m->queue_io = 0;
 341                 goto failed;
 342         }
 343
 344         /* Were we instructed to switch PG? */
 345         if (m->next_pg) {
 346                 pg = m->next_pg;
 347                 m->next_pg = NULL;
 348                 if (!__choose_path_in_pg(m, pg, nr_bytes))
 349                         return;
 350         }
 351
 352         /* Don't change PG until it has no remaining paths */
 353         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 354                 return;
 355
 356         /*
 357          * Loop through priority groups until we find a valid path.
 358          * First time we skip PGs marked 'bypassed'.
 359          * Second time we only try the ones we skipped, but set
 360          * pg_init_delay_retry so we do not hammer controllers.
 361          */
 362         do {
 363                 list_for_each_entry(pg, &m->priority_groups, list) {
 364                         if (pg->bypassed == bypassed)
 365                                 continue;
 366                         if (!__choose_path_in_pg(m, pg, nr_bytes)) {
 367                                 if (!bypassed)
 368                                         m->pg_init_delay_retry = 1;
 369                                 return;
 370                         }
 371                 }
 372         } while (bypassed--);
 373
 374 failed:
 375         m->current_pgpath = NULL;
 376         m->current_pg = NULL;
 377 }
 378
 379 /*
 380  * Check whether bios must be queued in the device-mapper core rather
 381  * than here in the target.
 382  *
 383  * m->lock must be held on entry.
 384  *
 385  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 386  * same value then we are not between multipath_presuspend()
 387  * and multipath_resume() calls and we have no need to check
 388  * for the DMF_NOFLUSH_SUSPENDING flag.
 389  */
 390 static int __must_push_back(struct multipath *m)
 391 {
 392         return (m->queue_if_no_path ||
 393                 (m->queue_if_no_path != m->saved_queue_if_no_path &&
 394                  dm_noflush_suspending(m->ti)));
 395 }
 396
 397 /*
 398  * Map cloned requests
 399  */
 400 static int __multipath_map(struct dm_target *ti, struct request *clone,
 401                            union map_info *map_context,
 402                            struct request *rq, struct request **__clone)
 403 {
 404         struct multipath *m = (struct multipath *) ti->private;
 405         int r = DM_MAPIO_REQUEUE;
 406         size_t nr_bytes = clone ? blk_rq_bytes(clone) : blk_rq_bytes(rq);
 407         struct pgpath *pgpath;
 408         struct block_device *bdev;
 409         struct dm_mpath_io *mpio;
 410
 411         spin_lock_irq(&m->lock);
 412
 413         /* Do we need to select a new pgpath? */
 414         if (!m->current_pgpath ||
 415             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 416                 __choose_pgpath(m, nr_bytes);
 417
 418         pgpath = m->current_pgpath;
 419
 420         if (!pgpath) {
 421                 if (!__must_push_back(m))
 422                         r = -EIO;       /* Failed */
 423                 goto out_unlock;
 424         } else if (m->queue_io || m->pg_init_required) {
 425                 __pg_init_all_paths(m);
 426                 goto out_unlock;
 427         }
 428
 429         mpio = set_mpio(m, map_context);
 430         if (!mpio)
 431                 /* ENOMEM, requeue */
 432                 goto out_unlock;
 433
 434         mpio->pgpath = pgpath;
 435         mpio->nr_bytes = nr_bytes;
 436
 437         bdev = pgpath->path.dev->bdev;
 438
 439         spin_unlock_irq(&m->lock);
 440
 441         if (clone) {
 442                 /*
 443                  * Old request-based interface: allocated clone is passed in.
 444                  * Used by: .request_fn stacked on .request_fn path(s).
 445                  */
 446                 clone->q = bdev_get_queue(bdev);
 447                 clone->rq_disk = bdev->bd_disk;
 448                 clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 449         } else {
 450                 /*
 451                  * blk-mq request-based interface; used by both:
 452                  * .request_fn stacked on blk-mq path(s) and
 453                  * blk-mq stacked on blk-mq path(s).
 454                  */
 455                 *__clone = blk_get_request(bdev_get_queue(bdev),
 456                                            rq_data_dir(rq), GFP_ATOMIC);
 457                 if (IS_ERR(*__clone)) {
 458                         /* ENOMEM, requeue */
 459                         clear_request_fn_mpio(m, map_context);
 460                         return r;
 461                 }
 462                 (*__clone)->bio = (*__clone)->biotail = NULL;
 463                 (*__clone)->rq_disk = bdev->bd_disk;
 464                 (*__clone)->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 465         }
 466
 467         if (pgpath->pg->ps.type->start_io)
 468                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 469                                               &pgpath->path,
 470                                               nr_bytes);
 471         return DM_MAPIO_REMAPPED;
 472
 473 out_unlock:
 474         spin_unlock_irq(&m->lock);
 475
 476         return r;
 477 }
 478
 479 static int multipath_map(struct dm_target *ti, struct request *clone,
 480                          union map_info *map_context)
 481 {
 482         return __multipath_map(ti, clone, map_context, NULL, NULL);
 483 }
 484
 485 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 486                                    union map_info *map_context,
 487                                    struct request **clone)
 488 {
 489         return __multipath_map(ti, NULL, map_context, rq, clone);
 490 }
 491
 492 static void multipath_release_clone(struct request *clone)
 493 {
 494         blk_put_request(clone);
 495 }
 496
 497 /*
 498  * If we run out of usable paths, should we queue I/O or error it?
 499  */
 500 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 501                             unsigned save_old_value)
 502 {
 503         unsigned long flags;
 504
 505         spin_lock_irqsave(&m->lock, flags);
 506
 507         if (save_old_value)
 508                 m->saved_queue_if_no_path = m->queue_if_no_path;
 509         else
 510                 m->saved_queue_if_no_path = queue_if_no_path;
 511         m->queue_if_no_path = queue_if_no_path;
 512         spin_unlock_irqrestore(&m->lock, flags);
 513
 514         if (!queue_if_no_path)
 515                 dm_table_run_md_queue_async(m->ti->table);
 516
 517         return 0;
 518 }
 519
 520 /*
 521  * An event is triggered whenever a path is taken out of use.
 522  * Includes path failure and PG bypass.
 523  */
 524 static void trigger_event(struct work_struct *work)
 525 {
 526         struct multipath *m =
 527                 container_of(work, struct multipath, trigger_event);
 528
 529         dm_table_event(m->ti->table);
 530 }
 531
 532 /*-----------------------------------------------------------------
 533  * Constructor/argument parsing:
 534  * <#multipath feature args> [<arg>]*
 535  * <#hw_handler args> [hw_handler [<arg>]*]
 536  * <#priority groups>
 537  * <initial priority group>
 538  *     [<selector> <#selector args> [<arg>]*
 539  *      <#paths> <#per-path selector args>
 540  *         [<path> [<arg>]* ]+ ]+
 541  *---------------------------------------------------------------*/
 542 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 543                                struct dm_target *ti)
 544 {
 545         int r;
 546         struct path_selector_type *pst;
 547         unsigned ps_argc;
 548
 549         static struct dm_arg _args[] = {
 550                 {0, 1024, "invalid number of path selector args"},
 551         };
 552
 553         pst = dm_get_path_selector(dm_shift_arg(as));
 554         if (!pst) {
 555                 ti->error = "unknown path selector type";
 556                 return -EINVAL;
 557         }
 558
 559         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 560         if (r) {
 561                 dm_put_path_selector(pst);
 562                 return -EINVAL;
 563         }
 564
 565         r = pst->create(&pg->ps, ps_argc, as->argv);
 566         if (r) {
 567                 dm_put_path_selector(pst);
 568                 ti->error = "path selector constructor failed";
 569                 return r;
 570         }
 571
 572         pg->ps.type = pst;
 573         dm_consume_args(as, ps_argc);
 574
 575         return 0;
 576 }
 577
 578 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 579                                struct dm_target *ti)
 580 {
 581         int r;
 582         struct pgpath *p;
 583         struct multipath *m = ti->private;
 584         struct request_queue *q = NULL;
 585         const char *attached_handler_name;
 586
 587         /* we need at least a path arg */
 588         if (as->argc < 1) {
 589                 ti->error = "no device given";
 590                 return ERR_PTR(-EINVAL);
 591         }
 592
 593         p = alloc_pgpath();
 594         if (!p)
 595                 return ERR_PTR(-ENOMEM);
 596
 597         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 598                           &p->path.dev);
 599         if (r) {
 600                 ti->error = "error getting device";
 601                 goto bad;
 602         }
 603
 604         if (m->retain_attached_hw_handler || m->hw_handler_name)
 605                 q = bdev_get_queue(p->path.dev->bdev);
 606
 607         if (m->retain_attached_hw_handler) {
 608 retain:
 609                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 610                 if (attached_handler_name) {
 611                         /*
 612                          * Reset hw_handler_name to match the attached handler
 613                          * and clear any hw_handler_params associated with the
 614                          * ignored handler.
 615                          *
 616                          * NB. This modifies the table line to show the actual
 617                          * handler instead of the original table passed in.
 618                          */
 619                         kfree(m->hw_handler_name);
 620                         m->hw_handler_name = attached_handler_name;
 621
 622                         kfree(m->hw_handler_params);
 623                         m->hw_handler_params = NULL;
 624                 }
 625         }
 626
 627         if (m->hw_handler_name) {
 628                 r = scsi_dh_attach(q, m->hw_handler_name);
 629                 if (r == -EBUSY) {
 630                         char b[BDEVNAME_SIZE];
 631
 632                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 633                                 bdevname(p->path.dev->bdev, b));
 634                         goto retain;
 635                 }
 636                 if (r < 0) {
 637                         ti->error = "error attaching hardware handler";
 638                         dm_put_device(ti, p->path.dev);
 639                         goto bad;
 640                 }
 641
 642                 if (m->hw_handler_params) {
 643                         r = scsi_dh_set_params(q, m->hw_handler_params);
 644                         if (r < 0) {
 645                                 ti->error = "unable to set hardware "
 646                                                         "handler parameters";
 647                                 dm_put_device(ti, p->path.dev);
 648                                 goto bad;
 649                         }
 650                 }
 651         }
 652
 653         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 654         if (r) {
 655                 dm_put_device(ti, p->path.dev);
 656                 goto bad;
 657         }
 658
 659         return p;
 660
 661  bad:
 662         free_pgpath(p);
 663         return ERR_PTR(r);
 664 }
 665
 666 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 667                                                    struct multipath *m)
 668 {
 669         static struct dm_arg _args[] = {
 670                 {1, 1024, "invalid number of paths"},
 671                 {0, 1024, "invalid number of selector args"}
 672         };
 673
 674         int r;
 675         unsigned i, nr_selector_args, nr_args;
 676         struct priority_group *pg;
 677         struct dm_target *ti = m->ti;
 678
 679         if (as->argc < 2) {
 680                 as->argc = 0;
 681                 ti->error = "not enough priority group arguments";
 682                 return ERR_PTR(-EINVAL);
 683         }
 684
 685         pg = alloc_priority_group();
 686         if (!pg) {
 687                 ti->error = "couldn't allocate priority group";
 688                 return ERR_PTR(-ENOMEM);
 689         }
 690         pg->m = m;
 691
 692         r = parse_path_selector(as, pg, ti);
 693         if (r)
 694                 goto bad;
 695
 696         /*
 697          * read the paths
 698          */
 699         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 700         if (r)
 701                 goto bad;
 702
 703         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 704         if (r)
 705                 goto bad;
 706
 707         nr_args = 1 + nr_selector_args;
 708         for (i = 0; i < pg->nr_pgpaths; i++) {
 709                 struct pgpath *pgpath;
 710                 struct dm_arg_set path_args;
 711
 712                 if (as->argc < nr_args) {
 713                         ti->error = "not enough path parameters";
 714                         r = -EINVAL;
 715                         goto bad;
 716                 }
 717
 718                 path_args.argc = nr_args;
 719                 path_args.argv = as->argv;
 720
 721                 pgpath = parse_path(&path_args, &pg->ps, ti);
 722                 if (IS_ERR(pgpath)) {
 723                         r = PTR_ERR(pgpath);
 724                         goto bad;
 725                 }
 726
 727                 pgpath->pg = pg;
 728                 list_add_tail(&pgpath->list, &pg->pgpaths);
 729                 dm_consume_args(as, nr_args);
 730         }
 731
 732         return pg;
 733
 734  bad:
 735         free_priority_group(pg, ti);
 736         return ERR_PTR(r);
 737 }
 738
 739 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 740 {
 741         unsigned hw_argc;
 742         int ret;
 743         struct dm_target *ti = m->ti;
 744
 745         static struct dm_arg _args[] = {
 746                 {0, 1024, "invalid number of hardware handler args"},
 747         };
 748
 749         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 750                 return -EINVAL;
 751
 752         if (!hw_argc)
 753                 return 0;
 754
 755         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 756
 757         if (hw_argc > 1) {
 758                 char *p;
 759                 int i, j, len = 4;
 760
 761                 for (i = 0; i <= hw_argc - 2; i++)
 762                         len += strlen(as->argv[i]) + 1;
 763                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 764                 if (!p) {
 765                         ti->error = "memory allocation failed";
 766                         ret = -ENOMEM;
 767                         goto fail;
 768                 }
 769                 j = sprintf(p, "%d", hw_argc - 1);
 770                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 771                         j = sprintf(p, "%s", as->argv[i]);
 772         }
 773         dm_consume_args(as, hw_argc - 1);
 774
 775         return 0;
 776 fail:
 777         kfree(m->hw_handler_name);
 778         m->hw_handler_name = NULL;
 779         return ret;
 780 }
 781
 782 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 783 {
 784         int r;
 785         unsigned argc;
 786         struct dm_target *ti = m->ti;
 787         const char *arg_name;
 788
 789         static struct dm_arg _args[] = {
 790                 {0, 6, "invalid number of feature args"},
 791                 {1, 50, "pg_init_retries must be between 1 and 50"},
 792                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 793         };
 794
 795         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 796         if (r)
 797                 return -EINVAL;
 798
 799         if (!argc)
 800                 return 0;
 801
 802         do {
 803                 arg_name = dm_shift_arg(as);
 804                 argc--;
 805
 806                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 807                         r = queue_if_no_path(m, 1, 0);
 808                         continue;
 809                 }
 810
 811                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
 812                         m->retain_attached_hw_handler = 1;
 813                         continue;
 814                 }
 815
 816                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 817                     (argc >= 1)) {
 818                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
 819                         argc--;
 820                         continue;
 821                 }
 822
 823                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
 824                     (argc >= 1)) {
 825                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
 826                         argc--;
 827                         continue;
 828                 }
 829
 830                 ti->error = "Unrecognised multipath feature request";
 831                 r = -EINVAL;
 832         } while (argc && !r);
 833
 834         return r;
 835 }
 836
 837 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 838                          char **argv)
 839 {
 840         /* target arguments */
 841         static struct dm_arg _args[] = {
 842                 {0, 1024, "invalid number of priority groups"},
 843                 {0, 1024, "invalid initial priority group number"},
 844         };
 845
 846         int r;
 847         struct multipath *m;
 848         struct dm_arg_set as;
 849         unsigned pg_count = 0;
 850         unsigned next_pg_num;
 851         bool use_blk_mq = dm_use_blk_mq(dm_table_get_md(ti->table));
 852
 853         as.argc = argc;
 854         as.argv = argv;
 855
 856         m = alloc_multipath(ti, use_blk_mq);
 857         if (!m) {
 858                 ti->error = "can't allocate multipath";
 859                 return -EINVAL;
 860         }
 861
 862         r = parse_features(&as, m);
 863         if (r)
 864                 goto bad;
 865
 866         r = parse_hw_handler(&as, m);
 867         if (r)
 868                 goto bad;
 869
 870         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
 871         if (r)
 872                 goto bad;
 873
 874         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
 875         if (r)
 876                 goto bad;
 877
 878         if ((!m->nr_priority_groups && next_pg_num) ||
 879             (m->nr_priority_groups && !next_pg_num)) {
 880                 ti->error = "invalid initial priority group";
 881                 r = -EINVAL;
 882                 goto bad;
 883         }
 884
 885         /* parse the priority groups */
 886         while (as.argc) {
 887                 struct priority_group *pg;
 888
 889                 pg = parse_priority_group(&as, m);
 890                 if (IS_ERR(pg)) {
 891                         r = PTR_ERR(pg);
 892                         goto bad;
 893                 }
 894
 895                 m->nr_valid_paths += pg->nr_pgpaths;
 896                 list_add_tail(&pg->list, &m->priority_groups);
 897                 pg_count++;
 898                 pg->pg_num = pg_count;
 899                 if (!--next_pg_num)
 900                         m->next_pg = pg;
 901         }
 902
 903         if (pg_count != m->nr_priority_groups) {
 904                 ti->error = "priority group count mismatch";
 905                 r = -EINVAL;
 906                 goto bad;
 907         }
 908
 909         ti->num_flush_bios = 1;
 910         ti->num_discard_bios = 1;
 911         ti->num_write_same_bios = 1;
 912         if (use_blk_mq)
 913                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
 914
 915         return 0;
 916
 917  bad:
 918         free_multipath(m);
 919         return r;
 920 }
 921
 922 static void multipath_wait_for_pg_init_completion(struct multipath *m)
 923 {
 924         DECLARE_WAITQUEUE(wait, current);
 925         unsigned long flags;
 926
 927         add_wait_queue(&m->pg_init_wait, &wait);
 928
 929         while (1) {
 930                 set_current_state(TASK_UNINTERRUPTIBLE);
 931
 932                 spin_lock_irqsave(&m->lock, flags);
 933                 if (!m->pg_init_in_progress) {
 934                         spin_unlock_irqrestore(&m->lock, flags);
 935                         break;
 936                 }
 937                 spin_unlock_irqrestore(&m->lock, flags);
 938
 939                 io_schedule();
 940         }
 941         set_current_state(TASK_RUNNING);
 942
 943         remove_wait_queue(&m->pg_init_wait, &wait);
 944 }
 945
 946 static void flush_multipath_work(struct multipath *m)
 947 {
 948         unsigned long flags;
 949
 950         spin_lock_irqsave(&m->lock, flags);
 951         m->pg_init_disabled = 1;
 952         spin_unlock_irqrestore(&m->lock, flags);
 953
 954         flush_workqueue(kmpath_handlerd);
 955         multipath_wait_for_pg_init_completion(m);
 956         flush_workqueue(kmultipathd);
 957         flush_work(&m->trigger_event);
 958
 959         spin_lock_irqsave(&m->lock, flags);
 960         m->pg_init_disabled = 0;
 961         spin_unlock_irqrestore(&m->lock, flags);
 962 }
 963
 964 static void multipath_dtr(struct dm_target *ti)
 965 {
 966         struct multipath *m = ti->private;
 967
 968         flush_multipath_work(m);
 969         free_multipath(m);
 970 }
 971
 972 /*
 973  * Take a path out of use.
 974  */
 975 static int fail_path(struct pgpath *pgpath)
 976 {
 977         unsigned long flags;
 978         struct multipath *m = pgpath->pg->m;
 979
 980         spin_lock_irqsave(&m->lock, flags);
 981
 982         if (!pgpath->is_active)
 983                 goto out;
 984
 985         DMWARN("Failing path %s.", pgpath->path.dev->name);
 986
 987         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 988         pgpath->is_active = 0;
 989         pgpath->fail_count++;
 990
 991         m->nr_valid_paths--;
 992
 993         if (pgpath == m->current_pgpath)
 994                 m->current_pgpath = NULL;
 995
 996         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
 997                       pgpath->path.dev->name, m->nr_valid_paths);
 998
 999         schedule_work(&m->trigger_event);
1000
1001 out:
1002         spin_unlock_irqrestore(&m->lock, flags);
1003
1004         return 0;
1005 }
1006
1007 /*
1008  * Reinstate a previously-failed path
1009  */
1010 static int reinstate_path(struct pgpath *pgpath)
1011 {
1012         int r = 0, run_queue = 0;
1013         unsigned long flags;
1014         struct multipath *m = pgpath->pg->m;
1015
1016         spin_lock_irqsave(&m->lock, flags);
1017
1018         if (pgpath->is_active)
1019                 goto out;
1020
1021         if (!pgpath->pg->ps.type->reinstate_path) {
1022                 DMWARN("Reinstate path not supported by path selector %s",
1023                        pgpath->pg->ps.type->name);
1024                 r = -EINVAL;
1025                 goto out;
1026         }
1027
1028         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1029         if (r)
1030                 goto out;
1031
1032         pgpath->is_active = 1;
1033
1034         if (!m->nr_valid_paths++) {
1035                 m->current_pgpath = NULL;
1036                 run_queue = 1;
1037         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1038                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1039                         m->pg_init_in_progress++;
1040         }
1041
1042         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1043                       pgpath->path.dev->name, m->nr_valid_paths);
1044
1045         schedule_work(&m->trigger_event);
1046
1047 out:
1048         spin_unlock_irqrestore(&m->lock, flags);
1049         if (run_queue)
1050                 dm_table_run_md_queue_async(m->ti->table);
1051
1052         return r;
1053 }
1054
1055 /*
1056  * Fail or reinstate all paths that match the provided struct dm_dev.
1057  */
1058 static int action_dev(struct multipath *m, struct dm_dev *dev,
1059                       action_fn action)
1060 {
1061         int r = -EINVAL;
1062         struct pgpath *pgpath;
1063         struct priority_group *pg;
1064
1065         list_for_each_entry(pg, &m->priority_groups, list) {
1066                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1067                         if (pgpath->path.dev == dev)
1068                                 r = action(pgpath);
1069                 }
1070         }
1071
1072         return r;
1073 }
1074
1075 /*
1076  * Temporarily try to avoid having to use the specified PG
1077  */
1078 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1079                       int bypassed)
1080 {
1081         unsigned long flags;
1082
1083         spin_lock_irqsave(&m->lock, flags);
1084
1085         pg->bypassed = bypassed;
1086         m->current_pgpath = NULL;
1087         m->current_pg = NULL;
1088
1089         spin_unlock_irqrestore(&m->lock, flags);
1090
1091         schedule_work(&m->trigger_event);
1092 }
1093
1094 /*
1095  * Switch to using the specified PG from the next I/O that gets mapped
1096  */
1097 static int switch_pg_num(struct multipath *m, const char *pgstr)
1098 {
1099         struct priority_group *pg;
1100         unsigned pgnum;
1101         unsigned long flags;
1102         char dummy;
1103
1104         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1105             (pgnum > m->nr_priority_groups)) {
1106                 DMWARN("invalid PG number supplied to switch_pg_num");
1107                 return -EINVAL;
1108         }
1109
1110         spin_lock_irqsave(&m->lock, flags);
1111         list_for_each_entry(pg, &m->priority_groups, list) {
1112                 pg->bypassed = 0;
1113                 if (--pgnum)
1114                         continue;
1115
1116                 m->current_pgpath = NULL;
1117                 m->current_pg = NULL;
1118                 m->next_pg = pg;
1119         }
1120         spin_unlock_irqrestore(&m->lock, flags);
1121
1122         schedule_work(&m->trigger_event);
1123         return 0;
1124 }
1125
1126 /*
1127  * Set/clear bypassed status of a PG.
1128  * PGs are numbered upwards from 1 in the order they were declared.
1129  */
1130 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1131 {
1132         struct priority_group *pg;
1133         unsigned pgnum;
1134         char dummy;
1135
1136         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1137             (pgnum > m->nr_priority_groups)) {
1138                 DMWARN("invalid PG number supplied to bypass_pg");
1139                 return -EINVAL;
1140         }
1141
1142         list_for_each_entry(pg, &m->priority_groups, list) {
1143                 if (!--pgnum)
1144                         break;
1145         }
1146
1147         bypass_pg(m, pg, bypassed);
1148         return 0;
1149 }
1150
1151 /*
1152  * Should we retry pg_init immediately?
1153  */
1154 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1155 {
1156         unsigned long flags;
1157         int limit_reached = 0;
1158
1159         spin_lock_irqsave(&m->lock, flags);
1160
1161         if (m->pg_init_count <= m->pg_init_retries && !m->pg_init_disabled)
1162                 m->pg_init_required = 1;
1163         else
1164                 limit_reached = 1;
1165
1166         spin_unlock_irqrestore(&m->lock, flags);
1167
1168         return limit_reached;
1169 }
1170
1171 static void pg_init_done(void *data, int errors)
1172 {
1173         struct pgpath *pgpath = data;
1174         struct priority_group *pg = pgpath->pg;
1175         struct multipath *m = pg->m;
1176         unsigned long flags;
1177         unsigned delay_retry = 0;
1178
1179         /* device or driver problems */
1180         switch (errors) {
1181         case SCSI_DH_OK:
1182                 break;
1183         case SCSI_DH_NOSYS:
1184                 if (!m->hw_handler_name) {
1185                         errors = 0;
1186                         break;
1187                 }
1188                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1189                       "Error %d.", m->hw_handler_name, errors);
1190                 /*
1191                  * Fail path for now, so we do not ping pong
1192                  */
1193                 fail_path(pgpath);
1194                 break;
1195         case SCSI_DH_DEV_TEMP_BUSY:
1196                 /*
1197                  * Probably doing something like FW upgrade on the
1198                  * controller so try the other pg.
1199                  */
1200                 bypass_pg(m, pg, 1);
1201                 break;
1202         case SCSI_DH_RETRY:
1203                 /* Wait before retrying. */
1204                 delay_retry = 1;
1205         case SCSI_DH_IMM_RETRY:
1206         case SCSI_DH_RES_TEMP_UNAVAIL:
1207                 if (pg_init_limit_reached(m, pgpath))
1208                         fail_path(pgpath);
1209                 errors = 0;
1210                 break;
1211         default:
1212                 /*
1213                  * We probably do not want to fail the path for a device
1214                  * error, but this is what the old dm did. In future
1215                  * patches we can do more advanced handling.
1216                  */
1217                 fail_path(pgpath);
1218         }
1219
1220         spin_lock_irqsave(&m->lock, flags);
1221         if (errors) {
1222                 if (pgpath == m->current_pgpath) {
1223                         DMERR("Could not failover device. Error %d.", errors);
1224                         m->current_pgpath = NULL;
1225                         m->current_pg = NULL;
1226                 }
1227         } else if (!m->pg_init_required)
1228                 pg->bypassed = 0;
1229
1230         if (--m->pg_init_in_progress)
1231                 /* Activations of other paths are still on going */
1232                 goto out;
1233
1234         if (m->pg_init_required) {
1235                 m->pg_init_delay_retry = delay_retry;
1236                 if (__pg_init_all_paths(m))
1237                         goto out;
1238         }
1239         m->queue_io = 0;
1240
1241         /*
1242          * Wake up any thread waiting to suspend.
1243          */
1244         wake_up(&m->pg_init_wait);
1245
1246 out:
1247         spin_unlock_irqrestore(&m->lock, flags);
1248 }
1249
1250 static void activate_path(struct work_struct *work)
1251 {
1252         struct pgpath *pgpath =
1253                 container_of(work, struct pgpath, activate_path.work);
1254
1255         if (pgpath->is_active)
1256                 scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1257                                  pg_init_done, pgpath);
1258         else
1259                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1260 }
1261
1262 static int noretry_error(int error)
1263 {
1264         switch (error) {
1265         case -EOPNOTSUPP:
1266         case -EREMOTEIO:
1267         case -EILSEQ:
1268         case -ENODATA:
1269         case -ENOSPC:
1270                 return 1;
1271         }
1272
1273         /* Anything else could be a path failure, so should be retried */
1274         return 0;
1275 }
1276
1277 /*
1278  * end_io handling
1279  */
1280 static int do_end_io(struct multipath *m, struct request *clone,
1281                      int error, struct dm_mpath_io *mpio)
1282 {
1283         /*
1284          * We don't queue any clone request inside the multipath target
1285          * during end I/O handling, since those clone requests don't have
1286          * bio clones.  If we queue them inside the multipath target,
1287          * we need to make bio clones, that requires memory allocation.
1288          * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1289          *  don't have bio clones.)
1290          * Instead of queueing the clone request here, we queue the original
1291          * request into dm core, which will remake a clone request and
1292          * clone bios for it and resubmit it later.
1293          */
1294         int r = DM_ENDIO_REQUEUE;
1295         unsigned long flags;
1296
1297         if (!error && !clone->errors)
1298                 return 0;       /* I/O complete */
1299
1300         if (noretry_error(error))
1301                 return error;
1302
1303         if (mpio->pgpath)
1304                 fail_path(mpio->pgpath);
1305
1306         spin_lock_irqsave(&m->lock, flags);
1307         if (!m->nr_valid_paths) {
1308                 if (!m->queue_if_no_path) {
1309                         if (!__must_push_back(m))
1310                                 r = -EIO;
1311                 } else {
1312                         if (error == -EBADE)
1313                                 r = error;
1314                 }
1315         }
1316         spin_unlock_irqrestore(&m->lock, flags);
1317
1318         return r;
1319 }
1320
1321 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1322                             int error, union map_info *map_context)
1323 {
1324         struct multipath *m = ti->private;
1325         struct dm_mpath_io *mpio = get_mpio(map_context);
1326         struct pgpath *pgpath;
1327         struct path_selector *ps;
1328         int r;
1329
1330         BUG_ON(!mpio);
1331
1332         r = do_end_io(m, clone, error, mpio);
1333         pgpath = mpio->pgpath;
1334         if (pgpath) {
1335                 ps = &pgpath->pg->ps;
1336                 if (ps->type->end_io)
1337                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1338         }
1339         clear_request_fn_mpio(m, map_context);
1340
1341         return r;
1342 }
1343
1344 /*
1345  * Suspend can't complete until all the I/O is processed so if
1346  * the last path fails we must error any remaining I/O.
1347  * Note that if the freeze_bdev fails while suspending, the
1348  * queue_if_no_path state is lost - userspace should reset it.
1349  */
1350 static void multipath_presuspend(struct dm_target *ti)
1351 {
1352         struct multipath *m = (struct multipath *) ti->private;
1353
1354         queue_if_no_path(m, 0, 1);
1355 }
1356
1357 static void multipath_postsuspend(struct dm_target *ti)
1358 {
1359         struct multipath *m = ti->private;
1360
1361         mutex_lock(&m->work_mutex);
1362         flush_multipath_work(m);
1363         mutex_unlock(&m->work_mutex);
1364 }
1365
1366 /*
1367  * Restore the queue_if_no_path setting.
1368  */
1369 static void multipath_resume(struct dm_target *ti)
1370 {
1371         struct multipath *m = (struct multipath *) ti->private;
1372         unsigned long flags;
1373
1374         spin_lock_irqsave(&m->lock, flags);
1375         m->queue_if_no_path = m->saved_queue_if_no_path;
1376         spin_unlock_irqrestore(&m->lock, flags);
1377 }
1378
1379 /*
1380  * Info output has the following format:
1381  * num_multipath_feature_args [multipath_feature_args]*
1382  * num_handler_status_args [handler_status_args]*
1383  * num_groups init_group_number
1384  *            [A|D|E num_ps_status_args [ps_status_args]*
1385  *             num_paths num_selector_args
1386  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1387  *
1388  * Table output has the following format (identical to the constructor string):
1389  * num_feature_args [features_args]*
1390  * num_handler_args hw_handler [hw_handler_args]*
1391  * num_groups init_group_number
1392  *     [priority selector-name num_ps_args [ps_args]*
1393  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1394  */
1395 static void multipath_status(struct dm_target *ti, status_type_t type,
1396                              unsigned status_flags, char *result, unsigned maxlen)
1397 {
1398         int sz = 0;
1399         unsigned long flags;
1400         struct multipath *m = (struct multipath *) ti->private;
1401         struct priority_group *pg;
1402         struct pgpath *p;
1403         unsigned pg_num;
1404         char state;
1405
1406         spin_lock_irqsave(&m->lock, flags);
1407
1408         /* Features */
1409         if (type == STATUSTYPE_INFO)
1410                 DMEMIT("2 %u %u ", m->queue_io, m->pg_init_count);
1411         else {
1412                 DMEMIT("%u ", m->queue_if_no_path +
1413                               (m->pg_init_retries > 0) * 2 +
1414                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1415                               m->retain_attached_hw_handler);
1416                 if (m->queue_if_no_path)
1417                         DMEMIT("queue_if_no_path ");
1418                 if (m->pg_init_retries)
1419                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1420                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1421                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1422                 if (m->retain_attached_hw_handler)
1423                         DMEMIT("retain_attached_hw_handler ");
1424         }
1425
1426         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1427                 DMEMIT("0 ");
1428         else
1429                 DMEMIT("1 %s ", m->hw_handler_name);
1430
1431         DMEMIT("%u ", m->nr_priority_groups);
1432
1433         if (m->next_pg)
1434                 pg_num = m->next_pg->pg_num;
1435         else if (m->current_pg)
1436                 pg_num = m->current_pg->pg_num;
1437         else
1438                 pg_num = (m->nr_priority_groups ? 1 : 0);
1439
1440         DMEMIT("%u ", pg_num);
1441
1442         switch (type) {
1443         case STATUSTYPE_INFO:
1444                 list_for_each_entry(pg, &m->priority_groups, list) {
1445                         if (pg->bypassed)
1446                                 state = 'D';    /* Disabled */
1447                         else if (pg == m->current_pg)
1448                                 state = 'A';    /* Currently Active */
1449                         else
1450                                 state = 'E';    /* Enabled */
1451
1452                         DMEMIT("%c ", state);
1453
1454                         if (pg->ps.type->status)
1455                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1456                                                           result + sz,
1457                                                           maxlen - sz);
1458                         else
1459                                 DMEMIT("0 ");
1460
1461                         DMEMIT("%u %u ", pg->nr_pgpaths,
1462                                pg->ps.type->info_args);
1463
1464                         list_for_each_entry(p, &pg->pgpaths, list) {
1465                                 DMEMIT("%s %s %u ", p->path.dev->name,
1466                                        p->is_active ? "A" : "F",
1467                                        p->fail_count);
1468                                 if (pg->ps.type->status)
1469                                         sz += pg->ps.type->status(&pg->ps,
1470                                               &p->path, type, result + sz,
1471                                               maxlen - sz);
1472                         }
1473                 }
1474                 break;
1475
1476         case STATUSTYPE_TABLE:
1477                 list_for_each_entry(pg, &m->priority_groups, list) {
1478                         DMEMIT("%s ", pg->ps.type->name);
1479
1480                         if (pg->ps.type->status)
1481                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1482                                                           result + sz,
1483                                                           maxlen - sz);
1484                         else
1485                                 DMEMIT("0 ");
1486
1487                         DMEMIT("%u %u ", pg->nr_pgpaths,
1488                                pg->ps.type->table_args);
1489
1490                         list_for_each_entry(p, &pg->pgpaths, list) {
1491                                 DMEMIT("%s ", p->path.dev->name);
1492                                 if (pg->ps.type->status)
1493                                         sz += pg->ps.type->status(&pg->ps,
1494                                               &p->path, type, result + sz,
1495                                               maxlen - sz);
1496                         }
1497                 }
1498                 break;
1499         }
1500
1501         spin_unlock_irqrestore(&m->lock, flags);
1502 }
1503
1504 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1505 {
1506         int r = -EINVAL;
1507         struct dm_dev *dev;
1508         struct multipath *m = (struct multipath *) ti->private;
1509         action_fn action;
1510
1511         mutex_lock(&m->work_mutex);
1512
1513         if (dm_suspended(ti)) {
1514                 r = -EBUSY;
1515                 goto out;
1516         }
1517
1518         if (argc == 1) {
1519                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1520                         r = queue_if_no_path(m, 1, 0);
1521                         goto out;
1522                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1523                         r = queue_if_no_path(m, 0, 0);
1524                         goto out;
1525                 }
1526         }
1527
1528         if (argc != 2) {
1529                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1530                 goto out;
1531         }
1532
1533         if (!strcasecmp(argv[0], "disable_group")) {
1534                 r = bypass_pg_num(m, argv[1], 1);
1535                 goto out;
1536         } else if (!strcasecmp(argv[0], "enable_group")) {
1537                 r = bypass_pg_num(m, argv[1], 0);
1538                 goto out;
1539         } else if (!strcasecmp(argv[0], "switch_group")) {
1540                 r = switch_pg_num(m, argv[1]);
1541                 goto out;
1542         } else if (!strcasecmp(argv[0], "reinstate_path"))
1543                 action = reinstate_path;
1544         else if (!strcasecmp(argv[0], "fail_path"))
1545                 action = fail_path;
1546         else {
1547                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1548                 goto out;
1549         }
1550
1551         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1552         if (r) {
1553                 DMWARN("message: error getting device %s",
1554                        argv[1]);
1555                 goto out;
1556         }
1557
1558         r = action_dev(m, dev, action);
1559
1560         dm_put_device(ti, dev);
1561
1562 out:
1563         mutex_unlock(&m->work_mutex);
1564         return r;
1565 }
1566
1567 static int multipath_prepare_ioctl(struct dm_target *ti,
1568                 struct block_device **bdev, fmode_t *mode)
1569 {
1570         struct multipath *m = ti->private;
1571         unsigned long flags;
1572         int r;
1573
1574         spin_lock_irqsave(&m->lock, flags);
1575
1576         if (!m->current_pgpath)
1577                 __choose_pgpath(m, 0);
1578
1579         if (m->current_pgpath) {
1580                 if (!m->queue_io) {
1581                         *bdev = m->current_pgpath->path.dev->bdev;
1582                         *mode = m->current_pgpath->path.dev->mode;
1583                         r = 0;
1584                 } else {
1585                         /* pg_init has not started or completed */
1586                         r = -ENOTCONN;
1587                 }
1588         } else {
1589                 /* No path is available */
1590                 if (m->queue_if_no_path)
1591                         r = -ENOTCONN;
1592                 else
1593                         r = -EIO;
1594         }
1595
1596         spin_unlock_irqrestore(&m->lock, flags);
1597
1598         if (r == -ENOTCONN) {
1599                 spin_lock_irqsave(&m->lock, flags);
1600                 if (!m->current_pg) {
1601                         /* Path status changed, redo selection */
1602                         __choose_pgpath(m, 0);
1603                 }
1604                 if (m->pg_init_required)
1605                         __pg_init_all_paths(m);
1606                 spin_unlock_irqrestore(&m->lock, flags);
1607                 dm_table_run_md_queue_async(m->ti->table);
1608         }
1609
1610         /*
1611          * Only pass ioctls through if the device sizes match exactly.
1612          */
1613         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1614                 return 1;
1615         return r;
1616 }
1617
1618 static int multipath_iterate_devices(struct dm_target *ti,
1619                                      iterate_devices_callout_fn fn, void *data)
1620 {
1621         struct multipath *m = ti->private;
1622         struct priority_group *pg;
1623         struct pgpath *p;
1624         int ret = 0;
1625
1626         list_for_each_entry(pg, &m->priority_groups, list) {
1627                 list_for_each_entry(p, &pg->pgpaths, list) {
1628                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1629                         if (ret)
1630                                 goto out;
1631                 }
1632         }
1633
1634 out:
1635         return ret;
1636 }
1637
1638 static int __pgpath_busy(struct pgpath *pgpath)
1639 {
1640         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1641
1642         return blk_lld_busy(q);
1643 }
1644
1645 /*
1646  * We return "busy", only when we can map I/Os but underlying devices
1647  * are busy (so even if we map I/Os now, the I/Os will wait on
1648  * the underlying queue).
1649  * In other words, if we want to kill I/Os or queue them inside us
1650  * due to map unavailability, we don't return "busy".  Otherwise,
1651  * dm core won't give us the I/Os and we can't do what we want.
1652  */
1653 static int multipath_busy(struct dm_target *ti)
1654 {
1655         int busy = 0, has_active = 0;
1656         struct multipath *m = ti->private;
1657         struct priority_group *pg;
1658         struct pgpath *pgpath;
1659         unsigned long flags;
1660
1661         spin_lock_irqsave(&m->lock, flags);
1662
1663         /* pg_init in progress or no paths available */
1664         if (m->pg_init_in_progress ||
1665             (!m->nr_valid_paths && m->queue_if_no_path)) {
1666                 busy = 1;
1667                 goto out;
1668         }
1669         /* Guess which priority_group will be used at next mapping time */
1670         if (unlikely(!m->current_pgpath && m->next_pg))
1671                 pg = m->next_pg;
1672         else if (likely(m->current_pg))
1673                 pg = m->current_pg;
1674         else
1675                 /*
1676                  * We don't know which pg will be used at next mapping time.
1677                  * We don't call __choose_pgpath() here to avoid to trigger
1678                  * pg_init just by busy checking.
1679                  * So we don't know whether underlying devices we will be using
1680                  * at next mapping time are busy or not. Just try mapping.
1681                  */
1682                 goto out;
1683
1684         /*
1685          * If there is one non-busy active path at least, the path selector
1686          * will be able to select it. So we consider such a pg as not busy.
1687          */
1688         busy = 1;
1689         list_for_each_entry(pgpath, &pg->pgpaths, list)
1690                 if (pgpath->is_active) {
1691                         has_active = 1;
1692
1693                         if (!__pgpath_busy(pgpath)) {
1694                                 busy = 0;
1695                                 break;
1696                         }
1697                 }
1698
1699         if (!has_active)
1700                 /*
1701                  * No active path in this pg, so this pg won't be used and
1702                  * the current_pg will be changed at next mapping time.
1703                  * We need to try mapping to determine it.
1704                  */
1705                 busy = 0;
1706
1707 out:
1708         spin_unlock_irqrestore(&m->lock, flags);
1709
1710         return busy;
1711 }
1712
1713 /*-----------------------------------------------------------------
1714  * Module setup
1715  *---------------------------------------------------------------*/
1716 static struct target_type multipath_target = {
1717         .name = "multipath",
1718         .version = {1, 11, 0},
1719         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
1720         .module = THIS_MODULE,
1721         .ctr = multipath_ctr,
1722         .dtr = multipath_dtr,
1723         .map_rq = multipath_map,
1724         .clone_and_map_rq = multipath_clone_and_map,
1725         .release_clone_rq = multipath_release_clone,
1726         .rq_end_io = multipath_end_io,
1727         .presuspend = multipath_presuspend,
1728         .postsuspend = multipath_postsuspend,
1729         .resume = multipath_resume,
1730         .status = multipath_status,
1731         .message = multipath_message,
1732         .prepare_ioctl = multipath_prepare_ioctl,
1733         .iterate_devices = multipath_iterate_devices,
1734         .busy = multipath_busy,
1735 };
1736
1737 static int __init dm_multipath_init(void)
1738 {
1739         int r;
1740
1741         /* allocate a slab for the dm_ios */
1742         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1743         if (!_mpio_cache)
1744                 return -ENOMEM;
1745
1746         r = dm_register_target(&multipath_target);
1747         if (r < 0) {
1748                 DMERR("register failed %d", r);
1749                 r = -EINVAL;
1750                 goto bad_register_target;
1751         }
1752
1753         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1754         if (!kmultipathd) {
1755                 DMERR("failed to create workqueue kmpathd");
1756                 r = -ENOMEM;
1757                 goto bad_alloc_kmultipathd;
1758         }
1759
1760         /*
1761          * A separate workqueue is used to handle the device handlers
1762          * to avoid overloading existing workqueue. Overloading the
1763          * old workqueue would also create a bottleneck in the
1764          * path of the storage hardware device activation.
1765          */
1766         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1767                                                   WQ_MEM_RECLAIM);
1768         if (!kmpath_handlerd) {
1769                 DMERR("failed to create workqueue kmpath_handlerd");
1770                 r = -ENOMEM;
1771                 goto bad_alloc_kmpath_handlerd;
1772         }
1773
1774         DMINFO("version %u.%u.%u loaded",
1775                multipath_target.version[0], multipath_target.version[1],
1776                multipath_target.version[2]);
1777
1778         return 0;
1779
1780 bad_alloc_kmpath_handlerd:
1781         destroy_workqueue(kmultipathd);
1782 bad_alloc_kmultipathd:
1783         dm_unregister_target(&multipath_target);
1784 bad_register_target:
1785         kmem_cache_destroy(_mpio_cache);
1786
1787         return r;
1788 }
1789
1790 static void __exit dm_multipath_exit(void)
1791 {
1792         destroy_workqueue(kmpath_handlerd);
1793         destroy_workqueue(kmultipathd);
1794
1795         dm_unregister_target(&multipath_target);
1796         kmem_cache_destroy(_mpio_cache);
1797 }
1798
1799 module_init(dm_multipath_init);
1800 module_exit(dm_multipath_exit);
1801
1802 MODULE_DESCRIPTION(DM_NAME " multipath target");
1803 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1804 MODULE_LICENSE("GPL");