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-path-selector.h"
  11 #include "dm-uevent.h"
  12
  13 #include <linux/ctype.h>
  14 #include <linux/init.h>
  15 #include <linux/mempool.h>
  16 #include <linux/module.h>
  17 #include <linux/pagemap.h>
  18 #include <linux/slab.h>
  19 #include <linux/time.h>
  20 #include <linux/workqueue.h>
  21 #include <scsi/scsi_dh.h>
  22 #include <asm/atomic.h>
  23
  24 #define DM_MSG_PREFIX "multipath"
  25 #define MESG_STR(x) x, sizeof(x)
  26 #define DM_PG_INIT_DELAY_MSECS 2000
  27 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  28
  29 /* Path properties */
  30 struct pgpath {
  31         struct list_head list;
  32
  33         struct priority_group *pg;      /* Owning PG */
  34         unsigned is_active;             /* Path status */
  35         unsigned fail_count;            /* Cumulative failure count */
  36
  37         struct dm_path path;
  38         struct delayed_work activate_path;
  39 };
  40
  41 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  42
  43 /*
  44  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  45  * Each has a path selector which controls which path gets used.
  46  */
  47 struct priority_group {
  48         struct list_head list;
  49
  50         struct multipath *m;            /* Owning multipath instance */
  51         struct path_selector ps;
  52
  53         unsigned pg_num;                /* Reference number */
  54         unsigned bypassed;              /* Temporarily bypass this PG? */
  55
  56         unsigned nr_pgpaths;            /* Number of paths in PG */
  57         struct list_head pgpaths;
  58 };
  59
  60 /* Multipath context */
  61 struct multipath {
  62         struct list_head list;
  63         struct dm_target *ti;
  64
  65         spinlock_t lock;
  66
  67         const char *hw_handler_name;
  68         char *hw_handler_params;
  69
  70         unsigned nr_priority_groups;
  71         struct list_head priority_groups;
  72
  73         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  74
  75         unsigned pg_init_required;      /* pg_init needs calling? */
  76         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  77         unsigned pg_init_delay_retry;   /* Delay pg_init retry? */
  78
  79         unsigned nr_valid_paths;        /* Total number of usable paths */
  80         struct pgpath *current_pgpath;
  81         struct priority_group *current_pg;
  82         struct priority_group *next_pg; /* Switch to this PG if set */
  83         unsigned repeat_count;          /* I/Os left before calling PS again */
  84
  85         unsigned queue_io;              /* Must we queue all I/O? */
  86         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
  87         unsigned saved_queue_if_no_path;/* Saved state during suspension */
  88         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  89         unsigned pg_init_count;         /* Number of times pg_init called */
  90         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  91
  92         struct work_struct process_queued_ios;
  93         struct list_head queued_ios;
  94         unsigned queue_size;
  95
  96         struct work_struct trigger_event;
  97
  98         /*
  99          * We must use a mempool of dm_mpath_io structs so that we
 100          * can resubmit bios on error.
 101          */
 102         mempool_t *mpio_pool;
 103
 104         struct mutex work_mutex;
 105 };
 106
 107 /*
 108  * Context information attached to each bio we process.
 109  */
 110 struct dm_mpath_io {
 111         struct pgpath *pgpath;
 112         size_t nr_bytes;
 113 };
 114
 115 typedef int (*action_fn) (struct pgpath *pgpath);
 116
 117 #define MIN_IOS 256     /* Mempool size */
 118
 119 static struct kmem_cache *_mpio_cache;
 120
 121 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 122 static void process_queued_ios(struct work_struct *work);
 123 static void trigger_event(struct work_struct *work);
 124 static void activate_path(struct work_struct *work);
 125
 126
 127 /*-----------------------------------------------
 128  * Allocation routines
 129  *-----------------------------------------------*/
 130
 131 static struct pgpath *alloc_pgpath(void)
 132 {
 133         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 134
 135         if (pgpath) {
 136                 pgpath->is_active = 1;
 137                 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);
 138         }
 139
 140         return pgpath;
 141 }
 142
 143 static void free_pgpath(struct pgpath *pgpath)
 144 {
 145         kfree(pgpath);
 146 }
 147
 148 static struct priority_group *alloc_priority_group(void)
 149 {
 150         struct priority_group *pg;
 151
 152         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 153
 154         if (pg)
 155                 INIT_LIST_HEAD(&pg->pgpaths);
 156
 157         return pg;
 158 }
 159
 160 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 161 {
 162         struct pgpath *pgpath, *tmp;
 163         struct multipath *m = ti->private;
 164
 165         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 166                 list_del(&pgpath->list);
 167                 if (m->hw_handler_name)
 168                         scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 169                 dm_put_device(ti, pgpath->path.dev);
 170                 free_pgpath(pgpath);
 171         }
 172 }
 173
 174 static void free_priority_group(struct priority_group *pg,
 175                                 struct dm_target *ti)
 176 {
 177         struct path_selector *ps = &pg->ps;
 178
 179         if (ps->type) {
 180                 ps->type->destroy(ps);
 181                 dm_put_path_selector(ps->type);
 182         }
 183
 184         free_pgpaths(&pg->pgpaths, ti);
 185         kfree(pg);
 186 }
 187
 188 static struct multipath *alloc_multipath(struct dm_target *ti)
 189 {
 190         struct multipath *m;
 191
 192         m = kzalloc(sizeof(*m), GFP_KERNEL);
 193         if (m) {
 194                 INIT_LIST_HEAD(&m->priority_groups);
 195                 INIT_LIST_HEAD(&m->queued_ios);
 196                 spin_lock_init(&m->lock);
 197                 m->queue_io = 1;
 198                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 199                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
 200                 INIT_WORK(&m->trigger_event, trigger_event);
 201                 init_waitqueue_head(&m->pg_init_wait);
 202                 mutex_init(&m->work_mutex);
 203                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 204                 if (!m->mpio_pool) {
 205                         kfree(m);
 206                         return NULL;
 207                 }
 208                 m->ti = ti;
 209                 ti->private = m;
 210         }
 211
 212         return m;
 213 }
 214
 215 static void free_multipath(struct multipath *m)
 216 {
 217         struct priority_group *pg, *tmp;
 218
 219         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 220                 list_del(&pg->list);
 221                 free_priority_group(pg, m->ti);
 222         }
 223
 224         kfree(m->hw_handler_name);
 225         kfree(m->hw_handler_params);
 226         mempool_destroy(m->mpio_pool);
 227         kfree(m);
 228 }
 229
 230
 231 /*-----------------------------------------------
 232  * Path selection
 233  *-----------------------------------------------*/
 234
 235 static void __pg_init_all_paths(struct multipath *m)
 236 {
 237         struct pgpath *pgpath;
 238         unsigned long pg_init_delay = 0;
 239
 240         m->pg_init_count++;
 241         m->pg_init_required = 0;
 242         if (m->pg_init_delay_retry)
 243                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 244                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 245         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 246                 /* Skip failed paths */
 247                 if (!pgpath->is_active)
 248                         continue;
 249                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 250                                        pg_init_delay))
 251                         m->pg_init_in_progress++;
 252         }
 253 }
 254
 255 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 256 {
 257         m->current_pg = pgpath->pg;
 258
 259         /* Must we initialise the PG first, and queue I/O till it's ready? */
 260         if (m->hw_handler_name) {
 261                 m->pg_init_required = 1;
 262                 m->queue_io = 1;
 263         } else {
 264                 m->pg_init_required = 0;
 265                 m->queue_io = 0;
 266         }
 267
 268         m->pg_init_count = 0;
 269 }
 270
 271 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 272                                size_t nr_bytes)
 273 {
 274         struct dm_path *path;
 275
 276         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 277         if (!path)
 278                 return -ENXIO;
 279
 280         m->current_pgpath = path_to_pgpath(path);
 281
 282         if (m->current_pg != pg)
 283                 __switch_pg(m, m->current_pgpath);
 284
 285         return 0;
 286 }
 287
 288 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 289 {
 290         struct priority_group *pg;
 291         unsigned bypassed = 1;
 292
 293         if (!m->nr_valid_paths)
 294                 goto failed;
 295
 296         /* Were we instructed to switch PG? */
 297         if (m->next_pg) {
 298                 pg = m->next_pg;
 299                 m->next_pg = NULL;
 300                 if (!__choose_path_in_pg(m, pg, nr_bytes))
 301                         return;
 302         }
 303
 304         /* Don't change PG until it has no remaining paths */
 305         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 306                 return;
 307
 308         /*
 309          * Loop through priority groups until we find a valid path.
 310          * First time we skip PGs marked 'bypassed'.
 311          * Second time we only try the ones we skipped.
 312          */
 313         do {
 314                 list_for_each_entry(pg, &m->priority_groups, list) {
 315                         if (pg->bypassed == bypassed)
 316                                 continue;
 317                         if (!__choose_path_in_pg(m, pg, nr_bytes))
 318                                 return;
 319                 }
 320         } while (bypassed--);
 321
 322 failed:
 323         m->current_pgpath = NULL;
 324         m->current_pg = NULL;
 325 }
 326
 327 /*
 328  * Check whether bios must be queued in the device-mapper core rather
 329  * than here in the target.
 330  *
 331  * m->lock must be held on entry.
 332  *
 333  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 334  * same value then we are not between multipath_presuspend()
 335  * and multipath_resume() calls and we have no need to check
 336  * for the DMF_NOFLUSH_SUSPENDING flag.
 337  */
 338 static int __must_push_back(struct multipath *m)
 339 {
 340         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 341                 dm_noflush_suspending(m->ti));
 342 }
 343
 344 static int map_io(struct multipath *m, struct request *clone,
 345                   struct dm_mpath_io *mpio, unsigned was_queued)
 346 {
 347         int r = DM_MAPIO_REMAPPED;
 348         size_t nr_bytes = blk_rq_bytes(clone);
 349         unsigned long flags;
 350         struct pgpath *pgpath;
 351         struct block_device *bdev;
 352
 353         spin_lock_irqsave(&m->lock, flags);
 354
 355         /* Do we need to select a new pgpath? */
 356         if (!m->current_pgpath ||
 357             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 358                 __choose_pgpath(m, nr_bytes);
 359
 360         pgpath = m->current_pgpath;
 361
 362         if (was_queued)
 363                 m->queue_size--;
 364
 365         if ((pgpath && m->queue_io) ||
 366             (!pgpath && m->queue_if_no_path)) {
 367                 /* Queue for the daemon to resubmit */
 368                 list_add_tail(&clone->queuelist, &m->queued_ios);
 369                 m->queue_size++;
 370                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 371                     !m->queue_io)
 372                         queue_work(kmultipathd, &m->process_queued_ios);
 373                 pgpath = NULL;
 374                 r = DM_MAPIO_SUBMITTED;
 375         } else if (pgpath) {
 376                 bdev = pgpath->path.dev->bdev;
 377                 clone->q = bdev_get_queue(bdev);
 378                 clone->rq_disk = bdev->bd_disk;
 379         } else if (__must_push_back(m))
 380                 r = DM_MAPIO_REQUEUE;
 381         else
 382                 r = -EIO;       /* Failed */
 383
 384         mpio->pgpath = pgpath;
 385         mpio->nr_bytes = nr_bytes;
 386
 387         if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
 388                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path,
 389                                               nr_bytes);
 390
 391         spin_unlock_irqrestore(&m->lock, flags);
 392
 393         return r;
 394 }
 395
 396 /*
 397  * If we run out of usable paths, should we queue I/O or error it?
 398  */
 399 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 400                             unsigned save_old_value)
 401 {
 402         unsigned long flags;
 403
 404         spin_lock_irqsave(&m->lock, flags);
 405
 406         if (save_old_value)
 407                 m->saved_queue_if_no_path = m->queue_if_no_path;
 408         else
 409                 m->saved_queue_if_no_path = queue_if_no_path;
 410         m->queue_if_no_path = queue_if_no_path;
 411         if (!m->queue_if_no_path && m->queue_size)
 412                 queue_work(kmultipathd, &m->process_queued_ios);
 413
 414         spin_unlock_irqrestore(&m->lock, flags);
 415
 416         return 0;
 417 }
 418
 419 /*-----------------------------------------------------------------
 420  * The multipath daemon is responsible for resubmitting queued ios.
 421  *---------------------------------------------------------------*/
 422
 423 static void dispatch_queued_ios(struct multipath *m)
 424 {
 425         int r;
 426         unsigned long flags;
 427         struct dm_mpath_io *mpio;
 428         union map_info *info;
 429         struct request *clone, *n;
 430         LIST_HEAD(cl);
 431
 432         spin_lock_irqsave(&m->lock, flags);
 433         list_splice_init(&m->queued_ios, &cl);
 434         spin_unlock_irqrestore(&m->lock, flags);
 435
 436         list_for_each_entry_safe(clone, n, &cl, queuelist) {
 437                 list_del_init(&clone->queuelist);
 438
 439                 info = dm_get_rq_mapinfo(clone);
 440                 mpio = info->ptr;
 441
 442                 r = map_io(m, clone, mpio, 1);
 443                 if (r < 0) {
 444                         mempool_free(mpio, m->mpio_pool);
 445                         dm_kill_unmapped_request(clone, r);
 446                 } else if (r == DM_MAPIO_REMAPPED)
 447                         dm_dispatch_request(clone);
 448                 else if (r == DM_MAPIO_REQUEUE) {
 449                         mempool_free(mpio, m->mpio_pool);
 450                         dm_requeue_unmapped_request(clone);
 451                 }
 452         }
 453 }
 454
 455 static void process_queued_ios(struct work_struct *work)
 456 {
 457         struct multipath *m =
 458                 container_of(work, struct multipath, process_queued_ios);
 459         struct pgpath *pgpath = NULL;
 460         unsigned must_queue = 1;
 461         unsigned long flags;
 462
 463         spin_lock_irqsave(&m->lock, flags);
 464
 465         if (!m->queue_size)
 466                 goto out;
 467
 468         if (!m->current_pgpath)
 469                 __choose_pgpath(m, 0);
 470
 471         pgpath = m->current_pgpath;
 472
 473         if ((pgpath && !m->queue_io) ||
 474             (!pgpath && !m->queue_if_no_path))
 475                 must_queue = 0;
 476
 477         if (m->pg_init_required && !m->pg_init_in_progress && pgpath)
 478                 __pg_init_all_paths(m);
 479
 480 out:
 481         spin_unlock_irqrestore(&m->lock, flags);
 482         if (!must_queue)
 483                 dispatch_queued_ios(m);
 484 }
 485
 486 /*
 487  * An event is triggered whenever a path is taken out of use.
 488  * Includes path failure and PG bypass.
 489  */
 490 static void trigger_event(struct work_struct *work)
 491 {
 492         struct multipath *m =
 493                 container_of(work, struct multipath, trigger_event);
 494
 495         dm_table_event(m->ti->table);
 496 }
 497
 498 /*-----------------------------------------------------------------
 499  * Constructor/argument parsing:
 500  * <#multipath feature args> [<arg>]*
 501  * <#hw_handler args> [hw_handler [<arg>]*]
 502  * <#priority groups>
 503  * <initial priority group>
 504  *     [<selector> <#selector args> [<arg>]*
 505  *      <#paths> <#per-path selector args>
 506  *         [<path> [<arg>]* ]+ ]+
 507  *---------------------------------------------------------------*/
 508 struct param {
 509         unsigned min;
 510         unsigned max;
 511         char *error;
 512 };
 513
 514 static int read_param(struct param *param, char *str, unsigned *v, char **error)
 515 {
 516         if (!str ||
 517             (sscanf(str, "%u", v) != 1) ||
 518             (*v < param->min) ||
 519             (*v > param->max)) {
 520                 *error = param->error;
 521                 return -EINVAL;
 522         }
 523
 524         return 0;
 525 }
 526
 527 struct arg_set {
 528         unsigned argc;
 529         char **argv;
 530 };
 531
 532 static char *shift(struct arg_set *as)
 533 {
 534         char *r;
 535
 536         if (as->argc) {
 537                 as->argc--;
 538                 r = *as->argv;
 539                 as->argv++;
 540                 return r;
 541         }
 542
 543         return NULL;
 544 }
 545
 546 static void consume(struct arg_set *as, unsigned n)
 547 {
 548         BUG_ON (as->argc < n);
 549         as->argc -= n;
 550         as->argv += n;
 551 }
 552
 553 static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
 554                                struct dm_target *ti)
 555 {
 556         int r;
 557         struct path_selector_type *pst;
 558         unsigned ps_argc;
 559
 560         static struct param _params[] = {
 561                 {0, 1024, "invalid number of path selector args"},
 562         };
 563
 564         pst = dm_get_path_selector(shift(as));
 565         if (!pst) {
 566                 ti->error = "unknown path selector type";
 567                 return -EINVAL;
 568         }
 569
 570         r = read_param(_params, shift(as), &ps_argc, &ti->error);
 571         if (r) {
 572                 dm_put_path_selector(pst);
 573                 return -EINVAL;
 574         }
 575
 576         if (ps_argc > as->argc) {
 577                 dm_put_path_selector(pst);
 578                 ti->error = "not enough arguments for path selector";
 579                 return -EINVAL;
 580         }
 581
 582         r = pst->create(&pg->ps, ps_argc, as->argv);
 583         if (r) {
 584                 dm_put_path_selector(pst);
 585                 ti->error = "path selector constructor failed";
 586                 return r;
 587         }
 588
 589         pg->ps.type = pst;
 590         consume(as, ps_argc);
 591
 592         return 0;
 593 }
 594
 595 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
 596                                struct dm_target *ti)
 597 {
 598         int r;
 599         struct pgpath *p;
 600         struct multipath *m = ti->private;
 601
 602         /* we need at least a path arg */
 603         if (as->argc < 1) {
 604                 ti->error = "no device given";
 605                 return ERR_PTR(-EINVAL);
 606         }
 607
 608         p = alloc_pgpath();
 609         if (!p)
 610                 return ERR_PTR(-ENOMEM);
 611
 612         r = dm_get_device(ti, shift(as), dm_table_get_mode(ti->table),
 613                           &p->path.dev);
 614         if (r) {
 615                 ti->error = "error getting device";
 616                 goto bad;
 617         }
 618
 619         if (m->hw_handler_name) {
 620                 struct request_queue *q = bdev_get_queue(p->path.dev->bdev);
 621
 622                 r = scsi_dh_attach(q, m->hw_handler_name);
 623                 if (r == -EBUSY) {
 624                         /*
 625                          * Already attached to different hw_handler,
 626                          * try to reattach with correct one.
 627                          */
 628                         scsi_dh_detach(q);
 629                         r = scsi_dh_attach(q, m->hw_handler_name);
 630                 }
 631
 632                 if (r < 0) {
 633                         ti->error = "error attaching hardware handler";
 634                         dm_put_device(ti, p->path.dev);
 635                         goto bad;
 636                 }
 637
 638                 if (m->hw_handler_params) {
 639                         r = scsi_dh_set_params(q, m->hw_handler_params);
 640                         if (r < 0) {
 641                                 ti->error = "unable to set hardware "
 642                                                         "handler parameters";
 643                                 scsi_dh_detach(q);
 644                                 dm_put_device(ti, p->path.dev);
 645                                 goto bad;
 646                         }
 647                 }
 648         }
 649
 650         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 651         if (r) {
 652                 dm_put_device(ti, p->path.dev);
 653                 goto bad;
 654         }
 655
 656         return p;
 657
 658  bad:
 659         free_pgpath(p);
 660         return ERR_PTR(r);
 661 }
 662
 663 static struct priority_group *parse_priority_group(struct arg_set *as,
 664                                                    struct multipath *m)
 665 {
 666         static struct param _params[] = {
 667                 {1, 1024, "invalid number of paths"},
 668                 {0, 1024, "invalid number of selector args"}
 669         };
 670
 671         int r;
 672         unsigned i, nr_selector_args, nr_params;
 673         struct priority_group *pg;
 674         struct dm_target *ti = m->ti;
 675
 676         if (as->argc < 2) {
 677                 as->argc = 0;
 678                 ti->error = "not enough priority group arguments";
 679                 return ERR_PTR(-EINVAL);
 680         }
 681
 682         pg = alloc_priority_group();
 683         if (!pg) {
 684                 ti->error = "couldn't allocate priority group";
 685                 return ERR_PTR(-ENOMEM);
 686         }
 687         pg->m = m;
 688
 689         r = parse_path_selector(as, pg, ti);
 690         if (r)
 691                 goto bad;
 692
 693         /*
 694          * read the paths
 695          */
 696         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
 697         if (r)
 698                 goto bad;
 699
 700         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
 701         if (r)
 702                 goto bad;
 703
 704         nr_params = 1 + nr_selector_args;
 705         for (i = 0; i < pg->nr_pgpaths; i++) {
 706                 struct pgpath *pgpath;
 707                 struct arg_set path_args;
 708
 709                 if (as->argc < nr_params) {
 710                         ti->error = "not enough path parameters";
 711                         r = -EINVAL;
 712                         goto bad;
 713                 }
 714
 715                 path_args.argc = nr_params;
 716                 path_args.argv = as->argv;
 717
 718                 pgpath = parse_path(&path_args, &pg->ps, ti);
 719                 if (IS_ERR(pgpath)) {
 720                         r = PTR_ERR(pgpath);
 721                         goto bad;
 722                 }
 723
 724                 pgpath->pg = pg;
 725                 list_add_tail(&pgpath->list, &pg->pgpaths);
 726                 consume(as, nr_params);
 727         }
 728
 729         return pg;
 730
 731  bad:
 732         free_priority_group(pg, ti);
 733         return ERR_PTR(r);
 734 }
 735
 736 static int parse_hw_handler(struct arg_set *as, struct multipath *m)
 737 {
 738         unsigned hw_argc;
 739         int ret;
 740         struct dm_target *ti = m->ti;
 741
 742         static struct param _params[] = {
 743                 {0, 1024, "invalid number of hardware handler args"},
 744         };
 745
 746         if (read_param(_params, shift(as), &hw_argc, &ti->error))
 747                 return -EINVAL;
 748
 749         if (!hw_argc)
 750                 return 0;
 751
 752         if (hw_argc > as->argc) {
 753                 ti->error = "not enough arguments for hardware handler";
 754                 return -EINVAL;
 755         }
 756
 757         m->hw_handler_name = kstrdup(shift(as), GFP_KERNEL);
 758         request_module("scsi_dh_%s", m->hw_handler_name);
 759         if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
 760                 ti->error = "unknown hardware handler type";
 761                 ret = -EINVAL;
 762                 goto fail;
 763         }
 764
 765         if (hw_argc > 1) {
 766                 char *p;
 767                 int i, j, len = 4;
 768
 769                 for (i = 0; i <= hw_argc - 2; i++)
 770                         len += strlen(as->argv[i]) + 1;
 771                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 772                 if (!p) {
 773                         ti->error = "memory allocation failed";
 774                         ret = -ENOMEM;
 775                         goto fail;
 776                 }
 777                 j = sprintf(p, "%d", hw_argc - 1);
 778                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 779                         j = sprintf(p, "%s", as->argv[i]);
 780         }
 781         consume(as, hw_argc - 1);
 782
 783         return 0;
 784 fail:
 785         kfree(m->hw_handler_name);
 786         m->hw_handler_name = NULL;
 787         return ret;
 788 }
 789
 790 static int parse_features(struct arg_set *as, struct multipath *m)
 791 {
 792         int r;
 793         unsigned argc;
 794         struct dm_target *ti = m->ti;
 795         const char *param_name;
 796
 797         static struct param _params[] = {
 798                 {0, 5, "invalid number of feature args"},
 799                 {1, 50, "pg_init_retries must be between 1 and 50"},
 800                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 801         };
 802
 803         r = read_param(_params, shift(as), &argc, &ti->error);
 804         if (r)
 805                 return -EINVAL;
 806
 807         if (!argc)
 808                 return 0;
 809
 810         do {
 811                 param_name = shift(as);
 812                 argc--;
 813
 814                 if (!strnicmp(param_name, MESG_STR("queue_if_no_path"))) {
 815                         r = queue_if_no_path(m, 1, 0);
 816                         continue;
 817                 }
 818
 819                 if (!strnicmp(param_name, MESG_STR("pg_init_retries")) &&
 820                     (argc >= 1)) {
 821                         r = read_param(_params + 1, shift(as),
 822                                        &m->pg_init_retries, &ti->error);
 823                         argc--;
 824                         continue;
 825                 }
 826
 827                 if (!strnicmp(param_name, MESG_STR("pg_init_delay_msecs")) &&
 828                     (argc >= 1)) {
 829                         r = read_param(_params + 2, shift(as),
 830                                        &m->pg_init_delay_msecs, &ti->error);
 831                         argc--;
 832                         continue;
 833                 }
 834
 835                 ti->error = "Unrecognised multipath feature request";
 836                 r = -EINVAL;
 837         } while (argc && !r);
 838
 839         return r;
 840 }
 841
 842 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 843                          char **argv)
 844 {
 845         /* target parameters */
 846         static struct param _params[] = {
 847                 {1, 1024, "invalid number of priority groups"},
 848                 {1, 1024, "invalid initial priority group number"},
 849         };
 850
 851         int r;
 852         struct multipath *m;
 853         struct arg_set as;
 854         unsigned pg_count = 0;
 855         unsigned next_pg_num;
 856
 857         as.argc = argc;
 858         as.argv = argv;
 859
 860         m = alloc_multipath(ti);
 861         if (!m) {
 862                 ti->error = "can't allocate multipath";
 863                 return -EINVAL;
 864         }
 865
 866         r = parse_features(&as, m);
 867         if (r)
 868                 goto bad;
 869
 870         r = parse_hw_handler(&as, m);
 871         if (r)
 872                 goto bad;
 873
 874         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
 875         if (r)
 876                 goto bad;
 877
 878         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
 879         if (r)
 880                 goto bad;
 881
 882         /* parse the priority groups */
 883         while (as.argc) {
 884                 struct priority_group *pg;
 885
 886                 pg = parse_priority_group(&as, m);
 887                 if (IS_ERR(pg)) {
 888                         r = PTR_ERR(pg);
 889                         goto bad;
 890                 }
 891
 892                 m->nr_valid_paths += pg->nr_pgpaths;
 893                 list_add_tail(&pg->list, &m->priority_groups);
 894                 pg_count++;
 895                 pg->pg_num = pg_count;
 896                 if (!--next_pg_num)
 897                         m->next_pg = pg;
 898         }
 899
 900         if (pg_count != m->nr_priority_groups) {
 901                 ti->error = "priority group count mismatch";
 902                 r = -EINVAL;
 903                 goto bad;
 904         }
 905
 906         ti->num_flush_requests = 1;
 907         ti->num_discard_requests = 1;
 908
 909         return 0;
 910
 911  bad:
 912         free_multipath(m);
 913         return r;
 914 }
 915
 916 static void multipath_wait_for_pg_init_completion(struct multipath *m)
 917 {
 918         DECLARE_WAITQUEUE(wait, current);
 919         unsigned long flags;
 920
 921         add_wait_queue(&m->pg_init_wait, &wait);
 922
 923         while (1) {
 924                 set_current_state(TASK_UNINTERRUPTIBLE);
 925
 926                 spin_lock_irqsave(&m->lock, flags);
 927                 if (!m->pg_init_in_progress) {
 928                         spin_unlock_irqrestore(&m->lock, flags);
 929                         break;
 930                 }
 931                 spin_unlock_irqrestore(&m->lock, flags);
 932
 933                 io_schedule();
 934         }
 935         set_current_state(TASK_RUNNING);
 936
 937         remove_wait_queue(&m->pg_init_wait, &wait);
 938 }
 939
 940 static void flush_multipath_work(struct multipath *m)
 941 {
 942         flush_workqueue(kmpath_handlerd);
 943         multipath_wait_for_pg_init_completion(m);
 944         flush_workqueue(kmultipathd);
 945         flush_work_sync(&m->trigger_event);
 946 }
 947
 948 static void multipath_dtr(struct dm_target *ti)
 949 {
 950         struct multipath *m = ti->private;
 951
 952         flush_multipath_work(m);
 953         free_multipath(m);
 954 }
 955
 956 /*
 957  * Map cloned requests
 958  */
 959 static int multipath_map(struct dm_target *ti, struct request *clone,
 960                          union map_info *map_context)
 961 {
 962         int r;
 963         struct dm_mpath_io *mpio;
 964         struct multipath *m = (struct multipath *) ti->private;
 965
 966         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 967         if (!mpio)
 968                 /* ENOMEM, requeue */
 969                 return DM_MAPIO_REQUEUE;
 970         memset(mpio, 0, sizeof(*mpio));
 971
 972         map_context->ptr = mpio;
 973         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 974         r = map_io(m, clone, mpio, 0);
 975         if (r < 0 || r == DM_MAPIO_REQUEUE)
 976                 mempool_free(mpio, m->mpio_pool);
 977
 978         return r;
 979 }
 980
 981 /*
 982  * Take a path out of use.
 983  */
 984 static int fail_path(struct pgpath *pgpath)
 985 {
 986         unsigned long flags;
 987         struct multipath *m = pgpath->pg->m;
 988
 989         spin_lock_irqsave(&m->lock, flags);
 990
 991         if (!pgpath->is_active)
 992                 goto out;
 993
 994         DMWARN("Failing path %s.", pgpath->path.dev->name);
 995
 996         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 997         pgpath->is_active = 0;
 998         pgpath->fail_count++;
 999
1000         m->nr_valid_paths--;
1001
1002         if (pgpath == m->current_pgpath)
1003                 m->current_pgpath = NULL;
1004
1005         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1006                       pgpath->path.dev->name, m->nr_valid_paths);
1007
1008         schedule_work(&m->trigger_event);
1009
1010 out:
1011         spin_unlock_irqrestore(&m->lock, flags);
1012
1013         return 0;
1014 }
1015
1016 /*
1017  * Reinstate a previously-failed path
1018  */
1019 static int reinstate_path(struct pgpath *pgpath)
1020 {
1021         int r = 0;
1022         unsigned long flags;
1023         struct multipath *m = pgpath->pg->m;
1024
1025         spin_lock_irqsave(&m->lock, flags);
1026
1027         if (pgpath->is_active)
1028                 goto out;
1029
1030         if (!pgpath->pg->ps.type->reinstate_path) {
1031                 DMWARN("Reinstate path not supported by path selector %s",
1032                        pgpath->pg->ps.type->name);
1033                 r = -EINVAL;
1034                 goto out;
1035         }
1036
1037         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1038         if (r)
1039                 goto out;
1040
1041         pgpath->is_active = 1;
1042
1043         if (!m->nr_valid_paths++ && m->queue_size) {
1044                 m->current_pgpath = NULL;
1045                 queue_work(kmultipathd, &m->process_queued_ios);
1046         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1047                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1048                         m->pg_init_in_progress++;
1049         }
1050
1051         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1052                       pgpath->path.dev->name, m->nr_valid_paths);
1053
1054         schedule_work(&m->trigger_event);
1055
1056 out:
1057         spin_unlock_irqrestore(&m->lock, flags);
1058
1059         return r;
1060 }
1061
1062 /*
1063  * Fail or reinstate all paths that match the provided struct dm_dev.
1064  */
1065 static int action_dev(struct multipath *m, struct dm_dev *dev,
1066                       action_fn action)
1067 {
1068         int r = 0;
1069         struct pgpath *pgpath;
1070         struct priority_group *pg;
1071
1072         list_for_each_entry(pg, &m->priority_groups, list) {
1073                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1074                         if (pgpath->path.dev == dev)
1075                                 r = action(pgpath);
1076                 }
1077         }
1078
1079         return r;
1080 }
1081
1082 /*
1083  * Temporarily try to avoid having to use the specified PG
1084  */
1085 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1086                       int bypassed)
1087 {
1088         unsigned long flags;
1089
1090         spin_lock_irqsave(&m->lock, flags);
1091
1092         pg->bypassed = bypassed;
1093         m->current_pgpath = NULL;
1094         m->current_pg = NULL;
1095
1096         spin_unlock_irqrestore(&m->lock, flags);
1097
1098         schedule_work(&m->trigger_event);
1099 }
1100
1101 /*
1102  * Switch to using the specified PG from the next I/O that gets mapped
1103  */
1104 static int switch_pg_num(struct multipath *m, const char *pgstr)
1105 {
1106         struct priority_group *pg;
1107         unsigned pgnum;
1108         unsigned long flags;
1109
1110         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1111             (pgnum > m->nr_priority_groups)) {
1112                 DMWARN("invalid PG number supplied to switch_pg_num");
1113                 return -EINVAL;
1114         }
1115
1116         spin_lock_irqsave(&m->lock, flags);
1117         list_for_each_entry(pg, &m->priority_groups, list) {
1118                 pg->bypassed = 0;
1119                 if (--pgnum)
1120                         continue;
1121
1122                 m->current_pgpath = NULL;
1123                 m->current_pg = NULL;
1124                 m->next_pg = pg;
1125         }
1126         spin_unlock_irqrestore(&m->lock, flags);
1127
1128         schedule_work(&m->trigger_event);
1129         return 0;
1130 }
1131
1132 /*
1133  * Set/clear bypassed status of a PG.
1134  * PGs are numbered upwards from 1 in the order they were declared.
1135  */
1136 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1137 {
1138         struct priority_group *pg;
1139         unsigned pgnum;
1140
1141         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1142             (pgnum > m->nr_priority_groups)) {
1143                 DMWARN("invalid PG number supplied to bypass_pg");
1144                 return -EINVAL;
1145         }
1146
1147         list_for_each_entry(pg, &m->priority_groups, list) {
1148                 if (!--pgnum)
1149                         break;
1150         }
1151
1152         bypass_pg(m, pg, bypassed);
1153         return 0;
1154 }
1155
1156 /*
1157  * Should we retry pg_init immediately?
1158  */
1159 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1160 {
1161         unsigned long flags;
1162         int limit_reached = 0;
1163
1164         spin_lock_irqsave(&m->lock, flags);
1165
1166         if (m->pg_init_count <= m->pg_init_retries)
1167                 m->pg_init_required = 1;
1168         else
1169                 limit_reached = 1;
1170
1171         spin_unlock_irqrestore(&m->lock, flags);
1172
1173         return limit_reached;
1174 }
1175
1176 static void pg_init_done(void *data, int errors)
1177 {
1178         struct pgpath *pgpath = data;
1179         struct priority_group *pg = pgpath->pg;
1180         struct multipath *m = pg->m;
1181         unsigned long flags;
1182         unsigned delay_retry = 0;
1183
1184         /* device or driver problems */
1185         switch (errors) {
1186         case SCSI_DH_OK:
1187                 break;
1188         case SCSI_DH_NOSYS:
1189                 if (!m->hw_handler_name) {
1190                         errors = 0;
1191                         break;
1192                 }
1193                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1194                       "Error %d.", m->hw_handler_name, errors);
1195                 /*
1196                  * Fail path for now, so we do not ping pong
1197                  */
1198                 fail_path(pgpath);
1199                 break;
1200         case SCSI_DH_DEV_TEMP_BUSY:
1201                 /*
1202                  * Probably doing something like FW upgrade on the
1203                  * controller so try the other pg.
1204                  */
1205                 bypass_pg(m, pg, 1);
1206                 break;
1207         case SCSI_DH_RETRY:
1208                 /* Wait before retrying. */
1209                 delay_retry = 1;
1210         case SCSI_DH_IMM_RETRY:
1211         case SCSI_DH_RES_TEMP_UNAVAIL:
1212                 if (pg_init_limit_reached(m, pgpath))
1213                         fail_path(pgpath);
1214                 errors = 0;
1215                 break;
1216         default:
1217                 /*
1218                  * We probably do not want to fail the path for a device
1219                  * error, but this is what the old dm did. In future
1220                  * patches we can do more advanced handling.
1221                  */
1222                 fail_path(pgpath);
1223         }
1224
1225         spin_lock_irqsave(&m->lock, flags);
1226         if (errors) {
1227                 if (pgpath == m->current_pgpath) {
1228                         DMERR("Could not failover device. Error %d.", errors);
1229                         m->current_pgpath = NULL;
1230                         m->current_pg = NULL;
1231                 }
1232         } else if (!m->pg_init_required)
1233                 pg->bypassed = 0;
1234
1235         if (--m->pg_init_in_progress)
1236                 /* Activations of other paths are still on going */
1237                 goto out;
1238
1239         if (!m->pg_init_required)
1240                 m->queue_io = 0;
1241
1242         m->pg_init_delay_retry = delay_retry;
1243         queue_work(kmultipathd, &m->process_queued_ios);
1244
1245         /*
1246          * Wake up any thread waiting to suspend.
1247          */
1248         wake_up(&m->pg_init_wait);
1249
1250 out:
1251         spin_unlock_irqrestore(&m->lock, flags);
1252 }
1253
1254 static void activate_path(struct work_struct *work)
1255 {
1256         struct pgpath *pgpath =
1257                 container_of(work, struct pgpath, activate_path.work);
1258
1259         scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1260                                 pg_init_done, pgpath);
1261 }
1262
1263 /*
1264  * end_io handling
1265  */
1266 static int do_end_io(struct multipath *m, struct request *clone,
1267                      int error, struct dm_mpath_io *mpio)
1268 {
1269         /*
1270          * We don't queue any clone request inside the multipath target
1271          * during end I/O handling, since those clone requests don't have
1272          * bio clones.  If we queue them inside the multipath target,
1273          * we need to make bio clones, that requires memory allocation.
1274          * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1275          *  don't have bio clones.)
1276          * Instead of queueing the clone request here, we queue the original
1277          * request into dm core, which will remake a clone request and
1278          * clone bios for it and resubmit it later.
1279          */
1280         int r = DM_ENDIO_REQUEUE;
1281         unsigned long flags;
1282
1283         if (!error && !clone->errors)
1284                 return 0;       /* I/O complete */
1285
1286         if (error == -EOPNOTSUPP || error == -EREMOTEIO)
1287                 return error;
1288
1289         if (mpio->pgpath)
1290                 fail_path(mpio->pgpath);
1291
1292         spin_lock_irqsave(&m->lock, flags);
1293         if (!m->nr_valid_paths) {
1294                 if (!m->queue_if_no_path) {
1295                         if (!__must_push_back(m))
1296                                 r = -EIO;
1297                 } else {
1298                         if (error == -EBADE)
1299                                 r = error;
1300                 }
1301         }
1302         spin_unlock_irqrestore(&m->lock, flags);
1303
1304         return r;
1305 }
1306
1307 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1308                             int error, union map_info *map_context)
1309 {
1310         struct multipath *m = ti->private;
1311         struct dm_mpath_io *mpio = map_context->ptr;
1312         struct pgpath *pgpath = mpio->pgpath;
1313         struct path_selector *ps;
1314         int r;
1315
1316         r  = do_end_io(m, clone, error, mpio);
1317         if (pgpath) {
1318                 ps = &pgpath->pg->ps;
1319                 if (ps->type->end_io)
1320                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1321         }
1322         mempool_free(mpio, m->mpio_pool);
1323
1324         return r;
1325 }
1326
1327 /*
1328  * Suspend can't complete until all the I/O is processed so if
1329  * the last path fails we must error any remaining I/O.
1330  * Note that if the freeze_bdev fails while suspending, the
1331  * queue_if_no_path state is lost - userspace should reset it.
1332  */
1333 static void multipath_presuspend(struct dm_target *ti)
1334 {
1335         struct multipath *m = (struct multipath *) ti->private;
1336
1337         queue_if_no_path(m, 0, 1);
1338 }
1339
1340 static void multipath_postsuspend(struct dm_target *ti)
1341 {
1342         struct multipath *m = ti->private;
1343
1344         mutex_lock(&m->work_mutex);
1345         flush_multipath_work(m);
1346         mutex_unlock(&m->work_mutex);
1347 }
1348
1349 /*
1350  * Restore the queue_if_no_path setting.
1351  */
1352 static void multipath_resume(struct dm_target *ti)
1353 {
1354         struct multipath *m = (struct multipath *) ti->private;
1355         unsigned long flags;
1356
1357         spin_lock_irqsave(&m->lock, flags);
1358         m->queue_if_no_path = m->saved_queue_if_no_path;
1359         spin_unlock_irqrestore(&m->lock, flags);
1360 }
1361
1362 /*
1363  * Info output has the following format:
1364  * num_multipath_feature_args [multipath_feature_args]*
1365  * num_handler_status_args [handler_status_args]*
1366  * num_groups init_group_number
1367  *            [A|D|E num_ps_status_args [ps_status_args]*
1368  *             num_paths num_selector_args
1369  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1370  *
1371  * Table output has the following format (identical to the constructor string):
1372  * num_feature_args [features_args]*
1373  * num_handler_args hw_handler [hw_handler_args]*
1374  * num_groups init_group_number
1375  *     [priority selector-name num_ps_args [ps_args]*
1376  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1377  */
1378 static int multipath_status(struct dm_target *ti, status_type_t type,
1379                             char *result, unsigned int maxlen)
1380 {
1381         int sz = 0;
1382         unsigned long flags;
1383         struct multipath *m = (struct multipath *) ti->private;
1384         struct priority_group *pg;
1385         struct pgpath *p;
1386         unsigned pg_num;
1387         char state;
1388
1389         spin_lock_irqsave(&m->lock, flags);
1390
1391         /* Features */
1392         if (type == STATUSTYPE_INFO)
1393                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1394         else {
1395                 DMEMIT("%u ", m->queue_if_no_path +
1396                               (m->pg_init_retries > 0) * 2 +
1397                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2);
1398                 if (m->queue_if_no_path)
1399                         DMEMIT("queue_if_no_path ");
1400                 if (m->pg_init_retries)
1401                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1402                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1403                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1404         }
1405
1406         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1407                 DMEMIT("0 ");
1408         else
1409                 DMEMIT("1 %s ", m->hw_handler_name);
1410
1411         DMEMIT("%u ", m->nr_priority_groups);
1412
1413         if (m->next_pg)
1414                 pg_num = m->next_pg->pg_num;
1415         else if (m->current_pg)
1416                 pg_num = m->current_pg->pg_num;
1417         else
1418                         pg_num = 1;
1419
1420         DMEMIT("%u ", pg_num);
1421
1422         switch (type) {
1423         case STATUSTYPE_INFO:
1424                 list_for_each_entry(pg, &m->priority_groups, list) {
1425                         if (pg->bypassed)
1426                                 state = 'D';    /* Disabled */
1427                         else if (pg == m->current_pg)
1428                                 state = 'A';    /* Currently Active */
1429                         else
1430                                 state = 'E';    /* Enabled */
1431
1432                         DMEMIT("%c ", state);
1433
1434                         if (pg->ps.type->status)
1435                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1436                                                           result + sz,
1437                                                           maxlen - sz);
1438                         else
1439                                 DMEMIT("0 ");
1440
1441                         DMEMIT("%u %u ", pg->nr_pgpaths,
1442                                pg->ps.type->info_args);
1443
1444                         list_for_each_entry(p, &pg->pgpaths, list) {
1445                                 DMEMIT("%s %s %u ", p->path.dev->name,
1446                                        p->is_active ? "A" : "F",
1447                                        p->fail_count);
1448                                 if (pg->ps.type->status)
1449                                         sz += pg->ps.type->status(&pg->ps,
1450                                               &p->path, type, result + sz,
1451                                               maxlen - sz);
1452                         }
1453                 }
1454                 break;
1455
1456         case STATUSTYPE_TABLE:
1457                 list_for_each_entry(pg, &m->priority_groups, list) {
1458                         DMEMIT("%s ", pg->ps.type->name);
1459
1460                         if (pg->ps.type->status)
1461                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1462                                                           result + sz,
1463                                                           maxlen - sz);
1464                         else
1465                                 DMEMIT("0 ");
1466
1467                         DMEMIT("%u %u ", pg->nr_pgpaths,
1468                                pg->ps.type->table_args);
1469
1470                         list_for_each_entry(p, &pg->pgpaths, list) {
1471                                 DMEMIT("%s ", p->path.dev->name);
1472                                 if (pg->ps.type->status)
1473                                         sz += pg->ps.type->status(&pg->ps,
1474                                               &p->path, type, result + sz,
1475                                               maxlen - sz);
1476                         }
1477                 }
1478                 break;
1479         }
1480
1481         spin_unlock_irqrestore(&m->lock, flags);
1482
1483         return 0;
1484 }
1485
1486 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1487 {
1488         int r = -EINVAL;
1489         struct dm_dev *dev;
1490         struct multipath *m = (struct multipath *) ti->private;
1491         action_fn action;
1492
1493         mutex_lock(&m->work_mutex);
1494
1495         if (dm_suspended(ti)) {
1496                 r = -EBUSY;
1497                 goto out;
1498         }
1499
1500         if (argc == 1) {
1501                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path"))) {
1502                         r = queue_if_no_path(m, 1, 0);
1503                         goto out;
1504                 } else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path"))) {
1505                         r = queue_if_no_path(m, 0, 0);
1506                         goto out;
1507                 }
1508         }
1509
1510         if (argc != 2) {
1511                 DMWARN("Unrecognised multipath message received.");
1512                 goto out;
1513         }
1514
1515         if (!strnicmp(argv[0], MESG_STR("disable_group"))) {
1516                 r = bypass_pg_num(m, argv[1], 1);
1517                 goto out;
1518         } else if (!strnicmp(argv[0], MESG_STR("enable_group"))) {
1519                 r = bypass_pg_num(m, argv[1], 0);
1520                 goto out;
1521         } else if (!strnicmp(argv[0], MESG_STR("switch_group"))) {
1522                 r = switch_pg_num(m, argv[1]);
1523                 goto out;
1524         } else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1525                 action = reinstate_path;
1526         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1527                 action = fail_path;
1528         else {
1529                 DMWARN("Unrecognised multipath message received.");
1530                 goto out;
1531         }
1532
1533         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1534         if (r) {
1535                 DMWARN("message: error getting device %s",
1536                        argv[1]);
1537                 goto out;
1538         }
1539
1540         r = action_dev(m, dev, action);
1541
1542         dm_put_device(ti, dev);
1543
1544 out:
1545         mutex_unlock(&m->work_mutex);
1546         return r;
1547 }
1548
1549 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1550                            unsigned long arg)
1551 {
1552         struct multipath *m = (struct multipath *) ti->private;
1553         struct block_device *bdev = NULL;
1554         fmode_t mode = 0;
1555         unsigned long flags;
1556         int r = 0;
1557
1558         spin_lock_irqsave(&m->lock, flags);
1559
1560         if (!m->current_pgpath)
1561                 __choose_pgpath(m, 0);
1562
1563         if (m->current_pgpath) {
1564                 bdev = m->current_pgpath->path.dev->bdev;
1565                 mode = m->current_pgpath->path.dev->mode;
1566         }
1567
1568         if (m->queue_io)
1569                 r = -EAGAIN;
1570         else if (!bdev)
1571                 r = -EIO;
1572
1573         spin_unlock_irqrestore(&m->lock, flags);
1574
1575         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1576 }
1577
1578 static int multipath_iterate_devices(struct dm_target *ti,
1579                                      iterate_devices_callout_fn fn, void *data)
1580 {
1581         struct multipath *m = ti->private;
1582         struct priority_group *pg;
1583         struct pgpath *p;
1584         int ret = 0;
1585
1586         list_for_each_entry(pg, &m->priority_groups, list) {
1587                 list_for_each_entry(p, &pg->pgpaths, list) {
1588                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1589                         if (ret)
1590                                 goto out;
1591                 }
1592         }
1593
1594 out:
1595         return ret;
1596 }
1597
1598 static int __pgpath_busy(struct pgpath *pgpath)
1599 {
1600         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1601
1602         return dm_underlying_device_busy(q);
1603 }
1604
1605 /*
1606  * We return "busy", only when we can map I/Os but underlying devices
1607  * are busy (so even if we map I/Os now, the I/Os will wait on
1608  * the underlying queue).
1609  * In other words, if we want to kill I/Os or queue them inside us
1610  * due to map unavailability, we don't return "busy".  Otherwise,
1611  * dm core won't give us the I/Os and we can't do what we want.
1612  */
1613 static int multipath_busy(struct dm_target *ti)
1614 {
1615         int busy = 0, has_active = 0;
1616         struct multipath *m = ti->private;
1617         struct priority_group *pg;
1618         struct pgpath *pgpath;
1619         unsigned long flags;
1620
1621         spin_lock_irqsave(&m->lock, flags);
1622
1623         /* Guess which priority_group will be used at next mapping time */
1624         if (unlikely(!m->current_pgpath && m->next_pg))
1625                 pg = m->next_pg;
1626         else if (likely(m->current_pg))
1627                 pg = m->current_pg;
1628         else
1629                 /*
1630                  * We don't know which pg will be used at next mapping time.
1631                  * We don't call __choose_pgpath() here to avoid to trigger
1632                  * pg_init just by busy checking.
1633                  * So we don't know whether underlying devices we will be using
1634                  * at next mapping time are busy or not. Just try mapping.
1635                  */
1636                 goto out;
1637
1638         /*
1639          * If there is one non-busy active path at least, the path selector
1640          * will be able to select it. So we consider such a pg as not busy.
1641          */
1642         busy = 1;
1643         list_for_each_entry(pgpath, &pg->pgpaths, list)
1644                 if (pgpath->is_active) {
1645                         has_active = 1;
1646
1647                         if (!__pgpath_busy(pgpath)) {
1648                                 busy = 0;
1649                                 break;
1650                         }
1651                 }
1652
1653         if (!has_active)
1654                 /*
1655                  * No active path in this pg, so this pg won't be used and
1656                  * the current_pg will be changed at next mapping time.
1657                  * We need to try mapping to determine it.
1658                  */
1659                 busy = 0;
1660
1661 out:
1662         spin_unlock_irqrestore(&m->lock, flags);
1663
1664         return busy;
1665 }
1666
1667 /*-----------------------------------------------------------------
1668  * Module setup
1669  *---------------------------------------------------------------*/
1670 static struct target_type multipath_target = {
1671         .name = "multipath",
1672         .version = {1, 2, 0},
1673         .module = THIS_MODULE,
1674         .ctr = multipath_ctr,
1675         .dtr = multipath_dtr,
1676         .map_rq = multipath_map,
1677         .rq_end_io = multipath_end_io,
1678         .presuspend = multipath_presuspend,
1679         .postsuspend = multipath_postsuspend,
1680         .resume = multipath_resume,
1681         .status = multipath_status,
1682         .message = multipath_message,
1683         .ioctl  = multipath_ioctl,
1684         .iterate_devices = multipath_iterate_devices,
1685         .busy = multipath_busy,
1686 };
1687
1688 static int __init dm_multipath_init(void)
1689 {
1690         int r;
1691
1692         /* allocate a slab for the dm_ios */
1693         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1694         if (!_mpio_cache)
1695                 return -ENOMEM;
1696
1697         r = dm_register_target(&multipath_target);
1698         if (r < 0) {
1699                 DMERR("register failed %d", r);
1700                 kmem_cache_destroy(_mpio_cache);
1701                 return -EINVAL;
1702         }
1703
1704         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1705         if (!kmultipathd) {
1706                 DMERR("failed to create workqueue kmpathd");
1707                 dm_unregister_target(&multipath_target);
1708                 kmem_cache_destroy(_mpio_cache);
1709                 return -ENOMEM;
1710         }
1711
1712         /*
1713          * A separate workqueue is used to handle the device handlers
1714          * to avoid overloading existing workqueue. Overloading the
1715          * old workqueue would also create a bottleneck in the
1716          * path of the storage hardware device activation.
1717          */
1718         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1719                                                   WQ_MEM_RECLAIM);
1720         if (!kmpath_handlerd) {
1721                 DMERR("failed to create workqueue kmpath_handlerd");
1722                 destroy_workqueue(kmultipathd);
1723                 dm_unregister_target(&multipath_target);
1724                 kmem_cache_destroy(_mpio_cache);
1725                 return -ENOMEM;
1726         }
1727
1728         DMINFO("version %u.%u.%u loaded",
1729                multipath_target.version[0], multipath_target.version[1],
1730                multipath_target.version[2]);
1731
1732         return r;
1733 }
1734
1735 static void __exit dm_multipath_exit(void)
1736 {
1737         destroy_workqueue(kmpath_handlerd);
1738         destroy_workqueue(kmultipathd);
1739
1740         dm_unregister_target(&multipath_target);
1741         kmem_cache_destroy(_mpio_cache);
1742 }
1743
1744 module_init(dm_multipath_init);
1745 module_exit(dm_multipath_exit);
1746
1747 MODULE_DESCRIPTION(DM_NAME " multipath target");
1748 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1749 MODULE_LICENSE("GPL");