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
  27 /* Path properties */
  28 struct pgpath {
  29         struct list_head list;
  30
  31         struct priority_group *pg;      /* Owning PG */
  32         unsigned is_active;             /* Path status */
  33         unsigned fail_count;            /* Cumulative failure count */
  34
  35         struct dm_path path;
  36         struct work_struct deactivate_path;
  37         struct work_struct activate_path;
  38 };
  39
  40 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  41
  42 /*
  43  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  44  * Each has a path selector which controls which path gets used.
  45  */
  46 struct priority_group {
  47         struct list_head list;
  48
  49         struct multipath *m;            /* Owning multipath instance */
  50         struct path_selector ps;
  51
  52         unsigned pg_num;                /* Reference number */
  53         unsigned bypassed;              /* Temporarily bypass this PG? */
  54
  55         unsigned nr_pgpaths;            /* Number of paths in PG */
  56         struct list_head pgpaths;
  57 };
  58
  59 /* Multipath context */
  60 struct multipath {
  61         struct list_head list;
  62         struct dm_target *ti;
  63
  64         spinlock_t lock;
  65
  66         const char *hw_handler_name;
  67         char *hw_handler_params;
  68         unsigned nr_priority_groups;
  69         struct list_head priority_groups;
  70         unsigned pg_init_required;      /* pg_init needs calling? */
  71         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  72
  73         unsigned nr_valid_paths;        /* Total number of usable paths */
  74         struct pgpath *current_pgpath;
  75         struct priority_group *current_pg;
  76         struct priority_group *next_pg; /* Switch to this PG if set */
  77         unsigned repeat_count;          /* I/Os left before calling PS again */
  78
  79         unsigned queue_io;              /* Must we queue all I/O? */
  80         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
  81         unsigned saved_queue_if_no_path;/* Saved state during suspension */
  82         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  83         unsigned pg_init_count;         /* Number of times pg_init called */
  84
  85         struct work_struct process_queued_ios;
  86         struct list_head queued_ios;
  87         unsigned queue_size;
  88
  89         struct work_struct trigger_event;
  90
  91         /*
  92          * We must use a mempool of dm_mpath_io structs so that we
  93          * can resubmit bios on error.
  94          */
  95         mempool_t *mpio_pool;
  96
  97         struct mutex work_mutex;
  98 };
  99
 100 /*
 101  * Context information attached to each bio we process.
 102  */
 103 struct dm_mpath_io {
 104         struct pgpath *pgpath;
 105         size_t nr_bytes;
 106 };
 107
 108 typedef int (*action_fn) (struct pgpath *pgpath);
 109
 110 #define MIN_IOS 256     /* Mempool size */
 111
 112 static struct kmem_cache *_mpio_cache;
 113
 114 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 115 static void process_queued_ios(struct work_struct *work);
 116 static void trigger_event(struct work_struct *work);
 117 static void activate_path(struct work_struct *work);
 118 static void deactivate_path(struct work_struct *work);
 119
 120
 121 /*-----------------------------------------------
 122  * Allocation routines
 123  *-----------------------------------------------*/
 124
 125 static struct pgpath *alloc_pgpath(void)
 126 {
 127         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 128
 129         if (pgpath) {
 130                 pgpath->is_active = 1;
 131                 INIT_WORK(&pgpath->deactivate_path, deactivate_path);
 132                 INIT_WORK(&pgpath->activate_path, activate_path);
 133         }
 134
 135         return pgpath;
 136 }
 137
 138 static void free_pgpath(struct pgpath *pgpath)
 139 {
 140         kfree(pgpath);
 141 }
 142
 143 static void deactivate_path(struct work_struct *work)
 144 {
 145         struct pgpath *pgpath =
 146                 container_of(work, struct pgpath, deactivate_path);
 147
 148         blk_abort_queue(pgpath->path.dev->bdev->bd_disk->queue);
 149 }
 150
 151 static struct priority_group *alloc_priority_group(void)
 152 {
 153         struct priority_group *pg;
 154
 155         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 156
 157         if (pg)
 158                 INIT_LIST_HEAD(&pg->pgpaths);
 159
 160         return pg;
 161 }
 162
 163 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 164 {
 165         struct pgpath *pgpath, *tmp;
 166         struct multipath *m = ti->private;
 167
 168         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 169                 list_del(&pgpath->list);
 170                 if (m->hw_handler_name)
 171                         scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 172                 dm_put_device(ti, pgpath->path.dev);
 173                 free_pgpath(pgpath);
 174         }
 175 }
 176
 177 static void free_priority_group(struct priority_group *pg,
 178                                 struct dm_target *ti)
 179 {
 180         struct path_selector *ps = &pg->ps;
 181
 182         if (ps->type) {
 183                 ps->type->destroy(ps);
 184                 dm_put_path_selector(ps->type);
 185         }
 186
 187         free_pgpaths(&pg->pgpaths, ti);
 188         kfree(pg);
 189 }
 190
 191 static struct multipath *alloc_multipath(struct dm_target *ti)
 192 {
 193         struct multipath *m;
 194
 195         m = kzalloc(sizeof(*m), GFP_KERNEL);
 196         if (m) {
 197                 INIT_LIST_HEAD(&m->priority_groups);
 198                 INIT_LIST_HEAD(&m->queued_ios);
 199                 spin_lock_init(&m->lock);
 200                 m->queue_io = 1;
 201                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
 202                 INIT_WORK(&m->trigger_event, trigger_event);
 203                 mutex_init(&m->work_mutex);
 204                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 205                 if (!m->mpio_pool) {
 206                         kfree(m);
 207                         return NULL;
 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
 232 /*-----------------------------------------------
 233  * Path selection
 234  *-----------------------------------------------*/
 235
 236 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 237 {
 238         m->current_pg = pgpath->pg;
 239
 240         /* Must we initialise the PG first, and queue I/O till it's ready? */
 241         if (m->hw_handler_name) {
 242                 m->pg_init_required = 1;
 243                 m->queue_io = 1;
 244         } else {
 245                 m->pg_init_required = 0;
 246                 m->queue_io = 0;
 247         }
 248
 249         m->pg_init_count = 0;
 250 }
 251
 252 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 253                                size_t nr_bytes)
 254 {
 255         struct dm_path *path;
 256
 257         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 258         if (!path)
 259                 return -ENXIO;
 260
 261         m->current_pgpath = path_to_pgpath(path);
 262
 263         if (m->current_pg != pg)
 264                 __switch_pg(m, m->current_pgpath);
 265
 266         return 0;
 267 }
 268
 269 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 270 {
 271         struct priority_group *pg;
 272         unsigned bypassed = 1;
 273
 274         if (!m->nr_valid_paths)
 275                 goto failed;
 276
 277         /* Were we instructed to switch PG? */
 278         if (m->next_pg) {
 279                 pg = m->next_pg;
 280                 m->next_pg = NULL;
 281                 if (!__choose_path_in_pg(m, pg, nr_bytes))
 282                         return;
 283         }
 284
 285         /* Don't change PG until it has no remaining paths */
 286         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 287                 return;
 288
 289         /*
 290          * Loop through priority groups until we find a valid path.
 291          * First time we skip PGs marked 'bypassed'.
 292          * Second time we only try the ones we skipped.
 293          */
 294         do {
 295                 list_for_each_entry(pg, &m->priority_groups, list) {
 296                         if (pg->bypassed == bypassed)
 297                                 continue;
 298                         if (!__choose_path_in_pg(m, pg, nr_bytes))
 299                                 return;
 300                 }
 301         } while (bypassed--);
 302
 303 failed:
 304         m->current_pgpath = NULL;
 305         m->current_pg = NULL;
 306 }
 307
 308 /*
 309  * Check whether bios must be queued in the device-mapper core rather
 310  * than here in the target.
 311  *
 312  * m->lock must be held on entry.
 313  *
 314  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 315  * same value then we are not between multipath_presuspend()
 316  * and multipath_resume() calls and we have no need to check
 317  * for the DMF_NOFLUSH_SUSPENDING flag.
 318  */
 319 static int __must_push_back(struct multipath *m)
 320 {
 321         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 322                 dm_noflush_suspending(m->ti));
 323 }
 324
 325 static int map_io(struct multipath *m, struct request *clone,
 326                   struct dm_mpath_io *mpio, unsigned was_queued)
 327 {
 328         int r = DM_MAPIO_REMAPPED;
 329         size_t nr_bytes = blk_rq_bytes(clone);
 330         unsigned long flags;
 331         struct pgpath *pgpath;
 332         struct block_device *bdev;
 333
 334         spin_lock_irqsave(&m->lock, flags);
 335
 336         /* Do we need to select a new pgpath? */
 337         if (!m->current_pgpath ||
 338             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 339                 __choose_pgpath(m, nr_bytes);
 340
 341         pgpath = m->current_pgpath;
 342
 343         if (was_queued)
 344                 m->queue_size--;
 345
 346         if ((pgpath && m->queue_io) ||
 347             (!pgpath && m->queue_if_no_path)) {
 348                 /* Queue for the daemon to resubmit */
 349                 list_add_tail(&clone->queuelist, &m->queued_ios);
 350                 m->queue_size++;
 351                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 352                     !m->queue_io)
 353                         queue_work(kmultipathd, &m->process_queued_ios);
 354                 pgpath = NULL;
 355                 r = DM_MAPIO_SUBMITTED;
 356         } else if (pgpath) {
 357                 bdev = pgpath->path.dev->bdev;
 358                 clone->q = bdev_get_queue(bdev);
 359                 clone->rq_disk = bdev->bd_disk;
 360         } else if (__must_push_back(m))
 361                 r = DM_MAPIO_REQUEUE;
 362         else
 363                 r = -EIO;       /* Failed */
 364
 365         mpio->pgpath = pgpath;
 366         mpio->nr_bytes = nr_bytes;
 367
 368         if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
 369                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path,
 370                                               nr_bytes);
 371
 372         spin_unlock_irqrestore(&m->lock, flags);
 373
 374         return r;
 375 }
 376
 377 /*
 378  * If we run out of usable paths, should we queue I/O or error it?
 379  */
 380 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 381                             unsigned save_old_value)
 382 {
 383         unsigned long flags;
 384
 385         spin_lock_irqsave(&m->lock, flags);
 386
 387         if (save_old_value)
 388                 m->saved_queue_if_no_path = m->queue_if_no_path;
 389         else
 390                 m->saved_queue_if_no_path = queue_if_no_path;
 391         m->queue_if_no_path = queue_if_no_path;
 392         if (!m->queue_if_no_path && m->queue_size)
 393                 queue_work(kmultipathd, &m->process_queued_ios);
 394
 395         spin_unlock_irqrestore(&m->lock, flags);
 396
 397         return 0;
 398 }
 399
 400 /*-----------------------------------------------------------------
 401  * The multipath daemon is responsible for resubmitting queued ios.
 402  *---------------------------------------------------------------*/
 403
 404 static void dispatch_queued_ios(struct multipath *m)
 405 {
 406         int r;
 407         unsigned long flags;
 408         struct dm_mpath_io *mpio;
 409         union map_info *info;
 410         struct request *clone, *n;
 411         LIST_HEAD(cl);
 412
 413         spin_lock_irqsave(&m->lock, flags);
 414         list_splice_init(&m->queued_ios, &cl);
 415         spin_unlock_irqrestore(&m->lock, flags);
 416
 417         list_for_each_entry_safe(clone, n, &cl, queuelist) {
 418                 list_del_init(&clone->queuelist);
 419
 420                 info = dm_get_rq_mapinfo(clone);
 421                 mpio = info->ptr;
 422
 423                 r = map_io(m, clone, mpio, 1);
 424                 if (r < 0) {
 425                         mempool_free(mpio, m->mpio_pool);
 426                         dm_kill_unmapped_request(clone, r);
 427                 } else if (r == DM_MAPIO_REMAPPED)
 428                         dm_dispatch_request(clone);
 429                 else if (r == DM_MAPIO_REQUEUE) {
 430                         mempool_free(mpio, m->mpio_pool);
 431                         dm_requeue_unmapped_request(clone);
 432                 }
 433         }
 434 }
 435
 436 static void process_queued_ios(struct work_struct *work)
 437 {
 438         struct multipath *m =
 439                 container_of(work, struct multipath, process_queued_ios);
 440         struct pgpath *pgpath = NULL, *tmp;
 441         unsigned must_queue = 1;
 442         unsigned long flags;
 443
 444         spin_lock_irqsave(&m->lock, flags);
 445
 446         if (!m->queue_size)
 447                 goto out;
 448
 449         if (!m->current_pgpath)
 450                 __choose_pgpath(m, 0);
 451
 452         pgpath = m->current_pgpath;
 453
 454         if ((pgpath && !m->queue_io) ||
 455             (!pgpath && !m->queue_if_no_path))
 456                 must_queue = 0;
 457
 458         if (m->pg_init_required && !m->pg_init_in_progress && pgpath) {
 459                 m->pg_init_count++;
 460                 m->pg_init_required = 0;
 461                 list_for_each_entry(tmp, &pgpath->pg->pgpaths, list) {
 462                         /* Skip failed paths */
 463                         if (!tmp->is_active)
 464                                 continue;
 465                         if (queue_work(kmpath_handlerd, &tmp->activate_path))
 466                                 m->pg_init_in_progress++;
 467                 }
 468         }
 469 out:
 470         spin_unlock_irqrestore(&m->lock, flags);
 471         if (!must_queue)
 472                 dispatch_queued_ios(m);
 473 }
 474
 475 /*
 476  * An event is triggered whenever a path is taken out of use.
 477  * Includes path failure and PG bypass.
 478  */
 479 static void trigger_event(struct work_struct *work)
 480 {
 481         struct multipath *m =
 482                 container_of(work, struct multipath, trigger_event);
 483
 484         dm_table_event(m->ti->table);
 485 }
 486
 487 /*-----------------------------------------------------------------
 488  * Constructor/argument parsing:
 489  * <#multipath feature args> [<arg>]*
 490  * <#hw_handler args> [hw_handler [<arg>]*]
 491  * <#priority groups>
 492  * <initial priority group>
 493  *     [<selector> <#selector args> [<arg>]*
 494  *      <#paths> <#per-path selector args>
 495  *         [<path> [<arg>]* ]+ ]+
 496  *---------------------------------------------------------------*/
 497 struct param {
 498         unsigned min;
 499         unsigned max;
 500         char *error;
 501 };
 502
 503 static int read_param(struct param *param, char *str, unsigned *v, char **error)
 504 {
 505         if (!str ||
 506             (sscanf(str, "%u", v) != 1) ||
 507             (*v < param->min) ||
 508             (*v > param->max)) {
 509                 *error = param->error;
 510                 return -EINVAL;
 511         }
 512
 513         return 0;
 514 }
 515
 516 struct arg_set {
 517         unsigned argc;
 518         char **argv;
 519 };
 520
 521 static char *shift(struct arg_set *as)
 522 {
 523         char *r;
 524
 525         if (as->argc) {
 526                 as->argc--;
 527                 r = *as->argv;
 528                 as->argv++;
 529                 return r;
 530         }
 531
 532         return NULL;
 533 }
 534
 535 static void consume(struct arg_set *as, unsigned n)
 536 {
 537         BUG_ON (as->argc < n);
 538         as->argc -= n;
 539         as->argv += n;
 540 }
 541
 542 static int parse_path_selector(struct 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 param _params[] = {
 550                 {0, 1024, "invalid number of path selector args"},
 551         };
 552
 553         pst = dm_get_path_selector(shift(as));
 554         if (!pst) {
 555                 ti->error = "unknown path selector type";
 556                 return -EINVAL;
 557         }
 558
 559         r = read_param(_params, shift(as), &ps_argc, &ti->error);
 560         if (r) {
 561                 dm_put_path_selector(pst);
 562                 return -EINVAL;
 563         }
 564
 565         if (ps_argc > as->argc) {
 566                 dm_put_path_selector(pst);
 567                 ti->error = "not enough arguments for path selector";
 568                 return -EINVAL;
 569         }
 570
 571         r = pst->create(&pg->ps, ps_argc, as->argv);
 572         if (r) {
 573                 dm_put_path_selector(pst);
 574                 ti->error = "path selector constructor failed";
 575                 return r;
 576         }
 577
 578         pg->ps.type = pst;
 579         consume(as, ps_argc);
 580
 581         return 0;
 582 }
 583
 584 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
 585                                struct dm_target *ti)
 586 {
 587         int r;
 588         struct pgpath *p;
 589         struct multipath *m = ti->private;
 590
 591         /* we need at least a path arg */
 592         if (as->argc < 1) {
 593                 ti->error = "no device given";
 594                 return ERR_PTR(-EINVAL);
 595         }
 596
 597         p = alloc_pgpath();
 598         if (!p)
 599                 return ERR_PTR(-ENOMEM);
 600
 601         r = dm_get_device(ti, shift(as), ti->begin, ti->len,
 602                           dm_table_get_mode(ti->table), &p->path.dev);
 603         if (r) {
 604                 ti->error = "error getting device";
 605                 goto bad;
 606         }
 607
 608         if (m->hw_handler_name) {
 609                 struct request_queue *q = bdev_get_queue(p->path.dev->bdev);
 610
 611                 r = scsi_dh_attach(q, m->hw_handler_name);
 612                 if (r == -EBUSY) {
 613                         /*
 614                          * Already attached to different hw_handler,
 615                          * try to reattach with correct one.
 616                          */
 617                         scsi_dh_detach(q);
 618                         r = scsi_dh_attach(q, m->hw_handler_name);
 619                 }
 620
 621                 if (r < 0) {
 622                         ti->error = "error attaching hardware handler";
 623                         dm_put_device(ti, p->path.dev);
 624                         goto bad;
 625                 }
 626
 627                 if (m->hw_handler_params) {
 628                         r = scsi_dh_set_params(q, m->hw_handler_params);
 629                         if (r < 0) {
 630                                 ti->error = "unable to set hardware "
 631                                                         "handler parameters";
 632                                 scsi_dh_detach(q);
 633                                 dm_put_device(ti, p->path.dev);
 634                                 goto bad;
 635                         }
 636                 }
 637         }
 638
 639         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 640         if (r) {
 641                 dm_put_device(ti, p->path.dev);
 642                 goto bad;
 643         }
 644
 645         return p;
 646
 647  bad:
 648         free_pgpath(p);
 649         return ERR_PTR(r);
 650 }
 651
 652 static struct priority_group *parse_priority_group(struct arg_set *as,
 653                                                    struct multipath *m)
 654 {
 655         static struct param _params[] = {
 656                 {1, 1024, "invalid number of paths"},
 657                 {0, 1024, "invalid number of selector args"}
 658         };
 659
 660         int r;
 661         unsigned i, nr_selector_args, nr_params;
 662         struct priority_group *pg;
 663         struct dm_target *ti = m->ti;
 664
 665         if (as->argc < 2) {
 666                 as->argc = 0;
 667                 ti->error = "not enough priority group arguments";
 668                 return ERR_PTR(-EINVAL);
 669         }
 670
 671         pg = alloc_priority_group();
 672         if (!pg) {
 673                 ti->error = "couldn't allocate priority group";
 674                 return ERR_PTR(-ENOMEM);
 675         }
 676         pg->m = m;
 677
 678         r = parse_path_selector(as, pg, ti);
 679         if (r)
 680                 goto bad;
 681
 682         /*
 683          * read the paths
 684          */
 685         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
 686         if (r)
 687                 goto bad;
 688
 689         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
 690         if (r)
 691                 goto bad;
 692
 693         nr_params = 1 + nr_selector_args;
 694         for (i = 0; i < pg->nr_pgpaths; i++) {
 695                 struct pgpath *pgpath;
 696                 struct arg_set path_args;
 697
 698                 if (as->argc < nr_params) {
 699                         ti->error = "not enough path parameters";
 700                         goto bad;
 701                 }
 702
 703                 path_args.argc = nr_params;
 704                 path_args.argv = as->argv;
 705
 706                 pgpath = parse_path(&path_args, &pg->ps, ti);
 707                 if (IS_ERR(pgpath)) {
 708                         r = PTR_ERR(pgpath);
 709                         goto bad;
 710                 }
 711
 712                 pgpath->pg = pg;
 713                 list_add_tail(&pgpath->list, &pg->pgpaths);
 714                 consume(as, nr_params);
 715         }
 716
 717         return pg;
 718
 719  bad:
 720         free_priority_group(pg, ti);
 721         return ERR_PTR(r);
 722 }
 723
 724 static int parse_hw_handler(struct arg_set *as, struct multipath *m)
 725 {
 726         unsigned hw_argc;
 727         int ret;
 728         struct dm_target *ti = m->ti;
 729
 730         static struct param _params[] = {
 731                 {0, 1024, "invalid number of hardware handler args"},
 732         };
 733
 734         if (read_param(_params, shift(as), &hw_argc, &ti->error))
 735                 return -EINVAL;
 736
 737         if (!hw_argc)
 738                 return 0;
 739
 740         if (hw_argc > as->argc) {
 741                 ti->error = "not enough arguments for hardware handler";
 742                 return -EINVAL;
 743         }
 744
 745         m->hw_handler_name = kstrdup(shift(as), GFP_KERNEL);
 746         request_module("scsi_dh_%s", m->hw_handler_name);
 747         if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
 748                 ti->error = "unknown hardware handler type";
 749                 ret = -EINVAL;
 750                 goto fail;
 751         }
 752
 753         if (hw_argc > 1) {
 754                 char *p;
 755                 int i, j, len = 4;
 756
 757                 for (i = 0; i <= hw_argc - 2; i++)
 758                         len += strlen(as->argv[i]) + 1;
 759                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 760                 if (!p) {
 761                         ti->error = "memory allocation failed";
 762                         ret = -ENOMEM;
 763                         goto fail;
 764                 }
 765                 j = sprintf(p, "%d", hw_argc - 1);
 766                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 767                         j = sprintf(p, "%s", as->argv[i]);
 768         }
 769         consume(as, hw_argc - 1);
 770
 771         return 0;
 772 fail:
 773         kfree(m->hw_handler_name);
 774         m->hw_handler_name = NULL;
 775         return ret;
 776 }
 777
 778 static int parse_features(struct arg_set *as, struct multipath *m)
 779 {
 780         int r;
 781         unsigned argc;
 782         struct dm_target *ti = m->ti;
 783         const char *param_name;
 784
 785         static struct param _params[] = {
 786                 {0, 3, "invalid number of feature args"},
 787                 {1, 50, "pg_init_retries must be between 1 and 50"},
 788         };
 789
 790         r = read_param(_params, shift(as), &argc, &ti->error);
 791         if (r)
 792                 return -EINVAL;
 793
 794         if (!argc)
 795                 return 0;
 796
 797         do {
 798                 param_name = shift(as);
 799                 argc--;
 800
 801                 if (!strnicmp(param_name, MESG_STR("queue_if_no_path"))) {
 802                         r = queue_if_no_path(m, 1, 0);
 803                         continue;
 804                 }
 805
 806                 if (!strnicmp(param_name, MESG_STR("pg_init_retries")) &&
 807                     (argc >= 1)) {
 808                         r = read_param(_params + 1, shift(as),
 809                                        &m->pg_init_retries, &ti->error);
 810                         argc--;
 811                         continue;
 812                 }
 813
 814                 ti->error = "Unrecognised multipath feature request";
 815                 r = -EINVAL;
 816         } while (argc && !r);
 817
 818         return r;
 819 }
 820
 821 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 822                          char **argv)
 823 {
 824         /* target parameters */
 825         static struct param _params[] = {
 826                 {1, 1024, "invalid number of priority groups"},
 827                 {1, 1024, "invalid initial priority group number"},
 828         };
 829
 830         int r;
 831         struct multipath *m;
 832         struct arg_set as;
 833         unsigned pg_count = 0;
 834         unsigned next_pg_num;
 835
 836         as.argc = argc;
 837         as.argv = argv;
 838
 839         m = alloc_multipath(ti);
 840         if (!m) {
 841                 ti->error = "can't allocate multipath";
 842                 return -EINVAL;
 843         }
 844
 845         r = parse_features(&as, m);
 846         if (r)
 847                 goto bad;
 848
 849         r = parse_hw_handler(&as, m);
 850         if (r)
 851                 goto bad;
 852
 853         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
 854         if (r)
 855                 goto bad;
 856
 857         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
 858         if (r)
 859                 goto bad;
 860
 861         /* parse the priority groups */
 862         while (as.argc) {
 863                 struct priority_group *pg;
 864
 865                 pg = parse_priority_group(&as, m);
 866                 if (IS_ERR(pg)) {
 867                         r = PTR_ERR(pg);
 868                         goto bad;
 869                 }
 870
 871                 m->nr_valid_paths += pg->nr_pgpaths;
 872                 list_add_tail(&pg->list, &m->priority_groups);
 873                 pg_count++;
 874                 pg->pg_num = pg_count;
 875                 if (!--next_pg_num)
 876                         m->next_pg = pg;
 877         }
 878
 879         if (pg_count != m->nr_priority_groups) {
 880                 ti->error = "priority group count mismatch";
 881                 r = -EINVAL;
 882                 goto bad;
 883         }
 884
 885         ti->num_flush_requests = 1;
 886
 887         return 0;
 888
 889  bad:
 890         free_multipath(m);
 891         return r;
 892 }
 893
 894 static void flush_multipath_work(void)
 895 {
 896         flush_workqueue(kmpath_handlerd);
 897         flush_workqueue(kmultipathd);
 898         flush_scheduled_work();
 899 }
 900
 901 static void multipath_dtr(struct dm_target *ti)
 902 {
 903         struct multipath *m = ti->private;
 904
 905         flush_multipath_work();
 906         free_multipath(m);
 907 }
 908
 909 /*
 910  * Map cloned requests
 911  */
 912 static int multipath_map(struct dm_target *ti, struct request *clone,
 913                          union map_info *map_context)
 914 {
 915         int r;
 916         struct dm_mpath_io *mpio;
 917         struct multipath *m = (struct multipath *) ti->private;
 918
 919         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 920         if (!mpio)
 921                 /* ENOMEM, requeue */
 922                 return DM_MAPIO_REQUEUE;
 923         memset(mpio, 0, sizeof(*mpio));
 924
 925         map_context->ptr = mpio;
 926         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 927         r = map_io(m, clone, mpio, 0);
 928         if (r < 0 || r == DM_MAPIO_REQUEUE)
 929                 mempool_free(mpio, m->mpio_pool);
 930
 931         return r;
 932 }
 933
 934 /*
 935  * Take a path out of use.
 936  */
 937 static int fail_path(struct pgpath *pgpath)
 938 {
 939         unsigned long flags;
 940         struct multipath *m = pgpath->pg->m;
 941
 942         spin_lock_irqsave(&m->lock, flags);
 943
 944         if (!pgpath->is_active)
 945                 goto out;
 946
 947         DMWARN("Failing path %s.", pgpath->path.dev->name);
 948
 949         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 950         pgpath->is_active = 0;
 951         pgpath->fail_count++;
 952
 953         m->nr_valid_paths--;
 954
 955         if (pgpath == m->current_pgpath)
 956                 m->current_pgpath = NULL;
 957
 958         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
 959                       pgpath->path.dev->name, m->nr_valid_paths);
 960
 961         schedule_work(&m->trigger_event);
 962         queue_work(kmultipathd, &pgpath->deactivate_path);
 963
 964 out:
 965         spin_unlock_irqrestore(&m->lock, flags);
 966
 967         return 0;
 968 }
 969
 970 /*
 971  * Reinstate a previously-failed path
 972  */
 973 static int reinstate_path(struct pgpath *pgpath)
 974 {
 975         int r = 0;
 976         unsigned long flags;
 977         struct multipath *m = pgpath->pg->m;
 978
 979         spin_lock_irqsave(&m->lock, flags);
 980
 981         if (pgpath->is_active)
 982                 goto out;
 983
 984         if (!pgpath->pg->ps.type->reinstate_path) {
 985                 DMWARN("Reinstate path not supported by path selector %s",
 986                        pgpath->pg->ps.type->name);
 987                 r = -EINVAL;
 988                 goto out;
 989         }
 990
 991         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
 992         if (r)
 993                 goto out;
 994
 995         pgpath->is_active = 1;
 996
 997         if (!m->nr_valid_paths++ && m->queue_size) {
 998                 m->current_pgpath = NULL;
 999                 queue_work(kmultipathd, &m->process_queued_ios);
1000         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1001                 if (queue_work(kmpath_handlerd, &pgpath->activate_path))
1002                         m->pg_init_in_progress++;
1003         }
1004
1005         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, 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 r;
1014 }
1015
1016 /*
1017  * Fail or reinstate all paths that match the provided struct dm_dev.
1018  */
1019 static int action_dev(struct multipath *m, struct dm_dev *dev,
1020                       action_fn action)
1021 {
1022         int r = 0;
1023         struct pgpath *pgpath;
1024         struct priority_group *pg;
1025
1026         list_for_each_entry(pg, &m->priority_groups, list) {
1027                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1028                         if (pgpath->path.dev == dev)
1029                                 r = action(pgpath);
1030                 }
1031         }
1032
1033         return r;
1034 }
1035
1036 /*
1037  * Temporarily try to avoid having to use the specified PG
1038  */
1039 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1040                       int bypassed)
1041 {
1042         unsigned long flags;
1043
1044         spin_lock_irqsave(&m->lock, flags);
1045
1046         pg->bypassed = bypassed;
1047         m->current_pgpath = NULL;
1048         m->current_pg = NULL;
1049
1050         spin_unlock_irqrestore(&m->lock, flags);
1051
1052         schedule_work(&m->trigger_event);
1053 }
1054
1055 /*
1056  * Switch to using the specified PG from the next I/O that gets mapped
1057  */
1058 static int switch_pg_num(struct multipath *m, const char *pgstr)
1059 {
1060         struct priority_group *pg;
1061         unsigned pgnum;
1062         unsigned long flags;
1063
1064         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1065             (pgnum > m->nr_priority_groups)) {
1066                 DMWARN("invalid PG number supplied to switch_pg_num");
1067                 return -EINVAL;
1068         }
1069
1070         spin_lock_irqsave(&m->lock, flags);
1071         list_for_each_entry(pg, &m->priority_groups, list) {
1072                 pg->bypassed = 0;
1073                 if (--pgnum)
1074                         continue;
1075
1076                 m->current_pgpath = NULL;
1077                 m->current_pg = NULL;
1078                 m->next_pg = pg;
1079         }
1080         spin_unlock_irqrestore(&m->lock, flags);
1081
1082         schedule_work(&m->trigger_event);
1083         return 0;
1084 }
1085
1086 /*
1087  * Set/clear bypassed status of a PG.
1088  * PGs are numbered upwards from 1 in the order they were declared.
1089  */
1090 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1091 {
1092         struct priority_group *pg;
1093         unsigned pgnum;
1094
1095         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1096             (pgnum > m->nr_priority_groups)) {
1097                 DMWARN("invalid PG number supplied to bypass_pg");
1098                 return -EINVAL;
1099         }
1100
1101         list_for_each_entry(pg, &m->priority_groups, list) {
1102                 if (!--pgnum)
1103                         break;
1104         }
1105
1106         bypass_pg(m, pg, bypassed);
1107         return 0;
1108 }
1109
1110 /*
1111  * Should we retry pg_init immediately?
1112  */
1113 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1114 {
1115         unsigned long flags;
1116         int limit_reached = 0;
1117
1118         spin_lock_irqsave(&m->lock, flags);
1119
1120         if (m->pg_init_count <= m->pg_init_retries)
1121                 m->pg_init_required = 1;
1122         else
1123                 limit_reached = 1;
1124
1125         spin_unlock_irqrestore(&m->lock, flags);
1126
1127         return limit_reached;
1128 }
1129
1130 static void pg_init_done(void *data, int errors)
1131 {
1132         struct pgpath *pgpath = data;
1133         struct priority_group *pg = pgpath->pg;
1134         struct multipath *m = pg->m;
1135         unsigned long flags;
1136
1137         /* device or driver problems */
1138         switch (errors) {
1139         case SCSI_DH_OK:
1140                 break;
1141         case SCSI_DH_NOSYS:
1142                 if (!m->hw_handler_name) {
1143                         errors = 0;
1144                         break;
1145                 }
1146                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1147                       "Error %d.", m->hw_handler_name, errors);
1148                 /*
1149                  * Fail path for now, so we do not ping pong
1150                  */
1151                 fail_path(pgpath);
1152                 break;
1153         case SCSI_DH_DEV_TEMP_BUSY:
1154                 /*
1155                  * Probably doing something like FW upgrade on the
1156                  * controller so try the other pg.
1157                  */
1158                 bypass_pg(m, pg, 1);
1159                 break;
1160         /* TODO: For SCSI_DH_RETRY we should wait a couple seconds */
1161         case SCSI_DH_RETRY:
1162         case SCSI_DH_IMM_RETRY:
1163         case SCSI_DH_RES_TEMP_UNAVAIL:
1164                 if (pg_init_limit_reached(m, pgpath))
1165                         fail_path(pgpath);
1166                 errors = 0;
1167                 break;
1168         default:
1169                 /*
1170                  * We probably do not want to fail the path for a device
1171                  * error, but this is what the old dm did. In future
1172                  * patches we can do more advanced handling.
1173                  */
1174                 fail_path(pgpath);
1175         }
1176
1177         spin_lock_irqsave(&m->lock, flags);
1178         if (errors) {
1179                 if (pgpath == m->current_pgpath) {
1180                         DMERR("Could not failover device. Error %d.", errors);
1181                         m->current_pgpath = NULL;
1182                         m->current_pg = NULL;
1183                 }
1184         } else if (!m->pg_init_required) {
1185                 m->queue_io = 0;
1186                 pg->bypassed = 0;
1187         }
1188
1189         m->pg_init_in_progress--;
1190         if (!m->pg_init_in_progress)
1191                 queue_work(kmultipathd, &m->process_queued_ios);
1192         spin_unlock_irqrestore(&m->lock, flags);
1193 }
1194
1195 static void activate_path(struct work_struct *work)
1196 {
1197         struct pgpath *pgpath =
1198                 container_of(work, struct pgpath, activate_path);
1199
1200         scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1201                                 pg_init_done, pgpath);
1202 }
1203
1204 /*
1205  * end_io handling
1206  */
1207 static int do_end_io(struct multipath *m, struct request *clone,
1208                      int error, struct dm_mpath_io *mpio)
1209 {
1210         /*
1211          * We don't queue any clone request inside the multipath target
1212          * during end I/O handling, since those clone requests don't have
1213          * bio clones.  If we queue them inside the multipath target,
1214          * we need to make bio clones, that requires memory allocation.
1215          * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1216          *  don't have bio clones.)
1217          * Instead of queueing the clone request here, we queue the original
1218          * request into dm core, which will remake a clone request and
1219          * clone bios for it and resubmit it later.
1220          */
1221         int r = DM_ENDIO_REQUEUE;
1222         unsigned long flags;
1223
1224         if (!error && !clone->errors)
1225                 return 0;       /* I/O complete */
1226
1227         if (error == -EOPNOTSUPP)
1228                 return error;
1229
1230         if (mpio->pgpath)
1231                 fail_path(mpio->pgpath);
1232
1233         spin_lock_irqsave(&m->lock, flags);
1234         if (!m->nr_valid_paths && !m->queue_if_no_path && !__must_push_back(m))
1235                 r = -EIO;
1236         spin_unlock_irqrestore(&m->lock, flags);
1237
1238         return r;
1239 }
1240
1241 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1242                             int error, union map_info *map_context)
1243 {
1244         struct multipath *m = ti->private;
1245         struct dm_mpath_io *mpio = map_context->ptr;
1246         struct pgpath *pgpath = mpio->pgpath;
1247         struct path_selector *ps;
1248         int r;
1249
1250         r  = do_end_io(m, clone, error, mpio);
1251         if (pgpath) {
1252                 ps = &pgpath->pg->ps;
1253                 if (ps->type->end_io)
1254                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1255         }
1256         mempool_free(mpio, m->mpio_pool);
1257
1258         return r;
1259 }
1260
1261 /*
1262  * Suspend can't complete until all the I/O is processed so if
1263  * the last path fails we must error any remaining I/O.
1264  * Note that if the freeze_bdev fails while suspending, the
1265  * queue_if_no_path state is lost - userspace should reset it.
1266  */
1267 static void multipath_presuspend(struct dm_target *ti)
1268 {
1269         struct multipath *m = (struct multipath *) ti->private;
1270
1271         queue_if_no_path(m, 0, 1);
1272 }
1273
1274 static void multipath_postsuspend(struct dm_target *ti)
1275 {
1276         struct multipath *m = ti->private;
1277
1278         mutex_lock(&m->work_mutex);
1279         flush_multipath_work();
1280         mutex_unlock(&m->work_mutex);
1281 }
1282
1283 /*
1284  * Restore the queue_if_no_path setting.
1285  */
1286 static void multipath_resume(struct dm_target *ti)
1287 {
1288         struct multipath *m = (struct multipath *) ti->private;
1289         unsigned long flags;
1290
1291         spin_lock_irqsave(&m->lock, flags);
1292         m->queue_if_no_path = m->saved_queue_if_no_path;
1293         spin_unlock_irqrestore(&m->lock, flags);
1294 }
1295
1296 /*
1297  * Info output has the following format:
1298  * num_multipath_feature_args [multipath_feature_args]*
1299  * num_handler_status_args [handler_status_args]*
1300  * num_groups init_group_number
1301  *            [A|D|E num_ps_status_args [ps_status_args]*
1302  *             num_paths num_selector_args
1303  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1304  *
1305  * Table output has the following format (identical to the constructor string):
1306  * num_feature_args [features_args]*
1307  * num_handler_args hw_handler [hw_handler_args]*
1308  * num_groups init_group_number
1309  *     [priority selector-name num_ps_args [ps_args]*
1310  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1311  */
1312 static int multipath_status(struct dm_target *ti, status_type_t type,
1313                             char *result, unsigned int maxlen)
1314 {
1315         int sz = 0;
1316         unsigned long flags;
1317         struct multipath *m = (struct multipath *) ti->private;
1318         struct priority_group *pg;
1319         struct pgpath *p;
1320         unsigned pg_num;
1321         char state;
1322
1323         spin_lock_irqsave(&m->lock, flags);
1324
1325         /* Features */
1326         if (type == STATUSTYPE_INFO)
1327                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1328         else {
1329                 DMEMIT("%u ", m->queue_if_no_path +
1330                               (m->pg_init_retries > 0) * 2);
1331                 if (m->queue_if_no_path)
1332                         DMEMIT("queue_if_no_path ");
1333                 if (m->pg_init_retries)
1334                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1335         }
1336
1337         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1338                 DMEMIT("0 ");
1339         else
1340                 DMEMIT("1 %s ", m->hw_handler_name);
1341
1342         DMEMIT("%u ", m->nr_priority_groups);
1343
1344         if (m->next_pg)
1345                 pg_num = m->next_pg->pg_num;
1346         else if (m->current_pg)
1347                 pg_num = m->current_pg->pg_num;
1348         else
1349                         pg_num = 1;
1350
1351         DMEMIT("%u ", pg_num);
1352
1353         switch (type) {
1354         case STATUSTYPE_INFO:
1355                 list_for_each_entry(pg, &m->priority_groups, list) {
1356                         if (pg->bypassed)
1357                                 state = 'D';    /* Disabled */
1358                         else if (pg == m->current_pg)
1359                                 state = 'A';    /* Currently Active */
1360                         else
1361                                 state = 'E';    /* Enabled */
1362
1363                         DMEMIT("%c ", state);
1364
1365                         if (pg->ps.type->status)
1366                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1367                                                           result + sz,
1368                                                           maxlen - sz);
1369                         else
1370                                 DMEMIT("0 ");
1371
1372                         DMEMIT("%u %u ", pg->nr_pgpaths,
1373                                pg->ps.type->info_args);
1374
1375                         list_for_each_entry(p, &pg->pgpaths, list) {
1376                                 DMEMIT("%s %s %u ", p->path.dev->name,
1377                                        p->is_active ? "A" : "F",
1378                                        p->fail_count);
1379                                 if (pg->ps.type->status)
1380                                         sz += pg->ps.type->status(&pg->ps,
1381                                               &p->path, type, result + sz,
1382                                               maxlen - sz);
1383                         }
1384                 }
1385                 break;
1386
1387         case STATUSTYPE_TABLE:
1388                 list_for_each_entry(pg, &m->priority_groups, list) {
1389                         DMEMIT("%s ", pg->ps.type->name);
1390
1391                         if (pg->ps.type->status)
1392                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1393                                                           result + sz,
1394                                                           maxlen - sz);
1395                         else
1396                                 DMEMIT("0 ");
1397
1398                         DMEMIT("%u %u ", pg->nr_pgpaths,
1399                                pg->ps.type->table_args);
1400
1401                         list_for_each_entry(p, &pg->pgpaths, list) {
1402                                 DMEMIT("%s ", p->path.dev->name);
1403                                 if (pg->ps.type->status)
1404                                         sz += pg->ps.type->status(&pg->ps,
1405                                               &p->path, type, result + sz,
1406                                               maxlen - sz);
1407                         }
1408                 }
1409                 break;
1410         }
1411
1412         spin_unlock_irqrestore(&m->lock, flags);
1413
1414         return 0;
1415 }
1416
1417 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1418 {
1419         int r = -EINVAL;
1420         struct dm_dev *dev;
1421         struct multipath *m = (struct multipath *) ti->private;
1422         action_fn action;
1423
1424         mutex_lock(&m->work_mutex);
1425
1426         if (dm_suspended(ti)) {
1427                 r = -EBUSY;
1428                 goto out;
1429         }
1430
1431         if (argc == 1) {
1432                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path"))) {
1433                         r = queue_if_no_path(m, 1, 0);
1434                         goto out;
1435                 } else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path"))) {
1436                         r = queue_if_no_path(m, 0, 0);
1437                         goto out;
1438                 }
1439         }
1440
1441         if (argc != 2) {
1442                 DMWARN("Unrecognised multipath message received.");
1443                 goto out;
1444         }
1445
1446         if (!strnicmp(argv[0], MESG_STR("disable_group"))) {
1447                 r = bypass_pg_num(m, argv[1], 1);
1448                 goto out;
1449         } else if (!strnicmp(argv[0], MESG_STR("enable_group"))) {
1450                 r = bypass_pg_num(m, argv[1], 0);
1451                 goto out;
1452         } else if (!strnicmp(argv[0], MESG_STR("switch_group"))) {
1453                 r = switch_pg_num(m, argv[1]);
1454                 goto out;
1455         } else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1456                 action = reinstate_path;
1457         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1458                 action = fail_path;
1459         else {
1460                 DMWARN("Unrecognised multipath message received.");
1461                 goto out;
1462         }
1463
1464         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
1465                           dm_table_get_mode(ti->table), &dev);
1466         if (r) {
1467                 DMWARN("message: error getting device %s",
1468                        argv[1]);
1469                 goto out;
1470         }
1471
1472         r = action_dev(m, dev, action);
1473
1474         dm_put_device(ti, dev);
1475
1476 out:
1477         mutex_unlock(&m->work_mutex);
1478         return r;
1479 }
1480
1481 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1482                            unsigned long arg)
1483 {
1484         struct multipath *m = (struct multipath *) ti->private;
1485         struct block_device *bdev = NULL;
1486         fmode_t mode = 0;
1487         unsigned long flags;
1488         int r = 0;
1489
1490         spin_lock_irqsave(&m->lock, flags);
1491
1492         if (!m->current_pgpath)
1493                 __choose_pgpath(m, 0);
1494
1495         if (m->current_pgpath) {
1496                 bdev = m->current_pgpath->path.dev->bdev;
1497                 mode = m->current_pgpath->path.dev->mode;
1498         }
1499
1500         if (m->queue_io)
1501                 r = -EAGAIN;
1502         else if (!bdev)
1503                 r = -EIO;
1504
1505         spin_unlock_irqrestore(&m->lock, flags);
1506
1507         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1508 }
1509
1510 static int multipath_iterate_devices(struct dm_target *ti,
1511                                      iterate_devices_callout_fn fn, void *data)
1512 {
1513         struct multipath *m = ti->private;
1514         struct priority_group *pg;
1515         struct pgpath *p;
1516         int ret = 0;
1517
1518         list_for_each_entry(pg, &m->priority_groups, list) {
1519                 list_for_each_entry(p, &pg->pgpaths, list) {
1520                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1521                         if (ret)
1522                                 goto out;
1523                 }
1524         }
1525
1526 out:
1527         return ret;
1528 }
1529
1530 static int __pgpath_busy(struct pgpath *pgpath)
1531 {
1532         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1533
1534         return dm_underlying_device_busy(q);
1535 }
1536
1537 /*
1538  * We return "busy", only when we can map I/Os but underlying devices
1539  * are busy (so even if we map I/Os now, the I/Os will wait on
1540  * the underlying queue).
1541  * In other words, if we want to kill I/Os or queue them inside us
1542  * due to map unavailability, we don't return "busy".  Otherwise,
1543  * dm core won't give us the I/Os and we can't do what we want.
1544  */
1545 static int multipath_busy(struct dm_target *ti)
1546 {
1547         int busy = 0, has_active = 0;
1548         struct multipath *m = ti->private;
1549         struct priority_group *pg;
1550         struct pgpath *pgpath;
1551         unsigned long flags;
1552
1553         spin_lock_irqsave(&m->lock, flags);
1554
1555         /* Guess which priority_group will be used at next mapping time */
1556         if (unlikely(!m->current_pgpath && m->next_pg))
1557                 pg = m->next_pg;
1558         else if (likely(m->current_pg))
1559                 pg = m->current_pg;
1560         else
1561                 /*
1562                  * We don't know which pg will be used at next mapping time.
1563                  * We don't call __choose_pgpath() here to avoid to trigger
1564                  * pg_init just by busy checking.
1565                  * So we don't know whether underlying devices we will be using
1566                  * at next mapping time are busy or not. Just try mapping.
1567                  */
1568                 goto out;
1569
1570         /*
1571          * If there is one non-busy active path at least, the path selector
1572          * will be able to select it. So we consider such a pg as not busy.
1573          */
1574         busy = 1;
1575         list_for_each_entry(pgpath, &pg->pgpaths, list)
1576                 if (pgpath->is_active) {
1577                         has_active = 1;
1578
1579                         if (!__pgpath_busy(pgpath)) {
1580                                 busy = 0;
1581                                 break;
1582                         }
1583                 }
1584
1585         if (!has_active)
1586                 /*
1587                  * No active path in this pg, so this pg won't be used and
1588                  * the current_pg will be changed at next mapping time.
1589                  * We need to try mapping to determine it.
1590                  */
1591                 busy = 0;
1592
1593 out:
1594         spin_unlock_irqrestore(&m->lock, flags);
1595
1596         return busy;
1597 }
1598
1599 /*-----------------------------------------------------------------
1600  * Module setup
1601  *---------------------------------------------------------------*/
1602 static struct target_type multipath_target = {
1603         .name = "multipath",
1604         .version = {1, 1, 1},
1605         .module = THIS_MODULE,
1606         .ctr = multipath_ctr,
1607         .dtr = multipath_dtr,
1608         .map_rq = multipath_map,
1609         .rq_end_io = multipath_end_io,
1610         .presuspend = multipath_presuspend,
1611         .postsuspend = multipath_postsuspend,
1612         .resume = multipath_resume,
1613         .status = multipath_status,
1614         .message = multipath_message,
1615         .ioctl  = multipath_ioctl,
1616         .iterate_devices = multipath_iterate_devices,
1617         .busy = multipath_busy,
1618 };
1619
1620 static int __init dm_multipath_init(void)
1621 {
1622         int r;
1623
1624         /* allocate a slab for the dm_ios */
1625         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1626         if (!_mpio_cache)
1627                 return -ENOMEM;
1628
1629         r = dm_register_target(&multipath_target);
1630         if (r < 0) {
1631                 DMERR("register failed %d", r);
1632                 kmem_cache_destroy(_mpio_cache);
1633                 return -EINVAL;
1634         }
1635
1636         kmultipathd = create_workqueue("kmpathd");
1637         if (!kmultipathd) {
1638                 DMERR("failed to create workqueue kmpathd");
1639                 dm_unregister_target(&multipath_target);
1640                 kmem_cache_destroy(_mpio_cache);
1641                 return -ENOMEM;
1642         }
1643
1644         /*
1645          * A separate workqueue is used to handle the device handlers
1646          * to avoid overloading existing workqueue. Overloading the
1647          * old workqueue would also create a bottleneck in the
1648          * path of the storage hardware device activation.
1649          */
1650         kmpath_handlerd = create_singlethread_workqueue("kmpath_handlerd");
1651         if (!kmpath_handlerd) {
1652                 DMERR("failed to create workqueue kmpath_handlerd");
1653                 destroy_workqueue(kmultipathd);
1654                 dm_unregister_target(&multipath_target);
1655                 kmem_cache_destroy(_mpio_cache);
1656                 return -ENOMEM;
1657         }
1658
1659         DMINFO("version %u.%u.%u loaded",
1660                multipath_target.version[0], multipath_target.version[1],
1661                multipath_target.version[2]);
1662
1663         return r;
1664 }
1665
1666 static void __exit dm_multipath_exit(void)
1667 {
1668         destroy_workqueue(kmpath_handlerd);
1669         destroy_workqueue(kmultipathd);
1670
1671         dm_unregister_target(&multipath_target);
1672         kmem_cache_destroy(_mpio_cache);
1673 }
1674
1675 module_init(dm_multipath_init);
1676 module_exit(dm_multipath_exit);
1677
1678 MODULE_DESCRIPTION(DM_NAME " multipath target");
1679 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1680 MODULE_LICENSE("GPL");