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         unsigned suspended;     /* Don't create new I/O internally when set. */
 100 };
 101
 102 /*
 103  * Context information attached to each bio we process.
 104  */
 105 struct dm_mpath_io {
 106         struct pgpath *pgpath;
 107         size_t nr_bytes;
 108 };
 109
 110 typedef int (*action_fn) (struct pgpath *pgpath);
 111
 112 #define MIN_IOS 256     /* Mempool size */
 113
 114 static struct kmem_cache *_mpio_cache;
 115
 116 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 117 static void process_queued_ios(struct work_struct *work);
 118 static void trigger_event(struct work_struct *work);
 119 static void activate_path(struct work_struct *work);
 120 static void deactivate_path(struct work_struct *work);
 121
 122
 123 /*-----------------------------------------------
 124  * Allocation routines
 125  *-----------------------------------------------*/
 126
 127 static struct pgpath *alloc_pgpath(void)
 128 {
 129         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 130
 131         if (pgpath) {
 132                 pgpath->is_active = 1;
 133                 INIT_WORK(&pgpath->deactivate_path, deactivate_path);
 134                 INIT_WORK(&pgpath->activate_path, activate_path);
 135         }
 136
 137         return pgpath;
 138 }
 139
 140 static void free_pgpath(struct pgpath *pgpath)
 141 {
 142         kfree(pgpath);
 143 }
 144
 145 static void deactivate_path(struct work_struct *work)
 146 {
 147         struct pgpath *pgpath =
 148                 container_of(work, struct pgpath, deactivate_path);
 149
 150         blk_abort_queue(pgpath->path.dev->bdev->bd_disk->queue);
 151 }
 152
 153 static struct priority_group *alloc_priority_group(void)
 154 {
 155         struct priority_group *pg;
 156
 157         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 158
 159         if (pg)
 160                 INIT_LIST_HEAD(&pg->pgpaths);
 161
 162         return pg;
 163 }
 164
 165 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 166 {
 167         struct pgpath *pgpath, *tmp;
 168         struct multipath *m = ti->private;
 169
 170         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 171                 list_del(&pgpath->list);
 172                 if (m->hw_handler_name)
 173                         scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 174                 dm_put_device(ti, pgpath->path.dev);
 175                 free_pgpath(pgpath);
 176         }
 177 }
 178
 179 static void free_priority_group(struct priority_group *pg,
 180                                 struct dm_target *ti)
 181 {
 182         struct path_selector *ps = &pg->ps;
 183
 184         if (ps->type) {
 185                 ps->type->destroy(ps);
 186                 dm_put_path_selector(ps->type);
 187         }
 188
 189         free_pgpaths(&pg->pgpaths, ti);
 190         kfree(pg);
 191 }
 192
 193 static struct multipath *alloc_multipath(struct dm_target *ti)
 194 {
 195         struct multipath *m;
 196
 197         m = kzalloc(sizeof(*m), GFP_KERNEL);
 198         if (m) {
 199                 INIT_LIST_HEAD(&m->priority_groups);
 200                 INIT_LIST_HEAD(&m->queued_ios);
 201                 spin_lock_init(&m->lock);
 202                 m->queue_io = 1;
 203                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
 204                 INIT_WORK(&m->trigger_event, trigger_event);
 205                 mutex_init(&m->work_mutex);
 206                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 207                 if (!m->mpio_pool) {
 208                         kfree(m);
 209                         return NULL;
 210                 }
 211                 m->ti = ti;
 212                 ti->private = m;
 213         }
 214
 215         return m;
 216 }
 217
 218 static void free_multipath(struct multipath *m)
 219 {
 220         struct priority_group *pg, *tmp;
 221
 222         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 223                 list_del(&pg->list);
 224                 free_priority_group(pg, m->ti);
 225         }
 226
 227         kfree(m->hw_handler_name);
 228         kfree(m->hw_handler_params);
 229         mempool_destroy(m->mpio_pool);
 230         kfree(m);
 231 }
 232
 233
 234 /*-----------------------------------------------
 235  * Path selection
 236  *-----------------------------------------------*/
 237
 238 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 239 {
 240         m->current_pg = pgpath->pg;
 241
 242         /* Must we initialise the PG first, and queue I/O till it's ready? */
 243         if (m->hw_handler_name) {
 244                 m->pg_init_required = 1;
 245                 m->queue_io = 1;
 246         } else {
 247                 m->pg_init_required = 0;
 248                 m->queue_io = 0;
 249         }
 250
 251         m->pg_init_count = 0;
 252 }
 253
 254 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 255                                size_t nr_bytes)
 256 {
 257         struct dm_path *path;
 258
 259         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 260         if (!path)
 261                 return -ENXIO;
 262
 263         m->current_pgpath = path_to_pgpath(path);
 264
 265         if (m->current_pg != pg)
 266                 __switch_pg(m, m->current_pgpath);
 267
 268         return 0;
 269 }
 270
 271 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 272 {
 273         struct priority_group *pg;
 274         unsigned bypassed = 1;
 275
 276         if (!m->nr_valid_paths)
 277                 goto failed;
 278
 279         /* Were we instructed to switch PG? */
 280         if (m->next_pg) {
 281                 pg = m->next_pg;
 282                 m->next_pg = NULL;
 283                 if (!__choose_path_in_pg(m, pg, nr_bytes))
 284                         return;
 285         }
 286
 287         /* Don't change PG until it has no remaining paths */
 288         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 289                 return;
 290
 291         /*
 292          * Loop through priority groups until we find a valid path.
 293          * First time we skip PGs marked 'bypassed'.
 294          * Second time we only try the ones we skipped.
 295          */
 296         do {
 297                 list_for_each_entry(pg, &m->priority_groups, list) {
 298                         if (pg->bypassed == bypassed)
 299                                 continue;
 300                         if (!__choose_path_in_pg(m, pg, nr_bytes))
 301                                 return;
 302                 }
 303         } while (bypassed--);
 304
 305 failed:
 306         m->current_pgpath = NULL;
 307         m->current_pg = NULL;
 308 }
 309
 310 /*
 311  * Check whether bios must be queued in the device-mapper core rather
 312  * than here in the target.
 313  *
 314  * m->lock must be held on entry.
 315  *
 316  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 317  * same value then we are not between multipath_presuspend()
 318  * and multipath_resume() calls and we have no need to check
 319  * for the DMF_NOFLUSH_SUSPENDING flag.
 320  */
 321 static int __must_push_back(struct multipath *m)
 322 {
 323         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 324                 dm_noflush_suspending(m->ti));
 325 }
 326
 327 static int map_io(struct multipath *m, struct request *clone,
 328                   struct dm_mpath_io *mpio, unsigned was_queued)
 329 {
 330         int r = DM_MAPIO_REMAPPED;
 331         size_t nr_bytes = blk_rq_bytes(clone);
 332         unsigned long flags;
 333         struct pgpath *pgpath;
 334         struct block_device *bdev;
 335
 336         spin_lock_irqsave(&m->lock, flags);
 337
 338         /* Do we need to select a new pgpath? */
 339         if (!m->current_pgpath ||
 340             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 341                 __choose_pgpath(m, nr_bytes);
 342
 343         pgpath = m->current_pgpath;
 344
 345         if (was_queued)
 346                 m->queue_size--;
 347
 348         if ((pgpath && m->queue_io) ||
 349             (!pgpath && m->queue_if_no_path)) {
 350                 /* Queue for the daemon to resubmit */
 351                 list_add_tail(&clone->queuelist, &m->queued_ios);
 352                 m->queue_size++;
 353                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 354                     !m->queue_io)
 355                         queue_work(kmultipathd, &m->process_queued_ios);
 356                 pgpath = NULL;
 357                 r = DM_MAPIO_SUBMITTED;
 358         } else if (pgpath) {
 359                 bdev = pgpath->path.dev->bdev;
 360                 clone->q = bdev_get_queue(bdev);
 361                 clone->rq_disk = bdev->bd_disk;
 362         } else if (__must_push_back(m))
 363                 r = DM_MAPIO_REQUEUE;
 364         else
 365                 r = -EIO;       /* Failed */
 366
 367         mpio->pgpath = pgpath;
 368         mpio->nr_bytes = nr_bytes;
 369
 370         if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
 371                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path,
 372                                               nr_bytes);
 373
 374         spin_unlock_irqrestore(&m->lock, flags);
 375
 376         return r;
 377 }
 378
 379 /*
 380  * If we run out of usable paths, should we queue I/O or error it?
 381  */
 382 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 383                             unsigned save_old_value)
 384 {
 385         unsigned long flags;
 386
 387         spin_lock_irqsave(&m->lock, flags);
 388
 389         if (save_old_value)
 390                 m->saved_queue_if_no_path = m->queue_if_no_path;
 391         else
 392                 m->saved_queue_if_no_path = queue_if_no_path;
 393         m->queue_if_no_path = queue_if_no_path;
 394         if (!m->queue_if_no_path && m->queue_size)
 395                 queue_work(kmultipathd, &m->process_queued_ios);
 396
 397         spin_unlock_irqrestore(&m->lock, flags);
 398
 399         return 0;
 400 }
 401
 402 /*-----------------------------------------------------------------
 403  * The multipath daemon is responsible for resubmitting queued ios.
 404  *---------------------------------------------------------------*/
 405
 406 static void dispatch_queued_ios(struct multipath *m)
 407 {
 408         int r;
 409         unsigned long flags;
 410         struct dm_mpath_io *mpio;
 411         union map_info *info;
 412         struct request *clone, *n;
 413         LIST_HEAD(cl);
 414
 415         spin_lock_irqsave(&m->lock, flags);
 416         list_splice_init(&m->queued_ios, &cl);
 417         spin_unlock_irqrestore(&m->lock, flags);
 418
 419         list_for_each_entry_safe(clone, n, &cl, queuelist) {
 420                 list_del_init(&clone->queuelist);
 421
 422                 info = dm_get_rq_mapinfo(clone);
 423                 mpio = info->ptr;
 424
 425                 r = map_io(m, clone, mpio, 1);
 426                 if (r < 0) {
 427                         mempool_free(mpio, m->mpio_pool);
 428                         dm_kill_unmapped_request(clone, r);
 429                 } else if (r == DM_MAPIO_REMAPPED)
 430                         dm_dispatch_request(clone);
 431                 else if (r == DM_MAPIO_REQUEUE) {
 432                         mempool_free(mpio, m->mpio_pool);
 433                         dm_requeue_unmapped_request(clone);
 434                 }
 435         }
 436 }
 437
 438 static void process_queued_ios(struct work_struct *work)
 439 {
 440         struct multipath *m =
 441                 container_of(work, struct multipath, process_queued_ios);
 442         struct pgpath *pgpath = NULL, *tmp;
 443         unsigned must_queue = 1;
 444         unsigned long flags;
 445
 446         spin_lock_irqsave(&m->lock, flags);
 447
 448         if (!m->queue_size)
 449                 goto out;
 450
 451         if (!m->current_pgpath)
 452                 __choose_pgpath(m, 0);
 453
 454         pgpath = m->current_pgpath;
 455
 456         if ((pgpath && !m->queue_io) ||
 457             (!pgpath && !m->queue_if_no_path))
 458                 must_queue = 0;
 459
 460         if (m->pg_init_required && !m->pg_init_in_progress && pgpath) {
 461                 m->pg_init_count++;
 462                 m->pg_init_required = 0;
 463                 list_for_each_entry(tmp, &pgpath->pg->pgpaths, list) {
 464                         if (queue_work(kmpath_handlerd, &tmp->activate_path))
 465                                 m->pg_init_in_progress++;
 466                 }
 467         }
 468 out:
 469         spin_unlock_irqrestore(&m->lock, flags);
 470         if (!must_queue)
 471                 dispatch_queued_ios(m);
 472 }
 473
 474 /*
 475  * An event is triggered whenever a path is taken out of use.
 476  * Includes path failure and PG bypass.
 477  */
 478 static void trigger_event(struct work_struct *work)
 479 {
 480         struct multipath *m =
 481                 container_of(work, struct multipath, trigger_event);
 482
 483         dm_table_event(m->ti->table);
 484 }
 485
 486 /*-----------------------------------------------------------------
 487  * Constructor/argument parsing:
 488  * <#multipath feature args> [<arg>]*
 489  * <#hw_handler args> [hw_handler [<arg>]*]
 490  * <#priority groups>
 491  * <initial priority group>
 492  *     [<selector> <#selector args> [<arg>]*
 493  *      <#paths> <#per-path selector args>
 494  *         [<path> [<arg>]* ]+ ]+
 495  *---------------------------------------------------------------*/
 496 struct param {
 497         unsigned min;
 498         unsigned max;
 499         char *error;
 500 };
 501
 502 static int read_param(struct param *param, char *str, unsigned *v, char **error)
 503 {
 504         if (!str ||
 505             (sscanf(str, "%u", v) != 1) ||
 506             (*v < param->min) ||
 507             (*v > param->max)) {
 508                 *error = param->error;
 509                 return -EINVAL;
 510         }
 511
 512         return 0;
 513 }
 514
 515 struct arg_set {
 516         unsigned argc;
 517         char **argv;
 518 };
 519
 520 static char *shift(struct arg_set *as)
 521 {
 522         char *r;
 523
 524         if (as->argc) {
 525                 as->argc--;
 526                 r = *as->argv;
 527                 as->argv++;
 528                 return r;
 529         }
 530
 531         return NULL;
 532 }
 533
 534 static void consume(struct arg_set *as, unsigned n)
 535 {
 536         BUG_ON (as->argc < n);
 537         as->argc -= n;
 538         as->argv += n;
 539 }
 540
 541 static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
 542                                struct dm_target *ti)
 543 {
 544         int r;
 545         struct path_selector_type *pst;
 546         unsigned ps_argc;
 547
 548         static struct param _params[] = {
 549                 {0, 1024, "invalid number of path selector args"},
 550         };
 551
 552         pst = dm_get_path_selector(shift(as));
 553         if (!pst) {
 554                 ti->error = "unknown path selector type";
 555                 return -EINVAL;
 556         }
 557
 558         r = read_param(_params, shift(as), &ps_argc, &ti->error);
 559         if (r) {
 560                 dm_put_path_selector(pst);
 561                 return -EINVAL;
 562         }
 563
 564         if (ps_argc > as->argc) {
 565                 dm_put_path_selector(pst);
 566                 ti->error = "not enough arguments for path selector";
 567                 return -EINVAL;
 568         }
 569
 570         r = pst->create(&pg->ps, ps_argc, as->argv);
 571         if (r) {
 572                 dm_put_path_selector(pst);
 573                 ti->error = "path selector constructor failed";
 574                 return r;
 575         }
 576
 577         pg->ps.type = pst;
 578         consume(as, ps_argc);
 579
 580         return 0;
 581 }
 582
 583 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
 584                                struct dm_target *ti)
 585 {
 586         int r;
 587         struct pgpath *p;
 588         struct multipath *m = ti->private;
 589
 590         /* we need at least a path arg */
 591         if (as->argc < 1) {
 592                 ti->error = "no device given";
 593                 return ERR_PTR(-EINVAL);
 594         }
 595
 596         p = alloc_pgpath();
 597         if (!p)
 598                 return ERR_PTR(-ENOMEM);
 599
 600         r = dm_get_device(ti, shift(as), ti->begin, ti->len,
 601                           dm_table_get_mode(ti->table), &p->path.dev);
 602         if (r) {
 603                 ti->error = "error getting device";
 604                 goto bad;
 605         }
 606
 607         if (m->hw_handler_name) {
 608                 struct request_queue *q = bdev_get_queue(p->path.dev->bdev);
 609
 610                 r = scsi_dh_attach(q, m->hw_handler_name);
 611                 if (r == -EBUSY) {
 612                         /*
 613                          * Already attached to different hw_handler,
 614                          * try to reattach with correct one.
 615                          */
 616                         scsi_dh_detach(q);
 617                         r = scsi_dh_attach(q, m->hw_handler_name);
 618                 }
 619
 620                 if (r < 0) {
 621                         ti->error = "error attaching hardware handler";
 622                         dm_put_device(ti, p->path.dev);
 623                         goto bad;
 624                 }
 625
 626                 if (m->hw_handler_params) {
 627                         r = scsi_dh_set_params(q, m->hw_handler_params);
 628                         if (r < 0) {
 629                                 ti->error = "unable to set hardware "
 630                                                         "handler parameters";
 631                                 scsi_dh_detach(q);
 632                                 dm_put_device(ti, p->path.dev);
 633                                 goto bad;
 634                         }
 635                 }
 636         }
 637
 638         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 639         if (r) {
 640                 dm_put_device(ti, p->path.dev);
 641                 goto bad;
 642         }
 643
 644         return p;
 645
 646  bad:
 647         free_pgpath(p);
 648         return ERR_PTR(r);
 649 }
 650
 651 static struct priority_group *parse_priority_group(struct arg_set *as,
 652                                                    struct multipath *m)
 653 {
 654         static struct param _params[] = {
 655                 {1, 1024, "invalid number of paths"},
 656                 {0, 1024, "invalid number of selector args"}
 657         };
 658
 659         int r;
 660         unsigned i, nr_selector_args, nr_params;
 661         struct priority_group *pg;
 662         struct dm_target *ti = m->ti;
 663
 664         if (as->argc < 2) {
 665                 as->argc = 0;
 666                 ti->error = "not enough priority group arguments";
 667                 return ERR_PTR(-EINVAL);
 668         }
 669
 670         pg = alloc_priority_group();
 671         if (!pg) {
 672                 ti->error = "couldn't allocate priority group";
 673                 return ERR_PTR(-ENOMEM);
 674         }
 675         pg->m = m;
 676
 677         r = parse_path_selector(as, pg, ti);
 678         if (r)
 679                 goto bad;
 680
 681         /*
 682          * read the paths
 683          */
 684         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
 685         if (r)
 686                 goto bad;
 687
 688         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
 689         if (r)
 690                 goto bad;
 691
 692         nr_params = 1 + nr_selector_args;
 693         for (i = 0; i < pg->nr_pgpaths; i++) {
 694                 struct pgpath *pgpath;
 695                 struct arg_set path_args;
 696
 697                 if (as->argc < nr_params) {
 698                         ti->error = "not enough path parameters";
 699                         goto bad;
 700                 }
 701
 702                 path_args.argc = nr_params;
 703                 path_args.argv = as->argv;
 704
 705                 pgpath = parse_path(&path_args, &pg->ps, ti);
 706                 if (IS_ERR(pgpath)) {
 707                         r = PTR_ERR(pgpath);
 708                         goto bad;
 709                 }
 710
 711                 pgpath->pg = pg;
 712                 list_add_tail(&pgpath->list, &pg->pgpaths);
 713                 consume(as, nr_params);
 714         }
 715
 716         return pg;
 717
 718  bad:
 719         free_priority_group(pg, ti);
 720         return ERR_PTR(r);
 721 }
 722
 723 static int parse_hw_handler(struct arg_set *as, struct multipath *m)
 724 {
 725         unsigned hw_argc;
 726         int ret;
 727         struct dm_target *ti = m->ti;
 728
 729         static struct param _params[] = {
 730                 {0, 1024, "invalid number of hardware handler args"},
 731         };
 732
 733         if (read_param(_params, shift(as), &hw_argc, &ti->error))
 734                 return -EINVAL;
 735
 736         if (!hw_argc)
 737                 return 0;
 738
 739         if (hw_argc > as->argc) {
 740                 ti->error = "not enough arguments for hardware handler";
 741                 return -EINVAL;
 742         }
 743
 744         m->hw_handler_name = kstrdup(shift(as), GFP_KERNEL);
 745         request_module("scsi_dh_%s", m->hw_handler_name);
 746         if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
 747                 ti->error = "unknown hardware handler type";
 748                 ret = -EINVAL;
 749                 goto fail;
 750         }
 751
 752         if (hw_argc > 1) {
 753                 char *p;
 754                 int i, j, len = 4;
 755
 756                 for (i = 0; i <= hw_argc - 2; i++)
 757                         len += strlen(as->argv[i]) + 1;
 758                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 759                 if (!p) {
 760                         ti->error = "memory allocation failed";
 761                         ret = -ENOMEM;
 762                         goto fail;
 763                 }
 764                 j = sprintf(p, "%d", hw_argc - 1);
 765                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 766                         j = sprintf(p, "%s", as->argv[i]);
 767         }
 768         consume(as, hw_argc - 1);
 769
 770         return 0;
 771 fail:
 772         kfree(m->hw_handler_name);
 773         m->hw_handler_name = NULL;
 774         return ret;
 775 }
 776
 777 static int parse_features(struct arg_set *as, struct multipath *m)
 778 {
 779         int r;
 780         unsigned argc;
 781         struct dm_target *ti = m->ti;
 782         const char *param_name;
 783
 784         static struct param _params[] = {
 785                 {0, 3, "invalid number of feature args"},
 786                 {1, 50, "pg_init_retries must be between 1 and 50"},
 787         };
 788
 789         r = read_param(_params, shift(as), &argc, &ti->error);
 790         if (r)
 791                 return -EINVAL;
 792
 793         if (!argc)
 794                 return 0;
 795
 796         do {
 797                 param_name = shift(as);
 798                 argc--;
 799
 800                 if (!strnicmp(param_name, MESG_STR("queue_if_no_path"))) {
 801                         r = queue_if_no_path(m, 1, 0);
 802                         continue;
 803                 }
 804
 805                 if (!strnicmp(param_name, MESG_STR("pg_init_retries")) &&
 806                     (argc >= 1)) {
 807                         r = read_param(_params + 1, shift(as),
 808                                        &m->pg_init_retries, &ti->error);
 809                         argc--;
 810                         continue;
 811                 }
 812
 813                 ti->error = "Unrecognised multipath feature request";
 814                 r = -EINVAL;
 815         } while (argc && !r);
 816
 817         return r;
 818 }
 819
 820 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 821                          char **argv)
 822 {
 823         /* target parameters */
 824         static struct param _params[] = {
 825                 {1, 1024, "invalid number of priority groups"},
 826                 {1, 1024, "invalid initial priority group number"},
 827         };
 828
 829         int r;
 830         struct multipath *m;
 831         struct arg_set as;
 832         unsigned pg_count = 0;
 833         unsigned next_pg_num;
 834
 835         as.argc = argc;
 836         as.argv = argv;
 837
 838         m = alloc_multipath(ti);
 839         if (!m) {
 840                 ti->error = "can't allocate multipath";
 841                 return -EINVAL;
 842         }
 843
 844         r = parse_features(&as, m);
 845         if (r)
 846                 goto bad;
 847
 848         r = parse_hw_handler(&as, m);
 849         if (r)
 850                 goto bad;
 851
 852         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
 853         if (r)
 854                 goto bad;
 855
 856         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
 857         if (r)
 858                 goto bad;
 859
 860         /* parse the priority groups */
 861         while (as.argc) {
 862                 struct priority_group *pg;
 863
 864                 pg = parse_priority_group(&as, m);
 865                 if (IS_ERR(pg)) {
 866                         r = PTR_ERR(pg);
 867                         goto bad;
 868                 }
 869
 870                 m->nr_valid_paths += pg->nr_pgpaths;
 871                 list_add_tail(&pg->list, &m->priority_groups);
 872                 pg_count++;
 873                 pg->pg_num = pg_count;
 874                 if (!--next_pg_num)
 875                         m->next_pg = pg;
 876         }
 877
 878         if (pg_count != m->nr_priority_groups) {
 879                 ti->error = "priority group count mismatch";
 880                 r = -EINVAL;
 881                 goto bad;
 882         }
 883
 884         ti->num_flush_requests = 1;
 885
 886         return 0;
 887
 888  bad:
 889         free_multipath(m);
 890         return r;
 891 }
 892
 893 static void flush_multipath_work(void)
 894 {
 895         flush_workqueue(kmpath_handlerd);
 896         flush_workqueue(kmultipathd);
 897         flush_scheduled_work();
 898 }
 899
 900 static void multipath_dtr(struct dm_target *ti)
 901 {
 902         struct multipath *m = ti->private;
 903
 904         flush_multipath_work();
 905         free_multipath(m);
 906 }
 907
 908 /*
 909  * Map cloned requests
 910  */
 911 static int multipath_map(struct dm_target *ti, struct request *clone,
 912                          union map_info *map_context)
 913 {
 914         int r;
 915         struct dm_mpath_io *mpio;
 916         struct multipath *m = (struct multipath *) ti->private;
 917
 918         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 919         if (!mpio)
 920                 /* ENOMEM, requeue */
 921                 return DM_MAPIO_REQUEUE;
 922         memset(mpio, 0, sizeof(*mpio));
 923
 924         map_context->ptr = mpio;
 925         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 926         r = map_io(m, clone, mpio, 0);
 927         if (r < 0 || r == DM_MAPIO_REQUEUE)
 928                 mempool_free(mpio, m->mpio_pool);
 929
 930         return r;
 931 }
 932
 933 /*
 934  * Take a path out of use.
 935  */
 936 static int fail_path(struct pgpath *pgpath)
 937 {
 938         unsigned long flags;
 939         struct multipath *m = pgpath->pg->m;
 940
 941         spin_lock_irqsave(&m->lock, flags);
 942
 943         if (!pgpath->is_active)
 944                 goto out;
 945
 946         DMWARN("Failing path %s.", pgpath->path.dev->name);
 947
 948         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 949         pgpath->is_active = 0;
 950         pgpath->fail_count++;
 951
 952         m->nr_valid_paths--;
 953
 954         if (pgpath == m->current_pgpath)
 955                 m->current_pgpath = NULL;
 956
 957         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
 958                       pgpath->path.dev->name, m->nr_valid_paths);
 959
 960         schedule_work(&m->trigger_event);
 961         queue_work(kmultipathd, &pgpath->deactivate_path);
 962
 963 out:
 964         spin_unlock_irqrestore(&m->lock, flags);
 965
 966         return 0;
 967 }
 968
 969 /*
 970  * Reinstate a previously-failed path
 971  */
 972 static int reinstate_path(struct pgpath *pgpath)
 973 {
 974         int r = 0;
 975         unsigned long flags;
 976         struct multipath *m = pgpath->pg->m;
 977
 978         spin_lock_irqsave(&m->lock, flags);
 979
 980         if (pgpath->is_active)
 981                 goto out;
 982
 983         if (!pgpath->pg->ps.type->reinstate_path) {
 984                 DMWARN("Reinstate path not supported by path selector %s",
 985                        pgpath->pg->ps.type->name);
 986                 r = -EINVAL;
 987                 goto out;
 988         }
 989
 990         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
 991         if (r)
 992                 goto out;
 993
 994         pgpath->is_active = 1;
 995
 996         if (!m->nr_valid_paths++ && m->queue_size) {
 997                 m->current_pgpath = NULL;
 998                 queue_work(kmultipathd, &m->process_queued_ios);
 999         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1000                 if (queue_work(kmpath_handlerd, &pgpath->activate_path))
1001                         m->pg_init_in_progress++;
1002         }
1003
1004         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1005                       pgpath->path.dev->name, m->nr_valid_paths);
1006
1007         schedule_work(&m->trigger_event);
1008
1009 out:
1010         spin_unlock_irqrestore(&m->lock, flags);
1011
1012         return r;
1013 }
1014
1015 /*
1016  * Fail or reinstate all paths that match the provided struct dm_dev.
1017  */
1018 static int action_dev(struct multipath *m, struct dm_dev *dev,
1019                       action_fn action)
1020 {
1021         int r = 0;
1022         struct pgpath *pgpath;
1023         struct priority_group *pg;
1024
1025         list_for_each_entry(pg, &m->priority_groups, list) {
1026                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1027                         if (pgpath->path.dev == dev)
1028                                 r = action(pgpath);
1029                 }
1030         }
1031
1032         return r;
1033 }
1034
1035 /*
1036  * Temporarily try to avoid having to use the specified PG
1037  */
1038 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1039                       int bypassed)
1040 {
1041         unsigned long flags;
1042
1043         spin_lock_irqsave(&m->lock, flags);
1044
1045         pg->bypassed = bypassed;
1046         m->current_pgpath = NULL;
1047         m->current_pg = NULL;
1048
1049         spin_unlock_irqrestore(&m->lock, flags);
1050
1051         schedule_work(&m->trigger_event);
1052 }
1053
1054 /*
1055  * Switch to using the specified PG from the next I/O that gets mapped
1056  */
1057 static int switch_pg_num(struct multipath *m, const char *pgstr)
1058 {
1059         struct priority_group *pg;
1060         unsigned pgnum;
1061         unsigned long flags;
1062
1063         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1064             (pgnum > m->nr_priority_groups)) {
1065                 DMWARN("invalid PG number supplied to switch_pg_num");
1066                 return -EINVAL;
1067         }
1068
1069         spin_lock_irqsave(&m->lock, flags);
1070         list_for_each_entry(pg, &m->priority_groups, list) {
1071                 pg->bypassed = 0;
1072                 if (--pgnum)
1073                         continue;
1074
1075                 m->current_pgpath = NULL;
1076                 m->current_pg = NULL;
1077                 m->next_pg = pg;
1078         }
1079         spin_unlock_irqrestore(&m->lock, flags);
1080
1081         schedule_work(&m->trigger_event);
1082         return 0;
1083 }
1084
1085 /*
1086  * Set/clear bypassed status of a PG.
1087  * PGs are numbered upwards from 1 in the order they were declared.
1088  */
1089 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1090 {
1091         struct priority_group *pg;
1092         unsigned pgnum;
1093
1094         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1095             (pgnum > m->nr_priority_groups)) {
1096                 DMWARN("invalid PG number supplied to bypass_pg");
1097                 return -EINVAL;
1098         }
1099
1100         list_for_each_entry(pg, &m->priority_groups, list) {
1101                 if (!--pgnum)
1102                         break;
1103         }
1104
1105         bypass_pg(m, pg, bypassed);
1106         return 0;
1107 }
1108
1109 /*
1110  * Should we retry pg_init immediately?
1111  */
1112 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1113 {
1114         unsigned long flags;
1115         int limit_reached = 0;
1116
1117         spin_lock_irqsave(&m->lock, flags);
1118
1119         if (m->pg_init_count <= m->pg_init_retries)
1120                 m->pg_init_required = 1;
1121         else
1122                 limit_reached = 1;
1123
1124         spin_unlock_irqrestore(&m->lock, flags);
1125
1126         return limit_reached;
1127 }
1128
1129 static void pg_init_done(void *data, int errors)
1130 {
1131         struct dm_path *path = data;
1132         struct pgpath *pgpath = path_to_pgpath(path);
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("Cannot failover device because scsi_dh_%s was not "
1147                       "loaded.", m->hw_handler_name);
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->path);
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         m->suspended = 1;
1280         flush_multipath_work();
1281         mutex_unlock(&m->work_mutex);
1282 }
1283
1284 /*
1285  * Restore the queue_if_no_path setting.
1286  */
1287 static void multipath_resume(struct dm_target *ti)
1288 {
1289         struct multipath *m = (struct multipath *) ti->private;
1290         unsigned long flags;
1291
1292         mutex_lock(&m->work_mutex);
1293         m->suspended = 0;
1294         mutex_unlock(&m->work_mutex);
1295
1296         spin_lock_irqsave(&m->lock, flags);
1297         m->queue_if_no_path = m->saved_queue_if_no_path;
1298         spin_unlock_irqrestore(&m->lock, flags);
1299 }
1300
1301 /*
1302  * Info output has the following format:
1303  * num_multipath_feature_args [multipath_feature_args]*
1304  * num_handler_status_args [handler_status_args]*
1305  * num_groups init_group_number
1306  *            [A|D|E num_ps_status_args [ps_status_args]*
1307  *             num_paths num_selector_args
1308  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1309  *
1310  * Table output has the following format (identical to the constructor string):
1311  * num_feature_args [features_args]*
1312  * num_handler_args hw_handler [hw_handler_args]*
1313  * num_groups init_group_number
1314  *     [priority selector-name num_ps_args [ps_args]*
1315  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1316  */
1317 static int multipath_status(struct dm_target *ti, status_type_t type,
1318                             char *result, unsigned int maxlen)
1319 {
1320         int sz = 0;
1321         unsigned long flags;
1322         struct multipath *m = (struct multipath *) ti->private;
1323         struct priority_group *pg;
1324         struct pgpath *p;
1325         unsigned pg_num;
1326         char state;
1327
1328         spin_lock_irqsave(&m->lock, flags);
1329
1330         /* Features */
1331         if (type == STATUSTYPE_INFO)
1332                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1333         else {
1334                 DMEMIT("%u ", m->queue_if_no_path +
1335                               (m->pg_init_retries > 0) * 2);
1336                 if (m->queue_if_no_path)
1337                         DMEMIT("queue_if_no_path ");
1338                 if (m->pg_init_retries)
1339                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1340         }
1341
1342         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1343                 DMEMIT("0 ");
1344         else
1345                 DMEMIT("1 %s ", m->hw_handler_name);
1346
1347         DMEMIT("%u ", m->nr_priority_groups);
1348
1349         if (m->next_pg)
1350                 pg_num = m->next_pg->pg_num;
1351         else if (m->current_pg)
1352                 pg_num = m->current_pg->pg_num;
1353         else
1354                         pg_num = 1;
1355
1356         DMEMIT("%u ", pg_num);
1357
1358         switch (type) {
1359         case STATUSTYPE_INFO:
1360                 list_for_each_entry(pg, &m->priority_groups, list) {
1361                         if (pg->bypassed)
1362                                 state = 'D';    /* Disabled */
1363                         else if (pg == m->current_pg)
1364                                 state = 'A';    /* Currently Active */
1365                         else
1366                                 state = 'E';    /* Enabled */
1367
1368                         DMEMIT("%c ", state);
1369
1370                         if (pg->ps.type->status)
1371                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1372                                                           result + sz,
1373                                                           maxlen - sz);
1374                         else
1375                                 DMEMIT("0 ");
1376
1377                         DMEMIT("%u %u ", pg->nr_pgpaths,
1378                                pg->ps.type->info_args);
1379
1380                         list_for_each_entry(p, &pg->pgpaths, list) {
1381                                 DMEMIT("%s %s %u ", p->path.dev->name,
1382                                        p->is_active ? "A" : "F",
1383                                        p->fail_count);
1384                                 if (pg->ps.type->status)
1385                                         sz += pg->ps.type->status(&pg->ps,
1386                                               &p->path, type, result + sz,
1387                                               maxlen - sz);
1388                         }
1389                 }
1390                 break;
1391
1392         case STATUSTYPE_TABLE:
1393                 list_for_each_entry(pg, &m->priority_groups, list) {
1394                         DMEMIT("%s ", pg->ps.type->name);
1395
1396                         if (pg->ps.type->status)
1397                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1398                                                           result + sz,
1399                                                           maxlen - sz);
1400                         else
1401                                 DMEMIT("0 ");
1402
1403                         DMEMIT("%u %u ", pg->nr_pgpaths,
1404                                pg->ps.type->table_args);
1405
1406                         list_for_each_entry(p, &pg->pgpaths, list) {
1407                                 DMEMIT("%s ", p->path.dev->name);
1408                                 if (pg->ps.type->status)
1409                                         sz += pg->ps.type->status(&pg->ps,
1410                                               &p->path, type, result + sz,
1411                                               maxlen - sz);
1412                         }
1413                 }
1414                 break;
1415         }
1416
1417         spin_unlock_irqrestore(&m->lock, flags);
1418
1419         return 0;
1420 }
1421
1422 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1423 {
1424         int r = -EINVAL;
1425         struct dm_dev *dev;
1426         struct multipath *m = (struct multipath *) ti->private;
1427         action_fn action;
1428
1429         mutex_lock(&m->work_mutex);
1430
1431         if (m->suspended) {
1432                 r = -EBUSY;
1433                 goto out;
1434         }
1435
1436         if (dm_suspended(ti)) {
1437                 r = -EBUSY;
1438                 goto out;
1439         }
1440
1441         if (argc == 1) {
1442                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path"))) {
1443                         r = queue_if_no_path(m, 1, 0);
1444                         goto out;
1445                 } else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path"))) {
1446                         r = queue_if_no_path(m, 0, 0);
1447                         goto out;
1448                 }
1449         }
1450
1451         if (argc != 2) {
1452                 DMWARN("Unrecognised multipath message received.");
1453                 goto out;
1454         }
1455
1456         if (!strnicmp(argv[0], MESG_STR("disable_group"))) {
1457                 r = bypass_pg_num(m, argv[1], 1);
1458                 goto out;
1459         } else if (!strnicmp(argv[0], MESG_STR("enable_group"))) {
1460                 r = bypass_pg_num(m, argv[1], 0);
1461                 goto out;
1462         } else if (!strnicmp(argv[0], MESG_STR("switch_group"))) {
1463                 r = switch_pg_num(m, argv[1]);
1464                 goto out;
1465         } else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1466                 action = reinstate_path;
1467         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1468                 action = fail_path;
1469         else {
1470                 DMWARN("Unrecognised multipath message received.");
1471                 goto out;
1472         }
1473
1474         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
1475                           dm_table_get_mode(ti->table), &dev);
1476         if (r) {
1477                 DMWARN("message: error getting device %s",
1478                        argv[1]);
1479                 goto out;
1480         }
1481
1482         r = action_dev(m, dev, action);
1483
1484         dm_put_device(ti, dev);
1485
1486 out:
1487         mutex_unlock(&m->work_mutex);
1488         return r;
1489 }
1490
1491 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1492                            unsigned long arg)
1493 {
1494         struct multipath *m = (struct multipath *) ti->private;
1495         struct block_device *bdev = NULL;
1496         fmode_t mode = 0;
1497         unsigned long flags;
1498         int r = 0;
1499
1500         spin_lock_irqsave(&m->lock, flags);
1501
1502         if (!m->current_pgpath)
1503                 __choose_pgpath(m, 0);
1504
1505         if (m->current_pgpath) {
1506                 bdev = m->current_pgpath->path.dev->bdev;
1507                 mode = m->current_pgpath->path.dev->mode;
1508         }
1509
1510         if (m->queue_io)
1511                 r = -EAGAIN;
1512         else if (!bdev)
1513                 r = -EIO;
1514
1515         spin_unlock_irqrestore(&m->lock, flags);
1516
1517         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1518 }
1519
1520 static int multipath_iterate_devices(struct dm_target *ti,
1521                                      iterate_devices_callout_fn fn, void *data)
1522 {
1523         struct multipath *m = ti->private;
1524         struct priority_group *pg;
1525         struct pgpath *p;
1526         int ret = 0;
1527
1528         list_for_each_entry(pg, &m->priority_groups, list) {
1529                 list_for_each_entry(p, &pg->pgpaths, list) {
1530                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1531                         if (ret)
1532                                 goto out;
1533                 }
1534         }
1535
1536 out:
1537         return ret;
1538 }
1539
1540 static int __pgpath_busy(struct pgpath *pgpath)
1541 {
1542         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1543
1544         return dm_underlying_device_busy(q);
1545 }
1546
1547 /*
1548  * We return "busy", only when we can map I/Os but underlying devices
1549  * are busy (so even if we map I/Os now, the I/Os will wait on
1550  * the underlying queue).
1551  * In other words, if we want to kill I/Os or queue them inside us
1552  * due to map unavailability, we don't return "busy".  Otherwise,
1553  * dm core won't give us the I/Os and we can't do what we want.
1554  */
1555 static int multipath_busy(struct dm_target *ti)
1556 {
1557         int busy = 0, has_active = 0;
1558         struct multipath *m = ti->private;
1559         struct priority_group *pg;
1560         struct pgpath *pgpath;
1561         unsigned long flags;
1562
1563         spin_lock_irqsave(&m->lock, flags);
1564
1565         /* Guess which priority_group will be used at next mapping time */
1566         if (unlikely(!m->current_pgpath && m->next_pg))
1567                 pg = m->next_pg;
1568         else if (likely(m->current_pg))
1569                 pg = m->current_pg;
1570         else
1571                 /*
1572                  * We don't know which pg will be used at next mapping time.
1573                  * We don't call __choose_pgpath() here to avoid to trigger
1574                  * pg_init just by busy checking.
1575                  * So we don't know whether underlying devices we will be using
1576                  * at next mapping time are busy or not. Just try mapping.
1577                  */
1578                 goto out;
1579
1580         /*
1581          * If there is one non-busy active path at least, the path selector
1582          * will be able to select it. So we consider such a pg as not busy.
1583          */
1584         busy = 1;
1585         list_for_each_entry(pgpath, &pg->pgpaths, list)
1586                 if (pgpath->is_active) {
1587                         has_active = 1;
1588
1589                         if (!__pgpath_busy(pgpath)) {
1590                                 busy = 0;
1591                                 break;
1592                         }
1593                 }
1594
1595         if (!has_active)
1596                 /*
1597                  * No active path in this pg, so this pg won't be used and
1598                  * the current_pg will be changed at next mapping time.
1599                  * We need to try mapping to determine it.
1600                  */
1601                 busy = 0;
1602
1603 out:
1604         spin_unlock_irqrestore(&m->lock, flags);
1605
1606         return busy;
1607 }
1608
1609 /*-----------------------------------------------------------------
1610  * Module setup
1611  *---------------------------------------------------------------*/
1612 static struct target_type multipath_target = {
1613         .name = "multipath",
1614         .version = {1, 1, 1},
1615         .module = THIS_MODULE,
1616         .ctr = multipath_ctr,
1617         .dtr = multipath_dtr,
1618         .map_rq = multipath_map,
1619         .rq_end_io = multipath_end_io,
1620         .presuspend = multipath_presuspend,
1621         .postsuspend = multipath_postsuspend,
1622         .resume = multipath_resume,
1623         .status = multipath_status,
1624         .message = multipath_message,
1625         .ioctl  = multipath_ioctl,
1626         .iterate_devices = multipath_iterate_devices,
1627         .busy = multipath_busy,
1628 };
1629
1630 static int __init dm_multipath_init(void)
1631 {
1632         int r;
1633
1634         /* allocate a slab for the dm_ios */
1635         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1636         if (!_mpio_cache)
1637                 return -ENOMEM;
1638
1639         r = dm_register_target(&multipath_target);
1640         if (r < 0) {
1641                 DMERR("register failed %d", r);
1642                 kmem_cache_destroy(_mpio_cache);
1643                 return -EINVAL;
1644         }
1645
1646         kmultipathd = create_workqueue("kmpathd");
1647         if (!kmultipathd) {
1648                 DMERR("failed to create workqueue kmpathd");
1649                 dm_unregister_target(&multipath_target);
1650                 kmem_cache_destroy(_mpio_cache);
1651                 return -ENOMEM;
1652         }
1653
1654         /*
1655          * A separate workqueue is used to handle the device handlers
1656          * to avoid overloading existing workqueue. Overloading the
1657          * old workqueue would also create a bottleneck in the
1658          * path of the storage hardware device activation.
1659          */
1660         kmpath_handlerd = create_singlethread_workqueue("kmpath_handlerd");
1661         if (!kmpath_handlerd) {
1662                 DMERR("failed to create workqueue kmpath_handlerd");
1663                 destroy_workqueue(kmultipathd);
1664                 dm_unregister_target(&multipath_target);
1665                 kmem_cache_destroy(_mpio_cache);
1666                 return -ENOMEM;
1667         }
1668
1669         DMINFO("version %u.%u.%u loaded",
1670                multipath_target.version[0], multipath_target.version[1],
1671                multipath_target.version[2]);
1672
1673         return r;
1674 }
1675
1676 static void __exit dm_multipath_exit(void)
1677 {
1678         destroy_workqueue(kmpath_handlerd);
1679         destroy_workqueue(kmultipathd);
1680
1681         dm_unregister_target(&multipath_target);
1682         kmem_cache_destroy(_mpio_cache);
1683 }
1684
1685 module_init(dm_multipath_init);
1686 module_exit(dm_multipath_exit);
1687
1688 MODULE_DESCRIPTION(DM_NAME " multipath target");
1689 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1690 MODULE_LICENSE("GPL");