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