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 <linux/atomic.h>
  23
  24 #define DM_MSG_PREFIX "multipath"
  25 #define DM_PG_INIT_DELAY_MSECS 2000
  26 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  27
  28 /* Path properties */
  29 struct pgpath {
  30         struct list_head list;
  31
  32         struct priority_group *pg;      /* Owning PG */
  33         unsigned is_active;             /* Path status */
  34         unsigned fail_count;            /* Cumulative failure count */
  35
  36         struct dm_path path;
  37         struct delayed_work 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
  69         unsigned nr_priority_groups;
  70         struct list_head priority_groups;
  71
  72         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  73
  74         unsigned pg_init_required;      /* pg_init needs calling? */
  75         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  76         unsigned pg_init_delay_retry;   /* Delay pg_init retry? */
  77
  78         unsigned nr_valid_paths;        /* Total number of usable paths */
  79         struct pgpath *current_pgpath;
  80         struct priority_group *current_pg;
  81         struct priority_group *next_pg; /* Switch to this PG if set */
  82         unsigned repeat_count;          /* I/Os left before calling PS again */
  83
  84         unsigned queue_io;              /* Must we queue all I/O? */
  85         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
  86         unsigned saved_queue_if_no_path;/* Saved state during suspension */
  87         unsigned pg_init_disabled:1;    /* pg_init is not currently allowed */
  88         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  89         unsigned pg_init_count;         /* Number of times pg_init called */
  90         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  91
  92         struct work_struct process_queued_ios;
  93         struct list_head queued_ios;
  94         unsigned queue_size;
  95
  96         struct work_struct trigger_event;
  97
  98         /*
  99          * We must use a mempool of dm_mpath_io structs so that we
 100          * can resubmit bios on error.
 101          */
 102         mempool_t *mpio_pool;
 103
 104         struct mutex work_mutex;
 105 };
 106
 107 /*
 108  * Context information attached to each bio we process.
 109  */
 110 struct dm_mpath_io {
 111         struct pgpath *pgpath;
 112         size_t nr_bytes;
 113 };
 114
 115 typedef int (*action_fn) (struct pgpath *pgpath);
 116
 117 #define MIN_IOS 256     /* Mempool size */
 118
 119 static struct kmem_cache *_mpio_cache;
 120
 121 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 122 static void process_queued_ios(struct work_struct *work);
 123 static void trigger_event(struct work_struct *work);
 124 static void activate_path(struct work_struct *work);
 125
 126
 127 /*-----------------------------------------------
 128  * Allocation routines
 129  *-----------------------------------------------*/
 130
 131 static struct pgpath *alloc_pgpath(void)
 132 {
 133         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 134
 135         if (pgpath) {
 136                 pgpath->is_active = 1;
 137                 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);
 138         }
 139
 140         return pgpath;
 141 }
 142
 143 static void free_pgpath(struct pgpath *pgpath)
 144 {
 145         kfree(pgpath);
 146 }
 147
 148 static struct priority_group *alloc_priority_group(void)
 149 {
 150         struct priority_group *pg;
 151
 152         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 153
 154         if (pg)
 155                 INIT_LIST_HEAD(&pg->pgpaths);
 156
 157         return pg;
 158 }
 159
 160 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 161 {
 162         struct pgpath *pgpath, *tmp;
 163         struct multipath *m = ti->private;
 164
 165         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 166                 list_del(&pgpath->list);
 167                 if (m->hw_handler_name)
 168                         scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 169                 dm_put_device(ti, pgpath->path.dev);
 170                 free_pgpath(pgpath);
 171         }
 172 }
 173
 174 static void free_priority_group(struct priority_group *pg,
 175                                 struct dm_target *ti)
 176 {
 177         struct path_selector *ps = &pg->ps;
 178
 179         if (ps->type) {
 180                 ps->type->destroy(ps);
 181                 dm_put_path_selector(ps->type);
 182         }
 183
 184         free_pgpaths(&pg->pgpaths, ti);
 185         kfree(pg);
 186 }
 187
 188 static struct multipath *alloc_multipath(struct dm_target *ti)
 189 {
 190         struct multipath *m;
 191
 192         m = kzalloc(sizeof(*m), GFP_KERNEL);
 193         if (m) {
 194                 INIT_LIST_HEAD(&m->priority_groups);
 195                 INIT_LIST_HEAD(&m->queued_ios);
 196                 spin_lock_init(&m->lock);
 197                 m->queue_io = 1;
 198                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 199                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
 200                 INIT_WORK(&m->trigger_event, trigger_event);
 201                 init_waitqueue_head(&m->pg_init_wait);
 202                 mutex_init(&m->work_mutex);
 203                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 204                 if (!m->mpio_pool) {
 205                         kfree(m);
 206                         return NULL;
 207                 }
 208                 m->ti = ti;
 209                 ti->private = m;
 210         }
 211
 212         return m;
 213 }
 214
 215 static void free_multipath(struct multipath *m)
 216 {
 217         struct priority_group *pg, *tmp;
 218
 219         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 220                 list_del(&pg->list);
 221                 free_priority_group(pg, m->ti);
 222         }
 223
 224         kfree(m->hw_handler_name);
 225         kfree(m->hw_handler_params);
 226         mempool_destroy(m->mpio_pool);
 227         kfree(m);
 228 }
 229
 230
 231 /*-----------------------------------------------
 232  * Path selection
 233  *-----------------------------------------------*/
 234
 235 static void __pg_init_all_paths(struct multipath *m)
 236 {
 237         struct pgpath *pgpath;
 238         unsigned long pg_init_delay = 0;
 239
 240         m->pg_init_count++;
 241         m->pg_init_required = 0;
 242         if (m->pg_init_delay_retry)
 243                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 244                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 245         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 246                 /* Skip failed paths */
 247                 if (!pgpath->is_active)
 248                         continue;
 249                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 250                                        pg_init_delay))
 251                         m->pg_init_in_progress++;
 252         }
 253 }
 254
 255 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 256 {
 257         m->current_pg = pgpath->pg;
 258
 259         /* Must we initialise the PG first, and queue I/O till it's ready? */
 260         if (m->hw_handler_name) {
 261                 m->pg_init_required = 1;
 262                 m->queue_io = 1;
 263         } else {
 264                 m->pg_init_required = 0;
 265                 m->queue_io = 0;
 266         }
 267
 268         m->pg_init_count = 0;
 269 }
 270
 271 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 272                                size_t nr_bytes)
 273 {
 274         struct dm_path *path;
 275
 276         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 277         if (!path)
 278                 return -ENXIO;
 279
 280         m->current_pgpath = path_to_pgpath(path);
 281
 282         if (m->current_pg != pg)
 283                 __switch_pg(m, m->current_pgpath);
 284
 285         return 0;
 286 }
 287
 288 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 289 {
 290         struct priority_group *pg;
 291         unsigned bypassed = 1;
 292
 293         if (!m->nr_valid_paths)
 294                 goto failed;
 295
 296         /* Were we instructed to switch PG? */
 297         if (m->next_pg) {
 298                 pg = m->next_pg;
 299                 m->next_pg = NULL;
 300                 if (!__choose_path_in_pg(m, pg, nr_bytes))
 301                         return;
 302         }
 303
 304         /* Don't change PG until it has no remaining paths */
 305         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 306                 return;
 307
 308         /*
 309          * Loop through priority groups until we find a valid path.
 310          * First time we skip PGs marked 'bypassed'.
 311          * Second time we only try the ones we skipped.
 312          */
 313         do {
 314                 list_for_each_entry(pg, &m->priority_groups, list) {
 315                         if (pg->bypassed == bypassed)
 316                                 continue;
 317                         if (!__choose_path_in_pg(m, pg, nr_bytes))
 318                                 return;
 319                 }
 320         } while (bypassed--);
 321
 322 failed:
 323         m->current_pgpath = NULL;
 324         m->current_pg = NULL;
 325 }
 326
 327 /*
 328  * Check whether bios must be queued in the device-mapper core rather
 329  * than here in the target.
 330  *
 331  * m->lock must be held on entry.
 332  *
 333  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 334  * same value then we are not between multipath_presuspend()
 335  * and multipath_resume() calls and we have no need to check
 336  * for the DMF_NOFLUSH_SUSPENDING flag.
 337  */
 338 static int __must_push_back(struct multipath *m)
 339 {
 340         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 341                 dm_noflush_suspending(m->ti));
 342 }
 343
 344 static int map_io(struct multipath *m, struct request *clone,
 345                   struct dm_mpath_io *mpio, unsigned was_queued)
 346 {
 347         int r = DM_MAPIO_REMAPPED;
 348         size_t nr_bytes = blk_rq_bytes(clone);
 349         unsigned long flags;
 350         struct pgpath *pgpath;
 351         struct block_device *bdev;
 352
 353         spin_lock_irqsave(&m->lock, flags);
 354
 355         /* Do we need to select a new pgpath? */
 356         if (!m->current_pgpath ||
 357             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 358                 __choose_pgpath(m, nr_bytes);
 359
 360         pgpath = m->current_pgpath;
 361
 362         if (was_queued)
 363                 m->queue_size--;
 364
 365         if ((pgpath && m->queue_io) ||
 366             (!pgpath && m->queue_if_no_path)) {
 367                 /* Queue for the daemon to resubmit */
 368                 list_add_tail(&clone->queuelist, &m->queued_ios);
 369                 m->queue_size++;
 370                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 371                     !m->queue_io)
 372                         queue_work(kmultipathd, &m->process_queued_ios);
 373                 pgpath = NULL;
 374                 r = DM_MAPIO_SUBMITTED;
 375         } else if (pgpath) {
 376                 bdev = pgpath->path.dev->bdev;
 377                 clone->q = bdev_get_queue(bdev);
 378                 clone->rq_disk = bdev->bd_disk;
 379         } else if (__must_push_back(m))
 380                 r = DM_MAPIO_REQUEUE;
 381         else
 382                 r = -EIO;       /* Failed */
 383
 384         mpio->pgpath = pgpath;
 385         mpio->nr_bytes = nr_bytes;
 386
 387         if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
 388                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path,
 389                                               nr_bytes);
 390
 391         spin_unlock_irqrestore(&m->lock, flags);
 392
 393         return r;
 394 }
 395
 396 /*
 397  * If we run out of usable paths, should we queue I/O or error it?
 398  */
 399 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 400                             unsigned save_old_value)
 401 {
 402         unsigned long flags;
 403
 404         spin_lock_irqsave(&m->lock, flags);
 405
 406         if (save_old_value)
 407                 m->saved_queue_if_no_path = m->queue_if_no_path;
 408         else
 409                 m->saved_queue_if_no_path = queue_if_no_path;
 410         m->queue_if_no_path = queue_if_no_path;
 411         if (!m->queue_if_no_path && m->queue_size)
 412                 queue_work(kmultipathd, &m->process_queued_ios);
 413
 414         spin_unlock_irqrestore(&m->lock, flags);
 415
 416         return 0;
 417 }
 418
 419 /*-----------------------------------------------------------------
 420  * The multipath daemon is responsible for resubmitting queued ios.
 421  *---------------------------------------------------------------*/
 422
 423 static void dispatch_queued_ios(struct multipath *m)
 424 {
 425         int r;
 426         unsigned long flags;
 427         struct dm_mpath_io *mpio;
 428         union map_info *info;
 429         struct request *clone, *n;
 430         LIST_HEAD(cl);
 431
 432         spin_lock_irqsave(&m->lock, flags);
 433         list_splice_init(&m->queued_ios, &cl);
 434         spin_unlock_irqrestore(&m->lock, flags);
 435
 436         list_for_each_entry_safe(clone, n, &cl, queuelist) {
 437                 list_del_init(&clone->queuelist);
 438
 439                 info = dm_get_rq_mapinfo(clone);
 440                 mpio = info->ptr;
 441
 442                 r = map_io(m, clone, mpio, 1);
 443                 if (r < 0) {
 444                         mempool_free(mpio, m->mpio_pool);
 445                         dm_kill_unmapped_request(clone, r);
 446                 } else if (r == DM_MAPIO_REMAPPED)
 447                         dm_dispatch_request(clone);
 448                 else if (r == DM_MAPIO_REQUEUE) {
 449                         mempool_free(mpio, m->mpio_pool);
 450                         dm_requeue_unmapped_request(clone);
 451                 }
 452         }
 453 }
 454
 455 static void process_queued_ios(struct work_struct *work)
 456 {
 457         struct multipath *m =
 458                 container_of(work, struct multipath, process_queued_ios);
 459         struct pgpath *pgpath = NULL;
 460         unsigned must_queue = 1;
 461         unsigned long flags;
 462
 463         spin_lock_irqsave(&m->lock, flags);
 464
 465         if (!m->queue_size)
 466                 goto out;
 467
 468         if (!m->current_pgpath)
 469                 __choose_pgpath(m, 0);
 470
 471         pgpath = m->current_pgpath;
 472
 473         if ((pgpath && !m->queue_io) ||
 474             (!pgpath && !m->queue_if_no_path))
 475                 must_queue = 0;
 476
 477         if (m->pg_init_required && !m->pg_init_in_progress && pgpath &&
 478             !m->pg_init_disabled)
 479                 __pg_init_all_paths(m);
 480
 481 out:
 482         spin_unlock_irqrestore(&m->lock, flags);
 483         if (!must_queue)
 484                 dispatch_queued_ios(m);
 485 }
 486
 487 /*
 488  * An event is triggered whenever a path is taken out of use.
 489  * Includes path failure and PG bypass.
 490  */
 491 static void trigger_event(struct work_struct *work)
 492 {
 493         struct multipath *m =
 494                 container_of(work, struct multipath, trigger_event);
 495
 496         dm_table_event(m->ti->table);
 497 }
 498
 499 /*-----------------------------------------------------------------
 500  * Constructor/argument parsing:
 501  * <#multipath feature args> [<arg>]*
 502  * <#hw_handler args> [hw_handler [<arg>]*]
 503  * <#priority groups>
 504  * <initial priority group>
 505  *     [<selector> <#selector args> [<arg>]*
 506  *      <#paths> <#per-path selector args>
 507  *         [<path> [<arg>]* ]+ ]+
 508  *---------------------------------------------------------------*/
 509 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 510                                struct dm_target *ti)
 511 {
 512         int r;
 513         struct path_selector_type *pst;
 514         unsigned ps_argc;
 515
 516         static struct dm_arg _args[] = {
 517                 {0, 1024, "invalid number of path selector args"},
 518         };
 519
 520         pst = dm_get_path_selector(dm_shift_arg(as));
 521         if (!pst) {
 522                 ti->error = "unknown path selector type";
 523                 return -EINVAL;
 524         }
 525
 526         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 527         if (r) {
 528                 dm_put_path_selector(pst);
 529                 return -EINVAL;
 530         }
 531
 532         r = pst->create(&pg->ps, ps_argc, as->argv);
 533         if (r) {
 534                 dm_put_path_selector(pst);
 535                 ti->error = "path selector constructor failed";
 536                 return r;
 537         }
 538
 539         pg->ps.type = pst;
 540         dm_consume_args(as, ps_argc);
 541
 542         return 0;
 543 }
 544
 545 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 546                                struct dm_target *ti)
 547 {
 548         int r;
 549         struct pgpath *p;
 550         struct multipath *m = ti->private;
 551
 552         /* we need at least a path arg */
 553         if (as->argc < 1) {
 554                 ti->error = "no device given";
 555                 return ERR_PTR(-EINVAL);
 556         }
 557
 558         p = alloc_pgpath();
 559         if (!p)
 560                 return ERR_PTR(-ENOMEM);
 561
 562         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 563                           &p->path.dev);
 564         if (r) {
 565                 ti->error = "error getting device";
 566                 goto bad;
 567         }
 568
 569         if (m->hw_handler_name) {
 570                 struct request_queue *q = bdev_get_queue(p->path.dev->bdev);
 571
 572                 r = scsi_dh_attach(q, m->hw_handler_name);
 573                 if (r == -EBUSY) {
 574                         /*
 575                          * Already attached to different hw_handler,
 576                          * try to reattach with correct one.
 577                          */
 578                         scsi_dh_detach(q);
 579                         r = scsi_dh_attach(q, m->hw_handler_name);
 580                 }
 581
 582                 if (r < 0) {
 583                         ti->error = "error attaching hardware handler";
 584                         dm_put_device(ti, p->path.dev);
 585                         goto bad;
 586                 }
 587
 588                 if (m->hw_handler_params) {
 589                         r = scsi_dh_set_params(q, m->hw_handler_params);
 590                         if (r < 0) {
 591                                 ti->error = "unable to set hardware "
 592                                                         "handler parameters";
 593                                 scsi_dh_detach(q);
 594                                 dm_put_device(ti, p->path.dev);
 595                                 goto bad;
 596                         }
 597                 }
 598         }
 599
 600         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 601         if (r) {
 602                 dm_put_device(ti, p->path.dev);
 603                 goto bad;
 604         }
 605
 606         return p;
 607
 608  bad:
 609         free_pgpath(p);
 610         return ERR_PTR(r);
 611 }
 612
 613 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 614                                                    struct multipath *m)
 615 {
 616         static struct dm_arg _args[] = {
 617                 {1, 1024, "invalid number of paths"},
 618                 {0, 1024, "invalid number of selector args"}
 619         };
 620
 621         int r;
 622         unsigned i, nr_selector_args, nr_args;
 623         struct priority_group *pg;
 624         struct dm_target *ti = m->ti;
 625
 626         if (as->argc < 2) {
 627                 as->argc = 0;
 628                 ti->error = "not enough priority group arguments";
 629                 return ERR_PTR(-EINVAL);
 630         }
 631
 632         pg = alloc_priority_group();
 633         if (!pg) {
 634                 ti->error = "couldn't allocate priority group";
 635                 return ERR_PTR(-ENOMEM);
 636         }
 637         pg->m = m;
 638
 639         r = parse_path_selector(as, pg, ti);
 640         if (r)
 641                 goto bad;
 642
 643         /*
 644          * read the paths
 645          */
 646         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 647         if (r)
 648                 goto bad;
 649
 650         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 651         if (r)
 652                 goto bad;
 653
 654         nr_args = 1 + nr_selector_args;
 655         for (i = 0; i < pg->nr_pgpaths; i++) {
 656                 struct pgpath *pgpath;
 657                 struct dm_arg_set path_args;
 658
 659                 if (as->argc < nr_args) {
 660                         ti->error = "not enough path parameters";
 661                         r = -EINVAL;
 662                         goto bad;
 663                 }
 664
 665                 path_args.argc = nr_args;
 666                 path_args.argv = as->argv;
 667
 668                 pgpath = parse_path(&path_args, &pg->ps, ti);
 669                 if (IS_ERR(pgpath)) {
 670                         r = PTR_ERR(pgpath);
 671                         goto bad;
 672                 }
 673
 674                 pgpath->pg = pg;
 675                 list_add_tail(&pgpath->list, &pg->pgpaths);
 676                 dm_consume_args(as, nr_args);
 677         }
 678
 679         return pg;
 680
 681  bad:
 682         free_priority_group(pg, ti);
 683         return ERR_PTR(r);
 684 }
 685
 686 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 687 {
 688         unsigned hw_argc;
 689         int ret;
 690         struct dm_target *ti = m->ti;
 691
 692         static struct dm_arg _args[] = {
 693                 {0, 1024, "invalid number of hardware handler args"},
 694         };
 695
 696         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 697                 return -EINVAL;
 698
 699         if (!hw_argc)
 700                 return 0;
 701
 702         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 703         if (!try_then_request_module(scsi_dh_handler_exist(m->hw_handler_name),
 704                                      "scsi_dh_%s", m->hw_handler_name)) {
 705                 ti->error = "unknown hardware handler type";
 706                 ret = -EINVAL;
 707                 goto fail;
 708         }
 709
 710         if (hw_argc > 1) {
 711                 char *p;
 712                 int i, j, len = 4;
 713
 714                 for (i = 0; i <= hw_argc - 2; i++)
 715                         len += strlen(as->argv[i]) + 1;
 716                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 717                 if (!p) {
 718                         ti->error = "memory allocation failed";
 719                         ret = -ENOMEM;
 720                         goto fail;
 721                 }
 722                 j = sprintf(p, "%d", hw_argc - 1);
 723                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 724                         j = sprintf(p, "%s", as->argv[i]);
 725         }
 726         dm_consume_args(as, hw_argc - 1);
 727
 728         return 0;
 729 fail:
 730         kfree(m->hw_handler_name);
 731         m->hw_handler_name = NULL;
 732         return ret;
 733 }
 734
 735 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 736 {
 737         int r;
 738         unsigned argc;
 739         struct dm_target *ti = m->ti;
 740         const char *arg_name;
 741
 742         static struct dm_arg _args[] = {
 743                 {0, 5, "invalid number of feature args"},
 744                 {1, 50, "pg_init_retries must be between 1 and 50"},
 745                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 746         };
 747
 748         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 749         if (r)
 750                 return -EINVAL;
 751
 752         if (!argc)
 753                 return 0;
 754
 755         do {
 756                 arg_name = dm_shift_arg(as);
 757                 argc--;
 758
 759                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 760                         r = queue_if_no_path(m, 1, 0);
 761                         continue;
 762                 }
 763
 764                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 765                     (argc >= 1)) {
 766                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
 767                         argc--;
 768                         continue;
 769                 }
 770
 771                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
 772                     (argc >= 1)) {
 773                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
 774                         argc--;
 775                         continue;
 776                 }
 777
 778                 ti->error = "Unrecognised multipath feature request";
 779                 r = -EINVAL;
 780         } while (argc && !r);
 781
 782         return r;
 783 }
 784
 785 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 786                          char **argv)
 787 {
 788         /* target arguments */
 789         static struct dm_arg _args[] = {
 790                 {0, 1024, "invalid number of priority groups"},
 791                 {0, 1024, "invalid initial priority group number"},
 792         };
 793
 794         int r;
 795         struct multipath *m;
 796         struct dm_arg_set as;
 797         unsigned pg_count = 0;
 798         unsigned next_pg_num;
 799
 800         as.argc = argc;
 801         as.argv = argv;
 802
 803         m = alloc_multipath(ti);
 804         if (!m) {
 805                 ti->error = "can't allocate multipath";
 806                 return -EINVAL;
 807         }
 808
 809         r = parse_features(&as, m);
 810         if (r)
 811                 goto bad;
 812
 813         r = parse_hw_handler(&as, m);
 814         if (r)
 815                 goto bad;
 816
 817         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
 818         if (r)
 819                 goto bad;
 820
 821         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
 822         if (r)
 823                 goto bad;
 824
 825         if ((!m->nr_priority_groups && next_pg_num) ||
 826             (m->nr_priority_groups && !next_pg_num)) {
 827                 ti->error = "invalid initial priority group";
 828                 r = -EINVAL;
 829                 goto bad;
 830         }
 831
 832         /* parse the priority groups */
 833         while (as.argc) {
 834                 struct priority_group *pg;
 835
 836                 pg = parse_priority_group(&as, m);
 837                 if (IS_ERR(pg)) {
 838                         r = PTR_ERR(pg);
 839                         goto bad;
 840                 }
 841
 842                 m->nr_valid_paths += pg->nr_pgpaths;
 843                 list_add_tail(&pg->list, &m->priority_groups);
 844                 pg_count++;
 845                 pg->pg_num = pg_count;
 846                 if (!--next_pg_num)
 847                         m->next_pg = pg;
 848         }
 849
 850         if (pg_count != m->nr_priority_groups) {
 851                 ti->error = "priority group count mismatch";
 852                 r = -EINVAL;
 853                 goto bad;
 854         }
 855
 856         ti->num_flush_requests = 1;
 857         ti->num_discard_requests = 1;
 858
 859         return 0;
 860
 861  bad:
 862         free_multipath(m);
 863         return r;
 864 }
 865
 866 static void multipath_wait_for_pg_init_completion(struct multipath *m)
 867 {
 868         DECLARE_WAITQUEUE(wait, current);
 869         unsigned long flags;
 870
 871         add_wait_queue(&m->pg_init_wait, &wait);
 872
 873         while (1) {
 874                 set_current_state(TASK_UNINTERRUPTIBLE);
 875
 876                 spin_lock_irqsave(&m->lock, flags);
 877                 if (!m->pg_init_in_progress) {
 878                         spin_unlock_irqrestore(&m->lock, flags);
 879                         break;
 880                 }
 881                 spin_unlock_irqrestore(&m->lock, flags);
 882
 883                 io_schedule();
 884         }
 885         set_current_state(TASK_RUNNING);
 886
 887         remove_wait_queue(&m->pg_init_wait, &wait);
 888 }
 889
 890 static void flush_multipath_work(struct multipath *m)
 891 {
 892         unsigned long flags;
 893
 894         spin_lock_irqsave(&m->lock, flags);
 895         m->pg_init_disabled = 1;
 896         spin_unlock_irqrestore(&m->lock, flags);
 897
 898         flush_workqueue(kmpath_handlerd);
 899         multipath_wait_for_pg_init_completion(m);
 900         flush_workqueue(kmultipathd);
 901         flush_work_sync(&m->trigger_event);
 902
 903         spin_lock_irqsave(&m->lock, flags);
 904         m->pg_init_disabled = 0;
 905         spin_unlock_irqrestore(&m->lock, flags);
 906 }
 907
 908 static void multipath_dtr(struct dm_target *ti)
 909 {
 910         struct multipath *m = ti->private;
 911
 912         flush_multipath_work(m);
 913         free_multipath(m);
 914 }
 915
 916 /*
 917  * Map cloned requests
 918  */
 919 static int multipath_map(struct dm_target *ti, struct request *clone,
 920                          union map_info *map_context)
 921 {
 922         int r;
 923         struct dm_mpath_io *mpio;
 924         struct multipath *m = (struct multipath *) ti->private;
 925
 926         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 927         if (!mpio)
 928                 /* ENOMEM, requeue */
 929                 return DM_MAPIO_REQUEUE;
 930         memset(mpio, 0, sizeof(*mpio));
 931
 932         map_context->ptr = mpio;
 933         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 934         r = map_io(m, clone, mpio, 0);
 935         if (r < 0 || r == DM_MAPIO_REQUEUE)
 936                 mempool_free(mpio, m->mpio_pool);
 937
 938         return r;
 939 }
 940
 941 /*
 942  * Take a path out of use.
 943  */
 944 static int fail_path(struct pgpath *pgpath)
 945 {
 946         unsigned long flags;
 947         struct multipath *m = pgpath->pg->m;
 948
 949         spin_lock_irqsave(&m->lock, flags);
 950
 951         if (!pgpath->is_active)
 952                 goto out;
 953
 954         DMWARN("Failing path %s.", pgpath->path.dev->name);
 955
 956         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 957         pgpath->is_active = 0;
 958         pgpath->fail_count++;
 959
 960         m->nr_valid_paths--;
 961
 962         if (pgpath == m->current_pgpath)
 963                 m->current_pgpath = NULL;
 964
 965         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
 966                       pgpath->path.dev->name, m->nr_valid_paths);
 967
 968         schedule_work(&m->trigger_event);
 969
 970 out:
 971         spin_unlock_irqrestore(&m->lock, flags);
 972
 973         return 0;
 974 }
 975
 976 /*
 977  * Reinstate a previously-failed path
 978  */
 979 static int reinstate_path(struct pgpath *pgpath)
 980 {
 981         int r = 0;
 982         unsigned long flags;
 983         struct multipath *m = pgpath->pg->m;
 984
 985         spin_lock_irqsave(&m->lock, flags);
 986
 987         if (pgpath->is_active)
 988                 goto out;
 989
 990         if (!pgpath->pg->ps.type->reinstate_path) {
 991                 DMWARN("Reinstate path not supported by path selector %s",
 992                        pgpath->pg->ps.type->name);
 993                 r = -EINVAL;
 994                 goto out;
 995         }
 996
 997         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
 998         if (r)
 999                 goto out;
1000
1001         pgpath->is_active = 1;
1002
1003         if (!m->nr_valid_paths++ && m->queue_size) {
1004                 m->current_pgpath = NULL;
1005                 queue_work(kmultipathd, &m->process_queued_ios);
1006         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1007                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1008                         m->pg_init_in_progress++;
1009         }
1010
1011         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1012                       pgpath->path.dev->name, m->nr_valid_paths);
1013
1014         schedule_work(&m->trigger_event);
1015
1016 out:
1017         spin_unlock_irqrestore(&m->lock, flags);
1018
1019         return r;
1020 }
1021
1022 /*
1023  * Fail or reinstate all paths that match the provided struct dm_dev.
1024  */
1025 static int action_dev(struct multipath *m, struct dm_dev *dev,
1026                       action_fn action)
1027 {
1028         int r = -EINVAL;
1029         struct pgpath *pgpath;
1030         struct priority_group *pg;
1031
1032         list_for_each_entry(pg, &m->priority_groups, list) {
1033                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1034                         if (pgpath->path.dev == dev)
1035                                 r = action(pgpath);
1036                 }
1037         }
1038
1039         return r;
1040 }
1041
1042 /*
1043  * Temporarily try to avoid having to use the specified PG
1044  */
1045 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1046                       int bypassed)
1047 {
1048         unsigned long flags;
1049
1050         spin_lock_irqsave(&m->lock, flags);
1051
1052         pg->bypassed = bypassed;
1053         m->current_pgpath = NULL;
1054         m->current_pg = NULL;
1055
1056         spin_unlock_irqrestore(&m->lock, flags);
1057
1058         schedule_work(&m->trigger_event);
1059 }
1060
1061 /*
1062  * Switch to using the specified PG from the next I/O that gets mapped
1063  */
1064 static int switch_pg_num(struct multipath *m, const char *pgstr)
1065 {
1066         struct priority_group *pg;
1067         unsigned pgnum;
1068         unsigned long flags;
1069
1070         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1071             (pgnum > m->nr_priority_groups)) {
1072                 DMWARN("invalid PG number supplied to switch_pg_num");
1073                 return -EINVAL;
1074         }
1075
1076         spin_lock_irqsave(&m->lock, flags);
1077         list_for_each_entry(pg, &m->priority_groups, list) {
1078                 pg->bypassed = 0;
1079                 if (--pgnum)
1080                         continue;
1081
1082                 m->current_pgpath = NULL;
1083                 m->current_pg = NULL;
1084                 m->next_pg = pg;
1085         }
1086         spin_unlock_irqrestore(&m->lock, flags);
1087
1088         schedule_work(&m->trigger_event);
1089         return 0;
1090 }
1091
1092 /*
1093  * Set/clear bypassed status of a PG.
1094  * PGs are numbered upwards from 1 in the order they were declared.
1095  */
1096 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1097 {
1098         struct priority_group *pg;
1099         unsigned pgnum;
1100
1101         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1102             (pgnum > m->nr_priority_groups)) {
1103                 DMWARN("invalid PG number supplied to bypass_pg");
1104                 return -EINVAL;
1105         }
1106
1107         list_for_each_entry(pg, &m->priority_groups, list) {
1108                 if (!--pgnum)
1109                         break;
1110         }
1111
1112         bypass_pg(m, pg, bypassed);
1113         return 0;
1114 }
1115
1116 /*
1117  * Should we retry pg_init immediately?
1118  */
1119 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1120 {
1121         unsigned long flags;
1122         int limit_reached = 0;
1123
1124         spin_lock_irqsave(&m->lock, flags);
1125
1126         if (m->pg_init_count <= m->pg_init_retries && !m->pg_init_disabled)
1127                 m->pg_init_required = 1;
1128         else
1129                 limit_reached = 1;
1130
1131         spin_unlock_irqrestore(&m->lock, flags);
1132
1133         return limit_reached;
1134 }
1135
1136 static void pg_init_done(void *data, int errors)
1137 {
1138         struct pgpath *pgpath = data;
1139         struct priority_group *pg = pgpath->pg;
1140         struct multipath *m = pg->m;
1141         unsigned long flags;
1142         unsigned delay_retry = 0;
1143
1144         /* device or driver problems */
1145         switch (errors) {
1146         case SCSI_DH_OK:
1147                 break;
1148         case SCSI_DH_NOSYS:
1149                 if (!m->hw_handler_name) {
1150                         errors = 0;
1151                         break;
1152                 }
1153                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1154                       "Error %d.", m->hw_handler_name, errors);
1155                 /*
1156                  * Fail path for now, so we do not ping pong
1157                  */
1158                 fail_path(pgpath);
1159                 break;
1160         case SCSI_DH_DEV_TEMP_BUSY:
1161                 /*
1162                  * Probably doing something like FW upgrade on the
1163                  * controller so try the other pg.
1164                  */
1165                 bypass_pg(m, pg, 1);
1166                 break;
1167         case SCSI_DH_RETRY:
1168                 /* Wait before retrying. */
1169                 delay_retry = 1;
1170         case SCSI_DH_IMM_RETRY:
1171         case SCSI_DH_RES_TEMP_UNAVAIL:
1172                 if (pg_init_limit_reached(m, pgpath))
1173                         fail_path(pgpath);
1174                 errors = 0;
1175                 break;
1176         default:
1177                 /*
1178                  * We probably do not want to fail the path for a device
1179                  * error, but this is what the old dm did. In future
1180                  * patches we can do more advanced handling.
1181                  */
1182                 fail_path(pgpath);
1183         }
1184
1185         spin_lock_irqsave(&m->lock, flags);
1186         if (errors) {
1187                 if (pgpath == m->current_pgpath) {
1188                         DMERR("Could not failover device. Error %d.", errors);
1189                         m->current_pgpath = NULL;
1190                         m->current_pg = NULL;
1191                 }
1192         } else if (!m->pg_init_required)
1193                 pg->bypassed = 0;
1194
1195         if (--m->pg_init_in_progress)
1196                 /* Activations of other paths are still on going */
1197                 goto out;
1198
1199         if (!m->pg_init_required)
1200                 m->queue_io = 0;
1201
1202         m->pg_init_delay_retry = delay_retry;
1203         queue_work(kmultipathd, &m->process_queued_ios);
1204
1205         /*
1206          * Wake up any thread waiting to suspend.
1207          */
1208         wake_up(&m->pg_init_wait);
1209
1210 out:
1211         spin_unlock_irqrestore(&m->lock, flags);
1212 }
1213
1214 static void activate_path(struct work_struct *work)
1215 {
1216         struct pgpath *pgpath =
1217                 container_of(work, struct pgpath, activate_path.work);
1218
1219         scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1220                                 pg_init_done, pgpath);
1221 }
1222
1223 /*
1224  * end_io handling
1225  */
1226 static int do_end_io(struct multipath *m, struct request *clone,
1227                      int error, struct dm_mpath_io *mpio)
1228 {
1229         /*
1230          * We don't queue any clone request inside the multipath target
1231          * during end I/O handling, since those clone requests don't have
1232          * bio clones.  If we queue them inside the multipath target,
1233          * we need to make bio clones, that requires memory allocation.
1234          * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1235          *  don't have bio clones.)
1236          * Instead of queueing the clone request here, we queue the original
1237          * request into dm core, which will remake a clone request and
1238          * clone bios for it and resubmit it later.
1239          */
1240         int r = DM_ENDIO_REQUEUE;
1241         unsigned long flags;
1242
1243         if (!error && !clone->errors)
1244                 return 0;       /* I/O complete */
1245
1246         if (error == -EOPNOTSUPP || error == -EREMOTEIO || error == -EILSEQ)
1247                 return error;
1248
1249         if (mpio->pgpath)
1250                 fail_path(mpio->pgpath);
1251
1252         spin_lock_irqsave(&m->lock, flags);
1253         if (!m->nr_valid_paths) {
1254                 if (!m->queue_if_no_path) {
1255                         if (!__must_push_back(m))
1256                                 r = -EIO;
1257                 } else {
1258                         if (error == -EBADE)
1259                                 r = error;
1260                 }
1261         }
1262         spin_unlock_irqrestore(&m->lock, flags);
1263
1264         return r;
1265 }
1266
1267 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1268                             int error, union map_info *map_context)
1269 {
1270         struct multipath *m = ti->private;
1271         struct dm_mpath_io *mpio = map_context->ptr;
1272         struct pgpath *pgpath = mpio->pgpath;
1273         struct path_selector *ps;
1274         int r;
1275
1276         r  = do_end_io(m, clone, error, mpio);
1277         if (pgpath) {
1278                 ps = &pgpath->pg->ps;
1279                 if (ps->type->end_io)
1280                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1281         }
1282         mempool_free(mpio, m->mpio_pool);
1283
1284         return r;
1285 }
1286
1287 /*
1288  * Suspend can't complete until all the I/O is processed so if
1289  * the last path fails we must error any remaining I/O.
1290  * Note that if the freeze_bdev fails while suspending, the
1291  * queue_if_no_path state is lost - userspace should reset it.
1292  */
1293 static void multipath_presuspend(struct dm_target *ti)
1294 {
1295         struct multipath *m = (struct multipath *) ti->private;
1296
1297         queue_if_no_path(m, 0, 1);
1298 }
1299
1300 static void multipath_postsuspend(struct dm_target *ti)
1301 {
1302         struct multipath *m = ti->private;
1303
1304         mutex_lock(&m->work_mutex);
1305         flush_multipath_work(m);
1306         mutex_unlock(&m->work_mutex);
1307 }
1308
1309 /*
1310  * Restore the queue_if_no_path setting.
1311  */
1312 static void multipath_resume(struct dm_target *ti)
1313 {
1314         struct multipath *m = (struct multipath *) ti->private;
1315         unsigned long flags;
1316
1317         spin_lock_irqsave(&m->lock, flags);
1318         m->queue_if_no_path = m->saved_queue_if_no_path;
1319         spin_unlock_irqrestore(&m->lock, flags);
1320 }
1321
1322 /*
1323  * Info output has the following format:
1324  * num_multipath_feature_args [multipath_feature_args]*
1325  * num_handler_status_args [handler_status_args]*
1326  * num_groups init_group_number
1327  *            [A|D|E num_ps_status_args [ps_status_args]*
1328  *             num_paths num_selector_args
1329  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1330  *
1331  * Table output has the following format (identical to the constructor string):
1332  * num_feature_args [features_args]*
1333  * num_handler_args hw_handler [hw_handler_args]*
1334  * num_groups init_group_number
1335  *     [priority selector-name num_ps_args [ps_args]*
1336  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1337  */
1338 static void multipath_status(struct dm_target *ti, status_type_t type,
1339                              char *result, unsigned maxlen)
1340 {
1341         int sz = 0;
1342         unsigned long flags;
1343         struct multipath *m = (struct multipath *) ti->private;
1344         struct priority_group *pg;
1345         struct pgpath *p;
1346         unsigned pg_num;
1347         char state;
1348
1349         spin_lock_irqsave(&m->lock, flags);
1350
1351         /* Features */
1352         if (type == STATUSTYPE_INFO)
1353                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1354         else {
1355                 DMEMIT("%u ", m->queue_if_no_path +
1356                               (m->pg_init_retries > 0) * 2 +
1357                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2);
1358                 if (m->queue_if_no_path)
1359                         DMEMIT("queue_if_no_path ");
1360                 if (m->pg_init_retries)
1361                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1362                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1363                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1364         }
1365
1366         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1367                 DMEMIT("0 ");
1368         else
1369                 DMEMIT("1 %s ", m->hw_handler_name);
1370
1371         DMEMIT("%u ", m->nr_priority_groups);
1372
1373         if (m->next_pg)
1374                 pg_num = m->next_pg->pg_num;
1375         else if (m->current_pg)
1376                 pg_num = m->current_pg->pg_num;
1377         else
1378                 pg_num = (m->nr_priority_groups ? 1 : 0);
1379
1380         DMEMIT("%u ", pg_num);
1381
1382         switch (type) {
1383         case STATUSTYPE_INFO:
1384                 list_for_each_entry(pg, &m->priority_groups, list) {
1385                         if (pg->bypassed)
1386                                 state = 'D';    /* Disabled */
1387                         else if (pg == m->current_pg)
1388                                 state = 'A';    /* Currently Active */
1389                         else
1390                                 state = 'E';    /* Enabled */
1391
1392                         DMEMIT("%c ", state);
1393
1394                         if (pg->ps.type->status)
1395                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1396                                                           result + sz,
1397                                                           maxlen - sz);
1398                         else
1399                                 DMEMIT("0 ");
1400
1401                         DMEMIT("%u %u ", pg->nr_pgpaths,
1402                                pg->ps.type->info_args);
1403
1404                         list_for_each_entry(p, &pg->pgpaths, list) {
1405                                 DMEMIT("%s %s %u ", p->path.dev->name,
1406                                        p->is_active ? "A" : "F",
1407                                        p->fail_count);
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         case STATUSTYPE_TABLE:
1417                 list_for_each_entry(pg, &m->priority_groups, list) {
1418                         DMEMIT("%s ", pg->ps.type->name);
1419
1420                         if (pg->ps.type->status)
1421                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1422                                                           result + sz,
1423                                                           maxlen - sz);
1424                         else
1425                                 DMEMIT("0 ");
1426
1427                         DMEMIT("%u %u ", pg->nr_pgpaths,
1428                                pg->ps.type->table_args);
1429
1430                         list_for_each_entry(p, &pg->pgpaths, list) {
1431                                 DMEMIT("%s ", p->path.dev->name);
1432                                 if (pg->ps.type->status)
1433                                         sz += pg->ps.type->status(&pg->ps,
1434                                               &p->path, type, result + sz,
1435                                               maxlen - sz);
1436                         }
1437                 }
1438                 break;
1439         }
1440
1441         spin_unlock_irqrestore(&m->lock, flags);
1442 }
1443
1444 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1445 {
1446         int r = -EINVAL;
1447         struct dm_dev *dev;
1448         struct multipath *m = (struct multipath *) ti->private;
1449         action_fn action;
1450
1451         mutex_lock(&m->work_mutex);
1452
1453         if (dm_suspended(ti)) {
1454                 r = -EBUSY;
1455                 goto out;
1456         }
1457
1458         if (argc == 1) {
1459                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1460                         r = queue_if_no_path(m, 1, 0);
1461                         goto out;
1462                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1463                         r = queue_if_no_path(m, 0, 0);
1464                         goto out;
1465                 }
1466         }
1467
1468         if (argc != 2) {
1469                 DMWARN("Unrecognised multipath message received.");
1470                 goto out;
1471         }
1472
1473         if (!strcasecmp(argv[0], "disable_group")) {
1474                 r = bypass_pg_num(m, argv[1], 1);
1475                 goto out;
1476         } else if (!strcasecmp(argv[0], "enable_group")) {
1477                 r = bypass_pg_num(m, argv[1], 0);
1478                 goto out;
1479         } else if (!strcasecmp(argv[0], "switch_group")) {
1480                 r = switch_pg_num(m, argv[1]);
1481                 goto out;
1482         } else if (!strcasecmp(argv[0], "reinstate_path"))
1483                 action = reinstate_path;
1484         else if (!strcasecmp(argv[0], "fail_path"))
1485                 action = fail_path;
1486         else {
1487                 DMWARN("Unrecognised multipath message received.");
1488                 goto out;
1489         }
1490
1491         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1492         if (r) {
1493                 DMWARN("message: error getting device %s",
1494                        argv[1]);
1495                 goto out;
1496         }
1497
1498         r = action_dev(m, dev, action);
1499
1500         dm_put_device(ti, dev);
1501
1502 out:
1503         mutex_unlock(&m->work_mutex);
1504         return r;
1505 }
1506
1507 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1508                            unsigned long arg)
1509 {
1510         struct multipath *m = (struct multipath *) ti->private;
1511         struct block_device *bdev = NULL;
1512         fmode_t mode = 0;
1513         unsigned long flags;
1514         int r = 0;
1515
1516         spin_lock_irqsave(&m->lock, flags);
1517
1518         if (!m->current_pgpath)
1519                 __choose_pgpath(m, 0);
1520
1521         if (m->current_pgpath) {
1522                 bdev = m->current_pgpath->path.dev->bdev;
1523                 mode = m->current_pgpath->path.dev->mode;
1524         }
1525
1526         if (m->queue_io)
1527                 r = -EAGAIN;
1528         else if (!bdev)
1529                 r = -EIO;
1530
1531         spin_unlock_irqrestore(&m->lock, flags);
1532
1533         /*
1534          * Only pass ioctls through if the device sizes match exactly.
1535          */
1536         if (!r && ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
1537                 r = scsi_verify_blk_ioctl(NULL, cmd);
1538
1539         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1540 }
1541
1542 static int multipath_iterate_devices(struct dm_target *ti,
1543                                      iterate_devices_callout_fn fn, void *data)
1544 {
1545         struct multipath *m = ti->private;
1546         struct priority_group *pg;
1547         struct pgpath *p;
1548         int ret = 0;
1549
1550         list_for_each_entry(pg, &m->priority_groups, list) {
1551                 list_for_each_entry(p, &pg->pgpaths, list) {
1552                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1553                         if (ret)
1554                                 goto out;
1555                 }
1556         }
1557
1558 out:
1559         return ret;
1560 }
1561
1562 static int __pgpath_busy(struct pgpath *pgpath)
1563 {
1564         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1565
1566         return dm_underlying_device_busy(q);
1567 }
1568
1569 /*
1570  * We return "busy", only when we can map I/Os but underlying devices
1571  * are busy (so even if we map I/Os now, the I/Os will wait on
1572  * the underlying queue).
1573  * In other words, if we want to kill I/Os or queue them inside us
1574  * due to map unavailability, we don't return "busy".  Otherwise,
1575  * dm core won't give us the I/Os and we can't do what we want.
1576  */
1577 static int multipath_busy(struct dm_target *ti)
1578 {
1579         int busy = 0, has_active = 0;
1580         struct multipath *m = ti->private;
1581         struct priority_group *pg;
1582         struct pgpath *pgpath;
1583         unsigned long flags;
1584
1585         spin_lock_irqsave(&m->lock, flags);
1586
1587         /* Guess which priority_group will be used at next mapping time */
1588         if (unlikely(!m->current_pgpath && m->next_pg))
1589                 pg = m->next_pg;
1590         else if (likely(m->current_pg))
1591                 pg = m->current_pg;
1592         else
1593                 /*
1594                  * We don't know which pg will be used at next mapping time.
1595                  * We don't call __choose_pgpath() here to avoid to trigger
1596                  * pg_init just by busy checking.
1597                  * So we don't know whether underlying devices we will be using
1598                  * at next mapping time are busy or not. Just try mapping.
1599                  */
1600                 goto out;
1601
1602         /*
1603          * If there is one non-busy active path at least, the path selector
1604          * will be able to select it. So we consider such a pg as not busy.
1605          */
1606         busy = 1;
1607         list_for_each_entry(pgpath, &pg->pgpaths, list)
1608                 if (pgpath->is_active) {
1609                         has_active = 1;
1610
1611                         if (!__pgpath_busy(pgpath)) {
1612                                 busy = 0;
1613                                 break;
1614                         }
1615                 }
1616
1617         if (!has_active)
1618                 /*
1619                  * No active path in this pg, so this pg won't be used and
1620                  * the current_pg will be changed at next mapping time.
1621                  * We need to try mapping to determine it.
1622                  */
1623                 busy = 0;
1624
1625 out:
1626         spin_unlock_irqrestore(&m->lock, flags);
1627
1628         return busy;
1629 }
1630
1631 /*-----------------------------------------------------------------
1632  * Module setup
1633  *---------------------------------------------------------------*/
1634 static struct target_type multipath_target = {
1635         .name = "multipath",
1636         .version = {1, 3, 2},
1637         .module = THIS_MODULE,
1638         .ctr = multipath_ctr,
1639         .dtr = multipath_dtr,
1640         .map_rq = multipath_map,
1641         .rq_end_io = multipath_end_io,
1642         .presuspend = multipath_presuspend,
1643         .postsuspend = multipath_postsuspend,
1644         .resume = multipath_resume,
1645         .status = multipath_status,
1646         .message = multipath_message,
1647         .ioctl  = multipath_ioctl,
1648         .iterate_devices = multipath_iterate_devices,
1649         .busy = multipath_busy,
1650 };
1651
1652 static int __init dm_multipath_init(void)
1653 {
1654         int r;
1655
1656         /* allocate a slab for the dm_ios */
1657         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1658         if (!_mpio_cache)
1659                 return -ENOMEM;
1660
1661         r = dm_register_target(&multipath_target);
1662         if (r < 0) {
1663                 DMERR("register failed %d", r);
1664                 kmem_cache_destroy(_mpio_cache);
1665                 return -EINVAL;
1666         }
1667
1668         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1669         if (!kmultipathd) {
1670                 DMERR("failed to create workqueue kmpathd");
1671                 dm_unregister_target(&multipath_target);
1672                 kmem_cache_destroy(_mpio_cache);
1673                 return -ENOMEM;
1674         }
1675
1676         /*
1677          * A separate workqueue is used to handle the device handlers
1678          * to avoid overloading existing workqueue. Overloading the
1679          * old workqueue would also create a bottleneck in the
1680          * path of the storage hardware device activation.
1681          */
1682         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1683                                                   WQ_MEM_RECLAIM);
1684         if (!kmpath_handlerd) {
1685                 DMERR("failed to create workqueue kmpath_handlerd");
1686                 destroy_workqueue(kmultipathd);
1687                 dm_unregister_target(&multipath_target);
1688                 kmem_cache_destroy(_mpio_cache);
1689                 return -ENOMEM;
1690         }
1691
1692         DMINFO("version %u.%u.%u loaded",
1693                multipath_target.version[0], multipath_target.version[1],
1694                multipath_target.version[2]);
1695
1696         return r;
1697 }
1698
1699 static void __exit dm_multipath_exit(void)
1700 {
1701         destroy_workqueue(kmpath_handlerd);
1702         destroy_workqueue(kmultipathd);
1703
1704         dm_unregister_target(&multipath_target);
1705         kmem_cache_destroy(_mpio_cache);
1706 }
1707
1708 module_init(dm_multipath_init);
1709 module_exit(dm_multipath_exit);
1710
1711 MODULE_DESCRIPTION(DM_NAME " multipath target");
1712 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1713 MODULE_LICENSE("GPL");