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 <linux/delay.h>
  22 #include <scsi/scsi_dh.h>
  23 #include <linux/atomic.h>
  24
  25 #define DM_MSG_PREFIX "multipath"
  26 #define DM_PG_INIT_DELAY_MSECS 2000
  27 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  28
  29 /* Path properties */
  30 struct pgpath {
  31         struct list_head list;
  32
  33         struct priority_group *pg;      /* Owning PG */
  34         unsigned is_active;             /* Path status */
  35         unsigned fail_count;            /* Cumulative failure count */
  36
  37         struct dm_path path;
  38         struct delayed_work activate_path;
  39 };
  40
  41 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  42
  43 /*
  44  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  45  * Each has a path selector which controls which path gets used.
  46  */
  47 struct priority_group {
  48         struct list_head list;
  49
  50         struct multipath *m;            /* Owning multipath instance */
  51         struct path_selector ps;
  52
  53         unsigned pg_num;                /* Reference number */
  54         unsigned bypassed;              /* Temporarily bypass this PG? */
  55
  56         unsigned nr_pgpaths;            /* Number of paths in PG */
  57         struct list_head pgpaths;
  58 };
  59
  60 /* Multipath context */
  61 struct multipath {
  62         struct list_head list;
  63         struct dm_target *ti;
  64
  65         const char *hw_handler_name;
  66         char *hw_handler_params;
  67
  68         spinlock_t lock;
  69
  70         unsigned nr_priority_groups;
  71         struct list_head priority_groups;
  72
  73         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  74
  75         unsigned pg_init_required;      /* pg_init needs calling? */
  76         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  77         unsigned pg_init_delay_retry;   /* Delay pg_init retry? */
  78
  79         unsigned nr_valid_paths;        /* Total number of usable paths */
  80         struct pgpath *current_pgpath;
  81         struct priority_group *current_pg;
  82         struct priority_group *next_pg; /* Switch to this PG if set */
  83         unsigned repeat_count;          /* I/Os left before calling PS again */
  84
  85         unsigned queue_io:1;            /* Must we queue all I/O? */
  86         unsigned queue_if_no_path:1;    /* Queue I/O if last path fails? */
  87         unsigned saved_queue_if_no_path:1; /* Saved state during suspension */
  88         unsigned retain_attached_hw_handler:1; /* If there's already a hw_handler present, don't change it. */
  89
  90         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  91         unsigned pg_init_count;         /* Number of times pg_init called */
  92         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  93
  94         unsigned queue_size;
  95         struct work_struct process_queued_ios;
  96         struct list_head queued_ios;
  97
  98         struct work_struct trigger_event;
  99
 100         /*
 101          * We must use a mempool of dm_mpath_io structs so that we
 102          * can resubmit bios on error.
 103          */
 104         mempool_t *mpio_pool;
 105
 106         struct mutex work_mutex;
 107 };
 108
 109 /*
 110  * Context information attached to each bio we process.
 111  */
 112 struct dm_mpath_io {
 113         struct pgpath *pgpath;
 114         size_t nr_bytes;
 115 };
 116
 117 typedef int (*action_fn) (struct pgpath *pgpath);
 118
 119 #define MIN_IOS 256     /* Mempool size */
 120
 121 static struct kmem_cache *_mpio_cache;
 122
 123 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 124 static void process_queued_ios(struct work_struct *work);
 125 static void trigger_event(struct work_struct *work);
 126 static void activate_path(struct work_struct *work);
 127
 128
 129 /*-----------------------------------------------
 130  * Allocation routines
 131  *-----------------------------------------------*/
 132
 133 static struct pgpath *alloc_pgpath(void)
 134 {
 135         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 136
 137         if (pgpath) {
 138                 pgpath->is_active = 1;
 139                 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);
 140         }
 141
 142         return pgpath;
 143 }
 144
 145 static void free_pgpath(struct pgpath *pgpath)
 146 {
 147         kfree(pgpath);
 148 }
 149
 150 static struct priority_group *alloc_priority_group(void)
 151 {
 152         struct priority_group *pg;
 153
 154         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 155
 156         if (pg)
 157                 INIT_LIST_HEAD(&pg->pgpaths);
 158
 159         return pg;
 160 }
 161
 162 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 163 {
 164         struct pgpath *pgpath, *tmp;
 165         struct multipath *m = ti->private;
 166
 167         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 168                 list_del(&pgpath->list);
 169                 if (m->hw_handler_name)
 170                         scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 171                 dm_put_device(ti, pgpath->path.dev);
 172                 free_pgpath(pgpath);
 173         }
 174 }
 175
 176 static void free_priority_group(struct priority_group *pg,
 177                                 struct dm_target *ti)
 178 {
 179         struct path_selector *ps = &pg->ps;
 180
 181         if (ps->type) {
 182                 ps->type->destroy(ps);
 183                 dm_put_path_selector(ps->type);
 184         }
 185
 186         free_pgpaths(&pg->pgpaths, ti);
 187         kfree(pg);
 188 }
 189
 190 static struct multipath *alloc_multipath(struct dm_target *ti)
 191 {
 192         struct multipath *m;
 193
 194         m = kzalloc(sizeof(*m), GFP_KERNEL);
 195         if (m) {
 196                 INIT_LIST_HEAD(&m->priority_groups);
 197                 INIT_LIST_HEAD(&m->queued_ios);
 198                 spin_lock_init(&m->lock);
 199                 m->queue_io = 1;
 200                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 201                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
 202                 INIT_WORK(&m->trigger_event, trigger_event);
 203                 init_waitqueue_head(&m->pg_init_wait);
 204                 mutex_init(&m->work_mutex);
 205                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 206                 if (!m->mpio_pool) {
 207                         kfree(m);
 208                         return NULL;
 209                 }
 210                 m->ti = ti;
 211                 ti->private = m;
 212         }
 213
 214         return m;
 215 }
 216
 217 static void free_multipath(struct multipath *m)
 218 {
 219         struct priority_group *pg, *tmp;
 220
 221         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 222                 list_del(&pg->list);
 223                 free_priority_group(pg, m->ti);
 224         }
 225
 226         kfree(m->hw_handler_name);
 227         kfree(m->hw_handler_params);
 228         mempool_destroy(m->mpio_pool);
 229         kfree(m);
 230 }
 231
 232 static int set_mapinfo(struct multipath *m, union map_info *info)
 233 {
 234         struct dm_mpath_io *mpio;
 235
 236         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 237         if (!mpio)
 238                 return -ENOMEM;
 239
 240         memset(mpio, 0, sizeof(*mpio));
 241         info->ptr = mpio;
 242
 243         return 0;
 244 }
 245
 246 static void clear_mapinfo(struct multipath *m, union map_info *info)
 247 {
 248         struct dm_mpath_io *mpio = info->ptr;
 249
 250         info->ptr = NULL;
 251         mempool_free(mpio, m->mpio_pool);
 252 }
 253
 254 /*-----------------------------------------------
 255  * Path selection
 256  *-----------------------------------------------*/
 257
 258 static void __pg_init_all_paths(struct multipath *m)
 259 {
 260         struct pgpath *pgpath;
 261         unsigned long pg_init_delay = 0;
 262
 263         m->pg_init_count++;
 264         m->pg_init_required = 0;
 265         if (m->pg_init_delay_retry)
 266                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 267                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 268         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 269                 /* Skip failed paths */
 270                 if (!pgpath->is_active)
 271                         continue;
 272                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 273                                        pg_init_delay))
 274                         m->pg_init_in_progress++;
 275         }
 276 }
 277
 278 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 279 {
 280         m->current_pg = pgpath->pg;
 281
 282         /* Must we initialise the PG first, and queue I/O till it's ready? */
 283         if (m->hw_handler_name) {
 284                 m->pg_init_required = 1;
 285                 m->queue_io = 1;
 286         } else {
 287                 m->pg_init_required = 0;
 288                 m->queue_io = 0;
 289         }
 290
 291         m->pg_init_count = 0;
 292 }
 293
 294 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 295                                size_t nr_bytes)
 296 {
 297         struct dm_path *path;
 298
 299         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 300         if (!path)
 301                 return -ENXIO;
 302
 303         m->current_pgpath = path_to_pgpath(path);
 304
 305         if (m->current_pg != pg)
 306                 __switch_pg(m, m->current_pgpath);
 307
 308         return 0;
 309 }
 310
 311 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 312 {
 313         struct priority_group *pg;
 314         unsigned bypassed = 1;
 315
 316         if (!m->nr_valid_paths)
 317                 goto failed;
 318
 319         /* Were we instructed to switch PG? */
 320         if (m->next_pg) {
 321                 pg = m->next_pg;
 322                 m->next_pg = NULL;
 323                 if (!__choose_path_in_pg(m, pg, nr_bytes))
 324                         return;
 325         }
 326
 327         /* Don't change PG until it has no remaining paths */
 328         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 329                 return;
 330
 331         /*
 332          * Loop through priority groups until we find a valid path.
 333          * First time we skip PGs marked 'bypassed'.
 334          * Second time we only try the ones we skipped, but set
 335          * pg_init_delay_retry so we do not hammer controllers.
 336          */
 337         do {
 338                 list_for_each_entry(pg, &m->priority_groups, list) {
 339                         if (pg->bypassed == bypassed)
 340                                 continue;
 341                         if (!__choose_path_in_pg(m, pg, nr_bytes)) {
 342                                 if (!bypassed)
 343                                         m->pg_init_delay_retry = 1;
 344                                 return;
 345                         }
 346                 }
 347         } while (bypassed--);
 348
 349 failed:
 350         m->current_pgpath = NULL;
 351         m->current_pg = NULL;
 352 }
 353
 354 /*
 355  * Check whether bios must be queued in the device-mapper core rather
 356  * than here in the target.
 357  *
 358  * m->lock must be held on entry.
 359  *
 360  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 361  * same value then we are not between multipath_presuspend()
 362  * and multipath_resume() calls and we have no need to check
 363  * for the DMF_NOFLUSH_SUSPENDING flag.
 364  */
 365 static int __must_push_back(struct multipath *m)
 366 {
 367         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 368                 dm_noflush_suspending(m->ti));
 369 }
 370
 371 static int map_io(struct multipath *m, struct request *clone,
 372                   union map_info *map_context, unsigned was_queued)
 373 {
 374         int r = DM_MAPIO_REMAPPED;
 375         size_t nr_bytes = blk_rq_bytes(clone);
 376         unsigned long flags;
 377         struct pgpath *pgpath;
 378         struct block_device *bdev;
 379         struct dm_mpath_io *mpio = map_context->ptr;
 380
 381         spin_lock_irqsave(&m->lock, flags);
 382
 383         /* Do we need to select a new pgpath? */
 384         if (!m->current_pgpath ||
 385             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 386                 __choose_pgpath(m, nr_bytes);
 387
 388         pgpath = m->current_pgpath;
 389
 390         if (was_queued)
 391                 m->queue_size--;
 392
 393         if ((pgpath && m->queue_io) ||
 394             (!pgpath && m->queue_if_no_path)) {
 395                 /* Queue for the daemon to resubmit */
 396                 list_add_tail(&clone->queuelist, &m->queued_ios);
 397                 m->queue_size++;
 398                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 399                     !m->queue_io)
 400                         queue_work(kmultipathd, &m->process_queued_ios);
 401                 pgpath = NULL;
 402                 r = DM_MAPIO_SUBMITTED;
 403         } else if (pgpath) {
 404                 bdev = pgpath->path.dev->bdev;
 405                 clone->q = bdev_get_queue(bdev);
 406                 clone->rq_disk = bdev->bd_disk;
 407         } else if (__must_push_back(m))
 408                 r = DM_MAPIO_REQUEUE;
 409         else
 410                 r = -EIO;       /* Failed */
 411
 412         mpio->pgpath = pgpath;
 413         mpio->nr_bytes = nr_bytes;
 414
 415         if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
 416                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path,
 417                                               nr_bytes);
 418
 419         spin_unlock_irqrestore(&m->lock, flags);
 420
 421         return r;
 422 }
 423
 424 /*
 425  * If we run out of usable paths, should we queue I/O or error it?
 426  */
 427 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 428                             unsigned save_old_value)
 429 {
 430         unsigned long flags;
 431
 432         spin_lock_irqsave(&m->lock, flags);
 433
 434         if (save_old_value)
 435                 m->saved_queue_if_no_path = m->queue_if_no_path;
 436         else
 437                 m->saved_queue_if_no_path = queue_if_no_path;
 438         m->queue_if_no_path = queue_if_no_path;
 439         if (!m->queue_if_no_path && m->queue_size)
 440                 queue_work(kmultipathd, &m->process_queued_ios);
 441
 442         spin_unlock_irqrestore(&m->lock, flags);
 443
 444         return 0;
 445 }
 446
 447 /*-----------------------------------------------------------------
 448  * The multipath daemon is responsible for resubmitting queued ios.
 449  *---------------------------------------------------------------*/
 450
 451 static void dispatch_queued_ios(struct multipath *m)
 452 {
 453         int r;
 454         unsigned long flags;
 455         union map_info *info;
 456         struct request *clone, *n;
 457         LIST_HEAD(cl);
 458
 459         spin_lock_irqsave(&m->lock, flags);
 460         list_splice_init(&m->queued_ios, &cl);
 461         spin_unlock_irqrestore(&m->lock, flags);
 462
 463         list_for_each_entry_safe(clone, n, &cl, queuelist) {
 464                 list_del_init(&clone->queuelist);
 465
 466                 info = dm_get_rq_mapinfo(clone);
 467
 468                 r = map_io(m, clone, info, 1);
 469                 if (r < 0) {
 470                         clear_mapinfo(m, info);
 471                         dm_kill_unmapped_request(clone, r);
 472                 } else if (r == DM_MAPIO_REMAPPED)
 473                         dm_dispatch_request(clone);
 474                 else if (r == DM_MAPIO_REQUEUE) {
 475                         clear_mapinfo(m, info);
 476                         dm_requeue_unmapped_request(clone);
 477                 }
 478         }
 479 }
 480
 481 static void process_queued_ios(struct work_struct *work)
 482 {
 483         struct multipath *m =
 484                 container_of(work, struct multipath, process_queued_ios);
 485         struct pgpath *pgpath = NULL;
 486         unsigned must_queue = 1;
 487         unsigned long flags;
 488
 489         spin_lock_irqsave(&m->lock, flags);
 490
 491         if (!m->current_pgpath)
 492                 __choose_pgpath(m, 0);
 493
 494         pgpath = m->current_pgpath;
 495
 496         if ((pgpath && !m->queue_io) ||
 497             (!pgpath && !m->queue_if_no_path))
 498                 must_queue = 0;
 499
 500         if (m->pg_init_required && !m->pg_init_in_progress && pgpath)
 501                 __pg_init_all_paths(m);
 502
 503         spin_unlock_irqrestore(&m->lock, flags);
 504         if (!must_queue)
 505                 dispatch_queued_ios(m);
 506 }
 507
 508 /*
 509  * An event is triggered whenever a path is taken out of use.
 510  * Includes path failure and PG bypass.
 511  */
 512 static void trigger_event(struct work_struct *work)
 513 {
 514         struct multipath *m =
 515                 container_of(work, struct multipath, trigger_event);
 516
 517         dm_table_event(m->ti->table);
 518 }
 519
 520 /*-----------------------------------------------------------------
 521  * Constructor/argument parsing:
 522  * <#multipath feature args> [<arg>]*
 523  * <#hw_handler args> [hw_handler [<arg>]*]
 524  * <#priority groups>
 525  * <initial priority group>
 526  *     [<selector> <#selector args> [<arg>]*
 527  *      <#paths> <#per-path selector args>
 528  *         [<path> [<arg>]* ]+ ]+
 529  *---------------------------------------------------------------*/
 530 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 531                                struct dm_target *ti)
 532 {
 533         int r;
 534         struct path_selector_type *pst;
 535         unsigned ps_argc;
 536
 537         static struct dm_arg _args[] = {
 538                 {0, 1024, "invalid number of path selector args"},
 539         };
 540
 541         pst = dm_get_path_selector(dm_shift_arg(as));
 542         if (!pst) {
 543                 ti->error = "unknown path selector type";
 544                 return -EINVAL;
 545         }
 546
 547         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 548         if (r) {
 549                 dm_put_path_selector(pst);
 550                 return -EINVAL;
 551         }
 552
 553         r = pst->create(&pg->ps, ps_argc, as->argv);
 554         if (r) {
 555                 dm_put_path_selector(pst);
 556                 ti->error = "path selector constructor failed";
 557                 return r;
 558         }
 559
 560         pg->ps.type = pst;
 561         dm_consume_args(as, ps_argc);
 562
 563         return 0;
 564 }
 565
 566 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 567                                struct dm_target *ti)
 568 {
 569         int r;
 570         struct pgpath *p;
 571         struct multipath *m = ti->private;
 572         struct request_queue *q = NULL;
 573         const char *attached_handler_name;
 574
 575         /* we need at least a path arg */
 576         if (as->argc < 1) {
 577                 ti->error = "no device given";
 578                 return ERR_PTR(-EINVAL);
 579         }
 580
 581         p = alloc_pgpath();
 582         if (!p)
 583                 return ERR_PTR(-ENOMEM);
 584
 585         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 586                           &p->path.dev);
 587         if (r) {
 588                 ti->error = "error getting device";
 589                 goto bad;
 590         }
 591
 592         if (m->retain_attached_hw_handler || m->hw_handler_name)
 593                 q = bdev_get_queue(p->path.dev->bdev);
 594
 595         if (m->retain_attached_hw_handler) {
 596                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 597                 if (attached_handler_name) {
 598                         /*
 599                          * Reset hw_handler_name to match the attached handler
 600                          * and clear any hw_handler_params associated with the
 601                          * ignored handler.
 602                          *
 603                          * NB. This modifies the table line to show the actual
 604                          * handler instead of the original table passed in.
 605                          */
 606                         kfree(m->hw_handler_name);
 607                         m->hw_handler_name = attached_handler_name;
 608
 609                         kfree(m->hw_handler_params);
 610                         m->hw_handler_params = NULL;
 611                 }
 612         }
 613
 614         if (m->hw_handler_name) {
 615                 /*
 616                  * Increments scsi_dh reference, even when using an
 617                  * already-attached handler.
 618                  */
 619                 r = scsi_dh_attach(q, m->hw_handler_name);
 620                 if (r == -EBUSY) {
 621                         /*
 622                          * Already attached to different hw_handler:
 623                          * try to reattach with correct one.
 624                          */
 625                         scsi_dh_detach(q);
 626                         r = scsi_dh_attach(q, m->hw_handler_name);
 627                 }
 628
 629                 if (r < 0) {
 630                         ti->error = "error attaching hardware handler";
 631                         dm_put_device(ti, p->path.dev);
 632                         goto bad;
 633                 }
 634
 635                 if (m->hw_handler_params) {
 636                         r = scsi_dh_set_params(q, m->hw_handler_params);
 637                         if (r < 0) {
 638                                 ti->error = "unable to set hardware "
 639                                                         "handler parameters";
 640                                 scsi_dh_detach(q);
 641                                 dm_put_device(ti, p->path.dev);
 642                                 goto bad;
 643                         }
 644                 }
 645         }
 646
 647         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 648         if (r) {
 649                 dm_put_device(ti, p->path.dev);
 650                 goto bad;
 651         }
 652
 653         return p;
 654
 655  bad:
 656         free_pgpath(p);
 657         return ERR_PTR(r);
 658 }
 659
 660 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 661                                                    struct multipath *m)
 662 {
 663         static struct dm_arg _args[] = {
 664                 {1, 1024, "invalid number of paths"},
 665                 {0, 1024, "invalid number of selector args"}
 666         };
 667
 668         int r;
 669         unsigned i, nr_selector_args, nr_args;
 670         struct priority_group *pg;
 671         struct dm_target *ti = m->ti;
 672
 673         if (as->argc < 2) {
 674                 as->argc = 0;
 675                 ti->error = "not enough priority group arguments";
 676                 return ERR_PTR(-EINVAL);
 677         }
 678
 679         pg = alloc_priority_group();
 680         if (!pg) {
 681                 ti->error = "couldn't allocate priority group";
 682                 return ERR_PTR(-ENOMEM);
 683         }
 684         pg->m = m;
 685
 686         r = parse_path_selector(as, pg, ti);
 687         if (r)
 688                 goto bad;
 689
 690         /*
 691          * read the paths
 692          */
 693         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 694         if (r)
 695                 goto bad;
 696
 697         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 698         if (r)
 699                 goto bad;
 700
 701         nr_args = 1 + nr_selector_args;
 702         for (i = 0; i < pg->nr_pgpaths; i++) {
 703                 struct pgpath *pgpath;
 704                 struct dm_arg_set path_args;
 705
 706                 if (as->argc < nr_args) {
 707                         ti->error = "not enough path parameters";
 708                         r = -EINVAL;
 709                         goto bad;
 710                 }
 711
 712                 path_args.argc = nr_args;
 713                 path_args.argv = as->argv;
 714
 715                 pgpath = parse_path(&path_args, &pg->ps, ti);
 716                 if (IS_ERR(pgpath)) {
 717                         r = PTR_ERR(pgpath);
 718                         goto bad;
 719                 }
 720
 721                 pgpath->pg = pg;
 722                 list_add_tail(&pgpath->list, &pg->pgpaths);
 723                 dm_consume_args(as, nr_args);
 724         }
 725
 726         return pg;
 727
 728  bad:
 729         free_priority_group(pg, ti);
 730         return ERR_PTR(r);
 731 }
 732
 733 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 734 {
 735         unsigned hw_argc;
 736         int ret;
 737         struct dm_target *ti = m->ti;
 738
 739         static struct dm_arg _args[] = {
 740                 {0, 1024, "invalid number of hardware handler args"},
 741         };
 742
 743         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 744                 return -EINVAL;
 745
 746         if (!hw_argc)
 747                 return 0;
 748
 749         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 750         if (!try_then_request_module(scsi_dh_handler_exist(m->hw_handler_name),
 751                                      "scsi_dh_%s", m->hw_handler_name)) {
 752                 ti->error = "unknown hardware handler type";
 753                 ret = -EINVAL;
 754                 goto fail;
 755         }
 756
 757         if (hw_argc > 1) {
 758                 char *p;
 759                 int i, j, len = 4;
 760
 761                 for (i = 0; i <= hw_argc - 2; i++)
 762                         len += strlen(as->argv[i]) + 1;
 763                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 764                 if (!p) {
 765                         ti->error = "memory allocation failed";
 766                         ret = -ENOMEM;
 767                         goto fail;
 768                 }
 769                 j = sprintf(p, "%d", hw_argc - 1);
 770                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 771                         j = sprintf(p, "%s", as->argv[i]);
 772         }
 773         dm_consume_args(as, hw_argc - 1);
 774
 775         return 0;
 776 fail:
 777         kfree(m->hw_handler_name);
 778         m->hw_handler_name = NULL;
 779         return ret;
 780 }
 781
 782 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 783 {
 784         int r;
 785         unsigned argc;
 786         struct dm_target *ti = m->ti;
 787         const char *arg_name;
 788
 789         static struct dm_arg _args[] = {
 790                 {0, 6, "invalid number of feature args"},
 791                 {1, 50, "pg_init_retries must be between 1 and 50"},
 792                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 793         };
 794
 795         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 796         if (r)
 797                 return -EINVAL;
 798
 799         if (!argc)
 800                 return 0;
 801
 802         do {
 803                 arg_name = dm_shift_arg(as);
 804                 argc--;
 805
 806                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 807                         r = queue_if_no_path(m, 1, 0);
 808                         continue;
 809                 }
 810
 811                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
 812                         m->retain_attached_hw_handler = 1;
 813                         continue;
 814                 }
 815
 816                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 817                     (argc >= 1)) {
 818                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
 819                         argc--;
 820                         continue;
 821                 }
 822
 823                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
 824                     (argc >= 1)) {
 825                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
 826                         argc--;
 827                         continue;
 828                 }
 829
 830                 ti->error = "Unrecognised multipath feature request";
 831                 r = -EINVAL;
 832         } while (argc && !r);
 833
 834         return r;
 835 }
 836
 837 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 838                          char **argv)
 839 {
 840         /* target arguments */
 841         static struct dm_arg _args[] = {
 842                 {0, 1024, "invalid number of priority groups"},
 843                 {0, 1024, "invalid initial priority group number"},
 844         };
 845
 846         int r;
 847         struct multipath *m;
 848         struct dm_arg_set as;
 849         unsigned pg_count = 0;
 850         unsigned next_pg_num;
 851
 852         as.argc = argc;
 853         as.argv = argv;
 854
 855         m = alloc_multipath(ti);
 856         if (!m) {
 857                 ti->error = "can't allocate multipath";
 858                 return -EINVAL;
 859         }
 860
 861         r = parse_features(&as, m);
 862         if (r)
 863                 goto bad;
 864
 865         r = parse_hw_handler(&as, m);
 866         if (r)
 867                 goto bad;
 868
 869         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
 870         if (r)
 871                 goto bad;
 872
 873         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
 874         if (r)
 875                 goto bad;
 876
 877         if ((!m->nr_priority_groups && next_pg_num) ||
 878             (m->nr_priority_groups && !next_pg_num)) {
 879                 ti->error = "invalid initial priority group";
 880                 r = -EINVAL;
 881                 goto bad;
 882         }
 883
 884         /* parse the priority groups */
 885         while (as.argc) {
 886                 struct priority_group *pg;
 887
 888                 pg = parse_priority_group(&as, m);
 889                 if (IS_ERR(pg)) {
 890                         r = PTR_ERR(pg);
 891                         goto bad;
 892                 }
 893
 894                 m->nr_valid_paths += pg->nr_pgpaths;
 895                 list_add_tail(&pg->list, &m->priority_groups);
 896                 pg_count++;
 897                 pg->pg_num = pg_count;
 898                 if (!--next_pg_num)
 899                         m->next_pg = pg;
 900         }
 901
 902         if (pg_count != m->nr_priority_groups) {
 903                 ti->error = "priority group count mismatch";
 904                 r = -EINVAL;
 905                 goto bad;
 906         }
 907
 908         ti->num_flush_requests = 1;
 909         ti->num_discard_requests = 1;
 910
 911         return 0;
 912
 913  bad:
 914         free_multipath(m);
 915         return r;
 916 }
 917
 918 static void multipath_wait_for_pg_init_completion(struct multipath *m)
 919 {
 920         DECLARE_WAITQUEUE(wait, current);
 921         unsigned long flags;
 922
 923         add_wait_queue(&m->pg_init_wait, &wait);
 924
 925         while (1) {
 926                 set_current_state(TASK_UNINTERRUPTIBLE);
 927
 928                 spin_lock_irqsave(&m->lock, flags);
 929                 if (!m->pg_init_in_progress) {
 930                         spin_unlock_irqrestore(&m->lock, flags);
 931                         break;
 932                 }
 933                 spin_unlock_irqrestore(&m->lock, flags);
 934
 935                 io_schedule();
 936         }
 937         set_current_state(TASK_RUNNING);
 938
 939         remove_wait_queue(&m->pg_init_wait, &wait);
 940 }
 941
 942 static void flush_multipath_work(struct multipath *m)
 943 {
 944         flush_workqueue(kmpath_handlerd);
 945         multipath_wait_for_pg_init_completion(m);
 946         flush_workqueue(kmultipathd);
 947         flush_work_sync(&m->trigger_event);
 948 }
 949
 950 static void multipath_dtr(struct dm_target *ti)
 951 {
 952         struct multipath *m = ti->private;
 953
 954         flush_multipath_work(m);
 955         free_multipath(m);
 956 }
 957
 958 /*
 959  * Map cloned requests
 960  */
 961 static int multipath_map(struct dm_target *ti, struct request *clone,
 962                          union map_info *map_context)
 963 {
 964         int r;
 965         struct multipath *m = (struct multipath *) ti->private;
 966
 967         if (set_mapinfo(m, map_context) < 0)
 968                 /* ENOMEM, requeue */
 969                 return DM_MAPIO_REQUEUE;
 970
 971         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 972         r = map_io(m, clone, map_context, 0);
 973         if (r < 0 || r == DM_MAPIO_REQUEUE)
 974                 clear_mapinfo(m, map_context);
 975
 976         return r;
 977 }
 978
 979 /*
 980  * Take a path out of use.
 981  */
 982 static int fail_path(struct pgpath *pgpath)
 983 {
 984         unsigned long flags;
 985         struct multipath *m = pgpath->pg->m;
 986
 987         spin_lock_irqsave(&m->lock, flags);
 988
 989         if (!pgpath->is_active)
 990                 goto out;
 991
 992         DMWARN("Failing path %s.", pgpath->path.dev->name);
 993
 994         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 995         pgpath->is_active = 0;
 996         pgpath->fail_count++;
 997
 998         m->nr_valid_paths--;
 999
1000         if (pgpath == m->current_pgpath)
1001                 m->current_pgpath = NULL;
1002
1003         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1004                       pgpath->path.dev->name, m->nr_valid_paths);
1005
1006         schedule_work(&m->trigger_event);
1007
1008 out:
1009         spin_unlock_irqrestore(&m->lock, flags);
1010
1011         return 0;
1012 }
1013
1014 /*
1015  * Reinstate a previously-failed path
1016  */
1017 static int reinstate_path(struct pgpath *pgpath)
1018 {
1019         int r = 0;
1020         unsigned long flags;
1021         struct multipath *m = pgpath->pg->m;
1022
1023         spin_lock_irqsave(&m->lock, flags);
1024
1025         if (pgpath->is_active)
1026                 goto out;
1027
1028         if (!pgpath->pg->ps.type->reinstate_path) {
1029                 DMWARN("Reinstate path not supported by path selector %s",
1030                        pgpath->pg->ps.type->name);
1031                 r = -EINVAL;
1032                 goto out;
1033         }
1034
1035         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1036         if (r)
1037                 goto out;
1038
1039         pgpath->is_active = 1;
1040
1041         if (!m->nr_valid_paths++ && m->queue_size) {
1042                 m->current_pgpath = NULL;
1043                 queue_work(kmultipathd, &m->process_queued_ios);
1044         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1045                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1046                         m->pg_init_in_progress++;
1047         }
1048
1049         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1050                       pgpath->path.dev->name, m->nr_valid_paths);
1051
1052         schedule_work(&m->trigger_event);
1053
1054 out:
1055         spin_unlock_irqrestore(&m->lock, flags);
1056
1057         return r;
1058 }
1059
1060 /*
1061  * Fail or reinstate all paths that match the provided struct dm_dev.
1062  */
1063 static int action_dev(struct multipath *m, struct dm_dev *dev,
1064                       action_fn action)
1065 {
1066         int r = -EINVAL;
1067         struct pgpath *pgpath;
1068         struct priority_group *pg;
1069
1070         list_for_each_entry(pg, &m->priority_groups, list) {
1071                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1072                         if (pgpath->path.dev == dev)
1073                                 r = action(pgpath);
1074                 }
1075         }
1076
1077         return r;
1078 }
1079
1080 /*
1081  * Temporarily try to avoid having to use the specified PG
1082  */
1083 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1084                       int bypassed)
1085 {
1086         unsigned long flags;
1087
1088         spin_lock_irqsave(&m->lock, flags);
1089
1090         pg->bypassed = bypassed;
1091         m->current_pgpath = NULL;
1092         m->current_pg = NULL;
1093
1094         spin_unlock_irqrestore(&m->lock, flags);
1095
1096         schedule_work(&m->trigger_event);
1097 }
1098
1099 /*
1100  * Switch to using the specified PG from the next I/O that gets mapped
1101  */
1102 static int switch_pg_num(struct multipath *m, const char *pgstr)
1103 {
1104         struct priority_group *pg;
1105         unsigned pgnum;
1106         unsigned long flags;
1107         char dummy;
1108
1109         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1110             (pgnum > m->nr_priority_groups)) {
1111                 DMWARN("invalid PG number supplied to switch_pg_num");
1112                 return -EINVAL;
1113         }
1114
1115         spin_lock_irqsave(&m->lock, flags);
1116         list_for_each_entry(pg, &m->priority_groups, list) {
1117                 pg->bypassed = 0;
1118                 if (--pgnum)
1119                         continue;
1120
1121                 m->current_pgpath = NULL;
1122                 m->current_pg = NULL;
1123                 m->next_pg = pg;
1124         }
1125         spin_unlock_irqrestore(&m->lock, flags);
1126
1127         schedule_work(&m->trigger_event);
1128         return 0;
1129 }
1130
1131 /*
1132  * Set/clear bypassed status of a PG.
1133  * PGs are numbered upwards from 1 in the order they were declared.
1134  */
1135 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1136 {
1137         struct priority_group *pg;
1138         unsigned pgnum;
1139         char dummy;
1140
1141         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1142             (pgnum > m->nr_priority_groups)) {
1143                 DMWARN("invalid PG number supplied to bypass_pg");
1144                 return -EINVAL;
1145         }
1146
1147         list_for_each_entry(pg, &m->priority_groups, list) {
1148                 if (!--pgnum)
1149                         break;
1150         }
1151
1152         bypass_pg(m, pg, bypassed);
1153         return 0;
1154 }
1155
1156 /*
1157  * Should we retry pg_init immediately?
1158  */
1159 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1160 {
1161         unsigned long flags;
1162         int limit_reached = 0;
1163
1164         spin_lock_irqsave(&m->lock, flags);
1165
1166         if (m->pg_init_count <= m->pg_init_retries)
1167                 m->pg_init_required = 1;
1168         else
1169                 limit_reached = 1;
1170
1171         spin_unlock_irqrestore(&m->lock, flags);
1172
1173         return limit_reached;
1174 }
1175
1176 static void pg_init_done(void *data, int errors)
1177 {
1178         struct pgpath *pgpath = data;
1179         struct priority_group *pg = pgpath->pg;
1180         struct multipath *m = pg->m;
1181         unsigned long flags;
1182         unsigned delay_retry = 0;
1183
1184         /* device or driver problems */
1185         switch (errors) {
1186         case SCSI_DH_OK:
1187                 break;
1188         case SCSI_DH_NOSYS:
1189                 if (!m->hw_handler_name) {
1190                         errors = 0;
1191                         break;
1192                 }
1193                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1194                       "Error %d.", m->hw_handler_name, errors);
1195                 /*
1196                  * Fail path for now, so we do not ping pong
1197                  */
1198                 fail_path(pgpath);
1199                 break;
1200         case SCSI_DH_DEV_TEMP_BUSY:
1201                 /*
1202                  * Probably doing something like FW upgrade on the
1203                  * controller so try the other pg.
1204                  */
1205                 bypass_pg(m, pg, 1);
1206                 break;
1207         case SCSI_DH_RETRY:
1208                 /* Wait before retrying. */
1209                 delay_retry = 1;
1210         case SCSI_DH_IMM_RETRY:
1211         case SCSI_DH_RES_TEMP_UNAVAIL:
1212                 if (pg_init_limit_reached(m, pgpath))
1213                         fail_path(pgpath);
1214                 errors = 0;
1215                 break;
1216         default:
1217                 /*
1218                  * We probably do not want to fail the path for a device
1219                  * error, but this is what the old dm did. In future
1220                  * patches we can do more advanced handling.
1221                  */
1222                 fail_path(pgpath);
1223         }
1224
1225         spin_lock_irqsave(&m->lock, flags);
1226         if (errors) {
1227                 if (pgpath == m->current_pgpath) {
1228                         DMERR("Could not failover device. Error %d.", errors);
1229                         m->current_pgpath = NULL;
1230                         m->current_pg = NULL;
1231                 }
1232         } else if (!m->pg_init_required)
1233                 pg->bypassed = 0;
1234
1235         if (--m->pg_init_in_progress)
1236                 /* Activations of other paths are still on going */
1237                 goto out;
1238
1239         if (!m->pg_init_required)
1240                 m->queue_io = 0;
1241
1242         m->pg_init_delay_retry = delay_retry;
1243         queue_work(kmultipathd, &m->process_queued_ios);
1244
1245         /*
1246          * Wake up any thread waiting to suspend.
1247          */
1248         wake_up(&m->pg_init_wait);
1249
1250 out:
1251         spin_unlock_irqrestore(&m->lock, flags);
1252 }
1253
1254 static void activate_path(struct work_struct *work)
1255 {
1256         struct pgpath *pgpath =
1257                 container_of(work, struct pgpath, activate_path.work);
1258
1259         scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1260                                 pg_init_done, pgpath);
1261 }
1262
1263 /*
1264  * end_io handling
1265  */
1266 static int do_end_io(struct multipath *m, struct request *clone,
1267                      int error, struct dm_mpath_io *mpio)
1268 {
1269         /*
1270          * We don't queue any clone request inside the multipath target
1271          * during end I/O handling, since those clone requests don't have
1272          * bio clones.  If we queue them inside the multipath target,
1273          * we need to make bio clones, that requires memory allocation.
1274          * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1275          *  don't have bio clones.)
1276          * Instead of queueing the clone request here, we queue the original
1277          * request into dm core, which will remake a clone request and
1278          * clone bios for it and resubmit it later.
1279          */
1280         int r = DM_ENDIO_REQUEUE;
1281         unsigned long flags;
1282
1283         if (!error && !clone->errors)
1284                 return 0;       /* I/O complete */
1285
1286         if (error == -EOPNOTSUPP || error == -EREMOTEIO || error == -EILSEQ)
1287                 return error;
1288
1289         if (mpio->pgpath)
1290                 fail_path(mpio->pgpath);
1291
1292         spin_lock_irqsave(&m->lock, flags);
1293         if (!m->nr_valid_paths) {
1294                 if (!m->queue_if_no_path) {
1295                         if (!__must_push_back(m))
1296                                 r = -EIO;
1297                 } else {
1298                         if (error == -EBADE)
1299                                 r = error;
1300                 }
1301         }
1302         spin_unlock_irqrestore(&m->lock, flags);
1303
1304         return r;
1305 }
1306
1307 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1308                             int error, union map_info *map_context)
1309 {
1310         struct multipath *m = ti->private;
1311         struct dm_mpath_io *mpio = map_context->ptr;
1312         struct pgpath *pgpath = mpio->pgpath;
1313         struct path_selector *ps;
1314         int r;
1315
1316         BUG_ON(!mpio);
1317
1318         r  = do_end_io(m, clone, error, mpio);
1319         if (pgpath) {
1320                 ps = &pgpath->pg->ps;
1321                 if (ps->type->end_io)
1322                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1323         }
1324         clear_mapinfo(m, map_context);
1325
1326         return r;
1327 }
1328
1329 /*
1330  * Suspend can't complete until all the I/O is processed so if
1331  * the last path fails we must error any remaining I/O.
1332  * Note that if the freeze_bdev fails while suspending, the
1333  * queue_if_no_path state is lost - userspace should reset it.
1334  */
1335 static void multipath_presuspend(struct dm_target *ti)
1336 {
1337         struct multipath *m = (struct multipath *) ti->private;
1338
1339         queue_if_no_path(m, 0, 1);
1340 }
1341
1342 static void multipath_postsuspend(struct dm_target *ti)
1343 {
1344         struct multipath *m = ti->private;
1345
1346         mutex_lock(&m->work_mutex);
1347         flush_multipath_work(m);
1348         mutex_unlock(&m->work_mutex);
1349 }
1350
1351 /*
1352  * Restore the queue_if_no_path setting.
1353  */
1354 static void multipath_resume(struct dm_target *ti)
1355 {
1356         struct multipath *m = (struct multipath *) ti->private;
1357         unsigned long flags;
1358
1359         spin_lock_irqsave(&m->lock, flags);
1360         m->queue_if_no_path = m->saved_queue_if_no_path;
1361         spin_unlock_irqrestore(&m->lock, flags);
1362 }
1363
1364 /*
1365  * Info output has the following format:
1366  * num_multipath_feature_args [multipath_feature_args]*
1367  * num_handler_status_args [handler_status_args]*
1368  * num_groups init_group_number
1369  *            [A|D|E num_ps_status_args [ps_status_args]*
1370  *             num_paths num_selector_args
1371  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1372  *
1373  * Table output has the following format (identical to the constructor string):
1374  * num_feature_args [features_args]*
1375  * num_handler_args hw_handler [hw_handler_args]*
1376  * num_groups init_group_number
1377  *     [priority selector-name num_ps_args [ps_args]*
1378  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1379  */
1380 static int multipath_status(struct dm_target *ti, status_type_t type,
1381                             unsigned status_flags, char *result, unsigned maxlen)
1382 {
1383         int sz = 0;
1384         unsigned long flags;
1385         struct multipath *m = (struct multipath *) ti->private;
1386         struct priority_group *pg;
1387         struct pgpath *p;
1388         unsigned pg_num;
1389         char state;
1390
1391         spin_lock_irqsave(&m->lock, flags);
1392
1393         /* Features */
1394         if (type == STATUSTYPE_INFO)
1395                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1396         else {
1397                 DMEMIT("%u ", m->queue_if_no_path +
1398                               (m->pg_init_retries > 0) * 2 +
1399                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1400                               m->retain_attached_hw_handler);
1401                 if (m->queue_if_no_path)
1402                         DMEMIT("queue_if_no_path ");
1403                 if (m->pg_init_retries)
1404                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1405                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1406                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1407                 if (m->retain_attached_hw_handler)
1408                         DMEMIT("retain_attached_hw_handler ");
1409         }
1410
1411         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1412                 DMEMIT("0 ");
1413         else
1414                 DMEMIT("1 %s ", m->hw_handler_name);
1415
1416         DMEMIT("%u ", m->nr_priority_groups);
1417
1418         if (m->next_pg)
1419                 pg_num = m->next_pg->pg_num;
1420         else if (m->current_pg)
1421                 pg_num = m->current_pg->pg_num;
1422         else
1423                 pg_num = (m->nr_priority_groups ? 1 : 0);
1424
1425         DMEMIT("%u ", pg_num);
1426
1427         switch (type) {
1428         case STATUSTYPE_INFO:
1429                 list_for_each_entry(pg, &m->priority_groups, list) {
1430                         if (pg->bypassed)
1431                                 state = 'D';    /* Disabled */
1432                         else if (pg == m->current_pg)
1433                                 state = 'A';    /* Currently Active */
1434                         else
1435                                 state = 'E';    /* Enabled */
1436
1437                         DMEMIT("%c ", state);
1438
1439                         if (pg->ps.type->status)
1440                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1441                                                           result + sz,
1442                                                           maxlen - sz);
1443                         else
1444                                 DMEMIT("0 ");
1445
1446                         DMEMIT("%u %u ", pg->nr_pgpaths,
1447                                pg->ps.type->info_args);
1448
1449                         list_for_each_entry(p, &pg->pgpaths, list) {
1450                                 DMEMIT("%s %s %u ", p->path.dev->name,
1451                                        p->is_active ? "A" : "F",
1452                                        p->fail_count);
1453                                 if (pg->ps.type->status)
1454                                         sz += pg->ps.type->status(&pg->ps,
1455                                               &p->path, type, result + sz,
1456                                               maxlen - sz);
1457                         }
1458                 }
1459                 break;
1460
1461         case STATUSTYPE_TABLE:
1462                 list_for_each_entry(pg, &m->priority_groups, list) {
1463                         DMEMIT("%s ", pg->ps.type->name);
1464
1465                         if (pg->ps.type->status)
1466                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1467                                                           result + sz,
1468                                                           maxlen - sz);
1469                         else
1470                                 DMEMIT("0 ");
1471
1472                         DMEMIT("%u %u ", pg->nr_pgpaths,
1473                                pg->ps.type->table_args);
1474
1475                         list_for_each_entry(p, &pg->pgpaths, list) {
1476                                 DMEMIT("%s ", p->path.dev->name);
1477                                 if (pg->ps.type->status)
1478                                         sz += pg->ps.type->status(&pg->ps,
1479                                               &p->path, type, result + sz,
1480                                               maxlen - sz);
1481                         }
1482                 }
1483                 break;
1484         }
1485
1486         spin_unlock_irqrestore(&m->lock, flags);
1487
1488         return 0;
1489 }
1490
1491 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1492 {
1493         int r = -EINVAL;
1494         struct dm_dev *dev;
1495         struct multipath *m = (struct multipath *) ti->private;
1496         action_fn action;
1497
1498         mutex_lock(&m->work_mutex);
1499
1500         if (dm_suspended(ti)) {
1501                 r = -EBUSY;
1502                 goto out;
1503         }
1504
1505         if (argc == 1) {
1506                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1507                         r = queue_if_no_path(m, 1, 0);
1508                         goto out;
1509                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1510                         r = queue_if_no_path(m, 0, 0);
1511                         goto out;
1512                 }
1513         }
1514
1515         if (argc != 2) {
1516                 DMWARN("Unrecognised multipath message received.");
1517                 goto out;
1518         }
1519
1520         if (!strcasecmp(argv[0], "disable_group")) {
1521                 r = bypass_pg_num(m, argv[1], 1);
1522                 goto out;
1523         } else if (!strcasecmp(argv[0], "enable_group")) {
1524                 r = bypass_pg_num(m, argv[1], 0);
1525                 goto out;
1526         } else if (!strcasecmp(argv[0], "switch_group")) {
1527                 r = switch_pg_num(m, argv[1]);
1528                 goto out;
1529         } else if (!strcasecmp(argv[0], "reinstate_path"))
1530                 action = reinstate_path;
1531         else if (!strcasecmp(argv[0], "fail_path"))
1532                 action = fail_path;
1533         else {
1534                 DMWARN("Unrecognised multipath message received.");
1535                 goto out;
1536         }
1537
1538         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1539         if (r) {
1540                 DMWARN("message: error getting device %s",
1541                        argv[1]);
1542                 goto out;
1543         }
1544
1545         r = action_dev(m, dev, action);
1546
1547         dm_put_device(ti, dev);
1548
1549 out:
1550         mutex_unlock(&m->work_mutex);
1551         return r;
1552 }
1553
1554 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1555                            unsigned long arg)
1556 {
1557         struct multipath *m = ti->private;
1558         struct block_device *bdev;
1559         fmode_t mode;
1560         unsigned long flags;
1561         int r;
1562
1563 again:
1564         bdev = NULL;
1565         mode = 0;
1566         r = 0;
1567
1568         spin_lock_irqsave(&m->lock, flags);
1569
1570         if (!m->current_pgpath)
1571                 __choose_pgpath(m, 0);
1572
1573         if (m->current_pgpath) {
1574                 bdev = m->current_pgpath->path.dev->bdev;
1575                 mode = m->current_pgpath->path.dev->mode;
1576         }
1577
1578         if (m->queue_io)
1579                 r = -EAGAIN;
1580         else if (!bdev)
1581                 r = -EIO;
1582
1583         spin_unlock_irqrestore(&m->lock, flags);
1584
1585         /*
1586          * Only pass ioctls through if the device sizes match exactly.
1587          */
1588         if (!r && ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
1589                 r = scsi_verify_blk_ioctl(NULL, cmd);
1590
1591         if (r == -EAGAIN && !fatal_signal_pending(current)) {
1592                 queue_work(kmultipathd, &m->process_queued_ios);
1593                 msleep(10);
1594                 goto again;
1595         }
1596
1597         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1598 }
1599
1600 static int multipath_iterate_devices(struct dm_target *ti,
1601                                      iterate_devices_callout_fn fn, void *data)
1602 {
1603         struct multipath *m = ti->private;
1604         struct priority_group *pg;
1605         struct pgpath *p;
1606         int ret = 0;
1607
1608         list_for_each_entry(pg, &m->priority_groups, list) {
1609                 list_for_each_entry(p, &pg->pgpaths, list) {
1610                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1611                         if (ret)
1612                                 goto out;
1613                 }
1614         }
1615
1616 out:
1617         return ret;
1618 }
1619
1620 static int __pgpath_busy(struct pgpath *pgpath)
1621 {
1622         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1623
1624         return dm_underlying_device_busy(q);
1625 }
1626
1627 /*
1628  * We return "busy", only when we can map I/Os but underlying devices
1629  * are busy (so even if we map I/Os now, the I/Os will wait on
1630  * the underlying queue).
1631  * In other words, if we want to kill I/Os or queue them inside us
1632  * due to map unavailability, we don't return "busy".  Otherwise,
1633  * dm core won't give us the I/Os and we can't do what we want.
1634  */
1635 static int multipath_busy(struct dm_target *ti)
1636 {
1637         int busy = 0, has_active = 0;
1638         struct multipath *m = ti->private;
1639         struct priority_group *pg;
1640         struct pgpath *pgpath;
1641         unsigned long flags;
1642
1643         spin_lock_irqsave(&m->lock, flags);
1644
1645         /* Guess which priority_group will be used at next mapping time */
1646         if (unlikely(!m->current_pgpath && m->next_pg))
1647                 pg = m->next_pg;
1648         else if (likely(m->current_pg))
1649                 pg = m->current_pg;
1650         else
1651                 /*
1652                  * We don't know which pg will be used at next mapping time.
1653                  * We don't call __choose_pgpath() here to avoid to trigger
1654                  * pg_init just by busy checking.
1655                  * So we don't know whether underlying devices we will be using
1656                  * at next mapping time are busy or not. Just try mapping.
1657                  */
1658                 goto out;
1659
1660         /*
1661          * If there is one non-busy active path at least, the path selector
1662          * will be able to select it. So we consider such a pg as not busy.
1663          */
1664         busy = 1;
1665         list_for_each_entry(pgpath, &pg->pgpaths, list)
1666                 if (pgpath->is_active) {
1667                         has_active = 1;
1668
1669                         if (!__pgpath_busy(pgpath)) {
1670                                 busy = 0;
1671                                 break;
1672                         }
1673                 }
1674
1675         if (!has_active)
1676                 /*
1677                  * No active path in this pg, so this pg won't be used and
1678                  * the current_pg will be changed at next mapping time.
1679                  * We need to try mapping to determine it.
1680                  */
1681                 busy = 0;
1682
1683 out:
1684         spin_unlock_irqrestore(&m->lock, flags);
1685
1686         return busy;
1687 }
1688
1689 /*-----------------------------------------------------------------
1690  * Module setup
1691  *---------------------------------------------------------------*/
1692 static struct target_type multipath_target = {
1693         .name = "multipath",
1694         .version = {1, 5, 0},
1695         .module = THIS_MODULE,
1696         .ctr = multipath_ctr,
1697         .dtr = multipath_dtr,
1698         .map_rq = multipath_map,
1699         .rq_end_io = multipath_end_io,
1700         .presuspend = multipath_presuspend,
1701         .postsuspend = multipath_postsuspend,
1702         .resume = multipath_resume,
1703         .status = multipath_status,
1704         .message = multipath_message,
1705         .ioctl  = multipath_ioctl,
1706         .iterate_devices = multipath_iterate_devices,
1707         .busy = multipath_busy,
1708 };
1709
1710 static int __init dm_multipath_init(void)
1711 {
1712         int r;
1713
1714         /* allocate a slab for the dm_ios */
1715         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1716         if (!_mpio_cache)
1717                 return -ENOMEM;
1718
1719         r = dm_register_target(&multipath_target);
1720         if (r < 0) {
1721                 DMERR("register failed %d", r);
1722                 kmem_cache_destroy(_mpio_cache);
1723                 return -EINVAL;
1724         }
1725
1726         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1727         if (!kmultipathd) {
1728                 DMERR("failed to create workqueue kmpathd");
1729                 dm_unregister_target(&multipath_target);
1730                 kmem_cache_destroy(_mpio_cache);
1731                 return -ENOMEM;
1732         }
1733
1734         /*
1735          * A separate workqueue is used to handle the device handlers
1736          * to avoid overloading existing workqueue. Overloading the
1737          * old workqueue would also create a bottleneck in the
1738          * path of the storage hardware device activation.
1739          */
1740         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1741                                                   WQ_MEM_RECLAIM);
1742         if (!kmpath_handlerd) {
1743                 DMERR("failed to create workqueue kmpath_handlerd");
1744                 destroy_workqueue(kmultipathd);
1745                 dm_unregister_target(&multipath_target);
1746                 kmem_cache_destroy(_mpio_cache);
1747                 return -ENOMEM;
1748         }
1749
1750         DMINFO("version %u.%u.%u loaded",
1751                multipath_target.version[0], multipath_target.version[1],
1752                multipath_target.version[2]);
1753
1754         return r;
1755 }
1756
1757 static void __exit dm_multipath_exit(void)
1758 {
1759         destroy_workqueue(kmpath_handlerd);
1760         destroy_workqueue(kmultipathd);
1761
1762         dm_unregister_target(&multipath_target);
1763         kmem_cache_destroy(_mpio_cache);
1764 }
1765
1766 module_init(dm_multipath_init);
1767 module_exit(dm_multipath_exit);
1768
1769 MODULE_DESCRIPTION(DM_NAME " multipath target");
1770 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1771 MODULE_LICENSE("GPL");