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 "dm.h"
   9 #include "dm-path-selector.h"
  10 #include "dm-hw-handler.h"
  11 #include "dm-bio-list.h"
  12 #include "dm-bio-record.h"
  13
  14 #include <linux/ctype.h>
  15 #include <linux/init.h>
  16 #include <linux/mempool.h>
  17 #include <linux/module.h>
  18 #include <linux/pagemap.h>
  19 #include <linux/slab.h>
  20 #include <linux/time.h>
  21 #include <linux/workqueue.h>
  22 #include <asm/atomic.h>
  23
  24 #define DM_MSG_PREFIX "multipath"
  25 #define MESG_STR(x) x, sizeof(x)
  26
  27 /* Path properties */
  28 struct pgpath {
  29         struct list_head list;
  30
  31         struct priority_group *pg;      /* Owning PG */
  32         unsigned fail_count;            /* Cumulative failure count */
  33
  34         struct dm_path path;
  35 };
  36
  37 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  38
  39 /*
  40  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  41  * Each has a path selector which controls which path gets used.
  42  */
  43 struct priority_group {
  44         struct list_head list;
  45
  46         struct multipath *m;            /* Owning multipath instance */
  47         struct path_selector ps;
  48
  49         unsigned pg_num;                /* Reference number */
  50         unsigned bypassed;              /* Temporarily bypass this PG? */
  51
  52         unsigned nr_pgpaths;            /* Number of paths in PG */
  53         struct list_head pgpaths;
  54 };
  55
  56 /* Multipath context */
  57 struct multipath {
  58         struct list_head list;
  59         struct dm_target *ti;
  60
  61         spinlock_t lock;
  62
  63         struct hw_handler hw_handler;
  64         unsigned nr_priority_groups;
  65         struct list_head priority_groups;
  66         unsigned pg_init_required;      /* pg_init needs calling? */
  67         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  68
  69         unsigned nr_valid_paths;        /* Total number of usable paths */
  70         struct pgpath *current_pgpath;
  71         struct priority_group *current_pg;
  72         struct priority_group *next_pg; /* Switch to this PG if set */
  73         unsigned repeat_count;          /* I/Os left before calling PS again */
  74
  75         unsigned queue_io;              /* Must we queue all I/O? */
  76         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
  77         unsigned saved_queue_if_no_path;/* Saved state during suspension */
  78
  79         struct work_struct process_queued_ios;
  80         struct bio_list queued_ios;
  81         unsigned queue_size;
  82
  83         struct work_struct trigger_event;
  84
  85         /*
  86          * We must use a mempool of mpath_io structs so that we
  87          * can resubmit bios on error.
  88          */
  89         mempool_t *mpio_pool;
  90 };
  91
  92 /*
  93  * Context information attached to each bio we process.
  94  */
  95 struct mpath_io {
  96         struct pgpath *pgpath;
  97         struct dm_bio_details details;
  98 };
  99
 100 typedef int (*action_fn) (struct pgpath *pgpath);
 101
 102 #define MIN_IOS 256     /* Mempool size */
 103
 104 static struct kmem_cache *_mpio_cache;
 105
 106 struct workqueue_struct *kmultipathd;
 107 static void process_queued_ios(struct work_struct *work);
 108 static void trigger_event(struct work_struct *work);
 109
 110
 111 /*-----------------------------------------------
 112  * Allocation routines
 113  *-----------------------------------------------*/
 114
 115 static struct pgpath *alloc_pgpath(void)
 116 {
 117         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 118
 119         if (pgpath)
 120                 pgpath->path.is_active = 1;
 121
 122         return pgpath;
 123 }
 124
 125 static inline void free_pgpath(struct pgpath *pgpath)
 126 {
 127         kfree(pgpath);
 128 }
 129
 130 static struct priority_group *alloc_priority_group(void)
 131 {
 132         struct priority_group *pg;
 133
 134         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 135
 136         if (pg)
 137                 INIT_LIST_HEAD(&pg->pgpaths);
 138
 139         return pg;
 140 }
 141
 142 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 143 {
 144         struct pgpath *pgpath, *tmp;
 145
 146         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 147                 list_del(&pgpath->list);
 148                 dm_put_device(ti, pgpath->path.dev);
 149                 free_pgpath(pgpath);
 150         }
 151 }
 152
 153 static void free_priority_group(struct priority_group *pg,
 154                                 struct dm_target *ti)
 155 {
 156         struct path_selector *ps = &pg->ps;
 157
 158         if (ps->type) {
 159                 ps->type->destroy(ps);
 160                 dm_put_path_selector(ps->type);
 161         }
 162
 163         free_pgpaths(&pg->pgpaths, ti);
 164         kfree(pg);
 165 }
 166
 167 static struct multipath *alloc_multipath(struct dm_target *ti)
 168 {
 169         struct multipath *m;
 170
 171         m = kzalloc(sizeof(*m), GFP_KERNEL);
 172         if (m) {
 173                 INIT_LIST_HEAD(&m->priority_groups);
 174                 spin_lock_init(&m->lock);
 175                 m->queue_io = 1;
 176                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
 177                 INIT_WORK(&m->trigger_event, trigger_event);
 178                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 179                 if (!m->mpio_pool) {
 180                         kfree(m);
 181                         return NULL;
 182                 }
 183                 m->ti = ti;
 184                 ti->private = m;
 185         }
 186
 187         return m;
 188 }
 189
 190 static void free_multipath(struct multipath *m)
 191 {
 192         struct priority_group *pg, *tmp;
 193         struct hw_handler *hwh = &m->hw_handler;
 194
 195         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 196                 list_del(&pg->list);
 197                 free_priority_group(pg, m->ti);
 198         }
 199
 200         if (hwh->type) {
 201                 hwh->type->destroy(hwh);
 202                 dm_put_hw_handler(hwh->type);
 203         }
 204
 205         mempool_destroy(m->mpio_pool);
 206         kfree(m);
 207 }
 208
 209
 210 /*-----------------------------------------------
 211  * Path selection
 212  *-----------------------------------------------*/
 213
 214 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 215 {
 216         struct hw_handler *hwh = &m->hw_handler;
 217
 218         m->current_pg = pgpath->pg;
 219
 220         /* Must we initialise the PG first, and queue I/O till it's ready? */
 221         if (hwh->type && hwh->type->pg_init) {
 222                 m->pg_init_required = 1;
 223                 m->queue_io = 1;
 224         } else {
 225                 m->pg_init_required = 0;
 226                 m->queue_io = 0;
 227         }
 228 }
 229
 230 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg)
 231 {
 232         struct dm_path *path;
 233
 234         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count);
 235         if (!path)
 236                 return -ENXIO;
 237
 238         m->current_pgpath = path_to_pgpath(path);
 239
 240         if (m->current_pg != pg)
 241                 __switch_pg(m, m->current_pgpath);
 242
 243         return 0;
 244 }
 245
 246 static void __choose_pgpath(struct multipath *m)
 247 {
 248         struct priority_group *pg;
 249         unsigned bypassed = 1;
 250
 251         if (!m->nr_valid_paths)
 252                 goto failed;
 253
 254         /* Were we instructed to switch PG? */
 255         if (m->next_pg) {
 256                 pg = m->next_pg;
 257                 m->next_pg = NULL;
 258                 if (!__choose_path_in_pg(m, pg))
 259                         return;
 260         }
 261
 262         /* Don't change PG until it has no remaining paths */
 263         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg))
 264                 return;
 265
 266         /*
 267          * Loop through priority groups until we find a valid path.
 268          * First time we skip PGs marked 'bypassed'.
 269          * Second time we only try the ones we skipped.
 270          */
 271         do {
 272                 list_for_each_entry(pg, &m->priority_groups, list) {
 273                         if (pg->bypassed == bypassed)
 274                                 continue;
 275                         if (!__choose_path_in_pg(m, pg))
 276                                 return;
 277                 }
 278         } while (bypassed--);
 279
 280 failed:
 281         m->current_pgpath = NULL;
 282         m->current_pg = NULL;
 283 }
 284
 285 /*
 286  * Check whether bios must be queued in the device-mapper core rather
 287  * than here in the target.
 288  *
 289  * m->lock must be held on entry.
 290  *
 291  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 292  * same value then we are not between multipath_presuspend()
 293  * and multipath_resume() calls and we have no need to check
 294  * for the DMF_NOFLUSH_SUSPENDING flag.
 295  */
 296 static int __must_push_back(struct multipath *m)
 297 {
 298         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 299                 dm_noflush_suspending(m->ti));
 300 }
 301
 302 static int map_io(struct multipath *m, struct bio *bio, struct mpath_io *mpio,
 303                   unsigned was_queued)
 304 {
 305         int r = DM_MAPIO_REMAPPED;
 306         unsigned long flags;
 307         struct pgpath *pgpath;
 308
 309         spin_lock_irqsave(&m->lock, flags);
 310
 311         /* Do we need to select a new pgpath? */
 312         if (!m->current_pgpath ||
 313             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 314                 __choose_pgpath(m);
 315
 316         pgpath = m->current_pgpath;
 317
 318         if (was_queued)
 319                 m->queue_size--;
 320
 321         if ((pgpath && m->queue_io) ||
 322             (!pgpath && m->queue_if_no_path)) {
 323                 /* Queue for the daemon to resubmit */
 324                 bio_list_add(&m->queued_ios, bio);
 325                 m->queue_size++;
 326                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 327                     !m->queue_io)
 328                         queue_work(kmultipathd, &m->process_queued_ios);
 329                 pgpath = NULL;
 330                 r = DM_MAPIO_SUBMITTED;
 331         } else if (pgpath)
 332                 bio->bi_bdev = pgpath->path.dev->bdev;
 333         else if (__must_push_back(m))
 334                 r = DM_MAPIO_REQUEUE;
 335         else
 336                 r = -EIO;       /* Failed */
 337
 338         mpio->pgpath = pgpath;
 339
 340         spin_unlock_irqrestore(&m->lock, flags);
 341
 342         return r;
 343 }
 344
 345 /*
 346  * If we run out of usable paths, should we queue I/O or error it?
 347  */
 348 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 349                             unsigned save_old_value)
 350 {
 351         unsigned long flags;
 352
 353         spin_lock_irqsave(&m->lock, flags);
 354
 355         if (save_old_value)
 356                 m->saved_queue_if_no_path = m->queue_if_no_path;
 357         else
 358                 m->saved_queue_if_no_path = queue_if_no_path;
 359         m->queue_if_no_path = queue_if_no_path;
 360         if (!m->queue_if_no_path && m->queue_size)
 361                 queue_work(kmultipathd, &m->process_queued_ios);
 362
 363         spin_unlock_irqrestore(&m->lock, flags);
 364
 365         return 0;
 366 }
 367
 368 /*-----------------------------------------------------------------
 369  * The multipath daemon is responsible for resubmitting queued ios.
 370  *---------------------------------------------------------------*/
 371
 372 static void dispatch_queued_ios(struct multipath *m)
 373 {
 374         int r;
 375         unsigned long flags;
 376         struct bio *bio = NULL, *next;
 377         struct mpath_io *mpio;
 378         union map_info *info;
 379
 380         spin_lock_irqsave(&m->lock, flags);
 381         bio = bio_list_get(&m->queued_ios);
 382         spin_unlock_irqrestore(&m->lock, flags);
 383
 384         while (bio) {
 385                 next = bio->bi_next;
 386                 bio->bi_next = NULL;
 387
 388                 info = dm_get_mapinfo(bio);
 389                 mpio = info->ptr;
 390
 391                 r = map_io(m, bio, mpio, 1);
 392                 if (r < 0)
 393                         bio_endio(bio, bio->bi_size, r);
 394                 else if (r == DM_MAPIO_REMAPPED)
 395                         generic_make_request(bio);
 396                 else if (r == DM_MAPIO_REQUEUE)
 397                         bio_endio(bio, bio->bi_size, -EIO);
 398
 399                 bio = next;
 400         }
 401 }
 402
 403 static void process_queued_ios(struct work_struct *work)
 404 {
 405         struct multipath *m =
 406                 container_of(work, struct multipath, process_queued_ios);
 407         struct hw_handler *hwh = &m->hw_handler;
 408         struct pgpath *pgpath = NULL;
 409         unsigned init_required = 0, must_queue = 1;
 410         unsigned long flags;
 411
 412         spin_lock_irqsave(&m->lock, flags);
 413
 414         if (!m->queue_size)
 415                 goto out;
 416
 417         if (!m->current_pgpath)
 418                 __choose_pgpath(m);
 419
 420         pgpath = m->current_pgpath;
 421
 422         if ((pgpath && !m->queue_io) ||
 423             (!pgpath && !m->queue_if_no_path))
 424                 must_queue = 0;
 425
 426         if (m->pg_init_required && !m->pg_init_in_progress) {
 427                 m->pg_init_required = 0;
 428                 m->pg_init_in_progress = 1;
 429                 init_required = 1;
 430         }
 431
 432 out:
 433         spin_unlock_irqrestore(&m->lock, flags);
 434
 435         if (init_required)
 436                 hwh->type->pg_init(hwh, pgpath->pg->bypassed, &pgpath->path);
 437
 438         if (!must_queue)
 439                 dispatch_queued_ios(m);
 440 }
 441
 442 /*
 443  * An event is triggered whenever a path is taken out of use.
 444  * Includes path failure and PG bypass.
 445  */
 446 static void trigger_event(struct work_struct *work)
 447 {
 448         struct multipath *m =
 449                 container_of(work, struct multipath, trigger_event);
 450
 451         dm_table_event(m->ti->table);
 452 }
 453
 454 /*-----------------------------------------------------------------
 455  * Constructor/argument parsing:
 456  * <#multipath feature args> [<arg>]*
 457  * <#hw_handler args> [hw_handler [<arg>]*]
 458  * <#priority groups>
 459  * <initial priority group>
 460  *     [<selector> <#selector args> [<arg>]*
 461  *      <#paths> <#per-path selector args>
 462  *         [<path> [<arg>]* ]+ ]+
 463  *---------------------------------------------------------------*/
 464 struct param {
 465         unsigned min;
 466         unsigned max;
 467         char *error;
 468 };
 469
 470 static int read_param(struct param *param, char *str, unsigned *v, char **error)
 471 {
 472         if (!str ||
 473             (sscanf(str, "%u", v) != 1) ||
 474             (*v < param->min) ||
 475             (*v > param->max)) {
 476                 *error = param->error;
 477                 return -EINVAL;
 478         }
 479
 480         return 0;
 481 }
 482
 483 struct arg_set {
 484         unsigned argc;
 485         char **argv;
 486 };
 487
 488 static char *shift(struct arg_set *as)
 489 {
 490         char *r;
 491
 492         if (as->argc) {
 493                 as->argc--;
 494                 r = *as->argv;
 495                 as->argv++;
 496                 return r;
 497         }
 498
 499         return NULL;
 500 }
 501
 502 static void consume(struct arg_set *as, unsigned n)
 503 {
 504         BUG_ON (as->argc < n);
 505         as->argc -= n;
 506         as->argv += n;
 507 }
 508
 509 static int parse_path_selector(struct 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 param _params[] = {
 517                 {0, 1024, "invalid number of path selector args"},
 518         };
 519
 520         pst = dm_get_path_selector(shift(as));
 521         if (!pst) {
 522                 ti->error = "unknown path selector type";
 523                 return -EINVAL;
 524         }
 525
 526         r = read_param(_params, shift(as), &ps_argc, &ti->error);
 527         if (r)
 528                 return -EINVAL;
 529
 530         r = pst->create(&pg->ps, ps_argc, as->argv);
 531         if (r) {
 532                 dm_put_path_selector(pst);
 533                 ti->error = "path selector constructor failed";
 534                 return r;
 535         }
 536
 537         pg->ps.type = pst;
 538         consume(as, ps_argc);
 539
 540         return 0;
 541 }
 542
 543 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
 544                                struct dm_target *ti)
 545 {
 546         int r;
 547         struct pgpath *p;
 548
 549         /* we need at least a path arg */
 550         if (as->argc < 1) {
 551                 ti->error = "no device given";
 552                 return NULL;
 553         }
 554
 555         p = alloc_pgpath();
 556         if (!p)
 557                 return NULL;
 558
 559         r = dm_get_device(ti, shift(as), ti->begin, ti->len,
 560                           dm_table_get_mode(ti->table), &p->path.dev);
 561         if (r) {
 562                 ti->error = "error getting device";
 563                 goto bad;
 564         }
 565
 566         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 567         if (r) {
 568                 dm_put_device(ti, p->path.dev);
 569                 goto bad;
 570         }
 571
 572         return p;
 573
 574  bad:
 575         free_pgpath(p);
 576         return NULL;
 577 }
 578
 579 static struct priority_group *parse_priority_group(struct arg_set *as,
 580                                                    struct multipath *m)
 581 {
 582         static struct param _params[] = {
 583                 {1, 1024, "invalid number of paths"},
 584                 {0, 1024, "invalid number of selector args"}
 585         };
 586
 587         int r;
 588         unsigned i, nr_selector_args, nr_params;
 589         struct priority_group *pg;
 590         struct dm_target *ti = m->ti;
 591
 592         if (as->argc < 2) {
 593                 as->argc = 0;
 594                 ti->error = "not enough priority group aruments";
 595                 return NULL;
 596         }
 597
 598         pg = alloc_priority_group();
 599         if (!pg) {
 600                 ti->error = "couldn't allocate priority group";
 601                 return NULL;
 602         }
 603         pg->m = m;
 604
 605         r = parse_path_selector(as, pg, ti);
 606         if (r)
 607                 goto bad;
 608
 609         /*
 610          * read the paths
 611          */
 612         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
 613         if (r)
 614                 goto bad;
 615
 616         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
 617         if (r)
 618                 goto bad;
 619
 620         nr_params = 1 + nr_selector_args;
 621         for (i = 0; i < pg->nr_pgpaths; i++) {
 622                 struct pgpath *pgpath;
 623                 struct arg_set path_args;
 624
 625                 if (as->argc < nr_params)
 626                         goto bad;
 627
 628                 path_args.argc = nr_params;
 629                 path_args.argv = as->argv;
 630
 631                 pgpath = parse_path(&path_args, &pg->ps, ti);
 632                 if (!pgpath)
 633                         goto bad;
 634
 635                 pgpath->pg = pg;
 636                 list_add_tail(&pgpath->list, &pg->pgpaths);
 637                 consume(as, nr_params);
 638         }
 639
 640         return pg;
 641
 642  bad:
 643         free_priority_group(pg, ti);
 644         return NULL;
 645 }
 646
 647 static int parse_hw_handler(struct arg_set *as, struct multipath *m)
 648 {
 649         int r;
 650         struct hw_handler_type *hwht;
 651         unsigned hw_argc;
 652         struct dm_target *ti = m->ti;
 653
 654         static struct param _params[] = {
 655                 {0, 1024, "invalid number of hardware handler args"},
 656         };
 657
 658         r = read_param(_params, shift(as), &hw_argc, &ti->error);
 659         if (r)
 660                 return -EINVAL;
 661
 662         if (!hw_argc)
 663                 return 0;
 664
 665         hwht = dm_get_hw_handler(shift(as));
 666         if (!hwht) {
 667                 ti->error = "unknown hardware handler type";
 668                 return -EINVAL;
 669         }
 670
 671         m->hw_handler.md = dm_table_get_md(ti->table);
 672         dm_put(m->hw_handler.md);
 673
 674         r = hwht->create(&m->hw_handler, hw_argc - 1, as->argv);
 675         if (r) {
 676                 dm_put_hw_handler(hwht);
 677                 ti->error = "hardware handler constructor failed";
 678                 return r;
 679         }
 680
 681         m->hw_handler.type = hwht;
 682         consume(as, hw_argc - 1);
 683
 684         return 0;
 685 }
 686
 687 static int parse_features(struct arg_set *as, struct multipath *m)
 688 {
 689         int r;
 690         unsigned argc;
 691         struct dm_target *ti = m->ti;
 692
 693         static struct param _params[] = {
 694                 {0, 1, "invalid number of feature args"},
 695         };
 696
 697         r = read_param(_params, shift(as), &argc, &ti->error);
 698         if (r)
 699                 return -EINVAL;
 700
 701         if (!argc)
 702                 return 0;
 703
 704         if (!strnicmp(shift(as), MESG_STR("queue_if_no_path")))
 705                 return queue_if_no_path(m, 1, 0);
 706         else {
 707                 ti->error = "Unrecognised multipath feature request";
 708                 return -EINVAL;
 709         }
 710 }
 711
 712 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 713                          char **argv)
 714 {
 715         /* target parameters */
 716         static struct param _params[] = {
 717                 {1, 1024, "invalid number of priority groups"},
 718                 {1, 1024, "invalid initial priority group number"},
 719         };
 720
 721         int r;
 722         struct multipath *m;
 723         struct arg_set as;
 724         unsigned pg_count = 0;
 725         unsigned next_pg_num;
 726
 727         as.argc = argc;
 728         as.argv = argv;
 729
 730         m = alloc_multipath(ti);
 731         if (!m) {
 732                 ti->error = "can't allocate multipath";
 733                 return -EINVAL;
 734         }
 735
 736         r = parse_features(&as, m);
 737         if (r)
 738                 goto bad;
 739
 740         r = parse_hw_handler(&as, m);
 741         if (r)
 742                 goto bad;
 743
 744         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
 745         if (r)
 746                 goto bad;
 747
 748         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
 749         if (r)
 750                 goto bad;
 751
 752         /* parse the priority groups */
 753         while (as.argc) {
 754                 struct priority_group *pg;
 755
 756                 pg = parse_priority_group(&as, m);
 757                 if (!pg) {
 758                         r = -EINVAL;
 759                         goto bad;
 760                 }
 761
 762                 m->nr_valid_paths += pg->nr_pgpaths;
 763                 list_add_tail(&pg->list, &m->priority_groups);
 764                 pg_count++;
 765                 pg->pg_num = pg_count;
 766                 if (!--next_pg_num)
 767                         m->next_pg = pg;
 768         }
 769
 770         if (pg_count != m->nr_priority_groups) {
 771                 ti->error = "priority group count mismatch";
 772                 r = -EINVAL;
 773                 goto bad;
 774         }
 775
 776         return 0;
 777
 778  bad:
 779         free_multipath(m);
 780         return r;
 781 }
 782
 783 static void multipath_dtr(struct dm_target *ti)
 784 {
 785         struct multipath *m = (struct multipath *) ti->private;
 786
 787         flush_workqueue(kmultipathd);
 788         free_multipath(m);
 789 }
 790
 791 /*
 792  * Map bios, recording original fields for later in case we have to resubmit
 793  */
 794 static int multipath_map(struct dm_target *ti, struct bio *bio,
 795                          union map_info *map_context)
 796 {
 797         int r;
 798         struct mpath_io *mpio;
 799         struct multipath *m = (struct multipath *) ti->private;
 800
 801         if (bio_barrier(bio))
 802                 return -EOPNOTSUPP;
 803
 804         mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
 805         dm_bio_record(&mpio->details, bio);
 806
 807         map_context->ptr = mpio;
 808         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
 809         r = map_io(m, bio, mpio, 0);
 810         if (r < 0 || r == DM_MAPIO_REQUEUE)
 811                 mempool_free(mpio, m->mpio_pool);
 812
 813         return r;
 814 }
 815
 816 /*
 817  * Take a path out of use.
 818  */
 819 static int fail_path(struct pgpath *pgpath)
 820 {
 821         unsigned long flags;
 822         struct multipath *m = pgpath->pg->m;
 823
 824         spin_lock_irqsave(&m->lock, flags);
 825
 826         if (!pgpath->path.is_active)
 827                 goto out;
 828
 829         DMWARN("Failing path %s.", pgpath->path.dev->name);
 830
 831         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 832         pgpath->path.is_active = 0;
 833         pgpath->fail_count++;
 834
 835         m->nr_valid_paths--;
 836
 837         if (pgpath == m->current_pgpath)
 838                 m->current_pgpath = NULL;
 839
 840         queue_work(kmultipathd, &m->trigger_event);
 841
 842 out:
 843         spin_unlock_irqrestore(&m->lock, flags);
 844
 845         return 0;
 846 }
 847
 848 /*
 849  * Reinstate a previously-failed path
 850  */
 851 static int reinstate_path(struct pgpath *pgpath)
 852 {
 853         int r = 0;
 854         unsigned long flags;
 855         struct multipath *m = pgpath->pg->m;
 856
 857         spin_lock_irqsave(&m->lock, flags);
 858
 859         if (pgpath->path.is_active)
 860                 goto out;
 861
 862         if (!pgpath->pg->ps.type) {
 863                 DMWARN("Reinstate path not supported by path selector %s",
 864                        pgpath->pg->ps.type->name);
 865                 r = -EINVAL;
 866                 goto out;
 867         }
 868
 869         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
 870         if (r)
 871                 goto out;
 872
 873         pgpath->path.is_active = 1;
 874
 875         m->current_pgpath = NULL;
 876         if (!m->nr_valid_paths++ && m->queue_size)
 877                 queue_work(kmultipathd, &m->process_queued_ios);
 878
 879         queue_work(kmultipathd, &m->trigger_event);
 880
 881 out:
 882         spin_unlock_irqrestore(&m->lock, flags);
 883
 884         return r;
 885 }
 886
 887 /*
 888  * Fail or reinstate all paths that match the provided struct dm_dev.
 889  */
 890 static int action_dev(struct multipath *m, struct dm_dev *dev,
 891                       action_fn action)
 892 {
 893         int r = 0;
 894         struct pgpath *pgpath;
 895         struct priority_group *pg;
 896
 897         list_for_each_entry(pg, &m->priority_groups, list) {
 898                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
 899                         if (pgpath->path.dev == dev)
 900                                 r = action(pgpath);
 901                 }
 902         }
 903
 904         return r;
 905 }
 906
 907 /*
 908  * Temporarily try to avoid having to use the specified PG
 909  */
 910 static void bypass_pg(struct multipath *m, struct priority_group *pg,
 911                       int bypassed)
 912 {
 913         unsigned long flags;
 914
 915         spin_lock_irqsave(&m->lock, flags);
 916
 917         pg->bypassed = bypassed;
 918         m->current_pgpath = NULL;
 919         m->current_pg = NULL;
 920
 921         spin_unlock_irqrestore(&m->lock, flags);
 922
 923         queue_work(kmultipathd, &m->trigger_event);
 924 }
 925
 926 /*
 927  * Switch to using the specified PG from the next I/O that gets mapped
 928  */
 929 static int switch_pg_num(struct multipath *m, const char *pgstr)
 930 {
 931         struct priority_group *pg;
 932         unsigned pgnum;
 933         unsigned long flags;
 934
 935         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
 936             (pgnum > m->nr_priority_groups)) {
 937                 DMWARN("invalid PG number supplied to switch_pg_num");
 938                 return -EINVAL;
 939         }
 940
 941         spin_lock_irqsave(&m->lock, flags);
 942         list_for_each_entry(pg, &m->priority_groups, list) {
 943                 pg->bypassed = 0;
 944                 if (--pgnum)
 945                         continue;
 946
 947                 m->current_pgpath = NULL;
 948                 m->current_pg = NULL;
 949                 m->next_pg = pg;
 950         }
 951         spin_unlock_irqrestore(&m->lock, flags);
 952
 953         queue_work(kmultipathd, &m->trigger_event);
 954         return 0;
 955 }
 956
 957 /*
 958  * Set/clear bypassed status of a PG.
 959  * PGs are numbered upwards from 1 in the order they were declared.
 960  */
 961 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
 962 {
 963         struct priority_group *pg;
 964         unsigned pgnum;
 965
 966         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
 967             (pgnum > m->nr_priority_groups)) {
 968                 DMWARN("invalid PG number supplied to bypass_pg");
 969                 return -EINVAL;
 970         }
 971
 972         list_for_each_entry(pg, &m->priority_groups, list) {
 973                 if (!--pgnum)
 974                         break;
 975         }
 976
 977         bypass_pg(m, pg, bypassed);
 978         return 0;
 979 }
 980
 981 /*
 982  * pg_init must call this when it has completed its initialisation
 983  */
 984 void dm_pg_init_complete(struct dm_path *path, unsigned err_flags)
 985 {
 986         struct pgpath *pgpath = path_to_pgpath(path);
 987         struct priority_group *pg = pgpath->pg;
 988         struct multipath *m = pg->m;
 989         unsigned long flags;
 990
 991         /* We insist on failing the path if the PG is already bypassed. */
 992         if (err_flags && pg->bypassed)
 993                 err_flags |= MP_FAIL_PATH;
 994
 995         if (err_flags & MP_FAIL_PATH)
 996                 fail_path(pgpath);
 997
 998         if (err_flags & MP_BYPASS_PG)
 999                 bypass_pg(m, pg, 1);
1000
1001         spin_lock_irqsave(&m->lock, flags);
1002         if (err_flags) {
1003                 m->current_pgpath = NULL;
1004                 m->current_pg = NULL;
1005         } else if (!m->pg_init_required)
1006                 m->queue_io = 0;
1007
1008         m->pg_init_in_progress = 0;
1009         queue_work(kmultipathd, &m->process_queued_ios);
1010         spin_unlock_irqrestore(&m->lock, flags);
1011 }
1012
1013 /*
1014  * end_io handling
1015  */
1016 static int do_end_io(struct multipath *m, struct bio *bio,
1017                      int error, struct mpath_io *mpio)
1018 {
1019         struct hw_handler *hwh = &m->hw_handler;
1020         unsigned err_flags = MP_FAIL_PATH;      /* Default behavior */
1021         unsigned long flags;
1022
1023         if (!error)
1024                 return 0;       /* I/O complete */
1025
1026         if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
1027                 return error;
1028
1029         if (error == -EOPNOTSUPP)
1030                 return error;
1031
1032         spin_lock_irqsave(&m->lock, flags);
1033         if (!m->nr_valid_paths) {
1034                 if (__must_push_back(m)) {
1035                         spin_unlock_irqrestore(&m->lock, flags);
1036                         return DM_ENDIO_REQUEUE;
1037                 } else if (!m->queue_if_no_path) {
1038                         spin_unlock_irqrestore(&m->lock, flags);
1039                         return -EIO;
1040                 } else {
1041                         spin_unlock_irqrestore(&m->lock, flags);
1042                         goto requeue;
1043                 }
1044         }
1045         spin_unlock_irqrestore(&m->lock, flags);
1046
1047         if (hwh->type && hwh->type->error)
1048                 err_flags = hwh->type->error(hwh, bio);
1049
1050         if (mpio->pgpath) {
1051                 if (err_flags & MP_FAIL_PATH)
1052                         fail_path(mpio->pgpath);
1053
1054                 if (err_flags & MP_BYPASS_PG)
1055                         bypass_pg(m, mpio->pgpath->pg, 1);
1056         }
1057
1058         if (err_flags & MP_ERROR_IO)
1059                 return -EIO;
1060
1061       requeue:
1062         dm_bio_restore(&mpio->details, bio);
1063
1064         /* queue for the daemon to resubmit or fail */
1065         spin_lock_irqsave(&m->lock, flags);
1066         bio_list_add(&m->queued_ios, bio);
1067         m->queue_size++;
1068         if (!m->queue_io)
1069                 queue_work(kmultipathd, &m->process_queued_ios);
1070         spin_unlock_irqrestore(&m->lock, flags);
1071
1072         return DM_ENDIO_INCOMPLETE;     /* io not complete */
1073 }
1074
1075 static int multipath_end_io(struct dm_target *ti, struct bio *bio,
1076                             int error, union map_info *map_context)
1077 {
1078         struct multipath *m = (struct multipath *) ti->private;
1079         struct mpath_io *mpio = (struct mpath_io *) map_context->ptr;
1080         struct pgpath *pgpath = mpio->pgpath;
1081         struct path_selector *ps;
1082         int r;
1083
1084         r  = do_end_io(m, bio, error, mpio);
1085         if (pgpath) {
1086                 ps = &pgpath->pg->ps;
1087                 if (ps->type->end_io)
1088                         ps->type->end_io(ps, &pgpath->path);
1089         }
1090         if (r != DM_ENDIO_INCOMPLETE)
1091                 mempool_free(mpio, m->mpio_pool);
1092
1093         return r;
1094 }
1095
1096 /*
1097  * Suspend can't complete until all the I/O is processed so if
1098  * the last path fails we must error any remaining I/O.
1099  * Note that if the freeze_bdev fails while suspending, the
1100  * queue_if_no_path state is lost - userspace should reset it.
1101  */
1102 static void multipath_presuspend(struct dm_target *ti)
1103 {
1104         struct multipath *m = (struct multipath *) ti->private;
1105
1106         queue_if_no_path(m, 0, 1);
1107 }
1108
1109 /*
1110  * Restore the queue_if_no_path setting.
1111  */
1112 static void multipath_resume(struct dm_target *ti)
1113 {
1114         struct multipath *m = (struct multipath *) ti->private;
1115         unsigned long flags;
1116
1117         spin_lock_irqsave(&m->lock, flags);
1118         m->queue_if_no_path = m->saved_queue_if_no_path;
1119         spin_unlock_irqrestore(&m->lock, flags);
1120 }
1121
1122 /*
1123  * Info output has the following format:
1124  * num_multipath_feature_args [multipath_feature_args]*
1125  * num_handler_status_args [handler_status_args]*
1126  * num_groups init_group_number
1127  *            [A|D|E num_ps_status_args [ps_status_args]*
1128  *             num_paths num_selector_args
1129  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1130  *
1131  * Table output has the following format (identical to the constructor string):
1132  * num_feature_args [features_args]*
1133  * num_handler_args hw_handler [hw_handler_args]*
1134  * num_groups init_group_number
1135  *     [priority selector-name num_ps_args [ps_args]*
1136  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1137  */
1138 static int multipath_status(struct dm_target *ti, status_type_t type,
1139                             char *result, unsigned int maxlen)
1140 {
1141         int sz = 0;
1142         unsigned long flags;
1143         struct multipath *m = (struct multipath *) ti->private;
1144         struct hw_handler *hwh = &m->hw_handler;
1145         struct priority_group *pg;
1146         struct pgpath *p;
1147         unsigned pg_num;
1148         char state;
1149
1150         spin_lock_irqsave(&m->lock, flags);
1151
1152         /* Features */
1153         if (type == STATUSTYPE_INFO)
1154                 DMEMIT("1 %u ", m->queue_size);
1155         else if (m->queue_if_no_path)
1156                 DMEMIT("1 queue_if_no_path ");
1157         else
1158                 DMEMIT("0 ");
1159
1160         if (hwh->type && hwh->type->status)
1161                 sz += hwh->type->status(hwh, type, result + sz, maxlen - sz);
1162         else if (!hwh->type || type == STATUSTYPE_INFO)
1163                 DMEMIT("0 ");
1164         else
1165                 DMEMIT("1 %s ", hwh->type->name);
1166
1167         DMEMIT("%u ", m->nr_priority_groups);
1168
1169         if (m->next_pg)
1170                 pg_num = m->next_pg->pg_num;
1171         else if (m->current_pg)
1172                 pg_num = m->current_pg->pg_num;
1173         else
1174                         pg_num = 1;
1175
1176         DMEMIT("%u ", pg_num);
1177
1178         switch (type) {
1179         case STATUSTYPE_INFO:
1180                 list_for_each_entry(pg, &m->priority_groups, list) {
1181                         if (pg->bypassed)
1182                                 state = 'D';    /* Disabled */
1183                         else if (pg == m->current_pg)
1184                                 state = 'A';    /* Currently Active */
1185                         else
1186                                 state = 'E';    /* Enabled */
1187
1188                         DMEMIT("%c ", state);
1189
1190                         if (pg->ps.type->status)
1191                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1192                                                           result + sz,
1193                                                           maxlen - sz);
1194                         else
1195                                 DMEMIT("0 ");
1196
1197                         DMEMIT("%u %u ", pg->nr_pgpaths,
1198                                pg->ps.type->info_args);
1199
1200                         list_for_each_entry(p, &pg->pgpaths, list) {
1201                                 DMEMIT("%s %s %u ", p->path.dev->name,
1202                                        p->path.is_active ? "A" : "F",
1203                                        p->fail_count);
1204                                 if (pg->ps.type->status)
1205                                         sz += pg->ps.type->status(&pg->ps,
1206                                               &p->path, type, result + sz,
1207                                               maxlen - sz);
1208                         }
1209                 }
1210                 break;
1211
1212         case STATUSTYPE_TABLE:
1213                 list_for_each_entry(pg, &m->priority_groups, list) {
1214                         DMEMIT("%s ", pg->ps.type->name);
1215
1216                         if (pg->ps.type->status)
1217                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1218                                                           result + sz,
1219                                                           maxlen - sz);
1220                         else
1221                                 DMEMIT("0 ");
1222
1223                         DMEMIT("%u %u ", pg->nr_pgpaths,
1224                                pg->ps.type->table_args);
1225
1226                         list_for_each_entry(p, &pg->pgpaths, list) {
1227                                 DMEMIT("%s ", p->path.dev->name);
1228                                 if (pg->ps.type->status)
1229                                         sz += pg->ps.type->status(&pg->ps,
1230                                               &p->path, type, result + sz,
1231                                               maxlen - sz);
1232                         }
1233                 }
1234                 break;
1235         }
1236
1237         spin_unlock_irqrestore(&m->lock, flags);
1238
1239         return 0;
1240 }
1241
1242 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1243 {
1244         int r;
1245         struct dm_dev *dev;
1246         struct multipath *m = (struct multipath *) ti->private;
1247         action_fn action;
1248
1249         if (argc == 1) {
1250                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path")))
1251                         return queue_if_no_path(m, 1, 0);
1252                 else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path")))
1253                         return queue_if_no_path(m, 0, 0);
1254         }
1255
1256         if (argc != 2)
1257                 goto error;
1258
1259         if (!strnicmp(argv[0], MESG_STR("disable_group")))
1260                 return bypass_pg_num(m, argv[1], 1);
1261         else if (!strnicmp(argv[0], MESG_STR("enable_group")))
1262                 return bypass_pg_num(m, argv[1], 0);
1263         else if (!strnicmp(argv[0], MESG_STR("switch_group")))
1264                 return switch_pg_num(m, argv[1]);
1265         else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1266                 action = reinstate_path;
1267         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1268                 action = fail_path;
1269         else
1270                 goto error;
1271
1272         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
1273                           dm_table_get_mode(ti->table), &dev);
1274         if (r) {
1275                 DMWARN("message: error getting device %s",
1276                        argv[1]);
1277                 return -EINVAL;
1278         }
1279
1280         r = action_dev(m, dev, action);
1281
1282         dm_put_device(ti, dev);
1283
1284         return r;
1285
1286 error:
1287         DMWARN("Unrecognised multipath message received.");
1288         return -EINVAL;
1289 }
1290
1291 static int multipath_ioctl(struct dm_target *ti, struct inode *inode,
1292                            struct file *filp, unsigned int cmd,
1293                            unsigned long arg)
1294 {
1295         struct multipath *m = (struct multipath *) ti->private;
1296         struct block_device *bdev = NULL;
1297         unsigned long flags;
1298         struct file fake_file = {};
1299         struct dentry fake_dentry = {};
1300         int r = 0;
1301
1302         fake_file.f_path.dentry = &fake_dentry;
1303
1304         spin_lock_irqsave(&m->lock, flags);
1305
1306         if (!m->current_pgpath)
1307                 __choose_pgpath(m);
1308
1309         if (m->current_pgpath) {
1310                 bdev = m->current_pgpath->path.dev->bdev;
1311                 fake_dentry.d_inode = bdev->bd_inode;
1312                 fake_file.f_mode = m->current_pgpath->path.dev->mode;
1313         }
1314
1315         if (m->queue_io)
1316                 r = -EAGAIN;
1317         else if (!bdev)
1318                 r = -EIO;
1319
1320         spin_unlock_irqrestore(&m->lock, flags);
1321
1322         return r ? : blkdev_driver_ioctl(bdev->bd_inode, &fake_file,
1323                                          bdev->bd_disk, cmd, arg);
1324 }
1325
1326 /*-----------------------------------------------------------------
1327  * Module setup
1328  *---------------------------------------------------------------*/
1329 static struct target_type multipath_target = {
1330         .name = "multipath",
1331         .version = {1, 0, 5},
1332         .module = THIS_MODULE,
1333         .ctr = multipath_ctr,
1334         .dtr = multipath_dtr,
1335         .map = multipath_map,
1336         .end_io = multipath_end_io,
1337         .presuspend = multipath_presuspend,
1338         .resume = multipath_resume,
1339         .status = multipath_status,
1340         .message = multipath_message,
1341         .ioctl  = multipath_ioctl,
1342 };
1343
1344 static int __init dm_multipath_init(void)
1345 {
1346         int r;
1347
1348         /* allocate a slab for the dm_ios */
1349         _mpio_cache = kmem_cache_create("dm_mpath", sizeof(struct mpath_io),
1350                                         0, 0, NULL, NULL);
1351         if (!_mpio_cache)
1352                 return -ENOMEM;
1353
1354         r = dm_register_target(&multipath_target);
1355         if (r < 0) {
1356                 DMERR("%s: register failed %d", multipath_target.name, r);
1357                 kmem_cache_destroy(_mpio_cache);
1358                 return -EINVAL;
1359         }
1360
1361         kmultipathd = create_workqueue("kmpathd");
1362         if (!kmultipathd) {
1363                 DMERR("%s: failed to create workqueue kmpathd",
1364                                 multipath_target.name);
1365                 dm_unregister_target(&multipath_target);
1366                 kmem_cache_destroy(_mpio_cache);
1367                 return -ENOMEM;
1368         }
1369
1370         DMINFO("version %u.%u.%u loaded",
1371                multipath_target.version[0], multipath_target.version[1],
1372                multipath_target.version[2]);
1373
1374         return r;
1375 }
1376
1377 static void __exit dm_multipath_exit(void)
1378 {
1379         int r;
1380
1381         destroy_workqueue(kmultipathd);
1382
1383         r = dm_unregister_target(&multipath_target);
1384         if (r < 0)
1385                 DMERR("%s: target unregister failed %d",
1386                       multipath_target.name, r);
1387         kmem_cache_destroy(_mpio_cache);
1388 }
1389
1390 EXPORT_SYMBOL_GPL(dm_pg_init_complete);
1391
1392 module_init(dm_multipath_init);
1393 module_exit(dm_multipath_exit);
1394
1395 MODULE_DESCRIPTION(DM_NAME " multipath target");
1396 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1397 MODULE_LICENSE("GPL");