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         r = hwht->create(&m->hw_handler, hw_argc - 1, as->argv);
 672         if (r) {
 673                 dm_put_hw_handler(hwht);
 674                 ti->error = "hardware handler constructor failed";
 675                 return r;
 676         }
 677
 678         m->hw_handler.type = hwht;
 679         consume(as, hw_argc - 1);
 680
 681         return 0;
 682 }
 683
 684 static int parse_features(struct arg_set *as, struct multipath *m)
 685 {
 686         int r;
 687         unsigned argc;
 688         struct dm_target *ti = m->ti;
 689
 690         static struct param _params[] = {
 691                 {0, 1, "invalid number of feature args"},
 692         };
 693
 694         r = read_param(_params, shift(as), &argc, &ti->error);
 695         if (r)
 696                 return -EINVAL;
 697
 698         if (!argc)
 699                 return 0;
 700
 701         if (!strnicmp(shift(as), MESG_STR("queue_if_no_path")))
 702                 return queue_if_no_path(m, 1, 0);
 703         else {
 704                 ti->error = "Unrecognised multipath feature request";
 705                 return -EINVAL;
 706         }
 707 }
 708
 709 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 710                          char **argv)
 711 {
 712         /* target parameters */
 713         static struct param _params[] = {
 714                 {1, 1024, "invalid number of priority groups"},
 715                 {1, 1024, "invalid initial priority group number"},
 716         };
 717
 718         int r;
 719         struct multipath *m;
 720         struct arg_set as;
 721         unsigned pg_count = 0;
 722         unsigned next_pg_num;
 723
 724         as.argc = argc;
 725         as.argv = argv;
 726
 727         m = alloc_multipath(ti);
 728         if (!m) {
 729                 ti->error = "can't allocate multipath";
 730                 return -EINVAL;
 731         }
 732
 733         r = parse_features(&as, m);
 734         if (r)
 735                 goto bad;
 736
 737         r = parse_hw_handler(&as, m);
 738         if (r)
 739                 goto bad;
 740
 741         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
 742         if (r)
 743                 goto bad;
 744
 745         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
 746         if (r)
 747                 goto bad;
 748
 749         /* parse the priority groups */
 750         while (as.argc) {
 751                 struct priority_group *pg;
 752
 753                 pg = parse_priority_group(&as, m);
 754                 if (!pg) {
 755                         r = -EINVAL;
 756                         goto bad;
 757                 }
 758
 759                 m->nr_valid_paths += pg->nr_pgpaths;
 760                 list_add_tail(&pg->list, &m->priority_groups);
 761                 pg_count++;
 762                 pg->pg_num = pg_count;
 763                 if (!--next_pg_num)
 764                         m->next_pg = pg;
 765         }
 766
 767         if (pg_count != m->nr_priority_groups) {
 768                 ti->error = "priority group count mismatch";
 769                 r = -EINVAL;
 770                 goto bad;
 771         }
 772
 773         return 0;
 774
 775  bad:
 776         free_multipath(m);
 777         return r;
 778 }
 779
 780 static void multipath_dtr(struct dm_target *ti)
 781 {
 782         struct multipath *m = (struct multipath *) ti->private;
 783
 784         flush_workqueue(kmultipathd);
 785         free_multipath(m);
 786 }
 787
 788 /*
 789  * Map bios, recording original fields for later in case we have to resubmit
 790  */
 791 static int multipath_map(struct dm_target *ti, struct bio *bio,
 792                          union map_info *map_context)
 793 {
 794         int r;
 795         struct mpath_io *mpio;
 796         struct multipath *m = (struct multipath *) ti->private;
 797
 798         if (bio_barrier(bio))
 799                 return -EOPNOTSUPP;
 800
 801         mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
 802         dm_bio_record(&mpio->details, bio);
 803
 804         map_context->ptr = mpio;
 805         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
 806         r = map_io(m, bio, mpio, 0);
 807         if (r < 0 || r == DM_MAPIO_REQUEUE)
 808                 mempool_free(mpio, m->mpio_pool);
 809
 810         return r;
 811 }
 812
 813 /*
 814  * Take a path out of use.
 815  */
 816 static int fail_path(struct pgpath *pgpath)
 817 {
 818         unsigned long flags;
 819         struct multipath *m = pgpath->pg->m;
 820
 821         spin_lock_irqsave(&m->lock, flags);
 822
 823         if (!pgpath->path.is_active)
 824                 goto out;
 825
 826         DMWARN("Failing path %s.", pgpath->path.dev->name);
 827
 828         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 829         pgpath->path.is_active = 0;
 830         pgpath->fail_count++;
 831
 832         m->nr_valid_paths--;
 833
 834         if (pgpath == m->current_pgpath)
 835                 m->current_pgpath = NULL;
 836
 837         queue_work(kmultipathd, &m->trigger_event);
 838
 839 out:
 840         spin_unlock_irqrestore(&m->lock, flags);
 841
 842         return 0;
 843 }
 844
 845 /*
 846  * Reinstate a previously-failed path
 847  */
 848 static int reinstate_path(struct pgpath *pgpath)
 849 {
 850         int r = 0;
 851         unsigned long flags;
 852         struct multipath *m = pgpath->pg->m;
 853
 854         spin_lock_irqsave(&m->lock, flags);
 855
 856         if (pgpath->path.is_active)
 857                 goto out;
 858
 859         if (!pgpath->pg->ps.type) {
 860                 DMWARN("Reinstate path not supported by path selector %s",
 861                        pgpath->pg->ps.type->name);
 862                 r = -EINVAL;
 863                 goto out;
 864         }
 865
 866         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
 867         if (r)
 868                 goto out;
 869
 870         pgpath->path.is_active = 1;
 871
 872         m->current_pgpath = NULL;
 873         if (!m->nr_valid_paths++ && m->queue_size)
 874                 queue_work(kmultipathd, &m->process_queued_ios);
 875
 876         queue_work(kmultipathd, &m->trigger_event);
 877
 878 out:
 879         spin_unlock_irqrestore(&m->lock, flags);
 880
 881         return r;
 882 }
 883
 884 /*
 885  * Fail or reinstate all paths that match the provided struct dm_dev.
 886  */
 887 static int action_dev(struct multipath *m, struct dm_dev *dev,
 888                       action_fn action)
 889 {
 890         int r = 0;
 891         struct pgpath *pgpath;
 892         struct priority_group *pg;
 893
 894         list_for_each_entry(pg, &m->priority_groups, list) {
 895                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
 896                         if (pgpath->path.dev == dev)
 897                                 r = action(pgpath);
 898                 }
 899         }
 900
 901         return r;
 902 }
 903
 904 /*
 905  * Temporarily try to avoid having to use the specified PG
 906  */
 907 static void bypass_pg(struct multipath *m, struct priority_group *pg,
 908                       int bypassed)
 909 {
 910         unsigned long flags;
 911
 912         spin_lock_irqsave(&m->lock, flags);
 913
 914         pg->bypassed = bypassed;
 915         m->current_pgpath = NULL;
 916         m->current_pg = NULL;
 917
 918         spin_unlock_irqrestore(&m->lock, flags);
 919
 920         queue_work(kmultipathd, &m->trigger_event);
 921 }
 922
 923 /*
 924  * Switch to using the specified PG from the next I/O that gets mapped
 925  */
 926 static int switch_pg_num(struct multipath *m, const char *pgstr)
 927 {
 928         struct priority_group *pg;
 929         unsigned pgnum;
 930         unsigned long flags;
 931
 932         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
 933             (pgnum > m->nr_priority_groups)) {
 934                 DMWARN("invalid PG number supplied to switch_pg_num");
 935                 return -EINVAL;
 936         }
 937
 938         spin_lock_irqsave(&m->lock, flags);
 939         list_for_each_entry(pg, &m->priority_groups, list) {
 940                 pg->bypassed = 0;
 941                 if (--pgnum)
 942                         continue;
 943
 944                 m->current_pgpath = NULL;
 945                 m->current_pg = NULL;
 946                 m->next_pg = pg;
 947         }
 948         spin_unlock_irqrestore(&m->lock, flags);
 949
 950         queue_work(kmultipathd, &m->trigger_event);
 951         return 0;
 952 }
 953
 954 /*
 955  * Set/clear bypassed status of a PG.
 956  * PGs are numbered upwards from 1 in the order they were declared.
 957  */
 958 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
 959 {
 960         struct priority_group *pg;
 961         unsigned pgnum;
 962
 963         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
 964             (pgnum > m->nr_priority_groups)) {
 965                 DMWARN("invalid PG number supplied to bypass_pg");
 966                 return -EINVAL;
 967         }
 968
 969         list_for_each_entry(pg, &m->priority_groups, list) {
 970                 if (!--pgnum)
 971                         break;
 972         }
 973
 974         bypass_pg(m, pg, bypassed);
 975         return 0;
 976 }
 977
 978 /*
 979  * pg_init must call this when it has completed its initialisation
 980  */
 981 void dm_pg_init_complete(struct dm_path *path, unsigned err_flags)
 982 {
 983         struct pgpath *pgpath = path_to_pgpath(path);
 984         struct priority_group *pg = pgpath->pg;
 985         struct multipath *m = pg->m;
 986         unsigned long flags;
 987
 988         /* We insist on failing the path if the PG is already bypassed. */
 989         if (err_flags && pg->bypassed)
 990                 err_flags |= MP_FAIL_PATH;
 991
 992         if (err_flags & MP_FAIL_PATH)
 993                 fail_path(pgpath);
 994
 995         if (err_flags & MP_BYPASS_PG)
 996                 bypass_pg(m, pg, 1);
 997
 998         spin_lock_irqsave(&m->lock, flags);
 999         if (err_flags) {
1000                 m->current_pgpath = NULL;
1001                 m->current_pg = NULL;
1002         } else if (!m->pg_init_required)
1003                 m->queue_io = 0;
1004
1005         m->pg_init_in_progress = 0;
1006         queue_work(kmultipathd, &m->process_queued_ios);
1007         spin_unlock_irqrestore(&m->lock, flags);
1008 }
1009
1010 /*
1011  * end_io handling
1012  */
1013 static int do_end_io(struct multipath *m, struct bio *bio,
1014                      int error, struct mpath_io *mpio)
1015 {
1016         struct hw_handler *hwh = &m->hw_handler;
1017         unsigned err_flags = MP_FAIL_PATH;      /* Default behavior */
1018         unsigned long flags;
1019
1020         if (!error)
1021                 return 0;       /* I/O complete */
1022
1023         if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
1024                 return error;
1025
1026         if (error == -EOPNOTSUPP)
1027                 return error;
1028
1029         spin_lock_irqsave(&m->lock, flags);
1030         if (!m->nr_valid_paths) {
1031                 if (__must_push_back(m)) {
1032                         spin_unlock_irqrestore(&m->lock, flags);
1033                         return DM_ENDIO_REQUEUE;
1034                 } else if (!m->queue_if_no_path) {
1035                         spin_unlock_irqrestore(&m->lock, flags);
1036                         return -EIO;
1037                 } else {
1038                         spin_unlock_irqrestore(&m->lock, flags);
1039                         goto requeue;
1040                 }
1041         }
1042         spin_unlock_irqrestore(&m->lock, flags);
1043
1044         if (hwh->type && hwh->type->error)
1045                 err_flags = hwh->type->error(hwh, bio);
1046
1047         if (mpio->pgpath) {
1048                 if (err_flags & MP_FAIL_PATH)
1049                         fail_path(mpio->pgpath);
1050
1051                 if (err_flags & MP_BYPASS_PG)
1052                         bypass_pg(m, mpio->pgpath->pg, 1);
1053         }
1054
1055         if (err_flags & MP_ERROR_IO)
1056                 return -EIO;
1057
1058       requeue:
1059         dm_bio_restore(&mpio->details, bio);
1060
1061         /* queue for the daemon to resubmit or fail */
1062         spin_lock_irqsave(&m->lock, flags);
1063         bio_list_add(&m->queued_ios, bio);
1064         m->queue_size++;
1065         if (!m->queue_io)
1066                 queue_work(kmultipathd, &m->process_queued_ios);
1067         spin_unlock_irqrestore(&m->lock, flags);
1068
1069         return DM_ENDIO_INCOMPLETE;     /* io not complete */
1070 }
1071
1072 static int multipath_end_io(struct dm_target *ti, struct bio *bio,
1073                             int error, union map_info *map_context)
1074 {
1075         struct multipath *m = (struct multipath *) ti->private;
1076         struct mpath_io *mpio = (struct mpath_io *) map_context->ptr;
1077         struct pgpath *pgpath = mpio->pgpath;
1078         struct path_selector *ps;
1079         int r;
1080
1081         r  = do_end_io(m, bio, error, mpio);
1082         if (pgpath) {
1083                 ps = &pgpath->pg->ps;
1084                 if (ps->type->end_io)
1085                         ps->type->end_io(ps, &pgpath->path);
1086         }
1087         if (r != DM_ENDIO_INCOMPLETE)
1088                 mempool_free(mpio, m->mpio_pool);
1089
1090         return r;
1091 }
1092
1093 /*
1094  * Suspend can't complete until all the I/O is processed so if
1095  * the last path fails we must error any remaining I/O.
1096  * Note that if the freeze_bdev fails while suspending, the
1097  * queue_if_no_path state is lost - userspace should reset it.
1098  */
1099 static void multipath_presuspend(struct dm_target *ti)
1100 {
1101         struct multipath *m = (struct multipath *) ti->private;
1102
1103         queue_if_no_path(m, 0, 1);
1104 }
1105
1106 /*
1107  * Restore the queue_if_no_path setting.
1108  */
1109 static void multipath_resume(struct dm_target *ti)
1110 {
1111         struct multipath *m = (struct multipath *) ti->private;
1112         unsigned long flags;
1113
1114         spin_lock_irqsave(&m->lock, flags);
1115         m->queue_if_no_path = m->saved_queue_if_no_path;
1116         spin_unlock_irqrestore(&m->lock, flags);
1117 }
1118
1119 /*
1120  * Info output has the following format:
1121  * num_multipath_feature_args [multipath_feature_args]*
1122  * num_handler_status_args [handler_status_args]*
1123  * num_groups init_group_number
1124  *            [A|D|E num_ps_status_args [ps_status_args]*
1125  *             num_paths num_selector_args
1126  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1127  *
1128  * Table output has the following format (identical to the constructor string):
1129  * num_feature_args [features_args]*
1130  * num_handler_args hw_handler [hw_handler_args]*
1131  * num_groups init_group_number
1132  *     [priority selector-name num_ps_args [ps_args]*
1133  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1134  */
1135 static int multipath_status(struct dm_target *ti, status_type_t type,
1136                             char *result, unsigned int maxlen)
1137 {
1138         int sz = 0;
1139         unsigned long flags;
1140         struct multipath *m = (struct multipath *) ti->private;
1141         struct hw_handler *hwh = &m->hw_handler;
1142         struct priority_group *pg;
1143         struct pgpath *p;
1144         unsigned pg_num;
1145         char state;
1146
1147         spin_lock_irqsave(&m->lock, flags);
1148
1149         /* Features */
1150         if (type == STATUSTYPE_INFO)
1151                 DMEMIT("1 %u ", m->queue_size);
1152         else if (m->queue_if_no_path)
1153                 DMEMIT("1 queue_if_no_path ");
1154         else
1155                 DMEMIT("0 ");
1156
1157         if (hwh->type && hwh->type->status)
1158                 sz += hwh->type->status(hwh, type, result + sz, maxlen - sz);
1159         else if (!hwh->type || type == STATUSTYPE_INFO)
1160                 DMEMIT("0 ");
1161         else
1162                 DMEMIT("1 %s ", hwh->type->name);
1163
1164         DMEMIT("%u ", m->nr_priority_groups);
1165
1166         if (m->next_pg)
1167                 pg_num = m->next_pg->pg_num;
1168         else if (m->current_pg)
1169                 pg_num = m->current_pg->pg_num;
1170         else
1171                         pg_num = 1;
1172
1173         DMEMIT("%u ", pg_num);
1174
1175         switch (type) {
1176         case STATUSTYPE_INFO:
1177                 list_for_each_entry(pg, &m->priority_groups, list) {
1178                         if (pg->bypassed)
1179                                 state = 'D';    /* Disabled */
1180                         else if (pg == m->current_pg)
1181                                 state = 'A';    /* Currently Active */
1182                         else
1183                                 state = 'E';    /* Enabled */
1184
1185                         DMEMIT("%c ", state);
1186
1187                         if (pg->ps.type->status)
1188                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1189                                                           result + sz,
1190                                                           maxlen - sz);
1191                         else
1192                                 DMEMIT("0 ");
1193
1194                         DMEMIT("%u %u ", pg->nr_pgpaths,
1195                                pg->ps.type->info_args);
1196
1197                         list_for_each_entry(p, &pg->pgpaths, list) {
1198                                 DMEMIT("%s %s %u ", p->path.dev->name,
1199                                        p->path.is_active ? "A" : "F",
1200                                        p->fail_count);
1201                                 if (pg->ps.type->status)
1202                                         sz += pg->ps.type->status(&pg->ps,
1203                                               &p->path, type, result + sz,
1204                                               maxlen - sz);
1205                         }
1206                 }
1207                 break;
1208
1209         case STATUSTYPE_TABLE:
1210                 list_for_each_entry(pg, &m->priority_groups, list) {
1211                         DMEMIT("%s ", pg->ps.type->name);
1212
1213                         if (pg->ps.type->status)
1214                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1215                                                           result + sz,
1216                                                           maxlen - sz);
1217                         else
1218                                 DMEMIT("0 ");
1219
1220                         DMEMIT("%u %u ", pg->nr_pgpaths,
1221                                pg->ps.type->table_args);
1222
1223                         list_for_each_entry(p, &pg->pgpaths, list) {
1224                                 DMEMIT("%s ", p->path.dev->name);
1225                                 if (pg->ps.type->status)
1226                                         sz += pg->ps.type->status(&pg->ps,
1227                                               &p->path, type, result + sz,
1228                                               maxlen - sz);
1229                         }
1230                 }
1231                 break;
1232         }
1233
1234         spin_unlock_irqrestore(&m->lock, flags);
1235
1236         return 0;
1237 }
1238
1239 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1240 {
1241         int r;
1242         struct dm_dev *dev;
1243         struct multipath *m = (struct multipath *) ti->private;
1244         action_fn action;
1245
1246         if (argc == 1) {
1247                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path")))
1248                         return queue_if_no_path(m, 1, 0);
1249                 else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path")))
1250                         return queue_if_no_path(m, 0, 0);
1251         }
1252
1253         if (argc != 2)
1254                 goto error;
1255
1256         if (!strnicmp(argv[0], MESG_STR("disable_group")))
1257                 return bypass_pg_num(m, argv[1], 1);
1258         else if (!strnicmp(argv[0], MESG_STR("enable_group")))
1259                 return bypass_pg_num(m, argv[1], 0);
1260         else if (!strnicmp(argv[0], MESG_STR("switch_group")))
1261                 return switch_pg_num(m, argv[1]);
1262         else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1263                 action = reinstate_path;
1264         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1265                 action = fail_path;
1266         else
1267                 goto error;
1268
1269         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
1270                           dm_table_get_mode(ti->table), &dev);
1271         if (r) {
1272                 DMWARN("message: error getting device %s",
1273                        argv[1]);
1274                 return -EINVAL;
1275         }
1276
1277         r = action_dev(m, dev, action);
1278
1279         dm_put_device(ti, dev);
1280
1281         return r;
1282
1283 error:
1284         DMWARN("Unrecognised multipath message received.");
1285         return -EINVAL;
1286 }
1287
1288 static int multipath_ioctl(struct dm_target *ti, struct inode *inode,
1289                            struct file *filp, unsigned int cmd,
1290                            unsigned long arg)
1291 {
1292         struct multipath *m = (struct multipath *) ti->private;
1293         struct block_device *bdev = NULL;
1294         unsigned long flags;
1295         struct file fake_file = {};
1296         struct dentry fake_dentry = {};
1297         int r = 0;
1298
1299         fake_file.f_path.dentry = &fake_dentry;
1300
1301         spin_lock_irqsave(&m->lock, flags);
1302
1303         if (!m->current_pgpath)
1304                 __choose_pgpath(m);
1305
1306         if (m->current_pgpath) {
1307                 bdev = m->current_pgpath->path.dev->bdev;
1308                 fake_dentry.d_inode = bdev->bd_inode;
1309                 fake_file.f_mode = m->current_pgpath->path.dev->mode;
1310         }
1311
1312         if (m->queue_io)
1313                 r = -EAGAIN;
1314         else if (!bdev)
1315                 r = -EIO;
1316
1317         spin_unlock_irqrestore(&m->lock, flags);
1318
1319         return r ? : blkdev_driver_ioctl(bdev->bd_inode, &fake_file,
1320                                          bdev->bd_disk, cmd, arg);
1321 }
1322
1323 /*-----------------------------------------------------------------
1324  * Module setup
1325  *---------------------------------------------------------------*/
1326 static struct target_type multipath_target = {
1327         .name = "multipath",
1328         .version = {1, 0, 5},
1329         .module = THIS_MODULE,
1330         .ctr = multipath_ctr,
1331         .dtr = multipath_dtr,
1332         .map = multipath_map,
1333         .end_io = multipath_end_io,
1334         .presuspend = multipath_presuspend,
1335         .resume = multipath_resume,
1336         .status = multipath_status,
1337         .message = multipath_message,
1338         .ioctl  = multipath_ioctl,
1339 };
1340
1341 static int __init dm_multipath_init(void)
1342 {
1343         int r;
1344
1345         /* allocate a slab for the dm_ios */
1346         _mpio_cache = kmem_cache_create("dm_mpath", sizeof(struct mpath_io),
1347                                         0, 0, NULL, NULL);
1348         if (!_mpio_cache)
1349                 return -ENOMEM;
1350
1351         r = dm_register_target(&multipath_target);
1352         if (r < 0) {
1353                 DMERR("%s: register failed %d", multipath_target.name, r);
1354                 kmem_cache_destroy(_mpio_cache);
1355                 return -EINVAL;
1356         }
1357
1358         kmultipathd = create_workqueue("kmpathd");
1359         if (!kmultipathd) {
1360                 DMERR("%s: failed to create workqueue kmpathd",
1361                                 multipath_target.name);
1362                 dm_unregister_target(&multipath_target);
1363                 kmem_cache_destroy(_mpio_cache);
1364                 return -ENOMEM;
1365         }
1366
1367         DMINFO("version %u.%u.%u loaded",
1368                multipath_target.version[0], multipath_target.version[1],
1369                multipath_target.version[2]);
1370
1371         return r;
1372 }
1373
1374 static void __exit dm_multipath_exit(void)
1375 {
1376         int r;
1377
1378         destroy_workqueue(kmultipathd);
1379
1380         r = dm_unregister_target(&multipath_target);
1381         if (r < 0)
1382                 DMERR("%s: target unregister failed %d",
1383                       multipath_target.name, r);
1384         kmem_cache_destroy(_mpio_cache);
1385 }
1386
1387 EXPORT_SYMBOL_GPL(dm_pg_init_complete);
1388
1389 module_init(dm_multipath_init);
1390 module_exit(dm_multipath_exit);
1391
1392 MODULE_DESCRIPTION(DM_NAME " multipath target");
1393 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1394 MODULE_LICENSE("GPL");