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 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 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 static int map_io(struct multipath *m, struct bio *bio, struct mpath_io *mpio,
 286                   unsigned was_queued)
 287 {
 288         int r = 1;
 289         unsigned long flags;
 290         struct pgpath *pgpath;
 291
 292         spin_lock_irqsave(&m->lock, flags);
 293
 294         /* Do we need to select a new pgpath? */
 295         if (!m->current_pgpath ||
 296             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 297                 __choose_pgpath(m);
 298
 299         pgpath = m->current_pgpath;
 300
 301         if (was_queued)
 302                 m->queue_size--;
 303
 304         if ((pgpath && m->queue_io) ||
 305             (!pgpath && m->queue_if_no_path)) {
 306                 /* Queue for the daemon to resubmit */
 307                 bio_list_add(&m->queued_ios, bio);
 308                 m->queue_size++;
 309                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 310                     !m->queue_io)
 311                         queue_work(kmultipathd, &m->process_queued_ios);
 312                 pgpath = NULL;
 313                 r = 0;
 314         } else if (!pgpath)
 315                 r = -EIO;               /* Failed */
 316         else
 317                 bio->bi_bdev = pgpath->path.dev->bdev;
 318
 319         mpio->pgpath = pgpath;
 320
 321         spin_unlock_irqrestore(&m->lock, flags);
 322
 323         return r;
 324 }
 325
 326 /*
 327  * If we run out of usable paths, should we queue I/O or error it?
 328  */
 329 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 330                             unsigned save_old_value)
 331 {
 332         unsigned long flags;
 333
 334         spin_lock_irqsave(&m->lock, flags);
 335
 336         if (save_old_value)
 337                 m->saved_queue_if_no_path = m->queue_if_no_path;
 338         else
 339                 m->saved_queue_if_no_path = queue_if_no_path;
 340         m->queue_if_no_path = queue_if_no_path;
 341         if (!m->queue_if_no_path && m->queue_size)
 342                 queue_work(kmultipathd, &m->process_queued_ios);
 343
 344         spin_unlock_irqrestore(&m->lock, flags);
 345
 346         return 0;
 347 }
 348
 349 /*-----------------------------------------------------------------
 350  * The multipath daemon is responsible for resubmitting queued ios.
 351  *---------------------------------------------------------------*/
 352
 353 static void dispatch_queued_ios(struct multipath *m)
 354 {
 355         int r;
 356         unsigned long flags;
 357         struct bio *bio = NULL, *next;
 358         struct mpath_io *mpio;
 359         union map_info *info;
 360
 361         spin_lock_irqsave(&m->lock, flags);
 362         bio = bio_list_get(&m->queued_ios);
 363         spin_unlock_irqrestore(&m->lock, flags);
 364
 365         while (bio) {
 366                 next = bio->bi_next;
 367                 bio->bi_next = NULL;
 368
 369                 info = dm_get_mapinfo(bio);
 370                 mpio = info->ptr;
 371
 372                 r = map_io(m, bio, mpio, 1);
 373                 if (r < 0)
 374                         bio_endio(bio, bio->bi_size, r);
 375                 else if (r == 1)
 376                         generic_make_request(bio);
 377
 378                 bio = next;
 379         }
 380 }
 381
 382 static void process_queued_ios(struct work_struct *work)
 383 {
 384         struct multipath *m =
 385                 container_of(work, struct multipath, process_queued_ios);
 386         struct hw_handler *hwh = &m->hw_handler;
 387         struct pgpath *pgpath = NULL;
 388         unsigned init_required = 0, must_queue = 1;
 389         unsigned long flags;
 390
 391         spin_lock_irqsave(&m->lock, flags);
 392
 393         if (!m->queue_size)
 394                 goto out;
 395
 396         if (!m->current_pgpath)
 397                 __choose_pgpath(m);
 398
 399         pgpath = m->current_pgpath;
 400
 401         if ((pgpath && !m->queue_io) ||
 402             (!pgpath && !m->queue_if_no_path))
 403                 must_queue = 0;
 404
 405         if (m->pg_init_required && !m->pg_init_in_progress) {
 406                 m->pg_init_required = 0;
 407                 m->pg_init_in_progress = 1;
 408                 init_required = 1;
 409         }
 410
 411 out:
 412         spin_unlock_irqrestore(&m->lock, flags);
 413
 414         if (init_required)
 415                 hwh->type->pg_init(hwh, pgpath->pg->bypassed, &pgpath->path);
 416
 417         if (!must_queue)
 418                 dispatch_queued_ios(m);
 419 }
 420
 421 /*
 422  * An event is triggered whenever a path is taken out of use.
 423  * Includes path failure and PG bypass.
 424  */
 425 static void trigger_event(struct work_struct *work)
 426 {
 427         struct multipath *m =
 428                 container_of(work, struct multipath, trigger_event);
 429
 430         dm_table_event(m->ti->table);
 431 }
 432
 433 /*-----------------------------------------------------------------
 434  * Constructor/argument parsing:
 435  * <#multipath feature args> [<arg>]*
 436  * <#hw_handler args> [hw_handler [<arg>]*]
 437  * <#priority groups>
 438  * <initial priority group>
 439  *     [<selector> <#selector args> [<arg>]*
 440  *      <#paths> <#per-path selector args>
 441  *         [<path> [<arg>]* ]+ ]+
 442  *---------------------------------------------------------------*/
 443 struct param {
 444         unsigned min;
 445         unsigned max;
 446         char *error;
 447 };
 448
 449 static int read_param(struct param *param, char *str, unsigned *v, char **error)
 450 {
 451         if (!str ||
 452             (sscanf(str, "%u", v) != 1) ||
 453             (*v < param->min) ||
 454             (*v > param->max)) {
 455                 *error = param->error;
 456                 return -EINVAL;
 457         }
 458
 459         return 0;
 460 }
 461
 462 struct arg_set {
 463         unsigned argc;
 464         char **argv;
 465 };
 466
 467 static char *shift(struct arg_set *as)
 468 {
 469         char *r;
 470
 471         if (as->argc) {
 472                 as->argc--;
 473                 r = *as->argv;
 474                 as->argv++;
 475                 return r;
 476         }
 477
 478         return NULL;
 479 }
 480
 481 static void consume(struct arg_set *as, unsigned n)
 482 {
 483         BUG_ON (as->argc < n);
 484         as->argc -= n;
 485         as->argv += n;
 486 }
 487
 488 static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
 489                                struct dm_target *ti)
 490 {
 491         int r;
 492         struct path_selector_type *pst;
 493         unsigned ps_argc;
 494
 495         static struct param _params[] = {
 496                 {0, 1024, "invalid number of path selector args"},
 497         };
 498
 499         pst = dm_get_path_selector(shift(as));
 500         if (!pst) {
 501                 ti->error = "unknown path selector type";
 502                 return -EINVAL;
 503         }
 504
 505         r = read_param(_params, shift(as), &ps_argc, &ti->error);
 506         if (r)
 507                 return -EINVAL;
 508
 509         r = pst->create(&pg->ps, ps_argc, as->argv);
 510         if (r) {
 511                 dm_put_path_selector(pst);
 512                 ti->error = "path selector constructor failed";
 513                 return r;
 514         }
 515
 516         pg->ps.type = pst;
 517         consume(as, ps_argc);
 518
 519         return 0;
 520 }
 521
 522 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
 523                                struct dm_target *ti)
 524 {
 525         int r;
 526         struct pgpath *p;
 527
 528         /* we need at least a path arg */
 529         if (as->argc < 1) {
 530                 ti->error = "no device given";
 531                 return NULL;
 532         }
 533
 534         p = alloc_pgpath();
 535         if (!p)
 536                 return NULL;
 537
 538         r = dm_get_device(ti, shift(as), ti->begin, ti->len,
 539                           dm_table_get_mode(ti->table), &p->path.dev);
 540         if (r) {
 541                 ti->error = "error getting device";
 542                 goto bad;
 543         }
 544
 545         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 546         if (r) {
 547                 dm_put_device(ti, p->path.dev);
 548                 goto bad;
 549         }
 550
 551         return p;
 552
 553  bad:
 554         free_pgpath(p);
 555         return NULL;
 556 }
 557
 558 static struct priority_group *parse_priority_group(struct arg_set *as,
 559                                                    struct multipath *m)
 560 {
 561         static struct param _params[] = {
 562                 {1, 1024, "invalid number of paths"},
 563                 {0, 1024, "invalid number of selector args"}
 564         };
 565
 566         int r;
 567         unsigned i, nr_selector_args, nr_params;
 568         struct priority_group *pg;
 569         struct dm_target *ti = m->ti;
 570
 571         if (as->argc < 2) {
 572                 as->argc = 0;
 573                 ti->error = "not enough priority group aruments";
 574                 return NULL;
 575         }
 576
 577         pg = alloc_priority_group();
 578         if (!pg) {
 579                 ti->error = "couldn't allocate priority group";
 580                 return NULL;
 581         }
 582         pg->m = m;
 583
 584         r = parse_path_selector(as, pg, ti);
 585         if (r)
 586                 goto bad;
 587
 588         /*
 589          * read the paths
 590          */
 591         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
 592         if (r)
 593                 goto bad;
 594
 595         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
 596         if (r)
 597                 goto bad;
 598
 599         nr_params = 1 + nr_selector_args;
 600         for (i = 0; i < pg->nr_pgpaths; i++) {
 601                 struct pgpath *pgpath;
 602                 struct arg_set path_args;
 603
 604                 if (as->argc < nr_params)
 605                         goto bad;
 606
 607                 path_args.argc = nr_params;
 608                 path_args.argv = as->argv;
 609
 610                 pgpath = parse_path(&path_args, &pg->ps, ti);
 611                 if (!pgpath)
 612                         goto bad;
 613
 614                 pgpath->pg = pg;
 615                 list_add_tail(&pgpath->list, &pg->pgpaths);
 616                 consume(as, nr_params);
 617         }
 618
 619         return pg;
 620
 621  bad:
 622         free_priority_group(pg, ti);
 623         return NULL;
 624 }
 625
 626 static int parse_hw_handler(struct arg_set *as, struct multipath *m)
 627 {
 628         int r;
 629         struct hw_handler_type *hwht;
 630         unsigned hw_argc;
 631         struct dm_target *ti = m->ti;
 632
 633         static struct param _params[] = {
 634                 {0, 1024, "invalid number of hardware handler args"},
 635         };
 636
 637         r = read_param(_params, shift(as), &hw_argc, &ti->error);
 638         if (r)
 639                 return -EINVAL;
 640
 641         if (!hw_argc)
 642                 return 0;
 643
 644         hwht = dm_get_hw_handler(shift(as));
 645         if (!hwht) {
 646                 ti->error = "unknown hardware handler type";
 647                 return -EINVAL;
 648         }
 649
 650         r = hwht->create(&m->hw_handler, hw_argc - 1, as->argv);
 651         if (r) {
 652                 dm_put_hw_handler(hwht);
 653                 ti->error = "hardware handler constructor failed";
 654                 return r;
 655         }
 656
 657         m->hw_handler.type = hwht;
 658         consume(as, hw_argc - 1);
 659
 660         return 0;
 661 }
 662
 663 static int parse_features(struct arg_set *as, struct multipath *m)
 664 {
 665         int r;
 666         unsigned argc;
 667         struct dm_target *ti = m->ti;
 668
 669         static struct param _params[] = {
 670                 {0, 1, "invalid number of feature args"},
 671         };
 672
 673         r = read_param(_params, shift(as), &argc, &ti->error);
 674         if (r)
 675                 return -EINVAL;
 676
 677         if (!argc)
 678                 return 0;
 679
 680         if (!strnicmp(shift(as), MESG_STR("queue_if_no_path")))
 681                 return queue_if_no_path(m, 1, 0);
 682         else {
 683                 ti->error = "Unrecognised multipath feature request";
 684                 return -EINVAL;
 685         }
 686 }
 687
 688 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 689                          char **argv)
 690 {
 691         /* target parameters */
 692         static struct param _params[] = {
 693                 {1, 1024, "invalid number of priority groups"},
 694                 {1, 1024, "invalid initial priority group number"},
 695         };
 696
 697         int r;
 698         struct multipath *m;
 699         struct arg_set as;
 700         unsigned pg_count = 0;
 701         unsigned next_pg_num;
 702
 703         as.argc = argc;
 704         as.argv = argv;
 705
 706         m = alloc_multipath(ti);
 707         if (!m) {
 708                 ti->error = "can't allocate multipath";
 709                 return -EINVAL;
 710         }
 711
 712         r = parse_features(&as, m);
 713         if (r)
 714                 goto bad;
 715
 716         r = parse_hw_handler(&as, m);
 717         if (r)
 718                 goto bad;
 719
 720         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
 721         if (r)
 722                 goto bad;
 723
 724         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
 725         if (r)
 726                 goto bad;
 727
 728         /* parse the priority groups */
 729         while (as.argc) {
 730                 struct priority_group *pg;
 731
 732                 pg = parse_priority_group(&as, m);
 733                 if (!pg) {
 734                         r = -EINVAL;
 735                         goto bad;
 736                 }
 737
 738                 m->nr_valid_paths += pg->nr_pgpaths;
 739                 list_add_tail(&pg->list, &m->priority_groups);
 740                 pg_count++;
 741                 pg->pg_num = pg_count;
 742                 if (!--next_pg_num)
 743                         m->next_pg = pg;
 744         }
 745
 746         if (pg_count != m->nr_priority_groups) {
 747                 ti->error = "priority group count mismatch";
 748                 r = -EINVAL;
 749                 goto bad;
 750         }
 751
 752         return 0;
 753
 754  bad:
 755         free_multipath(m);
 756         return r;
 757 }
 758
 759 static void multipath_dtr(struct dm_target *ti)
 760 {
 761         struct multipath *m = (struct multipath *) ti->private;
 762
 763         flush_workqueue(kmultipathd);
 764         free_multipath(m);
 765 }
 766
 767 /*
 768  * Map bios, recording original fields for later in case we have to resubmit
 769  */
 770 static int multipath_map(struct dm_target *ti, struct bio *bio,
 771                          union map_info *map_context)
 772 {
 773         int r;
 774         struct mpath_io *mpio;
 775         struct multipath *m = (struct multipath *) ti->private;
 776
 777         if (bio_barrier(bio))
 778                 return -EOPNOTSUPP;
 779
 780         mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
 781         dm_bio_record(&mpio->details, bio);
 782
 783         map_context->ptr = mpio;
 784         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
 785         r = map_io(m, bio, mpio, 0);
 786         if (r < 0)
 787                 mempool_free(mpio, m->mpio_pool);
 788
 789         return r;
 790 }
 791
 792 /*
 793  * Take a path out of use.
 794  */
 795 static int fail_path(struct pgpath *pgpath)
 796 {
 797         unsigned long flags;
 798         struct multipath *m = pgpath->pg->m;
 799
 800         spin_lock_irqsave(&m->lock, flags);
 801
 802         if (!pgpath->path.is_active)
 803                 goto out;
 804
 805         DMWARN("Failing path %s.", pgpath->path.dev->name);
 806
 807         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 808         pgpath->path.is_active = 0;
 809         pgpath->fail_count++;
 810
 811         m->nr_valid_paths--;
 812
 813         if (pgpath == m->current_pgpath)
 814                 m->current_pgpath = NULL;
 815
 816         queue_work(kmultipathd, &m->trigger_event);
 817
 818 out:
 819         spin_unlock_irqrestore(&m->lock, flags);
 820
 821         return 0;
 822 }
 823
 824 /*
 825  * Reinstate a previously-failed path
 826  */
 827 static int reinstate_path(struct pgpath *pgpath)
 828 {
 829         int r = 0;
 830         unsigned long flags;
 831         struct multipath *m = pgpath->pg->m;
 832
 833         spin_lock_irqsave(&m->lock, flags);
 834
 835         if (pgpath->path.is_active)
 836                 goto out;
 837
 838         if (!pgpath->pg->ps.type) {
 839                 DMWARN("Reinstate path not supported by path selector %s",
 840                        pgpath->pg->ps.type->name);
 841                 r = -EINVAL;
 842                 goto out;
 843         }
 844
 845         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
 846         if (r)
 847                 goto out;
 848
 849         pgpath->path.is_active = 1;
 850
 851         m->current_pgpath = NULL;
 852         if (!m->nr_valid_paths++ && m->queue_size)
 853                 queue_work(kmultipathd, &m->process_queued_ios);
 854
 855         queue_work(kmultipathd, &m->trigger_event);
 856
 857 out:
 858         spin_unlock_irqrestore(&m->lock, flags);
 859
 860         return r;
 861 }
 862
 863 /*
 864  * Fail or reinstate all paths that match the provided struct dm_dev.
 865  */
 866 static int action_dev(struct multipath *m, struct dm_dev *dev,
 867                       action_fn action)
 868 {
 869         int r = 0;
 870         struct pgpath *pgpath;
 871         struct priority_group *pg;
 872
 873         list_for_each_entry(pg, &m->priority_groups, list) {
 874                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
 875                         if (pgpath->path.dev == dev)
 876                                 r = action(pgpath);
 877                 }
 878         }
 879
 880         return r;
 881 }
 882
 883 /*
 884  * Temporarily try to avoid having to use the specified PG
 885  */
 886 static void bypass_pg(struct multipath *m, struct priority_group *pg,
 887                       int bypassed)
 888 {
 889         unsigned long flags;
 890
 891         spin_lock_irqsave(&m->lock, flags);
 892
 893         pg->bypassed = bypassed;
 894         m->current_pgpath = NULL;
 895         m->current_pg = NULL;
 896
 897         spin_unlock_irqrestore(&m->lock, flags);
 898
 899         queue_work(kmultipathd, &m->trigger_event);
 900 }
 901
 902 /*
 903  * Switch to using the specified PG from the next I/O that gets mapped
 904  */
 905 static int switch_pg_num(struct multipath *m, const char *pgstr)
 906 {
 907         struct priority_group *pg;
 908         unsigned pgnum;
 909         unsigned long flags;
 910
 911         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
 912             (pgnum > m->nr_priority_groups)) {
 913                 DMWARN("invalid PG number supplied to switch_pg_num");
 914                 return -EINVAL;
 915         }
 916
 917         spin_lock_irqsave(&m->lock, flags);
 918         list_for_each_entry(pg, &m->priority_groups, list) {
 919                 pg->bypassed = 0;
 920                 if (--pgnum)
 921                         continue;
 922
 923                 m->current_pgpath = NULL;
 924                 m->current_pg = NULL;
 925                 m->next_pg = pg;
 926         }
 927         spin_unlock_irqrestore(&m->lock, flags);
 928
 929         queue_work(kmultipathd, &m->trigger_event);
 930         return 0;
 931 }
 932
 933 /*
 934  * Set/clear bypassed status of a PG.
 935  * PGs are numbered upwards from 1 in the order they were declared.
 936  */
 937 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
 938 {
 939         struct priority_group *pg;
 940         unsigned pgnum;
 941
 942         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
 943             (pgnum > m->nr_priority_groups)) {
 944                 DMWARN("invalid PG number supplied to bypass_pg");
 945                 return -EINVAL;
 946         }
 947
 948         list_for_each_entry(pg, &m->priority_groups, list) {
 949                 if (!--pgnum)
 950                         break;
 951         }
 952
 953         bypass_pg(m, pg, bypassed);
 954         return 0;
 955 }
 956
 957 /*
 958  * pg_init must call this when it has completed its initialisation
 959  */
 960 void dm_pg_init_complete(struct path *path, unsigned err_flags)
 961 {
 962         struct pgpath *pgpath = path_to_pgpath(path);
 963         struct priority_group *pg = pgpath->pg;
 964         struct multipath *m = pg->m;
 965         unsigned long flags;
 966
 967         /* We insist on failing the path if the PG is already bypassed. */
 968         if (err_flags && pg->bypassed)
 969                 err_flags |= MP_FAIL_PATH;
 970
 971         if (err_flags & MP_FAIL_PATH)
 972                 fail_path(pgpath);
 973
 974         if (err_flags & MP_BYPASS_PG)
 975                 bypass_pg(m, pg, 1);
 976
 977         spin_lock_irqsave(&m->lock, flags);
 978         if (err_flags) {
 979                 m->current_pgpath = NULL;
 980                 m->current_pg = NULL;
 981         } else if (!m->pg_init_required)
 982                 m->queue_io = 0;
 983
 984         m->pg_init_in_progress = 0;
 985         queue_work(kmultipathd, &m->process_queued_ios);
 986         spin_unlock_irqrestore(&m->lock, flags);
 987 }
 988
 989 /*
 990  * end_io handling
 991  */
 992 static int do_end_io(struct multipath *m, struct bio *bio,
 993                      int error, struct mpath_io *mpio)
 994 {
 995         struct hw_handler *hwh = &m->hw_handler;
 996         unsigned err_flags = MP_FAIL_PATH;      /* Default behavior */
 997         unsigned long flags;
 998
 999         if (!error)
1000                 return 0;       /* I/O complete */
1001
1002         if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
1003                 return error;
1004
1005         if (error == -EOPNOTSUPP)
1006                 return error;
1007
1008         spin_lock_irqsave(&m->lock, flags);
1009         if (!m->nr_valid_paths) {
1010                 if (!m->queue_if_no_path) {
1011                         spin_unlock_irqrestore(&m->lock, flags);
1012                         return -EIO;
1013                 } else {
1014                         spin_unlock_irqrestore(&m->lock, flags);
1015                         goto requeue;
1016                 }
1017         }
1018         spin_unlock_irqrestore(&m->lock, flags);
1019
1020         if (hwh->type && hwh->type->error)
1021                 err_flags = hwh->type->error(hwh, bio);
1022
1023         if (mpio->pgpath) {
1024                 if (err_flags & MP_FAIL_PATH)
1025                         fail_path(mpio->pgpath);
1026
1027                 if (err_flags & MP_BYPASS_PG)
1028                         bypass_pg(m, mpio->pgpath->pg, 1);
1029         }
1030
1031         if (err_flags & MP_ERROR_IO)
1032                 return -EIO;
1033
1034       requeue:
1035         dm_bio_restore(&mpio->details, bio);
1036
1037         /* queue for the daemon to resubmit or fail */
1038         spin_lock_irqsave(&m->lock, flags);
1039         bio_list_add(&m->queued_ios, bio);
1040         m->queue_size++;
1041         if (!m->queue_io)
1042                 queue_work(kmultipathd, &m->process_queued_ios);
1043         spin_unlock_irqrestore(&m->lock, flags);
1044
1045         return 1;       /* io not complete */
1046 }
1047
1048 static int multipath_end_io(struct dm_target *ti, struct bio *bio,
1049                             int error, union map_info *map_context)
1050 {
1051         struct multipath *m = (struct multipath *) ti->private;
1052         struct mpath_io *mpio = (struct mpath_io *) map_context->ptr;
1053         struct pgpath *pgpath = mpio->pgpath;
1054         struct path_selector *ps;
1055         int r;
1056
1057         r  = do_end_io(m, bio, error, mpio);
1058         if (pgpath) {
1059                 ps = &pgpath->pg->ps;
1060                 if (ps->type->end_io)
1061                         ps->type->end_io(ps, &pgpath->path);
1062         }
1063         if (r <= 0)
1064                 mempool_free(mpio, m->mpio_pool);
1065
1066         return r;
1067 }
1068
1069 /*
1070  * Suspend can't complete until all the I/O is processed so if
1071  * the last path fails we must error any remaining I/O.
1072  * Note that if the freeze_bdev fails while suspending, the
1073  * queue_if_no_path state is lost - userspace should reset it.
1074  */
1075 static void multipath_presuspend(struct dm_target *ti)
1076 {
1077         struct multipath *m = (struct multipath *) ti->private;
1078
1079         queue_if_no_path(m, 0, 1);
1080 }
1081
1082 /*
1083  * Restore the queue_if_no_path setting.
1084  */
1085 static void multipath_resume(struct dm_target *ti)
1086 {
1087         struct multipath *m = (struct multipath *) ti->private;
1088         unsigned long flags;
1089
1090         spin_lock_irqsave(&m->lock, flags);
1091         m->queue_if_no_path = m->saved_queue_if_no_path;
1092         spin_unlock_irqrestore(&m->lock, flags);
1093 }
1094
1095 /*
1096  * Info output has the following format:
1097  * num_multipath_feature_args [multipath_feature_args]*
1098  * num_handler_status_args [handler_status_args]*
1099  * num_groups init_group_number
1100  *            [A|D|E num_ps_status_args [ps_status_args]*
1101  *             num_paths num_selector_args
1102  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1103  *
1104  * Table output has the following format (identical to the constructor string):
1105  * num_feature_args [features_args]*
1106  * num_handler_args hw_handler [hw_handler_args]*
1107  * num_groups init_group_number
1108  *     [priority selector-name num_ps_args [ps_args]*
1109  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1110  */
1111 static int multipath_status(struct dm_target *ti, status_type_t type,
1112                             char *result, unsigned int maxlen)
1113 {
1114         int sz = 0;
1115         unsigned long flags;
1116         struct multipath *m = (struct multipath *) ti->private;
1117         struct hw_handler *hwh = &m->hw_handler;
1118         struct priority_group *pg;
1119         struct pgpath *p;
1120         unsigned pg_num;
1121         char state;
1122
1123         spin_lock_irqsave(&m->lock, flags);
1124
1125         /* Features */
1126         if (type == STATUSTYPE_INFO)
1127                 DMEMIT("1 %u ", m->queue_size);
1128         else if (m->queue_if_no_path)
1129                 DMEMIT("1 queue_if_no_path ");
1130         else
1131                 DMEMIT("0 ");
1132
1133         if (hwh->type && hwh->type->status)
1134                 sz += hwh->type->status(hwh, type, result + sz, maxlen - sz);
1135         else if (!hwh->type || type == STATUSTYPE_INFO)
1136                 DMEMIT("0 ");
1137         else
1138                 DMEMIT("1 %s ", hwh->type->name);
1139
1140         DMEMIT("%u ", m->nr_priority_groups);
1141
1142         if (m->next_pg)
1143                 pg_num = m->next_pg->pg_num;
1144         else if (m->current_pg)
1145                 pg_num = m->current_pg->pg_num;
1146         else
1147                         pg_num = 1;
1148
1149         DMEMIT("%u ", pg_num);
1150
1151         switch (type) {
1152         case STATUSTYPE_INFO:
1153                 list_for_each_entry(pg, &m->priority_groups, list) {
1154                         if (pg->bypassed)
1155                                 state = 'D';    /* Disabled */
1156                         else if (pg == m->current_pg)
1157                                 state = 'A';    /* Currently Active */
1158                         else
1159                                 state = 'E';    /* Enabled */
1160
1161                         DMEMIT("%c ", state);
1162
1163                         if (pg->ps.type->status)
1164                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1165                                                           result + sz,
1166                                                           maxlen - sz);
1167                         else
1168                                 DMEMIT("0 ");
1169
1170                         DMEMIT("%u %u ", pg->nr_pgpaths,
1171                                pg->ps.type->info_args);
1172
1173                         list_for_each_entry(p, &pg->pgpaths, list) {
1174                                 DMEMIT("%s %s %u ", p->path.dev->name,
1175                                        p->path.is_active ? "A" : "F",
1176                                        p->fail_count);
1177                                 if (pg->ps.type->status)
1178                                         sz += pg->ps.type->status(&pg->ps,
1179                                               &p->path, type, result + sz,
1180                                               maxlen - sz);
1181                         }
1182                 }
1183                 break;
1184
1185         case STATUSTYPE_TABLE:
1186                 list_for_each_entry(pg, &m->priority_groups, list) {
1187                         DMEMIT("%s ", pg->ps.type->name);
1188
1189                         if (pg->ps.type->status)
1190                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1191                                                           result + sz,
1192                                                           maxlen - sz);
1193                         else
1194                                 DMEMIT("0 ");
1195
1196                         DMEMIT("%u %u ", pg->nr_pgpaths,
1197                                pg->ps.type->table_args);
1198
1199                         list_for_each_entry(p, &pg->pgpaths, list) {
1200                                 DMEMIT("%s ", p->path.dev->name);
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
1210         spin_unlock_irqrestore(&m->lock, flags);
1211
1212         return 0;
1213 }
1214
1215 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1216 {
1217         int r;
1218         struct dm_dev *dev;
1219         struct multipath *m = (struct multipath *) ti->private;
1220         action_fn action;
1221
1222         if (argc == 1) {
1223                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path")))
1224                         return queue_if_no_path(m, 1, 0);
1225                 else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path")))
1226                         return queue_if_no_path(m, 0, 0);
1227         }
1228
1229         if (argc != 2)
1230                 goto error;
1231
1232         if (!strnicmp(argv[0], MESG_STR("disable_group")))
1233                 return bypass_pg_num(m, argv[1], 1);
1234         else if (!strnicmp(argv[0], MESG_STR("enable_group")))
1235                 return bypass_pg_num(m, argv[1], 0);
1236         else if (!strnicmp(argv[0], MESG_STR("switch_group")))
1237                 return switch_pg_num(m, argv[1]);
1238         else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1239                 action = reinstate_path;
1240         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1241                 action = fail_path;
1242         else
1243                 goto error;
1244
1245         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
1246                           dm_table_get_mode(ti->table), &dev);
1247         if (r) {
1248                 DMWARN("message: error getting device %s",
1249                        argv[1]);
1250                 return -EINVAL;
1251         }
1252
1253         r = action_dev(m, dev, action);
1254
1255         dm_put_device(ti, dev);
1256
1257         return r;
1258
1259 error:
1260         DMWARN("Unrecognised multipath message received.");
1261         return -EINVAL;
1262 }
1263
1264 static int multipath_ioctl(struct dm_target *ti, struct inode *inode,
1265                            struct file *filp, unsigned int cmd,
1266                            unsigned long arg)
1267 {
1268         struct multipath *m = (struct multipath *) ti->private;
1269         struct block_device *bdev = NULL;
1270         unsigned long flags;
1271         struct file fake_file = {};
1272         struct dentry fake_dentry = {};
1273         int r = 0;
1274
1275         fake_file.f_dentry = &fake_dentry;
1276
1277         spin_lock_irqsave(&m->lock, flags);
1278
1279         if (!m->current_pgpath)
1280                 __choose_pgpath(m);
1281
1282         if (m->current_pgpath) {
1283                 bdev = m->current_pgpath->path.dev->bdev;
1284                 fake_dentry.d_inode = bdev->bd_inode;
1285                 fake_file.f_mode = m->current_pgpath->path.dev->mode;
1286         }
1287
1288         if (m->queue_io)
1289                 r = -EAGAIN;
1290         else if (!bdev)
1291                 r = -EIO;
1292
1293         spin_unlock_irqrestore(&m->lock, flags);
1294
1295         return r ? : blkdev_driver_ioctl(bdev->bd_inode, &fake_file,
1296                                          bdev->bd_disk, cmd, arg);
1297 }
1298
1299 /*-----------------------------------------------------------------
1300  * Module setup
1301  *---------------------------------------------------------------*/
1302 static struct target_type multipath_target = {
1303         .name = "multipath",
1304         .version = {1, 0, 5},
1305         .module = THIS_MODULE,
1306         .ctr = multipath_ctr,
1307         .dtr = multipath_dtr,
1308         .map = multipath_map,
1309         .end_io = multipath_end_io,
1310         .presuspend = multipath_presuspend,
1311         .resume = multipath_resume,
1312         .status = multipath_status,
1313         .message = multipath_message,
1314         .ioctl  = multipath_ioctl,
1315 };
1316
1317 static int __init dm_multipath_init(void)
1318 {
1319         int r;
1320
1321         /* allocate a slab for the dm_ios */
1322         _mpio_cache = kmem_cache_create("dm_mpath", sizeof(struct mpath_io),
1323                                         0, 0, NULL, NULL);
1324         if (!_mpio_cache)
1325                 return -ENOMEM;
1326
1327         r = dm_register_target(&multipath_target);
1328         if (r < 0) {
1329                 DMERR("%s: register failed %d", multipath_target.name, r);
1330                 kmem_cache_destroy(_mpio_cache);
1331                 return -EINVAL;
1332         }
1333
1334         kmultipathd = create_workqueue("kmpathd");
1335         if (!kmultipathd) {
1336                 DMERR("%s: failed to create workqueue kmpathd",
1337                                 multipath_target.name);
1338                 dm_unregister_target(&multipath_target);
1339                 kmem_cache_destroy(_mpio_cache);
1340                 return -ENOMEM;
1341         }
1342
1343         DMINFO("version %u.%u.%u loaded",
1344                multipath_target.version[0], multipath_target.version[1],
1345                multipath_target.version[2]);
1346
1347         return r;
1348 }
1349
1350 static void __exit dm_multipath_exit(void)
1351 {
1352         int r;
1353
1354         destroy_workqueue(kmultipathd);
1355
1356         r = dm_unregister_target(&multipath_target);
1357         if (r < 0)
1358                 DMERR("%s: target unregister failed %d",
1359                       multipath_target.name, r);
1360         kmem_cache_destroy(_mpio_cache);
1361 }
1362
1363 EXPORT_SYMBOL_GPL(dm_pg_init_complete);
1364
1365 module_init(dm_multipath_init);
1366 module_exit(dm_multipath_exit);
1367
1368 MODULE_DESCRIPTION(DM_NAME " multipath target");
1369 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1370 MODULE_LICENSE("GPL");