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 MESG_STR(x) x, sizeof(x)
  25
  26 /* Path properties */
  27 struct pgpath {
  28         struct list_head list;
  29
  30         struct priority_group *pg;      /* Owning PG */
  31         unsigned fail_count;            /* Cumulative failure count */
  32
  33         struct path path;
  34 };
  35
  36 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  37
  38 /*
  39  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  40  * Each has a path selector which controls which path gets used.
  41  */
  42 struct priority_group {
  43         struct list_head list;
  44
  45         struct multipath *m;            /* Owning multipath instance */
  46         struct path_selector ps;
  47
  48         unsigned pg_num;                /* Reference number */
  49         unsigned bypassed;              /* Temporarily bypass this PG? */
  50
  51         unsigned nr_pgpaths;            /* Number of paths in PG */
  52         struct list_head pgpaths;
  53 };
  54
  55 /* Multipath context */
  56 struct multipath {
  57         struct list_head list;
  58         struct dm_target *ti;
  59
  60         spinlock_t lock;
  61
  62         struct hw_handler hw_handler;
  63         unsigned nr_priority_groups;
  64         struct list_head priority_groups;
  65         unsigned pg_init_required;      /* pg_init needs calling? */
  66         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  67
  68         unsigned nr_valid_paths;        /* Total number of usable paths */
  69         struct pgpath *current_pgpath;
  70         struct priority_group *current_pg;
  71         struct priority_group *next_pg; /* Switch to this PG if set */
  72         unsigned repeat_count;          /* I/Os left before calling PS again */
  73
  74         unsigned queue_io;              /* Must we queue all I/O? */
  75         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
  76         unsigned saved_queue_if_no_path;/* Saved state during suspension */
  77
  78         struct work_struct process_queued_ios;
  79         struct bio_list queued_ios;
  80         unsigned queue_size;
  81
  82         struct work_struct trigger_event;
  83
  84         /*
  85          * We must use a mempool of mpath_io structs so that we
  86          * can resubmit bios on error.
  87          */
  88         mempool_t *mpio_pool;
  89 };
  90
  91 /*
  92  * Context information attached to each bio we process.
  93  */
  94 struct mpath_io {
  95         struct pgpath *pgpath;
  96         struct dm_bio_details details;
  97 };
  98
  99 typedef int (*action_fn) (struct pgpath *pgpath);
 100
 101 #define MIN_IOS 256     /* Mempool size */
 102
 103 static kmem_cache_t *_mpio_cache;
 104
 105 struct workqueue_struct *kmultipathd;
 106 static void process_queued_ios(void *data);
 107 static void trigger_event(void *data);
 108
 109
 110 /*-----------------------------------------------
 111  * Allocation routines
 112  *-----------------------------------------------*/
 113
 114 static struct pgpath *alloc_pgpath(void)
 115 {
 116         struct pgpath *pgpath = kmalloc(sizeof(*pgpath), GFP_KERNEL);
 117
 118         if (pgpath) {
 119                 memset(pgpath, 0, sizeof(*pgpath));
 120                 pgpath->path.is_active = 1;
 121         }
 122
 123         return pgpath;
 124 }
 125
 126 static inline void free_pgpath(struct pgpath *pgpath)
 127 {
 128         kfree(pgpath);
 129 }
 130
 131 static struct priority_group *alloc_priority_group(void)
 132 {
 133         struct priority_group *pg;
 134
 135         pg = kmalloc(sizeof(*pg), GFP_KERNEL);
 136         if (!pg)
 137                 return NULL;
 138
 139         memset(pg, 0, sizeof(*pg));
 140         INIT_LIST_HEAD(&pg->pgpaths);
 141
 142         return pg;
 143 }
 144
 145 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 146 {
 147         struct pgpath *pgpath, *tmp;
 148
 149         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 150                 list_del(&pgpath->list);
 151                 dm_put_device(ti, pgpath->path.dev);
 152                 free_pgpath(pgpath);
 153         }
 154 }
 155
 156 static void free_priority_group(struct priority_group *pg,
 157                                 struct dm_target *ti)
 158 {
 159         struct path_selector *ps = &pg->ps;
 160
 161         if (ps->type) {
 162                 ps->type->destroy(ps);
 163                 dm_put_path_selector(ps->type);
 164         }
 165
 166         free_pgpaths(&pg->pgpaths, ti);
 167         kfree(pg);
 168 }
 169
 170 static struct multipath *alloc_multipath(void)
 171 {
 172         struct multipath *m;
 173
 174         m = kmalloc(sizeof(*m), GFP_KERNEL);
 175         if (m) {
 176                 memset(m, 0, sizeof(*m));
 177                 INIT_LIST_HEAD(&m->priority_groups);
 178                 spin_lock_init(&m->lock);
 179                 m->queue_io = 1;
 180                 INIT_WORK(&m->process_queued_ios, process_queued_ios, m);
 181                 INIT_WORK(&m->trigger_event, trigger_event, m);
 182                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 183                 if (!m->mpio_pool) {
 184                         kfree(m);
 185                         return NULL;
 186                 }
 187         }
 188
 189         return m;
 190 }
 191
 192 static void free_multipath(struct multipath *m)
 193 {
 194         struct priority_group *pg, *tmp;
 195         struct hw_handler *hwh = &m->hw_handler;
 196
 197         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 198                 list_del(&pg->list);
 199                 free_priority_group(pg, m->ti);
 200         }
 201
 202         if (hwh->type) {
 203                 hwh->type->destroy(hwh);
 204                 dm_put_hw_handler(hwh->type);
 205         }
 206
 207         mempool_destroy(m->mpio_pool);
 208         kfree(m);
 209 }
 210
 211
 212 /*-----------------------------------------------
 213  * Path selection
 214  *-----------------------------------------------*/
 215
 216 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 217 {
 218         struct hw_handler *hwh = &m->hw_handler;
 219
 220         m->current_pg = pgpath->pg;
 221
 222         /* Must we initialise the PG first, and queue I/O till it's ready? */
 223         if (hwh->type && hwh->type->pg_init) {
 224                 m->pg_init_required = 1;
 225                 m->queue_io = 1;
 226         } else {
 227                 m->pg_init_required = 0;
 228                 m->queue_io = 0;
 229         }
 230 }
 231
 232 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg)
 233 {
 234         struct path *path;
 235
 236         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count);
 237         if (!path)
 238                 return -ENXIO;
 239
 240         m->current_pgpath = path_to_pgpath(path);
 241
 242         if (m->current_pg != pg)
 243                 __switch_pg(m, m->current_pgpath);
 244
 245         return 0;
 246 }
 247
 248 static void __choose_pgpath(struct multipath *m)
 249 {
 250         struct priority_group *pg;
 251         unsigned bypassed = 1;
 252
 253         if (!m->nr_valid_paths)
 254                 goto failed;
 255
 256         /* Were we instructed to switch PG? */
 257         if (m->next_pg) {
 258                 pg = m->next_pg;
 259                 m->next_pg = NULL;
 260                 if (!__choose_path_in_pg(m, pg))
 261                         return;
 262         }
 263
 264         /* Don't change PG until it has no remaining paths */
 265         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg))
 266                 return;
 267
 268         /*
 269          * Loop through priority groups until we find a valid path.
 270          * First time we skip PGs marked 'bypassed'.
 271          * Second time we only try the ones we skipped.
 272          */
 273         do {
 274                 list_for_each_entry(pg, &m->priority_groups, list) {
 275                         if (pg->bypassed == bypassed)
 276                                 continue;
 277                         if (!__choose_path_in_pg(m, pg))
 278                                 return;
 279                 }
 280         } while (bypassed--);
 281
 282 failed:
 283         m->current_pgpath = NULL;
 284         m->current_pg = NULL;
 285 }
 286
 287 static int map_io(struct multipath *m, struct bio *bio, struct mpath_io *mpio,
 288                   unsigned was_queued)
 289 {
 290         int r = 1;
 291         unsigned long flags;
 292         struct pgpath *pgpath;
 293
 294         spin_lock_irqsave(&m->lock, flags);
 295
 296         /* Do we need to select a new pgpath? */
 297         if (!m->current_pgpath ||
 298             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 299                 __choose_pgpath(m);
 300
 301         pgpath = m->current_pgpath;
 302
 303         if (was_queued)
 304                 m->queue_size--;
 305
 306         if ((pgpath && m->queue_io) ||
 307             (!pgpath && m->queue_if_no_path)) {
 308                 /* Queue for the daemon to resubmit */
 309                 bio_list_add(&m->queued_ios, bio);
 310                 m->queue_size++;
 311                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 312                     !m->queue_io)
 313                         queue_work(kmultipathd, &m->process_queued_ios);
 314                 pgpath = NULL;
 315                 r = 0;
 316         } else if (!pgpath)
 317                 r = -EIO;               /* Failed */
 318         else
 319                 bio->bi_bdev = pgpath->path.dev->bdev;
 320
 321         mpio->pgpath = pgpath;
 322
 323         spin_unlock_irqrestore(&m->lock, flags);
 324
 325         return r;
 326 }
 327
 328 /*
 329  * If we run out of usable paths, should we queue I/O or error it?
 330  */
 331 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 332                             unsigned save_old_value)
 333 {
 334         unsigned long flags;
 335
 336         spin_lock_irqsave(&m->lock, flags);
 337
 338         if (save_old_value)
 339                 m->saved_queue_if_no_path = m->queue_if_no_path;
 340         else
 341                 m->saved_queue_if_no_path = queue_if_no_path;
 342         m->queue_if_no_path = queue_if_no_path;
 343         if (!m->queue_if_no_path && m->queue_size)
 344                 queue_work(kmultipathd, &m->process_queued_ios);
 345
 346         spin_unlock_irqrestore(&m->lock, flags);
 347
 348         return 0;
 349 }
 350
 351 /*-----------------------------------------------------------------
 352  * The multipath daemon is responsible for resubmitting queued ios.
 353  *---------------------------------------------------------------*/
 354
 355 static void dispatch_queued_ios(struct multipath *m)
 356 {
 357         int r;
 358         unsigned long flags;
 359         struct bio *bio = NULL, *next;
 360         struct mpath_io *mpio;
 361         union map_info *info;
 362
 363         spin_lock_irqsave(&m->lock, flags);
 364         bio = bio_list_get(&m->queued_ios);
 365         spin_unlock_irqrestore(&m->lock, flags);
 366
 367         while (bio) {
 368                 next = bio->bi_next;
 369                 bio->bi_next = NULL;
 370
 371                 info = dm_get_mapinfo(bio);
 372                 mpio = info->ptr;
 373
 374                 r = map_io(m, bio, mpio, 1);
 375                 if (r < 0)
 376                         bio_endio(bio, bio->bi_size, r);
 377                 else if (r == 1)
 378                         generic_make_request(bio);
 379
 380                 bio = next;
 381         }
 382 }
 383
 384 static void process_queued_ios(void *data)
 385 {
 386         struct multipath *m = (struct multipath *) data;
 387         struct hw_handler *hwh = &m->hw_handler;
 388         struct pgpath *pgpath = NULL;
 389         unsigned init_required = 0, must_queue = 1;
 390         unsigned long flags;
 391
 392         spin_lock_irqsave(&m->lock, flags);
 393
 394         if (!m->queue_size)
 395                 goto out;
 396
 397         if (!m->current_pgpath)
 398                 __choose_pgpath(m);
 399
 400         pgpath = m->current_pgpath;
 401
 402         if ((pgpath && !m->queue_io) ||
 403             (!pgpath && !m->queue_if_no_path))
 404                 must_queue = 0;
 405
 406         if (m->pg_init_required && !m->pg_init_in_progress) {
 407                 m->pg_init_required = 0;
 408                 m->pg_init_in_progress = 1;
 409                 init_required = 1;
 410         }
 411
 412 out:
 413         spin_unlock_irqrestore(&m->lock, flags);
 414
 415         if (init_required)
 416                 hwh->type->pg_init(hwh, pgpath->pg->bypassed, &pgpath->path);
 417
 418         if (!must_queue)
 419                 dispatch_queued_ios(m);
 420 }
 421
 422 /*
 423  * An event is triggered whenever a path is taken out of use.
 424  * Includes path failure and PG bypass.
 425  */
 426 static void trigger_event(void *data)
 427 {
 428         struct multipath *m = (struct multipath *) data;
 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 #define ESTR(s) ("dm-multipath: " s)
 450
 451 static int read_param(struct param *param, char *str, unsigned *v, char **error)
 452 {
 453         if (!str ||
 454             (sscanf(str, "%u", v) != 1) ||
 455             (*v < param->min) ||
 456             (*v > param->max)) {
 457                 *error = param->error;
 458                 return -EINVAL;
 459         }
 460
 461         return 0;
 462 }
 463
 464 struct arg_set {
 465         unsigned argc;
 466         char **argv;
 467 };
 468
 469 static char *shift(struct arg_set *as)
 470 {
 471         char *r;
 472
 473         if (as->argc) {
 474                 as->argc--;
 475                 r = *as->argv;
 476                 as->argv++;
 477                 return r;
 478         }
 479
 480         return NULL;
 481 }
 482
 483 static void consume(struct arg_set *as, unsigned n)
 484 {
 485         BUG_ON (as->argc < n);
 486         as->argc -= n;
 487         as->argv += n;
 488 }
 489
 490 static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
 491                                struct dm_target *ti)
 492 {
 493         int r;
 494         struct path_selector_type *pst;
 495         unsigned ps_argc;
 496
 497         static struct param _params[] = {
 498                 {0, 1024, ESTR("invalid number of path selector args")},
 499         };
 500
 501         pst = dm_get_path_selector(shift(as));
 502         if (!pst) {
 503                 ti->error = ESTR("unknown path selector type");
 504                 return -EINVAL;
 505         }
 506
 507         r = read_param(_params, shift(as), &ps_argc, &ti->error);
 508         if (r)
 509                 return -EINVAL;
 510
 511         r = pst->create(&pg->ps, ps_argc, as->argv);
 512         if (r) {
 513                 dm_put_path_selector(pst);
 514                 ti->error = ESTR("path selector constructor failed");
 515                 return r;
 516         }
 517
 518         pg->ps.type = pst;
 519         consume(as, ps_argc);
 520
 521         return 0;
 522 }
 523
 524 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
 525                                struct dm_target *ti)
 526 {
 527         int r;
 528         struct pgpath *p;
 529
 530         /* we need at least a path arg */
 531         if (as->argc < 1) {
 532                 ti->error = ESTR("no device given");
 533                 return NULL;
 534         }
 535
 536         p = alloc_pgpath();
 537         if (!p)
 538                 return NULL;
 539
 540         r = dm_get_device(ti, shift(as), ti->begin, ti->len,
 541                           dm_table_get_mode(ti->table), &p->path.dev);
 542         if (r) {
 543                 ti->error = ESTR("error getting device");
 544                 goto bad;
 545         }
 546
 547         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 548         if (r) {
 549                 dm_put_device(ti, p->path.dev);
 550                 goto bad;
 551         }
 552
 553         return p;
 554
 555  bad:
 556         free_pgpath(p);
 557         return NULL;
 558 }
 559
 560 static struct priority_group *parse_priority_group(struct arg_set *as,
 561                                                    struct multipath *m,
 562                                                    struct dm_target *ti)
 563 {
 564         static struct param _params[] = {
 565                 {1, 1024, ESTR("invalid number of paths")},
 566                 {0, 1024, ESTR("invalid number of selector args")}
 567         };
 568
 569         int r;
 570         unsigned i, nr_selector_args, nr_params;
 571         struct priority_group *pg;
 572
 573         if (as->argc < 2) {
 574                 as->argc = 0;
 575                 ti->error = ESTR("not enough priority group aruments");
 576                 return NULL;
 577         }
 578
 579         pg = alloc_priority_group();
 580         if (!pg) {
 581                 ti->error = ESTR("couldn't allocate priority group");
 582                 return NULL;
 583         }
 584         pg->m = m;
 585
 586         r = parse_path_selector(as, pg, ti);
 587         if (r)
 588                 goto bad;
 589
 590         /*
 591          * read the paths
 592          */
 593         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
 594         if (r)
 595                 goto bad;
 596
 597         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
 598         if (r)
 599                 goto bad;
 600
 601         nr_params = 1 + nr_selector_args;
 602         for (i = 0; i < pg->nr_pgpaths; i++) {
 603                 struct pgpath *pgpath;
 604                 struct arg_set path_args;
 605
 606                 if (as->argc < nr_params)
 607                         goto bad;
 608
 609                 path_args.argc = nr_params;
 610                 path_args.argv = as->argv;
 611
 612                 pgpath = parse_path(&path_args, &pg->ps, ti);
 613                 if (!pgpath)
 614                         goto bad;
 615
 616                 pgpath->pg = pg;
 617                 list_add_tail(&pgpath->list, &pg->pgpaths);
 618                 consume(as, nr_params);
 619         }
 620
 621         return pg;
 622
 623  bad:
 624         free_priority_group(pg, ti);
 625         return NULL;
 626 }
 627
 628 static int parse_hw_handler(struct arg_set *as, struct multipath *m,
 629                             struct dm_target *ti)
 630 {
 631         int r;
 632         struct hw_handler_type *hwht;
 633         unsigned hw_argc;
 634
 635         static struct param _params[] = {
 636                 {0, 1024, ESTR("invalid number of hardware handler args")},
 637         };
 638
 639         r = read_param(_params, shift(as), &hw_argc, &ti->error);
 640         if (r)
 641                 return -EINVAL;
 642
 643         if (!hw_argc)
 644                 return 0;
 645
 646         hwht = dm_get_hw_handler(shift(as));
 647         if (!hwht) {
 648                 ti->error = ESTR("unknown hardware handler type");
 649                 return -EINVAL;
 650         }
 651
 652         r = hwht->create(&m->hw_handler, hw_argc - 1, as->argv);
 653         if (r) {
 654                 dm_put_hw_handler(hwht);
 655                 ti->error = ESTR("hardware handler constructor failed");
 656                 return r;
 657         }
 658
 659         m->hw_handler.type = hwht;
 660         consume(as, hw_argc - 1);
 661
 662         return 0;
 663 }
 664
 665 static int parse_features(struct arg_set *as, struct multipath *m,
 666                           struct dm_target *ti)
 667 {
 668         int r;
 669         unsigned argc;
 670
 671         static struct param _params[] = {
 672                 {0, 1, ESTR("invalid number of feature args")},
 673         };
 674
 675         r = read_param(_params, shift(as), &argc, &ti->error);
 676         if (r)
 677                 return -EINVAL;
 678
 679         if (!argc)
 680                 return 0;
 681
 682         if (!strnicmp(shift(as), MESG_STR("queue_if_no_path")))
 683                 return queue_if_no_path(m, 1, 0);
 684         else {
 685                 ti->error = "Unrecognised multipath feature request";
 686                 return -EINVAL;
 687         }
 688 }
 689
 690 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 691                          char **argv)
 692 {
 693         /* target parameters */
 694         static struct param _params[] = {
 695                 {1, 1024, ESTR("invalid number of priority groups")},
 696                 {1, 1024, ESTR("invalid initial priority group number")},
 697         };
 698
 699         int r;
 700         struct multipath *m;
 701         struct arg_set as;
 702         unsigned pg_count = 0;
 703         unsigned next_pg_num;
 704
 705         as.argc = argc;
 706         as.argv = argv;
 707
 708         m = alloc_multipath();
 709         if (!m) {
 710                 ti->error = ESTR("can't allocate multipath");
 711                 return -EINVAL;
 712         }
 713
 714         r = parse_features(&as, m, ti);
 715         if (r)
 716                 goto bad;
 717
 718         r = parse_hw_handler(&as, m, ti);
 719         if (r)
 720                 goto bad;
 721
 722         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
 723         if (r)
 724                 goto bad;
 725
 726         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
 727         if (r)
 728                 goto bad;
 729
 730         /* parse the priority groups */
 731         while (as.argc) {
 732                 struct priority_group *pg;
 733
 734                 pg = parse_priority_group(&as, m, ti);
 735                 if (!pg) {
 736                         r = -EINVAL;
 737                         goto bad;
 738                 }
 739
 740                 m->nr_valid_paths += pg->nr_pgpaths;
 741                 list_add_tail(&pg->list, &m->priority_groups);
 742                 pg_count++;
 743                 pg->pg_num = pg_count;
 744                 if (!--next_pg_num)
 745                         m->next_pg = pg;
 746         }
 747
 748         if (pg_count != m->nr_priority_groups) {
 749                 ti->error = ESTR("priority group count mismatch");
 750                 r = -EINVAL;
 751                 goto bad;
 752         }
 753
 754         ti->private = m;
 755         m->ti = ti;
 756
 757         return 0;
 758
 759  bad:
 760         free_multipath(m);
 761         return r;
 762 }
 763
 764 static void multipath_dtr(struct dm_target *ti)
 765 {
 766         struct multipath *m = (struct multipath *) ti->private;
 767
 768         flush_workqueue(kmultipathd);
 769         free_multipath(m);
 770 }
 771
 772 /*
 773  * Map bios, recording original fields for later in case we have to resubmit
 774  */
 775 static int multipath_map(struct dm_target *ti, struct bio *bio,
 776                          union map_info *map_context)
 777 {
 778         int r;
 779         struct mpath_io *mpio;
 780         struct multipath *m = (struct multipath *) ti->private;
 781
 782         if (bio_barrier(bio))
 783                 return -EOPNOTSUPP;
 784
 785         mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
 786         dm_bio_record(&mpio->details, bio);
 787
 788         map_context->ptr = mpio;
 789         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
 790         r = map_io(m, bio, mpio, 0);
 791         if (r < 0)
 792                 mempool_free(mpio, m->mpio_pool);
 793
 794         return r;
 795 }
 796
 797 /*
 798  * Take a path out of use.
 799  */
 800 static int fail_path(struct pgpath *pgpath)
 801 {
 802         unsigned long flags;
 803         struct multipath *m = pgpath->pg->m;
 804
 805         spin_lock_irqsave(&m->lock, flags);
 806
 807         if (!pgpath->path.is_active)
 808                 goto out;
 809
 810         DMWARN("dm-multipath: Failing path %s.", pgpath->path.dev->name);
 811
 812         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 813         pgpath->path.is_active = 0;
 814         pgpath->fail_count++;
 815
 816         m->nr_valid_paths--;
 817
 818         if (pgpath == m->current_pgpath)
 819                 m->current_pgpath = NULL;
 820
 821         queue_work(kmultipathd, &m->trigger_event);
 822
 823 out:
 824         spin_unlock_irqrestore(&m->lock, flags);
 825
 826         return 0;
 827 }
 828
 829 /*
 830  * Reinstate a previously-failed path
 831  */
 832 static int reinstate_path(struct pgpath *pgpath)
 833 {
 834         int r = 0;
 835         unsigned long flags;
 836         struct multipath *m = pgpath->pg->m;
 837
 838         spin_lock_irqsave(&m->lock, flags);
 839
 840         if (pgpath->path.is_active)
 841                 goto out;
 842
 843         if (!pgpath->pg->ps.type) {
 844                 DMWARN("Reinstate path not supported by path selector %s",
 845                        pgpath->pg->ps.type->name);
 846                 r = -EINVAL;
 847                 goto out;
 848         }
 849
 850         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
 851         if (r)
 852                 goto out;
 853
 854         pgpath->path.is_active = 1;
 855
 856         m->current_pgpath = NULL;
 857         if (!m->nr_valid_paths++ && m->queue_size)
 858                 queue_work(kmultipathd, &m->process_queued_ios);
 859
 860         queue_work(kmultipathd, &m->trigger_event);
 861
 862 out:
 863         spin_unlock_irqrestore(&m->lock, flags);
 864
 865         return r;
 866 }
 867
 868 /*
 869  * Fail or reinstate all paths that match the provided struct dm_dev.
 870  */
 871 static int action_dev(struct multipath *m, struct dm_dev *dev,
 872                       action_fn action)
 873 {
 874         int r = 0;
 875         struct pgpath *pgpath;
 876         struct priority_group *pg;
 877
 878         list_for_each_entry(pg, &m->priority_groups, list) {
 879                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
 880                         if (pgpath->path.dev == dev)
 881                                 r = action(pgpath);
 882                 }
 883         }
 884
 885         return r;
 886 }
 887
 888 /*
 889  * Temporarily try to avoid having to use the specified PG
 890  */
 891 static void bypass_pg(struct multipath *m, struct priority_group *pg,
 892                       int bypassed)
 893 {
 894         unsigned long flags;
 895
 896         spin_lock_irqsave(&m->lock, flags);
 897
 898         pg->bypassed = bypassed;
 899         m->current_pgpath = NULL;
 900         m->current_pg = NULL;
 901
 902         spin_unlock_irqrestore(&m->lock, flags);
 903
 904         queue_work(kmultipathd, &m->trigger_event);
 905 }
 906
 907 /*
 908  * Switch to using the specified PG from the next I/O that gets mapped
 909  */
 910 static int switch_pg_num(struct multipath *m, const char *pgstr)
 911 {
 912         struct priority_group *pg;
 913         unsigned pgnum;
 914         unsigned long flags;
 915
 916         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
 917             (pgnum > m->nr_priority_groups)) {
 918                 DMWARN("invalid PG number supplied to switch_pg_num");
 919                 return -EINVAL;
 920         }
 921
 922         spin_lock_irqsave(&m->lock, flags);
 923         list_for_each_entry(pg, &m->priority_groups, list) {
 924                 pg->bypassed = 0;
 925                 if (--pgnum)
 926                         continue;
 927
 928                 m->current_pgpath = NULL;
 929                 m->current_pg = NULL;
 930                 m->next_pg = pg;
 931         }
 932         spin_unlock_irqrestore(&m->lock, flags);
 933
 934         queue_work(kmultipathd, &m->trigger_event);
 935         return 0;
 936 }
 937
 938 /*
 939  * Set/clear bypassed status of a PG.
 940  * PGs are numbered upwards from 1 in the order they were declared.
 941  */
 942 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
 943 {
 944         struct priority_group *pg;
 945         unsigned pgnum;
 946
 947         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
 948             (pgnum > m->nr_priority_groups)) {
 949                 DMWARN("invalid PG number supplied to bypass_pg");
 950                 return -EINVAL;
 951         }
 952
 953         list_for_each_entry(pg, &m->priority_groups, list) {
 954                 if (!--pgnum)
 955                         break;
 956         }
 957
 958         bypass_pg(m, pg, bypassed);
 959         return 0;
 960 }
 961
 962 /*
 963  * pg_init must call this when it has completed its initialisation
 964  */
 965 void dm_pg_init_complete(struct path *path, unsigned err_flags)
 966 {
 967         struct pgpath *pgpath = path_to_pgpath(path);
 968         struct priority_group *pg = pgpath->pg;
 969         struct multipath *m = pg->m;
 970         unsigned long flags;
 971
 972         /* We insist on failing the path if the PG is already bypassed. */
 973         if (err_flags && pg->bypassed)
 974                 err_flags |= MP_FAIL_PATH;
 975
 976         if (err_flags & MP_FAIL_PATH)
 977                 fail_path(pgpath);
 978
 979         if (err_flags & MP_BYPASS_PG)
 980                 bypass_pg(m, pg, 1);
 981
 982         spin_lock_irqsave(&m->lock, flags);
 983         if (err_flags) {
 984                 m->current_pgpath = NULL;
 985                 m->current_pg = NULL;
 986         } else if (!m->pg_init_required)
 987                 m->queue_io = 0;
 988
 989         m->pg_init_in_progress = 0;
 990         queue_work(kmultipathd, &m->process_queued_ios);
 991         spin_unlock_irqrestore(&m->lock, flags);
 992 }
 993
 994 /*
 995  * end_io handling
 996  */
 997 static int do_end_io(struct multipath *m, struct bio *bio,
 998                      int error, struct mpath_io *mpio)
 999 {
1000         struct hw_handler *hwh = &m->hw_handler;
1001         unsigned err_flags = MP_FAIL_PATH;      /* Default behavior */
1002         unsigned long flags;
1003
1004         if (!error)
1005                 return 0;       /* I/O complete */
1006
1007         if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
1008                 return error;
1009
1010         if (error == -EOPNOTSUPP)
1011                 return error;
1012
1013         spin_lock_irqsave(&m->lock, flags);
1014         if (!m->nr_valid_paths) {
1015                 if (!m->queue_if_no_path) {
1016                         spin_unlock_irqrestore(&m->lock, flags);
1017                         return -EIO;
1018                 } else {
1019                         spin_unlock_irqrestore(&m->lock, flags);
1020                         goto requeue;
1021                 }
1022         }
1023         spin_unlock_irqrestore(&m->lock, flags);
1024
1025         if (hwh->type && hwh->type->error)
1026                 err_flags = hwh->type->error(hwh, bio);
1027
1028         if (mpio->pgpath) {
1029                 if (err_flags & MP_FAIL_PATH)
1030                         fail_path(mpio->pgpath);
1031
1032                 if (err_flags & MP_BYPASS_PG)
1033                         bypass_pg(m, mpio->pgpath->pg, 1);
1034         }
1035
1036         if (err_flags & MP_ERROR_IO)
1037                 return -EIO;
1038
1039       requeue:
1040         dm_bio_restore(&mpio->details, bio);
1041
1042         /* queue for the daemon to resubmit or fail */
1043         spin_lock_irqsave(&m->lock, flags);
1044         bio_list_add(&m->queued_ios, bio);
1045         m->queue_size++;
1046         if (!m->queue_io)
1047                 queue_work(kmultipathd, &m->process_queued_ios);
1048         spin_unlock_irqrestore(&m->lock, flags);
1049
1050         return 1;       /* io not complete */
1051 }
1052
1053 static int multipath_end_io(struct dm_target *ti, struct bio *bio,
1054                             int error, union map_info *map_context)
1055 {
1056         struct multipath *m = (struct multipath *) ti->private;
1057         struct mpath_io *mpio = (struct mpath_io *) map_context->ptr;
1058         struct pgpath *pgpath = mpio->pgpath;
1059         struct path_selector *ps;
1060         int r;
1061
1062         r  = do_end_io(m, bio, error, mpio);
1063         if (pgpath) {
1064                 ps = &pgpath->pg->ps;
1065                 if (ps->type->end_io)
1066                         ps->type->end_io(ps, &pgpath->path);
1067         }
1068         if (r <= 0)
1069                 mempool_free(mpio, m->mpio_pool);
1070
1071         return r;
1072 }
1073
1074 /*
1075  * Suspend can't complete until all the I/O is processed so if
1076  * the last path fails we must error any remaining I/O.
1077  * Note that if the freeze_bdev fails while suspending, the
1078  * queue_if_no_path state is lost - userspace should reset it.
1079  */
1080 static void multipath_presuspend(struct dm_target *ti)
1081 {
1082         struct multipath *m = (struct multipath *) ti->private;
1083
1084         queue_if_no_path(m, 0, 1);
1085 }
1086
1087 /*
1088  * Restore the queue_if_no_path setting.
1089  */
1090 static void multipath_resume(struct dm_target *ti)
1091 {
1092         struct multipath *m = (struct multipath *) ti->private;
1093         unsigned long flags;
1094
1095         spin_lock_irqsave(&m->lock, flags);
1096         m->queue_if_no_path = m->saved_queue_if_no_path;
1097         spin_unlock_irqrestore(&m->lock, flags);
1098 }
1099
1100 /*
1101  * Info output has the following format:
1102  * num_multipath_feature_args [multipath_feature_args]*
1103  * num_handler_status_args [handler_status_args]*
1104  * num_groups init_group_number
1105  *            [A|D|E num_ps_status_args [ps_status_args]*
1106  *             num_paths num_selector_args
1107  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1108  *
1109  * Table output has the following format (identical to the constructor string):
1110  * num_feature_args [features_args]*
1111  * num_handler_args hw_handler [hw_handler_args]*
1112  * num_groups init_group_number
1113  *     [priority selector-name num_ps_args [ps_args]*
1114  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1115  */
1116 static int multipath_status(struct dm_target *ti, status_type_t type,
1117                             char *result, unsigned int maxlen)
1118 {
1119         int sz = 0;
1120         unsigned long flags;
1121         struct multipath *m = (struct multipath *) ti->private;
1122         struct hw_handler *hwh = &m->hw_handler;
1123         struct priority_group *pg;
1124         struct pgpath *p;
1125         unsigned pg_num;
1126         char state;
1127
1128         spin_lock_irqsave(&m->lock, flags);
1129
1130         /* Features */
1131         if (type == STATUSTYPE_INFO)
1132                 DMEMIT("1 %u ", m->queue_size);
1133         else if (m->queue_if_no_path)
1134                 DMEMIT("1 queue_if_no_path ");
1135         else
1136                 DMEMIT("0 ");
1137
1138         if (hwh->type && hwh->type->status)
1139                 sz += hwh->type->status(hwh, type, result + sz, maxlen - sz);
1140         else if (!hwh->type || type == STATUSTYPE_INFO)
1141                 DMEMIT("0 ");
1142         else
1143                 DMEMIT("1 %s ", hwh->type->name);
1144
1145         DMEMIT("%u ", m->nr_priority_groups);
1146
1147         if (m->next_pg)
1148                 pg_num = m->next_pg->pg_num;
1149         else if (m->current_pg)
1150                 pg_num = m->current_pg->pg_num;
1151         else
1152                         pg_num = 1;
1153
1154         DMEMIT("%u ", pg_num);
1155
1156         switch (type) {
1157         case STATUSTYPE_INFO:
1158                 list_for_each_entry(pg, &m->priority_groups, list) {
1159                         if (pg->bypassed)
1160                                 state = 'D';    /* Disabled */
1161                         else if (pg == m->current_pg)
1162                                 state = 'A';    /* Currently Active */
1163                         else
1164                                 state = 'E';    /* Enabled */
1165
1166                         DMEMIT("%c ", state);
1167
1168                         if (pg->ps.type->status)
1169                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1170                                                           result + sz,
1171                                                           maxlen - sz);
1172                         else
1173                                 DMEMIT("0 ");
1174
1175                         DMEMIT("%u %u ", pg->nr_pgpaths,
1176                                pg->ps.type->info_args);
1177
1178                         list_for_each_entry(p, &pg->pgpaths, list) {
1179                                 DMEMIT("%s %s %u ", p->path.dev->name,
1180                                        p->path.is_active ? "A" : "F",
1181                                        p->fail_count);
1182                                 if (pg->ps.type->status)
1183                                         sz += pg->ps.type->status(&pg->ps,
1184                                               &p->path, type, result + sz,
1185                                               maxlen - sz);
1186                         }
1187                 }
1188                 break;
1189
1190         case STATUSTYPE_TABLE:
1191                 list_for_each_entry(pg, &m->priority_groups, list) {
1192                         DMEMIT("%s ", pg->ps.type->name);
1193
1194                         if (pg->ps.type->status)
1195                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1196                                                           result + sz,
1197                                                           maxlen - sz);
1198                         else
1199                                 DMEMIT("0 ");
1200
1201                         DMEMIT("%u %u ", pg->nr_pgpaths,
1202                                pg->ps.type->table_args);
1203
1204                         list_for_each_entry(p, &pg->pgpaths, list) {
1205                                 DMEMIT("%s ", p->path.dev->name);
1206                                 if (pg->ps.type->status)
1207                                         sz += pg->ps.type->status(&pg->ps,
1208                                               &p->path, type, result + sz,
1209                                               maxlen - sz);
1210                         }
1211                 }
1212                 break;
1213         }
1214
1215         spin_unlock_irqrestore(&m->lock, flags);
1216
1217         return 0;
1218 }
1219
1220 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1221 {
1222         int r;
1223         struct dm_dev *dev;
1224         struct multipath *m = (struct multipath *) ti->private;
1225         action_fn action;
1226
1227         if (argc == 1) {
1228                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path")))
1229                         return queue_if_no_path(m, 1, 0);
1230                 else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path")))
1231                         return queue_if_no_path(m, 0, 0);
1232         }
1233
1234         if (argc != 2)
1235                 goto error;
1236
1237         if (!strnicmp(argv[0], MESG_STR("disable_group")))
1238                 return bypass_pg_num(m, argv[1], 1);
1239         else if (!strnicmp(argv[0], MESG_STR("enable_group")))
1240                 return bypass_pg_num(m, argv[1], 0);
1241         else if (!strnicmp(argv[0], MESG_STR("switch_group")))
1242                 return switch_pg_num(m, argv[1]);
1243         else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1244                 action = reinstate_path;
1245         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1246                 action = fail_path;
1247         else
1248                 goto error;
1249
1250         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
1251                           dm_table_get_mode(ti->table), &dev);
1252         if (r) {
1253                 DMWARN("dm-multipath message: error getting device %s",
1254                        argv[1]);
1255                 return -EINVAL;
1256         }
1257
1258         r = action_dev(m, dev, action);
1259
1260         dm_put_device(ti, dev);
1261
1262         return r;
1263
1264 error:
1265         DMWARN("Unrecognised multipath message received.");
1266         return -EINVAL;
1267 }
1268
1269 /*-----------------------------------------------------------------
1270  * Module setup
1271  *---------------------------------------------------------------*/
1272 static struct target_type multipath_target = {
1273         .name = "multipath",
1274         .version = {1, 0, 4},
1275         .module = THIS_MODULE,
1276         .ctr = multipath_ctr,
1277         .dtr = multipath_dtr,
1278         .map = multipath_map,
1279         .end_io = multipath_end_io,
1280         .presuspend = multipath_presuspend,
1281         .resume = multipath_resume,
1282         .status = multipath_status,
1283         .message = multipath_message,
1284 };
1285
1286 static int __init dm_multipath_init(void)
1287 {
1288         int r;
1289
1290         /* allocate a slab for the dm_ios */
1291         _mpio_cache = kmem_cache_create("dm_mpath", sizeof(struct mpath_io),
1292                                         0, 0, NULL, NULL);
1293         if (!_mpio_cache)
1294                 return -ENOMEM;
1295
1296         r = dm_register_target(&multipath_target);
1297         if (r < 0) {
1298                 DMERR("%s: register failed %d", multipath_target.name, r);
1299                 kmem_cache_destroy(_mpio_cache);
1300                 return -EINVAL;
1301         }
1302
1303         kmultipathd = create_workqueue("kmpathd");
1304         if (!kmultipathd) {
1305                 DMERR("%s: failed to create workqueue kmpathd",
1306                                 multipath_target.name);
1307                 dm_unregister_target(&multipath_target);
1308                 kmem_cache_destroy(_mpio_cache);
1309                 return -ENOMEM;
1310         }
1311
1312         DMINFO("dm-multipath version %u.%u.%u loaded",
1313                multipath_target.version[0], multipath_target.version[1],
1314                multipath_target.version[2]);
1315
1316         return r;
1317 }
1318
1319 static void __exit dm_multipath_exit(void)
1320 {
1321         int r;
1322
1323         destroy_workqueue(kmultipathd);
1324
1325         r = dm_unregister_target(&multipath_target);
1326         if (r < 0)
1327                 DMERR("%s: target unregister failed %d",
1328                       multipath_target.name, r);
1329         kmem_cache_destroy(_mpio_cache);
1330 }
1331
1332 EXPORT_SYMBOL_GPL(dm_pg_init_complete);
1333
1334 module_init(dm_multipath_init);
1335 module_exit(dm_multipath_exit);
1336
1337 MODULE_DESCRIPTION(DM_NAME " multipath target");
1338 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1339 MODULE_LICENSE("GPL");