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-bio-list.h"
  11 #include "dm-bio-record.h"
  12 #include "dm-uevent.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 <scsi/scsi_dh.h>
  23 #include <asm/atomic.h>
  24
  25 #define DM_MSG_PREFIX "multipath"
  26 #define MESG_STR(x) x, sizeof(x)
  27
  28 /* Path properties */
  29 struct pgpath {
  30         struct list_head list;
  31
  32         struct priority_group *pg;      /* Owning PG */
  33         unsigned fail_count;            /* Cumulative failure count */
  34
  35         struct dm_path path;
  36 };
  37
  38 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  39
  40 /*
  41  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  42  * Each has a path selector which controls which path gets used.
  43  */
  44 struct priority_group {
  45         struct list_head list;
  46
  47         struct multipath *m;            /* Owning multipath instance */
  48         struct path_selector ps;
  49
  50         unsigned pg_num;                /* Reference number */
  51         unsigned bypassed;              /* Temporarily bypass this PG? */
  52
  53         unsigned nr_pgpaths;            /* Number of paths in PG */
  54         struct list_head pgpaths;
  55 };
  56
  57 /* Multipath context */
  58 struct multipath {
  59         struct list_head list;
  60         struct dm_target *ti;
  61
  62         spinlock_t lock;
  63
  64         const char *hw_handler_name;
  65         struct work_struct activate_path;
  66         unsigned nr_priority_groups;
  67         struct list_head priority_groups;
  68         unsigned pg_init_required;      /* pg_init needs calling? */
  69         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  70
  71         unsigned nr_valid_paths;        /* Total number of usable paths */
  72         struct pgpath *current_pgpath;
  73         struct priority_group *current_pg;
  74         struct priority_group *next_pg; /* Switch to this PG if set */
  75         unsigned repeat_count;          /* I/Os left before calling PS again */
  76
  77         unsigned queue_io;              /* Must we queue all I/O? */
  78         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
  79         unsigned saved_queue_if_no_path;/* Saved state during suspension */
  80         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  81         unsigned pg_init_count;         /* Number of times pg_init called */
  82
  83         struct work_struct process_queued_ios;
  84         struct bio_list queued_ios;
  85         unsigned queue_size;
  86
  87         struct work_struct trigger_event;
  88
  89         /*
  90          * We must use a mempool of dm_mpath_io structs so that we
  91          * can resubmit bios on error.
  92          */
  93         mempool_t *mpio_pool;
  94 };
  95
  96 /*
  97  * Context information attached to each bio we process.
  98  */
  99 struct dm_mpath_io {
 100         struct pgpath *pgpath;
 101         struct dm_bio_details details;
 102 };
 103
 104 typedef int (*action_fn) (struct pgpath *pgpath);
 105
 106 #define MIN_IOS 256     /* Mempool size */
 107
 108 static struct kmem_cache *_mpio_cache;
 109
 110 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 111 static void process_queued_ios(struct work_struct *work);
 112 static void trigger_event(struct work_struct *work);
 113 static void activate_path(struct work_struct *work);
 114
 115
 116 /*-----------------------------------------------
 117  * Allocation routines
 118  *-----------------------------------------------*/
 119
 120 static struct pgpath *alloc_pgpath(void)
 121 {
 122         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 123
 124         if (pgpath)
 125                 pgpath->path.is_active = 1;
 126
 127         return pgpath;
 128 }
 129
 130 static void free_pgpath(struct pgpath *pgpath)
 131 {
 132         kfree(pgpath);
 133 }
 134
 135 static struct priority_group *alloc_priority_group(void)
 136 {
 137         struct priority_group *pg;
 138
 139         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 140
 141         if (pg)
 142                 INIT_LIST_HEAD(&pg->pgpaths);
 143
 144         return pg;
 145 }
 146
 147 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 148 {
 149         struct pgpath *pgpath, *tmp;
 150
 151         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 152                 list_del(&pgpath->list);
 153                 dm_put_device(ti, pgpath->path.dev);
 154                 free_pgpath(pgpath);
 155         }
 156 }
 157
 158 static void free_priority_group(struct priority_group *pg,
 159                                 struct dm_target *ti)
 160 {
 161         struct path_selector *ps = &pg->ps;
 162
 163         if (ps->type) {
 164                 ps->type->destroy(ps);
 165                 dm_put_path_selector(ps->type);
 166         }
 167
 168         free_pgpaths(&pg->pgpaths, ti);
 169         kfree(pg);
 170 }
 171
 172 static struct multipath *alloc_multipath(struct dm_target *ti)
 173 {
 174         struct multipath *m;
 175
 176         m = kzalloc(sizeof(*m), GFP_KERNEL);
 177         if (m) {
 178                 INIT_LIST_HEAD(&m->priority_groups);
 179                 spin_lock_init(&m->lock);
 180                 m->queue_io = 1;
 181                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
 182                 INIT_WORK(&m->trigger_event, trigger_event);
 183                 INIT_WORK(&m->activate_path, activate_path);
 184                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 185                 if (!m->mpio_pool) {
 186                         kfree(m);
 187                         return NULL;
 188                 }
 189                 m->ti = ti;
 190                 ti->private = m;
 191         }
 192
 193         return m;
 194 }
 195
 196 static void free_multipath(struct multipath *m)
 197 {
 198         struct priority_group *pg, *tmp;
 199
 200         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 201                 list_del(&pg->list);
 202                 free_priority_group(pg, m->ti);
 203         }
 204
 205         kfree(m->hw_handler_name);
 206         mempool_destroy(m->mpio_pool);
 207         kfree(m);
 208 }
 209
 210
 211 /*-----------------------------------------------
 212  * Path selection
 213  *-----------------------------------------------*/
 214
 215 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 216 {
 217         m->current_pg = pgpath->pg;
 218
 219         /* Must we initialise the PG first, and queue I/O till it's ready? */
 220         if (m->hw_handler_name) {
 221                 m->pg_init_required = 1;
 222                 m->queue_io = 1;
 223         } else {
 224                 m->pg_init_required = 0;
 225                 m->queue_io = 0;
 226         }
 227
 228         m->pg_init_count = 0;
 229 }
 230
 231 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg)
 232 {
 233         struct dm_path *path;
 234
 235         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count);
 236         if (!path)
 237                 return -ENXIO;
 238
 239         m->current_pgpath = path_to_pgpath(path);
 240
 241         if (m->current_pg != pg)
 242                 __switch_pg(m, m->current_pgpath);
 243
 244         return 0;
 245 }
 246
 247 static void __choose_pgpath(struct multipath *m)
 248 {
 249         struct priority_group *pg;
 250         unsigned bypassed = 1;
 251
 252         if (!m->nr_valid_paths)
 253                 goto failed;
 254
 255         /* Were we instructed to switch PG? */
 256         if (m->next_pg) {
 257                 pg = m->next_pg;
 258                 m->next_pg = NULL;
 259                 if (!__choose_path_in_pg(m, pg))
 260                         return;
 261         }
 262
 263         /* Don't change PG until it has no remaining paths */
 264         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg))
 265                 return;
 266
 267         /*
 268          * Loop through priority groups until we find a valid path.
 269          * First time we skip PGs marked 'bypassed'.
 270          * Second time we only try the ones we skipped.
 271          */
 272         do {
 273                 list_for_each_entry(pg, &m->priority_groups, list) {
 274                         if (pg->bypassed == bypassed)
 275                                 continue;
 276                         if (!__choose_path_in_pg(m, pg))
 277                                 return;
 278                 }
 279         } while (bypassed--);
 280
 281 failed:
 282         m->current_pgpath = NULL;
 283         m->current_pg = NULL;
 284 }
 285
 286 /*
 287  * Check whether bios must be queued in the device-mapper core rather
 288  * than here in the target.
 289  *
 290  * m->lock must be held on entry.
 291  *
 292  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 293  * same value then we are not between multipath_presuspend()
 294  * and multipath_resume() calls and we have no need to check
 295  * for the DMF_NOFLUSH_SUSPENDING flag.
 296  */
 297 static int __must_push_back(struct multipath *m)
 298 {
 299         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 300                 dm_noflush_suspending(m->ti));
 301 }
 302
 303 static int map_io(struct multipath *m, struct bio *bio,
 304                   struct dm_mpath_io *mpio, unsigned was_queued)
 305 {
 306         int r = DM_MAPIO_REMAPPED;
 307         unsigned long flags;
 308         struct pgpath *pgpath;
 309
 310         spin_lock_irqsave(&m->lock, flags);
 311
 312         /* Do we need to select a new pgpath? */
 313         if (!m->current_pgpath ||
 314             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 315                 __choose_pgpath(m);
 316
 317         pgpath = m->current_pgpath;
 318
 319         if (was_queued)
 320                 m->queue_size--;
 321
 322         if ((pgpath && m->queue_io) ||
 323             (!pgpath && m->queue_if_no_path)) {
 324                 /* Queue for the daemon to resubmit */
 325                 bio_list_add(&m->queued_ios, bio);
 326                 m->queue_size++;
 327                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 328                     !m->queue_io)
 329                         queue_work(kmultipathd, &m->process_queued_ios);
 330                 pgpath = NULL;
 331                 r = DM_MAPIO_SUBMITTED;
 332         } else if (pgpath)
 333                 bio->bi_bdev = pgpath->path.dev->bdev;
 334         else if (__must_push_back(m))
 335                 r = DM_MAPIO_REQUEUE;
 336         else
 337                 r = -EIO;       /* Failed */
 338
 339         mpio->pgpath = pgpath;
 340
 341         spin_unlock_irqrestore(&m->lock, flags);
 342
 343         return r;
 344 }
 345
 346 /*
 347  * If we run out of usable paths, should we queue I/O or error it?
 348  */
 349 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 350                             unsigned save_old_value)
 351 {
 352         unsigned long flags;
 353
 354         spin_lock_irqsave(&m->lock, flags);
 355
 356         if (save_old_value)
 357                 m->saved_queue_if_no_path = m->queue_if_no_path;
 358         else
 359                 m->saved_queue_if_no_path = queue_if_no_path;
 360         m->queue_if_no_path = queue_if_no_path;
 361         if (!m->queue_if_no_path && m->queue_size)
 362                 queue_work(kmultipathd, &m->process_queued_ios);
 363
 364         spin_unlock_irqrestore(&m->lock, flags);
 365
 366         return 0;
 367 }
 368
 369 /*-----------------------------------------------------------------
 370  * The multipath daemon is responsible for resubmitting queued ios.
 371  *---------------------------------------------------------------*/
 372
 373 static void dispatch_queued_ios(struct multipath *m)
 374 {
 375         int r;
 376         unsigned long flags;
 377         struct bio *bio = NULL, *next;
 378         struct dm_mpath_io *mpio;
 379         union map_info *info;
 380
 381         spin_lock_irqsave(&m->lock, flags);
 382         bio = bio_list_get(&m->queued_ios);
 383         spin_unlock_irqrestore(&m->lock, flags);
 384
 385         while (bio) {
 386                 next = bio->bi_next;
 387                 bio->bi_next = NULL;
 388
 389                 info = dm_get_mapinfo(bio);
 390                 mpio = info->ptr;
 391
 392                 r = map_io(m, bio, mpio, 1);
 393                 if (r < 0)
 394                         bio_endio(bio, r);
 395                 else if (r == DM_MAPIO_REMAPPED)
 396                         generic_make_request(bio);
 397                 else if (r == DM_MAPIO_REQUEUE)
 398                         bio_endio(bio, -EIO);
 399
 400                 bio = next;
 401         }
 402 }
 403
 404 static void process_queued_ios(struct work_struct *work)
 405 {
 406         struct multipath *m =
 407                 container_of(work, struct multipath, process_queued_ios);
 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_count++;
 428                 m->pg_init_required = 0;
 429                 m->pg_init_in_progress = 1;
 430                 init_required = 1;
 431         }
 432
 433 out:
 434         spin_unlock_irqrestore(&m->lock, flags);
 435
 436         if (init_required)
 437                 queue_work(kmpath_handlerd, &m->activate_path);
 438
 439         if (!must_queue)
 440                 dispatch_queued_ios(m);
 441 }
 442
 443 /*
 444  * An event is triggered whenever a path is taken out of use.
 445  * Includes path failure and PG bypass.
 446  */
 447 static void trigger_event(struct work_struct *work)
 448 {
 449         struct multipath *m =
 450                 container_of(work, struct multipath, trigger_event);
 451
 452         dm_table_event(m->ti->table);
 453 }
 454
 455 /*-----------------------------------------------------------------
 456  * Constructor/argument parsing:
 457  * <#multipath feature args> [<arg>]*
 458  * <#hw_handler args> [hw_handler [<arg>]*]
 459  * <#priority groups>
 460  * <initial priority group>
 461  *     [<selector> <#selector args> [<arg>]*
 462  *      <#paths> <#per-path selector args>
 463  *         [<path> [<arg>]* ]+ ]+
 464  *---------------------------------------------------------------*/
 465 struct param {
 466         unsigned min;
 467         unsigned max;
 468         char *error;
 469 };
 470
 471 static int read_param(struct param *param, char *str, unsigned *v, char **error)
 472 {
 473         if (!str ||
 474             (sscanf(str, "%u", v) != 1) ||
 475             (*v < param->min) ||
 476             (*v > param->max)) {
 477                 *error = param->error;
 478                 return -EINVAL;
 479         }
 480
 481         return 0;
 482 }
 483
 484 struct arg_set {
 485         unsigned argc;
 486         char **argv;
 487 };
 488
 489 static char *shift(struct arg_set *as)
 490 {
 491         char *r;
 492
 493         if (as->argc) {
 494                 as->argc--;
 495                 r = *as->argv;
 496                 as->argv++;
 497                 return r;
 498         }
 499
 500         return NULL;
 501 }
 502
 503 static void consume(struct arg_set *as, unsigned n)
 504 {
 505         BUG_ON (as->argc < n);
 506         as->argc -= n;
 507         as->argv += n;
 508 }
 509
 510 static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
 511                                struct dm_target *ti)
 512 {
 513         int r;
 514         struct path_selector_type *pst;
 515         unsigned ps_argc;
 516
 517         static struct param _params[] = {
 518                 {0, 1024, "invalid number of path selector args"},
 519         };
 520
 521         pst = dm_get_path_selector(shift(as));
 522         if (!pst) {
 523                 ti->error = "unknown path selector type";
 524                 return -EINVAL;
 525         }
 526
 527         r = read_param(_params, shift(as), &ps_argc, &ti->error);
 528         if (r) {
 529                 dm_put_path_selector(pst);
 530                 return -EINVAL;
 531         }
 532
 533         r = pst->create(&pg->ps, ps_argc, as->argv);
 534         if (r) {
 535                 dm_put_path_selector(pst);
 536                 ti->error = "path selector constructor failed";
 537                 return r;
 538         }
 539
 540         pg->ps.type = pst;
 541         consume(as, ps_argc);
 542
 543         return 0;
 544 }
 545
 546 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
 547                                struct dm_target *ti)
 548 {
 549         int r;
 550         struct pgpath *p;
 551
 552         /* we need at least a path arg */
 553         if (as->argc < 1) {
 554                 ti->error = "no device given";
 555                 return NULL;
 556         }
 557
 558         p = alloc_pgpath();
 559         if (!p)
 560                 return NULL;
 561
 562         r = dm_get_device(ti, shift(as), ti->begin, ti->len,
 563                           dm_table_get_mode(ti->table), &p->path.dev);
 564         if (r) {
 565                 ti->error = "error getting device";
 566                 goto bad;
 567         }
 568
 569         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 570         if (r) {
 571                 dm_put_device(ti, p->path.dev);
 572                 goto bad;
 573         }
 574
 575         return p;
 576
 577  bad:
 578         free_pgpath(p);
 579         return NULL;
 580 }
 581
 582 static struct priority_group *parse_priority_group(struct arg_set *as,
 583                                                    struct multipath *m)
 584 {
 585         static struct param _params[] = {
 586                 {1, 1024, "invalid number of paths"},
 587                 {0, 1024, "invalid number of selector args"}
 588         };
 589
 590         int r;
 591         unsigned i, nr_selector_args, nr_params;
 592         struct priority_group *pg;
 593         struct dm_target *ti = m->ti;
 594
 595         if (as->argc < 2) {
 596                 as->argc = 0;
 597                 ti->error = "not enough priority group aruments";
 598                 return NULL;
 599         }
 600
 601         pg = alloc_priority_group();
 602         if (!pg) {
 603                 ti->error = "couldn't allocate priority group";
 604                 return NULL;
 605         }
 606         pg->m = m;
 607
 608         r = parse_path_selector(as, pg, ti);
 609         if (r)
 610                 goto bad;
 611
 612         /*
 613          * read the paths
 614          */
 615         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
 616         if (r)
 617                 goto bad;
 618
 619         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
 620         if (r)
 621                 goto bad;
 622
 623         nr_params = 1 + nr_selector_args;
 624         for (i = 0; i < pg->nr_pgpaths; i++) {
 625                 struct pgpath *pgpath;
 626                 struct arg_set path_args;
 627
 628                 if (as->argc < nr_params) {
 629                         ti->error = "not enough path parameters";
 630                         goto bad;
 631                 }
 632
 633                 path_args.argc = nr_params;
 634                 path_args.argv = as->argv;
 635
 636                 pgpath = parse_path(&path_args, &pg->ps, ti);
 637                 if (!pgpath)
 638                         goto bad;
 639
 640                 pgpath->pg = pg;
 641                 list_add_tail(&pgpath->list, &pg->pgpaths);
 642                 consume(as, nr_params);
 643         }
 644
 645         return pg;
 646
 647  bad:
 648         free_priority_group(pg, ti);
 649         return NULL;
 650 }
 651
 652 static int parse_hw_handler(struct arg_set *as, struct multipath *m)
 653 {
 654         unsigned hw_argc;
 655         struct dm_target *ti = m->ti;
 656
 657         static struct param _params[] = {
 658                 {0, 1024, "invalid number of hardware handler args"},
 659         };
 660
 661         if (read_param(_params, shift(as), &hw_argc, &ti->error))
 662                 return -EINVAL;
 663
 664         if (!hw_argc)
 665                 return 0;
 666
 667         m->hw_handler_name = kstrdup(shift(as), GFP_KERNEL);
 668         request_module("scsi_dh_%s", m->hw_handler_name);
 669         if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
 670                 ti->error = "unknown hardware handler type";
 671                 kfree(m->hw_handler_name);
 672                 m->hw_handler_name = NULL;
 673                 return -EINVAL;
 674         }
 675         consume(as, hw_argc - 1);
 676
 677         return 0;
 678 }
 679
 680 static int parse_features(struct arg_set *as, struct multipath *m)
 681 {
 682         int r;
 683         unsigned argc;
 684         struct dm_target *ti = m->ti;
 685         const char *param_name;
 686
 687         static struct param _params[] = {
 688                 {0, 3, "invalid number of feature args"},
 689                 {1, 50, "pg_init_retries must be between 1 and 50"},
 690         };
 691
 692         r = read_param(_params, shift(as), &argc, &ti->error);
 693         if (r)
 694                 return -EINVAL;
 695
 696         if (!argc)
 697                 return 0;
 698
 699         do {
 700                 param_name = shift(as);
 701                 argc--;
 702
 703                 if (!strnicmp(param_name, MESG_STR("queue_if_no_path"))) {
 704                         r = queue_if_no_path(m, 1, 0);
 705                         continue;
 706                 }
 707
 708                 if (!strnicmp(param_name, MESG_STR("pg_init_retries")) &&
 709                     (argc >= 1)) {
 710                         r = read_param(_params + 1, shift(as),
 711                                        &m->pg_init_retries, &ti->error);
 712                         argc--;
 713                         continue;
 714                 }
 715
 716                 ti->error = "Unrecognised multipath feature request";
 717                 r = -EINVAL;
 718         } while (argc && !r);
 719
 720         return r;
 721 }
 722
 723 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 724                          char **argv)
 725 {
 726         /* target parameters */
 727         static struct param _params[] = {
 728                 {1, 1024, "invalid number of priority groups"},
 729                 {1, 1024, "invalid initial priority group number"},
 730         };
 731
 732         int r;
 733         struct multipath *m;
 734         struct arg_set as;
 735         unsigned pg_count = 0;
 736         unsigned next_pg_num;
 737
 738         as.argc = argc;
 739         as.argv = argv;
 740
 741         m = alloc_multipath(ti);
 742         if (!m) {
 743                 ti->error = "can't allocate multipath";
 744                 return -EINVAL;
 745         }
 746
 747         r = parse_features(&as, m);
 748         if (r)
 749                 goto bad;
 750
 751         r = parse_hw_handler(&as, m);
 752         if (r)
 753                 goto bad;
 754
 755         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
 756         if (r)
 757                 goto bad;
 758
 759         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
 760         if (r)
 761                 goto bad;
 762
 763         /* parse the priority groups */
 764         while (as.argc) {
 765                 struct priority_group *pg;
 766
 767                 pg = parse_priority_group(&as, m);
 768                 if (!pg) {
 769                         r = -EINVAL;
 770                         goto bad;
 771                 }
 772
 773                 m->nr_valid_paths += pg->nr_pgpaths;
 774                 list_add_tail(&pg->list, &m->priority_groups);
 775                 pg_count++;
 776                 pg->pg_num = pg_count;
 777                 if (!--next_pg_num)
 778                         m->next_pg = pg;
 779         }
 780
 781         if (pg_count != m->nr_priority_groups) {
 782                 ti->error = "priority group count mismatch";
 783                 r = -EINVAL;
 784                 goto bad;
 785         }
 786
 787         return 0;
 788
 789  bad:
 790         free_multipath(m);
 791         return r;
 792 }
 793
 794 static void multipath_dtr(struct dm_target *ti)
 795 {
 796         struct multipath *m = (struct multipath *) ti->private;
 797
 798         flush_workqueue(kmpath_handlerd);
 799         flush_workqueue(kmultipathd);
 800         free_multipath(m);
 801 }
 802
 803 /*
 804  * Map bios, recording original fields for later in case we have to resubmit
 805  */
 806 static int multipath_map(struct dm_target *ti, struct bio *bio,
 807                          union map_info *map_context)
 808 {
 809         int r;
 810         struct dm_mpath_io *mpio;
 811         struct multipath *m = (struct multipath *) ti->private;
 812
 813         mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
 814         dm_bio_record(&mpio->details, bio);
 815
 816         map_context->ptr = mpio;
 817         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
 818         r = map_io(m, bio, mpio, 0);
 819         if (r < 0 || r == DM_MAPIO_REQUEUE)
 820                 mempool_free(mpio, m->mpio_pool);
 821
 822         return r;
 823 }
 824
 825 /*
 826  * Take a path out of use.
 827  */
 828 static int fail_path(struct pgpath *pgpath)
 829 {
 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         DMWARN("Failing path %s.", pgpath->path.dev->name);
 839
 840         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 841         pgpath->path.is_active = 0;
 842         pgpath->fail_count++;
 843
 844         m->nr_valid_paths--;
 845
 846         if (pgpath == m->current_pgpath)
 847                 m->current_pgpath = NULL;
 848
 849         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
 850                       pgpath->path.dev->name, m->nr_valid_paths);
 851
 852         queue_work(kmultipathd, &m->trigger_event);
 853
 854 out:
 855         spin_unlock_irqrestore(&m->lock, flags);
 856
 857         return 0;
 858 }
 859
 860 /*
 861  * Reinstate a previously-failed path
 862  */
 863 static int reinstate_path(struct pgpath *pgpath)
 864 {
 865         int r = 0;
 866         unsigned long flags;
 867         struct multipath *m = pgpath->pg->m;
 868
 869         spin_lock_irqsave(&m->lock, flags);
 870
 871         if (pgpath->path.is_active)
 872                 goto out;
 873
 874         if (!pgpath->pg->ps.type->reinstate_path) {
 875                 DMWARN("Reinstate path not supported by path selector %s",
 876                        pgpath->pg->ps.type->name);
 877                 r = -EINVAL;
 878                 goto out;
 879         }
 880
 881         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
 882         if (r)
 883                 goto out;
 884
 885         pgpath->path.is_active = 1;
 886
 887         m->current_pgpath = NULL;
 888         if (!m->nr_valid_paths++ && m->queue_size)
 889                 queue_work(kmultipathd, &m->process_queued_ios);
 890
 891         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
 892                       pgpath->path.dev->name, m->nr_valid_paths);
 893
 894         queue_work(kmultipathd, &m->trigger_event);
 895
 896 out:
 897         spin_unlock_irqrestore(&m->lock, flags);
 898
 899         return r;
 900 }
 901
 902 /*
 903  * Fail or reinstate all paths that match the provided struct dm_dev.
 904  */
 905 static int action_dev(struct multipath *m, struct dm_dev *dev,
 906                       action_fn action)
 907 {
 908         int r = 0;
 909         struct pgpath *pgpath;
 910         struct priority_group *pg;
 911
 912         list_for_each_entry(pg, &m->priority_groups, list) {
 913                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
 914                         if (pgpath->path.dev == dev)
 915                                 r = action(pgpath);
 916                 }
 917         }
 918
 919         return r;
 920 }
 921
 922 /*
 923  * Temporarily try to avoid having to use the specified PG
 924  */
 925 static void bypass_pg(struct multipath *m, struct priority_group *pg,
 926                       int bypassed)
 927 {
 928         unsigned long flags;
 929
 930         spin_lock_irqsave(&m->lock, flags);
 931
 932         pg->bypassed = bypassed;
 933         m->current_pgpath = NULL;
 934         m->current_pg = NULL;
 935
 936         spin_unlock_irqrestore(&m->lock, flags);
 937
 938         queue_work(kmultipathd, &m->trigger_event);
 939 }
 940
 941 /*
 942  * Switch to using the specified PG from the next I/O that gets mapped
 943  */
 944 static int switch_pg_num(struct multipath *m, const char *pgstr)
 945 {
 946         struct priority_group *pg;
 947         unsigned pgnum;
 948         unsigned long flags;
 949
 950         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
 951             (pgnum > m->nr_priority_groups)) {
 952                 DMWARN("invalid PG number supplied to switch_pg_num");
 953                 return -EINVAL;
 954         }
 955
 956         spin_lock_irqsave(&m->lock, flags);
 957         list_for_each_entry(pg, &m->priority_groups, list) {
 958                 pg->bypassed = 0;
 959                 if (--pgnum)
 960                         continue;
 961
 962                 m->current_pgpath = NULL;
 963                 m->current_pg = NULL;
 964                 m->next_pg = pg;
 965         }
 966         spin_unlock_irqrestore(&m->lock, flags);
 967
 968         queue_work(kmultipathd, &m->trigger_event);
 969         return 0;
 970 }
 971
 972 /*
 973  * Set/clear bypassed status of a PG.
 974  * PGs are numbered upwards from 1 in the order they were declared.
 975  */
 976 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
 977 {
 978         struct priority_group *pg;
 979         unsigned pgnum;
 980
 981         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
 982             (pgnum > m->nr_priority_groups)) {
 983                 DMWARN("invalid PG number supplied to bypass_pg");
 984                 return -EINVAL;
 985         }
 986
 987         list_for_each_entry(pg, &m->priority_groups, list) {
 988                 if (!--pgnum)
 989                         break;
 990         }
 991
 992         bypass_pg(m, pg, bypassed);
 993         return 0;
 994 }
 995
 996 /*
 997  * Should we retry pg_init immediately?
 998  */
 999 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1000 {
1001         unsigned long flags;
1002         int limit_reached = 0;
1003
1004         spin_lock_irqsave(&m->lock, flags);
1005
1006         if (m->pg_init_count <= m->pg_init_retries)
1007                 m->pg_init_required = 1;
1008         else
1009                 limit_reached = 1;
1010
1011         spin_unlock_irqrestore(&m->lock, flags);
1012
1013         return limit_reached;
1014 }
1015
1016 static void pg_init_done(struct dm_path *path, int errors)
1017 {
1018         struct pgpath *pgpath = path_to_pgpath(path);
1019         struct priority_group *pg = pgpath->pg;
1020         struct multipath *m = pg->m;
1021         unsigned long flags;
1022
1023         /* device or driver problems */
1024         switch (errors) {
1025         case SCSI_DH_OK:
1026                 break;
1027         case SCSI_DH_NOSYS:
1028                 if (!m->hw_handler_name) {
1029                         errors = 0;
1030                         break;
1031                 }
1032                 DMERR("Cannot failover device because scsi_dh_%s was not "
1033                       "loaded.", m->hw_handler_name);
1034                 /*
1035                  * Fail path for now, so we do not ping pong
1036                  */
1037                 fail_path(pgpath);
1038                 break;
1039         case SCSI_DH_DEV_TEMP_BUSY:
1040                 /*
1041                  * Probably doing something like FW upgrade on the
1042                  * controller so try the other pg.
1043                  */
1044                 bypass_pg(m, pg, 1);
1045                 break;
1046         /* TODO: For SCSI_DH_RETRY we should wait a couple seconds */
1047         case SCSI_DH_RETRY:
1048         case SCSI_DH_IMM_RETRY:
1049         case SCSI_DH_RES_TEMP_UNAVAIL:
1050                 if (pg_init_limit_reached(m, pgpath))
1051                         fail_path(pgpath);
1052                 errors = 0;
1053                 break;
1054         default:
1055                 /*
1056                  * We probably do not want to fail the path for a device
1057                  * error, but this is what the old dm did. In future
1058                  * patches we can do more advanced handling.
1059                  */
1060                 fail_path(pgpath);
1061         }
1062
1063         spin_lock_irqsave(&m->lock, flags);
1064         if (errors) {
1065                 DMERR("Could not failover device. Error %d.", errors);
1066                 m->current_pgpath = NULL;
1067                 m->current_pg = NULL;
1068         } else if (!m->pg_init_required) {
1069                 m->queue_io = 0;
1070                 pg->bypassed = 0;
1071         }
1072
1073         m->pg_init_in_progress = 0;
1074         queue_work(kmultipathd, &m->process_queued_ios);
1075         spin_unlock_irqrestore(&m->lock, flags);
1076 }
1077
1078 static void activate_path(struct work_struct *work)
1079 {
1080         int ret;
1081         struct multipath *m =
1082                 container_of(work, struct multipath, activate_path);
1083         struct dm_path *path = &m->current_pgpath->path;
1084
1085         ret = scsi_dh_activate(bdev_get_queue(path->dev->bdev));
1086         pg_init_done(path, ret);
1087 }
1088
1089 /*
1090  * end_io handling
1091  */
1092 static int do_end_io(struct multipath *m, struct bio *bio,
1093                      int error, struct dm_mpath_io *mpio)
1094 {
1095         unsigned long flags;
1096
1097         if (!error)
1098                 return 0;       /* I/O complete */
1099
1100         if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
1101                 return error;
1102
1103         if (error == -EOPNOTSUPP)
1104                 return error;
1105
1106         spin_lock_irqsave(&m->lock, flags);
1107         if (!m->nr_valid_paths) {
1108                 if (__must_push_back(m)) {
1109                         spin_unlock_irqrestore(&m->lock, flags);
1110                         return DM_ENDIO_REQUEUE;
1111                 } else if (!m->queue_if_no_path) {
1112                         spin_unlock_irqrestore(&m->lock, flags);
1113                         return -EIO;
1114                 } else {
1115                         spin_unlock_irqrestore(&m->lock, flags);
1116                         goto requeue;
1117                 }
1118         }
1119         spin_unlock_irqrestore(&m->lock, flags);
1120
1121         if (mpio->pgpath)
1122                 fail_path(mpio->pgpath);
1123
1124       requeue:
1125         dm_bio_restore(&mpio->details, bio);
1126
1127         /* queue for the daemon to resubmit or fail */
1128         spin_lock_irqsave(&m->lock, flags);
1129         bio_list_add(&m->queued_ios, bio);
1130         m->queue_size++;
1131         if (!m->queue_io)
1132                 queue_work(kmultipathd, &m->process_queued_ios);
1133         spin_unlock_irqrestore(&m->lock, flags);
1134
1135         return DM_ENDIO_INCOMPLETE;     /* io not complete */
1136 }
1137
1138 static int multipath_end_io(struct dm_target *ti, struct bio *bio,
1139                             int error, union map_info *map_context)
1140 {
1141         struct multipath *m = ti->private;
1142         struct dm_mpath_io *mpio = map_context->ptr;
1143         struct pgpath *pgpath = mpio->pgpath;
1144         struct path_selector *ps;
1145         int r;
1146
1147         r  = do_end_io(m, bio, error, mpio);
1148         if (pgpath) {
1149                 ps = &pgpath->pg->ps;
1150                 if (ps->type->end_io)
1151                         ps->type->end_io(ps, &pgpath->path);
1152         }
1153         if (r != DM_ENDIO_INCOMPLETE)
1154                 mempool_free(mpio, m->mpio_pool);
1155
1156         return r;
1157 }
1158
1159 /*
1160  * Suspend can't complete until all the I/O is processed so if
1161  * the last path fails we must error any remaining I/O.
1162  * Note that if the freeze_bdev fails while suspending, the
1163  * queue_if_no_path state is lost - userspace should reset it.
1164  */
1165 static void multipath_presuspend(struct dm_target *ti)
1166 {
1167         struct multipath *m = (struct multipath *) ti->private;
1168
1169         queue_if_no_path(m, 0, 1);
1170 }
1171
1172 /*
1173  * Restore the queue_if_no_path setting.
1174  */
1175 static void multipath_resume(struct dm_target *ti)
1176 {
1177         struct multipath *m = (struct multipath *) ti->private;
1178         unsigned long flags;
1179
1180         spin_lock_irqsave(&m->lock, flags);
1181         m->queue_if_no_path = m->saved_queue_if_no_path;
1182         spin_unlock_irqrestore(&m->lock, flags);
1183 }
1184
1185 /*
1186  * Info output has the following format:
1187  * num_multipath_feature_args [multipath_feature_args]*
1188  * num_handler_status_args [handler_status_args]*
1189  * num_groups init_group_number
1190  *            [A|D|E num_ps_status_args [ps_status_args]*
1191  *             num_paths num_selector_args
1192  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1193  *
1194  * Table output has the following format (identical to the constructor string):
1195  * num_feature_args [features_args]*
1196  * num_handler_args hw_handler [hw_handler_args]*
1197  * num_groups init_group_number
1198  *     [priority selector-name num_ps_args [ps_args]*
1199  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1200  */
1201 static int multipath_status(struct dm_target *ti, status_type_t type,
1202                             char *result, unsigned int maxlen)
1203 {
1204         int sz = 0;
1205         unsigned long flags;
1206         struct multipath *m = (struct multipath *) ti->private;
1207         struct priority_group *pg;
1208         struct pgpath *p;
1209         unsigned pg_num;
1210         char state;
1211
1212         spin_lock_irqsave(&m->lock, flags);
1213
1214         /* Features */
1215         if (type == STATUSTYPE_INFO)
1216                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1217         else {
1218                 DMEMIT("%u ", m->queue_if_no_path +
1219                               (m->pg_init_retries > 0) * 2);
1220                 if (m->queue_if_no_path)
1221                         DMEMIT("queue_if_no_path ");
1222                 if (m->pg_init_retries)
1223                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1224         }
1225
1226         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1227                 DMEMIT("0 ");
1228         else
1229                 DMEMIT("1 %s ", m->hw_handler_name);
1230
1231         DMEMIT("%u ", m->nr_priority_groups);
1232
1233         if (m->next_pg)
1234                 pg_num = m->next_pg->pg_num;
1235         else if (m->current_pg)
1236                 pg_num = m->current_pg->pg_num;
1237         else
1238                         pg_num = 1;
1239
1240         DMEMIT("%u ", pg_num);
1241
1242         switch (type) {
1243         case STATUSTYPE_INFO:
1244                 list_for_each_entry(pg, &m->priority_groups, list) {
1245                         if (pg->bypassed)
1246                                 state = 'D';    /* Disabled */
1247                         else if (pg == m->current_pg)
1248                                 state = 'A';    /* Currently Active */
1249                         else
1250                                 state = 'E';    /* Enabled */
1251
1252                         DMEMIT("%c ", state);
1253
1254                         if (pg->ps.type->status)
1255                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1256                                                           result + sz,
1257                                                           maxlen - sz);
1258                         else
1259                                 DMEMIT("0 ");
1260
1261                         DMEMIT("%u %u ", pg->nr_pgpaths,
1262                                pg->ps.type->info_args);
1263
1264                         list_for_each_entry(p, &pg->pgpaths, list) {
1265                                 DMEMIT("%s %s %u ", p->path.dev->name,
1266                                        p->path.is_active ? "A" : "F",
1267                                        p->fail_count);
1268                                 if (pg->ps.type->status)
1269                                         sz += pg->ps.type->status(&pg->ps,
1270                                               &p->path, type, result + sz,
1271                                               maxlen - sz);
1272                         }
1273                 }
1274                 break;
1275
1276         case STATUSTYPE_TABLE:
1277                 list_for_each_entry(pg, &m->priority_groups, list) {
1278                         DMEMIT("%s ", pg->ps.type->name);
1279
1280                         if (pg->ps.type->status)
1281                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1282                                                           result + sz,
1283                                                           maxlen - sz);
1284                         else
1285                                 DMEMIT("0 ");
1286
1287                         DMEMIT("%u %u ", pg->nr_pgpaths,
1288                                pg->ps.type->table_args);
1289
1290                         list_for_each_entry(p, &pg->pgpaths, list) {
1291                                 DMEMIT("%s ", p->path.dev->name);
1292                                 if (pg->ps.type->status)
1293                                         sz += pg->ps.type->status(&pg->ps,
1294                                               &p->path, type, result + sz,
1295                                               maxlen - sz);
1296                         }
1297                 }
1298                 break;
1299         }
1300
1301         spin_unlock_irqrestore(&m->lock, flags);
1302
1303         return 0;
1304 }
1305
1306 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1307 {
1308         int r;
1309         struct dm_dev *dev;
1310         struct multipath *m = (struct multipath *) ti->private;
1311         action_fn action;
1312
1313         if (argc == 1) {
1314                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path")))
1315                         return queue_if_no_path(m, 1, 0);
1316                 else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path")))
1317                         return queue_if_no_path(m, 0, 0);
1318         }
1319
1320         if (argc != 2)
1321                 goto error;
1322
1323         if (!strnicmp(argv[0], MESG_STR("disable_group")))
1324                 return bypass_pg_num(m, argv[1], 1);
1325         else if (!strnicmp(argv[0], MESG_STR("enable_group")))
1326                 return bypass_pg_num(m, argv[1], 0);
1327         else if (!strnicmp(argv[0], MESG_STR("switch_group")))
1328                 return switch_pg_num(m, argv[1]);
1329         else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1330                 action = reinstate_path;
1331         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1332                 action = fail_path;
1333         else
1334                 goto error;
1335
1336         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
1337                           dm_table_get_mode(ti->table), &dev);
1338         if (r) {
1339                 DMWARN("message: error getting device %s",
1340                        argv[1]);
1341                 return -EINVAL;
1342         }
1343
1344         r = action_dev(m, dev, action);
1345
1346         dm_put_device(ti, dev);
1347
1348         return r;
1349
1350 error:
1351         DMWARN("Unrecognised multipath message received.");
1352         return -EINVAL;
1353 }
1354
1355 static int multipath_ioctl(struct dm_target *ti, struct inode *inode,
1356                            struct file *filp, unsigned int cmd,
1357                            unsigned long arg)
1358 {
1359         struct multipath *m = (struct multipath *) ti->private;
1360         struct block_device *bdev = NULL;
1361         unsigned long flags;
1362         struct file fake_file = {};
1363         struct dentry fake_dentry = {};
1364         int r = 0;
1365
1366         fake_file.f_path.dentry = &fake_dentry;
1367
1368         spin_lock_irqsave(&m->lock, flags);
1369
1370         if (!m->current_pgpath)
1371                 __choose_pgpath(m);
1372
1373         if (m->current_pgpath) {
1374                 bdev = m->current_pgpath->path.dev->bdev;
1375                 fake_dentry.d_inode = bdev->bd_inode;
1376                 fake_file.f_mode = m->current_pgpath->path.dev->mode;
1377         }
1378
1379         if (m->queue_io)
1380                 r = -EAGAIN;
1381         else if (!bdev)
1382                 r = -EIO;
1383
1384         spin_unlock_irqrestore(&m->lock, flags);
1385
1386         return r ? : blkdev_driver_ioctl(bdev->bd_inode, &fake_file,
1387                                          bdev->bd_disk, cmd, arg);
1388 }
1389
1390 /*-----------------------------------------------------------------
1391  * Module setup
1392  *---------------------------------------------------------------*/
1393 static struct target_type multipath_target = {
1394         .name = "multipath",
1395         .version = {1, 0, 5},
1396         .module = THIS_MODULE,
1397         .ctr = multipath_ctr,
1398         .dtr = multipath_dtr,
1399         .map = multipath_map,
1400         .end_io = multipath_end_io,
1401         .presuspend = multipath_presuspend,
1402         .resume = multipath_resume,
1403         .status = multipath_status,
1404         .message = multipath_message,
1405         .ioctl  = multipath_ioctl,
1406 };
1407
1408 static int __init dm_multipath_init(void)
1409 {
1410         int r;
1411
1412         /* allocate a slab for the dm_ios */
1413         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1414         if (!_mpio_cache)
1415                 return -ENOMEM;
1416
1417         r = dm_register_target(&multipath_target);
1418         if (r < 0) {
1419                 DMERR("register failed %d", r);
1420                 kmem_cache_destroy(_mpio_cache);
1421                 return -EINVAL;
1422         }
1423
1424         kmultipathd = create_workqueue("kmpathd");
1425         if (!kmultipathd) {
1426                 DMERR("failed to create workqueue kmpathd");
1427                 dm_unregister_target(&multipath_target);
1428                 kmem_cache_destroy(_mpio_cache);
1429                 return -ENOMEM;
1430         }
1431
1432         /*
1433          * A separate workqueue is used to handle the device handlers
1434          * to avoid overloading existing workqueue. Overloading the
1435          * old workqueue would also create a bottleneck in the
1436          * path of the storage hardware device activation.
1437          */
1438         kmpath_handlerd = create_singlethread_workqueue("kmpath_handlerd");
1439         if (!kmpath_handlerd) {
1440                 DMERR("failed to create workqueue kmpath_handlerd");
1441                 destroy_workqueue(kmultipathd);
1442                 dm_unregister_target(&multipath_target);
1443                 kmem_cache_destroy(_mpio_cache);
1444                 return -ENOMEM;
1445         }
1446
1447         DMINFO("version %u.%u.%u loaded",
1448                multipath_target.version[0], multipath_target.version[1],
1449                multipath_target.version[2]);
1450
1451         return r;
1452 }
1453
1454 static void __exit dm_multipath_exit(void)
1455 {
1456         int r;
1457
1458         destroy_workqueue(kmpath_handlerd);
1459         destroy_workqueue(kmultipathd);
1460
1461         r = dm_unregister_target(&multipath_target);
1462         if (r < 0)
1463                 DMERR("target unregister failed %d", r);
1464         kmem_cache_destroy(_mpio_cache);
1465 }
1466
1467 module_init(dm_multipath_init);
1468 module_exit(dm_multipath_exit);
1469
1470 MODULE_DESCRIPTION(DM_NAME " multipath target");
1471 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1472 MODULE_LICENSE("GPL");