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   1 /*
   2  * multipath.c : Multiple Devices driver for Linux
   3  *
   4  * Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
   5  *
   6  * Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
   7  *
   8  * MULTIPATH management functions.
   9  *
  10  * derived from raid1.c.
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2, or (at your option)
  15  * any later version.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * (for example /usr/src/linux/COPYING); if not, write to the Free
  19  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22 #include <linux/module.h>
  23 #include <linux/slab.h>
  24 #include <linux/spinlock.h>
  25 #include <linux/raid/multipath.h>
  26 #include <linux/buffer_head.h>
  27 #include <asm/atomic.h>
  28
  29 #define MAJOR_NR MD_MAJOR
  30 #define MD_DRIVER
  31 #define MD_PERSONALITY
  32
  33 #define MAX_WORK_PER_DISK 128
  34
  35 #define NR_RESERVED_BUFS        32
  36
  37
  38 static mdk_personality_t multipath_personality;
  39
  40
  41 static void *mp_pool_alloc(gfp_t gfp_flags, void *data)
  42 {
  43         struct multipath_bh *mpb;
  44         mpb = kmalloc(sizeof(*mpb), gfp_flags);
  45         if (mpb)
  46                 memset(mpb, 0, sizeof(*mpb));
  47         return mpb;
  48 }
  49
  50 static void mp_pool_free(void *mpb, void *data)
  51 {
  52         kfree(mpb);
  53 }
  54
  55 static int multipath_map (multipath_conf_t *conf)
  56 {
  57         int i, disks = conf->raid_disks;
  58
  59         /*
  60          * Later we do read balancing on the read side
  61          * now we use the first available disk.
  62          */
  63
  64         rcu_read_lock();
  65         for (i = 0; i < disks; i++) {
  66                 mdk_rdev_t *rdev = conf->multipaths[i].rdev;
  67                 if (rdev && rdev->in_sync) {
  68                         atomic_inc(&rdev->nr_pending);
  69                         rcu_read_unlock();
  70                         return i;
  71                 }
  72         }
  73         rcu_read_unlock();
  74
  75         printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
  76         return (-1);
  77 }
  78
  79 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
  80 {
  81         unsigned long flags;
  82         mddev_t *mddev = mp_bh->mddev;
  83         multipath_conf_t *conf = mddev_to_conf(mddev);
  84
  85         spin_lock_irqsave(&conf->device_lock, flags);
  86         list_add(&mp_bh->retry_list, &conf->retry_list);
  87         spin_unlock_irqrestore(&conf->device_lock, flags);
  88         md_wakeup_thread(mddev->thread);
  89 }
  90
  91
  92 /*
  93  * multipath_end_bh_io() is called when we have finished servicing a multipathed
  94  * operation and are ready to return a success/failure code to the buffer
  95  * cache layer.
  96  */
  97 static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
  98 {
  99         struct bio *bio = mp_bh->master_bio;
 100         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
 101
 102         bio_endio(bio, bio->bi_size, err);
 103         mempool_free(mp_bh, conf->pool);
 104 }
 105
 106 static int multipath_end_request(struct bio *bio, unsigned int bytes_done,
 107                                  int error)
 108 {
 109         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
 110         struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
 111         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
 112         mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
 113
 114         if (bio->bi_size)
 115                 return 1;
 116
 117         if (uptodate)
 118                 multipath_end_bh_io(mp_bh, 0);
 119         else if (!bio_rw_ahead(bio)) {
 120                 /*
 121                  * oops, IO error:
 122                  */
 123                 char b[BDEVNAME_SIZE];
 124                 md_error (mp_bh->mddev, rdev);
 125                 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
 126                        bdevname(rdev->bdev,b),
 127                        (unsigned long long)bio->bi_sector);
 128                 multipath_reschedule_retry(mp_bh);
 129         } else
 130                 multipath_end_bh_io(mp_bh, error);
 131         rdev_dec_pending(rdev, conf->mddev);
 132         return 0;
 133 }
 134
 135 static void unplug_slaves(mddev_t *mddev)
 136 {
 137         multipath_conf_t *conf = mddev_to_conf(mddev);
 138         int i;
 139
 140         rcu_read_lock();
 141         for (i=0; i<mddev->raid_disks; i++) {
 142                 mdk_rdev_t *rdev = conf->multipaths[i].rdev;
 143                 if (rdev && !rdev->faulty && atomic_read(&rdev->nr_pending)) {
 144                         request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
 145
 146                         atomic_inc(&rdev->nr_pending);
 147                         rcu_read_unlock();
 148
 149                         if (r_queue->unplug_fn)
 150                                 r_queue->unplug_fn(r_queue);
 151
 152                         rdev_dec_pending(rdev, mddev);
 153                         rcu_read_lock();
 154                 }
 155         }
 156         rcu_read_unlock();
 157 }
 158
 159 static void multipath_unplug(request_queue_t *q)
 160 {
 161         unplug_slaves(q->queuedata);
 162 }
 163
 164
 165 static int multipath_make_request (request_queue_t *q, struct bio * bio)
 166 {
 167         mddev_t *mddev = q->queuedata;
 168         multipath_conf_t *conf = mddev_to_conf(mddev);
 169         struct multipath_bh * mp_bh;
 170         struct multipath_info *multipath;
 171         const int rw = bio_data_dir(bio);
 172
 173         if (unlikely(bio_barrier(bio))) {
 174                 bio_endio(bio, bio->bi_size, -EOPNOTSUPP);
 175                 return 0;
 176         }
 177
 178         mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
 179
 180         mp_bh->master_bio = bio;
 181         mp_bh->mddev = mddev;
 182
 183         disk_stat_inc(mddev->gendisk, ios[rw]);
 184         disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));
 185
 186         mp_bh->path = multipath_map(conf);
 187         if (mp_bh->path < 0) {
 188                 bio_endio(bio, bio->bi_size, -EIO);
 189                 mempool_free(mp_bh, conf->pool);
 190                 return 0;
 191         }
 192         multipath = conf->multipaths + mp_bh->path;
 193
 194         mp_bh->bio = *bio;
 195         mp_bh->bio.bi_sector += multipath->rdev->data_offset;
 196         mp_bh->bio.bi_bdev = multipath->rdev->bdev;
 197         mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST);
 198         mp_bh->bio.bi_end_io = multipath_end_request;
 199         mp_bh->bio.bi_private = mp_bh;
 200         generic_make_request(&mp_bh->bio);
 201         return 0;
 202 }
 203
 204 static void multipath_status (struct seq_file *seq, mddev_t *mddev)
 205 {
 206         multipath_conf_t *conf = mddev_to_conf(mddev);
 207         int i;
 208
 209         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
 210                                                  conf->working_disks);
 211         for (i = 0; i < conf->raid_disks; i++)
 212                 seq_printf (seq, "%s",
 213                                conf->multipaths[i].rdev &&
 214                                conf->multipaths[i].rdev->in_sync ? "U" : "_");
 215         seq_printf (seq, "]");
 216 }
 217
 218 static int multipath_issue_flush(request_queue_t *q, struct gendisk *disk,
 219                                  sector_t *error_sector)
 220 {
 221         mddev_t *mddev = q->queuedata;
 222         multipath_conf_t *conf = mddev_to_conf(mddev);
 223         int i, ret = 0;
 224
 225         rcu_read_lock();
 226         for (i=0; i<mddev->raid_disks && ret == 0; i++) {
 227                 mdk_rdev_t *rdev = conf->multipaths[i].rdev;
 228                 if (rdev && !rdev->faulty) {
 229                         struct block_device *bdev = rdev->bdev;
 230                         request_queue_t *r_queue = bdev_get_queue(bdev);
 231
 232                         if (!r_queue->issue_flush_fn)
 233                                 ret = -EOPNOTSUPP;
 234                         else {
 235                                 atomic_inc(&rdev->nr_pending);
 236                                 rcu_read_unlock();
 237                                 ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk,
 238                                                               error_sector);
 239                                 rdev_dec_pending(rdev, mddev);
 240                                 rcu_read_lock();
 241                         }
 242                 }
 243         }
 244         rcu_read_unlock();
 245         return ret;
 246 }
 247
 248 /*
 249  * Careful, this can execute in IRQ contexts as well!
 250  */
 251 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
 252 {
 253         multipath_conf_t *conf = mddev_to_conf(mddev);
 254
 255         if (conf->working_disks <= 1) {
 256                 /*
 257                  * Uh oh, we can do nothing if this is our last path, but
 258                  * first check if this is a queued request for a device
 259                  * which has just failed.
 260                  */
 261                 printk(KERN_ALERT
 262                         "multipath: only one IO path left and IO error.\n");
 263                 /* leave it active... it's all we have */
 264         } else {
 265                 /*
 266                  * Mark disk as unusable
 267                  */
 268                 if (!rdev->faulty) {
 269                         char b[BDEVNAME_SIZE];
 270                         rdev->in_sync = 0;
 271                         rdev->faulty = 1;
 272                         mddev->sb_dirty = 1;
 273                         conf->working_disks--;
 274                         printk(KERN_ALERT "multipath: IO failure on %s,"
 275                                 " disabling IO path. \n Operation continuing"
 276                                 " on %d IO paths.\n",
 277                                 bdevname (rdev->bdev,b),
 278                                 conf->working_disks);
 279                 }
 280         }
 281 }
 282
 283 static void print_multipath_conf (multipath_conf_t *conf)
 284 {
 285         int i;
 286         struct multipath_info *tmp;
 287
 288         printk("MULTIPATH conf printout:\n");
 289         if (!conf) {
 290                 printk("(conf==NULL)\n");
 291                 return;
 292         }
 293         printk(" --- wd:%d rd:%d\n", conf->working_disks,
 294                          conf->raid_disks);
 295
 296         for (i = 0; i < conf->raid_disks; i++) {
 297                 char b[BDEVNAME_SIZE];
 298                 tmp = conf->multipaths + i;
 299                 if (tmp->rdev)
 300                         printk(" disk%d, o:%d, dev:%s\n",
 301                                 i,!tmp->rdev->faulty,
 302                                bdevname(tmp->rdev->bdev,b));
 303         }
 304 }
 305
 306
 307 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
 308 {
 309         multipath_conf_t *conf = mddev->private;
 310         int found = 0;
 311         int path;
 312         struct multipath_info *p;
 313
 314         print_multipath_conf(conf);
 315
 316         for (path=0; path<mddev->raid_disks; path++)
 317                 if ((p=conf->multipaths+path)->rdev == NULL) {
 318                         blk_queue_stack_limits(mddev->queue,
 319                                                rdev->bdev->bd_disk->queue);
 320
 321                 /* as we don't honour merge_bvec_fn, we must never risk
 322                  * violating it, so limit ->max_sector to one PAGE, as
 323                  * a one page request is never in violation.
 324                  * (Note: it is very unlikely that a device with
 325                  * merge_bvec_fn will be involved in multipath.)
 326                  */
 327                         if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
 328                             mddev->queue->max_sectors > (PAGE_SIZE>>9))
 329                                 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 330
 331                         conf->working_disks++;
 332                         rdev->raid_disk = path;
 333                         rdev->in_sync = 1;
 334                         p->rdev = rdev;
 335                         found = 1;
 336                 }
 337
 338         print_multipath_conf(conf);
 339         return found;
 340 }
 341
 342 static int multipath_remove_disk(mddev_t *mddev, int number)
 343 {
 344         multipath_conf_t *conf = mddev->private;
 345         int err = 0;
 346         mdk_rdev_t *rdev;
 347         struct multipath_info *p = conf->multipaths + number;
 348
 349         print_multipath_conf(conf);
 350
 351         rdev = p->rdev;
 352         if (rdev) {
 353                 if (rdev->in_sync ||
 354                     atomic_read(&rdev->nr_pending)) {
 355                         printk(KERN_ERR "hot-remove-disk, slot %d is identified"                                " but is still operational!\n", number);
 356                         err = -EBUSY;
 357                         goto abort;
 358                 }
 359                 p->rdev = NULL;
 360                 synchronize_rcu();
 361                 if (atomic_read(&rdev->nr_pending)) {
 362                         /* lost the race, try later */
 363                         err = -EBUSY;
 364                         p->rdev = rdev;
 365                 }
 366         }
 367 abort:
 368
 369         print_multipath_conf(conf);
 370         return err;
 371 }
 372
 373
 374
 375 /*
 376  * This is a kernel thread which:
 377  *
 378  *      1.      Retries failed read operations on working multipaths.
 379  *      2.      Updates the raid superblock when problems encounter.
 380  *      3.      Performs writes following reads for array syncronising.
 381  */
 382
 383 static void multipathd (mddev_t *mddev)
 384 {
 385         struct multipath_bh *mp_bh;
 386         struct bio *bio;
 387         unsigned long flags;
 388         multipath_conf_t *conf = mddev_to_conf(mddev);
 389         struct list_head *head = &conf->retry_list;
 390
 391         md_check_recovery(mddev);
 392         for (;;) {
 393                 char b[BDEVNAME_SIZE];
 394                 spin_lock_irqsave(&conf->device_lock, flags);
 395                 if (list_empty(head))
 396                         break;
 397                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
 398                 list_del(head->prev);
 399                 spin_unlock_irqrestore(&conf->device_lock, flags);
 400
 401                 bio = &mp_bh->bio;
 402                 bio->bi_sector = mp_bh->master_bio->bi_sector;
 403
 404                 if ((mp_bh->path = multipath_map (conf))<0) {
 405                         printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
 406                                 " error for block %llu\n",
 407                                 bdevname(bio->bi_bdev,b),
 408                                 (unsigned long long)bio->bi_sector);
 409                         multipath_end_bh_io(mp_bh, -EIO);
 410                 } else {
 411                         printk(KERN_ERR "multipath: %s: redirecting sector %llu"
 412                                 " to another IO path\n",
 413                                 bdevname(bio->bi_bdev,b),
 414                                 (unsigned long long)bio->bi_sector);
 415                         *bio = *(mp_bh->master_bio);
 416                         bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
 417                         bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
 418                         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
 419                         bio->bi_end_io = multipath_end_request;
 420                         bio->bi_private = mp_bh;
 421                         generic_make_request(bio);
 422                 }
 423         }
 424         spin_unlock_irqrestore(&conf->device_lock, flags);
 425 }
 426
 427 static int multipath_run (mddev_t *mddev)
 428 {
 429         multipath_conf_t *conf;
 430         int disk_idx;
 431         struct multipath_info *disk;
 432         mdk_rdev_t *rdev;
 433         struct list_head *tmp;
 434
 435         if (mddev->level != LEVEL_MULTIPATH) {
 436                 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
 437                        mdname(mddev), mddev->level);
 438                 goto out;
 439         }
 440         /*
 441          * copy the already verified devices into our private MULTIPATH
 442          * bookkeeping area. [whatever we allocate in multipath_run(),
 443          * should be freed in multipath_stop()]
 444          */
 445
 446         conf = kmalloc(sizeof(multipath_conf_t), GFP_KERNEL);
 447         mddev->private = conf;
 448         if (!conf) {
 449                 printk(KERN_ERR
 450                         "multipath: couldn't allocate memory for %s\n",
 451                         mdname(mddev));
 452                 goto out;
 453         }
 454         memset(conf, 0, sizeof(*conf));
 455
 456         conf->multipaths = kmalloc(sizeof(struct multipath_info)*mddev->raid_disks,
 457                                    GFP_KERNEL);
 458         if (!conf->multipaths) {
 459                 printk(KERN_ERR
 460                         "multipath: couldn't allocate memory for %s\n",
 461                         mdname(mddev));
 462                 goto out_free_conf;
 463         }
 464         memset(conf->multipaths, 0, sizeof(struct multipath_info)*mddev->raid_disks);
 465
 466         conf->working_disks = 0;
 467         ITERATE_RDEV(mddev,rdev,tmp) {
 468                 disk_idx = rdev->raid_disk;
 469                 if (disk_idx < 0 ||
 470                     disk_idx >= mddev->raid_disks)
 471                         continue;
 472
 473                 disk = conf->multipaths + disk_idx;
 474                 disk->rdev = rdev;
 475
 476                 blk_queue_stack_limits(mddev->queue,
 477                                        rdev->bdev->bd_disk->queue);
 478                 /* as we don't honour merge_bvec_fn, we must never risk
 479                  * violating it, not that we ever expect a device with
 480                  * a merge_bvec_fn to be involved in multipath */
 481                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
 482                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
 483                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 484
 485                 if (!rdev->faulty)
 486                         conf->working_disks++;
 487         }
 488
 489         conf->raid_disks = mddev->raid_disks;
 490         mddev->sb_dirty = 1;
 491         conf->mddev = mddev;
 492         spin_lock_init(&conf->device_lock);
 493         INIT_LIST_HEAD(&conf->retry_list);
 494
 495         if (!conf->working_disks) {
 496                 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
 497                         mdname(mddev));
 498                 goto out_free_conf;
 499         }
 500         mddev->degraded = conf->raid_disks = conf->working_disks;
 501
 502         conf->pool = mempool_create(NR_RESERVED_BUFS,
 503                                     mp_pool_alloc, mp_pool_free,
 504                                     NULL);
 505         if (conf->pool == NULL) {
 506                 printk(KERN_ERR
 507                         "multipath: couldn't allocate memory for %s\n",
 508                         mdname(mddev));
 509                 goto out_free_conf;
 510         }
 511
 512         {
 513                 mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
 514                 if (!mddev->thread) {
 515                         printk(KERN_ERR "multipath: couldn't allocate thread"
 516                                 " for %s\n", mdname(mddev));
 517                         goto out_free_conf;
 518                 }
 519         }
 520
 521         printk(KERN_INFO
 522                 "multipath: array %s active with %d out of %d IO paths\n",
 523                 mdname(mddev), conf->working_disks, mddev->raid_disks);
 524         /*
 525          * Ok, everything is just fine now
 526          */
 527         mddev->array_size = mddev->size;
 528
 529         mddev->queue->unplug_fn = multipath_unplug;
 530         mddev->queue->issue_flush_fn = multipath_issue_flush;
 531
 532         return 0;
 533
 534 out_free_conf:
 535         if (conf->pool)
 536                 mempool_destroy(conf->pool);
 537         kfree(conf->multipaths);
 538         kfree(conf);
 539         mddev->private = NULL;
 540 out:
 541         return -EIO;
 542 }
 543
 544
 545 static int multipath_stop (mddev_t *mddev)
 546 {
 547         multipath_conf_t *conf = mddev_to_conf(mddev);
 548
 549         md_unregister_thread(mddev->thread);
 550         mddev->thread = NULL;
 551         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 552         mempool_destroy(conf->pool);
 553         kfree(conf->multipaths);
 554         kfree(conf);
 555         mddev->private = NULL;
 556         return 0;
 557 }
 558
 559 static mdk_personality_t multipath_personality=
 560 {
 561         .name           = "multipath",
 562         .owner          = THIS_MODULE,
 563         .make_request   = multipath_make_request,
 564         .run            = multipath_run,
 565         .stop           = multipath_stop,
 566         .status         = multipath_status,
 567         .error_handler  = multipath_error,
 568         .hot_add_disk   = multipath_add_disk,
 569         .hot_remove_disk= multipath_remove_disk,
 570 };
 571
 572 static int __init multipath_init (void)
 573 {
 574         return register_md_personality (MULTIPATH, &multipath_personality);
 575 }
 576
 577 static void __exit multipath_exit (void)
 578 {
 579         unregister_md_personality (MULTIPATH);
 580 }
 581
 582 module_init(multipath_init);
 583 module_exit(multipath_exit);
 584 MODULE_LICENSE("GPL");
 585 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */