drivers/md/multipath.c

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