git.oblomov.eu Git - linux-2.6/blob - 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         int cpu;
 151
 152         if (unlikely(bio_barrier(bio))) {
 153                 bio_endio(bio, -EOPNOTSUPP);
 154                 return 0;
 155         }
 156
 157         mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
 158
 159         mp_bh->master_bio = bio;
 160         mp_bh->mddev = mddev;
 161
 162         cpu = part_stat_lock();
 163         part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
 164         part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw],
 165                       bio_sectors(bio));
 166         part_stat_unlock();
 167
 168         mp_bh->path = multipath_map(conf);
 169         if (mp_bh->path < 0) {
 170                 bio_endio(bio, -EIO);
 171                 mempool_free(mp_bh, conf->pool);
 172                 return 0;
 173         }
 174         multipath = conf->multipaths + mp_bh->path;
 175
 176         mp_bh->bio = *bio;
 177         mp_bh->bio.bi_sector += multipath->rdev->data_offset;
 178         mp_bh->bio.bi_bdev = multipath->rdev->bdev;
 179         mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST);
 180         mp_bh->bio.bi_end_io = multipath_end_request;
 181         mp_bh->bio.bi_private = mp_bh;
 182         generic_make_request(&mp_bh->bio);
 183         return 0;
 184 }
 185
 186 static void multipath_status (struct seq_file *seq, mddev_t *mddev)
 187 {
 188         multipath_conf_t *conf = mddev_to_conf(mddev);
 189         int i;
 190
 191         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
 192                                                  conf->working_disks);
 193         for (i = 0; i < conf->raid_disks; i++)
 194                 seq_printf (seq, "%s",
 195                                conf->multipaths[i].rdev &&
 196                                test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
 197         seq_printf (seq, "]");
 198 }
 199
 200 static int multipath_congested(void *data, int bits)
 201 {
 202         mddev_t *mddev = data;
 203         multipath_conf_t *conf = mddev_to_conf(mddev);
 204         int i, ret = 0;
 205
 206         rcu_read_lock();
 207         for (i = 0; i < mddev->raid_disks ; i++) {
 208                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
 209                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
 210                         struct request_queue *q = bdev_get_queue(rdev->bdev);
 211
 212                         ret |= bdi_congested(&q->backing_dev_info, bits);
 213                         /* Just like multipath_map, we just check the
 214                          * first available device
 215                          */
 216                         break;
 217                 }
 218         }
 219         rcu_read_unlock();
 220         return ret;
 221 }
 222
 223 /*
 224  * Careful, this can execute in IRQ contexts as well!
 225  */
 226 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
 227 {
 228         multipath_conf_t *conf = mddev_to_conf(mddev);
 229
 230         if (conf->working_disks <= 1) {
 231                 /*
 232                  * Uh oh, we can do nothing if this is our last path, but
 233                  * first check if this is a queued request for a device
 234                  * which has just failed.
 235                  */
 236                 printk(KERN_ALERT
 237                         "multipath: only one IO path left and IO error.\n");
 238                 /* leave it active... it's all we have */
 239         } else {
 240                 /*
 241                  * Mark disk as unusable
 242                  */
 243                 if (!test_bit(Faulty, &rdev->flags)) {
 244                         char b[BDEVNAME_SIZE];
 245                         clear_bit(In_sync, &rdev->flags);
 246                         set_bit(Faulty, &rdev->flags);
 247                         set_bit(MD_CHANGE_DEVS, &mddev->flags);
 248                         conf->working_disks--;
 249                         mddev->degraded++;
 250                         printk(KERN_ALERT "multipath: IO failure on %s,"
 251                                 " disabling IO path.\n"
 252                                 "multipath: Operation continuing"
 253                                 " on %d IO paths.\n",
 254                                 bdevname (rdev->bdev,b),
 255                                 conf->working_disks);
 256                 }
 257         }
 258 }
 259
 260 static void print_multipath_conf (multipath_conf_t *conf)
 261 {
 262         int i;
 263         struct multipath_info *tmp;
 264
 265         printk("MULTIPATH conf printout:\n");
 266         if (!conf) {
 267                 printk("(conf==NULL)\n");
 268                 return;
 269         }
 270         printk(" --- wd:%d rd:%d\n", conf->working_disks,
 271                          conf->raid_disks);
 272
 273         for (i = 0; i < conf->raid_disks; i++) {
 274                 char b[BDEVNAME_SIZE];
 275                 tmp = conf->multipaths + i;
 276                 if (tmp->rdev)
 277                         printk(" disk%d, o:%d, dev:%s\n",
 278                                 i,!test_bit(Faulty, &tmp->rdev->flags),
 279                                bdevname(tmp->rdev->bdev,b));
 280         }
 281 }
 282
 283
 284 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
 285 {
 286         multipath_conf_t *conf = mddev->private;
 287         struct request_queue *q;
 288         int err = -EEXIST;
 289         int path;
 290         struct multipath_info *p;
 291         int first = 0;
 292         int last = mddev->raid_disks - 1;
 293
 294         if (rdev->raid_disk >= 0)
 295                 first = last = rdev->raid_disk;
 296
 297         print_multipath_conf(conf);
 298
 299         for (path = first; path <= last; path++)
 300                 if ((p=conf->multipaths+path)->rdev == NULL) {
 301                         q = rdev->bdev->bd_disk->queue;
 302                         blk_queue_stack_limits(mddev->queue, q);
 303
 304                 /* as we don't honour merge_bvec_fn, we must never risk
 305                  * violating it, so limit ->max_sector to one PAGE, as
 306                  * a one page request is never in violation.
 307                  * (Note: it is very unlikely that a device with
 308                  * merge_bvec_fn will be involved in multipath.)
 309                  */
 310                         if (q->merge_bvec_fn &&
 311                             mddev->queue->max_sectors > (PAGE_SIZE>>9))
 312                                 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 313
 314                         conf->working_disks++;
 315                         mddev->degraded--;
 316                         rdev->raid_disk = path;
 317                         set_bit(In_sync, &rdev->flags);
 318                         rcu_assign_pointer(p->rdev, rdev);
 319                         err = 0;
 320                         break;
 321                 }
 322
 323         print_multipath_conf(conf);
 324
 325         return err;
 326 }
 327
 328 static int multipath_remove_disk(mddev_t *mddev, int number)
 329 {
 330         multipath_conf_t *conf = mddev->private;
 331         int err = 0;
 332         mdk_rdev_t *rdev;
 333         struct multipath_info *p = conf->multipaths + number;
 334
 335         print_multipath_conf(conf);
 336
 337         rdev = p->rdev;
 338         if (rdev) {
 339                 if (test_bit(In_sync, &rdev->flags) ||
 340                     atomic_read(&rdev->nr_pending)) {
 341                         printk(KERN_ERR "hot-remove-disk, slot %d is identified"
 342                                " but is still operational!\n", number);
 343                         err = -EBUSY;
 344                         goto abort;
 345                 }
 346                 p->rdev = NULL;
 347                 synchronize_rcu();
 348                 if (atomic_read(&rdev->nr_pending)) {
 349                         /* lost the race, try later */
 350                         err = -EBUSY;
 351                         p->rdev = rdev;
 352                 }
 353         }
 354 abort:
 355
 356         print_multipath_conf(conf);
 357         return err;
 358 }
 359
 360
 361
 362 /*
 363  * This is a kernel thread which:
 364  *
 365  *      1.      Retries failed read operations on working multipaths.
 366  *      2.      Updates the raid superblock when problems encounter.
 367  *      3.      Performs writes following reads for array syncronising.
 368  */
 369
 370 static void multipathd (mddev_t *mddev)
 371 {
 372         struct multipath_bh *mp_bh;
 373         struct bio *bio;
 374         unsigned long flags;
 375         multipath_conf_t *conf = mddev_to_conf(mddev);
 376         struct list_head *head = &conf->retry_list;
 377
 378         md_check_recovery(mddev);
 379         for (;;) {
 380                 char b[BDEVNAME_SIZE];
 381                 spin_lock_irqsave(&conf->device_lock, flags);
 382                 if (list_empty(head))
 383                         break;
 384                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
 385                 list_del(head->prev);
 386                 spin_unlock_irqrestore(&conf->device_lock, flags);
 387
 388                 bio = &mp_bh->bio;
 389                 bio->bi_sector = mp_bh->master_bio->bi_sector;
 390
 391                 if ((mp_bh->path = multipath_map (conf))<0) {
 392                         printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
 393                                 " error for block %llu\n",
 394                                 bdevname(bio->bi_bdev,b),
 395                                 (unsigned long long)bio->bi_sector);
 396                         multipath_end_bh_io(mp_bh, -EIO);
 397                 } else {
 398                         printk(KERN_ERR "multipath: %s: redirecting sector %llu"
 399                                 " to another IO path\n",
 400                                 bdevname(bio->bi_bdev,b),
 401                                 (unsigned long long)bio->bi_sector);
 402                         *bio = *(mp_bh->master_bio);
 403                         bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
 404                         bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
 405                         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
 406                         bio->bi_end_io = multipath_end_request;
 407                         bio->bi_private = mp_bh;
 408                         generic_make_request(bio);
 409                 }
 410         }
 411         spin_unlock_irqrestore(&conf->device_lock, flags);
 412 }
 413
 414 static int multipath_run (mddev_t *mddev)
 415 {
 416         multipath_conf_t *conf;
 417         int disk_idx;
 418         struct multipath_info *disk;
 419         mdk_rdev_t *rdev;
 420         struct list_head *tmp;
 421
 422         if (mddev->level != LEVEL_MULTIPATH) {
 423                 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
 424                        mdname(mddev), mddev->level);
 425                 goto out;
 426         }
 427         /*
 428          * copy the already verified devices into our private MULTIPATH
 429          * bookkeeping area. [whatever we allocate in multipath_run(),
 430          * should be freed in multipath_stop()]
 431          */
 432         mddev->queue->queue_lock = &mddev->queue->__queue_lock;
 433
 434         conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
 435         mddev->private = conf;
 436         if (!conf) {
 437                 printk(KERN_ERR
 438                         "multipath: couldn't allocate memory for %s\n",
 439                         mdname(mddev));
 440                 goto out;
 441         }
 442
 443         conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
 444                                    GFP_KERNEL);
 445         if (!conf->multipaths) {
 446                 printk(KERN_ERR
 447                         "multipath: couldn't allocate memory for %s\n",
 448                         mdname(mddev));
 449                 goto out_free_conf;
 450         }
 451
 452         conf->working_disks = 0;
 453         rdev_for_each(rdev, tmp, mddev) {
 454                 disk_idx = rdev->raid_disk;
 455                 if (disk_idx < 0 ||
 456                     disk_idx >= mddev->raid_disks)
 457                         continue;
 458
 459                 disk = conf->multipaths + disk_idx;
 460                 disk->rdev = rdev;
 461
 462                 blk_queue_stack_limits(mddev->queue,
 463                                        rdev->bdev->bd_disk->queue);
 464                 /* as we don't honour merge_bvec_fn, we must never risk
 465                  * violating it, not that we ever expect a device with
 466                  * a merge_bvec_fn to be involved in multipath */
 467                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
 468                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
 469                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 470
 471                 if (!test_bit(Faulty, &rdev->flags))
 472                         conf->working_disks++;
 473         }
 474
 475         conf->raid_disks = mddev->raid_disks;
 476         conf->mddev = mddev;
 477         spin_lock_init(&conf->device_lock);
 478         INIT_LIST_HEAD(&conf->retry_list);
 479
 480         if (!conf->working_disks) {
 481                 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
 482                         mdname(mddev));
 483                 goto out_free_conf;
 484         }
 485         mddev->degraded = conf->raid_disks - conf->working_disks;
 486
 487         conf->pool = mempool_create_kzalloc_pool(NR_RESERVED_BUFS,
 488                                                  sizeof(struct multipath_bh));
 489         if (conf->pool == NULL) {
 490                 printk(KERN_ERR
 491                         "multipath: couldn't allocate memory for %s\n",
 492                         mdname(mddev));
 493                 goto out_free_conf;
 494         }
 495
 496         {
 497                 mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
 498                 if (!mddev->thread) {
 499                         printk(KERN_ERR "multipath: couldn't allocate thread"
 500                                 " for %s\n", mdname(mddev));
 501                         goto out_free_conf;
 502                 }
 503         }
 504
 505         printk(KERN_INFO
 506                 "multipath: array %s active with %d out of %d IO paths\n",
 507                 mdname(mddev), conf->working_disks, mddev->raid_disks);
 508         /*
 509          * Ok, everything is just fine now
 510          */
 511         mddev->array_sectors = mddev->size * 2;
 512
 513         mddev->queue->unplug_fn = multipath_unplug;
 514         mddev->queue->backing_dev_info.congested_fn = multipath_congested;
 515         mddev->queue->backing_dev_info.congested_data = mddev;
 516
 517         return 0;
 518
 519 out_free_conf:
 520         if (conf->pool)
 521                 mempool_destroy(conf->pool);
 522         kfree(conf->multipaths);
 523         kfree(conf);
 524         mddev->private = NULL;
 525 out:
 526         return -EIO;
 527 }
 528
 529
 530 static int multipath_stop (mddev_t *mddev)
 531 {
 532         multipath_conf_t *conf = mddev_to_conf(mddev);
 533
 534         md_unregister_thread(mddev->thread);
 535         mddev->thread = NULL;
 536         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 537         mempool_destroy(conf->pool);
 538         kfree(conf->multipaths);
 539         kfree(conf);
 540         mddev->private = NULL;
 541         return 0;
 542 }
 543
 544 static struct mdk_personality multipath_personality =
 545 {
 546         .name           = "multipath",
 547         .level          = LEVEL_MULTIPATH,
 548         .owner          = THIS_MODULE,
 549         .make_request   = multipath_make_request,
 550         .run            = multipath_run,
 551         .stop           = multipath_stop,
 552         .status         = multipath_status,
 553         .error_handler  = multipath_error,
 554         .hot_add_disk   = multipath_add_disk,
 555         .hot_remove_disk= multipath_remove_disk,
 556 };
 557
 558 static int __init multipath_init (void)
 559 {
 560         return register_md_personality (&multipath_personality);
 561 }
 562
 563 static void __exit multipath_exit (void)
 564 {
 565         unregister_md_personality (&multipath_personality);
 566 }
 567
 568 module_init(multipath_init);
 569 module_exit(multipath_exit);
 570 MODULE_LICENSE("GPL");
 571 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
 572 MODULE_ALIAS("md-multipath");
 573 MODULE_ALIAS("md-level--4");