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