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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/raid/multipath.h>
  23
  24 #define MAX_WORK_PER_DISK 128
  25
  26 #define NR_RESERVED_BUFS        32
  27
  28
  29 static int multipath_map (multipath_conf_t *conf)
  30 {
  31         int i, disks = conf->raid_disks;
  32
  33         /*
  34          * Later we do read balancing on the read side
  35          * now we use the first available disk.
  36          */
  37
  38         rcu_read_lock();
  39         for (i = 0; i < disks; i++) {
  40                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
  41                 if (rdev && test_bit(In_sync, &rdev->flags)) {
  42                         atomic_inc(&rdev->nr_pending);
  43                         rcu_read_unlock();
  44                         return i;
  45                 }
  46         }
  47         rcu_read_unlock();
  48
  49         printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
  50         return (-1);
  51 }
  52
  53 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
  54 {
  55         unsigned long flags;
  56         mddev_t *mddev = mp_bh->mddev;
  57         multipath_conf_t *conf = mddev_to_conf(mddev);
  58
  59         spin_lock_irqsave(&conf->device_lock, flags);
  60         list_add(&mp_bh->retry_list, &conf->retry_list);
  61         spin_unlock_irqrestore(&conf->device_lock, flags);
  62         md_wakeup_thread(mddev->thread);
  63 }
  64
  65
  66 /*
  67  * multipath_end_bh_io() is called when we have finished servicing a multipathed
  68  * operation and are ready to return a success/failure code to the buffer
  69  * cache layer.
  70  */
  71 static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
  72 {
  73         struct bio *bio = mp_bh->master_bio;
  74         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
  75
  76         bio_endio(bio, err);
  77         mempool_free(mp_bh, conf->pool);
  78 }
  79
  80 static void multipath_end_request(struct bio *bio, int error)
  81 {
  82         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  83         struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
  84         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
  85         mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
  86
  87         if (uptodate)
  88                 multipath_end_bh_io(mp_bh, 0);
  89         else if (!bio_rw_ahead(bio)) {
  90                 /*
  91                  * oops, IO error:
  92                  */
  93                 char b[BDEVNAME_SIZE];
  94                 md_error (mp_bh->mddev, rdev);
  95                 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
  96                        bdevname(rdev->bdev,b),
  97                        (unsigned long long)bio->bi_sector);
  98                 multipath_reschedule_retry(mp_bh);
  99         } else
 100                 multipath_end_bh_io(mp_bh, error);
 101         rdev_dec_pending(rdev, conf->mddev);
 102 }
 103
 104 static void unplug_slaves(mddev_t *mddev)
 105 {
 106         multipath_conf_t *conf = mddev_to_conf(mddev);
 107         int i;
 108
 109         rcu_read_lock();
 110         for (i=0; i<mddev->raid_disks; i++) {
 111                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
 112                 if (rdev && !test_bit(Faulty, &rdev->flags)
 113                     && atomic_read(&rdev->nr_pending)) {
 114                         struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
 115
 116                         atomic_inc(&rdev->nr_pending);
 117                         rcu_read_unlock();
 118
 119                         blk_unplug(r_queue);
 120
 121                         rdev_dec_pending(rdev, mddev);
 122                         rcu_read_lock();
 123                 }
 124         }
 125         rcu_read_unlock();
 126 }
 127
 128 static void multipath_unplug(struct request_queue *q)
 129 {
 130         unplug_slaves(q->queuedata);
 131 }
 132
 133
 134 static int multipath_make_request (struct request_queue *q, struct bio * bio)
 135 {
 136         mddev_t *mddev = q->queuedata;
 137         multipath_conf_t *conf = mddev_to_conf(mddev);
 138         struct multipath_bh * mp_bh;
 139         struct multipath_info *multipath;
 140         const int rw = bio_data_dir(bio);
 141         int cpu;
 142
 143         if (unlikely(bio_barrier(bio))) {
 144                 bio_endio(bio, -EOPNOTSUPP);
 145                 return 0;
 146         }
 147
 148         mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
 149
 150         mp_bh->master_bio = bio;
 151         mp_bh->mddev = mddev;
 152
 153         cpu = part_stat_lock();
 154         part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
 155         part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw],
 156                       bio_sectors(bio));
 157         part_stat_unlock();
 158
 159         mp_bh->path = multipath_map(conf);
 160         if (mp_bh->path < 0) {
 161                 bio_endio(bio, -EIO);
 162                 mempool_free(mp_bh, conf->pool);
 163                 return 0;
 164         }
 165         multipath = conf->multipaths + mp_bh->path;
 166
 167         mp_bh->bio = *bio;
 168         mp_bh->bio.bi_sector += multipath->rdev->data_offset;
 169         mp_bh->bio.bi_bdev = multipath->rdev->bdev;
 170         mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST_TRANSPORT);
 171         mp_bh->bio.bi_end_io = multipath_end_request;
 172         mp_bh->bio.bi_private = mp_bh;
 173         generic_make_request(&mp_bh->bio);
 174         return 0;
 175 }
 176
 177 static void multipath_status (struct seq_file *seq, mddev_t *mddev)
 178 {
 179         multipath_conf_t *conf = mddev_to_conf(mddev);
 180         int i;
 181
 182         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
 183                                                  conf->working_disks);
 184         for (i = 0; i < conf->raid_disks; i++)
 185                 seq_printf (seq, "%s",
 186                                conf->multipaths[i].rdev &&
 187                                test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
 188         seq_printf (seq, "]");
 189 }
 190
 191 static int multipath_congested(void *data, int bits)
 192 {
 193         mddev_t *mddev = data;
 194         multipath_conf_t *conf = mddev_to_conf(mddev);
 195         int i, ret = 0;
 196
 197         rcu_read_lock();
 198         for (i = 0; i < mddev->raid_disks ; i++) {
 199                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
 200                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
 201                         struct request_queue *q = bdev_get_queue(rdev->bdev);
 202
 203                         ret |= bdi_congested(&q->backing_dev_info, bits);
 204                         /* Just like multipath_map, we just check the
 205                          * first available device
 206                          */
 207                         break;
 208                 }
 209         }
 210         rcu_read_unlock();
 211         return ret;
 212 }
 213
 214 /*
 215  * Careful, this can execute in IRQ contexts as well!
 216  */
 217 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
 218 {
 219         multipath_conf_t *conf = mddev_to_conf(mddev);
 220
 221         if (conf->working_disks <= 1) {
 222                 /*
 223                  * Uh oh, we can do nothing if this is our last path, but
 224                  * first check if this is a queued request for a device
 225                  * which has just failed.
 226                  */
 227                 printk(KERN_ALERT
 228                         "multipath: only one IO path left and IO error.\n");
 229                 /* leave it active... it's all we have */
 230         } else {
 231                 /*
 232                  * Mark disk as unusable
 233                  */
 234                 if (!test_bit(Faulty, &rdev->flags)) {
 235                         char b[BDEVNAME_SIZE];
 236                         clear_bit(In_sync, &rdev->flags);
 237                         set_bit(Faulty, &rdev->flags);
 238                         set_bit(MD_CHANGE_DEVS, &mddev->flags);
 239                         conf->working_disks--;
 240                         mddev->degraded++;
 241                         printk(KERN_ALERT "multipath: IO failure on %s,"
 242                                 " disabling IO path.\n"
 243                                 "multipath: Operation continuing"
 244                                 " on %d IO paths.\n",
 245                                 bdevname (rdev->bdev,b),
 246                                 conf->working_disks);
 247                 }
 248         }
 249 }
 250
 251 static void print_multipath_conf (multipath_conf_t *conf)
 252 {
 253         int i;
 254         struct multipath_info *tmp;
 255
 256         printk("MULTIPATH conf printout:\n");
 257         if (!conf) {
 258                 printk("(conf==NULL)\n");
 259                 return;
 260         }
 261         printk(" --- wd:%d rd:%d\n", conf->working_disks,
 262                          conf->raid_disks);
 263
 264         for (i = 0; i < conf->raid_disks; i++) {
 265                 char b[BDEVNAME_SIZE];
 266                 tmp = conf->multipaths + i;
 267                 if (tmp->rdev)
 268                         printk(" disk%d, o:%d, dev:%s\n",
 269                                 i,!test_bit(Faulty, &tmp->rdev->flags),
 270                                bdevname(tmp->rdev->bdev,b));
 271         }
 272 }
 273
 274
 275 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
 276 {
 277         multipath_conf_t *conf = mddev->private;
 278         struct request_queue *q;
 279         int err = -EEXIST;
 280         int path;
 281         struct multipath_info *p;
 282         int first = 0;
 283         int last = mddev->raid_disks - 1;
 284
 285         if (rdev->raid_disk >= 0)
 286                 first = last = rdev->raid_disk;
 287
 288         print_multipath_conf(conf);
 289
 290         for (path = first; path <= last; path++)
 291                 if ((p=conf->multipaths+path)->rdev == NULL) {
 292                         q = rdev->bdev->bd_disk->queue;
 293                         blk_queue_stack_limits(mddev->queue, q);
 294
 295                 /* as we don't honour merge_bvec_fn, we must never risk
 296                  * violating it, so limit ->max_sector to one PAGE, as
 297                  * a one page request is never in violation.
 298                  * (Note: it is very unlikely that a device with
 299                  * merge_bvec_fn will be involved in multipath.)
 300                  */
 301                         if (q->merge_bvec_fn &&
 302                             mddev->queue->max_sectors > (PAGE_SIZE>>9))
 303                                 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 304
 305                         conf->working_disks++;
 306                         mddev->degraded--;
 307                         rdev->raid_disk = path;
 308                         set_bit(In_sync, &rdev->flags);
 309                         rcu_assign_pointer(p->rdev, rdev);
 310                         err = 0;
 311                         break;
 312                 }
 313
 314         print_multipath_conf(conf);
 315
 316         return err;
 317 }
 318
 319 static int multipath_remove_disk(mddev_t *mddev, int number)
 320 {
 321         multipath_conf_t *conf = mddev->private;
 322         int err = 0;
 323         mdk_rdev_t *rdev;
 324         struct multipath_info *p = conf->multipaths + number;
 325
 326         print_multipath_conf(conf);
 327
 328         rdev = p->rdev;
 329         if (rdev) {
 330                 if (test_bit(In_sync, &rdev->flags) ||
 331                     atomic_read(&rdev->nr_pending)) {
 332                         printk(KERN_ERR "hot-remove-disk, slot %d is identified"
 333                                " but is still operational!\n", number);
 334                         err = -EBUSY;
 335                         goto abort;
 336                 }
 337                 p->rdev = NULL;
 338                 synchronize_rcu();
 339                 if (atomic_read(&rdev->nr_pending)) {
 340                         /* lost the race, try later */
 341                         err = -EBUSY;
 342                         p->rdev = rdev;
 343                 }
 344         }
 345 abort:
 346
 347         print_multipath_conf(conf);
 348         return err;
 349 }
 350
 351
 352
 353 /*
 354  * This is a kernel thread which:
 355  *
 356  *      1.      Retries failed read operations on working multipaths.
 357  *      2.      Updates the raid superblock when problems encounter.
 358  *      3.      Performs writes following reads for array syncronising.
 359  */
 360
 361 static void multipathd (mddev_t *mddev)
 362 {
 363         struct multipath_bh *mp_bh;
 364         struct bio *bio;
 365         unsigned long flags;
 366         multipath_conf_t *conf = mddev_to_conf(mddev);
 367         struct list_head *head = &conf->retry_list;
 368
 369         md_check_recovery(mddev);
 370         for (;;) {
 371                 char b[BDEVNAME_SIZE];
 372                 spin_lock_irqsave(&conf->device_lock, flags);
 373                 if (list_empty(head))
 374                         break;
 375                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
 376                 list_del(head->prev);
 377                 spin_unlock_irqrestore(&conf->device_lock, flags);
 378
 379                 bio = &mp_bh->bio;
 380                 bio->bi_sector = mp_bh->master_bio->bi_sector;
 381
 382                 if ((mp_bh->path = multipath_map (conf))<0) {
 383                         printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
 384                                 " error for block %llu\n",
 385                                 bdevname(bio->bi_bdev,b),
 386                                 (unsigned long long)bio->bi_sector);
 387                         multipath_end_bh_io(mp_bh, -EIO);
 388                 } else {
 389                         printk(KERN_ERR "multipath: %s: redirecting sector %llu"
 390                                 " to another IO path\n",
 391                                 bdevname(bio->bi_bdev,b),
 392                                 (unsigned long long)bio->bi_sector);
 393                         *bio = *(mp_bh->master_bio);
 394                         bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
 395                         bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
 396                         bio->bi_rw |= (1 << BIO_RW_FAILFAST_TRANSPORT);
 397                         bio->bi_end_io = multipath_end_request;
 398                         bio->bi_private = mp_bh;
 399                         generic_make_request(bio);
 400                 }
 401         }
 402         spin_unlock_irqrestore(&conf->device_lock, flags);
 403 }
 404
 405 static int multipath_run (mddev_t *mddev)
 406 {
 407         multipath_conf_t *conf;
 408         int disk_idx;
 409         struct multipath_info *disk;
 410         mdk_rdev_t *rdev;
 411         struct list_head *tmp;
 412
 413         if (mddev->level != LEVEL_MULTIPATH) {
 414                 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
 415                        mdname(mddev), mddev->level);
 416                 goto out;
 417         }
 418         /*
 419          * copy the already verified devices into our private MULTIPATH
 420          * bookkeeping area. [whatever we allocate in multipath_run(),
 421          * should be freed in multipath_stop()]
 422          */
 423         mddev->queue->queue_lock = &mddev->queue->__queue_lock;
 424
 425         conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
 426         mddev->private = conf;
 427         if (!conf) {
 428                 printk(KERN_ERR
 429                         "multipath: couldn't allocate memory for %s\n",
 430                         mdname(mddev));
 431                 goto out;
 432         }
 433
 434         conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
 435                                    GFP_KERNEL);
 436         if (!conf->multipaths) {
 437                 printk(KERN_ERR
 438                         "multipath: couldn't allocate memory for %s\n",
 439                         mdname(mddev));
 440                 goto out_free_conf;
 441         }
 442
 443         conf->working_disks = 0;
 444         rdev_for_each(rdev, tmp, mddev) {
 445                 disk_idx = rdev->raid_disk;
 446                 if (disk_idx < 0 ||
 447                     disk_idx >= mddev->raid_disks)
 448                         continue;
 449
 450                 disk = conf->multipaths + disk_idx;
 451                 disk->rdev = rdev;
 452
 453                 blk_queue_stack_limits(mddev->queue,
 454                                        rdev->bdev->bd_disk->queue);
 455                 /* as we don't honour merge_bvec_fn, we must never risk
 456                  * violating it, not that we ever expect a device with
 457                  * a merge_bvec_fn to be involved in multipath */
 458                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
 459                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
 460                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 461
 462                 if (!test_bit(Faulty, &rdev->flags))
 463                         conf->working_disks++;
 464         }
 465
 466         conf->raid_disks = mddev->raid_disks;
 467         conf->mddev = mddev;
 468         spin_lock_init(&conf->device_lock);
 469         INIT_LIST_HEAD(&conf->retry_list);
 470
 471         if (!conf->working_disks) {
 472                 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
 473                         mdname(mddev));
 474                 goto out_free_conf;
 475         }
 476         mddev->degraded = conf->raid_disks - conf->working_disks;
 477
 478         conf->pool = mempool_create_kzalloc_pool(NR_RESERVED_BUFS,
 479                                                  sizeof(struct multipath_bh));
 480         if (conf->pool == NULL) {
 481                 printk(KERN_ERR
 482                         "multipath: couldn't allocate memory for %s\n",
 483                         mdname(mddev));
 484                 goto out_free_conf;
 485         }
 486
 487         {
 488                 mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
 489                 if (!mddev->thread) {
 490                         printk(KERN_ERR "multipath: couldn't allocate thread"
 491                                 " for %s\n", mdname(mddev));
 492                         goto out_free_conf;
 493                 }
 494         }
 495
 496         printk(KERN_INFO
 497                 "multipath: array %s active with %d out of %d IO paths\n",
 498                 mdname(mddev), conf->working_disks, mddev->raid_disks);
 499         /*
 500          * Ok, everything is just fine now
 501          */
 502         mddev->array_sectors = mddev->size * 2;
 503
 504         mddev->queue->unplug_fn = multipath_unplug;
 505         mddev->queue->backing_dev_info.congested_fn = multipath_congested;
 506         mddev->queue->backing_dev_info.congested_data = mddev;
 507
 508         return 0;
 509
 510 out_free_conf:
 511         if (conf->pool)
 512                 mempool_destroy(conf->pool);
 513         kfree(conf->multipaths);
 514         kfree(conf);
 515         mddev->private = NULL;
 516 out:
 517         return -EIO;
 518 }
 519
 520
 521 static int multipath_stop (mddev_t *mddev)
 522 {
 523         multipath_conf_t *conf = mddev_to_conf(mddev);
 524
 525         md_unregister_thread(mddev->thread);
 526         mddev->thread = NULL;
 527         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 528         mempool_destroy(conf->pool);
 529         kfree(conf->multipaths);
 530         kfree(conf);
 531         mddev->private = NULL;
 532         return 0;
 533 }
 534
 535 static struct mdk_personality multipath_personality =
 536 {
 537         .name           = "multipath",
 538         .level          = LEVEL_MULTIPATH,
 539         .owner          = THIS_MODULE,
 540         .make_request   = multipath_make_request,
 541         .run            = multipath_run,
 542         .stop           = multipath_stop,
 543         .status         = multipath_status,
 544         .error_handler  = multipath_error,
 545         .hot_add_disk   = multipath_add_disk,
 546         .hot_remove_disk= multipath_remove_disk,
 547 };
 548
 549 static int __init multipath_init (void)
 550 {
 551         return register_md_personality (&multipath_personality);
 552 }
 553
 554 static void __exit multipath_exit (void)
 555 {
 556         unregister_md_personality (&multipath_personality);
 557 }
 558
 559 module_init(multipath_init);
 560 module_exit(multipath_exit);
 561 MODULE_LICENSE("GPL");
 562 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
 563 MODULE_ALIAS("md-multipath");
 564 MODULE_ALIAS("md-level--4");