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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/blkdev.h>
  23 #include <linux/raid/md_u.h>
  24 #include <linux/seq_file.h>
  25 #include "md.h"
  26 #include "multipath.h"
  27
  28 #define MAX_WORK_PER_DISK 128
  29
  30 #define NR_RESERVED_BUFS        32
  31
  32
  33 static int multipath_map (multipath_conf_t *conf)
  34 {
  35         int i, disks = conf->raid_disks;
  36
  37         /*
  38          * Later we do read balancing on the read side
  39          * now we use the first available disk.
  40          */
  41
  42         rcu_read_lock();
  43         for (i = 0; i < disks; i++) {
  44                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
  45                 if (rdev && test_bit(In_sync, &rdev->flags)) {
  46                         atomic_inc(&rdev->nr_pending);
  47                         rcu_read_unlock();
  48                         return i;
  49                 }
  50         }
  51         rcu_read_unlock();
  52
  53         printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
  54         return (-1);
  55 }
  56
  57 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
  58 {
  59         unsigned long flags;
  60         mddev_t *mddev = mp_bh->mddev;
  61         multipath_conf_t *conf = mddev->private;
  62
  63         spin_lock_irqsave(&conf->device_lock, flags);
  64         list_add(&mp_bh->retry_list, &conf->retry_list);
  65         spin_unlock_irqrestore(&conf->device_lock, flags);
  66         md_wakeup_thread(mddev->thread);
  67 }
  68
  69
  70 /*
  71  * multipath_end_bh_io() is called when we have finished servicing a multipathed
  72  * operation and are ready to return a success/failure code to the buffer
  73  * cache layer.
  74  */
  75 static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
  76 {
  77         struct bio *bio = mp_bh->master_bio;
  78         multipath_conf_t *conf = mp_bh->mddev->private;
  79
  80         bio_endio(bio, err);
  81         mempool_free(mp_bh, conf->pool);
  82 }
  83
  84 static void multipath_end_request(struct bio *bio, int error)
  85 {
  86         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  87         struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
  88         multipath_conf_t *conf = mp_bh->mddev->private;
  89         mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
  90
  91         if (uptodate)
  92                 multipath_end_bh_io(mp_bh, 0);
  93         else if (!bio_rw_flagged(bio, BIO_RW_AHEAD)) {
  94                 /*
  95                  * oops, IO error:
  96                  */
  97                 char b[BDEVNAME_SIZE];
  98                 md_error (mp_bh->mddev, rdev);
  99                 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
 100                        bdevname(rdev->bdev,b),
 101                        (unsigned long long)bio->bi_sector);
 102                 multipath_reschedule_retry(mp_bh);
 103         } else
 104                 multipath_end_bh_io(mp_bh, error);
 105         rdev_dec_pending(rdev, conf->mddev);
 106 }
 107
 108 static void unplug_slaves(mddev_t *mddev)
 109 {
 110         multipath_conf_t *conf = mddev->private;
 111         int i;
 112
 113         rcu_read_lock();
 114         for (i=0; i<mddev->raid_disks; i++) {
 115                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
 116                 if (rdev && !test_bit(Faulty, &rdev->flags)
 117                     && atomic_read(&rdev->nr_pending)) {
 118                         struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
 119
 120                         atomic_inc(&rdev->nr_pending);
 121                         rcu_read_unlock();
 122
 123                         blk_unplug(r_queue);
 124
 125                         rdev_dec_pending(rdev, mddev);
 126                         rcu_read_lock();
 127                 }
 128         }
 129         rcu_read_unlock();
 130 }
 131
 132 static void multipath_unplug(struct request_queue *q)
 133 {
 134         unplug_slaves(q->queuedata);
 135 }
 136
 137
 138 static int multipath_make_request (struct request_queue *q, struct bio * bio)
 139 {
 140         mddev_t *mddev = q->queuedata;
 141         multipath_conf_t *conf = mddev->private;
 142         struct multipath_bh * mp_bh;
 143         struct multipath_info *multipath;
 144         const int rw = bio_data_dir(bio);
 145         int cpu;
 146
 147         if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER))) {
 148                 bio_endio(bio, -EOPNOTSUPP);
 149                 return 0;
 150         }
 151
 152         mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
 153         memset(mp_bh, 0, sizeof(*mp_bh));
 154
 155         mp_bh->master_bio = bio;
 156         mp_bh->mddev = mddev;
 157
 158         cpu = part_stat_lock();
 159         part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
 160         part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw],
 161                       bio_sectors(bio));
 162         part_stat_unlock();
 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_TRANSPORT);
 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->private;
 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->private;
 200         int i, ret = 0;
 201
 202         if (mddev_congested(mddev, bits))
 203                 return 1;
 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->private;
 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                         disk_stack_limits(mddev->gendisk, rdev->bdev,
 302                                           rdev->data_offset << 9);
 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                             queue_max_sectors(q) > (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                         md_integrity_add_rdev(rdev, mddev);
 321                         break;
 322                 }
 323
 324         print_multipath_conf(conf);
 325
 326         return err;
 327 }
 328
 329 static int multipath_remove_disk(mddev_t *mddev, int number)
 330 {
 331         multipath_conf_t *conf = mddev->private;
 332         int err = 0;
 333         mdk_rdev_t *rdev;
 334         struct multipath_info *p = conf->multipaths + number;
 335
 336         print_multipath_conf(conf);
 337
 338         rdev = p->rdev;
 339         if (rdev) {
 340                 if (test_bit(In_sync, &rdev->flags) ||
 341                     atomic_read(&rdev->nr_pending)) {
 342                         printk(KERN_ERR "hot-remove-disk, slot %d is identified"
 343                                " but is still operational!\n", number);
 344                         err = -EBUSY;
 345                         goto abort;
 346                 }
 347                 p->rdev = NULL;
 348                 synchronize_rcu();
 349                 if (atomic_read(&rdev->nr_pending)) {
 350                         /* lost the race, try later */
 351                         err = -EBUSY;
 352                         p->rdev = rdev;
 353                         goto abort;
 354                 }
 355                 md_integrity_register(mddev);
 356         }
 357 abort:
 358
 359         print_multipath_conf(conf);
 360         return err;
 361 }
 362
 363
 364
 365 /*
 366  * This is a kernel thread which:
 367  *
 368  *      1.      Retries failed read operations on working multipaths.
 369  *      2.      Updates the raid superblock when problems encounter.
 370  *      3.      Performs writes following reads for array syncronising.
 371  */
 372
 373 static void multipathd (mddev_t *mddev)
 374 {
 375         struct multipath_bh *mp_bh;
 376         struct bio *bio;
 377         unsigned long flags;
 378         multipath_conf_t *conf = mddev->private;
 379         struct list_head *head = &conf->retry_list;
 380
 381         md_check_recovery(mddev);
 382         for (;;) {
 383                 char b[BDEVNAME_SIZE];
 384                 spin_lock_irqsave(&conf->device_lock, flags);
 385                 if (list_empty(head))
 386                         break;
 387                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
 388                 list_del(head->prev);
 389                 spin_unlock_irqrestore(&conf->device_lock, flags);
 390
 391                 bio = &mp_bh->bio;
 392                 bio->bi_sector = mp_bh->master_bio->bi_sector;
 393
 394                 if ((mp_bh->path = multipath_map (conf))<0) {
 395                         printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
 396                                 " error for block %llu\n",
 397                                 bdevname(bio->bi_bdev,b),
 398                                 (unsigned long long)bio->bi_sector);
 399                         multipath_end_bh_io(mp_bh, -EIO);
 400                 } else {
 401                         printk(KERN_ERR "multipath: %s: redirecting sector %llu"
 402                                 " to another IO path\n",
 403                                 bdevname(bio->bi_bdev,b),
 404                                 (unsigned long long)bio->bi_sector);
 405                         *bio = *(mp_bh->master_bio);
 406                         bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
 407                         bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
 408                         bio->bi_rw |= (1 << BIO_RW_FAILFAST_TRANSPORT);
 409                         bio->bi_end_io = multipath_end_request;
 410                         bio->bi_private = mp_bh;
 411                         generic_make_request(bio);
 412                 }
 413         }
 414         spin_unlock_irqrestore(&conf->device_lock, flags);
 415 }
 416
 417 static sector_t multipath_size(mddev_t *mddev, sector_t sectors, int raid_disks)
 418 {
 419         WARN_ONCE(sectors || raid_disks,
 420                   "%s does not support generic reshape\n", __func__);
 421
 422         return mddev->dev_sectors;
 423 }
 424
 425 static int multipath_run (mddev_t *mddev)
 426 {
 427         multipath_conf_t *conf;
 428         int disk_idx;
 429         struct multipath_info *disk;
 430         mdk_rdev_t *rdev;
 431
 432         if (md_check_no_bitmap(mddev))
 433                 return -EINVAL;
 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         mddev->queue->queue_lock = &mddev->queue->__queue_lock;
 446
 447         conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
 448         mddev->private = conf;
 449         if (!conf) {
 450                 printk(KERN_ERR
 451                         "multipath: couldn't allocate memory for %s\n",
 452                         mdname(mddev));
 453                 goto out;
 454         }
 455
 456         conf->multipaths = kzalloc(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
 465         conf->working_disks = 0;
 466         list_for_each_entry(rdev, &mddev->disks, same_set) {
 467                 disk_idx = rdev->raid_disk;
 468                 if (disk_idx < 0 ||
 469                     disk_idx >= mddev->raid_disks)
 470                         continue;
 471
 472                 disk = conf->multipaths + disk_idx;
 473                 disk->rdev = rdev;
 474                 disk_stack_limits(mddev->gendisk, rdev->bdev,
 475                                   rdev->data_offset << 9);
 476
 477                 /* as we don't honour merge_bvec_fn, we must never risk
 478                  * violating it, not that we ever expect a device with
 479                  * a merge_bvec_fn to be involved in multipath */
 480                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
 481                     queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
 482                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 483
 484                 if (!test_bit(Faulty, &rdev->flags))
 485                         conf->working_disks++;
 486         }
 487
 488         conf->raid_disks = mddev->raid_disks;
 489         conf->mddev = mddev;
 490         spin_lock_init(&conf->device_lock);
 491         INIT_LIST_HEAD(&conf->retry_list);
 492
 493         if (!conf->working_disks) {
 494                 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
 495                         mdname(mddev));
 496                 goto out_free_conf;
 497         }
 498         mddev->degraded = conf->raid_disks - conf->working_disks;
 499
 500         conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS,
 501                                                  sizeof(struct multipath_bh));
 502         if (conf->pool == NULL) {
 503                 printk(KERN_ERR
 504                         "multipath: couldn't allocate memory for %s\n",
 505                         mdname(mddev));
 506                 goto out_free_conf;
 507         }
 508
 509         {
 510                 mddev->thread = md_register_thread(multipathd, mddev, NULL);
 511                 if (!mddev->thread) {
 512                         printk(KERN_ERR "multipath: couldn't allocate thread"
 513                                 " for %s\n", mdname(mddev));
 514                         goto out_free_conf;
 515                 }
 516         }
 517
 518         printk(KERN_INFO
 519                 "multipath: array %s active with %d out of %d IO paths\n",
 520                 mdname(mddev), conf->working_disks, mddev->raid_disks);
 521         /*
 522          * Ok, everything is just fine now
 523          */
 524         md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
 525
 526         mddev->queue->unplug_fn = multipath_unplug;
 527         mddev->queue->backing_dev_info.congested_fn = multipath_congested;
 528         mddev->queue->backing_dev_info.congested_data = mddev;
 529         md_integrity_register(mddev);
 530         return 0;
 531
 532 out_free_conf:
 533         if (conf->pool)
 534                 mempool_destroy(conf->pool);
 535         kfree(conf->multipaths);
 536         kfree(conf);
 537         mddev->private = NULL;
 538 out:
 539         return -EIO;
 540 }
 541
 542
 543 static int multipath_stop (mddev_t *mddev)
 544 {
 545         multipath_conf_t *conf = mddev->private;
 546
 547         md_unregister_thread(mddev->thread);
 548         mddev->thread = NULL;
 549         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 550         mempool_destroy(conf->pool);
 551         kfree(conf->multipaths);
 552         kfree(conf);
 553         mddev->private = NULL;
 554         return 0;
 555 }
 556
 557 static struct mdk_personality multipath_personality =
 558 {
 559         .name           = "multipath",
 560         .level          = LEVEL_MULTIPATH,
 561         .owner          = THIS_MODULE,
 562         .make_request   = multipath_make_request,
 563         .run            = multipath_run,
 564         .stop           = multipath_stop,
 565         .status         = multipath_status,
 566         .error_handler  = multipath_error,
 567         .hot_add_disk   = multipath_add_disk,
 568         .hot_remove_disk= multipath_remove_disk,
 569         .size           = multipath_size,
 570 };
 571
 572 static int __init multipath_init (void)
 573 {
 574         return register_md_personality (&multipath_personality);
 575 }
 576
 577 static void __exit multipath_exit (void)
 578 {
 579         unregister_md_personality (&multipath_personality);
 580 }
 581
 582 module_init(multipath_init);
 583 module_exit(multipath_exit);
 584 MODULE_LICENSE("GPL");
 585 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
 586 MODULE_ALIAS("md-multipath");
 587 MODULE_ALIAS("md-level--4");