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