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                     !test_bit(Faulty, &rdev->flags)) {
  48                         atomic_inc(&rdev->nr_pending);
  49                         rcu_read_unlock();
  50                         return i;
  51                 }
  52         }
  53         rcu_read_unlock();
  54
  55         pr_crit_ratelimited("multipath_map(): no more operational IO paths?\n");
  56         return (-1);
  57 }
  58
  59 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
  60 {
  61         unsigned long flags;
  62         struct mddev *mddev = mp_bh->mddev;
  63         struct mpconf *conf = mddev->private;
  64
  65         spin_lock_irqsave(&conf->device_lock, flags);
  66         list_add(&mp_bh->retry_list, &conf->retry_list);
  67         spin_unlock_irqrestore(&conf->device_lock, flags);
  68         md_wakeup_thread(mddev->thread);
  69 }
  70
  71 /*
  72  * multipath_end_bh_io() is called when we have finished servicing a multipathed
  73  * operation and are ready to return a success/failure code to the buffer
  74  * cache layer.
  75  */
  76 static void multipath_end_bh_io(struct multipath_bh *mp_bh, blk_status_t status)
  77 {
  78         struct bio *bio = mp_bh->master_bio;
  79         struct mpconf *conf = mp_bh->mddev->private;
  80
  81         bio->bi_status = status;
  82         bio_endio(bio);
  83         mempool_free(mp_bh, conf->pool);
  84 }
  85
  86 static void multipath_end_request(struct bio *bio)
  87 {
  88         struct multipath_bh *mp_bh = bio->bi_private;
  89         struct mpconf *conf = mp_bh->mddev->private;
  90         struct md_rdev *rdev = conf->multipaths[mp_bh->path].rdev;
  91
  92         if (!bio->bi_status)
  93                 multipath_end_bh_io(mp_bh, 0);
  94         else if (!(bio->bi_opf & REQ_RAHEAD)) {
  95                 /*
  96                  * oops, IO error:
  97                  */
  98                 char b[BDEVNAME_SIZE];
  99                 md_error (mp_bh->mddev, rdev);
 100                 pr_info("multipath: %s: rescheduling sector %llu\n",
 101                         bdevname(rdev->bdev,b),
 102                         (unsigned long long)bio->bi_iter.bi_sector);
 103                 multipath_reschedule_retry(mp_bh);
 104         } else
 105                 multipath_end_bh_io(mp_bh, bio->bi_status);
 106         rdev_dec_pending(rdev, conf->mddev);
 107 }
 108
 109 static bool multipath_make_request(struct mddev *mddev, struct bio * bio)
 110 {
 111         struct mpconf *conf = mddev->private;
 112         struct multipath_bh * mp_bh;
 113         struct multipath_info *multipath;
 114
 115         if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
 116                 md_flush_request(mddev, bio);
 117                 return true;
 118         }
 119
 120         mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
 121
 122         mp_bh->master_bio = bio;
 123         mp_bh->mddev = mddev;
 124
 125         mp_bh->path = multipath_map(conf);
 126         if (mp_bh->path < 0) {
 127                 bio_io_error(bio);
 128                 mempool_free(mp_bh, conf->pool);
 129                 return true;
 130         }
 131         multipath = conf->multipaths + mp_bh->path;
 132
 133         bio_init(&mp_bh->bio, NULL, 0);
 134         __bio_clone_fast(&mp_bh->bio, bio);
 135
 136         mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset;
 137         bio_set_dev(&mp_bh->bio, multipath->rdev->bdev);
 138         mp_bh->bio.bi_opf |= REQ_FAILFAST_TRANSPORT;
 139         mp_bh->bio.bi_end_io = multipath_end_request;
 140         mp_bh->bio.bi_private = mp_bh;
 141         mddev_check_writesame(mddev, &mp_bh->bio);
 142         mddev_check_write_zeroes(mddev, &mp_bh->bio);
 143         generic_make_request(&mp_bh->bio);
 144         return true;
 145 }
 146
 147 static void multipath_status(struct seq_file *seq, struct mddev *mddev)
 148 {
 149         struct mpconf *conf = mddev->private;
 150         int i;
 151
 152         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
 153                     conf->raid_disks - mddev->degraded);
 154         rcu_read_lock();
 155         for (i = 0; i < conf->raid_disks; i++) {
 156                 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
 157                 seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
 158         }
 159         rcu_read_unlock();
 160         seq_printf (seq, "]");
 161 }
 162
 163 static int multipath_congested(struct mddev *mddev, int bits)
 164 {
 165         struct mpconf *conf = mddev->private;
 166         int i, ret = 0;
 167
 168         rcu_read_lock();
 169         for (i = 0; i < mddev->raid_disks ; i++) {
 170                 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
 171                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
 172                         struct request_queue *q = bdev_get_queue(rdev->bdev);
 173
 174                         ret |= bdi_congested(q->backing_dev_info, bits);
 175                         /* Just like multipath_map, we just check the
 176                          * first available device
 177                          */
 178                         break;
 179                 }
 180         }
 181         rcu_read_unlock();
 182         return ret;
 183 }
 184
 185 /*
 186  * Careful, this can execute in IRQ contexts as well!
 187  */
 188 static void multipath_error (struct mddev *mddev, struct md_rdev *rdev)
 189 {
 190         struct mpconf *conf = mddev->private;
 191         char b[BDEVNAME_SIZE];
 192
 193         if (conf->raid_disks - mddev->degraded <= 1) {
 194                 /*
 195                  * Uh oh, we can do nothing if this is our last path, but
 196                  * first check if this is a queued request for a device
 197                  * which has just failed.
 198                  */
 199                 pr_warn("multipath: only one IO path left and IO error.\n");
 200                 /* leave it active... it's all we have */
 201                 return;
 202         }
 203         /*
 204          * Mark disk as unusable
 205          */
 206         if (test_and_clear_bit(In_sync, &rdev->flags)) {
 207                 unsigned long flags;
 208                 spin_lock_irqsave(&conf->device_lock, flags);
 209                 mddev->degraded++;
 210                 spin_unlock_irqrestore(&conf->device_lock, flags);
 211         }
 212         set_bit(Faulty, &rdev->flags);
 213         set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
 214         pr_err("multipath: IO failure on %s, disabling IO path.\n"
 215                "multipath: Operation continuing 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         pr_debug("MULTIPATH conf printout:\n");
 226         if (!conf) {
 227                 pr_debug("(conf==NULL)\n");
 228                 return;
 229         }
 230         pr_debug(" --- 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                         pr_debug(" 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                         err = md_integrity_add_rdev(rdev, mddev);
 265                         if (err)
 266                                 break;
 267                         spin_lock_irq(&conf->device_lock);
 268                         mddev->degraded--;
 269                         rdev->raid_disk = path;
 270                         set_bit(In_sync, &rdev->flags);
 271                         spin_unlock_irq(&conf->device_lock);
 272                         rcu_assign_pointer(p->rdev, rdev);
 273                         err = 0;
 274                         break;
 275                 }
 276
 277         print_multipath_conf(conf);
 278
 279         return err;
 280 }
 281
 282 static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
 283 {
 284         struct mpconf *conf = mddev->private;
 285         int err = 0;
 286         int number = rdev->raid_disk;
 287         struct multipath_info *p = conf->multipaths + number;
 288
 289         print_multipath_conf(conf);
 290
 291         if (rdev == p->rdev) {
 292                 if (test_bit(In_sync, &rdev->flags) ||
 293                     atomic_read(&rdev->nr_pending)) {
 294                         pr_warn("hot-remove-disk, slot %d is identified but is still operational!\n", number);
 295                         err = -EBUSY;
 296                         goto abort;
 297                 }
 298                 p->rdev = NULL;
 299                 if (!test_bit(RemoveSynchronized, &rdev->flags)) {
 300                         synchronize_rcu();
 301                         if (atomic_read(&rdev->nr_pending)) {
 302                                 /* lost the race, try later */
 303                                 err = -EBUSY;
 304                                 p->rdev = rdev;
 305                                 goto abort;
 306                         }
 307                 }
 308                 err = md_integrity_register(mddev);
 309         }
 310 abort:
 311
 312         print_multipath_conf(conf);
 313         return err;
 314 }
 315
 316 /*
 317  * This is a kernel thread which:
 318  *
 319  *      1.      Retries failed read operations on working multipaths.
 320  *      2.      Updates the raid superblock when problems encounter.
 321  *      3.      Performs writes following reads for array syncronising.
 322  */
 323
 324 static void multipathd(struct md_thread *thread)
 325 {
 326         struct mddev *mddev = thread->mddev;
 327         struct multipath_bh *mp_bh;
 328         struct bio *bio;
 329         unsigned long flags;
 330         struct mpconf *conf = mddev->private;
 331         struct list_head *head = &conf->retry_list;
 332
 333         md_check_recovery(mddev);
 334         for (;;) {
 335                 char b[BDEVNAME_SIZE];
 336                 spin_lock_irqsave(&conf->device_lock, flags);
 337                 if (list_empty(head))
 338                         break;
 339                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
 340                 list_del(head->prev);
 341                 spin_unlock_irqrestore(&conf->device_lock, flags);
 342
 343                 bio = &mp_bh->bio;
 344                 bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector;
 345
 346                 if ((mp_bh->path = multipath_map (conf))<0) {
 347                         pr_err("multipath: %s: unrecoverable IO read error for block %llu\n",
 348                                bio_devname(bio, b),
 349                                (unsigned long long)bio->bi_iter.bi_sector);
 350                         multipath_end_bh_io(mp_bh, BLK_STS_IOERR);
 351                 } else {
 352                         pr_err("multipath: %s: redirecting sector %llu to another IO path\n",
 353                                bio_devname(bio, b),
 354                                (unsigned long long)bio->bi_iter.bi_sector);
 355                         *bio = *(mp_bh->master_bio);
 356                         bio->bi_iter.bi_sector +=
 357                                 conf->multipaths[mp_bh->path].rdev->data_offset;
 358                         bio_set_dev(bio, conf->multipaths[mp_bh->path].rdev->bdev);
 359                         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 360                         bio->bi_end_io = multipath_end_request;
 361                         bio->bi_private = mp_bh;
 362                         generic_make_request(bio);
 363                 }
 364         }
 365         spin_unlock_irqrestore(&conf->device_lock, flags);
 366 }
 367
 368 static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks)
 369 {
 370         WARN_ONCE(sectors || raid_disks,
 371                   "%s does not support generic reshape\n", __func__);
 372
 373         return mddev->dev_sectors;
 374 }
 375
 376 static int multipath_run (struct mddev *mddev)
 377 {
 378         struct mpconf *conf;
 379         int disk_idx;
 380         struct multipath_info *disk;
 381         struct md_rdev *rdev;
 382         int working_disks;
 383
 384         if (md_check_no_bitmap(mddev))
 385                 return -EINVAL;
 386
 387         if (mddev->level != LEVEL_MULTIPATH) {
 388                 pr_warn("multipath: %s: raid level not set to multipath IO (%d)\n",
 389                         mdname(mddev), mddev->level);
 390                 goto out;
 391         }
 392         /*
 393          * copy the already verified devices into our private MULTIPATH
 394          * bookkeeping area. [whatever we allocate in multipath_run(),
 395          * should be freed in multipath_free()]
 396          */
 397
 398         conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL);
 399         mddev->private = conf;
 400         if (!conf)
 401                 goto out;
 402
 403         conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
 404                                    GFP_KERNEL);
 405         if (!conf->multipaths)
 406                 goto out_free_conf;
 407
 408         working_disks = 0;
 409         rdev_for_each(rdev, mddev) {
 410                 disk_idx = rdev->raid_disk;
 411                 if (disk_idx < 0 ||
 412                     disk_idx >= mddev->raid_disks)
 413                         continue;
 414
 415                 disk = conf->multipaths + disk_idx;
 416                 disk->rdev = rdev;
 417                 disk_stack_limits(mddev->gendisk, rdev->bdev,
 418                                   rdev->data_offset << 9);
 419
 420                 if (!test_bit(Faulty, &rdev->flags))
 421                         working_disks++;
 422         }
 423
 424         conf->raid_disks = mddev->raid_disks;
 425         conf->mddev = mddev;
 426         spin_lock_init(&conf->device_lock);
 427         INIT_LIST_HEAD(&conf->retry_list);
 428
 429         if (!working_disks) {
 430                 pr_warn("multipath: no operational IO paths for %s\n",
 431                         mdname(mddev));
 432                 goto out_free_conf;
 433         }
 434         mddev->degraded = conf->raid_disks - working_disks;
 435
 436         conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS,
 437                                                  sizeof(struct multipath_bh));
 438         if (conf->pool == NULL)
 439                 goto out_free_conf;
 440
 441         mddev->thread = md_register_thread(multipathd, mddev,
 442                                            "multipath");
 443         if (!mddev->thread)
 444                 goto out_free_conf;
 445
 446         pr_info("multipath: array %s active with %d out of %d IO paths\n",
 447                 mdname(mddev), conf->raid_disks - mddev->degraded,
 448                 mddev->raid_disks);
 449         /*
 450          * Ok, everything is just fine now
 451          */
 452         md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
 453
 454         if (md_integrity_register(mddev))
 455                 goto out_free_conf;
 456
 457         return 0;
 458
 459 out_free_conf:
 460         mempool_destroy(conf->pool);
 461         kfree(conf->multipaths);
 462         kfree(conf);
 463         mddev->private = NULL;
 464 out:
 465         return -EIO;
 466 }
 467
 468 static void multipath_free(struct mddev *mddev, void *priv)
 469 {
 470         struct mpconf *conf = priv;
 471
 472         mempool_destroy(conf->pool);
 473         kfree(conf->multipaths);
 474         kfree(conf);
 475 }
 476
 477 static struct md_personality multipath_personality =
 478 {
 479         .name           = "multipath",
 480         .level          = LEVEL_MULTIPATH,
 481         .owner          = THIS_MODULE,
 482         .make_request   = multipath_make_request,
 483         .run            = multipath_run,
 484         .free           = multipath_free,
 485         .status         = multipath_status,
 486         .error_handler  = multipath_error,
 487         .hot_add_disk   = multipath_add_disk,
 488         .hot_remove_disk= multipath_remove_disk,
 489         .size           = multipath_size,
 490         .congested      = multipath_congested,
 491 };
 492
 493 static int __init multipath_init (void)
 494 {
 495         return register_md_personality (&multipath_personality);
 496 }
 497
 498 static void __exit multipath_exit (void)
 499 {
 500         unregister_md_personality (&multipath_personality);
 501 }
 502
 503 module_init(multipath_init);
 504 module_exit(multipath_exit);
 505 MODULE_LICENSE("GPL");
 506 MODULE_DESCRIPTION("simple multi-path personality for MD");
 507 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
 508 MODULE_ALIAS("md-multipath");
 509 MODULE_ALIAS("md-level--4");