drivers/md/md-multipath.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * multipath.c : Multiple Devices driver for Linux
   4  *
   5  * Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
   6  *
   7  * Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
   8  *
   9  * MULTIPATH management functions.
  10  *
  11  * derived from raid1.c.
  12  */
  13
  14 #include <linux/blkdev.h>
  15 #include <linux/module.h>
  16 #include <linux/raid/md_u.h>
  17 #include <linux/seq_file.h>
  18 #include <linux/slab.h>
  19 #include "md.h"
  20 #include "md-multipath.h"
  21
  22 #define MAX_WORK_PER_DISK 128
  23
  24 #define NR_RESERVED_BUFS        32
  25
  26 static int multipath_map (struct mpconf *conf)
  27 {
  28         int i, disks = conf->raid_disks;
  29
  30         /*
  31          * Later we do read balancing on the read side
  32          * now we use the first available disk.
  33          */
  34
  35         rcu_read_lock();
  36         for (i = 0; i < disks; i++) {
  37                 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
  38                 if (rdev && test_bit(In_sync, &rdev->flags) &&
  39                     !test_bit(Faulty, &rdev->flags)) {
  40                         atomic_inc(&rdev->nr_pending);
  41                         rcu_read_unlock();
  42                         return i;
  43                 }
  44         }
  45         rcu_read_unlock();
  46
  47         pr_crit_ratelimited("multipath_map(): no more operational IO paths?\n");
  48         return (-1);
  49 }
  50
  51 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
  52 {
  53         unsigned long flags;
  54         struct mddev *mddev = mp_bh->mddev;
  55         struct mpconf *conf = mddev->private;
  56
  57         spin_lock_irqsave(&conf->device_lock, flags);
  58         list_add(&mp_bh->retry_list, &conf->retry_list);
  59         spin_unlock_irqrestore(&conf->device_lock, flags);
  60         md_wakeup_thread(mddev->thread);
  61 }
  62
  63 /*
  64  * multipath_end_bh_io() is called when we have finished servicing a multipathed
  65  * operation and are ready to return a success/failure code to the buffer
  66  * cache layer.
  67  */
  68 static void multipath_end_bh_io(struct multipath_bh *mp_bh, blk_status_t status)
  69 {
  70         struct bio *bio = mp_bh->master_bio;
  71         struct mpconf *conf = mp_bh->mddev->private;
  72
  73         bio->bi_status = status;
  74         bio_endio(bio);
  75         mempool_free(mp_bh, &conf->pool);
  76 }
  77
  78 static void multipath_end_request(struct bio *bio)
  79 {
  80         struct multipath_bh *mp_bh = bio->bi_private;
  81         struct mpconf *conf = mp_bh->mddev->private;
  82         struct md_rdev *rdev = conf->multipaths[mp_bh->path].rdev;
  83
  84         if (!bio->bi_status)
  85                 multipath_end_bh_io(mp_bh, 0);
  86         else if (!(bio->bi_opf & REQ_RAHEAD)) {
  87                 /*
  88                  * oops, IO error:
  89                  */
  90                 char b[BDEVNAME_SIZE];
  91                 md_error (mp_bh->mddev, rdev);
  92                 pr_info("multipath: %s: rescheduling sector %llu\n",
  93                         bdevname(rdev->bdev,b),
  94                         (unsigned long long)bio->bi_iter.bi_sector);
  95                 multipath_reschedule_retry(mp_bh);
  96         } else
  97                 multipath_end_bh_io(mp_bh, bio->bi_status);
  98         rdev_dec_pending(rdev, conf->mddev);
  99 }
 100
 101 static bool multipath_make_request(struct mddev *mddev, struct bio * bio)
 102 {
 103         struct mpconf *conf = mddev->private;
 104         struct multipath_bh * mp_bh;
 105         struct multipath_info *multipath;
 106
 107         if (unlikely(bio->bi_opf & REQ_PREFLUSH)
 108             && md_flush_request(mddev, bio))
 109                 return true;
 110
 111         mp_bh = mempool_alloc(&conf->pool, GFP_NOIO);
 112
 113         mp_bh->master_bio = bio;
 114         mp_bh->mddev = mddev;
 115
 116         mp_bh->path = multipath_map(conf);
 117         if (mp_bh->path < 0) {
 118                 bio_io_error(bio);
 119                 mempool_free(mp_bh, &conf->pool);
 120                 return true;
 121         }
 122         multipath = conf->multipaths + mp_bh->path;
 123
 124         bio_init(&mp_bh->bio, NULL, 0);
 125         __bio_clone_fast(&mp_bh->bio, bio);
 126
 127         mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset;
 128         bio_set_dev(&mp_bh->bio, multipath->rdev->bdev);
 129         mp_bh->bio.bi_opf |= REQ_FAILFAST_TRANSPORT;
 130         mp_bh->bio.bi_end_io = multipath_end_request;
 131         mp_bh->bio.bi_private = mp_bh;
 132         mddev_check_writesame(mddev, &mp_bh->bio);
 133         mddev_check_write_zeroes(mddev, &mp_bh->bio);
 134         submit_bio_noacct(&mp_bh->bio);
 135         return true;
 136 }
 137
 138 static void multipath_status(struct seq_file *seq, struct mddev *mddev)
 139 {
 140         struct mpconf *conf = mddev->private;
 141         int i;
 142
 143         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
 144                     conf->raid_disks - mddev->degraded);
 145         rcu_read_lock();
 146         for (i = 0; i < conf->raid_disks; i++) {
 147                 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
 148                 seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
 149         }
 150         rcu_read_unlock();
 151         seq_putc(seq, ']');
 152 }
 153
 154 /*
 155  * Careful, this can execute in IRQ contexts as well!
 156  */
 157 static void multipath_error (struct mddev *mddev, struct md_rdev *rdev)
 158 {
 159         struct mpconf *conf = mddev->private;
 160         char b[BDEVNAME_SIZE];
 161
 162         if (conf->raid_disks - mddev->degraded <= 1) {
 163                 /*
 164                  * Uh oh, we can do nothing if this is our last path, but
 165                  * first check if this is a queued request for a device
 166                  * which has just failed.
 167                  */
 168                 pr_warn("multipath: only one IO path left and IO error.\n");
 169                 /* leave it active... it's all we have */
 170                 return;
 171         }
 172         /*
 173          * Mark disk as unusable
 174          */
 175         if (test_and_clear_bit(In_sync, &rdev->flags)) {
 176                 unsigned long flags;
 177                 spin_lock_irqsave(&conf->device_lock, flags);
 178                 mddev->degraded++;
 179                 spin_unlock_irqrestore(&conf->device_lock, flags);
 180         }
 181         set_bit(Faulty, &rdev->flags);
 182         set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
 183         pr_err("multipath: IO failure on %s, disabling IO path.\n"
 184                "multipath: Operation continuing on %d IO paths.\n",
 185                bdevname(rdev->bdev, b),
 186                conf->raid_disks - mddev->degraded);
 187 }
 188
 189 static void print_multipath_conf (struct mpconf *conf)
 190 {
 191         int i;
 192         struct multipath_info *tmp;
 193
 194         pr_debug("MULTIPATH conf printout:\n");
 195         if (!conf) {
 196                 pr_debug("(conf==NULL)\n");
 197                 return;
 198         }
 199         pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
 200                  conf->raid_disks);
 201
 202         for (i = 0; i < conf->raid_disks; i++) {
 203                 char b[BDEVNAME_SIZE];
 204                 tmp = conf->multipaths + i;
 205                 if (tmp->rdev)
 206                         pr_debug(" disk%d, o:%d, dev:%s\n",
 207                                  i,!test_bit(Faulty, &tmp->rdev->flags),
 208                                  bdevname(tmp->rdev->bdev,b));
 209         }
 210 }
 211
 212 static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev)
 213 {
 214         struct mpconf *conf = mddev->private;
 215         int err = -EEXIST;
 216         int path;
 217         struct multipath_info *p;
 218         int first = 0;
 219         int last = mddev->raid_disks - 1;
 220
 221         if (rdev->raid_disk >= 0)
 222                 first = last = rdev->raid_disk;
 223
 224         print_multipath_conf(conf);
 225
 226         for (path = first; path <= last; path++)
 227                 if ((p=conf->multipaths+path)->rdev == NULL) {
 228                         disk_stack_limits(mddev->gendisk, rdev->bdev,
 229                                           rdev->data_offset << 9);
 230
 231                         err = md_integrity_add_rdev(rdev, mddev);
 232                         if (err)
 233                                 break;
 234                         spin_lock_irq(&conf->device_lock);
 235                         mddev->degraded--;
 236                         rdev->raid_disk = path;
 237                         set_bit(In_sync, &rdev->flags);
 238                         spin_unlock_irq(&conf->device_lock);
 239                         rcu_assign_pointer(p->rdev, rdev);
 240                         err = 0;
 241                         break;
 242                 }
 243
 244         print_multipath_conf(conf);
 245
 246         return err;
 247 }
 248
 249 static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
 250 {
 251         struct mpconf *conf = mddev->private;
 252         int err = 0;
 253         int number = rdev->raid_disk;
 254         struct multipath_info *p = conf->multipaths + number;
 255
 256         print_multipath_conf(conf);
 257
 258         if (rdev == p->rdev) {
 259                 if (test_bit(In_sync, &rdev->flags) ||
 260                     atomic_read(&rdev->nr_pending)) {
 261                         pr_warn("hot-remove-disk, slot %d is identified but is still operational!\n", number);
 262                         err = -EBUSY;
 263                         goto abort;
 264                 }
 265                 p->rdev = NULL;
 266                 if (!test_bit(RemoveSynchronized, &rdev->flags)) {
 267                         synchronize_rcu();
 268                         if (atomic_read(&rdev->nr_pending)) {
 269                                 /* lost the race, try later */
 270                                 err = -EBUSY;
 271                                 p->rdev = rdev;
 272                                 goto abort;
 273                         }
 274                 }
 275                 err = md_integrity_register(mddev);
 276         }
 277 abort:
 278
 279         print_multipath_conf(conf);
 280         return err;
 281 }
 282
 283 /*
 284  * This is a kernel thread which:
 285  *
 286  *      1.      Retries failed read operations on working multipaths.
 287  *      2.      Updates the raid superblock when problems encounter.
 288  *      3.      Performs writes following reads for array syncronising.
 289  */
 290
 291 static void multipathd(struct md_thread *thread)
 292 {
 293         struct mddev *mddev = thread->mddev;
 294         struct multipath_bh *mp_bh;
 295         struct bio *bio;
 296         unsigned long flags;
 297         struct mpconf *conf = mddev->private;
 298         struct list_head *head = &conf->retry_list;
 299
 300         md_check_recovery(mddev);
 301         for (;;) {
 302                 char b[BDEVNAME_SIZE];
 303                 spin_lock_irqsave(&conf->device_lock, flags);
 304                 if (list_empty(head))
 305                         break;
 306                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
 307                 list_del(head->prev);
 308                 spin_unlock_irqrestore(&conf->device_lock, flags);
 309
 310                 bio = &mp_bh->bio;
 311                 bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector;
 312
 313                 if ((mp_bh->path = multipath_map (conf))<0) {
 314                         pr_err("multipath: %s: unrecoverable IO read error for block %llu\n",
 315                                bio_devname(bio, b),
 316                                (unsigned long long)bio->bi_iter.bi_sector);
 317                         multipath_end_bh_io(mp_bh, BLK_STS_IOERR);
 318                 } else {
 319                         pr_err("multipath: %s: redirecting sector %llu to another IO path\n",
 320                                bio_devname(bio, b),
 321                                (unsigned long long)bio->bi_iter.bi_sector);
 322                         *bio = *(mp_bh->master_bio);
 323                         bio->bi_iter.bi_sector +=
 324                                 conf->multipaths[mp_bh->path].rdev->data_offset;
 325                         bio_set_dev(bio, conf->multipaths[mp_bh->path].rdev->bdev);
 326                         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 327                         bio->bi_end_io = multipath_end_request;
 328                         bio->bi_private = mp_bh;
 329                         submit_bio_noacct(bio);
 330                 }
 331         }
 332         spin_unlock_irqrestore(&conf->device_lock, flags);
 333 }
 334
 335 static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks)
 336 {
 337         WARN_ONCE(sectors || raid_disks,
 338                   "%s does not support generic reshape\n", __func__);
 339
 340         return mddev->dev_sectors;
 341 }
 342
 343 static int multipath_run (struct mddev *mddev)
 344 {
 345         struct mpconf *conf;
 346         int disk_idx;
 347         struct multipath_info *disk;
 348         struct md_rdev *rdev;
 349         int working_disks;
 350         int ret;
 351
 352         if (md_check_no_bitmap(mddev))
 353                 return -EINVAL;
 354
 355         if (mddev->level != LEVEL_MULTIPATH) {
 356                 pr_warn("multipath: %s: raid level not set to multipath IO (%d)\n",
 357                         mdname(mddev), mddev->level);
 358                 goto out;
 359         }
 360         /*
 361          * copy the already verified devices into our private MULTIPATH
 362          * bookkeeping area. [whatever we allocate in multipath_run(),
 363          * should be freed in multipath_free()]
 364          */
 365
 366         conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL);
 367         mddev->private = conf;
 368         if (!conf)
 369                 goto out;
 370
 371         conf->multipaths = kcalloc(mddev->raid_disks,
 372                                    sizeof(struct multipath_info),
 373                                    GFP_KERNEL);
 374         if (!conf->multipaths)
 375                 goto out_free_conf;
 376
 377         working_disks = 0;
 378         rdev_for_each(rdev, mddev) {
 379                 disk_idx = rdev->raid_disk;
 380                 if (disk_idx < 0 ||
 381                     disk_idx >= mddev->raid_disks)
 382                         continue;
 383
 384                 disk = conf->multipaths + disk_idx;
 385                 disk->rdev = rdev;
 386                 disk_stack_limits(mddev->gendisk, rdev->bdev,
 387                                   rdev->data_offset << 9);
 388
 389                 if (!test_bit(Faulty, &rdev->flags))
 390                         working_disks++;
 391         }
 392
 393         conf->raid_disks = mddev->raid_disks;
 394         conf->mddev = mddev;
 395         spin_lock_init(&conf->device_lock);
 396         INIT_LIST_HEAD(&conf->retry_list);
 397
 398         if (!working_disks) {
 399                 pr_warn("multipath: no operational IO paths for %s\n",
 400                         mdname(mddev));
 401                 goto out_free_conf;
 402         }
 403         mddev->degraded = conf->raid_disks - working_disks;
 404
 405         ret = mempool_init_kmalloc_pool(&conf->pool, NR_RESERVED_BUFS,
 406                                         sizeof(struct multipath_bh));
 407         if (ret)
 408                 goto out_free_conf;
 409
 410         mddev->thread = md_register_thread(multipathd, mddev,
 411                                            "multipath");
 412         if (!mddev->thread)
 413                 goto out_free_conf;
 414
 415         pr_info("multipath: array %s active with %d out of %d IO paths\n",
 416                 mdname(mddev), conf->raid_disks - mddev->degraded,
 417                 mddev->raid_disks);
 418         /*
 419          * Ok, everything is just fine now
 420          */
 421         md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
 422
 423         if (md_integrity_register(mddev))
 424                 goto out_free_conf;
 425
 426         return 0;
 427
 428 out_free_conf:
 429         mempool_exit(&conf->pool);
 430         kfree(conf->multipaths);
 431         kfree(conf);
 432         mddev->private = NULL;
 433 out:
 434         return -EIO;
 435 }
 436
 437 static void multipath_free(struct mddev *mddev, void *priv)
 438 {
 439         struct mpconf *conf = priv;
 440
 441         mempool_exit(&conf->pool);
 442         kfree(conf->multipaths);
 443         kfree(conf);
 444 }
 445
 446 static struct md_personality multipath_personality =
 447 {
 448         .name           = "multipath",
 449         .level          = LEVEL_MULTIPATH,
 450         .owner          = THIS_MODULE,
 451         .make_request   = multipath_make_request,
 452         .run            = multipath_run,
 453         .free           = multipath_free,
 454         .status         = multipath_status,
 455         .error_handler  = multipath_error,
 456         .hot_add_disk   = multipath_add_disk,
 457         .hot_remove_disk= multipath_remove_disk,
 458         .size           = multipath_size,
 459 };
 460
 461 static int __init multipath_init (void)
 462 {
 463         return register_md_personality (&multipath_personality);
 464 }
 465
 466 static void __exit multipath_exit (void)
 467 {
 468         unregister_md_personality (&multipath_personality);
 469 }
 470
 471 module_init(multipath_init);
 472 module_exit(multipath_exit);
 473 MODULE_LICENSE("GPL");
 474 MODULE_DESCRIPTION("simple multi-path personality for MD");
 475 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
 476 MODULE_ALIAS("md-multipath");
 477 MODULE_ALIAS("md-level--4");