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 generic_make_request(&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 static int multipath_congested(struct mddev *mddev, int bits) 155 { 156 struct mpconf *conf = mddev->private; 157 int i, ret = 0; 158 159 rcu_read_lock(); 160 for (i = 0; i < mddev->raid_disks ; i++) { 161 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev); 162 if (rdev && !test_bit(Faulty, &rdev->flags)) { 163 struct request_queue *q = bdev_get_queue(rdev->bdev); 164 165 ret |= bdi_congested(q->backing_dev_info, bits); 166 /* Just like multipath_map, we just check the 167 * first available device 168 */ 169 break; 170 } 171 } 172 rcu_read_unlock(); 173 return ret; 174 } 175 176 /* 177 * Careful, this can execute in IRQ contexts as well! 178 */ 179 static void multipath_error (struct mddev *mddev, struct md_rdev *rdev) 180 { 181 struct mpconf *conf = mddev->private; 182 char b[BDEVNAME_SIZE]; 183 184 if (conf->raid_disks - mddev->degraded <= 1) { 185 /* 186 * Uh oh, we can do nothing if this is our last path, but 187 * first check if this is a queued request for a device 188 * which has just failed. 189 */ 190 pr_warn("multipath: only one IO path left and IO error.\n"); 191 /* leave it active... it's all we have */ 192 return; 193 } 194 /* 195 * Mark disk as unusable 196 */ 197 if (test_and_clear_bit(In_sync, &rdev->flags)) { 198 unsigned long flags; 199 spin_lock_irqsave(&conf->device_lock, flags); 200 mddev->degraded++; 201 spin_unlock_irqrestore(&conf->device_lock, flags); 202 } 203 set_bit(Faulty, &rdev->flags); 204 set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags); 205 pr_err("multipath: IO failure on %s, disabling IO path.\n" 206 "multipath: Operation continuing on %d IO paths.\n", 207 bdevname(rdev->bdev, b), 208 conf->raid_disks - mddev->degraded); 209 } 210 211 static void print_multipath_conf (struct mpconf *conf) 212 { 213 int i; 214 struct multipath_info *tmp; 215 216 pr_debug("MULTIPATH conf printout:\n"); 217 if (!conf) { 218 pr_debug("(conf==NULL)\n"); 219 return; 220 } 221 pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded, 222 conf->raid_disks); 223 224 for (i = 0; i < conf->raid_disks; i++) { 225 char b[BDEVNAME_SIZE]; 226 tmp = conf->multipaths + i; 227 if (tmp->rdev) 228 pr_debug(" disk%d, o:%d, dev:%s\n", 229 i,!test_bit(Faulty, &tmp->rdev->flags), 230 bdevname(tmp->rdev->bdev,b)); 231 } 232 } 233 234 static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev) 235 { 236 struct mpconf *conf = mddev->private; 237 int err = -EEXIST; 238 int path; 239 struct multipath_info *p; 240 int first = 0; 241 int last = mddev->raid_disks - 1; 242 243 if (rdev->raid_disk >= 0) 244 first = last = rdev->raid_disk; 245 246 print_multipath_conf(conf); 247 248 for (path = first; path <= last; path++) 249 if ((p=conf->multipaths+path)->rdev == NULL) { 250 disk_stack_limits(mddev->gendisk, rdev->bdev, 251 rdev->data_offset << 9); 252 253 err = md_integrity_add_rdev(rdev, mddev); 254 if (err) 255 break; 256 spin_lock_irq(&conf->device_lock); 257 mddev->degraded--; 258 rdev->raid_disk = path; 259 set_bit(In_sync, &rdev->flags); 260 spin_unlock_irq(&conf->device_lock); 261 rcu_assign_pointer(p->rdev, rdev); 262 err = 0; 263 break; 264 } 265 266 print_multipath_conf(conf); 267 268 return err; 269 } 270 271 static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev) 272 { 273 struct mpconf *conf = mddev->private; 274 int err = 0; 275 int number = rdev->raid_disk; 276 struct multipath_info *p = conf->multipaths + number; 277 278 print_multipath_conf(conf); 279 280 if (rdev == p->rdev) { 281 if (test_bit(In_sync, &rdev->flags) || 282 atomic_read(&rdev->nr_pending)) { 283 pr_warn("hot-remove-disk, slot %d is identified but is still operational!\n", number); 284 err = -EBUSY; 285 goto abort; 286 } 287 p->rdev = NULL; 288 if (!test_bit(RemoveSynchronized, &rdev->flags)) { 289 synchronize_rcu(); 290 if (atomic_read(&rdev->nr_pending)) { 291 /* lost the race, try later */ 292 err = -EBUSY; 293 p->rdev = rdev; 294 goto abort; 295 } 296 } 297 err = md_integrity_register(mddev); 298 } 299 abort: 300 301 print_multipath_conf(conf); 302 return err; 303 } 304 305 /* 306 * This is a kernel thread which: 307 * 308 * 1. Retries failed read operations on working multipaths. 309 * 2. Updates the raid superblock when problems encounter. 310 * 3. Performs writes following reads for array syncronising. 311 */ 312 313 static void multipathd(struct md_thread *thread) 314 { 315 struct mddev *mddev = thread->mddev; 316 struct multipath_bh *mp_bh; 317 struct bio *bio; 318 unsigned long flags; 319 struct mpconf *conf = mddev->private; 320 struct list_head *head = &conf->retry_list; 321 322 md_check_recovery(mddev); 323 for (;;) { 324 char b[BDEVNAME_SIZE]; 325 spin_lock_irqsave(&conf->device_lock, flags); 326 if (list_empty(head)) 327 break; 328 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list); 329 list_del(head->prev); 330 spin_unlock_irqrestore(&conf->device_lock, flags); 331 332 bio = &mp_bh->bio; 333 bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector; 334 335 if ((mp_bh->path = multipath_map (conf))<0) { 336 pr_err("multipath: %s: unrecoverable IO read error for block %llu\n", 337 bio_devname(bio, b), 338 (unsigned long long)bio->bi_iter.bi_sector); 339 multipath_end_bh_io(mp_bh, BLK_STS_IOERR); 340 } else { 341 pr_err("multipath: %s: redirecting sector %llu to another IO path\n", 342 bio_devname(bio, b), 343 (unsigned long long)bio->bi_iter.bi_sector); 344 *bio = *(mp_bh->master_bio); 345 bio->bi_iter.bi_sector += 346 conf->multipaths[mp_bh->path].rdev->data_offset; 347 bio_set_dev(bio, conf->multipaths[mp_bh->path].rdev->bdev); 348 bio->bi_opf |= REQ_FAILFAST_TRANSPORT; 349 bio->bi_end_io = multipath_end_request; 350 bio->bi_private = mp_bh; 351 generic_make_request(bio); 352 } 353 } 354 spin_unlock_irqrestore(&conf->device_lock, flags); 355 } 356 357 static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks) 358 { 359 WARN_ONCE(sectors || raid_disks, 360 "%s does not support generic reshape\n", __func__); 361 362 return mddev->dev_sectors; 363 } 364 365 static int multipath_run (struct mddev *mddev) 366 { 367 struct mpconf *conf; 368 int disk_idx; 369 struct multipath_info *disk; 370 struct md_rdev *rdev; 371 int working_disks; 372 int ret; 373 374 if (md_check_no_bitmap(mddev)) 375 return -EINVAL; 376 377 if (mddev->level != LEVEL_MULTIPATH) { 378 pr_warn("multipath: %s: raid level not set to multipath IO (%d)\n", 379 mdname(mddev), mddev->level); 380 goto out; 381 } 382 /* 383 * copy the already verified devices into our private MULTIPATH 384 * bookkeeping area. [whatever we allocate in multipath_run(), 385 * should be freed in multipath_free()] 386 */ 387 388 conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL); 389 mddev->private = conf; 390 if (!conf) 391 goto out; 392 393 conf->multipaths = kcalloc(mddev->raid_disks, 394 sizeof(struct multipath_info), 395 GFP_KERNEL); 396 if (!conf->multipaths) 397 goto out_free_conf; 398 399 working_disks = 0; 400 rdev_for_each(rdev, mddev) { 401 disk_idx = rdev->raid_disk; 402 if (disk_idx < 0 || 403 disk_idx >= mddev->raid_disks) 404 continue; 405 406 disk = conf->multipaths + disk_idx; 407 disk->rdev = rdev; 408 disk_stack_limits(mddev->gendisk, rdev->bdev, 409 rdev->data_offset << 9); 410 411 if (!test_bit(Faulty, &rdev->flags)) 412 working_disks++; 413 } 414 415 conf->raid_disks = mddev->raid_disks; 416 conf->mddev = mddev; 417 spin_lock_init(&conf->device_lock); 418 INIT_LIST_HEAD(&conf->retry_list); 419 420 if (!working_disks) { 421 pr_warn("multipath: no operational IO paths for %s\n", 422 mdname(mddev)); 423 goto out_free_conf; 424 } 425 mddev->degraded = conf->raid_disks - working_disks; 426 427 ret = mempool_init_kmalloc_pool(&conf->pool, NR_RESERVED_BUFS, 428 sizeof(struct multipath_bh)); 429 if (ret) 430 goto out_free_conf; 431 432 mddev->thread = md_register_thread(multipathd, mddev, 433 "multipath"); 434 if (!mddev->thread) 435 goto out_free_conf; 436 437 pr_info("multipath: array %s active with %d out of %d IO paths\n", 438 mdname(mddev), conf->raid_disks - mddev->degraded, 439 mddev->raid_disks); 440 /* 441 * Ok, everything is just fine now 442 */ 443 md_set_array_sectors(mddev, multipath_size(mddev, 0, 0)); 444 445 if (md_integrity_register(mddev)) 446 goto out_free_conf; 447 448 return 0; 449 450 out_free_conf: 451 mempool_exit(&conf->pool); 452 kfree(conf->multipaths); 453 kfree(conf); 454 mddev->private = NULL; 455 out: 456 return -EIO; 457 } 458 459 static void multipath_free(struct mddev *mddev, void *priv) 460 { 461 struct mpconf *conf = priv; 462 463 mempool_exit(&conf->pool); 464 kfree(conf->multipaths); 465 kfree(conf); 466 } 467 468 static struct md_personality multipath_personality = 469 { 470 .name = "multipath", 471 .level = LEVEL_MULTIPATH, 472 .owner = THIS_MODULE, 473 .make_request = multipath_make_request, 474 .run = multipath_run, 475 .free = multipath_free, 476 .status = multipath_status, 477 .error_handler = multipath_error, 478 .hot_add_disk = multipath_add_disk, 479 .hot_remove_disk= multipath_remove_disk, 480 .size = multipath_size, 481 .congested = multipath_congested, 482 }; 483 484 static int __init multipath_init (void) 485 { 486 return register_md_personality (&multipath_personality); 487 } 488 489 static void __exit multipath_exit (void) 490 { 491 unregister_md_personality (&multipath_personality); 492 } 493 494 module_init(multipath_init); 495 module_exit(multipath_exit); 496 MODULE_LICENSE("GPL"); 497 MODULE_DESCRIPTION("simple multi-path personality for MD"); 498 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */ 499 MODULE_ALIAS("md-multipath"); 500 MODULE_ALIAS("md-level--4"); 501