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_clone(multipath->rdev->bdev, &mp_bh->bio, bio, GFP_NOIO); 125 126 mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset; 127 mp_bh->bio.bi_opf |= REQ_FAILFAST_TRANSPORT; 128 mp_bh->bio.bi_end_io = multipath_end_request; 129 mp_bh->bio.bi_private = mp_bh; 130 mddev_check_write_zeroes(mddev, &mp_bh->bio); 131 submit_bio_noacct(&mp_bh->bio); 132 return true; 133 } 134 135 static void multipath_status(struct seq_file *seq, struct mddev *mddev) 136 { 137 struct mpconf *conf = mddev->private; 138 int i; 139 140 seq_printf (seq, " [%d/%d] [", conf->raid_disks, 141 conf->raid_disks - mddev->degraded); 142 rcu_read_lock(); 143 for (i = 0; i < conf->raid_disks; i++) { 144 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev); 145 seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_"); 146 } 147 rcu_read_unlock(); 148 seq_putc(seq, ']'); 149 } 150 151 /* 152 * Careful, this can execute in IRQ contexts as well! 153 */ 154 static void multipath_error (struct mddev *mddev, struct md_rdev *rdev) 155 { 156 struct mpconf *conf = mddev->private; 157 char b[BDEVNAME_SIZE]; 158 159 if (conf->raid_disks - mddev->degraded <= 1) { 160 /* 161 * Uh oh, we can do nothing if this is our last path, but 162 * first check if this is a queued request for a device 163 * which has just failed. 164 */ 165 pr_warn("multipath: only one IO path left and IO error.\n"); 166 /* leave it active... it's all we have */ 167 return; 168 } 169 /* 170 * Mark disk as unusable 171 */ 172 if (test_and_clear_bit(In_sync, &rdev->flags)) { 173 unsigned long flags; 174 spin_lock_irqsave(&conf->device_lock, flags); 175 mddev->degraded++; 176 spin_unlock_irqrestore(&conf->device_lock, flags); 177 } 178 set_bit(Faulty, &rdev->flags); 179 set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags); 180 pr_err("multipath: IO failure on %s, disabling IO path.\n" 181 "multipath: Operation continuing on %d IO paths.\n", 182 bdevname(rdev->bdev, b), 183 conf->raid_disks - mddev->degraded); 184 } 185 186 static void print_multipath_conf (struct mpconf *conf) 187 { 188 int i; 189 struct multipath_info *tmp; 190 191 pr_debug("MULTIPATH conf printout:\n"); 192 if (!conf) { 193 pr_debug("(conf==NULL)\n"); 194 return; 195 } 196 pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded, 197 conf->raid_disks); 198 199 for (i = 0; i < conf->raid_disks; i++) { 200 char b[BDEVNAME_SIZE]; 201 tmp = conf->multipaths + i; 202 if (tmp->rdev) 203 pr_debug(" disk%d, o:%d, dev:%s\n", 204 i,!test_bit(Faulty, &tmp->rdev->flags), 205 bdevname(tmp->rdev->bdev,b)); 206 } 207 } 208 209 static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev) 210 { 211 struct mpconf *conf = mddev->private; 212 int err = -EEXIST; 213 int path; 214 struct multipath_info *p; 215 int first = 0; 216 int last = mddev->raid_disks - 1; 217 218 if (rdev->raid_disk >= 0) 219 first = last = rdev->raid_disk; 220 221 print_multipath_conf(conf); 222 223 for (path = first; path <= last; path++) 224 if ((p=conf->multipaths+path)->rdev == NULL) { 225 disk_stack_limits(mddev->gendisk, rdev->bdev, 226 rdev->data_offset << 9); 227 228 err = md_integrity_add_rdev(rdev, mddev); 229 if (err) 230 break; 231 spin_lock_irq(&conf->device_lock); 232 mddev->degraded--; 233 rdev->raid_disk = path; 234 set_bit(In_sync, &rdev->flags); 235 spin_unlock_irq(&conf->device_lock); 236 rcu_assign_pointer(p->rdev, rdev); 237 err = 0; 238 break; 239 } 240 241 print_multipath_conf(conf); 242 243 return err; 244 } 245 246 static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev) 247 { 248 struct mpconf *conf = mddev->private; 249 int err = 0; 250 int number = rdev->raid_disk; 251 struct multipath_info *p = conf->multipaths + number; 252 253 print_multipath_conf(conf); 254 255 if (rdev == p->rdev) { 256 if (test_bit(In_sync, &rdev->flags) || 257 atomic_read(&rdev->nr_pending)) { 258 pr_warn("hot-remove-disk, slot %d is identified but is still operational!\n", number); 259 err = -EBUSY; 260 goto abort; 261 } 262 p->rdev = NULL; 263 if (!test_bit(RemoveSynchronized, &rdev->flags)) { 264 synchronize_rcu(); 265 if (atomic_read(&rdev->nr_pending)) { 266 /* lost the race, try later */ 267 err = -EBUSY; 268 p->rdev = rdev; 269 goto abort; 270 } 271 } 272 err = md_integrity_register(mddev); 273 } 274 abort: 275 276 print_multipath_conf(conf); 277 return err; 278 } 279 280 /* 281 * This is a kernel thread which: 282 * 283 * 1. Retries failed read operations on working multipaths. 284 * 2. Updates the raid superblock when problems encounter. 285 * 3. Performs writes following reads for array syncronising. 286 */ 287 288 static void multipathd(struct md_thread *thread) 289 { 290 struct mddev *mddev = thread->mddev; 291 struct multipath_bh *mp_bh; 292 struct bio *bio; 293 unsigned long flags; 294 struct mpconf *conf = mddev->private; 295 struct list_head *head = &conf->retry_list; 296 297 md_check_recovery(mddev); 298 for (;;) { 299 spin_lock_irqsave(&conf->device_lock, flags); 300 if (list_empty(head)) 301 break; 302 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list); 303 list_del(head->prev); 304 spin_unlock_irqrestore(&conf->device_lock, flags); 305 306 bio = &mp_bh->bio; 307 bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector; 308 309 if ((mp_bh->path = multipath_map (conf))<0) { 310 pr_err("multipath: %pg: unrecoverable IO read error for block %llu\n", 311 bio->bi_bdev, 312 (unsigned long long)bio->bi_iter.bi_sector); 313 multipath_end_bh_io(mp_bh, BLK_STS_IOERR); 314 } else { 315 pr_err("multipath: %pg: redirecting sector %llu to another IO path\n", 316 bio->bi_bdev, 317 (unsigned long long)bio->bi_iter.bi_sector); 318 *bio = *(mp_bh->master_bio); 319 bio->bi_iter.bi_sector += 320 conf->multipaths[mp_bh->path].rdev->data_offset; 321 bio_set_dev(bio, conf->multipaths[mp_bh->path].rdev->bdev); 322 bio->bi_opf |= REQ_FAILFAST_TRANSPORT; 323 bio->bi_end_io = multipath_end_request; 324 bio->bi_private = mp_bh; 325 submit_bio_noacct(bio); 326 } 327 } 328 spin_unlock_irqrestore(&conf->device_lock, flags); 329 } 330 331 static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks) 332 { 333 WARN_ONCE(sectors || raid_disks, 334 "%s does not support generic reshape\n", __func__); 335 336 return mddev->dev_sectors; 337 } 338 339 static int multipath_run (struct mddev *mddev) 340 { 341 struct mpconf *conf; 342 int disk_idx; 343 struct multipath_info *disk; 344 struct md_rdev *rdev; 345 int working_disks; 346 int ret; 347 348 if (md_check_no_bitmap(mddev)) 349 return -EINVAL; 350 351 if (mddev->level != LEVEL_MULTIPATH) { 352 pr_warn("multipath: %s: raid level not set to multipath IO (%d)\n", 353 mdname(mddev), mddev->level); 354 goto out; 355 } 356 /* 357 * copy the already verified devices into our private MULTIPATH 358 * bookkeeping area. [whatever we allocate in multipath_run(), 359 * should be freed in multipath_free()] 360 */ 361 362 conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL); 363 mddev->private = conf; 364 if (!conf) 365 goto out; 366 367 conf->multipaths = kcalloc(mddev->raid_disks, 368 sizeof(struct multipath_info), 369 GFP_KERNEL); 370 if (!conf->multipaths) 371 goto out_free_conf; 372 373 working_disks = 0; 374 rdev_for_each(rdev, mddev) { 375 disk_idx = rdev->raid_disk; 376 if (disk_idx < 0 || 377 disk_idx >= mddev->raid_disks) 378 continue; 379 380 disk = conf->multipaths + disk_idx; 381 disk->rdev = rdev; 382 disk_stack_limits(mddev->gendisk, rdev->bdev, 383 rdev->data_offset << 9); 384 385 if (!test_bit(Faulty, &rdev->flags)) 386 working_disks++; 387 } 388 389 conf->raid_disks = mddev->raid_disks; 390 conf->mddev = mddev; 391 spin_lock_init(&conf->device_lock); 392 INIT_LIST_HEAD(&conf->retry_list); 393 394 if (!working_disks) { 395 pr_warn("multipath: no operational IO paths for %s\n", 396 mdname(mddev)); 397 goto out_free_conf; 398 } 399 mddev->degraded = conf->raid_disks - working_disks; 400 401 ret = mempool_init_kmalloc_pool(&conf->pool, NR_RESERVED_BUFS, 402 sizeof(struct multipath_bh)); 403 if (ret) 404 goto out_free_conf; 405 406 mddev->thread = md_register_thread(multipathd, mddev, 407 "multipath"); 408 if (!mddev->thread) 409 goto out_free_conf; 410 411 pr_info("multipath: array %s active with %d out of %d IO paths\n", 412 mdname(mddev), conf->raid_disks - mddev->degraded, 413 mddev->raid_disks); 414 /* 415 * Ok, everything is just fine now 416 */ 417 md_set_array_sectors(mddev, multipath_size(mddev, 0, 0)); 418 419 if (md_integrity_register(mddev)) 420 goto out_free_conf; 421 422 return 0; 423 424 out_free_conf: 425 mempool_exit(&conf->pool); 426 kfree(conf->multipaths); 427 kfree(conf); 428 mddev->private = NULL; 429 out: 430 return -EIO; 431 } 432 433 static void multipath_free(struct mddev *mddev, void *priv) 434 { 435 struct mpconf *conf = priv; 436 437 mempool_exit(&conf->pool); 438 kfree(conf->multipaths); 439 kfree(conf); 440 } 441 442 static struct md_personality multipath_personality = 443 { 444 .name = "multipath", 445 .level = LEVEL_MULTIPATH, 446 .owner = THIS_MODULE, 447 .make_request = multipath_make_request, 448 .run = multipath_run, 449 .free = multipath_free, 450 .status = multipath_status, 451 .error_handler = multipath_error, 452 .hot_add_disk = multipath_add_disk, 453 .hot_remove_disk= multipath_remove_disk, 454 .size = multipath_size, 455 }; 456 457 static int __init multipath_init (void) 458 { 459 return register_md_personality (&multipath_personality); 460 } 461 462 static void __exit multipath_exit (void) 463 { 464 unregister_md_personality (&multipath_personality); 465 } 466 467 module_init(multipath_init); 468 module_exit(multipath_exit); 469 MODULE_LICENSE("GPL"); 470 MODULE_DESCRIPTION("simple multi-path personality for MD (deprecated)"); 471 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */ 472 MODULE_ALIAS("md-multipath"); 473 MODULE_ALIAS("md-level--4"); 474