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