1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2010-2012 by Dell Inc. All rights reserved. 4 * Copyright (C) 2011-2013 Red Hat, Inc. 5 * 6 * This file is released under the GPL. 7 * 8 * dm-switch is a device-mapper target that maps IO to underlying block 9 * devices efficiently when there are a large number of fixed-sized 10 * address regions but there is no simple pattern to allow for a compact 11 * mapping representation such as dm-stripe. 12 */ 13 14 #include <linux/device-mapper.h> 15 16 #include <linux/module.h> 17 #include <linux/init.h> 18 #include <linux/vmalloc.h> 19 20 #define DM_MSG_PREFIX "switch" 21 22 /* 23 * One region_table_slot_t holds <region_entries_per_slot> region table 24 * entries each of which is <region_table_entry_bits> in size. 25 */ 26 typedef unsigned long region_table_slot_t; 27 28 /* 29 * A device with the offset to its start sector. 30 */ 31 struct switch_path { 32 struct dm_dev *dmdev; 33 sector_t start; 34 }; 35 36 /* 37 * Context block for a dm switch device. 38 */ 39 struct switch_ctx { 40 struct dm_target *ti; 41 42 unsigned int nr_paths; /* Number of paths in path_list. */ 43 44 unsigned int region_size; /* Region size in 512-byte sectors */ 45 unsigned long nr_regions; /* Number of regions making up the device */ 46 signed char region_size_bits; /* log2 of region_size or -1 */ 47 48 unsigned char region_table_entry_bits; /* Number of bits in one region table entry */ 49 unsigned char region_entries_per_slot; /* Number of entries in one region table slot */ 50 signed char region_entries_per_slot_bits; /* log2 of region_entries_per_slot or -1 */ 51 52 region_table_slot_t *region_table; /* Region table */ 53 54 /* 55 * Array of dm devices to switch between. 56 */ 57 struct switch_path path_list[]; 58 }; 59 60 static struct switch_ctx *alloc_switch_ctx(struct dm_target *ti, unsigned int nr_paths, 61 unsigned int region_size) 62 { 63 struct switch_ctx *sctx; 64 65 sctx = kzalloc(struct_size(sctx, path_list, nr_paths), GFP_KERNEL); 66 if (!sctx) 67 return NULL; 68 69 sctx->ti = ti; 70 sctx->region_size = region_size; 71 72 ti->private = sctx; 73 74 return sctx; 75 } 76 77 static int alloc_region_table(struct dm_target *ti, unsigned int nr_paths) 78 { 79 struct switch_ctx *sctx = ti->private; 80 sector_t nr_regions = ti->len; 81 sector_t nr_slots; 82 83 if (!(sctx->region_size & (sctx->region_size - 1))) 84 sctx->region_size_bits = __ffs(sctx->region_size); 85 else 86 sctx->region_size_bits = -1; 87 88 sctx->region_table_entry_bits = 1; 89 while (sctx->region_table_entry_bits < sizeof(region_table_slot_t) * 8 && 90 (region_table_slot_t)1 << sctx->region_table_entry_bits < nr_paths) 91 sctx->region_table_entry_bits++; 92 93 sctx->region_entries_per_slot = (sizeof(region_table_slot_t) * 8) / sctx->region_table_entry_bits; 94 if (!(sctx->region_entries_per_slot & (sctx->region_entries_per_slot - 1))) 95 sctx->region_entries_per_slot_bits = __ffs(sctx->region_entries_per_slot); 96 else 97 sctx->region_entries_per_slot_bits = -1; 98 99 if (sector_div(nr_regions, sctx->region_size)) 100 nr_regions++; 101 102 if (nr_regions >= ULONG_MAX) { 103 ti->error = "Region table too large"; 104 return -EINVAL; 105 } 106 sctx->nr_regions = nr_regions; 107 108 nr_slots = nr_regions; 109 if (sector_div(nr_slots, sctx->region_entries_per_slot)) 110 nr_slots++; 111 112 if (nr_slots > ULONG_MAX / sizeof(region_table_slot_t)) { 113 ti->error = "Region table too large"; 114 return -EINVAL; 115 } 116 117 sctx->region_table = vmalloc(array_size(nr_slots, 118 sizeof(region_table_slot_t))); 119 if (!sctx->region_table) { 120 ti->error = "Cannot allocate region table"; 121 return -ENOMEM; 122 } 123 124 return 0; 125 } 126 127 static void switch_get_position(struct switch_ctx *sctx, unsigned long region_nr, 128 unsigned long *region_index, unsigned int *bit) 129 { 130 if (sctx->region_entries_per_slot_bits >= 0) { 131 *region_index = region_nr >> sctx->region_entries_per_slot_bits; 132 *bit = region_nr & (sctx->region_entries_per_slot - 1); 133 } else { 134 *region_index = region_nr / sctx->region_entries_per_slot; 135 *bit = region_nr % sctx->region_entries_per_slot; 136 } 137 138 *bit *= sctx->region_table_entry_bits; 139 } 140 141 static unsigned int switch_region_table_read(struct switch_ctx *sctx, unsigned long region_nr) 142 { 143 unsigned long region_index; 144 unsigned int bit; 145 146 switch_get_position(sctx, region_nr, ®ion_index, &bit); 147 148 return (READ_ONCE(sctx->region_table[region_index]) >> bit) & 149 ((1 << sctx->region_table_entry_bits) - 1); 150 } 151 152 /* 153 * Find which path to use at given offset. 154 */ 155 static unsigned int switch_get_path_nr(struct switch_ctx *sctx, sector_t offset) 156 { 157 unsigned int path_nr; 158 sector_t p; 159 160 p = offset; 161 if (sctx->region_size_bits >= 0) 162 p >>= sctx->region_size_bits; 163 else 164 sector_div(p, sctx->region_size); 165 166 path_nr = switch_region_table_read(sctx, p); 167 168 /* This can only happen if the processor uses non-atomic stores. */ 169 if (unlikely(path_nr >= sctx->nr_paths)) 170 path_nr = 0; 171 172 return path_nr; 173 } 174 175 static void switch_region_table_write(struct switch_ctx *sctx, unsigned long region_nr, 176 unsigned int value) 177 { 178 unsigned long region_index; 179 unsigned int bit; 180 region_table_slot_t pte; 181 182 switch_get_position(sctx, region_nr, ®ion_index, &bit); 183 184 pte = sctx->region_table[region_index]; 185 pte &= ~((((region_table_slot_t)1 << sctx->region_table_entry_bits) - 1) << bit); 186 pte |= (region_table_slot_t)value << bit; 187 sctx->region_table[region_index] = pte; 188 } 189 190 /* 191 * Fill the region table with an initial round robin pattern. 192 */ 193 static void initialise_region_table(struct switch_ctx *sctx) 194 { 195 unsigned int path_nr = 0; 196 unsigned long region_nr; 197 198 for (region_nr = 0; region_nr < sctx->nr_regions; region_nr++) { 199 switch_region_table_write(sctx, region_nr, path_nr); 200 if (++path_nr >= sctx->nr_paths) 201 path_nr = 0; 202 } 203 } 204 205 static int parse_path(struct dm_arg_set *as, struct dm_target *ti) 206 { 207 struct switch_ctx *sctx = ti->private; 208 unsigned long long start; 209 int r; 210 211 r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table), 212 &sctx->path_list[sctx->nr_paths].dmdev); 213 if (r) { 214 ti->error = "Device lookup failed"; 215 return r; 216 } 217 218 if (kstrtoull(dm_shift_arg(as), 10, &start) || start != (sector_t)start) { 219 ti->error = "Invalid device starting offset"; 220 dm_put_device(ti, sctx->path_list[sctx->nr_paths].dmdev); 221 return -EINVAL; 222 } 223 224 sctx->path_list[sctx->nr_paths].start = start; 225 226 sctx->nr_paths++; 227 228 return 0; 229 } 230 231 /* 232 * Destructor: Don't free the dm_target, just the ti->private data (if any). 233 */ 234 static void switch_dtr(struct dm_target *ti) 235 { 236 struct switch_ctx *sctx = ti->private; 237 238 while (sctx->nr_paths--) 239 dm_put_device(ti, sctx->path_list[sctx->nr_paths].dmdev); 240 241 vfree(sctx->region_table); 242 kfree(sctx); 243 } 244 245 /* 246 * Constructor arguments: 247 * <num_paths> <region_size> <num_optional_args> [<optional_args>...] 248 * [<dev_path> <offset>]+ 249 * 250 * Optional args are to allow for future extension: currently this 251 * parameter must be 0. 252 */ 253 static int switch_ctr(struct dm_target *ti, unsigned int argc, char **argv) 254 { 255 static const struct dm_arg _args[] = { 256 {1, (KMALLOC_MAX_SIZE - sizeof(struct switch_ctx)) / sizeof(struct switch_path), "Invalid number of paths"}, 257 {1, UINT_MAX, "Invalid region size"}, 258 {0, 0, "Invalid number of optional args"}, 259 }; 260 261 struct switch_ctx *sctx; 262 struct dm_arg_set as; 263 unsigned int nr_paths, region_size, nr_optional_args; 264 int r; 265 266 as.argc = argc; 267 as.argv = argv; 268 269 r = dm_read_arg(_args, &as, &nr_paths, &ti->error); 270 if (r) 271 return -EINVAL; 272 273 r = dm_read_arg(_args + 1, &as, ®ion_size, &ti->error); 274 if (r) 275 return r; 276 277 r = dm_read_arg_group(_args + 2, &as, &nr_optional_args, &ti->error); 278 if (r) 279 return r; 280 /* parse optional arguments here, if we add any */ 281 282 if (as.argc != nr_paths * 2) { 283 ti->error = "Incorrect number of path arguments"; 284 return -EINVAL; 285 } 286 287 sctx = alloc_switch_ctx(ti, nr_paths, region_size); 288 if (!sctx) { 289 ti->error = "Cannot allocate redirection context"; 290 return -ENOMEM; 291 } 292 293 r = dm_set_target_max_io_len(ti, region_size); 294 if (r) 295 goto error; 296 297 while (as.argc) { 298 r = parse_path(&as, ti); 299 if (r) 300 goto error; 301 } 302 303 r = alloc_region_table(ti, nr_paths); 304 if (r) 305 goto error; 306 307 initialise_region_table(sctx); 308 309 /* For UNMAP, sending the request down any path is sufficient */ 310 ti->num_discard_bios = 1; 311 312 return 0; 313 314 error: 315 switch_dtr(ti); 316 317 return r; 318 } 319 320 static int switch_map(struct dm_target *ti, struct bio *bio) 321 { 322 struct switch_ctx *sctx = ti->private; 323 sector_t offset = dm_target_offset(ti, bio->bi_iter.bi_sector); 324 unsigned int path_nr = switch_get_path_nr(sctx, offset); 325 326 bio_set_dev(bio, sctx->path_list[path_nr].dmdev->bdev); 327 bio->bi_iter.bi_sector = sctx->path_list[path_nr].start + offset; 328 329 return DM_MAPIO_REMAPPED; 330 } 331 332 /* 333 * We need to parse hex numbers in the message as quickly as possible. 334 * 335 * This table-based hex parser improves performance. 336 * It improves a time to load 1000000 entries compared to the condition-based 337 * parser. 338 * table-based parser condition-based parser 339 * PA-RISC 0.29s 0.31s 340 * Opteron 0.0495s 0.0498s 341 */ 342 static const unsigned char hex_table[256] = { 343 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 344 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 345 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 346 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255, 255, 255, 255, 255, 347 255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255, 348 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 349 255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255, 350 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 351 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 352 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 353 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 354 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 355 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 356 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 357 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 358 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255 359 }; 360 361 static __always_inline unsigned long parse_hex(const char **string) 362 { 363 unsigned char d; 364 unsigned long r = 0; 365 366 while ((d = hex_table[(unsigned char)**string]) < 16) { 367 r = (r << 4) | d; 368 (*string)++; 369 } 370 371 return r; 372 } 373 374 static int process_set_region_mappings(struct switch_ctx *sctx, 375 unsigned int argc, char **argv) 376 { 377 unsigned int i; 378 unsigned long region_index = 0; 379 380 for (i = 1; i < argc; i++) { 381 unsigned long path_nr; 382 const char *string = argv[i]; 383 384 if ((*string & 0xdf) == 'R') { 385 unsigned long cycle_length, num_write; 386 387 string++; 388 if (unlikely(*string == ',')) { 389 DMWARN("invalid set_region_mappings argument: '%s'", argv[i]); 390 return -EINVAL; 391 } 392 cycle_length = parse_hex(&string); 393 if (unlikely(*string != ',')) { 394 DMWARN("invalid set_region_mappings argument: '%s'", argv[i]); 395 return -EINVAL; 396 } 397 string++; 398 if (unlikely(!*string)) { 399 DMWARN("invalid set_region_mappings argument: '%s'", argv[i]); 400 return -EINVAL; 401 } 402 num_write = parse_hex(&string); 403 if (unlikely(*string)) { 404 DMWARN("invalid set_region_mappings argument: '%s'", argv[i]); 405 return -EINVAL; 406 } 407 408 if (unlikely(!cycle_length) || unlikely(cycle_length - 1 > region_index)) { 409 DMWARN("invalid set_region_mappings cycle length: %lu > %lu", 410 cycle_length - 1, region_index); 411 return -EINVAL; 412 } 413 if (unlikely(region_index + num_write < region_index) || 414 unlikely(region_index + num_write >= sctx->nr_regions)) { 415 DMWARN("invalid set_region_mappings region number: %lu + %lu >= %lu", 416 region_index, num_write, sctx->nr_regions); 417 return -EINVAL; 418 } 419 420 while (num_write--) { 421 region_index++; 422 path_nr = switch_region_table_read(sctx, region_index - cycle_length); 423 switch_region_table_write(sctx, region_index, path_nr); 424 } 425 426 continue; 427 } 428 429 if (*string == ':') 430 region_index++; 431 else { 432 region_index = parse_hex(&string); 433 if (unlikely(*string != ':')) { 434 DMWARN("invalid set_region_mappings argument: '%s'", argv[i]); 435 return -EINVAL; 436 } 437 } 438 439 string++; 440 if (unlikely(!*string)) { 441 DMWARN("invalid set_region_mappings argument: '%s'", argv[i]); 442 return -EINVAL; 443 } 444 445 path_nr = parse_hex(&string); 446 if (unlikely(*string)) { 447 DMWARN("invalid set_region_mappings argument: '%s'", argv[i]); 448 return -EINVAL; 449 } 450 if (unlikely(region_index >= sctx->nr_regions)) { 451 DMWARN("invalid set_region_mappings region number: %lu >= %lu", region_index, sctx->nr_regions); 452 return -EINVAL; 453 } 454 if (unlikely(path_nr >= sctx->nr_paths)) { 455 DMWARN("invalid set_region_mappings device: %lu >= %u", path_nr, sctx->nr_paths); 456 return -EINVAL; 457 } 458 459 switch_region_table_write(sctx, region_index, path_nr); 460 } 461 462 return 0; 463 } 464 465 /* 466 * Messages are processed one-at-a-time. 467 * 468 * Only set_region_mappings is supported. 469 */ 470 static int switch_message(struct dm_target *ti, unsigned int argc, char **argv, 471 char *result, unsigned int maxlen) 472 { 473 static DEFINE_MUTEX(message_mutex); 474 475 struct switch_ctx *sctx = ti->private; 476 int r = -EINVAL; 477 478 mutex_lock(&message_mutex); 479 480 if (!strcasecmp(argv[0], "set_region_mappings")) 481 r = process_set_region_mappings(sctx, argc, argv); 482 else 483 DMWARN("Unrecognised message received."); 484 485 mutex_unlock(&message_mutex); 486 487 return r; 488 } 489 490 static void switch_status(struct dm_target *ti, status_type_t type, 491 unsigned int status_flags, char *result, unsigned int maxlen) 492 { 493 struct switch_ctx *sctx = ti->private; 494 unsigned int sz = 0; 495 int path_nr; 496 497 switch (type) { 498 case STATUSTYPE_INFO: 499 result[0] = '\0'; 500 break; 501 502 case STATUSTYPE_TABLE: 503 DMEMIT("%u %u 0", sctx->nr_paths, sctx->region_size); 504 for (path_nr = 0; path_nr < sctx->nr_paths; path_nr++) 505 DMEMIT(" %s %llu", sctx->path_list[path_nr].dmdev->name, 506 (unsigned long long)sctx->path_list[path_nr].start); 507 break; 508 509 case STATUSTYPE_IMA: 510 result[0] = '\0'; 511 break; 512 } 513 } 514 515 /* 516 * Switch ioctl: 517 * 518 * Passthrough all ioctls to the path for sector 0 519 */ 520 static int switch_prepare_ioctl(struct dm_target *ti, struct block_device **bdev) 521 { 522 struct switch_ctx *sctx = ti->private; 523 unsigned int path_nr; 524 525 path_nr = switch_get_path_nr(sctx, 0); 526 527 *bdev = sctx->path_list[path_nr].dmdev->bdev; 528 529 /* 530 * Only pass ioctls through if the device sizes match exactly. 531 */ 532 if (ti->len + sctx->path_list[path_nr].start != 533 bdev_nr_sectors((*bdev))) 534 return 1; 535 return 0; 536 } 537 538 static int switch_iterate_devices(struct dm_target *ti, 539 iterate_devices_callout_fn fn, void *data) 540 { 541 struct switch_ctx *sctx = ti->private; 542 int path_nr; 543 int r; 544 545 for (path_nr = 0; path_nr < sctx->nr_paths; path_nr++) { 546 r = fn(ti, sctx->path_list[path_nr].dmdev, 547 sctx->path_list[path_nr].start, ti->len, data); 548 if (r) 549 return r; 550 } 551 552 return 0; 553 } 554 555 static struct target_type switch_target = { 556 .name = "switch", 557 .version = {1, 1, 0}, 558 .features = DM_TARGET_NOWAIT, 559 .module = THIS_MODULE, 560 .ctr = switch_ctr, 561 .dtr = switch_dtr, 562 .map = switch_map, 563 .message = switch_message, 564 .status = switch_status, 565 .prepare_ioctl = switch_prepare_ioctl, 566 .iterate_devices = switch_iterate_devices, 567 }; 568 569 static int __init dm_switch_init(void) 570 { 571 int r; 572 573 r = dm_register_target(&switch_target); 574 if (r < 0) 575 DMERR("dm_register_target() failed %d", r); 576 577 return r; 578 } 579 580 static void __exit dm_switch_exit(void) 581 { 582 dm_unregister_target(&switch_target); 583 } 584 585 module_init(dm_switch_init); 586 module_exit(dm_switch_exit); 587 588 MODULE_DESCRIPTION(DM_NAME " dynamic path switching target"); 589 MODULE_AUTHOR("Kevin D. O'Kelley <Kevin_OKelley@dell.com>"); 590 MODULE_AUTHOR("Narendran Ganapathy <Narendran_Ganapathy@dell.com>"); 591 MODULE_AUTHOR("Jim Ramsay <Jim_Ramsay@dell.com>"); 592 MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>"); 593 MODULE_LICENSE("GPL"); 594