1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 22 /* 23 * Copyright (c) 2011, 2015 by Delphix. All rights reserved. 24 */ 25 26 #include <sys/zfs_context.h> 27 #include <sys/zfeature.h> 28 #include <sys/dmu.h> 29 #include <sys/nvpair.h> 30 #include <sys/zap.h> 31 #include <sys/dmu_tx.h> 32 #include "zfeature_common.h" 33 #include <sys/spa_impl.h> 34 35 /* 36 * ZFS Feature Flags 37 * ----------------- 38 * 39 * ZFS feature flags are used to provide fine-grained versioning to the ZFS 40 * on-disk format. Once enabled on a pool feature flags replace the old 41 * spa_version() number. 42 * 43 * Each new on-disk format change will be given a uniquely identifying string 44 * guid rather than a version number. This avoids the problem of different 45 * organizations creating new on-disk formats with the same version number. To 46 * keep feature guids unique they should consist of the reverse dns name of the 47 * organization which implemented the feature and a short name for the feature, 48 * separated by a colon (e.g. com.delphix:async_destroy). 49 * 50 * Reference Counts 51 * ---------------- 52 * 53 * Within each pool features can be in one of three states: disabled, enabled, 54 * or active. These states are differentiated by a reference count stored on 55 * disk for each feature: 56 * 57 * 1) If there is no reference count stored on disk the feature is disabled. 58 * 2) If the reference count is 0 a system administrator has enabled the 59 * feature, but the feature has not been used yet, so no on-disk 60 * format changes have been made. 61 * 3) If the reference count is greater than 0 the feature is active. 62 * The format changes required by the feature are currently on disk. 63 * Note that if the feature's format changes are reversed the feature 64 * may choose to set its reference count back to 0. 65 * 66 * Feature flags makes no differentiation between non-zero reference counts 67 * for an active feature (e.g. a reference count of 1 means the same thing as a 68 * reference count of 27834721), but feature implementations may choose to use 69 * the reference count to store meaningful information. For example, a new RAID 70 * implementation might set the reference count to the number of vdevs using 71 * it. If all those disks are removed from the pool the feature goes back to 72 * having a reference count of 0. 73 * 74 * It is the responsibility of the individual features to maintain a non-zero 75 * reference count as long as the feature's format changes are present on disk. 76 * 77 * Dependencies 78 * ------------ 79 * 80 * Each feature may depend on other features. The only effect of this 81 * relationship is that when a feature is enabled all of its dependencies are 82 * automatically enabled as well. Any future work to support disabling of 83 * features would need to ensure that features cannot be disabled if other 84 * enabled features depend on them. 85 * 86 * On-disk Format 87 * -------------- 88 * 89 * When feature flags are enabled spa_version() is set to SPA_VERSION_FEATURES 90 * (5000). In order for this to work the pool is automatically upgraded to 91 * SPA_VERSION_BEFORE_FEATURES (28) first, so all pre-feature flags on disk 92 * format changes will be in use. 93 * 94 * Information about features is stored in 3 ZAP objects in the pool's MOS. 95 * These objects are linked to by the following names in the pool directory 96 * object: 97 * 98 * 1) features_for_read: feature guid -> reference count 99 * Features needed to open the pool for reading. 100 * 2) features_for_write: feature guid -> reference count 101 * Features needed to open the pool for writing. 102 * 3) feature_descriptions: feature guid -> descriptive string 103 * A human readable string. 104 * 105 * All enabled features appear in either features_for_read or 106 * features_for_write, but not both. 107 * 108 * To open a pool in read-only mode only the features listed in 109 * features_for_read need to be supported. 110 * 111 * To open the pool in read-write mode features in both features_for_read and 112 * features_for_write need to be supported. 113 * 114 * Some features may be required to read the ZAP objects containing feature 115 * information. To allow software to check for compatibility with these features 116 * before the pool is opened their names must be stored in the label in a 117 * new "features_for_read" entry (note that features that are only required 118 * to write to a pool never need to be stored in the label since the 119 * features_for_write ZAP object can be read before the pool is written to). 120 * To save space in the label features must be explicitly marked as needing to 121 * be written to the label. Also, reference counts are not stored in the label, 122 * instead any feature whose reference count drops to 0 is removed from the 123 * label. 124 * 125 * Adding New Features 126 * ------------------- 127 * 128 * Features must be registered in zpool_feature_init() function in 129 * zfeature_common.c using the zfeature_register() function. This function 130 * has arguments to specify if the feature should be stored in the 131 * features_for_read or features_for_write ZAP object and if it needs to be 132 * written to the label when active. 133 * 134 * Once a feature is registered it will appear as a "feature@<feature name>" 135 * property which can be set by an administrator. Feature implementors should 136 * use the spa_feature_is_enabled() and spa_feature_is_active() functions to 137 * query the state of a feature and the spa_feature_incr() and 138 * spa_feature_decr() functions to change an enabled feature's reference count. 139 * Reference counts may only be updated in the syncing context. 140 * 141 * Features may not perform enable-time initialization. Instead, any such 142 * initialization should occur when the feature is first used. This design 143 * enforces that on-disk changes be made only when features are used. Code 144 * should only check if a feature is enabled using spa_feature_is_enabled(), 145 * not by relying on any feature specific metadata existing. If a feature is 146 * enabled, but the feature's metadata is not on disk yet then it should be 147 * created as needed. 148 * 149 * As an example, consider the com.delphix:async_destroy feature. This feature 150 * relies on the existence of a bptree in the MOS that store blocks for 151 * asynchronous freeing. This bptree is not created when async_destroy is 152 * enabled. Instead, when a dataset is destroyed spa_feature_is_enabled() is 153 * called to check if async_destroy is enabled. If it is and the bptree object 154 * does not exist yet, the bptree object is created as part of the dataset 155 * destroy and async_destroy's reference count is incremented to indicate it 156 * has made an on-disk format change. Later, after the destroyed dataset's 157 * blocks have all been asynchronously freed there is no longer any use for the 158 * bptree object, so it is destroyed and async_destroy's reference count is 159 * decremented back to 0 to indicate that it has undone its on-disk format 160 * changes. 161 */ 162 163 typedef enum { 164 FEATURE_ACTION_INCR, 165 FEATURE_ACTION_DECR, 166 } feature_action_t; 167 168 /* 169 * Checks that the active features in the pool are supported by 170 * this software. Adds each unsupported feature (name -> description) to 171 * the supplied nvlist. 172 */ 173 boolean_t 174 spa_features_check(spa_t *spa, boolean_t for_write, 175 nvlist_t *unsup_feat, nvlist_t *enabled_feat) 176 { 177 objset_t *os = spa->spa_meta_objset; 178 boolean_t supported; 179 zap_cursor_t zc; 180 zap_attribute_t za; 181 uint64_t obj = for_write ? 182 spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj; 183 184 supported = B_TRUE; 185 for (zap_cursor_init(&zc, os, obj); 186 zap_cursor_retrieve(&zc, &za) == 0; 187 zap_cursor_advance(&zc)) { 188 ASSERT(za.za_integer_length == sizeof (uint64_t) && 189 za.za_num_integers == 1); 190 191 if (NULL != enabled_feat) { 192 fnvlist_add_uint64(enabled_feat, za.za_name, 193 za.za_first_integer); 194 } 195 196 if (za.za_first_integer != 0 && 197 !zfeature_is_supported(za.za_name)) { 198 supported = B_FALSE; 199 200 if (NULL != unsup_feat) { 201 char *desc = ""; 202 char buf[MAXPATHLEN]; 203 204 if (zap_lookup(os, spa->spa_feat_desc_obj, 205 za.za_name, 1, sizeof (buf), buf) == 0) 206 desc = buf; 207 208 VERIFY(nvlist_add_string(unsup_feat, za.za_name, 209 desc) == 0); 210 } 211 } 212 } 213 zap_cursor_fini(&zc); 214 215 return (supported); 216 } 217 218 /* 219 * Use an in-memory cache of feature refcounts for quick retrieval. 220 * 221 * Note: well-designed features will not need to use this; they should 222 * use spa_feature_is_enabled() and spa_feature_is_active() instead. 223 * However, this is non-static for zdb and zhack. 224 */ 225 int 226 feature_get_refcount(spa_t *spa, zfeature_info_t *feature, uint64_t *res) 227 { 228 ASSERT(VALID_FEATURE_FID(feature->fi_feature)); 229 if (spa->spa_feat_refcount_cache[feature->fi_feature] == 230 SPA_FEATURE_DISABLED) { 231 return (SET_ERROR(ENOTSUP)); 232 } 233 *res = spa->spa_feat_refcount_cache[feature->fi_feature]; 234 return (0); 235 } 236 237 /* 238 * Note: well-designed features will not need to use this; they should 239 * use spa_feature_is_enabled() and spa_feature_is_active() instead. 240 * However, this is non-static for zdb and zhack. 241 */ 242 int 243 feature_get_refcount_from_disk(spa_t *spa, zfeature_info_t *feature, 244 uint64_t *res) 245 { 246 int err; 247 uint64_t refcount; 248 uint64_t zapobj = (feature->fi_flags & ZFEATURE_FLAG_READONLY_COMPAT) ? 249 spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj; 250 251 /* 252 * If the pool is currently being created, the feature objects may not 253 * have been allocated yet. Act as though all features are disabled. 254 */ 255 if (zapobj == 0) 256 return (SET_ERROR(ENOTSUP)); 257 258 err = zap_lookup(spa->spa_meta_objset, zapobj, 259 feature->fi_guid, sizeof (uint64_t), 1, &refcount); 260 if (err != 0) { 261 if (err == ENOENT) 262 return (SET_ERROR(ENOTSUP)); 263 else 264 return (err); 265 } 266 *res = refcount; 267 return (0); 268 } 269 270 271 static int 272 feature_get_enabled_txg(spa_t *spa, zfeature_info_t *feature, uint64_t *res) 273 { 274 uint64_t enabled_txg_obj = spa->spa_feat_enabled_txg_obj; 275 276 ASSERT(zfeature_depends_on(feature->fi_feature, 277 SPA_FEATURE_ENABLED_TXG)); 278 279 if (!spa_feature_is_enabled(spa, feature->fi_feature)) { 280 return (SET_ERROR(ENOTSUP)); 281 } 282 283 ASSERT(enabled_txg_obj != 0); 284 285 VERIFY0(zap_lookup(spa->spa_meta_objset, spa->spa_feat_enabled_txg_obj, 286 feature->fi_guid, sizeof (uint64_t), 1, res)); 287 288 return (0); 289 } 290 291 /* 292 * This function is non-static for zhack; it should otherwise not be used 293 * outside this file. 294 */ 295 void 296 feature_sync(spa_t *spa, zfeature_info_t *feature, uint64_t refcount, 297 dmu_tx_t *tx) 298 { 299 ASSERT(VALID_FEATURE_OR_NONE(feature->fi_feature)); 300 uint64_t zapobj = (feature->fi_flags & ZFEATURE_FLAG_READONLY_COMPAT) ? 301 spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj; 302 303 VERIFY0(zap_update(spa->spa_meta_objset, zapobj, feature->fi_guid, 304 sizeof (uint64_t), 1, &refcount, tx)); 305 306 /* 307 * feature_sync is called directly from zhack, allowing the 308 * creation of arbitrary features whose fi_feature field may 309 * be greater than SPA_FEATURES. When called from zhack, the 310 * zfeature_info_t object's fi_feature field will be set to 311 * SPA_FEATURE_NONE. 312 */ 313 if (feature->fi_feature != SPA_FEATURE_NONE) { 314 uint64_t *refcount_cache = 315 &spa->spa_feat_refcount_cache[feature->fi_feature]; 316 VERIFY3U(*refcount_cache, ==, 317 atomic_swap_64(refcount_cache, refcount)); 318 } 319 320 if (refcount == 0) 321 spa_deactivate_mos_feature(spa, feature->fi_guid); 322 else if (feature->fi_flags & ZFEATURE_FLAG_MOS) 323 spa_activate_mos_feature(spa, feature->fi_guid, tx); 324 } 325 326 /* 327 * This function is non-static for zhack; it should otherwise not be used 328 * outside this file. 329 */ 330 void 331 feature_enable_sync(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx) 332 { 333 uint64_t initial_refcount = 334 (feature->fi_flags & ZFEATURE_FLAG_ACTIVATE_ON_ENABLE) ? 1 : 0; 335 uint64_t zapobj = (feature->fi_flags & ZFEATURE_FLAG_READONLY_COMPAT) ? 336 spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj; 337 338 ASSERT(0 != zapobj); 339 ASSERT(zfeature_is_valid_guid(feature->fi_guid)); 340 ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES); 341 342 /* 343 * If the feature is already enabled, ignore the request. 344 */ 345 if (zap_contains(spa->spa_meta_objset, zapobj, feature->fi_guid) == 0) 346 return; 347 348 for (int i = 0; feature->fi_depends[i] != SPA_FEATURE_NONE; i++) 349 spa_feature_enable(spa, feature->fi_depends[i], tx); 350 351 VERIFY0(zap_update(spa->spa_meta_objset, spa->spa_feat_desc_obj, 352 feature->fi_guid, 1, strlen(feature->fi_desc) + 1, 353 feature->fi_desc, tx)); 354 355 feature_sync(spa, feature, initial_refcount, tx); 356 357 if (spa_feature_is_enabled(spa, SPA_FEATURE_ENABLED_TXG)) { 358 uint64_t enabling_txg = dmu_tx_get_txg(tx); 359 360 if (spa->spa_feat_enabled_txg_obj == 0ULL) { 361 spa->spa_feat_enabled_txg_obj = 362 zap_create_link(spa->spa_meta_objset, 363 DMU_OTN_ZAP_METADATA, DMU_POOL_DIRECTORY_OBJECT, 364 DMU_POOL_FEATURE_ENABLED_TXG, tx); 365 } 366 spa_feature_incr(spa, SPA_FEATURE_ENABLED_TXG, tx); 367 368 VERIFY0(zap_add(spa->spa_meta_objset, 369 spa->spa_feat_enabled_txg_obj, feature->fi_guid, 370 sizeof (uint64_t), 1, &enabling_txg, tx)); 371 } 372 } 373 374 static void 375 feature_do_action(spa_t *spa, spa_feature_t fid, feature_action_t action, 376 dmu_tx_t *tx) 377 { 378 uint64_t refcount; 379 zfeature_info_t *feature = &spa_feature_table[fid]; 380 uint64_t zapobj = (feature->fi_flags & ZFEATURE_FLAG_READONLY_COMPAT) ? 381 spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj; 382 383 ASSERT(VALID_FEATURE_FID(fid)); 384 ASSERT(0 != zapobj); 385 ASSERT(zfeature_is_valid_guid(feature->fi_guid)); 386 387 ASSERT(dmu_tx_is_syncing(tx)); 388 ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES); 389 390 VERIFY3U(feature_get_refcount(spa, feature, &refcount), !=, ENOTSUP); 391 392 switch (action) { 393 case FEATURE_ACTION_INCR: 394 VERIFY3U(refcount, !=, UINT64_MAX); 395 refcount++; 396 break; 397 case FEATURE_ACTION_DECR: 398 VERIFY3U(refcount, !=, 0); 399 refcount--; 400 break; 401 default: 402 ASSERT(0); 403 break; 404 } 405 406 feature_sync(spa, feature, refcount, tx); 407 } 408 409 void 410 spa_feature_create_zap_objects(spa_t *spa, dmu_tx_t *tx) 411 { 412 /* 413 * We create feature flags ZAP objects in two instances: during pool 414 * creation and during pool upgrade. 415 */ 416 ASSERT(dsl_pool_sync_context(spa_get_dsl(spa)) || (!spa->spa_sync_on && 417 tx->tx_txg == TXG_INITIAL)); 418 419 spa->spa_feat_for_read_obj = zap_create_link(spa->spa_meta_objset, 420 DMU_OTN_ZAP_METADATA, DMU_POOL_DIRECTORY_OBJECT, 421 DMU_POOL_FEATURES_FOR_READ, tx); 422 spa->spa_feat_for_write_obj = zap_create_link(spa->spa_meta_objset, 423 DMU_OTN_ZAP_METADATA, DMU_POOL_DIRECTORY_OBJECT, 424 DMU_POOL_FEATURES_FOR_WRITE, tx); 425 spa->spa_feat_desc_obj = zap_create_link(spa->spa_meta_objset, 426 DMU_OTN_ZAP_METADATA, DMU_POOL_DIRECTORY_OBJECT, 427 DMU_POOL_FEATURE_DESCRIPTIONS, tx); 428 } 429 430 /* 431 * Enable any required dependencies, then enable the requested feature. 432 */ 433 void 434 spa_feature_enable(spa_t *spa, spa_feature_t fid, dmu_tx_t *tx) 435 { 436 ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES); 437 ASSERT(VALID_FEATURE_FID(fid)); 438 feature_enable_sync(spa, &spa_feature_table[fid], tx); 439 } 440 441 void 442 spa_feature_incr(spa_t *spa, spa_feature_t fid, dmu_tx_t *tx) 443 { 444 feature_do_action(spa, fid, FEATURE_ACTION_INCR, tx); 445 } 446 447 void 448 spa_feature_decr(spa_t *spa, spa_feature_t fid, dmu_tx_t *tx) 449 { 450 feature_do_action(spa, fid, FEATURE_ACTION_DECR, tx); 451 } 452 453 boolean_t 454 spa_feature_is_enabled(spa_t *spa, spa_feature_t fid) 455 { 456 int err; 457 uint64_t refcount; 458 459 ASSERT(VALID_FEATURE_FID(fid)); 460 if (spa_version(spa) < SPA_VERSION_FEATURES) 461 return (B_FALSE); 462 463 err = feature_get_refcount(spa, &spa_feature_table[fid], &refcount); 464 ASSERT(err == 0 || err == ENOTSUP); 465 return (err == 0); 466 } 467 468 boolean_t 469 spa_feature_is_active(spa_t *spa, spa_feature_t fid) 470 { 471 int err; 472 uint64_t refcount; 473 474 ASSERT(VALID_FEATURE_FID(fid)); 475 if (spa_version(spa) < SPA_VERSION_FEATURES) 476 return (B_FALSE); 477 478 err = feature_get_refcount(spa, &spa_feature_table[fid], &refcount); 479 ASSERT(err == 0 || err == ENOTSUP); 480 return (err == 0 && refcount > 0); 481 } 482 483 /* 484 * For the feature specified by fid (which must depend on 485 * SPA_FEATURE_ENABLED_TXG), return the TXG at which it was enabled in the 486 * OUT txg argument. 487 * 488 * Returns B_TRUE if the feature is enabled, in which case txg will be filled 489 * with the transaction group in which the specified feature was enabled. 490 * Returns B_FALSE otherwise (i.e. if the feature is not enabled). 491 */ 492 boolean_t 493 spa_feature_enabled_txg(spa_t *spa, spa_feature_t fid, uint64_t *txg) 494 { 495 int err; 496 497 ASSERT(VALID_FEATURE_FID(fid)); 498 if (spa_version(spa) < SPA_VERSION_FEATURES) 499 return (B_FALSE); 500 501 err = feature_get_enabled_txg(spa, &spa_feature_table[fid], txg); 502 ASSERT(err == 0 || err == ENOTSUP); 503 504 return (err == 0); 505 } 506