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Diffstat (limited to 'sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfeature.c')
| -rw-r--r-- | sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfeature.c | 414 |
1 files changed, 414 insertions, 0 deletions
diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfeature.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfeature.c new file mode 100644 index 0000000..ba72208 --- /dev/null +++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfeature.c @@ -0,0 +1,414 @@ +/* + * CDDL HEADER START + * + * The contents of this file are subject to the terms of the + * Common Development and Distribution License (the "License"). + * You may not use this file except in compliance with the License. + * + * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE + * or http://www.opensolaris.org/os/licensing. + * See the License for the specific language governing permissions + * and limitations under the License. + * + * When distributing Covered Code, include this CDDL HEADER in each + * file and include the License file at usr/src/OPENSOLARIS.LICENSE. + * If applicable, add the following below this CDDL HEADER, with the + * fields enclosed by brackets "[]" replaced with your own identifying + * information: Portions Copyright [yyyy] [name of copyright owner] + * + * CDDL HEADER END + */ + +/* + * Copyright (c) 2012 by Delphix. All rights reserved. + */ + +#include <sys/zfs_context.h> +#include <sys/zfeature.h> +#include <sys/dmu.h> +#include <sys/nvpair.h> +#include <sys/zap.h> +#include <sys/dmu_tx.h> +#include "zfeature_common.h" +#include <sys/spa_impl.h> + +/* + * ZFS Feature Flags + * ----------------- + * + * ZFS feature flags are used to provide fine-grained versioning to the ZFS + * on-disk format. Once enabled on a pool feature flags replace the old + * spa_version() number. + * + * Each new on-disk format change will be given a uniquely identifying string + * guid rather than a version number. This avoids the problem of different + * organizations creating new on-disk formats with the same version number. To + * keep feature guids unique they should consist of the reverse dns name of the + * organization which implemented the feature and a short name for the feature, + * separated by a colon (e.g. com.delphix:async_destroy). + * + * Reference Counts + * ---------------- + * + * Within each pool features can be in one of three states: disabled, enabled, + * or active. These states are differentiated by a reference count stored on + * disk for each feature: + * + * 1) If there is no reference count stored on disk the feature is disabled. + * 2) If the reference count is 0 a system administrator has enabled the + * feature, but the feature has not been used yet, so no on-disk + * format changes have been made. + * 3) If the reference count is greater than 0 the feature is active. + * The format changes required by the feature are currently on disk. + * Note that if the feature's format changes are reversed the feature + * may choose to set its reference count back to 0. + * + * Feature flags makes no differentiation between non-zero reference counts + * for an active feature (e.g. a reference count of 1 means the same thing as a + * reference count of 27834721), but feature implementations may choose to use + * the reference count to store meaningful information. For example, a new RAID + * implementation might set the reference count to the number of vdevs using + * it. If all those disks are removed from the pool the feature goes back to + * having a reference count of 0. + * + * It is the responsibility of the individual features to maintain a non-zero + * reference count as long as the feature's format changes are present on disk. + * + * Dependencies + * ------------ + * + * Each feature may depend on other features. The only effect of this + * relationship is that when a feature is enabled all of its dependencies are + * automatically enabled as well. Any future work to support disabling of + * features would need to ensure that features cannot be disabled if other + * enabled features depend on them. + * + * On-disk Format + * -------------- + * + * When feature flags are enabled spa_version() is set to SPA_VERSION_FEATURES + * (5000). In order for this to work the pool is automatically upgraded to + * SPA_VERSION_BEFORE_FEATURES (28) first, so all pre-feature flags on disk + * format changes will be in use. + * + * Information about features is stored in 3 ZAP objects in the pool's MOS. + * These objects are linked to by the following names in the pool directory + * object: + * + * 1) features_for_read: feature guid -> reference count + * Features needed to open the pool for reading. + * 2) features_for_write: feature guid -> reference count + * Features needed to open the pool for writing. + * 3) feature_descriptions: feature guid -> descriptive string + * A human readable string. + * + * All enabled features appear in either features_for_read or + * features_for_write, but not both. + * + * To open a pool in read-only mode only the features listed in + * features_for_read need to be supported. + * + * To open the pool in read-write mode features in both features_for_read and + * features_for_write need to be supported. + * + * Some features may be required to read the ZAP objects containing feature + * information. To allow software to check for compatibility with these features + * before the pool is opened their names must be stored in the label in a + * new "features_for_read" entry (note that features that are only required + * to write to a pool never need to be stored in the label since the + * features_for_write ZAP object can be read before the pool is written to). + * To save space in the label features must be explicitly marked as needing to + * be written to the label. Also, reference counts are not stored in the label, + * instead any feature whose reference count drops to 0 is removed from the + * label. + * + * Adding New Features + * ------------------- + * + * Features must be registered in zpool_feature_init() function in + * zfeature_common.c using the zfeature_register() function. This function + * has arguments to specify if the feature should be stored in the + * features_for_read or features_for_write ZAP object and if it needs to be + * written to the label when active. + * + * Once a feature is registered it will appear as a "feature@<feature name>" + * property which can be set by an administrator. Feature implementors should + * use the spa_feature_is_enabled() and spa_feature_is_active() functions to + * query the state of a feature and the spa_feature_incr() and + * spa_feature_decr() functions to change an enabled feature's reference count. + * Reference counts may only be updated in the syncing context. + * + * Features may not perform enable-time initialization. Instead, any such + * initialization should occur when the feature is first used. This design + * enforces that on-disk changes be made only when features are used. Code + * should only check if a feature is enabled using spa_feature_is_enabled(), + * not by relying on any feature specific metadata existing. If a feature is + * enabled, but the feature's metadata is not on disk yet then it should be + * created as needed. + * + * As an example, consider the com.delphix:async_destroy feature. This feature + * relies on the existence of a bptree in the MOS that store blocks for + * asynchronous freeing. This bptree is not created when async_destroy is + * enabled. Instead, when a dataset is destroyed spa_feature_is_enabled() is + * called to check if async_destroy is enabled. If it is and the bptree object + * does not exist yet, the bptree object is created as part of the dataset + * destroy and async_destroy's reference count is incremented to indicate it + * has made an on-disk format change. Later, after the destroyed dataset's + * blocks have all been asynchronously freed there is no longer any use for the + * bptree object, so it is destroyed and async_destroy's reference count is + * decremented back to 0 to indicate that it has undone its on-disk format + * changes. + */ + +typedef enum { + FEATURE_ACTION_ENABLE, + FEATURE_ACTION_INCR, + FEATURE_ACTION_DECR, +} feature_action_t; + +/* + * Checks that the features active in the specified object are supported by + * this software. Adds each unsupported feature (name -> description) to + * the supplied nvlist. + */ +boolean_t +feature_is_supported(objset_t *os, uint64_t obj, uint64_t desc_obj, + nvlist_t *unsup_feat) +{ + boolean_t supported; + zap_cursor_t zc; + zap_attribute_t za; + + supported = B_TRUE; + for (zap_cursor_init(&zc, os, obj); + zap_cursor_retrieve(&zc, &za) == 0; + zap_cursor_advance(&zc)) { + ASSERT(za.za_integer_length == sizeof (uint64_t) && + za.za_num_integers == 1); + + if (za.za_first_integer != 0 && + !zfeature_is_supported(za.za_name)) { + supported = B_FALSE; + + if (unsup_feat != NULL) { + char *desc = ""; + char buf[MAXPATHLEN]; + + if (zap_lookup(os, desc_obj, za.za_name, + 1, sizeof (buf), buf) == 0) + desc = buf; + + VERIFY(nvlist_add_string(unsup_feat, za.za_name, + desc) == 0); + } + } + } + zap_cursor_fini(&zc); + + return (supported); +} + +static int +feature_get_refcount(objset_t *os, uint64_t read_obj, uint64_t write_obj, + zfeature_info_t *feature, uint64_t *res) +{ + int err; + uint64_t refcount; + uint64_t zapobj = feature->fi_can_readonly ? write_obj : read_obj; + + ASSERT(0 != zapobj); + + err = zap_lookup(os, zapobj, feature->fi_guid, sizeof (uint64_t), 1, + &refcount); + if (err != 0) { + if (err == ENOENT) + return (ENOTSUP); + else + return (err); + } + *res = refcount; + return (0); +} + +static int +feature_do_action(objset_t *os, uint64_t read_obj, uint64_t write_obj, + uint64_t desc_obj, zfeature_info_t *feature, feature_action_t action, + dmu_tx_t *tx) +{ + int error; + uint64_t refcount; + uint64_t zapobj = feature->fi_can_readonly ? write_obj : read_obj; + + ASSERT(0 != zapobj); + ASSERT(zfeature_is_valid_guid(feature->fi_guid)); + + error = zap_lookup(os, zapobj, feature->fi_guid, + sizeof (uint64_t), 1, &refcount); + + /* + * If we can't ascertain the status of the specified feature, an I/O + * error occurred. + */ + if (error != 0 && error != ENOENT) + return (error); + + switch (action) { + case FEATURE_ACTION_ENABLE: + /* + * If the feature is already enabled, ignore the request. + */ + if (error == 0) + return (0); + refcount = 0; + break; + case FEATURE_ACTION_INCR: + if (error == ENOENT) + return (ENOTSUP); + if (refcount == UINT64_MAX) + return (EOVERFLOW); + refcount++; + break; + case FEATURE_ACTION_DECR: + if (error == ENOENT) + return (ENOTSUP); + if (refcount == 0) + return (EOVERFLOW); + refcount--; + break; + default: + ASSERT(0); + break; + } + + if (action == FEATURE_ACTION_ENABLE) { + int i; + + for (i = 0; feature->fi_depends[i] != NULL; i++) { + zfeature_info_t *dep = feature->fi_depends[i]; + + error = feature_do_action(os, read_obj, write_obj, + desc_obj, dep, FEATURE_ACTION_ENABLE, tx); + if (error != 0) + return (error); + } + } + + error = zap_update(os, zapobj, feature->fi_guid, + sizeof (uint64_t), 1, &refcount, tx); + if (error != 0) + return (error); + + if (action == FEATURE_ACTION_ENABLE) { + error = zap_update(os, desc_obj, + feature->fi_guid, 1, strlen(feature->fi_desc) + 1, + feature->fi_desc, tx); + if (error != 0) + return (error); + } + + if (action == FEATURE_ACTION_INCR && refcount == 1 && feature->fi_mos) { + spa_activate_mos_feature(dmu_objset_spa(os), feature->fi_guid); + } + + if (action == FEATURE_ACTION_DECR && refcount == 0) { + spa_deactivate_mos_feature(dmu_objset_spa(os), + feature->fi_guid); + } + + return (0); +} + +void +spa_feature_create_zap_objects(spa_t *spa, dmu_tx_t *tx) +{ + /* + * We create feature flags ZAP objects in two instances: during pool + * creation and during pool upgrade. + */ + ASSERT(dsl_pool_sync_context(spa_get_dsl(spa)) || (!spa->spa_sync_on && + tx->tx_txg == TXG_INITIAL)); + + spa->spa_feat_for_read_obj = zap_create_link(spa->spa_meta_objset, + DMU_OTN_ZAP_METADATA, DMU_POOL_DIRECTORY_OBJECT, + DMU_POOL_FEATURES_FOR_READ, tx); + spa->spa_feat_for_write_obj = zap_create_link(spa->spa_meta_objset, + DMU_OTN_ZAP_METADATA, DMU_POOL_DIRECTORY_OBJECT, + DMU_POOL_FEATURES_FOR_WRITE, tx); + spa->spa_feat_desc_obj = zap_create_link(spa->spa_meta_objset, + DMU_OTN_ZAP_METADATA, DMU_POOL_DIRECTORY_OBJECT, + DMU_POOL_FEATURE_DESCRIPTIONS, tx); +} + +/* + * Enable any required dependencies, then enable the requested feature. + */ +void +spa_feature_enable(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx) +{ + ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES); + VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset, + spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj, + spa->spa_feat_desc_obj, feature, FEATURE_ACTION_ENABLE, tx)); +} + +/* + * If the specified feature has not yet been enabled, this function returns + * ENOTSUP; otherwise, this function increments the feature's refcount (or + * returns EOVERFLOW if the refcount cannot be incremented). This function must + * be called from syncing context. + */ +void +spa_feature_incr(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx) +{ + ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES); + VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset, + spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj, + spa->spa_feat_desc_obj, feature, FEATURE_ACTION_INCR, tx)); +} + +/* + * If the specified feature has not yet been enabled, this function returns + * ENOTSUP; otherwise, this function decrements the feature's refcount (or + * returns EOVERFLOW if the refcount is already 0). This function must + * be called from syncing context. + */ +void +spa_feature_decr(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx) +{ + ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES); + VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset, + spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj, + spa->spa_feat_desc_obj, feature, FEATURE_ACTION_DECR, tx)); +} + +boolean_t +spa_feature_is_enabled(spa_t *spa, zfeature_info_t *feature) +{ + int err; + uint64_t refcount; + + if (spa_version(spa) < SPA_VERSION_FEATURES) + return (B_FALSE); + + err = feature_get_refcount(spa->spa_meta_objset, + spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj, + feature, &refcount); + ASSERT(err == 0 || err == ENOTSUP); + return (err == 0); +} + +boolean_t +spa_feature_is_active(spa_t *spa, zfeature_info_t *feature) +{ + int err; + uint64_t refcount; + + if (spa_version(spa) < SPA_VERSION_FEATURES) + return (B_FALSE); + + err = feature_get_refcount(spa->spa_meta_objset, + spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj, + feature, &refcount); + ASSERT(err == 0 || err == ENOTSUP); + return (err == 0 && refcount > 0); +} |
