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+/*
+ * 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) 2011, 2015 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_INCR,
+ FEATURE_ACTION_DECR,
+} feature_action_t;
+
+/*
+ * Checks that the active features in the pool are supported by
+ * this software. Adds each unsupported feature (name -> description) to
+ * the supplied nvlist.
+ */
+boolean_t
+spa_features_check(spa_t *spa, boolean_t for_write,
+ nvlist_t *unsup_feat, nvlist_t *enabled_feat)
+{
+ objset_t *os = spa->spa_meta_objset;
+ boolean_t supported;
+ zap_cursor_t *zc;
+ zap_attribute_t *za;
+ uint64_t obj = for_write ?
+ spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj;
+ char *buf;
+
+ zc = kmem_alloc(sizeof (zap_cursor_t), KM_SLEEP);
+ za = kmem_alloc(sizeof (zap_attribute_t), KM_SLEEP);
+ buf = kmem_alloc(MAXPATHLEN, KM_SLEEP);
+
+ 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 (NULL != enabled_feat) {
+ fnvlist_add_uint64(enabled_feat, za->za_name,
+ za->za_first_integer);
+ }
+
+ if (za->za_first_integer != 0 &&
+ !zfeature_is_supported(za->za_name)) {
+ supported = B_FALSE;
+
+ if (NULL != unsup_feat) {
+ char *desc = "";
+
+ if (zap_lookup(os, spa->spa_feat_desc_obj,
+ za->za_name, 1, MAXPATHLEN, buf) == 0)
+ desc = buf;
+
+ VERIFY(nvlist_add_string(unsup_feat,
+ za->za_name, desc) == 0);
+ }
+ }
+ }
+ zap_cursor_fini(zc);
+
+ kmem_free(buf, MAXPATHLEN);
+ kmem_free(za, sizeof (zap_attribute_t));
+ kmem_free(zc, sizeof (zap_cursor_t));
+
+ return (supported);
+}
+
+/*
+ * Use an in-memory cache of feature refcounts for quick retrieval.
+ *
+ * Note: well-designed features will not need to use this; they should
+ * use spa_feature_is_enabled() and spa_feature_is_active() instead.
+ * However, this is non-static for zdb, zhack, and spa_add_feature_stats().
+ */
+int
+feature_get_refcount(spa_t *spa, zfeature_info_t *feature, uint64_t *res)
+{
+ ASSERT(VALID_FEATURE_FID(feature->fi_feature));
+ if (spa->spa_feat_refcount_cache[feature->fi_feature] ==
+ SPA_FEATURE_DISABLED) {
+ return (SET_ERROR(ENOTSUP));
+ }
+ *res = spa->spa_feat_refcount_cache[feature->fi_feature];
+ return (0);
+}
+
+/*
+ * Note: well-designed features will not need to use this; they should
+ * use spa_feature_is_enabled() and spa_feature_is_active() instead.
+ * However, this is non-static for zdb and zhack.
+ */
+int
+feature_get_refcount_from_disk(spa_t *spa, zfeature_info_t *feature,
+ uint64_t *res)
+{
+ int err;
+ uint64_t refcount;
+ uint64_t zapobj = (feature->fi_flags & ZFEATURE_FLAG_READONLY_COMPAT) ?
+ spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj;
+
+ /*
+ * If the pool is currently being created, the feature objects may not
+ * have been allocated yet. Act as though all features are disabled.
+ */
+ if (zapobj == 0)
+ return (SET_ERROR(ENOTSUP));
+
+ err = zap_lookup(spa->spa_meta_objset, zapobj,
+ feature->fi_guid, sizeof (uint64_t), 1, &refcount);
+ if (err != 0) {
+ if (err == ENOENT)
+ return (SET_ERROR(ENOTSUP));
+ else
+ return (err);
+ }
+ *res = refcount;
+ return (0);
+}
+
+
+static int
+feature_get_enabled_txg(spa_t *spa, zfeature_info_t *feature, uint64_t *res)
+{
+ uint64_t enabled_txg_obj __maybe_unused = spa->spa_feat_enabled_txg_obj;
+
+ ASSERT(zfeature_depends_on(feature->fi_feature,
+ SPA_FEATURE_ENABLED_TXG));
+
+ if (!spa_feature_is_enabled(spa, feature->fi_feature)) {
+ return (SET_ERROR(ENOTSUP));
+ }
+
+ ASSERT(enabled_txg_obj != 0);
+
+ VERIFY0(zap_lookup(spa->spa_meta_objset, spa->spa_feat_enabled_txg_obj,
+ feature->fi_guid, sizeof (uint64_t), 1, res));
+
+ return (0);
+}
+
+/*
+ * This function is non-static for zhack; it should otherwise not be used
+ * outside this file.
+ */
+void
+feature_sync(spa_t *spa, zfeature_info_t *feature, uint64_t refcount,
+ dmu_tx_t *tx)
+{
+ ASSERT(VALID_FEATURE_OR_NONE(feature->fi_feature));
+ uint64_t zapobj = (feature->fi_flags & ZFEATURE_FLAG_READONLY_COMPAT) ?
+ spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj;
+ VERIFY0(zap_update(spa->spa_meta_objset, zapobj, feature->fi_guid,
+ sizeof (uint64_t), 1, &refcount, tx));
+
+ /*
+ * feature_sync is called directly from zhack, allowing the
+ * creation of arbitrary features whose fi_feature field may
+ * be greater than SPA_FEATURES. When called from zhack, the
+ * zfeature_info_t object's fi_feature field will be set to
+ * SPA_FEATURE_NONE.
+ */
+ if (feature->fi_feature != SPA_FEATURE_NONE) {
+ uint64_t *refcount_cache =
+ &spa->spa_feat_refcount_cache[feature->fi_feature];
+ VERIFY3U(*refcount_cache, ==,
+ atomic_swap_64(refcount_cache, refcount));
+ }
+
+ if (refcount == 0)
+ spa_deactivate_mos_feature(spa, feature->fi_guid);
+ else if (feature->fi_flags & ZFEATURE_FLAG_MOS)
+ spa_activate_mos_feature(spa, feature->fi_guid, tx);
+}
+
+/*
+ * This function is non-static for zhack; it should otherwise not be used
+ * outside this file.
+ */
+void
+feature_enable_sync(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx)
+{
+ uint64_t initial_refcount =
+ (feature->fi_flags & ZFEATURE_FLAG_ACTIVATE_ON_ENABLE) ? 1 : 0;
+ uint64_t zapobj = (feature->fi_flags & ZFEATURE_FLAG_READONLY_COMPAT) ?
+ spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj;
+
+ ASSERT(0 != zapobj);
+ ASSERT(zfeature_is_valid_guid(feature->fi_guid));
+ ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
+
+ /*
+ * If the feature is already enabled, ignore the request.
+ */
+ if (zap_contains(spa->spa_meta_objset, zapobj, feature->fi_guid) == 0)
+ return;
+
+ for (int i = 0; feature->fi_depends[i] != SPA_FEATURE_NONE; i++)
+ spa_feature_enable(spa, feature->fi_depends[i], tx);
+
+ VERIFY0(zap_update(spa->spa_meta_objset, spa->spa_feat_desc_obj,
+ feature->fi_guid, 1, strlen(feature->fi_desc) + 1,
+ feature->fi_desc, tx));
+
+ feature_sync(spa, feature, initial_refcount, tx);
+
+ if (spa_feature_is_enabled(spa, SPA_FEATURE_ENABLED_TXG)) {
+ uint64_t enabling_txg = dmu_tx_get_txg(tx);
+
+ if (spa->spa_feat_enabled_txg_obj == 0ULL) {
+ spa->spa_feat_enabled_txg_obj =
+ zap_create_link(spa->spa_meta_objset,
+ DMU_OTN_ZAP_METADATA, DMU_POOL_DIRECTORY_OBJECT,
+ DMU_POOL_FEATURE_ENABLED_TXG, tx);
+ }
+ spa_feature_incr(spa, SPA_FEATURE_ENABLED_TXG, tx);
+
+ VERIFY0(zap_add(spa->spa_meta_objset,
+ spa->spa_feat_enabled_txg_obj, feature->fi_guid,
+ sizeof (uint64_t), 1, &enabling_txg, tx));
+ }
+
+ /*
+ * Errata #4 is mostly a problem with encrypted datasets, but it
+ * is also a problem where the old encryption feature did not
+ * depend on the bookmark_v2 feature. If the pool does not have
+ * any encrypted datasets we can resolve this issue simply by
+ * enabling this dependency.
+ */
+ if (spa->spa_errata == ZPOOL_ERRATA_ZOL_8308_ENCRYPTION &&
+ spa_feature_is_enabled(spa, SPA_FEATURE_ENCRYPTION) &&
+ !spa_feature_is_active(spa, SPA_FEATURE_ENCRYPTION) &&
+ feature->fi_feature == SPA_FEATURE_BOOKMARK_V2)
+ spa->spa_errata = 0;
+}
+
+static void
+feature_do_action(spa_t *spa, spa_feature_t fid, feature_action_t action,
+ dmu_tx_t *tx)
+{
+ uint64_t refcount = 0;
+ zfeature_info_t *feature = &spa_feature_table[fid];
+ uint64_t zapobj __maybe_unused =
+ (feature->fi_flags & ZFEATURE_FLAG_READONLY_COMPAT) ?
+ spa->spa_feat_for_write_obj : spa->spa_feat_for_read_obj;
+
+ ASSERT(VALID_FEATURE_FID(fid));
+ ASSERT(0 != zapobj);
+ ASSERT(zfeature_is_valid_guid(feature->fi_guid));
+
+ ASSERT(dmu_tx_is_syncing(tx));
+ ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
+
+ VERIFY3U(feature_get_refcount(spa, feature, &refcount), !=, ENOTSUP);
+
+ switch (action) {
+ case FEATURE_ACTION_INCR:
+ VERIFY3U(refcount, !=, UINT64_MAX);
+ refcount++;
+ break;
+ case FEATURE_ACTION_DECR:
+ VERIFY3U(refcount, !=, 0);
+ refcount--;
+ break;
+ default:
+ ASSERT(0);
+ break;
+ }
+
+ feature_sync(spa, feature, refcount, tx);
+}
+
+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((!spa->spa_sync_on && tx->tx_txg == TXG_INITIAL) ||
+ dsl_pool_sync_context(spa_get_dsl(spa)));
+
+ 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, spa_feature_t fid, dmu_tx_t *tx)
+{
+ ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
+ ASSERT(VALID_FEATURE_FID(fid));
+ feature_enable_sync(spa, &spa_feature_table[fid], tx);
+}
+
+void
+spa_feature_incr(spa_t *spa, spa_feature_t fid, dmu_tx_t *tx)
+{
+ feature_do_action(spa, fid, FEATURE_ACTION_INCR, tx);
+}
+
+void
+spa_feature_decr(spa_t *spa, spa_feature_t fid, dmu_tx_t *tx)
+{
+ feature_do_action(spa, fid, FEATURE_ACTION_DECR, tx);
+}
+
+boolean_t
+spa_feature_is_enabled(spa_t *spa, spa_feature_t fid)
+{
+ int err;
+ uint64_t refcount = 0;
+
+ ASSERT(VALID_FEATURE_FID(fid));
+ if (spa_version(spa) < SPA_VERSION_FEATURES)
+ return (B_FALSE);
+
+ err = feature_get_refcount(spa, &spa_feature_table[fid], &refcount);
+ ASSERT(err == 0 || err == ENOTSUP);
+ return (err == 0);
+}
+
+boolean_t
+spa_feature_is_active(spa_t *spa, spa_feature_t fid)
+{
+ int err;
+ uint64_t refcount = 0;
+
+ ASSERT(VALID_FEATURE_FID(fid));
+ if (spa_version(spa) < SPA_VERSION_FEATURES)
+ return (B_FALSE);
+
+ err = feature_get_refcount(spa, &spa_feature_table[fid], &refcount);
+ ASSERT(err == 0 || err == ENOTSUP);
+ return (err == 0 && refcount > 0);
+}
+
+/*
+ * For the feature specified by fid (which must depend on
+ * SPA_FEATURE_ENABLED_TXG), return the TXG at which it was enabled in the
+ * OUT txg argument.
+ *
+ * Returns B_TRUE if the feature is enabled, in which case txg will be filled
+ * with the transaction group in which the specified feature was enabled.
+ * Returns B_FALSE otherwise (i.e. if the feature is not enabled).
+ */
+boolean_t
+spa_feature_enabled_txg(spa_t *spa, spa_feature_t fid, uint64_t *txg)
+{
+ int err;
+
+ ASSERT(VALID_FEATURE_FID(fid));
+ if (spa_version(spa) < SPA_VERSION_FEATURES)
+ return (B_FALSE);
+
+ err = feature_get_enabled_txg(spa, &spa_feature_table[fid], txg);
+ ASSERT(err == 0 || err == ENOTSUP);
+
+ return (err == 0);
+}
generated by cgit v1.2.3 (git 2.25.1) at 2025-05-22 14:51:43 +0000