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.
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.
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]
23 * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
26 #include <sys/zfs_context.h>
27 #include <sys/zfeature.h>
29 #include <sys/nvpair.h>
31 #include <sys/dmu_tx.h>
32 #include "zfeature_common.h"
33 #include <sys/spa_impl.h>
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.
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).
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:
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.
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.
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.
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.
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.
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
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.
105 * All enabled features appear in either features_for_read or
106 * features_for_write, but not both.
108 * To open a pool in read-only mode only the features listed in
109 * features_for_read need to be supported.
111 * To open the pool in read-write mode features in both features_for_read and
112 * features_for_write need to be supported.
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
125 * Adding New Features
126 * -------------------
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.
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.
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
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
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.
174 spa_features_check(spa_t
*spa
, boolean_t for_write
,
175 nvlist_t
*unsup_feat
, nvlist_t
*enabled_feat
)
177 objset_t
*os
= spa
->spa_meta_objset
;
181 uint64_t obj
= for_write
?
182 spa
->spa_feat_for_write_obj
: spa
->spa_feat_for_read_obj
;
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);
191 if (NULL
!= enabled_feat
) {
192 fnvlist_add_uint64(enabled_feat
, za
.za_name
,
193 za
.za_first_integer
);
196 if (za
.za_first_integer
!= 0 &&
197 !zfeature_is_supported(za
.za_name
)) {
200 if (NULL
!= unsup_feat
) {
202 char buf
[MAXPATHLEN
];
204 if (zap_lookup(os
, spa
->spa_feat_desc_obj
,
205 za
.za_name
, 1, sizeof (buf
), buf
) == 0)
208 VERIFY(nvlist_add_string(unsup_feat
, za
.za_name
,
213 zap_cursor_fini(&zc
);
219 * Use an in-memory cache of feature refcounts for quick retrieval.
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.
226 feature_get_refcount(spa_t
*spa
, zfeature_info_t
*feature
, uint64_t *res
)
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
));
233 *res
= spa
->spa_feat_refcount_cache
[feature
->fi_feature
];
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.
243 feature_get_refcount_from_disk(spa_t
*spa
, zfeature_info_t
*feature
,
248 uint64_t zapobj
= (feature
->fi_flags
& ZFEATURE_FLAG_READONLY_COMPAT
) ?
249 spa
->spa_feat_for_write_obj
: spa
->spa_feat_for_read_obj
;
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.
256 return (SET_ERROR(ENOTSUP
));
258 err
= zap_lookup(spa
->spa_meta_objset
, zapobj
,
259 feature
->fi_guid
, sizeof (uint64_t), 1, &refcount
);
262 return (SET_ERROR(ENOTSUP
));
272 feature_get_enabled_txg(spa_t
*spa
, zfeature_info_t
*feature
, uint64_t *res
)
274 uint64_t enabled_txg_obj
= spa
->spa_feat_enabled_txg_obj
;
276 ASSERT(zfeature_depends_on(feature
->fi_feature
,
277 SPA_FEATURE_ENABLED_TXG
));
279 if (!spa_feature_is_enabled(spa
, feature
->fi_feature
)) {
280 return (SET_ERROR(ENOTSUP
));
283 ASSERT(enabled_txg_obj
!= 0);
285 VERIFY0(zap_lookup(spa
->spa_meta_objset
, spa
->spa_feat_enabled_txg_obj
,
286 feature
->fi_guid
, sizeof (uint64_t), 1, res
));
292 * This function is non-static for zhack; it should otherwise not be used
296 feature_sync(spa_t
*spa
, zfeature_info_t
*feature
, uint64_t refcount
,
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
;
303 VERIFY0(zap_update(spa
->spa_meta_objset
, zapobj
, feature
->fi_guid
,
304 sizeof (uint64_t), 1, &refcount
, tx
));
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
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
));
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
);
327 * This function is non-static for zhack; it should otherwise not be used
331 feature_enable_sync(spa_t
*spa
, zfeature_info_t
*feature
, dmu_tx_t
*tx
)
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
;
339 ASSERT(zfeature_is_valid_guid(feature
->fi_guid
));
340 ASSERT3U(spa_version(spa
), >=, SPA_VERSION_FEATURES
);
343 * If the feature is already enabled, ignore the request.
345 if (zap_contains(spa
->spa_meta_objset
, zapobj
, feature
->fi_guid
) == 0)
348 for (int i
= 0; feature
->fi_depends
[i
] != SPA_FEATURE_NONE
; i
++)
349 spa_feature_enable(spa
, feature
->fi_depends
[i
], tx
);
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
));
355 feature_sync(spa
, feature
, initial_refcount
, tx
);
357 if (spa_feature_is_enabled(spa
, SPA_FEATURE_ENABLED_TXG
)) {
358 uint64_t enabling_txg
= dmu_tx_get_txg(tx
);
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
);
366 spa_feature_incr(spa
, SPA_FEATURE_ENABLED_TXG
, tx
);
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
));
375 feature_do_action(spa_t
*spa
, spa_feature_t fid
, feature_action_t action
,
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
;
383 ASSERT(VALID_FEATURE_FID(fid
));
385 ASSERT(zfeature_is_valid_guid(feature
->fi_guid
));
387 ASSERT(dmu_tx_is_syncing(tx
));
388 ASSERT3U(spa_version(spa
), >=, SPA_VERSION_FEATURES
);
390 VERIFY3U(feature_get_refcount(spa
, feature
, &refcount
), !=, ENOTSUP
);
393 case FEATURE_ACTION_INCR
:
394 VERIFY3U(refcount
, !=, UINT64_MAX
);
397 case FEATURE_ACTION_DECR
:
398 VERIFY3U(refcount
, !=, 0);
406 feature_sync(spa
, feature
, refcount
, tx
);
410 spa_feature_create_zap_objects(spa_t
*spa
, dmu_tx_t
*tx
)
413 * We create feature flags ZAP objects in two instances: during pool
414 * creation and during pool upgrade.
416 ASSERT(dsl_pool_sync_context(spa_get_dsl(spa
)) || (!spa
->spa_sync_on
&&
417 tx
->tx_txg
== TXG_INITIAL
));
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
);
431 * Enable any required dependencies, then enable the requested feature.
434 spa_feature_enable(spa_t
*spa
, spa_feature_t fid
, dmu_tx_t
*tx
)
436 ASSERT3U(spa_version(spa
), >=, SPA_VERSION_FEATURES
);
437 ASSERT(VALID_FEATURE_FID(fid
));
438 feature_enable_sync(spa
, &spa_feature_table
[fid
], tx
);
442 spa_feature_incr(spa_t
*spa
, spa_feature_t fid
, dmu_tx_t
*tx
)
444 feature_do_action(spa
, fid
, FEATURE_ACTION_INCR
, tx
);
448 spa_feature_decr(spa_t
*spa
, spa_feature_t fid
, dmu_tx_t
*tx
)
450 feature_do_action(spa
, fid
, FEATURE_ACTION_DECR
, tx
);
454 spa_feature_is_enabled(spa_t
*spa
, spa_feature_t fid
)
459 ASSERT(VALID_FEATURE_FID(fid
));
460 if (spa_version(spa
) < SPA_VERSION_FEATURES
)
463 err
= feature_get_refcount(spa
, &spa_feature_table
[fid
], &refcount
);
464 ASSERT(err
== 0 || err
== ENOTSUP
);
469 spa_feature_is_active(spa_t
*spa
, spa_feature_t fid
)
474 ASSERT(VALID_FEATURE_FID(fid
));
475 if (spa_version(spa
) < SPA_VERSION_FEATURES
)
478 err
= feature_get_refcount(spa
, &spa_feature_table
[fid
], &refcount
);
479 ASSERT(err
== 0 || err
== ENOTSUP
);
480 return (err
== 0 && refcount
> 0);
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
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).
493 spa_feature_enabled_txg(spa_t
*spa
, spa_feature_t fid
, uint64_t *txg
)
497 ASSERT(VALID_FEATURE_FID(fid
));
498 if (spa_version(spa
) < SPA_VERSION_FEATURES
)
501 err
= feature_get_enabled_txg(spa
, &spa_feature_table
[fid
], txg
);
502 ASSERT(err
== 0 || err
== ENOTSUP
);