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3006 VERIFY[S,U,P] and ASSERT[S,U,P] frequently check if first argument is zero
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--- old/usr/src/uts/common/fs/zfs/zfeature.c
+++ new/usr/src/uts/common/fs/zfs/zfeature.c
1 1 /*
2 2 * CDDL HEADER START
3 3 *
4 4 * The contents of this file are subject to the terms of the
5 5 * Common Development and Distribution License (the "License").
6 6 * You may not use this file except in compliance with the License.
7 7 *
8 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 9 * or http://www.opensolaris.org/os/licensing.
10 10 * See the License for the specific language governing permissions
11 11 * and limitations under the License.
12 12 *
13 13 * When distributing Covered Code, include this CDDL HEADER in each
14 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 15 * If applicable, add the following below this CDDL HEADER, with the
16 16 * fields enclosed by brackets "[]" replaced with your own identifying
17 17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 18 *
19 19 * CDDL HEADER END
20 20 */
21 21
22 22 /*
23 23 * Copyright (c) 2012 by Delphix. All rights reserved.
24 24 */
25 25
26 26 #include <sys/zfs_context.h>
27 27 #include <sys/zfeature.h>
28 28 #include <sys/dmu.h>
29 29 #include <sys/nvpair.h>
30 30 #include <sys/zap.h>
31 31 #include <sys/dmu_tx.h>
32 32 #include "zfeature_common.h"
33 33 #include <sys/spa_impl.h>
34 34
35 35 /*
36 36 * ZFS Feature Flags
37 37 * -----------------
38 38 *
39 39 * ZFS feature flags are used to provide fine-grained versioning to the ZFS
40 40 * on-disk format. Once enabled on a pool feature flags replace the old
41 41 * spa_version() number.
42 42 *
43 43 * Each new on-disk format change will be given a uniquely identifying string
44 44 * guid rather than a version number. This avoids the problem of different
45 45 * organizations creating new on-disk formats with the same version number. To
46 46 * keep feature guids unique they should consist of the reverse dns name of the
47 47 * organization which implemented the feature and a short name for the feature,
48 48 * separated by a colon (e.g. com.delphix:async_destroy).
49 49 *
50 50 * Reference Counts
51 51 * ----------------
52 52 *
53 53 * Within each pool features can be in one of three states: disabled, enabled,
54 54 * or active. These states are differentiated by a reference count stored on
55 55 * disk for each feature:
56 56 *
57 57 * 1) If there is no reference count stored on disk the feature is disabled.
58 58 * 2) If the reference count is 0 a system administrator has enabled the
59 59 * feature, but the feature has not been used yet, so no on-disk
60 60 * format changes have been made.
61 61 * 3) If the reference count is greater than 0 the feature is active.
62 62 * The format changes required by the feature are currently on disk.
63 63 * Note that if the feature's format changes are reversed the feature
64 64 * may choose to set its reference count back to 0.
65 65 *
66 66 * Feature flags makes no differentiation between non-zero reference counts
67 67 * for an active feature (e.g. a reference count of 1 means the same thing as a
68 68 * reference count of 27834721), but feature implementations may choose to use
69 69 * the reference count to store meaningful information. For example, a new RAID
70 70 * implementation might set the reference count to the number of vdevs using
71 71 * it. If all those disks are removed from the pool the feature goes back to
72 72 * having a reference count of 0.
73 73 *
74 74 * It is the responsibility of the individual features to maintain a non-zero
75 75 * reference count as long as the feature's format changes are present on disk.
76 76 *
77 77 * Dependencies
78 78 * ------------
79 79 *
80 80 * Each feature may depend on other features. The only effect of this
81 81 * relationship is that when a feature is enabled all of its dependencies are
82 82 * automatically enabled as well. Any future work to support disabling of
83 83 * features would need to ensure that features cannot be disabled if other
84 84 * enabled features depend on them.
85 85 *
86 86 * On-disk Format
87 87 * --------------
88 88 *
89 89 * When feature flags are enabled spa_version() is set to SPA_VERSION_FEATURES
90 90 * (5000). In order for this to work the pool is automatically upgraded to
91 91 * SPA_VERSION_BEFORE_FEATURES (28) first, so all pre-feature flags on disk
92 92 * format changes will be in use.
93 93 *
94 94 * Information about features is stored in 3 ZAP objects in the pool's MOS.
95 95 * These objects are linked to by the following names in the pool directory
96 96 * object:
97 97 *
98 98 * 1) features_for_read: feature guid -> reference count
99 99 * Features needed to open the pool for reading.
100 100 * 2) features_for_write: feature guid -> reference count
101 101 * Features needed to open the pool for writing.
102 102 * 3) feature_descriptions: feature guid -> descriptive string
103 103 * A human readable string.
104 104 *
105 105 * All enabled features appear in either features_for_read or
106 106 * features_for_write, but not both.
107 107 *
108 108 * To open a pool in read-only mode only the features listed in
109 109 * features_for_read need to be supported.
110 110 *
111 111 * To open the pool in read-write mode features in both features_for_read and
112 112 * features_for_write need to be supported.
113 113 *
114 114 * Some features may be required to read the ZAP objects containing feature
115 115 * information. To allow software to check for compatibility with these features
116 116 * before the pool is opened their names must be stored in the label in a
117 117 * new "features_for_read" entry (note that features that are only required
118 118 * to write to a pool never need to be stored in the label since the
119 119 * features_for_write ZAP object can be read before the pool is written to).
120 120 * To save space in the label features must be explicitly marked as needing to
121 121 * be written to the label. Also, reference counts are not stored in the label,
122 122 * instead any feature whose reference count drops to 0 is removed from the
123 123 * label.
124 124 *
125 125 * Adding New Features
126 126 * -------------------
127 127 *
128 128 * Features must be registered in zpool_feature_init() function in
129 129 * zfeature_common.c using the zfeature_register() function. This function
130 130 * has arguments to specify if the feature should be stored in the
131 131 * features_for_read or features_for_write ZAP object and if it needs to be
132 132 * written to the label when active.
133 133 *
134 134 * Once a feature is registered it will appear as a "feature@<feature name>"
135 135 * property which can be set by an administrator. Feature implementors should
136 136 * use the spa_feature_is_enabled() and spa_feature_is_active() functions to
137 137 * query the state of a feature and the spa_feature_incr() and
138 138 * spa_feature_decr() functions to change an enabled feature's reference count.
139 139 * Reference counts may only be updated in the syncing context.
140 140 *
141 141 * Features may not perform enable-time initialization. Instead, any such
142 142 * initialization should occur when the feature is first used. This design
143 143 * enforces that on-disk changes be made only when features are used. Code
144 144 * should only check if a feature is enabled using spa_feature_is_enabled(),
145 145 * not by relying on any feature specific metadata existing. If a feature is
146 146 * enabled, but the feature's metadata is not on disk yet then it should be
147 147 * created as needed.
148 148 *
149 149 * As an example, consider the com.delphix:async_destroy feature. This feature
150 150 * relies on the existence of a bptree in the MOS that store blocks for
151 151 * asynchronous freeing. This bptree is not created when async_destroy is
152 152 * enabled. Instead, when a dataset is destroyed spa_feature_is_enabled() is
153 153 * called to check if async_destroy is enabled. If it is and the bptree object
154 154 * does not exist yet, the bptree object is created as part of the dataset
155 155 * destroy and async_destroy's reference count is incremented to indicate it
156 156 * has made an on-disk format change. Later, after the destroyed dataset's
157 157 * blocks have all been asynchronously freed there is no longer any use for the
158 158 * bptree object, so it is destroyed and async_destroy's reference count is
159 159 * decremented back to 0 to indicate that it has undone its on-disk format
160 160 * changes.
161 161 */
162 162
163 163 typedef enum {
164 164 FEATURE_ACTION_ENABLE,
165 165 FEATURE_ACTION_INCR,
166 166 FEATURE_ACTION_DECR,
167 167 } feature_action_t;
168 168
169 169 /*
170 170 * Checks that the features active in the specified object are supported by
171 171 * this software. Adds each unsupported feature (name -> description) to
172 172 * the supplied nvlist.
173 173 */
174 174 boolean_t
175 175 feature_is_supported(objset_t *os, uint64_t obj, uint64_t desc_obj,
176 176 nvlist_t *unsup_feat)
177 177 {
178 178 boolean_t supported;
179 179 zap_cursor_t zc;
180 180 zap_attribute_t za;
181 181
182 182 supported = B_TRUE;
183 183 for (zap_cursor_init(&zc, os, obj);
184 184 zap_cursor_retrieve(&zc, &za) == 0;
185 185 zap_cursor_advance(&zc)) {
186 186 ASSERT(za.za_integer_length == sizeof (uint64_t) &&
187 187 za.za_num_integers == 1);
188 188
189 189 if (za.za_first_integer != 0 &&
190 190 !zfeature_is_supported(za.za_name)) {
191 191 supported = B_FALSE;
192 192
193 193 if (unsup_feat != NULL) {
194 194 char *desc = "";
195 195 char buf[MAXPATHLEN];
196 196
197 197 if (zap_lookup(os, desc_obj, za.za_name,
198 198 1, sizeof (buf), buf) == 0)
199 199 desc = buf;
200 200
201 201 VERIFY(nvlist_add_string(unsup_feat, za.za_name,
202 202 desc) == 0);
203 203 }
204 204 }
205 205 }
206 206 zap_cursor_fini(&zc);
207 207
208 208 return (supported);
209 209 }
210 210
211 211 static int
212 212 feature_get_refcount(objset_t *os, uint64_t read_obj, uint64_t write_obj,
213 213 zfeature_info_t *feature, uint64_t *res)
214 214 {
215 215 int err;
216 216 uint64_t refcount;
217 217 uint64_t zapobj = feature->fi_can_readonly ? write_obj : read_obj;
218 218
219 219 ASSERT(0 != zapobj);
220 220
221 221 err = zap_lookup(os, zapobj, feature->fi_guid, sizeof (uint64_t), 1,
222 222 &refcount);
223 223 if (err != 0) {
224 224 if (err == ENOENT)
225 225 return (ENOTSUP);
226 226 else
227 227 return (err);
228 228 }
229 229 *res = refcount;
230 230 return (0);
231 231 }
232 232
233 233 static int
234 234 feature_do_action(objset_t *os, uint64_t read_obj, uint64_t write_obj,
235 235 uint64_t desc_obj, zfeature_info_t *feature, feature_action_t action,
236 236 dmu_tx_t *tx)
237 237 {
238 238 int error;
239 239 uint64_t refcount;
240 240 uint64_t zapobj = feature->fi_can_readonly ? write_obj : read_obj;
241 241
242 242 ASSERT(0 != zapobj);
243 243 ASSERT(zfeature_is_valid_guid(feature->fi_guid));
244 244
245 245 error = zap_lookup(os, zapobj, feature->fi_guid,
246 246 sizeof (uint64_t), 1, &refcount);
247 247
248 248 /*
249 249 * If we can't ascertain the status of the specified feature, an I/O
250 250 * error occurred.
251 251 */
252 252 if (error != 0 && error != ENOENT)
253 253 return (error);
254 254
255 255 switch (action) {
256 256 case FEATURE_ACTION_ENABLE:
257 257 /*
258 258 * If the feature is already enabled, ignore the request.
259 259 */
260 260 if (error == 0)
261 261 return (0);
262 262 refcount = 0;
263 263 break;
264 264 case FEATURE_ACTION_INCR:
265 265 if (error == ENOENT)
266 266 return (ENOTSUP);
267 267 if (refcount == UINT64_MAX)
268 268 return (EOVERFLOW);
269 269 refcount++;
270 270 break;
271 271 case FEATURE_ACTION_DECR:
272 272 if (error == ENOENT)
273 273 return (ENOTSUP);
274 274 if (refcount == 0)
275 275 return (EOVERFLOW);
276 276 refcount--;
277 277 break;
278 278 default:
279 279 ASSERT(0);
280 280 break;
281 281 }
282 282
283 283 if (action == FEATURE_ACTION_ENABLE) {
284 284 int i;
285 285
286 286 for (i = 0; feature->fi_depends[i] != NULL; i++) {
287 287 zfeature_info_t *dep = feature->fi_depends[i];
288 288
289 289 error = feature_do_action(os, read_obj, write_obj,
290 290 desc_obj, dep, FEATURE_ACTION_ENABLE, tx);
291 291 if (error != 0)
292 292 return (error);
293 293 }
294 294 }
295 295
296 296 error = zap_update(os, zapobj, feature->fi_guid,
297 297 sizeof (uint64_t), 1, &refcount, tx);
298 298 if (error != 0)
299 299 return (error);
300 300
301 301 if (action == FEATURE_ACTION_ENABLE) {
302 302 error = zap_update(os, desc_obj,
303 303 feature->fi_guid, 1, strlen(feature->fi_desc) + 1,
304 304 feature->fi_desc, tx);
305 305 if (error != 0)
306 306 return (error);
307 307 }
308 308
309 309 if (action == FEATURE_ACTION_INCR && refcount == 1 && feature->fi_mos) {
310 310 spa_activate_mos_feature(dmu_objset_spa(os), feature->fi_guid);
311 311 }
312 312
313 313 if (action == FEATURE_ACTION_DECR && refcount == 0) {
314 314 spa_deactivate_mos_feature(dmu_objset_spa(os),
315 315 feature->fi_guid);
316 316 }
317 317
318 318 return (0);
319 319 }
320 320
321 321 void
322 322 spa_feature_create_zap_objects(spa_t *spa, dmu_tx_t *tx)
323 323 {
324 324 /*
325 325 * We create feature flags ZAP objects in two instances: during pool
326 326 * creation and during pool upgrade.
327 327 */
328 328 ASSERT(dsl_pool_sync_context(spa_get_dsl(spa)) || (!spa->spa_sync_on &&
329 329 tx->tx_txg == TXG_INITIAL));
330 330
331 331 spa->spa_feat_for_read_obj = zap_create_link(spa->spa_meta_objset,
332 332 DMU_OTN_ZAP_METADATA, DMU_POOL_DIRECTORY_OBJECT,
333 333 DMU_POOL_FEATURES_FOR_READ, tx);
334 334 spa->spa_feat_for_write_obj = zap_create_link(spa->spa_meta_objset,
335 335 DMU_OTN_ZAP_METADATA, DMU_POOL_DIRECTORY_OBJECT,
336 336 DMU_POOL_FEATURES_FOR_WRITE, tx);
337 337 spa->spa_feat_desc_obj = zap_create_link(spa->spa_meta_objset,
338 338 DMU_OTN_ZAP_METADATA, DMU_POOL_DIRECTORY_OBJECT,
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339 339 DMU_POOL_FEATURE_DESCRIPTIONS, tx);
340 340 }
341 341
342 342 /*
343 343 * Enable any required dependencies, then enable the requested feature.
344 344 */
345 345 void
346 346 spa_feature_enable(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx)
347 347 {
348 348 ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
349 - VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset,
349 + VERIFY0(feature_do_action(spa->spa_meta_objset,
350 350 spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
351 351 spa->spa_feat_desc_obj, feature, FEATURE_ACTION_ENABLE, tx));
352 352 }
353 353
354 354 /*
355 355 * If the specified feature has not yet been enabled, this function returns
356 356 * ENOTSUP; otherwise, this function increments the feature's refcount (or
357 357 * returns EOVERFLOW if the refcount cannot be incremented). This function must
358 358 * be called from syncing context.
359 359 */
360 360 void
361 361 spa_feature_incr(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx)
362 362 {
363 363 ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
364 - VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset,
364 + VERIFY0(feature_do_action(spa->spa_meta_objset,
365 365 spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
366 366 spa->spa_feat_desc_obj, feature, FEATURE_ACTION_INCR, tx));
367 367 }
368 368
369 369 /*
370 370 * If the specified feature has not yet been enabled, this function returns
371 371 * ENOTSUP; otherwise, this function decrements the feature's refcount (or
372 372 * returns EOVERFLOW if the refcount is already 0). This function must
373 373 * be called from syncing context.
374 374 */
375 375 void
376 376 spa_feature_decr(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx)
377 377 {
378 378 ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
379 - VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset,
379 + VERIFY0(feature_do_action(spa->spa_meta_objset,
380 380 spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
381 381 spa->spa_feat_desc_obj, feature, FEATURE_ACTION_DECR, tx));
382 382 }
383 383
384 384 boolean_t
385 385 spa_feature_is_enabled(spa_t *spa, zfeature_info_t *feature)
386 386 {
387 387 int err;
388 388 uint64_t refcount;
389 389
390 390 if (spa_version(spa) < SPA_VERSION_FEATURES)
391 391 return (B_FALSE);
392 392
393 393 err = feature_get_refcount(spa->spa_meta_objset,
394 394 spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
395 395 feature, &refcount);
396 396 ASSERT(err == 0 || err == ENOTSUP);
397 397 return (err == 0);
398 398 }
399 399
400 400 boolean_t
401 401 spa_feature_is_active(spa_t *spa, zfeature_info_t *feature)
402 402 {
403 403 int err;
404 404 uint64_t refcount;
405 405
406 406 if (spa_version(spa) < SPA_VERSION_FEATURES)
407 407 return (B_FALSE);
408 408
409 409 err = feature_get_refcount(spa->spa_meta_objset,
410 410 spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
411 411 feature, &refcount);
412 412 ASSERT(err == 0 || err == ENOTSUP);
413 413 return (err == 0 && refcount > 0);
414 414 }
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