xref: /freebsd/sys/contrib/openzfs/module/zfs/spa_errlog.c (revision 67be1e195acfaec99ce4fffeb17111ce085755f7)
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 https://opensource.org/licenses/CDDL-1.0.
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  * Copyright (c) 2006, 2010, Oracle and/or its affiliates. All rights reserved.
23  * Copyright (c) 2013, 2014, Delphix. All rights reserved.
24  * Copyright (c) 2019 Datto Inc.
25  * Copyright (c) 2021, 2022, George Amanakis. All rights reserved.
26  */
27 
28 /*
29  * Routines to manage the on-disk persistent error log.
30  *
31  * Each pool stores a log of all logical data errors seen during normal
32  * operation.  This is actually the union of two distinct logs: the last log,
33  * and the current log.  All errors seen are logged to the current log.  When a
34  * scrub completes, the current log becomes the last log, the last log is thrown
35  * out, and the current log is reinitialized.  This way, if an error is somehow
36  * corrected, a new scrub will show that it no longer exists, and will be
37  * deleted from the log when the scrub completes.
38  *
39  * The log is stored using a ZAP object whose key is a string form of the
40  * zbookmark_phys tuple (objset, object, level, blkid), and whose contents is an
41  * optional 'objset:object' human-readable string describing the data.  When an
42  * error is first logged, this string will be empty, indicating that no name is
43  * known.  This prevents us from having to issue a potentially large amount of
44  * I/O to discover the object name during an error path.  Instead, we do the
45  * calculation when the data is requested, storing the result so future queries
46  * will be faster.
47  *
48  * If the head_errlog feature is enabled, a different on-disk format is used.
49  * The error log of each head dataset is stored separately in the zap object
50  * and keyed by the head id. This enables listing every dataset affected in
51  * userland. In order to be able to track whether an error block has been
52  * modified or added to snapshots since it was marked as an error, a new tuple
53  * is introduced: zbookmark_err_phys_t. It allows the storage of the birth
54  * transaction group of an error block on-disk. The birth transaction group is
55  * used by check_filesystem() to assess whether this block was freed,
56  * re-written or added to a snapshot since its marking as an error.
57  *
58  * This log is then shipped into an nvlist where the key is the dataset name and
59  * the value is the object name.  Userland is then responsible for uniquifying
60  * this list and displaying it to the user.
61  */
62 
63 #include <sys/dmu_tx.h>
64 #include <sys/spa.h>
65 #include <sys/spa_impl.h>
66 #include <sys/zap.h>
67 #include <sys/zio.h>
68 #include <sys/dsl_dir.h>
69 #include <sys/dmu_objset.h>
70 #include <sys/dbuf.h>
71 #include <sys/zfs_znode.h>
72 
73 #define	NAME_MAX_LEN 64
74 
75 typedef struct clones {
76 	uint64_t clone_ds;
77 	list_node_t node;
78 } clones_t;
79 
80 /*
81  * spa_upgrade_errlog_limit : A zfs module parameter that controls the number
82  *		of on-disk error log entries that will be converted to the new
83  *		format when enabling head_errlog. Defaults to 0 which converts
84  *		all log entries.
85  */
86 static uint_t spa_upgrade_errlog_limit = 0;
87 
88 /*
89  * Convert a bookmark to a string.
90  */
91 static void
92 bookmark_to_name(zbookmark_phys_t *zb, char *buf, size_t len)
93 {
94 	(void) snprintf(buf, len, "%llx:%llx:%llx:%llx",
95 	    (u_longlong_t)zb->zb_objset, (u_longlong_t)zb->zb_object,
96 	    (u_longlong_t)zb->zb_level, (u_longlong_t)zb->zb_blkid);
97 }
98 
99 /*
100  * Convert an err_phys to a string.
101  */
102 static void
103 errphys_to_name(zbookmark_err_phys_t *zep, char *buf, size_t len)
104 {
105 	(void) snprintf(buf, len, "%llx:%llx:%llx:%llx",
106 	    (u_longlong_t)zep->zb_object, (u_longlong_t)zep->zb_level,
107 	    (u_longlong_t)zep->zb_blkid, (u_longlong_t)zep->zb_birth);
108 }
109 
110 /*
111  * Convert a string to a err_phys.
112  */
113 void
114 name_to_errphys(char *buf, zbookmark_err_phys_t *zep)
115 {
116 	zep->zb_object = zfs_strtonum(buf, &buf);
117 	ASSERT(*buf == ':');
118 	zep->zb_level = (int)zfs_strtonum(buf + 1, &buf);
119 	ASSERT(*buf == ':');
120 	zep->zb_blkid = zfs_strtonum(buf + 1, &buf);
121 	ASSERT(*buf == ':');
122 	zep->zb_birth = zfs_strtonum(buf + 1, &buf);
123 	ASSERT(*buf == '\0');
124 }
125 
126 /*
127  * Convert a string to a bookmark.
128  */
129 static void
130 name_to_bookmark(char *buf, zbookmark_phys_t *zb)
131 {
132 	zb->zb_objset = zfs_strtonum(buf, &buf);
133 	ASSERT(*buf == ':');
134 	zb->zb_object = zfs_strtonum(buf + 1, &buf);
135 	ASSERT(*buf == ':');
136 	zb->zb_level = (int)zfs_strtonum(buf + 1, &buf);
137 	ASSERT(*buf == ':');
138 	zb->zb_blkid = zfs_strtonum(buf + 1, &buf);
139 	ASSERT(*buf == '\0');
140 }
141 
142 void
143 zep_to_zb(uint64_t dataset, zbookmark_err_phys_t *zep, zbookmark_phys_t *zb)
144 {
145 	zb->zb_objset = dataset;
146 	zb->zb_object = zep->zb_object;
147 	zb->zb_level = zep->zb_level;
148 	zb->zb_blkid = zep->zb_blkid;
149 }
150 
151 static void
152 name_to_object(char *buf, uint64_t *obj)
153 {
154 	*obj = zfs_strtonum(buf, &buf);
155 	ASSERT(*buf == '\0');
156 }
157 
158 /*
159  * Retrieve the head filesystem.
160  */
161 static int get_head_ds(spa_t *spa, uint64_t dsobj, uint64_t *head_ds)
162 {
163 	dsl_dataset_t *ds;
164 	int error = dsl_dataset_hold_obj_flags(spa->spa_dsl_pool,
165 	    dsobj, DS_HOLD_FLAG_DECRYPT, FTAG, &ds);
166 
167 	if (error != 0)
168 		return (error);
169 
170 	ASSERT(head_ds);
171 	*head_ds = dsl_dir_phys(ds->ds_dir)->dd_head_dataset_obj;
172 	dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
173 
174 	return (error);
175 }
176 
177 /*
178  * Log an uncorrectable error to the persistent error log.  We add it to the
179  * spa's list of pending errors.  The changes are actually synced out to disk
180  * during spa_errlog_sync().
181  */
182 void
183 spa_log_error(spa_t *spa, const zbookmark_phys_t *zb, const uint64_t birth)
184 {
185 	spa_error_entry_t search;
186 	spa_error_entry_t *new;
187 	avl_tree_t *tree;
188 	avl_index_t where;
189 
190 	/*
191 	 * If we are trying to import a pool, ignore any errors, as we won't be
192 	 * writing to the pool any time soon.
193 	 */
194 	if (spa_load_state(spa) == SPA_LOAD_TRYIMPORT)
195 		return;
196 
197 	mutex_enter(&spa->spa_errlist_lock);
198 
199 	/*
200 	 * If we have had a request to rotate the log, log it to the next list
201 	 * instead of the current one.
202 	 */
203 	if (spa->spa_scrub_active || spa->spa_scrub_finished)
204 		tree = &spa->spa_errlist_scrub;
205 	else
206 		tree = &spa->spa_errlist_last;
207 
208 	search.se_bookmark = *zb;
209 	if (avl_find(tree, &search, &where) != NULL) {
210 		mutex_exit(&spa->spa_errlist_lock);
211 		return;
212 	}
213 
214 	new = kmem_zalloc(sizeof (spa_error_entry_t), KM_SLEEP);
215 	new->se_bookmark = *zb;
216 
217 	/*
218 	 * If the head_errlog feature is enabled, store the birth txg now. In
219 	 * case the file is deleted before spa_errlog_sync() runs, we will not
220 	 * be able to retrieve the birth txg.
221 	 */
222 	if (spa_feature_is_enabled(spa, SPA_FEATURE_HEAD_ERRLOG)) {
223 		new->se_zep.zb_object = zb->zb_object;
224 		new->se_zep.zb_level = zb->zb_level;
225 		new->se_zep.zb_blkid = zb->zb_blkid;
226 		new->se_zep.zb_birth = birth;
227 	}
228 
229 	avl_insert(tree, new, where);
230 	mutex_exit(&spa->spa_errlist_lock);
231 }
232 
233 int
234 find_birth_txg(dsl_dataset_t *ds, zbookmark_err_phys_t *zep,
235     uint64_t *birth_txg)
236 {
237 	objset_t *os;
238 	int error = dmu_objset_from_ds(ds, &os);
239 	if (error != 0)
240 		return (error);
241 
242 	dnode_t *dn;
243 	blkptr_t bp;
244 
245 	error = dnode_hold(os, zep->zb_object, FTAG, &dn);
246 	if (error != 0)
247 		return (error);
248 
249 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
250 	error = dbuf_dnode_findbp(dn, zep->zb_level, zep->zb_blkid, &bp, NULL,
251 	    NULL);
252 	if (error == 0 && BP_IS_HOLE(&bp))
253 		error = SET_ERROR(ENOENT);
254 
255 	*birth_txg = BP_GET_LOGICAL_BIRTH(&bp);
256 	rw_exit(&dn->dn_struct_rwlock);
257 	dnode_rele(dn, FTAG);
258 	return (error);
259 }
260 
261 /*
262  * This function finds the oldest affected filesystem containing an error
263  * block.
264  */
265 int
266 find_top_affected_fs(spa_t *spa, uint64_t head_ds, zbookmark_err_phys_t *zep,
267     uint64_t *top_affected_fs)
268 {
269 	uint64_t oldest_dsobj;
270 	int error = dsl_dataset_oldest_snapshot(spa, head_ds, zep->zb_birth,
271 	    &oldest_dsobj);
272 	if (error != 0)
273 		return (error);
274 
275 	dsl_dataset_t *ds;
276 	error = dsl_dataset_hold_obj_flags(spa->spa_dsl_pool, oldest_dsobj,
277 	    DS_HOLD_FLAG_DECRYPT, FTAG, &ds);
278 	if (error != 0)
279 		return (error);
280 
281 	*top_affected_fs =
282 	    dsl_dir_phys(ds->ds_dir)->dd_head_dataset_obj;
283 	dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
284 	return (0);
285 }
286 
287 
288 #ifdef _KERNEL
289 /*
290  * Copy the bookmark to the end of the user-space buffer which starts at
291  * uaddr and has *count unused entries, and decrement *count by 1.
292  */
293 static int
294 copyout_entry(const zbookmark_phys_t *zb, void *uaddr, uint64_t *count)
295 {
296 	if (*count == 0)
297 		return (SET_ERROR(ENOMEM));
298 
299 	*count -= 1;
300 	if (copyout(zb, (char *)uaddr + (*count) * sizeof (zbookmark_phys_t),
301 	    sizeof (zbookmark_phys_t)) != 0)
302 		return (SET_ERROR(EFAULT));
303 	return (0);
304 }
305 
306 /*
307  * Each time the error block is referenced by a snapshot or clone, add a
308  * zbookmark_phys_t entry to the userspace array at uaddr. The array is
309  * filled from the back and the in-out parameter *count is modified to be the
310  * number of unused entries at the beginning of the array. The function
311  * scrub_filesystem() is modelled after this one.
312  */
313 static int
314 check_filesystem(spa_t *spa, uint64_t head_ds, zbookmark_err_phys_t *zep,
315     void *uaddr, uint64_t *count, list_t *clones_list)
316 {
317 	dsl_dataset_t *ds;
318 	dsl_pool_t *dp = spa->spa_dsl_pool;
319 
320 	int error = dsl_dataset_hold_obj_flags(dp, head_ds,
321 	    DS_HOLD_FLAG_DECRYPT, FTAG, &ds);
322 	if (error != 0)
323 		return (error);
324 
325 	uint64_t latest_txg;
326 	uint64_t txg_to_consider = spa->spa_syncing_txg;
327 	boolean_t check_snapshot = B_TRUE;
328 	error = find_birth_txg(ds, zep, &latest_txg);
329 
330 	/*
331 	 * If find_birth_txg() errors out otherwise, let txg_to_consider be
332 	 * equal to the spa's syncing txg: if check_filesystem() errors out
333 	 * then affected snapshots or clones will not be checked.
334 	 */
335 	if (error == 0 && zep->zb_birth == latest_txg) {
336 		/* Block neither free nor rewritten. */
337 		zbookmark_phys_t zb;
338 		zep_to_zb(head_ds, zep, &zb);
339 		error = copyout_entry(&zb, uaddr, count);
340 		if (error != 0) {
341 			dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
342 			return (error);
343 		}
344 		check_snapshot = B_FALSE;
345 	} else if (error == 0) {
346 		txg_to_consider = latest_txg;
347 	}
348 
349 	/*
350 	 * Retrieve the number of snapshots if the dataset is not a snapshot.
351 	 */
352 	uint64_t snap_count = 0;
353 	if (dsl_dataset_phys(ds)->ds_snapnames_zapobj != 0) {
354 
355 		error = zap_count(spa->spa_meta_objset,
356 		    dsl_dataset_phys(ds)->ds_snapnames_zapobj, &snap_count);
357 
358 		if (error != 0) {
359 			dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
360 			return (error);
361 		}
362 	}
363 
364 	if (snap_count == 0) {
365 		/* Filesystem without snapshots. */
366 		dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
367 		return (0);
368 	}
369 
370 	uint64_t *snap_obj_array = kmem_zalloc(snap_count * sizeof (uint64_t),
371 	    KM_SLEEP);
372 
373 	int aff_snap_count = 0;
374 	uint64_t snap_obj = dsl_dataset_phys(ds)->ds_prev_snap_obj;
375 	uint64_t snap_obj_txg = dsl_dataset_phys(ds)->ds_prev_snap_txg;
376 	uint64_t zap_clone = dsl_dir_phys(ds->ds_dir)->dd_clones;
377 
378 	dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
379 
380 	/* Check only snapshots created from this file system. */
381 	while (snap_obj != 0 && zep->zb_birth < snap_obj_txg &&
382 	    snap_obj_txg <= txg_to_consider) {
383 
384 		error = dsl_dataset_hold_obj_flags(dp, snap_obj,
385 		    DS_HOLD_FLAG_DECRYPT, FTAG, &ds);
386 		if (error != 0)
387 			goto out;
388 
389 		if (dsl_dir_phys(ds->ds_dir)->dd_head_dataset_obj != head_ds) {
390 			snap_obj = dsl_dataset_phys(ds)->ds_prev_snap_obj;
391 			snap_obj_txg = dsl_dataset_phys(ds)->ds_prev_snap_txg;
392 			dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
393 			continue;
394 		}
395 
396 		boolean_t affected = B_TRUE;
397 		if (check_snapshot) {
398 			uint64_t blk_txg;
399 			error = find_birth_txg(ds, zep, &blk_txg);
400 			affected = (error == 0 && zep->zb_birth == blk_txg);
401 		}
402 
403 		/* Report errors in snapshots. */
404 		if (affected) {
405 			snap_obj_array[aff_snap_count] = snap_obj;
406 			aff_snap_count++;
407 
408 			zbookmark_phys_t zb;
409 			zep_to_zb(snap_obj, zep, &zb);
410 			error = copyout_entry(&zb, uaddr, count);
411 			if (error != 0) {
412 				dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT,
413 				    FTAG);
414 				goto out;
415 			}
416 		}
417 		snap_obj = dsl_dataset_phys(ds)->ds_prev_snap_obj;
418 		snap_obj_txg = dsl_dataset_phys(ds)->ds_prev_snap_txg;
419 		dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
420 	}
421 
422 	if (zap_clone == 0 || aff_snap_count == 0) {
423 		error = 0;
424 		goto out;
425 	}
426 
427 	/* Check clones. */
428 	zap_cursor_t *zc;
429 	zap_attribute_t *za;
430 
431 	zc = kmem_zalloc(sizeof (zap_cursor_t), KM_SLEEP);
432 	za = kmem_zalloc(sizeof (zap_attribute_t), KM_SLEEP);
433 
434 	for (zap_cursor_init(zc, spa->spa_meta_objset, zap_clone);
435 	    zap_cursor_retrieve(zc, za) == 0;
436 	    zap_cursor_advance(zc)) {
437 
438 		dsl_dataset_t *clone;
439 		error = dsl_dataset_hold_obj_flags(dp, za->za_first_integer,
440 		    DS_HOLD_FLAG_DECRYPT, FTAG, &clone);
441 
442 		if (error != 0)
443 			break;
444 
445 		/*
446 		 * Only clones whose origins were affected could also
447 		 * have affected snapshots.
448 		 */
449 		boolean_t found = B_FALSE;
450 		for (int i = 0; i < snap_count; i++) {
451 			if (dsl_dir_phys(clone->ds_dir)->dd_origin_obj
452 			    == snap_obj_array[i])
453 				found = B_TRUE;
454 		}
455 		dsl_dataset_rele_flags(clone, DS_HOLD_FLAG_DECRYPT, FTAG);
456 
457 		if (!found)
458 			continue;
459 
460 		clones_t *ct = kmem_zalloc(sizeof (*ct), KM_SLEEP);
461 		ct->clone_ds = za->za_first_integer;
462 		list_insert_tail(clones_list, ct);
463 	}
464 
465 	zap_cursor_fini(zc);
466 	kmem_free(za, sizeof (*za));
467 	kmem_free(zc, sizeof (*zc));
468 
469 out:
470 	kmem_free(snap_obj_array, sizeof (*snap_obj_array));
471 	return (error);
472 }
473 
474 static int
475 process_error_block(spa_t *spa, uint64_t head_ds, zbookmark_err_phys_t *zep,
476     void *uaddr, uint64_t *count)
477 {
478 	/*
479 	 * If zb_birth == 0 or head_ds == 0 it means we failed to retrieve the
480 	 * birth txg or the head filesystem of the block pointer. This may
481 	 * happen e.g. when an encrypted filesystem is not mounted or when
482 	 * the key is not loaded. In this case do not proceed to
483 	 * check_filesystem(), instead do the accounting here.
484 	 */
485 	if (zep->zb_birth == 0 || head_ds == 0) {
486 		zbookmark_phys_t zb;
487 		zep_to_zb(head_ds, zep, &zb);
488 		int error = copyout_entry(&zb, uaddr, count);
489 		if (error != 0) {
490 			return (error);
491 		}
492 		return (0);
493 	}
494 
495 	uint64_t top_affected_fs;
496 	uint64_t init_count = *count;
497 	int error = find_top_affected_fs(spa, head_ds, zep, &top_affected_fs);
498 	if (error == 0) {
499 		clones_t *ct;
500 		list_t clones_list;
501 
502 		list_create(&clones_list, sizeof (clones_t),
503 		    offsetof(clones_t, node));
504 
505 		error = check_filesystem(spa, top_affected_fs, zep,
506 		    uaddr, count, &clones_list);
507 
508 		while ((ct = list_remove_head(&clones_list)) != NULL) {
509 			error = check_filesystem(spa, ct->clone_ds, zep,
510 			    uaddr, count, &clones_list);
511 			kmem_free(ct, sizeof (*ct));
512 
513 			if (error) {
514 				while (!list_is_empty(&clones_list)) {
515 					ct = list_remove_head(&clones_list);
516 					kmem_free(ct, sizeof (*ct));
517 				}
518 				break;
519 			}
520 		}
521 
522 		list_destroy(&clones_list);
523 	}
524 	if (error == 0 && init_count == *count) {
525 		/*
526 		 * If we reach this point, no errors have been detected
527 		 * in the checked filesystems/snapshots. Before returning mark
528 		 * the error block to be removed from the error lists and logs.
529 		 */
530 		zbookmark_phys_t zb;
531 		zep_to_zb(head_ds, zep, &zb);
532 		spa_remove_error(spa, &zb, zep->zb_birth);
533 	}
534 
535 	return (error);
536 }
537 #endif
538 
539 /* Return the number of errors in the error log */
540 uint64_t
541 spa_get_last_errlog_size(spa_t *spa)
542 {
543 	uint64_t total = 0, count;
544 	mutex_enter(&spa->spa_errlog_lock);
545 
546 	if (spa->spa_errlog_last != 0 &&
547 	    zap_count(spa->spa_meta_objset, spa->spa_errlog_last,
548 	    &count) == 0)
549 		total += count;
550 	mutex_exit(&spa->spa_errlog_lock);
551 	return (total);
552 }
553 
554 /*
555  * If a healed bookmark matches an entry in the error log we stash it in a tree
556  * so that we can later remove the related log entries in sync context.
557  */
558 static void
559 spa_add_healed_error(spa_t *spa, uint64_t obj, zbookmark_phys_t *healed_zb,
560     const uint64_t birth)
561 {
562 	char name[NAME_MAX_LEN];
563 
564 	if (obj == 0)
565 		return;
566 
567 	boolean_t held_list = B_FALSE;
568 	boolean_t held_log = B_FALSE;
569 
570 	if (!spa_feature_is_enabled(spa, SPA_FEATURE_HEAD_ERRLOG)) {
571 		bookmark_to_name(healed_zb, name, sizeof (name));
572 
573 		if (zap_contains(spa->spa_meta_objset, healed_zb->zb_objset,
574 		    name) == 0) {
575 			if (!MUTEX_HELD(&spa->spa_errlog_lock)) {
576 				mutex_enter(&spa->spa_errlog_lock);
577 				held_log = B_TRUE;
578 			}
579 
580 			/*
581 			 * Found an error matching healed zb, add zb to our
582 			 * tree of healed errors
583 			 */
584 			avl_tree_t *tree = &spa->spa_errlist_healed;
585 			spa_error_entry_t search;
586 			spa_error_entry_t *new;
587 			avl_index_t where;
588 			search.se_bookmark = *healed_zb;
589 			if (!MUTEX_HELD(&spa->spa_errlist_lock)) {
590 				mutex_enter(&spa->spa_errlist_lock);
591 				held_list = B_TRUE;
592 			}
593 			if (avl_find(tree, &search, &where) != NULL) {
594 				if (held_list)
595 					mutex_exit(&spa->spa_errlist_lock);
596 				if (held_log)
597 					mutex_exit(&spa->spa_errlog_lock);
598 				return;
599 			}
600 			new = kmem_zalloc(sizeof (spa_error_entry_t), KM_SLEEP);
601 			new->se_bookmark = *healed_zb;
602 			avl_insert(tree, new, where);
603 			if (held_list)
604 				mutex_exit(&spa->spa_errlist_lock);
605 			if (held_log)
606 				mutex_exit(&spa->spa_errlog_lock);
607 		}
608 		return;
609 	}
610 
611 	zbookmark_err_phys_t healed_zep;
612 	healed_zep.zb_object = healed_zb->zb_object;
613 	healed_zep.zb_level = healed_zb->zb_level;
614 	healed_zep.zb_blkid = healed_zb->zb_blkid;
615 	healed_zep.zb_birth = birth;
616 
617 	errphys_to_name(&healed_zep, name, sizeof (name));
618 
619 	zap_cursor_t zc;
620 	zap_attribute_t za;
621 	for (zap_cursor_init(&zc, spa->spa_meta_objset, spa->spa_errlog_last);
622 	    zap_cursor_retrieve(&zc, &za) == 0; zap_cursor_advance(&zc)) {
623 		if (zap_contains(spa->spa_meta_objset, za.za_first_integer,
624 		    name) == 0) {
625 			if (!MUTEX_HELD(&spa->spa_errlog_lock)) {
626 				mutex_enter(&spa->spa_errlog_lock);
627 				held_log = B_TRUE;
628 			}
629 
630 			avl_tree_t *tree = &spa->spa_errlist_healed;
631 			spa_error_entry_t search;
632 			spa_error_entry_t *new;
633 			avl_index_t where;
634 			search.se_bookmark = *healed_zb;
635 
636 			if (!MUTEX_HELD(&spa->spa_errlist_lock)) {
637 				mutex_enter(&spa->spa_errlist_lock);
638 				held_list = B_TRUE;
639 			}
640 
641 			if (avl_find(tree, &search, &where) != NULL) {
642 				if (held_list)
643 					mutex_exit(&spa->spa_errlist_lock);
644 				if (held_log)
645 					mutex_exit(&spa->spa_errlog_lock);
646 				continue;
647 			}
648 			new = kmem_zalloc(sizeof (spa_error_entry_t), KM_SLEEP);
649 			new->se_bookmark = *healed_zb;
650 			new->se_zep = healed_zep;
651 			avl_insert(tree, new, where);
652 
653 			if (held_list)
654 				mutex_exit(&spa->spa_errlist_lock);
655 			if (held_log)
656 				mutex_exit(&spa->spa_errlog_lock);
657 		}
658 	}
659 	zap_cursor_fini(&zc);
660 }
661 
662 /*
663  * If this error exists in the given tree remove it.
664  */
665 static void
666 remove_error_from_list(spa_t *spa, avl_tree_t *t, const zbookmark_phys_t *zb)
667 {
668 	spa_error_entry_t search, *found;
669 	avl_index_t where;
670 
671 	mutex_enter(&spa->spa_errlist_lock);
672 	search.se_bookmark = *zb;
673 	if ((found = avl_find(t, &search, &where)) != NULL) {
674 		avl_remove(t, found);
675 		kmem_free(found, sizeof (spa_error_entry_t));
676 	}
677 	mutex_exit(&spa->spa_errlist_lock);
678 }
679 
680 
681 /*
682  * Removes all of the recv healed errors from both on-disk error logs
683  */
684 static void
685 spa_remove_healed_errors(spa_t *spa, avl_tree_t *s, avl_tree_t *l, dmu_tx_t *tx)
686 {
687 	char name[NAME_MAX_LEN];
688 	spa_error_entry_t *se;
689 	void *cookie = NULL;
690 
691 	ASSERT(MUTEX_HELD(&spa->spa_errlog_lock));
692 
693 	while ((se = avl_destroy_nodes(&spa->spa_errlist_healed,
694 	    &cookie)) != NULL) {
695 		remove_error_from_list(spa, s, &se->se_bookmark);
696 		remove_error_from_list(spa, l, &se->se_bookmark);
697 
698 		if (!spa_feature_is_enabled(spa, SPA_FEATURE_HEAD_ERRLOG)) {
699 			bookmark_to_name(&se->se_bookmark, name, sizeof (name));
700 			(void) zap_remove(spa->spa_meta_objset,
701 			    spa->spa_errlog_last, name, tx);
702 			(void) zap_remove(spa->spa_meta_objset,
703 			    spa->spa_errlog_scrub, name, tx);
704 		} else {
705 			errphys_to_name(&se->se_zep, name, sizeof (name));
706 			zap_cursor_t zc;
707 			zap_attribute_t za;
708 			for (zap_cursor_init(&zc, spa->spa_meta_objset,
709 			    spa->spa_errlog_last);
710 			    zap_cursor_retrieve(&zc, &za) == 0;
711 			    zap_cursor_advance(&zc)) {
712 				zap_remove(spa->spa_meta_objset,
713 				    za.za_first_integer, name, tx);
714 			}
715 			zap_cursor_fini(&zc);
716 
717 			for (zap_cursor_init(&zc, spa->spa_meta_objset,
718 			    spa->spa_errlog_scrub);
719 			    zap_cursor_retrieve(&zc, &za) == 0;
720 			    zap_cursor_advance(&zc)) {
721 				zap_remove(spa->spa_meta_objset,
722 				    za.za_first_integer, name, tx);
723 			}
724 			zap_cursor_fini(&zc);
725 		}
726 		kmem_free(se, sizeof (spa_error_entry_t));
727 	}
728 }
729 
730 /*
731  * Stash away healed bookmarks to remove them from the on-disk error logs
732  * later in spa_remove_healed_errors().
733  */
734 void
735 spa_remove_error(spa_t *spa, zbookmark_phys_t *zb, uint64_t birth)
736 {
737 	spa_add_healed_error(spa, spa->spa_errlog_last, zb, birth);
738 	spa_add_healed_error(spa, spa->spa_errlog_scrub, zb, birth);
739 }
740 
741 static uint64_t
742 approx_errlog_size_impl(spa_t *spa, uint64_t spa_err_obj)
743 {
744 	if (spa_err_obj == 0)
745 		return (0);
746 	uint64_t total = 0;
747 
748 	zap_cursor_t zc;
749 	zap_attribute_t za;
750 	for (zap_cursor_init(&zc, spa->spa_meta_objset, spa_err_obj);
751 	    zap_cursor_retrieve(&zc, &za) == 0; zap_cursor_advance(&zc)) {
752 		uint64_t count;
753 		if (zap_count(spa->spa_meta_objset, za.za_first_integer,
754 		    &count) == 0)
755 			total += count;
756 	}
757 	zap_cursor_fini(&zc);
758 	return (total);
759 }
760 
761 /*
762  * Return the approximate number of errors currently in the error log.  This
763  * will be nonzero if there are some errors, but otherwise it may be more
764  * or less than the number of entries returned by spa_get_errlog().
765  */
766 uint64_t
767 spa_approx_errlog_size(spa_t *spa)
768 {
769 	uint64_t total = 0;
770 
771 	if (!spa_feature_is_enabled(spa, SPA_FEATURE_HEAD_ERRLOG)) {
772 		mutex_enter(&spa->spa_errlog_lock);
773 		uint64_t count;
774 		if (spa->spa_errlog_scrub != 0 &&
775 		    zap_count(spa->spa_meta_objset, spa->spa_errlog_scrub,
776 		    &count) == 0)
777 			total += count;
778 
779 		if (spa->spa_errlog_last != 0 && !spa->spa_scrub_finished &&
780 		    zap_count(spa->spa_meta_objset, spa->spa_errlog_last,
781 		    &count) == 0)
782 			total += count;
783 		mutex_exit(&spa->spa_errlog_lock);
784 
785 	} else {
786 		mutex_enter(&spa->spa_errlog_lock);
787 		total += approx_errlog_size_impl(spa, spa->spa_errlog_last);
788 		total += approx_errlog_size_impl(spa, spa->spa_errlog_scrub);
789 		mutex_exit(&spa->spa_errlog_lock);
790 	}
791 	mutex_enter(&spa->spa_errlist_lock);
792 	total += avl_numnodes(&spa->spa_errlist_last);
793 	total += avl_numnodes(&spa->spa_errlist_scrub);
794 	mutex_exit(&spa->spa_errlist_lock);
795 	return (total);
796 }
797 
798 /*
799  * This function sweeps through an on-disk error log and stores all bookmarks
800  * as error bookmarks in a new ZAP object. At the end we discard the old one,
801  * and spa_update_errlog() will set the spa's on-disk error log to new ZAP
802  * object.
803  */
804 static void
805 sync_upgrade_errlog(spa_t *spa, uint64_t spa_err_obj, uint64_t *newobj,
806     dmu_tx_t *tx)
807 {
808 	zap_cursor_t zc;
809 	zap_attribute_t za;
810 	zbookmark_phys_t zb;
811 	uint64_t count;
812 
813 	*newobj = zap_create(spa->spa_meta_objset, DMU_OT_ERROR_LOG,
814 	    DMU_OT_NONE, 0, tx);
815 
816 	/*
817 	 * If we cannnot perform the upgrade we should clear the old on-disk
818 	 * error logs.
819 	 */
820 	if (zap_count(spa->spa_meta_objset, spa_err_obj, &count) != 0) {
821 		VERIFY0(dmu_object_free(spa->spa_meta_objset, spa_err_obj, tx));
822 		return;
823 	}
824 
825 	for (zap_cursor_init(&zc, spa->spa_meta_objset, spa_err_obj);
826 	    zap_cursor_retrieve(&zc, &za) == 0;
827 	    zap_cursor_advance(&zc)) {
828 		if (spa_upgrade_errlog_limit != 0 &&
829 		    zc.zc_cd == spa_upgrade_errlog_limit)
830 			break;
831 
832 		name_to_bookmark(za.za_name, &zb);
833 
834 		zbookmark_err_phys_t zep;
835 		zep.zb_object = zb.zb_object;
836 		zep.zb_level = zb.zb_level;
837 		zep.zb_blkid = zb.zb_blkid;
838 		zep.zb_birth = 0;
839 
840 		/*
841 		 * In case of an error we should simply continue instead of
842 		 * returning prematurely. See the next comment.
843 		 */
844 		uint64_t head_ds;
845 		dsl_pool_t *dp = spa->spa_dsl_pool;
846 		dsl_dataset_t *ds;
847 		objset_t *os;
848 
849 		int error = dsl_dataset_hold_obj_flags(dp, zb.zb_objset,
850 		    DS_HOLD_FLAG_DECRYPT, FTAG, &ds);
851 		if (error != 0)
852 			continue;
853 
854 		head_ds = dsl_dir_phys(ds->ds_dir)->dd_head_dataset_obj;
855 
856 		/*
857 		 * The objset and the dnode are required for getting the block
858 		 * pointer, which is used to determine if BP_IS_HOLE(). If
859 		 * getting the objset or the dnode fails, do not create a
860 		 * zap entry (presuming we know the dataset) as this may create
861 		 * spurious errors that we cannot ever resolve. If an error is
862 		 * truly persistent, it should re-appear after a scan.
863 		 */
864 		if (dmu_objset_from_ds(ds, &os) != 0) {
865 			dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
866 			continue;
867 		}
868 
869 		dnode_t *dn;
870 		blkptr_t bp;
871 
872 		if (dnode_hold(os, zep.zb_object, FTAG, &dn) != 0) {
873 			dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
874 			continue;
875 		}
876 
877 		rw_enter(&dn->dn_struct_rwlock, RW_READER);
878 		error = dbuf_dnode_findbp(dn, zep.zb_level, zep.zb_blkid, &bp,
879 		    NULL, NULL);
880 		if (error == EACCES)
881 			error = 0;
882 		else if (!error)
883 			zep.zb_birth = BP_GET_LOGICAL_BIRTH(&bp);
884 
885 		rw_exit(&dn->dn_struct_rwlock);
886 		dnode_rele(dn, FTAG);
887 		dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
888 
889 		if (error != 0 || BP_IS_HOLE(&bp))
890 			continue;
891 
892 		uint64_t err_obj;
893 		error = zap_lookup_int_key(spa->spa_meta_objset, *newobj,
894 		    head_ds, &err_obj);
895 
896 		if (error == ENOENT) {
897 			err_obj = zap_create(spa->spa_meta_objset,
898 			    DMU_OT_ERROR_LOG, DMU_OT_NONE, 0, tx);
899 
900 			(void) zap_update_int_key(spa->spa_meta_objset,
901 			    *newobj, head_ds, err_obj, tx);
902 		}
903 
904 		char buf[64];
905 		errphys_to_name(&zep, buf, sizeof (buf));
906 
907 		const char *name = "";
908 		(void) zap_update(spa->spa_meta_objset, err_obj,
909 		    buf, 1, strlen(name) + 1, name, tx);
910 	}
911 	zap_cursor_fini(&zc);
912 
913 	VERIFY0(dmu_object_free(spa->spa_meta_objset, spa_err_obj, tx));
914 }
915 
916 void
917 spa_upgrade_errlog(spa_t *spa, dmu_tx_t *tx)
918 {
919 	uint64_t newobj = 0;
920 
921 	mutex_enter(&spa->spa_errlog_lock);
922 	if (spa->spa_errlog_last != 0) {
923 		sync_upgrade_errlog(spa, spa->spa_errlog_last, &newobj, tx);
924 		spa->spa_errlog_last = newobj;
925 
926 		(void) zap_update(spa->spa_meta_objset,
927 		    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_ERRLOG_LAST,
928 		    sizeof (uint64_t), 1, &spa->spa_errlog_last, tx);
929 	}
930 
931 	if (spa->spa_errlog_scrub != 0) {
932 		sync_upgrade_errlog(spa, spa->spa_errlog_scrub, &newobj, tx);
933 		spa->spa_errlog_scrub = newobj;
934 
935 		(void) zap_update(spa->spa_meta_objset,
936 		    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_ERRLOG_SCRUB,
937 		    sizeof (uint64_t), 1, &spa->spa_errlog_scrub, tx);
938 	}
939 
940 	mutex_exit(&spa->spa_errlog_lock);
941 }
942 
943 #ifdef _KERNEL
944 /*
945  * If an error block is shared by two datasets it will be counted twice.
946  */
947 static int
948 process_error_log(spa_t *spa, uint64_t obj, void *uaddr, uint64_t *count)
949 {
950 	if (obj == 0)
951 		return (0);
952 
953 	zap_cursor_t *zc;
954 	zap_attribute_t *za;
955 
956 	zc = kmem_zalloc(sizeof (zap_cursor_t), KM_SLEEP);
957 	za = kmem_zalloc(sizeof (zap_attribute_t), KM_SLEEP);
958 
959 	if (!spa_feature_is_enabled(spa, SPA_FEATURE_HEAD_ERRLOG)) {
960 		for (zap_cursor_init(zc, spa->spa_meta_objset, obj);
961 		    zap_cursor_retrieve(zc, za) == 0;
962 		    zap_cursor_advance(zc)) {
963 			if (*count == 0) {
964 				zap_cursor_fini(zc);
965 				kmem_free(zc, sizeof (*zc));
966 				kmem_free(za, sizeof (*za));
967 				return (SET_ERROR(ENOMEM));
968 			}
969 
970 			zbookmark_phys_t zb;
971 			name_to_bookmark(za->za_name, &zb);
972 
973 			int error = copyout_entry(&zb, uaddr, count);
974 			if (error != 0) {
975 				zap_cursor_fini(zc);
976 				kmem_free(zc, sizeof (*zc));
977 				kmem_free(za, sizeof (*za));
978 				return (error);
979 			}
980 		}
981 		zap_cursor_fini(zc);
982 		kmem_free(zc, sizeof (*zc));
983 		kmem_free(za, sizeof (*za));
984 		return (0);
985 	}
986 
987 	for (zap_cursor_init(zc, spa->spa_meta_objset, obj);
988 	    zap_cursor_retrieve(zc, za) == 0;
989 	    zap_cursor_advance(zc)) {
990 
991 		zap_cursor_t *head_ds_cursor;
992 		zap_attribute_t *head_ds_attr;
993 
994 		head_ds_cursor = kmem_zalloc(sizeof (zap_cursor_t), KM_SLEEP);
995 		head_ds_attr = kmem_zalloc(sizeof (zap_attribute_t), KM_SLEEP);
996 
997 		uint64_t head_ds_err_obj = za->za_first_integer;
998 		uint64_t head_ds;
999 		name_to_object(za->za_name, &head_ds);
1000 		for (zap_cursor_init(head_ds_cursor, spa->spa_meta_objset,
1001 		    head_ds_err_obj); zap_cursor_retrieve(head_ds_cursor,
1002 		    head_ds_attr) == 0; zap_cursor_advance(head_ds_cursor)) {
1003 
1004 			zbookmark_err_phys_t head_ds_block;
1005 			name_to_errphys(head_ds_attr->za_name, &head_ds_block);
1006 			int error = process_error_block(spa, head_ds,
1007 			    &head_ds_block, uaddr, count);
1008 
1009 			if (error != 0) {
1010 				zap_cursor_fini(head_ds_cursor);
1011 				kmem_free(head_ds_cursor,
1012 				    sizeof (*head_ds_cursor));
1013 				kmem_free(head_ds_attr, sizeof (*head_ds_attr));
1014 
1015 				zap_cursor_fini(zc);
1016 				kmem_free(za, sizeof (*za));
1017 				kmem_free(zc, sizeof (*zc));
1018 				return (error);
1019 			}
1020 		}
1021 		zap_cursor_fini(head_ds_cursor);
1022 		kmem_free(head_ds_cursor, sizeof (*head_ds_cursor));
1023 		kmem_free(head_ds_attr, sizeof (*head_ds_attr));
1024 	}
1025 	zap_cursor_fini(zc);
1026 	kmem_free(za, sizeof (*za));
1027 	kmem_free(zc, sizeof (*zc));
1028 	return (0);
1029 }
1030 
1031 static int
1032 process_error_list(spa_t *spa, avl_tree_t *list, void *uaddr, uint64_t *count)
1033 {
1034 	spa_error_entry_t *se;
1035 
1036 	if (!spa_feature_is_enabled(spa, SPA_FEATURE_HEAD_ERRLOG)) {
1037 		for (se = avl_first(list); se != NULL;
1038 		    se = AVL_NEXT(list, se)) {
1039 			int error =
1040 			    copyout_entry(&se->se_bookmark, uaddr, count);
1041 			if (error != 0) {
1042 				return (error);
1043 			}
1044 		}
1045 		return (0);
1046 	}
1047 
1048 	for (se = avl_first(list); se != NULL; se = AVL_NEXT(list, se)) {
1049 		uint64_t head_ds = 0;
1050 		int error = get_head_ds(spa, se->se_bookmark.zb_objset,
1051 		    &head_ds);
1052 
1053 		/*
1054 		 * If get_head_ds() errors out, set the head filesystem
1055 		 * to the filesystem stored in the bookmark of the
1056 		 * error block.
1057 		 */
1058 		if (error != 0)
1059 			head_ds = se->se_bookmark.zb_objset;
1060 
1061 		error = process_error_block(spa, head_ds,
1062 		    &se->se_zep, uaddr, count);
1063 		if (error != 0)
1064 			return (error);
1065 	}
1066 	return (0);
1067 }
1068 #endif
1069 
1070 /*
1071  * Copy all known errors to userland as an array of bookmarks.  This is
1072  * actually a union of the on-disk last log and current log, as well as any
1073  * pending error requests.
1074  *
1075  * Because the act of reading the on-disk log could cause errors to be
1076  * generated, we have two separate locks: one for the error log and one for the
1077  * in-core error lists.  We only need the error list lock to log and error, so
1078  * we grab the error log lock while we read the on-disk logs, and only pick up
1079  * the error list lock when we are finished.
1080  */
1081 int
1082 spa_get_errlog(spa_t *spa, void *uaddr, uint64_t *count)
1083 {
1084 	int ret = 0;
1085 
1086 #ifdef _KERNEL
1087 	/*
1088 	 * The pool config lock is needed to hold a dataset_t via (among other
1089 	 * places) process_error_list() -> process_error_block()->
1090 	 * find_top_affected_fs(), and lock ordering requires that we get it
1091 	 * before the spa_errlog_lock.
1092 	 */
1093 	dsl_pool_config_enter(spa->spa_dsl_pool, FTAG);
1094 	mutex_enter(&spa->spa_errlog_lock);
1095 
1096 	ret = process_error_log(spa, spa->spa_errlog_scrub, uaddr, count);
1097 
1098 	if (!ret && !spa->spa_scrub_finished)
1099 		ret = process_error_log(spa, spa->spa_errlog_last, uaddr,
1100 		    count);
1101 
1102 	mutex_enter(&spa->spa_errlist_lock);
1103 	if (!ret)
1104 		ret = process_error_list(spa, &spa->spa_errlist_scrub, uaddr,
1105 		    count);
1106 	if (!ret)
1107 		ret = process_error_list(spa, &spa->spa_errlist_last, uaddr,
1108 		    count);
1109 	mutex_exit(&spa->spa_errlist_lock);
1110 
1111 	mutex_exit(&spa->spa_errlog_lock);
1112 	dsl_pool_config_exit(spa->spa_dsl_pool, FTAG);
1113 #else
1114 	(void) spa, (void) uaddr, (void) count;
1115 #endif
1116 
1117 	return (ret);
1118 }
1119 
1120 /*
1121  * Called when a scrub completes.  This simply set a bit which tells which AVL
1122  * tree to add new errors.  spa_errlog_sync() is responsible for actually
1123  * syncing the changes to the underlying objects.
1124  */
1125 void
1126 spa_errlog_rotate(spa_t *spa)
1127 {
1128 	mutex_enter(&spa->spa_errlist_lock);
1129 	spa->spa_scrub_finished = B_TRUE;
1130 	mutex_exit(&spa->spa_errlist_lock);
1131 }
1132 
1133 /*
1134  * Discard any pending errors from the spa_t.  Called when unloading a faulted
1135  * pool, as the errors encountered during the open cannot be synced to disk.
1136  */
1137 void
1138 spa_errlog_drain(spa_t *spa)
1139 {
1140 	spa_error_entry_t *se;
1141 	void *cookie;
1142 
1143 	mutex_enter(&spa->spa_errlist_lock);
1144 
1145 	cookie = NULL;
1146 	while ((se = avl_destroy_nodes(&spa->spa_errlist_last,
1147 	    &cookie)) != NULL)
1148 		kmem_free(se, sizeof (spa_error_entry_t));
1149 	cookie = NULL;
1150 	while ((se = avl_destroy_nodes(&spa->spa_errlist_scrub,
1151 	    &cookie)) != NULL)
1152 		kmem_free(se, sizeof (spa_error_entry_t));
1153 
1154 	mutex_exit(&spa->spa_errlist_lock);
1155 }
1156 
1157 /*
1158  * Process a list of errors into the current on-disk log.
1159  */
1160 void
1161 sync_error_list(spa_t *spa, avl_tree_t *t, uint64_t *obj, dmu_tx_t *tx)
1162 {
1163 	spa_error_entry_t *se;
1164 	char buf[NAME_MAX_LEN];
1165 	void *cookie;
1166 
1167 	if (avl_numnodes(t) == 0)
1168 		return;
1169 
1170 	/* create log if necessary */
1171 	if (*obj == 0)
1172 		*obj = zap_create(spa->spa_meta_objset, DMU_OT_ERROR_LOG,
1173 		    DMU_OT_NONE, 0, tx);
1174 
1175 	/* add errors to the current log */
1176 	if (!spa_feature_is_enabled(spa, SPA_FEATURE_HEAD_ERRLOG)) {
1177 		for (se = avl_first(t); se != NULL; se = AVL_NEXT(t, se)) {
1178 			bookmark_to_name(&se->se_bookmark, buf, sizeof (buf));
1179 
1180 			const char *name = se->se_name ? se->se_name : "";
1181 			(void) zap_update(spa->spa_meta_objset, *obj, buf, 1,
1182 			    strlen(name) + 1, name, tx);
1183 		}
1184 	} else {
1185 		for (se = avl_first(t); se != NULL; se = AVL_NEXT(t, se)) {
1186 			zbookmark_err_phys_t zep;
1187 			zep.zb_object = se->se_zep.zb_object;
1188 			zep.zb_level = se->se_zep.zb_level;
1189 			zep.zb_blkid = se->se_zep.zb_blkid;
1190 			zep.zb_birth = se->se_zep.zb_birth;
1191 
1192 			uint64_t head_ds = 0;
1193 			int error = get_head_ds(spa, se->se_bookmark.zb_objset,
1194 			    &head_ds);
1195 
1196 			/*
1197 			 * If get_head_ds() errors out, set the head filesystem
1198 			 * to the filesystem stored in the bookmark of the
1199 			 * error block.
1200 			 */
1201 			if (error != 0)
1202 				head_ds = se->se_bookmark.zb_objset;
1203 
1204 			uint64_t err_obj;
1205 			error = zap_lookup_int_key(spa->spa_meta_objset,
1206 			    *obj, head_ds, &err_obj);
1207 
1208 			if (error == ENOENT) {
1209 				err_obj = zap_create(spa->spa_meta_objset,
1210 				    DMU_OT_ERROR_LOG, DMU_OT_NONE, 0, tx);
1211 
1212 				(void) zap_update_int_key(spa->spa_meta_objset,
1213 				    *obj, head_ds, err_obj, tx);
1214 			}
1215 			errphys_to_name(&zep, buf, sizeof (buf));
1216 
1217 			const char *name = se->se_name ? se->se_name : "";
1218 			(void) zap_update(spa->spa_meta_objset,
1219 			    err_obj, buf, 1, strlen(name) + 1, name, tx);
1220 		}
1221 	}
1222 	/* purge the error list */
1223 	cookie = NULL;
1224 	while ((se = avl_destroy_nodes(t, &cookie)) != NULL)
1225 		kmem_free(se, sizeof (spa_error_entry_t));
1226 }
1227 
1228 static void
1229 delete_errlog(spa_t *spa, uint64_t spa_err_obj, dmu_tx_t *tx)
1230 {
1231 	if (spa_feature_is_enabled(spa, SPA_FEATURE_HEAD_ERRLOG)) {
1232 		zap_cursor_t zc;
1233 		zap_attribute_t za;
1234 		for (zap_cursor_init(&zc, spa->spa_meta_objset, spa_err_obj);
1235 		    zap_cursor_retrieve(&zc, &za) == 0;
1236 		    zap_cursor_advance(&zc)) {
1237 			VERIFY0(dmu_object_free(spa->spa_meta_objset,
1238 			    za.za_first_integer, tx));
1239 		}
1240 		zap_cursor_fini(&zc);
1241 	}
1242 	VERIFY0(dmu_object_free(spa->spa_meta_objset, spa_err_obj, tx));
1243 }
1244 
1245 /*
1246  * Sync the error log out to disk.  This is a little tricky because the act of
1247  * writing the error log requires the spa_errlist_lock.  So, we need to lock the
1248  * error lists, take a copy of the lists, and then reinitialize them.  Then, we
1249  * drop the error list lock and take the error log lock, at which point we
1250  * do the errlog processing.  Then, if we encounter an I/O error during this
1251  * process, we can successfully add the error to the list.  Note that this will
1252  * result in the perpetual recycling of errors, but it is an unlikely situation
1253  * and not a performance critical operation.
1254  */
1255 void
1256 spa_errlog_sync(spa_t *spa, uint64_t txg)
1257 {
1258 	dmu_tx_t *tx;
1259 	avl_tree_t scrub, last;
1260 	int scrub_finished;
1261 
1262 	mutex_enter(&spa->spa_errlist_lock);
1263 
1264 	/*
1265 	 * Bail out early under normal circumstances.
1266 	 */
1267 	if (avl_numnodes(&spa->spa_errlist_scrub) == 0 &&
1268 	    avl_numnodes(&spa->spa_errlist_last) == 0 &&
1269 	    avl_numnodes(&spa->spa_errlist_healed) == 0 &&
1270 	    !spa->spa_scrub_finished) {
1271 		mutex_exit(&spa->spa_errlist_lock);
1272 		return;
1273 	}
1274 
1275 	spa_get_errlists(spa, &last, &scrub);
1276 	scrub_finished = spa->spa_scrub_finished;
1277 	spa->spa_scrub_finished = B_FALSE;
1278 
1279 	mutex_exit(&spa->spa_errlist_lock);
1280 
1281 	/*
1282 	 * The pool config lock is needed to hold a dataset_t via
1283 	 * sync_error_list() -> get_head_ds(), and lock ordering
1284 	 * requires that we get it before the spa_errlog_lock.
1285 	 */
1286 	dsl_pool_config_enter(spa->spa_dsl_pool, FTAG);
1287 	mutex_enter(&spa->spa_errlog_lock);
1288 
1289 	tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);
1290 
1291 	/*
1292 	 * Remove healed errors from errors.
1293 	 */
1294 	spa_remove_healed_errors(spa, &last, &scrub, tx);
1295 
1296 	/*
1297 	 * Sync out the current list of errors.
1298 	 */
1299 	sync_error_list(spa, &last, &spa->spa_errlog_last, tx);
1300 
1301 	/*
1302 	 * Rotate the log if necessary.
1303 	 */
1304 	if (scrub_finished) {
1305 		if (spa->spa_errlog_last != 0)
1306 			delete_errlog(spa, spa->spa_errlog_last, tx);
1307 		spa->spa_errlog_last = spa->spa_errlog_scrub;
1308 		spa->spa_errlog_scrub = 0;
1309 
1310 		sync_error_list(spa, &scrub, &spa->spa_errlog_last, tx);
1311 	}
1312 
1313 	/*
1314 	 * Sync out any pending scrub errors.
1315 	 */
1316 	sync_error_list(spa, &scrub, &spa->spa_errlog_scrub, tx);
1317 
1318 	/*
1319 	 * Update the MOS to reflect the new values.
1320 	 */
1321 	(void) zap_update(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
1322 	    DMU_POOL_ERRLOG_LAST, sizeof (uint64_t), 1,
1323 	    &spa->spa_errlog_last, tx);
1324 	(void) zap_update(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
1325 	    DMU_POOL_ERRLOG_SCRUB, sizeof (uint64_t), 1,
1326 	    &spa->spa_errlog_scrub, tx);
1327 
1328 	dmu_tx_commit(tx);
1329 
1330 	mutex_exit(&spa->spa_errlog_lock);
1331 	dsl_pool_config_exit(spa->spa_dsl_pool, FTAG);
1332 }
1333 
1334 static void
1335 delete_dataset_errlog(spa_t *spa, uint64_t spa_err_obj, uint64_t ds,
1336     dmu_tx_t *tx)
1337 {
1338 	if (spa_err_obj == 0)
1339 		return;
1340 
1341 	zap_cursor_t zc;
1342 	zap_attribute_t za;
1343 	for (zap_cursor_init(&zc, spa->spa_meta_objset, spa_err_obj);
1344 	    zap_cursor_retrieve(&zc, &za) == 0; zap_cursor_advance(&zc)) {
1345 		uint64_t head_ds;
1346 		name_to_object(za.za_name, &head_ds);
1347 		if (head_ds == ds) {
1348 			(void) zap_remove(spa->spa_meta_objset, spa_err_obj,
1349 			    za.za_name, tx);
1350 			VERIFY0(dmu_object_free(spa->spa_meta_objset,
1351 			    za.za_first_integer, tx));
1352 			break;
1353 		}
1354 	}
1355 	zap_cursor_fini(&zc);
1356 }
1357 
1358 void
1359 spa_delete_dataset_errlog(spa_t *spa, uint64_t ds, dmu_tx_t *tx)
1360 {
1361 	mutex_enter(&spa->spa_errlog_lock);
1362 	delete_dataset_errlog(spa, spa->spa_errlog_scrub, ds, tx);
1363 	delete_dataset_errlog(spa, spa->spa_errlog_last, ds, tx);
1364 	mutex_exit(&spa->spa_errlog_lock);
1365 }
1366 
1367 static int
1368 find_txg_ancestor_snapshot(spa_t *spa, uint64_t new_head, uint64_t old_head,
1369     uint64_t *txg)
1370 {
1371 	dsl_dataset_t *ds;
1372 	dsl_pool_t *dp = spa->spa_dsl_pool;
1373 
1374 	int error = dsl_dataset_hold_obj_flags(dp, old_head,
1375 	    DS_HOLD_FLAG_DECRYPT, FTAG, &ds);
1376 	if (error != 0)
1377 		return (error);
1378 
1379 	uint64_t prev_obj = dsl_dataset_phys(ds)->ds_prev_snap_obj;
1380 	uint64_t prev_obj_txg = dsl_dataset_phys(ds)->ds_prev_snap_txg;
1381 
1382 	while (prev_obj != 0) {
1383 		dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
1384 		if ((error = dsl_dataset_hold_obj_flags(dp, prev_obj,
1385 		    DS_HOLD_FLAG_DECRYPT, FTAG, &ds)) == 0 &&
1386 		    dsl_dir_phys(ds->ds_dir)->dd_head_dataset_obj == new_head)
1387 			break;
1388 
1389 		if (error != 0)
1390 			return (error);
1391 
1392 		prev_obj_txg = dsl_dataset_phys(ds)->ds_prev_snap_txg;
1393 		prev_obj = dsl_dataset_phys(ds)->ds_prev_snap_obj;
1394 	}
1395 	dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
1396 	ASSERT(prev_obj != 0);
1397 	*txg = prev_obj_txg;
1398 	return (0);
1399 }
1400 
1401 static void
1402 swap_errlog(spa_t *spa, uint64_t spa_err_obj, uint64_t new_head, uint64_t
1403     old_head, dmu_tx_t *tx)
1404 {
1405 	if (spa_err_obj == 0)
1406 		return;
1407 
1408 	uint64_t old_head_errlog;
1409 	int error = zap_lookup_int_key(spa->spa_meta_objset, spa_err_obj,
1410 	    old_head, &old_head_errlog);
1411 
1412 	/* If no error log, then there is nothing to do. */
1413 	if (error != 0)
1414 		return;
1415 
1416 	uint64_t txg;
1417 	error = find_txg_ancestor_snapshot(spa, new_head, old_head, &txg);
1418 	if (error != 0)
1419 		return;
1420 
1421 	/*
1422 	 * Create an error log if the file system being promoted does not
1423 	 * already have one.
1424 	 */
1425 	uint64_t new_head_errlog;
1426 	error = zap_lookup_int_key(spa->spa_meta_objset, spa_err_obj, new_head,
1427 	    &new_head_errlog);
1428 
1429 	if (error != 0) {
1430 		new_head_errlog = zap_create(spa->spa_meta_objset,
1431 		    DMU_OT_ERROR_LOG, DMU_OT_NONE, 0, tx);
1432 
1433 		(void) zap_update_int_key(spa->spa_meta_objset, spa_err_obj,
1434 		    new_head, new_head_errlog, tx);
1435 	}
1436 
1437 	zap_cursor_t zc;
1438 	zap_attribute_t za;
1439 	zbookmark_err_phys_t err_block;
1440 	for (zap_cursor_init(&zc, spa->spa_meta_objset, old_head_errlog);
1441 	    zap_cursor_retrieve(&zc, &za) == 0; zap_cursor_advance(&zc)) {
1442 
1443 		const char *name = "";
1444 		name_to_errphys(za.za_name, &err_block);
1445 		if (err_block.zb_birth < txg) {
1446 			(void) zap_update(spa->spa_meta_objset, new_head_errlog,
1447 			    za.za_name, 1, strlen(name) + 1, name, tx);
1448 
1449 			(void) zap_remove(spa->spa_meta_objset, old_head_errlog,
1450 			    za.za_name, tx);
1451 		}
1452 	}
1453 	zap_cursor_fini(&zc);
1454 }
1455 
1456 void
1457 spa_swap_errlog(spa_t *spa, uint64_t new_head_ds, uint64_t old_head_ds,
1458     dmu_tx_t *tx)
1459 {
1460 	mutex_enter(&spa->spa_errlog_lock);
1461 	swap_errlog(spa, spa->spa_errlog_scrub, new_head_ds, old_head_ds, tx);
1462 	swap_errlog(spa, spa->spa_errlog_last, new_head_ds, old_head_ds, tx);
1463 	mutex_exit(&spa->spa_errlog_lock);
1464 }
1465 
1466 #if defined(_KERNEL)
1467 /* error handling */
1468 EXPORT_SYMBOL(spa_log_error);
1469 EXPORT_SYMBOL(spa_approx_errlog_size);
1470 EXPORT_SYMBOL(spa_get_last_errlog_size);
1471 EXPORT_SYMBOL(spa_get_errlog);
1472 EXPORT_SYMBOL(spa_errlog_rotate);
1473 EXPORT_SYMBOL(spa_errlog_drain);
1474 EXPORT_SYMBOL(spa_errlog_sync);
1475 EXPORT_SYMBOL(spa_get_errlists);
1476 EXPORT_SYMBOL(spa_delete_dataset_errlog);
1477 EXPORT_SYMBOL(spa_swap_errlog);
1478 EXPORT_SYMBOL(sync_error_list);
1479 EXPORT_SYMBOL(spa_upgrade_errlog);
1480 EXPORT_SYMBOL(find_top_affected_fs);
1481 EXPORT_SYMBOL(find_birth_txg);
1482 EXPORT_SYMBOL(zep_to_zb);
1483 EXPORT_SYMBOL(name_to_errphys);
1484 #endif
1485 
1486 /* BEGIN CSTYLED */
1487 ZFS_MODULE_PARAM(zfs_spa, spa_, upgrade_errlog_limit, UINT, ZMOD_RW,
1488 	"Limit the number of errors which will be upgraded to the new "
1489 	"on-disk error log when enabling head_errlog");
1490 /* END CSTYLED */
1491