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 http://www.opensolaris.org/os/licensing.
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) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23 * Copyright (c) 2011, 2017 by Delphix. All rights reserved.
24 * Copyright (c) 2013 Steven Hartland. All rights reserved.
25 * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
26 * Copyright (c) 2014 Integros [integros.com]
27 * Copyright 2016 Nexenta Systems, Inc.  All rights reserved.
28 */
29
30#include <sys/dsl_pool.h>
31#include <sys/dsl_dataset.h>
32#include <sys/dsl_prop.h>
33#include <sys/dsl_dir.h>
34#include <sys/dsl_synctask.h>
35#include <sys/dsl_scan.h>
36#include <sys/dnode.h>
37#include <sys/dmu_tx.h>
38#include <sys/dmu_objset.h>
39#include <sys/arc.h>
40#include <sys/zap.h>
41#include <sys/zio.h>
42#include <sys/zfs_context.h>
43#include <sys/fs/zfs.h>
44#include <sys/zfs_znode.h>
45#include <sys/spa_impl.h>
46#include <sys/dsl_deadlist.h>
47#include <sys/vdev_impl.h>
48#include <sys/metaslab_impl.h>
49#include <sys/bptree.h>
50#include <sys/zfeature.h>
51#include <sys/zil_impl.h>
52#include <sys/dsl_userhold.h>
53#include <sys/mmp.h>
54
55/*
56 * ZFS Write Throttle
57 * ------------------
58 *
59 * ZFS must limit the rate of incoming writes to the rate at which it is able
60 * to sync data modifications to the backend storage. Throttling by too much
61 * creates an artificial limit; throttling by too little can only be sustained
62 * for short periods and would lead to highly lumpy performance. On a per-pool
63 * basis, ZFS tracks the amount of modified (dirty) data. As operations change
64 * data, the amount of dirty data increases; as ZFS syncs out data, the amount
65 * of dirty data decreases. When the amount of dirty data exceeds a
66 * predetermined threshold further modifications are blocked until the amount
67 * of dirty data decreases (as data is synced out).
68 *
69 * The limit on dirty data is tunable, and should be adjusted according to
70 * both the IO capacity and available memory of the system. The larger the
71 * window, the more ZFS is able to aggregate and amortize metadata (and data)
72 * changes. However, memory is a limited resource, and allowing for more dirty
73 * data comes at the cost of keeping other useful data in memory (for example
74 * ZFS data cached by the ARC).
75 *
76 * Implementation
77 *
78 * As buffers are modified dsl_pool_willuse_space() increments both the per-
79 * txg (dp_dirty_pertxg[]) and poolwide (dp_dirty_total) accounting of
80 * dirty space used; dsl_pool_dirty_space() decrements those values as data
81 * is synced out from dsl_pool_sync(). While only the poolwide value is
82 * relevant, the per-txg value is useful for debugging. The tunable
83 * zfs_dirty_data_max determines the dirty space limit. Once that value is
84 * exceeded, new writes are halted until space frees up.
85 *
86 * The zfs_dirty_data_sync tunable dictates the threshold at which we
87 * ensure that there is a txg syncing (see the comment in txg.c for a full
88 * description of transaction group stages).
89 *
90 * The IO scheduler uses both the dirty space limit and current amount of
91 * dirty data as inputs. Those values affect the number of concurrent IOs ZFS
92 * issues. See the comment in vdev_queue.c for details of the IO scheduler.
93 *
94 * The delay is also calculated based on the amount of dirty data.  See the
95 * comment above dmu_tx_delay() for details.
96 */
97
98/*
99 * zfs_dirty_data_max will be set to zfs_dirty_data_max_percent% of all memory,
100 * capped at zfs_dirty_data_max_max.  It can also be overridden in /etc/system.
101 */
102uint64_t zfs_dirty_data_max;
103uint64_t zfs_dirty_data_max_max = 4ULL * 1024 * 1024 * 1024;
104int zfs_dirty_data_max_percent = 10;
105
106/*
107 * If there's at least this much dirty data (as a percentage of
108 * zfs_dirty_data_max), push out a txg.  This should be less than
109 * zfs_vdev_async_write_active_min_dirty_percent.
110 */
111uint64_t zfs_dirty_data_sync_pct = 20;
112
113/*
114 * Once there is this amount of dirty data, the dmu_tx_delay() will kick in
115 * and delay each transaction.
116 * This value should be >= zfs_vdev_async_write_active_max_dirty_percent.
117 */
118int zfs_delay_min_dirty_percent = 60;
119
120/*
121 * This controls how quickly the delay approaches infinity.
122 * Larger values cause it to delay more for a given amount of dirty data.
123 * Therefore larger values will cause there to be less dirty data for a
124 * given throughput.
125 *
126 * For the smoothest delay, this value should be about 1 billion divided
127 * by the maximum number of operations per second.  This will smoothly
128 * handle between 10x and 1/10th this number.
129 *
130 * Note: zfs_delay_scale * zfs_dirty_data_max must be < 2^64, due to the
131 * multiply in dmu_tx_delay().
132 */
133uint64_t zfs_delay_scale = 1000 * 1000 * 1000 / 2000;
134
135/*
136 * This determines the number of threads used by the dp_sync_taskq.
137 */
138int zfs_sync_taskq_batch_pct = 75;
139
140/*
141 * These tunables determine the behavior of how zil_itxg_clean() is
142 * called via zil_clean() in the context of spa_sync(). When an itxg
143 * list needs to be cleaned, TQ_NOSLEEP will be used when dispatching.
144 * If the dispatch fails, the call to zil_itxg_clean() will occur
145 * synchronously in the context of spa_sync(), which can negatively
146 * impact the performance of spa_sync() (e.g. in the case of the itxg
147 * list having a large number of itxs that needs to be cleaned).
148 *
149 * Thus, these tunables can be used to manipulate the behavior of the
150 * taskq used by zil_clean(); they determine the number of taskq entries
151 * that are pre-populated when the taskq is first created (via the
152 * "zfs_zil_clean_taskq_minalloc" tunable) and the maximum number of
153 * taskq entries that are cached after an on-demand allocation (via the
154 * "zfs_zil_clean_taskq_maxalloc").
155 *
156 * The idea being, we want to try reasonably hard to ensure there will
157 * already be a taskq entry pre-allocated by the time that it is needed
158 * by zil_clean(). This way, we can avoid the possibility of an
159 * on-demand allocation of a new taskq entry from failing, which would
160 * result in zil_itxg_clean() being called synchronously from zil_clean()
161 * (which can adversely affect performance of spa_sync()).
162 *
163 * Additionally, the number of threads used by the taskq can be
164 * configured via the "zfs_zil_clean_taskq_nthr_pct" tunable.
165 */
166int zfs_zil_clean_taskq_nthr_pct = 100;
167int zfs_zil_clean_taskq_minalloc = 1024;
168int zfs_zil_clean_taskq_maxalloc = 1024 * 1024;
169
170int
171dsl_pool_open_special_dir(dsl_pool_t *dp, const char *name, dsl_dir_t **ddp)
172{
173	uint64_t obj;
174	int err;
175
176	err = zap_lookup(dp->dp_meta_objset,
177	    dsl_dir_phys(dp->dp_root_dir)->dd_child_dir_zapobj,
178	    name, sizeof (obj), 1, &obj);
179	if (err)
180		return (err);
181
182	return (dsl_dir_hold_obj(dp, obj, name, dp, ddp));
183}
184
185static dsl_pool_t *
186dsl_pool_open_impl(spa_t *spa, uint64_t txg)
187{
188	dsl_pool_t *dp;
189	blkptr_t *bp = spa_get_rootblkptr(spa);
190
191	dp = kmem_zalloc(sizeof (dsl_pool_t), KM_SLEEP);
192	dp->dp_spa = spa;
193	dp->dp_meta_rootbp = *bp;
194	rrw_init(&dp->dp_config_rwlock, B_TRUE);
195	txg_init(dp, txg);
196	mmp_init(spa);
197
198	txg_list_create(&dp->dp_dirty_datasets, spa,
199	    offsetof(dsl_dataset_t, ds_dirty_link));
200	txg_list_create(&dp->dp_dirty_zilogs, spa,
201	    offsetof(zilog_t, zl_dirty_link));
202	txg_list_create(&dp->dp_dirty_dirs, spa,
203	    offsetof(dsl_dir_t, dd_dirty_link));
204	txg_list_create(&dp->dp_sync_tasks, spa,
205	    offsetof(dsl_sync_task_t, dst_node));
206	txg_list_create(&dp->dp_early_sync_tasks, spa,
207	    offsetof(dsl_sync_task_t, dst_node));
208
209	dp->dp_sync_taskq = taskq_create("dp_sync_taskq",
210	    zfs_sync_taskq_batch_pct, minclsyspri, 1, INT_MAX,
211	    TASKQ_THREADS_CPU_PCT);
212
213	dp->dp_zil_clean_taskq = taskq_create("dp_zil_clean_taskq",
214	    zfs_zil_clean_taskq_nthr_pct, minclsyspri,
215	    zfs_zil_clean_taskq_minalloc,
216	    zfs_zil_clean_taskq_maxalloc,
217	    TASKQ_PREPOPULATE | TASKQ_THREADS_CPU_PCT);
218
219	mutex_init(&dp->dp_lock, NULL, MUTEX_DEFAULT, NULL);
220	cv_init(&dp->dp_spaceavail_cv, NULL, CV_DEFAULT, NULL);
221
222	dp->dp_vnrele_taskq = taskq_create("zfs_vn_rele_taskq", 1, minclsyspri,
223	    1, 4, 0);
224
225	return (dp);
226}
227
228int
229dsl_pool_init(spa_t *spa, uint64_t txg, dsl_pool_t **dpp)
230{
231	int err;
232	dsl_pool_t *dp = dsl_pool_open_impl(spa, txg);
233
234	err = dmu_objset_open_impl(spa, NULL, &dp->dp_meta_rootbp,
235	    &dp->dp_meta_objset);
236	if (err != 0)
237		dsl_pool_close(dp);
238	else
239		*dpp = dp;
240
241	return (err);
242}
243
244int
245dsl_pool_open(dsl_pool_t *dp)
246{
247	int err;
248	dsl_dir_t *dd;
249	dsl_dataset_t *ds;
250	uint64_t obj;
251
252	rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG);
253	err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
254	    DMU_POOL_ROOT_DATASET, sizeof (uint64_t), 1,
255	    &dp->dp_root_dir_obj);
256	if (err)
257		goto out;
258
259	err = dsl_dir_hold_obj(dp, dp->dp_root_dir_obj,
260	    NULL, dp, &dp->dp_root_dir);
261	if (err)
262		goto out;
263
264	err = dsl_pool_open_special_dir(dp, MOS_DIR_NAME, &dp->dp_mos_dir);
265	if (err)
266		goto out;
267
268	if (spa_version(dp->dp_spa) >= SPA_VERSION_ORIGIN) {
269		err = dsl_pool_open_special_dir(dp, ORIGIN_DIR_NAME, &dd);
270		if (err)
271			goto out;
272		err = dsl_dataset_hold_obj(dp,
273		    dsl_dir_phys(dd)->dd_head_dataset_obj, FTAG, &ds);
274		if (err == 0) {
275			err = dsl_dataset_hold_obj(dp,
276			    dsl_dataset_phys(ds)->ds_prev_snap_obj, dp,
277			    &dp->dp_origin_snap);
278			dsl_dataset_rele(ds, FTAG);
279		}
280		dsl_dir_rele(dd, dp);
281		if (err)
282			goto out;
283	}
284
285	if (spa_version(dp->dp_spa) >= SPA_VERSION_DEADLISTS) {
286		err = dsl_pool_open_special_dir(dp, FREE_DIR_NAME,
287		    &dp->dp_free_dir);
288		if (err)
289			goto out;
290
291		err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
292		    DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj);
293		if (err)
294			goto out;
295		VERIFY0(bpobj_open(&dp->dp_free_bpobj,
296		    dp->dp_meta_objset, obj));
297	}
298
299	if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_OBSOLETE_COUNTS)) {
300		err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
301		    DMU_POOL_OBSOLETE_BPOBJ, sizeof (uint64_t), 1, &obj);
302		if (err == 0) {
303			VERIFY0(bpobj_open(&dp->dp_obsolete_bpobj,
304			    dp->dp_meta_objset, obj));
305		} else if (err == ENOENT) {
306			/*
307			 * We might not have created the remap bpobj yet.
308			 */
309			err = 0;
310		} else {
311			goto out;
312		}
313	}
314
315	/*
316	 * Note: errors ignored, because the these special dirs, used for
317	 * space accounting, are only created on demand.
318	 */
319	(void) dsl_pool_open_special_dir(dp, LEAK_DIR_NAME,
320	    &dp->dp_leak_dir);
321
322	if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_ASYNC_DESTROY)) {
323		err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
324		    DMU_POOL_BPTREE_OBJ, sizeof (uint64_t), 1,
325		    &dp->dp_bptree_obj);
326		if (err != 0)
327			goto out;
328	}
329
330	if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_EMPTY_BPOBJ)) {
331		err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
332		    DMU_POOL_EMPTY_BPOBJ, sizeof (uint64_t), 1,
333		    &dp->dp_empty_bpobj);
334		if (err != 0)
335			goto out;
336	}
337
338	err = zap_lookup(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
339	    DMU_POOL_TMP_USERREFS, sizeof (uint64_t), 1,
340	    &dp->dp_tmp_userrefs_obj);
341	if (err == ENOENT)
342		err = 0;
343	if (err)
344		goto out;
345
346	err = dsl_scan_init(dp, dp->dp_tx.tx_open_txg);
347
348out:
349	rrw_exit(&dp->dp_config_rwlock, FTAG);
350	return (err);
351}
352
353void
354dsl_pool_close(dsl_pool_t *dp)
355{
356	/*
357	 * Drop our references from dsl_pool_open().
358	 *
359	 * Since we held the origin_snap from "syncing" context (which
360	 * includes pool-opening context), it actually only got a "ref"
361	 * and not a hold, so just drop that here.
362	 */
363	if (dp->dp_origin_snap != NULL)
364		dsl_dataset_rele(dp->dp_origin_snap, dp);
365	if (dp->dp_mos_dir != NULL)
366		dsl_dir_rele(dp->dp_mos_dir, dp);
367	if (dp->dp_free_dir != NULL)
368		dsl_dir_rele(dp->dp_free_dir, dp);
369	if (dp->dp_leak_dir != NULL)
370		dsl_dir_rele(dp->dp_leak_dir, dp);
371	if (dp->dp_root_dir != NULL)
372		dsl_dir_rele(dp->dp_root_dir, dp);
373
374	bpobj_close(&dp->dp_free_bpobj);
375	bpobj_close(&dp->dp_obsolete_bpobj);
376
377	/* undo the dmu_objset_open_impl(mos) from dsl_pool_open() */
378	if (dp->dp_meta_objset != NULL)
379		dmu_objset_evict(dp->dp_meta_objset);
380
381	txg_list_destroy(&dp->dp_dirty_datasets);
382	txg_list_destroy(&dp->dp_dirty_zilogs);
383	txg_list_destroy(&dp->dp_sync_tasks);
384	txg_list_destroy(&dp->dp_early_sync_tasks);
385	txg_list_destroy(&dp->dp_dirty_dirs);
386
387	taskq_destroy(dp->dp_zil_clean_taskq);
388	taskq_destroy(dp->dp_sync_taskq);
389
390	/*
391	 * We can't set retry to TRUE since we're explicitly specifying
392	 * a spa to flush. This is good enough; any missed buffers for
393	 * this spa won't cause trouble, and they'll eventually fall
394	 * out of the ARC just like any other unused buffer.
395	 */
396	arc_flush(dp->dp_spa, FALSE);
397
398	mmp_fini(dp->dp_spa);
399	txg_fini(dp);
400	dsl_scan_fini(dp);
401	dmu_buf_user_evict_wait();
402
403	rrw_destroy(&dp->dp_config_rwlock);
404	mutex_destroy(&dp->dp_lock);
405	taskq_destroy(dp->dp_vnrele_taskq);
406	if (dp->dp_blkstats != NULL)
407		kmem_free(dp->dp_blkstats, sizeof (zfs_all_blkstats_t));
408	kmem_free(dp, sizeof (dsl_pool_t));
409}
410
411void
412dsl_pool_create_obsolete_bpobj(dsl_pool_t *dp, dmu_tx_t *tx)
413{
414	uint64_t obj;
415	/*
416	 * Currently, we only create the obsolete_bpobj where there are
417	 * indirect vdevs with referenced mappings.
418	 */
419	ASSERT(spa_feature_is_active(dp->dp_spa, SPA_FEATURE_DEVICE_REMOVAL));
420	/* create and open the obsolete_bpobj */
421	obj = bpobj_alloc(dp->dp_meta_objset, SPA_OLD_MAXBLOCKSIZE, tx);
422	VERIFY0(bpobj_open(&dp->dp_obsolete_bpobj, dp->dp_meta_objset, obj));
423	VERIFY0(zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
424	    DMU_POOL_OBSOLETE_BPOBJ, sizeof (uint64_t), 1, &obj, tx));
425	spa_feature_incr(dp->dp_spa, SPA_FEATURE_OBSOLETE_COUNTS, tx);
426}
427
428void
429dsl_pool_destroy_obsolete_bpobj(dsl_pool_t *dp, dmu_tx_t *tx)
430{
431	spa_feature_decr(dp->dp_spa, SPA_FEATURE_OBSOLETE_COUNTS, tx);
432	VERIFY0(zap_remove(dp->dp_meta_objset,
433	    DMU_POOL_DIRECTORY_OBJECT,
434	    DMU_POOL_OBSOLETE_BPOBJ, tx));
435	bpobj_free(dp->dp_meta_objset,
436	    dp->dp_obsolete_bpobj.bpo_object, tx);
437	bpobj_close(&dp->dp_obsolete_bpobj);
438}
439
440dsl_pool_t *
441dsl_pool_create(spa_t *spa, nvlist_t *zplprops, dsl_crypto_params_t *dcp,
442    uint64_t txg)
443{
444	int err;
445	dsl_pool_t *dp = dsl_pool_open_impl(spa, txg);
446	dmu_tx_t *tx = dmu_tx_create_assigned(dp, txg);
447	dsl_dataset_t *ds;
448	uint64_t obj;
449
450	rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG);
451
452	/* create and open the MOS (meta-objset) */
453	dp->dp_meta_objset = dmu_objset_create_impl(spa,
454	    NULL, &dp->dp_meta_rootbp, DMU_OST_META, tx);
455	spa->spa_meta_objset = dp->dp_meta_objset;
456
457	/* create the pool directory */
458	err = zap_create_claim(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
459	    DMU_OT_OBJECT_DIRECTORY, DMU_OT_NONE, 0, tx);
460	ASSERT0(err);
461
462	/* Initialize scan structures */
463	VERIFY0(dsl_scan_init(dp, txg));
464
465	/* create and open the root dir */
466	dp->dp_root_dir_obj = dsl_dir_create_sync(dp, NULL, NULL, tx);
467	VERIFY0(dsl_dir_hold_obj(dp, dp->dp_root_dir_obj,
468	    NULL, dp, &dp->dp_root_dir));
469
470	/* create and open the meta-objset dir */
471	(void) dsl_dir_create_sync(dp, dp->dp_root_dir, MOS_DIR_NAME, tx);
472	VERIFY0(dsl_pool_open_special_dir(dp,
473	    MOS_DIR_NAME, &dp->dp_mos_dir));
474
475	if (spa_version(spa) >= SPA_VERSION_DEADLISTS) {
476		/* create and open the free dir */
477		(void) dsl_dir_create_sync(dp, dp->dp_root_dir,
478		    FREE_DIR_NAME, tx);
479		VERIFY0(dsl_pool_open_special_dir(dp,
480		    FREE_DIR_NAME, &dp->dp_free_dir));
481
482		/* create and open the free_bplist */
483		obj = bpobj_alloc(dp->dp_meta_objset, SPA_OLD_MAXBLOCKSIZE, tx);
484		VERIFY(zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
485		    DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj, tx) == 0);
486		VERIFY0(bpobj_open(&dp->dp_free_bpobj,
487		    dp->dp_meta_objset, obj));
488	}
489
490	if (spa_version(spa) >= SPA_VERSION_DSL_SCRUB)
491		dsl_pool_create_origin(dp, tx);
492
493	/*
494	 * Some features may be needed when creating the root dataset, so we
495	 * create the feature objects here.
496	 */
497	if (spa_version(spa) >= SPA_VERSION_FEATURES)
498		spa_feature_create_zap_objects(spa, tx);
499
500	if (dcp != NULL && dcp->cp_crypt != ZIO_CRYPT_OFF &&
501	    dcp->cp_crypt != ZIO_CRYPT_INHERIT)
502		spa_feature_enable(spa, SPA_FEATURE_ENCRYPTION, tx);
503
504	/* create the root dataset */
505	obj = dsl_dataset_create_sync_dd(dp->dp_root_dir, NULL, dcp, 0, tx);
506
507	/* create the root objset */
508	VERIFY0(dsl_dataset_hold_obj_flags(dp, obj,
509	    DS_HOLD_FLAG_DECRYPT, FTAG, &ds));
510#ifdef _KERNEL
511	{
512		objset_t *os;
513		rrw_enter(&ds->ds_bp_rwlock, RW_READER, FTAG);
514		os = dmu_objset_create_impl(dp->dp_spa, ds,
515		    dsl_dataset_get_blkptr(ds), DMU_OST_ZFS, tx);
516		rrw_exit(&ds->ds_bp_rwlock, FTAG);
517		zfs_create_fs(os, kcred, zplprops, tx);
518	}
519#endif
520	dsl_dataset_rele_flags(ds, DS_HOLD_FLAG_DECRYPT, FTAG);
521
522	dmu_tx_commit(tx);
523
524	rrw_exit(&dp->dp_config_rwlock, FTAG);
525
526	return (dp);
527}
528
529/*
530 * Account for the meta-objset space in its placeholder dsl_dir.
531 */
532void
533dsl_pool_mos_diduse_space(dsl_pool_t *dp,
534    int64_t used, int64_t comp, int64_t uncomp)
535{
536	ASSERT3U(comp, ==, uncomp); /* it's all metadata */
537	mutex_enter(&dp->dp_lock);
538	dp->dp_mos_used_delta += used;
539	dp->dp_mos_compressed_delta += comp;
540	dp->dp_mos_uncompressed_delta += uncomp;
541	mutex_exit(&dp->dp_lock);
542}
543
544static void
545dsl_pool_sync_mos(dsl_pool_t *dp, dmu_tx_t *tx)
546{
547	zio_t *zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
548	dmu_objset_sync(dp->dp_meta_objset, zio, tx);
549	VERIFY0(zio_wait(zio));
550	dprintf_bp(&dp->dp_meta_rootbp, "meta objset rootbp is %s", "");
551	spa_set_rootblkptr(dp->dp_spa, &dp->dp_meta_rootbp);
552}
553
554static void
555dsl_pool_dirty_delta(dsl_pool_t *dp, int64_t delta)
556{
557	ASSERT(MUTEX_HELD(&dp->dp_lock));
558
559	if (delta < 0)
560		ASSERT3U(-delta, <=, dp->dp_dirty_total);
561
562	dp->dp_dirty_total += delta;
563
564	/*
565	 * Note: we signal even when increasing dp_dirty_total.
566	 * This ensures forward progress -- each thread wakes the next waiter.
567	 */
568	if (dp->dp_dirty_total < zfs_dirty_data_max)
569		cv_signal(&dp->dp_spaceavail_cv);
570}
571
572static boolean_t
573dsl_early_sync_task_verify(dsl_pool_t *dp, uint64_t txg)
574{
575	spa_t *spa = dp->dp_spa;
576	vdev_t *rvd = spa->spa_root_vdev;
577
578	for (uint64_t c = 0; c < rvd->vdev_children; c++) {
579		vdev_t *vd = rvd->vdev_child[c];
580		txg_list_t *tl = &vd->vdev_ms_list;
581		metaslab_t *ms;
582
583		for (ms = txg_list_head(tl, TXG_CLEAN(txg)); ms;
584		    ms = txg_list_next(tl, ms, TXG_CLEAN(txg))) {
585			VERIFY(range_tree_is_empty(ms->ms_freeing));
586			VERIFY(range_tree_is_empty(ms->ms_checkpointing));
587		}
588	}
589
590	return (B_TRUE);
591}
592
593void
594dsl_pool_sync(dsl_pool_t *dp, uint64_t txg)
595{
596	zio_t *zio;
597	dmu_tx_t *tx;
598	dsl_dir_t *dd;
599	dsl_dataset_t *ds;
600	objset_t *mos = dp->dp_meta_objset;
601	list_t synced_datasets;
602
603	list_create(&synced_datasets, sizeof (dsl_dataset_t),
604	    offsetof(dsl_dataset_t, ds_synced_link));
605
606	tx = dmu_tx_create_assigned(dp, txg);
607
608	/*
609	 * Run all early sync tasks before writing out any dirty blocks.
610	 * For more info on early sync tasks see block comment in
611	 * dsl_early_sync_task().
612	 */
613	if (!txg_list_empty(&dp->dp_early_sync_tasks, txg)) {
614		dsl_sync_task_t *dst;
615
616		ASSERT3U(spa_sync_pass(dp->dp_spa), ==, 1);
617		while ((dst =
618		    txg_list_remove(&dp->dp_early_sync_tasks, txg)) != NULL) {
619			ASSERT(dsl_early_sync_task_verify(dp, txg));
620			dsl_sync_task_sync(dst, tx);
621		}
622		ASSERT(dsl_early_sync_task_verify(dp, txg));
623	}
624
625	/*
626	 * Write out all dirty blocks of dirty datasets.
627	 */
628	zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
629	while ((ds = txg_list_remove(&dp->dp_dirty_datasets, txg)) != NULL) {
630		/*
631		 * We must not sync any non-MOS datasets twice, because
632		 * we may have taken a snapshot of them.  However, we
633		 * may sync newly-created datasets on pass 2.
634		 */
635		ASSERT(!list_link_active(&ds->ds_synced_link));
636		list_insert_tail(&synced_datasets, ds);
637		dsl_dataset_sync(ds, zio, tx);
638	}
639	VERIFY0(zio_wait(zio));
640
641	/*
642	 * We have written all of the accounted dirty data, so our
643	 * dp_space_towrite should now be zero.  However, some seldom-used
644	 * code paths do not adhere to this (e.g. dbuf_undirty(), also
645	 * rounding error in dbuf_write_physdone).
646	 * Shore up the accounting of any dirtied space now.
647	 */
648	dsl_pool_undirty_space(dp, dp->dp_dirty_pertxg[txg & TXG_MASK], txg);
649
650	/*
651	 * Update the long range free counter after
652	 * we're done syncing user data
653	 */
654	mutex_enter(&dp->dp_lock);
655	ASSERT(spa_sync_pass(dp->dp_spa) == 1 ||
656	    dp->dp_long_free_dirty_pertxg[txg & TXG_MASK] == 0);
657	dp->dp_long_free_dirty_pertxg[txg & TXG_MASK] = 0;
658	mutex_exit(&dp->dp_lock);
659
660	/*
661	 * After the data blocks have been written (ensured by the zio_wait()
662	 * above), update the user/group/project space accounting.  This happens
663	 * in tasks dispatched to dp_sync_taskq, so wait for them before
664	 * continuing.
665	 */
666	for (ds = list_head(&synced_datasets); ds != NULL;
667	    ds = list_next(&synced_datasets, ds)) {
668		dmu_objset_do_userquota_updates(ds->ds_objset, tx);
669	}
670	taskq_wait(dp->dp_sync_taskq);
671
672	/*
673	 * Sync the datasets again to push out the changes due to
674	 * userspace updates.  This must be done before we process the
675	 * sync tasks, so that any snapshots will have the correct
676	 * user accounting information (and we won't get confused
677	 * about which blocks are part of the snapshot).
678	 */
679	zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
680	while ((ds = txg_list_remove(&dp->dp_dirty_datasets, txg)) != NULL) {
681		objset_t *os = ds->ds_objset;
682
683		ASSERT(list_link_active(&ds->ds_synced_link));
684		dmu_buf_rele(ds->ds_dbuf, ds);
685		dsl_dataset_sync(ds, zio, tx);
686
687		/*
688		 * Release any key mappings created by calls to
689		 * dsl_dataset_dirty() from the userquota accounting
690		 * code paths.
691		 */
692		if (os->os_encrypted && !os->os_raw_receive &&
693		    !os->os_next_write_raw[txg & TXG_MASK]) {
694			ASSERT3P(ds->ds_key_mapping, !=, NULL);
695			key_mapping_rele(dp->dp_spa, ds->ds_key_mapping, ds);
696		}
697	}
698	VERIFY0(zio_wait(zio));
699
700	/*
701	 * Now that the datasets have been completely synced, we can
702	 * clean up our in-memory structures accumulated while syncing:
703	 *
704	 *  - move dead blocks from the pending deadlist to the on-disk deadlist
705	 *  - release hold from dsl_dataset_dirty()
706	 *  - release key mapping hold from dsl_dataset_dirty()
707	 */
708	while ((ds = list_remove_head(&synced_datasets)) != NULL) {
709		objset_t *os = ds->ds_objset;
710
711		if (os->os_encrypted && !os->os_raw_receive &&
712		    !os->os_next_write_raw[txg & TXG_MASK]) {
713			ASSERT3P(ds->ds_key_mapping, !=, NULL);
714			key_mapping_rele(dp->dp_spa, ds->ds_key_mapping, ds);
715		}
716
717		dsl_dataset_sync_done(ds, tx);
718	}
719	while ((dd = txg_list_remove(&dp->dp_dirty_dirs, txg)) != NULL) {
720		dsl_dir_sync(dd, tx);
721	}
722
723	/*
724	 * The MOS's space is accounted for in the pool/$MOS
725	 * (dp_mos_dir).  We can't modify the mos while we're syncing
726	 * it, so we remember the deltas and apply them here.
727	 */
728	if (dp->dp_mos_used_delta != 0 || dp->dp_mos_compressed_delta != 0 ||
729	    dp->dp_mos_uncompressed_delta != 0) {
730		dsl_dir_diduse_space(dp->dp_mos_dir, DD_USED_HEAD,
731		    dp->dp_mos_used_delta,
732		    dp->dp_mos_compressed_delta,
733		    dp->dp_mos_uncompressed_delta, tx);
734		dp->dp_mos_used_delta = 0;
735		dp->dp_mos_compressed_delta = 0;
736		dp->dp_mos_uncompressed_delta = 0;
737	}
738
739	if (!multilist_is_empty(mos->os_dirty_dnodes[txg & TXG_MASK])) {
740		dsl_pool_sync_mos(dp, tx);
741	}
742
743	/*
744	 * If we modify a dataset in the same txg that we want to destroy it,
745	 * its dsl_dir's dd_dbuf will be dirty, and thus have a hold on it.
746	 * dsl_dir_destroy_check() will fail if there are unexpected holds.
747	 * Therefore, we want to sync the MOS (thus syncing the dd_dbuf
748	 * and clearing the hold on it) before we process the sync_tasks.
749	 * The MOS data dirtied by the sync_tasks will be synced on the next
750	 * pass.
751	 */
752	if (!txg_list_empty(&dp->dp_sync_tasks, txg)) {
753		dsl_sync_task_t *dst;
754		/*
755		 * No more sync tasks should have been added while we
756		 * were syncing.
757		 */
758		ASSERT3U(spa_sync_pass(dp->dp_spa), ==, 1);
759		while ((dst = txg_list_remove(&dp->dp_sync_tasks, txg)) != NULL)
760			dsl_sync_task_sync(dst, tx);
761	}
762
763	dmu_tx_commit(tx);
764
765	DTRACE_PROBE2(dsl_pool_sync__done, dsl_pool_t *dp, dp, uint64_t, txg);
766}
767
768void
769dsl_pool_sync_done(dsl_pool_t *dp, uint64_t txg)
770{
771	zilog_t *zilog;
772
773	while (zilog = txg_list_head(&dp->dp_dirty_zilogs, txg)) {
774		dsl_dataset_t *ds = dmu_objset_ds(zilog->zl_os);
775		/*
776		 * We don't remove the zilog from the dp_dirty_zilogs
777		 * list until after we've cleaned it. This ensures that
778		 * callers of zilog_is_dirty() receive an accurate
779		 * answer when they are racing with the spa sync thread.
780		 */
781		zil_clean(zilog, txg);
782		(void) txg_list_remove_this(&dp->dp_dirty_zilogs, zilog, txg);
783		ASSERT(!dmu_objset_is_dirty(zilog->zl_os, txg));
784		dmu_buf_rele(ds->ds_dbuf, zilog);
785	}
786	ASSERT(!dmu_objset_is_dirty(dp->dp_meta_objset, txg));
787}
788
789/*
790 * TRUE if the current thread is the tx_sync_thread or if we
791 * are being called from SPA context during pool initialization.
792 */
793int
794dsl_pool_sync_context(dsl_pool_t *dp)
795{
796	return (curthread == dp->dp_tx.tx_sync_thread ||
797	    spa_is_initializing(dp->dp_spa) ||
798	    taskq_member(dp->dp_sync_taskq, curthread));
799}
800
801/*
802 * This function returns the amount of allocatable space in the pool
803 * minus whatever space is currently reserved by ZFS for specific
804 * purposes. Specifically:
805 *
806 * 1] Any reserved SLOP space
807 * 2] Any space used by the checkpoint
808 * 3] Any space used for deferred frees
809 *
810 * The latter 2 are especially important because they are needed to
811 * rectify the SPA's and DMU's different understanding of how much space
812 * is used. Now the DMU is aware of that extra space tracked by the SPA
813 * without having to maintain a separate special dir (e.g similar to
814 * $MOS, $FREEING, and $LEAKED).
815 *
816 * Note: By deferred frees here, we mean the frees that were deferred
817 * in spa_sync() after sync pass 1 (spa_deferred_bpobj), and not the
818 * segments placed in ms_defer trees during metaslab_sync_done().
819 */
820uint64_t
821dsl_pool_adjustedsize(dsl_pool_t *dp, zfs_space_check_t slop_policy)
822{
823	spa_t *spa = dp->dp_spa;
824	uint64_t space, resv, adjustedsize;
825	uint64_t spa_deferred_frees =
826	    spa->spa_deferred_bpobj.bpo_phys->bpo_bytes;
827
828	space = spa_get_dspace(spa)
829	    - spa_get_checkpoint_space(spa) - spa_deferred_frees;
830	resv = spa_get_slop_space(spa);
831
832	switch (slop_policy) {
833	case ZFS_SPACE_CHECK_NORMAL:
834		break;
835	case ZFS_SPACE_CHECK_RESERVED:
836		resv >>= 1;
837		break;
838	case ZFS_SPACE_CHECK_EXTRA_RESERVED:
839		resv >>= 2;
840		break;
841	case ZFS_SPACE_CHECK_NONE:
842		resv = 0;
843		break;
844	default:
845		panic("invalid slop policy value: %d", slop_policy);
846		break;
847	}
848	adjustedsize = (space >= resv) ? (space - resv) : 0;
849
850	return (adjustedsize);
851}
852
853uint64_t
854dsl_pool_unreserved_space(dsl_pool_t *dp, zfs_space_check_t slop_policy)
855{
856	uint64_t poolsize = dsl_pool_adjustedsize(dp, slop_policy);
857	uint64_t deferred =
858	    metaslab_class_get_deferred(spa_normal_class(dp->dp_spa));
859	uint64_t quota = (poolsize >= deferred) ? (poolsize - deferred) : 0;
860	return (quota);
861}
862
863boolean_t
864dsl_pool_need_dirty_delay(dsl_pool_t *dp)
865{
866	uint64_t delay_min_bytes =
867	    zfs_dirty_data_max * zfs_delay_min_dirty_percent / 100;
868	uint64_t dirty_min_bytes =
869	    zfs_dirty_data_max * zfs_dirty_data_sync_pct / 100;
870	boolean_t rv;
871
872	mutex_enter(&dp->dp_lock);
873	if (dp->dp_dirty_total > dirty_min_bytes)
874		txg_kick(dp);
875	rv = (dp->dp_dirty_total > delay_min_bytes);
876	mutex_exit(&dp->dp_lock);
877	return (rv);
878}
879
880void
881dsl_pool_dirty_space(dsl_pool_t *dp, int64_t space, dmu_tx_t *tx)
882{
883	if (space > 0) {
884		mutex_enter(&dp->dp_lock);
885		dp->dp_dirty_pertxg[tx->tx_txg & TXG_MASK] += space;
886		dsl_pool_dirty_delta(dp, space);
887		mutex_exit(&dp->dp_lock);
888	}
889}
890
891void
892dsl_pool_undirty_space(dsl_pool_t *dp, int64_t space, uint64_t txg)
893{
894	ASSERT3S(space, >=, 0);
895	if (space == 0)
896		return;
897	mutex_enter(&dp->dp_lock);
898	if (dp->dp_dirty_pertxg[txg & TXG_MASK] < space) {
899		/* XXX writing something we didn't dirty? */
900		space = dp->dp_dirty_pertxg[txg & TXG_MASK];
901	}
902	ASSERT3U(dp->dp_dirty_pertxg[txg & TXG_MASK], >=, space);
903	dp->dp_dirty_pertxg[txg & TXG_MASK] -= space;
904	ASSERT3U(dp->dp_dirty_total, >=, space);
905	dsl_pool_dirty_delta(dp, -space);
906	mutex_exit(&dp->dp_lock);
907}
908
909/* ARGSUSED */
910static int
911upgrade_clones_cb(dsl_pool_t *dp, dsl_dataset_t *hds, void *arg)
912{
913	dmu_tx_t *tx = arg;
914	dsl_dataset_t *ds, *prev = NULL;
915	int err;
916
917	err = dsl_dataset_hold_obj(dp, hds->ds_object, FTAG, &ds);
918	if (err)
919		return (err);
920
921	while (dsl_dataset_phys(ds)->ds_prev_snap_obj != 0) {
922		err = dsl_dataset_hold_obj(dp,
923		    dsl_dataset_phys(ds)->ds_prev_snap_obj, FTAG, &prev);
924		if (err) {
925			dsl_dataset_rele(ds, FTAG);
926			return (err);
927		}
928
929		if (dsl_dataset_phys(prev)->ds_next_snap_obj != ds->ds_object)
930			break;
931		dsl_dataset_rele(ds, FTAG);
932		ds = prev;
933		prev = NULL;
934	}
935
936	if (prev == NULL) {
937		prev = dp->dp_origin_snap;
938
939		/*
940		 * The $ORIGIN can't have any data, or the accounting
941		 * will be wrong.
942		 */
943		rrw_enter(&ds->ds_bp_rwlock, RW_READER, FTAG);
944		ASSERT0(dsl_dataset_phys(prev)->ds_bp.blk_birth);
945		rrw_exit(&ds->ds_bp_rwlock, FTAG);
946
947		/* The origin doesn't get attached to itself */
948		if (ds->ds_object == prev->ds_object) {
949			dsl_dataset_rele(ds, FTAG);
950			return (0);
951		}
952
953		dmu_buf_will_dirty(ds->ds_dbuf, tx);
954		dsl_dataset_phys(ds)->ds_prev_snap_obj = prev->ds_object;
955		dsl_dataset_phys(ds)->ds_prev_snap_txg =
956		    dsl_dataset_phys(prev)->ds_creation_txg;
957
958		dmu_buf_will_dirty(ds->ds_dir->dd_dbuf, tx);
959		dsl_dir_phys(ds->ds_dir)->dd_origin_obj = prev->ds_object;
960
961		dmu_buf_will_dirty(prev->ds_dbuf, tx);
962		dsl_dataset_phys(prev)->ds_num_children++;
963
964		if (dsl_dataset_phys(ds)->ds_next_snap_obj == 0) {
965			ASSERT(ds->ds_prev == NULL);
966			VERIFY0(dsl_dataset_hold_obj(dp,
967			    dsl_dataset_phys(ds)->ds_prev_snap_obj,
968			    ds, &ds->ds_prev));
969		}
970	}
971
972	ASSERT3U(dsl_dir_phys(ds->ds_dir)->dd_origin_obj, ==, prev->ds_object);
973	ASSERT3U(dsl_dataset_phys(ds)->ds_prev_snap_obj, ==, prev->ds_object);
974
975	if (dsl_dataset_phys(prev)->ds_next_clones_obj == 0) {
976		dmu_buf_will_dirty(prev->ds_dbuf, tx);
977		dsl_dataset_phys(prev)->ds_next_clones_obj =
978		    zap_create(dp->dp_meta_objset,
979		    DMU_OT_NEXT_CLONES, DMU_OT_NONE, 0, tx);
980	}
981	VERIFY0(zap_add_int(dp->dp_meta_objset,
982	    dsl_dataset_phys(prev)->ds_next_clones_obj, ds->ds_object, tx));
983
984	dsl_dataset_rele(ds, FTAG);
985	if (prev != dp->dp_origin_snap)
986		dsl_dataset_rele(prev, FTAG);
987	return (0);
988}
989
990void
991dsl_pool_upgrade_clones(dsl_pool_t *dp, dmu_tx_t *tx)
992{
993	ASSERT(dmu_tx_is_syncing(tx));
994	ASSERT(dp->dp_origin_snap != NULL);
995
996	VERIFY0(dmu_objset_find_dp(dp, dp->dp_root_dir_obj, upgrade_clones_cb,
997	    tx, DS_FIND_CHILDREN | DS_FIND_SERIALIZE));
998}
999
1000/* ARGSUSED */
1001static int
1002upgrade_dir_clones_cb(dsl_pool_t *dp, dsl_dataset_t *ds, void *arg)
1003{
1004	dmu_tx_t *tx = arg;
1005	objset_t *mos = dp->dp_meta_objset;
1006
1007	if (dsl_dir_phys(ds->ds_dir)->dd_origin_obj != 0) {
1008		dsl_dataset_t *origin;
1009
1010		VERIFY0(dsl_dataset_hold_obj(dp,
1011		    dsl_dir_phys(ds->ds_dir)->dd_origin_obj, FTAG, &origin));
1012
1013		if (dsl_dir_phys(origin->ds_dir)->dd_clones == 0) {
1014			dmu_buf_will_dirty(origin->ds_dir->dd_dbuf, tx);
1015			dsl_dir_phys(origin->ds_dir)->dd_clones =
1016			    zap_create(mos, DMU_OT_DSL_CLONES, DMU_OT_NONE,
1017			    0, tx);
1018		}
1019
1020		VERIFY0(zap_add_int(dp->dp_meta_objset,
1021		    dsl_dir_phys(origin->ds_dir)->dd_clones,
1022		    ds->ds_object, tx));
1023
1024		dsl_dataset_rele(origin, FTAG);
1025	}
1026	return (0);
1027}
1028
1029void
1030dsl_pool_upgrade_dir_clones(dsl_pool_t *dp, dmu_tx_t *tx)
1031{
1032	ASSERT(dmu_tx_is_syncing(tx));
1033	uint64_t obj;
1034
1035	(void) dsl_dir_create_sync(dp, dp->dp_root_dir, FREE_DIR_NAME, tx);
1036	VERIFY0(dsl_pool_open_special_dir(dp,
1037	    FREE_DIR_NAME, &dp->dp_free_dir));
1038
1039	/*
1040	 * We can't use bpobj_alloc(), because spa_version() still
1041	 * returns the old version, and we need a new-version bpobj with
1042	 * subobj support.  So call dmu_object_alloc() directly.
1043	 */
1044	obj = dmu_object_alloc(dp->dp_meta_objset, DMU_OT_BPOBJ,
1045	    SPA_OLD_MAXBLOCKSIZE, DMU_OT_BPOBJ_HDR, sizeof (bpobj_phys_t), tx);
1046	VERIFY0(zap_add(dp->dp_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
1047	    DMU_POOL_FREE_BPOBJ, sizeof (uint64_t), 1, &obj, tx));
1048	VERIFY0(bpobj_open(&dp->dp_free_bpobj, dp->dp_meta_objset, obj));
1049
1050	VERIFY0(dmu_objset_find_dp(dp, dp->dp_root_dir_obj,
1051	    upgrade_dir_clones_cb, tx, DS_FIND_CHILDREN | DS_FIND_SERIALIZE));
1052}
1053
1054void
1055dsl_pool_create_origin(dsl_pool_t *dp, dmu_tx_t *tx)
1056{
1057	uint64_t dsobj;
1058	dsl_dataset_t *ds;
1059
1060	ASSERT(dmu_tx_is_syncing(tx));
1061	ASSERT(dp->dp_origin_snap == NULL);
1062	ASSERT(rrw_held(&dp->dp_config_rwlock, RW_WRITER));
1063
1064	/* create the origin dir, ds, & snap-ds */
1065	dsobj = dsl_dataset_create_sync(dp->dp_root_dir, ORIGIN_DIR_NAME,
1066	    NULL, 0, kcred, NULL, tx);
1067	VERIFY0(dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds));
1068	dsl_dataset_snapshot_sync_impl(ds, ORIGIN_DIR_NAME, tx);
1069	VERIFY0(dsl_dataset_hold_obj(dp, dsl_dataset_phys(ds)->ds_prev_snap_obj,
1070	    dp, &dp->dp_origin_snap));
1071	dsl_dataset_rele(ds, FTAG);
1072}
1073
1074taskq_t *
1075dsl_pool_vnrele_taskq(dsl_pool_t *dp)
1076{
1077	return (dp->dp_vnrele_taskq);
1078}
1079
1080/*
1081 * Walk through the pool-wide zap object of temporary snapshot user holds
1082 * and release them.
1083 */
1084void
1085dsl_pool_clean_tmp_userrefs(dsl_pool_t *dp)
1086{
1087	zap_attribute_t za;
1088	zap_cursor_t zc;
1089	objset_t *mos = dp->dp_meta_objset;
1090	uint64_t zapobj = dp->dp_tmp_userrefs_obj;
1091	nvlist_t *holds;
1092
1093	if (zapobj == 0)
1094		return;
1095	ASSERT(spa_version(dp->dp_spa) >= SPA_VERSION_USERREFS);
1096
1097	holds = fnvlist_alloc();
1098
1099	for (zap_cursor_init(&zc, mos, zapobj);
1100	    zap_cursor_retrieve(&zc, &za) == 0;
1101	    zap_cursor_advance(&zc)) {
1102		char *htag;
1103		nvlist_t *tags;
1104
1105		htag = strchr(za.za_name, '-');
1106		*htag = '\0';
1107		++htag;
1108		if (nvlist_lookup_nvlist(holds, za.za_name, &tags) != 0) {
1109			tags = fnvlist_alloc();
1110			fnvlist_add_boolean(tags, htag);
1111			fnvlist_add_nvlist(holds, za.za_name, tags);
1112			fnvlist_free(tags);
1113		} else {
1114			fnvlist_add_boolean(tags, htag);
1115		}
1116	}
1117	dsl_dataset_user_release_tmp(dp, holds);
1118	fnvlist_free(holds);
1119	zap_cursor_fini(&zc);
1120}
1121
1122/*
1123 * Create the pool-wide zap object for storing temporary snapshot holds.
1124 */
1125void
1126dsl_pool_user_hold_create_obj(dsl_pool_t *dp, dmu_tx_t *tx)
1127{
1128	objset_t *mos = dp->dp_meta_objset;
1129
1130	ASSERT(dp->dp_tmp_userrefs_obj == 0);
1131	ASSERT(dmu_tx_is_syncing(tx));
1132
1133	dp->dp_tmp_userrefs_obj = zap_create_link(mos, DMU_OT_USERREFS,
1134	    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_TMP_USERREFS, tx);
1135}
1136
1137static int
1138dsl_pool_user_hold_rele_impl(dsl_pool_t *dp, uint64_t dsobj,
1139    const char *tag, uint64_t now, dmu_tx_t *tx, boolean_t holding)
1140{
1141	objset_t *mos = dp->dp_meta_objset;
1142	uint64_t zapobj = dp->dp_tmp_userrefs_obj;
1143	char *name;
1144	int error;
1145
1146	ASSERT(spa_version(dp->dp_spa) >= SPA_VERSION_USERREFS);
1147	ASSERT(dmu_tx_is_syncing(tx));
1148
1149	/*
1150	 * If the pool was created prior to SPA_VERSION_USERREFS, the
1151	 * zap object for temporary holds might not exist yet.
1152	 */
1153	if (zapobj == 0) {
1154		if (holding) {
1155			dsl_pool_user_hold_create_obj(dp, tx);
1156			zapobj = dp->dp_tmp_userrefs_obj;
1157		} else {
1158			return (SET_ERROR(ENOENT));
1159		}
1160	}
1161
1162	name = kmem_asprintf("%llx-%s", (u_longlong_t)dsobj, tag);
1163	if (holding)
1164		error = zap_add(mos, zapobj, name, 8, 1, &now, tx);
1165	else
1166		error = zap_remove(mos, zapobj, name, tx);
1167	strfree(name);
1168
1169	return (error);
1170}
1171
1172/*
1173 * Add a temporary hold for the given dataset object and tag.
1174 */
1175int
1176dsl_pool_user_hold(dsl_pool_t *dp, uint64_t dsobj, const char *tag,
1177    uint64_t now, dmu_tx_t *tx)
1178{
1179	return (dsl_pool_user_hold_rele_impl(dp, dsobj, tag, now, tx, B_TRUE));
1180}
1181
1182/*
1183 * Release a temporary hold for the given dataset object and tag.
1184 */
1185int
1186dsl_pool_user_release(dsl_pool_t *dp, uint64_t dsobj, const char *tag,
1187    dmu_tx_t *tx)
1188{
1189	return (dsl_pool_user_hold_rele_impl(dp, dsobj, tag, 0, tx, B_FALSE));
1190}
1191
1192/*
1193 * DSL Pool Configuration Lock
1194 *
1195 * The dp_config_rwlock protects against changes to DSL state (e.g. dataset
1196 * creation / destruction / rename / property setting).  It must be held for
1197 * read to hold a dataset or dsl_dir.  I.e. you must call
1198 * dsl_pool_config_enter() or dsl_pool_hold() before calling
1199 * dsl_{dataset,dir}_hold{_obj}.  In most circumstances, the dp_config_rwlock
1200 * must be held continuously until all datasets and dsl_dirs are released.
1201 *
1202 * The only exception to this rule is that if a "long hold" is placed on
1203 * a dataset, then the dp_config_rwlock may be dropped while the dataset
1204 * is still held.  The long hold will prevent the dataset from being
1205 * destroyed -- the destroy will fail with EBUSY.  A long hold can be
1206 * obtained by calling dsl_dataset_long_hold(), or by "owning" a dataset
1207 * (by calling dsl_{dataset,objset}_{try}own{_obj}).
1208 *
1209 * Legitimate long-holders (including owners) should be long-running, cancelable
1210 * tasks that should cause "zfs destroy" to fail.  This includes DMU
1211 * consumers (i.e. a ZPL filesystem being mounted or ZVOL being open),
1212 * "zfs send", and "zfs diff".  There are several other long-holders whose
1213 * uses are suboptimal (e.g. "zfs promote", and zil_suspend()).
1214 *
1215 * The usual formula for long-holding would be:
1216 * dsl_pool_hold()
1217 * dsl_dataset_hold()
1218 * ... perform checks ...
1219 * dsl_dataset_long_hold()
1220 * dsl_pool_rele()
1221 * ... perform long-running task ...
1222 * dsl_dataset_long_rele()
1223 * dsl_dataset_rele()
1224 *
1225 * Note that when the long hold is released, the dataset is still held but
1226 * the pool is not held.  The dataset may change arbitrarily during this time
1227 * (e.g. it could be destroyed).  Therefore you shouldn't do anything to the
1228 * dataset except release it.
1229 *
1230 * User-initiated operations (e.g. ioctls, zfs_ioc_*()) are either read-only
1231 * or modifying operations.
1232 *
1233 * Modifying operations should generally use dsl_sync_task().  The synctask
1234 * infrastructure enforces proper locking strategy with respect to the
1235 * dp_config_rwlock.  See the comment above dsl_sync_task() for details.
1236 *
1237 * Read-only operations will manually hold the pool, then the dataset, obtain
1238 * information from the dataset, then release the pool and dataset.
1239 * dmu_objset_{hold,rele}() are convenience routines that also do the pool
1240 * hold/rele.
1241 */
1242
1243int
1244dsl_pool_hold(const char *name, void *tag, dsl_pool_t **dp)
1245{
1246	spa_t *spa;
1247	int error;
1248
1249	error = spa_open(name, &spa, tag);
1250	if (error == 0) {
1251		*dp = spa_get_dsl(spa);
1252		dsl_pool_config_enter(*dp, tag);
1253	}
1254	return (error);
1255}
1256
1257void
1258dsl_pool_rele(dsl_pool_t *dp, void *tag)
1259{
1260	dsl_pool_config_exit(dp, tag);
1261	spa_close(dp->dp_spa, tag);
1262}
1263
1264void
1265dsl_pool_config_enter(dsl_pool_t *dp, void *tag)
1266{
1267	/*
1268	 * We use a "reentrant" reader-writer lock, but not reentrantly.
1269	 *
1270	 * The rrwlock can (with the track_all flag) track all reading threads,
1271	 * which is very useful for debugging which code path failed to release
1272	 * the lock, and for verifying that the *current* thread does hold
1273	 * the lock.
1274	 *
1275	 * (Unlike a rwlock, which knows that N threads hold it for
1276	 * read, but not *which* threads, so rw_held(RW_READER) returns TRUE
1277	 * if any thread holds it for read, even if this thread doesn't).
1278	 */
1279	ASSERT(!rrw_held(&dp->dp_config_rwlock, RW_READER));
1280	rrw_enter(&dp->dp_config_rwlock, RW_READER, tag);
1281}
1282
1283void
1284dsl_pool_config_enter_prio(dsl_pool_t *dp, void *tag)
1285{
1286	ASSERT(!rrw_held(&dp->dp_config_rwlock, RW_READER));
1287	rrw_enter_read_prio(&dp->dp_config_rwlock, tag);
1288}
1289
1290void
1291dsl_pool_config_exit(dsl_pool_t *dp, void *tag)
1292{
1293	rrw_exit(&dp->dp_config_rwlock, tag);
1294}
1295
1296boolean_t
1297dsl_pool_config_held(dsl_pool_t *dp)
1298{
1299	return (RRW_LOCK_HELD(&dp->dp_config_rwlock));
1300}
1301
1302boolean_t
1303dsl_pool_config_held_writer(dsl_pool_t *dp)
1304{
1305	return (RRW_WRITE_HELD(&dp->dp_config_rwlock));
1306}
1307