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      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 2007 Sun Microsystems, Inc.  All rights reserved.
     23  * Use is subject to license terms.
     24  */
     25 
     26 #pragma ident	"@(#)dmu_objset.c	1.35	07/12/09 SMI"
     27 
     28 #include <sys/cred.h>
     29 #include <sys/zfs_context.h>
     30 #include <sys/dmu_objset.h>
     31 #include <sys/dsl_dir.h>
     32 #include <sys/dsl_dataset.h>
     33 #include <sys/dsl_prop.h>
     34 #include <sys/dsl_pool.h>
     35 #include <sys/dsl_synctask.h>
     36 #include <sys/dsl_deleg.h>
     37 #include <sys/dnode.h>
     38 #include <sys/dbuf.h>
     39 #include <sys/zvol.h>
     40 #include <sys/dmu_tx.h>
     41 #include <sys/zio_checksum.h>
     42 #include <sys/zap.h>
     43 #include <sys/zil.h>
     44 #include <sys/dmu_impl.h>
     45 #include <sys/zfs_ioctl.h>
     46 
     47 spa_t *
     48 dmu_objset_spa(objset_t *os)
     49 {
     50 	return (os->os->os_spa);
     51 }
     52 
     53 zilog_t *
     54 dmu_objset_zil(objset_t *os)
     55 {
     56 	return (os->os->os_zil);
     57 }
     58 
     59 dsl_pool_t *
     60 dmu_objset_pool(objset_t *os)
     61 {
     62 	dsl_dataset_t *ds;
     63 
     64 	if ((ds = os->os->os_dsl_dataset) != NULL && ds->ds_dir)
     65 		return (ds->ds_dir->dd_pool);
     66 	else
     67 		return (spa_get_dsl(os->os->os_spa));
     68 }
     69 
     70 dsl_dataset_t *
     71 dmu_objset_ds(objset_t *os)
     72 {
     73 	return (os->os->os_dsl_dataset);
     74 }
     75 
     76 dmu_objset_type_t
     77 dmu_objset_type(objset_t *os)
     78 {
     79 	return (os->os->os_phys->os_type);
     80 }
     81 
     82 void
     83 dmu_objset_name(objset_t *os, char *buf)
     84 {
     85 	dsl_dataset_name(os->os->os_dsl_dataset, buf);
     86 }
     87 
     88 uint64_t
     89 dmu_objset_id(objset_t *os)
     90 {
     91 	dsl_dataset_t *ds = os->os->os_dsl_dataset;
     92 
     93 	return (ds ? ds->ds_object : 0);
     94 }
     95 
     96 static void
     97 checksum_changed_cb(void *arg, uint64_t newval)
     98 {
     99 	objset_impl_t *osi = arg;
    100 
    101 	/*
    102 	 * Inheritance should have been done by now.
    103 	 */
    104 	ASSERT(newval != ZIO_CHECKSUM_INHERIT);
    105 
    106 	osi->os_checksum = zio_checksum_select(newval, ZIO_CHECKSUM_ON_VALUE);
    107 }
    108 
    109 static void
    110 compression_changed_cb(void *arg, uint64_t newval)
    111 {
    112 	objset_impl_t *osi = arg;
    113 
    114 	/*
    115 	 * Inheritance and range checking should have been done by now.
    116 	 */
    117 	ASSERT(newval != ZIO_COMPRESS_INHERIT);
    118 
    119 	osi->os_compress = zio_compress_select(newval, ZIO_COMPRESS_ON_VALUE);
    120 }
    121 
    122 static void
    123 copies_changed_cb(void *arg, uint64_t newval)
    124 {
    125 	objset_impl_t *osi = arg;
    126 
    127 	/*
    128 	 * Inheritance and range checking should have been done by now.
    129 	 */
    130 	ASSERT(newval > 0);
    131 	ASSERT(newval <= spa_max_replication(osi->os_spa));
    132 
    133 	osi->os_copies = newval;
    134 }
    135 
    136 void
    137 dmu_objset_byteswap(void *buf, size_t size)
    138 {
    139 	objset_phys_t *osp = buf;
    140 
    141 	ASSERT(size == sizeof (objset_phys_t));
    142 	dnode_byteswap(&osp->os_meta_dnode);
    143 	byteswap_uint64_array(&osp->os_zil_header, sizeof (zil_header_t));
    144 	osp->os_type = BSWAP_64(osp->os_type);
    145 }
    146 
    147 int
    148 dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
    149     objset_impl_t **osip)
    150 {
    151 	objset_impl_t *osi;
    152 	int i, err, checksum;
    153 
    154 	ASSERT(ds == NULL || MUTEX_HELD(&ds->ds_opening_lock));
    155 
    156 	osi = kmem_zalloc(sizeof (objset_impl_t), KM_SLEEP);
    157 	osi->os.os = osi;
    158 	osi->os_dsl_dataset = ds;
    159 	osi->os_spa = spa;
    160 	osi->os_rootbp = bp;
    161 	if (!BP_IS_HOLE(osi->os_rootbp)) {
    162 		uint32_t aflags = ARC_WAIT;
    163 		zbookmark_t zb;
    164 		zb.zb_objset = ds ? ds->ds_object : 0;
    165 		zb.zb_object = 0;
    166 		zb.zb_level = -1;
    167 		zb.zb_blkid = 0;
    168 
    169 		dprintf_bp(osi->os_rootbp, "reading %s", "");
    170 		err = arc_read(NULL, spa, osi->os_rootbp,
    171 		    dmu_ot[DMU_OT_OBJSET].ot_byteswap,
    172 		    arc_getbuf_func, &osi->os_phys_buf,
    173 		    ZIO_PRIORITY_SYNC_READ, ZIO_FLAG_CANFAIL, &aflags, &zb);
    174 		if (err) {
    175 			kmem_free(osi, sizeof (objset_impl_t));
    176 			return (err);
    177 		}
    178 		osi->os_phys = osi->os_phys_buf->b_data;
    179 		if (ds == NULL || dsl_dataset_is_snapshot(ds) == 0)
    180 			arc_release(osi->os_phys_buf, &osi->os_phys_buf);
    181 	} else {
    182 		osi->os_phys_buf = arc_buf_alloc(spa, sizeof (objset_phys_t),
    183 		    &osi->os_phys_buf, ARC_BUFC_METADATA);
    184 		osi->os_phys = osi->os_phys_buf->b_data;
    185 		bzero(osi->os_phys, sizeof (objset_phys_t));
    186 	}
    187 
    188 	/*
    189 	 * Note: the changed_cb will be called once before the register
    190 	 * func returns, thus changing the checksum/compression from the
    191 	 * default (fletcher2/off).  Snapshots don't need to know, and
    192 	 * registering would complicate clone promotion.
    193 	 */
    194 	if (ds && ds->ds_phys->ds_num_children == 0) {
    195 		err = dsl_prop_register(ds, "checksum",
    196 		    checksum_changed_cb, osi);
    197 		if (err == 0)
    198 			err = dsl_prop_register(ds, "compression",
    199 			    compression_changed_cb, osi);
    200 		if (err == 0)
    201 			err = dsl_prop_register(ds, "copies",
    202 			    copies_changed_cb, osi);
    203 		if (err) {
    204 			VERIFY(arc_buf_remove_ref(osi->os_phys_buf,
    205 			    &osi->os_phys_buf) == 1);
    206 			kmem_free(osi, sizeof (objset_impl_t));
    207 			return (err);
    208 		}
    209 	} else if (ds == NULL) {
    210 		/* It's the meta-objset. */
    211 		osi->os_checksum = ZIO_CHECKSUM_FLETCHER_4;
    212 		osi->os_compress = ZIO_COMPRESS_LZJB;
    213 		osi->os_copies = spa_max_replication(spa);
    214 	}
    215 
    216 	osi->os_zil = zil_alloc(&osi->os, &osi->os_phys->os_zil_header);
    217 
    218 	/*
    219 	 * Metadata always gets compressed and checksummed.
    220 	 * If the data checksum is multi-bit correctable, and it's not
    221 	 * a ZBT-style checksum, then it's suitable for metadata as well.
    222 	 * Otherwise, the metadata checksum defaults to fletcher4.
    223 	 */
    224 	checksum = osi->os_checksum;
    225 
    226 	if (zio_checksum_table[checksum].ci_correctable &&
    227 	    !zio_checksum_table[checksum].ci_zbt)
    228 		osi->os_md_checksum = checksum;
    229 	else
    230 		osi->os_md_checksum = ZIO_CHECKSUM_FLETCHER_4;
    231 	osi->os_md_compress = ZIO_COMPRESS_LZJB;
    232 
    233 	for (i = 0; i < TXG_SIZE; i++) {
    234 		list_create(&osi->os_dirty_dnodes[i], sizeof (dnode_t),
    235 		    offsetof(dnode_t, dn_dirty_link[i]));
    236 		list_create(&osi->os_free_dnodes[i], sizeof (dnode_t),
    237 		    offsetof(dnode_t, dn_dirty_link[i]));
    238 	}
    239 	list_create(&osi->os_dnodes, sizeof (dnode_t),
    240 	    offsetof(dnode_t, dn_link));
    241 	list_create(&osi->os_downgraded_dbufs, sizeof (dmu_buf_impl_t),
    242 	    offsetof(dmu_buf_impl_t, db_link));
    243 
    244 	mutex_init(&osi->os_lock, NULL, MUTEX_DEFAULT, NULL);
    245 	mutex_init(&osi->os_obj_lock, NULL, MUTEX_DEFAULT, NULL);
    246 	mutex_init(&osi->os_user_ptr_lock, NULL, MUTEX_DEFAULT, NULL);
    247 
    248 	osi->os_meta_dnode = dnode_special_open(osi,
    249 	    &osi->os_phys->os_meta_dnode, DMU_META_DNODE_OBJECT);
    250 
    251 	/*
    252 	 * We should be the only thread trying to do this because we
    253 	 * have ds_opening_lock
    254 	 */
    255 	if (ds) {
    256 		VERIFY(NULL == dsl_dataset_set_user_ptr(ds, osi,
    257 		    dmu_objset_evict));
    258 	}
    259 
    260 	*osip = osi;
    261 	return (0);
    262 }
    263 
    264 static int
    265 dmu_objset_open_ds_os(dsl_dataset_t *ds, objset_t *os, dmu_objset_type_t type)
    266 {
    267 	objset_impl_t *osi;
    268 	int err;
    269 
    270 	mutex_enter(&ds->ds_opening_lock);
    271 	osi = dsl_dataset_get_user_ptr(ds);
    272 	if (osi == NULL) {
    273 		err = dmu_objset_open_impl(dsl_dataset_get_spa(ds),
    274 		    ds, &ds->ds_phys->ds_bp, &osi);
    275 		if (err)
    276 			return (err);
    277 	}
    278 	mutex_exit(&ds->ds_opening_lock);
    279 
    280 	os->os = osi;
    281 	os->os_mode = DS_MODE_NONE;
    282 
    283 	if (type != DMU_OST_ANY && type != os->os->os_phys->os_type)
    284 		return (EINVAL);
    285 	return (0);
    286 }
    287 
    288 int
    289 dmu_objset_open_ds(dsl_dataset_t *ds, dmu_objset_type_t type, objset_t **osp)
    290 {
    291 	objset_t *os;
    292 	int err;
    293 
    294 	os = kmem_alloc(sizeof (objset_t), KM_SLEEP);
    295 	err = dmu_objset_open_ds_os(ds, os, type);
    296 	if (err)
    297 		kmem_free(os, sizeof (objset_t));
    298 	else
    299 		*osp = os;
    300 	return (err);
    301 }
    302 
    303 /* called from zpl */
    304 int
    305 dmu_objset_open(const char *name, dmu_objset_type_t type, int mode,
    306     objset_t **osp)
    307 {
    308 	objset_t *os;
    309 	dsl_dataset_t *ds;
    310 	int err;
    311 
    312 	ASSERT(mode != DS_MODE_NONE);
    313 
    314 	os = kmem_alloc(sizeof (objset_t), KM_SLEEP);
    315 	err = dsl_dataset_open(name, mode, os, &ds);
    316 	if (err) {
    317 		kmem_free(os, sizeof (objset_t));
    318 		return (err);
    319 	}
    320 
    321 	err = dmu_objset_open_ds_os(ds, os, type);
    322 	os->os_mode = mode;
    323 	if (err) {
    324 		kmem_free(os, sizeof (objset_t));
    325 		dsl_dataset_close(ds, mode, os);
    326 	} else {
    327 		*osp = os;
    328 	}
    329 	return (err);
    330 }
    331 
    332 void
    333 dmu_objset_close(objset_t *os)
    334 {
    335 	if (os->os_mode != DS_MODE_NONE)
    336 		dsl_dataset_close(os->os->os_dsl_dataset, os->os_mode, os);
    337 	kmem_free(os, sizeof (objset_t));
    338 }
    339 
    340 int
    341 dmu_objset_evict_dbufs(objset_t *os)
    342 {
    343 	objset_impl_t *osi = os->os;
    344 	dnode_t *dn;
    345 
    346 	mutex_enter(&osi->os_lock);
    347 
    348 	/* process the mdn last, since the other dnodes have holds on it */
    349 	list_remove(&osi->os_dnodes, osi->os_meta_dnode);
    350 	list_insert_tail(&osi->os_dnodes, osi->os_meta_dnode);
    351 
    352 	/*
    353 	 * Find the first dnode with holds.  We have to do this dance
    354 	 * because dnode_add_ref() only works if you already have a
    355 	 * hold.  If there are no holds then it has no dbufs so OK to
    356 	 * skip.
    357 	 */
    358 	for (dn = list_head(&osi->os_dnodes);
    359 	    dn && !dnode_add_ref(dn, FTAG);
    360 	    dn = list_next(&osi->os_dnodes, dn))
    361 		continue;
    362 
    363 	while (dn) {
    364 		dnode_t *next_dn = dn;
    365 
    366 		do {
    367 			next_dn = list_next(&osi->os_dnodes, next_dn);
    368 		} while (next_dn && !dnode_add_ref(next_dn, FTAG));
    369 
    370 		mutex_exit(&osi->os_lock);
    371 		dnode_evict_dbufs(dn);
    372 		dnode_rele(dn, FTAG);
    373 		mutex_enter(&osi->os_lock);
    374 		dn = next_dn;
    375 	}
    376 	mutex_exit(&osi->os_lock);
    377 	return (list_head(&osi->os_dnodes) != osi->os_meta_dnode);
    378 }
    379 
    380 void
    381 dmu_objset_evict(dsl_dataset_t *ds, void *arg)
    382 {
    383 	objset_impl_t *osi = arg;
    384 	objset_t os;
    385 	int i;
    386 
    387 	for (i = 0; i < TXG_SIZE; i++) {
    388 		ASSERT(list_head(&osi->os_dirty_dnodes[i]) == NULL);
    389 		ASSERT(list_head(&osi->os_free_dnodes[i]) == NULL);
    390 	}
    391 
    392 	if (ds && ds->ds_phys->ds_num_children == 0) {
    393 		VERIFY(0 == dsl_prop_unregister(ds, "checksum",
    394 		    checksum_changed_cb, osi));
    395 		VERIFY(0 == dsl_prop_unregister(ds, "compression",
    396 		    compression_changed_cb, osi));
    397 		VERIFY(0 == dsl_prop_unregister(ds, "copies",
    398 		    copies_changed_cb, osi));
    399 	}
    400 
    401 	/*
    402 	 * We should need only a single pass over the dnode list, since
    403 	 * nothing can be added to the list at this point.
    404 	 */
    405 	os.os = osi;
    406 	(void) dmu_objset_evict_dbufs(&os);
    407 
    408 	ASSERT3P(list_head(&osi->os_dnodes), ==, osi->os_meta_dnode);
    409 	ASSERT3P(list_tail(&osi->os_dnodes), ==, osi->os_meta_dnode);
    410 	ASSERT3P(list_head(&osi->os_meta_dnode->dn_dbufs), ==, NULL);
    411 
    412 	dnode_special_close(osi->os_meta_dnode);
    413 	zil_free(osi->os_zil);
    414 
    415 	VERIFY(arc_buf_remove_ref(osi->os_phys_buf, &osi->os_phys_buf) == 1);
    416 	mutex_destroy(&osi->os_lock);
    417 	mutex_destroy(&osi->os_obj_lock);
    418 	mutex_destroy(&osi->os_user_ptr_lock);
    419 	kmem_free(osi, sizeof (objset_impl_t));
    420 }
    421 
    422 /* called from dsl for meta-objset */
    423 objset_impl_t *
    424 dmu_objset_create_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
    425     dmu_objset_type_t type, dmu_tx_t *tx)
    426 {
    427 	objset_impl_t *osi;
    428 	dnode_t *mdn;
    429 
    430 	ASSERT(dmu_tx_is_syncing(tx));
    431 	if (ds)
    432 		mutex_enter(&ds->ds_opening_lock);
    433 	VERIFY(0 == dmu_objset_open_impl(spa, ds, bp, &osi));
    434 	if (ds)
    435 		mutex_exit(&ds->ds_opening_lock);
    436 	mdn = osi->os_meta_dnode;
    437 
    438 	dnode_allocate(mdn, DMU_OT_DNODE, 1 << DNODE_BLOCK_SHIFT,
    439 	    DN_MAX_INDBLKSHIFT, DMU_OT_NONE, 0, tx);
    440 
    441 	/*
    442 	 * We don't want to have to increase the meta-dnode's nlevels
    443 	 * later, because then we could do it in quescing context while
    444 	 * we are also accessing it in open context.
    445 	 *
    446 	 * This precaution is not necessary for the MOS (ds == NULL),
    447 	 * because the MOS is only updated in syncing context.
    448 	 * This is most fortunate: the MOS is the only objset that
    449 	 * needs to be synced multiple times as spa_sync() iterates
    450 	 * to convergence, so minimizing its dn_nlevels matters.
    451 	 */
    452 	if (ds != NULL) {
    453 		int levels = 1;
    454 
    455 		/*
    456 		 * Determine the number of levels necessary for the meta-dnode
    457 		 * to contain DN_MAX_OBJECT dnodes.
    458 		 */
    459 		while ((uint64_t)mdn->dn_nblkptr << (mdn->dn_datablkshift +
    460 		    (levels - 1) * (mdn->dn_indblkshift - SPA_BLKPTRSHIFT)) <
    461 		    DN_MAX_OBJECT * sizeof (dnode_phys_t))
    462 			levels++;
    463 
    464 		mdn->dn_next_nlevels[tx->tx_txg & TXG_MASK] =
    465 		    mdn->dn_nlevels = levels;
    466 	}
    467 
    468 	ASSERT(type != DMU_OST_NONE);
    469 	ASSERT(type != DMU_OST_ANY);
    470 	ASSERT(type < DMU_OST_NUMTYPES);
    471 	osi->os_phys->os_type = type;
    472 
    473 	dsl_dataset_dirty(ds, tx);
    474 
    475 	return (osi);
    476 }
    477 
    478 struct oscarg {
    479 	void (*userfunc)(objset_t *os, void *arg, cred_t *cr, dmu_tx_t *tx);
    480 	void *userarg;
    481 	dsl_dataset_t *clone_parent;
    482 	const char *lastname;
    483 	dmu_objset_type_t type;
    484 };
    485 
    486 /*ARGSUSED*/
    487 static int
    488 dmu_objset_create_check(void *arg1, void *arg2, dmu_tx_t *tx)
    489 {
    490 	dsl_dir_t *dd = arg1;
    491 	struct oscarg *oa = arg2;
    492 	objset_t *mos = dd->dd_pool->dp_meta_objset;
    493 	int err;
    494 	uint64_t ddobj;
    495 
    496 	err = zap_lookup(mos, dd->dd_phys->dd_child_dir_zapobj,
    497 	    oa->lastname, sizeof (uint64_t), 1, &ddobj);
    498 	if (err != ENOENT)
    499 		return (err ? err : EEXIST);
    500 
    501 	if (oa->clone_parent != NULL) {
    502 		/*
    503 		 * You can't clone across pools.
    504 		 */
    505 		if (oa->clone_parent->ds_dir->dd_pool != dd->dd_pool)
    506 			return (EXDEV);
    507 
    508 		/*
    509 		 * You can only clone snapshots, not the head datasets.
    510 		 */
    511 		if (oa->clone_parent->ds_phys->ds_num_children == 0)
    512 			return (EINVAL);
    513 	}
    514 
    515 	return (0);
    516 }
    517 
    518 static void
    519 dmu_objset_create_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
    520 {
    521 	dsl_dir_t *dd = arg1;
    522 	struct oscarg *oa = arg2;
    523 	dsl_dataset_t *ds;
    524 	blkptr_t *bp;
    525 	uint64_t dsobj;
    526 
    527 	ASSERT(dmu_tx_is_syncing(tx));
    528 
    529 	dsobj = dsl_dataset_create_sync(dd, oa->lastname,
    530 	    oa->clone_parent, cr, tx);
    531 
    532 	VERIFY(0 == dsl_dataset_open_obj(dd->dd_pool, dsobj, NULL,
    533 	    DS_MODE_STANDARD | DS_MODE_READONLY, FTAG, &ds));
    534 	bp = dsl_dataset_get_blkptr(ds);
    535 	if (BP_IS_HOLE(bp)) {
    536 		objset_impl_t *osi;
    537 
    538 		/* This is an empty dmu_objset; not a clone. */
    539 		osi = dmu_objset_create_impl(dsl_dataset_get_spa(ds),
    540 		    ds, bp, oa->type, tx);
    541 
    542 		if (oa->userfunc)
    543 			oa->userfunc(&osi->os, oa->userarg, cr, tx);
    544 	}
    545 
    546 	spa_history_internal_log(LOG_DS_CREATE, dd->dd_pool->dp_spa,
    547 	    tx, cr, "dataset = %llu", dsobj);
    548 
    549 	dsl_dataset_close(ds, DS_MODE_STANDARD | DS_MODE_READONLY, FTAG);
    550 }
    551 
    552 int
    553 dmu_objset_create(const char *name, dmu_objset_type_t type,
    554     objset_t *clone_parent,
    555     void (*func)(objset_t *os, void *arg, cred_t *cr, dmu_tx_t *tx), void *arg)
    556 {
    557 	dsl_dir_t *pdd;
    558 	const char *tail;
    559 	int err = 0;
    560 	struct oscarg oa = { 0 };
    561 
    562 	ASSERT(strchr(name, '@') == NULL);
    563 	err = dsl_dir_open(name, FTAG, &pdd, &tail);
    564 	if (err)
    565 		return (err);
    566 	if (tail == NULL) {
    567 		dsl_dir_close(pdd, FTAG);
    568 		return (EEXIST);
    569 	}
    570 
    571 	dprintf("name=%s\n", name);
    572 
    573 	oa.userfunc = func;
    574 	oa.userarg = arg;
    575 	oa.lastname = tail;
    576 	oa.type = type;
    577 
    578 	if (clone_parent != NULL) {
    579 		/*
    580 		 * You can't clone to a different type.
    581 		 */
    582 		if (clone_parent->os->os_phys->os_type != type) {
    583 			dsl_dir_close(pdd, FTAG);
    584 			return (EINVAL);
    585 		}
    586 		oa.clone_parent = clone_parent->os->os_dsl_dataset;
    587 	}
    588 	err = dsl_sync_task_do(pdd->dd_pool, dmu_objset_create_check,
    589 	    dmu_objset_create_sync, pdd, &oa, 5);
    590 	dsl_dir_close(pdd, FTAG);
    591 	return (err);
    592 }
    593 
    594 int
    595 dmu_objset_destroy(const char *name)
    596 {
    597 	objset_t *os;
    598 	int error;
    599 
    600 	/*
    601 	 * If it looks like we'll be able to destroy it, and there's
    602 	 * an unplayed replay log sitting around, destroy the log.
    603 	 * It would be nicer to do this in dsl_dataset_destroy_sync(),
    604 	 * but the replay log objset is modified in open context.
    605 	 */
    606 	error = dmu_objset_open(name, DMU_OST_ANY,
    607 	    DS_MODE_EXCLUSIVE|DS_MODE_READONLY, &os);
    608 	if (error == 0) {
    609 		dsl_dataset_t *ds = os->os->os_dsl_dataset;
    610 		zil_destroy(dmu_objset_zil(os), B_FALSE);
    611 
    612 		/*
    613 		 * dsl_dataset_destroy() closes the ds.
    614 		 * os is just used as the tag after it's freed.
    615 		 */
    616 		kmem_free(os, sizeof (objset_t));
    617 		error = dsl_dataset_destroy(ds, os);
    618 	}
    619 
    620 	return (error);
    621 }
    622 
    623 /*
    624  * This will close the objset.
    625  */
    626 int
    627 dmu_objset_rollback(objset_t *os)
    628 {
    629 	int err;
    630 	dsl_dataset_t *ds;
    631 
    632 	ds = os->os->os_dsl_dataset;
    633 
    634 	if (!dsl_dataset_tryupgrade(ds, DS_MODE_STANDARD, DS_MODE_EXCLUSIVE)) {
    635 		dmu_objset_close(os);
    636 		return (EBUSY);
    637 	}
    638 
    639 	err = dsl_dataset_rollback(ds, os->os->os_phys->os_type);
    640 
    641 	/*
    642 	 * NB: we close the objset manually because the rollback
    643 	 * actually implicitly called dmu_objset_evict(), thus freeing
    644 	 * the objset_impl_t.
    645 	 */
    646 	dsl_dataset_close(ds, DS_MODE_EXCLUSIVE, os);
    647 	kmem_free(os, sizeof (objset_t));
    648 	return (err);
    649 }
    650 
    651 struct snaparg {
    652 	dsl_sync_task_group_t *dstg;
    653 	char *snapname;
    654 	char failed[MAXPATHLEN];
    655 	boolean_t checkperms;
    656 	list_t objsets;
    657 };
    658 
    659 struct osnode {
    660 	list_node_t node;
    661 	objset_t *os;
    662 };
    663 
    664 static int
    665 dmu_objset_snapshot_one(char *name, void *arg)
    666 {
    667 	struct snaparg *sn = arg;
    668 	objset_t *os;
    669 	dmu_objset_stats_t stat;
    670 	int err;
    671 
    672 	(void) strcpy(sn->failed, name);
    673 
    674 	/*
    675 	 * Check permissions only when requested.  This only applies when
    676 	 * doing a recursive snapshot.  The permission checks for the starting
    677 	 * dataset have already been performed in zfs_secpolicy_snapshot()
    678 	 */
    679 	if (sn->checkperms == B_TRUE &&
    680 	    (err = zfs_secpolicy_snapshot_perms(name, CRED())))
    681 		return (err);
    682 
    683 	err = dmu_objset_open(name, DMU_OST_ANY, DS_MODE_STANDARD, &os);
    684 	if (err != 0)
    685 		return (err);
    686 
    687 	/*
    688 	 * If the objset is in an inconsistent state, return busy.
    689 	 */
    690 	dmu_objset_fast_stat(os, &stat);
    691 	if (stat.dds_inconsistent) {
    692 		dmu_objset_close(os);
    693 		return (EBUSY);
    694 	}
    695 
    696 	/*
    697 	 * NB: we need to wait for all in-flight changes to get to disk,
    698 	 * so that we snapshot those changes.  zil_suspend does this as
    699 	 * a side effect.
    700 	 */
    701 	err = zil_suspend(dmu_objset_zil(os));
    702 	if (err == 0) {
    703 		struct osnode *osn;
    704 		dsl_sync_task_create(sn->dstg, dsl_dataset_snapshot_check,
    705 		    dsl_dataset_snapshot_sync, os->os->os_dsl_dataset,
    706 		    sn->snapname, 3);
    707 		osn = kmem_alloc(sizeof (struct osnode), KM_SLEEP);
    708 		osn->os = os;
    709 		list_insert_tail(&sn->objsets, osn);
    710 	} else {
    711 		dmu_objset_close(os);
    712 	}
    713 
    714 	return (err);
    715 }
    716 
    717 int
    718 dmu_objset_snapshot(char *fsname, char *snapname, boolean_t recursive)
    719 {
    720 	dsl_sync_task_t *dst;
    721 	struct osnode *osn;
    722 	struct snaparg sn = { 0 };
    723 	spa_t *spa;
    724 	int err;
    725 
    726 	(void) strcpy(sn.failed, fsname);
    727 
    728 	err = spa_open(fsname, &spa, FTAG);
    729 	if (err)
    730 		return (err);
    731 
    732 	sn.dstg = dsl_sync_task_group_create(spa_get_dsl(spa));
    733 	sn.snapname = snapname;
    734 	list_create(&sn.objsets, sizeof (struct osnode),
    735 	    offsetof(struct osnode, node));
    736 
    737 	if (recursive) {
    738 		sn.checkperms = B_TRUE;
    739 		err = dmu_objset_find(fsname,
    740 		    dmu_objset_snapshot_one, &sn, DS_FIND_CHILDREN);
    741 	} else {
    742 		sn.checkperms = B_FALSE;
    743 		err = dmu_objset_snapshot_one(fsname, &sn);
    744 	}
    745 
    746 	if (err)
    747 		goto out;
    748 
    749 	err = dsl_sync_task_group_wait(sn.dstg);
    750 
    751 	for (dst = list_head(&sn.dstg->dstg_tasks); dst;
    752 	    dst = list_next(&sn.dstg->dstg_tasks, dst)) {
    753 		dsl_dataset_t *ds = dst->dst_arg1;
    754 		if (dst->dst_err)
    755 			dsl_dataset_name(ds, sn.failed);
    756 	}
    757 
    758 	while (osn = list_head(&sn.objsets)) {
    759 		list_remove(&sn.objsets, osn);
    760 		zil_resume(dmu_objset_zil(osn->os));
    761 		dmu_objset_close(osn->os);
    762 		kmem_free(osn, sizeof (struct osnode));
    763 	}
    764 	list_destroy(&sn.objsets);
    765 out:
    766 	if (err)
    767 		(void) strcpy(fsname, sn.failed);
    768 	dsl_sync_task_group_destroy(sn.dstg);
    769 	spa_close(spa, FTAG);
    770 	return (err);
    771 }
    772 
    773 static void
    774 dmu_objset_sync_dnodes(list_t *list, dmu_tx_t *tx)
    775 {
    776 	dnode_t *dn;
    777 
    778 	while (dn = list_head(list)) {
    779 		ASSERT(dn->dn_object != DMU_META_DNODE_OBJECT);
    780 		ASSERT(dn->dn_dbuf->db_data_pending);
    781 		/*
    782 		 * Initialize dn_zio outside dnode_sync()
    783 		 * to accomodate meta-dnode
    784 		 */
    785 		dn->dn_zio = dn->dn_dbuf->db_data_pending->dr_zio;
    786 		ASSERT(dn->dn_zio);
    787 
    788 		ASSERT3U(dn->dn_nlevels, <=, DN_MAX_LEVELS);
    789 		list_remove(list, dn);
    790 		dnode_sync(dn, tx);
    791 	}
    792 }
    793 
    794 /* ARGSUSED */
    795 static void
    796 ready(zio_t *zio, arc_buf_t *abuf, void *arg)
    797 {
    798 	objset_impl_t *os = arg;
    799 	blkptr_t *bp = os->os_rootbp;
    800 	dnode_phys_t *dnp = &os->os_phys->os_meta_dnode;
    801 	int i;
    802 
    803 	ASSERT(bp == zio->io_bp);
    804 
    805 	/*
    806 	 * Update rootbp fill count.
    807 	 */
    808 	bp->blk_fill = 1;	/* count the meta-dnode */
    809 	for (i = 0; i < dnp->dn_nblkptr; i++)
    810 		bp->blk_fill += dnp->dn_blkptr[i].blk_fill;
    811 
    812 	BP_SET_TYPE(bp, DMU_OT_OBJSET);
    813 	BP_SET_LEVEL(bp, 0);
    814 
    815 	/* We must do this after we've set the bp's type and level */
    816 	if (!DVA_EQUAL(BP_IDENTITY(bp),
    817 	    BP_IDENTITY(&zio->io_bp_orig))) {
    818 		if (zio->io_bp_orig.blk_birth == os->os_synctx->tx_txg)
    819 			dsl_dataset_block_kill(os->os_dsl_dataset,
    820 			    &zio->io_bp_orig, NULL, os->os_synctx);
    821 		dsl_dataset_block_born(os->os_dsl_dataset, bp, os->os_synctx);
    822 	}
    823 }
    824 
    825 /* ARGSUSED */
    826 static void
    827 killer(zio_t *zio, arc_buf_t *abuf, void *arg)
    828 {
    829 	objset_impl_t *os = arg;
    830 
    831 	ASSERT3U(zio->io_error, ==, 0);
    832 	arc_release(os->os_phys_buf, &os->os_phys_buf);
    833 }
    834 
    835 /* called from dsl */
    836 void
    837 dmu_objset_sync(objset_impl_t *os, zio_t *pio, dmu_tx_t *tx)
    838 {
    839 	int txgoff;
    840 	zbookmark_t zb;
    841 	zio_t *zio;
    842 	list_t *list;
    843 	dbuf_dirty_record_t *dr;
    844 
    845 	dprintf_ds(os->os_dsl_dataset, "txg=%llu\n", tx->tx_txg);
    846 
    847 	ASSERT(dmu_tx_is_syncing(tx));
    848 	/* XXX the write_done callback should really give us the tx... */
    849 	os->os_synctx = tx;
    850 
    851 	if (os->os_dsl_dataset == NULL) {
    852 		/*
    853 		 * This is the MOS.  If we have upgraded,
    854 		 * spa_max_replication() could change, so reset
    855 		 * os_copies here.
    856 		 */
    857 		os->os_copies = spa_max_replication(os->os_spa);
    858 	}
    859 
    860 	/*
    861 	 * Create the root block IO
    862 	 */
    863 	zb.zb_objset = os->os_dsl_dataset ? os->os_dsl_dataset->ds_object : 0;
    864 	zb.zb_object = 0;
    865 	zb.zb_level = -1;
    866 	zb.zb_blkid = 0;
    867 	if (BP_IS_OLDER(os->os_rootbp, tx->tx_txg)) {
    868 		dsl_dataset_block_kill(os->os_dsl_dataset,
    869 		    os->os_rootbp, pio, tx);
    870 	}
    871 	zio = arc_write(pio, os->os_spa, os->os_md_checksum,
    872 	    os->os_md_compress,
    873 	    dmu_get_replication_level(os, &zb, DMU_OT_OBJSET),
    874 	    tx->tx_txg, os->os_rootbp, os->os_phys_buf, ready, killer, os,
    875 	    ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_MUSTSUCCEED | ZIO_FLAG_METADATA,
    876 	    &zb);
    877 
    878 	/*
    879 	 * Sync meta-dnode - the parent IO for the sync is the root block
    880 	 */
    881 	os->os_meta_dnode->dn_zio = zio;
    882 	dnode_sync(os->os_meta_dnode, tx);
    883 
    884 	txgoff = tx->tx_txg & TXG_MASK;
    885 
    886 	dmu_objset_sync_dnodes(&os->os_free_dnodes[txgoff], tx);
    887 	dmu_objset_sync_dnodes(&os->os_dirty_dnodes[txgoff], tx);
    888 
    889 	list = &os->os_meta_dnode->dn_dirty_records[txgoff];
    890 	while (dr = list_head(list)) {
    891 		ASSERT(dr->dr_dbuf->db_level == 0);
    892 		list_remove(list, dr);
    893 		if (dr->dr_zio)
    894 			zio_nowait(dr->dr_zio);
    895 	}
    896 	/*
    897 	 * Free intent log blocks up to this tx.
    898 	 */
    899 	zil_sync(os->os_zil, tx);
    900 	zio_nowait(zio);
    901 }
    902 
    903 void
    904 dmu_objset_space(objset_t *os, uint64_t *refdbytesp, uint64_t *availbytesp,
    905     uint64_t *usedobjsp, uint64_t *availobjsp)
    906 {
    907 	dsl_dataset_space(os->os->os_dsl_dataset, refdbytesp, availbytesp,
    908 	    usedobjsp, availobjsp);
    909 }
    910 
    911 uint64_t
    912 dmu_objset_fsid_guid(objset_t *os)
    913 {
    914 	return (dsl_dataset_fsid_guid(os->os->os_dsl_dataset));
    915 }
    916 
    917 void
    918 dmu_objset_fast_stat(objset_t *os, dmu_objset_stats_t *stat)
    919 {
    920 	stat->dds_type = os->os->os_phys->os_type;
    921 	if (os->os->os_dsl_dataset)
    922 		dsl_dataset_fast_stat(os->os->os_dsl_dataset, stat);
    923 }
    924 
    925 void
    926 dmu_objset_stats(objset_t *os, nvlist_t *nv)
    927 {
    928 	ASSERT(os->os->os_dsl_dataset ||
    929 	    os->os->os_phys->os_type == DMU_OST_META);
    930 
    931 	if (os->os->os_dsl_dataset != NULL)
    932 		dsl_dataset_stats(os->os->os_dsl_dataset, nv);
    933 
    934 	dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_TYPE,
    935 	    os->os->os_phys->os_type);
    936 }
    937 
    938 int
    939 dmu_objset_is_snapshot(objset_t *os)
    940 {
    941 	if (os->os->os_dsl_dataset != NULL)
    942 		return (dsl_dataset_is_snapshot(os->os->os_dsl_dataset));
    943 	else
    944 		return (B_FALSE);
    945 }
    946 
    947 int
    948 dmu_snapshot_list_next(objset_t *os, int namelen, char *name,
    949     uint64_t *idp, uint64_t *offp, boolean_t *case_conflict)
    950 {
    951 	dsl_dataset_t *ds = os->os->os_dsl_dataset;
    952 	zap_cursor_t cursor;
    953 	zap_attribute_t attr;
    954 
    955 	if (ds->ds_phys->ds_snapnames_zapobj == 0)
    956 		return (ENOENT);
    957 
    958 	zap_cursor_init_serialized(&cursor,
    959 	    ds->ds_dir->dd_pool->dp_meta_objset,
    960 	    ds->ds_phys->ds_snapnames_zapobj, *offp);
    961 
    962 	if (zap_cursor_retrieve(&cursor, &attr) != 0) {
    963 		zap_cursor_fini(&cursor);
    964 		return (ENOENT);
    965 	}
    966 
    967 	if (strlen(attr.za_name) + 1 > namelen) {
    968 		zap_cursor_fini(&cursor);
    969 		return (ENAMETOOLONG);
    970 	}
    971 
    972 	(void) strcpy(name, attr.za_name);
    973 	if (idp)
    974 		*idp = attr.za_first_integer;
    975 	if (case_conflict)
    976 		*case_conflict = attr.za_normalization_conflict;
    977 	zap_cursor_advance(&cursor);
    978 	*offp = zap_cursor_serialize(&cursor);
    979 	zap_cursor_fini(&cursor);
    980 
    981 	return (0);
    982 }
    983 
    984 int
    985 dmu_dir_list_next(objset_t *os, int namelen, char *name,
    986     uint64_t *idp, uint64_t *offp)
    987 {
    988 	dsl_dir_t *dd = os->os->os_dsl_dataset->ds_dir;
    989 	zap_cursor_t cursor;
    990 	zap_attribute_t attr;
    991 
    992 	/* there is no next dir on a snapshot! */
    993 	if (os->os->os_dsl_dataset->ds_object !=
    994 	    dd->dd_phys->dd_head_dataset_obj)
    995 		return (ENOENT);
    996 
    997 	zap_cursor_init_serialized(&cursor,
    998 	    dd->dd_pool->dp_meta_objset,
    999 	    dd->dd_phys->dd_child_dir_zapobj, *offp);
   1000 
   1001 	if (zap_cursor_retrieve(&cursor, &attr) != 0) {
   1002 		zap_cursor_fini(&cursor);
   1003 		return (ENOENT);
   1004 	}
   1005 
   1006 	if (strlen(attr.za_name) + 1 > namelen) {
   1007 		zap_cursor_fini(&cursor);
   1008 		return (ENAMETOOLONG);
   1009 	}
   1010 
   1011 	(void) strcpy(name, attr.za_name);
   1012 	if (idp)
   1013 		*idp = attr.za_first_integer;
   1014 	zap_cursor_advance(&cursor);
   1015 	*offp = zap_cursor_serialize(&cursor);
   1016 	zap_cursor_fini(&cursor);
   1017 
   1018 	return (0);
   1019 }
   1020 
   1021 /*
   1022  * Find all objsets under name, and for each, call 'func(child_name, arg)'.
   1023  */
   1024 int
   1025 dmu_objset_find(char *name, int func(char *, void *), void *arg, int flags)
   1026 {
   1027 	dsl_dir_t *dd;
   1028 	objset_t *os;
   1029 	uint64_t snapobj;
   1030 	zap_cursor_t zc;
   1031 	zap_attribute_t *attr;
   1032 	char *child;
   1033 	int do_self, err;
   1034 
   1035 	err = dsl_dir_open(name, FTAG, &dd, NULL);
   1036 	if (err)
   1037 		return (err);
   1038 
   1039 	/* NB: the $MOS dir doesn't have a head dataset */
   1040 	do_self = (dd->dd_phys->dd_head_dataset_obj != 0);
   1041 	attr = kmem_alloc(sizeof (zap_attribute_t), KM_SLEEP);
   1042 
   1043 	/*
   1044 	 * Iterate over all children.
   1045 	 */
   1046 	if (flags & DS_FIND_CHILDREN) {
   1047 		for (zap_cursor_init(&zc, dd->dd_pool->dp_meta_objset,
   1048 		    dd->dd_phys->dd_child_dir_zapobj);
   1049 		    zap_cursor_retrieve(&zc, attr) == 0;
   1050 		    (void) zap_cursor_advance(&zc)) {
   1051 			ASSERT(attr->za_integer_length == sizeof (uint64_t));
   1052 			ASSERT(attr->za_num_integers == 1);
   1053 
   1054 			/*
   1055 			 * No separating '/' because parent's name ends in /.
   1056 			 */
   1057 			child = kmem_alloc(MAXPATHLEN, KM_SLEEP);
   1058 			/* XXX could probably just use name here */
   1059 			dsl_dir_name(dd, child);
   1060 			(void) strcat(child, "/");
   1061 			(void) strcat(child, attr->za_name);
   1062 			err = dmu_objset_find(child, func, arg, flags);
   1063 			kmem_free(child, MAXPATHLEN);
   1064 			if (err)
   1065 				break;
   1066 		}
   1067 		zap_cursor_fini(&zc);
   1068 
   1069 		if (err) {
   1070 			dsl_dir_close(dd, FTAG);
   1071 			kmem_free(attr, sizeof (zap_attribute_t));
   1072 			return (err);
   1073 		}
   1074 	}
   1075 
   1076 	/*
   1077 	 * Iterate over all snapshots.
   1078 	 */
   1079 	if ((flags & DS_FIND_SNAPSHOTS) &&
   1080 	    dmu_objset_open(name, DMU_OST_ANY,
   1081 	    DS_MODE_STANDARD | DS_MODE_READONLY, &os) == 0) {
   1082 
   1083 		snapobj = os->os->os_dsl_dataset->ds_phys->ds_snapnames_zapobj;
   1084 		dmu_objset_close(os);
   1085 
   1086 		for (zap_cursor_init(&zc, dd->dd_pool->dp_meta_objset, snapobj);
   1087 		    zap_cursor_retrieve(&zc, attr) == 0;
   1088 		    (void) zap_cursor_advance(&zc)) {
   1089 			ASSERT(attr->za_integer_length == sizeof (uint64_t));
   1090 			ASSERT(attr->za_num_integers == 1);
   1091 
   1092 			child = kmem_alloc(MAXPATHLEN, KM_SLEEP);
   1093 			/* XXX could probably just use name here */
   1094 			dsl_dir_name(dd, child);
   1095 			(void) strcat(child, "@");
   1096 			(void) strcat(child, attr->za_name);
   1097 			err = func(child, arg);
   1098 			kmem_free(child, MAXPATHLEN);
   1099 			if (err)
   1100 				break;
   1101 		}
   1102 		zap_cursor_fini(&zc);
   1103 	}
   1104 
   1105 	dsl_dir_close(dd, FTAG);
   1106 	kmem_free(attr, sizeof (zap_attribute_t));
   1107 
   1108 	if (err)
   1109 		return (err);
   1110 
   1111 	/*
   1112 	 * Apply to self if appropriate.
   1113 	 */
   1114 	if (do_self)
   1115 		err = func(name, arg);
   1116 	return (err);
   1117 }
   1118 
   1119 void
   1120 dmu_objset_set_user(objset_t *os, void *user_ptr)
   1121 {
   1122 	ASSERT(MUTEX_HELD(&os->os->os_user_ptr_lock));
   1123 	os->os->os_user_ptr = user_ptr;
   1124 }
   1125 
   1126 void *
   1127 dmu_objset_get_user(objset_t *os)
   1128 {
   1129 	ASSERT(MUTEX_HELD(&os->os->os_user_ptr_lock));
   1130 	return (os->os->os_user_ptr);
   1131 }
   1132