xref: /illumos-gate/usr/src/uts/common/fs/zfs/dmu.c (revision 52abb70e)
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  */
24 /*
25  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
26  * Copyright (c) 2013, Joyent, Inc. All rights reserved.
27  * Copyright 2016 Nexenta Systems, Inc. All rights reserved.
28  * Copyright (c) 2011, 2017 by Delphix. All rights reserved.
29  * Copyright (c) 2018 DilOS
30  */
31 
32 #include <sys/dmu.h>
33 #include <sys/dmu_impl.h>
34 #include <sys/dmu_tx.h>
35 #include <sys/dbuf.h>
36 #include <sys/dnode.h>
37 #include <sys/zfs_context.h>
38 #include <sys/dmu_objset.h>
39 #include <sys/dmu_traverse.h>
40 #include <sys/dsl_dataset.h>
41 #include <sys/dsl_dir.h>
42 #include <sys/dsl_pool.h>
43 #include <sys/dsl_synctask.h>
44 #include <sys/dsl_prop.h>
45 #include <sys/dmu_zfetch.h>
46 #include <sys/zfs_ioctl.h>
47 #include <sys/zap.h>
48 #include <sys/zio_checksum.h>
49 #include <sys/zio_compress.h>
50 #include <sys/sa.h>
51 #include <sys/zfeature.h>
52 #include <sys/abd.h>
53 #ifdef _KERNEL
54 #include <sys/vmsystm.h>
55 #include <sys/zfs_znode.h>
56 #endif
57 
58 static xuio_stats_t xuio_stats = {
59 	{ "onloan_read_buf",	KSTAT_DATA_UINT64 },
60 	{ "onloan_write_buf",	KSTAT_DATA_UINT64 },
61 	{ "read_buf_copied",	KSTAT_DATA_UINT64 },
62 	{ "read_buf_nocopy",	KSTAT_DATA_UINT64 },
63 	{ "write_buf_copied",	KSTAT_DATA_UINT64 },
64 	{ "write_buf_nocopy",	KSTAT_DATA_UINT64 }
65 };
66 
67 #define	XUIOSTAT_INCR(stat, val)	\
68 	atomic_add_64(&xuio_stats.stat.value.ui64, (val))
69 #define	XUIOSTAT_BUMP(stat)	XUIOSTAT_INCR(stat, 1)
70 
71 /*
72  * Enable/disable nopwrite feature.
73  */
74 int zfs_nopwrite_enabled = 1;
75 
76 /*
77  * Tunable to control percentage of dirtied blocks from frees in one TXG.
78  * After this threshold is crossed, additional dirty blocks from frees
79  * wait until the next TXG.
80  * A value of zero will disable this throttle.
81  */
82 uint32_t zfs_per_txg_dirty_frees_percent = 30;
83 
84 /*
85  * This can be used for testing, to ensure that certain actions happen
86  * while in the middle of a remap (which might otherwise complete too
87  * quickly).
88  */
89 int zfs_object_remap_one_indirect_delay_ticks = 0;
90 
91 /*
92  * Limit the amount we can prefetch with one call to this amount.  This
93  * helps to limit the amount of memory that can be used by prefetching.
94  * Larger objects should be prefetched a bit at a time.
95  */
96 uint64_t dmu_prefetch_max = 8 * SPA_MAXBLOCKSIZE;
97 
98 const dmu_object_type_info_t dmu_ot[DMU_OT_NUMTYPES] = {
99 	{ DMU_BSWAP_UINT8,  TRUE,  FALSE,  "unallocated"		},
100 	{ DMU_BSWAP_ZAP,    TRUE,  TRUE,   "object directory"		},
101 	{ DMU_BSWAP_UINT64, TRUE,  TRUE,   "object array"		},
102 	{ DMU_BSWAP_UINT8,  TRUE,  FALSE,  "packed nvlist"		},
103 	{ DMU_BSWAP_UINT64, TRUE,  FALSE,  "packed nvlist size"		},
104 	{ DMU_BSWAP_UINT64, TRUE,  FALSE,  "bpobj"			},
105 	{ DMU_BSWAP_UINT64, TRUE,  FALSE,  "bpobj header"		},
106 	{ DMU_BSWAP_UINT64, TRUE,  FALSE,  "SPA space map header"	},
107 	{ DMU_BSWAP_UINT64, TRUE,  FALSE,  "SPA space map"		},
108 	{ DMU_BSWAP_UINT64, TRUE,  FALSE,  "ZIL intent log"		},
109 	{ DMU_BSWAP_DNODE,  TRUE,  FALSE,  "DMU dnode"			},
110 	{ DMU_BSWAP_OBJSET, TRUE,  TRUE,   "DMU objset"			},
111 	{ DMU_BSWAP_UINT64, TRUE,  TRUE,   "DSL directory"		},
112 	{ DMU_BSWAP_ZAP,    TRUE,  TRUE,   "DSL directory child map"	},
113 	{ DMU_BSWAP_ZAP,    TRUE,  TRUE,   "DSL dataset snap map"	},
114 	{ DMU_BSWAP_ZAP,    TRUE,  TRUE,   "DSL props"			},
115 	{ DMU_BSWAP_UINT64, TRUE,  TRUE,   "DSL dataset"		},
116 	{ DMU_BSWAP_ZNODE,  TRUE,  FALSE,  "ZFS znode"			},
117 	{ DMU_BSWAP_OLDACL, TRUE,  FALSE,  "ZFS V0 ACL"			},
118 	{ DMU_BSWAP_UINT8,  FALSE, FALSE,  "ZFS plain file"		},
119 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "ZFS directory"		},
120 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "ZFS master node"		},
121 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "ZFS delete queue"		},
122 	{ DMU_BSWAP_UINT8,  FALSE, FALSE,  "zvol object"		},
123 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "zvol prop"			},
124 	{ DMU_BSWAP_UINT8,  FALSE, FALSE,  "other uint8[]"		},
125 	{ DMU_BSWAP_UINT64, FALSE, FALSE,  "other uint64[]"		},
126 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "other ZAP"			},
127 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "persistent error log"	},
128 	{ DMU_BSWAP_UINT8,  TRUE,  FALSE,  "SPA history"		},
129 	{ DMU_BSWAP_UINT64, TRUE,  FALSE,  "SPA history offsets"	},
130 	{ DMU_BSWAP_ZAP,    TRUE,  TRUE,   "Pool properties"		},
131 	{ DMU_BSWAP_ZAP,    TRUE,  TRUE,   "DSL permissions"		},
132 	{ DMU_BSWAP_ACL,    TRUE,  FALSE,  "ZFS ACL"			},
133 	{ DMU_BSWAP_UINT8,  TRUE,  FALSE,  "ZFS SYSACL"			},
134 	{ DMU_BSWAP_UINT8,  TRUE,  FALSE,  "FUID table"			},
135 	{ DMU_BSWAP_UINT64, TRUE,  FALSE,  "FUID table size"		},
136 	{ DMU_BSWAP_ZAP,    TRUE,  TRUE,   "DSL dataset next clones"	},
137 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "scan work queue"		},
138 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "ZFS user/group used"	},
139 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "ZFS user/group quota"	},
140 	{ DMU_BSWAP_ZAP,    TRUE,  TRUE,   "snapshot refcount tags"	},
141 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "DDT ZAP algorithm"		},
142 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "DDT statistics"		},
143 	{ DMU_BSWAP_UINT8,  TRUE,  FALSE,  "System attributes"		},
144 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "SA master node"		},
145 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "SA attr registration"	},
146 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "SA attr layouts"		},
147 	{ DMU_BSWAP_ZAP,    TRUE,  FALSE,  "scan translations"		},
148 	{ DMU_BSWAP_UINT8,  FALSE, FALSE,  "deduplicated block"		},
149 	{ DMU_BSWAP_ZAP,    TRUE,  TRUE,   "DSL deadlist map"		},
150 	{ DMU_BSWAP_UINT64, TRUE,  TRUE,   "DSL deadlist map hdr"	},
151 	{ DMU_BSWAP_ZAP,    TRUE,  TRUE,   "DSL dir clones"		},
152 	{ DMU_BSWAP_UINT64, TRUE,  FALSE,  "bpobj subobj"		}
153 };
154 
155 const dmu_object_byteswap_info_t dmu_ot_byteswap[DMU_BSWAP_NUMFUNCS] = {
156 	{	byteswap_uint8_array,	"uint8"		},
157 	{	byteswap_uint16_array,	"uint16"	},
158 	{	byteswap_uint32_array,	"uint32"	},
159 	{	byteswap_uint64_array,	"uint64"	},
160 	{	zap_byteswap,		"zap"		},
161 	{	dnode_buf_byteswap,	"dnode"		},
162 	{	dmu_objset_byteswap,	"objset"	},
163 	{	zfs_znode_byteswap,	"znode"		},
164 	{	zfs_oldacl_byteswap,	"oldacl"	},
165 	{	zfs_acl_byteswap,	"acl"		}
166 };
167 
168 int
169 dmu_buf_hold_noread_by_dnode(dnode_t *dn, uint64_t offset,
170     void *tag, dmu_buf_t **dbp)
171 {
172 	uint64_t blkid;
173 	dmu_buf_impl_t *db;
174 
175 	blkid = dbuf_whichblock(dn, 0, offset);
176 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
177 	db = dbuf_hold(dn, blkid, tag);
178 	rw_exit(&dn->dn_struct_rwlock);
179 
180 	if (db == NULL) {
181 		*dbp = NULL;
182 		return (SET_ERROR(EIO));
183 	}
184 
185 	*dbp = &db->db;
186 	return (0);
187 }
188 int
189 dmu_buf_hold_noread(objset_t *os, uint64_t object, uint64_t offset,
190     void *tag, dmu_buf_t **dbp)
191 {
192 	dnode_t *dn;
193 	uint64_t blkid;
194 	dmu_buf_impl_t *db;
195 	int err;
196 
197 	err = dnode_hold(os, object, FTAG, &dn);
198 	if (err)
199 		return (err);
200 	blkid = dbuf_whichblock(dn, 0, offset);
201 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
202 	db = dbuf_hold(dn, blkid, tag);
203 	rw_exit(&dn->dn_struct_rwlock);
204 	dnode_rele(dn, FTAG);
205 
206 	if (db == NULL) {
207 		*dbp = NULL;
208 		return (SET_ERROR(EIO));
209 	}
210 
211 	*dbp = &db->db;
212 	return (err);
213 }
214 
215 int
216 dmu_buf_hold_by_dnode(dnode_t *dn, uint64_t offset,
217     void *tag, dmu_buf_t **dbp, int flags)
218 {
219 	int err;
220 	int db_flags = DB_RF_CANFAIL;
221 
222 	if (flags & DMU_READ_NO_PREFETCH)
223 		db_flags |= DB_RF_NOPREFETCH;
224 
225 	err = dmu_buf_hold_noread_by_dnode(dn, offset, tag, dbp);
226 	if (err == 0) {
227 		dmu_buf_impl_t *db = (dmu_buf_impl_t *)(*dbp);
228 		err = dbuf_read(db, NULL, db_flags);
229 		if (err != 0) {
230 			dbuf_rele(db, tag);
231 			*dbp = NULL;
232 		}
233 	}
234 
235 	return (err);
236 }
237 
238 int
239 dmu_buf_hold(objset_t *os, uint64_t object, uint64_t offset,
240     void *tag, dmu_buf_t **dbp, int flags)
241 {
242 	int err;
243 	int db_flags = DB_RF_CANFAIL;
244 
245 	if (flags & DMU_READ_NO_PREFETCH)
246 		db_flags |= DB_RF_NOPREFETCH;
247 
248 	err = dmu_buf_hold_noread(os, object, offset, tag, dbp);
249 	if (err == 0) {
250 		dmu_buf_impl_t *db = (dmu_buf_impl_t *)(*dbp);
251 		err = dbuf_read(db, NULL, db_flags);
252 		if (err != 0) {
253 			dbuf_rele(db, tag);
254 			*dbp = NULL;
255 		}
256 	}
257 
258 	return (err);
259 }
260 
261 int
262 dmu_bonus_max(void)
263 {
264 	return (DN_OLD_MAX_BONUSLEN);
265 }
266 
267 int
268 dmu_set_bonus(dmu_buf_t *db_fake, int newsize, dmu_tx_t *tx)
269 {
270 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
271 	dnode_t *dn;
272 	int error;
273 
274 	DB_DNODE_ENTER(db);
275 	dn = DB_DNODE(db);
276 
277 	if (dn->dn_bonus != db) {
278 		error = SET_ERROR(EINVAL);
279 	} else if (newsize < 0 || newsize > db_fake->db_size) {
280 		error = SET_ERROR(EINVAL);
281 	} else {
282 		dnode_setbonuslen(dn, newsize, tx);
283 		error = 0;
284 	}
285 
286 	DB_DNODE_EXIT(db);
287 	return (error);
288 }
289 
290 int
291 dmu_set_bonustype(dmu_buf_t *db_fake, dmu_object_type_t type, dmu_tx_t *tx)
292 {
293 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
294 	dnode_t *dn;
295 	int error;
296 
297 	DB_DNODE_ENTER(db);
298 	dn = DB_DNODE(db);
299 
300 	if (!DMU_OT_IS_VALID(type)) {
301 		error = SET_ERROR(EINVAL);
302 	} else if (dn->dn_bonus != db) {
303 		error = SET_ERROR(EINVAL);
304 	} else {
305 		dnode_setbonus_type(dn, type, tx);
306 		error = 0;
307 	}
308 
309 	DB_DNODE_EXIT(db);
310 	return (error);
311 }
312 
313 dmu_object_type_t
314 dmu_get_bonustype(dmu_buf_t *db_fake)
315 {
316 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
317 	dnode_t *dn;
318 	dmu_object_type_t type;
319 
320 	DB_DNODE_ENTER(db);
321 	dn = DB_DNODE(db);
322 	type = dn->dn_bonustype;
323 	DB_DNODE_EXIT(db);
324 
325 	return (type);
326 }
327 
328 int
329 dmu_rm_spill(objset_t *os, uint64_t object, dmu_tx_t *tx)
330 {
331 	dnode_t *dn;
332 	int error;
333 
334 	error = dnode_hold(os, object, FTAG, &dn);
335 	dbuf_rm_spill(dn, tx);
336 	rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
337 	dnode_rm_spill(dn, tx);
338 	rw_exit(&dn->dn_struct_rwlock);
339 	dnode_rele(dn, FTAG);
340 	return (error);
341 }
342 
343 /*
344  * returns ENOENT, EIO, or 0.
345  */
346 int
347 dmu_bonus_hold(objset_t *os, uint64_t object, void *tag, dmu_buf_t **dbp)
348 {
349 	dnode_t *dn;
350 	dmu_buf_impl_t *db;
351 	int error;
352 
353 	error = dnode_hold(os, object, FTAG, &dn);
354 	if (error)
355 		return (error);
356 
357 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
358 	if (dn->dn_bonus == NULL) {
359 		rw_exit(&dn->dn_struct_rwlock);
360 		rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
361 		if (dn->dn_bonus == NULL)
362 			dbuf_create_bonus(dn);
363 	}
364 	db = dn->dn_bonus;
365 
366 	/* as long as the bonus buf is held, the dnode will be held */
367 	if (zfs_refcount_add(&db->db_holds, tag) == 1) {
368 		VERIFY(dnode_add_ref(dn, db));
369 		atomic_inc_32(&dn->dn_dbufs_count);
370 	}
371 
372 	/*
373 	 * Wait to drop dn_struct_rwlock until after adding the bonus dbuf's
374 	 * hold and incrementing the dbuf count to ensure that dnode_move() sees
375 	 * a dnode hold for every dbuf.
376 	 */
377 	rw_exit(&dn->dn_struct_rwlock);
378 
379 	dnode_rele(dn, FTAG);
380 
381 	VERIFY(0 == dbuf_read(db, NULL, DB_RF_MUST_SUCCEED | DB_RF_NOPREFETCH));
382 
383 	*dbp = &db->db;
384 	return (0);
385 }
386 
387 /*
388  * returns ENOENT, EIO, or 0.
389  *
390  * This interface will allocate a blank spill dbuf when a spill blk
391  * doesn't already exist on the dnode.
392  *
393  * if you only want to find an already existing spill db, then
394  * dmu_spill_hold_existing() should be used.
395  */
396 int
397 dmu_spill_hold_by_dnode(dnode_t *dn, uint32_t flags, void *tag, dmu_buf_t **dbp)
398 {
399 	dmu_buf_impl_t *db = NULL;
400 	int err;
401 
402 	if ((flags & DB_RF_HAVESTRUCT) == 0)
403 		rw_enter(&dn->dn_struct_rwlock, RW_READER);
404 
405 	db = dbuf_hold(dn, DMU_SPILL_BLKID, tag);
406 
407 	if ((flags & DB_RF_HAVESTRUCT) == 0)
408 		rw_exit(&dn->dn_struct_rwlock);
409 
410 	ASSERT(db != NULL);
411 	err = dbuf_read(db, NULL, flags);
412 	if (err == 0)
413 		*dbp = &db->db;
414 	else
415 		dbuf_rele(db, tag);
416 	return (err);
417 }
418 
419 int
420 dmu_spill_hold_existing(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp)
421 {
422 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)bonus;
423 	dnode_t *dn;
424 	int err;
425 
426 	DB_DNODE_ENTER(db);
427 	dn = DB_DNODE(db);
428 
429 	if (spa_version(dn->dn_objset->os_spa) < SPA_VERSION_SA) {
430 		err = SET_ERROR(EINVAL);
431 	} else {
432 		rw_enter(&dn->dn_struct_rwlock, RW_READER);
433 
434 		if (!dn->dn_have_spill) {
435 			err = SET_ERROR(ENOENT);
436 		} else {
437 			err = dmu_spill_hold_by_dnode(dn,
438 			    DB_RF_HAVESTRUCT | DB_RF_CANFAIL, tag, dbp);
439 		}
440 
441 		rw_exit(&dn->dn_struct_rwlock);
442 	}
443 
444 	DB_DNODE_EXIT(db);
445 	return (err);
446 }
447 
448 int
449 dmu_spill_hold_by_bonus(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp)
450 {
451 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)bonus;
452 	dnode_t *dn;
453 	int err;
454 
455 	DB_DNODE_ENTER(db);
456 	dn = DB_DNODE(db);
457 	err = dmu_spill_hold_by_dnode(dn, DB_RF_CANFAIL, tag, dbp);
458 	DB_DNODE_EXIT(db);
459 
460 	return (err);
461 }
462 
463 /*
464  * Note: longer-term, we should modify all of the dmu_buf_*() interfaces
465  * to take a held dnode rather than <os, object> -- the lookup is wasteful,
466  * and can induce severe lock contention when writing to several files
467  * whose dnodes are in the same block.
468  */
469 int
470 dmu_buf_hold_array_by_dnode(dnode_t *dn, uint64_t offset, uint64_t length,
471     boolean_t read, void *tag, int *numbufsp, dmu_buf_t ***dbpp, uint32_t flags)
472 {
473 	dmu_buf_t **dbp;
474 	uint64_t blkid, nblks, i;
475 	uint32_t dbuf_flags;
476 	int err;
477 	zio_t *zio;
478 
479 	ASSERT(length <= DMU_MAX_ACCESS);
480 
481 	/*
482 	 * Note: We directly notify the prefetch code of this read, so that
483 	 * we can tell it about the multi-block read.  dbuf_read() only knows
484 	 * about the one block it is accessing.
485 	 */
486 	dbuf_flags = DB_RF_CANFAIL | DB_RF_NEVERWAIT | DB_RF_HAVESTRUCT |
487 	    DB_RF_NOPREFETCH;
488 
489 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
490 	if (dn->dn_datablkshift) {
491 		int blkshift = dn->dn_datablkshift;
492 		nblks = (P2ROUNDUP(offset + length, 1ULL << blkshift) -
493 		    P2ALIGN(offset, 1ULL << blkshift)) >> blkshift;
494 	} else {
495 		if (offset + length > dn->dn_datablksz) {
496 			zfs_panic_recover("zfs: accessing past end of object "
497 			    "%llx/%llx (size=%u access=%llu+%llu)",
498 			    (longlong_t)dn->dn_objset->
499 			    os_dsl_dataset->ds_object,
500 			    (longlong_t)dn->dn_object, dn->dn_datablksz,
501 			    (longlong_t)offset, (longlong_t)length);
502 			rw_exit(&dn->dn_struct_rwlock);
503 			return (SET_ERROR(EIO));
504 		}
505 		nblks = 1;
506 	}
507 	dbp = kmem_zalloc(sizeof (dmu_buf_t *) * nblks, KM_SLEEP);
508 
509 	zio = zio_root(dn->dn_objset->os_spa, NULL, NULL, ZIO_FLAG_CANFAIL);
510 	blkid = dbuf_whichblock(dn, 0, offset);
511 	for (i = 0; i < nblks; i++) {
512 		dmu_buf_impl_t *db = dbuf_hold(dn, blkid + i, tag);
513 		if (db == NULL) {
514 			rw_exit(&dn->dn_struct_rwlock);
515 			dmu_buf_rele_array(dbp, nblks, tag);
516 			zio_nowait(zio);
517 			return (SET_ERROR(EIO));
518 		}
519 
520 		/* initiate async i/o */
521 		if (read)
522 			(void) dbuf_read(db, zio, dbuf_flags);
523 		dbp[i] = &db->db;
524 	}
525 
526 	if ((flags & DMU_READ_NO_PREFETCH) == 0 &&
527 	    DNODE_META_IS_CACHEABLE(dn) && length <= zfetch_array_rd_sz) {
528 		dmu_zfetch(&dn->dn_zfetch, blkid, nblks,
529 		    read && DNODE_IS_CACHEABLE(dn));
530 	}
531 	rw_exit(&dn->dn_struct_rwlock);
532 
533 	/* wait for async i/o */
534 	err = zio_wait(zio);
535 	if (err) {
536 		dmu_buf_rele_array(dbp, nblks, tag);
537 		return (err);
538 	}
539 
540 	/* wait for other io to complete */
541 	if (read) {
542 		for (i = 0; i < nblks; i++) {
543 			dmu_buf_impl_t *db = (dmu_buf_impl_t *)dbp[i];
544 			mutex_enter(&db->db_mtx);
545 			while (db->db_state == DB_READ ||
546 			    db->db_state == DB_FILL)
547 				cv_wait(&db->db_changed, &db->db_mtx);
548 			if (db->db_state == DB_UNCACHED)
549 				err = SET_ERROR(EIO);
550 			mutex_exit(&db->db_mtx);
551 			if (err) {
552 				dmu_buf_rele_array(dbp, nblks, tag);
553 				return (err);
554 			}
555 		}
556 	}
557 
558 	*numbufsp = nblks;
559 	*dbpp = dbp;
560 	return (0);
561 }
562 
563 static int
564 dmu_buf_hold_array(objset_t *os, uint64_t object, uint64_t offset,
565     uint64_t length, int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp)
566 {
567 	dnode_t *dn;
568 	int err;
569 
570 	err = dnode_hold(os, object, FTAG, &dn);
571 	if (err)
572 		return (err);
573 
574 	err = dmu_buf_hold_array_by_dnode(dn, offset, length, read, tag,
575 	    numbufsp, dbpp, DMU_READ_PREFETCH);
576 
577 	dnode_rele(dn, FTAG);
578 
579 	return (err);
580 }
581 
582 int
583 dmu_buf_hold_array_by_bonus(dmu_buf_t *db_fake, uint64_t offset,
584     uint64_t length, boolean_t read, void *tag, int *numbufsp,
585     dmu_buf_t ***dbpp)
586 {
587 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
588 	dnode_t *dn;
589 	int err;
590 
591 	DB_DNODE_ENTER(db);
592 	dn = DB_DNODE(db);
593 	err = dmu_buf_hold_array_by_dnode(dn, offset, length, read, tag,
594 	    numbufsp, dbpp, DMU_READ_PREFETCH);
595 	DB_DNODE_EXIT(db);
596 
597 	return (err);
598 }
599 
600 void
601 dmu_buf_rele_array(dmu_buf_t **dbp_fake, int numbufs, void *tag)
602 {
603 	int i;
604 	dmu_buf_impl_t **dbp = (dmu_buf_impl_t **)dbp_fake;
605 
606 	if (numbufs == 0)
607 		return;
608 
609 	for (i = 0; i < numbufs; i++) {
610 		if (dbp[i])
611 			dbuf_rele(dbp[i], tag);
612 	}
613 
614 	kmem_free(dbp, sizeof (dmu_buf_t *) * numbufs);
615 }
616 
617 /*
618  * Issue prefetch i/os for the given blocks.  If level is greater than 0, the
619  * indirect blocks prefeteched will be those that point to the blocks containing
620  * the data starting at offset, and continuing to offset + len.
621  *
622  * Note that if the indirect blocks above the blocks being prefetched are not in
623  * cache, they will be asychronously read in.
624  */
625 void
626 dmu_prefetch(objset_t *os, uint64_t object, int64_t level, uint64_t offset,
627     uint64_t len, zio_priority_t pri)
628 {
629 	dnode_t *dn;
630 	uint64_t blkid;
631 	int nblks, err;
632 
633 	if (len == 0) {  /* they're interested in the bonus buffer */
634 		dn = DMU_META_DNODE(os);
635 
636 		if (object == 0 || object >= DN_MAX_OBJECT)
637 			return;
638 
639 		rw_enter(&dn->dn_struct_rwlock, RW_READER);
640 		blkid = dbuf_whichblock(dn, level,
641 		    object * sizeof (dnode_phys_t));
642 		dbuf_prefetch(dn, level, blkid, pri, 0);
643 		rw_exit(&dn->dn_struct_rwlock);
644 		return;
645 	}
646 
647 	/*
648 	 * See comment before the definition of dmu_prefetch_max.
649 	 */
650 	len = MIN(len, dmu_prefetch_max);
651 
652 	/*
653 	 * XXX - Note, if the dnode for the requested object is not
654 	 * already cached, we will do a *synchronous* read in the
655 	 * dnode_hold() call.  The same is true for any indirects.
656 	 */
657 	err = dnode_hold(os, object, FTAG, &dn);
658 	if (err != 0)
659 		return;
660 
661 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
662 	/*
663 	 * offset + len - 1 is the last byte we want to prefetch for, and offset
664 	 * is the first.  Then dbuf_whichblk(dn, level, off + len - 1) is the
665 	 * last block we want to prefetch, and dbuf_whichblock(dn, level,
666 	 * offset)  is the first.  Then the number we need to prefetch is the
667 	 * last - first + 1.
668 	 */
669 	if (level > 0 || dn->dn_datablkshift != 0) {
670 		nblks = dbuf_whichblock(dn, level, offset + len - 1) -
671 		    dbuf_whichblock(dn, level, offset) + 1;
672 	} else {
673 		nblks = (offset < dn->dn_datablksz);
674 	}
675 
676 	if (nblks != 0) {
677 		blkid = dbuf_whichblock(dn, level, offset);
678 		for (int i = 0; i < nblks; i++)
679 			dbuf_prefetch(dn, level, blkid + i, pri, 0);
680 	}
681 
682 	rw_exit(&dn->dn_struct_rwlock);
683 
684 	dnode_rele(dn, FTAG);
685 }
686 
687 /*
688  * Get the next "chunk" of file data to free.  We traverse the file from
689  * the end so that the file gets shorter over time (if we crashes in the
690  * middle, this will leave us in a better state).  We find allocated file
691  * data by simply searching the allocated level 1 indirects.
692  *
693  * On input, *start should be the first offset that does not need to be
694  * freed (e.g. "offset + length").  On return, *start will be the first
695  * offset that should be freed.
696  */
697 static int
698 get_next_chunk(dnode_t *dn, uint64_t *start, uint64_t minimum)
699 {
700 	uint64_t maxblks = DMU_MAX_ACCESS >> (dn->dn_indblkshift + 1);
701 	/* bytes of data covered by a level-1 indirect block */
702 	uint64_t iblkrange =
703 	    dn->dn_datablksz * EPB(dn->dn_indblkshift, SPA_BLKPTRSHIFT);
704 
705 	ASSERT3U(minimum, <=, *start);
706 
707 	if (*start - minimum <= iblkrange * maxblks) {
708 		*start = minimum;
709 		return (0);
710 	}
711 	ASSERT(ISP2(iblkrange));
712 
713 	for (uint64_t blks = 0; *start > minimum && blks < maxblks; blks++) {
714 		int err;
715 
716 		/*
717 		 * dnode_next_offset(BACKWARDS) will find an allocated L1
718 		 * indirect block at or before the input offset.  We must
719 		 * decrement *start so that it is at the end of the region
720 		 * to search.
721 		 */
722 		(*start)--;
723 		err = dnode_next_offset(dn,
724 		    DNODE_FIND_BACKWARDS, start, 2, 1, 0);
725 
726 		/* if there are no indirect blocks before start, we are done */
727 		if (err == ESRCH) {
728 			*start = minimum;
729 			break;
730 		} else if (err != 0) {
731 			return (err);
732 		}
733 
734 		/* set start to the beginning of this L1 indirect */
735 		*start = P2ALIGN(*start, iblkrange);
736 	}
737 	if (*start < minimum)
738 		*start = minimum;
739 	return (0);
740 }
741 
742 /*
743  * If this objset is of type OST_ZFS return true if vfs's unmounted flag is set,
744  * otherwise return false.
745  * Used below in dmu_free_long_range_impl() to enable abort when unmounting
746  */
747 /*ARGSUSED*/
748 static boolean_t
749 dmu_objset_zfs_unmounting(objset_t *os)
750 {
751 #ifdef _KERNEL
752 	if (dmu_objset_type(os) == DMU_OST_ZFS)
753 		return (zfs_get_vfs_flag_unmounted(os));
754 #endif
755 	return (B_FALSE);
756 }
757 
758 static int
759 dmu_free_long_range_impl(objset_t *os, dnode_t *dn, uint64_t offset,
760     uint64_t length)
761 {
762 	uint64_t object_size = (dn->dn_maxblkid + 1) * dn->dn_datablksz;
763 	int err;
764 	uint64_t dirty_frees_threshold;
765 	dsl_pool_t *dp = dmu_objset_pool(os);
766 
767 	if (offset >= object_size)
768 		return (0);
769 
770 	if (zfs_per_txg_dirty_frees_percent <= 100)
771 		dirty_frees_threshold =
772 		    zfs_per_txg_dirty_frees_percent * zfs_dirty_data_max / 100;
773 	else
774 		dirty_frees_threshold = zfs_dirty_data_max / 4;
775 
776 	if (length == DMU_OBJECT_END || offset + length > object_size)
777 		length = object_size - offset;
778 
779 	while (length != 0) {
780 		uint64_t chunk_end, chunk_begin, chunk_len;
781 		uint64_t long_free_dirty_all_txgs = 0;
782 		dmu_tx_t *tx;
783 
784 		if (dmu_objset_zfs_unmounting(dn->dn_objset))
785 			return (SET_ERROR(EINTR));
786 
787 		chunk_end = chunk_begin = offset + length;
788 
789 		/* move chunk_begin backwards to the beginning of this chunk */
790 		err = get_next_chunk(dn, &chunk_begin, offset);
791 		if (err)
792 			return (err);
793 		ASSERT3U(chunk_begin, >=, offset);
794 		ASSERT3U(chunk_begin, <=, chunk_end);
795 
796 		chunk_len = chunk_end - chunk_begin;
797 
798 		mutex_enter(&dp->dp_lock);
799 		for (int t = 0; t < TXG_SIZE; t++) {
800 			long_free_dirty_all_txgs +=
801 			    dp->dp_long_free_dirty_pertxg[t];
802 		}
803 		mutex_exit(&dp->dp_lock);
804 
805 		/*
806 		 * To avoid filling up a TXG with just frees wait for
807 		 * the next TXG to open before freeing more chunks if
808 		 * we have reached the threshold of frees
809 		 */
810 		if (dirty_frees_threshold != 0 &&
811 		    long_free_dirty_all_txgs >= dirty_frees_threshold) {
812 			txg_wait_open(dp, 0);
813 			continue;
814 		}
815 
816 		tx = dmu_tx_create(os);
817 		dmu_tx_hold_free(tx, dn->dn_object, chunk_begin, chunk_len);
818 
819 		/*
820 		 * Mark this transaction as typically resulting in a net
821 		 * reduction in space used.
822 		 */
823 		dmu_tx_mark_netfree(tx);
824 		err = dmu_tx_assign(tx, TXG_WAIT);
825 		if (err) {
826 			dmu_tx_abort(tx);
827 			return (err);
828 		}
829 
830 		mutex_enter(&dp->dp_lock);
831 		dp->dp_long_free_dirty_pertxg[dmu_tx_get_txg(tx) & TXG_MASK] +=
832 		    chunk_len;
833 		mutex_exit(&dp->dp_lock);
834 		DTRACE_PROBE3(free__long__range,
835 		    uint64_t, long_free_dirty_all_txgs, uint64_t, chunk_len,
836 		    uint64_t, dmu_tx_get_txg(tx));
837 		dnode_free_range(dn, chunk_begin, chunk_len, tx);
838 		dmu_tx_commit(tx);
839 
840 		length -= chunk_len;
841 	}
842 	return (0);
843 }
844 
845 int
846 dmu_free_long_range(objset_t *os, uint64_t object,
847     uint64_t offset, uint64_t length)
848 {
849 	dnode_t *dn;
850 	int err;
851 
852 	err = dnode_hold(os, object, FTAG, &dn);
853 	if (err != 0)
854 		return (err);
855 	err = dmu_free_long_range_impl(os, dn, offset, length);
856 
857 	/*
858 	 * It is important to zero out the maxblkid when freeing the entire
859 	 * file, so that (a) subsequent calls to dmu_free_long_range_impl()
860 	 * will take the fast path, and (b) dnode_reallocate() can verify
861 	 * that the entire file has been freed.
862 	 */
863 	if (err == 0 && offset == 0 && length == DMU_OBJECT_END)
864 		dn->dn_maxblkid = 0;
865 
866 	dnode_rele(dn, FTAG);
867 	return (err);
868 }
869 
870 int
871 dmu_free_long_object(objset_t *os, uint64_t object)
872 {
873 	dmu_tx_t *tx;
874 	int err;
875 
876 	err = dmu_free_long_range(os, object, 0, DMU_OBJECT_END);
877 	if (err != 0)
878 		return (err);
879 
880 	tx = dmu_tx_create(os);
881 	dmu_tx_hold_bonus(tx, object);
882 	dmu_tx_hold_free(tx, object, 0, DMU_OBJECT_END);
883 	dmu_tx_mark_netfree(tx);
884 	err = dmu_tx_assign(tx, TXG_WAIT);
885 	if (err == 0) {
886 		err = dmu_object_free(os, object, tx);
887 		dmu_tx_commit(tx);
888 	} else {
889 		dmu_tx_abort(tx);
890 	}
891 
892 	return (err);
893 }
894 
895 int
896 dmu_free_range(objset_t *os, uint64_t object, uint64_t offset,
897     uint64_t size, dmu_tx_t *tx)
898 {
899 	dnode_t *dn;
900 	int err = dnode_hold(os, object, FTAG, &dn);
901 	if (err)
902 		return (err);
903 	ASSERT(offset < UINT64_MAX);
904 	ASSERT(size == -1ULL || size <= UINT64_MAX - offset);
905 	dnode_free_range(dn, offset, size, tx);
906 	dnode_rele(dn, FTAG);
907 	return (0);
908 }
909 
910 static int
911 dmu_read_impl(dnode_t *dn, uint64_t offset, uint64_t size,
912     void *buf, uint32_t flags)
913 {
914 	dmu_buf_t **dbp;
915 	int numbufs, err = 0;
916 
917 	/*
918 	 * Deal with odd block sizes, where there can't be data past the first
919 	 * block.  If we ever do the tail block optimization, we will need to
920 	 * handle that here as well.
921 	 */
922 	if (dn->dn_maxblkid == 0) {
923 		int newsz = offset > dn->dn_datablksz ? 0 :
924 		    MIN(size, dn->dn_datablksz - offset);
925 		bzero((char *)buf + newsz, size - newsz);
926 		size = newsz;
927 	}
928 
929 	while (size > 0) {
930 		uint64_t mylen = MIN(size, DMU_MAX_ACCESS / 2);
931 		int i;
932 
933 		/*
934 		 * NB: we could do this block-at-a-time, but it's nice
935 		 * to be reading in parallel.
936 		 */
937 		err = dmu_buf_hold_array_by_dnode(dn, offset, mylen,
938 		    TRUE, FTAG, &numbufs, &dbp, flags);
939 		if (err)
940 			break;
941 
942 		for (i = 0; i < numbufs; i++) {
943 			int tocpy;
944 			int bufoff;
945 			dmu_buf_t *db = dbp[i];
946 
947 			ASSERT(size > 0);
948 
949 			bufoff = offset - db->db_offset;
950 			tocpy = (int)MIN(db->db_size - bufoff, size);
951 
952 			bcopy((char *)db->db_data + bufoff, buf, tocpy);
953 
954 			offset += tocpy;
955 			size -= tocpy;
956 			buf = (char *)buf + tocpy;
957 		}
958 		dmu_buf_rele_array(dbp, numbufs, FTAG);
959 	}
960 	return (err);
961 }
962 
963 int
964 dmu_read(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
965     void *buf, uint32_t flags)
966 {
967 	dnode_t *dn;
968 	int err;
969 
970 	err = dnode_hold(os, object, FTAG, &dn);
971 	if (err != 0)
972 		return (err);
973 
974 	err = dmu_read_impl(dn, offset, size, buf, flags);
975 	dnode_rele(dn, FTAG);
976 	return (err);
977 }
978 
979 int
980 dmu_read_by_dnode(dnode_t *dn, uint64_t offset, uint64_t size, void *buf,
981     uint32_t flags)
982 {
983 	return (dmu_read_impl(dn, offset, size, buf, flags));
984 }
985 
986 static void
987 dmu_write_impl(dmu_buf_t **dbp, int numbufs, uint64_t offset, uint64_t size,
988     const void *buf, dmu_tx_t *tx)
989 {
990 	int i;
991 
992 	for (i = 0; i < numbufs; i++) {
993 		int tocpy;
994 		int bufoff;
995 		dmu_buf_t *db = dbp[i];
996 
997 		ASSERT(size > 0);
998 
999 		bufoff = offset - db->db_offset;
1000 		tocpy = (int)MIN(db->db_size - bufoff, size);
1001 
1002 		ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
1003 
1004 		if (tocpy == db->db_size)
1005 			dmu_buf_will_fill(db, tx);
1006 		else
1007 			dmu_buf_will_dirty(db, tx);
1008 
1009 		bcopy(buf, (char *)db->db_data + bufoff, tocpy);
1010 
1011 		if (tocpy == db->db_size)
1012 			dmu_buf_fill_done(db, tx);
1013 
1014 		offset += tocpy;
1015 		size -= tocpy;
1016 		buf = (char *)buf + tocpy;
1017 	}
1018 }
1019 
1020 void
1021 dmu_write(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
1022     const void *buf, dmu_tx_t *tx)
1023 {
1024 	dmu_buf_t **dbp;
1025 	int numbufs;
1026 
1027 	if (size == 0)
1028 		return;
1029 
1030 	VERIFY0(dmu_buf_hold_array(os, object, offset, size,
1031 	    FALSE, FTAG, &numbufs, &dbp));
1032 	dmu_write_impl(dbp, numbufs, offset, size, buf, tx);
1033 	dmu_buf_rele_array(dbp, numbufs, FTAG);
1034 }
1035 
1036 void
1037 dmu_write_by_dnode(dnode_t *dn, uint64_t offset, uint64_t size,
1038     const void *buf, dmu_tx_t *tx)
1039 {
1040 	dmu_buf_t **dbp;
1041 	int numbufs;
1042 
1043 	if (size == 0)
1044 		return;
1045 
1046 	VERIFY0(dmu_buf_hold_array_by_dnode(dn, offset, size,
1047 	    FALSE, FTAG, &numbufs, &dbp, DMU_READ_PREFETCH));
1048 	dmu_write_impl(dbp, numbufs, offset, size, buf, tx);
1049 	dmu_buf_rele_array(dbp, numbufs, FTAG);
1050 }
1051 
1052 static int
1053 dmu_object_remap_one_indirect(objset_t *os, dnode_t *dn,
1054     uint64_t last_removal_txg, uint64_t offset)
1055 {
1056 	uint64_t l1blkid = dbuf_whichblock(dn, 1, offset);
1057 	int err = 0;
1058 
1059 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
1060 	dmu_buf_impl_t *dbuf = dbuf_hold_level(dn, 1, l1blkid, FTAG);
1061 	ASSERT3P(dbuf, !=, NULL);
1062 
1063 	/*
1064 	 * If the block hasn't been written yet, this default will ensure
1065 	 * we don't try to remap it.
1066 	 */
1067 	uint64_t birth = UINT64_MAX;
1068 	ASSERT3U(last_removal_txg, !=, UINT64_MAX);
1069 	if (dbuf->db_blkptr != NULL)
1070 		birth = dbuf->db_blkptr->blk_birth;
1071 	rw_exit(&dn->dn_struct_rwlock);
1072 
1073 	/*
1074 	 * If this L1 was already written after the last removal, then we've
1075 	 * already tried to remap it.
1076 	 */
1077 	if (birth <= last_removal_txg &&
1078 	    dbuf_read(dbuf, NULL, DB_RF_MUST_SUCCEED) == 0 &&
1079 	    dbuf_can_remap(dbuf)) {
1080 		dmu_tx_t *tx = dmu_tx_create(os);
1081 		dmu_tx_hold_remap_l1indirect(tx, dn->dn_object);
1082 		err = dmu_tx_assign(tx, TXG_WAIT);
1083 		if (err == 0) {
1084 			(void) dbuf_dirty(dbuf, tx);
1085 			dmu_tx_commit(tx);
1086 		} else {
1087 			dmu_tx_abort(tx);
1088 		}
1089 	}
1090 
1091 	dbuf_rele(dbuf, FTAG);
1092 
1093 	delay(zfs_object_remap_one_indirect_delay_ticks);
1094 
1095 	return (err);
1096 }
1097 
1098 /*
1099  * Remap all blockpointers in the object, if possible, so that they reference
1100  * only concrete vdevs.
1101  *
1102  * To do this, iterate over the L0 blockpointers and remap any that reference
1103  * an indirect vdev. Note that we only examine L0 blockpointers; since we
1104  * cannot guarantee that we can remap all blockpointer anyways (due to split
1105  * blocks), we do not want to make the code unnecessarily complicated to
1106  * catch the unlikely case that there is an L1 block on an indirect vdev that
1107  * contains no indirect blockpointers.
1108  */
1109 int
1110 dmu_object_remap_indirects(objset_t *os, uint64_t object,
1111     uint64_t last_removal_txg)
1112 {
1113 	uint64_t offset, l1span;
1114 	int err;
1115 	dnode_t *dn;
1116 
1117 	err = dnode_hold(os, object, FTAG, &dn);
1118 	if (err != 0) {
1119 		return (err);
1120 	}
1121 
1122 	if (dn->dn_nlevels <= 1) {
1123 		if (issig(JUSTLOOKING) && issig(FORREAL)) {
1124 			err = SET_ERROR(EINTR);
1125 		}
1126 
1127 		/*
1128 		 * If the dnode has no indirect blocks, we cannot dirty them.
1129 		 * We still want to remap the blkptr(s) in the dnode if
1130 		 * appropriate, so mark it as dirty.
1131 		 */
1132 		if (err == 0 && dnode_needs_remap(dn)) {
1133 			dmu_tx_t *tx = dmu_tx_create(os);
1134 			dmu_tx_hold_bonus(tx, dn->dn_object);
1135 			if ((err = dmu_tx_assign(tx, TXG_WAIT)) == 0) {
1136 				dnode_setdirty(dn, tx);
1137 				dmu_tx_commit(tx);
1138 			} else {
1139 				dmu_tx_abort(tx);
1140 			}
1141 		}
1142 
1143 		dnode_rele(dn, FTAG);
1144 		return (err);
1145 	}
1146 
1147 	offset = 0;
1148 	l1span = 1ULL << (dn->dn_indblkshift - SPA_BLKPTRSHIFT +
1149 	    dn->dn_datablkshift);
1150 	/*
1151 	 * Find the next L1 indirect that is not a hole.
1152 	 */
1153 	while (dnode_next_offset(dn, 0, &offset, 2, 1, 0) == 0) {
1154 		if (issig(JUSTLOOKING) && issig(FORREAL)) {
1155 			err = SET_ERROR(EINTR);
1156 			break;
1157 		}
1158 		if ((err = dmu_object_remap_one_indirect(os, dn,
1159 		    last_removal_txg, offset)) != 0) {
1160 			break;
1161 		}
1162 		offset += l1span;
1163 	}
1164 
1165 	dnode_rele(dn, FTAG);
1166 	return (err);
1167 }
1168 
1169 void
1170 dmu_prealloc(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
1171     dmu_tx_t *tx)
1172 {
1173 	dmu_buf_t **dbp;
1174 	int numbufs, i;
1175 
1176 	if (size == 0)
1177 		return;
1178 
1179 	VERIFY(0 == dmu_buf_hold_array(os, object, offset, size,
1180 	    FALSE, FTAG, &numbufs, &dbp));
1181 
1182 	for (i = 0; i < numbufs; i++) {
1183 		dmu_buf_t *db = dbp[i];
1184 
1185 		dmu_buf_will_not_fill(db, tx);
1186 	}
1187 	dmu_buf_rele_array(dbp, numbufs, FTAG);
1188 }
1189 
1190 void
1191 dmu_write_embedded(objset_t *os, uint64_t object, uint64_t offset,
1192     void *data, uint8_t etype, uint8_t comp, int uncompressed_size,
1193     int compressed_size, int byteorder, dmu_tx_t *tx)
1194 {
1195 	dmu_buf_t *db;
1196 
1197 	ASSERT3U(etype, <, NUM_BP_EMBEDDED_TYPES);
1198 	ASSERT3U(comp, <, ZIO_COMPRESS_FUNCTIONS);
1199 	VERIFY0(dmu_buf_hold_noread(os, object, offset,
1200 	    FTAG, &db));
1201 
1202 	dmu_buf_write_embedded(db,
1203 	    data, (bp_embedded_type_t)etype, (enum zio_compress)comp,
1204 	    uncompressed_size, compressed_size, byteorder, tx);
1205 
1206 	dmu_buf_rele(db, FTAG);
1207 }
1208 
1209 /*
1210  * DMU support for xuio
1211  */
1212 kstat_t *xuio_ksp = NULL;
1213 
1214 int
1215 dmu_xuio_init(xuio_t *xuio, int nblk)
1216 {
1217 	dmu_xuio_t *priv;
1218 	uio_t *uio = &xuio->xu_uio;
1219 
1220 	uio->uio_iovcnt = nblk;
1221 	uio->uio_iov = kmem_zalloc(nblk * sizeof (iovec_t), KM_SLEEP);
1222 
1223 	priv = kmem_zalloc(sizeof (dmu_xuio_t), KM_SLEEP);
1224 	priv->cnt = nblk;
1225 	priv->bufs = kmem_zalloc(nblk * sizeof (arc_buf_t *), KM_SLEEP);
1226 	priv->iovp = uio->uio_iov;
1227 	XUIO_XUZC_PRIV(xuio) = priv;
1228 
1229 	if (XUIO_XUZC_RW(xuio) == UIO_READ)
1230 		XUIOSTAT_INCR(xuiostat_onloan_rbuf, nblk);
1231 	else
1232 		XUIOSTAT_INCR(xuiostat_onloan_wbuf, nblk);
1233 
1234 	return (0);
1235 }
1236 
1237 void
1238 dmu_xuio_fini(xuio_t *xuio)
1239 {
1240 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
1241 	int nblk = priv->cnt;
1242 
1243 	kmem_free(priv->iovp, nblk * sizeof (iovec_t));
1244 	kmem_free(priv->bufs, nblk * sizeof (arc_buf_t *));
1245 	kmem_free(priv, sizeof (dmu_xuio_t));
1246 
1247 	if (XUIO_XUZC_RW(xuio) == UIO_READ)
1248 		XUIOSTAT_INCR(xuiostat_onloan_rbuf, -nblk);
1249 	else
1250 		XUIOSTAT_INCR(xuiostat_onloan_wbuf, -nblk);
1251 }
1252 
1253 /*
1254  * Initialize iov[priv->next] and priv->bufs[priv->next] with { off, n, abuf }
1255  * and increase priv->next by 1.
1256  */
1257 int
1258 dmu_xuio_add(xuio_t *xuio, arc_buf_t *abuf, offset_t off, size_t n)
1259 {
1260 	struct iovec *iov;
1261 	uio_t *uio = &xuio->xu_uio;
1262 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
1263 	int i = priv->next++;
1264 
1265 	ASSERT(i < priv->cnt);
1266 	ASSERT(off + n <= arc_buf_lsize(abuf));
1267 	iov = uio->uio_iov + i;
1268 	iov->iov_base = (char *)abuf->b_data + off;
1269 	iov->iov_len = n;
1270 	priv->bufs[i] = abuf;
1271 	return (0);
1272 }
1273 
1274 int
1275 dmu_xuio_cnt(xuio_t *xuio)
1276 {
1277 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
1278 	return (priv->cnt);
1279 }
1280 
1281 arc_buf_t *
1282 dmu_xuio_arcbuf(xuio_t *xuio, int i)
1283 {
1284 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
1285 
1286 	ASSERT(i < priv->cnt);
1287 	return (priv->bufs[i]);
1288 }
1289 
1290 void
1291 dmu_xuio_clear(xuio_t *xuio, int i)
1292 {
1293 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
1294 
1295 	ASSERT(i < priv->cnt);
1296 	priv->bufs[i] = NULL;
1297 }
1298 
1299 static void
1300 xuio_stat_init(void)
1301 {
1302 	xuio_ksp = kstat_create("zfs", 0, "xuio_stats", "misc",
1303 	    KSTAT_TYPE_NAMED, sizeof (xuio_stats) / sizeof (kstat_named_t),
1304 	    KSTAT_FLAG_VIRTUAL);
1305 	if (xuio_ksp != NULL) {
1306 		xuio_ksp->ks_data = &xuio_stats;
1307 		kstat_install(xuio_ksp);
1308 	}
1309 }
1310 
1311 static void
1312 xuio_stat_fini(void)
1313 {
1314 	if (xuio_ksp != NULL) {
1315 		kstat_delete(xuio_ksp);
1316 		xuio_ksp = NULL;
1317 	}
1318 }
1319 
1320 void
1321 xuio_stat_wbuf_copied(void)
1322 {
1323 	XUIOSTAT_BUMP(xuiostat_wbuf_copied);
1324 }
1325 
1326 void
1327 xuio_stat_wbuf_nocopy(void)
1328 {
1329 	XUIOSTAT_BUMP(xuiostat_wbuf_nocopy);
1330 }
1331 
1332 #ifdef _KERNEL
1333 int
1334 dmu_read_uio_dnode(dnode_t *dn, uio_t *uio, uint64_t size)
1335 {
1336 	dmu_buf_t **dbp;
1337 	int numbufs, i, err;
1338 	xuio_t *xuio = NULL;
1339 
1340 	/*
1341 	 * NB: we could do this block-at-a-time, but it's nice
1342 	 * to be reading in parallel.
1343 	 */
1344 	err = dmu_buf_hold_array_by_dnode(dn, uio->uio_loffset, size,
1345 	    TRUE, FTAG, &numbufs, &dbp, 0);
1346 	if (err)
1347 		return (err);
1348 
1349 	if (uio->uio_extflg == UIO_XUIO)
1350 		xuio = (xuio_t *)uio;
1351 
1352 	for (i = 0; i < numbufs; i++) {
1353 		int tocpy;
1354 		int bufoff;
1355 		dmu_buf_t *db = dbp[i];
1356 
1357 		ASSERT(size > 0);
1358 
1359 		bufoff = uio->uio_loffset - db->db_offset;
1360 		tocpy = (int)MIN(db->db_size - bufoff, size);
1361 
1362 		if (xuio) {
1363 			dmu_buf_impl_t *dbi = (dmu_buf_impl_t *)db;
1364 			arc_buf_t *dbuf_abuf = dbi->db_buf;
1365 			arc_buf_t *abuf = dbuf_loan_arcbuf(dbi);
1366 			err = dmu_xuio_add(xuio, abuf, bufoff, tocpy);
1367 			if (!err) {
1368 				uio->uio_resid -= tocpy;
1369 				uio->uio_loffset += tocpy;
1370 			}
1371 
1372 			if (abuf == dbuf_abuf)
1373 				XUIOSTAT_BUMP(xuiostat_rbuf_nocopy);
1374 			else
1375 				XUIOSTAT_BUMP(xuiostat_rbuf_copied);
1376 		} else {
1377 			err = uiomove((char *)db->db_data + bufoff, tocpy,
1378 			    UIO_READ, uio);
1379 		}
1380 		if (err)
1381 			break;
1382 
1383 		size -= tocpy;
1384 	}
1385 	dmu_buf_rele_array(dbp, numbufs, FTAG);
1386 
1387 	return (err);
1388 }
1389 
1390 /*
1391  * Read 'size' bytes into the uio buffer.
1392  * From object zdb->db_object.
1393  * Starting at offset uio->uio_loffset.
1394  *
1395  * If the caller already has a dbuf in the target object
1396  * (e.g. its bonus buffer), this routine is faster than dmu_read_uio(),
1397  * because we don't have to find the dnode_t for the object.
1398  */
1399 int
1400 dmu_read_uio_dbuf(dmu_buf_t *zdb, uio_t *uio, uint64_t size)
1401 {
1402 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)zdb;
1403 	dnode_t *dn;
1404 	int err;
1405 
1406 	if (size == 0)
1407 		return (0);
1408 
1409 	DB_DNODE_ENTER(db);
1410 	dn = DB_DNODE(db);
1411 	err = dmu_read_uio_dnode(dn, uio, size);
1412 	DB_DNODE_EXIT(db);
1413 
1414 	return (err);
1415 }
1416 
1417 /*
1418  * Read 'size' bytes into the uio buffer.
1419  * From the specified object
1420  * Starting at offset uio->uio_loffset.
1421  */
1422 int
1423 dmu_read_uio(objset_t *os, uint64_t object, uio_t *uio, uint64_t size)
1424 {
1425 	dnode_t *dn;
1426 	int err;
1427 
1428 	if (size == 0)
1429 		return (0);
1430 
1431 	err = dnode_hold(os, object, FTAG, &dn);
1432 	if (err)
1433 		return (err);
1434 
1435 	err = dmu_read_uio_dnode(dn, uio, size);
1436 
1437 	dnode_rele(dn, FTAG);
1438 
1439 	return (err);
1440 }
1441 
1442 int
1443 dmu_write_uio_dnode(dnode_t *dn, uio_t *uio, uint64_t size, dmu_tx_t *tx)
1444 {
1445 	dmu_buf_t **dbp;
1446 	int numbufs;
1447 	int err = 0;
1448 	int i;
1449 
1450 	err = dmu_buf_hold_array_by_dnode(dn, uio->uio_loffset, size,
1451 	    FALSE, FTAG, &numbufs, &dbp, DMU_READ_PREFETCH);
1452 	if (err)
1453 		return (err);
1454 
1455 	for (i = 0; i < numbufs; i++) {
1456 		int tocpy;
1457 		int bufoff;
1458 		dmu_buf_t *db = dbp[i];
1459 
1460 		ASSERT(size > 0);
1461 
1462 		bufoff = uio->uio_loffset - db->db_offset;
1463 		tocpy = (int)MIN(db->db_size - bufoff, size);
1464 
1465 		ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
1466 
1467 		if (tocpy == db->db_size)
1468 			dmu_buf_will_fill(db, tx);
1469 		else
1470 			dmu_buf_will_dirty(db, tx);
1471 
1472 		/*
1473 		 * XXX uiomove could block forever (eg. nfs-backed
1474 		 * pages).  There needs to be a uiolockdown() function
1475 		 * to lock the pages in memory, so that uiomove won't
1476 		 * block.
1477 		 */
1478 		err = uiomove((char *)db->db_data + bufoff, tocpy,
1479 		    UIO_WRITE, uio);
1480 
1481 		if (tocpy == db->db_size)
1482 			dmu_buf_fill_done(db, tx);
1483 
1484 		if (err)
1485 			break;
1486 
1487 		size -= tocpy;
1488 	}
1489 
1490 	dmu_buf_rele_array(dbp, numbufs, FTAG);
1491 	return (err);
1492 }
1493 
1494 /*
1495  * Write 'size' bytes from the uio buffer.
1496  * To object zdb->db_object.
1497  * Starting at offset uio->uio_loffset.
1498  *
1499  * If the caller already has a dbuf in the target object
1500  * (e.g. its bonus buffer), this routine is faster than dmu_write_uio(),
1501  * because we don't have to find the dnode_t for the object.
1502  */
1503 int
1504 dmu_write_uio_dbuf(dmu_buf_t *zdb, uio_t *uio, uint64_t size,
1505     dmu_tx_t *tx)
1506 {
1507 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)zdb;
1508 	dnode_t *dn;
1509 	int err;
1510 
1511 	if (size == 0)
1512 		return (0);
1513 
1514 	DB_DNODE_ENTER(db);
1515 	dn = DB_DNODE(db);
1516 	err = dmu_write_uio_dnode(dn, uio, size, tx);
1517 	DB_DNODE_EXIT(db);
1518 
1519 	return (err);
1520 }
1521 
1522 /*
1523  * Write 'size' bytes from the uio buffer.
1524  * To the specified object.
1525  * Starting at offset uio->uio_loffset.
1526  */
1527 int
1528 dmu_write_uio(objset_t *os, uint64_t object, uio_t *uio, uint64_t size,
1529     dmu_tx_t *tx)
1530 {
1531 	dnode_t *dn;
1532 	int err;
1533 
1534 	if (size == 0)
1535 		return (0);
1536 
1537 	err = dnode_hold(os, object, FTAG, &dn);
1538 	if (err)
1539 		return (err);
1540 
1541 	err = dmu_write_uio_dnode(dn, uio, size, tx);
1542 
1543 	dnode_rele(dn, FTAG);
1544 
1545 	return (err);
1546 }
1547 
1548 int
1549 dmu_write_pages(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
1550     page_t *pp, dmu_tx_t *tx)
1551 {
1552 	dmu_buf_t **dbp;
1553 	int numbufs, i;
1554 	int err;
1555 
1556 	if (size == 0)
1557 		return (0);
1558 
1559 	err = dmu_buf_hold_array(os, object, offset, size,
1560 	    FALSE, FTAG, &numbufs, &dbp);
1561 	if (err)
1562 		return (err);
1563 
1564 	for (i = 0; i < numbufs; i++) {
1565 		int tocpy, copied, thiscpy;
1566 		int bufoff;
1567 		dmu_buf_t *db = dbp[i];
1568 		caddr_t va;
1569 
1570 		ASSERT(size > 0);
1571 		ASSERT3U(db->db_size, >=, PAGESIZE);
1572 
1573 		bufoff = offset - db->db_offset;
1574 		tocpy = (int)MIN(db->db_size - bufoff, size);
1575 
1576 		ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
1577 
1578 		if (tocpy == db->db_size)
1579 			dmu_buf_will_fill(db, tx);
1580 		else
1581 			dmu_buf_will_dirty(db, tx);
1582 
1583 		for (copied = 0; copied < tocpy; copied += PAGESIZE) {
1584 			ASSERT3U(pp->p_offset, ==, db->db_offset + bufoff);
1585 			thiscpy = MIN(PAGESIZE, tocpy - copied);
1586 			va = zfs_map_page(pp, S_READ);
1587 			bcopy(va, (char *)db->db_data + bufoff, thiscpy);
1588 			zfs_unmap_page(pp, va);
1589 			pp = pp->p_next;
1590 			bufoff += PAGESIZE;
1591 		}
1592 
1593 		if (tocpy == db->db_size)
1594 			dmu_buf_fill_done(db, tx);
1595 
1596 		offset += tocpy;
1597 		size -= tocpy;
1598 	}
1599 	dmu_buf_rele_array(dbp, numbufs, FTAG);
1600 	return (err);
1601 }
1602 #endif
1603 
1604 /*
1605  * Allocate a loaned anonymous arc buffer.
1606  */
1607 arc_buf_t *
1608 dmu_request_arcbuf(dmu_buf_t *handle, int size)
1609 {
1610 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)handle;
1611 
1612 	return (arc_loan_buf(db->db_objset->os_spa, B_FALSE, size));
1613 }
1614 
1615 /*
1616  * Free a loaned arc buffer.
1617  */
1618 void
1619 dmu_return_arcbuf(arc_buf_t *buf)
1620 {
1621 	arc_return_buf(buf, FTAG);
1622 	arc_buf_destroy(buf, FTAG);
1623 }
1624 
1625 /*
1626  * When possible directly assign passed loaned arc buffer to a dbuf.
1627  * If this is not possible copy the contents of passed arc buf via
1628  * dmu_write().
1629  */
1630 void
1631 dmu_assign_arcbuf_dnode(dnode_t *dn, uint64_t offset, arc_buf_t *buf,
1632     dmu_tx_t *tx)
1633 {
1634 	dmu_buf_impl_t *db;
1635 	uint32_t blksz = (uint32_t)arc_buf_lsize(buf);
1636 	uint64_t blkid;
1637 
1638 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
1639 	blkid = dbuf_whichblock(dn, 0, offset);
1640 	VERIFY((db = dbuf_hold(dn, blkid, FTAG)) != NULL);
1641 	rw_exit(&dn->dn_struct_rwlock);
1642 
1643 	/*
1644 	 * We can only assign if the offset is aligned, the arc buf is the
1645 	 * same size as the dbuf, and the dbuf is not metadata.
1646 	 */
1647 	if (offset == db->db.db_offset && blksz == db->db.db_size) {
1648 		dbuf_assign_arcbuf(db, buf, tx);
1649 		dbuf_rele(db, FTAG);
1650 	} else {
1651 		objset_t *os;
1652 		uint64_t object;
1653 
1654 		/* compressed bufs must always be assignable to their dbuf */
1655 		ASSERT3U(arc_get_compression(buf), ==, ZIO_COMPRESS_OFF);
1656 		ASSERT(!(buf->b_flags & ARC_BUF_FLAG_COMPRESSED));
1657 
1658 		os = dn->dn_objset;
1659 		object = dn->dn_object;
1660 
1661 		dbuf_rele(db, FTAG);
1662 		dmu_write(os, object, offset, blksz, buf->b_data, tx);
1663 		dmu_return_arcbuf(buf);
1664 		XUIOSTAT_BUMP(xuiostat_wbuf_copied);
1665 	}
1666 }
1667 
1668 void
1669 dmu_assign_arcbuf(dmu_buf_t *handle, uint64_t offset, arc_buf_t *buf,
1670     dmu_tx_t *tx)
1671 {
1672 	dmu_buf_impl_t *dbuf = (dmu_buf_impl_t *)handle;
1673 
1674 	DB_DNODE_ENTER(dbuf);
1675 	dmu_assign_arcbuf_dnode(DB_DNODE(dbuf), offset, buf, tx);
1676 	DB_DNODE_EXIT(dbuf);
1677 }
1678 
1679 typedef struct {
1680 	dbuf_dirty_record_t	*dsa_dr;
1681 	dmu_sync_cb_t		*dsa_done;
1682 	zgd_t			*dsa_zgd;
1683 	dmu_tx_t		*dsa_tx;
1684 } dmu_sync_arg_t;
1685 
1686 /* ARGSUSED */
1687 static void
1688 dmu_sync_ready(zio_t *zio, arc_buf_t *buf, void *varg)
1689 {
1690 	dmu_sync_arg_t *dsa = varg;
1691 	dmu_buf_t *db = dsa->dsa_zgd->zgd_db;
1692 	blkptr_t *bp = zio->io_bp;
1693 
1694 	if (zio->io_error == 0) {
1695 		if (BP_IS_HOLE(bp)) {
1696 			/*
1697 			 * A block of zeros may compress to a hole, but the
1698 			 * block size still needs to be known for replay.
1699 			 */
1700 			BP_SET_LSIZE(bp, db->db_size);
1701 		} else if (!BP_IS_EMBEDDED(bp)) {
1702 			ASSERT(BP_GET_LEVEL(bp) == 0);
1703 			bp->blk_fill = 1;
1704 		}
1705 	}
1706 }
1707 
1708 static void
1709 dmu_sync_late_arrival_ready(zio_t *zio)
1710 {
1711 	dmu_sync_ready(zio, NULL, zio->io_private);
1712 }
1713 
1714 /* ARGSUSED */
1715 static void
1716 dmu_sync_done(zio_t *zio, arc_buf_t *buf, void *varg)
1717 {
1718 	dmu_sync_arg_t *dsa = varg;
1719 	dbuf_dirty_record_t *dr = dsa->dsa_dr;
1720 	dmu_buf_impl_t *db = dr->dr_dbuf;
1721 	zgd_t *zgd = dsa->dsa_zgd;
1722 
1723 	/*
1724 	 * Record the vdev(s) backing this blkptr so they can be flushed after
1725 	 * the writes for the lwb have completed.
1726 	 */
1727 	if (zio->io_error == 0) {
1728 		zil_lwb_add_block(zgd->zgd_lwb, zgd->zgd_bp);
1729 	}
1730 
1731 	mutex_enter(&db->db_mtx);
1732 	ASSERT(dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC);
1733 	if (zio->io_error == 0) {
1734 		dr->dt.dl.dr_nopwrite = !!(zio->io_flags & ZIO_FLAG_NOPWRITE);
1735 		if (dr->dt.dl.dr_nopwrite) {
1736 			blkptr_t *bp = zio->io_bp;
1737 			blkptr_t *bp_orig = &zio->io_bp_orig;
1738 			uint8_t chksum = BP_GET_CHECKSUM(bp_orig);
1739 
1740 			ASSERT(BP_EQUAL(bp, bp_orig));
1741 			VERIFY(BP_EQUAL(bp, db->db_blkptr));
1742 			ASSERT(zio->io_prop.zp_compress != ZIO_COMPRESS_OFF);
1743 			ASSERT(zio_checksum_table[chksum].ci_flags &
1744 			    ZCHECKSUM_FLAG_NOPWRITE);
1745 		}
1746 		dr->dt.dl.dr_overridden_by = *zio->io_bp;
1747 		dr->dt.dl.dr_override_state = DR_OVERRIDDEN;
1748 		dr->dt.dl.dr_copies = zio->io_prop.zp_copies;
1749 
1750 		/*
1751 		 * Old style holes are filled with all zeros, whereas
1752 		 * new-style holes maintain their lsize, type, level,
1753 		 * and birth time (see zio_write_compress). While we
1754 		 * need to reset the BP_SET_LSIZE() call that happened
1755 		 * in dmu_sync_ready for old style holes, we do *not*
1756 		 * want to wipe out the information contained in new
1757 		 * style holes. Thus, only zero out the block pointer if
1758 		 * it's an old style hole.
1759 		 */
1760 		if (BP_IS_HOLE(&dr->dt.dl.dr_overridden_by) &&
1761 		    dr->dt.dl.dr_overridden_by.blk_birth == 0)
1762 			BP_ZERO(&dr->dt.dl.dr_overridden_by);
1763 	} else {
1764 		dr->dt.dl.dr_override_state = DR_NOT_OVERRIDDEN;
1765 	}
1766 	cv_broadcast(&db->db_changed);
1767 	mutex_exit(&db->db_mtx);
1768 
1769 	dsa->dsa_done(dsa->dsa_zgd, zio->io_error);
1770 
1771 	kmem_free(dsa, sizeof (*dsa));
1772 }
1773 
1774 static void
1775 dmu_sync_late_arrival_done(zio_t *zio)
1776 {
1777 	blkptr_t *bp = zio->io_bp;
1778 	dmu_sync_arg_t *dsa = zio->io_private;
1779 	blkptr_t *bp_orig = &zio->io_bp_orig;
1780 	zgd_t *zgd = dsa->dsa_zgd;
1781 
1782 	if (zio->io_error == 0) {
1783 		/*
1784 		 * Record the vdev(s) backing this blkptr so they can be
1785 		 * flushed after the writes for the lwb have completed.
1786 		 */
1787 		zil_lwb_add_block(zgd->zgd_lwb, zgd->zgd_bp);
1788 
1789 		if (!BP_IS_HOLE(bp)) {
1790 			ASSERT(!(zio->io_flags & ZIO_FLAG_NOPWRITE));
1791 			ASSERT(BP_IS_HOLE(bp_orig) || !BP_EQUAL(bp, bp_orig));
1792 			ASSERT(zio->io_bp->blk_birth == zio->io_txg);
1793 			ASSERT(zio->io_txg > spa_syncing_txg(zio->io_spa));
1794 			zio_free(zio->io_spa, zio->io_txg, zio->io_bp);
1795 		}
1796 	}
1797 
1798 	dmu_tx_commit(dsa->dsa_tx);
1799 
1800 	dsa->dsa_done(dsa->dsa_zgd, zio->io_error);
1801 
1802 	abd_put(zio->io_abd);
1803 	kmem_free(dsa, sizeof (*dsa));
1804 }
1805 
1806 static int
1807 dmu_sync_late_arrival(zio_t *pio, objset_t *os, dmu_sync_cb_t *done, zgd_t *zgd,
1808     zio_prop_t *zp, zbookmark_phys_t *zb)
1809 {
1810 	dmu_sync_arg_t *dsa;
1811 	dmu_tx_t *tx;
1812 
1813 	tx = dmu_tx_create(os);
1814 	dmu_tx_hold_space(tx, zgd->zgd_db->db_size);
1815 	if (dmu_tx_assign(tx, TXG_WAIT) != 0) {
1816 		dmu_tx_abort(tx);
1817 		/* Make zl_get_data do txg_waited_synced() */
1818 		return (SET_ERROR(EIO));
1819 	}
1820 
1821 	/*
1822 	 * In order to prevent the zgd's lwb from being free'd prior to
1823 	 * dmu_sync_late_arrival_done() being called, we have to ensure
1824 	 * the lwb's "max txg" takes this tx's txg into account.
1825 	 */
1826 	zil_lwb_add_txg(zgd->zgd_lwb, dmu_tx_get_txg(tx));
1827 
1828 	dsa = kmem_alloc(sizeof (dmu_sync_arg_t), KM_SLEEP);
1829 	dsa->dsa_dr = NULL;
1830 	dsa->dsa_done = done;
1831 	dsa->dsa_zgd = zgd;
1832 	dsa->dsa_tx = tx;
1833 
1834 	/*
1835 	 * Since we are currently syncing this txg, it's nontrivial to
1836 	 * determine what BP to nopwrite against, so we disable nopwrite.
1837 	 *
1838 	 * When syncing, the db_blkptr is initially the BP of the previous
1839 	 * txg.  We can not nopwrite against it because it will be changed
1840 	 * (this is similar to the non-late-arrival case where the dbuf is
1841 	 * dirty in a future txg).
1842 	 *
1843 	 * Then dbuf_write_ready() sets bp_blkptr to the location we will write.
1844 	 * We can not nopwrite against it because although the BP will not
1845 	 * (typically) be changed, the data has not yet been persisted to this
1846 	 * location.
1847 	 *
1848 	 * Finally, when dbuf_write_done() is called, it is theoretically
1849 	 * possible to always nopwrite, because the data that was written in
1850 	 * this txg is the same data that we are trying to write.  However we
1851 	 * would need to check that this dbuf is not dirty in any future
1852 	 * txg's (as we do in the normal dmu_sync() path). For simplicity, we
1853 	 * don't nopwrite in this case.
1854 	 */
1855 	zp->zp_nopwrite = B_FALSE;
1856 
1857 	zio_nowait(zio_write(pio, os->os_spa, dmu_tx_get_txg(tx), zgd->zgd_bp,
1858 	    abd_get_from_buf(zgd->zgd_db->db_data, zgd->zgd_db->db_size),
1859 	    zgd->zgd_db->db_size, zgd->zgd_db->db_size, zp,
1860 	    dmu_sync_late_arrival_ready, NULL, NULL, dmu_sync_late_arrival_done,
1861 	    dsa, ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL, zb));
1862 
1863 	return (0);
1864 }
1865 
1866 /*
1867  * Intent log support: sync the block associated with db to disk.
1868  * N.B. and XXX: the caller is responsible for making sure that the
1869  * data isn't changing while dmu_sync() is writing it.
1870  *
1871  * Return values:
1872  *
1873  *	EEXIST: this txg has already been synced, so there's nothing to do.
1874  *		The caller should not log the write.
1875  *
1876  *	ENOENT: the block was dbuf_free_range()'d, so there's nothing to do.
1877  *		The caller should not log the write.
1878  *
1879  *	EALREADY: this block is already in the process of being synced.
1880  *		The caller should track its progress (somehow).
1881  *
1882  *	EIO: could not do the I/O.
1883  *		The caller should do a txg_wait_synced().
1884  *
1885  *	0: the I/O has been initiated.
1886  *		The caller should log this blkptr in the done callback.
1887  *		It is possible that the I/O will fail, in which case
1888  *		the error will be reported to the done callback and
1889  *		propagated to pio from zio_done().
1890  */
1891 int
1892 dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done, zgd_t *zgd)
1893 {
1894 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)zgd->zgd_db;
1895 	objset_t *os = db->db_objset;
1896 	dsl_dataset_t *ds = os->os_dsl_dataset;
1897 	dbuf_dirty_record_t *dr;
1898 	dmu_sync_arg_t *dsa;
1899 	zbookmark_phys_t zb;
1900 	zio_prop_t zp;
1901 	dnode_t *dn;
1902 
1903 	ASSERT(pio != NULL);
1904 	ASSERT(txg != 0);
1905 
1906 	SET_BOOKMARK(&zb, ds->ds_object,
1907 	    db->db.db_object, db->db_level, db->db_blkid);
1908 
1909 	DB_DNODE_ENTER(db);
1910 	dn = DB_DNODE(db);
1911 	dmu_write_policy(os, dn, db->db_level, WP_DMU_SYNC, &zp);
1912 	DB_DNODE_EXIT(db);
1913 
1914 	/*
1915 	 * If we're frozen (running ziltest), we always need to generate a bp.
1916 	 */
1917 	if (txg > spa_freeze_txg(os->os_spa))
1918 		return (dmu_sync_late_arrival(pio, os, done, zgd, &zp, &zb));
1919 
1920 	/*
1921 	 * Grabbing db_mtx now provides a barrier between dbuf_sync_leaf()
1922 	 * and us.  If we determine that this txg is not yet syncing,
1923 	 * but it begins to sync a moment later, that's OK because the
1924 	 * sync thread will block in dbuf_sync_leaf() until we drop db_mtx.
1925 	 */
1926 	mutex_enter(&db->db_mtx);
1927 
1928 	if (txg <= spa_last_synced_txg(os->os_spa)) {
1929 		/*
1930 		 * This txg has already synced.  There's nothing to do.
1931 		 */
1932 		mutex_exit(&db->db_mtx);
1933 		return (SET_ERROR(EEXIST));
1934 	}
1935 
1936 	if (txg <= spa_syncing_txg(os->os_spa)) {
1937 		/*
1938 		 * This txg is currently syncing, so we can't mess with
1939 		 * the dirty record anymore; just write a new log block.
1940 		 */
1941 		mutex_exit(&db->db_mtx);
1942 		return (dmu_sync_late_arrival(pio, os, done, zgd, &zp, &zb));
1943 	}
1944 
1945 	dr = db->db_last_dirty;
1946 	while (dr && dr->dr_txg != txg)
1947 		dr = dr->dr_next;
1948 
1949 	if (dr == NULL) {
1950 		/*
1951 		 * There's no dr for this dbuf, so it must have been freed.
1952 		 * There's no need to log writes to freed blocks, so we're done.
1953 		 */
1954 		mutex_exit(&db->db_mtx);
1955 		return (SET_ERROR(ENOENT));
1956 	}
1957 
1958 	ASSERT(dr->dr_next == NULL || dr->dr_next->dr_txg < txg);
1959 
1960 	if (db->db_blkptr != NULL) {
1961 		/*
1962 		 * We need to fill in zgd_bp with the current blkptr so that
1963 		 * the nopwrite code can check if we're writing the same
1964 		 * data that's already on disk.  We can only nopwrite if we
1965 		 * are sure that after making the copy, db_blkptr will not
1966 		 * change until our i/o completes.  We ensure this by
1967 		 * holding the db_mtx, and only allowing nopwrite if the
1968 		 * block is not already dirty (see below).  This is verified
1969 		 * by dmu_sync_done(), which VERIFYs that the db_blkptr has
1970 		 * not changed.
1971 		 */
1972 		*zgd->zgd_bp = *db->db_blkptr;
1973 	}
1974 
1975 	/*
1976 	 * Assume the on-disk data is X, the current syncing data (in
1977 	 * txg - 1) is Y, and the current in-memory data is Z (currently
1978 	 * in dmu_sync).
1979 	 *
1980 	 * We usually want to perform a nopwrite if X and Z are the
1981 	 * same.  However, if Y is different (i.e. the BP is going to
1982 	 * change before this write takes effect), then a nopwrite will
1983 	 * be incorrect - we would override with X, which could have
1984 	 * been freed when Y was written.
1985 	 *
1986 	 * (Note that this is not a concern when we are nop-writing from
1987 	 * syncing context, because X and Y must be identical, because
1988 	 * all previous txgs have been synced.)
1989 	 *
1990 	 * Therefore, we disable nopwrite if the current BP could change
1991 	 * before this TXG.  There are two ways it could change: by
1992 	 * being dirty (dr_next is non-NULL), or by being freed
1993 	 * (dnode_block_freed()).  This behavior is verified by
1994 	 * zio_done(), which VERIFYs that the override BP is identical
1995 	 * to the on-disk BP.
1996 	 */
1997 	DB_DNODE_ENTER(db);
1998 	dn = DB_DNODE(db);
1999 	if (dr->dr_next != NULL || dnode_block_freed(dn, db->db_blkid))
2000 		zp.zp_nopwrite = B_FALSE;
2001 	DB_DNODE_EXIT(db);
2002 
2003 	ASSERT(dr->dr_txg == txg);
2004 	if (dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC ||
2005 	    dr->dt.dl.dr_override_state == DR_OVERRIDDEN) {
2006 		/*
2007 		 * We have already issued a sync write for this buffer,
2008 		 * or this buffer has already been synced.  It could not
2009 		 * have been dirtied since, or we would have cleared the state.
2010 		 */
2011 		mutex_exit(&db->db_mtx);
2012 		return (SET_ERROR(EALREADY));
2013 	}
2014 
2015 	ASSERT(dr->dt.dl.dr_override_state == DR_NOT_OVERRIDDEN);
2016 	dr->dt.dl.dr_override_state = DR_IN_DMU_SYNC;
2017 	mutex_exit(&db->db_mtx);
2018 
2019 	dsa = kmem_alloc(sizeof (dmu_sync_arg_t), KM_SLEEP);
2020 	dsa->dsa_dr = dr;
2021 	dsa->dsa_done = done;
2022 	dsa->dsa_zgd = zgd;
2023 	dsa->dsa_tx = NULL;
2024 
2025 	zio_nowait(arc_write(pio, os->os_spa, txg,
2026 	    zgd->zgd_bp, dr->dt.dl.dr_data, DBUF_IS_L2CACHEABLE(db),
2027 	    &zp, dmu_sync_ready, NULL, NULL, dmu_sync_done, dsa,
2028 	    ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL, &zb));
2029 
2030 	return (0);
2031 }
2032 
2033 int
2034 dmu_object_set_blocksize(objset_t *os, uint64_t object, uint64_t size, int ibs,
2035     dmu_tx_t *tx)
2036 {
2037 	dnode_t *dn;
2038 	int err;
2039 
2040 	err = dnode_hold(os, object, FTAG, &dn);
2041 	if (err)
2042 		return (err);
2043 	err = dnode_set_blksz(dn, size, ibs, tx);
2044 	dnode_rele(dn, FTAG);
2045 	return (err);
2046 }
2047 
2048 void
2049 dmu_object_set_checksum(objset_t *os, uint64_t object, uint8_t checksum,
2050     dmu_tx_t *tx)
2051 {
2052 	dnode_t *dn;
2053 
2054 	/*
2055 	 * Send streams include each object's checksum function.  This
2056 	 * check ensures that the receiving system can understand the
2057 	 * checksum function transmitted.
2058 	 */
2059 	ASSERT3U(checksum, <, ZIO_CHECKSUM_LEGACY_FUNCTIONS);
2060 
2061 	VERIFY0(dnode_hold(os, object, FTAG, &dn));
2062 	ASSERT3U(checksum, <, ZIO_CHECKSUM_FUNCTIONS);
2063 	dn->dn_checksum = checksum;
2064 	dnode_setdirty(dn, tx);
2065 	dnode_rele(dn, FTAG);
2066 }
2067 
2068 void
2069 dmu_object_set_compress(objset_t *os, uint64_t object, uint8_t compress,
2070     dmu_tx_t *tx)
2071 {
2072 	dnode_t *dn;
2073 
2074 	/*
2075 	 * Send streams include each object's compression function.  This
2076 	 * check ensures that the receiving system can understand the
2077 	 * compression function transmitted.
2078 	 */
2079 	ASSERT3U(compress, <, ZIO_COMPRESS_LEGACY_FUNCTIONS);
2080 
2081 	VERIFY0(dnode_hold(os, object, FTAG, &dn));
2082 	dn->dn_compress = compress;
2083 	dnode_setdirty(dn, tx);
2084 	dnode_rele(dn, FTAG);
2085 }
2086 
2087 int zfs_mdcomp_disable = 0;
2088 
2089 /*
2090  * When the "redundant_metadata" property is set to "most", only indirect
2091  * blocks of this level and higher will have an additional ditto block.
2092  */
2093 int zfs_redundant_metadata_most_ditto_level = 2;
2094 
2095 void
2096 dmu_write_policy(objset_t *os, dnode_t *dn, int level, int wp, zio_prop_t *zp)
2097 {
2098 	dmu_object_type_t type = dn ? dn->dn_type : DMU_OT_OBJSET;
2099 	boolean_t ismd = (level > 0 || DMU_OT_IS_METADATA(type) ||
2100 	    (wp & WP_SPILL));
2101 	enum zio_checksum checksum = os->os_checksum;
2102 	enum zio_compress compress = os->os_compress;
2103 	enum zio_checksum dedup_checksum = os->os_dedup_checksum;
2104 	boolean_t dedup = B_FALSE;
2105 	boolean_t nopwrite = B_FALSE;
2106 	boolean_t dedup_verify = os->os_dedup_verify;
2107 	int copies = os->os_copies;
2108 
2109 	/*
2110 	 * We maintain different write policies for each of the following
2111 	 * types of data:
2112 	 *	 1. metadata
2113 	 *	 2. preallocated blocks (i.e. level-0 blocks of a dump device)
2114 	 *	 3. all other level 0 blocks
2115 	 */
2116 	if (ismd) {
2117 		if (zfs_mdcomp_disable) {
2118 			compress = ZIO_COMPRESS_EMPTY;
2119 		} else {
2120 			/*
2121 			 * XXX -- we should design a compression algorithm
2122 			 * that specializes in arrays of bps.
2123 			 */
2124 			compress = zio_compress_select(os->os_spa,
2125 			    ZIO_COMPRESS_ON, ZIO_COMPRESS_ON);
2126 		}
2127 
2128 		/*
2129 		 * Metadata always gets checksummed.  If the data
2130 		 * checksum is multi-bit correctable, and it's not a
2131 		 * ZBT-style checksum, then it's suitable for metadata
2132 		 * as well.  Otherwise, the metadata checksum defaults
2133 		 * to fletcher4.
2134 		 */
2135 		if (!(zio_checksum_table[checksum].ci_flags &
2136 		    ZCHECKSUM_FLAG_METADATA) ||
2137 		    (zio_checksum_table[checksum].ci_flags &
2138 		    ZCHECKSUM_FLAG_EMBEDDED))
2139 			checksum = ZIO_CHECKSUM_FLETCHER_4;
2140 
2141 		if (os->os_redundant_metadata == ZFS_REDUNDANT_METADATA_ALL ||
2142 		    (os->os_redundant_metadata ==
2143 		    ZFS_REDUNDANT_METADATA_MOST &&
2144 		    (level >= zfs_redundant_metadata_most_ditto_level ||
2145 		    DMU_OT_IS_METADATA(type) || (wp & WP_SPILL))))
2146 			copies++;
2147 	} else if (wp & WP_NOFILL) {
2148 		ASSERT(level == 0);
2149 
2150 		/*
2151 		 * If we're writing preallocated blocks, we aren't actually
2152 		 * writing them so don't set any policy properties.  These
2153 		 * blocks are currently only used by an external subsystem
2154 		 * outside of zfs (i.e. dump) and not written by the zio
2155 		 * pipeline.
2156 		 */
2157 		compress = ZIO_COMPRESS_OFF;
2158 		checksum = ZIO_CHECKSUM_NOPARITY;
2159 	} else {
2160 		compress = zio_compress_select(os->os_spa, dn->dn_compress,
2161 		    compress);
2162 
2163 		checksum = (dedup_checksum == ZIO_CHECKSUM_OFF) ?
2164 		    zio_checksum_select(dn->dn_checksum, checksum) :
2165 		    dedup_checksum;
2166 
2167 		/*
2168 		 * Determine dedup setting.  If we are in dmu_sync(),
2169 		 * we won't actually dedup now because that's all
2170 		 * done in syncing context; but we do want to use the
2171 		 * dedup checkum.  If the checksum is not strong
2172 		 * enough to ensure unique signatures, force
2173 		 * dedup_verify.
2174 		 */
2175 		if (dedup_checksum != ZIO_CHECKSUM_OFF) {
2176 			dedup = (wp & WP_DMU_SYNC) ? B_FALSE : B_TRUE;
2177 			if (!(zio_checksum_table[checksum].ci_flags &
2178 			    ZCHECKSUM_FLAG_DEDUP))
2179 				dedup_verify = B_TRUE;
2180 		}
2181 
2182 		/*
2183 		 * Enable nopwrite if we have secure enough checksum
2184 		 * algorithm (see comment in zio_nop_write) and
2185 		 * compression is enabled.  We don't enable nopwrite if
2186 		 * dedup is enabled as the two features are mutually
2187 		 * exclusive.
2188 		 */
2189 		nopwrite = (!dedup && (zio_checksum_table[checksum].ci_flags &
2190 		    ZCHECKSUM_FLAG_NOPWRITE) &&
2191 		    compress != ZIO_COMPRESS_OFF && zfs_nopwrite_enabled);
2192 	}
2193 
2194 	zp->zp_checksum = checksum;
2195 	zp->zp_compress = compress;
2196 	ASSERT3U(zp->zp_compress, !=, ZIO_COMPRESS_INHERIT);
2197 
2198 	zp->zp_type = (wp & WP_SPILL) ? dn->dn_bonustype : type;
2199 	zp->zp_level = level;
2200 	zp->zp_copies = MIN(copies, spa_max_replication(os->os_spa));
2201 	zp->zp_dedup = dedup;
2202 	zp->zp_dedup_verify = dedup && dedup_verify;
2203 	zp->zp_nopwrite = nopwrite;
2204 }
2205 
2206 int
2207 dmu_offset_next(objset_t *os, uint64_t object, boolean_t hole, uint64_t *off)
2208 {
2209 	dnode_t *dn;
2210 	int err;
2211 
2212 	/*
2213 	 * Sync any current changes before
2214 	 * we go trundling through the block pointers.
2215 	 */
2216 	err = dmu_object_wait_synced(os, object);
2217 	if (err) {
2218 		return (err);
2219 	}
2220 
2221 	err = dnode_hold(os, object, FTAG, &dn);
2222 	if (err) {
2223 		return (err);
2224 	}
2225 
2226 	err = dnode_next_offset(dn, (hole ? DNODE_FIND_HOLE : 0), off, 1, 1, 0);
2227 	dnode_rele(dn, FTAG);
2228 
2229 	return (err);
2230 }
2231 
2232 /*
2233  * Given the ZFS object, if it contains any dirty nodes
2234  * this function flushes all dirty blocks to disk. This
2235  * ensures the DMU object info is updated. A more efficient
2236  * future version might just find the TXG with the maximum
2237  * ID and wait for that to be synced.
2238  */
2239 int
2240 dmu_object_wait_synced(objset_t *os, uint64_t object)
2241 {
2242 	dnode_t *dn;
2243 	int error, i;
2244 
2245 	error = dnode_hold(os, object, FTAG, &dn);
2246 	if (error) {
2247 		return (error);
2248 	}
2249 
2250 	for (i = 0; i < TXG_SIZE; i++) {
2251 		if (list_link_active(&dn->dn_dirty_link[i])) {
2252 			break;
2253 		}
2254 	}
2255 	dnode_rele(dn, FTAG);
2256 	if (i != TXG_SIZE) {
2257 		txg_wait_synced(dmu_objset_pool(os), 0);
2258 	}
2259 
2260 	return (0);
2261 }
2262 
2263 void
2264 dmu_object_info_from_dnode(dnode_t *dn, dmu_object_info_t *doi)
2265 {
2266 	dnode_phys_t *dnp;
2267 
2268 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
2269 	mutex_enter(&dn->dn_mtx);
2270 
2271 	dnp = dn->dn_phys;
2272 
2273 	doi->doi_data_block_size = dn->dn_datablksz;
2274 	doi->doi_metadata_block_size = dn->dn_indblkshift ?
2275 	    1ULL << dn->dn_indblkshift : 0;
2276 	doi->doi_type = dn->dn_type;
2277 	doi->doi_bonus_type = dn->dn_bonustype;
2278 	doi->doi_bonus_size = dn->dn_bonuslen;
2279 	doi->doi_dnodesize = dn->dn_num_slots << DNODE_SHIFT;
2280 	doi->doi_indirection = dn->dn_nlevels;
2281 	doi->doi_checksum = dn->dn_checksum;
2282 	doi->doi_compress = dn->dn_compress;
2283 	doi->doi_nblkptr = dn->dn_nblkptr;
2284 	doi->doi_physical_blocks_512 = (DN_USED_BYTES(dnp) + 256) >> 9;
2285 	doi->doi_max_offset = (dn->dn_maxblkid + 1) * dn->dn_datablksz;
2286 	doi->doi_fill_count = 0;
2287 	for (int i = 0; i < dnp->dn_nblkptr; i++)
2288 		doi->doi_fill_count += BP_GET_FILL(&dnp->dn_blkptr[i]);
2289 
2290 	mutex_exit(&dn->dn_mtx);
2291 	rw_exit(&dn->dn_struct_rwlock);
2292 }
2293 
2294 /*
2295  * Get information on a DMU object.
2296  * If doi is NULL, just indicates whether the object exists.
2297  */
2298 int
2299 dmu_object_info(objset_t *os, uint64_t object, dmu_object_info_t *doi)
2300 {
2301 	dnode_t *dn;
2302 	int err = dnode_hold(os, object, FTAG, &dn);
2303 
2304 	if (err)
2305 		return (err);
2306 
2307 	if (doi != NULL)
2308 		dmu_object_info_from_dnode(dn, doi);
2309 
2310 	dnode_rele(dn, FTAG);
2311 	return (0);
2312 }
2313 
2314 /*
2315  * As above, but faster; can be used when you have a held dbuf in hand.
2316  */
2317 void
2318 dmu_object_info_from_db(dmu_buf_t *db_fake, dmu_object_info_t *doi)
2319 {
2320 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
2321 
2322 	DB_DNODE_ENTER(db);
2323 	dmu_object_info_from_dnode(DB_DNODE(db), doi);
2324 	DB_DNODE_EXIT(db);
2325 }
2326 
2327 /*
2328  * Faster still when you only care about the size.
2329  * This is specifically optimized for zfs_getattr().
2330  */
2331 void
2332 dmu_object_size_from_db(dmu_buf_t *db_fake, uint32_t *blksize,
2333     u_longlong_t *nblk512)
2334 {
2335 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
2336 	dnode_t *dn;
2337 
2338 	DB_DNODE_ENTER(db);
2339 	dn = DB_DNODE(db);
2340 
2341 	*blksize = dn->dn_datablksz;
2342 	/* add in number of slots used for the dnode itself */
2343 	*nblk512 = ((DN_USED_BYTES(dn->dn_phys) + SPA_MINBLOCKSIZE/2) >>
2344 	    SPA_MINBLOCKSHIFT) + dn->dn_num_slots;
2345 	DB_DNODE_EXIT(db);
2346 }
2347 
2348 void
2349 dmu_object_dnsize_from_db(dmu_buf_t *db_fake, int *dnsize)
2350 {
2351 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
2352 	dnode_t *dn;
2353 
2354 	DB_DNODE_ENTER(db);
2355 	dn = DB_DNODE(db);
2356 	*dnsize = dn->dn_num_slots << DNODE_SHIFT;
2357 	DB_DNODE_EXIT(db);
2358 }
2359 
2360 void
2361 byteswap_uint64_array(void *vbuf, size_t size)
2362 {
2363 	uint64_t *buf = vbuf;
2364 	size_t count = size >> 3;
2365 	int i;
2366 
2367 	ASSERT((size & 7) == 0);
2368 
2369 	for (i = 0; i < count; i++)
2370 		buf[i] = BSWAP_64(buf[i]);
2371 }
2372 
2373 void
2374 byteswap_uint32_array(void *vbuf, size_t size)
2375 {
2376 	uint32_t *buf = vbuf;
2377 	size_t count = size >> 2;
2378 	int i;
2379 
2380 	ASSERT((size & 3) == 0);
2381 
2382 	for (i = 0; i < count; i++)
2383 		buf[i] = BSWAP_32(buf[i]);
2384 }
2385 
2386 void
2387 byteswap_uint16_array(void *vbuf, size_t size)
2388 {
2389 	uint16_t *buf = vbuf;
2390 	size_t count = size >> 1;
2391 	int i;
2392 
2393 	ASSERT((size & 1) == 0);
2394 
2395 	for (i = 0; i < count; i++)
2396 		buf[i] = BSWAP_16(buf[i]);
2397 }
2398 
2399 /* ARGSUSED */
2400 void
2401 byteswap_uint8_array(void *vbuf, size_t size)
2402 {
2403 }
2404 
2405 void
2406 dmu_init(void)
2407 {
2408 	abd_init();
2409 	zfs_dbgmsg_init();
2410 	sa_cache_init();
2411 	xuio_stat_init();
2412 	dmu_objset_init();
2413 	dnode_init();
2414 	zfetch_init();
2415 	l2arc_init();
2416 	arc_init();
2417 	dbuf_init();
2418 }
2419 
2420 void
2421 dmu_fini(void)
2422 {
2423 	arc_fini(); /* arc depends on l2arc, so arc must go first */
2424 	l2arc_fini();
2425 	zfetch_fini();
2426 	dbuf_fini();
2427 	dnode_fini();
2428 	dmu_objset_fini();
2429 	xuio_stat_fini();
2430 	sa_cache_fini();
2431 	zfs_dbgmsg_fini();
2432 	abd_fini();
2433 }
2434