xref: /illumos-gate/usr/src/uts/common/fs/zfs/dmu.c (revision e77d42eaa49fe55bfae1e0e0065c6e99affc001b)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 /*
22  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23  * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
24  */
25 /* Copyright (c) 2013 by Saso Kiselkov. All rights reserved. */
26 /* Copyright (c) 2013, Joyent, Inc. All rights reserved. */
27 /* Copyright (c) 2014, Nexenta Systems, Inc. All rights reserved. */
28 
29 #include <sys/dmu.h>
30 #include <sys/dmu_impl.h>
31 #include <sys/dmu_tx.h>
32 #include <sys/dbuf.h>
33 #include <sys/dnode.h>
34 #include <sys/zfs_context.h>
35 #include <sys/dmu_objset.h>
36 #include <sys/dmu_traverse.h>
37 #include <sys/dsl_dataset.h>
38 #include <sys/dsl_dir.h>
39 #include <sys/dsl_pool.h>
40 #include <sys/dsl_synctask.h>
41 #include <sys/dsl_prop.h>
42 #include <sys/dmu_zfetch.h>
43 #include <sys/zfs_ioctl.h>
44 #include <sys/zap.h>
45 #include <sys/zio_checksum.h>
46 #include <sys/zio_compress.h>
47 #include <sys/sa.h>
48 #include <sys/zfeature.h>
49 #ifdef _KERNEL
50 #include <sys/vmsystm.h>
51 #include <sys/zfs_znode.h>
52 #endif
53 
54 /*
55  * Enable/disable nopwrite feature.
56  */
57 int zfs_nopwrite_enabled = 1;
58 
59 const dmu_object_type_info_t dmu_ot[DMU_OT_NUMTYPES] = {
60 	{	DMU_BSWAP_UINT8,	TRUE,	"unallocated"		},
61 	{	DMU_BSWAP_ZAP,		TRUE,	"object directory"	},
62 	{	DMU_BSWAP_UINT64,	TRUE,	"object array"		},
63 	{	DMU_BSWAP_UINT8,	TRUE,	"packed nvlist"		},
64 	{	DMU_BSWAP_UINT64,	TRUE,	"packed nvlist size"	},
65 	{	DMU_BSWAP_UINT64,	TRUE,	"bpobj"			},
66 	{	DMU_BSWAP_UINT64,	TRUE,	"bpobj header"		},
67 	{	DMU_BSWAP_UINT64,	TRUE,	"SPA space map header"	},
68 	{	DMU_BSWAP_UINT64,	TRUE,	"SPA space map"		},
69 	{	DMU_BSWAP_UINT64,	TRUE,	"ZIL intent log"	},
70 	{	DMU_BSWAP_DNODE,	TRUE,	"DMU dnode"		},
71 	{	DMU_BSWAP_OBJSET,	TRUE,	"DMU objset"		},
72 	{	DMU_BSWAP_UINT64,	TRUE,	"DSL directory"		},
73 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL directory child map"},
74 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL dataset snap map"	},
75 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL props"		},
76 	{	DMU_BSWAP_UINT64,	TRUE,	"DSL dataset"		},
77 	{	DMU_BSWAP_ZNODE,	TRUE,	"ZFS znode"		},
78 	{	DMU_BSWAP_OLDACL,	TRUE,	"ZFS V0 ACL"		},
79 	{	DMU_BSWAP_UINT8,	FALSE,	"ZFS plain file"	},
80 	{	DMU_BSWAP_ZAP,		TRUE,	"ZFS directory"		},
81 	{	DMU_BSWAP_ZAP,		TRUE,	"ZFS master node"	},
82 	{	DMU_BSWAP_ZAP,		TRUE,	"ZFS delete queue"	},
83 	{	DMU_BSWAP_UINT8,	FALSE,	"zvol object"		},
84 	{	DMU_BSWAP_ZAP,		TRUE,	"zvol prop"		},
85 	{	DMU_BSWAP_UINT8,	FALSE,	"other uint8[]"		},
86 	{	DMU_BSWAP_UINT64,	FALSE,	"other uint64[]"	},
87 	{	DMU_BSWAP_ZAP,		TRUE,	"other ZAP"		},
88 	{	DMU_BSWAP_ZAP,		TRUE,	"persistent error log"	},
89 	{	DMU_BSWAP_UINT8,	TRUE,	"SPA history"		},
90 	{	DMU_BSWAP_UINT64,	TRUE,	"SPA history offsets"	},
91 	{	DMU_BSWAP_ZAP,		TRUE,	"Pool properties"	},
92 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL permissions"	},
93 	{	DMU_BSWAP_ACL,		TRUE,	"ZFS ACL"		},
94 	{	DMU_BSWAP_UINT8,	TRUE,	"ZFS SYSACL"		},
95 	{	DMU_BSWAP_UINT8,	TRUE,	"FUID table"		},
96 	{	DMU_BSWAP_UINT64,	TRUE,	"FUID table size"	},
97 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL dataset next clones"},
98 	{	DMU_BSWAP_ZAP,		TRUE,	"scan work queue"	},
99 	{	DMU_BSWAP_ZAP,		TRUE,	"ZFS user/group used"	},
100 	{	DMU_BSWAP_ZAP,		TRUE,	"ZFS user/group quota"	},
101 	{	DMU_BSWAP_ZAP,		TRUE,	"snapshot refcount tags"},
102 	{	DMU_BSWAP_ZAP,		TRUE,	"DDT ZAP algorithm"	},
103 	{	DMU_BSWAP_ZAP,		TRUE,	"DDT statistics"	},
104 	{	DMU_BSWAP_UINT8,	TRUE,	"System attributes"	},
105 	{	DMU_BSWAP_ZAP,		TRUE,	"SA master node"	},
106 	{	DMU_BSWAP_ZAP,		TRUE,	"SA attr registration"	},
107 	{	DMU_BSWAP_ZAP,		TRUE,	"SA attr layouts"	},
108 	{	DMU_BSWAP_ZAP,		TRUE,	"scan translations"	},
109 	{	DMU_BSWAP_UINT8,	FALSE,	"deduplicated block"	},
110 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL deadlist map"	},
111 	{	DMU_BSWAP_UINT64,	TRUE,	"DSL deadlist map hdr"	},
112 	{	DMU_BSWAP_ZAP,		TRUE,	"DSL dir clones"	},
113 	{	DMU_BSWAP_UINT64,	TRUE,	"bpobj subobj"		}
114 };
115 
116 const dmu_object_byteswap_info_t dmu_ot_byteswap[DMU_BSWAP_NUMFUNCS] = {
117 	{	byteswap_uint8_array,	"uint8"		},
118 	{	byteswap_uint16_array,	"uint16"	},
119 	{	byteswap_uint32_array,	"uint32"	},
120 	{	byteswap_uint64_array,	"uint64"	},
121 	{	zap_byteswap,		"zap"		},
122 	{	dnode_buf_byteswap,	"dnode"		},
123 	{	dmu_objset_byteswap,	"objset"	},
124 	{	zfs_znode_byteswap,	"znode"		},
125 	{	zfs_oldacl_byteswap,	"oldacl"	},
126 	{	zfs_acl_byteswap,	"acl"		}
127 };
128 
129 int
130 dmu_buf_hold_noread(objset_t *os, uint64_t object, uint64_t offset,
131     void *tag, dmu_buf_t **dbp)
132 {
133 	dnode_t *dn;
134 	uint64_t blkid;
135 	dmu_buf_impl_t *db;
136 	int err;
137 
138 	err = dnode_hold(os, object, FTAG, &dn);
139 	if (err)
140 		return (err);
141 	blkid = dbuf_whichblock(dn, offset);
142 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
143 	db = dbuf_hold(dn, blkid, tag);
144 	rw_exit(&dn->dn_struct_rwlock);
145 	dnode_rele(dn, FTAG);
146 
147 	if (db == NULL) {
148 		*dbp = NULL;
149 		return (SET_ERROR(EIO));
150 	}
151 
152 	*dbp = &db->db;
153 	return (err);
154 }
155 
156 int
157 dmu_buf_hold(objset_t *os, uint64_t object, uint64_t offset,
158     void *tag, dmu_buf_t **dbp, int flags)
159 {
160 	int err;
161 	int db_flags = DB_RF_CANFAIL;
162 
163 	if (flags & DMU_READ_NO_PREFETCH)
164 		db_flags |= DB_RF_NOPREFETCH;
165 
166 	err = dmu_buf_hold_noread(os, object, offset, tag, dbp);
167 	if (err == 0) {
168 		dmu_buf_impl_t *db = (dmu_buf_impl_t *)(*dbp);
169 		err = dbuf_read(db, NULL, db_flags);
170 		if (err != 0) {
171 			dbuf_rele(db, tag);
172 			*dbp = NULL;
173 		}
174 	}
175 
176 	return (err);
177 }
178 
179 int
180 dmu_bonus_max(void)
181 {
182 	return (DN_MAX_BONUSLEN);
183 }
184 
185 int
186 dmu_set_bonus(dmu_buf_t *db_fake, int newsize, dmu_tx_t *tx)
187 {
188 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
189 	dnode_t *dn;
190 	int error;
191 
192 	DB_DNODE_ENTER(db);
193 	dn = DB_DNODE(db);
194 
195 	if (dn->dn_bonus != db) {
196 		error = SET_ERROR(EINVAL);
197 	} else if (newsize < 0 || newsize > db_fake->db_size) {
198 		error = SET_ERROR(EINVAL);
199 	} else {
200 		dnode_setbonuslen(dn, newsize, tx);
201 		error = 0;
202 	}
203 
204 	DB_DNODE_EXIT(db);
205 	return (error);
206 }
207 
208 int
209 dmu_set_bonustype(dmu_buf_t *db_fake, dmu_object_type_t type, dmu_tx_t *tx)
210 {
211 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
212 	dnode_t *dn;
213 	int error;
214 
215 	DB_DNODE_ENTER(db);
216 	dn = DB_DNODE(db);
217 
218 	if (!DMU_OT_IS_VALID(type)) {
219 		error = SET_ERROR(EINVAL);
220 	} else if (dn->dn_bonus != db) {
221 		error = SET_ERROR(EINVAL);
222 	} else {
223 		dnode_setbonus_type(dn, type, tx);
224 		error = 0;
225 	}
226 
227 	DB_DNODE_EXIT(db);
228 	return (error);
229 }
230 
231 dmu_object_type_t
232 dmu_get_bonustype(dmu_buf_t *db_fake)
233 {
234 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
235 	dnode_t *dn;
236 	dmu_object_type_t type;
237 
238 	DB_DNODE_ENTER(db);
239 	dn = DB_DNODE(db);
240 	type = dn->dn_bonustype;
241 	DB_DNODE_EXIT(db);
242 
243 	return (type);
244 }
245 
246 int
247 dmu_rm_spill(objset_t *os, uint64_t object, dmu_tx_t *tx)
248 {
249 	dnode_t *dn;
250 	int error;
251 
252 	error = dnode_hold(os, object, FTAG, &dn);
253 	dbuf_rm_spill(dn, tx);
254 	rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
255 	dnode_rm_spill(dn, tx);
256 	rw_exit(&dn->dn_struct_rwlock);
257 	dnode_rele(dn, FTAG);
258 	return (error);
259 }
260 
261 /*
262  * returns ENOENT, EIO, or 0.
263  */
264 int
265 dmu_bonus_hold(objset_t *os, uint64_t object, void *tag, dmu_buf_t **dbp)
266 {
267 	dnode_t *dn;
268 	dmu_buf_impl_t *db;
269 	int error;
270 
271 	error = dnode_hold(os, object, FTAG, &dn);
272 	if (error)
273 		return (error);
274 
275 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
276 	if (dn->dn_bonus == NULL) {
277 		rw_exit(&dn->dn_struct_rwlock);
278 		rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
279 		if (dn->dn_bonus == NULL)
280 			dbuf_create_bonus(dn);
281 	}
282 	db = dn->dn_bonus;
283 
284 	/* as long as the bonus buf is held, the dnode will be held */
285 	if (refcount_add(&db->db_holds, tag) == 1) {
286 		VERIFY(dnode_add_ref(dn, db));
287 		atomic_inc_32(&dn->dn_dbufs_count);
288 	}
289 
290 	/*
291 	 * Wait to drop dn_struct_rwlock until after adding the bonus dbuf's
292 	 * hold and incrementing the dbuf count to ensure that dnode_move() sees
293 	 * a dnode hold for every dbuf.
294 	 */
295 	rw_exit(&dn->dn_struct_rwlock);
296 
297 	dnode_rele(dn, FTAG);
298 
299 	VERIFY(0 == dbuf_read(db, NULL, DB_RF_MUST_SUCCEED | DB_RF_NOPREFETCH));
300 
301 	*dbp = &db->db;
302 	return (0);
303 }
304 
305 /*
306  * returns ENOENT, EIO, or 0.
307  *
308  * This interface will allocate a blank spill dbuf when a spill blk
309  * doesn't already exist on the dnode.
310  *
311  * if you only want to find an already existing spill db, then
312  * dmu_spill_hold_existing() should be used.
313  */
314 int
315 dmu_spill_hold_by_dnode(dnode_t *dn, uint32_t flags, void *tag, dmu_buf_t **dbp)
316 {
317 	dmu_buf_impl_t *db = NULL;
318 	int err;
319 
320 	if ((flags & DB_RF_HAVESTRUCT) == 0)
321 		rw_enter(&dn->dn_struct_rwlock, RW_READER);
322 
323 	db = dbuf_hold(dn, DMU_SPILL_BLKID, tag);
324 
325 	if ((flags & DB_RF_HAVESTRUCT) == 0)
326 		rw_exit(&dn->dn_struct_rwlock);
327 
328 	ASSERT(db != NULL);
329 	err = dbuf_read(db, NULL, flags);
330 	if (err == 0)
331 		*dbp = &db->db;
332 	else
333 		dbuf_rele(db, tag);
334 	return (err);
335 }
336 
337 int
338 dmu_spill_hold_existing(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp)
339 {
340 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)bonus;
341 	dnode_t *dn;
342 	int err;
343 
344 	DB_DNODE_ENTER(db);
345 	dn = DB_DNODE(db);
346 
347 	if (spa_version(dn->dn_objset->os_spa) < SPA_VERSION_SA) {
348 		err = SET_ERROR(EINVAL);
349 	} else {
350 		rw_enter(&dn->dn_struct_rwlock, RW_READER);
351 
352 		if (!dn->dn_have_spill) {
353 			err = SET_ERROR(ENOENT);
354 		} else {
355 			err = dmu_spill_hold_by_dnode(dn,
356 			    DB_RF_HAVESTRUCT | DB_RF_CANFAIL, tag, dbp);
357 		}
358 
359 		rw_exit(&dn->dn_struct_rwlock);
360 	}
361 
362 	DB_DNODE_EXIT(db);
363 	return (err);
364 }
365 
366 int
367 dmu_spill_hold_by_bonus(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp)
368 {
369 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)bonus;
370 	dnode_t *dn;
371 	int err;
372 
373 	DB_DNODE_ENTER(db);
374 	dn = DB_DNODE(db);
375 	err = dmu_spill_hold_by_dnode(dn, DB_RF_CANFAIL, tag, dbp);
376 	DB_DNODE_EXIT(db);
377 
378 	return (err);
379 }
380 
381 /*
382  * Note: longer-term, we should modify all of the dmu_buf_*() interfaces
383  * to take a held dnode rather than <os, object> -- the lookup is wasteful,
384  * and can induce severe lock contention when writing to several files
385  * whose dnodes are in the same block.
386  */
387 static int
388 dmu_buf_hold_array_by_dnode(dnode_t *dn, uint64_t offset, uint64_t length,
389     int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp, uint32_t flags)
390 {
391 	dmu_buf_t **dbp;
392 	uint64_t blkid, nblks, i;
393 	uint32_t dbuf_flags;
394 	int err;
395 	zio_t *zio;
396 
397 	ASSERT(length <= DMU_MAX_ACCESS);
398 
399 	dbuf_flags = DB_RF_CANFAIL | DB_RF_NEVERWAIT | DB_RF_HAVESTRUCT;
400 	if (flags & DMU_READ_NO_PREFETCH || length > zfetch_array_rd_sz)
401 		dbuf_flags |= DB_RF_NOPREFETCH;
402 
403 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
404 	if (dn->dn_datablkshift) {
405 		int blkshift = dn->dn_datablkshift;
406 		nblks = (P2ROUNDUP(offset+length, 1ULL<<blkshift) -
407 		    P2ALIGN(offset, 1ULL<<blkshift)) >> blkshift;
408 	} else {
409 		if (offset + length > dn->dn_datablksz) {
410 			zfs_panic_recover("zfs: accessing past end of object "
411 			    "%llx/%llx (size=%u access=%llu+%llu)",
412 			    (longlong_t)dn->dn_objset->
413 			    os_dsl_dataset->ds_object,
414 			    (longlong_t)dn->dn_object, dn->dn_datablksz,
415 			    (longlong_t)offset, (longlong_t)length);
416 			rw_exit(&dn->dn_struct_rwlock);
417 			return (SET_ERROR(EIO));
418 		}
419 		nblks = 1;
420 	}
421 	dbp = kmem_zalloc(sizeof (dmu_buf_t *) * nblks, KM_SLEEP);
422 
423 	zio = zio_root(dn->dn_objset->os_spa, NULL, NULL, ZIO_FLAG_CANFAIL);
424 	blkid = dbuf_whichblock(dn, offset);
425 	for (i = 0; i < nblks; i++) {
426 		dmu_buf_impl_t *db = dbuf_hold(dn, blkid+i, tag);
427 		if (db == NULL) {
428 			rw_exit(&dn->dn_struct_rwlock);
429 			dmu_buf_rele_array(dbp, nblks, tag);
430 			zio_nowait(zio);
431 			return (SET_ERROR(EIO));
432 		}
433 		/* initiate async i/o */
434 		if (read) {
435 			(void) dbuf_read(db, zio, dbuf_flags);
436 		}
437 		dbp[i] = &db->db;
438 	}
439 	rw_exit(&dn->dn_struct_rwlock);
440 
441 	/* wait for async i/o */
442 	err = zio_wait(zio);
443 	if (err) {
444 		dmu_buf_rele_array(dbp, nblks, tag);
445 		return (err);
446 	}
447 
448 	/* wait for other io to complete */
449 	if (read) {
450 		for (i = 0; i < nblks; i++) {
451 			dmu_buf_impl_t *db = (dmu_buf_impl_t *)dbp[i];
452 			mutex_enter(&db->db_mtx);
453 			while (db->db_state == DB_READ ||
454 			    db->db_state == DB_FILL)
455 				cv_wait(&db->db_changed, &db->db_mtx);
456 			if (db->db_state == DB_UNCACHED)
457 				err = SET_ERROR(EIO);
458 			mutex_exit(&db->db_mtx);
459 			if (err) {
460 				dmu_buf_rele_array(dbp, nblks, tag);
461 				return (err);
462 			}
463 		}
464 	}
465 
466 	*numbufsp = nblks;
467 	*dbpp = dbp;
468 	return (0);
469 }
470 
471 static int
472 dmu_buf_hold_array(objset_t *os, uint64_t object, uint64_t offset,
473     uint64_t length, int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp)
474 {
475 	dnode_t *dn;
476 	int err;
477 
478 	err = dnode_hold(os, object, FTAG, &dn);
479 	if (err)
480 		return (err);
481 
482 	err = dmu_buf_hold_array_by_dnode(dn, offset, length, read, tag,
483 	    numbufsp, dbpp, DMU_READ_PREFETCH);
484 
485 	dnode_rele(dn, FTAG);
486 
487 	return (err);
488 }
489 
490 int
491 dmu_buf_hold_array_by_bonus(dmu_buf_t *db_fake, uint64_t offset,
492     uint64_t length, int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp)
493 {
494 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
495 	dnode_t *dn;
496 	int err;
497 
498 	DB_DNODE_ENTER(db);
499 	dn = DB_DNODE(db);
500 	err = dmu_buf_hold_array_by_dnode(dn, offset, length, read, tag,
501 	    numbufsp, dbpp, DMU_READ_PREFETCH);
502 	DB_DNODE_EXIT(db);
503 
504 	return (err);
505 }
506 
507 void
508 dmu_buf_rele_array(dmu_buf_t **dbp_fake, int numbufs, void *tag)
509 {
510 	int i;
511 	dmu_buf_impl_t **dbp = (dmu_buf_impl_t **)dbp_fake;
512 
513 	if (numbufs == 0)
514 		return;
515 
516 	for (i = 0; i < numbufs; i++) {
517 		if (dbp[i])
518 			dbuf_rele(dbp[i], tag);
519 	}
520 
521 	kmem_free(dbp, sizeof (dmu_buf_t *) * numbufs);
522 }
523 
524 /*
525  * Issue prefetch i/os for the given blocks.
526  *
527  * Note: The assumption is that we *know* these blocks will be needed
528  * almost immediately.  Therefore, the prefetch i/os will be issued at
529  * ZIO_PRIORITY_SYNC_READ
530  *
531  * Note: indirect blocks and other metadata will be read synchronously,
532  * causing this function to block if they are not already cached.
533  */
534 void
535 dmu_prefetch(objset_t *os, uint64_t object, uint64_t offset, uint64_t len)
536 {
537 	dnode_t *dn;
538 	uint64_t blkid;
539 	int nblks, err;
540 
541 	if (zfs_prefetch_disable)
542 		return;
543 
544 	if (len == 0) {  /* they're interested in the bonus buffer */
545 		dn = DMU_META_DNODE(os);
546 
547 		if (object == 0 || object >= DN_MAX_OBJECT)
548 			return;
549 
550 		rw_enter(&dn->dn_struct_rwlock, RW_READER);
551 		blkid = dbuf_whichblock(dn, object * sizeof (dnode_phys_t));
552 		dbuf_prefetch(dn, blkid, ZIO_PRIORITY_SYNC_READ);
553 		rw_exit(&dn->dn_struct_rwlock);
554 		return;
555 	}
556 
557 	/*
558 	 * XXX - Note, if the dnode for the requested object is not
559 	 * already cached, we will do a *synchronous* read in the
560 	 * dnode_hold() call.  The same is true for any indirects.
561 	 */
562 	err = dnode_hold(os, object, FTAG, &dn);
563 	if (err != 0)
564 		return;
565 
566 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
567 	if (dn->dn_datablkshift) {
568 		int blkshift = dn->dn_datablkshift;
569 		nblks = (P2ROUNDUP(offset + len, 1 << blkshift) -
570 		    P2ALIGN(offset, 1 << blkshift)) >> blkshift;
571 	} else {
572 		nblks = (offset < dn->dn_datablksz);
573 	}
574 
575 	if (nblks != 0) {
576 		blkid = dbuf_whichblock(dn, offset);
577 		for (int i = 0; i < nblks; i++)
578 			dbuf_prefetch(dn, blkid + i, ZIO_PRIORITY_SYNC_READ);
579 	}
580 
581 	rw_exit(&dn->dn_struct_rwlock);
582 
583 	dnode_rele(dn, FTAG);
584 }
585 
586 /*
587  * Get the next "chunk" of file data to free.  We traverse the file from
588  * the end so that the file gets shorter over time (if we crashes in the
589  * middle, this will leave us in a better state).  We find allocated file
590  * data by simply searching the allocated level 1 indirects.
591  *
592  * On input, *start should be the first offset that does not need to be
593  * freed (e.g. "offset + length").  On return, *start will be the first
594  * offset that should be freed.
595  */
596 static int
597 get_next_chunk(dnode_t *dn, uint64_t *start, uint64_t minimum)
598 {
599 	uint64_t maxblks = DMU_MAX_ACCESS >> (dn->dn_indblkshift + 1);
600 	/* bytes of data covered by a level-1 indirect block */
601 	uint64_t iblkrange =
602 	    dn->dn_datablksz * EPB(dn->dn_indblkshift, SPA_BLKPTRSHIFT);
603 
604 	ASSERT3U(minimum, <=, *start);
605 
606 	if (*start - minimum <= iblkrange * maxblks) {
607 		*start = minimum;
608 		return (0);
609 	}
610 	ASSERT(ISP2(iblkrange));
611 
612 	for (uint64_t blks = 0; *start > minimum && blks < maxblks; blks++) {
613 		int err;
614 
615 		/*
616 		 * dnode_next_offset(BACKWARDS) will find an allocated L1
617 		 * indirect block at or before the input offset.  We must
618 		 * decrement *start so that it is at the end of the region
619 		 * to search.
620 		 */
621 		(*start)--;
622 		err = dnode_next_offset(dn,
623 		    DNODE_FIND_BACKWARDS, start, 2, 1, 0);
624 
625 		/* if there are no indirect blocks before start, we are done */
626 		if (err == ESRCH) {
627 			*start = minimum;
628 			break;
629 		} else if (err != 0) {
630 			return (err);
631 		}
632 
633 		/* set start to the beginning of this L1 indirect */
634 		*start = P2ALIGN(*start, iblkrange);
635 	}
636 	if (*start < minimum)
637 		*start = minimum;
638 	return (0);
639 }
640 
641 static int
642 dmu_free_long_range_impl(objset_t *os, dnode_t *dn, uint64_t offset,
643     uint64_t length)
644 {
645 	uint64_t object_size = (dn->dn_maxblkid + 1) * dn->dn_datablksz;
646 	int err;
647 
648 	if (offset >= object_size)
649 		return (0);
650 
651 	if (length == DMU_OBJECT_END || offset + length > object_size)
652 		length = object_size - offset;
653 
654 	while (length != 0) {
655 		uint64_t chunk_end, chunk_begin;
656 
657 		chunk_end = chunk_begin = offset + length;
658 
659 		/* move chunk_begin backwards to the beginning of this chunk */
660 		err = get_next_chunk(dn, &chunk_begin, offset);
661 		if (err)
662 			return (err);
663 		ASSERT3U(chunk_begin, >=, offset);
664 		ASSERT3U(chunk_begin, <=, chunk_end);
665 
666 		dmu_tx_t *tx = dmu_tx_create(os);
667 		dmu_tx_hold_free(tx, dn->dn_object,
668 		    chunk_begin, chunk_end - chunk_begin);
669 
670 		/*
671 		 * Mark this transaction as typically resulting in a net
672 		 * reduction in space used.
673 		 */
674 		dmu_tx_mark_netfree(tx);
675 		err = dmu_tx_assign(tx, TXG_WAIT);
676 		if (err) {
677 			dmu_tx_abort(tx);
678 			return (err);
679 		}
680 		dnode_free_range(dn, chunk_begin, chunk_end - chunk_begin, tx);
681 		dmu_tx_commit(tx);
682 
683 		length -= chunk_end - chunk_begin;
684 	}
685 	return (0);
686 }
687 
688 int
689 dmu_free_long_range(objset_t *os, uint64_t object,
690     uint64_t offset, uint64_t length)
691 {
692 	dnode_t *dn;
693 	int err;
694 
695 	err = dnode_hold(os, object, FTAG, &dn);
696 	if (err != 0)
697 		return (err);
698 	err = dmu_free_long_range_impl(os, dn, offset, length);
699 
700 	/*
701 	 * It is important to zero out the maxblkid when freeing the entire
702 	 * file, so that (a) subsequent calls to dmu_free_long_range_impl()
703 	 * will take the fast path, and (b) dnode_reallocate() can verify
704 	 * that the entire file has been freed.
705 	 */
706 	if (err == 0 && offset == 0 && length == DMU_OBJECT_END)
707 		dn->dn_maxblkid = 0;
708 
709 	dnode_rele(dn, FTAG);
710 	return (err);
711 }
712 
713 int
714 dmu_free_long_object(objset_t *os, uint64_t object)
715 {
716 	dmu_tx_t *tx;
717 	int err;
718 
719 	err = dmu_free_long_range(os, object, 0, DMU_OBJECT_END);
720 	if (err != 0)
721 		return (err);
722 
723 	tx = dmu_tx_create(os);
724 	dmu_tx_hold_bonus(tx, object);
725 	dmu_tx_hold_free(tx, object, 0, DMU_OBJECT_END);
726 	dmu_tx_mark_netfree(tx);
727 	err = dmu_tx_assign(tx, TXG_WAIT);
728 	if (err == 0) {
729 		err = dmu_object_free(os, object, tx);
730 		dmu_tx_commit(tx);
731 	} else {
732 		dmu_tx_abort(tx);
733 	}
734 
735 	return (err);
736 }
737 
738 int
739 dmu_free_range(objset_t *os, uint64_t object, uint64_t offset,
740     uint64_t size, dmu_tx_t *tx)
741 {
742 	dnode_t *dn;
743 	int err = dnode_hold(os, object, FTAG, &dn);
744 	if (err)
745 		return (err);
746 	ASSERT(offset < UINT64_MAX);
747 	ASSERT(size == -1ULL || size <= UINT64_MAX - offset);
748 	dnode_free_range(dn, offset, size, tx);
749 	dnode_rele(dn, FTAG);
750 	return (0);
751 }
752 
753 int
754 dmu_read(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
755     void *buf, uint32_t flags)
756 {
757 	dnode_t *dn;
758 	dmu_buf_t **dbp;
759 	int numbufs, err;
760 
761 	err = dnode_hold(os, object, FTAG, &dn);
762 	if (err)
763 		return (err);
764 
765 	/*
766 	 * Deal with odd block sizes, where there can't be data past the first
767 	 * block.  If we ever do the tail block optimization, we will need to
768 	 * handle that here as well.
769 	 */
770 	if (dn->dn_maxblkid == 0) {
771 		int newsz = offset > dn->dn_datablksz ? 0 :
772 		    MIN(size, dn->dn_datablksz - offset);
773 		bzero((char *)buf + newsz, size - newsz);
774 		size = newsz;
775 	}
776 
777 	while (size > 0) {
778 		uint64_t mylen = MIN(size, DMU_MAX_ACCESS / 2);
779 		int i;
780 
781 		/*
782 		 * NB: we could do this block-at-a-time, but it's nice
783 		 * to be reading in parallel.
784 		 */
785 		err = dmu_buf_hold_array_by_dnode(dn, offset, mylen,
786 		    TRUE, FTAG, &numbufs, &dbp, flags);
787 		if (err)
788 			break;
789 
790 		for (i = 0; i < numbufs; i++) {
791 			int tocpy;
792 			int bufoff;
793 			dmu_buf_t *db = dbp[i];
794 
795 			ASSERT(size > 0);
796 
797 			bufoff = offset - db->db_offset;
798 			tocpy = (int)MIN(db->db_size - bufoff, size);
799 
800 			bcopy((char *)db->db_data + bufoff, buf, tocpy);
801 
802 			offset += tocpy;
803 			size -= tocpy;
804 			buf = (char *)buf + tocpy;
805 		}
806 		dmu_buf_rele_array(dbp, numbufs, FTAG);
807 	}
808 	dnode_rele(dn, FTAG);
809 	return (err);
810 }
811 
812 void
813 dmu_write(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
814     const void *buf, dmu_tx_t *tx)
815 {
816 	dmu_buf_t **dbp;
817 	int numbufs, i;
818 
819 	if (size == 0)
820 		return;
821 
822 	VERIFY(0 == dmu_buf_hold_array(os, object, offset, size,
823 	    FALSE, FTAG, &numbufs, &dbp));
824 
825 	for (i = 0; i < numbufs; i++) {
826 		int tocpy;
827 		int bufoff;
828 		dmu_buf_t *db = dbp[i];
829 
830 		ASSERT(size > 0);
831 
832 		bufoff = offset - db->db_offset;
833 		tocpy = (int)MIN(db->db_size - bufoff, size);
834 
835 		ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
836 
837 		if (tocpy == db->db_size)
838 			dmu_buf_will_fill(db, tx);
839 		else
840 			dmu_buf_will_dirty(db, tx);
841 
842 		bcopy(buf, (char *)db->db_data + bufoff, tocpy);
843 
844 		if (tocpy == db->db_size)
845 			dmu_buf_fill_done(db, tx);
846 
847 		offset += tocpy;
848 		size -= tocpy;
849 		buf = (char *)buf + tocpy;
850 	}
851 	dmu_buf_rele_array(dbp, numbufs, FTAG);
852 }
853 
854 void
855 dmu_prealloc(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
856     dmu_tx_t *tx)
857 {
858 	dmu_buf_t **dbp;
859 	int numbufs, i;
860 
861 	if (size == 0)
862 		return;
863 
864 	VERIFY(0 == dmu_buf_hold_array(os, object, offset, size,
865 	    FALSE, FTAG, &numbufs, &dbp));
866 
867 	for (i = 0; i < numbufs; i++) {
868 		dmu_buf_t *db = dbp[i];
869 
870 		dmu_buf_will_not_fill(db, tx);
871 	}
872 	dmu_buf_rele_array(dbp, numbufs, FTAG);
873 }
874 
875 void
876 dmu_write_embedded(objset_t *os, uint64_t object, uint64_t offset,
877     void *data, uint8_t etype, uint8_t comp, int uncompressed_size,
878     int compressed_size, int byteorder, dmu_tx_t *tx)
879 {
880 	dmu_buf_t *db;
881 
882 	ASSERT3U(etype, <, NUM_BP_EMBEDDED_TYPES);
883 	ASSERT3U(comp, <, ZIO_COMPRESS_FUNCTIONS);
884 	VERIFY0(dmu_buf_hold_noread(os, object, offset,
885 	    FTAG, &db));
886 
887 	dmu_buf_write_embedded(db,
888 	    data, (bp_embedded_type_t)etype, (enum zio_compress)comp,
889 	    uncompressed_size, compressed_size, byteorder, tx);
890 
891 	dmu_buf_rele(db, FTAG);
892 }
893 
894 /*
895  * DMU support for xuio
896  */
897 kstat_t *xuio_ksp = NULL;
898 
899 int
900 dmu_xuio_init(xuio_t *xuio, int nblk)
901 {
902 	dmu_xuio_t *priv;
903 	uio_t *uio = &xuio->xu_uio;
904 
905 	uio->uio_iovcnt = nblk;
906 	uio->uio_iov = kmem_zalloc(nblk * sizeof (iovec_t), KM_SLEEP);
907 
908 	priv = kmem_zalloc(sizeof (dmu_xuio_t), KM_SLEEP);
909 	priv->cnt = nblk;
910 	priv->bufs = kmem_zalloc(nblk * sizeof (arc_buf_t *), KM_SLEEP);
911 	priv->iovp = uio->uio_iov;
912 	XUIO_XUZC_PRIV(xuio) = priv;
913 
914 	if (XUIO_XUZC_RW(xuio) == UIO_READ)
915 		XUIOSTAT_INCR(xuiostat_onloan_rbuf, nblk);
916 	else
917 		XUIOSTAT_INCR(xuiostat_onloan_wbuf, nblk);
918 
919 	return (0);
920 }
921 
922 void
923 dmu_xuio_fini(xuio_t *xuio)
924 {
925 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
926 	int nblk = priv->cnt;
927 
928 	kmem_free(priv->iovp, nblk * sizeof (iovec_t));
929 	kmem_free(priv->bufs, nblk * sizeof (arc_buf_t *));
930 	kmem_free(priv, sizeof (dmu_xuio_t));
931 
932 	if (XUIO_XUZC_RW(xuio) == UIO_READ)
933 		XUIOSTAT_INCR(xuiostat_onloan_rbuf, -nblk);
934 	else
935 		XUIOSTAT_INCR(xuiostat_onloan_wbuf, -nblk);
936 }
937 
938 /*
939  * Initialize iov[priv->next] and priv->bufs[priv->next] with { off, n, abuf }
940  * and increase priv->next by 1.
941  */
942 int
943 dmu_xuio_add(xuio_t *xuio, arc_buf_t *abuf, offset_t off, size_t n)
944 {
945 	struct iovec *iov;
946 	uio_t *uio = &xuio->xu_uio;
947 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
948 	int i = priv->next++;
949 
950 	ASSERT(i < priv->cnt);
951 	ASSERT(off + n <= arc_buf_size(abuf));
952 	iov = uio->uio_iov + i;
953 	iov->iov_base = (char *)abuf->b_data + off;
954 	iov->iov_len = n;
955 	priv->bufs[i] = abuf;
956 	return (0);
957 }
958 
959 int
960 dmu_xuio_cnt(xuio_t *xuio)
961 {
962 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
963 	return (priv->cnt);
964 }
965 
966 arc_buf_t *
967 dmu_xuio_arcbuf(xuio_t *xuio, int i)
968 {
969 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
970 
971 	ASSERT(i < priv->cnt);
972 	return (priv->bufs[i]);
973 }
974 
975 void
976 dmu_xuio_clear(xuio_t *xuio, int i)
977 {
978 	dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
979 
980 	ASSERT(i < priv->cnt);
981 	priv->bufs[i] = NULL;
982 }
983 
984 static void
985 xuio_stat_init(void)
986 {
987 	xuio_ksp = kstat_create("zfs", 0, "xuio_stats", "misc",
988 	    KSTAT_TYPE_NAMED, sizeof (xuio_stats) / sizeof (kstat_named_t),
989 	    KSTAT_FLAG_VIRTUAL);
990 	if (xuio_ksp != NULL) {
991 		xuio_ksp->ks_data = &xuio_stats;
992 		kstat_install(xuio_ksp);
993 	}
994 }
995 
996 static void
997 xuio_stat_fini(void)
998 {
999 	if (xuio_ksp != NULL) {
1000 		kstat_delete(xuio_ksp);
1001 		xuio_ksp = NULL;
1002 	}
1003 }
1004 
1005 void
1006 xuio_stat_wbuf_copied()
1007 {
1008 	XUIOSTAT_BUMP(xuiostat_wbuf_copied);
1009 }
1010 
1011 void
1012 xuio_stat_wbuf_nocopy()
1013 {
1014 	XUIOSTAT_BUMP(xuiostat_wbuf_nocopy);
1015 }
1016 
1017 #ifdef _KERNEL
1018 static int
1019 dmu_read_uio_dnode(dnode_t *dn, uio_t *uio, uint64_t size)
1020 {
1021 	dmu_buf_t **dbp;
1022 	int numbufs, i, err;
1023 	xuio_t *xuio = NULL;
1024 
1025 	/*
1026 	 * NB: we could do this block-at-a-time, but it's nice
1027 	 * to be reading in parallel.
1028 	 */
1029 	err = dmu_buf_hold_array_by_dnode(dn, uio->uio_loffset, size,
1030 	    TRUE, FTAG, &numbufs, &dbp, 0);
1031 	if (err)
1032 		return (err);
1033 
1034 	if (uio->uio_extflg == UIO_XUIO)
1035 		xuio = (xuio_t *)uio;
1036 
1037 	for (i = 0; i < numbufs; i++) {
1038 		int tocpy;
1039 		int bufoff;
1040 		dmu_buf_t *db = dbp[i];
1041 
1042 		ASSERT(size > 0);
1043 
1044 		bufoff = uio->uio_loffset - db->db_offset;
1045 		tocpy = (int)MIN(db->db_size - bufoff, size);
1046 
1047 		if (xuio) {
1048 			dmu_buf_impl_t *dbi = (dmu_buf_impl_t *)db;
1049 			arc_buf_t *dbuf_abuf = dbi->db_buf;
1050 			arc_buf_t *abuf = dbuf_loan_arcbuf(dbi);
1051 			err = dmu_xuio_add(xuio, abuf, bufoff, tocpy);
1052 			if (!err) {
1053 				uio->uio_resid -= tocpy;
1054 				uio->uio_loffset += tocpy;
1055 			}
1056 
1057 			if (abuf == dbuf_abuf)
1058 				XUIOSTAT_BUMP(xuiostat_rbuf_nocopy);
1059 			else
1060 				XUIOSTAT_BUMP(xuiostat_rbuf_copied);
1061 		} else {
1062 			err = uiomove((char *)db->db_data + bufoff, tocpy,
1063 			    UIO_READ, uio);
1064 		}
1065 		if (err)
1066 			break;
1067 
1068 		size -= tocpy;
1069 	}
1070 	dmu_buf_rele_array(dbp, numbufs, FTAG);
1071 
1072 	return (err);
1073 }
1074 
1075 /*
1076  * Read 'size' bytes into the uio buffer.
1077  * From object zdb->db_object.
1078  * Starting at offset uio->uio_loffset.
1079  *
1080  * If the caller already has a dbuf in the target object
1081  * (e.g. its bonus buffer), this routine is faster than dmu_read_uio(),
1082  * because we don't have to find the dnode_t for the object.
1083  */
1084 int
1085 dmu_read_uio_dbuf(dmu_buf_t *zdb, uio_t *uio, uint64_t size)
1086 {
1087 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)zdb;
1088 	dnode_t *dn;
1089 	int err;
1090 
1091 	if (size == 0)
1092 		return (0);
1093 
1094 	DB_DNODE_ENTER(db);
1095 	dn = DB_DNODE(db);
1096 	err = dmu_read_uio_dnode(dn, uio, size);
1097 	DB_DNODE_EXIT(db);
1098 
1099 	return (err);
1100 }
1101 
1102 /*
1103  * Read 'size' bytes into the uio buffer.
1104  * From the specified object
1105  * Starting at offset uio->uio_loffset.
1106  */
1107 int
1108 dmu_read_uio(objset_t *os, uint64_t object, uio_t *uio, uint64_t size)
1109 {
1110 	dnode_t *dn;
1111 	int err;
1112 
1113 	if (size == 0)
1114 		return (0);
1115 
1116 	err = dnode_hold(os, object, FTAG, &dn);
1117 	if (err)
1118 		return (err);
1119 
1120 	err = dmu_read_uio_dnode(dn, uio, size);
1121 
1122 	dnode_rele(dn, FTAG);
1123 
1124 	return (err);
1125 }
1126 
1127 static int
1128 dmu_write_uio_dnode(dnode_t *dn, uio_t *uio, uint64_t size, dmu_tx_t *tx)
1129 {
1130 	dmu_buf_t **dbp;
1131 	int numbufs;
1132 	int err = 0;
1133 	int i;
1134 
1135 	err = dmu_buf_hold_array_by_dnode(dn, uio->uio_loffset, size,
1136 	    FALSE, FTAG, &numbufs, &dbp, DMU_READ_PREFETCH);
1137 	if (err)
1138 		return (err);
1139 
1140 	for (i = 0; i < numbufs; i++) {
1141 		int tocpy;
1142 		int bufoff;
1143 		dmu_buf_t *db = dbp[i];
1144 
1145 		ASSERT(size > 0);
1146 
1147 		bufoff = uio->uio_loffset - db->db_offset;
1148 		tocpy = (int)MIN(db->db_size - bufoff, size);
1149 
1150 		ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
1151 
1152 		if (tocpy == db->db_size)
1153 			dmu_buf_will_fill(db, tx);
1154 		else
1155 			dmu_buf_will_dirty(db, tx);
1156 
1157 		/*
1158 		 * XXX uiomove could block forever (eg. nfs-backed
1159 		 * pages).  There needs to be a uiolockdown() function
1160 		 * to lock the pages in memory, so that uiomove won't
1161 		 * block.
1162 		 */
1163 		err = uiomove((char *)db->db_data + bufoff, tocpy,
1164 		    UIO_WRITE, uio);
1165 
1166 		if (tocpy == db->db_size)
1167 			dmu_buf_fill_done(db, tx);
1168 
1169 		if (err)
1170 			break;
1171 
1172 		size -= tocpy;
1173 	}
1174 
1175 	dmu_buf_rele_array(dbp, numbufs, FTAG);
1176 	return (err);
1177 }
1178 
1179 /*
1180  * Write 'size' bytes from the uio buffer.
1181  * To object zdb->db_object.
1182  * Starting at offset uio->uio_loffset.
1183  *
1184  * If the caller already has a dbuf in the target object
1185  * (e.g. its bonus buffer), this routine is faster than dmu_write_uio(),
1186  * because we don't have to find the dnode_t for the object.
1187  */
1188 int
1189 dmu_write_uio_dbuf(dmu_buf_t *zdb, uio_t *uio, uint64_t size,
1190     dmu_tx_t *tx)
1191 {
1192 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)zdb;
1193 	dnode_t *dn;
1194 	int err;
1195 
1196 	if (size == 0)
1197 		return (0);
1198 
1199 	DB_DNODE_ENTER(db);
1200 	dn = DB_DNODE(db);
1201 	err = dmu_write_uio_dnode(dn, uio, size, tx);
1202 	DB_DNODE_EXIT(db);
1203 
1204 	return (err);
1205 }
1206 
1207 /*
1208  * Write 'size' bytes from the uio buffer.
1209  * To the specified object.
1210  * Starting at offset uio->uio_loffset.
1211  */
1212 int
1213 dmu_write_uio(objset_t *os, uint64_t object, uio_t *uio, uint64_t size,
1214     dmu_tx_t *tx)
1215 {
1216 	dnode_t *dn;
1217 	int err;
1218 
1219 	if (size == 0)
1220 		return (0);
1221 
1222 	err = dnode_hold(os, object, FTAG, &dn);
1223 	if (err)
1224 		return (err);
1225 
1226 	err = dmu_write_uio_dnode(dn, uio, size, tx);
1227 
1228 	dnode_rele(dn, FTAG);
1229 
1230 	return (err);
1231 }
1232 
1233 int
1234 dmu_write_pages(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
1235     page_t *pp, dmu_tx_t *tx)
1236 {
1237 	dmu_buf_t **dbp;
1238 	int numbufs, i;
1239 	int err;
1240 
1241 	if (size == 0)
1242 		return (0);
1243 
1244 	err = dmu_buf_hold_array(os, object, offset, size,
1245 	    FALSE, FTAG, &numbufs, &dbp);
1246 	if (err)
1247 		return (err);
1248 
1249 	for (i = 0; i < numbufs; i++) {
1250 		int tocpy, copied, thiscpy;
1251 		int bufoff;
1252 		dmu_buf_t *db = dbp[i];
1253 		caddr_t va;
1254 
1255 		ASSERT(size > 0);
1256 		ASSERT3U(db->db_size, >=, PAGESIZE);
1257 
1258 		bufoff = offset - db->db_offset;
1259 		tocpy = (int)MIN(db->db_size - bufoff, size);
1260 
1261 		ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
1262 
1263 		if (tocpy == db->db_size)
1264 			dmu_buf_will_fill(db, tx);
1265 		else
1266 			dmu_buf_will_dirty(db, tx);
1267 
1268 		for (copied = 0; copied < tocpy; copied += PAGESIZE) {
1269 			ASSERT3U(pp->p_offset, ==, db->db_offset + bufoff);
1270 			thiscpy = MIN(PAGESIZE, tocpy - copied);
1271 			va = zfs_map_page(pp, S_READ);
1272 			bcopy(va, (char *)db->db_data + bufoff, thiscpy);
1273 			zfs_unmap_page(pp, va);
1274 			pp = pp->p_next;
1275 			bufoff += PAGESIZE;
1276 		}
1277 
1278 		if (tocpy == db->db_size)
1279 			dmu_buf_fill_done(db, tx);
1280 
1281 		offset += tocpy;
1282 		size -= tocpy;
1283 	}
1284 	dmu_buf_rele_array(dbp, numbufs, FTAG);
1285 	return (err);
1286 }
1287 #endif
1288 
1289 /*
1290  * Allocate a loaned anonymous arc buffer.
1291  */
1292 arc_buf_t *
1293 dmu_request_arcbuf(dmu_buf_t *handle, int size)
1294 {
1295 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)handle;
1296 
1297 	return (arc_loan_buf(db->db_objset->os_spa, size));
1298 }
1299 
1300 /*
1301  * Free a loaned arc buffer.
1302  */
1303 void
1304 dmu_return_arcbuf(arc_buf_t *buf)
1305 {
1306 	arc_return_buf(buf, FTAG);
1307 	VERIFY(arc_buf_remove_ref(buf, FTAG));
1308 }
1309 
1310 /*
1311  * When possible directly assign passed loaned arc buffer to a dbuf.
1312  * If this is not possible copy the contents of passed arc buf via
1313  * dmu_write().
1314  */
1315 void
1316 dmu_assign_arcbuf(dmu_buf_t *handle, uint64_t offset, arc_buf_t *buf,
1317     dmu_tx_t *tx)
1318 {
1319 	dmu_buf_impl_t *dbuf = (dmu_buf_impl_t *)handle;
1320 	dnode_t *dn;
1321 	dmu_buf_impl_t *db;
1322 	uint32_t blksz = (uint32_t)arc_buf_size(buf);
1323 	uint64_t blkid;
1324 
1325 	DB_DNODE_ENTER(dbuf);
1326 	dn = DB_DNODE(dbuf);
1327 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
1328 	blkid = dbuf_whichblock(dn, offset);
1329 	VERIFY((db = dbuf_hold(dn, blkid, FTAG)) != NULL);
1330 	rw_exit(&dn->dn_struct_rwlock);
1331 	DB_DNODE_EXIT(dbuf);
1332 
1333 	/*
1334 	 * We can only assign if the offset is aligned, the arc buf is the
1335 	 * same size as the dbuf, and the dbuf is not metadata.  It
1336 	 * can't be metadata because the loaned arc buf comes from the
1337 	 * user-data kmem arena.
1338 	 */
1339 	if (offset == db->db.db_offset && blksz == db->db.db_size &&
1340 	    DBUF_GET_BUFC_TYPE(db) == ARC_BUFC_DATA) {
1341 		dbuf_assign_arcbuf(db, buf, tx);
1342 		dbuf_rele(db, FTAG);
1343 	} else {
1344 		objset_t *os;
1345 		uint64_t object;
1346 
1347 		DB_DNODE_ENTER(dbuf);
1348 		dn = DB_DNODE(dbuf);
1349 		os = dn->dn_objset;
1350 		object = dn->dn_object;
1351 		DB_DNODE_EXIT(dbuf);
1352 
1353 		dbuf_rele(db, FTAG);
1354 		dmu_write(os, object, offset, blksz, buf->b_data, tx);
1355 		dmu_return_arcbuf(buf);
1356 		XUIOSTAT_BUMP(xuiostat_wbuf_copied);
1357 	}
1358 }
1359 
1360 typedef struct {
1361 	dbuf_dirty_record_t	*dsa_dr;
1362 	dmu_sync_cb_t		*dsa_done;
1363 	zgd_t			*dsa_zgd;
1364 	dmu_tx_t		*dsa_tx;
1365 } dmu_sync_arg_t;
1366 
1367 /* ARGSUSED */
1368 static void
1369 dmu_sync_ready(zio_t *zio, arc_buf_t *buf, void *varg)
1370 {
1371 	dmu_sync_arg_t *dsa = varg;
1372 	dmu_buf_t *db = dsa->dsa_zgd->zgd_db;
1373 	blkptr_t *bp = zio->io_bp;
1374 
1375 	if (zio->io_error == 0) {
1376 		if (BP_IS_HOLE(bp)) {
1377 			/*
1378 			 * A block of zeros may compress to a hole, but the
1379 			 * block size still needs to be known for replay.
1380 			 */
1381 			BP_SET_LSIZE(bp, db->db_size);
1382 		} else if (!BP_IS_EMBEDDED(bp)) {
1383 			ASSERT(BP_GET_LEVEL(bp) == 0);
1384 			bp->blk_fill = 1;
1385 		}
1386 	}
1387 }
1388 
1389 static void
1390 dmu_sync_late_arrival_ready(zio_t *zio)
1391 {
1392 	dmu_sync_ready(zio, NULL, zio->io_private);
1393 }
1394 
1395 /* ARGSUSED */
1396 static void
1397 dmu_sync_done(zio_t *zio, arc_buf_t *buf, void *varg)
1398 {
1399 	dmu_sync_arg_t *dsa = varg;
1400 	dbuf_dirty_record_t *dr = dsa->dsa_dr;
1401 	dmu_buf_impl_t *db = dr->dr_dbuf;
1402 
1403 	mutex_enter(&db->db_mtx);
1404 	ASSERT(dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC);
1405 	if (zio->io_error == 0) {
1406 		dr->dt.dl.dr_nopwrite = !!(zio->io_flags & ZIO_FLAG_NOPWRITE);
1407 		if (dr->dt.dl.dr_nopwrite) {
1408 			blkptr_t *bp = zio->io_bp;
1409 			blkptr_t *bp_orig = &zio->io_bp_orig;
1410 			uint8_t chksum = BP_GET_CHECKSUM(bp_orig);
1411 
1412 			ASSERT(BP_EQUAL(bp, bp_orig));
1413 			ASSERT(zio->io_prop.zp_compress != ZIO_COMPRESS_OFF);
1414 			ASSERT(zio_checksum_table[chksum].ci_dedup);
1415 		}
1416 		dr->dt.dl.dr_overridden_by = *zio->io_bp;
1417 		dr->dt.dl.dr_override_state = DR_OVERRIDDEN;
1418 		dr->dt.dl.dr_copies = zio->io_prop.zp_copies;
1419 		if (BP_IS_HOLE(&dr->dt.dl.dr_overridden_by))
1420 			BP_ZERO(&dr->dt.dl.dr_overridden_by);
1421 	} else {
1422 		dr->dt.dl.dr_override_state = DR_NOT_OVERRIDDEN;
1423 	}
1424 	cv_broadcast(&db->db_changed);
1425 	mutex_exit(&db->db_mtx);
1426 
1427 	dsa->dsa_done(dsa->dsa_zgd, zio->io_error);
1428 
1429 	kmem_free(dsa, sizeof (*dsa));
1430 }
1431 
1432 static void
1433 dmu_sync_late_arrival_done(zio_t *zio)
1434 {
1435 	blkptr_t *bp = zio->io_bp;
1436 	dmu_sync_arg_t *dsa = zio->io_private;
1437 	blkptr_t *bp_orig = &zio->io_bp_orig;
1438 
1439 	if (zio->io_error == 0 && !BP_IS_HOLE(bp)) {
1440 		/*
1441 		 * If we didn't allocate a new block (i.e. ZIO_FLAG_NOPWRITE)
1442 		 * then there is nothing to do here. Otherwise, free the
1443 		 * newly allocated block in this txg.
1444 		 */
1445 		if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
1446 			ASSERT(BP_EQUAL(bp, bp_orig));
1447 		} else {
1448 			ASSERT(BP_IS_HOLE(bp_orig) || !BP_EQUAL(bp, bp_orig));
1449 			ASSERT(zio->io_bp->blk_birth == zio->io_txg);
1450 			ASSERT(zio->io_txg > spa_syncing_txg(zio->io_spa));
1451 			zio_free(zio->io_spa, zio->io_txg, zio->io_bp);
1452 		}
1453 	}
1454 
1455 	dmu_tx_commit(dsa->dsa_tx);
1456 
1457 	dsa->dsa_done(dsa->dsa_zgd, zio->io_error);
1458 
1459 	kmem_free(dsa, sizeof (*dsa));
1460 }
1461 
1462 static int
1463 dmu_sync_late_arrival(zio_t *pio, objset_t *os, dmu_sync_cb_t *done, zgd_t *zgd,
1464     zio_prop_t *zp, zbookmark_phys_t *zb)
1465 {
1466 	dmu_sync_arg_t *dsa;
1467 	dmu_tx_t *tx;
1468 
1469 	tx = dmu_tx_create(os);
1470 	dmu_tx_hold_space(tx, zgd->zgd_db->db_size);
1471 	if (dmu_tx_assign(tx, TXG_WAIT) != 0) {
1472 		dmu_tx_abort(tx);
1473 		/* Make zl_get_data do txg_waited_synced() */
1474 		return (SET_ERROR(EIO));
1475 	}
1476 
1477 	dsa = kmem_alloc(sizeof (dmu_sync_arg_t), KM_SLEEP);
1478 	dsa->dsa_dr = NULL;
1479 	dsa->dsa_done = done;
1480 	dsa->dsa_zgd = zgd;
1481 	dsa->dsa_tx = tx;
1482 
1483 	zio_nowait(zio_write(pio, os->os_spa, dmu_tx_get_txg(tx), zgd->zgd_bp,
1484 	    zgd->zgd_db->db_data, zgd->zgd_db->db_size, zp,
1485 	    dmu_sync_late_arrival_ready, NULL, dmu_sync_late_arrival_done, dsa,
1486 	    ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL, zb));
1487 
1488 	return (0);
1489 }
1490 
1491 /*
1492  * Intent log support: sync the block associated with db to disk.
1493  * N.B. and XXX: the caller is responsible for making sure that the
1494  * data isn't changing while dmu_sync() is writing it.
1495  *
1496  * Return values:
1497  *
1498  *	EEXIST: this txg has already been synced, so there's nothing to do.
1499  *		The caller should not log the write.
1500  *
1501  *	ENOENT: the block was dbuf_free_range()'d, so there's nothing to do.
1502  *		The caller should not log the write.
1503  *
1504  *	EALREADY: this block is already in the process of being synced.
1505  *		The caller should track its progress (somehow).
1506  *
1507  *	EIO: could not do the I/O.
1508  *		The caller should do a txg_wait_synced().
1509  *
1510  *	0: the I/O has been initiated.
1511  *		The caller should log this blkptr in the done callback.
1512  *		It is possible that the I/O will fail, in which case
1513  *		the error will be reported to the done callback and
1514  *		propagated to pio from zio_done().
1515  */
1516 int
1517 dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done, zgd_t *zgd)
1518 {
1519 	blkptr_t *bp = zgd->zgd_bp;
1520 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)zgd->zgd_db;
1521 	objset_t *os = db->db_objset;
1522 	dsl_dataset_t *ds = os->os_dsl_dataset;
1523 	dbuf_dirty_record_t *dr;
1524 	dmu_sync_arg_t *dsa;
1525 	zbookmark_phys_t zb;
1526 	zio_prop_t zp;
1527 	dnode_t *dn;
1528 
1529 	ASSERT(pio != NULL);
1530 	ASSERT(txg != 0);
1531 
1532 	SET_BOOKMARK(&zb, ds->ds_object,
1533 	    db->db.db_object, db->db_level, db->db_blkid);
1534 
1535 	DB_DNODE_ENTER(db);
1536 	dn = DB_DNODE(db);
1537 	dmu_write_policy(os, dn, db->db_level, WP_DMU_SYNC, &zp);
1538 	DB_DNODE_EXIT(db);
1539 
1540 	/*
1541 	 * If we're frozen (running ziltest), we always need to generate a bp.
1542 	 */
1543 	if (txg > spa_freeze_txg(os->os_spa))
1544 		return (dmu_sync_late_arrival(pio, os, done, zgd, &zp, &zb));
1545 
1546 	/*
1547 	 * Grabbing db_mtx now provides a barrier between dbuf_sync_leaf()
1548 	 * and us.  If we determine that this txg is not yet syncing,
1549 	 * but it begins to sync a moment later, that's OK because the
1550 	 * sync thread will block in dbuf_sync_leaf() until we drop db_mtx.
1551 	 */
1552 	mutex_enter(&db->db_mtx);
1553 
1554 	if (txg <= spa_last_synced_txg(os->os_spa)) {
1555 		/*
1556 		 * This txg has already synced.  There's nothing to do.
1557 		 */
1558 		mutex_exit(&db->db_mtx);
1559 		return (SET_ERROR(EEXIST));
1560 	}
1561 
1562 	if (txg <= spa_syncing_txg(os->os_spa)) {
1563 		/*
1564 		 * This txg is currently syncing, so we can't mess with
1565 		 * the dirty record anymore; just write a new log block.
1566 		 */
1567 		mutex_exit(&db->db_mtx);
1568 		return (dmu_sync_late_arrival(pio, os, done, zgd, &zp, &zb));
1569 	}
1570 
1571 	dr = db->db_last_dirty;
1572 	while (dr && dr->dr_txg != txg)
1573 		dr = dr->dr_next;
1574 
1575 	if (dr == NULL) {
1576 		/*
1577 		 * There's no dr for this dbuf, so it must have been freed.
1578 		 * There's no need to log writes to freed blocks, so we're done.
1579 		 */
1580 		mutex_exit(&db->db_mtx);
1581 		return (SET_ERROR(ENOENT));
1582 	}
1583 
1584 	ASSERT(dr->dr_next == NULL || dr->dr_next->dr_txg < txg);
1585 
1586 	/*
1587 	 * Assume the on-disk data is X, the current syncing data is Y,
1588 	 * and the current in-memory data is Z (currently in dmu_sync).
1589 	 * X and Z are identical but Y is has been modified. Normally,
1590 	 * when X and Z are the same we will perform a nopwrite but if Y
1591 	 * is different we must disable nopwrite since the resulting write
1592 	 * of Y to disk can free the block containing X. If we allowed a
1593 	 * nopwrite to occur the block pointing to Z would reference a freed
1594 	 * block. Since this is a rare case we simplify this by disabling
1595 	 * nopwrite if the current dmu_sync-ing dbuf has been modified in
1596 	 * a previous transaction.
1597 	 */
1598 	if (dr->dr_next)
1599 		zp.zp_nopwrite = B_FALSE;
1600 
1601 	ASSERT(dr->dr_txg == txg);
1602 	if (dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC ||
1603 	    dr->dt.dl.dr_override_state == DR_OVERRIDDEN) {
1604 		/*
1605 		 * We have already issued a sync write for this buffer,
1606 		 * or this buffer has already been synced.  It could not
1607 		 * have been dirtied since, or we would have cleared the state.
1608 		 */
1609 		mutex_exit(&db->db_mtx);
1610 		return (SET_ERROR(EALREADY));
1611 	}
1612 
1613 	ASSERT(dr->dt.dl.dr_override_state == DR_NOT_OVERRIDDEN);
1614 	dr->dt.dl.dr_override_state = DR_IN_DMU_SYNC;
1615 	mutex_exit(&db->db_mtx);
1616 
1617 	dsa = kmem_alloc(sizeof (dmu_sync_arg_t), KM_SLEEP);
1618 	dsa->dsa_dr = dr;
1619 	dsa->dsa_done = done;
1620 	dsa->dsa_zgd = zgd;
1621 	dsa->dsa_tx = NULL;
1622 
1623 	zio_nowait(arc_write(pio, os->os_spa, txg,
1624 	    bp, dr->dt.dl.dr_data, DBUF_IS_L2CACHEABLE(db),
1625 	    DBUF_IS_L2COMPRESSIBLE(db), &zp, dmu_sync_ready,
1626 	    NULL, dmu_sync_done, dsa, ZIO_PRIORITY_SYNC_WRITE,
1627 	    ZIO_FLAG_CANFAIL, &zb));
1628 
1629 	return (0);
1630 }
1631 
1632 int
1633 dmu_object_set_blocksize(objset_t *os, uint64_t object, uint64_t size, int ibs,
1634 	dmu_tx_t *tx)
1635 {
1636 	dnode_t *dn;
1637 	int err;
1638 
1639 	err = dnode_hold(os, object, FTAG, &dn);
1640 	if (err)
1641 		return (err);
1642 	err = dnode_set_blksz(dn, size, ibs, tx);
1643 	dnode_rele(dn, FTAG);
1644 	return (err);
1645 }
1646 
1647 void
1648 dmu_object_set_checksum(objset_t *os, uint64_t object, uint8_t checksum,
1649 	dmu_tx_t *tx)
1650 {
1651 	dnode_t *dn;
1652 
1653 	/*
1654 	 * Send streams include each object's checksum function.  This
1655 	 * check ensures that the receiving system can understand the
1656 	 * checksum function transmitted.
1657 	 */
1658 	ASSERT3U(checksum, <, ZIO_CHECKSUM_LEGACY_FUNCTIONS);
1659 
1660 	VERIFY0(dnode_hold(os, object, FTAG, &dn));
1661 	ASSERT3U(checksum, <, ZIO_CHECKSUM_FUNCTIONS);
1662 	dn->dn_checksum = checksum;
1663 	dnode_setdirty(dn, tx);
1664 	dnode_rele(dn, FTAG);
1665 }
1666 
1667 void
1668 dmu_object_set_compress(objset_t *os, uint64_t object, uint8_t compress,
1669 	dmu_tx_t *tx)
1670 {
1671 	dnode_t *dn;
1672 
1673 	/*
1674 	 * Send streams include each object's compression function.  This
1675 	 * check ensures that the receiving system can understand the
1676 	 * compression function transmitted.
1677 	 */
1678 	ASSERT3U(compress, <, ZIO_COMPRESS_LEGACY_FUNCTIONS);
1679 
1680 	VERIFY0(dnode_hold(os, object, FTAG, &dn));
1681 	dn->dn_compress = compress;
1682 	dnode_setdirty(dn, tx);
1683 	dnode_rele(dn, FTAG);
1684 }
1685 
1686 int zfs_mdcomp_disable = 0;
1687 
1688 /*
1689  * When the "redundant_metadata" property is set to "most", only indirect
1690  * blocks of this level and higher will have an additional ditto block.
1691  */
1692 int zfs_redundant_metadata_most_ditto_level = 2;
1693 
1694 void
1695 dmu_write_policy(objset_t *os, dnode_t *dn, int level, int wp, zio_prop_t *zp)
1696 {
1697 	dmu_object_type_t type = dn ? dn->dn_type : DMU_OT_OBJSET;
1698 	boolean_t ismd = (level > 0 || DMU_OT_IS_METADATA(type) ||
1699 	    (wp & WP_SPILL));
1700 	enum zio_checksum checksum = os->os_checksum;
1701 	enum zio_compress compress = os->os_compress;
1702 	enum zio_checksum dedup_checksum = os->os_dedup_checksum;
1703 	boolean_t dedup = B_FALSE;
1704 	boolean_t nopwrite = B_FALSE;
1705 	boolean_t dedup_verify = os->os_dedup_verify;
1706 	int copies = os->os_copies;
1707 
1708 	/*
1709 	 * We maintain different write policies for each of the following
1710 	 * types of data:
1711 	 *	 1. metadata
1712 	 *	 2. preallocated blocks (i.e. level-0 blocks of a dump device)
1713 	 *	 3. all other level 0 blocks
1714 	 */
1715 	if (ismd) {
1716 		/*
1717 		 * XXX -- we should design a compression algorithm
1718 		 * that specializes in arrays of bps.
1719 		 */
1720 		boolean_t lz4_ac = spa_feature_is_active(os->os_spa,
1721 		    SPA_FEATURE_LZ4_COMPRESS);
1722 
1723 		if (zfs_mdcomp_disable) {
1724 			compress = ZIO_COMPRESS_EMPTY;
1725 		} else if (lz4_ac) {
1726 			compress = ZIO_COMPRESS_LZ4;
1727 		} else {
1728 			compress = ZIO_COMPRESS_LZJB;
1729 		}
1730 
1731 		/*
1732 		 * Metadata always gets checksummed.  If the data
1733 		 * checksum is multi-bit correctable, and it's not a
1734 		 * ZBT-style checksum, then it's suitable for metadata
1735 		 * as well.  Otherwise, the metadata checksum defaults
1736 		 * to fletcher4.
1737 		 */
1738 		if (zio_checksum_table[checksum].ci_correctable < 1 ||
1739 		    zio_checksum_table[checksum].ci_eck)
1740 			checksum = ZIO_CHECKSUM_FLETCHER_4;
1741 
1742 		if (os->os_redundant_metadata == ZFS_REDUNDANT_METADATA_ALL ||
1743 		    (os->os_redundant_metadata ==
1744 		    ZFS_REDUNDANT_METADATA_MOST &&
1745 		    (level >= zfs_redundant_metadata_most_ditto_level ||
1746 		    DMU_OT_IS_METADATA(type) || (wp & WP_SPILL))))
1747 			copies++;
1748 	} else if (wp & WP_NOFILL) {
1749 		ASSERT(level == 0);
1750 
1751 		/*
1752 		 * If we're writing preallocated blocks, we aren't actually
1753 		 * writing them so don't set any policy properties.  These
1754 		 * blocks are currently only used by an external subsystem
1755 		 * outside of zfs (i.e. dump) and not written by the zio
1756 		 * pipeline.
1757 		 */
1758 		compress = ZIO_COMPRESS_OFF;
1759 		checksum = ZIO_CHECKSUM_NOPARITY;
1760 	} else {
1761 		compress = zio_compress_select(dn->dn_compress, compress);
1762 
1763 		checksum = (dedup_checksum == ZIO_CHECKSUM_OFF) ?
1764 		    zio_checksum_select(dn->dn_checksum, checksum) :
1765 		    dedup_checksum;
1766 
1767 		/*
1768 		 * Determine dedup setting.  If we are in dmu_sync(),
1769 		 * we won't actually dedup now because that's all
1770 		 * done in syncing context; but we do want to use the
1771 		 * dedup checkum.  If the checksum is not strong
1772 		 * enough to ensure unique signatures, force
1773 		 * dedup_verify.
1774 		 */
1775 		if (dedup_checksum != ZIO_CHECKSUM_OFF) {
1776 			dedup = (wp & WP_DMU_SYNC) ? B_FALSE : B_TRUE;
1777 			if (!zio_checksum_table[checksum].ci_dedup)
1778 				dedup_verify = B_TRUE;
1779 		}
1780 
1781 		/*
1782 		 * Enable nopwrite if we have a cryptographically secure
1783 		 * checksum that has no known collisions (i.e. SHA-256)
1784 		 * and compression is enabled.  We don't enable nopwrite if
1785 		 * dedup is enabled as the two features are mutually exclusive.
1786 		 */
1787 		nopwrite = (!dedup && zio_checksum_table[checksum].ci_dedup &&
1788 		    compress != ZIO_COMPRESS_OFF && zfs_nopwrite_enabled);
1789 	}
1790 
1791 	zp->zp_checksum = checksum;
1792 	zp->zp_compress = compress;
1793 	zp->zp_type = (wp & WP_SPILL) ? dn->dn_bonustype : type;
1794 	zp->zp_level = level;
1795 	zp->zp_copies = MIN(copies, spa_max_replication(os->os_spa));
1796 	zp->zp_dedup = dedup;
1797 	zp->zp_dedup_verify = dedup && dedup_verify;
1798 	zp->zp_nopwrite = nopwrite;
1799 }
1800 
1801 int
1802 dmu_offset_next(objset_t *os, uint64_t object, boolean_t hole, uint64_t *off)
1803 {
1804 	dnode_t *dn;
1805 	int i, err;
1806 
1807 	err = dnode_hold(os, object, FTAG, &dn);
1808 	if (err)
1809 		return (err);
1810 	/*
1811 	 * Sync any current changes before
1812 	 * we go trundling through the block pointers.
1813 	 */
1814 	for (i = 0; i < TXG_SIZE; i++) {
1815 		if (list_link_active(&dn->dn_dirty_link[i]))
1816 			break;
1817 	}
1818 	if (i != TXG_SIZE) {
1819 		dnode_rele(dn, FTAG);
1820 		txg_wait_synced(dmu_objset_pool(os), 0);
1821 		err = dnode_hold(os, object, FTAG, &dn);
1822 		if (err)
1823 			return (err);
1824 	}
1825 
1826 	err = dnode_next_offset(dn, (hole ? DNODE_FIND_HOLE : 0), off, 1, 1, 0);
1827 	dnode_rele(dn, FTAG);
1828 
1829 	return (err);
1830 }
1831 
1832 void
1833 dmu_object_info_from_dnode(dnode_t *dn, dmu_object_info_t *doi)
1834 {
1835 	dnode_phys_t *dnp;
1836 
1837 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
1838 	mutex_enter(&dn->dn_mtx);
1839 
1840 	dnp = dn->dn_phys;
1841 
1842 	doi->doi_data_block_size = dn->dn_datablksz;
1843 	doi->doi_metadata_block_size = dn->dn_indblkshift ?
1844 	    1ULL << dn->dn_indblkshift : 0;
1845 	doi->doi_type = dn->dn_type;
1846 	doi->doi_bonus_type = dn->dn_bonustype;
1847 	doi->doi_bonus_size = dn->dn_bonuslen;
1848 	doi->doi_indirection = dn->dn_nlevels;
1849 	doi->doi_checksum = dn->dn_checksum;
1850 	doi->doi_compress = dn->dn_compress;
1851 	doi->doi_nblkptr = dn->dn_nblkptr;
1852 	doi->doi_physical_blocks_512 = (DN_USED_BYTES(dnp) + 256) >> 9;
1853 	doi->doi_max_offset = (dn->dn_maxblkid + 1) * dn->dn_datablksz;
1854 	doi->doi_fill_count = 0;
1855 	for (int i = 0; i < dnp->dn_nblkptr; i++)
1856 		doi->doi_fill_count += BP_GET_FILL(&dnp->dn_blkptr[i]);
1857 
1858 	mutex_exit(&dn->dn_mtx);
1859 	rw_exit(&dn->dn_struct_rwlock);
1860 }
1861 
1862 /*
1863  * Get information on a DMU object.
1864  * If doi is NULL, just indicates whether the object exists.
1865  */
1866 int
1867 dmu_object_info(objset_t *os, uint64_t object, dmu_object_info_t *doi)
1868 {
1869 	dnode_t *dn;
1870 	int err = dnode_hold(os, object, FTAG, &dn);
1871 
1872 	if (err)
1873 		return (err);
1874 
1875 	if (doi != NULL)
1876 		dmu_object_info_from_dnode(dn, doi);
1877 
1878 	dnode_rele(dn, FTAG);
1879 	return (0);
1880 }
1881 
1882 /*
1883  * As above, but faster; can be used when you have a held dbuf in hand.
1884  */
1885 void
1886 dmu_object_info_from_db(dmu_buf_t *db_fake, dmu_object_info_t *doi)
1887 {
1888 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
1889 
1890 	DB_DNODE_ENTER(db);
1891 	dmu_object_info_from_dnode(DB_DNODE(db), doi);
1892 	DB_DNODE_EXIT(db);
1893 }
1894 
1895 /*
1896  * Faster still when you only care about the size.
1897  * This is specifically optimized for zfs_getattr().
1898  */
1899 void
1900 dmu_object_size_from_db(dmu_buf_t *db_fake, uint32_t *blksize,
1901     u_longlong_t *nblk512)
1902 {
1903 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
1904 	dnode_t *dn;
1905 
1906 	DB_DNODE_ENTER(db);
1907 	dn = DB_DNODE(db);
1908 
1909 	*blksize = dn->dn_datablksz;
1910 	/* add 1 for dnode space */
1911 	*nblk512 = ((DN_USED_BYTES(dn->dn_phys) + SPA_MINBLOCKSIZE/2) >>
1912 	    SPA_MINBLOCKSHIFT) + 1;
1913 	DB_DNODE_EXIT(db);
1914 }
1915 
1916 void
1917 byteswap_uint64_array(void *vbuf, size_t size)
1918 {
1919 	uint64_t *buf = vbuf;
1920 	size_t count = size >> 3;
1921 	int i;
1922 
1923 	ASSERT((size & 7) == 0);
1924 
1925 	for (i = 0; i < count; i++)
1926 		buf[i] = BSWAP_64(buf[i]);
1927 }
1928 
1929 void
1930 byteswap_uint32_array(void *vbuf, size_t size)
1931 {
1932 	uint32_t *buf = vbuf;
1933 	size_t count = size >> 2;
1934 	int i;
1935 
1936 	ASSERT((size & 3) == 0);
1937 
1938 	for (i = 0; i < count; i++)
1939 		buf[i] = BSWAP_32(buf[i]);
1940 }
1941 
1942 void
1943 byteswap_uint16_array(void *vbuf, size_t size)
1944 {
1945 	uint16_t *buf = vbuf;
1946 	size_t count = size >> 1;
1947 	int i;
1948 
1949 	ASSERT((size & 1) == 0);
1950 
1951 	for (i = 0; i < count; i++)
1952 		buf[i] = BSWAP_16(buf[i]);
1953 }
1954 
1955 /* ARGSUSED */
1956 void
1957 byteswap_uint8_array(void *vbuf, size_t size)
1958 {
1959 }
1960 
1961 void
1962 dmu_init(void)
1963 {
1964 	zfs_dbgmsg_init();
1965 	sa_cache_init();
1966 	xuio_stat_init();
1967 	dmu_objset_init();
1968 	dnode_init();
1969 	dbuf_init();
1970 	zfetch_init();
1971 	l2arc_init();
1972 	arc_init();
1973 }
1974 
1975 void
1976 dmu_fini(void)
1977 {
1978 	arc_fini(); /* arc depends on l2arc, so arc must go first */
1979 	l2arc_fini();
1980 	zfetch_fini();
1981 	dbuf_fini();
1982 	dnode_fini();
1983 	dmu_objset_fini();
1984 	xuio_stat_fini();
1985 	sa_cache_fini();
1986 	zfs_dbgmsg_fini();
1987 }
1988