xref: /freebsd/sys/contrib/openzfs/module/zfs/dmu_tx.c (revision fe815331bb40604ba31312acf7e4619674631777)
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 2011 Nexenta Systems, Inc.  All rights reserved.
24  * Copyright (c) 2012, 2017 by Delphix. All rights reserved.
25  */
26 
27 #include <sys/dmu.h>
28 #include <sys/dmu_impl.h>
29 #include <sys/dbuf.h>
30 #include <sys/dmu_tx.h>
31 #include <sys/dmu_objset.h>
32 #include <sys/dsl_dataset.h>
33 #include <sys/dsl_dir.h>
34 #include <sys/dsl_pool.h>
35 #include <sys/zap_impl.h>
36 #include <sys/spa.h>
37 #include <sys/sa.h>
38 #include <sys/sa_impl.h>
39 #include <sys/zfs_context.h>
40 #include <sys/trace_zfs.h>
41 
42 typedef void (*dmu_tx_hold_func_t)(dmu_tx_t *tx, struct dnode *dn,
43     uint64_t arg1, uint64_t arg2);
44 
45 dmu_tx_stats_t dmu_tx_stats = {
46 	{ "dmu_tx_assigned",		KSTAT_DATA_UINT64 },
47 	{ "dmu_tx_delay",		KSTAT_DATA_UINT64 },
48 	{ "dmu_tx_error",		KSTAT_DATA_UINT64 },
49 	{ "dmu_tx_suspended",		KSTAT_DATA_UINT64 },
50 	{ "dmu_tx_group",		KSTAT_DATA_UINT64 },
51 	{ "dmu_tx_memory_reserve",	KSTAT_DATA_UINT64 },
52 	{ "dmu_tx_memory_reclaim",	KSTAT_DATA_UINT64 },
53 	{ "dmu_tx_dirty_throttle",	KSTAT_DATA_UINT64 },
54 	{ "dmu_tx_dirty_delay",		KSTAT_DATA_UINT64 },
55 	{ "dmu_tx_dirty_over_max",	KSTAT_DATA_UINT64 },
56 	{ "dmu_tx_dirty_frees_delay",	KSTAT_DATA_UINT64 },
57 	{ "dmu_tx_quota",		KSTAT_DATA_UINT64 },
58 };
59 
60 static kstat_t *dmu_tx_ksp;
61 
62 dmu_tx_t *
63 dmu_tx_create_dd(dsl_dir_t *dd)
64 {
65 	dmu_tx_t *tx = kmem_zalloc(sizeof (dmu_tx_t), KM_SLEEP);
66 	tx->tx_dir = dd;
67 	if (dd != NULL)
68 		tx->tx_pool = dd->dd_pool;
69 	list_create(&tx->tx_holds, sizeof (dmu_tx_hold_t),
70 	    offsetof(dmu_tx_hold_t, txh_node));
71 	list_create(&tx->tx_callbacks, sizeof (dmu_tx_callback_t),
72 	    offsetof(dmu_tx_callback_t, dcb_node));
73 	tx->tx_start = gethrtime();
74 	return (tx);
75 }
76 
77 dmu_tx_t *
78 dmu_tx_create(objset_t *os)
79 {
80 	dmu_tx_t *tx = dmu_tx_create_dd(os->os_dsl_dataset->ds_dir);
81 	tx->tx_objset = os;
82 	return (tx);
83 }
84 
85 dmu_tx_t *
86 dmu_tx_create_assigned(struct dsl_pool *dp, uint64_t txg)
87 {
88 	dmu_tx_t *tx = dmu_tx_create_dd(NULL);
89 
90 	TXG_VERIFY(dp->dp_spa, txg);
91 	tx->tx_pool = dp;
92 	tx->tx_txg = txg;
93 	tx->tx_anyobj = TRUE;
94 
95 	return (tx);
96 }
97 
98 int
99 dmu_tx_is_syncing(dmu_tx_t *tx)
100 {
101 	return (tx->tx_anyobj);
102 }
103 
104 int
105 dmu_tx_private_ok(dmu_tx_t *tx)
106 {
107 	return (tx->tx_anyobj);
108 }
109 
110 static dmu_tx_hold_t *
111 dmu_tx_hold_dnode_impl(dmu_tx_t *tx, dnode_t *dn, enum dmu_tx_hold_type type,
112     uint64_t arg1, uint64_t arg2)
113 {
114 	dmu_tx_hold_t *txh;
115 
116 	if (dn != NULL) {
117 		(void) zfs_refcount_add(&dn->dn_holds, tx);
118 		if (tx->tx_txg != 0) {
119 			mutex_enter(&dn->dn_mtx);
120 			/*
121 			 * dn->dn_assigned_txg == tx->tx_txg doesn't pose a
122 			 * problem, but there's no way for it to happen (for
123 			 * now, at least).
124 			 */
125 			ASSERT(dn->dn_assigned_txg == 0);
126 			dn->dn_assigned_txg = tx->tx_txg;
127 			(void) zfs_refcount_add(&dn->dn_tx_holds, tx);
128 			mutex_exit(&dn->dn_mtx);
129 		}
130 	}
131 
132 	txh = kmem_zalloc(sizeof (dmu_tx_hold_t), KM_SLEEP);
133 	txh->txh_tx = tx;
134 	txh->txh_dnode = dn;
135 	zfs_refcount_create(&txh->txh_space_towrite);
136 	zfs_refcount_create(&txh->txh_memory_tohold);
137 	txh->txh_type = type;
138 	txh->txh_arg1 = arg1;
139 	txh->txh_arg2 = arg2;
140 	list_insert_tail(&tx->tx_holds, txh);
141 
142 	return (txh);
143 }
144 
145 static dmu_tx_hold_t *
146 dmu_tx_hold_object_impl(dmu_tx_t *tx, objset_t *os, uint64_t object,
147     enum dmu_tx_hold_type type, uint64_t arg1, uint64_t arg2)
148 {
149 	dnode_t *dn = NULL;
150 	dmu_tx_hold_t *txh;
151 	int err;
152 
153 	if (object != DMU_NEW_OBJECT) {
154 		err = dnode_hold(os, object, FTAG, &dn);
155 		if (err != 0) {
156 			tx->tx_err = err;
157 			return (NULL);
158 		}
159 	}
160 	txh = dmu_tx_hold_dnode_impl(tx, dn, type, arg1, arg2);
161 	if (dn != NULL)
162 		dnode_rele(dn, FTAG);
163 	return (txh);
164 }
165 
166 void
167 dmu_tx_add_new_object(dmu_tx_t *tx, dnode_t *dn)
168 {
169 	/*
170 	 * If we're syncing, they can manipulate any object anyhow, and
171 	 * the hold on the dnode_t can cause problems.
172 	 */
173 	if (!dmu_tx_is_syncing(tx))
174 		(void) dmu_tx_hold_dnode_impl(tx, dn, THT_NEWOBJECT, 0, 0);
175 }
176 
177 /*
178  * This function reads specified data from disk.  The specified data will
179  * be needed to perform the transaction -- i.e, it will be read after
180  * we do dmu_tx_assign().  There are two reasons that we read the data now
181  * (before dmu_tx_assign()):
182  *
183  * 1. Reading it now has potentially better performance.  The transaction
184  * has not yet been assigned, so the TXG is not held open, and also the
185  * caller typically has less locks held when calling dmu_tx_hold_*() than
186  * after the transaction has been assigned.  This reduces the lock (and txg)
187  * hold times, thus reducing lock contention.
188  *
189  * 2. It is easier for callers (primarily the ZPL) to handle i/o errors
190  * that are detected before they start making changes to the DMU state
191  * (i.e. now).  Once the transaction has been assigned, and some DMU
192  * state has been changed, it can be difficult to recover from an i/o
193  * error (e.g. to undo the changes already made in memory at the DMU
194  * layer).  Typically code to do so does not exist in the caller -- it
195  * assumes that the data has already been cached and thus i/o errors are
196  * not possible.
197  *
198  * It has been observed that the i/o initiated here can be a performance
199  * problem, and it appears to be optional, because we don't look at the
200  * data which is read.  However, removing this read would only serve to
201  * move the work elsewhere (after the dmu_tx_assign()), where it may
202  * have a greater impact on performance (in addition to the impact on
203  * fault tolerance noted above).
204  */
205 static int
206 dmu_tx_check_ioerr(zio_t *zio, dnode_t *dn, int level, uint64_t blkid)
207 {
208 	int err;
209 	dmu_buf_impl_t *db;
210 
211 	rw_enter(&dn->dn_struct_rwlock, RW_READER);
212 	db = dbuf_hold_level(dn, level, blkid, FTAG);
213 	rw_exit(&dn->dn_struct_rwlock);
214 	if (db == NULL)
215 		return (SET_ERROR(EIO));
216 	err = dbuf_read(db, zio, DB_RF_CANFAIL | DB_RF_NOPREFETCH);
217 	dbuf_rele(db, FTAG);
218 	return (err);
219 }
220 
221 /* ARGSUSED */
222 static void
223 dmu_tx_count_write(dmu_tx_hold_t *txh, uint64_t off, uint64_t len)
224 {
225 	dnode_t *dn = txh->txh_dnode;
226 	int err = 0;
227 
228 	if (len == 0)
229 		return;
230 
231 	(void) zfs_refcount_add_many(&txh->txh_space_towrite, len, FTAG);
232 
233 	if (zfs_refcount_count(&txh->txh_space_towrite) > 2 * DMU_MAX_ACCESS)
234 		err = SET_ERROR(EFBIG);
235 
236 	if (dn == NULL)
237 		return;
238 
239 	/*
240 	 * For i/o error checking, read the blocks that will be needed
241 	 * to perform the write: the first and last level-0 blocks (if
242 	 * they are not aligned, i.e. if they are partial-block writes),
243 	 * and all the level-1 blocks.
244 	 */
245 	if (dn->dn_maxblkid == 0) {
246 		if (off < dn->dn_datablksz &&
247 		    (off > 0 || len < dn->dn_datablksz)) {
248 			err = dmu_tx_check_ioerr(NULL, dn, 0, 0);
249 			if (err != 0) {
250 				txh->txh_tx->tx_err = err;
251 			}
252 		}
253 	} else {
254 		zio_t *zio = zio_root(dn->dn_objset->os_spa,
255 		    NULL, NULL, ZIO_FLAG_CANFAIL);
256 
257 		/* first level-0 block */
258 		uint64_t start = off >> dn->dn_datablkshift;
259 		if (P2PHASE(off, dn->dn_datablksz) || len < dn->dn_datablksz) {
260 			err = dmu_tx_check_ioerr(zio, dn, 0, start);
261 			if (err != 0) {
262 				txh->txh_tx->tx_err = err;
263 			}
264 		}
265 
266 		/* last level-0 block */
267 		uint64_t end = (off + len - 1) >> dn->dn_datablkshift;
268 		if (end != start && end <= dn->dn_maxblkid &&
269 		    P2PHASE(off + len, dn->dn_datablksz)) {
270 			err = dmu_tx_check_ioerr(zio, dn, 0, end);
271 			if (err != 0) {
272 				txh->txh_tx->tx_err = err;
273 			}
274 		}
275 
276 		/* level-1 blocks */
277 		if (dn->dn_nlevels > 1) {
278 			int shft = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
279 			for (uint64_t i = (start >> shft) + 1;
280 			    i < end >> shft; i++) {
281 				err = dmu_tx_check_ioerr(zio, dn, 1, i);
282 				if (err != 0) {
283 					txh->txh_tx->tx_err = err;
284 				}
285 			}
286 		}
287 
288 		err = zio_wait(zio);
289 		if (err != 0) {
290 			txh->txh_tx->tx_err = err;
291 		}
292 	}
293 }
294 
295 static void
296 dmu_tx_count_dnode(dmu_tx_hold_t *txh)
297 {
298 	(void) zfs_refcount_add_many(&txh->txh_space_towrite,
299 	    DNODE_MIN_SIZE, FTAG);
300 }
301 
302 void
303 dmu_tx_hold_write(dmu_tx_t *tx, uint64_t object, uint64_t off, int len)
304 {
305 	dmu_tx_hold_t *txh;
306 
307 	ASSERT0(tx->tx_txg);
308 	ASSERT3U(len, <=, DMU_MAX_ACCESS);
309 	ASSERT(len == 0 || UINT64_MAX - off >= len - 1);
310 
311 	txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
312 	    object, THT_WRITE, off, len);
313 	if (txh != NULL) {
314 		dmu_tx_count_write(txh, off, len);
315 		dmu_tx_count_dnode(txh);
316 	}
317 }
318 
319 void
320 dmu_tx_hold_write_by_dnode(dmu_tx_t *tx, dnode_t *dn, uint64_t off, int len)
321 {
322 	dmu_tx_hold_t *txh;
323 
324 	ASSERT0(tx->tx_txg);
325 	ASSERT3U(len, <=, DMU_MAX_ACCESS);
326 	ASSERT(len == 0 || UINT64_MAX - off >= len - 1);
327 
328 	txh = dmu_tx_hold_dnode_impl(tx, dn, THT_WRITE, off, len);
329 	if (txh != NULL) {
330 		dmu_tx_count_write(txh, off, len);
331 		dmu_tx_count_dnode(txh);
332 	}
333 }
334 
335 /*
336  * This function marks the transaction as being a "net free".  The end
337  * result is that refquotas will be disabled for this transaction, and
338  * this transaction will be able to use half of the pool space overhead
339  * (see dsl_pool_adjustedsize()).  Therefore this function should only
340  * be called for transactions that we expect will not cause a net increase
341  * in the amount of space used (but it's OK if that is occasionally not true).
342  */
343 void
344 dmu_tx_mark_netfree(dmu_tx_t *tx)
345 {
346 	tx->tx_netfree = B_TRUE;
347 }
348 
349 static void
350 dmu_tx_hold_free_impl(dmu_tx_hold_t *txh, uint64_t off, uint64_t len)
351 {
352 	dmu_tx_t *tx = txh->txh_tx;
353 	dnode_t *dn = txh->txh_dnode;
354 	int err;
355 
356 	ASSERT(tx->tx_txg == 0);
357 
358 	dmu_tx_count_dnode(txh);
359 
360 	if (off >= (dn->dn_maxblkid + 1) * dn->dn_datablksz)
361 		return;
362 	if (len == DMU_OBJECT_END)
363 		len = (dn->dn_maxblkid + 1) * dn->dn_datablksz - off;
364 
365 	dmu_tx_count_dnode(txh);
366 
367 	/*
368 	 * For i/o error checking, we read the first and last level-0
369 	 * blocks if they are not aligned, and all the level-1 blocks.
370 	 *
371 	 * Note:  dbuf_free_range() assumes that we have not instantiated
372 	 * any level-0 dbufs that will be completely freed.  Therefore we must
373 	 * exercise care to not read or count the first and last blocks
374 	 * if they are blocksize-aligned.
375 	 */
376 	if (dn->dn_datablkshift == 0) {
377 		if (off != 0 || len < dn->dn_datablksz)
378 			dmu_tx_count_write(txh, 0, dn->dn_datablksz);
379 	} else {
380 		/* first block will be modified if it is not aligned */
381 		if (!IS_P2ALIGNED(off, 1 << dn->dn_datablkshift))
382 			dmu_tx_count_write(txh, off, 1);
383 		/* last block will be modified if it is not aligned */
384 		if (!IS_P2ALIGNED(off + len, 1 << dn->dn_datablkshift))
385 			dmu_tx_count_write(txh, off + len, 1);
386 	}
387 
388 	/*
389 	 * Check level-1 blocks.
390 	 */
391 	if (dn->dn_nlevels > 1) {
392 		int shift = dn->dn_datablkshift + dn->dn_indblkshift -
393 		    SPA_BLKPTRSHIFT;
394 		uint64_t start = off >> shift;
395 		uint64_t end = (off + len) >> shift;
396 
397 		ASSERT(dn->dn_indblkshift != 0);
398 
399 		/*
400 		 * dnode_reallocate() can result in an object with indirect
401 		 * blocks having an odd data block size.  In this case,
402 		 * just check the single block.
403 		 */
404 		if (dn->dn_datablkshift == 0)
405 			start = end = 0;
406 
407 		zio_t *zio = zio_root(tx->tx_pool->dp_spa,
408 		    NULL, NULL, ZIO_FLAG_CANFAIL);
409 		for (uint64_t i = start; i <= end; i++) {
410 			uint64_t ibyte = i << shift;
411 			err = dnode_next_offset(dn, 0, &ibyte, 2, 1, 0);
412 			i = ibyte >> shift;
413 			if (err == ESRCH || i > end)
414 				break;
415 			if (err != 0) {
416 				tx->tx_err = err;
417 				(void) zio_wait(zio);
418 				return;
419 			}
420 
421 			(void) zfs_refcount_add_many(&txh->txh_memory_tohold,
422 			    1 << dn->dn_indblkshift, FTAG);
423 
424 			err = dmu_tx_check_ioerr(zio, dn, 1, i);
425 			if (err != 0) {
426 				tx->tx_err = err;
427 				(void) zio_wait(zio);
428 				return;
429 			}
430 		}
431 		err = zio_wait(zio);
432 		if (err != 0) {
433 			tx->tx_err = err;
434 			return;
435 		}
436 	}
437 }
438 
439 void
440 dmu_tx_hold_free(dmu_tx_t *tx, uint64_t object, uint64_t off, uint64_t len)
441 {
442 	dmu_tx_hold_t *txh;
443 
444 	txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
445 	    object, THT_FREE, off, len);
446 	if (txh != NULL)
447 		(void) dmu_tx_hold_free_impl(txh, off, len);
448 }
449 
450 void
451 dmu_tx_hold_free_by_dnode(dmu_tx_t *tx, dnode_t *dn, uint64_t off, uint64_t len)
452 {
453 	dmu_tx_hold_t *txh;
454 
455 	txh = dmu_tx_hold_dnode_impl(tx, dn, THT_FREE, off, len);
456 	if (txh != NULL)
457 		(void) dmu_tx_hold_free_impl(txh, off, len);
458 }
459 
460 static void
461 dmu_tx_hold_zap_impl(dmu_tx_hold_t *txh, const char *name)
462 {
463 	dmu_tx_t *tx = txh->txh_tx;
464 	dnode_t *dn = txh->txh_dnode;
465 	int err;
466 
467 	ASSERT(tx->tx_txg == 0);
468 
469 	dmu_tx_count_dnode(txh);
470 
471 	/*
472 	 * Modifying a almost-full microzap is around the worst case (128KB)
473 	 *
474 	 * If it is a fat zap, the worst case would be 7*16KB=112KB:
475 	 * - 3 blocks overwritten: target leaf, ptrtbl block, header block
476 	 * - 4 new blocks written if adding:
477 	 *    - 2 blocks for possibly split leaves,
478 	 *    - 2 grown ptrtbl blocks
479 	 */
480 	(void) zfs_refcount_add_many(&txh->txh_space_towrite,
481 	    MZAP_MAX_BLKSZ, FTAG);
482 
483 	if (dn == NULL)
484 		return;
485 
486 	ASSERT3U(DMU_OT_BYTESWAP(dn->dn_type), ==, DMU_BSWAP_ZAP);
487 
488 	if (dn->dn_maxblkid == 0 || name == NULL) {
489 		/*
490 		 * This is a microzap (only one block), or we don't know
491 		 * the name.  Check the first block for i/o errors.
492 		 */
493 		err = dmu_tx_check_ioerr(NULL, dn, 0, 0);
494 		if (err != 0) {
495 			tx->tx_err = err;
496 		}
497 	} else {
498 		/*
499 		 * Access the name so that we'll check for i/o errors to
500 		 * the leaf blocks, etc.  We ignore ENOENT, as this name
501 		 * may not yet exist.
502 		 */
503 		err = zap_lookup_by_dnode(dn, name, 8, 0, NULL);
504 		if (err == EIO || err == ECKSUM || err == ENXIO) {
505 			tx->tx_err = err;
506 		}
507 	}
508 }
509 
510 void
511 dmu_tx_hold_zap(dmu_tx_t *tx, uint64_t object, int add, const char *name)
512 {
513 	dmu_tx_hold_t *txh;
514 
515 	ASSERT0(tx->tx_txg);
516 
517 	txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
518 	    object, THT_ZAP, add, (uintptr_t)name);
519 	if (txh != NULL)
520 		dmu_tx_hold_zap_impl(txh, name);
521 }
522 
523 void
524 dmu_tx_hold_zap_by_dnode(dmu_tx_t *tx, dnode_t *dn, int add, const char *name)
525 {
526 	dmu_tx_hold_t *txh;
527 
528 	ASSERT0(tx->tx_txg);
529 	ASSERT(dn != NULL);
530 
531 	txh = dmu_tx_hold_dnode_impl(tx, dn, THT_ZAP, add, (uintptr_t)name);
532 	if (txh != NULL)
533 		dmu_tx_hold_zap_impl(txh, name);
534 }
535 
536 void
537 dmu_tx_hold_bonus(dmu_tx_t *tx, uint64_t object)
538 {
539 	dmu_tx_hold_t *txh;
540 
541 	ASSERT(tx->tx_txg == 0);
542 
543 	txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
544 	    object, THT_BONUS, 0, 0);
545 	if (txh)
546 		dmu_tx_count_dnode(txh);
547 }
548 
549 void
550 dmu_tx_hold_bonus_by_dnode(dmu_tx_t *tx, dnode_t *dn)
551 {
552 	dmu_tx_hold_t *txh;
553 
554 	ASSERT0(tx->tx_txg);
555 
556 	txh = dmu_tx_hold_dnode_impl(tx, dn, THT_BONUS, 0, 0);
557 	if (txh)
558 		dmu_tx_count_dnode(txh);
559 }
560 
561 void
562 dmu_tx_hold_space(dmu_tx_t *tx, uint64_t space)
563 {
564 	dmu_tx_hold_t *txh;
565 
566 	ASSERT(tx->tx_txg == 0);
567 
568 	txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
569 	    DMU_NEW_OBJECT, THT_SPACE, space, 0);
570 	if (txh) {
571 		(void) zfs_refcount_add_many(
572 		    &txh->txh_space_towrite, space, FTAG);
573 	}
574 }
575 
576 #ifdef ZFS_DEBUG
577 void
578 dmu_tx_dirty_buf(dmu_tx_t *tx, dmu_buf_impl_t *db)
579 {
580 	boolean_t match_object = B_FALSE;
581 	boolean_t match_offset = B_FALSE;
582 
583 	DB_DNODE_ENTER(db);
584 	dnode_t *dn = DB_DNODE(db);
585 	ASSERT(tx->tx_txg != 0);
586 	ASSERT(tx->tx_objset == NULL || dn->dn_objset == tx->tx_objset);
587 	ASSERT3U(dn->dn_object, ==, db->db.db_object);
588 
589 	if (tx->tx_anyobj) {
590 		DB_DNODE_EXIT(db);
591 		return;
592 	}
593 
594 	/* XXX No checking on the meta dnode for now */
595 	if (db->db.db_object == DMU_META_DNODE_OBJECT) {
596 		DB_DNODE_EXIT(db);
597 		return;
598 	}
599 
600 	for (dmu_tx_hold_t *txh = list_head(&tx->tx_holds); txh != NULL;
601 	    txh = list_next(&tx->tx_holds, txh)) {
602 		ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
603 		if (txh->txh_dnode == dn && txh->txh_type != THT_NEWOBJECT)
604 			match_object = TRUE;
605 		if (txh->txh_dnode == NULL || txh->txh_dnode == dn) {
606 			int datablkshift = dn->dn_datablkshift ?
607 			    dn->dn_datablkshift : SPA_MAXBLOCKSHIFT;
608 			int epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
609 			int shift = datablkshift + epbs * db->db_level;
610 			uint64_t beginblk = shift >= 64 ? 0 :
611 			    (txh->txh_arg1 >> shift);
612 			uint64_t endblk = shift >= 64 ? 0 :
613 			    ((txh->txh_arg1 + txh->txh_arg2 - 1) >> shift);
614 			uint64_t blkid = db->db_blkid;
615 
616 			/* XXX txh_arg2 better not be zero... */
617 
618 			dprintf("found txh type %x beginblk=%llx endblk=%llx\n",
619 			    txh->txh_type, beginblk, endblk);
620 
621 			switch (txh->txh_type) {
622 			case THT_WRITE:
623 				if (blkid >= beginblk && blkid <= endblk)
624 					match_offset = TRUE;
625 				/*
626 				 * We will let this hold work for the bonus
627 				 * or spill buffer so that we don't need to
628 				 * hold it when creating a new object.
629 				 */
630 				if (blkid == DMU_BONUS_BLKID ||
631 				    blkid == DMU_SPILL_BLKID)
632 					match_offset = TRUE;
633 				/*
634 				 * They might have to increase nlevels,
635 				 * thus dirtying the new TLIBs.  Or the
636 				 * might have to change the block size,
637 				 * thus dirying the new lvl=0 blk=0.
638 				 */
639 				if (blkid == 0)
640 					match_offset = TRUE;
641 				break;
642 			case THT_FREE:
643 				/*
644 				 * We will dirty all the level 1 blocks in
645 				 * the free range and perhaps the first and
646 				 * last level 0 block.
647 				 */
648 				if (blkid >= beginblk && (blkid <= endblk ||
649 				    txh->txh_arg2 == DMU_OBJECT_END))
650 					match_offset = TRUE;
651 				break;
652 			case THT_SPILL:
653 				if (blkid == DMU_SPILL_BLKID)
654 					match_offset = TRUE;
655 				break;
656 			case THT_BONUS:
657 				if (blkid == DMU_BONUS_BLKID)
658 					match_offset = TRUE;
659 				break;
660 			case THT_ZAP:
661 				match_offset = TRUE;
662 				break;
663 			case THT_NEWOBJECT:
664 				match_object = TRUE;
665 				break;
666 			default:
667 				cmn_err(CE_PANIC, "bad txh_type %d",
668 				    txh->txh_type);
669 			}
670 		}
671 		if (match_object && match_offset) {
672 			DB_DNODE_EXIT(db);
673 			return;
674 		}
675 	}
676 	DB_DNODE_EXIT(db);
677 	panic("dirtying dbuf obj=%llx lvl=%u blkid=%llx but not tx_held\n",
678 	    (u_longlong_t)db->db.db_object, db->db_level,
679 	    (u_longlong_t)db->db_blkid);
680 }
681 #endif
682 
683 /*
684  * If we can't do 10 iops, something is wrong.  Let us go ahead
685  * and hit zfs_dirty_data_max.
686  */
687 hrtime_t zfs_delay_max_ns = 100 * MICROSEC; /* 100 milliseconds */
688 int zfs_delay_resolution_ns = 100 * 1000; /* 100 microseconds */
689 
690 /*
691  * We delay transactions when we've determined that the backend storage
692  * isn't able to accommodate the rate of incoming writes.
693  *
694  * If there is already a transaction waiting, we delay relative to when
695  * that transaction finishes waiting.  This way the calculated min_time
696  * is independent of the number of threads concurrently executing
697  * transactions.
698  *
699  * If we are the only waiter, wait relative to when the transaction
700  * started, rather than the current time.  This credits the transaction for
701  * "time already served", e.g. reading indirect blocks.
702  *
703  * The minimum time for a transaction to take is calculated as:
704  *     min_time = scale * (dirty - min) / (max - dirty)
705  *     min_time is then capped at zfs_delay_max_ns.
706  *
707  * The delay has two degrees of freedom that can be adjusted via tunables.
708  * The percentage of dirty data at which we start to delay is defined by
709  * zfs_delay_min_dirty_percent. This should typically be at or above
710  * zfs_vdev_async_write_active_max_dirty_percent so that we only start to
711  * delay after writing at full speed has failed to keep up with the incoming
712  * write rate. The scale of the curve is defined by zfs_delay_scale. Roughly
713  * speaking, this variable determines the amount of delay at the midpoint of
714  * the curve.
715  *
716  * delay
717  *  10ms +-------------------------------------------------------------*+
718  *       |                                                             *|
719  *   9ms +                                                             *+
720  *       |                                                             *|
721  *   8ms +                                                             *+
722  *       |                                                            * |
723  *   7ms +                                                            * +
724  *       |                                                            * |
725  *   6ms +                                                            * +
726  *       |                                                            * |
727  *   5ms +                                                           *  +
728  *       |                                                           *  |
729  *   4ms +                                                           *  +
730  *       |                                                           *  |
731  *   3ms +                                                          *   +
732  *       |                                                          *   |
733  *   2ms +                                              (midpoint) *    +
734  *       |                                                  |    **     |
735  *   1ms +                                                  v ***       +
736  *       |             zfs_delay_scale ---------->     ********         |
737  *     0 +-------------------------------------*********----------------+
738  *       0%                    <- zfs_dirty_data_max ->               100%
739  *
740  * Note that since the delay is added to the outstanding time remaining on the
741  * most recent transaction, the delay is effectively the inverse of IOPS.
742  * Here the midpoint of 500us translates to 2000 IOPS. The shape of the curve
743  * was chosen such that small changes in the amount of accumulated dirty data
744  * in the first 3/4 of the curve yield relatively small differences in the
745  * amount of delay.
746  *
747  * The effects can be easier to understand when the amount of delay is
748  * represented on a log scale:
749  *
750  * delay
751  * 100ms +-------------------------------------------------------------++
752  *       +                                                              +
753  *       |                                                              |
754  *       +                                                             *+
755  *  10ms +                                                             *+
756  *       +                                                           ** +
757  *       |                                              (midpoint)  **  |
758  *       +                                                  |     **    +
759  *   1ms +                                                  v ****      +
760  *       +             zfs_delay_scale ---------->        *****         +
761  *       |                                             ****             |
762  *       +                                          ****                +
763  * 100us +                                        **                    +
764  *       +                                       *                      +
765  *       |                                      *                       |
766  *       +                                     *                        +
767  *  10us +                                     *                        +
768  *       +                                                              +
769  *       |                                                              |
770  *       +                                                              +
771  *       +--------------------------------------------------------------+
772  *       0%                    <- zfs_dirty_data_max ->               100%
773  *
774  * Note here that only as the amount of dirty data approaches its limit does
775  * the delay start to increase rapidly. The goal of a properly tuned system
776  * should be to keep the amount of dirty data out of that range by first
777  * ensuring that the appropriate limits are set for the I/O scheduler to reach
778  * optimal throughput on the backend storage, and then by changing the value
779  * of zfs_delay_scale to increase the steepness of the curve.
780  */
781 static void
782 dmu_tx_delay(dmu_tx_t *tx, uint64_t dirty)
783 {
784 	dsl_pool_t *dp = tx->tx_pool;
785 	uint64_t delay_min_bytes =
786 	    zfs_dirty_data_max * zfs_delay_min_dirty_percent / 100;
787 	hrtime_t wakeup, min_tx_time, now;
788 
789 	if (dirty <= delay_min_bytes)
790 		return;
791 
792 	/*
793 	 * The caller has already waited until we are under the max.
794 	 * We make them pass us the amount of dirty data so we don't
795 	 * have to handle the case of it being >= the max, which could
796 	 * cause a divide-by-zero if it's == the max.
797 	 */
798 	ASSERT3U(dirty, <, zfs_dirty_data_max);
799 
800 	now = gethrtime();
801 	min_tx_time = zfs_delay_scale *
802 	    (dirty - delay_min_bytes) / (zfs_dirty_data_max - dirty);
803 	min_tx_time = MIN(min_tx_time, zfs_delay_max_ns);
804 	if (now > tx->tx_start + min_tx_time)
805 		return;
806 
807 	DTRACE_PROBE3(delay__mintime, dmu_tx_t *, tx, uint64_t, dirty,
808 	    uint64_t, min_tx_time);
809 
810 	mutex_enter(&dp->dp_lock);
811 	wakeup = MAX(tx->tx_start + min_tx_time,
812 	    dp->dp_last_wakeup + min_tx_time);
813 	dp->dp_last_wakeup = wakeup;
814 	mutex_exit(&dp->dp_lock);
815 
816 	zfs_sleep_until(wakeup);
817 }
818 
819 /*
820  * This routine attempts to assign the transaction to a transaction group.
821  * To do so, we must determine if there is sufficient free space on disk.
822  *
823  * If this is a "netfree" transaction (i.e. we called dmu_tx_mark_netfree()
824  * on it), then it is assumed that there is sufficient free space,
825  * unless there's insufficient slop space in the pool (see the comment
826  * above spa_slop_shift in spa_misc.c).
827  *
828  * If it is not a "netfree" transaction, then if the data already on disk
829  * is over the allowed usage (e.g. quota), this will fail with EDQUOT or
830  * ENOSPC.  Otherwise, if the current rough estimate of pending changes,
831  * plus the rough estimate of this transaction's changes, may exceed the
832  * allowed usage, then this will fail with ERESTART, which will cause the
833  * caller to wait for the pending changes to be written to disk (by waiting
834  * for the next TXG to open), and then check the space usage again.
835  *
836  * The rough estimate of pending changes is comprised of the sum of:
837  *
838  *  - this transaction's holds' txh_space_towrite
839  *
840  *  - dd_tempreserved[], which is the sum of in-flight transactions'
841  *    holds' txh_space_towrite (i.e. those transactions that have called
842  *    dmu_tx_assign() but not yet called dmu_tx_commit()).
843  *
844  *  - dd_space_towrite[], which is the amount of dirtied dbufs.
845  *
846  * Note that all of these values are inflated by spa_get_worst_case_asize(),
847  * which means that we may get ERESTART well before we are actually in danger
848  * of running out of space, but this also mitigates any small inaccuracies
849  * in the rough estimate (e.g. txh_space_towrite doesn't take into account
850  * indirect blocks, and dd_space_towrite[] doesn't take into account changes
851  * to the MOS).
852  *
853  * Note that due to this algorithm, it is possible to exceed the allowed
854  * usage by one transaction.  Also, as we approach the allowed usage,
855  * we will allow a very limited amount of changes into each TXG, thus
856  * decreasing performance.
857  */
858 static int
859 dmu_tx_try_assign(dmu_tx_t *tx, uint64_t txg_how)
860 {
861 	spa_t *spa = tx->tx_pool->dp_spa;
862 
863 	ASSERT0(tx->tx_txg);
864 
865 	if (tx->tx_err) {
866 		DMU_TX_STAT_BUMP(dmu_tx_error);
867 		return (tx->tx_err);
868 	}
869 
870 	if (spa_suspended(spa)) {
871 		DMU_TX_STAT_BUMP(dmu_tx_suspended);
872 
873 		/*
874 		 * If the user has indicated a blocking failure mode
875 		 * then return ERESTART which will block in dmu_tx_wait().
876 		 * Otherwise, return EIO so that an error can get
877 		 * propagated back to the VOP calls.
878 		 *
879 		 * Note that we always honor the txg_how flag regardless
880 		 * of the failuremode setting.
881 		 */
882 		if (spa_get_failmode(spa) == ZIO_FAILURE_MODE_CONTINUE &&
883 		    !(txg_how & TXG_WAIT))
884 			return (SET_ERROR(EIO));
885 
886 		return (SET_ERROR(ERESTART));
887 	}
888 
889 	if (!tx->tx_dirty_delayed &&
890 	    dsl_pool_need_dirty_delay(tx->tx_pool)) {
891 		tx->tx_wait_dirty = B_TRUE;
892 		DMU_TX_STAT_BUMP(dmu_tx_dirty_delay);
893 		return (SET_ERROR(ERESTART));
894 	}
895 
896 	tx->tx_txg = txg_hold_open(tx->tx_pool, &tx->tx_txgh);
897 	tx->tx_needassign_txh = NULL;
898 
899 	/*
900 	 * NB: No error returns are allowed after txg_hold_open, but
901 	 * before processing the dnode holds, due to the
902 	 * dmu_tx_unassign() logic.
903 	 */
904 
905 	uint64_t towrite = 0;
906 	uint64_t tohold = 0;
907 	for (dmu_tx_hold_t *txh = list_head(&tx->tx_holds); txh != NULL;
908 	    txh = list_next(&tx->tx_holds, txh)) {
909 		dnode_t *dn = txh->txh_dnode;
910 		if (dn != NULL) {
911 			/*
912 			 * This thread can't hold the dn_struct_rwlock
913 			 * while assigning the tx, because this can lead to
914 			 * deadlock. Specifically, if this dnode is already
915 			 * assigned to an earlier txg, this thread may need
916 			 * to wait for that txg to sync (the ERESTART case
917 			 * below).  The other thread that has assigned this
918 			 * dnode to an earlier txg prevents this txg from
919 			 * syncing until its tx can complete (calling
920 			 * dmu_tx_commit()), but it may need to acquire the
921 			 * dn_struct_rwlock to do so (e.g. via
922 			 * dmu_buf_hold*()).
923 			 *
924 			 * Note that this thread can't hold the lock for
925 			 * read either, but the rwlock doesn't record
926 			 * enough information to make that assertion.
927 			 */
928 			ASSERT(!RW_WRITE_HELD(&dn->dn_struct_rwlock));
929 
930 			mutex_enter(&dn->dn_mtx);
931 			if (dn->dn_assigned_txg == tx->tx_txg - 1) {
932 				mutex_exit(&dn->dn_mtx);
933 				tx->tx_needassign_txh = txh;
934 				DMU_TX_STAT_BUMP(dmu_tx_group);
935 				return (SET_ERROR(ERESTART));
936 			}
937 			if (dn->dn_assigned_txg == 0)
938 				dn->dn_assigned_txg = tx->tx_txg;
939 			ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
940 			(void) zfs_refcount_add(&dn->dn_tx_holds, tx);
941 			mutex_exit(&dn->dn_mtx);
942 		}
943 		towrite += zfs_refcount_count(&txh->txh_space_towrite);
944 		tohold += zfs_refcount_count(&txh->txh_memory_tohold);
945 	}
946 
947 	/* needed allocation: worst-case estimate of write space */
948 	uint64_t asize = spa_get_worst_case_asize(tx->tx_pool->dp_spa, towrite);
949 	/* calculate memory footprint estimate */
950 	uint64_t memory = towrite + tohold;
951 
952 	if (tx->tx_dir != NULL && asize != 0) {
953 		int err = dsl_dir_tempreserve_space(tx->tx_dir, memory,
954 		    asize, tx->tx_netfree, &tx->tx_tempreserve_cookie, tx);
955 		if (err != 0)
956 			return (err);
957 	}
958 
959 	DMU_TX_STAT_BUMP(dmu_tx_assigned);
960 
961 	return (0);
962 }
963 
964 static void
965 dmu_tx_unassign(dmu_tx_t *tx)
966 {
967 	if (tx->tx_txg == 0)
968 		return;
969 
970 	txg_rele_to_quiesce(&tx->tx_txgh);
971 
972 	/*
973 	 * Walk the transaction's hold list, removing the hold on the
974 	 * associated dnode, and notifying waiters if the refcount drops to 0.
975 	 */
976 	for (dmu_tx_hold_t *txh = list_head(&tx->tx_holds);
977 	    txh && txh != tx->tx_needassign_txh;
978 	    txh = list_next(&tx->tx_holds, txh)) {
979 		dnode_t *dn = txh->txh_dnode;
980 
981 		if (dn == NULL)
982 			continue;
983 		mutex_enter(&dn->dn_mtx);
984 		ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
985 
986 		if (zfs_refcount_remove(&dn->dn_tx_holds, tx) == 0) {
987 			dn->dn_assigned_txg = 0;
988 			cv_broadcast(&dn->dn_notxholds);
989 		}
990 		mutex_exit(&dn->dn_mtx);
991 	}
992 
993 	txg_rele_to_sync(&tx->tx_txgh);
994 
995 	tx->tx_lasttried_txg = tx->tx_txg;
996 	tx->tx_txg = 0;
997 }
998 
999 /*
1000  * Assign tx to a transaction group; txg_how is a bitmask:
1001  *
1002  * If TXG_WAIT is set and the currently open txg is full, this function
1003  * will wait until there's a new txg. This should be used when no locks
1004  * are being held. With this bit set, this function will only fail if
1005  * we're truly out of space (or over quota).
1006  *
1007  * If TXG_WAIT is *not* set and we can't assign into the currently open
1008  * txg without blocking, this function will return immediately with
1009  * ERESTART. This should be used whenever locks are being held.  On an
1010  * ERESTART error, the caller should drop all locks, call dmu_tx_wait(),
1011  * and try again.
1012  *
1013  * If TXG_NOTHROTTLE is set, this indicates that this tx should not be
1014  * delayed due on the ZFS Write Throttle (see comments in dsl_pool.c for
1015  * details on the throttle). This is used by the VFS operations, after
1016  * they have already called dmu_tx_wait() (though most likely on a
1017  * different tx).
1018  */
1019 int
1020 dmu_tx_assign(dmu_tx_t *tx, uint64_t txg_how)
1021 {
1022 	int err;
1023 
1024 	ASSERT(tx->tx_txg == 0);
1025 	ASSERT0(txg_how & ~(TXG_WAIT | TXG_NOTHROTTLE));
1026 	ASSERT(!dsl_pool_sync_context(tx->tx_pool));
1027 
1028 	/* If we might wait, we must not hold the config lock. */
1029 	IMPLY((txg_how & TXG_WAIT), !dsl_pool_config_held(tx->tx_pool));
1030 
1031 	if ((txg_how & TXG_NOTHROTTLE))
1032 		tx->tx_dirty_delayed = B_TRUE;
1033 
1034 	while ((err = dmu_tx_try_assign(tx, txg_how)) != 0) {
1035 		dmu_tx_unassign(tx);
1036 
1037 		if (err != ERESTART || !(txg_how & TXG_WAIT))
1038 			return (err);
1039 
1040 		dmu_tx_wait(tx);
1041 	}
1042 
1043 	txg_rele_to_quiesce(&tx->tx_txgh);
1044 
1045 	return (0);
1046 }
1047 
1048 void
1049 dmu_tx_wait(dmu_tx_t *tx)
1050 {
1051 	spa_t *spa = tx->tx_pool->dp_spa;
1052 	dsl_pool_t *dp = tx->tx_pool;
1053 	hrtime_t before;
1054 
1055 	ASSERT(tx->tx_txg == 0);
1056 	ASSERT(!dsl_pool_config_held(tx->tx_pool));
1057 
1058 	before = gethrtime();
1059 
1060 	if (tx->tx_wait_dirty) {
1061 		uint64_t dirty;
1062 
1063 		/*
1064 		 * dmu_tx_try_assign() has determined that we need to wait
1065 		 * because we've consumed much or all of the dirty buffer
1066 		 * space.
1067 		 */
1068 		mutex_enter(&dp->dp_lock);
1069 		if (dp->dp_dirty_total >= zfs_dirty_data_max)
1070 			DMU_TX_STAT_BUMP(dmu_tx_dirty_over_max);
1071 		while (dp->dp_dirty_total >= zfs_dirty_data_max)
1072 			cv_wait(&dp->dp_spaceavail_cv, &dp->dp_lock);
1073 		dirty = dp->dp_dirty_total;
1074 		mutex_exit(&dp->dp_lock);
1075 
1076 		dmu_tx_delay(tx, dirty);
1077 
1078 		tx->tx_wait_dirty = B_FALSE;
1079 
1080 		/*
1081 		 * Note: setting tx_dirty_delayed only has effect if the
1082 		 * caller used TX_WAIT.  Otherwise they are going to
1083 		 * destroy this tx and try again.  The common case,
1084 		 * zfs_write(), uses TX_WAIT.
1085 		 */
1086 		tx->tx_dirty_delayed = B_TRUE;
1087 	} else if (spa_suspended(spa) || tx->tx_lasttried_txg == 0) {
1088 		/*
1089 		 * If the pool is suspended we need to wait until it
1090 		 * is resumed.  Note that it's possible that the pool
1091 		 * has become active after this thread has tried to
1092 		 * obtain a tx.  If that's the case then tx_lasttried_txg
1093 		 * would not have been set.
1094 		 */
1095 		txg_wait_synced(dp, spa_last_synced_txg(spa) + 1);
1096 	} else if (tx->tx_needassign_txh) {
1097 		dnode_t *dn = tx->tx_needassign_txh->txh_dnode;
1098 
1099 		mutex_enter(&dn->dn_mtx);
1100 		while (dn->dn_assigned_txg == tx->tx_lasttried_txg - 1)
1101 			cv_wait(&dn->dn_notxholds, &dn->dn_mtx);
1102 		mutex_exit(&dn->dn_mtx);
1103 		tx->tx_needassign_txh = NULL;
1104 	} else {
1105 		/*
1106 		 * If we have a lot of dirty data just wait until we sync
1107 		 * out a TXG at which point we'll hopefully have synced
1108 		 * a portion of the changes.
1109 		 */
1110 		txg_wait_synced(dp, spa_last_synced_txg(spa) + 1);
1111 	}
1112 
1113 	spa_tx_assign_add_nsecs(spa, gethrtime() - before);
1114 }
1115 
1116 static void
1117 dmu_tx_destroy(dmu_tx_t *tx)
1118 {
1119 	dmu_tx_hold_t *txh;
1120 
1121 	while ((txh = list_head(&tx->tx_holds)) != NULL) {
1122 		dnode_t *dn = txh->txh_dnode;
1123 
1124 		list_remove(&tx->tx_holds, txh);
1125 		zfs_refcount_destroy_many(&txh->txh_space_towrite,
1126 		    zfs_refcount_count(&txh->txh_space_towrite));
1127 		zfs_refcount_destroy_many(&txh->txh_memory_tohold,
1128 		    zfs_refcount_count(&txh->txh_memory_tohold));
1129 		kmem_free(txh, sizeof (dmu_tx_hold_t));
1130 		if (dn != NULL)
1131 			dnode_rele(dn, tx);
1132 	}
1133 
1134 	list_destroy(&tx->tx_callbacks);
1135 	list_destroy(&tx->tx_holds);
1136 	kmem_free(tx, sizeof (dmu_tx_t));
1137 }
1138 
1139 void
1140 dmu_tx_commit(dmu_tx_t *tx)
1141 {
1142 	ASSERT(tx->tx_txg != 0);
1143 
1144 	/*
1145 	 * Go through the transaction's hold list and remove holds on
1146 	 * associated dnodes, notifying waiters if no holds remain.
1147 	 */
1148 	for (dmu_tx_hold_t *txh = list_head(&tx->tx_holds); txh != NULL;
1149 	    txh = list_next(&tx->tx_holds, txh)) {
1150 		dnode_t *dn = txh->txh_dnode;
1151 
1152 		if (dn == NULL)
1153 			continue;
1154 
1155 		mutex_enter(&dn->dn_mtx);
1156 		ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
1157 
1158 		if (zfs_refcount_remove(&dn->dn_tx_holds, tx) == 0) {
1159 			dn->dn_assigned_txg = 0;
1160 			cv_broadcast(&dn->dn_notxholds);
1161 		}
1162 		mutex_exit(&dn->dn_mtx);
1163 	}
1164 
1165 	if (tx->tx_tempreserve_cookie)
1166 		dsl_dir_tempreserve_clear(tx->tx_tempreserve_cookie, tx);
1167 
1168 	if (!list_is_empty(&tx->tx_callbacks))
1169 		txg_register_callbacks(&tx->tx_txgh, &tx->tx_callbacks);
1170 
1171 	if (tx->tx_anyobj == FALSE)
1172 		txg_rele_to_sync(&tx->tx_txgh);
1173 
1174 	dmu_tx_destroy(tx);
1175 }
1176 
1177 void
1178 dmu_tx_abort(dmu_tx_t *tx)
1179 {
1180 	ASSERT(tx->tx_txg == 0);
1181 
1182 	/*
1183 	 * Call any registered callbacks with an error code.
1184 	 */
1185 	if (!list_is_empty(&tx->tx_callbacks))
1186 		dmu_tx_do_callbacks(&tx->tx_callbacks, SET_ERROR(ECANCELED));
1187 
1188 	dmu_tx_destroy(tx);
1189 }
1190 
1191 uint64_t
1192 dmu_tx_get_txg(dmu_tx_t *tx)
1193 {
1194 	ASSERT(tx->tx_txg != 0);
1195 	return (tx->tx_txg);
1196 }
1197 
1198 dsl_pool_t *
1199 dmu_tx_pool(dmu_tx_t *tx)
1200 {
1201 	ASSERT(tx->tx_pool != NULL);
1202 	return (tx->tx_pool);
1203 }
1204 
1205 void
1206 dmu_tx_callback_register(dmu_tx_t *tx, dmu_tx_callback_func_t *func, void *data)
1207 {
1208 	dmu_tx_callback_t *dcb;
1209 
1210 	dcb = kmem_alloc(sizeof (dmu_tx_callback_t), KM_SLEEP);
1211 
1212 	dcb->dcb_func = func;
1213 	dcb->dcb_data = data;
1214 
1215 	list_insert_tail(&tx->tx_callbacks, dcb);
1216 }
1217 
1218 /*
1219  * Call all the commit callbacks on a list, with a given error code.
1220  */
1221 void
1222 dmu_tx_do_callbacks(list_t *cb_list, int error)
1223 {
1224 	dmu_tx_callback_t *dcb;
1225 
1226 	while ((dcb = list_tail(cb_list)) != NULL) {
1227 		list_remove(cb_list, dcb);
1228 		dcb->dcb_func(dcb->dcb_data, error);
1229 		kmem_free(dcb, sizeof (dmu_tx_callback_t));
1230 	}
1231 }
1232 
1233 /*
1234  * Interface to hold a bunch of attributes.
1235  * used for creating new files.
1236  * attrsize is the total size of all attributes
1237  * to be added during object creation
1238  *
1239  * For updating/adding a single attribute dmu_tx_hold_sa() should be used.
1240  */
1241 
1242 /*
1243  * hold necessary attribute name for attribute registration.
1244  * should be a very rare case where this is needed.  If it does
1245  * happen it would only happen on the first write to the file system.
1246  */
1247 static void
1248 dmu_tx_sa_registration_hold(sa_os_t *sa, dmu_tx_t *tx)
1249 {
1250 	if (!sa->sa_need_attr_registration)
1251 		return;
1252 
1253 	for (int i = 0; i != sa->sa_num_attrs; i++) {
1254 		if (!sa->sa_attr_table[i].sa_registered) {
1255 			if (sa->sa_reg_attr_obj)
1256 				dmu_tx_hold_zap(tx, sa->sa_reg_attr_obj,
1257 				    B_TRUE, sa->sa_attr_table[i].sa_name);
1258 			else
1259 				dmu_tx_hold_zap(tx, DMU_NEW_OBJECT,
1260 				    B_TRUE, sa->sa_attr_table[i].sa_name);
1261 		}
1262 	}
1263 }
1264 
1265 void
1266 dmu_tx_hold_spill(dmu_tx_t *tx, uint64_t object)
1267 {
1268 	dmu_tx_hold_t *txh;
1269 
1270 	txh = dmu_tx_hold_object_impl(tx, tx->tx_objset, object,
1271 	    THT_SPILL, 0, 0);
1272 	if (txh != NULL)
1273 		(void) zfs_refcount_add_many(&txh->txh_space_towrite,
1274 		    SPA_OLD_MAXBLOCKSIZE, FTAG);
1275 }
1276 
1277 void
1278 dmu_tx_hold_sa_create(dmu_tx_t *tx, int attrsize)
1279 {
1280 	sa_os_t *sa = tx->tx_objset->os_sa;
1281 
1282 	dmu_tx_hold_bonus(tx, DMU_NEW_OBJECT);
1283 
1284 	if (tx->tx_objset->os_sa->sa_master_obj == 0)
1285 		return;
1286 
1287 	if (tx->tx_objset->os_sa->sa_layout_attr_obj) {
1288 		dmu_tx_hold_zap(tx, sa->sa_layout_attr_obj, B_TRUE, NULL);
1289 	} else {
1290 		dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_LAYOUTS);
1291 		dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_REGISTRY);
1292 		dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
1293 		dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
1294 	}
1295 
1296 	dmu_tx_sa_registration_hold(sa, tx);
1297 
1298 	if (attrsize <= DN_OLD_MAX_BONUSLEN && !sa->sa_force_spill)
1299 		return;
1300 
1301 	(void) dmu_tx_hold_object_impl(tx, tx->tx_objset, DMU_NEW_OBJECT,
1302 	    THT_SPILL, 0, 0);
1303 }
1304 
1305 /*
1306  * Hold SA attribute
1307  *
1308  * dmu_tx_hold_sa(dmu_tx_t *tx, sa_handle_t *, attribute, add, size)
1309  *
1310  * variable_size is the total size of all variable sized attributes
1311  * passed to this function.  It is not the total size of all
1312  * variable size attributes that *may* exist on this object.
1313  */
1314 void
1315 dmu_tx_hold_sa(dmu_tx_t *tx, sa_handle_t *hdl, boolean_t may_grow)
1316 {
1317 	uint64_t object;
1318 	sa_os_t *sa = tx->tx_objset->os_sa;
1319 
1320 	ASSERT(hdl != NULL);
1321 
1322 	object = sa_handle_object(hdl);
1323 
1324 	dmu_buf_impl_t *db = (dmu_buf_impl_t *)hdl->sa_bonus;
1325 	DB_DNODE_ENTER(db);
1326 	dmu_tx_hold_bonus_by_dnode(tx, DB_DNODE(db));
1327 	DB_DNODE_EXIT(db);
1328 
1329 	if (tx->tx_objset->os_sa->sa_master_obj == 0)
1330 		return;
1331 
1332 	if (tx->tx_objset->os_sa->sa_reg_attr_obj == 0 ||
1333 	    tx->tx_objset->os_sa->sa_layout_attr_obj == 0) {
1334 		dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_LAYOUTS);
1335 		dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_REGISTRY);
1336 		dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
1337 		dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
1338 	}
1339 
1340 	dmu_tx_sa_registration_hold(sa, tx);
1341 
1342 	if (may_grow && tx->tx_objset->os_sa->sa_layout_attr_obj)
1343 		dmu_tx_hold_zap(tx, sa->sa_layout_attr_obj, B_TRUE, NULL);
1344 
1345 	if (sa->sa_force_spill || may_grow || hdl->sa_spill) {
1346 		ASSERT(tx->tx_txg == 0);
1347 		dmu_tx_hold_spill(tx, object);
1348 	} else {
1349 		dnode_t *dn;
1350 
1351 		DB_DNODE_ENTER(db);
1352 		dn = DB_DNODE(db);
1353 		if (dn->dn_have_spill) {
1354 			ASSERT(tx->tx_txg == 0);
1355 			dmu_tx_hold_spill(tx, object);
1356 		}
1357 		DB_DNODE_EXIT(db);
1358 	}
1359 }
1360 
1361 void
1362 dmu_tx_init(void)
1363 {
1364 	dmu_tx_ksp = kstat_create("zfs", 0, "dmu_tx", "misc",
1365 	    KSTAT_TYPE_NAMED, sizeof (dmu_tx_stats) / sizeof (kstat_named_t),
1366 	    KSTAT_FLAG_VIRTUAL);
1367 
1368 	if (dmu_tx_ksp != NULL) {
1369 		dmu_tx_ksp->ks_data = &dmu_tx_stats;
1370 		kstat_install(dmu_tx_ksp);
1371 	}
1372 }
1373 
1374 void
1375 dmu_tx_fini(void)
1376 {
1377 	if (dmu_tx_ksp != NULL) {
1378 		kstat_delete(dmu_tx_ksp);
1379 		dmu_tx_ksp = NULL;
1380 	}
1381 }
1382 
1383 #if defined(_KERNEL)
1384 EXPORT_SYMBOL(dmu_tx_create);
1385 EXPORT_SYMBOL(dmu_tx_hold_write);
1386 EXPORT_SYMBOL(dmu_tx_hold_write_by_dnode);
1387 EXPORT_SYMBOL(dmu_tx_hold_free);
1388 EXPORT_SYMBOL(dmu_tx_hold_free_by_dnode);
1389 EXPORT_SYMBOL(dmu_tx_hold_zap);
1390 EXPORT_SYMBOL(dmu_tx_hold_zap_by_dnode);
1391 EXPORT_SYMBOL(dmu_tx_hold_bonus);
1392 EXPORT_SYMBOL(dmu_tx_hold_bonus_by_dnode);
1393 EXPORT_SYMBOL(dmu_tx_abort);
1394 EXPORT_SYMBOL(dmu_tx_assign);
1395 EXPORT_SYMBOL(dmu_tx_wait);
1396 EXPORT_SYMBOL(dmu_tx_commit);
1397 EXPORT_SYMBOL(dmu_tx_mark_netfree);
1398 EXPORT_SYMBOL(dmu_tx_get_txg);
1399 EXPORT_SYMBOL(dmu_tx_callback_register);
1400 EXPORT_SYMBOL(dmu_tx_do_callbacks);
1401 EXPORT_SYMBOL(dmu_tx_hold_spill);
1402 EXPORT_SYMBOL(dmu_tx_hold_sa_create);
1403 EXPORT_SYMBOL(dmu_tx_hold_sa);
1404 #endif
1405