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.
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.
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]
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) 2013 by Delphix. All rights reserved.
28 #include <sys/dmu_impl.h>
30 #include <sys/dmu_tx.h>
31 #include <sys/dmu_objset.h>
32 #include <sys/dsl_dataset.h> /* for dsl_dataset_block_freeable() */
33 #include <sys/dsl_dir.h> /* for dsl_dir_tempreserve_*() */
34 #include <sys/dsl_pool.h>
35 #include <sys/zap_impl.h> /* for fzap_default_block_shift */
38 #include <sys/sa_impl.h>
39 #include <sys/zfs_context.h>
40 #include <sys/varargs.h>
42 typedef void (*dmu_tx_hold_func_t)(dmu_tx_t *tx, struct dnode *dn,
43 uint64_t arg1, uint64_t arg2);
47 dmu_tx_create_dd(dsl_dir_t *dd)
49 dmu_tx_t *tx = kmem_zalloc(sizeof (dmu_tx_t), KM_SLEEP);
52 tx->tx_pool = dd->dd_pool;
53 list_create(&tx->tx_holds, sizeof (dmu_tx_hold_t),
54 offsetof(dmu_tx_hold_t, txh_node));
55 list_create(&tx->tx_callbacks, sizeof (dmu_tx_callback_t),
56 offsetof(dmu_tx_callback_t, dcb_node));
57 tx->tx_start = gethrtime();
59 refcount_create(&tx->tx_space_written);
60 refcount_create(&tx->tx_space_freed);
66 dmu_tx_create(objset_t *os)
68 dmu_tx_t *tx = dmu_tx_create_dd(os->os_dsl_dataset->ds_dir);
70 tx->tx_lastsnap_txg = dsl_dataset_prev_snap_txg(os->os_dsl_dataset);
75 dmu_tx_create_assigned(struct dsl_pool *dp, uint64_t txg)
77 dmu_tx_t *tx = dmu_tx_create_dd(NULL);
79 ASSERT3U(txg, <=, dp->dp_tx.tx_open_txg);
88 dmu_tx_is_syncing(dmu_tx_t *tx)
90 return (tx->tx_anyobj);
94 dmu_tx_private_ok(dmu_tx_t *tx)
96 return (tx->tx_anyobj);
99 static dmu_tx_hold_t *
100 dmu_tx_hold_object_impl(dmu_tx_t *tx, objset_t *os, uint64_t object,
101 enum dmu_tx_hold_type type, uint64_t arg1, uint64_t arg2)
107 if (object != DMU_NEW_OBJECT) {
108 err = dnode_hold(os, object, tx, &dn);
114 if (err == 0 && tx->tx_txg != 0) {
115 mutex_enter(&dn->dn_mtx);
117 * dn->dn_assigned_txg == tx->tx_txg doesn't pose a
118 * problem, but there's no way for it to happen (for
121 ASSERT(dn->dn_assigned_txg == 0);
122 dn->dn_assigned_txg = tx->tx_txg;
123 (void) refcount_add(&dn->dn_tx_holds, tx);
124 mutex_exit(&dn->dn_mtx);
128 txh = kmem_zalloc(sizeof (dmu_tx_hold_t), KM_SLEEP);
132 txh->txh_type = type;
133 txh->txh_arg1 = arg1;
134 txh->txh_arg2 = arg2;
136 list_insert_tail(&tx->tx_holds, txh);
142 dmu_tx_add_new_object(dmu_tx_t *tx, objset_t *os, uint64_t object)
145 * If we're syncing, they can manipulate any object anyhow, and
146 * the hold on the dnode_t can cause problems.
148 if (!dmu_tx_is_syncing(tx)) {
149 (void) dmu_tx_hold_object_impl(tx, os,
150 object, THT_NEWOBJECT, 0, 0);
155 dmu_tx_check_ioerr(zio_t *zio, dnode_t *dn, int level, uint64_t blkid)
160 rw_enter(&dn->dn_struct_rwlock, RW_READER);
161 db = dbuf_hold_level(dn, level, blkid, FTAG);
162 rw_exit(&dn->dn_struct_rwlock);
164 return (SET_ERROR(EIO));
165 err = dbuf_read(db, zio, DB_RF_CANFAIL | DB_RF_NOPREFETCH);
171 dmu_tx_count_twig(dmu_tx_hold_t *txh, dnode_t *dn, dmu_buf_impl_t *db,
172 int level, uint64_t blkid, boolean_t freeable, uint64_t *history)
174 objset_t *os = dn->dn_objset;
175 dsl_dataset_t *ds = os->os_dsl_dataset;
176 int epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
177 dmu_buf_impl_t *parent = NULL;
181 if (level >= dn->dn_nlevels || history[level] == blkid)
184 history[level] = blkid;
186 space = (level == 0) ? dn->dn_datablksz : (1ULL << dn->dn_indblkshift);
188 if (db == NULL || db == dn->dn_dbuf) {
192 ASSERT(DB_DNODE(db) == dn);
193 ASSERT(db->db_level == level);
194 ASSERT(db->db.db_size == space);
195 ASSERT(db->db_blkid == blkid);
197 parent = db->db_parent;
200 freeable = (bp && (freeable ||
201 dsl_dataset_block_freeable(ds, bp, bp->blk_birth)));
204 txh->txh_space_tooverwrite += space;
206 txh->txh_space_towrite += space;
208 txh->txh_space_tounref += bp_get_dsize(os->os_spa, bp);
210 dmu_tx_count_twig(txh, dn, parent, level + 1,
211 blkid >> epbs, freeable, history);
216 dmu_tx_count_write(dmu_tx_hold_t *txh, uint64_t off, uint64_t len)
218 dnode_t *dn = txh->txh_dnode;
219 uint64_t start, end, i;
220 int min_bs, max_bs, min_ibs, max_ibs, epbs, bits;
226 min_bs = SPA_MINBLOCKSHIFT;
227 max_bs = SPA_MAXBLOCKSHIFT;
228 min_ibs = DN_MIN_INDBLKSHIFT;
229 max_ibs = DN_MAX_INDBLKSHIFT;
232 uint64_t history[DN_MAX_LEVELS];
233 int nlvls = dn->dn_nlevels;
237 * For i/o error checking, read the first and last level-0
238 * blocks (if they are not aligned), and all the level-1 blocks.
240 if (dn->dn_maxblkid == 0) {
241 delta = dn->dn_datablksz;
242 start = (off < dn->dn_datablksz) ? 0 : 1;
243 end = (off+len <= dn->dn_datablksz) ? 0 : 1;
244 if (start == 0 && (off > 0 || len < dn->dn_datablksz)) {
245 err = dmu_tx_check_ioerr(NULL, dn, 0, 0);
251 zio_t *zio = zio_root(dn->dn_objset->os_spa,
252 NULL, NULL, ZIO_FLAG_CANFAIL);
254 /* first level-0 block */
255 start = off >> dn->dn_datablkshift;
256 if (P2PHASE(off, dn->dn_datablksz) ||
257 len < dn->dn_datablksz) {
258 err = dmu_tx_check_ioerr(zio, dn, 0, start);
263 /* last level-0 block */
264 end = (off+len-1) >> dn->dn_datablkshift;
265 if (end != start && end <= dn->dn_maxblkid &&
266 P2PHASE(off+len, dn->dn_datablksz)) {
267 err = dmu_tx_check_ioerr(zio, dn, 0, end);
274 int shft = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
275 for (i = (start>>shft)+1; i < end>>shft; i++) {
276 err = dmu_tx_check_ioerr(zio, dn, 1, i);
285 delta = P2NPHASE(off, dn->dn_datablksz);
288 min_ibs = max_ibs = dn->dn_indblkshift;
289 if (dn->dn_maxblkid > 0) {
291 * The blocksize can't change,
292 * so we can make a more precise estimate.
294 ASSERT(dn->dn_datablkshift != 0);
295 min_bs = max_bs = dn->dn_datablkshift;
299 * If this write is not off the end of the file
300 * we need to account for overwrites/unref.
302 if (start <= dn->dn_maxblkid) {
303 for (int l = 0; l < DN_MAX_LEVELS; l++)
306 while (start <= dn->dn_maxblkid) {
309 rw_enter(&dn->dn_struct_rwlock, RW_READER);
310 err = dbuf_hold_impl(dn, 0, start, FALSE, FTAG, &db);
311 rw_exit(&dn->dn_struct_rwlock);
314 txh->txh_tx->tx_err = err;
318 dmu_tx_count_twig(txh, dn, db, 0, start, B_FALSE,
323 * Account for new indirects appearing
324 * before this IO gets assigned into a txg.
327 epbs = min_ibs - SPA_BLKPTRSHIFT;
328 for (bits -= epbs * (nlvls - 1);
329 bits >= 0; bits -= epbs)
330 txh->txh_fudge += 1ULL << max_ibs;
336 delta = dn->dn_datablksz;
341 * 'end' is the last thing we will access, not one past.
342 * This way we won't overflow when accessing the last byte.
344 start = P2ALIGN(off, 1ULL << max_bs);
345 end = P2ROUNDUP(off + len, 1ULL << max_bs) - 1;
346 txh->txh_space_towrite += end - start + 1;
351 epbs = min_ibs - SPA_BLKPTRSHIFT;
354 * The object contains at most 2^(64 - min_bs) blocks,
355 * and each indirect level maps 2^epbs.
357 for (bits = 64 - min_bs; bits >= 0; bits -= epbs) {
360 ASSERT3U(end, >=, start);
361 txh->txh_space_towrite += (end - start + 1) << max_ibs;
364 * We also need a new blkid=0 indirect block
365 * to reference any existing file data.
367 txh->txh_space_towrite += 1ULL << max_ibs;
372 if (txh->txh_space_towrite + txh->txh_space_tooverwrite >
374 err = SET_ERROR(EFBIG);
377 txh->txh_tx->tx_err = err;
381 dmu_tx_count_dnode(dmu_tx_hold_t *txh)
383 dnode_t *dn = txh->txh_dnode;
384 dnode_t *mdn = DMU_META_DNODE(txh->txh_tx->tx_objset);
385 uint64_t space = mdn->dn_datablksz +
386 ((mdn->dn_nlevels-1) << mdn->dn_indblkshift);
388 if (dn && dn->dn_dbuf->db_blkptr &&
389 dsl_dataset_block_freeable(dn->dn_objset->os_dsl_dataset,
390 dn->dn_dbuf->db_blkptr, dn->dn_dbuf->db_blkptr->blk_birth)) {
391 txh->txh_space_tooverwrite += space;
392 txh->txh_space_tounref += space;
394 txh->txh_space_towrite += space;
395 if (dn && dn->dn_dbuf->db_blkptr)
396 txh->txh_space_tounref += space;
401 dmu_tx_hold_write(dmu_tx_t *tx, uint64_t object, uint64_t off, int len)
405 ASSERT(tx->tx_txg == 0);
406 ASSERT(len < DMU_MAX_ACCESS);
407 ASSERT(len == 0 || UINT64_MAX - off >= len - 1);
409 txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
410 object, THT_WRITE, off, len);
414 dmu_tx_count_write(txh, off, len);
415 dmu_tx_count_dnode(txh);
419 dmu_tx_count_free(dmu_tx_hold_t *txh, uint64_t off, uint64_t len)
421 uint64_t blkid, nblks, lastblk;
422 uint64_t space = 0, unref = 0, skipped = 0;
423 dnode_t *dn = txh->txh_dnode;
424 dsl_dataset_t *ds = dn->dn_objset->os_dsl_dataset;
425 spa_t *spa = txh->txh_tx->tx_pool->dp_spa;
427 uint64_t l0span = 0, nl1blks = 0;
429 if (dn->dn_nlevels == 0)
433 * The struct_rwlock protects us against dn_nlevels
434 * changing, in case (against all odds) we manage to dirty &
435 * sync out the changes after we check for being dirty.
436 * Also, dbuf_hold_impl() wants us to have the struct_rwlock.
438 rw_enter(&dn->dn_struct_rwlock, RW_READER);
439 epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
440 if (dn->dn_maxblkid == 0) {
441 if (off == 0 && len >= dn->dn_datablksz) {
445 rw_exit(&dn->dn_struct_rwlock);
449 blkid = off >> dn->dn_datablkshift;
450 nblks = (len + dn->dn_datablksz - 1) >> dn->dn_datablkshift;
452 if (blkid > dn->dn_maxblkid) {
453 rw_exit(&dn->dn_struct_rwlock);
456 if (blkid + nblks > dn->dn_maxblkid)
457 nblks = dn->dn_maxblkid - blkid + 1;
460 l0span = nblks; /* save for later use to calc level > 1 overhead */
461 if (dn->dn_nlevels == 1) {
463 for (i = 0; i < nblks; i++) {
464 blkptr_t *bp = dn->dn_phys->dn_blkptr;
465 ASSERT3U(blkid + i, <, dn->dn_nblkptr);
467 if (dsl_dataset_block_freeable(ds, bp, bp->blk_birth)) {
468 dprintf_bp(bp, "can free old%s", "");
469 space += bp_get_dsize(spa, bp);
471 unref += BP_GET_ASIZE(bp);
477 lastblk = blkid + nblks - 1;
479 dmu_buf_impl_t *dbuf;
480 uint64_t ibyte, new_blkid;
482 int err, i, blkoff, tochk;
485 ibyte = blkid << dn->dn_datablkshift;
486 err = dnode_next_offset(dn,
487 DNODE_FIND_HAVELOCK, &ibyte, 2, 1, 0);
488 new_blkid = ibyte >> dn->dn_datablkshift;
490 skipped += (lastblk >> epbs) - (blkid >> epbs) + 1;
494 txh->txh_tx->tx_err = err;
497 if (new_blkid > lastblk) {
498 skipped += (lastblk >> epbs) - (blkid >> epbs) + 1;
502 if (new_blkid > blkid) {
503 ASSERT((new_blkid >> epbs) > (blkid >> epbs));
504 skipped += (new_blkid >> epbs) - (blkid >> epbs) - 1;
505 nblks -= new_blkid - blkid;
508 blkoff = P2PHASE(blkid, epb);
509 tochk = MIN(epb - blkoff, nblks);
511 err = dbuf_hold_impl(dn, 1, blkid >> epbs, FALSE, FTAG, &dbuf);
513 txh->txh_tx->tx_err = err;
517 txh->txh_memory_tohold += dbuf->db.db_size;
520 * We don't check memory_tohold against DMU_MAX_ACCESS because
521 * memory_tohold is an over-estimation (especially the >L1
522 * indirect blocks), so it could fail. Callers should have
523 * already verified that they will not be holding too much
527 err = dbuf_read(dbuf, NULL, DB_RF_HAVESTRUCT | DB_RF_CANFAIL);
529 txh->txh_tx->tx_err = err;
530 dbuf_rele(dbuf, FTAG);
534 bp = dbuf->db.db_data;
537 for (i = 0; i < tochk; i++) {
538 if (dsl_dataset_block_freeable(ds, &bp[i],
540 dprintf_bp(&bp[i], "can free old%s", "");
541 space += bp_get_dsize(spa, &bp[i]);
543 unref += BP_GET_ASIZE(bp);
545 dbuf_rele(dbuf, FTAG);
551 rw_exit(&dn->dn_struct_rwlock);
554 * Add in memory requirements of higher-level indirects.
555 * This assumes a worst-possible scenario for dn_nlevels and a
556 * worst-possible distribution of l1-blocks over the region to free.
559 uint64_t blkcnt = 1 + ((l0span >> epbs) >> epbs);
562 * Here we don't use DN_MAX_LEVEL, but calculate it with the
563 * given datablkshift and indblkshift. This makes the
564 * difference between 19 and 8 on large files.
566 int maxlevel = 2 + (DN_MAX_OFFSET_SHIFT - dn->dn_datablkshift) /
567 (dn->dn_indblkshift - SPA_BLKPTRSHIFT);
569 while (level++ < maxlevel) {
570 txh->txh_memory_tohold += MAX(MIN(blkcnt, nl1blks), 1)
571 << dn->dn_indblkshift;
572 blkcnt = 1 + (blkcnt >> epbs);
576 /* account for new level 1 indirect blocks that might show up */
578 txh->txh_fudge += skipped << dn->dn_indblkshift;
579 skipped = MIN(skipped, DMU_MAX_DELETEBLKCNT >> epbs);
580 txh->txh_memory_tohold += skipped << dn->dn_indblkshift;
582 txh->txh_space_tofree += space;
583 txh->txh_space_tounref += unref;
587 dmu_tx_hold_free(dmu_tx_t *tx, uint64_t object, uint64_t off, uint64_t len)
594 ASSERT(tx->tx_txg == 0);
596 txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
597 object, THT_FREE, off, len);
601 dmu_tx_count_dnode(txh);
603 if (off >= (dn->dn_maxblkid+1) * dn->dn_datablksz)
605 if (len == DMU_OBJECT_END)
606 len = (dn->dn_maxblkid+1) * dn->dn_datablksz - off;
610 * For i/o error checking, we read the first and last level-0
611 * blocks if they are not aligned, and all the level-1 blocks.
613 * Note: dbuf_free_range() assumes that we have not instantiated
614 * any level-0 dbufs that will be completely freed. Therefore we must
615 * exercise care to not read or count the first and last blocks
616 * if they are blocksize-aligned.
618 if (dn->dn_datablkshift == 0) {
619 if (off != 0 || len < dn->dn_datablksz)
620 dmu_tx_count_write(txh, 0, dn->dn_datablksz);
622 /* first block will be modified if it is not aligned */
623 if (!IS_P2ALIGNED(off, 1 << dn->dn_datablkshift))
624 dmu_tx_count_write(txh, off, 1);
625 /* last block will be modified if it is not aligned */
626 if (!IS_P2ALIGNED(off + len, 1 << dn->dn_datablkshift))
627 dmu_tx_count_write(txh, off+len, 1);
631 * Check level-1 blocks.
633 if (dn->dn_nlevels > 1) {
634 int shift = dn->dn_datablkshift + dn->dn_indblkshift -
636 uint64_t start = off >> shift;
637 uint64_t end = (off + len) >> shift;
639 ASSERT(dn->dn_indblkshift != 0);
642 * dnode_reallocate() can result in an object with indirect
643 * blocks having an odd data block size. In this case,
644 * just check the single block.
646 if (dn->dn_datablkshift == 0)
649 zio = zio_root(tx->tx_pool->dp_spa,
650 NULL, NULL, ZIO_FLAG_CANFAIL);
651 for (uint64_t i = start; i <= end; i++) {
652 uint64_t ibyte = i << shift;
653 err = dnode_next_offset(dn, 0, &ibyte, 2, 1, 0);
662 err = dmu_tx_check_ioerr(zio, dn, 1, i);
675 dmu_tx_count_free(txh, off, len);
679 dmu_tx_hold_zap(dmu_tx_t *tx, uint64_t object, int add, const char *name)
686 ASSERT(tx->tx_txg == 0);
688 txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
689 object, THT_ZAP, add, (uintptr_t)name);
694 dmu_tx_count_dnode(txh);
698 * We will be able to fit a new object's entries into one leaf
699 * block. So there will be at most 2 blocks total,
700 * including the header block.
702 dmu_tx_count_write(txh, 0, 2 << fzap_default_block_shift);
706 ASSERT3P(DMU_OT_BYTESWAP(dn->dn_type), ==, DMU_BSWAP_ZAP);
708 if (dn->dn_maxblkid == 0 && !add) {
712 * If there is only one block (i.e. this is a micro-zap)
713 * and we are not adding anything, the accounting is simple.
715 err = dmu_tx_check_ioerr(NULL, dn, 0, 0);
722 * Use max block size here, since we don't know how much
723 * the size will change between now and the dbuf dirty call.
725 bp = &dn->dn_phys->dn_blkptr[0];
726 if (dsl_dataset_block_freeable(dn->dn_objset->os_dsl_dataset,
728 txh->txh_space_tooverwrite += SPA_MAXBLOCKSIZE;
730 txh->txh_space_towrite += SPA_MAXBLOCKSIZE;
732 txh->txh_space_tounref += SPA_MAXBLOCKSIZE;
736 if (dn->dn_maxblkid > 0 && name) {
738 * access the name in this fat-zap so that we'll check
739 * for i/o errors to the leaf blocks, etc.
741 err = zap_lookup(dn->dn_objset, dn->dn_object, name,
749 err = zap_count_write(dn->dn_objset, dn->dn_object, name, add,
750 &txh->txh_space_towrite, &txh->txh_space_tooverwrite);
753 * If the modified blocks are scattered to the four winds,
754 * we'll have to modify an indirect twig for each.
756 epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
757 for (nblocks = dn->dn_maxblkid >> epbs; nblocks != 0; nblocks >>= epbs)
758 if (dn->dn_objset->os_dsl_dataset->ds_phys->ds_prev_snap_obj)
759 txh->txh_space_towrite += 3 << dn->dn_indblkshift;
761 txh->txh_space_tooverwrite += 3 << dn->dn_indblkshift;
765 dmu_tx_hold_bonus(dmu_tx_t *tx, uint64_t object)
769 ASSERT(tx->tx_txg == 0);
771 txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
772 object, THT_BONUS, 0, 0);
774 dmu_tx_count_dnode(txh);
778 dmu_tx_hold_space(dmu_tx_t *tx, uint64_t space)
781 ASSERT(tx->tx_txg == 0);
783 txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
784 DMU_NEW_OBJECT, THT_SPACE, space, 0);
786 txh->txh_space_towrite += space;
790 dmu_tx_holds(dmu_tx_t *tx, uint64_t object)
796 * By asserting that the tx is assigned, we're counting the
797 * number of dn_tx_holds, which is the same as the number of
798 * dn_holds. Otherwise, we'd be counting dn_holds, but
799 * dn_tx_holds could be 0.
801 ASSERT(tx->tx_txg != 0);
803 /* if (tx->tx_anyobj == TRUE) */
806 for (txh = list_head(&tx->tx_holds); txh;
807 txh = list_next(&tx->tx_holds, txh)) {
808 if (txh->txh_dnode && txh->txh_dnode->dn_object == object)
817 dmu_tx_dirty_buf(dmu_tx_t *tx, dmu_buf_impl_t *db)
820 int match_object = FALSE, match_offset = FALSE;
825 ASSERT(tx->tx_txg != 0);
826 ASSERT(tx->tx_objset == NULL || dn->dn_objset == tx->tx_objset);
827 ASSERT3U(dn->dn_object, ==, db->db.db_object);
834 /* XXX No checking on the meta dnode for now */
835 if (db->db.db_object == DMU_META_DNODE_OBJECT) {
840 for (txh = list_head(&tx->tx_holds); txh;
841 txh = list_next(&tx->tx_holds, txh)) {
842 ASSERT(dn == NULL || dn->dn_assigned_txg == tx->tx_txg);
843 if (txh->txh_dnode == dn && txh->txh_type != THT_NEWOBJECT)
845 if (txh->txh_dnode == NULL || txh->txh_dnode == dn) {
846 int datablkshift = dn->dn_datablkshift ?
847 dn->dn_datablkshift : SPA_MAXBLOCKSHIFT;
848 int epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
849 int shift = datablkshift + epbs * db->db_level;
850 uint64_t beginblk = shift >= 64 ? 0 :
851 (txh->txh_arg1 >> shift);
852 uint64_t endblk = shift >= 64 ? 0 :
853 ((txh->txh_arg1 + txh->txh_arg2 - 1) >> shift);
854 uint64_t blkid = db->db_blkid;
856 /* XXX txh_arg2 better not be zero... */
858 dprintf("found txh type %x beginblk=%llx endblk=%llx\n",
859 txh->txh_type, beginblk, endblk);
861 switch (txh->txh_type) {
863 if (blkid >= beginblk && blkid <= endblk)
866 * We will let this hold work for the bonus
867 * or spill buffer so that we don't need to
868 * hold it when creating a new object.
870 if (blkid == DMU_BONUS_BLKID ||
871 blkid == DMU_SPILL_BLKID)
874 * They might have to increase nlevels,
875 * thus dirtying the new TLIBs. Or the
876 * might have to change the block size,
877 * thus dirying the new lvl=0 blk=0.
884 * We will dirty all the level 1 blocks in
885 * the free range and perhaps the first and
886 * last level 0 block.
888 if (blkid >= beginblk && (blkid <= endblk ||
889 txh->txh_arg2 == DMU_OBJECT_END))
893 if (blkid == DMU_SPILL_BLKID)
897 if (blkid == DMU_BONUS_BLKID)
907 ASSERT(!"bad txh_type");
910 if (match_object && match_offset) {
916 panic("dirtying dbuf obj=%llx lvl=%u blkid=%llx but not tx_held\n",
917 (u_longlong_t)db->db.db_object, db->db_level,
918 (u_longlong_t)db->db_blkid);
923 * If we can't do 10 iops, something is wrong. Let us go ahead
924 * and hit zfs_dirty_data_max.
926 hrtime_t zfs_delay_max_ns = MSEC2NSEC(100);
927 int zfs_delay_resolution_ns = 100 * 1000; /* 100 microseconds */
930 * We delay transactions when we've determined that the backend storage
931 * isn't able to accommodate the rate of incoming writes.
933 * If there is already a transaction waiting, we delay relative to when
934 * that transaction finishes waiting. This way the calculated min_time
935 * is independent of the number of threads concurrently executing
938 * If we are the only waiter, wait relative to when the transaction
939 * started, rather than the current time. This credits the transaction for
940 * "time already served", e.g. reading indirect blocks.
942 * The minimum time for a transaction to take is calculated as:
943 * min_time = scale * (dirty - min) / (max - dirty)
944 * min_time is then capped at zfs_delay_max_ns.
946 * The delay has two degrees of freedom that can be adjusted via tunables.
947 * The percentage of dirty data at which we start to delay is defined by
948 * zfs_delay_min_dirty_percent. This should typically be at or above
949 * zfs_vdev_async_write_active_max_dirty_percent so that we only start to
950 * delay after writing at full speed has failed to keep up with the incoming
951 * write rate. The scale of the curve is defined by zfs_delay_scale. Roughly
952 * speaking, this variable determines the amount of delay at the midpoint of
956 * 10ms +-------------------------------------------------------------*+
972 * 2ms + (midpoint) * +
975 * | zfs_delay_scale ----------> ******** |
976 * 0 +-------------------------------------*********----------------+
977 * 0% <- zfs_dirty_data_max -> 100%
979 * Note that since the delay is added to the outstanding time remaining on the
980 * most recent transaction, the delay is effectively the inverse of IOPS.
981 * Here the midpoint of 500us translates to 2000 IOPS. The shape of the curve
982 * was chosen such that small changes in the amount of accumulated dirty data
983 * in the first 3/4 of the curve yield relatively small differences in the
986 * The effects can be easier to understand when the amount of delay is
987 * represented on a log scale:
990 * 100ms +-------------------------------------------------------------++
999 * + zfs_delay_scale ----------> ***** +
1010 * +--------------------------------------------------------------+
1011 * 0% <- zfs_dirty_data_max -> 100%
1013 * Note here that only as the amount of dirty data approaches its limit does
1014 * the delay start to increase rapidly. The goal of a properly tuned system
1015 * should be to keep the amount of dirty data out of that range by first
1016 * ensuring that the appropriate limits are set for the I/O scheduler to reach
1017 * optimal throughput on the backend storage, and then by changing the value
1018 * of zfs_delay_scale to increase the steepness of the curve.
1021 dmu_tx_delay(dmu_tx_t *tx, uint64_t dirty)
1023 dsl_pool_t *dp = tx->tx_pool;
1024 uint64_t delay_min_bytes =
1025 zfs_dirty_data_max * zfs_delay_min_dirty_percent / 100;
1026 hrtime_t wakeup, min_tx_time, now;
1028 if (dirty <= delay_min_bytes)
1032 * The caller has already waited until we are under the max.
1033 * We make them pass us the amount of dirty data so we don't
1034 * have to handle the case of it being >= the max, which could
1035 * cause a divide-by-zero if it's == the max.
1037 ASSERT3U(dirty, <, zfs_dirty_data_max);
1040 min_tx_time = zfs_delay_scale *
1041 (dirty - delay_min_bytes) / (zfs_dirty_data_max - dirty);
1042 if (now > tx->tx_start + min_tx_time)
1045 min_tx_time = MIN(min_tx_time, zfs_delay_max_ns);
1047 DTRACE_PROBE3(delay__mintime, dmu_tx_t *, tx, uint64_t, dirty,
1048 uint64_t, min_tx_time);
1050 mutex_enter(&dp->dp_lock);
1051 wakeup = MAX(tx->tx_start + min_tx_time,
1052 dp->dp_last_wakeup + min_tx_time);
1053 dp->dp_last_wakeup = wakeup;
1054 mutex_exit(&dp->dp_lock);
1058 mutex_enter(&curthread->t_delay_lock);
1059 while (cv_timedwait_hires(&curthread->t_delay_cv,
1060 &curthread->t_delay_lock, wakeup, zfs_delay_resolution_ns,
1061 CALLOUT_FLAG_ABSOLUTE | CALLOUT_FLAG_ROUNDUP) > 0)
1063 mutex_exit(&curthread->t_delay_lock);
1065 pause_sbt("dmu_tx_delay", wakeup * SBT_1NS,
1066 zfs_delay_resolution_ns * SBT_1NS, C_ABSOLUTE);
1069 hrtime_t delta = wakeup - gethrtime();
1071 ts.tv_sec = delta / NANOSEC;
1072 ts.tv_nsec = delta % NANOSEC;
1073 (void) nanosleep(&ts, NULL);
1078 dmu_tx_try_assign(dmu_tx_t *tx, txg_how_t txg_how)
1081 spa_t *spa = tx->tx_pool->dp_spa;
1082 uint64_t memory, asize, fsize, usize;
1083 uint64_t towrite, tofree, tooverwrite, tounref, tohold, fudge;
1085 ASSERT0(tx->tx_txg);
1088 return (tx->tx_err);
1090 if (spa_suspended(spa)) {
1092 * If the user has indicated a blocking failure mode
1093 * then return ERESTART which will block in dmu_tx_wait().
1094 * Otherwise, return EIO so that an error can get
1095 * propagated back to the VOP calls.
1097 * Note that we always honor the txg_how flag regardless
1098 * of the failuremode setting.
1100 if (spa_get_failmode(spa) == ZIO_FAILURE_MODE_CONTINUE &&
1101 txg_how != TXG_WAIT)
1102 return (SET_ERROR(EIO));
1104 return (SET_ERROR(ERESTART));
1107 if (!tx->tx_waited &&
1108 dsl_pool_need_dirty_delay(tx->tx_pool)) {
1109 tx->tx_wait_dirty = B_TRUE;
1110 return (SET_ERROR(ERESTART));
1113 tx->tx_txg = txg_hold_open(tx->tx_pool, &tx->tx_txgh);
1114 tx->tx_needassign_txh = NULL;
1117 * NB: No error returns are allowed after txg_hold_open, but
1118 * before processing the dnode holds, due to the
1119 * dmu_tx_unassign() logic.
1122 towrite = tofree = tooverwrite = tounref = tohold = fudge = 0;
1123 for (txh = list_head(&tx->tx_holds); txh;
1124 txh = list_next(&tx->tx_holds, txh)) {
1125 dnode_t *dn = txh->txh_dnode;
1127 mutex_enter(&dn->dn_mtx);
1128 if (dn->dn_assigned_txg == tx->tx_txg - 1) {
1129 mutex_exit(&dn->dn_mtx);
1130 tx->tx_needassign_txh = txh;
1131 return (SET_ERROR(ERESTART));
1133 if (dn->dn_assigned_txg == 0)
1134 dn->dn_assigned_txg = tx->tx_txg;
1135 ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
1136 (void) refcount_add(&dn->dn_tx_holds, tx);
1137 mutex_exit(&dn->dn_mtx);
1139 towrite += txh->txh_space_towrite;
1140 tofree += txh->txh_space_tofree;
1141 tooverwrite += txh->txh_space_tooverwrite;
1142 tounref += txh->txh_space_tounref;
1143 tohold += txh->txh_memory_tohold;
1144 fudge += txh->txh_fudge;
1148 * If a snapshot has been taken since we made our estimates,
1149 * assume that we won't be able to free or overwrite anything.
1151 if (tx->tx_objset &&
1152 dsl_dataset_prev_snap_txg(tx->tx_objset->os_dsl_dataset) >
1153 tx->tx_lastsnap_txg) {
1154 towrite += tooverwrite;
1155 tooverwrite = tofree = 0;
1158 /* needed allocation: worst-case estimate of write space */
1159 asize = spa_get_asize(tx->tx_pool->dp_spa, towrite + tooverwrite);
1160 /* freed space estimate: worst-case overwrite + free estimate */
1161 fsize = spa_get_asize(tx->tx_pool->dp_spa, tooverwrite) + tofree;
1162 /* convert unrefd space to worst-case estimate */
1163 usize = spa_get_asize(tx->tx_pool->dp_spa, tounref);
1164 /* calculate memory footprint estimate */
1165 memory = towrite + tooverwrite + tohold;
1169 * Add in 'tohold' to account for our dirty holds on this memory
1170 * XXX - the "fudge" factor is to account for skipped blocks that
1171 * we missed because dnode_next_offset() misses in-core-only blocks.
1173 tx->tx_space_towrite = asize +
1174 spa_get_asize(tx->tx_pool->dp_spa, tohold + fudge);
1175 tx->tx_space_tofree = tofree;
1176 tx->tx_space_tooverwrite = tooverwrite;
1177 tx->tx_space_tounref = tounref;
1180 if (tx->tx_dir && asize != 0) {
1181 int err = dsl_dir_tempreserve_space(tx->tx_dir, memory,
1182 asize, fsize, usize, &tx->tx_tempreserve_cookie, tx);
1191 dmu_tx_unassign(dmu_tx_t *tx)
1195 if (tx->tx_txg == 0)
1198 txg_rele_to_quiesce(&tx->tx_txgh);
1201 * Walk the transaction's hold list, removing the hold on the
1202 * associated dnode, and notifying waiters if the refcount drops to 0.
1204 for (txh = list_head(&tx->tx_holds); txh != tx->tx_needassign_txh;
1205 txh = list_next(&tx->tx_holds, txh)) {
1206 dnode_t *dn = txh->txh_dnode;
1210 mutex_enter(&dn->dn_mtx);
1211 ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
1213 if (refcount_remove(&dn->dn_tx_holds, tx) == 0) {
1214 dn->dn_assigned_txg = 0;
1215 cv_broadcast(&dn->dn_notxholds);
1217 mutex_exit(&dn->dn_mtx);
1220 txg_rele_to_sync(&tx->tx_txgh);
1222 tx->tx_lasttried_txg = tx->tx_txg;
1227 * Assign tx to a transaction group. txg_how can be one of:
1229 * (1) TXG_WAIT. If the current open txg is full, waits until there's
1230 * a new one. This should be used when you're not holding locks.
1231 * It will only fail if we're truly out of space (or over quota).
1233 * (2) TXG_NOWAIT. If we can't assign into the current open txg without
1234 * blocking, returns immediately with ERESTART. This should be used
1235 * whenever you're holding locks. On an ERESTART error, the caller
1236 * should drop locks, do a dmu_tx_wait(tx), and try again.
1238 * (3) TXG_WAITED. Like TXG_NOWAIT, but indicates that dmu_tx_wait()
1239 * has already been called on behalf of this operation (though
1240 * most likely on a different tx).
1243 dmu_tx_assign(dmu_tx_t *tx, txg_how_t txg_how)
1247 ASSERT(tx->tx_txg == 0);
1248 ASSERT(txg_how == TXG_WAIT || txg_how == TXG_NOWAIT ||
1249 txg_how == TXG_WAITED);
1250 ASSERT(!dsl_pool_sync_context(tx->tx_pool));
1252 /* If we might wait, we must not hold the config lock. */
1253 ASSERT(txg_how != TXG_WAIT || !dsl_pool_config_held(tx->tx_pool));
1255 if (txg_how == TXG_WAITED)
1256 tx->tx_waited = B_TRUE;
1258 while ((err = dmu_tx_try_assign(tx, txg_how)) != 0) {
1259 dmu_tx_unassign(tx);
1261 if (err != ERESTART || txg_how != TXG_WAIT)
1267 txg_rele_to_quiesce(&tx->tx_txgh);
1273 dmu_tx_wait(dmu_tx_t *tx)
1275 spa_t *spa = tx->tx_pool->dp_spa;
1276 dsl_pool_t *dp = tx->tx_pool;
1278 ASSERT(tx->tx_txg == 0);
1279 ASSERT(!dsl_pool_config_held(tx->tx_pool));
1281 if (tx->tx_wait_dirty) {
1283 * dmu_tx_try_assign() has determined that we need to wait
1284 * because we've consumed much or all of the dirty buffer
1287 mutex_enter(&dp->dp_lock);
1288 while (dp->dp_dirty_total >= zfs_dirty_data_max)
1289 cv_wait(&dp->dp_spaceavail_cv, &dp->dp_lock);
1290 uint64_t dirty = dp->dp_dirty_total;
1291 mutex_exit(&dp->dp_lock);
1293 dmu_tx_delay(tx, dirty);
1295 tx->tx_wait_dirty = B_FALSE;
1298 * Note: setting tx_waited only has effect if the caller
1299 * used TX_WAIT. Otherwise they are going to destroy
1300 * this tx and try again. The common case, zfs_write(),
1303 tx->tx_waited = B_TRUE;
1304 } else if (spa_suspended(spa) || tx->tx_lasttried_txg == 0) {
1306 * If the pool is suspended we need to wait until it
1307 * is resumed. Note that it's possible that the pool
1308 * has become active after this thread has tried to
1309 * obtain a tx. If that's the case then tx_lasttried_txg
1310 * would not have been set.
1312 txg_wait_synced(dp, spa_last_synced_txg(spa) + 1);
1313 } else if (tx->tx_needassign_txh) {
1315 * A dnode is assigned to the quiescing txg. Wait for its
1316 * transaction to complete.
1318 dnode_t *dn = tx->tx_needassign_txh->txh_dnode;
1320 mutex_enter(&dn->dn_mtx);
1321 while (dn->dn_assigned_txg == tx->tx_lasttried_txg - 1)
1322 cv_wait(&dn->dn_notxholds, &dn->dn_mtx);
1323 mutex_exit(&dn->dn_mtx);
1324 tx->tx_needassign_txh = NULL;
1326 txg_wait_open(tx->tx_pool, tx->tx_lasttried_txg + 1);
1331 dmu_tx_willuse_space(dmu_tx_t *tx, int64_t delta)
1334 if (tx->tx_dir == NULL || delta == 0)
1338 ASSERT3U(refcount_count(&tx->tx_space_written) + delta, <=,
1339 tx->tx_space_towrite);
1340 (void) refcount_add_many(&tx->tx_space_written, delta, NULL);
1342 (void) refcount_add_many(&tx->tx_space_freed, -delta, NULL);
1348 dmu_tx_commit(dmu_tx_t *tx)
1352 ASSERT(tx->tx_txg != 0);
1355 * Go through the transaction's hold list and remove holds on
1356 * associated dnodes, notifying waiters if no holds remain.
1358 while (txh = list_head(&tx->tx_holds)) {
1359 dnode_t *dn = txh->txh_dnode;
1361 list_remove(&tx->tx_holds, txh);
1362 kmem_free(txh, sizeof (dmu_tx_hold_t));
1365 mutex_enter(&dn->dn_mtx);
1366 ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
1368 if (refcount_remove(&dn->dn_tx_holds, tx) == 0) {
1369 dn->dn_assigned_txg = 0;
1370 cv_broadcast(&dn->dn_notxholds);
1372 mutex_exit(&dn->dn_mtx);
1376 if (tx->tx_tempreserve_cookie)
1377 dsl_dir_tempreserve_clear(tx->tx_tempreserve_cookie, tx);
1379 if (!list_is_empty(&tx->tx_callbacks))
1380 txg_register_callbacks(&tx->tx_txgh, &tx->tx_callbacks);
1382 if (tx->tx_anyobj == FALSE)
1383 txg_rele_to_sync(&tx->tx_txgh);
1385 list_destroy(&tx->tx_callbacks);
1386 list_destroy(&tx->tx_holds);
1388 dprintf("towrite=%llu written=%llu tofree=%llu freed=%llu\n",
1389 tx->tx_space_towrite, refcount_count(&tx->tx_space_written),
1390 tx->tx_space_tofree, refcount_count(&tx->tx_space_freed));
1391 refcount_destroy_many(&tx->tx_space_written,
1392 refcount_count(&tx->tx_space_written));
1393 refcount_destroy_many(&tx->tx_space_freed,
1394 refcount_count(&tx->tx_space_freed));
1396 kmem_free(tx, sizeof (dmu_tx_t));
1400 dmu_tx_abort(dmu_tx_t *tx)
1404 ASSERT(tx->tx_txg == 0);
1406 while (txh = list_head(&tx->tx_holds)) {
1407 dnode_t *dn = txh->txh_dnode;
1409 list_remove(&tx->tx_holds, txh);
1410 kmem_free(txh, sizeof (dmu_tx_hold_t));
1416 * Call any registered callbacks with an error code.
1418 if (!list_is_empty(&tx->tx_callbacks))
1419 dmu_tx_do_callbacks(&tx->tx_callbacks, ECANCELED);
1421 list_destroy(&tx->tx_callbacks);
1422 list_destroy(&tx->tx_holds);
1424 refcount_destroy_many(&tx->tx_space_written,
1425 refcount_count(&tx->tx_space_written));
1426 refcount_destroy_many(&tx->tx_space_freed,
1427 refcount_count(&tx->tx_space_freed));
1429 kmem_free(tx, sizeof (dmu_tx_t));
1433 dmu_tx_get_txg(dmu_tx_t *tx)
1435 ASSERT(tx->tx_txg != 0);
1436 return (tx->tx_txg);
1440 dmu_tx_pool(dmu_tx_t *tx)
1442 ASSERT(tx->tx_pool != NULL);
1443 return (tx->tx_pool);
1448 dmu_tx_callback_register(dmu_tx_t *tx, dmu_tx_callback_func_t *func, void *data)
1450 dmu_tx_callback_t *dcb;
1452 dcb = kmem_alloc(sizeof (dmu_tx_callback_t), KM_SLEEP);
1454 dcb->dcb_func = func;
1455 dcb->dcb_data = data;
1457 list_insert_tail(&tx->tx_callbacks, dcb);
1461 * Call all the commit callbacks on a list, with a given error code.
1464 dmu_tx_do_callbacks(list_t *cb_list, int error)
1466 dmu_tx_callback_t *dcb;
1468 while (dcb = list_head(cb_list)) {
1469 list_remove(cb_list, dcb);
1470 dcb->dcb_func(dcb->dcb_data, error);
1471 kmem_free(dcb, sizeof (dmu_tx_callback_t));
1476 * Interface to hold a bunch of attributes.
1477 * used for creating new files.
1478 * attrsize is the total size of all attributes
1479 * to be added during object creation
1481 * For updating/adding a single attribute dmu_tx_hold_sa() should be used.
1485 * hold necessary attribute name for attribute registration.
1486 * should be a very rare case where this is needed. If it does
1487 * happen it would only happen on the first write to the file system.
1490 dmu_tx_sa_registration_hold(sa_os_t *sa, dmu_tx_t *tx)
1494 if (!sa->sa_need_attr_registration)
1497 for (i = 0; i != sa->sa_num_attrs; i++) {
1498 if (!sa->sa_attr_table[i].sa_registered) {
1499 if (sa->sa_reg_attr_obj)
1500 dmu_tx_hold_zap(tx, sa->sa_reg_attr_obj,
1501 B_TRUE, sa->sa_attr_table[i].sa_name);
1503 dmu_tx_hold_zap(tx, DMU_NEW_OBJECT,
1504 B_TRUE, sa->sa_attr_table[i].sa_name);
1511 dmu_tx_hold_spill(dmu_tx_t *tx, uint64_t object)
1516 txh = dmu_tx_hold_object_impl(tx, tx->tx_objset, object,
1519 dn = txh->txh_dnode;
1524 /* If blkptr doesn't exist then add space to towrite */
1525 if (!(dn->dn_phys->dn_flags & DNODE_FLAG_SPILL_BLKPTR)) {
1526 txh->txh_space_towrite += SPA_MAXBLOCKSIZE;
1530 bp = &dn->dn_phys->dn_spill;
1531 if (dsl_dataset_block_freeable(dn->dn_objset->os_dsl_dataset,
1533 txh->txh_space_tooverwrite += SPA_MAXBLOCKSIZE;
1535 txh->txh_space_towrite += SPA_MAXBLOCKSIZE;
1536 if (!BP_IS_HOLE(bp))
1537 txh->txh_space_tounref += SPA_MAXBLOCKSIZE;
1542 dmu_tx_hold_sa_create(dmu_tx_t *tx, int attrsize)
1544 sa_os_t *sa = tx->tx_objset->os_sa;
1546 dmu_tx_hold_bonus(tx, DMU_NEW_OBJECT);
1548 if (tx->tx_objset->os_sa->sa_master_obj == 0)
1551 if (tx->tx_objset->os_sa->sa_layout_attr_obj)
1552 dmu_tx_hold_zap(tx, sa->sa_layout_attr_obj, B_TRUE, NULL);
1554 dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_LAYOUTS);
1555 dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_REGISTRY);
1556 dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
1557 dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
1560 dmu_tx_sa_registration_hold(sa, tx);
1562 if (attrsize <= DN_MAX_BONUSLEN && !sa->sa_force_spill)
1565 (void) dmu_tx_hold_object_impl(tx, tx->tx_objset, DMU_NEW_OBJECT,
1572 * dmu_tx_hold_sa(dmu_tx_t *tx, sa_handle_t *, attribute, add, size)
1574 * variable_size is the total size of all variable sized attributes
1575 * passed to this function. It is not the total size of all
1576 * variable size attributes that *may* exist on this object.
1579 dmu_tx_hold_sa(dmu_tx_t *tx, sa_handle_t *hdl, boolean_t may_grow)
1582 sa_os_t *sa = tx->tx_objset->os_sa;
1584 ASSERT(hdl != NULL);
1586 object = sa_handle_object(hdl);
1588 dmu_tx_hold_bonus(tx, object);
1590 if (tx->tx_objset->os_sa->sa_master_obj == 0)
1593 if (tx->tx_objset->os_sa->sa_reg_attr_obj == 0 ||
1594 tx->tx_objset->os_sa->sa_layout_attr_obj == 0) {
1595 dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_LAYOUTS);
1596 dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_REGISTRY);
1597 dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
1598 dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
1601 dmu_tx_sa_registration_hold(sa, tx);
1603 if (may_grow && tx->tx_objset->os_sa->sa_layout_attr_obj)
1604 dmu_tx_hold_zap(tx, sa->sa_layout_attr_obj, B_TRUE, NULL);
1606 if (sa->sa_force_spill || may_grow || hdl->sa_spill) {
1607 ASSERT(tx->tx_txg == 0);
1608 dmu_tx_hold_spill(tx, object);
1610 dmu_buf_impl_t *db = (dmu_buf_impl_t *)hdl->sa_bonus;
1615 if (dn->dn_have_spill) {
1616 ASSERT(tx->tx_txg == 0);
1617 dmu_tx_hold_spill(tx, object);