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 2009 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
26 #include <sys/zfs_context.h>
28 #include <sys/dnode.h>
30 #include <sys/dmu_impl.h>
31 #include <sys/dmu_tx.h>
32 #include <sys/dmu_objset.h>
33 #include <sys/dsl_dir.h>
34 #include <sys/dsl_dataset.h>
37 #include <sys/dmu_zfetch.h>
39 static int free_range_compar(const void *node1, const void *node2);
41 static kmem_cache_t *dnode_cache;
43 static dnode_phys_t dnode_phys_zero;
45 int zfs_default_bs = SPA_MINBLOCKSHIFT;
46 int zfs_default_ibs = DN_MAX_INDBLKSHIFT;
50 dnode_cons(void *arg, void *unused, int kmflag)
54 bzero(dn, sizeof (dnode_t));
56 rw_init(&dn->dn_struct_rwlock, NULL, RW_DEFAULT, NULL);
57 mutex_init(&dn->dn_mtx, NULL, MUTEX_DEFAULT, NULL);
58 mutex_init(&dn->dn_dbufs_mtx, NULL, MUTEX_DEFAULT, NULL);
59 cv_init(&dn->dn_notxholds, NULL, CV_DEFAULT, NULL);
61 refcount_create(&dn->dn_holds);
62 refcount_create(&dn->dn_tx_holds);
64 for (i = 0; i < TXG_SIZE; i++) {
65 avl_create(&dn->dn_ranges[i], free_range_compar,
66 sizeof (free_range_t),
67 offsetof(struct free_range, fr_node));
68 list_create(&dn->dn_dirty_records[i],
69 sizeof (dbuf_dirty_record_t),
70 offsetof(dbuf_dirty_record_t, dr_dirty_node));
73 list_create(&dn->dn_dbufs, sizeof (dmu_buf_impl_t),
74 offsetof(dmu_buf_impl_t, db_link));
81 dnode_dest(void *arg, void *unused)
86 rw_destroy(&dn->dn_struct_rwlock);
87 mutex_destroy(&dn->dn_mtx);
88 mutex_destroy(&dn->dn_dbufs_mtx);
89 cv_destroy(&dn->dn_notxholds);
90 refcount_destroy(&dn->dn_holds);
91 refcount_destroy(&dn->dn_tx_holds);
93 for (i = 0; i < TXG_SIZE; i++) {
94 avl_destroy(&dn->dn_ranges[i]);
95 list_destroy(&dn->dn_dirty_records[i]);
98 list_destroy(&dn->dn_dbufs);
104 dnode_cache = kmem_cache_create("dnode_t",
106 0, dnode_cons, dnode_dest, NULL, NULL, NULL, 0);
112 kmem_cache_destroy(dnode_cache);
118 dnode_verify(dnode_t *dn)
120 int drop_struct_lock = FALSE;
123 ASSERT(dn->dn_objset);
125 ASSERT(dn->dn_phys->dn_type < DMU_OT_NUMTYPES);
127 if (!(zfs_flags & ZFS_DEBUG_DNODE_VERIFY))
130 if (!RW_WRITE_HELD(&dn->dn_struct_rwlock)) {
131 rw_enter(&dn->dn_struct_rwlock, RW_READER);
132 drop_struct_lock = TRUE;
134 if (dn->dn_phys->dn_type != DMU_OT_NONE || dn->dn_allocated_txg != 0) {
136 ASSERT3U(dn->dn_indblkshift, >=, 0);
137 ASSERT3U(dn->dn_indblkshift, <=, SPA_MAXBLOCKSHIFT);
138 if (dn->dn_datablkshift) {
139 ASSERT3U(dn->dn_datablkshift, >=, SPA_MINBLOCKSHIFT);
140 ASSERT3U(dn->dn_datablkshift, <=, SPA_MAXBLOCKSHIFT);
141 ASSERT3U(1<<dn->dn_datablkshift, ==, dn->dn_datablksz);
143 ASSERT3U(dn->dn_nlevels, <=, 30);
144 ASSERT3U(dn->dn_type, <=, DMU_OT_NUMTYPES);
145 ASSERT3U(dn->dn_nblkptr, >=, 1);
146 ASSERT3U(dn->dn_nblkptr, <=, DN_MAX_NBLKPTR);
147 ASSERT3U(dn->dn_bonuslen, <=, DN_MAX_BONUSLEN);
148 ASSERT3U(dn->dn_datablksz, ==,
149 dn->dn_datablkszsec << SPA_MINBLOCKSHIFT);
150 ASSERT3U(ISP2(dn->dn_datablksz), ==, dn->dn_datablkshift != 0);
151 ASSERT3U((dn->dn_nblkptr - 1) * sizeof (blkptr_t) +
152 dn->dn_bonuslen, <=, DN_MAX_BONUSLEN);
153 for (i = 0; i < TXG_SIZE; i++) {
154 ASSERT3U(dn->dn_next_nlevels[i], <=, dn->dn_nlevels);
157 if (dn->dn_phys->dn_type != DMU_OT_NONE)
158 ASSERT3U(dn->dn_phys->dn_nlevels, <=, dn->dn_nlevels);
159 ASSERT(dn->dn_object == DMU_META_DNODE_OBJECT || dn->dn_dbuf != NULL);
160 if (dn->dn_dbuf != NULL) {
161 ASSERT3P(dn->dn_phys, ==,
162 (dnode_phys_t *)dn->dn_dbuf->db.db_data +
163 (dn->dn_object % (dn->dn_dbuf->db.db_size >> DNODE_SHIFT)));
165 if (drop_struct_lock)
166 rw_exit(&dn->dn_struct_rwlock);
171 dnode_byteswap(dnode_phys_t *dnp)
173 uint64_t *buf64 = (void*)&dnp->dn_blkptr;
176 if (dnp->dn_type == DMU_OT_NONE) {
177 bzero(dnp, sizeof (dnode_phys_t));
181 dnp->dn_datablkszsec = BSWAP_16(dnp->dn_datablkszsec);
182 dnp->dn_bonuslen = BSWAP_16(dnp->dn_bonuslen);
183 dnp->dn_maxblkid = BSWAP_64(dnp->dn_maxblkid);
184 dnp->dn_used = BSWAP_64(dnp->dn_used);
187 * dn_nblkptr is only one byte, so it's OK to read it in either
188 * byte order. We can't read dn_bouslen.
190 ASSERT(dnp->dn_indblkshift <= SPA_MAXBLOCKSHIFT);
191 ASSERT(dnp->dn_nblkptr <= DN_MAX_NBLKPTR);
192 for (i = 0; i < dnp->dn_nblkptr * sizeof (blkptr_t)/8; i++)
193 buf64[i] = BSWAP_64(buf64[i]);
196 * OK to check dn_bonuslen for zero, because it won't matter if
197 * we have the wrong byte order. This is necessary because the
198 * dnode dnode is smaller than a regular dnode.
200 if (dnp->dn_bonuslen != 0) {
202 * Note that the bonus length calculated here may be
203 * longer than the actual bonus buffer. This is because
204 * we always put the bonus buffer after the last block
205 * pointer (instead of packing it against the end of the
208 int off = (dnp->dn_nblkptr-1) * sizeof (blkptr_t);
209 size_t len = DN_MAX_BONUSLEN - off;
210 ASSERT3U(dnp->dn_bonustype, <, DMU_OT_NUMTYPES);
211 dmu_ot[dnp->dn_bonustype].ot_byteswap(dnp->dn_bonus + off, len);
216 dnode_buf_byteswap(void *vbuf, size_t size)
218 dnode_phys_t *buf = vbuf;
221 ASSERT3U(sizeof (dnode_phys_t), ==, (1<<DNODE_SHIFT));
222 ASSERT((size & (sizeof (dnode_phys_t)-1)) == 0);
224 size >>= DNODE_SHIFT;
225 for (i = 0; i < size; i++) {
232 free_range_compar(const void *node1, const void *node2)
234 const free_range_t *rp1 = node1;
235 const free_range_t *rp2 = node2;
237 if (rp1->fr_blkid < rp2->fr_blkid)
239 else if (rp1->fr_blkid > rp2->fr_blkid)
245 dnode_setbonuslen(dnode_t *dn, int newsize, dmu_tx_t *tx)
247 ASSERT3U(refcount_count(&dn->dn_holds), >=, 1);
249 dnode_setdirty(dn, tx);
250 rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
251 ASSERT3U(newsize, <=, DN_MAX_BONUSLEN -
252 (dn->dn_nblkptr-1) * sizeof (blkptr_t));
253 dn->dn_bonuslen = newsize;
255 dn->dn_next_bonuslen[tx->tx_txg & TXG_MASK] = DN_ZERO_BONUSLEN;
257 dn->dn_next_bonuslen[tx->tx_txg & TXG_MASK] = dn->dn_bonuslen;
258 rw_exit(&dn->dn_struct_rwlock);
262 dnode_setdblksz(dnode_t *dn, int size)
264 ASSERT3U(P2PHASE(size, SPA_MINBLOCKSIZE), ==, 0);
265 ASSERT3U(size, <=, SPA_MAXBLOCKSIZE);
266 ASSERT3U(size, >=, SPA_MINBLOCKSIZE);
267 ASSERT3U(size >> SPA_MINBLOCKSHIFT, <,
268 1<<(sizeof (dn->dn_phys->dn_datablkszsec) * 8));
269 dn->dn_datablksz = size;
270 dn->dn_datablkszsec = size >> SPA_MINBLOCKSHIFT;
271 dn->dn_datablkshift = ISP2(size) ? highbit(size - 1) : 0;
275 dnode_create(objset_impl_t *os, dnode_phys_t *dnp, dmu_buf_impl_t *db,
278 dnode_t *dn = kmem_cache_alloc(dnode_cache, KM_SLEEP);
279 (void) dnode_cons(dn, NULL, 0); /* XXX */
282 dn->dn_object = object;
286 if (dnp->dn_datablkszsec)
287 dnode_setdblksz(dn, dnp->dn_datablkszsec << SPA_MINBLOCKSHIFT);
288 dn->dn_indblkshift = dnp->dn_indblkshift;
289 dn->dn_nlevels = dnp->dn_nlevels;
290 dn->dn_type = dnp->dn_type;
291 dn->dn_nblkptr = dnp->dn_nblkptr;
292 dn->dn_checksum = dnp->dn_checksum;
293 dn->dn_compress = dnp->dn_compress;
294 dn->dn_bonustype = dnp->dn_bonustype;
295 dn->dn_bonuslen = dnp->dn_bonuslen;
296 dn->dn_maxblkid = dnp->dn_maxblkid;
298 dmu_zfetch_init(&dn->dn_zfetch, dn);
300 ASSERT(dn->dn_phys->dn_type < DMU_OT_NUMTYPES);
301 mutex_enter(&os->os_lock);
302 list_insert_head(&os->os_dnodes, dn);
303 mutex_exit(&os->os_lock);
305 arc_space_consume(sizeof (dnode_t), ARC_SPACE_OTHER);
310 dnode_destroy(dnode_t *dn)
312 objset_impl_t *os = dn->dn_objset;
317 for (i = 0; i < TXG_SIZE; i++) {
318 ASSERT(!list_link_active(&dn->dn_dirty_link[i]));
319 ASSERT(NULL == list_head(&dn->dn_dirty_records[i]));
320 ASSERT(0 == avl_numnodes(&dn->dn_ranges[i]));
322 ASSERT(NULL == list_head(&dn->dn_dbufs));
325 mutex_enter(&os->os_lock);
326 list_remove(&os->os_dnodes, dn);
327 mutex_exit(&os->os_lock);
329 if (dn->dn_dirtyctx_firstset) {
330 kmem_free(dn->dn_dirtyctx_firstset, 1);
331 dn->dn_dirtyctx_firstset = NULL;
333 dmu_zfetch_rele(&dn->dn_zfetch);
335 mutex_enter(&dn->dn_bonus->db_mtx);
336 dbuf_evict(dn->dn_bonus);
339 kmem_cache_free(dnode_cache, dn);
340 arc_space_return(sizeof (dnode_t), ARC_SPACE_OTHER);
344 dnode_allocate(dnode_t *dn, dmu_object_type_t ot, int blocksize, int ibs,
345 dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx)
350 blocksize = 1 << zfs_default_bs;
351 else if (blocksize > SPA_MAXBLOCKSIZE)
352 blocksize = SPA_MAXBLOCKSIZE;
354 blocksize = P2ROUNDUP(blocksize, SPA_MINBLOCKSIZE);
357 ibs = zfs_default_ibs;
359 ibs = MIN(MAX(ibs, DN_MIN_INDBLKSHIFT), DN_MAX_INDBLKSHIFT);
361 dprintf("os=%p obj=%llu txg=%llu blocksize=%d ibs=%d\n", dn->dn_objset,
362 dn->dn_object, tx->tx_txg, blocksize, ibs);
364 ASSERT(dn->dn_type == DMU_OT_NONE);
365 ASSERT(bcmp(dn->dn_phys, &dnode_phys_zero, sizeof (dnode_phys_t)) == 0);
366 ASSERT(dn->dn_phys->dn_type == DMU_OT_NONE);
367 ASSERT(ot != DMU_OT_NONE);
368 ASSERT3U(ot, <, DMU_OT_NUMTYPES);
369 ASSERT((bonustype == DMU_OT_NONE && bonuslen == 0) ||
370 (bonustype != DMU_OT_NONE && bonuslen != 0));
371 ASSERT3U(bonustype, <, DMU_OT_NUMTYPES);
372 ASSERT3U(bonuslen, <=, DN_MAX_BONUSLEN);
373 ASSERT(dn->dn_type == DMU_OT_NONE);
374 ASSERT3U(dn->dn_maxblkid, ==, 0);
375 ASSERT3U(dn->dn_allocated_txg, ==, 0);
376 ASSERT3U(dn->dn_assigned_txg, ==, 0);
377 ASSERT(refcount_is_zero(&dn->dn_tx_holds));
378 ASSERT3U(refcount_count(&dn->dn_holds), <=, 1);
379 ASSERT3P(list_head(&dn->dn_dbufs), ==, NULL);
381 for (i = 0; i < TXG_SIZE; i++) {
382 ASSERT3U(dn->dn_next_nlevels[i], ==, 0);
383 ASSERT3U(dn->dn_next_indblkshift[i], ==, 0);
384 ASSERT3U(dn->dn_next_bonuslen[i], ==, 0);
385 ASSERT3U(dn->dn_next_blksz[i], ==, 0);
386 ASSERT(!list_link_active(&dn->dn_dirty_link[i]));
387 ASSERT3P(list_head(&dn->dn_dirty_records[i]), ==, NULL);
388 ASSERT3U(avl_numnodes(&dn->dn_ranges[i]), ==, 0);
392 dnode_setdblksz(dn, blocksize);
393 dn->dn_indblkshift = ibs;
395 dn->dn_nblkptr = 1 + ((DN_MAX_BONUSLEN - bonuslen) >> SPA_BLKPTRSHIFT);
396 dn->dn_bonustype = bonustype;
397 dn->dn_bonuslen = bonuslen;
398 dn->dn_checksum = ZIO_CHECKSUM_INHERIT;
399 dn->dn_compress = ZIO_COMPRESS_INHERIT;
403 if (dn->dn_dirtyctx_firstset) {
404 kmem_free(dn->dn_dirtyctx_firstset, 1);
405 dn->dn_dirtyctx_firstset = NULL;
408 dn->dn_allocated_txg = tx->tx_txg;
410 dnode_setdirty(dn, tx);
411 dn->dn_next_indblkshift[tx->tx_txg & TXG_MASK] = ibs;
412 dn->dn_next_bonuslen[tx->tx_txg & TXG_MASK] = dn->dn_bonuslen;
413 dn->dn_next_blksz[tx->tx_txg & TXG_MASK] = dn->dn_datablksz;
417 dnode_reallocate(dnode_t *dn, dmu_object_type_t ot, int blocksize,
418 dmu_object_type_t bonustype, int bonuslen, dmu_tx_t *tx)
421 dmu_buf_impl_t *db = NULL;
423 ASSERT3U(blocksize, >=, SPA_MINBLOCKSIZE);
424 ASSERT3U(blocksize, <=, SPA_MAXBLOCKSIZE);
425 ASSERT3U(blocksize % SPA_MINBLOCKSIZE, ==, 0);
426 ASSERT(dn->dn_object != DMU_META_DNODE_OBJECT || dmu_tx_private_ok(tx));
427 ASSERT(tx->tx_txg != 0);
428 ASSERT((bonustype == DMU_OT_NONE && bonuslen == 0) ||
429 (bonustype != DMU_OT_NONE && bonuslen != 0));
430 ASSERT3U(bonustype, <, DMU_OT_NUMTYPES);
431 ASSERT3U(bonuslen, <=, DN_MAX_BONUSLEN);
433 for (i = 0; i < TXG_SIZE; i++)
434 ASSERT(!list_link_active(&dn->dn_dirty_link[i]));
436 /* clean up any unreferenced dbufs */
437 dnode_evict_dbufs(dn);
438 ASSERT3P(list_head(&dn->dn_dbufs), ==, NULL);
441 * XXX I should really have a generation number to tell if we
444 if (blocksize != dn->dn_datablksz ||
445 dn->dn_bonustype != bonustype || dn->dn_bonuslen != bonuslen) {
446 /* free all old data */
447 dnode_free_range(dn, 0, -1ULL, tx);
450 nblkptr = 1 + ((DN_MAX_BONUSLEN - bonuslen) >> SPA_BLKPTRSHIFT);
452 /* change blocksize */
453 rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
454 if (blocksize != dn->dn_datablksz &&
455 (!BP_IS_HOLE(&dn->dn_phys->dn_blkptr[0]) ||
456 list_head(&dn->dn_dbufs) != NULL)) {
457 db = dbuf_hold(dn, 0, FTAG);
458 dbuf_new_size(db, blocksize, tx);
460 dnode_setdblksz(dn, blocksize);
461 dnode_setdirty(dn, tx);
462 dn->dn_next_bonuslen[tx->tx_txg&TXG_MASK] = bonuslen;
463 dn->dn_next_blksz[tx->tx_txg&TXG_MASK] = blocksize;
464 if (dn->dn_nblkptr != nblkptr)
465 dn->dn_next_nblkptr[tx->tx_txg&TXG_MASK] = nblkptr;
466 rw_exit(&dn->dn_struct_rwlock);
473 /* change bonus size and type */
474 mutex_enter(&dn->dn_mtx);
475 dn->dn_bonustype = bonustype;
476 dn->dn_bonuslen = bonuslen;
477 dn->dn_nblkptr = nblkptr;
478 dn->dn_checksum = ZIO_CHECKSUM_INHERIT;
479 dn->dn_compress = ZIO_COMPRESS_INHERIT;
480 ASSERT3U(dn->dn_nblkptr, <=, DN_MAX_NBLKPTR);
482 /* fix up the bonus db_size */
484 dn->dn_bonus->db.db_size =
485 DN_MAX_BONUSLEN - (dn->dn_nblkptr-1) * sizeof (blkptr_t);
486 ASSERT(dn->dn_bonuslen <= dn->dn_bonus->db.db_size);
489 dn->dn_allocated_txg = tx->tx_txg;
490 mutex_exit(&dn->dn_mtx);
494 dnode_special_close(dnode_t *dn)
497 * Wait for final references to the dnode to clear. This can
498 * only happen if the arc is asyncronously evicting state that
499 * has a hold on this dnode while we are trying to evict this
502 while (refcount_count(&dn->dn_holds) > 0)
508 dnode_special_open(objset_impl_t *os, dnode_phys_t *dnp, uint64_t object)
510 dnode_t *dn = dnode_create(os, dnp, NULL, object);
516 dnode_buf_pageout(dmu_buf_t *db, void *arg)
518 dnode_t **children_dnodes = arg;
520 int epb = db->db_size >> DNODE_SHIFT;
522 for (i = 0; i < epb; i++) {
523 dnode_t *dn = children_dnodes[i];
530 * If there are holds on this dnode, then there should
531 * be holds on the dnode's containing dbuf as well; thus
532 * it wouldn't be eligable for eviction and this function
533 * would not have been called.
535 ASSERT(refcount_is_zero(&dn->dn_holds));
536 ASSERT(list_head(&dn->dn_dbufs) == NULL);
537 ASSERT(refcount_is_zero(&dn->dn_tx_holds));
539 for (n = 0; n < TXG_SIZE; n++)
540 ASSERT(!list_link_active(&dn->dn_dirty_link[n]));
542 children_dnodes[i] = NULL;
545 kmem_free(children_dnodes, epb * sizeof (dnode_t *));
550 * EINVAL - invalid object number.
552 * succeeds even for free dnodes.
555 dnode_hold_impl(objset_impl_t *os, uint64_t object, int flag,
556 void *tag, dnode_t **dnp)
559 int drop_struct_lock = FALSE;
564 dnode_t **children_dnodes;
567 * If you are holding the spa config lock as writer, you shouldn't
568 * be asking the DMU to do *anything*.
570 ASSERT(spa_config_held(os->os_spa, SCL_ALL, RW_WRITER) == 0);
572 if (object == 0 || object >= DN_MAX_OBJECT)
575 mdn = os->os_meta_dnode;
579 if (!RW_WRITE_HELD(&mdn->dn_struct_rwlock)) {
580 rw_enter(&mdn->dn_struct_rwlock, RW_READER);
581 drop_struct_lock = TRUE;
584 blk = dbuf_whichblock(mdn, object * sizeof (dnode_phys_t));
586 db = dbuf_hold(mdn, blk, FTAG);
587 if (drop_struct_lock)
588 rw_exit(&mdn->dn_struct_rwlock);
591 err = dbuf_read(db, NULL, DB_RF_CANFAIL);
597 ASSERT3U(db->db.db_size, >=, 1<<DNODE_SHIFT);
598 epb = db->db.db_size >> DNODE_SHIFT;
600 idx = object & (epb-1);
602 children_dnodes = dmu_buf_get_user(&db->db);
603 if (children_dnodes == NULL) {
605 children_dnodes = kmem_zalloc(epb * sizeof (dnode_t *),
607 if (winner = dmu_buf_set_user(&db->db, children_dnodes, NULL,
608 dnode_buf_pageout)) {
609 kmem_free(children_dnodes, epb * sizeof (dnode_t *));
610 children_dnodes = winner;
614 if ((dn = children_dnodes[idx]) == NULL) {
615 dnode_phys_t *dnp = (dnode_phys_t *)db->db.db_data+idx;
618 dn = dnode_create(os, dnp, db, object);
619 winner = atomic_cas_ptr(&children_dnodes[idx], NULL, dn);
620 if (winner != NULL) {
626 mutex_enter(&dn->dn_mtx);
628 if (dn->dn_free_txg ||
629 ((flag & DNODE_MUST_BE_ALLOCATED) && type == DMU_OT_NONE) ||
630 ((flag & DNODE_MUST_BE_FREE) && type != DMU_OT_NONE)) {
631 mutex_exit(&dn->dn_mtx);
633 return (type == DMU_OT_NONE ? ENOENT : EEXIST);
635 mutex_exit(&dn->dn_mtx);
637 if (refcount_add(&dn->dn_holds, tag) == 1)
638 dbuf_add_ref(db, dn);
641 ASSERT3P(dn->dn_dbuf, ==, db);
642 ASSERT3U(dn->dn_object, ==, object);
650 * Return held dnode if the object is allocated, NULL if not.
653 dnode_hold(objset_impl_t *os, uint64_t object, void *tag, dnode_t **dnp)
655 return (dnode_hold_impl(os, object, DNODE_MUST_BE_ALLOCATED, tag, dnp));
659 * Can only add a reference if there is already at least one
660 * reference on the dnode. Returns FALSE if unable to add a
664 dnode_add_ref(dnode_t *dn, void *tag)
666 mutex_enter(&dn->dn_mtx);
667 if (refcount_is_zero(&dn->dn_holds)) {
668 mutex_exit(&dn->dn_mtx);
671 VERIFY(1 < refcount_add(&dn->dn_holds, tag));
672 mutex_exit(&dn->dn_mtx);
677 dnode_rele(dnode_t *dn, void *tag)
681 mutex_enter(&dn->dn_mtx);
682 refs = refcount_remove(&dn->dn_holds, tag);
683 mutex_exit(&dn->dn_mtx);
684 /* NOTE: the DNODE_DNODE does not have a dn_dbuf */
685 if (refs == 0 && dn->dn_dbuf)
686 dbuf_rele(dn->dn_dbuf, dn);
690 dnode_setdirty(dnode_t *dn, dmu_tx_t *tx)
692 objset_impl_t *os = dn->dn_objset;
693 uint64_t txg = tx->tx_txg;
695 if (dn->dn_object == DMU_META_DNODE_OBJECT)
701 mutex_enter(&dn->dn_mtx);
702 ASSERT(dn->dn_phys->dn_type || dn->dn_allocated_txg);
703 /* ASSERT(dn->dn_free_txg == 0 || dn->dn_free_txg >= txg); */
704 mutex_exit(&dn->dn_mtx);
707 mutex_enter(&os->os_lock);
710 * If we are already marked dirty, we're done.
712 if (list_link_active(&dn->dn_dirty_link[txg & TXG_MASK])) {
713 mutex_exit(&os->os_lock);
717 ASSERT(!refcount_is_zero(&dn->dn_holds) || list_head(&dn->dn_dbufs));
718 ASSERT(dn->dn_datablksz != 0);
719 ASSERT3U(dn->dn_next_bonuslen[txg&TXG_MASK], ==, 0);
720 ASSERT3U(dn->dn_next_blksz[txg&TXG_MASK], ==, 0);
722 dprintf_ds(os->os_dsl_dataset, "obj=%llu txg=%llu\n",
725 if (dn->dn_free_txg > 0 && dn->dn_free_txg <= txg) {
726 list_insert_tail(&os->os_free_dnodes[txg&TXG_MASK], dn);
728 list_insert_tail(&os->os_dirty_dnodes[txg&TXG_MASK], dn);
731 mutex_exit(&os->os_lock);
734 * The dnode maintains a hold on its containing dbuf as
735 * long as there are holds on it. Each instantiated child
736 * dbuf maintaines a hold on the dnode. When the last child
737 * drops its hold, the dnode will drop its hold on the
738 * containing dbuf. We add a "dirty hold" here so that the
739 * dnode will hang around after we finish processing its
742 VERIFY(dnode_add_ref(dn, (void *)(uintptr_t)tx->tx_txg));
744 (void) dbuf_dirty(dn->dn_dbuf, tx);
746 dsl_dataset_dirty(os->os_dsl_dataset, tx);
750 dnode_free(dnode_t *dn, dmu_tx_t *tx)
752 int txgoff = tx->tx_txg & TXG_MASK;
754 dprintf("dn=%p txg=%llu\n", dn, tx->tx_txg);
756 /* we should be the only holder... hopefully */
757 /* ASSERT3U(refcount_count(&dn->dn_holds), ==, 1); */
759 mutex_enter(&dn->dn_mtx);
760 if (dn->dn_type == DMU_OT_NONE || dn->dn_free_txg) {
761 mutex_exit(&dn->dn_mtx);
764 dn->dn_free_txg = tx->tx_txg;
765 mutex_exit(&dn->dn_mtx);
768 * If the dnode is already dirty, it needs to be moved from
769 * the dirty list to the free list.
771 mutex_enter(&dn->dn_objset->os_lock);
772 if (list_link_active(&dn->dn_dirty_link[txgoff])) {
773 list_remove(&dn->dn_objset->os_dirty_dnodes[txgoff], dn);
774 list_insert_tail(&dn->dn_objset->os_free_dnodes[txgoff], dn);
775 mutex_exit(&dn->dn_objset->os_lock);
777 mutex_exit(&dn->dn_objset->os_lock);
778 dnode_setdirty(dn, tx);
783 * Try to change the block size for the indicated dnode. This can only
784 * succeed if there are no blocks allocated or dirty beyond first block
787 dnode_set_blksz(dnode_t *dn, uint64_t size, int ibs, dmu_tx_t *tx)
789 dmu_buf_impl_t *db, *db_next;
793 size = SPA_MINBLOCKSIZE;
794 if (size > SPA_MAXBLOCKSIZE)
795 size = SPA_MAXBLOCKSIZE;
797 size = P2ROUNDUP(size, SPA_MINBLOCKSIZE);
799 if (ibs == dn->dn_indblkshift)
802 if (size >> SPA_MINBLOCKSHIFT == dn->dn_datablkszsec && ibs == 0)
805 rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
807 /* Check for any allocated blocks beyond the first */
808 if (dn->dn_phys->dn_maxblkid != 0)
811 mutex_enter(&dn->dn_dbufs_mtx);
812 for (db = list_head(&dn->dn_dbufs); db; db = db_next) {
813 db_next = list_next(&dn->dn_dbufs, db);
815 if (db->db_blkid != 0 && db->db_blkid != DB_BONUS_BLKID) {
816 mutex_exit(&dn->dn_dbufs_mtx);
820 mutex_exit(&dn->dn_dbufs_mtx);
822 if (ibs && dn->dn_nlevels != 1)
825 /* resize the old block */
826 err = dbuf_hold_impl(dn, 0, 0, TRUE, FTAG, &db);
828 dbuf_new_size(db, size, tx);
829 else if (err != ENOENT)
832 dnode_setdblksz(dn, size);
833 dnode_setdirty(dn, tx);
834 dn->dn_next_blksz[tx->tx_txg&TXG_MASK] = size;
836 dn->dn_indblkshift = ibs;
837 dn->dn_next_indblkshift[tx->tx_txg&TXG_MASK] = ibs;
839 /* rele after we have fixed the blocksize in the dnode */
843 rw_exit(&dn->dn_struct_rwlock);
847 rw_exit(&dn->dn_struct_rwlock);
851 /* read-holding callers must not rely on the lock being continuously held */
853 dnode_new_blkid(dnode_t *dn, uint64_t blkid, dmu_tx_t *tx, boolean_t have_read)
855 uint64_t txgoff = tx->tx_txg & TXG_MASK;
856 int epbs, new_nlevels;
859 ASSERT(blkid != DB_BONUS_BLKID);
862 RW_READ_HELD(&dn->dn_struct_rwlock) :
863 RW_WRITE_HELD(&dn->dn_struct_rwlock));
866 * if we have a read-lock, check to see if we need to do any work
867 * before upgrading to a write-lock.
870 if (blkid <= dn->dn_maxblkid)
873 if (!rw_tryupgrade(&dn->dn_struct_rwlock)) {
874 rw_exit(&dn->dn_struct_rwlock);
875 rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
879 if (blkid <= dn->dn_maxblkid)
882 dn->dn_maxblkid = blkid;
885 * Compute the number of levels necessary to support the new maxblkid.
888 epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
889 for (sz = dn->dn_nblkptr;
890 sz <= blkid && sz >= dn->dn_nblkptr; sz <<= epbs)
893 if (new_nlevels > dn->dn_nlevels) {
894 int old_nlevels = dn->dn_nlevels;
897 dbuf_dirty_record_t *new, *dr, *dr_next;
899 dn->dn_nlevels = new_nlevels;
901 ASSERT3U(new_nlevels, >, dn->dn_next_nlevels[txgoff]);
902 dn->dn_next_nlevels[txgoff] = new_nlevels;
904 /* dirty the left indirects */
905 db = dbuf_hold_level(dn, old_nlevels, 0, FTAG);
906 new = dbuf_dirty(db, tx);
909 /* transfer the dirty records to the new indirect */
910 mutex_enter(&dn->dn_mtx);
911 mutex_enter(&new->dt.di.dr_mtx);
912 list = &dn->dn_dirty_records[txgoff];
913 for (dr = list_head(list); dr; dr = dr_next) {
914 dr_next = list_next(&dn->dn_dirty_records[txgoff], dr);
915 if (dr->dr_dbuf->db_level != new_nlevels-1 &&
916 dr->dr_dbuf->db_blkid != DB_BONUS_BLKID) {
917 ASSERT(dr->dr_dbuf->db_level == old_nlevels-1);
918 list_remove(&dn->dn_dirty_records[txgoff], dr);
919 list_insert_tail(&new->dt.di.dr_children, dr);
923 mutex_exit(&new->dt.di.dr_mtx);
924 mutex_exit(&dn->dn_mtx);
929 rw_downgrade(&dn->dn_struct_rwlock);
933 dnode_clear_range(dnode_t *dn, uint64_t blkid, uint64_t nblks, dmu_tx_t *tx)
935 avl_tree_t *tree = &dn->dn_ranges[tx->tx_txg&TXG_MASK];
938 free_range_t rp_tofind;
939 uint64_t endblk = blkid + nblks;
941 ASSERT(MUTEX_HELD(&dn->dn_mtx));
942 ASSERT(nblks <= UINT64_MAX - blkid); /* no overflow */
944 dprintf_dnode(dn, "blkid=%llu nblks=%llu txg=%llu\n",
945 blkid, nblks, tx->tx_txg);
946 rp_tofind.fr_blkid = blkid;
947 rp = avl_find(tree, &rp_tofind, &where);
949 rp = avl_nearest(tree, where, AVL_BEFORE);
951 rp = avl_nearest(tree, where, AVL_AFTER);
953 while (rp && (rp->fr_blkid <= blkid + nblks)) {
954 uint64_t fr_endblk = rp->fr_blkid + rp->fr_nblks;
955 free_range_t *nrp = AVL_NEXT(tree, rp);
957 if (blkid <= rp->fr_blkid && endblk >= fr_endblk) {
958 /* clear this entire range */
959 avl_remove(tree, rp);
960 kmem_free(rp, sizeof (free_range_t));
961 } else if (blkid <= rp->fr_blkid &&
962 endblk > rp->fr_blkid && endblk < fr_endblk) {
963 /* clear the beginning of this range */
964 rp->fr_blkid = endblk;
965 rp->fr_nblks = fr_endblk - endblk;
966 } else if (blkid > rp->fr_blkid && blkid < fr_endblk &&
967 endblk >= fr_endblk) {
968 /* clear the end of this range */
969 rp->fr_nblks = blkid - rp->fr_blkid;
970 } else if (blkid > rp->fr_blkid && endblk < fr_endblk) {
971 /* clear a chunk out of this range */
972 free_range_t *new_rp =
973 kmem_alloc(sizeof (free_range_t), KM_SLEEP);
975 new_rp->fr_blkid = endblk;
976 new_rp->fr_nblks = fr_endblk - endblk;
977 avl_insert_here(tree, new_rp, rp, AVL_AFTER);
978 rp->fr_nblks = blkid - rp->fr_blkid;
980 /* there may be no overlap */
986 dnode_free_range(dnode_t *dn, uint64_t off, uint64_t len, dmu_tx_t *tx)
989 uint64_t blkoff, blkid, nblks;
990 int blksz, blkshift, head, tail;
994 rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
995 blksz = dn->dn_datablksz;
996 blkshift = dn->dn_datablkshift;
997 epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
1000 len = UINT64_MAX - off;
1005 * First, block align the region to free:
1008 head = P2NPHASE(off, blksz);
1009 blkoff = P2PHASE(off, blksz);
1010 if ((off >> blkshift) > dn->dn_maxblkid)
1013 ASSERT(dn->dn_maxblkid == 0);
1014 if (off == 0 && len >= blksz) {
1015 /* Freeing the whole block; fast-track this request */
1019 } else if (off >= blksz) {
1020 /* Freeing past end-of-data */
1023 /* Freeing part of the block. */
1025 ASSERT3U(head, >, 0);
1029 /* zero out any partial block data at the start of the range */
1031 ASSERT3U(blkoff + head, ==, blksz);
1034 if (dbuf_hold_impl(dn, 0, dbuf_whichblock(dn, off), TRUE,
1038 /* don't dirty if it isn't on disk and isn't dirty */
1039 if (db->db_last_dirty ||
1040 (db->db_blkptr && !BP_IS_HOLE(db->db_blkptr))) {
1041 rw_exit(&dn->dn_struct_rwlock);
1042 dbuf_will_dirty(db, tx);
1043 rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
1044 data = db->db.db_data;
1045 bzero(data + blkoff, head);
1047 dbuf_rele(db, FTAG);
1053 /* If the range was less than one block, we're done */
1057 /* If the remaining range is past end of file, we're done */
1058 if ((off >> blkshift) > dn->dn_maxblkid)
1061 ASSERT(ISP2(blksz));
1065 tail = P2PHASE(len, blksz);
1067 ASSERT3U(P2PHASE(off, blksz), ==, 0);
1068 /* zero out any partial block data at the end of the range */
1072 if (dbuf_hold_impl(dn, 0, dbuf_whichblock(dn, off+len),
1073 TRUE, FTAG, &db) == 0) {
1074 /* don't dirty if not on disk and not dirty */
1075 if (db->db_last_dirty ||
1076 (db->db_blkptr && !BP_IS_HOLE(db->db_blkptr))) {
1077 rw_exit(&dn->dn_struct_rwlock);
1078 dbuf_will_dirty(db, tx);
1079 rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
1080 bzero(db->db.db_data, tail);
1082 dbuf_rele(db, FTAG);
1087 /* If the range did not include a full block, we are done */
1091 ASSERT(IS_P2ALIGNED(off, blksz));
1092 ASSERT(trunc || IS_P2ALIGNED(len, blksz));
1093 blkid = off >> blkshift;
1094 nblks = len >> blkshift;
1099 * Read in and mark all the level-1 indirects dirty,
1100 * so that they will stay in memory until syncing phase.
1101 * Always dirty the first and last indirect to make sure
1102 * we dirty all the partial indirects.
1104 if (dn->dn_nlevels > 1) {
1105 uint64_t i, first, last;
1106 int shift = epbs + dn->dn_datablkshift;
1108 first = blkid >> epbs;
1109 if (db = dbuf_hold_level(dn, 1, first, FTAG)) {
1110 dbuf_will_dirty(db, tx);
1111 dbuf_rele(db, FTAG);
1114 last = dn->dn_maxblkid >> epbs;
1116 last = (blkid + nblks - 1) >> epbs;
1117 if (last > first && (db = dbuf_hold_level(dn, 1, last, FTAG))) {
1118 dbuf_will_dirty(db, tx);
1119 dbuf_rele(db, FTAG);
1121 for (i = first + 1; i < last; i++) {
1122 uint64_t ibyte = i << shift;
1125 err = dnode_next_offset(dn,
1126 DNODE_FIND_HAVELOCK, &ibyte, 1, 1, 0);
1128 if (err == ESRCH || i >= last)
1131 db = dbuf_hold_level(dn, 1, i, FTAG);
1133 dbuf_will_dirty(db, tx);
1134 dbuf_rele(db, FTAG);
1140 * Add this range to the dnode range list.
1141 * We will finish up this free operation in the syncing phase.
1143 mutex_enter(&dn->dn_mtx);
1144 dnode_clear_range(dn, blkid, nblks, tx);
1146 free_range_t *rp, *found;
1148 avl_tree_t *tree = &dn->dn_ranges[tx->tx_txg&TXG_MASK];
1150 /* Add new range to dn_ranges */
1151 rp = kmem_alloc(sizeof (free_range_t), KM_SLEEP);
1152 rp->fr_blkid = blkid;
1153 rp->fr_nblks = nblks;
1154 found = avl_find(tree, rp, &where);
1155 ASSERT(found == NULL);
1156 avl_insert(tree, rp, where);
1157 dprintf_dnode(dn, "blkid=%llu nblks=%llu txg=%llu\n",
1158 blkid, nblks, tx->tx_txg);
1160 mutex_exit(&dn->dn_mtx);
1162 dbuf_free_range(dn, blkid, blkid + nblks - 1, tx);
1163 dnode_setdirty(dn, tx);
1165 if (trunc && dn->dn_maxblkid >= (off >> blkshift))
1166 dn->dn_maxblkid = (off >> blkshift ? (off >> blkshift) - 1 : 0);
1168 rw_exit(&dn->dn_struct_rwlock);
1171 /* return TRUE if this blkid was freed in a recent txg, or FALSE if it wasn't */
1173 dnode_block_freed(dnode_t *dn, uint64_t blkid)
1175 free_range_t range_tofind;
1176 void *dp = spa_get_dsl(dn->dn_objset->os_spa);
1179 if (blkid == DB_BONUS_BLKID)
1183 * If we're in the process of opening the pool, dp will not be
1184 * set yet, but there shouldn't be anything dirty.
1189 if (dn->dn_free_txg)
1193 * If dn_datablkshift is not set, then there's only a single
1194 * block, in which case there will never be a free range so it
1197 range_tofind.fr_blkid = blkid;
1198 mutex_enter(&dn->dn_mtx);
1199 for (i = 0; i < TXG_SIZE; i++) {
1200 free_range_t *range_found;
1203 range_found = avl_find(&dn->dn_ranges[i], &range_tofind, &idx);
1205 ASSERT(range_found->fr_nblks > 0);
1208 range_found = avl_nearest(&dn->dn_ranges[i], idx, AVL_BEFORE);
1210 range_found->fr_blkid + range_found->fr_nblks > blkid)
1213 mutex_exit(&dn->dn_mtx);
1214 return (i < TXG_SIZE);
1217 /* call from syncing context when we actually write/free space for this dnode */
1219 dnode_diduse_space(dnode_t *dn, int64_t delta)
1222 dprintf_dnode(dn, "dn=%p dnp=%p used=%llu delta=%lld\n",
1224 (u_longlong_t)dn->dn_phys->dn_used,
1227 mutex_enter(&dn->dn_mtx);
1228 space = DN_USED_BYTES(dn->dn_phys);
1230 ASSERT3U(space + delta, >=, space); /* no overflow */
1232 ASSERT3U(space, >=, -delta); /* no underflow */
1235 if (spa_version(dn->dn_objset->os_spa) < SPA_VERSION_DNODE_BYTES) {
1236 ASSERT((dn->dn_phys->dn_flags & DNODE_FLAG_USED_BYTES) == 0);
1237 ASSERT3U(P2PHASE(space, 1<<DEV_BSHIFT), ==, 0);
1238 dn->dn_phys->dn_used = space >> DEV_BSHIFT;
1240 dn->dn_phys->dn_used = space;
1241 dn->dn_phys->dn_flags |= DNODE_FLAG_USED_BYTES;
1243 mutex_exit(&dn->dn_mtx);
1247 * Call when we think we're going to write/free space in open context.
1248 * Be conservative (ie. OK to write less than this or free more than
1249 * this, but don't write more or free less).
1252 dnode_willuse_space(dnode_t *dn, int64_t space, dmu_tx_t *tx)
1254 objset_impl_t *os = dn->dn_objset;
1255 dsl_dataset_t *ds = os->os_dsl_dataset;
1258 space = spa_get_asize(os->os_spa, space);
1261 dsl_dir_willuse_space(ds->ds_dir, space, tx);
1263 dmu_tx_willuse_space(tx, space);
1267 dnode_next_offset_level(dnode_t *dn, int flags, uint64_t *offset,
1268 int lvl, uint64_t blkfill, uint64_t txg)
1270 dmu_buf_impl_t *db = NULL;
1272 uint64_t epbs = dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT;
1273 uint64_t epb = 1ULL << epbs;
1274 uint64_t minfill, maxfill;
1276 int i, inc, error, span;
1278 dprintf("probing object %llu offset %llx level %d of %u\n",
1279 dn->dn_object, *offset, lvl, dn->dn_phys->dn_nlevels);
1281 hole = flags & DNODE_FIND_HOLE;
1282 inc = (flags & DNODE_FIND_BACKWARDS) ? -1 : 1;
1283 ASSERT(txg == 0 || !hole);
1285 if (lvl == dn->dn_phys->dn_nlevels) {
1287 epb = dn->dn_phys->dn_nblkptr;
1288 data = dn->dn_phys->dn_blkptr;
1290 uint64_t blkid = dbuf_whichblock(dn, *offset) >> (epbs * lvl);
1291 error = dbuf_hold_impl(dn, lvl, blkid, TRUE, FTAG, &db);
1293 if (error != ENOENT)
1298 * This can only happen when we are searching up
1299 * the block tree for data. We don't really need to
1300 * adjust the offset, as we will just end up looking
1301 * at the pointer to this block in its parent, and its
1302 * going to be unallocated, so we will skip over it.
1306 error = dbuf_read(db, NULL, DB_RF_CANFAIL | DB_RF_HAVESTRUCT);
1308 dbuf_rele(db, FTAG);
1311 data = db->db.db_data;
1315 (db->db_blkptr == NULL || db->db_blkptr->blk_birth <= txg)) {
1317 * This can only happen when we are searching up the tree
1318 * and these conditions mean that we need to keep climbing.
1321 } else if (lvl == 0) {
1322 dnode_phys_t *dnp = data;
1324 ASSERT(dn->dn_type == DMU_OT_DNODE);
1326 for (i = (*offset >> span) & (blkfill - 1);
1327 i >= 0 && i < blkfill; i += inc) {
1328 boolean_t newcontents = B_TRUE;
1331 newcontents = B_FALSE;
1332 for (j = 0; j < dnp[i].dn_nblkptr; j++) {
1333 if (dnp[i].dn_blkptr[j].blk_birth > txg)
1334 newcontents = B_TRUE;
1337 if (!dnp[i].dn_type == hole && newcontents)
1339 *offset += (1ULL << span) * inc;
1341 if (i < 0 || i == blkfill)
1344 blkptr_t *bp = data;
1345 span = (lvl - 1) * epbs + dn->dn_datablkshift;
1347 maxfill = blkfill << ((lvl - 1) * epbs);
1354 for (i = (*offset >> span) & ((1ULL << epbs) - 1);
1355 i >= 0 && i < epb; i += inc) {
1356 if (bp[i].blk_fill >= minfill &&
1357 bp[i].blk_fill <= maxfill &&
1358 (hole || bp[i].blk_birth > txg))
1360 if (inc < 0 && *offset < (1ULL << span))
1363 *offset += (1ULL << span) * inc;
1365 if (i < 0 || i == epb)
1370 dbuf_rele(db, FTAG);
1376 * Find the next hole, data, or sparse region at or after *offset.
1377 * The value 'blkfill' tells us how many items we expect to find
1378 * in an L0 data block; this value is 1 for normal objects,
1379 * DNODES_PER_BLOCK for the meta dnode, and some fraction of
1380 * DNODES_PER_BLOCK when searching for sparse regions thereof.
1384 * dnode_next_offset(dn, flags, offset, 1, 1, 0);
1385 * Finds the next/previous hole/data in a file.
1386 * Used in dmu_offset_next().
1388 * dnode_next_offset(mdn, flags, offset, 0, DNODES_PER_BLOCK, txg);
1389 * Finds the next free/allocated dnode an objset's meta-dnode.
1390 * Only finds objects that have new contents since txg (ie.
1391 * bonus buffer changes and content removal are ignored).
1392 * Used in dmu_object_next().
1394 * dnode_next_offset(mdn, DNODE_FIND_HOLE, offset, 2, DNODES_PER_BLOCK >> 2, 0);
1395 * Finds the next L2 meta-dnode bp that's at most 1/4 full.
1396 * Used in dmu_object_alloc().
1399 dnode_next_offset(dnode_t *dn, int flags, uint64_t *offset,
1400 int minlvl, uint64_t blkfill, uint64_t txg)
1402 uint64_t initial_offset = *offset;
1406 if (!(flags & DNODE_FIND_HAVELOCK))
1407 rw_enter(&dn->dn_struct_rwlock, RW_READER);
1409 if (dn->dn_phys->dn_nlevels == 0) {
1414 if (dn->dn_datablkshift == 0) {
1415 if (*offset < dn->dn_datablksz) {
1416 if (flags & DNODE_FIND_HOLE)
1417 *offset = dn->dn_datablksz;
1424 maxlvl = dn->dn_phys->dn_nlevels;
1426 for (lvl = minlvl; lvl <= maxlvl; lvl++) {
1427 error = dnode_next_offset_level(dn,
1428 flags, offset, lvl, blkfill, txg);
1433 while (error == 0 && --lvl >= minlvl) {
1434 error = dnode_next_offset_level(dn,
1435 flags, offset, lvl, blkfill, txg);
1438 if (error == 0 && (flags & DNODE_FIND_BACKWARDS ?
1439 initial_offset < *offset : initial_offset > *offset))
1442 if (!(flags & DNODE_FIND_HAVELOCK))
1443 rw_exit(&dn->dn_struct_rwlock);