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) 2013 by Delphix. All rights reserved.
  25  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
  26  */
  27 
  28 #include <sys/zfs_context.h>
  29 #include <sys/dmu.h>
  30 #include <sys/dmu_send.h>
  31 #include <sys/dmu_impl.h>
  32 #include <sys/dbuf.h>
  33 #include <sys/dmu_objset.h>
  34 #include <sys/dsl_dataset.h>
  35 #include <sys/dsl_dir.h>
  36 #include <sys/dmu_tx.h>
  37 #include <sys/spa.h>
  38 #include <sys/zio.h>
  39 #include <sys/dmu_zfetch.h>
  40 #include <sys/sa.h>
  41 #include <sys/sa_impl.h>
  42 
  43 static void dbuf_destroy(dmu_buf_impl_t *db);
  44 static boolean_t dbuf_undirty(dmu_buf_impl_t *db, dmu_tx_t *tx);
  45 static void dbuf_write(dbuf_dirty_record_t *dr, arc_buf_t *data, dmu_tx_t *tx);
  46 
  47 /*
  48  * Global data structures and functions for the dbuf cache.
  49  */
  50 static kmem_cache_t *dbuf_cache;
  51 
  52 /* ARGSUSED */
  53 static int
  54 dbuf_cons(void *vdb, void *unused, int kmflag)
  55 {
  56         dmu_buf_impl_t *db = vdb;
  57         bzero(db, sizeof (dmu_buf_impl_t));
  58 
  59         mutex_init(&db->db_mtx, NULL, MUTEX_DEFAULT, NULL);
  60         cv_init(&db->db_changed, NULL, CV_DEFAULT, NULL);
  61         refcount_create(&db->db_holds);
  62         return (0);
  63 }
  64 
  65 /* ARGSUSED */
  66 static void
  67 dbuf_dest(void *vdb, void *unused)
  68 {
  69         dmu_buf_impl_t *db = vdb;
  70         mutex_destroy(&db->db_mtx);
  71         cv_destroy(&db->db_changed);
  72         refcount_destroy(&db->db_holds);
  73 }
  74 
  75 /*
  76  * dbuf hash table routines
  77  */
  78 static dbuf_hash_table_t dbuf_hash_table;
  79 
  80 static uint64_t dbuf_hash_count;
  81 
  82 static uint64_t
  83 dbuf_hash(void *os, uint64_t obj, uint8_t lvl, uint64_t blkid)
  84 {
  85         uintptr_t osv = (uintptr_t)os;
  86         uint64_t crc = -1ULL;
  87 
  88         ASSERT(zfs_crc64_table[128] == ZFS_CRC64_POLY);
  89         crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (lvl)) & 0xFF];
  90         crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (osv >> 6)) & 0xFF];
  91         crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (obj >> 0)) & 0xFF];
  92         crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (obj >> 8)) & 0xFF];
  93         crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (blkid >> 0)) & 0xFF];
  94         crc = (crc >> 8) ^ zfs_crc64_table[(crc ^ (blkid >> 8)) & 0xFF];
  95 
  96         crc ^= (osv>>14) ^ (obj>>16) ^ (blkid>>16);
  97 
  98         return (crc);
  99 }
 100 
 101 #define DBUF_HASH(os, obj, level, blkid) dbuf_hash(os, obj, level, blkid);
 102 
 103 #define DBUF_EQUAL(dbuf, os, obj, level, blkid)         \
 104         ((dbuf)->db.db_object == (obj) &&            \
 105         (dbuf)->db_objset == (os) &&                 \
 106         (dbuf)->db_level == (level) &&                       \
 107         (dbuf)->db_blkid == (blkid))
 108 
 109 dmu_buf_impl_t *
 110 dbuf_find(dnode_t *dn, uint8_t level, uint64_t blkid)
 111 {
 112         dbuf_hash_table_t *h = &dbuf_hash_table;
 113         objset_t *os = dn->dn_objset;
 114         uint64_t obj = dn->dn_object;
 115         uint64_t hv = DBUF_HASH(os, obj, level, blkid);
 116         uint64_t idx = hv & h->hash_table_mask;
 117         dmu_buf_impl_t *db;
 118 
 119         mutex_enter(DBUF_HASH_MUTEX(h, idx));
 120         for (db = h->hash_table[idx]; db != NULL; db = db->db_hash_next) {
 121                 if (DBUF_EQUAL(db, os, obj, level, blkid)) {
 122                         mutex_enter(&db->db_mtx);
 123                         if (db->db_state != DB_EVICTING) {
 124                                 mutex_exit(DBUF_HASH_MUTEX(h, idx));
 125                                 return (db);
 126                         }
 127                         mutex_exit(&db->db_mtx);
 128                 }
 129         }
 130         mutex_exit(DBUF_HASH_MUTEX(h, idx));
 131         return (NULL);
 132 }
 133 
 134 /*
 135  * Insert an entry into the hash table.  If there is already an element
 136  * equal to elem in the hash table, then the already existing element
 137  * will be returned and the new element will not be inserted.
 138  * Otherwise returns NULL.
 139  */
 140 static dmu_buf_impl_t *
 141 dbuf_hash_insert(dmu_buf_impl_t *db)
 142 {
 143         dbuf_hash_table_t *h = &dbuf_hash_table;
 144         objset_t *os = db->db_objset;
 145         uint64_t obj = db->db.db_object;
 146         int level = db->db_level;
 147         uint64_t blkid = db->db_blkid;
 148         uint64_t hv = DBUF_HASH(os, obj, level, blkid);
 149         uint64_t idx = hv & h->hash_table_mask;
 150         dmu_buf_impl_t *dbf;
 151 
 152         mutex_enter(DBUF_HASH_MUTEX(h, idx));
 153         for (dbf = h->hash_table[idx]; dbf != NULL; dbf = dbf->db_hash_next) {
 154                 if (DBUF_EQUAL(dbf, os, obj, level, blkid)) {
 155                         mutex_enter(&dbf->db_mtx);
 156                         if (dbf->db_state != DB_EVICTING) {
 157                                 mutex_exit(DBUF_HASH_MUTEX(h, idx));
 158                                 return (dbf);
 159                         }
 160                         mutex_exit(&dbf->db_mtx);
 161                 }
 162         }
 163 
 164         mutex_enter(&db->db_mtx);
 165         db->db_hash_next = h->hash_table[idx];
 166         h->hash_table[idx] = db;
 167         mutex_exit(DBUF_HASH_MUTEX(h, idx));
 168         atomic_add_64(&dbuf_hash_count, 1);
 169 
 170         return (NULL);
 171 }
 172 
 173 /*
 174  * Remove an entry from the hash table.  This operation will
 175  * fail if there are any existing holds on the db.
 176  */
 177 static void
 178 dbuf_hash_remove(dmu_buf_impl_t *db)
 179 {
 180         dbuf_hash_table_t *h = &dbuf_hash_table;
 181         uint64_t hv = DBUF_HASH(db->db_objset, db->db.db_object,
 182             db->db_level, db->db_blkid);
 183         uint64_t idx = hv & h->hash_table_mask;
 184         dmu_buf_impl_t *dbf, **dbp;
 185 
 186         /*
 187          * We musn't hold db_mtx to maintin lock ordering:
 188          * DBUF_HASH_MUTEX > db_mtx.
 189          */
 190         ASSERT(refcount_is_zero(&db->db_holds));
 191         ASSERT(db->db_state == DB_EVICTING);
 192         ASSERT(!MUTEX_HELD(&db->db_mtx));
 193 
 194         mutex_enter(DBUF_HASH_MUTEX(h, idx));
 195         dbp = &h->hash_table[idx];
 196         while ((dbf = *dbp) != db) {
 197                 dbp = &dbf->db_hash_next;
 198                 ASSERT(dbf != NULL);
 199         }
 200         *dbp = db->db_hash_next;
 201         db->db_hash_next = NULL;
 202         mutex_exit(DBUF_HASH_MUTEX(h, idx));
 203         atomic_add_64(&dbuf_hash_count, -1);
 204 }
 205 
 206 static arc_evict_func_t dbuf_do_evict;
 207 
 208 static void
 209 dbuf_evict_user(dmu_buf_impl_t *db)
 210 {
 211         ASSERT(MUTEX_HELD(&db->db_mtx));
 212 
 213         if (db->db_level != 0 || db->db_evict_func == NULL)
 214                 return;
 215 
 216         if (db->db_user_data_ptr_ptr)
 217                 *db->db_user_data_ptr_ptr = db->db.db_data;
 218         db->db_evict_func(&db->db, db->db_user_ptr);
 219         db->db_user_ptr = NULL;
 220         db->db_user_data_ptr_ptr = NULL;
 221         db->db_evict_func = NULL;
 222 }
 223 
 224 boolean_t
 225 dbuf_is_metadata(dmu_buf_impl_t *db)
 226 {
 227         if (db->db_level > 0) {
 228                 return (B_TRUE);
 229         } else {
 230                 boolean_t is_metadata;
 231 
 232                 DB_DNODE_ENTER(db);
 233                 is_metadata = DMU_OT_IS_METADATA(DB_DNODE(db)->dn_type);
 234                 DB_DNODE_EXIT(db);
 235 
 236                 return (is_metadata);
 237         }
 238 }
 239 
 240 void
 241 dbuf_evict(dmu_buf_impl_t *db)
 242 {
 243         ASSERT(MUTEX_HELD(&db->db_mtx));
 244         ASSERT(db->db_buf == NULL);
 245         ASSERT(db->db_data_pending == NULL);
 246 
 247         dbuf_clear(db);
 248         dbuf_destroy(db);
 249 }
 250 
 251 void
 252 dbuf_init(void)
 253 {
 254         uint64_t hsize = 1ULL << 16;
 255         dbuf_hash_table_t *h = &dbuf_hash_table;
 256         int i;
 257 
 258         /*
 259          * The hash table is big enough to fill all of physical memory
 260          * with an average 4K block size.  The table will take up
 261          * totalmem*sizeof(void*)/4K (i.e. 2MB/GB with 8-byte pointers).
 262          */
 263         while (hsize * 4096 < physmem * PAGESIZE)
 264                 hsize <<= 1;
 265 
 266 retry:
 267         h->hash_table_mask = hsize - 1;
 268         h->hash_table = kmem_zalloc(hsize * sizeof (void *), KM_NOSLEEP);
 269         if (h->hash_table == NULL) {
 270                 /* XXX - we should really return an error instead of assert */
 271                 ASSERT(hsize > (1ULL << 10));
 272                 hsize >>= 1;
 273                 goto retry;
 274         }
 275 
 276         dbuf_cache = kmem_cache_create("dmu_buf_impl_t",
 277             sizeof (dmu_buf_impl_t),
 278             0, dbuf_cons, dbuf_dest, NULL, NULL, NULL, 0);
 279 
 280         for (i = 0; i < DBUF_MUTEXES; i++)
 281                 mutex_init(&h->hash_mutexes[i], NULL, MUTEX_DEFAULT, NULL);
 282 }
 283 
 284 void
 285 dbuf_fini(void)
 286 {
 287         dbuf_hash_table_t *h = &dbuf_hash_table;
 288         int i;
 289 
 290         for (i = 0; i < DBUF_MUTEXES; i++)
 291                 mutex_destroy(&h->hash_mutexes[i]);
 292         kmem_free(h->hash_table, (h->hash_table_mask + 1) * sizeof (void *));
 293         kmem_cache_destroy(dbuf_cache);
 294 }
 295 
 296 /*
 297  * Other stuff.
 298  */
 299 
 300 #ifdef ZFS_DEBUG
 301 static void
 302 dbuf_verify(dmu_buf_impl_t *db)
 303 {
 304         dnode_t *dn;
 305         dbuf_dirty_record_t *dr;
 306 
 307         ASSERT(MUTEX_HELD(&db->db_mtx));
 308 
 309         if (!(zfs_flags & ZFS_DEBUG_DBUF_VERIFY))
 310                 return;
 311 
 312         ASSERT(db->db_objset != NULL);
 313         DB_DNODE_ENTER(db);
 314         dn = DB_DNODE(db);
 315         if (dn == NULL) {
 316                 ASSERT(db->db_parent == NULL);
 317                 ASSERT(db->db_blkptr == NULL);
 318         } else {
 319                 ASSERT3U(db->db.db_object, ==, dn->dn_object);
 320                 ASSERT3P(db->db_objset, ==, dn->dn_objset);
 321                 ASSERT3U(db->db_level, <, dn->dn_nlevels);
 322                 ASSERT(db->db_blkid == DMU_BONUS_BLKID ||
 323                     db->db_blkid == DMU_SPILL_BLKID ||
 324                     !list_is_empty(&dn->dn_dbufs));
 325         }
 326         if (db->db_blkid == DMU_BONUS_BLKID) {
 327                 ASSERT(dn != NULL);
 328                 ASSERT3U(db->db.db_size, >=, dn->dn_bonuslen);
 329                 ASSERT3U(db->db.db_offset, ==, DMU_BONUS_BLKID);
 330         } else if (db->db_blkid == DMU_SPILL_BLKID) {
 331                 ASSERT(dn != NULL);
 332                 ASSERT3U(db->db.db_size, >=, dn->dn_bonuslen);
 333                 ASSERT0(db->db.db_offset);
 334         } else {
 335                 ASSERT3U(db->db.db_offset, ==, db->db_blkid * db->db.db_size);
 336         }
 337 
 338         for (dr = db->db_data_pending; dr != NULL; dr = dr->dr_next)
 339                 ASSERT(dr->dr_dbuf == db);
 340 
 341         for (dr = db->db_last_dirty; dr != NULL; dr = dr->dr_next)
 342                 ASSERT(dr->dr_dbuf == db);
 343 
 344         /*
 345          * We can't assert that db_size matches dn_datablksz because it
 346          * can be momentarily different when another thread is doing
 347          * dnode_set_blksz().
 348          */
 349         if (db->db_level == 0 && db->db.db_object == DMU_META_DNODE_OBJECT) {
 350                 dr = db->db_data_pending;
 351                 /*
 352                  * It should only be modified in syncing context, so
 353                  * make sure we only have one copy of the data.
 354                  */
 355                 ASSERT(dr == NULL || dr->dt.dl.dr_data == db->db_buf);
 356         }
 357 
 358         /* verify db->db_blkptr */
 359         if (db->db_blkptr) {
 360                 if (db->db_parent == dn->dn_dbuf) {
 361                         /* db is pointed to by the dnode */
 362                         /* ASSERT3U(db->db_blkid, <, dn->dn_nblkptr); */
 363                         if (DMU_OBJECT_IS_SPECIAL(db->db.db_object))
 364                                 ASSERT(db->db_parent == NULL);
 365                         else
 366                                 ASSERT(db->db_parent != NULL);
 367                         if (db->db_blkid != DMU_SPILL_BLKID)
 368                                 ASSERT3P(db->db_blkptr, ==,
 369                                     &dn->dn_phys->dn_blkptr[db->db_blkid]);
 370                 } else {
 371                         /* db is pointed to by an indirect block */
 372                         int epb = db->db_parent->db.db_size >> SPA_BLKPTRSHIFT;
 373                         ASSERT3U(db->db_parent->db_level, ==, db->db_level+1);
 374                         ASSERT3U(db->db_parent->db.db_object, ==,
 375                             db->db.db_object);
 376                         /*
 377                          * dnode_grow_indblksz() can make this fail if we don't
 378                          * have the struct_rwlock.  XXX indblksz no longer
 379                          * grows.  safe to do this now?
 380                          */
 381                         if (RW_WRITE_HELD(&dn->dn_struct_rwlock)) {
 382                                 ASSERT3P(db->db_blkptr, ==,
 383                                     ((blkptr_t *)db->db_parent->db.db_data +
 384                                     db->db_blkid % epb));
 385                         }
 386                 }
 387         }
 388         if ((db->db_blkptr == NULL || BP_IS_HOLE(db->db_blkptr)) &&
 389             (db->db_buf == NULL || db->db_buf->b_data) &&
 390             db->db.db_data && db->db_blkid != DMU_BONUS_BLKID &&
 391             db->db_state != DB_FILL && !dn->dn_free_txg) {
 392                 /*
 393                  * If the blkptr isn't set but they have nonzero data,
 394                  * it had better be dirty, otherwise we'll lose that
 395                  * data when we evict this buffer.
 396                  */
 397                 if (db->db_dirtycnt == 0) {
 398                         uint64_t *buf = db->db.db_data;
 399                         int i;
 400 
 401                         for (i = 0; i < db->db.db_size >> 3; i++) {
 402                                 ASSERT(buf[i] == 0);
 403                         }
 404                 }
 405         }
 406         DB_DNODE_EXIT(db);
 407 }
 408 #endif
 409 
 410 static void
 411 dbuf_update_data(dmu_buf_impl_t *db)
 412 {
 413         ASSERT(MUTEX_HELD(&db->db_mtx));
 414         if (db->db_level == 0 && db->db_user_data_ptr_ptr) {
 415                 ASSERT(!refcount_is_zero(&db->db_holds));
 416                 *db->db_user_data_ptr_ptr = db->db.db_data;
 417         }
 418 }
 419 
 420 static void
 421 dbuf_set_data(dmu_buf_impl_t *db, arc_buf_t *buf)
 422 {
 423         ASSERT(MUTEX_HELD(&db->db_mtx));
 424         ASSERT(db->db_buf == NULL || !arc_has_callback(db->db_buf));
 425         db->db_buf = buf;
 426         if (buf != NULL) {
 427                 ASSERT(buf->b_data != NULL);
 428                 db->db.db_data = buf->b_data;
 429                 if (!arc_released(buf))
 430                         arc_set_callback(buf, dbuf_do_evict, db);
 431                 dbuf_update_data(db);
 432         } else {
 433                 dbuf_evict_user(db);
 434                 db->db.db_data = NULL;
 435                 if (db->db_state != DB_NOFILL)
 436                         db->db_state = DB_UNCACHED;
 437         }
 438 }
 439 
 440 /*
 441  * Loan out an arc_buf for read.  Return the loaned arc_buf.
 442  */
 443 arc_buf_t *
 444 dbuf_loan_arcbuf(dmu_buf_impl_t *db)
 445 {
 446         arc_buf_t *abuf;
 447 
 448         mutex_enter(&db->db_mtx);
 449         if (arc_released(db->db_buf) || refcount_count(&db->db_holds) > 1) {
 450                 int blksz = db->db.db_size;
 451                 spa_t *spa;
 452 
 453                 mutex_exit(&db->db_mtx);
 454                 DB_GET_SPA(&spa, db);
 455                 abuf = arc_loan_buf(spa, blksz);
 456                 bcopy(db->db.db_data, abuf->b_data, blksz);
 457         } else {
 458                 abuf = db->db_buf;
 459                 arc_loan_inuse_buf(abuf, db);
 460                 dbuf_set_data(db, NULL);
 461                 mutex_exit(&db->db_mtx);
 462         }
 463         return (abuf);
 464 }
 465 
 466 uint64_t
 467 dbuf_whichblock(dnode_t *dn, uint64_t offset)
 468 {
 469         if (dn->dn_datablkshift) {
 470                 return (offset >> dn->dn_datablkshift);
 471         } else {
 472                 ASSERT3U(offset, <, dn->dn_datablksz);
 473                 return (0);
 474         }
 475 }
 476 
 477 static void
 478 dbuf_read_done(zio_t *zio, arc_buf_t *buf, void *vdb)
 479 {
 480         dmu_buf_impl_t *db = vdb;
 481 
 482         mutex_enter(&db->db_mtx);
 483         ASSERT3U(db->db_state, ==, DB_READ);
 484         /*
 485          * All reads are synchronous, so we must have a hold on the dbuf
 486          */
 487         ASSERT(refcount_count(&db->db_holds) > 0);
 488         ASSERT(db->db_buf == NULL);
 489         ASSERT(db->db.db_data == NULL);
 490         if (db->db_level == 0 && db->db_freed_in_flight) {
 491                 /* we were freed in flight; disregard any error */
 492                 arc_release(buf, db);
 493                 bzero(buf->b_data, db->db.db_size);
 494                 arc_buf_freeze(buf);
 495                 db->db_freed_in_flight = FALSE;
 496                 dbuf_set_data(db, buf);
 497                 db->db_state = DB_CACHED;
 498         } else if (zio == NULL || zio->io_error == 0) {
 499                 dbuf_set_data(db, buf);
 500                 db->db_state = DB_CACHED;
 501         } else {
 502                 ASSERT(db->db_blkid != DMU_BONUS_BLKID);
 503                 ASSERT3P(db->db_buf, ==, NULL);
 504                 VERIFY(arc_buf_remove_ref(buf, db));
 505                 db->db_state = DB_UNCACHED;
 506         }
 507         cv_broadcast(&db->db_changed);
 508         dbuf_rele_and_unlock(db, NULL);
 509 }
 510 
 511 static void
 512 dbuf_read_impl(dmu_buf_impl_t *db, zio_t *zio, uint32_t *flags)
 513 {
 514         dnode_t *dn;
 515         spa_t *spa;
 516         zbookmark_t zb;
 517         uint32_t aflags = ARC_NOWAIT;
 518 
 519         DB_DNODE_ENTER(db);
 520         dn = DB_DNODE(db);
 521         ASSERT(!refcount_is_zero(&db->db_holds));
 522         /* We need the struct_rwlock to prevent db_blkptr from changing. */
 523         ASSERT(RW_LOCK_HELD(&dn->dn_struct_rwlock));
 524         ASSERT(MUTEX_HELD(&db->db_mtx));
 525         ASSERT(db->db_state == DB_UNCACHED);
 526         ASSERT(db->db_buf == NULL);
 527 
 528         if (db->db_blkid == DMU_BONUS_BLKID) {
 529                 int bonuslen = MIN(dn->dn_bonuslen, dn->dn_phys->dn_bonuslen);
 530 
 531                 ASSERT3U(bonuslen, <=, db->db.db_size);
 532                 db->db.db_data = zio_buf_alloc(DN_MAX_BONUSLEN);
 533                 arc_space_consume(DN_MAX_BONUSLEN, ARC_SPACE_OTHER);
 534                 if (bonuslen < DN_MAX_BONUSLEN)
 535                         bzero(db->db.db_data, DN_MAX_BONUSLEN);
 536                 if (bonuslen)
 537                         bcopy(DN_BONUS(dn->dn_phys), db->db.db_data, bonuslen);
 538                 DB_DNODE_EXIT(db);
 539                 dbuf_update_data(db);
 540                 db->db_state = DB_CACHED;
 541                 mutex_exit(&db->db_mtx);
 542                 return;
 543         }
 544 
 545         /*
 546          * Recheck BP_IS_HOLE() after dnode_block_freed() in case dnode_sync()
 547          * processes the delete record and clears the bp while we are waiting
 548          * for the dn_mtx (resulting in a "no" from block_freed).
 549          */
 550         if (db->db_blkptr == NULL || BP_IS_HOLE(db->db_blkptr) ||
 551             (db->db_level == 0 && (dnode_block_freed(dn, db->db_blkid) ||
 552             BP_IS_HOLE(db->db_blkptr)))) {
 553                 arc_buf_contents_t type = DBUF_GET_BUFC_TYPE(db);
 554 
 555                 dbuf_set_data(db, arc_buf_alloc(dn->dn_objset->os_spa,
 556                     db->db.db_size, db, type));
 557                 DB_DNODE_EXIT(db);
 558                 bzero(db->db.db_data, db->db.db_size);
 559                 db->db_state = DB_CACHED;
 560                 *flags |= DB_RF_CACHED;
 561                 mutex_exit(&db->db_mtx);
 562                 return;
 563         }
 564 
 565         spa = dn->dn_objset->os_spa;
 566         DB_DNODE_EXIT(db);
 567 
 568         db->db_state = DB_READ;
 569         mutex_exit(&db->db_mtx);
 570 
 571         if (DBUF_IS_L2CACHEABLE(db))
 572                 aflags |= ARC_L2CACHE;
 573         if (DBUF_IS_L2COMPRESSIBLE(db))
 574                 aflags |= ARC_L2COMPRESS;
 575 
 576         SET_BOOKMARK(&zb, db->db_objset->os_dsl_dataset ?
 577             db->db_objset->os_dsl_dataset->ds_object : DMU_META_OBJSET,
 578             db->db.db_object, db->db_level, db->db_blkid);
 579 
 580         dbuf_add_ref(db, NULL);
 581 
 582         (void) arc_read(zio, spa, db->db_blkptr,
 583             dbuf_read_done, db, ZIO_PRIORITY_SYNC_READ,
 584             (*flags & DB_RF_CANFAIL) ? ZIO_FLAG_CANFAIL : ZIO_FLAG_MUSTSUCCEED,
 585             &aflags, &zb);
 586         if (aflags & ARC_CACHED)
 587                 *flags |= DB_RF_CACHED;
 588 }
 589 
 590 int
 591 dbuf_read(dmu_buf_impl_t *db, zio_t *zio, uint32_t flags)
 592 {
 593         int err = 0;
 594         int havepzio = (zio != NULL);
 595         int prefetch;
 596         dnode_t *dn;
 597 
 598         /*
 599          * We don't have to hold the mutex to check db_state because it
 600          * can't be freed while we have a hold on the buffer.
 601          */
 602         ASSERT(!refcount_is_zero(&db->db_holds));
 603 
 604         if (db->db_state == DB_NOFILL)
 605                 return (SET_ERROR(EIO));
 606 
 607         DB_DNODE_ENTER(db);
 608         dn = DB_DNODE(db);
 609         if ((flags & DB_RF_HAVESTRUCT) == 0)
 610                 rw_enter(&dn->dn_struct_rwlock, RW_READER);
 611 
 612         prefetch = db->db_level == 0 && db->db_blkid != DMU_BONUS_BLKID &&
 613             (flags & DB_RF_NOPREFETCH) == 0 && dn != NULL &&
 614             DBUF_IS_CACHEABLE(db);
 615 
 616         mutex_enter(&db->db_mtx);
 617         if (db->db_state == DB_CACHED) {
 618                 mutex_exit(&db->db_mtx);
 619                 if (prefetch)
 620                         dmu_zfetch(&dn->dn_zfetch, db->db.db_offset,
 621                             db->db.db_size, TRUE);
 622                 if ((flags & DB_RF_HAVESTRUCT) == 0)
 623                         rw_exit(&dn->dn_struct_rwlock);
 624                 DB_DNODE_EXIT(db);
 625         } else if (db->db_state == DB_UNCACHED) {
 626                 spa_t *spa = dn->dn_objset->os_spa;
 627 
 628                 if (zio == NULL)
 629                         zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CANFAIL);
 630                 dbuf_read_impl(db, zio, &flags);
 631 
 632                 /* dbuf_read_impl has dropped db_mtx for us */
 633 
 634                 if (prefetch)
 635                         dmu_zfetch(&dn->dn_zfetch, db->db.db_offset,
 636                             db->db.db_size, flags & DB_RF_CACHED);
 637 
 638                 if ((flags & DB_RF_HAVESTRUCT) == 0)
 639                         rw_exit(&dn->dn_struct_rwlock);
 640                 DB_DNODE_EXIT(db);
 641 
 642                 if (!havepzio)
 643                         err = zio_wait(zio);
 644         } else {
 645                 /*
 646                  * Another reader came in while the dbuf was in flight
 647                  * between UNCACHED and CACHED.  Either a writer will finish
 648                  * writing the buffer (sending the dbuf to CACHED) or the
 649                  * first reader's request will reach the read_done callback
 650                  * and send the dbuf to CACHED.  Otherwise, a failure
 651                  * occurred and the dbuf went to UNCACHED.
 652                  */
 653                 mutex_exit(&db->db_mtx);
 654                 if (prefetch)
 655                         dmu_zfetch(&dn->dn_zfetch, db->db.db_offset,
 656                             db->db.db_size, TRUE);
 657                 if ((flags & DB_RF_HAVESTRUCT) == 0)
 658                         rw_exit(&dn->dn_struct_rwlock);
 659                 DB_DNODE_EXIT(db);
 660 
 661                 /* Skip the wait per the caller's request. */
 662                 mutex_enter(&db->db_mtx);
 663                 if ((flags & DB_RF_NEVERWAIT) == 0) {
 664                         while (db->db_state == DB_READ ||
 665                             db->db_state == DB_FILL) {
 666                                 ASSERT(db->db_state == DB_READ ||
 667                                     (flags & DB_RF_HAVESTRUCT) == 0);
 668                                 cv_wait(&db->db_changed, &db->db_mtx);
 669                         }
 670                         if (db->db_state == DB_UNCACHED)
 671                                 err = SET_ERROR(EIO);
 672                 }
 673                 mutex_exit(&db->db_mtx);
 674         }
 675 
 676         ASSERT(err || havepzio || db->db_state == DB_CACHED);
 677         return (err);
 678 }
 679 
 680 static void
 681 dbuf_noread(dmu_buf_impl_t *db)
 682 {
 683         ASSERT(!refcount_is_zero(&db->db_holds));
 684         ASSERT(db->db_blkid != DMU_BONUS_BLKID);
 685         mutex_enter(&db->db_mtx);
 686         while (db->db_state == DB_READ || db->db_state == DB_FILL)
 687                 cv_wait(&db->db_changed, &db->db_mtx);
 688         if (db->db_state == DB_UNCACHED) {
 689                 arc_buf_contents_t type = DBUF_GET_BUFC_TYPE(db);
 690                 spa_t *spa;
 691 
 692                 ASSERT(db->db_buf == NULL);
 693                 ASSERT(db->db.db_data == NULL);
 694                 DB_GET_SPA(&spa, db);
 695                 dbuf_set_data(db, arc_buf_alloc(spa, db->db.db_size, db, type));
 696                 db->db_state = DB_FILL;
 697         } else if (db->db_state == DB_NOFILL) {
 698                 dbuf_set_data(db, NULL);
 699         } else {
 700                 ASSERT3U(db->db_state, ==, DB_CACHED);
 701         }
 702         mutex_exit(&db->db_mtx);
 703 }
 704 
 705 /*
 706  * This is our just-in-time copy function.  It makes a copy of
 707  * buffers, that have been modified in a previous transaction
 708  * group, before we modify them in the current active group.
 709  *
 710  * This function is used in two places: when we are dirtying a
 711  * buffer for the first time in a txg, and when we are freeing
 712  * a range in a dnode that includes this buffer.
 713  *
 714  * Note that when we are called from dbuf_free_range() we do
 715  * not put a hold on the buffer, we just traverse the active
 716  * dbuf list for the dnode.
 717  */
 718 static void
 719 dbuf_fix_old_data(dmu_buf_impl_t *db, uint64_t txg)
 720 {
 721         dbuf_dirty_record_t *dr = db->db_last_dirty;
 722 
 723         ASSERT(MUTEX_HELD(&db->db_mtx));
 724         ASSERT(db->db.db_data != NULL);
 725         ASSERT(db->db_level == 0);
 726         ASSERT(db->db.db_object != DMU_META_DNODE_OBJECT);
 727 
 728         if (dr == NULL ||
 729             (dr->dt.dl.dr_data !=
 730             ((db->db_blkid  == DMU_BONUS_BLKID) ? db->db.db_data : db->db_buf)))
 731                 return;
 732 
 733         /*
 734          * If the last dirty record for this dbuf has not yet synced
 735          * and its referencing the dbuf data, either:
 736          *      reset the reference to point to a new copy,
 737          * or (if there a no active holders)
 738          *      just null out the current db_data pointer.
 739          */
 740         ASSERT(dr->dr_txg >= txg - 2);
 741         if (db->db_blkid == DMU_BONUS_BLKID) {
 742                 /* Note that the data bufs here are zio_bufs */
 743                 dr->dt.dl.dr_data = zio_buf_alloc(DN_MAX_BONUSLEN);
 744                 arc_space_consume(DN_MAX_BONUSLEN, ARC_SPACE_OTHER);
 745                 bcopy(db->db.db_data, dr->dt.dl.dr_data, DN_MAX_BONUSLEN);
 746         } else if (refcount_count(&db->db_holds) > db->db_dirtycnt) {
 747                 int size = db->db.db_size;
 748                 arc_buf_contents_t type = DBUF_GET_BUFC_TYPE(db);
 749                 spa_t *spa;
 750 
 751                 DB_GET_SPA(&spa, db);
 752                 dr->dt.dl.dr_data = arc_buf_alloc(spa, size, db, type);
 753                 bcopy(db->db.db_data, dr->dt.dl.dr_data->b_data, size);
 754         } else {
 755                 dbuf_set_data(db, NULL);
 756         }
 757 }
 758 
 759 void
 760 dbuf_unoverride(dbuf_dirty_record_t *dr)
 761 {
 762         dmu_buf_impl_t *db = dr->dr_dbuf;
 763         blkptr_t *bp = &dr->dt.dl.dr_overridden_by;
 764         uint64_t txg = dr->dr_txg;
 765 
 766         ASSERT(MUTEX_HELD(&db->db_mtx));
 767         ASSERT(dr->dt.dl.dr_override_state != DR_IN_DMU_SYNC);
 768         ASSERT(db->db_level == 0);
 769 
 770         if (db->db_blkid == DMU_BONUS_BLKID ||
 771             dr->dt.dl.dr_override_state == DR_NOT_OVERRIDDEN)
 772                 return;
 773 
 774         ASSERT(db->db_data_pending != dr);
 775 
 776         /* free this block */
 777         if (!BP_IS_HOLE(bp) && !dr->dt.dl.dr_nopwrite) {
 778                 spa_t *spa;
 779 
 780                 DB_GET_SPA(&spa, db);
 781                 zio_free(spa, txg, bp);
 782         }
 783         dr->dt.dl.dr_override_state = DR_NOT_OVERRIDDEN;
 784         dr->dt.dl.dr_nopwrite = B_FALSE;
 785 
 786         /*
 787          * Release the already-written buffer, so we leave it in
 788          * a consistent dirty state.  Note that all callers are
 789          * modifying the buffer, so they will immediately do
 790          * another (redundant) arc_release().  Therefore, leave
 791          * the buf thawed to save the effort of freezing &
 792          * immediately re-thawing it.
 793          */
 794         arc_release(dr->dt.dl.dr_data, db);
 795 }
 796 
 797 /*
 798  * Evict (if its unreferenced) or clear (if its referenced) any level-0
 799  * data blocks in the free range, so that any future readers will find
 800  * empty blocks.  Also, if we happen across any level-1 dbufs in the
 801  * range that have not already been marked dirty, mark them dirty so
 802  * they stay in memory.
 803  *
 804  * This is a no-op if the dataset is in the middle of an incremental
 805  * receive; see comment below for details.
 806  */
 807 void
 808 dbuf_free_range(dnode_t *dn, uint64_t start, uint64_t end, dmu_tx_t *tx)
 809 {
 810         dmu_buf_impl_t *db, *db_next;
 811         uint64_t txg = tx->tx_txg;
 812         int epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
 813         uint64_t first_l1 = start >> epbs;
 814         uint64_t last_l1 = end >> epbs;
 815 
 816         if (end > dn->dn_maxblkid && (end != DMU_SPILL_BLKID)) {
 817                 end = dn->dn_maxblkid;
 818                 last_l1 = end >> epbs;
 819         }
 820         dprintf_dnode(dn, "start=%llu end=%llu\n", start, end);
 821 
 822         if (dmu_objset_is_receiving(dn->dn_objset)) {
 823                 /*
 824                  * When processing a free record from a zfs receive,
 825                  * there should have been no previous modifications to the
 826                  * data in this range.  Therefore there should be no dbufs
 827                  * in the range.  Searching dn_dbufs for these non-existent
 828                  * dbufs can be very expensive, so simply ignore this.
 829                  */
 830                 VERIFY3P(dbuf_find(dn, 0, start), ==, NULL);
 831                 VERIFY3P(dbuf_find(dn, 0, end), ==, NULL);
 832                 return;
 833         }
 834 
 835         mutex_enter(&dn->dn_dbufs_mtx);
 836         for (db = list_head(&dn->dn_dbufs); db; db = db_next) {
 837                 db_next = list_next(&dn->dn_dbufs, db);
 838                 ASSERT(db->db_blkid != DMU_BONUS_BLKID);
 839 
 840                 if (db->db_level == 1 &&
 841                     db->db_blkid >= first_l1 && db->db_blkid <= last_l1) {
 842                         mutex_enter(&db->db_mtx);
 843                         if (db->db_last_dirty &&
 844                             db->db_last_dirty->dr_txg < txg) {
 845                                 dbuf_add_ref(db, FTAG);
 846                                 mutex_exit(&db->db_mtx);
 847                                 dbuf_will_dirty(db, tx);
 848                                 dbuf_rele(db, FTAG);
 849                         } else {
 850                                 mutex_exit(&db->db_mtx);
 851                         }
 852                 }
 853 
 854                 if (db->db_level != 0)
 855                         continue;
 856                 dprintf_dbuf(db, "found buf %s\n", "");
 857                 if (db->db_blkid < start || db->db_blkid > end)
 858                         continue;
 859 
 860                 /* found a level 0 buffer in the range */
 861                 mutex_enter(&db->db_mtx);
 862                 if (dbuf_undirty(db, tx)) {
 863                         /* mutex has been dropped and dbuf destroyed */
 864                         continue;
 865                 }
 866 
 867                 if (db->db_state == DB_UNCACHED ||
 868                     db->db_state == DB_NOFILL ||
 869                     db->db_state == DB_EVICTING) {
 870                         ASSERT(db->db.db_data == NULL);
 871                         mutex_exit(&db->db_mtx);
 872                         continue;
 873                 }
 874                 if (db->db_state == DB_READ || db->db_state == DB_FILL) {
 875                         /* will be handled in dbuf_read_done or dbuf_rele */
 876                         db->db_freed_in_flight = TRUE;
 877                         mutex_exit(&db->db_mtx);
 878                         continue;
 879                 }
 880                 if (refcount_count(&db->db_holds) == 0) {
 881                         ASSERT(db->db_buf);
 882                         dbuf_clear(db);
 883                         continue;
 884                 }
 885                 /* The dbuf is referenced */
 886 
 887                 if (db->db_last_dirty != NULL) {
 888                         dbuf_dirty_record_t *dr = db->db_last_dirty;
 889 
 890                         if (dr->dr_txg == txg) {
 891                                 /*
 892                                  * This buffer is "in-use", re-adjust the file
 893                                  * size to reflect that this buffer may
 894                                  * contain new data when we sync.
 895                                  */
 896                                 if (db->db_blkid != DMU_SPILL_BLKID &&
 897                                     db->db_blkid > dn->dn_maxblkid)
 898                                         dn->dn_maxblkid = db->db_blkid;
 899                                 dbuf_unoverride(dr);
 900                         } else {
 901                                 /*
 902                                  * This dbuf is not dirty in the open context.
 903                                  * Either uncache it (if its not referenced in
 904                                  * the open context) or reset its contents to
 905                                  * empty.
 906                                  */
 907                                 dbuf_fix_old_data(db, txg);
 908                         }
 909                 }
 910                 /* clear the contents if its cached */
 911                 if (db->db_state == DB_CACHED) {
 912                         ASSERT(db->db.db_data != NULL);
 913                         arc_release(db->db_buf, db);
 914                         bzero(db->db.db_data, db->db.db_size);
 915                         arc_buf_freeze(db->db_buf);
 916                 }
 917 
 918                 mutex_exit(&db->db_mtx);
 919         }
 920         mutex_exit(&dn->dn_dbufs_mtx);
 921 }
 922 
 923 static int
 924 dbuf_block_freeable(dmu_buf_impl_t *db)
 925 {
 926         dsl_dataset_t *ds = db->db_objset->os_dsl_dataset;
 927         uint64_t birth_txg = 0;
 928 
 929         /*
 930          * We don't need any locking to protect db_blkptr:
 931          * If it's syncing, then db_last_dirty will be set
 932          * so we'll ignore db_blkptr.
 933          */
 934         ASSERT(MUTEX_HELD(&db->db_mtx));
 935         if (db->db_last_dirty)
 936                 birth_txg = db->db_last_dirty->dr_txg;
 937         else if (db->db_blkptr)
 938                 birth_txg = db->db_blkptr->blk_birth;
 939 
 940         /*
 941          * If we don't exist or are in a snapshot, we can't be freed.
 942          * Don't pass the bp to dsl_dataset_block_freeable() since we
 943          * are holding the db_mtx lock and might deadlock if we are
 944          * prefetching a dedup-ed block.
 945          */
 946         if (birth_txg)
 947                 return (ds == NULL ||
 948                     dsl_dataset_block_freeable(ds, NULL, birth_txg));
 949         else
 950                 return (FALSE);
 951 }
 952 
 953 void
 954 dbuf_new_size(dmu_buf_impl_t *db, int size, dmu_tx_t *tx)
 955 {
 956         arc_buf_t *buf, *obuf;
 957         int osize = db->db.db_size;
 958         arc_buf_contents_t type = DBUF_GET_BUFC_TYPE(db);
 959         dnode_t *dn;
 960 
 961         ASSERT(db->db_blkid != DMU_BONUS_BLKID);
 962 
 963         DB_DNODE_ENTER(db);
 964         dn = DB_DNODE(db);
 965 
 966         /* XXX does *this* func really need the lock? */
 967         ASSERT(RW_WRITE_HELD(&dn->dn_struct_rwlock));
 968 
 969         /*
 970          * This call to dbuf_will_dirty() with the dn_struct_rwlock held
 971          * is OK, because there can be no other references to the db
 972          * when we are changing its size, so no concurrent DB_FILL can
 973          * be happening.
 974          */
 975         /*
 976          * XXX we should be doing a dbuf_read, checking the return
 977          * value and returning that up to our callers
 978          */
 979         dbuf_will_dirty(db, tx);
 980 
 981         /* create the data buffer for the new block */
 982         buf = arc_buf_alloc(dn->dn_objset->os_spa, size, db, type);
 983 
 984         /* copy old block data to the new block */
 985         obuf = db->db_buf;
 986         bcopy(obuf->b_data, buf->b_data, MIN(osize, size));
 987         /* zero the remainder */
 988         if (size > osize)
 989                 bzero((uint8_t *)buf->b_data + osize, size - osize);
 990 
 991         mutex_enter(&db->db_mtx);
 992         dbuf_set_data(db, buf);
 993         VERIFY(arc_buf_remove_ref(obuf, db));
 994         db->db.db_size = size;
 995 
 996         if (db->db_level == 0) {
 997                 ASSERT3U(db->db_last_dirty->dr_txg, ==, tx->tx_txg);
 998                 db->db_last_dirty->dt.dl.dr_data = buf;
 999         }
1000         mutex_exit(&db->db_mtx);
1001 
1002         dnode_willuse_space(dn, size-osize, tx);
1003         DB_DNODE_EXIT(db);
1004 }
1005 
1006 void
1007 dbuf_release_bp(dmu_buf_impl_t *db)
1008 {
1009         objset_t *os;
1010 
1011         DB_GET_OBJSET(&os, db);
1012         ASSERT(dsl_pool_sync_context(dmu_objset_pool(os)));
1013         ASSERT(arc_released(os->os_phys_buf) ||
1014             list_link_active(&os->os_dsl_dataset->ds_synced_link));
1015         ASSERT(db->db_parent == NULL || arc_released(db->db_parent->db_buf));
1016 
1017         (void) arc_release(db->db_buf, db);
1018 }
1019 
1020 dbuf_dirty_record_t *
1021 dbuf_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx)
1022 {
1023         dnode_t *dn;
1024         objset_t *os;
1025         dbuf_dirty_record_t **drp, *dr;
1026         int drop_struct_lock = FALSE;
1027         boolean_t do_free_accounting = B_FALSE;
1028         int txgoff = tx->tx_txg & TXG_MASK;
1029 
1030         ASSERT(tx->tx_txg != 0);
1031         ASSERT(!refcount_is_zero(&db->db_holds));
1032         DMU_TX_DIRTY_BUF(tx, db);
1033 
1034         DB_DNODE_ENTER(db);
1035         dn = DB_DNODE(db);
1036         /*
1037          * Shouldn't dirty a regular buffer in syncing context.  Private
1038          * objects may be dirtied in syncing context, but only if they
1039          * were already pre-dirtied in open context.
1040          */
1041         ASSERT(!dmu_tx_is_syncing(tx) ||
1042             BP_IS_HOLE(dn->dn_objset->os_rootbp) ||
1043             DMU_OBJECT_IS_SPECIAL(dn->dn_object) ||
1044             dn->dn_objset->os_dsl_dataset == NULL);
1045         /*
1046          * We make this assert for private objects as well, but after we
1047          * check if we're already dirty.  They are allowed to re-dirty
1048          * in syncing context.
1049          */
1050         ASSERT(dn->dn_object == DMU_META_DNODE_OBJECT ||
1051             dn->dn_dirtyctx == DN_UNDIRTIED || dn->dn_dirtyctx ==
1052             (dmu_tx_is_syncing(tx) ? DN_DIRTY_SYNC : DN_DIRTY_OPEN));
1053 
1054         mutex_enter(&db->db_mtx);
1055         /*
1056          * XXX make this true for indirects too?  The problem is that
1057          * transactions created with dmu_tx_create_assigned() from
1058          * syncing context don't bother holding ahead.
1059          */
1060         ASSERT(db->db_level != 0 ||
1061             db->db_state == DB_CACHED || db->db_state == DB_FILL ||
1062             db->db_state == DB_NOFILL);
1063 
1064         mutex_enter(&dn->dn_mtx);
1065         /*
1066          * Don't set dirtyctx to SYNC if we're just modifying this as we
1067          * initialize the objset.
1068          */
1069         if (dn->dn_dirtyctx == DN_UNDIRTIED &&
1070             !BP_IS_HOLE(dn->dn_objset->os_rootbp)) {
1071                 dn->dn_dirtyctx =
1072                     (dmu_tx_is_syncing(tx) ? DN_DIRTY_SYNC : DN_DIRTY_OPEN);
1073                 ASSERT(dn->dn_dirtyctx_firstset == NULL);
1074                 dn->dn_dirtyctx_firstset = kmem_alloc(1, KM_SLEEP);
1075         }
1076         mutex_exit(&dn->dn_mtx);
1077 
1078         if (db->db_blkid == DMU_SPILL_BLKID)
1079                 dn->dn_have_spill = B_TRUE;
1080 
1081         /*
1082          * If this buffer is already dirty, we're done.
1083          */
1084         drp = &db->db_last_dirty;
1085         ASSERT(*drp == NULL || (*drp)->dr_txg <= tx->tx_txg ||
1086             db->db.db_object == DMU_META_DNODE_OBJECT);
1087         while ((dr = *drp) != NULL && dr->dr_txg > tx->tx_txg)
1088                 drp = &dr->dr_next;
1089         if (dr && dr->dr_txg == tx->tx_txg) {
1090                 DB_DNODE_EXIT(db);
1091 
1092                 if (db->db_level == 0 && db->db_blkid != DMU_BONUS_BLKID) {
1093                         /*
1094                          * If this buffer has already been written out,
1095                          * we now need to reset its state.
1096                          */
1097                         dbuf_unoverride(dr);
1098                         if (db->db.db_object != DMU_META_DNODE_OBJECT &&
1099                             db->db_state != DB_NOFILL)
1100                                 arc_buf_thaw(db->db_buf);
1101                 }
1102                 mutex_exit(&db->db_mtx);
1103                 return (dr);
1104         }
1105 
1106         /*
1107          * Only valid if not already dirty.
1108          */
1109         ASSERT(dn->dn_object == 0 ||
1110             dn->dn_dirtyctx == DN_UNDIRTIED || dn->dn_dirtyctx ==
1111             (dmu_tx_is_syncing(tx) ? DN_DIRTY_SYNC : DN_DIRTY_OPEN));
1112 
1113         ASSERT3U(dn->dn_nlevels, >, db->db_level);
1114         ASSERT((dn->dn_phys->dn_nlevels == 0 && db->db_level == 0) ||
1115             dn->dn_phys->dn_nlevels > db->db_level ||
1116             dn->dn_next_nlevels[txgoff] > db->db_level ||
1117             dn->dn_next_nlevels[(tx->tx_txg-1) & TXG_MASK] > db->db_level ||
1118             dn->dn_next_nlevels[(tx->tx_txg-2) & TXG_MASK] > db->db_level);
1119 
1120         /*
1121          * We should only be dirtying in syncing context if it's the
1122          * mos or we're initializing the os or it's a special object.
1123          * However, we are allowed to dirty in syncing context provided
1124          * we already dirtied it in open context.  Hence we must make
1125          * this assertion only if we're not already dirty.
1126          */
1127         os = dn->dn_objset;
1128         ASSERT(!dmu_tx_is_syncing(tx) || DMU_OBJECT_IS_SPECIAL(dn->dn_object) ||
1129             os->os_dsl_dataset == NULL || BP_IS_HOLE(os->os_rootbp));
1130         ASSERT(db->db.db_size != 0);
1131 
1132         dprintf_dbuf(db, "size=%llx\n", (u_longlong_t)db->db.db_size);
1133 
1134         if (db->db_blkid != DMU_BONUS_BLKID) {
1135                 /*
1136                  * Update the accounting.
1137                  * Note: we delay "free accounting" until after we drop
1138                  * the db_mtx.  This keeps us from grabbing other locks
1139                  * (and possibly deadlocking) in bp_get_dsize() while
1140                  * also holding the db_mtx.
1141                  */
1142                 dnode_willuse_space(dn, db->db.db_size, tx);
1143                 do_free_accounting = dbuf_block_freeable(db);
1144         }
1145 
1146         /*
1147          * If this buffer is dirty in an old transaction group we need
1148          * to make a copy of it so that the changes we make in this
1149          * transaction group won't leak out when we sync the older txg.
1150          */
1151         dr = kmem_zalloc(sizeof (dbuf_dirty_record_t), KM_SLEEP);
1152         if (db->db_level == 0) {
1153                 void *data_old = db->db_buf;
1154 
1155                 if (db->db_state != DB_NOFILL) {
1156                         if (db->db_blkid == DMU_BONUS_BLKID) {
1157                                 dbuf_fix_old_data(db, tx->tx_txg);
1158                                 data_old = db->db.db_data;
1159                         } else if (db->db.db_object != DMU_META_DNODE_OBJECT) {
1160                                 /*
1161                                  * Release the data buffer from the cache so
1162                                  * that we can modify it without impacting
1163                                  * possible other users of this cached data
1164                                  * block.  Note that indirect blocks and
1165                                  * private objects are not released until the
1166                                  * syncing state (since they are only modified
1167                                  * then).
1168                                  */
1169                                 arc_release(db->db_buf, db);
1170                                 dbuf_fix_old_data(db, tx->tx_txg);
1171                                 data_old = db->db_buf;
1172                         }
1173                         ASSERT(data_old != NULL);
1174                 }
1175                 dr->dt.dl.dr_data = data_old;
1176         } else {
1177                 mutex_init(&dr->dt.di.dr_mtx, NULL, MUTEX_DEFAULT, NULL);
1178                 list_create(&dr->dt.di.dr_children,
1179                     sizeof (dbuf_dirty_record_t),
1180                     offsetof(dbuf_dirty_record_t, dr_dirty_node));
1181         }
1182         dr->dr_dbuf = db;
1183         dr->dr_txg = tx->tx_txg;
1184         dr->dr_next = *drp;
1185         *drp = dr;
1186 
1187         /*
1188          * We could have been freed_in_flight between the dbuf_noread
1189          * and dbuf_dirty.  We win, as though the dbuf_noread() had
1190          * happened after the free.
1191          */
1192         if (db->db_level == 0 && db->db_blkid != DMU_BONUS_BLKID &&
1193             db->db_blkid != DMU_SPILL_BLKID) {
1194                 mutex_enter(&dn->dn_mtx);
1195                 dnode_clear_range(dn, db->db_blkid, 1, tx);
1196                 mutex_exit(&dn->dn_mtx);
1197                 db->db_freed_in_flight = FALSE;
1198         }
1199 
1200         /*
1201          * This buffer is now part of this txg
1202          */
1203         dbuf_add_ref(db, (void *)(uintptr_t)tx->tx_txg);
1204         db->db_dirtycnt += 1;
1205         ASSERT3U(db->db_dirtycnt, <=, 3);
1206 
1207         mutex_exit(&db->db_mtx);
1208 
1209         if (db->db_blkid == DMU_BONUS_BLKID ||
1210             db->db_blkid == DMU_SPILL_BLKID) {
1211                 mutex_enter(&dn->dn_mtx);
1212                 ASSERT(!list_link_active(&dr->dr_dirty_node));
1213                 list_insert_tail(&dn->dn_dirty_records[txgoff], dr);
1214                 mutex_exit(&dn->dn_mtx);
1215                 dnode_setdirty(dn, tx);
1216                 DB_DNODE_EXIT(db);
1217                 return (dr);
1218         } else if (do_free_accounting) {
1219                 blkptr_t *bp = db->db_blkptr;
1220                 int64_t willfree = (bp && !BP_IS_HOLE(bp)) ?
1221                     bp_get_dsize(os->os_spa, bp) : db->db.db_size;
1222                 /*
1223                  * This is only a guess -- if the dbuf is dirty
1224                  * in a previous txg, we don't know how much
1225                  * space it will use on disk yet.  We should
1226                  * really have the struct_rwlock to access
1227                  * db_blkptr, but since this is just a guess,
1228                  * it's OK if we get an odd answer.
1229                  */
1230                 ddt_prefetch(os->os_spa, bp);
1231                 dnode_willuse_space(dn, -willfree, tx);
1232         }
1233 
1234         if (!RW_WRITE_HELD(&dn->dn_struct_rwlock)) {
1235                 rw_enter(&dn->dn_struct_rwlock, RW_READER);
1236                 drop_struct_lock = TRUE;
1237         }
1238 
1239         if (db->db_level == 0) {
1240                 dnode_new_blkid(dn, db->db_blkid, tx, drop_struct_lock);
1241                 ASSERT(dn->dn_maxblkid >= db->db_blkid);
1242         }
1243 
1244         if (db->db_level+1 < dn->dn_nlevels) {
1245                 dmu_buf_impl_t *parent = db->db_parent;
1246                 dbuf_dirty_record_t *di;
1247                 int parent_held = FALSE;
1248 
1249                 if (db->db_parent == NULL || db->db_parent == dn->dn_dbuf) {
1250                         int epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
1251 
1252                         parent = dbuf_hold_level(dn, db->db_level+1,
1253                             db->db_blkid >> epbs, FTAG);
1254                         ASSERT(parent != NULL);
1255                         parent_held = TRUE;
1256                 }
1257                 if (drop_struct_lock)
1258                         rw_exit(&dn->dn_struct_rwlock);
1259                 ASSERT3U(db->db_level+1, ==, parent->db_level);
1260                 di = dbuf_dirty(parent, tx);
1261                 if (parent_held)
1262                         dbuf_rele(parent, FTAG);
1263 
1264                 mutex_enter(&db->db_mtx);
1265                 /*  possible race with dbuf_undirty() */
1266                 if (db->db_last_dirty == dr ||
1267                     dn->dn_object == DMU_META_DNODE_OBJECT) {
1268                         mutex_enter(&di->dt.di.dr_mtx);
1269                         ASSERT3U(di->dr_txg, ==, tx->tx_txg);
1270                         ASSERT(!list_link_active(&dr->dr_dirty_node));
1271                         list_insert_tail(&di->dt.di.dr_children, dr);
1272                         mutex_exit(&di->dt.di.dr_mtx);
1273                         dr->dr_parent = di;
1274                 }
1275                 mutex_exit(&db->db_mtx);
1276         } else {
1277                 ASSERT(db->db_level+1 == dn->dn_nlevels);
1278                 ASSERT(db->db_blkid < dn->dn_nblkptr);
1279                 ASSERT(db->db_parent == NULL || db->db_parent == dn->dn_dbuf);
1280                 mutex_enter(&dn->dn_mtx);
1281                 ASSERT(!list_link_active(&dr->dr_dirty_node));
1282                 list_insert_tail(&dn->dn_dirty_records[txgoff], dr);
1283                 mutex_exit(&dn->dn_mtx);
1284                 if (drop_struct_lock)
1285                         rw_exit(&dn->dn_struct_rwlock);
1286         }
1287 
1288         dnode_setdirty(dn, tx);
1289         DB_DNODE_EXIT(db);
1290         return (dr);
1291 }
1292 
1293 /*
1294  * Undirty a buffer in the transaction group referenced by the given
1295  * transaction.  Return whether this evicted the dbuf.
1296  */
1297 static boolean_t
1298 dbuf_undirty(dmu_buf_impl_t *db, dmu_tx_t *tx)
1299 {
1300         dnode_t *dn;
1301         uint64_t txg = tx->tx_txg;
1302         dbuf_dirty_record_t *dr, **drp;
1303 
1304         ASSERT(txg != 0);
1305         ASSERT(db->db_blkid != DMU_BONUS_BLKID);
1306         ASSERT0(db->db_level);
1307         ASSERT(MUTEX_HELD(&db->db_mtx));
1308 
1309         /*
1310          * If this buffer is not dirty, we're done.
1311          */
1312         for (drp = &db->db_last_dirty; (dr = *drp) != NULL; drp = &dr->dr_next)
1313                 if (dr->dr_txg <= txg)
1314                         break;
1315         if (dr == NULL || dr->dr_txg < txg)
1316                 return (B_FALSE);
1317         ASSERT(dr->dr_txg == txg);
1318         ASSERT(dr->dr_dbuf == db);
1319 
1320         DB_DNODE_ENTER(db);
1321         dn = DB_DNODE(db);
1322 
1323         /*
1324          * Note:  This code will probably work even if there are concurrent
1325          * holders, but it is untested in that scenerio, as the ZPL and
1326          * ztest have additional locking (the range locks) that prevents
1327          * that type of concurrent access.
1328          */
1329         ASSERT3U(refcount_count(&db->db_holds), ==, db->db_dirtycnt);
1330 
1331         dprintf_dbuf(db, "size=%llx\n", (u_longlong_t)db->db.db_size);
1332 
1333         ASSERT(db->db.db_size != 0);
1334 
1335         /* XXX would be nice to fix up dn_towrite_space[] */
1336 
1337         *drp = dr->dr_next;
1338 
1339         /*
1340          * Note that there are three places in dbuf_dirty()
1341          * where this dirty record may be put on a list.
1342          * Make sure to do a list_remove corresponding to
1343          * every one of those list_insert calls.
1344          */
1345         if (dr->dr_parent) {
1346                 mutex_enter(&dr->dr_parent->dt.di.dr_mtx);
1347                 list_remove(&dr->dr_parent->dt.di.dr_children, dr);
1348                 mutex_exit(&dr->dr_parent->dt.di.dr_mtx);
1349         } else if (db->db_blkid == DMU_SPILL_BLKID ||
1350             db->db_level+1 == dn->dn_nlevels) {
1351                 ASSERT(db->db_blkptr == NULL || db->db_parent == dn->dn_dbuf);
1352                 mutex_enter(&dn->dn_mtx);
1353                 list_remove(&dn->dn_dirty_records[txg & TXG_MASK], dr);
1354                 mutex_exit(&dn->dn_mtx);
1355         }
1356         DB_DNODE_EXIT(db);
1357 
1358         if (db->db_state != DB_NOFILL) {
1359                 dbuf_unoverride(dr);
1360 
1361                 ASSERT(db->db_buf != NULL);
1362                 ASSERT(dr->dt.dl.dr_data != NULL);
1363                 if (dr->dt.dl.dr_data != db->db_buf)
1364                         VERIFY(arc_buf_remove_ref(dr->dt.dl.dr_data, db));
1365         }
1366         kmem_free(dr, sizeof (dbuf_dirty_record_t));
1367 
1368         ASSERT(db->db_dirtycnt > 0);
1369         db->db_dirtycnt -= 1;
1370 
1371         if (refcount_remove(&db->db_holds, (void *)(uintptr_t)txg) == 0) {
1372                 arc_buf_t *buf = db->db_buf;
1373 
1374                 ASSERT(db->db_state == DB_NOFILL || arc_released(buf));
1375                 dbuf_set_data(db, NULL);
1376                 VERIFY(arc_buf_remove_ref(buf, db));
1377                 dbuf_evict(db);
1378                 return (B_TRUE);
1379         }
1380 
1381         return (B_FALSE);
1382 }
1383 
1384 #pragma weak dmu_buf_will_dirty = dbuf_will_dirty
1385 void
1386 dbuf_will_dirty(dmu_buf_impl_t *db, dmu_tx_t *tx)
1387 {
1388         int rf = DB_RF_MUST_SUCCEED | DB_RF_NOPREFETCH;
1389 
1390         ASSERT(tx->tx_txg != 0);
1391         ASSERT(!refcount_is_zero(&db->db_holds));
1392 
1393         DB_DNODE_ENTER(db);
1394         if (RW_WRITE_HELD(&DB_DNODE(db)->dn_struct_rwlock))
1395                 rf |= DB_RF_HAVESTRUCT;
1396         DB_DNODE_EXIT(db);
1397         (void) dbuf_read(db, NULL, rf);
1398         (void) dbuf_dirty(db, tx);
1399 }
1400 
1401 void
1402 dmu_buf_will_not_fill(dmu_buf_t *db_fake, dmu_tx_t *tx)
1403 {
1404         dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
1405 
1406         db->db_state = DB_NOFILL;
1407 
1408         dmu_buf_will_fill(db_fake, tx);
1409 }
1410 
1411 void
1412 dmu_buf_will_fill(dmu_buf_t *db_fake, dmu_tx_t *tx)
1413 {
1414         dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
1415 
1416         ASSERT(db->db_blkid != DMU_BONUS_BLKID);
1417         ASSERT(tx->tx_txg != 0);
1418         ASSERT(db->db_level == 0);
1419         ASSERT(!refcount_is_zero(&db->db_holds));
1420 
1421         ASSERT(db->db.db_object != DMU_META_DNODE_OBJECT ||
1422             dmu_tx_private_ok(tx));
1423 
1424         dbuf_noread(db);
1425         (void) dbuf_dirty(db, tx);
1426 }
1427 
1428 #pragma weak dmu_buf_fill_done = dbuf_fill_done
1429 /* ARGSUSED */
1430 void
1431 dbuf_fill_done(dmu_buf_impl_t *db, dmu_tx_t *tx)
1432 {
1433         mutex_enter(&db->db_mtx);
1434         DBUF_VERIFY(db);
1435 
1436         if (db->db_state == DB_FILL) {
1437                 if (db->db_level == 0 && db->db_freed_in_flight) {
1438                         ASSERT(db->db_blkid != DMU_BONUS_BLKID);
1439                         /* we were freed while filling */
1440                         /* XXX dbuf_undirty? */
1441                         bzero(db->db.db_data, db->db.db_size);
1442                         db->db_freed_in_flight = FALSE;
1443                 }
1444                 db->db_state = DB_CACHED;
1445                 cv_broadcast(&db->db_changed);
1446         }
1447         mutex_exit(&db->db_mtx);
1448 }
1449 
1450 /*
1451  * Directly assign a provided arc buf to a given dbuf if it's not referenced
1452  * by anybody except our caller. Otherwise copy arcbuf's contents to dbuf.
1453  */
1454 void
1455 dbuf_assign_arcbuf(dmu_buf_impl_t *db, arc_buf_t *buf, dmu_tx_t *tx)
1456 {
1457         ASSERT(!refcount_is_zero(&db->db_holds));
1458         ASSERT(db->db_blkid != DMU_BONUS_BLKID);
1459         ASSERT(db->db_level == 0);
1460         ASSERT(DBUF_GET_BUFC_TYPE(db) == ARC_BUFC_DATA);
1461         ASSERT(buf != NULL);
1462         ASSERT(arc_buf_size(buf) == db->db.db_size);
1463         ASSERT(tx->tx_txg != 0);
1464 
1465         arc_return_buf(buf, db);
1466         ASSERT(arc_released(buf));
1467 
1468         mutex_enter(&db->db_mtx);
1469 
1470         while (db->db_state == DB_READ || db->db_state == DB_FILL)
1471                 cv_wait(&db->db_changed, &db->db_mtx);
1472 
1473         ASSERT(db->db_state == DB_CACHED || db->db_state == DB_UNCACHED);
1474 
1475         if (db->db_state == DB_CACHED &&
1476             refcount_count(&db->db_holds) - 1 > db->db_dirtycnt) {
1477                 mutex_exit(&db->db_mtx);
1478                 (void) dbuf_dirty(db, tx);
1479                 bcopy(buf->b_data, db->db.db_data, db->db.db_size);
1480                 VERIFY(arc_buf_remove_ref(buf, db));
1481                 xuio_stat_wbuf_copied();
1482                 return;
1483         }
1484 
1485         xuio_stat_wbuf_nocopy();
1486         if (db->db_state == DB_CACHED) {
1487                 dbuf_dirty_record_t *dr = db->db_last_dirty;
1488 
1489                 ASSERT(db->db_buf != NULL);
1490                 if (dr != NULL && dr->dr_txg == tx->tx_txg) {
1491                         ASSERT(dr->dt.dl.dr_data == db->db_buf);
1492                         if (!arc_released(db->db_buf)) {
1493                                 ASSERT(dr->dt.dl.dr_override_state ==
1494                                     DR_OVERRIDDEN);
1495                                 arc_release(db->db_buf, db);
1496                         }
1497                         dr->dt.dl.dr_data = buf;
1498                         VERIFY(arc_buf_remove_ref(db->db_buf, db));
1499                 } else if (dr == NULL || dr->dt.dl.dr_data != db->db_buf) {
1500                         arc_release(db->db_buf, db);
1501                         VERIFY(arc_buf_remove_ref(db->db_buf, db));
1502                 }
1503                 db->db_buf = NULL;
1504         }
1505         ASSERT(db->db_buf == NULL);
1506         dbuf_set_data(db, buf);
1507         db->db_state = DB_FILL;
1508         mutex_exit(&db->db_mtx);
1509         (void) dbuf_dirty(db, tx);
1510         dbuf_fill_done(db, tx);
1511 }
1512 
1513 /*
1514  * "Clear" the contents of this dbuf.  This will mark the dbuf
1515  * EVICTING and clear *most* of its references.  Unfortunetely,
1516  * when we are not holding the dn_dbufs_mtx, we can't clear the
1517  * entry in the dn_dbufs list.  We have to wait until dbuf_destroy()
1518  * in this case.  For callers from the DMU we will usually see:
1519  *      dbuf_clear()->arc_buf_evict()->dbuf_do_evict()->dbuf_destroy()
1520  * For the arc callback, we will usually see:
1521  *      dbuf_do_evict()->dbuf_clear();dbuf_destroy()
1522  * Sometimes, though, we will get a mix of these two:
1523  *      DMU: dbuf_clear()->arc_buf_evict()
1524  *      ARC: dbuf_do_evict()->dbuf_destroy()
1525  */
1526 void
1527 dbuf_clear(dmu_buf_impl_t *db)
1528 {
1529         dnode_t *dn;
1530         dmu_buf_impl_t *parent = db->db_parent;
1531         dmu_buf_impl_t *dndb;
1532         int dbuf_gone = FALSE;
1533 
1534         ASSERT(MUTEX_HELD(&db->db_mtx));
1535         ASSERT(refcount_is_zero(&db->db_holds));
1536 
1537         dbuf_evict_user(db);
1538 
1539         if (db->db_state == DB_CACHED) {
1540                 ASSERT(db->db.db_data != NULL);
1541                 if (db->db_blkid == DMU_BONUS_BLKID) {
1542                         zio_buf_free(db->db.db_data, DN_MAX_BONUSLEN);
1543                         arc_space_return(DN_MAX_BONUSLEN, ARC_SPACE_OTHER);
1544                 }
1545                 db->db.db_data = NULL;
1546                 db->db_state = DB_UNCACHED;
1547         }
1548 
1549         ASSERT(db->db_state == DB_UNCACHED || db->db_state == DB_NOFILL);
1550         ASSERT(db->db_data_pending == NULL);
1551 
1552         db->db_state = DB_EVICTING;
1553         db->db_blkptr = NULL;
1554 
1555         DB_DNODE_ENTER(db);
1556         dn = DB_DNODE(db);
1557         dndb = dn->dn_dbuf;
1558         if (db->db_blkid != DMU_BONUS_BLKID && MUTEX_HELD(&dn->dn_dbufs_mtx)) {
1559                 list_remove(&dn->dn_dbufs, db);
1560                 (void) atomic_dec_32_nv(&dn->dn_dbufs_count);
1561                 membar_producer();
1562                 DB_DNODE_EXIT(db);
1563                 /*
1564                  * Decrementing the dbuf count means that the hold corresponding
1565                  * to the removed dbuf is no longer discounted in dnode_move(),
1566                  * so the dnode cannot be moved until after we release the hold.
1567                  * The membar_producer() ensures visibility of the decremented
1568                  * value in dnode_move(), since DB_DNODE_EXIT doesn't actually
1569                  * release any lock.
1570                  */
1571                 dnode_rele(dn, db);
1572                 db->db_dnode_handle = NULL;
1573         } else {
1574                 DB_DNODE_EXIT(db);
1575         }
1576 
1577         if (db->db_buf)
1578                 dbuf_gone = arc_buf_evict(db->db_buf);
1579 
1580         if (!dbuf_gone)
1581                 mutex_exit(&db->db_mtx);
1582 
1583         /*
1584          * If this dbuf is referenced from an indirect dbuf,
1585          * decrement the ref count on the indirect dbuf.
1586          */
1587         if (parent && parent != dndb)
1588                 dbuf_rele(parent, db);
1589 }
1590 
1591 static int
1592 dbuf_findbp(dnode_t *dn, int level, uint64_t blkid, int fail_sparse,
1593     dmu_buf_impl_t **parentp, blkptr_t **bpp)
1594 {
1595         int nlevels, epbs;
1596 
1597         *parentp = NULL;
1598         *bpp = NULL;
1599 
1600         ASSERT(blkid != DMU_BONUS_BLKID);
1601 
1602         if (blkid == DMU_SPILL_BLKID) {
1603                 mutex_enter(&dn->dn_mtx);
1604                 if (dn->dn_have_spill &&
1605                     (dn->dn_phys->dn_flags & DNODE_FLAG_SPILL_BLKPTR))
1606                         *bpp = &dn->dn_phys->dn_spill;
1607                 else
1608                         *bpp = NULL;
1609                 dbuf_add_ref(dn->dn_dbuf, NULL);
1610                 *parentp = dn->dn_dbuf;
1611                 mutex_exit(&dn->dn_mtx);
1612                 return (0);
1613         }
1614 
1615         if (dn->dn_phys->dn_nlevels == 0)
1616                 nlevels = 1;
1617         else
1618                 nlevels = dn->dn_phys->dn_nlevels;
1619 
1620         epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
1621 
1622         ASSERT3U(level * epbs, <, 64);
1623         ASSERT(RW_LOCK_HELD(&dn->dn_struct_rwlock));
1624         if (level >= nlevels ||
1625             (blkid > (dn->dn_phys->dn_maxblkid >> (level * epbs)))) {
1626                 /* the buffer has no parent yet */
1627                 return (SET_ERROR(ENOENT));
1628         } else if (level < nlevels-1) {
1629                 /* this block is referenced from an indirect block */
1630                 int err = dbuf_hold_impl(dn, level+1,
1631                     blkid >> epbs, fail_sparse, NULL, parentp);
1632                 if (err)
1633                         return (err);
1634                 err = dbuf_read(*parentp, NULL,
1635                     (DB_RF_HAVESTRUCT | DB_RF_NOPREFETCH | DB_RF_CANFAIL));
1636                 if (err) {
1637                         dbuf_rele(*parentp, NULL);
1638                         *parentp = NULL;
1639                         return (err);
1640                 }
1641                 *bpp = ((blkptr_t *)(*parentp)->db.db_data) +
1642                     (blkid & ((1ULL << epbs) - 1));
1643                 return (0);
1644         } else {
1645                 /* the block is referenced from the dnode */
1646                 ASSERT3U(level, ==, nlevels-1);
1647                 ASSERT(dn->dn_phys->dn_nblkptr == 0 ||
1648                     blkid < dn->dn_phys->dn_nblkptr);
1649                 if (dn->dn_dbuf) {
1650                         dbuf_add_ref(dn->dn_dbuf, NULL);
1651                         *parentp = dn->dn_dbuf;
1652                 }
1653                 *bpp = &dn->dn_phys->dn_blkptr[blkid];
1654                 return (0);
1655         }
1656 }
1657 
1658 static dmu_buf_impl_t *
1659 dbuf_create(dnode_t *dn, uint8_t level, uint64_t blkid,
1660     dmu_buf_impl_t *parent, blkptr_t *blkptr)
1661 {
1662         objset_t *os = dn->dn_objset;
1663         dmu_buf_impl_t *db, *odb;
1664 
1665         ASSERT(RW_LOCK_HELD(&dn->dn_struct_rwlock));
1666         ASSERT(dn->dn_type != DMU_OT_NONE);
1667 
1668         db = kmem_cache_alloc(dbuf_cache, KM_SLEEP);
1669 
1670         db->db_objset = os;
1671         db->db.db_object = dn->dn_object;
1672         db->db_level = level;
1673         db->db_blkid = blkid;
1674         db->db_last_dirty = NULL;
1675         db->db_dirtycnt = 0;
1676         db->db_dnode_handle = dn->dn_handle;
1677         db->db_parent = parent;
1678         db->db_blkptr = blkptr;
1679 
1680         db->db_user_ptr = NULL;
1681         db->db_user_data_ptr_ptr = NULL;
1682         db->db_evict_func = NULL;
1683         db->db_immediate_evict = 0;
1684         db->db_freed_in_flight = 0;
1685 
1686         if (blkid == DMU_BONUS_BLKID) {
1687                 ASSERT3P(parent, ==, dn->dn_dbuf);
1688                 db->db.db_size = DN_MAX_BONUSLEN -
1689                     (dn->dn_nblkptr-1) * sizeof (blkptr_t);
1690                 ASSERT3U(db->db.db_size, >=, dn->dn_bonuslen);
1691                 db->db.db_offset = DMU_BONUS_BLKID;
1692                 db->db_state = DB_UNCACHED;
1693                 /* the bonus dbuf is not placed in the hash table */
1694                 arc_space_consume(sizeof (dmu_buf_impl_t), ARC_SPACE_OTHER);
1695                 return (db);
1696         } else if (blkid == DMU_SPILL_BLKID) {
1697                 db->db.db_size = (blkptr != NULL) ?
1698                     BP_GET_LSIZE(blkptr) : SPA_MINBLOCKSIZE;
1699                 db->db.db_offset = 0;
1700         } else {
1701                 int blocksize =
1702                     db->db_level ? 1<<dn->dn_indblkshift :  dn->dn_datablksz;
1703                 db->db.db_size = blocksize;
1704                 db->db.db_offset = db->db_blkid * blocksize;
1705         }
1706 
1707         /*
1708          * Hold the dn_dbufs_mtx while we get the new dbuf
1709          * in the hash table *and* added to the dbufs list.
1710          * This prevents a possible deadlock with someone
1711          * trying to look up this dbuf before its added to the
1712          * dn_dbufs list.
1713          */
1714         mutex_enter(&dn->dn_dbufs_mtx);
1715         db->db_state = DB_EVICTING;
1716         if ((odb = dbuf_hash_insert(db)) != NULL) {
1717                 /* someone else inserted it first */
1718                 kmem_cache_free(dbuf_cache, db);
1719                 mutex_exit(&dn->dn_dbufs_mtx);
1720                 return (odb);
1721         }
1722         list_insert_head(&dn->dn_dbufs, db);
1723         db->db_state = DB_UNCACHED;
1724         mutex_exit(&dn->dn_dbufs_mtx);
1725         arc_space_consume(sizeof (dmu_buf_impl_t), ARC_SPACE_OTHER);
1726 
1727         if (parent && parent != dn->dn_dbuf)
1728                 dbuf_add_ref(parent, db);
1729 
1730         ASSERT(dn->dn_object == DMU_META_DNODE_OBJECT ||
1731             refcount_count(&dn->dn_holds) > 0);
1732         (void) refcount_add(&dn->dn_holds, db);
1733         (void) atomic_inc_32_nv(&dn->dn_dbufs_count);
1734 
1735         dprintf_dbuf(db, "db=%p\n", db);
1736 
1737         return (db);
1738 }
1739 
1740 static int
1741 dbuf_do_evict(void *private)
1742 {
1743         arc_buf_t *buf = private;
1744         dmu_buf_impl_t *db = buf->b_private;
1745 
1746         if (!MUTEX_HELD(&db->db_mtx))
1747                 mutex_enter(&db->db_mtx);
1748 
1749         ASSERT(refcount_is_zero(&db->db_holds));
1750 
1751         if (db->db_state != DB_EVICTING) {
1752                 ASSERT(db->db_state == DB_CACHED);
1753                 DBUF_VERIFY(db);
1754                 db->db_buf = NULL;
1755                 dbuf_evict(db);
1756         } else {
1757                 mutex_exit(&db->db_mtx);
1758                 dbuf_destroy(db);
1759         }
1760         return (0);
1761 }
1762 
1763 static void
1764 dbuf_destroy(dmu_buf_impl_t *db)
1765 {
1766         ASSERT(refcount_is_zero(&db->db_holds));
1767 
1768         if (db->db_blkid != DMU_BONUS_BLKID) {
1769                 /*
1770                  * If this dbuf is still on the dn_dbufs list,
1771                  * remove it from that list.
1772                  */
1773                 if (db->db_dnode_handle != NULL) {
1774                         dnode_t *dn;
1775 
1776                         DB_DNODE_ENTER(db);
1777                         dn = DB_DNODE(db);
1778                         mutex_enter(&dn->dn_dbufs_mtx);
1779                         list_remove(&dn->dn_dbufs, db);
1780                         (void) atomic_dec_32_nv(&dn->dn_dbufs_count);
1781                         mutex_exit(&dn->dn_dbufs_mtx);
1782                         DB_DNODE_EXIT(db);
1783                         /*
1784                          * Decrementing the dbuf count means that the hold
1785                          * corresponding to the removed dbuf is no longer
1786                          * discounted in dnode_move(), so the dnode cannot be
1787                          * moved until after we release the hold.
1788                          */
1789                         dnode_rele(dn, db);
1790                         db->db_dnode_handle = NULL;
1791                 }
1792                 dbuf_hash_remove(db);
1793         }
1794         db->db_parent = NULL;
1795         db->db_buf = NULL;
1796 
1797         ASSERT(!list_link_active(&db->db_link));
1798         ASSERT(db->db.db_data == NULL);
1799         ASSERT(db->db_hash_next == NULL);
1800         ASSERT(db->db_blkptr == NULL);
1801         ASSERT(db->db_data_pending == NULL);
1802 
1803         kmem_cache_free(dbuf_cache, db);
1804         arc_space_return(sizeof (dmu_buf_impl_t), ARC_SPACE_OTHER);
1805 }
1806 
1807 void
1808 dbuf_prefetch(dnode_t *dn, uint64_t blkid)
1809 {
1810         dmu_buf_impl_t *db = NULL;
1811         blkptr_t *bp = NULL;
1812 
1813         ASSERT(blkid != DMU_BONUS_BLKID);
1814         ASSERT(RW_LOCK_HELD(&dn->dn_struct_rwlock));
1815 
1816         if (dnode_block_freed(dn, blkid))
1817                 return;
1818 
1819         /* dbuf_find() returns with db_mtx held */
1820         if (db = dbuf_find(dn, 0, blkid)) {
1821                 /*
1822                  * This dbuf is already in the cache.  We assume that
1823                  * it is already CACHED, or else about to be either
1824                  * read or filled.
1825                  */
1826                 mutex_exit(&db->db_mtx);
1827                 return;
1828         }
1829 
1830         if (dbuf_findbp(dn, 0, blkid, TRUE, &db, &bp) == 0) {
1831                 if (bp && !BP_IS_HOLE(bp)) {
1832                         int priority = dn->dn_type == DMU_OT_DDT_ZAP ?
1833                             ZIO_PRIORITY_DDT_PREFETCH : ZIO_PRIORITY_ASYNC_READ;
1834                         dsl_dataset_t *ds = dn->dn_objset->os_dsl_dataset;
1835                         uint32_t aflags = ARC_NOWAIT | ARC_PREFETCH;
1836                         zbookmark_t zb;
1837 
1838                         SET_BOOKMARK(&zb, ds ? ds->ds_object : DMU_META_OBJSET,
1839                             dn->dn_object, 0, blkid);
1840 
1841                         (void) arc_read(NULL, dn->dn_objset->os_spa,
1842                             bp, NULL, NULL, priority,
1843                             ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE,
1844                             &aflags, &zb);
1845                 }
1846                 if (db)
1847                         dbuf_rele(db, NULL);
1848         }
1849 }
1850 
1851 /*
1852  * Returns with db_holds incremented, and db_mtx not held.
1853  * Note: dn_struct_rwlock must be held.
1854  */
1855 int
1856 dbuf_hold_impl(dnode_t *dn, uint8_t level, uint64_t blkid, int fail_sparse,
1857     void *tag, dmu_buf_impl_t **dbp)
1858 {
1859         dmu_buf_impl_t *db, *parent = NULL;
1860 
1861         ASSERT(blkid != DMU_BONUS_BLKID);
1862         ASSERT(RW_LOCK_HELD(&dn->dn_struct_rwlock));
1863         ASSERT3U(dn->dn_nlevels, >, level);
1864 
1865         *dbp = NULL;
1866 top:
1867         /* dbuf_find() returns with db_mtx held */
1868         db = dbuf_find(dn, level, blkid);
1869 
1870         if (db == NULL) {
1871                 blkptr_t *bp = NULL;
1872                 int err;
1873 
1874                 ASSERT3P(parent, ==, NULL);
1875                 err = dbuf_findbp(dn, level, blkid, fail_sparse, &parent, &bp);
1876                 if (fail_sparse) {
1877                         if (err == 0 && bp && BP_IS_HOLE(bp))
1878                                 err = SET_ERROR(ENOENT);
1879                         if (err) {
1880                                 if (parent)
1881                                         dbuf_rele(parent, NULL);
1882                                 return (err);
1883                         }
1884                 }
1885                 if (err && err != ENOENT)
1886                         return (err);
1887                 db = dbuf_create(dn, level, blkid, parent, bp);
1888         }
1889 
1890         if (db->db_buf && refcount_is_zero(&db->db_holds)) {
1891                 arc_buf_add_ref(db->db_buf, db);
1892                 if (db->db_buf->b_data == NULL) {
1893                         dbuf_clear(db);
1894                         if (parent) {
1895                                 dbuf_rele(parent, NULL);
1896                                 parent = NULL;
1897                         }
1898                         goto top;
1899                 }
1900                 ASSERT3P(db->db.db_data, ==, db->db_buf->b_data);
1901         }
1902 
1903         ASSERT(db->db_buf == NULL || arc_referenced(db->db_buf));
1904 
1905         /*
1906          * If this buffer is currently syncing out, and we are are
1907          * still referencing it from db_data, we need to make a copy
1908          * of it in case we decide we want to dirty it again in this txg.
1909          */
1910         if (db->db_level == 0 && db->db_blkid != DMU_BONUS_BLKID &&
1911             dn->dn_object != DMU_META_DNODE_OBJECT &&
1912             db->db_state == DB_CACHED && db->db_data_pending) {
1913                 dbuf_dirty_record_t *dr = db->db_data_pending;
1914 
1915                 if (dr->dt.dl.dr_data == db->db_buf) {
1916                         arc_buf_contents_t type = DBUF_GET_BUFC_TYPE(db);
1917 
1918                         dbuf_set_data(db,
1919                             arc_buf_alloc(dn->dn_objset->os_spa,
1920                             db->db.db_size, db, type));
1921                         bcopy(dr->dt.dl.dr_data->b_data, db->db.db_data,
1922                             db->db.db_size);
1923                 }
1924         }
1925 
1926         (void) refcount_add(&db->db_holds, tag);
1927         dbuf_update_data(db);
1928         DBUF_VERIFY(db);
1929         mutex_exit(&db->db_mtx);
1930 
1931         /* NOTE: we can't rele the parent until after we drop the db_mtx */
1932         if (parent)
1933                 dbuf_rele(parent, NULL);
1934 
1935         ASSERT3P(DB_DNODE(db), ==, dn);
1936         ASSERT3U(db->db_blkid, ==, blkid);
1937         ASSERT3U(db->db_level, ==, level);
1938         *dbp = db;
1939 
1940         return (0);
1941 }
1942 
1943 dmu_buf_impl_t *
1944 dbuf_hold(dnode_t *dn, uint64_t blkid, void *tag)
1945 {
1946         dmu_buf_impl_t *db;
1947         int err = dbuf_hold_impl(dn, 0, blkid, FALSE, tag, &db);
1948         return (err ? NULL : db);
1949 }
1950 
1951 dmu_buf_impl_t *
1952 dbuf_hold_level(dnode_t *dn, int level, uint64_t blkid, void *tag)
1953 {
1954         dmu_buf_impl_t *db;
1955         int err = dbuf_hold_impl(dn, level, blkid, FALSE, tag, &db);
1956         return (err ? NULL : db);
1957 }
1958 
1959 void
1960 dbuf_create_bonus(dnode_t *dn)
1961 {
1962         ASSERT(RW_WRITE_HELD(&dn->dn_struct_rwlock));
1963 
1964         ASSERT(dn->dn_bonus == NULL);
1965         dn->dn_bonus = dbuf_create(dn, 0, DMU_BONUS_BLKID, dn->dn_dbuf, NULL);
1966 }
1967 
1968 int
1969 dbuf_spill_set_blksz(dmu_buf_t *db_fake, uint64_t blksz, dmu_tx_t *tx)
1970 {
1971         dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
1972         dnode_t *dn;
1973 
1974         if (db->db_blkid != DMU_SPILL_BLKID)
1975                 return (SET_ERROR(ENOTSUP));
1976         if (blksz == 0)
1977                 blksz = SPA_MINBLOCKSIZE;
1978         if (blksz > SPA_MAXBLOCKSIZE)
1979                 blksz = SPA_MAXBLOCKSIZE;
1980         else
1981                 blksz = P2ROUNDUP(blksz, SPA_MINBLOCKSIZE);
1982 
1983         DB_DNODE_ENTER(db);
1984         dn = DB_DNODE(db);
1985         rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
1986         dbuf_new_size(db, blksz, tx);
1987         rw_exit(&dn->dn_struct_rwlock);
1988         DB_DNODE_EXIT(db);
1989 
1990         return (0);
1991 }
1992 
1993 void
1994 dbuf_rm_spill(dnode_t *dn, dmu_tx_t *tx)
1995 {
1996         dbuf_free_range(dn, DMU_SPILL_BLKID, DMU_SPILL_BLKID, tx);
1997 }
1998 
1999 #pragma weak dmu_buf_add_ref = dbuf_add_ref
2000 void
2001 dbuf_add_ref(dmu_buf_impl_t *db, void *tag)
2002 {
2003         int64_t holds = refcount_add(&db->db_holds, tag);
2004         ASSERT(holds > 1);
2005 }
2006 
2007 /*
2008  * If you call dbuf_rele() you had better not be referencing the dnode handle
2009  * unless you have some other direct or indirect hold on the dnode. (An indirect
2010  * hold is a hold on one of the dnode's dbufs, including the bonus buffer.)
2011  * Without that, the dbuf_rele() could lead to a dnode_rele() followed by the
2012  * dnode's parent dbuf evicting its dnode handles.
2013  */
2014 #pragma weak dmu_buf_rele = dbuf_rele
2015 void
2016 dbuf_rele(dmu_buf_impl_t *db, void *tag)
2017 {
2018         mutex_enter(&db->db_mtx);
2019         dbuf_rele_and_unlock(db, tag);
2020 }
2021 
2022 /*
2023  * dbuf_rele() for an already-locked dbuf.  This is necessary to allow
2024  * db_dirtycnt and db_holds to be updated atomically.
2025  */
2026 void
2027 dbuf_rele_and_unlock(dmu_buf_impl_t *db, void *tag)
2028 {
2029         int64_t holds;
2030 
2031         ASSERT(MUTEX_HELD(&db->db_mtx));
2032         DBUF_VERIFY(db);
2033 
2034         /*
2035          * Remove the reference to the dbuf before removing its hold on the
2036          * dnode so we can guarantee in dnode_move() that a referenced bonus
2037          * buffer has a corresponding dnode hold.
2038          */
2039         holds = refcount_remove(&db->db_holds, tag);
2040         ASSERT(holds >= 0);
2041 
2042         /*
2043          * We can't freeze indirects if there is a possibility that they
2044          * may be modified in the current syncing context.
2045          */
2046         if (db->db_buf && holds == (db->db_level == 0 ? db->db_dirtycnt : 0))
2047                 arc_buf_freeze(db->db_buf);
2048 
2049         if (holds == db->db_dirtycnt &&
2050             db->db_level == 0 && db->db_immediate_evict)
2051                 dbuf_evict_user(db);
2052 
2053         if (holds == 0) {
2054                 if (db->db_blkid == DMU_BONUS_BLKID) {
2055                         mutex_exit(&db->db_mtx);
2056 
2057                         /*
2058                          * If the dnode moves here, we cannot cross this barrier
2059                          * until the move completes.
2060                          */
2061                         DB_DNODE_ENTER(db);
2062                         (void) atomic_dec_32_nv(&DB_DNODE(db)->dn_dbufs_count);
2063                         DB_DNODE_EXIT(db);
2064                         /*
2065                          * The bonus buffer's dnode hold is no longer discounted
2066                          * in dnode_move(). The dnode cannot move until after
2067                          * the dnode_rele().
2068                          */
2069                         dnode_rele(DB_DNODE(db), db);
2070                 } else if (db->db_buf == NULL) {
2071                         /*
2072                          * This is a special case: we never associated this
2073                          * dbuf with any data allocated from the ARC.
2074                          */
2075                         ASSERT(db->db_state == DB_UNCACHED ||
2076                             db->db_state == DB_NOFILL);
2077                         dbuf_evict(db);
2078                 } else if (arc_released(db->db_buf)) {
2079                         arc_buf_t *buf = db->db_buf;
2080                         /*
2081                          * This dbuf has anonymous data associated with it.
2082                          */
2083                         dbuf_set_data(db, NULL);
2084                         VERIFY(arc_buf_remove_ref(buf, db));
2085                         dbuf_evict(db);
2086                 } else {
2087                         VERIFY(!arc_buf_remove_ref(db->db_buf, db));
2088 
2089                         /*
2090                          * A dbuf will be eligible for eviction if either the
2091                          * 'primarycache' property is set or a duplicate
2092                          * copy of this buffer is already cached in the arc.
2093                          *
2094                          * In the case of the 'primarycache' a buffer
2095                          * is considered for eviction if it matches the
2096                          * criteria set in the property.
2097                          *
2098                          * To decide if our buffer is considered a
2099                          * duplicate, we must call into the arc to determine
2100                          * if multiple buffers are referencing the same
2101                          * block on-disk. If so, then we simply evict
2102                          * ourselves.
2103                          */
2104                         if (!DBUF_IS_CACHEABLE(db) ||
2105                             arc_buf_eviction_needed(db->db_buf))
2106                                 dbuf_clear(db);
2107                         else
2108                                 mutex_exit(&db->db_mtx);
2109                 }
2110         } else {
2111                 mutex_exit(&db->db_mtx);
2112         }
2113 }
2114 
2115 #pragma weak dmu_buf_refcount = dbuf_refcount
2116 uint64_t
2117 dbuf_refcount(dmu_buf_impl_t *db)
2118 {
2119         return (refcount_count(&db->db_holds));
2120 }
2121 
2122 void *
2123 dmu_buf_set_user(dmu_buf_t *db_fake, void *user_ptr, void *user_data_ptr_ptr,
2124     dmu_buf_evict_func_t *evict_func)
2125 {
2126         return (dmu_buf_update_user(db_fake, NULL, user_ptr,
2127             user_data_ptr_ptr, evict_func));
2128 }
2129 
2130 void *
2131 dmu_buf_set_user_ie(dmu_buf_t *db_fake, void *user_ptr, void *user_data_ptr_ptr,
2132     dmu_buf_evict_func_t *evict_func)
2133 {
2134         dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
2135 
2136         db->db_immediate_evict = TRUE;
2137         return (dmu_buf_update_user(db_fake, NULL, user_ptr,
2138             user_data_ptr_ptr, evict_func));
2139 }
2140 
2141 void *
2142 dmu_buf_update_user(dmu_buf_t *db_fake, void *old_user_ptr, void *user_ptr,
2143     void *user_data_ptr_ptr, dmu_buf_evict_func_t *evict_func)
2144 {
2145         dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
2146         ASSERT(db->db_level == 0);
2147 
2148         ASSERT((user_ptr == NULL) == (evict_func == NULL));
2149 
2150         mutex_enter(&db->db_mtx);
2151 
2152         if (db->db_user_ptr == old_user_ptr) {
2153                 db->db_user_ptr = user_ptr;
2154                 db->db_user_data_ptr_ptr = user_data_ptr_ptr;
2155                 db->db_evict_func = evict_func;
2156 
2157                 dbuf_update_data(db);
2158         } else {
2159                 old_user_ptr = db->db_user_ptr;
2160         }
2161 
2162         mutex_exit(&db->db_mtx);
2163         return (old_user_ptr);
2164 }
2165 
2166 void *
2167 dmu_buf_get_user(dmu_buf_t *db_fake)
2168 {
2169         dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
2170         ASSERT(!refcount_is_zero(&db->db_holds));
2171 
2172         return (db->db_user_ptr);
2173 }
2174 
2175 boolean_t
2176 dmu_buf_freeable(dmu_buf_t *dbuf)
2177 {
2178         boolean_t res = B_FALSE;
2179         dmu_buf_impl_t *db = (dmu_buf_impl_t *)dbuf;
2180 
2181         if (db->db_blkptr)
2182                 res = dsl_dataset_block_freeable(db->db_objset->os_dsl_dataset,
2183                     db->db_blkptr, db->db_blkptr->blk_birth);
2184 
2185         return (res);
2186 }
2187 
2188 blkptr_t *
2189 dmu_buf_get_blkptr(dmu_buf_t *db)
2190 {
2191         dmu_buf_impl_t *dbi = (dmu_buf_impl_t *)db;
2192         return (dbi->db_blkptr);
2193 }
2194 
2195 static void
2196 dbuf_check_blkptr(dnode_t *dn, dmu_buf_impl_t *db)
2197 {
2198         /* ASSERT(dmu_tx_is_syncing(tx) */
2199         ASSERT(MUTEX_HELD(&db->db_mtx));
2200 
2201         if (db->db_blkptr != NULL)
2202                 return;
2203 
2204         if (db->db_blkid == DMU_SPILL_BLKID) {
2205                 db->db_blkptr = &dn->dn_phys->dn_spill;
2206                 BP_ZERO(db->db_blkptr);
2207                 return;
2208         }
2209         if (db->db_level == dn->dn_phys->dn_nlevels-1) {
2210                 /*
2211                  * This buffer was allocated at a time when there was
2212                  * no available blkptrs from the dnode, or it was
2213                  * inappropriate to hook it in (i.e., nlevels mis-match).
2214                  */
2215                 ASSERT(db->db_blkid < dn->dn_phys->dn_nblkptr);
2216                 ASSERT(db->db_parent == NULL);
2217                 db->db_parent = dn->dn_dbuf;
2218                 db->db_blkptr = &dn->dn_phys->dn_blkptr[db->db_blkid];
2219                 DBUF_VERIFY(db);
2220         } else {
2221                 dmu_buf_impl_t *parent = db->db_parent;
2222                 int epbs = dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT;
2223 
2224                 ASSERT(dn->dn_phys->dn_nlevels > 1);
2225                 if (parent == NULL) {
2226                         mutex_exit(&db->db_mtx);
2227                         rw_enter(&dn->dn_struct_rwlock, RW_READER);
2228                         (void) dbuf_hold_impl(dn, db->db_level+1,
2229                             db->db_blkid >> epbs, FALSE, db, &parent);
2230                         rw_exit(&dn->dn_struct_rwlock);
2231                         mutex_enter(&db->db_mtx);
2232                         db->db_parent = parent;
2233                 }
2234                 db->db_blkptr = (blkptr_t *)parent->db.db_data +
2235                     (db->db_blkid & ((1ULL << epbs) - 1));
2236                 DBUF_VERIFY(db);
2237         }
2238 }
2239 
2240 static void
2241 dbuf_sync_indirect(dbuf_dirty_record_t *dr, dmu_tx_t *tx)
2242 {
2243         dmu_buf_impl_t *db = dr->dr_dbuf;
2244         dnode_t *dn;
2245         zio_t *zio;
2246 
2247         ASSERT(dmu_tx_is_syncing(tx));
2248 
2249         dprintf_dbuf_bp(db, db->db_blkptr, "blkptr=%p", db->db_blkptr);
2250 
2251         mutex_enter(&db->db_mtx);
2252 
2253         ASSERT(db->db_level > 0);
2254         DBUF_VERIFY(db);
2255 
2256         /* Read the block if it hasn't been read yet. */
2257         if (db->db_buf == NULL) {
2258                 mutex_exit(&db->db_mtx);
2259                 (void) dbuf_read(db, NULL, DB_RF_MUST_SUCCEED);
2260                 mutex_enter(&db->db_mtx);
2261         }
2262         ASSERT3U(db->db_state, ==, DB_CACHED);
2263         ASSERT(db->db_buf != NULL);
2264 
2265         DB_DNODE_ENTER(db);
2266         dn = DB_DNODE(db);
2267         /* Indirect block size must match what the dnode thinks it is. */
2268         ASSERT3U(db->db.db_size, ==, 1<<dn->dn_phys->dn_indblkshift);
2269         dbuf_check_blkptr(dn, db);
2270         DB_DNODE_EXIT(db);
2271 
2272         /* Provide the pending dirty record to child dbufs */
2273         db->db_data_pending = dr;
2274 
2275         mutex_exit(&db->db_mtx);
2276         dbuf_write(dr, db->db_buf, tx);
2277 
2278         zio = dr->dr_zio;
2279         mutex_enter(&dr->dt.di.dr_mtx);
2280         dbuf_sync_list(&dr->dt.di.dr_children, tx);
2281         ASSERT(list_head(&dr->dt.di.dr_children) == NULL);
2282         mutex_exit(&dr->dt.di.dr_mtx);
2283         zio_nowait(zio);
2284 }
2285 
2286 static void
2287 dbuf_sync_leaf(dbuf_dirty_record_t *dr, dmu_tx_t *tx)
2288 {
2289         arc_buf_t **datap = &dr->dt.dl.dr_data;
2290         dmu_buf_impl_t *db = dr->dr_dbuf;
2291         dnode_t *dn;
2292         objset_t *os;
2293         uint64_t txg = tx->tx_txg;
2294 
2295         ASSERT(dmu_tx_is_syncing(tx));
2296 
2297         dprintf_dbuf_bp(db, db->db_blkptr, "blkptr=%p", db->db_blkptr);
2298 
2299         mutex_enter(&db->db_mtx);
2300         /*
2301          * To be synced, we must be dirtied.  But we
2302          * might have been freed after the dirty.
2303          */
2304         if (db->db_state == DB_UNCACHED) {
2305                 /* This buffer has been freed since it was dirtied */
2306                 ASSERT(db->db.db_data == NULL);
2307         } else if (db->db_state == DB_FILL) {
2308                 /* This buffer was freed and is now being re-filled */
2309                 ASSERT(db->db.db_data != dr->dt.dl.dr_data);
2310         } else {
2311                 ASSERT(db->db_state == DB_CACHED || db->db_state == DB_NOFILL);
2312         }
2313         DBUF_VERIFY(db);
2314 
2315         DB_DNODE_ENTER(db);
2316         dn = DB_DNODE(db);
2317 
2318         if (db->db_blkid == DMU_SPILL_BLKID) {
2319                 mutex_enter(&dn->dn_mtx);
2320                 dn->dn_phys->dn_flags |= DNODE_FLAG_SPILL_BLKPTR;
2321                 mutex_exit(&dn->dn_mtx);
2322         }
2323 
2324         /*
2325          * If this is a bonus buffer, simply copy the bonus data into the
2326          * dnode.  It will be written out when the dnode is synced (and it
2327          * will be synced, since it must have been dirty for dbuf_sync to
2328          * be called).
2329          */
2330         if (db->db_blkid == DMU_BONUS_BLKID) {
2331                 dbuf_dirty_record_t **drp;
2332 
2333                 ASSERT(*datap != NULL);
2334                 ASSERT0(db->db_level);
2335                 ASSERT3U(dn->dn_phys->dn_bonuslen, <=, DN_MAX_BONUSLEN);
2336                 bcopy(*datap, DN_BONUS(dn->dn_phys), dn->dn_phys->dn_bonuslen);
2337                 DB_DNODE_EXIT(db);
2338 
2339                 if (*datap != db->db.db_data) {
2340                         zio_buf_free(*datap, DN_MAX_BONUSLEN);
2341                         arc_space_return(DN_MAX_BONUSLEN, ARC_SPACE_OTHER);
2342                 }
2343                 db->db_data_pending = NULL;
2344                 drp = &db->db_last_dirty;
2345                 while (*drp != dr)
2346                         drp = &(*drp)->dr_next;
2347                 ASSERT(dr->dr_next == NULL);
2348                 ASSERT(dr->dr_dbuf == db);
2349                 *drp = dr->dr_next;
2350                 kmem_free(dr, sizeof (dbuf_dirty_record_t));
2351                 ASSERT(db->db_dirtycnt > 0);
2352                 db->db_dirtycnt -= 1;
2353                 dbuf_rele_and_unlock(db, (void *)(uintptr_t)txg);
2354                 return;
2355         }
2356 
2357         os = dn->dn_objset;
2358 
2359         /*
2360          * This function may have dropped the db_mtx lock allowing a dmu_sync
2361          * operation to sneak in. As a result, we need to ensure that we
2362          * don't check the dr_override_state until we have returned from
2363          * dbuf_check_blkptr.
2364          */
2365         dbuf_check_blkptr(dn, db);
2366 
2367         /*
2368          * If this buffer is in the middle of an immediate write,
2369          * wait for the synchronous IO to complete.
2370          */
2371         while (dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC) {
2372                 ASSERT(dn->dn_object != DMU_META_DNODE_OBJECT);
2373                 cv_wait(&db->db_changed, &db->db_mtx);
2374                 ASSERT(dr->dt.dl.dr_override_state != DR_NOT_OVERRIDDEN);
2375         }
2376 
2377         if (db->db_state != DB_NOFILL &&
2378             dn->dn_object != DMU_META_DNODE_OBJECT &&
2379             refcount_count(&db->db_holds) > 1 &&
2380             dr->dt.dl.dr_override_state != DR_OVERRIDDEN &&
2381             *datap == db->db_buf) {
2382                 /*
2383                  * If this buffer is currently "in use" (i.e., there
2384                  * are active holds and db_data still references it),
2385                  * then make a copy before we start the write so that
2386                  * any modifications from the open txg will not leak
2387                  * into this write.
2388                  *
2389                  * NOTE: this copy does not need to be made for
2390                  * objects only modified in the syncing context (e.g.
2391                  * DNONE_DNODE blocks).
2392                  */
2393                 int blksz = arc_buf_size(*datap);
2394                 arc_buf_contents_t type = DBUF_GET_BUFC_TYPE(db);
2395                 *datap = arc_buf_alloc(os->os_spa, blksz, db, type);
2396                 bcopy(db->db.db_data, (*datap)->b_data, blksz);
2397         }
2398         db->db_data_pending = dr;
2399 
2400         mutex_exit(&db->db_mtx);
2401 
2402         dbuf_write(dr, *datap, tx);
2403 
2404         ASSERT(!list_link_active(&dr->dr_dirty_node));
2405         if (dn->dn_object == DMU_META_DNODE_OBJECT) {
2406                 list_insert_tail(&dn->dn_dirty_records[txg&TXG_MASK], dr);
2407                 DB_DNODE_EXIT(db);
2408         } else {
2409                 /*
2410                  * Although zio_nowait() does not "wait for an IO", it does
2411                  * initiate the IO. If this is an empty write it seems plausible
2412                  * that the IO could actually be completed before the nowait
2413                  * returns. We need to DB_DNODE_EXIT() first in case
2414                  * zio_nowait() invalidates the dbuf.
2415                  */
2416                 DB_DNODE_EXIT(db);
2417                 zio_nowait(dr->dr_zio);
2418         }
2419 }
2420 
2421 void
2422 dbuf_sync_list(list_t *list, dmu_tx_t *tx)
2423 {
2424         dbuf_dirty_record_t *dr;
2425 
2426         while (dr = list_head(list)) {
2427                 if (dr->dr_zio != NULL) {
2428                         /*
2429                          * If we find an already initialized zio then we
2430                          * are processing the meta-dnode, and we have finished.
2431                          * The dbufs for all dnodes are put back on the list
2432                          * during processing, so that we can zio_wait()
2433                          * these IOs after initiating all child IOs.
2434                          */
2435                         ASSERT3U(dr->dr_dbuf->db.db_object, ==,
2436                             DMU_META_DNODE_OBJECT);
2437                         break;
2438                 }
2439                 list_remove(list, dr);
2440                 if (dr->dr_dbuf->db_level > 0)
2441                         dbuf_sync_indirect(dr, tx);
2442                 else
2443                         dbuf_sync_leaf(dr, tx);
2444         }
2445 }
2446 
2447 /* ARGSUSED */
2448 static void
2449 dbuf_write_ready(zio_t *zio, arc_buf_t *buf, void *vdb)
2450 {
2451         dmu_buf_impl_t *db = vdb;
2452         dnode_t *dn;
2453         blkptr_t *bp = zio->io_bp;
2454         blkptr_t *bp_orig = &zio->io_bp_orig;
2455         spa_t *spa = zio->io_spa;
2456         int64_t delta;
2457         uint64_t fill = 0;
2458         int i;
2459 
2460         ASSERT(db->db_blkptr == bp);
2461 
2462         DB_DNODE_ENTER(db);
2463         dn = DB_DNODE(db);
2464         delta = bp_get_dsize_sync(spa, bp) - bp_get_dsize_sync(spa, bp_orig);
2465         dnode_diduse_space(dn, delta - zio->io_prev_space_delta);
2466         zio->io_prev_space_delta = delta;
2467 
2468         if (BP_IS_HOLE(bp)) {
2469                 ASSERT(bp->blk_fill == 0);
2470                 DB_DNODE_EXIT(db);
2471                 return;
2472         }
2473 
2474         ASSERT((db->db_blkid != DMU_SPILL_BLKID &&
2475             BP_GET_TYPE(bp) == dn->dn_type) ||
2476             (db->db_blkid == DMU_SPILL_BLKID &&
2477             BP_GET_TYPE(bp) == dn->dn_bonustype));
2478         ASSERT(BP_GET_LEVEL(bp) == db->db_level);
2479 
2480         mutex_enter(&db->db_mtx);
2481 
2482 #ifdef ZFS_DEBUG
2483         if (db->db_blkid == DMU_SPILL_BLKID) {
2484                 ASSERT(dn->dn_phys->dn_flags & DNODE_FLAG_SPILL_BLKPTR);
2485                 ASSERT(!(BP_IS_HOLE(db->db_blkptr)) &&
2486                     db->db_blkptr == &dn->dn_phys->dn_spill);
2487         }
2488 #endif
2489 
2490         if (db->db_level == 0) {
2491                 mutex_enter(&dn->dn_mtx);
2492                 if (db->db_blkid > dn->dn_phys->dn_maxblkid &&
2493                     db->db_blkid != DMU_SPILL_BLKID)
2494                         dn->dn_phys->dn_maxblkid = db->db_blkid;
2495                 mutex_exit(&dn->dn_mtx);
2496 
2497                 if (dn->dn_type == DMU_OT_DNODE) {
2498                         dnode_phys_t *dnp = db->db.db_data;
2499                         for (i = db->db.db_size >> DNODE_SHIFT; i > 0;
2500                             i--, dnp++) {
2501                                 if (dnp->dn_type != DMU_OT_NONE)
2502                                         fill++;
2503                         }
2504                 } else {
2505                         fill = 1;
2506                 }
2507         } else {
2508                 blkptr_t *ibp = db->db.db_data;
2509                 ASSERT3U(db->db.db_size, ==, 1<<dn->dn_phys->dn_indblkshift);
2510                 for (i = db->db.db_size >> SPA_BLKPTRSHIFT; i > 0; i--, ibp++) {
2511                         if (BP_IS_HOLE(ibp))
2512                                 continue;
2513                         fill += ibp->blk_fill;
2514                 }
2515         }
2516         DB_DNODE_EXIT(db);
2517 
2518         bp->blk_fill = fill;
2519 
2520         mutex_exit(&db->db_mtx);
2521 }
2522 
2523 /* ARGSUSED */
2524 static void
2525 dbuf_write_done(zio_t *zio, arc_buf_t *buf, void *vdb)
2526 {
2527         dmu_buf_impl_t *db = vdb;
2528         blkptr_t *bp = zio->io_bp;
2529         blkptr_t *bp_orig = &zio->io_bp_orig;
2530         uint64_t txg = zio->io_txg;
2531         dbuf_dirty_record_t **drp, *dr;
2532 
2533         ASSERT0(zio->io_error);
2534         ASSERT(db->db_blkptr == bp);
2535 
2536         /*
2537          * For nopwrites and rewrites we ensure that the bp matches our
2538          * original and bypass all the accounting.
2539          */
2540         if (zio->io_flags & (ZIO_FLAG_IO_REWRITE | ZIO_FLAG_NOPWRITE)) {
2541                 ASSERT(BP_EQUAL(bp, bp_orig));
2542         } else {
2543                 objset_t *os;
2544                 dsl_dataset_t *ds;
2545                 dmu_tx_t *tx;
2546 
2547                 DB_GET_OBJSET(&os, db);
2548                 ds = os->os_dsl_dataset;
2549                 tx = os->os_synctx;
2550 
2551                 (void) dsl_dataset_block_kill(ds, bp_orig, tx, B_TRUE);
2552                 dsl_dataset_block_born(ds, bp, tx);
2553         }
2554 
2555         mutex_enter(&db->db_mtx);
2556 
2557         DBUF_VERIFY(db);
2558 
2559         drp = &db->db_last_dirty;
2560         while ((dr = *drp) != db->db_data_pending)
2561                 drp = &dr->dr_next;
2562         ASSERT(!list_link_active(&dr->dr_dirty_node));
2563         ASSERT(dr->dr_txg == txg);
2564         ASSERT(dr->dr_dbuf == db);
2565         ASSERT(dr->dr_next == NULL);
2566         *drp = dr->dr_next;
2567 
2568 #ifdef ZFS_DEBUG
2569         if (db->db_blkid == DMU_SPILL_BLKID) {
2570                 dnode_t *dn;
2571 
2572                 DB_DNODE_ENTER(db);
2573                 dn = DB_DNODE(db);
2574                 ASSERT(dn->dn_phys->dn_flags & DNODE_FLAG_SPILL_BLKPTR);
2575                 ASSERT(!(BP_IS_HOLE(db->db_blkptr)) &&
2576                     db->db_blkptr == &dn->dn_phys->dn_spill);
2577                 DB_DNODE_EXIT(db);
2578         }
2579 #endif
2580 
2581         if (db->db_level == 0) {
2582                 ASSERT(db->db_blkid != DMU_BONUS_BLKID);
2583                 ASSERT(dr->dt.dl.dr_override_state == DR_NOT_OVERRIDDEN);
2584                 if (db->db_state != DB_NOFILL) {
2585                         if (dr->dt.dl.dr_data != db->db_buf)
2586                                 VERIFY(arc_buf_remove_ref(dr->dt.dl.dr_data,
2587                                     db));
2588                         else if (!arc_released(db->db_buf))
2589                                 arc_set_callback(db->db_buf, dbuf_do_evict, db);
2590                 }
2591         } else {
2592                 dnode_t *dn;
2593 
2594                 DB_DNODE_ENTER(db);
2595                 dn = DB_DNODE(db);
2596                 ASSERT(list_head(&dr->dt.di.dr_children) == NULL);
2597                 ASSERT3U(db->db.db_size, ==, 1<<dn->dn_phys->dn_indblkshift);
2598                 if (!BP_IS_HOLE(db->db_blkptr)) {
2599                         int epbs =
2600                             dn->dn_phys->dn_indblkshift - SPA_BLKPTRSHIFT;
2601                         ASSERT3U(BP_GET_LSIZE(db->db_blkptr), ==,
2602                             db->db.db_size);
2603                         ASSERT3U(dn->dn_phys->dn_maxblkid
2604                             >> (db->db_level * epbs), >=, db->db_blkid);
2605                         arc_set_callback(db->db_buf, dbuf_do_evict, db);
2606                 }
2607                 DB_DNODE_EXIT(db);
2608                 mutex_destroy(&dr->dt.di.dr_mtx);
2609                 list_destroy(&dr->dt.di.dr_children);
2610         }
2611         kmem_free(dr, sizeof (dbuf_dirty_record_t));
2612 
2613         cv_broadcast(&db->db_changed);
2614         ASSERT(db->db_dirtycnt > 0);
2615         db->db_dirtycnt -= 1;
2616         db->db_data_pending = NULL;
2617         dbuf_rele_and_unlock(db, (void *)(uintptr_t)txg);
2618 }
2619 
2620 static void
2621 dbuf_write_nofill_ready(zio_t *zio)
2622 {
2623         dbuf_write_ready(zio, NULL, zio->io_private);
2624 }
2625 
2626 static void
2627 dbuf_write_nofill_done(zio_t *zio)
2628 {
2629         dbuf_write_done(zio, NULL, zio->io_private);
2630 }
2631 
2632 static void
2633 dbuf_write_override_ready(zio_t *zio)
2634 {
2635         dbuf_dirty_record_t *dr = zio->io_private;
2636         dmu_buf_impl_t *db = dr->dr_dbuf;
2637 
2638         dbuf_write_ready(zio, NULL, db);
2639 }
2640 
2641 static void
2642 dbuf_write_override_done(zio_t *zio)
2643 {
2644         dbuf_dirty_record_t *dr = zio->io_private;
2645         dmu_buf_impl_t *db = dr->dr_dbuf;
2646         blkptr_t *obp = &dr->dt.dl.dr_overridden_by;
2647 
2648         mutex_enter(&db->db_mtx);
2649         if (!BP_EQUAL(zio->io_bp, obp)) {
2650                 if (!BP_IS_HOLE(obp))
2651                         dsl_free(spa_get_dsl(zio->io_spa), zio->io_txg, obp);
2652                 arc_release(dr->dt.dl.dr_data, db);
2653         }
2654         mutex_exit(&db->db_mtx);
2655 
2656         dbuf_write_done(zio, NULL, db);
2657 }
2658 
2659 /* Issue I/O to commit a dirty buffer to disk. */
2660 static void
2661 dbuf_write(dbuf_dirty_record_t *dr, arc_buf_t *data, dmu_tx_t *tx)
2662 {
2663         dmu_buf_impl_t *db = dr->dr_dbuf;
2664         dnode_t *dn;
2665         objset_t *os;
2666         dmu_buf_impl_t *parent = db->db_parent;
2667         uint64_t txg = tx->tx_txg;
2668         zbookmark_t zb;
2669         zio_prop_t zp;
2670         zio_t *zio;
2671         int wp_flag = 0;
2672 
2673         DB_DNODE_ENTER(db);
2674         dn = DB_DNODE(db);
2675         os = dn->dn_objset;
2676 
2677         if (db->db_state != DB_NOFILL) {
2678                 if (db->db_level > 0 || dn->dn_type == DMU_OT_DNODE) {
2679                         /*
2680                          * Private object buffers are released here rather
2681                          * than in dbuf_dirty() since they are only modified
2682                          * in the syncing context and we don't want the
2683                          * overhead of making multiple copies of the data.
2684                          */
2685                         if (BP_IS_HOLE(db->db_blkptr)) {
2686                                 arc_buf_thaw(data);
2687                         } else {
2688                                 dbuf_release_bp(db);
2689                         }
2690                 }
2691         }
2692 
2693         if (parent != dn->dn_dbuf) {
2694                 /* Our parent is an indirect block. */
2695                 /* We have a dirty parent that has been scheduled for write. */
2696                 ASSERT(parent && parent->db_data_pending);
2697                 /* Our parent's buffer is one level closer to the dnode. */
2698                 ASSERT(db->db_level == parent->db_level-1);
2699                 /*
2700                  * We're about to modify our parent's db_data by modifying
2701                  * our block pointer, so the parent must be released.
2702                  */
2703                 ASSERT(arc_released(parent->db_buf));
2704                 zio = parent->db_data_pending->dr_zio;
2705         } else {
2706                 /* Our parent is the dnode itself. */
2707                 ASSERT((db->db_level == dn->dn_phys->dn_nlevels-1 &&
2708                     db->db_blkid != DMU_SPILL_BLKID) ||
2709                     (db->db_blkid == DMU_SPILL_BLKID && db->db_level == 0));
2710                 if (db->db_blkid != DMU_SPILL_BLKID)
2711                         ASSERT3P(db->db_blkptr, ==,
2712                             &dn->dn_phys->dn_blkptr[db->db_blkid]);
2713                 zio = dn->dn_zio;
2714         }
2715 
2716         ASSERT(db->db_level == 0 || data == db->db_buf);
2717         ASSERT3U(db->db_blkptr->blk_birth, <=, txg);
2718         ASSERT(zio);
2719 
2720         SET_BOOKMARK(&zb, os->os_dsl_dataset ?
2721             os->os_dsl_dataset->ds_object : DMU_META_OBJSET,
2722             db->db.db_object, db->db_level, db->db_blkid);
2723 
2724         if (db->db_blkid == DMU_SPILL_BLKID)
2725                 wp_flag = WP_SPILL;
2726         wp_flag |= (db->db_state == DB_NOFILL) ? WP_NOFILL : 0;
2727 
2728         dmu_write_policy(os, dn, db->db_level, wp_flag, &zp);
2729         DB_DNODE_EXIT(db);
2730 
2731         if (db->db_level == 0 && dr->dt.dl.dr_override_state == DR_OVERRIDDEN) {
2732                 ASSERT(db->db_state != DB_NOFILL);
2733                 dr->dr_zio = zio_write(zio, os->os_spa, txg,
2734                     db->db_blkptr, data->b_data, arc_buf_size(data), &zp,
2735                     dbuf_write_override_ready, dbuf_write_override_done, dr,
2736                     ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_MUSTSUCCEED, &zb);
2737                 mutex_enter(&db->db_mtx);
2738                 dr->dt.dl.dr_override_state = DR_NOT_OVERRIDDEN;
2739                 zio_write_override(dr->dr_zio, &dr->dt.dl.dr_overridden_by,
2740                     dr->dt.dl.dr_copies, dr->dt.dl.dr_nopwrite);
2741                 mutex_exit(&db->db_mtx);
2742         } else if (db->db_state == DB_NOFILL) {
2743                 ASSERT(zp.zp_checksum == ZIO_CHECKSUM_OFF);
2744                 dr->dr_zio = zio_write(zio, os->os_spa, txg,
2745                     db->db_blkptr, NULL, db->db.db_size, &zp,
2746                     dbuf_write_nofill_ready, dbuf_write_nofill_done, db,
2747                     ZIO_PRIORITY_ASYNC_WRITE,
2748                     ZIO_FLAG_MUSTSUCCEED | ZIO_FLAG_NODATA, &zb);
2749         } else {
2750                 ASSERT(arc_released(data));
2751                 dr->dr_zio = arc_write(zio, os->os_spa, txg,
2752                     db->db_blkptr, data, DBUF_IS_L2CACHEABLE(db),
2753                     DBUF_IS_L2COMPRESSIBLE(db), &zp, dbuf_write_ready,
2754                     dbuf_write_done, db, ZIO_PRIORITY_ASYNC_WRITE,
2755                     ZIO_FLAG_MUSTSUCCEED, &zb);
2756         }
2757 }