1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  23  * Copyright (c) 2013 by Delphix. All rights reserved.
  24  */
  25 
  26 #include <sys/dmu.h>
  27 #include <sys/dmu_impl.h>
  28 #include <sys/dmu_tx.h>
  29 #include <sys/dbuf.h>
  30 #include <sys/dnode.h>
  31 #include <sys/zfs_context.h>
  32 #include <sys/dmu_objset.h>
  33 #include <sys/dmu_traverse.h>
  34 #include <sys/dsl_dataset.h>
  35 #include <sys/dsl_dir.h>
  36 #include <sys/dsl_pool.h>
  37 #include <sys/dsl_synctask.h>
  38 #include <sys/dsl_prop.h>
  39 #include <sys/dmu_zfetch.h>
  40 #include <sys/zfs_ioctl.h>
  41 #include <sys/zap.h>
  42 #include <sys/zio_checksum.h>
  43 #include <sys/zio_compress.h>
  44 #include <sys/sa.h>
  45 #ifdef _KERNEL
  46 #include <sys/vmsystm.h>
  47 #include <sys/zfs_znode.h>
  48 #endif
  49 
  50 /*
  51  * Enable/disable nopwrite feature.
  52  */
  53 int zfs_nopwrite_enabled = 1;
  54 
  55 const dmu_object_type_info_t dmu_ot[DMU_OT_NUMTYPES] = {
  56         {       DMU_BSWAP_UINT8,        TRUE,   "unallocated"           },
  57         {       DMU_BSWAP_ZAP,          TRUE,   "object directory"      },
  58         {       DMU_BSWAP_UINT64,       TRUE,   "object array"          },
  59         {       DMU_BSWAP_UINT8,        TRUE,   "packed nvlist"         },
  60         {       DMU_BSWAP_UINT64,       TRUE,   "packed nvlist size"    },
  61         {       DMU_BSWAP_UINT64,       TRUE,   "bpobj"                 },
  62         {       DMU_BSWAP_UINT64,       TRUE,   "bpobj header"          },
  63         {       DMU_BSWAP_UINT64,       TRUE,   "SPA space map header"  },
  64         {       DMU_BSWAP_UINT64,       TRUE,   "SPA space map"         },
  65         {       DMU_BSWAP_UINT64,       TRUE,   "ZIL intent log"        },
  66         {       DMU_BSWAP_DNODE,        TRUE,   "DMU dnode"             },
  67         {       DMU_BSWAP_OBJSET,       TRUE,   "DMU objset"            },
  68         {       DMU_BSWAP_UINT64,       TRUE,   "DSL directory"         },
  69         {       DMU_BSWAP_ZAP,          TRUE,   "DSL directory child map"},
  70         {       DMU_BSWAP_ZAP,          TRUE,   "DSL dataset snap map"  },
  71         {       DMU_BSWAP_ZAP,          TRUE,   "DSL props"             },
  72         {       DMU_BSWAP_UINT64,       TRUE,   "DSL dataset"           },
  73         {       DMU_BSWAP_ZNODE,        TRUE,   "ZFS znode"             },
  74         {       DMU_BSWAP_OLDACL,       TRUE,   "ZFS V0 ACL"            },
  75         {       DMU_BSWAP_UINT8,        FALSE,  "ZFS plain file"        },
  76         {       DMU_BSWAP_ZAP,          TRUE,   "ZFS directory"         },
  77         {       DMU_BSWAP_ZAP,          TRUE,   "ZFS master node"       },
  78         {       DMU_BSWAP_ZAP,          TRUE,   "ZFS delete queue"      },
  79         {       DMU_BSWAP_UINT8,        FALSE,  "zvol object"           },
  80         {       DMU_BSWAP_ZAP,          TRUE,   "zvol prop"             },
  81         {       DMU_BSWAP_UINT8,        FALSE,  "other uint8[]"         },
  82         {       DMU_BSWAP_UINT64,       FALSE,  "other uint64[]"        },
  83         {       DMU_BSWAP_ZAP,          TRUE,   "other ZAP"             },
  84         {       DMU_BSWAP_ZAP,          TRUE,   "persistent error log"  },
  85         {       DMU_BSWAP_UINT8,        TRUE,   "SPA history"           },
  86         {       DMU_BSWAP_UINT64,       TRUE,   "SPA history offsets"   },
  87         {       DMU_BSWAP_ZAP,          TRUE,   "Pool properties"       },
  88         {       DMU_BSWAP_ZAP,          TRUE,   "DSL permissions"       },
  89         {       DMU_BSWAP_ACL,          TRUE,   "ZFS ACL"               },
  90         {       DMU_BSWAP_UINT8,        TRUE,   "ZFS SYSACL"            },
  91         {       DMU_BSWAP_UINT8,        TRUE,   "FUID table"            },
  92         {       DMU_BSWAP_UINT64,       TRUE,   "FUID table size"       },
  93         {       DMU_BSWAP_ZAP,          TRUE,   "DSL dataset next clones"},
  94         {       DMU_BSWAP_ZAP,          TRUE,   "scan work queue"       },
  95         {       DMU_BSWAP_ZAP,          TRUE,   "ZFS user/group used"   },
  96         {       DMU_BSWAP_ZAP,          TRUE,   "ZFS user/group quota"  },
  97         {       DMU_BSWAP_ZAP,          TRUE,   "snapshot refcount tags"},
  98         {       DMU_BSWAP_ZAP,          TRUE,   "DDT ZAP algorithm"     },
  99         {       DMU_BSWAP_ZAP,          TRUE,   "DDT statistics"        },
 100         {       DMU_BSWAP_UINT8,        TRUE,   "System attributes"     },
 101         {       DMU_BSWAP_ZAP,          TRUE,   "SA master node"        },
 102         {       DMU_BSWAP_ZAP,          TRUE,   "SA attr registration"  },
 103         {       DMU_BSWAP_ZAP,          TRUE,   "SA attr layouts"       },
 104         {       DMU_BSWAP_ZAP,          TRUE,   "scan translations"     },
 105         {       DMU_BSWAP_UINT8,        FALSE,  "deduplicated block"    },
 106         {       DMU_BSWAP_ZAP,          TRUE,   "DSL deadlist map"      },
 107         {       DMU_BSWAP_UINT64,       TRUE,   "DSL deadlist map hdr"  },
 108         {       DMU_BSWAP_ZAP,          TRUE,   "DSL dir clones"        },
 109         {       DMU_BSWAP_UINT64,       TRUE,   "bpobj subobj"          }
 110 };
 111 
 112 const dmu_object_byteswap_info_t dmu_ot_byteswap[DMU_BSWAP_NUMFUNCS] = {
 113         {       byteswap_uint8_array,   "uint8"         },
 114         {       byteswap_uint16_array,  "uint16"        },
 115         {       byteswap_uint32_array,  "uint32"        },
 116         {       byteswap_uint64_array,  "uint64"        },
 117         {       zap_byteswap,           "zap"           },
 118         {       dnode_buf_byteswap,     "dnode"         },
 119         {       dmu_objset_byteswap,    "objset"        },
 120         {       zfs_znode_byteswap,     "znode"         },
 121         {       zfs_oldacl_byteswap,    "oldacl"        },
 122         {       zfs_acl_byteswap,       "acl"           }
 123 };
 124 
 125 int
 126 dmu_buf_hold(objset_t *os, uint64_t object, uint64_t offset,
 127     void *tag, dmu_buf_t **dbp, int flags)
 128 {
 129         dnode_t *dn;
 130         uint64_t blkid;
 131         dmu_buf_impl_t *db;
 132         int err;
 133         int db_flags = DB_RF_CANFAIL;
 134 
 135         if (flags & DMU_READ_NO_PREFETCH)
 136                 db_flags |= DB_RF_NOPREFETCH;
 137 
 138         err = dnode_hold(os, object, FTAG, &dn);
 139         if (err)
 140                 return (err);
 141         blkid = dbuf_whichblock(dn, offset);
 142         rw_enter(&dn->dn_struct_rwlock, RW_READER);
 143         db = dbuf_hold(dn, blkid, tag);
 144         rw_exit(&dn->dn_struct_rwlock);
 145         if (db == NULL) {
 146                 err = SET_ERROR(EIO);
 147         } else {
 148                 err = dbuf_read(db, NULL, db_flags);
 149                 if (err) {
 150                         dbuf_rele(db, tag);
 151                         db = NULL;
 152                 }
 153         }
 154 
 155         dnode_rele(dn, FTAG);
 156         *dbp = &db->db; /* NULL db plus first field offset is NULL */
 157         return (err);
 158 }
 159 
 160 int
 161 dmu_bonus_max(void)
 162 {
 163         return (DN_MAX_BONUSLEN);
 164 }
 165 
 166 int
 167 dmu_set_bonus(dmu_buf_t *db_fake, int newsize, dmu_tx_t *tx)
 168 {
 169         dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
 170         dnode_t *dn;
 171         int error;
 172 
 173         DB_DNODE_ENTER(db);
 174         dn = DB_DNODE(db);
 175 
 176         if (dn->dn_bonus != db) {
 177                 error = SET_ERROR(EINVAL);
 178         } else if (newsize < 0 || newsize > db_fake->db_size) {
 179                 error = SET_ERROR(EINVAL);
 180         } else {
 181                 dnode_setbonuslen(dn, newsize, tx);
 182                 error = 0;
 183         }
 184 
 185         DB_DNODE_EXIT(db);
 186         return (error);
 187 }
 188 
 189 int
 190 dmu_set_bonustype(dmu_buf_t *db_fake, dmu_object_type_t type, dmu_tx_t *tx)
 191 {
 192         dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
 193         dnode_t *dn;
 194         int error;
 195 
 196         DB_DNODE_ENTER(db);
 197         dn = DB_DNODE(db);
 198 
 199         if (!DMU_OT_IS_VALID(type)) {
 200                 error = SET_ERROR(EINVAL);
 201         } else if (dn->dn_bonus != db) {
 202                 error = SET_ERROR(EINVAL);
 203         } else {
 204                 dnode_setbonus_type(dn, type, tx);
 205                 error = 0;
 206         }
 207 
 208         DB_DNODE_EXIT(db);
 209         return (error);
 210 }
 211 
 212 dmu_object_type_t
 213 dmu_get_bonustype(dmu_buf_t *db_fake)
 214 {
 215         dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
 216         dnode_t *dn;
 217         dmu_object_type_t type;
 218 
 219         DB_DNODE_ENTER(db);
 220         dn = DB_DNODE(db);
 221         type = dn->dn_bonustype;
 222         DB_DNODE_EXIT(db);
 223 
 224         return (type);
 225 }
 226 
 227 int
 228 dmu_rm_spill(objset_t *os, uint64_t object, dmu_tx_t *tx)
 229 {
 230         dnode_t *dn;
 231         int error;
 232 
 233         error = dnode_hold(os, object, FTAG, &dn);
 234         dbuf_rm_spill(dn, tx);
 235         rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
 236         dnode_rm_spill(dn, tx);
 237         rw_exit(&dn->dn_struct_rwlock);
 238         dnode_rele(dn, FTAG);
 239         return (error);
 240 }
 241 
 242 /*
 243  * returns ENOENT, EIO, or 0.
 244  */
 245 int
 246 dmu_bonus_hold(objset_t *os, uint64_t object, void *tag, dmu_buf_t **dbp)
 247 {
 248         dnode_t *dn;
 249         dmu_buf_impl_t *db;
 250         int error;
 251 
 252         error = dnode_hold(os, object, FTAG, &dn);
 253         if (error)
 254                 return (error);
 255 
 256         rw_enter(&dn->dn_struct_rwlock, RW_READER);
 257         if (dn->dn_bonus == NULL) {
 258                 rw_exit(&dn->dn_struct_rwlock);
 259                 rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
 260                 if (dn->dn_bonus == NULL)
 261                         dbuf_create_bonus(dn);
 262         }
 263         db = dn->dn_bonus;
 264 
 265         /* as long as the bonus buf is held, the dnode will be held */
 266         if (refcount_add(&db->db_holds, tag) == 1) {
 267                 VERIFY(dnode_add_ref(dn, db));
 268                 (void) atomic_inc_32_nv(&dn->dn_dbufs_count);
 269         }
 270 
 271         /*
 272          * Wait to drop dn_struct_rwlock until after adding the bonus dbuf's
 273          * hold and incrementing the dbuf count to ensure that dnode_move() sees
 274          * a dnode hold for every dbuf.
 275          */
 276         rw_exit(&dn->dn_struct_rwlock);
 277 
 278         dnode_rele(dn, FTAG);
 279 
 280         VERIFY(0 == dbuf_read(db, NULL, DB_RF_MUST_SUCCEED | DB_RF_NOPREFETCH));
 281 
 282         *dbp = &db->db;
 283         return (0);
 284 }
 285 
 286 /*
 287  * returns ENOENT, EIO, or 0.
 288  *
 289  * This interface will allocate a blank spill dbuf when a spill blk
 290  * doesn't already exist on the dnode.
 291  *
 292  * if you only want to find an already existing spill db, then
 293  * dmu_spill_hold_existing() should be used.
 294  */
 295 int
 296 dmu_spill_hold_by_dnode(dnode_t *dn, uint32_t flags, void *tag, dmu_buf_t **dbp)
 297 {
 298         dmu_buf_impl_t *db = NULL;
 299         int err;
 300 
 301         if ((flags & DB_RF_HAVESTRUCT) == 0)
 302                 rw_enter(&dn->dn_struct_rwlock, RW_READER);
 303 
 304         db = dbuf_hold(dn, DMU_SPILL_BLKID, tag);
 305 
 306         if ((flags & DB_RF_HAVESTRUCT) == 0)
 307                 rw_exit(&dn->dn_struct_rwlock);
 308 
 309         ASSERT(db != NULL);
 310         err = dbuf_read(db, NULL, flags);
 311         if (err == 0)
 312                 *dbp = &db->db;
 313         else
 314                 dbuf_rele(db, tag);
 315         return (err);
 316 }
 317 
 318 int
 319 dmu_spill_hold_existing(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp)
 320 {
 321         dmu_buf_impl_t *db = (dmu_buf_impl_t *)bonus;
 322         dnode_t *dn;
 323         int err;
 324 
 325         DB_DNODE_ENTER(db);
 326         dn = DB_DNODE(db);
 327 
 328         if (spa_version(dn->dn_objset->os_spa) < SPA_VERSION_SA) {
 329                 err = SET_ERROR(EINVAL);
 330         } else {
 331                 rw_enter(&dn->dn_struct_rwlock, RW_READER);
 332 
 333                 if (!dn->dn_have_spill) {
 334                         err = SET_ERROR(ENOENT);
 335                 } else {
 336                         err = dmu_spill_hold_by_dnode(dn,
 337                             DB_RF_HAVESTRUCT | DB_RF_CANFAIL, tag, dbp);
 338                 }
 339 
 340                 rw_exit(&dn->dn_struct_rwlock);
 341         }
 342 
 343         DB_DNODE_EXIT(db);
 344         return (err);
 345 }
 346 
 347 int
 348 dmu_spill_hold_by_bonus(dmu_buf_t *bonus, void *tag, dmu_buf_t **dbp)
 349 {
 350         dmu_buf_impl_t *db = (dmu_buf_impl_t *)bonus;
 351         dnode_t *dn;
 352         int err;
 353 
 354         DB_DNODE_ENTER(db);
 355         dn = DB_DNODE(db);
 356         err = dmu_spill_hold_by_dnode(dn, DB_RF_CANFAIL, tag, dbp);
 357         DB_DNODE_EXIT(db);
 358 
 359         return (err);
 360 }
 361 
 362 /*
 363  * Note: longer-term, we should modify all of the dmu_buf_*() interfaces
 364  * to take a held dnode rather than <os, object> -- the lookup is wasteful,
 365  * and can induce severe lock contention when writing to several files
 366  * whose dnodes are in the same block.
 367  */
 368 static int
 369 dmu_buf_hold_array_by_dnode(dnode_t *dn, uint64_t offset, uint64_t length,
 370     int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp, uint32_t flags)
 371 {
 372         dsl_pool_t *dp = NULL;
 373         dmu_buf_t **dbp;
 374         uint64_t blkid, nblks, i;
 375         uint32_t dbuf_flags;
 376         int err;
 377         zio_t *zio;
 378         hrtime_t start;
 379 
 380         ASSERT(length <= DMU_MAX_ACCESS);
 381 
 382         dbuf_flags = DB_RF_CANFAIL | DB_RF_NEVERWAIT | DB_RF_HAVESTRUCT;
 383         if (flags & DMU_READ_NO_PREFETCH || length > zfetch_array_rd_sz)
 384                 dbuf_flags |= DB_RF_NOPREFETCH;
 385 
 386         rw_enter(&dn->dn_struct_rwlock, RW_READER);
 387         if (dn->dn_datablkshift) {
 388                 int blkshift = dn->dn_datablkshift;
 389                 nblks = (P2ROUNDUP(offset+length, 1ULL<<blkshift) -
 390                     P2ALIGN(offset, 1ULL<<blkshift)) >> blkshift;
 391         } else {
 392                 if (offset + length > dn->dn_datablksz) {
 393                         zfs_panic_recover("zfs: accessing past end of object "
 394                             "%llx/%llx (size=%u access=%llu+%llu)",
 395                             (longlong_t)dn->dn_objset->
 396                             os_dsl_dataset->ds_object,
 397                             (longlong_t)dn->dn_object, dn->dn_datablksz,
 398                             (longlong_t)offset, (longlong_t)length);
 399                         rw_exit(&dn->dn_struct_rwlock);
 400                         return (SET_ERROR(EIO));
 401                 }
 402                 nblks = 1;
 403         }
 404         dbp = kmem_zalloc(sizeof (dmu_buf_t *) * nblks, KM_SLEEP);
 405 
 406         if (dn->dn_objset->os_dsl_dataset)
 407                 dp = dn->dn_objset->os_dsl_dataset->ds_dir->dd_pool;
 408         start = gethrtime();
 409         zio = zio_root(dn->dn_objset->os_spa, NULL, NULL, ZIO_FLAG_CANFAIL);
 410         blkid = dbuf_whichblock(dn, offset);
 411         for (i = 0; i < nblks; i++) {
 412                 dmu_buf_impl_t *db = dbuf_hold(dn, blkid+i, tag);
 413                 if (db == NULL) {
 414                         rw_exit(&dn->dn_struct_rwlock);
 415                         dmu_buf_rele_array(dbp, nblks, tag);
 416                         zio_nowait(zio);
 417                         return (SET_ERROR(EIO));
 418                 }
 419                 /* initiate async i/o */
 420                 if (read) {
 421                         (void) dbuf_read(db, zio, dbuf_flags);
 422                 }
 423                 dbp[i] = &db->db;
 424         }
 425         rw_exit(&dn->dn_struct_rwlock);
 426 
 427         /* wait for async i/o */
 428         err = zio_wait(zio);
 429         /* track read overhead when we are in sync context */
 430         if (dp && dsl_pool_sync_context(dp))
 431                 dp->dp_read_overhead += gethrtime() - start;
 432         if (err) {
 433                 dmu_buf_rele_array(dbp, nblks, tag);
 434                 return (err);
 435         }
 436 
 437         /* wait for other io to complete */
 438         if (read) {
 439                 for (i = 0; i < nblks; i++) {
 440                         dmu_buf_impl_t *db = (dmu_buf_impl_t *)dbp[i];
 441                         mutex_enter(&db->db_mtx);
 442                         while (db->db_state == DB_READ ||
 443                             db->db_state == DB_FILL)
 444                                 cv_wait(&db->db_changed, &db->db_mtx);
 445                         if (db->db_state == DB_UNCACHED)
 446                                 err = SET_ERROR(EIO);
 447                         mutex_exit(&db->db_mtx);
 448                         if (err) {
 449                                 dmu_buf_rele_array(dbp, nblks, tag);
 450                                 return (err);
 451                         }
 452                 }
 453         }
 454 
 455         *numbufsp = nblks;
 456         *dbpp = dbp;
 457         return (0);
 458 }
 459 
 460 static int
 461 dmu_buf_hold_array(objset_t *os, uint64_t object, uint64_t offset,
 462     uint64_t length, int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp)
 463 {
 464         dnode_t *dn;
 465         int err;
 466 
 467         err = dnode_hold(os, object, FTAG, &dn);
 468         if (err)
 469                 return (err);
 470 
 471         err = dmu_buf_hold_array_by_dnode(dn, offset, length, read, tag,
 472             numbufsp, dbpp, DMU_READ_PREFETCH);
 473 
 474         dnode_rele(dn, FTAG);
 475 
 476         return (err);
 477 }
 478 
 479 int
 480 dmu_buf_hold_array_by_bonus(dmu_buf_t *db_fake, uint64_t offset,
 481     uint64_t length, int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp)
 482 {
 483         dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
 484         dnode_t *dn;
 485         int err;
 486 
 487         DB_DNODE_ENTER(db);
 488         dn = DB_DNODE(db);
 489         err = dmu_buf_hold_array_by_dnode(dn, offset, length, read, tag,
 490             numbufsp, dbpp, DMU_READ_PREFETCH);
 491         DB_DNODE_EXIT(db);
 492 
 493         return (err);
 494 }
 495 
 496 void
 497 dmu_buf_rele_array(dmu_buf_t **dbp_fake, int numbufs, void *tag)
 498 {
 499         int i;
 500         dmu_buf_impl_t **dbp = (dmu_buf_impl_t **)dbp_fake;
 501 
 502         if (numbufs == 0)
 503                 return;
 504 
 505         for (i = 0; i < numbufs; i++) {
 506                 if (dbp[i])
 507                         dbuf_rele(dbp[i], tag);
 508         }
 509 
 510         kmem_free(dbp, sizeof (dmu_buf_t *) * numbufs);
 511 }
 512 
 513 void
 514 dmu_prefetch(objset_t *os, uint64_t object, uint64_t offset, uint64_t len)
 515 {
 516         dnode_t *dn;
 517         uint64_t blkid;
 518         int nblks, i, err;
 519 
 520         if (zfs_prefetch_disable)
 521                 return;
 522 
 523         if (len == 0) {  /* they're interested in the bonus buffer */
 524                 dn = DMU_META_DNODE(os);
 525 
 526                 if (object == 0 || object >= DN_MAX_OBJECT)
 527                         return;
 528 
 529                 rw_enter(&dn->dn_struct_rwlock, RW_READER);
 530                 blkid = dbuf_whichblock(dn, object * sizeof (dnode_phys_t));
 531                 dbuf_prefetch(dn, blkid);
 532                 rw_exit(&dn->dn_struct_rwlock);
 533                 return;
 534         }
 535 
 536         /*
 537          * XXX - Note, if the dnode for the requested object is not
 538          * already cached, we will do a *synchronous* read in the
 539          * dnode_hold() call.  The same is true for any indirects.
 540          */
 541         err = dnode_hold(os, object, FTAG, &dn);
 542         if (err != 0)
 543                 return;
 544 
 545         rw_enter(&dn->dn_struct_rwlock, RW_READER);
 546         if (dn->dn_datablkshift) {
 547                 int blkshift = dn->dn_datablkshift;
 548                 nblks = (P2ROUNDUP(offset+len, 1<<blkshift) -
 549                     P2ALIGN(offset, 1<<blkshift)) >> blkshift;
 550         } else {
 551                 nblks = (offset < dn->dn_datablksz);
 552         }
 553 
 554         if (nblks != 0) {
 555                 blkid = dbuf_whichblock(dn, offset);
 556                 for (i = 0; i < nblks; i++)
 557                         dbuf_prefetch(dn, blkid+i);
 558         }
 559 
 560         rw_exit(&dn->dn_struct_rwlock);
 561 
 562         dnode_rele(dn, FTAG);
 563 }
 564 
 565 /*
 566  * Get the next "chunk" of file data to free.  We traverse the file from
 567  * the end so that the file gets shorter over time (if we crashes in the
 568  * middle, this will leave us in a better state).  We find allocated file
 569  * data by simply searching the allocated level 1 indirects.
 570  */
 571 static int
 572 get_next_chunk(dnode_t *dn, uint64_t *start, uint64_t limit)
 573 {
 574         uint64_t len = *start - limit;
 575         uint64_t blkcnt = 0;
 576         uint64_t maxblks = DMU_MAX_ACCESS / (1ULL << (dn->dn_indblkshift + 1));
 577         uint64_t iblkrange =
 578             dn->dn_datablksz * EPB(dn->dn_indblkshift, SPA_BLKPTRSHIFT);
 579 
 580         ASSERT(limit <= *start);
 581 
 582         if (len <= iblkrange * maxblks) {
 583                 *start = limit;
 584                 return (0);
 585         }
 586         ASSERT(ISP2(iblkrange));
 587 
 588         while (*start > limit && blkcnt < maxblks) {
 589                 int err;
 590 
 591                 /* find next allocated L1 indirect */
 592                 err = dnode_next_offset(dn,
 593                     DNODE_FIND_BACKWARDS, start, 2, 1, 0);
 594 
 595                 /* if there are no more, then we are done */
 596                 if (err == ESRCH) {
 597                         *start = limit;
 598                         return (0);
 599                 } else if (err) {
 600                         return (err);
 601                 }
 602                 blkcnt += 1;
 603 
 604                 /* reset offset to end of "next" block back */
 605                 *start = P2ALIGN(*start, iblkrange);
 606                 if (*start <= limit)
 607                         *start = limit;
 608                 else
 609                         *start -= 1;
 610         }
 611         return (0);
 612 }
 613 
 614 static int
 615 dmu_free_long_range_impl(objset_t *os, dnode_t *dn, uint64_t offset,
 616     uint64_t length, boolean_t free_dnode)
 617 {
 618         dmu_tx_t *tx;
 619         uint64_t object_size, start, end, len;
 620         boolean_t trunc = (length == DMU_OBJECT_END);
 621         int align, err;
 622 
 623         align = 1 << dn->dn_datablkshift;
 624         ASSERT(align > 0);
 625         object_size = align == 1 ? dn->dn_datablksz :
 626             (dn->dn_maxblkid + 1) << dn->dn_datablkshift;
 627 
 628         end = offset + length;
 629         if (trunc || end > object_size)
 630                 end = object_size;
 631         if (end <= offset)
 632                 return (0);
 633         length = end - offset;
 634 
 635         while (length) {
 636                 start = end;
 637                 /* assert(offset <= start) */
 638                 err = get_next_chunk(dn, &start, offset);
 639                 if (err)
 640                         return (err);
 641                 len = trunc ? DMU_OBJECT_END : end - start;
 642 
 643                 tx = dmu_tx_create(os);
 644                 dmu_tx_hold_free(tx, dn->dn_object, start, len);
 645                 err = dmu_tx_assign(tx, TXG_WAIT);
 646                 if (err) {
 647                         dmu_tx_abort(tx);
 648                         return (err);
 649                 }
 650 
 651                 dnode_free_range(dn, start, trunc ? -1 : len, tx);
 652 
 653                 if (start == 0 && free_dnode) {
 654                         ASSERT(trunc);
 655                         dnode_free(dn, tx);
 656                 }
 657 
 658                 length -= end - start;
 659 
 660                 dmu_tx_commit(tx);
 661                 end = start;
 662         }
 663         return (0);
 664 }
 665 
 666 int
 667 dmu_free_long_range(objset_t *os, uint64_t object,
 668     uint64_t offset, uint64_t length)
 669 {
 670         dnode_t *dn;
 671         int err;
 672 
 673         err = dnode_hold(os, object, FTAG, &dn);
 674         if (err != 0)
 675                 return (err);
 676         err = dmu_free_long_range_impl(os, dn, offset, length, FALSE);
 677         dnode_rele(dn, FTAG);
 678         return (err);
 679 }
 680 
 681 int
 682 dmu_free_object(objset_t *os, uint64_t object)
 683 {
 684         dnode_t *dn;
 685         dmu_tx_t *tx;
 686         int err;
 687 
 688         err = dnode_hold_impl(os, object, DNODE_MUST_BE_ALLOCATED,
 689             FTAG, &dn);
 690         if (err != 0)
 691                 return (err);
 692         if (dn->dn_nlevels == 1) {
 693                 tx = dmu_tx_create(os);
 694                 dmu_tx_hold_bonus(tx, object);
 695                 dmu_tx_hold_free(tx, dn->dn_object, 0, DMU_OBJECT_END);
 696                 err = dmu_tx_assign(tx, TXG_WAIT);
 697                 if (err == 0) {
 698                         dnode_free_range(dn, 0, DMU_OBJECT_END, tx);
 699                         dnode_free(dn, tx);
 700                         dmu_tx_commit(tx);
 701                 } else {
 702                         dmu_tx_abort(tx);
 703                 }
 704         } else {
 705                 err = dmu_free_long_range_impl(os, dn, 0, DMU_OBJECT_END, TRUE);
 706         }
 707         dnode_rele(dn, FTAG);
 708         return (err);
 709 }
 710 
 711 int
 712 dmu_free_range(objset_t *os, uint64_t object, uint64_t offset,
 713     uint64_t size, dmu_tx_t *tx)
 714 {
 715         dnode_t *dn;
 716         int err = dnode_hold(os, object, FTAG, &dn);
 717         if (err)
 718                 return (err);
 719         ASSERT(offset < UINT64_MAX);
 720         ASSERT(size == -1ULL || size <= UINT64_MAX - offset);
 721         dnode_free_range(dn, offset, size, tx);
 722         dnode_rele(dn, FTAG);
 723         return (0);
 724 }
 725 
 726 int
 727 dmu_read(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
 728     void *buf, uint32_t flags)
 729 {
 730         dnode_t *dn;
 731         dmu_buf_t **dbp;
 732         int numbufs, err;
 733 
 734         err = dnode_hold(os, object, FTAG, &dn);
 735         if (err)
 736                 return (err);
 737 
 738         /*
 739          * Deal with odd block sizes, where there can't be data past the first
 740          * block.  If we ever do the tail block optimization, we will need to
 741          * handle that here as well.
 742          */
 743         if (dn->dn_maxblkid == 0) {
 744                 int newsz = offset > dn->dn_datablksz ? 0 :
 745                     MIN(size, dn->dn_datablksz - offset);
 746                 bzero((char *)buf + newsz, size - newsz);
 747                 size = newsz;
 748         }
 749 
 750         while (size > 0) {
 751                 uint64_t mylen = MIN(size, DMU_MAX_ACCESS / 2);
 752                 int i;
 753 
 754                 /*
 755                  * NB: we could do this block-at-a-time, but it's nice
 756                  * to be reading in parallel.
 757                  */
 758                 err = dmu_buf_hold_array_by_dnode(dn, offset, mylen,
 759                     TRUE, FTAG, &numbufs, &dbp, flags);
 760                 if (err)
 761                         break;
 762 
 763                 for (i = 0; i < numbufs; i++) {
 764                         int tocpy;
 765                         int bufoff;
 766                         dmu_buf_t *db = dbp[i];
 767 
 768                         ASSERT(size > 0);
 769 
 770                         bufoff = offset - db->db_offset;
 771                         tocpy = (int)MIN(db->db_size - bufoff, size);
 772 
 773                         bcopy((char *)db->db_data + bufoff, buf, tocpy);
 774 
 775                         offset += tocpy;
 776                         size -= tocpy;
 777                         buf = (char *)buf + tocpy;
 778                 }
 779                 dmu_buf_rele_array(dbp, numbufs, FTAG);
 780         }
 781         dnode_rele(dn, FTAG);
 782         return (err);
 783 }
 784 
 785 void
 786 dmu_write(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
 787     const void *buf, dmu_tx_t *tx)
 788 {
 789         dmu_buf_t **dbp;
 790         int numbufs, i;
 791 
 792         if (size == 0)
 793                 return;
 794 
 795         VERIFY(0 == dmu_buf_hold_array(os, object, offset, size,
 796             FALSE, FTAG, &numbufs, &dbp));
 797 
 798         for (i = 0; i < numbufs; i++) {
 799                 int tocpy;
 800                 int bufoff;
 801                 dmu_buf_t *db = dbp[i];
 802 
 803                 ASSERT(size > 0);
 804 
 805                 bufoff = offset - db->db_offset;
 806                 tocpy = (int)MIN(db->db_size - bufoff, size);
 807 
 808                 ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
 809 
 810                 if (tocpy == db->db_size)
 811                         dmu_buf_will_fill(db, tx);
 812                 else
 813                         dmu_buf_will_dirty(db, tx);
 814 
 815                 bcopy(buf, (char *)db->db_data + bufoff, tocpy);
 816 
 817                 if (tocpy == db->db_size)
 818                         dmu_buf_fill_done(db, tx);
 819 
 820                 offset += tocpy;
 821                 size -= tocpy;
 822                 buf = (char *)buf + tocpy;
 823         }
 824         dmu_buf_rele_array(dbp, numbufs, FTAG);
 825 }
 826 
 827 void
 828 dmu_prealloc(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
 829     dmu_tx_t *tx)
 830 {
 831         dmu_buf_t **dbp;
 832         int numbufs, i;
 833 
 834         if (size == 0)
 835                 return;
 836 
 837         VERIFY(0 == dmu_buf_hold_array(os, object, offset, size,
 838             FALSE, FTAG, &numbufs, &dbp));
 839 
 840         for (i = 0; i < numbufs; i++) {
 841                 dmu_buf_t *db = dbp[i];
 842 
 843                 dmu_buf_will_not_fill(db, tx);
 844         }
 845         dmu_buf_rele_array(dbp, numbufs, FTAG);
 846 }
 847 
 848 /*
 849  * DMU support for xuio
 850  */
 851 kstat_t *xuio_ksp = NULL;
 852 
 853 int
 854 dmu_xuio_init(xuio_t *xuio, int nblk)
 855 {
 856         dmu_xuio_t *priv;
 857         uio_t *uio = &xuio->xu_uio;
 858 
 859         uio->uio_iovcnt = nblk;
 860         uio->uio_iov = kmem_zalloc(nblk * sizeof (iovec_t), KM_SLEEP);
 861 
 862         priv = kmem_zalloc(sizeof (dmu_xuio_t), KM_SLEEP);
 863         priv->cnt = nblk;
 864         priv->bufs = kmem_zalloc(nblk * sizeof (arc_buf_t *), KM_SLEEP);
 865         priv->iovp = uio->uio_iov;
 866         XUIO_XUZC_PRIV(xuio) = priv;
 867 
 868         if (XUIO_XUZC_RW(xuio) == UIO_READ)
 869                 XUIOSTAT_INCR(xuiostat_onloan_rbuf, nblk);
 870         else
 871                 XUIOSTAT_INCR(xuiostat_onloan_wbuf, nblk);
 872 
 873         return (0);
 874 }
 875 
 876 void
 877 dmu_xuio_fini(xuio_t *xuio)
 878 {
 879         dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
 880         int nblk = priv->cnt;
 881 
 882         kmem_free(priv->iovp, nblk * sizeof (iovec_t));
 883         kmem_free(priv->bufs, nblk * sizeof (arc_buf_t *));
 884         kmem_free(priv, sizeof (dmu_xuio_t));
 885 
 886         if (XUIO_XUZC_RW(xuio) == UIO_READ)
 887                 XUIOSTAT_INCR(xuiostat_onloan_rbuf, -nblk);
 888         else
 889                 XUIOSTAT_INCR(xuiostat_onloan_wbuf, -nblk);
 890 }
 891 
 892 /*
 893  * Initialize iov[priv->next] and priv->bufs[priv->next] with { off, n, abuf }
 894  * and increase priv->next by 1.
 895  */
 896 int
 897 dmu_xuio_add(xuio_t *xuio, arc_buf_t *abuf, offset_t off, size_t n)
 898 {
 899         struct iovec *iov;
 900         uio_t *uio = &xuio->xu_uio;
 901         dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
 902         int i = priv->next++;
 903 
 904         ASSERT(i < priv->cnt);
 905         ASSERT(off + n <= arc_buf_size(abuf));
 906         iov = uio->uio_iov + i;
 907         iov->iov_base = (char *)abuf->b_data + off;
 908         iov->iov_len = n;
 909         priv->bufs[i] = abuf;
 910         return (0);
 911 }
 912 
 913 int
 914 dmu_xuio_cnt(xuio_t *xuio)
 915 {
 916         dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
 917         return (priv->cnt);
 918 }
 919 
 920 arc_buf_t *
 921 dmu_xuio_arcbuf(xuio_t *xuio, int i)
 922 {
 923         dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
 924 
 925         ASSERT(i < priv->cnt);
 926         return (priv->bufs[i]);
 927 }
 928 
 929 void
 930 dmu_xuio_clear(xuio_t *xuio, int i)
 931 {
 932         dmu_xuio_t *priv = XUIO_XUZC_PRIV(xuio);
 933 
 934         ASSERT(i < priv->cnt);
 935         priv->bufs[i] = NULL;
 936 }
 937 
 938 static void
 939 xuio_stat_init(void)
 940 {
 941         xuio_ksp = kstat_create("zfs", 0, "xuio_stats", "misc",
 942             KSTAT_TYPE_NAMED, sizeof (xuio_stats) / sizeof (kstat_named_t),
 943             KSTAT_FLAG_VIRTUAL);
 944         if (xuio_ksp != NULL) {
 945                 xuio_ksp->ks_data = &xuio_stats;
 946                 kstat_install(xuio_ksp);
 947         }
 948 }
 949 
 950 static void
 951 xuio_stat_fini(void)
 952 {
 953         if (xuio_ksp != NULL) {
 954                 kstat_delete(xuio_ksp);
 955                 xuio_ksp = NULL;
 956         }
 957 }
 958 
 959 void
 960 xuio_stat_wbuf_copied()
 961 {
 962         XUIOSTAT_BUMP(xuiostat_wbuf_copied);
 963 }
 964 
 965 void
 966 xuio_stat_wbuf_nocopy()
 967 {
 968         XUIOSTAT_BUMP(xuiostat_wbuf_nocopy);
 969 }
 970 
 971 #ifdef _KERNEL
 972 int
 973 dmu_read_uio(objset_t *os, uint64_t object, uio_t *uio, uint64_t size)
 974 {
 975         dmu_buf_t **dbp;
 976         int numbufs, i, err;
 977         xuio_t *xuio = NULL;
 978 
 979         /*
 980          * NB: we could do this block-at-a-time, but it's nice
 981          * to be reading in parallel.
 982          */
 983         err = dmu_buf_hold_array(os, object, uio->uio_loffset, size, TRUE, FTAG,
 984             &numbufs, &dbp);
 985         if (err)
 986                 return (err);
 987 
 988         if (uio->uio_extflg == UIO_XUIO)
 989                 xuio = (xuio_t *)uio;
 990 
 991         for (i = 0; i < numbufs; i++) {
 992                 int tocpy;
 993                 int bufoff;
 994                 dmu_buf_t *db = dbp[i];
 995 
 996                 ASSERT(size > 0);
 997 
 998                 bufoff = uio->uio_loffset - db->db_offset;
 999                 tocpy = (int)MIN(db->db_size - bufoff, size);
1000 
1001                 if (xuio) {
1002                         dmu_buf_impl_t *dbi = (dmu_buf_impl_t *)db;
1003                         arc_buf_t *dbuf_abuf = dbi->db_buf;
1004                         arc_buf_t *abuf = dbuf_loan_arcbuf(dbi);
1005                         err = dmu_xuio_add(xuio, abuf, bufoff, tocpy);
1006                         if (!err) {
1007                                 uio->uio_resid -= tocpy;
1008                                 uio->uio_loffset += tocpy;
1009                         }
1010 
1011                         if (abuf == dbuf_abuf)
1012                                 XUIOSTAT_BUMP(xuiostat_rbuf_nocopy);
1013                         else
1014                                 XUIOSTAT_BUMP(xuiostat_rbuf_copied);
1015                 } else {
1016                         err = uiomove((char *)db->db_data + bufoff, tocpy,
1017                             UIO_READ, uio);
1018                 }
1019                 if (err)
1020                         break;
1021 
1022                 size -= tocpy;
1023         }
1024         dmu_buf_rele_array(dbp, numbufs, FTAG);
1025 
1026         return (err);
1027 }
1028 
1029 static int
1030 dmu_write_uio_dnode(dnode_t *dn, uio_t *uio, uint64_t size, dmu_tx_t *tx)
1031 {
1032         dmu_buf_t **dbp;
1033         int numbufs;
1034         int err = 0;
1035         int i;
1036 
1037         err = dmu_buf_hold_array_by_dnode(dn, uio->uio_loffset, size,
1038             FALSE, FTAG, &numbufs, &dbp, DMU_READ_PREFETCH);
1039         if (err)
1040                 return (err);
1041 
1042         for (i = 0; i < numbufs; i++) {
1043                 int tocpy;
1044                 int bufoff;
1045                 dmu_buf_t *db = dbp[i];
1046 
1047                 ASSERT(size > 0);
1048 
1049                 bufoff = uio->uio_loffset - db->db_offset;
1050                 tocpy = (int)MIN(db->db_size - bufoff, size);
1051 
1052                 ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
1053 
1054                 if (tocpy == db->db_size)
1055                         dmu_buf_will_fill(db, tx);
1056                 else
1057                         dmu_buf_will_dirty(db, tx);
1058 
1059                 /*
1060                  * XXX uiomove could block forever (eg. nfs-backed
1061                  * pages).  There needs to be a uiolockdown() function
1062                  * to lock the pages in memory, so that uiomove won't
1063                  * block.
1064                  */
1065                 err = uiomove((char *)db->db_data + bufoff, tocpy,
1066                     UIO_WRITE, uio);
1067 
1068                 if (tocpy == db->db_size)
1069                         dmu_buf_fill_done(db, tx);
1070 
1071                 if (err)
1072                         break;
1073 
1074                 size -= tocpy;
1075         }
1076 
1077         dmu_buf_rele_array(dbp, numbufs, FTAG);
1078         return (err);
1079 }
1080 
1081 int
1082 dmu_write_uio_dbuf(dmu_buf_t *zdb, uio_t *uio, uint64_t size,
1083     dmu_tx_t *tx)
1084 {
1085         dmu_buf_impl_t *db = (dmu_buf_impl_t *)zdb;
1086         dnode_t *dn;
1087         int err;
1088 
1089         if (size == 0)
1090                 return (0);
1091 
1092         DB_DNODE_ENTER(db);
1093         dn = DB_DNODE(db);
1094         err = dmu_write_uio_dnode(dn, uio, size, tx);
1095         DB_DNODE_EXIT(db);
1096 
1097         return (err);
1098 }
1099 
1100 int
1101 dmu_write_uio(objset_t *os, uint64_t object, uio_t *uio, uint64_t size,
1102     dmu_tx_t *tx)
1103 {
1104         dnode_t *dn;
1105         int err;
1106 
1107         if (size == 0)
1108                 return (0);
1109 
1110         err = dnode_hold(os, object, FTAG, &dn);
1111         if (err)
1112                 return (err);
1113 
1114         err = dmu_write_uio_dnode(dn, uio, size, tx);
1115 
1116         dnode_rele(dn, FTAG);
1117 
1118         return (err);
1119 }
1120 
1121 int
1122 dmu_write_pages(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
1123     page_t *pp, dmu_tx_t *tx)
1124 {
1125         dmu_buf_t **dbp;
1126         int numbufs, i;
1127         int err;
1128 
1129         if (size == 0)
1130                 return (0);
1131 
1132         err = dmu_buf_hold_array(os, object, offset, size,
1133             FALSE, FTAG, &numbufs, &dbp);
1134         if (err)
1135                 return (err);
1136 
1137         for (i = 0; i < numbufs; i++) {
1138                 int tocpy, copied, thiscpy;
1139                 int bufoff;
1140                 dmu_buf_t *db = dbp[i];
1141                 caddr_t va;
1142 
1143                 ASSERT(size > 0);
1144                 ASSERT3U(db->db_size, >=, PAGESIZE);
1145 
1146                 bufoff = offset - db->db_offset;
1147                 tocpy = (int)MIN(db->db_size - bufoff, size);
1148 
1149                 ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);
1150 
1151                 if (tocpy == db->db_size)
1152                         dmu_buf_will_fill(db, tx);
1153                 else
1154                         dmu_buf_will_dirty(db, tx);
1155 
1156                 for (copied = 0; copied < tocpy; copied += PAGESIZE) {
1157                         ASSERT3U(pp->p_offset, ==, db->db_offset + bufoff);
1158                         thiscpy = MIN(PAGESIZE, tocpy - copied);
1159                         va = zfs_map_page(pp, S_READ);
1160                         bcopy(va, (char *)db->db_data + bufoff, thiscpy);
1161                         zfs_unmap_page(pp, va);
1162                         pp = pp->p_next;
1163                         bufoff += PAGESIZE;
1164                 }
1165 
1166                 if (tocpy == db->db_size)
1167                         dmu_buf_fill_done(db, tx);
1168 
1169                 offset += tocpy;
1170                 size -= tocpy;
1171         }
1172         dmu_buf_rele_array(dbp, numbufs, FTAG);
1173         return (err);
1174 }
1175 #endif
1176 
1177 /*
1178  * Allocate a loaned anonymous arc buffer.
1179  */
1180 arc_buf_t *
1181 dmu_request_arcbuf(dmu_buf_t *handle, int size)
1182 {
1183         dmu_buf_impl_t *db = (dmu_buf_impl_t *)handle;
1184         spa_t *spa;
1185 
1186         DB_GET_SPA(&spa, db);
1187         return (arc_loan_buf(spa, size));
1188 }
1189 
1190 /*
1191  * Free a loaned arc buffer.
1192  */
1193 void
1194 dmu_return_arcbuf(arc_buf_t *buf)
1195 {
1196         arc_return_buf(buf, FTAG);
1197         VERIFY(arc_buf_remove_ref(buf, FTAG));
1198 }
1199 
1200 /*
1201  * When possible directly assign passed loaned arc buffer to a dbuf.
1202  * If this is not possible copy the contents of passed arc buf via
1203  * dmu_write().
1204  */
1205 void
1206 dmu_assign_arcbuf(dmu_buf_t *handle, uint64_t offset, arc_buf_t *buf,
1207     dmu_tx_t *tx)
1208 {
1209         dmu_buf_impl_t *dbuf = (dmu_buf_impl_t *)handle;
1210         dnode_t *dn;
1211         dmu_buf_impl_t *db;
1212         uint32_t blksz = (uint32_t)arc_buf_size(buf);
1213         uint64_t blkid;
1214 
1215         DB_DNODE_ENTER(dbuf);
1216         dn = DB_DNODE(dbuf);
1217         rw_enter(&dn->dn_struct_rwlock, RW_READER);
1218         blkid = dbuf_whichblock(dn, offset);
1219         VERIFY((db = dbuf_hold(dn, blkid, FTAG)) != NULL);
1220         rw_exit(&dn->dn_struct_rwlock);
1221         DB_DNODE_EXIT(dbuf);
1222 
1223         if (offset == db->db.db_offset && blksz == db->db.db_size) {
1224                 dbuf_assign_arcbuf(db, buf, tx);
1225                 dbuf_rele(db, FTAG);
1226         } else {
1227                 objset_t *os;
1228                 uint64_t object;
1229 
1230                 DB_DNODE_ENTER(dbuf);
1231                 dn = DB_DNODE(dbuf);
1232                 os = dn->dn_objset;
1233                 object = dn->dn_object;
1234                 DB_DNODE_EXIT(dbuf);
1235 
1236                 dbuf_rele(db, FTAG);
1237                 dmu_write(os, object, offset, blksz, buf->b_data, tx);
1238                 dmu_return_arcbuf(buf);
1239                 XUIOSTAT_BUMP(xuiostat_wbuf_copied);
1240         }
1241 }
1242 
1243 typedef struct {
1244         dbuf_dirty_record_t     *dsa_dr;
1245         dmu_sync_cb_t           *dsa_done;
1246         zgd_t                   *dsa_zgd;
1247         dmu_tx_t                *dsa_tx;
1248 } dmu_sync_arg_t;
1249 
1250 /* ARGSUSED */
1251 static void
1252 dmu_sync_ready(zio_t *zio, arc_buf_t *buf, void *varg)
1253 {
1254         dmu_sync_arg_t *dsa = varg;
1255         dmu_buf_t *db = dsa->dsa_zgd->zgd_db;
1256         blkptr_t *bp = zio->io_bp;
1257 
1258         if (zio->io_error == 0) {
1259                 if (BP_IS_HOLE(bp)) {
1260                         /*
1261                          * A block of zeros may compress to a hole, but the
1262                          * block size still needs to be known for replay.
1263                          */
1264                         BP_SET_LSIZE(bp, db->db_size);
1265                 } else {
1266                         ASSERT(BP_GET_LEVEL(bp) == 0);
1267                         bp->blk_fill = 1;
1268                 }
1269         }
1270 }
1271 
1272 static void
1273 dmu_sync_late_arrival_ready(zio_t *zio)
1274 {
1275         dmu_sync_ready(zio, NULL, zio->io_private);
1276 }
1277 
1278 /* ARGSUSED */
1279 static void
1280 dmu_sync_done(zio_t *zio, arc_buf_t *buf, void *varg)
1281 {
1282         dmu_sync_arg_t *dsa = varg;
1283         dbuf_dirty_record_t *dr = dsa->dsa_dr;
1284         dmu_buf_impl_t *db = dr->dr_dbuf;
1285 
1286         mutex_enter(&db->db_mtx);
1287         ASSERT(dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC);
1288         if (zio->io_error == 0) {
1289                 dr->dt.dl.dr_nopwrite = !!(zio->io_flags & ZIO_FLAG_NOPWRITE);
1290                 if (dr->dt.dl.dr_nopwrite) {
1291                         blkptr_t *bp = zio->io_bp;
1292                         blkptr_t *bp_orig = &zio->io_bp_orig;
1293                         uint8_t chksum = BP_GET_CHECKSUM(bp_orig);
1294 
1295                         ASSERT(BP_EQUAL(bp, bp_orig));
1296                         ASSERT(zio->io_prop.zp_compress != ZIO_COMPRESS_OFF);
1297                         ASSERT(zio_checksum_table[chksum].ci_dedup);
1298                 }
1299                 dr->dt.dl.dr_overridden_by = *zio->io_bp;
1300                 dr->dt.dl.dr_override_state = DR_OVERRIDDEN;
1301                 dr->dt.dl.dr_copies = zio->io_prop.zp_copies;
1302                 if (BP_IS_HOLE(&dr->dt.dl.dr_overridden_by))
1303                         BP_ZERO(&dr->dt.dl.dr_overridden_by);
1304         } else {
1305                 dr->dt.dl.dr_override_state = DR_NOT_OVERRIDDEN;
1306         }
1307         cv_broadcast(&db->db_changed);
1308         mutex_exit(&db->db_mtx);
1309 
1310         dsa->dsa_done(dsa->dsa_zgd, zio->io_error);
1311 
1312         kmem_free(dsa, sizeof (*dsa));
1313 }
1314 
1315 static void
1316 dmu_sync_late_arrival_done(zio_t *zio)
1317 {
1318         blkptr_t *bp = zio->io_bp;
1319         dmu_sync_arg_t *dsa = zio->io_private;
1320         blkptr_t *bp_orig = &zio->io_bp_orig;
1321 
1322         if (zio->io_error == 0 && !BP_IS_HOLE(bp)) {
1323                 /*
1324                  * If we didn't allocate a new block (i.e. ZIO_FLAG_NOPWRITE)
1325                  * then there is nothing to do here. Otherwise, free the
1326                  * newly allocated block in this txg.
1327                  */
1328                 if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
1329                         ASSERT(BP_EQUAL(bp, bp_orig));
1330                 } else {
1331                         ASSERT(BP_IS_HOLE(bp_orig) || !BP_EQUAL(bp, bp_orig));
1332                         ASSERT(zio->io_bp->blk_birth == zio->io_txg);
1333                         ASSERT(zio->io_txg > spa_syncing_txg(zio->io_spa));
1334                         zio_free(zio->io_spa, zio->io_txg, zio->io_bp);
1335                 }
1336         }
1337 
1338         dmu_tx_commit(dsa->dsa_tx);
1339 
1340         dsa->dsa_done(dsa->dsa_zgd, zio->io_error);
1341 
1342         kmem_free(dsa, sizeof (*dsa));
1343 }
1344 
1345 static int
1346 dmu_sync_late_arrival(zio_t *pio, objset_t *os, dmu_sync_cb_t *done, zgd_t *zgd,
1347     zio_prop_t *zp, zbookmark_t *zb)
1348 {
1349         dmu_sync_arg_t *dsa;
1350         dmu_tx_t *tx;
1351 
1352         tx = dmu_tx_create(os);
1353         dmu_tx_hold_space(tx, zgd->zgd_db->db_size);
1354         if (dmu_tx_assign(tx, TXG_WAIT) != 0) {
1355                 dmu_tx_abort(tx);
1356                 /* Make zl_get_data do txg_waited_synced() */
1357                 return (SET_ERROR(EIO));
1358         }
1359 
1360         dsa = kmem_alloc(sizeof (dmu_sync_arg_t), KM_SLEEP);
1361         dsa->dsa_dr = NULL;
1362         dsa->dsa_done = done;
1363         dsa->dsa_zgd = zgd;
1364         dsa->dsa_tx = tx;
1365 
1366         zio_nowait(zio_write(pio, os->os_spa, dmu_tx_get_txg(tx), zgd->zgd_bp,
1367             zgd->zgd_db->db_data, zgd->zgd_db->db_size, zp,
1368             dmu_sync_late_arrival_ready, dmu_sync_late_arrival_done, dsa,
1369             ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL, zb));
1370 
1371         return (0);
1372 }
1373 
1374 /*
1375  * Intent log support: sync the block associated with db to disk.
1376  * N.B. and XXX: the caller is responsible for making sure that the
1377  * data isn't changing while dmu_sync() is writing it.
1378  *
1379  * Return values:
1380  *
1381  *      EEXIST: this txg has already been synced, so there's nothing to do.
1382  *              The caller should not log the write.
1383  *
1384  *      ENOENT: the block was dbuf_free_range()'d, so there's nothing to do.
1385  *              The caller should not log the write.
1386  *
1387  *      EALREADY: this block is already in the process of being synced.
1388  *              The caller should track its progress (somehow).
1389  *
1390  *      EIO: could not do the I/O.
1391  *              The caller should do a txg_wait_synced().
1392  *
1393  *      0: the I/O has been initiated.
1394  *              The caller should log this blkptr in the done callback.
1395  *              It is possible that the I/O will fail, in which case
1396  *              the error will be reported to the done callback and
1397  *              propagated to pio from zio_done().
1398  */
1399 int
1400 dmu_sync(zio_t *pio, uint64_t txg, dmu_sync_cb_t *done, zgd_t *zgd)
1401 {
1402         blkptr_t *bp = zgd->zgd_bp;
1403         dmu_buf_impl_t *db = (dmu_buf_impl_t *)zgd->zgd_db;
1404         objset_t *os = db->db_objset;
1405         dsl_dataset_t *ds = os->os_dsl_dataset;
1406         dbuf_dirty_record_t *dr;
1407         dmu_sync_arg_t *dsa;
1408         zbookmark_t zb;
1409         zio_prop_t zp;
1410         dnode_t *dn;
1411 
1412         ASSERT(pio != NULL);
1413         ASSERT(txg != 0);
1414 
1415         SET_BOOKMARK(&zb, ds->ds_object,
1416             db->db.db_object, db->db_level, db->db_blkid);
1417 
1418         DB_DNODE_ENTER(db);
1419         dn = DB_DNODE(db);
1420         dmu_write_policy(os, dn, db->db_level, WP_DMU_SYNC, &zp);
1421         DB_DNODE_EXIT(db);
1422 
1423         /*
1424          * If we're frozen (running ziltest), we always need to generate a bp.
1425          */
1426         if (txg > spa_freeze_txg(os->os_spa))
1427                 return (dmu_sync_late_arrival(pio, os, done, zgd, &zp, &zb));
1428 
1429         /*
1430          * Grabbing db_mtx now provides a barrier between dbuf_sync_leaf()
1431          * and us.  If we determine that this txg is not yet syncing,
1432          * but it begins to sync a moment later, that's OK because the
1433          * sync thread will block in dbuf_sync_leaf() until we drop db_mtx.
1434          */
1435         mutex_enter(&db->db_mtx);
1436 
1437         if (txg <= spa_last_synced_txg(os->os_spa)) {
1438                 /*
1439                  * This txg has already synced.  There's nothing to do.
1440                  */
1441                 mutex_exit(&db->db_mtx);
1442                 return (SET_ERROR(EEXIST));
1443         }
1444 
1445         if (txg <= spa_syncing_txg(os->os_spa)) {
1446                 /*
1447                  * This txg is currently syncing, so we can't mess with
1448                  * the dirty record anymore; just write a new log block.
1449                  */
1450                 mutex_exit(&db->db_mtx);
1451                 return (dmu_sync_late_arrival(pio, os, done, zgd, &zp, &zb));
1452         }
1453 
1454         dr = db->db_last_dirty;
1455         while (dr && dr->dr_txg != txg)
1456                 dr = dr->dr_next;
1457 
1458         if (dr == NULL) {
1459                 /*
1460                  * There's no dr for this dbuf, so it must have been freed.
1461                  * There's no need to log writes to freed blocks, so we're done.
1462                  */
1463                 mutex_exit(&db->db_mtx);
1464                 return (SET_ERROR(ENOENT));
1465         }
1466 
1467         ASSERT(dr->dr_next == NULL || dr->dr_next->dr_txg < txg);
1468 
1469         /*
1470          * Assume the on-disk data is X, the current syncing data is Y,
1471          * and the current in-memory data is Z (currently in dmu_sync).
1472          * X and Z are identical but Y is has been modified. Normally,
1473          * when X and Z are the same we will perform a nopwrite but if Y
1474          * is different we must disable nopwrite since the resulting write
1475          * of Y to disk can free the block containing X. If we allowed a
1476          * nopwrite to occur the block pointing to Z would reference a freed
1477          * block. Since this is a rare case we simplify this by disabling
1478          * nopwrite if the current dmu_sync-ing dbuf has been modified in
1479          * a previous transaction.
1480          */
1481         if (dr->dr_next)
1482                 zp.zp_nopwrite = B_FALSE;
1483 
1484         ASSERT(dr->dr_txg == txg);
1485         if (dr->dt.dl.dr_override_state == DR_IN_DMU_SYNC ||
1486             dr->dt.dl.dr_override_state == DR_OVERRIDDEN) {
1487                 /*
1488                  * We have already issued a sync write for this buffer,
1489                  * or this buffer has already been synced.  It could not
1490                  * have been dirtied since, or we would have cleared the state.
1491                  */
1492                 mutex_exit(&db->db_mtx);
1493                 return (SET_ERROR(EALREADY));
1494         }
1495 
1496         ASSERT(dr->dt.dl.dr_override_state == DR_NOT_OVERRIDDEN);
1497         dr->dt.dl.dr_override_state = DR_IN_DMU_SYNC;
1498         mutex_exit(&db->db_mtx);
1499 
1500         dsa = kmem_alloc(sizeof (dmu_sync_arg_t), KM_SLEEP);
1501         dsa->dsa_dr = dr;
1502         dsa->dsa_done = done;
1503         dsa->dsa_zgd = zgd;
1504         dsa->dsa_tx = NULL;
1505 
1506         zio_nowait(arc_write(pio, os->os_spa, txg,
1507             bp, dr->dt.dl.dr_data, DBUF_IS_L2CACHEABLE(db), &zp,
1508             dmu_sync_ready, dmu_sync_done, dsa,
1509             ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_CANFAIL, &zb));
1510 
1511         return (0);
1512 }
1513 
1514 int
1515 dmu_object_set_blocksize(objset_t *os, uint64_t object, uint64_t size, int ibs,
1516         dmu_tx_t *tx)
1517 {
1518         dnode_t *dn;
1519         int err;
1520 
1521         err = dnode_hold(os, object, FTAG, &dn);
1522         if (err)
1523                 return (err);
1524         err = dnode_set_blksz(dn, size, ibs, tx);
1525         dnode_rele(dn, FTAG);
1526         return (err);
1527 }
1528 
1529 void
1530 dmu_object_set_checksum(objset_t *os, uint64_t object, uint8_t checksum,
1531         dmu_tx_t *tx)
1532 {
1533         dnode_t *dn;
1534 
1535         /* XXX assumes dnode_hold will not get an i/o error */
1536         (void) dnode_hold(os, object, FTAG, &dn);
1537         ASSERT(checksum < ZIO_CHECKSUM_FUNCTIONS);
1538         dn->dn_checksum = checksum;
1539         dnode_setdirty(dn, tx);
1540         dnode_rele(dn, FTAG);
1541 }
1542 
1543 void
1544 dmu_object_set_compress(objset_t *os, uint64_t object, uint8_t compress,
1545         dmu_tx_t *tx)
1546 {
1547         dnode_t *dn;
1548 
1549         /* XXX assumes dnode_hold will not get an i/o error */
1550         (void) dnode_hold(os, object, FTAG, &dn);
1551         ASSERT(compress < ZIO_COMPRESS_FUNCTIONS);
1552         dn->dn_compress = compress;
1553         dnode_setdirty(dn, tx);
1554         dnode_rele(dn, FTAG);
1555 }
1556 
1557 int zfs_mdcomp_disable = 0;
1558 
1559 void
1560 dmu_write_policy(objset_t *os, dnode_t *dn, int level, int wp, zio_prop_t *zp)
1561 {
1562         dmu_object_type_t type = dn ? dn->dn_type : DMU_OT_OBJSET;
1563         boolean_t ismd = (level > 0 || DMU_OT_IS_METADATA(type) ||
1564             (wp & WP_SPILL));
1565         enum zio_checksum checksum = os->os_checksum;
1566         enum zio_compress compress = os->os_compress;
1567         enum zio_checksum dedup_checksum = os->os_dedup_checksum;
1568         boolean_t dedup = B_FALSE;
1569         boolean_t nopwrite = B_FALSE;
1570         boolean_t dedup_verify = os->os_dedup_verify;
1571         int copies = os->os_copies;
1572 
1573         /*
1574          * We maintain different write policies for each of the following
1575          * types of data:
1576          *       1. metadata
1577          *       2. preallocated blocks (i.e. level-0 blocks of a dump device)
1578          *       3. all other level 0 blocks
1579          */
1580         if (ismd) {
1581                 /*
1582                  * XXX -- we should design a compression algorithm
1583                  * that specializes in arrays of bps.
1584                  */
1585                 compress = zfs_mdcomp_disable ? ZIO_COMPRESS_EMPTY :
1586                     ZIO_COMPRESS_LZJB;
1587 
1588                 /*
1589                  * Metadata always gets checksummed.  If the data
1590                  * checksum is multi-bit correctable, and it's not a
1591                  * ZBT-style checksum, then it's suitable for metadata
1592                  * as well.  Otherwise, the metadata checksum defaults
1593                  * to fletcher4.
1594                  */
1595                 if (zio_checksum_table[checksum].ci_correctable < 1 ||
1596                     zio_checksum_table[checksum].ci_eck)
1597                         checksum = ZIO_CHECKSUM_FLETCHER_4;
1598         } else if (wp & WP_NOFILL) {
1599                 ASSERT(level == 0);
1600 
1601                 /*
1602                  * If we're writing preallocated blocks, we aren't actually
1603                  * writing them so don't set any policy properties.  These
1604                  * blocks are currently only used by an external subsystem
1605                  * outside of zfs (i.e. dump) and not written by the zio
1606                  * pipeline.
1607                  */
1608                 compress = ZIO_COMPRESS_OFF;
1609                 checksum = ZIO_CHECKSUM_OFF;
1610         } else {
1611                 compress = zio_compress_select(dn->dn_compress, compress);
1612 
1613                 checksum = (dedup_checksum == ZIO_CHECKSUM_OFF) ?
1614                     zio_checksum_select(dn->dn_checksum, checksum) :
1615                     dedup_checksum;
1616 
1617                 /*
1618                  * Determine dedup setting.  If we are in dmu_sync(),
1619                  * we won't actually dedup now because that's all
1620                  * done in syncing context; but we do want to use the
1621                  * dedup checkum.  If the checksum is not strong
1622                  * enough to ensure unique signatures, force
1623                  * dedup_verify.
1624                  */
1625                 if (dedup_checksum != ZIO_CHECKSUM_OFF) {
1626                         dedup = (wp & WP_DMU_SYNC) ? B_FALSE : B_TRUE;
1627                         if (!zio_checksum_table[checksum].ci_dedup)
1628                                 dedup_verify = B_TRUE;
1629                 }
1630 
1631                 /*
1632                  * Enable nopwrite if we have a cryptographically secure
1633                  * checksum that has no known collisions (i.e. SHA-256)
1634                  * and compression is enabled.  We don't enable nopwrite if
1635                  * dedup is enabled as the two features are mutually exclusive.
1636                  */
1637                 nopwrite = (!dedup && zio_checksum_table[checksum].ci_dedup &&
1638                     compress != ZIO_COMPRESS_OFF && zfs_nopwrite_enabled);
1639         }
1640 
1641         zp->zp_checksum = checksum;
1642         zp->zp_compress = compress;
1643         zp->zp_type = (wp & WP_SPILL) ? dn->dn_bonustype : type;
1644         zp->zp_level = level;
1645         zp->zp_copies = MIN(copies + ismd, spa_max_replication(os->os_spa));
1646         zp->zp_dedup = dedup;
1647         zp->zp_dedup_verify = dedup && dedup_verify;
1648         zp->zp_nopwrite = nopwrite;
1649 }
1650 
1651 int
1652 dmu_offset_next(objset_t *os, uint64_t object, boolean_t hole, uint64_t *off)
1653 {
1654         dnode_t *dn;
1655         int i, err;
1656 
1657         err = dnode_hold(os, object, FTAG, &dn);
1658         if (err)
1659                 return (err);
1660         /*
1661          * Sync any current changes before
1662          * we go trundling through the block pointers.
1663          */
1664         for (i = 0; i < TXG_SIZE; i++) {
1665                 if (list_link_active(&dn->dn_dirty_link[i]))
1666                         break;
1667         }
1668         if (i != TXG_SIZE) {
1669                 dnode_rele(dn, FTAG);
1670                 txg_wait_synced(dmu_objset_pool(os), 0);
1671                 err = dnode_hold(os, object, FTAG, &dn);
1672                 if (err)
1673                         return (err);
1674         }
1675 
1676         err = dnode_next_offset(dn, (hole ? DNODE_FIND_HOLE : 0), off, 1, 1, 0);
1677         dnode_rele(dn, FTAG);
1678 
1679         return (err);
1680 }
1681 
1682 void
1683 dmu_object_info_from_dnode(dnode_t *dn, dmu_object_info_t *doi)
1684 {
1685         dnode_phys_t *dnp;
1686 
1687         rw_enter(&dn->dn_struct_rwlock, RW_READER);
1688         mutex_enter(&dn->dn_mtx);
1689 
1690         dnp = dn->dn_phys;
1691 
1692         doi->doi_data_block_size = dn->dn_datablksz;
1693         doi->doi_metadata_block_size = dn->dn_indblkshift ?
1694             1ULL << dn->dn_indblkshift : 0;
1695         doi->doi_type = dn->dn_type;
1696         doi->doi_bonus_type = dn->dn_bonustype;
1697         doi->doi_bonus_size = dn->dn_bonuslen;
1698         doi->doi_indirection = dn->dn_nlevels;
1699         doi->doi_checksum = dn->dn_checksum;
1700         doi->doi_compress = dn->dn_compress;
1701         doi->doi_physical_blocks_512 = (DN_USED_BYTES(dnp) + 256) >> 9;
1702         doi->doi_max_offset = (dn->dn_maxblkid + 1) * dn->dn_datablksz;
1703         doi->doi_fill_count = 0;
1704         for (int i = 0; i < dnp->dn_nblkptr; i++)
1705                 doi->doi_fill_count += dnp->dn_blkptr[i].blk_fill;
1706 
1707         mutex_exit(&dn->dn_mtx);
1708         rw_exit(&dn->dn_struct_rwlock);
1709 }
1710 
1711 /*
1712  * Get information on a DMU object.
1713  * If doi is NULL, just indicates whether the object exists.
1714  */
1715 int
1716 dmu_object_info(objset_t *os, uint64_t object, dmu_object_info_t *doi)
1717 {
1718         dnode_t *dn;
1719         int err = dnode_hold(os, object, FTAG, &dn);
1720 
1721         if (err)
1722                 return (err);
1723 
1724         if (doi != NULL)
1725                 dmu_object_info_from_dnode(dn, doi);
1726 
1727         dnode_rele(dn, FTAG);
1728         return (0);
1729 }
1730 
1731 /*
1732  * As above, but faster; can be used when you have a held dbuf in hand.
1733  */
1734 void
1735 dmu_object_info_from_db(dmu_buf_t *db_fake, dmu_object_info_t *doi)
1736 {
1737         dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
1738 
1739         DB_DNODE_ENTER(db);
1740         dmu_object_info_from_dnode(DB_DNODE(db), doi);
1741         DB_DNODE_EXIT(db);
1742 }
1743 
1744 /*
1745  * Faster still when you only care about the size.
1746  * This is specifically optimized for zfs_getattr().
1747  */
1748 void
1749 dmu_object_size_from_db(dmu_buf_t *db_fake, uint32_t *blksize,
1750     u_longlong_t *nblk512)
1751 {
1752         dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
1753         dnode_t *dn;
1754 
1755         DB_DNODE_ENTER(db);
1756         dn = DB_DNODE(db);
1757 
1758         *blksize = dn->dn_datablksz;
1759         /* add 1 for dnode space */
1760         *nblk512 = ((DN_USED_BYTES(dn->dn_phys) + SPA_MINBLOCKSIZE/2) >>
1761             SPA_MINBLOCKSHIFT) + 1;
1762         DB_DNODE_EXIT(db);
1763 }
1764 
1765 void
1766 byteswap_uint64_array(void *vbuf, size_t size)
1767 {
1768         uint64_t *buf = vbuf;
1769         size_t count = size >> 3;
1770         int i;
1771 
1772         ASSERT((size & 7) == 0);
1773 
1774         for (i = 0; i < count; i++)
1775                 buf[i] = BSWAP_64(buf[i]);
1776 }
1777 
1778 void
1779 byteswap_uint32_array(void *vbuf, size_t size)
1780 {
1781         uint32_t *buf = vbuf;
1782         size_t count = size >> 2;
1783         int i;
1784 
1785         ASSERT((size & 3) == 0);
1786 
1787         for (i = 0; i < count; i++)
1788                 buf[i] = BSWAP_32(buf[i]);
1789 }
1790 
1791 void
1792 byteswap_uint16_array(void *vbuf, size_t size)
1793 {
1794         uint16_t *buf = vbuf;
1795         size_t count = size >> 1;
1796         int i;
1797 
1798         ASSERT((size & 1) == 0);
1799 
1800         for (i = 0; i < count; i++)
1801                 buf[i] = BSWAP_16(buf[i]);
1802 }
1803 
1804 /* ARGSUSED */
1805 void
1806 byteswap_uint8_array(void *vbuf, size_t size)
1807 {
1808 }
1809 
1810 void
1811 dmu_init(void)
1812 {
1813         zfs_dbgmsg_init();
1814         sa_cache_init();
1815         xuio_stat_init();
1816         dmu_objset_init();
1817         dnode_init();
1818         dbuf_init();
1819         zfetch_init();
1820         l2arc_init();
1821         arc_init();
1822 }
1823 
1824 void
1825 dmu_fini(void)
1826 {
1827         arc_fini(); /* arc depends on l2arc, so arc must go first */
1828         l2arc_fini();
1829         zfetch_fini();
1830         dbuf_fini();
1831         dnode_fini();
1832         dmu_objset_fini();
1833         xuio_stat_fini();
1834         sa_cache_fini();
1835         zfs_dbgmsg_fini();
1836 }