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  */
  26 
  27 #include <sys/dmu.h>
  28 #include <sys/dmu_impl.h>
  29 #include <sys/dbuf.h>
  30 #include <sys/dmu_tx.h>
  31 #include <sys/dmu_objset.h>
  32 #include <sys/dsl_dataset.h> /* for dsl_dataset_block_freeable() */
  33 #include <sys/dsl_dir.h> /* for dsl_dir_tempreserve_*() */
  34 #include <sys/dsl_pool.h>
  35 #include <sys/zap_impl.h> /* for fzap_default_block_shift */
  36 #include <sys/spa.h>
  37 #include <sys/sa.h>
  38 #include <sys/sa_impl.h>
  39 #include <sys/zfs_context.h>
  40 #include <sys/varargs.h>
  41 
  42 typedef void (*dmu_tx_hold_func_t)(dmu_tx_t *tx, struct dnode *dn,
  43     uint64_t arg1, uint64_t arg2);
  44 
  45 
  46 dmu_tx_t *
  47 dmu_tx_create_dd(dsl_dir_t *dd)
  48 {
  49         dmu_tx_t *tx = kmem_zalloc(sizeof (dmu_tx_t), KM_SLEEP);
  50         tx->tx_dir = dd;
  51         if (dd != NULL)
  52                 tx->tx_pool = dd->dd_pool;
  53         list_create(&tx->tx_holds, sizeof (dmu_tx_hold_t),
  54             offsetof(dmu_tx_hold_t, txh_node));
  55         list_create(&tx->tx_callbacks, sizeof (dmu_tx_callback_t),
  56             offsetof(dmu_tx_callback_t, dcb_node));
  57         tx->tx_start = gethrtime();
  58 #ifdef ZFS_DEBUG
  59         refcount_create(&tx->tx_space_written);
  60         refcount_create(&tx->tx_space_freed);
  61 #endif
  62         return (tx);
  63 }
  64 
  65 dmu_tx_t *
  66 dmu_tx_create(objset_t *os)
  67 {
  68         dmu_tx_t *tx = dmu_tx_create_dd(os->os_dsl_dataset->ds_dir);
  69         tx->tx_objset = os;
  70         tx->tx_lastsnap_txg = dsl_dataset_prev_snap_txg(os->os_dsl_dataset);
  71         return (tx);
  72 }
  73 
  74 dmu_tx_t *
  75 dmu_tx_create_assigned(struct dsl_pool *dp, uint64_t txg)
  76 {
  77         dmu_tx_t *tx = dmu_tx_create_dd(NULL);
  78 
  79         ASSERT3U(txg, <=, dp->dp_tx.tx_open_txg);
  80         tx->tx_pool = dp;
  81         tx->tx_txg = txg;
  82         tx->tx_anyobj = TRUE;
  83 
  84         return (tx);
  85 }
  86 
  87 int
  88 dmu_tx_is_syncing(dmu_tx_t *tx)
  89 {
  90         return (tx->tx_anyobj);
  91 }
  92 
  93 int
  94 dmu_tx_private_ok(dmu_tx_t *tx)
  95 {
  96         return (tx->tx_anyobj);
  97 }
  98 
  99 static dmu_tx_hold_t *
 100 dmu_tx_hold_object_impl(dmu_tx_t *tx, objset_t *os, uint64_t object,
 101     enum dmu_tx_hold_type type, uint64_t arg1, uint64_t arg2)
 102 {
 103         dmu_tx_hold_t *txh;
 104         dnode_t *dn = NULL;
 105         int err;
 106 
 107         if (object != DMU_NEW_OBJECT) {
 108                 err = dnode_hold(os, object, tx, &dn);
 109                 if (err) {
 110                         tx->tx_err = err;
 111                         return (NULL);
 112                 }
 113 
 114                 if (err == 0 && tx->tx_txg != 0) {
 115                         mutex_enter(&dn->dn_mtx);
 116                         /*
 117                          * dn->dn_assigned_txg == tx->tx_txg doesn't pose a
 118                          * problem, but there's no way for it to happen (for
 119                          * now, at least).
 120                          */
 121                         ASSERT(dn->dn_assigned_txg == 0);
 122                         dn->dn_assigned_txg = tx->tx_txg;
 123                         (void) refcount_add(&dn->dn_tx_holds, tx);
 124                         mutex_exit(&dn->dn_mtx);
 125                 }
 126         }
 127 
 128         txh = kmem_zalloc(sizeof (dmu_tx_hold_t), KM_SLEEP);
 129         txh->txh_tx = tx;
 130         txh->txh_dnode = dn;
 131 #ifdef ZFS_DEBUG
 132         txh->txh_type = type;
 133         txh->txh_arg1 = arg1;
 134         txh->txh_arg2 = arg2;
 135 #endif
 136         list_insert_tail(&tx->tx_holds, txh);
 137 
 138         return (txh);
 139 }
 140 
 141 void
 142 dmu_tx_add_new_object(dmu_tx_t *tx, objset_t *os, uint64_t object)
 143 {
 144         /*
 145          * If we're syncing, they can manipulate any object anyhow, and
 146          * the hold on the dnode_t can cause problems.
 147          */
 148         if (!dmu_tx_is_syncing(tx)) {
 149                 (void) dmu_tx_hold_object_impl(tx, os,
 150                     object, THT_NEWOBJECT, 0, 0);
 151         }
 152 }
 153 
 154 static int
 155 dmu_tx_check_ioerr(zio_t *zio, dnode_t *dn, int level, uint64_t blkid)
 156 {
 157         int err;
 158         dmu_buf_impl_t *db;
 159 
 160         rw_enter(&dn->dn_struct_rwlock, RW_READER);
 161         db = dbuf_hold_level(dn, level, blkid, FTAG);
 162         rw_exit(&dn->dn_struct_rwlock);
 163         if (db == NULL)
 164                 return (SET_ERROR(EIO));
 165         err = dbuf_read(db, zio, DB_RF_CANFAIL | DB_RF_NOPREFETCH);
 166         dbuf_rele(db, FTAG);
 167         return (err);
 168 }
 169 
 170 static void
 171 dmu_tx_count_twig(dmu_tx_hold_t *txh, dnode_t *dn, dmu_buf_impl_t *db,
 172     int level, uint64_t blkid, boolean_t freeable, uint64_t *history)
 173 {
 174         objset_t *os = dn->dn_objset;
 175         dsl_dataset_t *ds = os->os_dsl_dataset;
 176         int epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
 177         dmu_buf_impl_t *parent = NULL;
 178         blkptr_t *bp = NULL;
 179         uint64_t space;
 180 
 181         if (level >= dn->dn_nlevels || history[level] == blkid)
 182                 return;
 183 
 184         history[level] = blkid;
 185 
 186         space = (level == 0) ? dn->dn_datablksz : (1ULL << dn->dn_indblkshift);
 187 
 188         if (db == NULL || db == dn->dn_dbuf) {
 189                 ASSERT(level != 0);
 190                 db = NULL;
 191         } else {
 192                 ASSERT(DB_DNODE(db) == dn);
 193                 ASSERT(db->db_level == level);
 194                 ASSERT(db->db.db_size == space);
 195                 ASSERT(db->db_blkid == blkid);
 196                 bp = db->db_blkptr;
 197                 parent = db->db_parent;
 198         }
 199 
 200         freeable = (bp && (freeable ||
 201             dsl_dataset_block_freeable(ds, bp, bp->blk_birth)));
 202 
 203         if (freeable)
 204                 txh->txh_space_tooverwrite += space;
 205         else
 206                 txh->txh_space_towrite += space;
 207         if (bp)
 208                 txh->txh_space_tounref += bp_get_dsize(os->os_spa, bp);
 209 
 210         dmu_tx_count_twig(txh, dn, parent, level + 1,
 211             blkid >> epbs, freeable, history);
 212 }
 213 
 214 /* ARGSUSED */
 215 static void
 216 dmu_tx_count_write(dmu_tx_hold_t *txh, uint64_t off, uint64_t len)
 217 {
 218         dnode_t *dn = txh->txh_dnode;
 219         uint64_t start, end, i;
 220         int min_bs, max_bs, min_ibs, max_ibs, epbs, bits;
 221         int err = 0;
 222 
 223         if (len == 0)
 224                 return;
 225 
 226         min_bs = SPA_MINBLOCKSHIFT;
 227         max_bs = SPA_MAXBLOCKSHIFT;
 228         min_ibs = DN_MIN_INDBLKSHIFT;
 229         max_ibs = DN_MAX_INDBLKSHIFT;
 230 
 231         if (dn) {
 232                 uint64_t history[DN_MAX_LEVELS];
 233                 int nlvls = dn->dn_nlevels;
 234                 int delta;
 235 
 236                 /*
 237                  * For i/o error checking, read the first and last level-0
 238                  * blocks (if they are not aligned), and all the level-1 blocks.
 239                  */
 240                 if (dn->dn_maxblkid == 0) {
 241                         delta = dn->dn_datablksz;
 242                         start = (off < dn->dn_datablksz) ? 0 : 1;
 243                         end = (off+len <= dn->dn_datablksz) ? 0 : 1;
 244                         if (start == 0 && (off > 0 || len < dn->dn_datablksz)) {
 245                                 err = dmu_tx_check_ioerr(NULL, dn, 0, 0);
 246                                 if (err)
 247                                         goto out;
 248                                 delta -= off;
 249                         }
 250                 } else {
 251                         zio_t *zio = zio_root(dn->dn_objset->os_spa,
 252                             NULL, NULL, ZIO_FLAG_CANFAIL);
 253 
 254                         /* first level-0 block */
 255                         start = off >> dn->dn_datablkshift;
 256                         if (P2PHASE(off, dn->dn_datablksz) ||
 257                             len < dn->dn_datablksz) {
 258                                 err = dmu_tx_check_ioerr(zio, dn, 0, start);
 259                                 if (err)
 260                                         goto out;
 261                         }
 262 
 263                         /* last level-0 block */
 264                         end = (off+len-1) >> dn->dn_datablkshift;
 265                         if (end != start && end <= dn->dn_maxblkid &&
 266                             P2PHASE(off+len, dn->dn_datablksz)) {
 267                                 err = dmu_tx_check_ioerr(zio, dn, 0, end);
 268                                 if (err)
 269                                         goto out;
 270                         }
 271 
 272                         /* level-1 blocks */
 273                         if (nlvls > 1) {
 274                                 int shft = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
 275                                 for (i = (start>>shft)+1; i < end>>shft; i++) {
 276                                         err = dmu_tx_check_ioerr(zio, dn, 1, i);
 277                                         if (err)
 278                                                 goto out;
 279                                 }
 280                         }
 281 
 282                         err = zio_wait(zio);
 283                         if (err)
 284                                 goto out;
 285                         delta = P2NPHASE(off, dn->dn_datablksz);
 286                 }
 287 
 288                 min_ibs = max_ibs = dn->dn_indblkshift;
 289                 if (dn->dn_maxblkid > 0) {
 290                         /*
 291                          * The blocksize can't change,
 292                          * so we can make a more precise estimate.
 293                          */
 294                         ASSERT(dn->dn_datablkshift != 0);
 295                         min_bs = max_bs = dn->dn_datablkshift;
 296                 }
 297 
 298                 /*
 299                  * If this write is not off the end of the file
 300                  * we need to account for overwrites/unref.
 301                  */
 302                 if (start <= dn->dn_maxblkid) {
 303                         for (int l = 0; l < DN_MAX_LEVELS; l++)
 304                                 history[l] = -1ULL;
 305                 }
 306                 while (start <= dn->dn_maxblkid) {
 307                         dmu_buf_impl_t *db;
 308 
 309                         rw_enter(&dn->dn_struct_rwlock, RW_READER);
 310                         err = dbuf_hold_impl(dn, 0, start, FALSE, FTAG, &db);
 311                         rw_exit(&dn->dn_struct_rwlock);
 312 
 313                         if (err) {
 314                                 txh->txh_tx->tx_err = err;
 315                                 return;
 316                         }
 317 
 318                         dmu_tx_count_twig(txh, dn, db, 0, start, B_FALSE,
 319                             history);
 320                         dbuf_rele(db, FTAG);
 321                         if (++start > end) {
 322                                 /*
 323                                  * Account for new indirects appearing
 324                                  * before this IO gets assigned into a txg.
 325                                  */
 326                                 bits = 64 - min_bs;
 327                                 epbs = min_ibs - SPA_BLKPTRSHIFT;
 328                                 for (bits -= epbs * (nlvls - 1);
 329                                     bits >= 0; bits -= epbs)
 330                                         txh->txh_fudge += 1ULL << max_ibs;
 331                                 goto out;
 332                         }
 333                         off += delta;
 334                         if (len >= delta)
 335                                 len -= delta;
 336                         delta = dn->dn_datablksz;
 337                 }
 338         }
 339 
 340         /*
 341          * 'end' is the last thing we will access, not one past.
 342          * This way we won't overflow when accessing the last byte.
 343          */
 344         start = P2ALIGN(off, 1ULL << max_bs);
 345         end = P2ROUNDUP(off + len, 1ULL << max_bs) - 1;
 346         txh->txh_space_towrite += end - start + 1;
 347 
 348         start >>= min_bs;
 349         end >>= min_bs;
 350 
 351         epbs = min_ibs - SPA_BLKPTRSHIFT;
 352 
 353         /*
 354          * The object contains at most 2^(64 - min_bs) blocks,
 355          * and each indirect level maps 2^epbs.
 356          */
 357         for (bits = 64 - min_bs; bits >= 0; bits -= epbs) {
 358                 start >>= epbs;
 359                 end >>= epbs;
 360                 ASSERT3U(end, >=, start);
 361                 txh->txh_space_towrite += (end - start + 1) << max_ibs;
 362                 if (start != 0) {
 363                         /*
 364                          * We also need a new blkid=0 indirect block
 365                          * to reference any existing file data.
 366                          */
 367                         txh->txh_space_towrite += 1ULL << max_ibs;
 368                 }
 369         }
 370 
 371 out:
 372         if (txh->txh_space_towrite + txh->txh_space_tooverwrite >
 373             2 * DMU_MAX_ACCESS)
 374                 err = SET_ERROR(EFBIG);
 375 
 376         if (err)
 377                 txh->txh_tx->tx_err = err;
 378 }
 379 
 380 static void
 381 dmu_tx_count_dnode(dmu_tx_hold_t *txh)
 382 {
 383         dnode_t *dn = txh->txh_dnode;
 384         dnode_t *mdn = DMU_META_DNODE(txh->txh_tx->tx_objset);
 385         uint64_t space = mdn->dn_datablksz +
 386             ((mdn->dn_nlevels-1) << mdn->dn_indblkshift);
 387 
 388         if (dn && dn->dn_dbuf->db_blkptr &&
 389             dsl_dataset_block_freeable(dn->dn_objset->os_dsl_dataset,
 390             dn->dn_dbuf->db_blkptr, dn->dn_dbuf->db_blkptr->blk_birth)) {
 391                 txh->txh_space_tooverwrite += space;
 392                 txh->txh_space_tounref += space;
 393         } else {
 394                 txh->txh_space_towrite += space;
 395                 if (dn && dn->dn_dbuf->db_blkptr)
 396                         txh->txh_space_tounref += space;
 397         }
 398 }
 399 
 400 void
 401 dmu_tx_hold_write(dmu_tx_t *tx, uint64_t object, uint64_t off, int len)
 402 {
 403         dmu_tx_hold_t *txh;
 404 
 405         ASSERT(tx->tx_txg == 0);
 406         ASSERT(len < DMU_MAX_ACCESS);
 407         ASSERT(len == 0 || UINT64_MAX - off >= len - 1);
 408 
 409         txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
 410             object, THT_WRITE, off, len);
 411         if (txh == NULL)
 412                 return;
 413 
 414         dmu_tx_count_write(txh, off, len);
 415         dmu_tx_count_dnode(txh);
 416 }
 417 
 418 static void
 419 dmu_tx_count_free(dmu_tx_hold_t *txh, uint64_t off, uint64_t len)
 420 {
 421         uint64_t blkid, nblks, lastblk;
 422         uint64_t space = 0, unref = 0, skipped = 0;
 423         dnode_t *dn = txh->txh_dnode;
 424         dsl_dataset_t *ds = dn->dn_objset->os_dsl_dataset;
 425         spa_t *spa = txh->txh_tx->tx_pool->dp_spa;
 426         int epbs;
 427         uint64_t l0span = 0, nl1blks = 0;
 428 
 429         if (dn->dn_nlevels == 0)
 430                 return;
 431 
 432         /*
 433          * The struct_rwlock protects us against dn_nlevels
 434          * changing, in case (against all odds) we manage to dirty &
 435          * sync out the changes after we check for being dirty.
 436          * Also, dbuf_hold_impl() wants us to have the struct_rwlock.
 437          */
 438         rw_enter(&dn->dn_struct_rwlock, RW_READER);
 439         epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
 440         if (dn->dn_maxblkid == 0) {
 441                 if (off == 0 && len >= dn->dn_datablksz) {
 442                         blkid = 0;
 443                         nblks = 1;
 444                 } else {
 445                         rw_exit(&dn->dn_struct_rwlock);
 446                         return;
 447                 }
 448         } else {
 449                 blkid = off >> dn->dn_datablkshift;
 450                 nblks = (len + dn->dn_datablksz - 1) >> dn->dn_datablkshift;
 451 
 452                 if (blkid > dn->dn_maxblkid) {
 453                         rw_exit(&dn->dn_struct_rwlock);
 454                         return;
 455                 }
 456                 if (blkid + nblks > dn->dn_maxblkid)
 457                         nblks = dn->dn_maxblkid - blkid + 1;
 458 
 459         }
 460         l0span = nblks;    /* save for later use to calc level > 1 overhead */
 461         if (dn->dn_nlevels == 1) {
 462                 int i;
 463                 for (i = 0; i < nblks; i++) {
 464                         blkptr_t *bp = dn->dn_phys->dn_blkptr;
 465                         ASSERT3U(blkid + i, <, dn->dn_nblkptr);
 466                         bp += blkid + i;
 467                         if (dsl_dataset_block_freeable(ds, bp, bp->blk_birth)) {
 468                                 dprintf_bp(bp, "can free old%s", "");
 469                                 space += bp_get_dsize(spa, bp);
 470                         }
 471                         unref += BP_GET_ASIZE(bp);
 472                 }
 473                 nl1blks = 1;
 474                 nblks = 0;
 475         }
 476 
 477         lastblk = blkid + nblks - 1;
 478         while (nblks) {
 479                 dmu_buf_impl_t *dbuf;
 480                 uint64_t ibyte, new_blkid;
 481                 int epb = 1 << epbs;
 482                 int err, i, blkoff, tochk;
 483                 blkptr_t *bp;
 484 
 485                 ibyte = blkid << dn->dn_datablkshift;
 486                 err = dnode_next_offset(dn,
 487                     DNODE_FIND_HAVELOCK, &ibyte, 2, 1, 0);
 488                 new_blkid = ibyte >> dn->dn_datablkshift;
 489                 if (err == ESRCH) {
 490                         skipped += (lastblk >> epbs) - (blkid >> epbs) + 1;
 491                         break;
 492                 }
 493                 if (err) {
 494                         txh->txh_tx->tx_err = err;
 495                         break;
 496                 }
 497                 if (new_blkid > lastblk) {
 498                         skipped += (lastblk >> epbs) - (blkid >> epbs) + 1;
 499                         break;
 500                 }
 501 
 502                 if (new_blkid > blkid) {
 503                         ASSERT((new_blkid >> epbs) > (blkid >> epbs));
 504                         skipped += (new_blkid >> epbs) - (blkid >> epbs) - 1;
 505                         nblks -= new_blkid - blkid;
 506                         blkid = new_blkid;
 507                 }
 508                 blkoff = P2PHASE(blkid, epb);
 509                 tochk = MIN(epb - blkoff, nblks);
 510 
 511                 err = dbuf_hold_impl(dn, 1, blkid >> epbs, FALSE, FTAG, &dbuf);
 512                 if (err) {
 513                         txh->txh_tx->tx_err = err;
 514                         break;
 515                 }
 516 
 517                 txh->txh_memory_tohold += dbuf->db.db_size;
 518 
 519                 /*
 520                  * We don't check memory_tohold against DMU_MAX_ACCESS because
 521                  * memory_tohold is an over-estimation (especially the >L1
 522                  * indirect blocks), so it could fail.  Callers should have
 523                  * already verified that they will not be holding too much
 524                  * memory.
 525                  */
 526 
 527                 err = dbuf_read(dbuf, NULL, DB_RF_HAVESTRUCT | DB_RF_CANFAIL);
 528                 if (err != 0) {
 529                         txh->txh_tx->tx_err = err;
 530                         dbuf_rele(dbuf, FTAG);
 531                         break;
 532                 }
 533 
 534                 bp = dbuf->db.db_data;
 535                 bp += blkoff;
 536 
 537                 for (i = 0; i < tochk; i++) {
 538                         if (dsl_dataset_block_freeable(ds, &bp[i],
 539                             bp[i].blk_birth)) {
 540                                 dprintf_bp(&bp[i], "can free old%s", "");
 541                                 space += bp_get_dsize(spa, &bp[i]);
 542                         }
 543                         unref += BP_GET_ASIZE(bp);
 544                 }
 545                 dbuf_rele(dbuf, FTAG);
 546 
 547                 ++nl1blks;
 548                 blkid += tochk;
 549                 nblks -= tochk;
 550         }
 551         rw_exit(&dn->dn_struct_rwlock);
 552 
 553         /*
 554          * Add in memory requirements of higher-level indirects.
 555          * This assumes a worst-possible scenario for dn_nlevels and a
 556          * worst-possible distribution of l1-blocks over the region to free.
 557          */
 558         {
 559                 uint64_t blkcnt = 1 + ((l0span >> epbs) >> epbs);
 560                 int level = 2;
 561                 /*
 562                  * Here we don't use DN_MAX_LEVEL, but calculate it with the
 563                  * given datablkshift and indblkshift. This makes the
 564                  * difference between 19 and 8 on large files.
 565                  */
 566                 int maxlevel = 2 + (DN_MAX_OFFSET_SHIFT - dn->dn_datablkshift) /
 567                     (dn->dn_indblkshift - SPA_BLKPTRSHIFT);
 568 
 569                 while (level++ < maxlevel) {
 570                         txh->txh_memory_tohold += MAX(MIN(blkcnt, nl1blks), 1)
 571                             << dn->dn_indblkshift;
 572                         blkcnt = 1 + (blkcnt >> epbs);
 573                 }
 574         }
 575 
 576         /* account for new level 1 indirect blocks that might show up */
 577         if (skipped > 0) {
 578                 txh->txh_fudge += skipped << dn->dn_indblkshift;
 579                 skipped = MIN(skipped, DMU_MAX_DELETEBLKCNT >> epbs);
 580                 txh->txh_memory_tohold += skipped << dn->dn_indblkshift;
 581         }
 582         txh->txh_space_tofree += space;
 583         txh->txh_space_tounref += unref;
 584 }
 585 
 586 void
 587 dmu_tx_hold_free(dmu_tx_t *tx, uint64_t object, uint64_t off, uint64_t len)
 588 {
 589         dmu_tx_hold_t *txh;
 590         dnode_t *dn;
 591         int err;
 592         zio_t *zio;
 593 
 594         ASSERT(tx->tx_txg == 0);
 595 
 596         txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
 597             object, THT_FREE, off, len);
 598         if (txh == NULL)
 599                 return;
 600         dn = txh->txh_dnode;
 601         dmu_tx_count_dnode(txh);
 602 
 603         if (off >= (dn->dn_maxblkid+1) * dn->dn_datablksz)
 604                 return;
 605         if (len == DMU_OBJECT_END)
 606                 len = (dn->dn_maxblkid+1) * dn->dn_datablksz - off;
 607 
 608         /*
 609          * For i/o error checking, we read the first and last level-0
 610          * blocks if they are not aligned, and all the level-1 blocks.
 611          *
 612          * Note:  dbuf_free_range() assumes that we have not instantiated
 613          * any level-0 dbufs that will be completely freed.  Therefore we must
 614          * exercise care to not read or count the first and last blocks
 615          * if they are blocksize-aligned.
 616          */
 617         if (dn->dn_datablkshift == 0) {
 618                 if (off != 0 || len < dn->dn_datablksz)
 619                         dmu_tx_count_write(txh, 0, dn->dn_datablksz);
 620         } else {
 621                 /* first block will be modified if it is not aligned */
 622                 if (!IS_P2ALIGNED(off, 1 << dn->dn_datablkshift))
 623                         dmu_tx_count_write(txh, off, 1);
 624                 /* last block will be modified if it is not aligned */
 625                 if (!IS_P2ALIGNED(off + len, 1 << dn->dn_datablkshift))
 626                         dmu_tx_count_write(txh, off+len, 1);
 627         }
 628 
 629         /*
 630          * Check level-1 blocks.
 631          */
 632         if (dn->dn_nlevels > 1) {
 633                 int shift = dn->dn_datablkshift + dn->dn_indblkshift -
 634                     SPA_BLKPTRSHIFT;
 635                 uint64_t start = off >> shift;
 636                 uint64_t end = (off + len) >> shift;
 637 
 638                 ASSERT(dn->dn_indblkshift != 0);
 639 
 640                 /*
 641                  * dnode_reallocate() can result in an object with indirect
 642                  * blocks having an odd data block size.  In this case,
 643                  * just check the single block.
 644                  */
 645                 if (dn->dn_datablkshift == 0)
 646                         start = end = 0;
 647 
 648                 zio = zio_root(tx->tx_pool->dp_spa,
 649                     NULL, NULL, ZIO_FLAG_CANFAIL);
 650                 for (uint64_t i = start; i <= end; i++) {
 651                         uint64_t ibyte = i << shift;
 652                         err = dnode_next_offset(dn, 0, &ibyte, 2, 1, 0);
 653                         i = ibyte >> shift;
 654                         if (err == ESRCH)
 655                                 break;
 656                         if (err) {
 657                                 tx->tx_err = err;
 658                                 return;
 659                         }
 660 
 661                         err = dmu_tx_check_ioerr(zio, dn, 1, i);
 662                         if (err) {
 663                                 tx->tx_err = err;
 664                                 return;
 665                         }
 666                 }
 667                 err = zio_wait(zio);
 668                 if (err) {
 669                         tx->tx_err = err;
 670                         return;
 671                 }
 672         }
 673 
 674         dmu_tx_count_free(txh, off, len);
 675 }
 676 
 677 void
 678 dmu_tx_hold_zap(dmu_tx_t *tx, uint64_t object, int add, const char *name)
 679 {
 680         dmu_tx_hold_t *txh;
 681         dnode_t *dn;
 682         uint64_t nblocks;
 683         int epbs, err;
 684 
 685         ASSERT(tx->tx_txg == 0);
 686 
 687         txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
 688             object, THT_ZAP, add, (uintptr_t)name);
 689         if (txh == NULL)
 690                 return;
 691         dn = txh->txh_dnode;
 692 
 693         dmu_tx_count_dnode(txh);
 694 
 695         if (dn == NULL) {
 696                 /*
 697                  * We will be able to fit a new object's entries into one leaf
 698                  * block.  So there will be at most 2 blocks total,
 699                  * including the header block.
 700                  */
 701                 dmu_tx_count_write(txh, 0, 2 << fzap_default_block_shift);
 702                 return;
 703         }
 704 
 705         ASSERT3P(DMU_OT_BYTESWAP(dn->dn_type), ==, DMU_BSWAP_ZAP);
 706 
 707         if (dn->dn_maxblkid == 0 && !add) {
 708                 blkptr_t *bp;
 709 
 710                 /*
 711                  * If there is only one block  (i.e. this is a micro-zap)
 712                  * and we are not adding anything, the accounting is simple.
 713                  */
 714                 err = dmu_tx_check_ioerr(NULL, dn, 0, 0);
 715                 if (err) {
 716                         tx->tx_err = err;
 717                         return;
 718                 }
 719 
 720                 /*
 721                  * Use max block size here, since we don't know how much
 722                  * the size will change between now and the dbuf dirty call.
 723                  */
 724                 bp = &dn->dn_phys->dn_blkptr[0];
 725                 if (dsl_dataset_block_freeable(dn->dn_objset->os_dsl_dataset,
 726                     bp, bp->blk_birth))
 727                         txh->txh_space_tooverwrite += SPA_MAXBLOCKSIZE;
 728                 else
 729                         txh->txh_space_towrite += SPA_MAXBLOCKSIZE;
 730                 if (!BP_IS_HOLE(bp))
 731                         txh->txh_space_tounref += SPA_MAXBLOCKSIZE;
 732                 return;
 733         }
 734 
 735         if (dn->dn_maxblkid > 0 && name) {
 736                 /*
 737                  * access the name in this fat-zap so that we'll check
 738                  * for i/o errors to the leaf blocks, etc.
 739                  */
 740                 err = zap_lookup(dn->dn_objset, dn->dn_object, name,
 741                     8, 0, NULL);
 742                 if (err == EIO) {
 743                         tx->tx_err = err;
 744                         return;
 745                 }
 746         }
 747 
 748         err = zap_count_write(dn->dn_objset, dn->dn_object, name, add,
 749             &txh->txh_space_towrite, &txh->txh_space_tooverwrite);
 750 
 751         /*
 752          * If the modified blocks are scattered to the four winds,
 753          * we'll have to modify an indirect twig for each.
 754          */
 755         epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
 756         for (nblocks = dn->dn_maxblkid >> epbs; nblocks != 0; nblocks >>= epbs)
 757                 if (dn->dn_objset->os_dsl_dataset->ds_phys->ds_prev_snap_obj)
 758                         txh->txh_space_towrite += 3 << dn->dn_indblkshift;
 759                 else
 760                         txh->txh_space_tooverwrite += 3 << dn->dn_indblkshift;
 761 }
 762 
 763 void
 764 dmu_tx_hold_bonus(dmu_tx_t *tx, uint64_t object)
 765 {
 766         dmu_tx_hold_t *txh;
 767 
 768         ASSERT(tx->tx_txg == 0);
 769 
 770         txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
 771             object, THT_BONUS, 0, 0);
 772         if (txh)
 773                 dmu_tx_count_dnode(txh);
 774 }
 775 
 776 void
 777 dmu_tx_hold_space(dmu_tx_t *tx, uint64_t space)
 778 {
 779         dmu_tx_hold_t *txh;
 780         ASSERT(tx->tx_txg == 0);
 781 
 782         txh = dmu_tx_hold_object_impl(tx, tx->tx_objset,
 783             DMU_NEW_OBJECT, THT_SPACE, space, 0);
 784 
 785         txh->txh_space_towrite += space;
 786 }
 787 
 788 int
 789 dmu_tx_holds(dmu_tx_t *tx, uint64_t object)
 790 {
 791         dmu_tx_hold_t *txh;
 792         int holds = 0;
 793 
 794         /*
 795          * By asserting that the tx is assigned, we're counting the
 796          * number of dn_tx_holds, which is the same as the number of
 797          * dn_holds.  Otherwise, we'd be counting dn_holds, but
 798          * dn_tx_holds could be 0.
 799          */
 800         ASSERT(tx->tx_txg != 0);
 801 
 802         /* if (tx->tx_anyobj == TRUE) */
 803                 /* return (0); */
 804 
 805         for (txh = list_head(&tx->tx_holds); txh;
 806             txh = list_next(&tx->tx_holds, txh)) {
 807                 if (txh->txh_dnode && txh->txh_dnode->dn_object == object)
 808                         holds++;
 809         }
 810 
 811         return (holds);
 812 }
 813 
 814 #ifdef ZFS_DEBUG
 815 void
 816 dmu_tx_dirty_buf(dmu_tx_t *tx, dmu_buf_impl_t *db)
 817 {
 818         dmu_tx_hold_t *txh;
 819         int match_object = FALSE, match_offset = FALSE;
 820         dnode_t *dn;
 821 
 822         DB_DNODE_ENTER(db);
 823         dn = DB_DNODE(db);
 824         ASSERT(tx->tx_txg != 0);
 825         ASSERT(tx->tx_objset == NULL || dn->dn_objset == tx->tx_objset);
 826         ASSERT3U(dn->dn_object, ==, db->db.db_object);
 827 
 828         if (tx->tx_anyobj) {
 829                 DB_DNODE_EXIT(db);
 830                 return;
 831         }
 832 
 833         /* XXX No checking on the meta dnode for now */
 834         if (db->db.db_object == DMU_META_DNODE_OBJECT) {
 835                 DB_DNODE_EXIT(db);
 836                 return;
 837         }
 838 
 839         for (txh = list_head(&tx->tx_holds); txh;
 840             txh = list_next(&tx->tx_holds, txh)) {
 841                 ASSERT(dn == NULL || dn->dn_assigned_txg == tx->tx_txg);
 842                 if (txh->txh_dnode == dn && txh->txh_type != THT_NEWOBJECT)
 843                         match_object = TRUE;
 844                 if (txh->txh_dnode == NULL || txh->txh_dnode == dn) {
 845                         int datablkshift = dn->dn_datablkshift ?
 846                             dn->dn_datablkshift : SPA_MAXBLOCKSHIFT;
 847                         int epbs = dn->dn_indblkshift - SPA_BLKPTRSHIFT;
 848                         int shift = datablkshift + epbs * db->db_level;
 849                         uint64_t beginblk = shift >= 64 ? 0 :
 850                             (txh->txh_arg1 >> shift);
 851                         uint64_t endblk = shift >= 64 ? 0 :
 852                             ((txh->txh_arg1 + txh->txh_arg2 - 1) >> shift);
 853                         uint64_t blkid = db->db_blkid;
 854 
 855                         /* XXX txh_arg2 better not be zero... */
 856 
 857                         dprintf("found txh type %x beginblk=%llx endblk=%llx\n",
 858                             txh->txh_type, beginblk, endblk);
 859 
 860                         switch (txh->txh_type) {
 861                         case THT_WRITE:
 862                                 if (blkid >= beginblk && blkid <= endblk)
 863                                         match_offset = TRUE;
 864                                 /*
 865                                  * We will let this hold work for the bonus
 866                                  * or spill buffer so that we don't need to
 867                                  * hold it when creating a new object.
 868                                  */
 869                                 if (blkid == DMU_BONUS_BLKID ||
 870                                     blkid == DMU_SPILL_BLKID)
 871                                         match_offset = TRUE;
 872                                 /*
 873                                  * They might have to increase nlevels,
 874                                  * thus dirtying the new TLIBs.  Or the
 875                                  * might have to change the block size,
 876                                  * thus dirying the new lvl=0 blk=0.
 877                                  */
 878                                 if (blkid == 0)
 879                                         match_offset = TRUE;
 880                                 break;
 881                         case THT_FREE:
 882                                 /*
 883                                  * We will dirty all the level 1 blocks in
 884                                  * the free range and perhaps the first and
 885                                  * last level 0 block.
 886                                  */
 887                                 if (blkid >= beginblk && (blkid <= endblk ||
 888                                     txh->txh_arg2 == DMU_OBJECT_END))
 889                                         match_offset = TRUE;
 890                                 break;
 891                         case THT_SPILL:
 892                                 if (blkid == DMU_SPILL_BLKID)
 893                                         match_offset = TRUE;
 894                                 break;
 895                         case THT_BONUS:
 896                                 if (blkid == DMU_BONUS_BLKID)
 897                                         match_offset = TRUE;
 898                                 break;
 899                         case THT_ZAP:
 900                                 match_offset = TRUE;
 901                                 break;
 902                         case THT_NEWOBJECT:
 903                                 match_object = TRUE;
 904                                 break;
 905                         default:
 906                                 ASSERT(!"bad txh_type");
 907                         }
 908                 }
 909                 if (match_object && match_offset) {
 910                         DB_DNODE_EXIT(db);
 911                         return;
 912                 }
 913         }
 914         DB_DNODE_EXIT(db);
 915         panic("dirtying dbuf obj=%llx lvl=%u blkid=%llx but not tx_held\n",
 916             (u_longlong_t)db->db.db_object, db->db_level,
 917             (u_longlong_t)db->db_blkid);
 918 }
 919 #endif
 920 
 921 /*
 922  * If we can't do 10 iops, something is wrong.  Let us go ahead
 923  * and hit zfs_dirty_data_max.
 924  */
 925 hrtime_t zfs_delay_max_ns = MSEC2NSEC(100);
 926 int zfs_delay_resolution_ns = 100 * 1000; /* 100 microseconds */
 927 
 928 /*
 929  * We delay transactions when we've determined that the backend storage
 930  * isn't able to accommodate the rate of incoming writes.
 931  *
 932  * If there is already a transaction waiting, we delay relative to when
 933  * that transaction finishes waiting.  This way the calculated min_time
 934  * is independent of the number of threads concurrently executing
 935  * transactions.
 936  *
 937  * If we are the only waiter, wait relative to when the transaction
 938  * started, rather than the current time.  This credits the transaction for
 939  * "time already served", e.g. reading indirect blocks.
 940  *
 941  * The minimum time for a transaction to take is calculated as:
 942  *     min_time = scale * (dirty - min) / (max - dirty)
 943  *     min_time is then capped at zfs_delay_max_ns.
 944  *
 945  * The delay has two degrees of freedom that can be adjusted via tunables.
 946  * The percentage of dirty data at which we start to delay is defined by
 947  * zfs_delay_min_dirty_percent. This should typically be at or above
 948  * zfs_vdev_async_write_active_max_dirty_percent so that we only start to
 949  * delay after writing at full speed has failed to keep up with the incoming
 950  * write rate. The scale of the curve is defined by zfs_delay_scale. Roughly
 951  * speaking, this variable determines the amount of delay at the midpoint of
 952  * the curve.
 953  *
 954  * delay
 955  *  10ms +-------------------------------------------------------------*+
 956  *       |                                                             *|
 957  *   9ms +                                                             *+
 958  *       |                                                             *|
 959  *   8ms +                                                             *+
 960  *       |                                                            * |
 961  *   7ms +                                                            * +
 962  *       |                                                            * |
 963  *   6ms +                                                            * +
 964  *       |                                                            * |
 965  *   5ms +                                                           *  +
 966  *       |                                                           *  |
 967  *   4ms +                                                           *  +
 968  *       |                                                           *  |
 969  *   3ms +                                                          *   +
 970  *       |                                                          *   |
 971  *   2ms +                                              (midpoint) *    +
 972  *       |                                                  |    **     |
 973  *   1ms +                                                  v ***       +
 974  *       |             zfs_delay_scale ---------->     ********         |
 975  *     0 +-------------------------------------*********----------------+
 976  *       0%                    <- zfs_dirty_data_max ->               100%
 977  *
 978  * Note that since the delay is added to the outstanding time remaining on the
 979  * most recent transaction, the delay is effectively the inverse of IOPS.
 980  * Here the midpoint of 500us translates to 2000 IOPS. The shape of the curve
 981  * was chosen such that small changes in the amount of accumulated dirty data
 982  * in the first 3/4 of the curve yield relatively small differences in the
 983  * amount of delay.
 984  *
 985  * The effects can be easier to understand when the amount of delay is
 986  * represented on a log scale:
 987  *
 988  * delay
 989  * 100ms +-------------------------------------------------------------++
 990  *       +                                                              +
 991  *       |                                                              |
 992  *       +                                                             *+
 993  *  10ms +                                                             *+
 994  *       +                                                           ** +
 995  *       |                                              (midpoint)  **  |
 996  *       +                                                  |     **    +
 997  *   1ms +                                                  v ****      +
 998  *       +             zfs_delay_scale ---------->        *****         +
 999  *       |                                             ****             |
1000  *       +                                          ****                +
1001  * 100us +                                        **                    +
1002  *       +                                       *                      +
1003  *       |                                      *                       |
1004  *       +                                     *                        +
1005  *  10us +                                     *                        +
1006  *       +                                                              +
1007  *       |                                                              |
1008  *       +                                                              +
1009  *       +--------------------------------------------------------------+
1010  *       0%                    <- zfs_dirty_data_max ->               100%
1011  *
1012  * Note here that only as the amount of dirty data approaches its limit does
1013  * the delay start to increase rapidly. The goal of a properly tuned system
1014  * should be to keep the amount of dirty data out of that range by first
1015  * ensuring that the appropriate limits are set for the I/O scheduler to reach
1016  * optimal throughput on the backend storage, and then by changing the value
1017  * of zfs_delay_scale to increase the steepness of the curve.
1018  */
1019 static void
1020 dmu_tx_delay(dmu_tx_t *tx, uint64_t dirty)
1021 {
1022         dsl_pool_t *dp = tx->tx_pool;
1023         uint64_t delay_min_bytes =
1024             zfs_dirty_data_max * zfs_delay_min_dirty_percent / 100;
1025         hrtime_t wakeup, min_tx_time, now;
1026 
1027         if (dirty <= delay_min_bytes)
1028                 return;
1029 
1030         /*
1031          * The caller has already waited until we are under the max.
1032          * We make them pass us the amount of dirty data so we don't
1033          * have to handle the case of it being >= the max, which could
1034          * cause a divide-by-zero if it's == the max.
1035          */
1036         ASSERT3U(dirty, <, zfs_dirty_data_max);
1037 
1038         now = gethrtime();
1039         min_tx_time = zfs_delay_scale *
1040             (dirty - delay_min_bytes) / (zfs_dirty_data_max - dirty);
1041         if (now > tx->tx_start + min_tx_time)
1042                 return;
1043 
1044         min_tx_time = MIN(min_tx_time, zfs_delay_max_ns);
1045 
1046         DTRACE_PROBE3(delay__mintime, dmu_tx_t *, tx, uint64_t, dirty,
1047             uint64_t, min_tx_time);
1048 
1049         mutex_enter(&dp->dp_lock);
1050         wakeup = MAX(tx->tx_start + min_tx_time,
1051             dp->dp_last_wakeup + min_tx_time);
1052         dp->dp_last_wakeup = wakeup;
1053         mutex_exit(&dp->dp_lock);
1054 
1055 #ifdef _KERNEL
1056         mutex_enter(&curthread->t_delay_lock);
1057         while (cv_timedwait_hires(&curthread->t_delay_cv,
1058             &curthread->t_delay_lock, wakeup, zfs_delay_resolution_ns,
1059             CALLOUT_FLAG_ABSOLUTE | CALLOUT_FLAG_ROUNDUP) > 0)
1060                 continue;
1061         mutex_exit(&curthread->t_delay_lock);
1062 #else
1063         hrtime_t delta = wakeup - gethrtime();
1064         struct timespec ts;
1065         ts.tv_sec = delta / NANOSEC;
1066         ts.tv_nsec = delta % NANOSEC;
1067         (void) nanosleep(&ts, NULL);
1068 #endif
1069 }
1070 
1071 static int
1072 dmu_tx_try_assign(dmu_tx_t *tx, txg_how_t txg_how)
1073 {
1074         dmu_tx_hold_t *txh;
1075         spa_t *spa = tx->tx_pool->dp_spa;
1076         uint64_t memory, asize, fsize, usize;
1077         uint64_t towrite, tofree, tooverwrite, tounref, tohold, fudge;
1078 
1079         ASSERT0(tx->tx_txg);
1080 
1081         if (tx->tx_err)
1082                 return (tx->tx_err);
1083 
1084         if (spa_suspended(spa)) {
1085                 /*
1086                  * If the user has indicated a blocking failure mode
1087                  * then return ERESTART which will block in dmu_tx_wait().
1088                  * Otherwise, return EIO so that an error can get
1089                  * propagated back to the VOP calls.
1090                  *
1091                  * Note that we always honor the txg_how flag regardless
1092                  * of the failuremode setting.
1093                  */
1094                 if (spa_get_failmode(spa) == ZIO_FAILURE_MODE_CONTINUE &&
1095                     txg_how != TXG_WAIT)
1096                         return (SET_ERROR(EIO));
1097 
1098                 return (SET_ERROR(ERESTART));
1099         }
1100 
1101         if (!tx->tx_waited &&
1102             dsl_pool_need_dirty_delay(tx->tx_pool)) {
1103                 tx->tx_wait_dirty = B_TRUE;
1104                 return (SET_ERROR(ERESTART));
1105         }
1106 
1107         tx->tx_txg = txg_hold_open(tx->tx_pool, &tx->tx_txgh);
1108         tx->tx_needassign_txh = NULL;
1109 
1110         /*
1111          * NB: No error returns are allowed after txg_hold_open, but
1112          * before processing the dnode holds, due to the
1113          * dmu_tx_unassign() logic.
1114          */
1115 
1116         towrite = tofree = tooverwrite = tounref = tohold = fudge = 0;
1117         for (txh = list_head(&tx->tx_holds); txh;
1118             txh = list_next(&tx->tx_holds, txh)) {
1119                 dnode_t *dn = txh->txh_dnode;
1120                 if (dn != NULL) {
1121                         mutex_enter(&dn->dn_mtx);
1122                         if (dn->dn_assigned_txg == tx->tx_txg - 1) {
1123                                 mutex_exit(&dn->dn_mtx);
1124                                 tx->tx_needassign_txh = txh;
1125                                 return (SET_ERROR(ERESTART));
1126                         }
1127                         if (dn->dn_assigned_txg == 0)
1128                                 dn->dn_assigned_txg = tx->tx_txg;
1129                         ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
1130                         (void) refcount_add(&dn->dn_tx_holds, tx);
1131                         mutex_exit(&dn->dn_mtx);
1132                 }
1133                 towrite += txh->txh_space_towrite;
1134                 tofree += txh->txh_space_tofree;
1135                 tooverwrite += txh->txh_space_tooverwrite;
1136                 tounref += txh->txh_space_tounref;
1137                 tohold += txh->txh_memory_tohold;
1138                 fudge += txh->txh_fudge;
1139         }
1140 
1141         /*
1142          * If a snapshot has been taken since we made our estimates,
1143          * assume that we won't be able to free or overwrite anything.
1144          */
1145         if (tx->tx_objset &&
1146             dsl_dataset_prev_snap_txg(tx->tx_objset->os_dsl_dataset) >
1147             tx->tx_lastsnap_txg) {
1148                 towrite += tooverwrite;
1149                 tooverwrite = tofree = 0;
1150         }
1151 
1152         /* needed allocation: worst-case estimate of write space */
1153         asize = spa_get_asize(tx->tx_pool->dp_spa, towrite + tooverwrite);
1154         /* freed space estimate: worst-case overwrite + free estimate */
1155         fsize = spa_get_asize(tx->tx_pool->dp_spa, tooverwrite) + tofree;
1156         /* convert unrefd space to worst-case estimate */
1157         usize = spa_get_asize(tx->tx_pool->dp_spa, tounref);
1158         /* calculate memory footprint estimate */
1159         memory = towrite + tooverwrite + tohold;
1160 
1161 #ifdef ZFS_DEBUG
1162         /*
1163          * Add in 'tohold' to account for our dirty holds on this memory
1164          * XXX - the "fudge" factor is to account for skipped blocks that
1165          * we missed because dnode_next_offset() misses in-core-only blocks.
1166          */
1167         tx->tx_space_towrite = asize +
1168             spa_get_asize(tx->tx_pool->dp_spa, tohold + fudge);
1169         tx->tx_space_tofree = tofree;
1170         tx->tx_space_tooverwrite = tooverwrite;
1171         tx->tx_space_tounref = tounref;
1172 #endif
1173 
1174         if (tx->tx_dir && asize != 0) {
1175                 int err = dsl_dir_tempreserve_space(tx->tx_dir, memory,
1176                     asize, fsize, usize, &tx->tx_tempreserve_cookie, tx);
1177                 if (err)
1178                         return (err);
1179         }
1180 
1181         return (0);
1182 }
1183 
1184 static void
1185 dmu_tx_unassign(dmu_tx_t *tx)
1186 {
1187         dmu_tx_hold_t *txh;
1188 
1189         if (tx->tx_txg == 0)
1190                 return;
1191 
1192         txg_rele_to_quiesce(&tx->tx_txgh);
1193 
1194         /*
1195          * Walk the transaction's hold list, removing the hold on the
1196          * associated dnode, and notifying waiters if the refcount drops to 0.
1197          */
1198         for (txh = list_head(&tx->tx_holds); txh != tx->tx_needassign_txh;
1199             txh = list_next(&tx->tx_holds, txh)) {
1200                 dnode_t *dn = txh->txh_dnode;
1201 
1202                 if (dn == NULL)
1203                         continue;
1204                 mutex_enter(&dn->dn_mtx);
1205                 ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
1206 
1207                 if (refcount_remove(&dn->dn_tx_holds, tx) == 0) {
1208                         dn->dn_assigned_txg = 0;
1209                         cv_broadcast(&dn->dn_notxholds);
1210                 }
1211                 mutex_exit(&dn->dn_mtx);
1212         }
1213 
1214         txg_rele_to_sync(&tx->tx_txgh);
1215 
1216         tx->tx_lasttried_txg = tx->tx_txg;
1217         tx->tx_txg = 0;
1218 }
1219 
1220 /*
1221  * Assign tx to a transaction group.  txg_how can be one of:
1222  *
1223  * (1)  TXG_WAIT.  If the current open txg is full, waits until there's
1224  *      a new one.  This should be used when you're not holding locks.
1225  *      It will only fail if we're truly out of space (or over quota).
1226  *
1227  * (2)  TXG_NOWAIT.  If we can't assign into the current open txg without
1228  *      blocking, returns immediately with ERESTART.  This should be used
1229  *      whenever you're holding locks.  On an ERESTART error, the caller
1230  *      should drop locks, do a dmu_tx_wait(tx), and try again.
1231  *
1232  * (3)  TXG_WAITED.  Like TXG_NOWAIT, but indicates that dmu_tx_wait()
1233  *      has already been called on behalf of this operation (though
1234  *      most likely on a different tx).
1235  */
1236 int
1237 dmu_tx_assign(dmu_tx_t *tx, txg_how_t txg_how)
1238 {
1239         int err;
1240 
1241         ASSERT(tx->tx_txg == 0);
1242         ASSERT(txg_how == TXG_WAIT || txg_how == TXG_NOWAIT ||
1243             txg_how == TXG_WAITED);
1244         ASSERT(!dsl_pool_sync_context(tx->tx_pool));
1245 
1246         /* If we might wait, we must not hold the config lock. */
1247         ASSERT(txg_how != TXG_WAIT || !dsl_pool_config_held(tx->tx_pool));
1248 
1249         if (txg_how == TXG_WAITED)
1250                 tx->tx_waited = B_TRUE;
1251 
1252         while ((err = dmu_tx_try_assign(tx, txg_how)) != 0) {
1253                 dmu_tx_unassign(tx);
1254 
1255                 if (err != ERESTART || txg_how != TXG_WAIT)
1256                         return (err);
1257 
1258                 dmu_tx_wait(tx);
1259         }
1260 
1261         txg_rele_to_quiesce(&tx->tx_txgh);
1262 
1263         return (0);
1264 }
1265 
1266 void
1267 dmu_tx_wait(dmu_tx_t *tx)
1268 {
1269         spa_t *spa = tx->tx_pool->dp_spa;
1270         dsl_pool_t *dp = tx->tx_pool;
1271 
1272         ASSERT(tx->tx_txg == 0);
1273         ASSERT(!dsl_pool_config_held(tx->tx_pool));
1274 
1275         if (tx->tx_wait_dirty) {
1276                 /*
1277                  * dmu_tx_try_assign() has determined that we need to wait
1278                  * because we've consumed much or all of the dirty buffer
1279                  * space.
1280                  */
1281                 mutex_enter(&dp->dp_lock);
1282                 while (dp->dp_dirty_total >= zfs_dirty_data_max)
1283                         cv_wait(&dp->dp_spaceavail_cv, &dp->dp_lock);
1284                 uint64_t dirty = dp->dp_dirty_total;
1285                 mutex_exit(&dp->dp_lock);
1286 
1287                 dmu_tx_delay(tx, dirty);
1288 
1289                 tx->tx_wait_dirty = B_FALSE;
1290 
1291                 /*
1292                  * Note: setting tx_waited only has effect if the caller
1293                  * used TX_WAIT.  Otherwise they are going to destroy
1294                  * this tx and try again.  The common case, zfs_write(),
1295                  * uses TX_WAIT.
1296                  */
1297                 tx->tx_waited = B_TRUE;
1298         } else if (spa_suspended(spa) || tx->tx_lasttried_txg == 0) {
1299                 /*
1300                  * If the pool is suspended we need to wait until it
1301                  * is resumed.  Note that it's possible that the pool
1302                  * has become active after this thread has tried to
1303                  * obtain a tx.  If that's the case then tx_lasttried_txg
1304                  * would not have been set.
1305                  */
1306                 txg_wait_synced(dp, spa_last_synced_txg(spa) + 1);
1307         } else if (tx->tx_needassign_txh) {
1308                 /*
1309                  * A dnode is assigned to the quiescing txg.  Wait for its
1310                  * transaction to complete.
1311                  */
1312                 dnode_t *dn = tx->tx_needassign_txh->txh_dnode;
1313 
1314                 mutex_enter(&dn->dn_mtx);
1315                 while (dn->dn_assigned_txg == tx->tx_lasttried_txg - 1)
1316                         cv_wait(&dn->dn_notxholds, &dn->dn_mtx);
1317                 mutex_exit(&dn->dn_mtx);
1318                 tx->tx_needassign_txh = NULL;
1319         } else {
1320                 txg_wait_open(tx->tx_pool, tx->tx_lasttried_txg + 1);
1321         }
1322 }
1323 
1324 void
1325 dmu_tx_willuse_space(dmu_tx_t *tx, int64_t delta)
1326 {
1327 #ifdef ZFS_DEBUG
1328         if (tx->tx_dir == NULL || delta == 0)
1329                 return;
1330 
1331         if (delta > 0) {
1332                 ASSERT3U(refcount_count(&tx->tx_space_written) + delta, <=,
1333                     tx->tx_space_towrite);
1334                 (void) refcount_add_many(&tx->tx_space_written, delta, NULL);
1335         } else {
1336                 (void) refcount_add_many(&tx->tx_space_freed, -delta, NULL);
1337         }
1338 #endif
1339 }
1340 
1341 void
1342 dmu_tx_commit(dmu_tx_t *tx)
1343 {
1344         dmu_tx_hold_t *txh;
1345 
1346         ASSERT(tx->tx_txg != 0);
1347 
1348         /*
1349          * Go through the transaction's hold list and remove holds on
1350          * associated dnodes, notifying waiters if no holds remain.
1351          */
1352         while (txh = list_head(&tx->tx_holds)) {
1353                 dnode_t *dn = txh->txh_dnode;
1354 
1355                 list_remove(&tx->tx_holds, txh);
1356                 kmem_free(txh, sizeof (dmu_tx_hold_t));
1357                 if (dn == NULL)
1358                         continue;
1359                 mutex_enter(&dn->dn_mtx);
1360                 ASSERT3U(dn->dn_assigned_txg, ==, tx->tx_txg);
1361 
1362                 if (refcount_remove(&dn->dn_tx_holds, tx) == 0) {
1363                         dn->dn_assigned_txg = 0;
1364                         cv_broadcast(&dn->dn_notxholds);
1365                 }
1366                 mutex_exit(&dn->dn_mtx);
1367                 dnode_rele(dn, tx);
1368         }
1369 
1370         if (tx->tx_tempreserve_cookie)
1371                 dsl_dir_tempreserve_clear(tx->tx_tempreserve_cookie, tx);
1372 
1373         if (!list_is_empty(&tx->tx_callbacks))
1374                 txg_register_callbacks(&tx->tx_txgh, &tx->tx_callbacks);
1375 
1376         if (tx->tx_anyobj == FALSE)
1377                 txg_rele_to_sync(&tx->tx_txgh);
1378 
1379         list_destroy(&tx->tx_callbacks);
1380         list_destroy(&tx->tx_holds);
1381 #ifdef ZFS_DEBUG
1382         dprintf("towrite=%llu written=%llu tofree=%llu freed=%llu\n",
1383             tx->tx_space_towrite, refcount_count(&tx->tx_space_written),
1384             tx->tx_space_tofree, refcount_count(&tx->tx_space_freed));
1385         refcount_destroy_many(&tx->tx_space_written,
1386             refcount_count(&tx->tx_space_written));
1387         refcount_destroy_many(&tx->tx_space_freed,
1388             refcount_count(&tx->tx_space_freed));
1389 #endif
1390         kmem_free(tx, sizeof (dmu_tx_t));
1391 }
1392 
1393 void
1394 dmu_tx_abort(dmu_tx_t *tx)
1395 {
1396         dmu_tx_hold_t *txh;
1397 
1398         ASSERT(tx->tx_txg == 0);
1399 
1400         while (txh = list_head(&tx->tx_holds)) {
1401                 dnode_t *dn = txh->txh_dnode;
1402 
1403                 list_remove(&tx->tx_holds, txh);
1404                 kmem_free(txh, sizeof (dmu_tx_hold_t));
1405                 if (dn != NULL)
1406                         dnode_rele(dn, tx);
1407         }
1408 
1409         /*
1410          * Call any registered callbacks with an error code.
1411          */
1412         if (!list_is_empty(&tx->tx_callbacks))
1413                 dmu_tx_do_callbacks(&tx->tx_callbacks, ECANCELED);
1414 
1415         list_destroy(&tx->tx_callbacks);
1416         list_destroy(&tx->tx_holds);
1417 #ifdef ZFS_DEBUG
1418         refcount_destroy_many(&tx->tx_space_written,
1419             refcount_count(&tx->tx_space_written));
1420         refcount_destroy_many(&tx->tx_space_freed,
1421             refcount_count(&tx->tx_space_freed));
1422 #endif
1423         kmem_free(tx, sizeof (dmu_tx_t));
1424 }
1425 
1426 uint64_t
1427 dmu_tx_get_txg(dmu_tx_t *tx)
1428 {
1429         ASSERT(tx->tx_txg != 0);
1430         return (tx->tx_txg);
1431 }
1432 
1433 dsl_pool_t *
1434 dmu_tx_pool(dmu_tx_t *tx)
1435 {
1436         ASSERT(tx->tx_pool != NULL);
1437         return (tx->tx_pool);
1438 }
1439 
1440 
1441 void
1442 dmu_tx_callback_register(dmu_tx_t *tx, dmu_tx_callback_func_t *func, void *data)
1443 {
1444         dmu_tx_callback_t *dcb;
1445 
1446         dcb = kmem_alloc(sizeof (dmu_tx_callback_t), KM_SLEEP);
1447 
1448         dcb->dcb_func = func;
1449         dcb->dcb_data = data;
1450 
1451         list_insert_tail(&tx->tx_callbacks, dcb);
1452 }
1453 
1454 /*
1455  * Call all the commit callbacks on a list, with a given error code.
1456  */
1457 void
1458 dmu_tx_do_callbacks(list_t *cb_list, int error)
1459 {
1460         dmu_tx_callback_t *dcb;
1461 
1462         while (dcb = list_head(cb_list)) {
1463                 list_remove(cb_list, dcb);
1464                 dcb->dcb_func(dcb->dcb_data, error);
1465                 kmem_free(dcb, sizeof (dmu_tx_callback_t));
1466         }
1467 }
1468 
1469 /*
1470  * Interface to hold a bunch of attributes.
1471  * used for creating new files.
1472  * attrsize is the total size of all attributes
1473  * to be added during object creation
1474  *
1475  * For updating/adding a single attribute dmu_tx_hold_sa() should be used.
1476  */
1477 
1478 /*
1479  * hold necessary attribute name for attribute registration.
1480  * should be a very rare case where this is needed.  If it does
1481  * happen it would only happen on the first write to the file system.
1482  */
1483 static void
1484 dmu_tx_sa_registration_hold(sa_os_t *sa, dmu_tx_t *tx)
1485 {
1486         int i;
1487 
1488         if (!sa->sa_need_attr_registration)
1489                 return;
1490 
1491         for (i = 0; i != sa->sa_num_attrs; i++) {
1492                 if (!sa->sa_attr_table[i].sa_registered) {
1493                         if (sa->sa_reg_attr_obj)
1494                                 dmu_tx_hold_zap(tx, sa->sa_reg_attr_obj,
1495                                     B_TRUE, sa->sa_attr_table[i].sa_name);
1496                         else
1497                                 dmu_tx_hold_zap(tx, DMU_NEW_OBJECT,
1498                                     B_TRUE, sa->sa_attr_table[i].sa_name);
1499                 }
1500         }
1501 }
1502 
1503 
1504 void
1505 dmu_tx_hold_spill(dmu_tx_t *tx, uint64_t object)
1506 {
1507         dnode_t *dn;
1508         dmu_tx_hold_t *txh;
1509 
1510         txh = dmu_tx_hold_object_impl(tx, tx->tx_objset, object,
1511             THT_SPILL, 0, 0);
1512 
1513         dn = txh->txh_dnode;
1514 
1515         if (dn == NULL)
1516                 return;
1517 
1518         /* If blkptr doesn't exist then add space to towrite */
1519         if (!(dn->dn_phys->dn_flags & DNODE_FLAG_SPILL_BLKPTR)) {
1520                 txh->txh_space_towrite += SPA_MAXBLOCKSIZE;
1521         } else {
1522                 blkptr_t *bp;
1523 
1524                 bp = &dn->dn_phys->dn_spill;
1525                 if (dsl_dataset_block_freeable(dn->dn_objset->os_dsl_dataset,
1526                     bp, bp->blk_birth))
1527                         txh->txh_space_tooverwrite += SPA_MAXBLOCKSIZE;
1528                 else
1529                         txh->txh_space_towrite += SPA_MAXBLOCKSIZE;
1530                 if (!BP_IS_HOLE(bp))
1531                         txh->txh_space_tounref += SPA_MAXBLOCKSIZE;
1532         }
1533 }
1534 
1535 void
1536 dmu_tx_hold_sa_create(dmu_tx_t *tx, int attrsize)
1537 {
1538         sa_os_t *sa = tx->tx_objset->os_sa;
1539 
1540         dmu_tx_hold_bonus(tx, DMU_NEW_OBJECT);
1541 
1542         if (tx->tx_objset->os_sa->sa_master_obj == 0)
1543                 return;
1544 
1545         if (tx->tx_objset->os_sa->sa_layout_attr_obj)
1546                 dmu_tx_hold_zap(tx, sa->sa_layout_attr_obj, B_TRUE, NULL);
1547         else {
1548                 dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_LAYOUTS);
1549                 dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_REGISTRY);
1550                 dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
1551                 dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
1552         }
1553 
1554         dmu_tx_sa_registration_hold(sa, tx);
1555 
1556         if (attrsize <= DN_MAX_BONUSLEN && !sa->sa_force_spill)
1557                 return;
1558 
1559         (void) dmu_tx_hold_object_impl(tx, tx->tx_objset, DMU_NEW_OBJECT,
1560             THT_SPILL, 0, 0);
1561 }
1562 
1563 /*
1564  * Hold SA attribute
1565  *
1566  * dmu_tx_hold_sa(dmu_tx_t *tx, sa_handle_t *, attribute, add, size)
1567  *
1568  * variable_size is the total size of all variable sized attributes
1569  * passed to this function.  It is not the total size of all
1570  * variable size attributes that *may* exist on this object.
1571  */
1572 void
1573 dmu_tx_hold_sa(dmu_tx_t *tx, sa_handle_t *hdl, boolean_t may_grow)
1574 {
1575         uint64_t object;
1576         sa_os_t *sa = tx->tx_objset->os_sa;
1577 
1578         ASSERT(hdl != NULL);
1579 
1580         object = sa_handle_object(hdl);
1581 
1582         dmu_tx_hold_bonus(tx, object);
1583 
1584         if (tx->tx_objset->os_sa->sa_master_obj == 0)
1585                 return;
1586 
1587         if (tx->tx_objset->os_sa->sa_reg_attr_obj == 0 ||
1588             tx->tx_objset->os_sa->sa_layout_attr_obj == 0) {
1589                 dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_LAYOUTS);
1590                 dmu_tx_hold_zap(tx, sa->sa_master_obj, B_TRUE, SA_REGISTRY);
1591                 dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
1592                 dmu_tx_hold_zap(tx, DMU_NEW_OBJECT, B_TRUE, NULL);
1593         }
1594 
1595         dmu_tx_sa_registration_hold(sa, tx);
1596 
1597         if (may_grow && tx->tx_objset->os_sa->sa_layout_attr_obj)
1598                 dmu_tx_hold_zap(tx, sa->sa_layout_attr_obj, B_TRUE, NULL);
1599 
1600         if (sa->sa_force_spill || may_grow || hdl->sa_spill) {
1601                 ASSERT(tx->tx_txg == 0);
1602                 dmu_tx_hold_spill(tx, object);
1603         } else {
1604                 dmu_buf_impl_t *db = (dmu_buf_impl_t *)hdl->sa_bonus;
1605                 dnode_t *dn;
1606 
1607                 DB_DNODE_ENTER(db);
1608                 dn = DB_DNODE(db);
1609                 if (dn->dn_have_spill) {
1610                         ASSERT(tx->tx_txg == 0);
1611                         dmu_tx_hold_spill(tx, object);
1612                 }
1613                 DB_DNODE_EXIT(db);
1614         }
1615 }