module/zfs/dsl_deadlist.c

   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) 2010, Oracle and/or its affiliates. All rights reserved.
  23  * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
  24  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
  25  */
  26
  27 #include <sys/dsl_dataset.h>
  28 #include <sys/dmu.h>
  29 #include <sys/refcount.h>
  30 #include <sys/zap.h>
  31 #include <sys/zfs_context.h>
  32 #include <sys/dsl_pool.h>
  33
  34 /*
  35  * Deadlist concurrency:
  36  *
  37  * Deadlists can only be modified from the syncing thread.
  38  *
  39  * Except for dsl_deadlist_insert(), it can only be modified with the
  40  * dp_config_rwlock held with RW_WRITER.
  41  *
  42  * The accessors (dsl_deadlist_space() and dsl_deadlist_space_range()) can
  43  * be called concurrently, from open context, with the dl_config_rwlock held
  44  * with RW_READER.
  45  *
  46  * Therefore, we only need to provide locking between dsl_deadlist_insert() and
  47  * the accessors, protecting:
  48  *     dl_phys->dl_used,comp,uncomp
  49  *     and protecting the dl_tree from being loaded.
  50  * The locking is provided by dl_lock.  Note that locking on the bpobj_t
  51  * provides its own locking, and dl_oldfmt is immutable.
  52  */
  53
  54 static int
  55 dsl_deadlist_compare(const void *arg1, const void *arg2)
  56 {
  57         const dsl_deadlist_entry_t *dle1 = (const dsl_deadlist_entry_t *)arg1;
  58         const dsl_deadlist_entry_t *dle2 = (const dsl_deadlist_entry_t *)arg2;
  59
  60         return (AVL_CMP(dle1->dle_mintxg, dle2->dle_mintxg));
  61 }
  62
  63 static void
  64 dsl_deadlist_load_tree(dsl_deadlist_t *dl)
  65 {
  66         zap_cursor_t zc;
  67         zap_attribute_t za;
  68
  69         ASSERT(MUTEX_HELD(&dl->dl_lock));
  70
  71         ASSERT(!dl->dl_oldfmt);
  72         if (dl->dl_havetree)
  73                 return;
  74
  75         avl_create(&dl->dl_tree, dsl_deadlist_compare,
  76             sizeof (dsl_deadlist_entry_t),
  77             offsetof(dsl_deadlist_entry_t, dle_node));
  78         for (zap_cursor_init(&zc, dl->dl_os, dl->dl_object);
  79             zap_cursor_retrieve(&zc, &za) == 0;
  80             zap_cursor_advance(&zc)) {
  81                 dsl_deadlist_entry_t *dle;
  82
  83                 dle = kmem_alloc(sizeof (*dle), KM_SLEEP);
  84                 dle->dle_mintxg = strtonum(za.za_name, NULL);
  85                 VERIFY3U(0, ==, bpobj_open(&dle->dle_bpobj, dl->dl_os,
  86                     za.za_first_integer));
  87                 avl_add(&dl->dl_tree, dle);
  88         }
  89         zap_cursor_fini(&zc);
  90         dl->dl_havetree = B_TRUE;
  91 }
  92
  93 void
  94 dsl_deadlist_open(dsl_deadlist_t *dl, objset_t *os, uint64_t object)
  95 {
  96         dmu_object_info_t doi;
  97
  98         mutex_init(&dl->dl_lock, NULL, MUTEX_DEFAULT, NULL);
  99         dl->dl_os = os;
 100         dl->dl_object = object;
 101         VERIFY3U(0, ==, dmu_bonus_hold(os, object, dl, &dl->dl_dbuf));
 102         dmu_object_info_from_db(dl->dl_dbuf, &doi);
 103         if (doi.doi_type == DMU_OT_BPOBJ) {
 104                 dmu_buf_rele(dl->dl_dbuf, dl);
 105                 dl->dl_dbuf = NULL;
 106                 dl->dl_oldfmt = B_TRUE;
 107                 VERIFY3U(0, ==, bpobj_open(&dl->dl_bpobj, os, object));
 108                 return;
 109         }
 110
 111         dl->dl_oldfmt = B_FALSE;
 112         dl->dl_phys = dl->dl_dbuf->db_data;
 113         dl->dl_havetree = B_FALSE;
 114 }
 115
 116 void
 117 dsl_deadlist_close(dsl_deadlist_t *dl)
 118 {
 119         void *cookie = NULL;
 120         dsl_deadlist_entry_t *dle;
 121
 122         dl->dl_os = NULL;
 123         mutex_destroy(&dl->dl_lock);
 124
 125         if (dl->dl_oldfmt) {
 126                 dl->dl_oldfmt = B_FALSE;
 127                 bpobj_close(&dl->dl_bpobj);
 128                 return;
 129         }
 130
 131         if (dl->dl_havetree) {
 132                 while ((dle = avl_destroy_nodes(&dl->dl_tree, &cookie))
 133                     != NULL) {
 134                         bpobj_close(&dle->dle_bpobj);
 135                         kmem_free(dle, sizeof (*dle));
 136                 }
 137                 avl_destroy(&dl->dl_tree);
 138         }
 139         dmu_buf_rele(dl->dl_dbuf, dl);
 140         dl->dl_dbuf = NULL;
 141         dl->dl_phys = NULL;
 142 }
 143
 144 uint64_t
 145 dsl_deadlist_alloc(objset_t *os, dmu_tx_t *tx)
 146 {
 147         if (spa_version(dmu_objset_spa(os)) < SPA_VERSION_DEADLISTS)
 148                 return (bpobj_alloc(os, SPA_OLD_MAXBLOCKSIZE, tx));
 149         return (zap_create(os, DMU_OT_DEADLIST, DMU_OT_DEADLIST_HDR,
 150             sizeof (dsl_deadlist_phys_t), tx));
 151 }
 152
 153 void
 154 dsl_deadlist_free(objset_t *os, uint64_t dlobj, dmu_tx_t *tx)
 155 {
 156         dmu_object_info_t doi;
 157         zap_cursor_t zc;
 158         zap_attribute_t za;
 159
 160         VERIFY3U(0, ==, dmu_object_info(os, dlobj, &doi));
 161         if (doi.doi_type == DMU_OT_BPOBJ) {
 162                 bpobj_free(os, dlobj, tx);
 163                 return;
 164         }
 165
 166         for (zap_cursor_init(&zc, os, dlobj);
 167             zap_cursor_retrieve(&zc, &za) == 0;
 168             zap_cursor_advance(&zc)) {
 169                 uint64_t obj = za.za_first_integer;
 170                 if (obj == dmu_objset_pool(os)->dp_empty_bpobj)
 171                         bpobj_decr_empty(os, tx);
 172                 else
 173                         bpobj_free(os, obj, tx);
 174         }
 175         zap_cursor_fini(&zc);
 176         VERIFY3U(0, ==, dmu_object_free(os, dlobj, tx));
 177 }
 178
 179 static void
 180 dle_enqueue(dsl_deadlist_t *dl, dsl_deadlist_entry_t *dle,
 181     const blkptr_t *bp, dmu_tx_t *tx)
 182 {
 183         ASSERT(MUTEX_HELD(&dl->dl_lock));
 184         if (dle->dle_bpobj.bpo_object ==
 185             dmu_objset_pool(dl->dl_os)->dp_empty_bpobj) {
 186                 uint64_t obj = bpobj_alloc(dl->dl_os, SPA_OLD_MAXBLOCKSIZE, tx);
 187                 bpobj_close(&dle->dle_bpobj);
 188                 bpobj_decr_empty(dl->dl_os, tx);
 189                 VERIFY3U(0, ==, bpobj_open(&dle->dle_bpobj, dl->dl_os, obj));
 190                 VERIFY3U(0, ==, zap_update_int_key(dl->dl_os, dl->dl_object,
 191                     dle->dle_mintxg, obj, tx));
 192         }
 193         bpobj_enqueue(&dle->dle_bpobj, bp, tx);
 194 }
 195
 196 static void
 197 dle_enqueue_subobj(dsl_deadlist_t *dl, dsl_deadlist_entry_t *dle,
 198     uint64_t obj, dmu_tx_t *tx)
 199 {
 200         ASSERT(MUTEX_HELD(&dl->dl_lock));
 201         if (dle->dle_bpobj.bpo_object !=
 202             dmu_objset_pool(dl->dl_os)->dp_empty_bpobj) {
 203                 bpobj_enqueue_subobj(&dle->dle_bpobj, obj, tx);
 204         } else {
 205                 bpobj_close(&dle->dle_bpobj);
 206                 bpobj_decr_empty(dl->dl_os, tx);
 207                 VERIFY3U(0, ==, bpobj_open(&dle->dle_bpobj, dl->dl_os, obj));
 208                 VERIFY3U(0, ==, zap_update_int_key(dl->dl_os, dl->dl_object,
 209                     dle->dle_mintxg, obj, tx));
 210         }
 211 }
 212
 213 void
 214 dsl_deadlist_insert(dsl_deadlist_t *dl, const blkptr_t *bp, dmu_tx_t *tx)
 215 {
 216         dsl_deadlist_entry_t dle_tofind;
 217         dsl_deadlist_entry_t *dle;
 218         avl_index_t where;
 219
 220         if (dl->dl_oldfmt) {
 221                 bpobj_enqueue(&dl->dl_bpobj, bp, tx);
 222                 return;
 223         }
 224
 225         mutex_enter(&dl->dl_lock);
 226         dsl_deadlist_load_tree(dl);
 227
 228         dmu_buf_will_dirty(dl->dl_dbuf, tx);
 229         dl->dl_phys->dl_used +=
 230             bp_get_dsize_sync(dmu_objset_spa(dl->dl_os), bp);
 231         dl->dl_phys->dl_comp += BP_GET_PSIZE(bp);
 232         dl->dl_phys->dl_uncomp += BP_GET_UCSIZE(bp);
 233
 234         dle_tofind.dle_mintxg = bp->blk_birth;
 235         dle = avl_find(&dl->dl_tree, &dle_tofind, &where);
 236         if (dle == NULL)
 237                 dle = avl_nearest(&dl->dl_tree, where, AVL_BEFORE);
 238         else
 239                 dle = AVL_PREV(&dl->dl_tree, dle);
 240
 241         if (dle == NULL) {
 242                 zfs_panic_recover("blkptr at %p has invalid BLK_BIRTH %llu",
 243                     bp, (longlong_t)bp->blk_birth);
 244                 dle = avl_first(&dl->dl_tree);
 245         }
 246
 247         ASSERT3P(dle, !=, NULL);
 248         dle_enqueue(dl, dle, bp, tx);
 249         mutex_exit(&dl->dl_lock);
 250 }
 251
 252 /*
 253  * Insert new key in deadlist, which must be > all current entries.
 254  * mintxg is not inclusive.
 255  */
 256 void
 257 dsl_deadlist_add_key(dsl_deadlist_t *dl, uint64_t mintxg, dmu_tx_t *tx)
 258 {
 259         uint64_t obj;
 260         dsl_deadlist_entry_t *dle;
 261
 262         if (dl->dl_oldfmt)
 263                 return;
 264
 265         dle = kmem_alloc(sizeof (*dle), KM_SLEEP);
 266         dle->dle_mintxg = mintxg;
 267
 268         mutex_enter(&dl->dl_lock);
 269         dsl_deadlist_load_tree(dl);
 270
 271         obj = bpobj_alloc_empty(dl->dl_os, SPA_OLD_MAXBLOCKSIZE, tx);
 272         VERIFY3U(0, ==, bpobj_open(&dle->dle_bpobj, dl->dl_os, obj));
 273         avl_add(&dl->dl_tree, dle);
 274
 275         VERIFY3U(0, ==, zap_add_int_key(dl->dl_os, dl->dl_object,
 276             mintxg, obj, tx));
 277         mutex_exit(&dl->dl_lock);
 278 }
 279
 280 /*
 281  * Remove this key, merging its entries into the previous key.
 282  */
 283 void
 284 dsl_deadlist_remove_key(dsl_deadlist_t *dl, uint64_t mintxg, dmu_tx_t *tx)
 285 {
 286         dsl_deadlist_entry_t dle_tofind;
 287         dsl_deadlist_entry_t *dle, *dle_prev;
 288
 289         if (dl->dl_oldfmt)
 290                 return;
 291
 292         mutex_enter(&dl->dl_lock);
 293         dsl_deadlist_load_tree(dl);
 294
 295         dle_tofind.dle_mintxg = mintxg;
 296         dle = avl_find(&dl->dl_tree, &dle_tofind, NULL);
 297         dle_prev = AVL_PREV(&dl->dl_tree, dle);
 298
 299         dle_enqueue_subobj(dl, dle_prev, dle->dle_bpobj.bpo_object, tx);
 300
 301         avl_remove(&dl->dl_tree, dle);
 302         bpobj_close(&dle->dle_bpobj);
 303         kmem_free(dle, sizeof (*dle));
 304
 305         VERIFY3U(0, ==, zap_remove_int(dl->dl_os, dl->dl_object, mintxg, tx));
 306         mutex_exit(&dl->dl_lock);
 307 }
 308
 309 /*
 310  * Walk ds's snapshots to regenerate generate ZAP & AVL.
 311  */
 312 static void
 313 dsl_deadlist_regenerate(objset_t *os, uint64_t dlobj,
 314     uint64_t mrs_obj, dmu_tx_t *tx)
 315 {
 316         dsl_deadlist_t dl;
 317         dsl_pool_t *dp = dmu_objset_pool(os);
 318
 319         dsl_deadlist_open(&dl, os, dlobj);
 320         if (dl.dl_oldfmt) {
 321                 dsl_deadlist_close(&dl);
 322                 return;
 323         }
 324
 325         while (mrs_obj != 0) {
 326                 dsl_dataset_t *ds;
 327                 VERIFY3U(0, ==, dsl_dataset_hold_obj(dp, mrs_obj, FTAG, &ds));
 328                 dsl_deadlist_add_key(&dl,
 329                     dsl_dataset_phys(ds)->ds_prev_snap_txg, tx);
 330                 mrs_obj = dsl_dataset_phys(ds)->ds_prev_snap_obj;
 331                 dsl_dataset_rele(ds, FTAG);
 332         }
 333         dsl_deadlist_close(&dl);
 334 }
 335
 336 uint64_t
 337 dsl_deadlist_clone(dsl_deadlist_t *dl, uint64_t maxtxg,
 338     uint64_t mrs_obj, dmu_tx_t *tx)
 339 {
 340         dsl_deadlist_entry_t *dle;
 341         uint64_t newobj;
 342
 343         newobj = dsl_deadlist_alloc(dl->dl_os, tx);
 344
 345         if (dl->dl_oldfmt) {
 346                 dsl_deadlist_regenerate(dl->dl_os, newobj, mrs_obj, tx);
 347                 return (newobj);
 348         }
 349
 350         mutex_enter(&dl->dl_lock);
 351         dsl_deadlist_load_tree(dl);
 352
 353         for (dle = avl_first(&dl->dl_tree); dle;
 354             dle = AVL_NEXT(&dl->dl_tree, dle)) {
 355                 uint64_t obj;
 356
 357                 if (dle->dle_mintxg >= maxtxg)
 358                         break;
 359
 360                 obj = bpobj_alloc_empty(dl->dl_os, SPA_OLD_MAXBLOCKSIZE, tx);
 361                 VERIFY3U(0, ==, zap_add_int_key(dl->dl_os, newobj,
 362                     dle->dle_mintxg, obj, tx));
 363         }
 364         mutex_exit(&dl->dl_lock);
 365         return (newobj);
 366 }
 367
 368 void
 369 dsl_deadlist_space(dsl_deadlist_t *dl,
 370     uint64_t *usedp, uint64_t *compp, uint64_t *uncompp)
 371 {
 372         if (dl->dl_oldfmt) {
 373                 VERIFY3U(0, ==, bpobj_space(&dl->dl_bpobj,
 374                     usedp, compp, uncompp));
 375                 return;
 376         }
 377
 378         mutex_enter(&dl->dl_lock);
 379         *usedp = dl->dl_phys->dl_used;
 380         *compp = dl->dl_phys->dl_comp;
 381         *uncompp = dl->dl_phys->dl_uncomp;
 382         mutex_exit(&dl->dl_lock);
 383 }
 384
 385 /*
 386  * return space used in the range (mintxg, maxtxg].
 387  * Includes maxtxg, does not include mintxg.
 388  * mintxg and maxtxg must both be keys in the deadlist (unless maxtxg is
 389  * larger than any bp in the deadlist (eg. UINT64_MAX)).
 390  */
 391 void
 392 dsl_deadlist_space_range(dsl_deadlist_t *dl, uint64_t mintxg, uint64_t maxtxg,
 393     uint64_t *usedp, uint64_t *compp, uint64_t *uncompp)
 394 {
 395         dsl_deadlist_entry_t *dle;
 396         dsl_deadlist_entry_t dle_tofind;
 397         avl_index_t where;
 398
 399         if (dl->dl_oldfmt) {
 400                 VERIFY3U(0, ==, bpobj_space_range(&dl->dl_bpobj,
 401                     mintxg, maxtxg, usedp, compp, uncompp));
 402                 return;
 403         }
 404
 405         *usedp = *compp = *uncompp = 0;
 406
 407         mutex_enter(&dl->dl_lock);
 408         dsl_deadlist_load_tree(dl);
 409         dle_tofind.dle_mintxg = mintxg;
 410         dle = avl_find(&dl->dl_tree, &dle_tofind, &where);
 411         /*
 412          * If we don't find this mintxg, there shouldn't be anything
 413          * after it either.
 414          */
 415         ASSERT(dle != NULL ||
 416             avl_nearest(&dl->dl_tree, where, AVL_AFTER) == NULL);
 417
 418         for (; dle && dle->dle_mintxg < maxtxg;
 419             dle = AVL_NEXT(&dl->dl_tree, dle)) {
 420                 uint64_t used, comp, uncomp;
 421
 422                 VERIFY3U(0, ==, bpobj_space(&dle->dle_bpobj,
 423                     &used, &comp, &uncomp));
 424
 425                 *usedp += used;
 426                 *compp += comp;
 427                 *uncompp += uncomp;
 428         }
 429         mutex_exit(&dl->dl_lock);
 430 }
 431
 432 static void
 433 dsl_deadlist_insert_bpobj(dsl_deadlist_t *dl, uint64_t obj, uint64_t birth,
 434     dmu_tx_t *tx)
 435 {
 436         dsl_deadlist_entry_t dle_tofind;
 437         dsl_deadlist_entry_t *dle;
 438         avl_index_t where;
 439         uint64_t used, comp, uncomp;
 440         bpobj_t bpo;
 441
 442         ASSERT(MUTEX_HELD(&dl->dl_lock));
 443
 444         VERIFY3U(0, ==, bpobj_open(&bpo, dl->dl_os, obj));
 445         VERIFY3U(0, ==, bpobj_space(&bpo, &used, &comp, &uncomp));
 446         bpobj_close(&bpo);
 447
 448         dsl_deadlist_load_tree(dl);
 449
 450         dmu_buf_will_dirty(dl->dl_dbuf, tx);
 451         dl->dl_phys->dl_used += used;
 452         dl->dl_phys->dl_comp += comp;
 453         dl->dl_phys->dl_uncomp += uncomp;
 454
 455         dle_tofind.dle_mintxg = birth;
 456         dle = avl_find(&dl->dl_tree, &dle_tofind, &where);
 457         if (dle == NULL)
 458                 dle = avl_nearest(&dl->dl_tree, where, AVL_BEFORE);
 459         dle_enqueue_subobj(dl, dle, obj, tx);
 460 }
 461
 462 static int
 463 dsl_deadlist_insert_cb(void *arg, const blkptr_t *bp, dmu_tx_t *tx)
 464 {
 465         dsl_deadlist_t *dl = arg;
 466         dsl_deadlist_insert(dl, bp, tx);
 467         return (0);
 468 }
 469
 470 /*
 471  * Merge the deadlist pointed to by 'obj' into dl.  obj will be left as
 472  * an empty deadlist.
 473  */
 474 void
 475 dsl_deadlist_merge(dsl_deadlist_t *dl, uint64_t obj, dmu_tx_t *tx)
 476 {
 477         zap_cursor_t zc;
 478         zap_attribute_t za;
 479         dmu_buf_t *bonus;
 480         dsl_deadlist_phys_t *dlp;
 481         dmu_object_info_t doi;
 482
 483         VERIFY3U(0, ==, dmu_object_info(dl->dl_os, obj, &doi));
 484         if (doi.doi_type == DMU_OT_BPOBJ) {
 485                 bpobj_t bpo;
 486                 VERIFY3U(0, ==, bpobj_open(&bpo, dl->dl_os, obj));
 487                 VERIFY3U(0, ==, bpobj_iterate(&bpo,
 488                     dsl_deadlist_insert_cb, dl, tx));
 489                 bpobj_close(&bpo);
 490                 return;
 491         }
 492
 493         mutex_enter(&dl->dl_lock);
 494         for (zap_cursor_init(&zc, dl->dl_os, obj);
 495             zap_cursor_retrieve(&zc, &za) == 0;
 496             zap_cursor_advance(&zc)) {
 497                 uint64_t mintxg = strtonum(za.za_name, NULL);
 498                 dsl_deadlist_insert_bpobj(dl, za.za_first_integer, mintxg, tx);
 499                 VERIFY3U(0, ==, zap_remove_int(dl->dl_os, obj, mintxg, tx));
 500         }
 501         zap_cursor_fini(&zc);
 502
 503         VERIFY3U(0, ==, dmu_bonus_hold(dl->dl_os, obj, FTAG, &bonus));
 504         dlp = bonus->db_data;
 505         dmu_buf_will_dirty(bonus, tx);
 506         bzero(dlp, sizeof (*dlp));
 507         dmu_buf_rele(bonus, FTAG);
 508         mutex_exit(&dl->dl_lock);
 509 }
 510
 511 /*
 512  * Remove entries on dl that are >= mintxg, and put them on the bpobj.
 513  */
 514 void
 515 dsl_deadlist_move_bpobj(dsl_deadlist_t *dl, bpobj_t *bpo, uint64_t mintxg,
 516     dmu_tx_t *tx)
 517 {
 518         dsl_deadlist_entry_t dle_tofind;
 519         dsl_deadlist_entry_t *dle;
 520         avl_index_t where;
 521
 522         ASSERT(!dl->dl_oldfmt);
 523
 524         mutex_enter(&dl->dl_lock);
 525         dmu_buf_will_dirty(dl->dl_dbuf, tx);
 526         dsl_deadlist_load_tree(dl);
 527
 528         dle_tofind.dle_mintxg = mintxg;
 529         dle = avl_find(&dl->dl_tree, &dle_tofind, &where);
 530         if (dle == NULL)
 531                 dle = avl_nearest(&dl->dl_tree, where, AVL_AFTER);
 532         while (dle) {
 533                 uint64_t used, comp, uncomp;
 534                 dsl_deadlist_entry_t *dle_next;
 535
 536                 bpobj_enqueue_subobj(bpo, dle->dle_bpobj.bpo_object, tx);
 537
 538                 VERIFY3U(0, ==, bpobj_space(&dle->dle_bpobj,
 539                     &used, &comp, &uncomp));
 540                 ASSERT3U(dl->dl_phys->dl_used, >=, used);
 541                 ASSERT3U(dl->dl_phys->dl_comp, >=, comp);
 542                 ASSERT3U(dl->dl_phys->dl_uncomp, >=, uncomp);
 543                 dl->dl_phys->dl_used -= used;
 544                 dl->dl_phys->dl_comp -= comp;
 545                 dl->dl_phys->dl_uncomp -= uncomp;
 546
 547                 VERIFY3U(0, ==, zap_remove_int(dl->dl_os, dl->dl_object,
 548                     dle->dle_mintxg, tx));
 549
 550                 dle_next = AVL_NEXT(&dl->dl_tree, dle);
 551                 avl_remove(&dl->dl_tree, dle);
 552                 bpobj_close(&dle->dle_bpobj);
 553                 kmem_free(dle, sizeof (*dle));
 554                 dle = dle_next;
 555         }
 556         mutex_exit(&dl->dl_lock);
 557 }