sys/vfs/hammer/hammer_ioctl.c

   1 /*
   2  * Copyright (c) 2008 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.com>
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  *
  34  * $DragonFly: src/sys/vfs/hammer/hammer_ioctl.c,v 1.14 2008/05/10 22:56:36 dillon Exp $
  35  */
  36
  37 #include "hammer.h"
  38
  39 static int hammer_ioc_prune(hammer_transaction_t trans, hammer_inode_t ip,
  40                                 struct hammer_ioc_prune *prune);
  41 static int hammer_ioc_gethistory(hammer_transaction_t trans, hammer_inode_t ip,
  42                                 struct hammer_ioc_history *hist);
  43
  44 int
  45 hammer_ioctl(hammer_inode_t ip, u_long com, caddr_t data, int fflag,
  46              struct ucred *cred)
  47 {
  48         struct hammer_transaction trans;
  49         int error;
  50
  51         error = suser_cred(cred, PRISON_ROOT);
  52
  53         hammer_start_transaction(&trans, ip->hmp);
  54
  55         switch(com) {
  56         case HAMMERIOC_PRUNE:
  57                 if (error == 0) {
  58                         error = hammer_ioc_prune(&trans, ip,
  59                                         (struct hammer_ioc_prune *)data);
  60                 }
  61                 break;
  62         case HAMMERIOC_GETHISTORY:
  63                 error = hammer_ioc_gethistory(&trans, ip,
  64                                         (struct hammer_ioc_history *)data);
  65                 break;
  66         case HAMMERIOC_REBLOCK:
  67                 error = hammer_ioc_reblock(&trans, ip,
  68                                         (struct hammer_ioc_reblock *)data);
  69                 break;
  70         default:
  71                 error = EOPNOTSUPP;
  72                 break;
  73         }
  74         hammer_done_transaction(&trans);
  75         return (error);
  76 }
  77
  78 /*
  79  * Iterate through the specified range of object ids and remove any
  80  * deleted records that fall entirely within a prune modulo.
  81  *
  82  * A reverse iteration is used to prevent overlapping records from being
  83  * created during the iteration due to alignments.  This also allows us
  84  * to adjust alignments without blowing up the B-Tree.
  85  */
  86 static int check_prune(struct hammer_ioc_prune *prune, hammer_btree_elm_t elm,
  87                         int *realign_cre, int *realign_del);
  88 static int realign_prune(struct hammer_ioc_prune *prune, hammer_cursor_t cursor,
  89                         int realign_cre, int realign_del);
  90
  91 static int
  92 hammer_ioc_prune(hammer_transaction_t trans, hammer_inode_t ip,
  93                  struct hammer_ioc_prune *prune)
  94 {
  95         struct hammer_cursor cursor;
  96         hammer_btree_elm_t elm;
  97         int error;
  98         int isdir;
  99         int realign_cre;
 100         int realign_del;
 101
 102         if (prune->nelms < 0 || prune->nelms > HAMMER_MAX_PRUNE_ELMS)
 103                 return(EINVAL);
 104         if (prune->beg_obj_id >= prune->end_obj_id)
 105                 return(EINVAL);
 106         if ((prune->head.flags & HAMMER_IOC_PRUNE_ALL) && prune->nelms)
 107                 return(EINVAL);
 108
 109 retry:
 110         error = hammer_init_cursor(trans, &cursor, NULL, NULL);
 111         if (error) {
 112                 hammer_done_cursor(&cursor);
 113                 return(error);
 114         }
 115         cursor.key_beg.obj_id = prune->beg_obj_id;
 116         cursor.key_beg.key = HAMMER_MIN_KEY;
 117         cursor.key_beg.create_tid = 1;
 118         cursor.key_beg.delete_tid = 0;
 119         cursor.key_beg.rec_type = HAMMER_MIN_RECTYPE;
 120         cursor.key_beg.obj_type = 0;
 121
 122         cursor.key_end.obj_id = prune->end_obj_id;
 123         cursor.key_end.key = HAMMER_MAX_KEY;
 124         cursor.key_end.create_tid = HAMMER_MAX_TID - 1;
 125         cursor.key_end.delete_tid = 0;
 126         cursor.key_end.rec_type = HAMMER_MAX_RECTYPE;
 127         cursor.key_end.obj_type = 0;
 128
 129         cursor.flags |= HAMMER_CURSOR_END_INCLUSIVE;
 130         cursor.flags |= HAMMER_CURSOR_BACKEND;
 131
 132         prune->cur_obj_id = cursor.key_end.obj_id;
 133         prune->cur_key = cursor.key_end.key;
 134
 135         error = hammer_btree_last(&cursor);
 136         while (error == 0) {
 137                 elm = &cursor.node->ondisk->elms[cursor.index];
 138                 prune->cur_obj_id = elm->base.obj_id;
 139                 prune->cur_key = elm->base.key;
 140
 141                 if (prune->stat_oldest_tid > elm->leaf.base.create_tid)
 142                         prune->stat_oldest_tid = elm->leaf.base.create_tid;
 143
 144                 if (check_prune(prune, elm, &realign_cre, &realign_del) == 0) {
 145                         if (hammer_debug_general & 0x0200) {
 146                                 kprintf("check %016llx %016llx: DELETE\n",
 147                                         elm->base.obj_id, elm->base.key);
 148                         }
 149
 150                         /*
 151                          * NOTE: This can return EDEADLK
 152                          *
 153                          * Acquiring the sync lock guarantees that the
 154                          * operation will not cross a synchronization
 155                          * boundary (see the flusher).
 156                          */
 157                         isdir = (elm->base.rec_type == HAMMER_RECTYPE_DIRENTRY);
 158
 159                         hammer_lock_ex(&trans->hmp->sync_lock);
 160                         error = hammer_delete_at_cursor(&cursor,
 161                                                         &prune->stat_bytes);
 162                         hammer_unlock(&trans->hmp->sync_lock);
 163                         if (error)
 164                                 break;
 165
 166                         if (isdir)
 167                                 ++prune->stat_dirrecords;
 168                         else
 169                                 ++prune->stat_rawrecords;
 170                 } else if (realign_cre >= 0 || realign_del >= 0) {
 171                         hammer_lock_ex(&trans->hmp->sync_lock);
 172                         error = realign_prune(prune, &cursor,
 173                                               realign_cre, realign_del);
 174                         hammer_unlock(&trans->hmp->sync_lock);
 175                         if (error == 0) {
 176                                 cursor.flags |= HAMMER_CURSOR_ATEDISK;
 177                                 if (hammer_debug_general & 0x0200) {
 178                                         kprintf("check %016llx %016llx: "
 179                                                 "REALIGN\n",
 180                                                 elm->base.obj_id,
 181                                                 elm->base.key);
 182                                 }
 183                         }
 184                 } else {
 185                         cursor.flags |= HAMMER_CURSOR_ATEDISK;
 186                         if (hammer_debug_general & 0x0100) {
 187                                 kprintf("check %016llx %016llx: SKIP\n",
 188                                         elm->base.obj_id, elm->base.key);
 189                         }
 190                 }
 191                 ++prune->stat_scanrecords;
 192
 193                 /*
 194                  * Bad hack for now, don't blow out the kernel's buffer
 195                  * cache.  NOTE: We still hold locks on the cursor, we
 196                  * cannot call the flusher synchronously.
 197                  */
 198                 if (trans->hmp->locked_dirty_count > hammer_limit_dirtybufs) {
 199                         hammer_flusher_async(trans->hmp);
 200                         tsleep(trans, 0, "hmrslo", hz / 10);
 201                 }
 202                 error = hammer_signal_check(trans->hmp);
 203                 if (error == 0)
 204                         error = hammer_btree_iterate_reverse(&cursor);
 205         }
 206         if (error == ENOENT)
 207                 error = 0;
 208         hammer_done_cursor(&cursor);
 209         if (error == EDEADLK)
 210                 goto retry;
 211         if (error == EINTR) {
 212                 prune->head.flags |= HAMMER_IOC_HEAD_INTR;
 213                 error = 0;
 214         }
 215         return(error);
 216 }
 217
 218 /*
 219  * Check pruning list.  The list must be sorted in descending order.
 220  */
 221 static int
 222 check_prune(struct hammer_ioc_prune *prune, hammer_btree_elm_t elm,
 223             int *realign_cre, int *realign_del)
 224 {
 225         struct hammer_ioc_prune_elm *scan;
 226         int i;
 227
 228         *realign_cre = -1;
 229         *realign_del = -1;
 230
 231         /*
 232          * If pruning everything remove all records with a non-zero
 233          * delete_tid.
 234          */
 235         if (prune->head.flags & HAMMER_IOC_PRUNE_ALL) {
 236                 if (elm->base.delete_tid != 0)
 237                         return(0);
 238                 return(-1);
 239         }
 240
 241         for (i = 0; i < prune->nelms; ++i) {
 242                 scan = &prune->elms[i];
 243
 244                 /*
 245                  * Locate the scan index covering the create and delete TIDs.
 246                  */
 247                 if (*realign_cre < 0 &&
 248                     elm->base.create_tid >= scan->beg_tid &&
 249                     elm->base.create_tid < scan->end_tid) {
 250                         *realign_cre = i;
 251                 }
 252                 if (*realign_del < 0 && elm->base.delete_tid &&
 253                     elm->base.delete_tid > scan->beg_tid &&
 254                     elm->base.delete_tid <= scan->end_tid) {
 255                         *realign_del = i;
 256                 }
 257
 258                 /*
 259                  * Now check for loop termination.
 260                  */
 261                 if (elm->base.create_tid >= scan->end_tid ||
 262                     elm->base.delete_tid > scan->end_tid) {
 263                         break;
 264                 }
 265
 266                 /*
 267                  * Now determine if we can delete the record.
 268                  */
 269                 if (elm->base.delete_tid &&
 270                     elm->base.create_tid >= scan->beg_tid &&
 271                     elm->base.delete_tid <= scan->end_tid &&
 272                     elm->base.create_tid / scan->mod_tid ==
 273                     elm->base.delete_tid / scan->mod_tid) {
 274                         return(0);
 275                 }
 276         }
 277         return(-1);
 278 }
 279
 280 /*
 281  * Align the record to cover any gaps created through the deletion of
 282  * records within the pruning space.  If we were to just delete the records
 283  * there would be gaps which in turn would cause a snapshot that is NOT on
 284  * a pruning boundary to appear corrupt to the user.  Forcing alignment
 285  * of the create_tid and delete_tid for retained records 'reconnects'
 286  * the previously contiguous space, making it contiguous again after the
 287  * deletions.
 288  *
 289  * The use of a reverse iteration allows us to safely align the records and
 290  * related elements without creating temporary overlaps.  XXX we should
 291  * add ordering dependancies for record buffers to guarantee consistency
 292  * during recovery.
 293  */
 294 static int
 295 realign_prune(struct hammer_ioc_prune *prune,
 296               hammer_cursor_t cursor, int realign_cre, int realign_del)
 297 {
 298         hammer_btree_elm_t elm;
 299         hammer_tid_t delta;
 300         hammer_tid_t mod;
 301         hammer_tid_t tid;
 302         int error;
 303
 304         hammer_cursor_downgrade(cursor);
 305
 306         elm = &cursor->node->ondisk->elms[cursor->index];
 307         ++prune->stat_realignments;
 308
 309         /*
 310          * Align the create_tid.  By doing a reverse iteration we guarantee
 311          * that all records after our current record have already been
 312          * aligned, allowing us to safely correct the right-hand-boundary
 313          * (because no record to our right if otherwise exactly matching
 314          * will have a create_tid to the left of our aligned create_tid).
 315          *
 316          * Ordering is important here XXX but disk write ordering for
 317          * inter-cluster corrections is not currently guaranteed.
 318          */
 319         error = 0;
 320         if (realign_cre >= 0) {
 321                 mod = prune->elms[realign_cre].mod_tid;
 322                 delta = elm->leaf.base.create_tid % mod;
 323                 if (delta) {
 324                         tid = elm->leaf.base.create_tid - delta + mod;
 325
 326                         /* can EDEADLK */
 327                         error = hammer_btree_correct_rhb(cursor, tid + 1);
 328                         if (error == 0) {
 329                                 error = hammer_btree_extract(cursor,
 330                                                      HAMMER_CURSOR_GET_RECORD);
 331                         }
 332                         if (error == 0) {
 333                                 /* can EDEADLK */
 334                                 error = hammer_cursor_upgrade(cursor);
 335                         }
 336                         if (error == 0) {
 337                                 hammer_modify_record_field(cursor->trans,
 338                                             cursor->record_buffer,
 339                                             cursor->record,
 340                                             base.base.create_tid, 0);
 341                                 cursor->record->base.base.create_tid = tid;
 342                                 hammer_modify_record_done(
 343                                             cursor->record_buffer,
 344                                             cursor->record);
 345                                 hammer_modify_node(cursor->trans, cursor->node,
 346                                             &elm->leaf.base.create_tid,
 347                                             sizeof(elm->leaf.base.create_tid));
 348                                 elm->leaf.base.create_tid = tid;
 349                                 hammer_modify_node_done(cursor->node);
 350                         }
 351                 }
 352         }
 353
 354         /*
 355          * Align the delete_tid.  This only occurs if the record is historical
 356          * was deleted at some point.  Realigning the delete_tid does not
 357          * move the record within the B-Tree but may cause it to temporarily
 358          * overlap a record that has not yet been pruned.
 359          */
 360         if (error == 0 && realign_del >= 0) {
 361                 mod = prune->elms[realign_del].mod_tid;
 362                 delta = elm->leaf.base.delete_tid % mod;
 363                 if (delta) {
 364                         error = hammer_btree_extract(cursor,
 365                                                      HAMMER_CURSOR_GET_RECORD);
 366                         if (error == 0) {
 367                                 hammer_modify_node(cursor->trans, cursor->node,
 368                                             &elm->leaf.base.delete_tid,
 369                                             sizeof(elm->leaf.base.delete_tid));
 370                                 elm->leaf.base.delete_tid =
 371                                             elm->leaf.base.delete_tid -
 372                                             delta + mod;
 373                                 hammer_modify_node_done(cursor->node);
 374                                 hammer_modify_record_field(cursor->trans,
 375                                             cursor->record_buffer,
 376                                             cursor->record,
 377                                             base.base.delete_tid, 0);
 378                                 cursor->record->base.base.delete_tid =
 379                                             elm->leaf.base.delete_tid;
 380                                 hammer_modify_record_done(cursor->record_buffer,
 381                                             cursor->record);
 382                         }
 383                 }
 384         }
 385         return (error);
 386 }
 387
 388 /*
 389  * Iterate through an object's inode or an object's records and record
 390  * modification TIDs.
 391  */
 392 static void add_history(hammer_inode_t ip, struct hammer_ioc_history *hist,
 393                         hammer_btree_elm_t elm);
 394
 395 static
 396 int
 397 hammer_ioc_gethistory(hammer_transaction_t trans, hammer_inode_t ip,
 398                       struct hammer_ioc_history *hist)
 399 {
 400         struct hammer_cursor cursor;
 401         hammer_btree_elm_t elm;
 402         int error;
 403
 404         /*
 405          * Validate the structure and initialize for return.
 406          */
 407         if (hist->beg_tid > hist->end_tid)
 408                 return(EINVAL);
 409         if (hist->head.flags & HAMMER_IOC_HISTORY_ATKEY) {
 410                 if (hist->key > hist->nxt_key)
 411                         return(EINVAL);
 412         }
 413
 414         hist->obj_id = ip->obj_id;
 415         hist->count = 0;
 416         hist->nxt_tid = hist->end_tid;
 417         hist->head.flags &= ~HAMMER_IOC_HISTORY_NEXT_TID;
 418         hist->head.flags &= ~HAMMER_IOC_HISTORY_NEXT_KEY;
 419         hist->head.flags &= ~HAMMER_IOC_HISTORY_EOF;
 420         hist->head.flags &= ~HAMMER_IOC_HISTORY_UNSYNCED;
 421         if ((ip->flags & HAMMER_INODE_MODMASK) & ~HAMMER_INODE_ITIMES)
 422                 hist->head.flags |= HAMMER_IOC_HISTORY_UNSYNCED;
 423
 424         /*
 425          * Setup the cursor.  We can't handle undeletable records
 426          * (create_tid of 0) at the moment.  A create_tid of 0 has
 427          * a special meaning and cannot be specified in the cursor.
 428          */
 429         error = hammer_init_cursor(trans, &cursor, &ip->cache[0], NULL);
 430         if (error) {
 431                 hammer_done_cursor(&cursor);
 432                 return(error);
 433         }
 434
 435         cursor.key_beg.obj_id = hist->obj_id;
 436         cursor.key_beg.create_tid = hist->beg_tid;
 437         cursor.key_beg.delete_tid = 0;
 438         cursor.key_beg.obj_type = 0;
 439         if (cursor.key_beg.create_tid == HAMMER_MIN_TID)
 440                 cursor.key_beg.create_tid = 1;
 441
 442         cursor.key_end.obj_id = hist->obj_id;
 443         cursor.key_end.create_tid = hist->end_tid;
 444         cursor.key_end.delete_tid = 0;
 445         cursor.key_end.obj_type = 0;
 446
 447         cursor.flags |= HAMMER_CURSOR_END_EXCLUSIVE;
 448
 449         if (hist->head.flags & HAMMER_IOC_HISTORY_ATKEY) {
 450                 /*
 451                  * key-range within the file.  For a regular file the
 452                  * on-disk key represents BASE+LEN, not BASE, so the
 453                  * first possible record containing the offset 'key'
 454                  * has an on-disk key of (key + 1).
 455                  */
 456                 cursor.key_beg.key = hist->key;
 457                 cursor.key_end.key = HAMMER_MAX_KEY;
 458
 459                 switch(ip->ino_rec.base.base.obj_type) {
 460                 case HAMMER_OBJTYPE_REGFILE:
 461                         ++cursor.key_beg.key;
 462                         cursor.key_beg.rec_type = HAMMER_RECTYPE_DATA;
 463                         break;
 464                 case HAMMER_OBJTYPE_DIRECTORY:
 465                         cursor.key_beg.rec_type = HAMMER_RECTYPE_DIRENTRY;
 466                         break;
 467                 case HAMMER_OBJTYPE_DBFILE:
 468                         cursor.key_beg.rec_type = HAMMER_RECTYPE_DB;
 469                         break;
 470                 default:
 471                         error = EINVAL;
 472                         break;
 473                 }
 474                 cursor.key_end.rec_type = cursor.key_beg.rec_type;
 475         } else {
 476                 /*
 477                  * The inode itself.
 478                  */
 479                 cursor.key_beg.key = 0;
 480                 cursor.key_end.key = 0;
 481                 cursor.key_beg.rec_type = HAMMER_RECTYPE_INODE;
 482                 cursor.key_end.rec_type = HAMMER_RECTYPE_INODE;
 483         }
 484
 485         error = hammer_btree_first(&cursor);
 486         while (error == 0) {
 487                 elm = &cursor.node->ondisk->elms[cursor.index];
 488
 489                 add_history(ip, hist, elm);
 490                 if (hist->head.flags & (HAMMER_IOC_HISTORY_NEXT_TID |
 491                                         HAMMER_IOC_HISTORY_NEXT_KEY |
 492                                         HAMMER_IOC_HISTORY_EOF)) {
 493                         break;
 494                 }
 495                 error = hammer_btree_iterate(&cursor);
 496         }
 497         if (error == ENOENT) {
 498                 hist->head.flags |= HAMMER_IOC_HISTORY_EOF;
 499                 error = 0;
 500         }
 501         hammer_done_cursor(&cursor);
 502         return(error);
 503 }
 504
 505 /*
 506  * Add the scanned element to the ioctl return structure.  Some special
 507  * casing is required for regular files to accomodate how data ranges are
 508  * stored on-disk.
 509  */
 510 static void
 511 add_history(hammer_inode_t ip, struct hammer_ioc_history *hist,
 512             hammer_btree_elm_t elm)
 513 {
 514         if (elm->base.btype != HAMMER_BTREE_TYPE_RECORD)
 515                 return;
 516         if ((hist->head.flags & HAMMER_IOC_HISTORY_ATKEY) &&
 517             ip->ino_rec.base.base.obj_type == HAMMER_OBJTYPE_REGFILE) {
 518                 /*
 519                  * Adjust nxt_key
 520                  */
 521                 if (hist->nxt_key > elm->leaf.base.key - elm->leaf.data_len &&
 522                     hist->key < elm->leaf.base.key - elm->leaf.data_len) {
 523                         hist->nxt_key = elm->leaf.base.key - elm->leaf.data_len;
 524                 }
 525                 if (hist->nxt_key > elm->leaf.base.key)
 526                         hist->nxt_key = elm->leaf.base.key;
 527
 528                 /*
 529                  * Record is beyond MAXPHYS, there won't be any more records
 530                  * in the iteration covering the requested offset (key).
 531                  */
 532                 if (elm->leaf.base.key >= MAXPHYS &&
 533                     elm->leaf.base.key - MAXPHYS > hist->key) {
 534                         hist->head.flags |= HAMMER_IOC_HISTORY_NEXT_KEY;
 535                 }
 536
 537                 /*
 538                  * Data-range of record does not cover the key.
 539                  */
 540                 if (elm->leaf.base.key - elm->leaf.data_len > hist->key)
 541                         return;
 542
 543         } else if (hist->head.flags & HAMMER_IOC_HISTORY_ATKEY) {
 544                 /*
 545                  * Adjust nxt_key
 546                  */
 547                 if (hist->nxt_key > elm->leaf.base.key &&
 548                     hist->key < elm->leaf.base.key) {
 549                         hist->nxt_key = elm->leaf.base.key;
 550                 }
 551
 552                 /*
 553                  * Record is beyond the requested key.
 554                  */
 555                 if (elm->leaf.base.key > hist->key)
 556                         hist->head.flags |= HAMMER_IOC_HISTORY_NEXT_KEY;
 557         }
 558
 559         /*
 560          * Add create_tid if it is in-bounds.
 561          */
 562         if ((hist->count == 0 ||
 563              elm->leaf.base.create_tid != hist->tid_ary[hist->count - 1]) &&
 564             elm->leaf.base.create_tid >= hist->beg_tid &&
 565             elm->leaf.base.create_tid < hist->end_tid) {
 566                 if (hist->count == HAMMER_MAX_HISTORY_ELMS) {
 567                         hist->nxt_tid = elm->leaf.base.create_tid;
 568                         hist->head.flags |= HAMMER_IOC_HISTORY_NEXT_TID;
 569                         return;
 570                 }
 571                 hist->tid_ary[hist->count++] = elm->leaf.base.create_tid;
 572         }
 573
 574         /*
 575          * Add delete_tid if it is in-bounds.  Note that different portions
 576          * of the history may have overlapping data ranges with different
 577          * delete_tid's.  If this case occurs the delete_tid may match the
 578          * create_tid of a following record.  XXX
 579          *
 580          *      [        ]
 581          *            [     ]
 582          */
 583         if (elm->leaf.base.delete_tid &&
 584             elm->leaf.base.delete_tid >= hist->beg_tid &&
 585             elm->leaf.base.delete_tid < hist->end_tid) {
 586                 if (hist->count == HAMMER_MAX_HISTORY_ELMS) {
 587                         hist->nxt_tid = elm->leaf.base.delete_tid;
 588                         hist->head.flags |= HAMMER_IOC_HISTORY_NEXT_TID;
 589                         return;
 590                 }
 591                 hist->tid_ary[hist->count++] = elm->leaf.base.delete_tid;
 592         }
 593 }
 594