The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/vfs/hammer/hammer_undo.c

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    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 
   35 /*
   36  * HAMMER undo - undo buffer/FIFO management.
   37  */
   38 
   39 #include "hammer.h"
   40 
   41 static int hammer_und_rb_compare(hammer_undo_t node1, hammer_undo_t node2);
   42 
   43 RB_GENERATE2(hammer_und_rb_tree, hammer_undo, rb_node,
   44              hammer_und_rb_compare, hammer_off_t, offset);
   45 
   46 /*
   47  * Convert a zone-3 undo offset into a zone-2 buffer offset.
   48  */
   49 hammer_off_t
   50 hammer_undo_lookup(hammer_mount_t hmp, hammer_off_t zone3_off, int *errorp)
   51 {
   52         hammer_volume_t root_volume;
   53         hammer_blockmap_t undomap __debugvar;
   54         hammer_off_t result_offset;
   55         int i;
   56 
   57         KKASSERT((zone3_off & HAMMER_OFF_ZONE_MASK) == HAMMER_ZONE_UNDO);
   58         root_volume = hammer_get_root_volume(hmp, errorp);
   59         if (*errorp)
   60                 return(0);
   61         undomap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
   62         KKASSERT(HAMMER_ZONE_DECODE(undomap->alloc_offset) == HAMMER_ZONE_UNDO_INDEX);
   63         KKASSERT(zone3_off < undomap->alloc_offset);
   64 
   65         i = (zone3_off & HAMMER_OFF_SHORT_MASK) / HAMMER_LARGEBLOCK_SIZE;
   66         result_offset = root_volume->ondisk->vol0_undo_array[i] +
   67                         (zone3_off & HAMMER_LARGEBLOCK_MASK64);
   68 
   69         hammer_rel_volume(root_volume, 0);
   70         return(result_offset);
   71 }
   72 
   73 /*
   74  * Generate UNDO record(s) for the block of data at the specified zone1
   75  * or zone2 offset.
   76  *
   77  * The recovery code will execute UNDOs in reverse order, allowing overlaps.
   78  * All the UNDOs are executed together so if we already laid one down we
   79  * do not have to lay another one down for the same range.
   80  *
   81  * For HAMMER version 4+ UNDO a 512 byte boundary is enforced and a PAD
   82  * will be laid down for any unused space.  UNDO FIFO media structures
   83  * will implement the hdr_seq field (it used to be reserved01), and
   84  * both flush and recovery mechanics will be very different.
   85  *
   86  * WARNING!  See also hammer_generate_redo() in hammer_redo.c
   87  */
   88 int
   89 hammer_generate_undo(hammer_transaction_t trans,
   90                      hammer_off_t zone_off, void *base, int len)
   91 {
   92         hammer_mount_t hmp;
   93         hammer_volume_t root_volume;
   94         hammer_blockmap_t undomap;
   95         hammer_buffer_t buffer = NULL;
   96         hammer_fifo_undo_t undo;
   97         hammer_fifo_tail_t tail;
   98         hammer_off_t next_offset;
   99         int error;
  100         int bytes;
  101         int n;
  102 
  103         hmp = trans->hmp;
  104 
  105         /*
  106          * A SYNC record may be required before we can lay down a general
  107          * UNDO.  This ensures that the nominal recovery span contains
  108          * at least one SYNC record telling the recovery code how far
  109          * out-of-span it must go to run the REDOs.
  110          */
  111         if ((hmp->flags & HAMMER_MOUNT_REDO_SYNC) == 0 &&
  112             hmp->version >= HAMMER_VOL_VERSION_FOUR) {
  113                 hammer_generate_redo_sync(trans);
  114         }
  115 
  116         /*
  117          * Enter the offset into our undo history.  If there is an existing
  118          * undo we do not have to generate a new one.
  119          */
  120         if (hammer_enter_undo_history(hmp, zone_off, len) == EALREADY)
  121                 return(0);
  122 
  123         root_volume = trans->rootvol;
  124         undomap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
  125 
  126         /* no undo recursion */
  127         hammer_modify_volume(NULL, root_volume, NULL, 0);
  128         hammer_lock_ex(&hmp->undo_lock);
  129 
  130         /* undo had better not roll over (loose test) */
  131         if (hammer_undo_space(trans) < len + HAMMER_BUFSIZE*3)
  132                 panic("hammer: insufficient undo FIFO space!");
  133 
  134         /*
  135          * Loop until the undo for the entire range has been laid down.
  136          */
  137         while (len) {
  138                 /*
  139                  * Fetch the layout offset in the UNDO FIFO, wrap it as
  140                  * necessary.
  141                  */
  142                 if (undomap->next_offset == undomap->alloc_offset) {
  143                         undomap->next_offset =
  144                                 HAMMER_ZONE_ENCODE(HAMMER_ZONE_UNDO_INDEX, 0);
  145                 }
  146                 next_offset = undomap->next_offset;
  147 
  148                 /*
  149                  * This is a tail-chasing FIFO, when we hit the start of a new
  150                  * buffer we don't have to read it in.
  151                  */
  152                 if ((next_offset & HAMMER_BUFMASK) == 0) {
  153                         undo = hammer_bnew(hmp, next_offset, &error, &buffer);
  154                         hammer_format_undo(undo, hmp->undo_seqno ^ 0x40000000);
  155                 } else {
  156                         undo = hammer_bread(hmp, next_offset, &error, &buffer);
  157                 }
  158                 if (error)
  159                         break;
  160                 hammer_modify_buffer(NULL, buffer, NULL, 0);
  161 
  162                 /*
  163                  * Calculate how big a media structure fits up to the next
  164                  * alignment point and how large a data payload we can
  165                  * accomodate.
  166                  *
  167                  * If n calculates to 0 or negative there is no room for
  168                  * anything but a PAD.
  169                  */
  170                 bytes = HAMMER_UNDO_ALIGN -
  171                         ((int)next_offset & HAMMER_UNDO_MASK);
  172                 n = bytes -
  173                     (int)sizeof(struct hammer_fifo_undo) -
  174                     (int)sizeof(struct hammer_fifo_tail);
  175 
  176                 /*
  177                  * If available space is insufficient for any payload
  178                  * we have to lay down a PAD.
  179                  *
  180                  * The minimum PAD is 8 bytes and the head and tail will
  181                  * overlap each other in that case.  PADs do not have
  182                  * sequence numbers or CRCs.
  183                  *
  184                  * A PAD may not start on a boundary.  That is, every
  185                  * 512-byte block in the UNDO/REDO FIFO must begin with
  186                  * a record containing a sequence number.
  187                  */
  188                 if (n <= 0) {
  189                         KKASSERT(bytes >= sizeof(struct hammer_fifo_tail));
  190                         KKASSERT(((int)next_offset & HAMMER_UNDO_MASK) != 0);
  191                         tail = (void *)((char *)undo + bytes - sizeof(*tail));
  192                         if ((void *)undo != (void *)tail) {
  193                                 tail->tail_signature = HAMMER_TAIL_SIGNATURE;
  194                                 tail->tail_type = HAMMER_HEAD_TYPE_PAD;
  195                                 tail->tail_size = bytes;
  196                         }
  197                         undo->head.hdr_signature = HAMMER_HEAD_SIGNATURE;
  198                         undo->head.hdr_type = HAMMER_HEAD_TYPE_PAD;
  199                         undo->head.hdr_size = bytes;
  200                         /* NO CRC OR SEQ NO */
  201                         undomap->next_offset += bytes;
  202                         hammer_modify_buffer_done(buffer);
  203                         hammer_stats_undo += bytes;
  204                         continue;
  205                 }
  206 
  207                 /*
  208                  * Calculate the actual payload and recalculate the size
  209                  * of the media structure as necessary.
  210                  */
  211                 if (n > len) {
  212                         n = len;
  213                         bytes = ((n + HAMMER_HEAD_ALIGN_MASK) &
  214                                  ~HAMMER_HEAD_ALIGN_MASK) +
  215                                 (int)sizeof(struct hammer_fifo_undo) +
  216                                 (int)sizeof(struct hammer_fifo_tail);
  217                 }
  218                 if (hammer_debug_general & 0x0080) {
  219                         kprintf("undo %016llx %d %d\n",
  220                                 (long long)next_offset, bytes, n);
  221                 }
  222 
  223                 undo->head.hdr_signature = HAMMER_HEAD_SIGNATURE;
  224                 undo->head.hdr_type = HAMMER_HEAD_TYPE_UNDO;
  225                 undo->head.hdr_size = bytes;
  226                 undo->head.hdr_seq = hmp->undo_seqno++;
  227                 undo->head.hdr_crc = 0;
  228                 undo->undo_offset = zone_off;
  229                 undo->undo_data_bytes = n;
  230                 bcopy(base, undo + 1, n);
  231 
  232                 tail = (void *)((char *)undo + bytes - sizeof(*tail));
  233                 tail->tail_signature = HAMMER_TAIL_SIGNATURE;
  234                 tail->tail_type = HAMMER_HEAD_TYPE_UNDO;
  235                 tail->tail_size = bytes;
  236 
  237                 KKASSERT(bytes >= sizeof(undo->head));
  238                 undo->head.hdr_crc = crc32(undo, HAMMER_FIFO_HEAD_CRCOFF) ^
  239                              crc32(&undo->head + 1, bytes - sizeof(undo->head));
  240                 undomap->next_offset += bytes;
  241                 hammer_stats_undo += bytes;
  242 
  243                 /*
  244                  * Before we finish off the buffer we have to deal with any
  245                  * junk between the end of the media structure we just laid
  246                  * down and the UNDO alignment boundary.  We do this by laying
  247                  * down a dummy PAD.  Even though we will probably overwrite
  248                  * it almost immediately we have to do this so recovery runs
  249                  * can iterate the UNDO space without having to depend on
  250                  * the indices in the volume header.
  251                  *
  252                  * This dummy PAD will be overwritten on the next undo so
  253                  * we do not adjust undomap->next_offset.
  254                  */
  255                 bytes = HAMMER_UNDO_ALIGN -
  256                         ((int)undomap->next_offset & HAMMER_UNDO_MASK);
  257                 if (bytes != HAMMER_UNDO_ALIGN) {
  258                         KKASSERT(bytes >= sizeof(struct hammer_fifo_tail));
  259                         undo = (void *)(tail + 1);
  260                         tail = (void *)((char *)undo + bytes - sizeof(*tail));
  261                         if ((void *)undo != (void *)tail) {
  262                                 tail->tail_signature = HAMMER_TAIL_SIGNATURE;
  263                                 tail->tail_type = HAMMER_HEAD_TYPE_PAD;
  264                                 tail->tail_size = bytes;
  265                         }
  266                         undo->head.hdr_signature = HAMMER_HEAD_SIGNATURE;
  267                         undo->head.hdr_type = HAMMER_HEAD_TYPE_PAD;
  268                         undo->head.hdr_size = bytes;
  269                         /* NO CRC OR SEQ NO */
  270                 }
  271                 hammer_modify_buffer_done(buffer);
  272 
  273                 /*
  274                  * Adjust for loop
  275                  */
  276                 len -= n;
  277                 base = (char *)base + n;
  278                 zone_off += n;
  279         }
  280         hammer_modify_volume_done(root_volume);
  281         hammer_unlock(&hmp->undo_lock);
  282 
  283         if (buffer)
  284                 hammer_rel_buffer(buffer, 0);
  285         return(error);
  286 }
  287 
  288 /*
  289  * Preformat a new UNDO block.  We could read the old one in but we get
  290  * better performance if we just pre-format a new one.
  291  *
  292  * The recovery code always works forwards so the caller just makes sure the
  293  * seqno is not contiguous with prior UNDOs or ancient UNDOs now being
  294  * overwritten.
  295  *
  296  * The preformatted UNDO headers use the smallest possible sector size
  297  * (512) to ensure that any missed media writes are caught.
  298  *
  299  * NOTE: Also used by the REDO code.
  300  */
  301 void
  302 hammer_format_undo(void *base, u_int32_t seqno)
  303 {
  304         hammer_fifo_head_t head;
  305         hammer_fifo_tail_t tail;
  306         int i;
  307         int bytes = HAMMER_UNDO_ALIGN;
  308 
  309         bzero(base, HAMMER_BUFSIZE);
  310 
  311         for (i = 0; i < HAMMER_BUFSIZE; i += bytes) {
  312                 head = (void *)((char *)base + i);
  313                 tail = (void *)((char *)head + bytes - sizeof(*tail));
  314 
  315                 head->hdr_signature = HAMMER_HEAD_SIGNATURE;
  316                 head->hdr_type = HAMMER_HEAD_TYPE_DUMMY;
  317                 head->hdr_size = bytes;
  318                 head->hdr_seq = seqno++;
  319                 head->hdr_crc = 0;
  320 
  321                 tail->tail_signature = HAMMER_TAIL_SIGNATURE;
  322                 tail->tail_type = HAMMER_HEAD_TYPE_DUMMY;
  323                 tail->tail_size = bytes;
  324 
  325                 head->hdr_crc = crc32(head, HAMMER_FIFO_HEAD_CRCOFF) ^
  326                              crc32(head + 1, bytes - sizeof(*head));
  327         }
  328 }
  329 
  330 /*
  331  * HAMMER version 4+ conversion support.
  332  *
  333  * Convert a HAMMER version < 4 UNDO FIFO area to a 4+ UNDO FIFO area.
  334  * The 4+ UNDO FIFO area is backwards compatible.  The conversion is
  335  * needed to initialize the sequence space and place headers on the
  336  * new 512-byte undo boundary.
  337  */
  338 int
  339 hammer_upgrade_undo_4(hammer_transaction_t trans)
  340 {
  341         hammer_mount_t hmp;
  342         hammer_volume_t root_volume;
  343         hammer_blockmap_t undomap;
  344         hammer_buffer_t buffer = NULL;
  345         hammer_fifo_head_t head;
  346         hammer_fifo_tail_t tail;
  347         hammer_off_t next_offset;
  348         u_int32_t seqno;
  349         int error;
  350         int bytes;
  351 
  352         hmp = trans->hmp;
  353 
  354         root_volume = trans->rootvol;
  355 
  356         /* no undo recursion */
  357         hammer_lock_ex(&hmp->undo_lock);
  358         hammer_modify_volume(NULL, root_volume, NULL, 0);
  359 
  360         /*
  361          * Adjust the in-core undomap and the on-disk undomap.
  362          */
  363         next_offset = HAMMER_ZONE_ENCODE(HAMMER_ZONE_UNDO_INDEX, 0);
  364         undomap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
  365         undomap->next_offset = next_offset;
  366         undomap->first_offset = next_offset;
  367 
  368         undomap = &root_volume->ondisk->vol0_blockmap[HAMMER_ZONE_UNDO_INDEX];
  369         undomap->next_offset = next_offset;
  370         undomap->first_offset = next_offset;
  371 
  372         /*
  373          * Loop over the entire UNDO space creating DUMMY entries.  Sequence
  374          * numbers are assigned.
  375          */
  376         seqno = 0;
  377         bytes = HAMMER_UNDO_ALIGN;
  378 
  379         while (next_offset != undomap->alloc_offset) {
  380                 head = hammer_bnew(hmp, next_offset, &error, &buffer);
  381                 if (error)
  382                         break;
  383                 hammer_modify_buffer(NULL, buffer, NULL, 0);
  384                 tail = (void *)((char *)head + bytes - sizeof(*tail));
  385 
  386                 head->hdr_signature = HAMMER_HEAD_SIGNATURE;
  387                 head->hdr_type = HAMMER_HEAD_TYPE_DUMMY;
  388                 head->hdr_size = bytes;
  389                 head->hdr_seq = seqno;
  390                 head->hdr_crc = 0;
  391 
  392                 tail = (void *)((char *)head + bytes - sizeof(*tail));
  393                 tail->tail_signature = HAMMER_TAIL_SIGNATURE;
  394                 tail->tail_type = HAMMER_HEAD_TYPE_DUMMY;
  395                 tail->tail_size = bytes;
  396 
  397                 head->hdr_crc = crc32(head, HAMMER_FIFO_HEAD_CRCOFF) ^
  398                              crc32(head + 1, bytes - sizeof(*head));
  399                 hammer_modify_buffer_done(buffer);
  400 
  401                 hammer_stats_undo += bytes;
  402                 next_offset += HAMMER_UNDO_ALIGN;
  403                 ++seqno;
  404         }
  405 
  406         /*
  407          * The sequence number will be the next sequence number to lay down.
  408          */
  409         hmp->undo_seqno = seqno;
  410         kprintf("version upgrade seqno start %08x\n", seqno);
  411 
  412         hammer_modify_volume_done(root_volume);
  413         hammer_unlock(&hmp->undo_lock);
  414 
  415         if (buffer)
  416                 hammer_rel_buffer(buffer, 0);
  417         return (error);
  418 }
  419 
  420 /*
  421  * UNDO HISTORY API
  422  *
  423  * It is not necessary to layout an undo record for the same address space
  424  * multiple times.  Maintain a cache of recent undo's.
  425  */
  426 
  427 /*
  428  * Enter an undo into the history.  Return EALREADY if the request completely
  429  * covers a previous request.
  430  */
  431 int
  432 hammer_enter_undo_history(hammer_mount_t hmp, hammer_off_t offset, int bytes)
  433 {
  434         hammer_undo_t node;
  435         hammer_undo_t onode __debugvar;
  436 
  437         node = RB_LOOKUP(hammer_und_rb_tree, &hmp->rb_undo_root, offset);
  438         if (node) {
  439                 TAILQ_REMOVE(&hmp->undo_lru_list, node, lru_entry);
  440                 TAILQ_INSERT_TAIL(&hmp->undo_lru_list, node, lru_entry);
  441                 if (bytes <= node->bytes)
  442                         return(EALREADY);
  443                 node->bytes = bytes;
  444                 return(0);
  445         }
  446         if (hmp->undo_alloc != HAMMER_MAX_UNDOS) {
  447                 node = &hmp->undos[hmp->undo_alloc++];
  448         } else {
  449                 node = TAILQ_FIRST(&hmp->undo_lru_list);
  450                 TAILQ_REMOVE(&hmp->undo_lru_list, node, lru_entry);
  451                 RB_REMOVE(hammer_und_rb_tree, &hmp->rb_undo_root, node);
  452         }
  453         node->offset = offset;
  454         node->bytes = bytes;
  455         TAILQ_INSERT_TAIL(&hmp->undo_lru_list, node, lru_entry);
  456         onode = RB_INSERT(hammer_und_rb_tree, &hmp->rb_undo_root, node);
  457         KKASSERT(onode == NULL);
  458         return(0);
  459 }
  460 
  461 void
  462 hammer_clear_undo_history(hammer_mount_t hmp)
  463 {
  464         RB_INIT(&hmp->rb_undo_root);
  465         TAILQ_INIT(&hmp->undo_lru_list);
  466         hmp->undo_alloc = 0;
  467 }
  468 
  469 /*
  470  * Return how much of the undo FIFO has been used
  471  *
  472  * The calculation includes undo FIFO space still reserved from a previous
  473  * flush (because it will still be run on recovery if a crash occurs and
  474  * we can't overwrite it yet).
  475  */
  476 int64_t
  477 hammer_undo_used(hammer_transaction_t trans)
  478 {
  479         hammer_blockmap_t cundomap;
  480         hammer_blockmap_t dundomap;
  481         int64_t max_bytes __debugvar;
  482         int64_t bytes;
  483 
  484         cundomap = &trans->hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
  485         dundomap = &trans->rootvol->ondisk->
  486                                 vol0_blockmap[HAMMER_ZONE_UNDO_INDEX];
  487 
  488         if (dundomap->first_offset <= cundomap->next_offset) {
  489                 bytes = cundomap->next_offset - dundomap->first_offset;
  490         } else {
  491                 bytes = cundomap->alloc_offset - dundomap->first_offset +
  492                         (cundomap->next_offset & HAMMER_OFF_LONG_MASK);
  493         }
  494         max_bytes = cundomap->alloc_offset & HAMMER_OFF_SHORT_MASK;
  495         KKASSERT(bytes <= max_bytes);
  496         return(bytes);
  497 }
  498 
  499 /*
  500  * Return how much of the undo FIFO is available for new records.
  501  */
  502 int64_t
  503 hammer_undo_space(hammer_transaction_t trans)
  504 {
  505         hammer_blockmap_t rootmap;
  506         int64_t max_bytes;
  507 
  508         rootmap = &trans->hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
  509         max_bytes = rootmap->alloc_offset & HAMMER_OFF_SHORT_MASK;
  510         return(max_bytes - hammer_undo_used(trans));
  511 }
  512 
  513 int64_t
  514 hammer_undo_max(hammer_mount_t hmp)
  515 {
  516         hammer_blockmap_t rootmap;
  517         int64_t max_bytes;
  518 
  519         rootmap = &hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
  520         max_bytes = rootmap->alloc_offset & HAMMER_OFF_SHORT_MASK;
  521 
  522         return(max_bytes);
  523 }
  524 
  525 /*
  526  * Returns 1 if the undo buffer should be reclaimed on release.  The
  527  * only undo buffer we do NOT want to reclaim is the one at the current
  528  * append offset.
  529  */
  530 int
  531 hammer_undo_reclaim(hammer_io_t io)
  532 {
  533         hammer_blockmap_t undomap;
  534         hammer_off_t next_offset;
  535 
  536         undomap = &io->hmp->blockmap[HAMMER_ZONE_UNDO_INDEX];
  537         next_offset = undomap->next_offset & ~HAMMER_BUFMASK64;
  538         if (((struct hammer_buffer *)io)->zoneX_offset == next_offset)
  539                 return(0);
  540         return(1);
  541 }
  542 
  543 static int
  544 hammer_und_rb_compare(hammer_undo_t node1, hammer_undo_t node2)
  545 {
  546         if (node1->offset < node2->offset)
  547                 return(-1);
  548         if (node1->offset > node2->offset)
  549                 return(1);
  550         return(0);
  551 }
  552 

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