The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_lockf.c

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    1 /*
    2  * Copyright (c) 1982, 1986, 1989, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software contributed to Berkeley by
    6  * Scooter Morris at Genentech Inc.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   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 the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 3. All advertising materials mentioning features or use of this software
   17  *    must display the following acknowledgement:
   18  *      This product includes software developed by the University of
   19  *      California, Berkeley and its contributors.
   20  * 4. Neither the name of the University nor the names of its contributors
   21  *    may be used to endorse or promote products derived from this software
   22  *    without specific prior written permission.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   34  * SUCH DAMAGE.
   35  *
   36  *      @(#)ufs_lockf.c 8.3 (Berkeley) 1/6/94
   37  * $FreeBSD$
   38  */
   39 
   40 #include "opt_debug_lockf.h"
   41 
   42 #include <sys/param.h>
   43 #include <sys/systm.h>
   44 #include <sys/kernel.h>
   45 #include <sys/lock.h>
   46 #include <sys/proc.h>
   47 #include <sys/unistd.h>
   48 #include <sys/vnode.h>
   49 #include <sys/malloc.h>
   50 #include <sys/fcntl.h>
   51 
   52 #include <sys/lockf.h>
   53 
   54 /*
   55  * This variable controls the maximum number of processes that will
   56  * be checked in doing deadlock detection.
   57  */
   58 static int maxlockdepth = MAXDEPTH;
   59 
   60 #ifdef LOCKF_DEBUG
   61 #include <sys/kernel.h>
   62 #include <sys/sysctl.h>
   63 
   64 #include <ufs/ufs/quota.h>
   65 #include <ufs/ufs/inode.h>
   66 
   67 
   68 static int      lockf_debug = 0;
   69 SYSCTL_INT(_debug, OID_AUTO, lockf_debug, CTLFLAG_RW, &lockf_debug, 0, "");
   70 #endif
   71 
   72 static MALLOC_DEFINE(M_LOCKF, "lockf", "Byte-range locking structures");
   73 
   74 #define NOLOCKF (struct lockf *)0
   75 #define SELF    0x1
   76 #define OTHERS  0x2
   77 static int       lf_clearlock __P((struct lockf *));
   78 static int       lf_findoverlap __P((struct lockf *,
   79             struct lockf *, int, struct lockf ***, struct lockf **));
   80 static struct lockf *
   81          lf_getblock __P((struct lockf *));
   82 static int       lf_getlock __P((struct lockf *, struct flock *));
   83 static int       lf_setlock __P((struct lockf *));
   84 static void      lf_split __P((struct lockf *, struct lockf *));
   85 static void      lf_wakelock __P((struct lockf *));
   86 
   87 /*
   88  * Advisory record locking support
   89  */
   90 int
   91 lf_advlock(ap, head, size)
   92         struct vop_advlock_args /* {
   93                 struct vnode *a_vp;
   94                 caddr_t  a_id;
   95                 int  a_op;
   96                 struct flock *a_fl;
   97                 int  a_flags;
   98         } */ *ap;
   99         struct lockf **head;
  100         u_quad_t size;
  101 {
  102         register struct flock *fl = ap->a_fl;
  103         register struct lockf *lock;
  104         off_t start, end;
  105         int error;
  106 
  107         /*
  108          * Convert the flock structure into a start and end.
  109          */
  110         switch (fl->l_whence) {
  111 
  112         case SEEK_SET:
  113         case SEEK_CUR:
  114                 /*
  115                  * Caller is responsible for adding any necessary offset
  116                  * when SEEK_CUR is used.
  117                  */
  118                 start = fl->l_start;
  119                 break;
  120 
  121         case SEEK_END:
  122                 start = size + fl->l_start;
  123                 break;
  124 
  125         default:
  126                 return (EINVAL);
  127         }
  128         if (start < 0)
  129                 return (EINVAL);
  130         if (fl->l_len == 0)
  131                 end = -1;
  132         else {
  133                 end = start + fl->l_len - 1;
  134                 if (end < start)
  135                         return (EINVAL);
  136         }
  137         /*
  138          * Avoid the common case of unlocking when inode has no locks.
  139          */
  140         if (*head == (struct lockf *)0) {
  141                 if (ap->a_op != F_SETLK) {
  142                         fl->l_type = F_UNLCK;
  143                         return (0);
  144                 }
  145         }
  146         /*
  147          * Create the lockf structure
  148          */
  149         MALLOC(lock, struct lockf *, sizeof *lock, M_LOCKF, M_WAITOK);
  150         lock->lf_start = start;
  151         lock->lf_end = end;
  152         lock->lf_id = ap->a_id;
  153 /*      lock->lf_inode = ip; */ /* XXX JH */
  154         lock->lf_type = fl->l_type;
  155         lock->lf_head = head;
  156         lock->lf_next = (struct lockf *)0;
  157         TAILQ_INIT(&lock->lf_blkhd);
  158         lock->lf_flags = ap->a_flags;
  159         /*
  160          * Do the requested operation.
  161          */
  162         switch(ap->a_op) {
  163         case F_SETLK:
  164                 return (lf_setlock(lock));
  165 
  166         case F_UNLCK:
  167                 error = lf_clearlock(lock);
  168                 FREE(lock, M_LOCKF);
  169                 return (error);
  170 
  171         case F_GETLK:
  172                 error = lf_getlock(lock, fl);
  173                 FREE(lock, M_LOCKF);
  174                 return (error);
  175 
  176         default:
  177                 free(lock, M_LOCKF);
  178                 return (EINVAL);
  179         }
  180         /* NOTREACHED */
  181 }
  182 
  183 /*
  184  * Set a byte-range lock.
  185  */
  186 static int
  187 lf_setlock(lock)
  188         register struct lockf *lock;
  189 {
  190         register struct lockf *block;
  191         struct lockf **head = lock->lf_head;
  192         struct lockf **prev, *overlap, *ltmp;
  193         static char lockstr[] = "lockf";
  194         int ovcase, priority, needtolink, error;
  195 
  196 #ifdef LOCKF_DEBUG
  197         if (lockf_debug & 1)
  198                 lf_print("lf_setlock", lock);
  199 #endif /* LOCKF_DEBUG */
  200 
  201         /*
  202          * Set the priority
  203          */
  204         priority = PLOCK;
  205         if (lock->lf_type == F_WRLCK)
  206                 priority += 4;
  207         priority |= PCATCH;
  208         /*
  209          * Scan lock list for this file looking for locks that would block us.
  210          */
  211         while ((block = lf_getblock(lock))) {
  212                 /*
  213                  * Free the structure and return if nonblocking.
  214                  */
  215                 if ((lock->lf_flags & F_WAIT) == 0) {
  216                         FREE(lock, M_LOCKF);
  217                         return (EAGAIN);
  218                 }
  219                 /*
  220                  * We are blocked. Since flock style locks cover
  221                  * the whole file, there is no chance for deadlock.
  222                  * For byte-range locks we must check for deadlock.
  223                  *
  224                  * Deadlock detection is done by looking through the
  225                  * wait channels to see if there are any cycles that
  226                  * involve us. MAXDEPTH is set just to make sure we
  227                  * do not go off into neverland.
  228                  */
  229                 if ((lock->lf_flags & F_POSIX) &&
  230                     (block->lf_flags & F_POSIX)) {
  231                         register struct proc *wproc;
  232                         register struct lockf *waitblock;
  233                         int i = 0;
  234 
  235                         /* The block is waiting on something */
  236                         wproc = (struct proc *)block->lf_id;
  237                         while (wproc->p_wchan &&
  238                                (wproc->p_wmesg == lockstr) &&
  239                                (i++ < maxlockdepth)) {
  240                                 waitblock = (struct lockf *)wproc->p_wchan;
  241                                 /* Get the owner of the blocking lock */
  242                                 waitblock = waitblock->lf_next;
  243                                 if ((waitblock->lf_flags & F_POSIX) == 0)
  244                                         break;
  245                                 wproc = (struct proc *)waitblock->lf_id;
  246                                 if (wproc == (struct proc *)lock->lf_id) {
  247                                         free(lock, M_LOCKF);
  248                                         return (EDEADLK);
  249                                 }
  250                         }
  251                 }
  252                 /*
  253                  * For flock type locks, we must first remove
  254                  * any shared locks that we hold before we sleep
  255                  * waiting for an exclusive lock.
  256                  */
  257                 if ((lock->lf_flags & F_FLOCK) &&
  258                     lock->lf_type == F_WRLCK) {
  259                         lock->lf_type = F_UNLCK;
  260                         (void) lf_clearlock(lock);
  261                         lock->lf_type = F_WRLCK;
  262                 }
  263                 /*
  264                  * Add our lock to the blocked list and sleep until we're free.
  265                  * Remember who blocked us (for deadlock detection).
  266                  */
  267                 lock->lf_next = block;
  268                 TAILQ_INSERT_TAIL(&block->lf_blkhd, lock, lf_block);
  269 #ifdef LOCKF_DEBUG
  270                 if (lockf_debug & 1) {
  271                         lf_print("lf_setlock: blocking on", block);
  272                         lf_printlist("lf_setlock", block);
  273                 }
  274 #endif /* LOCKF_DEBUG */
  275                 error = tsleep((caddr_t)lock, priority, lockstr, 0);
  276                 /*
  277                  * We may have been awakened by a signal and/or by a
  278                  * debugger continuing us (in which cases we must remove
  279                  * ourselves from the blocked list) and/or by another
  280                  * process releasing a lock (in which case we have
  281                  * already been removed from the blocked list and our
  282                  * lf_next field set to NOLOCKF).
  283                  */
  284                 if (lock->lf_next) {
  285                         TAILQ_REMOVE(&lock->lf_next->lf_blkhd, lock, lf_block);
  286                         lock->lf_next = NOLOCKF;
  287                 }
  288                 if (error) {
  289                         free(lock, M_LOCKF);
  290                         return (error);
  291                 }
  292         }
  293         /*
  294          * No blocks!!  Add the lock.  Note that we will
  295          * downgrade or upgrade any overlapping locks this
  296          * process already owns.
  297          *
  298          * Skip over locks owned by other processes.
  299          * Handle any locks that overlap and are owned by ourselves.
  300          */
  301         prev = head;
  302         block = *head;
  303         needtolink = 1;
  304         for (;;) {
  305                 ovcase = lf_findoverlap(block, lock, SELF, &prev, &overlap);
  306                 if (ovcase)
  307                         block = overlap->lf_next;
  308                 /*
  309                  * Six cases:
  310                  *      0) no overlap
  311                  *      1) overlap == lock
  312                  *      2) overlap contains lock
  313                  *      3) lock contains overlap
  314                  *      4) overlap starts before lock
  315                  *      5) overlap ends after lock
  316                  */
  317                 switch (ovcase) {
  318                 case 0: /* no overlap */
  319                         if (needtolink) {
  320                                 *prev = lock;
  321                                 lock->lf_next = overlap;
  322                         }
  323                         break;
  324 
  325                 case 1: /* overlap == lock */
  326                         /*
  327                          * If downgrading lock, others may be
  328                          * able to acquire it.
  329                          */
  330                         if (lock->lf_type == F_RDLCK &&
  331                             overlap->lf_type == F_WRLCK)
  332                                 lf_wakelock(overlap);
  333                         overlap->lf_type = lock->lf_type;
  334                         FREE(lock, M_LOCKF);
  335                         lock = overlap; /* for debug output below */
  336                         break;
  337 
  338                 case 2: /* overlap contains lock */
  339                         /*
  340                          * Check for common starting point and different types.
  341                          */
  342                         if (overlap->lf_type == lock->lf_type) {
  343                                 free(lock, M_LOCKF);
  344                                 lock = overlap; /* for debug output below */
  345                                 break;
  346                         }
  347                         if (overlap->lf_start == lock->lf_start) {
  348                                 *prev = lock;
  349                                 lock->lf_next = overlap;
  350                                 overlap->lf_start = lock->lf_end + 1;
  351                         } else
  352                                 lf_split(overlap, lock);
  353                         lf_wakelock(overlap);
  354                         break;
  355 
  356                 case 3: /* lock contains overlap */
  357                         /*
  358                          * If downgrading lock, others may be able to
  359                          * acquire it, otherwise take the list.
  360                          */
  361                         if (lock->lf_type == F_RDLCK &&
  362                             overlap->lf_type == F_WRLCK) {
  363                                 lf_wakelock(overlap);
  364                         } else {
  365                                 while ((ltmp = overlap->lf_blkhd.tqh_first) !=
  366                                     NOLOCKF) {
  367                                         TAILQ_REMOVE(&overlap->lf_blkhd, ltmp,
  368                                             lf_block);
  369                                         TAILQ_INSERT_TAIL(&lock->lf_blkhd,
  370                                             ltmp, lf_block);
  371                                         ltmp->lf_next = lock;
  372                                 }
  373                         }
  374                         /*
  375                          * Add the new lock if necessary and delete the overlap.
  376                          */
  377                         if (needtolink) {
  378                                 *prev = lock;
  379                                 lock->lf_next = overlap->lf_next;
  380                                 prev = &lock->lf_next;
  381                                 needtolink = 0;
  382                         } else
  383                                 *prev = overlap->lf_next;
  384                         free(overlap, M_LOCKF);
  385                         continue;
  386 
  387                 case 4: /* overlap starts before lock */
  388                         /*
  389                          * Add lock after overlap on the list.
  390                          */
  391                         lock->lf_next = overlap->lf_next;
  392                         overlap->lf_next = lock;
  393                         overlap->lf_end = lock->lf_start - 1;
  394                         prev = &lock->lf_next;
  395                         lf_wakelock(overlap);
  396                         needtolink = 0;
  397                         continue;
  398 
  399                 case 5: /* overlap ends after lock */
  400                         /*
  401                          * Add the new lock before overlap.
  402                          */
  403                         if (needtolink) {
  404                                 *prev = lock;
  405                                 lock->lf_next = overlap;
  406                         }
  407                         overlap->lf_start = lock->lf_end + 1;
  408                         lf_wakelock(overlap);
  409                         break;
  410                 }
  411                 break;
  412         }
  413 #ifdef LOCKF_DEBUG
  414         if (lockf_debug & 1) {
  415                 lf_print("lf_setlock: got the lock", lock);
  416                 lf_printlist("lf_setlock", lock);
  417         }
  418 #endif /* LOCKF_DEBUG */
  419         return (0);
  420 }
  421 
  422 /*
  423  * Remove a byte-range lock on an inode.
  424  *
  425  * Generally, find the lock (or an overlap to that lock)
  426  * and remove it (or shrink it), then wakeup anyone we can.
  427  */
  428 static int
  429 lf_clearlock(unlock)
  430         register struct lockf *unlock;
  431 {
  432         struct lockf **head = unlock->lf_head;
  433         register struct lockf *lf = *head;
  434         struct lockf *overlap, **prev;
  435         int ovcase;
  436 
  437         if (lf == NOLOCKF)
  438                 return (0);
  439 #ifdef LOCKF_DEBUG
  440         if (unlock->lf_type != F_UNLCK)
  441                 panic("lf_clearlock: bad type");
  442         if (lockf_debug & 1)
  443                 lf_print("lf_clearlock", unlock);
  444 #endif /* LOCKF_DEBUG */
  445         prev = head;
  446         while ((ovcase = lf_findoverlap(lf, unlock, SELF, &prev, &overlap))) {
  447                 /*
  448                  * Wakeup the list of locks to be retried.
  449                  */
  450                 lf_wakelock(overlap);
  451 
  452                 switch (ovcase) {
  453 
  454                 case 1: /* overlap == lock */
  455                         *prev = overlap->lf_next;
  456                         FREE(overlap, M_LOCKF);
  457                         break;
  458 
  459                 case 2: /* overlap contains lock: split it */
  460                         if (overlap->lf_start == unlock->lf_start) {
  461                                 overlap->lf_start = unlock->lf_end + 1;
  462                                 break;
  463                         }
  464                         lf_split(overlap, unlock);
  465                         overlap->lf_next = unlock->lf_next;
  466                         break;
  467 
  468                 case 3: /* lock contains overlap */
  469                         *prev = overlap->lf_next;
  470                         lf = overlap->lf_next;
  471                         free(overlap, M_LOCKF);
  472                         continue;
  473 
  474                 case 4: /* overlap starts before lock */
  475                         overlap->lf_end = unlock->lf_start - 1;
  476                         prev = &overlap->lf_next;
  477                         lf = overlap->lf_next;
  478                         continue;
  479 
  480                 case 5: /* overlap ends after lock */
  481                         overlap->lf_start = unlock->lf_end + 1;
  482                         break;
  483                 }
  484                 break;
  485         }
  486 #ifdef LOCKF_DEBUG
  487         if (lockf_debug & 1)
  488                 lf_printlist("lf_clearlock", unlock);
  489 #endif /* LOCKF_DEBUG */
  490         return (0);
  491 }
  492 
  493 /*
  494  * Check whether there is a blocking lock,
  495  * and if so return its process identifier.
  496  */
  497 static int
  498 lf_getlock(lock, fl)
  499         register struct lockf *lock;
  500         register struct flock *fl;
  501 {
  502         register struct lockf *block;
  503 
  504 #ifdef LOCKF_DEBUG
  505         if (lockf_debug & 1)
  506                 lf_print("lf_getlock", lock);
  507 #endif /* LOCKF_DEBUG */
  508 
  509         if ((block = lf_getblock(lock))) {
  510                 fl->l_type = block->lf_type;
  511                 fl->l_whence = SEEK_SET;
  512                 fl->l_start = block->lf_start;
  513                 if (block->lf_end == -1)
  514                         fl->l_len = 0;
  515                 else
  516                         fl->l_len = block->lf_end - block->lf_start + 1;
  517                 if (block->lf_flags & F_POSIX)
  518                         fl->l_pid = ((struct proc *)(block->lf_id))->p_pid;
  519                 else
  520                         fl->l_pid = -1;
  521         } else {
  522                 fl->l_type = F_UNLCK;
  523         }
  524         return (0);
  525 }
  526 
  527 /*
  528  * Walk the list of locks for an inode and
  529  * return the first blocking lock.
  530  */
  531 static struct lockf *
  532 lf_getblock(lock)
  533         register struct lockf *lock;
  534 {
  535         struct lockf **prev, *overlap, *lf = *(lock->lf_head);
  536         int ovcase;
  537 
  538         prev = lock->lf_head;
  539         while ((ovcase = lf_findoverlap(lf, lock, OTHERS, &prev, &overlap))) {
  540                 /*
  541                  * We've found an overlap, see if it blocks us
  542                  */
  543                 if ((lock->lf_type == F_WRLCK || overlap->lf_type == F_WRLCK))
  544                         return (overlap);
  545                 /*
  546                  * Nope, point to the next one on the list and
  547                  * see if it blocks us
  548                  */
  549                 lf = overlap->lf_next;
  550         }
  551         return (NOLOCKF);
  552 }
  553 
  554 /*
  555  * Walk the list of locks for an inode to
  556  * find an overlapping lock (if any).
  557  *
  558  * NOTE: this returns only the FIRST overlapping lock.  There
  559  *       may be more than one.
  560  */
  561 static int
  562 lf_findoverlap(lf, lock, type, prev, overlap)
  563         register struct lockf *lf;
  564         struct lockf *lock;
  565         int type;
  566         struct lockf ***prev;
  567         struct lockf **overlap;
  568 {
  569         off_t start, end;
  570 
  571         *overlap = lf;
  572         if (lf == NOLOCKF)
  573                 return (0);
  574 #ifdef LOCKF_DEBUG
  575         if (lockf_debug & 2)
  576                 lf_print("lf_findoverlap: looking for overlap in", lock);
  577 #endif /* LOCKF_DEBUG */
  578         start = lock->lf_start;
  579         end = lock->lf_end;
  580         while (lf != NOLOCKF) {
  581                 if (((type & SELF) && lf->lf_id != lock->lf_id) ||
  582                     ((type & OTHERS) && lf->lf_id == lock->lf_id)) {
  583                         *prev = &lf->lf_next;
  584                         *overlap = lf = lf->lf_next;
  585                         continue;
  586                 }
  587 #ifdef LOCKF_DEBUG
  588                 if (lockf_debug & 2)
  589                         lf_print("\tchecking", lf);
  590 #endif /* LOCKF_DEBUG */
  591                 /*
  592                  * OK, check for overlap
  593                  *
  594                  * Six cases:
  595                  *      0) no overlap
  596                  *      1) overlap == lock
  597                  *      2) overlap contains lock
  598                  *      3) lock contains overlap
  599                  *      4) overlap starts before lock
  600                  *      5) overlap ends after lock
  601                  */
  602                 if ((lf->lf_end != -1 && start > lf->lf_end) ||
  603                     (end != -1 && lf->lf_start > end)) {
  604                         /* Case 0 */
  605 #ifdef LOCKF_DEBUG
  606                         if (lockf_debug & 2)
  607                                 printf("no overlap\n");
  608 #endif /* LOCKF_DEBUG */
  609                         if ((type & SELF) && end != -1 && lf->lf_start > end)
  610                                 return (0);
  611                         *prev = &lf->lf_next;
  612                         *overlap = lf = lf->lf_next;
  613                         continue;
  614                 }
  615                 if ((lf->lf_start == start) && (lf->lf_end == end)) {
  616                         /* Case 1 */
  617 #ifdef LOCKF_DEBUG
  618                         if (lockf_debug & 2)
  619                                 printf("overlap == lock\n");
  620 #endif /* LOCKF_DEBUG */
  621                         return (1);
  622                 }
  623                 if ((lf->lf_start <= start) &&
  624                     (end != -1) &&
  625                     ((lf->lf_end >= end) || (lf->lf_end == -1))) {
  626                         /* Case 2 */
  627 #ifdef LOCKF_DEBUG
  628                         if (lockf_debug & 2)
  629                                 printf("overlap contains lock\n");
  630 #endif /* LOCKF_DEBUG */
  631                         return (2);
  632                 }
  633                 if (start <= lf->lf_start &&
  634                            (end == -1 ||
  635                            (lf->lf_end != -1 && end >= lf->lf_end))) {
  636                         /* Case 3 */
  637 #ifdef LOCKF_DEBUG
  638                         if (lockf_debug & 2)
  639                                 printf("lock contains overlap\n");
  640 #endif /* LOCKF_DEBUG */
  641                         return (3);
  642                 }
  643                 if ((lf->lf_start < start) &&
  644                         ((lf->lf_end >= start) || (lf->lf_end == -1))) {
  645                         /* Case 4 */
  646 #ifdef LOCKF_DEBUG
  647                         if (lockf_debug & 2)
  648                                 printf("overlap starts before lock\n");
  649 #endif /* LOCKF_DEBUG */
  650                         return (4);
  651                 }
  652                 if ((lf->lf_start > start) &&
  653                         (end != -1) &&
  654                         ((lf->lf_end > end) || (lf->lf_end == -1))) {
  655                         /* Case 5 */
  656 #ifdef LOCKF_DEBUG
  657                         if (lockf_debug & 2)
  658                                 printf("overlap ends after lock\n");
  659 #endif /* LOCKF_DEBUG */
  660                         return (5);
  661                 }
  662                 panic("lf_findoverlap: default");
  663         }
  664         return (0);
  665 }
  666 
  667 /*
  668  * Split a lock and a contained region into
  669  * two or three locks as necessary.
  670  */
  671 static void
  672 lf_split(lock1, lock2)
  673         register struct lockf *lock1;
  674         register struct lockf *lock2;
  675 {
  676         register struct lockf *splitlock;
  677 
  678 #ifdef LOCKF_DEBUG
  679         if (lockf_debug & 2) {
  680                 lf_print("lf_split", lock1);
  681                 lf_print("splitting from", lock2);
  682         }
  683 #endif /* LOCKF_DEBUG */
  684         /*
  685          * Check to see if spliting into only two pieces.
  686          */
  687         if (lock1->lf_start == lock2->lf_start) {
  688                 lock1->lf_start = lock2->lf_end + 1;
  689                 lock2->lf_next = lock1;
  690                 return;
  691         }
  692         if (lock1->lf_end == lock2->lf_end) {
  693                 lock1->lf_end = lock2->lf_start - 1;
  694                 lock2->lf_next = lock1->lf_next;
  695                 lock1->lf_next = lock2;
  696                 return;
  697         }
  698         /*
  699          * Make a new lock consisting of the last part of
  700          * the encompassing lock
  701          */
  702         MALLOC(splitlock, struct lockf *, sizeof *splitlock, M_LOCKF, M_WAITOK);
  703         bcopy((caddr_t)lock1, (caddr_t)splitlock, sizeof *splitlock);
  704         splitlock->lf_start = lock2->lf_end + 1;
  705         TAILQ_INIT(&splitlock->lf_blkhd);
  706         lock1->lf_end = lock2->lf_start - 1;
  707         /*
  708          * OK, now link it in
  709          */
  710         splitlock->lf_next = lock1->lf_next;
  711         lock2->lf_next = splitlock;
  712         lock1->lf_next = lock2;
  713 }
  714 
  715 /*
  716  * Wakeup a blocklist
  717  */
  718 static void
  719 lf_wakelock(listhead)
  720         struct lockf *listhead;
  721 {
  722         register struct lockf *wakelock;
  723 
  724         while ((wakelock = listhead->lf_blkhd.tqh_first) != NOLOCKF) {
  725                 TAILQ_REMOVE(&listhead->lf_blkhd, wakelock, lf_block);
  726                 wakelock->lf_next = NOLOCKF;
  727 #ifdef LOCKF_DEBUG
  728                 if (lockf_debug & 2)
  729                         lf_print("lf_wakelock: awakening", wakelock);
  730 #endif /* LOCKF_DEBUG */
  731                 wakeup((caddr_t)wakelock);
  732         }
  733 }
  734 
  735 #ifdef LOCKF_DEBUG
  736 /*
  737  * Print out a lock.
  738  */
  739 void
  740 lf_print(tag, lock)
  741         char *tag;
  742         register struct lockf *lock;
  743 {
  744 
  745         printf("%s: lock %p for ", tag, (void *)lock);
  746         if (lock->lf_flags & F_POSIX)
  747                 printf("proc %ld", (long)((struct proc *)lock->lf_id)->p_pid);
  748         else
  749                 printf("id %p", (void *)lock->lf_id);
  750         /* XXX no %qd in kernel.  Truncate. */
  751         printf(" in ino %lu on dev <%d, %d>, %s, start %ld, end %ld",
  752             (u_long)lock->lf_inode->i_number,
  753             major(lock->lf_inode->i_dev),
  754             minor(lock->lf_inode->i_dev),
  755             lock->lf_type == F_RDLCK ? "shared" :
  756             lock->lf_type == F_WRLCK ? "exclusive" :
  757             lock->lf_type == F_UNLCK ? "unlock" :
  758             "unknown", (long)lock->lf_start, (long)lock->lf_end);
  759         if (lock->lf_blkhd.tqh_first)
  760                 printf(" block %p\n", (void *)lock->lf_blkhd.tqh_first);
  761         else
  762                 printf("\n");
  763 }
  764 
  765 void
  766 lf_printlist(tag, lock)
  767         char *tag;
  768         struct lockf *lock;
  769 {
  770         register struct lockf *lf, *blk;
  771 
  772         printf("%s: Lock list for ino %lu on dev <%d, %d>:\n",
  773             tag, (u_long)lock->lf_inode->i_number,
  774             major(lock->lf_inode->i_dev),
  775             minor(lock->lf_inode->i_dev));
  776         for (lf = lock->lf_inode->i_lockf; lf; lf = lf->lf_next) {
  777                 printf("\tlock %p for ",(void *)lf);
  778                 if (lf->lf_flags & F_POSIX)
  779                         printf("proc %ld",
  780                             (long)((struct proc *)lf->lf_id)->p_pid);
  781                 else
  782                         printf("id %p", (void *)lf->lf_id);
  783                 /* XXX no %qd in kernel.  Truncate. */
  784                 printf(", %s, start %ld, end %ld",
  785                     lf->lf_type == F_RDLCK ? "shared" :
  786                     lf->lf_type == F_WRLCK ? "exclusive" :
  787                     lf->lf_type == F_UNLCK ? "unlock" :
  788                     "unknown", (long)lf->lf_start, (long)lf->lf_end);
  789                 for (blk = lf->lf_blkhd.tqh_first; blk;
  790                      blk = blk->lf_block.tqe_next) {
  791                         printf("\n\t\tlock request %p for ", (void *)blk);
  792                         if (blk->lf_flags & F_POSIX)
  793                                 printf("proc %ld",
  794                                     (long)((struct proc *)blk->lf_id)->p_pid);
  795                         else
  796                                 printf("id %p", (void *)blk->lf_id);
  797                         /* XXX no %qd in kernel.  Truncate. */
  798                         printf(", %s, start %ld, end %ld",
  799                             blk->lf_type == F_RDLCK ? "shared" :
  800                             blk->lf_type == F_WRLCK ? "exclusive" :
  801                             blk->lf_type == F_UNLCK ? "unlock" :
  802                             "unknown", (long)blk->lf_start,
  803                             (long)blk->lf_end);
  804                         if (blk->lf_blkhd.tqh_first)
  805                                 panic("lf_printlist: bad list");
  806                 }
  807                 printf("\n");
  808         }
  809 }
  810 #endif /* LOCKF_DEBUG */

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