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: src/sys/kern/kern_lockf.c,v 1.6.2.3 1999/09/05 08:14:56 peter Exp $
   38  */
   39 
   40 #include <sys/param.h>
   41 #include <sys/systm.h>
   42 #include <sys/kernel.h>
   43 #include <sys/proc.h>
   44 #include <sys/unistd.h>
   45 #include <sys/vnode.h>
   46 #include <sys/malloc.h>
   47 #include <sys/fcntl.h>
   48 
   49 #include <sys/lockf.h>
   50 
   51 /*
   52  * This variable controls the maximum number of processes that will
   53  * be checked in doing deadlock detection.
   54  */
   55 int maxlockdepth = MAXDEPTH;
   56 
   57 #ifdef LOCKF_DEBUG
   58 int     lockf_debug = 0;
   59 #endif
   60 
   61 #define NOLOCKF (struct lockf *)0
   62 #define SELF    0x1
   63 #define OTHERS  0x2
   64 static void      lf_addblock __P((struct lockf *, struct lockf *));
   65 static int       lf_clearlock __P((struct lockf *));
   66 static int       lf_findoverlap __P((struct lockf *,
   67             struct lockf *, int, struct lockf ***, struct lockf **));
   68 static struct lockf *
   69          lf_getblock __P((struct lockf *));
   70 static int       lf_getlock __P((struct lockf *, struct flock *));
   71 static int       lf_setlock __P((struct lockf *));
   72 static void      lf_split __P((struct lockf *, struct lockf *));
   73 static void      lf_wakelock __P((struct lockf *));
   74 
   75 /*
   76  * Advisory record locking support
   77  */
   78 int
   79 lf_advlock(ap, head, size)
   80         struct vop_advlock_args /* {
   81                 struct vnode *a_vp;
   82                 caddr_t  a_id;
   83                 int  a_op;
   84                 struct flock *a_fl;
   85                 int  a_flags;
   86         } */ *ap;
   87         struct lockf **head;
   88         u_quad_t size;
   89 {
   90         register struct flock *fl = ap->a_fl;
   91         register struct lockf *lock;
   92         off_t start, end;
   93         int error;
   94 
   95         /*
   96          * Convert the flock structure into a start and end.
   97          */
   98         switch (fl->l_whence) {
   99 
  100         case SEEK_SET:
  101         case SEEK_CUR:
  102                 /*
  103                  * Caller is responsible for adding any necessary offset
  104                  * when SEEK_CUR is used.
  105                  */
  106                 start = fl->l_start;
  107                 break;
  108 
  109         case SEEK_END:
  110                 start = size + fl->l_start;
  111                 break;
  112 
  113         default:
  114                 return (EINVAL);
  115         }
  116         if (start < 0)
  117                 return (EINVAL);
  118         if (fl->l_len == 0)
  119                 end = -1;
  120         else {
  121                 end = start + fl->l_len - 1;
  122                 if (end < start)
  123                         return (EINVAL);
  124         }
  125         /*
  126          * Avoid the common case of unlocking when inode has no locks.
  127          */
  128         if (*head == (struct lockf *)0) {
  129                 if (ap->a_op != F_SETLK) {
  130                         fl->l_type = F_UNLCK;
  131                         return (0);
  132                 }
  133         }
  134         /*
  135          * Create the lockf structure
  136          */
  137         MALLOC(lock, struct lockf *, sizeof *lock, M_LOCKF, M_WAITOK);
  138         lock->lf_start = start;
  139         lock->lf_end = end;
  140         lock->lf_id = ap->a_id;
  141         lock->lf_head = head;
  142         lock->lf_type = fl->l_type;
  143         lock->lf_next = (struct lockf *)0;
  144         lock->lf_block = (struct lockf *)0;
  145         lock->lf_flags = ap->a_flags;
  146         /*
  147          * Do the requested operation.
  148          */
  149         switch(ap->a_op) {
  150         case F_SETLK:
  151                 return (lf_setlock(lock));
  152 
  153         case F_UNLCK:
  154                 error = lf_clearlock(lock);
  155                 FREE(lock, M_LOCKF);
  156                 return (error);
  157 
  158         case F_GETLK:
  159                 error = lf_getlock(lock, fl);
  160                 FREE(lock, M_LOCKF);
  161                 return (error);
  162 
  163         default:
  164                 free(lock, M_LOCKF);
  165                 return (EINVAL);
  166         }
  167         /* NOTREACHED */
  168 }
  169 
  170 /*
  171  * Set a byte-range lock.
  172  */
  173 static int
  174 lf_setlock(lock)
  175         register struct lockf *lock;
  176 {
  177         register struct lockf *block;
  178         struct lockf **head = lock->lf_head;
  179         struct lockf **prev, *overlap, *ltmp;
  180         static char lockstr[] = "lockf";
  181         int ovcase, priority, needtolink, error;
  182 
  183 #ifdef LOCKF_DEBUG
  184         if (lockf_debug & 1)
  185                 lf_print("lf_setlock", lock);
  186 #endif /* LOCKF_DEBUG */
  187 
  188         /*
  189          * Set the priority
  190          */
  191         priority = PLOCK;
  192         if (lock->lf_type == F_WRLCK)
  193                 priority += 4;
  194         priority |= PCATCH;
  195         /*
  196          * Scan lock list for this file looking for locks that would block us.
  197          */
  198         while ((block = lf_getblock(lock))) {
  199                 /*
  200                  * Free the structure and return if nonblocking.
  201                  */
  202                 if ((lock->lf_flags & F_WAIT) == 0) {
  203                         FREE(lock, M_LOCKF);
  204                         return (EAGAIN);
  205                 }
  206                 /*
  207                  * We are blocked. Since flock style locks cover
  208                  * the whole file, there is no chance for deadlock.
  209                  * For byte-range locks we must check for deadlock.
  210                  *
  211                  * Deadlock detection is done by looking through the
  212                  * wait channels to see if there are any cycles that
  213                  * involve us. MAXDEPTH is set just to make sure we
  214                  * do not go off into neverland.
  215                  */
  216                 if ((lock->lf_flags & F_POSIX) &&
  217                     (block->lf_flags & F_POSIX)) {
  218                         register struct proc *wproc;
  219                         register struct lockf *waitblock;
  220                         int i = 0;
  221 
  222                         /* The block is waiting on something */
  223                         wproc = (struct proc *)block->lf_id;
  224                         while (wproc->p_wchan &&
  225                                (wproc->p_wmesg == lockstr) &&
  226                                (i++ < maxlockdepth)) {
  227                                 waitblock = (struct lockf *)wproc->p_wchan;
  228                                 /* Get the owner of the blocking lock */
  229                                 waitblock = waitblock->lf_next;
  230                                 if ((waitblock->lf_flags & F_POSIX) == 0)
  231                                         break;
  232                                 wproc = (struct proc *)waitblock->lf_id;
  233                                 if (wproc == (struct proc *)lock->lf_id) {
  234                                         free(lock, M_LOCKF);
  235                                         return (EDEADLK);
  236                                 }
  237                         }
  238                 }
  239                 /*
  240                  * For flock type locks, we must first remove
  241                  * any shared locks that we hold before we sleep
  242                  * waiting for an exclusive lock.
  243                  */
  244                 if ((lock->lf_flags & F_FLOCK) &&
  245                     lock->lf_type == F_WRLCK) {
  246                         lock->lf_type = F_UNLCK;
  247                         (void) lf_clearlock(lock);
  248                         lock->lf_type = F_WRLCK;
  249                 }
  250                 /*
  251                  * Add our lock to the blocked list and sleep until we're free.
  252                  * Remember who blocked us (for deadlock detection).
  253                  */
  254                 lock->lf_next = block;
  255                 lf_addblock(block, lock);
  256 #ifdef LOCKF_DEBUG
  257                 if (lockf_debug & 1) {
  258                         lf_print("lf_setlock: blocking on", block);
  259                         lf_printlist("lf_setlock", block);
  260                 }
  261 #endif /* LOCKF_DEBUG */
  262                 if ((error = tsleep((caddr_t)lock, priority, lockstr, 0))) {
  263                         /*
  264                          * Delete ourselves from the waiting to lock list.
  265                          */
  266                         for (block = lock->lf_next;
  267                              block != NOLOCKF;
  268                              block = block->lf_block) {
  269                                 if (block->lf_block != lock)
  270                                         continue;
  271                                 block->lf_block = block->lf_block->lf_block;
  272                                 break;
  273                         }
  274                         free(lock, M_LOCKF);
  275                         return (error);
  276                 }
  277         }
  278         /*
  279          * No blocks!!  Add the lock.  Note that we will
  280          * downgrade or upgrade any overlapping locks this
  281          * process already owns.
  282          *
  283          * Skip over locks owned by other processes.
  284          * Handle any locks that overlap and are owned by ourselves.
  285          */
  286         prev = head;
  287         block = *head;
  288         needtolink = 1;
  289         for (;;) {
  290                 ovcase = lf_findoverlap(block, lock, SELF, &prev, &overlap);
  291                 if (ovcase)
  292                         block = overlap->lf_next;
  293                 /*
  294                  * Six cases:
  295                  *      0) no overlap
  296                  *      1) overlap == lock
  297                  *      2) overlap contains lock
  298                  *      3) lock contains overlap
  299                  *      4) overlap starts before lock
  300                  *      5) overlap ends after lock
  301                  */
  302                 switch (ovcase) {
  303                 case 0: /* no overlap */
  304                         if (needtolink) {
  305                                 *prev = lock;
  306                                 lock->lf_next = overlap;
  307                         }
  308                         break;
  309 
  310                 case 1: /* overlap == lock */
  311                         /*
  312                          * If downgrading lock, others may be
  313                          * able to acquire it.
  314                          */
  315                         if (lock->lf_type == F_RDLCK &&
  316                             overlap->lf_type == F_WRLCK)
  317                                 lf_wakelock(overlap);
  318                         overlap->lf_type = lock->lf_type;
  319                         FREE(lock, M_LOCKF);
  320                         lock = overlap; /* for debug output below */
  321                         break;
  322 
  323                 case 2: /* overlap contains lock */
  324                         /*
  325                          * Check for common starting point and different types.
  326                          */
  327                         if (overlap->lf_type == lock->lf_type) {
  328                                 free(lock, M_LOCKF);
  329                                 lock = overlap; /* for debug output below */
  330                                 break;
  331                         }
  332                         if (overlap->lf_start == lock->lf_start) {
  333                                 *prev = lock;
  334                                 lock->lf_next = overlap;
  335                                 overlap->lf_start = lock->lf_end + 1;
  336                         } else
  337                                 lf_split(overlap, lock);
  338                         lf_wakelock(overlap);
  339                         break;
  340 
  341                 case 3: /* lock contains overlap */
  342                         /*
  343                          * If downgrading lock, others may be able to
  344                          * acquire it, otherwise take the list.
  345                          */
  346                         if (lock->lf_type == F_RDLCK &&
  347                             overlap->lf_type == F_WRLCK) {
  348                                 lf_wakelock(overlap);
  349                         } else {
  350                                 ltmp = lock->lf_block;
  351                                 lock->lf_block = overlap->lf_block;
  352                                 lf_addblock(lock, ltmp);
  353                         }
  354                         /*
  355                          * Add the new lock if necessary and delete the overlap.
  356                          */
  357                         if (needtolink) {
  358                                 *prev = lock;
  359                                 lock->lf_next = overlap->lf_next;
  360                                 prev = &lock->lf_next;
  361                                 needtolink = 0;
  362                         } else
  363                                 *prev = overlap->lf_next;
  364                         free(overlap, M_LOCKF);
  365                         continue;
  366 
  367                 case 4: /* overlap starts before lock */
  368                         /*
  369                          * Add lock after overlap on the list.
  370                          */
  371                         lock->lf_next = overlap->lf_next;
  372                         overlap->lf_next = lock;
  373                         overlap->lf_end = lock->lf_start - 1;
  374                         prev = &lock->lf_next;
  375                         lf_wakelock(overlap);
  376                         needtolink = 0;
  377                         continue;
  378 
  379                 case 5: /* overlap ends after lock */
  380                         /*
  381                          * Add the new lock before overlap.
  382                          */
  383                         if (needtolink) {
  384                                 *prev = lock;
  385                                 lock->lf_next = overlap;
  386                         }
  387                         overlap->lf_start = lock->lf_end + 1;
  388                         lf_wakelock(overlap);
  389                         break;
  390                 }
  391                 break;
  392         }
  393 #ifdef LOCKF_DEBUG
  394         if (lockf_debug & 1) {
  395                 lf_print("lf_setlock: got the lock", lock);
  396                 lf_printlist("lf_setlock", lock);
  397         }
  398 #endif /* LOCKF_DEBUG */
  399         return (0);
  400 }
  401 
  402 /*
  403  * Remove a byte-range lock on an inode.
  404  *
  405  * Generally, find the lock (or an overlap to that lock)
  406  * and remove it (or shrink it), then wakeup anyone we can.
  407  */
  408 static int
  409 lf_clearlock(unlock)
  410         register struct lockf *unlock;
  411 {
  412         struct lockf **head = unlock->lf_head;
  413         register struct lockf *lf = *head;
  414         struct lockf *overlap, **prev;
  415         int ovcase;
  416 
  417         if (lf == NOLOCKF)
  418                 return (0);
  419 #ifdef LOCKF_DEBUG
  420         if (unlock->lf_type != F_UNLCK)
  421                 panic("lf_clearlock: bad type");
  422         if (lockf_debug & 1)
  423                 lf_print("lf_clearlock", unlock);
  424 #endif /* LOCKF_DEBUG */
  425         prev = head;
  426         while ((ovcase = lf_findoverlap(lf, unlock, SELF, &prev, &overlap))) {
  427                 /*
  428                  * Wakeup the list of locks to be retried.
  429                  */
  430                 lf_wakelock(overlap);
  431 
  432                 switch (ovcase) {
  433 
  434                 case 1: /* overlap == lock */
  435                         *prev = overlap->lf_next;
  436                         FREE(overlap, M_LOCKF);
  437                         break;
  438 
  439                 case 2: /* overlap contains lock: split it */
  440                         if (overlap->lf_start == unlock->lf_start) {
  441                                 overlap->lf_start = unlock->lf_end + 1;
  442                                 break;
  443                         }
  444                         lf_split(overlap, unlock);
  445                         overlap->lf_next = unlock->lf_next;
  446                         break;
  447 
  448                 case 3: /* lock contains overlap */
  449                         *prev = overlap->lf_next;
  450                         lf = overlap->lf_next;
  451                         free(overlap, M_LOCKF);
  452                         continue;
  453 
  454                 case 4: /* overlap starts before lock */
  455                         overlap->lf_end = unlock->lf_start - 1;
  456                         prev = &overlap->lf_next;
  457                         lf = overlap->lf_next;
  458                         continue;
  459 
  460                 case 5: /* overlap ends after lock */
  461                         overlap->lf_start = unlock->lf_end + 1;
  462                         break;
  463                 }
  464                 break;
  465         }
  466 #ifdef LOCKF_DEBUG
  467         if (lockf_debug & 1)
  468                 lf_printlist("lf_clearlock", unlock);
  469 #endif /* LOCKF_DEBUG */
  470         return (0);
  471 }
  472 
  473 /*
  474  * Check whether there is a blocking lock,
  475  * and if so return its process identifier.
  476  */
  477 static int
  478 lf_getlock(lock, fl)
  479         register struct lockf *lock;
  480         register struct flock *fl;
  481 {
  482         register struct lockf *block;
  483 
  484 #ifdef LOCKF_DEBUG
  485         if (lockf_debug & 1)
  486                 lf_print("lf_getlock", lock);
  487 #endif /* LOCKF_DEBUG */
  488 
  489         if ((block = lf_getblock(lock))) {
  490                 fl->l_type = block->lf_type;
  491                 fl->l_whence = SEEK_SET;
  492                 fl->l_start = block->lf_start;
  493                 if (block->lf_end == -1)
  494                         fl->l_len = 0;
  495                 else
  496                         fl->l_len = block->lf_end - block->lf_start + 1;
  497                 if (block->lf_flags & F_POSIX)
  498                         fl->l_pid = ((struct proc *)(block->lf_id))->p_pid;
  499                 else
  500                         fl->l_pid = -1;
  501         } else {
  502                 fl->l_type = F_UNLCK;
  503         }
  504         return (0);
  505 }
  506 
  507 /*
  508  * Walk the list of locks for an inode and
  509  * return the first blocking lock.
  510  */
  511 static struct lockf *
  512 lf_getblock(lock)
  513         register struct lockf *lock;
  514 {
  515         struct lockf **prev, *overlap, *lf = *(lock->lf_head);
  516         int ovcase;
  517 
  518         prev = lock->lf_head;
  519         while ((ovcase = lf_findoverlap(lf, lock, OTHERS, &prev, &overlap))) {
  520                 /*
  521                  * We've found an overlap, see if it blocks us
  522                  */
  523                 if ((lock->lf_type == F_WRLCK || overlap->lf_type == F_WRLCK))
  524                         return (overlap);
  525                 /*
  526                  * Nope, point to the next one on the list and
  527                  * see if it blocks us
  528                  */
  529                 lf = overlap->lf_next;
  530         }
  531         return (NOLOCKF);
  532 }
  533 
  534 /*
  535  * Walk the list of locks for an inode to
  536  * find an overlapping lock (if any).
  537  *
  538  * NOTE: this returns only the FIRST overlapping lock.  There
  539  *       may be more than one.
  540  */
  541 static int
  542 lf_findoverlap(lf, lock, type, prev, overlap)
  543         register struct lockf *lf;
  544         struct lockf *lock;
  545         int type;
  546         struct lockf ***prev;
  547         struct lockf **overlap;
  548 {
  549         off_t start, end;
  550 
  551         *overlap = lf;
  552         if (lf == NOLOCKF)
  553                 return (0);
  554 #ifdef LOCKF_DEBUG
  555         if (lockf_debug & 2)
  556                 lf_print("lf_findoverlap: looking for overlap in", lock);
  557 #endif /* LOCKF_DEBUG */
  558         start = lock->lf_start;
  559         end = lock->lf_end;
  560         while (lf != NOLOCKF) {
  561                 if (((type & SELF) && lf->lf_id != lock->lf_id) ||
  562                     ((type & OTHERS) && lf->lf_id == lock->lf_id)) {
  563                         *prev = &lf->lf_next;
  564                         *overlap = lf = lf->lf_next;
  565                         continue;
  566                 }
  567 #ifdef LOCKF_DEBUG
  568                 if (lockf_debug & 2)
  569                         lf_print("\tchecking", lf);
  570 #endif /* LOCKF_DEBUG */
  571                 /*
  572                  * OK, check for overlap
  573                  *
  574                  * Six cases:
  575                  *      0) no overlap
  576                  *      1) overlap == lock
  577                  *      2) overlap contains lock
  578                  *      3) lock contains overlap
  579                  *      4) overlap starts before lock
  580                  *      5) overlap ends after lock
  581                  */
  582                 if ((lf->lf_end != -1 && start > lf->lf_end) ||
  583                     (end != -1 && lf->lf_start > end)) {
  584                         /* Case 0 */
  585 #ifdef LOCKF_DEBUG
  586                         if (lockf_debug & 2)
  587                                 printf("no overlap\n");
  588 #endif /* LOCKF_DEBUG */
  589                         if ((type & SELF) && end != -1 && lf->lf_start > end)
  590                                 return (0);
  591                         *prev = &lf->lf_next;
  592                         *overlap = lf = lf->lf_next;
  593                         continue;
  594                 }
  595                 if ((lf->lf_start == start) && (lf->lf_end == end)) {
  596                         /* Case 1 */
  597 #ifdef LOCKF_DEBUG
  598                         if (lockf_debug & 2)
  599                                 printf("overlap == lock\n");
  600 #endif /* LOCKF_DEBUG */
  601                         return (1);
  602                 }
  603                 if ((lf->lf_start <= start) &&
  604                     (end != -1) &&
  605                     ((lf->lf_end >= end) || (lf->lf_end == -1))) {
  606                         /* Case 2 */
  607 #ifdef LOCKF_DEBUG
  608                         if (lockf_debug & 2)
  609                                 printf("overlap contains lock\n");
  610 #endif /* LOCKF_DEBUG */
  611                         return (2);
  612                 }
  613                 if (start <= lf->lf_start &&
  614                            (end == -1 ||
  615                            (lf->lf_end != -1 && end >= lf->lf_end))) {
  616                         /* Case 3 */
  617 #ifdef LOCKF_DEBUG
  618                         if (lockf_debug & 2)
  619                                 printf("lock contains overlap\n");
  620 #endif /* LOCKF_DEBUG */
  621                         return (3);
  622                 }
  623                 if ((lf->lf_start < start) &&
  624                         ((lf->lf_end >= start) || (lf->lf_end == -1))) {
  625                         /* Case 4 */
  626 #ifdef LOCKF_DEBUG
  627                         if (lockf_debug & 2)
  628                                 printf("overlap starts before lock\n");
  629 #endif /* LOCKF_DEBUG */
  630                         return (4);
  631                 }
  632                 if ((lf->lf_start > start) &&
  633                         (end != -1) &&
  634                         ((lf->lf_end > end) || (lf->lf_end == -1))) {
  635                         /* Case 5 */
  636 #ifdef LOCKF_DEBUG
  637                         if (lockf_debug & 2)
  638                                 printf("overlap ends after lock\n");
  639 #endif /* LOCKF_DEBUG */
  640                         return (5);
  641                 }
  642                 panic("lf_findoverlap: default");
  643         }
  644         return (0);
  645 }
  646 
  647 /*
  648  * Add a lock to the end of the blocked list.
  649  */
  650 static void
  651 lf_addblock(blocklist, lock)
  652         struct lockf *blocklist;
  653         struct lockf *lock;
  654 {
  655         register struct lockf *lf;
  656 
  657         if (lock == NOLOCKF)
  658                 return;
  659 #ifdef LOCKF_DEBUG
  660         if (lockf_debug & 2) {
  661                 lf_print("addblock: adding", lock);
  662                 lf_print("to blocked list of", blocklist);
  663         }
  664 #endif /* LOCKF_DEBUG */
  665         if ((lf = blocklist->lf_block) == NOLOCKF) {
  666                 blocklist->lf_block = lock;
  667                 return;
  668         }
  669         while (lf->lf_block != NOLOCKF)
  670                 lf = lf->lf_block;
  671         lf->lf_block = lock;
  672         return;
  673 }
  674 
  675 /*
  676  * Split a lock and a contained region into
  677  * two or three locks as necessary.
  678  */
  679 static void
  680 lf_split(lock1, lock2)
  681         register struct lockf *lock1;
  682         register struct lockf *lock2;
  683 {
  684         register struct lockf *splitlock;
  685 
  686 #ifdef LOCKF_DEBUG
  687         if (lockf_debug & 2) {
  688                 lf_print("lf_split", lock1);
  689                 lf_print("splitting from", lock2);
  690         }
  691 #endif /* LOCKF_DEBUG */
  692         /*
  693          * Check to see if spliting into only two pieces.
  694          */
  695         if (lock1->lf_start == lock2->lf_start) {
  696                 lock1->lf_start = lock2->lf_end + 1;
  697                 lock2->lf_next = lock1;
  698                 return;
  699         }
  700         if (lock1->lf_end == lock2->lf_end) {
  701                 lock1->lf_end = lock2->lf_start - 1;
  702                 lock2->lf_next = lock1->lf_next;
  703                 lock1->lf_next = lock2;
  704                 return;
  705         }
  706         /*
  707          * Make a new lock consisting of the last part of
  708          * the encompassing lock
  709          */
  710         MALLOC(splitlock, struct lockf *, sizeof *splitlock, M_LOCKF, M_WAITOK);
  711         bcopy((caddr_t)lock1, (caddr_t)splitlock, sizeof *splitlock);
  712         splitlock->lf_start = lock2->lf_end + 1;
  713         splitlock->lf_block = NOLOCKF;
  714         lock1->lf_end = lock2->lf_start - 1;
  715         /*
  716          * OK, now link it in
  717          */
  718         splitlock->lf_next = lock1->lf_next;
  719         lock2->lf_next = splitlock;
  720         lock1->lf_next = lock2;
  721 }
  722 
  723 /*
  724  * Wakeup a blocklist
  725  */
  726 static void
  727 lf_wakelock(listhead)
  728         struct lockf *listhead;
  729 {
  730         register struct lockf *blocklist, *wakelock;
  731 
  732         blocklist = listhead->lf_block;
  733         listhead->lf_block = NOLOCKF;
  734         while (blocklist != NOLOCKF) {
  735                 wakelock = blocklist;
  736                 blocklist = blocklist->lf_block;
  737                 wakelock->lf_block = NOLOCKF;
  738                 wakelock->lf_next = NOLOCKF;
  739 #ifdef LOCKF_DEBUG
  740                 if (lockf_debug & 2)
  741                         lf_print("lf_wakelock: awakening", wakelock);
  742 #endif /* LOCKF_DEBUG */
  743                 wakeup((caddr_t)wakelock);
  744         }
  745 }
  746 
  747 #ifdef LOCKF_DEBUG
  748 /*
  749  * Print out a lock.
  750  */
  751 void
  752 lf_print(tag, lock)
  753         char *tag;
  754         register struct lockf *lock;
  755 {
  756 
  757         printf("%s: lock 0x%lx for ", tag, lock);
  758         if (lock->lf_flags & F_POSIX)
  759                 printf("proc %d", ((struct proc *)(lock->lf_id))->p_pid);
  760         else
  761                 printf("id 0x%x", lock->lf_id);
  762         printf(" in ino %d on dev <%d, %d>, %s, start %d, end %d",
  763                 lock->lf_inode->i_number,
  764                 major(lock->lf_inode->i_dev),
  765                 minor(lock->lf_inode->i_dev),
  766                 lock->lf_type == F_RDLCK ? "shared" :
  767                 lock->lf_type == F_WRLCK ? "exclusive" :
  768                 lock->lf_type == F_UNLCK ? "unlock" :
  769                 "unknown", lock->lf_start, lock->lf_end);
  770         if (lock->lf_block)
  771                 printf(" block 0x%x\n", lock->lf_block);
  772         else
  773                 printf("\n");
  774 }
  775 
  776 void
  777 lf_printlist(tag, lock)
  778         char *tag;
  779         struct lockf *lock;
  780 {
  781         register struct lockf *lf;
  782 
  783         printf("%s: Lock list for ino %d on dev <%d, %d>:\n",
  784                 tag, lock->lf_inode->i_number,
  785                 major(lock->lf_inode->i_dev),
  786                 minor(lock->lf_inode->i_dev));
  787         for (lf = lock->lf_inode->i_lockf; lf; lf = lf->lf_next) {
  788                 printf("\tlock 0x%lx for ", lf);
  789                 if (lf->lf_flags & F_POSIX)
  790                         printf("proc %d", ((struct proc *)(lf->lf_id))->p_pid);
  791                 else
  792                         printf("id 0x%x", lf->lf_id);
  793                 printf(", %s, start %d, end %d",
  794                         lf->lf_type == F_RDLCK ? "shared" :
  795                         lf->lf_type == F_WRLCK ? "exclusive" :
  796                         lf->lf_type == F_UNLCK ? "unlock" :
  797                         "unknown", lf->lf_start, lf->lf_end);
  798                 if (lf->lf_block)
  799                         printf(" block 0x%x\n", lf->lf_block);
  800                 else
  801                         printf("\n");
  802         }
  803 }
  804 #endif /* LOCKF_DEBUG */

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