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: releng/5.0/sys/kern/kern_lockf.c 106584 2002-11-07 21:56:05Z mux $
   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/mount.h>
   47 #include <sys/mutex.h>
   48 #include <sys/proc.h>
   49 #include <sys/unistd.h>
   50 #include <sys/vnode.h>
   51 #include <sys/malloc.h>
   52 #include <sys/fcntl.h>
   53 #include <sys/lockf.h>
   54 #include <sys/stdint.h>
   55 
   56 #include <machine/limits.h>
   57 
   58 /*
   59  * This variable controls the maximum number of processes that will
   60  * be checked in doing deadlock detection.
   61  */
   62 static int maxlockdepth = MAXDEPTH;
   63 
   64 #ifdef LOCKF_DEBUG
   65 #include <sys/sysctl.h>
   66 
   67 #include <ufs/ufs/quota.h>
   68 #include <ufs/ufs/inode.h>
   69 
   70 
   71 static int      lockf_debug = 0;
   72 SYSCTL_INT(_debug, OID_AUTO, lockf_debug, CTLFLAG_RW, &lockf_debug, 0, "");
   73 #endif
   74 
   75 MALLOC_DEFINE(M_LOCKF, "lockf", "Byte-range locking structures");
   76 
   77 #define NOLOCKF (struct lockf *)0
   78 #define SELF    0x1
   79 #define OTHERS  0x2
   80 static int       lf_clearlock(struct lockf *);
   81 static int       lf_findoverlap(struct lockf *,
   82             struct lockf *, int, struct lockf ***, struct lockf **);
   83 static struct lockf *
   84          lf_getblock(struct lockf *);
   85 static int       lf_getlock(struct lockf *, struct flock *);
   86 static int       lf_setlock(struct lockf *);
   87 static void      lf_split(struct lockf *, struct lockf *);
   88 static void      lf_wakelock(struct lockf *);
   89 
   90 /*
   91  * Advisory record locking support
   92  */
   93 int
   94 lf_advlock(ap, head, size)
   95         struct vop_advlock_args /* {
   96                 struct vnode *a_vp;
   97                 caddr_t  a_id;
   98                 int  a_op;
   99                 struct flock *a_fl;
  100                 int  a_flags;
  101         } */ *ap;
  102         struct lockf **head;
  103         u_quad_t size;
  104 {
  105         register struct flock *fl = ap->a_fl;
  106         register struct lockf *lock;
  107         off_t start, end, oadd;
  108         int error;
  109 
  110         /*
  111          * Convert the flock structure into a start and end.
  112          */
  113         switch (fl->l_whence) {
  114 
  115         case SEEK_SET:
  116         case SEEK_CUR:
  117                 /*
  118                  * Caller is responsible for adding any necessary offset
  119                  * when SEEK_CUR is used.
  120                  */
  121                 start = fl->l_start;
  122                 break;
  123 
  124         case SEEK_END:
  125                 if (size > OFF_MAX ||
  126                     (fl->l_start > 0 && size > OFF_MAX - fl->l_start))
  127                         return (EOVERFLOW);
  128                 start = size + fl->l_start;
  129                 break;
  130 
  131         default:
  132                 return (EINVAL);
  133         }
  134         if (start < 0)
  135                 return (EINVAL);
  136         if (fl->l_len < 0) {
  137                 if (start == 0)
  138                         return (EINVAL);
  139                 end = start - 1;
  140                 start += fl->l_len;
  141                 if (start < 0)
  142                         return (EINVAL);
  143         } else if (fl->l_len == 0)
  144                 end = -1;
  145         else {
  146                 oadd = fl->l_len - 1;
  147                 if (oadd > OFF_MAX - start)
  148                         return (EOVERFLOW);
  149                 end = start + oadd;
  150         }
  151         /*
  152          * Avoid the common case of unlocking when inode has no locks.
  153          */
  154         if (*head == (struct lockf *)0) {
  155                 if (ap->a_op != F_SETLK) {
  156                         fl->l_type = F_UNLCK;
  157                         return (0);
  158                 }
  159         }
  160         /*
  161          * Create the lockf structure
  162          */
  163         MALLOC(lock, struct lockf *, sizeof *lock, M_LOCKF, M_WAITOK);
  164         lock->lf_start = start;
  165         lock->lf_end = end;
  166         lock->lf_id = ap->a_id;
  167         /*
  168          * XXX The problem is that VTOI is ufs specific, so it will
  169          * break LOCKF_DEBUG for all other FS's other than UFS because
  170          * it casts the vnode->data ptr to struct inode *.
  171          */
  172 /*      lock->lf_inode = VTOI(ap->a_vp); */
  173         lock->lf_inode = (struct inode *)0;
  174         lock->lf_type = fl->l_type;
  175         lock->lf_head = head;
  176         lock->lf_next = (struct lockf *)0;
  177         TAILQ_INIT(&lock->lf_blkhd);
  178         lock->lf_flags = ap->a_flags;
  179         /*
  180          * Do the requested operation.
  181          */
  182         switch(ap->a_op) {
  183         case F_SETLK:
  184                 return (lf_setlock(lock));
  185 
  186         case F_UNLCK:
  187                 error = lf_clearlock(lock);
  188                 FREE(lock, M_LOCKF);
  189                 return (error);
  190 
  191         case F_GETLK:
  192                 error = lf_getlock(lock, fl);
  193                 FREE(lock, M_LOCKF);
  194                 return (error);
  195 
  196         default:
  197                 free(lock, M_LOCKF);
  198                 return (EINVAL);
  199         }
  200         /* NOTREACHED */
  201 }
  202 
  203 /*
  204  * Set a byte-range lock.
  205  */
  206 static int
  207 lf_setlock(lock)
  208         register struct lockf *lock;
  209 {
  210         register struct lockf *block;
  211         struct lockf **head = lock->lf_head;
  212         struct lockf **prev, *overlap, *ltmp;
  213         static char lockstr[] = "lockf";
  214         int ovcase, priority, needtolink, error;
  215 
  216 #ifdef LOCKF_DEBUG
  217         if (lockf_debug & 1)
  218                 lf_print("lf_setlock", lock);
  219 #endif /* LOCKF_DEBUG */
  220 
  221         /*
  222          * Set the priority
  223          */
  224         priority = PLOCK;
  225         if (lock->lf_type == F_WRLCK)
  226                 priority += 4;
  227         priority |= PCATCH;
  228         /*
  229          * Scan lock list for this file looking for locks that would block us.
  230          */
  231         while ((block = lf_getblock(lock))) {
  232                 /*
  233                  * Free the structure and return if nonblocking.
  234                  */
  235                 if ((lock->lf_flags & F_WAIT) == 0) {
  236                         FREE(lock, M_LOCKF);
  237                         return (EAGAIN);
  238                 }
  239                 /*
  240                  * We are blocked. Since flock style locks cover
  241                  * the whole file, there is no chance for deadlock.
  242                  * For byte-range locks we must check for deadlock.
  243                  *
  244                  * Deadlock detection is done by looking through the
  245                  * wait channels to see if there are any cycles that
  246                  * involve us. MAXDEPTH is set just to make sure we
  247                  * do not go off into neverland.
  248                  */
  249                 if ((lock->lf_flags & F_POSIX) &&
  250                     (block->lf_flags & F_POSIX)) {
  251                         register struct proc *wproc;
  252                         struct thread *td;
  253                         register struct lockf *waitblock;
  254                         int i = 0;
  255 
  256                         /* The block is waiting on something */
  257                         /* XXXKSE this is not complete under threads */
  258                         wproc = (struct proc *)block->lf_id;
  259                         mtx_lock_spin(&sched_lock);
  260                         FOREACH_THREAD_IN_PROC(wproc, td) {
  261                                 while (td->td_wchan &&
  262                                     (td->td_wmesg == lockstr) &&
  263                                     (i++ < maxlockdepth)) {
  264                                         waitblock = (struct lockf *)td->td_wchan;
  265                                         /* Get the owner of the blocking lock */
  266                                         waitblock = waitblock->lf_next;
  267                                         if ((waitblock->lf_flags & F_POSIX) == 0)
  268                                                 break;
  269                                         wproc = (struct proc *)waitblock->lf_id;
  270                                         if (wproc == (struct proc *)lock->lf_id) {
  271                                                 mtx_unlock_spin(&sched_lock);
  272                                                 free(lock, M_LOCKF);
  273                                                 return (EDEADLK);
  274                                         }
  275                                 }
  276                         }
  277                         mtx_unlock_spin(&sched_lock);
  278                 }
  279                 /*
  280                  * For flock type locks, we must first remove
  281                  * any shared locks that we hold before we sleep
  282                  * waiting for an exclusive lock.
  283                  */
  284                 if ((lock->lf_flags & F_FLOCK) &&
  285                     lock->lf_type == F_WRLCK) {
  286                         lock->lf_type = F_UNLCK;
  287                         (void) lf_clearlock(lock);
  288                         lock->lf_type = F_WRLCK;
  289                 }
  290                 /*
  291                  * Add our lock to the blocked list and sleep until we're free.
  292                  * Remember who blocked us (for deadlock detection).
  293                  */
  294                 lock->lf_next = block;
  295                 TAILQ_INSERT_TAIL(&block->lf_blkhd, lock, lf_block);
  296 #ifdef LOCKF_DEBUG
  297                 if (lockf_debug & 1) {
  298                         lf_print("lf_setlock: blocking on", block);
  299                         lf_printlist("lf_setlock", block);
  300                 }
  301 #endif /* LOCKF_DEBUG */
  302                 error = tsleep(lock, priority, lockstr, 0);
  303                 /*
  304                  * We may have been awakened by a signal and/or by a
  305                  * debugger continuing us (in which cases we must remove
  306                  * ourselves from the blocked list) and/or by another
  307                  * process releasing a lock (in which case we have
  308                  * already been removed from the blocked list and our
  309                  * lf_next field set to NOLOCKF).
  310                  */
  311                 if (lock->lf_next) {
  312                         TAILQ_REMOVE(&lock->lf_next->lf_blkhd, lock, lf_block);
  313                         lock->lf_next = NOLOCKF;
  314                 }
  315                 if (error) {
  316                         free(lock, M_LOCKF);
  317                         return (error);
  318                 }
  319         }
  320         /*
  321          * No blocks!!  Add the lock.  Note that we will
  322          * downgrade or upgrade any overlapping locks this
  323          * process already owns.
  324          *
  325          * Skip over locks owned by other processes.
  326          * Handle any locks that overlap and are owned by ourselves.
  327          */
  328         prev = head;
  329         block = *head;
  330         needtolink = 1;
  331         for (;;) {
  332                 ovcase = lf_findoverlap(block, lock, SELF, &prev, &overlap);
  333                 if (ovcase)
  334                         block = overlap->lf_next;
  335                 /*
  336                  * Six cases:
  337                  *      0) no overlap
  338                  *      1) overlap == lock
  339                  *      2) overlap contains lock
  340                  *      3) lock contains overlap
  341                  *      4) overlap starts before lock
  342                  *      5) overlap ends after lock
  343                  */
  344                 switch (ovcase) {
  345                 case 0: /* no overlap */
  346                         if (needtolink) {
  347                                 *prev = lock;
  348                                 lock->lf_next = overlap;
  349                         }
  350                         break;
  351 
  352                 case 1: /* overlap == lock */
  353                         /*
  354                          * If downgrading lock, others may be
  355                          * able to acquire it.
  356                          */
  357                         if (lock->lf_type == F_RDLCK &&
  358                             overlap->lf_type == F_WRLCK)
  359                                 lf_wakelock(overlap);
  360                         overlap->lf_type = lock->lf_type;
  361                         FREE(lock, M_LOCKF);
  362                         lock = overlap; /* for debug output below */
  363                         break;
  364 
  365                 case 2: /* overlap contains lock */
  366                         /*
  367                          * Check for common starting point and different types.
  368                          */
  369                         if (overlap->lf_type == lock->lf_type) {
  370                                 free(lock, M_LOCKF);
  371                                 lock = overlap; /* for debug output below */
  372                                 break;
  373                         }
  374                         if (overlap->lf_start == lock->lf_start) {
  375                                 *prev = lock;
  376                                 lock->lf_next = overlap;
  377                                 overlap->lf_start = lock->lf_end + 1;
  378                         } else
  379                                 lf_split(overlap, lock);
  380                         lf_wakelock(overlap);
  381                         break;
  382 
  383                 case 3: /* lock contains overlap */
  384                         /*
  385                          * If downgrading lock, others may be able to
  386                          * acquire it, otherwise take the list.
  387                          */
  388                         if (lock->lf_type == F_RDLCK &&
  389                             overlap->lf_type == F_WRLCK) {
  390                                 lf_wakelock(overlap);
  391                         } else {
  392                                 while (!TAILQ_EMPTY(&overlap->lf_blkhd)) {
  393                                         ltmp = TAILQ_FIRST(&overlap->lf_blkhd);
  394                                         TAILQ_REMOVE(&overlap->lf_blkhd, ltmp,
  395                                             lf_block);
  396                                         TAILQ_INSERT_TAIL(&lock->lf_blkhd,
  397                                             ltmp, lf_block);
  398                                         ltmp->lf_next = lock;
  399                                 }
  400                         }
  401                         /*
  402                          * Add the new lock if necessary and delete the overlap.
  403                          */
  404                         if (needtolink) {
  405                                 *prev = lock;
  406                                 lock->lf_next = overlap->lf_next;
  407                                 prev = &lock->lf_next;
  408                                 needtolink = 0;
  409                         } else
  410                                 *prev = overlap->lf_next;
  411                         free(overlap, M_LOCKF);
  412                         continue;
  413 
  414                 case 4: /* overlap starts before lock */
  415                         /*
  416                          * Add lock after overlap on the list.
  417                          */
  418                         lock->lf_next = overlap->lf_next;
  419                         overlap->lf_next = lock;
  420                         overlap->lf_end = lock->lf_start - 1;
  421                         prev = &lock->lf_next;
  422                         lf_wakelock(overlap);
  423                         needtolink = 0;
  424                         continue;
  425 
  426                 case 5: /* overlap ends after lock */
  427                         /*
  428                          * Add the new lock before overlap.
  429                          */
  430                         if (needtolink) {
  431                                 *prev = lock;
  432                                 lock->lf_next = overlap;
  433                         }
  434                         overlap->lf_start = lock->lf_end + 1;
  435                         lf_wakelock(overlap);
  436                         break;
  437                 }
  438                 break;
  439         }
  440 #ifdef LOCKF_DEBUG
  441         if (lockf_debug & 1) {
  442                 lf_print("lf_setlock: got the lock", lock);
  443                 lf_printlist("lf_setlock", lock);
  444         }
  445 #endif /* LOCKF_DEBUG */
  446         return (0);
  447 }
  448 
  449 /*
  450  * Remove a byte-range lock on an inode.
  451  *
  452  * Generally, find the lock (or an overlap to that lock)
  453  * and remove it (or shrink it), then wakeup anyone we can.
  454  */
  455 static int
  456 lf_clearlock(unlock)
  457         register struct lockf *unlock;
  458 {
  459         struct lockf **head = unlock->lf_head;
  460         register struct lockf *lf = *head;
  461         struct lockf *overlap, **prev;
  462         int ovcase;
  463 
  464         if (lf == NOLOCKF)
  465                 return (0);
  466 #ifdef LOCKF_DEBUG
  467         if (unlock->lf_type != F_UNLCK)
  468                 panic("lf_clearlock: bad type");
  469         if (lockf_debug & 1)
  470                 lf_print("lf_clearlock", unlock);
  471 #endif /* LOCKF_DEBUG */
  472         prev = head;
  473         while ((ovcase = lf_findoverlap(lf, unlock, SELF, &prev, &overlap))) {
  474                 /*
  475                  * Wakeup the list of locks to be retried.
  476                  */
  477                 lf_wakelock(overlap);
  478 
  479                 switch (ovcase) {
  480 
  481                 case 1: /* overlap == lock */
  482                         *prev = overlap->lf_next;
  483                         FREE(overlap, M_LOCKF);
  484                         break;
  485 
  486                 case 2: /* overlap contains lock: split it */
  487                         if (overlap->lf_start == unlock->lf_start) {
  488                                 overlap->lf_start = unlock->lf_end + 1;
  489                                 break;
  490                         }
  491                         lf_split(overlap, unlock);
  492                         overlap->lf_next = unlock->lf_next;
  493                         break;
  494 
  495                 case 3: /* lock contains overlap */
  496                         *prev = overlap->lf_next;
  497                         lf = overlap->lf_next;
  498                         free(overlap, M_LOCKF);
  499                         continue;
  500 
  501                 case 4: /* overlap starts before lock */
  502                         overlap->lf_end = unlock->lf_start - 1;
  503                         prev = &overlap->lf_next;
  504                         lf = overlap->lf_next;
  505                         continue;
  506 
  507                 case 5: /* overlap ends after lock */
  508                         overlap->lf_start = unlock->lf_end + 1;
  509                         break;
  510                 }
  511                 break;
  512         }
  513 #ifdef LOCKF_DEBUG
  514         if (lockf_debug & 1)
  515                 lf_printlist("lf_clearlock", unlock);
  516 #endif /* LOCKF_DEBUG */
  517         return (0);
  518 }
  519 
  520 /*
  521  * Check whether there is a blocking lock,
  522  * and if so return its process identifier.
  523  */
  524 static int
  525 lf_getlock(lock, fl)
  526         register struct lockf *lock;
  527         register struct flock *fl;
  528 {
  529         register struct lockf *block;
  530 
  531 #ifdef LOCKF_DEBUG
  532         if (lockf_debug & 1)
  533                 lf_print("lf_getlock", lock);
  534 #endif /* LOCKF_DEBUG */
  535 
  536         if ((block = lf_getblock(lock))) {
  537                 fl->l_type = block->lf_type;
  538                 fl->l_whence = SEEK_SET;
  539                 fl->l_start = block->lf_start;
  540                 if (block->lf_end == -1)
  541                         fl->l_len = 0;
  542                 else
  543                         fl->l_len = block->lf_end - block->lf_start + 1;
  544                 if (block->lf_flags & F_POSIX)
  545                         fl->l_pid = ((struct proc *)(block->lf_id))->p_pid;
  546                 else
  547                         fl->l_pid = -1;
  548         } else {
  549                 fl->l_type = F_UNLCK;
  550         }
  551         return (0);
  552 }
  553 
  554 /*
  555  * Walk the list of locks for an inode and
  556  * return the first blocking lock.
  557  */
  558 static struct lockf *
  559 lf_getblock(lock)
  560         register struct lockf *lock;
  561 {
  562         struct lockf **prev, *overlap, *lf = *(lock->lf_head);
  563         int ovcase;
  564 
  565         prev = lock->lf_head;
  566         while ((ovcase = lf_findoverlap(lf, lock, OTHERS, &prev, &overlap))) {
  567                 /*
  568                  * We've found an overlap, see if it blocks us
  569                  */
  570                 if ((lock->lf_type == F_WRLCK || overlap->lf_type == F_WRLCK))
  571                         return (overlap);
  572                 /*
  573                  * Nope, point to the next one on the list and
  574                  * see if it blocks us
  575                  */
  576                 lf = overlap->lf_next;
  577         }
  578         return (NOLOCKF);
  579 }
  580 
  581 /*
  582  * Walk the list of locks for an inode to
  583  * find an overlapping lock (if any).
  584  *
  585  * NOTE: this returns only the FIRST overlapping lock.  There
  586  *       may be more than one.
  587  */
  588 static int
  589 lf_findoverlap(lf, lock, type, prev, overlap)
  590         register struct lockf *lf;
  591         struct lockf *lock;
  592         int type;
  593         struct lockf ***prev;
  594         struct lockf **overlap;
  595 {
  596         off_t start, end;
  597 
  598         *overlap = lf;
  599         if (lf == NOLOCKF)
  600                 return (0);
  601 #ifdef LOCKF_DEBUG
  602         if (lockf_debug & 2)
  603                 lf_print("lf_findoverlap: looking for overlap in", lock);
  604 #endif /* LOCKF_DEBUG */
  605         start = lock->lf_start;
  606         end = lock->lf_end;
  607         while (lf != NOLOCKF) {
  608                 if (((type & SELF) && lf->lf_id != lock->lf_id) ||
  609                     ((type & OTHERS) && lf->lf_id == lock->lf_id)) {
  610                         *prev = &lf->lf_next;
  611                         *overlap = lf = lf->lf_next;
  612                         continue;
  613                 }
  614 #ifdef LOCKF_DEBUG
  615                 if (lockf_debug & 2)
  616                         lf_print("\tchecking", lf);
  617 #endif /* LOCKF_DEBUG */
  618                 /*
  619                  * OK, check for overlap
  620                  *
  621                  * Six cases:
  622                  *      0) no overlap
  623                  *      1) overlap == lock
  624                  *      2) overlap contains lock
  625                  *      3) lock contains overlap
  626                  *      4) overlap starts before lock
  627                  *      5) overlap ends after lock
  628                  */
  629                 if ((lf->lf_end != -1 && start > lf->lf_end) ||
  630                     (end != -1 && lf->lf_start > end)) {
  631                         /* Case 0 */
  632 #ifdef LOCKF_DEBUG
  633                         if (lockf_debug & 2)
  634                                 printf("no overlap\n");
  635 #endif /* LOCKF_DEBUG */
  636                         if ((type & SELF) && end != -1 && lf->lf_start > end)
  637                                 return (0);
  638                         *prev = &lf->lf_next;
  639                         *overlap = lf = lf->lf_next;
  640                         continue;
  641                 }
  642                 if ((lf->lf_start == start) && (lf->lf_end == end)) {
  643                         /* Case 1 */
  644 #ifdef LOCKF_DEBUG
  645                         if (lockf_debug & 2)
  646                                 printf("overlap == lock\n");
  647 #endif /* LOCKF_DEBUG */
  648                         return (1);
  649                 }
  650                 if ((lf->lf_start <= start) &&
  651                     (end != -1) &&
  652                     ((lf->lf_end >= end) || (lf->lf_end == -1))) {
  653                         /* Case 2 */
  654 #ifdef LOCKF_DEBUG
  655                         if (lockf_debug & 2)
  656                                 printf("overlap contains lock\n");
  657 #endif /* LOCKF_DEBUG */
  658                         return (2);
  659                 }
  660                 if (start <= lf->lf_start &&
  661                            (end == -1 ||
  662                            (lf->lf_end != -1 && end >= lf->lf_end))) {
  663                         /* Case 3 */
  664 #ifdef LOCKF_DEBUG
  665                         if (lockf_debug & 2)
  666                                 printf("lock contains overlap\n");
  667 #endif /* LOCKF_DEBUG */
  668                         return (3);
  669                 }
  670                 if ((lf->lf_start < start) &&
  671                         ((lf->lf_end >= start) || (lf->lf_end == -1))) {
  672                         /* Case 4 */
  673 #ifdef LOCKF_DEBUG
  674                         if (lockf_debug & 2)
  675                                 printf("overlap starts before lock\n");
  676 #endif /* LOCKF_DEBUG */
  677                         return (4);
  678                 }
  679                 if ((lf->lf_start > start) &&
  680                         (end != -1) &&
  681                         ((lf->lf_end > end) || (lf->lf_end == -1))) {
  682                         /* Case 5 */
  683 #ifdef LOCKF_DEBUG
  684                         if (lockf_debug & 2)
  685                                 printf("overlap ends after lock\n");
  686 #endif /* LOCKF_DEBUG */
  687                         return (5);
  688                 }
  689                 panic("lf_findoverlap: default");
  690         }
  691         return (0);
  692 }
  693 
  694 /*
  695  * Split a lock and a contained region into
  696  * two or three locks as necessary.
  697  */
  698 static void
  699 lf_split(lock1, lock2)
  700         register struct lockf *lock1;
  701         register struct lockf *lock2;
  702 {
  703         register struct lockf *splitlock;
  704 
  705 #ifdef LOCKF_DEBUG
  706         if (lockf_debug & 2) {
  707                 lf_print("lf_split", lock1);
  708                 lf_print("splitting from", lock2);
  709         }
  710 #endif /* LOCKF_DEBUG */
  711         /*
  712          * Check to see if spliting into only two pieces.
  713          */
  714         if (lock1->lf_start == lock2->lf_start) {
  715                 lock1->lf_start = lock2->lf_end + 1;
  716                 lock2->lf_next = lock1;
  717                 return;
  718         }
  719         if (lock1->lf_end == lock2->lf_end) {
  720                 lock1->lf_end = lock2->lf_start - 1;
  721                 lock2->lf_next = lock1->lf_next;
  722                 lock1->lf_next = lock2;
  723                 return;
  724         }
  725         /*
  726          * Make a new lock consisting of the last part of
  727          * the encompassing lock
  728          */
  729         MALLOC(splitlock, struct lockf *, sizeof *splitlock, M_LOCKF, M_WAITOK);
  730         bcopy(lock1, splitlock, sizeof *splitlock);
  731         splitlock->lf_start = lock2->lf_end + 1;
  732         TAILQ_INIT(&splitlock->lf_blkhd);
  733         lock1->lf_end = lock2->lf_start - 1;
  734         /*
  735          * OK, now link it in
  736          */
  737         splitlock->lf_next = lock1->lf_next;
  738         lock2->lf_next = splitlock;
  739         lock1->lf_next = lock2;
  740 }
  741 
  742 /*
  743  * Wakeup a blocklist
  744  */
  745 static void
  746 lf_wakelock(listhead)
  747         struct lockf *listhead;
  748 {
  749         register struct lockf *wakelock;
  750 
  751         while (!TAILQ_EMPTY(&listhead->lf_blkhd)) {
  752                 wakelock = TAILQ_FIRST(&listhead->lf_blkhd);
  753                 TAILQ_REMOVE(&listhead->lf_blkhd, wakelock, lf_block);
  754                 wakelock->lf_next = NOLOCKF;
  755 #ifdef LOCKF_DEBUG
  756                 if (lockf_debug & 2)
  757                         lf_print("lf_wakelock: awakening", wakelock);
  758 #endif /* LOCKF_DEBUG */
  759                 wakeup(wakelock);
  760         }
  761 }
  762 
  763 #ifdef LOCKF_DEBUG
  764 /*
  765  * Print out a lock.
  766  */
  767 void
  768 lf_print(tag, lock)
  769         char *tag;
  770         register struct lockf *lock;
  771 {
  772 
  773         printf("%s: lock %p for ", tag, (void *)lock);
  774         if (lock->lf_flags & F_POSIX)
  775                 printf("proc %ld", (long)((struct proc *)lock->lf_id)->p_pid);
  776         else
  777                 printf("id %p", (void *)lock->lf_id);
  778         if (lock->lf_inode != (struct inode *)0)
  779                 printf(" in ino %ju on dev <%d, %d>, %s, start %jd, end %jd",
  780                     (uintmax_t)lock->lf_inode->i_number,
  781                     major(lock->lf_inode->i_dev),
  782                     minor(lock->lf_inode->i_dev),
  783                     lock->lf_type == F_RDLCK ? "shared" :
  784                     lock->lf_type == F_WRLCK ? "exclusive" :
  785                     lock->lf_type == F_UNLCK ? "unlock" : "unknown",
  786                     (intmax_t)lock->lf_start, (intmax_t)lock->lf_end);
  787         else
  788                 printf(" %s, start %jd, end %jd",
  789                     lock->lf_type == F_RDLCK ? "shared" :
  790                     lock->lf_type == F_WRLCK ? "exclusive" :
  791                     lock->lf_type == F_UNLCK ? "unlock" : "unknown",
  792                     (intmax_t)lock->lf_start, (intmax_t)lock->lf_end);
  793         if (!TAILQ_EMPTY(&lock->lf_blkhd))
  794                 printf(" block %p\n", (void *)TAILQ_FIRST(&lock->lf_blkhd));
  795         else
  796                 printf("\n");
  797 }
  798 
  799 void
  800 lf_printlist(tag, lock)
  801         char *tag;
  802         struct lockf *lock;
  803 {
  804         register struct lockf *lf, *blk;
  805 
  806         if (lock->lf_inode == (struct inode *)0)
  807                 return;
  808 
  809         printf("%s: Lock list for ino %ju on dev <%d, %d>:\n",
  810             tag, (uintmax_t)lock->lf_inode->i_number,
  811             major(lock->lf_inode->i_dev),
  812             minor(lock->lf_inode->i_dev));
  813         for (lf = lock->lf_inode->i_lockf; lf; lf = lf->lf_next) {
  814                 printf("\tlock %p for ",(void *)lf);
  815                 if (lf->lf_flags & F_POSIX)
  816                         printf("proc %ld",
  817                             (long)((struct proc *)lf->lf_id)->p_pid);
  818                 else
  819                         printf("id %p", (void *)lf->lf_id);
  820                 printf(", %s, start %jd, end %jd",
  821                     lf->lf_type == F_RDLCK ? "shared" :
  822                     lf->lf_type == F_WRLCK ? "exclusive" :
  823                     lf->lf_type == F_UNLCK ? "unlock" :
  824                     "unknown", (intmax_t)lf->lf_start, (intmax_t)lf->lf_end);
  825                 TAILQ_FOREACH(blk, &lf->lf_blkhd, lf_block) {
  826                         printf("\n\t\tlock request %p for ", (void *)blk);
  827                         if (blk->lf_flags & F_POSIX)
  828                                 printf("proc %ld",
  829                                     (long)((struct proc *)blk->lf_id)->p_pid);
  830                         else
  831                                 printf("id %p", (void *)blk->lf_id);
  832                         printf(", %s, start %jd, end %jd",
  833                             blk->lf_type == F_RDLCK ? "shared" :
  834                             blk->lf_type == F_WRLCK ? "exclusive" :
  835                             blk->lf_type == F_UNLCK ? "unlock" :
  836                             "unknown", (intmax_t)blk->lf_start,
  837                             (intmax_t)blk->lf_end);
  838                         if (!TAILQ_EMPTY(&blk->lf_blkhd))
  839                                 panic("lf_printlist: bad list");
  840                 }
  841                 printf("\n");
  842         }
  843 }
  844 #endif /* LOCKF_DEBUG */

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