diplodocus.org Git - nmh/blob - sbr/lock_file.c

   1
   2 /*
   3  * lock.c -- routines to lock/unlock files
   4  *
   5  * $Id$
   6  *
   7  * This code is Copyright (c) 2002, by the authors of nmh.  See the
   8  * COPYRIGHT file in the root directory of the nmh distribution for
   9  * complete copyright information.
  10  */
  11
  12 /* Modified by Ruud de Rooij to support Miquel van Smoorenburg's liblockfile
  13  *
  14  * Since liblockfile locking shares most of its code with dot locking, it
  15  * is enabled by defining both DOT_LOCKING and HAVE_LIBLOCKFILE.
  16  *
  17  * Ruud de Rooij <ruud@debian.org>  Sun, 28 Mar 1999 15:34:03 +0200
  18  */
  19
  20 #include <h/mh.h>
  21 #include <h/signals.h>
  22
  23 #ifdef TIME_WITH_SYS_TIME
  24 # include <sys/time.h>
  25 # include <time.h>
  26 #else
  27 # ifdef TM_IN_SYS_TIME
  28 #  include <sys/time.h>
  29 # else
  30 #  include <time.h>
  31 # endif
  32 #endif
  33
  34 #ifdef HAVE_ERRNO_H
  35 # include <errno.h>
  36 #endif
  37
  38 #ifdef MMDFONLY
  39 # include <mmdfonly.h>
  40 # include <lockonly.h>
  41 #endif /* MMDFONLY */
  42
  43 #ifdef HAVE_FCNTL_H
  44 # include <fcntl.h>
  45 #else
  46 # include <sys/file.h>
  47 #endif
  48
  49 #if defined(LOCKF_LOCKING) || defined(FLOCK_LOCKING)
  50 # include <sys/file.h>
  51 #endif
  52
  53 #include <signal.h>
  54
  55 #if defined(HAVE_LIBLOCKFILE)
  56 #include <lockfile.h>
  57 #endif
  58
  59 extern int errno;
  60
  61 #ifdef LOCKDIR
  62 char *lockdir = LOCKDIR;
  63 #endif
  64
  65 /* Are we using any kernel locking? */
  66 #if defined (FLOCK_LOCKING) || defined(LOCKF_LOCKING) || defined(FCNTL_LOCKING)
  67 # define KERNEL_LOCKING
  68 #endif
  69
  70 #ifdef DOT_LOCKING
  71
  72 /* struct for getting name of lock file to create */
  73 struct lockinfo {
  74     char curlock[BUFSIZ];
  75 #if !defined(HAVE_LIBLOCKFILE)
  76     char tmplock[BUFSIZ];
  77 #endif
  78 };
  79
  80 /*
  81  * Amount of time to wait before
  82  * updating ctime of lock file.
  83  */
  84 #define NSECS 20
  85
  86 #if !defined(HAVE_LIBLOCKFILE)
  87 /*
  88  * How old does a lock file need to be
  89  * before we remove it.
  90  */
  91 #define RSECS 180
  92 #endif /* HAVE_LIBLOCKFILE */
  93
  94 /* struct for recording and updating locks */
  95 struct lock {
  96     int l_fd;
  97     char *l_lock;
  98     struct lock *l_next;
  99 };
 100
 101 /* top of list containing all open locks */
 102 static struct lock *l_top = NULL;
 103 #endif /* DOT_LOCKING */
 104
 105 /*
 106  * static prototypes
 107  */
 108 #ifdef KERNEL_LOCKING
 109 static int lkopen_kernel (char *, int, mode_t);
 110 #endif
 111
 112 #ifdef DOT_LOCKING
 113 static int lkopen_dot (char *, int, mode_t);
 114 static int lockit (struct lockinfo *);
 115 static void lockname (char *, struct lockinfo *, int);
 116 static void timerON (char *, int);
 117 static void timerOFF (int);
 118 static RETSIGTYPE alrmser (int);
 119 #endif
 120
 121
 122 /*
 123  * Base routine to open and lock a file,
 124  * and return a file descriptor.
 125  */
 126
 127 int
 128 lkopen (char *file, int access, mode_t mode)
 129 {
 130 #ifdef KERNEL_LOCKING
 131     return lkopen_kernel(file, access, mode);
 132 #endif
 133
 134 #ifdef DOT_LOCKING
 135     return lkopen_dot(file, access, mode);
 136 #endif
 137 }
 138
 139
 140 /*
 141  * Base routine to close and unlock a file,
 142  * given a file descriptor.
 143  */
 144
 145 int
 146 lkclose (int fd, char *file)
 147 {
 148 #ifdef FCNTL_LOCKING
 149     struct flock buf;
 150 #endif
 151
 152 #ifdef DOT_LOCKING
 153     struct lockinfo lkinfo;
 154 #endif
 155
 156     if (fd == -1)
 157         return 0;
 158
 159 #ifdef FCNTL_LOCKING
 160     buf.l_type   = F_UNLCK;
 161     buf.l_whence = SEEK_SET;
 162     buf.l_start  = 0;
 163     buf.l_len    = 0;
 164     fcntl(fd, F_SETLK, &buf);
 165 #endif
 166
 167 #ifdef FLOCK_LOCKING
 168     flock (fd, LOCK_UN);
 169 #endif
 170
 171 #ifdef LOCKF_LOCKING
 172     /* make sure we unlock the whole thing */
 173     lseek (fd, (off_t) 0, SEEK_SET);
 174     lockf (fd, F_ULOCK, 0L);
 175 #endif
 176
 177 #ifdef DOT_LOCKING
 178     lockname (file, &lkinfo, 0);        /* get name of lock file */
 179 #if !defined(HAVE_LIBLOCKFILE)
 180     unlink (lkinfo.curlock);            /* remove lock file      */
 181 #else
 182     lockfile_remove(lkinfo.curlock);
 183 #endif /* HAVE_LIBLOCKFILE */
 184     timerOFF (fd);                      /* turn off lock timer   */
 185 #endif /* DOT_LOCKING */
 186
 187     return (close (fd));
 188 }
 189
 190
 191 /*
 192  * Base routine to open and lock a file,
 193  * and return a FILE pointer
 194  */
 195
 196 FILE *
 197 lkfopen (char *file, char *mode)
 198 {
 199     int fd, access;
 200     FILE *fp;
 201
 202     if (strcmp (mode, "r") == 0)
 203         access = O_RDONLY;
 204     else if (strcmp (mode, "r+") == 0)
 205         access = O_RDWR;
 206     else if (strcmp (mode, "w") == 0)
 207         access = O_WRONLY | O_CREAT | O_TRUNC;
 208     else if (strcmp (mode, "w+") == 0)
 209         access = O_RDWR | O_CREAT | O_TRUNC;
 210     else if (strcmp (mode, "a") == 0)
 211         access = O_WRONLY | O_CREAT | O_APPEND;
 212     else if (strcmp (mode, "a+") == 0)
 213         access = O_RDWR | O_CREAT | O_APPEND;
 214     else {
 215         errno = EINVAL;
 216         return NULL;
 217     }
 218
 219     if ((fd = lkopen (file, access, 0666)) == -1)
 220         return NULL;
 221
 222     if ((fp = fdopen (fd, mode)) == NULL) {
 223         close (fd);
 224         return NULL;
 225     }
 226
 227     return fp;
 228 }
 229
 230
 231 /*
 232  * Base routine to close and unlock a file,
 233  * given a FILE pointer
 234  */
 235
 236 int
 237 lkfclose (FILE *fp, char *file)
 238 {
 239 #ifdef FCNTL_LOCKING
 240     struct flock buf;
 241 #endif
 242
 243 #ifdef DOT_LOCKING
 244     struct lockinfo lkinfo;
 245 #endif
 246
 247     if (fp == NULL)
 248         return 0;
 249
 250 #ifdef FCNTL_LOCKING
 251     buf.l_type   = F_UNLCK;
 252     buf.l_whence = SEEK_SET;
 253     buf.l_start  = 0;
 254     buf.l_len    = 0;
 255     fcntl(fileno(fp), F_SETLK, &buf);
 256 #endif
 257
 258 #ifdef FLOCK_LOCKING
 259     flock (fileno(fp), LOCK_UN);
 260 #endif
 261
 262 #ifdef LOCKF_LOCKING
 263     /* make sure we unlock the whole thing */
 264     fseek (fp, 0L, SEEK_SET);
 265     lockf (fileno(fp), F_ULOCK, 0L);
 266 #endif
 267
 268 #ifdef DOT_LOCKING
 269     lockname (file, &lkinfo, 0);        /* get name of lock file */
 270 #if !defined(HAVE_LIBLOCKFILE)
 271     unlink (lkinfo.curlock);            /* remove lock file      */
 272 #else
 273     lockfile_remove(lkinfo.curlock);
 274 #endif /* HAVE_LIBLOCKFILE */
 275     timerOFF (fileno(fp));              /* turn off lock timer   */
 276 #endif /* DOT_LOCKING */
 277
 278     return (fclose (fp));
 279 }
 280
 281
 282 #ifdef KERNEL_LOCKING
 283
 284 /*
 285  * open and lock a file, using kernel locking
 286  */
 287
 288 static int
 289 lkopen_kernel (char *file, int access, mode_t mode)
 290 {
 291     int fd, i, j;
 292
 293 # ifdef FCNTL_LOCKING
 294     struct flock buf;
 295 # endif /* FCNTL_LOCKING */
 296
 297     for (i = 0; i < 5; i++) {
 298
 299 # if defined(LOCKF_LOCKING) || defined(FCNTL_LOCKING)
 300         /* remember the original mode */
 301         j = access;
 302
 303         /* make sure we open at the beginning */
 304         access &= ~O_APPEND;
 305
 306         /*
 307          * We MUST have write permission or
 308          * lockf/fcntl() won't work
 309          */
 310         if ((access & 03) == O_RDONLY) {
 311             access &= ~O_RDONLY;
 312             access |= O_RDWR;
 313         }
 314 # endif /* LOCKF_LOCKING || FCNTL_LOCKING */
 315
 316         if ((fd = open (file, access | O_NDELAY, mode)) == -1)
 317             return -1;
 318
 319 # ifdef FCNTL_LOCKING
 320         buf.l_type   = F_WRLCK;
 321         buf.l_whence = SEEK_SET;
 322         buf.l_start  = 0;
 323         buf.l_len    = 0;
 324         if (fcntl (fd, F_SETLK, &buf) != -1)
 325             return fd;
 326 # endif
 327
 328 # ifdef FLOCK_LOCKING
 329         if (flock (fd, (((access & 03) == O_RDONLY) ? LOCK_SH : LOCK_EX)
 330                    | LOCK_NB) != -1)
 331             return fd;
 332 # endif
 333
 334 # ifdef LOCKF_LOCKING
 335         if (lockf (fd, F_TLOCK, 0L) != -1) {
 336             /* see if we should be at the end */
 337             if (j & O_APPEND)
 338                 lseek (fd, (off_t) 0, SEEK_END);
 339             return fd;
 340         }
 341 # endif
 342
 343         j = errno;
 344         close (fd);
 345         sleep (5);
 346     }
 347
 348     close (fd);
 349     errno = j;
 350     return -1;
 351 }
 352
 353 #endif /* KERNEL_LOCKING */
 354
 355
 356 #ifdef DOT_LOCKING
 357
 358 /*
 359  * open and lock a file, using dot locking
 360  */
 361
 362 static int
 363 lkopen_dot (char *file, int access, mode_t mode)
 364 {
 365     int i, fd;
 366     time_t curtime;
 367     struct lockinfo lkinfo;
 368     struct stat st;
 369
 370     /* open the file */
 371     if ((fd = open (file, access, mode)) == -1)
 372         return -1;
 373
 374     /*
 375      * Get the name of the eventual lock file, as well
 376      * as a name for a temporary lock file.
 377      */
 378     lockname (file, &lkinfo, 1);
 379
 380 #if !defined(HAVE_LIBLOCKFILE)
 381     for (i = 0;;) {
 382         /* attempt to create lock file */
 383         if (lockit (&lkinfo) == 0) {
 384             /* if successful, turn on timer and return */
 385             timerON (lkinfo.curlock, fd);
 386             return fd;
 387         } else {
 388             /*
 389              * Abort locking, if we fail to lock after 5 attempts
 390              * and are never able to stat the lock file.
 391              */
 392             if (stat (lkinfo.curlock, &st) == -1) {
 393                 if (i++ > 5)
 394                     return -1;
 395                 sleep (5);
 396             } else {
 397                 i = 0;
 398                 time (&curtime);
 399
 400                 /* check for stale lockfile, else sleep */
 401                 if (curtime > st.st_ctime + RSECS)
 402                     unlink (lkinfo.curlock);
 403                 else
 404                     sleep (5);
 405             }
 406         }
 407     }
 408 #else
 409     if (lockfile_create(lkinfo.curlock, 5, 0) == L_SUCCESS) {
 410         timerON(lkinfo.curlock, fd);
 411         return fd;
 412     }
 413     else {
 414         close(fd);
 415         return -1;
 416     }
 417 #endif /* HAVE_LIBLOCKFILE */
 418 }
 419
 420 #if !defined(HAVE_LIBLOCKFILE)
 421 /*
 422  * Routine that actually tries to create
 423  * the lock file.
 424  */
 425
 426 static int
 427 lockit (struct lockinfo *li)
 428 {
 429     int fd;
 430     char *curlock, *tmplock;
 431
 432 #if 0
 433     char buffer[128];
 434 #endif
 435
 436     curlock = li->curlock;
 437     tmplock = li->tmplock;
 438
 439 #ifdef HAVE_MKSTEMP
 440     if ((fd = mkstemp(tmplock)) == -1)
 441         return -1;
 442 #else
 443     if (mktemp(tmplock) == NULL)
 444         return -1;
 445     if (unlink(tmplock) == -1 && errno != ENOENT)
 446         return -1;
 447     /* create the temporary lock file */
 448     if ((fd = creat(tmplock, 0600)) == -1)
 449         return -1;
 450 #endif
 451
 452 #if 0
 453     /* write our process id into lock file */
 454     snprintf (buffer, sizeof(buffer), "nmh lock: pid %d\n", (int) getpid());
 455     write(fd, buffer, strlen(buffer) + 1);
 456 #endif
 457
 458     close (fd);
 459
 460     /*
 461      * Now try to create the real lock file
 462      * by linking to the temporary file.
 463      */
 464     fd = link(tmplock, curlock);
 465     unlink(tmplock);
 466
 467     return (fd == -1 ? -1 : 0);
 468 }
 469 #endif /* HAVE_LIBLOCKFILE */
 470
 471 /*
 472  * Get name of lock file, and temporary lock file
 473  */
 474
 475 static void
 476 lockname (char *file, struct lockinfo *li, int isnewlock)
 477 {
 478     int bplen, tmplen;
 479     char *bp, *cp;
 480
 481 #if 0
 482     struct stat st;
 483 #endif
 484
 485     if ((cp = strrchr (file, '/')) == NULL || *++cp == 0)
 486         cp = file;
 487
 488     bp = li->curlock;
 489     bplen = 0;
 490 #ifdef LOCKDIR
 491     snprintf (bp, sizeof(li->curlock), "%s/", lockdir);
 492     tmplen = strlen (bp);
 493     bp    += tmplen;
 494     bplen += tmplen;
 495 #else
 496     if (cp != file) {
 497         snprintf (bp, sizeof(li->curlock), "%.*s", cp - file, file);
 498         tmplen = strlen (bp);
 499         bp    += tmplen;
 500         bplen += tmplen;
 501     }
 502 #endif
 503
 504 #if 0
 505     /*
 506      * mmdf style dot locking.  Currently not supported.
 507      * If we start supporting mmdf style dot locking,
 508      * we will need to change the return value of lockname
 509      */
 510     if (stat (file, &st) == -1)
 511         return -1;
 512
 513     snprintf (bp, sizeof(li->curlock) - bplen, "LCK%05d.%05d",
 514         st.st_dev, st.st_ino);
 515 #endif
 516
 517     snprintf (bp, sizeof(li->curlock) - bplen, "%s.lock", cp);
 518
 519 #if !defined(HAVE_LIBLOCKFILE)
 520     /*
 521      * If this is for a new lock, create a name for
 522      * the temporary lock file for lockit()
 523      */
 524     if (isnewlock) {
 525         if ((cp = strrchr (li->curlock, '/')) == NULL || *++cp == 0)
 526             strncpy (li->tmplock, ",LCK.XXXXXX", sizeof(li->tmplock));
 527         else
 528             snprintf (li->tmplock, sizeof(li->tmplock), "%.*s,LCK.XXXXXX",
 529                      cp - li->curlock, li->curlock);
 530     }
 531 #endif
 532 }
 533
 534
 535 /*
 536  * Add new lockfile to the list of open lockfiles
 537  * and start the lock file timer.
 538  */
 539
 540 static void
 541 timerON (char *curlock, int fd)
 542 {
 543     struct lock *lp;
 544     size_t len;
 545
 546     if (!(lp = (struct lock *) malloc (sizeof(*lp))))
 547         return;
 548
 549     len = strlen(curlock) + 1;
 550     lp->l_fd = fd;
 551     if (!(lp->l_lock = malloc (len))) {
 552         free ((char *) lp);
 553         return;
 554     }
 555     memcpy (lp->l_lock, curlock, len);
 556     lp->l_next = l_top;
 557
 558     if (!l_top) {
 559         /* perhaps SIGT{STP,TIN,TOU} ? */
 560         SIGNAL (SIGALRM, alrmser);
 561         alarm (NSECS);
 562     }
 563
 564     l_top = lp;
 565 }
 566
 567
 568 /*
 569  * Search through the list of lockfiles for the
 570  * current lockfile, and remove it from the list.
 571  */
 572
 573 static void
 574 timerOFF (int fd)
 575 {
 576     struct lock *pp, *lp;
 577
 578     alarm(0);
 579
 580     if (l_top) {
 581         for (pp = lp = l_top; lp; pp = lp, lp = lp->l_next) {
 582             if (lp->l_fd == fd)
 583                 break;
 584         }
 585         if (lp) {
 586             if (lp == l_top)
 587                 l_top = lp->l_next;
 588             else
 589                 pp->l_next = lp->l_next;
 590
 591             free (lp->l_lock);
 592             free (lp);
 593         }
 594     }
 595
 596     /* if there are locks left, restart timer */
 597     if (l_top)
 598         alarm (NSECS);
 599 }
 600
 601
 602 /*
 603  * If timer goes off, we update the ctime of all open
 604  * lockfiles, so another command doesn't remove them.
 605  */
 606
 607 static RETSIGTYPE
 608 alrmser (int sig)
 609 {
 610     int j;
 611     char *lockfile;
 612     struct lock *lp;
 613
 614 #ifndef RELIABLE_SIGNALS
 615     SIGNAL (SIGALRM, alrmser);
 616 #endif
 617
 618     /* update the ctime of all the lock files */
 619     for (lp = l_top; lp; lp = lp->l_next) {
 620         lockfile = lp->l_lock;
 621 #if !defined(HAVE_LIBLOCKFILE)
 622         if (*lockfile && (j = creat (lockfile, 0600)) != -1)
 623             close (j);
 624 #else
 625     lockfile_touch(lockfile);
 626 #endif
 627     }
 628
 629     /* restart the alarm */
 630     alarm (NSECS);
 631 }
 632
 633 #endif /* DOT_LOCKING */