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