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

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