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
 205         access = O_RDWR;
 206
 207     if ((fd = lkopen (file, access, 0)) == -1)
 208         return NULL;
 209
 210     if ((fp = fdopen (fd, mode)) == NULL) {
 211         close (fd);
 212         return NULL;
 213     }
 214
 215     return fp;
 216 }
 217
 218
 219 /*
 220  * Base routine to close and unlock a file,
 221  * given a FILE pointer
 222  */
 223
 224 int
 225 lkfclose (FILE *fp, char *file)
 226 {
 227 #ifdef FCNTL_LOCKING
 228     struct flock buf;
 229 #endif
 230
 231 #ifdef DOT_LOCKING
 232     struct lockinfo lkinfo;
 233 #endif
 234
 235     if (fp == NULL)
 236         return 0;
 237
 238 #ifdef FCNTL_LOCKING
 239     buf.l_type   = F_UNLCK;
 240     buf.l_whence = SEEK_SET;
 241     buf.l_start  = 0;
 242     buf.l_len    = 0;
 243     fcntl(fileno(fp), F_SETLK, &buf);
 244 #endif
 245
 246 #ifdef FLOCK_LOCKING
 247     flock (fileno(fp), LOCK_UN);
 248 #endif
 249
 250 #ifdef LOCKF_LOCKING
 251     /* make sure we unlock the whole thing */
 252     fseek (fp, 0L, SEEK_SET);
 253     lockf (fileno(fp), F_ULOCK, 0L);
 254 #endif
 255
 256 #ifdef DOT_LOCKING
 257     lockname (file, &lkinfo, 0);        /* get name of lock file */
 258 #if !defined(HAVE_LIBLOCKFILE)
 259     unlink (lkinfo.curlock);            /* remove lock file      */
 260 #else
 261     lockfile_remove(lkinfo.curlock);
 262 #endif /* HAVE_LIBLOCKFILE */
 263     timerOFF (fileno(fp));              /* turn off lock timer   */
 264 #endif /* DOT_LOCKING */
 265
 266     return (fclose (fp));
 267 }
 268
 269
 270 #ifdef KERNEL_LOCKING
 271
 272 /*
 273  * open and lock a file, using kernel locking
 274  */
 275
 276 static int
 277 lkopen_kernel (char *file, int access, mode_t mode)
 278 {
 279     int fd, i, j;
 280
 281 # ifdef FCNTL_LOCKING
 282     struct flock buf;
 283 # endif /* FCNTL_LOCKING */
 284
 285     for (i = 0; i < 5; i++) {
 286
 287 # if defined(LOCKF_LOCKING) || defined(FCNTL_LOCKING)
 288         /* remember the original mode */
 289         j = access;
 290
 291         /* make sure we open at the beginning */
 292         access &= ~O_APPEND;
 293
 294         /*
 295          * We MUST have write permission or
 296          * lockf/fcntl() won't work
 297          */
 298         if ((access & 03) == O_RDONLY) {
 299             access &= ~O_RDONLY;
 300             access |= O_RDWR;
 301         }
 302 # endif /* LOCKF_LOCKING || FCNTL_LOCKING */
 303
 304         if ((fd = open (file, access | O_NDELAY, mode)) == -1)
 305             return -1;
 306
 307 # ifdef FCNTL_LOCKING
 308         buf.l_type   = F_WRLCK;
 309         buf.l_whence = SEEK_SET;
 310         buf.l_start  = 0;
 311         buf.l_len    = 0;
 312         if (fcntl (fd, F_SETLK, &buf) != -1)
 313             return fd;
 314 # endif
 315
 316 # ifdef FLOCK_LOCKING
 317         if (flock (fd, LOCK_EX | LOCK_NB) != -1)
 318             return fd;
 319 # endif
 320
 321 # ifdef LOCKF_LOCKING
 322         if (lockf (fd, F_TLOCK, 0L) != -1) {
 323             /* see if we should be at the end */
 324             if (j & O_APPEND)
 325                 lseek (fd, (off_t) 0, SEEK_END);
 326             return fd;
 327         }
 328 # endif
 329
 330         j = errno;
 331         close (fd);
 332         sleep (5);
 333     }
 334
 335     close (fd);
 336     errno = j;
 337     return -1;
 338 }
 339
 340 #endif /* KERNEL_LOCKING */
 341
 342
 343 #ifdef DOT_LOCKING
 344
 345 /*
 346  * open and lock a file, using dot locking
 347  */
 348
 349 static int
 350 lkopen_dot (char *file, int access, mode_t mode)
 351 {
 352     int i, fd;
 353     time_t curtime;
 354     struct lockinfo lkinfo;
 355     struct stat st;
 356
 357     /* open the file */
 358     if ((fd = open (file, access, mode)) == -1)
 359         return -1;
 360
 361     /*
 362      * Get the name of the eventual lock file, as well
 363      * as a name for a temporary lock file.
 364      */
 365     lockname (file, &lkinfo, 1);
 366
 367 #if !defined(HAVE_LIBLOCKFILE)
 368     for (i = 0;;) {
 369         /* attempt to create lock file */
 370         if (lockit (&lkinfo) == 0) {
 371             /* if successful, turn on timer and return */
 372             timerON (lkinfo.curlock, fd);
 373             return fd;
 374         } else {
 375             /*
 376              * Abort locking, if we fail to lock after 5 attempts
 377              * and are never able to stat the lock file.
 378              */
 379             if (stat (lkinfo.curlock, &st) == -1) {
 380                 if (i++ > 5)
 381                     return -1;
 382                 sleep (5);
 383             } else {
 384                 i = 0;
 385                 time (&curtime);
 386
 387                 /* check for stale lockfile, else sleep */
 388                 if (curtime > st.st_ctime + RSECS)
 389                     unlink (lkinfo.curlock);
 390                 else
 391                     sleep (5);
 392             }
 393         }
 394     }
 395 #else
 396     if (lockfile_create(lkinfo.curlock, 5, 0) == L_SUCCESS) {
 397         timerON(lkinfo.curlock, fd);
 398         return fd;
 399     }
 400     else {
 401         close(fd);
 402         return -1;
 403     }
 404 #endif /* HAVE_LIBLOCKFILE */
 405 }
 406
 407 #if !defined(HAVE_LIBLOCKFILE)
 408 /*
 409  * Routine that actually tries to create
 410  * the lock file.
 411  */
 412
 413 static int
 414 lockit (struct lockinfo *li)
 415 {
 416     int fd;
 417     char *curlock, *tmplock;
 418
 419 #if 0
 420     char buffer[128];
 421 #endif
 422
 423     curlock = li->curlock;
 424     tmplock = li->tmplock;
 425
 426 #ifdef HAVE_MKSTEMP
 427     if ((fd = mkstemp(tmplock)) == -1)
 428         return -1;
 429 #else
 430     if (mktemp(tmplock) == NULL)
 431         return -1;
 432     if (unlink(tmplock) == -1 && errno != ENOENT)
 433         return -1;
 434     /* create the temporary lock file */
 435     if ((fd = creat(tmplock, 0600)) == -1)
 436         return -1;
 437 #endif
 438
 439 #if 0
 440     /* write our process id into lock file */
 441     snprintf (buffer, sizeof(buffer), "nmh lock: pid %d\n", (int) getpid());
 442     write(fd, buffer, strlen(buffer) + 1);
 443 #endif
 444
 445     close (fd);
 446
 447     /*
 448      * Now try to create the real lock file
 449      * by linking to the temporary file.
 450      */
 451     fd = link(tmplock, curlock);
 452     unlink(tmplock);
 453
 454     return (fd == -1 ? -1 : 0);
 455 }
 456 #endif /* HAVE_LIBLOCKFILE */
 457
 458 /*
 459  * Get name of lock file, and temporary lock file
 460  */
 461
 462 static void
 463 lockname (char *file, struct lockinfo *li, int isnewlock)
 464 {
 465     int bplen, tmplen;
 466     char *bp, *cp;
 467
 468 #if 0
 469     struct stat st;
 470 #endif
 471
 472     if ((cp = strrchr (file, '/')) == NULL || *++cp == 0)
 473         cp = file;
 474
 475     bp = li->curlock;
 476     bplen = 0;
 477 #ifdef LOCKDIR
 478     snprintf (bp, sizeof(li->curlock), "%s/", lockdir);
 479     tmplen = strlen (bp);
 480     bp    += tmplen;
 481     bplen += tmplen;
 482 #else
 483     if (cp != file) {
 484         snprintf (bp, sizeof(li->curlock), "%.*s", cp - file, file);
 485         tmplen = strlen (bp);
 486         bp    += tmplen;
 487         bplen += tmplen;
 488     }
 489 #endif
 490
 491 #if 0
 492     /*
 493      * mmdf style dot locking.  Currently not supported.
 494      * If we start supporting mmdf style dot locking,
 495      * we will need to change the return value of lockname
 496      */
 497     if (stat (file, &st) == -1)
 498         return -1;
 499
 500     snprintf (bp, sizeof(li->curlock) - bplen, "LCK%05d.%05d",
 501         st.st_dev, st.st_ino);
 502 #endif
 503
 504     snprintf (bp, sizeof(li->curlock) - bplen, "%s.lock", cp);
 505
 506 #if !defined(HAVE_LIBLOCKFILE)
 507     /*
 508      * If this is for a new lock, create a name for
 509      * the temporary lock file for lockit()
 510      */
 511     if (isnewlock) {
 512         if ((cp = strrchr (li->curlock, '/')) == NULL || *++cp == 0)
 513             strncpy (li->tmplock, ",LCK.XXXXXX", sizeof(li->tmplock));
 514         else
 515             snprintf (li->tmplock, sizeof(li->tmplock), "%.*s,LCK.XXXXXX",
 516                      cp - li->curlock, li->curlock);
 517     }
 518 #endif
 519 }
 520
 521
 522 /*
 523  * Add new lockfile to the list of open lockfiles
 524  * and start the lock file timer.
 525  */
 526
 527 static void
 528 timerON (char *curlock, int fd)
 529 {
 530     struct lock *lp;
 531     size_t len;
 532
 533     if (!(lp = (struct lock *) malloc (sizeof(*lp))))
 534         return;
 535
 536     len = strlen(curlock) + 1;
 537     lp->l_fd = fd;
 538     if (!(lp->l_lock = malloc (len))) {
 539         free ((char *) lp);
 540         return;
 541     }
 542     memcpy (lp->l_lock, curlock, len);
 543     lp->l_next = l_top;
 544
 545     if (!l_top) {
 546         /* perhaps SIGT{STP,TIN,TOU} ? */
 547         SIGNAL (SIGALRM, alrmser);
 548         alarm (NSECS);
 549     }
 550
 551     l_top = lp;
 552 }
 553
 554
 555 /*
 556  * Search through the list of lockfiles for the
 557  * current lockfile, and remove it from the list.
 558  */
 559
 560 static void
 561 timerOFF (int fd)
 562 {
 563     struct lock *pp, *lp;
 564
 565     alarm(0);
 566
 567     if (l_top) {
 568         for (pp = lp = l_top; lp; pp = lp, lp = lp->l_next) {
 569             if (lp->l_fd == fd)
 570                 break;
 571         }
 572         if (lp) {
 573             if (lp == l_top)
 574                 l_top = lp->l_next;
 575             else
 576                 pp->l_next = lp->l_next;
 577
 578             free (lp->l_lock);
 579             free (lp);
 580         }
 581     }
 582
 583     /* if there are locks left, restart timer */
 584     if (l_top)
 585         alarm (NSECS);
 586 }
 587
 588
 589 /*
 590  * If timer goes off, we update the ctime of all open
 591  * lockfiles, so another command doesn't remove them.
 592  */
 593
 594 static RETSIGTYPE
 595 alrmser (int sig)
 596 {
 597     int j;
 598     char *lockfile;
 599     struct lock *lp;
 600
 601 #ifndef RELIABLE_SIGNALS
 602     SIGNAL (SIGALRM, alrmser);
 603 #endif
 604
 605     /* update the ctime of all the lock files */
 606     for (lp = l_top; lp; lp = lp->l_next) {
 607         lockfile = lp->l_lock;
 608 #if !defined(HAVE_LIBLOCKFILE)
 609         if (*lockfile && (j = creat (lockfile, 0600)) != -1)
 610             close (j);
 611 #else
 612     lockfile_touch(lockfile);
 613 #endif
 614     }
 615
 616     /* restart the alarm */
 617     alarm (NSECS);
 618 }
 619
 620 #endif /* DOT_LOCKING */