diff options
Diffstat (limited to 'mount/sundries.c')
| -rw-r--r-- | mount/sundries.c | 62 |
1 files changed, 55 insertions, 7 deletions
diff --git a/mount/sundries.c b/mount/sundries.c index 45e0e14d8..5ebf0195f 100644 --- a/mount/sundries.c +++ b/mount/sundries.c @@ -1,9 +1,12 @@ /* * Support functions. Exported functions are prototyped in sundries.h. * sundries.c,v 1.1.1.1 1993/11/18 08:40:51 jrs Exp + * + * added fcntl locking by Kjetil T. (kjetilho@math.uio.no) - aeb, 950927 */ #include "sundries.h" +#include "mount.h" /* File pointer for /etc/mtab. */ FILE *F_mtab = NULL; @@ -14,6 +17,9 @@ FILE *F_temp = NULL; /* File descriptor for lock. Value tested in unlock_mtab() to remove race. */ static int lock = -1; +/* Flag for already existing lock file. */ +static int old_lockfile = 1; + /* String list constructor. (car() and cdr() are defined in "sundries.h"). */ string_list cons (char *a, const string_list b) @@ -75,6 +81,7 @@ error (const char *fmt, ...) { va_list args; + if (mount_quiet) return; va_start (args, fmt); vfprintf (stderr, fmt, args); fprintf (stderr, "\n"); @@ -103,6 +110,12 @@ handler (int sig) die (2, "%s", sys_siglist[sig]); } +static void +setlkw_timeout (int sig) +{ + /* nothing, fcntl will fail anyway */ +} + /* Create the lock file. The lock file will be removed if we catch a signal or when we exit. The value of lock is tested to remove the race. */ void @@ -110,20 +123,54 @@ lock_mtab (void) { int sig = 0; struct sigaction sa; + struct flock flock; /* If this is the first time, ensure that the lock will be removed. */ if (lock < 0) { + struct stat st; sa.sa_handler = handler; sa.sa_flags = 0; sigfillset (&sa.sa_mask); while (sigismember (&sa.sa_mask, ++sig) != -1) - sigaction (sig, &sa, (struct sigaction *) 0); - - if ((lock = open (MOUNTED_LOCK, O_WRONLY|O_CREAT|O_EXCL, 0)) < 0) - die (2, "can't create lock file %s: %s", - MOUNTED_LOCK, strerror (errno)); + { + if (sig == SIGALRM) + sa.sa_handler = setlkw_timeout; + else + sa.sa_handler = handler; + sigaction (sig, &sa, (struct sigaction *) 0); + } + + /* This stat is performed so we know when not to be overly eager + when cleaning up after signals. The window between stat and + open is not significant. */ + if (lstat (MOUNTED_LOCK, &st) < 0 && errno == ENOENT) + old_lockfile = 0; + + lock = open (MOUNTED_LOCK, O_WRONLY|O_CREAT, 0); + if (lock < 0) + { + die (2, "can't create lock file %s: %s", + MOUNTED_LOCK, strerror (errno)); + } + + flock.l_type = F_WRLCK; + flock.l_whence = SEEK_SET; + flock.l_start = 0; + flock.l_len = 0; + + alarm(LOCK_BUSY); + if (fcntl (lock, F_SETLKW, &flock) < 0) + { + close (lock); + /* The file should not be removed */ + lock = -1; + die (2, "can't lock lock file %s: %s", + MOUNTED_LOCK, errno == EINTR ? "timed out" : strerror (errno)); + } + /* We have now access to the lock, and it can always be removed */ + old_lockfile = 0; } } @@ -133,8 +180,9 @@ unlock_mtab (void) { if (lock != -1) { - close( lock ); - unlink (MOUNTED_LOCK); + close (lock); + if (!old_lockfile) + unlink (MOUNTED_LOCK); } } |