int
lock_mtab (void) {
int i;
struct timespec waittime;
struct timeval maxtime;
char linktargetfile[MOUNTLOCK_LINKTARGET_LTH];
if (!signals_have_been_setup) {
int sig = 0;
struct sigaction sa;
sa.sa_handler = handler;
sa.sa_flags = 0;
sigfillset (&sa.sa_mask);
while (sigismember (&sa.sa_mask, ++sig) != -1
&& sig != SIGCHLD) {
if (sig == SIGALRM)
sa.sa_handler = setlkw_timeout;
else
sa.sa_handler = handler;
sigaction (sig, &sa, (struct sigaction *) 0);
}
signals_have_been_setup = 1;
}
sprintf(linktargetfile, MOUNTLOCK_LINKTARGET, getpid ());
i = open (linktargetfile, O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR);
if (i < 0) {
/* linktargetfile does not exist (as a file)
and we cannot create it. Read-only filesystem?
Too many files open in the system?
Filesystem full? */
return EX_FILEIO;
}
close(i);
maxtime = mono_time();
maxtime.tv_sec += MOUNTLOCK_MAXTIME;
waittime.tv_sec = 0;
waittime.tv_nsec = (1000 * MOUNTLOCK_WAITTIME);
/* Repeat until it was us who made the link */
while (!we_created_lockfile) {
struct timeval now;
struct flock flock;
int errsv, j;
j = link(linktargetfile, _PATH_MOUNTED_LOCK);
errsv = errno;
if (j == 0)
we_created_lockfile = 1;
if (j < 0 && errsv != EEXIST) {
(void) unlink(linktargetfile);
return EX_FILEIO;
}
lockfile_fd = open (_PATH_MOUNTED_LOCK, O_WRONLY);
if (lockfile_fd < 0) {
/* Strange... Maybe the file was just deleted? */
now = mono_time();
if (errno == ENOENT && now.tv_sec < maxtime.tv_sec) {
we_created_lockfile = 0;
continue;
}
(void) unlink(linktargetfile);
return EX_FILEIO;
}
flock.l_type = F_WRLCK;
flock.l_whence = SEEK_SET;
flock.l_start = 0;
flock.l_len = 0;
if (j == 0) {
/* We made the link. Now claim the lock. If we can't
* get it, continue anyway
*/
fcntl (lockfile_fd, F_SETLK, &flock);
(void) unlink(linktargetfile);
} else {
/* Someone else made the link. Wait. */
now = mono_time();
if (now.tv_sec < maxtime.tv_sec) {
alarm(maxtime.tv_sec - now.tv_sec);
if (fcntl (lockfile_fd, F_SETLKW, &flock) == -1) {
(void) unlink(linktargetfile);
return EX_FILEIO;
}
alarm(0);
nanosleep(&waittime, NULL);
} else {
(void) unlink(linktargetfile);
return EX_FILEIO;
}
close(lockfile_fd);
}
}
return 0;
}
int main(int argc, char **argv)
{
double t0, t1;
if (argc != 5) {
puts("Usage: syncbench file write_size write_qty (d|s)");
return 1;
}
if (strlen(argv[4]) != 1) {
puts("You're a bad person.");
return 1;
}
int d;
if (argv[4][0] == 'd') {
d = 1;
} else if (argv[4][0] == 's') {
d = 0;
} else {
puts("That last parameter should have been either 'd' or 's'.");
return 1;
}
int write_size = atoi(argv[2]);
int no_of_writes = atoi(argv[3]);
if ((write_size <= 0) || (no_of_writes <= 0)) {
puts("You want me to write no bytes?");
return 1;
}
int fd = open(argv[1], O_CREAT | O_WRONLY | O_EXCL);
if (fd == -1) {
if (errno == EEXIST) {
printf("Refusing to nuke existing file %s.\n", argv[1]);
} else {
printf("Can't open %s for write.\n", argv[1]);
}
return 1;
}
char *bytes = malloc(write_size);
if (bytes == NULL) {
puts("malloc() failed, FML.");
return 1;
}
int i;
for (i = 0; i < write_size; i++) {
bytes[i] = '0' + (i % 10);
}
if (mono_time(&t0)) {
puts("can't consult a clock.");
return 1;
}
for (i = 0; i < no_of_writes; i++) {
ssize_t r = write(fd, bytes, write_size);
if (r != write_size) {
puts("write() failed.");
return 1;
}
if (d) {
if (fdatasync(fd)) {
puts("fdatasync() failed.");
return 1;
}
} else {
if (fsync(fd)) {
puts("fsync() failed.");
return 1;
}
}
}
if (mono_time(&t1)) {
puts("really, can't consult the clock?");
return 1;
}
char *c = d ? "fdatasync" : "fsync";
printf("Performed %d %s()s in %f seconds.\n", no_of_writes, c, t1 - t0);
double rate = no_of_writes / (t1 - t0);
printf("That's %f calls/second, or %f seconds/call.\n", rate, 1 / rate);
return 0;
}
