diff options
Diffstat (limited to 'client/mtab.c')
| -rw-r--r-- | client/mtab.c | 220 |
1 files changed, 0 insertions, 220 deletions
diff --git a/client/mtab.c b/client/mtab.c deleted file mode 100644 index 70789bcb9d..0000000000 --- a/client/mtab.c +++ /dev/null @@ -1,220 +0,0 @@ -/* - * mtab locking routines for use with mount.cifs and umount.cifs - * Copyright (C) 2008 Jeff Layton (jlayton@samba.org) - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 3 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program. If not, see <http://www.gnu.org/licenses/>. -*/ - -/* - * This code was copied from the util-linux-ng sources and modified: - * - * git://git.kernel.org/pub/scm/utils/util-linux-ng/util-linux-ng.git - * - * ...specifically from mount/fstab.c. That file has no explicit license. The - * "default" license for anything in that tree is apparently GPLv2+, so I - * believe we're OK to copy it here. - * - * Jeff Layton <jlayton@samba.org> - */ - -#include <unistd.h> -#include <errno.h> -#include <stdio.h> -#include <sys/time.h> -#include <sys/stat.h> -#include <time.h> -#include <fcntl.h> -#include <mntent.h> -#include <stdlib.h> -#include <signal.h> -#include "mount.h" - - -/* Updating mtab ----------------------------------------------*/ - -/* Flag for already existing lock file. */ -static int we_created_lockfile = 0; -static int lockfile_fd = -1; - -/* Flag to indicate that signals have been set up. */ -static int signals_have_been_setup = 0; - -static void -handler (int sig) { - exit(EX_USER); -} - -static void -setlkw_timeout (int sig) { - /* nothing, fcntl will fail anyway */ -} - -/* Remove lock file. */ -void -unlock_mtab (void) { - if (we_created_lockfile) { - close(lockfile_fd); - lockfile_fd = -1; - unlink (_PATH_MOUNTED_LOCK); - we_created_lockfile = 0; - } -} - -/* Create the lock file. - The lock file will be removed if we catch a signal or when we exit. */ -/* The old code here used flock on a lock file /etc/mtab~ and deleted - this lock file afterwards. However, as rgooch remarks, that has a - race: a second mount may be waiting on the lock and proceed as - soon as the lock file is deleted by the first mount, and immediately - afterwards a third mount comes, creates a new /etc/mtab~, applies - flock to that, and also proceeds, so that the second and third mount - now both are scribbling in /etc/mtab. - The new code uses a link() instead of a creat(), where we proceed - only if it was us that created the lock, and hence we always have - to delete the lock afterwards. Now the use of flock() is in principle - superfluous, but avoids an arbitrary sleep(). */ - -/* Where does the link point to? Obvious choices are mtab and mtab~~. - HJLu points out that the latter leads to races. Right now we use - mtab~.<pid> instead. Use 20 as upper bound for the length of %d. */ -#define MOUNTLOCK_LINKTARGET _PATH_MOUNTED_LOCK "%d" -#define MOUNTLOCK_LINKTARGET_LTH (sizeof(_PATH_MOUNTED_LOCK)+20) - -/* - * The original mount locking code has used sleep(1) between attempts and - * maximal number of attemps has been 5. - * - * There was very small number of attempts and extremely long waiting (1s) - * that is useless on machines with large number of concurret mount processes. - * - * Now we wait few thousand microseconds between attempts and we have global - * time limit (30s) rather than limit for number of attempts. The advantage - * is that this method also counts time which we spend in fcntl(F_SETLKW) and - * number of attempts is not so much restricted. - * - * -- kzak@redhat.com [2007-Mar-2007] - */ - -/* maximum seconds between first and last attempt */ -#define MOUNTLOCK_MAXTIME 30 - -/* sleep time (in microseconds, max=999999) between attempts */ -#define MOUNTLOCK_WAITTIME 5000 - -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); - - gettimeofday(&maxtime, NULL); - 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? */ - gettimeofday(&now, NULL); - 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. */ - gettimeofday(&now, NULL); - 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; -} - |