+++ /dev/null
-
-/*
- * this code lifted from util-linux-ng, licensed GPLv2+,
- *
- * git://git.kernel.org/pub/scm/utils/util-linux-ng/util-linux-ng.git
- *
- * whoever decided that each special mount program is responsible
- * for updating /etc/mtab should be spanked.
- *
- * <sage@newdream.net>
- */
-#include <unistd.h>
-#include <errno.h>
-#include <fcntl.h>
-#include <signal.h>
-#include <stdio.h>
-#include <string.h>
-#include <sys/stat.h>
-#include <sys/time.h>
-#include <sys/types.h>
-#include <sys/vfs.h>
-#include <time.h>
-#include <mntent.h>
-#include <stdarg.h>
-
-#include "mount/canonicalize.c"
-
-
-/* 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;
-
-/* Ensure that the lock is released if we are interrupted. */
-extern char *strsignal(int sig); /* not always in <string.h> */
-
-static void
-setlkw_timeout (int sig) {
- /* nothing, fcntl will fail anyway */
-}
-
-#define _PATH_MOUNTED "/etc/mtab"
-#define _PATH_MOUNTED_LOCK "/etc/mtab~"
-#define PROC_SUPER_MAGIC 0x9fa0
-
-/* exit status - bits below are ORed */
-#define EX_USAGE 1 /* incorrect invocation or permission */
-#define EX_SYSERR 2 /* out of memory, cannot fork, ... */
-#define EX_SOFTWARE 4 /* internal mount bug or wrong version */
-#define EX_USER 8 /* user interrupt */
-#define EX_FILEIO 16 /* problems writing, locking, ... mtab/fstab */
-#define EX_FAIL 32 /* mount failure */
-#define EX_SOMEOK 64 /* some mount succeeded */
-
-int die(int err, const char *fmt, ...) {
- va_list args;
-
- va_start(args, fmt);
- vfprintf(stderr, fmt, args);
- fprintf(stderr, "\n");
- va_end(args);
-
- exit(err);
-}
-
-static void
-handler (int sig) {
- die(EX_USER, "%s", strsignal(sig));
-}
-
-/* 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
-
-void
-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;
- }
-
- snprintf(linktargetfile, sizeof(linktargetfile), MOUNTLOCK_LINKTARGET,
- getpid ());
-
- i = open (linktargetfile, O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR);
- if (i < 0) {
- int errsv = errno;
- /* linktargetfile does not exist (as a file)
- and we cannot create it. Read-only filesystem?
- Too many files open in the system?
- Filesystem full? */
- die (EX_FILEIO, "can't create lock file %s: %s "
- "(use -n flag to override)",
- linktargetfile, strerror (errsv));
- }
- 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);
- die (EX_FILEIO, "can't link lock file %s: %s "
- "(use -n flag to override)",
- _PATH_MOUNTED_LOCK, strerror (errsv));
- }
-
- lockfile_fd = open (_PATH_MOUNTED_LOCK, O_WRONLY);
-
- if (lockfile_fd < 0) {
- /* Strange... Maybe the file was just deleted? */
- int errsv = errno;
- gettimeofday(&now, NULL);
- if (errno == ENOENT && now.tv_sec < maxtime.tv_sec) {
- we_created_lockfile = 0;
- continue;
- }
- (void) unlink(linktargetfile);
- die (EX_FILEIO, "can't open lock file %s: %s "
- "(use -n flag to override)",
- _PATH_MOUNTED_LOCK, strerror (errsv));
- }
-
- 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 (fcntl (lockfile_fd, F_SETLK, &flock) == -1) {
- /* proceed, since it was us who created the lockfile anyway */
- }
- (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) {
- int errsv = errno;
- (void) unlink(linktargetfile);
- die (EX_FILEIO, "can't lock lock file %s: %s",
- _PATH_MOUNTED_LOCK, (errno == EINTR) ?
- "timed out" : strerror (errsv));
- }
- alarm(0);
-
- nanosleep(&waittime, NULL);
- } else {
- (void) unlink(linktargetfile);
- die (EX_FILEIO, "Cannot create link %s\n"
- "Perhaps there is a stale lock file?\n",
- _PATH_MOUNTED_LOCK);
- }
- close(lockfile_fd);
- }
- }
-}
-
-static void
-update_mtab_entry(const char *spec, const char *node, const char *type,
- const char *opts, int flags, int freq, int pass) {
- struct statfs buf;
- int err = statfs(_PATH_MOUNTED, &buf);
- if (err) {
- printf("mount: can't statfs %s: %s", _PATH_MOUNTED,
- strerror (err));
- return;
- }
- /* /etc/mtab is symbol link to /proc/self/mounts? */
- if (buf.f_type == PROC_SUPER_MAGIC)
- return;
-
- if (!opts)
- opts = "rw";
-
- struct mntent mnt;
- mnt.mnt_fsname = strdup(spec);
- mnt.mnt_dir = canonicalize_path(node);
- mnt.mnt_type = strdup(type);
- mnt.mnt_opts = strdup(opts);
- mnt.mnt_freq = freq;
- mnt.mnt_passno = pass;
-
- FILE *fp;
-
- lock_mtab();
- fp = setmntent(_PATH_MOUNTED, "a+");
- if (fp == NULL) {
- int errsv = errno;
- printf("mount: can't open %s: %s", _PATH_MOUNTED,
- strerror (errsv));
- } else {
- if ((addmntent (fp, &mnt)) == 1) {
- int errsv = errno;
- printf("mount: error writing %s: %s",
- _PATH_MOUNTED, strerror (errsv));
- }
- }
- endmntent(fp);
- unlock_mtab();
-
- free(mnt.mnt_fsname);
- free(mnt.mnt_dir);
- free(mnt.mnt_type);
- free(mnt.mnt_opts);
-}
Code Review / stor4nfv.git / blobdiff