Adding upstream version 18.2.2.upstream/18.2.2

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 294 insertions, 0 deletions

diff --git a/src/mount/mtab.c b/src/mount/mtab.c
new file mode 100644
index 000000000..3ce368fd3
--- /dev/null
+++ b/src/mount/mtab.c
@@ -0,0 +1,294 @@
+
+/*
+ * 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 attempts 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);
+}