update umount procedure

If umount(8) supports --fake and --no-canonicalize (util-linux-ng
version 2.18 or later), and umount(2) supports the UMOUNT_NOFOLLOW
flag (linux kernel version 2.6.35 or later) then, "fusermount -u" will
call the umount(2) system call and use "umount --fake ..." to update
/etc/mtab

Added --disable-legacy-umount option to configure.  This disables the
runtime checking of umount(8) version.  When built with this option
then "fusermount -u" will fail if umount(8) doesn't support the --fake
and --no-canonicalize options.

2 files changed, 50 insertions, 0 deletions

diff --git a/lib/mount_util.c b/lib/mount_util.c
index 25b7e43..edbba12 100644
--- a/lib/mount_util.c
+++ b/lib/mount_util.c
@@ -262,6 +262,55 @@ int fuse_mnt_umount(const char *progname, const char *abs_mnt,
 	return exec_umount(progname, rel_mnt, lazy);
 }
 
+static int remove_mount(const char *progname, const char *mnt)
+{
+	int res;
+	int status;
+	sigset_t blockmask;
+	sigset_t oldmask;
+
+	sigemptyset(&blockmask);
+	sigaddset(&blockmask, SIGCHLD);
+	res = sigprocmask(SIG_BLOCK, &blockmask, &oldmask);
+	if (res == -1) {
+		fprintf(stderr, "%s: sigprocmask: %s\n", progname, strerror(errno));
+		return -1;
+	}
+
+	res = fork();
+	if (res == -1) {
+		fprintf(stderr, "%s: fork: %s\n", progname, strerror(errno));
+		goto out_restore;
+	}
+	if (res == 0) {
+		sigprocmask(SIG_SETMASK, &oldmask, NULL);
+		setuid(geteuid());
+		execl("/bin/umount", "/bin/umount", "--no-canonicalize", "-i",
+		      "--fake", mnt, NULL);
+		fprintf(stderr, "%s: failed to execute /bin/umount: %s\n",
+			progname, strerror(errno));
+		exit(1);
+	}
+	res = waitpid(res, &status, 0);
+	if (res == -1)
+		fprintf(stderr, "%s: waitpid: %s\n", progname, strerror(errno));
+
+	if (status != 0)
+		res = -1;
+
+ out_restore:
+	sigprocmask(SIG_SETMASK, &oldmask, NULL);
+	return res;
+}
+
+int fuse_mnt_remove_mount(const char *progname, const char *mnt)
+{
+	if (!mtab_needs_update(mnt))
+		return 0;
+
+	return remove_mount(progname, mnt);
+}
+
 char *fuse_mnt_resolve_path(const char *progname, const char *orig)
 {
 	char buf[PATH_MAX];
diff --git a/lib/mount_util.h b/lib/mount_util.h
index f392f99..dc5c916 100644
--- a/lib/mount_util.h
+++ b/lib/mount_util.h
@@ -10,6 +10,7 @@
 
 int fuse_mnt_add_mount(const char *progname, const char *fsname,
 		       const char *mnt, const char *type, const char *opts);
+int fuse_mnt_remove_mount(const char *progname, const char *mnt);
 int fuse_mnt_umount(const char *progname, const char *abs_mnt,
 		    const char *rel_mnt, int lazy);
 char *fuse_mnt_resolve_path(const char *progname, const char *orig);