[PATCH 2/2] mount: add --enable-libmount-mount

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This patch allows to link mount.nfs with libmount from util-linux >=
v2.19. The new libmount based code is enabled by CONFIG_LIBMOUNT and
is stored in mount_libmount.c. The old code is not affected by this
change.

The libmount does not have officially stable API yet, so the
--enable-libmount-mount is marked as experimental in the configure
help output.

The ./configure option is the same as we use in util-linux to enable
support for libmount in mount(8).

The addr= (and some other options necessary for remount/umount) are
stored to /etc/mtab or to /dev/.mount/utab. The utab file is *private*
libmount file. It's possible that some mount options (for example
user=) will be moved to kernel, so the utab will not be necessary.

About libmount:

  * supports systems without and with regular /etc/mtab
  * does not store VFS and FS mount options in userspace
  * manages user= option and evaluate permissions
  * parses VFS mount options and generate MS_* flags
  * parses /etc/{fstab,mtab}, /proc/mounts or /proc/self/mountinfo
  * long-term goal is to use the same code in all mount.<type> helpers

Note, use

   LIBMOUNT_DEBUG=0xffff mount.nfs foo:/path /path

to debug the library.

On systems with util-linux v2.19 the findmnt(8) command uses libmount
to list all/selected mount points:

   $ findmnt /path
   $ findmnt --mtab /path

the --mtab appends userspace mount options (e.g. user=) to the output.

CC: Chuck Lever <chuck.lever@xxxxxxxxxx>
CC: Steve Dickson <steved@xxxxxxxxxx>
Signed-off-by: Karel Zak <kzak@xxxxxxxxxx>
---
 configure.ac                 |   16 ++
 utils/mount/Makefile.am      |   13 +-
 utils/mount/mount_libmount.c |  413 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 440 insertions(+), 2 deletions(-)
 create mode 100644 utils/mount/mount_libmount.c

diff --git a/configure.ac b/configure.ac
index 2e074d9..9c384d8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -132,6 +132,15 @@ AC_ARG_ENABLE(mount,
 	enable_mount=$enableval,
 	enable_mount=yes)
 	AM_CONDITIONAL(CONFIG_MOUNT, [test "$enable_mount" = "yes"])
+
+if test "$enable_mount" = yes; then
+	AC_ARG_ENABLE(libmount-mount,
+		[AC_HELP_STRING([--enable-libmount-mount],
+				[Link mount.nfs with libmount (EXPERIMENTAL)])],
+		enable_libmount=yes,
+		enable_libmount=no)
+fi
+
 AC_ARG_ENABLE(tirpc,
 	[AC_HELP_STRING([--enable-tirpc],
 			[enable use of TI-RPC @<:@default=yes@:>@])],
@@ -285,6 +294,13 @@ AC_SUBST(LIBCRYPT)
 AC_SUBST(LIBBSD)
 AC_SUBST(LIBBLKID)
 
+if test "$enable_libmount" != no; then
+   AC_CHECK_LIB(mount, mnt_context_do_mount, [LIBMOUNT="-lmount"], AC_MSG_ERROR([libmount needed]))
+   AC_CHECK_HEADER(libmount/libmount.h, , AC_MSG_ERROR([Cannot find libmount header file libmount/libmount.h]))
+fi
+AM_CONDITIONAL(CONFIG_LIBMOUNT, [test "$enable_libmount" = "yes"])
+AC_SUBST(LIBMOUNT)
+
 if test "$enable_gss" = yes; then
   dnl 'gss' requires getnameinfo - at least for gssd_proc.c
   AC_CHECK_FUNC([getnameinfo], , [AC_MSG_ERROR([GSSAPI support requires 'getnameinfo' function])])
diff --git a/utils/mount/Makefile.am b/utils/mount/Makefile.am
index a9553dc..056293c 100644
--- a/utils/mount/Makefile.am
+++ b/utils/mount/Makefile.am
@@ -9,7 +9,7 @@ man5_MANS	= nfs.man
 
 sbin_PROGRAMS	= mount.nfs
 EXTRA_DIST = nfsmount.x $(man8_MANS) $(man5_MANS)
-mount_nfs_SOURCES = mount.c error.c network.c fstab.c token.c \
+mount_common = error.c network.c fstab.c token.c \
 		    parse_opt.c parse_dev.c \
 		    nfsmount.c nfs4mount.c stropts.c\
 		    nfsumount.c \
@@ -19,7 +19,7 @@ mount_nfs_SOURCES = mount.c error.c network.c fstab.c token.c \
 		    mount_config.h utils.c utils.h
 
 if MOUNT_CONFIG
-mount_nfs_SOURCES += configfile.c
+mount_common += configfile.c
 man5_MANS += nfsmount.conf.man
 EXTRA_DIST += nfsmount.conf
 endif
@@ -27,6 +27,15 @@ endif
 mount_nfs_LDADD = ../../support/nfs/libnfs.a \
 		  ../../support/export/libexport.a
 
+mount_nfs_SOURCES = $(mount_common)
+
+if CONFIG_LIBMOUNT
+mount_nfs_SOURCES += mount_libmount.c
+mount_nfs_LDADD += $(LIBMOUNT)
+else
+mount_nfs_SOURCES += mount.c
+endif
+
 MAINTAINERCLEANFILES = Makefile.in
 
 install-exec-hook:
diff --git a/utils/mount/mount_libmount.c b/utils/mount/mount_libmount.c
new file mode 100644
index 0000000..6dd6484
--- /dev/null
+++ b/utils/mount/mount_libmount.c
@@ -0,0 +1,413 @@
+/*
+ * mount_libmount.c -- Linux NFS [u]mount based on libmount
+ *
+ * Copyright (C) 2011 Karel Zak <kzak@xxxxxxxxxx>
+ *
+ * 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 2, 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, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ *
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <getopt.h>
+
+#include <libmount/libmount.h>
+
+#include "nls.h"
+#include "mount_config.h"
+
+#include "nfs_mount.h"
+#include "nfs4_mount.h"
+#include "stropts.h"
+#include "version.h"
+#include "xcommon.h"
+
+#include "error.h"
+#include "utils.h"
+
+char *progname;
+int nfs_mount_data_version;
+int verbose;
+int sloppy;
+int string;
+int nomtab;
+
+#define FOREGROUND	(0)
+#define BACKGROUND	(1)
+
+/*
+ * Store mount options to mtab (or /dev/.mount/utab), called from mount.nfs.
+ *
+ * Note that on systems without /etc/mtab the fs-specific options are not
+ * managed by libmount at all. We have to use "mount attributes" that are
+ * private for mount.<type> helpers.
+ */
+static void store_mount_options(struct libmnt_fs *fs, const char *opts)
+{
+	mnt_fs_set_fs_options(fs, opts);	/* for mtab */
+	mnt_fs_set_attributes(fs, opts);	/* for non-mtab systems */
+}
+
+/*
+ * Retrieve mount options from mtab (or /dev/.mount/utab) called from umount.nfs.
+ *
+ * The result can passed to free().
+ */
+char *retrieve_mount_options(struct libmnt_fs *fs)
+{
+	const char *opts;
+
+	if (!fs)
+		return NULL;
+
+	opts = mnt_fs_get_attributes(fs);	/* /dev/.mount/utab */
+	if (opts)
+		return strdup(opts);
+
+	return mnt_fs_strdup_options(fs);	/* /etc/mtab */
+}
+
+static int try_mount(struct libmnt_context *cxt, int bg)
+{
+	struct libmnt_fs *fs;
+	const char *p;
+	char *src = NULL, *tgt = NULL, *type = NULL, *opts = NULL;
+	unsigned long flags = 0;
+	int fake, ret = 0;
+
+	fs = mnt_context_get_fs(cxt);
+
+	/* libmount returns read-only pointers (const char)
+	 * so, reallocate for nfsmount() functions.
+	 */
+	if ((p = mnt_fs_get_source(fs)))	/* spec */
+		src = strdup(p);
+	if ((p = mnt_fs_get_target(fs)))	/* mountpoint */
+		tgt = strdup(p);
+	if ((p = mnt_fs_get_fstype(fs)))	/* FS type */
+		type = strdup(p);
+	if ((p = mnt_fs_get_fs_options(fs)))	/* mount options */
+		opts = strdup(p);
+
+	mnt_context_get_mflags(cxt, &flags);	/* mount(2) flags */
+	fake = mnt_context_is_fake(cxt);
+
+	if (string)
+		ret = nfsmount_string(src, tgt, type, flags, &opts, fake, bg);
+
+	else if (strcmp(type, "nfs4") == 0)
+		ret = nfs4mount(src, tgt, flags, &opts, fake, bg);
+	else
+		ret = nfsmount(src, tgt, flags, &opts, fake, bg);
+
+	/* Store mount options if not called with mount --no-mtab */
+	if (!ret && !mnt_context_is_nomtab(cxt))
+		store_mount_options(fs, opts);
+
+	free(src);
+	free(tgt);
+	free(type);
+	free(opts);
+
+	return ret;
+}
+
+/* returns: error = -1, success = 0 , unknown = 1 */
+static int is_vers4(struct libmnt_context *cxt)
+{
+	struct libmnt_fs *fs = mnt_context_get_fs(cxt);
+	struct libmnt_table *tb = NULL;
+	const char *src = mnt_context_get_source(cxt),
+		   *tgt = mnt_context_get_target(cxt);
+	int rc = 1;
+
+	if (!src || !tgt)
+		return -1;
+
+	if (!mnt_fs_is_kernel(fs)) {
+		struct libmnt_table *tb = mnt_new_table_from_file("/proc/mounts");
+
+		if (!tb)
+			return -1;
+		fs = mnt_table_find_pair(tb, src, tgt, MNT_ITER_BACKWARD);
+	}
+
+	if (fs) {
+		const char *type = mnt_fs_get_fstype(fs);
+		if (type && strcmp(type, "nfs4") == 0)
+			rc = 0;
+	}
+	mnt_free_table(tb);
+	return rc;
+}
+
+static int umount_main(struct libmnt_context *cxt, int argc, char **argv)
+{
+	int rc, c;
+	char *spec = NULL, *opts = NULL;
+
+	static const struct option longopts[] = {
+		{ "force", 0, 0, 'f' },
+		{ "help", 0, 0, 'h' },
+		{ "no-mtab", 0, 0, 'n' },
+		{ "verbose", 0, 0, 'v' },
+		{ "read-only", 0, 0, 'r' },
+		{ "lazy", 0, 0, 'l' },
+		{ "types", 1, 0, 't' },
+		{ NULL, 0, 0, 0 }
+	};
+
+	mnt_context_init_helper(cxt, MNT_ACT_UMOUNT, 0);
+
+	while ((c = getopt_long (argc, argv, "fvnrlh", longopts, NULL)) != -1) {
+
+		rc = mnt_context_helper_setopt(cxt, c, optarg);
+		if (rc == 0)		/* valid option */
+			continue;
+		if (rc < 0)		/* error (probably ENOMEM) */
+			goto err;
+					/* rc==1 means unknow option */
+		umount_usage();
+		return EX_USAGE;
+	}
+
+	if (optind < argc)
+		spec = argv[optind++];
+
+	if (!spec || (*spec != '/' && strchr(spec,':') == NULL)) {
+		nfs_error(_("%s: no mount point provided"), progname);
+		return EX_USAGE;
+	}
+
+	if (mnt_context_set_target(cxt, spec))
+		goto err;
+	if (mnt_context_set_fstype_pattern(cxt, "nfs,nfs4"))	/* restrict filesystems */
+		goto err;
+
+	/* read mtab/fstab, evaluate permissions, etc. */
+	rc = mnt_context_prepare_umount(cxt);
+	if (rc) {
+		nfs_error(_("%s: failed to prepare umount: %s\n"),
+					progname, strerror(-rc));
+		goto err;
+	}
+
+	opts = retrieve_mount_options(mnt_context_get_fs(cxt));
+
+	if (!mnt_context_is_lazy(cxt)) {
+		if (opts) {
+			/* we have full FS description (e.g. from mtab or /proc) */
+			switch (is_vers4(cxt)) {
+			case 0:
+				/* We ignore the error from nfs_umount23.
+				 * If the actual umount succeeds (in del_mtab),
+				 * we don't want to signal an error, as that
+				 * could cause /sbin/mount to retry!
+				 */
+				nfs_umount23(mnt_context_get_source(cxt), opts);
+				break;
+			case 1:			/* unknown */
+				break;
+			default:		/* error */
+				goto err;
+			}
+		} else
+			/* strange, no entry in mtab or /proc not mounted */
+			nfs_umount23(spec, "tcp,v3");
+	}
+
+	rc = mnt_context_do_umount(cxt);	/* call umount(2) syscall */
+	mnt_context_finalize_mount(cxt);	/* mtab update */
+
+	if (rc && !mnt_context_get_status(cxt)) {
+		/* mnt_context_do_umount() returns errno if umount(2) failed */
+		umount_error(rc, spec);
+		goto err;
+	}
+
+	free(opts);
+	return EX_SUCCESS;
+err:
+	free(opts);
+	return EX_FAIL;
+}
+
+static int mount_main(struct libmnt_context *cxt, int argc, char **argv)
+{
+	int rc, c;
+	struct libmnt_fs *fs;
+	char *spec = NULL, *mount_point = NULL, *opts = NULL;
+
+	static const struct option longopts[] = {
+	  { "fake", 0, 0, 'f' },
+	  { "help", 0, 0, 'h' },
+	  { "no-mtab", 0, 0, 'n' },
+	  { "read-only", 0, 0, 'r' },
+	  { "ro", 0, 0, 'r' },
+	  { "verbose", 0, 0, 'v' },
+	  { "version", 0, 0, 'V' },
+	  { "read-write", 0, 0, 'w' },
+	  { "rw", 0, 0, 'w' },
+	  { "options", 1, 0, 'o' },
+	  { "sloppy", 0, 0, 's' },
+	  { NULL, 0, 0, 0 }
+	};
+
+	mount_config_init(progname);
+	mnt_context_init_helper(cxt, MNT_ACT_MOUNT, 0);
+
+	while ((c = getopt_long(argc, argv, "fhnrVvwo:s", longopts, NULL)) != -1) {
+
+		rc = mnt_context_helper_setopt(cxt, c, optarg);
+		if (rc == 0)		/* valid option */
+			continue;
+		if (rc < 0)		/* error (probably ENOMEM) */
+			goto err;
+					/* rc==1 means unknow option */
+		switch (c) {
+		case 'V':
+			printf("%s: ("PACKAGE_STRING")\n", progname);
+			return EX_SUCCESS;
+		case 'h':
+		default:
+			mount_usage();
+			return EX_USAGE;
+		}
+	}
+
+	if (optind < argc)
+		spec = argv[optind++];
+	if (optind < argc)
+		mount_point = argv[optind++];
+
+	if (!mount_point) {
+		nfs_error(_("%s: no mount point provided"), progname);
+		goto err;
+	}
+	if (!spec) {
+		nfs_error(_("%s: no mount spec provided"), progname);
+		goto err;
+	}
+
+	if (geteuid() != 0) {
+		nfs_error(_("%s: not installed setuid - "
+			    "\"user\" NFS mounts not supported."), progname);
+		goto err;
+	}
+
+	verbose = mnt_context_is_verbose(cxt);
+	sloppy = mnt_context_is_sloppy(cxt);
+	nomtab = mnt_context_is_nomtab(cxt);
+
+	if (strcmp(progname, "mount.nfs4") == 0)
+		mnt_context_set_fstype(cxt, "nfs4");
+	else
+		mnt_context_set_fstype(cxt, "nfs");	/* default */
+
+	rc = mnt_context_set_source(cxt, spec);
+	if (!rc)
+		mnt_context_set_target(cxt, mount_point);
+	if (rc) {
+		nfs_error(_("%s: failed to set spec or mountpoint: %s"),
+				progname, strerror(errno));
+		goto err;
+	}
+
+	mount_point = mnt_resolve_path(mount_point,
+				       mnt_context_get_cache(cxt));
+
+	if (chk_mountpoint(mount_point))
+		goto err;
+	/*
+	 * Concatenate mount options from the configuration file
+	 */
+	fs = mnt_context_get_fs(cxt);
+	if (fs) {
+		opts = mnt_fs_strdup_options(fs);
+
+		opts = mount_config_opts(spec, mount_point, opts);
+		mnt_fs_set_options(fs, opts);
+	}
+
+	rc = mnt_context_prepare_mount(cxt);
+	if (rc) {
+		nfs_error(_("%s: failed to prepare mount: %s\n"),
+					progname, strerror(-rc));
+		goto err;
+	}
+
+	rc = try_mount(cxt, FOREGROUND);
+
+	if (rc == EX_BG) {
+		printf(_("%s: backgrounding \"%s\"\n"),
+			progname, mnt_context_get_source(cxt));
+		printf(_("%s: mount options: \"%s\"\n"),
+			progname, opts);
+
+		fflush(stdout);
+
+		if (daemon(0, 0)) {
+			nfs_error(_("%s: failed to start "
+					"background process: %s\n"),
+					progname, strerror(errno));
+			exit(EX_FAIL);
+		}
+
+		rc = try_mount(cxt, BACKGROUND);
+
+		if (verbose && rc)
+			printf(_("%s: giving up \"%s\"\n"),
+				progname, mnt_context_get_source(cxt));
+	}
+
+	mnt_context_set_syscall_status(cxt, rc == EX_SUCCESS ? 0 : -1);
+	mnt_context_finalize_mount(cxt);	/* mtab update */
+	return rc;
+err:
+	return EX_FAIL;
+}
+
+int main(int argc, char *argv[])
+{
+	struct libmnt_context *cxt;
+	int rc;
+
+	mnt_init_debug(0);
+	cxt = mnt_new_context();
+	if (!cxt) {
+		nfs_error(_("Can't initilize libmount: %s"),
+					strerror(errno));
+		rc = EX_FAIL;
+		goto done;
+	}
+
+	progname = basename(argv[0]);
+	nfs_mount_data_version = discover_nfs_mount_data_version(&string);
+
+	if(strncmp(progname, "umount", 6) == 0)
+		rc = umount_main(cxt, argc, argv);
+	else
+		rc = mount_main(cxt, argc, argv);
+done:
+	mnt_free_context(cxt);
+	return rc;
+}
-- 
1.7.3.4

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