util-linux/mount.c

/* vi: set sw=4 ts=4: */
/*
 * Mini mount implementation for busybox
 *
 * Copyright (C) 1995, 1996 by Bruce Perens <bruce@pixar.com>.
 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
 * Copyright (C) 2005-2006 by Rob Landley <rob@landley.net>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */
// Design notes: There is no spec for mount.  Remind me to write one.
//
// mount_main() calls singlemount() which calls mount_it_now().
//
// mount_main() can loop through /etc/fstab for mount -a
// singlemount() can loop through /etc/filesystems for fstype detection.
// mount_it_now() does the actual mount.
//

//config:config MOUNT
//config:	bool "mount (23 kb)"
//config:	default y
//config:	help
//config:	All files and filesystems in Unix are arranged into one big directory
//config:	tree. The 'mount' utility is used to graft a filesystem onto a
//config:	particular part of the tree. A filesystem can either live on a block
//config:	device, or it can be accessible over the network, as is the case with
//config:	NFS filesystems.
//config:
//config:config FEATURE_MOUNT_FAKE
//config:	bool "Support -f (fake mount)"
//config:	default y
//config:	depends on MOUNT
//config:	help
//config:	Enable support for faking a file system mount.
//config:
//config:config FEATURE_MOUNT_VERBOSE
//config:	bool "Support -v (verbose)"
//config:	default y
//config:	depends on MOUNT
//config:	help
//config:	Enable multi-level -v[vv...] verbose messages. Useful if you
//config:	debug mount problems and want to see what is exactly passed
//config:	to the kernel.
//config:
//config:config FEATURE_MOUNT_HELPERS
//config:	bool "Support mount helpers"
//config:	default n
//config:	depends on MOUNT
//config:	help
//config:	Enable mounting of virtual file systems via external helpers.
//config:	E.g. "mount obexfs#-b00.11.22.33.44.55 /mnt" will in effect call
//config:	"obexfs -b00.11.22.33.44.55 /mnt"
//config:	Also "mount -t sometype [-o opts] fs /mnt" will try
//config:	"sometype [-o opts] fs /mnt" if simple mount syscall fails.
//config:	The idea is to use such virtual filesystems in /etc/fstab.
//config:
//config:config FEATURE_MOUNT_LABEL
//config:	bool "Support specifying devices by label or UUID"
//config:	default y
//config:	depends on MOUNT
//config:	select VOLUMEID
//config:	help
//config:	This allows for specifying a device by label or uuid, rather than by
//config:	name. This feature utilizes the same functionality as blkid/findfs.
//config:
//config:config FEATURE_MOUNT_NFS
//config:	bool "Support mounting NFS file systems on Linux < 2.6.23"
//config:	default n
//config:	depends on MOUNT
//config:	select FEATURE_SYSLOG
//config:	help
//config:	Enable mounting of NFS file systems on Linux kernels prior
//config:	to version 2.6.23. Note that in this case mounting of NFS
//config:	over IPv6 will not be possible.
//config:
//config:	Note that this option links in RPC support from libc,
//config:	which is rather large (~10 kbytes on uclibc).
//config:
//config:config FEATURE_MOUNT_CIFS
//config:	bool "Support mounting CIFS/SMB file systems"
//config:	default y
//config:	depends on MOUNT
//config:	help
//config:	Enable support for samba mounts.
//config:
//config:config FEATURE_MOUNT_FLAGS
//config:	depends on MOUNT
//config:	bool "Support lots of -o flags"
//config:	default y
//config:	help
//config:	Without this, mount only supports ro/rw/remount. With this, it
//config:	supports nosuid, suid, dev, nodev, exec, noexec, sync, async, atime,
//config:	noatime, diratime, nodiratime, loud, bind, move, shared, slave,
//config:	private, unbindable, rshared, rslave, rprivate, and runbindable.
//config:
//config:config FEATURE_MOUNT_FSTAB
//config:	depends on MOUNT
//config:	bool "Support /etc/fstab and -a (mount all)"
//config:	default y
//config:	help
//config:	Support mount all and looking for files in /etc/fstab.
//config:
//config:config FEATURE_MOUNT_OTHERTAB
//config:	depends on FEATURE_MOUNT_FSTAB
//config:	bool "Support -T <alt_fstab>"
//config:	default y
//config:	help
//config:	Support mount -T (specifying an alternate fstab)

/* On full-blown systems, requires suid for user mounts.
 * But it's not unthinkable to have it available in non-suid flavor on some systems,
 * for viewing mount table.
 * Therefore we use BB_SUID_MAYBE instead of BB_SUID_REQUIRE: */
//applet:IF_MOUNT(APPLET(mount, BB_DIR_BIN, IF_DESKTOP(BB_SUID_MAYBE) IF_NOT_DESKTOP(BB_SUID_DROP)))

//kbuild:lib-$(CONFIG_MOUNT) += mount.o

//usage:#define mount_trivial_usage
//usage:       "[OPTIONS] [-o OPT] DEVICE NODE"
//usage:#define mount_full_usage "\n\n"
//usage:       "Mount a filesystem. Filesystem autodetection requires /proc.\n"
//usage:     "\n	-a		Mount all filesystems in fstab"
//usage:	IF_FEATURE_MOUNT_FAKE(
//usage:	IF_FEATURE_MTAB_SUPPORT(
//usage:     "\n	-f		Update /etc/mtab, but don't mount"
//usage:	)
//usage:	IF_NOT_FEATURE_MTAB_SUPPORT(
//usage:     "\n	-f		Dry run"
//usage:	)
//usage:	)
//usage:	IF_FEATURE_MOUNT_HELPERS(
//usage:     "\n	-i		Don't run mount helper"
//usage:	)
//usage:	IF_FEATURE_MTAB_SUPPORT(
//usage:     "\n	-n		Don't update /etc/mtab"
//usage:	)
//usage:	IF_FEATURE_MOUNT_VERBOSE(
//usage:     "\n	-v		Verbose"
//usage:	)
////usage:   "\n	-s		Sloppy (ignored)"
//usage:     "\n	-r		Read-only mount"
////usage:     "\n	-w		Read-write mount (default)"
//usage:     "\n	-t FSTYPE[,...]	Filesystem type(s)"
//usage:	IF_FEATURE_MOUNT_OTHERTAB(
//usage:     "\n	-T FILE		Read FILE instead of /etc/fstab"
//usage:	)
//usage:     "\n	-O OPT		Mount only filesystems with option OPT (-a only)"
//usage:     "\n-o OPT:"
//usage:	IF_FEATURE_MOUNT_LOOP(
//usage:     "\n	loop		Ignored (loop devices are autodetected)"
//usage:	)
//usage:	IF_FEATURE_MOUNT_FLAGS(
//usage:     "\n	[a]sync		Writes are [a]synchronous"
//usage:     "\n	[no]atime	Disable/enable updates to inode access times"
//usage:     "\n	[no]diratime	Disable/enable atime updates to directories"
//usage:     "\n	[no]relatime	Disable/enable atime updates relative to modification time"
//usage:     "\n	[no]dev		(Dis)allow use of special device files"
//usage:     "\n	[no]exec	(Dis)allow use of executable files"
//usage:     "\n	[no]suid	(Dis)allow set-user-id-root programs"
//usage:     "\n	[r]shared	Convert [recursively] to a shared subtree"
//usage:     "\n	[r]slave	Convert [recursively] to a slave subtree"
//usage:     "\n	[r]private	Convert [recursively] to a private subtree"
//usage:     "\n	[un]bindable	Make mount point [un]able to be bind mounted"
//usage:     "\n	[r]bind		Bind a file or directory [recursively] to another location"
//usage:     "\n	move		Relocate an existing mount point"
//usage:	)
//usage:     "\n	remount		Remount a mounted filesystem, changing flags"
//usage:     "\n	ro		Same as -r"
//usage:     "\n"
//usage:     "\nThere are filesystem-specific -o flags."
//usage:
//usage:#define mount_example_usage
//usage:       "$ mount\n"
//usage:       "/dev/hda3 on / type minix (rw)\n"
//usage:       "proc on /proc type proc (rw)\n"
//usage:       "devpts on /dev/pts type devpts (rw)\n"
//usage:       "$ mount /dev/fd0 /mnt -t msdos -o ro\n"
//usage:       "$ mount /tmp/diskimage /opt -t ext2 -o loop\n"
//usage:       "$ mount cd_image.iso mydir\n"
//usage:#define mount_notes_usage
//usage:       "Returns 0 for success, number of failed mounts for -a, or errno for one mount."

#include <mntent.h>
#if ENABLE_FEATURE_SYSLOG
#include <syslog.h>
#endif
#include <sys/mount.h>
// Grab more as needed from util-linux's mount/mount_constants.h
#ifndef MS_DIRSYNC
# define MS_DIRSYNC     (1 << 7) // Directory modifications are synchronous
#endif
#ifndef MS_NOSYMFOLLOW
# define MS_NOSYMFOLLOW (1 << 8)
#endif
#ifndef MS_BIND
# define MS_BIND        (1 << 12)
#endif
#ifndef MS_MOVE
# define MS_MOVE        (1 << 13)
#endif
#ifndef MS_RECURSIVE
# define MS_RECURSIVE   (1 << 14)
#endif
#ifndef MS_SILENT
# define MS_SILENT      (1 << 15)
#endif
// The shared subtree stuff, which went in around 2.6.15
#ifndef MS_UNBINDABLE
# define MS_UNBINDABLE  (1 << 17)
#endif
#ifndef MS_PRIVATE
# define MS_PRIVATE     (1 << 18)
#endif
#ifndef MS_SLAVE
# define MS_SLAVE       (1 << 19)
#endif
#ifndef MS_SHARED
# define MS_SHARED      (1 << 20)
#endif

#ifndef MS_RELATIME
# define MS_RELATIME    (1 << 21)
#endif
#ifndef MS_STRICTATIME
# define MS_STRICTATIME (1 << 24)
#endif
#ifndef MS_LAZYTIME
# define MS_LAZYTIME    (1 << 25)
#endif

/* Any ~MS_FOO value has this bit set: */
#define BB_MS_INVERTED_VALUE (1u << 31)

#include "libbb.h"
#include "common_bufsiz.h"
#if ENABLE_FEATURE_MOUNT_LABEL
# include "volume_id.h"
#else
# define resolve_mount_spec(fsname) ((void)0)
#endif

// Needed for nfs support only
#include <sys/utsname.h>
#undef TRUE
#undef FALSE
#if ENABLE_FEATURE_MOUNT_NFS
/* This is just a warning of a common mistake.  Possibly this should be a
 * uclibc faq entry rather than in busybox... */
# if defined(__UCLIBC__) && ! defined(__UCLIBC_HAS_RPC__)
#  warning "You probably need to build uClibc with UCLIBC_HAS_RPC for NFS support"
   /* not #error, since user may be using e.g. libtirpc instead.
    * This might work:
    * CONFIG_EXTRA_CFLAGS="-I/usr/include/tirpc"
    * CONFIG_EXTRA_LDLIBS="tirpc"
    */
# endif
# include <rpc/rpc.h>
# include <rpc/pmap_prot.h>
# include <rpc/pmap_clnt.h>
#endif


#if defined(__dietlibc__)
// 16.12.2006, Sampo Kellomaki (sampo@iki.fi)
// dietlibc-0.30 does not have implementation of getmntent_r()
static struct mntent *getmntent_r(FILE* stream, struct mntent* result,
		char* buffer UNUSED_PARAM, int bufsize UNUSED_PARAM)
{
	struct mntent* ment = getmntent(stream);
	return memcpy(result, ment, sizeof(*ment));
}
#endif


// Not real flags, but we want to be able to check for this.
enum {
	MOUNT_USERS  = (1 << 27) * ENABLE_DESKTOP,
	MOUNT_NOFAIL = (1 << 28) * ENABLE_DESKTOP,
	MOUNT_NOAUTO = (1 << 29),
	MOUNT_SWAP   = (1 << 30),
	MOUNT_FAKEFLAGS = MOUNT_USERS | MOUNT_NOFAIL | MOUNT_NOAUTO | MOUNT_SWAP
};


#define OPTION_STR "o:*t:rwanfvsiO:" IF_FEATURE_MOUNT_OTHERTAB("T:")
enum {
	OPT_o = (1 << 0),
	OPT_t = (1 << 1),
	OPT_r = (1 << 2),
	OPT_w = (1 << 3),
	OPT_a = (1 << 4),
	OPT_n = (1 << 5),
	OPT_f = (1 << 6),
	OPT_v = (1 << 7),
	OPT_s = (1 << 8),
	OPT_i = (1 << 9),
	OPT_O = (1 << 10),
	OPT_T = (1 << 11),
};

#if ENABLE_FEATURE_MTAB_SUPPORT
#define USE_MTAB (!(option_mask32 & OPT_n))
#else
#define USE_MTAB 0
#endif

#if ENABLE_FEATURE_MOUNT_FAKE
#define FAKE_IT (option_mask32 & OPT_f)
#else
#define FAKE_IT 0
#endif

#if ENABLE_FEATURE_MOUNT_HELPERS
#define HELPERS_ALLOWED (!(option_mask32 & OPT_i))
#else
#define HELPERS_ALLOWED 0
#endif


// TODO: more "user" flag compatibility.
// "user" option (from mount manpage):
// Only the user that mounted a filesystem can unmount it again.
// If any user should be able to unmount, then use users instead of user
// in the fstab line.  The owner option is similar to the user option,
// with the restriction that the user must be the owner of the special file.
// This may be useful e.g. for /dev/fd if a login script makes
// the console user owner of this device.

// Standard mount options (from -o options or --options),
// with corresponding flags
static const int32_t mount_options[] ALIGN4 = {
	// MS_FLAGS set a bit.  ~MS_FLAGS disable that bit.  0 flags are NOPs.

	IF_FEATURE_MOUNT_LOOP(
		/* "loop" */ 0,
	)

	IF_FEATURE_MOUNT_FSTAB(
		/* "defaults" */ 0,
		/* "quiet" 0 - do not filter out, vfat wants to see it */
		/* "noauto" */ MOUNT_NOAUTO,
		/* "sw"     */ MOUNT_SWAP,
		/* "swap"   */ MOUNT_SWAP,
		IF_DESKTOP(/* "user"  */ MOUNT_USERS,)
		IF_DESKTOP(/* "users" */ MOUNT_USERS,)
		IF_DESKTOP(/* "nofail" */ MOUNT_NOFAIL,)
		/* "_netdev" */ 0,
		IF_DESKTOP(/* "comment=" */ 0,) /* systemd uses this in fstab */
	)

	IF_FEATURE_MOUNT_FLAGS(
		// vfs flags
		/* "nosuid"      */ MS_NOSUID,
		/* "suid"        */ ~MS_NOSUID,
		/* "dev"         */ ~MS_NODEV,
		/* "nodev"       */ MS_NODEV,
		/* "exec"        */ ~MS_NOEXEC,
		/* "noexec"      */ MS_NOEXEC,
		/* "sync"        */ MS_SYNCHRONOUS,
		/* "dirsync"     */ MS_DIRSYNC,
		/* "async"       */ ~MS_SYNCHRONOUS,
		/* "atime"       */ ~MS_NOATIME,
		/* "noatime"     */ MS_NOATIME,
		/* "diratime"    */ ~MS_NODIRATIME,
		/* "nodiratime"  */ MS_NODIRATIME,
		/* "relatime"    */ MS_RELATIME,
		/* "norelatime"  */ ~MS_RELATIME,
		/* "strictatime" */ MS_STRICTATIME,
		/* "nostrictatime"*/ ~MS_STRICTATIME,
		/* "lazytime"    */ MS_LAZYTIME,
		/* "nolazytime"  */ ~MS_LAZYTIME,
		/* "nosymfollow" */ MS_NOSYMFOLLOW,
		/* "mand"        */ MS_MANDLOCK,
		/* "nomand"      */ ~MS_MANDLOCK,
		/* "loud"      	 */ ~MS_SILENT,

		// action flags
		/* "rbind"       */ MS_BIND|MS_RECURSIVE,
		/* "bind"        */ MS_BIND,
		/* "move"        */ MS_MOVE,
		/* "shared"      */ MS_SHARED,
		/* "slave"       */ MS_SLAVE,
		/* "private"     */ MS_PRIVATE,
		/* "unbindable"  */ MS_UNBINDABLE,
		/* "rshared"     */ MS_SHARED|MS_RECURSIVE,
		/* "rslave"      */ MS_SLAVE|MS_RECURSIVE,
		/* "rprivate"    */ MS_PRIVATE|MS_RECURSIVE,
		/* "runbindable" */ MS_UNBINDABLE|MS_RECURSIVE,
	)

	// Always understood.
	/* "ro"      */ MS_RDONLY,  // vfs flag
	/* "rw"      */ ~MS_RDONLY, // vfs flag
	/* "remount" */ MS_REMOUNT  // action flag
};

static const char mount_option_str[] ALIGN1 =
	IF_FEATURE_MOUNT_LOOP(
		"loop\0"
	)
	IF_FEATURE_MOUNT_FSTAB(
		"defaults\0"
		// "quiet\0" - do not filter out, vfat wants to see it
		"noauto\0"
		"sw\0"
		"swap\0"
		IF_DESKTOP("user\0")
		IF_DESKTOP("users\0")
		IF_DESKTOP("nofail\0")
		"_netdev\0"
		IF_DESKTOP("comment=\0") /* systemd uses this in fstab */
	)
	IF_FEATURE_MOUNT_FLAGS(
		// vfs flags
		"nosuid"       "\0"
		"suid"         "\0"
		"dev"          "\0"
		"nodev"        "\0"
		"exec"         "\0"
		"noexec"       "\0"
		"sync"         "\0"
		"dirsync"      "\0"
		"async"        "\0"
		"atime"        "\0"
		"noatime"      "\0"
		"diratime"     "\0"
		"nodiratime"   "\0"
		"relatime"     "\0"
		"norelatime"   "\0"
		"strictatime"  "\0"
		"nostrictatime""\0"
		"lazytime"     "\0"
		"nolazytime"   "\0"
		"nosymfollow"  "\0"
		"mand"         "\0"
		"nomand"       "\0"
		"loud"         "\0"

		// action flags
		"rbind\0"
		"bind\0"
		"move\0"
		"make-shared\0"
		"make-slave\0"
		"make-private\0"
		"make-unbindable\0"
		"make-rshared\0"
		"make-rslave\0"
		"make-rprivate\0"
		"make-runbindable\0"
	)

	// Always understood.
	"ro\0"        // vfs flag
	"rw\0"        // vfs flag
	"remount\0"   // action flag
;


struct globals {
#if ENABLE_FEATURE_MOUNT_NFS
	smalluint nfs_mount_version;
#endif
#if ENABLE_FEATURE_MOUNT_VERBOSE
	unsigned verbose;
#endif
	llist_t *fslist;
	char getmntent_buf[1];
} FIX_ALIASING;
enum { GETMNTENT_BUFSIZE = COMMON_BUFSIZE - offsetof(struct globals, getmntent_buf) };
#define G (*(struct globals*)bb_common_bufsiz1)
#define nfs_mount_version (G.nfs_mount_version)
#if ENABLE_FEATURE_MOUNT_VERBOSE
#define verbose           (G.verbose          )
#else
#define verbose           0
#endif
#define fslist            (G.fslist           )
#define getmntent_buf     (G.getmntent_buf    )
#define INIT_G() do { setup_common_bufsiz(); } while (0)

#if ENABLE_FEATURE_MTAB_SUPPORT
/*
 * update_mtab_entry_on_move() is used to update entry in case of mount --move.
 * we are looking for existing entries mnt_dir which is equal to mnt_fsname of
 * input mntent and replace it by new one.
 */
static void FAST_FUNC update_mtab_entry_on_move(const struct mntent *mp)
{
	struct mntent *entries, *m;
	int i, count;
	FILE *mountTable;

	mountTable = setmntent(bb_path_mtab_file, "r");
	if (!mountTable) {
		bb_simple_perror_msg(bb_path_mtab_file);
		return;
	}

	entries = NULL;
	count = 0;
	while ((m = getmntent(mountTable)) != NULL) {
		entries = xrealloc_vector(entries, 3, count);
		entries[count].mnt_fsname = xstrdup(m->mnt_fsname);
		entries[count].mnt_dir = xstrdup(m->mnt_dir);
		entries[count].mnt_type = xstrdup(m->mnt_type);
		entries[count].mnt_opts = xstrdup(m->mnt_opts);
		entries[count].mnt_freq = m->mnt_freq;
		entries[count].mnt_passno = m->mnt_passno;
		count++;
	}
	endmntent(mountTable);

	mountTable = setmntent(bb_path_mtab_file, "w");
	if (mountTable) {
		for (i = 0; i < count; i++) {
			if (strcmp(entries[i].mnt_dir, mp->mnt_fsname) != 0)
				addmntent(mountTable, &entries[i]);
			else
				addmntent(mountTable, mp);
		}
		endmntent(mountTable);
	} else if (errno != EROFS)
		bb_simple_perror_msg(bb_path_mtab_file);

	if (ENABLE_FEATURE_CLEAN_UP) {
		for (i = 0; i < count; i++) {
			free(entries[i].mnt_fsname);
			free(entries[i].mnt_dir);
			free(entries[i].mnt_type);
			free(entries[i].mnt_opts);
		}
		free(entries);
	}
}
#endif

#if ENABLE_FEATURE_MOUNT_VERBOSE
static int verbose_mount(const char *source, const char *target,
		const char *filesystemtype,
		unsigned long mountflags, const void *data)
{
	int rc;

	errno = 0;
	rc = mount(source, target, filesystemtype, mountflags, data);
	if (verbose >= 2)
		bb_perror_msg("mount('%s','%s','%s',0x%08lx,'%s'):%d",
			source, target, filesystemtype,
			mountflags, (char*)data, rc);
	return rc;
}
#else
#define verbose_mount(...) mount(__VA_ARGS__)
#endif

// Append mount options to string
static void append_mount_options(char **oldopts, const char *newopts)
{
	if (*oldopts && **oldopts) {
		// Do not insert options which are already there
		while (newopts[0]) {
			char *p;
			int len = strlen(newopts);
			p = strchr(newopts, ',');
			if (p) len = p - newopts;
			p = *oldopts;
			while (1) {
				if (!strncmp(p, newopts, len)
				 && (p[len] == ',' || p[len] == '\0'))
					goto skip;
				p = strchr(p,',');
				if (!p) break;
				p++;
			}
			p = xasprintf("%s,%.*s", *oldopts, len, newopts);
			free(*oldopts);
			*oldopts = p;
 skip:
			newopts += len;
			while (newopts[0] == ',') newopts++;
		}
	} else {
		if (ENABLE_FEATURE_CLEAN_UP) free(*oldopts);
		*oldopts = xstrdup(newopts);
	}
}

// Use the mount_options list to parse options into flags.
// Also update list of unrecognized options if unrecognized != NULL
static unsigned long parse_mount_options(char *options, char **unrecognized)
{
	unsigned long flags = MS_SILENT;

	// Loop through options
	for (;;) {
		unsigned i;
		char *comma = strchr(options, ',');
		const char *option_str = mount_option_str;

		if (comma) *comma = '\0';

// FIXME: use hasmntopt()
		// Find this option in mount_options
		for (i = 0; i < ARRAY_SIZE(mount_options); i++) {
			unsigned opt_len = strlen(option_str);

			if (strncasecmp(option_str, options, opt_len) == 0
			 && (options[opt_len] == '\0'
			    /* or is it "comment=" thingy in fstab? */
			    IF_FEATURE_MOUNT_FSTAB(IF_DESKTOP( || option_str[opt_len-1] == '=' ))
			    )
			) {
				unsigned long fl = mount_options[i];
				if (fl & BB_MS_INVERTED_VALUE)
					flags &= fl;
				else
					flags |= fl;
				goto found;
			}
			option_str += opt_len + 1;
		}
		// We did not recognize this option.
		// If "unrecognized" is not NULL, append option there.
		// Note that we should not append *empty* option -
		// in this case we want to pass NULL, not "", to "data"
		// parameter of mount(2) syscall.
		// This is crucial for filesystems that don't accept
		// any arbitrary mount options, like cgroup fs:
		// "mount -t cgroup none /mnt"
		if (options[0] && unrecognized) {
			// Add it to strflags, to pass on to kernel
			char *p = *unrecognized;
			unsigned len = p ? strlen(p) : 0;
			*unrecognized = p = xrealloc(p, len + strlen(options) + 2);

			// Comma separated if it's not the first one
			if (len) p[len++] = ',';
			strcpy(p + len, options);
		}
 found:
		if (!comma)
			break;
		// Advance to next option
		*comma = ',';
		options = ++comma;
	}

	return flags;
}

// Return a list of all block device backed filesystems
static llist_t *get_block_backed_filesystems(void)
{
	static const char filesystems[2][sizeof("/proc/filesystems")] ALIGN1 = {
		"/etc/filesystems",
		"/proc/filesystems",
	};
	char *fs, *buf;
	llist_t *list = NULL;
	int i;
	FILE *f;

	for (i = 0; i < 2; i++) {
		f = fopen_for_read(filesystems[i]);
		if (!f) continue;

		while ((buf = xmalloc_fgetline(f)) != NULL) {
			if (is_prefixed_with(buf, "nodev") && isspace(buf[5]))
				goto next;
			fs = skip_whitespace(buf);
			if (*fs == '#' || *fs == '*' || !*fs)
				goto next;

			llist_add_to_end(&list, xstrdup(fs));
 next:
			free(buf);
		}
		if (ENABLE_FEATURE_CLEAN_UP) fclose(f);
	}

	return list;
}

#if ENABLE_FEATURE_CLEAN_UP
static void delete_block_backed_filesystems(void)
{
	llist_free(fslist, free);
}
#else
void delete_block_backed_filesystems(void);
#endif

// Perform actual mount of specific filesystem at specific location.
// NB: mp->xxx fields may be trashed on exit
static int mount_it_now(struct mntent *mp, unsigned long vfsflags, char *filteropts)
{
	int rc = 0;

	vfsflags &= ~(unsigned long)MOUNT_FAKEFLAGS;

	if (FAKE_IT) {
		if (verbose >= 2)
			bb_error_msg("would do mount('%s','%s','%s',0x%08lx,'%s')",
				mp->mnt_fsname, mp->mnt_dir, mp->mnt_type,
				vfsflags, filteropts);
		goto mtab;
	}

	// Mount, with fallback to read-only if necessary.
	for (;;) {
		errno = 0;
		rc = verbose_mount(mp->mnt_fsname, mp->mnt_dir, mp->mnt_type,
				vfsflags, filteropts);

		// If mount failed, try
		// helper program mount.<mnt_type>
		if (HELPERS_ALLOWED && rc && mp->mnt_type) {
			char *args[8];
			int errno_save = errno;
			args[0] = xasprintf("mount.%s", mp->mnt_type);
			rc = 1;
			if (FAKE_IT)
				args[rc++] = (char *)"-f";
			if (ENABLE_FEATURE_MTAB_SUPPORT && !USE_MTAB)
				args[rc++] = (char *)"-n";
			args[rc++] = mp->mnt_fsname;
			args[rc++] = mp->mnt_dir;
			if (filteropts) {
				args[rc++] = (char *)"-o";
				args[rc++] = filteropts;
			}
			args[rc] = NULL;
			rc = spawn_and_wait(args);
			free(args[0]);
			if (!rc)
				break;
			errno = errno_save;
		}

		if (!rc || (vfsflags & MS_RDONLY) || (errno != EACCES && errno != EROFS))
			break;
		if (!(vfsflags & MS_SILENT))
			bb_error_msg("%s is write-protected, mounting read-only",
						mp->mnt_fsname);
		vfsflags |= MS_RDONLY;
	}

	// Abort entirely if permission denied.

	if (rc && errno == EPERM)
		bb_simple_error_msg_and_die(bb_msg_perm_denied_are_you_root);

	// If the mount was successful, and we're maintaining an old-style
	// mtab file by hand, add the new entry to it now.
 mtab:
	if (USE_MTAB && !rc && !(vfsflags & MS_REMOUNT)) {
		char *fsname;
		FILE *mountTable = setmntent(bb_path_mtab_file, "a+");
		const char *option_str = mount_option_str;
		int i;

		if (!mountTable) {
			bb_simple_perror_msg(bb_path_mtab_file);
			goto ret;
		}

		// Add vfs string flags
		for (i = 0; mount_options[i] != MS_REMOUNT; i++) {
			if (mount_options[i] > 0 && (mount_options[i] & vfsflags))
				append_mount_options(&(mp->mnt_opts), option_str);
			option_str += strlen(option_str) + 1;
		}

		// Remove trailing / (if any) from directory we mounted on
		i = strlen(mp->mnt_dir) - 1;
		while (i > 0 && mp->mnt_dir[i] == '/')
			mp->mnt_dir[i--] = '\0';

		// Convert to canonical pathnames as needed
		mp->mnt_dir = bb_simplify_path(mp->mnt_dir);
		fsname = NULL;
		if (!mp->mnt_type || !*mp->mnt_type) { // bind mount
			mp->mnt_fsname = fsname = bb_simplify_path(mp->mnt_fsname);
			mp->mnt_type = (char*)"bind";
		}
		mp->mnt_freq = mp->mnt_passno = 0;

		// Write and close
#if ENABLE_FEATURE_MTAB_SUPPORT
		if (vfsflags & MS_MOVE)
			update_mtab_entry_on_move(mp);
		else
#endif
			addmntent(mountTable, mp);
		endmntent(mountTable);

		if (ENABLE_FEATURE_CLEAN_UP) {
			free(mp->mnt_dir);
			free(fsname);
		}
	}
 ret:
	return rc;
}

#if ENABLE_FEATURE_MOUNT_NFS

/*
 * Linux NFS mount
 * Copyright (C) 1993 Rick Sladkey <jrs@world.std.com>
 *
 * Licensed under GPLv2, see file LICENSE in this source tree.
 *
 * Wed Feb  8 12:51:48 1995, biro@yggdrasil.com (Ross Biro): allow all port
 * numbers to be specified on the command line.
 *
 * Fri, 8 Mar 1996 18:01:39, Swen Thuemmler <swen@uni-paderborn.de>:
 * Omit the call to connect() for Linux version 1.3.11 or later.
 *
 * Wed Oct  1 23:55:28 1997: Dick Streefland <dick_streefland@tasking.com>
 * Implemented the "bg", "fg" and "retry" mount options for NFS.
 *
 * 1999-02-22 Arkadiusz Mickiewicz <misiek@misiek.eu.org>
 * - added Native Language Support
 *
 * Modified by Olaf Kirch and Trond Myklebust for new NFS code,
 * plus NFSv3 stuff.
 */

#define MOUNTPORT 635
#define MNTPATHLEN 1024
#define MNTNAMLEN 255
#define FHSIZE 32
#define FHSIZE3 64

typedef char fhandle[FHSIZE];

typedef struct {
	unsigned int fhandle3_len;
	char *fhandle3_val;
} fhandle3;

enum mountstat3 {
	MNT_OK = 0,
	MNT3ERR_PERM = 1,
	MNT3ERR_NOENT = 2,
	MNT3ERR_IO = 5,
	MNT3ERR_ACCES = 13,
	MNT3ERR_NOTDIR = 20,
	MNT3ERR_INVAL = 22,
	MNT3ERR_NAMETOOLONG = 63,
	MNT3ERR_NOTSUPP = 10004,
	MNT3ERR_SERVERFAULT = 10006,
};
typedef enum mountstat3 mountstat3;

struct fhstatus {
	unsigned int fhs_status;
	union {
		fhandle fhs_fhandle;
	} fhstatus_u;
};
typedef struct fhstatus fhstatus;

struct mountres3_ok {
	fhandle3 fhandle;
	struct {
		unsigned int auth_flavours_len;
		char *auth_flavours_val;
	} auth_flavours;
};
typedef struct mountres3_ok mountres3_ok;

struct mountres3 {
	mountstat3 fhs_status;
	union {
		mountres3_ok mountinfo;
	} mountres3_u;
};
typedef struct mountres3 mountres3;

typedef char *dirpath;

typedef char *name;

typedef struct mountbody *mountlist;

struct mountbody {
	name ml_hostname;
	dirpath ml_directory;
	mountlist ml_next;
};
typedef struct mountbody mountbody;

typedef struct groupnode *groups;

struct groupnode {
	name gr_name;
	groups gr_next;
};
typedef struct groupnode groupnode;

typedef struct exportnode *exports;

struct exportnode {
	dirpath ex_dir;
	groups ex_groups;
	exports ex_next;
};
typedef struct exportnode exportnode;

struct ppathcnf {
	int pc_link_max;
	short pc_max_canon;
	short pc_max_input;
	short pc_name_max;
	short pc_path_max;
	short pc_pipe_buf;
	uint8_t pc_vdisable;
	char pc_xxx;
	short pc_mask[2];
};
typedef struct ppathcnf ppathcnf;

#define MOUNTPROG 100005
#define MOUNTVERS 1

#define MOUNTPROC_NULL 0
#define MOUNTPROC_MNT 1
#define MOUNTPROC_DUMP 2
#define MOUNTPROC_UMNT 3
#define MOUNTPROC_UMNTALL 4
#define MOUNTPROC_EXPORT 5
#define MOUNTPROC_EXPORTALL 6

#define MOUNTVERS_POSIX 2

#define MOUNTPROC_PATHCONF 7

#define MOUNT_V3 3

#define MOUNTPROC3_NULL 0
#define MOUNTPROC3_MNT 1
#define MOUNTPROC3_DUMP 2
#define MOUNTPROC3_UMNT 3
#define MOUNTPROC3_UMNTALL 4
#define MOUNTPROC3_EXPORT 5

enum {
#ifndef NFS_FHSIZE
	NFS_FHSIZE = 32,
#endif
#ifndef NFS_PORT
	NFS_PORT = 2049
#endif
};

/*
 * We want to be able to compile mount on old kernels in such a way
 * that the binary will work well on more recent kernels.
 * Thus, if necessary we teach nfsmount.c the structure of new fields
 * that will come later.
 *
 * Moreover, the new kernel includes conflict with glibc includes
 * so it is easiest to ignore the kernel altogether (at compile time).
 */

struct nfs2_fh {
	char            data[32];
};
struct nfs3_fh {
	unsigned short  size;
	unsigned char   data[64];
};

struct nfs_mount_data {
	int		version;	/* 1 */
	int		fd;		/* 1 */
	struct nfs2_fh	old_root;	/* 1 */
	int		flags;		/* 1 */
	int		rsize;		/* 1 */
	int		wsize;		/* 1 */
	int		timeo;		/* 1 */
	int		retrans;	/* 1 */
	int		acregmin;	/* 1 */
	int		acregmax;	/* 1 */
	int		acdirmin;	/* 1 */
	int		acdirmax;	/* 1 */
	struct sockaddr_in addr;	/* 1 */
	char		hostname[256];	/* 1 */
	int		namlen;		/* 2 */
	unsigned int	bsize;		/* 3 */
	struct nfs3_fh	root;		/* 4 */
};

/* bits in the flags field */
enum {
	NFS_MOUNT_SOFT = 0x0001,	/* 1 */
	NFS_MOUNT_INTR = 0x0002,	/* 1 */
	NFS_MOUNT_SECURE = 0x0004,	/* 1 */
	NFS_MOUNT_POSIX = 0x0008,	/* 1 */
	NFS_MOUNT_NOCTO = 0x0010,	/* 1 */
	NFS_MOUNT_NOAC = 0x0020,	/* 1 */
	NFS_MOUNT_TCP = 0x0040,		/* 2 */
	NFS_MOUNT_VER3 = 0x0080,	/* 3 */
	NFS_MOUNT_KERBEROS = 0x0100,	/* 3 */
	NFS_MOUNT_NONLM = 0x0200,	/* 3 */
	NFS_MOUNT_NOACL = 0x0800,	/* 4 */
	NFS_MOUNT_NORDIRPLUS = 0x4000
};


/*
 * We need to translate between nfs status return values and
 * the local errno values which may not be the same.
 *
 * Andreas Schwab <schwab@LS5.informatik.uni-dortmund.de>: change errno:
 * "after #include <errno.h> the symbol errno is reserved for any use,
 *  it cannot even be used as a struct tag or field name".
 */
#ifndef EDQUOT
# define EDQUOT ENOSPC
#endif
/* Convert each NFSERR_BLAH into EBLAH */
static const uint8_t nfs_err_stat[] ALIGN1 = {
	 1,  2,  5,  6, 13, 17,
	19, 20, 21, 22, 27, 28,
	30, 63, 66, 69, 70, 71
};
#if ( \
	EPERM | ENOENT      | EIO      | ENXIO | EACCES| EEXIST | \
	ENODEV| ENOTDIR     | EISDIR   | EINVAL| EFBIG | ENOSPC | \
	EROFS | ENAMETOOLONG| ENOTEMPTY| EDQUOT| ESTALE| EREMOTE) < 256
typedef uint8_t nfs_err_type;
#else
typedef uint16_t nfs_err_type;
#endif
static const nfs_err_type nfs_err_errnum[] ALIGN2 = {
	EPERM , ENOENT      , EIO      , ENXIO , EACCES, EEXIST,
	ENODEV, ENOTDIR     , EISDIR   , EINVAL, EFBIG , ENOSPC,
	EROFS , ENAMETOOLONG, ENOTEMPTY, EDQUOT, ESTALE, EREMOTE
};
static char *nfs_strerror(int status)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(nfs_err_stat); i++) {
		if (nfs_err_stat[i] == status)
			return strerror(nfs_err_errnum[i]);
	}
	return xasprintf("unknown nfs status return value: %d", status);
}

static bool_t xdr_fhandle(XDR *xdrs, fhandle objp)
{
	return xdr_opaque(xdrs, objp, FHSIZE);
}

static bool_t xdr_fhstatus(XDR *xdrs, fhstatus *objp)
{
	if (!xdr_u_int(xdrs, &objp->fhs_status))
		return FALSE;
	if (objp->fhs_status == 0)
		return xdr_fhandle(xdrs, objp->fhstatus_u.fhs_fhandle);
	return TRUE;
}

static bool_t xdr_dirpath(XDR *xdrs, dirpath *objp)
{
	return xdr_string(xdrs, objp, MNTPATHLEN);
}

static bool_t xdr_fhandle3(XDR *xdrs, fhandle3 *objp)
{
	return xdr_bytes(xdrs, (char **)&objp->fhandle3_val,
			(unsigned int *) &objp->fhandle3_len,
			FHSIZE3);
}

static bool_t xdr_mountres3_ok(XDR *xdrs, mountres3_ok *objp)
{
	if (!xdr_fhandle3(xdrs, &objp->fhandle))
		return FALSE;
	return xdr_array(xdrs, &(objp->auth_flavours.auth_flavours_val),
			&(objp->auth_flavours.auth_flavours_len),
			~0,
			sizeof(int),
			(xdrproc_t) xdr_int);
}

static bool_t xdr_mountstat3(XDR *xdrs, mountstat3 *objp)
{
	return xdr_enum(xdrs, (enum_t *) objp);
}

static bool_t xdr_mountres3(XDR *xdrs, mountres3 *objp)
{
	if (!xdr_mountstat3(xdrs, &objp->fhs_status))
		return FALSE;
	if (objp->fhs_status == MNT_OK)
		return xdr_mountres3_ok(xdrs, &objp->mountres3_u.mountinfo);
	return TRUE;
}

#define MAX_NFSPROT ((nfs_mount_version >= 4) ? 3 : 2)

/*
 * Unfortunately, the kernel prints annoying console messages
 * in case of an unexpected nfs mount version (instead of
 * just returning some error).  Therefore we'll have to try
 * and figure out what version the kernel expects.
 *
 * Variables:
 *	KERNEL_NFS_MOUNT_VERSION: kernel sources at compile time
 *	NFS_MOUNT_VERSION: these nfsmount sources at compile time
 *	nfs_mount_version: version this source and running kernel can handle
 */
static void
find_kernel_nfs_mount_version(void)
{
	int kernel_version;

	if (nfs_mount_version)
		return;

	nfs_mount_version = 4; /* default */

	kernel_version = get_linux_version_code();
	if (kernel_version) {
		if (kernel_version < KERNEL_VERSION(2,2,18))
			nfs_mount_version = 3;
		/* else v4 since 2.3.99pre4 */
	}
}

static void
get_mountport(struct pmap *pm_mnt,
	struct sockaddr_in *server_addr,
	long unsigned prog,
	long unsigned version,
	long unsigned proto,
	long unsigned port)
{
	struct pmaplist *pmap;

	server_addr->sin_port = PMAPPORT;
/* glibc 2.4 (still) has pmap_getmaps(struct sockaddr_in *).
 * I understand it like "IPv6 for this is not 100% ready" */
	pmap = pmap_getmaps(server_addr);

	if (version > MAX_NFSPROT)
		version = MAX_NFSPROT;
	if (!prog)
		prog = MOUNTPROG;
	pm_mnt->pm_prog = prog;
	pm_mnt->pm_vers = version;
	pm_mnt->pm_prot = proto;
	pm_mnt->pm_port = port;

	while (pmap) {
		if (pmap->pml_map.pm_prog != prog)
			goto next;
		if (!version && pm_mnt->pm_vers > pmap->pml_map.pm_vers)
			goto next;
		if (version > 2 && pmap->pml_map.pm_vers != version)
			goto next;
		if (version && version <= 2 && pmap->pml_map.pm_vers > 2)
			goto next;
		if (pmap->pml_map.pm_vers > MAX_NFSPROT
		 || (proto && pm_mnt->pm_prot && pmap->pml_map.pm_prot != proto)
		 || (port && pmap->pml_map.pm_port != port)
		) {
			goto next;
		}
		memcpy(pm_mnt, &pmap->pml_map, sizeof(*pm_mnt));
 next:
		pmap = pmap->pml_next;
	}
	if (!pm_mnt->pm_vers)
		pm_mnt->pm_vers = MOUNTVERS;
	if (!pm_mnt->pm_port)
		pm_mnt->pm_port = MOUNTPORT;
	if (!pm_mnt->pm_prot)
		pm_mnt->pm_prot = IPPROTO_TCP;
}

#if BB_MMU
static int daemonize(void)
{
	int pid = fork();
	if (pid < 0) /* error */
		return -errno;
	if (pid > 0) /* parent */
		return 0;
	/* child */
	close(0);
	xopen(bb_dev_null, O_RDWR);
	xdup2(0, 1);
	xdup2(0, 2);
	setsid();
	openlog(applet_name, LOG_PID, LOG_DAEMON);
	logmode = LOGMODE_SYSLOG;
	return 1;
}
#else
static inline int daemonize(void)
{
	return -ENOSYS;
}
#endif

/* TODO */
static inline int we_saw_this_host_before(const char *hostname UNUSED_PARAM)
{
	return 0;
}

/* RPC strerror analogs are terminally idiotic:
 * *mandatory* prefix and \n at end.
 * This hopefully helps. Usage:
 * error_msg_rpc(clnt_*error*(" ")) */
static void error_msg_rpc(const char *msg)
{
	int len;
	while (msg[0] == ' ' || msg[0] == ':') msg++;
	len = strlen(msg);
	while (len && msg[len-1] == '\n') len--;
	bb_error_msg("%.*s", len, msg);
}

/* NB: mp->xxx fields may be trashed on exit */
static NOINLINE int nfsmount(struct mntent *mp, unsigned long vfsflags, char *filteropts)
{
	CLIENT *mclient;
	char *hostname;
	char *pathname;
	char *mounthost;
	/* prior to 2.6.23, kernel took NFS options in a form of this struct
	 * only. 2.6.23+ looks at data->version, and if it's not 1..6,
	 * then data pointer is interpreted as a string. */
	struct nfs_mount_data data;
	char *opt;
	char *tokstate;
	struct hostent *hp;
	struct sockaddr_in server_addr;
	struct sockaddr_in mount_server_addr;
	int msock, fsock;
	union {
		struct fhstatus nfsv2;
		struct mountres3 nfsv3;
	} status;
	int daemonized;
	char *s;
	int port;
	int mountport;
	int proto;
#if BB_MMU
	smallint bg = 0;
#else
	enum { bg = 0 };
#endif
	int retry;
	int mountprog;
	int mountvers;
	int nfsprog;
	int nfsvers;
	int retval;
	/* these all are one-bit really. gcc 4.3.1 likes this combination: */
	smallint tcp;
	smallint soft;
	int intr;
	int posix;
	int nocto;
	int noac;
	int nordirplus;
	int nolock;
	int noacl;

	find_kernel_nfs_mount_version();

	daemonized = 0;
	mounthost = NULL;
	retval = ETIMEDOUT;
	msock = fsock = -1;
	mclient = NULL;

	/* NB: hostname, mounthost, filteropts must be free()d prior to return */

	filteropts = xstrdup(filteropts); /* going to trash it later... */

	hostname = xstrdup(mp->mnt_fsname);
	/* mount_main() guarantees that ':' is there */
	s = strchr(hostname, ':');
	pathname = s + 1;
	*s = '\0';
	/* Ignore all but first hostname in replicated mounts
	 * until they can be fully supported. (mack@sgi.com) */
	s = strchr(hostname, ',');
	if (s) {
		*s = '\0';
		bb_simple_error_msg("warning: multiple hostnames not supported");
	}

	server_addr.sin_family = AF_INET;
	if (!inet_aton(hostname, &server_addr.sin_addr)) {
		hp = gethostbyname(hostname);
		if (hp == NULL) {
			bb_simple_herror_msg(hostname);
			goto fail;
		}
		if (hp->h_length != (int)sizeof(struct in_addr)) {
			bb_simple_error_msg_and_die("only IPv4 is supported");
		}
		memcpy(&server_addr.sin_addr, hp->h_addr_list[0], sizeof(struct in_addr));
	}

	memcpy(&mount_server_addr, &server_addr, sizeof(mount_server_addr));

	/* add IP address to mtab options for use when unmounting */

	if (!mp->mnt_opts) { /* TODO: actually mp->mnt_opts is never NULL */
		mp->mnt_opts = xasprintf("addr=%s", inet_ntoa(server_addr.sin_addr));
	} else {
		char *tmp = xasprintf("%s%saddr=%s", mp->mnt_opts,
					mp->mnt_opts[0] ? "," : "",
					inet_ntoa(server_addr.sin_addr));
		free(mp->mnt_opts);
		mp->mnt_opts = tmp;
	}

	/* Set default options.
	 * rsize/wsize (and bsize, for ver >= 3) are left 0 in order to
	 * let the kernel decide.
	 * timeo is filled in after we know whether it'll be TCP or UDP. */
	memset(&data, 0, sizeof(data));
	data.retrans  = 3;
	data.acregmin = 3;
	data.acregmax = 60;
	data.acdirmin = 30;
	data.acdirmax = 60;
	data.namlen   = NAME_MAX;

	soft = 0;
	intr = 0;
	posix = 0;
	nocto = 0;
	nolock = 0;
	noac = 0;
	nordirplus = 0;
	noacl = 0;
	retry = 10000;		/* 10000 minutes ~ 1 week */
	tcp = 1;			/* nfs-utils uses tcp per default */

	mountprog = MOUNTPROG;
	mountvers = 0;
	port = 0;
	mountport = 0;
	nfsprog = 100003;
	nfsvers = 0;

	/* parse options */
	if (filteropts)	for (opt = strtok_r(filteropts, ",", &tokstate); opt; opt = strtok_r(NULL, ",", &tokstate)) {
		char *opteq = strchr(opt, '=');
		if (opteq) {
			int val, idx;
			static const char options[] ALIGN1 =
				/* 0 */ "rsize\0"
				/* 1 */ "wsize\0"
				/* 2 */ "timeo\0"
				/* 3 */ "retrans\0"
				/* 4 */ "acregmin\0"
				/* 5 */ "acregmax\0"
				/* 6 */ "acdirmin\0"
				/* 7 */ "acdirmax\0"
				/* 8 */ "actimeo\0"
				/* 9 */ "retry\0"
				/* 10 */ "port\0"
				/* 11 */ "mountport\0"
				/* 12 */ "mounthost\0"
				/* 13 */ "mountprog\0"
				/* 14 */ "mountvers\0"
				/* 15 */ "nfsprog\0"
				/* 16 */ "nfsvers\0"
				/* 17 */ "vers\0"
				/* 18 */ "proto\0"
				/* 19 */ "namlen\0"
				/* 20 */ "addr\0";

			*opteq++ = '\0';
			idx = index_in_strings(options, opt);
			switch (idx) {
			case 12: // "mounthost"
				mounthost = xstrndup(opteq,
						strcspn(opteq, " \t\n\r,"));
				continue;
			case 18: // "proto"
				if (is_prefixed_with(opteq, "tcp"))
					tcp = 1;
				else if (is_prefixed_with(opteq, "udp"))
					tcp = 0;
				else
					bb_simple_error_msg("warning: unrecognized proto= option");
				continue;
			case 20: // "addr" - ignore
				continue;
			case -1: // unknown
				if (vfsflags & MS_REMOUNT)
					continue;
			}

			val = xatoi_positive(opteq);
			switch (idx) {
			case 0: // "rsize"
				data.rsize = val;
				continue;
			case 1: // "wsize"
				data.wsize = val;
				continue;
			case 2: // "timeo"
				data.timeo = val;
				continue;
			case 3: // "retrans"
				data.retrans = val;
				continue;
			case 4: // "acregmin"
				data.acregmin = val;
				continue;
			case 5: // "acregmax"
				data.acregmax = val;
				continue;
			case 6: // "acdirmin"
				data.acdirmin = val;
				continue;
			case 7: // "acdirmax"
				data.acdirmax = val;
				continue;
			case 8: // "actimeo"
				data.acregmin = val;
				data.acregmax = val;
				data.acdirmin = val;
				data.acdirmax = val;
				continue;
			case 9: // "retry"
				retry = val;
				continue;
			case 10: // "port"
				port = val;
				continue;
			case 11: // "mountport"
				mountport = val;
				continue;
			case 13: // "mountprog"
				mountprog = val;
				continue;
			case 14: // "mountvers"
				mountvers = val;
				continue;
			case 15: // "nfsprog"
				nfsprog = val;
				continue;
			case 16: // "nfsvers"
			case 17: // "vers"
				nfsvers = val;
				continue;
			case 19: // "namlen"
				//if (nfs_mount_version >= 2)
					data.namlen = val;
				//else
				//	bb_error_msg("warning: option namlen is not supported\n");
				continue;
			default:
				bb_error_msg("unknown nfs mount parameter: %s=%d", opt, val);
				goto fail;
			}
		}
		else { /* not of the form opt=val */
			static const char options[] ALIGN1 =
				"bg\0"
				"fg\0"
				"soft\0"
				"hard\0"
				"intr\0"
				"posix\0"
				"cto\0"
				"ac\0"
				"tcp\0"
				"udp\0"
				"lock\0"
				"rdirplus\0"
				"acl\0";
			int val = 1;
			if (is_prefixed_with(opt, "no")) {
				val = 0;
				opt += 2;
			}
			switch (index_in_strings(options, opt)) {
			case 0: // "bg"
#if BB_MMU
				bg = val;
#endif
				break;
			case 1: // "fg"
#if BB_MMU
				bg = !val;
#endif
				break;
			case 2: // "soft"
				soft = val;
				break;
			case 3: // "hard"
				soft = !val;
				break;
			case 4: // "intr"
				intr = val;
				break;
			case 5: // "posix"
				posix = val;
				break;
			case 6: // "cto"
				nocto = !val;
				break;
			case 7: // "ac"
				noac = !val;
				break;
			case 8: // "tcp"
				tcp = val;
				break;
			case 9: // "udp"
				tcp = !val;
				break;
			case 10: // "lock"
				if (nfs_mount_version >= 3)
					nolock = !val;
				else
					bb_simple_error_msg("warning: option nolock is not supported");
				break;
			case 11: //rdirplus
				nordirplus = !val;
				break;
			case 12: // acl
				noacl = !val;
				break;
			default:
				bb_error_msg("unknown nfs mount option: %s%s", val ? "" : "no", opt);
				goto fail;
			}
		}
	}
	proto = (tcp) ? IPPROTO_TCP : IPPROTO_UDP;

	data.flags = (soft ? NFS_MOUNT_SOFT : 0)
		| (intr ? NFS_MOUNT_INTR : 0)
		| (posix ? NFS_MOUNT_POSIX : 0)
		| (nocto ? NFS_MOUNT_NOCTO : 0)
		| (noac ? NFS_MOUNT_NOAC : 0)
		| (nordirplus ? NFS_MOUNT_NORDIRPLUS : 0)
		| (noacl ? NFS_MOUNT_NOACL : 0);
	if (nfs_mount_version >= 2)
		data.flags |= (tcp ? NFS_MOUNT_TCP : 0);
	if (nfs_mount_version >= 3)
		data.flags |= (nolock ? NFS_MOUNT_NONLM : 0);
	if (nfsvers > MAX_NFSPROT || mountvers > MAX_NFSPROT) {
		bb_error_msg("NFSv%d not supported", nfsvers);
		goto fail;
	}
	if (nfsvers && !mountvers)
		mountvers = (nfsvers < 3) ? 1 : nfsvers;
	if (nfsvers && nfsvers < mountvers) {
		mountvers = nfsvers;
	}

	/* Adjust options if none specified */
	if (!data.timeo)
		data.timeo = tcp ? 70 : 7;

	data.version = nfs_mount_version;

	if (vfsflags & MS_REMOUNT)
		goto do_mount;

	/*
	 * If the previous mount operation on the same host was
	 * backgrounded, and the "bg" for this mount is also set,
	 * give up immediately, to avoid the initial timeout.
	 */
	if (bg && we_saw_this_host_before(hostname)) {
		daemonized = daemonize();
		if (daemonized <= 0) { /* parent or error */
			retval = -daemonized;
			goto ret;
		}
	}

	/* Create mount daemon client */
	/* See if the nfs host = mount host. */
	if (mounthost) {
		if (mounthost[0] >= '0' && mounthost[0] <= '9') {
			mount_server_addr.sin_family = AF_INET;
			mount_server_addr.sin_addr.s_addr = inet_addr(hostname);
		} else {
			hp = gethostbyname(mounthost);
			if (hp == NULL) {
				bb_simple_herror_msg(mounthost);
				goto fail;
			}
			if (hp->h_length != (int)sizeof(struct in_addr)) {
				bb_simple_error_msg_and_die("only IPv4 is supported");
			}
			mount_server_addr.sin_family = AF_INET;
			memcpy(&mount_server_addr.sin_addr, hp->h_addr_list[0], sizeof(struct in_addr));
		}
	}

	/*
	 * The following loop implements the mount retries. When the mount
	 * times out, and the "bg" option is set, we background ourself
	 * and continue trying.
	 *
	 * The case where the mount point is not present and the "bg"
	 * option is set, is treated as a timeout. This is done to
	 * support nested mounts.
	 *
	 * The "retry" count specified by the user is the number of
	 * minutes to retry before giving up.
	 */
	{
		struct timeval total_timeout;
		struct timeval retry_timeout;
		struct pmap pm_mnt;
		time_t t;
		time_t prevt;
		time_t timeout;

		retry_timeout.tv_sec = 3;
		retry_timeout.tv_usec = 0;
		total_timeout.tv_sec = 20;
		total_timeout.tv_usec = 0;
/* FIXME: use monotonic()? */
		timeout = time(NULL) + 60 * retry;
		prevt = 0;
		t = 30;
 retry:
		/* Be careful not to use too many CPU cycles */
		if (t - prevt < 30)
			sleep(30);

		get_mountport(&pm_mnt, &mount_server_addr,
				mountprog,
				mountvers,
				proto,
				mountport);
		nfsvers = (pm_mnt.pm_vers < 2) ? 2 : pm_mnt.pm_vers;

		/* contact the mount daemon via TCP */
		mount_server_addr.sin_port = htons(pm_mnt.pm_port);
		msock = RPC_ANYSOCK;

		switch (pm_mnt.pm_prot) {
		case IPPROTO_UDP:
			mclient = clntudp_create(&mount_server_addr,
						pm_mnt.pm_prog,
						pm_mnt.pm_vers,
						retry_timeout,
						&msock);
			if (mclient)
				break;
			mount_server_addr.sin_port = htons(pm_mnt.pm_port);
			msock = RPC_ANYSOCK;
		case IPPROTO_TCP:
			mclient = clnttcp_create(&mount_server_addr,
						pm_mnt.pm_prog,
						pm_mnt.pm_vers,
						&msock, 0, 0);
			break;
		default:
			mclient = NULL;
		}
		if (!mclient) {
			if (!daemonized && prevt == 0)
				error_msg_rpc(clnt_spcreateerror(" "));
		} else {
			enum clnt_stat clnt_stat;

			/* Try to mount hostname:pathname */
			mclient->cl_auth = authunix_create_default();

			/* Make pointers in xdr_mountres3 NULL so
			 * that xdr_array allocates memory for us
			 */
			memset(&status, 0, sizeof(status));

			if (pm_mnt.pm_vers == 3)
				clnt_stat = clnt_call(mclient, MOUNTPROC3_MNT,
						(xdrproc_t) xdr_dirpath,
						(caddr_t) &pathname,
						(xdrproc_t) xdr_mountres3,
						(caddr_t) &status,
						total_timeout);
			else
				clnt_stat = clnt_call(mclient, MOUNTPROC_MNT,
						(xdrproc_t) xdr_dirpath,
						(caddr_t) &pathname,
						(xdrproc_t) xdr_fhstatus,
						(caddr_t) &status,
						total_timeout);

			if (clnt_stat == RPC_SUCCESS)
				goto prepare_kernel_data; /* we're done */
			if (errno != ECONNREFUSED) {
				error_msg_rpc(clnt_sperror(mclient, " "));
				goto fail;	/* don't retry */
			}
			/* Connection refused */
			if (!daemonized && prevt == 0) /* print just once */
				error_msg_rpc(clnt_sperror(mclient, " "));
			auth_destroy(mclient->cl_auth);
			clnt_destroy(mclient);
			mclient = NULL;
			close(msock);
			msock = -1;
		}

		/* Timeout. We are going to retry... maybe */
		if (!bg)
			goto fail;
		if (!daemonized) {
			daemonized = daemonize();
			if (daemonized <= 0) { /* parent or error */
				retval = -daemonized;
				goto ret;
			}
		}
		prevt = t;
		t = time(NULL);
		if (t >= timeout)
			/* TODO error message */
			goto fail;

		goto retry;
	}

 prepare_kernel_data:

	if (nfsvers == 2) {
		if (status.nfsv2.fhs_status != 0) {
			bb_error_msg("%s:%s failed, reason given by server: %s",
				hostname, pathname,
				nfs_strerror(status.nfsv2.fhs_status));
			goto fail;
		}
		memcpy(data.root.data,
				(char *) status.nfsv2.fhstatus_u.fhs_fhandle,
				NFS_FHSIZE);
		data.root.size = NFS_FHSIZE;
		memcpy(data.old_root.data,
				(char *) status.nfsv2.fhstatus_u.fhs_fhandle,
				NFS_FHSIZE);
	} else {
		fhandle3 *my_fhandle;
		if (status.nfsv3.fhs_status != 0) {
			bb_error_msg("%s:%s failed, reason given by server: %s",
				hostname, pathname,
				nfs_strerror(status.nfsv3.fhs_status));
			goto fail;
		}
		my_fhandle = &status.nfsv3.mountres3_u.mountinfo.fhandle;
		memset(data.old_root.data, 0, NFS_FHSIZE);
		memset(&data.root, 0, sizeof(data.root));
		data.root.size = my_fhandle->fhandle3_len;
		memcpy(data.root.data,
				(char *) my_fhandle->fhandle3_val,
				my_fhandle->fhandle3_len);

		data.flags |= NFS_MOUNT_VER3;
	}

	/* Create nfs socket for kernel */
	if (tcp) {
		if (nfs_mount_version < 3) {
			bb_simple_error_msg("NFS over TCP is not supported");
			goto fail;
		}
		fsock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	} else
		fsock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if (fsock < 0) {
		bb_simple_perror_msg("nfs socket");
		goto fail;
	}
	if (bindresvport(fsock, 0) < 0) {
		bb_simple_perror_msg("nfs bindresvport");
		goto fail;
	}
	if (port == 0) {
		server_addr.sin_port = PMAPPORT;
		port = pmap_getport(&server_addr, nfsprog, nfsvers,
					tcp ? IPPROTO_TCP : IPPROTO_UDP);
		if (port == 0)
			port = NFS_PORT;
	}
	server_addr.sin_port = htons(port);

	/* Prepare data structure for kernel */
	data.fd = fsock;
	memcpy((char *) &data.addr, (char *) &server_addr, sizeof(data.addr));
	strncpy(data.hostname, hostname, sizeof(data.hostname));

	/* Clean up */
	auth_destroy(mclient->cl_auth);
	clnt_destroy(mclient);
	close(msock);
	msock = -1;

	if (bg) {
		/* We must wait until mount directory is available */
		struct stat statbuf;
		int delay = 1;
		while (stat(mp->mnt_dir, &statbuf) == -1) {
			if (!daemonized) {
				daemonized = daemonize();
				if (daemonized <= 0) { /* parent or error */
/* FIXME: parent doesn't close fsock - ??! */
					retval = -daemonized;
					goto ret;
				}
			}
			sleep(delay);	/* 1, 2, 4, 8, 16, 30, ... */
			delay *= 2;
			if (delay > 30)
				delay = 30;
		}
	}

	/* Perform actual mount */
 do_mount:
	retval = mount_it_now(mp, vfsflags, (char*)&data);
	goto ret;

	/* Abort */
 fail:
	if (msock >= 0) {
		if (mclient) {
			auth_destroy(mclient->cl_auth);
			clnt_destroy(mclient);
		}
		close(msock);
	}
	if (fsock >= 0)
		close(fsock);

 ret:
	free(hostname);
	free(mounthost);
	free(filteropts);
	return retval;
}

#else // !ENABLE_FEATURE_MOUNT_NFS

/* Linux 2.6.23+ supports nfs mounts with options passed as a string.
 * For older kernels, you must build busybox with ENABLE_FEATURE_MOUNT_NFS.
 * (However, note that then you lose any chances that NFS over IPv6 would work).
 */
static int nfsmount(struct mntent *mp, unsigned long vfsflags, char *filteropts)
{
	len_and_sockaddr *lsa;
	char *opts;
	char *end;
	char *dotted;
	int ret;

# if ENABLE_FEATURE_IPV6
	end = strchr(mp->mnt_fsname, ']');
	if (end && end[1] == ':')
		end++;
	else
# endif
		/* mount_main() guarantees that ':' is there */
		end = strchr(mp->mnt_fsname, ':');

	*end = '\0';
	lsa = xhost2sockaddr(mp->mnt_fsname, /*port:*/ 0);
	*end = ':';
	dotted = xmalloc_sockaddr2dotted_noport(&lsa->u.sa);
	if (ENABLE_FEATURE_CLEAN_UP) free(lsa);
	opts = xasprintf("%s%saddr=%s",
		filteropts ? filteropts : "",
		filteropts ? "," : "",
		dotted
	);
	if (ENABLE_FEATURE_CLEAN_UP) free(dotted);
	ret = mount_it_now(mp, vfsflags, opts);
	if (ENABLE_FEATURE_CLEAN_UP) free(opts);

	return ret;
}

#endif // !ENABLE_FEATURE_MOUNT_NFS

// Find "...,NAME=NUM,..." in the option string, remove "NAME=NUM" option
// and return NUM.
// Return 0 if not found.
// All instances must be parsed and removed (for example, since kernel 5.4
//      squashfs: Unknown parameter 'sizelimit'
// will result if loopback mount option "sizelimit=NNN" is not removed
// and squashfs sees it in option string).
static unsigned long long cut_out_ull_opt(char *opts, const char *name_eq)
{
	unsigned long long ret = 0;

	if (!opts) // allow NULL opts (simplifies callers' work)
		return ret;

	for (;;) {
		char *end;
		char *opt;

		// Find comma-delimited "NAME="
		for (;;) {
			opt = strstr(opts, name_eq);
			if (!opt)
				return ret;
			if (opt == opts)
				break; // found it (it's first opt)
			if (opt[-1] == ',') {
				opts = opt - 1;
				break; // found it (it's not a first opt)
			}
			// False positive like "VNAME=", we are at "N".
			// - skip it, loop back to searching
			opts = opt + 1;
		}

		ret = bb_strtoull(opt + strlen(name_eq), &end, 0);
		if (errno && errno != EINVAL) {
 err:
			bb_error_msg_and_die("bad option '%s'", opt);
		}
		if (*end == '\0') {
			// It is "[,]NAME=NUM\0" - truncate it and return
			*opts = '\0';
			return ret;
		}
		if (*end != ',')
			goto err;
		// We are at trailing comma
		// Remove "NAME=NUM," and loop back to check for duplicate opts
		overlapping_strcpy(opt, end + 1);
	}
}

// Mount one directory.  Handles CIFS, NFS, loopback, autobind, and filesystem
// type detection.  Returns 0 for success, nonzero for failure.
// NB: mp->xxx fields may be trashed on exit
static int singlemount(struct mntent *mp, int ignore_busy)
{
	int loopfd = -1;
	int rc = -1;
	unsigned long vfsflags;
	char *loopFile = NULL, *filteropts = NULL;
	llist_t *fl = NULL;
	struct stat st;

	errno = 0;

	vfsflags = parse_mount_options(mp->mnt_opts, &filteropts);

	// Treat fstype "auto" as unspecified
	if (mp->mnt_type && strcmp(mp->mnt_type, "auto") == 0)
		mp->mnt_type = NULL;

	// Might this be a virtual filesystem?
	if (ENABLE_FEATURE_MOUNT_HELPERS && strchr(mp->mnt_fsname, '#')) {
		char *args[35];
		char *s;
		int n;
		// fsname: "cmd#arg1#arg2..."
		// WARNING: allows execution of arbitrary commands!
		// Try "mount 'sh#-c#sh' bogus_dir".
		// It is safe ONLY because non-root
		// cannot use two-argument mount command
		// and using one-argument "mount 'sh#-c#sh'" doesn't work:
		// "mount: can't find sh#-c#sh in /etc/fstab"
		// (if /etc/fstab has it, it's ok: root sets up /etc/fstab).

		s = mp->mnt_fsname;
		n = 0;
		args[n++] = s;
		while (*s && n < 35 - 2) {
			if (*s++ == '#' && *s != '#') {
				s[-1] = '\0';
				args[n++] = s;
			}
		}
		args[n++] = mp->mnt_dir;
		args[n] = NULL;
		rc = spawn_and_wait(args);
		goto report_error;
	}

	// Might this be an CIFS filesystem?
	if (ENABLE_FEATURE_MOUNT_CIFS
	 && (!mp->mnt_type || strcmp(mp->mnt_type, "cifs") == 0)
	 && (mp->mnt_fsname[0] == '/' || mp->mnt_fsname[0] == '\\')
	 && mp->mnt_fsname[0] == mp->mnt_fsname[1]
	) {
		int len;
		char c;
		char *hostname, *share;
		len_and_sockaddr *lsa;

		// Parse mp->mnt_fsname of the form "//hostname/share[/dir1/dir2]"

		hostname = mp->mnt_fsname + 2;
		len = strcspn(hostname, "/\\");
		share = hostname + len + 1;
		if (len == 0          // 3rd char is a [back]slash (IOW: empty hostname)
		 || share[-1] == '\0' // no [back]slash after hostname
		 || share[0] == '\0'  // empty share name
		) {
			goto report_error;
		}
		c = share[-1];
		share[-1] = '\0';
		len = strcspn(share, "/\\");

		// "unc=\\hostname\share" option is mandatory
		// after CIFS option parsing was rewritten in Linux 3.4.
		// Must use backslashes.
		// If /dir1/dir2 is present, also add "prefixpath=dir1/dir2"
		{
			char *unc = xasprintf(
				share[len] != '\0'  /* "/dir1/dir2" exists? */
					? "unc=\\\\%s\\%.*s,prefixpath=%s"
					: "unc=\\\\%s\\%.*s",
				hostname,
				len, share,
				share + len + 1  /* "dir1/dir2" */
			);
			parse_mount_options(unc, &filteropts);
			if (ENABLE_FEATURE_CLEAN_UP) free(unc);
		}

		lsa = host2sockaddr(hostname, 0);
		share[-1] = c;
		if (!lsa)
			goto report_error;

		// If there is no "ip=..." option yet
		if (!is_prefixed_with(filteropts, ",ip="+1)
		 && !strstr(filteropts, ",ip=")
		) {
			char *dotted, *ip;
			// Insert "ip=..." option into options
			dotted = xmalloc_sockaddr2dotted_noport(&lsa->u.sa);
			if (ENABLE_FEATURE_CLEAN_UP) free(lsa);
			ip = xasprintf("ip=%s", dotted);
			if (ENABLE_FEATURE_CLEAN_UP) free(dotted);
// Note: IPv6 scoped addresses ("host%iface", see RFC 4007) should be
// handled by libc in getnameinfo() (inside xmalloc_sockaddr2dotted_noport()).
// Currently, glibc does not support that (has no NI_NUMERICSCOPE),
// musl apparently does. This results in "ip=numericIPv6%iface_name"
// (instead of _numeric_ iface_id) with glibc.
// This probably should be fixed in glibc, not here.
// The workaround is to manually specify correct "ip=ADDR%n" option.
			parse_mount_options(ip, &filteropts);
			if (ENABLE_FEATURE_CLEAN_UP) free(ip);
		}

		mp->mnt_type = (char*)"cifs";
		rc = mount_it_now(mp, vfsflags, filteropts);

		goto report_error;
	}

	// Might this be an NFS filesystem?
	if (!(vfsflags & (MS_BIND | MS_MOVE))
	 && (!mp->mnt_type || is_prefixed_with(mp->mnt_type, "nfs"))
	) {
		char *colon = strchr(mp->mnt_fsname, ':');
		if (colon // looks like "hostname:..."
		 && strchrnul(mp->mnt_fsname, '/') > colon // "hostname:" has no slashes
		) {
			if (!mp->mnt_type)
				mp->mnt_type = (char*)"nfs";
			rc = nfsmount(mp, vfsflags, filteropts);
			goto report_error;
		}
	}

	// Look at the file.  (Not found isn't a failure for remount, or for
	// a synthetic filesystem like proc or sysfs.)
	// (We use stat, not lstat, in order to allow
	// mount symlink_to_file_or_blkdev dir)
	if (!stat(mp->mnt_fsname, &st)
	 && !(vfsflags & (MS_REMOUNT | MS_BIND | MS_MOVE))
	) {
		// Do we need to allocate a loopback device for it?
		if (ENABLE_FEATURE_MOUNT_LOOP && S_ISREG(st.st_mode)) {
			unsigned long long offset;
			unsigned long long sizelimit;

			loopFile = bb_simplify_path(mp->mnt_fsname);
			mp->mnt_fsname = NULL; // will receive malloced loop dev name

			// Parse and remove loopback options
			offset = cut_out_ull_opt(filteropts, "offset=");
			sizelimit = cut_out_ull_opt(filteropts, "sizelimit=");

			// mount always creates AUTOCLEARed loopdevs, so that umounting
			// drops them without any code in the userspace.
			// This happens since circa linux-2.6.25:
			// commit 96c5865559cee0f9cbc5173f3c949f6ce3525581
			// Date:    Wed Feb 6 01:36:27 2008 -0800
			// Subject: Allow auto-destruction of loop devices
			loopfd = set_loop(&mp->mnt_fsname,
					loopFile,
					offset,
					sizelimit,
					((vfsflags & MS_RDONLY) ? BB_LO_FLAGS_READ_ONLY : 0)
						| BB_LO_FLAGS_AUTOCLEAR
			);
			if (loopfd < 0) {
				if (errno == EPERM || errno == EACCES)
					bb_simple_error_msg(bb_msg_perm_denied_are_you_root);
				else
					bb_simple_perror_msg("can't setup loop device");
				return loopfd; // was "return errno", but it can be 0 here
			}

		// Autodetect bind mounts
		} else if (S_ISDIR(st.st_mode) && !mp->mnt_type)
			vfsflags |= MS_BIND;
	}

	// If we know the fstype (or don't need to), jump straight
	// to the actual mount.
	if (mp->mnt_type || (vfsflags & (MS_REMOUNT | MS_BIND | MS_MOVE))) {
		char *next;
		for (;;) {
			next = mp->mnt_type ? strchr(mp->mnt_type, ',') : NULL;
			if (next)
				*next = '\0';
			rc = mount_it_now(mp, vfsflags, filteropts);
			if (rc == 0 || !next)
				break;
			mp->mnt_type = next + 1;
		}
	} else {
		// Loop through filesystem types until mount succeeds
		// or we run out

		// Initialize list of block backed filesystems.
		// This has to be done here so that during "mount -a",
		// mounts after /proc shows up can autodetect.
		if (!fslist) {
			fslist = get_block_backed_filesystems();
			if (ENABLE_FEATURE_CLEAN_UP && fslist)
				atexit(delete_block_backed_filesystems);
		}

		for (fl = fslist; fl; fl = fl->link) {
			mp->mnt_type = fl->data;
			rc = mount_it_now(mp, vfsflags, filteropts);
			if (rc == 0)
				break;
		}
	}

	// If mount failed, clean up loop file (if any).
	// (Newer kernels which support LO_FLAGS_AUTOCLEAR should not need this,
	// merely "close(loopfd)" should do it?)
	if (ENABLE_FEATURE_MOUNT_LOOP && rc && loopFile) {
		del_loop(mp->mnt_fsname);
		if (ENABLE_FEATURE_CLEAN_UP) {
			free(loopFile);
			/* No, "rc != 0" needs it: free(mp->mnt_fsname); */
		}
	}

 report_error:
	if (ENABLE_FEATURE_CLEAN_UP)
		free(filteropts);

	if (loopfd >= 0)
		close(loopfd);

	if (errno == EBUSY && ignore_busy)
		return 0;
	if (errno == ENOENT && (vfsflags & MOUNT_NOFAIL))
		return 0;
	if (rc != 0)
		bb_perror_msg("mounting %s on %s failed", mp->mnt_fsname, mp->mnt_dir);
	return rc;
}

// -O support
//    -O interprets a list of filter options which select whether a mount
// point will be mounted: only mounts with options matching *all* filtering
// options will be selected.
//    By default each -O filter option must be present in the list of mount
// options, but if it is prefixed by "no" then it must be absent.
// For example,
//  -O a,nob,c  matches  -o a,c  but fails to match  -o a,b,c
//              (and also fails to match  -o a  because  -o c  is absent).
//
// It is different from -t in that each option is matched exactly; a leading
// "no" at the beginning of one option does not negate the rest.
static int match_opt(const char *fs_opt_in, const char *O_opt)
{
	if (!O_opt)
		return 1;

	while (*O_opt) {
		const char *fs_opt = fs_opt_in;
		int O_len;
		int match;

		// If option begins with "no" then treat as an inverted match:
		// matching is a failure
		match = 0;
		if (O_opt[0] == 'n' && O_opt[1] == 'o') {
			match = 1;
			O_opt += 2;
		}
		// Isolate the current O option
		O_len = strchrnul(O_opt, ',') - O_opt;
		// Check for a match against existing options
		while (1) {
			if (strncmp(fs_opt, O_opt, O_len) == 0
			 && (fs_opt[O_len] == '\0' || fs_opt[O_len] == ',')
			) {
				if (match)
					return 0;  // "no" prefix, but option found
				match = 1;  // current O option found, go check next one
				break;
			}
			fs_opt = strchr(fs_opt, ',');
			if (!fs_opt)
				break;
			fs_opt++;
		}
		if (match == 0)
			return 0;     // match wanted but not found
		if (O_opt[O_len] == '\0') // end?
			break;
		// Step to the next O option
		O_opt += O_len + 1;
	}
	// If we get here then everything matched
	return 1;
}

// Parse options, if necessary parse fstab/mtab, and call singlemount for
// each directory to be mounted.
int mount_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int mount_main(int argc UNUSED_PARAM, char **argv)
{
	char *cmdopts = xzalloc(1);
	char *fstype = NULL;
	char *O_optmatch = NULL;
	char *storage_path;
	llist_t *lst_o = NULL;
	const char *fstabname = "/etc/fstab";
	FILE *fstab;
	int i, j;
	int rc = EXIT_SUCCESS;
	unsigned long cmdopt_flags;
	unsigned opt;
	struct mntent mtpair[2], *mtcur = mtpair;
	IF_NOT_DESKTOP(const int nonroot = 0;)

	IF_DESKTOP(int nonroot = ) sanitize_env_if_suid();

	INIT_G();

	// Parse long options, like --bind and --move.  Note that -o option
	// and --option are synonymous.  Yes, this means --remount,rw works.
	for (i = j = 1; argv[i]; i++) {
		if (argv[i][0] == '-' && argv[i][1] == '-')
			append_mount_options(&cmdopts, argv[i] + 2);
		else
			argv[j++] = argv[i];
	}
	argv[j] = NULL;

	// Parse remaining options
	// Max 2 params; -o is a list, -v is a counter
	opt = getopt32(argv, "^"
		OPTION_STR
		"\0" "?2"IF_FEATURE_MOUNT_VERBOSE("vv"),
		&lst_o, &fstype, &O_optmatch
		IF_FEATURE_MOUNT_OTHERTAB(, &fstabname)
		IF_FEATURE_MOUNT_VERBOSE(, &verbose)
	);

	while (lst_o) append_mount_options(&cmdopts, llist_pop(&lst_o)); // -o
	if (opt & OPT_r) append_mount_options(&cmdopts, "ro"); // -r
	if (opt & OPT_w) append_mount_options(&cmdopts, "rw"); // -w
	argv += optind;

	// If we have no arguments, show currently mounted filesystems
	if (!argv[0]) {
		if (!(opt & OPT_a)) {
			FILE *mountTable = setmntent(bb_path_mtab_file, "r");

			if (!mountTable)
				bb_error_msg_and_die("no %s", bb_path_mtab_file);

			while (getmntent_r(mountTable, &mtpair[0], getmntent_buf,
								GETMNTENT_BUFSIZE))
			{
				// Don't show rootfs. FIXME: why??
				// util-linux 2.12a happily shows rootfs...
				//if (strcmp(mtpair->mnt_fsname, "rootfs") == 0) continue;

				if (!fstype || strcmp(mtpair->mnt_type, fstype) == 0)
					printf("%s on %s type %s (%s)\n", mtpair->mnt_fsname,
							mtpair->mnt_dir, mtpair->mnt_type,
							mtpair->mnt_opts);
			}
			if (ENABLE_FEATURE_CLEAN_UP)
				endmntent(mountTable);
			return EXIT_SUCCESS;
		}
		storage_path = NULL;
	} else {
		// When we have two arguments, the second is the directory and we can
		// skip looking at fstab entirely.  We can always abspath() the directory
		// argument when we get it.
		if (argv[1]) {
			if (nonroot)
				bb_simple_error_msg_and_die(bb_msg_you_must_be_root);
			mtpair->mnt_fsname = argv[0];
			mtpair->mnt_dir = argv[1];
			mtpair->mnt_type = fstype;
			mtpair->mnt_opts = cmdopts;
			resolve_mount_spec(&mtpair->mnt_fsname);
			rc = singlemount(mtpair, /*ignore_busy:*/ 0);
			return rc;
		}
		storage_path = bb_simplify_path(argv[0]); // malloced
	}

	// Past this point, we are handling either "mount -a [opts]"
	// or "mount [opts] single_param"

	cmdopt_flags = parse_mount_options(cmdopts, NULL);
	if (nonroot && (cmdopt_flags & ~MS_SILENT)) // Non-root users cannot specify flags
		bb_simple_error_msg_and_die(bb_msg_you_must_be_root);

	// If we have a shared subtree flag, don't worry about fstab or mtab.
	if (ENABLE_FEATURE_MOUNT_FLAGS
	 && (cmdopt_flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
	) {
		// verbose_mount(source, target, type, flags, data)
		rc = verbose_mount("", argv[0], "", cmdopt_flags, "");
		if (rc)
			bb_simple_perror_msg_and_die(argv[0]);
		return rc;
	}

	// A malicious user could overmount /usr without this.
	if (ENABLE_FEATURE_MOUNT_OTHERTAB && nonroot)
		fstabname = "/etc/fstab";
	// Open either fstab or mtab
	if (cmdopt_flags & MS_REMOUNT) {
		// WARNING. I am not sure this matches util-linux's
		// behavior. It's possible util-linux does not
		// take -o opts from mtab (takes only mount source).
		fstabname = bb_path_mtab_file;
	}
	fstab = setmntent(fstabname, "r");
	if (!fstab)
		bb_perror_msg_and_die("can't read '%s'", fstabname);

	// Loop through entries until we find what we're looking for
	memset(mtpair, 0, sizeof(mtpair));
	for (;;) {
		struct mntent *mtother = (mtcur==mtpair ? mtpair+1 : mtpair);

		// Get next fstab entry
		if (!getmntent_r(fstab, mtcur, getmntent_buf
					+ (mtcur==mtpair ? GETMNTENT_BUFSIZE/2 : 0),
				GETMNTENT_BUFSIZE/2)
		) { // End of fstab/mtab is reached
			mtcur = mtother; // the thing we found last time
			break;
		}

		// If we're trying to mount something specific and this isn't it,
		// skip it.  Note we must match the exact text in fstab (ala
		// "proc") or a full path from root
		if (argv[0]) {

			// Is this what we're looking for?
			if (strcmp(argv[0], mtcur->mnt_fsname) != 0
			 && strcmp(storage_path, mtcur->mnt_fsname) != 0
			 && strcmp(argv[0], mtcur->mnt_dir) != 0
			 && strcmp(storage_path, mtcur->mnt_dir) != 0
			) {
				continue; // no
			}

			// Remember this entry.  Something later may have
			// overmounted it, and we want the _last_ match.
			mtcur = mtother;

		// If we're mounting all
		} else {
			struct mntent *mp;
			// No, mount -a won't mount anything,
			// even user mounts, for mere humans
			if (nonroot)
				bb_simple_error_msg_and_die(bb_msg_you_must_be_root);

			// Does type match? (NULL matches always)
			if (!fstype_matches(mtcur->mnt_type, fstype))
				continue;

			// Skip noauto and swap anyway
			if ((parse_mount_options(mtcur->mnt_opts, NULL) & (MOUNT_NOAUTO | MOUNT_SWAP))
			// swap is bogus "fstype", parse_mount_options can't check fstypes
			 || strcasecmp(mtcur->mnt_type, "swap") == 0
			) {
				continue;
			}

			// Does (at least one) option match?
			// (NULL matches always)
			if (!match_opt(mtcur->mnt_opts, O_optmatch))
				continue;

			resolve_mount_spec(&mtcur->mnt_fsname);

			// NFS mounts want this to be xrealloc-able
			mtcur->mnt_opts = xstrdup(mtcur->mnt_opts);

			// If nothing is mounted on this directory...
			// (otherwise repeated "mount -a" mounts everything again)
			mp = find_mount_point(mtcur->mnt_dir, /*subdir_too:*/ 0);
			// We do not check fsname match of found mount point -
			// "/" may have fsname of "/dev/root" while fstab
			// says "/dev/something_else".
			if (mp) {
				if (verbose) {
					bb_error_msg("according to %s, "
						"%s is already mounted on %s",
						bb_path_mtab_file,
						mp->mnt_fsname, mp->mnt_dir);
				}
			} else {
				// ...mount this thing
				if (singlemount(mtcur, /*ignore_busy:*/ 1)) {
					// Count number of failed mounts
					rc++;
				}
			}
			free(mtcur->mnt_opts);
		}
	}

	// End of fstab/mtab is reached.
	// Were we looking for something specific?
	if (argv[0]) { // yes
		unsigned long l;

		// If we didn't find anything, complain
		if (!mtcur->mnt_fsname)
			bb_error_msg_and_die("can't find %s in %s",
				argv[0], fstabname);

		// What happens when we try to "mount swap_partition"?
		// (fstab containts "swap_partition swap swap defaults 0 0")
		// util-linux-ng 2.13.1 does this:
		// stat("/sbin/mount.swap", 0x7fff62a3a350) = -1 ENOENT (No such file or directory)
		// mount("swap_partition", "swap", "swap", MS_MGC_VAL, NULL) = -1 ENOENT (No such file or directory)
		// lstat("swap", 0x7fff62a3a640)           = -1 ENOENT (No such file or directory)
		// write(2, "mount: mount point swap does not exist\n", 39) = 39
		// exit_group(32)                          = ?
#if 0
		// In case we want to simply skip swap partitions:
		l = parse_mount_options(mtcur->mnt_opts, NULL);
		if ((l & MOUNT_SWAP)
		// swap is bogus "fstype", parse_mount_options can't check fstypes
		 || strcasecmp(mtcur->mnt_type, "swap") == 0
		) {
			goto ret;
		}
#endif
		if (nonroot) {
			// fstab must have "users" or "user"
			l = parse_mount_options(mtcur->mnt_opts, NULL);
			if (!(l & MOUNT_USERS))
				bb_simple_error_msg_and_die(bb_msg_you_must_be_root);
		}

		//util-linux-2.12 does not do this check.
		//// If nothing is mounted on this directory...
		//// (otherwise repeated "mount FOO" mounts FOO again)
		//mp = find_mount_point(mtcur->mnt_dir, /*subdir_too:*/ 0);
		//if (mp) {
		//	bb_error_msg("according to %s, "
		//		"%s is already mounted on %s",
		//		bb_path_mtab_file,
		//		mp->mnt_fsname, mp->mnt_dir);
		//} else {
			// ...mount the last thing we found
			mtcur->mnt_opts = xstrdup(mtcur->mnt_opts);
			append_mount_options(&(mtcur->mnt_opts), cmdopts);
			resolve_mount_spec(&mtpair->mnt_fsname);
			rc = singlemount(mtcur, /*ignore_busy:*/ 0);
			if (ENABLE_FEATURE_CLEAN_UP)
				free(mtcur->mnt_opts);
		//}
	}

 //ret:
	if (ENABLE_FEATURE_CLEAN_UP)
		endmntent(fstab);
	if (ENABLE_FEATURE_CLEAN_UP) {
		free(storage_path);
		free(cmdopts);
	}

//TODO: exitcode should be ORed mask of (from "man mount"):
// 0 success
// 1 incorrect invocation or permissions
// 2 system error (out of memory, cannot fork, no more loop devices)
// 4 internal mount bug or missing nfs support in mount
// 8 user interrupt
//16 problems writing or locking /etc/mtab
//32 mount failure
//64 some mount succeeded
	return rc;
}