fstab.c

Util-linux 软件包包含许多工具。其中比较重要的是加载、卸载、格式化、分区和管理硬盘驱动器

/* 1999-02-22 Arkadiusz Mi秌iewicz <[e-mail]>
 * - added Native Language Support
 * Sun Mar 21 1999 - Arnaldo Carvalho de Melo <[e-mail]>
 * - fixed strerr(errno) in gettext calls
 */

#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include "mntent.h"
#include "fstab.h"
#include "sundries.h"		/* for xmalloc() etc */
#include "mount_blkid.h"
#include "paths.h"
#include "nls.h"

#define streq(s, t)	(strcmp ((s), (t)) == 0)

#define PROC_MOUNTS		"/proc/mounts"


/* Information about mtab. ------------------------------------*/
static int have_mtab_info = 0;
static int var_mtab_does_not_exist = 0;
static int var_mtab_is_a_symlink = 0;

static void
get_mtab_info(void) {
	struct stat mtab_stat;

	if (!have_mtab_info) {
		if (lstat(MOUNTED, &mtab_stat))
			var_mtab_does_not_exist = 1;
		else if (S_ISLNK(mtab_stat.st_mode))
			var_mtab_is_a_symlink = 1;
		have_mtab_info = 1;
	}
}

int
mtab_does_not_exist(void) {
	get_mtab_info();
	return var_mtab_does_not_exist;
}

int
mtab_is_a_symlink(void) {
	get_mtab_info();
	return var_mtab_is_a_symlink;
}

int
mtab_is_writable() {
	static int ret = -1;

	/* Should we write to /etc/mtab upon an update?
	   Probably not if it is a symlink to /proc/mounts, since that
	   would create a file /proc/mounts in case the proc filesystem
	   is not mounted. */
	if (mtab_is_a_symlink())
		return 0;

	if (ret == -1) {
		int fd = open(MOUNTED, O_RDWR | O_CREAT, 0644);
		if (fd >= 0) {
			close(fd);
			ret = 1;
		} else
			ret = 0;
	}
	return ret;
}

/* Contents of mtab and fstab ---------------------------------*/

struct mntentchn mounttable, fstab;
static int got_mtab = 0;
static int got_fstab = 0;

static void read_mounttable(void), read_fstab(void);

struct mntentchn *
mtab_head() {
	if (!got_mtab)
		read_mounttable();
	return &mounttable;
}

struct mntentchn *
fstab_head() {
	if (!got_fstab)
		read_fstab();
	return &fstab;
}

static void
my_free(const void *s) {
	if (s)
		free((void *) s);
}

static void
discard_mntentchn(struct mntentchn *mc0) {
	struct mntentchn *mc, *mc1;

	for (mc = mc0->nxt; mc && mc != mc0; mc = mc1) {
		mc1 = mc->nxt;
		my_free(mc->m.mnt_fsname);
		my_free(mc->m.mnt_dir);
		my_free(mc->m.mnt_type);
		my_free(mc->m.mnt_opts);
		free(mc);
	}
}

static void
read_mntentchn(mntFILE *mfp, const char *fnam, struct mntentchn *mc0) {
	struct mntentchn *mc = mc0;
	struct my_mntent *mnt;

	while ((mnt = my_getmntent(mfp)) != NULL) {
		if (!streq(mnt->mnt_type, MNTTYPE_IGNORE)) {
			mc->nxt = (struct mntentchn *) xmalloc(sizeof(*mc));
			mc->nxt->prev = mc;
			mc = mc->nxt;
			mc->m = *mnt;
			mc->nxt = mc0;
		}
	}
	mc0->prev = mc;
	if (ferror(mfp->mntent_fp)) {
		int errsv = errno;
		error(_("warning: error reading %s: %s"),
		      fnam, strerror (errsv));
		mc0->nxt = mc0->prev = NULL;
	}
	my_endmntent(mfp);
}

/*
 * Read /etc/mtab.  If that fails, try /proc/mounts.
 * This produces a linked list. The list head mounttable is a dummy.
 * Return 0 on success.
 */
static void
read_mounttable() {
	mntFILE *mfp;
	const char *fnam;
	struct mntentchn *mc = &mounttable;

	got_mtab = 1;
	mc->nxt = mc->prev = NULL;

	fnam = MOUNTED;
	mfp = my_setmntent (fnam, "r");
	if (mfp == NULL || mfp->mntent_fp == NULL) {
		int errsv = errno;
		fnam = PROC_MOUNTS;
		mfp = my_setmntent (fnam, "r");
		if (mfp == NULL || mfp->mntent_fp == NULL) {
			error(_("warning: can't open %s: %s"),
			      MOUNTED, strerror (errsv));
			return;
		}
		if (verbose)
			printf (_("mount: could not open %s - "
				  "using %s instead\n"),
				MOUNTED, PROC_MOUNTS);
	}
	read_mntentchn(mfp, fnam, mc);
}

static void
read_fstab() {
	mntFILE *mfp = NULL;
	const char *fnam;
	struct mntentchn *mc = &fstab;

	got_fstab = 1;
	mc->nxt = mc->prev = NULL;

	fnam = _PATH_FSTAB;
	mfp = my_setmntent (fnam, "r");
	if (mfp == NULL || mfp->mntent_fp == NULL) {
		int errsv = errno;
		error(_("warning: can't open %s: %s"),
		      _PATH_FSTAB, strerror (errsv));
		return;
	}
	read_mntentchn(mfp, fnam, mc);
}
     

/* Given the name NAME, try to find it in mtab.  */ 
struct mntentchn *
getmntfile (const char *name) {
	struct mntentchn *mc, *mc0;

	mc0 = mtab_head();
	for (mc = mc0->nxt; mc && mc != mc0; mc = mc->nxt)
		if (streq(mc->m.mnt_dir, name) ||
		    streq(mc->m.mnt_fsname, name))
			return mc;
	return NULL;
}

/*
 * Given the directory name NAME, and the place MCPREV we found it last time,
 * try to find more occurrences.
 */ 
struct mntentchn *
getmntdirbackward (const char *name, struct mntentchn *mcprev) {
	struct mntentchn *mc, *mc0;

	mc0 = mtab_head();
	if (!mcprev)
		mcprev = mc0;
	for (mc = mcprev->prev; mc && mc != mc0; mc = mc->prev)
		if (streq(mc->m.mnt_dir, name))
			return mc;
	return NULL;
}

/*
 * Given the device name NAME, and the place MCPREV we found it last time,
 * try to find more occurrences.
 */ 
struct mntentchn *
getmntdevbackward (const char *name, struct mntentchn *mcprev) {
	struct mntentchn *mc, *mc0;

	mc0 = mtab_head();
	if (!mcprev)
		mcprev = mc0;
	for (mc = mcprev->prev; mc && mc != mc0; mc = mc->prev)
		if (streq(mc->m.mnt_fsname, name))
			return mc;
	return NULL;
}

/*
 * Given the name NAME, check that it occurs precisely once as dir or dev.
 */
int
is_mounted_once(const char *name) {
	struct mntentchn *mc, *mc0;
	int ct = 0;

	mc0 = mtab_head();
	for (mc = mc0->prev; mc && mc != mc0; mc = mc->prev)
		if (streq(mc->m.mnt_dir, name) ||
		    streq(mc->m.mnt_fsname, name))
			ct++;
	return (ct == 1);
}

/* Given the name FILE, try to find the option "loop=FILE" in mtab.  */ 
struct mntentchn *
getmntoptfile (const char *file) {
	struct mntentchn *mc, *mc0;
	const char *opts, *s;
	int l;

	if (!file)
		return NULL;

	l = strlen(file);

	mc0 = mtab_head();
	for (mc = mc0->nxt; mc && mc != mc0; mc = mc->nxt)
		if ((opts = mc->m.mnt_opts) != NULL
		    && (s = strstr(opts, "loop="))
		    && !strncmp(s+5, file, l)
		    && (s == opts || s[-1] == ',')
		    && (s[l+5] == 0 || s[l+5] == ','))
			return mc;
	return NULL;
}

static int
has_label(const char *device, const char *label) {
	const char *devlabel;
	int ret;

	devlabel = mount_get_volume_label_by_spec(device);
	ret = !strcmp(label, devlabel);
	/* free(devlabel); */
	return ret;
}

static int
has_uuid(const char *device, const char *uuid){
	const char *devuuid;
	int ret;

	devuuid = mount_get_devname_by_uuid(device);
	ret = !strcmp(uuid, devuuid);
	/* free(devuuid); */
	return ret;
}

/* Find the entry (SPEC,FILE) in fstab */
struct mntentchn *
getfsspecfile (const char *spec, const char *file) {
	struct mntentchn *mc, *mc0;

	mc0 = fstab_head();

	/* first attempt: names occur precisely as given */
	for (mc = mc0->nxt; mc && mc != mc0; mc = mc->nxt)
		if (streq(mc->m.mnt_dir, file) &&
		    streq(mc->m.mnt_fsname, spec))
			return mc;

	/* second attempt: names found after symlink resolution */
	for (mc = mc0->nxt; mc && mc != mc0; mc = mc->nxt)
		if ((streq(mc->m.mnt_dir, file) ||
		     streq(canonicalize(mc->m.mnt_dir), file))
		    && (streq(mc->m.mnt_fsname, spec) ||
			streq(canonicalize(mc->m.mnt_fsname), spec)))
			return mc;

	/* third attempt: names found after LABEL= or UUID= resolution */
	for (mc = mc0->nxt; mc && mc != mc0; mc = mc->nxt) {
		if (!strncmp (mc->m.mnt_fsname, "LABEL=", 6) &&
		    (streq(mc->m.mnt_dir, file) ||
		     streq(canonicalize(mc->m.mnt_dir), file))) {
			if (has_label(spec, mc->m.mnt_fsname+6))
				return mc;
		}
		if (!strncmp (mc->m.mnt_fsname, "UUID=", 5) &&