[unix-history] / usr / src / usr.sbin / amd / config / mtab_file.c

/*
 * Copyright (c) 1990 Jan-Simon Pendry
 * Copyright (c) 1990 Imperial College of Science, Technology & Medicine
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Jan-Simon Pendry at Imperial College, London.
 *
 * %sccs.include.redist.c%
 *
 *	@(#)mtab_file.c	8.1 (Berkeley) %G%
 *
 * $Id: mtab_file.c,v 5.2.2.1 1992/02/09 15:10:42 jsp beta $
 *
 */

#include "am.h"

#ifdef READ_MTAB_FROM_FILE

#ifdef USE_FCNTL
#include <fcntl.h>
#else
#include <sys/file.h>
#endif /* USE_FCNTL */

#ifdef UPDATE_MTAB

/*
 * Do strict /etc/mtab locking
 */
#define	MTAB_LOCKING

/*
 * Firewall mtab entries
 */
#define	MTAB_STRIPNL

#include <sys/stat.h>
static FILE *mnt_file;

/*
 * If the system is being trashed by something, then
 * opening mtab may fail with ENFILE.  So, go to sleep
 * for a second and try again. (Yes - this has happened to me.)
 *
 * Note that this *may* block the automounter, oh well. 
 * If we get to this state then things are badly wrong anyway...
 *
 * Give the system 10 seconds to recover but then give up.
 * Hopefully something else will exit and free up some file
 * table slots in that time.
 */
#define	NFILE_RETRIES	10 /* seconds */

#ifdef MTAB_LOCKING
#ifdef LOCK_FCNTL
static int lock(fd)
{
	int rc;
	struct flock lk;

	lk.l_type = F_WRLCK;
	lk.l_whence = 0;
	lk.l_start = 0;
	lk.l_len = 0;

again:
	rc = fcntl(fd, F_SETLKW, (caddr_t) &lk);
	if (rc < 0 && (errno == EACCES || errno == EAGAIN)) {
#ifdef DEBUG
		dlog("Blocked, trying to obtain exclusive mtab lock");
#endif /* DEBUG */
		sleep(1);
		goto again;
	}
	return rc;
}
#else
#define lock(fd) (flock((fd), LOCK_EX))
#endif /* LOCK_FCNTL */
#endif /* MTAB_LOCKING */

static FILE *open_locked_mtab(mtab_file, mode, fs)
char *mtab_file;
char *mode;
char *fs;
{
	FILE *mfp = 0;

#ifdef UPDATE_MTAB
	/*
	 * There is a possible race condition if two processes enter
	 * this routine at the same time.  One will be blocked by the
	 * exclusive lock below (or by the shared lock in setmntent)
	 * and by the time the second process has the exclusive lock
	 * it will be on the wrong underlying object.  To check for this
	 * the mtab file is stat'ed before and after all the locking
	 * sequence, and if it is a different file then we assume that
	 * it may be the wrong file (only "may", since there is another
	 * race between the initial stat and the setmntent).
	 *
	 * Simpler solutions to this problem are invited...
	 */
	int racing = 2;
#ifdef MTAB_LOCKING
	int rc;
	int retries = 0;
	struct stat st_before, st_after;
#endif /* MTAB_LOCKING */

	if (mnt_file) {
#ifdef DEBUG
		dlog("Forced close on %s in read_mtab", mtab_file);
#endif /* DEBUG */
		endmntent(mnt_file);
		mnt_file = 0;
	}

#ifdef MTAB_LOCKING
again:
	if (mfp) {
		endmntent(mfp);
		mfp = 0;
	}

	clock_valid = 0;
	if (stat(mtab_file, &st_before) < 0) {
		plog(XLOG_ERROR, "%s: stat: %m", mtab_file);
		if (errno == ESTALE) {
			/* happens occasionally */
			sleep(1);
			goto again;
		}
		return 0;
	}
#endif /* MTAB_LOCKING */
#endif /* UPDATE_MTAB */

eacces:
	mfp = setmntent(mtab_file, mode);
	if (!mfp) {
		/*
		 * Since setmntent locks the descriptor, it
		 * is possible it can fail... so retry if
		 * needed.
		 */
		if (errno == EACCES || errno == EAGAIN) {
#ifdef DEBUG
			dlog("Blocked, trying to obtain exclusive mtab lock");
#endif /* DEBUG */
			goto eacces;
		} else if (errno == ENFILE && retries++ < NFILE_RETRIES) {
			sleep(1);
			goto eacces;
		}

		plog(XLOG_ERROR, "setmntent(\"%s\", \"%s\"): %m", mtab_file, mode);
		return 0;
	}

#ifdef MTAB_LOCKING
#ifdef UPDATE_MTAB
	/*
	 * At this point we have an exclusive lock on the mount list,
	 * but it may be the wrong one so...
	 */

	/*
	 * Need to get an exclusive lock on the current
	 * mount table until we have a new copy written
	 * out, when the lock is released in free_mntlist.
	 * flock is good enough since the mount table is
	 * not shared between machines.
	 */
	do
		rc = lock(fileno(mfp));
	while (rc < 0 && errno == EINTR);
	if (rc < 0) {
		plog(XLOG_ERROR, "Couldn't lock %s: %m", mtab_file);
		endmntent(mfp);
		return 0;
	}
	/*
	 * Now check whether the mtab file has changed under our feet
	 */
	if (stat(mtab_file, &st_after) < 0) {
		plog(XLOG_ERROR, "%s: stat", mtab_file);
		goto again;
	}

	if (st_before.st_dev != st_after.st_dev ||
		st_before.st_ino != st_after.st_ino) {
			struct timeval tv;
			if (racing == 0) {
				/* Sometimes print a warning */
				plog(XLOG_WARNING,
					"Possible mount table race - retrying %s", fs);
			}
			racing = (racing+1) & 3;
			/*
			 * Take a nap.  From: Doug Kingston <dpk@morgan.com>
			 */
			tv.tv_sec = 0;
			tv.tv_usec = (mypid & 0x07) << 17;
			if (tv.tv_usec)
				if (select(0, (voidp) 0, (voidp) 0, (voidp) 0, &tv) < 0)
					plog(XLOG_WARNING, "mtab nap failed: %m");

			goto again;
	}
#endif /* UPDATE_MTAB */
#endif /* MTAB_LOCKING */

	return mfp;
}

/*
 * Unlock the mount table
 */
void unlock_mntlist P((void));
void unlock_mntlist()
{
	/*
	 * Release file lock, by closing the file
	 */
	if (mnt_file) {
		endmntent(mnt_file);
		mnt_file = 0;
	}
}

/*
 * Write out a mount list
 */
void rewrite_mtab(mp)
mntlist *mp;
{
	FILE *mfp;
	int error = 0;

	/*
	 * Concoct a temporary name in the same
	 * directory as the target mount table
	 * so that rename() will work.
	 */
	char tmpname[64];
	int retries;
	int tmpfd;
	char *cp;
	char *mcp = mtab;
	cp = strrchr(mcp, '/');
	if (cp) {
		bcopy(mcp, tmpname, cp - mcp);
		tmpname[cp-mcp] = '\0';
	} else {
		plog(XLOG_WARNING, "No '/' in mtab (%s), using \".\" as tmp directory", mtab);
		tmpname[0] = '.'; tmpname[1] = '\0';
	}
	strcat(tmpname, "/mtabXXXXXX");
	mktemp(tmpname);
	retries = 0;
enfile1:
	if ((tmpfd = open(tmpname, O_RDWR|O_CREAT|O_TRUNC, 0644)) < 0) {
		if (errno == ENFILE && retries++ < NFILE_RETRIES) {
			sleep(1);
			goto enfile1;
		}
		plog(XLOG_ERROR, "%s: open: %m", tmpname);
		return;
	}
	if (close(tmpfd) < 0)
		plog(XLOG_ERROR, "Couldn't close tmp file descriptor: %m");

	retries = 0;
enfile2:
	mfp = setmntent(tmpname, "w");
	if (!mfp) {
		if (errno == ENFILE && retries++ < NFILE_RETRIES) {
			sleep(1);
			goto enfile2;
		}
		plog(XLOG_ERROR, "setmntent(\"%s\", \"w\"): %m", tmpname);
		error = 1;
		goto out;
	}

	while (mp) {
		if (mp->mnt) {
			if (addmntent(mfp, mp->mnt)) {
				plog(XLOG_ERROR, "Can't write entry to %s", tmpname);
				error = 1;
				goto out;
			}
		}
		mp = mp->mnext;
	}

	/*
	 * SunOS 4.1 manuals say that the return code from entmntent()
	 * is always 1 and to treat as a void.  That means we need to
	 * call fflush() to make sure the new mtab file got written.
	 */
	if (fflush(mfp)) {
		plog(XLOG_ERROR, "flush new mtab file: %m");
		error = 1;
		goto out;
	}

	(void) endmntent(mfp);

	/*
	 * Rename temporary mtab to real mtab
	 */
	if (rename(tmpname, mtab) < 0) {
		plog(XLOG_ERROR, "rename %s to %s: %m", tmpname, mtab);
		error = 1;
		goto out;
	}

out:
	if (error)
		(void) unlink(tmpname);
}

#ifdef MTAB_STRIPNL
static void mtab_stripnl(s)
char *s;
{
	do {
		s = strchr(s, '\n');
		if (s)
			*s++ = ' ';
	} while (s);
}
#endif /* MTAB_STRIPNL */

/*
 * Append a mntent structure to the
 * current mount table.
 */
void write_mntent(mp)
struct mntent *mp;
{
	int retries = 0;
	FILE *mfp;
enfile:
	mfp = open_locked_mtab(mtab, "a", mp->mnt_dir);
	if (mfp) {
#ifdef MTAB_STRIPNL
		mtab_stripnl(mp->mnt_opts);
#endif /* MTAB_STRIPNL */
		if (addmntent(mfp, mp))
			plog(XLOG_ERROR, "Couldn't write %s: %m", mtab);
		if (fflush(mfp))
			plog(XLOG_ERROR, "Couldn't flush %s: %m", mtab);
		(void) endmntent(mfp);
	} else {
		if (errno == ENFILE && retries < NFILE_RETRIES) {
			sleep(1);
			goto enfile;
		}
		plog(XLOG_ERROR, "setmntent(\"%s\", \"a\"): %m", mtab);
	}
}

#endif /* UPDATE_MTAB */

static struct mntent *mnt_dup(mp)
struct mntent *mp;
{
	struct mntent *new_mp = ALLOC(mntent);

	new_mp->mnt_fsname = strdup(mp->mnt_fsname);
	new_mp->mnt_dir = strdup(mp->mnt_dir);
	new_mp->mnt_type = strdup(mp->mnt_type);
	new_mp->mnt_opts = strdup(mp->mnt_opts);

	new_mp->mnt_freq = mp->mnt_freq;
	new_mp->mnt_passno = mp->mnt_passno;

#ifdef FIXUP_MNTENT_DUP
	/*
	 * Additional fields get dup'ed here
	 */
	FIXUP_MNTENT_DUP(new_mp, mp);
#endif

	return new_mp;
}

/*
 * Read a mount table into memory
 */
mntlist *read_mtab(fs)
char *fs;
{
	mntlist **mpp, *mhp;

	struct mntent *mep;
	FILE *mfp = open_locked_mtab(mtab, "r+", fs);

	if (!mfp)
		return 0;

	mpp = &mhp;

/*
 * XXX - In SunOS 4 there is (yet another) memory leak
 * which loses 1K the first time getmntent is called.
 * (jsp)
 */
	while (mep = getmntent(mfp)) {
		/*
		 * Allocate a new slot
		 */
		*mpp = ALLOC(mntlist);

		/*
		 * Copy the data returned by getmntent
		 */
		(*mpp)->mnt = mnt_dup(mep);

		/*
		 * Move to next pointer
		 */
		mpp = &(*mpp)->mnext;
	}
	*mpp = 0;

#ifdef UPDATE_MTAB
	/*
	 * If we are not updating the mount table then we
	 * can free the resources held here, otherwise they
	 * must be held until the mount table update is complete
	 */
	mnt_file = mfp;
#else
	endmntent(mfp);
#endif /* UPDATE_MTAB */

	return mhp;
}

#endif /* READ_MTAB_FROM_FILE */
Commit	Line	Data
e1a31032	1	/*
e1a31032 KM	2	* Copyright (c) 1990 Jan-Simon Pendry
e1a31032 KM	3	* Copyright (c) 1990 Imperial College of Science, Technology & Medicine
16f2cf2d KB	4	* Copyright (c) 1990, 1993
16f2cf2d KB	5	* The Regents of the University of California. All rights reserved.
e1a31032 KM	6	*
	7	* This code is derived from software contributed to Berkeley by
	8	* Jan-Simon Pendry at Imperial College, London.
	9	*
	10	* %sccs.include.redist.c%
	11	*
16f2cf2d	12	* @(#)mtab_file.c 8.1 (Berkeley) %G%
8d2991d5	13	*
332f0791	14	* $Id: mtab_file.c,v 5.2.2.1 1992/02/09 15:10:42 jsp beta $
8d2991d5	15	*
e1a31032 KM	16	*/
	17
	18	#include "am.h"
	19
	20	#ifdef READ_MTAB_FROM_FILE
	21
	22	#ifdef USE_FCNTL
	23	#include <fcntl.h>
	24	#else
	25	#include <sys/file.h>
	26	#endif /* USE_FCNTL */
	27
	28	#ifdef UPDATE_MTAB
	29
	30	/*
	31	* Do strict /etc/mtab locking
	32	*/
	33	#define MTAB_LOCKING
	34
	35	/*
	36	* Firewall mtab entries
	37	*/
	38	#define MTAB_STRIPNL
	39
	40	#include <sys/stat.h>
	41	static FILE *mnt_file;
	42
	43	/*
	44	* If the system is being trashed by something, then
	45	* opening mtab may fail with ENFILE. So, go to sleep
	46	* for a second and try again. (Yes - this has happened to me.)
	47	*
	48	* Note that this may block the automounter, oh well.
	49	* If we get to this state then things are badly wrong anyway...
	50	*
	51	* Give the system 10 seconds to recover but then give up.
	52	* Hopefully something else will exit and free up some file
	53	* table slots in that time.
	54	*/
	55	#define NFILE_RETRIES 10 /* seconds */
	56
	57	#ifdef MTAB_LOCKING
	58	#ifdef LOCK_FCNTL
	59	static int lock(fd)
	60	{
	61	int rc;
	62	struct flock lk;
	63
	64	lk.l_type = F_WRLCK;
	65	lk.l_whence = 0;
	66	lk.l_start = 0;
	67	lk.l_len = 0;
	68
	69	again:
	70	rc = fcntl(fd, F_SETLKW, (caddr_t) &lk);
	71	if (rc < 0 && (errno == EACCES \|\| errno == EAGAIN)) {
	72	#ifdef DEBUG
	73	dlog("Blocked, trying to obtain exclusive mtab lock");
	74	#endif /* DEBUG */
	75	sleep(1);
	76	goto again;
	77	}
	78	return rc;
	79	}
80	#else
81	#define lock(fd) (flock((fd), LOCK_EX))
82	#endif /* LOCK_FCNTL */
83	#endif /* MTAB_LOCKING */
84
2f619045 JSP	85	static FILE *open_locked_mtab(mtab_file, mode, fs)
	86	char *mtab_file;
	87	char *mode;
	88	char *fs;
	89	{
	90	FILE *mfp = 0;
	91
	92	#ifdef UPDATE_MTAB
	93	/*
	94	* There is a possible race condition if two processes enter
	95	* this routine at the same time. One will be blocked by the
	96	* exclusive lock below (or by the shared lock in setmntent)
	97	* and by the time the second process has the exclusive lock
	98	* it will be on the wrong underlying object. To check for this
	99	* the mtab file is stat'ed before and after all the locking
	100	* sequence, and if it is a different file then we assume that
	101	* it may be the wrong file (only "may", since there is another
	102	* race between the initial stat and the setmntent).
	103	*
	104	* Simpler solutions to this problem are invited...
	105	*/
	106	int racing = 2;
	107	#ifdef MTAB_LOCKING
	108	int rc;
	109	int retries = 0;
	110	struct stat st_before, st_after;
	111	#endif /* MTAB_LOCKING */
	112
	113	if (mnt_file) {
	114	#ifdef DEBUG
	115	dlog("Forced close on %s in read_mtab", mtab_file);
	116	#endif /* DEBUG */
	117	endmntent(mnt_file);
	118	mnt_file = 0;
	119	}
	120
	121	#ifdef MTAB_LOCKING
	122	again:
	123	if (mfp) {
	124	endmntent(mfp);
	125	mfp = 0;
	126	}
	127
	128	clock_valid = 0;
	129	if (stat(mtab_file, &st_before) < 0) {
	130	plog(XLOG_ERROR, "%s: stat: %m", mtab_file);
	131	if (errno == ESTALE) {
	132	/* happens occasionally */
	133	sleep(1);
	134	goto again;
	135	}
	136	return 0;
	137	}
	138	#endif /* MTAB_LOCKING */
	139	#endif /* UPDATE_MTAB */
	140
	141	eacces:
	142	mfp = setmntent(mtab_file, mode);
	143	if (!mfp) {
	144	/*
	145	* Since setmntent locks the descriptor, it
	146	* is possible it can fail... so retry if
	147	* needed.
	148	*/
149	if (errno == EACCES \|\| errno == EAGAIN) {
150	#ifdef DEBUG
151	dlog("Blocked, trying to obtain exclusive mtab lock");
152	#endif /* DEBUG */
153	goto eacces;
154	} else if (errno == ENFILE && retries++ < NFILE_RETRIES) {
155	sleep(1);
156	goto eacces;
157	}
158
159	plog(XLOG_ERROR, "setmntent(\"%s\", \"%s\"): %m", mtab_file, mode);
160	return 0;
161	}
162
163	#ifdef MTAB_LOCKING
164	#ifdef UPDATE_MTAB
165	/*
166	* At this point we have an exclusive lock on the mount list,
167	* but it may be the wrong one so...
168	*/
169
170	/*
171	* Need to get an exclusive lock on the current
172	* mount table until we have a new copy written
173	* out, when the lock is released in free_mntlist.
174	* flock is good enough since the mount table is
175	* not shared between machines.
176	*/
177	do
178	rc = lock(fileno(mfp));
179	while (rc < 0 && errno == EINTR);
180	if (rc < 0) {
181	plog(XLOG_ERROR, "Couldn't lock %s: %m", mtab_file);
182	endmntent(mfp);
183	return 0;
184	}
185	/*
186	* Now check whether the mtab file has changed under our feet
187	*/
188	if (stat(mtab_file, &st_after) < 0) {
189	plog(XLOG_ERROR, "%s: stat", mtab_file);
190	goto again;
191	}
192
193	if (st_before.st_dev != st_after.st_dev \|\|
194	st_before.st_ino != st_after.st_ino) {
195	struct timeval tv;
196	if (racing == 0) {
197	/* Sometimes print a warning */
198	plog(XLOG_WARNING,
199	"Possible mount table race - retrying %s", fs);
200	}
201	racing = (racing+1) & 3;
202	/*
203	* Take a nap. From: Doug Kingston <dpk@morgan.com>
204	*/
205	tv.tv_sec = 0;
206	tv.tv_usec = (mypid & 0x07) << 17;
207	if (tv.tv_usec)
208	if (select(0, (voidp) 0, (voidp) 0, (voidp) 0, &tv) < 0)
209	plog(XLOG_WARNING, "mtab nap failed: %m");
210
211	goto again;
212	}
213	#endif /* UPDATE_MTAB */
214	#endif /* MTAB_LOCKING */
215
216	return mfp;
217	}
218
e1a31032 KM	219	/*
	220	* Unlock the mount table
	221	*/
2f619045	222	void unlock_mntlist P((void));
e1a31032 KM	223	void unlock_mntlist()
	224	{
	225	/*
	226	* Release file lock, by closing the file
	227	*/
	228	if (mnt_file) {
	229	endmntent(mnt_file);
	230	mnt_file = 0;
	231	}
	232	}
	233
	234	/*
	235	* Write out a mount list
	236	*/
	237	void rewrite_mtab(mp)
	238	mntlist *mp;
	239	{
	240	FILE *mfp;
332f0791	241	int error = 0;
e1a31032 KM	242
	243	/*
	244	* Concoct a temporary name in the same
	245	* directory as the target mount table
	246	* so that rename() will work.
	247	*/
	248	char tmpname[64];
	249	int retries;
	250	int tmpfd;
	251	char *cp;
	252	char *mcp = mtab;
	253	cp = strrchr(mcp, '/');
	254	if (cp) {
	255	bcopy(mcp, tmpname, cp - mcp);
	256	tmpname[cp-mcp] = '\0';
	257	} else {
	258	plog(XLOG_WARNING, "No '/' in mtab (%s), using \".\" as tmp directory", mtab);
	259	tmpname[0] = '.'; tmpname[1] = '\0';
	260	}
	261	strcat(tmpname, "/mtabXXXXXX");
	262	mktemp(tmpname);
	263	retries = 0;
	264	enfile1:
	265	if ((tmpfd = open(tmpname, O_RDWR\|O_CREAT\|O_TRUNC, 0644)) < 0) {
	266	if (errno == ENFILE && retries++ < NFILE_RETRIES) {
	267	sleep(1);
	268	goto enfile1;
	269	}
	270	plog(XLOG_ERROR, "%s: open: %m", tmpname);
	271	return;
	272	}
	273	if (close(tmpfd) < 0)
	274	plog(XLOG_ERROR, "Couldn't close tmp file descriptor: %m");
	275
	276	retries = 0;
	277	enfile2:
	278	mfp = setmntent(tmpname, "w");
	279	if (!mfp) {
	280	if (errno == ENFILE && retries++ < NFILE_RETRIES) {
	281	sleep(1);
	282	goto enfile2;
	283	}
	284	plog(XLOG_ERROR, "setmntent(\"%s\", \"w\"): %m", tmpname);
332f0791 JSP	285	error = 1;
332f0791 JSP	286	goto out;
e1a31032 KM	287	}
	288
	289	while (mp) {
332f0791 JSP	290	if (mp->mnt) {
332f0791 JSP	291	if (addmntent(mfp, mp->mnt)) {
e1a31032	292	plog(XLOG_ERROR, "Can't write entry to %s", tmpname);
332f0791 JSP	293	error = 1;
	294	goto out;
	295	}
	296	}
e1a31032 KM	297	mp = mp->mnext;
	298	}
	299
332f0791 JSP	300	/*
	301	* SunOS 4.1 manuals say that the return code from entmntent()
	302	* is always 1 and to treat as a void. That means we need to
	303	* call fflush() to make sure the new mtab file got written.
	304	*/
	305	if (fflush(mfp)) {
	306	plog(XLOG_ERROR, "flush new mtab file: %m");
	307	error = 1;
	308	goto out;
	309	}
	310
	311	(void) endmntent(mfp);
e1a31032 KM	312
	313	/*
	314	* Rename temporary mtab to real mtab
	315	*/
332f0791	316	if (rename(tmpname, mtab) < 0) {
e1a31032	317	plog(XLOG_ERROR, "rename %s to %s: %m", tmpname, mtab);
332f0791 JSP	318	error = 1;
	319	goto out;
	320	}
	321
	322	out:
	323	if (error)
	324	(void) unlink(tmpname);
e1a31032 KM	325	}
	326
	327	#ifdef MTAB_STRIPNL
	328	static void mtab_stripnl(s)
	329	char *s;
	330	{
	331	do {
	332	s = strchr(s, '\n');
	333	if (s)
	334	*s++ = ' ';
	335	} while (s);
	336	}
	337	#endif /* MTAB_STRIPNL */
	338
	339	/*
	340	* Append a mntent structure to the
	341	* current mount table.
	342	*/
	343	void write_mntent(mp)
	344	struct mntent *mp;
	345	{
	346	int retries = 0;
	347	FILE *mfp;
	348	enfile:
2f619045	349	mfp = open_locked_mtab(mtab, "a", mp->mnt_dir);
e1a31032 KM	350	if (mfp) {
	351	#ifdef MTAB_STRIPNL
	352	mtab_stripnl(mp->mnt_opts);
	353	#endif /* MTAB_STRIPNL */
	354	if (addmntent(mfp, mp))
	355	plog(XLOG_ERROR, "Couldn't write %s: %m", mtab);
332f0791 JSP	356	if (fflush(mfp))
	357	plog(XLOG_ERROR, "Couldn't flush %s: %m", mtab);
	358	(void) endmntent(mfp);
e1a31032 KM	359	} else {
	360	if (errno == ENFILE && retries < NFILE_RETRIES) {
	361	sleep(1);
	362	goto enfile;
	363	}
	364	plog(XLOG_ERROR, "setmntent(\"%s\", \"a\"): %m", mtab);
	365	}
	366	}
	367
	368	#endif /* UPDATE_MTAB */
	369
	370	static struct mntent *mnt_dup(mp)
	371	struct mntent *mp;
	372	{
	373	struct mntent *new_mp = ALLOC(mntent);
	374
	375	new_mp->mnt_fsname = strdup(mp->mnt_fsname);
	376	new_mp->mnt_dir = strdup(mp->mnt_dir);
	377	new_mp->mnt_type = strdup(mp->mnt_type);
	378	new_mp->mnt_opts = strdup(mp->mnt_opts);
	379
	380	new_mp->mnt_freq = mp->mnt_freq;
	381	new_mp->mnt_passno = mp->mnt_passno;
	382
2f619045 JSP	383	#ifdef FIXUP_MNTENT_DUP
	384	/*
	385	* Additional fields get dup'ed here
	386	*/
	387	FIXUP_MNTENT_DUP(new_mp, mp);
	388	#endif
	389
e1a31032 KM	390	return new_mp;
	391	}
	392
	393	/*
	394	* Read a mount table into memory
	395	*/
	396	mntlist *read_mtab(fs)
	397	char *fs;
	398	{
	399	mntlist *mpp, mhp;
	400
	401	struct mntent *mep;
2f619045	402	FILE *mfp = open_locked_mtab(mtab, "r+", fs);
e1a31032	403
2f619045	404	if (!mfp)
e1a31032	405	return 0;
e1a31032 KM	406
	407	mpp = &mhp;
	408
	409	/*
	410	* XXX - In SunOS 4 there is (yet another) memory leak
	411	* which loses 1K the first time getmntent is called.
	412	* (jsp)
	413	*/
	414	while (mep = getmntent(mfp)) {
	415	/*
	416	* Allocate a new slot
	417	*/
	418	*mpp = ALLOC(mntlist);
	419
	420	/*
	421	* Copy the data returned by getmntent
	422	*/
	423	(*mpp)->mnt = mnt_dup(mep);
	424
	425	/*
	426	* Move to next pointer
	427	*/
	428	mpp = &(*mpp)->mnext;
	429	}
	430	*mpp = 0;
	431
	432	#ifdef UPDATE_MTAB
	433	/*
	434	* If we are not updating the mount table then we
	435	* can free the resources held here, otherwise they
	436	* must be held until the mount table update is complete
	437	*/
	438	mnt_file = mfp;
	439	#else
	440	endmntent(mfp);
	441	#endif /* UPDATE_MTAB */
	442
	443	return mhp;
	444	}
	445
	446	#endif /* READ_MTAB_FROM_FILE */