495 lines
12 KiB
C
495 lines
12 KiB
C
/* $NetBSD: mtab_mach3.c,v 1.1.1.1 2000/06/07 00:52:20 dogcow Exp $ */
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/*
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* Copyright (c) 1997-2000 Erez Zadok
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* Copyright (c) 1990 Jan-Simon Pendry
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* Copyright (c) 1990 Imperial College of Science, Technology & Medicine
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Jan-Simon Pendry at Imperial College, London.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgment:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* %W% (Berkeley) %G%
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*
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* Id: mtab_mach3.c,v 1.4 2000/01/12 16:44:43 ezk Exp
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*
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*/
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif /* HAVE_CONFIG_H */
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#include <am_defs.h>
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#include <amu.h>
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#define NFILE_RETRIES 10 /* number of retries (seconds) */
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static FILE *mnt_file;
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/*
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* If the system is being trashed by something, then
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* opening mtab may fail with ENFILE. So, go to sleep
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* for a second and try again. (Yes - this has happened to me.)
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*
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* Note that this *may* block the automounter, oh well.
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* If we get to this state then things are badly wrong anyway...
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*
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* Give the system 10 seconds to recover but then give up.
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* Hopefully something else will exit and free up some file
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* table slots in that time.
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*/
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#ifdef HAVE_FCNTL_H
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static int
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lock(int fd)
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{
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int rc;
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struct flock lk;
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lk.l_type = F_WRLCK;
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lk.l_whence = 0;
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lk.l_start = 0;
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lk.l_len = 0;
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again:
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rc = fcntl(fd, F_SETLKW, (caddr_t) & lk);
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if (rc < 0 && (errno == EACCES || errno == EAGAIN)) {
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# ifdef DEBUG
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dlog("Blocked, trying to obtain exclusive mtab lock");
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# endif /* DEBUG */
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sleep(1);
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goto again;
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}
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return rc;
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}
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#else /* not HAVE_FCNTL_H */
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# define lock(fd) (flock((fd), LOCK_EX))
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#endif /* not HAVE_FCNTL_H */
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static FILE *
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open_locked_mtab(char *mnttabname, char *mode, char *fs)
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{
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FILE *mfp = 0;
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/*
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* There is a possible race condition if two processes enter
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* this routine at the same time. One will be blocked by the
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* exclusive lock below (or by the shared lock in setmntent)
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* and by the time the second process has the exclusive lock
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* it will be on the wrong underlying object. To check for this
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* the mtab file is stat'ed before and after all the locking
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* sequence, and if it is a different file then we assume that
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* it may be the wrong file (only "may", since there is another
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* race between the initial stat and the setmntent).
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*
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* Simpler solutions to this problem are invited...
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*/
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int racing = 2;
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int rc;
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int retries = 0;
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struct stat st_before, st_after;
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if (mnt_file) {
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#ifdef DEBUG
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dlog("Forced close on %s in read_mtab", mnttabname);
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#endif /* DEBUG */
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endmntent(mnt_file);
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mnt_file = 0;
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}
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again:
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if (mfp) {
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endmntent(mfp);
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mfp = 0;
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}
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clock_valid = 0;
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if (stat(mnttabname, &st_before) < 0) {
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plog(XLOG_ERROR, "%s: stat: %m", mnttabname);
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if (errno == ESTALE) {
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/* happens occasionally */
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sleep(1);
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goto again;
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}
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return 0;
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}
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eacces:
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mfp = setmntent(mnttabname, mode);
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if (!mfp) {
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/*
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* Since setmntent locks the descriptor, it
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* is possible it can fail... so retry if
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* needed.
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*/
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if (errno == EACCES || errno == EAGAIN) {
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#ifdef DEBUG
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dlog("Blocked, trying to obtain exclusive mtab lock");
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#endif /* DEBUG */
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goto eacces;
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} else if (errno == ENFILE && retries++ < NFILE_RETRIES) {
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sleep(1);
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goto eacces;
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}
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plog(XLOG_ERROR, "setmntent(\"%s\", \"%s\"): %m", mnttabname, mode);
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return 0;
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}
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/*
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* At this point we have an exclusive lock on the mount list,
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* but it may be the wrong one so...
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*/
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/*
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* Need to get an exclusive lock on the current
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* mount table until we have a new copy written
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* out, when the lock is released in free_mntlist.
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* flock is good enough since the mount table is
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* not shared between machines.
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*/
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do
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rc = lock(fileno(mfp));
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while (rc < 0 && errno == EINTR);
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if (rc < 0) {
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plog(XLOG_ERROR, "Couldn't lock %s: %m", mnttabname);
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endmntent(mfp);
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return 0;
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}
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/*
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* Now check whether the mtab file has changed under our feet
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*/
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if (stat(mnttabname, &st_after) < 0) {
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plog(XLOG_ERROR, "%s: stat", mnttabname);
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goto again;
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}
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if (st_before.st_dev != st_after.st_dev ||
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st_before.st_ino != st_after.st_ino) {
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struct timeval tv;
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if (racing == 0) {
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/* Sometimes print a warning */
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plog(XLOG_WARNING,
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"Possible mount table race - retrying %s", fs);
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}
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racing = (racing + 1) & 3;
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/*
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* Take a nap. From: Doug Kingston <dpk@morgan.com>
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*/
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tv.tv_sec = 0;
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tv.tv_usec = (am_mypid & 0x07) << 17;
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if (tv.tv_usec)
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if (select(0, (voidp) 0, (voidp) 0, (voidp) 0, &tv) < 0)
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plog(XLOG_WARNING, "mtab nap failed: %m");
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goto again;
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}
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return mfp;
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}
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/*
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* Unlock the mount table
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*/
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void
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unlock_mntlist(void)
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{
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/*
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* Release file lock, by closing the file
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*/
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if (mnt_file) {
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endmntent(mnt_file);
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mnt_file = 0;
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}
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}
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/*
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* routine to convert notation "/@honeydew" to the notation
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* honeydew:/ and vice versa (honeydew:/ to /@honeydew)
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* This lets you put /@honeydew in /etc/fstab without changing
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* fstab.c and it lets you use EITHER notation on the command line!
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*/
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static char *
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convert(register char *s, char bad, char good)
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{
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char *index();
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register char *t, *p;
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register int len1, len2, i;
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char *ptr;
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if ((p = index(s, bad)) == NULL) {
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return (s);
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}
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ptr = t = (char *) xzalloc(MAXPATHLEN * sizeof(char));
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len1 = p - s;
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len2 = strlen(s) - len1 - 1;
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p++;
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for (i = 0; i < len2; i++)
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*t++ = p[i];
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*t++ = good;
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for (i = 0; i < len1; i++)
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*t++ = s[i];
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return (ptr);
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}
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static
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mntprtent3(FILE *mnttabp, register mntent_t *mnt)
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{
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char *cvtd = convert(mnt->mnt_fsname, ':', '@');
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dlog("%x:%s:%s:%s:%d:%d:%s:%s:\n",
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mnttabp,
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(cvtd ? cvtd : ""),
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(mnt->mnt_dir ? mnt->mnt_dir : ""),
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(mnt->mnt_opts ? mnt->mnt_opts : ""),
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mnt->mnt_freq,
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mnt->mnt_passno,
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(mnt->mnt_type ? mnt->mnt_type : ""),
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(mnt->mnt_opts2 ? mnt->mnt_opts2 : "")
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);
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fprintf(mnttabp, "%s:%s:%s:%d:%d:%s:%s:\n",
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(cvtd ? cvtd : ""),
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(mnt->mnt_dir ? mnt->mnt_dir : ""),
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(mnt->mnt_opts ? mnt->mnt_opts : ""),
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mnt->mnt_freq,
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mnt->mnt_passno,
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(mnt->mnt_type ? mnt->mnt_type : ""),
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(mnt->mnt_opts2 ? mnt->mnt_opts2 : "")
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);
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XFREE(cvtd);
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cvtd = NULL;
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return (0);
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}
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addmntent3(FILE *mnttabp, register mntent_t *mnt)
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{
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if (fseek(mnttabp, 0, 2) < 0) {
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return (1);
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}
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mntprtent3(mnttabp, mnt);
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return (0);
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}
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/*
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* Write out a mount list
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*/
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void
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rewrite_mtab(mntlist *mp, const char *mnttabname)
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{
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FILE *mfp;
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int error = 0;
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/*
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* Concoct a temporary name in the same
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* directory as the target mount table
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* so that rename() will work.
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*/
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char tmpname[64];
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int retries;
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int tmpfd;
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char *cp;
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char *mcp = mnttabname;
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cp = strrchr(mcp, '/');
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if (cp) {
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memmove(tmpname, mcp, cp - mcp);
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tmpname[cp - mcp] = '\0';
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} else {
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plog(XLOG_WARNING, "No '/' in mtab (%s), using \".\" as tmp directory", mnttabname);
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tmpname[0] = '.';
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tmpname[1] = '\0';
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}
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strcat(tmpname, "/mtabXXXXXX");
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mktemp(tmpname);
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retries = 0;
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enfile1:
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if ((tmpfd = open(tmpname, O_RDWR | O_CREAT | O_TRUNC, 0644)) < 0) {
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if (errno == ENFILE && retries++ < NFILE_RETRIES) {
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sleep(1);
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goto enfile1;
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}
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plog(XLOG_ERROR, "%s: open: %m", tmpname);
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return;
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}
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if (close(tmpfd) < 0)
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plog(XLOG_ERROR, "Couldn't close tmp file descriptor: %m");
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retries = 0;
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enfile2:
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mfp = setmntent(tmpname, "w");
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if (!mfp) {
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if (errno == ENFILE && retries++ < NFILE_RETRIES) {
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sleep(1);
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goto enfile2;
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}
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plog(XLOG_ERROR, "setmntent(\"%s\", \"w\"): %m", tmpname);
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error = 1;
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goto out;
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}
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while (mp) {
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if (mp->mnt) {
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if (addmntent3(mfp, mp->mnt)) {
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plog(XLOG_ERROR, "Can't write entry to %s", tmpname);
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error = 1;
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goto out;
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}
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}
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mp = mp->mnext;
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}
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/*
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* SunOS 4.1 manuals say that the return code from endmntent()
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* is always 1 and to treat as a void. That means we need to
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* call fflush() to make sure the new mtab file got written.
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*/
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if (fflush(mfp)) {
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plog(XLOG_ERROR, "flush new mtab file: %m");
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error = 1;
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goto out;
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}
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(void) endmntent(mfp);
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/*
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* Rename temporary mtab to real mtab
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*/
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if (rename(tmpname, mnttabname) < 0) {
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plog(XLOG_ERROR, "rename %s to %s: %m", tmpname, mnttabname);
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error = 1;
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goto out;
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}
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out:
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if (error)
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(void) unlink(tmpname);
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}
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static void
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mtab_stripnl(char *s)
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{
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do {
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s = strchr(s, '\n');
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if (s)
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*s++ = ' ';
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} while (s);
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}
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/*
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* Append a mntent structure to the
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* current mount table.
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*/
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void
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write_mntent(mntent_t *mp, const char *mnttabname)
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{
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int retries = 0;
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FILE *mfp;
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enfile:
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mfp = open_locked_mtab(mnttabname, "a", mp->mnt_dir);
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if (mfp) {
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mtab_stripnl(mp->mnt_opts);
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if (addmntent3(mfp, mp))
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plog(XLOG_ERROR, "Couldn't write %s: %m", mnttabname);
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if (fflush(mfp))
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plog(XLOG_ERROR, "Couldn't flush %s: %m", mnttabname);
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(void) endmntent(mfp);
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} else {
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if (errno == ENFILE && retries < NFILE_RETRIES) {
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sleep(1);
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goto enfile;
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}
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plog(XLOG_ERROR, "setmntent(\"%s\", \"a\"): %m", mnttabname);
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}
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}
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static mntent_t *
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mnt_dup(mntent_t *mp)
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{
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mntent_t *new_mp = ALLOC(mntent_t);
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new_mp->mnt_fsname = convert(mp->mnt_fsname, '@', ':');
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new_mp->mnt_dir = strdup(mp->mnt_dir);
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new_mp->mnt_type = strdup(mp->mnt_type);
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new_mp->mnt_opts = strdup(mp->mnt_opts);
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new_mp->mnt_freq = mp->mnt_freq;
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new_mp->mnt_passno = mp->mnt_passno;
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return new_mp;
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}
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/*
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* Read a mount table into memory
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*/
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mntlist *
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read_mtab(char *fs, const char *mnttabname)
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{
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mntlist **mpp, *mhp;
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mntent_t *mep;
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FILE *mfp = open_locked_mtab(mnttabname, "r+", fs);
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if (!mfp)
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return 0;
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mpp = &mhp;
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/*
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* XXX - In SunOS 4 there is (yet another) memory leak
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* which loses 1K the first time getmntent is called.
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* (jsp)
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*/
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while (mep = getmntent(mfp)) {
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/*
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* Allocate a new slot
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*/
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*mpp = ALLOC(struct mntlist);
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/*
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* Copy the data returned by getmntent
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*/
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(*mpp)->mnt = mnt_dup(mep);
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/*
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* Move to next pointer
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*/
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mpp = &(*mpp)->mnext;
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}
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*mpp = 0;
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/*
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* If we are not updating the mount table then we
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* can free the resources held here, otherwise they
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* must be held until the mount table update is complete
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*/
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mnt_file = mfp;
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return mhp;
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}
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