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opendir.c revision 1.16 
      1 /*	$NetBSD: opendir.c,v 1.16 1998/02/27 18:21:19 perry Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1983, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #include <sys/cdefs.h>
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 #if 0
     39 static char sccsid[] = "@(#)opendir.c	8.7 (Berkeley) 12/10/94";
     40 #else
     41 __RCSID("$NetBSD: opendir.c,v 1.16 1998/02/27 18:21:19 perry Exp $");
     42 #endif
     43 #endif /* LIBC_SCCS and not lint */
     44 
     45 #include "namespace.h"
     46 #include <sys/param.h>
     47 #include <sys/mount.h>
     48 #include <sys/stat.h>
     49 
     50 #include <dirent.h>
     51 #include <errno.h>
     52 #include <fcntl.h>
     53 #include <stdlib.h>
     54 #include <string.h>
     55 #include <unistd.h>
     56 
     57 #ifdef __weak_alias
     58 __weak_alias(opendir,_opendir);
     59 #endif
     60 
     61 /*
     62  * Open a directory.
     63  */
     64 DIR *
     65 opendir(name)
     66 	const char *name;
     67 {
     68 
     69 	return (__opendir2(name, DTF_HIDEW|DTF_NODUP));
     70 }
     71 
     72 DIR *
     73 __opendir2(name, flags)
     74 	const char *name;
     75 	int flags;
     76 {
     77 	DIR *dirp;
     78 	int fd;
     79 	struct stat sb;
     80 	int pagesz;
     81 	int incr;
     82 	int unionstack, nfsdir;
     83 	struct statfs sfb;
     84 
     85 	if ((fd = open(name, O_RDONLY | O_NONBLOCK)) == -1)
     86 		return (NULL);
     87 	if (fstat(fd, &sb) || !S_ISDIR(sb.st_mode)) {
     88 		errno = ENOTDIR;
     89 		close(fd);
     90 		return (NULL);
     91 	}
     92 	if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1 ||
     93 	    (dirp = (DIR *)malloc(sizeof(DIR))) == NULL) {
     94 		close(fd);
     95 		return (NULL);
     96 	}
     97 
     98 	/*
     99 	 * If the machine's page size is an exact multiple of DIRBLKSIZ,
    100 	 * use a buffer that is cluster boundary aligned.
    101 	 * Hopefully this can be a big win someday by allowing page trades
    102 	 * to user space to be done by getdirentries()
    103 	 */
    104 	if (((pagesz = getpagesize()) % DIRBLKSIZ) == 0)
    105 		incr = pagesz;
    106 	else
    107 		incr = DIRBLKSIZ;
    108 
    109 	/*
    110 	 * Determine whether this directory is the top of a union stack.
    111 	 */
    112 
    113 	if (fstatfs(fd, &sfb) < 0) {
    114 		free(dirp);
    115 		close(fd);
    116 		return (NULL);
    117 	}
    118 
    119 	if (flags & DTF_NODUP)
    120 		unionstack = !(strncmp(sfb.f_fstypename, MOUNT_UNION,
    121 		    MFSNAMELEN)) || (sfb.f_flags & MNT_UNION);
    122 	else
    123 		unionstack = 0;
    124 
    125 	nfsdir = !(strncmp(sfb.f_fstypename, MOUNT_NFS, MFSNAMELEN));
    126 
    127 	if (unionstack || nfsdir) {
    128 		size_t len;
    129 		size_t space;
    130 		char *buf;
    131 		char *ddptr;
    132 		char *ddeptr;
    133 		int n;
    134 		struct dirent **dpv;
    135 
    136 		/*
    137 		 * The strategy here for directories on top of a union stack
    138 		 * is to read all the directory entries into a buffer, sort
    139 		 * the buffer, and remove duplicate entries by setting the
    140 		 * inode number to zero.
    141 		 *
    142 		 * For directories on an NFS mounted filesystem, we try
    143 	 	 * to get a consistent snapshot by trying until we have
    144 		 * successfully read all of the directory without errors
    145 		 * (i.e. 'bad cookie' errors from the server because
    146 		 * the directory was modified). These errors should not
    147 		 * happen often, but need to be dealt with.
    148 		 */
    149 retry:
    150 		len = 0;
    151 		space = 0;
    152 		buf = 0;
    153 		ddptr = 0;
    154 
    155 		do {
    156 			/*
    157 			 * Always make at least DIRBLKSIZ bytes
    158 			 * available to getdirentries
    159 			 */
    160 			if (space < DIRBLKSIZ) {
    161 				space += incr;
    162 				len += incr;
    163 				buf = realloc(buf, len);
    164 				if (buf == NULL) {
    165 					free(dirp);
    166 					close(fd);
    167 					return (NULL);
    168 				}
    169 				ddptr = buf + (len - space);
    170 			}
    171 
    172 			dirp->dd_seek = lseek(fd, (off_t)0, SEEK_CUR);
    173 			n = getdents(fd, ddptr, space);
    174 			/*
    175 			 * For NFS: EINVAL means a bad cookie error
    176 			 * from the server. Keep trying to get a
    177 			 * consistent view, in this case this means
    178 			 * starting all over again.
    179 			 */
    180 			if (n == -1 && errno == EINVAL && nfsdir) {
    181 				free(buf);
    182 				lseek(fd, (off_t)0, SEEK_SET);
    183 				goto retry;
    184 			}
    185 			if (n > 0) {
    186 				ddptr += n;
    187 				space -= n;
    188 			}
    189 		} while (n > 0);
    190 
    191 		ddeptr = ddptr;
    192 		flags |= __DTF_READALL;
    193 
    194 		/*
    195 		 * Re-open the directory.
    196 		 * This has the effect of rewinding back to the
    197 		 * top of the union stack and is needed by
    198 		 * programs which plan to fchdir to a descriptor
    199 		 * which has also been read -- see fts.c.
    200 		 */
    201 		if (flags & DTF_REWIND) {
    202 			(void) close(fd);
    203 			if ((fd = open(name, O_RDONLY)) == -1) {
    204 				free(buf);
    205 				free(dirp);
    206 				return (NULL);
    207 			}
    208 		}
    209 
    210 		/*
    211 		 * There is now a buffer full of (possibly) duplicate
    212 		 * names.
    213 		 */
    214 		dirp->dd_buf = buf;
    215 
    216 		/*
    217 		 * Go round this loop twice...
    218 		 *
    219 		 * Scan through the buffer, counting entries.
    220 		 * On the second pass, save pointers to each one.
    221 		 * Then sort the pointers and remove duplicate names.
    222 		 */
    223 		if (!nfsdir) {
    224 			for (dpv = 0;;) {
    225 				for (n = 0, ddptr = buf; ddptr < ddeptr;) {
    226 					struct dirent *dp;
    227 
    228 					dp = (struct dirent *) ddptr;
    229 					if ((long)dp & 03)
    230 						break;
    231 					if ((dp->d_reclen <= 0) ||
    232 				    	(dp->d_reclen > (ddeptr + 1 - ddptr)))
    233 						break;
    234 					ddptr += dp->d_reclen;
    235 					if (dp->d_fileno) {
    236 						if (dpv)
    237 							dpv[n] = dp;
    238 						n++;
    239 					}
    240 				}
    241 
    242 				if (dpv) {
    243 					struct dirent *xp;
    244 
    245 					/*
    246 					 * This sort must be stable.
    247 					 */
    248 					mergesort(dpv, (size_t)n, sizeof(*dpv),
    249 					    alphasort);
    250 
    251 					dpv[n] = NULL;
    252 					xp = NULL;
    253 
    254 					/*
    255 					 * Scan through the buffer in sort
    256 					 * order, zapping the inode number
    257 					 * of any duplicate names.
    258 					 */
    259 					for (n = 0; dpv[n]; n++) {
    260 						struct dirent *dp = dpv[n];
    261 
    262 						if ((xp == NULL) ||
    263 						    strcmp(dp->d_name,
    264 						      xp->d_name))
    265 							xp = dp;
    266 						else
    267 							dp->d_fileno = 0;
    268 						if (dp->d_type == DT_WHT &&
    269 						    (flags & DTF_HIDEW))
    270 							dp->d_fileno = 0;
    271 					}
    272 
    273 					free(dpv);
    274 					break;
    275 				} else {
    276 					dpv = malloc((n+1) * sizeof(struct dirent *));
    277 					if (dpv == NULL)
    278 						break;
    279 				}
    280 			}
    281 		}
    282 
    283 		dirp->dd_len = len;
    284 		dirp->dd_size = ddptr - dirp->dd_buf;
    285 	} else {
    286 		dirp->dd_len = incr;
    287 		dirp->dd_buf = malloc((size_t)dirp->dd_len);
    288 		if (dirp->dd_buf == NULL) {
    289 			free(dirp);
    290 			close (fd);
    291 			return (NULL);
    292 		}
    293 		dirp->dd_seek = 0;
    294 		flags &= ~DTF_REWIND;
    295 	}
    296 
    297 	dirp->dd_loc = 0;
    298 	dirp->dd_fd = fd;
    299 	dirp->dd_flags = flags;
    300 
    301 	/*
    302 	 * Set up seek point for rewinddir.
    303 	 */
    304 	dirp->dd_rewind = telldir(dirp);
    305 
    306 	return (dirp);
    307 }
    308