1 /* $NetBSD: filecore_lookup.c,v 1.13 2010/06/24 13:03:09 hannken Exp $ */ 2 3 /*- 4 * Copyright (c) 1989, 1993, 1994 The Regents of the University of California. 5 * 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. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * filecore_lookup.c 1.1 1998/6/26 32 */ 33 34 /*- 35 * Copyright (c) 1998 Andrew McMurry 36 * 37 * Redistribution and use in source and binary forms, with or without 38 * modification, are permitted provided that the following conditions 39 * are met: 40 * 1. Redistributions of source code must retain the above copyright 41 * notice, this list of conditions and the following disclaimer. 42 * 2. Redistributions in binary form must reproduce the above copyright 43 * notice, this list of conditions and the following disclaimer in the 44 * documentation and/or other materials provided with the distribution. 45 * 3. All advertising materials mentioning features or use of this software 46 * must display the following acknowledgement: 47 * This product includes software developed by the University of 48 * California, Berkeley and its contributors. 49 * 4. Neither the name of the University nor the names of its contributors 50 * may be used to endorse or promote products derived from this software 51 * without specific prior written permission. 52 * 53 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 54 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 55 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 56 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 57 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 58 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 59 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 60 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 61 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 62 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 63 * SUCH DAMAGE. 64 * 65 * filecore_lookup.c 1.1 1998/6/26 66 */ 67 68 #include <sys/cdefs.h> 69 __KERNEL_RCSID(0, "$NetBSD: filecore_lookup.c,v 1.13 2010/06/24 13:03:09 hannken Exp $"); 70 71 #include <sys/param.h> 72 #include <sys/namei.h> 73 #include <sys/buf.h> 74 #include <sys/file.h> 75 #include <sys/vnode.h> 76 #include <sys/mount.h> 77 #include <sys/systm.h> 78 79 #include <fs/filecorefs/filecore.h> 80 #include <fs/filecorefs/filecore_extern.h> 81 #include <fs/filecorefs/filecore_node.h> 82 83 struct nchstats filecore_nchstats; 84 85 /* 86 * Convert a component of a pathname into a pointer to a locked inode. 87 * This is a very central and rather complicated routine. 88 * If the file system is not maintained in a strict tree hierarchy, 89 * this can result in a deadlock situation (see comments in code below). 90 * 91 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on 92 * whether the name is to be looked up, created, renamed, or deleted. 93 * When CREATE, RENAME, or DELETE is specified, information usable in 94 * creating, renaming, or deleting a directory entry may be calculated. 95 * If flag has LOCKPARENT or'ed into it and the target of the pathname 96 * exists, lookup returns both the target and its parent directory locked. 97 * When creating or renaming and LOCKPARENT is specified, the target may 98 * not be ".". When deleting and LOCKPARENT is specified, the target may 99 * be "."., but the caller must check to ensure it does an vrele and iput 100 * instead of two iputs. 101 * 102 * Overall outline of ufs_lookup: 103 * 104 * check accessibility of directory 105 * look for name in cache, if found, then if at end of path 106 * and deleting or creating, drop it, else return name 107 * search for name in directory, to found or notfound 108 * notfound: 109 * if creating, return locked directory, leaving info on available slots 110 * else return error 111 * found: 112 * if at end of path and deleting, return information to allow delete 113 * if at end of path and rewriting (RENAME and LOCKPARENT), lock target 114 * inode and return info to allow rewrite 115 * if not at end, add name to cache; if at end and neither creating 116 * nor deleting, add name to cache 117 * 118 * NOTE: (LOOKUP | LOCKPARENT) currently returns the parent inode unlocked. 119 */ 120 int 121 filecore_lookup(void *v) 122 { 123 struct vop_lookup_args /* { 124 struct vnode *a_dvp; 125 struct vnode **a_vpp; 126 struct componentname *a_cnp; 127 } */ *ap = v; 128 struct vnode *vdp; /* vnode for directory being searched */ 129 struct filecore_node *dp; /* inode for directory being searched */ 130 struct filecore_mnt *fcmp; /* file system that directory is in */ 131 struct buf *bp; /* a buffer of directory entries */ 132 struct filecore_direntry *de; 133 int numdirpasses; /* strategy for directory search */ 134 struct vnode *pdp; /* saved dp during symlink work */ 135 struct vnode *tdp; /* returned by filecore_vget_internal */ 136 int error; 137 u_short namelen; 138 int res; 139 const char *name; 140 struct vnode **vpp = ap->a_vpp; 141 struct componentname *cnp = ap->a_cnp; 142 kauth_cred_t cred = cnp->cn_cred; 143 int flags; 144 int nameiop = cnp->cn_nameiop; 145 int i, endsearch; 146 147 flags = cnp->cn_flags; 148 149 bp = NULL; 150 *vpp = NULL; 151 vdp = ap->a_dvp; 152 dp = VTOI(vdp); 153 fcmp = dp->i_mnt; 154 155 /* 156 * Check accessiblity of directory. 157 */ 158 if ((error = VOP_ACCESS(vdp, VEXEC, cred)) != 0) 159 return (error); 160 161 if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) && 162 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) 163 return (EROFS); 164 165 /* 166 * We now have a segment name to search for, and a directory to search. 167 * 168 * Before tediously performing a linear scan of the directory, 169 * check the name cache to see if the directory/name pair 170 * we are looking for is known already. 171 */ 172 if ((error = cache_lookup(vdp, vpp, cnp)) >= 0) 173 return (error); 174 175 name = cnp->cn_nameptr; 176 namelen = cnp->cn_namelen; 177 178 /* 179 * If there is cached information on a previous search of 180 * this directory, pick up where we last left off. 181 * We cache only lookups as these are the most common 182 * and have the greatest payoff. Caching CREATE has little 183 * benefit as it usually must search the entire directory 184 * to determine that the entry does not exist. Caching the 185 * location of the last DELETE or RENAME has not reduced 186 * profiling time and hence has been removed in the interest 187 * of simplicity. 188 */ 189 if (nameiop != LOOKUP || dp->i_diroff == 0 || 190 dp->i_diroff >= FILECORE_MAXDIRENTS) { 191 i = 0; 192 numdirpasses = 1; 193 } else { 194 i = dp->i_diroff; 195 numdirpasses = 2; 196 filecore_nchstats.ncs_2passes++; 197 } 198 endsearch = FILECORE_MAXDIRENTS; 199 200 if ((flags & ISDOTDOT) || (name[0] == '.' && namelen == 1)) 201 goto found; 202 203 error = filecore_dbread(dp, &bp); 204 if (error) { 205 brelse(bp, 0); 206 return error; 207 } 208 209 de = fcdirentry(bp->b_data, i); 210 211 searchloop: 212 while (de->name[0] != 0 && i < endsearch) { 213 /* 214 * Check for a name match. 215 */ 216 res = filecore_fncmp(de->name, name, namelen); 217 218 if (res == 0) 219 goto found; 220 if (res < 0) 221 goto notfound; 222 223 i++; 224 de++; 225 } 226 227 notfound: 228 /* 229 * If we started in the middle of the directory and failed 230 * to find our target, we must check the beginning as well. 231 */ 232 if (numdirpasses == 2) { 233 numdirpasses--; 234 i = 0; 235 de = fcdirentry(bp->b_data, i); 236 endsearch = dp->i_diroff; 237 goto searchloop; 238 } 239 if (bp != NULL) { 240 #ifdef FILECORE_DEBUG_BR 241 printf("brelse(%p) lo1\n", bp); 242 #endif 243 brelse(bp, 0); 244 } 245 246 /* 247 * Insert name into cache (as non-existent) if appropriate. 248 */ 249 if (cnp->cn_flags & MAKEENTRY) 250 cache_enter(vdp, *vpp, cnp); 251 if (nameiop == CREATE || nameiop == RENAME) 252 return (EROFS); 253 return (ENOENT); 254 255 found: 256 if (numdirpasses == 2) 257 filecore_nchstats.ncs_pass2++; 258 259 /* 260 * Found component in pathname. 261 * If the final component of path name, save information 262 * in the cache as to where the entry was found. 263 */ 264 if ((flags & ISLASTCN) && nameiop == LOOKUP) 265 dp->i_diroff = i; 266 267 /* 268 * Step through the translation in the name. We do not `iput' the 269 * directory because we may need it again if a symbolic link 270 * is relative to the current directory. Instead we save it 271 * unlocked as "pdp". We must get the target inode before unlocking 272 * the directory to insure that the inode will not be removed 273 * before we get it. We prevent deadlock by always fetching 274 * inodes from the root, moving down the directory tree. Thus 275 * when following backward pointers ".." we must unlock the 276 * parent directory before getting the requested directory. 277 * There is a potential race condition here if both the current 278 * and parent directories are removed before the `iget' for the 279 * inode associated with ".." returns. We hope that this occurs 280 * infrequently since we cannot avoid this race condition without 281 * implementing a sophisticated deadlock detection algorithm. 282 * Note also that this simple deadlock detection scheme will not 283 * work if the file system has any hard links other than ".." 284 * that point backwards in the directory structure. 285 */ 286 pdp = vdp; 287 288 /* 289 * If ino is different from dp->i_ino, 290 * it's a relocated directory. 291 */ 292 if (flags & ISDOTDOT) { 293 ino_t pin = filecore_getparent(dp); 294 295 VOP_UNLOCK(pdp); /* race to get the inode */ 296 error = VFS_VGET(vdp->v_mount, pin, &tdp); 297 vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY); 298 if (error) { 299 return error; 300 } 301 *vpp = tdp; 302 } else if (name[0] == '.' && namelen == 1) { 303 vref(vdp); /* we want ourself, ie "." */ 304 *vpp = vdp; 305 } else { 306 #ifdef FILECORE_DEBUG_BR 307 printf("brelse(%p) lo4\n", bp); 308 #endif 309 brelse(bp, 0); 310 error = VFS_VGET(vdp->v_mount, dp->i_dirent.addr | 311 (i << FILECORE_INO_INDEX), &tdp); 312 if (error) 313 return (error); 314 *vpp = tdp; 315 } 316 317 /* 318 * Insert name into cache if appropriate. 319 */ 320 if (cnp->cn_flags & MAKEENTRY) 321 cache_enter(vdp, *vpp, cnp); 322 return (0); 323 } 324