filecore_lookup.c revision 1.19
1 /* $NetBSD: filecore_lookup.c,v 1.19 2014/02/07 15:29:21 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 1.19 2014/02/07 15:29:21 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_v2_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 buf *bp; /* a buffer of directory entries */ 131 struct filecore_direntry *de; 132 int numdirpasses; /* strategy for directory search */ 133 struct vnode *pdp; /* saved dp during symlink work */ 134 struct vnode *tdp; /* returned by filecore_vget_internal */ 135 int error; 136 u_short namelen; 137 int res; 138 const char *name; 139 struct vnode **vpp = ap->a_vpp; 140 struct componentname *cnp = ap->a_cnp; 141 kauth_cred_t cred = cnp->cn_cred; 142 int flags; 143 int nameiop = cnp->cn_nameiop; 144 int i, endsearch; 145 146 flags = cnp->cn_flags; 147 148 bp = NULL; 149 *vpp = NULL; 150 vdp = ap->a_dvp; 151 dp = VTOI(vdp); 152 153 /* 154 * Check accessiblity of directory. 155 */ 156 if ((error = VOP_ACCESS(vdp, VEXEC, cred)) != 0) 157 return (error); 158 159 if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) && 160 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) 161 return (EROFS); 162 163 /* 164 * We now have a segment name to search for, and a directory to search. 165 * 166 * Before tediously performing a linear scan of the directory, 167 * check the name cache to see if the directory/name pair 168 * we are looking for is known already. 169 */ 170 if (cache_lookup(vdp, cnp->cn_nameptr, cnp->cn_namelen, 171 cnp->cn_nameiop, cnp->cn_flags, NULL, vpp)) { 172 return *vpp == NULLVP ? ENOENT : 0; 173 } 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 return error; 206 } 207 208 de = fcdirentry(bp->b_data, i); 209 210 searchloop: 211 while (de->name[0] != 0 && i < endsearch) { 212 /* 213 * Check for a name match. 214 */ 215 res = filecore_fncmp(de->name, name, namelen); 216 217 if (res == 0) 218 goto found; 219 if (res < 0) 220 goto notfound; 221 222 i++; 223 de++; 224 } 225 226 notfound: 227 /* 228 * If we started in the middle of the directory and failed 229 * to find our target, we must check the beginning as well. 230 */ 231 if (numdirpasses == 2) { 232 numdirpasses--; 233 i = 0; 234 de = fcdirentry(bp->b_data, i); 235 endsearch = dp->i_diroff; 236 goto searchloop; 237 } 238 if (bp != NULL) { 239 #ifdef FILECORE_DEBUG_BR 240 printf("brelse(%p) lo1\n", bp); 241 #endif 242 brelse(bp, 0); 243 } 244 245 /* 246 * Insert name into cache (as non-existent) if appropriate. 247 */ 248 cache_enter(vdp, *vpp, cnp->cn_nameptr, cnp->cn_namelen, 249 cnp->cn_flags); 250 return (nameiop == CREATE || nameiop == RENAME) ? EROFS : ENOENT; 251 252 found: 253 if (numdirpasses == 2) 254 filecore_nchstats.ncs_pass2++; 255 256 /* 257 * Found component in pathname. 258 * If the final component of path name, save information 259 * in the cache as to where the entry was found. 260 */ 261 if ((flags & ISLASTCN) && nameiop == LOOKUP) 262 dp->i_diroff = i; 263 264 /* 265 * Step through the translation in the name. We do not `iput' the 266 * directory because we may need it again if a symbolic link 267 * is relative to the current directory. Instead we save it 268 * unlocked as "pdp". We must get the target inode before unlocking 269 * the directory to insure that the inode will not be removed 270 * before we get it. We prevent deadlock by always fetching 271 * inodes from the root, moving down the directory tree. Thus 272 * when following backward pointers ".." we must unlock the 273 * parent directory before getting the requested directory. 274 * There is a potential race condition here if both the current 275 * and parent directories are removed before the `iget' for the 276 * inode associated with ".." returns. We hope that this occurs 277 * infrequently since we cannot avoid this race condition without 278 * implementing a sophisticated deadlock detection algorithm. 279 * Note also that this simple deadlock detection scheme will not 280 * work if the file system has any hard links other than ".." 281 * that point backwards in the directory structure. 282 */ 283 pdp = vdp; 284 285 /* 286 * If ino is different from dp->i_ino, 287 * it's a relocated directory. 288 */ 289 if (flags & ISDOTDOT) { 290 ino_t pin = filecore_getparent(dp); 291 292 VOP_UNLOCK(pdp); /* race to get the inode */ 293 error = VFS_VGET(vdp->v_mount, pin, &tdp); 294 vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY); 295 if (error) { 296 return error; 297 } 298 *vpp = tdp; 299 } else if (name[0] == '.' && namelen == 1) { 300 vref(vdp); /* we want ourself, ie "." */ 301 *vpp = vdp; 302 } else { 303 #ifdef FILECORE_DEBUG_BR 304 printf("brelse(%p) lo4\n", bp); 305 #endif 306 brelse(bp, 0); 307 error = VFS_VGET(vdp->v_mount, dp->i_dirent.addr | 308 (i << FILECORE_INO_INDEX), &tdp); 309 if (error) 310 return (error); 311 *vpp = tdp; 312 } 313 314 /* 315 * Insert name into cache if appropriate. 316 */ 317 cache_enter(vdp, *vpp, cnp->cn_nameptr, cnp->cn_namelen, 318 cnp->cn_flags); 319 if (*vpp != vdp) 320 VOP_UNLOCK(*vpp); 321 return 0; 322 } 323
Indexes created Thu Oct 02 14:10:14 GMT 2025