1 /* $NetBSD: filecore_lookup.c,v 1.4 2003/08/07 16:31:37 agc 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 1.4 2003/08/07 16:31:37 agc 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(v) 122 void *v; 123 { 124 struct vop_lookup_args /* { 125 struct vnode *a_dvp; 126 struct vnode **a_vpp; 127 struct componentname *a_cnp; 128 } */ *ap = v; 129 struct vnode *vdp; /* vnode for directory being searched */ 130 struct filecore_node *dp; /* inode for directory being searched */ 131 struct filecore_mnt *fcmp; /* file system that directory is in */ 132 struct buf *bp; /* a buffer of directory entries */ 133 struct filecore_direntry *de; 134 int numdirpasses; /* strategy for directory search */ 135 struct vnode *pdp; /* saved dp during symlink work */ 136 struct vnode *tdp; /* returned by filecore_vget_internal */ 137 int lockparent; /* 1 => lockparent flag is set */ 138 int wantparent; /* 1 => wantparent or lockparent flag */ 139 int error; 140 u_short namelen; 141 int res; 142 const char *name; 143 struct vnode **vpp = ap->a_vpp; 144 struct componentname *cnp = ap->a_cnp; 145 struct ucred *cred = cnp->cn_cred; 146 int flags; 147 int nameiop = cnp->cn_nameiop; 148 int i, endsearch; 149 150 cnp->cn_flags &= ~PDIRUNLOCK; 151 flags = cnp->cn_flags; 152 153 bp = NULL; 154 *vpp = NULL; 155 vdp = ap->a_dvp; 156 dp = VTOI(vdp); 157 fcmp = dp->i_mnt; 158 lockparent = flags & LOCKPARENT; 159 wantparent = flags & (LOCKPARENT|WANTPARENT); 160 161 /* 162 * Check accessiblity of directory. 163 */ 164 if ((error = VOP_ACCESS(vdp, VEXEC, cred, cnp->cn_proc)) != 0) 165 return (error); 166 167 if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) && 168 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) 169 return (EROFS); 170 171 /* 172 * We now have a segment name to search for, and a directory to search. 173 * 174 * Before tediously performing a linear scan of the directory, 175 * check the name cache to see if the directory/name pair 176 * we are looking for is known already. 177 */ 178 if ((error = cache_lookup(vdp, vpp, cnp)) >= 0) 179 return (error); 180 181 name = cnp->cn_nameptr; 182 namelen = cnp->cn_namelen; 183 184 /* 185 * If there is cached information on a previous search of 186 * this directory, pick up where we last left off. 187 * We cache only lookups as these are the most common 188 * and have the greatest payoff. Caching CREATE has little 189 * benefit as it usually must search the entire directory 190 * to determine that the entry does not exist. Caching the 191 * location of the last DELETE or RENAME has not reduced 192 * profiling time and hence has been removed in the interest 193 * of simplicity. 194 */ 195 if (nameiop != LOOKUP || dp->i_diroff == 0 || 196 dp->i_diroff >= FILECORE_MAXDIRENTS) { 197 i = 0; 198 numdirpasses = 1; 199 } else { 200 i = dp->i_diroff; 201 numdirpasses = 2; 202 filecore_nchstats.ncs_2passes++; 203 } 204 endsearch = FILECORE_MAXDIRENTS; 205 206 if ((flags & ISDOTDOT) || (name[0] == '.' && namelen == 1)) 207 goto found; 208 209 error = filecore_dbread(dp, &bp); 210 if (error) { 211 brelse(bp); 212 return error; 213 } 214 215 de = fcdirentry(bp->b_data, i); 216 217 searchloop: 218 while (de->name[0] != 0 && i < endsearch) { 219 /* 220 * Check for a name match. 221 */ 222 res = filecore_fncmp(de->name, name, namelen); 223 224 if (res == 0) 225 goto found; 226 if (res < 0) 227 goto notfound; 228 229 i++; 230 de++; 231 } 232 233 notfound: 234 /* 235 * If we started in the middle of the directory and failed 236 * to find our target, we must check the beginning as well. 237 */ 238 if (numdirpasses == 2) { 239 numdirpasses--; 240 i = 0; 241 de = fcdirentry(bp->b_data, i); 242 endsearch = dp->i_diroff; 243 goto searchloop; 244 } 245 if (bp != NULL) { 246 #ifdef FILECORE_DEBUG_BR 247 printf("brelse(%p) lo1\n", bp); 248 #endif 249 brelse(bp); 250 } 251 252 /* 253 * Insert name into cache (as non-existent) if appropriate. 254 */ 255 if (cnp->cn_flags & MAKEENTRY) 256 cache_enter(vdp, *vpp, cnp); 257 if (nameiop == CREATE || nameiop == RENAME) 258 return (EROFS); 259 return (ENOENT); 260 261 found: 262 if (numdirpasses == 2) 263 filecore_nchstats.ncs_pass2++; 264 265 /* 266 * Found component in pathname. 267 * If the final component of path name, save information 268 * in the cache as to where the entry was found. 269 */ 270 if ((flags & ISLASTCN) && nameiop == LOOKUP) 271 dp->i_diroff = i; 272 273 /* 274 * Step through the translation in the name. We do not `iput' the 275 * directory because we may need it again if a symbolic link 276 * is relative to the current directory. Instead we save it 277 * unlocked as "pdp". We must get the target inode before unlocking 278 * the directory to insure that the inode will not be removed 279 * before we get it. We prevent deadlock by always fetching 280 * inodes from the root, moving down the directory tree. Thus 281 * when following backward pointers ".." we must unlock the 282 * parent directory before getting the requested directory. 283 * There is a potential race condition here if both the current 284 * and parent directories are removed before the `iget' for the 285 * inode associated with ".." returns. We hope that this occurs 286 * infrequently since we cannot avoid this race condition without 287 * implementing a sophisticated deadlock detection algorithm. 288 * Note also that this simple deadlock detection scheme will not 289 * work if the file system has any hard links other than ".." 290 * that point backwards in the directory structure. 291 */ 292 pdp = vdp; 293 /* 294 * If ino is different from dp->i_ino, 295 * it's a relocated directory. 296 */ 297 if (flags & ISDOTDOT) { 298 ino_t pin = filecore_getparent(dp); 299 VOP_UNLOCK(pdp, 0); /* race to get the inode */ 300 cnp->cn_flags |= PDIRUNLOCK; 301 error = VFS_VGET(vdp->v_mount, pin, &tdp); 302 if (error) { 303 if (vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY) == 0) 304 cnp->cn_flags &= ~PDIRUNLOCK; 305 return (error); 306 } 307 if (lockparent && (flags & ISLASTCN)) { 308 if ((error = vn_lock(pdp, LK_EXCLUSIVE))) { 309 vput(tdp); 310 return (error); 311 } 312 cnp->cn_flags &= ~PDIRUNLOCK; 313 } 314 *vpp = tdp; 315 } else if (name[0] == '.' && namelen == 1) { 316 VREF(vdp); /* we want ourself, ie "." */ 317 *vpp = vdp; 318 } else { 319 #ifdef FILECORE_DEBUG_BR 320 printf("brelse(%p) lo4\n", bp); 321 #endif 322 brelse(bp); 323 error = VFS_VGET(vdp->v_mount, dp->i_dirent.addr | 324 (i << FILECORE_INO_INDEX), &tdp); 325 if (error) 326 return (error); 327 if (!lockparent || !(flags & ISLASTCN)) { 328 VOP_UNLOCK(pdp, 0); 329 cnp->cn_flags |= PDIRUNLOCK; 330 } 331 *vpp = tdp; 332 } 333 334 /* 335 * Insert name into cache if appropriate. 336 */ 337 if (cnp->cn_flags & MAKEENTRY) 338 cache_enter(vdp, *vpp, cnp); 339 return (0); 340 } 341