filecore_lookup.c revision 1.5.4.3
1 /* $NetBSD: filecore_lookup.c,v 1.5.4.3 2007/10/27 11:35:02 yamt 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 1.5.4.3 2007/10/27 11:35:02 yamt 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 error; 138 u_short namelen; 139 int res; 140 const char *name; 141 struct vnode **vpp = ap->a_vpp; 142 struct componentname *cnp = ap->a_cnp; 143 kauth_cred_t cred = cnp->cn_cred; 144 int flags; 145 int nameiop = cnp->cn_nameiop; 146 int i, endsearch; 147 148 flags = cnp->cn_flags; 149 150 bp = NULL; 151 *vpp = NULL; 152 vdp = ap->a_dvp; 153 dp = VTOI(vdp); 154 fcmp = dp->i_mnt; 155 156 /* 157 * Check accessiblity of directory. 158 */ 159 if ((error = VOP_ACCESS(vdp, VEXEC, cred, cnp->cn_lwp)) != 0) 160 return (error); 161 162 if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) && 163 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) 164 return (EROFS); 165 166 /* 167 * We now have a segment name to search for, and a directory to search. 168 * 169 * Before tediously performing a linear scan of the directory, 170 * check the name cache to see if the directory/name pair 171 * we are looking for is known already. 172 */ 173 if ((error = cache_lookup(vdp, vpp, cnp)) >= 0) 174 return (error); 175 176 name = cnp->cn_nameptr; 177 namelen = cnp->cn_namelen; 178 179 /* 180 * If there is cached information on a previous search of 181 * this directory, pick up where we last left off. 182 * We cache only lookups as these are the most common 183 * and have the greatest payoff. Caching CREATE has little 184 * benefit as it usually must search the entire directory 185 * to determine that the entry does not exist. Caching the 186 * location of the last DELETE or RENAME has not reduced 187 * profiling time and hence has been removed in the interest 188 * of simplicity. 189 */ 190 if (nameiop != LOOKUP || dp->i_diroff == 0 || 191 dp->i_diroff >= FILECORE_MAXDIRENTS) { 192 i = 0; 193 numdirpasses = 1; 194 } else { 195 i = dp->i_diroff; 196 numdirpasses = 2; 197 filecore_nchstats.ncs_2passes++; 198 } 199 endsearch = FILECORE_MAXDIRENTS; 200 201 if ((flags & ISDOTDOT) || (name[0] == '.' && namelen == 1)) 202 goto found; 203 204 error = filecore_dbread(dp, &bp); 205 if (error) { 206 brelse(bp, 0); 207 return error; 208 } 209 210 de = fcdirentry(bp->b_data, i); 211 212 searchloop: 213 while (de->name[0] != 0 && i < endsearch) { 214 /* 215 * Check for a name match. 216 */ 217 res = filecore_fncmp(de->name, name, namelen); 218 219 if (res == 0) 220 goto found; 221 if (res < 0) 222 goto notfound; 223 224 i++; 225 de++; 226 } 227 228 notfound: 229 /* 230 * If we started in the middle of the directory and failed 231 * to find our target, we must check the beginning as well. 232 */ 233 if (numdirpasses == 2) { 234 numdirpasses--; 235 i = 0; 236 de = fcdirentry(bp->b_data, i); 237 endsearch = dp->i_diroff; 238 goto searchloop; 239 } 240 if (bp != NULL) { 241 #ifdef FILECORE_DEBUG_BR 242 printf("brelse(%p) lo1\n", bp); 243 #endif 244 brelse(bp, 0); 245 } 246 247 /* 248 * Insert name into cache (as non-existent) if appropriate. 249 */ 250 if (cnp->cn_flags & MAKEENTRY) 251 cache_enter(vdp, *vpp, cnp); 252 if (nameiop == CREATE || nameiop == RENAME) 253 return (EROFS); 254 return (ENOENT); 255 256 found: 257 if (numdirpasses == 2) 258 filecore_nchstats.ncs_pass2++; 259 260 /* 261 * Found component in pathname. 262 * If the final component of path name, save information 263 * in the cache as to where the entry was found. 264 */ 265 if ((flags & ISLASTCN) && nameiop == LOOKUP) 266 dp->i_diroff = i; 267 268 /* 269 * Step through the translation in the name. We do not `iput' the 270 * directory because we may need it again if a symbolic link 271 * is relative to the current directory. Instead we save it 272 * unlocked as "pdp". We must get the target inode before unlocking 273 * the directory to insure that the inode will not be removed 274 * before we get it. We prevent deadlock by always fetching 275 * inodes from the root, moving down the directory tree. Thus 276 * when following backward pointers ".." we must unlock the 277 * parent directory before getting the requested directory. 278 * There is a potential race condition here if both the current 279 * and parent directories are removed before the `iget' for the 280 * inode associated with ".." returns. We hope that this occurs 281 * infrequently since we cannot avoid this race condition without 282 * implementing a sophisticated deadlock detection algorithm. 283 * Note also that this simple deadlock detection scheme will not 284 * work if the file system has any hard links other than ".." 285 * that point backwards in the directory structure. 286 */ 287 pdp = vdp; 288 289 /* 290 * If ino is different from dp->i_ino, 291 * it's a relocated directory. 292 */ 293 if (flags & ISDOTDOT) { 294 ino_t pin = filecore_getparent(dp); 295 296 VOP_UNLOCK(pdp, 0); /* race to get the inode */ 297 error = VFS_VGET(vdp->v_mount, pin, &tdp); 298 vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY); 299 if (error) { 300 return error; 301 } 302 *vpp = tdp; 303 } else if (name[0] == '.' && namelen == 1) { 304 VREF(vdp); /* we want ourself, ie "." */ 305 *vpp = vdp; 306 } else { 307 #ifdef FILECORE_DEBUG_BR 308 printf("brelse(%p) lo4\n", bp); 309 #endif 310 brelse(bp, 0); 311 error = VFS_VGET(vdp->v_mount, dp->i_dirent.addr | 312 (i << FILECORE_INO_INDEX), &tdp); 313 if (error) 314 return (error); 315 *vpp = tdp; 316 } 317 318 /* 319 * Insert name into cache if appropriate. 320 */ 321 if (cnp->cn_flags & MAKEENTRY) 322 cache_enter(vdp, *vpp, cnp); 323 return (0); 324 } 325
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