1 /* $NetBSD: filecore_lookup.c,v 1.3 2003/06/29 22:31:09 fvdl Exp $ */ 2 3 /*- 4 * Copyright (c) 1998 Andrew McMurry 5 * Copyright (c) 1989, 1993, 1994 The Regents of the University of California. 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * filecore_lookup.c 1.1 1998/6/26 37 */ 38 39 #include <sys/cdefs.h> 40 __KERNEL_RCSID(0, "$NetBSD: filecore_lookup.c,v 1.3 2003/06/29 22:31:09 fvdl Exp $"); 41 42 #include <sys/param.h> 43 #include <sys/namei.h> 44 #include <sys/buf.h> 45 #include <sys/file.h> 46 #include <sys/vnode.h> 47 #include <sys/mount.h> 48 #include <sys/systm.h> 49 50 #include <fs/filecorefs/filecore.h> 51 #include <fs/filecorefs/filecore_extern.h> 52 #include <fs/filecorefs/filecore_node.h> 53 54 struct nchstats filecore_nchstats; 55 56 /* 57 * Convert a component of a pathname into a pointer to a locked inode. 58 * This is a very central and rather complicated routine. 59 * If the file system is not maintained in a strict tree hierarchy, 60 * this can result in a deadlock situation (see comments in code below). 61 * 62 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on 63 * whether the name is to be looked up, created, renamed, or deleted. 64 * When CREATE, RENAME, or DELETE is specified, information usable in 65 * creating, renaming, or deleting a directory entry may be calculated. 66 * If flag has LOCKPARENT or'ed into it and the target of the pathname 67 * exists, lookup returns both the target and its parent directory locked. 68 * When creating or renaming and LOCKPARENT is specified, the target may 69 * not be ".". When deleting and LOCKPARENT is specified, the target may 70 * be "."., but the caller must check to ensure it does an vrele and iput 71 * instead of two iputs. 72 * 73 * Overall outline of ufs_lookup: 74 * 75 * check accessibility of directory 76 * look for name in cache, if found, then if at end of path 77 * and deleting or creating, drop it, else return name 78 * search for name in directory, to found or notfound 79 * notfound: 80 * if creating, return locked directory, leaving info on available slots 81 * else return error 82 * found: 83 * if at end of path and deleting, return information to allow delete 84 * if at end of path and rewriting (RENAME and LOCKPARENT), lock target 85 * inode and return info to allow rewrite 86 * if not at end, add name to cache; if at end and neither creating 87 * nor deleting, add name to cache 88 * 89 * NOTE: (LOOKUP | LOCKPARENT) currently returns the parent inode unlocked. 90 */ 91 int 92 filecore_lookup(v) 93 void *v; 94 { 95 struct vop_lookup_args /* { 96 struct vnode *a_dvp; 97 struct vnode **a_vpp; 98 struct componentname *a_cnp; 99 } */ *ap = v; 100 struct vnode *vdp; /* vnode for directory being searched */ 101 struct filecore_node *dp; /* inode for directory being searched */ 102 struct filecore_mnt *fcmp; /* file system that directory is in */ 103 struct buf *bp; /* a buffer of directory entries */ 104 struct filecore_direntry *de; 105 int numdirpasses; /* strategy for directory search */ 106 struct vnode *pdp; /* saved dp during symlink work */ 107 struct vnode *tdp; /* returned by filecore_vget_internal */ 108 int lockparent; /* 1 => lockparent flag is set */ 109 int wantparent; /* 1 => wantparent or lockparent flag */ 110 int error; 111 u_short namelen; 112 int res; 113 const char *name; 114 struct vnode **vpp = ap->a_vpp; 115 struct componentname *cnp = ap->a_cnp; 116 struct ucred *cred = cnp->cn_cred; 117 int flags; 118 int nameiop = cnp->cn_nameiop; 119 int i, endsearch; 120 121 cnp->cn_flags &= ~PDIRUNLOCK; 122 flags = cnp->cn_flags; 123 124 bp = NULL; 125 *vpp = NULL; 126 vdp = ap->a_dvp; 127 dp = VTOI(vdp); 128 fcmp = dp->i_mnt; 129 lockparent = flags & LOCKPARENT; 130 wantparent = flags & (LOCKPARENT|WANTPARENT); 131 132 /* 133 * Check accessiblity of directory. 134 */ 135 if ((error = VOP_ACCESS(vdp, VEXEC, cred, cnp->cn_proc)) != 0) 136 return (error); 137 138 if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) && 139 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) 140 return (EROFS); 141 142 /* 143 * We now have a segment name to search for, and a directory to search. 144 * 145 * Before tediously performing a linear scan of the directory, 146 * check the name cache to see if the directory/name pair 147 * we are looking for is known already. 148 */ 149 if ((error = cache_lookup(vdp, vpp, cnp)) >= 0) 150 return (error); 151 152 name = cnp->cn_nameptr; 153 namelen = cnp->cn_namelen; 154 155 /* 156 * If there is cached information on a previous search of 157 * this directory, pick up where we last left off. 158 * We cache only lookups as these are the most common 159 * and have the greatest payoff. Caching CREATE has little 160 * benefit as it usually must search the entire directory 161 * to determine that the entry does not exist. Caching the 162 * location of the last DELETE or RENAME has not reduced 163 * profiling time and hence has been removed in the interest 164 * of simplicity. 165 */ 166 if (nameiop != LOOKUP || dp->i_diroff == 0 || 167 dp->i_diroff >= FILECORE_MAXDIRENTS) { 168 i = 0; 169 numdirpasses = 1; 170 } else { 171 i = dp->i_diroff; 172 numdirpasses = 2; 173 filecore_nchstats.ncs_2passes++; 174 } 175 endsearch = FILECORE_MAXDIRENTS; 176 177 if ((flags & ISDOTDOT) || (name[0] == '.' && namelen == 1)) 178 goto found; 179 180 error = filecore_dbread(dp, &bp); 181 if (error) { 182 brelse(bp); 183 return error; 184 } 185 186 de = fcdirentry(bp->b_data, i); 187 188 searchloop: 189 while (de->name[0] != 0 && i < endsearch) { 190 /* 191 * Check for a name match. 192 */ 193 res = filecore_fncmp(de->name, name, namelen); 194 195 if (res == 0) 196 goto found; 197 if (res < 0) 198 goto notfound; 199 200 i++; 201 de++; 202 } 203 204 notfound: 205 /* 206 * If we started in the middle of the directory and failed 207 * to find our target, we must check the beginning as well. 208 */ 209 if (numdirpasses == 2) { 210 numdirpasses--; 211 i = 0; 212 de = fcdirentry(bp->b_data, i); 213 endsearch = dp->i_diroff; 214 goto searchloop; 215 } 216 if (bp != NULL) { 217 #ifdef FILECORE_DEBUG_BR 218 printf("brelse(%p) lo1\n", bp); 219 #endif 220 brelse(bp); 221 } 222 223 /* 224 * Insert name into cache (as non-existent) if appropriate. 225 */ 226 if (cnp->cn_flags & MAKEENTRY) 227 cache_enter(vdp, *vpp, cnp); 228 if (nameiop == CREATE || nameiop == RENAME) 229 return (EROFS); 230 return (ENOENT); 231 232 found: 233 if (numdirpasses == 2) 234 filecore_nchstats.ncs_pass2++; 235 236 /* 237 * Found component in pathname. 238 * If the final component of path name, save information 239 * in the cache as to where the entry was found. 240 */ 241 if ((flags & ISLASTCN) && nameiop == LOOKUP) 242 dp->i_diroff = i; 243 244 /* 245 * Step through the translation in the name. We do not `iput' the 246 * directory because we may need it again if a symbolic link 247 * is relative to the current directory. Instead we save it 248 * unlocked as "pdp". We must get the target inode before unlocking 249 * the directory to insure that the inode will not be removed 250 * before we get it. We prevent deadlock by always fetching 251 * inodes from the root, moving down the directory tree. Thus 252 * when following backward pointers ".." we must unlock the 253 * parent directory before getting the requested directory. 254 * There is a potential race condition here if both the current 255 * and parent directories are removed before the `iget' for the 256 * inode associated with ".." returns. We hope that this occurs 257 * infrequently since we cannot avoid this race condition without 258 * implementing a sophisticated deadlock detection algorithm. 259 * Note also that this simple deadlock detection scheme will not 260 * work if the file system has any hard links other than ".." 261 * that point backwards in the directory structure. 262 */ 263 pdp = vdp; 264 /* 265 * If ino is different from dp->i_ino, 266 * it's a relocated directory. 267 */ 268 if (flags & ISDOTDOT) { 269 ino_t pin = filecore_getparent(dp); 270 VOP_UNLOCK(pdp, 0); /* race to get the inode */ 271 cnp->cn_flags |= PDIRUNLOCK; 272 error = VFS_VGET(vdp->v_mount, pin, &tdp); 273 if (error) { 274 if (vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY) == 0) 275 cnp->cn_flags &= ~PDIRUNLOCK; 276 return (error); 277 } 278 if (lockparent && (flags & ISLASTCN)) { 279 if ((error = vn_lock(pdp, LK_EXCLUSIVE))) { 280 vput(tdp); 281 return (error); 282 } 283 cnp->cn_flags &= ~PDIRUNLOCK; 284 } 285 *vpp = tdp; 286 } else if (name[0] == '.' && namelen == 1) { 287 VREF(vdp); /* we want ourself, ie "." */ 288 *vpp = vdp; 289 } else { 290 #ifdef FILECORE_DEBUG_BR 291 printf("brelse(%p) lo4\n", bp); 292 #endif 293 brelse(bp); 294 error = VFS_VGET(vdp->v_mount, dp->i_dirent.addr | 295 (i << FILECORE_INO_INDEX), &tdp); 296 if (error) 297 return (error); 298 if (!lockparent || !(flags & ISLASTCN)) { 299 VOP_UNLOCK(pdp, 0); 300 cnp->cn_flags |= PDIRUNLOCK; 301 } 302 *vpp = tdp; 303 } 304 305 /* 306 * Insert name into cache if appropriate. 307 */ 308 if (cnp->cn_flags & MAKEENTRY) 309 cache_enter(vdp, *vpp, cnp); 310 return (0); 311 } 312