1 /* $OpenBSD: vfs_cache.c,v 1.33 2010/05/19 08:31:23 thib Exp $ */ 2 /* $NetBSD: vfs_cache.c,v 1.13 1996/02/04 02:18:09 christos Exp $ */ 3 4 /* 5 * Copyright (c) 1989, 1993 6 * The Regents of the University of California. 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. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)vfs_cache.c 8.3 (Berkeley) 8/22/94 33 */ 34 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/time.h> 38 #include <sys/mount.h> 39 #include <sys/vnode.h> 40 #include <sys/namei.h> 41 #include <sys/errno.h> 42 #include <sys/malloc.h> 43 #include <sys/pool.h> 44 45 /* 46 * TODO: namecache access should really be locked. 47 */ 48 49 /* 50 * For simplicity (and economy of storage), names longer than 51 * a maximum length of NCHNAMLEN are not cached; they occur 52 * infrequently in any case, and are almost never of interest. 53 * 54 * Upon reaching the last segment of a path, if the reference 55 * is for DELETE, or NOCACHE is set (rewrite), and the 56 * name is located in the cache, it will be dropped. 57 */ 58 59 /* 60 * Structures associated with name caching. 61 */ 62 long numcache; /* total number of cache entries allocated */ 63 long numneg; /* number of negative cache entries */ 64 65 TAILQ_HEAD(, namecache) nclruhead; /* Regular Entry LRU chain */ 66 TAILQ_HEAD(, namecache) nclruneghead; /* Negative Entry LRU chain */ 67 struct nchstats nchstats; /* cache effectiveness statistics */ 68 69 int doingcache = 1; /* 1 => enable the cache */ 70 71 struct pool nch_pool; 72 73 void cache_zap(struct namecache *); 74 u_long nextvnodeid; 75 76 static int 77 namecache_compare(struct namecache *n1, struct namecache *n2) 78 { 79 if (n1->nc_nlen == n2->nc_nlen) 80 return (memcmp(n1->nc_name, n2->nc_name, n1->nc_nlen)); 81 else 82 return (n1->nc_nlen - n2->nc_nlen); 83 } 84 85 RB_GENERATE(namecache_rb_cache, namecache, n_rbcache, namecache_compare); 86 87 /* 88 * blow away a namecache entry 89 */ 90 void 91 cache_zap(struct namecache *ncp) 92 { 93 struct vnode *dvp = NULL; 94 95 if (ncp->nc_vp != NULL) { 96 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 97 numcache--; 98 } else { 99 TAILQ_REMOVE(&nclruneghead, ncp, nc_neg); 100 numneg--; 101 } 102 if (ncp->nc_dvp) { 103 RB_REMOVE(namecache_rb_cache, &ncp->nc_dvp->v_nc_tree, ncp); 104 if (RB_EMPTY(&ncp->nc_dvp->v_nc_tree)) 105 dvp = ncp->nc_dvp; 106 } 107 if (ncp->nc_vp && (ncp->nc_vpid == ncp->nc_vp->v_id)) { 108 if (ncp->nc_vp != ncp->nc_dvp && 109 ncp->nc_vp->v_type == VDIR && 110 (ncp->nc_nlen > 2 || 111 (ncp->nc_nlen > 1 && 112 ncp->nc_name[1] != '.') || 113 (ncp->nc_nlen > 0 && 114 ncp->nc_name[0] != '.'))) { 115 TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst, ncp, nc_me); 116 } 117 } 118 pool_put(&nch_pool, ncp); 119 if (dvp) 120 vdrop(dvp); 121 } 122 123 /* 124 * Look for a name in the cache. We don't do this if the segment name is 125 * long, simply so the cache can avoid holding long names (which would 126 * either waste space, or add greatly to the complexity). 127 * dvp points to the directory to search. The componentname cnp holds 128 * the information on the entry being sought, such as its length 129 * and its name. If the lookup succeeds, vpp is set to point to the vnode 130 * and an error of 0 is returned. If the lookup determines the name does 131 * not exist (negative caching) an error of ENOENT is returned. If the 132 * lookup fails, an error of -1 is returned. 133 */ 134 int 135 cache_lookup(struct vnode *dvp, struct vnode **vpp, 136 struct componentname *cnp) 137 { 138 struct namecache *ncp; 139 struct namecache n; 140 struct vnode *vp; 141 struct proc *p = curproc; 142 u_long vpid; 143 int error; 144 145 *vpp = NULL; 146 147 if (!doingcache) { 148 cnp->cn_flags &= ~MAKEENTRY; 149 return (-1); 150 } 151 if (cnp->cn_namelen > NCHNAMLEN) { 152 nchstats.ncs_long++; 153 cnp->cn_flags &= ~MAKEENTRY; 154 return (-1); 155 } 156 157 /* lookup in directory vnode's redblack tree */ 158 n.nc_nlen = cnp->cn_namelen; 159 memcpy(n.nc_name, cnp->cn_nameptr, n.nc_nlen); 160 ncp = RB_FIND(namecache_rb_cache, &dvp->v_nc_tree, &n); 161 162 if (ncp == NULL) { 163 nchstats.ncs_miss++; 164 return (-1); 165 } 166 if ((cnp->cn_flags & MAKEENTRY) == 0) { 167 nchstats.ncs_badhits++; 168 goto remove; 169 } else if (ncp->nc_vp == NULL) { 170 if (cnp->cn_nameiop != CREATE || 171 (cnp->cn_flags & ISLASTCN) == 0) { 172 nchstats.ncs_neghits++; 173 /* 174 * Move this slot to end of the negative LRU chain, 175 */ 176 if (TAILQ_NEXT(ncp, nc_neg) != NULL) { 177 TAILQ_REMOVE(&nclruneghead, ncp, nc_neg); 178 TAILQ_INSERT_TAIL(&nclruneghead, ncp, 179 nc_neg); 180 } 181 return (ENOENT); 182 } else { 183 nchstats.ncs_badhits++; 184 goto remove; 185 } 186 } else if (ncp->nc_vpid != ncp->nc_vp->v_id) { 187 nchstats.ncs_falsehits++; 188 goto remove; 189 } 190 191 vp = ncp->nc_vp; 192 vpid = vp->v_id; 193 if (vp == dvp) { /* lookup on "." */ 194 vref(dvp); 195 error = 0; 196 } else if (cnp->cn_flags & ISDOTDOT) { 197 VOP_UNLOCK(dvp, 0, p); 198 cnp->cn_flags |= PDIRUNLOCK; 199 error = vget(vp, LK_EXCLUSIVE, p); 200 /* 201 * If the above vget() succeeded and both LOCKPARENT and 202 * ISLASTCN is set, lock the directory vnode as well. 203 */ 204 if (!error && (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) == 0) { 205 if ((error = vn_lock(dvp, LK_EXCLUSIVE, p)) != 0) { 206 vput(vp); 207 return (error); 208 } 209 cnp->cn_flags &= ~PDIRUNLOCK; 210 } 211 } else { 212 error = vget(vp, LK_EXCLUSIVE, p); 213 /* 214 * If the above vget() failed or either of LOCKPARENT or 215 * ISLASTCN is set, unlock the directory vnode. 216 */ 217 if (error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { 218 VOP_UNLOCK(dvp, 0, p); 219 cnp->cn_flags |= PDIRUNLOCK; 220 } 221 } 222 223 /* 224 * Check that the lock succeeded, and that the capability number did 225 * not change while we were waiting for the lock. 226 */ 227 if (error || vpid != vp->v_id) { 228 if (!error) { 229 vput(vp); 230 nchstats.ncs_falsehits++; 231 } else 232 nchstats.ncs_badhits++; 233 /* 234 * The parent needs to be locked when we return to VOP_LOOKUP(). 235 * The `.' case here should be extremely rare (if it can happen 236 * at all), so we don't bother optimizing out the unlock/relock. 237 */ 238 if (vp == dvp || error || 239 (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { 240 if ((error = vn_lock(dvp, LK_EXCLUSIVE, p)) != 0) 241 return (error); 242 cnp->cn_flags &= ~PDIRUNLOCK; 243 } 244 return (-1); 245 } 246 247 nchstats.ncs_goodhits++; 248 /* 249 * Move this slot to end of the regular LRU chain. 250 */ 251 if (TAILQ_NEXT(ncp, nc_lru) != NULL) { 252 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 253 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 254 } 255 *vpp = vp; 256 return (0); 257 258 remove: 259 /* 260 * Last component and we are renaming or deleting, 261 * the cache entry is invalid, or otherwise don't 262 * want cache entry to exist. 263 */ 264 cache_zap(ncp); 265 return (-1); 266 } 267 268 /* 269 * Scan cache looking for name of directory entry pointing at vp. 270 * 271 * Fill in dvpp. 272 * 273 * If bufp is non-NULL, also place the name in the buffer which starts 274 * at bufp, immediately before *bpp, and move bpp backwards to point 275 * at the start of it. (Yes, this is a little baroque, but it's done 276 * this way to cater to the whims of getcwd). 277 * 278 * Returns 0 on success, -1 on cache miss, positive errno on failure. 279 * 280 * TODO: should we return *dvpp locked? 281 */ 282 283 int 284 cache_revlookup(struct vnode *vp, struct vnode **dvpp, char **bpp, char *bufp) 285 { 286 struct namecache *ncp; 287 struct vnode *dvp = NULL; 288 char *bp; 289 290 if (!doingcache) 291 goto out; 292 TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_me) { 293 dvp = ncp->nc_dvp; 294 if (dvp && dvp != vp && ncp->nc_dvpid == dvp->v_id) 295 goto found; 296 } 297 goto miss; 298 found: 299 #ifdef DIAGNOSTIC 300 if (ncp->nc_nlen == 1 && 301 ncp->nc_name[0] == '.') 302 panic("cache_revlookup: found entry for ."); 303 if (ncp->nc_nlen == 2 && 304 ncp->nc_name[0] == '.' && 305 ncp->nc_name[1] == '.') 306 panic("cache_revlookup: found entry for .."); 307 #endif 308 nchstats.ncs_revhits++; 309 310 if (bufp != NULL) { 311 bp = *bpp; 312 bp -= ncp->nc_nlen; 313 if (bp <= bufp) { 314 *dvpp = NULL; 315 return (ERANGE); 316 } 317 memcpy(bp, ncp->nc_name, ncp->nc_nlen); 318 *bpp = bp; 319 } 320 321 *dvpp = dvp; 322 323 /* 324 * XXX: Should we vget() here to have more 325 * consistent semantics with cache_lookup()? 326 */ 327 return (0); 328 329 miss: 330 nchstats.ncs_revmiss++; 331 out: 332 *dvpp = NULL; 333 return (-1); 334 } 335 336 /* 337 * Add an entry to the cache 338 */ 339 void 340 cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp) 341 { 342 struct namecache *ncp, *lncp; 343 344 if (!doingcache || cnp->cn_namelen > NCHNAMLEN) 345 return; 346 347 /* 348 * allocate, or recycle (free and allocate) an ncp. 349 */ 350 if (numcache >= desiredvnodes) { 351 if ((ncp = TAILQ_FIRST(&nclruhead)) != NULL) 352 cache_zap(ncp); 353 else if ((ncp = TAILQ_FIRST(&nclruneghead)) != NULL) 354 cache_zap(ncp); 355 else 356 panic("wtf? leak?"); 357 } 358 ncp = pool_get(&nch_pool, PR_WAITOK|PR_ZERO); 359 360 /* grab the vnode we just found */ 361 ncp->nc_vp = vp; 362 if (vp) 363 ncp->nc_vpid = vp->v_id; 364 365 /* fill in cache info */ 366 ncp->nc_dvp = dvp; 367 ncp->nc_dvpid = dvp->v_id; 368 ncp->nc_nlen = cnp->cn_namelen; 369 bcopy(cnp->cn_nameptr, ncp->nc_name, (unsigned)ncp->nc_nlen); 370 if (RB_EMPTY(&dvp->v_nc_tree)) { 371 vhold(dvp); 372 } 373 if ((lncp = RB_INSERT(namecache_rb_cache, &dvp->v_nc_tree, ncp)) 374 != NULL) { 375 /* someone has raced us and added a different entry 376 * for the same vnode (different ncp) - we don't need 377 * this entry, so free it and we are done. 378 */ 379 pool_put(&nch_pool, ncp); 380 /* we know now dvp->v_nc_tree is not empty, no need 381 * to vdrop here 382 */ 383 goto done; 384 } 385 if (vp) { 386 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 387 numcache++; 388 /* don't put . or .. in the reverse map */ 389 if (vp != dvp && vp->v_type == VDIR && 390 (ncp->nc_nlen > 2 || 391 (ncp->nc_nlen > 1 && 392 ncp->nc_name[1] != '.') || 393 (ncp->nc_nlen > 0 && 394 ncp->nc_name[0] != '.'))) 395 TAILQ_INSERT_TAIL(&vp->v_cache_dst, ncp, 396 nc_me); 397 } else { 398 TAILQ_INSERT_TAIL(&nclruneghead, ncp, nc_neg); 399 numneg++; 400 } 401 if (numneg > desiredvnodes) { 402 if ((ncp = TAILQ_FIRST(&nclruneghead)) 403 != NULL) 404 cache_zap(ncp); 405 } 406 done: 407 return; 408 } 409 410 411 /* 412 * Name cache initialization, from vfs_init() when we are booting 413 */ 414 void 415 nchinit() 416 { 417 TAILQ_INIT(&nclruhead); 418 TAILQ_INIT(&nclruneghead); 419 pool_init(&nch_pool, sizeof(struct namecache), 0, 0, 0, "nchpl", 420 &pool_allocator_nointr); 421 } 422 423 /* 424 * Cache flush, a particular vnode; called when a vnode is renamed to 425 * hide entries that would now be invalid 426 */ 427 void 428 cache_purge(struct vnode *vp) 429 { 430 struct namecache *ncp; 431 432 while ((ncp = TAILQ_FIRST(&vp->v_cache_dst))) 433 cache_zap(ncp); 434 while ((ncp = RB_ROOT(&vp->v_nc_tree))) 435 cache_zap(ncp); 436 437 /* XXX this blows goats */ 438 vp->v_id = ++nextvnodeid; 439 if (vp->v_id == 0) 440 vp->v_id = ++nextvnodeid; 441 } 442 443 /* 444 * Cache flush, a whole filesystem; called when filesys is umounted to 445 * remove entries that would now be invalid 446 * 447 * The line "nxtcp = nchhead" near the end is to avoid potential problems 448 * if the cache lru chain is modified while we are dumping the 449 * inode. This makes the algorithm O(n^2), but do you think I care? 450 */ 451 void 452 cache_purgevfs(struct mount *mp) 453 { 454 struct namecache *ncp, *nxtcp; 455 456 /* whack the regular entries */ 457 for (ncp = TAILQ_FIRST(&nclruhead); ncp != TAILQ_END(&nclruhead); 458 ncp = nxtcp) { 459 if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) { 460 nxtcp = TAILQ_NEXT(ncp, nc_lru); 461 continue; 462 } 463 /* free the resources we had */ 464 cache_zap(ncp); 465 /* cause rescan of list, it may have altered */ 466 nxtcp = TAILQ_FIRST(&nclruhead); 467 } 468 /* whack the negative entries */ 469 for (ncp = TAILQ_FIRST(&nclruneghead); ncp != TAILQ_END(&nclruneghead); 470 ncp = nxtcp) { 471 if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) { 472 nxtcp = TAILQ_NEXT(ncp, nc_neg); 473 continue; 474 } 475 /* free the resources we had */ 476 cache_zap(ncp); 477 /* cause rescan of list, it may have altered */ 478 nxtcp = TAILQ_FIRST(&nclruneghead); 479 } 480 } 481