1 /* $NetBSD: vfs_cache.c,v 1.28 2000/11/24 07:25:51 chs Exp $ */ 2 3 /* 4 * Copyright (c) 1989, 1993 5 * The Regents of the University of California. 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. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * @(#)vfs_cache.c 8.3 (Berkeley) 8/22/94 36 */ 37 38 #include "opt_ddb.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/time.h> 43 #include <sys/mount.h> 44 #include <sys/vnode.h> 45 #include <sys/namei.h> 46 #include <sys/errno.h> 47 #include <sys/malloc.h> 48 #include <sys/pool.h> 49 50 /* 51 * Name caching works as follows: 52 * 53 * Names found by directory scans are retained in a cache 54 * for future reference. It is managed LRU, so frequently 55 * used names will hang around. Cache is indexed by hash value 56 * obtained from (dvp, name) where dvp refers to the directory 57 * containing name. 58 * 59 * For simplicity (and economy of storage), names longer than 60 * a maximum length of NCHNAMLEN are not cached; they occur 61 * infrequently in any case, and are almost never of interest. 62 * 63 * Upon reaching the last segment of a path, if the reference 64 * is for DELETE, or NOCACHE is set (rewrite), and the 65 * name is located in the cache, it will be dropped. 66 * The entry is dropped also when it was not possible to lock 67 * the cached vnode, either because vget() failed or the generation 68 * number has changed while waiting for the lock. 69 */ 70 71 /* 72 * Structures associated with name cacheing. 73 */ 74 LIST_HEAD(nchashhead, namecache) *nchashtbl; 75 u_long nchash; /* size of hash table - 1 */ 76 long numcache; /* number of cache entries allocated */ 77 78 LIST_HEAD(ncvhashhead, namecache) *ncvhashtbl; 79 u_long ncvhash; /* size of hash table - 1 */ 80 81 TAILQ_HEAD(, namecache) nclruhead; /* LRU chain */ 82 struct nchstats nchstats; /* cache effectiveness statistics */ 83 84 struct pool namecache_pool; 85 86 int doingcache = 1; /* 1 => enable the cache */ 87 88 /* 89 * Look for a the name in the cache. We don't do this 90 * if the segment name is long, simply so the cache can avoid 91 * holding long names (which would either waste space, or 92 * add greatly to the complexity). 93 * 94 * Lookup is called with ni_dvp pointing to the directory to search, 95 * ni_ptr pointing to the name of the entry being sought, ni_namelen 96 * tells the length of the name, and ni_hash contains a hash of 97 * the name. If the lookup succeeds, the vnode is locked, stored in ni_vp 98 * and a status of zero is returned. If the locking fails for whatever 99 * reason, the vnode is unlocked and the error is returned to caller. 100 * If the lookup determines that the name does not exist (negative cacheing), 101 * a status of ENOENT is returned. If the lookup fails, a status of -1 102 * is returned. 103 */ 104 int 105 cache_lookup(dvp, vpp, cnp) 106 struct vnode *dvp; 107 struct vnode **vpp; 108 struct componentname *cnp; 109 { 110 struct namecache *ncp; 111 struct nchashhead *ncpp; 112 struct vnode *vp; 113 int vpid, error; 114 115 if (!doingcache) { 116 cnp->cn_flags &= ~MAKEENTRY; 117 *vpp = 0; 118 return (-1); 119 } 120 if (cnp->cn_namelen > NCHNAMLEN) { 121 nchstats.ncs_long++; 122 cnp->cn_flags &= ~MAKEENTRY; 123 *vpp = 0; 124 return (-1); 125 } 126 ncpp = &nchashtbl[(cnp->cn_hash ^ dvp->v_id) & nchash]; 127 LIST_FOREACH(ncp, ncpp, nc_hash) { 128 if (ncp->nc_dvp == dvp && 129 ncp->nc_dvpid == dvp->v_id && 130 ncp->nc_nlen == cnp->cn_namelen && 131 !memcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen)) 132 break; 133 } 134 if (ncp == 0) { 135 nchstats.ncs_miss++; 136 *vpp = 0; 137 return (-1); 138 } 139 if ((cnp->cn_flags & MAKEENTRY) == 0) { 140 nchstats.ncs_badhits++; 141 goto remove; 142 } else if (ncp->nc_vp == NULL) { 143 /* 144 * Restore the ISWHITEOUT flag saved earlier. 145 */ 146 cnp->cn_flags |= ncp->nc_vpid; 147 if (cnp->cn_nameiop != CREATE || 148 (cnp->cn_flags & ISLASTCN) == 0) { 149 nchstats.ncs_neghits++; 150 /* 151 * Move this slot to end of LRU chain, 152 * if not already there. 153 */ 154 if (ncp->nc_lru.tqe_next != 0) { 155 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 156 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 157 } 158 return (ENOENT); 159 } else { 160 nchstats.ncs_badhits++; 161 goto remove; 162 } 163 } else if (ncp->nc_vpid != ncp->nc_vp->v_id) { 164 nchstats.ncs_falsehits++; 165 goto remove; 166 } 167 168 vp = ncp->nc_vp; 169 vpid = vp->v_id; 170 if (vp == dvp) { /* lookup on "." */ 171 VREF(dvp); 172 error = 0; 173 } else if (cnp->cn_flags & ISDOTDOT) { 174 VOP_UNLOCK(dvp, 0); 175 cnp->cn_flags |= PDIRUNLOCK; 176 error = vget(vp, LK_EXCLUSIVE); 177 /* if the above vget() succeeded and both LOCKPARENT and 178 * ISLASTCN is set, lock the directory vnode as well */ 179 if (!error && (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) == 0) { 180 if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0) { 181 vput(vp); 182 return (error); 183 } 184 cnp->cn_flags &= ~PDIRUNLOCK; 185 } 186 } else { 187 error = vget(vp, LK_EXCLUSIVE); 188 /* if the above vget() failed or either of LOCKPARENT or 189 * ISLASTCN is set, unlock the directory vnode */ 190 if (error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { 191 VOP_UNLOCK(dvp, 0); 192 cnp->cn_flags |= PDIRUNLOCK; 193 } 194 } 195 196 /* 197 * Check that the lock succeeded, and that the capability number did 198 * not change while we were waiting for the lock. 199 */ 200 if (error || vpid != vp->v_id) { 201 if (!error) { 202 vput(vp); 203 nchstats.ncs_falsehits++; 204 } else 205 nchstats.ncs_badhits++; 206 /* 207 * The parent needs to be locked when we return to VOP_LOOKUP(). 208 * The `.' case here should be extremely rare (if it can happen 209 * at all), so we don't bother optimizing out the unlock/relock. 210 */ 211 if (vp == dvp || 212 error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { 213 if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0) 214 return (error); 215 cnp->cn_flags &= ~PDIRUNLOCK; 216 } 217 goto remove; 218 } 219 220 nchstats.ncs_goodhits++; 221 /* 222 * move this slot to end of LRU chain, if not already there 223 */ 224 if (ncp->nc_lru.tqe_next != 0) { 225 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 226 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 227 } 228 *vpp = vp; 229 return (0); 230 231 remove: 232 /* 233 * Last component and we are renaming or deleting, 234 * the cache entry is invalid, or otherwise don't 235 * want cache entry to exist. 236 */ 237 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 238 LIST_REMOVE(ncp, nc_hash); 239 ncp->nc_hash.le_prev = 0; 240 if (ncp->nc_vhash.le_prev != NULL) { 241 LIST_REMOVE(ncp, nc_vhash); 242 ncp->nc_vhash.le_prev = 0; 243 } 244 TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru); 245 *vpp = 0; 246 return (-1); 247 } 248 249 /* 250 * Scan cache looking for name of directory entry pointing at vp. 251 * 252 * Fill in dvpp. 253 * 254 * If bufp is non-NULL, also place the name in the buffer which starts 255 * at bufp, immediately before *bpp, and move bpp backwards to point 256 * at the start of it. (Yes, this is a little baroque, but it's done 257 * this way to cater to the whims of getcwd). 258 * 259 * Returns 0 on success, -1 on cache miss, positive errno on failure. 260 */ 261 int 262 cache_revlookup (vp, dvpp, bpp, bufp) 263 struct vnode *vp, **dvpp; 264 char **bpp; 265 char *bufp; 266 { 267 struct namecache *ncp; 268 struct vnode *dvp; 269 struct ncvhashhead *nvcpp; 270 271 if (!doingcache) 272 goto out; 273 274 nvcpp = &ncvhashtbl[(vp->v_id & ncvhash)]; 275 276 LIST_FOREACH(ncp, nvcpp, nc_vhash) { 277 if ((ncp->nc_vp == vp) && 278 (ncp->nc_vpid == vp->v_id) && 279 ((dvp = ncp->nc_dvp) != 0) && 280 (dvp != vp) && /* avoid pesky . entries.. */ 281 (dvp->v_id == ncp->nc_dvpid)) 282 { 283 char *bp; 284 285 #ifdef DIAGNOSTIC 286 if ((ncp->nc_nlen == 1) && 287 (ncp->nc_name[0] == '.')) 288 panic("cache_revlookup: found entry for ."); 289 290 if ((ncp->nc_nlen == 2) && 291 (ncp->nc_name[0] == '.') && 292 (ncp->nc_name[1] == '.')) 293 panic("cache_revlookup: found entry for .."); 294 #endif 295 nchstats.ncs_revhits++; 296 297 if (bufp) { 298 bp = *bpp; 299 bp -= ncp->nc_nlen; 300 if (bp <= bufp) { 301 *dvpp = 0; 302 return ERANGE; 303 } 304 memcpy(bp, ncp->nc_name, ncp->nc_nlen); 305 *bpp = bp; 306 } 307 308 /* XXX MP: how do we know dvp won't evaporate? */ 309 *dvpp = dvp; 310 return 0; 311 } 312 } 313 nchstats.ncs_revmiss++; 314 out: 315 *dvpp = 0; 316 return -1; 317 } 318 319 /* 320 * Add an entry to the cache 321 */ 322 void 323 cache_enter(dvp, vp, cnp) 324 struct vnode *dvp; 325 struct vnode *vp; 326 struct componentname *cnp; 327 { 328 struct namecache *ncp; 329 struct nchashhead *ncpp; 330 struct ncvhashhead *nvcpp; 331 332 #ifdef DIAGNOSTIC 333 if (cnp->cn_namelen > NCHNAMLEN) 334 panic("cache_enter: name too long"); 335 #endif 336 if (!doingcache) 337 return; 338 /* 339 * Free the cache slot at head of lru chain. 340 */ 341 if (numcache < numvnodes) { 342 ncp = pool_get(&namecache_pool, PR_WAITOK); 343 memset(ncp, 0, sizeof(*ncp)); 344 numcache++; 345 } else if ((ncp = TAILQ_FIRST(&nclruhead)) != NULL) { 346 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 347 if (ncp->nc_hash.le_prev != 0) { 348 LIST_REMOVE(ncp, nc_hash); 349 ncp->nc_hash.le_prev = 0; 350 } 351 if (ncp->nc_vhash.le_prev != 0) { 352 LIST_REMOVE(ncp, nc_vhash); 353 ncp->nc_vhash.le_prev = 0; 354 } 355 } else 356 return; 357 /* grab the vnode we just found */ 358 ncp->nc_vp = vp; 359 if (vp) 360 ncp->nc_vpid = vp->v_id; 361 else { 362 /* 363 * For negative hits, save the ISWHITEOUT flag so we can 364 * restore it later when the cache entry is used again. 365 */ 366 ncp->nc_vpid = cnp->cn_flags & ISWHITEOUT; 367 } 368 /* fill in cache info */ 369 ncp->nc_dvp = dvp; 370 ncp->nc_dvpid = dvp->v_id; 371 ncp->nc_nlen = cnp->cn_namelen; 372 memcpy(ncp->nc_name, cnp->cn_nameptr, (unsigned)ncp->nc_nlen); 373 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 374 ncpp = &nchashtbl[(cnp->cn_hash ^ dvp->v_id) & nchash]; 375 LIST_INSERT_HEAD(ncpp, ncp, nc_hash); 376 377 ncp->nc_vhash.le_prev = 0; 378 ncp->nc_vhash.le_next = 0; 379 380 /* 381 * Create reverse-cache entries (used in getcwd) for directories. 382 */ 383 if (vp && 384 (vp != dvp) && 385 (vp->v_type == VDIR) && 386 ((ncp->nc_nlen > 2) || 387 ((ncp->nc_nlen == 2) && (ncp->nc_name[0] != '.') && (ncp->nc_name[1] != '.')) || 388 ((ncp->nc_nlen == 1) && (ncp->nc_name[0] != '.')))) 389 { 390 nvcpp = &ncvhashtbl[(vp->v_id & ncvhash)]; 391 LIST_INSERT_HEAD(nvcpp, ncp, nc_vhash); 392 } 393 394 } 395 396 /* 397 * Name cache initialization, from vfs_init() when we are booting 398 */ 399 void 400 nchinit() 401 { 402 403 TAILQ_INIT(&nclruhead); 404 nchashtbl = 405 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &nchash); 406 ncvhashtbl = 407 hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash); 408 pool_init(&namecache_pool, sizeof(struct namecache), 0, 0, 0, 409 "ncachepl", 0, pool_page_alloc_nointr, pool_page_free_nointr, 410 M_CACHE); 411 } 412 413 /* 414 * Cache flush, a particular vnode; called when a vnode is renamed to 415 * hide entries that would now be invalid 416 */ 417 void 418 cache_purge(vp) 419 struct vnode *vp; 420 { 421 struct namecache *ncp; 422 struct nchashhead *ncpp; 423 static u_long nextvnodeid; 424 425 vp->v_id = ++nextvnodeid; 426 if (nextvnodeid != 0) 427 return; 428 for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) { 429 LIST_FOREACH(ncp, ncpp, nc_hash) { 430 ncp->nc_vpid = 0; 431 ncp->nc_dvpid = 0; 432 } 433 } 434 vp->v_id = ++nextvnodeid; 435 } 436 437 /* 438 * Cache flush, a whole filesystem; called when filesys is umounted to 439 * remove entries that would now be invalid. 440 */ 441 void 442 cache_purgevfs(mp) 443 struct mount *mp; 444 { 445 struct namecache *ncp, *nxtcp; 446 447 for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) { 448 nxtcp = TAILQ_NEXT(ncp, nc_lru); 449 if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) { 450 continue; 451 } 452 /* free the resources we had */ 453 ncp->nc_vp = NULL; 454 ncp->nc_dvp = NULL; 455 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 456 if (ncp->nc_hash.le_prev != 0) { 457 LIST_REMOVE(ncp, nc_hash); 458 ncp->nc_hash.le_prev = 0; 459 } 460 if (ncp->nc_vhash.le_prev != 0) { 461 LIST_REMOVE(ncp, nc_vhash); 462 ncp->nc_vhash.le_prev = 0; 463 } 464 TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru); 465 } 466 } 467 468 #ifdef DDB 469 void 470 namecache_print(struct vnode *vp, void (*pr)(const char *, ...)) 471 { 472 struct vnode *dvp = NULL; 473 struct namecache *ncp; 474 475 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 476 if (ncp->nc_vp == vp && ncp->nc_vpid == vp->v_id) { 477 (*pr)("name %.*s\n", ncp->nc_nlen, ncp->nc_name); 478 dvp = ncp->nc_dvp; 479 } 480 } 481 if (dvp == NULL) { 482 (*pr)("name not found\n"); 483 return; 484 } 485 vp = dvp; 486 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 487 if (ncp->nc_vp == vp && ncp->nc_vpid == vp->v_id) { 488 (*pr)("parent %.*s\n", ncp->nc_nlen, ncp->nc_name); 489 } 490 } 491 } 492 #endif 493