1 /* $NetBSD: vfs_cache.c,v 1.35 2002/03/08 20:48:42 thorpej 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 <sys/cdefs.h> 39 __KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.35 2002/03/08 20:48:42 thorpej Exp $"); 40 41 #include "opt_ddb.h" 42 #include "opt_revcache.h" 43 44 #include <sys/param.h> 45 #include <sys/systm.h> 46 #include <sys/time.h> 47 #include <sys/mount.h> 48 #include <sys/vnode.h> 49 #include <sys/namei.h> 50 #include <sys/errno.h> 51 #include <sys/malloc.h> 52 #include <sys/pool.h> 53 54 /* 55 * Name caching works as follows: 56 * 57 * Names found by directory scans are retained in a cache 58 * for future reference. It is managed LRU, so frequently 59 * used names will hang around. Cache is indexed by hash value 60 * obtained from (dvp, name) where dvp refers to the directory 61 * containing name. 62 * 63 * For simplicity (and economy of storage), names longer than 64 * a maximum length of NCHNAMLEN are not cached; they occur 65 * infrequently in any case, and are almost never of interest. 66 * 67 * Upon reaching the last segment of a path, if the reference 68 * is for DELETE, or NOCACHE is set (rewrite), and the 69 * name is located in the cache, it will be dropped. 70 * The entry is dropped also when it was not possible to lock 71 * the cached vnode, either because vget() failed or the generation 72 * number has changed while waiting for the lock. 73 */ 74 75 /* 76 * Structures associated with name cacheing. 77 */ 78 LIST_HEAD(nchashhead, namecache) *nchashtbl; 79 u_long nchash; /* size of hash table - 1 */ 80 long numcache; /* number of cache entries allocated */ 81 #define NCHASH(cnp, dvp) (((cnp)->cn_hash ^ (dvp)->v_id) & nchash) 82 83 LIST_HEAD(ncvhashhead, namecache) *ncvhashtbl; 84 u_long ncvhash; /* size of hash table - 1 */ 85 #define NCVHASH(vp) ((vp)->v_id & ncvhash) 86 87 TAILQ_HEAD(, namecache) nclruhead; /* LRU chain */ 88 struct nchstats nchstats; /* cache effectiveness statistics */ 89 90 struct pool namecache_pool; 91 92 int doingcache = 1; /* 1 => enable the cache */ 93 94 /* 95 * Look for a the name in the cache. We don't do this 96 * if the segment name is long, simply so the cache can avoid 97 * holding long names (which would either waste space, or 98 * add greatly to the complexity). 99 * 100 * Lookup is called with ni_dvp pointing to the directory to search, 101 * ni_ptr pointing to the name of the entry being sought, ni_namelen 102 * tells the length of the name, and ni_hash contains a hash of 103 * the name. If the lookup succeeds, the vnode is locked, stored in ni_vp 104 * and a status of zero is returned. If the locking fails for whatever 105 * reason, the vnode is unlocked and the error is returned to caller. 106 * If the lookup determines that the name does not exist (negative cacheing), 107 * a status of ENOENT is returned. If the lookup fails, a status of -1 108 * is returned. 109 */ 110 int 111 cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp) 112 { 113 struct namecache *ncp; 114 struct nchashhead *ncpp; 115 struct vnode *vp; 116 int vpid, error; 117 118 if (!doingcache) { 119 cnp->cn_flags &= ~MAKEENTRY; 120 *vpp = NULL; 121 return (-1); 122 } 123 if (cnp->cn_namelen > NCHNAMLEN) { 124 nchstats.ncs_long++; 125 cnp->cn_flags &= ~MAKEENTRY; 126 *vpp = NULL; 127 return (-1); 128 } 129 ncpp = &nchashtbl[NCHASH(cnp, dvp)]; 130 LIST_FOREACH(ncp, ncpp, nc_hash) { 131 if (ncp->nc_dvp == dvp && 132 ncp->nc_dvpid == dvp->v_id && 133 ncp->nc_nlen == cnp->cn_namelen && 134 !memcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen)) 135 break; 136 } 137 if (ncp == 0) { 138 nchstats.ncs_miss++; 139 *vpp = NULL; 140 return (-1); 141 } 142 if ((cnp->cn_flags & MAKEENTRY) == 0) { 143 nchstats.ncs_badhits++; 144 goto remove; 145 } else if (ncp->nc_vp == NULL) { 146 /* 147 * Restore the ISWHITEOUT flag saved earlier. 148 */ 149 cnp->cn_flags |= ncp->nc_vpid; 150 if (cnp->cn_nameiop != CREATE || 151 (cnp->cn_flags & ISLASTCN) == 0) { 152 nchstats.ncs_neghits++; 153 /* 154 * Move this slot to end of LRU chain, 155 * if not already there. 156 */ 157 if (ncp->nc_lru.tqe_next != 0) { 158 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 159 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 160 } 161 return (ENOENT); 162 } else { 163 nchstats.ncs_badhits++; 164 goto remove; 165 } 166 } else if (ncp->nc_vpid != ncp->nc_vp->v_id) { 167 nchstats.ncs_falsehits++; 168 goto remove; 169 } 170 171 vp = ncp->nc_vp; 172 vpid = vp->v_id; 173 if (vp == dvp) { /* lookup on "." */ 174 VREF(dvp); 175 error = 0; 176 } else if (cnp->cn_flags & ISDOTDOT) { 177 VOP_UNLOCK(dvp, 0); 178 cnp->cn_flags |= PDIRUNLOCK; 179 error = vget(vp, LK_EXCLUSIVE); 180 /* 181 * If the above vget() succeeded and both LOCKPARENT and 182 * ISLASTCN is set, lock the directory vnode as well. 183 */ 184 if (!error && (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) == 0) { 185 if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0) { 186 vput(vp); 187 return (error); 188 } 189 cnp->cn_flags &= ~PDIRUNLOCK; 190 } 191 } else { 192 error = vget(vp, LK_EXCLUSIVE); 193 /* 194 * If the above vget() failed or either of LOCKPARENT or 195 * ISLASTCN is set, unlock the directory vnode. 196 */ 197 if (error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { 198 VOP_UNLOCK(dvp, 0); 199 cnp->cn_flags |= PDIRUNLOCK; 200 } 201 } 202 203 /* 204 * Check that the lock succeeded, and that the capability number did 205 * not change while we were waiting for the lock. 206 */ 207 if (error || vpid != vp->v_id) { 208 if (!error) { 209 vput(vp); 210 nchstats.ncs_falsehits++; 211 } else 212 nchstats.ncs_badhits++; 213 /* 214 * The parent needs to be locked when we return to VOP_LOOKUP(). 215 * The `.' case here should be extremely rare (if it can happen 216 * at all), so we don't bother optimizing out the unlock/relock. 217 */ 218 if (vp == dvp || 219 error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { 220 if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0) 221 return (error); 222 cnp->cn_flags &= ~PDIRUNLOCK; 223 } 224 *vpp = NULL; 225 return (-1); 226 } 227 228 nchstats.ncs_goodhits++; 229 /* 230 * Move this slot to end of LRU chain, if not already there. 231 */ 232 if (ncp->nc_lru.tqe_next != 0) { 233 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 234 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 235 } 236 *vpp = vp; 237 return (0); 238 239 remove: 240 /* 241 * Last component and we are renaming or deleting, 242 * the cache entry is invalid, or otherwise don't 243 * want cache entry to exist. 244 */ 245 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 246 LIST_REMOVE(ncp, nc_hash); 247 ncp->nc_hash.le_prev = NULL; 248 if (ncp->nc_vhash.le_prev != NULL) { 249 LIST_REMOVE(ncp, nc_vhash); 250 ncp->nc_vhash.le_prev = NULL; 251 } 252 TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru); 253 *vpp = NULL; 254 return (-1); 255 } 256 257 /* 258 * Scan cache looking for name of directory entry pointing at vp. 259 * 260 * Fill in dvpp. 261 * 262 * If bufp is non-NULL, also place the name in the buffer which starts 263 * at bufp, immediately before *bpp, and move bpp backwards to point 264 * at the start of it. (Yes, this is a little baroque, but it's done 265 * this way to cater to the whims of getcwd). 266 * 267 * Returns 0 on success, -1 on cache miss, positive errno on failure. 268 */ 269 int 270 cache_revlookup(struct vnode *vp, struct vnode **dvpp, char **bpp, char *bufp) 271 { 272 struct namecache *ncp; 273 struct vnode *dvp; 274 struct ncvhashhead *nvcpp; 275 char *bp; 276 277 if (!doingcache) 278 goto out; 279 280 nvcpp = &ncvhashtbl[NCVHASH(vp)]; 281 282 LIST_FOREACH(ncp, nvcpp, nc_vhash) { 283 if (ncp->nc_vp == vp && 284 ncp->nc_vpid == vp->v_id && 285 (dvp = ncp->nc_dvp) != NULL && 286 dvp != vp && /* avoid pesky . entries.. */ 287 dvp->v_id == ncp->nc_dvpid) { 288 289 #ifdef DIAGNOSTIC 290 if (ncp->nc_nlen == 1 && 291 ncp->nc_name[0] == '.') 292 panic("cache_revlookup: found entry for ."); 293 294 if (ncp->nc_nlen == 2 && 295 ncp->nc_name[0] == '.' && 296 ncp->nc_name[1] == '.') 297 panic("cache_revlookup: found entry for .."); 298 #endif 299 nchstats.ncs_revhits++; 300 301 if (bufp) { 302 bp = *bpp; 303 bp -= ncp->nc_nlen; 304 if (bp <= bufp) { 305 *dvpp = NULL; 306 return (ERANGE); 307 } 308 memcpy(bp, ncp->nc_name, ncp->nc_nlen); 309 *bpp = bp; 310 } 311 312 /* XXX MP: how do we know dvp won't evaporate? */ 313 *dvpp = dvp; 314 return (0); 315 } 316 } 317 nchstats.ncs_revmiss++; 318 out: 319 *dvpp = NULL; 320 return (-1); 321 } 322 323 /* 324 * Add an entry to the cache 325 */ 326 void 327 cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp) 328 { 329 struct namecache *ncp; 330 struct nchashhead *ncpp; 331 struct ncvhashhead *nvcpp; 332 333 #ifdef DIAGNOSTIC 334 if (cnp->cn_namelen > NCHNAMLEN) 335 panic("cache_enter: name too long"); 336 #endif 337 if (!doingcache) 338 return; 339 /* 340 * Free the cache slot at head of lru chain. 341 */ 342 if (numcache < numvnodes) { 343 ncp = pool_get(&namecache_pool, PR_WAITOK); 344 memset(ncp, 0, sizeof(*ncp)); 345 numcache++; 346 } else if ((ncp = TAILQ_FIRST(&nclruhead)) != NULL) { 347 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 348 if (ncp->nc_hash.le_prev != NULL) { 349 LIST_REMOVE(ncp, nc_hash); 350 ncp->nc_hash.le_prev = NULL; 351 } 352 if (ncp->nc_vhash.le_prev != NULL) { 353 LIST_REMOVE(ncp, nc_vhash); 354 ncp->nc_vhash.le_prev = NULL; 355 } 356 } else 357 return; 358 /* Grab the vnode we just found. */ 359 ncp->nc_vp = vp; 360 if (vp) 361 ncp->nc_vpid = vp->v_id; 362 else { 363 /* 364 * For negative hits, save the ISWHITEOUT flag so we can 365 * restore it later when the cache entry is used again. 366 */ 367 ncp->nc_vpid = cnp->cn_flags & ISWHITEOUT; 368 } 369 /* Fill in cache info. */ 370 ncp->nc_dvp = dvp; 371 ncp->nc_dvpid = dvp->v_id; 372 ncp->nc_nlen = cnp->cn_namelen; 373 memcpy(ncp->nc_name, cnp->cn_nameptr, (unsigned)ncp->nc_nlen); 374 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 375 ncpp = &nchashtbl[NCHASH(cnp, dvp)]; 376 LIST_INSERT_HEAD(ncpp, ncp, nc_hash); 377 378 ncp->nc_vhash.le_prev = NULL; 379 ncp->nc_vhash.le_next = NULL; 380 381 /* 382 * Create reverse-cache entries (used in getcwd) for directories. 383 */ 384 if (vp != NULL && 385 vp != dvp && 386 #ifndef NAMECACHE_ENTER_REVERSE 387 vp->v_type == VDIR && 388 #endif 389 (ncp->nc_nlen > 2 || 390 (ncp->nc_nlen > 1 && ncp->nc_name[1] != '.') || 391 (/* ncp->nc_nlen > 0 && */ ncp->nc_name[0] != '.'))) { 392 nvcpp = &ncvhashtbl[NCVHASH(vp)]; 393 LIST_INSERT_HEAD(nvcpp, ncp, nc_vhash); 394 } 395 } 396 397 /* 398 * Name cache initialization, from vfs_init() when we are booting 399 */ 400 void 401 nchinit(void) 402 { 403 404 TAILQ_INIT(&nclruhead); 405 nchashtbl = 406 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &nchash); 407 ncvhashtbl = 408 #ifdef NAMECACHE_ENTER_REVERSE 409 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash); 410 #else 411 hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash); 412 #endif 413 pool_init(&namecache_pool, sizeof(struct namecache), 0, 0, 0, 414 "ncachepl", &pool_allocator_nointr); 415 } 416 417 /* 418 * Name cache reinitialization, for when the maximum number of vnodes increases. 419 */ 420 void 421 nchreinit(void) 422 { 423 struct namecache *ncp; 424 struct nchashhead *oldhash1, *hash1; 425 struct ncvhashhead *oldhash2, *hash2; 426 u_long oldmask1, oldmask2, mask1, mask2; 427 int i; 428 429 hash1 = hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask1); 430 hash2 = 431 #ifdef NAMECACHE_ENTER_REVERSE 432 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask2); 433 #else 434 hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &mask2); 435 #endif 436 oldhash1 = nchashtbl; 437 oldmask1 = nchash; 438 nchashtbl = hash1; 439 nchash = mask1; 440 oldhash2 = ncvhashtbl; 441 oldmask2 = ncvhash; 442 ncvhashtbl = hash2; 443 ncvhash = mask2; 444 for (i = 0; i <= oldmask1; i++) { 445 while ((ncp = LIST_FIRST(&oldhash1[i])) != NULL) { 446 LIST_REMOVE(ncp, nc_hash); 447 ncp->nc_hash.le_prev = NULL; 448 } 449 } 450 for (i = 0; i <= oldmask2; i++) { 451 while ((ncp = LIST_FIRST(&oldhash2[i])) != NULL) { 452 LIST_REMOVE(ncp, nc_vhash); 453 ncp->nc_vhash.le_prev = NULL; 454 } 455 } 456 hashdone(oldhash1, M_CACHE); 457 hashdone(oldhash2, M_CACHE); 458 } 459 460 /* 461 * Cache flush, a particular vnode; called when a vnode is renamed to 462 * hide entries that would now be invalid 463 */ 464 void 465 cache_purge(struct vnode *vp) 466 { 467 struct namecache *ncp; 468 struct nchashhead *ncpp; 469 static u_long nextvnodeid; 470 471 vp->v_id = ++nextvnodeid; 472 if (nextvnodeid != 0) 473 return; 474 for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) { 475 LIST_FOREACH(ncp, ncpp, nc_hash) { 476 ncp->nc_vpid = 0; 477 ncp->nc_dvpid = 0; 478 } 479 } 480 vp->v_id = ++nextvnodeid; 481 } 482 483 /* 484 * Cache flush, a whole filesystem; called when filesys is umounted to 485 * remove entries that would now be invalid. 486 */ 487 void 488 cache_purgevfs(struct mount *mp) 489 { 490 struct namecache *ncp, *nxtcp; 491 492 for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) { 493 nxtcp = TAILQ_NEXT(ncp, nc_lru); 494 if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) { 495 continue; 496 } 497 /* Free the resources we had. */ 498 ncp->nc_vp = NULL; 499 ncp->nc_dvp = NULL; 500 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 501 if (ncp->nc_hash.le_prev != NULL) { 502 LIST_REMOVE(ncp, nc_hash); 503 ncp->nc_hash.le_prev = NULL; 504 } 505 if (ncp->nc_vhash.le_prev != NULL) { 506 LIST_REMOVE(ncp, nc_vhash); 507 ncp->nc_vhash.le_prev = NULL; 508 } 509 TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru); 510 } 511 } 512 513 #ifdef DDB 514 void 515 namecache_print(struct vnode *vp, void (*pr)(const char *, ...)) 516 { 517 struct vnode *dvp = NULL; 518 struct namecache *ncp; 519 520 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 521 if (ncp->nc_vp == vp && ncp->nc_vpid == vp->v_id) { 522 (*pr)("name %.*s\n", ncp->nc_nlen, ncp->nc_name); 523 dvp = ncp->nc_dvp; 524 } 525 } 526 if (dvp == NULL) { 527 (*pr)("name not found\n"); 528 return; 529 } 530 vp = dvp; 531 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 532 if (ncp->nc_vp == vp && ncp->nc_vpid == vp->v_id) { 533 (*pr)("parent %.*s\n", ncp->nc_nlen, ncp->nc_name); 534 } 535 } 536 } 537 #endif 538