1 /* $NetBSD: vfs_cache.c,v 1.38 2003/02/01 06:23:45 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 1.38 2003/02/01 06:23:45 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 MALLOC_DEFINE(M_CACHE, "namecache", "Dynamically allocated cache entries"); 93 94 int doingcache = 1; /* 1 => enable the cache */ 95 96 /* 97 * Look for a the name in the cache. We don't do this 98 * if the segment name is long, simply so the cache can avoid 99 * holding long names (which would either waste space, or 100 * add greatly to the complexity). 101 * 102 * Lookup is called with ni_dvp pointing to the directory to search, 103 * ni_ptr pointing to the name of the entry being sought, ni_namelen 104 * tells the length of the name, and ni_hash contains a hash of 105 * the name. If the lookup succeeds, the vnode is locked, stored in ni_vp 106 * and a status of zero is returned. If the locking fails for whatever 107 * reason, the vnode is unlocked and the error is returned to caller. 108 * If the lookup determines that the name does not exist (negative cacheing), 109 * a status of ENOENT is returned. If the lookup fails, a status of -1 110 * is returned. 111 */ 112 int 113 cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp) 114 { 115 struct namecache *ncp; 116 struct nchashhead *ncpp; 117 struct vnode *vp; 118 u_long vpid; 119 int error; 120 121 if (!doingcache) { 122 cnp->cn_flags &= ~MAKEENTRY; 123 *vpp = NULL; 124 return (-1); 125 } 126 if (cnp->cn_namelen > NCHNAMLEN) { 127 nchstats.ncs_long++; 128 cnp->cn_flags &= ~MAKEENTRY; 129 *vpp = NULL; 130 return (-1); 131 } 132 ncpp = &nchashtbl[NCHASH(cnp, dvp)]; 133 LIST_FOREACH(ncp, ncpp, nc_hash) { 134 if (ncp->nc_dvp == dvp && 135 ncp->nc_dvpid == dvp->v_id && 136 ncp->nc_nlen == cnp->cn_namelen && 137 !memcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen)) 138 break; 139 } 140 if (ncp == 0) { 141 nchstats.ncs_miss++; 142 *vpp = NULL; 143 return (-1); 144 } 145 if ((cnp->cn_flags & MAKEENTRY) == 0) { 146 nchstats.ncs_badhits++; 147 goto remove; 148 } else if (ncp->nc_vp == NULL) { 149 /* 150 * Restore the ISWHITEOUT flag saved earlier. 151 */ 152 cnp->cn_flags |= ncp->nc_vpid; 153 if (cnp->cn_nameiop != CREATE || 154 (cnp->cn_flags & ISLASTCN) == 0) { 155 nchstats.ncs_neghits++; 156 /* 157 * Move this slot to end of LRU chain, 158 * if not already there. 159 */ 160 if (TAILQ_NEXT(ncp, nc_lru) != 0) { 161 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 162 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 163 } 164 return (ENOENT); 165 } else { 166 nchstats.ncs_badhits++; 167 goto remove; 168 } 169 } else if (ncp->nc_vpid != ncp->nc_vp->v_id) { 170 nchstats.ncs_falsehits++; 171 goto remove; 172 } 173 174 vp = ncp->nc_vp; 175 vpid = vp->v_id; 176 if (vp == dvp) { /* lookup on "." */ 177 VREF(dvp); 178 error = 0; 179 } else if (cnp->cn_flags & ISDOTDOT) { 180 VOP_UNLOCK(dvp, 0); 181 cnp->cn_flags |= PDIRUNLOCK; 182 error = vget(vp, LK_EXCLUSIVE); 183 /* 184 * If the above vget() succeeded and both LOCKPARENT and 185 * ISLASTCN is set, lock the directory vnode as well. 186 */ 187 if (!error && (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) == 0) { 188 if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0) { 189 vput(vp); 190 return (error); 191 } 192 cnp->cn_flags &= ~PDIRUNLOCK; 193 } 194 } else { 195 error = vget(vp, LK_EXCLUSIVE); 196 /* 197 * If the above vget() failed or either of LOCKPARENT or 198 * ISLASTCN is set, unlock the directory vnode. 199 */ 200 if (error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { 201 VOP_UNLOCK(dvp, 0); 202 cnp->cn_flags |= PDIRUNLOCK; 203 } 204 } 205 206 /* 207 * Check that the lock succeeded, and that the capability number did 208 * not change while we were waiting for the lock. 209 */ 210 if (error || vpid != vp->v_id) { 211 if (!error) { 212 vput(vp); 213 nchstats.ncs_falsehits++; 214 } else 215 nchstats.ncs_badhits++; 216 /* 217 * The parent needs to be locked when we return to VOP_LOOKUP(). 218 * The `.' case here should be extremely rare (if it can happen 219 * at all), so we don't bother optimizing out the unlock/relock. 220 */ 221 if (vp == dvp || 222 error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { 223 if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0) 224 return (error); 225 cnp->cn_flags &= ~PDIRUNLOCK; 226 } 227 *vpp = NULL; 228 return (-1); 229 } 230 231 nchstats.ncs_goodhits++; 232 /* 233 * Move this slot to end of LRU chain, if not already there. 234 */ 235 if (TAILQ_NEXT(ncp, nc_lru) != 0) { 236 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 237 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 238 } 239 *vpp = vp; 240 return (0); 241 242 remove: 243 /* 244 * Last component and we are renaming or deleting, 245 * the cache entry is invalid, or otherwise don't 246 * want cache entry to exist. 247 */ 248 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 249 LIST_REMOVE(ncp, nc_hash); 250 ncp->nc_hash.le_prev = NULL; 251 if (ncp->nc_vhash.le_prev != NULL) { 252 LIST_REMOVE(ncp, nc_vhash); 253 ncp->nc_vhash.le_prev = NULL; 254 } 255 TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru); 256 *vpp = NULL; 257 return (-1); 258 } 259 260 /* 261 * Scan cache looking for name of directory entry pointing at vp. 262 * 263 * Fill in dvpp. 264 * 265 * If bufp is non-NULL, also place the name in the buffer which starts 266 * at bufp, immediately before *bpp, and move bpp backwards to point 267 * at the start of it. (Yes, this is a little baroque, but it's done 268 * this way to cater to the whims of getcwd). 269 * 270 * Returns 0 on success, -1 on cache miss, positive errno on failure. 271 */ 272 int 273 cache_revlookup(struct vnode *vp, struct vnode **dvpp, char **bpp, char *bufp) 274 { 275 struct namecache *ncp; 276 struct vnode *dvp; 277 struct ncvhashhead *nvcpp; 278 char *bp; 279 280 if (!doingcache) 281 goto out; 282 283 nvcpp = &ncvhashtbl[NCVHASH(vp)]; 284 285 LIST_FOREACH(ncp, nvcpp, nc_vhash) { 286 if (ncp->nc_vp == vp && 287 ncp->nc_vpid == vp->v_id && 288 (dvp = ncp->nc_dvp) != NULL && 289 dvp != vp && /* avoid pesky . entries.. */ 290 dvp->v_id == ncp->nc_dvpid) { 291 292 #ifdef DIAGNOSTIC 293 if (ncp->nc_nlen == 1 && 294 ncp->nc_name[0] == '.') 295 panic("cache_revlookup: found entry for ."); 296 297 if (ncp->nc_nlen == 2 && 298 ncp->nc_name[0] == '.' && 299 ncp->nc_name[1] == '.') 300 panic("cache_revlookup: found entry for .."); 301 #endif 302 nchstats.ncs_revhits++; 303 304 if (bufp) { 305 bp = *bpp; 306 bp -= ncp->nc_nlen; 307 if (bp <= bufp) { 308 *dvpp = NULL; 309 return (ERANGE); 310 } 311 memcpy(bp, ncp->nc_name, ncp->nc_nlen); 312 *bpp = bp; 313 } 314 315 /* XXX MP: how do we know dvp won't evaporate? */ 316 *dvpp = dvp; 317 return (0); 318 } 319 } 320 nchstats.ncs_revmiss++; 321 out: 322 *dvpp = NULL; 323 return (-1); 324 } 325 326 /* 327 * Add an entry to the cache 328 */ 329 void 330 cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp) 331 { 332 struct namecache *ncp; 333 struct nchashhead *ncpp; 334 struct ncvhashhead *nvcpp; 335 336 #ifdef DIAGNOSTIC 337 if (cnp->cn_namelen > NCHNAMLEN) 338 panic("cache_enter: name too long"); 339 #endif 340 if (!doingcache) 341 return; 342 /* 343 * Free the cache slot at head of lru chain. 344 */ 345 if (numcache < numvnodes) { 346 ncp = pool_get(&namecache_pool, PR_WAITOK); 347 memset(ncp, 0, sizeof(*ncp)); 348 numcache++; 349 } else if ((ncp = TAILQ_FIRST(&nclruhead)) != NULL) { 350 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 351 if (ncp->nc_hash.le_prev != NULL) { 352 LIST_REMOVE(ncp, nc_hash); 353 ncp->nc_hash.le_prev = NULL; 354 } 355 if (ncp->nc_vhash.le_prev != NULL) { 356 LIST_REMOVE(ncp, nc_vhash); 357 ncp->nc_vhash.le_prev = NULL; 358 } 359 } else 360 return; 361 /* Grab the vnode we just found. */ 362 ncp->nc_vp = vp; 363 if (vp) 364 ncp->nc_vpid = vp->v_id; 365 else { 366 /* 367 * For negative hits, save the ISWHITEOUT flag so we can 368 * restore it later when the cache entry is used again. 369 */ 370 ncp->nc_vpid = cnp->cn_flags & ISWHITEOUT; 371 } 372 /* Fill in cache info. */ 373 ncp->nc_dvp = dvp; 374 ncp->nc_dvpid = dvp->v_id; 375 ncp->nc_nlen = cnp->cn_namelen; 376 memcpy(ncp->nc_name, cnp->cn_nameptr, (unsigned)ncp->nc_nlen); 377 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 378 ncpp = &nchashtbl[NCHASH(cnp, dvp)]; 379 LIST_INSERT_HEAD(ncpp, ncp, nc_hash); 380 381 ncp->nc_vhash.le_prev = NULL; 382 ncp->nc_vhash.le_next = NULL; 383 384 /* 385 * Create reverse-cache entries (used in getcwd) for directories. 386 */ 387 if (vp != NULL && 388 vp != dvp && 389 #ifndef NAMECACHE_ENTER_REVERSE 390 vp->v_type == VDIR && 391 #endif 392 (ncp->nc_nlen > 2 || 393 (ncp->nc_nlen > 1 && ncp->nc_name[1] != '.') || 394 (/* ncp->nc_nlen > 0 && */ ncp->nc_name[0] != '.'))) { 395 nvcpp = &ncvhashtbl[NCVHASH(vp)]; 396 LIST_INSERT_HEAD(nvcpp, ncp, nc_vhash); 397 } 398 } 399 400 /* 401 * Name cache initialization, from vfs_init() when we are booting 402 */ 403 void 404 nchinit(void) 405 { 406 407 TAILQ_INIT(&nclruhead); 408 nchashtbl = 409 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &nchash); 410 ncvhashtbl = 411 #ifdef NAMECACHE_ENTER_REVERSE 412 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash); 413 #else 414 hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash); 415 #endif 416 pool_init(&namecache_pool, sizeof(struct namecache), 0, 0, 0, 417 "ncachepl", &pool_allocator_nointr); 418 } 419 420 /* 421 * Name cache reinitialization, for when the maximum number of vnodes increases. 422 */ 423 void 424 nchreinit(void) 425 { 426 struct namecache *ncp; 427 struct nchashhead *oldhash1, *hash1; 428 struct ncvhashhead *oldhash2, *hash2; 429 u_long i, oldmask1, oldmask2, mask1, mask2; 430 431 hash1 = hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask1); 432 hash2 = 433 #ifdef NAMECACHE_ENTER_REVERSE 434 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask2); 435 #else 436 hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &mask2); 437 #endif 438 oldhash1 = nchashtbl; 439 oldmask1 = nchash; 440 nchashtbl = hash1; 441 nchash = mask1; 442 oldhash2 = ncvhashtbl; 443 oldmask2 = ncvhash; 444 ncvhashtbl = hash2; 445 ncvhash = mask2; 446 for (i = 0; i <= oldmask1; i++) { 447 while ((ncp = LIST_FIRST(&oldhash1[i])) != NULL) { 448 LIST_REMOVE(ncp, nc_hash); 449 ncp->nc_hash.le_prev = NULL; 450 } 451 } 452 for (i = 0; i <= oldmask2; i++) { 453 while ((ncp = LIST_FIRST(&oldhash2[i])) != NULL) { 454 LIST_REMOVE(ncp, nc_vhash); 455 ncp->nc_vhash.le_prev = NULL; 456 } 457 } 458 hashdone(oldhash1, M_CACHE); 459 hashdone(oldhash2, M_CACHE); 460 } 461 462 /* 463 * Cache flush, a particular vnode; called when a vnode is renamed to 464 * hide entries that would now be invalid 465 */ 466 void 467 cache_purge(struct vnode *vp) 468 { 469 struct namecache *ncp; 470 struct nchashhead *ncpp; 471 static u_long nextvnodeid; 472 473 vp->v_id = ++nextvnodeid; 474 if (nextvnodeid != 0) 475 return; 476 for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) { 477 LIST_FOREACH(ncp, ncpp, nc_hash) { 478 ncp->nc_vpid = 0; 479 ncp->nc_dvpid = 0; 480 } 481 } 482 vp->v_id = ++nextvnodeid; 483 } 484 485 /* 486 * Cache flush, a whole filesystem; called when filesys is umounted to 487 * remove entries that would now be invalid. 488 */ 489 void 490 cache_purgevfs(struct mount *mp) 491 { 492 struct namecache *ncp, *nxtcp; 493 494 for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) { 495 nxtcp = TAILQ_NEXT(ncp, nc_lru); 496 if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) { 497 continue; 498 } 499 /* Free the resources we had. */ 500 ncp->nc_vp = NULL; 501 ncp->nc_dvp = NULL; 502 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 503 if (ncp->nc_hash.le_prev != NULL) { 504 LIST_REMOVE(ncp, nc_hash); 505 ncp->nc_hash.le_prev = NULL; 506 } 507 if (ncp->nc_vhash.le_prev != NULL) { 508 LIST_REMOVE(ncp, nc_vhash); 509 ncp->nc_vhash.le_prev = NULL; 510 } 511 TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru); 512 } 513 } 514 515 #ifdef DDB 516 void 517 namecache_print(struct vnode *vp, void (*pr)(const char *, ...)) 518 { 519 struct vnode *dvp = NULL; 520 struct namecache *ncp; 521 522 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 523 if (ncp->nc_vp == vp && ncp->nc_vpid == vp->v_id) { 524 (*pr)("name %.*s\n", ncp->nc_nlen, ncp->nc_name); 525 dvp = ncp->nc_dvp; 526 } 527 } 528 if (dvp == NULL) { 529 (*pr)("name not found\n"); 530 return; 531 } 532 vp = dvp; 533 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 534 if (ncp->nc_vp == vp && ncp->nc_vpid == vp->v_id) { 535 (*pr)("parent %.*s\n", ncp->nc_nlen, ncp->nc_name); 536 } 537 } 538 } 539 #endif 540