vfs_cache.c revision 1.32
1 /* $NetBSD: vfs_cache.c,v 1.32 2001/11/12 15:25:36 lukem 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 1.32 2001/11/12 15:25:36 lukem 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(dvp, vpp, cnp) 112 struct vnode *dvp; 113 struct vnode **vpp; 114 struct componentname *cnp; 115 { 116 struct namecache *ncp; 117 struct nchashhead *ncpp; 118 struct vnode *vp; 119 int vpid, error; 120 121 if (!doingcache) { 122 cnp->cn_flags &= ~MAKEENTRY; 123 *vpp = 0; 124 return (-1); 125 } 126 if (cnp->cn_namelen > NCHNAMLEN) { 127 nchstats.ncs_long++; 128 cnp->cn_flags &= ~MAKEENTRY; 129 *vpp = 0; 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 = 0; 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 (ncp->nc_lru.tqe_next != 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 /* if the above vget() succeeded and both LOCKPARENT and 184 * ISLASTCN is set, lock the directory vnode as well */ 185 if (!error && (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) == 0) { 186 if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0) { 187 vput(vp); 188 return (error); 189 } 190 cnp->cn_flags &= ~PDIRUNLOCK; 191 } 192 } else { 193 error = vget(vp, LK_EXCLUSIVE); 194 /* if the above vget() failed or either of LOCKPARENT or 195 * ISLASTCN is set, unlock the directory vnode */ 196 if (error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { 197 VOP_UNLOCK(dvp, 0); 198 cnp->cn_flags |= PDIRUNLOCK; 199 } 200 } 201 202 /* 203 * Check that the lock succeeded, and that the capability number did 204 * not change while we were waiting for the lock. 205 */ 206 if (error || vpid != vp->v_id) { 207 if (!error) { 208 vput(vp); 209 nchstats.ncs_falsehits++; 210 } else 211 nchstats.ncs_badhits++; 212 /* 213 * The parent needs to be locked when we return to VOP_LOOKUP(). 214 * The `.' case here should be extremely rare (if it can happen 215 * at all), so we don't bother optimizing out the unlock/relock. 216 */ 217 if (vp == dvp || 218 error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { 219 if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0) 220 return (error); 221 cnp->cn_flags &= ~PDIRUNLOCK; 222 } 223 *vpp = NULL; 224 return (-1); 225 } 226 227 nchstats.ncs_goodhits++; 228 /* 229 * move this slot to end of LRU chain, if not already there 230 */ 231 if (ncp->nc_lru.tqe_next != 0) { 232 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 233 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 234 } 235 *vpp = vp; 236 return (0); 237 238 remove: 239 /* 240 * Last component and we are renaming or deleting, 241 * the cache entry is invalid, or otherwise don't 242 * want cache entry to exist. 243 */ 244 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 245 LIST_REMOVE(ncp, nc_hash); 246 ncp->nc_hash.le_prev = 0; 247 if (ncp->nc_vhash.le_prev != NULL) { 248 LIST_REMOVE(ncp, nc_vhash); 249 ncp->nc_vhash.le_prev = 0; 250 } 251 TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru); 252 *vpp = 0; 253 return (-1); 254 } 255 256 /* 257 * Scan cache looking for name of directory entry pointing at vp. 258 * 259 * Fill in dvpp. 260 * 261 * If bufp is non-NULL, also place the name in the buffer which starts 262 * at bufp, immediately before *bpp, and move bpp backwards to point 263 * at the start of it. (Yes, this is a little baroque, but it's done 264 * this way to cater to the whims of getcwd). 265 * 266 * Returns 0 on success, -1 on cache miss, positive errno on failure. 267 */ 268 int 269 cache_revlookup (vp, dvpp, bpp, bufp) 270 struct vnode *vp, **dvpp; 271 char **bpp; 272 char *bufp; 273 { 274 struct namecache *ncp; 275 struct vnode *dvp; 276 struct ncvhashhead *nvcpp; 277 278 if (!doingcache) 279 goto out; 280 281 nvcpp = &ncvhashtbl[NCVHASH(vp)]; 282 283 LIST_FOREACH(ncp, nvcpp, nc_vhash) { 284 if ((ncp->nc_vp == vp) && 285 (ncp->nc_vpid == vp->v_id) && 286 ((dvp = ncp->nc_dvp) != 0) && 287 (dvp != vp) && /* avoid pesky . entries.. */ 288 (dvp->v_id == ncp->nc_dvpid)) 289 { 290 char *bp; 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 = 0; 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 = 0; 323 return -1; 324 } 325 326 /* 327 * Add an entry to the cache 328 */ 329 void 330 cache_enter(dvp, vp, cnp) 331 struct vnode *dvp; 332 struct vnode *vp; 333 struct componentname *cnp; 334 { 335 struct namecache *ncp; 336 struct nchashhead *ncpp; 337 struct ncvhashhead *nvcpp; 338 339 #ifdef DIAGNOSTIC 340 if (cnp->cn_namelen > NCHNAMLEN) 341 panic("cache_enter: name too long"); 342 #endif 343 if (!doingcache) 344 return; 345 /* 346 * Free the cache slot at head of lru chain. 347 */ 348 if (numcache < numvnodes) { 349 ncp = pool_get(&namecache_pool, PR_WAITOK); 350 memset(ncp, 0, sizeof(*ncp)); 351 numcache++; 352 } else if ((ncp = TAILQ_FIRST(&nclruhead)) != NULL) { 353 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 354 if (ncp->nc_hash.le_prev != 0) { 355 LIST_REMOVE(ncp, nc_hash); 356 ncp->nc_hash.le_prev = 0; 357 } 358 if (ncp->nc_vhash.le_prev != 0) { 359 LIST_REMOVE(ncp, nc_vhash); 360 ncp->nc_vhash.le_prev = 0; 361 } 362 } else 363 return; 364 /* grab the vnode we just found */ 365 ncp->nc_vp = vp; 366 if (vp) 367 ncp->nc_vpid = vp->v_id; 368 else { 369 /* 370 * For negative hits, save the ISWHITEOUT flag so we can 371 * restore it later when the cache entry is used again. 372 */ 373 ncp->nc_vpid = cnp->cn_flags & ISWHITEOUT; 374 } 375 /* fill in cache info */ 376 ncp->nc_dvp = dvp; 377 ncp->nc_dvpid = dvp->v_id; 378 ncp->nc_nlen = cnp->cn_namelen; 379 memcpy(ncp->nc_name, cnp->cn_nameptr, (unsigned)ncp->nc_nlen); 380 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 381 ncpp = &nchashtbl[NCHASH(cnp, dvp)]; 382 LIST_INSERT_HEAD(ncpp, ncp, nc_hash); 383 384 ncp->nc_vhash.le_prev = 0; 385 ncp->nc_vhash.le_next = 0; 386 387 /* 388 * Create reverse-cache entries (used in getcwd) for directories. 389 */ 390 if (vp && 391 (vp != dvp) && 392 #ifndef NAMECACHE_ENTER_REVERSE 393 (vp->v_type == VDIR) && 394 #endif 395 ((ncp->nc_nlen > 2) || 396 ((ncp->nc_nlen == 2) && (ncp->nc_name[0] != '.') && (ncp->nc_name[1] != '.')) || 397 ((ncp->nc_nlen == 1) && (ncp->nc_name[0] != '.')))) 398 { 399 nvcpp = &ncvhashtbl[NCVHASH(vp)]; 400 LIST_INSERT_HEAD(nvcpp, ncp, nc_vhash); 401 } 402 403 } 404 405 /* 406 * Name cache initialization, from vfs_init() when we are booting 407 */ 408 void 409 nchinit() 410 { 411 412 TAILQ_INIT(&nclruhead); 413 nchashtbl = 414 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &nchash); 415 ncvhashtbl = 416 #ifdef NAMECACHE_ENTER_REVERSE 417 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash); 418 #else 419 hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash); 420 #endif 421 pool_init(&namecache_pool, sizeof(struct namecache), 0, 0, 0, 422 "ncachepl", 0, pool_page_alloc_nointr, pool_page_free_nointr, 423 M_CACHE); 424 } 425 426 /* 427 * Name cache reinitialization, for when the maximum number of vnodes increases. 428 */ 429 void 430 nchreinit() 431 { 432 struct namecache *ncp; 433 struct nchashhead *oldhash1, *hash1; 434 struct ncvhashhead *oldhash2, *hash2; 435 u_long oldmask1, oldmask2, mask1, mask2; 436 int i; 437 438 hash1 = hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask1); 439 hash2 = 440 #ifdef NAMECACHE_ENTER_REVERSE 441 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask2); 442 #else 443 hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &mask2); 444 #endif 445 oldhash1 = nchashtbl; 446 oldmask1 = nchash; 447 nchashtbl = hash1; 448 nchash = mask1; 449 oldhash2 = ncvhashtbl; 450 oldmask2 = ncvhash; 451 ncvhashtbl = hash2; 452 ncvhash = mask2; 453 for (i = 0; i <= oldmask1; i++) { 454 while ((ncp = LIST_FIRST(&oldhash1[i])) != NULL) { 455 LIST_REMOVE(ncp, nc_hash); 456 ncp->nc_hash.le_prev = NULL; 457 } 458 } 459 for (i = 0; i <= oldmask2; i++) { 460 while ((ncp = LIST_FIRST(&oldhash2[i])) != NULL) { 461 LIST_REMOVE(ncp, nc_vhash); 462 ncp->nc_vhash.le_prev = NULL; 463 } 464 } 465 hashdone(oldhash1, M_CACHE); 466 hashdone(oldhash2, M_CACHE); 467 } 468 469 /* 470 * Cache flush, a particular vnode; called when a vnode is renamed to 471 * hide entries that would now be invalid 472 */ 473 void 474 cache_purge(vp) 475 struct vnode *vp; 476 { 477 struct namecache *ncp; 478 struct nchashhead *ncpp; 479 static u_long nextvnodeid; 480 481 vp->v_id = ++nextvnodeid; 482 if (nextvnodeid != 0) 483 return; 484 for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) { 485 LIST_FOREACH(ncp, ncpp, nc_hash) { 486 ncp->nc_vpid = 0; 487 ncp->nc_dvpid = 0; 488 } 489 } 490 vp->v_id = ++nextvnodeid; 491 } 492 493 /* 494 * Cache flush, a whole filesystem; called when filesys is umounted to 495 * remove entries that would now be invalid. 496 */ 497 void 498 cache_purgevfs(mp) 499 struct mount *mp; 500 { 501 struct namecache *ncp, *nxtcp; 502 503 for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) { 504 nxtcp = TAILQ_NEXT(ncp, nc_lru); 505 if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) { 506 continue; 507 } 508 /* free the resources we had */ 509 ncp->nc_vp = NULL; 510 ncp->nc_dvp = NULL; 511 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 512 if (ncp->nc_hash.le_prev != 0) { 513 LIST_REMOVE(ncp, nc_hash); 514 ncp->nc_hash.le_prev = 0; 515 } 516 if (ncp->nc_vhash.le_prev != 0) { 517 LIST_REMOVE(ncp, nc_vhash); 518 ncp->nc_vhash.le_prev = 0; 519 } 520 TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru); 521 } 522 } 523 524 #ifdef DDB 525 void 526 namecache_print(struct vnode *vp, void (*pr)(const char *, ...)) 527 { 528 struct vnode *dvp = NULL; 529 struct namecache *ncp; 530 531 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 532 if (ncp->nc_vp == vp && ncp->nc_vpid == vp->v_id) { 533 (*pr)("name %.*s\n", ncp->nc_nlen, ncp->nc_name); 534 dvp = ncp->nc_dvp; 535 } 536 } 537 if (dvp == NULL) { 538 (*pr)("name not found\n"); 539 return; 540 } 541 vp = dvp; 542 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 543 if (ncp->nc_vp == vp && ncp->nc_vpid == vp->v_id) { 544 (*pr)("parent %.*s\n", ncp->nc_nlen, ncp->nc_name); 545 } 546 } 547 } 548 #endif 549
Indexes created Thu Sep 25 16:09:42 GMT 2025