1 /* $NetBSD: vfs_cache.c,v 1.53 2003/08/08 20:19:56 yamt 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. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)vfs_cache.c 8.3 (Berkeley) 8/22/94 32 */ 33 34 #include <sys/cdefs.h> 35 __KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.53 2003/08/08 20:19:56 yamt Exp $"); 36 37 #include "opt_ddb.h" 38 #include "opt_revcache.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 #include <sys/lock.h> 50 51 /* 52 * Name caching works as follows: 53 * 54 * Names found by directory scans are retained in a cache 55 * for future reference. It is managed LRU, so frequently 56 * used names will hang around. Cache is indexed by hash value 57 * obtained from (dvp, name) where dvp refers to the directory 58 * containing name. 59 * 60 * For simplicity (and economy of storage), names longer than 61 * a maximum length of NCHNAMLEN are not cached; they occur 62 * infrequently in any case, and are almost never of interest. 63 * 64 * Upon reaching the last segment of a path, if the reference 65 * is for DELETE, or NOCACHE is set (rewrite), and the 66 * name is located in the cache, it will be dropped. 67 * The entry is dropped also when it was not possible to lock 68 * the cached vnode, either because vget() failed or the generation 69 * number has changed while waiting for the lock. 70 */ 71 72 /* 73 * Structures associated with name cacheing. 74 */ 75 LIST_HEAD(nchashhead, namecache) *nchashtbl; 76 u_long nchash; /* size of hash table - 1 */ 77 long numcache; /* number of cache entries allocated */ 78 #define NCHASH(cnp, dvp) \ 79 (((cnp)->cn_hash ^ ((uintptr_t)(dvp) >> 3)) & nchash) 80 81 LIST_HEAD(ncvhashhead, namecache) *ncvhashtbl; 82 u_long ncvhash; /* size of hash table - 1 */ 83 #define NCVHASH(vp) (((uintptr_t)(vp) >> 3) & ncvhash) 84 85 TAILQ_HEAD(, namecache) nclruhead; /* LRU chain */ 86 struct nchstats nchstats; /* cache effectiveness statistics */ 87 88 struct pool namecache_pool; 89 90 MALLOC_DEFINE(M_CACHE, "namecache", "Dynamically allocated cache entries"); 91 92 int doingcache = 1; /* 1 => enable the cache */ 93 94 /* A single lock to protect cache insertion, removal and lookup */ 95 static struct simplelock namecache_slock = SIMPLELOCK_INITIALIZER; 96 97 static void cache_remove(struct namecache *); 98 static void cache_free(struct namecache *); 99 100 static void 101 cache_remove(struct namecache *ncp) 102 { 103 104 LOCK_ASSERT(simple_lock_held(&namecache_slock)); 105 106 ncp->nc_dvp = NULL; 107 ncp->nc_vp = NULL; 108 109 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 110 if (ncp->nc_hash.le_prev != NULL) { 111 LIST_REMOVE(ncp, nc_hash); 112 ncp->nc_hash.le_prev = NULL; 113 } 114 if (ncp->nc_vhash.le_prev != NULL) { 115 LIST_REMOVE(ncp, nc_vhash); 116 ncp->nc_vhash.le_prev = NULL; 117 } 118 if (ncp->nc_vlist.le_prev != NULL) { 119 LIST_REMOVE(ncp, nc_vlist); 120 ncp->nc_vlist.le_prev = NULL; 121 } 122 if (ncp->nc_dvlist.le_prev != NULL) { 123 LIST_REMOVE(ncp, nc_dvlist); 124 ncp->nc_dvlist.le_prev = NULL; 125 } 126 } 127 128 static void 129 cache_free(struct namecache *ncp) 130 { 131 132 pool_put(&namecache_pool, ncp); 133 numcache--; /* XXX MP */ 134 } 135 136 /* 137 * Look for a the name in the cache. We don't do this 138 * if the segment name is long, simply so the cache can avoid 139 * holding long names (which would either waste space, or 140 * add greatly to the complexity). 141 * 142 * Lookup is called with ni_dvp pointing to the directory to search, 143 * ni_ptr pointing to the name of the entry being sought, ni_namelen 144 * tells the length of the name, and ni_hash contains a hash of 145 * the name. If the lookup succeeds, the vnode is locked, stored in ni_vp 146 * and a status of zero is returned. If the locking fails for whatever 147 * reason, the vnode is unlocked and the error is returned to caller. 148 * If the lookup determines that the name does not exist (negative cacheing), 149 * a status of ENOENT is returned. If the lookup fails, a status of -1 150 * is returned. 151 */ 152 int 153 cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp) 154 { 155 struct namecache *ncp; 156 struct nchashhead *ncpp; 157 struct vnode *vp; 158 int error; 159 160 if (!doingcache) { 161 cnp->cn_flags &= ~MAKEENTRY; 162 *vpp = NULL; 163 return (-1); 164 } 165 166 if (cnp->cn_namelen > NCHNAMLEN) { 167 /* XXXSMP - updating stats without lock; do we care? */ 168 nchstats.ncs_long++; 169 cnp->cn_flags &= ~MAKEENTRY; 170 goto fail; 171 } 172 ncpp = &nchashtbl[NCHASH(cnp, dvp)]; 173 simple_lock(&namecache_slock); 174 LIST_FOREACH(ncp, ncpp, nc_hash) { 175 if (ncp->nc_dvp == dvp && 176 ncp->nc_nlen == cnp->cn_namelen && 177 !memcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen)) 178 break; 179 } 180 if (ncp == 0) { 181 nchstats.ncs_miss++; 182 goto fail_wlock; 183 } 184 if ((cnp->cn_flags & MAKEENTRY) == 0) { 185 nchstats.ncs_badhits++; 186 goto remove; 187 } else if (ncp->nc_vp == NULL) { 188 /* 189 * Restore the ISWHITEOUT flag saved earlier. 190 */ 191 cnp->cn_flags |= ncp->nc_flags; 192 if (cnp->cn_nameiop != CREATE || 193 (cnp->cn_flags & ISLASTCN) == 0) { 194 nchstats.ncs_neghits++; 195 /* 196 * Move this slot to end of LRU chain, 197 * if not already there. 198 */ 199 if (TAILQ_NEXT(ncp, nc_lru) != 0) { 200 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 201 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 202 } 203 simple_unlock(&namecache_slock); 204 return (ENOENT); 205 } else { 206 nchstats.ncs_badhits++; 207 goto remove; 208 } 209 } 210 211 vp = ncp->nc_vp; 212 213 /* 214 * Move this slot to end of LRU chain, if not already there. 215 */ 216 if (TAILQ_NEXT(ncp, nc_lru) != 0) { 217 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 218 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 219 } 220 221 if (vp != dvp) 222 simple_lock(&vp->v_interlock); 223 224 /* Release the name cache mutex while we acquire vnode locks */ 225 simple_unlock(&namecache_slock); 226 227 #ifdef DEBUG 228 /* 229 * since we released namecache_slock, 230 * we can't use this pointer any more. 231 */ 232 ncp = NULL; 233 #endif /* DEBUG */ 234 235 if (vp != dvp && __predict_false(vp->v_flag & VXLOCK)) { 236 /* 237 * this vnode is being cleaned out. 238 */ 239 simple_unlock(&vp->v_interlock); 240 nchstats.ncs_falsehits++; /* XXX badhits? */ 241 goto fail; 242 } 243 244 if (vp == dvp) { /* lookup on "." */ 245 VREF(dvp); 246 error = 0; 247 } else if (cnp->cn_flags & ISDOTDOT) { 248 VOP_UNLOCK(dvp, 0); 249 cnp->cn_flags |= PDIRUNLOCK; 250 error = vget(vp, LK_EXCLUSIVE | LK_INTERLOCK); 251 /* 252 * If the above vget() succeeded and both LOCKPARENT and 253 * ISLASTCN is set, lock the directory vnode as well. 254 */ 255 if (!error && (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) == 0) { 256 if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0) { 257 vput(vp); 258 return (error); 259 } 260 cnp->cn_flags &= ~PDIRUNLOCK; 261 } 262 } else { 263 error = vget(vp, LK_EXCLUSIVE | LK_INTERLOCK); 264 /* 265 * If the above vget() failed or either of LOCKPARENT or 266 * ISLASTCN is set, unlock the directory vnode. 267 */ 268 if (error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { 269 VOP_UNLOCK(dvp, 0); 270 cnp->cn_flags |= PDIRUNLOCK; 271 } 272 } 273 274 /* 275 * Check that the lock succeeded, and that the capability number did 276 * not change while we were waiting for the lock. 277 */ 278 if (error) { 279 /* XXXSMP - updating stats without lock; do we care? */ 280 nchstats.ncs_badhits++; 281 282 /* 283 * The parent needs to be locked when we return to VOP_LOOKUP(). 284 * The `.' case here should be extremely rare (if it can happen 285 * at all), so we don't bother optimizing out the unlock/relock. 286 */ 287 if (vp == dvp || 288 error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { 289 if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0) 290 return (error); 291 cnp->cn_flags &= ~PDIRUNLOCK; 292 } 293 *vpp = NULL; 294 return (-1); 295 } 296 297 /* XXXSMP - updating stats without lock; do we care? */ 298 nchstats.ncs_goodhits++; 299 *vpp = vp; 300 return (0); 301 302 remove: 303 /* 304 * Last component and we are renaming or deleting, 305 * the cache entry is invalid, or otherwise don't 306 * want cache entry to exist. 307 */ 308 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 309 LIST_REMOVE(ncp, nc_hash); 310 ncp->nc_hash.le_prev = NULL; 311 if (ncp->nc_vhash.le_prev != NULL) { 312 LIST_REMOVE(ncp, nc_vhash); 313 ncp->nc_vhash.le_prev = NULL; 314 } 315 TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru); 316 317 fail_wlock: 318 simple_unlock(&namecache_slock); 319 fail: 320 *vpp = NULL; 321 return (-1); 322 } 323 324 /* 325 * Scan cache looking for name of directory entry pointing at vp. 326 * 327 * Fill in dvpp. 328 * 329 * If bufp is non-NULL, also place the name in the buffer which starts 330 * at bufp, immediately before *bpp, and move bpp backwards to point 331 * at the start of it. (Yes, this is a little baroque, but it's done 332 * this way to cater to the whims of getcwd). 333 * 334 * Returns 0 on success, -1 on cache miss, positive errno on failure. 335 */ 336 int 337 cache_revlookup(struct vnode *vp, struct vnode **dvpp, char **bpp, char *bufp) 338 { 339 struct namecache *ncp; 340 struct vnode *dvp; 341 struct ncvhashhead *nvcpp; 342 char *bp; 343 344 if (!doingcache) 345 goto out; 346 347 nvcpp = &ncvhashtbl[NCVHASH(vp)]; 348 349 simple_lock(&namecache_slock); 350 LIST_FOREACH(ncp, nvcpp, nc_vhash) { 351 if (ncp->nc_vp == vp && 352 (dvp = ncp->nc_dvp) != NULL && 353 dvp != vp) { /* avoid pesky . entries.. */ 354 355 #ifdef DIAGNOSTIC 356 if (ncp->nc_nlen == 1 && 357 ncp->nc_name[0] == '.') 358 panic("cache_revlookup: found entry for ."); 359 360 if (ncp->nc_nlen == 2 && 361 ncp->nc_name[0] == '.' && 362 ncp->nc_name[1] == '.') 363 panic("cache_revlookup: found entry for .."); 364 #endif 365 nchstats.ncs_revhits++; 366 367 if (bufp) { 368 bp = *bpp; 369 bp -= ncp->nc_nlen; 370 if (bp <= bufp) { 371 *dvpp = NULL; 372 simple_unlock(&namecache_slock); 373 return (ERANGE); 374 } 375 memcpy(bp, ncp->nc_name, ncp->nc_nlen); 376 *bpp = bp; 377 } 378 379 /* XXX MP: how do we know dvp won't evaporate? */ 380 *dvpp = dvp; 381 simple_unlock(&namecache_slock); 382 return (0); 383 } 384 } 385 nchstats.ncs_revmiss++; 386 simple_unlock(&namecache_slock); 387 out: 388 *dvpp = NULL; 389 return (-1); 390 } 391 392 /* 393 * Add an entry to the cache 394 */ 395 void 396 cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp) 397 { 398 struct namecache *ncp; 399 struct nchashhead *ncpp; 400 struct ncvhashhead *nvcpp; 401 402 #ifdef DIAGNOSTIC 403 if (cnp->cn_namelen > NCHNAMLEN) 404 panic("cache_enter: name too long"); 405 #endif 406 if (!doingcache) 407 return; 408 /* 409 * Free the cache slot at head of lru chain. 410 */ 411 simple_lock(&namecache_slock); 412 if (numcache < numvnodes) { 413 numcache++; 414 simple_unlock(&namecache_slock); 415 ncp = pool_get(&namecache_pool, PR_WAITOK); 416 memset(ncp, 0, sizeof(*ncp)); 417 simple_lock(&namecache_slock); 418 } else if ((ncp = TAILQ_FIRST(&nclruhead)) != NULL) { 419 cache_remove(ncp); 420 } else { 421 simple_unlock(&namecache_slock); 422 return; 423 } 424 /* Grab the vnode we just found. */ 425 ncp->nc_vp = vp; 426 if (vp == NULL) { 427 /* 428 * For negative hits, save the ISWHITEOUT flag so we can 429 * restore it later when the cache entry is used again. 430 */ 431 ncp->nc_flags = cnp->cn_flags & ISWHITEOUT; 432 } 433 /* Fill in cache info. */ 434 ncp->nc_dvp = dvp; 435 LIST_INSERT_HEAD(&dvp->v_dnclist, ncp, nc_dvlist); 436 if (vp) 437 LIST_INSERT_HEAD(&vp->v_nclist, ncp, nc_vlist); 438 ncp->nc_nlen = cnp->cn_namelen; 439 memcpy(ncp->nc_name, cnp->cn_nameptr, (unsigned)ncp->nc_nlen); 440 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 441 ncpp = &nchashtbl[NCHASH(cnp, dvp)]; 442 LIST_INSERT_HEAD(ncpp, ncp, nc_hash); 443 444 ncp->nc_vhash.le_prev = NULL; 445 ncp->nc_vhash.le_next = NULL; 446 447 /* 448 * Create reverse-cache entries (used in getcwd) for directories. 449 */ 450 if (vp != NULL && 451 vp != dvp && 452 #ifndef NAMECACHE_ENTER_REVERSE 453 vp->v_type == VDIR && 454 #endif 455 (ncp->nc_nlen > 2 || 456 (ncp->nc_nlen > 1 && ncp->nc_name[1] != '.') || 457 (/* ncp->nc_nlen > 0 && */ ncp->nc_name[0] != '.'))) { 458 nvcpp = &ncvhashtbl[NCVHASH(vp)]; 459 LIST_INSERT_HEAD(nvcpp, ncp, nc_vhash); 460 } 461 simple_unlock(&namecache_slock); 462 } 463 464 /* 465 * Name cache initialization, from vfs_init() when we are booting 466 */ 467 void 468 nchinit(void) 469 { 470 471 TAILQ_INIT(&nclruhead); 472 nchashtbl = 473 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &nchash); 474 ncvhashtbl = 475 #ifdef NAMECACHE_ENTER_REVERSE 476 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash); 477 #else 478 hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash); 479 #endif 480 pool_init(&namecache_pool, sizeof(struct namecache), 0, 0, 0, 481 "ncachepl", &pool_allocator_nointr); 482 } 483 484 /* 485 * Name cache reinitialization, for when the maximum number of vnodes increases. 486 */ 487 void 488 nchreinit(void) 489 { 490 struct namecache *ncp; 491 struct nchashhead *oldhash1, *hash1; 492 struct ncvhashhead *oldhash2, *hash2; 493 u_long i, oldmask1, oldmask2, mask1, mask2; 494 495 hash1 = hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask1); 496 hash2 = 497 #ifdef NAMECACHE_ENTER_REVERSE 498 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask2); 499 #else 500 hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &mask2); 501 #endif 502 simple_lock(&namecache_slock); 503 oldhash1 = nchashtbl; 504 oldmask1 = nchash; 505 nchashtbl = hash1; 506 nchash = mask1; 507 oldhash2 = ncvhashtbl; 508 oldmask2 = ncvhash; 509 ncvhashtbl = hash2; 510 ncvhash = mask2; 511 for (i = 0; i <= oldmask1; i++) { 512 while ((ncp = LIST_FIRST(&oldhash1[i])) != NULL) { 513 LIST_REMOVE(ncp, nc_hash); 514 ncp->nc_hash.le_prev = NULL; 515 } 516 } 517 for (i = 0; i <= oldmask2; i++) { 518 while ((ncp = LIST_FIRST(&oldhash2[i])) != NULL) { 519 LIST_REMOVE(ncp, nc_vhash); 520 ncp->nc_vhash.le_prev = NULL; 521 } 522 } 523 simple_unlock(&namecache_slock); 524 hashdone(oldhash1, M_CACHE); 525 hashdone(oldhash2, M_CACHE); 526 } 527 528 /* 529 * Cache flush, a particular vnode; called when a vnode is renamed to 530 * hide entries that would now be invalid 531 */ 532 void 533 cache_purge(struct vnode *vp) 534 { 535 struct namecache *ncp, *ncnext; 536 537 simple_lock(&namecache_slock); 538 for (ncp = LIST_FIRST(&vp->v_nclist); ncp != NULL; ncp = ncnext) { 539 ncnext = LIST_NEXT(ncp, nc_vlist); 540 cache_remove(ncp); 541 cache_free(ncp); 542 } 543 for (ncp = LIST_FIRST(&vp->v_dnclist); ncp != NULL; ncp = ncnext) { 544 ncnext = LIST_NEXT(ncp, nc_dvlist); 545 cache_remove(ncp); 546 cache_free(ncp); 547 } 548 simple_unlock(&namecache_slock); 549 } 550 551 /* 552 * Cache flush, a whole filesystem; called when filesys is umounted to 553 * remove entries that would now be invalid. 554 */ 555 void 556 cache_purgevfs(struct mount *mp) 557 { 558 struct namecache *ncp, *nxtcp; 559 560 simple_lock(&namecache_slock); 561 for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) { 562 nxtcp = TAILQ_NEXT(ncp, nc_lru); 563 if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) { 564 continue; 565 } 566 /* Free the resources we had. */ 567 cache_remove(ncp); 568 cache_free(ncp); 569 } 570 simple_unlock(&namecache_slock); 571 } 572 573 #ifdef DDB 574 void 575 namecache_print(struct vnode *vp, void (*pr)(const char *, ...)) 576 { 577 struct vnode *dvp = NULL; 578 struct namecache *ncp; 579 580 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 581 if (ncp->nc_vp == vp) { 582 (*pr)("name %.*s\n", ncp->nc_nlen, ncp->nc_name); 583 dvp = ncp->nc_dvp; 584 } 585 } 586 if (dvp == NULL) { 587 (*pr)("name not found\n"); 588 return; 589 } 590 vp = dvp; 591 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 592 if (ncp->nc_vp == vp) { 593 (*pr)("parent %.*s\n", ncp->nc_nlen, ncp->nc_name); 594 } 595 } 596 } 597 #endif 598