1 /* $NetBSD: vfs_cache.c,v 1.72 2007/11/11 23:22:25 matt 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 1.72 2007/11/11 23:22:25 matt 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/mutex.h> 50 51 #define NAMECACHE_ENTER_REVERSE 52 /* 53 * Name caching works as follows: 54 * 55 * Names found by directory scans are retained in a cache 56 * for future reference. It is managed LRU, so frequently 57 * used names will hang around. Cache is indexed by hash value 58 * obtained from (dvp, name) where dvp refers to the directory 59 * containing name. 60 * 61 * For simplicity (and economy of storage), names longer than 62 * a maximum length of NCHNAMLEN are not cached; they occur 63 * infrequently in any case, and are almost never of interest. 64 * 65 * Upon reaching the last segment of a path, if the reference 66 * is for DELETE, or NOCACHE is set (rewrite), and the 67 * name is located in the cache, it will be dropped. 68 * The entry is dropped also when it was not possible to lock 69 * the cached vnode, either because vget() failed or the generation 70 * number has changed while waiting for the lock. 71 */ 72 73 /* 74 * Structures associated with name cacheing. 75 */ 76 LIST_HEAD(nchashhead, namecache) *nchashtbl; 77 u_long nchash; /* size of hash table - 1 */ 78 long numcache; /* number of cache entries allocated */ 79 #define NCHASH(cnp, dvp) \ 80 (((cnp)->cn_hash ^ ((uintptr_t)(dvp) >> 3)) & nchash) 81 82 LIST_HEAD(ncvhashhead, namecache) *ncvhashtbl; 83 u_long ncvhash; /* size of hash table - 1 */ 84 #define NCVHASH(vp) (((uintptr_t)(vp) >> 3) & ncvhash) 85 86 TAILQ_HEAD(, namecache) nclruhead = /* LRU chain */ 87 TAILQ_HEAD_INITIALIZER(nclruhead); 88 struct nchstats nchstats; /* cache effectiveness statistics */ 89 90 static pool_cache_t namecache_cache; 91 92 MALLOC_DEFINE(M_CACHE, "namecache", "Dynamically allocated cache entries"); 93 94 int doingcache = 1; /* 1 => enable the cache */ 95 96 /* A single lock to protect cache insertion, removal and lookup */ 97 static kmutex_t namecache_lock; 98 99 static void cache_remove(struct namecache *); 100 static void cache_free(struct namecache *); 101 static inline struct namecache *cache_lookup_entry( 102 const struct vnode *, const struct componentname *); 103 104 static void 105 cache_remove(struct namecache *ncp) 106 { 107 108 KASSERT(mutex_owned(&namecache_lock)); 109 110 ncp->nc_dvp = NULL; 111 ncp->nc_vp = NULL; 112 113 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 114 if (ncp->nc_hash.le_prev != NULL) { 115 LIST_REMOVE(ncp, nc_hash); 116 ncp->nc_hash.le_prev = NULL; 117 } 118 if (ncp->nc_vhash.le_prev != NULL) { 119 LIST_REMOVE(ncp, nc_vhash); 120 ncp->nc_vhash.le_prev = NULL; 121 } 122 if (ncp->nc_vlist.le_prev != NULL) { 123 LIST_REMOVE(ncp, nc_vlist); 124 ncp->nc_vlist.le_prev = NULL; 125 } 126 if (ncp->nc_dvlist.le_prev != NULL) { 127 LIST_REMOVE(ncp, nc_dvlist); 128 ncp->nc_dvlist.le_prev = NULL; 129 } 130 } 131 132 static void 133 cache_free(struct namecache *ncp) 134 { 135 136 pool_cache_put(namecache_cache, ncp); 137 numcache--; 138 } 139 140 static inline struct namecache * 141 cache_lookup_entry(const struct vnode *dvp, const struct componentname *cnp) 142 { 143 struct nchashhead *ncpp; 144 struct namecache *ncp; 145 146 KASSERT(mutex_owned(&namecache_lock)); 147 148 ncpp = &nchashtbl[NCHASH(cnp, dvp)]; 149 150 LIST_FOREACH(ncp, ncpp, nc_hash) { 151 if (ncp->nc_dvp == dvp && 152 ncp->nc_nlen == cnp->cn_namelen && 153 !memcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen)) 154 break; 155 } 156 157 return ncp; 158 } 159 160 /* 161 * Look for a the name in the cache. We don't do this 162 * if the segment name is long, simply so the cache can avoid 163 * holding long names (which would either waste space, or 164 * add greatly to the complexity). 165 * 166 * Lookup is called with ni_dvp pointing to the directory to search, 167 * ni_ptr pointing to the name of the entry being sought, ni_namelen 168 * tells the length of the name, and ni_hash contains a hash of 169 * the name. If the lookup succeeds, the vnode is locked, stored in ni_vp 170 * and a status of zero is returned. If the locking fails for whatever 171 * reason, the vnode is unlocked and the error is returned to caller. 172 * If the lookup determines that the name does not exist (negative cacheing), 173 * a status of ENOENT is returned. If the lookup fails, a status of -1 174 * is returned. 175 */ 176 int 177 cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp) 178 { 179 struct namecache *ncp; 180 struct vnode *vp; 181 int error; 182 183 if (!doingcache) { 184 cnp->cn_flags &= ~MAKEENTRY; 185 *vpp = NULL; 186 return (-1); 187 } 188 189 if (cnp->cn_namelen > NCHNAMLEN) { 190 /* Unlocked, but only for stats. */ 191 nchstats.ncs_long++; 192 cnp->cn_flags &= ~MAKEENTRY; 193 goto fail; 194 } 195 mutex_enter(&namecache_lock); 196 ncp = cache_lookup_entry(dvp, cnp); 197 if (ncp == NULL) { 198 nchstats.ncs_miss++; 199 goto fail_wlock; 200 } 201 if ((cnp->cn_flags & MAKEENTRY) == 0) { 202 nchstats.ncs_badhits++; 203 goto remove; 204 } else if (ncp->nc_vp == NULL) { 205 /* 206 * Restore the ISWHITEOUT flag saved earlier. 207 */ 208 cnp->cn_flags |= ncp->nc_flags; 209 if (cnp->cn_nameiop != CREATE || 210 (cnp->cn_flags & ISLASTCN) == 0) { 211 nchstats.ncs_neghits++; 212 /* 213 * Move this slot to end of LRU chain, 214 * 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 mutex_exit(&namecache_lock); 221 return (ENOENT); 222 } else { 223 nchstats.ncs_badhits++; 224 goto remove; 225 } 226 } 227 228 vp = ncp->nc_vp; 229 230 /* 231 * Move this slot to end of LRU chain, if not already there. 232 */ 233 if (TAILQ_NEXT(ncp, nc_lru) != 0) { 234 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 235 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 236 } 237 238 error = vget(vp, LK_NOWAIT); 239 240 /* Release the name cache mutex while we get reference to the vnode */ 241 mutex_exit(&namecache_lock); 242 243 #ifdef DEBUG 244 /* 245 * since we released namecache_lock, 246 * we can't use this pointer any more. 247 */ 248 ncp = NULL; 249 #endif /* DEBUG */ 250 251 if (error) { 252 KASSERT(error == EBUSY); 253 /* 254 * this vnode is being cleaned out. 255 */ 256 nchstats.ncs_falsehits++; /* XXX badhits? */ 257 goto fail; 258 } 259 260 if (vp == dvp) { /* lookup on "." */ 261 error = 0; 262 } else if (cnp->cn_flags & ISDOTDOT) { 263 VOP_UNLOCK(dvp, 0); 264 error = vn_lock(vp, LK_EXCLUSIVE); 265 vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY); 266 } else { 267 error = vn_lock(vp, LK_EXCLUSIVE); 268 } 269 270 /* 271 * Check that the lock succeeded. 272 */ 273 if (error) { 274 /* Unlocked, but only for stats. */ 275 nchstats.ncs_badhits++; 276 *vpp = NULL; 277 return (-1); 278 } 279 280 /* Unlocked, but only for stats. */ 281 nchstats.ncs_goodhits++; 282 *vpp = vp; 283 return (0); 284 285 remove: 286 /* 287 * Last component and we are renaming or deleting, 288 * the cache entry is invalid, or otherwise don't 289 * want cache entry to exist. 290 */ 291 cache_remove(ncp); 292 cache_free(ncp); 293 294 fail_wlock: 295 mutex_exit(&namecache_lock); 296 fail: 297 *vpp = NULL; 298 return (-1); 299 } 300 301 int 302 cache_lookup_raw(struct vnode *dvp, struct vnode **vpp, 303 struct componentname *cnp) 304 { 305 struct namecache *ncp; 306 struct vnode *vp; 307 int error; 308 309 if (!doingcache) { 310 cnp->cn_flags &= ~MAKEENTRY; 311 *vpp = NULL; 312 return (-1); 313 } 314 315 if (cnp->cn_namelen > NCHNAMLEN) { 316 /* Unlocked, but only for stats. */ 317 nchstats.ncs_long++; 318 cnp->cn_flags &= ~MAKEENTRY; 319 goto fail; 320 } 321 mutex_enter(&namecache_lock); 322 ncp = cache_lookup_entry(dvp, cnp); 323 if (ncp == NULL) { 324 nchstats.ncs_miss++; 325 goto fail_wlock; 326 } 327 /* 328 * Move this slot to end of LRU chain, 329 * if not already there. 330 */ 331 if (TAILQ_NEXT(ncp, nc_lru) != 0) { 332 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 333 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 334 } 335 336 vp = ncp->nc_vp; 337 if (vp == NULL) { 338 /* 339 * Restore the ISWHITEOUT flag saved earlier. 340 */ 341 cnp->cn_flags |= ncp->nc_flags; 342 nchstats.ncs_neghits++; 343 mutex_exit(&namecache_lock); 344 return (ENOENT); 345 } 346 347 error = vget(vp, LK_NOWAIT); 348 349 /* Release the name cache mutex while we get reference to the vnode */ 350 mutex_exit(&namecache_lock); 351 352 if (error) { 353 KASSERT(error == EBUSY); 354 /* 355 * this vnode is being cleaned out. 356 */ 357 nchstats.ncs_falsehits++; /* XXX badhits? */ 358 goto fail; 359 } 360 361 *vpp = vp; 362 363 return 0; 364 365 fail_wlock: 366 mutex_exit(&namecache_lock); 367 fail: 368 *vpp = NULL; 369 return -1; 370 } 371 372 /* 373 * Scan cache looking for name of directory entry pointing at vp. 374 * 375 * Fill in dvpp. 376 * 377 * If bufp is non-NULL, also place the name in the buffer which starts 378 * at bufp, immediately before *bpp, and move bpp backwards to point 379 * at the start of it. (Yes, this is a little baroque, but it's done 380 * this way to cater to the whims of getcwd). 381 * 382 * Returns 0 on success, -1 on cache miss, positive errno on failure. 383 */ 384 int 385 cache_revlookup(struct vnode *vp, struct vnode **dvpp, char **bpp, char *bufp) 386 { 387 struct namecache *ncp; 388 struct vnode *dvp; 389 struct ncvhashhead *nvcpp; 390 char *bp; 391 392 if (!doingcache) 393 goto out; 394 395 nvcpp = &ncvhashtbl[NCVHASH(vp)]; 396 397 mutex_enter(&namecache_lock); 398 LIST_FOREACH(ncp, nvcpp, nc_vhash) { 399 if (ncp->nc_vp == vp && 400 (dvp = ncp->nc_dvp) != NULL && 401 dvp != vp) { /* avoid pesky . entries.. */ 402 403 #ifdef DIAGNOSTIC 404 if (ncp->nc_nlen == 1 && 405 ncp->nc_name[0] == '.') 406 panic("cache_revlookup: found entry for ."); 407 408 if (ncp->nc_nlen == 2 && 409 ncp->nc_name[0] == '.' && 410 ncp->nc_name[1] == '.') 411 panic("cache_revlookup: found entry for .."); 412 #endif 413 nchstats.ncs_revhits++; 414 415 if (bufp) { 416 bp = *bpp; 417 bp -= ncp->nc_nlen; 418 if (bp <= bufp) { 419 *dvpp = NULL; 420 mutex_exit(&namecache_lock); 421 return (ERANGE); 422 } 423 memcpy(bp, ncp->nc_name, ncp->nc_nlen); 424 *bpp = bp; 425 } 426 427 /* XXX MP: how do we know dvp won't evaporate? */ 428 *dvpp = dvp; 429 mutex_exit(&namecache_lock); 430 return (0); 431 } 432 } 433 nchstats.ncs_revmiss++; 434 mutex_exit(&namecache_lock); 435 out: 436 *dvpp = NULL; 437 return (-1); 438 } 439 440 /* 441 * Add an entry to the cache 442 */ 443 void 444 cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp) 445 { 446 struct namecache *ncp; 447 struct namecache *oncp; 448 struct nchashhead *ncpp; 449 struct ncvhashhead *nvcpp; 450 451 #ifdef DIAGNOSTIC 452 if (cnp->cn_namelen > NCHNAMLEN) 453 panic("cache_enter: name too long"); 454 #endif 455 if (!doingcache) 456 return; 457 /* 458 * Free the cache slot at head of lru chain. 459 */ 460 mutex_enter(&namecache_lock); 461 462 if (numcache < numvnodes) { 463 numcache++; 464 mutex_exit(&namecache_lock); 465 ncp = pool_cache_get(namecache_cache, PR_WAITOK); 466 memset(ncp, 0, sizeof(*ncp)); 467 mutex_enter(&namecache_lock); 468 } else if ((ncp = TAILQ_FIRST(&nclruhead)) != NULL) { 469 cache_remove(ncp); 470 } else { 471 mutex_exit(&namecache_lock); 472 return; 473 } 474 475 /* 476 * Concurrent lookups in the same directory may race for a 477 * cache entry. if there's a duplicated entry, free it. 478 */ 479 oncp = cache_lookup_entry(dvp, cnp); 480 if (oncp) { 481 cache_remove(oncp); 482 cache_free(oncp); 483 } 484 KASSERT(cache_lookup_entry(dvp, cnp) == NULL); 485 486 /* Grab the vnode we just found. */ 487 ncp->nc_vp = vp; 488 if (vp == NULL) { 489 /* 490 * For negative hits, save the ISWHITEOUT flag so we can 491 * restore it later when the cache entry is used again. 492 */ 493 ncp->nc_flags = cnp->cn_flags & ISWHITEOUT; 494 } 495 /* Fill in cache info. */ 496 ncp->nc_dvp = dvp; 497 LIST_INSERT_HEAD(&dvp->v_dnclist, ncp, nc_dvlist); 498 if (vp) 499 LIST_INSERT_HEAD(&vp->v_nclist, ncp, nc_vlist); 500 ncp->nc_nlen = cnp->cn_namelen; 501 memcpy(ncp->nc_name, cnp->cn_nameptr, (unsigned)ncp->nc_nlen); 502 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 503 ncpp = &nchashtbl[NCHASH(cnp, dvp)]; 504 LIST_INSERT_HEAD(ncpp, ncp, nc_hash); 505 506 ncp->nc_vhash.le_prev = NULL; 507 ncp->nc_vhash.le_next = NULL; 508 509 /* 510 * Create reverse-cache entries (used in getcwd) for directories. 511 * (and in linux procfs exe node) 512 */ 513 if (vp != NULL && 514 vp != dvp && 515 #ifndef NAMECACHE_ENTER_REVERSE 516 vp->v_type == VDIR && 517 #endif 518 (ncp->nc_nlen > 2 || 519 (ncp->nc_nlen > 1 && ncp->nc_name[1] != '.') || 520 (/* ncp->nc_nlen > 0 && */ ncp->nc_name[0] != '.'))) { 521 nvcpp = &ncvhashtbl[NCVHASH(vp)]; 522 LIST_INSERT_HEAD(nvcpp, ncp, nc_vhash); 523 } 524 mutex_exit(&namecache_lock); 525 } 526 527 /* 528 * Name cache initialization, from vfs_init() when we are booting 529 */ 530 void 531 nchinit(void) 532 { 533 534 namecache_cache = pool_cache_init(sizeof(struct namecache), 0, 0, 0, 535 "ncachepl", NULL, IPL_NONE, NULL, NULL, NULL); 536 KASSERT(namecache_cache != NULL); 537 538 mutex_init(&namecache_lock, MUTEX_DEFAULT, IPL_NONE); 539 nchashtbl = 540 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &nchash); 541 ncvhashtbl = 542 #ifdef NAMECACHE_ENTER_REVERSE 543 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash); 544 #else 545 hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash); 546 #endif 547 } 548 549 /* 550 * Name cache reinitialization, for when the maximum number of vnodes increases. 551 */ 552 void 553 nchreinit(void) 554 { 555 struct namecache *ncp; 556 struct nchashhead *oldhash1, *hash1; 557 struct ncvhashhead *oldhash2, *hash2; 558 u_long i, oldmask1, oldmask2, mask1, mask2; 559 560 hash1 = hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask1); 561 hash2 = 562 #ifdef NAMECACHE_ENTER_REVERSE 563 hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask2); 564 #else 565 hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &mask2); 566 #endif 567 mutex_enter(&namecache_lock); 568 oldhash1 = nchashtbl; 569 oldmask1 = nchash; 570 nchashtbl = hash1; 571 nchash = mask1; 572 oldhash2 = ncvhashtbl; 573 oldmask2 = ncvhash; 574 ncvhashtbl = hash2; 575 ncvhash = mask2; 576 for (i = 0; i <= oldmask1; i++) { 577 while ((ncp = LIST_FIRST(&oldhash1[i])) != NULL) { 578 LIST_REMOVE(ncp, nc_hash); 579 ncp->nc_hash.le_prev = NULL; 580 } 581 } 582 for (i = 0; i <= oldmask2; i++) { 583 while ((ncp = LIST_FIRST(&oldhash2[i])) != NULL) { 584 LIST_REMOVE(ncp, nc_vhash); 585 ncp->nc_vhash.le_prev = NULL; 586 } 587 } 588 mutex_exit(&namecache_lock); 589 hashdone(oldhash1, M_CACHE); 590 hashdone(oldhash2, M_CACHE); 591 } 592 593 /* 594 * Cache flush, a particular vnode; called when a vnode is renamed to 595 * hide entries that would now be invalid 596 */ 597 void 598 cache_purge1(struct vnode *vp, const struct componentname *cnp, int flags) 599 { 600 struct namecache *ncp, *ncnext; 601 602 mutex_enter(&namecache_lock); 603 if (flags & PURGE_PARENTS) { 604 for (ncp = LIST_FIRST(&vp->v_nclist); ncp != NULL; 605 ncp = ncnext) { 606 ncnext = LIST_NEXT(ncp, nc_vlist); 607 cache_remove(ncp); 608 cache_free(ncp); 609 } 610 } 611 if (flags & PURGE_CHILDREN) { 612 for (ncp = LIST_FIRST(&vp->v_dnclist); ncp != NULL; 613 ncp = ncnext) { 614 ncnext = LIST_NEXT(ncp, nc_dvlist); 615 cache_remove(ncp); 616 cache_free(ncp); 617 } 618 } 619 if (cnp != NULL) { 620 ncp = cache_lookup_entry(vp, cnp); 621 if (ncp) { 622 cache_remove(ncp); 623 cache_free(ncp); 624 } 625 } 626 mutex_exit(&namecache_lock); 627 } 628 629 /* 630 * Cache flush, a whole filesystem; called when filesys is umounted to 631 * remove entries that would now be invalid. 632 */ 633 void 634 cache_purgevfs(struct mount *mp) 635 { 636 struct namecache *ncp, *nxtcp; 637 638 mutex_enter(&namecache_lock); 639 for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) { 640 nxtcp = TAILQ_NEXT(ncp, nc_lru); 641 if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) { 642 continue; 643 } 644 /* Free the resources we had. */ 645 cache_remove(ncp); 646 cache_free(ncp); 647 } 648 mutex_exit(&namecache_lock); 649 } 650 651 #ifdef DDB 652 void 653 namecache_print(struct vnode *vp, void (*pr)(const char *, ...)) 654 { 655 struct vnode *dvp = NULL; 656 struct namecache *ncp; 657 658 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 659 if (ncp->nc_vp == vp) { 660 (*pr)("name %.*s\n", ncp->nc_nlen, ncp->nc_name); 661 dvp = ncp->nc_dvp; 662 } 663 } 664 if (dvp == NULL) { 665 (*pr)("name not found\n"); 666 return; 667 } 668 vp = dvp; 669 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 670 if (ncp->nc_vp == vp) { 671 (*pr)("parent %.*s\n", ncp->nc_nlen, ncp->nc_name); 672 } 673 } 674 } 675 #endif 676