1 /* $NetBSD: vfs_cache.c,v 1.84 2009/02/18 13:36:11 yamt Exp $ */ 2 3 /*- 4 * Copyright (c) 2008 The NetBSD Foundation, Inc. 5 * 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 * 16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 26 * POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 /* 30 * Copyright (c) 1989, 1993 31 * The Regents of the University of California. All rights reserved. 32 * 33 * Redistribution and use in source and binary forms, with or without 34 * modification, are permitted provided that the following conditions 35 * are met: 36 * 1. Redistributions of source code must retain the above copyright 37 * notice, this list of conditions and the following disclaimer. 38 * 2. Redistributions in binary form must reproduce the above copyright 39 * notice, this list of conditions and the following disclaimer in the 40 * documentation and/or other materials provided with the distribution. 41 * 3. Neither the name of the University nor the names of its contributors 42 * may be used to endorse or promote products derived from this software 43 * without specific prior written permission. 44 * 45 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 46 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 47 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 48 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 49 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 50 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 51 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 52 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 53 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 54 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 55 * SUCH DAMAGE. 56 * 57 * @(#)vfs_cache.c 8.3 (Berkeley) 8/22/94 58 */ 59 60 #include <sys/cdefs.h> 61 __KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.84 2009/02/18 13:36:11 yamt Exp $"); 62 63 #include "opt_ddb.h" 64 #include "opt_revcache.h" 65 66 #include <sys/param.h> 67 #include <sys/systm.h> 68 #include <sys/time.h> 69 #include <sys/mount.h> 70 #include <sys/vnode.h> 71 #include <sys/namei.h> 72 #include <sys/errno.h> 73 #include <sys/pool.h> 74 #include <sys/mutex.h> 75 #include <sys/atomic.h> 76 #include <sys/kthread.h> 77 #include <sys/kernel.h> 78 #include <sys/cpu.h> 79 #include <sys/evcnt.h> 80 81 #define NAMECACHE_ENTER_REVERSE 82 /* 83 * Name caching works as follows: 84 * 85 * Names found by directory scans are retained in a cache 86 * for future reference. It is managed LRU, so frequently 87 * used names will hang around. Cache is indexed by hash value 88 * obtained from (dvp, name) where dvp refers to the directory 89 * containing name. 90 * 91 * For simplicity (and economy of storage), names longer than 92 * a maximum length of NCHNAMLEN are not cached; they occur 93 * infrequently in any case, and are almost never of interest. 94 * 95 * Upon reaching the last segment of a path, if the reference 96 * is for DELETE, or NOCACHE is set (rewrite), and the 97 * name is located in the cache, it will be dropped. 98 * The entry is dropped also when it was not possible to lock 99 * the cached vnode, either because vget() failed or the generation 100 * number has changed while waiting for the lock. 101 */ 102 103 /* 104 * Per-cpu namecache data. 105 */ 106 struct nchcpu { 107 kmutex_t cpu_lock; 108 struct nchstats cpu_stats; 109 }; 110 111 /* 112 * Structures associated with name cacheing. 113 */ 114 LIST_HEAD(nchashhead, namecache) *nchashtbl; 115 u_long nchash; /* size of hash table - 1 */ 116 #define NCHASH(cnp, dvp) \ 117 (((cnp)->cn_hash ^ ((uintptr_t)(dvp) >> 3)) & nchash) 118 119 LIST_HEAD(ncvhashhead, namecache) *ncvhashtbl; 120 u_long ncvhash; /* size of hash table - 1 */ 121 #define NCVHASH(vp) (((uintptr_t)(vp) >> 3) & ncvhash) 122 123 long numcache; /* number of cache entries allocated */ 124 static u_int cache_gcpend; /* number of entries pending GC */ 125 static void *cache_gcqueue; /* garbage collection queue */ 126 127 TAILQ_HEAD(, namecache) nclruhead = /* LRU chain */ 128 TAILQ_HEAD_INITIALIZER(nclruhead); 129 #define COUNT(c,x) (c.x++) 130 struct nchstats nchstats; /* cache effectiveness statistics */ 131 132 static pool_cache_t namecache_cache; 133 134 int cache_lowat = 95; 135 int cache_hiwat = 98; 136 int cache_hottime = 5; /* number of seconds */ 137 int doingcache = 1; /* 1 => enable the cache */ 138 139 static struct evcnt cache_ev_scan; 140 static struct evcnt cache_ev_gc; 141 static struct evcnt cache_ev_over; 142 static struct evcnt cache_ev_under; 143 static struct evcnt cache_ev_forced; 144 145 /* A single lock to serialize modifications. */ 146 static kmutex_t *namecache_lock; 147 148 static void cache_invalidate(struct namecache *); 149 static inline struct namecache *cache_lookup_entry( 150 const struct vnode *, const struct componentname *); 151 static void cache_thread(void *); 152 static void cache_invalidate(struct namecache *); 153 static void cache_disassociate(struct namecache *); 154 static void cache_reclaim(void); 155 static int cache_ctor(void *, void *, int); 156 static void cache_dtor(void *, void *); 157 158 /* 159 * Invalidate a cache entry and enqueue it for garbage collection. 160 */ 161 static void 162 cache_invalidate(struct namecache *ncp) 163 { 164 void *head; 165 166 KASSERT(mutex_owned(&ncp->nc_lock)); 167 168 if (ncp->nc_dvp != NULL) { 169 ncp->nc_vp = NULL; 170 ncp->nc_dvp = NULL; 171 do { 172 head = cache_gcqueue; 173 ncp->nc_gcqueue = head; 174 } while (atomic_cas_ptr(&cache_gcqueue, head, ncp) != head); 175 atomic_inc_uint(&cache_gcpend); 176 } 177 } 178 179 /* 180 * Disassociate a namecache entry from any vnodes it is attached to, 181 * and remove from the global LRU list. 182 */ 183 static void 184 cache_disassociate(struct namecache *ncp) 185 { 186 187 KASSERT(mutex_owned(namecache_lock)); 188 KASSERT(ncp->nc_dvp == NULL); 189 190 if (ncp->nc_lru.tqe_prev != NULL) { 191 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 192 ncp->nc_lru.tqe_prev = NULL; 193 } 194 if (ncp->nc_vhash.le_prev != NULL) { 195 LIST_REMOVE(ncp, nc_vhash); 196 ncp->nc_vhash.le_prev = NULL; 197 } 198 if (ncp->nc_vlist.le_prev != NULL) { 199 LIST_REMOVE(ncp, nc_vlist); 200 ncp->nc_vlist.le_prev = NULL; 201 } 202 if (ncp->nc_dvlist.le_prev != NULL) { 203 LIST_REMOVE(ncp, nc_dvlist); 204 ncp->nc_dvlist.le_prev = NULL; 205 } 206 } 207 208 /* 209 * Lock all CPUs to prevent any cache lookup activity. Conceptually, 210 * this locks out all "readers". 211 */ 212 static void 213 cache_lock_cpus(void) 214 { 215 CPU_INFO_ITERATOR cii; 216 struct cpu_info *ci; 217 struct nchcpu *cpup; 218 long *s, *d, *m; 219 220 for (CPU_INFO_FOREACH(cii, ci)) { 221 cpup = ci->ci_data.cpu_nch; 222 mutex_enter(&cpup->cpu_lock); 223 224 /* Collate statistics. */ 225 d = (long *)&nchstats; 226 s = (long *)&cpup->cpu_stats; 227 m = s + sizeof(nchstats) / sizeof(long); 228 for (; s < m; s++, d++) { 229 *d += *s; 230 *s = 0; 231 } 232 } 233 } 234 235 /* 236 * Release all CPU locks. 237 */ 238 static void 239 cache_unlock_cpus(void) 240 { 241 CPU_INFO_ITERATOR cii; 242 struct cpu_info *ci; 243 struct nchcpu *cpup; 244 245 for (CPU_INFO_FOREACH(cii, ci)) { 246 cpup = ci->ci_data.cpu_nch; 247 mutex_exit(&cpup->cpu_lock); 248 } 249 } 250 251 /* 252 * Find a single cache entry and return it locked. 'namecache_lock' or 253 * at least one of the per-CPU locks must be held. 254 */ 255 static struct namecache * 256 cache_lookup_entry(const struct vnode *dvp, const struct componentname *cnp) 257 { 258 struct nchashhead *ncpp; 259 struct namecache *ncp; 260 261 KASSERT(dvp != NULL); 262 ncpp = &nchashtbl[NCHASH(cnp, dvp)]; 263 264 LIST_FOREACH(ncp, ncpp, nc_hash) { 265 if (ncp->nc_dvp != dvp || 266 ncp->nc_nlen != cnp->cn_namelen || 267 memcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen)) 268 continue; 269 mutex_enter(&ncp->nc_lock); 270 if (__predict_true(ncp->nc_dvp == dvp)) { 271 ncp->nc_hittime = hardclock_ticks; 272 return ncp; 273 } 274 /* Raced: entry has been nullified. */ 275 mutex_exit(&ncp->nc_lock); 276 } 277 278 return NULL; 279 } 280 281 /* 282 * Look for a the name in the cache. We don't do this 283 * if the segment name is long, simply so the cache can avoid 284 * holding long names (which would either waste space, or 285 * add greatly to the complexity). 286 * 287 * Lookup is called with ni_dvp pointing to the directory to search, 288 * ni_ptr pointing to the name of the entry being sought, ni_namelen 289 * tells the length of the name, and ni_hash contains a hash of 290 * the name. If the lookup succeeds, the vnode is locked, stored in ni_vp 291 * and a status of zero is returned. If the locking fails for whatever 292 * reason, the vnode is unlocked and the error is returned to caller. 293 * If the lookup determines that the name does not exist (negative cacheing), 294 * a status of ENOENT is returned. If the lookup fails, a status of -1 295 * is returned. 296 */ 297 int 298 cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp) 299 { 300 struct namecache *ncp; 301 struct vnode *vp; 302 struct nchcpu *cpup; 303 int error; 304 305 if (__predict_false(!doingcache)) { 306 cnp->cn_flags &= ~MAKEENTRY; 307 *vpp = NULL; 308 return -1; 309 } 310 311 cpup = curcpu()->ci_data.cpu_nch; 312 mutex_enter(&cpup->cpu_lock); 313 if (__predict_false(cnp->cn_namelen > NCHNAMLEN)) { 314 COUNT(cpup->cpu_stats, ncs_long); 315 cnp->cn_flags &= ~MAKEENTRY; 316 mutex_exit(&cpup->cpu_lock); 317 *vpp = NULL; 318 return -1; 319 } 320 ncp = cache_lookup_entry(dvp, cnp); 321 if (__predict_false(ncp == NULL)) { 322 COUNT(cpup->cpu_stats, ncs_miss); 323 mutex_exit(&cpup->cpu_lock); 324 *vpp = NULL; 325 return -1; 326 } 327 if ((cnp->cn_flags & MAKEENTRY) == 0) { 328 COUNT(cpup->cpu_stats, ncs_badhits); 329 /* 330 * Last component and we are renaming or deleting, 331 * the cache entry is invalid, or otherwise don't 332 * want cache entry to exist. 333 */ 334 cache_invalidate(ncp); 335 mutex_exit(&ncp->nc_lock); 336 mutex_exit(&cpup->cpu_lock); 337 *vpp = NULL; 338 return -1; 339 } else if (ncp->nc_vp == NULL) { 340 /* 341 * Restore the ISWHITEOUT flag saved earlier. 342 */ 343 KASSERT((ncp->nc_flags & ~ISWHITEOUT) == 0); 344 cnp->cn_flags |= ncp->nc_flags; 345 if (__predict_true(cnp->cn_nameiop != CREATE || 346 (cnp->cn_flags & ISLASTCN) == 0)) { 347 COUNT(cpup->cpu_stats, ncs_neghits); 348 mutex_exit(&ncp->nc_lock); 349 mutex_exit(&cpup->cpu_lock); 350 return ENOENT; 351 } else { 352 COUNT(cpup->cpu_stats, ncs_badhits); 353 /* 354 * Last component and we are renaming or 355 * deleting, the cache entry is invalid, 356 * or otherwise don't want cache entry to 357 * exist. 358 */ 359 cache_invalidate(ncp); 360 mutex_exit(&ncp->nc_lock); 361 mutex_exit(&cpup->cpu_lock); 362 *vpp = NULL; 363 return -1; 364 } 365 } 366 367 vp = ncp->nc_vp; 368 if (vtryget(vp)) { 369 mutex_exit(&ncp->nc_lock); 370 mutex_exit(&cpup->cpu_lock); 371 } else { 372 mutex_enter(&vp->v_interlock); 373 mutex_exit(&ncp->nc_lock); 374 mutex_exit(&cpup->cpu_lock); 375 error = vget(vp, LK_NOWAIT | LK_INTERLOCK); 376 if (error) { 377 KASSERT(error == EBUSY); 378 /* 379 * This vnode is being cleaned out. 380 * XXX badhits? 381 */ 382 COUNT(cpup->cpu_stats, ncs_falsehits); 383 *vpp = NULL; 384 return -1; 385 } 386 } 387 388 #ifdef DEBUG 389 /* 390 * since we released nb->nb_lock, 391 * we can't use this pointer any more. 392 */ 393 ncp = NULL; 394 #endif /* DEBUG */ 395 396 if (vp == dvp) { /* lookup on "." */ 397 error = 0; 398 } else if (cnp->cn_flags & ISDOTDOT) { 399 VOP_UNLOCK(dvp, 0); 400 error = vn_lock(vp, LK_EXCLUSIVE); 401 vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY); 402 } else { 403 error = vn_lock(vp, LK_EXCLUSIVE); 404 } 405 406 /* 407 * Check that the lock succeeded. 408 */ 409 if (error) { 410 /* Unlocked, but only for stats. */ 411 COUNT(cpup->cpu_stats, ncs_badhits); 412 vrele(vp); 413 *vpp = NULL; 414 return -1; 415 } 416 417 /* Unlocked, but only for stats. */ 418 COUNT(cpup->cpu_stats, ncs_goodhits); 419 *vpp = vp; 420 return 0; 421 } 422 423 int 424 cache_lookup_raw(struct vnode *dvp, struct vnode **vpp, 425 struct componentname *cnp) 426 { 427 struct namecache *ncp; 428 struct vnode *vp; 429 struct nchcpu *cpup; 430 int error; 431 432 if (__predict_false(!doingcache)) { 433 cnp->cn_flags &= ~MAKEENTRY; 434 *vpp = NULL; 435 return (-1); 436 } 437 438 cpup = curcpu()->ci_data.cpu_nch; 439 mutex_enter(&cpup->cpu_lock); 440 if (__predict_false(cnp->cn_namelen > NCHNAMLEN)) { 441 COUNT(cpup->cpu_stats, ncs_long); 442 cnp->cn_flags &= ~MAKEENTRY; 443 mutex_exit(&cpup->cpu_lock); 444 *vpp = NULL; 445 return -1; 446 } 447 ncp = cache_lookup_entry(dvp, cnp); 448 if (__predict_false(ncp == NULL)) { 449 COUNT(cpup->cpu_stats, ncs_miss); 450 mutex_exit(&cpup->cpu_lock); 451 *vpp = NULL; 452 return -1; 453 } 454 vp = ncp->nc_vp; 455 if (vp == NULL) { 456 /* 457 * Restore the ISWHITEOUT flag saved earlier. 458 */ 459 KASSERT((ncp->nc_flags & ~ISWHITEOUT) == 0); 460 cnp->cn_flags |= ncp->nc_flags; 461 COUNT(cpup->cpu_stats, ncs_neghits); 462 mutex_exit(&ncp->nc_lock); 463 mutex_exit(&cpup->cpu_lock); 464 return ENOENT; 465 } 466 if (vtryget(vp)) { 467 mutex_exit(&ncp->nc_lock); 468 mutex_exit(&cpup->cpu_lock); 469 } else { 470 mutex_enter(&vp->v_interlock); 471 mutex_exit(&ncp->nc_lock); 472 mutex_exit(&cpup->cpu_lock); 473 error = vget(vp, LK_NOWAIT | LK_INTERLOCK); 474 if (error) { 475 KASSERT(error == EBUSY); 476 /* 477 * This vnode is being cleaned out. 478 * XXX badhits? 479 */ 480 COUNT(cpup->cpu_stats, ncs_falsehits); 481 *vpp = NULL; 482 return -1; 483 } 484 } 485 486 /* Unlocked, but only for stats. */ 487 COUNT(cpup->cpu_stats, ncs_goodhits); /* XXX can be "badhits" */ 488 *vpp = vp; 489 return 0; 490 } 491 492 /* 493 * Scan cache looking for name of directory entry pointing at vp. 494 * 495 * Fill in dvpp. 496 * 497 * If bufp is non-NULL, also place the name in the buffer which starts 498 * at bufp, immediately before *bpp, and move bpp backwards to point 499 * at the start of it. (Yes, this is a little baroque, but it's done 500 * this way to cater to the whims of getcwd). 501 * 502 * Returns 0 on success, -1 on cache miss, positive errno on failure. 503 */ 504 int 505 cache_revlookup(struct vnode *vp, struct vnode **dvpp, char **bpp, char *bufp) 506 { 507 struct namecache *ncp; 508 struct vnode *dvp; 509 struct ncvhashhead *nvcpp; 510 char *bp; 511 512 if (!doingcache) 513 goto out; 514 515 nvcpp = &ncvhashtbl[NCVHASH(vp)]; 516 517 mutex_enter(namecache_lock); 518 LIST_FOREACH(ncp, nvcpp, nc_vhash) { 519 mutex_enter(&ncp->nc_lock); 520 if (ncp->nc_vp == vp && 521 (dvp = ncp->nc_dvp) != NULL && 522 dvp != vp) { /* avoid pesky . entries.. */ 523 524 #ifdef DIAGNOSTIC 525 if (ncp->nc_nlen == 1 && 526 ncp->nc_name[0] == '.') 527 panic("cache_revlookup: found entry for ."); 528 529 if (ncp->nc_nlen == 2 && 530 ncp->nc_name[0] == '.' && 531 ncp->nc_name[1] == '.') 532 panic("cache_revlookup: found entry for .."); 533 #endif 534 COUNT(nchstats, ncs_revhits); 535 536 if (bufp) { 537 bp = *bpp; 538 bp -= ncp->nc_nlen; 539 if (bp <= bufp) { 540 *dvpp = NULL; 541 mutex_exit(&ncp->nc_lock); 542 mutex_exit(namecache_lock); 543 return (ERANGE); 544 } 545 memcpy(bp, ncp->nc_name, ncp->nc_nlen); 546 *bpp = bp; 547 } 548 549 /* XXX MP: how do we know dvp won't evaporate? */ 550 *dvpp = dvp; 551 mutex_exit(&ncp->nc_lock); 552 mutex_exit(namecache_lock); 553 return (0); 554 } 555 mutex_exit(&ncp->nc_lock); 556 } 557 COUNT(nchstats, ncs_revmiss); 558 mutex_exit(namecache_lock); 559 out: 560 *dvpp = NULL; 561 return (-1); 562 } 563 564 /* 565 * Add an entry to the cache 566 */ 567 void 568 cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp) 569 { 570 struct namecache *ncp; 571 struct namecache *oncp; 572 struct nchashhead *ncpp; 573 struct ncvhashhead *nvcpp; 574 575 #ifdef DIAGNOSTIC 576 if (cnp->cn_namelen > NCHNAMLEN) 577 panic("cache_enter: name too long"); 578 #endif 579 if (!doingcache) 580 return; 581 582 if (numcache > desiredvnodes) { 583 mutex_enter(namecache_lock); 584 cache_ev_forced.ev_count++; 585 cache_reclaim(); 586 mutex_exit(namecache_lock); 587 } 588 589 ncp = pool_cache_get(namecache_cache, PR_WAITOK); 590 mutex_enter(namecache_lock); 591 numcache++; 592 593 /* 594 * Concurrent lookups in the same directory may race for a 595 * cache entry. if there's a duplicated entry, free it. 596 */ 597 oncp = cache_lookup_entry(dvp, cnp); 598 if (oncp) { 599 cache_invalidate(oncp); 600 mutex_exit(&oncp->nc_lock); 601 } 602 603 /* Grab the vnode we just found. */ 604 mutex_enter(&ncp->nc_lock); 605 ncp->nc_vp = vp; 606 ncp->nc_flags = 0; 607 ncp->nc_hittime = 0; 608 ncp->nc_gcqueue = NULL; 609 if (vp == NULL) { 610 /* 611 * For negative hits, save the ISWHITEOUT flag so we can 612 * restore it later when the cache entry is used again. 613 */ 614 ncp->nc_flags = cnp->cn_flags & ISWHITEOUT; 615 } 616 /* Fill in cache info. */ 617 ncp->nc_dvp = dvp; 618 LIST_INSERT_HEAD(&dvp->v_dnclist, ncp, nc_dvlist); 619 if (vp) 620 LIST_INSERT_HEAD(&vp->v_nclist, ncp, nc_vlist); 621 else { 622 ncp->nc_vlist.le_prev = NULL; 623 ncp->nc_vlist.le_next = NULL; 624 } 625 ncp->nc_nlen = cnp->cn_namelen; 626 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 627 memcpy(ncp->nc_name, cnp->cn_nameptr, (unsigned)ncp->nc_nlen); 628 ncpp = &nchashtbl[NCHASH(cnp, dvp)]; 629 630 /* 631 * Flush updates before making visible in table. No need for a 632 * memory barrier on the other side: to see modifications the 633 * list must be followed, meaning a dependent pointer load. 634 * The below is LIST_INSERT_HEAD() inlined, with the memory 635 * barrier included in the correct place. 636 */ 637 if ((ncp->nc_hash.le_next = ncpp->lh_first) != NULL) 638 ncpp->lh_first->nc_hash.le_prev = &ncp->nc_hash.le_next; 639 ncp->nc_hash.le_prev = &ncpp->lh_first; 640 membar_producer(); 641 ncpp->lh_first = ncp; 642 643 ncp->nc_vhash.le_prev = NULL; 644 ncp->nc_vhash.le_next = NULL; 645 646 /* 647 * Create reverse-cache entries (used in getcwd) for directories. 648 * (and in linux procfs exe node) 649 */ 650 if (vp != NULL && 651 vp != dvp && 652 #ifndef NAMECACHE_ENTER_REVERSE 653 vp->v_type == VDIR && 654 #endif 655 (ncp->nc_nlen > 2 || 656 (ncp->nc_nlen > 1 && ncp->nc_name[1] != '.') || 657 (/* ncp->nc_nlen > 0 && */ ncp->nc_name[0] != '.'))) { 658 nvcpp = &ncvhashtbl[NCVHASH(vp)]; 659 LIST_INSERT_HEAD(nvcpp, ncp, nc_vhash); 660 } 661 mutex_exit(&ncp->nc_lock); 662 mutex_exit(namecache_lock); 663 } 664 665 /* 666 * Name cache initialization, from vfs_init() when we are booting 667 */ 668 void 669 nchinit(void) 670 { 671 int error; 672 673 namecache_cache = pool_cache_init(sizeof(struct namecache), 674 coherency_unit, 0, 0, "ncache", NULL, IPL_NONE, cache_ctor, 675 cache_dtor, NULL); 676 KASSERT(namecache_cache != NULL); 677 678 namecache_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE); 679 680 nchashtbl = hashinit(desiredvnodes, HASH_LIST, true, &nchash); 681 ncvhashtbl = 682 #ifdef NAMECACHE_ENTER_REVERSE 683 hashinit(desiredvnodes, HASH_LIST, true, &ncvhash); 684 #else 685 hashinit(desiredvnodes/8, HASH_LIST, true, &ncvhash); 686 #endif 687 688 error = kthread_create(PRI_VM, KTHREAD_MPSAFE, NULL, cache_thread, 689 NULL, NULL, "cachegc"); 690 if (error != 0) 691 panic("nchinit %d", error); 692 693 evcnt_attach_dynamic(&cache_ev_scan, EVCNT_TYPE_MISC, NULL, 694 "namecache", "entries scanned"); 695 evcnt_attach_dynamic(&cache_ev_gc, EVCNT_TYPE_MISC, NULL, 696 "namecache", "entries collected"); 697 evcnt_attach_dynamic(&cache_ev_over, EVCNT_TYPE_MISC, NULL, 698 "namecache", "over scan target"); 699 evcnt_attach_dynamic(&cache_ev_under, EVCNT_TYPE_MISC, NULL, 700 "namecache", "under scan target"); 701 evcnt_attach_dynamic(&cache_ev_forced, EVCNT_TYPE_MISC, NULL, 702 "namecache", "forced reclaims"); 703 } 704 705 static int 706 cache_ctor(void *arg, void *obj, int flag) 707 { 708 struct namecache *ncp; 709 710 ncp = obj; 711 mutex_init(&ncp->nc_lock, MUTEX_DEFAULT, IPL_NONE); 712 713 return 0; 714 } 715 716 static void 717 cache_dtor(void *arg, void *obj) 718 { 719 struct namecache *ncp; 720 721 ncp = obj; 722 mutex_destroy(&ncp->nc_lock); 723 } 724 725 /* 726 * Called once for each CPU in the system as attached. 727 */ 728 void 729 cache_cpu_init(struct cpu_info *ci) 730 { 731 struct nchcpu *cpup; 732 size_t sz; 733 734 sz = roundup2(sizeof(*cpup), coherency_unit) + coherency_unit; 735 cpup = kmem_zalloc(sz, KM_SLEEP); 736 cpup = (void *)roundup2((uintptr_t)cpup, coherency_unit); 737 mutex_init(&cpup->cpu_lock, MUTEX_DEFAULT, IPL_NONE); 738 ci->ci_data.cpu_nch = cpup; 739 } 740 741 /* 742 * Name cache reinitialization, for when the maximum number of vnodes increases. 743 */ 744 void 745 nchreinit(void) 746 { 747 struct namecache *ncp; 748 struct nchashhead *oldhash1, *hash1; 749 struct ncvhashhead *oldhash2, *hash2; 750 u_long i, oldmask1, oldmask2, mask1, mask2; 751 752 hash1 = hashinit(desiredvnodes, HASH_LIST, true, &mask1); 753 hash2 = 754 #ifdef NAMECACHE_ENTER_REVERSE 755 hashinit(desiredvnodes, HASH_LIST, true, &mask2); 756 #else 757 hashinit(desiredvnodes/8, HASH_LIST, true, &mask2); 758 #endif 759 mutex_enter(namecache_lock); 760 cache_lock_cpus(); 761 oldhash1 = nchashtbl; 762 oldmask1 = nchash; 763 nchashtbl = hash1; 764 nchash = mask1; 765 oldhash2 = ncvhashtbl; 766 oldmask2 = ncvhash; 767 ncvhashtbl = hash2; 768 ncvhash = mask2; 769 for (i = 0; i <= oldmask1; i++) { 770 while ((ncp = LIST_FIRST(&oldhash1[i])) != NULL) { 771 LIST_REMOVE(ncp, nc_hash); 772 ncp->nc_hash.le_prev = NULL; 773 } 774 } 775 for (i = 0; i <= oldmask2; i++) { 776 while ((ncp = LIST_FIRST(&oldhash2[i])) != NULL) { 777 LIST_REMOVE(ncp, nc_vhash); 778 ncp->nc_vhash.le_prev = NULL; 779 } 780 } 781 cache_unlock_cpus(); 782 mutex_exit(namecache_lock); 783 hashdone(oldhash1, HASH_LIST, oldmask1); 784 hashdone(oldhash2, HASH_LIST, oldmask2); 785 } 786 787 /* 788 * Cache flush, a particular vnode; called when a vnode is renamed to 789 * hide entries that would now be invalid 790 */ 791 void 792 cache_purge1(struct vnode *vp, const struct componentname *cnp, int flags) 793 { 794 struct namecache *ncp, *ncnext; 795 796 mutex_enter(namecache_lock); 797 if (flags & PURGE_PARENTS) { 798 for (ncp = LIST_FIRST(&vp->v_nclist); ncp != NULL; 799 ncp = ncnext) { 800 ncnext = LIST_NEXT(ncp, nc_vlist); 801 mutex_enter(&ncp->nc_lock); 802 cache_invalidate(ncp); 803 mutex_exit(&ncp->nc_lock); 804 cache_disassociate(ncp); 805 } 806 } 807 if (flags & PURGE_CHILDREN) { 808 for (ncp = LIST_FIRST(&vp->v_dnclist); ncp != NULL; 809 ncp = ncnext) { 810 ncnext = LIST_NEXT(ncp, nc_dvlist); 811 mutex_enter(&ncp->nc_lock); 812 cache_invalidate(ncp); 813 mutex_exit(&ncp->nc_lock); 814 cache_disassociate(ncp); 815 } 816 } 817 if (cnp != NULL) { 818 ncp = cache_lookup_entry(vp, cnp); 819 if (ncp) { 820 cache_invalidate(ncp); 821 mutex_exit(&ncp->nc_lock); 822 cache_disassociate(ncp); 823 } 824 } 825 mutex_exit(namecache_lock); 826 } 827 828 /* 829 * Cache flush, a whole filesystem; called when filesys is umounted to 830 * remove entries that would now be invalid. 831 */ 832 void 833 cache_purgevfs(struct mount *mp) 834 { 835 struct namecache *ncp, *nxtcp; 836 837 mutex_enter(namecache_lock); 838 for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) { 839 nxtcp = TAILQ_NEXT(ncp, nc_lru); 840 mutex_enter(&ncp->nc_lock); 841 if (ncp->nc_dvp != NULL && ncp->nc_dvp->v_mount == mp) { 842 /* Free the resources we had. */ 843 cache_invalidate(ncp); 844 cache_disassociate(ncp); 845 } 846 mutex_exit(&ncp->nc_lock); 847 } 848 cache_reclaim(); 849 mutex_exit(namecache_lock); 850 } 851 852 /* 853 * Scan global list invalidating entries until we meet a preset target. 854 * Prefer to invalidate entries that have not scored a hit within 855 * cache_hottime seconds. We sort the LRU list only for this routine's 856 * benefit. 857 */ 858 static void 859 cache_prune(int incache, int target) 860 { 861 struct namecache *ncp, *nxtcp, *sentinel; 862 int items, recent, tryharder; 863 864 KASSERT(mutex_owned(namecache_lock)); 865 866 items = 0; 867 tryharder = 0; 868 recent = hardclock_ticks - hz * cache_hottime; 869 sentinel = NULL; 870 for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) { 871 if (incache <= target) 872 break; 873 items++; 874 nxtcp = TAILQ_NEXT(ncp, nc_lru); 875 if (ncp->nc_dvp == NULL) 876 continue; 877 if (ncp == sentinel) { 878 /* 879 * If we looped back on ourself, then ignore 880 * recent entries and purge whatever we find. 881 */ 882 tryharder = 1; 883 } 884 if (!tryharder && (ncp->nc_hittime - recent) > 0) { 885 if (sentinel == NULL) 886 sentinel = ncp; 887 TAILQ_REMOVE(&nclruhead, ncp, nc_lru); 888 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); 889 continue; 890 } 891 mutex_enter(&ncp->nc_lock); 892 if (ncp->nc_dvp != NULL) { 893 cache_invalidate(ncp); 894 cache_disassociate(ncp); 895 incache--; 896 } 897 mutex_exit(&ncp->nc_lock); 898 } 899 cache_ev_scan.ev_count += items; 900 } 901 902 /* 903 * Collect dead cache entries from all CPUs and garbage collect. 904 */ 905 static void 906 cache_reclaim(void) 907 { 908 struct namecache *ncp, *next; 909 int items; 910 911 KASSERT(mutex_owned(namecache_lock)); 912 913 /* 914 * If the number of extant entries not awaiting garbage collection 915 * exceeds the high water mark, then reclaim stale entries until we 916 * reach our low water mark. 917 */ 918 items = numcache - cache_gcpend; 919 if (items > (uint64_t)desiredvnodes * cache_hiwat / 100) { 920 cache_prune(items, (int)((uint64_t)desiredvnodes * 921 cache_lowat / 100)); 922 cache_ev_over.ev_count++; 923 } else 924 cache_ev_under.ev_count++; 925 926 /* 927 * Stop forward lookup activity on all CPUs and garbage collect dead 928 * entries. 929 */ 930 cache_lock_cpus(); 931 ncp = cache_gcqueue; 932 cache_gcqueue = NULL; 933 items = cache_gcpend; 934 cache_gcpend = 0; 935 while (ncp != NULL) { 936 next = ncp->nc_gcqueue; 937 cache_disassociate(ncp); 938 KASSERT(ncp->nc_dvp == NULL); 939 if (ncp->nc_hash.le_prev != NULL) { 940 LIST_REMOVE(ncp, nc_hash); 941 ncp->nc_hash.le_prev = NULL; 942 } 943 pool_cache_put(namecache_cache, ncp); 944 ncp = next; 945 } 946 cache_unlock_cpus(); 947 numcache -= items; 948 cache_ev_gc.ev_count += items; 949 } 950 951 /* 952 * Cache maintainence thread, awakening once per second to: 953 * 954 * => keep number of entries below the high water mark 955 * => sort pseudo-LRU list 956 * => garbage collect dead entries 957 */ 958 static void 959 cache_thread(void *arg) 960 { 961 962 mutex_enter(namecache_lock); 963 for (;;) { 964 cache_reclaim(); 965 kpause("cachegc", false, hz, namecache_lock); 966 } 967 } 968 969 #ifdef DDB 970 void 971 namecache_print(struct vnode *vp, void (*pr)(const char *, ...)) 972 { 973 struct vnode *dvp = NULL; 974 struct namecache *ncp; 975 976 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 977 if (ncp->nc_vp == vp && ncp->nc_dvp != NULL) { 978 (*pr)("name %.*s\n", ncp->nc_nlen, ncp->nc_name); 979 dvp = ncp->nc_dvp; 980 } 981 } 982 if (dvp == NULL) { 983 (*pr)("name not found\n"); 984 return; 985 } 986 vp = dvp; 987 TAILQ_FOREACH(ncp, &nclruhead, nc_lru) { 988 if (ncp->nc_vp == vp) { 989 (*pr)("parent %.*s\n", ncp->nc_nlen, ncp->nc_name); 990 } 991 } 992 } 993 #endif 994