1 /* 2 * Copyright (c) 2003,2004,2009 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Matthew Dillon <dillon@backplane.com> 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 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 3. Neither the name of The DragonFly Project nor the names of its 18 * contributors may be used to endorse or promote products derived 19 * from this software without specific, prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * Copyright (c) 1989, 1993, 1995 35 * The Regents of the University of California. All rights reserved. 36 * 37 * This code is derived from software contributed to Berkeley by 38 * Poul-Henning Kamp of the FreeBSD Project. 39 * 40 * Redistribution and use in source and binary forms, with or without 41 * modification, are permitted provided that the following conditions 42 * are met: 43 * 1. Redistributions of source code must retain the above copyright 44 * notice, this list of conditions and the following disclaimer. 45 * 2. Redistributions in binary form must reproduce the above copyright 46 * notice, this list of conditions and the following disclaimer in the 47 * documentation and/or other materials provided with the distribution. 48 * 3. Neither the name of the University nor the names of its contributors 49 * may be used to endorse or promote products derived from this software 50 * without specific prior written permission. 51 * 52 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 53 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 54 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 55 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 56 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 57 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 58 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 59 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 60 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 61 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 62 * SUCH DAMAGE. 63 */ 64 65 #include <sys/param.h> 66 #include <sys/systm.h> 67 #include <sys/uio.h> 68 #include <sys/kernel.h> 69 #include <sys/sysctl.h> 70 #include <sys/mount.h> 71 #include <sys/vnode.h> 72 #include <sys/malloc.h> 73 #include <sys/sysproto.h> 74 #include <sys/spinlock.h> 75 #include <sys/proc.h> 76 #include <sys/namei.h> 77 #include <sys/nlookup.h> 78 #include <sys/filedesc.h> 79 #include <sys/fnv_hash.h> 80 #include <sys/globaldata.h> 81 #include <sys/kern_syscall.h> 82 #include <sys/dirent.h> 83 #include <ddb/ddb.h> 84 85 #include <sys/spinlock2.h> 86 87 #define MAX_RECURSION_DEPTH 64 88 89 /* 90 * Random lookups in the cache are accomplished with a hash table using 91 * a hash key of (nc_src_vp, name). Each hash chain has its own spin lock. 92 * 93 * Negative entries may exist and correspond to resolved namecache 94 * structures where nc_vp is NULL. In a negative entry, NCF_WHITEOUT 95 * will be set if the entry corresponds to a whited-out directory entry 96 * (verses simply not finding the entry at all). pcpu_ncache[n].neg_list 97 * is locked via pcpu_ncache[n].neg_spin; 98 * 99 * MPSAFE RULES: 100 * 101 * (1) A ncp must be referenced before it can be locked. 102 * 103 * (2) A ncp must be locked in order to modify it. 104 * 105 * (3) ncp locks are always ordered child -> parent. That may seem 106 * backwards but forward scans use the hash table and thus can hold 107 * the parent unlocked when traversing downward. 108 * 109 * This allows insert/rename/delete/dot-dot and other operations 110 * to use ncp->nc_parent links. 111 * 112 * This also prevents a locked up e.g. NFS node from creating a 113 * chain reaction all the way back to the root vnode / namecache. 114 * 115 * (4) parent linkages require both the parent and child to be locked. 116 */ 117 118 /* 119 * Structures associated with name cacheing. 120 */ 121 #define NCHHASH(hash) (&nchashtbl[(hash) & nchash]) 122 #define MINNEG 1024 123 #define MINPOS 1024 124 #define NCMOUNT_NUMCACHE 32768 /* power of 2 */ 125 126 MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries"); 127 128 TAILQ_HEAD(nchash_list, namecache); 129 130 /* 131 * Don't cachealign, but at least pad to 32 bytes so entries 132 * don't cross a cache line. 133 */ 134 struct nchash_head { 135 struct nchash_list list; /* 16 bytes */ 136 struct spinlock spin; /* 8 bytes */ 137 long pad01; /* 8 bytes */ 138 }; 139 140 struct ncmount_cache { 141 struct spinlock spin; 142 struct namecache *ncp; 143 struct mount *mp; 144 int isneg; /* if != 0 mp is originator and not target */ 145 int ticks; 146 } __cachealign; 147 148 struct pcpu_ncache { 149 struct spinlock neg_spin; /* for neg_list and neg_count */ 150 struct namecache_list neg_list; 151 long neg_count; 152 long vfscache_negs; 153 long vfscache_count; 154 long vfscache_leafs; 155 long numdefered; 156 } __cachealign; 157 158 __read_mostly static struct nchash_head *nchashtbl; 159 __read_mostly static struct pcpu_ncache *pcpu_ncache; 160 static struct ncmount_cache ncmount_cache[NCMOUNT_NUMCACHE]; 161 162 /* 163 * ncvp_debug - debug cache_fromvp(). This is used by the NFS server 164 * to create the namecache infrastructure leading to a dangling vnode. 165 * 166 * 0 Only errors are reported 167 * 1 Successes are reported 168 * 2 Successes + the whole directory scan is reported 169 * 3 Force the directory scan code run as if the parent vnode did not 170 * have a namecache record, even if it does have one. 171 */ 172 __read_mostly static int ncvp_debug; 173 SYSCTL_INT(_debug, OID_AUTO, ncvp_debug, CTLFLAG_RW, &ncvp_debug, 0, 174 "Namecache debug level (0-3)"); 175 176 __read_mostly static u_long nchash; /* size of hash table */ 177 SYSCTL_ULONG(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0, 178 "Size of namecache hash table"); 179 180 __read_mostly static int ncnegflush = 10; /* burst for negative flush */ 181 SYSCTL_INT(_debug, OID_AUTO, ncnegflush, CTLFLAG_RW, &ncnegflush, 0, 182 "Batch flush negative entries"); 183 184 __read_mostly static int ncposflush = 10; /* burst for positive flush */ 185 SYSCTL_INT(_debug, OID_AUTO, ncposflush, CTLFLAG_RW, &ncposflush, 0, 186 "Batch flush positive entries"); 187 188 __read_mostly static int ncnegfactor = 16; /* ratio of negative entries */ 189 SYSCTL_INT(_debug, OID_AUTO, ncnegfactor, CTLFLAG_RW, &ncnegfactor, 0, 190 "Ratio of namecache negative entries"); 191 192 __read_mostly static int nclockwarn; /* warn on locked entries in ticks */ 193 SYSCTL_INT(_debug, OID_AUTO, nclockwarn, CTLFLAG_RW, &nclockwarn, 0, 194 "Warn on locked namecache entries in ticks"); 195 196 __read_mostly static int ncposlimit; /* number of cache entries allocated */ 197 SYSCTL_INT(_debug, OID_AUTO, ncposlimit, CTLFLAG_RW, &ncposlimit, 0, 198 "Number of cache entries allocated"); 199 200 __read_mostly static int ncp_shared_lock_disable = 0; 201 SYSCTL_INT(_debug, OID_AUTO, ncp_shared_lock_disable, CTLFLAG_RW, 202 &ncp_shared_lock_disable, 0, "Disable shared namecache locks"); 203 204 SYSCTL_INT(_debug, OID_AUTO, vnsize, CTLFLAG_RD, 0, sizeof(struct vnode), 205 "sizeof(struct vnode)"); 206 SYSCTL_INT(_debug, OID_AUTO, ncsize, CTLFLAG_RD, 0, sizeof(struct namecache), 207 "sizeof(struct namecache)"); 208 209 __read_mostly static int ncmount_cache_enable = 1; 210 SYSCTL_INT(_debug, OID_AUTO, ncmount_cache_enable, CTLFLAG_RW, 211 &ncmount_cache_enable, 0, "mount point cache"); 212 213 static __inline void _cache_drop(struct namecache *ncp); 214 static int cache_resolve_mp(struct mount *mp); 215 static struct vnode *cache_dvpref(struct namecache *ncp); 216 static void _cache_lock(struct namecache *ncp); 217 static void _cache_setunresolved(struct namecache *ncp); 218 static void _cache_cleanneg(long count); 219 static void _cache_cleanpos(long count); 220 static void _cache_cleandefered(void); 221 static void _cache_unlink(struct namecache *ncp); 222 #if 0 223 static void vfscache_rollup_all(void); 224 #endif 225 226 /* 227 * The new name cache statistics (these are rolled up globals and not 228 * modified in the critical path, see struct pcpu_ncache). 229 */ 230 SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW, 0, "Name cache statistics"); 231 static long vfscache_negs; 232 SYSCTL_LONG(_vfs_cache, OID_AUTO, numneg, CTLFLAG_RD, &vfscache_negs, 0, 233 "Number of negative namecache entries"); 234 static long vfscache_count; 235 SYSCTL_LONG(_vfs_cache, OID_AUTO, numcache, CTLFLAG_RD, &vfscache_count, 0, 236 "Number of namecaches entries"); 237 static long vfscache_leafs; 238 SYSCTL_LONG(_vfs_cache, OID_AUTO, numleafs, CTLFLAG_RD, &vfscache_leafs, 0, 239 "Number of namecaches entries"); 240 static long numdefered; 241 SYSCTL_LONG(_debug, OID_AUTO, numdefered, CTLFLAG_RD, &numdefered, 0, 242 "Number of cache entries allocated"); 243 244 245 struct nchstats nchstats[SMP_MAXCPU]; 246 /* 247 * Export VFS cache effectiveness statistics to user-land. 248 * 249 * The statistics are left for aggregation to user-land so 250 * neat things can be achieved, like observing per-CPU cache 251 * distribution. 252 */ 253 static int 254 sysctl_nchstats(SYSCTL_HANDLER_ARGS) 255 { 256 struct globaldata *gd; 257 int i, error; 258 259 error = 0; 260 for (i = 0; i < ncpus; ++i) { 261 gd = globaldata_find(i); 262 if ((error = SYSCTL_OUT(req, (void *)&(*gd->gd_nchstats), 263 sizeof(struct nchstats)))) 264 break; 265 } 266 267 return (error); 268 } 269 SYSCTL_PROC(_vfs_cache, OID_AUTO, nchstats, CTLTYPE_OPAQUE|CTLFLAG_RD, 270 0, 0, sysctl_nchstats, "S,nchstats", "VFS cache effectiveness statistics"); 271 272 static struct namecache *cache_zap(struct namecache *ncp, int nonblock); 273 274 /* 275 * Cache mount points and namecache records in order to avoid unnecessary 276 * atomic ops on mnt_refs and ncp->refs. This improves concurrent SMP 277 * performance and is particularly important on multi-socket systems to 278 * reduce cache-line ping-ponging. 279 * 280 * Try to keep the pcpu structure within one cache line (~64 bytes). 281 */ 282 #define MNTCACHE_COUNT 5 283 284 struct mntcache { 285 struct mount *mntary[MNTCACHE_COUNT]; 286 struct namecache *ncp1; 287 struct namecache *ncp2; 288 struct nchandle ncdir; 289 int iter; 290 int unused01; 291 } __cachealign; 292 293 static struct mntcache pcpu_mntcache[MAXCPU]; 294 295 static 296 void 297 _cache_mntref(struct mount *mp) 298 { 299 struct mntcache *cache = &pcpu_mntcache[mycpu->gd_cpuid]; 300 int i; 301 302 for (i = 0; i < MNTCACHE_COUNT; ++i) { 303 if (cache->mntary[i] != mp) 304 continue; 305 if (atomic_cmpset_ptr((void *)&cache->mntary[i], mp, NULL)) 306 return; 307 } 308 atomic_add_int(&mp->mnt_refs, 1); 309 } 310 311 static 312 void 313 _cache_mntrel(struct mount *mp) 314 { 315 struct mntcache *cache = &pcpu_mntcache[mycpu->gd_cpuid]; 316 int i; 317 318 for (i = 0; i < MNTCACHE_COUNT; ++i) { 319 if (cache->mntary[i] == NULL) { 320 mp = atomic_swap_ptr((void *)&cache->mntary[i], mp); 321 if (mp == NULL) 322 return; 323 } 324 } 325 i = (int)((uint32_t)++cache->iter % (uint32_t)MNTCACHE_COUNT); 326 mp = atomic_swap_ptr((void *)&cache->mntary[i], mp); 327 if (mp) 328 atomic_add_int(&mp->mnt_refs, -1); 329 } 330 331 /* 332 * Clears all cached mount points on all cpus. This routine should only 333 * be called when we are waiting for a mount to clear, e.g. so we can 334 * unmount. 335 */ 336 void 337 cache_clearmntcache(void) 338 { 339 int n; 340 341 for (n = 0; n < ncpus; ++n) { 342 struct mntcache *cache = &pcpu_mntcache[n]; 343 struct namecache *ncp; 344 struct mount *mp; 345 int i; 346 347 for (i = 0; i < MNTCACHE_COUNT; ++i) { 348 if (cache->mntary[i]) { 349 mp = atomic_swap_ptr( 350 (void *)&cache->mntary[i], NULL); 351 if (mp) 352 atomic_add_int(&mp->mnt_refs, -1); 353 } 354 } 355 if (cache->ncp1) { 356 ncp = atomic_swap_ptr((void *)&cache->ncp1, NULL); 357 if (ncp) 358 _cache_drop(ncp); 359 } 360 if (cache->ncp2) { 361 ncp = atomic_swap_ptr((void *)&cache->ncp2, NULL); 362 if (ncp) 363 _cache_drop(ncp); 364 } 365 if (cache->ncdir.ncp) { 366 ncp = atomic_swap_ptr((void *)&cache->ncdir.ncp, NULL); 367 if (ncp) 368 _cache_drop(ncp); 369 } 370 if (cache->ncdir.mount) { 371 mp = atomic_swap_ptr((void *)&cache->ncdir.mount, NULL); 372 if (mp) 373 atomic_add_int(&mp->mnt_refs, -1); 374 } 375 } 376 } 377 378 379 /* 380 * Namespace locking. The caller must already hold a reference to the 381 * namecache structure in order to lock/unlock it. This function prevents 382 * the namespace from being created or destroyed by accessors other then 383 * the lock holder. 384 * 385 * Note that holding a locked namecache structure prevents other threads 386 * from making namespace changes (e.g. deleting or creating), prevents 387 * vnode association state changes by other threads, and prevents the 388 * namecache entry from being resolved or unresolved by other threads. 389 * 390 * An exclusive lock owner has full authority to associate/disassociate 391 * vnodes and resolve/unresolve the locked ncp. 392 * 393 * A shared lock owner only has authority to acquire the underlying vnode, 394 * if any. 395 * 396 * The primary lock field is nc_lockstatus. nc_locktd is set after the 397 * fact (when locking) or cleared prior to unlocking. 398 * 399 * WARNING! Holding a locked ncp will prevent a vnode from being destroyed 400 * or recycled, but it does NOT help you if the vnode had already 401 * initiated a recyclement. If this is important, use cache_get() 402 * rather then cache_lock() (and deal with the differences in the 403 * way the refs counter is handled). Or, alternatively, make an 404 * unconditional call to cache_validate() or cache_resolve() 405 * after cache_lock() returns. 406 */ 407 static 408 void 409 _cache_lock(struct namecache *ncp) 410 { 411 thread_t td; 412 int didwarn; 413 int begticks; 414 int error; 415 u_int count; 416 417 KKASSERT(ncp->nc_refs != 0); 418 didwarn = 0; 419 begticks = 0; 420 td = curthread; 421 422 for (;;) { 423 count = ncp->nc_lockstatus; 424 cpu_ccfence(); 425 426 if ((count & ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) == 0) { 427 if (atomic_cmpset_int(&ncp->nc_lockstatus, 428 count, count + 1)) { 429 /* 430 * The vp associated with a locked ncp must 431 * be held to prevent it from being recycled. 432 * 433 * WARNING! If VRECLAIMED is set the vnode 434 * could already be in the middle of a recycle. 435 * Callers must use cache_vref() or 436 * cache_vget() on the locked ncp to 437 * validate the vp or set the cache entry 438 * to unresolved. 439 * 440 * NOTE! vhold() is allowed if we hold a 441 * lock on the ncp (which we do). 442 */ 443 ncp->nc_locktd = td; 444 if (ncp->nc_vp) 445 vhold(ncp->nc_vp); 446 break; 447 } 448 /* cmpset failed */ 449 continue; 450 } 451 if (ncp->nc_locktd == td) { 452 KKASSERT((count & NC_SHLOCK_FLAG) == 0); 453 if (atomic_cmpset_int(&ncp->nc_lockstatus, 454 count, count + 1)) { 455 break; 456 } 457 /* cmpset failed */ 458 continue; 459 } 460 tsleep_interlock(&ncp->nc_locktd, 0); 461 if (atomic_cmpset_int(&ncp->nc_lockstatus, count, 462 count | NC_EXLOCK_REQ) == 0) { 463 /* cmpset failed */ 464 continue; 465 } 466 if (begticks == 0) 467 begticks = ticks; 468 error = tsleep(&ncp->nc_locktd, PINTERLOCKED, 469 "clock", nclockwarn); 470 if (error == EWOULDBLOCK) { 471 if (didwarn == 0) { 472 didwarn = ticks; 473 kprintf("[diagnostic] cache_lock: " 474 "%s blocked on %p %08x", 475 td->td_comm, ncp, count); 476 kprintf(" \"%*.*s\"\n", 477 ncp->nc_nlen, ncp->nc_nlen, 478 ncp->nc_name); 479 } 480 } 481 /* loop */ 482 } 483 if (didwarn) { 484 kprintf("[diagnostic] cache_lock: %s unblocked %*.*s after " 485 "%d secs\n", 486 td->td_comm, 487 ncp->nc_nlen, ncp->nc_nlen, ncp->nc_name, 488 (int)(ticks + (hz / 2) - begticks) / hz); 489 } 490 } 491 492 /* 493 * The shared lock works similarly to the exclusive lock except 494 * nc_locktd is left NULL and we need an interlock (VHOLD) to 495 * prevent vhold() races, since the moment our cmpset_int succeeds 496 * another cpu can come in and get its own shared lock. 497 * 498 * A critical section is needed to prevent interruption during the 499 * VHOLD interlock. 500 */ 501 static 502 void 503 _cache_lock_shared(struct namecache *ncp) 504 { 505 int didwarn; 506 int error; 507 u_int count; 508 u_int optreq = NC_EXLOCK_REQ; 509 510 KKASSERT(ncp->nc_refs != 0); 511 didwarn = 0; 512 513 for (;;) { 514 count = ncp->nc_lockstatus; 515 cpu_ccfence(); 516 517 if ((count & ~NC_SHLOCK_REQ) == 0) { 518 crit_enter(); 519 if (atomic_cmpset_int(&ncp->nc_lockstatus, 520 count, 521 (count + 1) | NC_SHLOCK_FLAG | 522 NC_SHLOCK_VHOLD)) { 523 /* 524 * The vp associated with a locked ncp must 525 * be held to prevent it from being recycled. 526 * 527 * WARNING! If VRECLAIMED is set the vnode 528 * could already be in the middle of a recycle. 529 * Callers must use cache_vref() or 530 * cache_vget() on the locked ncp to 531 * validate the vp or set the cache entry 532 * to unresolved. 533 * 534 * NOTE! vhold() is allowed if we hold a 535 * lock on the ncp (which we do). 536 */ 537 if (ncp->nc_vp) 538 vhold(ncp->nc_vp); 539 atomic_clear_int(&ncp->nc_lockstatus, 540 NC_SHLOCK_VHOLD); 541 crit_exit(); 542 break; 543 } 544 /* cmpset failed */ 545 crit_exit(); 546 continue; 547 } 548 549 /* 550 * If already held shared we can just bump the count, but 551 * only allow this if nobody is trying to get the lock 552 * exclusively. If we are blocking too long ignore excl 553 * requests (which can race/deadlock us). 554 * 555 * VHOLD is a bit of a hack. Even though we successfully 556 * added another shared ref, the cpu that got the first 557 * shared ref might not yet have held the vnode. 558 */ 559 if ((count & (optreq|NC_SHLOCK_FLAG)) == NC_SHLOCK_FLAG) { 560 KKASSERT((count & ~(NC_EXLOCK_REQ | 561 NC_SHLOCK_REQ | 562 NC_SHLOCK_FLAG)) > 0); 563 if (atomic_cmpset_int(&ncp->nc_lockstatus, 564 count, count + 1)) { 565 while (ncp->nc_lockstatus & NC_SHLOCK_VHOLD) 566 cpu_pause(); 567 break; 568 } 569 continue; 570 } 571 tsleep_interlock(ncp, 0); 572 if (atomic_cmpset_int(&ncp->nc_lockstatus, count, 573 count | NC_SHLOCK_REQ) == 0) { 574 /* cmpset failed */ 575 continue; 576 } 577 error = tsleep(ncp, PINTERLOCKED, "clocksh", nclockwarn); 578 if (error == EWOULDBLOCK) { 579 optreq = 0; 580 if (didwarn == 0) { 581 didwarn = ticks - nclockwarn; 582 kprintf("[diagnostic] cache_lock_shared: " 583 "%s blocked on %p %08x " 584 "\"%*.*s\"\n", 585 curthread->td_comm, ncp, count, 586 ncp->nc_nlen, ncp->nc_nlen, 587 ncp->nc_name); 588 } 589 } 590 /* loop */ 591 } 592 if (didwarn) { 593 kprintf("[diagnostic] cache_lock_shared: " 594 "%s unblocked %*.*s after %d secs\n", 595 curthread->td_comm, 596 ncp->nc_nlen, ncp->nc_nlen, ncp->nc_name, 597 (int)(ticks - didwarn) / hz); 598 } 599 } 600 601 /* 602 * Lock ncp exclusively, return 0 on success. 603 * 604 * NOTE: nc_refs may be zero if the ncp is interlocked by circumstance, 605 * such as the case where one of its children is locked. 606 */ 607 static 608 int 609 _cache_lock_nonblock(struct namecache *ncp) 610 { 611 thread_t td; 612 u_int count; 613 614 td = curthread; 615 616 for (;;) { 617 count = ncp->nc_lockstatus; 618 619 if ((count & ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) == 0) { 620 if (atomic_cmpset_int(&ncp->nc_lockstatus, 621 count, count + 1)) { 622 /* 623 * The vp associated with a locked ncp must 624 * be held to prevent it from being recycled. 625 * 626 * WARNING! If VRECLAIMED is set the vnode 627 * could already be in the middle of a recycle. 628 * Callers must use cache_vref() or 629 * cache_vget() on the locked ncp to 630 * validate the vp or set the cache entry 631 * to unresolved. 632 * 633 * NOTE! vhold() is allowed if we hold a 634 * lock on the ncp (which we do). 635 */ 636 ncp->nc_locktd = td; 637 if (ncp->nc_vp) 638 vhold(ncp->nc_vp); 639 break; 640 } 641 /* cmpset failed */ 642 continue; 643 } 644 if (ncp->nc_locktd == td) { 645 if (atomic_cmpset_int(&ncp->nc_lockstatus, 646 count, count + 1)) { 647 break; 648 } 649 /* cmpset failed */ 650 continue; 651 } 652 return(EWOULDBLOCK); 653 } 654 return(0); 655 } 656 657 /* 658 * The shared lock works similarly to the exclusive lock except 659 * nc_locktd is left NULL and we need an interlock (VHOLD) to 660 * prevent vhold() races, since the moment our cmpset_int succeeds 661 * another cpu can come in and get its own shared lock. 662 * 663 * A critical section is needed to prevent interruption during the 664 * VHOLD interlock. 665 */ 666 static 667 int 668 _cache_lock_shared_nonblock(struct namecache *ncp) 669 { 670 u_int count; 671 672 for (;;) { 673 count = ncp->nc_lockstatus; 674 675 if ((count & ~NC_SHLOCK_REQ) == 0) { 676 crit_enter(); 677 if (atomic_cmpset_int(&ncp->nc_lockstatus, 678 count, 679 (count + 1) | NC_SHLOCK_FLAG | 680 NC_SHLOCK_VHOLD)) { 681 /* 682 * The vp associated with a locked ncp must 683 * be held to prevent it from being recycled. 684 * 685 * WARNING! If VRECLAIMED is set the vnode 686 * could already be in the middle of a recycle. 687 * Callers must use cache_vref() or 688 * cache_vget() on the locked ncp to 689 * validate the vp or set the cache entry 690 * to unresolved. 691 * 692 * NOTE! vhold() is allowed if we hold a 693 * lock on the ncp (which we do). 694 */ 695 if (ncp->nc_vp) 696 vhold(ncp->nc_vp); 697 atomic_clear_int(&ncp->nc_lockstatus, 698 NC_SHLOCK_VHOLD); 699 crit_exit(); 700 break; 701 } 702 /* cmpset failed */ 703 crit_exit(); 704 continue; 705 } 706 707 /* 708 * If already held shared we can just bump the count, but 709 * only allow this if nobody is trying to get the lock 710 * exclusively. 711 * 712 * VHOLD is a bit of a hack. Even though we successfully 713 * added another shared ref, the cpu that got the first 714 * shared ref might not yet have held the vnode. 715 */ 716 if ((count & (NC_EXLOCK_REQ|NC_SHLOCK_FLAG)) == 717 NC_SHLOCK_FLAG) { 718 KKASSERT((count & ~(NC_EXLOCK_REQ | 719 NC_SHLOCK_REQ | 720 NC_SHLOCK_FLAG)) > 0); 721 if (atomic_cmpset_int(&ncp->nc_lockstatus, 722 count, count + 1)) { 723 while (ncp->nc_lockstatus & NC_SHLOCK_VHOLD) 724 cpu_pause(); 725 break; 726 } 727 continue; 728 } 729 return(EWOULDBLOCK); 730 } 731 return(0); 732 } 733 734 /* 735 * Helper function 736 * 737 * NOTE: nc_refs can be 0 (degenerate case during _cache_drop). 738 * 739 * nc_locktd must be NULLed out prior to nc_lockstatus getting cleared. 740 */ 741 static 742 void 743 _cache_unlock(struct namecache *ncp) 744 { 745 thread_t td __debugvar = curthread; 746 u_int count; 747 u_int ncount; 748 struct vnode *dropvp; 749 750 KKASSERT(ncp->nc_refs >= 0); 751 KKASSERT((ncp->nc_lockstatus & ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) > 0); 752 KKASSERT((ncp->nc_lockstatus & NC_SHLOCK_FLAG) || ncp->nc_locktd == td); 753 754 count = ncp->nc_lockstatus; 755 cpu_ccfence(); 756 757 /* 758 * Clear nc_locktd prior to the atomic op (excl lock only) 759 */ 760 if ((count & ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) == 1) 761 ncp->nc_locktd = NULL; 762 dropvp = NULL; 763 764 for (;;) { 765 if ((count & 766 ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ|NC_SHLOCK_FLAG)) == 1) { 767 dropvp = ncp->nc_vp; 768 if (count & NC_EXLOCK_REQ) 769 ncount = count & NC_SHLOCK_REQ; /* cnt->0 */ 770 else 771 ncount = 0; 772 773 if (atomic_cmpset_int(&ncp->nc_lockstatus, 774 count, ncount)) { 775 if (count & NC_EXLOCK_REQ) 776 wakeup(&ncp->nc_locktd); 777 else if (count & NC_SHLOCK_REQ) 778 wakeup(ncp); 779 break; 780 } 781 dropvp = NULL; 782 } else { 783 KKASSERT((count & NC_SHLOCK_VHOLD) == 0); 784 KKASSERT((count & ~(NC_EXLOCK_REQ | 785 NC_SHLOCK_REQ | 786 NC_SHLOCK_FLAG)) > 1); 787 if (atomic_cmpset_int(&ncp->nc_lockstatus, 788 count, count - 1)) { 789 break; 790 } 791 } 792 count = ncp->nc_lockstatus; 793 cpu_ccfence(); 794 } 795 796 /* 797 * Don't actually drop the vp until we successfully clean out 798 * the lock, otherwise we may race another shared lock. 799 */ 800 if (dropvp) 801 vdrop(dropvp); 802 } 803 804 static 805 int 806 _cache_lockstatus(struct namecache *ncp) 807 { 808 if (ncp->nc_locktd == curthread) 809 return(LK_EXCLUSIVE); 810 if (ncp->nc_lockstatus & NC_SHLOCK_FLAG) 811 return(LK_SHARED); 812 return(-1); 813 } 814 815 /* 816 * cache_hold() and cache_drop() prevent the premature deletion of a 817 * namecache entry but do not prevent operations (such as zapping) on 818 * that namecache entry. 819 * 820 * This routine may only be called from outside this source module if 821 * nc_refs is already at least 1. 822 * 823 * This is a rare case where callers are allowed to hold a spinlock, 824 * so we can't ourselves. 825 */ 826 static __inline 827 struct namecache * 828 _cache_hold(struct namecache *ncp) 829 { 830 atomic_add_int(&ncp->nc_refs, 1); 831 return(ncp); 832 } 833 834 /* 835 * Drop a cache entry, taking care to deal with races. 836 * 837 * For potential 1->0 transitions we must hold the ncp lock to safely 838 * test its flags. An unresolved entry with no children must be zapped 839 * to avoid leaks. 840 * 841 * The call to cache_zap() itself will handle all remaining races and 842 * will decrement the ncp's refs regardless. If we are resolved or 843 * have children nc_refs can safely be dropped to 0 without having to 844 * zap the entry. 845 * 846 * NOTE: cache_zap() will re-check nc_refs and nc_list in a MPSAFE fashion. 847 * 848 * NOTE: cache_zap() may return a non-NULL referenced parent which must 849 * be dropped in a loop. 850 */ 851 static __inline 852 void 853 _cache_drop(struct namecache *ncp) 854 { 855 int refs; 856 857 while (ncp) { 858 KKASSERT(ncp->nc_refs > 0); 859 refs = ncp->nc_refs; 860 861 if (refs == 1) { 862 if (_cache_lock_nonblock(ncp) == 0) { 863 ncp->nc_flag &= ~NCF_DEFEREDZAP; 864 if ((ncp->nc_flag & NCF_UNRESOLVED) && 865 TAILQ_EMPTY(&ncp->nc_list)) { 866 ncp = cache_zap(ncp, 1); 867 continue; 868 } 869 if (atomic_cmpset_int(&ncp->nc_refs, 1, 0)) { 870 _cache_unlock(ncp); 871 break; 872 } 873 _cache_unlock(ncp); 874 } 875 } else { 876 if (atomic_cmpset_int(&ncp->nc_refs, refs, refs - 1)) 877 break; 878 } 879 cpu_pause(); 880 } 881 } 882 883 /* 884 * Link a new namecache entry to its parent and to the hash table. Be 885 * careful to avoid races if vhold() blocks in the future. 886 * 887 * Both ncp and par must be referenced and locked. 888 * 889 * NOTE: The hash table spinlock is held during this call, we can't do 890 * anything fancy. 891 */ 892 static void 893 _cache_link_parent(struct namecache *ncp, struct namecache *par, 894 struct nchash_head *nchpp) 895 { 896 struct pcpu_ncache *pn = &pcpu_ncache[mycpu->gd_cpuid]; 897 898 KKASSERT(ncp->nc_parent == NULL); 899 ncp->nc_parent = par; 900 ncp->nc_head = nchpp; 901 902 /* 903 * Set inheritance flags. Note that the parent flags may be 904 * stale due to getattr potentially not having been run yet 905 * (it gets run during nlookup()'s). 906 */ 907 ncp->nc_flag &= ~(NCF_SF_PNOCACHE | NCF_UF_PCACHE); 908 if (par->nc_flag & (NCF_SF_NOCACHE | NCF_SF_PNOCACHE)) 909 ncp->nc_flag |= NCF_SF_PNOCACHE; 910 if (par->nc_flag & (NCF_UF_CACHE | NCF_UF_PCACHE)) 911 ncp->nc_flag |= NCF_UF_PCACHE; 912 913 /* 914 * Add to hash table and parent, adjust accounting 915 */ 916 TAILQ_INSERT_HEAD(&nchpp->list, ncp, nc_hash); 917 atomic_add_long(&pn->vfscache_count, 1); 918 if (TAILQ_EMPTY(&ncp->nc_list)) 919 atomic_add_long(&pn->vfscache_leafs, 1); 920 921 if (TAILQ_EMPTY(&par->nc_list)) { 922 TAILQ_INSERT_HEAD(&par->nc_list, ncp, nc_entry); 923 atomic_add_long(&pn->vfscache_leafs, -1); 924 /* 925 * Any vp associated with an ncp which has children must 926 * be held to prevent it from being recycled. 927 */ 928 if (par->nc_vp) 929 vhold(par->nc_vp); 930 } else { 931 TAILQ_INSERT_HEAD(&par->nc_list, ncp, nc_entry); 932 } 933 } 934 935 /* 936 * Remove the parent and hash associations from a namecache structure. 937 * If this is the last child of the parent the cache_drop(par) will 938 * attempt to recursively zap the parent. 939 * 940 * ncp must be locked. This routine will acquire a temporary lock on 941 * the parent as wlel as the appropriate hash chain. 942 */ 943 static void 944 _cache_unlink_parent(struct namecache *ncp) 945 { 946 struct pcpu_ncache *pn = &pcpu_ncache[mycpu->gd_cpuid]; 947 struct namecache *par; 948 struct vnode *dropvp; 949 950 if ((par = ncp->nc_parent) != NULL) { 951 KKASSERT(ncp->nc_parent == par); 952 _cache_hold(par); 953 _cache_lock(par); 954 spin_lock(&ncp->nc_head->spin); 955 956 /* 957 * Remove from hash table and parent, adjust accounting 958 */ 959 TAILQ_REMOVE(&ncp->nc_head->list, ncp, nc_hash); 960 TAILQ_REMOVE(&par->nc_list, ncp, nc_entry); 961 atomic_add_long(&pn->vfscache_count, -1); 962 if (TAILQ_EMPTY(&ncp->nc_list)) 963 atomic_add_long(&pn->vfscache_leafs, -1); 964 965 dropvp = NULL; 966 if (TAILQ_EMPTY(&par->nc_list)) { 967 atomic_add_long(&pn->vfscache_leafs, 1); 968 if (par->nc_vp) 969 dropvp = par->nc_vp; 970 } 971 spin_unlock(&ncp->nc_head->spin); 972 ncp->nc_parent = NULL; 973 ncp->nc_head = NULL; 974 _cache_unlock(par); 975 _cache_drop(par); 976 977 /* 978 * We can only safely vdrop with no spinlocks held. 979 */ 980 if (dropvp) 981 vdrop(dropvp); 982 } 983 } 984 985 /* 986 * Allocate a new namecache structure. Most of the code does not require 987 * zero-termination of the string but it makes vop_compat_ncreate() easier. 988 */ 989 static struct namecache * 990 cache_alloc(int nlen) 991 { 992 struct namecache *ncp; 993 994 ncp = kmalloc(sizeof(*ncp), M_VFSCACHE, M_WAITOK|M_ZERO); 995 if (nlen) 996 ncp->nc_name = kmalloc(nlen + 1, M_VFSCACHE, M_WAITOK); 997 ncp->nc_nlen = nlen; 998 ncp->nc_flag = NCF_UNRESOLVED; 999 ncp->nc_error = ENOTCONN; /* needs to be resolved */ 1000 ncp->nc_refs = 1; 1001 1002 TAILQ_INIT(&ncp->nc_list); 1003 _cache_lock(ncp); 1004 return(ncp); 1005 } 1006 1007 /* 1008 * Can only be called for the case where the ncp has never been 1009 * associated with anything (so no spinlocks are needed). 1010 */ 1011 static void 1012 _cache_free(struct namecache *ncp) 1013 { 1014 KKASSERT(ncp->nc_refs == 1 && ncp->nc_lockstatus == 1); 1015 if (ncp->nc_name) 1016 kfree(ncp->nc_name, M_VFSCACHE); 1017 kfree(ncp, M_VFSCACHE); 1018 } 1019 1020 /* 1021 * [re]initialize a nchandle. 1022 */ 1023 void 1024 cache_zero(struct nchandle *nch) 1025 { 1026 nch->ncp = NULL; 1027 nch->mount = NULL; 1028 } 1029 1030 /* 1031 * Ref and deref a namecache structure. 1032 * 1033 * The caller must specify a stable ncp pointer, typically meaning the 1034 * ncp is already referenced but this can also occur indirectly through 1035 * e.g. holding a lock on a direct child. 1036 * 1037 * WARNING: Caller may hold an unrelated read spinlock, which means we can't 1038 * use read spinlocks here. 1039 */ 1040 struct nchandle * 1041 cache_hold(struct nchandle *nch) 1042 { 1043 _cache_hold(nch->ncp); 1044 _cache_mntref(nch->mount); 1045 return(nch); 1046 } 1047 1048 /* 1049 * Create a copy of a namecache handle for an already-referenced 1050 * entry. 1051 */ 1052 void 1053 cache_copy(struct nchandle *nch, struct nchandle *target) 1054 { 1055 struct mntcache *cache = &pcpu_mntcache[mycpu->gd_cpuid]; 1056 struct namecache *ncp; 1057 1058 *target = *nch; 1059 _cache_mntref(target->mount); 1060 ncp = target->ncp; 1061 if (ncp) { 1062 if (ncp == cache->ncp1) { 1063 if (atomic_cmpset_ptr((void *)&cache->ncp1, ncp, NULL)) 1064 return; 1065 } 1066 if (ncp == cache->ncp2) { 1067 if (atomic_cmpset_ptr((void *)&cache->ncp2, ncp, NULL)) 1068 return; 1069 } 1070 _cache_hold(ncp); 1071 } 1072 } 1073 1074 /* 1075 * Caller wants to copy the current directory, copy it out from our 1076 * pcpu cache if possible (the entire critical path is just two localized 1077 * cmpset ops). If the pcpu cache has a snapshot at all it will be a 1078 * valid one, so we don't have to lock p->p_fd even though we are loading 1079 * two fields. 1080 * 1081 * This has a limited effect since nlookup must still ref and shlock the 1082 * vnode to check perms. We do avoid the per-proc spin-lock though, which 1083 * can aid threaded programs. 1084 */ 1085 void 1086 cache_copy_ncdir(struct proc *p, struct nchandle *target) 1087 { 1088 struct mntcache *cache = &pcpu_mntcache[mycpu->gd_cpuid]; 1089 1090 *target = p->p_fd->fd_ncdir; 1091 if (target->ncp == cache->ncdir.ncp && 1092 target->mount == cache->ncdir.mount) { 1093 if (atomic_cmpset_ptr((void *)&cache->ncdir.ncp, 1094 target->ncp, NULL)) { 1095 if (atomic_cmpset_ptr((void *)&cache->ncdir.mount, 1096 target->mount, NULL)) { 1097 /* CRITICAL PATH */ 1098 return; 1099 } 1100 _cache_drop(target->ncp); 1101 } 1102 } 1103 spin_lock_shared(&p->p_fd->fd_spin); 1104 cache_copy(&p->p_fd->fd_ncdir, target); 1105 spin_unlock_shared(&p->p_fd->fd_spin); 1106 } 1107 1108 void 1109 cache_changemount(struct nchandle *nch, struct mount *mp) 1110 { 1111 _cache_mntref(mp); 1112 _cache_mntrel(nch->mount); 1113 nch->mount = mp; 1114 } 1115 1116 void 1117 cache_drop(struct nchandle *nch) 1118 { 1119 _cache_mntrel(nch->mount); 1120 _cache_drop(nch->ncp); 1121 nch->ncp = NULL; 1122 nch->mount = NULL; 1123 } 1124 1125 /* 1126 * Drop the nchandle, but try to cache the ref to avoid global atomic 1127 * ops. This is typically done on the system root and jail root nchandles. 1128 */ 1129 void 1130 cache_drop_and_cache(struct nchandle *nch) 1131 { 1132 struct mntcache *cache = &pcpu_mntcache[mycpu->gd_cpuid]; 1133 struct namecache *ncp; 1134 1135 _cache_mntrel(nch->mount); 1136 ncp = nch->ncp; 1137 if (cache->ncp1 == NULL) { 1138 ncp = atomic_swap_ptr((void *)&cache->ncp1, ncp); 1139 if (ncp == NULL) 1140 goto done; 1141 } 1142 if (cache->ncp2 == NULL) { 1143 ncp = atomic_swap_ptr((void *)&cache->ncp2, ncp); 1144 if (ncp == NULL) 1145 goto done; 1146 } 1147 if (++cache->iter & 1) 1148 ncp = atomic_swap_ptr((void *)&cache->ncp2, ncp); 1149 else 1150 ncp = atomic_swap_ptr((void *)&cache->ncp1, ncp); 1151 if (ncp) 1152 _cache_drop(ncp); 1153 done: 1154 nch->ncp = NULL; 1155 nch->mount = NULL; 1156 } 1157 1158 /* 1159 * We are dropping what the caller believes is the current directory, 1160 * unconditionally store it in our pcpu cache. Anything already in 1161 * the cache will be discarded. 1162 */ 1163 void 1164 cache_drop_ncdir(struct nchandle *nch) 1165 { 1166 struct mntcache *cache = &pcpu_mntcache[mycpu->gd_cpuid]; 1167 1168 nch->ncp = atomic_swap_ptr((void *)&cache->ncdir.ncp, nch->ncp); 1169 nch->mount = atomic_swap_ptr((void *)&cache->ncdir.mount, nch->mount); 1170 if (nch->ncp) 1171 _cache_drop(nch->ncp); 1172 if (nch->mount) 1173 _cache_mntrel(nch->mount); 1174 nch->ncp = NULL; 1175 nch->mount = NULL; 1176 } 1177 1178 int 1179 cache_lockstatus(struct nchandle *nch) 1180 { 1181 return(_cache_lockstatus(nch->ncp)); 1182 } 1183 1184 void 1185 cache_lock(struct nchandle *nch) 1186 { 1187 _cache_lock(nch->ncp); 1188 } 1189 1190 void 1191 cache_lock_maybe_shared(struct nchandle *nch, int excl) 1192 { 1193 struct namecache *ncp = nch->ncp; 1194 1195 if (ncp_shared_lock_disable || excl || 1196 (ncp->nc_flag & NCF_UNRESOLVED)) { 1197 _cache_lock(ncp); 1198 } else { 1199 _cache_lock_shared(ncp); 1200 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) { 1201 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED)) { 1202 _cache_unlock(ncp); 1203 _cache_lock(ncp); 1204 } 1205 } else { 1206 _cache_unlock(ncp); 1207 _cache_lock(ncp); 1208 } 1209 } 1210 } 1211 1212 /* 1213 * Relock nch1 given an unlocked nch1 and a locked nch2. The caller 1214 * is responsible for checking both for validity on return as they 1215 * may have become invalid. 1216 * 1217 * We have to deal with potential deadlocks here, just ping pong 1218 * the lock until we get it (we will always block somewhere when 1219 * looping so this is not cpu-intensive). 1220 * 1221 * which = 0 nch1 not locked, nch2 is locked 1222 * which = 1 nch1 is locked, nch2 is not locked 1223 */ 1224 void 1225 cache_relock(struct nchandle *nch1, struct ucred *cred1, 1226 struct nchandle *nch2, struct ucred *cred2) 1227 { 1228 int which; 1229 1230 which = 0; 1231 1232 for (;;) { 1233 if (which == 0) { 1234 if (cache_lock_nonblock(nch1) == 0) { 1235 cache_resolve(nch1, cred1); 1236 break; 1237 } 1238 cache_unlock(nch2); 1239 cache_lock(nch1); 1240 cache_resolve(nch1, cred1); 1241 which = 1; 1242 } else { 1243 if (cache_lock_nonblock(nch2) == 0) { 1244 cache_resolve(nch2, cred2); 1245 break; 1246 } 1247 cache_unlock(nch1); 1248 cache_lock(nch2); 1249 cache_resolve(nch2, cred2); 1250 which = 0; 1251 } 1252 } 1253 } 1254 1255 int 1256 cache_lock_nonblock(struct nchandle *nch) 1257 { 1258 return(_cache_lock_nonblock(nch->ncp)); 1259 } 1260 1261 void 1262 cache_unlock(struct nchandle *nch) 1263 { 1264 _cache_unlock(nch->ncp); 1265 } 1266 1267 /* 1268 * ref-and-lock, unlock-and-deref functions. 1269 * 1270 * This function is primarily used by nlookup. Even though cache_lock 1271 * holds the vnode, it is possible that the vnode may have already 1272 * initiated a recyclement. 1273 * 1274 * We want cache_get() to return a definitively usable vnode or a 1275 * definitively unresolved ncp. 1276 */ 1277 static 1278 struct namecache * 1279 _cache_get(struct namecache *ncp) 1280 { 1281 _cache_hold(ncp); 1282 _cache_lock(ncp); 1283 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED)) 1284 _cache_setunresolved(ncp); 1285 return(ncp); 1286 } 1287 1288 /* 1289 * Attempt to obtain a shared lock on the ncp. A shared lock will only 1290 * be obtained if the ncp is resolved and the vnode (if not ENOENT) is 1291 * valid. Otherwise an exclusive lock will be acquired instead. 1292 */ 1293 static 1294 struct namecache * 1295 _cache_get_maybe_shared(struct namecache *ncp, int excl) 1296 { 1297 if (ncp_shared_lock_disable || excl || 1298 (ncp->nc_flag & NCF_UNRESOLVED)) { 1299 return(_cache_get(ncp)); 1300 } 1301 _cache_hold(ncp); 1302 _cache_lock_shared(ncp); 1303 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) { 1304 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED)) { 1305 _cache_unlock(ncp); 1306 ncp = _cache_get(ncp); 1307 _cache_drop(ncp); 1308 } 1309 } else { 1310 _cache_unlock(ncp); 1311 ncp = _cache_get(ncp); 1312 _cache_drop(ncp); 1313 } 1314 return(ncp); 1315 } 1316 1317 /* 1318 * This is a special form of _cache_lock() which only succeeds if 1319 * it can get a pristine, non-recursive lock. The caller must have 1320 * already ref'd the ncp. 1321 * 1322 * On success the ncp will be locked, on failure it will not. The 1323 * ref count does not change either way. 1324 * 1325 * We want _cache_lock_special() (on success) to return a definitively 1326 * usable vnode or a definitively unresolved ncp. 1327 */ 1328 static int 1329 _cache_lock_special(struct namecache *ncp) 1330 { 1331 if (_cache_lock_nonblock(ncp) == 0) { 1332 if ((ncp->nc_lockstatus & 1333 ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) == 1) { 1334 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED)) 1335 _cache_setunresolved(ncp); 1336 return(0); 1337 } 1338 _cache_unlock(ncp); 1339 } 1340 return(EWOULDBLOCK); 1341 } 1342 1343 /* 1344 * This function tries to get a shared lock but will back-off to an exclusive 1345 * lock if: 1346 * 1347 * (1) Some other thread is trying to obtain an exclusive lock 1348 * (to prevent the exclusive requester from getting livelocked out 1349 * by many shared locks). 1350 * 1351 * (2) The current thread already owns an exclusive lock (to avoid 1352 * deadlocking). 1353 * 1354 * WARNING! On machines with lots of cores we really want to try hard to 1355 * get a shared lock or concurrent path lookups can chain-react 1356 * into a very high-latency exclusive lock. 1357 */ 1358 static int 1359 _cache_lock_shared_special(struct namecache *ncp) 1360 { 1361 /* 1362 * Only honor a successful shared lock (returning 0) if there is 1363 * no exclusive request pending and the vnode, if present, is not 1364 * in a reclaimed state. 1365 */ 1366 if (_cache_lock_shared_nonblock(ncp) == 0) { 1367 if ((ncp->nc_lockstatus & NC_EXLOCK_REQ) == 0) { 1368 if (ncp->nc_vp == NULL || 1369 (ncp->nc_vp->v_flag & VRECLAIMED) == 0) { 1370 return(0); 1371 } 1372 } 1373 _cache_unlock(ncp); 1374 return(EWOULDBLOCK); 1375 } 1376 1377 /* 1378 * Non-blocking shared lock failed. If we already own the exclusive 1379 * lock just acquire another exclusive lock (instead of deadlocking). 1380 * Otherwise acquire a shared lock. 1381 */ 1382 if (ncp->nc_locktd == curthread) { 1383 _cache_lock(ncp); 1384 return(0); 1385 } 1386 _cache_lock_shared(ncp); 1387 return(0); 1388 } 1389 1390 1391 /* 1392 * NOTE: The same nchandle can be passed for both arguments. 1393 */ 1394 void 1395 cache_get(struct nchandle *nch, struct nchandle *target) 1396 { 1397 KKASSERT(nch->ncp->nc_refs > 0); 1398 target->mount = nch->mount; 1399 target->ncp = _cache_get(nch->ncp); 1400 _cache_mntref(target->mount); 1401 } 1402 1403 void 1404 cache_get_maybe_shared(struct nchandle *nch, struct nchandle *target, int excl) 1405 { 1406 KKASSERT(nch->ncp->nc_refs > 0); 1407 target->mount = nch->mount; 1408 target->ncp = _cache_get_maybe_shared(nch->ncp, excl); 1409 _cache_mntref(target->mount); 1410 } 1411 1412 /* 1413 * 1414 */ 1415 static __inline 1416 void 1417 _cache_put(struct namecache *ncp) 1418 { 1419 _cache_unlock(ncp); 1420 _cache_drop(ncp); 1421 } 1422 1423 /* 1424 * 1425 */ 1426 void 1427 cache_put(struct nchandle *nch) 1428 { 1429 _cache_mntrel(nch->mount); 1430 _cache_put(nch->ncp); 1431 nch->ncp = NULL; 1432 nch->mount = NULL; 1433 } 1434 1435 /* 1436 * Resolve an unresolved ncp by associating a vnode with it. If the 1437 * vnode is NULL, a negative cache entry is created. 1438 * 1439 * The ncp should be locked on entry and will remain locked on return. 1440 */ 1441 static 1442 void 1443 _cache_setvp(struct mount *mp, struct namecache *ncp, struct vnode *vp) 1444 { 1445 KKASSERT(ncp->nc_flag & NCF_UNRESOLVED); 1446 KKASSERT(_cache_lockstatus(ncp) == LK_EXCLUSIVE); 1447 1448 if (vp != NULL) { 1449 /* 1450 * Any vp associated with an ncp which has children must 1451 * be held. Any vp associated with a locked ncp must be held. 1452 */ 1453 if (!TAILQ_EMPTY(&ncp->nc_list)) 1454 vhold(vp); 1455 spin_lock(&vp->v_spin); 1456 ncp->nc_vp = vp; 1457 TAILQ_INSERT_HEAD(&vp->v_namecache, ncp, nc_vnode); 1458 spin_unlock(&vp->v_spin); 1459 if (ncp->nc_lockstatus & ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) 1460 vhold(vp); 1461 1462 /* 1463 * Set auxiliary flags 1464 */ 1465 switch(vp->v_type) { 1466 case VDIR: 1467 ncp->nc_flag |= NCF_ISDIR; 1468 break; 1469 case VLNK: 1470 ncp->nc_flag |= NCF_ISSYMLINK; 1471 /* XXX cache the contents of the symlink */ 1472 break; 1473 default: 1474 break; 1475 } 1476 ncp->nc_error = 0; 1477 /* XXX: this is a hack to work-around the lack of a real pfs vfs 1478 * implementation*/ 1479 if (mp != NULL) 1480 if (strncmp(mp->mnt_stat.f_fstypename, "null", 5) == 0) 1481 vp->v_pfsmp = mp; 1482 } else { 1483 /* 1484 * When creating a negative cache hit we set the 1485 * namecache_gen. A later resolve will clean out the 1486 * negative cache hit if the mount point's namecache_gen 1487 * has changed. Used by devfs, could also be used by 1488 * other remote FSs. 1489 */ 1490 struct pcpu_ncache *pn = &pcpu_ncache[mycpu->gd_cpuid]; 1491 1492 ncp->nc_vp = NULL; 1493 ncp->nc_negcpu = mycpu->gd_cpuid; 1494 spin_lock(&pn->neg_spin); 1495 TAILQ_INSERT_TAIL(&pn->neg_list, ncp, nc_vnode); 1496 ++pn->neg_count; 1497 spin_unlock(&pn->neg_spin); 1498 atomic_add_long(&pn->vfscache_negs, 1); 1499 1500 ncp->nc_error = ENOENT; 1501 if (mp) 1502 VFS_NCPGEN_SET(mp, ncp); 1503 } 1504 ncp->nc_flag &= ~(NCF_UNRESOLVED | NCF_DEFEREDZAP); 1505 } 1506 1507 /* 1508 * 1509 */ 1510 void 1511 cache_setvp(struct nchandle *nch, struct vnode *vp) 1512 { 1513 _cache_setvp(nch->mount, nch->ncp, vp); 1514 } 1515 1516 /* 1517 * 1518 */ 1519 void 1520 cache_settimeout(struct nchandle *nch, int nticks) 1521 { 1522 struct namecache *ncp = nch->ncp; 1523 1524 if ((ncp->nc_timeout = ticks + nticks) == 0) 1525 ncp->nc_timeout = 1; 1526 } 1527 1528 /* 1529 * Disassociate the vnode or negative-cache association and mark a 1530 * namecache entry as unresolved again. Note that the ncp is still 1531 * left in the hash table and still linked to its parent. 1532 * 1533 * The ncp should be locked and refd on entry and will remain locked and refd 1534 * on return. 1535 * 1536 * This routine is normally never called on a directory containing children. 1537 * However, NFS often does just that in its rename() code as a cop-out to 1538 * avoid complex namespace operations. This disconnects a directory vnode 1539 * from its namecache and can cause the OLDAPI and NEWAPI to get out of 1540 * sync. 1541 * 1542 */ 1543 static 1544 void 1545 _cache_setunresolved(struct namecache *ncp) 1546 { 1547 struct vnode *vp; 1548 1549 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) { 1550 ncp->nc_flag |= NCF_UNRESOLVED; 1551 ncp->nc_timeout = 0; 1552 ncp->nc_error = ENOTCONN; 1553 if ((vp = ncp->nc_vp) != NULL) { 1554 spin_lock(&vp->v_spin); 1555 ncp->nc_vp = NULL; 1556 TAILQ_REMOVE(&vp->v_namecache, ncp, nc_vnode); 1557 spin_unlock(&vp->v_spin); 1558 1559 /* 1560 * Any vp associated with an ncp with children is 1561 * held by that ncp. Any vp associated with a locked 1562 * ncp is held by that ncp. These conditions must be 1563 * undone when the vp is cleared out from the ncp. 1564 */ 1565 if (!TAILQ_EMPTY(&ncp->nc_list)) 1566 vdrop(vp); 1567 if (ncp->nc_lockstatus & ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) 1568 vdrop(vp); 1569 } else { 1570 struct pcpu_ncache *pn; 1571 1572 pn = &pcpu_ncache[ncp->nc_negcpu]; 1573 1574 atomic_add_long(&pn->vfscache_negs, -1); 1575 spin_lock(&pn->neg_spin); 1576 TAILQ_REMOVE(&pn->neg_list, ncp, nc_vnode); 1577 --pn->neg_count; 1578 spin_unlock(&pn->neg_spin); 1579 } 1580 ncp->nc_flag &= ~(NCF_WHITEOUT|NCF_ISDIR|NCF_ISSYMLINK); 1581 } 1582 } 1583 1584 /* 1585 * The cache_nresolve() code calls this function to automatically 1586 * set a resolved cache element to unresolved if it has timed out 1587 * or if it is a negative cache hit and the mount point namecache_gen 1588 * has changed. 1589 */ 1590 static __inline int 1591 _cache_auto_unresolve_test(struct mount *mp, struct namecache *ncp) 1592 { 1593 /* 1594 * Try to zap entries that have timed out. We have 1595 * to be careful here because locked leafs may depend 1596 * on the vnode remaining intact in a parent, so only 1597 * do this under very specific conditions. 1598 */ 1599 if (ncp->nc_timeout && (int)(ncp->nc_timeout - ticks) < 0 && 1600 TAILQ_EMPTY(&ncp->nc_list)) { 1601 return 1; 1602 } 1603 1604 /* 1605 * If a resolved negative cache hit is invalid due to 1606 * the mount's namecache generation being bumped, zap it. 1607 */ 1608 if (ncp->nc_vp == NULL && VFS_NCPGEN_TEST(mp, ncp)) { 1609 return 1; 1610 } 1611 1612 /* 1613 * Otherwise we are good 1614 */ 1615 return 0; 1616 } 1617 1618 static __inline void 1619 _cache_auto_unresolve(struct mount *mp, struct namecache *ncp) 1620 { 1621 /* 1622 * Already in an unresolved state, nothing to do. 1623 */ 1624 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) { 1625 if (_cache_auto_unresolve_test(mp, ncp)) 1626 _cache_setunresolved(ncp); 1627 } 1628 } 1629 1630 /* 1631 * 1632 */ 1633 void 1634 cache_setunresolved(struct nchandle *nch) 1635 { 1636 _cache_setunresolved(nch->ncp); 1637 } 1638 1639 /* 1640 * Determine if we can clear NCF_ISMOUNTPT by scanning the mountlist 1641 * looking for matches. This flag tells the lookup code when it must 1642 * check for a mount linkage and also prevents the directories in question 1643 * from being deleted or renamed. 1644 */ 1645 static 1646 int 1647 cache_clrmountpt_callback(struct mount *mp, void *data) 1648 { 1649 struct nchandle *nch = data; 1650 1651 if (mp->mnt_ncmounton.ncp == nch->ncp) 1652 return(1); 1653 if (mp->mnt_ncmountpt.ncp == nch->ncp) 1654 return(1); 1655 return(0); 1656 } 1657 1658 /* 1659 * Clear NCF_ISMOUNTPT on nch->ncp if it is no longer associated 1660 * with a mount point. 1661 */ 1662 void 1663 cache_clrmountpt(struct nchandle *nch) 1664 { 1665 int count; 1666 1667 count = mountlist_scan(cache_clrmountpt_callback, nch, 1668 MNTSCAN_FORWARD | MNTSCAN_NOBUSY | 1669 MNTSCAN_NOUNLOCK); 1670 if (count == 0) 1671 nch->ncp->nc_flag &= ~NCF_ISMOUNTPT; 1672 } 1673 1674 /* 1675 * Invalidate portions of the namecache topology given a starting entry. 1676 * The passed ncp is set to an unresolved state and: 1677 * 1678 * The passed ncp must be referencxed and locked. The routine may unlock 1679 * and relock ncp several times, and will recheck the children and loop 1680 * to catch races. When done the passed ncp will be returned with the 1681 * reference and lock intact. 1682 * 1683 * CINV_DESTROY - Set a flag in the passed ncp entry indicating 1684 * that the physical underlying nodes have been 1685 * destroyed... as in deleted. For example, when 1686 * a directory is removed. This will cause record 1687 * lookups on the name to no longer be able to find 1688 * the record and tells the resolver to return failure 1689 * rather then trying to resolve through the parent. 1690 * 1691 * The topology itself, including ncp->nc_name, 1692 * remains intact. 1693 * 1694 * This only applies to the passed ncp, if CINV_CHILDREN 1695 * is specified the children are not flagged. 1696 * 1697 * CINV_CHILDREN - Set all children (recursively) to an unresolved 1698 * state as well. 1699 * 1700 * Note that this will also have the side effect of 1701 * cleaning out any unreferenced nodes in the topology 1702 * from the leaves up as the recursion backs out. 1703 * 1704 * Note that the topology for any referenced nodes remains intact, but 1705 * the nodes will be marked as having been destroyed and will be set 1706 * to an unresolved state. 1707 * 1708 * It is possible for cache_inval() to race a cache_resolve(), meaning that 1709 * the namecache entry may not actually be invalidated on return if it was 1710 * revalidated while recursing down into its children. This code guarentees 1711 * that the node(s) will go through an invalidation cycle, but does not 1712 * guarentee that they will remain in an invalidated state. 1713 * 1714 * Returns non-zero if a revalidation was detected during the invalidation 1715 * recursion, zero otherwise. Note that since only the original ncp is 1716 * locked the revalidation ultimately can only indicate that the original ncp 1717 * *MIGHT* no have been reresolved. 1718 * 1719 * DEEP RECURSION HANDLING - If a recursive invalidation recurses deeply we 1720 * have to avoid blowing out the kernel stack. We do this by saving the 1721 * deep namecache node and aborting the recursion, then re-recursing at that 1722 * node using a depth-first algorithm in order to allow multiple deep 1723 * recursions to chain through each other, then we restart the invalidation 1724 * from scratch. 1725 */ 1726 1727 struct cinvtrack { 1728 struct namecache *resume_ncp; 1729 int depth; 1730 }; 1731 1732 static int _cache_inval_internal(struct namecache *, int, struct cinvtrack *); 1733 1734 static 1735 int 1736 _cache_inval(struct namecache *ncp, int flags) 1737 { 1738 struct cinvtrack track; 1739 struct namecache *ncp2; 1740 int r; 1741 1742 track.depth = 0; 1743 track.resume_ncp = NULL; 1744 1745 for (;;) { 1746 r = _cache_inval_internal(ncp, flags, &track); 1747 if (track.resume_ncp == NULL) 1748 break; 1749 _cache_unlock(ncp); 1750 while ((ncp2 = track.resume_ncp) != NULL) { 1751 track.resume_ncp = NULL; 1752 _cache_lock(ncp2); 1753 _cache_inval_internal(ncp2, flags & ~CINV_DESTROY, 1754 &track); 1755 _cache_put(ncp2); 1756 } 1757 _cache_lock(ncp); 1758 } 1759 return(r); 1760 } 1761 1762 int 1763 cache_inval(struct nchandle *nch, int flags) 1764 { 1765 return(_cache_inval(nch->ncp, flags)); 1766 } 1767 1768 /* 1769 * Helper for _cache_inval(). The passed ncp is refd and locked and 1770 * remains that way on return, but may be unlocked/relocked multiple 1771 * times by the routine. 1772 */ 1773 static int 1774 _cache_inval_internal(struct namecache *ncp, int flags, struct cinvtrack *track) 1775 { 1776 struct namecache *nextkid; 1777 int rcnt = 0; 1778 1779 KKASSERT(_cache_lockstatus(ncp) == LK_EXCLUSIVE); 1780 1781 _cache_setunresolved(ncp); 1782 if (flags & CINV_DESTROY) { 1783 ncp->nc_flag |= NCF_DESTROYED; 1784 ++ncp->nc_generation; 1785 } 1786 while ((flags & CINV_CHILDREN) && 1787 (nextkid = TAILQ_FIRST(&ncp->nc_list)) != NULL 1788 ) { 1789 struct namecache *kid; 1790 int restart; 1791 1792 restart = 0; 1793 _cache_hold(nextkid); 1794 if (++track->depth > MAX_RECURSION_DEPTH) { 1795 track->resume_ncp = ncp; 1796 _cache_hold(ncp); 1797 ++rcnt; 1798 } 1799 while ((kid = nextkid) != NULL) { 1800 /* 1801 * Parent (ncp) must be locked for the iteration. 1802 */ 1803 nextkid = NULL; 1804 if (kid->nc_parent != ncp) { 1805 _cache_drop(kid); 1806 kprintf("cache_inval_internal restartA %s\n", 1807 ncp->nc_name); 1808 restart = 1; 1809 break; 1810 } 1811 if ((nextkid = TAILQ_NEXT(kid, nc_entry)) != NULL) 1812 _cache_hold(nextkid); 1813 1814 /* 1815 * Parent unlocked for this section to avoid 1816 * deadlocks. 1817 */ 1818 _cache_unlock(ncp); 1819 if (track->resume_ncp) { 1820 _cache_drop(kid); 1821 _cache_lock(ncp); 1822 break; 1823 } 1824 if ((kid->nc_flag & NCF_UNRESOLVED) == 0 || 1825 TAILQ_FIRST(&kid->nc_list) 1826 ) { 1827 _cache_lock(kid); 1828 if (kid->nc_parent != ncp) { 1829 kprintf("cache_inval_internal " 1830 "restartB %s\n", 1831 ncp->nc_name); 1832 restart = 1; 1833 _cache_unlock(kid); 1834 _cache_drop(kid); 1835 _cache_lock(ncp); 1836 break; 1837 } 1838 1839 rcnt += _cache_inval_internal(kid, flags & ~CINV_DESTROY, track); 1840 _cache_unlock(kid); 1841 } 1842 _cache_drop(kid); 1843 _cache_lock(ncp); 1844 } 1845 if (nextkid) 1846 _cache_drop(nextkid); 1847 --track->depth; 1848 if (restart == 0) 1849 break; 1850 } 1851 1852 /* 1853 * Someone could have gotten in there while ncp was unlocked, 1854 * retry if so. 1855 */ 1856 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) 1857 ++rcnt; 1858 return (rcnt); 1859 } 1860 1861 /* 1862 * Invalidate a vnode's namecache associations. To avoid races against 1863 * the resolver we do not invalidate a node which we previously invalidated 1864 * but which was then re-resolved while we were in the invalidation loop. 1865 * 1866 * Returns non-zero if any namecache entries remain after the invalidation 1867 * loop completed. 1868 * 1869 * NOTE: Unlike the namecache topology which guarentees that ncp's will not 1870 * be ripped out of the topology while held, the vnode's v_namecache 1871 * list has no such restriction. NCP's can be ripped out of the list 1872 * at virtually any time if not locked, even if held. 1873 * 1874 * In addition, the v_namecache list itself must be locked via 1875 * the vnode's spinlock. 1876 */ 1877 int 1878 cache_inval_vp(struct vnode *vp, int flags) 1879 { 1880 struct namecache *ncp; 1881 struct namecache *next; 1882 1883 restart: 1884 spin_lock(&vp->v_spin); 1885 ncp = TAILQ_FIRST(&vp->v_namecache); 1886 if (ncp) 1887 _cache_hold(ncp); 1888 while (ncp) { 1889 /* loop entered with ncp held and vp spin-locked */ 1890 if ((next = TAILQ_NEXT(ncp, nc_vnode)) != NULL) 1891 _cache_hold(next); 1892 spin_unlock(&vp->v_spin); 1893 _cache_lock(ncp); 1894 if (ncp->nc_vp != vp) { 1895 kprintf("Warning: cache_inval_vp: race-A detected on " 1896 "%s\n", ncp->nc_name); 1897 _cache_put(ncp); 1898 if (next) 1899 _cache_drop(next); 1900 goto restart; 1901 } 1902 _cache_inval(ncp, flags); 1903 _cache_put(ncp); /* also releases reference */ 1904 ncp = next; 1905 spin_lock(&vp->v_spin); 1906 if (ncp && ncp->nc_vp != vp) { 1907 spin_unlock(&vp->v_spin); 1908 kprintf("Warning: cache_inval_vp: race-B detected on " 1909 "%s\n", ncp->nc_name); 1910 _cache_drop(ncp); 1911 goto restart; 1912 } 1913 } 1914 spin_unlock(&vp->v_spin); 1915 return(TAILQ_FIRST(&vp->v_namecache) != NULL); 1916 } 1917 1918 /* 1919 * This routine is used instead of the normal cache_inval_vp() when we 1920 * are trying to recycle otherwise good vnodes. 1921 * 1922 * Return 0 on success, non-zero if not all namecache records could be 1923 * disassociated from the vnode (for various reasons). 1924 */ 1925 int 1926 cache_inval_vp_nonblock(struct vnode *vp) 1927 { 1928 struct namecache *ncp; 1929 struct namecache *next; 1930 1931 spin_lock(&vp->v_spin); 1932 ncp = TAILQ_FIRST(&vp->v_namecache); 1933 if (ncp) 1934 _cache_hold(ncp); 1935 while (ncp) { 1936 /* loop entered with ncp held */ 1937 if ((next = TAILQ_NEXT(ncp, nc_vnode)) != NULL) 1938 _cache_hold(next); 1939 spin_unlock(&vp->v_spin); 1940 if (_cache_lock_nonblock(ncp)) { 1941 _cache_drop(ncp); 1942 if (next) 1943 _cache_drop(next); 1944 goto done; 1945 } 1946 if (ncp->nc_vp != vp) { 1947 kprintf("Warning: cache_inval_vp: race-A detected on " 1948 "%s\n", ncp->nc_name); 1949 _cache_put(ncp); 1950 if (next) 1951 _cache_drop(next); 1952 goto done; 1953 } 1954 _cache_inval(ncp, 0); 1955 _cache_put(ncp); /* also releases reference */ 1956 ncp = next; 1957 spin_lock(&vp->v_spin); 1958 if (ncp && ncp->nc_vp != vp) { 1959 spin_unlock(&vp->v_spin); 1960 kprintf("Warning: cache_inval_vp: race-B detected on " 1961 "%s\n", ncp->nc_name); 1962 _cache_drop(ncp); 1963 goto done; 1964 } 1965 } 1966 spin_unlock(&vp->v_spin); 1967 done: 1968 return(TAILQ_FIRST(&vp->v_namecache) != NULL); 1969 } 1970 1971 /* 1972 * Clears the universal directory search 'ok' flag. This flag allows 1973 * nlookup() to bypass normal vnode checks. This flag is a cached flag 1974 * so clearing it simply forces revalidation. 1975 */ 1976 void 1977 cache_inval_wxok(struct vnode *vp) 1978 { 1979 struct namecache *ncp; 1980 1981 spin_lock(&vp->v_spin); 1982 TAILQ_FOREACH(ncp, &vp->v_namecache, nc_vnode) { 1983 if (ncp->nc_flag & (NCF_WXOK | NCF_NOTX)) 1984 atomic_clear_short(&ncp->nc_flag, NCF_WXOK | NCF_NOTX); 1985 } 1986 spin_unlock(&vp->v_spin); 1987 } 1988 1989 /* 1990 * The source ncp has been renamed to the target ncp. Both fncp and tncp 1991 * must be locked. The target ncp is destroyed (as a normal rename-over 1992 * would destroy the target file or directory). 1993 * 1994 * Because there may be references to the source ncp we cannot copy its 1995 * contents to the target. Instead the source ncp is relinked as the target 1996 * and the target ncp is removed from the namecache topology. 1997 */ 1998 void 1999 cache_rename(struct nchandle *fnch, struct nchandle *tnch) 2000 { 2001 struct namecache *fncp = fnch->ncp; 2002 struct namecache *tncp = tnch->ncp; 2003 struct namecache *tncp_par; 2004 struct nchash_head *nchpp; 2005 u_int32_t hash; 2006 char *oname; 2007 char *nname; 2008 2009 ++fncp->nc_generation; 2010 ++tncp->nc_generation; 2011 if (tncp->nc_nlen) { 2012 nname = kmalloc(tncp->nc_nlen + 1, M_VFSCACHE, M_WAITOK); 2013 bcopy(tncp->nc_name, nname, tncp->nc_nlen); 2014 nname[tncp->nc_nlen] = 0; 2015 } else { 2016 nname = NULL; 2017 } 2018 2019 /* 2020 * Rename fncp (unlink) 2021 */ 2022 _cache_unlink_parent(fncp); 2023 oname = fncp->nc_name; 2024 fncp->nc_name = nname; 2025 fncp->nc_nlen = tncp->nc_nlen; 2026 if (oname) 2027 kfree(oname, M_VFSCACHE); 2028 2029 tncp_par = tncp->nc_parent; 2030 _cache_hold(tncp_par); 2031 _cache_lock(tncp_par); 2032 2033 /* 2034 * Rename fncp (relink) 2035 */ 2036 hash = fnv_32_buf(fncp->nc_name, fncp->nc_nlen, FNV1_32_INIT); 2037 hash = fnv_32_buf(&tncp_par, sizeof(tncp_par), hash); 2038 nchpp = NCHHASH(hash); 2039 2040 spin_lock(&nchpp->spin); 2041 _cache_link_parent(fncp, tncp_par, nchpp); 2042 spin_unlock(&nchpp->spin); 2043 2044 _cache_put(tncp_par); 2045 2046 /* 2047 * Get rid of the overwritten tncp (unlink) 2048 */ 2049 _cache_unlink(tncp); 2050 } 2051 2052 /* 2053 * Perform actions consistent with unlinking a file. The passed-in ncp 2054 * must be locked. 2055 * 2056 * The ncp is marked DESTROYED so it no longer shows up in searches, 2057 * and will be physically deleted when the vnode goes away. 2058 * 2059 * If the related vnode has no refs then we cycle it through vget()/vput() 2060 * to (possibly if we don't have a ref race) trigger a deactivation, 2061 * allowing the VFS to trivially detect and recycle the deleted vnode 2062 * via VOP_INACTIVE(). 2063 * 2064 * NOTE: _cache_rename() will automatically call _cache_unlink() on the 2065 * target ncp. 2066 */ 2067 void 2068 cache_unlink(struct nchandle *nch) 2069 { 2070 _cache_unlink(nch->ncp); 2071 } 2072 2073 static void 2074 _cache_unlink(struct namecache *ncp) 2075 { 2076 struct vnode *vp; 2077 2078 /* 2079 * Causes lookups to fail and allows another ncp with the same 2080 * name to be created under ncp->nc_parent. 2081 */ 2082 ncp->nc_flag |= NCF_DESTROYED; 2083 ++ncp->nc_generation; 2084 2085 /* 2086 * Attempt to trigger a deactivation. Set VREF_FINALIZE to 2087 * force action on the 1->0 transition. 2088 */ 2089 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0 && 2090 (vp = ncp->nc_vp) != NULL) { 2091 atomic_set_int(&vp->v_refcnt, VREF_FINALIZE); 2092 if (VREFCNT(vp) <= 0) { 2093 if (vget(vp, LK_SHARED) == 0) 2094 vput(vp); 2095 } 2096 } 2097 } 2098 2099 /* 2100 * Return non-zero if the nch might be associated with an open and/or mmap()'d 2101 * file. The easy solution is to just return non-zero if the vnode has refs. 2102 * Used to interlock hammer2 reclaims (VREF_FINALIZE should already be set to 2103 * force the reclaim). 2104 */ 2105 int 2106 cache_isopen(struct nchandle *nch) 2107 { 2108 struct vnode *vp; 2109 struct namecache *ncp = nch->ncp; 2110 2111 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0 && 2112 (vp = ncp->nc_vp) != NULL && 2113 VREFCNT(vp)) { 2114 return 1; 2115 } 2116 return 0; 2117 } 2118 2119 2120 /* 2121 * vget the vnode associated with the namecache entry. Resolve the namecache 2122 * entry if necessary. The passed ncp must be referenced and locked. If 2123 * the ncp is resolved it might be locked shared. 2124 * 2125 * lk_type may be LK_SHARED, LK_EXCLUSIVE. A ref'd, possibly locked 2126 * (depending on the passed lk_type) will be returned in *vpp with an error 2127 * of 0, or NULL will be returned in *vpp with a non-0 error code. The 2128 * most typical error is ENOENT, meaning that the ncp represents a negative 2129 * cache hit and there is no vnode to retrieve, but other errors can occur 2130 * too. 2131 * 2132 * The vget() can race a reclaim. If this occurs we re-resolve the 2133 * namecache entry. 2134 * 2135 * There are numerous places in the kernel where vget() is called on a 2136 * vnode while one or more of its namecache entries is locked. Releasing 2137 * a vnode never deadlocks against locked namecache entries (the vnode 2138 * will not get recycled while referenced ncp's exist). This means we 2139 * can safely acquire the vnode. In fact, we MUST NOT release the ncp 2140 * lock when acquiring the vp lock or we might cause a deadlock. 2141 * 2142 * NOTE: The passed-in ncp must be locked exclusively if it is initially 2143 * unresolved. If a reclaim race occurs the passed-in ncp will be 2144 * relocked exclusively before being re-resolved. 2145 */ 2146 int 2147 cache_vget(struct nchandle *nch, struct ucred *cred, 2148 int lk_type, struct vnode **vpp) 2149 { 2150 struct namecache *ncp; 2151 struct vnode *vp; 2152 int error; 2153 2154 ncp = nch->ncp; 2155 again: 2156 vp = NULL; 2157 if (ncp->nc_flag & NCF_UNRESOLVED) 2158 error = cache_resolve(nch, cred); 2159 else 2160 error = 0; 2161 2162 if (error == 0 && (vp = ncp->nc_vp) != NULL) { 2163 error = vget(vp, lk_type); 2164 if (error) { 2165 /* 2166 * VRECLAIM race 2167 * 2168 * The ncp may have been locked shared, we must relock 2169 * it exclusively before we can set it to unresolved. 2170 */ 2171 if (error == ENOENT) { 2172 kprintf("Warning: vnode reclaim race detected " 2173 "in cache_vget on %p (%s)\n", 2174 vp, ncp->nc_name); 2175 _cache_unlock(ncp); 2176 _cache_lock(ncp); 2177 _cache_setunresolved(ncp); 2178 goto again; 2179 } 2180 2181 /* 2182 * Not a reclaim race, some other error. 2183 */ 2184 KKASSERT(ncp->nc_vp == vp); 2185 vp = NULL; 2186 } else { 2187 KKASSERT(ncp->nc_vp == vp); 2188 KKASSERT((vp->v_flag & VRECLAIMED) == 0); 2189 } 2190 } 2191 if (error == 0 && vp == NULL) 2192 error = ENOENT; 2193 *vpp = vp; 2194 return(error); 2195 } 2196 2197 /* 2198 * Similar to cache_vget() but only acquires a ref on the vnode. 2199 * 2200 * NOTE: The passed-in ncp must be locked exclusively if it is initially 2201 * unresolved. If a reclaim race occurs the passed-in ncp will be 2202 * relocked exclusively before being re-resolved. 2203 */ 2204 int 2205 cache_vref(struct nchandle *nch, struct ucred *cred, struct vnode **vpp) 2206 { 2207 struct namecache *ncp; 2208 struct vnode *vp; 2209 int error; 2210 2211 ncp = nch->ncp; 2212 again: 2213 vp = NULL; 2214 if (ncp->nc_flag & NCF_UNRESOLVED) 2215 error = cache_resolve(nch, cred); 2216 else 2217 error = 0; 2218 2219 if (error == 0 && (vp = ncp->nc_vp) != NULL) { 2220 error = vget(vp, LK_SHARED); 2221 if (error) { 2222 /* 2223 * VRECLAIM race 2224 */ 2225 if (error == ENOENT) { 2226 kprintf("Warning: vnode reclaim race detected " 2227 "in cache_vget on %p (%s)\n", 2228 vp, ncp->nc_name); 2229 _cache_unlock(ncp); 2230 _cache_lock(ncp); 2231 _cache_setunresolved(ncp); 2232 goto again; 2233 } 2234 2235 /* 2236 * Not a reclaim race, some other error. 2237 */ 2238 KKASSERT(ncp->nc_vp == vp); 2239 vp = NULL; 2240 } else { 2241 KKASSERT(ncp->nc_vp == vp); 2242 KKASSERT((vp->v_flag & VRECLAIMED) == 0); 2243 /* caller does not want a lock */ 2244 vn_unlock(vp); 2245 } 2246 } 2247 if (error == 0 && vp == NULL) 2248 error = ENOENT; 2249 *vpp = vp; 2250 return(error); 2251 } 2252 2253 /* 2254 * Return a referenced vnode representing the parent directory of 2255 * ncp. 2256 * 2257 * Because the caller has locked the ncp it should not be possible for 2258 * the parent ncp to go away. However, the parent can unresolve its 2259 * dvp at any time so we must be able to acquire a lock on the parent 2260 * to safely access nc_vp. 2261 * 2262 * We have to leave par unlocked when vget()ing dvp to avoid a deadlock, 2263 * so use vhold()/vdrop() while holding the lock to prevent dvp from 2264 * getting destroyed. 2265 * 2266 * NOTE: vhold() is allowed when dvp has 0 refs if we hold a 2267 * lock on the ncp in question.. 2268 */ 2269 static struct vnode * 2270 cache_dvpref(struct namecache *ncp) 2271 { 2272 struct namecache *par; 2273 struct vnode *dvp; 2274 2275 dvp = NULL; 2276 if ((par = ncp->nc_parent) != NULL) { 2277 _cache_hold(par); 2278 _cache_lock(par); 2279 if ((par->nc_flag & NCF_UNRESOLVED) == 0) { 2280 if ((dvp = par->nc_vp) != NULL) 2281 vhold(dvp); 2282 } 2283 _cache_unlock(par); 2284 if (dvp) { 2285 if (vget(dvp, LK_SHARED) == 0) { 2286 vn_unlock(dvp); 2287 vdrop(dvp); 2288 /* return refd, unlocked dvp */ 2289 } else { 2290 vdrop(dvp); 2291 dvp = NULL; 2292 } 2293 } 2294 _cache_drop(par); 2295 } 2296 return(dvp); 2297 } 2298 2299 /* 2300 * Convert a directory vnode to a namecache record without any other 2301 * knowledge of the topology. This ONLY works with directory vnodes and 2302 * is ONLY used by the NFS server. dvp must be refd but unlocked, and the 2303 * returned ncp (if not NULL) will be held and unlocked. 2304 * 2305 * If 'makeit' is 0 and dvp has no existing namecache record, NULL is returned. 2306 * If 'makeit' is 1 we attempt to track-down and create the namecache topology 2307 * for dvp. This will fail only if the directory has been deleted out from 2308 * under the caller. 2309 * 2310 * Callers must always check for a NULL return no matter the value of 'makeit'. 2311 * 2312 * To avoid underflowing the kernel stack each recursive call increments 2313 * the makeit variable. 2314 */ 2315 2316 static int cache_inefficient_scan(struct nchandle *nch, struct ucred *cred, 2317 struct vnode *dvp, char *fakename); 2318 static int cache_fromdvp_try(struct vnode *dvp, struct ucred *cred, 2319 struct vnode **saved_dvp); 2320 2321 int 2322 cache_fromdvp(struct vnode *dvp, struct ucred *cred, int makeit, 2323 struct nchandle *nch) 2324 { 2325 struct vnode *saved_dvp; 2326 struct vnode *pvp; 2327 char *fakename; 2328 int error; 2329 2330 nch->ncp = NULL; 2331 nch->mount = dvp->v_mount; 2332 saved_dvp = NULL; 2333 fakename = NULL; 2334 2335 /* 2336 * Handle the makeit == 0 degenerate case 2337 */ 2338 if (makeit == 0) { 2339 spin_lock_shared(&dvp->v_spin); 2340 nch->ncp = TAILQ_FIRST(&dvp->v_namecache); 2341 if (nch->ncp) 2342 cache_hold(nch); 2343 spin_unlock_shared(&dvp->v_spin); 2344 } 2345 2346 /* 2347 * Loop until resolution, inside code will break out on error. 2348 */ 2349 while (makeit) { 2350 /* 2351 * Break out if we successfully acquire a working ncp. 2352 */ 2353 spin_lock_shared(&dvp->v_spin); 2354 nch->ncp = TAILQ_FIRST(&dvp->v_namecache); 2355 if (nch->ncp) { 2356 cache_hold(nch); 2357 spin_unlock_shared(&dvp->v_spin); 2358 break; 2359 } 2360 spin_unlock_shared(&dvp->v_spin); 2361 2362 /* 2363 * If dvp is the root of its filesystem it should already 2364 * have a namecache pointer associated with it as a side 2365 * effect of the mount, but it may have been disassociated. 2366 */ 2367 if (dvp->v_flag & VROOT) { 2368 nch->ncp = _cache_get(nch->mount->mnt_ncmountpt.ncp); 2369 error = cache_resolve_mp(nch->mount); 2370 _cache_put(nch->ncp); 2371 if (ncvp_debug) { 2372 kprintf("cache_fromdvp: resolve root of mount %p error %d", 2373 dvp->v_mount, error); 2374 } 2375 if (error) { 2376 if (ncvp_debug) 2377 kprintf(" failed\n"); 2378 nch->ncp = NULL; 2379 break; 2380 } 2381 if (ncvp_debug) 2382 kprintf(" succeeded\n"); 2383 continue; 2384 } 2385 2386 /* 2387 * If we are recursed too deeply resort to an O(n^2) 2388 * algorithm to resolve the namecache topology. The 2389 * resolved pvp is left referenced in saved_dvp to 2390 * prevent the tree from being destroyed while we loop. 2391 */ 2392 if (makeit > 20) { 2393 error = cache_fromdvp_try(dvp, cred, &saved_dvp); 2394 if (error) { 2395 kprintf("lookupdotdot(longpath) failed %d " 2396 "dvp %p\n", error, dvp); 2397 nch->ncp = NULL; 2398 break; 2399 } 2400 continue; 2401 } 2402 2403 /* 2404 * Get the parent directory and resolve its ncp. 2405 */ 2406 if (fakename) { 2407 kfree(fakename, M_TEMP); 2408 fakename = NULL; 2409 } 2410 error = vop_nlookupdotdot(*dvp->v_ops, dvp, &pvp, cred, 2411 &fakename); 2412 if (error) { 2413 kprintf("lookupdotdot failed %d dvp %p\n", error, dvp); 2414 break; 2415 } 2416 vn_unlock(pvp); 2417 2418 /* 2419 * Reuse makeit as a recursion depth counter. On success 2420 * nch will be fully referenced. 2421 */ 2422 cache_fromdvp(pvp, cred, makeit + 1, nch); 2423 vrele(pvp); 2424 if (nch->ncp == NULL) 2425 break; 2426 2427 /* 2428 * Do an inefficient scan of pvp (embodied by ncp) to look 2429 * for dvp. This will create a namecache record for dvp on 2430 * success. We loop up to recheck on success. 2431 * 2432 * ncp and dvp are both held but not locked. 2433 */ 2434 error = cache_inefficient_scan(nch, cred, dvp, fakename); 2435 if (error) { 2436 kprintf("cache_fromdvp: scan %p (%s) failed on dvp=%p\n", 2437 pvp, nch->ncp->nc_name, dvp); 2438 cache_drop(nch); 2439 /* nch was NULLed out, reload mount */ 2440 nch->mount = dvp->v_mount; 2441 break; 2442 } 2443 if (ncvp_debug) { 2444 kprintf("cache_fromdvp: scan %p (%s) succeeded\n", 2445 pvp, nch->ncp->nc_name); 2446 } 2447 cache_drop(nch); 2448 /* nch was NULLed out, reload mount */ 2449 nch->mount = dvp->v_mount; 2450 } 2451 2452 /* 2453 * If nch->ncp is non-NULL it will have been held already. 2454 */ 2455 if (fakename) 2456 kfree(fakename, M_TEMP); 2457 if (saved_dvp) 2458 vrele(saved_dvp); 2459 if (nch->ncp) 2460 return (0); 2461 return (EINVAL); 2462 } 2463 2464 /* 2465 * Go up the chain of parent directories until we find something 2466 * we can resolve into the namecache. This is very inefficient. 2467 */ 2468 static 2469 int 2470 cache_fromdvp_try(struct vnode *dvp, struct ucred *cred, 2471 struct vnode **saved_dvp) 2472 { 2473 struct nchandle nch; 2474 struct vnode *pvp; 2475 int error; 2476 static time_t last_fromdvp_report; 2477 char *fakename; 2478 2479 /* 2480 * Loop getting the parent directory vnode until we get something we 2481 * can resolve in the namecache. 2482 */ 2483 vref(dvp); 2484 nch.mount = dvp->v_mount; 2485 nch.ncp = NULL; 2486 fakename = NULL; 2487 2488 for (;;) { 2489 if (fakename) { 2490 kfree(fakename, M_TEMP); 2491 fakename = NULL; 2492 } 2493 error = vop_nlookupdotdot(*dvp->v_ops, dvp, &pvp, cred, 2494 &fakename); 2495 if (error) { 2496 vrele(dvp); 2497 break; 2498 } 2499 vn_unlock(pvp); 2500 spin_lock_shared(&pvp->v_spin); 2501 if ((nch.ncp = TAILQ_FIRST(&pvp->v_namecache)) != NULL) { 2502 _cache_hold(nch.ncp); 2503 spin_unlock_shared(&pvp->v_spin); 2504 vrele(pvp); 2505 break; 2506 } 2507 spin_unlock_shared(&pvp->v_spin); 2508 if (pvp->v_flag & VROOT) { 2509 nch.ncp = _cache_get(pvp->v_mount->mnt_ncmountpt.ncp); 2510 error = cache_resolve_mp(nch.mount); 2511 _cache_unlock(nch.ncp); 2512 vrele(pvp); 2513 if (error) { 2514 _cache_drop(nch.ncp); 2515 nch.ncp = NULL; 2516 vrele(dvp); 2517 } 2518 break; 2519 } 2520 vrele(dvp); 2521 dvp = pvp; 2522 } 2523 if (error == 0) { 2524 if (last_fromdvp_report != time_uptime) { 2525 last_fromdvp_report = time_uptime; 2526 kprintf("Warning: extremely inefficient path " 2527 "resolution on %s\n", 2528 nch.ncp->nc_name); 2529 } 2530 error = cache_inefficient_scan(&nch, cred, dvp, fakename); 2531 2532 /* 2533 * Hopefully dvp now has a namecache record associated with 2534 * it. Leave it referenced to prevent the kernel from 2535 * recycling the vnode. Otherwise extremely long directory 2536 * paths could result in endless recycling. 2537 */ 2538 if (*saved_dvp) 2539 vrele(*saved_dvp); 2540 *saved_dvp = dvp; 2541 _cache_drop(nch.ncp); 2542 } 2543 if (fakename) 2544 kfree(fakename, M_TEMP); 2545 return (error); 2546 } 2547 2548 /* 2549 * Do an inefficient scan of the directory represented by ncp looking for 2550 * the directory vnode dvp. ncp must be held but not locked on entry and 2551 * will be held on return. dvp must be refd but not locked on entry and 2552 * will remain refd on return. 2553 * 2554 * Why do this at all? Well, due to its stateless nature the NFS server 2555 * converts file handles directly to vnodes without necessarily going through 2556 * the namecache ops that would otherwise create the namecache topology 2557 * leading to the vnode. We could either (1) Change the namecache algorithms 2558 * to allow disconnect namecache records that are re-merged opportunistically, 2559 * or (2) Make the NFS server backtrack and scan to recover a connected 2560 * namecache topology in order to then be able to issue new API lookups. 2561 * 2562 * It turns out that (1) is a huge mess. It takes a nice clean set of 2563 * namecache algorithms and introduces a lot of complication in every subsystem 2564 * that calls into the namecache to deal with the re-merge case, especially 2565 * since we are using the namecache to placehold negative lookups and the 2566 * vnode might not be immediately assigned. (2) is certainly far less 2567 * efficient then (1), but since we are only talking about directories here 2568 * (which are likely to remain cached), the case does not actually run all 2569 * that often and has the supreme advantage of not polluting the namecache 2570 * algorithms. 2571 * 2572 * If a fakename is supplied just construct a namecache entry using the 2573 * fake name. 2574 */ 2575 static int 2576 cache_inefficient_scan(struct nchandle *nch, struct ucred *cred, 2577 struct vnode *dvp, char *fakename) 2578 { 2579 struct nlcomponent nlc; 2580 struct nchandle rncp; 2581 struct dirent *den; 2582 struct vnode *pvp; 2583 struct vattr vat; 2584 struct iovec iov; 2585 struct uio uio; 2586 int blksize; 2587 int eofflag; 2588 int bytes; 2589 char *rbuf; 2590 int error; 2591 2592 vat.va_blocksize = 0; 2593 if ((error = VOP_GETATTR(dvp, &vat)) != 0) 2594 return (error); 2595 cache_lock(nch); 2596 error = cache_vref(nch, cred, &pvp); 2597 cache_unlock(nch); 2598 if (error) 2599 return (error); 2600 if (ncvp_debug) { 2601 kprintf("inefficient_scan of (%p,%s): directory iosize %ld " 2602 "vattr fileid = %lld\n", 2603 nch->ncp, nch->ncp->nc_name, 2604 vat.va_blocksize, 2605 (long long)vat.va_fileid); 2606 } 2607 2608 /* 2609 * Use the supplied fakename if not NULL. Fake names are typically 2610 * not in the actual filesystem hierarchy. This is used by HAMMER 2611 * to glue @@timestamp recursions together. 2612 */ 2613 if (fakename) { 2614 nlc.nlc_nameptr = fakename; 2615 nlc.nlc_namelen = strlen(fakename); 2616 rncp = cache_nlookup(nch, &nlc); 2617 goto done; 2618 } 2619 2620 if ((blksize = vat.va_blocksize) == 0) 2621 blksize = DEV_BSIZE; 2622 rbuf = kmalloc(blksize, M_TEMP, M_WAITOK); 2623 rncp.ncp = NULL; 2624 2625 eofflag = 0; 2626 uio.uio_offset = 0; 2627 again: 2628 iov.iov_base = rbuf; 2629 iov.iov_len = blksize; 2630 uio.uio_iov = &iov; 2631 uio.uio_iovcnt = 1; 2632 uio.uio_resid = blksize; 2633 uio.uio_segflg = UIO_SYSSPACE; 2634 uio.uio_rw = UIO_READ; 2635 uio.uio_td = curthread; 2636 2637 if (ncvp_debug >= 2) 2638 kprintf("cache_inefficient_scan: readdir @ %08x\n", (int)uio.uio_offset); 2639 error = VOP_READDIR(pvp, &uio, cred, &eofflag, NULL, NULL); 2640 if (error == 0) { 2641 den = (struct dirent *)rbuf; 2642 bytes = blksize - uio.uio_resid; 2643 2644 while (bytes > 0) { 2645 if (ncvp_debug >= 2) { 2646 kprintf("cache_inefficient_scan: %*.*s\n", 2647 den->d_namlen, den->d_namlen, 2648 den->d_name); 2649 } 2650 if (den->d_type != DT_WHT && 2651 den->d_ino == vat.va_fileid) { 2652 if (ncvp_debug) { 2653 kprintf("cache_inefficient_scan: " 2654 "MATCHED inode %lld path %s/%*.*s\n", 2655 (long long)vat.va_fileid, 2656 nch->ncp->nc_name, 2657 den->d_namlen, den->d_namlen, 2658 den->d_name); 2659 } 2660 nlc.nlc_nameptr = den->d_name; 2661 nlc.nlc_namelen = den->d_namlen; 2662 rncp = cache_nlookup(nch, &nlc); 2663 KKASSERT(rncp.ncp != NULL); 2664 break; 2665 } 2666 bytes -= _DIRENT_DIRSIZ(den); 2667 den = _DIRENT_NEXT(den); 2668 } 2669 if (rncp.ncp == NULL && eofflag == 0 && uio.uio_resid != blksize) 2670 goto again; 2671 } 2672 kfree(rbuf, M_TEMP); 2673 done: 2674 vrele(pvp); 2675 if (rncp.ncp) { 2676 if (rncp.ncp->nc_flag & NCF_UNRESOLVED) { 2677 _cache_setvp(rncp.mount, rncp.ncp, dvp); 2678 if (ncvp_debug >= 2) { 2679 kprintf("cache_inefficient_scan: setvp %s/%s = %p\n", 2680 nch->ncp->nc_name, rncp.ncp->nc_name, dvp); 2681 } 2682 } else { 2683 if (ncvp_debug >= 2) { 2684 kprintf("cache_inefficient_scan: setvp %s/%s already set %p/%p\n", 2685 nch->ncp->nc_name, rncp.ncp->nc_name, dvp, 2686 rncp.ncp->nc_vp); 2687 } 2688 } 2689 if (rncp.ncp->nc_vp == NULL) 2690 error = rncp.ncp->nc_error; 2691 /* 2692 * Release rncp after a successful nlookup. rncp was fully 2693 * referenced. 2694 */ 2695 cache_put(&rncp); 2696 } else { 2697 kprintf("cache_inefficient_scan: dvp %p NOT FOUND in %s\n", 2698 dvp, nch->ncp->nc_name); 2699 error = ENOENT; 2700 } 2701 return (error); 2702 } 2703 2704 /* 2705 * Zap a namecache entry. The ncp is unconditionally set to an unresolved 2706 * state, which disassociates it from its vnode or pcpu_ncache[n].neg_list. 2707 * 2708 * Then, if there are no additional references to the ncp and no children, 2709 * the ncp is removed from the topology and destroyed. 2710 * 2711 * References and/or children may exist if the ncp is in the middle of the 2712 * topology, preventing the ncp from being destroyed. 2713 * 2714 * This function must be called with the ncp held and locked and will unlock 2715 * and drop it during zapping. 2716 * 2717 * If nonblock is non-zero and the parent ncp cannot be locked we give up. 2718 * This case can occur in the cache_drop() path. 2719 * 2720 * This function may returned a held (but NOT locked) parent node which the 2721 * caller must drop. We do this so _cache_drop() can loop, to avoid 2722 * blowing out the kernel stack. 2723 * 2724 * WARNING! For MPSAFE operation this routine must acquire up to three 2725 * spin locks to be able to safely test nc_refs. Lock order is 2726 * very important. 2727 * 2728 * hash spinlock if on hash list 2729 * parent spinlock if child of parent 2730 * (the ncp is unresolved so there is no vnode association) 2731 */ 2732 static struct namecache * 2733 cache_zap(struct namecache *ncp, int nonblock) 2734 { 2735 struct namecache *par; 2736 struct vnode *dropvp; 2737 struct nchash_head *nchpp; 2738 int refs; 2739 2740 /* 2741 * Disassociate the vnode or negative cache ref and set NCF_UNRESOLVED. 2742 */ 2743 _cache_setunresolved(ncp); 2744 2745 /* 2746 * Try to scrap the entry and possibly tail-recurse on its parent. 2747 * We only scrap unref'd (other then our ref) unresolved entries, 2748 * we do not scrap 'live' entries. 2749 * 2750 * Note that once the spinlocks are acquired if nc_refs == 1 no 2751 * other references are possible. If it isn't, however, we have 2752 * to decrement but also be sure to avoid a 1->0 transition. 2753 */ 2754 KKASSERT(ncp->nc_flag & NCF_UNRESOLVED); 2755 KKASSERT(ncp->nc_refs > 0); 2756 2757 /* 2758 * Acquire locks. Note that the parent can't go away while we hold 2759 * a child locked. 2760 */ 2761 nchpp = NULL; 2762 if ((par = ncp->nc_parent) != NULL) { 2763 if (nonblock) { 2764 for (;;) { 2765 if (_cache_lock_nonblock(par) == 0) 2766 break; 2767 refs = ncp->nc_refs; 2768 ncp->nc_flag |= NCF_DEFEREDZAP; 2769 atomic_add_long( 2770 &pcpu_ncache[mycpu->gd_cpuid].numdefered, 2771 1); 2772 if (atomic_cmpset_int(&ncp->nc_refs, 2773 refs, refs - 1)) { 2774 _cache_unlock(ncp); 2775 return(NULL); 2776 } 2777 cpu_pause(); 2778 } 2779 _cache_hold(par); 2780 } else { 2781 _cache_hold(par); 2782 _cache_lock(par); 2783 } 2784 nchpp = ncp->nc_head; 2785 spin_lock(&nchpp->spin); 2786 } 2787 2788 /* 2789 * At this point if we find refs == 1 it should not be possible for 2790 * anyone else to have access to the ncp. We are holding the only 2791 * possible access point left (nchpp) spin-locked. 2792 * 2793 * If someone other then us has a ref or we have children 2794 * we cannot zap the entry. The 1->0 transition and any 2795 * further list operation is protected by the spinlocks 2796 * we have acquired but other transitions are not. 2797 */ 2798 for (;;) { 2799 refs = ncp->nc_refs; 2800 cpu_ccfence(); 2801 if (refs == 1 && TAILQ_EMPTY(&ncp->nc_list)) 2802 break; 2803 if (atomic_cmpset_int(&ncp->nc_refs, refs, refs - 1)) { 2804 if (par) { 2805 spin_unlock(&nchpp->spin); 2806 _cache_put(par); 2807 } 2808 _cache_unlock(ncp); 2809 return(NULL); 2810 } 2811 cpu_pause(); 2812 } 2813 2814 /* 2815 * We are the only ref and with the spinlocks held no further 2816 * refs can be acquired by others. 2817 * 2818 * Remove us from the hash list and parent list. We have to 2819 * drop a ref on the parent's vp if the parent's list becomes 2820 * empty. 2821 */ 2822 dropvp = NULL; 2823 if (par) { 2824 struct pcpu_ncache *pn = &pcpu_ncache[mycpu->gd_cpuid]; 2825 2826 KKASSERT(nchpp == ncp->nc_head); 2827 TAILQ_REMOVE(&ncp->nc_head->list, ncp, nc_hash); 2828 TAILQ_REMOVE(&par->nc_list, ncp, nc_entry); 2829 atomic_add_long(&pn->vfscache_count, -1); 2830 if (TAILQ_EMPTY(&ncp->nc_list)) 2831 atomic_add_long(&pn->vfscache_leafs, -1); 2832 2833 if (TAILQ_EMPTY(&par->nc_list)) { 2834 atomic_add_long(&pn->vfscache_leafs, 1); 2835 if (par->nc_vp) 2836 dropvp = par->nc_vp; 2837 } 2838 ncp->nc_head = NULL; 2839 ncp->nc_parent = NULL; 2840 spin_unlock(&nchpp->spin); 2841 _cache_unlock(par); 2842 } else { 2843 KKASSERT(ncp->nc_head == NULL); 2844 } 2845 2846 /* 2847 * ncp should not have picked up any refs. Physically 2848 * destroy the ncp. 2849 */ 2850 if (ncp->nc_refs != 1) { 2851 int save_refs = ncp->nc_refs; 2852 cpu_ccfence(); 2853 panic("cache_zap: %p bad refs %d (%d)\n", 2854 ncp, save_refs, atomic_fetchadd_int(&ncp->nc_refs, 0)); 2855 } 2856 KKASSERT(ncp->nc_refs == 1); 2857 /* _cache_unlock(ncp) not required */ 2858 ncp->nc_refs = -1; /* safety */ 2859 if (ncp->nc_name) 2860 kfree(ncp->nc_name, M_VFSCACHE); 2861 kfree(ncp, M_VFSCACHE); 2862 2863 /* 2864 * Delayed drop (we had to release our spinlocks) 2865 * 2866 * The refed parent (if not NULL) must be dropped. The 2867 * caller is responsible for looping. 2868 */ 2869 if (dropvp) 2870 vdrop(dropvp); 2871 return(par); 2872 } 2873 2874 /* 2875 * Clean up dangling negative cache and defered-drop entries in the 2876 * namecache. 2877 * 2878 * This routine is called in the critical path and also called from 2879 * vnlru(). When called from vnlru we use a lower limit to try to 2880 * deal with the negative cache before the critical path has to start 2881 * dealing with it. 2882 */ 2883 typedef enum { CHI_LOW, CHI_HIGH } cache_hs_t; 2884 2885 static cache_hs_t neg_cache_hysteresis_state[2] = { CHI_LOW, CHI_LOW }; 2886 static cache_hs_t pos_cache_hysteresis_state[2] = { CHI_LOW, CHI_LOW }; 2887 2888 void 2889 cache_hysteresis(int critpath) 2890 { 2891 long poslimit; 2892 long neglimit = maxvnodes / ncnegfactor; 2893 long xnumcache = vfscache_leafs; 2894 2895 if (critpath == 0) 2896 neglimit = neglimit * 8 / 10; 2897 2898 /* 2899 * Don't cache too many negative hits. We use hysteresis to reduce 2900 * the impact on the critical path. 2901 */ 2902 switch(neg_cache_hysteresis_state[critpath]) { 2903 case CHI_LOW: 2904 if (vfscache_negs > MINNEG && vfscache_negs > neglimit) { 2905 if (critpath) 2906 _cache_cleanneg(ncnegflush); 2907 else 2908 _cache_cleanneg(ncnegflush + 2909 vfscache_negs - neglimit); 2910 neg_cache_hysteresis_state[critpath] = CHI_HIGH; 2911 } 2912 break; 2913 case CHI_HIGH: 2914 if (vfscache_negs > MINNEG * 9 / 10 && 2915 vfscache_negs * 9 / 10 > neglimit 2916 ) { 2917 if (critpath) 2918 _cache_cleanneg(ncnegflush); 2919 else 2920 _cache_cleanneg(ncnegflush + 2921 vfscache_negs * 9 / 10 - 2922 neglimit); 2923 } else { 2924 neg_cache_hysteresis_state[critpath] = CHI_LOW; 2925 } 2926 break; 2927 } 2928 2929 /* 2930 * Don't cache too many positive hits. We use hysteresis to reduce 2931 * the impact on the critical path. 2932 * 2933 * Excessive positive hits can accumulate due to large numbers of 2934 * hardlinks (the vnode cache will not prevent hl ncps from growing 2935 * into infinity). 2936 */ 2937 if ((poslimit = ncposlimit) == 0) 2938 poslimit = maxvnodes * 2; 2939 if (critpath == 0) 2940 poslimit = poslimit * 8 / 10; 2941 2942 switch(pos_cache_hysteresis_state[critpath]) { 2943 case CHI_LOW: 2944 if (xnumcache > poslimit && xnumcache > MINPOS) { 2945 if (critpath) 2946 _cache_cleanpos(ncposflush); 2947 else 2948 _cache_cleanpos(ncposflush + 2949 xnumcache - poslimit); 2950 pos_cache_hysteresis_state[critpath] = CHI_HIGH; 2951 } 2952 break; 2953 case CHI_HIGH: 2954 if (xnumcache > poslimit * 5 / 6 && xnumcache > MINPOS) { 2955 if (critpath) 2956 _cache_cleanpos(ncposflush); 2957 else 2958 _cache_cleanpos(ncposflush + 2959 xnumcache - poslimit * 5 / 6); 2960 } else { 2961 pos_cache_hysteresis_state[critpath] = CHI_LOW; 2962 } 2963 break; 2964 } 2965 2966 /* 2967 * Clean out dangling defered-zap ncps which could not be cleanly 2968 * dropped if too many build up. Note that numdefered is 2969 * heuristical. Make sure we are real-time for the current cpu, 2970 * plus the global rollup. 2971 */ 2972 if (pcpu_ncache[mycpu->gd_cpuid].numdefered + numdefered > neglimit) { 2973 _cache_cleandefered(); 2974 } 2975 } 2976 2977 /* 2978 * NEW NAMECACHE LOOKUP API 2979 * 2980 * Lookup an entry in the namecache. The passed par_nch must be referenced 2981 * and unlocked. A referenced and locked nchandle with a non-NULL nch.ncp 2982 * is ALWAYS returned, eve if the supplied component is illegal. 2983 * 2984 * The resulting namecache entry should be returned to the system with 2985 * cache_put() or cache_unlock() + cache_drop(). 2986 * 2987 * namecache locks are recursive but care must be taken to avoid lock order 2988 * reversals (hence why the passed par_nch must be unlocked). Locking 2989 * rules are to order for parent traversals, not for child traversals. 2990 * 2991 * Nobody else will be able to manipulate the associated namespace (e.g. 2992 * create, delete, rename, rename-target) until the caller unlocks the 2993 * entry. 2994 * 2995 * The returned entry will be in one of three states: positive hit (non-null 2996 * vnode), negative hit (null vnode), or unresolved (NCF_UNRESOLVED is set). 2997 * Unresolved entries must be resolved through the filesystem to associate the 2998 * vnode and/or determine whether a positive or negative hit has occured. 2999 * 3000 * It is not necessary to lock a directory in order to lock namespace under 3001 * that directory. In fact, it is explicitly not allowed to do that. A 3002 * directory is typically only locked when being created, renamed, or 3003 * destroyed. 3004 * 3005 * The directory (par) may be unresolved, in which case any returned child 3006 * will likely also be marked unresolved. Likely but not guarenteed. Since 3007 * the filesystem lookup requires a resolved directory vnode the caller is 3008 * responsible for resolving the namecache chain top-down. This API 3009 * specifically allows whole chains to be created in an unresolved state. 3010 */ 3011 struct nchandle 3012 cache_nlookup(struct nchandle *par_nch, struct nlcomponent *nlc) 3013 { 3014 struct nchandle nch; 3015 struct namecache *ncp; 3016 struct namecache *new_ncp; 3017 struct namecache *rep_ncp; /* reuse a destroyed ncp */ 3018 struct nchash_head *nchpp; 3019 struct mount *mp; 3020 u_int32_t hash; 3021 globaldata_t gd; 3022 int par_locked; 3023 3024 gd = mycpu; 3025 mp = par_nch->mount; 3026 par_locked = 0; 3027 3028 /* 3029 * This is a good time to call it, no ncp's are locked by 3030 * the caller or us. 3031 */ 3032 cache_hysteresis(1); 3033 3034 /* 3035 * Try to locate an existing entry 3036 */ 3037 hash = fnv_32_buf(nlc->nlc_nameptr, nlc->nlc_namelen, FNV1_32_INIT); 3038 hash = fnv_32_buf(&par_nch->ncp, sizeof(par_nch->ncp), hash); 3039 new_ncp = NULL; 3040 nchpp = NCHHASH(hash); 3041 restart: 3042 rep_ncp = NULL; 3043 if (new_ncp) 3044 spin_lock(&nchpp->spin); 3045 else 3046 spin_lock_shared(&nchpp->spin); 3047 3048 TAILQ_FOREACH(ncp, &nchpp->list, nc_hash) { 3049 /* 3050 * Break out if we find a matching entry. Note that 3051 * UNRESOLVED entries may match, but DESTROYED entries 3052 * do not. 3053 * 3054 * We may be able to reuse DESTROYED entries that we come 3055 * across, even if the name does not match, as long as 3056 * nc_nlen is correct. 3057 */ 3058 if (ncp->nc_parent == par_nch->ncp && 3059 ncp->nc_nlen == nlc->nlc_namelen) { 3060 if (ncp->nc_flag & NCF_DESTROYED) { 3061 if (ncp->nc_refs == 0 && rep_ncp == NULL) 3062 rep_ncp = ncp; 3063 continue; 3064 } 3065 if (bcmp(ncp->nc_name, nlc->nlc_nameptr, ncp->nc_nlen)) 3066 continue; 3067 _cache_hold(ncp); 3068 if (new_ncp) 3069 spin_unlock(&nchpp->spin); 3070 else 3071 spin_unlock_shared(&nchpp->spin); 3072 if (par_locked) { 3073 _cache_unlock(par_nch->ncp); 3074 par_locked = 0; 3075 } 3076 if (_cache_lock_special(ncp) == 0) { 3077 /* 3078 * Successfully locked but we must re-test 3079 * conditions that might have changed since 3080 * we did not have the lock before. 3081 */ 3082 if (ncp->nc_parent != par_nch->ncp || 3083 ncp->nc_nlen != nlc->nlc_namelen || 3084 bcmp(ncp->nc_name, nlc->nlc_nameptr, 3085 ncp->nc_nlen) || 3086 (ncp->nc_flag & NCF_DESTROYED)) { 3087 _cache_put(ncp); 3088 goto restart; 3089 } 3090 _cache_auto_unresolve(mp, ncp); 3091 if (new_ncp) 3092 _cache_free(new_ncp); 3093 goto found; 3094 } 3095 _cache_get(ncp); /* cycle the lock to block */ 3096 _cache_put(ncp); 3097 _cache_drop(ncp); 3098 goto restart; 3099 } 3100 } 3101 3102 /* 3103 * We failed to locate the entry, try to resurrect a destroyed 3104 * entry that we did find that is already correctly linked into 3105 * nchpp and the parent. We must re-test conditions after 3106 * successfully locking rep_ncp. 3107 * 3108 * This case can occur under heavy loads due to not being able 3109 * to safely lock the parent in cache_zap(). Nominally a repeated 3110 * create/unlink load, but only the namelen needs to match. 3111 */ 3112 if (rep_ncp && new_ncp == NULL) { 3113 if (_cache_lock_nonblock(rep_ncp) == 0) { 3114 _cache_hold(rep_ncp); 3115 if (rep_ncp->nc_parent == par_nch->ncp && 3116 rep_ncp->nc_nlen == nlc->nlc_namelen && 3117 (rep_ncp->nc_flag & NCF_DESTROYED)) { 3118 /* 3119 * Update nc_name as reuse as new. 3120 */ 3121 ncp = rep_ncp; 3122 bcopy(nlc->nlc_nameptr, ncp->nc_name, 3123 nlc->nlc_namelen); 3124 spin_unlock_shared(&nchpp->spin); 3125 _cache_setunresolved(ncp); 3126 ncp->nc_flag = NCF_UNRESOLVED; 3127 ncp->nc_error = ENOTCONN; 3128 goto found; 3129 } 3130 _cache_put(rep_ncp); 3131 } 3132 } 3133 3134 /* 3135 * Otherwise create a new entry and add it to the cache. The parent 3136 * ncp must also be locked so we can link into it. 3137 * 3138 * We have to relookup after possibly blocking in kmalloc or 3139 * when locking par_nch. 3140 * 3141 * NOTE: nlc_namelen can be 0 and nlc_nameptr NULL as a special 3142 * mount case, in which case nc_name will be NULL. 3143 */ 3144 if (new_ncp == NULL) { 3145 spin_unlock_shared(&nchpp->spin); 3146 new_ncp = cache_alloc(nlc->nlc_namelen); 3147 if (nlc->nlc_namelen) { 3148 bcopy(nlc->nlc_nameptr, new_ncp->nc_name, 3149 nlc->nlc_namelen); 3150 new_ncp->nc_name[nlc->nlc_namelen] = 0; 3151 } 3152 goto restart; 3153 } 3154 3155 /* 3156 * NOTE! The spinlock is held exclusively here because new_ncp 3157 * is non-NULL. 3158 */ 3159 if (par_locked == 0) { 3160 spin_unlock(&nchpp->spin); 3161 _cache_lock(par_nch->ncp); 3162 par_locked = 1; 3163 goto restart; 3164 } 3165 3166 /* 3167 * WARNING! We still hold the spinlock. We have to set the hash 3168 * table entry atomically. 3169 */ 3170 ncp = new_ncp; 3171 _cache_link_parent(ncp, par_nch->ncp, nchpp); 3172 spin_unlock(&nchpp->spin); 3173 _cache_unlock(par_nch->ncp); 3174 /* par_locked = 0 - not used */ 3175 found: 3176 /* 3177 * stats and namecache size management 3178 */ 3179 if (ncp->nc_flag & NCF_UNRESOLVED) 3180 ++gd->gd_nchstats->ncs_miss; 3181 else if (ncp->nc_vp) 3182 ++gd->gd_nchstats->ncs_goodhits; 3183 else 3184 ++gd->gd_nchstats->ncs_neghits; 3185 nch.mount = mp; 3186 nch.ncp = ncp; 3187 _cache_mntref(nch.mount); 3188 3189 return(nch); 3190 } 3191 3192 /* 3193 * Attempt to lookup a namecache entry and return with a shared namecache 3194 * lock. 3195 */ 3196 int 3197 cache_nlookup_maybe_shared(struct nchandle *par_nch, struct nlcomponent *nlc, 3198 int excl, struct nchandle *res_nch) 3199 { 3200 struct namecache *ncp; 3201 struct nchash_head *nchpp; 3202 struct mount *mp; 3203 u_int32_t hash; 3204 globaldata_t gd; 3205 3206 /* 3207 * If exclusive requested or shared namecache locks are disabled, 3208 * return failure. 3209 */ 3210 if (ncp_shared_lock_disable || excl) 3211 return(EWOULDBLOCK); 3212 3213 gd = mycpu; 3214 mp = par_nch->mount; 3215 3216 /* 3217 * This is a good time to call it, no ncp's are locked by 3218 * the caller or us. 3219 */ 3220 cache_hysteresis(1); 3221 3222 /* 3223 * Try to locate an existing entry 3224 */ 3225 hash = fnv_32_buf(nlc->nlc_nameptr, nlc->nlc_namelen, FNV1_32_INIT); 3226 hash = fnv_32_buf(&par_nch->ncp, sizeof(par_nch->ncp), hash); 3227 nchpp = NCHHASH(hash); 3228 3229 spin_lock_shared(&nchpp->spin); 3230 3231 TAILQ_FOREACH(ncp, &nchpp->list, nc_hash) { 3232 /* 3233 * Break out if we find a matching entry. Note that 3234 * UNRESOLVED entries may match, but DESTROYED entries 3235 * do not. 3236 */ 3237 if (ncp->nc_parent == par_nch->ncp && 3238 ncp->nc_nlen == nlc->nlc_namelen && 3239 bcmp(ncp->nc_name, nlc->nlc_nameptr, ncp->nc_nlen) == 0 && 3240 (ncp->nc_flag & NCF_DESTROYED) == 0 3241 ) { 3242 _cache_hold(ncp); 3243 spin_unlock_shared(&nchpp->spin); 3244 if (_cache_lock_shared_special(ncp) == 0) { 3245 if (ncp->nc_parent == par_nch->ncp && 3246 ncp->nc_nlen == nlc->nlc_namelen && 3247 bcmp(ncp->nc_name, nlc->nlc_nameptr, 3248 ncp->nc_nlen) == 0 && 3249 (ncp->nc_flag & NCF_DESTROYED) == 0 && 3250 (ncp->nc_flag & NCF_UNRESOLVED) == 0 && 3251 _cache_auto_unresolve_test(mp, ncp) == 0) { 3252 goto found; 3253 } 3254 _cache_unlock(ncp); 3255 } 3256 _cache_drop(ncp); 3257 spin_lock_shared(&nchpp->spin); 3258 break; 3259 } 3260 } 3261 3262 /* 3263 * Failure 3264 */ 3265 spin_unlock_shared(&nchpp->spin); 3266 return(EWOULDBLOCK); 3267 3268 /* 3269 * Success 3270 * 3271 * Note that nc_error might be non-zero (e.g ENOENT). 3272 */ 3273 found: 3274 res_nch->mount = mp; 3275 res_nch->ncp = ncp; 3276 ++gd->gd_nchstats->ncs_goodhits; 3277 _cache_mntref(res_nch->mount); 3278 3279 KKASSERT(ncp->nc_error != EWOULDBLOCK); 3280 return(ncp->nc_error); 3281 } 3282 3283 /* 3284 * This is a non-blocking verison of cache_nlookup() used by 3285 * nfs_readdirplusrpc_uio(). It can fail for any reason and 3286 * will return nch.ncp == NULL in that case. 3287 */ 3288 struct nchandle 3289 cache_nlookup_nonblock(struct nchandle *par_nch, struct nlcomponent *nlc) 3290 { 3291 struct nchandle nch; 3292 struct namecache *ncp; 3293 struct namecache *new_ncp; 3294 struct nchash_head *nchpp; 3295 struct mount *mp; 3296 u_int32_t hash; 3297 globaldata_t gd; 3298 int par_locked; 3299 3300 gd = mycpu; 3301 mp = par_nch->mount; 3302 par_locked = 0; 3303 3304 /* 3305 * Try to locate an existing entry 3306 */ 3307 hash = fnv_32_buf(nlc->nlc_nameptr, nlc->nlc_namelen, FNV1_32_INIT); 3308 hash = fnv_32_buf(&par_nch->ncp, sizeof(par_nch->ncp), hash); 3309 new_ncp = NULL; 3310 nchpp = NCHHASH(hash); 3311 restart: 3312 spin_lock(&nchpp->spin); 3313 TAILQ_FOREACH(ncp, &nchpp->list, nc_hash) { 3314 /* 3315 * Break out if we find a matching entry. Note that 3316 * UNRESOLVED entries may match, but DESTROYED entries 3317 * do not. 3318 */ 3319 if (ncp->nc_parent == par_nch->ncp && 3320 ncp->nc_nlen == nlc->nlc_namelen && 3321 bcmp(ncp->nc_name, nlc->nlc_nameptr, ncp->nc_nlen) == 0 && 3322 (ncp->nc_flag & NCF_DESTROYED) == 0 3323 ) { 3324 _cache_hold(ncp); 3325 spin_unlock(&nchpp->spin); 3326 if (par_locked) { 3327 _cache_unlock(par_nch->ncp); 3328 par_locked = 0; 3329 } 3330 if (_cache_lock_special(ncp) == 0) { 3331 if (ncp->nc_parent != par_nch->ncp || 3332 ncp->nc_nlen != nlc->nlc_namelen || 3333 bcmp(ncp->nc_name, nlc->nlc_nameptr, ncp->nc_nlen) || 3334 (ncp->nc_flag & NCF_DESTROYED)) { 3335 kprintf("cache_lookup_nonblock: " 3336 "ncp-race %p %*.*s\n", 3337 ncp, 3338 nlc->nlc_namelen, 3339 nlc->nlc_namelen, 3340 nlc->nlc_nameptr); 3341 _cache_unlock(ncp); 3342 _cache_drop(ncp); 3343 goto failed; 3344 } 3345 _cache_auto_unresolve(mp, ncp); 3346 if (new_ncp) { 3347 _cache_free(new_ncp); 3348 new_ncp = NULL; 3349 } 3350 goto found; 3351 } 3352 _cache_drop(ncp); 3353 goto failed; 3354 } 3355 } 3356 3357 /* 3358 * We failed to locate an entry, create a new entry and add it to 3359 * the cache. The parent ncp must also be locked so we 3360 * can link into it. 3361 * 3362 * We have to relookup after possibly blocking in kmalloc or 3363 * when locking par_nch. 3364 * 3365 * NOTE: nlc_namelen can be 0 and nlc_nameptr NULL as a special 3366 * mount case, in which case nc_name will be NULL. 3367 */ 3368 if (new_ncp == NULL) { 3369 spin_unlock(&nchpp->spin); 3370 new_ncp = cache_alloc(nlc->nlc_namelen); 3371 if (nlc->nlc_namelen) { 3372 bcopy(nlc->nlc_nameptr, new_ncp->nc_name, 3373 nlc->nlc_namelen); 3374 new_ncp->nc_name[nlc->nlc_namelen] = 0; 3375 } 3376 goto restart; 3377 } 3378 if (par_locked == 0) { 3379 spin_unlock(&nchpp->spin); 3380 if (_cache_lock_nonblock(par_nch->ncp) == 0) { 3381 par_locked = 1; 3382 goto restart; 3383 } 3384 goto failed; 3385 } 3386 3387 /* 3388 * WARNING! We still hold the spinlock. We have to set the hash 3389 * table entry atomically. 3390 */ 3391 ncp = new_ncp; 3392 _cache_link_parent(ncp, par_nch->ncp, nchpp); 3393 spin_unlock(&nchpp->spin); 3394 _cache_unlock(par_nch->ncp); 3395 /* par_locked = 0 - not used */ 3396 found: 3397 /* 3398 * stats and namecache size management 3399 */ 3400 if (ncp->nc_flag & NCF_UNRESOLVED) 3401 ++gd->gd_nchstats->ncs_miss; 3402 else if (ncp->nc_vp) 3403 ++gd->gd_nchstats->ncs_goodhits; 3404 else 3405 ++gd->gd_nchstats->ncs_neghits; 3406 nch.mount = mp; 3407 nch.ncp = ncp; 3408 _cache_mntref(nch.mount); 3409 3410 return(nch); 3411 failed: 3412 if (new_ncp) { 3413 _cache_free(new_ncp); 3414 new_ncp = NULL; 3415 } 3416 nch.mount = NULL; 3417 nch.ncp = NULL; 3418 return(nch); 3419 } 3420 3421 /* 3422 * The namecache entry is marked as being used as a mount point. 3423 * Locate the mount if it is visible to the caller. The DragonFly 3424 * mount system allows arbitrary loops in the topology and disentangles 3425 * those loops by matching against (mp, ncp) rather than just (ncp). 3426 * This means any given ncp can dive any number of mounts, depending 3427 * on the relative mount (e.g. nullfs) the caller is at in the topology. 3428 * 3429 * We use a very simple frontend cache to reduce SMP conflicts, 3430 * which we have to do because the mountlist scan needs an exclusive 3431 * lock around its ripout info list. Not to mention that there might 3432 * be a lot of mounts. 3433 * 3434 * The hash table is 4-way set-associative and will either return the 3435 * matching slot or the best slot to reuse. 3436 */ 3437 struct findmount_info { 3438 struct mount *result; 3439 struct mount *nch_mount; 3440 struct namecache *nch_ncp; 3441 }; 3442 3443 static 3444 struct ncmount_cache * 3445 ncmount_cache_lookup4(struct mount *mp, struct namecache *ncp) 3446 { 3447 uintptr_t hash; 3448 3449 hash = ((uintptr_t)mp / sizeof(*mp)) * 3450 ((uintptr_t)ncp / sizeof(*ncp)); 3451 hash ^= (uintptr_t)ncp >> 12; 3452 hash ^= (uintptr_t)mp >> 12; 3453 hash = hash & ((NCMOUNT_NUMCACHE - 1) & ~3); 3454 3455 return (&ncmount_cache[hash]); 3456 } 3457 3458 static 3459 struct ncmount_cache * 3460 ncmount_cache_lookup(struct mount *mp, struct namecache *ncp) 3461 { 3462 struct ncmount_cache *ncc; 3463 struct ncmount_cache *best; 3464 uintptr_t hash; 3465 int delta; 3466 int best_delta; 3467 int i; 3468 3469 hash = ((uintptr_t)mp / sizeof(*mp)) * 3470 ((uintptr_t)ncp / sizeof(*ncp)); 3471 hash ^= (uintptr_t)ncp >> 12; 3472 hash ^= (uintptr_t)mp >> 12; 3473 hash = hash & ((NCMOUNT_NUMCACHE - 1) & ~3); 3474 3475 ncc = &ncmount_cache[hash]; 3476 3477 /* 3478 * NOTE: When checking for a ticks overflow implement a slop of 3479 * 2 ticks just to be safe, because ticks is accessed 3480 * non-atomically one CPU can increment it while another 3481 * is still using the old value. 3482 */ 3483 if (ncc->mp == mp && ncc->ncp == ncp) /* 0 */ 3484 return ncc; 3485 delta = (int)(ticks - ncc->ticks); /* beware GCC opts */ 3486 if (delta < -2) /* overflow reset */ 3487 ncc->ticks = ticks; 3488 best = ncc; 3489 best_delta = delta; 3490 3491 for (i = 1; i < 4; ++i) { /* 1, 2, 3 */ 3492 ++ncc; 3493 if (ncc->mp == mp && ncc->ncp == ncp) 3494 return ncc; 3495 delta = (int)(ticks - ncc->ticks); 3496 if (delta < -2) 3497 ncc->ticks = ticks; 3498 if (delta > best_delta) { 3499 best_delta = delta; 3500 best = ncc; 3501 } 3502 } 3503 return best; 3504 } 3505 3506 static 3507 int 3508 cache_findmount_callback(struct mount *mp, void *data) 3509 { 3510 struct findmount_info *info = data; 3511 3512 /* 3513 * Check the mount's mounted-on point against the passed nch. 3514 */ 3515 if (mp->mnt_ncmounton.mount == info->nch_mount && 3516 mp->mnt_ncmounton.ncp == info->nch_ncp 3517 ) { 3518 info->result = mp; 3519 _cache_mntref(mp); 3520 return(-1); 3521 } 3522 return(0); 3523 } 3524 3525 /* 3526 * Find the recursive mountpoint (mp, ncp) -> mtpt 3527 */ 3528 struct mount * 3529 cache_findmount(struct nchandle *nch) 3530 { 3531 struct findmount_info info; 3532 struct ncmount_cache *ncc; 3533 struct mount *mp; 3534 3535 /* 3536 * Fast 3537 */ 3538 if (ncmount_cache_enable == 0) { 3539 ncc = NULL; 3540 goto skip; 3541 } 3542 ncc = ncmount_cache_lookup(nch->mount, nch->ncp); 3543 if (ncc->ncp == nch->ncp) { 3544 spin_lock_shared(&ncc->spin); 3545 if (ncc->isneg == 0 && 3546 ncc->ncp == nch->ncp && (mp = ncc->mp) != NULL) { 3547 if (mp->mnt_ncmounton.mount == nch->mount && 3548 mp->mnt_ncmounton.ncp == nch->ncp) { 3549 /* 3550 * Cache hit (positive) (avoid dirtying 3551 * the cache line if possible) 3552 */ 3553 if (ncc->ticks != (int)ticks) 3554 ncc->ticks = (int)ticks; 3555 _cache_mntref(mp); 3556 spin_unlock_shared(&ncc->spin); 3557 return(mp); 3558 } 3559 /* else cache miss */ 3560 } 3561 if (ncc->isneg && 3562 ncc->ncp == nch->ncp && ncc->mp == nch->mount) { 3563 /* 3564 * Cache hit (negative) (avoid dirtying 3565 * the cache line if possible) 3566 */ 3567 if (ncc->ticks != (int)ticks) 3568 ncc->ticks = (int)ticks; 3569 spin_unlock_shared(&ncc->spin); 3570 return(NULL); 3571 } 3572 spin_unlock_shared(&ncc->spin); 3573 } 3574 skip: 3575 3576 /* 3577 * Slow 3578 */ 3579 info.result = NULL; 3580 info.nch_mount = nch->mount; 3581 info.nch_ncp = nch->ncp; 3582 mountlist_scan(cache_findmount_callback, &info, 3583 MNTSCAN_FORWARD | MNTSCAN_NOBUSY | MNTSCAN_NOUNLOCK); 3584 3585 /* 3586 * Cache the result. 3587 * 3588 * Negative lookups: We cache the originating {ncp,mp}. (mp) is 3589 * only used for pointer comparisons and is not 3590 * referenced (otherwise there would be dangling 3591 * refs). 3592 * 3593 * Positive lookups: We cache the originating {ncp} and the target 3594 * (mp). (mp) is referenced. 3595 * 3596 * Indeterminant: If the match is undergoing an unmount we do 3597 * not cache it to avoid racing cache_unmounting(), 3598 * but still return the match. 3599 */ 3600 if (ncc) { 3601 spin_lock(&ncc->spin); 3602 if (info.result == NULL) { 3603 if (ncc->isneg == 0 && ncc->mp) 3604 _cache_mntrel(ncc->mp); 3605 ncc->ncp = nch->ncp; 3606 ncc->mp = nch->mount; 3607 ncc->isneg = 1; 3608 ncc->ticks = (int)ticks; 3609 spin_unlock(&ncc->spin); 3610 } else if ((info.result->mnt_kern_flag & MNTK_UNMOUNT) == 0) { 3611 if (ncc->isneg == 0 && ncc->mp) 3612 _cache_mntrel(ncc->mp); 3613 _cache_mntref(info.result); 3614 ncc->ncp = nch->ncp; 3615 ncc->mp = info.result; 3616 ncc->isneg = 0; 3617 ncc->ticks = (int)ticks; 3618 spin_unlock(&ncc->spin); 3619 } else { 3620 spin_unlock(&ncc->spin); 3621 } 3622 } 3623 return(info.result); 3624 } 3625 3626 void 3627 cache_dropmount(struct mount *mp) 3628 { 3629 _cache_mntrel(mp); 3630 } 3631 3632 void 3633 cache_ismounting(struct mount *mp) 3634 { 3635 struct nchandle *nch = &mp->mnt_ncmounton; 3636 struct ncmount_cache *ncc; 3637 int i; 3638 3639 ncc = ncmount_cache_lookup4(nch->mount, nch->ncp); 3640 for (i = 0; i < 4; ++i) { 3641 if (ncc->isneg && 3642 ncc->ncp == nch->ncp && ncc->mp == nch->mount) { 3643 spin_lock(&ncc->spin); 3644 if (ncc->isneg && 3645 ncc->ncp == nch->ncp && ncc->mp == nch->mount) { 3646 ncc->ncp = NULL; 3647 ncc->mp = NULL; 3648 ncc->ticks = (int)ticks - hz * 120; 3649 } 3650 spin_unlock(&ncc->spin); 3651 } 3652 ++ncc; 3653 } 3654 } 3655 3656 void 3657 cache_unmounting(struct mount *mp) 3658 { 3659 struct nchandle *nch = &mp->mnt_ncmounton; 3660 struct ncmount_cache *ncc; 3661 int i; 3662 3663 ncc = ncmount_cache_lookup4(nch->mount, nch->ncp); 3664 for (i = 0; i < 4; ++i) { 3665 if (ncc->isneg == 0 && 3666 ncc->ncp == nch->ncp && ncc->mp == mp) { 3667 spin_lock(&ncc->spin); 3668 if (ncc->isneg == 0 && 3669 ncc->ncp == nch->ncp && ncc->mp == mp) { 3670 _cache_mntrel(mp); 3671 ncc->ncp = NULL; 3672 ncc->mp = NULL; 3673 ncc->ticks = (int)ticks - hz * 120; 3674 } 3675 spin_unlock(&ncc->spin); 3676 } 3677 ++ncc; 3678 } 3679 } 3680 3681 /* 3682 * Resolve an unresolved namecache entry, generally by looking it up. 3683 * The passed ncp must be locked and refd. 3684 * 3685 * Theoretically since a vnode cannot be recycled while held, and since 3686 * the nc_parent chain holds its vnode as long as children exist, the 3687 * direct parent of the cache entry we are trying to resolve should 3688 * have a valid vnode. If not then generate an error that we can 3689 * determine is related to a resolver bug. 3690 * 3691 * However, if a vnode was in the middle of a recyclement when the NCP 3692 * got locked, ncp->nc_vp might point to a vnode that is about to become 3693 * invalid. cache_resolve() handles this case by unresolving the entry 3694 * and then re-resolving it. 3695 * 3696 * Note that successful resolution does not necessarily return an error 3697 * code of 0. If the ncp resolves to a negative cache hit then ENOENT 3698 * will be returned. 3699 */ 3700 int 3701 cache_resolve(struct nchandle *nch, struct ucred *cred) 3702 { 3703 struct namecache *par_tmp; 3704 struct namecache *par; 3705 struct namecache *ncp; 3706 struct nchandle nctmp; 3707 struct mount *mp; 3708 struct vnode *dvp; 3709 int error; 3710 3711 ncp = nch->ncp; 3712 mp = nch->mount; 3713 KKASSERT(_cache_lockstatus(ncp) == LK_EXCLUSIVE); 3714 restart: 3715 /* 3716 * If the ncp is already resolved we have nothing to do. However, 3717 * we do want to guarentee that a usable vnode is returned when 3718 * a vnode is present, so make sure it hasn't been reclaimed. 3719 */ 3720 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) { 3721 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED)) 3722 _cache_setunresolved(ncp); 3723 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) 3724 return (ncp->nc_error); 3725 } 3726 3727 /* 3728 * If the ncp was destroyed it will never resolve again. This 3729 * can basically only happen when someone is chdir'd into an 3730 * empty directory which is then rmdir'd. We want to catch this 3731 * here and not dive the VFS because the VFS might actually 3732 * have a way to re-resolve the disconnected ncp, which will 3733 * result in inconsistencies in the cdir/nch for proc->p_fd. 3734 */ 3735 if (ncp->nc_flag & NCF_DESTROYED) 3736 return(EINVAL); 3737 3738 /* 3739 * Mount points need special handling because the parent does not 3740 * belong to the same filesystem as the ncp. 3741 */ 3742 if (ncp == mp->mnt_ncmountpt.ncp) 3743 return (cache_resolve_mp(mp)); 3744 3745 /* 3746 * We expect an unbroken chain of ncps to at least the mount point, 3747 * and even all the way to root (but this code doesn't have to go 3748 * past the mount point). 3749 */ 3750 if (ncp->nc_parent == NULL) { 3751 kprintf("EXDEV case 1 %p %*.*s\n", ncp, 3752 ncp->nc_nlen, ncp->nc_nlen, ncp->nc_name); 3753 ncp->nc_error = EXDEV; 3754 return(ncp->nc_error); 3755 } 3756 3757 /* 3758 * The vp's of the parent directories in the chain are held via vhold() 3759 * due to the existance of the child, and should not disappear. 3760 * However, there are cases where they can disappear: 3761 * 3762 * - due to filesystem I/O errors. 3763 * - due to NFS being stupid about tracking the namespace and 3764 * destroys the namespace for entire directories quite often. 3765 * - due to forced unmounts. 3766 * - due to an rmdir (parent will be marked DESTROYED) 3767 * 3768 * When this occurs we have to track the chain backwards and resolve 3769 * it, looping until the resolver catches up to the current node. We 3770 * could recurse here but we might run ourselves out of kernel stack 3771 * so we do it in a more painful manner. This situation really should 3772 * not occur all that often, or if it does not have to go back too 3773 * many nodes to resolve the ncp. 3774 */ 3775 while ((dvp = cache_dvpref(ncp)) == NULL) { 3776 /* 3777 * This case can occur if a process is CD'd into a 3778 * directory which is then rmdir'd. If the parent is marked 3779 * destroyed there is no point trying to resolve it. 3780 */ 3781 if (ncp->nc_parent->nc_flag & NCF_DESTROYED) 3782 return(ENOENT); 3783 par = ncp->nc_parent; 3784 _cache_hold(par); 3785 _cache_lock(par); 3786 while ((par_tmp = par->nc_parent) != NULL && 3787 par_tmp->nc_vp == NULL) { 3788 _cache_hold(par_tmp); 3789 _cache_lock(par_tmp); 3790 _cache_put(par); 3791 par = par_tmp; 3792 } 3793 if (par->nc_parent == NULL) { 3794 kprintf("EXDEV case 2 %*.*s\n", 3795 par->nc_nlen, par->nc_nlen, par->nc_name); 3796 _cache_put(par); 3797 return (EXDEV); 3798 } 3799 /* 3800 * The parent is not set in stone, ref and lock it to prevent 3801 * it from disappearing. Also note that due to renames it 3802 * is possible for our ncp to move and for par to no longer 3803 * be one of its parents. We resolve it anyway, the loop 3804 * will handle any moves. 3805 */ 3806 _cache_get(par); /* additional hold/lock */ 3807 _cache_put(par); /* from earlier hold/lock */ 3808 if (par == nch->mount->mnt_ncmountpt.ncp) { 3809 cache_resolve_mp(nch->mount); 3810 } else if ((dvp = cache_dvpref(par)) == NULL) { 3811 kprintf("[diagnostic] cache_resolve: raced on %*.*s\n", par->nc_nlen, par->nc_nlen, par->nc_name); 3812 _cache_put(par); 3813 continue; 3814 } else { 3815 if (par->nc_flag & NCF_UNRESOLVED) { 3816 nctmp.mount = mp; 3817 nctmp.ncp = par; 3818 par->nc_error = VOP_NRESOLVE(&nctmp, dvp, cred); 3819 } 3820 vrele(dvp); 3821 } 3822 if ((error = par->nc_error) != 0) { 3823 if (par->nc_error != EAGAIN) { 3824 kprintf("EXDEV case 3 %*.*s error %d\n", 3825 par->nc_nlen, par->nc_nlen, par->nc_name, 3826 par->nc_error); 3827 _cache_put(par); 3828 return(error); 3829 } 3830 kprintf("[diagnostic] cache_resolve: EAGAIN par %p %*.*s\n", 3831 par, par->nc_nlen, par->nc_nlen, par->nc_name); 3832 } 3833 _cache_put(par); 3834 /* loop */ 3835 } 3836 3837 /* 3838 * Call VOP_NRESOLVE() to get the vp, then scan for any disconnected 3839 * ncp's and reattach them. If this occurs the original ncp is marked 3840 * EAGAIN to force a relookup. 3841 * 3842 * NOTE: in order to call VOP_NRESOLVE(), the parent of the passed 3843 * ncp must already be resolved. 3844 */ 3845 if (dvp) { 3846 nctmp.mount = mp; 3847 nctmp.ncp = ncp; 3848 ncp->nc_error = VOP_NRESOLVE(&nctmp, dvp, cred); 3849 vrele(dvp); 3850 } else { 3851 ncp->nc_error = EPERM; 3852 } 3853 if (ncp->nc_error == EAGAIN) { 3854 kprintf("[diagnostic] cache_resolve: EAGAIN ncp %p %*.*s\n", 3855 ncp, ncp->nc_nlen, ncp->nc_nlen, ncp->nc_name); 3856 goto restart; 3857 } 3858 return(ncp->nc_error); 3859 } 3860 3861 /* 3862 * Resolve the ncp associated with a mount point. Such ncp's almost always 3863 * remain resolved and this routine is rarely called. NFS MPs tends to force 3864 * re-resolution more often due to its mac-truck-smash-the-namecache 3865 * method of tracking namespace changes. 3866 * 3867 * The semantics for this call is that the passed ncp must be locked on 3868 * entry and will be locked on return. However, if we actually have to 3869 * resolve the mount point we temporarily unlock the entry in order to 3870 * avoid race-to-root deadlocks due to e.g. dead NFS mounts. Because of 3871 * the unlock we have to recheck the flags after we relock. 3872 */ 3873 static int 3874 cache_resolve_mp(struct mount *mp) 3875 { 3876 struct namecache *ncp = mp->mnt_ncmountpt.ncp; 3877 struct vnode *vp; 3878 int error; 3879 3880 KKASSERT(mp != NULL); 3881 3882 /* 3883 * If the ncp is already resolved we have nothing to do. However, 3884 * we do want to guarentee that a usable vnode is returned when 3885 * a vnode is present, so make sure it hasn't been reclaimed. 3886 */ 3887 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) { 3888 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED)) 3889 _cache_setunresolved(ncp); 3890 } 3891 3892 if (ncp->nc_flag & NCF_UNRESOLVED) { 3893 _cache_unlock(ncp); 3894 while (vfs_busy(mp, 0)) 3895 ; 3896 error = VFS_ROOT(mp, &vp); 3897 _cache_lock(ncp); 3898 3899 /* 3900 * recheck the ncp state after relocking. 3901 */ 3902 if (ncp->nc_flag & NCF_UNRESOLVED) { 3903 ncp->nc_error = error; 3904 if (error == 0) { 3905 _cache_setvp(mp, ncp, vp); 3906 vput(vp); 3907 } else { 3908 kprintf("[diagnostic] cache_resolve_mp: failed" 3909 " to resolve mount %p err=%d ncp=%p\n", 3910 mp, error, ncp); 3911 _cache_setvp(mp, ncp, NULL); 3912 } 3913 } else if (error == 0) { 3914 vput(vp); 3915 } 3916 vfs_unbusy(mp); 3917 } 3918 return(ncp->nc_error); 3919 } 3920 3921 /* 3922 * Clean out negative cache entries when too many have accumulated. 3923 */ 3924 static void 3925 _cache_cleanneg(long count) 3926 { 3927 struct pcpu_ncache *pn; 3928 struct namecache *ncp; 3929 static uint32_t neg_rover; 3930 uint32_t n; 3931 long vnegs; 3932 3933 n = neg_rover++; /* SMP heuristical, race ok */ 3934 cpu_ccfence(); 3935 n = n % (uint32_t)ncpus; 3936 3937 /* 3938 * Normalize vfscache_negs and count. count is sometimes based 3939 * on vfscache_negs. vfscache_negs is heuristical and can sometimes 3940 * have crazy values. 3941 */ 3942 vnegs = vfscache_negs; 3943 cpu_ccfence(); 3944 if (vnegs <= MINNEG) 3945 vnegs = MINNEG; 3946 if (count < 1) 3947 count = 1; 3948 3949 pn = &pcpu_ncache[n]; 3950 spin_lock(&pn->neg_spin); 3951 count = pn->neg_count * count / vnegs + 1; 3952 spin_unlock(&pn->neg_spin); 3953 3954 /* 3955 * Attempt to clean out the specified number of negative cache 3956 * entries. 3957 */ 3958 while (count > 0) { 3959 spin_lock(&pn->neg_spin); 3960 ncp = TAILQ_FIRST(&pn->neg_list); 3961 if (ncp == NULL) { 3962 spin_unlock(&pn->neg_spin); 3963 break; 3964 } 3965 TAILQ_REMOVE(&pn->neg_list, ncp, nc_vnode); 3966 TAILQ_INSERT_TAIL(&pn->neg_list, ncp, nc_vnode); 3967 _cache_hold(ncp); 3968 spin_unlock(&pn->neg_spin); 3969 3970 /* 3971 * This can race, so we must re-check that the ncp 3972 * is on the ncneg.list after successfully locking it. 3973 */ 3974 if (_cache_lock_special(ncp) == 0) { 3975 if (ncp->nc_vp == NULL && 3976 (ncp->nc_flag & NCF_UNRESOLVED) == 0) { 3977 ncp = cache_zap(ncp, 1); 3978 if (ncp) 3979 _cache_drop(ncp); 3980 } else { 3981 _cache_unlock(ncp); 3982 _cache_drop(ncp); 3983 } 3984 } else { 3985 _cache_drop(ncp); 3986 } 3987 --count; 3988 } 3989 } 3990 3991 /* 3992 * Clean out positive cache entries when too many have accumulated. 3993 */ 3994 static void 3995 _cache_cleanpos(long count) 3996 { 3997 static volatile int rover; 3998 struct nchash_head *nchpp; 3999 struct namecache *ncp; 4000 int rover_copy; 4001 4002 /* 4003 * Attempt to clean out the specified number of negative cache 4004 * entries. 4005 */ 4006 while (count > 0) { 4007 rover_copy = ++rover; /* MPSAFEENOUGH */ 4008 cpu_ccfence(); 4009 nchpp = NCHHASH(rover_copy); 4010 4011 if (TAILQ_FIRST(&nchpp->list) == NULL) { 4012 --count; 4013 continue; 4014 } 4015 4016 /* 4017 * Cycle ncp on list, ignore and do not move DUMMY 4018 * ncps. These are temporary list iterators. 4019 * 4020 * We must cycle the ncp to the end of the list to 4021 * ensure that all ncp's have an equal chance of 4022 * being removed. 4023 */ 4024 spin_lock(&nchpp->spin); 4025 ncp = TAILQ_FIRST(&nchpp->list); 4026 while (ncp && (ncp->nc_flag & NCF_DUMMY)) 4027 ncp = TAILQ_NEXT(ncp, nc_hash); 4028 if (ncp) { 4029 TAILQ_REMOVE(&nchpp->list, ncp, nc_hash); 4030 TAILQ_INSERT_TAIL(&nchpp->list, ncp, nc_hash); 4031 _cache_hold(ncp); 4032 } 4033 spin_unlock(&nchpp->spin); 4034 4035 if (ncp) { 4036 if (_cache_lock_special(ncp) == 0) { 4037 ncp = cache_zap(ncp, 1); 4038 if (ncp) 4039 _cache_drop(ncp); 4040 } else { 4041 _cache_drop(ncp); 4042 } 4043 } 4044 --count; 4045 } 4046 } 4047 4048 /* 4049 * This is a kitchen sink function to clean out ncps which we 4050 * tried to zap from cache_drop() but failed because we were 4051 * unable to acquire the parent lock. 4052 * 4053 * Such entries can also be removed via cache_inval_vp(), such 4054 * as when unmounting. 4055 */ 4056 static void 4057 _cache_cleandefered(void) 4058 { 4059 struct nchash_head *nchpp; 4060 struct namecache *ncp; 4061 struct namecache dummy; 4062 int i; 4063 4064 /* 4065 * Create a list iterator. DUMMY indicates that this is a list 4066 * iterator, DESTROYED prevents matches by lookup functions. 4067 */ 4068 numdefered = 0; 4069 pcpu_ncache[mycpu->gd_cpuid].numdefered = 0; 4070 bzero(&dummy, sizeof(dummy)); 4071 dummy.nc_flag = NCF_DESTROYED | NCF_DUMMY; 4072 dummy.nc_refs = 1; 4073 4074 for (i = 0; i <= nchash; ++i) { 4075 nchpp = &nchashtbl[i]; 4076 4077 spin_lock(&nchpp->spin); 4078 TAILQ_INSERT_HEAD(&nchpp->list, &dummy, nc_hash); 4079 ncp = &dummy; 4080 while ((ncp = TAILQ_NEXT(ncp, nc_hash)) != NULL) { 4081 if ((ncp->nc_flag & NCF_DEFEREDZAP) == 0) 4082 continue; 4083 TAILQ_REMOVE(&nchpp->list, &dummy, nc_hash); 4084 TAILQ_INSERT_AFTER(&nchpp->list, ncp, &dummy, nc_hash); 4085 _cache_hold(ncp); 4086 spin_unlock(&nchpp->spin); 4087 if (_cache_lock_nonblock(ncp) == 0) { 4088 ncp->nc_flag &= ~NCF_DEFEREDZAP; 4089 _cache_unlock(ncp); 4090 } 4091 _cache_drop(ncp); 4092 spin_lock(&nchpp->spin); 4093 ncp = &dummy; 4094 } 4095 TAILQ_REMOVE(&nchpp->list, &dummy, nc_hash); 4096 spin_unlock(&nchpp->spin); 4097 } 4098 } 4099 4100 /* 4101 * Name cache initialization, from vfsinit() when we are booting 4102 */ 4103 void 4104 nchinit(void) 4105 { 4106 struct pcpu_ncache *pn; 4107 globaldata_t gd; 4108 int i; 4109 4110 /* 4111 * Per-cpu accounting and negative hit list 4112 */ 4113 pcpu_ncache = kmalloc(sizeof(*pcpu_ncache) * ncpus, 4114 M_VFSCACHE, M_WAITOK|M_ZERO); 4115 for (i = 0; i < ncpus; ++i) { 4116 pn = &pcpu_ncache[i]; 4117 TAILQ_INIT(&pn->neg_list); 4118 spin_init(&pn->neg_spin, "ncneg"); 4119 } 4120 4121 /* 4122 * Initialise per-cpu namecache effectiveness statistics. 4123 */ 4124 for (i = 0; i < ncpus; ++i) { 4125 gd = globaldata_find(i); 4126 gd->gd_nchstats = &nchstats[i]; 4127 } 4128 4129 /* 4130 * Create a generous namecache hash table 4131 */ 4132 nchashtbl = hashinit_ext(vfs_inodehashsize(), 4133 sizeof(struct nchash_head), 4134 M_VFSCACHE, &nchash); 4135 for (i = 0; i <= (int)nchash; ++i) { 4136 TAILQ_INIT(&nchashtbl[i].list); 4137 spin_init(&nchashtbl[i].spin, "nchinit_hash"); 4138 } 4139 for (i = 0; i < NCMOUNT_NUMCACHE; ++i) 4140 spin_init(&ncmount_cache[i].spin, "nchinit_cache"); 4141 nclockwarn = 5 * hz; 4142 } 4143 4144 /* 4145 * Called from start_init() to bootstrap the root filesystem. Returns 4146 * a referenced, unlocked namecache record. 4147 */ 4148 void 4149 cache_allocroot(struct nchandle *nch, struct mount *mp, struct vnode *vp) 4150 { 4151 nch->ncp = cache_alloc(0); 4152 nch->mount = mp; 4153 _cache_mntref(mp); 4154 if (vp) 4155 _cache_setvp(nch->mount, nch->ncp, vp); 4156 } 4157 4158 /* 4159 * vfs_cache_setroot() 4160 * 4161 * Create an association between the root of our namecache and 4162 * the root vnode. This routine may be called several times during 4163 * booting. 4164 * 4165 * If the caller intends to save the returned namecache pointer somewhere 4166 * it must cache_hold() it. 4167 */ 4168 void 4169 vfs_cache_setroot(struct vnode *nvp, struct nchandle *nch) 4170 { 4171 struct vnode *ovp; 4172 struct nchandle onch; 4173 4174 ovp = rootvnode; 4175 onch = rootnch; 4176 rootvnode = nvp; 4177 if (nch) 4178 rootnch = *nch; 4179 else 4180 cache_zero(&rootnch); 4181 if (ovp) 4182 vrele(ovp); 4183 if (onch.ncp) 4184 cache_drop(&onch); 4185 } 4186 4187 /* 4188 * XXX OLD API COMPAT FUNCTION. This really messes up the new namecache 4189 * topology and is being removed as quickly as possible. The new VOP_N*() 4190 * API calls are required to make specific adjustments using the supplied 4191 * ncp pointers rather then just bogusly purging random vnodes. 4192 * 4193 * Invalidate all namecache entries to a particular vnode as well as 4194 * any direct children of that vnode in the namecache. This is a 4195 * 'catch all' purge used by filesystems that do not know any better. 4196 * 4197 * Note that the linkage between the vnode and its namecache entries will 4198 * be removed, but the namecache entries themselves might stay put due to 4199 * active references from elsewhere in the system or due to the existance of 4200 * the children. The namecache topology is left intact even if we do not 4201 * know what the vnode association is. Such entries will be marked 4202 * NCF_UNRESOLVED. 4203 */ 4204 void 4205 cache_purge(struct vnode *vp) 4206 { 4207 cache_inval_vp(vp, CINV_DESTROY | CINV_CHILDREN); 4208 } 4209 4210 static int disablecwd; 4211 SYSCTL_INT(_debug, OID_AUTO, disablecwd, CTLFLAG_RW, &disablecwd, 0, 4212 "Disable getcwd"); 4213 4214 static u_long numcwdcalls; 4215 SYSCTL_ULONG(_vfs_cache, OID_AUTO, numcwdcalls, CTLFLAG_RD, &numcwdcalls, 0, 4216 "Number of current directory resolution calls"); 4217 static u_long numcwdfailnf; 4218 SYSCTL_ULONG(_vfs_cache, OID_AUTO, numcwdfailnf, CTLFLAG_RD, &numcwdfailnf, 0, 4219 "Number of current directory failures due to lack of file"); 4220 static u_long numcwdfailsz; 4221 SYSCTL_ULONG(_vfs_cache, OID_AUTO, numcwdfailsz, CTLFLAG_RD, &numcwdfailsz, 0, 4222 "Number of current directory failures due to large result"); 4223 static u_long numcwdfound; 4224 SYSCTL_ULONG(_vfs_cache, OID_AUTO, numcwdfound, CTLFLAG_RD, &numcwdfound, 0, 4225 "Number of current directory resolution successes"); 4226 4227 /* 4228 * MPALMOSTSAFE 4229 */ 4230 int 4231 sys___getcwd(struct __getcwd_args *uap) 4232 { 4233 u_int buflen; 4234 int error; 4235 char *buf; 4236 char *bp; 4237 4238 if (disablecwd) 4239 return (ENODEV); 4240 4241 buflen = uap->buflen; 4242 if (buflen == 0) 4243 return (EINVAL); 4244 if (buflen > MAXPATHLEN) 4245 buflen = MAXPATHLEN; 4246 4247 buf = kmalloc(buflen, M_TEMP, M_WAITOK); 4248 bp = kern_getcwd(buf, buflen, &error); 4249 if (error == 0) 4250 error = copyout(bp, uap->buf, strlen(bp) + 1); 4251 kfree(buf, M_TEMP); 4252 return (error); 4253 } 4254 4255 char * 4256 kern_getcwd(char *buf, size_t buflen, int *error) 4257 { 4258 struct proc *p = curproc; 4259 char *bp; 4260 int i, slash_prefixed; 4261 struct filedesc *fdp; 4262 struct nchandle nch; 4263 struct namecache *ncp; 4264 4265 numcwdcalls++; 4266 bp = buf; 4267 bp += buflen - 1; 4268 *bp = '\0'; 4269 fdp = p->p_fd; 4270 slash_prefixed = 0; 4271 4272 nch = fdp->fd_ncdir; 4273 ncp = nch.ncp; 4274 if (ncp) 4275 _cache_hold(ncp); 4276 4277 while (ncp && (ncp != fdp->fd_nrdir.ncp || 4278 nch.mount != fdp->fd_nrdir.mount) 4279 ) { 4280 /* 4281 * While traversing upwards if we encounter the root 4282 * of the current mount we have to skip to the mount point 4283 * in the underlying filesystem. 4284 */ 4285 if (ncp == nch.mount->mnt_ncmountpt.ncp) { 4286 nch = nch.mount->mnt_ncmounton; 4287 _cache_drop(ncp); 4288 ncp = nch.ncp; 4289 if (ncp) 4290 _cache_hold(ncp); 4291 continue; 4292 } 4293 4294 /* 4295 * Prepend the path segment 4296 */ 4297 for (i = ncp->nc_nlen - 1; i >= 0; i--) { 4298 if (bp == buf) { 4299 numcwdfailsz++; 4300 *error = ERANGE; 4301 bp = NULL; 4302 goto done; 4303 } 4304 *--bp = ncp->nc_name[i]; 4305 } 4306 if (bp == buf) { 4307 numcwdfailsz++; 4308 *error = ERANGE; 4309 bp = NULL; 4310 goto done; 4311 } 4312 *--bp = '/'; 4313 slash_prefixed = 1; 4314 4315 /* 4316 * Go up a directory. This isn't a mount point so we don't 4317 * have to check again. 4318 */ 4319 while ((nch.ncp = ncp->nc_parent) != NULL) { 4320 if (ncp_shared_lock_disable) 4321 _cache_lock(ncp); 4322 else 4323 _cache_lock_shared(ncp); 4324 if (nch.ncp != ncp->nc_parent) { 4325 _cache_unlock(ncp); 4326 continue; 4327 } 4328 _cache_hold(nch.ncp); 4329 _cache_unlock(ncp); 4330 break; 4331 } 4332 _cache_drop(ncp); 4333 ncp = nch.ncp; 4334 } 4335 if (ncp == NULL) { 4336 numcwdfailnf++; 4337 *error = ENOENT; 4338 bp = NULL; 4339 goto done; 4340 } 4341 if (!slash_prefixed) { 4342 if (bp == buf) { 4343 numcwdfailsz++; 4344 *error = ERANGE; 4345 bp = NULL; 4346 goto done; 4347 } 4348 *--bp = '/'; 4349 } 4350 numcwdfound++; 4351 *error = 0; 4352 done: 4353 if (ncp) 4354 _cache_drop(ncp); 4355 return (bp); 4356 } 4357 4358 /* 4359 * Thus begins the fullpath magic. 4360 * 4361 * The passed nchp is referenced but not locked. 4362 */ 4363 static int disablefullpath; 4364 SYSCTL_INT(_debug, OID_AUTO, disablefullpath, CTLFLAG_RW, 4365 &disablefullpath, 0, 4366 "Disable fullpath lookups"); 4367 4368 int 4369 cache_fullpath(struct proc *p, struct nchandle *nchp, struct nchandle *nchbase, 4370 char **retbuf, char **freebuf, int guess) 4371 { 4372 struct nchandle fd_nrdir; 4373 struct nchandle nch; 4374 struct namecache *ncp; 4375 struct mount *mp, *new_mp; 4376 char *bp, *buf; 4377 int slash_prefixed; 4378 int error = 0; 4379 int i; 4380 4381 *retbuf = NULL; 4382 *freebuf = NULL; 4383 4384 buf = kmalloc(MAXPATHLEN, M_TEMP, M_WAITOK); 4385 bp = buf + MAXPATHLEN - 1; 4386 *bp = '\0'; 4387 if (nchbase) 4388 fd_nrdir = *nchbase; 4389 else if (p != NULL) 4390 fd_nrdir = p->p_fd->fd_nrdir; 4391 else 4392 fd_nrdir = rootnch; 4393 slash_prefixed = 0; 4394 nch = *nchp; 4395 ncp = nch.ncp; 4396 if (ncp) 4397 _cache_hold(ncp); 4398 mp = nch.mount; 4399 4400 while (ncp && (ncp != fd_nrdir.ncp || mp != fd_nrdir.mount)) { 4401 new_mp = NULL; 4402 4403 /* 4404 * If we are asked to guess the upwards path, we do so whenever 4405 * we encounter an ncp marked as a mountpoint. We try to find 4406 * the actual mountpoint by finding the mountpoint with this 4407 * ncp. 4408 */ 4409 if (guess && (ncp->nc_flag & NCF_ISMOUNTPT)) { 4410 new_mp = mount_get_by_nc(ncp); 4411 } 4412 /* 4413 * While traversing upwards if we encounter the root 4414 * of the current mount we have to skip to the mount point. 4415 */ 4416 if (ncp == mp->mnt_ncmountpt.ncp) { 4417 new_mp = mp; 4418 } 4419 if (new_mp) { 4420 nch = new_mp->mnt_ncmounton; 4421 _cache_drop(ncp); 4422 ncp = nch.ncp; 4423 if (ncp) 4424 _cache_hold(ncp); 4425 mp = nch.mount; 4426 continue; 4427 } 4428 4429 /* 4430 * Prepend the path segment 4431 */ 4432 for (i = ncp->nc_nlen - 1; i >= 0; i--) { 4433 if (bp == buf) { 4434 kfree(buf, M_TEMP); 4435 error = ENOMEM; 4436 goto done; 4437 } 4438 *--bp = ncp->nc_name[i]; 4439 } 4440 if (bp == buf) { 4441 kfree(buf, M_TEMP); 4442 error = ENOMEM; 4443 goto done; 4444 } 4445 *--bp = '/'; 4446 slash_prefixed = 1; 4447 4448 /* 4449 * Go up a directory. This isn't a mount point so we don't 4450 * have to check again. 4451 * 4452 * We can only safely access nc_parent with ncp held locked. 4453 */ 4454 while ((nch.ncp = ncp->nc_parent) != NULL) { 4455 _cache_lock(ncp); 4456 if (nch.ncp != ncp->nc_parent) { 4457 _cache_unlock(ncp); 4458 continue; 4459 } 4460 _cache_hold(nch.ncp); 4461 _cache_unlock(ncp); 4462 break; 4463 } 4464 _cache_drop(ncp); 4465 ncp = nch.ncp; 4466 } 4467 if (ncp == NULL) { 4468 kfree(buf, M_TEMP); 4469 error = ENOENT; 4470 goto done; 4471 } 4472 4473 if (!slash_prefixed) { 4474 if (bp == buf) { 4475 kfree(buf, M_TEMP); 4476 error = ENOMEM; 4477 goto done; 4478 } 4479 *--bp = '/'; 4480 } 4481 *retbuf = bp; 4482 *freebuf = buf; 4483 error = 0; 4484 done: 4485 if (ncp) 4486 _cache_drop(ncp); 4487 return(error); 4488 } 4489 4490 int 4491 vn_fullpath(struct proc *p, struct vnode *vn, char **retbuf, 4492 char **freebuf, int guess) 4493 { 4494 struct namecache *ncp; 4495 struct nchandle nch; 4496 int error; 4497 4498 *freebuf = NULL; 4499 if (disablefullpath) 4500 return (ENODEV); 4501 4502 if (p == NULL) 4503 return (EINVAL); 4504 4505 /* vn is NULL, client wants us to use p->p_textvp */ 4506 if (vn == NULL) { 4507 if ((vn = p->p_textvp) == NULL) 4508 return (EINVAL); 4509 } 4510 spin_lock_shared(&vn->v_spin); 4511 TAILQ_FOREACH(ncp, &vn->v_namecache, nc_vnode) { 4512 if (ncp->nc_nlen) 4513 break; 4514 } 4515 if (ncp == NULL) { 4516 spin_unlock_shared(&vn->v_spin); 4517 return (EINVAL); 4518 } 4519 _cache_hold(ncp); 4520 spin_unlock_shared(&vn->v_spin); 4521 4522 nch.ncp = ncp; 4523 nch.mount = vn->v_mount; 4524 error = cache_fullpath(p, &nch, NULL, retbuf, freebuf, guess); 4525 _cache_drop(ncp); 4526 return (error); 4527 } 4528 4529 void 4530 vfscache_rollup_cpu(struct globaldata *gd) 4531 { 4532 struct pcpu_ncache *pn; 4533 long count; 4534 4535 if (pcpu_ncache == NULL) 4536 return; 4537 pn = &pcpu_ncache[gd->gd_cpuid]; 4538 4539 if (pn->vfscache_count) { 4540 count = atomic_swap_long(&pn->vfscache_count, 0); 4541 atomic_add_long(&vfscache_count, count); 4542 } 4543 if (pn->vfscache_leafs) { 4544 count = atomic_swap_long(&pn->vfscache_leafs, 0); 4545 atomic_add_long(&vfscache_leafs, count); 4546 } 4547 if (pn->vfscache_negs) { 4548 count = atomic_swap_long(&pn->vfscache_negs, 0); 4549 atomic_add_long(&vfscache_negs, count); 4550 } 4551 if (pn->numdefered) { 4552 count = atomic_swap_long(&pn->numdefered, 0); 4553 atomic_add_long(&numdefered, count); 4554 } 4555 } 4556 4557 #if 0 4558 static void 4559 vfscache_rollup_all(void) 4560 { 4561 int n; 4562 4563 for (n = 0; n < ncpus; ++n) 4564 vfscache_rollup_cpu(globaldata_find(n)); 4565 } 4566 #endif 4567