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/kernel.h> 68 #include <sys/sysctl.h> 69 #include <sys/mount.h> 70 #include <sys/vnode.h> 71 #include <sys/malloc.h> 72 #include <sys/sysproto.h> 73 #include <sys/spinlock.h> 74 #include <sys/proc.h> 75 #include <sys/namei.h> 76 #include <sys/nlookup.h> 77 #include <sys/filedesc.h> 78 #include <sys/fnv_hash.h> 79 #include <sys/globaldata.h> 80 #include <sys/kern_syscall.h> 81 #include <sys/dirent.h> 82 #include <ddb/ddb.h> 83 84 #include <sys/sysref2.h> 85 #include <sys/spinlock2.h> 86 #include <sys/mplock2.h> 87 88 #define MAX_RECURSION_DEPTH 64 89 90 /* 91 * Random lookups in the cache are accomplished with a hash table using 92 * a hash key of (nc_src_vp, name). Each hash chain has its own spin lock. 93 * 94 * Negative entries may exist and correspond to resolved namecache 95 * structures where nc_vp is NULL. In a negative entry, NCF_WHITEOUT 96 * will be set if the entry corresponds to a whited-out directory entry 97 * (verses simply not finding the entry at all). ncneglist is locked 98 * with a global spinlock (ncspin). 99 * 100 * MPSAFE RULES: 101 * 102 * (1) A ncp must be referenced before it can be locked. 103 * 104 * (2) A ncp must be locked in order to modify it. 105 * 106 * (3) ncp locks are always ordered child -> parent. That may seem 107 * backwards but forward scans use the hash table and thus can hold 108 * the parent unlocked when traversing downward. 109 * 110 * This allows insert/rename/delete/dot-dot and other operations 111 * to use ncp->nc_parent links. 112 * 113 * This also prevents a locked up e.g. NFS node from creating a 114 * chain reaction all the way back to the root vnode / namecache. 115 * 116 * (4) parent linkages require both the parent and child to be locked. 117 */ 118 119 /* 120 * Structures associated with name cacheing. 121 */ 122 #define NCHHASH(hash) (&nchashtbl[(hash) & nchash]) 123 #define MINNEG 1024 124 #define MINPOS 1024 125 #define NCMOUNT_NUMCACHE 1009 /* prime number */ 126 127 MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries"); 128 129 LIST_HEAD(nchash_list, namecache); 130 131 struct nchash_head { 132 struct nchash_list list; 133 struct spinlock spin; 134 }; 135 136 struct ncmount_cache { 137 struct spinlock spin; 138 struct namecache *ncp; 139 struct mount *mp; 140 int isneg; /* if != 0 mp is originator and not target */ 141 }; 142 143 static struct nchash_head *nchashtbl; 144 static struct namecache_list ncneglist; 145 static struct spinlock ncspin; 146 static struct ncmount_cache ncmount_cache[NCMOUNT_NUMCACHE]; 147 148 /* 149 * ncvp_debug - debug cache_fromvp(). This is used by the NFS server 150 * to create the namecache infrastructure leading to a dangling vnode. 151 * 152 * 0 Only errors are reported 153 * 1 Successes are reported 154 * 2 Successes + the whole directory scan is reported 155 * 3 Force the directory scan code run as if the parent vnode did not 156 * have a namecache record, even if it does have one. 157 */ 158 static int ncvp_debug; 159 SYSCTL_INT(_debug, OID_AUTO, ncvp_debug, CTLFLAG_RW, &ncvp_debug, 0, 160 "Namecache debug level (0-3)"); 161 162 static u_long nchash; /* size of hash table */ 163 SYSCTL_ULONG(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0, 164 "Size of namecache hash table"); 165 166 static int ncnegflush = 10; /* burst for negative flush */ 167 SYSCTL_INT(_debug, OID_AUTO, ncnegflush, CTLFLAG_RW, &ncnegflush, 0, 168 "Batch flush negative entries"); 169 170 static int ncposflush = 10; /* burst for positive flush */ 171 SYSCTL_INT(_debug, OID_AUTO, ncposflush, CTLFLAG_RW, &ncposflush, 0, 172 "Batch flush positive entries"); 173 174 static int ncnegfactor = 16; /* ratio of negative entries */ 175 SYSCTL_INT(_debug, OID_AUTO, ncnegfactor, CTLFLAG_RW, &ncnegfactor, 0, 176 "Ratio of namecache negative entries"); 177 178 static int nclockwarn; /* warn on locked entries in ticks */ 179 SYSCTL_INT(_debug, OID_AUTO, nclockwarn, CTLFLAG_RW, &nclockwarn, 0, 180 "Warn on locked namecache entries in ticks"); 181 182 static int numdefered; /* number of cache entries allocated */ 183 SYSCTL_INT(_debug, OID_AUTO, numdefered, CTLFLAG_RD, &numdefered, 0, 184 "Number of cache entries allocated"); 185 186 static int ncposlimit; /* number of cache entries allocated */ 187 SYSCTL_INT(_debug, OID_AUTO, ncposlimit, CTLFLAG_RW, &ncposlimit, 0, 188 "Number of cache entries allocated"); 189 190 static int ncp_shared_lock_disable = 0; 191 SYSCTL_INT(_debug, OID_AUTO, ncp_shared_lock_disable, CTLFLAG_RW, 192 &ncp_shared_lock_disable, 0, "Disable shared namecache locks"); 193 194 SYSCTL_INT(_debug, OID_AUTO, vnsize, CTLFLAG_RD, 0, sizeof(struct vnode), 195 "sizeof(struct vnode)"); 196 SYSCTL_INT(_debug, OID_AUTO, ncsize, CTLFLAG_RD, 0, sizeof(struct namecache), 197 "sizeof(struct namecache)"); 198 199 static int ncmount_cache_enable = 1; 200 SYSCTL_INT(_debug, OID_AUTO, ncmount_cache_enable, CTLFLAG_RW, 201 &ncmount_cache_enable, 0, "mount point cache"); 202 static long ncmount_cache_hit; 203 SYSCTL_LONG(_debug, OID_AUTO, ncmount_cache_hit, CTLFLAG_RW, 204 &ncmount_cache_hit, 0, "mpcache hits"); 205 static long ncmount_cache_miss; 206 SYSCTL_LONG(_debug, OID_AUTO, ncmount_cache_miss, CTLFLAG_RW, 207 &ncmount_cache_miss, 0, "mpcache misses"); 208 static long ncmount_cache_overwrite; 209 SYSCTL_LONG(_debug, OID_AUTO, ncmount_cache_overwrite, CTLFLAG_RW, 210 &ncmount_cache_overwrite, 0, "mpcache entry overwrites"); 211 212 static int cache_resolve_mp(struct mount *mp); 213 static struct vnode *cache_dvpref(struct namecache *ncp); 214 static void _cache_lock(struct namecache *ncp); 215 static void _cache_setunresolved(struct namecache *ncp); 216 static void _cache_cleanneg(int count); 217 static void _cache_cleanpos(int count); 218 static void _cache_cleandefered(void); 219 static void _cache_unlink(struct namecache *ncp); 220 221 /* 222 * The new name cache statistics 223 */ 224 SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW, 0, "Name cache statistics"); 225 static int numneg; 226 SYSCTL_INT(_vfs_cache, OID_AUTO, numneg, CTLFLAG_RD, &numneg, 0, 227 "Number of negative namecache entries"); 228 static int numcache; 229 SYSCTL_INT(_vfs_cache, OID_AUTO, numcache, CTLFLAG_RD, &numcache, 0, 230 "Number of namecaches entries"); 231 static u_long numcalls; 232 SYSCTL_ULONG(_vfs_cache, OID_AUTO, numcalls, CTLFLAG_RD, &numcalls, 0, 233 "Number of namecache lookups"); 234 static u_long numchecks; 235 SYSCTL_ULONG(_vfs_cache, OID_AUTO, numchecks, CTLFLAG_RD, &numchecks, 0, 236 "Number of checked entries in namecache lookups"); 237 238 struct nchstats nchstats[SMP_MAXCPU]; 239 /* 240 * Export VFS cache effectiveness statistics to user-land. 241 * 242 * The statistics are left for aggregation to user-land so 243 * neat things can be achieved, like observing per-CPU cache 244 * distribution. 245 */ 246 static int 247 sysctl_nchstats(SYSCTL_HANDLER_ARGS) 248 { 249 struct globaldata *gd; 250 int i, error; 251 252 error = 0; 253 for (i = 0; i < ncpus; ++i) { 254 gd = globaldata_find(i); 255 if ((error = SYSCTL_OUT(req, (void *)&(*gd->gd_nchstats), 256 sizeof(struct nchstats)))) 257 break; 258 } 259 260 return (error); 261 } 262 SYSCTL_PROC(_vfs_cache, OID_AUTO, nchstats, CTLTYPE_OPAQUE|CTLFLAG_RD, 263 0, 0, sysctl_nchstats, "S,nchstats", "VFS cache effectiveness statistics"); 264 265 static struct namecache *cache_zap(struct namecache *ncp, int nonblock); 266 267 /* 268 * Namespace locking. The caller must already hold a reference to the 269 * namecache structure in order to lock/unlock it. This function prevents 270 * the namespace from being created or destroyed by accessors other then 271 * the lock holder. 272 * 273 * Note that holding a locked namecache structure prevents other threads 274 * from making namespace changes (e.g. deleting or creating), prevents 275 * vnode association state changes by other threads, and prevents the 276 * namecache entry from being resolved or unresolved by other threads. 277 * 278 * An exclusive lock owner has full authority to associate/disassociate 279 * vnodes and resolve/unresolve the locked ncp. 280 * 281 * A shared lock owner only has authority to acquire the underlying vnode, 282 * if any. 283 * 284 * The primary lock field is nc_lockstatus. nc_locktd is set after the 285 * fact (when locking) or cleared prior to unlocking. 286 * 287 * WARNING! Holding a locked ncp will prevent a vnode from being destroyed 288 * or recycled, but it does NOT help you if the vnode had already 289 * initiated a recyclement. If this is important, use cache_get() 290 * rather then cache_lock() (and deal with the differences in the 291 * way the refs counter is handled). Or, alternatively, make an 292 * unconditional call to cache_validate() or cache_resolve() 293 * after cache_lock() returns. 294 */ 295 static 296 void 297 _cache_lock(struct namecache *ncp) 298 { 299 thread_t td; 300 int didwarn; 301 int begticks; 302 int error; 303 u_int count; 304 305 KKASSERT(ncp->nc_refs != 0); 306 didwarn = 0; 307 begticks = 0; 308 td = curthread; 309 310 for (;;) { 311 count = ncp->nc_lockstatus; 312 cpu_ccfence(); 313 314 if ((count & ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) == 0) { 315 if (atomic_cmpset_int(&ncp->nc_lockstatus, 316 count, count + 1)) { 317 /* 318 * The vp associated with a locked ncp must 319 * be held to prevent it from being recycled. 320 * 321 * WARNING! If VRECLAIMED is set the vnode 322 * could already be in the middle of a recycle. 323 * Callers must use cache_vref() or 324 * cache_vget() on the locked ncp to 325 * validate the vp or set the cache entry 326 * to unresolved. 327 * 328 * NOTE! vhold() is allowed if we hold a 329 * lock on the ncp (which we do). 330 */ 331 ncp->nc_locktd = td; 332 if (ncp->nc_vp) 333 vhold(ncp->nc_vp); 334 break; 335 } 336 /* cmpset failed */ 337 continue; 338 } 339 if (ncp->nc_locktd == td) { 340 KKASSERT((count & NC_SHLOCK_FLAG) == 0); 341 if (atomic_cmpset_int(&ncp->nc_lockstatus, 342 count, count + 1)) { 343 break; 344 } 345 /* cmpset failed */ 346 continue; 347 } 348 tsleep_interlock(&ncp->nc_locktd, 0); 349 if (atomic_cmpset_int(&ncp->nc_lockstatus, count, 350 count | NC_EXLOCK_REQ) == 0) { 351 /* cmpset failed */ 352 continue; 353 } 354 if (begticks == 0) 355 begticks = ticks; 356 error = tsleep(&ncp->nc_locktd, PINTERLOCKED, 357 "clock", nclockwarn); 358 if (error == EWOULDBLOCK) { 359 if (didwarn == 0) { 360 didwarn = ticks; 361 kprintf("[diagnostic] cache_lock: " 362 "blocked on %p %08x", 363 ncp, count); 364 kprintf(" \"%*.*s\"\n", 365 ncp->nc_nlen, ncp->nc_nlen, 366 ncp->nc_name); 367 } 368 } 369 /* loop */ 370 } 371 if (didwarn) { 372 kprintf("[diagnostic] cache_lock: unblocked %*.*s after " 373 "%d secs\n", 374 ncp->nc_nlen, ncp->nc_nlen, ncp->nc_name, 375 (int)(ticks + (hz / 2) - begticks) / hz); 376 } 377 } 378 379 /* 380 * The shared lock works similarly to the exclusive lock except 381 * nc_locktd is left NULL and we need an interlock (VHOLD) to 382 * prevent vhold() races, since the moment our cmpset_int succeeds 383 * another cpu can come in and get its own shared lock. 384 * 385 * A critical section is needed to prevent interruption during the 386 * VHOLD interlock. 387 */ 388 static 389 void 390 _cache_lock_shared(struct namecache *ncp) 391 { 392 int didwarn; 393 int error; 394 u_int count; 395 u_int optreq = NC_EXLOCK_REQ; 396 397 KKASSERT(ncp->nc_refs != 0); 398 didwarn = 0; 399 400 for (;;) { 401 count = ncp->nc_lockstatus; 402 cpu_ccfence(); 403 404 if ((count & ~NC_SHLOCK_REQ) == 0) { 405 crit_enter(); 406 if (atomic_cmpset_int(&ncp->nc_lockstatus, 407 count, 408 (count + 1) | NC_SHLOCK_FLAG | 409 NC_SHLOCK_VHOLD)) { 410 /* 411 * The vp associated with a locked ncp must 412 * be held to prevent it from being recycled. 413 * 414 * WARNING! If VRECLAIMED is set the vnode 415 * could already be in the middle of a recycle. 416 * Callers must use cache_vref() or 417 * cache_vget() on the locked ncp to 418 * validate the vp or set the cache entry 419 * to unresolved. 420 * 421 * NOTE! vhold() is allowed if we hold a 422 * lock on the ncp (which we do). 423 */ 424 if (ncp->nc_vp) 425 vhold(ncp->nc_vp); 426 atomic_clear_int(&ncp->nc_lockstatus, 427 NC_SHLOCK_VHOLD); 428 crit_exit(); 429 break; 430 } 431 /* cmpset failed */ 432 crit_exit(); 433 continue; 434 } 435 436 /* 437 * If already held shared we can just bump the count, but 438 * only allow this if nobody is trying to get the lock 439 * exclusively. If we are blocking too long ignore excl 440 * requests (which can race/deadlock us). 441 * 442 * VHOLD is a bit of a hack. Even though we successfully 443 * added another shared ref, the cpu that got the first 444 * shared ref might not yet have held the vnode. 445 */ 446 if ((count & (optreq|NC_SHLOCK_FLAG)) == NC_SHLOCK_FLAG) { 447 KKASSERT((count & ~(NC_EXLOCK_REQ | 448 NC_SHLOCK_REQ | 449 NC_SHLOCK_FLAG)) > 0); 450 if (atomic_cmpset_int(&ncp->nc_lockstatus, 451 count, count + 1)) { 452 while (ncp->nc_lockstatus & NC_SHLOCK_VHOLD) 453 cpu_pause(); 454 break; 455 } 456 continue; 457 } 458 tsleep_interlock(ncp, 0); 459 if (atomic_cmpset_int(&ncp->nc_lockstatus, count, 460 count | NC_SHLOCK_REQ) == 0) { 461 /* cmpset failed */ 462 continue; 463 } 464 error = tsleep(ncp, PINTERLOCKED, "clocksh", nclockwarn); 465 if (error == EWOULDBLOCK) { 466 optreq = 0; 467 if (didwarn == 0) { 468 didwarn = ticks; 469 kprintf("[diagnostic] cache_lock_shared: " 470 "blocked on %p %08x", 471 ncp, count); 472 kprintf(" \"%*.*s\"\n", 473 ncp->nc_nlen, ncp->nc_nlen, 474 ncp->nc_name); 475 } 476 } 477 /* loop */ 478 } 479 if (didwarn) { 480 kprintf("[diagnostic] cache_lock_shared: " 481 "unblocked %*.*s after %d secs\n", 482 ncp->nc_nlen, ncp->nc_nlen, ncp->nc_name, 483 (int)(ticks - didwarn) / hz); 484 } 485 } 486 487 /* 488 * NOTE: nc_refs may be zero if the ncp is interlocked by circumstance, 489 * such as the case where one of its children is locked. 490 */ 491 static 492 int 493 _cache_lock_nonblock(struct namecache *ncp) 494 { 495 thread_t td; 496 u_int count; 497 498 td = curthread; 499 500 for (;;) { 501 count = ncp->nc_lockstatus; 502 503 if ((count & ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) == 0) { 504 if (atomic_cmpset_int(&ncp->nc_lockstatus, 505 count, count + 1)) { 506 /* 507 * The vp associated with a locked ncp must 508 * be held to prevent it from being recycled. 509 * 510 * WARNING! If VRECLAIMED is set the vnode 511 * could already be in the middle of a recycle. 512 * Callers must use cache_vref() or 513 * cache_vget() on the locked ncp to 514 * validate the vp or set the cache entry 515 * to unresolved. 516 * 517 * NOTE! vhold() is allowed if we hold a 518 * lock on the ncp (which we do). 519 */ 520 ncp->nc_locktd = td; 521 if (ncp->nc_vp) 522 vhold(ncp->nc_vp); 523 break; 524 } 525 /* cmpset failed */ 526 continue; 527 } 528 if (ncp->nc_locktd == td) { 529 if (atomic_cmpset_int(&ncp->nc_lockstatus, 530 count, count + 1)) { 531 break; 532 } 533 /* cmpset failed */ 534 continue; 535 } 536 return(EWOULDBLOCK); 537 } 538 return(0); 539 } 540 541 /* 542 * The shared lock works similarly to the exclusive lock except 543 * nc_locktd is left NULL and we need an interlock (VHOLD) to 544 * prevent vhold() races, since the moment our cmpset_int succeeds 545 * another cpu can come in and get its own shared lock. 546 * 547 * A critical section is needed to prevent interruption during the 548 * VHOLD interlock. 549 */ 550 static 551 int 552 _cache_lock_shared_nonblock(struct namecache *ncp) 553 { 554 u_int count; 555 556 for (;;) { 557 count = ncp->nc_lockstatus; 558 559 if ((count & ~NC_SHLOCK_REQ) == 0) { 560 crit_enter(); 561 if (atomic_cmpset_int(&ncp->nc_lockstatus, 562 count, 563 (count + 1) | NC_SHLOCK_FLAG | 564 NC_SHLOCK_VHOLD)) { 565 /* 566 * The vp associated with a locked ncp must 567 * be held to prevent it from being recycled. 568 * 569 * WARNING! If VRECLAIMED is set the vnode 570 * could already be in the middle of a recycle. 571 * Callers must use cache_vref() or 572 * cache_vget() on the locked ncp to 573 * validate the vp or set the cache entry 574 * to unresolved. 575 * 576 * NOTE! vhold() is allowed if we hold a 577 * lock on the ncp (which we do). 578 */ 579 if (ncp->nc_vp) 580 vhold(ncp->nc_vp); 581 atomic_clear_int(&ncp->nc_lockstatus, 582 NC_SHLOCK_VHOLD); 583 crit_exit(); 584 break; 585 } 586 /* cmpset failed */ 587 crit_exit(); 588 continue; 589 } 590 591 /* 592 * If already held shared we can just bump the count, but 593 * only allow this if nobody is trying to get the lock 594 * exclusively. 595 * 596 * VHOLD is a bit of a hack. Even though we successfully 597 * added another shared ref, the cpu that got the first 598 * shared ref might not yet have held the vnode. 599 */ 600 if ((count & (NC_EXLOCK_REQ|NC_SHLOCK_FLAG)) == 601 NC_SHLOCK_FLAG) { 602 KKASSERT((count & ~(NC_EXLOCK_REQ | 603 NC_SHLOCK_REQ | 604 NC_SHLOCK_FLAG)) > 0); 605 if (atomic_cmpset_int(&ncp->nc_lockstatus, 606 count, count + 1)) { 607 while (ncp->nc_lockstatus & NC_SHLOCK_VHOLD) 608 cpu_pause(); 609 break; 610 } 611 continue; 612 } 613 return(EWOULDBLOCK); 614 } 615 return(0); 616 } 617 618 /* 619 * Helper function 620 * 621 * NOTE: nc_refs can be 0 (degenerate case during _cache_drop). 622 * 623 * nc_locktd must be NULLed out prior to nc_lockstatus getting cleared. 624 */ 625 static 626 void 627 _cache_unlock(struct namecache *ncp) 628 { 629 thread_t td __debugvar = curthread; 630 u_int count; 631 u_int ncount; 632 struct vnode *dropvp; 633 634 KKASSERT(ncp->nc_refs >= 0); 635 KKASSERT((ncp->nc_lockstatus & ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) > 0); 636 KKASSERT((ncp->nc_lockstatus & NC_SHLOCK_FLAG) || ncp->nc_locktd == td); 637 638 count = ncp->nc_lockstatus; 639 cpu_ccfence(); 640 641 /* 642 * Clear nc_locktd prior to the atomic op (excl lock only) 643 */ 644 if ((count & ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) == 1) 645 ncp->nc_locktd = NULL; 646 dropvp = NULL; 647 648 for (;;) { 649 if ((count & 650 ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ|NC_SHLOCK_FLAG)) == 1) { 651 dropvp = ncp->nc_vp; 652 if (count & NC_EXLOCK_REQ) 653 ncount = count & NC_SHLOCK_REQ; /* cnt->0 */ 654 else 655 ncount = 0; 656 657 if (atomic_cmpset_int(&ncp->nc_lockstatus, 658 count, ncount)) { 659 if (count & NC_EXLOCK_REQ) 660 wakeup(&ncp->nc_locktd); 661 else if (count & NC_SHLOCK_REQ) 662 wakeup(ncp); 663 break; 664 } 665 dropvp = NULL; 666 } else { 667 KKASSERT((count & NC_SHLOCK_VHOLD) == 0); 668 KKASSERT((count & ~(NC_EXLOCK_REQ | 669 NC_SHLOCK_REQ | 670 NC_SHLOCK_FLAG)) > 1); 671 if (atomic_cmpset_int(&ncp->nc_lockstatus, 672 count, count - 1)) { 673 break; 674 } 675 } 676 count = ncp->nc_lockstatus; 677 cpu_ccfence(); 678 } 679 680 /* 681 * Don't actually drop the vp until we successfully clean out 682 * the lock, otherwise we may race another shared lock. 683 */ 684 if (dropvp) 685 vdrop(dropvp); 686 } 687 688 static 689 int 690 _cache_lockstatus(struct namecache *ncp) 691 { 692 if (ncp->nc_locktd == curthread) 693 return(LK_EXCLUSIVE); 694 if (ncp->nc_lockstatus & NC_SHLOCK_FLAG) 695 return(LK_SHARED); 696 return(-1); 697 } 698 699 /* 700 * cache_hold() and cache_drop() prevent the premature deletion of a 701 * namecache entry but do not prevent operations (such as zapping) on 702 * that namecache entry. 703 * 704 * This routine may only be called from outside this source module if 705 * nc_refs is already at least 1. 706 * 707 * This is a rare case where callers are allowed to hold a spinlock, 708 * so we can't ourselves. 709 */ 710 static __inline 711 struct namecache * 712 _cache_hold(struct namecache *ncp) 713 { 714 atomic_add_int(&ncp->nc_refs, 1); 715 return(ncp); 716 } 717 718 /* 719 * Drop a cache entry, taking care to deal with races. 720 * 721 * For potential 1->0 transitions we must hold the ncp lock to safely 722 * test its flags. An unresolved entry with no children must be zapped 723 * to avoid leaks. 724 * 725 * The call to cache_zap() itself will handle all remaining races and 726 * will decrement the ncp's refs regardless. If we are resolved or 727 * have children nc_refs can safely be dropped to 0 without having to 728 * zap the entry. 729 * 730 * NOTE: cache_zap() will re-check nc_refs and nc_list in a MPSAFE fashion. 731 * 732 * NOTE: cache_zap() may return a non-NULL referenced parent which must 733 * be dropped in a loop. 734 */ 735 static __inline 736 void 737 _cache_drop(struct namecache *ncp) 738 { 739 int refs; 740 741 while (ncp) { 742 KKASSERT(ncp->nc_refs > 0); 743 refs = ncp->nc_refs; 744 745 if (refs == 1) { 746 if (_cache_lock_nonblock(ncp) == 0) { 747 ncp->nc_flag &= ~NCF_DEFEREDZAP; 748 if ((ncp->nc_flag & NCF_UNRESOLVED) && 749 TAILQ_EMPTY(&ncp->nc_list)) { 750 ncp = cache_zap(ncp, 1); 751 continue; 752 } 753 if (atomic_cmpset_int(&ncp->nc_refs, 1, 0)) { 754 _cache_unlock(ncp); 755 break; 756 } 757 _cache_unlock(ncp); 758 } 759 } else { 760 if (atomic_cmpset_int(&ncp->nc_refs, refs, refs - 1)) 761 break; 762 } 763 cpu_pause(); 764 } 765 } 766 767 /* 768 * Link a new namecache entry to its parent and to the hash table. Be 769 * careful to avoid races if vhold() blocks in the future. 770 * 771 * Both ncp and par must be referenced and locked. 772 * 773 * NOTE: The hash table spinlock is held during this call, we can't do 774 * anything fancy. 775 */ 776 static void 777 _cache_link_parent(struct namecache *ncp, struct namecache *par, 778 struct nchash_head *nchpp) 779 { 780 KKASSERT(ncp->nc_parent == NULL); 781 ncp->nc_parent = par; 782 ncp->nc_head = nchpp; 783 784 /* 785 * Set inheritance flags. Note that the parent flags may be 786 * stale due to getattr potentially not having been run yet 787 * (it gets run during nlookup()'s). 788 */ 789 ncp->nc_flag &= ~(NCF_SF_PNOCACHE | NCF_UF_PCACHE); 790 if (par->nc_flag & (NCF_SF_NOCACHE | NCF_SF_PNOCACHE)) 791 ncp->nc_flag |= NCF_SF_PNOCACHE; 792 if (par->nc_flag & (NCF_UF_CACHE | NCF_UF_PCACHE)) 793 ncp->nc_flag |= NCF_UF_PCACHE; 794 795 LIST_INSERT_HEAD(&nchpp->list, ncp, nc_hash); 796 797 if (TAILQ_EMPTY(&par->nc_list)) { 798 TAILQ_INSERT_HEAD(&par->nc_list, ncp, nc_entry); 799 /* 800 * Any vp associated with an ncp which has children must 801 * be held to prevent it from being recycled. 802 */ 803 if (par->nc_vp) 804 vhold(par->nc_vp); 805 } else { 806 TAILQ_INSERT_HEAD(&par->nc_list, ncp, nc_entry); 807 } 808 } 809 810 /* 811 * Remove the parent and hash associations from a namecache structure. 812 * If this is the last child of the parent the cache_drop(par) will 813 * attempt to recursively zap the parent. 814 * 815 * ncp must be locked. This routine will acquire a temporary lock on 816 * the parent as wlel as the appropriate hash chain. 817 */ 818 static void 819 _cache_unlink_parent(struct namecache *ncp) 820 { 821 struct namecache *par; 822 struct vnode *dropvp; 823 824 if ((par = ncp->nc_parent) != NULL) { 825 KKASSERT(ncp->nc_parent == par); 826 _cache_hold(par); 827 _cache_lock(par); 828 spin_lock(&ncp->nc_head->spin); 829 LIST_REMOVE(ncp, nc_hash); 830 TAILQ_REMOVE(&par->nc_list, ncp, nc_entry); 831 dropvp = NULL; 832 if (par->nc_vp && TAILQ_EMPTY(&par->nc_list)) 833 dropvp = par->nc_vp; 834 spin_unlock(&ncp->nc_head->spin); 835 ncp->nc_parent = NULL; 836 ncp->nc_head = NULL; 837 _cache_unlock(par); 838 _cache_drop(par); 839 840 /* 841 * We can only safely vdrop with no spinlocks held. 842 */ 843 if (dropvp) 844 vdrop(dropvp); 845 } 846 } 847 848 /* 849 * Allocate a new namecache structure. Most of the code does not require 850 * zero-termination of the string but it makes vop_compat_ncreate() easier. 851 */ 852 static struct namecache * 853 cache_alloc(int nlen) 854 { 855 struct namecache *ncp; 856 857 ncp = kmalloc(sizeof(*ncp), M_VFSCACHE, M_WAITOK|M_ZERO); 858 if (nlen) 859 ncp->nc_name = kmalloc(nlen + 1, M_VFSCACHE, M_WAITOK); 860 ncp->nc_nlen = nlen; 861 ncp->nc_flag = NCF_UNRESOLVED; 862 ncp->nc_error = ENOTCONN; /* needs to be resolved */ 863 ncp->nc_refs = 1; 864 865 TAILQ_INIT(&ncp->nc_list); 866 _cache_lock(ncp); 867 return(ncp); 868 } 869 870 /* 871 * Can only be called for the case where the ncp has never been 872 * associated with anything (so no spinlocks are needed). 873 */ 874 static void 875 _cache_free(struct namecache *ncp) 876 { 877 KKASSERT(ncp->nc_refs == 1 && ncp->nc_lockstatus == 1); 878 if (ncp->nc_name) 879 kfree(ncp->nc_name, M_VFSCACHE); 880 kfree(ncp, M_VFSCACHE); 881 } 882 883 /* 884 * [re]initialize a nchandle. 885 */ 886 void 887 cache_zero(struct nchandle *nch) 888 { 889 nch->ncp = NULL; 890 nch->mount = NULL; 891 } 892 893 /* 894 * Ref and deref a namecache structure. 895 * 896 * The caller must specify a stable ncp pointer, typically meaning the 897 * ncp is already referenced but this can also occur indirectly through 898 * e.g. holding a lock on a direct child. 899 * 900 * WARNING: Caller may hold an unrelated read spinlock, which means we can't 901 * use read spinlocks here. 902 * 903 * MPSAFE if nch is 904 */ 905 struct nchandle * 906 cache_hold(struct nchandle *nch) 907 { 908 _cache_hold(nch->ncp); 909 atomic_add_int(&nch->mount->mnt_refs, 1); 910 return(nch); 911 } 912 913 /* 914 * Create a copy of a namecache handle for an already-referenced 915 * entry. 916 * 917 * MPSAFE if nch is 918 */ 919 void 920 cache_copy(struct nchandle *nch, struct nchandle *target) 921 { 922 *target = *nch; 923 if (target->ncp) 924 _cache_hold(target->ncp); 925 atomic_add_int(&nch->mount->mnt_refs, 1); 926 } 927 928 /* 929 * MPSAFE if nch is 930 */ 931 void 932 cache_changemount(struct nchandle *nch, struct mount *mp) 933 { 934 atomic_add_int(&nch->mount->mnt_refs, -1); 935 nch->mount = mp; 936 atomic_add_int(&nch->mount->mnt_refs, 1); 937 } 938 939 void 940 cache_drop(struct nchandle *nch) 941 { 942 atomic_add_int(&nch->mount->mnt_refs, -1); 943 _cache_drop(nch->ncp); 944 nch->ncp = NULL; 945 nch->mount = NULL; 946 } 947 948 int 949 cache_lockstatus(struct nchandle *nch) 950 { 951 return(_cache_lockstatus(nch->ncp)); 952 } 953 954 void 955 cache_lock(struct nchandle *nch) 956 { 957 _cache_lock(nch->ncp); 958 } 959 960 void 961 cache_lock_maybe_shared(struct nchandle *nch, int excl) 962 { 963 struct namecache *ncp = nch->ncp; 964 965 if (ncp_shared_lock_disable || excl || 966 (ncp->nc_flag & NCF_UNRESOLVED)) { 967 _cache_lock(ncp); 968 } else { 969 _cache_lock_shared(ncp); 970 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) { 971 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED)) { 972 _cache_unlock(ncp); 973 _cache_lock(ncp); 974 } 975 } else { 976 _cache_unlock(ncp); 977 _cache_lock(ncp); 978 } 979 } 980 } 981 982 /* 983 * Relock nch1 given an unlocked nch1 and a locked nch2. The caller 984 * is responsible for checking both for validity on return as they 985 * may have become invalid. 986 * 987 * We have to deal with potential deadlocks here, just ping pong 988 * the lock until we get it (we will always block somewhere when 989 * looping so this is not cpu-intensive). 990 * 991 * which = 0 nch1 not locked, nch2 is locked 992 * which = 1 nch1 is locked, nch2 is not locked 993 */ 994 void 995 cache_relock(struct nchandle *nch1, struct ucred *cred1, 996 struct nchandle *nch2, struct ucred *cred2) 997 { 998 int which; 999 1000 which = 0; 1001 1002 for (;;) { 1003 if (which == 0) { 1004 if (cache_lock_nonblock(nch1) == 0) { 1005 cache_resolve(nch1, cred1); 1006 break; 1007 } 1008 cache_unlock(nch2); 1009 cache_lock(nch1); 1010 cache_resolve(nch1, cred1); 1011 which = 1; 1012 } else { 1013 if (cache_lock_nonblock(nch2) == 0) { 1014 cache_resolve(nch2, cred2); 1015 break; 1016 } 1017 cache_unlock(nch1); 1018 cache_lock(nch2); 1019 cache_resolve(nch2, cred2); 1020 which = 0; 1021 } 1022 } 1023 } 1024 1025 int 1026 cache_lock_nonblock(struct nchandle *nch) 1027 { 1028 return(_cache_lock_nonblock(nch->ncp)); 1029 } 1030 1031 void 1032 cache_unlock(struct nchandle *nch) 1033 { 1034 _cache_unlock(nch->ncp); 1035 } 1036 1037 /* 1038 * ref-and-lock, unlock-and-deref functions. 1039 * 1040 * This function is primarily used by nlookup. Even though cache_lock 1041 * holds the vnode, it is possible that the vnode may have already 1042 * initiated a recyclement. 1043 * 1044 * We want cache_get() to return a definitively usable vnode or a 1045 * definitively unresolved ncp. 1046 */ 1047 static 1048 struct namecache * 1049 _cache_get(struct namecache *ncp) 1050 { 1051 _cache_hold(ncp); 1052 _cache_lock(ncp); 1053 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED)) 1054 _cache_setunresolved(ncp); 1055 return(ncp); 1056 } 1057 1058 /* 1059 * Attempt to obtain a shared lock on the ncp. A shared lock will only 1060 * be obtained if the ncp is resolved and the vnode (if not ENOENT) is 1061 * valid. Otherwise an exclusive lock will be acquired instead. 1062 */ 1063 static 1064 struct namecache * 1065 _cache_get_maybe_shared(struct namecache *ncp, int excl) 1066 { 1067 if (ncp_shared_lock_disable || excl || 1068 (ncp->nc_flag & NCF_UNRESOLVED)) { 1069 return(_cache_get(ncp)); 1070 } 1071 _cache_hold(ncp); 1072 _cache_lock_shared(ncp); 1073 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) { 1074 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED)) { 1075 _cache_unlock(ncp); 1076 ncp = _cache_get(ncp); 1077 _cache_drop(ncp); 1078 } 1079 } else { 1080 _cache_unlock(ncp); 1081 ncp = _cache_get(ncp); 1082 _cache_drop(ncp); 1083 } 1084 return(ncp); 1085 } 1086 1087 /* 1088 * This is a special form of _cache_lock() which only succeeds if 1089 * it can get a pristine, non-recursive lock. The caller must have 1090 * already ref'd the ncp. 1091 * 1092 * On success the ncp will be locked, on failure it will not. The 1093 * ref count does not change either way. 1094 * 1095 * We want _cache_lock_special() (on success) to return a definitively 1096 * usable vnode or a definitively unresolved ncp. 1097 */ 1098 static int 1099 _cache_lock_special(struct namecache *ncp) 1100 { 1101 if (_cache_lock_nonblock(ncp) == 0) { 1102 if ((ncp->nc_lockstatus & 1103 ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) == 1) { 1104 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED)) 1105 _cache_setunresolved(ncp); 1106 return(0); 1107 } 1108 _cache_unlock(ncp); 1109 } 1110 return(EWOULDBLOCK); 1111 } 1112 1113 /* 1114 * This function tries to get a shared lock but will back-off to an exclusive 1115 * lock if: 1116 * 1117 * (1) Some other thread is trying to obtain an exclusive lock 1118 * (to prevent the exclusive requester from getting livelocked out 1119 * by many shared locks). 1120 * 1121 * (2) The current thread already owns an exclusive lock (to avoid 1122 * deadlocking). 1123 * 1124 * WARNING! On machines with lots of cores we really want to try hard to 1125 * get a shared lock or concurrent path lookups can chain-react 1126 * into a very high-latency exclusive lock. 1127 */ 1128 static int 1129 _cache_lock_shared_special(struct namecache *ncp) 1130 { 1131 /* 1132 * Only honor a successful shared lock (returning 0) if there is 1133 * no exclusive request pending and the vnode, if present, is not 1134 * in a reclaimed state. 1135 */ 1136 if (_cache_lock_shared_nonblock(ncp) == 0) { 1137 if ((ncp->nc_lockstatus & NC_EXLOCK_REQ) == 0) { 1138 if (ncp->nc_vp == NULL || 1139 (ncp->nc_vp->v_flag & VRECLAIMED) == 0) { 1140 return(0); 1141 } 1142 } 1143 _cache_unlock(ncp); 1144 return(EWOULDBLOCK); 1145 } 1146 1147 /* 1148 * Non-blocking shared lock failed. If we already own the exclusive 1149 * lock just acquire another exclusive lock (instead of deadlocking). 1150 * Otherwise acquire a shared lock. 1151 */ 1152 if (ncp->nc_locktd == curthread) { 1153 _cache_lock(ncp); 1154 return(0); 1155 } 1156 _cache_lock_shared(ncp); 1157 return(0); 1158 } 1159 1160 1161 /* 1162 * NOTE: The same nchandle can be passed for both arguments. 1163 */ 1164 void 1165 cache_get(struct nchandle *nch, struct nchandle *target) 1166 { 1167 KKASSERT(nch->ncp->nc_refs > 0); 1168 target->mount = nch->mount; 1169 target->ncp = _cache_get(nch->ncp); 1170 atomic_add_int(&target->mount->mnt_refs, 1); 1171 } 1172 1173 void 1174 cache_get_maybe_shared(struct nchandle *nch, struct nchandle *target, int excl) 1175 { 1176 KKASSERT(nch->ncp->nc_refs > 0); 1177 target->mount = nch->mount; 1178 target->ncp = _cache_get_maybe_shared(nch->ncp, excl); 1179 atomic_add_int(&target->mount->mnt_refs, 1); 1180 } 1181 1182 /* 1183 * 1184 */ 1185 static __inline 1186 void 1187 _cache_put(struct namecache *ncp) 1188 { 1189 _cache_unlock(ncp); 1190 _cache_drop(ncp); 1191 } 1192 1193 /* 1194 * 1195 */ 1196 void 1197 cache_put(struct nchandle *nch) 1198 { 1199 atomic_add_int(&nch->mount->mnt_refs, -1); 1200 _cache_put(nch->ncp); 1201 nch->ncp = NULL; 1202 nch->mount = NULL; 1203 } 1204 1205 /* 1206 * Resolve an unresolved ncp by associating a vnode with it. If the 1207 * vnode is NULL, a negative cache entry is created. 1208 * 1209 * The ncp should be locked on entry and will remain locked on return. 1210 */ 1211 static 1212 void 1213 _cache_setvp(struct mount *mp, struct namecache *ncp, struct vnode *vp) 1214 { 1215 KKASSERT(ncp->nc_flag & NCF_UNRESOLVED); 1216 KKASSERT(_cache_lockstatus(ncp) == LK_EXCLUSIVE); 1217 1218 if (vp != NULL) { 1219 /* 1220 * Any vp associated with an ncp which has children must 1221 * be held. Any vp associated with a locked ncp must be held. 1222 */ 1223 if (!TAILQ_EMPTY(&ncp->nc_list)) 1224 vhold(vp); 1225 spin_lock(&vp->v_spin); 1226 ncp->nc_vp = vp; 1227 TAILQ_INSERT_HEAD(&vp->v_namecache, ncp, nc_vnode); 1228 spin_unlock(&vp->v_spin); 1229 if (ncp->nc_lockstatus & ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) 1230 vhold(vp); 1231 1232 /* 1233 * Set auxiliary flags 1234 */ 1235 switch(vp->v_type) { 1236 case VDIR: 1237 ncp->nc_flag |= NCF_ISDIR; 1238 break; 1239 case VLNK: 1240 ncp->nc_flag |= NCF_ISSYMLINK; 1241 /* XXX cache the contents of the symlink */ 1242 break; 1243 default: 1244 break; 1245 } 1246 atomic_add_int(&numcache, 1); 1247 ncp->nc_error = 0; 1248 /* XXX: this is a hack to work-around the lack of a real pfs vfs 1249 * implementation*/ 1250 if (mp != NULL) 1251 if (strncmp(mp->mnt_stat.f_fstypename, "null", 5) == 0) 1252 vp->v_pfsmp = mp; 1253 } else { 1254 /* 1255 * When creating a negative cache hit we set the 1256 * namecache_gen. A later resolve will clean out the 1257 * negative cache hit if the mount point's namecache_gen 1258 * has changed. Used by devfs, could also be used by 1259 * other remote FSs. 1260 */ 1261 ncp->nc_vp = NULL; 1262 spin_lock(&ncspin); 1263 TAILQ_INSERT_TAIL(&ncneglist, ncp, nc_vnode); 1264 ++numneg; 1265 spin_unlock(&ncspin); 1266 ncp->nc_error = ENOENT; 1267 if (mp) 1268 VFS_NCPGEN_SET(mp, ncp); 1269 } 1270 ncp->nc_flag &= ~(NCF_UNRESOLVED | NCF_DEFEREDZAP); 1271 } 1272 1273 /* 1274 * 1275 */ 1276 void 1277 cache_setvp(struct nchandle *nch, struct vnode *vp) 1278 { 1279 _cache_setvp(nch->mount, nch->ncp, vp); 1280 } 1281 1282 /* 1283 * 1284 */ 1285 void 1286 cache_settimeout(struct nchandle *nch, int nticks) 1287 { 1288 struct namecache *ncp = nch->ncp; 1289 1290 if ((ncp->nc_timeout = ticks + nticks) == 0) 1291 ncp->nc_timeout = 1; 1292 } 1293 1294 /* 1295 * Disassociate the vnode or negative-cache association and mark a 1296 * namecache entry as unresolved again. Note that the ncp is still 1297 * left in the hash table and still linked to its parent. 1298 * 1299 * The ncp should be locked and refd on entry and will remain locked and refd 1300 * on return. 1301 * 1302 * This routine is normally never called on a directory containing children. 1303 * However, NFS often does just that in its rename() code as a cop-out to 1304 * avoid complex namespace operations. This disconnects a directory vnode 1305 * from its namecache and can cause the OLDAPI and NEWAPI to get out of 1306 * sync. 1307 * 1308 */ 1309 static 1310 void 1311 _cache_setunresolved(struct namecache *ncp) 1312 { 1313 struct vnode *vp; 1314 1315 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) { 1316 ncp->nc_flag |= NCF_UNRESOLVED; 1317 ncp->nc_timeout = 0; 1318 ncp->nc_error = ENOTCONN; 1319 if ((vp = ncp->nc_vp) != NULL) { 1320 atomic_add_int(&numcache, -1); 1321 spin_lock(&vp->v_spin); 1322 ncp->nc_vp = NULL; 1323 TAILQ_REMOVE(&vp->v_namecache, ncp, nc_vnode); 1324 spin_unlock(&vp->v_spin); 1325 1326 /* 1327 * Any vp associated with an ncp with children is 1328 * held by that ncp. Any vp associated with a locked 1329 * ncp is held by that ncp. These conditions must be 1330 * undone when the vp is cleared out from the ncp. 1331 */ 1332 if (!TAILQ_EMPTY(&ncp->nc_list)) 1333 vdrop(vp); 1334 if (ncp->nc_lockstatus & ~(NC_EXLOCK_REQ|NC_SHLOCK_REQ)) 1335 vdrop(vp); 1336 } else { 1337 spin_lock(&ncspin); 1338 TAILQ_REMOVE(&ncneglist, ncp, nc_vnode); 1339 --numneg; 1340 spin_unlock(&ncspin); 1341 } 1342 ncp->nc_flag &= ~(NCF_WHITEOUT|NCF_ISDIR|NCF_ISSYMLINK); 1343 } 1344 } 1345 1346 /* 1347 * The cache_nresolve() code calls this function to automatically 1348 * set a resolved cache element to unresolved if it has timed out 1349 * or if it is a negative cache hit and the mount point namecache_gen 1350 * has changed. 1351 */ 1352 static __inline int 1353 _cache_auto_unresolve_test(struct mount *mp, struct namecache *ncp) 1354 { 1355 /* 1356 * Try to zap entries that have timed out. We have 1357 * to be careful here because locked leafs may depend 1358 * on the vnode remaining intact in a parent, so only 1359 * do this under very specific conditions. 1360 */ 1361 if (ncp->nc_timeout && (int)(ncp->nc_timeout - ticks) < 0 && 1362 TAILQ_EMPTY(&ncp->nc_list)) { 1363 return 1; 1364 } 1365 1366 /* 1367 * If a resolved negative cache hit is invalid due to 1368 * the mount's namecache generation being bumped, zap it. 1369 */ 1370 if (ncp->nc_vp == NULL && VFS_NCPGEN_TEST(mp, ncp)) { 1371 return 1; 1372 } 1373 1374 /* 1375 * Otherwise we are good 1376 */ 1377 return 0; 1378 } 1379 1380 static __inline void 1381 _cache_auto_unresolve(struct mount *mp, struct namecache *ncp) 1382 { 1383 /* 1384 * Already in an unresolved state, nothing to do. 1385 */ 1386 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) { 1387 if (_cache_auto_unresolve_test(mp, ncp)) 1388 _cache_setunresolved(ncp); 1389 } 1390 } 1391 1392 /* 1393 * 1394 */ 1395 void 1396 cache_setunresolved(struct nchandle *nch) 1397 { 1398 _cache_setunresolved(nch->ncp); 1399 } 1400 1401 /* 1402 * Determine if we can clear NCF_ISMOUNTPT by scanning the mountlist 1403 * looking for matches. This flag tells the lookup code when it must 1404 * check for a mount linkage and also prevents the directories in question 1405 * from being deleted or renamed. 1406 */ 1407 static 1408 int 1409 cache_clrmountpt_callback(struct mount *mp, void *data) 1410 { 1411 struct nchandle *nch = data; 1412 1413 if (mp->mnt_ncmounton.ncp == nch->ncp) 1414 return(1); 1415 if (mp->mnt_ncmountpt.ncp == nch->ncp) 1416 return(1); 1417 return(0); 1418 } 1419 1420 /* 1421 * 1422 */ 1423 void 1424 cache_clrmountpt(struct nchandle *nch) 1425 { 1426 int count; 1427 1428 count = mountlist_scan(cache_clrmountpt_callback, nch, 1429 MNTSCAN_FORWARD|MNTSCAN_NOBUSY); 1430 if (count == 0) 1431 nch->ncp->nc_flag &= ~NCF_ISMOUNTPT; 1432 } 1433 1434 /* 1435 * Invalidate portions of the namecache topology given a starting entry. 1436 * The passed ncp is set to an unresolved state and: 1437 * 1438 * The passed ncp must be referencxed and locked. The routine may unlock 1439 * and relock ncp several times, and will recheck the children and loop 1440 * to catch races. When done the passed ncp will be returned with the 1441 * reference and lock intact. 1442 * 1443 * CINV_DESTROY - Set a flag in the passed ncp entry indicating 1444 * that the physical underlying nodes have been 1445 * destroyed... as in deleted. For example, when 1446 * a directory is removed. This will cause record 1447 * lookups on the name to no longer be able to find 1448 * the record and tells the resolver to return failure 1449 * rather then trying to resolve through the parent. 1450 * 1451 * The topology itself, including ncp->nc_name, 1452 * remains intact. 1453 * 1454 * This only applies to the passed ncp, if CINV_CHILDREN 1455 * is specified the children are not flagged. 1456 * 1457 * CINV_CHILDREN - Set all children (recursively) to an unresolved 1458 * state as well. 1459 * 1460 * Note that this will also have the side effect of 1461 * cleaning out any unreferenced nodes in the topology 1462 * from the leaves up as the recursion backs out. 1463 * 1464 * Note that the topology for any referenced nodes remains intact, but 1465 * the nodes will be marked as having been destroyed and will be set 1466 * to an unresolved state. 1467 * 1468 * It is possible for cache_inval() to race a cache_resolve(), meaning that 1469 * the namecache entry may not actually be invalidated on return if it was 1470 * revalidated while recursing down into its children. This code guarentees 1471 * that the node(s) will go through an invalidation cycle, but does not 1472 * guarentee that they will remain in an invalidated state. 1473 * 1474 * Returns non-zero if a revalidation was detected during the invalidation 1475 * recursion, zero otherwise. Note that since only the original ncp is 1476 * locked the revalidation ultimately can only indicate that the original ncp 1477 * *MIGHT* no have been reresolved. 1478 * 1479 * DEEP RECURSION HANDLING - If a recursive invalidation recurses deeply we 1480 * have to avoid blowing out the kernel stack. We do this by saving the 1481 * deep namecache node and aborting the recursion, then re-recursing at that 1482 * node using a depth-first algorithm in order to allow multiple deep 1483 * recursions to chain through each other, then we restart the invalidation 1484 * from scratch. 1485 */ 1486 1487 struct cinvtrack { 1488 struct namecache *resume_ncp; 1489 int depth; 1490 }; 1491 1492 static int _cache_inval_internal(struct namecache *, int, struct cinvtrack *); 1493 1494 static 1495 int 1496 _cache_inval(struct namecache *ncp, int flags) 1497 { 1498 struct cinvtrack track; 1499 struct namecache *ncp2; 1500 int r; 1501 1502 track.depth = 0; 1503 track.resume_ncp = NULL; 1504 1505 for (;;) { 1506 r = _cache_inval_internal(ncp, flags, &track); 1507 if (track.resume_ncp == NULL) 1508 break; 1509 kprintf("Warning: deep namecache recursion at %s\n", 1510 ncp->nc_name); 1511 _cache_unlock(ncp); 1512 while ((ncp2 = track.resume_ncp) != NULL) { 1513 track.resume_ncp = NULL; 1514 _cache_lock(ncp2); 1515 _cache_inval_internal(ncp2, flags & ~CINV_DESTROY, 1516 &track); 1517 _cache_put(ncp2); 1518 } 1519 _cache_lock(ncp); 1520 } 1521 return(r); 1522 } 1523 1524 int 1525 cache_inval(struct nchandle *nch, int flags) 1526 { 1527 return(_cache_inval(nch->ncp, flags)); 1528 } 1529 1530 /* 1531 * Helper for _cache_inval(). The passed ncp is refd and locked and 1532 * remains that way on return, but may be unlocked/relocked multiple 1533 * times by the routine. 1534 */ 1535 static int 1536 _cache_inval_internal(struct namecache *ncp, int flags, struct cinvtrack *track) 1537 { 1538 struct namecache *kid; 1539 struct namecache *nextkid; 1540 int rcnt = 0; 1541 1542 KKASSERT(_cache_lockstatus(ncp) == LK_EXCLUSIVE); 1543 1544 _cache_setunresolved(ncp); 1545 if (flags & CINV_DESTROY) 1546 ncp->nc_flag |= NCF_DESTROYED; 1547 if ((flags & CINV_CHILDREN) && 1548 (kid = TAILQ_FIRST(&ncp->nc_list)) != NULL 1549 ) { 1550 _cache_hold(kid); 1551 if (++track->depth > MAX_RECURSION_DEPTH) { 1552 track->resume_ncp = ncp; 1553 _cache_hold(ncp); 1554 ++rcnt; 1555 } 1556 _cache_unlock(ncp); 1557 while (kid) { 1558 if (track->resume_ncp) { 1559 _cache_drop(kid); 1560 break; 1561 } 1562 if ((nextkid = TAILQ_NEXT(kid, nc_entry)) != NULL) 1563 _cache_hold(nextkid); 1564 if ((kid->nc_flag & NCF_UNRESOLVED) == 0 || 1565 TAILQ_FIRST(&kid->nc_list) 1566 ) { 1567 _cache_lock(kid); 1568 rcnt += _cache_inval_internal(kid, flags & ~CINV_DESTROY, track); 1569 _cache_unlock(kid); 1570 } 1571 _cache_drop(kid); 1572 kid = nextkid; 1573 } 1574 --track->depth; 1575 _cache_lock(ncp); 1576 } 1577 1578 /* 1579 * Someone could have gotten in there while ncp was unlocked, 1580 * retry if so. 1581 */ 1582 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) 1583 ++rcnt; 1584 return (rcnt); 1585 } 1586 1587 /* 1588 * Invalidate a vnode's namecache associations. To avoid races against 1589 * the resolver we do not invalidate a node which we previously invalidated 1590 * but which was then re-resolved while we were in the invalidation loop. 1591 * 1592 * Returns non-zero if any namecache entries remain after the invalidation 1593 * loop completed. 1594 * 1595 * NOTE: Unlike the namecache topology which guarentees that ncp's will not 1596 * be ripped out of the topology while held, the vnode's v_namecache 1597 * list has no such restriction. NCP's can be ripped out of the list 1598 * at virtually any time if not locked, even if held. 1599 * 1600 * In addition, the v_namecache list itself must be locked via 1601 * the vnode's spinlock. 1602 */ 1603 int 1604 cache_inval_vp(struct vnode *vp, int flags) 1605 { 1606 struct namecache *ncp; 1607 struct namecache *next; 1608 1609 restart: 1610 spin_lock(&vp->v_spin); 1611 ncp = TAILQ_FIRST(&vp->v_namecache); 1612 if (ncp) 1613 _cache_hold(ncp); 1614 while (ncp) { 1615 /* loop entered with ncp held and vp spin-locked */ 1616 if ((next = TAILQ_NEXT(ncp, nc_vnode)) != NULL) 1617 _cache_hold(next); 1618 spin_unlock(&vp->v_spin); 1619 _cache_lock(ncp); 1620 if (ncp->nc_vp != vp) { 1621 kprintf("Warning: cache_inval_vp: race-A detected on " 1622 "%s\n", ncp->nc_name); 1623 _cache_put(ncp); 1624 if (next) 1625 _cache_drop(next); 1626 goto restart; 1627 } 1628 _cache_inval(ncp, flags); 1629 _cache_put(ncp); /* also releases reference */ 1630 ncp = next; 1631 spin_lock(&vp->v_spin); 1632 if (ncp && ncp->nc_vp != vp) { 1633 spin_unlock(&vp->v_spin); 1634 kprintf("Warning: cache_inval_vp: race-B detected on " 1635 "%s\n", ncp->nc_name); 1636 _cache_drop(ncp); 1637 goto restart; 1638 } 1639 } 1640 spin_unlock(&vp->v_spin); 1641 return(TAILQ_FIRST(&vp->v_namecache) != NULL); 1642 } 1643 1644 /* 1645 * This routine is used instead of the normal cache_inval_vp() when we 1646 * are trying to recycle otherwise good vnodes. 1647 * 1648 * Return 0 on success, non-zero if not all namecache records could be 1649 * disassociated from the vnode (for various reasons). 1650 */ 1651 int 1652 cache_inval_vp_nonblock(struct vnode *vp) 1653 { 1654 struct namecache *ncp; 1655 struct namecache *next; 1656 1657 spin_lock(&vp->v_spin); 1658 ncp = TAILQ_FIRST(&vp->v_namecache); 1659 if (ncp) 1660 _cache_hold(ncp); 1661 while (ncp) { 1662 /* loop entered with ncp held */ 1663 if ((next = TAILQ_NEXT(ncp, nc_vnode)) != NULL) 1664 _cache_hold(next); 1665 spin_unlock(&vp->v_spin); 1666 if (_cache_lock_nonblock(ncp)) { 1667 _cache_drop(ncp); 1668 if (next) 1669 _cache_drop(next); 1670 goto done; 1671 } 1672 if (ncp->nc_vp != vp) { 1673 kprintf("Warning: cache_inval_vp: race-A detected on " 1674 "%s\n", ncp->nc_name); 1675 _cache_put(ncp); 1676 if (next) 1677 _cache_drop(next); 1678 goto done; 1679 } 1680 _cache_inval(ncp, 0); 1681 _cache_put(ncp); /* also releases reference */ 1682 ncp = next; 1683 spin_lock(&vp->v_spin); 1684 if (ncp && ncp->nc_vp != vp) { 1685 spin_unlock(&vp->v_spin); 1686 kprintf("Warning: cache_inval_vp: race-B detected on " 1687 "%s\n", ncp->nc_name); 1688 _cache_drop(ncp); 1689 goto done; 1690 } 1691 } 1692 spin_unlock(&vp->v_spin); 1693 done: 1694 return(TAILQ_FIRST(&vp->v_namecache) != NULL); 1695 } 1696 1697 /* 1698 * The source ncp has been renamed to the target ncp. Both fncp and tncp 1699 * must be locked. The target ncp is destroyed (as a normal rename-over 1700 * would destroy the target file or directory). 1701 * 1702 * Because there may be references to the source ncp we cannot copy its 1703 * contents to the target. Instead the source ncp is relinked as the target 1704 * and the target ncp is removed from the namecache topology. 1705 */ 1706 void 1707 cache_rename(struct nchandle *fnch, struct nchandle *tnch) 1708 { 1709 struct namecache *fncp = fnch->ncp; 1710 struct namecache *tncp = tnch->ncp; 1711 struct namecache *tncp_par; 1712 struct nchash_head *nchpp; 1713 u_int32_t hash; 1714 char *oname; 1715 char *nname; 1716 1717 if (tncp->nc_nlen) { 1718 nname = kmalloc(tncp->nc_nlen + 1, M_VFSCACHE, M_WAITOK); 1719 bcopy(tncp->nc_name, nname, tncp->nc_nlen); 1720 nname[tncp->nc_nlen] = 0; 1721 } else { 1722 nname = NULL; 1723 } 1724 1725 /* 1726 * Rename fncp (unlink) 1727 */ 1728 _cache_unlink_parent(fncp); 1729 oname = fncp->nc_name; 1730 fncp->nc_name = nname; 1731 fncp->nc_nlen = tncp->nc_nlen; 1732 if (oname) 1733 kfree(oname, M_VFSCACHE); 1734 1735 tncp_par = tncp->nc_parent; 1736 _cache_hold(tncp_par); 1737 _cache_lock(tncp_par); 1738 1739 /* 1740 * Rename fncp (relink) 1741 */ 1742 hash = fnv_32_buf(fncp->nc_name, fncp->nc_nlen, FNV1_32_INIT); 1743 hash = fnv_32_buf(&tncp_par, sizeof(tncp_par), hash); 1744 nchpp = NCHHASH(hash); 1745 1746 spin_lock(&nchpp->spin); 1747 _cache_link_parent(fncp, tncp_par, nchpp); 1748 spin_unlock(&nchpp->spin); 1749 1750 _cache_put(tncp_par); 1751 1752 /* 1753 * Get rid of the overwritten tncp (unlink) 1754 */ 1755 _cache_unlink(tncp); 1756 } 1757 1758 /* 1759 * Perform actions consistent with unlinking a file. The passed-in ncp 1760 * must be locked. 1761 * 1762 * The ncp is marked DESTROYED so it no longer shows up in searches, 1763 * and will be physically deleted when the vnode goes away. 1764 * 1765 * If the related vnode has no refs then we cycle it through vget()/vput() 1766 * to (possibly if we don't have a ref race) trigger a deactivation, 1767 * allowing the VFS to trivially detect and recycle the deleted vnode 1768 * via VOP_INACTIVE(). 1769 * 1770 * NOTE: _cache_rename() will automatically call _cache_unlink() on the 1771 * target ncp. 1772 */ 1773 void 1774 cache_unlink(struct nchandle *nch) 1775 { 1776 _cache_unlink(nch->ncp); 1777 } 1778 1779 static void 1780 _cache_unlink(struct namecache *ncp) 1781 { 1782 struct vnode *vp; 1783 1784 /* 1785 * Causes lookups to fail and allows another ncp with the same 1786 * name to be created under ncp->nc_parent. 1787 */ 1788 ncp->nc_flag |= NCF_DESTROYED; 1789 1790 /* 1791 * Attempt to trigger a deactivation. Set VAUX_FINALIZE to 1792 * force action on the 1->0 transition. 1793 */ 1794 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0 && 1795 (vp = ncp->nc_vp) != NULL) { 1796 atomic_set_int(&vp->v_refcnt, VREF_FINALIZE); 1797 if (VREFCNT(vp) <= 0) { 1798 if (vget(vp, LK_SHARED) == 0) 1799 vput(vp); 1800 } 1801 } 1802 } 1803 1804 /* 1805 * vget the vnode associated with the namecache entry. Resolve the namecache 1806 * entry if necessary. The passed ncp must be referenced and locked. If 1807 * the ncp is resolved it might be locked shared. 1808 * 1809 * lk_type may be LK_SHARED, LK_EXCLUSIVE. A ref'd, possibly locked 1810 * (depending on the passed lk_type) will be returned in *vpp with an error 1811 * of 0, or NULL will be returned in *vpp with a non-0 error code. The 1812 * most typical error is ENOENT, meaning that the ncp represents a negative 1813 * cache hit and there is no vnode to retrieve, but other errors can occur 1814 * too. 1815 * 1816 * The vget() can race a reclaim. If this occurs we re-resolve the 1817 * namecache entry. 1818 * 1819 * There are numerous places in the kernel where vget() is called on a 1820 * vnode while one or more of its namecache entries is locked. Releasing 1821 * a vnode never deadlocks against locked namecache entries (the vnode 1822 * will not get recycled while referenced ncp's exist). This means we 1823 * can safely acquire the vnode. In fact, we MUST NOT release the ncp 1824 * lock when acquiring the vp lock or we might cause a deadlock. 1825 * 1826 * NOTE: The passed-in ncp must be locked exclusively if it is initially 1827 * unresolved. If a reclaim race occurs the passed-in ncp will be 1828 * relocked exclusively before being re-resolved. 1829 */ 1830 int 1831 cache_vget(struct nchandle *nch, struct ucred *cred, 1832 int lk_type, struct vnode **vpp) 1833 { 1834 struct namecache *ncp; 1835 struct vnode *vp; 1836 int error; 1837 1838 ncp = nch->ncp; 1839 again: 1840 vp = NULL; 1841 if (ncp->nc_flag & NCF_UNRESOLVED) 1842 error = cache_resolve(nch, cred); 1843 else 1844 error = 0; 1845 1846 if (error == 0 && (vp = ncp->nc_vp) != NULL) { 1847 error = vget(vp, lk_type); 1848 if (error) { 1849 /* 1850 * VRECLAIM race 1851 * 1852 * The ncp may have been locked shared, we must relock 1853 * it exclusively before we can set it to unresolved. 1854 */ 1855 if (error == ENOENT) { 1856 kprintf("Warning: vnode reclaim race detected " 1857 "in cache_vget on %p (%s)\n", 1858 vp, ncp->nc_name); 1859 _cache_unlock(ncp); 1860 _cache_lock(ncp); 1861 _cache_setunresolved(ncp); 1862 goto again; 1863 } 1864 1865 /* 1866 * Not a reclaim race, some other error. 1867 */ 1868 KKASSERT(ncp->nc_vp == vp); 1869 vp = NULL; 1870 } else { 1871 KKASSERT(ncp->nc_vp == vp); 1872 KKASSERT((vp->v_flag & VRECLAIMED) == 0); 1873 } 1874 } 1875 if (error == 0 && vp == NULL) 1876 error = ENOENT; 1877 *vpp = vp; 1878 return(error); 1879 } 1880 1881 /* 1882 * Similar to cache_vget() but only acquires a ref on the vnode. 1883 * 1884 * NOTE: The passed-in ncp must be locked exclusively if it is initially 1885 * unresolved. If a reclaim race occurs the passed-in ncp will be 1886 * relocked exclusively before being re-resolved. 1887 */ 1888 int 1889 cache_vref(struct nchandle *nch, struct ucred *cred, struct vnode **vpp) 1890 { 1891 struct namecache *ncp; 1892 struct vnode *vp; 1893 int error; 1894 1895 ncp = nch->ncp; 1896 again: 1897 vp = NULL; 1898 if (ncp->nc_flag & NCF_UNRESOLVED) 1899 error = cache_resolve(nch, cred); 1900 else 1901 error = 0; 1902 1903 if (error == 0 && (vp = ncp->nc_vp) != NULL) { 1904 error = vget(vp, LK_SHARED); 1905 if (error) { 1906 /* 1907 * VRECLAIM race 1908 */ 1909 if (error == ENOENT) { 1910 kprintf("Warning: vnode reclaim race detected " 1911 "in cache_vget on %p (%s)\n", 1912 vp, ncp->nc_name); 1913 _cache_unlock(ncp); 1914 _cache_lock(ncp); 1915 _cache_setunresolved(ncp); 1916 goto again; 1917 } 1918 1919 /* 1920 * Not a reclaim race, some other error. 1921 */ 1922 KKASSERT(ncp->nc_vp == vp); 1923 vp = NULL; 1924 } else { 1925 KKASSERT(ncp->nc_vp == vp); 1926 KKASSERT((vp->v_flag & VRECLAIMED) == 0); 1927 /* caller does not want a lock */ 1928 vn_unlock(vp); 1929 } 1930 } 1931 if (error == 0 && vp == NULL) 1932 error = ENOENT; 1933 *vpp = vp; 1934 return(error); 1935 } 1936 1937 /* 1938 * Return a referenced vnode representing the parent directory of 1939 * ncp. 1940 * 1941 * Because the caller has locked the ncp it should not be possible for 1942 * the parent ncp to go away. However, the parent can unresolve its 1943 * dvp at any time so we must be able to acquire a lock on the parent 1944 * to safely access nc_vp. 1945 * 1946 * We have to leave par unlocked when vget()ing dvp to avoid a deadlock, 1947 * so use vhold()/vdrop() while holding the lock to prevent dvp from 1948 * getting destroyed. 1949 * 1950 * NOTE: vhold() is allowed when dvp has 0 refs if we hold a 1951 * lock on the ncp in question.. 1952 */ 1953 static struct vnode * 1954 cache_dvpref(struct namecache *ncp) 1955 { 1956 struct namecache *par; 1957 struct vnode *dvp; 1958 1959 dvp = NULL; 1960 if ((par = ncp->nc_parent) != NULL) { 1961 _cache_hold(par); 1962 _cache_lock(par); 1963 if ((par->nc_flag & NCF_UNRESOLVED) == 0) { 1964 if ((dvp = par->nc_vp) != NULL) 1965 vhold(dvp); 1966 } 1967 _cache_unlock(par); 1968 if (dvp) { 1969 if (vget(dvp, LK_SHARED) == 0) { 1970 vn_unlock(dvp); 1971 vdrop(dvp); 1972 /* return refd, unlocked dvp */ 1973 } else { 1974 vdrop(dvp); 1975 dvp = NULL; 1976 } 1977 } 1978 _cache_drop(par); 1979 } 1980 return(dvp); 1981 } 1982 1983 /* 1984 * Convert a directory vnode to a namecache record without any other 1985 * knowledge of the topology. This ONLY works with directory vnodes and 1986 * is ONLY used by the NFS server. dvp must be refd but unlocked, and the 1987 * returned ncp (if not NULL) will be held and unlocked. 1988 * 1989 * If 'makeit' is 0 and dvp has no existing namecache record, NULL is returned. 1990 * If 'makeit' is 1 we attempt to track-down and create the namecache topology 1991 * for dvp. This will fail only if the directory has been deleted out from 1992 * under the caller. 1993 * 1994 * Callers must always check for a NULL return no matter the value of 'makeit'. 1995 * 1996 * To avoid underflowing the kernel stack each recursive call increments 1997 * the makeit variable. 1998 */ 1999 2000 static int cache_inefficient_scan(struct nchandle *nch, struct ucred *cred, 2001 struct vnode *dvp, char *fakename); 2002 static int cache_fromdvp_try(struct vnode *dvp, struct ucred *cred, 2003 struct vnode **saved_dvp); 2004 2005 int 2006 cache_fromdvp(struct vnode *dvp, struct ucred *cred, int makeit, 2007 struct nchandle *nch) 2008 { 2009 struct vnode *saved_dvp; 2010 struct vnode *pvp; 2011 char *fakename; 2012 int error; 2013 2014 nch->ncp = NULL; 2015 nch->mount = dvp->v_mount; 2016 saved_dvp = NULL; 2017 fakename = NULL; 2018 2019 /* 2020 * Handle the makeit == 0 degenerate case 2021 */ 2022 if (makeit == 0) { 2023 spin_lock_shared(&dvp->v_spin); 2024 nch->ncp = TAILQ_FIRST(&dvp->v_namecache); 2025 if (nch->ncp) 2026 cache_hold(nch); 2027 spin_unlock_shared(&dvp->v_spin); 2028 } 2029 2030 /* 2031 * Loop until resolution, inside code will break out on error. 2032 */ 2033 while (makeit) { 2034 /* 2035 * Break out if we successfully acquire a working ncp. 2036 */ 2037 spin_lock_shared(&dvp->v_spin); 2038 nch->ncp = TAILQ_FIRST(&dvp->v_namecache); 2039 if (nch->ncp) { 2040 cache_hold(nch); 2041 spin_unlock_shared(&dvp->v_spin); 2042 break; 2043 } 2044 spin_unlock_shared(&dvp->v_spin); 2045 2046 /* 2047 * If dvp is the root of its filesystem it should already 2048 * have a namecache pointer associated with it as a side 2049 * effect of the mount, but it may have been disassociated. 2050 */ 2051 if (dvp->v_flag & VROOT) { 2052 nch->ncp = _cache_get(nch->mount->mnt_ncmountpt.ncp); 2053 error = cache_resolve_mp(nch->mount); 2054 _cache_put(nch->ncp); 2055 if (ncvp_debug) { 2056 kprintf("cache_fromdvp: resolve root of mount %p error %d", 2057 dvp->v_mount, error); 2058 } 2059 if (error) { 2060 if (ncvp_debug) 2061 kprintf(" failed\n"); 2062 nch->ncp = NULL; 2063 break; 2064 } 2065 if (ncvp_debug) 2066 kprintf(" succeeded\n"); 2067 continue; 2068 } 2069 2070 /* 2071 * If we are recursed too deeply resort to an O(n^2) 2072 * algorithm to resolve the namecache topology. The 2073 * resolved pvp is left referenced in saved_dvp to 2074 * prevent the tree from being destroyed while we loop. 2075 */ 2076 if (makeit > 20) { 2077 error = cache_fromdvp_try(dvp, cred, &saved_dvp); 2078 if (error) { 2079 kprintf("lookupdotdot(longpath) failed %d " 2080 "dvp %p\n", error, dvp); 2081 nch->ncp = NULL; 2082 break; 2083 } 2084 continue; 2085 } 2086 2087 /* 2088 * Get the parent directory and resolve its ncp. 2089 */ 2090 if (fakename) { 2091 kfree(fakename, M_TEMP); 2092 fakename = NULL; 2093 } 2094 error = vop_nlookupdotdot(*dvp->v_ops, dvp, &pvp, cred, 2095 &fakename); 2096 if (error) { 2097 kprintf("lookupdotdot failed %d dvp %p\n", error, dvp); 2098 break; 2099 } 2100 vn_unlock(pvp); 2101 2102 /* 2103 * Reuse makeit as a recursion depth counter. On success 2104 * nch will be fully referenced. 2105 */ 2106 cache_fromdvp(pvp, cred, makeit + 1, nch); 2107 vrele(pvp); 2108 if (nch->ncp == NULL) 2109 break; 2110 2111 /* 2112 * Do an inefficient scan of pvp (embodied by ncp) to look 2113 * for dvp. This will create a namecache record for dvp on 2114 * success. We loop up to recheck on success. 2115 * 2116 * ncp and dvp are both held but not locked. 2117 */ 2118 error = cache_inefficient_scan(nch, cred, dvp, fakename); 2119 if (error) { 2120 kprintf("cache_fromdvp: scan %p (%s) failed on dvp=%p\n", 2121 pvp, nch->ncp->nc_name, dvp); 2122 cache_drop(nch); 2123 /* nch was NULLed out, reload mount */ 2124 nch->mount = dvp->v_mount; 2125 break; 2126 } 2127 if (ncvp_debug) { 2128 kprintf("cache_fromdvp: scan %p (%s) succeeded\n", 2129 pvp, nch->ncp->nc_name); 2130 } 2131 cache_drop(nch); 2132 /* nch was NULLed out, reload mount */ 2133 nch->mount = dvp->v_mount; 2134 } 2135 2136 /* 2137 * If nch->ncp is non-NULL it will have been held already. 2138 */ 2139 if (fakename) 2140 kfree(fakename, M_TEMP); 2141 if (saved_dvp) 2142 vrele(saved_dvp); 2143 if (nch->ncp) 2144 return (0); 2145 return (EINVAL); 2146 } 2147 2148 /* 2149 * Go up the chain of parent directories until we find something 2150 * we can resolve into the namecache. This is very inefficient. 2151 */ 2152 static 2153 int 2154 cache_fromdvp_try(struct vnode *dvp, struct ucred *cred, 2155 struct vnode **saved_dvp) 2156 { 2157 struct nchandle nch; 2158 struct vnode *pvp; 2159 int error; 2160 static time_t last_fromdvp_report; 2161 char *fakename; 2162 2163 /* 2164 * Loop getting the parent directory vnode until we get something we 2165 * can resolve in the namecache. 2166 */ 2167 vref(dvp); 2168 nch.mount = dvp->v_mount; 2169 nch.ncp = NULL; 2170 fakename = NULL; 2171 2172 for (;;) { 2173 if (fakename) { 2174 kfree(fakename, M_TEMP); 2175 fakename = NULL; 2176 } 2177 error = vop_nlookupdotdot(*dvp->v_ops, dvp, &pvp, cred, 2178 &fakename); 2179 if (error) { 2180 vrele(dvp); 2181 break; 2182 } 2183 vn_unlock(pvp); 2184 spin_lock_shared(&pvp->v_spin); 2185 if ((nch.ncp = TAILQ_FIRST(&pvp->v_namecache)) != NULL) { 2186 _cache_hold(nch.ncp); 2187 spin_unlock_shared(&pvp->v_spin); 2188 vrele(pvp); 2189 break; 2190 } 2191 spin_unlock_shared(&pvp->v_spin); 2192 if (pvp->v_flag & VROOT) { 2193 nch.ncp = _cache_get(pvp->v_mount->mnt_ncmountpt.ncp); 2194 error = cache_resolve_mp(nch.mount); 2195 _cache_unlock(nch.ncp); 2196 vrele(pvp); 2197 if (error) { 2198 _cache_drop(nch.ncp); 2199 nch.ncp = NULL; 2200 vrele(dvp); 2201 } 2202 break; 2203 } 2204 vrele(dvp); 2205 dvp = pvp; 2206 } 2207 if (error == 0) { 2208 if (last_fromdvp_report != time_uptime) { 2209 last_fromdvp_report = time_uptime; 2210 kprintf("Warning: extremely inefficient path " 2211 "resolution on %s\n", 2212 nch.ncp->nc_name); 2213 } 2214 error = cache_inefficient_scan(&nch, cred, dvp, fakename); 2215 2216 /* 2217 * Hopefully dvp now has a namecache record associated with 2218 * it. Leave it referenced to prevent the kernel from 2219 * recycling the vnode. Otherwise extremely long directory 2220 * paths could result in endless recycling. 2221 */ 2222 if (*saved_dvp) 2223 vrele(*saved_dvp); 2224 *saved_dvp = dvp; 2225 _cache_drop(nch.ncp); 2226 } 2227 if (fakename) 2228 kfree(fakename, M_TEMP); 2229 return (error); 2230 } 2231 2232 /* 2233 * Do an inefficient scan of the directory represented by ncp looking for 2234 * the directory vnode dvp. ncp must be held but not locked on entry and 2235 * will be held on return. dvp must be refd but not locked on entry and 2236 * will remain refd on return. 2237 * 2238 * Why do this at all? Well, due to its stateless nature the NFS server 2239 * converts file handles directly to vnodes without necessarily going through 2240 * the namecache ops that would otherwise create the namecache topology 2241 * leading to the vnode. We could either (1) Change the namecache algorithms 2242 * to allow disconnect namecache records that are re-merged opportunistically, 2243 * or (2) Make the NFS server backtrack and scan to recover a connected 2244 * namecache topology in order to then be able to issue new API lookups. 2245 * 2246 * It turns out that (1) is a huge mess. It takes a nice clean set of 2247 * namecache algorithms and introduces a lot of complication in every subsystem 2248 * that calls into the namecache to deal with the re-merge case, especially 2249 * since we are using the namecache to placehold negative lookups and the 2250 * vnode might not be immediately assigned. (2) is certainly far less 2251 * efficient then (1), but since we are only talking about directories here 2252 * (which are likely to remain cached), the case does not actually run all 2253 * that often and has the supreme advantage of not polluting the namecache 2254 * algorithms. 2255 * 2256 * If a fakename is supplied just construct a namecache entry using the 2257 * fake name. 2258 */ 2259 static int 2260 cache_inefficient_scan(struct nchandle *nch, struct ucred *cred, 2261 struct vnode *dvp, char *fakename) 2262 { 2263 struct nlcomponent nlc; 2264 struct nchandle rncp; 2265 struct dirent *den; 2266 struct vnode *pvp; 2267 struct vattr vat; 2268 struct iovec iov; 2269 struct uio uio; 2270 int blksize; 2271 int eofflag; 2272 int bytes; 2273 char *rbuf; 2274 int error; 2275 2276 vat.va_blocksize = 0; 2277 if ((error = VOP_GETATTR(dvp, &vat)) != 0) 2278 return (error); 2279 cache_lock(nch); 2280 error = cache_vref(nch, cred, &pvp); 2281 cache_unlock(nch); 2282 if (error) 2283 return (error); 2284 if (ncvp_debug) { 2285 kprintf("inefficient_scan: directory iosize %ld " 2286 "vattr fileid = %lld\n", 2287 vat.va_blocksize, 2288 (long long)vat.va_fileid); 2289 } 2290 2291 /* 2292 * Use the supplied fakename if not NULL. Fake names are typically 2293 * not in the actual filesystem hierarchy. This is used by HAMMER 2294 * to glue @@timestamp recursions together. 2295 */ 2296 if (fakename) { 2297 nlc.nlc_nameptr = fakename; 2298 nlc.nlc_namelen = strlen(fakename); 2299 rncp = cache_nlookup(nch, &nlc); 2300 goto done; 2301 } 2302 2303 if ((blksize = vat.va_blocksize) == 0) 2304 blksize = DEV_BSIZE; 2305 rbuf = kmalloc(blksize, M_TEMP, M_WAITOK); 2306 rncp.ncp = NULL; 2307 2308 eofflag = 0; 2309 uio.uio_offset = 0; 2310 again: 2311 iov.iov_base = rbuf; 2312 iov.iov_len = blksize; 2313 uio.uio_iov = &iov; 2314 uio.uio_iovcnt = 1; 2315 uio.uio_resid = blksize; 2316 uio.uio_segflg = UIO_SYSSPACE; 2317 uio.uio_rw = UIO_READ; 2318 uio.uio_td = curthread; 2319 2320 if (ncvp_debug >= 2) 2321 kprintf("cache_inefficient_scan: readdir @ %08x\n", (int)uio.uio_offset); 2322 error = VOP_READDIR(pvp, &uio, cred, &eofflag, NULL, NULL); 2323 if (error == 0) { 2324 den = (struct dirent *)rbuf; 2325 bytes = blksize - uio.uio_resid; 2326 2327 while (bytes > 0) { 2328 if (ncvp_debug >= 2) { 2329 kprintf("cache_inefficient_scan: %*.*s\n", 2330 den->d_namlen, den->d_namlen, 2331 den->d_name); 2332 } 2333 if (den->d_type != DT_WHT && 2334 den->d_ino == vat.va_fileid) { 2335 if (ncvp_debug) { 2336 kprintf("cache_inefficient_scan: " 2337 "MATCHED inode %lld path %s/%*.*s\n", 2338 (long long)vat.va_fileid, 2339 nch->ncp->nc_name, 2340 den->d_namlen, den->d_namlen, 2341 den->d_name); 2342 } 2343 nlc.nlc_nameptr = den->d_name; 2344 nlc.nlc_namelen = den->d_namlen; 2345 rncp = cache_nlookup(nch, &nlc); 2346 KKASSERT(rncp.ncp != NULL); 2347 break; 2348 } 2349 bytes -= _DIRENT_DIRSIZ(den); 2350 den = _DIRENT_NEXT(den); 2351 } 2352 if (rncp.ncp == NULL && eofflag == 0 && uio.uio_resid != blksize) 2353 goto again; 2354 } 2355 kfree(rbuf, M_TEMP); 2356 done: 2357 vrele(pvp); 2358 if (rncp.ncp) { 2359 if (rncp.ncp->nc_flag & NCF_UNRESOLVED) { 2360 _cache_setvp(rncp.mount, rncp.ncp, dvp); 2361 if (ncvp_debug >= 2) { 2362 kprintf("cache_inefficient_scan: setvp %s/%s = %p\n", 2363 nch->ncp->nc_name, rncp.ncp->nc_name, dvp); 2364 } 2365 } else { 2366 if (ncvp_debug >= 2) { 2367 kprintf("cache_inefficient_scan: setvp %s/%s already set %p/%p\n", 2368 nch->ncp->nc_name, rncp.ncp->nc_name, dvp, 2369 rncp.ncp->nc_vp); 2370 } 2371 } 2372 if (rncp.ncp->nc_vp == NULL) 2373 error = rncp.ncp->nc_error; 2374 /* 2375 * Release rncp after a successful nlookup. rncp was fully 2376 * referenced. 2377 */ 2378 cache_put(&rncp); 2379 } else { 2380 kprintf("cache_inefficient_scan: dvp %p NOT FOUND in %s\n", 2381 dvp, nch->ncp->nc_name); 2382 error = ENOENT; 2383 } 2384 return (error); 2385 } 2386 2387 /* 2388 * Zap a namecache entry. The ncp is unconditionally set to an unresolved 2389 * state, which disassociates it from its vnode or ncneglist. 2390 * 2391 * Then, if there are no additional references to the ncp and no children, 2392 * the ncp is removed from the topology and destroyed. 2393 * 2394 * References and/or children may exist if the ncp is in the middle of the 2395 * topology, preventing the ncp from being destroyed. 2396 * 2397 * This function must be called with the ncp held and locked and will unlock 2398 * and drop it during zapping. 2399 * 2400 * If nonblock is non-zero and the parent ncp cannot be locked we give up. 2401 * This case can occur in the cache_drop() path. 2402 * 2403 * This function may returned a held (but NOT locked) parent node which the 2404 * caller must drop. We do this so _cache_drop() can loop, to avoid 2405 * blowing out the kernel stack. 2406 * 2407 * WARNING! For MPSAFE operation this routine must acquire up to three 2408 * spin locks to be able to safely test nc_refs. Lock order is 2409 * very important. 2410 * 2411 * hash spinlock if on hash list 2412 * parent spinlock if child of parent 2413 * (the ncp is unresolved so there is no vnode association) 2414 */ 2415 static struct namecache * 2416 cache_zap(struct namecache *ncp, int nonblock) 2417 { 2418 struct namecache *par; 2419 struct vnode *dropvp; 2420 int refs; 2421 2422 /* 2423 * Disassociate the vnode or negative cache ref and set NCF_UNRESOLVED. 2424 */ 2425 _cache_setunresolved(ncp); 2426 2427 /* 2428 * Try to scrap the entry and possibly tail-recurse on its parent. 2429 * We only scrap unref'd (other then our ref) unresolved entries, 2430 * we do not scrap 'live' entries. 2431 * 2432 * Note that once the spinlocks are acquired if nc_refs == 1 no 2433 * other references are possible. If it isn't, however, we have 2434 * to decrement but also be sure to avoid a 1->0 transition. 2435 */ 2436 KKASSERT(ncp->nc_flag & NCF_UNRESOLVED); 2437 KKASSERT(ncp->nc_refs > 0); 2438 2439 /* 2440 * Acquire locks. Note that the parent can't go away while we hold 2441 * a child locked. 2442 */ 2443 if ((par = ncp->nc_parent) != NULL) { 2444 if (nonblock) { 2445 for (;;) { 2446 if (_cache_lock_nonblock(par) == 0) 2447 break; 2448 refs = ncp->nc_refs; 2449 ncp->nc_flag |= NCF_DEFEREDZAP; 2450 ++numdefered; /* MP race ok */ 2451 if (atomic_cmpset_int(&ncp->nc_refs, 2452 refs, refs - 1)) { 2453 _cache_unlock(ncp); 2454 return(NULL); 2455 } 2456 cpu_pause(); 2457 } 2458 _cache_hold(par); 2459 } else { 2460 _cache_hold(par); 2461 _cache_lock(par); 2462 } 2463 spin_lock(&ncp->nc_head->spin); 2464 } 2465 2466 /* 2467 * If someone other then us has a ref or we have children 2468 * we cannot zap the entry. The 1->0 transition and any 2469 * further list operation is protected by the spinlocks 2470 * we have acquired but other transitions are not. 2471 */ 2472 for (;;) { 2473 refs = ncp->nc_refs; 2474 if (refs == 1 && TAILQ_EMPTY(&ncp->nc_list)) 2475 break; 2476 if (atomic_cmpset_int(&ncp->nc_refs, refs, refs - 1)) { 2477 if (par) { 2478 spin_unlock(&ncp->nc_head->spin); 2479 _cache_put(par); 2480 } 2481 _cache_unlock(ncp); 2482 return(NULL); 2483 } 2484 cpu_pause(); 2485 } 2486 2487 /* 2488 * We are the only ref and with the spinlocks held no further 2489 * refs can be acquired by others. 2490 * 2491 * Remove us from the hash list and parent list. We have to 2492 * drop a ref on the parent's vp if the parent's list becomes 2493 * empty. 2494 */ 2495 dropvp = NULL; 2496 if (par) { 2497 struct nchash_head *nchpp = ncp->nc_head; 2498 2499 KKASSERT(nchpp != NULL); 2500 LIST_REMOVE(ncp, nc_hash); 2501 TAILQ_REMOVE(&par->nc_list, ncp, nc_entry); 2502 if (par->nc_vp && TAILQ_EMPTY(&par->nc_list)) 2503 dropvp = par->nc_vp; 2504 ncp->nc_head = NULL; 2505 ncp->nc_parent = NULL; 2506 spin_unlock(&nchpp->spin); 2507 _cache_unlock(par); 2508 } else { 2509 KKASSERT(ncp->nc_head == NULL); 2510 } 2511 2512 /* 2513 * ncp should not have picked up any refs. Physically 2514 * destroy the ncp. 2515 */ 2516 KKASSERT(ncp->nc_refs == 1); 2517 /* _cache_unlock(ncp) not required */ 2518 ncp->nc_refs = -1; /* safety */ 2519 if (ncp->nc_name) 2520 kfree(ncp->nc_name, M_VFSCACHE); 2521 kfree(ncp, M_VFSCACHE); 2522 2523 /* 2524 * Delayed drop (we had to release our spinlocks) 2525 * 2526 * The refed parent (if not NULL) must be dropped. The 2527 * caller is responsible for looping. 2528 */ 2529 if (dropvp) 2530 vdrop(dropvp); 2531 return(par); 2532 } 2533 2534 /* 2535 * Clean up dangling negative cache and defered-drop entries in the 2536 * namecache. 2537 * 2538 * This routine is called in the critical path and also called from 2539 * vnlru(). When called from vnlru we use a lower limit to try to 2540 * deal with the negative cache before the critical path has to start 2541 * dealing with it. 2542 */ 2543 typedef enum { CHI_LOW, CHI_HIGH } cache_hs_t; 2544 2545 static cache_hs_t neg_cache_hysteresis_state[2] = { CHI_LOW, CHI_LOW }; 2546 static cache_hs_t pos_cache_hysteresis_state[2] = { CHI_LOW, CHI_LOW }; 2547 2548 void 2549 cache_hysteresis(int critpath) 2550 { 2551 int poslimit; 2552 int neglimit = desiredvnodes / ncnegfactor; 2553 int xnumcache = numcache; 2554 2555 if (critpath == 0) 2556 neglimit = neglimit * 8 / 10; 2557 2558 /* 2559 * Don't cache too many negative hits. We use hysteresis to reduce 2560 * the impact on the critical path. 2561 */ 2562 switch(neg_cache_hysteresis_state[critpath]) { 2563 case CHI_LOW: 2564 if (numneg > MINNEG && numneg > neglimit) { 2565 if (critpath) 2566 _cache_cleanneg(ncnegflush); 2567 else 2568 _cache_cleanneg(ncnegflush + 2569 numneg - neglimit); 2570 neg_cache_hysteresis_state[critpath] = CHI_HIGH; 2571 } 2572 break; 2573 case CHI_HIGH: 2574 if (numneg > MINNEG * 9 / 10 && 2575 numneg * 9 / 10 > neglimit 2576 ) { 2577 if (critpath) 2578 _cache_cleanneg(ncnegflush); 2579 else 2580 _cache_cleanneg(ncnegflush + 2581 numneg * 9 / 10 - neglimit); 2582 } else { 2583 neg_cache_hysteresis_state[critpath] = CHI_LOW; 2584 } 2585 break; 2586 } 2587 2588 /* 2589 * Don't cache too many positive hits. We use hysteresis to reduce 2590 * the impact on the critical path. 2591 * 2592 * Excessive positive hits can accumulate due to large numbers of 2593 * hardlinks (the vnode cache will not prevent hl ncps from growing 2594 * into infinity). 2595 */ 2596 if ((poslimit = ncposlimit) == 0) 2597 poslimit = desiredvnodes * 2; 2598 if (critpath == 0) 2599 poslimit = poslimit * 8 / 10; 2600 2601 switch(pos_cache_hysteresis_state[critpath]) { 2602 case CHI_LOW: 2603 if (xnumcache > poslimit && xnumcache > MINPOS) { 2604 if (critpath) 2605 _cache_cleanpos(ncposflush); 2606 else 2607 _cache_cleanpos(ncposflush + 2608 xnumcache - poslimit); 2609 pos_cache_hysteresis_state[critpath] = CHI_HIGH; 2610 } 2611 break; 2612 case CHI_HIGH: 2613 if (xnumcache > poslimit * 5 / 6 && xnumcache > MINPOS) { 2614 if (critpath) 2615 _cache_cleanpos(ncposflush); 2616 else 2617 _cache_cleanpos(ncposflush + 2618 xnumcache - poslimit * 5 / 6); 2619 } else { 2620 pos_cache_hysteresis_state[critpath] = CHI_LOW; 2621 } 2622 break; 2623 } 2624 2625 /* 2626 * Clean out dangling defered-zap ncps which could not 2627 * be cleanly dropped if too many build up. Note 2628 * that numdefered is not an exact number as such ncps 2629 * can be reused and the counter is not handled in a MP 2630 * safe manner by design. 2631 */ 2632 if (numdefered > neglimit) { 2633 _cache_cleandefered(); 2634 } 2635 } 2636 2637 /* 2638 * NEW NAMECACHE LOOKUP API 2639 * 2640 * Lookup an entry in the namecache. The passed par_nch must be referenced 2641 * and unlocked. A referenced and locked nchandle with a non-NULL nch.ncp 2642 * is ALWAYS returned, eve if the supplied component is illegal. 2643 * 2644 * The resulting namecache entry should be returned to the system with 2645 * cache_put() or cache_unlock() + cache_drop(). 2646 * 2647 * namecache locks are recursive but care must be taken to avoid lock order 2648 * reversals (hence why the passed par_nch must be unlocked). Locking 2649 * rules are to order for parent traversals, not for child traversals. 2650 * 2651 * Nobody else will be able to manipulate the associated namespace (e.g. 2652 * create, delete, rename, rename-target) until the caller unlocks the 2653 * entry. 2654 * 2655 * The returned entry will be in one of three states: positive hit (non-null 2656 * vnode), negative hit (null vnode), or unresolved (NCF_UNRESOLVED is set). 2657 * Unresolved entries must be resolved through the filesystem to associate the 2658 * vnode and/or determine whether a positive or negative hit has occured. 2659 * 2660 * It is not necessary to lock a directory in order to lock namespace under 2661 * that directory. In fact, it is explicitly not allowed to do that. A 2662 * directory is typically only locked when being created, renamed, or 2663 * destroyed. 2664 * 2665 * The directory (par) may be unresolved, in which case any returned child 2666 * will likely also be marked unresolved. Likely but not guarenteed. Since 2667 * the filesystem lookup requires a resolved directory vnode the caller is 2668 * responsible for resolving the namecache chain top-down. This API 2669 * specifically allows whole chains to be created in an unresolved state. 2670 */ 2671 struct nchandle 2672 cache_nlookup(struct nchandle *par_nch, struct nlcomponent *nlc) 2673 { 2674 struct nchandle nch; 2675 struct namecache *ncp; 2676 struct namecache *new_ncp; 2677 struct nchash_head *nchpp; 2678 struct mount *mp; 2679 u_int32_t hash; 2680 globaldata_t gd; 2681 int par_locked; 2682 2683 numcalls++; 2684 gd = mycpu; 2685 mp = par_nch->mount; 2686 par_locked = 0; 2687 2688 /* 2689 * This is a good time to call it, no ncp's are locked by 2690 * the caller or us. 2691 */ 2692 cache_hysteresis(1); 2693 2694 /* 2695 * Try to locate an existing entry 2696 */ 2697 hash = fnv_32_buf(nlc->nlc_nameptr, nlc->nlc_namelen, FNV1_32_INIT); 2698 hash = fnv_32_buf(&par_nch->ncp, sizeof(par_nch->ncp), hash); 2699 new_ncp = NULL; 2700 nchpp = NCHHASH(hash); 2701 restart: 2702 if (new_ncp) 2703 spin_lock(&nchpp->spin); 2704 else 2705 spin_lock_shared(&nchpp->spin); 2706 2707 LIST_FOREACH(ncp, &nchpp->list, nc_hash) { 2708 numchecks++; 2709 2710 /* 2711 * Break out if we find a matching entry. Note that 2712 * UNRESOLVED entries may match, but DESTROYED entries 2713 * do not. 2714 */ 2715 if (ncp->nc_parent == par_nch->ncp && 2716 ncp->nc_nlen == nlc->nlc_namelen && 2717 bcmp(ncp->nc_name, nlc->nlc_nameptr, ncp->nc_nlen) == 0 && 2718 (ncp->nc_flag & NCF_DESTROYED) == 0 2719 ) { 2720 _cache_hold(ncp); 2721 if (new_ncp) 2722 spin_unlock(&nchpp->spin); 2723 else 2724 spin_unlock_shared(&nchpp->spin); 2725 if (par_locked) { 2726 _cache_unlock(par_nch->ncp); 2727 par_locked = 0; 2728 } 2729 if (_cache_lock_special(ncp) == 0) { 2730 /* 2731 * Successfully locked but we must re-test 2732 * conditions that might have changed since 2733 * we did not have the lock before. 2734 */ 2735 if ((ncp->nc_flag & NCF_DESTROYED) || 2736 ncp->nc_parent != par_nch->ncp) { 2737 _cache_put(ncp); 2738 goto restart; 2739 } 2740 _cache_auto_unresolve(mp, ncp); 2741 if (new_ncp) 2742 _cache_free(new_ncp); 2743 goto found; 2744 } 2745 _cache_get(ncp); /* cycle the lock to block */ 2746 _cache_put(ncp); 2747 _cache_drop(ncp); 2748 goto restart; 2749 } 2750 } 2751 2752 /* 2753 * We failed to locate an entry, create a new entry and add it to 2754 * the cache. The parent ncp must also be locked so we 2755 * can link into it. 2756 * 2757 * We have to relookup after possibly blocking in kmalloc or 2758 * when locking par_nch. 2759 * 2760 * NOTE: nlc_namelen can be 0 and nlc_nameptr NULL as a special 2761 * mount case, in which case nc_name will be NULL. 2762 */ 2763 if (new_ncp == NULL) { 2764 spin_unlock_shared(&nchpp->spin); 2765 new_ncp = cache_alloc(nlc->nlc_namelen); 2766 if (nlc->nlc_namelen) { 2767 bcopy(nlc->nlc_nameptr, new_ncp->nc_name, 2768 nlc->nlc_namelen); 2769 new_ncp->nc_name[nlc->nlc_namelen] = 0; 2770 } 2771 goto restart; 2772 } 2773 2774 /* 2775 * NOTE! The spinlock is held exclusively here because new_ncp 2776 * is non-NULL. 2777 */ 2778 if (par_locked == 0) { 2779 spin_unlock(&nchpp->spin); 2780 _cache_lock(par_nch->ncp); 2781 par_locked = 1; 2782 goto restart; 2783 } 2784 2785 /* 2786 * WARNING! We still hold the spinlock. We have to set the hash 2787 * table entry atomically. 2788 */ 2789 ncp = new_ncp; 2790 _cache_link_parent(ncp, par_nch->ncp, nchpp); 2791 spin_unlock(&nchpp->spin); 2792 _cache_unlock(par_nch->ncp); 2793 /* par_locked = 0 - not used */ 2794 found: 2795 /* 2796 * stats and namecache size management 2797 */ 2798 if (ncp->nc_flag & NCF_UNRESOLVED) 2799 ++gd->gd_nchstats->ncs_miss; 2800 else if (ncp->nc_vp) 2801 ++gd->gd_nchstats->ncs_goodhits; 2802 else 2803 ++gd->gd_nchstats->ncs_neghits; 2804 nch.mount = mp; 2805 nch.ncp = ncp; 2806 atomic_add_int(&nch.mount->mnt_refs, 1); 2807 return(nch); 2808 } 2809 2810 /* 2811 * Attempt to lookup a namecache entry and return with a shared namecache 2812 * lock. 2813 */ 2814 int 2815 cache_nlookup_maybe_shared(struct nchandle *par_nch, struct nlcomponent *nlc, 2816 int excl, struct nchandle *res_nch) 2817 { 2818 struct namecache *ncp; 2819 struct nchash_head *nchpp; 2820 struct mount *mp; 2821 u_int32_t hash; 2822 globaldata_t gd; 2823 2824 /* 2825 * If exclusive requested or shared namecache locks are disabled, 2826 * return failure. 2827 */ 2828 if (ncp_shared_lock_disable || excl) 2829 return(EWOULDBLOCK); 2830 2831 numcalls++; 2832 gd = mycpu; 2833 mp = par_nch->mount; 2834 2835 /* 2836 * This is a good time to call it, no ncp's are locked by 2837 * the caller or us. 2838 */ 2839 cache_hysteresis(1); 2840 2841 /* 2842 * Try to locate an existing entry 2843 */ 2844 hash = fnv_32_buf(nlc->nlc_nameptr, nlc->nlc_namelen, FNV1_32_INIT); 2845 hash = fnv_32_buf(&par_nch->ncp, sizeof(par_nch->ncp), hash); 2846 nchpp = NCHHASH(hash); 2847 2848 spin_lock_shared(&nchpp->spin); 2849 2850 LIST_FOREACH(ncp, &nchpp->list, nc_hash) { 2851 numchecks++; 2852 2853 /* 2854 * Break out if we find a matching entry. Note that 2855 * UNRESOLVED entries may match, but DESTROYED entries 2856 * do not. 2857 */ 2858 if (ncp->nc_parent == par_nch->ncp && 2859 ncp->nc_nlen == nlc->nlc_namelen && 2860 bcmp(ncp->nc_name, nlc->nlc_nameptr, ncp->nc_nlen) == 0 && 2861 (ncp->nc_flag & NCF_DESTROYED) == 0 2862 ) { 2863 _cache_hold(ncp); 2864 spin_unlock_shared(&nchpp->spin); 2865 if (_cache_lock_shared_special(ncp) == 0) { 2866 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0 && 2867 (ncp->nc_flag & NCF_DESTROYED) == 0 && 2868 _cache_auto_unresolve_test(mp, ncp) == 0) { 2869 goto found; 2870 } 2871 _cache_unlock(ncp); 2872 } 2873 _cache_drop(ncp); 2874 spin_lock_shared(&nchpp->spin); 2875 break; 2876 } 2877 } 2878 2879 /* 2880 * Failure 2881 */ 2882 spin_unlock_shared(&nchpp->spin); 2883 return(EWOULDBLOCK); 2884 2885 /* 2886 * Success 2887 * 2888 * Note that nc_error might be non-zero (e.g ENOENT). 2889 */ 2890 found: 2891 res_nch->mount = mp; 2892 res_nch->ncp = ncp; 2893 ++gd->gd_nchstats->ncs_goodhits; 2894 atomic_add_int(&res_nch->mount->mnt_refs, 1); 2895 2896 KKASSERT(ncp->nc_error != EWOULDBLOCK); 2897 return(ncp->nc_error); 2898 } 2899 2900 /* 2901 * This is a non-blocking verison of cache_nlookup() used by 2902 * nfs_readdirplusrpc_uio(). It can fail for any reason and 2903 * will return nch.ncp == NULL in that case. 2904 */ 2905 struct nchandle 2906 cache_nlookup_nonblock(struct nchandle *par_nch, struct nlcomponent *nlc) 2907 { 2908 struct nchandle nch; 2909 struct namecache *ncp; 2910 struct namecache *new_ncp; 2911 struct nchash_head *nchpp; 2912 struct mount *mp; 2913 u_int32_t hash; 2914 globaldata_t gd; 2915 int par_locked; 2916 2917 numcalls++; 2918 gd = mycpu; 2919 mp = par_nch->mount; 2920 par_locked = 0; 2921 2922 /* 2923 * Try to locate an existing entry 2924 */ 2925 hash = fnv_32_buf(nlc->nlc_nameptr, nlc->nlc_namelen, FNV1_32_INIT); 2926 hash = fnv_32_buf(&par_nch->ncp, sizeof(par_nch->ncp), hash); 2927 new_ncp = NULL; 2928 nchpp = NCHHASH(hash); 2929 restart: 2930 spin_lock(&nchpp->spin); 2931 LIST_FOREACH(ncp, &nchpp->list, nc_hash) { 2932 numchecks++; 2933 2934 /* 2935 * Break out if we find a matching entry. Note that 2936 * UNRESOLVED entries may match, but DESTROYED entries 2937 * do not. 2938 */ 2939 if (ncp->nc_parent == par_nch->ncp && 2940 ncp->nc_nlen == nlc->nlc_namelen && 2941 bcmp(ncp->nc_name, nlc->nlc_nameptr, ncp->nc_nlen) == 0 && 2942 (ncp->nc_flag & NCF_DESTROYED) == 0 2943 ) { 2944 _cache_hold(ncp); 2945 spin_unlock(&nchpp->spin); 2946 if (par_locked) { 2947 _cache_unlock(par_nch->ncp); 2948 par_locked = 0; 2949 } 2950 if (_cache_lock_special(ncp) == 0) { 2951 _cache_auto_unresolve(mp, ncp); 2952 if (new_ncp) { 2953 _cache_free(new_ncp); 2954 new_ncp = NULL; 2955 } 2956 goto found; 2957 } 2958 _cache_drop(ncp); 2959 goto failed; 2960 } 2961 } 2962 2963 /* 2964 * We failed to locate an entry, create a new entry and add it to 2965 * the cache. The parent ncp must also be locked so we 2966 * can link into it. 2967 * 2968 * We have to relookup after possibly blocking in kmalloc or 2969 * when locking par_nch. 2970 * 2971 * NOTE: nlc_namelen can be 0 and nlc_nameptr NULL as a special 2972 * mount case, in which case nc_name will be NULL. 2973 */ 2974 if (new_ncp == NULL) { 2975 spin_unlock(&nchpp->spin); 2976 new_ncp = cache_alloc(nlc->nlc_namelen); 2977 if (nlc->nlc_namelen) { 2978 bcopy(nlc->nlc_nameptr, new_ncp->nc_name, 2979 nlc->nlc_namelen); 2980 new_ncp->nc_name[nlc->nlc_namelen] = 0; 2981 } 2982 goto restart; 2983 } 2984 if (par_locked == 0) { 2985 spin_unlock(&nchpp->spin); 2986 if (_cache_lock_nonblock(par_nch->ncp) == 0) { 2987 par_locked = 1; 2988 goto restart; 2989 } 2990 goto failed; 2991 } 2992 2993 /* 2994 * WARNING! We still hold the spinlock. We have to set the hash 2995 * table entry atomically. 2996 */ 2997 ncp = new_ncp; 2998 _cache_link_parent(ncp, par_nch->ncp, nchpp); 2999 spin_unlock(&nchpp->spin); 3000 _cache_unlock(par_nch->ncp); 3001 /* par_locked = 0 - not used */ 3002 found: 3003 /* 3004 * stats and namecache size management 3005 */ 3006 if (ncp->nc_flag & NCF_UNRESOLVED) 3007 ++gd->gd_nchstats->ncs_miss; 3008 else if (ncp->nc_vp) 3009 ++gd->gd_nchstats->ncs_goodhits; 3010 else 3011 ++gd->gd_nchstats->ncs_neghits; 3012 nch.mount = mp; 3013 nch.ncp = ncp; 3014 atomic_add_int(&nch.mount->mnt_refs, 1); 3015 return(nch); 3016 failed: 3017 if (new_ncp) { 3018 _cache_free(new_ncp); 3019 new_ncp = NULL; 3020 } 3021 nch.mount = NULL; 3022 nch.ncp = NULL; 3023 return(nch); 3024 } 3025 3026 /* 3027 * The namecache entry is marked as being used as a mount point. 3028 * Locate the mount if it is visible to the caller. The DragonFly 3029 * mount system allows arbitrary loops in the topology and disentangles 3030 * those loops by matching against (mp, ncp) rather than just (ncp). 3031 * This means any given ncp can dive any number of mounts, depending 3032 * on the relative mount (e.g. nullfs) the caller is at in the topology. 3033 * 3034 * We use a very simple frontend cache to reduce SMP conflicts, 3035 * which we have to do because the mountlist scan needs an exclusive 3036 * lock around its ripout info list. Not to mention that there might 3037 * be a lot of mounts. 3038 */ 3039 struct findmount_info { 3040 struct mount *result; 3041 struct mount *nch_mount; 3042 struct namecache *nch_ncp; 3043 }; 3044 3045 static 3046 struct ncmount_cache * 3047 ncmount_cache_lookup(struct mount *mp, struct namecache *ncp) 3048 { 3049 int hash; 3050 3051 hash = ((int)(intptr_t)mp / sizeof(*mp)) ^ 3052 ((int)(intptr_t)ncp / sizeof(*ncp)); 3053 hash = (hash & 0x7FFFFFFF) % NCMOUNT_NUMCACHE; 3054 return (&ncmount_cache[hash]); 3055 } 3056 3057 static 3058 int 3059 cache_findmount_callback(struct mount *mp, void *data) 3060 { 3061 struct findmount_info *info = data; 3062 3063 /* 3064 * Check the mount's mounted-on point against the passed nch. 3065 */ 3066 if (mp->mnt_ncmounton.mount == info->nch_mount && 3067 mp->mnt_ncmounton.ncp == info->nch_ncp 3068 ) { 3069 info->result = mp; 3070 atomic_add_int(&mp->mnt_refs, 1); 3071 return(-1); 3072 } 3073 return(0); 3074 } 3075 3076 struct mount * 3077 cache_findmount(struct nchandle *nch) 3078 { 3079 struct findmount_info info; 3080 struct ncmount_cache *ncc; 3081 struct mount *mp; 3082 3083 /* 3084 * Fast 3085 */ 3086 if (ncmount_cache_enable == 0) { 3087 ncc = NULL; 3088 goto skip; 3089 } 3090 ncc = ncmount_cache_lookup(nch->mount, nch->ncp); 3091 if (ncc->ncp == nch->ncp) { 3092 spin_lock_shared(&ncc->spin); 3093 if (ncc->isneg == 0 && 3094 ncc->ncp == nch->ncp && (mp = ncc->mp) != NULL) { 3095 if (mp->mnt_ncmounton.mount == nch->mount && 3096 mp->mnt_ncmounton.ncp == nch->ncp) { 3097 /* 3098 * Cache hit (positive) 3099 */ 3100 atomic_add_int(&mp->mnt_refs, 1); 3101 spin_unlock_shared(&ncc->spin); 3102 ++ncmount_cache_hit; 3103 return(mp); 3104 } 3105 /* else cache miss */ 3106 } 3107 if (ncc->isneg && 3108 ncc->ncp == nch->ncp && ncc->mp == nch->mount) { 3109 /* 3110 * Cache hit (negative) 3111 */ 3112 spin_unlock_shared(&ncc->spin); 3113 ++ncmount_cache_hit; 3114 return(NULL); 3115 } 3116 spin_unlock_shared(&ncc->spin); 3117 } 3118 skip: 3119 3120 /* 3121 * Slow 3122 */ 3123 info.result = NULL; 3124 info.nch_mount = nch->mount; 3125 info.nch_ncp = nch->ncp; 3126 mountlist_scan(cache_findmount_callback, &info, 3127 MNTSCAN_FORWARD|MNTSCAN_NOBUSY); 3128 3129 /* 3130 * Cache the result. 3131 * 3132 * Negative lookups: We cache the originating {ncp,mp}. (mp) is 3133 * only used for pointer comparisons and is not 3134 * referenced (otherwise there would be dangling 3135 * refs). 3136 * 3137 * Positive lookups: We cache the originating {ncp} and the target 3138 * (mp). (mp) is referenced. 3139 * 3140 * Indeterminant: If the match is undergoing an unmount we do 3141 * not cache it to avoid racing cache_unmounting(), 3142 * but still return the match. 3143 */ 3144 if (ncc) { 3145 spin_lock(&ncc->spin); 3146 if (info.result == NULL) { 3147 if (ncc->isneg == 0 && ncc->mp) 3148 atomic_add_int(&ncc->mp->mnt_refs, -1); 3149 ncc->ncp = nch->ncp; 3150 ncc->mp = nch->mount; 3151 ncc->isneg = 1; 3152 spin_unlock(&ncc->spin); 3153 ++ncmount_cache_overwrite; 3154 } else if ((info.result->mnt_kern_flag & MNTK_UNMOUNT) == 0) { 3155 if (ncc->isneg == 0 && ncc->mp) 3156 atomic_add_int(&ncc->mp->mnt_refs, -1); 3157 atomic_add_int(&info.result->mnt_refs, 1); 3158 ncc->ncp = nch->ncp; 3159 ncc->mp = info.result; 3160 ncc->isneg = 0; 3161 spin_unlock(&ncc->spin); 3162 ++ncmount_cache_overwrite; 3163 } else { 3164 spin_unlock(&ncc->spin); 3165 } 3166 ++ncmount_cache_miss; 3167 } 3168 return(info.result); 3169 } 3170 3171 void 3172 cache_dropmount(struct mount *mp) 3173 { 3174 atomic_add_int(&mp->mnt_refs, -1); 3175 } 3176 3177 void 3178 cache_ismounting(struct mount *mp) 3179 { 3180 struct nchandle *nch = &mp->mnt_ncmounton; 3181 struct ncmount_cache *ncc; 3182 3183 ncc = ncmount_cache_lookup(nch->mount, nch->ncp); 3184 if (ncc->isneg && 3185 ncc->ncp == nch->ncp && ncc->mp == nch->mount) { 3186 spin_lock(&ncc->spin); 3187 if (ncc->isneg && 3188 ncc->ncp == nch->ncp && ncc->mp == nch->mount) { 3189 ncc->ncp = NULL; 3190 ncc->mp = NULL; 3191 } 3192 spin_unlock(&ncc->spin); 3193 } 3194 } 3195 3196 void 3197 cache_unmounting(struct mount *mp) 3198 { 3199 struct nchandle *nch = &mp->mnt_ncmounton; 3200 struct ncmount_cache *ncc; 3201 3202 ncc = ncmount_cache_lookup(nch->mount, nch->ncp); 3203 if (ncc->isneg == 0 && 3204 ncc->ncp == nch->ncp && ncc->mp == mp) { 3205 spin_lock(&ncc->spin); 3206 if (ncc->isneg == 0 && 3207 ncc->ncp == nch->ncp && ncc->mp == mp) { 3208 atomic_add_int(&mp->mnt_refs, -1); 3209 ncc->ncp = NULL; 3210 ncc->mp = NULL; 3211 } 3212 spin_unlock(&ncc->spin); 3213 } 3214 } 3215 3216 /* 3217 * Resolve an unresolved namecache entry, generally by looking it up. 3218 * The passed ncp must be locked and refd. 3219 * 3220 * Theoretically since a vnode cannot be recycled while held, and since 3221 * the nc_parent chain holds its vnode as long as children exist, the 3222 * direct parent of the cache entry we are trying to resolve should 3223 * have a valid vnode. If not then generate an error that we can 3224 * determine is related to a resolver bug. 3225 * 3226 * However, if a vnode was in the middle of a recyclement when the NCP 3227 * got locked, ncp->nc_vp might point to a vnode that is about to become 3228 * invalid. cache_resolve() handles this case by unresolving the entry 3229 * and then re-resolving it. 3230 * 3231 * Note that successful resolution does not necessarily return an error 3232 * code of 0. If the ncp resolves to a negative cache hit then ENOENT 3233 * will be returned. 3234 */ 3235 int 3236 cache_resolve(struct nchandle *nch, struct ucred *cred) 3237 { 3238 struct namecache *par_tmp; 3239 struct namecache *par; 3240 struct namecache *ncp; 3241 struct nchandle nctmp; 3242 struct mount *mp; 3243 struct vnode *dvp; 3244 int error; 3245 3246 ncp = nch->ncp; 3247 mp = nch->mount; 3248 KKASSERT(_cache_lockstatus(ncp) == LK_EXCLUSIVE); 3249 restart: 3250 /* 3251 * If the ncp is already resolved we have nothing to do. However, 3252 * we do want to guarentee that a usable vnode is returned when 3253 * a vnode is present, so make sure it hasn't been reclaimed. 3254 */ 3255 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) { 3256 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED)) 3257 _cache_setunresolved(ncp); 3258 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) 3259 return (ncp->nc_error); 3260 } 3261 3262 /* 3263 * If the ncp was destroyed it will never resolve again. This 3264 * can basically only happen when someone is chdir'd into an 3265 * empty directory which is then rmdir'd. We want to catch this 3266 * here and not dive the VFS because the VFS might actually 3267 * have a way to re-resolve the disconnected ncp, which will 3268 * result in inconsistencies in the cdir/nch for proc->p_fd. 3269 */ 3270 if (ncp->nc_flag & NCF_DESTROYED) { 3271 kprintf("Warning: cache_resolve: ncp '%s' was unlinked\n", 3272 ncp->nc_name); 3273 return(EINVAL); 3274 } 3275 3276 /* 3277 * Mount points need special handling because the parent does not 3278 * belong to the same filesystem as the ncp. 3279 */ 3280 if (ncp == mp->mnt_ncmountpt.ncp) 3281 return (cache_resolve_mp(mp)); 3282 3283 /* 3284 * We expect an unbroken chain of ncps to at least the mount point, 3285 * and even all the way to root (but this code doesn't have to go 3286 * past the mount point). 3287 */ 3288 if (ncp->nc_parent == NULL) { 3289 kprintf("EXDEV case 1 %p %*.*s\n", ncp, 3290 ncp->nc_nlen, ncp->nc_nlen, ncp->nc_name); 3291 ncp->nc_error = EXDEV; 3292 return(ncp->nc_error); 3293 } 3294 3295 /* 3296 * The vp's of the parent directories in the chain are held via vhold() 3297 * due to the existance of the child, and should not disappear. 3298 * However, there are cases where they can disappear: 3299 * 3300 * - due to filesystem I/O errors. 3301 * - due to NFS being stupid about tracking the namespace and 3302 * destroys the namespace for entire directories quite often. 3303 * - due to forced unmounts. 3304 * - due to an rmdir (parent will be marked DESTROYED) 3305 * 3306 * When this occurs we have to track the chain backwards and resolve 3307 * it, looping until the resolver catches up to the current node. We 3308 * could recurse here but we might run ourselves out of kernel stack 3309 * so we do it in a more painful manner. This situation really should 3310 * not occur all that often, or if it does not have to go back too 3311 * many nodes to resolve the ncp. 3312 */ 3313 while ((dvp = cache_dvpref(ncp)) == NULL) { 3314 /* 3315 * This case can occur if a process is CD'd into a 3316 * directory which is then rmdir'd. If the parent is marked 3317 * destroyed there is no point trying to resolve it. 3318 */ 3319 if (ncp->nc_parent->nc_flag & NCF_DESTROYED) 3320 return(ENOENT); 3321 par = ncp->nc_parent; 3322 _cache_hold(par); 3323 _cache_lock(par); 3324 while ((par_tmp = par->nc_parent) != NULL && 3325 par_tmp->nc_vp == NULL) { 3326 _cache_hold(par_tmp); 3327 _cache_lock(par_tmp); 3328 _cache_put(par); 3329 par = par_tmp; 3330 } 3331 if (par->nc_parent == NULL) { 3332 kprintf("EXDEV case 2 %*.*s\n", 3333 par->nc_nlen, par->nc_nlen, par->nc_name); 3334 _cache_put(par); 3335 return (EXDEV); 3336 } 3337 kprintf("[diagnostic] cache_resolve: had to recurse on %*.*s\n", 3338 par->nc_nlen, par->nc_nlen, par->nc_name); 3339 /* 3340 * The parent is not set in stone, ref and lock it to prevent 3341 * it from disappearing. Also note that due to renames it 3342 * is possible for our ncp to move and for par to no longer 3343 * be one of its parents. We resolve it anyway, the loop 3344 * will handle any moves. 3345 */ 3346 _cache_get(par); /* additional hold/lock */ 3347 _cache_put(par); /* from earlier hold/lock */ 3348 if (par == nch->mount->mnt_ncmountpt.ncp) { 3349 cache_resolve_mp(nch->mount); 3350 } else if ((dvp = cache_dvpref(par)) == NULL) { 3351 kprintf("[diagnostic] cache_resolve: raced on %*.*s\n", par->nc_nlen, par->nc_nlen, par->nc_name); 3352 _cache_put(par); 3353 continue; 3354 } else { 3355 if (par->nc_flag & NCF_UNRESOLVED) { 3356 nctmp.mount = mp; 3357 nctmp.ncp = par; 3358 par->nc_error = VOP_NRESOLVE(&nctmp, dvp, cred); 3359 } 3360 vrele(dvp); 3361 } 3362 if ((error = par->nc_error) != 0) { 3363 if (par->nc_error != EAGAIN) { 3364 kprintf("EXDEV case 3 %*.*s error %d\n", 3365 par->nc_nlen, par->nc_nlen, par->nc_name, 3366 par->nc_error); 3367 _cache_put(par); 3368 return(error); 3369 } 3370 kprintf("[diagnostic] cache_resolve: EAGAIN par %p %*.*s\n", 3371 par, par->nc_nlen, par->nc_nlen, par->nc_name); 3372 } 3373 _cache_put(par); 3374 /* loop */ 3375 } 3376 3377 /* 3378 * Call VOP_NRESOLVE() to get the vp, then scan for any disconnected 3379 * ncp's and reattach them. If this occurs the original ncp is marked 3380 * EAGAIN to force a relookup. 3381 * 3382 * NOTE: in order to call VOP_NRESOLVE(), the parent of the passed 3383 * ncp must already be resolved. 3384 */ 3385 if (dvp) { 3386 nctmp.mount = mp; 3387 nctmp.ncp = ncp; 3388 ncp->nc_error = VOP_NRESOLVE(&nctmp, dvp, cred); 3389 vrele(dvp); 3390 } else { 3391 ncp->nc_error = EPERM; 3392 } 3393 if (ncp->nc_error == EAGAIN) { 3394 kprintf("[diagnostic] cache_resolve: EAGAIN ncp %p %*.*s\n", 3395 ncp, ncp->nc_nlen, ncp->nc_nlen, ncp->nc_name); 3396 goto restart; 3397 } 3398 return(ncp->nc_error); 3399 } 3400 3401 /* 3402 * Resolve the ncp associated with a mount point. Such ncp's almost always 3403 * remain resolved and this routine is rarely called. NFS MPs tends to force 3404 * re-resolution more often due to its mac-truck-smash-the-namecache 3405 * method of tracking namespace changes. 3406 * 3407 * The semantics for this call is that the passed ncp must be locked on 3408 * entry and will be locked on return. However, if we actually have to 3409 * resolve the mount point we temporarily unlock the entry in order to 3410 * avoid race-to-root deadlocks due to e.g. dead NFS mounts. Because of 3411 * the unlock we have to recheck the flags after we relock. 3412 */ 3413 static int 3414 cache_resolve_mp(struct mount *mp) 3415 { 3416 struct namecache *ncp = mp->mnt_ncmountpt.ncp; 3417 struct vnode *vp; 3418 int error; 3419 3420 KKASSERT(mp != NULL); 3421 3422 /* 3423 * If the ncp is already resolved we have nothing to do. However, 3424 * we do want to guarentee that a usable vnode is returned when 3425 * a vnode is present, so make sure it hasn't been reclaimed. 3426 */ 3427 if ((ncp->nc_flag & NCF_UNRESOLVED) == 0) { 3428 if (ncp->nc_vp && (ncp->nc_vp->v_flag & VRECLAIMED)) 3429 _cache_setunresolved(ncp); 3430 } 3431 3432 if (ncp->nc_flag & NCF_UNRESOLVED) { 3433 _cache_unlock(ncp); 3434 while (vfs_busy(mp, 0)) 3435 ; 3436 error = VFS_ROOT(mp, &vp); 3437 _cache_lock(ncp); 3438 3439 /* 3440 * recheck the ncp state after relocking. 3441 */ 3442 if (ncp->nc_flag & NCF_UNRESOLVED) { 3443 ncp->nc_error = error; 3444 if (error == 0) { 3445 _cache_setvp(mp, ncp, vp); 3446 vput(vp); 3447 } else { 3448 kprintf("[diagnostic] cache_resolve_mp: failed" 3449 " to resolve mount %p err=%d ncp=%p\n", 3450 mp, error, ncp); 3451 _cache_setvp(mp, ncp, NULL); 3452 } 3453 } else if (error == 0) { 3454 vput(vp); 3455 } 3456 vfs_unbusy(mp); 3457 } 3458 return(ncp->nc_error); 3459 } 3460 3461 /* 3462 * Clean out negative cache entries when too many have accumulated. 3463 */ 3464 static void 3465 _cache_cleanneg(int count) 3466 { 3467 struct namecache *ncp; 3468 3469 /* 3470 * Attempt to clean out the specified number of negative cache 3471 * entries. 3472 */ 3473 while (count) { 3474 spin_lock(&ncspin); 3475 ncp = TAILQ_FIRST(&ncneglist); 3476 if (ncp == NULL) { 3477 spin_unlock(&ncspin); 3478 break; 3479 } 3480 TAILQ_REMOVE(&ncneglist, ncp, nc_vnode); 3481 TAILQ_INSERT_TAIL(&ncneglist, ncp, nc_vnode); 3482 _cache_hold(ncp); 3483 spin_unlock(&ncspin); 3484 3485 /* 3486 * This can race, so we must re-check that the ncp 3487 * is on the ncneglist after successfully locking it. 3488 */ 3489 if (_cache_lock_special(ncp) == 0) { 3490 if (ncp->nc_vp == NULL && 3491 (ncp->nc_flag & NCF_UNRESOLVED) == 0) { 3492 ncp = cache_zap(ncp, 1); 3493 if (ncp) 3494 _cache_drop(ncp); 3495 } else { 3496 kprintf("cache_cleanneg: race avoided\n"); 3497 _cache_unlock(ncp); 3498 } 3499 } else { 3500 _cache_drop(ncp); 3501 } 3502 --count; 3503 } 3504 } 3505 3506 /* 3507 * Clean out positive cache entries when too many have accumulated. 3508 */ 3509 static void 3510 _cache_cleanpos(int count) 3511 { 3512 static volatile int rover; 3513 struct nchash_head *nchpp; 3514 struct namecache *ncp; 3515 int rover_copy; 3516 3517 /* 3518 * Attempt to clean out the specified number of negative cache 3519 * entries. 3520 */ 3521 while (count) { 3522 rover_copy = ++rover; /* MPSAFEENOUGH */ 3523 cpu_ccfence(); 3524 nchpp = NCHHASH(rover_copy); 3525 3526 spin_lock_shared(&nchpp->spin); 3527 ncp = LIST_FIRST(&nchpp->list); 3528 while (ncp && (ncp->nc_flag & NCF_DESTROYED)) 3529 ncp = LIST_NEXT(ncp, nc_hash); 3530 if (ncp) 3531 _cache_hold(ncp); 3532 spin_unlock_shared(&nchpp->spin); 3533 3534 if (ncp) { 3535 if (_cache_lock_special(ncp) == 0) { 3536 ncp = cache_zap(ncp, 1); 3537 if (ncp) 3538 _cache_drop(ncp); 3539 } else { 3540 _cache_drop(ncp); 3541 } 3542 } 3543 --count; 3544 } 3545 } 3546 3547 /* 3548 * This is a kitchen sink function to clean out ncps which we 3549 * tried to zap from cache_drop() but failed because we were 3550 * unable to acquire the parent lock. 3551 * 3552 * Such entries can also be removed via cache_inval_vp(), such 3553 * as when unmounting. 3554 */ 3555 static void 3556 _cache_cleandefered(void) 3557 { 3558 struct nchash_head *nchpp; 3559 struct namecache *ncp; 3560 struct namecache dummy; 3561 int i; 3562 3563 numdefered = 0; 3564 bzero(&dummy, sizeof(dummy)); 3565 dummy.nc_flag = NCF_DESTROYED; 3566 dummy.nc_refs = 1; 3567 3568 for (i = 0; i <= nchash; ++i) { 3569 nchpp = &nchashtbl[i]; 3570 3571 spin_lock(&nchpp->spin); 3572 LIST_INSERT_HEAD(&nchpp->list, &dummy, nc_hash); 3573 ncp = &dummy; 3574 while ((ncp = LIST_NEXT(ncp, nc_hash)) != NULL) { 3575 if ((ncp->nc_flag & NCF_DEFEREDZAP) == 0) 3576 continue; 3577 LIST_REMOVE(&dummy, nc_hash); 3578 LIST_INSERT_AFTER(ncp, &dummy, nc_hash); 3579 _cache_hold(ncp); 3580 spin_unlock(&nchpp->spin); 3581 if (_cache_lock_nonblock(ncp) == 0) { 3582 ncp->nc_flag &= ~NCF_DEFEREDZAP; 3583 _cache_unlock(ncp); 3584 } 3585 _cache_drop(ncp); 3586 spin_lock(&nchpp->spin); 3587 ncp = &dummy; 3588 } 3589 LIST_REMOVE(&dummy, nc_hash); 3590 spin_unlock(&nchpp->spin); 3591 } 3592 } 3593 3594 /* 3595 * Name cache initialization, from vfsinit() when we are booting 3596 */ 3597 void 3598 nchinit(void) 3599 { 3600 int i; 3601 globaldata_t gd; 3602 3603 /* initialise per-cpu namecache effectiveness statistics. */ 3604 for (i = 0; i < ncpus; ++i) { 3605 gd = globaldata_find(i); 3606 gd->gd_nchstats = &nchstats[i]; 3607 } 3608 TAILQ_INIT(&ncneglist); 3609 spin_init(&ncspin); 3610 nchashtbl = hashinit_ext(desiredvnodes / 2, 3611 sizeof(struct nchash_head), 3612 M_VFSCACHE, &nchash); 3613 for (i = 0; i <= (int)nchash; ++i) { 3614 LIST_INIT(&nchashtbl[i].list); 3615 spin_init(&nchashtbl[i].spin); 3616 } 3617 for (i = 0; i < NCMOUNT_NUMCACHE; ++i) 3618 spin_init(&ncmount_cache[i].spin); 3619 nclockwarn = 5 * hz; 3620 } 3621 3622 /* 3623 * Called from start_init() to bootstrap the root filesystem. Returns 3624 * a referenced, unlocked namecache record. 3625 */ 3626 void 3627 cache_allocroot(struct nchandle *nch, struct mount *mp, struct vnode *vp) 3628 { 3629 nch->ncp = cache_alloc(0); 3630 nch->mount = mp; 3631 atomic_add_int(&mp->mnt_refs, 1); 3632 if (vp) 3633 _cache_setvp(nch->mount, nch->ncp, vp); 3634 } 3635 3636 /* 3637 * vfs_cache_setroot() 3638 * 3639 * Create an association between the root of our namecache and 3640 * the root vnode. This routine may be called several times during 3641 * booting. 3642 * 3643 * If the caller intends to save the returned namecache pointer somewhere 3644 * it must cache_hold() it. 3645 */ 3646 void 3647 vfs_cache_setroot(struct vnode *nvp, struct nchandle *nch) 3648 { 3649 struct vnode *ovp; 3650 struct nchandle onch; 3651 3652 ovp = rootvnode; 3653 onch = rootnch; 3654 rootvnode = nvp; 3655 if (nch) 3656 rootnch = *nch; 3657 else 3658 cache_zero(&rootnch); 3659 if (ovp) 3660 vrele(ovp); 3661 if (onch.ncp) 3662 cache_drop(&onch); 3663 } 3664 3665 /* 3666 * XXX OLD API COMPAT FUNCTION. This really messes up the new namecache 3667 * topology and is being removed as quickly as possible. The new VOP_N*() 3668 * API calls are required to make specific adjustments using the supplied 3669 * ncp pointers rather then just bogusly purging random vnodes. 3670 * 3671 * Invalidate all namecache entries to a particular vnode as well as 3672 * any direct children of that vnode in the namecache. This is a 3673 * 'catch all' purge used by filesystems that do not know any better. 3674 * 3675 * Note that the linkage between the vnode and its namecache entries will 3676 * be removed, but the namecache entries themselves might stay put due to 3677 * active references from elsewhere in the system or due to the existance of 3678 * the children. The namecache topology is left intact even if we do not 3679 * know what the vnode association is. Such entries will be marked 3680 * NCF_UNRESOLVED. 3681 */ 3682 void 3683 cache_purge(struct vnode *vp) 3684 { 3685 cache_inval_vp(vp, CINV_DESTROY | CINV_CHILDREN); 3686 } 3687 3688 /* 3689 * Flush all entries referencing a particular filesystem. 3690 * 3691 * Since we need to check it anyway, we will flush all the invalid 3692 * entries at the same time. 3693 */ 3694 #if 0 3695 3696 void 3697 cache_purgevfs(struct mount *mp) 3698 { 3699 struct nchash_head *nchpp; 3700 struct namecache *ncp, *nnp; 3701 3702 /* 3703 * Scan hash tables for applicable entries. 3704 */ 3705 for (nchpp = &nchashtbl[nchash]; nchpp >= nchashtbl; nchpp--) { 3706 spin_lock_wr(&nchpp->spin); XXX 3707 ncp = LIST_FIRST(&nchpp->list); 3708 if (ncp) 3709 _cache_hold(ncp); 3710 while (ncp) { 3711 nnp = LIST_NEXT(ncp, nc_hash); 3712 if (nnp) 3713 _cache_hold(nnp); 3714 if (ncp->nc_mount == mp) { 3715 _cache_lock(ncp); 3716 ncp = cache_zap(ncp, 0); 3717 if (ncp) 3718 _cache_drop(ncp); 3719 } else { 3720 _cache_drop(ncp); 3721 } 3722 ncp = nnp; 3723 } 3724 spin_unlock_wr(&nchpp->spin); XXX 3725 } 3726 } 3727 3728 #endif 3729 3730 static int disablecwd; 3731 SYSCTL_INT(_debug, OID_AUTO, disablecwd, CTLFLAG_RW, &disablecwd, 0, 3732 "Disable getcwd"); 3733 3734 static u_long numcwdcalls; 3735 SYSCTL_ULONG(_vfs_cache, OID_AUTO, numcwdcalls, CTLFLAG_RD, &numcwdcalls, 0, 3736 "Number of current directory resolution calls"); 3737 static u_long numcwdfailnf; 3738 SYSCTL_ULONG(_vfs_cache, OID_AUTO, numcwdfailnf, CTLFLAG_RD, &numcwdfailnf, 0, 3739 "Number of current directory failures due to lack of file"); 3740 static u_long numcwdfailsz; 3741 SYSCTL_ULONG(_vfs_cache, OID_AUTO, numcwdfailsz, CTLFLAG_RD, &numcwdfailsz, 0, 3742 "Number of current directory failures due to large result"); 3743 static u_long numcwdfound; 3744 SYSCTL_ULONG(_vfs_cache, OID_AUTO, numcwdfound, CTLFLAG_RD, &numcwdfound, 0, 3745 "Number of current directory resolution successes"); 3746 3747 /* 3748 * MPALMOSTSAFE 3749 */ 3750 int 3751 sys___getcwd(struct __getcwd_args *uap) 3752 { 3753 u_int buflen; 3754 int error; 3755 char *buf; 3756 char *bp; 3757 3758 if (disablecwd) 3759 return (ENODEV); 3760 3761 buflen = uap->buflen; 3762 if (buflen == 0) 3763 return (EINVAL); 3764 if (buflen > MAXPATHLEN) 3765 buflen = MAXPATHLEN; 3766 3767 buf = kmalloc(buflen, M_TEMP, M_WAITOK); 3768 bp = kern_getcwd(buf, buflen, &error); 3769 if (error == 0) 3770 error = copyout(bp, uap->buf, strlen(bp) + 1); 3771 kfree(buf, M_TEMP); 3772 return (error); 3773 } 3774 3775 char * 3776 kern_getcwd(char *buf, size_t buflen, int *error) 3777 { 3778 struct proc *p = curproc; 3779 char *bp; 3780 int i, slash_prefixed; 3781 struct filedesc *fdp; 3782 struct nchandle nch; 3783 struct namecache *ncp; 3784 3785 numcwdcalls++; 3786 bp = buf; 3787 bp += buflen - 1; 3788 *bp = '\0'; 3789 fdp = p->p_fd; 3790 slash_prefixed = 0; 3791 3792 nch = fdp->fd_ncdir; 3793 ncp = nch.ncp; 3794 if (ncp) 3795 _cache_hold(ncp); 3796 3797 while (ncp && (ncp != fdp->fd_nrdir.ncp || 3798 nch.mount != fdp->fd_nrdir.mount) 3799 ) { 3800 /* 3801 * While traversing upwards if we encounter the root 3802 * of the current mount we have to skip to the mount point 3803 * in the underlying filesystem. 3804 */ 3805 if (ncp == nch.mount->mnt_ncmountpt.ncp) { 3806 nch = nch.mount->mnt_ncmounton; 3807 _cache_drop(ncp); 3808 ncp = nch.ncp; 3809 if (ncp) 3810 _cache_hold(ncp); 3811 continue; 3812 } 3813 3814 /* 3815 * Prepend the path segment 3816 */ 3817 for (i = ncp->nc_nlen - 1; i >= 0; i--) { 3818 if (bp == buf) { 3819 numcwdfailsz++; 3820 *error = ERANGE; 3821 bp = NULL; 3822 goto done; 3823 } 3824 *--bp = ncp->nc_name[i]; 3825 } 3826 if (bp == buf) { 3827 numcwdfailsz++; 3828 *error = ERANGE; 3829 bp = NULL; 3830 goto done; 3831 } 3832 *--bp = '/'; 3833 slash_prefixed = 1; 3834 3835 /* 3836 * Go up a directory. This isn't a mount point so we don't 3837 * have to check again. 3838 */ 3839 while ((nch.ncp = ncp->nc_parent) != NULL) { 3840 if (ncp_shared_lock_disable) 3841 _cache_lock(ncp); 3842 else 3843 _cache_lock_shared(ncp); 3844 if (nch.ncp != ncp->nc_parent) { 3845 _cache_unlock(ncp); 3846 continue; 3847 } 3848 _cache_hold(nch.ncp); 3849 _cache_unlock(ncp); 3850 break; 3851 } 3852 _cache_drop(ncp); 3853 ncp = nch.ncp; 3854 } 3855 if (ncp == NULL) { 3856 numcwdfailnf++; 3857 *error = ENOENT; 3858 bp = NULL; 3859 goto done; 3860 } 3861 if (!slash_prefixed) { 3862 if (bp == buf) { 3863 numcwdfailsz++; 3864 *error = ERANGE; 3865 bp = NULL; 3866 goto done; 3867 } 3868 *--bp = '/'; 3869 } 3870 numcwdfound++; 3871 *error = 0; 3872 done: 3873 if (ncp) 3874 _cache_drop(ncp); 3875 return (bp); 3876 } 3877 3878 /* 3879 * Thus begins the fullpath magic. 3880 * 3881 * The passed nchp is referenced but not locked. 3882 */ 3883 static int disablefullpath; 3884 SYSCTL_INT(_debug, OID_AUTO, disablefullpath, CTLFLAG_RW, 3885 &disablefullpath, 0, 3886 "Disable fullpath lookups"); 3887 3888 static u_int numfullpathcalls; 3889 SYSCTL_UINT(_vfs_cache, OID_AUTO, numfullpathcalls, CTLFLAG_RD, 3890 &numfullpathcalls, 0, 3891 "Number of full path resolutions in progress"); 3892 static u_int numfullpathfailnf; 3893 SYSCTL_UINT(_vfs_cache, OID_AUTO, numfullpathfailnf, CTLFLAG_RD, 3894 &numfullpathfailnf, 0, 3895 "Number of full path resolution failures due to lack of file"); 3896 static u_int numfullpathfailsz; 3897 SYSCTL_UINT(_vfs_cache, OID_AUTO, numfullpathfailsz, CTLFLAG_RD, 3898 &numfullpathfailsz, 0, 3899 "Number of full path resolution failures due to insufficient memory"); 3900 static u_int numfullpathfound; 3901 SYSCTL_UINT(_vfs_cache, OID_AUTO, numfullpathfound, CTLFLAG_RD, 3902 &numfullpathfound, 0, 3903 "Number of full path resolution successes"); 3904 3905 int 3906 cache_fullpath(struct proc *p, struct nchandle *nchp, struct nchandle *nchbase, 3907 char **retbuf, char **freebuf, int guess) 3908 { 3909 struct nchandle fd_nrdir; 3910 struct nchandle nch; 3911 struct namecache *ncp; 3912 struct mount *mp, *new_mp; 3913 char *bp, *buf; 3914 int slash_prefixed; 3915 int error = 0; 3916 int i; 3917 3918 atomic_add_int(&numfullpathcalls, -1); 3919 3920 *retbuf = NULL; 3921 *freebuf = NULL; 3922 3923 buf = kmalloc(MAXPATHLEN, M_TEMP, M_WAITOK); 3924 bp = buf + MAXPATHLEN - 1; 3925 *bp = '\0'; 3926 if (nchbase) 3927 fd_nrdir = *nchbase; 3928 else if (p != NULL) 3929 fd_nrdir = p->p_fd->fd_nrdir; 3930 else 3931 fd_nrdir = rootnch; 3932 slash_prefixed = 0; 3933 nch = *nchp; 3934 ncp = nch.ncp; 3935 if (ncp) 3936 _cache_hold(ncp); 3937 mp = nch.mount; 3938 3939 while (ncp && (ncp != fd_nrdir.ncp || mp != fd_nrdir.mount)) { 3940 new_mp = NULL; 3941 3942 /* 3943 * If we are asked to guess the upwards path, we do so whenever 3944 * we encounter an ncp marked as a mountpoint. We try to find 3945 * the actual mountpoint by finding the mountpoint with this 3946 * ncp. 3947 */ 3948 if (guess && (ncp->nc_flag & NCF_ISMOUNTPT)) { 3949 new_mp = mount_get_by_nc(ncp); 3950 } 3951 /* 3952 * While traversing upwards if we encounter the root 3953 * of the current mount we have to skip to the mount point. 3954 */ 3955 if (ncp == mp->mnt_ncmountpt.ncp) { 3956 new_mp = mp; 3957 } 3958 if (new_mp) { 3959 nch = new_mp->mnt_ncmounton; 3960 _cache_drop(ncp); 3961 ncp = nch.ncp; 3962 if (ncp) 3963 _cache_hold(ncp); 3964 mp = nch.mount; 3965 continue; 3966 } 3967 3968 /* 3969 * Prepend the path segment 3970 */ 3971 for (i = ncp->nc_nlen - 1; i >= 0; i--) { 3972 if (bp == buf) { 3973 numfullpathfailsz++; 3974 kfree(buf, M_TEMP); 3975 error = ENOMEM; 3976 goto done; 3977 } 3978 *--bp = ncp->nc_name[i]; 3979 } 3980 if (bp == buf) { 3981 numfullpathfailsz++; 3982 kfree(buf, M_TEMP); 3983 error = ENOMEM; 3984 goto done; 3985 } 3986 *--bp = '/'; 3987 slash_prefixed = 1; 3988 3989 /* 3990 * Go up a directory. This isn't a mount point so we don't 3991 * have to check again. 3992 * 3993 * We can only safely access nc_parent with ncp held locked. 3994 */ 3995 while ((nch.ncp = ncp->nc_parent) != NULL) { 3996 _cache_lock(ncp); 3997 if (nch.ncp != ncp->nc_parent) { 3998 _cache_unlock(ncp); 3999 continue; 4000 } 4001 _cache_hold(nch.ncp); 4002 _cache_unlock(ncp); 4003 break; 4004 } 4005 _cache_drop(ncp); 4006 ncp = nch.ncp; 4007 } 4008 if (ncp == NULL) { 4009 numfullpathfailnf++; 4010 kfree(buf, M_TEMP); 4011 error = ENOENT; 4012 goto done; 4013 } 4014 4015 if (!slash_prefixed) { 4016 if (bp == buf) { 4017 numfullpathfailsz++; 4018 kfree(buf, M_TEMP); 4019 error = ENOMEM; 4020 goto done; 4021 } 4022 *--bp = '/'; 4023 } 4024 numfullpathfound++; 4025 *retbuf = bp; 4026 *freebuf = buf; 4027 error = 0; 4028 done: 4029 if (ncp) 4030 _cache_drop(ncp); 4031 return(error); 4032 } 4033 4034 int 4035 vn_fullpath(struct proc *p, struct vnode *vn, char **retbuf, 4036 char **freebuf, int guess) 4037 { 4038 struct namecache *ncp; 4039 struct nchandle nch; 4040 int error; 4041 4042 *freebuf = NULL; 4043 atomic_add_int(&numfullpathcalls, 1); 4044 if (disablefullpath) 4045 return (ENODEV); 4046 4047 if (p == NULL) 4048 return (EINVAL); 4049 4050 /* vn is NULL, client wants us to use p->p_textvp */ 4051 if (vn == NULL) { 4052 if ((vn = p->p_textvp) == NULL) 4053 return (EINVAL); 4054 } 4055 spin_lock_shared(&vn->v_spin); 4056 TAILQ_FOREACH(ncp, &vn->v_namecache, nc_vnode) { 4057 if (ncp->nc_nlen) 4058 break; 4059 } 4060 if (ncp == NULL) { 4061 spin_unlock_shared(&vn->v_spin); 4062 return (EINVAL); 4063 } 4064 _cache_hold(ncp); 4065 spin_unlock_shared(&vn->v_spin); 4066 4067 atomic_add_int(&numfullpathcalls, -1); 4068 nch.ncp = ncp; 4069 nch.mount = vn->v_mount; 4070 error = cache_fullpath(p, &nch, NULL, retbuf, freebuf, guess); 4071 _cache_drop(ncp); 4072 return (error); 4073 } 4074