The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/vfs_cache.c

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    1 /*-
    2  * Copyright (c) 1989, 1993, 1995
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software contributed to Berkeley by
    6  * Poul-Henning Kamp of the FreeBSD Project.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   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 the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 4. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  *      @(#)vfs_cache.c 8.5 (Berkeley) 3/22/95
   33  */
   34 
   35 #include <sys/cdefs.h>
   36 __FBSDID("$FreeBSD: releng/10.0/sys/kern/vfs_cache.c 253075 2013-07-09 08:58:34Z avg $");
   37 
   38 #include "opt_kdtrace.h"
   39 #include "opt_ktrace.h"
   40 
   41 #include <sys/param.h>
   42 #include <sys/systm.h>
   43 #include <sys/filedesc.h>
   44 #include <sys/fnv_hash.h>
   45 #include <sys/kernel.h>
   46 #include <sys/lock.h>
   47 #include <sys/malloc.h>
   48 #include <sys/fcntl.h>
   49 #include <sys/mount.h>
   50 #include <sys/namei.h>
   51 #include <sys/proc.h>
   52 #include <sys/rwlock.h>
   53 #include <sys/sdt.h>
   54 #include <sys/syscallsubr.h>
   55 #include <sys/sysctl.h>
   56 #include <sys/sysproto.h>
   57 #include <sys/vnode.h>
   58 #ifdef KTRACE
   59 #include <sys/ktrace.h>
   60 #endif
   61 
   62 #include <vm/uma.h>
   63 
   64 SDT_PROVIDER_DECLARE(vfs);
   65 SDT_PROBE_DEFINE3(vfs, namecache, enter, done, done, "struct vnode *", "char *",
   66     "struct vnode *");
   67 SDT_PROBE_DEFINE2(vfs, namecache, enter_negative, done, done, "struct vnode *",
   68     "char *");
   69 SDT_PROBE_DEFINE1(vfs, namecache, fullpath, entry, entry, "struct vnode *");
   70 SDT_PROBE_DEFINE3(vfs, namecache, fullpath, hit, hit, "struct vnode *",
   71     "char *", "struct vnode *");
   72 SDT_PROBE_DEFINE1(vfs, namecache, fullpath, miss, miss, "struct vnode *");
   73 SDT_PROBE_DEFINE3(vfs, namecache, fullpath, return, return, "int",
   74     "struct vnode *", "char *");
   75 SDT_PROBE_DEFINE3(vfs, namecache, lookup, hit, hit, "struct vnode *", "char *",
   76     "struct vnode *");
   77 SDT_PROBE_DEFINE2(vfs, namecache, lookup, hit_negative, hit-negative,
   78     "struct vnode *", "char *");
   79 SDT_PROBE_DEFINE2(vfs, namecache, lookup, miss, miss, "struct vnode *",
   80     "char *");
   81 SDT_PROBE_DEFINE1(vfs, namecache, purge, done, done, "struct vnode *");
   82 SDT_PROBE_DEFINE1(vfs, namecache, purge_negative, done, done, "struct vnode *");
   83 SDT_PROBE_DEFINE1(vfs, namecache, purgevfs, done, done, "struct mount *");
   84 SDT_PROBE_DEFINE3(vfs, namecache, zap, done, done, "struct vnode *", "char *",
   85     "struct vnode *");
   86 SDT_PROBE_DEFINE2(vfs, namecache, zap_negative, done, done, "struct vnode *",
   87     "char *");
   88 
   89 /*
   90  * This structure describes the elements in the cache of recent
   91  * names looked up by namei.
   92  */
   93 
   94 struct  namecache {
   95         LIST_ENTRY(namecache) nc_hash;  /* hash chain */
   96         LIST_ENTRY(namecache) nc_src;   /* source vnode list */
   97         TAILQ_ENTRY(namecache) nc_dst;  /* destination vnode list */
   98         struct  vnode *nc_dvp;          /* vnode of parent of name */
   99         struct  vnode *nc_vp;           /* vnode the name refers to */
  100         u_char  nc_flag;                /* flag bits */
  101         u_char  nc_nlen;                /* length of name */
  102         char    nc_name[0];             /* segment name + nul */
  103 };
  104 
  105 /*
  106  * struct namecache_ts repeats struct namecache layout up to the
  107  * nc_nlen member.
  108  * struct namecache_ts is used in place of struct namecache when time(s) need
  109  * to be stored.  The nc_dotdottime field is used when a cache entry is mapping
  110  * both a non-dotdot directory name plus dotdot for the directory's
  111  * parent.
  112  */
  113 struct  namecache_ts {
  114         LIST_ENTRY(namecache) nc_hash;  /* hash chain */
  115         LIST_ENTRY(namecache) nc_src;   /* source vnode list */
  116         TAILQ_ENTRY(namecache) nc_dst;  /* destination vnode list */
  117         struct  vnode *nc_dvp;          /* vnode of parent of name */
  118         struct  vnode *nc_vp;           /* vnode the name refers to */
  119         u_char  nc_flag;                /* flag bits */
  120         u_char  nc_nlen;                /* length of name */
  121         struct  timespec nc_time;       /* timespec provided by fs */
  122         struct  timespec nc_dotdottime; /* dotdot timespec provided by fs */
  123         int     nc_ticks;               /* ticks value when entry was added */
  124         char    nc_name[0];             /* segment name + nul */
  125 };
  126 
  127 /*
  128  * Flags in namecache.nc_flag
  129  */
  130 #define NCF_WHITE       0x01
  131 #define NCF_ISDOTDOT    0x02
  132 #define NCF_TS          0x04
  133 #define NCF_DTS         0x08
  134 
  135 /*
  136  * Name caching works as follows:
  137  *
  138  * Names found by directory scans are retained in a cache
  139  * for future reference.  It is managed LRU, so frequently
  140  * used names will hang around.  Cache is indexed by hash value
  141  * obtained from (vp, name) where vp refers to the directory
  142  * containing name.
  143  *
  144  * If it is a "negative" entry, (i.e. for a name that is known NOT to
  145  * exist) the vnode pointer will be NULL.
  146  *
  147  * Upon reaching the last segment of a path, if the reference
  148  * is for DELETE, or NOCACHE is set (rewrite), and the
  149  * name is located in the cache, it will be dropped.
  150  */
  151 
  152 /*
  153  * Structures associated with name cacheing.
  154  */
  155 #define NCHHASH(hash) \
  156         (&nchashtbl[(hash) & nchash])
  157 static LIST_HEAD(nchashhead, namecache) *nchashtbl;     /* Hash Table */
  158 static TAILQ_HEAD(, namecache) ncneg;   /* Hash Table */
  159 static u_long   nchash;                 /* size of hash table */
  160 SYSCTL_ULONG(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0,
  161     "Size of namecache hash table");
  162 static u_long   ncnegfactor = 16;       /* ratio of negative entries */
  163 SYSCTL_ULONG(_vfs, OID_AUTO, ncnegfactor, CTLFLAG_RW, &ncnegfactor, 0,
  164     "Ratio of negative namecache entries");
  165 static u_long   numneg;                 /* number of negative entries allocated */
  166 SYSCTL_ULONG(_debug, OID_AUTO, numneg, CTLFLAG_RD, &numneg, 0,
  167     "Number of negative entries in namecache");
  168 static u_long   numcache;               /* number of cache entries allocated */
  169 SYSCTL_ULONG(_debug, OID_AUTO, numcache, CTLFLAG_RD, &numcache, 0,
  170     "Number of namecache entries");
  171 static u_long   numcachehv;             /* number of cache entries with vnodes held */
  172 SYSCTL_ULONG(_debug, OID_AUTO, numcachehv, CTLFLAG_RD, &numcachehv, 0,
  173     "Number of namecache entries with vnodes held");
  174 static u_int    ncsizefactor = 2;
  175 SYSCTL_UINT(_vfs, OID_AUTO, ncsizefactor, CTLFLAG_RW, &ncsizefactor, 0,
  176     "Size factor for namecache");
  177 
  178 struct nchstats nchstats;               /* cache effectiveness statistics */
  179 
  180 static struct rwlock cache_lock;
  181 RW_SYSINIT(vfscache, &cache_lock, "Name Cache");
  182 
  183 #define CACHE_UPGRADE_LOCK()    rw_try_upgrade(&cache_lock)
  184 #define CACHE_RLOCK()           rw_rlock(&cache_lock)
  185 #define CACHE_RUNLOCK()         rw_runlock(&cache_lock)
  186 #define CACHE_WLOCK()           rw_wlock(&cache_lock)
  187 #define CACHE_WUNLOCK()         rw_wunlock(&cache_lock)
  188 
  189 /*
  190  * UMA zones for the VFS cache.
  191  *
  192  * The small cache is used for entries with short names, which are the
  193  * most common.  The large cache is used for entries which are too big to
  194  * fit in the small cache.
  195  */
  196 static uma_zone_t cache_zone_small;
  197 static uma_zone_t cache_zone_small_ts;
  198 static uma_zone_t cache_zone_large;
  199 static uma_zone_t cache_zone_large_ts;
  200 
  201 #define CACHE_PATH_CUTOFF       35
  202 
  203 static struct namecache *
  204 cache_alloc(int len, int ts)
  205 {
  206 
  207         if (len > CACHE_PATH_CUTOFF) {
  208                 if (ts)
  209                         return (uma_zalloc(cache_zone_large_ts, M_WAITOK));
  210                 else
  211                         return (uma_zalloc(cache_zone_large, M_WAITOK));
  212         }
  213         if (ts)
  214                 return (uma_zalloc(cache_zone_small_ts, M_WAITOK));
  215         else
  216                 return (uma_zalloc(cache_zone_small, M_WAITOK));
  217 }
  218 
  219 static void
  220 cache_free(struct namecache *ncp)
  221 {
  222         int ts;
  223 
  224         if (ncp == NULL)
  225                 return;
  226         ts = ncp->nc_flag & NCF_TS;
  227         if (ncp->nc_nlen <= CACHE_PATH_CUTOFF) {
  228                 if (ts)
  229                         uma_zfree(cache_zone_small_ts, ncp);
  230                 else
  231                         uma_zfree(cache_zone_small, ncp);
  232         } else if (ts)
  233                 uma_zfree(cache_zone_large_ts, ncp);
  234         else
  235                 uma_zfree(cache_zone_large, ncp);
  236 }
  237 
  238 static char *
  239 nc_get_name(struct namecache *ncp)
  240 {
  241         struct namecache_ts *ncp_ts;
  242 
  243         if ((ncp->nc_flag & NCF_TS) == 0)
  244                 return (ncp->nc_name);
  245         ncp_ts = (struct namecache_ts *)ncp;
  246         return (ncp_ts->nc_name);
  247 }
  248 
  249 static void
  250 cache_out_ts(struct namecache *ncp, struct timespec *tsp, int *ticksp)
  251 {
  252 
  253         KASSERT((ncp->nc_flag & NCF_TS) != 0 ||
  254             (tsp == NULL && ticksp == NULL),
  255             ("No NCF_TS"));
  256 
  257         if (tsp != NULL)
  258                 *tsp = ((struct namecache_ts *)ncp)->nc_time;
  259         if (ticksp != NULL)
  260                 *ticksp = ((struct namecache_ts *)ncp)->nc_ticks;
  261 }
  262 
  263 static int      doingcache = 1;         /* 1 => enable the cache */
  264 SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0,
  265     "VFS namecache enabled");
  266 
  267 /* Export size information to userland */
  268 SYSCTL_INT(_debug_sizeof, OID_AUTO, namecache, CTLFLAG_RD, 0,
  269     sizeof(struct namecache), "sizeof(struct namecache)");
  270 
  271 /*
  272  * The new name cache statistics
  273  */
  274 static SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW, 0,
  275     "Name cache statistics");
  276 #define STATNODE(mode, name, var, descr) \
  277         SYSCTL_ULONG(_vfs_cache, OID_AUTO, name, mode, var, 0, descr);
  278 STATNODE(CTLFLAG_RD, numneg, &numneg, "Number of negative cache entries");
  279 STATNODE(CTLFLAG_RD, numcache, &numcache, "Number of cache entries");
  280 static u_long numcalls; STATNODE(CTLFLAG_RD, numcalls, &numcalls,
  281     "Number of cache lookups");
  282 static u_long dothits; STATNODE(CTLFLAG_RD, dothits, &dothits,
  283     "Number of '.' hits");
  284 static u_long dotdothits; STATNODE(CTLFLAG_RD, dotdothits, &dotdothits,
  285     "Number of '..' hits");
  286 static u_long numchecks; STATNODE(CTLFLAG_RD, numchecks, &numchecks,
  287     "Number of checks in lookup");
  288 static u_long nummiss; STATNODE(CTLFLAG_RD, nummiss, &nummiss,
  289     "Number of cache misses");
  290 static u_long nummisszap; STATNODE(CTLFLAG_RD, nummisszap, &nummisszap,
  291     "Number of cache misses we do not want to cache");
  292 static u_long numposzaps; STATNODE(CTLFLAG_RD, numposzaps, &numposzaps, 
  293     "Number of cache hits (positive) we do not want to cache");
  294 static u_long numposhits; STATNODE(CTLFLAG_RD, numposhits, &numposhits,
  295     "Number of cache hits (positive)");
  296 static u_long numnegzaps; STATNODE(CTLFLAG_RD, numnegzaps, &numnegzaps,
  297     "Number of cache hits (negative) we do not want to cache");
  298 static u_long numneghits; STATNODE(CTLFLAG_RD, numneghits, &numneghits,
  299     "Number of cache hits (negative)");
  300 static u_long numupgrades; STATNODE(CTLFLAG_RD, numupgrades, &numupgrades,
  301     "Number of updates of the cache after lookup (write lock + retry)");
  302 
  303 SYSCTL_OPAQUE(_vfs_cache, OID_AUTO, nchstats, CTLFLAG_RD | CTLFLAG_MPSAFE,
  304     &nchstats, sizeof(nchstats), "LU",
  305     "VFS cache effectiveness statistics");
  306 
  307 
  308 
  309 static void cache_zap(struct namecache *ncp);
  310 static int vn_vptocnp_locked(struct vnode **vp, struct ucred *cred, char *buf,
  311     u_int *buflen);
  312 static int vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
  313     char *buf, char **retbuf, u_int buflen);
  314 
  315 static MALLOC_DEFINE(M_VFSCACHE, "vfscache", "VFS name cache entries");
  316 
  317 #ifdef DIAGNOSTIC
  318 /*
  319  * Grab an atomic snapshot of the name cache hash chain lengths
  320  */
  321 static SYSCTL_NODE(_debug, OID_AUTO, hashstat, CTLFLAG_RW, NULL,
  322     "hash table stats");
  323 
  324 static int
  325 sysctl_debug_hashstat_rawnchash(SYSCTL_HANDLER_ARGS)
  326 {
  327         int error;
  328         struct nchashhead *ncpp;
  329         struct namecache *ncp;
  330         int n_nchash;
  331         int count;
  332 
  333         n_nchash = nchash + 1;  /* nchash is max index, not count */
  334         if (!req->oldptr)
  335                 return SYSCTL_OUT(req, 0, n_nchash * sizeof(int));
  336 
  337         /* Scan hash tables for applicable entries */
  338         for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) {
  339                 CACHE_RLOCK();
  340                 count = 0;
  341                 LIST_FOREACH(ncp, ncpp, nc_hash) {
  342                         count++;
  343                 }
  344                 CACHE_RUNLOCK();
  345                 error = SYSCTL_OUT(req, &count, sizeof(count));
  346                 if (error)
  347                         return (error);
  348         }
  349         return (0);
  350 }
  351 SYSCTL_PROC(_debug_hashstat, OID_AUTO, rawnchash, CTLTYPE_INT|CTLFLAG_RD|
  352     CTLFLAG_MPSAFE, 0, 0, sysctl_debug_hashstat_rawnchash, "S,int",
  353     "nchash chain lengths");
  354 
  355 static int
  356 sysctl_debug_hashstat_nchash(SYSCTL_HANDLER_ARGS)
  357 {
  358         int error;
  359         struct nchashhead *ncpp;
  360         struct namecache *ncp;
  361         int n_nchash;
  362         int count, maxlength, used, pct;
  363 
  364         if (!req->oldptr)
  365                 return SYSCTL_OUT(req, 0, 4 * sizeof(int));
  366 
  367         n_nchash = nchash + 1;  /* nchash is max index, not count */
  368         used = 0;
  369         maxlength = 0;
  370 
  371         /* Scan hash tables for applicable entries */
  372         for (ncpp = nchashtbl; n_nchash > 0; n_nchash--, ncpp++) {
  373                 count = 0;
  374                 CACHE_RLOCK();
  375                 LIST_FOREACH(ncp, ncpp, nc_hash) {
  376                         count++;
  377                 }
  378                 CACHE_RUNLOCK();
  379                 if (count)
  380                         used++;
  381                 if (maxlength < count)
  382                         maxlength = count;
  383         }
  384         n_nchash = nchash + 1;
  385         pct = (used * 100) / (n_nchash / 100);
  386         error = SYSCTL_OUT(req, &n_nchash, sizeof(n_nchash));
  387         if (error)
  388                 return (error);
  389         error = SYSCTL_OUT(req, &used, sizeof(used));
  390         if (error)
  391                 return (error);
  392         error = SYSCTL_OUT(req, &maxlength, sizeof(maxlength));
  393         if (error)
  394                 return (error);
  395         error = SYSCTL_OUT(req, &pct, sizeof(pct));
  396         if (error)
  397                 return (error);
  398         return (0);
  399 }
  400 SYSCTL_PROC(_debug_hashstat, OID_AUTO, nchash, CTLTYPE_INT|CTLFLAG_RD|
  401     CTLFLAG_MPSAFE, 0, 0, sysctl_debug_hashstat_nchash, "I",
  402     "nchash statistics (number of total/used buckets, maximum chain length, usage percentage)");
  403 #endif
  404 
  405 /*
  406  * cache_zap():
  407  *
  408  *   Removes a namecache entry from cache, whether it contains an actual
  409  *   pointer to a vnode or if it is just a negative cache entry.
  410  */
  411 static void
  412 cache_zap(ncp)
  413         struct namecache *ncp;
  414 {
  415         struct vnode *vp;
  416 
  417         rw_assert(&cache_lock, RA_WLOCKED);
  418         CTR2(KTR_VFS, "cache_zap(%p) vp %p", ncp, ncp->nc_vp);
  419 #ifdef KDTRACE_HOOKS
  420         if (ncp->nc_vp != NULL) {
  421                 SDT_PROBE(vfs, namecache, zap, done, ncp->nc_dvp,
  422                     nc_get_name(ncp), ncp->nc_vp, 0, 0);
  423         } else {
  424                 SDT_PROBE(vfs, namecache, zap_negative, done, ncp->nc_dvp,
  425                     nc_get_name(ncp), 0, 0, 0);
  426         }
  427 #endif
  428         vp = NULL;
  429         LIST_REMOVE(ncp, nc_hash);
  430         if (ncp->nc_flag & NCF_ISDOTDOT) {
  431                 if (ncp == ncp->nc_dvp->v_cache_dd)
  432                         ncp->nc_dvp->v_cache_dd = NULL;
  433         } else {
  434                 LIST_REMOVE(ncp, nc_src);
  435                 if (LIST_EMPTY(&ncp->nc_dvp->v_cache_src)) {
  436                         vp = ncp->nc_dvp;
  437                         numcachehv--;
  438                 }
  439         }
  440         if (ncp->nc_vp) {
  441                 TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst, ncp, nc_dst);
  442                 if (ncp == ncp->nc_vp->v_cache_dd)
  443                         ncp->nc_vp->v_cache_dd = NULL;
  444         } else {
  445                 TAILQ_REMOVE(&ncneg, ncp, nc_dst);
  446                 numneg--;
  447         }
  448         numcache--;
  449         cache_free(ncp);
  450         if (vp)
  451                 vdrop(vp);
  452 }
  453 
  454 /*
  455  * Lookup an entry in the cache
  456  *
  457  * Lookup is called with dvp pointing to the directory to search,
  458  * cnp pointing to the name of the entry being sought. If the lookup
  459  * succeeds, the vnode is returned in *vpp, and a status of -1 is
  460  * returned. If the lookup determines that the name does not exist
  461  * (negative cacheing), a status of ENOENT is returned. If the lookup
  462  * fails, a status of zero is returned.  If the directory vnode is
  463  * recycled out from under us due to a forced unmount, a status of
  464  * ENOENT is returned.
  465  *
  466  * vpp is locked and ref'd on return.  If we're looking up DOTDOT, dvp is
  467  * unlocked.  If we're looking up . an extra ref is taken, but the lock is
  468  * not recursively acquired.
  469  */
  470 
  471 int
  472 cache_lookup(dvp, vpp, cnp, tsp, ticksp)
  473         struct vnode *dvp;
  474         struct vnode **vpp;
  475         struct componentname *cnp;
  476         struct timespec *tsp;
  477         int *ticksp;
  478 {
  479         struct namecache *ncp;
  480         uint32_t hash;
  481         int error, ltype, wlocked;
  482 
  483         if (!doingcache) {
  484                 cnp->cn_flags &= ~MAKEENTRY;
  485                 return (0);
  486         }
  487 retry:
  488         CACHE_RLOCK();
  489         wlocked = 0;
  490         numcalls++;
  491         error = 0;
  492 
  493 retry_wlocked:
  494         if (cnp->cn_nameptr[0] == '.') {
  495                 if (cnp->cn_namelen == 1) {
  496                         *vpp = dvp;
  497                         CTR2(KTR_VFS, "cache_lookup(%p, %s) found via .",
  498                             dvp, cnp->cn_nameptr);
  499                         dothits++;
  500                         SDT_PROBE(vfs, namecache, lookup, hit, dvp, ".",
  501                             *vpp, 0, 0);
  502                         if (tsp != NULL)
  503                                 timespecclear(tsp);
  504                         if (ticksp != NULL)
  505                                 *ticksp = ticks;
  506                         goto success;
  507                 }
  508                 if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
  509                         dotdothits++;
  510                         if (dvp->v_cache_dd == NULL) {
  511                                 SDT_PROBE(vfs, namecache, lookup, miss, dvp,
  512                                     "..", NULL, 0, 0);
  513                                 goto unlock;
  514                         }
  515                         if ((cnp->cn_flags & MAKEENTRY) == 0) {
  516                                 if (!wlocked && !CACHE_UPGRADE_LOCK())
  517                                         goto wlock;
  518                                 if (dvp->v_cache_dd->nc_flag & NCF_ISDOTDOT)
  519                                         cache_zap(dvp->v_cache_dd);
  520                                 dvp->v_cache_dd = NULL;
  521                                 CACHE_WUNLOCK();
  522                                 return (0);
  523                         }
  524                         ncp = dvp->v_cache_dd;
  525                         if (ncp->nc_flag & NCF_ISDOTDOT)
  526                                 *vpp = ncp->nc_vp;
  527                         else
  528                                 *vpp = ncp->nc_dvp;
  529                         /* Return failure if negative entry was found. */
  530                         if (*vpp == NULL)
  531                                 goto negative_success;
  532                         CTR3(KTR_VFS, "cache_lookup(%p, %s) found %p via ..",
  533                             dvp, cnp->cn_nameptr, *vpp);
  534                         SDT_PROBE(vfs, namecache, lookup, hit, dvp, "..",
  535                             *vpp, 0, 0);
  536                         cache_out_ts(ncp, tsp, ticksp);
  537                         if ((ncp->nc_flag & (NCF_ISDOTDOT | NCF_DTS)) ==
  538                             NCF_DTS && tsp != NULL)
  539                                 *tsp = ((struct namecache_ts *)ncp)->
  540                                     nc_dotdottime;
  541                         goto success;
  542                 }
  543         }
  544 
  545         hash = fnv_32_buf(cnp->cn_nameptr, cnp->cn_namelen, FNV1_32_INIT);
  546         hash = fnv_32_buf(&dvp, sizeof(dvp), hash);
  547         LIST_FOREACH(ncp, (NCHHASH(hash)), nc_hash) {
  548                 numchecks++;
  549                 if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen &&
  550                     !bcmp(nc_get_name(ncp), cnp->cn_nameptr, ncp->nc_nlen))
  551                         break;
  552         }
  553 
  554         /* We failed to find an entry */
  555         if (ncp == NULL) {
  556                 SDT_PROBE(vfs, namecache, lookup, miss, dvp, cnp->cn_nameptr,
  557                     NULL, 0, 0);
  558                 if ((cnp->cn_flags & MAKEENTRY) == 0) {
  559                         nummisszap++;
  560                 } else {
  561                         nummiss++;
  562                 }
  563                 nchstats.ncs_miss++;
  564                 goto unlock;
  565         }
  566 
  567         /* We don't want to have an entry, so dump it */
  568         if ((cnp->cn_flags & MAKEENTRY) == 0) {
  569                 numposzaps++;
  570                 nchstats.ncs_badhits++;
  571                 if (!wlocked && !CACHE_UPGRADE_LOCK())
  572                         goto wlock;
  573                 cache_zap(ncp);
  574                 CACHE_WUNLOCK();
  575                 return (0);
  576         }
  577 
  578         /* We found a "positive" match, return the vnode */
  579         if (ncp->nc_vp) {
  580                 numposhits++;
  581                 nchstats.ncs_goodhits++;
  582                 *vpp = ncp->nc_vp;
  583                 CTR4(KTR_VFS, "cache_lookup(%p, %s) found %p via ncp %p",
  584                     dvp, cnp->cn_nameptr, *vpp, ncp);
  585                 SDT_PROBE(vfs, namecache, lookup, hit, dvp, nc_get_name(ncp),
  586                     *vpp, 0, 0);
  587                 cache_out_ts(ncp, tsp, ticksp);
  588                 goto success;
  589         }
  590 
  591 negative_success:
  592         /* We found a negative match, and want to create it, so purge */
  593         if (cnp->cn_nameiop == CREATE) {
  594                 numnegzaps++;
  595                 nchstats.ncs_badhits++;
  596                 if (!wlocked && !CACHE_UPGRADE_LOCK())
  597                         goto wlock;
  598                 cache_zap(ncp);
  599                 CACHE_WUNLOCK();
  600                 return (0);
  601         }
  602 
  603         if (!wlocked && !CACHE_UPGRADE_LOCK())
  604                 goto wlock;
  605         numneghits++;
  606         /*
  607          * We found a "negative" match, so we shift it to the end of
  608          * the "negative" cache entries queue to satisfy LRU.  Also,
  609          * check to see if the entry is a whiteout; indicate this to
  610          * the componentname, if so.
  611          */
  612         TAILQ_REMOVE(&ncneg, ncp, nc_dst);
  613         TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst);
  614         nchstats.ncs_neghits++;
  615         if (ncp->nc_flag & NCF_WHITE)
  616                 cnp->cn_flags |= ISWHITEOUT;
  617         SDT_PROBE(vfs, namecache, lookup, hit_negative, dvp, nc_get_name(ncp),
  618             0, 0, 0);
  619         cache_out_ts(ncp, tsp, ticksp);
  620         CACHE_WUNLOCK();
  621         return (ENOENT);
  622 
  623 wlock:
  624         /*
  625          * We need to update the cache after our lookup, so upgrade to
  626          * a write lock and retry the operation.
  627          */
  628         CACHE_RUNLOCK();
  629         CACHE_WLOCK();
  630         numupgrades++;
  631         wlocked = 1;
  632         goto retry_wlocked;
  633 
  634 success:
  635         /*
  636          * On success we return a locked and ref'd vnode as per the lookup
  637          * protocol.
  638          */
  639         if (dvp == *vpp) {   /* lookup on "." */
  640                 VREF(*vpp);
  641                 if (wlocked)
  642                         CACHE_WUNLOCK();
  643                 else
  644                         CACHE_RUNLOCK();
  645                 /*
  646                  * When we lookup "." we still can be asked to lock it
  647                  * differently...
  648                  */
  649                 ltype = cnp->cn_lkflags & LK_TYPE_MASK;
  650                 if (ltype != VOP_ISLOCKED(*vpp)) {
  651                         if (ltype == LK_EXCLUSIVE) {
  652                                 vn_lock(*vpp, LK_UPGRADE | LK_RETRY);
  653                                 if ((*vpp)->v_iflag & VI_DOOMED) {
  654                                         /* forced unmount */
  655                                         vrele(*vpp);
  656                                         *vpp = NULL;
  657                                         return (ENOENT);
  658                                 }
  659                         } else
  660                                 vn_lock(*vpp, LK_DOWNGRADE | LK_RETRY);
  661                 }
  662                 return (-1);
  663         }
  664         ltype = 0;      /* silence gcc warning */
  665         if (cnp->cn_flags & ISDOTDOT) {
  666                 ltype = VOP_ISLOCKED(dvp);
  667                 VOP_UNLOCK(dvp, 0);
  668         }
  669         VI_LOCK(*vpp);
  670         if (wlocked)
  671                 CACHE_WUNLOCK();
  672         else
  673                 CACHE_RUNLOCK();
  674         error = vget(*vpp, cnp->cn_lkflags | LK_INTERLOCK, cnp->cn_thread);
  675         if (cnp->cn_flags & ISDOTDOT) {
  676                 vn_lock(dvp, ltype | LK_RETRY);
  677                 if (dvp->v_iflag & VI_DOOMED) {
  678                         if (error == 0)
  679                                 vput(*vpp);
  680                         *vpp = NULL;
  681                         return (ENOENT);
  682                 }
  683         }
  684         if (error) {
  685                 *vpp = NULL;
  686                 goto retry;
  687         }
  688         if ((cnp->cn_flags & ISLASTCN) &&
  689             (cnp->cn_lkflags & LK_TYPE_MASK) == LK_EXCLUSIVE) {
  690                 ASSERT_VOP_ELOCKED(*vpp, "cache_lookup");
  691         }
  692         return (-1);
  693 
  694 unlock:
  695         if (wlocked)
  696                 CACHE_WUNLOCK();
  697         else
  698                 CACHE_RUNLOCK();
  699         return (0);
  700 }
  701 
  702 /*
  703  * Add an entry to the cache.
  704  */
  705 void
  706 cache_enter_time(dvp, vp, cnp, tsp, dtsp)
  707         struct vnode *dvp;
  708         struct vnode *vp;
  709         struct componentname *cnp;
  710         struct timespec *tsp;
  711         struct timespec *dtsp;
  712 {
  713         struct namecache *ncp, *n2;
  714         struct namecache_ts *n3;
  715         struct nchashhead *ncpp;
  716         uint32_t hash;
  717         int flag;
  718         int hold;
  719         int zap;
  720         int len;
  721 
  722         CTR3(KTR_VFS, "cache_enter(%p, %p, %s)", dvp, vp, cnp->cn_nameptr);
  723         VNASSERT(vp == NULL || (vp->v_iflag & VI_DOOMED) == 0, vp,
  724             ("cache_enter: Adding a doomed vnode"));
  725         VNASSERT(dvp == NULL || (dvp->v_iflag & VI_DOOMED) == 0, dvp,
  726             ("cache_enter: Doomed vnode used as src"));
  727 
  728         if (!doingcache)
  729                 return;
  730 
  731         /*
  732          * Avoid blowout in namecache entries.
  733          */
  734         if (numcache >= desiredvnodes * ncsizefactor)
  735                 return;
  736 
  737         flag = 0;
  738         if (cnp->cn_nameptr[0] == '.') {
  739                 if (cnp->cn_namelen == 1)
  740                         return;
  741                 if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') {
  742                         CACHE_WLOCK();
  743                         /*
  744                          * If dotdot entry already exists, just retarget it
  745                          * to new parent vnode, otherwise continue with new
  746                          * namecache entry allocation.
  747                          */
  748                         if ((ncp = dvp->v_cache_dd) != NULL &&
  749                             ncp->nc_flag & NCF_ISDOTDOT) {
  750                                 KASSERT(ncp->nc_dvp == dvp,
  751                                     ("wrong isdotdot parent"));
  752                                 if (ncp->nc_vp != NULL)
  753                                         TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst,
  754                                             ncp, nc_dst);
  755                                 else
  756                                         TAILQ_REMOVE(&ncneg, ncp, nc_dst);
  757                                 if (vp != NULL)
  758                                         TAILQ_INSERT_HEAD(&vp->v_cache_dst,
  759                                             ncp, nc_dst);
  760                                 else
  761                                         TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst);
  762                                 ncp->nc_vp = vp;
  763                                 CACHE_WUNLOCK();
  764                                 return;
  765                         }
  766                         dvp->v_cache_dd = NULL;
  767                         SDT_PROBE(vfs, namecache, enter, done, dvp, "..", vp,
  768                             0, 0);
  769                         CACHE_WUNLOCK();
  770                         flag = NCF_ISDOTDOT;
  771                 }
  772         }
  773 
  774         hold = 0;
  775         zap = 0;
  776 
  777         /*
  778          * Calculate the hash key and setup as much of the new
  779          * namecache entry as possible before acquiring the lock.
  780          */
  781         ncp = cache_alloc(cnp->cn_namelen, tsp != NULL);
  782         ncp->nc_vp = vp;
  783         ncp->nc_dvp = dvp;
  784         ncp->nc_flag = flag;
  785         if (tsp != NULL) {
  786                 n3 = (struct namecache_ts *)ncp;
  787                 n3->nc_time = *tsp;
  788                 n3->nc_ticks = ticks;
  789                 n3->nc_flag |= NCF_TS;
  790                 if (dtsp != NULL) {
  791                         n3->nc_dotdottime = *dtsp;
  792                         n3->nc_flag |= NCF_DTS;
  793                 }
  794         }
  795         len = ncp->nc_nlen = cnp->cn_namelen;
  796         hash = fnv_32_buf(cnp->cn_nameptr, len, FNV1_32_INIT);
  797         strlcpy(nc_get_name(ncp), cnp->cn_nameptr, len + 1);
  798         hash = fnv_32_buf(&dvp, sizeof(dvp), hash);
  799         CACHE_WLOCK();
  800 
  801         /*
  802          * See if this vnode or negative entry is already in the cache
  803          * with this name.  This can happen with concurrent lookups of
  804          * the same path name.
  805          */
  806         ncpp = NCHHASH(hash);
  807         LIST_FOREACH(n2, ncpp, nc_hash) {
  808                 if (n2->nc_dvp == dvp &&
  809                     n2->nc_nlen == cnp->cn_namelen &&
  810                     !bcmp(nc_get_name(n2), cnp->cn_nameptr, n2->nc_nlen)) {
  811                         if (tsp != NULL) {
  812                                 KASSERT((n2->nc_flag & NCF_TS) != 0,
  813                                     ("no NCF_TS"));
  814                                 n3 = (struct namecache_ts *)n2;
  815                                 n3->nc_time =
  816                                     ((struct namecache_ts *)ncp)->nc_time;
  817                                 n3->nc_ticks =
  818                                     ((struct namecache_ts *)ncp)->nc_ticks;
  819                                 if (dtsp != NULL) {
  820                                         n3->nc_dotdottime =
  821                                             ((struct namecache_ts *)ncp)->
  822                                             nc_dotdottime;
  823                                         n3->nc_flag |= NCF_DTS;
  824                                 }
  825                         }
  826                         CACHE_WUNLOCK();
  827                         cache_free(ncp);
  828                         return;
  829                 }
  830         }
  831 
  832         if (flag == NCF_ISDOTDOT) {
  833                 /*
  834                  * See if we are trying to add .. entry, but some other lookup
  835                  * has populated v_cache_dd pointer already.
  836                  */
  837                 if (dvp->v_cache_dd != NULL) {
  838                     CACHE_WUNLOCK();
  839                     cache_free(ncp);
  840                     return;
  841                 }
  842                 KASSERT(vp == NULL || vp->v_type == VDIR,
  843                     ("wrong vnode type %p", vp));
  844                 dvp->v_cache_dd = ncp;
  845         }
  846 
  847         numcache++;
  848         if (!vp) {
  849                 numneg++;
  850                 if (cnp->cn_flags & ISWHITEOUT)
  851                         ncp->nc_flag |= NCF_WHITE;
  852         } else if (vp->v_type == VDIR) {
  853                 if (flag != NCF_ISDOTDOT) {
  854                         /*
  855                          * For this case, the cache entry maps both the
  856                          * directory name in it and the name ".." for the
  857                          * directory's parent.
  858                          */
  859                         if ((n2 = vp->v_cache_dd) != NULL &&
  860                             (n2->nc_flag & NCF_ISDOTDOT) != 0)
  861                                 cache_zap(n2);
  862                         vp->v_cache_dd = ncp;
  863                 }
  864         } else {
  865                 vp->v_cache_dd = NULL;
  866         }
  867 
  868         /*
  869          * Insert the new namecache entry into the appropriate chain
  870          * within the cache entries table.
  871          */
  872         LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
  873         if (flag != NCF_ISDOTDOT) {
  874                 if (LIST_EMPTY(&dvp->v_cache_src)) {
  875                         hold = 1;
  876                         numcachehv++;
  877                 }
  878                 LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src);
  879         }
  880 
  881         /*
  882          * If the entry is "negative", we place it into the
  883          * "negative" cache queue, otherwise, we place it into the
  884          * destination vnode's cache entries queue.
  885          */
  886         if (vp) {
  887                 TAILQ_INSERT_HEAD(&vp->v_cache_dst, ncp, nc_dst);
  888                 SDT_PROBE(vfs, namecache, enter, done, dvp, nc_get_name(ncp),
  889                     vp, 0, 0);
  890         } else {
  891                 TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst);
  892                 SDT_PROBE(vfs, namecache, enter_negative, done, dvp,
  893                     nc_get_name(ncp), 0, 0, 0);
  894         }
  895         if (numneg * ncnegfactor > numcache) {
  896                 ncp = TAILQ_FIRST(&ncneg);
  897                 zap = 1;
  898         }
  899         if (hold)
  900                 vhold(dvp);
  901         if (zap)
  902                 cache_zap(ncp);
  903         CACHE_WUNLOCK();
  904 }
  905 
  906 /*
  907  * Name cache initialization, from vfs_init() when we are booting
  908  */
  909 static void
  910 nchinit(void *dummy __unused)
  911 {
  912 
  913         TAILQ_INIT(&ncneg);
  914 
  915         cache_zone_small = uma_zcreate("S VFS Cache",
  916             sizeof(struct namecache) + CACHE_PATH_CUTOFF + 1,
  917             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
  918         cache_zone_small_ts = uma_zcreate("STS VFS Cache",
  919             sizeof(struct namecache_ts) + CACHE_PATH_CUTOFF + 1,
  920             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
  921         cache_zone_large = uma_zcreate("L VFS Cache",
  922             sizeof(struct namecache) + NAME_MAX + 1,
  923             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
  924         cache_zone_large_ts = uma_zcreate("LTS VFS Cache",
  925             sizeof(struct namecache_ts) + NAME_MAX + 1,
  926             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
  927 
  928         nchashtbl = hashinit(desiredvnodes * 2, M_VFSCACHE, &nchash);
  929 }
  930 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nchinit, NULL);
  931 
  932 
  933 /*
  934  * Invalidate all entries to a particular vnode.
  935  */
  936 void
  937 cache_purge(vp)
  938         struct vnode *vp;
  939 {
  940 
  941         CTR1(KTR_VFS, "cache_purge(%p)", vp);
  942         SDT_PROBE(vfs, namecache, purge, done, vp, 0, 0, 0, 0);
  943         CACHE_WLOCK();
  944         while (!LIST_EMPTY(&vp->v_cache_src))
  945                 cache_zap(LIST_FIRST(&vp->v_cache_src));
  946         while (!TAILQ_EMPTY(&vp->v_cache_dst))
  947                 cache_zap(TAILQ_FIRST(&vp->v_cache_dst));
  948         if (vp->v_cache_dd != NULL) {
  949                 KASSERT(vp->v_cache_dd->nc_flag & NCF_ISDOTDOT,
  950                    ("lost dotdot link"));
  951                 cache_zap(vp->v_cache_dd);
  952         }
  953         KASSERT(vp->v_cache_dd == NULL, ("incomplete purge"));
  954         CACHE_WUNLOCK();
  955 }
  956 
  957 /*
  958  * Invalidate all negative entries for a particular directory vnode.
  959  */
  960 void
  961 cache_purge_negative(vp)
  962         struct vnode *vp;
  963 {
  964         struct namecache *cp, *ncp;
  965 
  966         CTR1(KTR_VFS, "cache_purge_negative(%p)", vp);
  967         SDT_PROBE(vfs, namecache, purge_negative, done, vp, 0, 0, 0, 0);
  968         CACHE_WLOCK();
  969         LIST_FOREACH_SAFE(cp, &vp->v_cache_src, nc_src, ncp) {
  970                 if (cp->nc_vp == NULL)
  971                         cache_zap(cp);
  972         }
  973         CACHE_WUNLOCK();
  974 }
  975 
  976 /*
  977  * Flush all entries referencing a particular filesystem.
  978  */
  979 void
  980 cache_purgevfs(mp)
  981         struct mount *mp;
  982 {
  983         struct nchashhead *ncpp;
  984         struct namecache *ncp, *nnp;
  985 
  986         /* Scan hash tables for applicable entries */
  987         SDT_PROBE(vfs, namecache, purgevfs, done, mp, 0, 0, 0, 0);
  988         CACHE_WLOCK();
  989         for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) {
  990                 LIST_FOREACH_SAFE(ncp, ncpp, nc_hash, nnp) {
  991                         if (ncp->nc_dvp->v_mount == mp)
  992                                 cache_zap(ncp);
  993                 }
  994         }
  995         CACHE_WUNLOCK();
  996 }
  997 
  998 /*
  999  * Perform canonical checks and cache lookup and pass on to filesystem
 1000  * through the vop_cachedlookup only if needed.
 1001  */
 1002 
 1003 int
 1004 vfs_cache_lookup(ap)
 1005         struct vop_lookup_args /* {
 1006                 struct vnode *a_dvp;
 1007                 struct vnode **a_vpp;
 1008                 struct componentname *a_cnp;
 1009         } */ *ap;
 1010 {
 1011         struct vnode *dvp;
 1012         int error;
 1013         struct vnode **vpp = ap->a_vpp;
 1014         struct componentname *cnp = ap->a_cnp;
 1015         struct ucred *cred = cnp->cn_cred;
 1016         int flags = cnp->cn_flags;
 1017         struct thread *td = cnp->cn_thread;
 1018 
 1019         *vpp = NULL;
 1020         dvp = ap->a_dvp;
 1021 
 1022         if (dvp->v_type != VDIR)
 1023                 return (ENOTDIR);
 1024 
 1025         if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
 1026             (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
 1027                 return (EROFS);
 1028 
 1029         error = VOP_ACCESS(dvp, VEXEC, cred, td);
 1030         if (error)
 1031                 return (error);
 1032 
 1033         error = cache_lookup(dvp, vpp, cnp, NULL, NULL);
 1034         if (error == 0)
 1035                 return (VOP_CACHEDLOOKUP(dvp, vpp, cnp));
 1036         if (error == -1)
 1037                 return (0);
 1038         return (error);
 1039 }
 1040 
 1041 
 1042 #ifndef _SYS_SYSPROTO_H_
 1043 struct  __getcwd_args {
 1044         u_char  *buf;
 1045         u_int   buflen;
 1046 };
 1047 #endif
 1048 
 1049 /*
 1050  * XXX All of these sysctls would probably be more productive dead.
 1051  */
 1052 static int disablecwd;
 1053 SYSCTL_INT(_debug, OID_AUTO, disablecwd, CTLFLAG_RW, &disablecwd, 0,
 1054    "Disable the getcwd syscall");
 1055 
 1056 /* Implementation of the getcwd syscall. */
 1057 int
 1058 sys___getcwd(td, uap)
 1059         struct thread *td;
 1060         struct __getcwd_args *uap;
 1061 {
 1062 
 1063         return (kern___getcwd(td, uap->buf, UIO_USERSPACE, uap->buflen));
 1064 }
 1065 
 1066 int
 1067 kern___getcwd(struct thread *td, u_char *buf, enum uio_seg bufseg, u_int buflen)
 1068 {
 1069         char *bp, *tmpbuf;
 1070         struct filedesc *fdp;
 1071         struct vnode *cdir, *rdir;
 1072         int error;
 1073 
 1074         if (disablecwd)
 1075                 return (ENODEV);
 1076         if (buflen < 2)
 1077                 return (EINVAL);
 1078         if (buflen > MAXPATHLEN)
 1079                 buflen = MAXPATHLEN;
 1080 
 1081         tmpbuf = malloc(buflen, M_TEMP, M_WAITOK);
 1082         fdp = td->td_proc->p_fd;
 1083         FILEDESC_SLOCK(fdp);
 1084         cdir = fdp->fd_cdir;
 1085         VREF(cdir);
 1086         rdir = fdp->fd_rdir;
 1087         VREF(rdir);
 1088         FILEDESC_SUNLOCK(fdp);
 1089         error = vn_fullpath1(td, cdir, rdir, tmpbuf, &bp, buflen);
 1090         vrele(rdir);
 1091         vrele(cdir);
 1092 
 1093         if (!error) {
 1094                 if (bufseg == UIO_SYSSPACE)
 1095                         bcopy(bp, buf, strlen(bp) + 1);
 1096                 else
 1097                         error = copyout(bp, buf, strlen(bp) + 1);
 1098 #ifdef KTRACE
 1099         if (KTRPOINT(curthread, KTR_NAMEI))
 1100                 ktrnamei(bp);
 1101 #endif
 1102         }
 1103         free(tmpbuf, M_TEMP);
 1104         return (error);
 1105 }
 1106 
 1107 /*
 1108  * Thus begins the fullpath magic.
 1109  */
 1110 
 1111 #undef STATNODE
 1112 #define STATNODE(name, descr)                                           \
 1113         static u_int name;                                              \
 1114         SYSCTL_UINT(_vfs_cache, OID_AUTO, name, CTLFLAG_RD, &name, 0, descr)
 1115 
 1116 static int disablefullpath;
 1117 SYSCTL_INT(_debug, OID_AUTO, disablefullpath, CTLFLAG_RW, &disablefullpath, 0,
 1118     "Disable the vn_fullpath function");
 1119 
 1120 /* These count for kern___getcwd(), too. */
 1121 STATNODE(numfullpathcalls, "Number of fullpath search calls");
 1122 STATNODE(numfullpathfail1, "Number of fullpath search errors (ENOTDIR)");
 1123 STATNODE(numfullpathfail2,
 1124     "Number of fullpath search errors (VOP_VPTOCNP failures)");
 1125 STATNODE(numfullpathfail4, "Number of fullpath search errors (ENOMEM)");
 1126 STATNODE(numfullpathfound, "Number of successful fullpath calls");
 1127 
 1128 /*
 1129  * Retrieve the full filesystem path that correspond to a vnode from the name
 1130  * cache (if available)
 1131  */
 1132 int
 1133 vn_fullpath(struct thread *td, struct vnode *vn, char **retbuf, char **freebuf)
 1134 {
 1135         char *buf;
 1136         struct filedesc *fdp;
 1137         struct vnode *rdir;
 1138         int error;
 1139 
 1140         if (disablefullpath)
 1141                 return (ENODEV);
 1142         if (vn == NULL)
 1143                 return (EINVAL);
 1144 
 1145         buf = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
 1146         fdp = td->td_proc->p_fd;
 1147         FILEDESC_SLOCK(fdp);
 1148         rdir = fdp->fd_rdir;
 1149         VREF(rdir);
 1150         FILEDESC_SUNLOCK(fdp);
 1151         error = vn_fullpath1(td, vn, rdir, buf, retbuf, MAXPATHLEN);
 1152         vrele(rdir);
 1153 
 1154         if (!error)
 1155                 *freebuf = buf;
 1156         else
 1157                 free(buf, M_TEMP);
 1158         return (error);
 1159 }
 1160 
 1161 /*
 1162  * This function is similar to vn_fullpath, but it attempts to lookup the
 1163  * pathname relative to the global root mount point.  This is required for the
 1164  * auditing sub-system, as audited pathnames must be absolute, relative to the
 1165  * global root mount point.
 1166  */
 1167 int
 1168 vn_fullpath_global(struct thread *td, struct vnode *vn,
 1169     char **retbuf, char **freebuf)
 1170 {
 1171         char *buf;
 1172         int error;
 1173 
 1174         if (disablefullpath)
 1175                 return (ENODEV);
 1176         if (vn == NULL)
 1177                 return (EINVAL);
 1178         buf = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
 1179         error = vn_fullpath1(td, vn, rootvnode, buf, retbuf, MAXPATHLEN);
 1180         if (!error)
 1181                 *freebuf = buf;
 1182         else
 1183                 free(buf, M_TEMP);
 1184         return (error);
 1185 }
 1186 
 1187 int
 1188 vn_vptocnp(struct vnode **vp, struct ucred *cred, char *buf, u_int *buflen)
 1189 {
 1190         int error;
 1191 
 1192         CACHE_RLOCK();
 1193         error = vn_vptocnp_locked(vp, cred, buf, buflen);
 1194         if (error == 0)
 1195                 CACHE_RUNLOCK();
 1196         return (error);
 1197 }
 1198 
 1199 static int
 1200 vn_vptocnp_locked(struct vnode **vp, struct ucred *cred, char *buf,
 1201     u_int *buflen)
 1202 {
 1203         struct vnode *dvp;
 1204         struct namecache *ncp;
 1205         int error;
 1206 
 1207         TAILQ_FOREACH(ncp, &((*vp)->v_cache_dst), nc_dst) {
 1208                 if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
 1209                         break;
 1210         }
 1211         if (ncp != NULL) {
 1212                 if (*buflen < ncp->nc_nlen) {
 1213                         CACHE_RUNLOCK();
 1214                         vrele(*vp);
 1215                         numfullpathfail4++;
 1216                         error = ENOMEM;
 1217                         SDT_PROBE(vfs, namecache, fullpath, return, error,
 1218                             vp, NULL, 0, 0);
 1219                         return (error);
 1220                 }
 1221                 *buflen -= ncp->nc_nlen;
 1222                 memcpy(buf + *buflen, nc_get_name(ncp), ncp->nc_nlen);
 1223                 SDT_PROBE(vfs, namecache, fullpath, hit, ncp->nc_dvp,
 1224                     nc_get_name(ncp), vp, 0, 0);
 1225                 dvp = *vp;
 1226                 *vp = ncp->nc_dvp;
 1227                 vref(*vp);
 1228                 CACHE_RUNLOCK();
 1229                 vrele(dvp);
 1230                 CACHE_RLOCK();
 1231                 return (0);
 1232         }
 1233         SDT_PROBE(vfs, namecache, fullpath, miss, vp, 0, 0, 0, 0);
 1234 
 1235         CACHE_RUNLOCK();
 1236         vn_lock(*vp, LK_SHARED | LK_RETRY);
 1237         error = VOP_VPTOCNP(*vp, &dvp, cred, buf, buflen);
 1238         vput(*vp);
 1239         if (error) {
 1240                 numfullpathfail2++;
 1241                 SDT_PROBE(vfs, namecache, fullpath, return,  error, vp,
 1242                     NULL, 0, 0);
 1243                 return (error);
 1244         }
 1245 
 1246         *vp = dvp;
 1247         CACHE_RLOCK();
 1248         if (dvp->v_iflag & VI_DOOMED) {
 1249                 /* forced unmount */
 1250                 CACHE_RUNLOCK();
 1251                 vrele(dvp);
 1252                 error = ENOENT;
 1253                 SDT_PROBE(vfs, namecache, fullpath, return, error, vp,
 1254                     NULL, 0, 0);
 1255                 return (error);
 1256         }
 1257         /*
 1258          * *vp has its use count incremented still.
 1259          */
 1260 
 1261         return (0);
 1262 }
 1263 
 1264 /*
 1265  * The magic behind kern___getcwd() and vn_fullpath().
 1266  */
 1267 static int
 1268 vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
 1269     char *buf, char **retbuf, u_int buflen)
 1270 {
 1271         int error, slash_prefixed;
 1272 #ifdef KDTRACE_HOOKS
 1273         struct vnode *startvp = vp;
 1274 #endif
 1275         struct vnode *vp1;
 1276 
 1277         buflen--;
 1278         buf[buflen] = '\0';
 1279         error = 0;
 1280         slash_prefixed = 0;
 1281 
 1282         SDT_PROBE(vfs, namecache, fullpath, entry, vp, 0, 0, 0, 0);
 1283         numfullpathcalls++;
 1284         vref(vp);
 1285         CACHE_RLOCK();
 1286         if (vp->v_type != VDIR) {
 1287                 error = vn_vptocnp_locked(&vp, td->td_ucred, buf, &buflen);
 1288                 if (error)
 1289                         return (error);
 1290                 if (buflen == 0) {
 1291                         CACHE_RUNLOCK();
 1292                         vrele(vp);
 1293                         return (ENOMEM);
 1294                 }
 1295                 buf[--buflen] = '/';
 1296                 slash_prefixed = 1;
 1297         }
 1298         while (vp != rdir && vp != rootvnode) {
 1299                 if (vp->v_vflag & VV_ROOT) {
 1300                         if (vp->v_iflag & VI_DOOMED) {  /* forced unmount */
 1301                                 CACHE_RUNLOCK();
 1302                                 vrele(vp);
 1303                                 error = ENOENT;
 1304                                 SDT_PROBE(vfs, namecache, fullpath, return,
 1305                                     error, vp, NULL, 0, 0);
 1306                                 break;
 1307                         }
 1308                         vp1 = vp->v_mount->mnt_vnodecovered;
 1309                         vref(vp1);
 1310                         CACHE_RUNLOCK();
 1311                         vrele(vp);
 1312                         vp = vp1;
 1313                         CACHE_RLOCK();
 1314                         continue;
 1315                 }
 1316                 if (vp->v_type != VDIR) {
 1317                         CACHE_RUNLOCK();
 1318                         vrele(vp);
 1319                         numfullpathfail1++;
 1320                         error = ENOTDIR;
 1321                         SDT_PROBE(vfs, namecache, fullpath, return,
 1322                             error, vp, NULL, 0, 0);
 1323                         break;
 1324                 }
 1325                 error = vn_vptocnp_locked(&vp, td->td_ucred, buf, &buflen);
 1326                 if (error)
 1327                         break;
 1328                 if (buflen == 0) {
 1329                         CACHE_RUNLOCK();
 1330                         vrele(vp);
 1331                         error = ENOMEM;
 1332                         SDT_PROBE(vfs, namecache, fullpath, return, error,
 1333                             startvp, NULL, 0, 0);
 1334                         break;
 1335                 }
 1336                 buf[--buflen] = '/';
 1337                 slash_prefixed = 1;
 1338         }
 1339         if (error)
 1340                 return (error);
 1341         if (!slash_prefixed) {
 1342                 if (buflen == 0) {
 1343                         CACHE_RUNLOCK();
 1344                         vrele(vp);
 1345                         numfullpathfail4++;
 1346                         SDT_PROBE(vfs, namecache, fullpath, return, ENOMEM,
 1347                             startvp, NULL, 0, 0);
 1348                         return (ENOMEM);
 1349                 }
 1350                 buf[--buflen] = '/';
 1351         }
 1352         numfullpathfound++;
 1353         CACHE_RUNLOCK();
 1354         vrele(vp);
 1355 
 1356         SDT_PROBE(vfs, namecache, fullpath, return, 0, startvp, buf + buflen,
 1357             0, 0);
 1358         *retbuf = buf + buflen;
 1359         return (0);
 1360 }
 1361 
 1362 struct vnode *
 1363 vn_dir_dd_ino(struct vnode *vp)
 1364 {
 1365         struct namecache *ncp;
 1366         struct vnode *ddvp;
 1367 
 1368         ASSERT_VOP_LOCKED(vp, "vn_dir_dd_ino");
 1369         CACHE_RLOCK();
 1370         TAILQ_FOREACH(ncp, &(vp->v_cache_dst), nc_dst) {
 1371                 if ((ncp->nc_flag & NCF_ISDOTDOT) != 0)
 1372                         continue;
 1373                 ddvp = ncp->nc_dvp;
 1374                 VI_LOCK(ddvp);
 1375                 CACHE_RUNLOCK();
 1376                 if (vget(ddvp, LK_INTERLOCK | LK_SHARED | LK_NOWAIT, curthread))
 1377                         return (NULL);
 1378                 return (ddvp);
 1379         }
 1380         CACHE_RUNLOCK();
 1381         return (NULL);
 1382 }
 1383 
 1384 int
 1385 vn_commname(struct vnode *vp, char *buf, u_int buflen)
 1386 {
 1387         struct namecache *ncp;
 1388         int l;
 1389 
 1390         CACHE_RLOCK();
 1391         TAILQ_FOREACH(ncp, &vp->v_cache_dst, nc_dst)
 1392                 if ((ncp->nc_flag & NCF_ISDOTDOT) == 0)
 1393                         break;
 1394         if (ncp == NULL) {
 1395                 CACHE_RUNLOCK();
 1396                 return (ENOENT);
 1397         }
 1398         l = min(ncp->nc_nlen, buflen - 1);
 1399         memcpy(buf, nc_get_name(ncp), l);
 1400         CACHE_RUNLOCK();
 1401         buf[l] = '\0';
 1402         return (0);
 1403 }
 1404 
 1405 /* ABI compat shims for old kernel modules. */
 1406 #undef cache_enter
 1407 
 1408 void    cache_enter(struct vnode *dvp, struct vnode *vp,
 1409             struct componentname *cnp);
 1410 
 1411 void
 1412 cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
 1413 {
 1414 
 1415         cache_enter_time(dvp, vp, cnp, NULL, NULL);
 1416 }
 1417 
 1418 /*
 1419  * This function updates path string to vnode's full global path
 1420  * and checks the size of the new path string against the pathlen argument.
 1421  *
 1422  * Requires a locked, referenced vnode and GIANT lock held.
 1423  * Vnode is re-locked on success or ENODEV, otherwise unlocked.
 1424  *
 1425  * If sysctl debug.disablefullpath is set, ENODEV is returned,
 1426  * vnode is left locked and path remain untouched.
 1427  *
 1428  * If vp is a directory, the call to vn_fullpath_global() always succeeds
 1429  * because it falls back to the ".." lookup if the namecache lookup fails.
 1430  */
 1431 int
 1432 vn_path_to_global_path(struct thread *td, struct vnode *vp, char *path,
 1433     u_int pathlen)
 1434 {
 1435         struct nameidata nd;
 1436         struct vnode *vp1;
 1437         char *rpath, *fbuf;
 1438         int error;
 1439 
 1440         ASSERT_VOP_ELOCKED(vp, __func__);
 1441 
 1442         /* Return ENODEV if sysctl debug.disablefullpath==1 */
 1443         if (disablefullpath)
 1444                 return (ENODEV);
 1445 
 1446         /* Construct global filesystem path from vp. */
 1447         VOP_UNLOCK(vp, 0);
 1448         error = vn_fullpath_global(td, vp, &rpath, &fbuf);
 1449 
 1450         if (error != 0) {
 1451                 vrele(vp);
 1452                 return (error);
 1453         }
 1454 
 1455         if (strlen(rpath) >= pathlen) {
 1456                 vrele(vp);
 1457                 error = ENAMETOOLONG;
 1458                 goto out;
 1459         }
 1460 
 1461         /*
 1462          * Re-lookup the vnode by path to detect a possible rename.
 1463          * As a side effect, the vnode is relocked.
 1464          * If vnode was renamed, return ENOENT.
 1465          */
 1466         NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | AUDITVNODE1,
 1467             UIO_SYSSPACE, path, td);
 1468         error = namei(&nd);
 1469         if (error != 0) {
 1470                 vrele(vp);
 1471                 goto out;
 1472         }
 1473         NDFREE(&nd, NDF_ONLY_PNBUF);
 1474         vp1 = nd.ni_vp;
 1475         vrele(vp);
 1476         if (vp1 == vp)
 1477                 strcpy(path, rpath);
 1478         else {
 1479                 vput(vp1);
 1480                 error = ENOENT;
 1481         }
 1482 
 1483 out:
 1484         free(fbuf, M_TEMP);
 1485         return (error);
 1486 }

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