The Design and Implementation of the FreeBSD Operating System, Second Edition
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sys/kern/vfs_cache.c

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    1 /*      $NetBSD: vfs_cache.c,v 1.61 2004/06/27 08:50:44 yamt Exp $      */
    2 
    3 /*
    4  * Copyright (c) 1989, 1993
    5  *      The Regents of the University of California.  All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Neither the name of the University nor the names of its contributors
   16  *    may be used to endorse or promote products derived from this software
   17  *    without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  *
   31  *      @(#)vfs_cache.c 8.3 (Berkeley) 8/22/94
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __KERNEL_RCSID(0, "$NetBSD: vfs_cache.c,v 1.61 2004/06/27 08:50:44 yamt Exp $");
   36 
   37 #include "opt_ddb.h"
   38 #include "opt_revcache.h"
   39 
   40 #include <sys/param.h>
   41 #include <sys/systm.h>
   42 #include <sys/time.h>
   43 #include <sys/mount.h>
   44 #include <sys/vnode.h>
   45 #include <sys/namei.h>
   46 #include <sys/errno.h>
   47 #include <sys/malloc.h>
   48 #include <sys/pool.h>
   49 #include <sys/lock.h>
   50 
   51 /*
   52  * Name caching works as follows:
   53  *
   54  * Names found by directory scans are retained in a cache
   55  * for future reference.  It is managed LRU, so frequently
   56  * used names will hang around.  Cache is indexed by hash value
   57  * obtained from (dvp, name) where dvp refers to the directory
   58  * containing name.
   59  *
   60  * For simplicity (and economy of storage), names longer than
   61  * a maximum length of NCHNAMLEN are not cached; they occur
   62  * infrequently in any case, and are almost never of interest.
   63  *
   64  * Upon reaching the last segment of a path, if the reference
   65  * is for DELETE, or NOCACHE is set (rewrite), and the
   66  * name is located in the cache, it will be dropped.
   67  * The entry is dropped also when it was not possible to lock
   68  * the cached vnode, either because vget() failed or the generation
   69  * number has changed while waiting for the lock.
   70  */
   71 
   72 /*
   73  * Structures associated with name cacheing.
   74  */
   75 LIST_HEAD(nchashhead, namecache) *nchashtbl;
   76 u_long  nchash;                         /* size of hash table - 1 */
   77 long    numcache;                       /* number of cache entries allocated */
   78 #define NCHASH(cnp, dvp)        \
   79         (((cnp)->cn_hash ^ ((uintptr_t)(dvp) >> 3)) & nchash)
   80 
   81 LIST_HEAD(ncvhashhead, namecache) *ncvhashtbl;
   82 u_long  ncvhash;                        /* size of hash table - 1 */
   83 #define NCVHASH(vp)             (((uintptr_t)(vp) >> 3) & ncvhash)
   84 
   85 TAILQ_HEAD(, namecache) nclruhead;              /* LRU chain */
   86 struct  nchstats nchstats;              /* cache effectiveness statistics */
   87 
   88 POOL_INIT(namecache_pool, sizeof(struct namecache), 0, 0, 0, "ncachepl",
   89     &pool_allocator_nointr);
   90 
   91 MALLOC_DEFINE(M_CACHE, "namecache", "Dynamically allocated cache entries");
   92 
   93 int doingcache = 1;                     /* 1 => enable the cache */
   94 
   95 /* A single lock to protect cache insertion, removal and lookup */
   96 static struct simplelock namecache_slock = SIMPLELOCK_INITIALIZER;
   97 
   98 static void cache_remove(struct namecache *);
   99 static void cache_free(struct namecache *);
  100 static __inline struct namecache *cache_lookup_entry(
  101     const struct vnode *, const struct componentname *);
  102 
  103 static void
  104 cache_remove(struct namecache *ncp)
  105 {
  106 
  107         LOCK_ASSERT(simple_lock_held(&namecache_slock));
  108 
  109         ncp->nc_dvp = NULL;
  110         ncp->nc_vp = NULL;
  111 
  112         TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
  113         if (ncp->nc_hash.le_prev != NULL) {
  114                 LIST_REMOVE(ncp, nc_hash);
  115                 ncp->nc_hash.le_prev = NULL;
  116         }
  117         if (ncp->nc_vhash.le_prev != NULL) {
  118                 LIST_REMOVE(ncp, nc_vhash);
  119                 ncp->nc_vhash.le_prev = NULL;
  120         }
  121         if (ncp->nc_vlist.le_prev != NULL) {
  122                 LIST_REMOVE(ncp, nc_vlist);
  123                 ncp->nc_vlist.le_prev = NULL;
  124         }
  125         if (ncp->nc_dvlist.le_prev != NULL) {
  126                 LIST_REMOVE(ncp, nc_dvlist);
  127                 ncp->nc_dvlist.le_prev = NULL;
  128         }
  129 }
  130 
  131 static void
  132 cache_free(struct namecache *ncp)
  133 {
  134 
  135         pool_put(&namecache_pool, ncp);
  136         numcache--;
  137 }
  138 
  139 static __inline struct namecache *
  140 cache_lookup_entry(const struct vnode *dvp, const struct componentname *cnp)
  141 {
  142         struct nchashhead *ncpp;
  143         struct namecache *ncp;
  144 
  145         LOCK_ASSERT(simple_lock_held(&namecache_slock));
  146 
  147         ncpp = &nchashtbl[NCHASH(cnp, dvp)];
  148 
  149         LIST_FOREACH(ncp, ncpp, nc_hash) {
  150                 if (ncp->nc_dvp == dvp &&
  151                     ncp->nc_nlen == cnp->cn_namelen &&
  152                     !memcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen))
  153                         break;
  154         }
  155 
  156         return ncp;
  157 }
  158 
  159 /*
  160  * Look for a the name in the cache. We don't do this
  161  * if the segment name is long, simply so the cache can avoid
  162  * holding long names (which would either waste space, or
  163  * add greatly to the complexity).
  164  *
  165  * Lookup is called with ni_dvp pointing to the directory to search,
  166  * ni_ptr pointing to the name of the entry being sought, ni_namelen
  167  * tells the length of the name, and ni_hash contains a hash of
  168  * the name. If the lookup succeeds, the vnode is locked, stored in ni_vp
  169  * and a status of zero is returned. If the locking fails for whatever
  170  * reason, the vnode is unlocked and the error is returned to caller.
  171  * If the lookup determines that the name does not exist (negative cacheing),
  172  * a status of ENOENT is returned. If the lookup fails, a status of -1
  173  * is returned.
  174  */
  175 int
  176 cache_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp)
  177 {
  178         struct namecache *ncp;
  179         struct vnode *vp;
  180         int error;
  181 
  182         if (!doingcache) {
  183                 cnp->cn_flags &= ~MAKEENTRY;
  184                 *vpp = NULL;
  185                 return (-1);
  186         }
  187 
  188         if (cnp->cn_namelen > NCHNAMLEN) {
  189                 /* XXXSMP - updating stats without lock; do we care? */
  190                 nchstats.ncs_long++;
  191                 cnp->cn_flags &= ~MAKEENTRY;
  192                 goto fail;
  193         }
  194         simple_lock(&namecache_slock);
  195         ncp = cache_lookup_entry(dvp, cnp);
  196         if (ncp == NULL) {
  197                 nchstats.ncs_miss++;
  198                 goto fail_wlock;
  199         }
  200         if ((cnp->cn_flags & MAKEENTRY) == 0) {
  201                 nchstats.ncs_badhits++;
  202                 goto remove;
  203         } else if (ncp->nc_vp == NULL) {
  204                 /*
  205                  * Restore the ISWHITEOUT flag saved earlier.
  206                  */
  207                 cnp->cn_flags |= ncp->nc_flags;
  208                 if (cnp->cn_nameiop != CREATE ||
  209                     (cnp->cn_flags & ISLASTCN) == 0) {
  210                         nchstats.ncs_neghits++;
  211                         /*
  212                          * Move this slot to end of LRU chain,
  213                          * if not already there.
  214                          */
  215                         if (TAILQ_NEXT(ncp, nc_lru) != 0) {
  216                                 TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
  217                                 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru);
  218                         }
  219                         simple_unlock(&namecache_slock);
  220                         return (ENOENT);
  221                 } else {
  222                         nchstats.ncs_badhits++;
  223                         goto remove;
  224                 }
  225         }
  226 
  227         vp = ncp->nc_vp;
  228 
  229         /*
  230          * Move this slot to end of LRU chain, if not already there.
  231          */
  232         if (TAILQ_NEXT(ncp, nc_lru) != 0) {
  233                 TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
  234                 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru);
  235         }
  236 
  237         error = vget(vp, LK_NOWAIT);
  238 
  239         /* Release the name cache mutex while we get reference to the vnode */
  240         simple_unlock(&namecache_slock);
  241 
  242 #ifdef DEBUG
  243         /*
  244          * since we released namecache_slock,
  245          * we can't use this pointer any more.
  246          */
  247         ncp = NULL;
  248 #endif /* DEBUG */
  249 
  250         if (error) {
  251                 KASSERT(error == EBUSY);
  252                 /*
  253                  * this vnode is being cleaned out.
  254                  */
  255                 nchstats.ncs_falsehits++; /* XXX badhits? */
  256                 goto fail;
  257         }
  258 
  259         if (vp == dvp) {        /* lookup on "." */
  260                 error = 0;
  261         } else if (cnp->cn_flags & ISDOTDOT) {
  262                 VOP_UNLOCK(dvp, 0);
  263                 cnp->cn_flags |= PDIRUNLOCK;
  264                 error = vn_lock(vp, LK_EXCLUSIVE);
  265                 /*
  266                  * If the above vn_lock() succeeded and both LOCKPARENT and
  267                  * ISLASTCN is set, lock the directory vnode as well.
  268                  */
  269                 if (!error && (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) == 0) {
  270                         if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0) {
  271                                 vput(vp);
  272                                 return (error);
  273                         }
  274                         cnp->cn_flags &= ~PDIRUNLOCK;
  275                 }
  276         } else {
  277                 error = vn_lock(vp, LK_EXCLUSIVE);
  278                 /*
  279                  * If the above vn_lock() failed or either of LOCKPARENT or
  280                  * ISLASTCN is set, unlock the directory vnode.
  281                  */
  282                 if (error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) {
  283                         VOP_UNLOCK(dvp, 0);
  284                         cnp->cn_flags |= PDIRUNLOCK;
  285                 }
  286         }
  287 
  288         /*
  289          * Check that the lock succeeded.
  290          */
  291         if (error) {
  292                 /* XXXSMP - updating stats without lock; do we care? */
  293                 nchstats.ncs_badhits++;
  294 
  295                 /*
  296                  * The parent needs to be locked when we return to VOP_LOOKUP().
  297                  * The `.' case here should be extremely rare (if it can happen
  298                  * at all), so we don't bother optimizing out the unlock/relock.
  299                  */
  300                 if (vp == dvp ||
  301                     error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) {
  302                         if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0)
  303                                 return (error);
  304                         cnp->cn_flags &= ~PDIRUNLOCK;
  305                 }
  306                 *vpp = NULL;
  307                 return (-1);
  308         }
  309 
  310         /* XXXSMP - updating stats without lock; do we care? */
  311         nchstats.ncs_goodhits++;
  312         *vpp = vp;
  313         return (0);
  314 
  315 remove:
  316         /*
  317          * Last component and we are renaming or deleting,
  318          * the cache entry is invalid, or otherwise don't
  319          * want cache entry to exist.
  320          */
  321         cache_remove(ncp);
  322         cache_free(ncp);
  323 
  324 fail_wlock:
  325         simple_unlock(&namecache_slock);
  326 fail:
  327         *vpp = NULL;
  328         return (-1);
  329 }
  330 
  331 int
  332 cache_lookup_raw(struct vnode *dvp, struct vnode **vpp,
  333     struct componentname *cnp)
  334 {
  335         struct namecache *ncp;
  336         struct vnode *vp;
  337         int error;
  338 
  339         if (!doingcache) {
  340                 cnp->cn_flags &= ~MAKEENTRY;
  341                 *vpp = NULL;
  342                 return (-1);
  343         }
  344 
  345         if (cnp->cn_namelen > NCHNAMLEN) {
  346                 /* XXXSMP - updating stats without lock; do we care? */
  347                 nchstats.ncs_long++;
  348                 cnp->cn_flags &= ~MAKEENTRY;
  349                 goto fail;
  350         }
  351         simple_lock(&namecache_slock);
  352         ncp = cache_lookup_entry(dvp, cnp);
  353         if (ncp == NULL) {
  354                 nchstats.ncs_miss++;
  355                 goto fail_wlock;
  356         }
  357         /*
  358          * Move this slot to end of LRU chain,
  359          * if not already there.
  360          */
  361         if (TAILQ_NEXT(ncp, nc_lru) != 0) {
  362                 TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
  363                 TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru);
  364         }
  365 
  366         vp = ncp->nc_vp;
  367         if (vp == NULL) {
  368                 /*
  369                  * Restore the ISWHITEOUT flag saved earlier.
  370                  */
  371                 cnp->cn_flags |= ncp->nc_flags;
  372                 nchstats.ncs_neghits++;
  373                 simple_unlock(&namecache_slock);
  374                 return (ENOENT);
  375         }
  376 
  377         error = vget(vp, LK_NOWAIT);
  378 
  379         /* Release the name cache mutex while we get reference to the vnode */
  380         simple_unlock(&namecache_slock);
  381 
  382         if (error) {
  383                 KASSERT(error == EBUSY);
  384                 /*
  385                  * this vnode is being cleaned out.
  386                  */
  387                 nchstats.ncs_falsehits++; /* XXX badhits? */
  388                 goto fail;
  389         }
  390 
  391         *vpp = vp;
  392 
  393         return 0;
  394 
  395 fail_wlock:
  396         simple_unlock(&namecache_slock);
  397 fail:
  398         *vpp = NULL;
  399         return -1;
  400 }
  401 
  402 /*
  403  * Scan cache looking for name of directory entry pointing at vp.
  404  *
  405  * Fill in dvpp.
  406  *
  407  * If bufp is non-NULL, also place the name in the buffer which starts
  408  * at bufp, immediately before *bpp, and move bpp backwards to point
  409  * at the start of it.  (Yes, this is a little baroque, but it's done
  410  * this way to cater to the whims of getcwd).
  411  *
  412  * Returns 0 on success, -1 on cache miss, positive errno on failure.
  413  */
  414 int
  415 cache_revlookup(struct vnode *vp, struct vnode **dvpp, char **bpp, char *bufp)
  416 {
  417         struct namecache *ncp;
  418         struct vnode *dvp;
  419         struct ncvhashhead *nvcpp;
  420         char *bp;
  421 
  422         if (!doingcache)
  423                 goto out;
  424 
  425         nvcpp = &ncvhashtbl[NCVHASH(vp)];
  426 
  427         simple_lock(&namecache_slock);
  428         LIST_FOREACH(ncp, nvcpp, nc_vhash) {
  429                 if (ncp->nc_vp == vp &&
  430                     (dvp = ncp->nc_dvp) != NULL &&
  431                     dvp != vp) {                /* avoid pesky . entries.. */
  432 
  433 #ifdef DIAGNOSTIC
  434                         if (ncp->nc_nlen == 1 &&
  435                             ncp->nc_name[0] == '.')
  436                                 panic("cache_revlookup: found entry for .");
  437 
  438                         if (ncp->nc_nlen == 2 &&
  439                             ncp->nc_name[0] == '.' &&
  440                             ncp->nc_name[1] == '.')
  441                                 panic("cache_revlookup: found entry for ..");
  442 #endif
  443                         nchstats.ncs_revhits++;
  444 
  445                         if (bufp) {
  446                                 bp = *bpp;
  447                                 bp -= ncp->nc_nlen;
  448                                 if (bp <= bufp) {
  449                                         *dvpp = NULL;
  450                                         simple_unlock(&namecache_slock);
  451                                         return (ERANGE);
  452                                 }
  453                                 memcpy(bp, ncp->nc_name, ncp->nc_nlen);
  454                                 *bpp = bp;
  455                         }
  456 
  457                         /* XXX MP: how do we know dvp won't evaporate? */
  458                         *dvpp = dvp;
  459                         simple_unlock(&namecache_slock);
  460                         return (0);
  461                 }
  462         }
  463         nchstats.ncs_revmiss++;
  464         simple_unlock(&namecache_slock);
  465  out:
  466         *dvpp = NULL;
  467         return (-1);
  468 }
  469 
  470 /*
  471  * Add an entry to the cache
  472  */
  473 void
  474 cache_enter(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
  475 {
  476         struct namecache *ncp;
  477         struct namecache *oncp;
  478         struct nchashhead *ncpp;
  479         struct ncvhashhead *nvcpp;
  480 
  481 #ifdef DIAGNOSTIC
  482         if (cnp->cn_namelen > NCHNAMLEN)
  483                 panic("cache_enter: name too long");
  484 #endif
  485         if (!doingcache)
  486                 return;
  487         /*
  488          * Free the cache slot at head of lru chain.
  489          */
  490         simple_lock(&namecache_slock);
  491 
  492         if (numcache < numvnodes) {
  493                 numcache++;
  494                 simple_unlock(&namecache_slock);
  495                 ncp = pool_get(&namecache_pool, PR_WAITOK);
  496                 memset(ncp, 0, sizeof(*ncp));
  497                 simple_lock(&namecache_slock);
  498         } else if ((ncp = TAILQ_FIRST(&nclruhead)) != NULL) {
  499                 cache_remove(ncp);
  500         } else {
  501                 simple_unlock(&namecache_slock);
  502                 return;
  503         }
  504 
  505         /*
  506          * Concurrent lookups in the same directory may race for a
  507          * cache entry.  if there's a duplicated entry, free it.
  508          */
  509         oncp = cache_lookup_entry(dvp, cnp);
  510         if (oncp) {
  511                 cache_remove(oncp);
  512                 cache_free(oncp);
  513         }
  514         KASSERT(cache_lookup_entry(dvp, cnp) == NULL);
  515 
  516         /* Grab the vnode we just found. */
  517         ncp->nc_vp = vp;
  518         if (vp == NULL) {
  519                 /*
  520                  * For negative hits, save the ISWHITEOUT flag so we can
  521                  * restore it later when the cache entry is used again.
  522                  */
  523                 ncp->nc_flags = cnp->cn_flags & ISWHITEOUT;
  524         }
  525         /* Fill in cache info. */
  526         ncp->nc_dvp = dvp;
  527         LIST_INSERT_HEAD(&dvp->v_dnclist, ncp, nc_dvlist);
  528         if (vp)
  529                 LIST_INSERT_HEAD(&vp->v_nclist, ncp, nc_vlist);
  530         ncp->nc_nlen = cnp->cn_namelen;
  531         memcpy(ncp->nc_name, cnp->cn_nameptr, (unsigned)ncp->nc_nlen);
  532         TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru);
  533         ncpp = &nchashtbl[NCHASH(cnp, dvp)];
  534         LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
  535 
  536         ncp->nc_vhash.le_prev = NULL;
  537         ncp->nc_vhash.le_next = NULL;
  538 
  539         /*
  540          * Create reverse-cache entries (used in getcwd) for directories.
  541          */
  542         if (vp != NULL &&
  543             vp != dvp &&
  544 #ifndef NAMECACHE_ENTER_REVERSE
  545             vp->v_type == VDIR &&
  546 #endif
  547             (ncp->nc_nlen > 2 ||
  548             (ncp->nc_nlen > 1 && ncp->nc_name[1] != '.') ||
  549             (/* ncp->nc_nlen > 0 && */ ncp->nc_name[0] != '.'))) {
  550                 nvcpp = &ncvhashtbl[NCVHASH(vp)];
  551                 LIST_INSERT_HEAD(nvcpp, ncp, nc_vhash);
  552         }
  553         simple_unlock(&namecache_slock);
  554 }
  555 
  556 /*
  557  * Name cache initialization, from vfs_init() when we are booting
  558  */
  559 void
  560 nchinit(void)
  561 {
  562 
  563         TAILQ_INIT(&nclruhead);
  564         nchashtbl =
  565             hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &nchash);
  566         ncvhashtbl =
  567 #ifdef NAMECACHE_ENTER_REVERSE
  568             hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash);
  569 #else
  570             hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &ncvhash);
  571 #endif
  572 }
  573 
  574 /*
  575  * Name cache reinitialization, for when the maximum number of vnodes increases.
  576  */
  577 void
  578 nchreinit(void)
  579 {
  580         struct namecache *ncp;
  581         struct nchashhead *oldhash1, *hash1;
  582         struct ncvhashhead *oldhash2, *hash2;
  583         u_long i, oldmask1, oldmask2, mask1, mask2;
  584 
  585         hash1 = hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask1);
  586         hash2 =
  587 #ifdef NAMECACHE_ENTER_REVERSE
  588             hashinit(desiredvnodes, HASH_LIST, M_CACHE, M_WAITOK, &mask2);
  589 #else
  590             hashinit(desiredvnodes/8, HASH_LIST, M_CACHE, M_WAITOK, &mask2);
  591 #endif
  592         simple_lock(&namecache_slock);
  593         oldhash1 = nchashtbl;
  594         oldmask1 = nchash;
  595         nchashtbl = hash1;
  596         nchash = mask1;
  597         oldhash2 = ncvhashtbl;
  598         oldmask2 = ncvhash;
  599         ncvhashtbl = hash2;
  600         ncvhash = mask2;
  601         for (i = 0; i <= oldmask1; i++) {
  602                 while ((ncp = LIST_FIRST(&oldhash1[i])) != NULL) {
  603                         LIST_REMOVE(ncp, nc_hash);
  604                         ncp->nc_hash.le_prev = NULL;
  605                 }
  606         }
  607         for (i = 0; i <= oldmask2; i++) {
  608                 while ((ncp = LIST_FIRST(&oldhash2[i])) != NULL) {
  609                         LIST_REMOVE(ncp, nc_vhash);
  610                         ncp->nc_vhash.le_prev = NULL;
  611                 }
  612         }
  613         simple_unlock(&namecache_slock);
  614         hashdone(oldhash1, M_CACHE);
  615         hashdone(oldhash2, M_CACHE);
  616 }
  617 
  618 /*
  619  * Cache flush, a particular vnode; called when a vnode is renamed to
  620  * hide entries that would now be invalid
  621  */
  622 void
  623 cache_purge1(struct vnode *vp, const struct componentname *cnp, int flags)
  624 {
  625         struct namecache *ncp, *ncnext;
  626 
  627         simple_lock(&namecache_slock);
  628         if (flags & PURGE_PARENTS) {
  629                 for (ncp = LIST_FIRST(&vp->v_nclist); ncp != NULL;
  630                     ncp = ncnext) {
  631                         ncnext = LIST_NEXT(ncp, nc_vlist);
  632                         cache_remove(ncp);
  633                         cache_free(ncp);
  634                 }
  635         }
  636         if (flags & PURGE_CHILDREN) {
  637                 for (ncp = LIST_FIRST(&vp->v_dnclist); ncp != NULL;
  638                     ncp = ncnext) {
  639                         ncnext = LIST_NEXT(ncp, nc_dvlist);
  640                         cache_remove(ncp);
  641                         cache_free(ncp);
  642                 }
  643         }
  644         if (cnp != NULL) {
  645                 ncp = cache_lookup_entry(vp, cnp);
  646                 if (ncp) {
  647                         cache_remove(ncp);
  648                         cache_free(ncp);
  649                 }
  650         }
  651         simple_unlock(&namecache_slock);
  652 }
  653 
  654 /*
  655  * Cache flush, a whole filesystem; called when filesys is umounted to
  656  * remove entries that would now be invalid.
  657  */
  658 void
  659 cache_purgevfs(struct mount *mp)
  660 {
  661         struct namecache *ncp, *nxtcp;
  662 
  663         simple_lock(&namecache_slock);
  664         for (ncp = TAILQ_FIRST(&nclruhead); ncp != NULL; ncp = nxtcp) {
  665                 nxtcp = TAILQ_NEXT(ncp, nc_lru);
  666                 if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) {
  667                         continue;
  668                 }
  669                 /* Free the resources we had. */
  670                 cache_remove(ncp);
  671                 cache_free(ncp);
  672         }
  673         simple_unlock(&namecache_slock);
  674 }
  675 
  676 #ifdef DDB
  677 void
  678 namecache_print(struct vnode *vp, void (*pr)(const char *, ...))
  679 {
  680         struct vnode *dvp = NULL;
  681         struct namecache *ncp;
  682 
  683         TAILQ_FOREACH(ncp, &nclruhead, nc_lru) {
  684                 if (ncp->nc_vp == vp) {
  685                         (*pr)("name %.*s\n", ncp->nc_nlen, ncp->nc_name);
  686                         dvp = ncp->nc_dvp;
  687                 }
  688         }
  689         if (dvp == NULL) {
  690                 (*pr)("name not found\n");
  691                 return;
  692         }
  693         vp = dvp;
  694         TAILQ_FOREACH(ncp, &nclruhead, nc_lru) {
  695                 if (ncp->nc_vp == vp) {
  696                         (*pr)("parent %.*s\n", ncp->nc_nlen, ncp->nc_name);
  697                 }
  698         }
  699 }
  700 #endif

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