325 lines
9.4 KiB
C
325 lines
9.4 KiB
C
/*
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* Copyright (c) 1989 The Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: @(#)vfs_cache.c 7.8 (Berkeley) 2/28/91
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* $Id: vfs_cache.c,v 1.3 1993/09/07 15:41:10 ws Exp $
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*/
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#include "param.h"
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#include "systm.h"
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#include "time.h"
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#include "mount.h"
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#include "vnode.h"
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#include "namei.h"
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#include "errno.h"
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#include "malloc.h"
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/*
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* Name caching works as follows:
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*
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* Names found by directory scans are retained in a cache
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* for future reference. It is managed LRU, so frequently
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* used names will hang around. Cache is indexed by hash value
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* obtained from (vp, name) where vp refers to the directory
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* containing name.
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*
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* For simplicity (and economy of storage), names longer than
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* a maximum length of NCHNAMLEN are not cached; they occur
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* infrequently in any case, and are almost never of interest.
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*
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* Upon reaching the last segment of a path, if the reference
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* is for DELETE, or NOCACHE is set (rewrite), and the
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* name is located in the cache, it will be dropped.
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*/
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/*
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* Structures associated with name cacheing.
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*/
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union nchash {
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union nchash *nch_head[2];
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struct namecache *nch_chain[2];
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} *nchashtbl;
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#define nch_forw nch_chain[0]
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#define nch_back nch_chain[1]
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u_long nchash; /* size of hash table - 1 */
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long numcache; /* number of cache entries allocated */
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struct namecache *nchhead, **nchtail; /* LRU chain pointers */
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struct nchstats nchstats; /* cache effectiveness statistics */
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int doingcache = 1; /* 1 => enable the cache */
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/*
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* Look for a the name in the cache. We don't do this
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* if the segment name is long, simply so the cache can avoid
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* holding long names (which would either waste space, or
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* add greatly to the complexity).
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*
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* Lookup is called with ni_dvp pointing to the directory to search,
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* ni_ptr pointing to the name of the entry being sought, ni_namelen
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* tells the length of the name, and ni_hash contains a hash of
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* the name and directory vnode. If the lookup succeeds, the vnode is
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* returned in ni_vp and a status of -1 is returned. If the lookup
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* determines that the name does not exist (negative cacheing),
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* a status of ENOENT is returned.
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* If the lookup fails, a status of zero is returned.
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*/
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cache_lookup(ndp)
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register struct nameidata *ndp;
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{
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register struct vnode *dvp;
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register struct namecache *ncp;
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union nchash *nhp;
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if (!doingcache)
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return (0);
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if (ndp->ni_namelen > NCHNAMLEN) {
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nchstats.ncs_long++;
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ndp->ni_makeentry = 0;
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return (0);
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}
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dvp = ndp->ni_dvp;
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nhp = &nchashtbl[ndp->ni_hash & nchash];
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for (ncp = nhp->nch_forw; ncp != (struct namecache *)nhp;
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ncp = ncp->nc_forw) {
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if (ncp->nc_dvp == dvp &&
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ncp->nc_dvpid == dvp->v_id &&
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ncp->nc_nlen == ndp->ni_namelen &&
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!bcmp(ncp->nc_name, ndp->ni_ptr, (unsigned)ncp->nc_nlen))
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break;
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}
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if (ncp == (struct namecache *)nhp) {
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nchstats.ncs_miss++;
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return (0);
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}
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if (!ndp->ni_makeentry) {
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nchstats.ncs_badhits++;
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} else if (ncp->nc_vp == NULL) {
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if ((ndp->ni_nameiop & OPMASK) != CREATE) {
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nchstats.ncs_neghits++;
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/*
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* Move this slot to end of LRU chain,
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* if not already there.
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*/
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if (ncp->nc_nxt) {
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/* remove from LRU chain */
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*ncp->nc_prev = ncp->nc_nxt;
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ncp->nc_nxt->nc_prev = ncp->nc_prev;
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/* and replace at end of it */
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ncp->nc_nxt = NULL;
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ncp->nc_prev = nchtail;
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*nchtail = ncp;
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nchtail = &ncp->nc_nxt;
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}
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return (ENOENT);
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}
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} else if (ncp->nc_vpid != ncp->nc_vp->v_id) {
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nchstats.ncs_falsehits++;
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} else {
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nchstats.ncs_goodhits++;
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/*
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* move this slot to end of LRU chain, if not already there
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*/
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if (ncp->nc_nxt) {
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/* remove from LRU chain */
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*ncp->nc_prev = ncp->nc_nxt;
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ncp->nc_nxt->nc_prev = ncp->nc_prev;
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/* and replace at end of it */
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ncp->nc_nxt = NULL;
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ncp->nc_prev = nchtail;
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*nchtail = ncp;
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nchtail = &ncp->nc_nxt;
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}
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ndp->ni_vp = ncp->nc_vp;
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return (-1);
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}
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/*
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* Last component and we are renaming or deleting,
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* the cache entry is invalid, or otherwise don't
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* want cache entry to exist.
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*/
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/* remove from LRU chain */
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*ncp->nc_prev = ncp->nc_nxt;
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if (ncp->nc_nxt)
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ncp->nc_nxt->nc_prev = ncp->nc_prev;
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else
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nchtail = ncp->nc_prev;
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/* remove from hash chain */
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remque(ncp);
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/* insert at head of LRU list (first to grab) */
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ncp->nc_nxt = nchhead;
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ncp->nc_prev = &nchhead;
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nchhead->nc_prev = &ncp->nc_nxt;
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nchhead = ncp;
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/* and make a dummy hash chain */
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ncp->nc_forw = ncp;
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ncp->nc_back = ncp;
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return (0);
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}
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/*
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* Add an entry to the cache
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*/
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cache_enter(ndp)
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register struct nameidata *ndp;
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{
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register struct namecache *ncp;
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union nchash *nhp;
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if (!doingcache)
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return;
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/*
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* Free the cache slot at head of lru chain.
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*/
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if (numcache < desiredvnodes) {
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ncp = (struct namecache *)
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malloc((u_long)sizeof *ncp, M_CACHE, M_WAITOK);
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bzero((char *)ncp, sizeof *ncp);
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numcache++;
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} else if (ncp = nchhead) {
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/* remove from lru chain */
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*ncp->nc_prev = ncp->nc_nxt;
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if (ncp->nc_nxt)
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ncp->nc_nxt->nc_prev = ncp->nc_prev;
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else
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nchtail = ncp->nc_prev;
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/* remove from old hash chain */
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remque(ncp);
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} else
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return;
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/* grab the vnode we just found */
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ncp->nc_vp = ndp->ni_vp;
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if (ndp->ni_vp)
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ncp->nc_vpid = ndp->ni_vp->v_id;
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else
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ncp->nc_vpid = 0;
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/* fill in cache info */
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ncp->nc_dvp = ndp->ni_dvp;
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ncp->nc_dvpid = ndp->ni_dvp->v_id;
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ncp->nc_nlen = ndp->ni_namelen;
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bcopy(ndp->ni_ptr, ncp->nc_name, (unsigned)ncp->nc_nlen);
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/* link at end of lru chain */
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ncp->nc_nxt = NULL;
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ncp->nc_prev = nchtail;
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*nchtail = ncp;
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nchtail = &ncp->nc_nxt;
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/* and insert on hash chain */
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nhp = &nchashtbl[ndp->ni_hash & nchash];
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insque(ncp, nhp);
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}
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/*
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* Name cache initialization, from vfs_init() when we are booting
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*/
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nchinit()
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{
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register union nchash *nchp;
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long nchashsize;
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nchhead = 0;
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nchtail = &nchhead;
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nchashsize = roundup((desiredvnodes + 1) * sizeof *nchp / 2,
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NBPG * CLSIZE);
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nchashtbl = (union nchash *)malloc((u_long)nchashsize,
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M_CACHE, M_WAITOK);
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for (nchash = 1; nchash <= nchashsize / sizeof *nchp; nchash <<= 1)
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/* void */;
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nchash = (nchash >> 1) - 1;
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for (nchp = &nchashtbl[nchash]; nchp >= nchashtbl; nchp--) {
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nchp->nch_head[0] = nchp;
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nchp->nch_head[1] = nchp;
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}
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}
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/*
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* Cache flush, a particular vnode; called when a vnode is renamed to
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* hide entries that would now be invalid
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*/
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cache_purge(vp)
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struct vnode *vp;
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{
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union nchash *nhp;
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struct namecache *ncp;
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vp->v_id = ++nextvnodeid;
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if (nextvnodeid != 0)
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return;
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for (nhp = &nchashtbl[nchash]; nhp >= nchashtbl; nhp--) {
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for (ncp = nhp->nch_forw; ncp != (struct namecache *)nhp;
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ncp = ncp->nc_forw) {
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ncp->nc_vpid = 0;
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ncp->nc_dvpid = 0;
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}
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}
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vp->v_id = ++nextvnodeid;
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}
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/*
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* Cache flush, a whole filesystem; called when filesys is umounted to
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* remove entries that would now be invalid
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*
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* The line "nxtcp = nchhead" near the end is to avoid potential problems
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* if the cache lru chain is modified while we are dumping the
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* inode. This makes the algorithm O(n^2), but do you think I care?
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*/
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cache_purgevfs(mp)
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struct mount *mp;
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{
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register struct namecache *ncp, *nxtcp;
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for (ncp = nchhead; ncp; ncp = nxtcp) {
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nxtcp = ncp->nc_nxt;
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if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp)
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continue;
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/* free the resources we had */
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ncp->nc_vp = NULL;
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ncp->nc_dvp = NULL;
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remque(ncp); /* remove entry from its hash chain */
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ncp->nc_forw = ncp; /* and make a dummy one */
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ncp->nc_back = ncp;
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/* delete this entry from LRU chain */
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*ncp->nc_prev = nxtcp;
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if (nxtcp)
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nxtcp->nc_prev = ncp->nc_prev;
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else
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nchtail = ncp->nc_prev;
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/* cause rescan of list, it may have altered */
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nxtcp = nchhead;
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/* put the now-free entry at head of LRU */
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ncp->nc_nxt = nxtcp;
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ncp->nc_prev = &nchhead;
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nxtcp->nc_prev = &ncp->nc_nxt;
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nchhead = ncp;
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}
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}
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