470 lines
13 KiB
C
470 lines
13 KiB
C
/* $NetBSD: vfs_cache.c,v 1.25 2000/04/16 21:41:49 chs Exp $ */
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/*
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* Copyright (c) 1989, 1993
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* The Regents of the University of California. 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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* @(#)vfs_cache.c 8.3 (Berkeley) 8/22/94
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/time.h>
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#include <sys/mount.h>
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#include <sys/vnode.h>
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#include <sys/namei.h>
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#include <sys/errno.h>
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#include <sys/malloc.h>
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#include <sys/pool.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 (dvp, name) where dvp 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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* The entry is dropped also when it was not possible to lock
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* the cached vnode, either because vget() failed or the generation
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* number has changed while waiting for the lock.
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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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LIST_HEAD(nchashhead, namecache) *nchashtbl;
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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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LIST_HEAD(ncvhashhead, namecache) *ncvhashtbl;
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u_long ncvhash; /* size of hash table - 1 */
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TAILQ_HEAD(, namecache) nclruhead; /* LRU chain */
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struct nchstats nchstats; /* cache effectiveness statistics */
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struct pool namecache_pool;
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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. If the lookup succeeds, the vnode is locked, stored in ni_vp
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* and a status of zero is returned. If the locking fails for whatever
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* reason, the vnode is unlocked and the error is returned to caller.
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* If the lookup determines that the name does not exist (negative cacheing),
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* a status of ENOENT is returned. If the lookup fails, a status of -1
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* is returned.
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*/
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int
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cache_lookup(dvp, vpp, cnp)
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struct vnode *dvp;
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struct vnode **vpp;
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struct componentname *cnp;
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{
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struct namecache *ncp;
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struct nchashhead *ncpp;
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struct vnode *vp;
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int vpid, error;
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if (!doingcache) {
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cnp->cn_flags &= ~MAKEENTRY;
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*vpp = 0;
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return (-1);
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}
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if (cnp->cn_namelen > NCHNAMLEN) {
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nchstats.ncs_long++;
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cnp->cn_flags &= ~MAKEENTRY;
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*vpp = 0;
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return (-1);
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}
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ncpp = &nchashtbl[(cnp->cn_hash ^ dvp->v_id) & nchash];
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for (ncp = ncpp->lh_first; ncp != 0; ncp = ncp->nc_hash.le_next) {
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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 == cnp->cn_namelen &&
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!memcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen))
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break;
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}
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if (ncp == 0) {
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nchstats.ncs_miss++;
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*vpp = 0;
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return (-1);
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}
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if ((cnp->cn_flags & MAKEENTRY) == 0) {
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nchstats.ncs_badhits++;
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goto remove;
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} else if (ncp->nc_vp == NULL) {
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/*
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* Restore the ISWHITEOUT flag saved earlier.
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*/
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cnp->cn_flags |= ncp->nc_vpid;
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if (cnp->cn_nameiop != CREATE ||
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(cnp->cn_flags & ISLASTCN) == 0) {
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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_lru.tqe_next != 0) {
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TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
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TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru);
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}
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return (ENOENT);
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} else {
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nchstats.ncs_badhits++;
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goto remove;
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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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goto remove;
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}
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vp = ncp->nc_vp;
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vpid = vp->v_id;
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if (vp == dvp) { /* lookup on "." */
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VREF(dvp);
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error = 0;
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} else if (cnp->cn_flags & ISDOTDOT) {
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VOP_UNLOCK(dvp, 0);
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cnp->cn_flags |= PDIRUNLOCK;
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error = vget(vp, LK_EXCLUSIVE);
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/* if the above vget() succeeded and both LOCKPARENT and
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* ISLASTCN is set, lock the directory vnode as well */
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if (!error && (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) == 0) {
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if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0) {
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vput(vp);
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return (error);
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}
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cnp->cn_flags &= ~PDIRUNLOCK;
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}
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} else {
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error = vget(vp, LK_EXCLUSIVE);
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/* if the above vget() failed or either of LOCKPARENT or
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* ISLASTCN is set, unlock the directory vnode */
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if (error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) {
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VOP_UNLOCK(dvp, 0);
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cnp->cn_flags |= PDIRUNLOCK;
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}
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}
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/*
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* Check that the lock succeeded, and that the capability number did
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* not change while we were waiting for the lock.
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*/
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if (error || vpid != vp->v_id) {
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if (!error) {
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vput(vp);
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nchstats.ncs_falsehits++;
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} else
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nchstats.ncs_badhits++;
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/*
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* The parent needs to be locked when we return to VOP_LOOKUP().
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* The `.' case here should be extremely rare (if it can happen
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* at all), so we don't bother optimizing out the unlock/relock.
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*/
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if (vp == dvp ||
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error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) {
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if ((error = vn_lock(dvp, LK_EXCLUSIVE)) != 0)
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return (error);
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cnp->cn_flags &= ~PDIRUNLOCK;
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}
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goto remove;
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}
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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_lru.tqe_next != 0) {
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TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
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TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru);
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}
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*vpp = vp;
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return (0);
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remove:
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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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TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
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LIST_REMOVE(ncp, nc_hash);
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ncp->nc_hash.le_prev = 0;
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if (ncp->nc_vhash.le_prev != NULL) {
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LIST_REMOVE(ncp, nc_vhash);
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ncp->nc_vhash.le_prev = 0;
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}
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TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru);
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*vpp = 0;
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return (-1);
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}
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/*
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* Scan cache looking for name of directory entry pointing at vp.
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*
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* Fill in dvpp.
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*
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* If bufp is non-NULL, also place the name in the buffer which starts
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* at bufp, immediately before *bpp, and move bpp backwards to point
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* at the start of it. (Yes, this is a little baroque, but it's done
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* this way to cater to the whims of getcwd).
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*
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* Returns 0 on success, -1 on cache miss, positive errno on failure.
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*/
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int
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cache_revlookup (vp, dvpp, bpp, bufp)
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struct vnode *vp, **dvpp;
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char **bpp;
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char *bufp;
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{
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struct namecache *ncp;
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struct vnode *dvp;
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struct ncvhashhead *nvcpp;
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if (!doingcache)
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goto out;
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nvcpp = &ncvhashtbl[(vp->v_id & ncvhash)];
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for (ncp = nvcpp->lh_first; ncp != 0; ncp = ncp->nc_vhash.le_next) {
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if ((ncp->nc_vp == vp) &&
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(ncp->nc_vpid == vp->v_id) &&
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((dvp = ncp->nc_dvp) != 0) &&
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(dvp != vp) && /* avoid pesky . entries.. */
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(dvp->v_id == ncp->nc_dvpid))
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{
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char *bp;
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#ifdef DIAGNOSTIC
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if ((ncp->nc_nlen == 1) &&
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(ncp->nc_name[0] == '.'))
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panic("cache_revlookup: found entry for .");
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if ((ncp->nc_nlen == 2) &&
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(ncp->nc_name[0] == '.') &&
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(ncp->nc_name[1] == '.'))
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panic("cache_revlookup: found entry for ..");
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#endif
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nchstats.ncs_revhits++;
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if (bufp) {
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bp = *bpp;
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bp -= ncp->nc_nlen;
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if (bp <= bufp) {
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*dvpp = 0;
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return ERANGE;
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}
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memcpy(bp, ncp->nc_name, ncp->nc_nlen);
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*bpp = bp;
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}
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/* XXX MP: how do we know dvp won't evaporate? */
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*dvpp = dvp;
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return 0;
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}
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}
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nchstats.ncs_revmiss++;
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out:
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*dvpp = 0;
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return -1;
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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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void
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cache_enter(dvp, vp, cnp)
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struct vnode *dvp;
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struct vnode *vp;
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struct componentname *cnp;
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{
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struct namecache *ncp;
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struct nchashhead *ncpp;
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struct ncvhashhead *nvcpp;
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#ifdef DIAGNOSTIC
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if (cnp->cn_namelen > NCHNAMLEN)
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panic("cache_enter: name too long");
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#endif
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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 < numvnodes) {
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ncp = pool_get(&namecache_pool, PR_WAITOK);
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memset((char *)ncp, 0, sizeof(*ncp));
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numcache++;
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} else if ((ncp = nclruhead.tqh_first) != NULL) {
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TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
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if (ncp->nc_hash.le_prev != 0) {
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LIST_REMOVE(ncp, nc_hash);
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ncp->nc_hash.le_prev = 0;
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}
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if (ncp->nc_vhash.le_prev != 0) {
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LIST_REMOVE(ncp, nc_vhash);
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ncp->nc_vhash.le_prev = 0;
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}
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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 = vp;
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if (vp)
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ncp->nc_vpid = vp->v_id;
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else {
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/*
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* For negative hits, save the ISWHITEOUT flag so we can
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* restore it later when the cache entry is used again.
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*/
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ncp->nc_vpid = cnp->cn_flags & ISWHITEOUT;
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}
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/* fill in cache info */
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ncp->nc_dvp = dvp;
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ncp->nc_dvpid = dvp->v_id;
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ncp->nc_nlen = cnp->cn_namelen;
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memcpy(ncp->nc_name, cnp->cn_nameptr, (unsigned)ncp->nc_nlen);
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TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru);
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ncpp = &nchashtbl[(cnp->cn_hash ^ dvp->v_id) & nchash];
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LIST_INSERT_HEAD(ncpp, ncp, nc_hash);
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ncp->nc_vhash.le_prev = 0;
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ncp->nc_vhash.le_next = 0;
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/*
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* Create reverse-cache entries (used in getcwd) for directories.
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*/
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if (vp &&
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(vp != dvp) &&
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(vp->v_type == VDIR) &&
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((ncp->nc_nlen > 2) ||
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((ncp->nc_nlen == 2) && (ncp->nc_name[0] != '.') && (ncp->nc_name[1] != '.')) ||
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((ncp->nc_nlen == 1) && (ncp->nc_name[0] != '.'))))
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{
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nvcpp = &ncvhashtbl[(vp->v_id & ncvhash)];
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LIST_INSERT_HEAD(nvcpp, ncp, nc_vhash);
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}
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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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void
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nchinit()
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{
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TAILQ_INIT(&nclruhead);
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nchashtbl = hashinit(desiredvnodes, M_CACHE, M_WAITOK, &nchash);
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ncvhashtbl = hashinit(desiredvnodes/8, M_CACHE, M_WAITOK, &ncvhash);
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pool_init(&namecache_pool, sizeof(struct namecache), 0, 0, 0,
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"ncachepl", 0, pool_page_alloc_nointr, pool_page_free_nointr,
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M_CACHE);
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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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void
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cache_purge(vp)
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struct vnode *vp;
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{
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struct namecache *ncp;
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struct nchashhead *ncpp;
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static u_long nextvnodeid;
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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 (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) {
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for (ncp = ncpp->lh_first; ncp != 0; ncp = ncp->nc_hash.le_next) {
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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 = nclruhead.tqh_first" near the end is to avoid potential
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* problems if the cache lru chain is modified while we are dumping the inode.
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* This makes the algorithm O(n^2), but do you think I care?
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*/
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void
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cache_purgevfs(mp)
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struct mount *mp;
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{
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struct namecache *ncp, *nxtcp;
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for (ncp = nclruhead.tqh_first; ncp != 0; ncp = nxtcp) {
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if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) {
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nxtcp = ncp->nc_lru.tqe_next;
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continue;
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}
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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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TAILQ_REMOVE(&nclruhead, ncp, nc_lru);
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if (ncp->nc_hash.le_prev != 0) {
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LIST_REMOVE(ncp, nc_hash);
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ncp->nc_hash.le_prev = 0;
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}
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if (ncp->nc_vhash.le_prev != 0) {
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LIST_REMOVE(ncp, nc_vhash);
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ncp->nc_vhash.le_prev = 0;
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}
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/* cause rescan of list, it may have altered */
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nxtcp = nclruhead.tqh_first;
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TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru);
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}
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}
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