/* $NetBSD: vfs_cache.c,v 1.9 1994/08/30 03:06:11 mycroft Exp $ */ /* * Copyright (c) 1989, 1993 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)vfs_cache.c 8.1 (Berkeley) 6/10/93 */ #include #include #include #include #include #include #include #include /* * Name caching works as follows: * * Names found by directory scans are retained in a cache * for future reference. It is managed LRU, so frequently * used names will hang around. Cache is indexed by hash value * obtained from (vp, name) where vp refers to the directory * containing name. * * For simplicity (and economy of storage), names longer than * a maximum length of NCHNAMLEN are not cached; they occur * infrequently in any case, and are almost never of interest. * * Upon reaching the last segment of a path, if the reference * is for DELETE, or NOCACHE is set (rewrite), and the * name is located in the cache, it will be dropped. */ /* * Structures associated with name cacheing. */ LIST_HEAD(nchashhead, namecache) *nchashtbl; u_long nchash; /* size of hash table - 1 */ long numcache; /* number of cache entries allocated */ TAILQ_HEAD(, namecache) nclruhead; /* LRU chain */ struct nchstats nchstats; /* cache effectiveness statistics */ int doingcache = 1; /* 1 => enable the cache */ /* * Look for a the name in the cache. We don't do this * if the segment name is long, simply so the cache can avoid * holding long names (which would either waste space, or * add greatly to the complexity). * * Lookup is called with ni_dvp pointing to the directory to search, * ni_ptr pointing to the name of the entry being sought, ni_namelen * tells the length of the name, and ni_hash contains a hash of * the name. If the lookup succeeds, the vnode is returned in ni_vp * and a status of -1 is returned. If the lookup determines that * the name does not exist (negative cacheing), a status of ENOENT * is returned. If the lookup fails, a status of zero is returned. */ int cache_lookup(dvp, vpp, cnp) struct vnode *dvp; struct vnode **vpp; struct componentname *cnp; { register struct namecache *ncp; register struct nchashhead *ncpp; if (!doingcache) { cnp->cn_flags &= ~MAKEENTRY; return (0); } if (cnp->cn_namelen > NCHNAMLEN) { nchstats.ncs_long++; cnp->cn_flags &= ~MAKEENTRY; return (0); } ncpp = &nchashtbl[cnp->cn_hash & nchash]; for (ncp = ncpp->lh_first; ncp != 0; ncp = ncp->nc_hash.le_next) { if (ncp->nc_dvp == dvp && ncp->nc_dvpid == dvp->v_id && ncp->nc_nlen == cnp->cn_namelen && !bcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen)) break; } if (ncp == 0) { nchstats.ncs_miss++; return (0); } if ((cnp->cn_flags & MAKEENTRY) == 0) { nchstats.ncs_badhits++; } else if (ncp->nc_vp == NULL) { if (cnp->cn_nameiop != CREATE) { nchstats.ncs_neghits++; /* * Move this slot to end of LRU chain, * if not already there. */ if (ncp->nc_lru.tqe_next != 0) { TAILQ_REMOVE(&nclruhead, ncp, nc_lru); TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); } return (ENOENT); } } else if (ncp->nc_vpid != ncp->nc_vp->v_id) { nchstats.ncs_falsehits++; } else { nchstats.ncs_goodhits++; /* * move this slot to end of LRU chain, if not already there */ if (ncp->nc_lru.tqe_next != 0) { TAILQ_REMOVE(&nclruhead, ncp, nc_lru); TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); } *vpp = ncp->nc_vp; return (-1); } /* * Last component and we are renaming or deleting, * the cache entry is invalid, or otherwise don't * want cache entry to exist. */ TAILQ_REMOVE(&nclruhead, ncp, nc_lru); LIST_REMOVE(ncp, nc_hash); ncp->nc_hash.le_prev = 0; TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru); return (0); } /* * Add an entry to the cache */ cache_enter(dvp, vp, cnp) struct vnode *dvp; struct vnode *vp; struct componentname *cnp; { register struct namecache *ncp; register struct nchashhead *ncpp; #ifdef DIAGNOSTIC if (cnp->cn_namelen > NCHNAMLEN) panic("cache_enter: name too long"); #endif if (!doingcache) return; /* * Free the cache slot at head of lru chain. */ if (numcache < desiredvnodes) { ncp = (struct namecache *) malloc((u_long)sizeof *ncp, M_CACHE, M_WAITOK); bzero((char *)ncp, sizeof *ncp); numcache++; } else if (ncp = nclruhead.tqh_first) { TAILQ_REMOVE(&nclruhead, ncp, nc_lru); if (ncp->nc_hash.le_prev != 0) { LIST_REMOVE(ncp, nc_hash); ncp->nc_hash.le_prev = 0; } } else return; /* grab the vnode we just found */ ncp->nc_vp = vp; if (vp) ncp->nc_vpid = vp->v_id; else ncp->nc_vpid = 0; /* fill in cache info */ ncp->nc_dvp = dvp; ncp->nc_dvpid = dvp->v_id; ncp->nc_nlen = cnp->cn_namelen; bcopy(cnp->cn_nameptr, ncp->nc_name, (unsigned)ncp->nc_nlen); TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); ncpp = &nchashtbl[cnp->cn_hash & nchash]; LIST_INSERT_HEAD(ncpp, ncp, nc_hash); } /* * Name cache initialization, from vfs_init() when we are booting */ nchinit() { TAILQ_INIT(&nclruhead); nchashtbl = hashinit(desiredvnodes, M_CACHE, &nchash); } /* * Cache flush, a particular vnode; called when a vnode is renamed to * hide entries that would now be invalid */ cache_purge(vp) struct vnode *vp; { struct namecache *ncp; struct nchashhead *ncpp; vp->v_id = ++nextvnodeid; if (nextvnodeid != 0) return; for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) { for (ncp = ncpp->lh_first; ncp != 0; ncp = ncp->nc_hash.le_next) { ncp->nc_vpid = 0; ncp->nc_dvpid = 0; } } vp->v_id = ++nextvnodeid; } /* * Cache flush, a whole filesystem; called when filesys is umounted to * remove entries that would now be invalid * * The line "nxtcp = nchhead" near the end is to avoid potential problems * if the cache lru chain is modified while we are dumping the * inode. This makes the algorithm O(n^2), but do you think I care? */ cache_purgevfs(mp) struct mount *mp; { register struct namecache *ncp, *nxtcp; for (ncp = nclruhead.tqh_first; ncp != 0; ncp = nxtcp) { if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) { nxtcp = ncp->nc_lru.tqe_next; continue; } /* free the resources we had */ ncp->nc_vp = NULL; ncp->nc_dvp = NULL; TAILQ_REMOVE(&nclruhead, ncp, nc_lru); if (ncp->nc_hash.le_prev != 0) { LIST_REMOVE(ncp, nc_hash); ncp->nc_hash.le_prev = 0; } /* cause rescan of list, it may have altered */ nxtcp = nclruhead.tqh_first; TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru); } }