/* $OpenBSD: vfs_cache.c,v 1.10 2003/02/25 09:48:33 tedu Exp $ */ /* $NetBSD: vfs_cache.c,v 1.13 1996/02/04 02:18:09 christos 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 8.3 (Berkeley) 8/22/94 */ #include <sys/param.h> #include <sys/systm.h> #include <sys/time.h> #include <sys/mount.h> #include <sys/vnode.h> #include <sys/namei.h> #include <sys/errno.h> #include <sys/malloc.h> #include <sys/pool.h> #include <sys/hash.h> /* * 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 */ struct pool nch_pool; u_long nextvnodeid; /* * 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 0 is returned. If the locking fails for whatever * reason, the vnode is unlocked and the error is returned to caller. * 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 -1 * is returned. */ int cache_lookup(dvp, vpp, cnp) struct vnode *dvp; struct vnode **vpp; struct componentname *cnp; { struct namecache *ncp; struct nchashhead *ncpp; struct vnode *vp; struct proc *p = curproc; u_long vpid; int error; *vpp = NULL; if (!doingcache) { cnp->cn_flags &= ~MAKEENTRY; return (-1); } if (cnp->cn_namelen > NCHNAMLEN) { nchstats.ncs_long++; cnp->cn_flags &= ~MAKEENTRY; return (-1); } ncpp = &nchashtbl[ hash32_buf(&dvp->v_id, sizeof(dvp->v_id), cnp->cn_hash) & nchash]; LIST_FOREACH(ncp, ncpp, nc_hash) { if (ncp->nc_dvp == dvp && ncp->nc_dvpid == dvp->v_id && ncp->nc_nlen == cnp->cn_namelen && !memcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen)) break; } if (ncp == 0) { nchstats.ncs_miss++; return (-1); } if ((cnp->cn_flags & MAKEENTRY) == 0) { nchstats.ncs_badhits++; goto remove; } else if (ncp->nc_vp == NULL) { /* * Restore the ISWHITEOUT flag saved earlier. */ cnp->cn_flags |= ncp->nc_vpid; if (cnp->cn_nameiop != CREATE || (cnp->cn_flags & ISLASTCN) == 0) { nchstats.ncs_neghits++; /* * Move this slot to end of LRU chain, * if not already there. */ if (TAILQ_NEXT(ncp, nc_lru) != NULL) { TAILQ_REMOVE(&nclruhead, ncp, nc_lru); TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); } return (ENOENT); } else { nchstats.ncs_badhits++; goto remove; } } else if (ncp->nc_vpid != ncp->nc_vp->v_id) { nchstats.ncs_falsehits++; goto remove; } vp = ncp->nc_vp; vpid = vp->v_id; if (vp == dvp) { /* lookup on "." */ VREF(dvp); error = 0; } else if (cnp->cn_flags & ISDOTDOT) { VOP_UNLOCK(dvp, 0, p); cnp->cn_flags |= PDIRUNLOCK; error = vget(vp, LK_EXCLUSIVE, p); /* * If the above vget() succeeded and both LOCKPARENT and * ISLASTCN is set, lock the directory vnode as well. */ if (!error && (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) == 0) { if ((error = vn_lock(dvp, LK_EXCLUSIVE, p)) != 0) { vput(vp); return (error); } cnp->cn_flags &= ~PDIRUNLOCK; } } else { error = vget(vp, LK_EXCLUSIVE, p); /* * If the above vget() failed or either of LOCKPARENT or * ISLASTCN is set, unlock the directory vnode. */ if (error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { VOP_UNLOCK(dvp, 0, p); cnp->cn_flags |= PDIRUNLOCK; } } /* * Check that the lock succeeded, and that the capability number did * not change while we were waiting for the lock. */ if (error || vpid != vp->v_id) { if (!error) { vput(vp); nchstats.ncs_falsehits++; } else nchstats.ncs_badhits++; /* * The parent needs to be locked when we return to VOP_LOOKUP(). * The `.' case here should be extremely rare (if it can happen * at all), so we don't bother optimizing out the unlock/relock. */ if (vp == dvp || error || (~cnp->cn_flags & (LOCKPARENT|ISLASTCN)) != 0) { if ((error = vn_lock(dvp, LK_EXCLUSIVE, p)) != 0) return (error); cnp->cn_flags &= ~PDIRUNLOCK; } return (-1); } nchstats.ncs_goodhits++; /* * Move this slot to end of LRU chain, if not already there. */ if (TAILQ_NEXT(ncp, nc_lru) != NULL) { TAILQ_REMOVE(&nclruhead, ncp, nc_lru); TAILQ_INSERT_TAIL(&nclruhead, ncp, nc_lru); } *vpp = vp; return (0); remove: /* * 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 = NULL; #if 0 if (ncp->nc_vhash.le_prev != NULL) { LIST_REMOVE(ncp, nc_vhash); ncp->nc_vhash.le_prev = NULL; } #endif TAILQ_INSERT_HEAD(&nclruhead, ncp, nc_lru); return (-1); } /* * Add an entry to the cache */ void 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 = pool_get(&nch_pool, PR_WAITOK); bzero((char *)ncp, sizeof *ncp); numcache++; } else if ((ncp = nclruhead.tqh_first) != 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; } } else return; /* grab the vnode we just found */ ncp->nc_vp = vp; if (vp) ncp->nc_vpid = vp->v_id; else { /* * For negative hits, save the ISWHITEOUT flag so we can * restore it later when the cache entry is used again. */ ncp->nc_vpid = cnp->cn_flags & ISWHITEOUT; } /* 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[ hash32_buf(&dvp->v_id, sizeof(dvp->v_id), cnp->cn_hash) & nchash]; LIST_INSERT_HEAD(ncpp, ncp, nc_hash); } /* * Name cache initialization, from vfs_init() when we are booting */ void nchinit() { TAILQ_INIT(&nclruhead); nchashtbl = hashinit(desiredvnodes, M_CACHE, M_WAITOK, &nchash); pool_init(&nch_pool, sizeof(struct namecache), 0, 0, 0, "nchpl", &pool_allocator_nointr); } /* * Cache flush, a particular vnode; called when a vnode is renamed to * hide entries that would now be invalid */ void 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? */ void 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); } }