1 /* 2 * Copyright (c) 1989, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)vfs_cache.c 8.1 (Berkeley) 6/10/93 34 * $Id$ 35 */ 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/time.h> 40 #include <sys/mount.h> 41 #include <sys/vnode.h> 42 #include <sys/namei.h> 43 #include <sys/errno.h> 44 #include <sys/malloc.h> 45 46 /* 47 * Name caching works as follows: 48 * 49 * Names found by directory scans are retained in a cache 50 * for future reference. It is managed LRU, so frequently 51 * used names will hang around. Cache is indexed by hash value 52 * obtained from (vp, name) where vp refers to the directory 53 * containing name. 54 * 55 * For simplicity (and economy of storage), names longer than 56 * a maximum length of NCHNAMLEN are not cached; they occur 57 * infrequently in any case, and are almost never of interest. 58 * 59 * Upon reaching the last segment of a path, if the reference 60 * is for DELETE, or NOCACHE is set (rewrite), and the 61 * name is located in the cache, it will be dropped. 62 */ 63 64 /* 65 * Structures associated with name cacheing. 66 */ 67 struct namecache **nchashtbl; 68 u_long nchash; /* size of hash table - 1 */ 69 long numcache; /* number of cache entries allocated */ 70 struct namecache *nchhead, **nchtail; /* LRU chain pointers */ 71 struct nchstats nchstats; /* cache effectiveness statistics */ 72 73 int doingcache = 1; /* 1 => enable the cache */ 74 75 /* 76 * Look for a the name in the cache. We don't do this 77 * if the segment name is long, simply so the cache can avoid 78 * holding long names (which would either waste space, or 79 * add greatly to the complexity). 80 * 81 * Lookup is called with ni_dvp pointing to the directory to search, 82 * ni_ptr pointing to the name of the entry being sought, ni_namelen 83 * tells the length of the name, and ni_hash contains a hash of 84 * the name. If the lookup succeeds, the vnode is returned in ni_vp 85 * and a status of -1 is returned. If the lookup determines that 86 * the name does not exist (negative cacheing), a status of ENOENT 87 * is returned. If the lookup fails, a status of zero is returned. 88 */ 89 int 90 cache_lookup(dvp, vpp, cnp) 91 struct vnode *dvp; 92 struct vnode **vpp; 93 struct componentname *cnp; 94 { 95 register struct namecache *ncp, *ncq, **ncpp; 96 97 if (!doingcache) 98 return (0); 99 if (cnp->cn_namelen > NCHNAMLEN) { 100 nchstats.ncs_long++; 101 cnp->cn_flags &= ~MAKEENTRY; 102 return (0); 103 } 104 ncpp = &nchashtbl[cnp->cn_hash & nchash]; 105 for (ncp = *ncpp; ncp; ncp = ncp->nc_forw) { 106 if (ncp->nc_dvp == dvp && 107 ncp->nc_dvpid == dvp->v_id && 108 ncp->nc_nlen == cnp->cn_namelen && 109 !bcmp(ncp->nc_name, cnp->cn_nameptr, (u_int)ncp->nc_nlen)) 110 break; 111 } 112 if (ncp == NULL) { 113 nchstats.ncs_miss++; 114 return (0); 115 } 116 if (!(cnp->cn_flags & MAKEENTRY)) { 117 nchstats.ncs_badhits++; 118 } else if (ncp->nc_vp == NULL) { 119 if (cnp->cn_nameiop != CREATE) { 120 nchstats.ncs_neghits++; 121 /* 122 * Move this slot to end of LRU chain, 123 * if not already there. 124 */ 125 if (ncp->nc_nxt) { 126 /* remove from LRU chain */ 127 *ncp->nc_prev = ncp->nc_nxt; 128 ncp->nc_nxt->nc_prev = ncp->nc_prev; 129 /* and replace at end of it */ 130 ncp->nc_nxt = NULL; 131 ncp->nc_prev = nchtail; 132 *nchtail = ncp; 133 nchtail = &ncp->nc_nxt; 134 } 135 return (ENOENT); 136 } 137 } else if (ncp->nc_vpid != ncp->nc_vp->v_id) { 138 nchstats.ncs_falsehits++; 139 } else { 140 nchstats.ncs_goodhits++; 141 /* 142 * move this slot to end of LRU chain, if not already there 143 */ 144 if (ncp->nc_nxt) { 145 /* remove from LRU chain */ 146 *ncp->nc_prev = ncp->nc_nxt; 147 ncp->nc_nxt->nc_prev = ncp->nc_prev; 148 /* and replace at end of it */ 149 ncp->nc_nxt = NULL; 150 ncp->nc_prev = nchtail; 151 *nchtail = ncp; 152 nchtail = &ncp->nc_nxt; 153 } 154 *vpp = ncp->nc_vp; 155 return (-1); 156 } 157 158 /* 159 * Last component and we are renaming or deleting, 160 * the cache entry is invalid, or otherwise don't 161 * want cache entry to exist. 162 */ 163 /* remove from LRU chain */ 164 if (ncq = ncp->nc_nxt) 165 ncq->nc_prev = ncp->nc_prev; 166 else 167 nchtail = ncp->nc_prev; 168 *ncp->nc_prev = ncq; 169 /* remove from hash chain */ 170 if (ncq = ncp->nc_forw) 171 ncq->nc_back = ncp->nc_back; 172 *ncp->nc_back = ncq; 173 /* and make a dummy hash chain */ 174 ncp->nc_forw = NULL; 175 ncp->nc_back = NULL; 176 /* insert at head of LRU list (first to grab) */ 177 if (ncq = nchhead) 178 ncq->nc_prev = &ncp->nc_nxt; 179 else 180 nchtail = &ncp->nc_nxt; 181 nchhead = ncp; 182 ncp->nc_nxt = ncq; 183 ncp->nc_prev = &nchhead; 184 return (0); 185 } 186 187 /* 188 * Add an entry to the cache 189 */ 190 void 191 cache_enter(dvp, vp, cnp) 192 struct vnode *dvp; 193 struct vnode *vp; 194 struct componentname *cnp; 195 { 196 register struct namecache *ncp, *ncq, **ncpp; 197 198 #ifdef DIAGNOSTIC 199 if (cnp->cn_namelen > NCHNAMLEN) 200 panic("cache_enter: name too long"); 201 #endif 202 if (!doingcache) 203 return; 204 /* 205 * Free the cache slot at head of lru chain. 206 */ 207 if (numcache < desiredvnodes) { 208 ncp = (struct namecache *) 209 malloc((u_long)sizeof *ncp, M_CACHE, M_WAITOK); 210 bzero((char *)ncp, sizeof *ncp); 211 numcache++; 212 } else if (ncp = nchhead) { 213 /* remove from lru chain */ 214 if (ncq = ncp->nc_nxt) 215 ncq->nc_prev = ncp->nc_prev; 216 else 217 nchtail = ncp->nc_prev; 218 *ncp->nc_prev = ncq; 219 /* remove from old hash chain, if on one */ 220 if (ncp->nc_back) { 221 if (ncq = ncp->nc_forw) 222 ncq->nc_back = ncp->nc_back; 223 *ncp->nc_back = ncq; 224 ncp->nc_forw = NULL; 225 ncp->nc_back = NULL; 226 } 227 } else 228 return; 229 /* grab the vnode we just found */ 230 ncp->nc_vp = vp; 231 if (vp) 232 ncp->nc_vpid = vp->v_id; 233 else 234 ncp->nc_vpid = 0; 235 /* fill in cache info */ 236 ncp->nc_dvp = dvp; 237 ncp->nc_dvpid = dvp->v_id; 238 ncp->nc_nlen = cnp->cn_namelen; 239 bcopy(cnp->cn_nameptr, ncp->nc_name, (unsigned)ncp->nc_nlen); 240 /* link at end of lru chain */ 241 ncp->nc_nxt = NULL; 242 ncp->nc_prev = nchtail; 243 *nchtail = ncp; 244 nchtail = &ncp->nc_nxt; 245 /* and insert on hash chain */ 246 ncpp = &nchashtbl[cnp->cn_hash & nchash]; 247 if (ncq = *ncpp) 248 ncq->nc_back = &ncp->nc_forw; 249 ncp->nc_forw = ncq; 250 ncp->nc_back = ncpp; 251 *ncpp = ncp; 252 } 253 254 /* 255 * Name cache initialization, from vfs_init() when we are booting 256 */ 257 void 258 nchinit() 259 { 260 261 nchtail = &nchhead; 262 nchashtbl = hashinit(desiredvnodes, M_CACHE, &nchash); 263 } 264 265 /* 266 * Cache flush, a particular vnode; called when a vnode is renamed to 267 * hide entries that would now be invalid 268 */ 269 void 270 cache_purge(vp) 271 struct vnode *vp; 272 { 273 struct namecache *ncp, **ncpp; 274 275 vp->v_id = ++nextvnodeid; 276 if (nextvnodeid != 0) 277 return; 278 for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) { 279 for (ncp = *ncpp; ncp; ncp = ncp->nc_forw) { 280 ncp->nc_vpid = 0; 281 ncp->nc_dvpid = 0; 282 } 283 } 284 vp->v_id = ++nextvnodeid; 285 } 286 287 /* 288 * Cache flush, a whole filesystem; called when filesys is umounted to 289 * remove entries that would now be invalid 290 * 291 * The line "nxtcp = nchhead" near the end is to avoid potential problems 292 * if the cache lru chain is modified while we are dumping the 293 * inode. This makes the algorithm O(n^2), but do you think I care? 294 */ 295 void 296 cache_purgevfs(mp) 297 struct mount *mp; 298 { 299 register struct namecache *ncp, *nxtcp; 300 301 for (ncp = nchhead; ncp; ncp = nxtcp) { 302 if (ncp->nc_dvp == NULL || ncp->nc_dvp->v_mount != mp) { 303 nxtcp = ncp->nc_nxt; 304 continue; 305 } 306 /* free the resources we had */ 307 ncp->nc_vp = NULL; 308 ncp->nc_dvp = NULL; 309 /* remove from old hash chain, if on one */ 310 if (ncp->nc_back) { 311 if (nxtcp = ncp->nc_forw) 312 nxtcp->nc_back = ncp->nc_back; 313 *ncp->nc_back = nxtcp; 314 ncp->nc_forw = NULL; 315 ncp->nc_back = NULL; 316 } 317 /* delete this entry from LRU chain */ 318 if (nxtcp = ncp->nc_nxt) 319 nxtcp->nc_prev = ncp->nc_prev; 320 else 321 nchtail = ncp->nc_prev; 322 *ncp->nc_prev = nxtcp; 323 /* cause rescan of list, it may have altered */ 324 /* also put the now-free entry at head of LRU */ 325 if (nxtcp = nchhead) 326 nxtcp->nc_prev = &ncp->nc_nxt; 327 else 328 nchtail = &ncp->nc_nxt; 329 nchhead = ncp; 330 ncp->nc_nxt = nxtcp; 331 ncp->nc_prev = &nchhead; 332 } 333 } 334