1 /* 2 * Copyright (c) 1989, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * Poul-Henning Kamp of the FreeBSD Project. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)vfs_cache.c 8.5 (Berkeley) 3/22/95 37 * $Id: vfs_cache.c,v 1.38 1998/09/09 07:41:41 bde Exp $ 38 */ 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/kernel.h> 43 #include <sys/sysctl.h> 44 #include <sys/mount.h> 45 #include <sys/vnode.h> 46 #include <sys/namei.h> 47 #include <sys/malloc.h> 48 49 50 /* 51 * Name caching works as follows: 52 * 53 * Names found by directory scans are retained in a cache 54 * for future reference. It is managed LRU, so frequently 55 * used names will hang around. Cache is indexed by hash value 56 * obtained from (vp, name) where vp refers to the directory 57 * containing name. 58 * 59 * If it is a "negative" entry, (i.e. for a name that is known NOT to 60 * exist) the vnode pointer will be NULL. 61 * 62 * Upon reaching the last segment of a path, if the reference 63 * is for DELETE, or NOCACHE is set (rewrite), and the 64 * name is located in the cache, it will be dropped. 65 */ 66 67 /* 68 * Structures associated with name cacheing. 69 */ 70 #define NCHHASH(dvp, cnp) \ 71 (&nchashtbl[((dvp)->v_id + (cnp)->cn_hash) & nchash]) 72 static LIST_HEAD(nchashhead, namecache) *nchashtbl; /* Hash Table */ 73 static TAILQ_HEAD(, namecache) ncneg; /* Hash Table */ 74 static u_long nchash; /* size of hash table */ 75 SYSCTL_INT(_debug, OID_AUTO, nchash, CTLFLAG_RD, &nchash, 0, ""); 76 static u_long ncnegfactor = 16; /* ratio of negative entries */ 77 SYSCTL_INT(_debug, OID_AUTO, ncnegfactor, CTLFLAG_RW, &ncnegfactor, 0, ""); 78 static u_long numneg; /* number of cache entries allocated */ 79 SYSCTL_INT(_debug, OID_AUTO, numneg, CTLFLAG_RD, &numneg, 0, ""); 80 static u_long numcache; /* number of cache entries allocated */ 81 SYSCTL_INT(_debug, OID_AUTO, numcache, CTLFLAG_RD, &numcache, 0, ""); 82 struct nchstats nchstats; /* cache effectiveness statistics */ 83 84 static int doingcache = 1; /* 1 => enable the cache */ 85 SYSCTL_INT(_debug, OID_AUTO, vfscache, CTLFLAG_RW, &doingcache, 0, ""); 86 SYSCTL_INT(_debug, OID_AUTO, vnsize, CTLFLAG_RD, 0, sizeof(struct vnode), ""); 87 SYSCTL_INT(_debug, OID_AUTO, ncsize, CTLFLAG_RD, 0, sizeof(struct namecache), ""); 88 89 /* 90 * The new name cache statistics 91 */ 92 SYSCTL_NODE(_vfs, OID_AUTO, cache, CTLFLAG_RW, 0, "Name cache statistics"); 93 #define STATNODE(mode, name, var) \ 94 SYSCTL_INT(_vfs_cache, OID_AUTO, name, mode, var, 0, ""); 95 STATNODE(CTLFLAG_RD, numneg, &numneg); 96 STATNODE(CTLFLAG_RD, numcache, &numcache); 97 static u_long numcalls; STATNODE(CTLFLAG_RD, numcalls, &numcalls); 98 static u_long dothits; STATNODE(CTLFLAG_RD, dothits, &dothits); 99 static u_long dotdothits; STATNODE(CTLFLAG_RD, dotdothits, &dotdothits); 100 static u_long numchecks; STATNODE(CTLFLAG_RD, numchecks, &numchecks); 101 static u_long nummiss; STATNODE(CTLFLAG_RD, nummiss, &nummiss); 102 static u_long nummisszap; STATNODE(CTLFLAG_RD, nummisszap, &nummisszap); 103 static u_long numposzaps; STATNODE(CTLFLAG_RD, numposzaps, &numposzaps); 104 static u_long numposhits; STATNODE(CTLFLAG_RD, numposhits, &numposhits); 105 static u_long numnegzaps; STATNODE(CTLFLAG_RD, numnegzaps, &numnegzaps); 106 static u_long numneghits; STATNODE(CTLFLAG_RD, numneghits, &numneghits); 107 108 109 static void cache_zap __P((struct namecache *ncp)); 110 111 /* 112 * Flags in namecache.nc_flag 113 */ 114 #define NCF_WHITE 1 115 /* 116 * Delete an entry from its hash list and move it to the front 117 * of the LRU list for immediate reuse. 118 */ 119 static void 120 cache_zap(ncp) 121 struct namecache *ncp; 122 { 123 LIST_REMOVE(ncp, nc_hash); 124 LIST_REMOVE(ncp, nc_src); 125 if (LIST_EMPTY(&ncp->nc_dvp->v_cache_src)) 126 vdrop(ncp->nc_dvp); 127 if (ncp->nc_vp) { 128 TAILQ_REMOVE(&ncp->nc_vp->v_cache_dst, ncp, nc_dst); 129 } else { 130 TAILQ_REMOVE(&ncneg, ncp, nc_dst); 131 numneg--; 132 } 133 numcache--; 134 free(ncp, M_CACHE); 135 } 136 137 /* 138 * Lookup an entry in the cache 139 * 140 * We don't do this if the segment name is long, simply so the cache 141 * can avoid holding long names (which would either waste space, or 142 * add greatly to the complexity). 143 * 144 * Lookup is called with dvp pointing to the directory to search, 145 * cnp pointing to the name of the entry being sought. If the lookup 146 * succeeds, the vnode is returned in *vpp, and a status of -1 is 147 * returned. If the lookup determines that the name does not exist 148 * (negative cacheing), a status of ENOENT is returned. If the lookup 149 * fails, a status of zero is returned. 150 */ 151 152 int 153 cache_lookup(dvp, vpp, cnp) 154 struct vnode *dvp; 155 struct vnode **vpp; 156 struct componentname *cnp; 157 { 158 register struct namecache *ncp; 159 160 if (!doingcache) { 161 cnp->cn_flags &= ~MAKEENTRY; 162 return (0); 163 } 164 165 numcalls++; 166 167 if (cnp->cn_nameptr[0] == '.') { 168 if (cnp->cn_namelen == 1) { 169 *vpp = dvp; 170 dothits++; 171 return (-1); 172 } 173 if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') { 174 dotdothits++; 175 if (dvp->v_dd->v_id != dvp->v_ddid || 176 (cnp->cn_flags & MAKEENTRY) == 0) { 177 dvp->v_ddid = 0; 178 return (0); 179 } 180 *vpp = dvp->v_dd; 181 return (-1); 182 } 183 } 184 185 LIST_FOREACH(ncp, (NCHHASH(dvp, cnp)), nc_hash) { 186 numchecks++; 187 if (ncp->nc_dvp == dvp && ncp->nc_nlen == cnp->cn_namelen && 188 !bcmp(ncp->nc_name, cnp->cn_nameptr, ncp->nc_nlen)) 189 break; 190 } 191 192 /* We failed to find an entry */ 193 if (ncp == 0) { 194 if ((cnp->cn_flags & MAKEENTRY) == 0) { 195 nummisszap++; 196 } else { 197 nummiss++; 198 } 199 nchstats.ncs_miss++; 200 return (0); 201 } 202 203 /* We don't want to have an entry, so dump it */ 204 if ((cnp->cn_flags & MAKEENTRY) == 0) { 205 numposzaps++; 206 nchstats.ncs_badhits++; 207 cache_zap(ncp); 208 return (0); 209 } 210 211 /* We found a "positive" match, return the vnode */ 212 if (ncp->nc_vp) { 213 numposhits++; 214 nchstats.ncs_goodhits++; 215 *vpp = ncp->nc_vp; 216 return (-1); 217 } 218 219 /* We found a negative match, and want to create it, so purge */ 220 if (cnp->cn_nameiop == CREATE) { 221 numnegzaps++; 222 nchstats.ncs_badhits++; 223 cache_zap(ncp); 224 return (0); 225 } 226 227 numneghits++; 228 /* 229 * We found a "negative" match, ENOENT notifies client of this match. 230 * The nc_vpid field records whether this is a whiteout. 231 */ 232 TAILQ_REMOVE(&ncneg, ncp, nc_dst); 233 TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst); 234 nchstats.ncs_neghits++; 235 if (ncp->nc_flag & NCF_WHITE) 236 cnp->cn_flags |= ISWHITEOUT; 237 return (ENOENT); 238 } 239 240 /* 241 * Add an entry to the cache. 242 */ 243 void 244 cache_enter(dvp, vp, cnp) 245 struct vnode *dvp; 246 struct vnode *vp; 247 struct componentname *cnp; 248 { 249 register struct namecache *ncp; 250 register struct nchashhead *ncpp; 251 252 if (!doingcache) 253 return; 254 255 if (cnp->cn_nameptr[0] == '.') { 256 if (cnp->cn_namelen == 1) { 257 return; 258 } 259 if (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.') { 260 if (vp) { 261 dvp->v_dd = vp; 262 dvp->v_ddid = vp->v_id; 263 } else { 264 dvp->v_dd = dvp; 265 dvp->v_ddid = 0; 266 } 267 return; 268 } 269 } 270 271 ncp = (struct namecache *) 272 malloc(sizeof *ncp + cnp->cn_namelen, M_CACHE, M_WAITOK); 273 bzero((char *)ncp, sizeof *ncp); 274 numcache++; 275 if (!vp) { 276 numneg++; 277 ncp->nc_flag = cnp->cn_flags & ISWHITEOUT ? NCF_WHITE : 0; 278 } else if (vp->v_type == VDIR) { 279 vp->v_dd = dvp; 280 vp->v_ddid = dvp->v_id; 281 } 282 283 /* 284 * Fill in cache info, if vp is NULL this is a "negative" cache entry. 285 * For negative entries, we have to record whether it is a whiteout. 286 * the whiteout flag is stored in the nc_vpid field which is 287 * otherwise unused. 288 */ 289 ncp->nc_vp = vp; 290 ncp->nc_dvp = dvp; 291 ncp->nc_nlen = cnp->cn_namelen; 292 bcopy(cnp->cn_nameptr, ncp->nc_name, ncp->nc_nlen); 293 ncpp = NCHHASH(dvp, cnp); 294 LIST_INSERT_HEAD(ncpp, ncp, nc_hash); 295 if (LIST_EMPTY(&dvp->v_cache_src)) 296 vhold(dvp); 297 LIST_INSERT_HEAD(&dvp->v_cache_src, ncp, nc_src); 298 if (vp) { 299 TAILQ_INSERT_HEAD(&vp->v_cache_dst, ncp, nc_dst); 300 } else { 301 TAILQ_INSERT_TAIL(&ncneg, ncp, nc_dst); 302 } 303 if (numneg*ncnegfactor > numcache) { 304 ncp = TAILQ_FIRST(&ncneg); 305 cache_zap(ncp); 306 } 307 } 308 309 /* 310 * Name cache initialization, from vfs_init() when we are booting 311 */ 312 void 313 nchinit() 314 { 315 316 TAILQ_INIT(&ncneg); 317 nchashtbl = hashinit(desiredvnodes*2, M_CACHE, &nchash); 318 } 319 320 /* 321 * Invalidate all entries to a particular vnode. 322 * 323 * Remove all entries in the namecache relating to this vnode and 324 * change the v_id. We take the v_id from a global counter, since 325 * it becomes a handy sequence number in crash-dumps that way. 326 * No valid vnode will ever have (v_id == 0). 327 * 328 * XXX: Only time and the size of v_id prevents this from failing: 329 * XXX: In theory we should hunt down all (struct vnode*, v_id) 330 * XXX: soft references and nuke them, at least on the global 331 * XXX: v_id wraparound. The period of resistance can be extended 332 * XXX: by incrementing each vnodes v_id individually instead of 333 * XXX: using the global v_id. 334 */ 335 336 void 337 cache_purge(vp) 338 struct vnode *vp; 339 { 340 static u_long nextid; 341 342 while (!LIST_EMPTY(&vp->v_cache_src)) 343 cache_zap(LIST_FIRST(&vp->v_cache_src)); 344 while (!TAILQ_EMPTY(&vp->v_cache_dst)) 345 cache_zap(TAILQ_FIRST(&vp->v_cache_dst)); 346 347 do 348 nextid++; 349 while (nextid == vp->v_id || !nextid); 350 vp->v_id = nextid; 351 vp->v_dd = vp; 352 vp->v_ddid = 0; 353 } 354 355 /* 356 * Flush all entries referencing a particular filesystem. 357 * 358 * Since we need to check it anyway, we will flush all the invalid 359 * entries at the same time. 360 */ 361 void 362 cache_purgevfs(mp) 363 struct mount *mp; 364 { 365 struct nchashhead *ncpp; 366 struct namecache *ncp, *nnp; 367 368 /* Scan hash tables for applicable entries */ 369 for (ncpp = &nchashtbl[nchash]; ncpp >= nchashtbl; ncpp--) { 370 for (ncp = LIST_FIRST(ncpp); ncp != 0; ncp = nnp) { 371 nnp = LIST_NEXT(ncp, nc_hash); 372 if (ncp->nc_dvp->v_mount == mp) { 373 cache_zap(ncp); 374 } 375 } 376 } 377 } 378 379 /* 380 * Perform canonical checks and cache lookup and pass on to filesystem 381 * through the vop_cachedlookup only if needed. 382 */ 383 384 int 385 vfs_cache_lookup(ap) 386 struct vop_lookup_args /* { 387 struct vnode *a_dvp; 388 struct vnode **a_vpp; 389 struct componentname *a_cnp; 390 } */ *ap; 391 { 392 struct vnode *vdp; 393 struct vnode *pdp; 394 int lockparent; 395 int error; 396 struct vnode **vpp = ap->a_vpp; 397 struct componentname *cnp = ap->a_cnp; 398 struct ucred *cred = cnp->cn_cred; 399 int flags = cnp->cn_flags; 400 struct proc *p = cnp->cn_proc; 401 u_long vpid; /* capability number of vnode */ 402 403 *vpp = NULL; 404 vdp = ap->a_dvp; 405 lockparent = flags & LOCKPARENT; 406 407 if (vdp->v_type != VDIR) 408 return (ENOTDIR); 409 410 if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) && 411 (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) 412 return (EROFS); 413 414 error = VOP_ACCESS(vdp, VEXEC, cred, cnp->cn_proc); 415 416 if (error) 417 return (error); 418 419 error = cache_lookup(vdp, vpp, cnp); 420 421 if (!error) 422 return (VOP_CACHEDLOOKUP(ap->a_dvp, ap->a_vpp, ap->a_cnp)); 423 424 if (error == ENOENT) 425 return (error); 426 427 pdp = vdp; 428 vdp = *vpp; 429 vpid = vdp->v_id; 430 if (pdp == vdp) { /* lookup on "." */ 431 VREF(vdp); 432 error = 0; 433 } else if (flags & ISDOTDOT) { 434 VOP_UNLOCK(pdp, 0, p); 435 error = vget(vdp, LK_EXCLUSIVE, p); 436 if (!error && lockparent && (flags & ISLASTCN)) 437 error = vn_lock(pdp, LK_EXCLUSIVE, p); 438 } else { 439 error = vget(vdp, LK_EXCLUSIVE, p); 440 if (!lockparent || error || !(flags & ISLASTCN)) 441 VOP_UNLOCK(pdp, 0, p); 442 } 443 /* 444 * Check that the capability number did not change 445 * while we were waiting for the lock. 446 */ 447 if (!error) { 448 if (vpid == vdp->v_id) 449 return (0); 450 vput(vdp); 451 if (lockparent && pdp != vdp && (flags & ISLASTCN)) 452 VOP_UNLOCK(pdp, 0, p); 453 } 454 error = vn_lock(pdp, LK_EXCLUSIVE, p); 455 if (error) 456 return (error); 457 return (VOP_CACHEDLOOKUP(ap->a_dvp, ap->a_vpp, ap->a_cnp)); 458 } 459