1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 2001 Dag-Erling Coïdan Smørgrav 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer 12 * in this position and unchanged. 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. The name of the author may not be used to endorse or promote products 17 * derived from this software without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 */ 30 31 #include <sys/cdefs.h> 32 __FBSDID("$FreeBSD$"); 33 34 #include "opt_pseudofs.h" 35 36 #include <sys/param.h> 37 #include <sys/kernel.h> 38 #include <sys/systm.h> 39 #include <sys/eventhandler.h> 40 #include <sys/lock.h> 41 #include <sys/malloc.h> 42 #include <sys/mutex.h> 43 #include <sys/proc.h> 44 #include <sys/sysctl.h> 45 #include <sys/vnode.h> 46 47 #include <fs/pseudofs/pseudofs.h> 48 #include <fs/pseudofs/pseudofs_internal.h> 49 50 static MALLOC_DEFINE(M_PFSVNCACHE, "pfs_vncache", "pseudofs vnode cache"); 51 52 static struct mtx pfs_vncache_mutex; 53 static eventhandler_tag pfs_exit_tag; 54 static void pfs_exit(void *arg, struct proc *p); 55 static void pfs_purge_all(void); 56 57 static SYSCTL_NODE(_vfs_pfs, OID_AUTO, vncache, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 58 "pseudofs vnode cache"); 59 60 static int pfs_vncache_entries; 61 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, entries, CTLFLAG_RD, 62 &pfs_vncache_entries, 0, 63 "number of entries in the vnode cache"); 64 65 static int pfs_vncache_maxentries; 66 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, maxentries, CTLFLAG_RD, 67 &pfs_vncache_maxentries, 0, 68 "highest number of entries in the vnode cache"); 69 70 static int pfs_vncache_hits; 71 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, hits, CTLFLAG_RD, 72 &pfs_vncache_hits, 0, 73 "number of cache hits since initialization"); 74 75 static int pfs_vncache_misses; 76 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, misses, CTLFLAG_RD, 77 &pfs_vncache_misses, 0, 78 "number of cache misses since initialization"); 79 80 extern struct vop_vector pfs_vnodeops; /* XXX -> .h file */ 81 82 static SLIST_HEAD(pfs_vncache_head, pfs_vdata) *pfs_vncache_hashtbl; 83 static u_long pfs_vncache_hash; 84 #define PFS_VNCACHE_HASH(pid) (&pfs_vncache_hashtbl[(pid) & pfs_vncache_hash]) 85 86 /* 87 * Initialize vnode cache 88 */ 89 void 90 pfs_vncache_load(void) 91 { 92 93 mtx_init(&pfs_vncache_mutex, "pfs_vncache", NULL, MTX_DEF); 94 pfs_vncache_hashtbl = hashinit(maxproc / 4, M_PFSVNCACHE, &pfs_vncache_hash); 95 pfs_exit_tag = EVENTHANDLER_REGISTER(process_exit, pfs_exit, NULL, 96 EVENTHANDLER_PRI_ANY); 97 } 98 99 /* 100 * Tear down vnode cache 101 */ 102 void 103 pfs_vncache_unload(void) 104 { 105 106 EVENTHANDLER_DEREGISTER(process_exit, pfs_exit_tag); 107 pfs_purge_all(); 108 KASSERT(pfs_vncache_entries == 0, 109 ("%d vncache entries remaining", pfs_vncache_entries)); 110 mtx_destroy(&pfs_vncache_mutex); 111 hashdestroy(pfs_vncache_hashtbl, M_PFSVNCACHE, pfs_vncache_hash); 112 } 113 114 /* 115 * Allocate a vnode 116 */ 117 int 118 pfs_vncache_alloc(struct mount *mp, struct vnode **vpp, 119 struct pfs_node *pn, pid_t pid) 120 { 121 struct pfs_vncache_head *hash; 122 struct pfs_vdata *pvd, *pvd2; 123 struct vnode *vp; 124 enum vgetstate vs; 125 int error; 126 127 /* 128 * See if the vnode is in the cache. 129 */ 130 hash = PFS_VNCACHE_HASH(pid); 131 if (SLIST_EMPTY(hash)) 132 goto alloc; 133 retry: 134 mtx_lock(&pfs_vncache_mutex); 135 SLIST_FOREACH(pvd, hash, pvd_hash) { 136 if (pvd->pvd_pn == pn && pvd->pvd_pid == pid && 137 pvd->pvd_vnode->v_mount == mp) { 138 vp = pvd->pvd_vnode; 139 vs = vget_prep(vp); 140 mtx_unlock(&pfs_vncache_mutex); 141 if (vget_finish(vp, LK_EXCLUSIVE, vs) == 0) { 142 ++pfs_vncache_hits; 143 *vpp = vp; 144 /* 145 * Some callers cache_enter(vp) later, so 146 * we have to make sure it's not in the 147 * VFS cache so it doesn't get entered 148 * twice. A better solution would be to 149 * make pfs_vncache_alloc() responsible 150 * for entering the vnode in the VFS 151 * cache. 152 */ 153 cache_purge(vp); 154 return (0); 155 } 156 goto retry; 157 } 158 } 159 mtx_unlock(&pfs_vncache_mutex); 160 alloc: 161 /* nope, get a new one */ 162 pvd = malloc(sizeof *pvd, M_PFSVNCACHE, M_WAITOK); 163 error = getnewvnode("pseudofs", mp, &pfs_vnodeops, vpp); 164 if (error) { 165 free(pvd, M_PFSVNCACHE); 166 return (error); 167 } 168 pvd->pvd_pn = pn; 169 pvd->pvd_pid = pid; 170 (*vpp)->v_data = pvd; 171 switch (pn->pn_type) { 172 case pfstype_root: 173 (*vpp)->v_vflag = VV_ROOT; 174 #if 0 175 printf("root vnode allocated\n"); 176 #endif 177 /* fall through */ 178 case pfstype_dir: 179 case pfstype_this: 180 case pfstype_parent: 181 case pfstype_procdir: 182 (*vpp)->v_type = VDIR; 183 break; 184 case pfstype_file: 185 (*vpp)->v_type = VREG; 186 break; 187 case pfstype_symlink: 188 (*vpp)->v_type = VLNK; 189 break; 190 case pfstype_none: 191 KASSERT(0, ("pfs_vncache_alloc called for null node\n")); 192 default: 193 panic("%s has unexpected type: %d", pn->pn_name, pn->pn_type); 194 } 195 /* 196 * Propagate flag through to vnode so users know it can change 197 * if the process changes (i.e. execve) 198 */ 199 if ((pn->pn_flags & PFS_PROCDEP) != 0) 200 (*vpp)->v_vflag |= VV_PROCDEP; 201 pvd->pvd_vnode = *vpp; 202 vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY); 203 VN_LOCK_AREC(*vpp); 204 error = insmntque(*vpp, mp); 205 if (error != 0) { 206 free(pvd, M_PFSVNCACHE); 207 *vpp = NULLVP; 208 return (error); 209 } 210 retry2: 211 mtx_lock(&pfs_vncache_mutex); 212 /* 213 * Other thread may race with us, creating the entry we are 214 * going to insert into the cache. Recheck after 215 * pfs_vncache_mutex is reacquired. 216 */ 217 SLIST_FOREACH(pvd2, hash, pvd_hash) { 218 if (pvd2->pvd_pn == pn && pvd2->pvd_pid == pid && 219 pvd2->pvd_vnode->v_mount == mp) { 220 vp = pvd2->pvd_vnode; 221 vs = vget_prep(vp); 222 mtx_unlock(&pfs_vncache_mutex); 223 if (vget_finish(vp, LK_EXCLUSIVE, vs) == 0) { 224 ++pfs_vncache_hits; 225 vgone(*vpp); 226 vput(*vpp); 227 *vpp = vp; 228 cache_purge(vp); 229 return (0); 230 } 231 goto retry2; 232 } 233 } 234 ++pfs_vncache_misses; 235 if (++pfs_vncache_entries > pfs_vncache_maxentries) 236 pfs_vncache_maxentries = pfs_vncache_entries; 237 SLIST_INSERT_HEAD(hash, pvd, pvd_hash); 238 mtx_unlock(&pfs_vncache_mutex); 239 return (0); 240 } 241 242 /* 243 * Free a vnode 244 */ 245 int 246 pfs_vncache_free(struct vnode *vp) 247 { 248 struct pfs_vdata *pvd, *pvd2; 249 250 mtx_lock(&pfs_vncache_mutex); 251 pvd = (struct pfs_vdata *)vp->v_data; 252 KASSERT(pvd != NULL, ("pfs_vncache_free(): no vnode data\n")); 253 SLIST_FOREACH(pvd2, PFS_VNCACHE_HASH(pvd->pvd_pid), pvd_hash) { 254 if (pvd2 != pvd) 255 continue; 256 SLIST_REMOVE(PFS_VNCACHE_HASH(pvd->pvd_pid), pvd, pfs_vdata, pvd_hash); 257 --pfs_vncache_entries; 258 break; 259 } 260 mtx_unlock(&pfs_vncache_mutex); 261 262 free(pvd, M_PFSVNCACHE); 263 vp->v_data = NULL; 264 return (0); 265 } 266 267 /* 268 * Purge the cache of dead entries 269 * 270 * The code is not very efficient and this perhaps can be addressed without 271 * a complete rewrite. Previous iteration was walking a linked list from 272 * scratch every time. This code only walks the relevant hash chain (if pid 273 * is provided), but still resorts to scanning the entire cache at least twice 274 * if a specific component is to be removed which is slower. This can be 275 * augmented with resizing the hash. 276 * 277 * Explanation of the previous state: 278 * 279 * This is extremely inefficient due to the fact that vgone() not only 280 * indirectly modifies the vnode cache, but may also sleep. We can 281 * neither hold pfs_vncache_mutex across a vgone() call, nor make any 282 * assumptions about the state of the cache after vgone() returns. In 283 * consequence, we must start over after every vgone() call, and keep 284 * trying until we manage to traverse the entire cache. 285 * 286 * The only way to improve this situation is to change the data structure 287 * used to implement the cache. 288 */ 289 290 static void 291 pfs_purge_one(struct vnode *vnp) 292 { 293 294 VOP_LOCK(vnp, LK_EXCLUSIVE); 295 vgone(vnp); 296 VOP_UNLOCK(vnp); 297 vdrop(vnp); 298 } 299 300 void 301 pfs_purge(struct pfs_node *pn) 302 { 303 struct pfs_vdata *pvd; 304 struct vnode *vnp; 305 u_long i, removed; 306 307 mtx_lock(&pfs_vncache_mutex); 308 restart: 309 removed = 0; 310 for (i = 0; i < pfs_vncache_hash; i++) { 311 restart_chain: 312 SLIST_FOREACH(pvd, &pfs_vncache_hashtbl[i], pvd_hash) { 313 if (pn != NULL && pvd->pvd_pn != pn) 314 continue; 315 vnp = pvd->pvd_vnode; 316 vhold(vnp); 317 mtx_unlock(&pfs_vncache_mutex); 318 pfs_purge_one(vnp); 319 removed++; 320 mtx_lock(&pfs_vncache_mutex); 321 goto restart_chain; 322 } 323 } 324 if (removed > 0) 325 goto restart; 326 mtx_unlock(&pfs_vncache_mutex); 327 } 328 329 static void 330 pfs_purge_all(void) 331 { 332 333 pfs_purge(NULL); 334 } 335 336 /* 337 * Free all vnodes associated with a defunct process 338 */ 339 static void 340 pfs_exit(void *arg, struct proc *p) 341 { 342 struct pfs_vncache_head *hash; 343 struct pfs_vdata *pvd; 344 struct vnode *vnp; 345 int pid; 346 347 pid = p->p_pid; 348 hash = PFS_VNCACHE_HASH(pid); 349 if (SLIST_EMPTY(hash)) 350 return; 351 restart: 352 mtx_lock(&pfs_vncache_mutex); 353 SLIST_FOREACH(pvd, hash, pvd_hash) { 354 if (pvd->pvd_pid != pid) 355 continue; 356 vnp = pvd->pvd_vnode; 357 vhold(vnp); 358 mtx_unlock(&pfs_vncache_mutex); 359 pfs_purge_one(vnp); 360 goto restart; 361 } 362 mtx_unlock(&pfs_vncache_mutex); 363 } 364