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 } 112 113 /* 114 * Allocate a vnode 115 */ 116 int 117 pfs_vncache_alloc(struct mount *mp, struct vnode **vpp, 118 struct pfs_node *pn, pid_t pid) 119 { 120 struct pfs_vncache_head *hash; 121 struct pfs_vdata *pvd, *pvd2; 122 struct vnode *vp; 123 enum vgetstate vs; 124 int error; 125 126 /* 127 * See if the vnode is in the cache. 128 */ 129 hash = PFS_VNCACHE_HASH(pid); 130 if (SLIST_EMPTY(hash)) 131 goto alloc; 132 retry: 133 mtx_lock(&pfs_vncache_mutex); 134 SLIST_FOREACH(pvd, hash, pvd_hash) { 135 if (pvd->pvd_pn == pn && pvd->pvd_pid == pid && 136 pvd->pvd_vnode->v_mount == mp) { 137 vp = pvd->pvd_vnode; 138 vs = vget_prep(vp); 139 mtx_unlock(&pfs_vncache_mutex); 140 if (vget_finish(vp, LK_EXCLUSIVE, vs) == 0) { 141 ++pfs_vncache_hits; 142 *vpp = vp; 143 /* 144 * Some callers cache_enter(vp) later, so 145 * we have to make sure it's not in the 146 * VFS cache so it doesn't get entered 147 * twice. A better solution would be to 148 * make pfs_vncache_alloc() responsible 149 * for entering the vnode in the VFS 150 * cache. 151 */ 152 cache_purge(vp); 153 return (0); 154 } 155 goto retry; 156 } 157 } 158 mtx_unlock(&pfs_vncache_mutex); 159 alloc: 160 /* nope, get a new one */ 161 pvd = malloc(sizeof *pvd, M_PFSVNCACHE, M_WAITOK); 162 error = getnewvnode("pseudofs", mp, &pfs_vnodeops, vpp); 163 if (error) { 164 free(pvd, M_PFSVNCACHE); 165 return (error); 166 } 167 pvd->pvd_pn = pn; 168 pvd->pvd_pid = pid; 169 (*vpp)->v_data = pvd; 170 switch (pn->pn_type) { 171 case pfstype_root: 172 (*vpp)->v_vflag = VV_ROOT; 173 #if 0 174 printf("root vnode allocated\n"); 175 #endif 176 /* fall through */ 177 case pfstype_dir: 178 case pfstype_this: 179 case pfstype_parent: 180 case pfstype_procdir: 181 (*vpp)->v_type = VDIR; 182 break; 183 case pfstype_file: 184 (*vpp)->v_type = VREG; 185 break; 186 case pfstype_symlink: 187 (*vpp)->v_type = VLNK; 188 break; 189 case pfstype_none: 190 KASSERT(0, ("pfs_vncache_alloc called for null node\n")); 191 default: 192 panic("%s has unexpected type: %d", pn->pn_name, pn->pn_type); 193 } 194 /* 195 * Propagate flag through to vnode so users know it can change 196 * if the process changes (i.e. execve) 197 */ 198 if ((pn->pn_flags & PFS_PROCDEP) != 0) 199 (*vpp)->v_vflag |= VV_PROCDEP; 200 pvd->pvd_vnode = *vpp; 201 vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY); 202 VN_LOCK_AREC(*vpp); 203 error = insmntque(*vpp, mp); 204 if (error != 0) { 205 free(pvd, M_PFSVNCACHE); 206 *vpp = NULLVP; 207 return (error); 208 } 209 retry2: 210 mtx_lock(&pfs_vncache_mutex); 211 /* 212 * Other thread may race with us, creating the entry we are 213 * going to insert into the cache. Recheck after 214 * pfs_vncache_mutex is reacquired. 215 */ 216 SLIST_FOREACH(pvd2, hash, pvd_hash) { 217 if (pvd2->pvd_pn == pn && pvd2->pvd_pid == pid && 218 pvd2->pvd_vnode->v_mount == mp) { 219 vp = pvd2->pvd_vnode; 220 VI_LOCK(vp); 221 mtx_unlock(&pfs_vncache_mutex); 222 if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK) == 0) { 223 ++pfs_vncache_hits; 224 vgone(*vpp); 225 vput(*vpp); 226 *vpp = vp; 227 cache_purge(vp); 228 return (0); 229 } 230 goto retry2; 231 } 232 } 233 ++pfs_vncache_misses; 234 if (++pfs_vncache_entries > pfs_vncache_maxentries) 235 pfs_vncache_maxentries = pfs_vncache_entries; 236 SLIST_INSERT_HEAD(hash, pvd, pvd_hash); 237 mtx_unlock(&pfs_vncache_mutex); 238 return (0); 239 } 240 241 /* 242 * Free a vnode 243 */ 244 int 245 pfs_vncache_free(struct vnode *vp) 246 { 247 struct pfs_vdata *pvd, *pvd2; 248 249 mtx_lock(&pfs_vncache_mutex); 250 pvd = (struct pfs_vdata *)vp->v_data; 251 KASSERT(pvd != NULL, ("pfs_vncache_free(): no vnode data\n")); 252 SLIST_FOREACH(pvd2, PFS_VNCACHE_HASH(pvd->pvd_pid), pvd_hash) { 253 if (pvd2 != pvd) 254 continue; 255 SLIST_REMOVE(PFS_VNCACHE_HASH(pvd->pvd_pid), pvd, pfs_vdata, pvd_hash); 256 --pfs_vncache_entries; 257 break; 258 } 259 mtx_unlock(&pfs_vncache_mutex); 260 261 free(pvd, M_PFSVNCACHE); 262 vp->v_data = NULL; 263 return (0); 264 } 265 266 /* 267 * Purge the cache of dead entries 268 * 269 * The code is not very efficient and this perhaps can be addressed without 270 * a complete rewrite. Previous iteration was walking a linked list from 271 * scratch every time. This code only walks the relevant hash chain (if pid 272 * is provided), but still resorts to scanning the entire cache at least twice 273 * if a specific component is to be removed which is slower. This can be 274 * augmented with resizing the hash. 275 * 276 * Explanation of the previous state: 277 * 278 * This is extremely inefficient due to the fact that vgone() not only 279 * indirectly modifies the vnode cache, but may also sleep. We can 280 * neither hold pfs_vncache_mutex across a vgone() call, nor make any 281 * assumptions about the state of the cache after vgone() returns. In 282 * consequence, we must start over after every vgone() call, and keep 283 * trying until we manage to traverse the entire cache. 284 * 285 * The only way to improve this situation is to change the data structure 286 * used to implement the cache. 287 */ 288 289 static void 290 pfs_purge_one(struct vnode *vnp) 291 { 292 293 VOP_LOCK(vnp, LK_EXCLUSIVE); 294 vgone(vnp); 295 VOP_UNLOCK(vnp); 296 vdrop(vnp); 297 } 298 299 void 300 pfs_purge(struct pfs_node *pn) 301 { 302 struct pfs_vdata *pvd; 303 struct vnode *vnp; 304 u_long i, removed; 305 306 mtx_lock(&pfs_vncache_mutex); 307 restart: 308 removed = 0; 309 for (i = 0; i < pfs_vncache_hash; i++) { 310 restart_chain: 311 SLIST_FOREACH(pvd, &pfs_vncache_hashtbl[i], pvd_hash) { 312 if (pn != NULL && pvd->pvd_pn != pn) 313 continue; 314 vnp = pvd->pvd_vnode; 315 vhold(vnp); 316 mtx_unlock(&pfs_vncache_mutex); 317 pfs_purge_one(vnp); 318 removed++; 319 mtx_lock(&pfs_vncache_mutex); 320 goto restart_chain; 321 } 322 } 323 if (removed > 0) 324 goto restart; 325 mtx_unlock(&pfs_vncache_mutex); 326 } 327 328 static void 329 pfs_purge_all(void) 330 { 331 332 pfs_purge(NULL); 333 } 334 335 /* 336 * Free all vnodes associated with a defunct process 337 */ 338 static void 339 pfs_exit(void *arg, struct proc *p) 340 { 341 struct pfs_vncache_head *hash; 342 struct pfs_vdata *pvd; 343 struct vnode *vnp; 344 int pid; 345 346 pid = p->p_pid; 347 hash = PFS_VNCACHE_HASH(pid); 348 if (SLIST_EMPTY(hash)) 349 return; 350 restart: 351 mtx_lock(&pfs_vncache_mutex); 352 SLIST_FOREACH(pvd, hash, pvd_hash) { 353 if (pvd->pvd_pid != pid) 354 continue; 355 vnp = pvd->pvd_vnode; 356 vhold(vnp); 357 mtx_unlock(&pfs_vncache_mutex); 358 pfs_purge_one(vnp); 359 goto restart; 360 } 361 mtx_unlock(&pfs_vncache_mutex); 362 } 363