1/*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 2001 Dag-Erling Sm��rgrav 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#include "opt_pseudofs.h" 33 34#include <sys/param.h> 35#include <sys/kernel.h> 36#include <sys/systm.h> 37#include <sys/eventhandler.h> 38#include <sys/lock.h> 39#include <sys/malloc.h> 40#include <sys/mutex.h> 41#include <sys/proc.h> 42#include <sys/sysctl.h> 43#include <sys/vnode.h> 44 45#include <fs/pseudofs/pseudofs.h> 46#include <fs/pseudofs/pseudofs_internal.h> 47 48static MALLOC_DEFINE(M_PFSVNCACHE, "pfs_vncache", "pseudofs vnode cache"); 49 50static struct mtx pfs_vncache_mutex; 51static eventhandler_tag pfs_exit_tag; 52static void pfs_exit(void *arg, struct proc *p); 53static void pfs_purge_all(void); 54 55static SYSCTL_NODE(_vfs_pfs, OID_AUTO, vncache, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 56 "pseudofs vnode cache"); 57 58static int pfs_vncache_entries; 59SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, entries, CTLFLAG_RD, 60 &pfs_vncache_entries, 0, 61 "number of entries in the vnode cache"); 62 63static int pfs_vncache_maxentries; 64SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, maxentries, CTLFLAG_RD, 65 &pfs_vncache_maxentries, 0, 66 "highest number of entries in the vnode cache"); 67 68static int pfs_vncache_hits; 69SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, hits, CTLFLAG_RD, 70 &pfs_vncache_hits, 0, 71 "number of cache hits since initialization"); 72 73static int pfs_vncache_misses; 74SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, misses, CTLFLAG_RD, 75 &pfs_vncache_misses, 0, 76 "number of cache misses since initialization"); 77 78extern struct vop_vector pfs_vnodeops; /* XXX -> .h file */ 79 80static SLIST_HEAD(pfs_vncache_head, pfs_vdata) *pfs_vncache_hashtbl; 81static u_long pfs_vncache_hash; 82#define PFS_VNCACHE_HASH(pid) (&pfs_vncache_hashtbl[(pid) & pfs_vncache_hash]) 83 84/* 85 * Initialize vnode cache 86 */ 87void 88pfs_vncache_load(void) 89{ 90 91 mtx_init(&pfs_vncache_mutex, "pfs_vncache", NULL, MTX_DEF); 92 pfs_vncache_hashtbl = hashinit(maxproc / 4, M_PFSVNCACHE, &pfs_vncache_hash); 93 pfs_exit_tag = EVENTHANDLER_REGISTER(process_exit, pfs_exit, NULL, 94 EVENTHANDLER_PRI_ANY); 95} 96 97/* 98 * Tear down vnode cache 99 */ 100void 101pfs_vncache_unload(void) 102{ 103 104 EVENTHANDLER_DEREGISTER(process_exit, pfs_exit_tag); 105 pfs_purge_all(); 106 KASSERT(pfs_vncache_entries == 0, 107 ("%d vncache entries remaining", pfs_vncache_entries)); 108 mtx_destroy(&pfs_vncache_mutex); 109 hashdestroy(pfs_vncache_hashtbl, M_PFSVNCACHE, pfs_vncache_hash); 110} 111 112/* 113 * Allocate a vnode 114 */ 115int 116pfs_vncache_alloc(struct mount *mp, struct vnode **vpp, 117 struct pfs_node *pn, pid_t pid) 118{ 119 struct pfs_vncache_head *hash; 120 struct pfs_vdata *pvd, *pvd2; 121 struct vnode *vp; 122 enum vgetstate vs; 123 int error; 124 125 /* 126 * See if the vnode is in the cache. 127 */ 128 hash = PFS_VNCACHE_HASH(pid); 129 if (SLIST_EMPTY(hash)) 130 goto alloc; 131retry: 132 mtx_lock(&pfs_vncache_mutex); 133 SLIST_FOREACH(pvd, hash, pvd_hash) { 134 if (pvd->pvd_pn == pn && pvd->pvd_pid == pid && 135 pvd->pvd_vnode->v_mount == mp) { 136 vp = pvd->pvd_vnode; 137 vs = vget_prep(vp); 138 mtx_unlock(&pfs_vncache_mutex); 139 if (vget_finish(vp, LK_EXCLUSIVE, vs) == 0) { 140 ++pfs_vncache_hits; 141 *vpp = vp; 142 /* 143 * Some callers cache_enter(vp) later, so 144 * we have to make sure it's not in the 145 * VFS cache so it doesn't get entered 146 * twice. A better solution would be to 147 * make pfs_vncache_alloc() responsible 148 * for entering the vnode in the VFS 149 * cache. 150 */ 151 cache_purge(vp); 152 return (0); 153 } 154 goto retry; 155 } 156 } 157 mtx_unlock(&pfs_vncache_mutex); 158alloc: 159 /* nope, get a new one */ 160 pvd = malloc(sizeof *pvd, M_PFSVNCACHE, M_WAITOK); 161 error = getnewvnode("pseudofs", mp, &pfs_vnodeops, vpp); 162 if (error) { 163 free(pvd, M_PFSVNCACHE); 164 return (error); 165 } 166 pvd->pvd_pn = pn; 167 pvd->pvd_pid = pid; 168 (*vpp)->v_data = pvd; 169 switch (pn->pn_type) { 170 case pfstype_root: 171 (*vpp)->v_vflag = VV_ROOT; 172#if 0 173 printf("root vnode allocated\n"); 174#endif 175 /* fall through */ 176 case pfstype_dir: 177 case pfstype_this: 178 case pfstype_parent: 179 case pfstype_procdir: 180 (*vpp)->v_type = VDIR; 181 break; 182 case pfstype_file: 183 (*vpp)->v_type = VREG; 184 break; 185 case pfstype_symlink: 186 (*vpp)->v_type = VLNK; 187 break; 188 case pfstype_none: 189 KASSERT(0, ("pfs_vncache_alloc called for null node\n")); 190 default: 191 panic("%s has unexpected type: %d", pn->pn_name, pn->pn_type); 192 } 193 /* 194 * Propagate flag through to vnode so users know it can change 195 * if the process changes (i.e. execve) 196 */ 197 if ((pn->pn_flags & PFS_PROCDEP) != 0) 198 (*vpp)->v_vflag |= VV_PROCDEP; 199 pvd->pvd_vnode = *vpp; 200 vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY); 201 VN_LOCK_AREC(*vpp); 202 error = insmntque(*vpp, mp); 203 if (error != 0) { 204 free(pvd, M_PFSVNCACHE); 205 *vpp = NULLVP; 206 return (error); 207 } 208 vn_set_state(*vpp, VSTATE_CONSTRUCTED); 209retry2: 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 vs = vget_prep(vp); 221 mtx_unlock(&pfs_vncache_mutex); 222 if (vget_finish(vp, LK_EXCLUSIVE, vs) == 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 */ 244int 245pfs_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 289static void 290pfs_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 299void 300pfs_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); 307restart: 308 removed = 0; 309 for (i = 0; i <= pfs_vncache_hash; i++) { 310restart_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 328static void 329pfs_purge_all(void) 330{ 331 332 pfs_purge(NULL); 333} 334 335/* 336 * Free all vnodes associated with a defunct process 337 */ 338static void 339pfs_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; 350restart: 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