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 struct pfs_vdata *pfs_vncache; 54 static eventhandler_tag pfs_exit_tag; 55 static void pfs_exit(void *arg, struct proc *p); 56 static void pfs_purge_locked(struct pfs_node *pn, bool force); 57 58 static SYSCTL_NODE(_vfs_pfs, OID_AUTO, vncache, CTLFLAG_RW, 0, 59 "pseudofs vnode cache"); 60 61 static int pfs_vncache_entries; 62 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, entries, CTLFLAG_RD, 63 &pfs_vncache_entries, 0, 64 "number of entries in the vnode cache"); 65 66 static int pfs_vncache_maxentries; 67 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, maxentries, CTLFLAG_RD, 68 &pfs_vncache_maxentries, 0, 69 "highest number of entries in the vnode cache"); 70 71 static int pfs_vncache_hits; 72 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, hits, CTLFLAG_RD, 73 &pfs_vncache_hits, 0, 74 "number of cache hits since initialization"); 75 76 static int pfs_vncache_misses; 77 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, misses, CTLFLAG_RD, 78 &pfs_vncache_misses, 0, 79 "number of cache misses since initialization"); 80 81 extern struct vop_vector pfs_vnodeops; /* XXX -> .h file */ 82 83 /* 84 * Initialize vnode cache 85 */ 86 void 87 pfs_vncache_load(void) 88 { 89 90 mtx_init(&pfs_vncache_mutex, "pfs_vncache", NULL, MTX_DEF); 91 pfs_exit_tag = EVENTHANDLER_REGISTER(process_exit, pfs_exit, NULL, 92 EVENTHANDLER_PRI_ANY); 93 } 94 95 /* 96 * Tear down vnode cache 97 */ 98 void 99 pfs_vncache_unload(void) 100 { 101 102 EVENTHANDLER_DEREGISTER(process_exit, pfs_exit_tag); 103 mtx_lock(&pfs_vncache_mutex); 104 pfs_purge_locked(NULL, true); 105 mtx_unlock(&pfs_vncache_mutex); 106 KASSERT(pfs_vncache_entries == 0, 107 ("%d vncache entries remaining", pfs_vncache_entries)); 108 mtx_destroy(&pfs_vncache_mutex); 109 } 110 111 /* 112 * Allocate a vnode 113 */ 114 int 115 pfs_vncache_alloc(struct mount *mp, struct vnode **vpp, 116 struct pfs_node *pn, pid_t pid) 117 { 118 struct pfs_vdata *pvd, *pvd2; 119 struct vnode *vp; 120 int error; 121 122 /* 123 * See if the vnode is in the cache. 124 * XXX linear search is not very efficient. 125 */ 126 retry: 127 mtx_lock(&pfs_vncache_mutex); 128 for (pvd = pfs_vncache; pvd; pvd = pvd->pvd_next) { 129 if (pvd->pvd_pn == pn && pvd->pvd_pid == pid && 130 pvd->pvd_vnode->v_mount == mp) { 131 vp = pvd->pvd_vnode; 132 VI_LOCK(vp); 133 mtx_unlock(&pfs_vncache_mutex); 134 if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK, curthread) == 0) { 135 ++pfs_vncache_hits; 136 *vpp = vp; 137 /* 138 * Some callers cache_enter(vp) later, so 139 * we have to make sure it's not in the 140 * VFS cache so it doesn't get entered 141 * twice. A better solution would be to 142 * make pfs_vncache_alloc() responsible 143 * for entering the vnode in the VFS 144 * cache. 145 */ 146 cache_purge(vp); 147 return (0); 148 } 149 goto retry; 150 } 151 } 152 mtx_unlock(&pfs_vncache_mutex); 153 154 /* nope, get a new one */ 155 pvd = malloc(sizeof *pvd, M_PFSVNCACHE, M_WAITOK); 156 pvd->pvd_next = pvd->pvd_prev = NULL; 157 error = getnewvnode("pseudofs", mp, &pfs_vnodeops, vpp); 158 if (error) { 159 free(pvd, M_PFSVNCACHE); 160 return (error); 161 } 162 pvd->pvd_pn = pn; 163 pvd->pvd_pid = pid; 164 (*vpp)->v_data = pvd; 165 switch (pn->pn_type) { 166 case pfstype_root: 167 (*vpp)->v_vflag = VV_ROOT; 168 #if 0 169 printf("root vnode allocated\n"); 170 #endif 171 /* fall through */ 172 case pfstype_dir: 173 case pfstype_this: 174 case pfstype_parent: 175 case pfstype_procdir: 176 (*vpp)->v_type = VDIR; 177 break; 178 case pfstype_file: 179 (*vpp)->v_type = VREG; 180 break; 181 case pfstype_symlink: 182 (*vpp)->v_type = VLNK; 183 break; 184 case pfstype_none: 185 KASSERT(0, ("pfs_vncache_alloc called for null node\n")); 186 default: 187 panic("%s has unexpected type: %d", pn->pn_name, pn->pn_type); 188 } 189 /* 190 * Propagate flag through to vnode so users know it can change 191 * if the process changes (i.e. execve) 192 */ 193 if ((pn->pn_flags & PFS_PROCDEP) != 0) 194 (*vpp)->v_vflag |= VV_PROCDEP; 195 pvd->pvd_vnode = *vpp; 196 vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY); 197 VN_LOCK_AREC(*vpp); 198 error = insmntque(*vpp, mp); 199 if (error != 0) { 200 free(pvd, M_PFSVNCACHE); 201 *vpp = NULLVP; 202 return (error); 203 } 204 retry2: 205 mtx_lock(&pfs_vncache_mutex); 206 /* 207 * Other thread may race with us, creating the entry we are 208 * going to insert into the cache. Recheck after 209 * pfs_vncache_mutex is reacquired. 210 */ 211 for (pvd2 = pfs_vncache; pvd2; pvd2 = pvd2->pvd_next) { 212 if (pvd2->pvd_pn == pn && pvd2->pvd_pid == pid && 213 pvd2->pvd_vnode->v_mount == mp) { 214 vp = pvd2->pvd_vnode; 215 VI_LOCK(vp); 216 mtx_unlock(&pfs_vncache_mutex); 217 if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK, curthread) == 0) { 218 ++pfs_vncache_hits; 219 vgone(*vpp); 220 vput(*vpp); 221 *vpp = vp; 222 cache_purge(vp); 223 return (0); 224 } 225 goto retry2; 226 } 227 } 228 ++pfs_vncache_misses; 229 if (++pfs_vncache_entries > pfs_vncache_maxentries) 230 pfs_vncache_maxentries = pfs_vncache_entries; 231 pvd->pvd_prev = NULL; 232 pvd->pvd_next = pfs_vncache; 233 if (pvd->pvd_next) 234 pvd->pvd_next->pvd_prev = pvd; 235 pfs_vncache = pvd; 236 mtx_unlock(&pfs_vncache_mutex); 237 return (0); 238 } 239 240 /* 241 * Free a vnode 242 */ 243 int 244 pfs_vncache_free(struct vnode *vp) 245 { 246 struct pfs_vdata *pvd; 247 248 mtx_lock(&pfs_vncache_mutex); 249 pvd = (struct pfs_vdata *)vp->v_data; 250 KASSERT(pvd != NULL, ("pfs_vncache_free(): no vnode data\n")); 251 if (pvd->pvd_next) 252 pvd->pvd_next->pvd_prev = pvd->pvd_prev; 253 if (pvd->pvd_prev) { 254 pvd->pvd_prev->pvd_next = pvd->pvd_next; 255 --pfs_vncache_entries; 256 } else if (pfs_vncache == pvd) { 257 pfs_vncache = pvd->pvd_next; 258 --pfs_vncache_entries; 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 * This is extremely inefficient due to the fact that vgone() not only 271 * indirectly modifies the vnode cache, but may also sleep. We can 272 * neither hold pfs_vncache_mutex across a vgone() call, nor make any 273 * assumptions about the state of the cache after vgone() returns. In 274 * consequence, we must start over after every vgone() call, and keep 275 * trying until we manage to traverse the entire cache. 276 * 277 * The only way to improve this situation is to change the data structure 278 * used to implement the cache. 279 */ 280 static void 281 pfs_purge_locked(struct pfs_node *pn, bool force) 282 { 283 struct pfs_vdata *pvd; 284 struct vnode *vnp; 285 286 mtx_assert(&pfs_vncache_mutex, MA_OWNED); 287 pvd = pfs_vncache; 288 while (pvd != NULL) { 289 if (force || pvd->pvd_dead || 290 (pn != NULL && pvd->pvd_pn == pn)) { 291 vnp = pvd->pvd_vnode; 292 vhold(vnp); 293 mtx_unlock(&pfs_vncache_mutex); 294 VOP_LOCK(vnp, LK_EXCLUSIVE); 295 vgone(vnp); 296 VOP_UNLOCK(vnp, 0); 297 mtx_lock(&pfs_vncache_mutex); 298 vdrop(vnp); 299 pvd = pfs_vncache; 300 } else { 301 pvd = pvd->pvd_next; 302 } 303 } 304 } 305 306 void 307 pfs_purge(struct pfs_node *pn) 308 { 309 310 mtx_lock(&pfs_vncache_mutex); 311 pfs_purge_locked(pn, false); 312 mtx_unlock(&pfs_vncache_mutex); 313 } 314 315 /* 316 * Free all vnodes associated with a defunct process 317 */ 318 static void 319 pfs_exit(void *arg, struct proc *p) 320 { 321 struct pfs_vdata *pvd; 322 int dead; 323 324 if (pfs_vncache == NULL) 325 return; 326 mtx_lock(&pfs_vncache_mutex); 327 for (pvd = pfs_vncache, dead = 0; pvd != NULL; pvd = pvd->pvd_next) 328 if (pvd->pvd_pid == p->p_pid) 329 dead = pvd->pvd_dead = 1; 330 if (dead) 331 pfs_purge_locked(NULL, false); 332 mtx_unlock(&pfs_vncache_mutex); 333 } 334