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 }
Cache object: 4fc4d065f05a357eda280c7dbf31fb1b
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