1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 2001 Dag-Erling 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 #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
48 static MALLOC_DEFINE(M_PFSVNCACHE, "pfs_vncache", "pseudofs vnode cache");
49
50 static struct mtx pfs_vncache_mutex;
51 static eventhandler_tag pfs_exit_tag;
52 static void pfs_exit(void *arg, struct proc *p);
53 static void pfs_purge_all(void);
54
55 static SYSCTL_NODE(_vfs_pfs, OID_AUTO, vncache, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
56 "pseudofs vnode cache");
57
58 static int pfs_vncache_entries;
59 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, entries, CTLFLAG_RD,
60 &pfs_vncache_entries, 0,
61 "number of entries in the vnode cache");
62
63 static int pfs_vncache_maxentries;
64 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, maxentries, CTLFLAG_RD,
65 &pfs_vncache_maxentries, 0,
66 "highest number of entries in the vnode cache");
67
68 static int pfs_vncache_hits;
69 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, hits, CTLFLAG_RD,
70 &pfs_vncache_hits, 0,
71 "number of cache hits since initialization");
72
73 static int pfs_vncache_misses;
74 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, misses, CTLFLAG_RD,
75 &pfs_vncache_misses, 0,
76 "number of cache misses since initialization");
77
78 extern struct vop_vector pfs_vnodeops; /* XXX -> .h file */
79
SLIST_HEAD(pfs_vncache_head,pfs_vdata)80 static SLIST_HEAD(pfs_vncache_head, pfs_vdata) *pfs_vncache_hashtbl;
81 static 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 */
87 void
88 pfs_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 */
100 void
pfs_vncache_unload(void)101 pfs_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 */
115 int
pfs_vncache_alloc(struct mount * mp,struct vnode ** vpp,struct pfs_node * pn,pid_t pid)116 pfs_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;
131 retry:
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);
158 alloc:
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);
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 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 */
244 int
pfs_vncache_free(struct vnode * vp)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
pfs_purge_one(struct vnode * vnp)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
pfs_purge(struct pfs_node * pn)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
pfs_purge_all(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
pfs_exit(void * arg,struct proc * p)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