1 /*-
2 * Copyright (c) 2001 Dag-Erling Coïdan Smørgrav
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer
10 * in this position and unchanged.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. The name of the author may not be used to endorse or promote products
15 * derived from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD: releng/6.4/sys/fs/pseudofs/pseudofs_vncache.c 170191 2007-06-01 20:56:18Z des $");
31
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 struct pfs_vdata *pfs_vncache;
52 static eventhandler_tag pfs_exit_tag;
53 static void pfs_exit(void *arg, struct proc *p);
54
55 SYSCTL_NODE(_vfs_pfs, OID_AUTO, vncache, CTLFLAG_RW, 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
80 /*
81 * Initialize vnode cache
82 */
83 void
84 pfs_vncache_load(void)
85 {
86
87 mtx_assert(&Giant, MA_OWNED);
88 mtx_init(&pfs_vncache_mutex, "pfs_vncache", NULL, MTX_DEF);
89 pfs_exit_tag = EVENTHANDLER_REGISTER(process_exit, pfs_exit, NULL,
90 EVENTHANDLER_PRI_ANY);
91 }
92
93 /*
94 * Tear down vnode cache
95 */
96 void
97 pfs_vncache_unload(void)
98 {
99
100 mtx_assert(&Giant, MA_OWNED);
101 EVENTHANDLER_DEREGISTER(process_exit, pfs_exit_tag);
102 KASSERT(pfs_vncache_entries == 0,
103 ("%d vncache entries remaining", pfs_vncache_entries));
104 mtx_destroy(&pfs_vncache_mutex);
105 }
106
107 /*
108 * Allocate a vnode
109 */
110 int
111 pfs_vncache_alloc(struct mount *mp, struct vnode **vpp,
112 struct pfs_node *pn, pid_t pid)
113 {
114 struct pfs_vdata *pvd;
115 struct vnode *vp;
116 int error;
117
118 /*
119 * See if the vnode is in the cache.
120 * XXX linear search is not very efficient.
121 */
122 retry:
123 mtx_lock(&pfs_vncache_mutex);
124 for (pvd = pfs_vncache; pvd; pvd = pvd->pvd_next) {
125 if (pvd->pvd_pn == pn && pvd->pvd_pid == pid &&
126 pvd->pvd_vnode->v_mount == mp) {
127 vp = pvd->pvd_vnode;
128 VI_LOCK(vp);
129 mtx_unlock(&pfs_vncache_mutex);
130 if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK, curthread) == 0) {
131 ++pfs_vncache_hits;
132 *vpp = vp;
133 /*
134 * Some callers cache_enter(vp) later, so
135 * we have to make sure it's not in the
136 * VFS cache so it doesn't get entered
137 * twice. A better solution would be to
138 * make pfs_vncache_alloc() responsible
139 * for entering the vnode in the VFS
140 * cache.
141 */
142 cache_purge(vp);
143 return (0);
144 }
145 goto retry;
146 }
147 }
148 mtx_unlock(&pfs_vncache_mutex);
149 ++pfs_vncache_misses;
150
151 /* nope, get a new one */
152 MALLOC(pvd, struct pfs_vdata *, sizeof *pvd, M_PFSVNCACHE, M_WAITOK);
153 if (++pfs_vncache_entries > pfs_vncache_maxentries)
154 pfs_vncache_maxentries = pfs_vncache_entries;
155 error = getnewvnode("pseudofs", mp, &pfs_vnodeops, vpp);
156 if (error) {
157 FREE(pvd, M_PFSVNCACHE);
158 return (error);
159 }
160 pvd->pvd_pn = pn;
161 pvd->pvd_pid = pid;
162 (*vpp)->v_data = pvd;
163 switch (pn->pn_type) {
164 case pfstype_root:
165 (*vpp)->v_vflag = VV_ROOT;
166 #if 0
167 printf("root vnode allocated\n");
168 #endif
169 /* fall through */
170 case pfstype_dir:
171 case pfstype_this:
172 case pfstype_parent:
173 case pfstype_procdir:
174 (*vpp)->v_type = VDIR;
175 break;
176 case pfstype_file:
177 (*vpp)->v_type = VREG;
178 break;
179 case pfstype_symlink:
180 (*vpp)->v_type = VLNK;
181 break;
182 case pfstype_none:
183 KASSERT(0, ("pfs_vncache_alloc called for null node\n"));
184 default:
185 panic("%s has unexpected type: %d", pn->pn_name, pn->pn_type);
186 }
187 /*
188 * Propagate flag through to vnode so users know it can change
189 * if the process changes (i.e. execve)
190 */
191 if ((pn->pn_flags & PFS_PROCDEP) != 0)
192 (*vpp)->v_vflag |= VV_PROCDEP;
193 pvd->pvd_vnode = *vpp;
194 mtx_lock(&pfs_vncache_mutex);
195 pvd->pvd_prev = NULL;
196 pvd->pvd_next = pfs_vncache;
197 if (pvd->pvd_next)
198 pvd->pvd_next->pvd_prev = pvd;
199 pfs_vncache = pvd;
200 mtx_unlock(&pfs_vncache_mutex);
201 (*vpp)->v_vnlock->lk_flags |= LK_CANRECURSE;
202 vn_lock(*vpp, LK_RETRY | LK_EXCLUSIVE, curthread);
203 return (0);
204 }
205
206 /*
207 * Free a vnode
208 */
209 int
210 pfs_vncache_free(struct vnode *vp)
211 {
212 struct pfs_vdata *pvd;
213
214 mtx_lock(&pfs_vncache_mutex);
215 pvd = (struct pfs_vdata *)vp->v_data;
216 KASSERT(pvd != NULL, ("pfs_vncache_free(): no vnode data\n"));
217 if (pvd->pvd_next)
218 pvd->pvd_next->pvd_prev = pvd->pvd_prev;
219 if (pvd->pvd_prev)
220 pvd->pvd_prev->pvd_next = pvd->pvd_next;
221 else
222 pfs_vncache = pvd->pvd_next;
223 mtx_unlock(&pfs_vncache_mutex);
224
225 --pfs_vncache_entries;
226 FREE(pvd, M_PFSVNCACHE);
227 vp->v_data = NULL;
228 return (0);
229 }
230
231 /*
232 * Purge the cache of dead / disabled entries
233 *
234 * This is extremely inefficient due to the fact that vgone() not only
235 * indirectly modifies the vnode cache, but may also sleep. We can
236 * neither hold pfs_vncache_mutex across a vgone() call, nor make any
237 * assumptions about the state of the cache after vgone() returns. In
238 * consequence, we must start over after every vgone() call, and keep
239 * trying until we manage to traverse the entire cache.
240 *
241 * The only way to improve this situation is to change the data structure
242 * used to implement the cache.
243 */
244 void
245 pfs_purge(struct pfs_node *pn)
246 {
247 struct pfs_vdata *pvd;
248 struct vnode *vnp;
249
250 mtx_lock(&pfs_vncache_mutex);
251 pvd = pfs_vncache;
252 while (pvd != NULL) {
253 if (pvd->pvd_dead || (pn != NULL && pvd->pvd_pn == pn)) {
254 vnp = pvd->pvd_vnode;
255 vhold(vnp);
256 mtx_unlock(&pfs_vncache_mutex);
257 VOP_LOCK(vnp, LK_EXCLUSIVE, curthread);
258 vgone(vnp);
259 VOP_UNLOCK(vnp, 0, curthread);
260 vdrop(vnp);
261 mtx_lock(&pfs_vncache_mutex);
262 pvd = pfs_vncache;
263 } else {
264 pvd = pvd->pvd_next;
265 }
266 }
267 mtx_unlock(&pfs_vncache_mutex);
268 }
269
270 /*
271 * Free all vnodes associated with a defunct process
272 *
273 * XXXRW: It is unfortunate that pfs_exit() always acquires and releases two
274 * mutexes (one of which is Giant) for every process exit, even if procfs
275 * isn't mounted.
276 */
277 static void
278 pfs_exit(void *arg, struct proc *p)
279 {
280 struct pfs_vdata *pvd;
281 int dead;
282
283 if (pfs_vncache == NULL)
284 return;
285 mtx_lock(&Giant);
286 mtx_lock(&pfs_vncache_mutex);
287 for (pvd = pfs_vncache, dead = 0; pvd != NULL; pvd = pvd->pvd_next)
288 if (pvd->pvd_pid == p->p_pid)
289 dead = pvd->pvd_dead = 1;
290 mtx_unlock(&pfs_vncache_mutex);
291 if (dead)
292 pfs_purge(NULL);
293 mtx_unlock(&Giant);
294 }
295
296 /*
297 * Disable a pseudofs node, and free all vnodes associated with it
298 */
299 int
300 pfs_disable(struct pfs_node *pn)
301 {
302 if (pn->pn_flags & PFS_DISABLED)
303 return (0);
304 pn->pn_flags |= PFS_DISABLED;
305 pfs_purge(pn);
306 return (0);
307 }
308
309 /*
310 * Re-enable a disabled pseudofs node
311 */
312 int
313 pfs_enable(struct pfs_node *pn)
314 {
315 pn->pn_flags &= ~PFS_DISABLED;
316 return (0);
317 }
Cache object: 7219e3a18fd2bff7fe9fc009f72b38ef
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