xref: /freebsd/sys/fs/pseudofs/pseudofs_vncache.c (revision f856af0466c076beef4ea9b15d088e1119a945b8)
1 /*-
2  * Copyright (c) 2001 Dag-Erling Co�dan Sm�rgrav
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("$FreeBSD$");
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 	mtx_init(&pfs_vncache_mutex, "pseudofs_vncache", NULL, MTX_DEF);
87 	pfs_exit_tag = EVENTHANDLER_REGISTER(process_exit, pfs_exit, NULL,
88 	    EVENTHANDLER_PRI_ANY);
89 }
90 
91 /*
92  * Tear down vnode cache
93  */
94 void
95 pfs_vncache_unload(void)
96 {
97 	EVENTHANDLER_DEREGISTER(process_exit, pfs_exit_tag);
98 	if (pfs_vncache_entries != 0)
99 		printf("pfs_vncache_unload(): %d entries remaining\n",
100 		    pfs_vncache_entries);
101 	mtx_destroy(&pfs_vncache_mutex);
102 }
103 
104 /*
105  * Allocate a vnode
106  */
107 int
108 pfs_vncache_alloc(struct mount *mp, struct vnode **vpp,
109 		  struct pfs_node *pn, pid_t pid)
110 {
111 	struct pfs_vdata *pvd;
112 	struct vnode *vp;
113 	int error;
114 
115 	/*
116 	 * See if the vnode is in the cache.
117 	 * XXX linear search is not very efficient.
118 	 */
119 retry:
120 	mtx_lock(&pfs_vncache_mutex);
121 	for (pvd = pfs_vncache; pvd; pvd = pvd->pvd_next) {
122 		if (pvd->pvd_pn == pn && pvd->pvd_pid == pid &&
123 		    pvd->pvd_vnode->v_mount == mp) {
124 			vp = pvd->pvd_vnode;
125 			VI_LOCK(vp);
126 			mtx_unlock(&pfs_vncache_mutex);
127 			if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK, curthread) == 0) {
128 				++pfs_vncache_hits;
129 				*vpp = vp;
130 				/* XXX see comment at top of pfs_lookup() */
131 				cache_purge(vp);
132 				return (0);
133 			}
134 			goto retry;
135 		}
136 	}
137 	mtx_unlock(&pfs_vncache_mutex);
138 	++pfs_vncache_misses;
139 
140 	/* nope, get a new one */
141 	MALLOC(pvd, struct pfs_vdata *, sizeof *pvd, M_PFSVNCACHE, M_WAITOK);
142 	if (++pfs_vncache_entries > pfs_vncache_maxentries)
143 		pfs_vncache_maxentries = pfs_vncache_entries;
144 	error = getnewvnode("pseudofs", mp, &pfs_vnodeops, vpp);
145 	if (error) {
146 		FREE(pvd, M_PFSVNCACHE);
147 		return (error);
148 	}
149 	pvd->pvd_pn = pn;
150 	pvd->pvd_pid = pid;
151 	(*vpp)->v_data = pvd;
152 	switch (pn->pn_type) {
153 	case pfstype_root:
154 		(*vpp)->v_vflag = VV_ROOT;
155 #if 0
156 		printf("root vnode allocated\n");
157 #endif
158 		/* fall through */
159 	case pfstype_dir:
160 	case pfstype_this:
161 	case pfstype_parent:
162 	case pfstype_procdir:
163 		(*vpp)->v_type = VDIR;
164 		break;
165 	case pfstype_file:
166 		(*vpp)->v_type = VREG;
167 		break;
168 	case pfstype_symlink:
169 		(*vpp)->v_type = VLNK;
170 		break;
171 	case pfstype_none:
172 		KASSERT(0, ("pfs_vncache_alloc called for null node\n"));
173 	default:
174 		panic("%s has unexpected type: %d", pn->pn_name, pn->pn_type);
175 	}
176 	/*
177 	 * Propagate flag through to vnode so users know it can change
178 	 * if the process changes (i.e. execve)
179 	 */
180 	if ((pn->pn_flags & PFS_PROCDEP) != 0)
181 		(*vpp)->v_vflag |= VV_PROCDEP;
182 	pvd->pvd_vnode = *vpp;
183 	mtx_lock(&pfs_vncache_mutex);
184 	pvd->pvd_prev = NULL;
185 	pvd->pvd_next = pfs_vncache;
186 	if (pvd->pvd_next)
187 		pvd->pvd_next->pvd_prev = pvd;
188 	pfs_vncache = pvd;
189 	mtx_unlock(&pfs_vncache_mutex);
190         (*vpp)->v_vnlock->lk_flags |= LK_CANRECURSE;
191 	vn_lock(*vpp, LK_RETRY | LK_EXCLUSIVE, curthread);
192 	return (0);
193 }
194 
195 /*
196  * Free a vnode
197  */
198 int
199 pfs_vncache_free(struct vnode *vp)
200 {
201 	struct pfs_vdata *pvd;
202 
203 	mtx_lock(&pfs_vncache_mutex);
204 	pvd = (struct pfs_vdata *)vp->v_data;
205 	KASSERT(pvd != NULL, ("pfs_vncache_free(): no vnode data\n"));
206 	if (pvd->pvd_next)
207 		pvd->pvd_next->pvd_prev = pvd->pvd_prev;
208 	if (pvd->pvd_prev)
209 		pvd->pvd_prev->pvd_next = pvd->pvd_next;
210 	else
211 		pfs_vncache = pvd->pvd_next;
212 	mtx_unlock(&pfs_vncache_mutex);
213 
214 	--pfs_vncache_entries;
215 	FREE(pvd, M_PFSVNCACHE);
216 	vp->v_data = NULL;
217 	return (0);
218 }
219 
220 /*
221  * Free all vnodes associated with a defunct process
222  *
223  * XXXRW: It is unfortunate that pfs_exit() always acquires and releases two
224  * mutexes (one of which is Giant) for every process exit, even if procfs
225  * isn't mounted.
226  */
227 static void
228 pfs_exit(void *arg, struct proc *p)
229 {
230 	struct pfs_vdata *pvd;
231 	struct vnode *vnp;
232 
233 	if (pfs_vncache == NULL)
234 		return;
235 	mtx_lock(&Giant);
236 	/*
237 	 * This is extremely inefficient due to the fact that vgone() not
238 	 * only indirectly modifies the vnode cache, but may also sleep.
239 	 * We can neither hold pfs_vncache_mutex across a vgone() call,
240 	 * nor make any assumptions about the state of the cache after
241 	 * vgone() returns.  In consequence, we must start over after
242 	 * every vgone() call, and keep trying until we manage to traverse
243 	 * the entire cache.
244 	 *
245 	 * The only way to improve this situation is to change the data
246 	 * structure used to implement the cache.  An obvious choice in
247 	 * this particular case would be a BST sorted by PID.
248 	 */
249 	mtx_lock(&pfs_vncache_mutex);
250 	pvd = pfs_vncache;
251 	while (pvd != NULL) {
252 		if (pvd->pvd_pid == p->p_pid) {
253 			vnp = pvd->pvd_vnode;
254 			vhold(vnp);
255 			mtx_unlock(&pfs_vncache_mutex);
256 			VOP_LOCK(vnp, LK_EXCLUSIVE, curthread);
257 			vgone(vnp);
258 			VOP_UNLOCK(vnp, 0, curthread);
259 			vdrop(vnp);
260 			mtx_lock(&pfs_vncache_mutex);
261 			pvd = pfs_vncache;
262 		} else {
263 			pvd = pvd->pvd_next;
264 		}
265 	}
266 	mtx_unlock(&pfs_vncache_mutex);
267 	mtx_unlock(&Giant);
268 }
269 
270 /*
271  * Disable a pseudofs node, and free all vnodes associated with it
272  */
273 int
274 pfs_disable(struct pfs_node *pn)
275 {
276 	struct pfs_vdata *pvd;
277 	struct vnode *vnp;
278 
279 	if (pn->pn_flags & PFS_DISABLED)
280 		return (0);
281 	pn->pn_flags |= PFS_DISABLED;
282 	/* XXX see comment above nearly identical code in pfs_exit() */
283 	mtx_lock(&pfs_vncache_mutex);
284 	pvd = pfs_vncache;
285 	while (pvd != NULL) {
286 		if (pvd->pvd_pn == pn) {
287 			vnp = pvd->pvd_vnode;
288 			vhold(vnp);
289 			mtx_unlock(&pfs_vncache_mutex);
290 			VOP_LOCK(vnp, LK_EXCLUSIVE, curthread);
291 			vgone(vnp);
292 			VOP_UNLOCK(vnp, 0, curthread);
293 			vdrop(vnp);
294 			mtx_lock(&pfs_vncache_mutex);
295 			pvd = pfs_vncache;
296 		} else {
297 			pvd = pvd->pvd_next;
298 		}
299 	}
300 	mtx_unlock(&pfs_vncache_mutex);
301 	return (0);
302 }
303 
304 /*
305  * Re-enable a disabled pseudofs node
306  */
307 int
308 pfs_enable(struct pfs_node *pn)
309 {
310 	pn->pn_flags &= ~PFS_DISABLED;
311 	return (0);
312 }
313