1 /*-
2 * Copyright (c) 1992, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software donated to Berkeley by
6 * Jan-Simon Pendry.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
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 * 4. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * @(#)null_subr.c 8.7 (Berkeley) 5/14/95
33 *
34 * $FreeBSD: releng/8.4/sys/fs/nullfs/null_subr.c 232665 2012-03-07 18:33:11Z kib $
35 */
36
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/kernel.h>
40 #include <sys/lock.h>
41 #include <sys/mutex.h>
42 #include <sys/malloc.h>
43 #include <sys/mount.h>
44 #include <sys/proc.h>
45 #include <sys/vnode.h>
46
47 #include <fs/nullfs/null.h>
48
49 #define LOG2_SIZEVNODE 8 /* log2(sizeof struct vnode) */
50 #define NNULLNODECACHE 16
51
52 /*
53 * Null layer cache:
54 * Each cache entry holds a reference to the lower vnode
55 * along with a pointer to the alias vnode. When an
56 * entry is added the lower vnode is VREF'd. When the
57 * alias is removed the lower vnode is vrele'd.
58 */
59
60 #define NULL_NHASH(vp) \
61 (&null_node_hashtbl[(((uintptr_t)vp)>>LOG2_SIZEVNODE) & null_node_hash])
62
63 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
64 static u_long null_node_hash;
65 struct mtx null_hashmtx;
66
67 static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table");
68 MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part");
69
70 static struct vnode * null_hashget(struct mount *, struct vnode *);
71 static struct vnode * null_hashins(struct mount *, struct null_node *);
72
73 /*
74 * Initialise cache headers
75 */
76 int
77 nullfs_init(vfsp)
78 struct vfsconf *vfsp;
79 {
80
81 NULLFSDEBUG("nullfs_init\n"); /* printed during system boot */
82 null_node_hashtbl = hashinit(NNULLNODECACHE, M_NULLFSHASH, &null_node_hash);
83 mtx_init(&null_hashmtx, "nullhs", NULL, MTX_DEF);
84 return (0);
85 }
86
87 int
88 nullfs_uninit(vfsp)
89 struct vfsconf *vfsp;
90 {
91
92 mtx_destroy(&null_hashmtx);
93 hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_node_hash);
94 return (0);
95 }
96
97 /*
98 * Return a VREF'ed alias for lower vnode if already exists, else 0.
99 * Lower vnode should be locked on entry and will be left locked on exit.
100 */
101 static struct vnode *
102 null_hashget(mp, lowervp)
103 struct mount *mp;
104 struct vnode *lowervp;
105 {
106 struct null_node_hashhead *hd;
107 struct null_node *a;
108 struct vnode *vp;
109
110 ASSERT_VOP_LOCKED(lowervp, "null_hashget");
111
112 /*
113 * Find hash base, and then search the (two-way) linked
114 * list looking for a null_node structure which is referencing
115 * the lower vnode. If found, the increment the null_node
116 * reference count (but NOT the lower vnode's VREF counter).
117 */
118 hd = NULL_NHASH(lowervp);
119 mtx_lock(&null_hashmtx);
120 LIST_FOREACH(a, hd, null_hash) {
121 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
122 /*
123 * Since we have the lower node locked the nullfs
124 * node can not be in the process of recycling. If
125 * it had been recycled before we grabed the lower
126 * lock it would not have been found on the hash.
127 */
128 vp = NULLTOV(a);
129 vref(vp);
130 mtx_unlock(&null_hashmtx);
131 return (vp);
132 }
133 }
134 mtx_unlock(&null_hashmtx);
135 return (NULLVP);
136 }
137
138 /*
139 * Act like null_hashget, but add passed null_node to hash if no existing
140 * node found.
141 */
142 static struct vnode *
143 null_hashins(mp, xp)
144 struct mount *mp;
145 struct null_node *xp;
146 {
147 struct null_node_hashhead *hd;
148 struct null_node *oxp;
149 struct vnode *ovp;
150
151 hd = NULL_NHASH(xp->null_lowervp);
152 mtx_lock(&null_hashmtx);
153 LIST_FOREACH(oxp, hd, null_hash) {
154 if (oxp->null_lowervp == xp->null_lowervp &&
155 NULLTOV(oxp)->v_mount == mp) {
156 /*
157 * See null_hashget for a description of this
158 * operation.
159 */
160 ovp = NULLTOV(oxp);
161 vref(ovp);
162 mtx_unlock(&null_hashmtx);
163 return (ovp);
164 }
165 }
166 LIST_INSERT_HEAD(hd, xp, null_hash);
167 mtx_unlock(&null_hashmtx);
168 return (NULLVP);
169 }
170
171 static void
172 null_destroy_proto(struct vnode *vp, void *xp)
173 {
174
175 lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
176 VI_LOCK(vp);
177 vp->v_data = NULL;
178 vp->v_vnlock = &vp->v_lock;
179 vp->v_op = &dead_vnodeops;
180 VI_UNLOCK(vp);
181 vgone(vp);
182 vput(vp);
183 free(xp, M_NULLFSNODE);
184 }
185
186 static void
187 null_insmntque_dtr(struct vnode *vp, void *xp)
188 {
189
190 vput(((struct null_node *)xp)->null_lowervp);
191 null_destroy_proto(vp, xp);
192 }
193
194 /*
195 * Make a new or get existing nullfs node.
196 * Vp is the alias vnode, lowervp is the lower vnode.
197 *
198 * The lowervp assumed to be locked and having "spare" reference. This routine
199 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers"
200 * the caller's "spare" reference to created nullfs vnode.
201 */
202 int
203 null_nodeget(mp, lowervp, vpp)
204 struct mount *mp;
205 struct vnode *lowervp;
206 struct vnode **vpp;
207 {
208 struct null_node *xp;
209 struct vnode *vp;
210 int error;
211
212 /*
213 * The insmntque1() call below requires the exclusive lock on
214 * the nullfs vnode.
215 */
216 ASSERT_VOP_ELOCKED(lowervp, "lowervp");
217 KASSERT(lowervp->v_usecount >= 1, ("Unreferenced vnode %p\n", lowervp));
218
219 /* Lookup the hash firstly */
220 *vpp = null_hashget(mp, lowervp);
221 if (*vpp != NULL) {
222 vrele(lowervp);
223 return (0);
224 }
225
226 /*
227 * We do not serialize vnode creation, instead we will check for
228 * duplicates later, when adding new vnode to hash.
229 * Note that duplicate can only appear in hash if the lowervp is
230 * locked LK_SHARED.
231 *
232 * Do the MALLOC before the getnewvnode since doing so afterward
233 * might cause a bogus v_data pointer to get dereferenced
234 * elsewhere if MALLOC should block.
235 */
236 xp = malloc(sizeof(struct null_node),
237 M_NULLFSNODE, M_WAITOK);
238
239 error = getnewvnode("null", mp, &null_vnodeops, &vp);
240 if (error) {
241 vput(lowervp);
242 free(xp, M_NULLFSNODE);
243 return (error);
244 }
245
246 xp->null_vnode = vp;
247 xp->null_lowervp = lowervp;
248 vp->v_type = lowervp->v_type;
249 vp->v_data = xp;
250 vp->v_vnlock = lowervp->v_vnlock;
251 if (vp->v_vnlock == NULL)
252 panic("null_nodeget: Passed a NULL vnlock.\n");
253 error = insmntque1(vp, mp, null_insmntque_dtr, xp);
254 if (error != 0)
255 return (error);
256 /*
257 * Atomically insert our new node into the hash or vget existing
258 * if someone else has beaten us to it.
259 */
260 *vpp = null_hashins(mp, xp);
261 if (*vpp != NULL) {
262 vrele(lowervp);
263 null_destroy_proto(vp, xp);
264 return (0);
265 }
266 *vpp = vp;
267
268 return (0);
269 }
270
271 /*
272 * Remove node from hash.
273 */
274 void
275 null_hashrem(xp)
276 struct null_node *xp;
277 {
278
279 mtx_lock(&null_hashmtx);
280 LIST_REMOVE(xp, null_hash);
281 mtx_unlock(&null_hashmtx);
282 }
283
284 #ifdef DIAGNOSTIC
285
286 struct vnode *
287 null_checkvp(vp, fil, lno)
288 struct vnode *vp;
289 char *fil;
290 int lno;
291 {
292 struct null_node *a = VTONULL(vp);
293
294 #ifdef notyet
295 /*
296 * Can't do this check because vop_reclaim runs
297 * with a funny vop vector.
298 */
299 if (vp->v_op != null_vnodeop_p) {
300 printf ("null_checkvp: on non-null-node\n");
301 panic("null_checkvp");
302 }
303 #endif
304 if (a->null_lowervp == NULLVP) {
305 /* Should never happen */
306 panic("null_checkvp %p", vp);
307 }
308 VI_LOCK_FLAGS(a->null_lowervp, MTX_DUPOK);
309 if (a->null_lowervp->v_usecount < 1)
310 panic ("null with unref'ed lowervp, vp %p lvp %p",
311 vp, a->null_lowervp);
312 VI_UNLOCK(a->null_lowervp);
313 #ifdef notyet
314 printf("null %x/%d -> %x/%d [%s, %d]\n",
315 NULLTOV(a), vrefcnt(NULLTOV(a)),
316 a->null_lowervp, vrefcnt(a->null_lowervp),
317 fil, lno);
318 #endif
319 return (a->null_lowervp);
320 }
321 #endif
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