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/6.0/sys/fs/nullfs/null_subr.c 144904 2005-04-11 11:17:20Z jeff $
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 free(null_node_hashtbl, M_NULLFSHASH);
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 thread *td = curthread; /* XXX */
107 struct null_node_hashhead *hd;
108 struct null_node *a;
109 struct vnode *vp;
110
111 /*
112 * Find hash base, and then search the (two-way) linked
113 * list looking for a null_node structure which is referencing
114 * the lower vnode. If found, the increment the null_node
115 * reference count (but NOT the lower vnode's VREF counter).
116 */
117 hd = NULL_NHASH(lowervp);
118 loop:
119 mtx_lock(&null_hashmtx);
120 LIST_FOREACH(a, hd, null_hash) {
121 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
122 vp = NULLTOV(a);
123 VI_LOCK(vp);
124 /*
125 * If the nullfs node is being recycled we have
126 * to wait until it finishes prior to scanning
127 * again.
128 */
129 mtx_unlock(&null_hashmtx);
130 if ((vp->v_iflag & VI_DOOMED) != 0) {
131 /* Wait for recycling to finish. */
132 VOP_LOCK(vp, LK_EXCLUSIVE|LK_INTERLOCK, td);
133 VOP_UNLOCK(vp, 0, td);
134 goto loop;
135 }
136 /*
137 * We need to clear the OWEINACT flag here as this
138 * may lead vget() to try to lock our vnode which
139 * is already locked via lowervp.
140 */
141 vp->v_iflag &= ~VI_OWEINACT;
142 vget(vp, LK_INTERLOCK, td);
143 return (vp);
144 }
145 }
146 mtx_unlock(&null_hashmtx);
147 return (NULLVP);
148 }
149
150 /*
151 * Act like null_hashget, but add passed null_node to hash if no existing
152 * node found.
153 */
154 static struct vnode *
155 null_hashins(mp, xp)
156 struct mount *mp;
157 struct null_node *xp;
158 {
159 struct thread *td = curthread; /* XXX */
160 struct null_node_hashhead *hd;
161 struct null_node *oxp;
162 struct vnode *ovp;
163
164 hd = NULL_NHASH(xp->null_lowervp);
165 loop:
166 mtx_lock(&null_hashmtx);
167 LIST_FOREACH(oxp, hd, null_hash) {
168 if (oxp->null_lowervp == xp->null_lowervp &&
169 NULLTOV(oxp)->v_mount == mp) {
170 ovp = NULLTOV(oxp);
171 VI_LOCK(ovp);
172 /*
173 * If the nullfs node is being recycled we have
174 * to wait until it finishes prior to scanning
175 * again.
176 */
177 mtx_unlock(&null_hashmtx);
178 if ((ovp->v_iflag & VI_DOOMED) != 0) {
179 VOP_LOCK(ovp, LK_EXCLUSIVE|LK_INTERLOCK, td);
180 VOP_UNLOCK(ovp, 0, td);
181 goto loop;
182 }
183 ovp->v_iflag &= ~VI_OWEINACT; /* see hashget comment */
184 vget(ovp, LK_INTERLOCK, td);
185 return (ovp);
186 }
187 }
188 LIST_INSERT_HEAD(hd, xp, null_hash);
189 mtx_unlock(&null_hashmtx);
190 return (NULLVP);
191 }
192
193 /*
194 * Make a new or get existing nullfs node.
195 * Vp is the alias vnode, lowervp is the lower vnode.
196 *
197 * The lowervp assumed to be locked and having "spare" reference. This routine
198 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers"
199 * the caller's "spare" reference to created nullfs vnode.
200 */
201 int
202 null_nodeget(mp, lowervp, vpp)
203 struct mount *mp;
204 struct vnode *lowervp;
205 struct vnode **vpp;
206 {
207 struct null_node *xp;
208 struct vnode *vp;
209 int error;
210
211 /* Lookup the hash firstly */
212 *vpp = null_hashget(mp, lowervp);
213 if (*vpp != NULL) {
214 vrele(lowervp);
215 return (0);
216 }
217
218 /*
219 * We do not serialize vnode creation, instead we will check for
220 * duplicates later, when adding new vnode to hash.
221 *
222 * Note that duplicate can only appear in hash if the lowervp is
223 * locked LK_SHARED.
224 */
225
226 /*
227 * Do the MALLOC before the getnewvnode since doing so afterward
228 * might cause a bogus v_data pointer to get dereferenced
229 * elsewhere if MALLOC should block.
230 */
231 MALLOC(xp, struct null_node *, sizeof(struct null_node),
232 M_NULLFSNODE, M_WAITOK);
233
234 error = getnewvnode("null", mp, &null_vnodeops, &vp);
235 if (error) {
236 FREE(xp, M_NULLFSNODE);
237 return (error);
238 }
239
240 xp->null_vnode = vp;
241 xp->null_lowervp = lowervp;
242 vp->v_type = lowervp->v_type;
243 vp->v_data = xp;
244 vp->v_vnlock = lowervp->v_vnlock;
245 if (vp->v_vnlock == NULL)
246 panic("null_nodeget: Passed a NULL vnlock.\n");
247 /*
248 * Atomically insert our new node into the hash or vget existing
249 * if someone else has beaten us to it.
250 */
251 *vpp = null_hashins(mp, xp);
252 if (*vpp != NULL) {
253 vrele(lowervp);
254 vp->v_vnlock = &vp->v_lock;
255 xp->null_lowervp = NULL;
256 vrele(vp);
257 return (0);
258 }
259 *vpp = vp;
260
261 return (0);
262 }
263
264 /*
265 * Remove node from hash.
266 */
267 void
268 null_hashrem(xp)
269 struct null_node *xp;
270 {
271
272 mtx_lock(&null_hashmtx);
273 LIST_REMOVE(xp, null_hash);
274 mtx_unlock(&null_hashmtx);
275 }
276
277 #ifdef DIAGNOSTIC
278
279 #ifdef KDB
280 #define null_checkvp_barrier 1
281 #else
282 #define null_checkvp_barrier 0
283 #endif
284
285 struct vnode *
286 null_checkvp(vp, fil, lno)
287 struct vnode *vp;
288 char *fil;
289 int lno;
290 {
291 struct null_node *a = VTONULL(vp);
292 #ifdef notyet
293 /*
294 * Can't do this check because vop_reclaim runs
295 * with a funny vop vector.
296 */
297 if (vp->v_op != null_vnodeop_p) {
298 printf ("null_checkvp: on non-null-node\n");
299 while (null_checkvp_barrier) /*WAIT*/ ;
300 panic("null_checkvp");
301 };
302 #endif
303 if (a->null_lowervp == NULLVP) {
304 /* Should never happen */
305 int i; u_long *p;
306 printf("vp = %p, ZERO ptr\n", (void *)vp);
307 for (p = (u_long *) a, i = 0; i < 8; i++)
308 printf(" %lx", p[i]);
309 printf("\n");
310 /* wait for debugger */
311 while (null_checkvp_barrier) /*WAIT*/ ;
312 panic("null_checkvp");
313 }
314 if (vrefcnt(a->null_lowervp) < 1) {
315 int i; u_long *p;
316 printf("vp = %p, unref'ed lowervp\n", (void *)vp);
317 for (p = (u_long *) a, i = 0; i < 8; i++)
318 printf(" %lx", p[i]);
319 printf("\n");
320 /* wait for debugger */
321 while (null_checkvp_barrier) /*WAIT*/ ;
322 panic ("null with unref'ed lowervp");
323 };
324 #ifdef notyet
325 printf("null %x/%d -> %x/%d [%s, %d]\n",
326 NULLTOV(a), vrefcnt(NULLTOV(a)),
327 a->null_lowervp, vrefcnt(a->null_lowervp),
328 fil, lno);
329 #endif
330 return a->null_lowervp;
331 }
332 #endif
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