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/10.4/sys/fs/nullfs/null_subr.c 250505 2013-05-11 11:17:44Z 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 /*
50 * Null layer cache:
51 * Each cache entry holds a reference to the lower vnode
52 * along with a pointer to the alias vnode. When an
53 * entry is added the lower vnode is VREF'd. When the
54 * alias is removed the lower vnode is vrele'd.
55 */
56
57 #define NULL_NHASH(vp) (&null_node_hashtbl[vfs_hash_index(vp) & null_hash_mask])
58
59 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
60 static struct mtx null_hashmtx;
61 static u_long null_hash_mask;
62
63 static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table");
64 MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part");
65
66 static struct vnode * null_hashins(struct mount *, struct null_node *);
67
68 /*
69 * Initialise cache headers
70 */
71 int
72 nullfs_init(vfsp)
73 struct vfsconf *vfsp;
74 {
75
76 null_node_hashtbl = hashinit(desiredvnodes, M_NULLFSHASH,
77 &null_hash_mask);
78 mtx_init(&null_hashmtx, "nullhs", NULL, MTX_DEF);
79 return (0);
80 }
81
82 int
83 nullfs_uninit(vfsp)
84 struct vfsconf *vfsp;
85 {
86
87 mtx_destroy(&null_hashmtx);
88 hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_hash_mask);
89 return (0);
90 }
91
92 /*
93 * Return a VREF'ed alias for lower vnode if already exists, else 0.
94 * Lower vnode should be locked on entry and will be left locked on exit.
95 */
96 struct vnode *
97 null_hashget(mp, lowervp)
98 struct mount *mp;
99 struct vnode *lowervp;
100 {
101 struct null_node_hashhead *hd;
102 struct null_node *a;
103 struct vnode *vp;
104
105 ASSERT_VOP_LOCKED(lowervp, "null_hashget");
106
107 /*
108 * Find hash base, and then search the (two-way) linked
109 * list looking for a null_node structure which is referencing
110 * the lower vnode. If found, the increment the null_node
111 * reference count (but NOT the lower vnode's VREF counter).
112 */
113 hd = NULL_NHASH(lowervp);
114 mtx_lock(&null_hashmtx);
115 LIST_FOREACH(a, hd, null_hash) {
116 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
117 /*
118 * Since we have the lower node locked the nullfs
119 * node can not be in the process of recycling. If
120 * it had been recycled before we grabed the lower
121 * lock it would not have been found on the hash.
122 */
123 vp = NULLTOV(a);
124 vref(vp);
125 mtx_unlock(&null_hashmtx);
126 return (vp);
127 }
128 }
129 mtx_unlock(&null_hashmtx);
130 return (NULLVP);
131 }
132
133 /*
134 * Act like null_hashget, but add passed null_node to hash if no existing
135 * node found.
136 */
137 static struct vnode *
138 null_hashins(mp, xp)
139 struct mount *mp;
140 struct null_node *xp;
141 {
142 struct null_node_hashhead *hd;
143 struct null_node *oxp;
144 struct vnode *ovp;
145
146 hd = NULL_NHASH(xp->null_lowervp);
147 mtx_lock(&null_hashmtx);
148 LIST_FOREACH(oxp, hd, null_hash) {
149 if (oxp->null_lowervp == xp->null_lowervp &&
150 NULLTOV(oxp)->v_mount == mp) {
151 /*
152 * See null_hashget for a description of this
153 * operation.
154 */
155 ovp = NULLTOV(oxp);
156 vref(ovp);
157 mtx_unlock(&null_hashmtx);
158 return (ovp);
159 }
160 }
161 LIST_INSERT_HEAD(hd, xp, null_hash);
162 mtx_unlock(&null_hashmtx);
163 return (NULLVP);
164 }
165
166 static void
167 null_destroy_proto(struct vnode *vp, void *xp)
168 {
169
170 lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
171 VI_LOCK(vp);
172 vp->v_data = NULL;
173 vp->v_vnlock = &vp->v_lock;
174 vp->v_op = &dead_vnodeops;
175 VI_UNLOCK(vp);
176 vgone(vp);
177 vput(vp);
178 free(xp, M_NULLFSNODE);
179 }
180
181 static void
182 null_insmntque_dtr(struct vnode *vp, void *xp)
183 {
184
185 vput(((struct null_node *)xp)->null_lowervp);
186 null_destroy_proto(vp, xp);
187 }
188
189 /*
190 * Make a new or get existing nullfs node.
191 * Vp is the alias vnode, lowervp is the lower vnode.
192 *
193 * The lowervp assumed to be locked and having "spare" reference. This routine
194 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers"
195 * the caller's "spare" reference to created nullfs vnode.
196 */
197 int
198 null_nodeget(mp, lowervp, vpp)
199 struct mount *mp;
200 struct vnode *lowervp;
201 struct vnode **vpp;
202 {
203 struct null_node *xp;
204 struct vnode *vp;
205 int error;
206
207 ASSERT_VOP_LOCKED(lowervp, "lowervp");
208 KASSERT(lowervp->v_usecount >= 1, ("Unreferenced vnode %p", lowervp));
209
210 /* Lookup the hash firstly. */
211 *vpp = null_hashget(mp, lowervp);
212 if (*vpp != NULL) {
213 vrele(lowervp);
214 return (0);
215 }
216
217 /*
218 * The insmntque1() call below requires the exclusive lock on
219 * the nullfs vnode. Upgrade the lock now if hash failed to
220 * provide ready to use vnode.
221 */
222 if (VOP_ISLOCKED(lowervp) != LK_EXCLUSIVE) {
223 KASSERT((MOUNTTONULLMOUNT(mp)->nullm_flags & NULLM_CACHE) != 0,
224 ("lowervp %p is not excl locked and cache is disabled",
225 lowervp));
226 vn_lock(lowervp, LK_UPGRADE | LK_RETRY);
227 if ((lowervp->v_iflag & VI_DOOMED) != 0) {
228 vput(lowervp);
229 return (ENOENT);
230 }
231 }
232
233 /*
234 * We do not serialize vnode creation, instead we will check for
235 * duplicates later, when adding new vnode to hash.
236 * Note that duplicate can only appear in hash if the lowervp is
237 * locked LK_SHARED.
238 */
239 xp = malloc(sizeof(struct null_node), M_NULLFSNODE, M_WAITOK);
240
241 error = getnewvnode("null", mp, &null_vnodeops, &vp);
242 if (error) {
243 vput(lowervp);
244 free(xp, M_NULLFSNODE);
245 return (error);
246 }
247
248 xp->null_vnode = vp;
249 xp->null_lowervp = lowervp;
250 xp->null_flags = 0;
251 vp->v_type = lowervp->v_type;
252 vp->v_data = xp;
253 vp->v_vnlock = lowervp->v_vnlock;
254 error = insmntque1(vp, mp, null_insmntque_dtr, xp);
255 if (error != 0)
256 return (error);
257 /*
258 * Atomically insert our new node into the hash or vget existing
259 * if someone else has beaten us to it.
260 */
261 *vpp = null_hashins(mp, xp);
262 if (*vpp != NULL) {
263 vrele(lowervp);
264 null_destroy_proto(vp, xp);
265 return (0);
266 }
267 *vpp = vp;
268
269 return (0);
270 }
271
272 /*
273 * Remove node from hash.
274 */
275 void
276 null_hashrem(xp)
277 struct null_node *xp;
278 {
279
280 mtx_lock(&null_hashmtx);
281 LIST_REMOVE(xp, null_hash);
282 mtx_unlock(&null_hashmtx);
283 }
284
285 #ifdef DIAGNOSTIC
286
287 struct vnode *
288 null_checkvp(vp, fil, lno)
289 struct vnode *vp;
290 char *fil;
291 int lno;
292 {
293 struct null_node *a = VTONULL(vp);
294
295 #ifdef notyet
296 /*
297 * Can't do this check because vop_reclaim runs
298 * with a funny vop vector.
299 */
300 if (vp->v_op != null_vnodeop_p) {
301 printf ("null_checkvp: on non-null-node\n");
302 panic("null_checkvp");
303 }
304 #endif
305 if (a->null_lowervp == NULLVP) {
306 /* Should never happen */
307 panic("null_checkvp %p", vp);
308 }
309 VI_LOCK_FLAGS(a->null_lowervp, MTX_DUPOK);
310 if (a->null_lowervp->v_usecount < 1)
311 panic ("null with unref'ed lowervp, vp %p lvp %p",
312 vp, a->null_lowervp);
313 VI_UNLOCK(a->null_lowervp);
314 #ifdef notyet
315 printf("null %x/%d -> %x/%d [%s, %d]\n",
316 NULLTOV(a), vrefcnt(NULLTOV(a)),
317 a->null_lowervp, vrefcnt(a->null_lowervp),
318 fil, lno);
319 #endif
320 return (a->null_lowervp);
321 }
322 #endif
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