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