FreeBSD/Linux Kernel Cross Reference
sys/kern/vfs_hash.c
1 /*-
2 * Copyright (c) 2005 Poul-Henning Kamp
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 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 */
27
28 #include <sys/cdefs.h>
29 __FBSDID("$FreeBSD: releng/10.4/sys/kern/vfs_hash.c 300140 2016-05-18 11:58:16Z kib $");
30
31 #include <sys/param.h>
32 #include <sys/systm.h>
33 #include <sys/kernel.h>
34 #include <sys/malloc.h>
35 #include <sys/mount.h>
36 #include <sys/vnode.h>
37
38 static MALLOC_DEFINE(M_VFS_HASH, "vfs_hash", "VFS hash table");
39
40 static LIST_HEAD(vfs_hash_head, vnode) *vfs_hash_tbl;
41 static LIST_HEAD(,vnode) vfs_hash_side;
42 static u_long vfs_hash_mask;
43 static struct mtx vfs_hash_mtx;
44
45 static void
46 vfs_hashinit(void *dummy __unused)
47 {
48
49 vfs_hash_tbl = hashinit(desiredvnodes, M_VFS_HASH, &vfs_hash_mask);
50 mtx_init(&vfs_hash_mtx, "vfs hash", NULL, MTX_DEF);
51 LIST_INIT(&vfs_hash_side);
52 }
53
54 /* Must be SI_ORDER_SECOND so desiredvnodes is available */
55 SYSINIT(vfs_hash, SI_SUB_VFS, SI_ORDER_SECOND, vfs_hashinit, NULL);
56
57 u_int
58 vfs_hash_index(struct vnode *vp)
59 {
60
61 return (vp->v_hash + vp->v_mount->mnt_hashseed);
62 }
63
64 static struct vfs_hash_head *
65 vfs_hash_bucket(const struct mount *mp, u_int hash)
66 {
67
68 return (&vfs_hash_tbl[(hash + mp->mnt_hashseed) & vfs_hash_mask]);
69 }
70
71 int
72 vfs_hash_get(const struct mount *mp, u_int hash, int flags, struct thread *td,
73 struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
74 {
75 struct vnode *vp;
76 int error;
77
78 while (1) {
79 mtx_lock(&vfs_hash_mtx);
80 LIST_FOREACH(vp, vfs_hash_bucket(mp, hash), v_hashlist) {
81 if (vp->v_hash != hash)
82 continue;
83 if (vp->v_mount != mp)
84 continue;
85 if (fn != NULL && fn(vp, arg))
86 continue;
87 VI_LOCK(vp);
88 mtx_unlock(&vfs_hash_mtx);
89 error = vget(vp, flags | LK_INTERLOCK, td);
90 if (error == ENOENT && (flags & LK_NOWAIT) == 0)
91 break;
92 if (error)
93 return (error);
94 *vpp = vp;
95 return (0);
96 }
97 if (vp == NULL) {
98 mtx_unlock(&vfs_hash_mtx);
99 *vpp = NULL;
100 return (0);
101 }
102 }
103 }
104
105 void
106 vfs_hash_ref(const struct mount *mp, u_int hash, struct thread *td,
107 struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
108 {
109 struct vnode *vp;
110
111 while (1) {
112 mtx_lock(&vfs_hash_mtx);
113 LIST_FOREACH(vp, vfs_hash_bucket(mp, hash), v_hashlist) {
114 if (vp->v_hash != hash)
115 continue;
116 if (vp->v_mount != mp)
117 continue;
118 if (fn != NULL && fn(vp, arg))
119 continue;
120 vhold(vp);
121 mtx_unlock(&vfs_hash_mtx);
122 vref(vp);
123 vdrop(vp);
124 *vpp = vp;
125 return;
126 }
127 if (vp == NULL) {
128 mtx_unlock(&vfs_hash_mtx);
129 *vpp = NULL;
130 return;
131 }
132 }
133 }
134
135 void
136 vfs_hash_remove(struct vnode *vp)
137 {
138
139 mtx_lock(&vfs_hash_mtx);
140 LIST_REMOVE(vp, v_hashlist);
141 mtx_unlock(&vfs_hash_mtx);
142 }
143
144 int
145 vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td,
146 struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
147 {
148 struct vnode *vp2;
149 int error;
150
151 *vpp = NULL;
152 while (1) {
153 mtx_lock(&vfs_hash_mtx);
154 LIST_FOREACH(vp2,
155 vfs_hash_bucket(vp->v_mount, hash), v_hashlist) {
156 if (vp2->v_hash != hash)
157 continue;
158 if (vp2->v_mount != vp->v_mount)
159 continue;
160 if (fn != NULL && fn(vp2, arg))
161 continue;
162 VI_LOCK(vp2);
163 mtx_unlock(&vfs_hash_mtx);
164 error = vget(vp2, flags | LK_INTERLOCK, td);
165 if (error == ENOENT && (flags & LK_NOWAIT) == 0)
166 break;
167 mtx_lock(&vfs_hash_mtx);
168 LIST_INSERT_HEAD(&vfs_hash_side, vp, v_hashlist);
169 mtx_unlock(&vfs_hash_mtx);
170 vput(vp);
171 if (!error)
172 *vpp = vp2;
173 return (error);
174 }
175 if (vp2 == NULL)
176 break;
177
178 }
179 vp->v_hash = hash;
180 LIST_INSERT_HEAD(vfs_hash_bucket(vp->v_mount, hash), vp, v_hashlist);
181 mtx_unlock(&vfs_hash_mtx);
182 return (0);
183 }
184
185 void
186 vfs_hash_rehash(struct vnode *vp, u_int hash)
187 {
188
189 mtx_lock(&vfs_hash_mtx);
190 LIST_REMOVE(vp, v_hashlist);
191 LIST_INSERT_HEAD(vfs_hash_bucket(vp->v_mount, hash), vp, v_hashlist);
192 vp->v_hash = hash;
193 mtx_unlock(&vfs_hash_mtx);
194 }
195
196 void
197 vfs_hash_changesize(int newmaxvnodes)
198 {
199 struct vfs_hash_head *vfs_hash_newtbl, *vfs_hash_oldtbl;
200 u_long vfs_hash_newmask, vfs_hash_oldmask;
201 struct vnode *vp;
202 int i;
203
204 vfs_hash_newtbl = hashinit(newmaxvnodes, M_VFS_HASH,
205 &vfs_hash_newmask);
206 /* If same hash table size, nothing to do */
207 if (vfs_hash_mask == vfs_hash_newmask) {
208 free(vfs_hash_newtbl, M_VFS_HASH);
209 return;
210 }
211 /*
212 * Move everything from the old hash table to the new table.
213 * None of the vnodes in the table can be recycled because to
214 * do so, they have to be removed from the hash table.
215 */
216 mtx_lock(&vfs_hash_mtx);
217 vfs_hash_oldtbl = vfs_hash_tbl;
218 vfs_hash_oldmask = vfs_hash_mask;
219 vfs_hash_tbl = vfs_hash_newtbl;
220 vfs_hash_mask = vfs_hash_newmask;
221 for (i = 0; i <= vfs_hash_oldmask; i++) {
222 while ((vp = LIST_FIRST(&vfs_hash_oldtbl[i])) != NULL) {
223 LIST_REMOVE(vp, v_hashlist);
224 LIST_INSERT_HEAD(
225 vfs_hash_bucket(vp->v_mount, vp->v_hash),
226 vp, v_hashlist);
227 }
228 }
229 mtx_unlock(&vfs_hash_mtx);
230 free(vfs_hash_oldtbl, M_VFS_HASH);
231 }
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