xref: /freebsd/sys/kern/vfs_hash.c (revision a0ee8cc636cd5c2374ec44ca71226564ea0bca95)
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("$FreeBSD$");
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/rwlock.h>
37 #include <sys/vnode.h>
38 
39 static MALLOC_DEFINE(M_VFS_HASH, "vfs_hash", "VFS hash table");
40 
41 static LIST_HEAD(vfs_hash_head, vnode)	*vfs_hash_tbl;
42 static LIST_HEAD(,vnode)		vfs_hash_side;
43 static u_long				vfs_hash_mask;
44 static struct rwlock			vfs_hash_lock;
45 
46 static void
47 vfs_hashinit(void *dummy __unused)
48 {
49 
50 	vfs_hash_tbl = hashinit(desiredvnodes, M_VFS_HASH, &vfs_hash_mask);
51 	rw_init(&vfs_hash_lock, "vfs hash");
52 	LIST_INIT(&vfs_hash_side);
53 }
54 
55 /* Must be SI_ORDER_SECOND so desiredvnodes is available */
56 SYSINIT(vfs_hash, SI_SUB_VFS, SI_ORDER_SECOND, vfs_hashinit, NULL);
57 
58 u_int
59 vfs_hash_index(struct vnode *vp)
60 {
61 
62 	return (vp->v_hash + vp->v_mount->mnt_hashseed);
63 }
64 
65 static struct vfs_hash_head *
66 vfs_hash_bucket(const struct mount *mp, u_int hash)
67 {
68 
69 	return (&vfs_hash_tbl[(hash + mp->mnt_hashseed) & vfs_hash_mask]);
70 }
71 
72 int
73 vfs_hash_get(const struct mount *mp, u_int hash, int flags, struct thread *td, struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
74 {
75 	struct vnode *vp;
76 	int error;
77 
78 	while (1) {
79 		rw_rlock(&vfs_hash_lock);
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 			vhold(vp);
88 			rw_runlock(&vfs_hash_lock);
89 			error = vget(vp, flags | LK_VNHELD, 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 			rw_runlock(&vfs_hash_lock);
99 			*vpp = NULL;
100 			return (0);
101 		}
102 	}
103 }
104 
105 void
106 vfs_hash_remove(struct vnode *vp)
107 {
108 
109 	rw_wlock(&vfs_hash_lock);
110 	LIST_REMOVE(vp, v_hashlist);
111 	rw_wunlock(&vfs_hash_lock);
112 }
113 
114 int
115 vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td, struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
116 {
117 	struct vnode *vp2;
118 	int error;
119 
120 	*vpp = NULL;
121 	while (1) {
122 		rw_wlock(&vfs_hash_lock);
123 		LIST_FOREACH(vp2,
124 		    vfs_hash_bucket(vp->v_mount, hash), v_hashlist) {
125 			if (vp2->v_hash != hash)
126 				continue;
127 			if (vp2->v_mount != vp->v_mount)
128 				continue;
129 			if (fn != NULL && fn(vp2, arg))
130 				continue;
131 			vhold(vp2);
132 			rw_wunlock(&vfs_hash_lock);
133 			error = vget(vp2, flags | LK_VNHELD, td);
134 			if (error == ENOENT && (flags & LK_NOWAIT) == 0)
135 				break;
136 			rw_wlock(&vfs_hash_lock);
137 			LIST_INSERT_HEAD(&vfs_hash_side, vp, v_hashlist);
138 			rw_wunlock(&vfs_hash_lock);
139 			vput(vp);
140 			if (!error)
141 				*vpp = vp2;
142 			return (error);
143 		}
144 		if (vp2 == NULL)
145 			break;
146 
147 	}
148 	vp->v_hash = hash;
149 	LIST_INSERT_HEAD(vfs_hash_bucket(vp->v_mount, hash), vp, v_hashlist);
150 	rw_wunlock(&vfs_hash_lock);
151 	return (0);
152 }
153 
154 void
155 vfs_hash_rehash(struct vnode *vp, u_int hash)
156 {
157 
158 	rw_wlock(&vfs_hash_lock);
159 	LIST_REMOVE(vp, v_hashlist);
160 	LIST_INSERT_HEAD(vfs_hash_bucket(vp->v_mount, hash), vp, v_hashlist);
161 	vp->v_hash = hash;
162 	rw_wunlock(&vfs_hash_lock);
163 }
164 
165 void
166 vfs_hash_changesize(int newmaxvnodes)
167 {
168 	struct vfs_hash_head *vfs_hash_newtbl, *vfs_hash_oldtbl;
169 	u_long vfs_hash_newmask, vfs_hash_oldmask;
170 	struct vnode *vp;
171 	int i;
172 
173 	vfs_hash_newtbl = hashinit(newmaxvnodes, M_VFS_HASH,
174 		&vfs_hash_newmask);
175 	/* If same hash table size, nothing to do */
176 	if (vfs_hash_mask == vfs_hash_newmask) {
177 		free(vfs_hash_newtbl, M_VFS_HASH);
178 		return;
179 	}
180 	/*
181 	 * Move everything from the old hash table to the new table.
182 	 * None of the vnodes in the table can be recycled because to
183 	 * do so, they have to be removed from the hash table.
184 	 */
185 	rw_wlock(&vfs_hash_lock);
186 	vfs_hash_oldtbl = vfs_hash_tbl;
187 	vfs_hash_oldmask = vfs_hash_mask;
188 	vfs_hash_tbl = vfs_hash_newtbl;
189 	vfs_hash_mask = vfs_hash_newmask;
190 	for (i = 0; i <= vfs_hash_oldmask; i++) {
191 		while ((vp = LIST_FIRST(&vfs_hash_oldtbl[i])) != NULL) {
192 			LIST_REMOVE(vp, v_hashlist);
193 			LIST_INSERT_HEAD(
194 			    vfs_hash_bucket(vp->v_mount, vp->v_hash),
195 			    vp, v_hashlist);
196 		}
197 	}
198 	rw_wunlock(&vfs_hash_lock);
199 	free(vfs_hash_oldtbl, M_VFS_HASH);
200 }
201