xref: /freebsd/sys/kern/vfs_hash.c (revision 195ebc7e9e4b129de810833791a19dfb4349d6a9)
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/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 static struct vfs_hash_head *
58 vfs_hash_index(const struct mount *mp, u_int hash)
59 {
60 
61 	return(&vfs_hash_tbl[(hash + mp->mnt_hashseed) & vfs_hash_mask]);
62 }
63 
64 int
65 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)
66 {
67 	struct vnode *vp;
68 	int error;
69 
70 	while (1) {
71 		mtx_lock(&vfs_hash_mtx);
72 		LIST_FOREACH(vp, vfs_hash_index(mp, hash), v_hashlist) {
73 			if (vp->v_hash != hash)
74 				continue;
75 			if (vp->v_mount != mp)
76 				continue;
77 			if (fn != NULL && fn(vp, arg))
78 				continue;
79 			VI_LOCK(vp);
80 			mtx_unlock(&vfs_hash_mtx);
81 			error = vget(vp, flags | LK_INTERLOCK, td);
82 			if (error == ENOENT && (flags & LK_NOWAIT) == 0)
83 				break;
84 			if (error)
85 				return (error);
86 			*vpp = vp;
87 			return (0);
88 		}
89 		if (vp == NULL) {
90 			mtx_unlock(&vfs_hash_mtx);
91 			*vpp = NULL;
92 			return (0);
93 		}
94 	}
95 }
96 
97 void
98 vfs_hash_remove(struct vnode *vp)
99 {
100 
101 	mtx_lock(&vfs_hash_mtx);
102 	LIST_REMOVE(vp, v_hashlist);
103 	mtx_unlock(&vfs_hash_mtx);
104 }
105 
106 int
107 vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td, struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
108 {
109 	struct vnode *vp2;
110 	int error;
111 
112 	*vpp = NULL;
113 	while (1) {
114 		mtx_lock(&vfs_hash_mtx);
115 		LIST_FOREACH(vp2,
116 		    vfs_hash_index(vp->v_mount, hash), v_hashlist) {
117 			if (vp2->v_hash != hash)
118 				continue;
119 			if (vp2->v_mount != vp->v_mount)
120 				continue;
121 			if (fn != NULL && fn(vp2, arg))
122 				continue;
123 			VI_LOCK(vp2);
124 			mtx_unlock(&vfs_hash_mtx);
125 			error = vget(vp2, flags | LK_INTERLOCK, td);
126 			if (error == ENOENT && (flags & LK_NOWAIT) == 0)
127 				break;
128 			mtx_lock(&vfs_hash_mtx);
129 			LIST_INSERT_HEAD(&vfs_hash_side, vp, v_hashlist);
130 			mtx_unlock(&vfs_hash_mtx);
131 			vput(vp);
132 			if (!error)
133 				*vpp = vp2;
134 			return (error);
135 		}
136 		if (vp2 == NULL)
137 			break;
138 
139 	}
140 	vp->v_hash = hash;
141 	LIST_INSERT_HEAD(vfs_hash_index(vp->v_mount, hash), vp, v_hashlist);
142 	mtx_unlock(&vfs_hash_mtx);
143 	return (0);
144 }
145 
146 void
147 vfs_hash_rehash(struct vnode *vp, u_int hash)
148 {
149 
150 	mtx_lock(&vfs_hash_mtx);
151 	LIST_REMOVE(vp, v_hashlist);
152 	LIST_INSERT_HEAD(vfs_hash_index(vp->v_mount, hash), vp, v_hashlist);
153 	vp->v_hash = hash;
154 	mtx_unlock(&vfs_hash_mtx);
155 }
156