vfs_hash.c revision 143619 
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: head/sys/kern/vfs_hash.c 143619 2005-03-15 08:07:07Z phk $");
30
31#include <sys/param.h>
32#include <sys/systm.h>
33#include <sys/kernel.h>
34#include <sys/malloc.h>
35#include <sys/vnode.h>
36
37static MALLOC_DEFINE(M_VFS_HASH, "VFS hash", "VFS hash table");
38
39static LIST_HEAD(vfs_hashhead, vnode)	*vfs_hash_tbl;
40static u_long				vfs_hash_mask;
41static struct mtx			vfs_hash_mtx;
42
43static void
44vfs_hashinit(void *dummy __unused)
45{
46
47	vfs_hash_tbl = hashinit(desiredvnodes, M_VFS_HASH, &vfs_hash_mask);
48	mtx_init(&vfs_hash_mtx, "vfs hash", NULL, MTX_DEF);
49}
50
51/* Must be SI_ORDER_SECOND so desiredvnodes is available */
52SYSINIT(vfs_hash, SI_SUB_VFS, SI_ORDER_SECOND, vfs_hashinit, NULL)
53
54int
55vfs_hash_get(struct mount *mp, u_int hash, int flags, struct thread *td, struct vnode **vpp)
56{
57	struct vnode *vp;
58	int error;
59
60	while (1) {
61		mtx_lock(&vfs_hash_mtx);
62		LIST_FOREACH(vp,
63		    &vfs_hash_tbl[hash & vfs_hash_mask], v_hashlist) {
64			if (vp->v_hash != hash)
65				continue;
66			if (vp->v_mount != mp)
67				continue;
68			VI_LOCK(vp);
69			mtx_unlock(&vfs_hash_mtx);
70			error = vget(vp, flags | LK_INTERLOCK, td);
71			if (error == ENOENT)
72				break;
73			if (error)
74				return (error);
75			*vpp = vp;
76			return (0);
77		}
78		if (vp == NULL) {
79			mtx_unlock(&vfs_hash_mtx);
80			*vpp = NULL;
81			return (0);
82		}
83	}
84}
85
86void
87vfs_hash_remove(struct vnode *vp)
88{
89
90	mtx_lock(&vfs_hash_mtx);
91	VI_LOCK(vp);
92	VNASSERT(vp->v_iflag & VI_HASHED, vp, ("vfs_hash_remove: not hashed"));
93	LIST_REMOVE(vp, v_hashlist);
94	vp->v_iflag &= ~VI_HASHED;
95	VI_UNLOCK(vp);
96	mtx_unlock(&vfs_hash_mtx);
97}
98
99int
100vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td, struct vnode **vpp)
101{
102	struct vnode *vp2;
103	int error;
104
105	lockmgr(vp->v_vnlock, LK_EXCLUSIVE, NULL, td);
106	*vpp = NULL;
107	while (1) {
108		mtx_lock(&vfs_hash_mtx);
109		LIST_FOREACH(vp2,
110		    &vfs_hash_tbl[hash & vfs_hash_mask], v_hashlist) {
111			if (vp2->v_hash != hash)
112				continue;
113			if (vp2->v_mount != vp->v_mount)
114				continue;
115			VI_LOCK(vp2);
116			mtx_unlock(&vfs_hash_mtx);
117			error = vget(vp2, flags | LK_INTERLOCK, td);
118			if (error == ENOENT)
119				break;
120			if (error)
121				return (error);
122			*vpp = vp2;
123			return (0);
124		}
125		if (vp2 == NULL)
126			break;
127
128	}
129	VI_LOCK(vp);
130	VNASSERT(!(vp->v_iflag & VI_HASHED), vp,
131	    ("vfs_hash_insert: already hashed"));
132	vp->v_hash = hash;
133	LIST_INSERT_HEAD(&vfs_hash_tbl[hash & vfs_hash_mask], vp, v_hashlist);
134	vp->v_iflag |= VI_HASHED;
135	VI_UNLOCK(vp);
136	mtx_unlock(&vfs_hash_mtx);
137	return (0);
138}
139
140void
141vfs_hash_rehash(struct vnode *vp, u_int hash)
142{
143
144	mtx_lock(&vfs_hash_mtx);
145	VNASSERT(vp->v_iflag & VI_HASHED, vp, ("vfs_hash_rehash: not hashed"));
146	LIST_REMOVE(vp, v_hashlist);
147	LIST_INSERT_HEAD(&vfs_hash_tbl[hash & vfs_hash_mask], vp, v_hashlist);
148	vp->v_hash = hash;
149	mtx_unlock(&vfs_hash_mtx);
150}
151