vfs_hash.c revision 143680 
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 143680 2005-03-16 07:35:06Z 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/mount.h>
36#include <sys/vnode.h>
37
38static MALLOC_DEFINE(M_VFS_HASH, "VFS hash", "VFS hash table");
39
40static LIST_HEAD(vfs_hash_head, vnode)	*vfs_hash_tbl;
41static LIST_HEAD(,vnode)		vfs_hash_side;
42static u_long				vfs_hash_mask;
43static struct mtx			vfs_hash_mtx;
44
45static void
46vfs_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 */
55SYSINIT(vfs_hash, SI_SUB_VFS, SI_ORDER_SECOND, vfs_hashinit, NULL)
56
57static struct vfs_hash_head *
58vfs_hash_index(struct mount *mp, u_int hash)
59{
60
61	return(&vfs_hash_tbl[(hash + mp->mnt_hashseed) & vfs_hash_mask]);
62}
63
64int
65vfs_hash_get(struct mount *mp, u_int hash, int flags, struct thread *td, struct vnode **vpp)
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			VI_LOCK(vp);
78			mtx_unlock(&vfs_hash_mtx);
79			error = vget(vp, flags | LK_INTERLOCK, td);
80			if (error == ENOENT)
81				break;
82			if (error)
83				return (error);
84			*vpp = vp;
85			return (0);
86		}
87		if (vp == NULL) {
88			mtx_unlock(&vfs_hash_mtx);
89			*vpp = NULL;
90			return (0);
91		}
92	}
93}
94
95void
96vfs_hash_remove(struct vnode *vp)
97{
98
99	mtx_lock(&vfs_hash_mtx);
100	LIST_REMOVE(vp, v_hashlist);
101	mtx_unlock(&vfs_hash_mtx);
102}
103
104int
105vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td, struct vnode **vpp)
106{
107	struct vnode *vp2;
108	int error;
109
110	lockmgr(vp->v_vnlock, LK_EXCLUSIVE, NULL, td);
111	*vpp = NULL;
112	while (1) {
113		mtx_lock(&vfs_hash_mtx);
114		LIST_FOREACH(vp2,
115		    vfs_hash_index(vp->v_mount, hash), v_hashlist) {
116			if (vp2->v_hash != hash)
117				continue;
118			if (vp2->v_mount != vp->v_mount)
119				continue;
120			VI_LOCK(vp2);
121			mtx_unlock(&vfs_hash_mtx);
122			error = vget(vp2, flags | LK_INTERLOCK, td);
123			if (error == ENOENT)
124				break;
125			mtx_lock(&vfs_hash_mtx);
126			LIST_INSERT_HEAD(&vfs_hash_side, vp, v_hashlist);
127			mtx_unlock(&vfs_hash_mtx);
128			vput(vp);
129			if (!error)
130				*vpp = vp2;
131			return (error);
132		}
133		if (vp2 == NULL)
134			break;
135
136	}
137	vp->v_hash = hash;
138	LIST_INSERT_HEAD(vfs_hash_index(vp->v_mount, hash), vp, v_hashlist);
139	mtx_unlock(&vfs_hash_mtx);
140	return (0);
141}
142
143void
144vfs_hash_rehash(struct vnode *vp, u_int hash)
145{
146
147	mtx_lock(&vfs_hash_mtx);
148	LIST_REMOVE(vp, v_hashlist);
149	LIST_INSERT_HEAD(&vfs_hash_tbl[hash & vfs_hash_mask], vp, v_hashlist);
150	vp->v_hash = hash;
151	mtx_unlock(&vfs_hash_mtx);
152}
153