Commit | Line | Data |
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b991bc2d JSP |
1 | /* |
2 | * Copyright (c) 1994 Jan-Simon Pendry | |
3 | * Copyright (c) 1994 | |
4 | * The Regents of the University of California. All rights reserved. | |
5 | * | |
6 | * This code is derived from software contributed to Berkeley by | |
7 | * Jan-Simon Pendry. | |
8 | * | |
9 | * %sccs.include.redist.c% | |
10 | * | |
11 | * @(#)union_subr.c 1.1 (Berkeley) %G% | |
12 | */ | |
13 | ||
14 | #include <sys/param.h> | |
15 | #include <sys/systm.h> | |
16 | #include <sys/time.h> | |
17 | #include <sys/kernel.h> | |
18 | #include <sys/vnode.h> | |
19 | #include <sys/namei.h> | |
20 | #include <sys/malloc.h> | |
21 | #include "union.h" /*<miscfs/union/union.h>*/ | |
22 | ||
23 | static struct union_node *unhead; | |
24 | static int unvplock; | |
25 | ||
26 | int | |
27 | union_init() | |
28 | { | |
29 | ||
30 | unhead = 0; | |
31 | unvplock = 0; | |
32 | } | |
33 | ||
34 | /* | |
35 | * allocate a union_node/vnode pair. the vnode is | |
36 | * referenced and locked. | |
37 | * | |
38 | * all union_nodes are maintained on a singly-linked | |
39 | * list. new nodes are only allocated when they cannot | |
40 | * be found on this list. entries on the list are | |
41 | * removed when the vfs reclaim entry is called. | |
42 | * | |
43 | * a single lock is kept for the entire list. this is | |
44 | * needed because the getnewvnode() function can block | |
45 | * waiting for a vnode to become free, in which case there | |
46 | * may be more than one process trying to get the same | |
47 | * vnode. this lock is only taken if we are going to | |
48 | * call getnewvnode, since the kernel itself is single-threaded. | |
49 | * | |
50 | * if an entry is found on the list, then call vget() to | |
51 | * take a reference. this is done because there may be | |
52 | * zero references to it and so it needs to removed from | |
53 | * the vnode free list. | |
54 | */ | |
55 | int | |
56 | union_allocvp(vpp, mp, dvp, cnp, uppervp, lowervp) | |
57 | struct vnode **vpp; | |
58 | struct mount *mp; | |
59 | struct vnode *dvp; /* may be null */ | |
60 | struct componentname *cnp; /* may be null */ | |
61 | struct vnode *uppervp; /* may be null */ | |
62 | struct vnode *lowervp; /* may be null */ | |
63 | { | |
64 | int error; | |
65 | struct union_node *un; | |
66 | struct union_node **pp; | |
67 | ||
68 | loop: | |
69 | for (un = unhead; un != 0; un = un->un_next) { | |
70 | if ((un->un_lowervp == lowervp || | |
71 | un->un_lowervp == 0) && | |
72 | (un->un_uppervp == uppervp || | |
73 | un->un_uppervp == 0) && | |
74 | (UNIONTOV(un)->v_mount == mp)) { | |
75 | if (vget(un->un_vnode, 1)) | |
76 | goto loop; | |
77 | un->un_lowervp = lowervp; | |
78 | un->un_uppervp = uppervp; | |
79 | *vpp = un->un_vnode; | |
80 | return (0); | |
81 | } | |
82 | } | |
83 | ||
84 | /* | |
85 | * otherwise lock the vp list while we call getnewvnode | |
86 | * since that can block. | |
87 | */ | |
88 | if (unvplock & UN_LOCKED) { | |
89 | unvplock |= UN_WANT; | |
90 | sleep((caddr_t) &unvplock, PINOD); | |
91 | goto loop; | |
92 | } | |
93 | unvplock |= UN_LOCKED; | |
94 | ||
95 | error = getnewvnode(VT_UNION, mp, union_vnodeop_p, vpp); | |
96 | if (error) | |
97 | goto out; | |
98 | ||
99 | MALLOC((*vpp)->v_data, void *, sizeof(struct union_node), | |
100 | M_TEMP, M_WAITOK); | |
101 | ||
102 | un = VTOUNION(*vpp); | |
103 | un->un_next = 0; | |
104 | un->un_dirvp = dvp; | |
105 | un->un_uppervp = uppervp; | |
106 | un->un_lowervp = lowervp; | |
107 | un->un_vnode = *vpp; | |
108 | un->un_flags = 0; | |
109 | if (cnp) { | |
110 | un->un_path = malloc(cnp->cn_namelen+1, M_TEMP, M_WAITOK); | |
111 | bcopy(cnp->cn_nameptr, un->un_path, cnp->cn_namelen); | |
112 | un->un_path[cnp->cn_namelen] = '\0'; | |
113 | } else { | |
114 | un->un_path = 0; | |
115 | } | |
116 | ||
117 | #ifdef DIAGNOSTIC | |
118 | un->un_pid = 0; | |
119 | #endif | |
120 | ||
121 | /* add to union vnode list */ | |
122 | for (pp = &unhead; *pp; pp = &(*pp)->un_next) | |
123 | continue; | |
124 | *pp = un; | |
125 | ||
126 | out: | |
127 | unvplock &= ~UN_LOCKED; | |
128 | ||
129 | if (unvplock & UN_WANT) { | |
130 | unvplock &= ~UN_WANT; | |
131 | wakeup((caddr_t) &unvplock); | |
132 | } | |
133 | ||
134 | if (un) | |
135 | VOP_LOCK(UNIONTOV(un)); | |
136 | ||
137 | return (error); | |
138 | } | |
139 | ||
140 | int | |
141 | union_freevp(vp) | |
142 | struct vnode *vp; | |
143 | { | |
144 | struct union_node **unpp; | |
145 | struct union_node *un = VTOUNION(vp); | |
146 | ||
147 | for (unpp = &unhead; *unpp != 0; unpp = &(*unpp)->un_next) { | |
148 | if (*unpp == un) { | |
149 | *unpp = un->un_next; | |
150 | break; | |
151 | } | |
152 | } | |
153 | ||
154 | if (un->un_path) | |
155 | FREE(un->un_path, M_TEMP); | |
156 | ||
157 | FREE(vp->v_data, M_TEMP); | |
158 | vp->v_data = 0; | |
159 | return (0); | |
160 | } |