| 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 1.4 (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 | #ifdef DIAGNOSTIC |
| 24 | #include <sys/proc.h> |
| 25 | #endif |
| 26 | |
| 27 | static struct union_node *unhead; |
| 28 | static int unvplock; |
| 29 | |
| 30 | int |
| 31 | union_init() |
| 32 | { |
| 33 | |
| 34 | unhead = 0; |
| 35 | unvplock = 0; |
| 36 | } |
| 37 | |
| 38 | /* |
| 39 | * allocate a union_node/vnode pair. the vnode is |
| 40 | * referenced and locked. the new vnode is returned |
| 41 | * via (vpp). (mp) is the mountpoint of the union filesystem, |
| 42 | * (dvp) is the parent directory where the upper layer object |
| 43 | * should exist (but doesn't) and (cnp) is the componentname |
| 44 | * information which is partially copied to allow the upper |
| 45 | * layer object to be created at a later time. (uppervp) |
| 46 | * and (lowervp) reference the upper and lower layer objects |
| 47 | * being mapped. either, but not both, can be nil. |
| 48 | * |
| 49 | * all union_nodes are maintained on a singly-linked |
| 50 | * list. new nodes are only allocated when they cannot |
| 51 | * be found on this list. entries on the list are |
| 52 | * removed when the vfs reclaim entry is called. |
| 53 | * |
| 54 | * a single lock is kept for the entire list. this is |
| 55 | * needed because the getnewvnode() function can block |
| 56 | * waiting for a vnode to become free, in which case there |
| 57 | * may be more than one process trying to get the same |
| 58 | * vnode. this lock is only taken if we are going to |
| 59 | * call getnewvnode, since the kernel itself is single-threaded. |
| 60 | * |
| 61 | * if an entry is found on the list, then call vget() to |
| 62 | * take a reference. this is done because there may be |
| 63 | * zero references to it and so it needs to removed from |
| 64 | * the vnode free list. |
| 65 | */ |
| 66 | int |
| 67 | union_allocvp(vpp, mp, undvp, dvp, cnp, uppervp, lowervp) |
| 68 | struct vnode **vpp; |
| 69 | struct mount *mp; |
| 70 | struct vnode *undvp; |
| 71 | struct vnode *dvp; /* may be null */ |
| 72 | struct componentname *cnp; /* may be null */ |
| 73 | struct vnode *uppervp; /* may be null */ |
| 74 | struct vnode *lowervp; /* may be null */ |
| 75 | { |
| 76 | int error; |
| 77 | struct union_node *un; |
| 78 | struct union_node **pp; |
| 79 | struct vnode *xlowervp = 0; |
| 80 | |
| 81 | if (uppervp == 0 && lowervp == 0) |
| 82 | panic("union: unidentifiable allocation"); |
| 83 | |
| 84 | if (uppervp && lowervp && (uppervp->v_type != lowervp->v_type)) { |
| 85 | xlowervp = lowervp; |
| 86 | lowervp = 0; |
| 87 | } |
| 88 | |
| 89 | loop: |
| 90 | for (un = unhead; un != 0; un = un->un_next) { |
| 91 | if ((un->un_lowervp == lowervp || |
| 92 | un->un_lowervp == 0) && |
| 93 | (un->un_uppervp == uppervp || |
| 94 | un->un_uppervp == 0) && |
| 95 | (UNIONTOV(un)->v_mount == mp)) { |
| 96 | if (vget(UNIONTOV(un), 0)) |
| 97 | goto loop; |
| 98 | if (UNIONTOV(un) != undvp) |
| 99 | VOP_LOCK(UNIONTOV(un)); |
| 100 | if (uppervp != un->un_uppervp) { |
| 101 | if (un->un_uppervp) |
| 102 | vrele(un->un_uppervp); |
| 103 | un->un_uppervp = uppervp; |
| 104 | } |
| 105 | if (lowervp != un->un_lowervp) { |
| 106 | if (un->un_lowervp) |
| 107 | vrele(un->un_lowervp); |
| 108 | un->un_lowervp = lowervp; |
| 109 | } |
| 110 | *vpp = UNIONTOV(un); |
| 111 | return (0); |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | /* |
| 116 | * otherwise lock the vp list while we call getnewvnode |
| 117 | * since that can block. |
| 118 | */ |
| 119 | if (unvplock & UN_LOCKED) { |
| 120 | unvplock |= UN_WANT; |
| 121 | sleep((caddr_t) &unvplock, PINOD); |
| 122 | goto loop; |
| 123 | } |
| 124 | unvplock |= UN_LOCKED; |
| 125 | |
| 126 | error = getnewvnode(VT_UNION, mp, union_vnodeop_p, vpp); |
| 127 | if (error) |
| 128 | goto out; |
| 129 | |
| 130 | MALLOC((*vpp)->v_data, void *, sizeof(struct union_node), |
| 131 | M_TEMP, M_WAITOK); |
| 132 | |
| 133 | if (uppervp) |
| 134 | (*vpp)->v_type = uppervp->v_type; |
| 135 | else |
| 136 | (*vpp)->v_type = lowervp->v_type; |
| 137 | un = VTOUNION(*vpp); |
| 138 | un->un_vnode = *vpp; |
| 139 | un->un_next = 0; |
| 140 | un->un_uppervp = uppervp; |
| 141 | un->un_lowervp = lowervp; |
| 142 | un->un_flags = 0; |
| 143 | if (uppervp == 0 && cnp) { |
| 144 | un->un_path = malloc(cnp->cn_namelen+1, M_TEMP, M_WAITOK); |
| 145 | bcopy(cnp->cn_nameptr, un->un_path, cnp->cn_namelen); |
| 146 | un->un_path[cnp->cn_namelen] = '\0'; |
| 147 | VREF(dvp); |
| 148 | un->un_dirvp = dvp; |
| 149 | } else { |
| 150 | un->un_path = 0; |
| 151 | un->un_dirvp = 0; |
| 152 | } |
| 153 | |
| 154 | /* add to union vnode list */ |
| 155 | for (pp = &unhead; *pp; pp = &(*pp)->un_next) |
| 156 | continue; |
| 157 | *pp = un; |
| 158 | |
| 159 | un->un_flags |= UN_LOCKED; |
| 160 | |
| 161 | #ifdef DIAGNOSTIC |
| 162 | un->un_pid = curproc->p_pid; |
| 163 | #endif |
| 164 | |
| 165 | if (xlowervp) |
| 166 | vrele(xlowervp); |
| 167 | |
| 168 | out: |
| 169 | unvplock &= ~UN_LOCKED; |
| 170 | |
| 171 | if (unvplock & UN_WANT) { |
| 172 | unvplock &= ~UN_WANT; |
| 173 | wakeup((caddr_t) &unvplock); |
| 174 | } |
| 175 | |
| 176 | return (error); |
| 177 | } |
| 178 | |
| 179 | int |
| 180 | union_freevp(vp) |
| 181 | struct vnode *vp; |
| 182 | { |
| 183 | struct union_node **unpp; |
| 184 | struct union_node *un = VTOUNION(vp); |
| 185 | |
| 186 | for (unpp = &unhead; *unpp != 0; unpp = &(*unpp)->un_next) { |
| 187 | if (*unpp == un) { |
| 188 | *unpp = un->un_next; |
| 189 | break; |
| 190 | } |
| 191 | } |
| 192 | |
| 193 | if (un->un_path) |
| 194 | FREE(un->un_path, M_TEMP); |
| 195 | |
| 196 | FREE(vp->v_data, M_TEMP); |
| 197 | vp->v_data = 0; |
| 198 | return (0); |
| 199 | } |