2 * Copyright (c) 1992, 1993
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software donated to Berkeley by
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36 * @(#)null_subr.c 8.7 (Berkeley) 5/14/95
38 * $FreeBSD: src/sys/miscfs/nullfs/null_subr.c,v 1.21.2.4 2001/06/26 04:20:09 bp Exp $
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/kernel.h>
45 #include <sys/vnode.h>
46 #include <sys/mount.h>
47 #include <sys/malloc.h>
48 #include <miscfs/nullfs/null.h>
50 #define LOG2_SIZEVNODE 7 /* log2(sizeof struct vnode) */
51 #define NNULLNODECACHE 16
55 * Each cache entry holds a reference to the lower vnode
56 * along with a pointer to the alias vnode. When an
57 * entry is added the lower vnode is VREF'd. When the
58 * alias is removed the lower vnode is vrele'd.
61 #define NULL_NHASH(vp) \
62 (&null_node_hashtbl[(((uintptr_t)vp)>>LOG2_SIZEVNODE) & null_node_hash])
64 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
65 static u_long null_node_hash;
66 struct lock null_hashlock;
68 static MALLOC_DEFINE(M_NULLFSHASH, "NULLFS hash", "NULLFS hash table");
69 MALLOC_DEFINE(M_NULLFSNODE, "NULLFS node", "NULLFS vnode private part");
71 static int null_node_alloc(struct mount *mp, struct vnode *lowervp,
74 null_node_find(struct mount *mp, struct vnode *lowervp);
77 * Initialise cache headers
84 NULLFSDEBUG("nullfs_init\n"); /* printed during system boot */
85 null_node_hashtbl = hashinit(NNULLNODECACHE, M_NULLFSHASH, &null_node_hash);
86 lockinit(&null_hashlock, PVFS, "nullhs", 0, 0);
95 if (null_node_hashtbl) {
96 free(null_node_hashtbl, M_NULLFSHASH);
102 * Return a VREF'ed alias for lower vnode if already exists, else 0.
103 * Lower vnode should be locked on entry and will be left locked on exit.
105 static struct vnode *
106 null_node_find(mp, lowervp)
108 struct vnode *lowervp;
110 struct proc *p = curproc; /* XXX */
111 struct null_node_hashhead *hd;
116 * Find hash base, and then search the (two-way) linked
117 * list looking for a null_node structure which is referencing
118 * the lower vnode. If found, the increment the null_node
119 * reference count (but NOT the lower vnode's VREF counter).
121 hd = NULL_NHASH(lowervp);
123 lockmgr(&null_hashlock, LK_EXCLUSIVE, NULL, p);
124 LIST_FOREACH(a, hd, null_hash) {
125 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
127 lockmgr(&null_hashlock, LK_RELEASE, NULL, p);
129 * We need vget for the VXLOCK
130 * stuff, but we don't want to lock
133 if (vget(vp, LK_EXCLUSIVE | LK_CANRECURSE, p)) {
134 printf ("null_node_find: vget failed.\n");
137 VOP_UNLOCK(lowervp, 0, p);
141 lockmgr(&null_hashlock, LK_RELEASE, NULL, p);
148 * Make a new null_node node.
149 * Vp is the alias vnode, lofsvp is the lower vnode.
150 * Maintain a reference to (lowervp).
153 null_node_alloc(mp, lowervp, vpp)
155 struct vnode *lowervp;
158 struct proc *p = curproc; /* XXX */
159 struct null_node_hashhead *hd;
160 struct null_node *xp;
161 struct vnode *othervp, *vp;
165 * Do the MALLOC before the getnewvnode since doing so afterward
166 * might cause a bogus v_data pointer to get dereferenced
167 * elsewhere if MALLOC should block.
169 MALLOC(xp, struct null_node *, sizeof(struct null_node),
170 M_NULLFSNODE, M_WAITOK);
172 error = getnewvnode(VT_NULL, mp, null_vnodeop_p, vpp);
174 FREE(xp, M_NULLFSNODE);
179 vp->v_type = lowervp->v_type;
180 lockinit(&xp->null_lock, PINOD, "nullnode", 0, LK_CANRECURSE);
183 xp->null_lowervp = lowervp;
185 * Before we insert our new node onto the hash chains,
186 * check to see if someone else has beaten us to it.
187 * (We could have slept in MALLOC.)
189 othervp = null_node_find(mp, lowervp);
192 FREE(xp, M_NULLFSNODE);
193 vp->v_type = VBAD; /* node is discarded */
201 * Now lock the new node. We rely on the fact that we were passed
202 * a locked vnode. If the lower node is exporting a struct lock
203 * (v_vnlock != NULL) then we just set the upper v_vnlock to the
204 * lower one, and both are now locked. If the lower node is exporting
205 * NULL, then we copy that up and manually lock the new vnode.
208 lockmgr(&null_hashlock, LK_EXCLUSIVE, NULL, p);
209 vp->v_vnlock = lowervp->v_vnlock;
210 error = VOP_LOCK(vp, LK_EXCLUSIVE | LK_THISLAYER, p);
212 panic("null_node_alloc: can't lock new vnode\n");
215 hd = NULL_NHASH(lowervp);
216 LIST_INSERT_HEAD(hd, xp, null_hash);
217 lockmgr(&null_hashlock, LK_RELEASE, NULL, p);
223 * Try to find an existing null_node vnode refering to the given underlying
224 * vnode (which should be locked). If no vnode found, create a new null_node
225 * vnode which contains a reference to the lower vnode.
228 null_node_create(mp, lowervp, newvpp)
230 struct vnode *lowervp;
231 struct vnode **newvpp;
233 struct vnode *aliasvp;
235 aliasvp = null_node_find(mp, lowervp);
238 * null_node_find has taken another reference
239 * to the alias vnode.
243 vprint("null_node_create: exists", aliasvp);
251 NULLFSDEBUG("null_node_create: create new alias vnode\n");
254 * Make new vnode reference the null_node.
256 error = null_node_alloc(mp, lowervp, &aliasvp);
261 * aliasvp is already VREF'd by getnewvnode()
266 if (lowervp->v_usecount < 1) {
267 /* Should never happen... */
268 vprint ("null_node_create: alias ", aliasvp);
269 vprint ("null_node_create: lower ", lowervp);
270 panic ("null_node_create: lower has 0 usecount.");
275 vprint("null_node_create: alias", aliasvp);
276 vprint("null_node_create: lower", lowervp);
287 #define null_checkvp_barrier 1
289 #define null_checkvp_barrier 0
293 null_checkvp(vp, fil, lno)
298 struct null_node *a = VTONULL(vp);
301 * Can't do this check because vop_reclaim runs
302 * with a funny vop vector.
304 if (vp->v_op != null_vnodeop_p) {
305 printf ("null_checkvp: on non-null-node\n");
306 while (null_checkvp_barrier) /*WAIT*/ ;
307 panic("null_checkvp");
310 if (a->null_lowervp == NULLVP) {
311 /* Should never happen */
313 printf("vp = %p, ZERO ptr\n", (void *)vp);
314 for (p = (u_long *) a, i = 0; i < 8; i++)
315 printf(" %lx", p[i]);
317 /* wait for debugger */
318 while (null_checkvp_barrier) /*WAIT*/ ;
319 panic("null_checkvp");
321 if (a->null_lowervp->v_usecount < 1) {
323 printf("vp = %p, unref'ed lowervp\n", (void *)vp);
324 for (p = (u_long *) a, i = 0; i < 8; i++)
325 printf(" %lx", p[i]);
327 /* wait for debugger */
328 while (null_checkvp_barrier) /*WAIT*/ ;
329 panic ("null with unref'ed lowervp");
332 printf("null %x/%d -> %x/%d [%s, %d]\n",
333 NULLTOV(a), NULLTOV(a)->v_usecount,
334 a->null_lowervp, a->null_lowervp->v_usecount,
337 return a->null_lowervp;