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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 $
39 * $DragonFly: src/sys/vfs/nullfs/Attic/null_subr.c,v 1.5 2003/08/07 21:17:43 dillon Exp $
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/kernel.h>
46 #include <sys/vnode.h>
47 #include <sys/mount.h>
48 #include <sys/malloc.h>
51 #define LOG2_SIZEVNODE 7 /* log2(sizeof struct vnode) */
52 #define NNULLNODECACHE 16
56 * Each cache entry holds a reference to the lower vnode
57 * along with a pointer to the alias vnode. When an
58 * entry is added the lower vnode is VREF'd. When the
59 * alias is removed the lower vnode is vrele'd.
62 #define NULL_NHASH(vp) \
63 (&null_node_hashtbl[(((uintptr_t)vp)>>LOG2_SIZEVNODE) & null_node_hash])
65 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
66 static u_long null_node_hash;
67 struct lock null_hashlock;
69 static MALLOC_DEFINE(M_NULLFSHASH, "NULLFS hash", "NULLFS hash table");
70 MALLOC_DEFINE(M_NULLFSNODE, "NULLFS node", "NULLFS vnode private part");
72 static int null_node_alloc(struct mount *mp, struct vnode *lowervp,
75 null_node_find(struct mount *mp, struct vnode *lowervp);
78 * Initialise cache headers
85 NULLFSDEBUG("nullfs_init\n"); /* printed during system boot */
86 null_node_hashtbl = hashinit(NNULLNODECACHE, M_NULLFSHASH, &null_node_hash);
87 lockinit(&null_hashlock, 0, "nullhs", 0, 0);
96 if (null_node_hashtbl) {
97 free(null_node_hashtbl, M_NULLFSHASH);
103 * Return a VREF'ed alias for lower vnode if already exists, else 0.
104 * Lower vnode should be locked on entry and will be left locked on exit.
106 static struct vnode *
107 null_node_find(mp, lowervp)
109 struct vnode *lowervp;
111 struct thread *td = curthread; /* XXX */
112 struct null_node_hashhead *hd;
117 * Find hash base, and then search the (two-way) linked
118 * list looking for a null_node structure which is referencing
119 * the lower vnode. If found, the increment the null_node
120 * reference count (but NOT the lower vnode's VREF counter).
122 hd = NULL_NHASH(lowervp);
124 lockmgr(&null_hashlock, LK_EXCLUSIVE, NULL, td);
125 LIST_FOREACH(a, hd, null_hash) {
126 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
128 lockmgr(&null_hashlock, LK_RELEASE, NULL, td);
130 * We need vget for the VXLOCK
131 * stuff, but we don't want to lock
134 if (vget(vp, LK_EXCLUSIVE | LK_CANRECURSE, td)) {
135 printf ("null_node_find: vget failed.\n");
138 VOP_UNLOCK(lowervp, 0, td);
142 lockmgr(&null_hashlock, LK_RELEASE, NULL, td);
149 * Make a new null_node node.
150 * Vp is the alias vnode, lofsvp is the lower vnode.
151 * Maintain a reference to (lowervp).
154 null_node_alloc(mp, lowervp, vpp)
156 struct vnode *lowervp;
159 struct thread *td = curthread; /* XXX */
160 struct null_node_hashhead *hd;
161 struct null_node *xp;
162 struct vnode *othervp, *vp;
166 * Do the MALLOC before the getnewvnode since doing so afterward
167 * might cause a bogus v_data pointer to get dereferenced
168 * elsewhere if MALLOC should block.
170 MALLOC(xp, struct null_node *, sizeof(struct null_node),
171 M_NULLFSNODE, M_WAITOK);
173 error = getnewvnode(VT_NULL, mp, null_vnodeop_p, vpp);
175 FREE(xp, M_NULLFSNODE);
180 vp->v_type = lowervp->v_type;
181 lockinit(&xp->null_lock, 0, "nullnode", 0, LK_CANRECURSE);
184 xp->null_lowervp = lowervp;
186 * Before we insert our new node onto the hash chains,
187 * check to see if someone else has beaten us to it.
188 * (We could have slept in MALLOC.)
190 othervp = null_node_find(mp, lowervp);
193 FREE(xp, M_NULLFSNODE);
194 vp->v_type = VBAD; /* node is discarded */
202 * Now lock the new node. We rely on the fact that we were passed
203 * a locked vnode. If the lower node is exporting a struct lock
204 * (v_vnlock != NULL) then we just set the upper v_vnlock to the
205 * lower one, and both are now locked. If the lower node is exporting
206 * NULL, then we copy that up and manually lock the new vnode.
209 lockmgr(&null_hashlock, LK_EXCLUSIVE, NULL, td);
210 vp->v_vnlock = lowervp->v_vnlock;
211 error = VOP_LOCK(vp, LK_EXCLUSIVE | LK_THISLAYER, td);
213 panic("null_node_alloc: can't lock new vnode\n");
216 hd = NULL_NHASH(lowervp);
217 LIST_INSERT_HEAD(hd, xp, null_hash);
218 lockmgr(&null_hashlock, LK_RELEASE, NULL, td);
224 * Try to find an existing null_node vnode refering to the given underlying
225 * vnode (which should be locked). If no vnode found, create a new null_node
226 * vnode which contains a reference to the lower vnode.
229 null_node_create(mp, lowervp, newvpp)
231 struct vnode *lowervp;
232 struct vnode **newvpp;
234 struct vnode *aliasvp;
236 aliasvp = null_node_find(mp, lowervp);
239 * null_node_find has taken another reference
240 * to the alias vnode.
244 vprint("null_node_create: exists", aliasvp);
252 NULLFSDEBUG("null_node_create: create new alias vnode\n");
255 * Make new vnode reference the null_node.
257 error = null_node_alloc(mp, lowervp, &aliasvp);
262 * aliasvp is already VREF'd by getnewvnode()
267 if (lowervp->v_usecount < 1) {
268 /* Should never happen... */
269 vprint ("null_node_create: alias ", aliasvp);
270 vprint ("null_node_create: lower ", lowervp);
271 panic ("null_node_create: lower has 0 usecount.");
276 vprint("null_node_create: alias", aliasvp);
277 vprint("null_node_create: lower", lowervp);
288 #define null_checkvp_barrier 1
290 #define null_checkvp_barrier 0
294 null_checkvp(vp, fil, lno)
299 struct null_node *a = VTONULL(vp);
302 * Can't do this check because vop_reclaim runs
303 * with a funny vop vector.
305 if (vp->v_op != null_vnodeop_p) {
306 printf ("null_checkvp: on non-null-node\n");
307 while (null_checkvp_barrier) /*WAIT*/ ;
308 panic("null_checkvp");
311 if (a->null_lowervp == NULLVP) {
312 /* Should never happen */
314 printf("vp = %p, ZERO ptr\n", (void *)vp);
315 for (p = (u_long *) a, i = 0; i < 8; i++)
316 printf(" %lx", p[i]);
318 /* wait for debugger */
319 while (null_checkvp_barrier) /*WAIT*/ ;
320 panic("null_checkvp");
322 if (a->null_lowervp->v_usecount < 1) {
324 printf("vp = %p, unref'ed lowervp\n", (void *)vp);
325 for (p = (u_long *) a, i = 0; i < 8; i++)
326 printf(" %lx", p[i]);
328 /* wait for debugger */
329 while (null_checkvp_barrier) /*WAIT*/ ;
330 panic ("null with unref'ed lowervp");
333 printf("null %x/%d -> %x/%d [%s, %d]\n",
334 NULLTOV(a), NULLTOV(a)->v_usecount,
335 a->null_lowervp, a->null_lowervp->v_usecount,
338 return a->null_lowervp;