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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 1.7 2004/03/01 06:33:22 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, NULL, LK_EXCLUSIVE | LK_CANRECURSE, td)) {
135 printf ("null_node_find: vget failed.\n");
138 VOP_UNLOCK(lowervp, NULL, 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;
184 * When nullfs encounters sockets or device nodes, it
185 * has a hard time working with the normal vp union.
186 * This still needs to be investigated.
188 if (vp->v_type == VCHR || vp->v_type == VBLK)
189 addalias(vp, lowervp->v_un.vu_spec.vu_specinfo);
191 vp->v_un = lowervp->v_un;
192 lockinit(&xp->null_lock, 0, "nullnode", 0, LK_CANRECURSE);
195 xp->null_lowervp = lowervp;
197 * Before we insert our new node onto the hash chains,
198 * check to see if someone else has beaten us to it.
199 * (We could have slept in MALLOC.)
201 othervp = null_node_find(mp, lowervp);
204 FREE(xp, M_NULLFSNODE);
205 vp->v_type = VBAD; /* node is discarded */
213 * Now lock the new node. We rely on the fact that we were passed
214 * a locked vnode. If the lower node is exporting a struct lock
215 * (v_vnlock != NULL) then we just set the upper v_vnlock to the
216 * lower one, and both are now locked. If the lower node is exporting
217 * NULL, then we copy that up and manually lock the new vnode.
220 lockmgr(&null_hashlock, LK_EXCLUSIVE, NULL, td);
221 vp->v_vnlock = lowervp->v_vnlock;
222 error = VOP_LOCK(vp, NULL, LK_EXCLUSIVE | LK_THISLAYER, td);
224 panic("null_node_alloc: can't lock new vnode\n");
227 hd = NULL_NHASH(lowervp);
228 LIST_INSERT_HEAD(hd, xp, null_hash);
229 lockmgr(&null_hashlock, LK_RELEASE, NULL, td);
235 * Try to find an existing null_node vnode refering to the given underlying
236 * vnode (which should be locked). If no vnode found, create a new null_node
237 * vnode which contains a reference to the lower vnode.
240 null_node_create(mp, lowervp, newvpp)
242 struct vnode *lowervp;
243 struct vnode **newvpp;
245 struct vnode *aliasvp;
247 aliasvp = null_node_find(mp, lowervp);
250 * null_node_find has taken another reference
251 * to the alias vnode.
255 vprint("null_node_create: exists", aliasvp);
263 NULLFSDEBUG("null_node_create: create new alias vnode\n");
266 * Make new vnode reference the null_node.
268 error = null_node_alloc(mp, lowervp, &aliasvp);
273 * aliasvp is already VREF'd by getnewvnode()
278 if (lowervp->v_usecount < 1) {
279 /* Should never happen... */
280 vprint ("null_node_create: alias ", aliasvp);
281 vprint ("null_node_create: lower ", lowervp);
282 panic ("null_node_create: lower has 0 usecount.");
287 vprint("null_node_create: alias", aliasvp);
288 vprint("null_node_create: lower", lowervp);
299 #define null_checkvp_barrier 1
301 #define null_checkvp_barrier 0
305 null_checkvp(vp, fil, lno)
310 struct null_node *a = VTONULL(vp);
313 * Can't do this check because vop_reclaim runs
314 * with a funny vop vector.
316 if (vp->v_op != null_vnodeop_p) {
317 printf ("null_checkvp: on non-null-node\n");
318 while (null_checkvp_barrier) /*WAIT*/ ;
319 panic("null_checkvp");
322 if (a->null_lowervp == NULLVP) {
323 /* Should never happen */
325 printf("vp = %p, ZERO ptr\n", (void *)vp);
326 for (p = (u_long *) a, i = 0; i < 8; i++)
327 printf(" %lx", p[i]);
329 /* wait for debugger */
330 while (null_checkvp_barrier) /*WAIT*/ ;
331 panic("null_checkvp");
333 if (a->null_lowervp->v_usecount < 1) {
335 printf("vp = %p, unref'ed lowervp\n", (void *)vp);
336 for (p = (u_long *) a, i = 0; i < 8; i++)
337 printf(" %lx", p[i]);
339 /* wait for debugger */
340 while (null_checkvp_barrier) /*WAIT*/ ;
341 panic ("null with unref'ed lowervp");
344 printf("null %x/%d -> %x/%d [%s, %d]\n",
345 NULLTOV(a), NULLTOV(a)->v_usecount,
346 a->null_lowervp, a->null_lowervp->v_usecount,
349 return a->null_lowervp;