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32 * @(#)null_subr.c 8.7 (Berkeley) 5/14/95
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/kernel.h>
41 #include <sys/mutex.h>
42 #include <sys/malloc.h>
43 #include <sys/mount.h>
45 #include <sys/vnode.h>
47 #include <fs/nullfs/null.h>
49 #define LOG2_SIZEVNODE 8 /* log2(sizeof struct vnode) */
50 #define NNULLNODECACHE 16
54 * Each cache entry holds a reference to the lower vnode
55 * along with a pointer to the alias vnode. When an
56 * entry is added the lower vnode is VREF'd. When the
57 * alias is removed the lower vnode is vrele'd.
60 #define NULL_NHASH(vp) \
61 (&null_node_hashtbl[(((uintptr_t)vp)>>LOG2_SIZEVNODE) & null_node_hash])
63 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
64 static u_long null_node_hash;
65 struct mtx null_hashmtx;
67 static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table");
68 MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part");
70 static struct vnode * null_hashget(struct mount *, struct vnode *);
71 static struct vnode * null_hashins(struct mount *, struct null_node *);
74 * Initialise cache headers
81 NULLFSDEBUG("nullfs_init\n"); /* printed during system boot */
82 null_node_hashtbl = hashinit(NNULLNODECACHE, M_NULLFSHASH, &null_node_hash);
83 mtx_init(&null_hashmtx, "nullhs", NULL, MTX_DEF);
92 mtx_destroy(&null_hashmtx);
93 free(null_node_hashtbl, M_NULLFSHASH);
98 * Return a VREF'ed alias for lower vnode if already exists, else 0.
99 * Lower vnode should be locked on entry and will be left locked on exit.
101 static struct vnode *
102 null_hashget(mp, lowervp)
104 struct vnode *lowervp;
106 struct thread *td = curthread; /* XXX */
107 struct null_node_hashhead *hd;
112 ASSERT_VOP_LOCKED(lowervp, "null_hashget");
115 * Find hash base, and then search the (two-way) linked
116 * list looking for a null_node structure which is referencing
117 * the lower vnode. If found, the increment the null_node
118 * reference count (but NOT the lower vnode's VREF counter).
120 hd = NULL_NHASH(lowervp);
121 mtx_lock(&null_hashmtx);
122 LIST_FOREACH(a, hd, null_hash) {
123 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
126 mtx_unlock(&null_hashmtx);
128 * We need to clear the OWEINACT flag here as this
129 * may lead vget() to try to lock our vnode which
130 * is already locked via lowervp.
132 vp->v_iflag &= ~VI_OWEINACT;
133 error = vget(vp, LK_INTERLOCK, td);
135 * Since we have the lower node locked the nullfs
136 * node can not be in the process of recycling. If
137 * it had been recycled before we grabed the lower
138 * lock it would not have been found on the hash.
141 panic("null_hashget: vget error %d", error);
145 mtx_unlock(&null_hashmtx);
150 * Act like null_hashget, but add passed null_node to hash if no existing
153 static struct vnode *
156 struct null_node *xp;
158 struct thread *td = curthread; /* XXX */
159 struct null_node_hashhead *hd;
160 struct null_node *oxp;
164 hd = NULL_NHASH(xp->null_lowervp);
165 mtx_lock(&null_hashmtx);
166 LIST_FOREACH(oxp, hd, null_hash) {
167 if (oxp->null_lowervp == xp->null_lowervp &&
168 NULLTOV(oxp)->v_mount == mp) {
170 * See null_hashget for a description of this
175 mtx_unlock(&null_hashmtx);
176 ovp->v_iflag &= ~VI_OWEINACT;
177 error = vget(ovp, LK_INTERLOCK, td);
179 panic("null_hashins: vget error %d", error);
183 LIST_INSERT_HEAD(hd, xp, null_hash);
184 mtx_unlock(&null_hashmtx);
189 null_insmntque_dtr(struct vnode *vp, void *xp)
192 vp->v_vnlock = &vp->v_lock;
193 FREE(xp, M_NULLFSNODE);
194 vp->v_op = &dead_vnodeops;
195 (void) vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, curthread);
201 * Make a new or get existing nullfs node.
202 * Vp is the alias vnode, lowervp is the lower vnode.
204 * The lowervp assumed to be locked and having "spare" reference. This routine
205 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers"
206 * the caller's "spare" reference to created nullfs vnode.
209 null_nodeget(mp, lowervp, vpp)
211 struct vnode *lowervp;
214 struct null_node *xp;
218 /* Lookup the hash firstly */
219 *vpp = null_hashget(mp, lowervp);
226 * We do not serialize vnode creation, instead we will check for
227 * duplicates later, when adding new vnode to hash.
229 * Note that duplicate can only appear in hash if the lowervp is
234 * Do the MALLOC before the getnewvnode since doing so afterward
235 * might cause a bogus v_data pointer to get dereferenced
236 * elsewhere if MALLOC should block.
238 MALLOC(xp, struct null_node *, sizeof(struct null_node),
239 M_NULLFSNODE, M_WAITOK);
241 error = getnewvnode("null", mp, &null_vnodeops, &vp);
243 FREE(xp, M_NULLFSNODE);
248 xp->null_lowervp = lowervp;
249 vp->v_type = lowervp->v_type;
251 vp->v_vnlock = lowervp->v_vnlock;
252 if (vp->v_vnlock == NULL)
253 panic("null_nodeget: Passed a NULL vnlock.\n");
254 error = insmntque1(vp, mp, null_insmntque_dtr, xp);
258 * Atomically insert our new node into the hash or vget existing
259 * if someone else has beaten us to it.
261 *vpp = null_hashins(mp, xp);
264 vp->v_vnlock = &vp->v_lock;
265 xp->null_lowervp = NULL;
275 * Remove node from hash.
279 struct null_node *xp;
282 mtx_lock(&null_hashmtx);
283 LIST_REMOVE(xp, null_hash);
284 mtx_unlock(&null_hashmtx);
290 #define null_checkvp_barrier 1
292 #define null_checkvp_barrier 0
296 null_checkvp(vp, fil, lno)
302 struct null_node *a = VTONULL(vp);
305 * Can't do this check because vop_reclaim runs
306 * with a funny vop vector.
308 if (vp->v_op != null_vnodeop_p) {
309 printf ("null_checkvp: on non-null-node\n");
310 while (null_checkvp_barrier) /*WAIT*/ ;
311 panic("null_checkvp");
314 if (a->null_lowervp == NULLVP) {
315 /* Should never happen */
317 printf("vp = %p, ZERO ptr\n", (void *)vp);
318 for (p = (u_long *) a, i = 0; i < 8; i++)
319 printf(" %lx", p[i]);
321 /* wait for debugger */
322 while (null_checkvp_barrier) /*WAIT*/ ;
323 panic("null_checkvp");
325 if (mtx_owned(VI_MTX(vp)) != 0) {
329 if (vrefcnt(a->null_lowervp) < 1) {
331 printf("vp = %p, unref'ed lowervp\n", (void *)vp);
332 for (p = (u_long *) a, i = 0; i < 8; i++)
333 printf(" %lx", p[i]);
335 /* wait for debugger */
336 while (null_checkvp_barrier) /*WAIT*/ ;
337 panic ("null with unref'ed lowervp");
342 printf("null %x/%d -> %x/%d [%s, %d]\n",
343 NULLTOV(a), vrefcnt(NULLTOV(a)),
344 a->null_lowervp, vrefcnt(a->null_lowervp),
347 return a->null_lowervp;