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34 * @(#)null_subr.c 8.7 (Berkeley) 5/14/95
39 #include <sys/param.h>
40 #include <sys/systm.h>
41 #include <sys/kernel.h>
43 #include <sys/rwlock.h>
44 #include <sys/malloc.h>
45 #include <sys/mount.h>
47 #include <sys/vnode.h>
49 #include <fs/nullfs/null.h>
53 * Each cache entry holds a reference to the lower vnode
54 * along with a pointer to the alias vnode. When an
55 * entry is added the lower vnode is VREF'd. When the
56 * alias is removed the lower vnode is vrele'd.
59 #define NULL_NHASH(vp) (&null_node_hashtbl[vfs_hash_index(vp) & null_hash_mask])
61 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
62 static struct rwlock null_hash_lock;
63 static u_long null_hash_mask;
65 static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table");
66 MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part");
68 static struct vnode * null_hashins(struct mount *, struct null_node *);
71 * Initialise cache headers
78 null_node_hashtbl = hashinit(desiredvnodes, M_NULLFSHASH,
80 rw_init(&null_hash_lock, "nullhs");
89 rw_destroy(&null_hash_lock);
90 hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_hash_mask);
95 * Return a VREF'ed alias for lower vnode if already exists, else 0.
96 * Lower vnode should be locked on entry and will be left locked on exit.
99 null_hashget(mp, lowervp)
101 struct vnode *lowervp;
103 struct null_node_hashhead *hd;
107 ASSERT_VOP_LOCKED(lowervp, "null_hashget");
110 * Find hash base, and then search the (two-way) linked
111 * list looking for a null_node structure which is referencing
112 * the lower vnode. If found, the increment the null_node
113 * reference count (but NOT the lower vnode's VREF counter).
115 hd = NULL_NHASH(lowervp);
116 rw_rlock(&null_hash_lock);
117 LIST_FOREACH(a, hd, null_hash) {
118 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
120 * Since we have the lower node locked the nullfs
121 * node can not be in the process of recycling. If
122 * it had been recycled before we grabed the lower
123 * lock it would not have been found on the hash.
127 rw_runlock(&null_hash_lock);
131 rw_runlock(&null_hash_lock);
136 * Act like null_hashget, but add passed null_node to hash if no existing
139 static struct vnode *
142 struct null_node *xp;
144 struct null_node_hashhead *hd;
145 struct null_node *oxp;
148 hd = NULL_NHASH(xp->null_lowervp);
149 rw_wlock(&null_hash_lock);
150 LIST_FOREACH(oxp, hd, null_hash) {
151 if (oxp->null_lowervp == xp->null_lowervp &&
152 NULLTOV(oxp)->v_mount == mp) {
154 * See null_hashget for a description of this
159 rw_wunlock(&null_hash_lock);
163 LIST_INSERT_HEAD(hd, xp, null_hash);
164 rw_wunlock(&null_hash_lock);
169 null_destroy_proto(struct vnode *vp, void *xp)
172 lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
175 vp->v_vnlock = &vp->v_lock;
176 vp->v_op = &dead_vnodeops;
180 free(xp, M_NULLFSNODE);
184 null_insmntque_dtr(struct vnode *vp, void *xp)
187 vput(((struct null_node *)xp)->null_lowervp);
188 null_destroy_proto(vp, xp);
192 * Make a new or get existing nullfs node.
193 * Vp is the alias vnode, lowervp is the lower vnode.
195 * The lowervp assumed to be locked and having "spare" reference. This routine
196 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers"
197 * the caller's "spare" reference to created nullfs vnode.
200 null_nodeget(mp, lowervp, vpp)
202 struct vnode *lowervp;
205 struct null_node *xp;
209 ASSERT_VOP_LOCKED(lowervp, "lowervp");
210 KASSERT(lowervp->v_usecount >= 1, ("Unreferenced vnode %p", lowervp));
212 /* Lookup the hash firstly. */
213 *vpp = null_hashget(mp, lowervp);
220 * The insmntque1() call below requires the exclusive lock on
221 * the nullfs vnode. Upgrade the lock now if hash failed to
222 * provide ready to use vnode.
224 if (VOP_ISLOCKED(lowervp) != LK_EXCLUSIVE) {
225 KASSERT((MOUNTTONULLMOUNT(mp)->nullm_flags & NULLM_CACHE) != 0,
226 ("lowervp %p is not excl locked and cache is disabled",
228 vn_lock(lowervp, LK_UPGRADE | LK_RETRY);
229 if ((lowervp->v_iflag & VI_DOOMED) != 0) {
236 * We do not serialize vnode creation, instead we will check for
237 * duplicates later, when adding new vnode to hash.
238 * Note that duplicate can only appear in hash if the lowervp is
241 xp = malloc(sizeof(struct null_node), M_NULLFSNODE, M_WAITOK);
243 error = getnewvnode("nullfs", mp, &null_vnodeops, &vp);
246 free(xp, M_NULLFSNODE);
251 xp->null_lowervp = lowervp;
253 vp->v_type = lowervp->v_type;
255 vp->v_vnlock = lowervp->v_vnlock;
256 error = insmntque1(vp, mp, null_insmntque_dtr, xp);
260 * Atomically insert our new node into the hash or vget existing
261 * if someone else has beaten us to it.
263 *vpp = null_hashins(mp, xp);
266 null_destroy_proto(vp, xp);
275 * Remove node from hash.
279 struct null_node *xp;
282 rw_wlock(&null_hash_lock);
283 LIST_REMOVE(xp, null_hash);
284 rw_wunlock(&null_hash_lock);
290 null_checkvp(vp, fil, lno)
295 struct null_node *a = VTONULL(vp);
299 * Can't do this check because vop_reclaim runs
300 * with a funny vop vector.
302 if (vp->v_op != null_vnodeop_p) {
303 printf ("null_checkvp: on non-null-node\n");
304 panic("null_checkvp");
307 if (a->null_lowervp == NULLVP) {
308 /* Should never happen */
309 panic("null_checkvp %p", vp);
311 VI_LOCK_FLAGS(a->null_lowervp, MTX_DUPOK);
312 if (a->null_lowervp->v_usecount < 1)
313 panic ("null with unref'ed lowervp, vp %p lvp %p",
314 vp, a->null_lowervp);
315 VI_UNLOCK(a->null_lowervp);
317 printf("null %x/%d -> %x/%d [%s, %d]\n",
318 NULLTOV(a), vrefcnt(NULLTOV(a)),
319 a->null_lowervp, vrefcnt(a->null_lowervp),
322 return (a->null_lowervp);