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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/rwlock.h>
42 #include <sys/malloc.h>
43 #include <sys/mount.h>
45 #include <sys/vnode.h>
47 #include <fs/nullfs/null.h>
51 * Each cache entry holds a reference to the lower vnode
52 * along with a pointer to the alias vnode. When an
53 * entry is added the lower vnode is VREF'd. When the
54 * alias is removed the lower vnode is vrele'd.
57 #define NULL_NHASH(vp) (&null_node_hashtbl[vfs_hash_index(vp) & null_hash_mask])
59 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
60 static struct rwlock null_hash_lock;
61 static u_long null_hash_mask;
63 static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table");
64 MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part");
66 static struct vnode * null_hashins(struct mount *, struct null_node *);
69 * Initialise cache headers
76 null_node_hashtbl = hashinit(desiredvnodes, M_NULLFSHASH,
78 rw_init(&null_hash_lock, "nullhs");
87 rw_destroy(&null_hash_lock);
88 hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_hash_mask);
93 * Return a VREF'ed alias for lower vnode if already exists, else 0.
94 * Lower vnode should be locked on entry and will be left locked on exit.
97 null_hashget(mp, lowervp)
99 struct vnode *lowervp;
101 struct null_node_hashhead *hd;
105 ASSERT_VOP_LOCKED(lowervp, "null_hashget");
108 * Find hash base, and then search the (two-way) linked
109 * list looking for a null_node structure which is referencing
110 * the lower vnode. If found, the increment the null_node
111 * reference count (but NOT the lower vnode's VREF counter).
113 hd = NULL_NHASH(lowervp);
114 rw_rlock(&null_hash_lock);
115 LIST_FOREACH(a, hd, null_hash) {
116 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
118 * Since we have the lower node locked the nullfs
119 * node can not be in the process of recycling. If
120 * it had been recycled before we grabed the lower
121 * lock it would not have been found on the hash.
125 rw_runlock(&null_hash_lock);
129 rw_runlock(&null_hash_lock);
134 * Act like null_hashget, but add passed null_node to hash if no existing
137 static struct vnode *
140 struct null_node *xp;
142 struct null_node_hashhead *hd;
143 struct null_node *oxp;
146 hd = NULL_NHASH(xp->null_lowervp);
147 rw_wlock(&null_hash_lock);
148 LIST_FOREACH(oxp, hd, null_hash) {
149 if (oxp->null_lowervp == xp->null_lowervp &&
150 NULLTOV(oxp)->v_mount == mp) {
152 * See null_hashget for a description of this
157 rw_wunlock(&null_hash_lock);
161 LIST_INSERT_HEAD(hd, xp, null_hash);
162 rw_wunlock(&null_hash_lock);
167 null_destroy_proto(struct vnode *vp, void *xp)
170 lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
173 vp->v_vnlock = &vp->v_lock;
174 vp->v_op = &dead_vnodeops;
178 free(xp, M_NULLFSNODE);
182 null_insmntque_dtr(struct vnode *vp, void *xp)
185 vput(((struct null_node *)xp)->null_lowervp);
186 null_destroy_proto(vp, xp);
190 * Make a new or get existing nullfs node.
191 * Vp is the alias vnode, lowervp is the lower vnode.
193 * The lowervp assumed to be locked and having "spare" reference. This routine
194 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers"
195 * the caller's "spare" reference to created nullfs vnode.
198 null_nodeget(mp, lowervp, vpp)
200 struct vnode *lowervp;
203 struct null_node *xp;
207 ASSERT_VOP_LOCKED(lowervp, "lowervp");
208 KASSERT(lowervp->v_usecount >= 1, ("Unreferenced vnode %p", lowervp));
210 /* Lookup the hash firstly. */
211 *vpp = null_hashget(mp, lowervp);
218 * The insmntque1() call below requires the exclusive lock on
219 * the nullfs vnode. Upgrade the lock now if hash failed to
220 * provide ready to use vnode.
222 if (VOP_ISLOCKED(lowervp) != LK_EXCLUSIVE) {
223 KASSERT((MOUNTTONULLMOUNT(mp)->nullm_flags & NULLM_CACHE) != 0,
224 ("lowervp %p is not excl locked and cache is disabled",
226 vn_lock(lowervp, LK_UPGRADE | LK_RETRY);
227 if ((lowervp->v_iflag & VI_DOOMED) != 0) {
234 * We do not serialize vnode creation, instead we will check for
235 * duplicates later, when adding new vnode to hash.
236 * Note that duplicate can only appear in hash if the lowervp is
239 xp = malloc(sizeof(struct null_node), M_NULLFSNODE, M_WAITOK);
241 error = getnewvnode("nullfs", mp, &null_vnodeops, &vp);
244 free(xp, M_NULLFSNODE);
249 xp->null_lowervp = lowervp;
251 vp->v_type = lowervp->v_type;
253 vp->v_vnlock = lowervp->v_vnlock;
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 null_destroy_proto(vp, xp);
273 * Remove node from hash.
277 struct null_node *xp;
280 rw_wlock(&null_hash_lock);
281 LIST_REMOVE(xp, null_hash);
282 rw_wunlock(&null_hash_lock);
288 null_checkvp(vp, fil, lno)
293 struct null_node *a = VTONULL(vp);
297 * Can't do this check because vop_reclaim runs
298 * with a funny vop vector.
300 if (vp->v_op != null_vnodeop_p) {
301 printf ("null_checkvp: on non-null-node\n");
302 panic("null_checkvp");
305 if (a->null_lowervp == NULLVP) {
306 /* Should never happen */
307 panic("null_checkvp %p", vp);
309 VI_LOCK_FLAGS(a->null_lowervp, MTX_DUPOK);
310 if (a->null_lowervp->v_usecount < 1)
311 panic ("null with unref'ed lowervp, vp %p lvp %p",
312 vp, a->null_lowervp);
313 VI_UNLOCK(a->null_lowervp);
315 printf("null %x/%d -> %x/%d [%s, %d]\n",
316 NULLTOV(a), vrefcnt(NULLTOV(a)),
317 a->null_lowervp, vrefcnt(a->null_lowervp),
320 return (a->null_lowervp);