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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 null_node_hashhead *hd;
110 ASSERT_VOP_LOCKED(lowervp, "null_hashget");
113 * Find hash base, and then search the (two-way) linked
114 * list looking for a null_node structure which is referencing
115 * the lower vnode. If found, the increment the null_node
116 * reference count (but NOT the lower vnode's VREF counter).
118 hd = NULL_NHASH(lowervp);
119 mtx_lock(&null_hashmtx);
120 LIST_FOREACH(a, hd, null_hash) {
121 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
123 * Since we have the lower node locked the nullfs
124 * node can not be in the process of recycling. If
125 * it had been recycled before we grabed the lower
126 * lock it would not have been found on the hash.
130 mtx_unlock(&null_hashmtx);
134 mtx_unlock(&null_hashmtx);
139 * Act like null_hashget, but add passed null_node to hash if no existing
142 static struct vnode *
145 struct null_node *xp;
147 struct null_node_hashhead *hd;
148 struct null_node *oxp;
151 hd = NULL_NHASH(xp->null_lowervp);
152 mtx_lock(&null_hashmtx);
153 LIST_FOREACH(oxp, hd, null_hash) {
154 if (oxp->null_lowervp == xp->null_lowervp &&
155 NULLTOV(oxp)->v_mount == mp) {
157 * See null_hashget for a description of this
162 mtx_unlock(&null_hashmtx);
166 LIST_INSERT_HEAD(hd, xp, null_hash);
167 mtx_unlock(&null_hashmtx);
172 null_insmntque_dtr(struct vnode *vp, void *xp)
175 vp->v_vnlock = &vp->v_lock;
176 free(xp, M_NULLFSNODE);
177 vp->v_op = &dead_vnodeops;
178 (void) vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
184 * Make a new or get existing nullfs node.
185 * Vp is the alias vnode, lowervp is the lower vnode.
187 * The lowervp assumed to be locked and having "spare" reference. This routine
188 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers"
189 * the caller's "spare" reference to created nullfs vnode.
192 null_nodeget(mp, lowervp, vpp)
194 struct vnode *lowervp;
197 struct null_node *xp;
201 /* Lookup the hash firstly */
202 *vpp = null_hashget(mp, lowervp);
209 * We do not serialize vnode creation, instead we will check for
210 * duplicates later, when adding new vnode to hash.
212 * Note that duplicate can only appear in hash if the lowervp is
217 * Do the MALLOC before the getnewvnode since doing so afterward
218 * might cause a bogus v_data pointer to get dereferenced
219 * elsewhere if MALLOC should block.
221 xp = malloc(sizeof(struct null_node),
222 M_NULLFSNODE, M_WAITOK);
224 error = getnewvnode("null", mp, &null_vnodeops, &vp);
226 free(xp, M_NULLFSNODE);
231 xp->null_lowervp = lowervp;
232 vp->v_type = lowervp->v_type;
234 vp->v_vnlock = lowervp->v_vnlock;
235 if (vp->v_vnlock == NULL)
236 panic("null_nodeget: Passed a NULL vnlock.\n");
237 error = insmntque1(vp, mp, null_insmntque_dtr, xp);
241 * Atomically insert our new node into the hash or vget existing
242 * if someone else has beaten us to it.
244 *vpp = null_hashins(mp, xp);
247 vp->v_vnlock = &vp->v_lock;
248 xp->null_lowervp = NULL;
258 * Remove node from hash.
262 struct null_node *xp;
265 mtx_lock(&null_hashmtx);
266 LIST_REMOVE(xp, null_hash);
267 mtx_unlock(&null_hashmtx);
273 null_checkvp(vp, fil, lno)
278 struct null_node *a = VTONULL(vp);
282 * Can't do this check because vop_reclaim runs
283 * with a funny vop vector.
285 if (vp->v_op != null_vnodeop_p) {
286 printf ("null_checkvp: on non-null-node\n");
287 panic("null_checkvp");
290 if (a->null_lowervp == NULLVP) {
291 /* Should never happen */
293 printf("vp = %p, ZERO ptr\n", (void *)vp);
294 for (p = (u_long *) a, i = 0; i < 8; i++)
295 printf(" %lx", p[i]);
297 panic("null_checkvp");
299 VI_LOCK_FLAGS(a->null_lowervp, MTX_DUPOK);
300 if (a->null_lowervp->v_usecount < 1) {
302 printf("vp = %p, unref'ed lowervp\n", (void *)vp);
303 for (p = (u_long *) a, i = 0; i < 8; i++)
304 printf(" %lx", p[i]);
306 panic ("null with unref'ed lowervp");
308 VI_UNLOCK(a->null_lowervp);
310 printf("null %x/%d -> %x/%d [%s, %d]\n",
311 NULLTOV(a), vrefcnt(NULLTOV(a)),
312 a->null_lowervp, vrefcnt(a->null_lowervp),
315 return (a->null_lowervp);