/*- * Copyright (c) 1992, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software donated to Berkeley by * Jan-Simon Pendry. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)null_subr.c 8.7 (Berkeley) 5/14/95 * * $FreeBSD$ */ #include #include #include #include #include #include #include #include #include #include #define LOG2_SIZEVNODE 8 /* log2(sizeof struct vnode) */ #define NNULLNODECACHE 16 /* * Null layer cache: * Each cache entry holds a reference to the lower vnode * along with a pointer to the alias vnode. When an * entry is added the lower vnode is VREF'd. When the * alias is removed the lower vnode is vrele'd. */ #define NULL_NHASH(vp) \ (&null_node_hashtbl[(((uintptr_t)vp)>>LOG2_SIZEVNODE) & null_node_hash]) static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl; static u_long null_node_hash; struct mtx null_hashmtx; static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table"); MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part"); static struct vnode * null_hashget(struct mount *, struct vnode *); static struct vnode * null_hashins(struct mount *, struct null_node *); /* * Initialise cache headers */ int nullfs_init(vfsp) struct vfsconf *vfsp; { NULLFSDEBUG("nullfs_init\n"); /* printed during system boot */ null_node_hashtbl = hashinit(NNULLNODECACHE, M_NULLFSHASH, &null_node_hash); mtx_init(&null_hashmtx, "nullhs", NULL, MTX_DEF); return (0); } int nullfs_uninit(vfsp) struct vfsconf *vfsp; { mtx_destroy(&null_hashmtx); free(null_node_hashtbl, M_NULLFSHASH); return (0); } /* * Return a VREF'ed alias for lower vnode if already exists, else 0. * Lower vnode should be locked on entry and will be left locked on exit. */ static struct vnode * null_hashget(mp, lowervp) struct mount *mp; struct vnode *lowervp; { struct null_node_hashhead *hd; struct null_node *a; struct vnode *vp; ASSERT_VOP_LOCKED(lowervp, "null_hashget"); /* * Find hash base, and then search the (two-way) linked * list looking for a null_node structure which is referencing * the lower vnode. If found, the increment the null_node * reference count (but NOT the lower vnode's VREF counter). */ hd = NULL_NHASH(lowervp); mtx_lock(&null_hashmtx); LIST_FOREACH(a, hd, null_hash) { if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) { /* * Since we have the lower node locked the nullfs * node can not be in the process of recycling. If * it had been recycled before we grabed the lower * lock it would not have been found on the hash. */ vp = NULLTOV(a); vref(vp); mtx_unlock(&null_hashmtx); return (vp); } } mtx_unlock(&null_hashmtx); return (NULLVP); } /* * Act like null_hashget, but add passed null_node to hash if no existing * node found. */ static struct vnode * null_hashins(mp, xp) struct mount *mp; struct null_node *xp; { struct null_node_hashhead *hd; struct null_node *oxp; struct vnode *ovp; hd = NULL_NHASH(xp->null_lowervp); mtx_lock(&null_hashmtx); LIST_FOREACH(oxp, hd, null_hash) { if (oxp->null_lowervp == xp->null_lowervp && NULLTOV(oxp)->v_mount == mp) { /* * See null_hashget for a description of this * operation. */ ovp = NULLTOV(oxp); vref(ovp); mtx_unlock(&null_hashmtx); return (ovp); } } LIST_INSERT_HEAD(hd, xp, null_hash); mtx_unlock(&null_hashmtx); return (NULLVP); } static void null_insmntque_dtr(struct vnode *vp, void *xp) { vp->v_data = NULL; vp->v_vnlock = &vp->v_lock; free(xp, M_NULLFSNODE); vp->v_op = &dead_vnodeops; (void) vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); vgone(vp); vput(vp); } /* * Make a new or get existing nullfs node. * Vp is the alias vnode, lowervp is the lower vnode. * * The lowervp assumed to be locked and having "spare" reference. This routine * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers" * the caller's "spare" reference to created nullfs vnode. */ int null_nodeget(mp, lowervp, vpp) struct mount *mp; struct vnode *lowervp; struct vnode **vpp; { struct null_node *xp; struct vnode *vp; int error; /* Lookup the hash firstly */ *vpp = null_hashget(mp, lowervp); if (*vpp != NULL) { vrele(lowervp); return (0); } /* * We do not serialize vnode creation, instead we will check for * duplicates later, when adding new vnode to hash. * * Note that duplicate can only appear in hash if the lowervp is * locked LK_SHARED. */ /* * Do the MALLOC before the getnewvnode since doing so afterward * might cause a bogus v_data pointer to get dereferenced * elsewhere if MALLOC should block. */ xp = malloc(sizeof(struct null_node), M_NULLFSNODE, M_WAITOK); error = getnewvnode("null", mp, &null_vnodeops, &vp); if (error) { free(xp, M_NULLFSNODE); return (error); } xp->null_vnode = vp; xp->null_lowervp = lowervp; vp->v_type = lowervp->v_type; vp->v_data = xp; vp->v_vnlock = lowervp->v_vnlock; if (vp->v_vnlock == NULL) panic("null_nodeget: Passed a NULL vnlock.\n"); error = insmntque1(vp, mp, null_insmntque_dtr, xp); if (error != 0) return (error); /* * Atomically insert our new node into the hash or vget existing * if someone else has beaten us to it. */ *vpp = null_hashins(mp, xp); if (*vpp != NULL) { vrele(lowervp); vp->v_vnlock = &vp->v_lock; xp->null_lowervp = NULL; vrele(vp); return (0); } *vpp = vp; return (0); } /* * Remove node from hash. */ void null_hashrem(xp) struct null_node *xp; { mtx_lock(&null_hashmtx); LIST_REMOVE(xp, null_hash); mtx_unlock(&null_hashmtx); } #ifdef DIAGNOSTIC #ifdef KDB #define null_checkvp_barrier 1 #else #define null_checkvp_barrier 0 #endif struct vnode * null_checkvp(vp, fil, lno) struct vnode *vp; char *fil; int lno; { int interlock = 0; struct null_node *a = VTONULL(vp); #ifdef notyet /* * Can't do this check because vop_reclaim runs * with a funny vop vector. */ if (vp->v_op != null_vnodeop_p) { printf ("null_checkvp: on non-null-node\n"); while (null_checkvp_barrier) /*WAIT*/ ; panic("null_checkvp"); }; #endif if (a->null_lowervp == NULLVP) { /* Should never happen */ int i; u_long *p; printf("vp = %p, ZERO ptr\n", (void *)vp); for (p = (u_long *) a, i = 0; i < 8; i++) printf(" %lx", p[i]); printf("\n"); /* wait for debugger */ while (null_checkvp_barrier) /*WAIT*/ ; panic("null_checkvp"); } if (mtx_owned(VI_MTX(vp)) != 0) { VI_UNLOCK(vp); interlock = 1; } if (vrefcnt(a->null_lowervp) < 1) { int i; u_long *p; printf("vp = %p, unref'ed lowervp\n", (void *)vp); for (p = (u_long *) a, i = 0; i < 8; i++) printf(" %lx", p[i]); printf("\n"); /* wait for debugger */ while (null_checkvp_barrier) /*WAIT*/ ; panic ("null with unref'ed lowervp"); }; if (interlock != 0) VI_LOCK(vp); #ifdef notyet printf("null %x/%d -> %x/%d [%s, %d]\n", NULLTOV(a), vrefcnt(NULLTOV(a)), a->null_lowervp, vrefcnt(a->null_lowervp), fil, lno); #endif return a->null_lowervp; } #endif