317 lines
8.2 KiB
C
317 lines
8.2 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1992, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software donated to Berkeley by
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* Jan-Simon Pendry.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)null_subr.c 8.7 (Berkeley) 5/14/95
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/lock.h>
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#include <sys/rwlock.h>
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#include <sys/malloc.h>
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#include <sys/mount.h>
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#include <sys/proc.h>
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#include <sys/vnode.h>
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#include <fs/nullfs/null.h>
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/*
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* Null layer cache:
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* Each cache entry holds a reference to the lower vnode
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* along with a pointer to the alias vnode. When an
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* entry is added the lower vnode is VREF'd. When the
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* alias is removed the lower vnode is vrele'd.
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*/
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#define NULL_NHASH(vp) (&null_node_hashtbl[vfs_hash_index(vp) & null_hash_mask])
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static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
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static struct rwlock null_hash_lock;
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static u_long null_hash_mask;
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static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table");
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MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part");
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static void null_hashins(struct mount *, struct null_node *);
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/*
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* Initialise cache headers
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*/
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int
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nullfs_init(struct vfsconf *vfsp)
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{
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null_node_hashtbl = hashinit(desiredvnodes, M_NULLFSHASH,
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&null_hash_mask);
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rw_init(&null_hash_lock, "nullhs");
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return (0);
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}
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int
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nullfs_uninit(struct vfsconf *vfsp)
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{
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rw_destroy(&null_hash_lock);
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hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_hash_mask);
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return (0);
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}
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/*
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* Return a VREF'ed alias for lower vnode if already exists, else 0.
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* Lower vnode should be locked on entry and will be left locked on exit.
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*/
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static struct vnode *
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null_hashget_locked(struct mount *mp, struct vnode *lowervp)
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{
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struct null_node_hashhead *hd;
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struct null_node *a;
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struct vnode *vp;
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ASSERT_VOP_LOCKED(lowervp, "null_hashget");
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rw_assert(&null_hash_lock, RA_LOCKED);
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/*
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* Find hash base, and then search the (two-way) linked
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* list looking for a null_node structure which is referencing
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* the lower vnode. If found, the increment the null_node
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* reference count (but NOT the lower vnode's VREF counter).
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*/
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hd = NULL_NHASH(lowervp);
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LIST_FOREACH(a, hd, null_hash) {
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if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
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/*
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* Since we have the lower node locked the nullfs
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* node can not be in the process of recycling. If
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* it had been recycled before we grabed the lower
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* lock it would not have been found on the hash.
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*/
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vp = NULLTOV(a);
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vref(vp);
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return (vp);
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}
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}
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return (NULLVP);
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}
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struct vnode *
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null_hashget(struct mount *mp, struct vnode *lowervp)
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{
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struct null_node_hashhead *hd;
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struct vnode *vp;
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hd = NULL_NHASH(lowervp);
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if (LIST_EMPTY(hd))
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return (NULLVP);
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rw_rlock(&null_hash_lock);
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vp = null_hashget_locked(mp, lowervp);
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rw_runlock(&null_hash_lock);
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return (vp);
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}
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static void
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null_hashins(struct mount *mp, struct null_node *xp)
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{
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struct null_node_hashhead *hd;
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#ifdef INVARIANTS
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struct null_node *oxp;
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#endif
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rw_assert(&null_hash_lock, RA_WLOCKED);
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hd = NULL_NHASH(xp->null_lowervp);
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#ifdef INVARIANTS
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LIST_FOREACH(oxp, hd, null_hash) {
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if (oxp->null_lowervp == xp->null_lowervp &&
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NULLTOV(oxp)->v_mount == mp) {
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VNASSERT(0, NULLTOV(oxp),
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("vnode already in hash"));
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}
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}
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#endif
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LIST_INSERT_HEAD(hd, xp, null_hash);
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}
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static void
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null_destroy_proto(struct vnode *vp, void *xp)
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{
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lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
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VI_LOCK(vp);
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vp->v_data = NULL;
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vp->v_vnlock = &vp->v_lock;
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vp->v_op = &dead_vnodeops;
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VI_UNLOCK(vp);
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vgone(vp);
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vput(vp);
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free(xp, M_NULLFSNODE);
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}
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/*
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* Make a new or get existing nullfs node.
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* Vp is the alias vnode, lowervp is the lower vnode.
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*
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* The lowervp assumed to be locked and having "spare" reference. This routine
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* vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers"
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* the caller's "spare" reference to created nullfs vnode.
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*/
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int
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null_nodeget(struct mount *mp, struct vnode *lowervp, struct vnode **vpp)
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{
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struct null_node *xp;
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struct vnode *vp;
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int error;
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ASSERT_VOP_LOCKED(lowervp, "lowervp");
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VNPASS(lowervp->v_usecount > 0, lowervp);
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/* Lookup the hash firstly. */
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*vpp = null_hashget(mp, lowervp);
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if (*vpp != NULL) {
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vrele(lowervp);
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return (0);
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}
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/*
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* We do not serialize vnode creation, instead we will check for
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* duplicates later, when adding new vnode to hash.
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* Note that duplicate can only appear in hash if the lowervp is
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* locked LK_SHARED.
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*/
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xp = malloc(sizeof(struct null_node), M_NULLFSNODE, M_WAITOK);
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error = getnewvnode("nullfs", mp, &null_vnodeops, &vp);
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if (error) {
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vput(lowervp);
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free(xp, M_NULLFSNODE);
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return (error);
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}
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VNPASS(vp->v_object == NULL, vp);
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VNPASS((vn_irflag_read(vp) & VIRF_PGREAD) == 0, vp);
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rw_wlock(&null_hash_lock);
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xp->null_vnode = vp;
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xp->null_lowervp = lowervp;
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xp->null_flags = 0;
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vp->v_type = lowervp->v_type;
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vp->v_data = xp;
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vp->v_vnlock = lowervp->v_vnlock;
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*vpp = null_hashget_locked(mp, lowervp);
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if (*vpp != NULL) {
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rw_wunlock(&null_hash_lock);
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vrele(lowervp);
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null_destroy_proto(vp, xp);
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return (0);
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}
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/*
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* We might miss the case where lower vnode sets VIRF_PGREAD
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* some time after construction, which is typical case.
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* null_open rechecks.
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*/
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if ((vn_irflag_read(lowervp) & VIRF_PGREAD) != 0) {
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MPASS(lowervp->v_object != NULL);
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vp->v_object = lowervp->v_object;
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vn_irflag_set(vp, VIRF_PGREAD);
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}
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if (lowervp == MOUNTTONULLMOUNT(mp)->nullm_lowerrootvp)
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vp->v_vflag |= VV_ROOT;
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error = insmntque1(vp, mp);
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if (error != 0) {
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rw_wunlock(&null_hash_lock);
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vput(lowervp);
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vp->v_object = NULL;
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null_destroy_proto(vp, xp);
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return (error);
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}
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null_hashins(mp, xp);
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vn_set_state(vp, VSTATE_CONSTRUCTED);
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rw_wunlock(&null_hash_lock);
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*vpp = vp;
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return (0);
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}
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/*
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* Remove node from hash.
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*/
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void
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null_hashrem(struct null_node *xp)
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{
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rw_wlock(&null_hash_lock);
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LIST_REMOVE(xp, null_hash);
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rw_wunlock(&null_hash_lock);
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}
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#ifdef DIAGNOSTIC
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struct vnode *
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null_checkvp(struct vnode *vp, char *fil, int lno)
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{
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struct null_node *a = VTONULL(vp);
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#ifdef notyet
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/*
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* Can't do this check because vop_reclaim runs
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* with a funny vop vector.
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*/
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if (vp->v_op != null_vnodeop_p) {
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printf ("null_checkvp: on non-null-node\n");
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panic("null_checkvp");
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}
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#endif
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if (a->null_lowervp == NULLVP) {
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/* Should never happen */
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panic("null_checkvp %p", vp);
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}
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VI_LOCK_FLAGS(a->null_lowervp, MTX_DUPOK);
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if (a->null_lowervp->v_usecount < 1)
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panic ("null with unref'ed lowervp, vp %p lvp %p",
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vp, a->null_lowervp);
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VI_UNLOCK(a->null_lowervp);
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#ifdef notyet
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printf("null %x/%d -> %x/%d [%s, %d]\n",
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NULLTOV(a), vrefcnt(NULLTOV(a)),
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a->null_lowervp, vrefcnt(a->null_lowervp),
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fil, lno);
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#endif
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return (a->null_lowervp);
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}
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#endif
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