/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * 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.
 * 3. 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.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <sys/smr.h>
#include <sys/vnode.h>

#include <fs/nullfs/null.h>

#include <vm/uma.h>

VFS_SMR_DECLARE;

/*
 * 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[vfs_hash_index(vp) & null_hash_mask])

static CK_SLIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
static struct rwlock null_hash_lock;
static u_long null_hash_mask;

static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table");
uma_zone_t __read_mostly null_node_zone;

static void null_hashins(struct mount *, struct null_node *);

/*
 * Initialise cache headers
 */
int
nullfs_init(struct vfsconf *vfsp)
{

        null_node_hashtbl = hashinit(desiredvnodes, M_NULLFSHASH,
            &null_hash_mask);
        rw_init(&null_hash_lock, "nullhs");
        null_node_zone = uma_zcreate("nullfs node", sizeof(struct null_node),
            NULL, NULL, NULL, NULL, 0, UMA_ZONE_ZINIT);
        VFS_SMR_ZONE_SET(null_node_zone);

        return (0);
}

int
nullfs_uninit(struct vfsconf *vfsp)
{

        uma_zdestroy(null_node_zone);
        rw_destroy(&null_hash_lock);
        hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_hash_mask);
        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_locked(struct mount *mp, struct vnode *lowervp)
{
        struct null_node_hashhead *hd;
        struct null_node *a;
        struct vnode *vp;

        ASSERT_VOP_LOCKED(lowervp, __func__);
        rw_assert(&null_hash_lock, RA_LOCKED);

        /*
         * 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);
        CK_SLIST_FOREACH(a, hd, null_hash) {
                if (a->null_lowervp != lowervp)
                        continue;
                /*
                 * 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);
                VNPASS(!VN_IS_DOOMED(vp), vp);
                if (vp->v_mount != mp)
                        continue;
                vref(vp);
                return (vp);
        }
        return (NULL);
}

struct vnode *
null_hashget(struct mount *mp, struct vnode *lowervp)
{
        struct null_node_hashhead *hd;
        struct null_node *a;
        struct vnode *vp;
        enum vgetstate vs;

        ASSERT_VOP_LOCKED(lowervp, __func__);
        rw_assert(&null_hash_lock, RA_UNLOCKED);

        vfs_smr_enter();
        hd = NULL_NHASH(lowervp);
        CK_SLIST_FOREACH(a, hd, null_hash) {
                if (a->null_lowervp != lowervp)
                        continue;
                /*
                 * See null_hashget_locked as to why the nullfs vnode can't be
                 * doomed here.
                 */
                vp = NULLTOV(a);
                VNPASS(!VN_IS_DOOMED(vp), vp);
                if (vp->v_mount != mp)
                        continue;
                vs = vget_prep_smr(vp);
                vfs_smr_exit();
                VNPASS(vs != VGET_NONE, vp);
                vget_finish_ref(vp, vs);
                return (vp);
        }
        vfs_smr_exit();
        return (NULL);
}

static void
null_hashins(struct mount *mp, struct null_node *xp)
{
        struct null_node_hashhead *hd;
#ifdef INVARIANTS
        struct null_node *oxp;
#endif

        rw_assert(&null_hash_lock, RA_WLOCKED);

        hd = NULL_NHASH(xp->null_lowervp);
#ifdef INVARIANTS
        CK_SLIST_FOREACH(oxp, hd, null_hash) {
                if (oxp->null_lowervp == xp->null_lowervp &&
                    NULLTOV(oxp)->v_mount == mp) {
                        VNASSERT(0, NULLTOV(oxp),
                            ("vnode already in hash"));
                }
        }
#endif
        CK_SLIST_INSERT_HEAD(hd, xp, null_hash);
}

static void
null_destroy_proto(struct vnode *vp, void *xp)
{

        lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
        VI_LOCK(vp);
        vp->v_data = NULL;
        vp->v_vnlock = &vp->v_lock;
        vp->v_op = &dead_vnodeops;
        VI_UNLOCK(vp);
        vgone(vp);
        vput(vp);
        uma_zfree_smr(null_node_zone, xp);
}

/*
 * 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(struct mount *mp, struct vnode *lowervp, struct vnode **vpp)
{
        struct null_node *xp;
        struct vnode *vp;
        int error;

        ASSERT_VOP_LOCKED(lowervp, "lowervp");
        VNPASS(lowervp->v_usecount > 0, lowervp);

        /* 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.
         */
        xp = uma_zalloc_smr(null_node_zone, M_WAITOK);

        error = getnewvnode("nullfs", mp, (MOUNTTONULLMOUNT(mp)->nullm_flags &
            NULLM_NOUNPBYPASS) != 0 ? &null_vnodeops_no_unp_bypass :
            &null_vnodeops, &vp);
        if (error) {
                vput(lowervp);
                uma_zfree_smr(null_node_zone, xp);
                return (error);
        }

        VNPASS(vp->v_object == NULL, vp);
        VNPASS((vn_irflag_read(vp) & VIRF_PGREAD) == 0, vp);

        rw_wlock(&null_hash_lock);
        xp->null_vnode = vp;
        xp->null_lowervp = lowervp;
        xp->null_flags = 0;
        vp->v_type = lowervp->v_type;
        vp->v_data = xp;
        vp->v_vnlock = lowervp->v_vnlock;
        *vpp = null_hashget_locked(mp, lowervp);
        if (*vpp != NULL) {
                rw_wunlock(&null_hash_lock);
                vrele(lowervp);
                null_destroy_proto(vp, xp);
                return (0);
        }

        /*
         * We might miss the case where lower vnode sets VIRF_PGREAD
         * some time after construction, which is typical case.
         * null_open rechecks.
         */
        if ((vn_irflag_read(lowervp) & VIRF_PGREAD) != 0) {
                MPASS(lowervp->v_object != NULL);
                vp->v_object = lowervp->v_object;
                vn_irflag_set(vp, VIRF_PGREAD);
        }
        if ((vn_irflag_read(lowervp) & VIRF_INOTIFY) != 0)
                vn_irflag_set(vp, VIRF_INOTIFY);
        if ((vn_irflag_read(lowervp) & VIRF_INOTIFY_PARENT) != 0)
                vn_irflag_set(vp, VIRF_INOTIFY_PARENT);
        if (lowervp == MOUNTTONULLMOUNT(mp)->nullm_lowerrootvp)
                vp->v_vflag |= VV_ROOT;

        error = insmntque1(vp, mp);
        if (error != 0) {
                rw_wunlock(&null_hash_lock);
                vput(lowervp);
                vp->v_object = NULL;
                null_destroy_proto(vp, xp);
                return (error);
        }

        vn_set_state(vp, VSTATE_CONSTRUCTED);
        null_hashins(mp, xp);
        rw_wunlock(&null_hash_lock);
        *vpp = vp;

        return (0);
}

/*
 * Remove node from hash.
 */
void
null_hashrem(struct null_node *xp)
{
        struct null_node_hashhead *hd;

        hd = NULL_NHASH(xp->null_lowervp);
        rw_wlock(&null_hash_lock);
        CK_SLIST_REMOVE(hd, xp, null_node, null_hash);
        rw_wunlock(&null_hash_lock);
}

#ifdef DIAGNOSTIC

struct vnode *
null_checkvp(struct vnode *vp, char *fil, int lno)
{
        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");
                panic("null_checkvp");
        }
#endif
        if (a->null_lowervp == NULL) {
                /* Should never happen */
                panic("null_checkvp %p", vp);
        }
        VI_LOCK_FLAGS(a->null_lowervp, MTX_DUPOK);
        if (a->null_lowervp->v_usecount < 1)
                panic ("null with unref'ed lowervp, vp %p lvp %p",
                    vp, a->null_lowervp);
        VI_UNLOCK(a->null_lowervp);
#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