/*
 * Copyright (c) 1992 The Regents of the University of California
 * Copyright (c) 1990, 1992 Jan-Simon Pendry
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 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.
 *
 * From:
 *	Id: lofs_subr.c,v 4.1 1993/12/17 10:47:45 jsp Rel
 *
 *	$Id: lofs_subr.c,v 1.1 1994/01/05 14:15:34 cgd Exp $
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <miscfs/lofs/lofs.h>

#define LOG2_SIZEVNODE 8		/* log2(sizeof struct vnode) */
#define	NLOFSCACHE 16
#define	LOFS_NHASH(vp) ((((u_long)vp)>>LOG2_SIZEVNODE) & (NLOFSCACHE-1))

/*
 * Loopback cache:
 * Each cache entry holds a reference to the target vnode
 * along with a pointer to the alias vnode.  When an
 * entry is added the target vnode is VREF'd.  When the
 * alias is removed the target vnode is vrele'd.
 */

/*
 * Cache head
 */
struct lofscache {
	struct lofsnode	*ac_forw;
	struct lofsnode	*ac_back;
};

static struct lofscache lofscache[NLOFSCACHE];

/*
 * Initialise cache headers
 */
lofs_init()
{
	struct lofscache *ac;
#ifdef LOFS_DIAGNOSTIC
	printf("lofs_init\n");		/* printed during system boot */
#endif
	if (sizeof(struct lofsnode) > VN_MAXPRIVATE)
		printf("lofsnode: ERROR: sizeof(struct lofsnode) > VN_MAXPRIVATE\n");

	for (ac = lofscache; ac < lofscache + NLOFSCACHE; ac++)
		ac->ac_forw = ac->ac_back = (struct lofsnode *) ac;
}

/*
 * Compute hash list for given target vnode
 */
static struct lofscache *
lofs_hash(targetvp)
struct vnode *targetvp;
{
	return (&lofscache[LOFS_NHASH(targetvp)]);
}

/*
 * Make a new lofsnode node.
 * Vp is the alias vnode, lofsvp is the target vnode.
 * Maintain a reference to (targetvp).
 */
static void
lofs_alloc(vp, targetvp)
	struct vnode *vp;
	struct vnode *targetvp;
{
	struct lofscache *hd;
	struct lofsnode *a;

#ifdef LOFS_DIAGNOSTIC
	printf("lofs_alloc(%x, %x)\n", vp, targetvp);
#endif

 	a = LOFSP(vp);
	a->a_vnode = vp;
	VREF(targetvp);
	LOFSP(vp)->a_lofsvp = targetvp;
	hd = lofs_hash(targetvp);
	insque(a, hd);

#ifdef LOFS_DIAGNOSTIC
	vprint("alloc vp", vp);
	vprint("alloc targetvp", targetvp);
#endif
}

#ifdef LOFS_DIAGNOSTIC
void
lofs_flushmp(mp)
	struct mount *mp;
{
	struct lofscache *ac;
	int i = 0;
	struct lofsnode *roota;

	printf("lofs_flushmp(%x)\n", mp);

	roota = LOFSP(VFSTOLOFS(mp)->rootvp);

	for (ac = lofscache; ac < lofscache + NLOFSCACHE; ac++) {
		struct lofsnode *a = ac->ac_forw;
		while (a != (struct lofsnode *) ac) {
			if (a != roota && a->a_vnode->v_mount == mp) {
				struct vnode *vp = a->a_lofsvp;
				if (vp) {
					a->a_lofsvp = 0;
					vprint("would vrele", vp);
					/*vrele(vp);*/
					i++;
				}
			}
			a = a->a_forw;
		}
	}
	if (i > 0)
		printf("lofsnode: vrele'd %d aliases\n", i);
}
#endif

/*
 * Return alias for target vnode if already exists, else 0.
 */
static struct lofsnode *
lofs_find(mp, targetvp)
	struct mount *mp;
	struct vnode *targetvp;
{
	struct lofscache *hd;
	struct lofsnode *a;

#ifdef LOFS_DIAGNOSTIC
	printf("lofs_find(mp = %x, target = %x)\n", mp, targetvp);
#endif

	/*
	 * Find hash base, and then search the (two-way) linked
	 * list looking for a lofsnode structure which is referencing
	 * the target vnode.  If found, the increment the lofsnode
	 * reference count (but NOT the target vnode's VREF counter).
	 */
	hd = lofs_hash(targetvp);

	for (a = hd->ac_forw; a != (struct lofsnode *) hd; a = a->a_forw) {
		if (a->a_lofsvp == targetvp && a->a_vnode->v_mount == mp) {
#ifdef LOFS_DIAGNOSTIC
			printf("lofs_find(%x): found (%x,%x)->%x\n",
				targetvp, mp, a->a_vnode, targetvp);
#endif
			return (a);
		}
	}

#ifdef LOFS_DIAGNOSTIC
	printf("lofs_find(%x, %x): NOT found\n", mp, targetvp);
#endif

	return (0);
}

static int
lofs_alias(mp, targetvp, newvpp)
	struct mount *mp;
	struct vnode *targetvp;
	struct vnode **newvpp;
{
	struct lofsnode *ap;
	struct vnode *aliasvp;

	if (targetvp->v_type != VDIR || targetvp->v_op == &lofs_vnodeops) {
		*newvpp = targetvp;
		return;
	}

	ap = lofs_find(mp, targetvp);

	if (ap) {
		/*
		 * Take another reference to the alias vnode
		 */
#ifdef LOFS_DIAGNOSTIC
		vprint("lofs_alias: exists", ap->a_vnode);
#endif
		aliasvp = ap->a_vnode;
		VREF(aliasvp);
	} else {
		int error;

		/*
		 * Get new vnode.
		 */
#ifdef LOFS_DIAGNOSTIC
		printf("lofs_alias: create new alias vnode\n");
#endif
		if (error = getnewvnode(VT_UFS, mp, &lofs_vnodeops, &aliasvp))
			return (error);	/* XXX: VT_LOFS above */

		/*
		 * Must be a directory
		 */
		aliasvp->v_type = VDIR;

		/*
		 * Make new vnode reference the lofsnode.
		 */
		lofs_alloc(aliasvp, targetvp);

		/*
		 * aliasvp is already VREF'd by getnewvnode()
		 */
	}

	vrele(targetvp);

#ifdef LOFS_DIAGNOSTIC
	vprint("lofs_alias alias", aliasvp);
	vprint("lofs_alias target", targetvp);
#endif

	*newvpp = aliasvp;
	return (0);
}

/*
 * Try to find an existing lofsnode vnode refering
 * to it, otherwise make a new lofsnode vnode which
 * contains a reference to the target vnode.
 */
make_lofs(mp, ndp)
	struct mount *mp;
	struct nameidata *ndp;
{
	int error;
	struct vnode *aliasvp;
	struct vnode *aliasdvp;
	struct vnode *targetvp;
	struct vnode *targetdvp;

#ifdef LOFS_DIAGNOSTIC
	printf("make_lofs(mp = %x, nidvp = %x, nivp = %x)\n",
				mp, ndp->ni_dvp, ndp->ni_vp);
#endif

	/*
	 * (targetvp) is locked at this point.
	 */
	targetvp = ndp->ni_vp;
	targetdvp = ndp->ni_dvp;

#ifdef LOFS_DIAGNOSTIC
	if (targetvp == 0)
		panic("make_lofs: null vp");
#endif

	/*
	 * Try to find an existing reference to the target vnodes.
	 */
	error = lofs_alias(mp, targetvp, &aliasvp);
	if (error)
		return (error);
	if (targetdvp) {
		error = lofs_alias(mp, targetdvp, &aliasdvp);
		if (error)
			return (error);
	} else
		aliasdvp = NULLVP;

	ndp->ni_vp = aliasvp;
	ndp->ni_dvp = aliasdvp;

	return (0);
}

#ifdef LOFS_DIAGNOSTIC
struct vnode *
lofs_checkvp(vp, fil, lno)
	struct vnode *vp;
	char *fil;
	int lno;
{
	struct lofsnode *a = LOFSP(vp);
	if (a->a_lofsvp == 0) {
		int i; u_long *p;
		printf("vp = %x, ZERO ptr\n", vp);
#ifdef notdef
		for (p = (u_long *) a, i = 0; i < 8; i++)
			printf(" %x", p[i]);
		printf("\n");
		DELAY(2000000);
		panic("lofs_checkvp");
#endif
	}
	printf("aliasvp %x/%d -> %x/%d [%s, %d]\n",
		a->a_vnode, a->a_vnode->v_usecount,
		a->a_lofsvp, a->a_lofsvp ? a->a_lofsvp->v_usecount : -42,
		fil, lno);
	return a->a_lofsvp;
}
#endif