File:  [DragonFly] / src / sys / vfs / nullfs / Attic / null_subr.c
Revision 1.7: download - view: text, annotated - select for diffs
Mon Mar 1 06:33:22 2004 UTC (10 years, 5 months ago) by dillon
Branches: MAIN
CVS tags: HEAD
Newtoken commit.  Change the token implementation as follows:  (1) Obtaining
a token no longer enters a critical section.  (2) tokens can be held through
schedular switches and blocking conditions and are effectively released and
reacquired on resume.  Thus tokens serialize access only while the thread
is actually running.  Serialization is not broken by preemptive interrupts.
That is, interrupt threads which preempt do no release the preempted thread's
tokens.  (3) Unlike spl's, tokens will interlock w/ interrupt threads on
the same or on a different cpu.

The vnode interlock code has been rewritten and the API has changed.  The
mountlist vnode scanning code has been consolidated and all known races have
been fixed.  The vnode interlock is now a pool token.

The code that frees unreferenced vnodes whos last VM page has been freed has
been moved out of the low level vm_page_free() code and moved to the
periodic filesystem sycer code in vfs_msycn().

The SMP startup code and the IPI code has been cleaned up considerably.
Certain early token interactions on AP cpus have been moved to the BSP.

The LWKT rwlock API has been cleaned up and turned on.

Major testing by: David Rhodus

/*
 * 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. 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.
 *
 *	@(#)null_subr.c	8.7 (Berkeley) 5/14/95
 *
 * $FreeBSD: src/sys/miscfs/nullfs/null_subr.c,v 1.21.2.4 2001/06/26 04:20:09 bp Exp $
 * $DragonFly: src/sys/vfs/nullfs/null_subr.c,v 1.7 2004/03/01 06:33:22 dillon Exp $
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/malloc.h>
#include "null.h"

#define LOG2_SIZEVNODE 7		/* 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 lock null_hashlock;

static MALLOC_DEFINE(M_NULLFSHASH, "NULLFS hash", "NULLFS hash table");
MALLOC_DEFINE(M_NULLFSNODE, "NULLFS node", "NULLFS vnode private part");

static int	null_node_alloc(struct mount *mp, struct vnode *lowervp,
				     struct vnode **vpp);
static struct vnode *
		null_node_find(struct mount *mp, struct vnode *lowervp);

/*
 * 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);
	lockinit(&null_hashlock, 0, "nullhs", 0, 0);
	return (0);
}

int
nullfs_uninit(vfsp)
	struct vfsconf *vfsp;
{

        if (null_node_hashtbl) {
		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_node_find(mp, lowervp)
	struct mount *mp;
	struct vnode *lowervp;
{
	struct thread *td = curthread;	/* XXX */
	struct null_node_hashhead *hd;
	struct null_node *a;
	struct vnode *vp;

	/*
	 * 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);
loop:
	lockmgr(&null_hashlock, LK_EXCLUSIVE, NULL, td);
	LIST_FOREACH(a, hd, null_hash) {
		if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
			vp = NULLTOV(a);
			lockmgr(&null_hashlock, LK_RELEASE, NULL, td);
			/*
			 * We need vget for the VXLOCK
			 * stuff, but we don't want to lock
			 * the lower node.
			 */
			if (vget(vp, NULL, LK_EXCLUSIVE | LK_CANRECURSE, td)) {
				printf ("null_node_find: vget failed.\n");
				goto loop;
			}
			VOP_UNLOCK(lowervp, NULL, 0, td);
			return (vp);
		}
	}
	lockmgr(&null_hashlock, LK_RELEASE, NULL, td);

	return NULLVP;
}


/*
 * Make a new null_node node.
 * Vp is the alias vnode, lofsvp is the lower vnode.
 * Maintain a reference to (lowervp).
 */
static int
null_node_alloc(mp, lowervp, vpp)
	struct mount *mp;
	struct vnode *lowervp;
	struct vnode **vpp;
{
	struct thread *td = curthread;	/* XXX */
	struct null_node_hashhead *hd;
	struct null_node *xp;
	struct vnode *othervp, *vp;
	int error;

	/*
	 * 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.
	 */
	MALLOC(xp, struct null_node *, sizeof(struct null_node),
	    M_NULLFSNODE, M_WAITOK);

	error = getnewvnode(VT_NULL, mp, null_vnodeop_p, vpp);
	if (error) {
		FREE(xp, M_NULLFSNODE);
		return (error);
	}
	vp = *vpp;

	vp->v_type = lowervp->v_type;

	/*
	 * XXX:
	 * When nullfs encounters sockets or device nodes, it
	 * has a hard time working with the normal vp union.
	 * This still needs to be investigated.
	 */
	if (vp->v_type == VCHR || vp->v_type == VBLK)
		addalias(vp, lowervp->v_un.vu_spec.vu_specinfo);
	else
		vp->v_un = lowervp->v_un;
	lockinit(&xp->null_lock, 0, "nullnode", 0, LK_CANRECURSE);
	xp->null_vnode = vp;
	vp->v_data = xp;
	xp->null_lowervp = lowervp;
	/*
	 * Before we insert our new node onto the hash chains,
	 * check to see if someone else has beaten us to it.
	 * (We could have slept in MALLOC.)
	 */
	othervp = null_node_find(mp, lowervp);
	if (othervp) {
		vp->v_data = NULL;
		FREE(xp, M_NULLFSNODE);
		vp->v_type = VBAD;	/* node is discarded */
		vrele(vp);
		*vpp = othervp;
		return 0;
	}

	/*
	 * From NetBSD:
	 * Now lock the new node. We rely on the fact that we were passed
	 * a locked vnode. If the lower node is exporting a struct lock
	 * (v_vnlock != NULL) then we just set the upper v_vnlock to the
	 * lower one, and both are now locked. If the lower node is exporting
	 * NULL, then we copy that up and manually lock the new vnode.
	 */

	lockmgr(&null_hashlock, LK_EXCLUSIVE, NULL, td);
	vp->v_vnlock = lowervp->v_vnlock;
	error = VOP_LOCK(vp, NULL, LK_EXCLUSIVE | LK_THISLAYER, td);
	if (error)
		panic("null_node_alloc: can't lock new vnode\n");

	VREF(lowervp);
	hd = NULL_NHASH(lowervp);
	LIST_INSERT_HEAD(hd, xp, null_hash);
	lockmgr(&null_hashlock, LK_RELEASE, NULL, td);
	return 0;
}


/*
 * Try to find an existing null_node vnode refering to the given underlying
 * vnode (which should be locked). If no vnode found, create a new null_node
 * vnode which contains a reference to the lower vnode.
 */
int
null_node_create(mp, lowervp, newvpp)
	struct mount *mp;
	struct vnode *lowervp;
	struct vnode **newvpp;
{
	struct vnode *aliasvp;

	aliasvp = null_node_find(mp, lowervp);
	if (aliasvp) {
		/*
		 * null_node_find has taken another reference
		 * to the alias vnode.
		 */
		vrele(lowervp);
#ifdef NULLFS_DEBUG
		vprint("null_node_create: exists", aliasvp);
#endif
	} else {
		int error;

		/*
		 * Get new vnode.
		 */
		NULLFSDEBUG("null_node_create: create new alias vnode\n");

		/*
		 * Make new vnode reference the null_node.
		 */
		error = null_node_alloc(mp, lowervp, &aliasvp);
		if (error)
			return error;

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

#ifdef DIAGNOSTIC
	if (lowervp->v_usecount < 1) {
		/* Should never happen... */
		vprint ("null_node_create: alias ", aliasvp);
		vprint ("null_node_create: lower ", lowervp);
		panic ("null_node_create: lower has 0 usecount.");
	};
#endif

#ifdef NULLFS_DEBUG
	vprint("null_node_create: alias", aliasvp);
	vprint("null_node_create: lower", lowervp);
#endif

	*newvpp = aliasvp;
	return (0);
}

#ifdef DIAGNOSTIC
#include "opt_ddb.h"

#ifdef DDB
#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;
{
	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 (a->null_lowervp->v_usecount < 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");
	};
#ifdef notyet
	printf("null %x/%d -> %x/%d [%s, %d]\n",
	        NULLTOV(a), NULLTOV(a)->v_usecount,
		a->null_lowervp, a->null_lowervp->v_usecount,
		fil, lno);
#endif
	return a->null_lowervp;
}
#endif