xnu-517.7.7.tar.gz

[apple/xnu.git] / bsd / hfs / hfscommon / BTree / BTreeNodeReserve.c

/*
 * Copyright (c) 2003 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
#include "../headers/BTreesPrivate.h"
#include "sys/malloc.h"


/*
 * B-tree Node Reserve
 *
 * BTReserveSpace
 * BTReleaseReserve
 * BTUpdateReserve
 * BTAvailableNodes
 *
 * Each kernel thread can have it's own reserve of b-tree
 * nodes. This reserve info is kept in a hash table.
 *
 * Don't forget to call BTReleaseReserve when you're finished
 * or you will leave stale node reserves in the hash.
 */


/*
 * BE CAREFUL WHEN INCREASING THE SIZE OF THIS STRUCT!
 *
 * It must remain equal in size to the opaque cat_cookie_t
 * struct (in hfs_catalog.h).
 */
struct nreserve {
	LIST_ENTRY(nreserve) nr_hash;  /* hash chain */
	int  nr_nodecnt;               /* count of nodes held in reserve */
	int  nr_newnodes;              /* nodes that were allocated */
	struct	vnode *nr_btvp;        /* b-tree file vnode */
	void  *nr_tag;                 /* unique tag (per thread) */
};

#define NR_GET_TAG()	(current_act())

#define	NR_CACHE 17

#define NR_HASH(btvp, tag) \
	(&nr_hashtbl[((((int)(btvp)) >> 8) ^ ((int)(tag) >> 4)) & nr_hashmask])

LIST_HEAD(nodereserve, nreserve) *nr_hashtbl;

u_long nr_hashmask;


/* Internal Node Reserve Hash Routines (private) */
static void nr_insert (struct vnode *, struct nreserve *nrp, int);
static void nr_delete (struct vnode *, struct nreserve *nrp, int *);
static int  nr_lookup (struct vnode *);
static void nr_update (struct vnode *, int);


/*
 * BTReserveSetup - initialize the node reserve hash table
 */
__private_extern__
void
BTReserveSetup()
{
	if (sizeof(struct nreserve) != sizeof(cat_cookie_t))
		panic("BTReserveSetup: nreserve size != opaque struct size");

	nr_hashtbl = hashinit(NR_CACHE, M_HFSMNT, &nr_hashmask);
}


/*
 * BTAvailNodes - obtain the actual available nodes (for current thread)
 *
 */
__private_extern__
SInt32
BTAvailableNodes(BTreeControlBlock *btree)
{
	SInt32 availNodes;

	availNodes = (SInt32)btree->freeNodes - (SInt32)btree->reservedNodes;

	return (availNodes + nr_lookup(btree->fileRefNum));
}


/*
 * BTReserveSpace - obtain a node reserve (for current thread)
 *
 * Used by the Catalog Layer (hfs_catalog.c) to reserve space.
 */
__private_extern__
int
BTReserveSpace(FCB *file, int operations, void* data)
{
	BTreeControlBlock *btree;
	int rsrvNodes, availNodes, totalNodes;
	int height;
	int inserts, deletes;
	int err = 0;

	btree = (BTreeControlBlockPtr)file->fcbBTCBPtr;

	REQUIRE_FILE_LOCK(btree->fileRefNum, true);

	/*
	 * The node reserve is based on the number of b-tree
	 * operations (insert/deletes) and the height of the
	 * tree.
	 */
	height = btree->treeDepth;
	inserts = operations & 0xffff;
	deletes = operations >> 16;
	
	rsrvNodes = 1; /* allow for at least one root split */
	if (deletes)
		rsrvNodes += (deletes * (height - 1)) - 1;
	if (inserts)
		rsrvNodes += (inserts * height) + 1;

	availNodes = btree->freeNodes - btree->reservedNodes;
	
	if (rsrvNodes > availNodes) {
		totalNodes = rsrvNodes + btree->totalNodes - availNodes;
		
		/* See if we also need a map node */
		if (totalNodes > CalcMapBits(btree))
			++totalNodes;
		if ((err = ExtendBTree(btree, totalNodes)))
			return (err);
	}	

	btree->reservedNodes += rsrvNodes;
	nr_insert(btree->fileRefNum, (struct nreserve *)data, rsrvNodes);
	return (0);
}


/*
 * BTReleaseReserve - release the node reserve held by current thread
 *
 * Used by the Catalog Layer (hfs_catalog.c) to relinquish reserved space.
 */
__private_extern__
int
BTReleaseReserve(FCB *file, void* data)
{
	BTreeControlBlock *btree;
	int nodecnt;

	btree = (BTreeControlBlockPtr)file->fcbBTCBPtr;
	
	REQUIRE_FILE_LOCK(btree->fileRefNum, true);

	nr_delete(btree->fileRefNum, (struct nreserve *)data, &nodecnt);

	if (nodecnt)
		btree->reservedNodes -= nodecnt;

	return (0);
}

/*
 * BTUpdateReserve - update a node reserve for allocations that occured.
 */
__private_extern__
void
BTUpdateReserve(BTreeControlBlockPtr btreePtr, int nodes)
{
	nr_update(btreePtr->fileRefNum, nodes);
}


/*----------------------------------------------------------------------------*/
/* Node Reserve Hash Functions (private) */


int nrinserts = 0;
int nrdeletes = 0;

/*
 * Insert a new node reserve.
 */
static void
nr_insert(struct vnode * btvp, struct nreserve *nrp, int nodecnt)
{
	struct nodereserve *nrhead;
	struct nreserve *tmp_nrp;
	void * tag = NR_GET_TAG();

	/*
	 * Check the cache - there may already be a reserve
	 */
	nrhead = NR_HASH(btvp, tag);
	for (tmp_nrp = nrhead->lh_first; tmp_nrp;
	     tmp_nrp = tmp_nrp->nr_hash.le_next) {
		if ((tmp_nrp->nr_tag == tag) && (tmp_nrp->nr_btvp == btvp)) {
			nrp->nr_tag = 0;
			return;
		}
	}

	nrp->nr_nodecnt = nodecnt;
	nrp->nr_newnodes = 0;
	nrp->nr_btvp = btvp;
	nrp->nr_tag = tag;
	LIST_INSERT_HEAD(nrhead, nrp, nr_hash);
	++nrinserts;
}

/*
 * Delete a node reserve.
 */
static void
nr_delete(struct vnode * btvp, struct nreserve *nrp, int *nodecnt)
{
	void * tag = NR_GET_TAG();

	if (nrp->nr_tag) {
		if ((nrp->nr_tag != tag) || (nrp->nr_btvp != btvp))
			panic("nr_delete: invalid NR (%08x)", nrp);
		LIST_REMOVE(nrp, nr_hash);
		*nodecnt = nrp->nr_nodecnt;
		bzero(nrp, sizeof(struct nreserve));
		++nrdeletes;
	} else {
		*nodecnt = 0;
	}
}

/*
 * Lookup a node reserve.
 */
static int
nr_lookup(struct vnode * btvp)
{
	struct nodereserve *nrhead;
	struct nreserve *nrp;
	void* tag = NR_GET_TAG();

	nrhead = NR_HASH(btvp, tag);
	for (nrp = nrhead->lh_first; nrp; nrp = nrp->nr_hash.le_next) {
		if ((nrp->nr_tag == tag) && (nrp->nr_btvp == btvp))
			return (nrp->nr_nodecnt - nrp->nr_newnodes);
	}
	return (0);
}

/*
 * Update a node reserve for any allocations that occured.
 */
static void
nr_update(struct vnode * btvp, int nodecnt)
{
	struct nodereserve *nrhead;
	struct nreserve *nrp;
	void* tag = NR_GET_TAG();

	nrhead = NR_HASH(btvp, tag);
	for (nrp = nrhead->lh_first; nrp; nrp = nrp->nr_hash.le_next) {
		if ((nrp->nr_tag == tag) && (nrp->nr_btvp == btvp)) {			
			nrp->nr_newnodes += nodecnt;
			break;
		}
	}
}