BTreeNodeReserve.c   [plain text]

/*
 * Copyright (c) 2004-2008 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The 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, QUIET ENJOYMENT OR NON-INFRINGEMENT.
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 */
#include "../headers/BTreesPrivate.h"
#include "sys/malloc.h"
#include <kern/locks.h>


/*
 * B-tree Node Reserve
 *
 * BTReserveSpace
 * BTReleaseReserve
 * BTUpdateReserve
 *
 * 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_thread())

#define	NR_CACHE 17

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

LIST_HEAD(nodereserve, nreserve) *nr_hashtbl;

u_long nr_hashmask;

lck_grp_t * nr_lck_grp;
lck_grp_attr_t * nr_lck_grp_attr;
lck_attr_t * nr_lck_attr;

lck_mtx_t  nr_mutex;

/* 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 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("hfs: BTReserveSetup: nreserve size != opaque struct size");

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

	nr_lck_grp_attr= lck_grp_attr_alloc_init();
	nr_lck_grp  = lck_grp_alloc_init("btree_node_reserve", nr_lck_grp_attr);

	nr_lck_attr = lck_attr_alloc_init();

	lck_mtx_init(&nr_mutex, nr_lck_grp, nr_lck_attr);
}


/*
 * BTReserveSpace - obtain a node reserve (for current thread)
 *
 * Used by the Catalog Layer (hfs_catalog.c) to reserve space.
 *
 * When data is NULL, we only insure that there's enough space
 * but it is not reserved (assumes you keep the b-tree lock).
 */
__private_extern__
int
BTReserveSpace(FCB *file, int operations, void* data)
{
	BTreeControlBlock *btree;
	int rsrvNodes, availNodes, totalNodes;
	int height;
	int inserts, deletes;
	u_int32_t clumpsize;
	int err = 0;

	btree = (BTreeControlBlockPtr)file->fcbBTCBPtr;
	clumpsize = file->ff_clumpsize;

	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;
	if (height < 2)
		height = 2;  /* prevent underflow in rsrvNodes calculation */
	inserts = operations & 0xffff;
	deletes = operations >> 16;
	
	/*
	 * Allow for at least one root split.
	 *
	 * Each delete operation can propogate a big key up the
	 * index. This can cause a split at each level up.
	 *
	 * Each insert operation can cause a local split and a
	 * split at each level up.
	 */
	rsrvNodes = 1 + (deletes * (height - 2)) + (inserts * (height - 1));

	availNodes = btree->freeNodes - btree->reservedNodes;
	
	if (rsrvNodes > availNodes) {
		u_int32_t reqblks, freeblks, rsrvblks;
		struct hfsmount *hfsmp;

		/* Try and reserve the last 5% of the disk space for file blocks. */
		hfsmp = VTOVCB(btree->fileRefNum);
		rsrvblks = ((u_int64_t)hfsmp->allocLimit * 5) / 100;
		rsrvblks = MIN(rsrvblks, HFS_MAXRESERVE / hfsmp->blockSize);
		freeblks = hfs_freeblks(hfsmp, 0);
		if (freeblks <= rsrvblks) {
			/* When running low, disallow adding new items. */
			if ((inserts > 0) && (deletes == 0)) {
				return (ENOSPC);
			}
			freeblks = 0;
		} else {
			freeblks -= rsrvblks;
		}
		reqblks = clumpsize / hfsmp->blockSize;

		if (reqblks > freeblks) {
			reqblks = ((rsrvNodes - availNodes) * btree->nodeSize) / hfsmp->blockSize;
			/* When running low, disallow adding new items. */
			if ((reqblks > freeblks) && (inserts > 0) && (deletes == 0)) {
				return (ENOSPC);
			}
			file->ff_clumpsize = freeblks * hfsmp->blockSize;
		}
		totalNodes = rsrvNodes + btree->totalNodes - availNodes;
		
		/* See if we also need a map node */
		if (totalNodes > (int)CalcMapBits(btree)) {
			++totalNodes;
		}
		if ((err = ExtendBTree(btree, totalNodes))) {
			goto out;
		}
	}
	/* Save this reserve if this is a persistent request. */
	if (data) {
		btree->reservedNodes += rsrvNodes;
		nr_insert(btree->fileRefNum, (struct nreserve *)data, rsrvNodes);
	}
out:
	/* Put clump size back if it was changed. */
	if (file->ff_clumpsize != clumpsize)
		file->ff_clumpsize = clumpsize;

	return (err);
}


/*
 * 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 occurred.
 */
__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
	 */
	lck_mtx_lock(&nr_mutex);
	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;
			tmp_nrp->nr_nodecnt += nodecnt;
			lck_mtx_unlock(&nr_mutex);
			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;
	lck_mtx_unlock(&nr_mutex);
}

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

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


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

	lck_mtx_lock(&nr_mutex);

	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;
		}
	}
	lck_mtx_unlock(&nr_mutex);
}