[apple/libc.git] / db.subproj / hash.subproj / hash_buf.c

/*
 * Copyright (c) 1999 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@
 */
/*
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Margo Seltzer.
 *
 * 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.
 */


/*
 * PACKAGE: hash
 *
 * DESCRIPTION:
 *	Contains buffer management
 *
 * ROUTINES:
 * External
 *	__buf_init
 *	__get_buf
 *	__buf_free
 *	__reclaim_buf
 * Internal
 *	newbuf
 */

#include <sys/param.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#ifdef DEBUG
#include <assert.h>
#endif

#include <db.h>
#include "hash.h"
#include "page.h"
#include "extern.h"

static BUFHEAD *newbuf __P((HTAB *, u_int, BUFHEAD *));

/* Unlink B from its place in the lru */
#define BUF_REMOVE(B) { \
	(B)->prev->next = (B)->next; \
	(B)->next->prev = (B)->prev; \
}

/* Insert B after P */
#define BUF_INSERT(B, P) { \
	(B)->next = (P)->next; \
	(B)->prev = (P); \
	(P)->next = (B); \
	(B)->next->prev = (B); \
}

#define	MRU	hashp->bufhead.next
#define	LRU	hashp->bufhead.prev

#define MRU_INSERT(B)	BUF_INSERT((B), &hashp->bufhead)
#define LRU_INSERT(B)	BUF_INSERT((B), LRU)

/*
 * We are looking for a buffer with address "addr".  If prev_bp is NULL, then
 * address is a bucket index.  If prev_bp is not NULL, then it points to the
 * page previous to an overflow page that we are trying to find.
 *
 * CAVEAT:  The buffer header accessed via prev_bp's ovfl field may no longer
 * be valid.  Therefore, you must always verify that its address matches the
 * address you are seeking.
 */
extern BUFHEAD *
__get_buf(hashp, addr, prev_bp, newpage)
	HTAB *hashp;
	u_int addr;
	BUFHEAD *prev_bp;
	int newpage;	/* If prev_bp set, indicates a new overflow page. */
{
	register BUFHEAD *bp;
	register u_int is_disk_mask;
	register int is_disk, segment_ndx;
	SEGMENT segp;

	is_disk = 0;
	is_disk_mask = 0;
	if (prev_bp) {
		bp = prev_bp->ovfl;
		if (!bp || (bp->addr != addr))
			bp = NULL;
		if (!newpage)
			is_disk = BUF_DISK;
	} else {
		/* Grab buffer out of directory */
		segment_ndx = addr & (hashp->SGSIZE - 1);

		/* valid segment ensured by __call_hash() */
		segp = hashp->dir[addr >> hashp->SSHIFT];
#ifdef DEBUG
		assert(segp != NULL);
#endif
		bp = PTROF(segp[segment_ndx]);
		is_disk_mask = ISDISK(segp[segment_ndx]);
		is_disk = is_disk_mask || !hashp->new_file;
	}

	if (!bp) {
		bp = newbuf(hashp, addr, prev_bp);
		if (!bp ||
		    __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
			return (NULL);
		if (!prev_bp)
			segp[segment_ndx] =
			    (BUFHEAD *)((u_int)bp | is_disk_mask);
	} else {
		BUF_REMOVE(bp);
		MRU_INSERT(bp);
	}
	return (bp);
}

/*
 * We need a buffer for this page. Either allocate one, or evict a resident
 * one (if we have as many buffers as we're allowed) and put this one in.
 *
 * If newbuf finds an error (returning NULL), it also sets errno.
 */
static BUFHEAD *
newbuf(hashp, addr, prev_bp)
	HTAB *hashp;
	u_int addr;
	BUFHEAD *prev_bp;
{
	register BUFHEAD *bp;		/* The buffer we're going to use */
	register BUFHEAD *xbp;		/* Temp pointer */
	register BUFHEAD *next_xbp;
	SEGMENT segp;
	int segment_ndx;
	u_short oaddr, *shortp;

	oaddr = 0;
	bp = LRU;
	/*
	 * If LRU buffer is pinned, the buffer pool is too small. We need to
	 * allocate more buffers.
	 */
	if (hashp->nbufs || (bp->flags & BUF_PIN)) {
		/* Allocate a new one */
		if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL)
			return (NULL);
		if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) {
			free(bp);
			return (NULL);
		}
		if (hashp->nbufs)
			hashp->nbufs--;
	} else {
		/* Kick someone out */
		BUF_REMOVE(bp);
		/*
		 * If this is an overflow page with addr 0, it's already been
		 * flushed back in an overflow chain and initialized.
		 */
		if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
			/*
			 * Set oaddr before __put_page so that you get it
			 * before bytes are swapped.
			 */
			shortp = (u_short *)bp->page;
			if (shortp[0])
				oaddr = shortp[shortp[0] - 1];
			if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
			    bp->addr, (int)IS_BUCKET(bp->flags), 0))
				return (NULL);
			/*
			 * Update the pointer to this page (i.e. invalidate it).
			 *
			 * If this is a new file (i.e. we created it at open
			 * time), make sure that we mark pages which have been
			 * written to disk so we retrieve them from disk later,
			 * rather than allocating new pages.
			 */
			if (IS_BUCKET(bp->flags)) {
				segment_ndx = bp->addr & (hashp->SGSIZE - 1);
				segp = hashp->dir[bp->addr >> hashp->SSHIFT];
#ifdef DEBUG
				assert(segp != NULL);
#endif

				if (hashp->new_file &&
				    ((bp->flags & BUF_MOD) ||
				    ISDISK(segp[segment_ndx])))
					segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
				else
					segp[segment_ndx] = NULL;
			}
			/*
			 * Since overflow pages can only be access by means of
			 * their bucket, free overflow pages associated with
			 * this bucket.
			 */
			for (xbp = bp; xbp->ovfl;) {
				next_xbp = xbp->ovfl;
				xbp->ovfl = 0;
				xbp = next_xbp;

				/* Check that ovfl pointer is up date. */
				if (IS_BUCKET(xbp->flags) ||
				    (oaddr != xbp->addr))
					break;

				shortp = (u_short *)xbp->page;
				if (shortp[0])
					/* set before __put_page */
					oaddr = shortp[shortp[0] - 1];
				if ((xbp->flags & BUF_MOD) && __put_page(hashp,
				    xbp->page, xbp->addr, 0, 0))
					return (NULL);
				xbp->addr = 0;
				xbp->flags = 0;
				BUF_REMOVE(xbp);
				LRU_INSERT(xbp);
			}
		}
	}

	/* Now assign this buffer */
	bp->addr = addr;
#ifdef DEBUG1
	(void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
	    bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
#endif
	bp->ovfl = NULL;
	if (prev_bp) {
		/*
		 * If prev_bp is set, this is an overflow page, hook it in to
		 * the buffer overflow links.
		 */
#ifdef DEBUG1
		(void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
		    prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
		    (bp ? bp->addr : 0));
#endif
		prev_bp->ovfl = bp;
		bp->flags = 0;
	} else
		bp->flags = BUF_BUCKET;
	MRU_INSERT(bp);
	return (bp);
}

extern void
__buf_init(hashp, nbytes)
	HTAB *hashp;
	int nbytes;
{
	BUFHEAD *bfp;
	int npages;

	bfp = &(hashp->bufhead);
	npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
	npages = MAX(npages, MIN_BUFFERS);

	hashp->nbufs = npages;
	bfp->next = bfp;
	bfp->prev = bfp;
	/*
	 * This space is calloc'd so these are already null.
	 *
	 * bfp->ovfl = NULL;
	 * bfp->flags = 0;
	 * bfp->page = NULL;
	 * bfp->addr = 0;
	 */
}

extern int
__buf_free(hashp, do_free, to_disk)
	HTAB *hashp;
	int do_free, to_disk;
{
	BUFHEAD *bp;

	/* Need to make sure that buffer manager has been initialized */
	if (!LRU)
		return (0);
	for (bp = LRU; bp != &hashp->bufhead;) {
		/* Check that the buffer is valid */
		if (bp->addr || IS_BUCKET(bp->flags)) {
			if (to_disk && (bp->flags & BUF_MOD) &&
			    __put_page(hashp, bp->page,
			    bp->addr, IS_BUCKET(bp->flags), 0))
				return (-1);
		}
		/* Check if we are freeing stuff */
		if (do_free) {
			if (bp->page)
				free(bp->page);
			BUF_REMOVE(bp);
			free(bp);
			bp = LRU;
		} else
			bp = bp->prev;
	}
	return (0);
}

extern void
__reclaim_buf(hashp, bp)
	HTAB *hashp;
	BUFHEAD *bp;
{
	bp->ovfl = 0;
	bp->addr = 0;
	bp->flags = 0;
	BUF_REMOVE(bp);
	LRU_INSERT(bp);
}
Commit	Line	Data
e9ce8d39 A	1	/*
	2	* Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
	3	*
	4	* @APPLE_LICENSE_HEADER_START@
	5	*
	6	* The contents of this file constitute Original Code as defined in and
	7	* are subject to the Apple Public Source License Version 1.1 (the
	8	* "License"). You may not use this file except in compliance with the
	9	* License. Please obtain a copy of the License at
	10	* http://www.apple.com/publicsource and read it before using this file.
	11	*
	12	* This Original Code and all software distributed under the License are
	13	* distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
	14	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
	15	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
	16	* FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
	17	* License for the specific language governing rights and limitations
	18	* under the License.
	19	*
	20	* @APPLE_LICENSE_HEADER_END@
	21	*/
	22	/*
	23	* Copyright (c) 1990, 1993
	24	* The Regents of the University of California. All rights reserved.
	25	*
	26	* This code is derived from software contributed to Berkeley by
	27	* Margo Seltzer.
	28	*
	29	* Redistribution and use in source and binary forms, with or without
	30	* modification, are permitted provided that the following conditions
	31	* are met:
	32	* 1. Redistributions of source code must retain the above copyright
	33	* notice, this list of conditions and the following disclaimer.
	34	* 2. Redistributions in binary form must reproduce the above copyright
	35	* notice, this list of conditions and the following disclaimer in the
	36	* documentation and/or other materials provided with the distribution.
	37	* 3. All advertising materials mentioning features or use of this software
	38	* must display the following acknowledgement:
	39	* This product includes software developed by the University of
	40	* California, Berkeley and its contributors.
	41	* 4. Neither the name of the University nor the names of its contributors
	42	* may be used to endorse or promote products derived from this software
	43	* without specific prior written permission.
	44	*
	45	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	46	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	47	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	48	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	49	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	50	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	51	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	52	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	53	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	54	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	55	* SUCH DAMAGE.
	56	*/
	57
	58
	59	/*
	60	* PACKAGE: hash
	61	*
	62	* DESCRIPTION:
	63	* Contains buffer management
	64	*
65	* ROUTINES:
66	* External
67	* __buf_init
68	* __get_buf
69	* __buf_free
70	* __reclaim_buf
71	* Internal
72	* newbuf
73	*/
74
75	#include <sys/param.h>
76
77	#include <errno.h>
78	#include <stdio.h>
79	#include <stdlib.h>
80	#ifdef DEBUG
81	#include <assert.h>
82	#endif
83
84	#include <db.h>
85	#include "hash.h"
86	#include "page.h"
87	#include "extern.h"
88
89	static BUFHEAD newbuf __P((HTAB , u_int, BUFHEAD *));
90
91	/* Unlink B from its place in the lru */
92	#define BUF_REMOVE(B) { \
93	(B)->prev->next = (B)->next; \
94	(B)->next->prev = (B)->prev; \
95	}
96
97	/* Insert B after P */
98	#define BUF_INSERT(B, P) { \
99	(B)->next = (P)->next; \
100	(B)->prev = (P); \
101	(P)->next = (B); \
102	(B)->next->prev = (B); \
103	}
104
105	#define MRU hashp->bufhead.next
106	#define LRU hashp->bufhead.prev
107
108	#define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
109	#define LRU_INSERT(B) BUF_INSERT((B), LRU)
110
111	/*
112	* We are looking for a buffer with address "addr". If prev_bp is NULL, then
113	* address is a bucket index. If prev_bp is not NULL, then it points to the
114	* page previous to an overflow page that we are trying to find.
115	*
116	* CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
117	* be valid. Therefore, you must always verify that its address matches the
118	* address you are seeking.
119	*/
120	extern BUFHEAD *
121	__get_buf(hashp, addr, prev_bp, newpage)
122	HTAB *hashp;
123	u_int addr;
124	BUFHEAD *prev_bp;
125	int newpage; /* If prev_bp set, indicates a new overflow page. */
126	{
127	register BUFHEAD *bp;
128	register u_int is_disk_mask;
129	register int is_disk, segment_ndx;
130	SEGMENT segp;
131
132	is_disk = 0;
133	is_disk_mask = 0;
134	if (prev_bp) {
135	bp = prev_bp->ovfl;
136	if (!bp \|\| (bp->addr != addr))
137	bp = NULL;
138	if (!newpage)
139	is_disk = BUF_DISK;
140	} else {
141	/* Grab buffer out of directory */
142	segment_ndx = addr & (hashp->SGSIZE - 1);
143
144	/* valid segment ensured by __call_hash() */
145	segp = hashp->dir[addr >> hashp->SSHIFT];
146	#ifdef DEBUG
147	assert(segp != NULL);
148	#endif
149	bp = PTROF(segp[segment_ndx]);
150	is_disk_mask = ISDISK(segp[segment_ndx]);
151	is_disk = is_disk_mask \|\| !hashp->new_file;
152	}
153
154	if (!bp) {
155	bp = newbuf(hashp, addr, prev_bp);
156	if (!bp \|\|
157	__get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
158	return (NULL);
159	if (!prev_bp)
160	segp[segment_ndx] =
161	(BUFHEAD *)((u_int)bp \| is_disk_mask);
162	} else {
163	BUF_REMOVE(bp);
164	MRU_INSERT(bp);
165	}
166	return (bp);
167	}
168
169	/*
170	* We need a buffer for this page. Either allocate one, or evict a resident
171	* one (if we have as many buffers as we're allowed) and put this one in.
172	*
173	* If newbuf finds an error (returning NULL), it also sets errno.
174	*/
175	static BUFHEAD *
176	newbuf(hashp, addr, prev_bp)
177	HTAB *hashp;
178	u_int addr;
179	BUFHEAD *prev_bp;
180	{
181	register BUFHEAD bp; / The buffer we're going to use */
182	register BUFHEAD xbp; / Temp pointer */
183	register BUFHEAD *next_xbp;
184	SEGMENT segp;
185	int segment_ndx;
186	u_short oaddr, *shortp;
187
188	oaddr = 0;
189	bp = LRU;
190	/*
191	* If LRU buffer is pinned, the buffer pool is too small. We need to
192	* allocate more buffers.
193	*/
194	if (hashp->nbufs \|\| (bp->flags & BUF_PIN)) {
195	/* Allocate a new one */
196	if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL)
197	return (NULL);
198	if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) {
199	free(bp);
200	return (NULL);
201	}
202	if (hashp->nbufs)
203	hashp->nbufs--;
204	} else {
205	/* Kick someone out */
206	BUF_REMOVE(bp);
207	/*
208	* If this is an overflow page with addr 0, it's already been
209	* flushed back in an overflow chain and initialized.
210	*/
211	if ((bp->addr != 0) \|\| (bp->flags & BUF_BUCKET)) {
212	/*
213	* Set oaddr before __put_page so that you get it
214	* before bytes are swapped.
215	*/
216	shortp = (u_short *)bp->page;
217	if (shortp[0])
218	oaddr = shortp[shortp[0] - 1];
219	if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
220	bp->addr, (int)IS_BUCKET(bp->flags), 0))
221	return (NULL);
222	/*
223	* Update the pointer to this page (i.e. invalidate it).
224	*
225	* If this is a new file (i.e. we created it at open
226	* time), make sure that we mark pages which have been
227	* written to disk so we retrieve them from disk later,
228	* rather than allocating new pages.
229	*/
230	if (IS_BUCKET(bp->flags)) {
231	segment_ndx = bp->addr & (hashp->SGSIZE - 1);
232	segp = hashp->dir[bp->addr >> hashp->SSHIFT];
233	#ifdef DEBUG
234	assert(segp != NULL);
235	#endif
236
237	if (hashp->new_file &&
238	((bp->flags & BUF_MOD) \|\|
239	ISDISK(segp[segment_ndx])))
240	segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
241	else
242	segp[segment_ndx] = NULL;
243	}
244	/*
245	* Since overflow pages can only be access by means of
246	* their bucket, free overflow pages associated with
247	* this bucket.
248	*/
249	for (xbp = bp; xbp->ovfl;) {
250	next_xbp = xbp->ovfl;
251	xbp->ovfl = 0;
252	xbp = next_xbp;
253
254	/* Check that ovfl pointer is up date. */
255	if (IS_BUCKET(xbp->flags) \|\|
256	(oaddr != xbp->addr))
257	break;
258
259	shortp = (u_short *)xbp->page;
260	if (shortp[0])
261	/* set before __put_page */
262	oaddr = shortp[shortp[0] - 1];
263	if ((xbp->flags & BUF_MOD) && __put_page(hashp,
264	xbp->page, xbp->addr, 0, 0))
265	return (NULL);
266	xbp->addr = 0;
267	xbp->flags = 0;
268	BUF_REMOVE(xbp);
269	LRU_INSERT(xbp);
270	}
271	}
272	}
273
274	/* Now assign this buffer */
275	bp->addr = addr;
276	#ifdef DEBUG1
277	(void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
278	bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
279	#endif
280	bp->ovfl = NULL;
281	if (prev_bp) {
282	/*
283	* If prev_bp is set, this is an overflow page, hook it in to
284	* the buffer overflow links.
285	*/
286	#ifdef DEBUG1
287	(void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
288	prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
289	(bp ? bp->addr : 0));
290	#endif
291	prev_bp->ovfl = bp;
292	bp->flags = 0;
293	} else
294	bp->flags = BUF_BUCKET;
295	MRU_INSERT(bp);
296	return (bp);
297	}
298
299	extern void
300	__buf_init(hashp, nbytes)
301	HTAB *hashp;
302	int nbytes;
303	{
304	BUFHEAD *bfp;
305	int npages;
306
307	bfp = &(hashp->bufhead);
308	npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
309	npages = MAX(npages, MIN_BUFFERS);
310
311	hashp->nbufs = npages;
312	bfp->next = bfp;
313	bfp->prev = bfp;
314	/*
315	* This space is calloc'd so these are already null.
316	*
317	* bfp->ovfl = NULL;
318	* bfp->flags = 0;
319	* bfp->page = NULL;
320	* bfp->addr = 0;
321	*/
322	}
323
324	extern int
325	__buf_free(hashp, do_free, to_disk)
326	HTAB *hashp;
327	int do_free, to_disk;
328	{
329	BUFHEAD *bp;
330
331	/* Need to make sure that buffer manager has been initialized */
332	if (!LRU)
333	return (0);
334	for (bp = LRU; bp != &hashp->bufhead;) {
335	/* Check that the buffer is valid */
336	if (bp->addr \|\| IS_BUCKET(bp->flags)) {
337	if (to_disk && (bp->flags & BUF_MOD) &&
338	__put_page(hashp, bp->page,
339	bp->addr, IS_BUCKET(bp->flags), 0))
340	return (-1);
341	}
342	/* Check if we are freeing stuff */
343	if (do_free) {
344	if (bp->page)
345	free(bp->page);
346	BUF_REMOVE(bp);
347	free(bp);
348	bp = LRU;
349	} else
350	bp = bp->prev;
351	}
352	return (0);
353	}
354
355	extern void
356	__reclaim_buf(hashp, bp)
357	HTAB *hashp;
358	BUFHEAD *bp;
359	{
360	bp->ovfl = 0;
361	bp->addr = 0;
362	bp->flags = 0;
363	BUF_REMOVE(bp);
364	LRU_INSERT(bp);
365	}