1 /*-
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Margo Seltzer.
7 *
8 * %sccs.include.redist.c%
9 */
10
11 #if defined(LIBC_SCCS) && !defined(lint)
12 static char sccsid[] = "@(#)hash_buf.c 8.2 (Berkeley) 02/21/94";
13 #endif /* LIBC_SCCS and not lint */
14
15 /*
16 * PACKAGE: hash
17 *
18 * DESCRIPTION:
19 * Contains buffer management
20 *
21 * ROUTINES:
22 * External
23 * __buf_init
24 * __get_buf
25 * __buf_free
26 * __reclaim_buf
27 * Internal
28 * newbuf
29 */
30
31 #include <sys/param.h>
32
33 #include <errno.h>
34 #include <stdio.h>
35 #include <stdlib.h>
36 #ifdef DEBUG
37 #include <assert.h>
38 #endif
39
40 #include <db.h>
41 #include "hash.h"
42 #include "page.h"
43 #include "extern.h"
44
45 static BUFHEAD *newbuf __P((HTAB *, u_int, BUFHEAD *));
46
47 /* Unlink B from its place in the lru */
48 #define BUF_REMOVE(B) { \
49 (B)->prev->next = (B)->next; \
50 (B)->next->prev = (B)->prev; \
51 }
52
53 /* Insert B after P */
54 #define BUF_INSERT(B, P) { \
55 (B)->next = (P)->next; \
56 (B)->prev = (P); \
57 (P)->next = (B); \
58 (B)->next->prev = (B); \
59 }
60
61 #define MRU hashp->bufhead.next
62 #define LRU hashp->bufhead.prev
63
64 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
65 #define LRU_INSERT(B) BUF_INSERT((B), LRU)
66
67 /*
68 * We are looking for a buffer with address "addr". If prev_bp is NULL, then
69 * address is a bucket index. If prev_bp is not NULL, then it points to the
70 * page previous to an overflow page that we are trying to find.
71 *
72 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
73 * be valid. Therefore, you must always verify that its address matches the
74 * address you are seeking.
75 */
76 extern BUFHEAD *
77 __get_buf(hashp, addr, prev_bp, newpage)
78 HTAB *hashp;
79 u_int addr;
80 BUFHEAD *prev_bp;
81 int newpage; /* If prev_bp set, indicates a new overflow page. */
82 {
83 register BUFHEAD *bp;
84 register u_int is_disk_mask;
85 register int is_disk, segment_ndx;
86 SEGMENT segp;
87
88 is_disk = 0;
89 is_disk_mask = 0;
90 if (prev_bp) {
91 bp = prev_bp->ovfl;
92 if (!bp || (bp->addr != addr))
93 bp = NULL;
94 if (!newpage)
95 is_disk = BUF_DISK;
96 } else {
97 /* Grab buffer out of directory */
98 segment_ndx = addr & (hashp->SGSIZE - 1);
99
100 /* valid segment ensured by __call_hash() */
101 segp = hashp->dir[addr >> hashp->SSHIFT];
102 #ifdef DEBUG
103 assert(segp != NULL);
104 #endif
105 bp = PTROF(segp[segment_ndx]);
106 is_disk_mask = ISDISK(segp[segment_ndx]);
107 is_disk = is_disk_mask || !hashp->new_file;
108 }
109
110 if (!bp) {
111 bp = newbuf(hashp, addr, prev_bp);
112 if (!bp ||
113 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
114 return (NULL);
115 if (!prev_bp)
116 segp[segment_ndx] =
117 (BUFHEAD *)((u_int)bp | is_disk_mask);
118 } else {
119 BUF_REMOVE(bp);
120 MRU_INSERT(bp);
121 }
122 return (bp);
123 }
124
125 /*
126 * We need a buffer for this page. Either allocate one, or evict a resident
127 * one (if we have as many buffers as we're allowed) and put this one in.
128 *
129 * If newbuf finds an error (returning NULL), it also sets errno.
130 */
131 static BUFHEAD *
newbuf(hashp,addr,prev_bp)132 newbuf(hashp, addr, prev_bp)
133 HTAB *hashp;
134 u_int addr;
135 BUFHEAD *prev_bp;
136 {
137 register BUFHEAD *bp; /* The buffer we're going to use */
138 register BUFHEAD *xbp; /* Temp pointer */
139 register BUFHEAD *next_xbp;
140 SEGMENT segp;
141 int segment_ndx;
142 u_short oaddr, *shortp;
143
144 oaddr = 0;
145 bp = LRU;
146 /*
147 * If LRU buffer is pinned, the buffer pool is too small. We need to
148 * allocate more buffers.
149 */
150 if (hashp->nbufs || (bp->flags & BUF_PIN)) {
151 /* Allocate a new one */
152 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL)
153 return (NULL);
154 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) {
155 free(bp);
156 return (NULL);
157 }
158 if (hashp->nbufs)
159 hashp->nbufs--;
160 } else {
161 /* Kick someone out */
162 BUF_REMOVE(bp);
163 /*
164 * If this is an overflow page with addr 0, it's already been
165 * flushed back in an overflow chain and initialized.
166 */
167 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
168 /*
169 * Set oaddr before __put_page so that you get it
170 * before bytes are swapped.
171 */
172 shortp = (u_short *)bp->page;
173 if (shortp[0])
174 oaddr = shortp[shortp[0] - 1];
175 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
176 bp->addr, (int)IS_BUCKET(bp->flags), 0))
177 return (NULL);
178 /*
179 * Update the pointer to this page (i.e. invalidate it).
180 *
181 * If this is a new file (i.e. we created it at open
182 * time), make sure that we mark pages which have been
183 * written to disk so we retrieve them from disk later,
184 * rather than allocating new pages.
185 */
186 if (IS_BUCKET(bp->flags)) {
187 segment_ndx = bp->addr & (hashp->SGSIZE - 1);
188 segp = hashp->dir[bp->addr >> hashp->SSHIFT];
189 #ifdef DEBUG
190 assert(segp != NULL);
191 #endif
192
193 if (hashp->new_file &&
194 ((bp->flags & BUF_MOD) ||
195 ISDISK(segp[segment_ndx])))
196 segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
197 else
198 segp[segment_ndx] = NULL;
199 }
200 /*
201 * Since overflow pages can only be access by means of
202 * their bucket, free overflow pages associated with
203 * this bucket.
204 */
205 for (xbp = bp; xbp->ovfl;) {
206 next_xbp = xbp->ovfl;
207 xbp->ovfl = 0;
208 xbp = next_xbp;
209
210 /* Check that ovfl pointer is up date. */
211 if (IS_BUCKET(xbp->flags) ||
212 (oaddr != xbp->addr))
213 break;
214
215 shortp = (u_short *)xbp->page;
216 if (shortp[0])
217 /* set before __put_page */
218 oaddr = shortp[shortp[0] - 1];
219 if ((xbp->flags & BUF_MOD) && __put_page(hashp,
220 xbp->page, xbp->addr, 0, 0))
221 return (NULL);
222 xbp->addr = 0;
223 xbp->flags = 0;
224 BUF_REMOVE(xbp);
225 LRU_INSERT(xbp);
226 }
227 }
228 }
229
230 /* Now assign this buffer */
231 bp->addr = addr;
232 #ifdef DEBUG1
233 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
234 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
235 #endif
236 bp->ovfl = NULL;
237 if (prev_bp) {
238 /*
239 * If prev_bp is set, this is an overflow page, hook it in to
240 * the buffer overflow links.
241 */
242 #ifdef DEBUG1
243 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
244 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
245 (bp ? bp->addr : 0));
246 #endif
247 prev_bp->ovfl = bp;
248 bp->flags = 0;
249 } else
250 bp->flags = BUF_BUCKET;
251 MRU_INSERT(bp);
252 return (bp);
253 }
254
255 extern void
256 __buf_init(hashp, nbytes)
257 HTAB *hashp;
258 int nbytes;
259 {
260 BUFHEAD *bfp;
261 int npages;
262
263 bfp = &(hashp->bufhead);
264 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
265 npages = MAX(npages, MIN_BUFFERS);
266
267 hashp->nbufs = npages;
268 bfp->next = bfp;
269 bfp->prev = bfp;
270 /*
271 * This space is calloc'd so these are already null.
272 *
273 * bfp->ovfl = NULL;
274 * bfp->flags = 0;
275 * bfp->page = NULL;
276 * bfp->addr = 0;
277 */
278 }
279
280 extern int
281 __buf_free(hashp, do_free, to_disk)
282 HTAB *hashp;
283 int do_free, to_disk;
284 {
285 BUFHEAD *bp;
286
287 /* Need to make sure that buffer manager has been initialized */
288 if (!LRU)
289 return (0);
290 for (bp = LRU; bp != &hashp->bufhead;) {
291 /* Check that the buffer is valid */
292 if (bp->addr || IS_BUCKET(bp->flags)) {
293 if (to_disk && (bp->flags & BUF_MOD) &&
294 __put_page(hashp, bp->page,
295 bp->addr, IS_BUCKET(bp->flags), 0))
296 return (-1);
297 }
298 /* Check if we are freeing stuff */
299 if (do_free) {
300 if (bp->page)
301 free(bp->page);
302 BUF_REMOVE(bp);
303 free(bp);
304 bp = LRU;
305 } else
306 bp = bp->prev;
307 }
308 return (0);
309 }
310
311 extern void
312 __reclaim_buf(hashp, bp)
313 HTAB *hashp;
314 BUFHEAD *bp;
315 {
316 bp->ovfl = 0;
317 bp->addr = 0;
318 bp->flags = 0;
319 BUF_REMOVE(bp);
320 LRU_INSERT(bp);
321 }
322