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36 * $FreeBSD: src/lib/libc/db/hash/hash_buf.c,v 1.4.8.1 2001/03/05 07:38:05 obrien Exp $
39 #if defined(LIBC_SCCS) && !defined(lint)
40 static char sccsid[] = "@(#)hash_buf.c 8.5 (Berkeley) 7/15/94";
41 #endif /* LIBC_SCCS and not lint */
47 * Contains buffer management
59 #include <sys/param.h>
74 static BUFHEAD *newbuf __P((HTAB *, u_int32_t, BUFHEAD *));
76 /* Unlink B from its place in the lru */
77 #define BUF_REMOVE(B) { \
78 (B)->prev->next = (B)->next; \
79 (B)->next->prev = (B)->prev; \
82 /* Insert B after P */
83 #define BUF_INSERT(B, P) { \
84 (B)->next = (P)->next; \
87 (B)->next->prev = (B); \
90 #define MRU hashp->bufhead.next
91 #define LRU hashp->bufhead.prev
93 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
94 #define LRU_INSERT(B) BUF_INSERT((B), LRU)
97 * We are looking for a buffer with address "addr". If prev_bp is NULL, then
98 * address is a bucket index. If prev_bp is not NULL, then it points to the
99 * page previous to an overflow page that we are trying to find.
101 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
102 * be valid. Therefore, you must always verify that its address matches the
103 * address you are seeking.
106 __get_buf(hashp, addr, prev_bp, newpage)
110 int newpage; /* If prev_bp set, indicates a new overflow page. */
112 register BUFHEAD *bp;
113 register u_int32_t is_disk_mask;
114 register int is_disk, segment_ndx;
121 if (!bp || (bp->addr != addr))
126 /* Grab buffer out of directory */
127 segment_ndx = addr & (hashp->SGSIZE - 1);
129 /* valid segment ensured by __call_hash() */
130 segp = hashp->dir[addr >> hashp->SSHIFT];
132 assert(segp != NULL);
134 bp = PTROF(segp[segment_ndx]);
135 is_disk_mask = ISDISK(segp[segment_ndx]);
136 is_disk = is_disk_mask || !hashp->new_file;
140 bp = newbuf(hashp, addr, prev_bp);
142 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
146 (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask);
155 * We need a buffer for this page. Either allocate one, or evict a resident
156 * one (if we have as many buffers as we're allowed) and put this one in.
158 * If newbuf finds an error (returning NULL), it also sets errno.
161 newbuf(hashp, addr, prev_bp)
166 register BUFHEAD *bp; /* The buffer we're going to use */
167 register BUFHEAD *xbp; /* Temp pointer */
168 register BUFHEAD *next_xbp;
171 u_int16_t oaddr, *shortp;
176 * If LRU buffer is pinned, the buffer pool is too small. We need to
177 * allocate more buffers.
179 if (hashp->nbufs || (bp->flags & BUF_PIN)) {
180 /* Allocate a new one */
181 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL)
184 memset(bp, 0xff, sizeof(BUFHEAD));
186 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) {
191 memset(bp->page, 0xff, hashp->BSIZE);
196 /* Kick someone out */
199 * If this is an overflow page with addr 0, it's already been
200 * flushed back in an overflow chain and initialized.
202 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
204 * Set oaddr before __put_page so that you get it
205 * before bytes are swapped.
207 shortp = (u_int16_t *)bp->page;
209 oaddr = shortp[shortp[0] - 1];
210 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
211 bp->addr, (int)IS_BUCKET(bp->flags), 0))
214 * Update the pointer to this page (i.e. invalidate it).
216 * If this is a new file (i.e. we created it at open
217 * time), make sure that we mark pages which have been
218 * written to disk so we retrieve them from disk later,
219 * rather than allocating new pages.
221 if (IS_BUCKET(bp->flags)) {
222 segment_ndx = bp->addr & (hashp->SGSIZE - 1);
223 segp = hashp->dir[bp->addr >> hashp->SSHIFT];
225 assert(segp != NULL);
228 if (hashp->new_file &&
229 ((bp->flags & BUF_MOD) ||
230 ISDISK(segp[segment_ndx])))
231 segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
233 segp[segment_ndx] = NULL;
236 * Since overflow pages can only be access by means of
237 * their bucket, free overflow pages associated with
240 for (xbp = bp; xbp->ovfl;) {
241 next_xbp = xbp->ovfl;
245 /* Check that ovfl pointer is up date. */
246 if (IS_BUCKET(xbp->flags) ||
247 (oaddr != xbp->addr))
250 shortp = (u_int16_t *)xbp->page;
252 /* set before __put_page */
253 oaddr = shortp[shortp[0] - 1];
254 if ((xbp->flags & BUF_MOD) && __put_page(hashp,
255 xbp->page, xbp->addr, 0, 0))
265 /* Now assign this buffer */
268 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
269 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
274 * If prev_bp is set, this is an overflow page, hook it in to
275 * the buffer overflow links.
278 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
279 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
280 (bp ? bp->addr : 0));
285 bp->flags = BUF_BUCKET;
291 __buf_init(hashp, nbytes)
298 bfp = &(hashp->bufhead);
299 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
300 npages = MAX(npages, MIN_BUFFERS);
302 hashp->nbufs = npages;
306 * This space is calloc'd so these are already null.
316 __buf_free(hashp, do_free, to_disk)
318 int do_free, to_disk;
322 /* Need to make sure that buffer manager has been initialized */
325 for (bp = LRU; bp != &hashp->bufhead;) {
326 /* Check that the buffer is valid */
327 if (bp->addr || IS_BUCKET(bp->flags)) {
328 if (to_disk && (bp->flags & BUF_MOD) &&
329 __put_page(hashp, bp->page,
330 bp->addr, IS_BUCKET(bp->flags), 0))
333 /* Check if we are freeing stuff */
347 __reclaim_buf(hashp, bp)