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32 * $FreeBSD: src/lib/libc/db/hash/hash_buf.c,v 1.4.8.1 2001/03/05 07:38:05 obrien Exp $
33 * $DragonFly: src/lib/libc/db/hash/hash_buf.c,v 1.7 2005/11/19 20:46:32 swildner Exp $
35 * @(#)hash_buf.c 8.5 (Berkeley) 7/15/94
42 * Contains buffer management
54 #include <sys/param.h>
69 static BUFHEAD *newbuf (HTAB *, u_int32_t, BUFHEAD *);
71 /* Unlink B from its place in the lru */
72 #define BUF_REMOVE(B) { \
73 (B)->prev->next = (B)->next; \
74 (B)->next->prev = (B)->prev; \
77 /* Insert B after P */
78 #define BUF_INSERT(B, P) { \
79 (B)->next = (P)->next; \
82 (B)->next->prev = (B); \
85 #define MRU hashp->bufhead.next
86 #define LRU hashp->bufhead.prev
88 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
89 #define LRU_INSERT(B) BUF_INSERT((B), LRU)
92 * We are looking for a buffer with address "addr". If prev_bp is NULL, then
93 * address is a bucket index. If prev_bp is not NULL, then it points to the
94 * page previous to an overflow page that we are trying to find.
96 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
97 * be valid. Therefore, you must always verify that its address matches the
98 * address you are seeking.
101 * newpage: If prev_bp set, indicates a new overflow page
104 __get_buf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp, int newpage)
107 u_int32_t is_disk_mask;
108 int is_disk, segment_ndx;
117 if (!bp || (bp->addr != addr))
122 /* Grab buffer out of directory */
123 segment_ndx = addr & (hashp->SGSIZE - 1);
125 /* valid segment ensured by __call_hash() */
126 segp = hashp->dir[addr >> hashp->SSHIFT];
128 assert(segp != NULL);
130 bp = PTROF(segp[segment_ndx]);
131 is_disk_mask = ISDISK(segp[segment_ndx]);
132 is_disk = is_disk_mask || !hashp->new_file;
136 bp = newbuf(hashp, addr, prev_bp);
138 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
142 (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask);
151 * We need a buffer for this page. Either allocate one, or evict a resident
152 * one (if we have as many buffers as we're allowed) and put this one in.
154 * If newbuf finds an error (returning NULL), it also sets errno.
157 newbuf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp)
159 BUFHEAD *bp; /* The buffer we're going to use */
160 BUFHEAD *xbp; /* Temp pointer */
164 u_int16_t oaddr, *shortp;
169 * If LRU buffer is pinned, the buffer pool is too small. We need to
170 * allocate more buffers.
172 if (hashp->nbufs || (bp->flags & BUF_PIN)) {
173 /* Allocate a new one */
174 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL)
177 memset(bp, 0xff, sizeof(BUFHEAD));
179 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) {
184 memset(bp->page, 0xff, hashp->BSIZE);
189 /* Kick someone out */
192 * If this is an overflow page with addr 0, it's already been
193 * flushed back in an overflow chain and initialized.
195 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
197 * Set oaddr before __put_page so that you get it
198 * before bytes are swapped.
200 shortp = (u_int16_t *)bp->page;
202 oaddr = shortp[shortp[0] - 1];
203 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
204 bp->addr, (int)IS_BUCKET(bp->flags), 0))
207 * Update the pointer to this page (i.e. invalidate it).
209 * If this is a new file (i.e. we created it at open
210 * time), make sure that we mark pages which have been
211 * written to disk so we retrieve them from disk later,
212 * rather than allocating new pages.
214 if (IS_BUCKET(bp->flags)) {
215 segment_ndx = bp->addr & (hashp->SGSIZE - 1);
216 segp = hashp->dir[bp->addr >> hashp->SSHIFT];
218 assert(segp != NULL);
221 if (hashp->new_file &&
222 ((bp->flags & BUF_MOD) ||
223 ISDISK(segp[segment_ndx])))
224 segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
226 segp[segment_ndx] = NULL;
229 * Since overflow pages can only be access by means of
230 * their bucket, free overflow pages associated with
233 for (xbp = bp; xbp->ovfl;) {
234 next_xbp = xbp->ovfl;
238 /* Check that ovfl pointer is up date. */
239 if (IS_BUCKET(xbp->flags) ||
240 (oaddr != xbp->addr))
243 shortp = (u_int16_t *)xbp->page;
245 /* set before __put_page */
246 oaddr = shortp[shortp[0] - 1];
247 if ((xbp->flags & BUF_MOD) && __put_page(hashp,
248 xbp->page, xbp->addr, 0, 0))
258 /* Now assign this buffer */
261 fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
262 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
267 * If prev_bp is set, this is an overflow page, hook it in to
268 * the buffer overflow links.
271 fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
272 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
273 (bp ? bp->addr : 0));
278 bp->flags = BUF_BUCKET;
284 __buf_init(HTAB *hashp, int nbytes)
289 bfp = &(hashp->bufhead);
290 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
291 npages = MAX(npages, MIN_BUFFERS);
293 hashp->nbufs = npages;
297 * This space is calloc'd so these are already null.
307 __buf_free(HTAB *hashp, int do_free, int to_disk)
311 /* Need to make sure that buffer manager has been initialized */
314 for (bp = LRU; bp != &hashp->bufhead;) {
315 /* Check that the buffer is valid */
316 if (bp->addr || IS_BUCKET(bp->flags)) {
317 if (to_disk && (bp->flags & BUF_MOD) &&
318 __put_page(hashp, bp->page,
319 bp->addr, IS_BUCKET(bp->flags), 0))
322 /* Check if we are freeing stuff */
336 __reclaim_buf(HTAB *hashp, BUFHEAD *bp)