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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>
70 static BUFHEAD *newbuf (HTAB *, u_int32_t, BUFHEAD *);
72 /* Unlink B from its place in the lru */
73 #define BUF_REMOVE(B) { \
74 (B)->prev->next = (B)->next; \
75 (B)->next->prev = (B)->prev; \
78 /* Insert B after P */
79 #define BUF_INSERT(B, P) { \
80 (B)->next = (P)->next; \
83 (B)->next->prev = (B); \
86 #define MRU hashp->bufhead.next
87 #define LRU hashp->bufhead.prev
89 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
90 #define LRU_INSERT(B) BUF_INSERT((B), LRU)
93 * We are looking for a buffer with address "addr". If prev_bp is NULL, then
94 * address is a bucket index. If prev_bp is not NULL, then it points to the
95 * page previous to an overflow page that we are trying to find.
97 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
98 * be valid. Therefore, you must always verify that its address matches the
99 * address you are seeking.
102 * newpage: If prev_bp set, indicates a new overflow page
105 __get_buf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp, int newpage)
108 u_int32_t is_disk_mask;
109 int is_disk, segment_ndx;
118 if (!bp || (bp->addr != addr))
123 /* Grab buffer out of directory */
124 segment_ndx = addr & (hashp->SGSIZE - 1);
126 /* valid segment ensured by __call_hash() */
127 segp = hashp->dir[addr >> hashp->SSHIFT];
129 assert(segp != NULL);
131 bp = PTROF(segp[segment_ndx]);
132 is_disk_mask = ISDISK(segp[segment_ndx]);
133 is_disk = is_disk_mask || !hashp->new_file;
137 bp = newbuf(hashp, addr, prev_bp);
139 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
143 (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask);
152 * We need a buffer for this page. Either allocate one, or evict a resident
153 * one (if we have as many buffers as we're allowed) and put this one in.
155 * If newbuf finds an error (returning NULL), it also sets errno.
158 newbuf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp)
160 BUFHEAD *bp; /* The buffer we're going to use */
161 BUFHEAD *xbp; /* Temp pointer */
165 u_int16_t oaddr, *shortp;
170 * If LRU buffer is pinned, the buffer pool is too small. We need to
171 * allocate more buffers.
173 if (hashp->nbufs || (bp->flags & BUF_PIN)) {
174 /* Allocate a new one */
175 if ((bp = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL)
178 memset(bp, 0xff, sizeof(BUFHEAD));
180 if ((bp->page = (char *)calloc(1, hashp->BSIZE)) == NULL) {
185 memset(bp->page, 0xff, hashp->BSIZE);
190 /* Kick someone out */
193 * If this is an overflow page with addr 0, it's already been
194 * flushed back in an overflow chain and initialized.
196 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
198 * Set oaddr before __put_page so that you get it
199 * before bytes are swapped.
201 shortp = (u_int16_t *)bp->page;
203 oaddr = shortp[shortp[0] - 1];
204 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
205 bp->addr, (int)IS_BUCKET(bp->flags), 0))
208 * Update the pointer to this page (i.e. invalidate it).
210 * If this is a new file (i.e. we created it at open
211 * time), make sure that we mark pages which have been
212 * written to disk so we retrieve them from disk later,
213 * rather than allocating new pages.
215 if (IS_BUCKET(bp->flags)) {
216 segment_ndx = bp->addr & (hashp->SGSIZE - 1);
217 segp = hashp->dir[bp->addr >> hashp->SSHIFT];
219 assert(segp != NULL);
222 if (hashp->new_file &&
223 ((bp->flags & BUF_MOD) ||
224 ISDISK(segp[segment_ndx])))
225 segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
227 segp[segment_ndx] = NULL;
230 * Since overflow pages can only be access by means of
231 * their bucket, free overflow pages associated with
234 for (xbp = bp; xbp->ovfl;) {
235 next_xbp = xbp->ovfl;
239 /* Check that ovfl pointer is up date. */
240 if (IS_BUCKET(xbp->flags) ||
241 (oaddr != xbp->addr))
244 shortp = (u_int16_t *)xbp->page;
246 /* set before __put_page */
247 oaddr = shortp[shortp[0] - 1];
248 if ((xbp->flags & BUF_MOD) && __put_page(hashp,
249 xbp->page, xbp->addr, 0, 0))
259 /* Now assign this buffer */
262 fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
263 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
268 * If prev_bp is set, this is an overflow page, hook it in to
269 * the buffer overflow links.
272 fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
273 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
274 (bp ? bp->addr : 0));
279 bp->flags = BUF_BUCKET;
285 __buf_init(HTAB *hashp, int nbytes)
290 bfp = &(hashp->bufhead);
291 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
292 npages = MAX(npages, MIN_BUFFERS);
294 hashp->nbufs = npages;
298 * This space is calloc'd so these are already null.
308 __buf_free(HTAB *hashp, int do_free, int to_disk)
312 /* Need to make sure that buffer manager has been initialized */
315 for (bp = LRU; bp != &hashp->bufhead;) {
316 /* Check that the buffer is valid */
317 if (bp->addr || IS_BUCKET(bp->flags)) {
318 if (to_disk && (bp->flags & BUF_MOD) &&
319 __put_page(hashp, bp->page,
320 bp->addr, IS_BUCKET(bp->flags), 0))
323 /* Check if we are freeing stuff */
326 memset(bp->page, 0, hashp->BSIZE);
339 __reclaim_buf(HTAB *hashp, BUFHEAD *bp)