2 * Copyright (c) 1990, 1993, 1994
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
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20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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33 #if defined(LIBC_SCCS) && !defined(lint)
34 static char sccsid[] = "@(#)hash_buf.c 8.5 (Berkeley) 7/15/94";
35 #endif /* LIBC_SCCS and not lint */
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
43 * Contains buffer management
55 #include <sys/param.h>
71 static BUFHEAD *newbuf(HTAB *, u_int32_t, BUFHEAD *);
73 /* Unlink B from its place in the lru */
74 #define BUF_REMOVE(B) { \
75 (B)->prev->next = (B)->next; \
76 (B)->next->prev = (B)->prev; \
79 /* Insert B after P */
80 #define BUF_INSERT(B, P) { \
81 (B)->next = (P)->next; \
84 (B)->next->prev = (B); \
87 #define MRU hashp->bufhead.next
88 #define LRU hashp->bufhead.prev
90 #define MRU_INSERT(B) BUF_INSERT((B), &hashp->bufhead)
91 #define LRU_INSERT(B) BUF_INSERT((B), LRU)
94 * We are looking for a buffer with address "addr". If prev_bp is NULL, then
95 * address is a bucket index. If prev_bp is not NULL, then it points to the
96 * page previous to an overflow page that we are trying to find.
98 * CAVEAT: The buffer header accessed via prev_bp's ovfl field may no longer
99 * be valid. Therefore, you must always verify that its address matches the
100 * address you are seeking.
103 __get_buf(HTAB *hashp, u_int32_t addr,
104 BUFHEAD *prev_bp, /* If prev_bp set, indicates a new overflow page. */
108 u_int32_t is_disk_mask;
109 int is_disk, segment_ndx;
116 if (!bp || (bp->addr != addr))
121 /* Grab buffer out of directory */
122 segment_ndx = addr & (hashp->SGSIZE - 1);
124 /* valid segment ensured by __call_hash() */
125 segp = hashp->dir[addr >> hashp->SSHIFT];
127 assert(segp != NULL);
129 bp = PTROF(segp[segment_ndx]);
130 is_disk_mask = ISDISK(segp[segment_ndx]);
131 is_disk = is_disk_mask || !hashp->new_file;
135 bp = newbuf(hashp, addr, prev_bp);
137 __get_page(hashp, bp->page, addr, !prev_bp, is_disk, 0))
141 (BUFHEAD *)((ptrdiff_t)bp | is_disk_mask);
150 * We need a buffer for this page. Either allocate one, or evict a resident
151 * one (if we have as many buffers as we're allowed) and put this one in.
153 * If newbuf finds an error (returning NULL), it also sets errno.
156 newbuf(HTAB *hashp, u_int32_t addr, BUFHEAD *prev_bp)
158 BUFHEAD *bp; /* The buffer we're going to use */
159 BUFHEAD *xbp; /* Temp pointer */
163 u_int16_t oaddr, *shortp;
168 /* It is bad to overwrite the page under the cursor. */
169 if (bp == hashp->cpage) {
175 /* If prev_bp is part of bp overflow, create a new buffer. */
176 if (hashp->nbufs == 0 && prev_bp && bp->ovfl) {
179 for (ovfl = bp->ovfl; ovfl ; ovfl = ovfl->ovfl) {
180 if (ovfl == prev_bp) {
188 * If LRU buffer is pinned, the buffer pool is too small. We need to
189 * allocate more buffers.
191 if (hashp->nbufs || (bp->flags & BUF_PIN) || bp == hashp->cpage) {
192 /* Allocate a new one */
193 if ((bp = (BUFHEAD *)calloc(1, sizeof(BUFHEAD))) == NULL)
195 if ((bp->page = (char *)calloc(1, hashp->BSIZE)) == NULL) {
202 /* Kick someone out */
205 * If this is an overflow page with addr 0, it's already been
206 * flushed back in an overflow chain and initialized.
208 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
210 * Set oaddr before __put_page so that you get it
211 * before bytes are swapped.
213 shortp = (u_int16_t *)bp->page;
215 oaddr = shortp[shortp[0] - 1];
216 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
217 bp->addr, (int)IS_BUCKET(bp->flags), 0))
220 * Update the pointer to this page (i.e. invalidate it).
222 * If this is a new file (i.e. we created it at open
223 * time), make sure that we mark pages which have been
224 * written to disk so we retrieve them from disk later,
225 * rather than allocating new pages.
227 if (IS_BUCKET(bp->flags)) {
228 segment_ndx = bp->addr & (hashp->SGSIZE - 1);
229 segp = hashp->dir[bp->addr >> hashp->SSHIFT];
231 assert(segp != NULL);
234 if (hashp->new_file &&
235 ((bp->flags & BUF_MOD) ||
236 ISDISK(segp[segment_ndx])))
237 segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
239 segp[segment_ndx] = NULL;
242 * Since overflow pages can only be access by means of
243 * their bucket, free overflow pages associated with
246 for (xbp = bp; xbp->ovfl;) {
247 next_xbp = xbp->ovfl;
251 /* Check that ovfl pointer is up date. */
252 if (IS_BUCKET(xbp->flags) ||
253 (oaddr != xbp->addr))
256 shortp = (u_int16_t *)xbp->page;
258 /* set before __put_page */
259 oaddr = shortp[shortp[0] - 1];
260 if ((xbp->flags & BUF_MOD) && __put_page(hashp,
261 xbp->page, xbp->addr, 0, 0))
271 /* Now assign this buffer */
274 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
275 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
280 * If prev_bp is set, this is an overflow page, hook it in to
281 * the buffer overflow links.
284 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
285 prev_bp->addr, (prev_bp->ovfl ? prev_bp->ovfl->addr : 0),
286 (bp ? bp->addr : 0));
291 bp->flags = BUF_BUCKET;
297 __buf_init(HTAB *hashp, int nbytes)
302 bfp = &(hashp->bufhead);
303 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
304 npages = MAX(npages, MIN_BUFFERS);
306 hashp->nbufs = npages;
310 * This space is calloc'd so these are already null.
320 __buf_free(HTAB *hashp, int do_free, int to_disk)
324 /* Need to make sure that buffer manager has been initialized */
327 for (bp = LRU; bp != &hashp->bufhead;) {
328 /* Check that the buffer is valid */
329 if (bp->addr || IS_BUCKET(bp->flags)) {
330 if (to_disk && (bp->flags & BUF_MOD) &&
331 __put_page(hashp, bp->page,
332 bp->addr, IS_BUCKET(bp->flags), 0))
335 /* Check if we are freeing stuff */
338 (void)memset(bp->page, 0, hashp->BSIZE);
351 __reclaim_buf(HTAB *hashp, BUFHEAD *bp)