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>
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 __get_buf(hashp, addr, prev_bp, newpage)
106 int newpage; /* If prev_bp set, indicates a new overflow page. */
109 u_int32_t is_disk_mask;
110 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(hashp, addr, prev_bp)
162 BUFHEAD *bp; /* The buffer we're going to use */
163 BUFHEAD *xbp; /* Temp pointer */
167 u_int16_t oaddr, *shortp;
172 * If LRU buffer is pinned, the buffer pool is too small. We need to
173 * allocate more buffers.
175 if (hashp->nbufs || (bp->flags & BUF_PIN)) {
176 /* Allocate a new one */
177 if ((bp = (BUFHEAD *)malloc(sizeof(BUFHEAD))) == NULL)
180 memset(bp, 0xff, sizeof(BUFHEAD));
182 if ((bp->page = (char *)malloc(hashp->BSIZE)) == NULL) {
187 memset(bp->page, 0xff, hashp->BSIZE);
192 /* Kick someone out */
195 * If this is an overflow page with addr 0, it's already been
196 * flushed back in an overflow chain and initialized.
198 if ((bp->addr != 0) || (bp->flags & BUF_BUCKET)) {
200 * Set oaddr before __put_page so that you get it
201 * before bytes are swapped.
203 shortp = (u_int16_t *)bp->page;
205 oaddr = shortp[shortp[0] - 1];
206 if ((bp->flags & BUF_MOD) && __put_page(hashp, bp->page,
207 bp->addr, (int)IS_BUCKET(bp->flags), 0))
210 * Update the pointer to this page (i.e. invalidate it).
212 * If this is a new file (i.e. we created it at open
213 * time), make sure that we mark pages which have been
214 * written to disk so we retrieve them from disk later,
215 * rather than allocating new pages.
217 if (IS_BUCKET(bp->flags)) {
218 segment_ndx = bp->addr & (hashp->SGSIZE - 1);
219 segp = hashp->dir[bp->addr >> hashp->SSHIFT];
221 assert(segp != NULL);
224 if (hashp->new_file &&
225 ((bp->flags & BUF_MOD) ||
226 ISDISK(segp[segment_ndx])))
227 segp[segment_ndx] = (BUFHEAD *)BUF_DISK;
229 segp[segment_ndx] = NULL;
232 * Since overflow pages can only be access by means of
233 * their bucket, free overflow pages associated with
236 for (xbp = bp; xbp->ovfl;) {
237 next_xbp = xbp->ovfl;
241 /* Check that ovfl pointer is up date. */
242 if (IS_BUCKET(xbp->flags) ||
243 (oaddr != xbp->addr))
246 shortp = (u_int16_t *)xbp->page;
248 /* set before __put_page */
249 oaddr = shortp[shortp[0] - 1];
250 if ((xbp->flags & BUF_MOD) && __put_page(hashp,
251 xbp->page, xbp->addr, 0, 0))
261 /* Now assign this buffer */
264 (void)fprintf(stderr, "NEWBUF1: %d->ovfl was %d is now %d\n",
265 bp->addr, (bp->ovfl ? bp->ovfl->addr : 0), 0);
270 * If prev_bp is set, this is an overflow page, hook it in to
271 * the buffer overflow links.
274 (void)fprintf(stderr, "NEWBUF2: %d->ovfl was %d is now %d\n",
275 prev_bp->addr, (prev_bp->ovfl ? bp->ovfl->addr : 0),
276 (bp ? bp->addr : 0));
281 bp->flags = BUF_BUCKET;
287 __buf_init(hashp, nbytes)
294 bfp = &(hashp->bufhead);
295 npages = (nbytes + hashp->BSIZE - 1) >> hashp->BSHIFT;
296 npages = MAX(npages, MIN_BUFFERS);
298 hashp->nbufs = npages;
302 * This space is calloc'd so these are already null.
312 __buf_free(hashp, do_free, to_disk)
314 int do_free, to_disk;
318 /* Need to make sure that buffer manager has been initialized */
321 for (bp = LRU; bp != &hashp->bufhead;) {
322 /* Check that the buffer is valid */
323 if (bp->addr || IS_BUCKET(bp->flags)) {
324 if (to_disk && (bp->flags & BUF_MOD) &&
325 __put_page(hashp, bp->page,
326 bp->addr, IS_BUCKET(bp->flags), 0))
329 /* Check if we are freeing stuff */
343 __reclaim_buf(hashp, bp)