/*!
* \brief Create a new slot for a particular dbase page.
*/
static struct buffer *
newslot(struct ubik_dbase *adbase, afs_int32 afid, afs_int32 apage)
{
/* Find a usable buffer slot */
afs_int32 i;
struct buffer *pp, *tp;
pp = 0; /* last pure */
for (i = 0, tp = LruBuffer; i < nbuffers; i++, tp = tp->lru_next) {
if (!tp->lockers && !tp->dirty) {
pp = tp;
break;
}
}
if (pp == 0) {
/* There are no unlocked buffers that don't need to be written to the disk. */
ubik_print
("Ubik: Internal Error: Unable to find free buffer in ubik cache\n");
return NULL;
}
/* Now fill in the header. */
pp->dbase = adbase;
pp->file = afid;
pp->page = apage;
FixupBucket(pp); /* move to the right hash bucket */
Dmru(pp);
return pp;
}
/*!
* \brief Get a pointer to a particular buffer.
*/
static char *
DRead(struct ubik_trans *atrans, afs_int32 fid, int page)
{
/* Read a page from the disk. */
struct buffer *tb, *lastbuffer, *found_tb = NULL;
afs_int32 code;
struct ubik_dbase *dbase = atrans->dbase;
calls++;
lastbuffer = LruBuffer->lru_prev;
/* Skip for write transactions for a clean page - this may not be the right page to use */
if (MatchBuffer(lastbuffer, page, fid, atrans)
&& (atrans->type == UBIK_READTRANS || lastbuffer->dirty)) {
tb = lastbuffer;
tb->lockers++;
lastb++;
return tb->data;
}
for (tb = phTable[pHash(page)]; tb; tb = tb->hashNext) {
if (MatchBuffer(tb, page, fid, atrans)) {
if (tb->dirty || atrans->type == UBIK_READTRANS) {
found_tb = tb;
break;
}
/* Remember this clean page - we might use it */
found_tb = tb;
}
}
/* For a write transaction, use a matching clean page if no dirty one was found */
if (found_tb) {
Dmru(found_tb);
found_tb->lockers++;
return found_tb->data;
}
/* can't find it */
tb = newslot(dbase, fid, page);
if (!tb)
return 0;
memset(tb->data, 0, UBIK_PAGESIZE);
tb->lockers++;
code =
(*dbase->read) (dbase, fid, tb->data, page * UBIK_PAGESIZE,
UBIK_PAGESIZE);
if (code < 0) {
tb->file = BADFID;
Dlru(tb);
tb->lockers--;
ubik_print("Ubik: Error reading database file: errno=%d\n", errno);
return 0;
}
ios++;
/* Note that findslot sets the page field in the buffer equal to
* what it is searching for.
*/
return tb->data;
}
/*!
* \brief Get a pointer to a particular buffer.
*/
static char *
DRead(struct ubik_trans *atrans, afs_int32 fid, int page)
{
/* Read a page from the disk. */
struct buffer *tb, *lastbuffer;
afs_int32 code;
struct ubik_dbase *dbase = atrans->dbase;
calls++;
lastbuffer = LruBuffer->lru_prev;
if (MatchBuffer(lastbuffer, page, fid, atrans)) {
tb = lastbuffer;
tb->lockers++;
lastb++;
return tb->data;
}
for (tb = phTable[pHash(page)]; tb; tb = tb->hashNext) {
if (MatchBuffer(tb, page, fid, atrans)) {
Dmru(tb);
tb->lockers++;
return tb->data;
}
}
/* can't find it */
tb = newslot(dbase, fid, page);
if (!tb)
return 0;
memset(tb->data, 0, UBIK_PAGESIZE);
tb->lockers++;
code =
(*dbase->read) (dbase, fid, tb->data, page * UBIK_PAGESIZE,
UBIK_PAGESIZE);
if (code < 0) {
tb->file = BADFID;
Dlru(tb);
tb->lockers--;
ubik_print("Ubik: Error reading database file: errno=%d\n", errno);
return 0;
}
ios++;
/* Note that findslot sets the page field in the buffer equal to
* what it is searching for.
*/
return tb->data;
}
