/*!
* \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;
}
/**
* Invalidate any buffers that are duplicates of abuf. Duplicate buffers
* can appear if a read transaction reads a page that is dirty, then that
* dirty page is synced. The read transaction will skip over the dirty page,
* and create a new buffer, and when the dirty page is synced, it will be
* identical (except for contents) to the read-transaction buffer.
*/
static void
DedupBuffer(struct buffer *abuf)
{
struct buffer *tb;
for (tb = phTable[pHash(abuf->page)]; tb; tb = tb->hashNext) {
if (tb->page == abuf->page && tb != abuf && tb->file == abuf->file
&& tb->dbase == abuf->dbase) {
tb->file = BADFID;
Dlru(tb);
}
}
}
/*!
* \brief Mark an \p fid as invalid.
*/
int
udisk_Invalidate(struct ubik_dbase *adbase, afs_int32 afid)
{
struct buffer *tb;
int i;
for (i = 0, tb = Buffers; i < nbuffers; i++, tb++) {
if (tb->file == afid) {
tb->file = BADFID;
Dlru(tb);
}
}
return 0;
}
/*!
* \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;
}
/*!
* \brief Flush all modified buffers.
*/
static int
DAbort(struct ubik_trans *atrans)
{
int i;
struct buffer *tb;
tb = Buffers;
for (i = 0; i < nbuffers; i++, tb++) {
if (tb->dirty) {
tb->dirty = 0;
tb->file = BADFID;
Dlru(tb);
}
}
return 0;
}
/*!
* \brief Zap truncated pages.
*/
static int
DTrunc(struct ubik_trans *atrans, afs_int32 fid, afs_int32 length)
{
afs_int32 maxPage;
struct buffer *tb;
int i;
struct ubik_dbase *dbase = atrans->dbase;
maxPage = (length + UBIK_PAGESIZE - 1) >> UBIK_LOGPAGESIZE; /* first invalid page now in file */
for (i = 0, tb = Buffers; i < nbuffers; i++, tb++) {
if (tb->page >= maxPage && tb->file == fid && tb->dbase == dbase) {
tb->file = BADFID;
Dlru(tb);
}
}
return 0;
}