/* actually delete an entry in the database given the offset */
int tdb_do_delete(struct tdb_context *tdb, tdb_off_t rec_ptr, struct list_struct*rec)
{
tdb_off_t last_ptr, i;
struct list_struct lastrec;
if (tdb->read_only || tdb->traverse_read) return -1;
if (tdb_write_lock_record(tdb, rec_ptr) == -1) {
/* Someone traversing here: mark it as dead */
rec->magic = TDB_DEAD_MAGIC;
return tdb_rec_write(tdb, rec_ptr, rec);
}
if (tdb_write_unlock_record(tdb, rec_ptr) != 0)
return -1;
/* find previous record in hash chain */
if (tdb_ofs_read(tdb, TDB_HASH_TOP(rec->full_hash), &i) == -1)
return -1;
for (last_ptr = 0; i != rec_ptr; last_ptr = i, i = lastrec.next)
if (tdb_rec_read(tdb, i, &lastrec) == -1)
return -1;
/* unlink it: next ptr is at start of record. */
if (last_ptr == 0)
last_ptr = TDB_HASH_TOP(rec->full_hash);
if (tdb_ofs_write(tdb, last_ptr, &rec->next) == -1)
return -1;
/* recover the space */
if (tdb_free(tdb, rec_ptr, rec) == -1)
return -1;
return 0;
}
static int tdb_dump_chain(struct tdb_context *tdb, int i)
{
tdb_off_t rec_ptr, top;
if (i == -1) {
top = FREELIST_TOP;
} else {
top = TDB_HASH_TOP(i);
}
if (tdb_lock(tdb, i, F_WRLCK) != 0)
return -1;
if (tdb_ofs_read(tdb, top, &rec_ptr) == -1)
return tdb_unlock(tdb, i, F_WRLCK);
if (rec_ptr)
printf("hash=%d\n", i);
while (rec_ptr) {
rec_ptr = tdb_dump_record(tdb, i, rec_ptr);
}
return tdb_unlock(tdb, i, F_WRLCK);
}
/* Returns 0 on fail. On success, return offset of record, and fills
in rec */
static tdb_off_t tdb_find(struct tdb_context *tdb, TDB_DATA key, u32 hash,
struct list_struct *r)
{
tdb_off_t rec_ptr;
/* read in the hash top */
if (tdb_ofs_read(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1)
return 0;
/* keep looking until we find the right record */
while (rec_ptr) {
if (tdb_rec_read(tdb, rec_ptr, r) == -1)
return 0;
if (!TDB_DEAD(r) && hash==r->full_hash
&& key.dsize==r->key_len
&& tdb_parse_data(tdb, key, rec_ptr + sizeof(*r),
r->key_len, tdb_key_compare,
NULL) == 0) {
return rec_ptr;
}
rec_ptr = r->next;
}
return TDB_ERRCODE(TDB_ERR_NOEXIST, 0);
}
/*
* See if we have a dead record around with enough space
*/
static tdb_off_t tdb_find_dead(struct tdb_context *tdb, u32 hash,
struct list_struct *r, tdb_len_t length)
{
tdb_off_t rec_ptr;
/* read in the hash top */
if (tdb_ofs_read(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1)
return 0;
/* keep looking until we find the right record */
while (rec_ptr) {
if (tdb_rec_read(tdb, rec_ptr, r) == -1)
return 0;
if (TDB_DEAD(r) && r->rec_len >= length) {
/*
* First fit for simple coding, TODO: change to best
* fit
*/
return rec_ptr;
}
rec_ptr = r->next;
}
return 0;
}
/*
* Purge all DEAD records from a hash chain
*/
static int tdb_purge_dead(struct tdb_context *tdb, u32 hash)
{
int res = -1;
struct list_struct rec;
tdb_off_t rec_ptr;
if (tdb_lock(tdb, -1, F_WRLCK) == -1) {
return -1;
}
/* read in the hash top */
if (tdb_ofs_read(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1)
goto fail;
while (rec_ptr) {
tdb_off_t next;
if (tdb_rec_read(tdb, rec_ptr, &rec) == -1) {
goto fail;
}
next = rec.next;
if (rec.magic == TDB_DEAD_MAGIC
&& tdb_do_delete(tdb, rec_ptr, &rec) == -1) {
goto fail;
}
rec_ptr = next;
}
res = 0;
fail:
tdb_unlock(tdb, -1, F_WRLCK);
return res;
}
/* Returns 0 on fail. On success, return offset of record, and fills
in rec */
static tdb_off_t tdb_find(struct tdb_context *tdb, TDB_DATA key, uint32_t hash,
struct tdb_record *r)
{
tdb_off_t rec_ptr;
/* read in the hash top */
if (tdb_ofs_read(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1)
return 0;
/* keep looking until we find the right record */
while (rec_ptr) {
if (tdb_rec_read(tdb, rec_ptr, r) == -1)
return 0;
if (!TDB_DEAD(r) && hash==r->full_hash
&& key.dsize==r->key_len
&& tdb_parse_data(tdb, key, rec_ptr + sizeof(*r),
r->key_len, tdb_key_compare,
NULL) == 0) {
return rec_ptr;
}
/* detect tight infinite loop */
if (rec_ptr == r->next) {
tdb->ecode = TDB_ERR_CORRUPT;
TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_find: loop detected.\n"));
return 0;
}
rec_ptr = r->next;
}
tdb->ecode = TDB_ERR_NOEXIST;
return 0;
}
/*
do an unlocked scan of the hash table heads to find the next non-zero head. The value
will then be confirmed with the lock held
*/
static void tdb_next_hash_chain(struct tdb_context *tdb, uint32_t *chain)
{
uint32_t h = *chain;
if (tdb->map_ptr) {
for (;h < tdb->header.hash_size;h++) {
if (0 != *(uint32_t *)(TDB_HASH_TOP(h) + (unsigned char *)tdb->map_ptr)) {
break;
}
}
} else {
uint32_t off=0;
for (;h < tdb->header.hash_size;h++) {
if (tdb_ofs_read(tdb, TDB_HASH_TOP(h), &off) != 0 || off != 0) {
break;
}
}
}
(*chain) = h;
}
static size_t get_hash_length(struct tdb_context *tdb, unsigned int i)
{
tdb_off_t rec_ptr;
size_t count = 0;
if (tdb_ofs_read(tdb, TDB_HASH_TOP(i), &rec_ptr) == -1)
return 0;
/* keep looking until we find the right record */
while (rec_ptr) {
struct tdb_record r;
++count;
if (tdb_rec_read(tdb, rec_ptr, &r) == -1)
return 0;
rec_ptr = r.next;
}
return count;
}
static int tdb_count_dead(struct tdb_context *tdb, u32 hash)
{
int res = 0;
tdb_off_t rec_ptr;
struct list_struct rec;
/* read in the hash top */
if (tdb_ofs_read(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1)
return 0;
while (rec_ptr) {
if (tdb_rec_read(tdb, rec_ptr, &rec) == -1)
return 0;
if (rec.magic == TDB_DEAD_MAGIC) {
res += 1;
}
rec_ptr = rec.next;
}
return res;
}
/*
* Purge all DEAD records from a hash chain
*/
int tdb_purge_dead(struct tdb_context *tdb, uint32_t hash)
{
int res = -1;
struct tdb_record rec;
tdb_off_t rec_ptr;
if (tdb_lock_nonblock(tdb, -1, F_WRLCK) == -1) {
/*
* Don't block the freelist if not strictly necessary
*/
return -1;
}
/* read in the hash top */
if (tdb_ofs_read(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1)
goto fail;
while (rec_ptr) {
tdb_off_t next;
if (tdb_rec_read(tdb, rec_ptr, &rec) == -1) {
goto fail;
}
next = rec.next;
if (rec.magic == TDB_DEAD_MAGIC
&& tdb_do_delete(tdb, rec_ptr, &rec) == -1) {
goto fail;
}
rec_ptr = next;
}
res = 0;
fail:
tdb_unlock(tdb, -1, F_WRLCK);
return res;
}
/* Uses traverse lock: 0 = finish, TDB_NEXT_LOCK_ERR = error,
other = record offset */
static tdb_off_t tdb_next_lock(struct tdb_context *tdb, struct tdb_traverse_lock *tlock,
struct tdb_record *rec)
{
int want_next = (tlock->off != 0);
/* Lock each chain from the start one. */
for (; tlock->list < tdb->hash_size; tlock->list++) {
if (!tlock->off && tlock->list != 0) {
/* this is an optimisation for the common case where
the hash chain is empty, which is particularly
common for the use of tdb with ldb, where large
hashes are used. In that case we spend most of our
time in tdb_brlock(), locking empty hash chains.
To avoid this, we do an unlocked pre-check to see
if the hash chain is empty before starting to look
inside it. If it is empty then we can avoid that
hash chain. If it isn't empty then we can't believe
the value we get back, as we read it without a
lock, so instead we get the lock and re-fetch the
value below.
Notice that not doing this optimisation on the
first hash chain is critical. We must guarantee
that we have done at least one fcntl lock at the
start of a search to guarantee that memory is
coherent on SMP systems. If records are added by
others during the search then thats OK, and we
could possibly miss those with this trick, but we
could miss them anyway without this trick, so the
semantics don't change.
With a non-indexed ldb search this trick gains us a
factor of around 80 in speed on a linux 2.6.x
system (testing using ldbtest).
*/
tdb->methods->next_hash_chain(tdb, &tlock->list);
if (tlock->list == tdb->hash_size) {
continue;
}
}
if (tdb_lock(tdb, tlock->list, tlock->lock_rw) == -1)
return TDB_NEXT_LOCK_ERR;
/* No previous record? Start at top of chain. */
if (!tlock->off) {
if (tdb_ofs_read(tdb, TDB_HASH_TOP(tlock->list),
&tlock->off) == -1)
goto fail;
} else {
/* Otherwise unlock the previous record. */
if (tdb_unlock_record(tdb, tlock->off) != 0)
goto fail;
}
if (want_next) {
/* We have offset of old record: grab next */
if (tdb_rec_read(tdb, tlock->off, rec) == -1)
goto fail;
tlock->off = rec->next;
}
/* Iterate through chain */
while( tlock->off) {
tdb_off_t current;
if (tdb_rec_read(tdb, tlock->off, rec) == -1)
goto fail;
/* Detect infinite loops. From "Shlomi Yaakobovich" <*****@*****.**>. */
if (tlock->off == rec->next) {
tdb->ecode = TDB_ERR_CORRUPT;
TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: loop detected.\n"));
goto fail;
}
if (!TDB_DEAD(rec)) {
/* Woohoo: we found one! */
if (tdb_lock_record(tdb, tlock->off) != 0)
goto fail;
return tlock->off;
}
/* Try to clean dead ones from old traverses */
current = tlock->off;
tlock->off = rec->next;
if (!(tdb->read_only || tdb->traverse_read) &&
tdb_do_delete(tdb, current, rec) != 0)
goto fail;
}
tdb_unlock(tdb, tlock->list, tlock->lock_rw);
want_next = 0;
}
/* We finished iteration without finding anything */
tdb->ecode = TDB_SUCCESS;
return 0;
fail:
tlock->off = 0;
if (tdb_unlock(tdb, tlock->list, tlock->lock_rw) != 0)
TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_next_lock: On error unlock failed!\n"));
return TDB_NEXT_LOCK_ERR;
}
/* store an element in the database, replacing any existing element
with the same key
return 0 on success, -1 on failure
*/
int tdb_store(struct tdb_context *tdb, TDB_DATA key, TDB_DATA dbuf, int flag)
{
struct list_struct rec;
u32 hash;
tdb_off_t rec_ptr;
char *p = NULL;
int ret = -1;
if (tdb->read_only || tdb->traverse_read) {
tdb->ecode = TDB_ERR_RDONLY;
return -1;
}
/* find which hash bucket it is in */
hash = tdb->hash_fn(&key);
if (tdb_lock(tdb, BUCKET(hash), F_WRLCK) == -1)
return -1;
/* check for it existing, on insert. */
if (flag == TDB_INSERT) {
if (tdb_exists_hash(tdb, key, hash)) {
tdb->ecode = TDB_ERR_EXISTS;
goto fail;
}
} else {
/* first try in-place update, on modify or replace. */
if (tdb_update_hash(tdb, key, hash, dbuf) == 0) {
goto done;
}
if (tdb->ecode == TDB_ERR_NOEXIST &&
flag == TDB_MODIFY) {
/* if the record doesn't exist and we are in TDB_MODIFY mode then
we should fail the store */
goto fail;
}
}
/* reset the error code potentially set by the tdb_update() */
tdb->ecode = TDB_SUCCESS;
/* delete any existing record - if it doesn't exist we don't
care. Doing this first reduces fragmentation, and avoids
coalescing with `allocated' block before it's updated. */
if (flag != TDB_INSERT)
tdb_delete_hash(tdb, key, hash);
/* Copy key+value *before* allocating free space in case malloc
fails and we are left with a dead spot in the tdb. */
if (!(p = (char *)malloc(key.dsize + dbuf.dsize))) {
tdb->ecode = TDB_ERR_OOM;
goto fail;
}
memcpy(p, key.dptr, key.dsize);
if (dbuf.dsize)
memcpy(p+key.dsize, dbuf.dptr, dbuf.dsize);
if (tdb->max_dead_records != 0) {
/*
* Allow for some dead records per hash chain, look if we can
* find one that can hold the new record. We need enough space
* for key, data and tailer. If we find one, we don't have to
* consult the central freelist.
*/
rec_ptr = tdb_find_dead(
tdb, hash, &rec,
key.dsize + dbuf.dsize + sizeof(tdb_off_t));
if (rec_ptr != 0) {
rec.key_len = key.dsize;
rec.data_len = dbuf.dsize;
rec.full_hash = hash;
rec.magic = TDB_MAGIC;
if (tdb_rec_write(tdb, rec_ptr, &rec) == -1
|| tdb->methods->tdb_write(
tdb, rec_ptr + sizeof(rec),
p, key.dsize + dbuf.dsize) == -1) {
goto fail;
}
goto done;
}
}
/*
* We have to allocate some space from the freelist, so this means we
* have to lock it. Use the chance to purge all the DEAD records from
* the hash chain under the freelist lock.
*/
if (tdb_lock(tdb, -1, F_WRLCK) == -1) {
goto fail;
}
if ((tdb->max_dead_records != 0)
&& (tdb_purge_dead(tdb, hash) == -1)) {
tdb_unlock(tdb, -1, F_WRLCK);
goto fail;
}
/* we have to allocate some space */
rec_ptr = tdb_allocate(tdb, key.dsize + dbuf.dsize, &rec);
tdb_unlock(tdb, -1, F_WRLCK);
if (rec_ptr == 0) {
goto fail;
}
/* Read hash top into next ptr */
if (tdb_ofs_read(tdb, TDB_HASH_TOP(hash), &rec.next) == -1)
goto fail;
rec.key_len = key.dsize;
rec.data_len = dbuf.dsize;
rec.full_hash = hash;
rec.magic = TDB_MAGIC;
/* write out and point the top of the hash chain at it */
if (tdb_rec_write(tdb, rec_ptr, &rec) == -1
|| tdb->methods->tdb_write(tdb, rec_ptr+sizeof(rec), p, key.dsize+dbuf.dsize)==-1
|| tdb_ofs_write(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1) {
/* Need to tdb_unallocate() here */
goto fail;
}
done:
ret = 0;
fail:
if (ret == 0) {
tdb_increment_seqnum(tdb);
}
SAFE_FREE(p);
tdb_unlock(tdb, BUCKET(hash), F_WRLCK);
return ret;
}
/*
wipe the entire database, deleting all records. This can be done
very fast by using a global lock. The entire data portion of the
file becomes a single entry in the freelist.
This code carefully steps around the recovery area, leaving it alone
*/
int tdb_wipe_all(struct tdb_context *tdb)
{
int i;
tdb_off_t offset = 0;
ssize_t data_len;
tdb_off_t recovery_head;
tdb_len_t recovery_size = 0;
if (tdb_lockall(tdb) != 0) {
return -1;
}
/* see if the tdb has a recovery area, and remember its size
if so. We don't want to lose this as otherwise each
tdb_wipe_all() in a transaction will increase the size of
the tdb by the size of the recovery area */
if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &recovery_head) == -1) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_wipe_all: failed to read recovery head\n"));
goto failed;
}
if (recovery_head != 0) {
struct list_struct rec;
if (tdb->methods->tdb_read(tdb, recovery_head, &rec, sizeof(rec), DOCONV()) == -1) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_wipe_all: failed to read recovery record\n"));
return -1;
}
recovery_size = rec.rec_len + sizeof(rec);
}
/* wipe the hashes */
for (i=0;i<tdb->header.hash_size;i++) {
if (tdb_ofs_write(tdb, TDB_HASH_TOP(i), &offset) == -1) {
TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_wipe_all: failed to write hash %d\n", i));
goto failed;
}
}
/* wipe the freelist */
if (tdb_ofs_write(tdb, FREELIST_TOP, &offset) == -1) {
TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_wipe_all: failed to write freelist\n"));
goto failed;
}
/* add all the rest of the file to the freelist, possibly leaving a gap
for the recovery area */
if (recovery_size == 0) {
/* the simple case - the whole file can be used as a freelist */
data_len = (tdb->map_size - TDB_DATA_START(tdb->header.hash_size));
if (tdb_free_region(tdb, TDB_DATA_START(tdb->header.hash_size), data_len) != 0) {
goto failed;
}
} else {
/* we need to add two freelist entries - one on either
side of the recovery area
Note that we cannot shift the recovery area during
this operation. Only the transaction.c code may
move the recovery area or we risk subtle data
corruption
*/
data_len = (recovery_head - TDB_DATA_START(tdb->header.hash_size));
if (tdb_free_region(tdb, TDB_DATA_START(tdb->header.hash_size), data_len) != 0) {
goto failed;
}
/* and the 2nd free list entry after the recovery area - if any */
data_len = tdb->map_size - (recovery_head+recovery_size);
if (tdb_free_region(tdb, recovery_head+recovery_size, data_len) != 0) {
goto failed;
}
}
if (tdb_unlockall(tdb) != 0) {
TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_wipe_all: failed to unlock\n"));
goto failed;
}
return 0;
failed:
tdb_unlockall(tdb);
return -1;
}
