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r21722: Add the dead record functionality presented on samba-technical@samba.org. If

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you do a tdb_set_max_dead(tdb, n), then for this tdb a delete operation will
only mark a record as dead and re-use it if a new record is created. The
parameter n allows for at most n dead records per hash chain. If this number
is exceeded, all dead records are put on the central freelist.

Volker
(This used to be commit 97af3a019b)
This commit is contained in:
Volker Lendecke 2007-03-06 10:11:15 +00:00 committed by Gerald (Jerry) Carter
parent ba992d5ad7
commit 59285f16d6
4 changed files with 188 additions and 7 deletions
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10
source3/tdb/common/open.c
View File

@ -263,6 +263,7 @@ struct tdb_context *tdb_open_ex(const char *name, int hash_size, int tdb_flags,
tdb->map_size = st.st_size;
tdb->device = st.st_dev;
tdb->inode = st.st_ino;
tdb->max_dead_records = 0;
tdb_mmap(tdb);
if (locked) {
if (tdb->methods->tdb_brlock(tdb, ACTIVE_LOCK, F_UNLCK, F_SETLK, 0, 1) == -1) {
@ -321,6 +322,15 @@ struct tdb_context *tdb_open_ex(const char *name, int hash_size, int tdb_flags,
}
}
/*
* Set the maximum number of dead records per hash chain
*/
void tdb_set_max_dead(struct tdb_context *tdb, int max_dead)
{
tdb->max_dead_records = max_dead;
}
/**
* Close a database.
*

183
source3/tdb/common/tdb.c
View File

@ -258,6 +258,66 @@ int tdb_do_delete(struct tdb_context *tdb, tdb_off_t rec_ptr, struct list_struct
return 0;
}
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
*/
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;
}
/* delete an entry in the database given a key */
static int tdb_delete_hash(struct tdb_context *tdb, TDB_DATA key, u32 hash)
{
@ -265,9 +325,42 @@ static int tdb_delete_hash(struct tdb_context *tdb, TDB_DATA key, u32 hash)
struct list_struct rec;
int ret;
if (!(rec_ptr = tdb_find_lock_hash(tdb, key, hash, F_WRLCK, &rec)))
return -1;
ret = tdb_do_delete(tdb, rec_ptr, &rec);
if (tdb->max_dead_records != 0) {
/*
* Allow for some dead records per hash chain, mainly for
* tdb's with a very high create/delete rate like locking.tdb.
*/
if (tdb_lock(tdb, BUCKET(hash), F_WRLCK) == -1)
return -1;
if (tdb_count_dead(tdb, hash) >= tdb->max_dead_records) {
/*
* Don't let the per-chain freelist grow too large,
* delete all existing dead records
*/
tdb_purge_dead(tdb, hash);
}
if (!(rec_ptr = tdb_find(tdb, key, hash, &rec))) {
tdb_unlock(tdb, BUCKET(hash), F_WRLCK);
return -1;
}
/*
* Just mark the record as dead.
*/
rec.magic = TDB_DEAD_MAGIC;
ret = tdb_rec_write(tdb, rec_ptr, &rec);
}
else {
if (!(rec_ptr = tdb_find_lock_hash(tdb, key, hash, F_WRLCK,
&rec)))
return -1;
ret = tdb_do_delete(tdb, rec_ptr, &rec);
}
if (ret == 0) {
tdb_increment_seqnum(tdb);
@ -284,6 +377,35 @@ int tdb_delete(struct tdb_context *tdb, TDB_DATA key)
return tdb_delete_hash(tdb, key, hash);
}
/*
* 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;
}
/* store an element in the database, replacing any existing element
with the same key
@ -316,8 +438,7 @@ int tdb_store(struct tdb_context *tdb, TDB_DATA key, TDB_DATA dbuf, int flag)
} else {
/* first try in-place update, on modify or replace. */
if (tdb_update_hash(tdb, key, hash, dbuf) == 0) {
ret = 0;
goto fail; /* Well, not really failed */
goto done;
}
if (tdb->ecode == TDB_ERR_NOEXIST &&
flag == TDB_MODIFY) {
@ -347,9 +468,56 @@ int tdb_store(struct tdb_context *tdb, TDB_DATA key, TDB_DATA dbuf, int flag)
if (dbuf.dsize)
memcpy(p+key.dsize, dbuf.dptr, dbuf.dsize);
/* we have to allocate some space */
if (!(rec_ptr = tdb_allocate(tdb, key.dsize + dbuf.dsize, &rec)))
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)
@ -368,6 +536,7 @@ int tdb_store(struct tdb_context *tdb, TDB_DATA key, TDB_DATA dbuf, int flag)
goto fail;
}
done:
ret = 0;
fail:
if (ret == 0) {

1
source3/tdb/common/tdb_private.h
View File

@ -169,6 +169,7 @@ struct tdb_context {
const struct tdb_methods *methods;
struct tdb_transaction *transaction;
int page_size;
int max_dead_records;
};

1
source3/tdb/include/tdb.h
View File

@ -94,6 +94,7 @@ struct tdb_context *tdb_open_ex(const char *name, int hash_size, int tdb_flags,
int open_flags, mode_t mode,
const struct tdb_logging_context *log_ctx,
tdb_hash_func hash_fn);
void tdb_set_max_dead(struct tdb_context *tdb, int max_dead);
int tdb_reopen(struct tdb_context *tdb);
int tdb_reopen_all(int parent_longlived);