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authorVolker Lendecke <vlendec@samba.org>2007-03-06 10:11:15 +0000
committerGerald (Jerry) Carter <jerry@samba.org>2007-10-10 14:49:18 -0500
commit0aebd296cd6834567509d0b100d486f1ef4d104e (patch)
treebc473b0d17e6f1abcad2e407870a5942b05c289b /source4/lib/tdb/common
parent0fa6e86b5799637ade610915ffb4c6443334bc8e (diff)
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r21722: Add the dead record functionality presented on samba-technical@samba.org. If
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 98a27ab28a3cd554e370a9a0e3652f4dea8749e9)
Diffstat (limited to 'source4/lib/tdb/common')
-rw-r--r--source4/lib/tdb/common/open.c10
-rw-r--r--source4/lib/tdb/common/tdb.c181
-rw-r--r--source4/lib/tdb/common/tdb_private.h1
3 files changed, 186 insertions, 6 deletions
diff --git a/source4/lib/tdb/common/open.c b/source4/lib/tdb/common/open.c
index 3d6e222b96..47e3258c09 100644
--- a/source4/lib/tdb/common/open.c
+++ b/source4/lib/tdb/common/open.c
@@ -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.
*
diff --git a/source4/lib/tdb/common/tdb.c b/source4/lib/tdb/common/tdb.c
index 03a66804b3..a6b472ae94 100644
--- a/source4/lib/tdb/common/tdb.c
+++ b/source4/lib/tdb/common/tdb.c
@@ -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);
+ 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 */
- if (!(rec_ptr = tdb_allocate(tdb, key.dsize + dbuf.dsize, &rec)))
+ 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) {
diff --git a/source4/lib/tdb/common/tdb_private.h b/source4/lib/tdb/common/tdb_private.h
index a05f4da0cf..7219a1a2e2 100644
--- a/source4/lib/tdb/common/tdb_private.h
+++ b/source4/lib/tdb/common/tdb_private.h
@@ -169,6 +169,7 @@ struct tdb_context {
const struct tdb_methods *methods;
struct tdb_transaction *transaction;
int page_size;
+ int max_dead_records;
};