s3: Add dbwrap_cache

This is a caching layer for the notify database and potentially for the brlock
database. It caches the parse_record operation as long as the underlying seqnum
does not change.

2 files changed, 242 insertions, 0 deletions

diff --git a/source3/lib/dbwrap/dbwrap_cache.c b/source3/lib/dbwrap/dbwrap_cache.c
new file mode 100644
index 0000000000..43c85f7b09
--- /dev/null
+++ b/source3/lib/dbwrap/dbwrap_cache.c
@@ -0,0 +1,210 @@
+/*
+   Unix SMB/CIFS implementation.
+   Cache db contents for parse_record based on seqnum
+   Copyright (C) Volker Lendecke 2012
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "includes.h"
+#include "lib/dbwrap/dbwrap.h"
+#include "lib/dbwrap/dbwrap_private.h"
+#include "lib/dbwrap/dbwrap_rbt.h"
+#include "lib/dbwrap/dbwrap_cache.h"
+
+struct db_cache_ctx {
+	int seqnum;
+	struct db_context *backing;
+	struct db_context *positive;
+	struct db_context *negative;
+};
+
+static void dbwrap_cache_validate(struct db_cache_ctx *ctx)
+{
+	if (ctx->seqnum == dbwrap_get_seqnum(ctx->backing)) {
+		return;
+	}
+	TALLOC_FREE(ctx->positive);
+	ctx->positive = db_open_rbt(ctx);
+	TALLOC_FREE(ctx->negative);
+	ctx->negative = db_open_rbt(ctx);
+}
+
+static NTSTATUS dbwrap_cache_parse_record(
+	struct db_context *db, TDB_DATA key,
+	void (*parser)(TDB_DATA key, TDB_DATA data, void *private_data),
+	void *private_data)
+{
+	struct db_cache_ctx *ctx = talloc_get_type_abort(
+		db->private_data, struct db_cache_ctx);
+	TDB_DATA value;
+	NTSTATUS status;
+
+	dbwrap_cache_validate(ctx);
+
+	if (ctx->positive != NULL) {
+		status = dbwrap_parse_record(
+			ctx->positive, key, parser, private_data);
+		if (NT_STATUS_IS_OK(status)) {
+			return status;
+		}
+	}
+	if ((ctx->negative != NULL) && dbwrap_exists(ctx->negative, key)) {
+		return NT_STATUS_NOT_FOUND;
+	}
+
+	status = dbwrap_fetch(ctx->backing, talloc_tos(), key, &value);
+
+	if (NT_STATUS_IS_OK(status)) {
+		dbwrap_store(ctx->positive, key, value, 0);
+		parser(key, value, private_data);
+		TALLOC_FREE(value.dptr);
+		return NT_STATUS_OK;
+	}
+
+	if (NT_STATUS_EQUAL(status, NT_STATUS_NOT_FOUND)) {
+		char c = '\0';
+		value.dptr = (uint8_t *)&c;
+		value.dsize = sizeof(c);
+		dbwrap_store(ctx->negative, key, value, 0);
+		return NT_STATUS_NOT_FOUND;
+	}
+	return status;
+}
+
+static struct db_record *dbwrap_cache_fetch_locked(
+	struct db_context *db, TALLOC_CTX *mem_ctx, TDB_DATA key)
+{
+	struct db_cache_ctx *ctx = talloc_get_type_abort(
+		db->private_data, struct db_cache_ctx);
+	return dbwrap_fetch_locked(ctx->backing, mem_ctx, key);
+}
+
+static int dbwrap_cache_traverse(struct db_context *db,
+				 int (*f)(struct db_record *rec,
+					  void *private_data),
+				 void *private_data)
+{
+	struct db_cache_ctx *ctx = talloc_get_type_abort(
+		db->private_data, struct db_cache_ctx);
+	NTSTATUS status;
+	int ret;
+	status = dbwrap_traverse(ctx->backing, f, private_data, &ret);
+	if (!NT_STATUS_IS_OK(status)) {
+		return -1;
+	}
+	return ret;
+}
+
+static int dbwrap_cache_traverse_read(struct db_context *db,
+				      int (*f)(struct db_record *rec,
+					       void *private_data),
+				      void *private_data)
+{
+	struct db_cache_ctx *ctx = talloc_get_type_abort(
+		db->private_data, struct db_cache_ctx);
+	NTSTATUS status;
+	int ret;
+	status = dbwrap_traverse_read(ctx->backing, f, private_data, &ret);
+	if (!NT_STATUS_IS_OK(status)) {
+		return -1;
+	}
+	return ret;
+}
+
+static int dbwrap_cache_get_seqnum(struct db_context *db)
+{
+	struct db_cache_ctx *ctx = talloc_get_type_abort(
+		db->private_data, struct db_cache_ctx);
+	return dbwrap_get_seqnum(ctx->backing);
+}
+
+static int dbwrap_cache_get_flags(struct db_context *db)
+{
+	struct db_cache_ctx *ctx = talloc_get_type_abort(
+		db->private_data, struct db_cache_ctx);
+	return dbwrap_get_flags(ctx->backing);
+}
+
+static int dbwrap_cache_transaction_start(struct db_context *db)
+{
+	struct db_cache_ctx *ctx = talloc_get_type_abort(
+		db->private_data, struct db_cache_ctx);
+	return dbwrap_transaction_start(ctx->backing);
+}
+
+static int dbwrap_cache_transaction_commit(struct db_context *db)
+{
+	struct db_cache_ctx *ctx = talloc_get_type_abort(
+		db->private_data, struct db_cache_ctx);
+	return dbwrap_transaction_commit(ctx->backing);
+}
+
+static int dbwrap_cache_transaction_cancel(struct db_context *db)
+{
+	struct db_cache_ctx *ctx = talloc_get_type_abort(
+		db->private_data, struct db_cache_ctx);
+	return dbwrap_transaction_cancel(ctx->backing);
+}
+
+static int dbwrap_cache_exists(struct db_context *db, TDB_DATA key)
+{
+	struct db_cache_ctx *ctx = talloc_get_type_abort(
+		db->private_data, struct db_cache_ctx);
+
+	if (ctx->positive && dbwrap_exists(ctx->positive, key)) {
+		return true;
+	}
+	if (ctx->negative && dbwrap_exists(ctx->negative, key)) {
+		return false;
+	}
+	return dbwrap_exists(ctx->backing, key);
+}
+
+struct db_context *db_open_cache(TALLOC_CTX *mem_ctx,
+				 struct db_context *backing)
+{
+	struct db_context *db;
+	struct db_cache_ctx *ctx;
+
+	db = talloc(mem_ctx, struct db_context);
+	if (db == NULL) {
+		return NULL;
+	}
+	ctx = talloc_zero(db, struct db_cache_ctx);
+	if (ctx == NULL) {
+		TALLOC_FREE(db);
+		return NULL;
+	}
+
+	ctx->seqnum = -1;
+	ctx->backing = talloc_move(ctx, &backing);
+	db->private_data = ctx;
+	dbwrap_cache_validate(ctx);
+
+	db->fetch_locked = dbwrap_cache_fetch_locked;
+	db->traverse = dbwrap_cache_traverse;
+	db->traverse_read = dbwrap_cache_traverse_read;
+	db->get_seqnum = dbwrap_cache_get_seqnum;
+	db->get_flags = dbwrap_cache_get_flags;
+	db->transaction_start = dbwrap_cache_transaction_start;
+	db->transaction_commit = dbwrap_cache_transaction_commit;
+	db->transaction_cancel = dbwrap_cache_transaction_cancel;
+	db->parse_record = dbwrap_cache_parse_record;
+	db->exists = dbwrap_cache_exists;
+	db->wipe = NULL;
+	db->lock_order = 0;
+	db->persistent = false;
+	return db;
+}
diff --git a/source3/lib/dbwrap/dbwrap_cache.h b/source3/lib/dbwrap/dbwrap_cache.h
new file mode 100644
index 0000000000..cd290e15f8
--- /dev/null
+++ b/source3/lib/dbwrap/dbwrap_cache.h
@@ -0,0 +1,32 @@
+/*
+   Unix SMB/CIFS implementation.
+   Database interface wrapper around ctdbd
+   Copyright (C) Volker Lendecke 2012
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __DBWRAP_CACHE_H__
+#define __DBWRAP_CACHE_H__
+
+#include <talloc.h>
+
+#include "dbwrap/dbwrap_private.h"
+
+struct db_context;
+
+struct db_context *db_open_cache(TALLOC_CTX *mem_ctx,
+				 struct db_context *backing);
+
+#endif /* __DBWRAP_CACHE_H__ */