tdb transaction_prepare

Howard Chu hyc at highlandsun.com
Mon Mar 30 22:58:53 GMT 2009


Tridge, here's a first pass as we discussed on irc. I think that zeroing out 
the recovery data from the magic_offset needs to be moved into 
transaction_cancel but I haven't tried that yet.

-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/
-------------- next part --------------
diff --git a/lib/tdb/common/transaction.c b/lib/tdb/common/transaction.c
index 7acda64..10a3321 100644
--- a/lib/tdb/common/transaction.c
+++ b/lib/tdb/common/transaction.c
@@ -116,6 +116,10 @@ struct tdb_transaction {
 	   but don't create a new transaction */
 	int nesting;
 
+	/* set when a prepare has already occurred */
+	int prepared;
+	tdb_off_t magic_offset;
+
 	/* old file size before transaction */
 	tdb_len_t old_map_size;
 };
@@ -826,36 +830,33 @@ static int transaction_setup_recovery(struct tdb_context *tdb,
 }
 
 /*
-  commit the current transaction
+  prepare the current transaction
 */
-int tdb_transaction_commit(struct tdb_context *tdb)
+int tdb_transaction_prepare(struct tdb_context *tdb)
 {	
 	const struct tdb_methods *methods;
-	tdb_off_t magic_offset = 0;
 	uint32_t zero = 0;
 	int i;
 
 	if (tdb->transaction == NULL) {
-		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: no transaction\n"));
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare: no transaction\n"));
 		return -1;
 	}
 
 	if (tdb->transaction->transaction_error) {
 		tdb->ecode = TDB_ERR_IO;
 		tdb_transaction_cancel(tdb);
-		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: transaction error pending\n"));
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare: transaction error pending\n"));
 		return -1;
 	}
 
 
 	if (tdb->transaction->nesting != 0) {
-		tdb->transaction->nesting--;
 		return 0;
 	}		
 
 	/* check for a null transaction */
 	if (tdb->transaction->blocks == NULL) {
-		tdb_transaction_cancel(tdb);
 		return 0;
 	}
 
@@ -865,14 +866,14 @@ int tdb_transaction_commit(struct tdb_context *tdb)
 	   nested their locks properly, so fail the transaction */
 	if (tdb->num_locks || tdb->global_lock.count) {
 		tdb->ecode = TDB_ERR_LOCK;
-		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: locks pending on commit\n"));
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare: locks pending on commit\n"));
 		tdb_transaction_cancel(tdb);
 		return -1;
 	}
 
 	/* upgrade the main transaction lock region to a write lock */
 	if (tdb_brlock_upgrade(tdb, FREELIST_TOP, 0) == -1) {
-		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: failed to upgrade hash locks\n"));
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare: failed to upgrade hash locks\n"));
 		tdb->ecode = TDB_ERR_LOCK;
 		tdb_transaction_cancel(tdb);
 		return -1;
@@ -881,7 +882,7 @@ int tdb_transaction_commit(struct tdb_context *tdb)
 	/* get the global lock - this prevents new users attaching to the database
 	   during the commit */
 	if (tdb_brlock(tdb, GLOBAL_LOCK, F_WRLCK, F_SETLKW, 0, 1) == -1) {
-		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: failed to get global lock\n"));
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare: failed to get global lock\n"));
 		tdb->ecode = TDB_ERR_LOCK;
 		tdb_transaction_cancel(tdb);
 		return -1;
@@ -889,21 +890,23 @@ int tdb_transaction_commit(struct tdb_context *tdb)
 
 	if (!(tdb->flags & TDB_NOSYNC)) {
 		/* write the recovery data to the end of the file */
-		if (transaction_setup_recovery(tdb, &magic_offset) == -1) {
-			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: failed to setup recovery data\n"));
+		if (transaction_setup_recovery(tdb, &tdb->transaction->magic_offset) == -1) {
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare: failed to setup recovery data\n"));
 			tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
 			tdb_transaction_cancel(tdb);
 			return -1;
 		}
 	}
 
+	tdb->transaction->prepared = 1;
+
 	/* expand the file to the new size if needed */
 	if (tdb->map_size != tdb->transaction->old_map_size) {
 		if (methods->tdb_expand_file(tdb, tdb->transaction->old_map_size, 
 					     tdb->map_size - 
 					     tdb->transaction->old_map_size) == -1) {
 			tdb->ecode = TDB_ERR_IO;
-			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: expansion failed\n"));
+			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_prepare: expansion failed\n"));
 			tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0, 1);
 			tdb_transaction_cancel(tdb);
 			return -1;
@@ -912,6 +915,52 @@ int tdb_transaction_commit(struct tdb_context *tdb)
 		methods->tdb_oob(tdb, tdb->map_size + 1, 1);
 	}
 
+	/* Keep the global lock until the actual commit */
+
+	return 0;
+}
+
+/*
+  commit the current transaction
+*/
+int tdb_transaction_commit(struct tdb_context *tdb)
+{	
+	const struct tdb_methods *methods;
+	uint32_t zero = 0;
+	int i;
+
+	if (tdb->transaction == NULL) {
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: no transaction\n"));
+		return -1;
+	}
+
+	if (tdb->transaction->transaction_error) {
+		tdb->ecode = TDB_ERR_IO;
+		tdb_transaction_cancel(tdb);
+		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_commit: transaction error pending\n"));
+		return -1;
+	}
+
+
+	if (tdb->transaction->nesting != 0) {
+		tdb->transaction->nesting--;
+		return 0;
+	}
+
+	/* check for a null transaction */
+	if (tdb->transaction->blocks == NULL) {
+		tdb_transaction_cancel(tdb);
+		return 0;
+	}
+
+	if (!tdb->transaction->prepared) {
+		i = tdb_transaction_prepare(tdb);
+		if (i)
+			return i;
+	}
+
+	methods = tdb->transaction->io_methods;
+
 	/* perform all the writes */
 	for (i=0;i<tdb->transaction->num_blocks;i++) {
 		tdb_off_t offset;
@@ -955,13 +1004,13 @@ int tdb_transaction_commit(struct tdb_context *tdb)
 		}
 
 		/* remove the recovery marker */
-		if (methods->tdb_write(tdb, magic_offset, &zero, 4) == -1) {
+		if (methods->tdb_write(tdb, tdb->transaction->magic_offset, &zero, 4) == -1) {
 			TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_transaction_commit: failed to remove recovery magic\n"));
 			return -1;
 		}
 
 		/* ensure the recovery marker has been removed on disk */
-		if (transaction_sync(tdb, magic_offset, 4) == -1) {
+		if (transaction_sync(tdb, tdb->transaction->magic_offset, 4) == -1) {
 			return -1;
 		}
 	}


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