tdb: tdb_allrecord_lock/tdb_allrecord_unlock/tdb_allrecord_upgrade

Centralize locking of all chains of the tdb; rename _tdb_lockall to
tdb_allrecord_lock and _tdb_unlockall to tdb_allrecord_unlock, and
tdb_brlock_upgrade to tdb_allrecord_upgrade.

Then we use this in the transaction code.  Unfortunately, if the transaction
code records that it has grabbed the allrecord lock read-only, write locks
will fail, so we treat this upgradable lock as a write lock, and mark it
as upgradable using the otherwise-unused offset field.

One subtlety: now the transaction code is using the allrecord_lock, the
tdb_release_extra_locks() function drops it for us, so we no longer need
to do it manually in _tdb_transaction_cancel.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 5 insertions, 7 deletions

diff --git a/lib/tdb/common/transaction.c b/lib/tdb/common/transaction.c
index 69a622dae0..c9718a59b3 100644
--- a/lib/tdb/common/transaction.c
+++ b/lib/tdb/common/transaction.c
@@ -502,10 +502,9 @@ int tdb_transaction_start(struct tdb_context *tdb)
 	
 	/* get a read lock from the freelist to the end of file. This
 	   is upgraded to a write lock during the commit */
-	if (tdb_brlock(tdb, F_RDLCK, FREELIST_TOP, 0, TDB_LOCK_WAIT) == -1) {
+	if (tdb_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, true) == -1) {
 		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_start: failed to get hash locks\n"));
-		tdb->ecode = TDB_ERR_LOCK;
-		goto fail;
+		goto fail_allrecord_lock;
 	}
 
 	/* setup a copy of the hash table heads so the hash scan in
@@ -538,7 +537,8 @@ int tdb_transaction_start(struct tdb_context *tdb)
 	return 0;
 	
 fail:
-	tdb_brunlock(tdb, F_RDLCK, FREELIST_TOP, 0);
+	tdb_allrecord_unlock(tdb, F_RDLCK, false);
+fail_allrecord_lock:
 	tdb_transaction_unlock(tdb, F_WRLCK);
 	SAFE_FREE(tdb->transaction->blocks);
 	SAFE_FREE(tdb->transaction->hash_heads);
@@ -621,7 +621,6 @@ static int _tdb_transaction_cancel(struct tdb_context *tdb, int ltype)
 	/* restore the normal io methods */
 	tdb->methods = tdb->transaction->io_methods;
 
-	tdb_brunlock(tdb, ltype, FREELIST_TOP, 0);
 	tdb_transaction_unlock(tdb, F_WRLCK);
 	SAFE_FREE(tdb->transaction->hash_heads);
 	SAFE_FREE(tdb->transaction);
@@ -938,9 +937,8 @@ static int _tdb_transaction_prepare_commit(struct tdb_context *tdb)
 	}
 
 	/* upgrade the main transaction lock region to a write lock */
-	if (tdb_brlock_upgrade(tdb, FREELIST_TOP, 0) == -1) {
+	if (tdb_allrecord_upgrade(tdb) == -1) {
 		TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_transaction_prepare_commit: failed to upgrade hash locks\n"));
-		tdb->ecode = TDB_ERR_LOCK;
 		_tdb_transaction_cancel(tdb, F_RDLCK);
 		return -1;
 	}