Fix early transaction unlock when traverse done inside transaction.

Generalizes traverse in traverse fix from rusty@rustcorp.com.au-20090629073630-3eduhyypx2tp6u80

ccan/tdb/lock.c

@@ -302,6 +302,7 @@ int tdb_unlock(struct tdb_context *tdb, int list, int ltype)
 int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
 {
 	if (tdb->have_transaction_lock || tdb->global_lock.count) {
+		tdb->have_transaction_lock++;
 		return 0;
 	}
 	if (tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, ltype, 
@@ -310,7 +311,7 @@ int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
 		tdb->ecode = TDB_ERR_LOCK;
 		return -1;
 	}
-	tdb->have_transaction_lock = 1;
+	tdb->have_transaction_lock++;
 	return 0;
 }
 
@@ -319,15 +320,10 @@ int tdb_transaction_lock(struct tdb_context *tdb, int ltype)
  */
 int tdb_transaction_unlock(struct tdb_context *tdb)
 {
-	int ret;
-	if (!tdb->have_transaction_lock) {
+	if (--tdb->have_transaction_lock) {
 		return 0;
 	}
-	ret = tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1);
-	if (ret == 0) {
-		tdb->have_transaction_lock = 0;
-	}
-	return ret;
+	return tdb->methods->tdb_brlock(tdb, TRANSACTION_LOCK, F_UNLCK, F_SETLKW, 0, 1);
 }
 
 

ccan/tdb/tdb_private.h

@@ -215,7 +215,7 @@ struct tdb_context {
 	struct tdb_transaction *transaction;
 	int page_size;
 	int max_dead_records;
-	bool have_transaction_lock;
+	int have_transaction_lock;
 	int tracefd;
 	volatile sig_atomic_t *interrupt_sig_ptr;
 };

ccan/tdb/test/run-traverse-in-transaction.c

@@ -0,0 +1,70 @@
+#define _XOPEN_SOURCE 500
+#include "tdb/tdb.h"
+#include "tdb/io.c"
+#include "tdb/tdb.c"
+#include "tdb/lock.c"
+#include "tdb/freelist.c"
+#include "tdb/traverse.c"
+#include "tdb/transaction.c"
+#include "tdb/error.c"
+#include "tdb/open.c"
+#include "tap/tap.h"
+#include <stdlib.h>
+#include <stdbool.h>
+#include <err.h>
+
+static bool correct_key(TDB_DATA key)
+{
+	return key.dsize == strlen("hi")
+		&& memcmp(key.dptr, "hi", key.dsize) == 0;
+}
+
+static bool correct_data(TDB_DATA data)
+{
+	return data.dsize == strlen("world")
+		&& memcmp(data.dptr, "world", data.dsize) == 0;
+}
+
+static int traverse(struct tdb_context *tdb, TDB_DATA key, TDB_DATA data,
+		     void *p)
+{
+	ok1(correct_key(key));
+	ok1(correct_data(data));
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	struct tdb_context *tdb;
+	TDB_DATA key, data;
+
+	plan_tests(12);
+	tdb = tdb_open("/tmp/test.tdb", 1024, TDB_CLEAR_IF_FIRST,
+		       O_CREAT|O_TRUNC|O_RDWR, 0600);
+	ok1(tdb);
+
+	/* Tickle bug on appending zero length buffer to zero length buffer. */
+	key.dsize = strlen("hi");
+	key.dptr = (void *)"hi";
+	data.dptr = (void *)"world";
+	data.dsize = strlen("world");
+
+	ok1(tdb_store(tdb, key, data, TDB_INSERT) == 0);
+
+	ok1(tdb_transaction_start(tdb) == 0);
+	ok(tdb->have_transaction_lock, "Transaction lock in transaction");
+	tdb_traverse(tdb, traverse, NULL);
+
+	/* That should *not* release the transaction lock! */
+	ok(tdb->have_transaction_lock, "Transaction lock after traverse");
+	tdb_traverse_read(tdb, traverse, NULL);
+
+	/* That should *not* release the transaction lock! */
+	ok(tdb->have_transaction_lock, "Transaction lock after traverse_read");
+	ok1(tdb_transaction_commit(tdb) == 0);
+	ok(!tdb->have_transaction_lock, "Transaction unlock");
+
+	tdb_close(tdb);
+
+	return exit_status();
+}

ccan/tdb/traverse.c

@@ -211,7 +211,7 @@ int tdb_traverse_read(struct tdb_context *tdb,
 
 	/* we need to get a read lock on the transaction lock here to
 	   cope with the lock ordering semantics of solaris10 */
-	if (tdb->traverse_read == 0 && tdb_transaction_lock(tdb, F_RDLCK)) {
+	if (tdb_transaction_lock(tdb, F_RDLCK)) {
 		return -1;
 	}
 
@@ -220,9 +220,7 @@ int tdb_traverse_read(struct tdb_context *tdb,
 	ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
 	tdb->traverse_read--;
 
-	if (tdb->traverse_read == 0) {
-		tdb_transaction_unlock(tdb);
-	}
+	tdb_transaction_unlock(tdb);
 
 	return ret;
 }
@@ -244,8 +242,7 @@ int tdb_traverse(struct tdb_context *tdb,
 		return tdb_traverse_read(tdb, fn, private_data);
 	}
 
-	/* Nested traversals: transaction lock doesn't nest. */
-	if (tdb->traverse_write == 0 && tdb_transaction_lock(tdb, F_WRLCK)) {
+	if (tdb_transaction_lock(tdb, F_WRLCK)) {
 		return -1;
 	}
 
@@ -254,9 +251,7 @@ int tdb_traverse(struct tdb_context *tdb,
 	ret = tdb_traverse_internal(tdb, fn, private_data, &tl);
 	tdb->traverse_write--;
 
-	if (tdb->traverse_write == 0) {
-		tdb_transaction_unlock(tdb);
-	}
+	tdb_transaction_unlock(tdb);
 
 	return ret;
 }