tdb2: save openhook, allow tdb_get_attribute() on it.

This makes it easy to call it again after a fork(), such as for
re-establishing the CLEAR_IF_FIRST files locks.

ccan/tdb2/open.c

@@ -270,11 +270,11 @@ enum TDB_ERROR tdb_get_attribute(struct tdb_context *tdb,
 		attr->seed.seed = tdb->hash_seed;
 		break;
 	case TDB_ATTRIBUTE_OPENHOOK:
-		return tdb->last_error
-			= tdb_logerr(tdb, TDB_ERR_EINVAL,
-				     TDB_LOG_USE_ERROR,
-				     "tdb_get_attribute:"
-				     " cannot get TDB_ATTRIBUTE_OPENHOOK");
+		if (!tdb->openhook)
+			return tdb->last_error = TDB_ERR_NOEXIST;
+		attr->openhook.fn = tdb->openhook;
+		attr->openhook.data = tdb->openhook_data;
+		break;
 	case TDB_ATTRIBUTE_STATS: {
 		size_t size = attr->stats.size;
 		if (size > tdb->stats.size)
@@ -306,16 +306,16 @@ void tdb_unset_attribute(struct tdb_context *tdb,
 	case TDB_ATTRIBUTE_LOG:
 		tdb->log_fn = NULL;
 		break;
+	case TDB_ATTRIBUTE_OPENHOOK:
+		tdb->openhook = NULL;
+		break;
 	case TDB_ATTRIBUTE_HASH:
 	case TDB_ATTRIBUTE_SEED:
-	case TDB_ATTRIBUTE_OPENHOOK:
 		tdb_logerr(tdb, TDB_ERR_EINVAL, TDB_LOG_USE_ERROR,
 			   "tdb_unset_attribute: cannot unset %s after opening",
 			   type == TDB_ATTRIBUTE_HASH
 			   ? "TDB_ATTRIBUTE_HASH"
-			   : type == TDB_ATTRIBUTE_SEED
-			   ? "TDB_ATTRIBUTE_SEED"
-			   : "TDB_ATTRIBUTE_OPENHOOK");
+			   : "TDB_ATTRIBUTE_SEED");
 		break;
 	case TDB_ATTRIBUTE_STATS:
 		tdb_logerr(tdb, TDB_ERR_EINVAL,
@@ -347,7 +347,6 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 	ssize_t rlen;
 	struct tdb_header hdr;
 	struct tdb_attribute_seed *seed = NULL;
-	struct tdb_attribute_openhook *openhook = NULL;
 	tdb_bool_err berr;
 	enum TDB_ERROR ecode;
 	int openlock;
@@ -372,6 +371,7 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 	tdb->open_flags = open_flags;
 	tdb->last_error = TDB_SUCCESS;
 	tdb->file = NULL;
+	tdb->openhook = NULL;
 	tdb->lock_fn = tdb_fcntl_lock;
 	tdb->unlock_fn = tdb_fcntl_unlock;
 	tdb->hash_fn = jenkins_hash;
@@ -390,7 +390,8 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 			seed = &attr->seed;
 			break;
 		case TDB_ATTRIBUTE_OPENHOOK:
-			openhook = &attr->openhook;
+			tdb->openhook = attr->openhook.fn;
+			tdb->openhook_data = attr->openhook.data;
 			break;
 		default:
 			/* These are set as normal. */
@@ -498,8 +499,8 @@ struct tdb_context *tdb_open(const char *name, int tdb_flags,
 	}
 
 	/* call their open hook if they gave us one. */
-	if (openhook) {
-		ecode = openhook->fn(tdb->file->fd, openhook->data);
+	if (tdb->openhook) {
+		ecode = tdb->openhook(tdb->file->fd, tdb->openhook_data);
 		if (ecode != TDB_SUCCESS) {
 			tdb_logerr(tdb, ecode, TDB_LOG_ERROR,
 				   "tdb_open: open hook failed");

ccan/tdb2/private.h

@@ -362,6 +362,10 @@ struct tdb_context {
 	tdb_off_t ftable_off;
 	unsigned int ftable;
 
+	/* Our open hook, if any. */
+	enum TDB_ERROR (*openhook)(int fd, void *data);
+	void *openhook_data;
+
 	/* IO methods: changes for transactions. */
 	const struct tdb_methods *methods;
 

ccan/tdb2/tdb2.h

@@ -617,8 +617,6 @@ enum tdb_attribute_type {
  * This gets an attribute from a TDB which has previously been set (or
  * may return the default values).  Set @attr.base.attr to the
  * attribute type you want get.
- *
- * Currently this does not work for TDB_ATTRIBUTE_OPENHOOK.
  */
 enum TDB_ERROR tdb_get_attribute(struct tdb_context *tdb,
 				 union tdb_attribute *attr);

ccan/tdb2/test/failtest_helper.h

@@ -4,7 +4,7 @@
 #include <stdbool.h>
 
 /* FIXME: Check these! */
-#define INITIAL_TDB_MALLOC	"open.c", 355, FAILTEST_MALLOC
+#define INITIAL_TDB_MALLOC	"open.c", 354, FAILTEST_MALLOC
 #define URANDOM_OPEN		"open.c", 62, FAILTEST_OPEN
 #define URANDOM_READ		"open.c", 42, FAILTEST_READ