tdb2: suppress tdb1 backend logging when locking returns EINTR or EAGAIN

The TDB1 code logs multiple times on errors; we must prevent that in
the limited case where locking fails.  With TDB2, this can happen due
to the lock function attribute, where the user supplies replacement
locking functions which are allowed to return with errno EAGAIN or
EINTR for various special-effects.  Flooding the logs for this is
unfriendly.

ccan/tdb2/tdb1_lock.c

@@ -180,7 +180,8 @@ int tdb1_lock(struct tdb1_context *tdb, int list, int ltype)
 	int ret;
 
 	ret = tdb1_lock_list(tdb, list, ltype, TDB_LOCK_WAIT);
-	if (ret) {
+	/* Don't log for EAGAIN and EINTR: they could have overridden lock fns */
+	if (ret && errno != EAGAIN && errno != EINTR) {
 		tdb_logerr(tdb, tdb->last_error, TDB_LOG_ERROR,
 			   "tdb1_lock failed on list %d "
 			   "ltype=%d (%s)",  list, ltype, strerror(errno));

ccan/tdb2/tdb1_transaction.c

@@ -478,8 +478,11 @@ static int _tdb1_transaction_start(struct tdb1_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 (tdb1_allrecord_lock(tdb, F_RDLCK, TDB_LOCK_WAIT, true) == -1) {
-		tdb_logerr(tdb, tdb->last_error, TDB_LOG_ERROR,
-			   "tdb1_transaction_start: failed to get hash locks");
+		if (errno != EAGAIN && errno != EINTR) {
+			tdb_logerr(tdb, tdb->last_error, TDB_LOG_ERROR,
+				   "tdb1_transaction_start:"
+				   " failed to get hash locks");
+		}
 		goto fail_allrecord_lock;
 	}
 
@@ -955,9 +958,11 @@ static int _tdb1_transaction_prepare_commit(struct tdb1_context *tdb)
 
 	/* upgrade the main transaction lock region to a write lock */
 	if (tdb1_allrecord_upgrade(tdb) == -1) {
-		tdb_logerr(tdb, tdb->last_error, TDB_LOG_ERROR,
-			   "tdb1_transaction_prepare_commit:"
-			   " failed to upgrade hash locks");
+		if (errno != EAGAIN && errno != EINTR) {
+			tdb_logerr(tdb, tdb->last_error, TDB_LOG_ERROR,
+				   "tdb1_transaction_prepare_commit:"
+				   " failed to upgrade hash locks");
+		}
 		_tdb1_transaction_cancel(tdb);
 		return -1;
 	}
@@ -965,9 +970,11 @@ static int _tdb1_transaction_prepare_commit(struct tdb1_context *tdb)
 	/* get the open lock - this prevents new users attaching to the database
 	   during the commit */
 	if (tdb1_nest_lock(tdb, TDB1_OPEN_LOCK, F_WRLCK, TDB_LOCK_WAIT) == -1) {
-		tdb_logerr(tdb, tdb->last_error, TDB_LOG_ERROR,
-			   "tdb1_transaction_prepare_commit:"
-			   " failed to get open lock");
+		if (errno != EAGAIN && errno != EINTR) {
+			tdb_logerr(tdb, tdb->last_error, TDB_LOG_ERROR,
+				   "tdb1_transaction_prepare_commit:"
+				   " failed to get open lock");
+		}
 		_tdb1_transaction_cancel(tdb);
 		return -1;
 	}