Modern data centers adopt Remote Direct Memory Access (RDMA) to reduce CPU overhead and network latency. RDMA operates over a lossless network, and RDMA congestion control (CC) protocols are key enablers for achieving low-latency and high-throughput data delivery. Through in-depth experiment analysis, we reveal that existing RDMA CC protocols still suffer from sluggish congestion response and convergence speed. In this paper, we propose a switch-driven CC algorithm named \(FACC\) . \(FACC\)  enables switches to precisely identify flows that actually cause congestion and promptly notifies the congestion information to senders. At the sender, \(FACC\)  leverages the intrinsic packet conservation property of a lossless network to assess the extent of network congestion. Then, \(FACC\)  employs a PI controller to adaptively adjust the sending rate, thereby achieving rapid congestion elimination and improving both the transmission rate and convergence speed. We conduct extensive experiments to evaluate the performance of \(FACC\) . The results show that \(FACC\)  improves convergence speed while achieving at most 86.6% lower flow completion time (FCT) compared with state-of-the-art approaches.