This paper presents an analysis of a performance bottleneck in enterprise file servers using Linux and proposes a modification to this operation system for avoiding the bottleneck. The analysis shows that metadata cache de-allocation of current Linux causes large latency in file-request processing when the operational throughput of a file server becomes large. To eliminate the latency caused by metadata cache de-allocation, a new method, called 'split reclaim', which divides metadata cache de-allocation from conventional cache de-allocation, is proposed. It is experimentally shown that the split-reclaim method reduces the worst response time by more than 95% and achieves three times higher throughput under a metadata-intensive workload. The split-reclaim method also reduces latency caused by cache de-allocation under a general file-server workload by more than 99%. These results indicate that the split-reclaim method can eliminate metadata cache de-allocation latency and makes it possible to use low-cost commodity servers as enterprise file servers.