FAT32 File-System Seeing as Much as 265x Improvement with Linux 7.4

A small change to Linux’s FAT driver, merged for kernel 7.4, substantially speeds up a particular file-allocation operation on FAT32. The issue was how the driver handled requests using FALLOC_FL_KEEP_SIZE, a flag that reserves disk space for a file without increasing its reported size. When such a file needed to grow its allocated space, the existing code repeatedly requested allocation one cluster at a time, creating unnecessary overhead.

Developer Matheus Alves de Almeida changed the allocation path so it can request multiple clusters in a single call instead. Benchmarks he shared show gains across the tested workloads, reaching a maximum improvement of 265 times over the previous behavior. The result comes from only a few lines of code and targets this specific preallocation path; it does not imply that all FAT32 operations or general file access become hundreds of times faster. The patch was included in Linux 7.4 through a non-memory-management pull request sent by Andrew Morton. For systems that use FAT32 and rely on keeping files preallocated without changing their visible size, the kernel update can make that operation dramatically more efficient.