Linux 7.5 to deliver up to 4.06x FAT32 synchronous write speedup via batched mirror I/O

Open-source developer Matheus Alves de Almeida has submitted a patch to the Linux kernel that dramatically accelerates FAT32 performance on synchronous mounts by batching mirror writes rather than processing them buffer-by-buffer. Benchmarks demonstrate up to a 4.06x speed improvement, addressing a long-standing bottleneck where serialized I/O submission crippled throughput. The change is currently queued in Andrew Morton's mm-everything branch, positioning it for inclusion in Linux 7.5, which is expected to arrive in early 2027.

This improvement complements earlier FAT32 optimizations already slated for Linux 7.4, indicating renewed maintainer attention to the aging but still widely deployed file system. The patch specifically targets synchronous mount scenarios, which are commonly used for data integrity guarantees on removable media, embedded systems, and interoperability partitions.

FAT32 I/O batching and mirror write mechanics

• Synchronous mount bottleneck: The existing Linux FAT driver synchronizes buffer-by-buffer on synchronous mounts, forcing serialized I/O submission that limits throughput.
• Batching architecture: The new code batches FAT mirror writes together rather than flushing each buffer independently, reducing the number of synchronous operations.
• Submission pipeline improvements: The patch optimizes how batched writes are submitted to the block layer, cutting per-operation overhead.
• Measured gain: Benchmarks on FAT32 with synchronous mounts show performance scaling up to 4.06x compared to the current implementation.
• Integration path: The patch resides in Andrew Morton's mm-everything branch, following the standard MM qualification process toward Linux 7.5 merge.

Why it matters

FAT32 remains ubiquitous for SD cards, USB flash drives, EFI system partitions, and cross-platform removable media where synchronous mounts ensure data durability. This improvement will benefit embedded Linux deployments, digital cameras, automotive infotainment systems, and any workload relying on FAT32 with sync guarantees. For distributions and device manufacturers, the change reduces the performance penalty that previously pushed users toward riskier async mounts or alternative file systems.