Re: [LSF/MM/BPF TOPIC] User space RAID5 with ublk and io_uring BPF

[Keith Busch <kbusch@kernel.org>]

On Thu, Feb 19, 2026 at 01:38:46PM +0800, Xiao Ni wrote:
> Hi all
> 
> I'm doing some work on user-space RAID recently. I'd like to propose a
> topic for LSF/MM 2026 regarding the implementation of RAID5 in user
> space using ublk and io_uring bpf[1], particularly focusing on the
> challenges encountered and potential kernel improvements needed.
> 
> Ublk raid5 uses the ublk framework (tools/testing/selftests/ublk/),
> with the goal of leveraging io_uring's zero-copy capabilities and
> BPF[1] for performance optimization. The implementation includes:
> * RAID5 stripe handling with configurable chunk sizes
> * Multi-queue support via io_uring
> * Degraded mode for single disk failure tolerance
> * Integration with io_uring BPF struct_ops framework
> 
> During the implementation, I encountered several technical challenges.
> The primary challenge is performing XOR parity calculations in a true
> zero-copy manner:

Great use case. The indirect reference to memory from user space is a
bit of a blocker for various zero-copy plans, so being able to leverage
the kernel to perform parity and crypto transforms would be awesome. I
think there's potential for fuse as well as ublk.

Anyway, I'm interested in the topic.