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([2a01:4b00:bd21:4f00:7cc6:d3ca:494:116c]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b9084a4d6e1sm341510066b.0.2026.02.23.07.54.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Feb 2026 07:54:50 -0800 (PST) Message-ID: <7e772d91-a546-40ed-90c0-29e2a9721c53@gmail.com> Date: Mon, 23 Feb 2026 15:54:46 +0000 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [LSF/MM/BPF TOPIC] User space RAID5 with ublk and io_uring BPF To: Xiao Ni , lsf-pc@lists.linux-foundation.org, linux-block , bpf@vger.kernel.org Cc: Ming Lei References: Content-Language: en-US From: Pavel Begunkov In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/19/26 05:38, 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: I aim at similar use cases, i.e. interacting with registered buffers from BPF, but based on a different BPF-io_uring implementation. I'd be interesting to discuss how the kfunc API should look like. -- Pavel Begunkov