From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ed1-f52.google.com (mail-ed1-f52.google.com [209.85.208.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 928C6306B11 for ; Mon, 23 Feb 2026 15:54:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771862095; cv=none; b=PKngAkmyRYWPAnTn8leepn4RLo4Wby7Rhc79gHlCm/FA1FndFacLZ3ECEcIKqUKqeu642gvumKa5pUQtLwxW9Su91aKana/2BQ2WNiwPp36KeLvQSSrWgPbpm6nAIZElMCtVEbMdR9cjthQqIhtWJJeFDT6kgSnZR8B8i7GV50w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771862095; c=relaxed/simple; bh=R1AUHGXxe3dGgZHbFkQxH0f/b1HLtXH7ZZMS1myvRDw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=H5FbxRkRX4EpFl9WCTWQ+Lt0D69xidHud5bpzvPpcNiBv2vYBPUEs/Qh0S7qzxEjQtyf/5HNtXV8FCWbCHeKeTibHq4QEUEIj/GOrgg+F/mDSf/LPdaHw7uDSMkHVEpVWxPH/SImAqyxPHo2uGPUSIIelwr8/dgJGHQI3xaj0+8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=AV/trNVK; arc=none smtp.client-ip=209.85.208.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="AV/trNVK" Received: by mail-ed1-f52.google.com with SMTP id 4fb4d7f45d1cf-65a40f3f048so8340492a12.3 for ; Mon, 23 Feb 2026 07:54:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1771862091; x=1772466891; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=cyQb0+priOw9IUD9vV+F9EltCgHvh5WCMeDq2M8hato=; b=AV/trNVK+3bVsOKnp5bahBdRAH07bioQbb+KQdhDdReRC6BRzawScBjHSwKs+AhGUB iZ9AQZGG3s1e+nAmEEy0xHhD3d4xIMx8y6Z/yQ+wTJ4cVxHc/yg6MwgGVLPyxT8IAAou uhFX6ih3LF71xZRew+arQeEsEDozLUMo0ojuRIG+gJWYkQ5RxV+70Hk9wxWOgbNJv9qb MhGWm8RpXByui/rR61Hket8H6wtRBMr7N9b1zwc3gputqFhlSuzGn+NSwyrtYpPRpk/h VJ3oaez6xGsaRenOEca1c0+yQ/C/yHzImvR9FrZ7toR2aDszDqjbeA8idHsvmj2D/i1e QYXQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1771862091; x=1772466891; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=cyQb0+priOw9IUD9vV+F9EltCgHvh5WCMeDq2M8hato=; b=BJFCG/yFGbW8N6ZeZhwuXJw6kcqpAaVcjUNF5fuZxtZsjwluv1kNYEavBo3/2oaVLq ccCCS1G5gN4yMVux/KX6vnblmuiddTMIC9GRIzGbZt0ri6imxyoMA3ZRYZpQOJd2E4K/ Vg8z1HWRi7u7Vm4TWXLXiJCR0vhnOGoLAFxqeXEr+jH6oVeLoIzXnxz3HNiIsG19u5aT pGsIzLcWrEZJvfbpaEFTidVr4J+MM/KAB7DwO73DofCgGAc5T1eFlS+uXoW1uc+6W5fn 3x/9WlYaGw+NAi086sReCaV0Q8KlKlRM1mGcestKTyFUVa3LicsTpY4FgnsJC4ZJJDpR 0KoQ== X-Forwarded-Encrypted: i=1; AJvYcCUOZK0PV15s/eIdP0kpCvljeFLsTfoaGKkMTugAdmKQX5RIuGtnBPKtq6QYi2C/fl7E9b8=@vger.kernel.org X-Gm-Message-State: AOJu0YxXDXbYHZXgRnQ4vMc3+NodpslDayzQqYok3qRzkWmEjQD+CxTi Ne9yWACsgKbGQ4dTOTRwJIS0Q0JilSp5o4qWxbFdox2XbZ4iy2wS6I/5 X-Gm-Gg: AZuq6aJ1NnSFZCMy/eN4K1N9bwml2cD5ABNTpYqTdJ2e72Sec5wlId7Lx4aMGdCwR3q 4YfE3IQkyh/HJ+nzhM4LcSLGHZhMuyCM3Y1MlZ2MYql93N8OI/fz5AsafGjMp2zdaQbhIKLAD39 Obaruh9jfchRwF5lVdfZ3RPdWXvuaGJItpv2Ze80wBOpnuCNMzswCzH7+11TV1v+HsGFCCaOhhb rg10XT3LMXkg/lK9xoqvA8wXf6m8IiiVhMO5cHBsVeaEflnHSO9TDHzMKEmMj0Ra4alKKjJvd1R rD/YYxUdc07ecEN9NrJxoDQo976oLdyZNmNP/yAAqVe0TR5d0QaaSOU9Om+YHhwTACyrzNQBCj7 1gM/xZqvjVd7uuUWcrgeX4lJm2bh+Iq+9hxp3duPBVo3z4jKewz7PEoaaxIKryKJP2ZfMKt9LQh BVF2IR4eXVi8466hU+clFPtPMGyJbAI3wtCS3oY6h1wCQFa/rnDXzVAUOyG50P416eRVUiR9f4B r7q7cfguO2Tit/i8Y+u47TPH+QKvlQsHiBX99Q2iW8GY5/r7DHIJxGsSC66RyyFSshuRzZ5sL6w Ww== X-Received: by 2002:a17:906:19cb:b0:b8f:8e99:7860 with SMTP id a640c23a62f3a-b9081ba9436mr397974566b.46.1771862090575; Mon, 23 Feb 2026 07:54:50 -0800 (PST) Received: from ?IPV6:2a01:4b00:bd21:4f00:7cc6:d3ca:494:116c? ([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: bpf@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