From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f42.google.com (mail-wm1-f42.google.com [209.85.128.42]) (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 960C43E3150 for ; Tue, 14 Apr 2026 12:12:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.42 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776168723; cv=none; b=HhMEEliDh751iM/mDyLfMPnvRL81VSw6T2YUaqUZoL3ome5v4Mn3AEI39jurtIdm6zYey/SLQjZjGBnxFT0dJRo49WQZNkEjq/P2wss2RqKThjYi4AZmvYlRMEI0Ms4LCFupC1acLCUvZCQP2vBpHTrZU4Qo1iHjVM7h+EVUtNg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776168723; c=relaxed/simple; bh=EcyAyQAY07H09O3PSX0IfaghfmLvphSUvxDuGMY+c24=; h=From:To:Cc:Subject:In-Reply-To:References:Content-Type:Date: Message-Id; b=XqtaW5AKpYR/LjwJRhQt0i0HY2SyLCYl5YygN2G6/UlSpVUJU1BYoftQA+vQlStzm6MzAS2Bsu79yJHjkMv3B/NjnYt6DGRJZImNLYXoJANT8zAvkIgtS2PHIdRcl47Ioe49+0WEo+A0Mea9qCB4E3kO8VrbtBwuHEjd5IIcxGI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=hackers.camp; spf=pass smtp.mailfrom=gmail.com; arc=none smtp.client-ip=209.85.128.42 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=hackers.camp Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-wm1-f42.google.com with SMTP id 5b1f17b1804b1-488965a9ca1so6653015e9.2 for ; Tue, 14 Apr 2026 05:12:01 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776168720; x=1776773520; h=message-id:date:references:in-reply-to:subject:cc:to:from:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=EcyAyQAY07H09O3PSX0IfaghfmLvphSUvxDuGMY+c24=; b=qeRIYyvU3sOH9kewqtbGDs1sH2l5u1tvM+Nz9zwC3snn+GNZ1pdyaJ45/v031siMEx K8ATH3B+P8JmERlSEl+tW/AwBJojOBaGdux1OMadY3unGM/nib7DDA9bSKbno3TiSrW5 cQVUOqKFeyDAQ/ltZAxTjuoJzDxsB77ADr5TbHQ8TWQgg/tK3JAcF5QQRdS42VEnkzXO mQzNVFYSc6QQoVBHI53pe2hWIu3hIOdqoQNLffF0XRKuckTt8y/RonthA7O2gOSfAfDE Dz5U+fEjEG2mxs1qX8UQeTKtwYQlJCYUZ4iuU8kUqNKMGFRdlMYHaFSNGutdQjUOrp/M aC5g== X-Forwarded-Encrypted: i=1; AFNElJ9IzDu972v9tHpuyisqXytIkja87A4/elSDen7KKihOEHE311NfEO1X7OWjmQI3RoGkb5eRLqA7Hq1rwQI=@vger.kernel.org X-Gm-Message-State: AOJu0YzqYMsBlK/ihmb1Y4e4ns8I+IuC05OYkhqn9qF4mx9hJF+C7kGn ZNpa8pxA7aao/9FSoPBlXyy1ApCQ5ItTHpWW+dmOwr4VEv6goRIWW8Dt X-Gm-Gg: AeBDieufAmlo1xOJc7oAXYUr7KkZq2niLoMzuew4G/xhNW5idKZJyNpbQcT23sRVOXA T+5w2epSPevm/53NuCEjsDW1T7krOh/dkDUrHGYbb+EjfNs1u2wK8nXgcg9xAEi8YfbHotmf8qi bbyQTeFuztqRi6TlAUavKBrH5eMOZD9LPK46le6x00Vo+fCsC1ote0iGaWVyIO4XvQcaK3o/Kvt jF4tUSsv1qCYTo91G55WkktaSVSGLOyOqphf/356egM+Fo7fz7/h2US/4muTzaaLhuiAKFRkjvy DHJJFnshifjqOg0nwyr4vtAD41K7CgtiLIuGSkvwE69QRgUWQhWU0hZSj64kXvHYY3kKeG+bD4u 2mYzNKa489Sz0e2uOIBBXl2MEHWuJ3CsP0yrWXqRBMBSQd1Z9BR8RPeV3NWu+14eJSr0ISnstyg Y+9QUtWMPcMPNX6uEaFRNbYGbsgtYa8kr2Rmye8t5MuW3ro1gPpwoPpuxm1fw2iwbmt7AIgoI= X-Received: by 2002:a05:600c:19d4:b0:488:7e7b:dbc2 with SMTP id 5b1f17b1804b1-488d7f2509dmr120181455e9.3.1776168719869; Tue, 14 Apr 2026 05:11:59 -0700 (PDT) Received: from hackers.camp ([2a01:cb1c:784:2f00:708:2805:7128:7a75]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488d5dc7070sm120255145e9.10.2026.04.14.05.11.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2026 05:11:59 -0700 (PDT) Received: (nullmailer pid 12730 invoked by uid 1000); Tue, 14 Apr 2026 14:11:31 -0000 From: Aurelien DESBRIERES To: Andreas Dilger Cc: Pedro Falcato , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org Subject: Re: [RFC PATCH 0/10] ftrfs: Fault-Tolerant Radiation-Robust Filesystem In-Reply-To: References: <20260413142357.515792-1-aurelien@hackers.camp> Content-Type: text/plain; charset=UTF-8 Date: Tue, 14 Apr 2026 16:11:31 +0200 Message-Id: <1776175891.864729.12729.nullmailer@hackers.camp> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: On Mon, Apr 13, 2026 at 12:03:10PM -0600, Andreas Dilger wrote: > Modern ext4 has metadata checksums for many years, and fsverity can > be used to add Merkle-tree checksums for file data. Data redundancy > can be handled by the block layer. ext4 checksums and fsverity both detect corruption. Neither corrects it. On a single MRAM or NOR flash device in a nanosatellite, there is no block layer redundancy available. Detection without correction means data loss. RS FEC integrated at the filesystem block level corrects up to 8 symbol errors per 255-byte subblock in place, on a single device, without external redundancy. That is the specific gap that FTRFS addresses and that no existing Linux filesystem provides. > If code size/complexity is a significant issue for new embedded > satellite controllers, then implementing "read-only" support for ext4 > could be fairly straight forward development. Read-only ext4 does not solve the write path requirement. The target systems require read-write access to MRAM during mission operations (telemetry, payload data). A read-only filesystem is not sufficient. > You also have to consider that filesystems are critical components of > any computer, and having bugs in newly-developed filesystem code could > be as fatal to the satellite as the radiation. The general rule of > thumb is that filesystems take about 10 years to mature. Acknowledged. This is precisely why the design targets under 5000 lines of auditable code, why the on-disk format is deliberately simple (ext2-reminiscent), and why DO-178C / ECSS-E-ST-40C certification is an explicit design constraint. A smaller, auditable codebase reduces the bug surface. The maturity concern is real and will be addressed through progressive validation - the Yocto arm64 HPC cluster (Slurm 25.11.4, kernel 7.0) is the first step. Aurelien DESBRIERES