From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f49.google.com (mail-wm1-f49.google.com [209.85.128.49]) (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 572F21FC8 for ; Tue, 14 Apr 2026 12:07:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.49 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776168458; cv=none; b=Kp1uP93DuTpSWA5myiSkWvuT6CJ1c/u4F9anct42kJWLRCOAWSfGR51YlF4Bww4xn7AoQ8EpT7X9Tb0muFiEACzLQ68g+U5Kmqaox738M0uBVtGX+wJZsLORaVQSghd0r5Hljx6sxYK5KqAuC+GZacj7L0KrGNZFDxu+erDuuhs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776168458; c=relaxed/simple; bh=xyN07penaBjOnqjgXRleGdStAPrDLYXA2j+8PcQ2Ym8=; h=From:To:Cc:Subject:In-Reply-To:References:Content-Type:Date: Message-Id; b=t2Ns8LTMIEjC+/a9UEAuDkTC7TtOjOtniyqAEwjm+Ttt6+P4yoc0E0yHg3cnibwt5AHdk+CX9n7FHQ/rA+j7HEcvU8n8TDFNAqWUZ9xW9K4iKmAF0KdBxHJ4HpGk22sZFOfZOi3puKxDAPYtJJB8WN2sY/kIg7wHIWzHN711nQc= 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=209.85.128.49 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-f49.google.com with SMTP id 5b1f17b1804b1-488822b93c7so6115465e9.1 for ; Tue, 14 Apr 2026 05:07:37 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776168456; x=1776773256; 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=xyN07penaBjOnqjgXRleGdStAPrDLYXA2j+8PcQ2Ym8=; b=n4Ho6rIGoEejfPQBqczl+GzARStUjzQ85QycsSOmSzHpBUMXiEWGwtoiDCPGE9osTr UKnPNtqk9bXE05wN4BTNLPa+GiRk/Ncezz4hzlv5igRU6HQnY56Ufiad7mGtNt9dx+4P hIpT/TezEHwJZvDze4566v7YdPghpCFuMvaIiv+P6GSLtgGMWkq1DQzphrkmHRh5s90A wiEuq0XE79IFPZuOuxNgQNWNEOprrgtFtkuffbpvhbrLomoxMXAjIaO/iY7SQwhNvHcF +NMoDsYF6WijUyo2yYOjqpXxePYsewa3A4jaCs9GB4D+xKEJE2RQvFAPeMTLMiU7DaCE lLrA== X-Gm-Message-State: AOJu0YzEJq6wrBdGLMiP4d0KO/OTkUYVnH9dh0MeJTJgX57kxjBHOGsr 0qzzvHfuX+5/p2Wa9MRj4qDs4rDihVLKc0iooAgDEgUITYjT9xOYqE9eeVgidsG3 X-Gm-Gg: AeBDievlSR5MZgG4m3/J+t/c3wnFhyd1JsbEo1/xwb9D4JPp+VPemHK6AG54lAzb6b1 limR6IYVib26gDCIsElFjf6uzVqdHs6iGvZM4jo0b/gfbb+C3CZILt38ij/s0d1dSMGNL5+kbL+ hYFDB91ro5bj6cfzNh9cBFaJCH2xTue1G5upVzzYG5yZBWCRNxncBRg37y6V0NT0Kfpq1mbphDR WYiqxOojobEk+VjtTnYQVGmDpPpmMULDIsJ8lWMUaZCvZ34UI0pOJl9NHltp4QIlhME3JDyQwm1 IHpWiNJXP7R3wVLZO1F1zeMnoWVoCcwEA5AB1/8UGQ4PX6GfUE8pT38kfD6NvYH21tXUrHkvnKb 6yblbL6l5Sj4ezV6K8UDcQpf406mRXhflCvack1NNQmIjw7JQYt5D3VnWzbA4vUcKN3Y6WJrVCp f7B1yXkDXO8tSGB5rWMvg4Jbn98TwwnFyBjgfKlsyclX1SdTeNPKHDw44R5ip3fQXL53Qtmvb8B kvZClBc1vuxnSUg X-Received: by 2002:a05:600c:19d4:b0:488:7e7b:dbc2 with SMTP id 5b1f17b1804b1-488d7f2509dmr120055815e9.3.1776168455497; Tue, 14 Apr 2026 05:07:35 -0700 (PDT) Received: from hackers.camp ([2a01:cb1c:784:2f00:708:2805:7128:7a75]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488ede24977sm46608195e9.7.2026.04.14.05.07.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2026 05:07:34 -0700 (PDT) Received: (nullmailer pid 47961 invoked by uid 1000); Mon, 13 Apr 2026 17:26:55 -0000 From: Aurelien DESBRIERES To: djwong@kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org Subject: Re: [RFC PATCH 01/10] ftrfs: add on-disk format and in-memory data structures In-Reply-To: <20260413151158.GW6202@frogsfrogsfrogs> References: <20260413142357.515792-2-aurelien@hackers.camp> <20260413151158.GW6202@frogsfrogsfrogs> Content-Type: text/plain; charset=UTF-8 Date: Mon, 13 Apr 2026 19:26:55 +0200 Message-Id: <1776101215.268662.47960.nullmailer@me> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: On Mon, Apr 13, 2026 at 05:11:XX PM +0200, Darrick J. Wong wrote: > I don't see a block header for indirect blocks, so I guess this > filesystem only supports mapping ($block_size / 4) ^ 2 + > ($block_size / 4) + 12 blocks? IOWs, 1049612 of 4KiB blocks, > or about 4GB of data? Why is isize 64-bit then? Correct. With 4KiB blocks and 8-byte block pointers, the maximum addressable file size is (512 + 512^2 + 12) * 4096 = ~1GB, not 4GB. The 64-bit i_size is inconsistent with the block pointer scheme. For the intended use case (MRAM/NOR flash on embedded space hardware), files are small and a ~1GB limit is acceptable. i_size will be corrected to __le32 in v2, or explicitly documented as capped at ~1GB with a build-time assert. Thank you for the precise calculation. Aurelien DESBRIERES