From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout.gmx.net (mout.gmx.net [212.227.15.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8797C3BAD82; Wed, 20 May 2026 08:41:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=212.227.15.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779266494; cv=none; b=jo2Th0cyw1VLkenF4uTS08BZGx2q9g5HulfTLrDl+hpc5PDIR5oUbFRngB173vbqa5fq8HY48slsAXLsg83hUepuAoOiJWZkxsPzcli6rPg4PfCSfmotQN8BXD4wNFXlvwEpA7cu7VaWgaj/nVdeXmXE3gNIrzq+rT/6hvqppbY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779266494; c=relaxed/simple; bh=fMqNJlyV039u9ohm5+AApuHgWMYmRF2q9wy82/juDow=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=YYPHNYDzj3CALn6Sp+tcoyiM24WYg0k9vNT9EoAoVjgdieqMJy8/hjcCQdkBgWn956FpQfA+crQ0lXmBGkuWbZ4Efp0ToKx2AdC2FR03BZnA9Yu01KsJZ9AW7zcBXPVdM/dTeOkQo2bA+KdKe/p2fTQ2go94xLRKNX8grCfD2sk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=gmx.com; spf=pass smtp.mailfrom=gmx.com; dkim=pass (2048-bit key) header.d=gmx.com header.i=quwenruo.btrfs@gmx.com header.b=EvpRYish; arc=none smtp.client-ip=212.227.15.18 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=gmx.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmx.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmx.com header.i=quwenruo.btrfs@gmx.com header.b="EvpRYish" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmx.com; s=s31663417; t=1779266490; x=1779871290; i=quwenruo.btrfs@gmx.com; bh=KVGbQSGJqboMkQGEaBuh2n5D9Rw1MUG1r1v6327U8ig=; h=X-UI-Sender-Class:Message-ID:Date:MIME-Version:Subject:To:Cc: References:From:In-Reply-To:Content-Type: Content-Transfer-Encoding:cc:content-transfer-encoding: content-type:date:from:message-id:mime-version:reply-to:subject: to; b=EvpRYishcdZk67Wh9wQNUukQEGSMTh3LeuhbPSXJ2qlRtFUX0HnzOMz9+4Zr6Qj7 gnjQdK9oPj03fT+wBBsNd85hBqjAvkJZyWR0MrSrIJjd89wAoaXK549bm4yU9X8FD 1j2Z1ScTWcYRQrDtBB967afu8jjJjTnXJPZ0ts/A39IxKeTXh3U3ONbHA2vybY/Nj AgKhnNiHHdtgn8c0zlPAcXysh2EquxJ8FG4mnF7CK+bwR0akDtPLghlyl70CFX01D VrLq5JnLQ5x0W5aP711DNi8q4HG5ahPNDJ5y3ZNcrzqHLuQsRuXnSpK19p923QYsi dvaXtRVt/ztAg3bKxQ== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from client.hidden.invalid by mail.gmx.net (mrgmx005 [212.227.17.184]) with ESMTPSA (Nemesis) id 1MZTqW-1wtkYJ26tS-00KAV0; Wed, 20 May 2026 10:41:30 +0200 Message-ID: Date: Wed, 20 May 2026 18:11:09 +0930 Precedence: bulk X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 01/19] btrfs: require at least 4 devices for RAID 6 To: Christoph Hellwig , "H. Peter Anvin" Cc: kreijack@inwind.it, David Sterba , Andrew Morton , Catalin Marinas , Will Deacon , Ard Biesheuvel , Huacai Chen , WANG Xuerui , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Herbert Xu , Dan Williams , Chris Mason , David Sterba , Arnd Bergmann , Song Liu , Yu Kuai , Li Nan , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-crypto@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-arch@vger.kernel.org, linux-raid@vger.kernel.org References: <20260512052230.2947683-1-hch@lst.de> <20260512052230.2947683-2-hch@lst.de> <20260512114231.GG2558453@suse.cz> <20260513054742.GA1018@lst.de> <0a8d1ff4-f5a2-49e9-aa45-d25dbe4ded40@libero.it> <20260515043705.GA3855@lst.de> <34C16854-1065-4542-8836-DDED58EC1844@zytor.com> <20260518051207.GB9374@lst.de> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCZxF1YAUJEP5a sQAKCRDCPZHzoSX+qF+mB/9gXu9C3BV0omDZBDWevJHxpWpOwQ8DxZEbk9b9LcrQlWdhFhyn xi+l5lRziV9ZGyYXp7N35a9t7GQJndMCFUWYoEa+1NCuxDs6bslfrCaGEGG/+wd6oIPb85xo 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Peter Anvin wrote: >> I don't think this is a good idea. Error out; it is the btrfs maintaine= rs' job to ensure user data isn't lost. >> >> The RAID-6 code has *never* supported only 3 units, and if it ever work= ed for *any* of the implementations it was purely by accident. Speaking as= the original author I should know; this was deliberate as in some cases t= he degenerate case (3) would have required extra trays in the code to no u= ser benefit. >> >> I would not be surprised if the kernel crashed or corrupted the page ca= che in that case. >=20 > It does, that's why I wanted to exclude it. Anyway, for the about to be > resent version I'll drop this btrfs patch over the stated objection and > will otherwise not change anything. This means the (IMHO hypothetical) > users of this configuration will get a WARN_ON_ONCE triggered, but > otherwise keep working (or rather not working) as before. >=20 For the btrfs part, I believe I can get the current 2-disk-raid5 and=20 3-disk-raid6 to fallback to raid1 inside btrfs. I hope the btrfs part can be finished and reach the next merge window,=20 but I'm not 100% sure. What is the planned cycle to merge this raid5/6 cleanup? Thanks, Qu